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15937 lines
546 KiB
HTML
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<meta name="generator" content="groff -Thtml, see www.gnu.org">
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<title>BASH</title>
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<body>
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<h1 align="center">BASH</h1>
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<a href="#NAME">NAME</a><br>
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<a href="#SYNOPSIS">SYNOPSIS</a><br>
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<a href="#COPYRIGHT">COPYRIGHT</a><br>
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<a href="#DESCRIPTION">DESCRIPTION</a><br>
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<a href="#OPTIONS">OPTIONS</a><br>
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<a href="#ARGUMENTS">ARGUMENTS</a><br>
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<a href="#INVOCATION">INVOCATION</a><br>
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<a href="#DEFINITIONS">DEFINITIONS</a><br>
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<a href="#RESERVED WORDS">RESERVED WORDS</a><br>
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<a href="#SHELL GRAMMAR">SHELL GRAMMAR</a><br>
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<a href="#Simple Commands">Simple Commands</a><br>
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<a href="#Pipelines">Pipelines</a><br>
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<a href="#Lists">Lists</a><br>
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<a href="#Compound Commands">Compound Commands</a><br>
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<a href="#Coprocesses">Coprocesses</a><br>
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<a href="#Shell Function Definitions">Shell Function Definitions</a><br>
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<a href="#COMMENTS">COMMENTS</a><br>
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<a href="#QUOTING">QUOTING</a><br>
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<a href="#Translating Strings">Translating Strings</a><br>
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<a href="#PARAMETERS">PARAMETERS</a><br>
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<a href="#Positional Parameters">Positional Parameters</a><br>
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<a href="#Special Parameters">Special Parameters</a><br>
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<a href="#Shell Variables">Shell Variables</a><br>
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<a href="#Arrays">Arrays</a><br>
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<a href="#EXPANSION">EXPANSION</a><br>
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<a href="#Brace Expansion">Brace Expansion</a><br>
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<a href="#Tilde Expansion">Tilde Expansion</a><br>
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<a href="#Parameter Expansion">Parameter Expansion</a><br>
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<a href="#Command Substitution">Command Substitution</a><br>
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<a href="#Arithmetic Expansion">Arithmetic Expansion</a><br>
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<a href="#Process Substitution">Process Substitution</a><br>
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<a href="#Word Splitting">Word Splitting</a><br>
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<a href="#Pathname Expansion">Pathname Expansion</a><br>
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<a href="#Quote Removal">Quote Removal</a><br>
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<a href="#REDIRECTION">REDIRECTION</a><br>
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<a href="#Redirecting Input">Redirecting Input</a><br>
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<a href="#Redirecting Output">Redirecting Output</a><br>
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<a href="#Appending Redirected Output">Appending Redirected Output</a><br>
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<a href="#Redirecting Standard Output and Standard Error">Redirecting Standard Output and Standard Error</a><br>
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<a href="#Appending Standard Output and Standard Error">Appending Standard Output and Standard Error</a><br>
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<a href="#Here Documents">Here Documents</a><br>
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<a href="#Here Strings">Here Strings</a><br>
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<a href="#Duplicating File Descriptors">Duplicating File Descriptors</a><br>
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<a href="#Moving File Descriptors">Moving File Descriptors</a><br>
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<a href="#Opening File Descriptors for Reading and Writing">Opening File Descriptors for Reading and Writing</a><br>
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<a href="#ALIASES">ALIASES</a><br>
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<a href="#FUNCTIONS">FUNCTIONS</a><br>
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<a href="#ARITHMETIC EVALUATION">ARITHMETIC EVALUATION</a><br>
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<a href="#CONDITIONAL EXPRESSIONS">CONDITIONAL EXPRESSIONS</a><br>
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<a href="#SIMPLE COMMAND EXPANSION">SIMPLE COMMAND EXPANSION</a><br>
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<a href="#COMMAND EXECUTION">COMMAND EXECUTION</a><br>
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<a href="#COMMAND EXECUTION ENVIRONMENT">COMMAND EXECUTION ENVIRONMENT</a><br>
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<a href="#ENVIRONMENT">ENVIRONMENT</a><br>
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<a href="#EXIT STATUS">EXIT STATUS</a><br>
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<a href="#SIGNALS">SIGNALS</a><br>
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<a href="#JOB CONTROL">JOB CONTROL</a><br>
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<a href="#PROMPTING">PROMPTING</a><br>
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<a href="#READLINE">READLINE</a><br>
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<a href="#Readline Notation">Readline Notation</a><br>
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<a href="#Readline Initialization">Readline Initialization</a><br>
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<a href="#Readline Key Bindings">Readline Key Bindings</a><br>
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<a href="#Readline Variables">Readline Variables</a><br>
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<a href="#Readline Conditional Constructs">Readline Conditional Constructs</a><br>
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<a href="#Searching">Searching</a><br>
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<a href="#Readline Command Names">Readline Command Names</a><br>
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<a href="#Commands for Moving">Commands for Moving</a><br>
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<a href="#Commands for Manipulating the History">Commands for Manipulating the History</a><br>
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<a href="#Commands for Changing Text">Commands for Changing Text</a><br>
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<a href="#Killing and Yanking">Killing and Yanking</a><br>
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<a href="#Numeric Arguments">Numeric Arguments</a><br>
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<a href="#Completing">Completing</a><br>
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<a href="#Keyboard Macros">Keyboard Macros</a><br>
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<a href="#Miscellaneous">Miscellaneous</a><br>
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<a href="#Programmable Completion">Programmable Completion</a><br>
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<a href="#HISTORY">HISTORY</a><br>
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<a href="#HISTORY EXPANSION">HISTORY EXPANSION</a><br>
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<a href="#Event Designators">Event Designators</a><br>
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<a href="#Word Designators">Word Designators</a><br>
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<a href="#Modifiers">Modifiers</a><br>
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<a href="#SHELL BUILTIN COMMANDS">SHELL BUILTIN COMMANDS</a><br>
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<a href="#SHELL COMPATIBILITY MODE">SHELL COMPATIBILITY MODE</a><br>
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<a href="#RESTRICTED SHELL">RESTRICTED SHELL</a><br>
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<a href="#SEE ALSO">SEE ALSO</a><br>
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<a href="#FILES">FILES</a><br>
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<a href="#AUTHORS">AUTHORS</a><br>
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<a href="#BUG REPORTS">BUG REPORTS</a><br>
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<a href="#BUGS">BUGS</a><br>
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<hr>
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<h2>NAME
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<a name="NAME"></a>
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</h2>
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<p style="margin-left:6%; margin-top: 1em">bash - GNU
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Bourne-Again SHell</p>
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<h2>SYNOPSIS
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<a name="SYNOPSIS"></a>
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</h2>
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<p style="margin-left:6%; margin-top: 1em"><b>bash</b>
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[options] [command_string | file]</p>
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<h2>COPYRIGHT
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<a name="COPYRIGHT"></a>
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</h2>
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<p style="margin-left:6%; margin-top: 1em">Bash is
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Copyright (C) 1989-2026 by the Free Software Foundation,
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Inc.</p>
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<h2>DESCRIPTION
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<a name="DESCRIPTION"></a>
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</h2>
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<p style="margin-left:6%; margin-top: 1em"><b>Bash</b> is a
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command language interpreter that executes commands read
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from the standard input, from a string, or from a file. It
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is a reimplementation and extension of the Bourne shell, the
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historical Unix command language interpreter. <b>Bash</b>
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also incorporates useful features from the <i>Korn</i> and
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<i>C</i> shells (<b>ksh</b> and <b>csh</b>).</p>
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<p style="margin-left:6%; margin-top: 1em">POSIX is the
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name for a family of computing standards based on Unix.
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<b>Bash</b> is intended to be a conformant implementation of
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the Shell and Utilities portion of the IEEE POSIX
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specification (IEEE Standard 1003.1). <b>Bash</b> POSIX mode
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(hereafter referred to as <i>posix mode</i>) changes the
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shell’s behavior where its default operation differs
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from the standard to strictly conform to the standard. See
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<b>SEE ALSO</b> below for a reference to a document that
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details how posix mode affects <b>bash</b>’s behavior.
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<b>Bash</b> can be configured to be POSIX-conformant by
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default.</p>
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<h2>OPTIONS
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<a name="OPTIONS"></a>
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</h2>
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<p style="margin-left:6%; margin-top: 1em">All of the
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single-character shell options documented in the description
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of the <b>set</b> builtin command, including <b>-o</b>, can
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be used as options when the shell is invoked. In addition,
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<b>bash</b> interprets the following options when it is
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invoked:</p>
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<table width="100%" border="0" rules="none" frame="void"
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cellspacing="0" cellpadding="0">
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<tr valign="top" align="left">
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<td width="6%"></td>
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<td width="3%">
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<p><b>-c</b></p></td>
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<td width="10%"></td>
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<td width="81%">
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<p>If the <b>-c</b> option is present, then commands are
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read from the first non-option argument
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<i>command_string</i>. If there are arguments after the
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<i>command_string</i>, the first argument is assigned to
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<b>$0</b> and any remaining arguments are assigned to the
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positional parameters. The assignment to <b>$0</b> sets the
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name of the shell, which is used in warning and error
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messages.</p> </td></tr>
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<tr valign="top" align="left">
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<td width="6%"></td>
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<td width="3%">
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<p style="margin-top: 1em"><b>-i</b></p></td>
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<td width="10%"></td>
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<td width="81%">
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<p style="margin-top: 1em">If the <b>-i</b> option is
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present, the shell is <i>interactive</i>.</p></td></tr>
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<tr valign="top" align="left">
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<td width="6%"></td>
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<td width="3%">
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<p style="margin-top: 1em"><b>-l</b></p></td>
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<td width="10%"></td>
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<td width="81%">
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<p style="margin-top: 1em">Make <b>bash</b> act as if it
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had been invoked as a login shell (see <b>INVOCATION</b>
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below).</p> </td></tr>
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<tr valign="top" align="left">
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<td width="6%"></td>
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<td width="3%">
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<p style="margin-top: 1em"><b>-r</b></p></td>
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<td width="10%"></td>
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<td width="81%">
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<p style="margin-top: 1em">If the <b>-r</b> option is
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present, the shell becomes <i>restricted</i> (see
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<b>RESTRICTED SHELL</b> below).</p></td></tr>
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<tr valign="top" align="left">
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<td width="6%"></td>
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<td width="3%">
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<p style="margin-top: 1em"><b>-s</b></p></td>
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<td width="10%"></td>
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<td width="81%">
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<p style="margin-top: 1em">If the <b>-s</b> option is
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present, or if no arguments remain after option processing,
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the shell reads commands from the standard input. This
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option allows the positional parameters to be set when
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invoking an interactive shell or when reading input through
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a pipe.</p></td></tr>
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<tr valign="top" align="left">
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<td width="6%"></td>
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<td width="3%">
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<p style="margin-top: 1em"><b>-D</b></p></td>
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<td width="10%"></td>
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<td width="81%">
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<p style="margin-top: 1em">Print a list of all
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double-quoted strings preceded by <b>$</b> on the standard
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output. These are the strings that are subject to language
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translation when the current locale is not <b>C</b> or
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<b>POSIX</b>. This implies the <b>-n</b> option; no commands
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will be executed.</p></td></tr>
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</table>
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<p style="margin-left:6%;"><b>[-+]O
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[</b><i>shopt_option</i><b>]</b></p>
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<p style="margin-left:19%;"><i>shopt_option</i> is one of
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the shell options accepted by the <b>shopt</b> builtin (see
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<b>SHELL BUILTIN COMMANDS</b> below). If <i>shopt_option</i>
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is present, <b>-O</b> sets the value of that option;
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<b>+O</b> unsets it. If <i>shopt_option</i> is not supplied,
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<b>bash</b> prints the names and values of the shell options
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accepted by <b>shopt</b> on the standard output. If the
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invocation option is <b>+O</b>, the output is displayed in a
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format that may be reused as input.</p>
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<table width="100%" border="0" rules="none" frame="void"
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cellspacing="0" cellpadding="0">
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<tr valign="top" align="left">
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<td width="6%"></td>
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<td width="3%">
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<p><b>--</b></p></td>
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<td width="10%"></td>
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<td width="81%">
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<p>A <b>--</b> signals the end of options and disables
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further option processing. Any arguments after the <b>--</b>
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are treated as a shell script filename (see below) and
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arguments passed to that script. An argument of <b>-</b> is
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equivalent to <b>--</b>.</p></td></tr>
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</table>
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<p style="margin-left:6%; margin-top: 1em"><b>Bash</b> also
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interprets a number of multi-character options. These
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options must appear on the command line before the
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single-character options to be recognized. <b><br>
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--debugger</b></p>
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<p style="margin-left:15%;">Arrange for the debugger
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profile to be executed before the shell starts. Turns on
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extended debugging mode (see the description of the
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<b>extdebug</b> option to the <b>shopt</b> builtin
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below).</p>
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<p style="margin-left:6%;"><b>--dump-po-strings</b></p>
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<p style="margin-left:15%;">Equivalent to <b>-D</b>, but
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the output is in the GNU <i>gettext</i> “po”
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(portable object) file format.</p>
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<p style="margin-left:6%;"><b>--dump-strings</b></p>
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<p style="margin-left:15%;">Equivalent to <b>-D</b>.</p>
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<p style="margin-left:6%;"><b>--help</b></p>
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<p style="margin-left:15%;">Display a usage message on
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standard output and exit successfully.</p>
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<p style="margin-left:6%;"><b>--init-file</b> <i>file</i>
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<b><br>
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--rcfile</b> <i>file</i></p>
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<p style="margin-left:15%;">Execute commands from
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<i>file</i> instead of the standard personal initialization
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file <A HREF="file:~/.bashrc"><i>~/.bashrc</i></A> if the shell is interactive (see
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<b>INVOCATION</b> below).</p>
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<p style="margin-left:6%;"><b>--login</b></p>
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<p style="margin-left:15%;">Equivalent to <b>-l</b>.</p>
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<p style="margin-left:6%;"><b>--noediting</b></p>
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<p style="margin-left:15%;">Do not use the GNU
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<b>readline</b> library to read command lines when the shell
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is interactive.</p>
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<p style="margin-left:6%;"><b>--noprofile</b></p>
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<p style="margin-left:15%;">Do not read either the
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system-wide startup file <A HREF="file:/etc/profile"><i>/etc/profile</i></A> or any of the
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personal initialization files <A HREF="file:~/.bash_profile"><i>~/.bash_profile</i></A>,
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<A HREF="file:~/.bash_login"><i>~/.bash_login</i></A>, or <A HREF="file:~/.profile"><i>~/.profile</i></A>. By default,
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<b>bash</b> reads these files when it is invoked as a login
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shell (see <b>INVOCATION</b> below).</p>
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<p style="margin-left:6%;"><b>--norc</b></p>
|
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<p style="margin-left:15%;">Do not read and execute the
|
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personal initialization file <A HREF="file:~/.bashrc"><i>~/.bashrc</i></A> if the shell
|
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is interactive. This option is on by default if the shell is
|
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invoked as <b>sh</b>.</p>
|
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<p style="margin-left:6%;"><b>--posix</b></p>
|
|
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<p style="margin-left:15%;">Enable posix mode; change the
|
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behavior of <b>bash</b> where the default operation differs
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from the POSIX standard to match the standard.</p>
|
|
|
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<p style="margin-left:6%;"><b>--restricted</b></p>
|
|
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<p style="margin-left:15%;">The shell becomes restricted
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(see <b>RESTRICTED SHELL</b> below).</p>
|
|
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<p style="margin-left:6%;"><b>--verbose</b></p>
|
|
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<p style="margin-left:15%;">Equivalent to <b>-v</b>.</p>
|
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<p style="margin-left:6%;"><b>--version</b></p>
|
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|
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<p style="margin-left:15%;">Show version information for
|
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this instance of <b>bash</b> on the standard output and exit
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successfully.</p>
|
|
|
|
<h2>ARGUMENTS
|
|
<a name="ARGUMENTS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If arguments
|
|
remain after option processing, and neither the <b>-c</b>
|
|
nor the <b>-s</b> option has been supplied, the first
|
|
argument is treated as the name of a file containing shell
|
|
commands (a <i>shell script</i>). When <b>bash</b> is
|
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invoked in this fashion, <b>$0</b> is set to the name of the
|
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file, and the positional parameters are set to the remaining
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arguments. <b>Bash</b> reads and executes commands from this
|
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file, then exits. <b>Bash</b>’s exit status is the
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exit status of the last command executed in the script. If
|
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no commands are executed, the exit status is 0. <b>Bash</b>
|
|
first attempts to open the file in the current directory,
|
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and, if no file is found, searches the directories in
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<b>PATH</b> for the script.</p>
|
|
|
|
<h2>INVOCATION
|
|
<a name="INVOCATION"></a>
|
|
</h2>
|
|
|
|
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<p style="margin-left:6%; margin-top: 1em">A <i>login
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|
shell</i> is one whose first character of argument zero is a
|
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<b>-</b>, or one started with the <b>--login</b> option.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">An
|
|
<i>interactive shell</i> is one started without non-option
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arguments (unless <b>-s</b> is specified) and without the
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<b>-c</b> option, and whose standard input and standard
|
|
error are both connected to terminals (as determined by
|
|
<i>isatty</i>(3)), or one started with the <b>-i</b> option.
|
|
<b>Bash</b> sets <b>PS1</b> and <b>$-</b> includes <b>i</b>
|
|
if the shell is interactive, so a shell script or a startup
|
|
file can test this state.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A
|
|
<i>non-interactive shell</i> is, not surprisingly, one that
|
|
does not satisfy the tests for interactivity given above. A
|
|
non-interactive shell is usually started to run commands
|
|
from a script file supplied as an argument (a <i>shell
|
|
script</i>) or from a string supplied with the <b>-c</b>
|
|
option.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The following
|
|
paragraphs describe how <b>bash</b> executes its startup
|
|
files. If any of the files exist but cannot be read,
|
|
<b>bash</b> reports an error. Tildes in filenames are
|
|
expanded as described below under <b>Tilde Expansion</b> in
|
|
the <b>EXPANSION</b> section.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When <b>bash</b>
|
|
is invoked as an interactive login shell, or as a
|
|
non-interactive shell with the <b>--login</b> option, it
|
|
first reads and executes commands from the file
|
|
<A HREF="file:/etc/profile"><i>/etc/profile</i></A>, if that file exists. After reading that
|
|
file, it looks for <A HREF="file:~/.bash_profile"><i>~/.bash_profile</i></A>,
|
|
<A HREF="file:~/.bash_login"><i>~/.bash_login</i></A>, and <A HREF="file:~/.profile"><i>~/.profile</i></A>, in that order,
|
|
and reads and executes commands from the first one that
|
|
exists and is readable. The <b>--noprofile</b> option may be
|
|
used when the shell is started to inhibit this behavior.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When an
|
|
interactive login shell exits, or a non-interactive login
|
|
shell executes the <b>exit</b> builtin command, <b>bash</b>
|
|
reads and executes commands from the file
|
|
<A HREF="file:~/.bash_logout"><i>~/.bash_logout</i></A>, if it exists.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When an
|
|
interactive shell that is not a login shell is started,
|
|
<b>bash</b> reads and executes commands from
|
|
<A HREF="file:~/.bashrc"><i>~/.bashrc</i></A>, if that file exists. The <b>--norc</b>
|
|
option inhibits this behavior. The <b>--rcfile</b>
|
|
<i>file</i> option causes <b>bash</b> to use <i>file</i>
|
|
instead of <A HREF="file:~/.bashrc"><i>~/.bashrc</i></A>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When <b>bash</b>
|
|
is started non-interactively, it looks for the variable
|
|
<b>BASH_ENV</b> in the environment, expands its value if it
|
|
appears there, and uses the expanded value as the name of a
|
|
file to read and execute. <b>Bash</b> behaves as if the
|
|
following command were executed:</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">if [ -n
|
|
"$BASH_ENV" ]; then . "$BASH_ENV";
|
|
fi</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">but does not use
|
|
the value of the <b>PATH</b> variable to search for the
|
|
filename.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If <b>bash</b>
|
|
is invoked with the name <b>sh</b>, it tries to mimic the
|
|
startup behavior of historical versions of <b>sh</b> as
|
|
closely as possible, while conforming to the POSIX standard
|
|
as well. When invoked as an interactive login shell, or a
|
|
non-interactive shell with the <b>--login</b> option, it
|
|
first attempts to read and execute commands from
|
|
<A HREF="file:/etc/profile"><i>/etc/profile</i></A> and <A HREF="file:~/.profile"><i>~/.profile</i></A>, in that order.
|
|
The <b>--noprofile</b> option inhibits this behavior. When
|
|
invoked as an interactive shell with the name <b>sh</b>,
|
|
<b>bash</b> looks for the variable <b>ENV</b>, expands its
|
|
value if it is defined, and uses the expanded value as the
|
|
name of a file to read and execute. Since a shell invoked as
|
|
<b>sh</b> does not attempt to read and execute commands from
|
|
any other startup files, the <b>--rcfile</b> option has no
|
|
effect. A non-interactive shell invoked with the name
|
|
<b>sh</b> does not attempt to read any other startup
|
|
files.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When invoked as
|
|
<b>sh</b>, <b>bash</b> enters posix mode after reading the
|
|
startup files.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When <b>bash</b>
|
|
is started in posix mode, as with the <b>--posix</b> command
|
|
line option, it follows the POSIX standard for startup
|
|
files. In this mode, interactive shells expand the
|
|
<b>ENV</b> variable and read and execute commands from the
|
|
file whose name is the expanded value. A posix-mode shell
|
|
does not attempt to read any other startup files, even when
|
|
invoked as a login shell.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
attempts to determine when it is being run with its standard
|
|
input connected to a network connection, as when executed by
|
|
the secure shell daemon <i>sshd</i> or the historical and
|
|
rarely-seen remote shell daemon, usually <i>rshd</i>. If
|
|
<b>bash</b> determines it is being run non-interactively in
|
|
this fashion, it reads and executes commands from
|
|
<A HREF="file:~/.bashrc"><i>~/.bashrc</i></A>, if that file exists and is readable.
|
|
<b>Bash</b> does not read this file if invoked as <b>sh</b>.
|
|
The <b>--norc</b> option inhibits this behavior, and the
|
|
<b>--rcfile</b> option makes <b>bash</b> use a different
|
|
file instead of <A HREF="file:~/.bashrc"><i>~/.bashrc</i></A>, but neither <i>sshd</i>
|
|
nor <i>rshd</i> generally invoke the shell with those
|
|
options or allow them to be specified.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the shell is
|
|
started with the effective user (group) id not equal to the
|
|
real user (group) id, and the <b>-p</b> option is not
|
|
supplied, bash does not attempt to read any startup files or
|
|
<A HREF="file:~/.bash_logout"><i>~/.bash_logout</i></A>, does not inherit shell functions from
|
|
the environment, ignores the <b>SHELLOPTS</b>,
|
|
<b>BASHOPTS</b>, <b>CDPATH</b>, and <b>GLOBIGNORE</b>
|
|
variables, if they appear in the environment, and sets the
|
|
effective user id to the real user id. If the <b>-p</b>
|
|
option is supplied at invocation, the startup behavior is
|
|
the same, but <b>bash</b> does not reset the effective user
|
|
id.</p>
|
|
|
|
<h2>DEFINITIONS
|
|
<a name="DEFINITIONS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The following
|
|
definitions are used throughout the rest of this
|
|
document.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>blank</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="19%">
|
|
|
|
|
|
<p>A space or tab.</p></td>
|
|
<td width="66%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>whitespace</b></p>
|
|
|
|
<p style="margin-left:15%;">A character belonging to the
|
|
<b>space</b> character class in the current locale, or for
|
|
which <i>isspace</i>(3) returns true.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>word</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>A sequence of characters considered as a single unit by
|
|
the shell. Also known as a <b>token</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>name</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">A <i>word</i> consisting only of
|
|
alphanumeric characters and underscores, and beginning with
|
|
an alphabetic character or an underscore. Also referred to
|
|
as an <b>identifier</b>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>metacharacter</b></p>
|
|
|
|
<p style="margin-left:15%;">A character that, when
|
|
unquoted, separates words. One of the following: <b><br>
|
|
| & ; ( ) < > space tab newline</b></p>
|
|
|
|
<p style="margin-left:6%;"><b>control operator</b></p>
|
|
|
|
<p style="margin-left:15%;">A <i>token</i> that performs a
|
|
control function. It is one of the following symbols:
|
|
<b><br>
|
|
|| & && ; ;; ;& ;;& ( ) | |&
|
|
<newline></b></p>
|
|
|
|
<h2>RESERVED WORDS
|
|
<a name="RESERVED WORDS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b><i>Reserved
|
|
words</i></b> are words that have a special meaning to the
|
|
shell. The following words are recognized as reserved when
|
|
unquoted and either</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>the first word of a command (see <b>SHELL GRAMMAR</b>
|
|
below);</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">the first word following a
|
|
reserved word other than <b>case</b>, <b>for</b>,
|
|
<b>select</b>, or <b>in</b>;</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">the third word of a <b>case</b>
|
|
command (only <b>in</b> is valid);</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">the third word of a <b>for</b>
|
|
or <b>select</b> command (only <b>in</b> and <b>do</b> are
|
|
valid);</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">following a control
|
|
operator.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell will
|
|
also recognize reserved words where the syntax of a command
|
|
specifically requires the reserved word as the only correct
|
|
token.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The following
|
|
are reserved words:</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>! case coproc
|
|
do done elif else esac fi for function if in select then
|
|
until while { } time [[ ]]</b></p>
|
|
|
|
<h2>SHELL GRAMMAR
|
|
<a name="SHELL GRAMMAR"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This section
|
|
describes the syntax of the various forms of shell
|
|
commands.</p>
|
|
|
|
<h3>Simple Commands
|
|
<a name="Simple Commands"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A <i>simple
|
|
command</i> is a sequence of optional variable assignments
|
|
followed by <b>blank</b>-separated words and redirections,
|
|
and terminated by a <i>control operator</i>. The first word
|
|
specifies the command to be executed, and is passed as
|
|
argument zero. The remaining words are passed as arguments
|
|
to the invoked command.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The return value
|
|
of a <i>simple command</i> is its exit status, or
|
|
128+<i>n</i> if the command is terminated by signal
|
|
<i>n</i>.</p>
|
|
|
|
<h3>Pipelines
|
|
<a name="Pipelines"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A
|
|
<i>pipeline</i> is a sequence of one or more commands
|
|
separated by one of the control operators <b>|</b> or
|
|
<b>|&</b>. The format for a pipeline is:</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<b>time</b>
|
|
[<b>-p</b>]] [ ! ] <i>command1</i> [
|
|
[<b>|</b>⎪<b>|&</b>] <i>command2</i> ... ]</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The standard
|
|
output of <i>command1</i> is connected via a pipe to the
|
|
standard input of <i>command2</i>. This connection is
|
|
performed before any redirections specified by the
|
|
<i>command1</i>(see <b>REDIRECTION</b> below). If
|
|
<b>|&</b> is the pipeline operator,
|
|
<i>command1</i>’s standard error, in addition to its
|
|
standard output, is connected to <i>command2</i>’s
|
|
standard input through the pipe; it is shorthand for
|
|
<b>2>&1 |</b>. This implicit redirection of the
|
|
standard error to the standard output is performed after any
|
|
redirections specified by <i>command1</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The return
|
|
status of a pipeline is the exit status of the last command,
|
|
unless the <b>pipefail</b> option is enabled. If
|
|
<b>pipefail</b> is enabled, the pipeline’s return
|
|
status is the value of the last (rightmost) command to exit
|
|
with a non-zero status, or zero if all commands exit
|
|
successfully. If the reserved word <b>!</b> precedes a
|
|
pipeline, the exit status of that pipeline is the logical
|
|
negation of the exit status as described above. If a
|
|
pipeline is executed synchronously, the shell waits for all
|
|
commands in the pipeline to terminate before returning a
|
|
value.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
<b>time</b> reserved word precedes a pipeline, the shell
|
|
reports the elapsed as well as user and system time consumed
|
|
by its execution when the pipeline terminates. The <b>-p</b>
|
|
option changes the output format to that specified by POSIX.
|
|
When the shell is in posix mode, it does not recognize
|
|
<b>time</b> as a reserved word if the next token begins with
|
|
a “-”. The value of the <b>TIMEFORMAT</b>
|
|
variable is a format string that specifies how the timing
|
|
information should be displayed; see the description of
|
|
<b>TIMEFORMAT</b> below under <b>Shell Variables</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the shell
|
|
is in posix mode, <b>time</b> may appear by itself as the
|
|
only word in a simple command. In this case, the shell
|
|
displays the total user and system time consumed by the
|
|
shell and its children. The <b>TIMEFORMAT</b> variable
|
|
specifies the format of the time information.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Each command in
|
|
a multi-command pipeline, where pipes are created, is
|
|
executed in a <i>subshell</i>, which is a separate process.
|
|
See <b>COMMAND EXECUTION ENVIRONMENT</b> for a description
|
|
of subshells and a subshell environment. If the
|
|
<b>lastpipe</b> option is enabled using the <b>shopt</b>
|
|
builtin (see the description of <b>shopt</b> below), and job
|
|
control is not active, the last element of a pipeline may be
|
|
run by the shell process.</p>
|
|
|
|
<h3>Lists
|
|
<a name="Lists"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A <i>list</i> is
|
|
a sequence of one or more AND or OR lists separated by one
|
|
of the operators <b>;</b>, <b>&</b>, or
|
|
<b><newline></b>, and optionally terminated by one of
|
|
those three characters.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">AND and OR lists
|
|
are sequences of one or more pipelines separated by the
|
|
<b>&&</b> and <b>||</b> control operators,
|
|
respectively. AND and OR lists are executed with left
|
|
associativity.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">An AND list has
|
|
the form</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><i>command1</i>
|
|
<b>&&</b> <i>command2</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>command2</i>
|
|
is executed if, and only if, <i>command1</i> returns an exit
|
|
status of zero (success).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">An OR list has
|
|
the form</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><i>command1</i>
|
|
<b>||</b> <i>command2</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>command2</i>
|
|
is executed if, and only if, <i>command1</i> returns a
|
|
non-zero exit status. The return status of AND and OR lists
|
|
is the exit status of the last command executed in the
|
|
list.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Of these list
|
|
operators, <b>&&</b> and <b>||</b> have equal
|
|
precedence, followed by <b>;</b> and <b>&</b>, which
|
|
have equal precedence.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A sequence of
|
|
one or more newlines may appear in a <i>list</i> instead of
|
|
a semicolon to delimit commands.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a command is
|
|
terminated by the control operator <b>&</b>, the shell
|
|
executes the command asynchronously in a subshell. This is
|
|
known as executing a command in the <i>background</i>, and
|
|
these are referred to as <i>asynchronous</i> commands. The
|
|
shell does not wait for the command to finish, and the
|
|
return status is 0. When job control is not active, the
|
|
standard input for asynchronous commands, in the absence of
|
|
any explicit redirections involving the standard input, is
|
|
redirected from <i>/dev/null</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Commands
|
|
separated or terminated by <b>;</b> (or an equivalent
|
|
<b><newline></b>) are executed sequentially; the shell
|
|
waits for each command to terminate in turn.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The return
|
|
status of a list is the exit status of the last command
|
|
executed.</p>
|
|
|
|
<h3>Compound Commands
|
|
<a name="Compound Commands"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A <i>compound
|
|
command</i> is one of the following. In most cases a
|
|
<i>list</i> in a command’s description may be
|
|
separated from the rest of the command by one or more
|
|
newlines, and may be followed by a newline in place of a
|
|
semicolon. <br>
|
|
(<i>list</i>)</p>
|
|
|
|
<p style="margin-left:15%;"><i>list</i> is executed in a
|
|
subshell (see <b>COMMAND EXECUTION ENVIRONMENT</b> below for
|
|
a description of a subshell environment). Variable
|
|
assignments and builtin commands that affect the
|
|
shell’s environment do not remain in effect after the
|
|
command completes. The return status is the exit status of
|
|
<i>list</i>.</p>
|
|
|
|
<p style="margin-left:6%;">{ <i>list</i>; }</p>
|
|
|
|
<p style="margin-left:15%;"><i>list</i> is executed in the
|
|
current shell environment. <i>list</i> must be terminated
|
|
with a newline or semicolon. This is known as a <i>group
|
|
command</i>. The return status is the exit status of
|
|
<i>list</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Note that
|
|
unlike the metacharacters <b>(</b> and <b>)</b>, <b>{</b>
|
|
and <b>}</b> are <i>reserved words</i> and must occur where
|
|
a reserved word is permitted to be recognized. Since they do
|
|
not cause a word break, they must be separated from
|
|
<i>list</i> by whitespace or another shell
|
|
metacharacter.</p>
|
|
|
|
<p style="margin-left:6%;">((<i>expression</i>))</p>
|
|
|
|
<p style="margin-left:15%;">The arithmetic
|
|
<i>expression</i> is evaluated according to the rules
|
|
described below under <b>ARITHMETIC EVALUATION</b>. If the
|
|
value of the expression is non-zero, the return status is 0;
|
|
otherwise the return status is 1. The <i>expression</i>
|
|
undergoes the same expansions as if it were within double
|
|
quotes, but unescaped double quote characters in
|
|
<i>expression</i> are not treated specially and are removed.
|
|
Since this can potentially result in empty strings, this
|
|
command treats those as expressions that evaluate to 0.</p>
|
|
|
|
<p style="margin-left:6%;"><b>[[</b> <i>expression</i>
|
|
<b>]]</b></p>
|
|
|
|
<p style="margin-left:15%;">Evaluate the conditional
|
|
expression <i>expression</i> and return a status of zero
|
|
(true) or non-zero (false). Expressions are composed of the
|
|
primaries described below under <b>CONDITIONAL
|
|
EXPRESSIONS</b>. The words between the <b>[[</b> and
|
|
<b>]]</b> do not undergo word splitting and pathname
|
|
expansion. The shell performs tilde expansion, parameter and
|
|
variable expansion, arithmetic expansion, command
|
|
substitution, process substitution, and quote removal on
|
|
those words. Conditional operators such as <b>-f</b> must be
|
|
unquoted to be recognized as primaries.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When used with
|
|
<b>[[</b>, the <b><</b> and <b>></b> operators sort
|
|
lexicographically using the current locale.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When the
|
|
<b>==</b> and <b>!=</b> operators are used, the string to
|
|
the right of the operator is considered a pattern and
|
|
matched according to the rules described below under
|
|
<b>Pattern Matching</b>, as if the <b>extglob</b> shell
|
|
option were enabled. The <b>=</b> operator is equivalent to
|
|
<b>==</b>. If the <b>nocasematch</b> shell option is
|
|
enabled, the match is performed without regard to the case
|
|
of alphabetic characters. The return value is 0 if the
|
|
string matches (<b>==</b>) or does not match (<b>!=</b>) the
|
|
pattern, and 1 otherwise. If any part of the pattern is
|
|
quoted, the quoted portion is matched as a string: every
|
|
character in the quoted portion matches itself, instead of
|
|
having any special pattern matching meaning.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">An additional
|
|
binary operator, <b>=~</b>, is available, with the same
|
|
precedence as <b>==</b> and <b>!=</b>. When it is used, the
|
|
string to the right of the operator is considered a POSIX
|
|
extended regular expression and matched accordingly (using
|
|
the POSIX <i>regcomp</i> and <i>regexec</i> interfaces
|
|
usually described in <i>regex</i>(3)). The return value is 0
|
|
if the string matches the pattern, and 1 otherwise. If the
|
|
regular expression is syntactically incorrect, the
|
|
conditional expression’s return value is 2. If the
|
|
<b>nocasematch</b> shell option is enabled, the match is
|
|
performed without regard to the case of alphabetic
|
|
characters.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If any part of
|
|
the pattern is quoted, the quoted portion is matched
|
|
literally, as above. If the pattern is stored in a shell
|
|
variable, quoting the variable expansion forces the entire
|
|
pattern to be matched literally. Treat bracket expressions
|
|
in regular expressions carefully, since normal quoting and
|
|
pattern characters lose their meanings between brackets.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The match
|
|
succeeds if the pattern matches any part of the string.
|
|
Anchor the pattern using the <b>^</b> and <b>$</b> regular
|
|
expression operators to force it to match the entire
|
|
string.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The array
|
|
variable <b>BASH_REMATCH</b> records which parts of the
|
|
string matched the pattern. <b>Bash</b> unsets each element
|
|
of <b>BASH_REMATCH</b> before attempting the match, so if
|
|
there is no match, it remains empty. The element of
|
|
<b>BASH_REMATCH</b> with index 0 contains the portion of the
|
|
string matching the entire regular expression. Substrings
|
|
matched by parenthesized subexpressions within the regular
|
|
expression are saved in the remaining <b>BASH_REMATCH</b>
|
|
indices. The element of <b>BASH_REMATCH</b> with index
|
|
<i>n</i> is the portion of the string matching the
|
|
<i>n</i>th parenthesized subexpression. <b>Bash</b> sets
|
|
<b>BASH_REMATCH</b> in the global scope if it is not set; if
|
|
it is declared as a local variable before running <b>[[</b>,
|
|
<b>bash</b> keeps it a local variable.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Expressions may
|
|
be combined using the following operators, listed in
|
|
decreasing order of precedence: <b><br>
|
|
(</b> <i>expression</i> <b>)</b></p>
|
|
|
|
<p style="margin-left:24%;">Returns the value of
|
|
<i>expression</i>. This may be used to override the normal
|
|
precedence of operators.</p>
|
|
|
|
<p style="margin-left:15%;"><b>!</b> <i>expression</i></p>
|
|
|
|
<p style="margin-left:24%;">True if <i>expression</i> is
|
|
false.</p>
|
|
|
|
<p style="margin-left:15%;"><i>expression1</i>
|
|
<b>&&</b> <i>expression2</i></p>
|
|
|
|
<p style="margin-left:24%;">True if both <i>expression1</i>
|
|
and <i>expression2</i> are true.</p>
|
|
|
|
<p style="margin-left:15%;"><i>expression1</i> <b>||</b>
|
|
<i>expression2</i></p>
|
|
|
|
<p style="margin-left:24%;">True if either
|
|
<i>expression1</i> or <i>expression2</i> is true.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The
|
|
<b>&&</b> and <b>||</b> operators do not evaluate
|
|
<i>expression2</i> if the value of <i>expression1</i> is
|
|
sufficient to determine the return value of the entire
|
|
conditional expression.</p>
|
|
|
|
<p style="margin-left:6%;"><b>for</b> <i>name</i> [ [
|
|
<b>in</b> <i>word ...</i> ] ; ] <b>do</b> <i>list</i> ;
|
|
<b>done</b></p>
|
|
|
|
<p style="margin-left:15%;">First, expand the list of words
|
|
following <b>in</b>, generating a list of items. Then, the
|
|
variable <i>name</i> is set to each element of this list in
|
|
turn, and <i>list</i> is executed each time. If the
|
|
<b>in</b> <i>word</i> is omitted, the <b>for</b> command
|
|
executes <i>list</i> once for each positional parameter that
|
|
is set (see <b>PARAMETERS</b> below). The return status is
|
|
the exit status of the last command that executes. If the
|
|
expansion of the items following <b>in</b> results in an
|
|
empty list, no commands are executed, and the return status
|
|
is 0.</p>
|
|
|
|
<p style="margin-left:6%;"><b>for</b> (( <i>expr1</i> ;
|
|
<i>expr2</i> ; <i>expr3</i> )) [;] <b>do</b> <i>list</i> ;
|
|
<b>done</b></p>
|
|
|
|
<p style="margin-left:15%;">First, evaluate the arithmetic
|
|
expression <i>expr1</i> according to the rules described
|
|
below under <b>ARITHMETIC EVALUATION</b>. Then, repeatedly
|
|
evaluate the arithmetic expression <i>expr2</i> until it
|
|
evaluates to zero. Each time <i>expr2</i> evaluates to a
|
|
non-zero value, execute <i>list</i> and evaluate the
|
|
arithmetic expression <i>expr3</i>. If any expression is
|
|
omitted, it behaves as if it evaluates to 1. The return
|
|
value is the exit status of the last command in <i>list</i>
|
|
that is executed, or non-zero if any of the expressions is
|
|
invalid.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Use the
|
|
<b>break</b> and <b>continue</b> builtins (see <b>SHELL
|
|
BUILTIN COMMANDS</b> below) to control loop execution.</p>
|
|
|
|
<p style="margin-left:6%;"><b>select</b> <i>name</i> [ [
|
|
<b>in</b> <i>word ...</i> ] ; ] <b>do</b> <i>list</i> ;
|
|
<b>done</b></p>
|
|
|
|
<p style="margin-left:15%;">First, expand the list of words
|
|
following <b>in</b>, generating a list of items, and print
|
|
the set of expanded words the standard error, each preceded
|
|
by a number. If the <b>in</b> <i>word</i> is omitted, print
|
|
the positional parameters (see <b>PARAMETERS</b> below).
|
|
<b>select</b> then displays the <b>PS3</b> prompt and reads
|
|
a line from the standard input. If the line consists of a
|
|
number corresponding to one of the displayed words, then
|
|
<b>select</b> sets the value of <i>name</i> to that word. If
|
|
the line is empty, <b>select</b> displays the words and
|
|
prompt again. If EOF is read, <b>select</b> completes and
|
|
returns 1. Any other value sets <i>name</i> to null. The
|
|
line read is saved in the variable <b>REPLY</b>. The
|
|
<i>list</i> is executed after each selection until a
|
|
<b>break</b> command is executed. The exit status of
|
|
<b>select</b> is the exit status of the last command
|
|
executed in <i>list</i>, or zero if no commands were
|
|
executed.</p>
|
|
|
|
<p style="margin-left:6%;"><b>case</b> <i>word</i>
|
|
<b>in</b> [ [(] <i>pattern</i> [ <b>|</b> <i>pattern</i> ]
|
|
... ) <i>list</i> ;; ] ... <b>esac</b></p>
|
|
|
|
<p style="margin-left:15%;">A <b>case</b> command first
|
|
expands <i>word</i>, and tries to match it against each
|
|
<i>pattern</i> in turn, proceeding from first to last, using
|
|
the matching rules described under <b>Pattern Matching</b>
|
|
below. The <i>word</i> is expanded using tilde expansion,
|
|
parameter and variable expansion, arithmetic expansion,
|
|
command substitution, process substitution and quote
|
|
removal. Each <i>pattern</i> examined is expanded using
|
|
tilde expansion, parameter and variable expansion,
|
|
arithmetic expansion, command substitution, process
|
|
substitution, and quote removal. If the <b>nocasematch</b>
|
|
shell option is enabled, the match is performed without
|
|
regard to the case of alphabetic characters.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">A <i>pattern
|
|
list</i> is a set of one or more patterns separated by
|
|
<b>|</b>, and terminated by the <b>)</b> operator. A case
|
|
<i>clause</i> is a pattern list and an associated
|
|
<i>list</i>, terminated by <b>;;</b>, <b>;&</b>, or
|
|
<b>;;&</b>. The terminator is optional for the last
|
|
clause preceding <b>esac</b>. There may be an arbitrary
|
|
number of case clauses. The first pattern that matches
|
|
determines the <i>list</i> that is executed.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When a match is
|
|
found, <b>case</b> executes the corresponding <i>list</i>.
|
|
If the <b>;;</b> operator terminates the case clause, the
|
|
<b>case</b> command completes after the first match. Using
|
|
the <b>;&</b> terminator continues execution with the
|
|
<i>list</i> associated with the next clause, if any. Using
|
|
the <b>;;&</b> terminator causes the shell to test the
|
|
pattern list in the next clause, if any, and execute any
|
|
associated <i>list</i> if the match succeeds, continuing the
|
|
case statement execution as if the pattern list had not
|
|
matched.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The exit status
|
|
is zero if no pattern matches. Otherwise, it is the exit
|
|
status of the last command executed in the last <i>list</i>
|
|
executed.</p>
|
|
|
|
<p style="margin-left:6%;"><b>if</b> <i>list</i>;
|
|
<b>then</b> <i>list</i>; [ <b>elif</b> <i>list</i>;
|
|
<b>then</b> <i>list</i>; ] ... [ <b>else</b> <i>list</i>; ]
|
|
<b>fi</b></p>
|
|
|
|
<p style="margin-left:15%;">The <b>if</b> <i>list</i> is
|
|
executed. If its exit status is zero, the <b>then</b>
|
|
<i>list</i> is executed. Otherwise, each <b>elif</b>
|
|
<i>list</i> is executed in turn, and if its exit status is
|
|
zero, the corresponding <b>then</b> <i>list</i> is executed
|
|
and the command completes. Otherwise, the <b>else</b>
|
|
<i>list</i> is executed, if present. The exit status is the
|
|
exit status of the last command executed, or zero if no
|
|
condition tested true.</p>
|
|
|
|
<p style="margin-left:6%;"><b>while</b> <i>list-1</i>;
|
|
<b>do</b> <i>list-2</i>; <b>done <br>
|
|
until</b> <i>list-1</i>; <b>do</b> <i>list-2</i>;
|
|
<b>done</b></p>
|
|
|
|
<p style="margin-left:15%;">The <b>while</b> command
|
|
continuously executes the list <i>list-2</i> as long as the
|
|
last command in the list <i>list-1</i> returns an exit
|
|
status of zero. The <b>until</b> command is identical to the
|
|
<b>while</b> command, except that the test is negated:
|
|
<i>list-2</i> is executed as long as the last command in
|
|
<i>list-1</i> returns a non-zero exit status. The exit
|
|
status of the <b>while</b> and <b>until</b> commands is the
|
|
exit status of the last command executed in <i>list-2</i>,
|
|
or zero if none was executed.</p>
|
|
|
|
<h3>Coprocesses
|
|
<a name="Coprocesses"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A
|
|
<i>coprocess</i> is a shell command preceded by the
|
|
<b>coproc</b> reserved word. A coprocess is executed
|
|
asynchronously in a subshell, as if the command had been
|
|
terminated with the <b>&</b> control operator, with a
|
|
two-way pipe established between the executing shell and the
|
|
coprocess.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The syntax for a
|
|
coprocess is:</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>coproc</b>
|
|
[<i>NAME</i>] <i>command</i> [<i>redirections</i>]</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This creates a
|
|
coprocess named <i>NAME</i>. <i>command</i> may be either a
|
|
simple command or a compound command (see above).
|
|
<i>NAME</i> is a shell variable name. If <i>NAME</i> is not
|
|
supplied, the default name is <b>COPROC</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The recommended
|
|
form to use for a coprocess is</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>coproc</b>
|
|
<i>NAME</i> { <i>command</i> [<i>redirections</i>]; }</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This form is
|
|
preferred because simple commands result in the coprocess
|
|
always being named <b>COPROC</b>, and it is simpler to use
|
|
and more complete than the other compound commands.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If
|
|
<i>command</i> is a compound command, <i>NAME</i> is
|
|
optional. The word following <b>coproc</b> determines
|
|
whether that word is interpreted as a variable name: it is
|
|
interpreted as <i>NAME</i> if it is not a reserved word that
|
|
introduces a compound command. If <i>command</i> is a simple
|
|
command, <i>NAME</i> is not allowed; this is to avoid
|
|
confusion between <i>NAME</i> and the first word of the
|
|
simple command.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the
|
|
coprocess is executed, the shell creates an array variable
|
|
(see <b>Arrays</b> below) named <i>NAME</i> in the context
|
|
of the executing shell. The standard output of
|
|
<i>command</i> is connected via a pipe to a file descriptor
|
|
in the executing shell, and that file descriptor is assigned
|
|
to <i>NAME</i>[0]. The standard input of <i>command</i> is
|
|
connected via a pipe to a file descriptor in the executing
|
|
shell, and that file descriptor is assigned to
|
|
<i>NAME</i>[1]. This pipe is established before any
|
|
redirections specified by the command (see
|
|
<b>REDIRECTION</b> below). The file descriptors can be
|
|
utilized as arguments to shell commands and redirections
|
|
using standard word expansions. Other than those created to
|
|
execute command and process substitutions, the file
|
|
descriptors are not available in subshells.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The process ID
|
|
of the shell spawned to execute the coprocess is available
|
|
as the value of the variable <i>NAME</i>_PID. The
|
|
<b>wait</b> builtin may be used to wait for the coprocess to
|
|
terminate.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Since the
|
|
coprocess is created as an asynchronous command, the
|
|
<b>coproc</b> command always returns success. The return
|
|
status of a coprocess is the exit status of
|
|
<i>command</i>.</p>
|
|
|
|
<h3>Shell Function Definitions
|
|
<a name="Shell Function Definitions"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A shell function
|
|
is an object that is called like a simple command and
|
|
executes a compound command with a new set of positional
|
|
parameters. Shell functions are declared as follows: <i><br>
|
|
fname</i> () <i>compound-command</i> [<i>redirection</i>]
|
|
<b><br>
|
|
function</b> <i>fname</i> [()] <i>compound-command</i>
|
|
[<i>redirection</i>]</p>
|
|
|
|
<p style="margin-left:15%;">This defines a function named
|
|
<i>fname</i>. The reserved word <b>function</b> is optional.
|
|
If the <b>function</b> reserved word is supplied, the
|
|
parentheses are optional. The <i>body</i> of the function is
|
|
the compound command <i>compound-command</i> (see
|
|
<b>Compound Commands</b> above). That command is usually a
|
|
<i>list</i> of commands between { and }, but may be any
|
|
command listed under <b>Compound Commands</b> above. If the
|
|
<b>function</b> reserved word is used, but the parentheses
|
|
are not supplied, the braces are recommended.
|
|
<i>compound-command</i> is executed whenever <i>fname</i> is
|
|
specified as the name of a simple command. When in posix
|
|
mode, <i>fname</i> must be a valid shell <i>name</i> and may
|
|
not be the name of one of the POSIX <i>special builtins</i>.
|
|
In default mode, a function name can be any unquoted shell
|
|
word that does not contain <b>$</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Any redirections
|
|
(see <b>REDIRECTION</b> below) specified when a function is
|
|
defined are performed when the function is executed.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The exit status
|
|
of a function definition is zero unless a syntax error
|
|
occurs or a readonly function with the same name already
|
|
exists. When executed, the exit status of a function is the
|
|
exit status of the last command executed in the body. (See
|
|
<b>FUNCTIONS</b> below.)</p>
|
|
|
|
<h2>COMMENTS
|
|
<a name="COMMENTS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In a
|
|
non-interactive shell, or an interactive shell in which the
|
|
<b>interactive_comments</b> option to the <b>shopt</b>
|
|
builtin is enabled (see <b>SHELL BUILTIN COMMANDS</b>
|
|
below), a word beginning with <b>#</b> introduces a comment.
|
|
A word begins at the beginning of a line, after unquoted
|
|
whitespace, or after an operator. The comment causes that
|
|
word and all remaining characters on that line to be
|
|
ignored. An interactive shell without the
|
|
<b>interactive_comments</b> option enabled does not allow
|
|
comments. The <b>interactive_comments</b> option is enabled
|
|
by default in interactive shells.</p>
|
|
|
|
<h2>QUOTING
|
|
<a name="QUOTING"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>Quoting</i>
|
|
is used to remove the special meaning of certain characters
|
|
or words to the shell. Quoting can be used to disable
|
|
special treatment for special characters, to prevent
|
|
reserved words from being recognized as such, and to prevent
|
|
parameter expansion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Each of the
|
|
<i>metacharacters</i> listed above under <b>DEFINITIONS</b>
|
|
has special meaning to the shell and must be quoted if it is
|
|
to represent itself.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the command
|
|
history expansion facilities are being used (see <b>HISTORY
|
|
EXPANSION</b> below), the <i>history expansion</i>
|
|
character, usually <b>!</b>, must be quoted to prevent
|
|
history expansion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There are four
|
|
quoting mechanisms: the <i>escape character</i>, single
|
|
quotes, double quotes, and dollar-single quotes.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A non-quoted
|
|
backslash (<b>\</b>) is the <i>escape character</i>. It
|
|
preserves the literal value of the next character that
|
|
follows, removing any special meaning it has, with the
|
|
exception of <newline>. If a <b>\</b><newline>
|
|
pair appears, and the backslash is not itself quoted, the
|
|
<b>\</b><newline> is treated as a line continuation
|
|
(that is, it is removed from the input stream and
|
|
effectively ignored).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Enclosing
|
|
characters in single quotes preserves the literal value of
|
|
each character within the quotes. A single quote may not
|
|
occur between single quotes, even when preceded by a
|
|
backslash.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Enclosing
|
|
characters in double quotes preserves the literal value of
|
|
all characters within the quotes, with the exception of
|
|
<b>$</b>, <b>`</b>, <b>\</b>, and, when history expansion is
|
|
enabled, <b>!</b>. When the shell is in posix mode, the
|
|
<b>!</b> has no special meaning within double quotes, even
|
|
when history expansion is enabled. The characters <b>$</b>
|
|
and <b>`</b> retain their special meaning within double
|
|
quotes. The backslash retains its special meaning only when
|
|
followed by one of the following characters: <b>$</b>,
|
|
<b>`</b>, <b>"</b>, <b>\</b>, or
|
|
<b><newline></b>. Backslashes preceding characters
|
|
without a special meaning are left unmodified.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A double quote
|
|
may be quoted within double quotes by preceding it with a
|
|
backslash. If enabled, history expansion will be performed
|
|
unless an <b>!</b> appearing in double quotes is escaped
|
|
using a backslash. The backslash preceding the <b>!</b> is
|
|
not removed.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The special
|
|
parameters <b>*</b> and <b>@</b> have special meaning when
|
|
in double quotes (see <b>PARAMETERS</b> below).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Character
|
|
sequences of the form <b>$</b>'<i>string</i>' are treated as
|
|
a special variant of single quotes. The sequence expands to
|
|
<i>string</i>, with backslash-escaped characters in
|
|
<i>string</i> replaced as specified by the ANSI C standard.
|
|
Backslash escape sequences, if present, are decoded as
|
|
follows:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>\a</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>alert (bell)</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\b</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">backspace</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\e</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\E</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">an escape character</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\f</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">form feed</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\n</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">new line</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\r</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">carriage return</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\t</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">horizontal tab</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\v</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">vertical tab</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\\</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">backslash</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\'</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">single quote</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\"</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">double quote</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\?</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">question mark</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\</b><i>nnn</i></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The eight-bit character whose
|
|
value is the octal value <i>nnn</i> (one to three octal
|
|
digits).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\x</b><i>HH</i></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The eight-bit character whose
|
|
value is the hexadecimal value <i>HH</i> (one or two hex
|
|
digits).</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>\u</b><i>HHHH</i></p>
|
|
|
|
<p style="margin-left:24%;">The Unicode (ISO/IEC 10646)
|
|
character whose value is the hexadecimal value <i>HHHH</i>
|
|
(one to four hex digits).</p>
|
|
|
|
<p style="margin-left:15%;"><b>\U</b><i>HHHHHHHH</i></p>
|
|
|
|
<p style="margin-left:24%;">The Unicode (ISO/IEC 10646)
|
|
character whose value is the hexadecimal value
|
|
<i>HHHHHHHH</i> (one to eight hex digits).</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p><b>\c</b><i>x</i></p></td>
|
|
<td width="5%"></td>
|
|
<td width="27%">
|
|
|
|
|
|
<p>A control-<i>x</i> character.</p></td>
|
|
<td width="49%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The expanded
|
|
result is single-quoted, as if the dollar sign had not been
|
|
present.</p>
|
|
|
|
<h3>Translating Strings
|
|
<a name="Translating Strings"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A double-quoted
|
|
string preceded by a dollar sign
|
|
(<b>$</b>"<i>string</i>") causes the string to be
|
|
translated according to the current locale. The
|
|
<i>gettext</i> infrastructure performs the lookup and
|
|
translation, using the <b>LC_MESSAGES</b>,
|
|
<b>TEXTDOMAINDIR</b>, and <b>TEXTDOMAIN</b> shell variables.
|
|
If the current locale is <b>C</b> or <b>POSIX</b>, if there
|
|
are no translations available, or if the string is not
|
|
translated, the dollar sign is ignored, and the string is
|
|
treated as double-quoted as described above. This is a form
|
|
of double quoting, so the string remains double-quoted by
|
|
default, whether or not it is translated and replaced. If
|
|
the <b>noexpand_translation</b> option is enabled using the
|
|
<b>shopt</b> builtin, translated strings are single-quoted
|
|
instead of double-quoted. See the description of
|
|
<b>shopt</b> below under <b>SHELL BUILTIN COMMANDS</b>.</p>
|
|
|
|
<h2>PARAMETERS
|
|
<a name="PARAMETERS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A
|
|
<i>parameter</i> is an entity that stores values. It can be
|
|
a <i>name</i>, a number, or one of the special characters
|
|
listed below under <b>Special Parameters</b>. A
|
|
<i>variable</i> is a parameter denoted by a <i>name</i>. A
|
|
variable has a <i>value</i> and zero or more
|
|
<i>attributes</i>. Attributes are assigned using the
|
|
<b>declare</b> builtin command (see <b>declare</b> below in
|
|
<b>SHELL BUILTIN COMMANDS</b>). The <b>export</b> and
|
|
<b>readonly</b> builtins assign specific attributes.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A parameter is
|
|
set if it has been assigned a value. The null string is a
|
|
valid value. Once a variable is set, it may be unset only by
|
|
using the <b>unset</b> builtin command (see <b>SHELL BUILTIN
|
|
COMMANDS</b> below).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A
|
|
<i>variable</i> is assigned to using a statement of the
|
|
form</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><i>name</i>=[<i>value</i>]</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If <i>value</i>
|
|
is not given, the variable is assigned the null string. All
|
|
<i>values</i> undergo tilde expansion, parameter and
|
|
variable expansion, command substitution, arithmetic
|
|
expansion, and quote removal (see <b>EXPANSION</b> below).
|
|
If the variable has its <b>integer</b> attribute set, then
|
|
<i>value</i> is evaluated as an arithmetic expression even
|
|
if the <b>$((</b>...<b>))</b> expansion is not used (see
|
|
<b>Arithmetic Expansion</b> below). Word splitting and
|
|
pathname expansion are not performed. Assignment statements
|
|
may also appear as arguments to the <b>alias</b>,
|
|
<b>declare</b>, <b>typeset</b>, <b>export</b>,
|
|
<b>readonly</b>, and <b>local</b> builtin commands
|
|
(<i>declaration</i> commands). When in posix mode, these
|
|
builtins may appear in a command after one or more instances
|
|
of the <b>command</b> builtin and retain these assignment
|
|
statement properties.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In the context
|
|
where an assignment statement is assigning a value to a
|
|
shell variable or array index, the “+=” operator
|
|
appends to or adds to the variable’s previous value.
|
|
This includes arguments to <i>declaration</i> commands such
|
|
as <b>declare</b> that accept assignment statements. When
|
|
“+=” is applied to a variable for which the
|
|
<b>integer</b> attribute has been set, the variable’s
|
|
current value and <i>value</i> are each evaluated as
|
|
arithmetic expressions, and the sum of the results is
|
|
assigned as the variable’s value. The current value is
|
|
usually an integer constant, but may be an expression. When
|
|
“+=” is applied to an array variable using
|
|
compound assignment (see <b>Arrays</b> below), the
|
|
variable’s value is not unset (as it is when using
|
|
“=”), and new values are appended to the array
|
|
beginning at one greater than the array’s maximum
|
|
index (for indexed arrays) or added as additional key-value
|
|
pairs in an associative array. When applied to a
|
|
string-valued variable, <i>value</i> is expanded and
|
|
appended to the variable’s value.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A variable can
|
|
be assigned the <i>nameref</i> attribute using the <b>-n</b>
|
|
option to the <b>declare</b> or <b>local</b> builtin
|
|
commands (see the descriptions of <b>declare</b> and
|
|
<b>local</b> below) to create a <i>nameref</i>, or a
|
|
reference to another variable. This allows variables to be
|
|
manipulated indirectly. Whenever the nameref variable is
|
|
referenced, assigned to, unset, or has its attributes
|
|
modified (other than using or changing the <i>nameref</i>
|
|
attribute itself), the operation is actually performed on
|
|
the variable specified by the nameref variable’s
|
|
value. A nameref is commonly used within shell functions to
|
|
refer to a variable whose name is passed as an argument to
|
|
the function. For instance, if a variable name is passed to
|
|
a shell function as its first argument, running</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">declare -n
|
|
ref=$1</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">inside the
|
|
function creates a local nameref variable <b>ref</b> whose
|
|
value is the variable name passed as the first argument.
|
|
References and assignments to <b>ref</b>, and changes to its
|
|
attributes, are treated as references, assignments, and
|
|
attribute modifications to the variable whose name was
|
|
passed as <b>$1</b>. If the control variable in a <b>for</b>
|
|
loop has the nameref attribute, the list of words can be a
|
|
list of shell variables, and a name reference is established
|
|
for each word in the list, in turn, when the loop is
|
|
executed. Array variables cannot be given the <b>nameref</b>
|
|
attribute. However, nameref variables can reference array
|
|
variables and subscripted array variables. Namerefs can be
|
|
unset using the <b>-n</b> option to the <b>unset</b>
|
|
builtin. Otherwise, if <b>unset</b> is executed with the
|
|
name of a nameref variable as an argument, the variable
|
|
referenced by the nameref variable is unset.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the shell
|
|
starts, it reads its environment and creates a shell
|
|
variable from each environment variable that has a valid
|
|
name, as described below (see <b>ENVIRONMENT</b>).</p>
|
|
|
|
<h3>Positional Parameters
|
|
<a name="Positional Parameters"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A <i>positional
|
|
parameter</i> is a parameter denoted by one or more digits,
|
|
other than the single digit 0. Positional parameters are
|
|
assigned from the shell’s arguments when it is
|
|
invoked, and may be reassigned using the <b>set</b> builtin
|
|
command. Positional parameters may not be assigned to with
|
|
assignment statements. The positional parameters are
|
|
temporarily replaced when a shell function is executed (see
|
|
<b>FUNCTIONS</b> below).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a
|
|
positional parameter consisting of more than a single digit
|
|
is expanded, it must be enclosed in braces (see
|
|
<b>EXPANSION</b> below). Without braces, a digit following $
|
|
can only refer to one of the first nine positional
|
|
parameters (<b>$1-$9</b>) or the special parameter <b>$0</b>
|
|
(see the next section).</p>
|
|
|
|
<h3>Special Parameters
|
|
<a name="Special Parameters"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell treats
|
|
several parameters specially. These parameters may only be
|
|
referenced; assignment to them is not allowed. Special
|
|
parameters are denoted by one of the following
|
|
characters.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>*</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$*</b>) Expands to the
|
|
positional parameters, starting from one. When the expansion
|
|
is not within double quotes, each positional parameter
|
|
expands to a separate word. In contexts where word
|
|
expansions are performed, those words are subject to further
|
|
word splitting and pathname expansion. When the expansion
|
|
occurs within double quotes, it expands to a single word
|
|
with the value of each parameter separated by the first
|
|
character of the <b>IFS</b> variable. That is,
|
|
<b>"$*"</b> is equivalent to
|
|
<b>"$1</b><i>c</i><b>$2</b><i>c</i><b>..."</b>,
|
|
where <i>c</i> is the first character of the value of the
|
|
<b>IFS</b> variable. If <b>IFS</b> is unset, the parameters
|
|
are separated by spaces. If <b>IFS</b> is null, the
|
|
parameters are joined without intervening separators.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>@</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$@</b>) Expands to the
|
|
positional parameters, starting from one. In contexts where
|
|
word splitting is performed, this expands each positional
|
|
parameter to a separate word; if not within double quotes,
|
|
these words are subject to word splitting. In contexts where
|
|
word splitting is not performed, such as the value portion
|
|
of an assignment statement, this expands to a single word
|
|
with each positional parameter separated by a space. When
|
|
the expansion occurs within double quotes, and word
|
|
splitting is performed, each parameter expands to a separate
|
|
word. That is, <b>"$@"</b> is equivalent to
|
|
<b>"$1" "$2" ...</b> If the
|
|
double-quoted expansion occurs within a word, the expansion
|
|
of the first parameter is joined with the expansion of the
|
|
beginning part of the original word, and the expansion of
|
|
the last parameter is joined with the expansion of the last
|
|
part of the original word. When there are no positional
|
|
parameters, <b>"$@"</b> and <b>$@</b> expand to
|
|
nothing (i.e., they are removed).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>#</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$#</b>) Expands to the
|
|
number of positional parameters in decimal.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>?</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$?</b>) Expands to the exit
|
|
status of the most recently executed command.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$-</b>) Expands to the
|
|
current option flags as specified upon invocation, by the
|
|
<b>set</b> builtin command, or those set by the shell itself
|
|
(such as the <b>-i</b> option).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>$</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$$</b>) Expands to the
|
|
process ID of the shell. In a subshell, it expands to the
|
|
process ID of the parent shell, not the subshell.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>!</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$!</b>)Expands to the
|
|
process ID of the job most recently placed into the
|
|
background, whether executed as an asynchronous command or
|
|
using the <b>bg</b> builtin (see <b>JOB CONTROL</b>
|
|
below).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>0</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$0</b>) Expands to the name
|
|
of the shell or shell script. This is set at shell
|
|
initialization. If <b>bash</b> is invoked with a file of
|
|
commands, <b>$0</b> is set to the name of that file. If
|
|
<b>bash</b> is started with the <b>-c</b> option, then
|
|
<b>$0</b> is set to the first argument after the string to
|
|
be executed, if one is present. Otherwise, it is set to the
|
|
filename used to invoke <b>bash</b>, as given by argument
|
|
zero.</p> </td></tr>
|
|
</table>
|
|
|
|
<h3>Shell Variables
|
|
<a name="Shell Variables"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell sets
|
|
following variables:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>_</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">(<b>$_</b>, an underscore) This
|
|
has a number of meanings depending on context. At shell
|
|
startup, <b>_</b> is set to the pathname used to invoke the
|
|
shell or shell script being executed as passed in the
|
|
environment or argument list. Subsequently, it expands to
|
|
the last argument to the previous simple command executed in
|
|
the foreground, after expansion. It is also set to the full
|
|
pathname used to invoke each command executed and placed in
|
|
the environment exported to that command. When checking
|
|
mail, <b>$_</b> expands to the name of the mail file
|
|
currently being checked.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>BASH</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Expands to the full filename
|
|
used to invoke this instance of <b>bash</b>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>BASHOPTS</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of
|
|
enabled shell options. Each word in the list is a valid
|
|
argument for the <b>-s</b> option to the <b>shopt</b>
|
|
builtin command (see <b>SHELL BUILTIN COMMANDS</b> below).
|
|
The options appearing in <b>BASHOPTS</b> are those reported
|
|
as <i>on</i> by <b>shopt</b>. If this variable is in the
|
|
environment when <b>bash</b> starts up, the shell enables
|
|
each option in the list before reading any startup files. If
|
|
this variable is exported, child shells will enable each
|
|
option in the list. This variable is read-only.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASHPID</b></p>
|
|
|
|
<p style="margin-left:15%;">Expands to the process ID of
|
|
the current <b>bash</b> process. This differs from <b>$$</b>
|
|
under certain circumstances, such as subshells that do not
|
|
require <b>bash</b> to be re-initialized. Assignments to
|
|
<b>BASHPID</b> have no effect. If <b>BASHPID</b> is unset,
|
|
it loses its special properties, even if it is subsequently
|
|
reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_ALIASES</b></p>
|
|
|
|
<p style="margin-left:15%;">An associative array variable
|
|
whose members correspond to the internal list of aliases as
|
|
maintained by the <b>alias</b> builtin. Elements added to
|
|
this array appear in the alias list; however, unsetting
|
|
array elements currently does not remove aliases from the
|
|
alias list. If <b>BASH_ALIASES</b> is unset, it loses its
|
|
special properties, even if it is subsequently reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_ARGC</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable whose values
|
|
are the number of parameters in each frame of the current
|
|
<b>bash</b> execution call stack. The number of parameters
|
|
to the current subroutine (shell function or script executed
|
|
with <b>.</b> or <b>source</b>) is at the top of the stack.
|
|
When a subroutine is executed, the number of parameters
|
|
passed is pushed onto <b>BASH_ARGC</b>. The shell sets
|
|
<b>BASH_ARGC</b> only when in extended debugging mode (see
|
|
the description of the <b>extdebug</b> option to the
|
|
<b>shopt</b> builtin below). Setting <b>extdebug</b> after
|
|
the shell has started to execute a script, or referencing
|
|
this variable when <b>extdebug</b> is not set, may result in
|
|
inconsistent values. Assignments to <b>BASH_ARGC</b> have no
|
|
effect, and it may not be unset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_ARGV</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable containing
|
|
all of the parameters in the current <b>bash</b> execution
|
|
call stack. The final parameter of the last subroutine call
|
|
is at the top of the stack; the first parameter of the
|
|
initial call is at the bottom. When a subroutine is
|
|
executed, the shell pushes the supplied parameters onto
|
|
<b>BASH_ARGV</b>. The shell sets <b>BASH_ARGV</b> only when
|
|
in extended debugging mode (see the description of the
|
|
<b>extdebug</b> option to the <b>shopt</b> builtin below).
|
|
Setting <b>extdebug</b> after the shell has started to
|
|
execute a script, or referencing this variable when
|
|
<b>extdebug</b> is not set, may result in inconsistent
|
|
values. Assignments to <b>BASH_ARGV</b> have no effect, and
|
|
it may not be unset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_ARGV0</b></p>
|
|
|
|
<p style="margin-left:15%;">When referenced, this variable
|
|
expands to the name of the shell or shell script (identical
|
|
to <b>$0</b>; see the description of special parameter 0
|
|
above). Assigning a value to <b>BASH_ARGV0</b> sets
|
|
<b>$0</b> to the same value. If <b>BASH_ARGV0</b> is unset,
|
|
it loses its special properties, even if it is subsequently
|
|
reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_CMDS</b></p>
|
|
|
|
<p style="margin-left:15%;">An associative array variable
|
|
whose members correspond to the internal hash table of
|
|
commands as maintained by the <b>hash</b> builtin. Adding
|
|
elements to this array makes them appear in the hash table;
|
|
however, unsetting array elements currently does not remove
|
|
command names from the hash table. If <b>BASH_CMDS</b> is
|
|
unset, it loses its special properties, even if it is
|
|
subsequently reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_COMMAND</b></p>
|
|
|
|
<p style="margin-left:15%;">Expands to the command
|
|
currently being executed or about to be executed, unless the
|
|
shell is executing a command as the result of a trap, in
|
|
which case it is the command executing at the time of the
|
|
trap. If <b>BASH_COMMAND</b> is unset, it loses its special
|
|
properties, even if it is subsequently reset.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>BASH_EXECUTION_STRING</b></p>
|
|
|
|
<p style="margin-left:15%;">The command argument to the
|
|
<b>-c</b> invocation option.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_LINENO</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable whose members
|
|
are the line numbers in source files where each
|
|
corresponding member of <b>FUNCNAME</b> was invoked.
|
|
<b>${BASH_LINENO[</b><i>$i</i><b>]}</b> is the line number
|
|
in the source file
|
|
(<b>${BASH_SOURCE[</b><i>$i+1</i><b>]}</b>) where
|
|
<b>${FUNCNAME[</b><i>$i</i><b>]}</b> was called (or
|
|
<b>${BASH_LINENO[</b><i>$i-1</i><b>]}</b> if referenced
|
|
within another shell function). Use <b>LINENO</b> to obtain
|
|
the current line number. Assignments to <b>BASH_LINENO</b>
|
|
have no effect, and it may not be unset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_LOADABLES_PATH</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of
|
|
directories in which the <b>enable</b> command looks for
|
|
dynamically loadable builtins.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_MONOSECONDS</b></p>
|
|
|
|
<p style="margin-left:15%;">Each time this variable is
|
|
referenced, it expands to the value returned by the
|
|
system’s monotonic clock, if one is available. If
|
|
there is no monotonic clock, this is equivalent to
|
|
<b>EPOCHSECONDS</b>. If <b>BASH_MONOSECONDS</b> is unset, it
|
|
loses its special properties, even if it is subsequently
|
|
reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_REMATCH</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable whose members
|
|
are assigned by the <b>=~</b> binary operator to the
|
|
<b>[[</b> conditional command. The element with index 0 is
|
|
the portion of the string matching the entire regular
|
|
expression. The element with index <i>n</i> is the portion
|
|
of the string matching the <i>n</i>th parenthesized
|
|
subexpression.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_SOURCE</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable whose members
|
|
are the source filenames where the corresponding shell
|
|
function names in the <b>FUNCNAME</b> array variable are
|
|
defined. The shell function
|
|
<b>${FUNCNAME[</b><i>$i</i><b>]}</b> is defined in the file
|
|
<b>${BASH_SOURCE[</b><i>$i</i><b>]}</b> and called from
|
|
<b>${BASH_SOURCE[</b><i>$i+1</i><b>]}</b>. Assignments to
|
|
<b>BASH_SOURCE</b> have no effect, and it may not be
|
|
unset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_SUBSHELL</b></p>
|
|
|
|
<p style="margin-left:15%;">Incremented by one within each
|
|
subshell or subshell environment when the shell begins
|
|
executing in that environment. The initial value is 0. If
|
|
<b>BASH_SUBSHELL</b> is unset, it loses its special
|
|
properties, even if it is subsequently reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_TRAPSIG</b></p>
|
|
|
|
<p style="margin-left:15%;">Set to the signal number
|
|
corresponding to the trap action being executed during its
|
|
execution. See the description of <b>trap</b> under <b>SHELL
|
|
BUILTIN COMMANDS</b> below for information about signal
|
|
numbers and trap execution.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_VERSINFO</b></p>
|
|
|
|
<p style="margin-left:15%;">A readonly array variable whose
|
|
members hold version information for this instance of
|
|
<b>bash</b>. The values assigned to the array members are as
|
|
follows:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="20%">
|
|
|
|
|
|
<p><b>BASH_VERSINFO[</b>0<b>]</b></p></td>
|
|
<td width="10%"></td>
|
|
<td width="49%">
|
|
|
|
|
|
<p>The major version number (the <i>release</i>).</p></td>
|
|
<td width="6%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="20%">
|
|
|
|
|
|
|
|
<p style="margin-top: 1em"><b>BASH_VERSINFO[</b>1<b>]</b></p> </td>
|
|
<td width="10%"></td>
|
|
<td width="49%">
|
|
|
|
|
|
<p style="margin-top: 1em">The minor version number (the
|
|
<i>version</i>).</p> </td>
|
|
<td width="6%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="20%">
|
|
|
|
|
|
|
|
<p style="margin-top: 1em"><b>BASH_VERSINFO[</b>2<b>]</b></p> </td>
|
|
<td width="10%"></td>
|
|
<td width="49%">
|
|
|
|
|
|
<p style="margin-top: 1em">The patch level.</p></td>
|
|
<td width="6%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="20%">
|
|
|
|
|
|
|
|
<p style="margin-top: 1em"><b>BASH_VERSINFO[</b>3<b>]</b></p> </td>
|
|
<td width="10%"></td>
|
|
<td width="49%">
|
|
|
|
|
|
<p style="margin-top: 1em">The build version.</p></td>
|
|
<td width="6%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="20%">
|
|
|
|
|
|
|
|
<p style="margin-top: 1em"><b>BASH_VERSINFO[</b>4<b>]</b></p> </td>
|
|
<td width="10%"></td>
|
|
<td width="49%">
|
|
|
|
|
|
<p style="margin-top: 1em">The release status (e.g.,
|
|
<i>beta</i>).</p> </td>
|
|
<td width="6%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="20%">
|
|
|
|
|
|
|
|
<p style="margin-top: 1em"><b>BASH_VERSINFO[</b>5<b>]</b></p> </td>
|
|
<td width="10%"></td>
|
|
<td width="49%">
|
|
|
|
|
|
<p style="margin-top: 1em">The value of
|
|
<b>MACHTYPE</b>.</p> </td>
|
|
<td width="6%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_VERSION</b></p>
|
|
|
|
<p style="margin-left:15%;">Expands to a string describing
|
|
the version of this instance of <b>bash</b> (e.g.,
|
|
5.2.37(3)-release).</p>
|
|
|
|
<p style="margin-left:6%;"><b>COMP_CWORD</b></p>
|
|
|
|
<p style="margin-left:15%;">An index into
|
|
<b>${COMP_WORDS}</b> of the word containing the current
|
|
cursor position. This variable is available only in shell
|
|
functions invoked by the programmable completion facilities
|
|
(see <b>Programmable Completion</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>COMP_KEY</b></p>
|
|
|
|
<p style="margin-left:15%;">The key (or final key of a key
|
|
sequence) used to invoke the current completion function.
|
|
This variable is available only in shell functions and
|
|
external commands invoked by the programmable completion
|
|
facilities (see <b>Programmable Completion</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>COMP_LINE</b></p>
|
|
|
|
<p style="margin-left:15%;">The current command line. This
|
|
variable is available only in shell functions and external
|
|
commands invoked by the programmable completion facilities
|
|
(see <b>Programmable Completion</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>COMP_POINT</b></p>
|
|
|
|
<p style="margin-left:15%;">The index of the current cursor
|
|
position relative to the beginning of the current command.
|
|
If the current cursor position is at the end of the current
|
|
command, the value of this variable is equal to
|
|
<b>${#COMP_LINE}</b>. This variable is available only in
|
|
shell functions and external commands invoked by the
|
|
programmable completion facilities (see <b>Programmable
|
|
Completion</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>COMP_TYPE</b></p>
|
|
|
|
<p style="margin-left:15%;">Set to an integer value
|
|
corresponding to the type of attempted completion that
|
|
caused a completion function to be called: <i>TAB</i>, for
|
|
normal completion, <i>?</i>, for listing completions after
|
|
successive tabs, <i>!</i>, for listing alternatives on
|
|
partial word completion, <i>@</i>, to list completions if
|
|
the word is not unmodified, or <i>%</i>, for menu
|
|
completion. This variable is available only in shell
|
|
functions and external commands invoked by the programmable
|
|
completion facilities (see <b>Programmable Completion</b>
|
|
below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>COMP_WORDBREAKS</b></p>
|
|
|
|
<p style="margin-left:15%;">The set of characters that the
|
|
<b>readline</b> library treats as word separators when
|
|
performing word completion. If <b>COMP_WORDBREAKS</b> is
|
|
unset, it loses its special properties, even if it is
|
|
subsequently reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>COMP_WORDS</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable (see
|
|
<b>Arrays</b> below) consisting of the individual words in
|
|
the current command line. The line is split into words as
|
|
<b>readline</b> would split it, using <b>COMP_WORDBREAKS</b>
|
|
as described above. This variable is available only in shell
|
|
functions invoked by the programmable completion facilities
|
|
(see <b>Programmable Completion</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>COPROC</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable (see
|
|
<b>Arrays</b> below) created to hold the file descriptors
|
|
for output from and input to an unnamed coprocess (see
|
|
<b>Coprocesses</b> above).</p>
|
|
|
|
<p style="margin-left:6%;"><b>DIRSTACK</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable (see
|
|
<b>Arrays</b> below) containing the current contents of the
|
|
directory stack. Directories appear in the stack in the
|
|
order they are displayed by the <b>dirs</b> builtin.
|
|
Assigning to members of this array variable may be used to
|
|
modify directories already in the stack, but the
|
|
<b>pushd</b> and <b>popd</b> builtins must be used to add
|
|
and remove directories. Assigning to this variable does not
|
|
change the current directory. If <b>DIRSTACK</b> is unset,
|
|
it loses its special properties, even if it is subsequently
|
|
reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>EPOCHREALTIME</b></p>
|
|
|
|
<p style="margin-left:15%;">Each time this parameter is
|
|
referenced, it expands to the number of seconds since the
|
|
Unix Epoch (see <i>time</i>(3)) as a floating-point value
|
|
with micro-second granularity. Assignments to
|
|
<b>EPOCHREALTIME</b> are ignored. If <b>EPOCHREALTIME</b> is
|
|
unset, it loses its special properties, even if it is
|
|
subsequently reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>EPOCHSECONDS</b></p>
|
|
|
|
<p style="margin-left:15%;">Each time this parameter is
|
|
referenced, it expands to the number of seconds since the
|
|
Unix Epoch (see <i>time</i>(3)). Assignments to
|
|
<b>EPOCHSECONDS</b> are ignored. If <b>EPOCHSECONDS</b> is
|
|
unset, it loses its special properties, even if it is
|
|
subsequently reset.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>EUID</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Expands to the effective user ID of the current user,
|
|
initialized at shell startup. This variable is readonly.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>FUNCNAME</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable containing
|
|
the names of all shell functions currently in the execution
|
|
call stack. The element with index 0 is the name of any
|
|
currently-executing shell function. The bottom-most element
|
|
(the one with the highest index) is “main”. This
|
|
variable exists only when a shell function is executing.
|
|
Assignments to <b>FUNCNAME</b> have no effect. If
|
|
<b>FUNCNAME</b> is unset, it loses its special properties,
|
|
even if it is subsequently reset.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">This variable
|
|
can be used with <b>BASH_LINENO</b> and <b>BASH_SOURCE</b>.
|
|
Each element of <b>FUNCNAME</b> has corresponding elements
|
|
in <b>BASH_LINENO</b> and <b>BASH_SOURCE</b> to describe the
|
|
call stack. For instance,
|
|
<b>${FUNCNAME[</b><i>$i</i><b>]}</b> was called from the
|
|
file <b>${BASH_SOURCE[</b><i>$i+1</i><b>]}</b> at line
|
|
number <b>${BASH_LINENO[</b><i>$i</i><b>]}</b>. The
|
|
<b>caller</b> builtin displays the current call stack using
|
|
this information.</p>
|
|
|
|
<p style="margin-left:6%;"><b>GROUPS</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable containing
|
|
the list of groups of which the current user is a member.
|
|
Assignments to <b>GROUPS</b> have no effect. If
|
|
<b>GROUPS</b> is unset, it loses its special properties,
|
|
even if it is subsequently reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HISTCMD</b></p>
|
|
|
|
<p style="margin-left:15%;">The history number, or index in
|
|
the history list, of the current command. Assignments to
|
|
<b>HISTCMD</b> have no effect. If <b>HISTCMD</b> is unset,
|
|
it loses its special properties, even if it is subsequently
|
|
reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HOSTNAME</b></p>
|
|
|
|
<p style="margin-left:15%;">Automatically set to the name
|
|
of the current host.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HOSTTYPE</b></p>
|
|
|
|
<p style="margin-left:15%;">Automatically set to a string
|
|
that uniquely describes the type of machine on which
|
|
<b>bash</b> is executing. The default is
|
|
system-dependent.</p>
|
|
|
|
<p style="margin-left:6%;"><b>LINENO</b></p>
|
|
|
|
<p style="margin-left:15%;">Each time this parameter is
|
|
referenced, the shell substitutes a decimal number
|
|
representing the current sequential line number (starting
|
|
with 1) within a script or function. When not in a script or
|
|
function, the value substituted is not guaranteed to be
|
|
meaningful. If <b>LINENO</b> is unset, it loses its special
|
|
properties, even if it is subsequently reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>MACHTYPE</b></p>
|
|
|
|
<p style="margin-left:15%;">Automatically set to a string
|
|
that fully describes the system type on which <b>bash</b> is
|
|
executing, in the standard GNU <i>cpu-company-system</i>
|
|
format. The default is system-dependent.</p>
|
|
|
|
<p style="margin-left:6%;"><b>MAPFILE</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable (see
|
|
<b>Arrays</b> below) created to hold the text read by the
|
|
<b>mapfile</b> builtin when no variable name is
|
|
supplied.</p>
|
|
|
|
<p style="margin-left:6%;"><b>OLDPWD</b></p>
|
|
|
|
<p style="margin-left:15%;">The previous working directory
|
|
as set by the <b>cd</b> command.</p>
|
|
|
|
<p style="margin-left:6%;"><b>OPTARG</b></p>
|
|
|
|
<p style="margin-left:15%;">The value of the last option
|
|
argument processed by the <b>getopts</b> builtin command
|
|
(see <b>SHELL BUILTIN COMMANDS</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>OPTIND</b></p>
|
|
|
|
<p style="margin-left:15%;">The index of the next argument
|
|
to be processed by the <b>getopts</b> builtin command (see
|
|
<b>SHELL BUILTIN COMMANDS</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>OSTYPE</b></p>
|
|
|
|
<p style="margin-left:15%;">Automatically set to a string
|
|
that describes the operating system on which <b>bash</b> is
|
|
executing. The default is system-dependent.</p>
|
|
|
|
<p style="margin-left:6%;"><b>PIPESTATUS</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable (see
|
|
<b>Arrays</b> below) containing a list of exit status values
|
|
from the commands in the most-recently-executed foreground
|
|
pipeline, which may consist of only a simple command (see
|
|
<b>SHELL GRAMMAR</b> above). <b>Bash</b> sets
|
|
<b>PIPESTATUS</b> after executing multi-element pipelines,
|
|
timed and negated pipelines, simple commands, subshells
|
|
created with the ( operator, the <b>[[</b> and <b>((</b>
|
|
compound commands, and after error conditions that result in
|
|
the shell aborting command execution.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>PPID</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="81%">
|
|
|
|
|
|
<p>The process ID of the shell’s parent. This
|
|
variable is readonly.</p></td>
|
|
<td width="4%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>PWD</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="81%">
|
|
|
|
|
|
<p style="margin-top: 1em">The current working directory as
|
|
set by the <b>cd</b> command.</p></td>
|
|
<td width="4%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>RANDOM</b></p>
|
|
|
|
<p style="margin-left:15%;">Each time this parameter is
|
|
referenced, it expands to a random integer between 0 and
|
|
32767. Assigning a value to <b>RANDOM</b> initializes
|
|
(seeds) the sequence of random numbers. Seeding the random
|
|
number generator with the same constant value produces the
|
|
same sequence of values. If <b>RANDOM</b> is unset, it loses
|
|
its special properties, even if it is subsequently
|
|
reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>READLINE_ARGUMENT</b></p>
|
|
|
|
<p style="margin-left:15%;">Any numeric argument given to a
|
|
<b>readline</b> command that was defined using “bind
|
|
-x” (see <b>SHELL BUILTIN COMMANDS</b> below) when it
|
|
was invoked.</p>
|
|
|
|
<p style="margin-left:6%;"><b>READLINE_LINE</b></p>
|
|
|
|
<p style="margin-left:15%;">The contents of the
|
|
<b>readline</b> line buffer, for use with “bind
|
|
-x” (see <b>SHELL BUILTIN COMMANDS</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>READLINE_MARK</b></p>
|
|
|
|
<p style="margin-left:15%;">The position of the mark (saved
|
|
insertion point) in the <b>readline</b> line buffer, for use
|
|
with “bind -x” (see <b>SHELL BUILTIN
|
|
COMMANDS</b> below). The characters between the insertion
|
|
point and the mark are often called the <i>region</i>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>READLINE_POINT</b></p>
|
|
|
|
<p style="margin-left:15%;">The position of the insertion
|
|
point in the <b>readline</b> line buffer, for use with
|
|
“bind -x” (see <b>SHELL BUILTIN COMMANDS</b>
|
|
below).</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>REPLY</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Set to the line of input read by the <b>read</b> builtin
|
|
command when no arguments are supplied.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>SECONDS</b></p>
|
|
|
|
<p style="margin-left:15%;">Each time this parameter is
|
|
referenced, it expands to the number of seconds since shell
|
|
invocation. If a value is assigned to <b>SECONDS</b>, the
|
|
value returned upon subsequent references is the number of
|
|
seconds since the assignment plus the value assigned. The
|
|
number of seconds at shell invocation and the current time
|
|
are always determined by querying the system clock at
|
|
one-second resolution. If <b>SECONDS</b> is unset, it loses
|
|
its special properties, even if it is subsequently
|
|
reset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>SHELLOPTS</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of
|
|
enabled shell options. Each word in the list is a valid
|
|
argument for the <b>-o</b> option to the <b>set</b> builtin
|
|
command (see <b>SHELL BUILTIN COMMANDS</b> below). The
|
|
options appearing in <b>SHELLOPTS</b> are those reported as
|
|
<i>on</i> by <b>set -o</b>. If this variable is in the
|
|
environment when <b>bash</b> starts up, the shell enables
|
|
each option in the list before reading any startup files. If
|
|
this variable is exported, child shells will enable each
|
|
option in the list. This variable is read-only.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>SHLVL</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p>Incremented by one each time an instance of <b>bash</b>
|
|
is started.</p></td>
|
|
<td width="10%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>SRANDOM</b></p>
|
|
|
|
<p style="margin-left:15%;">Each time it is referenced,
|
|
this variable expands to a 32-bit pseudo-random number. The
|
|
random number generator is not linear on systems that
|
|
support <i>/dev/urandom</i> or <i>arc4random</i>(3), so each
|
|
returned number has no relationship to the numbers preceding
|
|
it. The random number generator cannot be seeded, so
|
|
assignments to this variable have no effect. If
|
|
<b>SRANDOM</b> is unset, it loses its special properties,
|
|
even if it is subsequently reset.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p><b>UID</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Expands to the user ID of the current user, initialized
|
|
at shell startup. This variable is readonly.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell uses
|
|
the following variables. In some cases, <b>bash</b> assigns
|
|
a default value to a variable; these cases are noted below.
|
|
<b><br>
|
|
BASH_COMPAT</b></p>
|
|
|
|
<p style="margin-left:15%;">The value is used to set the
|
|
shell’s compatibility level. See <b>SHELL
|
|
COMPATIBILITY MODE</b> below for a description of the
|
|
various compatibility levels and their effects. The value
|
|
may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
|
|
corresponding to the desired compatibility level. If
|
|
<b>BASH_COMPAT</b> is unset or set to the empty string, the
|
|
compatibility level is set to the default for the current
|
|
version. If <b>BASH_COMPAT</b> is set to a value that is not
|
|
one of the valid compatibility levels, the shell prints an
|
|
error message and sets the compatibility level to the
|
|
default for the current version. A subset of the valid
|
|
values correspond to the compatibility levels described
|
|
below under <b>SHELL COMPATIBILITY MODE</b>. For example,
|
|
4.2 and 42 are valid values that correspond to the
|
|
<b>compat42 shopt</b> option and set the compatibility level
|
|
to 42. The current version is also a valid value.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_ENV</b></p>
|
|
|
|
<p style="margin-left:15%;">If this parameter is set when
|
|
<b>bash</b> is executing a shell script, its expanded value
|
|
is interpreted as a filename containing commands to
|
|
initialize the shell before it reads and executes commands
|
|
from the script. The value of <b>BASH_ENV</b> is subjected
|
|
to parameter expansion, command substitution, and arithmetic
|
|
expansion before being interpreted as a filename.
|
|
<b>PATH</b> is not used to search for the resultant
|
|
filename.</p>
|
|
|
|
<p style="margin-left:6%;"><b>BASH_XTRACEFD</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to an integer
|
|
corresponding to a valid file descriptor, <b>bash</b> writes
|
|
the trace output generated when “set -x” is
|
|
enabled to that file descriptor, instead of the standard
|
|
error. The file descriptor is closed when
|
|
<b>BASH_XTRACEFD</b> is unset or assigned a new value.
|
|
Unsetting <b>BASH_XTRACEFD</b> or assigning it the empty
|
|
string causes the trace output to be sent to the standard
|
|
error. Note that setting <b>BASH_XTRACEFD</b> to 2 (the
|
|
standard error file descriptor) and then unsetting it will
|
|
result in the standard error being closed.</p>
|
|
|
|
<p style="margin-left:6%;"><b>CDPATH</b></p>
|
|
|
|
<p style="margin-left:15%;">The search path for the
|
|
<b>cd</b> command. This is a colon-separated list of
|
|
directories where the shell looks for directories specified
|
|
as arguments to the <b>cd</b> command. A sample value is
|
|
“.:~:/usr”.</p>
|
|
|
|
<p style="margin-left:6%;"><b>CHILD_MAX</b></p>
|
|
|
|
<p style="margin-left:15%;">Set the number of exited child
|
|
status values for the shell to remember. <b>Bash</b> will
|
|
not allow this value to be decreased below a POSIX-mandated
|
|
minimum, and there is a maximum value (currently 8192) that
|
|
this may not exceed. The minimum value is
|
|
system-dependent.</p>
|
|
|
|
<p style="margin-left:6%;"><b>COLUMNS</b></p>
|
|
|
|
<p style="margin-left:15%;">Used by the <b>select</b>
|
|
compound command to determine the terminal width when
|
|
printing selection lists. Automatically set if the
|
|
<b>checkwinsize</b> option is enabled or in an interactive
|
|
shell upon receipt of a <b>SIGWINCH</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>COMPREPLY</b></p>
|
|
|
|
<p style="margin-left:15%;">An array variable from which
|
|
<b>bash</b> reads the possible completions generated by a
|
|
shell function invoked by the programmable completion
|
|
facility (see <b>Programmable Completion</b> below). Each
|
|
array element contains one possible completion.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>EMACS</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>If <b>bash</b> finds this variable in the environment
|
|
when the shell starts with value “t”, it assumes
|
|
that the shell is running in an Emacs shell buffer and
|
|
disables line editing.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>ENV</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Expanded and executed similarly
|
|
to <b>BASH_ENV</b> (see <b>INVOCATION</b> above) when an
|
|
interactive shell is invoked in posix mode.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>EXECIGNORE</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of shell
|
|
patterns (see <b>Pattern Matching</b>) defining the set of
|
|
filenames to be ignored by command search using <b>PATH</b>.
|
|
Files whose full pathnames match one of these patterns are
|
|
not considered executable files for the purposes of
|
|
completion and command execution via <b>PATH</b> lookup.
|
|
This does not affect the behavior of the <b>[</b>,
|
|
<b>test</b>, and <b>[[</b> commands. Full pathnames in the
|
|
command hash table are not subject to <b>EXECIGNORE</b>. Use
|
|
this variable to ignore shared library files that have the
|
|
executable bit set, but are not executable files. The
|
|
pattern matching honors the setting of the <b>extglob</b>
|
|
shell option.</p>
|
|
|
|
<p style="margin-left:6%;"><b>FCEDIT</b></p>
|
|
|
|
<p style="margin-left:15%;">The default editor for the
|
|
<b>fc</b> builtin command.</p>
|
|
|
|
<p style="margin-left:6%;"><b>FIGNORE</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of
|
|
suffixes to ignore when performing filename completion (see
|
|
<b>READLINE</b> below). A filename whose suffix matches one
|
|
of the entries in <b>FIGNORE</b> is excluded from the list
|
|
of matched filenames. A sample value is “.o:~”.
|
|
Since tilde expansion takes place after “:” in
|
|
assignment statements, make sure to quote assignments
|
|
appropriately to avoid it as appropriate.</p>
|
|
|
|
<p style="margin-left:6%;"><b>FUNCNEST</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to a numeric value
|
|
greater than 0, defines a maximum function nesting level.
|
|
Function invocations that exceed this nesting level cause
|
|
the current command to abort.</p>
|
|
|
|
<p style="margin-left:6%;"><b>GLOBIGNORE</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of
|
|
patterns defining the set of file names to be ignored by
|
|
pathname expansion. If a file name matched by a pathname
|
|
expansion pattern also matches one of the patterns in
|
|
<b>GLOBIGNORE</b>, it is removed from the list of matches.
|
|
The pattern matching honors the setting of the
|
|
<b>extglob</b> shell option.</p>
|
|
|
|
<p style="margin-left:6%;"><b>GLOBSORT</b></p>
|
|
|
|
<p style="margin-left:15%;">Controls how the results of
|
|
pathname expansion are sorted. The value of this variable
|
|
specifies the sort criteria and sort order for the results
|
|
of pathname expansion. If this variable is unset or set to
|
|
the null string, pathname expansion uses the historical
|
|
behavior of sorting by name, in ascending lexicographic
|
|
order as determined by the <b>LC_COLLATE</b> shell
|
|
variable.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If set, a valid
|
|
value begins with an optional <i>+</i>, which is ignored, or
|
|
<i>-</i>, which reverses the sort order from ascending to
|
|
descending, followed by a sort specifier. The valid sort
|
|
specifiers are <i>name</i>, <i>numeric</i>, <i>size</i>,
|
|
<i>mtime</i>, <i>atime</i>, <i>ctime</i>, and <i>blocks</i>,
|
|
which sort the files on name, names in numeric rather than
|
|
lexicographic order, file size, modification time, access
|
|
time, inode change time, and number of blocks, respectively.
|
|
If any of the non-name keys compare as equal (e.g., if two
|
|
files are the same size), sorting uses the name as a
|
|
secondary sort key.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">For example, a
|
|
value of <i>-mtime</i> sorts the results in descending order
|
|
by modification time (newest first).</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The
|
|
<i>numeric</i> specifier treats names consisting solely of
|
|
digits as numbers and sorts them using their numeric value
|
|
(so “2” sorts before “10”, for
|
|
example). When using <i>numeric</i>, names containing
|
|
non-digits sort after all the all-digit names and are sorted
|
|
by name using the traditional behavior.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">A sort
|
|
specifier of <i>nosort</i> disables sorting completely;
|
|
<b>bash</b> returns the results in the order they are read
|
|
from the file system, ignoring any leading <i>-</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the sort
|
|
specifier is missing, it defaults to <i>name</i>, so a value
|
|
of <i>+</i> is equivalent to the null string, and a value of
|
|
<i>-</i> sorts by name in descending order. Any invalid
|
|
value restores the historical sorting behavior.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HISTCONTROL</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of
|
|
values controlling how commands are saved on the history
|
|
list. If the list of values includes <i>ignorespace</i>,
|
|
lines which begin with a <b>space</b> character are not
|
|
saved in the history list. A value of <i>ignoredups</i>
|
|
causes lines matching the previous history entry not to be
|
|
saved. A value of <i>ignoreboth</i> is shorthand for
|
|
<i>ignorespace</i> and <i>ignoredups</i>. A value of
|
|
<i>erasedups</i> causes all previous lines matching the
|
|
current line to be removed from the history list before that
|
|
line is saved. Any value not in the above list is ignored.
|
|
If <b>HISTCONTROL</b> is unset, or does not include a valid
|
|
value, <b>bash</b> saves all lines read by the shell parser
|
|
on the history list, subject to the value of
|
|
<b>HISTIGNORE</b>. If the first line of a multi-line
|
|
compound command was saved, the second and subsequent lines
|
|
are not tested, and are added to the history regardless of
|
|
the value of <b>HISTCONTROL</b>. If the first line was not
|
|
saved, the second and subsequent lines of the command are
|
|
not saved either.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HISTFILE</b></p>
|
|
|
|
<p style="margin-left:15%;">The name of the file in which
|
|
command history is saved (see <b>HISTORY</b> below).
|
|
<b>Bash</b> assigns a default value of
|
|
<A HREF="file:~/.bash_history"><i>~/.bash_history</i></A>. If <b>HISTFILE</b> is unset or null,
|
|
the shell does not save the command history when it
|
|
exits.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HISTFILESIZE</b></p>
|
|
|
|
<p style="margin-left:15%;">The maximum number of lines
|
|
contained in the history file. When this variable is
|
|
assigned a value, the history file is truncated, if
|
|
necessary, to contain no more than the number of history
|
|
entries that total no more than that number of lines by
|
|
removing the oldest entries. If the history list contains
|
|
multi-line entries, the history file may contain more lines
|
|
than this maximum to avoid leaving partial history entries.
|
|
The history file is also truncated to this size after
|
|
writing it when a shell exits or by the <b>history</b>
|
|
builtin. If the value is 0, the history file is truncated to
|
|
zero size. Non-numeric values and numeric values less than
|
|
zero inhibit truncation. The shell sets the default value to
|
|
the value of <b>HISTSIZE</b> after reading any startup
|
|
files.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HISTIGNORE</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of
|
|
patterns used to decide which command lines should be saved
|
|
on the history list. If a command line matches one of the
|
|
patterns in the value of <b>HISTIGNORE</b>, it is not saved
|
|
on the history list. Each pattern is anchored at the
|
|
beginning of the line and must match the complete line
|
|
(<b>bash</b> does not implicitly append a
|
|
“<b>*</b>”). Each pattern is tested against the
|
|
line after the checks specified by <b>HISTCONTROL</b> are
|
|
applied. In addition to the normal shell pattern matching
|
|
characters, “<b>&</b>” matches the previous
|
|
history line. A backslash escapes the
|
|
“<b>&</b>”; the backslash is removed before
|
|
attempting a match. If the first line of a multi-line
|
|
compound command was saved, the second and subsequent lines
|
|
are not tested, and are added to the history regardless of
|
|
the value of <b>HISTIGNORE</b>. If the first line was not
|
|
saved, the second and subsequent lines of the command are
|
|
not saved either. The pattern matching honors the setting of
|
|
the <b>extglob</b> shell option. <b><br>
|
|
HISTIGNORE</b> subsumes some of the function of
|
|
<b>HISTCONTROL</b>. A pattern of “&” is
|
|
identical to “ignoredups”, and a pattern of
|
|
“[ ]*” is identical to
|
|
“ignorespace”. Combining these two patterns,
|
|
separating them with a colon, provides the functionality of
|
|
“- ignoreboth”.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HISTSIZE</b></p>
|
|
|
|
<p style="margin-left:15%;">The number of commands to
|
|
remember in the command history (see <b>HISTORY</b> below).
|
|
If the value is 0, commands are not saved in the history
|
|
list. Numeric values less than zero result in every command
|
|
being saved on the history list (there is no limit). The
|
|
shell sets the default value to 500 after reading any
|
|
startup files.</p>
|
|
|
|
<p style="margin-left:6%;"><b>HISTTIMEFORMAT</b></p>
|
|
|
|
<p style="margin-left:15%;">If this variable is set and not
|
|
null, its value is used as a format string for
|
|
<i>strftime</i>(3) to print the time stamp associated with
|
|
each history entry displayed by the <b>history</b> builtin.
|
|
If this variable is set, the shell writes time stamps to the
|
|
history file so they may be preserved across shell sessions.
|
|
This uses the history comment character to distinguish
|
|
timestamps from other history lines.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>HOME</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>The home directory of the current user; the default
|
|
argument for the <b>cd</b> builtin command. The value of
|
|
this variable is also used when performing tilde
|
|
expansion.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>HOSTFILE</b></p>
|
|
|
|
<p style="margin-left:15%;">Contains the name of a file in
|
|
the same format as <i>/etc/hosts</i> that should be read
|
|
when the shell needs to complete a hostname. The list of
|
|
possible hostname completions may be changed while the shell
|
|
is running; the next time hostname completion is attempted
|
|
after the value is changed, <b>bash</b> adds the contents of
|
|
the new file to the existing list. If <b>HOSTFILE</b> is
|
|
set, but has no value, or does not name a readable file,
|
|
<b>bash</b> attempts to read <i>/etc/hosts</i> to obtain the
|
|
list of possible hostname completions. When <b>HOSTFILE</b>
|
|
is unset, <b>bash</b> clears the hostname list.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p><b>IFS</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>The <i>Internal Field Separator</i> that is used for
|
|
word splitting after expansion and to split lines into words
|
|
with the <b>read</b> builtin command. Word splitting is
|
|
described below under <b>EXPANSION</b>. The default value is
|
|
“<space><tab><newline>”.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>IGNOREEOF</b></p>
|
|
|
|
<p style="margin-left:15%;">Controls the action of an
|
|
interactive shell on receipt of an <b>EOF</b> character as
|
|
the sole input. If set, the value is the number of
|
|
consecutive <b>EOF</b> characters which must be typed as the
|
|
first characters on an input line before <b>bash</b> exits.
|
|
If the variable is set but does not have a numeric value, or
|
|
the value is null, the default value is 10. If it is unset,
|
|
<b>EOF</b> signifies the end of input to the shell.</p>
|
|
|
|
<p style="margin-left:6%;"><b>INPUTRC</b></p>
|
|
|
|
<p style="margin-left:15%;">The filename for the
|
|
<b>readline</b> startup file, overriding the default of
|
|
<A HREF="file:~/.inputrc"><i>~/.inputrc</i></A> (see <b>READLINE</b> below).</p>
|
|
|
|
<p style="margin-left:6%;"><b>INSIDE_EMACS</b></p>
|
|
|
|
<p style="margin-left:15%;">If this variable appears in the
|
|
environment when the shell starts, <b>bash</b> assumes that
|
|
it is running inside an Emacs shell buffer and may disable
|
|
line editing, depending on the value of <b>TERM</b>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>LANG</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Used to determine the locale category for any category
|
|
not specifically selected with a variable starting with
|
|
<b>LC_</b>.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>LC_ALL</b></p>
|
|
|
|
<p style="margin-left:15%;">This variable overrides the
|
|
value of <b>LANG</b> and any other <b>LC_</b> variable
|
|
specifying a locale category.</p>
|
|
|
|
<p style="margin-left:6%;"><b>LC_COLLATE</b></p>
|
|
|
|
<p style="margin-left:15%;">This variable determines the
|
|
collation order used when sorting the results of pathname
|
|
expansion, and determines the behavior of range expressions,
|
|
equivalence classes, and collating sequences within pathname
|
|
expansion and pattern matching.</p>
|
|
|
|
<p style="margin-left:6%;"><b>LC_CTYPE</b></p>
|
|
|
|
<p style="margin-left:15%;">This variable determines the
|
|
interpretation of characters and the behavior of character
|
|
classes within pathname expansion and pattern matching.</p>
|
|
|
|
<p style="margin-left:6%;"><b>LC_MESSAGES</b></p>
|
|
|
|
<p style="margin-left:15%;">This variable determines the
|
|
locale used to translate double-quoted strings preceded by a
|
|
<b>$</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>LC_NUMERIC</b></p>
|
|
|
|
<p style="margin-left:15%;">This variable determines the
|
|
locale category used for number formatting.</p>
|
|
|
|
<p style="margin-left:6%;"><b>LC_TIME</b></p>
|
|
|
|
<p style="margin-left:15%;">This variable determines the
|
|
locale category used for data and time formatting.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>LINES</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Used by the <b>select</b> compound command to determine
|
|
the column length for printing selection lists.
|
|
Automatically set if the <b>checkwinsize</b> option is
|
|
enabled or in an interactive shell upon receipt of a
|
|
<b>SIGWINCH</b>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>MAIL</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the value is set to a file or
|
|
directory name and the <b>MAILPATH</b> variable is not set,
|
|
<b>bash</b> informs the user of the arrival of mail in the
|
|
specified file or Maildir-format directory.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>MAILCHECK</b></p>
|
|
|
|
<p style="margin-left:15%;">Specifies how often (in
|
|
seconds) <b>bash</b> checks for mail. The default is 60
|
|
seconds. When it is time to check for mail, the shell does
|
|
so before displaying the primary prompt. If this variable is
|
|
unset, or set to a value that is not a number greater than
|
|
or equal to zero, the shell disables mail checking.</p>
|
|
|
|
<p style="margin-left:6%;"><b>MAILPATH</b></p>
|
|
|
|
<p style="margin-left:15%;">A colon-separated list of
|
|
filenames to be checked for mail. The message to be printed
|
|
when mail arrives in a particular file may be specified by
|
|
separating the filename from the message with a
|
|
“?”. When used in the text of the message,
|
|
<b>$_</b> expands to the name of the current mailfile. For
|
|
example: <b><br>
|
|
MAILPATH</b>='/var/mail/bfox?"You have
|
|
mail":~/shell-mail?"$_ has mail!"' <b><br>
|
|
Bash</b> can be configured to supply a default value for
|
|
this variable (there is no value by default), but the
|
|
location of the user mail files that it uses is system
|
|
dependent (e.g., /var/mail/<b>$USER</b>).</p>
|
|
|
|
<p style="margin-left:6%;"><b>OPTERR</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to the value 1,
|
|
<b>bash</b> displays error messages generated by the
|
|
<b>getopts</b> builtin command (see <b>SHELL BUILTIN
|
|
COMMANDS</b> below). <b>OPTERR</b> is initialized to 1 each
|
|
time the shell is invoked or a shell script is executed.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>PATH</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>The search path for commands. It is a colon-separated
|
|
list of directories in which the shell looks for commands
|
|
(see <b>COMMAND EXECUTION</b> below). A zero-length (null)
|
|
directory name in the value of <b>PATH</b> indicates the
|
|
current directory. A null directory name may appear as two
|
|
adjacent colons, or as an initial or trailing colon. The
|
|
default path is system-dependent, and is set by the
|
|
administrator who installs <b>bash</b>. A common value
|
|
is</p> </td></tr>
|
|
</table>
|
|
|
|
|
|
<p style="margin-left:21%;">/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin</p>
|
|
|
|
<p style="margin-left:6%;"><b>POSIXLY_CORRECT</b></p>
|
|
|
|
<p style="margin-left:15%;">If this variable is in the
|
|
environment when <b>bash</b> starts, the shell enters posix
|
|
mode before reading the startup files, as if the
|
|
<b>--posix</b> invocation option had been supplied. If it is
|
|
set while the shell is running, <b>bash</b> enables posix
|
|
mode, as if the command “set -o posix” had been
|
|
executed. When the shell enters posix mode, it sets this
|
|
variable if it was not already set.</p>
|
|
|
|
<p style="margin-left:6%;"><b>PROMPT_COMMAND</b></p>
|
|
|
|
<p style="margin-left:15%;">If this variable is set, and is
|
|
an array, the value of each set element is executed as a
|
|
command prior to issuing each primary prompt. If this is set
|
|
but not an array variable, its value is used as a command to
|
|
execute instead.</p>
|
|
|
|
<p style="margin-left:6%;"><b>PROMPT_DIRTRIM</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to a number greater than
|
|
zero, the value is used as the number of trailing directory
|
|
components to retain when expanding the <b>\w</b> and
|
|
<b>\W</b> prompt string escapes (see <b>PROMPTING</b>
|
|
below). Characters removed are replaced with an
|
|
ellipsis.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>PS0</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>The value of this parameter is expanded (see
|
|
<b>PROMPTING</b> below) and displayed by interactive shells
|
|
after reading a command and before the command is
|
|
executed.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>PS1</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The value of this parameter is
|
|
expanded (see <b>PROMPTING</b> below) and used as the
|
|
primary prompt string. The default value is
|
|
“\s-\v\$ ”.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>PS2</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The value of this parameter is
|
|
expanded as with <b>PS1</b> and used as the secondary prompt
|
|
string. The default is “> ”.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>PS3</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The value of this parameter is
|
|
used as the prompt for the <b>select</b> command (see
|
|
<b>SHELL GRAMMAR</b> above).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>PS4</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The value of this parameter is
|
|
expanded as with <b>PS1</b> and the value is printed before
|
|
each command <b>bash</b> displays during an execution trace.
|
|
The first character of the expanded value of <b>PS4</b> is
|
|
replicated multiple times, as necessary, to indicate
|
|
multiple levels of indirection. The default is
|
|
“+ ”.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>SHELL</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">This variable expands to the
|
|
full pathname to the shell. If it is not set when the shell
|
|
starts, <b>bash</b> assigns to it the full pathname of the
|
|
current user’s login shell.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>TIMEFORMAT</b></p>
|
|
|
|
<p style="margin-left:15%;">The value of this parameter is
|
|
used as a format string specifying how the timing
|
|
information for pipelines prefixed with the <b>time</b>
|
|
reserved word should be displayed. The <b>%</b> character
|
|
introduces an escape sequence that is expanded to a time
|
|
value or other information. The escape sequences and their
|
|
meanings are as follows; the brackets denote optional
|
|
portions.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="10%">
|
|
|
|
|
|
<p><b>%%</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="58%">
|
|
|
|
|
|
<p>A literal <b>%</b>.</p></td>
|
|
<td width="14%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="10%">
|
|
|
|
|
|
|
|
<p style="margin-top: 1em"><b>%[</b><i>p</i><b>][l]R</b></p> </td>
|
|
<td width="3%"></td>
|
|
<td width="58%">
|
|
|
|
|
|
<p style="margin-top: 1em">The elapsed time in seconds.</p></td>
|
|
<td width="14%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="10%">
|
|
|
|
|
|
|
|
<p style="margin-top: 1em"><b>%[</b><i>p</i><b>][l]U</b></p> </td>
|
|
<td width="3%"></td>
|
|
<td width="58%">
|
|
|
|
|
|
<p style="margin-top: 1em">The number of CPU seconds spent
|
|
in user mode.</p></td>
|
|
<td width="14%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="10%">
|
|
|
|
|
|
|
|
<p style="margin-top: 1em"><b>%[</b><i>p</i><b>][l]S</b></p> </td>
|
|
<td width="3%"></td>
|
|
<td width="58%">
|
|
|
|
|
|
<p style="margin-top: 1em">The number of CPU seconds spent
|
|
in system mode.</p></td>
|
|
<td width="14%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="10%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>%P</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="58%">
|
|
|
|
|
|
<p style="margin-top: 1em">The CPU percentage, computed as
|
|
(%U + %S) / %R.</p></td>
|
|
<td width="14%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The optional
|
|
<i>p</i> is a digit specifying the <i>precision</i>, the
|
|
number of fractional digits after a decimal point. A value
|
|
of 0 causes no decimal point or fraction to be output.
|
|
<b>time</b> prints at most six digits after the decimal
|
|
point; values of <i>p</i> greater than 6 are changed to 6.
|
|
If <i>p</i> is not specified, <b>time</b> prints three
|
|
digits after the decimal point.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The optional
|
|
<b>l</b> specifies a longer format, including minutes, of
|
|
the form <i>MM</i>m<i>SS</i>.<i>FF</i>s. The value of
|
|
<i>p</i> determines whether or not the fraction is
|
|
included.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If this
|
|
variable is not set, <b>bash</b> acts as if it had the value
|
|
<b>$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'</b>. If the value
|
|
is null, <b>bash</b> does not display any timing
|
|
information. A trailing newline is added when the format
|
|
string is displayed.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>TMOUT</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">If set to a value greater than
|
|
zero, the <b>read</b> builtin uses the value as its default
|
|
timeout. The <b>select</b> command terminates if input does
|
|
not arrive after <b>TMOUT</b> seconds when input is coming
|
|
from a terminal. In an interactive shell, the value is
|
|
interpreted as the number of seconds to wait for a line of
|
|
input after issuing the primary prompt. <b>Bash</b>
|
|
terminates after waiting for that number of seconds if a
|
|
complete line of input does not arrive.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>TMPDIR</b></p>
|
|
|
|
<p style="margin-left:15%;">If set, <b>bash</b> uses its
|
|
value as the name of a directory in which <b>bash</b>
|
|
creates temporary files for the shell’s use.</p>
|
|
|
|
<p style="margin-left:6%;"><b>auto_resume</b></p>
|
|
|
|
<p style="margin-left:15%;">This variable controls how the
|
|
shell interacts with the user and job control. If this
|
|
variable is set, simple commands consisting of only a single
|
|
word, without redirections, are treated as candidates for
|
|
resumption of an existing stopped job. There is no ambiguity
|
|
allowed; if there is more than one job beginning with or
|
|
containing the word, this selects the most recently accessed
|
|
job. The <i>name</i> of a stopped job, in this context, is
|
|
the command line used to start it, as displayed by
|
|
<b>jobs</b>. If set to the value <i>exact</i>, the word must
|
|
match the name of a stopped job exactly; if set to
|
|
<i>substring</i>, the word needs to match a substring of the
|
|
name of a stopped job. The <i>substring</i> value provides
|
|
functionality analogous to the <b>%?</b> job identifier (see
|
|
<b>JOB CONTROL</b> below). If set to any other value (e.g.,
|
|
<i>prefix</i>), the word must be a prefix of a stopped
|
|
job’s name; this provides functionality analogous to
|
|
the <b>%</b><i>string</i> job identifier.</p>
|
|
|
|
<p style="margin-left:6%;"><b>histchars</b></p>
|
|
|
|
<p style="margin-left:15%;">The two or three characters
|
|
which control history expansion, quick substitution, and
|
|
tokenization (see <b>HISTORY EXPANSION</b> below). The first
|
|
character is the <i>history expansion</i> character, the
|
|
character which begins a history expansion, normally
|
|
“<b>!</b>”. The second character is the <i>quick
|
|
substitution</i> character, normally “<b>^</b>”.
|
|
When it appears as the first character on the line, history
|
|
substitution repeats the previous command, replacing one
|
|
string with another. The optional third character is the
|
|
<i>history comment</i> character, normally
|
|
“<b>#</b>”, which indicates that the remainder
|
|
of the line is a comment when it appears as the first
|
|
character of a word. The history comment character disables
|
|
history substitution for the remaining words on the line. It
|
|
does not necessarily cause the shell parser to treat the
|
|
rest of the line as a comment.</p>
|
|
|
|
<h3>Arrays
|
|
<a name="Arrays"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
provides one-dimensional indexed and associative array
|
|
variables. Any variable may be used as an indexed array; the
|
|
<b>declare</b> builtin explicitly declares an array. There
|
|
is no maximum limit on the size of an array, nor any
|
|
requirement that members be indexed or assigned
|
|
contiguously. Indexed arrays are referenced using arithmetic
|
|
expressions that must expand to an integer (see
|
|
<b>ARITHMETIC EVALUATION</b> below) and are zero-based;
|
|
associative arrays are referenced using arbitrary strings.
|
|
Unless otherwise noted, indexed array indices must be
|
|
non-negative integers.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell
|
|
performs parameter and variable expansion, arithmetic
|
|
expansion, command substitution, and quote removal on
|
|
indexed array subscripts. Since this can potentially result
|
|
in empty strings, subscript indexing treats those as
|
|
expressions that evaluate to 0.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell
|
|
performs tilde expansion, parameter and variable expansion,
|
|
arithmetic expansion, command substitution, and quote
|
|
removal on associative array subscripts. Empty strings
|
|
cannot be used as associative array keys.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
automatically creates an indexed array if any variable is
|
|
assigned to using the syntax</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><i>name</i>[<i>subscript</i>]=<i>value</i>
|
|
.</p>
|
|
|
|
<p style="margin-left:6%;">The <i>subscript</i> is treated
|
|
as an arithmetic expression that must evaluate to a number
|
|
greater than or equal to zero. To explicitly declare an
|
|
indexed array, use</p>
|
|
|
|
<p style="margin-left:15%;"><b>declare
|
|
-a </b><i>name</i></p>
|
|
|
|
<p style="margin-left:6%;">(see <b>SHELL BUILTIN
|
|
COMMANDS</b> below).</p>
|
|
|
|
<p style="margin-left:15%;"><b>declare -a</b>
|
|
<i>name</i>[<i>subscript</i>]</p>
|
|
|
|
<p style="margin-left:6%;">is also accepted; the
|
|
<i>subscript</i> is ignored.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Associative
|
|
arrays are created using</p>
|
|
|
|
<p style="margin-left:15%;"><b>declare
|
|
-A </b><i>name</i></p>
|
|
|
|
<p style="margin-left:6%;">.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Attributes may
|
|
be specified for an array variable using the <b>declare</b>
|
|
and <b>readonly</b> builtins. Each attribute applies to all
|
|
members of an array.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Arrays are
|
|
assigned using compound assignments of the form
|
|
<i>name</i>=<b>(</b>value<i>1</i> ... value<i>n</i><b>)</b>,
|
|
where each <i>value</i> may be of the form
|
|
[<i>subscript</i>]=<i>string</i>. Indexed array assignments
|
|
do not require anything but <i>string</i>. Each <i>value</i>
|
|
in the list is expanded using the shell expansions described
|
|
below under <b>EXPANSION</b>, but <i>value</i>s that are
|
|
valid variable assignments including the brackets and
|
|
subscript do not undergo brace expansion and word splitting,
|
|
as with individual variable assignments.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When assigning
|
|
to indexed arrays, if the optional brackets and subscript
|
|
are supplied, that index is assigned to; otherwise the index
|
|
of the element assigned is the last index assigned to by the
|
|
statement plus one. Indexing starts at zero.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When assigning
|
|
to an associative array, the words in a compound assignment
|
|
may be either assignment statements, for which the subscript
|
|
is required, or a list of words that is interpreted as a
|
|
sequence of alternating keys and values:
|
|
<i>name</i>=<b>(</b> <i>key1 value1 key2 value2</i>
|
|
...<b>)</b>. These are treated identically to
|
|
<i>name</i>=<b>(</b> [<i>key1</i>]=<i>value1</i>
|
|
[<i>key2</i>]=<i>value2</i> ...<b>)</b>. The first word in
|
|
the list determines how the remaining words are interpreted;
|
|
all assignments in a list must be of the same type. When
|
|
using key/value pairs, the keys may not be missing or empty;
|
|
a final missing value is treated like the empty string.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This syntax is
|
|
also accepted by the <b>declare</b> builtin. Individual
|
|
array elements may be assigned to using the
|
|
<i>name</i>[<i>subscript</i>]=<i>value</i> syntax introduced
|
|
above.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When assigning
|
|
to an indexed array, if <i>name</i> is subscripted by a
|
|
negative number, that number is interpreted as relative to
|
|
one greater than the maximum index of <i>name</i>, so
|
|
negative indices count back from the end of the array, and
|
|
an index of -1 references the last element.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The
|
|
“+=” operator appends to an array variable when
|
|
assigning using the compound assignment syntax; see
|
|
<b>PARAMETERS</b> above.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If one of the
|
|
word expansions in a compound array assignment unsets the
|
|
variable, the results are unspecified.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">An array element
|
|
is referenced using ${<i>name</i>[<i>subscript</i>]}. The
|
|
braces are required to avoid conflicts with pathname
|
|
expansion. If <i>subscript</i> is <b>@</b> or <b>*</b>, the
|
|
word expands to all members of <i>name</i>, unless noted in
|
|
the description of a builtin or word expansion. These
|
|
subscripts differ only when the word appears within double
|
|
quotes. If the word is double-quoted, ${<i>name</i>[*]}
|
|
expands to a single word with the value of each array member
|
|
separated by the first character of the <b>IFS</b> special
|
|
variable, and ${<i>name</i>[@]} expands each element of
|
|
<i>name</i> to a separate word. When there are no array
|
|
members, ${<i>name</i>[@]} expands to nothing. If the
|
|
double-quoted expansion occurs within a word, the expansion
|
|
of the first parameter is joined with the beginning part of
|
|
the expansion of the original word, and the expansion of the
|
|
last parameter is joined with the last part of the expansion
|
|
of the original word. This is analogous to the expansion of
|
|
the special parameters <b>*</b> and <b>@</b> (see <b>Special
|
|
Parameters</b> above).</p>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">${#<i>name</i>[<i>subscript</i>]}
|
|
expands to the length of ${<i>name</i>[<i>subscript</i>]}.
|
|
If <i>subscript</i> is <b>*</b> or <b>@</b>, the expansion
|
|
is the number of elements in the array.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
<i>subscript</i> used to reference an element of an indexed
|
|
array evaluates to a number less than zero, it is
|
|
interpreted as relative to one greater than the maximum
|
|
index of the array, so negative indices count back from the
|
|
end of the array, and an index of -1 references the last
|
|
element.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Referencing an
|
|
array variable without a subscript is equivalent to
|
|
referencing the array with a subscript of 0. Any reference
|
|
to a variable using a valid subscript is valid; <b>bash</b>
|
|
creates an array if necessary.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">An array
|
|
variable is considered set if a subscript has been assigned
|
|
a value. The null string is a valid value.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">It is possible
|
|
to obtain the keys (indices) of an array as well as the
|
|
values. ${<b>!</b><i>name</i>[<i>@</i>]} and
|
|
${<b>!</b><i>name</i>[<i>*</i>]} expand to the indices
|
|
assigned in array variable <i>name</i>. The treatment when
|
|
in double quotes is similar to the expansion of the special
|
|
parameters <i>@</i> and <i>*</i> within double quotes.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <b>unset</b>
|
|
builtin is used to destroy arrays. <b>unset</b>
|
|
<i>name</i>[<i>subscript</i>] unsets the array element at
|
|
index <i>subscript</i>, for both indexed and associative
|
|
arrays. Negative subscripts to indexed arrays are
|
|
interpreted as described above. Unsetting the last element
|
|
of an array variable does not unset the variable.
|
|
<b>unset</b> <i>name</i>, where <i>name</i> is an array,
|
|
removes the entire array. <b>unset</b>
|
|
<i>name</i>[<i>subscript</i>] behaves differently depending
|
|
on whether <i>name</i> is an indexed or associative array
|
|
when <i>subscript</i> is <b>*</b> or <b>@</b>. If
|
|
<i>name</i> is an associative array, this unsets the element
|
|
with subscript <b>*</b> or <b>@</b>. If <i>name</i> is an
|
|
indexed array, unset removes all of the elements but does
|
|
not remove the array itself.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When using a
|
|
variable name with a subscript as an argument to a command,
|
|
such as with <b>unset</b>, without using the word expansion
|
|
syntax described above, (e.g., unset a[4]), the argument is
|
|
subject to pathname expansion. Quote the argument if
|
|
pathname expansion is not desired (e.g., unset 'a[4]').</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The
|
|
<b>declare</b>, <b>local</b>, and <b>readonly</b> builtins
|
|
each accept a <b>-a</b> option to specify an indexed array
|
|
and a <b>-A</b> option to specify an associative array. If
|
|
both options are supplied, <b>-A</b> takes precedence. The
|
|
<b>read</b> builtin accepts a <b>-a</b> option to assign a
|
|
list of words read from the standard input to an array. The
|
|
<b>set</b> and <b>declare</b> builtins display array values
|
|
in a way that allows them to be reused as assignments. Other
|
|
builtins accept array name arguments as well (e.g.,
|
|
<b>mapfile</b>); see the descriptions of individual builtins
|
|
below for details. The shell provides a number of builtin
|
|
array variables.</p>
|
|
|
|
<h2>EXPANSION
|
|
<a name="EXPANSION"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Expansion is
|
|
performed on the command line after it has been split into
|
|
words. The shell performs these expansions: <i>brace
|
|
expansion</i>, <i>tilde expansion</i>, <i>parameter and
|
|
variable expansion</i>, <i>command substitution</i>,
|
|
<i>arithmetic expansion</i>, <i>word splitting</i>,
|
|
<i>pathname expansion</i>, and <i>quote removal</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The order of
|
|
expansions is: brace expansion; tilde expansion, parameter
|
|
and variable expansion, arithmetic expansion, and command
|
|
substitution (done in a left-to-right fashion); word
|
|
splitting; pathname expansion; and quote removal.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">On systems that
|
|
can support it, there is an additional expansion available:
|
|
<i>process substitution</i>. This is performed at the same
|
|
time as tilde, parameter, variable, and arithmetic expansion
|
|
and command substitution.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>Quote
|
|
removal</i> is always performed last. It removes quote
|
|
characters present in the original word, not ones resulting
|
|
from one of the other expansions, unless they have been
|
|
quoted themselves.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Only brace
|
|
expansion, word splitting, and pathname expansion can
|
|
increase the number of words of the expansion; other
|
|
expansions expand a single word to a single word. The only
|
|
exceptions to this are the expansions of
|
|
<b>"$@"</b> and
|
|
<b>"${</b><i>name</i><b>[@]}"</b>, and, in most
|
|
cases, <b>$*</b> and <b>${</b><i>name</i><b>[*]}</b> as
|
|
explained above (see <b>PARAMETERS</b>).</p>
|
|
|
|
<h3>Brace Expansion
|
|
<a name="Brace Expansion"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>Brace
|
|
expansion</i> is a mechanism to generate arbitrary strings
|
|
sharing a common prefix and suffix, either of which can be
|
|
empty. This mechanism is similar to <i>pathname
|
|
expansion</i>, but the filenames generated need not exist.
|
|
Patterns to be brace expanded are formed from an optional
|
|
<i>preamble</i>, followed by either a series of
|
|
comma-separated strings or a sequence expression between a
|
|
pair of braces, followed by an optional <i>postscript</i>.
|
|
The preamble is prefixed to each string contained within the
|
|
braces, and the postscript is then appended to each
|
|
resulting string, expanding left to right.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Brace expansions
|
|
may be nested. The results of each expanded string are not
|
|
sorted; brace expansion preserves left to right order. For
|
|
example, a<b>{</b>d,c,b<b>}</b>e expands into “ade ace
|
|
abe”.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A sequence
|
|
expression takes the form
|
|
<i>x</i><b>..</b><i>y</i><b>[..</b><i>incr</i><b>]</b>,
|
|
where <i>x</i> and <i>y</i> are either integers or single
|
|
letters, and <i>incr</i>, an optional increment, is an
|
|
integer. When integers are supplied, the expression expands
|
|
to each number between <i>x</i> and <i>y</i>, inclusive. If
|
|
either <i>x</i> or <i>y</i> begins with a zero, each
|
|
generated term will contain the same number of digits,
|
|
zero-padding where necessary. When letters are supplied, the
|
|
expression expands to each character lexicographically
|
|
between <i>x</i> and <i>y</i>, inclusive, using the C
|
|
locale. Note that both <i>x</i> and <i>y</i> must be of the
|
|
same type (integer or letter). When the increment is
|
|
supplied, it is used as the difference between each term.
|
|
The default increment is 1 or -1 as appropriate.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Brace expansion
|
|
is performed before any other expansions, and any characters
|
|
special to other expansions are preserved in the result. It
|
|
is strictly textual. <b>Bash</b> does not apply any
|
|
syntactic interpretation to the context of the expansion or
|
|
the text between the braces.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A
|
|
correctly-formed brace expansion must contain unquoted
|
|
opening and closing braces, and at least one unquoted comma
|
|
or a valid sequence expression. Any incorrectly formed brace
|
|
expansion is left unchanged.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A
|
|
“{” or Q , may be quoted with a backslash to
|
|
prevent its being considered part of a brace expression. To
|
|
avoid conflicts with parameter expansion, the string
|
|
“${” is not considered eligible for brace
|
|
expansion, and inhibits brace expansion until the closing
|
|
“}”.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This construct
|
|
is typically used as shorthand when the common prefix of the
|
|
strings to be generated is longer than in the above
|
|
example:</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">mkdir
|
|
/usr/local/src/bash/{old,new,dist,bugs}</p>
|
|
|
|
<p style="margin-left:6%;">or</p>
|
|
|
|
<p style="margin-left:15%;">chown root
|
|
/usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Brace expansion
|
|
introduces a slight incompatibility with historical versions
|
|
of <b>sh</b>. <b>sh</b> does not treat opening or closing
|
|
braces specially when they appear as part of a word, and
|
|
preserves them in the output. <b>Bash</b> removes braces
|
|
from words as a consequence of brace expansion. For example,
|
|
a word entered to <b>sh</b> as “file{1,2}”
|
|
appears identically in the output. <b>Bash</b> outputs that
|
|
word as “file1 file2” after brace expansion.
|
|
Start <b>bash</b> with the <b>+B</b> option or disable brace
|
|
expansion with the <b>+B</b> option to the <b>set</b>
|
|
command (see <b>SHELL BUILTIN COMMANDS</b> below) for strict
|
|
<b>sh</b> compatibility.</p>
|
|
|
|
<h3>Tilde Expansion
|
|
<a name="Tilde Expansion"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a word begins
|
|
with an unquoted tilde character (“<b>~</b>”),
|
|
all of the characters preceding the first unquoted slash (or
|
|
all characters, if there is no unquoted slash) are
|
|
considered a <i>tilde-prefix</i>. If none of the characters
|
|
in the tilde-prefix are quoted, the characters in the
|
|
tilde-prefix following the tilde are treated as a possible
|
|
<i>login name</i>. If this login name is the null string,
|
|
the tilde is replaced with the value of the shell parameter
|
|
<b>HOME</b>. If <b>HOME</b> is unset, the tilde expands to
|
|
the home directory of the user executing the shell instead.
|
|
Otherwise, the tilde-prefix is replaced with the home
|
|
directory associated with the specified login name.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
tilde-prefix is a “~+”, the value of the shell
|
|
variable <b>PWD</b> replaces the tilde-prefix. If the
|
|
tilde-prefix is a “~-”, the shell substitutes
|
|
the value of the shell variable <b>OLDPWD</b>, if it is set.
|
|
If the characters following the tilde in the tilde-prefix
|
|
consist of a number <i>N</i>, optionally prefixed by a
|
|
“+” or a “-”, the tilde-prefix is
|
|
replaced with the corresponding element from the directory
|
|
stack, as it would be displayed by the <b>dirs</b> builtin
|
|
invoked with the characters following the tilde in the
|
|
tilde-prefix as an argument. If the characters following the
|
|
tilde in the tilde-prefix consist of a number without a
|
|
leading “+” or “-”, tilde expansion
|
|
assumes “+”.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The results of
|
|
tilde expansion are treated as if they were quoted, so the
|
|
replacement is not subject to word splitting and pathname
|
|
expansion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the login
|
|
name is invalid, or the tilde expansion fails, the
|
|
tilde-prefix is unchanged.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
checks each variable assignment for unquoted tilde-prefixes
|
|
immediately following a <b>:</b> or the first <b>=</b>, and
|
|
performs tilde expansion in these cases. Consequently, one
|
|
may use filenames with tildes in assignments to <b>PATH</b>,
|
|
<b>MAILPATH</b>, and <b>CDPATH</b>, and the shell assigns
|
|
the expanded value.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b> also
|
|
performs tilde expansion on words satisfying the conditions
|
|
of variable assignments (as described above under
|
|
<b>PARAMETERS</b>) when they appear as arguments to simple
|
|
commands. <b>Bash</b> does not do this, except for the
|
|
<i>declaration</i> commands listed above, when in posix
|
|
mode.</p>
|
|
|
|
<h3>Parameter Expansion
|
|
<a name="Parameter Expansion"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The
|
|
“<b>$</b>” character introduces parameter
|
|
expansion, command substitution, or arithmetic expansion.
|
|
The parameter name or symbol to be expanded may be enclosed
|
|
in braces, which are optional but serve to protect the
|
|
variable to be expanded from characters immediately
|
|
following it which could be interpreted as part of the
|
|
name.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When braces are
|
|
used, the matching ending brace is the first
|
|
“<b>}</b>” not escaped by a backslash or within
|
|
a quoted string, and not within an embedded arithmetic
|
|
expansion, command substitution, or parameter expansion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The basic form
|
|
of parameter expansion is</p>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">${<i>parameter</i>}</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">which
|
|
substitutes the value of <i>parameter</i>. The braces are
|
|
required when <i>parameter</i> is a positional parameter
|
|
with more than one digit, or when <i>parameter</i> is
|
|
followed by a character which is not to be interpreted as
|
|
part of its name. The <i>parameter</i> is a shell parameter
|
|
as described above (<b>PARAMETERS</b>) or an array reference
|
|
(<b>Arrays</b>).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the first
|
|
character of <i>parameter</i> is an exclamation point
|
|
(<b>!</b>), and <i>parameter</i> is not a <i>nameref</i>, it
|
|
introduces a level of indirection. <b>Bash</b> uses the
|
|
value formed by expanding the rest of <i>parameter</i> as
|
|
the new <i>parameter</i>; this new parameter is then
|
|
expanded and that value is used in the rest of the
|
|
expansion, rather than the expansion of the original
|
|
<i>parameter</i>. This is known as <i>indirect
|
|
expansion</i>. The value is subject to tilde expansion,
|
|
parameter expansion, command substitution, and arithmetic
|
|
expansion. If <i>parameter</i> is a nameref, this expands to
|
|
the name of the parameter referenced by <i>parameter</i>
|
|
instead of performing the complete indirect expansion, for
|
|
compatibility. The exceptions to this are the expansions of
|
|
${<b>!</b><i>prefix</i><b>*</b>} and
|
|
${<b>!</b><i>name</i>[<i>@</i>]} described below. The
|
|
exclamation point must immediately follow the left brace in
|
|
order to introduce indirection.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In each of the
|
|
cases below, <i>word</i> is subject to tilde expansion,
|
|
parameter expansion, command substitution, and arithmetic
|
|
expansion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When performing
|
|
the first four expansions documented below (<b>:-</b>,
|
|
<b>:=</b>, <b>:?</b>, and <b>:+</b>), including the colon,
|
|
<b>bash</b> tests for a parameter that is unset or null.
|
|
Omitting the colon tests only for a parameter that is unset.
|
|
<br>
|
|
${<i>parameter</i><b>:-</b><i>word</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Use Default Values</b>. If
|
|
<i>parameter</i> is unset or null, or unset if the colon is
|
|
not present, the expansion of <i>word</i> is substituted.
|
|
Otherwise, the value of <i>parameter</i> is substituted.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>:=</b><i>word</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Assign Default Values</b>.
|
|
If <i>parameter</i> is unset or null, or unset if the colon
|
|
is not present, the expansion of <i>word</i> is assigned to
|
|
<i>parameter</i>, and the expansion is the final value of
|
|
<i>parameter</i>. Positional parameters and special
|
|
parameters may not be assigned in this way.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>:?</b><i>word</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Display Error if Null or
|
|
Unset</b>. If <i>parameter</i> is unset or null, or unset if
|
|
the colon is not present, the shell writes the expansion of
|
|
<i>word</i> (or a message to that effect if <i>word</i> is
|
|
not present) to the standard error and, if it is not
|
|
interactive, exits with a non-zero status. An interactive
|
|
shell does not exit, but does not execute the command
|
|
associated with the expansion. Otherwise, the value of
|
|
<i>parameter</i> is substituted.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>:+</b><i>word</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Use Alternate Value</b>. If
|
|
<i>parameter</i> is unset or null, or unset if the colon is
|
|
not present, nothing is substituted, otherwise the expansion
|
|
of <i>word</i> is substituted. The value of <i>parameter</i>
|
|
is not used.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>:</b><i>offset</i>}
|
|
<br>
|
|
|
|
${<i>parameter</i><b>:</b><i>offset</i><b>:</b><i>length</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Substring Expansion</b>.
|
|
Expands to up to <i>length</i> characters of the value of
|
|
<i>parameter</i> starting at the character specified by
|
|
<i>offset</i>. If <i>parameter</i> is <b>@</b> or <b>*</b>,
|
|
an indexed array subscripted by <b>@</b> or <b>*</b>, or an
|
|
associative array name, the results differ as described
|
|
below. If <b>:</b><i>length</i> is omitted (the first form
|
|
above), this expands to the substring of the value of
|
|
<i>parameter</i> starting at the character specified by
|
|
<i>offset</i> and extending to the end of the value. If
|
|
<i>offset</i> is omitted, it is treated as 0. If
|
|
<i>length</i> is omitted, but the colon after <i>offset</i>
|
|
is present, it is treated as 0. <i>length</i> and
|
|
<i>offset</i> are arithmetic expressions (see <b>ARITHMETIC
|
|
EVALUATION</b> below).</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>offset</i> evaluates to a number less than zero, the
|
|
value is used as an offset in characters from the end of the
|
|
value of <i>parameter</i>. If <i>length</i> evaluates to a
|
|
number less than zero, it is interpreted as an offset in
|
|
characters from the end of the value of <i>parameter</i>
|
|
rather than a number of characters, and the expansion is the
|
|
characters between <i>offset</i> and that result. Note that
|
|
a negative offset must be separated from the colon by at
|
|
least one space to avoid being confused with the <b>:-</b>
|
|
expansion.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>parameter</i> is <b>@</b> or <b>*</b>, the result is
|
|
<i>length</i> positional parameters beginning at
|
|
<i>offset</i>. A negative <i>offset</i> is taken relative to
|
|
one greater than the greatest positional parameter, so an
|
|
offset of -1 evaluates to the last positional parameter (or
|
|
0 if there are no positional parameters). It is an expansion
|
|
error if <i>length</i> evaluates to a number less than
|
|
zero.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>parameter</i> is an indexed array name subscripted by @
|
|
or *, the result is the <i>length</i> members of the array
|
|
beginning with ${<i>parameter</i>[<i>offset</i>]}. A
|
|
negative <i>offset</i> is taken relative to one greater than
|
|
the maximum index of the specified array. It is an expansion
|
|
error if <i>length</i> evaluates to a number less than
|
|
zero.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Substring
|
|
expansion applied to an associative array produces undefined
|
|
results.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Substring
|
|
indexing is zero-based unless the positional parameters are
|
|
used, in which case the indexing starts at 1 by default. If
|
|
<i>offset</i> is 0, and the positional parameters are used,
|
|
<b>$0</b> is prefixed to the list.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<b>!</b><i>prefix</i><b>*</b>}
|
|
<br>
|
|
${<b>!</b><i>prefix</i><b>@</b>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Names matching prefix</b>.
|
|
Expands to the names of variables whose names begin with
|
|
<i>prefix</i>, separated by the first character of the
|
|
<b>IFS</b> special variable. When <i>@</i> is used and the
|
|
expansion appears within double quotes, each variable name
|
|
expands to a separate word.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<b>!</b><i>name</i>[<i>@</i>]}
|
|
<br>
|
|
${<b>!</b><i>name</i>[<i>*</i>]}</p>
|
|
|
|
<p style="margin-left:15%;"><b>List of array keys</b>. If
|
|
<i>name</i> is an array variable, expands to the list of
|
|
array indices (keys) assigned in <i>name</i>. If <i>name</i>
|
|
is not an array, expands to 0 if <i>name</i> is set and null
|
|
otherwise. When <i>@</i> is used and the expansion appears
|
|
within double quotes, each key expands to a separate
|
|
word.</p>
|
|
|
|
<p style="margin-left:6%;">${<b>#</b><i>parameter</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Parameter length</b>.
|
|
Substitutes the length in characters of the expanded value
|
|
of <i>parameter</i>. If <i>parameter</i> is <b>*</b> or
|
|
<b>@</b>, the value substituted is the number of positional
|
|
parameters. If <i>parameter</i> is an array name subscripted
|
|
by <b>*</b> or <b>@</b>, the value substituted is the number
|
|
of elements in the array. If <i>parameter</i> is an indexed
|
|
array name subscripted by a negative number, that number is
|
|
interpreted as relative to one greater than the maximum
|
|
index of <i>parameter</i>, so negative indices count back
|
|
from the end of the array, and an index of -1 references the
|
|
last element.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>#</b><i>word</i>}
|
|
<br>
|
|
${<i>parameter</i><b>##</b><i>word</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Remove matching prefix
|
|
pattern</b>. The <i>word</i> is expanded to produce a
|
|
pattern just as in pathname expansion, and matched against
|
|
the expanded value of <i>parameter</i> using the rules
|
|
described under <b>Pattern Matching</b> below. If the
|
|
pattern matches the beginning of the value of
|
|
<i>parameter</i>, then the result of the expansion is the
|
|
expanded value of <i>parameter</i> with the shortest
|
|
matching pattern (the “#” case) or the longest
|
|
matching pattern (the “##” case) deleted. If
|
|
<i>parameter</i> is <b>@</b> or <b>*</b>, the pattern
|
|
removal operation is applied to each positional parameter in
|
|
turn, and the expansion is the resultant list. If
|
|
<i>parameter</i> is an array variable subscripted with
|
|
<b>@</b> or <b>*</b>, the pattern removal operation is
|
|
applied to each member of the array in turn, and the
|
|
expansion is the resultant list.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>%</b><i>word</i>}
|
|
<br>
|
|
${<i>parameter</i><b>%%</b><i>word</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Remove matching suffix
|
|
pattern</b>. The <i>word</i> is expanded to produce a
|
|
pattern just as in pathname expansion, and matched against
|
|
the expanded value of <i>parameter</i> using the rules
|
|
described under <b>Pattern Matching</b> below. If the
|
|
pattern matches a trailing portion of the expanded value of
|
|
<i>parameter</i>, then the result of the expansion is the
|
|
expanded value of <i>parameter</i> with the shortest
|
|
matching pattern (the “%” case) or the longest
|
|
matching pattern (the “%%” case) deleted. If
|
|
<i>parameter</i> is <b>@</b> or <b>*</b>, the pattern
|
|
removal operation is applied to each positional parameter in
|
|
turn, and the expansion is the resultant list. If
|
|
<i>parameter</i> is an array variable subscripted with
|
|
<b>@</b> or <b>*</b>, the pattern removal operation is
|
|
applied to each member of the array in turn, and the
|
|
expansion is the resultant list.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>/</b><i>pattern</i><b>/</b><i>string</i>}
|
|
<br>
|
|
|
|
${<i>parameter</i><b>//</b><i>pattern</i><b>/</b><i>string</i>}
|
|
<br>
|
|
|
|
${<i>parameter</i><b>/#</b><i>pattern</i><b>/</b><i>string</i>}
|
|
<br>
|
|
|
|
${<i>parameter</i><b>/%</b><i>pattern</i><b>/</b><i>string</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Pattern substitution</b>.
|
|
The <i>pattern</i> is expanded to produce a pattern and
|
|
matched against the expanded value of <i>parameter</i> as
|
|
described under <b>Pattern Matching</b> below. The longest
|
|
match of <i>pattern</i> in the expanded value is replaced
|
|
with <i>string</i>. <i>string</i> undergoes tilde expansion,
|
|
parameter and variable expansion, arithmetic expansion,
|
|
command and process substitution, and quote removal.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">In the first
|
|
form above, only the first match is replaced. If there are
|
|
two slashes separating <i>parameter</i> and <i>pattern</i>
|
|
(the second form above), all matches of <i>pattern</i> are
|
|
replaced with <i>string</i>. If <i>pattern</i> is preceded
|
|
by <b>#</b> (the third form above), it must match at the
|
|
beginning of the expanded value of <i>parameter</i>. If
|
|
<i>pattern</i> is preceded by <b>%</b> (the fourth form
|
|
above), it must match at the end of the expanded value of
|
|
<i>parameter</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
expansion of <i>string</i> is null, matches of
|
|
<i>pattern</i> are deleted and the <b>/</b> following
|
|
<i>pattern</i> may be omitted.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>patsub_replacement</b> shell option is enabled using
|
|
<b>shopt</b>, any unquoted instances of <b>&</b> in
|
|
<i>string</i> are replaced with the matching portion of
|
|
<i>pattern</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Quoting any
|
|
part of <i>string</i> inhibits replacement in the expansion
|
|
of the quoted portion, including replacement strings stored
|
|
in shell variables. Backslash escapes <b>&</b> in
|
|
<i>string</i>; the backslash is removed in order to permit a
|
|
literal <b>&</b> in the replacement string. Backslash
|
|
can also be used to escape a backslash; <b>\\</b> results in
|
|
a literal backslash in the replacement. Users should take
|
|
care if <i>string</i> is double-quoted to avoid unwanted
|
|
interactions between the backslash and double-quoting, since
|
|
backslash has special meaning within double quotes. Pattern
|
|
substitution performs the check for unquoted <b>&</b>
|
|
after expanding <i>string</i>; shell programmers should
|
|
quote any occurrences of <b>&</b> they want to be taken
|
|
literally in the replacement and ensure any instances of
|
|
<b>&</b> they want to be replaced are unquoted.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Like the
|
|
pattern removal operators, double quotes surrounding the
|
|
replacement string quote the expanded characters, while
|
|
double quotes enclosing the entire parameter substitution do
|
|
not, since the expansion is performed in a context that
|
|
doesn’t take any enclosing double quotes into
|
|
account.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>nocasematch</b> shell option is enabled, the match is
|
|
performed without regard to the case of alphabetic
|
|
characters.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>parameter</i> is <b>@</b> or <b>*</b>, the substitution
|
|
operation is applied to each positional parameter in turn,
|
|
and the expansion is the resultant list. If <i>parameter</i>
|
|
is an array variable subscripted with <b>@</b> or <b>*</b>,
|
|
the substitution operation is applied to each member of the
|
|
array in turn, and the expansion is the resultant list.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>^</b><i>pattern</i>}
|
|
<br>
|
|
${<i>parameter</i><b>^^</b><i>pattern</i>} <br>
|
|
${<i>parameter</i><b>,</b><i>pattern</i>} <br>
|
|
${<i>parameter</i><b>,,</b><i>pattern</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Case modification</b>. This
|
|
expansion modifies the case of alphabetic characters in
|
|
<i>parameter</i>. First, the <i>pattern</i> is expanded to
|
|
produce a pattern as described below under <b>Pattern
|
|
Matching</b>. <b>Bash</b> then examines characters in the
|
|
expanded value of <i>parameter</i> against <i>pattern</i> as
|
|
described below. If a character matches the pattern, its
|
|
case is converted. The pattern should not attempt to match
|
|
more than one character.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Using
|
|
“^” converts lowercase letters matching
|
|
<i>pattern</i> to uppercase; “,” converts
|
|
matching uppercase letters to lowercase. The <b>^</b> and
|
|
<b>,</b> variants examine the first character in the
|
|
expanded value and convert its case if it matches
|
|
<i>pattern</i>; the <b>^^</b> and <b>,,</b> variants examine
|
|
all characters in the expanded value and convert each one
|
|
that matches <i>pattern</i>. If <i>pattern</i> is omitted,
|
|
it is treated like a <b>?</b>, which matches every
|
|
character.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>parameter</i> is <b>@</b> or <b>*</b>, the case
|
|
modification operation is applied to each positional
|
|
parameter in turn, and the expansion is the resultant list.
|
|
If <i>parameter</i> is an array variable subscripted with
|
|
<b>@</b> or <b>*</b>, the case modification operation is
|
|
applied to each member of the array in turn, and the
|
|
expansion is the resultant list.</p>
|
|
|
|
|
|
<p style="margin-left:6%;">${<i>parameter</i><b>@</b><i>operator</i>}</p>
|
|
|
|
<p style="margin-left:15%;"><b>Parameter
|
|
transformation</b>. The expansion is either a transformation
|
|
of the value of <i>parameter</i> or information about
|
|
<i>parameter</i> itself, depending on the value of
|
|
<i>operator</i>. Each <i>operator</i> is a single
|
|
letter:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p><b>U</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>The expansion is a string that is the value of
|
|
<i>parameter</i> with lowercase alphabetic characters
|
|
converted to uppercase.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>u</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expansion is a string that
|
|
is the value of <i>parameter</i> with the first character
|
|
converted to uppercase, if it is alphabetic.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>L</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expansion is a string that
|
|
is the value of <i>parameter</i> with uppercase alphabetic
|
|
characters converted to lowercase.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>Q</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expansion is a string that
|
|
is the value of <i>parameter</i> quoted in a format that can
|
|
be reused as input.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>E</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expansion is a string that
|
|
is the value of <i>parameter</i> with backslash escape
|
|
sequences expanded as with the <b>$'</b>...<b>'</b> quoting
|
|
mechanism.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>P</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expansion is a string that
|
|
is the result of expanding the value of <i>parameter</i> as
|
|
if it were a prompt string (see <b>PROMPTING</b> below).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>A</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expansion is a string in the
|
|
form of an assignment statement or <b>declare</b> command
|
|
that, if evaluated, recreates <i>parameter</i> with its
|
|
attributes and value.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>K</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Produces a possibly-quoted
|
|
version of the value of <i>parameter</i>, except that it
|
|
prints the values of indexed and associative arrays as a
|
|
sequence of quoted key-value pairs (see <b>Arrays</b>
|
|
above). The keys and values are quoted in a format that can
|
|
be reused as input.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>a</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expansion is a string
|
|
consisting of flag values representing
|
|
<i>parameter</i>’s attributes.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>k</b></p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Like the K transformation, but
|
|
expands the keys and values of indexed and associative
|
|
arrays to separate words after word splitting.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>parameter</i> is <b>@</b> or <b>*</b>, the operation is
|
|
applied to each positional parameter in turn, and the
|
|
expansion is the resultant list. If <i>parameter</i> is an
|
|
array variable subscripted with <b>@</b> or <b>*</b>, the
|
|
operation is applied to each member of the array in turn,
|
|
and the expansion is the resultant list.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The result of
|
|
the expansion is subject to word splitting and pathname
|
|
expansion as described below.</p>
|
|
|
|
<h3>Command Substitution
|
|
<a name="Command Substitution"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>Command
|
|
substitution</i> allows the output of a command to replace
|
|
the command itself. There are two standard forms:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>$(</b><i>command</i><b>)</b></p>
|
|
|
|
<p style="margin-left:6%;">or (deprecated)</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>`</b><i>command</i><b>`</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
performs the expansion by executing <i>command</i> in a
|
|
subshell environment and replacing the command substitution
|
|
with the standard output of the command, with any trailing
|
|
newlines deleted. Embedded newlines are not deleted, but
|
|
they may be removed during word splitting. The command
|
|
substitution <b>$(cat</b> <i>file</i><b>)</b> can be
|
|
replaced by the equivalent but faster <b>$(<</b>
|
|
<i>file</i><b>)</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">With the
|
|
old-style backquote form of substitution, backslash retains
|
|
its literal meaning except when followed by <b>$</b>,
|
|
<b>`</b>, or <b>\</b>. The first backquote not preceded by a
|
|
backslash terminates the command substitution. When using
|
|
the $(<i>command</i>) form, all characters between the
|
|
parentheses make up the command; none are treated
|
|
specially.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There is an
|
|
alternate form of command substitution:</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>${</b><i>c
|
|
command</i><b>;}</b></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">which executes
|
|
<i>command</i> in the current execution environment and
|
|
captures its output, again with trailing newlines
|
|
removed.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The character
|
|
<i>c</i> following the open brace must be a space, tab,
|
|
newline, “|”, or “;”; and the close
|
|
brace must be in a position where a reserved word may appear
|
|
(i.e., preceded by a command terminator such as semicolon).
|
|
<b>Bash</b> allows the close brace to be joined to the
|
|
remaining characters in the word without being followed by a
|
|
shell metacharacter as a reserved word would usually
|
|
require.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Any side effects
|
|
of <i>command</i> take effect immediately in the current
|
|
execution environment and persist in the current environment
|
|
after the command completes (e.g., the <b>exit</b> builtin
|
|
exits the shell).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This type of
|
|
command substitution superficially resembles executing an
|
|
unnamed shell function: local variables are created as when
|
|
a shell function is executing, and the <b>return</b> builtin
|
|
forces <i>command</i> to complete; however, the rest of the
|
|
execution environment, including the positional parameters,
|
|
is shared with the caller.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the first
|
|
character following the open brace is a “;”, the
|
|
construct behaves like the form above but preserves any
|
|
trailing newlines in the output of <i>command</i> instead of
|
|
removing them. This form is useful when the trailing
|
|
newlines are significant and should not be stripped from the
|
|
command’s output.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the first
|
|
character following the open brace is a “|”, the
|
|
construct expands to the value of the <b>REPLY</b> shell
|
|
variable after <i>command</i> executes, without removing any
|
|
trailing newlines, and the standard output of <i>command</i>
|
|
remains the same as in the calling shell. <b>Bash</b>
|
|
creates <b>REPLY</b> as an initially-unset local variable
|
|
when <i>command</i> executes, and restores <b>REPLY</b> to
|
|
the value it had before the command substitution after
|
|
<i>command</i> completes, as with any local variable.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Command
|
|
substitutions may be nested. To nest when using the
|
|
backquoted form, escape the inner backquotes with
|
|
backslashes.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
substitution appears within double quotes, <b>bash</b> does
|
|
not perform word splitting and pathname expansion on the
|
|
results.</p>
|
|
|
|
<h3>Arithmetic Expansion
|
|
<a name="Arithmetic Expansion"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Arithmetic
|
|
expansion evaluates an arithmetic expression and substitutes
|
|
the result. The format for arithmetic expansion is:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>$((</b><i>expression</i><b>))</b></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The
|
|
<i>expression</i> undergoes the same expansions as if it
|
|
were within double quotes, but unescaped double quote
|
|
characters in <i>expression</i> are not treated specially
|
|
and are removed. All tokens in the expression undergo
|
|
parameter and variable expansion, command substitution, and
|
|
quote removal. The result is treated as the arithmetic
|
|
expression to be evaluated. Since the way Bash handles
|
|
double quotes can potentially result in empty strings,
|
|
arithmetic expansion treats those as expressions that
|
|
evaluate to 0. Arithmetic expansions may be nested.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The evaluation
|
|
is performed according to the rules listed below under
|
|
<b>ARITHMETIC EVALUATION</b>. If <i>expression</i> is
|
|
invalid, <b>bash</b> prints a message to standard error
|
|
indicating failure, does not perform the substitution, and
|
|
does not continue to execute the command in which the error
|
|
occurs.</p>
|
|
|
|
<h3>Process Substitution
|
|
<a name="Process Substitution"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>Process
|
|
substitution</i> allows a process’s input or output to
|
|
be referred to using a filename. It takes the form of
|
|
<b><(</b><i>list</i><b>)</b> or
|
|
<b>>(</b><i>list</i><b>)</b>. The process <i>list</i>, as
|
|
long as it is not a null command without redirections, is
|
|
run asynchronously, and its input or output appears as a
|
|
filename. This filename is passed as an argument to the
|
|
current command as the result of the expansion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
<b>>(</b><i>list</i><b>)</b> form is used, writing to the
|
|
file provides input for <i>list</i>. If the
|
|
<b><(</b><i>list</i><b>)</b> form is used, reading the
|
|
file obtains the output of <i>list</i>. No space may appear
|
|
between the <b><</b> or <b>></b> and the left
|
|
parenthesis, otherwise the construct would be interpreted as
|
|
a redirection.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Process
|
|
substitution is supported on systems that support named
|
|
pipes (<i>FIFOs</i>) or the <i>/dev/fd</i> method of naming
|
|
open files.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When available,
|
|
process substitution is performed simultaneously with
|
|
parameter and variable expansion, command substitution, and
|
|
arithmetic expansion.</p>
|
|
|
|
<h3>Word Splitting
|
|
<a name="Word Splitting"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell scans
|
|
the results of parameter expansion, command substitution,
|
|
and arithmetic expansion that did not occur within double
|
|
quotes for <i>word splitting</i>. Words that were not
|
|
expanded are not split.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell treats
|
|
each character of <b>IFS</b> as a delimiter, and splits the
|
|
results of the other expansions into words using these
|
|
characters as field terminators.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">An <i>IFS
|
|
whitespace</i> character is whitespace as defined above (see
|
|
<b>Definitions</b>) that appears in the value of <b>IFS</b>.
|
|
Space, tab, and newline are always considered IFS
|
|
whitespace, even if they don’t appear in the
|
|
locale’s <b>space</b> category.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If <b>IFS</b> is
|
|
unset, field splitting acts as if its value were
|
|
<b><space><tab><newline></b>, and treats
|
|
these characters as IFS whitespace. If the value of
|
|
<b>IFS</b> is null, no word splitting occurs, but implicit
|
|
null arguments (see below) are still removed.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Word splitting
|
|
begins by removing sequences of IFS whitespace characters
|
|
from the beginning and end of the results of the previous
|
|
expansions, then splits the remaining words.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the value of
|
|
<b>IFS</b> consists solely of IFS whitespace, any sequence
|
|
of IFS whitespace characters delimits a field, so a field
|
|
consists of characters that are not unquoted IFS whitespace,
|
|
and null fields result only from quoting.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If <b>IFS</b>
|
|
contains a non-whitespace character, then any character in
|
|
the value of <b>IFS</b> that is not IFS whitespace, along
|
|
with any adjacent IFS whitespace characters, delimits a
|
|
field. This means that adjacent non-IFS-whitespace
|
|
delimiters produce a null field. A sequence of IFS
|
|
whitespace characters also delimits a field.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Explicit null
|
|
arguments (<b>""</b> or <b>''</b>) are retained
|
|
and passed to commands as empty strings. Unquoted implicit
|
|
null arguments, resulting from the expansion of parameters
|
|
that have no values, are removed. Expanding a parameter with
|
|
no value within double quotes produces a null field, which
|
|
is retained and passed to a command as an empty string.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a quoted
|
|
null argument appears as part of a word whose expansion is
|
|
non-null, word splitting removes the null argument portion,
|
|
leaving the non-null expansion. That is, the word
|
|
“-d''” becomes “-d” after word
|
|
splitting and null argument removal.</p>
|
|
|
|
<h3>Pathname Expansion
|
|
<a name="Pathname Expansion"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">After word
|
|
splitting, unless the <b>-f</b> option has been set,
|
|
<b>bash</b> scans each word for the characters <b>*</b>,
|
|
<b>?</b>, and <b>[</b>. If one of these characters appears,
|
|
and is not quoted, then the word is regarded as a
|
|
<i>pattern</i>, and replaced with a sorted list of filenames
|
|
matching the pattern (see <b>Pattern Matching</b> below)
|
|
subject to the value of the <b>GLOBSORT</b> shell
|
|
variable.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If no matching
|
|
filenames are found, and the shell option <b>nullglob</b> is
|
|
not enabled, the word is left unchanged. If the
|
|
<b>nullglob</b> option is set, and no matches are found, the
|
|
word is removed. If the <b>failglob</b> shell option is set,
|
|
and no matches are found, <b>bash</b> prints an error
|
|
message and does not execute the command. If the shell
|
|
option <b>nocaseglob</b> is enabled, the match is performed
|
|
without regard to the case of alphabetic characters.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a pattern
|
|
is used for pathname expansion, the character
|
|
“.” at the start of a name or immediately
|
|
following a slash must be matched explicitly, unless the
|
|
shell option <b>dotglob</b> is set. In order to match the
|
|
filenames <i>.</i> and <i>..</i>, the pattern must begin
|
|
with “.” (for example, “.?”), even
|
|
if <b>dotglob</b> is set. If the <b>globskipdots</b> shell
|
|
option is enabled, the filenames <i>.</i> and <i>..</i>
|
|
never match, even if the pattern begins with a
|
|
“.”. When not matching pathnames, the
|
|
“.” character is not treated specially.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When matching a
|
|
pathname, the slash character must always be matched
|
|
explicitly by a slash in the pattern, but in other matching
|
|
contexts it can be matched by a special pattern character as
|
|
described below under <b>Pattern Matching</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">See the
|
|
description of <b>shopt</b> below under <b>SHELL BUILTIN
|
|
COMMANDS</b> for a description of the <b>nocaseglob</b>,
|
|
<b>nullglob</b>, <b>globskipdots</b>, <b>failglob</b>, and
|
|
<b>dotglob</b> shell options.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The
|
|
<b>GLOBIGNORE</b> shell variable may be used to restrict the
|
|
set of file names matching a <i>pattern</i>. If
|
|
<b>GLOBIGNORE</b> is set, each matching file name that also
|
|
matches one of the patterns in <b>GLOBIGNORE</b> is removed
|
|
from the list of matches. If the <b>nocaseglob</b> option is
|
|
set, the matching against the patterns in <b>GLOBIGNORE</b>
|
|
is performed without regard to case. The filenames <i>.</i>
|
|
and <i>..</i> are always ignored when <b>GLOBIGNORE</b> is
|
|
set and not null. However, setting <b>GLOBIGNORE</b> to a
|
|
non-null value has the effect of enabling the <b>dotglob</b>
|
|
shell option, so all other filenames beginning with a
|
|
“.” match. To get the old behavior of ignoring
|
|
filenames beginning with a “.”, make
|
|
“.*” one of the patterns in <b>GLOBIGNORE</b>.
|
|
The <b>dotglob</b> option is disabled when <b>GLOBIGNORE</b>
|
|
is unset. The <b>GLOBIGNORE</b> pattern matching honors the
|
|
setting of the <b>extglob</b> shell option.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The value of the
|
|
<b>GLOBSORT</b> shell variable controls how the results of
|
|
pathname expansion are sorted, as described above under
|
|
<b>Shell Variables</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Pattern
|
|
Matching</b></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Any character
|
|
that appears in a pattern, other than the special pattern
|
|
characters described below, matches itself. The NUL
|
|
character may not occur in a pattern. A backslash escapes
|
|
the following character; the escaping backslash is discarded
|
|
when matching. The special pattern characters must be quoted
|
|
if they are to be matched literally.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The special
|
|
pattern characters have the following meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>*</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Matches any string, including
|
|
the null string. When the <b>globstar</b> shell option is
|
|
enabled, and <b>*</b> is used in a pathname expansion
|
|
context, two adjacent <b>*</b>s used as a single pattern
|
|
match all files and zero or more directories and
|
|
subdirectories. If followed by a <b>/</b>, two adjacent
|
|
<b>*</b>s match only directories and subdirectories.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>?</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Matches any single
|
|
character.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>[</b>...<b>]</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Matches any one of the
|
|
characters enclosed between the brackets. This is known as a
|
|
<i>bracket expression</i> and matches a single character. A
|
|
pair of characters separated by a hyphen denotes a <i>range
|
|
expression</i>; any character that falls between those two
|
|
characters, inclusive, using the current locale’s
|
|
collating sequence and character set, matches. If the first
|
|
character following the <b>[</b> is a <b>!</b> or a <b>^</b>
|
|
then any character not within the range matches. To match a
|
|
<b>-</b>, include it as the first or last character in the
|
|
set. To match a <b>]</b>, include it as the first character
|
|
in the set.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:24%; margin-top: 1em">The sorting
|
|
order of characters in range expressions, and the characters
|
|
included in the range, are determined by the collating
|
|
sequence of the current locale and the values of the
|
|
<b>LC_COLLATE</b> or <b>LC_ALL</b> shell variables, if
|
|
set.</p>
|
|
|
|
<p style="margin-left:24%; margin-top: 1em">For example, in
|
|
the C locale, <b>[a-d]</b> is equivalent to <b>[abcd]</b>.
|
|
Many locales sort characters in dictionary order, and in
|
|
these locales <b>[a-d]</b> is typically not equivalent to
|
|
<b>[abcd]</b>; it might be equivalent to <b>[aBbCcDd]</b> or
|
|
<b>[aAbBcCd]</b>. To obtain the traditional interpretation
|
|
of range expressions, where <b>[a-d]</b> is equivalent to
|
|
<b>[abcd]</b>, set the value of the <b>LC_COLLATE</b> or
|
|
<b>LC_ALL</b> shell variables to <b>C</b>, or enable the
|
|
<b>globasciiranges</b> shell option.</p>
|
|
|
|
<p style="margin-left:24%; margin-top: 1em">Within a
|
|
bracket expression, <i>character classes</i> can be
|
|
specified using the syntax <b>[:</b><i>class</i><b>:]</b>,
|
|
where <i>class</i> is one of the following classes defined
|
|
in the POSIX standard:</p>
|
|
|
|
<p style="margin-left:24%; margin-top: 1em"><b>alnum alpha
|
|
ascii blank cntrl digit graph lower print punct space upper
|
|
word xdigit</b></p>
|
|
|
|
<p style="margin-left:24%; margin-top: 1em">A character
|
|
class matches any character belonging to that class. The
|
|
<b>word</b> character class matches letters, digits, and the
|
|
character _.</p>
|
|
|
|
<p style="margin-left:24%; margin-top: 1em">Within a
|
|
bracket expression, an <i>equivalence class</i> can be
|
|
specified using the syntax <b>[=</b><i>c</i><b>=]</b>, which
|
|
matches all characters with the same collation weight (as
|
|
defined by the current locale) as the character
|
|
<i>c</i>.</p>
|
|
|
|
<p style="margin-left:24%; margin-top: 1em">Within a
|
|
bracket expression, the syntax
|
|
<b>[.</b><i>symbol</i><b>.]</b> matches the collating symbol
|
|
<i>symbol</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
<b>extglob</b> shell option is enabled using the
|
|
<b>shopt</b> builtin, the shell recognizes several extended
|
|
pattern matching operators. In the following description, a
|
|
<i>pattern-list</i> is a list of one or more patterns
|
|
separated by a <b>|</b>. Composite patterns may be formed
|
|
using one or more of the following sub-patterns:</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>?(</b><i>pattern-list</i><b>)</b></p>
|
|
|
|
<p style="margin-left:24%;">Matches zero or one occurrence
|
|
of the given patterns.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>*(</b><i>pattern-list</i><b>)</b></p>
|
|
|
|
<p style="margin-left:24%;">Matches zero or more
|
|
occurrences of the given patterns.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>+(</b><i>pattern-list</i><b>)</b></p>
|
|
|
|
<p style="margin-left:24%;">Matches one or more occurrences
|
|
of the given patterns.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>@(</b><i>pattern-list</i><b>)</b></p>
|
|
|
|
<p style="margin-left:24%;">Matches one of the given
|
|
patterns.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>!(</b><i>pattern-list</i><b>)</b></p>
|
|
|
|
<p style="margin-left:24%;">Matches anything except one of
|
|
the given patterns.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The
|
|
<b>extglob</b> option changes the behavior of the parser,
|
|
since the parentheses are normally treated as operators with
|
|
syntactic meaning. To ensure that extended matching patterns
|
|
are parsed correctly, make sure that <b>extglob</b> is
|
|
enabled before parsing constructs containing the patterns,
|
|
including shell functions and command substitutions.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When matching
|
|
filenames, the <b>dotglob</b> shell option determines the
|
|
set of filenames that are tested: when <b>dotglob</b> is
|
|
enabled, the set of filenames includes all files beginning
|
|
with “.”, but <i>.</i> and <i>..</i> must be
|
|
matched by a pattern or sub-pattern that begins with a dot;
|
|
when it is disabled, the set does not include any filenames
|
|
beginning with “.” unless the pattern or
|
|
sub-pattern begins with a “.”. If the
|
|
<b>globskipdots</b> shell option is enabled, the filenames
|
|
<i>.</i> and <i>..</i> never appear in the set. As above,
|
|
“.” only has a special meaning when matching
|
|
filenames.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Complicated
|
|
extended pattern matching against long strings is slow,
|
|
especially when the patterns contain alternations and the
|
|
strings contain multiple matches. Using separate matches
|
|
against shorter strings, or using arrays of strings instead
|
|
of a single long string, may be faster.</p>
|
|
|
|
<h3>Quote Removal
|
|
<a name="Quote Removal"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">After the
|
|
preceding expansions, all unquoted occurrences of the
|
|
characters <b>\</b>, <b>'</b>, and <b>"</b> that did
|
|
not result from one of the above expansions are removed.</p>
|
|
|
|
<h2>REDIRECTION
|
|
<a name="REDIRECTION"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Before a command
|
|
is executed, its input and output may be <i>redirected</i>
|
|
using a special notation interpreted by the shell.
|
|
<i>Redirection</i> allows commands’ file handles to be
|
|
duplicated, opened, closed, made to refer to different
|
|
files, and can change the files the command reads from and
|
|
writes to. When used with the <b>exec</b> builtin,
|
|
redirections modify file handles in the current shell
|
|
execution environment. The following redirection operators
|
|
may precede or appear anywhere within a <i>simple
|
|
command</i> or may follow a <i>command</i>. Redirections are
|
|
processed in the order they appear, from left to right.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Each redirection
|
|
that may be preceded by a file descriptor number may instead
|
|
be preceded by a word of the form {<i>varname</i>}. In this
|
|
case, for each redirection operator except <b>>&-</b>
|
|
and <b><&-</b>, the shell allocates a file descriptor
|
|
greater than or equal to 10 and assigns it to
|
|
<i>varname</i>. If {<i>varname</i>} precedes
|
|
<b>>&-</b> or <b><&-</b>, the value of
|
|
<i>varname</i> defines the file descriptor to close. If
|
|
{<i>varname</i>} is supplied, the redirection persists
|
|
beyond the scope of the command, which allows the shell
|
|
programmer to manage the file descriptor’s lifetime
|
|
manually without using the <b>exec</b> builtin. The
|
|
<b>varredir_close</b> shell option manages this
|
|
behavior.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In the following
|
|
descriptions, if the file descriptor number is omitted, and
|
|
the first character of the redirection operator is
|
|
“<”, the redirection refers to the standard
|
|
input (file descriptor 0). If the first character of the
|
|
redirection operator is “>”, the redirection
|
|
refers to the standard output (file descriptor 1).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <i>word</i>
|
|
following the redirection operator in the following
|
|
descriptions, unless otherwise noted, is subjected to brace
|
|
expansion, tilde expansion, parameter and variable
|
|
expansion, command substitution, arithmetic expansion, quote
|
|
removal, pathname expansion, and word splitting. If it
|
|
expands to more than one word, <b>bash</b> reports an
|
|
error.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The order of
|
|
redirections is significant. For example, the command</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">ls <b>></b>
|
|
dirlist 2<b>>&</b>1</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">directs both
|
|
standard output and standard error to the file
|
|
<i>dirlist</i>, while the command</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">ls
|
|
2<b>>&</b>1 <b>></b> dirlist</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">directs only the
|
|
standard output to file <i>dirlist</i>, because the standard
|
|
error was directed to the standard output before the
|
|
standard output was redirected to <i>dirlist</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
handles several filenames specially when they are used in
|
|
redirections, as described in the following table. If the
|
|
operating system on which <b>bash</b> is running provides
|
|
these special files, <b>bash</b> uses them; otherwise it
|
|
emulates them internally with the behavior described
|
|
below.</p>
|
|
|
|
<p style="margin-left:15%;"><b>/dev/fd/</b><i>fd</i></p>
|
|
|
|
<p style="margin-left:24%;">If <i>fd</i> is a valid
|
|
integer, duplicate file descriptor <i>fd</i>.</p>
|
|
|
|
<p style="margin-left:15%;"><b>/dev/stdin</b></p>
|
|
|
|
<p style="margin-left:24%;">File descriptor 0 is
|
|
duplicated.</p>
|
|
|
|
<p style="margin-left:15%;"><b>/dev/stdout</b></p>
|
|
|
|
<p style="margin-left:24%;">File descriptor 1 is
|
|
duplicated.</p>
|
|
|
|
<p style="margin-left:15%;"><b>/dev/stderr</b></p>
|
|
|
|
<p style="margin-left:24%;">File descriptor 2 is
|
|
duplicated.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>/dev/tcp/</b><i>host</i><b>/</b><i>port</i></p>
|
|
|
|
<p style="margin-left:24%;">If <i>host</i> is a valid
|
|
hostname or Internet address, and <i>port</i> is an integer
|
|
port number or service name, <b>bash</b> attempts to open
|
|
the corresponding TCP socket.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>/dev/udp/</b><i>host</i><b>/</b><i>port</i></p>
|
|
|
|
<p style="margin-left:24%;">If <i>host</i> is a valid
|
|
hostname or Internet address, and <i>port</i> is an integer
|
|
port number or service name, <b>bash</b> attempts to open
|
|
the corresponding UDP socket.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A failure to
|
|
open or create a file causes the redirection to fail.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Redirections
|
|
using file descriptors greater than 9 should be used with
|
|
care, as they may conflict with file descriptors the shell
|
|
uses internally.</p>
|
|
|
|
<h3>Redirecting Input
|
|
<a name="Redirecting Input"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Redirecting
|
|
input opens the file whose name results from the expansion
|
|
of <i>word</i> for reading on file descriptor <i>n</i>, or
|
|
the standard input (file descriptor 0) if <i>n</i> is not
|
|
specified.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The general
|
|
format for redirecting input is:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b><</b><i>word</i></p>
|
|
|
|
<h3>Redirecting Output
|
|
<a name="Redirecting Output"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Redirecting
|
|
output opens the file whose name results from the expansion
|
|
of <i>word</i> for writing on file descriptor <i>n</i>, or
|
|
the standard output (file descriptor 1) if <i>n</i> is not
|
|
specified. If the file does not exist it is created; if it
|
|
does exist it is truncated to zero size.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The general
|
|
format for redirecting output is:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b>></b><i>word</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
redirection operator is <b>></b>, and the
|
|
<b>noclobber</b> option to the <b>set</b> builtin command
|
|
has been enabled, the redirection fails if the file whose
|
|
name results from the expansion of <i>word</i> exists and is
|
|
a regular file. If the redirection operator is <b>>|</b>,
|
|
or the redirection operator is <b>></b> and the
|
|
<b>noclobber</b> option to the <b>set</b> builtin is not
|
|
enabled, <b>bash</b> attempts the redirection even if the
|
|
file named by <i>word</i> exists.</p>
|
|
|
|
<h3>Appending Redirected Output
|
|
<a name="Appending Redirected Output"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Redirecting
|
|
output in this fashion opens the file whose name results
|
|
from the expansion of <i>word</i> for appending on file
|
|
descriptor <i>n</i>, or the standard output (file descriptor
|
|
1) if <i>n</i> is not specified. If the file does not exist
|
|
it is created.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The general
|
|
format for appending output is:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b>>></b><i>word</i></p>
|
|
|
|
<h3>Redirecting Standard Output and Standard Error
|
|
<a name="Redirecting Standard Output and Standard Error"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This construct
|
|
redirects both the standard output (file descriptor 1) and
|
|
the standard error output (file descriptor 2) to the file
|
|
whose name is the expansion of <i>word</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There are two
|
|
formats for redirecting standard output and standard
|
|
error:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>&></b><i>word</i></p>
|
|
|
|
<p style="margin-left:6%;">and</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>>&</b><i>word</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Of the two
|
|
forms, the first is preferred. This is semantically
|
|
equivalent to</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>></b><i>word</i>
|
|
2<b>>&</b>1</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When using the
|
|
second form, <i>word</i> may not expand to a number or
|
|
<b>-</b>. If it does, other redirection operators apply (see
|
|
<b>Duplicating File Descriptors</b> below) for compatibility
|
|
reasons.</p>
|
|
|
|
<h3>Appending Standard Output and Standard Error
|
|
<a name="Appending Standard Output and Standard Error"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This construct
|
|
appends both the standard output (file descriptor 1) and the
|
|
standard error output (file descriptor 2) to the file whose
|
|
name is the expansion of <i>word</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The format for
|
|
appending standard output and standard error is:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>&>></b><i>word</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This is
|
|
semantically equivalent to</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>>></b><i>word</i>
|
|
2<b>>&</b>1</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">(see
|
|
<b>Duplicating File Descriptors</b> below).</p>
|
|
|
|
<h3>Here Documents
|
|
<a name="Here Documents"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This type of
|
|
redirection instructs the shell to read input from the
|
|
current source until it reads a line containing only
|
|
<i>delimiter</i> (with no trailing blanks). All of the lines
|
|
read up to that point then become the standard input (or
|
|
file descriptor <i>n</i> if <i>n</i> is specified) for a
|
|
command.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The format of
|
|
here-documents is:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b><<</b>[<b>-</b>]<i>word
|
|
<br>
|
|
here-document <br>
|
|
delimiter</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell does
|
|
not perform parameter and variable expansion, command
|
|
substitution, arithmetic expansion, or pathname expansion on
|
|
<i>word</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If any part of
|
|
<i>word</i> is quoted, the <i>delimiter</i> is the result of
|
|
quote removal on <i>word</i>, and the lines in the
|
|
here-document are not expanded. If <i>word</i> is unquoted,
|
|
the <i>delimiter</i> is <i>word</i> itself, and the
|
|
here-document text is treated similarly to a double-quoted
|
|
string: all lines of the here-document are subjected to
|
|
parameter expansion, command substitution, and arithmetic
|
|
expansion, the character sequence <b>\<newline></b> is
|
|
treated as a line continuation, and <b>\</b> must be used to
|
|
quote the characters <b>\</b>, <b>$</b>, and <b>`</b>;
|
|
however, double quote characters have no special
|
|
meaning.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
redirection operator is <b><<-</b>, then the shell
|
|
strips all leading tab characters from input lines and the
|
|
line containing <i>delimiter</i>. This allows here-documents
|
|
within shell scripts to be indented in a natural
|
|
fashion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the delimiter
|
|
is not quoted, the shell treats the <b>\<newline></b>
|
|
sequence as a line continuation: the two lines are joined
|
|
and the backslash-newline is removed. This happens while
|
|
reading the here-document, before the check for the ending
|
|
delimiter, so joined lines can form the end delimiter.</p>
|
|
|
|
<h3>Here Strings
|
|
<a name="Here Strings"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A variant of
|
|
here documents, the format is:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b><<<</b><i>word</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <i>word</i>
|
|
undergoes tilde expansion, parameter and variable expansion,
|
|
command substitution, arithmetic expansion, and quote
|
|
removal. Pathname expansion and word splitting are not
|
|
performed. The result is supplied as a single string, with a
|
|
newline appended, to the command on its standard input (or
|
|
file descriptor <i>n</i> if <i>n</i> is specified).</p>
|
|
|
|
<h3>Duplicating File Descriptors
|
|
<a name="Duplicating File Descriptors"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The redirection
|
|
operator</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b><&</b><i>word</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">is used to
|
|
duplicate input file descriptors. If <i>word</i> expands to
|
|
one or more digits, file descriptor <i>n</i> is made to be a
|
|
copy of that file descriptor. It is a redirection error if
|
|
the digits in <i>word</i> do not specify a file descriptor
|
|
open for input. If <i>word</i> evaluates to <b>-</b>, file
|
|
descriptor <i>n</i> is closed. If <i>n</i> is not specified,
|
|
this uses the standard input (file descriptor 0).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The operator</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b>>&</b><i>word</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">is used
|
|
similarly to duplicate output file descriptors. If <i>n</i>
|
|
is not specified, this uses the standard output (file
|
|
descriptor 1). It is a redirection error if the digits in
|
|
<i>word</i> do not specify a file descriptor open for
|
|
output. If <i>word</i> evaluates to <b>-</b>, file
|
|
descriptor <i>n</i> is closed. As a special case, if
|
|
<i>n</i> is omitted, and <i>word</i> does not expand to one
|
|
or more digits or <b>-</b>, this redirects the standard
|
|
output and standard error as described previously.</p>
|
|
|
|
<h3>Moving File Descriptors
|
|
<a name="Moving File Descriptors"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The redirection
|
|
operator</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b><&</b><i>digit</i><b>-</b></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">moves the file
|
|
descriptor <i>digit</i> to file descriptor <i>n</i>, or the
|
|
standard input (file descriptor 0) if <i>n</i> is not
|
|
specified. <i>digit</i> is closed after being duplicated to
|
|
<i>n</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Similarly, the
|
|
redirection operator</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b>>&</b><i>digit</i><b>-</b></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">moves the file
|
|
descriptor <i>digit</i> to file descriptor <i>n</i>, or the
|
|
standard output (file descriptor 1) if <i>n</i> is not
|
|
specified.</p>
|
|
|
|
<h3>Opening File Descriptors for Reading and Writing
|
|
<a name="Opening File Descriptors for Reading and Writing"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The redirection
|
|
operator</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[<i>n</i>]<b><></b><i>word</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">opens the file
|
|
whose name is the expansion of <i>word</i> for both reading
|
|
and writing on file descriptor <i>n</i>, or on file
|
|
descriptor 0 if <i>n</i> is not specified. If the file does
|
|
not exist, it is created.</p>
|
|
|
|
<h2>ALIASES
|
|
<a name="ALIASES"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>Aliases</i>
|
|
allow a string to be substituted for a word that is in a
|
|
position in the input where it can be the first word of a
|
|
simple command. Aliases have names and corresponding values
|
|
that are set and unset using the <b>alias</b> and
|
|
<b>unalias</b> builtin commands (see <b>SHELL BUILTIN
|
|
COMMANDS</b> below).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the shell
|
|
reads an unquoted word in the right position, it checks the
|
|
word to see if it matches an alias name. If it matches, the
|
|
shell replaces the word with the alias value, and reads that
|
|
value as if it had been read instead of the word. The shell
|
|
doesn’t look at any characters following the word
|
|
before attempting alias substitution.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The characters
|
|
<b>/</b>, <b>$</b>, <b>`</b>, and <b>=</b> and any of the
|
|
shell <i>metacharacters</i> or quoting characters listed
|
|
above may not appear in an alias name. The replacement text
|
|
may contain any valid shell input, including shell
|
|
metacharacters. The first word of the replacement text is
|
|
tested for aliases, but a word that is identical to an alias
|
|
being expanded is not expanded a second time. This means
|
|
that one may alias <b>ls</b> to <b>ls -F</b>, for instance,
|
|
and <b>bash</b> does not try to recursively expand the
|
|
replacement text.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the last
|
|
character of the alias value is a <i>blank</i>, the shell
|
|
checks the next command word following the alias for alias
|
|
expansion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Aliases are
|
|
created and listed with the <b>alias</b> command, and
|
|
removed with the <b>unalias</b> command.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There is no
|
|
mechanism for using arguments in the replacement text. If
|
|
arguments are needed, use a shell function (see
|
|
<b>FUNCTIONS</b> below) instead.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Aliases are not
|
|
expanded when the shell is not interactive, unless the
|
|
<b>expand_aliases</b> shell option is set using <b>shopt</b>
|
|
(see the description of <b>shopt</b> under <b>SHELL BUILTIN
|
|
COMMANDS</b> below).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The rules
|
|
concerning the definition and use of aliases are somewhat
|
|
confusing. <b>Bash</b> always reads at least one complete
|
|
line of input, and all lines that make up a compound
|
|
command, before executing any of the commands on that line
|
|
or the compound command. Aliases are expanded when a command
|
|
is read, not when it is executed. Therefore, an alias
|
|
definition appearing on the same line as another command
|
|
does not take effect until the shell reads the next line of
|
|
input, and an alias definition in a compound command does
|
|
not take effect until the shell parses and executes the
|
|
entire compound command. The commands following the alias
|
|
definition on that line, or in the rest of a compound
|
|
command, are not affected by the new alias. This behavior is
|
|
also an issue when functions are executed. Aliases are
|
|
expanded when a function definition is read, not when the
|
|
function is executed, because a function definition is
|
|
itself a command. As a consequence, aliases defined in a
|
|
function are not available until after that function is
|
|
executed. To be safe, always put alias definitions on a
|
|
separate line, and do not use <b>alias</b> in compound
|
|
commands.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">For almost every
|
|
purpose, shell functions are preferable to aliases.</p>
|
|
|
|
<h2>FUNCTIONS
|
|
<a name="FUNCTIONS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A shell
|
|
function, defined as described above under <b>SHELL
|
|
GRAMMAR</b>, stores a series of commands for later
|
|
execution. When the name of a shell function is used as a
|
|
simple command name, the shell executes the list of commands
|
|
associated with that function name. Functions are executed
|
|
in the context of the calling shell; there is no new process
|
|
created to interpret them (contrast this with the execution
|
|
of a shell script).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a function
|
|
is executed, the arguments to the function become the
|
|
positional parameters during its execution. The special
|
|
parameter <b>#</b> is updated to reflect the new positional
|
|
parameters. Special parameter <b>0</b> is unchanged. The
|
|
first element of the <b>FUNCNAME</b> variable is set to the
|
|
name of the function while the function is executing.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">All other
|
|
aspects of the shell execution environment are identical
|
|
between a function and its caller with these exceptions: the
|
|
<b>DEBUG</b> and <b>RETURN</b> traps (see the description of
|
|
the <b>trap</b> builtin under <b>SHELL BUILTIN COMMANDS</b>
|
|
below) are not inherited unless the function has been given
|
|
the <b>trace</b> attribute (see the description of the
|
|
<b>declare</b> builtin below) or the <b>-o functrace</b>
|
|
shell option has been enabled with the <b>set</b> builtin
|
|
(in which case all functions inherit the <b>DEBUG</b> and
|
|
<b>RETURN</b> traps), and the <b>ERR</b> trap is not
|
|
inherited unless the <b>-o errtrace</b> shell option has
|
|
been enabled.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Variables local
|
|
to the function are declared with the <b>local</b> builtin
|
|
command (<i>local variables</i>). Ordinarily, variables and
|
|
their values are shared between the function and its caller.
|
|
If a variable is declared <b>local</b>, the variable’s
|
|
visible scope is restricted to that function and its
|
|
children (including the functions it calls).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In the following
|
|
description, the <i>current scope</i> is a currently-
|
|
executing function. Previous scopes consist of that
|
|
function’s caller and so on, back to the
|
|
“global” scope, where the shell is not executing
|
|
any shell function. A local variable at the current scope is
|
|
a variable declared using the <b>local</b> or <b>declare</b>
|
|
builtins in the function that is currently executing.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Local variables
|
|
“shadow” variables with the same name declared
|
|
at previous scopes. For instance, a local variable declared
|
|
in a function hides variables with the same name declared at
|
|
previous scopes, including global variables: references and
|
|
assignments refer to the local variable, leaving the
|
|
variables at previous scopes unmodified. When the function
|
|
returns, the global variable is once again visible.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell uses
|
|
<i>dynamic scoping</i> to control a variable’s
|
|
visibility within functions. With dynamic scoping, visible
|
|
variables and their values are a result of the sequence of
|
|
function calls that caused execution to reach the current
|
|
function. The value of a variable that a function sees
|
|
depends on its value within its caller, if any, whether that
|
|
caller is the global scope or another shell function. This
|
|
is also the value that a local variable declaration shadows,
|
|
and the value that is restored when the function
|
|
returns.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">For example, if
|
|
a variable <i>var</i> is declared as local in function
|
|
<i>func1</i>, and <i>func1</i> calls another function
|
|
<i>func2</i>, references to <i>var</i> made from within
|
|
<i>func2</i> resolve to the local variable <i>var</i> from
|
|
<i>func1</i>, shadowing any global variable named
|
|
<i>var</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <b>unset</b>
|
|
builtin also acts using the same dynamic scope: if a
|
|
variable is local to the current scope, <b>unset</b> unsets
|
|
it; otherwise the unset will refer to the variable found in
|
|
any calling scope as described above. If a variable at the
|
|
current local scope is unset, it remains so (appearing as
|
|
unset) until it is reset in that scope or until the function
|
|
returns. Once the function returns, any instance of the
|
|
variable at a previous scope becomes visible. If the unset
|
|
acts on a variable at a previous scope, any instance of a
|
|
variable with that name that had been shadowed becomes
|
|
visible (see below how the <b>localvar_unset</b> shell
|
|
option changes this behavior).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The
|
|
<b>FUNCNEST</b> variable, if set to a numeric value greater
|
|
than 0, defines a maximum function nesting level. Function
|
|
invocations that exceed the limit cause the entire command
|
|
to abort.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the builtin
|
|
command <b>return</b> is executed in a function, the
|
|
function completes and execution resumes with the next
|
|
command after the function call. If <b>return</b> is
|
|
supplied a numeric argument, that is the function’s
|
|
return status; otherwise the function’s return status
|
|
is the exit status of the last command executed before the
|
|
<b>return</b>. Any command associated with the <b>RETURN</b>
|
|
trap is executed before execution resumes. When a function
|
|
completes, the values of the positional parameters and the
|
|
special parameter <b>#</b> are restored to the values they
|
|
had prior to the function’s execution.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <b>-f</b>
|
|
option to the <b>declare</b> or <b>typeset</b> builtin
|
|
commands lists function names and definitions. The <b>-F</b>
|
|
option to <b>declare</b> or <b>typeset</b> lists the
|
|
function names only (and optionally the source file and line
|
|
number, if the <b>extdebug</b> shell option is enabled).
|
|
Functions may be exported so that child shell processes
|
|
(those created when executing a separate shell invocation)
|
|
automatically have them defined with the <b>-f</b> option to
|
|
the <b>export</b> builtin. The <b>-f</b> option to the
|
|
<b>unset</b> builtin deletes a function definition.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Functions may be
|
|
recursive. The <b>FUNCNEST</b> variable may be used to limit
|
|
the depth of the function call stack and restrict the number
|
|
of function invocations. By default, <b>bash</b> imposes no
|
|
limit on the number of recursive calls.</p>
|
|
|
|
<h2>ARITHMETIC EVALUATION
|
|
<a name="ARITHMETIC EVALUATION"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell allows
|
|
arithmetic expressions to be evaluated, under certain
|
|
circumstances (see the <b>let</b> and <b>declare</b> builtin
|
|
commands, the <b>((</b> compound command, the arithmetic
|
|
<b>for</b> command, the <b>[[</b> conditional command, and
|
|
<b>Arithmetic Expansion</b>).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Evaluation is
|
|
done in the largest fixed-width integers available, with no
|
|
check for overflow, though division by 0 is trapped and
|
|
flagged as an error. The operators and their precedence,
|
|
associativity, and values are the same as in the C language.
|
|
The following list of operators is grouped into levels of
|
|
equal-precedence operators. The levels are listed in order
|
|
of decreasing precedence. <i><br>
|
|
id</i><b>++</b> <i>id</i><b>--</b></p>
|
|
|
|
<p style="margin-left:15%;">variable post-increment and
|
|
post-decrement</p>
|
|
|
|
<p style="margin-left:6%;"><b>++</b><i>id</i>
|
|
<b>--</b><i>id</i></p>
|
|
|
|
<p style="margin-left:15%;">variable pre-increment and
|
|
pre-decrement</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>- +</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="44%">
|
|
|
|
|
|
<p>unary minus and plus</p></td>
|
|
<td width="41%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>! ~</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="44%">
|
|
|
|
|
|
<p style="margin-top: 1em">logical and bitwise negation</p></td>
|
|
<td width="41%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>**</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="44%">
|
|
|
|
|
|
<p style="margin-top: 1em">exponentiation</p></td>
|
|
<td width="41%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>* / %</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="44%">
|
|
|
|
|
|
<p style="margin-top: 1em">multiplication, division,
|
|
remainder</p> </td>
|
|
<td width="41%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>+ -</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="44%">
|
|
|
|
|
|
<p style="margin-top: 1em">addition, subtraction</p></td>
|
|
<td width="41%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b><< >></b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="44%">
|
|
|
|
|
|
<p style="margin-top: 1em">left and right bitwise
|
|
shifts</p> </td>
|
|
<td width="41%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b><= >= < ></b></p>
|
|
|
|
<p style="margin-left:15%;">comparison</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>== !=</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="29%">
|
|
|
|
|
|
<p>equality and inequality</p></td>
|
|
<td width="56%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>&</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="29%">
|
|
|
|
|
|
<p style="margin-top: 1em">bitwise AND</p></td>
|
|
<td width="56%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>^</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="29%">
|
|
|
|
|
|
<p style="margin-top: 1em">bitwise exclusive OR</p></td>
|
|
<td width="56%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>|</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="29%">
|
|
|
|
|
|
<p style="margin-top: 1em">bitwise OR</p></td>
|
|
<td width="56%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>&&</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="29%">
|
|
|
|
|
|
<p style="margin-top: 1em">logical AND</p></td>
|
|
<td width="56%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>||</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="29%">
|
|
|
|
|
|
<p style="margin-top: 1em">logical OR</p></td>
|
|
<td width="56%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
|
|
<p style="margin-left:6%;"><i>expr</i><b>?</b><i>expr</i><b>:</b><i>expr</i></p>
|
|
|
|
<p style="margin-left:15%;">conditional operator</p>
|
|
|
|
<p style="margin-left:6%;"><b>= *= /= %= += -= <<=
|
|
>>= &= ^= |=</b></p>
|
|
|
|
<p style="margin-left:15%;">assignment</p>
|
|
|
|
<p style="margin-left:6%;"><i>expr1</i> <b>,</b>
|
|
<i>expr2</i></p>
|
|
|
|
<p style="margin-left:15%;">comma</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Shell variables
|
|
are allowed as operands; parameter expansion is performed
|
|
before the expression is evaluated. Within an expression,
|
|
shell variables may also be referenced by name without using
|
|
the parameter expansion syntax. This means you can use
|
|
"x", where <i>x</i> is a shell variable name, in
|
|
an arithmetic expression, and the shell will evaluate its
|
|
value as an expression and use the result. A shell variable
|
|
that is null or unset evaluates to 0 when referenced by name
|
|
in an expression.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The value of a
|
|
variable is evaluated as an arithmetic expression when it is
|
|
referenced, or when a variable which has been given the
|
|
<i>integer</i> attribute using <b>declare -i</b> is assigned
|
|
a value. A null value evaluates to 0. A shell variable need
|
|
not have its <i>integer</i> attribute enabled to be used in
|
|
an expression.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Integer
|
|
constants follow the C language definition, without suffixes
|
|
or character constants. Constants with a leading 0 are
|
|
interpreted as octal numbers. A leading 0x or 0X denotes
|
|
hexadecimal. Otherwise, numbers take the form
|
|
[<i>base#</i>]n, where the optional <i>base</i> is a decimal
|
|
number between 2 and 64 representing the arithmetic base,
|
|
and <i>n</i> is a number in that base. If <i>base#</i> is
|
|
omitted, then base 10 is used. When specifying <i>n</i>, if
|
|
a non-digit is required, the digits greater than 9 are
|
|
represented by the lowercase letters, the uppercase letters,
|
|
@, and _, in that order. If <i>base</i> is less than or
|
|
equal to 36, lowercase and uppercase letters may be used
|
|
interchangeably to represent numbers between 10 and 35.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Operators are
|
|
evaluated in precedence order. Sub-expressions in
|
|
parentheses are evaluated first and may override the
|
|
precedence rules above.</p>
|
|
|
|
<h2>CONDITIONAL EXPRESSIONS
|
|
<a name="CONDITIONAL EXPRESSIONS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Conditional
|
|
expressions are used by the <b>[[</b> compound command and
|
|
the <b>test</b> and <b>[</b> builtin commands to test file
|
|
attributes and perform string and arithmetic comparisons.
|
|
The <b>test</b> and <b>[</b> commands determine their
|
|
behavior based on the number of arguments; see the
|
|
descriptions of those commands for any other
|
|
command-specific actions.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Expressions are
|
|
formed from the unary or binary primaries listed below.
|
|
Unary expressions are often used to examine the status of a
|
|
file or shell variable. Binary operators are used for
|
|
string, numeric, and file attribute comparisons.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
handles several filenames specially when they are used in
|
|
expressions. If the operating system on which <b>bash</b> is
|
|
running provides these special files, bash will use them;
|
|
otherwise it will emulate them internally with this
|
|
behavior: If any <i>file</i> argument to one of the
|
|
primaries is of the form <i>/dev/fd/n</i>, then <b>bash</b>
|
|
checks file descriptor <i>n</i>. If the <i>file</i> argument
|
|
to one of the primaries is one of <i>/dev/stdin</i>,
|
|
<i>/dev/stdout</i>, or <i>/dev/stderr</i>, <b>bash</b>
|
|
checks file descriptor 0, 1, or 2, respectively.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Unless otherwise
|
|
specified, primaries that operate on files follow symbolic
|
|
links and operate on the target of the link, rather than the
|
|
link itself.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When used with
|
|
<b>[[</b>, or when the shell is in posix mode, the
|
|
<b><</b> and <b>></b> operators sort lexicographically
|
|
using the current locale. When the shell is not in posix
|
|
mode, the <b>test</b> command sorts using ASCII ordering.
|
|
<b><br>
|
|
-a</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-b</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is a block special file.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-c</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is a character special file.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-d</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is a directory.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-e</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-f</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is a regular file.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-g</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is set-group-id.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-h</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is a symbolic link.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-k</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
its “sticky” bit is set.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-p</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is a named pipe (FIFO).</p>
|
|
|
|
<p style="margin-left:6%;"><b>-r</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is readable.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-s</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
has a size greater than zero.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>-t</b> <i>fd</i></p></td>
|
|
<td width="2%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p>True if file descriptor <i>fd</i> is open and refers to
|
|
a terminal.</p></td>
|
|
<td width="10%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>-u</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
its set-user-id bit is set.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-w</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is writable.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-x</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is executable.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-G</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is owned by the effective group id.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-L</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is a symbolic link.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-N</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
has been modified since it was last accessed.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-O</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is owned by the effective user id.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-S</b> <i>file</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file</i> exists and
|
|
is a socket.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-o</b> <i>optname</i></p>
|
|
|
|
<p style="margin-left:15%;">True if the shell option
|
|
<i>optname</i> is enabled. See the list of options under the
|
|
description of the <b>-o</b> option to the <b>set</b>
|
|
builtin below.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-v</b> <i>varname</i></p>
|
|
|
|
<p style="margin-left:15%;">True if the shell variable
|
|
<i>varname</i> is set (has been assigned a value). If
|
|
<i>varname</i> is an indexed array variable name subscripted
|
|
by <i>@</i> or <i>*</i>, this returns true if the array has
|
|
any set elements. If <i>varname</i> is an associative array
|
|
variable name subscripted by <i>@</i> or <i>*</i>, this
|
|
returns true if an element with that key is set.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-R</b> <i>varname</i></p>
|
|
|
|
<p style="margin-left:15%;">True if the shell variable
|
|
<i>varname</i> is set and is a name reference.</p>
|
|
|
|
<p style="margin-left:6%;"><b>-z</b> <i>string</i></p>
|
|
|
|
<p style="margin-left:15%;">True if the length of
|
|
<i>string</i> is zero.</p>
|
|
|
|
<p style="margin-left:6%;"><i>string</i> <b><br>
|
|
-n</b> <i>string</i></p>
|
|
|
|
<p style="margin-left:15%;">True if the length of
|
|
<i>string</i> is non-zero.</p>
|
|
|
|
<p style="margin-left:6%;"><i>string1</i> <b>==</b>
|
|
<i>string2 <br>
|
|
string1</i> <b>=</b> <i>string2</i></p>
|
|
|
|
<p style="margin-left:15%;">True if the strings are equal.
|
|
<b>=</b> should be used with the <b>test</b> command for
|
|
POSIX conformance. When used with the <b>[[</b> command,
|
|
this performs pattern matching as described above
|
|
(<b>Compound Commands</b>).</p>
|
|
|
|
<p style="margin-left:6%;"><i>string1</i> <b>!=</b>
|
|
<i>string2</i></p>
|
|
|
|
<p style="margin-left:15%;">True if the strings are not
|
|
equal.</p>
|
|
|
|
<p style="margin-left:6%;"><i>string1</i> <b><</b>
|
|
<i>string2</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>string1</i> sorts
|
|
before <i>string2</i> lexicographically.</p>
|
|
|
|
<p style="margin-left:6%;"><i>string1</i> <b>></b>
|
|
<i>string2</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>string1</i> sorts
|
|
after <i>string2</i> lexicographically.</p>
|
|
|
|
<p style="margin-left:6%;"><i>file1</i> <b>-ef</b>
|
|
<i>file2</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file1</i> and
|
|
<i>file2</i> refer to the same device and inode numbers.</p>
|
|
|
|
<p style="margin-left:6%;"><i>file1</i> -<b>nt</b>
|
|
<i>file2</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file1</i> is newer
|
|
(according to modification date) than <i>file2</i>, or if
|
|
<i>file1</i> exists and <i>file2</i> does not.</p>
|
|
|
|
<p style="margin-left:6%;"><i>file1</i> -<b>ot</b>
|
|
<i>file2</i></p>
|
|
|
|
<p style="margin-left:15%;">True if <i>file1</i> is older
|
|
than <i>file2</i>, or if <i>file2</i> exists and
|
|
<i>file1</i> does not.</p>
|
|
|
|
<p style="margin-left:6%;"><i>arg1</i> <b>OP</b>
|
|
<i>arg2</i></p>
|
|
|
|
<p style="margin-left:15%;"><b>OP</b> is one of <b>-eq</b>,
|
|
<b>-ne</b>, <b>-lt</b>, <b>-le</b>, <b>-gt</b>, or
|
|
<b>-ge</b>. These arithmetic binary operators return true if
|
|
<i>arg1</i> is equal to, not equal to, less than, less than
|
|
or equal to, greater than, or greater than or equal to
|
|
<i>arg2</i>, respectively. <i>arg1</i> and <i>arg2</i> may
|
|
be positive or negative integers. When used with the
|
|
<b>[[</b> command, <i>arg1</i> and <i>arg2</i> are evaluated
|
|
as arithmetic expressions (see <b>ARITHMETIC EVALUATION</b>
|
|
above). Since the expansions the <b>[[</b> command performs
|
|
on <i>arg1</i> and <i>arg2</i> can potentially result in
|
|
empty strings, arithmetic expression evaluation treats those
|
|
as expressions that evaluate to 0.</p>
|
|
|
|
<h2>SIMPLE COMMAND EXPANSION
|
|
<a name="SIMPLE COMMAND EXPANSION"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the shell
|
|
executes a simple command, it performs the following
|
|
expansions, assignments, and redirections, from left to
|
|
right, in the following order.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p>1.</p></td>
|
|
<td width="6%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>The words that the parser has marked as variable
|
|
assignments (those preceding the command name) and
|
|
redirections are saved for later processing.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em">2.</p></td>
|
|
<td width="6%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The words that are not variable
|
|
assignments or redirections are expanded. If any words
|
|
remain after expansion, the first word is taken to be the
|
|
name of the command and the remaining words are the
|
|
arguments.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em">3.</p></td>
|
|
<td width="6%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Redirections are performed as
|
|
described above under <b>REDIRECTION</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em">4.</p></td>
|
|
<td width="6%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The text after the <b>=</b> in
|
|
each variable assignment undergoes tilde expansion,
|
|
parameter expansion, command substitution, arithmetic
|
|
expansion, and quote removal before being assigned to the
|
|
variable.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If no command
|
|
name results, the variable assignments affect the current
|
|
shell environment. In the case of such a command (one that
|
|
consists only of assignment statements and redirections),
|
|
assignment statements are performed before redirections.
|
|
Otherwise, the variables are added to the environment of the
|
|
executed command and do not affect the current shell
|
|
environment. If any of the assignments attempts to assign a
|
|
value to a readonly variable, an error occurs, and the
|
|
command exits with a non-zero status.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If no command
|
|
name results, redirections are performed, but do not affect
|
|
the current shell environment. A redirection error causes
|
|
the command to exit with a non-zero status.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If there is a
|
|
command name left after expansion, execution proceeds as
|
|
described below. Otherwise, the command exits. If one of the
|
|
expansions contained a command substitution, the exit status
|
|
of the command is the exit status of the last command
|
|
substitution performed. If there were no command
|
|
substitutions, the command exits with a zero status.</p>
|
|
|
|
<h2>COMMAND EXECUTION
|
|
<a name="COMMAND EXECUTION"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">After a command
|
|
has been split into words, if it results in a simple command
|
|
and an optional list of arguments, the shell performs the
|
|
following actions.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the command
|
|
name contains no slashes, the shell attempts to locate it.
|
|
If there exists a shell function by that name, that function
|
|
is invoked as described above in <b>FUNCTIONS</b>. If the
|
|
name does not match a function, the shell searches for it in
|
|
the list of shell builtins. If a match is found, that
|
|
builtin is invoked.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the name is
|
|
neither a shell function nor a builtin, and contains no
|
|
slashes, <b>bash</b> searches each element of the
|
|
<b>PATH</b> for a directory containing an executable file by
|
|
that name. <b>Bash</b> uses a hash table to remember the
|
|
full pathnames of executable files (see <b>hash</b> under
|
|
<b>SHELL BUILTIN COMMANDS</b> below). Bash performs a full
|
|
search of the directories in <b>PATH</b> only if the command
|
|
is not found in the hash table. If the search is
|
|
unsuccessful, the shell searches for a defined shell
|
|
function named <b>command_not_found_handle</b>. If that
|
|
function exists, it is invoked in a separate execution
|
|
environment with the original command and the original
|
|
command’s arguments as its arguments, and the
|
|
function’s exit status becomes the exit status of that
|
|
subshell. If that function is not defined, the shell prints
|
|
an error message and returns an exit status of 127.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the search is
|
|
successful, or if the command name contains one or more
|
|
slashes, the shell executes the named program in a separate
|
|
execution environment. Argument 0 is set to the name given,
|
|
and the remaining arguments to the command are set to the
|
|
arguments given, if any.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If this
|
|
execution fails because the file is not in executable
|
|
format, and the file is not a directory, it is assumed to be
|
|
a <i>shell script</i>, a file containing shell commands, and
|
|
the shell creates a new instance of itself to execute it.
|
|
Bash tries to determine whether the file is a text file or a
|
|
binary, and will not execute files it determines to be
|
|
binaries. This subshell reinitializes itself, so that the
|
|
effect is as if a new shell had been invoked to handle the
|
|
script, with the exception that the locations of commands
|
|
remembered by the parent (see <b>hash</b> below under
|
|
<b>SHELL BUILTIN COMMANDS</b> are retained by the child.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the program
|
|
is a file beginning with <b>#!</b>, the remainder of the
|
|
first line specifies an interpreter for the program. The
|
|
shell executes the specified interpreter on operating
|
|
systems that do not handle this executable format
|
|
themselves. The arguments to the interpreter consist of a
|
|
single optional argument following the interpreter name on
|
|
the first line of the program, followed by the name of the
|
|
program, followed by the command arguments, if any.</p>
|
|
|
|
<h2>COMMAND EXECUTION ENVIRONMENT
|
|
<a name="COMMAND EXECUTION ENVIRONMENT"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell has an
|
|
<i>execution environment</i>, which consists of the
|
|
following:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Open files inherited by the
|
|
shell at invocation, as modified by redirections supplied to
|
|
the <b>exec</b> builtin.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The current working directory as
|
|
set by <b>cd</b>, <b>pushd</b>, or <b>popd</b>, or inherited
|
|
by the shell at invocation.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The file creation mode mask as
|
|
set by <b>umask</b> or inherited from the shell’s
|
|
parent.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Current traps set by
|
|
<b>trap</b>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Shell parameters that are set by
|
|
variable assignment or with <b>set</b> or inherited from the
|
|
shell’s parent in the environment.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Shell functions defined during
|
|
execution or inherited from the shell’s parent in the
|
|
environment.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Options enabled at invocation
|
|
(either by default or with command-line arguments) or by
|
|
<b>set</b>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Options enabled by
|
|
<b>shopt</b>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Shell aliases defined with
|
|
<b>alias</b>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Various process IDs, including
|
|
those of background jobs, the value of <b>$$</b>, and the
|
|
value of <b>PPID</b>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a simple
|
|
command other than a builtin or shell function is to be
|
|
executed, it is invoked in a separate execution environment
|
|
that consists of the following. Unless otherwise noted, the
|
|
values are inherited from the shell.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The shell’s open files,
|
|
plus any modifications and additions specified by
|
|
redirections to the command.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The current working
|
|
directory.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The file creation mode mask.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Shell variables and functions
|
|
marked for export, along with variables exported for the
|
|
command, passed in the environment.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Traps caught by the shell are
|
|
reset to the values inherited from the shell’s parent,
|
|
and traps ignored by the shell are ignored.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A command
|
|
invoked in this separate environment cannot affect the
|
|
shell’s execution environment.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">A
|
|
<i>subshell</i> is a copy of the shell process.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Command
|
|
substitution, commands grouped with parentheses, and
|
|
asynchronous commands are invoked in a subshell environment
|
|
that is a duplicate of the shell environment, except that
|
|
traps caught by the shell are reset to the values that the
|
|
shell inherited from its parent at invocation. Builtin
|
|
commands that are invoked as part of a pipeline, except
|
|
possibly in the last element depending on the value of the
|
|
<b>lastpipe</b> shell option, are also executed in a
|
|
subshell environment. Changes made to the subshell
|
|
environment cannot affect the shell’s execution
|
|
environment.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the shell
|
|
is in posix mode, subshells spawned to execute command
|
|
substitutions inherit the value of the <b>-e</b> option from
|
|
their parent shell. When not in posix mode, <b>bash</b>
|
|
clears the <b>-e</b> option in such subshells. See the
|
|
description of the <b>inherit_errexit</b> shell option below
|
|
for how to control this behavior when not in posix mode.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a command is
|
|
followed by a <b>&</b> and job control is not active,
|
|
the default standard input for the command is the empty file
|
|
<i>/dev/null</i>, unless the command has an explicit
|
|
redirection involving the standard input. Otherwise, the
|
|
invoked command inherits the file descriptors of the calling
|
|
shell as modified by redirections.</p>
|
|
|
|
<h2>ENVIRONMENT
|
|
<a name="ENVIRONMENT"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a program
|
|
is invoked it is given an array of strings called the
|
|
<i>environment</i>. This is a list of
|
|
<i>name</i>-<i>value</i> pairs, of the form
|
|
<i>name</i>=<i>value</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell
|
|
provides several ways to manipulate the environment. On
|
|
invocation, the shell scans its own environment and creates
|
|
a parameter for each name found, automatically marking it
|
|
for <i>export</i> to child processes. Executed commands
|
|
inherit the environment. The <b>export</b>, <b>declare
|
|
-x</b>, and <b>unset</b> commands modify the environment by
|
|
adding and deleting parameters and functions. If the value
|
|
of a parameter in the environment is modified, the new value
|
|
automatically becomes part of the environment, replacing the
|
|
old. The environment inherited by any executed command
|
|
consists of the shell’s initial environment, whose
|
|
values may be modified in the shell, less any pairs removed
|
|
by the <b>unset</b> or <b>export -n</b> commands, plus any
|
|
additions via the <b>export</b> and <b>declare -x</b>
|
|
commands.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If any parameter
|
|
assignments, as described above in <b>PARAMETERS</b>, appear
|
|
before a <i>simple command</i>, the variable assignments are
|
|
part of that command’s environment for as long as it
|
|
executes. These assignment statements affect only the
|
|
environment seen by that command. If these assignments
|
|
precede a call to a shell function, the variables are local
|
|
to the function and exported to that function’s
|
|
children.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the <b>-k</b>
|
|
option is set (see the <b>set</b> builtin command below),
|
|
then <i>all</i> parameter assignments are placed in the
|
|
environment for a command, not just those that precede the
|
|
command name.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When <b>bash</b>
|
|
invokes an external command, the variable <b>_</b> is set to
|
|
the full pathname of the command and passed to that command
|
|
in its environment.</p>
|
|
|
|
<h2>EXIT STATUS
|
|
<a name="EXIT STATUS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The exit status
|
|
of an executed command is the value returned by the
|
|
<i>waitpid</i> system call or equivalent function. Exit
|
|
statuses fall between 0 and 255, though, as explained below,
|
|
the shell may use values above 125 specially. Exit statuses
|
|
from shell builtins and compound commands are also limited
|
|
to this range. Under certain circumstances, the shell will
|
|
use special values to indicate specific failure modes.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">For the
|
|
shell’s purposes, a command which exits with a zero
|
|
exit status has succeeded. So while an exit status of zero
|
|
indicates success, a non-zero exit status indicates
|
|
failure.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a command
|
|
terminates on a fatal signal <i>N</i>, <b>bash</b> uses the
|
|
value of 128+<i>N</i> as the exit status.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a command is
|
|
not found, the child process created to execute it returns a
|
|
status of 127. If a command is found but is not executable,
|
|
the return status is 126.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a command
|
|
fails because of an error during expansion or redirection,
|
|
the exit status is greater than zero.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Shell builtin
|
|
commands return a status of 0 (<i>true</i>) if successful,
|
|
and non-zero (<i>false</i>) if an error occurs while they
|
|
execute. All builtins return an exit status of 2 to indicate
|
|
incorrect usage, generally invalid options or missing
|
|
arguments.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The exit status
|
|
of the last command is available in the special parameter
|
|
$?.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
itself returns the exit status of the last command executed,
|
|
unless a syntax error occurs, in which case it exits with a
|
|
non-zero value. See also the <b>exit</b> builtin command
|
|
below.</p>
|
|
|
|
<h2>SIGNALS
|
|
<a name="SIGNALS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When <b>bash</b>
|
|
is interactive, in the absence of any traps, it ignores
|
|
<b>SIGTERM</b> (so that <b>kill 0</b> does not kill an
|
|
interactive shell), and catches and handles <b>SIGINT</b>
|
|
(so that the <b>wait</b> builtin is interruptible). When
|
|
<b>bash</b> receives <b>SIGINT</b>, it breaks out of any
|
|
executing loops and command lists. In all cases, <b>bash</b>
|
|
ignores <b>SIGQUIT</b>. If job control is in effect,
|
|
<b>bash</b> ignores <b>SIGTTIN</b>, <b>SIGTTOU</b>, and
|
|
<b>SIGTSTP</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <b>trap</b>
|
|
builtin modifies the shell’s signal handling, as
|
|
described below.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Non-builtin
|
|
commands <b>bash</b> executes have signal handlers set to
|
|
the values inherited by the shell from its parent, unless
|
|
<b>trap</b> sets them to be ignored, in which case the child
|
|
process will ignore them as well. When job control is not in
|
|
effect, asynchronous commands ignore <b>SIGINT</b> and
|
|
<b>SIGQUIT</b> in addition to these inherited handlers.
|
|
Commands run as a result of command substitution ignore the
|
|
keyboard-generated job control signals <b>SIGTTIN</b>,
|
|
<b>SIGTTOU</b>, and <b>SIGTSTP</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell exits
|
|
by default upon receipt of a <b>SIGHUP</b>. Before exiting,
|
|
an interactive shell resends the <b>SIGHUP</b> to all jobs,
|
|
running or stopped. The shell sends <b>SIGCONT</b> to
|
|
stopped jobs to ensure that they receive the <b>SIGHUP</b>
|
|
(see <b>JOB CONTROL</b> below for more information about
|
|
running and stopped jobs). To prevent the shell from sending
|
|
the signal to a particular job, remove it from the jobs
|
|
table with the <b>disown</b> builtin (see <b>SHELL BUILTIN
|
|
COMMANDS</b> below) or mark it not to receive <b>SIGHUP</b>
|
|
using <b>disown -h</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
<b>huponexit</b> shell option has been set using
|
|
<b>shopt</b>, <b>bash</b> sends a <b>SIGHUP</b> to all jobs
|
|
when an interactive login shell exits.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If <b>bash</b>
|
|
is waiting for a command to complete and receives a signal
|
|
for which a trap has been set, it will not execute the trap
|
|
until the command completes. If <b>bash</b> is waiting for
|
|
an asynchronous command via the <b>wait</b> builtin, and it
|
|
receives a signal for which a trap has been set, the
|
|
<b>wait</b> builtin will return immediately with an exit
|
|
status greater than 128, immediately after which the shell
|
|
executes the trap.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When job control
|
|
is not enabled, and <b>bash</b> is waiting for a foreground
|
|
command to complete, the shell receives keyboard-generated
|
|
signals such as <b>SIGINT</b> (usually generated by
|
|
<b>^C</b>) that users commonly intend to send to that
|
|
command. This happens because the shell and the command are
|
|
in the same process group as the terminal, and <b>^C</b>
|
|
sends <b>SIGINT</b> to all processes in that process group.
|
|
Since <b>bash</b> does not enable job control by default
|
|
when the shell is not interactive, this scenario is most
|
|
common in non-interactive shells.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When job control
|
|
is enabled, and <b>bash</b> is waiting for a foreground
|
|
command to complete, the shell does not receive
|
|
keyboard-generated signals, because it is not in the same
|
|
process group as the terminal. This scenario is most common
|
|
in interactive shells, where <b>bash</b> attempts to enable
|
|
job control by default. See <b>JOB CONTROL</b> below for
|
|
more information about process groups.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When job control
|
|
is not enabled, and <b>bash</b> receives <b>SIGINT</b> while
|
|
waiting for a foreground command, it waits until that
|
|
foreground command terminates and then decides what to do
|
|
about the <b>SIGINT</b>:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em">1.</p></td>
|
|
<td width="6%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the command terminates due to
|
|
the <b>SIGINT</b>, <b>bash</b> concludes that the user meant
|
|
to send the <b>SIGINT</b> to the shell as well, and acts on
|
|
the <b>SIGINT</b> (e.g., by running a <b>SIGINT</b> trap,
|
|
exiting a non-interactive shell, or returning to the top
|
|
level to read a new command).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em">2.</p></td>
|
|
<td width="6%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the command does not
|
|
terminate due to <b>SIGINT</b>, the program handled the
|
|
<b>SIGINT</b> itself and did not treat it as a fatal signal.
|
|
In that case, <b>bash</b> does not treat <b>SIGINT</b> as a
|
|
fatal signal, either, instead assuming that the
|
|
<b>SIGINT</b> was used as part of the program’s normal
|
|
operation (e.g., emacs uses it to abort editing commands) or
|
|
deliberately discarded. However, <b>bash</b> will run any
|
|
trap set on <b>SIGINT</b>, as it does with any other trapped
|
|
signal it receives while it is waiting for the foreground
|
|
command to complete, for compatibility.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When job control
|
|
is enabled, <b>bash</b> does not receive keyboard-generated
|
|
signals such as <b>SIGINT</b> while it is waiting for a
|
|
foreground command. An interactive shell does not pay
|
|
attention to the <b>SIGINT</b>, even if the foreground
|
|
command terminates as a result, other than noting its exit
|
|
status. If the shell is not interactive, and the foreground
|
|
command terminates due to the <b>SIGINT</b>, <b>bash</b>
|
|
pretends it received the <b>SIGINT</b> itself (scenario 1
|
|
above), for compatibility.</p>
|
|
|
|
<h2>JOB CONTROL
|
|
<a name="JOB CONTROL"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>Job
|
|
control</i> refers to the ability to selectively stop
|
|
(<i>suspend</i>) the execution of processes and continue
|
|
(<i>resume</i>) their execution at a later point. A user
|
|
typically employs this facility via an interactive interface
|
|
supplied jointly by the operating system kernel’s
|
|
terminal driver and <b>bash</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell
|
|
associates a <i>job</i> with each pipeline. It keeps a table
|
|
of currently executing jobs, which the <b>jobs</b> command
|
|
will display. Each job has a <i>job number</i>, which
|
|
<b>jobs</b> displays between brackets. Job numbers start at
|
|
1. When <b>bash</b> starts a job asynchronously (in the
|
|
<i>background</i>), it prints a line that looks like:</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">[1] 25647</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">indicating that
|
|
this job is job number 1 and that the process ID of the last
|
|
process in the pipeline associated with this job is 25647.
|
|
All of the processes in a single pipeline are members of the
|
|
same job. <b>Bash</b> uses the <i>job</i> abstraction as the
|
|
basis for job control.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">To facilitate
|
|
the implementation of the user interface to job control,
|
|
each process has a <i>process group ID</i>, and the
|
|
operating system maintains the notion of a <i>current
|
|
terminal process group ID</i>. This terminal process group
|
|
ID is associated with the <i>controlling terminal</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Processes that
|
|
have the same process group ID are said to be part of the
|
|
same <i>process group</i>. Members of the <i>foreground</i>
|
|
process group (processes whose process group ID is equal to
|
|
the current terminal process group ID) receive
|
|
keyboard-generated signals such as <b>SIGINT</b>. Processes
|
|
in the foreground process group are said to be
|
|
<i>foreground</i> processes. <i>Background</i> processes are
|
|
those whose process group ID differs from the controlling
|
|
terminal’s; such processes are immune to
|
|
keyboard-generated signals. Only foreground processes are
|
|
allowed to read from or, if the user so specifies with
|
|
“stty tostop”, write to the controlling
|
|
terminal. The system sends a <b>SIGTTIN (SIGTTOU)</b> signal
|
|
to background processes which attempt to read from (write to
|
|
when “tostop” is in effect) the terminal, which,
|
|
unless caught, suspends the process.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the operating
|
|
system on which <b>bash</b> is running supports job control,
|
|
<b>bash</b> contains facilities to use it. Typing the
|
|
<i>suspend</i> character (typically <b>^Z</b>, Control-Z)
|
|
while a process is running stops that process and returns
|
|
control to <b>bash</b>. Typing the <i>delayed suspend</i>
|
|
character (typically <b>^Y</b>, Control-Y) causes the
|
|
process stop when it attempts to read input from the
|
|
terminal, and returns control to <b>bash</b>. The user then
|
|
manipulates the state of this job, using the <b>bg</b>
|
|
command to continue it in the background, the <b>fg</b>
|
|
command to continue it in the foreground, or the <b>kill</b>
|
|
command to kill it. The suspend character takes effect
|
|
immediately, and has the additional side effect of
|
|
discarding any pending output and typeahead. To force a
|
|
background process to stop, or stop a process that’s
|
|
not associated with the current terminal session, send it
|
|
the <b>SIGSTOP</b> signal using <b>kill</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There are a
|
|
number of ways to refer to a job in the shell. The <b>%</b>
|
|
character introduces a job specification (jobspec).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Job number
|
|
<i>n</i> may be referred to as <b>%n</b>. A job may also be
|
|
referred to using a prefix of the name used to start it, or
|
|
using a substring that appears in its command line. For
|
|
example, <b>%ce</b> refers to a job whose command name
|
|
begins with <b>ce</b>. Using <b>%?ce</b>, on the other hand,
|
|
refers to any job containing the string <b>ce</b> in its
|
|
command line. If the prefix or substring matches more than
|
|
one job, <b>bash</b> reports an error.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The symbols
|
|
<b>%%</b> and <b>%+</b> refer to the shell’s notion of
|
|
the <i>current job</i>. A single % (with no accompanying job
|
|
specification) also refers to the current job. <b>%-</b>
|
|
refers to the <i>previous job</i>. When a job starts in the
|
|
background, a job stops while in the foreground, or a job is
|
|
resumed in the background, it becomes the current job. The
|
|
job that was the current job becomes the previous job. When
|
|
the current job terminates, the previous job becomes the
|
|
current job. If there is only a single job, <b>%+</b> and
|
|
<b>%-</b> can both be used to refer to that job. In output
|
|
pertaining to jobs (e.g., the output of the <b>jobs</b>
|
|
command), the current job is always marked with a <b>+</b>,
|
|
and the previous job with a <b>-</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Simply naming a
|
|
job can be used to bring it into the foreground: <b>%1</b>
|
|
is a synonym for “fg %1”, bringing job 1 from
|
|
the background into the foreground. Similarly, “%1
|
|
&” resumes job 1 in the background, equivalent to
|
|
“bg %1”.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell learns
|
|
immediately whenever a job changes state. Normally,
|
|
<b>bash</b> waits until it is about to print a prompt before
|
|
notifying the user about changes in a job’s status so
|
|
as to not interrupt any other output, though it will notify
|
|
of changes in a job’s status after a foreground
|
|
command in a list completes, before executing the next
|
|
command in the list. If the <b>-b</b> option to the
|
|
<b>set</b> builtin command is enabled, <b>bash</b> reports
|
|
status changes immediately. <b>Bash</b> executes any trap on
|
|
<b>SIGCHLD</b> for each child that terminates.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a job
|
|
terminates and <b>bash</b> notifies the user about it,
|
|
<b>bash</b> removes the job from the table. It will not
|
|
appear in <b>jobs</b> output, but <b>wait</b> will report
|
|
its exit status, as long as it’s supplied the process
|
|
ID associated with the job as an argument. When the table is
|
|
empty, job numbers start over at 1.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a user
|
|
attempts to exit <b>bash</b> while jobs are stopped (or, if
|
|
the <b>checkjobs</b> shell option has been enabled using the
|
|
<b>shopt</b> builtin, running), the shell prints a warning
|
|
message, and, if the <b>checkjobs</b> option is enabled,
|
|
lists the jobs and their statuses. The <b>jobs</b> command
|
|
may then be used to inspect their status. If the user
|
|
immediately attempts to exit again, without an intervening
|
|
command, <b>bash</b> does not print another warning, and
|
|
terminates any stopped jobs.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the shell
|
|
is waiting for a job or process using the <b>wait</b>
|
|
builtin, and job control is enabled, <b>wait</b> will return
|
|
when the job changes state. The <b>-f</b> option causes
|
|
<b>wait</b> to wait until the job or process terminates
|
|
before returning.</p>
|
|
|
|
<h2>PROMPTING
|
|
<a name="PROMPTING"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When executing
|
|
interactively, <b>bash</b> displays the primary prompt
|
|
<b>PS1</b> when it is ready to read a command, and the
|
|
secondary prompt <b>PS2</b> when it needs more input to
|
|
complete a command.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
examines the value of the array variable
|
|
<b>PROMPT_COMMAND</b> just before printing each primary
|
|
prompt. If any elements in <b>PROMPT_COMMAND</b> are set and
|
|
non-null, Bash executes each value, in numeric order, just
|
|
as if it had been typed on the command line. <b>Bash</b>
|
|
displays <b>PS0</b> after it reads a command but before
|
|
executing it.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
displays <b>PS4</b> as described above before tracing each
|
|
command when the <b>-x</b> option is enabled.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b>
|
|
allows the prompt strings <b>PS0</b>, <b>PS1</b>,
|
|
<b>PS2</b>, and <b>PS4</b>, to be customized by inserting a
|
|
number of backslash-escaped special characters that are
|
|
decoded as follows:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\a</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">An ASCII bell character
|
|
(07).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\d</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The date in “Weekday Month
|
|
Date” format (e.g., “Tue May 26”).</p></td></tr>
|
|
</table>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>\D{</b><i>format</i><b>}</b></p>
|
|
|
|
<p style="margin-left:24%;">The <i>format</i> is passed to
|
|
<i>strftime</i>(3) and the result is inserted into the
|
|
prompt string; an empty <i>format</i> results in a
|
|
locale-specific time representation. The braces are
|
|
required.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>\e</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>An ASCII escape character (033).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\h</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The hostname up to the first
|
|
“.”.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\H</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The hostname.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\j</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The number of jobs currently
|
|
managed by the shell.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\l</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The basename of the
|
|
shell’s terminal device name (e.g.,
|
|
“ttys0”).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\n</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">A newline.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\r</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">A carriage return.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\s</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The name of the shell: the
|
|
basename of <b>$0</b> (the portion following the final
|
|
slash).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\t</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The current time in 24-hour
|
|
HH:MM:SS format.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\T</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The current time in 12-hour
|
|
HH:MM:SS format.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\@</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The current time in 12-hour
|
|
am/pm format.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\A</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The current time in 24-hour
|
|
HH:MM format.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\u</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The username of the current
|
|
user.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\v</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The <b>bash</b> version (e.g.,
|
|
2.00).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\V</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The <b>bash</b> release, version
|
|
+ patch level (e.g., 2.00.0)</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\w</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The value of the <b>PWD</b>
|
|
shell variable (<b>$PWD</b>), with <b>$HOME</b> abbreviated
|
|
with a tilde (uses the value of the <b>PROMPT_DIRTRIM</b>
|
|
variable).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\W</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The basename of <b>$PWD</b>,
|
|
with <b>$HOME</b> abbreviated with a tilde.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\!</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The history number of this
|
|
command.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\#</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The command number of this
|
|
command.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\$</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the effective UID is 0, a
|
|
<b>#</b>, otherwise a <b>$</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\</b><i>nnn</i></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The character corresponding to
|
|
the octal number <i>nnn</i>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\\</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">A backslash.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\[</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Begin a sequence of non-printing
|
|
characters, which could be used to embed a terminal control
|
|
sequence into the prompt. This escape is only useful when
|
|
the prompt will be supplied to <b>readline</b>, and is
|
|
ignored and removed otherwise, so it shouldn’t be used
|
|
in <b>PS0</b> or <b>PS4</b> or when line editing is not
|
|
enabled.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\]</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">End a sequence of non-printing
|
|
characters begun with <b>\[</b>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The command
|
|
number and the history number are usually different: the
|
|
history number of a command is its position in the history
|
|
list, which may include commands restored from the history
|
|
file (see <b>HISTORY</b> below), while the command number is
|
|
the position in the sequence of commands executed during the
|
|
current shell session. After the string is decoded, it is
|
|
expanded via parameter expansion, command substitution,
|
|
arithmetic expansion, and quote removal, subject to the
|
|
value of the <b>promptvars</b> shell option (see the
|
|
description of the <b>shopt</b> command under <b>SHELL
|
|
BUILTIN COMMANDS</b> below). This can have unwanted side
|
|
effects if escaped portions of the string appear within
|
|
command substitution or contain characters special to word
|
|
expansion.</p>
|
|
|
|
<h2>READLINE
|
|
<a name="READLINE"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This is the
|
|
library that handles reading input when using an interactive
|
|
shell, unless the <b>--noediting</b> option is supplied at
|
|
shell invocation. Line editing is also used when using the
|
|
<b>-e</b> option to the <b>read</b> builtin. By default, the
|
|
line editing commands are similar to those of emacs; a
|
|
vi-style line editing interface is also available. Line
|
|
editing can be enabled at any time using the <b>-o emacs</b>
|
|
or <b>-o vi</b> options to the <b>set</b> builtin (see
|
|
<b>SHELL BUILTIN COMMANDS</b> below). To turn off line
|
|
editing after the shell is running, use the <b>+o emacs</b>
|
|
or <b>+o vi</b> options to the <b>set</b> builtin.</p>
|
|
|
|
<h3>Readline Notation
|
|
<a name="Readline Notation"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This section
|
|
uses Emacs-style editing concepts and uses its notation for
|
|
keystrokes. Control keys are denoted by C-<i>key</i>, e.g.,
|
|
C-n means Control-N. Similarly, <i>meta</i> keys are denoted
|
|
by M-<i>key</i>, so M-x means Meta-X. The Meta key is often
|
|
labeled “Alt” or “Option”.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">On keyboards
|
|
without a <i>Meta</i> key, M-<i>x</i> means ESC <i>x</i>,
|
|
i.e., press and release the Escape key, then press and
|
|
release the <i>x</i> key, in sequence. This makes ESC the
|
|
<i>meta prefix</i>. The combination M-C-<i>x</i> means ESC
|
|
Control-<i>x</i>: press and release the Escape key, then
|
|
press and hold the Control key while pressing the <i>x</i>
|
|
key, then release both.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">On some
|
|
keyboards, the Meta key modifier produces characters with
|
|
the eighth bit (0200) set. You can use the
|
|
<b>enable-meta-key</b> variable to control whether or not it
|
|
does this, if the keyboard allows it. On many others, the
|
|
terminal or terminal emulator converts the metafied key to a
|
|
key sequence beginning with ESC as described in the
|
|
preceding paragraph.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If your
|
|
<i>Meta</i> key produces a key sequence with the ESC meta
|
|
prefix, you can make M-<i>key</i> key bindings you specify
|
|
(see <b>Readline Key Bindings</b> below) do the same thing
|
|
by setting the <b>force-meta-prefix</b> variable.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Readline</b>
|
|
commands may be given numeric <i>arguments</i>, which
|
|
normally act as a repeat count. Sometimes, however, it is
|
|
the sign of the argument that is significant. Passing a
|
|
negative argument to a command that acts in the forward
|
|
direction (e.g., <b>kill-line</b>) makes that command act in
|
|
a backward direction. Commands whose behavior with arguments
|
|
deviates from this are noted below.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <i>point</i>
|
|
is the current cursor position, and <i>mark</i> refers to a
|
|
saved cursor position. The text between the point and mark
|
|
is referred to as the <i>region</i>. <b>Readline</b> has the
|
|
concept of an <i>active region</i>: when the region is
|
|
active, <b>readline</b> redisplay highlights the region
|
|
using the value of the <b>active-region-start-color</b>
|
|
variable. The <b>enable-active-region</b> variable turns
|
|
this on and off. Several commands set the region to active;
|
|
those are noted below.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a command
|
|
is described as <i>killing</i> text, the text deleted is
|
|
saved for possible future retrieval (<i>yanking</i>). The
|
|
killed text is saved in a <i>kill ring</i>. Consecutive
|
|
kills accumulate the deleted text into one unit, which can
|
|
be yanked all at once. Commands which do not kill text
|
|
separate the chunks of text on the kill ring.</p>
|
|
|
|
<h3>Readline Initialization
|
|
<a name="Readline Initialization"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Readline</b>
|
|
is customized by putting commands in an initialization file
|
|
(the <i>inputrc</i> file). The name of this file is taken
|
|
from the value of the <b>INPUTRC</b> shell variable. If that
|
|
variable is unset, the default is <A HREF="file:~/.inputrc"><i>~/.inputrc</i></A>. If that
|
|
file does not exist or cannot be read, <b>readline</b> looks
|
|
for <A HREF="file:/etc/inputrc"><i>/etc/inputrc</i></A>. When a program that uses the
|
|
<b>readline</b> library starts up, <b>readline</b> reads the
|
|
initialization file and sets the key bindings and variables
|
|
found there, before reading any user input.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There are only a
|
|
few basic constructs allowed in the inputrc file. Blank
|
|
lines are ignored. Lines beginning with a <b>#</b> are
|
|
comments. Lines beginning with a <b>$</b> indicate
|
|
conditional constructs. Other lines denote key bindings and
|
|
variable settings.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The default
|
|
key-bindings in this section may be changed using key
|
|
binding commands in the <i>inputrc</i> file. Programs that
|
|
use the <b>readline</b> library, including <b>bash</b>, may
|
|
add their own commands and bindings.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">For example,
|
|
placing</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">M-Control-u:
|
|
universal-argument</p>
|
|
|
|
<p style="margin-left:6%;">or</p>
|
|
|
|
<p style="margin-left:15%;">C-Meta-u:
|
|
universal-argument</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">into the
|
|
<i>inputrc</i> would make M-C-u execute the <b>readline</b>
|
|
command <i>universal-argument</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Key bindings may
|
|
contain the following symbolic character names: <i>DEL</i>,
|
|
<i>ESC</i>, <i>ESCAPE</i>, <i>LFD</i>, <i>NEWLINE</i>,
|
|
<i>RET</i>, <i>RETURN</i>, <i>RUBOUT</i> (a destructive
|
|
backspace), <i>SPACE</i>, <i>SPC</i>, and <i>TAB</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In addition to
|
|
command names, <b>readline</b> allows keys to be bound to a
|
|
string that is inserted when the key is pressed (a
|
|
<i>macro</i>). The difference between a macro and a command
|
|
is that a macro is enclosed in single or double quotes.</p>
|
|
|
|
<h3>Readline Key Bindings
|
|
<a name="Readline Key Bindings"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The syntax for
|
|
controlling key bindings in the <i>inputrc</i> file is
|
|
simple. All that is required is the name of the command or
|
|
the text of a macro and a key sequence to which it should be
|
|
bound. The key sequence may be specified in one of two ways:
|
|
as a symbolic key name, possibly with <i>Meta-</i> or
|
|
<i>Control-</i> prefixes, or as a key sequence composed of
|
|
one or more characters enclosed in double quotes. The key
|
|
sequence and name are separated by a colon. There can be no
|
|
whitespace between the name and the colon.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When using the
|
|
form <b>keyname</b>:<i>function-name</i> or <i>macro</i>,
|
|
<i>keyname</i> is the name of a key spelled out in English.
|
|
For example:</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Control-u:
|
|
universal-argument <br>
|
|
Meta-Rubout: backward-kill-word <br>
|
|
Control-o: "> output"</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In the above
|
|
example, <i>C-u</i> is bound to the function
|
|
<b>universal-argument</b>, <i>M-DEL</i> is bound to the
|
|
function <b>backward-kill-word</b>, and <i>C-o</i> is bound
|
|
to run the macro expressed on the right hand side (that is,
|
|
to insert the text “> output” into the
|
|
line).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In the second
|
|
form, <b>"keyseq"</b>:<i>function-name</i> or
|
|
<i>macro</i>, <b>keyseq</b> differs from <b>keyname</b>
|
|
above in that strings denoting an entire key sequence may be
|
|
specified by placing the sequence within double quotes. Some
|
|
GNU Emacs style key escapes can be used, as in the following
|
|
example, but none of the symbolic character names are
|
|
recognized.</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">"\C-u":
|
|
universal-argument <br>
|
|
"\C-x\C-r": re-read-init-file <br>
|
|
"\e[11~": "Function Key 1"</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In this example,
|
|
<i>C-u</i> is again bound to the function
|
|
<b>universal-argument</b>. <i>C-x C-r</i> is bound to the
|
|
function <b>re-read-init-file</b>, and <i>ESC [ 1 1 ~</i> is
|
|
bound to insert the text “Function Key 1”.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The full set of
|
|
GNU Emacs style escape sequences available when specifying
|
|
key sequences is</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\C-</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">A control prefix.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\M-</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Adding the meta prefix or
|
|
converting the following character to a meta character, as
|
|
described below under <b>force-meta-prefix</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\e</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">An escape character.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\\</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Backslash.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\"</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Literal ", a double
|
|
quote.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\'</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Literal ', a single quote.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In addition to
|
|
the GNU Emacs style escape sequences, a second set of
|
|
backslash escapes is available:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\a</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">alert (bell)</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\b</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">backspace</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\d</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">delete</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\f</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">form feed</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\n</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">newline</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\r</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">carriage return</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\t</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">horizontal tab</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\v</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">vertical tab</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\</b><i>nnn</i></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The eight-bit character whose
|
|
value is the octal value <i>nnn</i> (one to three
|
|
digits).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\x</b><i>HH</i></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The eight-bit character whose
|
|
value is the hexadecimal value <i>HH</i> (one or two hex
|
|
digits).</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When entering
|
|
the text of a macro, single or double quotes must be used to
|
|
indicate a macro definition. Unquoted text is assumed to be
|
|
a function name. The backslash escapes described above are
|
|
expanded in the macro body. Backslash quotes any other
|
|
character in the macro text, including " and '.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Bash</b> will
|
|
display or modify the current <b>readline</b> key bindings
|
|
with the <b>bind</b> builtin command. The <b>-o emacs</b> or
|
|
<b>-o vi</b> options to the <b>set</b> builtin (see <b>SHELL
|
|
BUILTIN COMMANDS</b> below) change the editing mode during
|
|
interactive use.</p>
|
|
|
|
<h3>Readline Variables
|
|
<a name="Readline Variables"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Readline</b>
|
|
has variables that can be used to further customize its
|
|
behavior. A variable may be set in the <i>inputrc</i> file
|
|
with a statement of the form</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>set</b>
|
|
<i>variable-name value</i></p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">or using the
|
|
<b>bind</b> builtin command (see <b>SHELL BUILTIN
|
|
COMMANDS</b> below).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Except where
|
|
noted, <b>readline</b> variables can take the values
|
|
<b>On</b> or <b>Off</b> (without regard to case).
|
|
Unrecognized variable names are ignored. When
|
|
<b>readline</b> reads a variable value, empty or null
|
|
values, “on” (case-insensitive), and
|
|
“1” are equivalent to <b>On</b>. All other
|
|
values are equivalent to <b>Off</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <b>bind
|
|
-V</b> command lists the current <b>readline</b> variable
|
|
names and values (see <b>SHELL BUILTIN COMMANDS</b>
|
|
below).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The variables
|
|
and their default values are: <b><br>
|
|
active-region-start-color</b></p>
|
|
|
|
<p style="margin-left:15%;">A string variable that controls
|
|
the text color and background when displaying the text in
|
|
the active region (see the description of
|
|
<b>enable-active-region</b> below). This string must not
|
|
take up any physical character positions on the display, so
|
|
it should consist only of terminal escape sequences. It is
|
|
output to the terminal before displaying the text in the
|
|
active region. This variable is reset to the default value
|
|
whenever the terminal type changes. The default value is the
|
|
string that puts the terminal in standout mode, as obtained
|
|
from the terminal’s terminfo description. A sample
|
|
value might be “\e[01;33m”.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>active-region-end-color</b></p>
|
|
|
|
<p style="margin-left:15%;">A string variable that
|
|
“undoes” the effects of
|
|
<b>active-region-start-color</b> and restores
|
|
“normal” terminal display appearance after
|
|
displaying text in the active region. This string must not
|
|
take up any physical character positions on the display, so
|
|
it should consist only of terminal escape sequences. It is
|
|
output to the terminal after displaying the text in the
|
|
active region. This variable is reset to the default value
|
|
whenever the terminal type changes. The default value is the
|
|
string that restores the terminal from standout mode, as
|
|
obtained from the terminal’s terminfo description. A
|
|
sample value might be “\e[0m”.</p>
|
|
|
|
<p style="margin-left:6%;"><b>bell-style (audible)</b></p>
|
|
|
|
<p style="margin-left:15%;">Controls what happens when
|
|
<b>readline</b> wants to ring the terminal bell. If set to
|
|
<b>none</b>, <b>readline</b> never rings the bell. If set to
|
|
<b>visible</b>, <b>readline</b> uses a visible bell if one
|
|
is available. If set to <b>audible</b>, <b>readline</b>
|
|
attempts to ring the terminal’s bell.</p>
|
|
|
|
<p style="margin-left:6%;"><b>bind-tty-special-chars
|
|
(On)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> attempts to bind the control characters that
|
|
are treated specially by the kernel’s terminal driver
|
|
to their <b>readline</b> equivalents. These override the
|
|
default <b>readline</b> bindings described here. Type
|
|
“stty -a” at a <b>bash</b> prompt to see your
|
|
current terminal settings, including the special control
|
|
characters (usually <b>cchars</b>). This binding takes place
|
|
on each call to <b>readline</b>, so changes made by
|
|
“stty” can take effect.</p>
|
|
|
|
<p style="margin-left:6%;"><b>blink-matching-paren
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> attempts to briefly move the cursor to an
|
|
opening parenthesis when a closing parenthesis is
|
|
inserted.</p>
|
|
|
|
<p style="margin-left:6%;"><b>colored-completion-prefix
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, when
|
|
listing completions, <b>readline</b> displays the common
|
|
prefix of the set of possible completions using a different
|
|
color. The color definitions are taken from the value of the
|
|
<b>LS_COLORS</b> environment variable. If there is a color
|
|
definition in <b>$LS_COLORS</b> for the custom suffix
|
|
“.readline-colored-completion-prefix”,
|
|
<b>readline</b> uses this color for the common prefix
|
|
instead of its default.</p>
|
|
|
|
<p style="margin-left:6%;"><b>colored-stats (Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> displays possible completions using
|
|
different colors to indicate their file type. The color
|
|
definitions are taken from the value of the <b>LS_COLORS</b>
|
|
environment variable.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>comment-begin (</b>“<b>#</b>”<b>)</b></p>
|
|
|
|
<p style="margin-left:15%;">The string that the <b>readline
|
|
insert-comment</b> command inserts. This command is bound to
|
|
<b>M-#</b> in emacs mode and to <b>#</b> in vi command
|
|
mode.</p>
|
|
|
|
<p style="margin-left:6%;"><b>completion-display-width
|
|
(-1)</b></p>
|
|
|
|
<p style="margin-left:15%;">The number of screen columns
|
|
used to display possible matches when performing completion.
|
|
The value is ignored if it is less than 0 or greater than
|
|
the terminal screen width. A value of 0 causes matches to be
|
|
displayed one per line. The default value is -1.</p>
|
|
|
|
<p style="margin-left:6%;"><b>completion-ignore-case
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> performs filename matching and completion in
|
|
a case-insensitive fashion.</p>
|
|
|
|
<p style="margin-left:6%;"><b>completion-map-case
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, and
|
|
<b>completion-ignore-case</b> is enabled, <b>readline</b>
|
|
treats hyphens (<i>-</i>) and underscores (<i>_</i>) as
|
|
equivalent when performing case-insensitive filename
|
|
matching and completion.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>completion-prefix-display-length
|
|
(0)</b></p>
|
|
|
|
<p style="margin-left:15%;">The maximum length in
|
|
characters of the common prefix of a list of possible
|
|
completions that is displayed without modification. When set
|
|
to a value greater than zero, <b>readline</b> replaces
|
|
common prefixes longer than this value with an ellipsis when
|
|
displaying possible completions. If a completion begins with
|
|
a period, and <b>eadline</b> is completing filenames, it
|
|
uses three underscores instead of an ellipsis.</p>
|
|
|
|
<p style="margin-left:6%;"><b>completion-query-items
|
|
(100)</b></p>
|
|
|
|
<p style="margin-left:15%;">This determines when the user
|
|
is queried about viewing the number of possible completions
|
|
generated by the <b>possible-completions</b> command. It may
|
|
be set to any integer value greater than or equal to zero.
|
|
If the number of possible completions is greater than or
|
|
equal to the value of this variable, <b>readline</b> asks
|
|
whether or not the user wishes to view them; otherwise
|
|
<b>readline</b> simply lists them on the terminal. A zero
|
|
value means <b>readline</b> should never ask; negative
|
|
values are treated as zero.</p>
|
|
|
|
<p style="margin-left:6%;"><b>convert-meta (On)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> converts characters it reads that have the
|
|
eighth bit set to an ASCII key sequence by clearing the
|
|
eighth bit and prefixing it with an escape character
|
|
(converting the character to have the meta prefix). The
|
|
default is <i>On</i>, but <b>readline</b> sets it to
|
|
<i>Off</i> if the locale contains characters whose encodings
|
|
may include bytes with the eighth bit set. This variable is
|
|
dependent on the <b>LC_CTYPE</b> locale category, and may
|
|
change if the locale changes. This variable also affects key
|
|
bindings; see the description of <b>force-meta-prefix</b>
|
|
below.</p>
|
|
|
|
<p style="margin-left:6%;"><b>disable-completion
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> inhibits word completion. Completion
|
|
characters are inserted into the line as if they had been
|
|
mapped to <b>self-insert</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>echo-control-characters
|
|
(On)</b></p>
|
|
|
|
<p style="margin-left:15%;">When set to <b>On</b>, on
|
|
operating systems that indicate they support it,
|
|
<b>readline</b> echoes a character corresponding to a signal
|
|
generated from the keyboard.</p>
|
|
|
|
<p style="margin-left:6%;"><b>editing-mode (emacs)</b></p>
|
|
|
|
<p style="margin-left:15%;">Controls whether
|
|
<b>readline</b> uses a set of key bindings similar to
|
|
<i>Emacs</i> or <i>vi</i>. <b>editing-mode</b> can be set to
|
|
either <b>emacs</b> or <b>vi</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>emacs-mode-string (@)</b></p>
|
|
|
|
<p style="margin-left:15%;">If the
|
|
<i>show-mode-in-prompt</i> variable is enabled, this string
|
|
is displayed immediately before the last line of the primary
|
|
prompt when emacs editing mode is active. The value is
|
|
expanded like a key binding, so the standard set of meta-
|
|
and control- prefixes and backslash escape sequences is
|
|
available. The \1 and \2 escapes begin and end sequences of
|
|
non-printing characters, which can be used to embed a
|
|
terminal control sequence into the mode string.</p>
|
|
|
|
<p style="margin-left:6%;"><b>enable-active-region
|
|
(On)</b></p>
|
|
|
|
<p style="margin-left:15%;">When this variable is set to
|
|
<i>On</i>, <b>readline</b> allows certain commands to
|
|
designate the region as <i>active</i>. When the region is
|
|
active, <b>readline</b> highlights the text in the region
|
|
using the value of the <b>active-region-start-color</b>
|
|
variable, which defaults to the string that enables the
|
|
terminal’s standout mode. The active region shows the
|
|
text inserted by bracketed-paste and any matching text found
|
|
by incremental and non-incremental history searches.</p>
|
|
|
|
<p style="margin-left:6%;"><b>enable-bracketed-paste
|
|
(On)</b></p>
|
|
|
|
<p style="margin-left:15%;">When set to <b>On</b>,
|
|
<b>readline</b> configures the terminal to insert each paste
|
|
into the editing buffer as a single string of characters,
|
|
instead of treating each character as if it had been read
|
|
from the keyboard. This is called <i>bracketed-paste
|
|
mode</i>; it prevents <b>readline</b> from executing any
|
|
editing commands bound to key sequences appearing in the
|
|
pasted text.</p>
|
|
|
|
<p style="margin-left:6%;"><b>enable-keypad (Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">When set to <b>On</b>,
|
|
<b>readline</b> tries to enable the application keypad when
|
|
it is called. Some systems need this to enable the arrow
|
|
keys.</p>
|
|
|
|
<p style="margin-left:6%;"><b>enable-meta-key (On)</b></p>
|
|
|
|
<p style="margin-left:15%;">When set to <b>On</b>,
|
|
<b>readline</b> tries to enable any meta modifier key the
|
|
terminal claims to support. On many terminals, the Meta key
|
|
is used to send eight-bit characters; this variable checks
|
|
for the terminal capability that indicates the terminal can
|
|
enable and disable a mode that sets the eighth bit of a
|
|
character (0200) if the Meta key is held down when the
|
|
character is typed (a meta character).</p>
|
|
|
|
<p style="margin-left:6%;"><b>expand-tilde (Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> performs tilde expansion when it attempts
|
|
word completion.</p>
|
|
|
|
<p style="margin-left:6%;"><b>force-meta-prefix
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> modifies its behavior when binding key
|
|
sequences containing \M- or Meta- (see <b>Key Bindings</b>
|
|
above) by converting a key sequence of the form \M-<i>C</i>
|
|
or Meta-<i>C</i> to the two-character sequence <b>ESC</b>
|
|
<i>C</i> (adding the meta prefix). If
|
|
<b>force-meta-prefix</b> is set to <b>Off</b> (the default),
|
|
<b>readline</b> uses the value of the <b>convert-meta</b>
|
|
variable to determine whether to perform this conversion: if
|
|
<b>convert-meta</b> is <b>On</b>, <b>readline</b> performs
|
|
the conversion described above; if it is <b>Off</b>,
|
|
<b>readline</b> converts <i>C</i> to a meta character by
|
|
setting the eighth bit (0200).</p>
|
|
|
|
<p style="margin-left:6%;"><b>history-preserve-point
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, the
|
|
history code attempts to place point at the same location on
|
|
each history line retrieved with <b>previous-history</b> or
|
|
<b>next-history</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>history-size (unset)</b></p>
|
|
|
|
<p style="margin-left:15%;">Set the maximum number of
|
|
history entries saved in the history list. If set to zero,
|
|
any existing history entries are deleted and no new entries
|
|
are saved. If set to a value less than zero, the number of
|
|
history entries is not limited. By default, <b>bash</b> sets
|
|
the maximum number of history entries to the value of the
|
|
<b>HISTSIZE</b> shell variable. Setting <i>history-size</i>
|
|
to a non-numeric value will set the maximum number of
|
|
history entries to 500.</p>
|
|
|
|
<p style="margin-left:6%;"><b>horizontal-scroll-mode
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">Setting this variable to
|
|
<b>On</b> makes <b>readline</b> use a single line for
|
|
display, scrolling the input horizontally on a single screen
|
|
line when it becomes longer than the screen width rather
|
|
than wrapping to a new line. This setting is automatically
|
|
enabled for terminals of height 1.</p>
|
|
|
|
<p style="margin-left:6%;"><b>input-meta (Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> enables eight-bit input (that is, it does
|
|
not clear the eighth bit in the characters it reads),
|
|
regardless of what the terminal claims it can support. The
|
|
default is <i>Off</i>, but <b>readline</b> sets it to
|
|
<i>On</i> if the locale contains characters whose encodings
|
|
may include bytes with the eighth bit set. This variable is
|
|
dependent on the <b>LC_CTYPE</b> locale category, and its
|
|
value may change if the locale changes. The name
|
|
<b>meta-flag</b> is a synonym for <b>input-meta</b>.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>isearch-terminators (</b>“<b>C-[C-j</b>”<b>)</b></p>
|
|
|
|
<p style="margin-left:15%;">The string of characters that
|
|
should terminate an incremental search without subsequently
|
|
executing the character as a command. If this variable has
|
|
not been given a value, the characters <i>ESC</i> and
|
|
<b>C-j</b> terminate an incremental search.</p>
|
|
|
|
<p style="margin-left:6%;"><b>keymap (emacs)</b></p>
|
|
|
|
<p style="margin-left:15%;">Set the current <b>readline</b>
|
|
keymap. The set of valid keymap names is <i>emacs,
|
|
emacs-standard, emacs-meta, emacs-ctlx, vi, vi-command</i>,
|
|
and <i>vi-insert</i>. <i>vi</i> is equivalent to
|
|
<i>vi-command</i>; <i>emacs</i> is equivalent to
|
|
<i>emacs-standard</i>. The default value is <i>emacs</i>;
|
|
the value of <b>editing-mode</b> also affects the default
|
|
keymap.</p>
|
|
|
|
<p style="margin-left:6%;"><b>keyseq-timeout (500)</b></p>
|
|
|
|
<p style="margin-left:15%;">Specifies the duration
|
|
<b>readline</b> will wait for a character when reading an
|
|
ambiguous key sequence (one that can form a complete key
|
|
sequence using the input read so far, or can take additional
|
|
input to complete a longer key sequence). If <b>readline</b>
|
|
does not receive any input within the timeout, it uses the
|
|
shorter but complete key sequence. The value is specified in
|
|
milliseconds, so a value of 1000 means that <b>readline</b>
|
|
will wait one second for additional input. If this variable
|
|
is set to a value less than or equal to zero, or to a
|
|
non-numeric value, <b>readline</b> waits until another key
|
|
is pressed to decide which key sequence to complete.</p>
|
|
|
|
<p style="margin-left:6%;"><b>mark-directories (On)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, completed
|
|
directory names have a slash appended.</p>
|
|
|
|
<p style="margin-left:6%;"><b>mark-modified-lines
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> displays history lines that have been
|
|
modified with a preceding asterisk (<b>*</b>).</p>
|
|
|
|
<p style="margin-left:6%;"><b>mark-symlinked-directories
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, completed
|
|
names which are symbolic links to directories have a slash
|
|
appended, subject to the value of
|
|
<b>mark-directories</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>match-hidden-files
|
|
(On)</b></p>
|
|
|
|
<p style="margin-left:15%;">This variable, when set to
|
|
<b>On</b>, forces <b>readline</b> to match files whose names
|
|
begin with a “.” (hidden files) when performing
|
|
filename completion. If set to <b>Off</b>, the user must
|
|
include the leading “.” in the filename to be
|
|
completed.</p>
|
|
|
|
<p style="margin-left:6%;"><b>menu-complete-display-prefix
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, menu
|
|
completion displays the common prefix of the list of
|
|
possible completions (which may be empty) before cycling
|
|
through the list.</p>
|
|
|
|
<p style="margin-left:6%;"><b>output-meta (Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> displays characters with the eighth bit set
|
|
directly rather than as a meta-prefixed escape sequence. The
|
|
default is <i>Off</i>, but <b>readline</b> sets it to
|
|
<i>On</i> if the locale contains characters whose encodings
|
|
may include bytes with the eighth bit set. This variable is
|
|
dependent on the <b>LC_CTYPE</b> locale category, and its
|
|
value may change if the locale changes.</p>
|
|
|
|
<p style="margin-left:6%;"><b>page-completions (On)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> uses an internal pager resembling
|
|
<i>more</i>(1) to display a screenful of possible
|
|
completions at a time.</p>
|
|
|
|
<p style="margin-left:6%;"><b>prefer-visible-bell</b></p>
|
|
|
|
<p style="margin-left:15%;">See <b>bell-style</b>.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>print-completions-horizontally
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> displays completions with matches sorted
|
|
horizontally in alphabetical order, rather than down the
|
|
screen.</p>
|
|
|
|
<p style="margin-left:6%;"><b>revert-all-at-newline
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> will undo all changes to history lines
|
|
before returning when executing <b>accept-line</b>. By
|
|
default, history lines may be modified and retain individual
|
|
undo lists across calls to <b>readline</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>search-ignore-case
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>,
|
|
<b>readline</b> performs incremental and non-incremental
|
|
history list searches in a case-insensitive fashion.</p>
|
|
|
|
<p style="margin-left:6%;"><b>show-all-if-ambiguous
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">This alters the default
|
|
behavior of the completion functions. If set to <b>On</b>,
|
|
words which have more than one possible completion cause the
|
|
matches to be listed immediately instead of ringing the
|
|
bell.</p>
|
|
|
|
<p style="margin-left:6%;"><b>show-all-if-unmodified
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">This alters the default
|
|
behavior of the completion functions in a fashion similar to
|
|
<b>show-all-if-ambiguous</b>. If set to <b>On</b>, words
|
|
which have more than one possible completion without any
|
|
possible partial completion (the possible completions
|
|
don’t share a common prefix) cause the matches to be
|
|
listed immediately instead of ringing the bell.</p>
|
|
|
|
<p style="margin-left:6%;"><b>show-mode-in-prompt
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, add a
|
|
string to the beginning of the prompt indicating the editing
|
|
mode: emacs, vi command, or vi insertion. The mode strings
|
|
are user-settable (e.g., <i>emacs-mode-string</i>).</p>
|
|
|
|
<p style="margin-left:6%;"><b>skip-completed-text
|
|
(Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, this
|
|
alters the default completion behavior when inserting a
|
|
single match into the line. It’s only active when
|
|
performing completion in the middle of a word. If enabled,
|
|
<b>readline</b> does not insert characters from the
|
|
completion that match characters after point in the word
|
|
being completed, so portions of the word following the
|
|
cursor are not duplicated.</p>
|
|
|
|
<p style="margin-left:6%;"><b>vi-cmd-mode-string
|
|
((cmd))</b></p>
|
|
|
|
<p style="margin-left:15%;">If the
|
|
<i>show-mode-in-prompt</i> variable is enabled, this string
|
|
is displayed immediately before the last line of the primary
|
|
prompt when vi editing mode is active and in command mode.
|
|
The value is expanded like a key binding, so the standard
|
|
set of meta- and control- prefixes and backslash escape
|
|
sequences is available. The \1 and \2 escapes begin and end
|
|
sequences of non-printing characters, which can be used to
|
|
embed a terminal control sequence into the mode string.</p>
|
|
|
|
<p style="margin-left:6%;"><b>vi-ins-mode-string
|
|
((ins))</b></p>
|
|
|
|
<p style="margin-left:15%;">If the
|
|
<i>show-mode-in-prompt</i> variable is enabled, this string
|
|
is displayed immediately before the last line of the primary
|
|
prompt when vi editing mode is active and in insertion mode.
|
|
The value is expanded like a key binding, so the standard
|
|
set of meta- and control- prefixes and backslash escape
|
|
sequences is available. The \1 and \2 escapes begin and end
|
|
sequences of non-printing characters, which can be used to
|
|
embed a terminal control sequence into the mode string.</p>
|
|
|
|
<p style="margin-left:6%;"><b>visible-stats (Off)</b></p>
|
|
|
|
<p style="margin-left:15%;">If set to <b>On</b>, a
|
|
character denoting a file’s type as reported by
|
|
<i>stat</i>(2) is appended to the filename when listing
|
|
possible completions.</p>
|
|
|
|
<h3>Readline Conditional Constructs
|
|
<a name="Readline Conditional Constructs"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Readline</b>
|
|
implements a facility similar in spirit to the conditional
|
|
compilation features of the C preprocessor which allows key
|
|
bindings and variable settings to be performed as the result
|
|
of tests. There are four parser directives available.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p><b>$if</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>The <b>$if</b> construct allows bindings to be made
|
|
based on the editing mode, the terminal being used, or the
|
|
application using <b>readline</b>. The text of the test,
|
|
after any comparison operator, extends to the end of the
|
|
line; unless otherwise noted, no characters are required to
|
|
isolate it.</p></td></tr>
|
|
</table>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>mode</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%"></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The <b>mode=</b> form of the
|
|
<b>$if</b> directive is used to test whether <b>readline</b>
|
|
is in emacs or vi mode. This may be used in conjunction with
|
|
the <b>set keymap</b> command, for instance, to set bindings
|
|
in the <i>emacs-standard</i> and <i>emacs-ctlx</i> keymaps
|
|
only if <b>readline</b> is starting out in emacs mode.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>term</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The <b>term=</b> form may be
|
|
used to include terminal-specific key bindings, perhaps to
|
|
bind the key sequences output by the terminal’s
|
|
function keys. The word on the right side of the <b>=</b> is
|
|
tested against both the full name of the terminal and the
|
|
portion of the terminal name before the first <b>-</b>. This
|
|
allows <i>xterm</i> to match both <i>xterm</i> and
|
|
<i>xterm-256color</i>, for instance.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>version</b></p>
|
|
|
|
<p style="margin-left:24%;">The <b>version</b> test may be
|
|
used to perform comparisons against specific <b>readline</b>
|
|
versions. The <b>version</b> expands to the current
|
|
<b>readline</b> version. The set of comparison operators
|
|
includes <b>=</b>, (and <b>==</b>), <b>!=</b>, <b><=</b>,
|
|
<b>>=</b>, <b><</b>, and <b>></b>. The version
|
|
number supplied on the right side of the operator consists
|
|
of a major version number, an optional decimal point, and an
|
|
optional minor version (e.g., <b>7.1</b>). If the minor
|
|
version is omitted, it defaults to <b>0</b>. The operator
|
|
may be separated from the string <b>version</b> and from the
|
|
version number argument by whitespace.</p>
|
|
|
|
<p style="margin-left:15%;"><i>application</i></p>
|
|
|
|
<p style="margin-left:24%;">The <i>application</i>
|
|
construct is used to include application-specific settings.
|
|
Each program using the <b>readline</b> library sets the
|
|
<i>application name</i>, and an initialization file can test
|
|
for a particular value. This could be used to bind key
|
|
sequences to functions useful for a specific program. For
|
|
instance, the following command adds a key sequence that
|
|
quotes the current or previous word in <b>bash</b>:</p>
|
|
|
|
<p style="margin-left:24%; margin-top: 1em"><b>$if</b> Bash
|
|
<br>
|
|
# Quote the current or previous word <br>
|
|
"\C-xq": "\eb\"\ef\"" <b><br>
|
|
$endif</b></p>
|
|
|
|
<p style="margin-left:15%;"><i>variable</i></p>
|
|
|
|
<p style="margin-left:24%;">The <i>variable</i> construct
|
|
provides simple equality tests for <b>readline</b> variables
|
|
and values. The permitted comparison operators are <i>=</i>,
|
|
<i>==</i>, and <i>!=</i>. The variable name must be
|
|
separated from the comparison operator by whitespace; the
|
|
operator may be separated from the value on the right hand
|
|
side by whitespace. String and boolean variables may be
|
|
tested. Boolean variables must be tested against the values
|
|
<i>on</i> and <i>off</i>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>$else</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Commands in this branch of the <b>$if</b> directive are
|
|
executed if the test fails.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>$endif</b></p>
|
|
|
|
<p style="margin-left:15%;">This command, as seen in the
|
|
previous example, terminates an <b>$if</b> command.</p>
|
|
|
|
<p style="margin-left:6%;"><b>$include</b></p>
|
|
|
|
<p style="margin-left:15%;">This directive takes a single
|
|
filename as an argument and reads commands and key bindings
|
|
from that file. For example, the following directive would
|
|
read <A HREF="file:/etc/inputrc"><i>/etc/inputrc</i></A>:</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>$include</b>
|
|
<A HREF="file:/etc/inputrc"><i>/etc/inputrc</i></A></p>
|
|
|
|
<h3>Searching
|
|
<a name="Searching"></a>
|
|
</h3>
|
|
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i><b>Readline</b></i>
|
|
provides commands for searching through the command history
|
|
(see <b>HISTORY</b> below) for lines containing a specified
|
|
string. There are two search modes: <i>incremental</i> and
|
|
<i>non-incremental</i>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Incremental
|
|
searches begin before the user has finished typing the
|
|
search string. As each character of the search string is
|
|
typed, <b>readline</b> displays the next entry from the
|
|
history matching the string typed so far. An incremental
|
|
search requires only as many characters as needed to find
|
|
the desired history entry. When using emacs editing mode,
|
|
type <b>C-r</b> to search backward in the history for a
|
|
particular string. Typing <b>C-s</b> searches forward
|
|
through the history. The characters present in the value of
|
|
the <b>isearch-terminators</b> variable are used to
|
|
terminate an incremental search. If that variable has not
|
|
been assigned a value, <i>ESC</i> and <b>C-j</b> terminate
|
|
an incremental search. <b>C-g</b> aborts an incremental
|
|
search and restores the original line. When the search is
|
|
terminated, the history entry containing the search string
|
|
becomes the current line.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">To find other
|
|
matching entries in the history list, type <b>C-r</b> or
|
|
<b>C-s</b> as appropriate. This searches backward or forward
|
|
in the history for the next entry matching the search string
|
|
typed so far. Any other key sequence bound to a
|
|
<b>readline</b> command terminates the search and executes
|
|
that command. For instance, a newline terminates the search
|
|
and accepts the line, thereby executing the command from the
|
|
history list. A movement command will terminate the search,
|
|
make the last line found the current line, and begin
|
|
editing.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>Readline</b>
|
|
remembers the last incremental search string. If two
|
|
<b>C-r</b>s are typed without any intervening characters
|
|
defining a new search string, <b>readline</b> uses any
|
|
remembered search string.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Non-incremental
|
|
searches read the entire search string before starting to
|
|
search for matching history entries. The search string may
|
|
be typed by the user or be part of the contents of the
|
|
current line.</p>
|
|
|
|
<h3>Readline Command Names
|
|
<a name="Readline Command Names"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The following is
|
|
a list of the names of the commands and the default key
|
|
sequences to which they are bound. Command names without an
|
|
accompanying key sequence are unbound by default.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">In the following
|
|
descriptions, <i>point</i> refers to the current cursor
|
|
position, and <i>mark</i> refers to a cursor position saved
|
|
by the <b>set-mark</b> command. The text between the point
|
|
and mark is referred to as the <i>region</i>.
|
|
<b>Readline</b> has the concept of an <i>active region</i>:
|
|
when the region is active, <b>readline</b> redisplay
|
|
highlights the region using the value of the
|
|
<b>active-region-start-color</b> variable. The
|
|
<b>enable-active-region readline</b> variable turns this on
|
|
and off. Several commands set the region to active; those
|
|
are noted below.</p>
|
|
|
|
<h3>Commands for Moving
|
|
<a name="Commands for Moving"></a>
|
|
</h3>
|
|
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>beginning-of-line
|
|
(C-a)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move to the start of the
|
|
current line. This may also be bound to the Home key on some
|
|
keyboards.</p>
|
|
|
|
<p style="margin-left:6%;"><b>end-of-line (C-e)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move to the end of the line.
|
|
This may also be bound to the End key on some keyboards.</p>
|
|
|
|
<p style="margin-left:6%;"><b>forward-char (C-f)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move forward a character. This
|
|
may also be bound to the right arrow key on some
|
|
keyboards.</p>
|
|
|
|
<p style="margin-left:6%;"><b>backward-char (C-b)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move back a character. This may
|
|
also be bound to the left arrow key on some keyboards.</p>
|
|
|
|
<p style="margin-left:6%;"><b>forward-word (M-f)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move forward to the end of the
|
|
next word. Words are composed of alphanumeric characters
|
|
(letters and digits).</p>
|
|
|
|
<p style="margin-left:6%;"><b>backward-word (M-b)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move back to the start of the
|
|
current or previous word. Words are composed of alphanumeric
|
|
characters (letters and digits).</p>
|
|
|
|
<p style="margin-left:6%;"><b>shell-forward-word
|
|
(M-C-f)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move forward to the end of the
|
|
next word. Words are delimited by non-quoted shell
|
|
metacharacters.</p>
|
|
|
|
<p style="margin-left:6%;"><b>shell-backward-word
|
|
(M-C-b)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move back to the start of the
|
|
current or previous word. Words are delimited by non-quoted
|
|
shell metacharacters.</p>
|
|
|
|
<p style="margin-left:6%;"><b>previous-screen-line</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt to move point to the
|
|
same physical screen column on the previous physical screen
|
|
line. This will not have the desired effect if the current
|
|
<b>readline</b> line does not take up more than one physical
|
|
line or if point is not greater than the length of the
|
|
prompt plus the screen width.</p>
|
|
|
|
<p style="margin-left:6%;"><b>next-screen-line</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt to move point to the
|
|
same physical screen column on the next physical screen
|
|
line. This will not have the desired effect if the current
|
|
<b>readline</b> line does not take up more than one physical
|
|
line or if the length of the current <b>readline</b> line is
|
|
not greater than the length of the prompt plus the screen
|
|
width.</p>
|
|
|
|
<p style="margin-left:6%;"><b>clear-display (M-C-l)</b></p>
|
|
|
|
<p style="margin-left:15%;">Clear the screen and, if
|
|
possible, the terminal’s scrollback buffer, then
|
|
redraw the current line, leaving the current line at the top
|
|
of the screen.</p>
|
|
|
|
<p style="margin-left:6%;"><b>clear-screen (C-l)</b></p>
|
|
|
|
<p style="margin-left:15%;">Clear the screen, then redraw
|
|
the current line, leaving the current line at the top of the
|
|
screen. With a numeric argument, refresh the current line
|
|
without clearing the screen.</p>
|
|
|
|
<p style="margin-left:6%;"><b>redraw-current-line</b></p>
|
|
|
|
<p style="margin-left:15%;">Refresh the current line.</p>
|
|
|
|
<h3>Commands for Manipulating the History
|
|
<a name="Commands for Manipulating the History"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>accept-line
|
|
(Newline, Return)</b></p>
|
|
|
|
<p style="margin-left:15%;">Accept the line regardless of
|
|
where the cursor is. If this line is non-empty, add it to
|
|
the history list according to the state of the
|
|
<b>HISTCONTROL</b> and <b>HISTIGNORE</b> variables. If the
|
|
line is a modified history line, restore the history line to
|
|
its original state.</p>
|
|
|
|
<p style="margin-left:6%;"><b>previous-history
|
|
(C-p)</b></p>
|
|
|
|
<p style="margin-left:15%;">Fetch the previous command from
|
|
the history list, moving back in the list. This may also be
|
|
bound to the up arrow key on some keyboards.</p>
|
|
|
|
<p style="margin-left:6%;"><b>next-history (C-n)</b></p>
|
|
|
|
<p style="margin-left:15%;">Fetch the next command from the
|
|
history list, moving forward in the list. This may also be
|
|
bound to the down arrow key on some keyboards.</p>
|
|
|
|
<p style="margin-left:6%;"><b>beginning-of-history
|
|
(M-<)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move to the first line in the
|
|
history.</p>
|
|
|
|
<p style="margin-left:6%;"><b>end-of-history
|
|
(M->)</b></p>
|
|
|
|
<p style="margin-left:15%;">Move to the end of the input
|
|
history, i.e., the line currently being entered.</p>
|
|
|
|
<p style="margin-left:6%;"><b>operate-and-get-next
|
|
(C-o)</b></p>
|
|
|
|
<p style="margin-left:15%;">Accept the current line for
|
|
execution as if a newline had been entered, and fetch the
|
|
next line relative to the current line from the history for
|
|
editing. A numeric argument, if supplied, specifies the
|
|
history entry to use instead of the current line.</p>
|
|
|
|
<p style="margin-left:6%;"><b>fetch-history</b></p>
|
|
|
|
<p style="margin-left:15%;">With a numeric argument, fetch
|
|
that entry from the history list and make it the current
|
|
line. Without an argument, move back to the first entry in
|
|
the history list.</p>
|
|
|
|
<p style="margin-left:6%;"><b>reverse-search-history
|
|
(C-r)</b></p>
|
|
|
|
<p style="margin-left:15%;">Search backward starting at the
|
|
current line and moving “up” through the history
|
|
as necessary. This is an incremental search. This command
|
|
sets the region to the matched text and activates the
|
|
region.</p>
|
|
|
|
<p style="margin-left:6%;"><b>forward-search-history
|
|
(C-s)</b></p>
|
|
|
|
<p style="margin-left:15%;">Search forward starting at the
|
|
current line and moving “down” through the
|
|
history as necessary. This is an incremental search. This
|
|
command sets the region to the matched text and activates
|
|
the region.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>non-incremental-reverse-search-history
|
|
(M-p)</b></p>
|
|
|
|
<p style="margin-left:15%;">Search backward through the
|
|
history starting at the current line using a non-incremental
|
|
search for a string supplied by the user. The search string
|
|
may match anywhere in a history line.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>non-incremental-forward-search-history
|
|
(M-n)</b></p>
|
|
|
|
<p style="margin-left:15%;">Search forward through the
|
|
history using a non-incremental search for a string supplied
|
|
by the user. The search string may match anywhere in a
|
|
history line.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>history-search-backward</b></p>
|
|
|
|
<p style="margin-left:15%;">Search backward through the
|
|
history for the string of characters between the start of
|
|
the current line and the point. The search string must match
|
|
at the beginning of a history line. This is a
|
|
non-incremental search. This may be bound to the Page Up key
|
|
on some keyboards.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>history-search-forward</b></p>
|
|
|
|
<p style="margin-left:15%;">Search forward through the
|
|
history for the string of characters between the start of
|
|
the current line and the point. The search string must match
|
|
at the beginning of a history line. This is a
|
|
non-incremental search. This may be bound to the Page Down
|
|
key on some keyboards.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>history-substring-search-backward</b></p>
|
|
|
|
<p style="margin-left:15%;">Search backward through the
|
|
history for the string of characters between the start of
|
|
the current line and the point. The search string may match
|
|
anywhere in a history line. This is a non-incremental
|
|
search.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>history-substring-search-forward</b></p>
|
|
|
|
<p style="margin-left:15%;">Search forward through the
|
|
history for the string of characters between the start of
|
|
the current line and the point. The search string may match
|
|
anywhere in a history line. This is a non-incremental
|
|
search.</p>
|
|
|
|
<p style="margin-left:6%;"><b>yank-nth-arg (M-C-y)</b></p>
|
|
|
|
<p style="margin-left:15%;">Insert the first argument to
|
|
the previous command (usually the second word on the
|
|
previous line) at point. With an argument <i>n</i>, insert
|
|
the <i>n</i>th word from the previous command (the words in
|
|
the previous command begin with word 0). A negative argument
|
|
inserts the <i>n</i>th word from the end of the previous
|
|
command. Once the argument <i>n</i> is computed, this uses
|
|
the history expansion facilities to extract the <i>n</i>th
|
|
word, as if the “!!:<i>n</i>” history expansion
|
|
had been specified.</p>
|
|
|
|
<p style="margin-left:6%;"><b>yank-last-arg (M-.,
|
|
M-_)</b></p>
|
|
|
|
<p style="margin-left:15%;">Insert the last argument to the
|
|
previous command (the last word of the previous history
|
|
entry). With a numeric argument, behave exactly like
|
|
<b>yank-nth-arg</b>. Successive calls to
|
|
<b>yank-last-arg</b> move back through the history list,
|
|
inserting the last word (or the word specified by the
|
|
argument to the first call) of each line in turn. Any
|
|
numeric argument supplied to these successive calls
|
|
determines the direction to move through the history. A
|
|
negative argument switches the direction through the history
|
|
(back or forward). This uses the history expansion
|
|
facilities to extract the last word, as if the
|
|
“!$” history expansion had been specified.</p>
|
|
|
|
<p style="margin-left:6%;"><b>shell-expand-line
|
|
(M-C-e)</b></p>
|
|
|
|
<p style="margin-left:15%;">Expand the line by performing
|
|
shell word expansions, treating the line as a single shell
|
|
word. This performs alias and history expansion,
|
|
<b>$</b>'<i>string</i>' and
|
|
<b>$</b>"<i>string</i>" quoting, tilde expansion,
|
|
parameter and variable expansion, arithmetic expansion,
|
|
command and process substitution, word splitting, and quote
|
|
removal. An explicit argument suppresses command and process
|
|
substitution. See <b>HISTORY EXPANSION</b> below for a
|
|
description of history expansion.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>shell-expand-and-requote-line
|
|
()</b></p>
|
|
|
|
<p style="margin-left:15%;">Expand the line by performing
|
|
shell word expansions, splitting the line into shell words
|
|
in the same way as for programmable completion. This
|
|
performs alias and history expansion,
|
|
<b>$</b>'<i>string</i>' and
|
|
<b>$</b>"<i>string</i>" quoting, tilde expansion,
|
|
parameter and variable expansion, arithmetic expansion,
|
|
command and process substitution, word splitting, and quote
|
|
removal on each word, then quotes the resulting words if
|
|
necessary to prevent further expansion. An explicit argument
|
|
suppresses command and process substitution and quotes each
|
|
resultant word. As usual, double-quoting a word will
|
|
suppress word splitting. This can be useful when combined
|
|
with suppressing command substitution, for instance, so the
|
|
words in the command substitution aren’t quoted
|
|
individually.</p>
|
|
|
|
<p style="margin-left:6%;"><b>history-expand-line
|
|
(M-^)</b></p>
|
|
|
|
<p style="margin-left:15%;">Perform history expansion on
|
|
the current line. See <b>HISTORY EXPANSION</b> below for a
|
|
description of history expansion.</p>
|
|
|
|
<p style="margin-left:6%;"><b>magic-space</b></p>
|
|
|
|
<p style="margin-left:15%;">Perform history expansion on
|
|
the current line and insert a space. See <b>HISTORY
|
|
EXPANSION</b> below for a description of history
|
|
expansion.</p>
|
|
|
|
<p style="margin-left:6%;"><b>alias-expand-line</b></p>
|
|
|
|
<p style="margin-left:15%;">Perform alias expansion on the
|
|
current line. See <b>ALIASES</b> above for a description of
|
|
alias expansion.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>history-and-alias-expand-line</b></p>
|
|
|
|
<p style="margin-left:15%;">Perform history and alias
|
|
expansion on the current line.</p>
|
|
|
|
<p style="margin-left:6%;"><b>insert-last-argument (M-.,
|
|
M-_)</b></p>
|
|
|
|
<p style="margin-left:15%;">A synonym for
|
|
<b>yank-last-arg</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>edit-and-execute-command (C-x
|
|
C-e)</b></p>
|
|
|
|
<p style="margin-left:15%;">Invoke an editor on the current
|
|
command line, and execute the result as shell commands.
|
|
<b>Bash</b> attempts to invoke <b>$VISUAL</b>,
|
|
<b>$EDITOR</b>, and <i>emacs</i> as the editor, in that
|
|
order.</p>
|
|
|
|
<h3>Commands for Changing Text
|
|
<a name="Commands for Changing Text"></a>
|
|
</h3>
|
|
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>end-of-file</i>
|
|
<b>(usually C-d)</b></p>
|
|
|
|
<p style="margin-left:15%;">The character indicating
|
|
end-of-file as set, for example, by <i>stty</i>(1). If this
|
|
character is read when there are no characters on the line,
|
|
and point is at the beginning of the line, <b>readline</b>
|
|
interprets it as the end of input and returns
|
|
<b>EOF</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>delete-char (C-d)</b></p>
|
|
|
|
<p style="margin-left:15%;">Delete the character at point.
|
|
If this function is bound to the same character as the tty
|
|
<b>EOF</b> character, as <b>C-d</b> commonly is, see above
|
|
for the effects. This may also be bound to the Delete key on
|
|
some keyboards.</p>
|
|
|
|
<p style="margin-left:6%;"><b>backward-delete-char
|
|
(Rubout)</b></p>
|
|
|
|
<p style="margin-left:15%;">Delete the character behind the
|
|
cursor. When given a numeric argument, save the deleted text
|
|
on the kill ring.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>forward-backward-delete-char</b></p>
|
|
|
|
<p style="margin-left:15%;">Delete the character under the
|
|
cursor, unless the cursor is at the end of the line, in
|
|
which case the character behind the cursor is deleted.</p>
|
|
|
|
<p style="margin-left:6%;"><b>quoted-insert (C-q,
|
|
C-v)</b></p>
|
|
|
|
<p style="margin-left:15%;">Add the next character typed to
|
|
the line verbatim. This is how to insert characters like
|
|
<b>C-q</b>, for example.</p>
|
|
|
|
<p style="margin-left:6%;"><b>tab-insert (C-v TAB)</b></p>
|
|
|
|
<p style="margin-left:15%;">Insert a tab character.</p>
|
|
|
|
<p style="margin-left:6%;"><b>self-insert (a, b, A, 1,
|
|
!,</b> ...<b>)</b></p>
|
|
|
|
<p style="margin-left:15%;">Insert the character typed.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>bracketed-paste-begin</b></p>
|
|
|
|
<p style="margin-left:15%;">This function is intended to be
|
|
bound to the “bracketed paste” escape sequence
|
|
sent by some terminals, and such a binding is assigned by
|
|
default. It allows <b>readline</b> to insert the pasted text
|
|
as a single unit without treating each character as if it
|
|
had been read from the keyboard. The pasted characters are
|
|
inserted as if each one was bound to <b>self-insert</b>
|
|
instead of executing any editing commands. <br>
|
|
Bracketed paste sets the region to the inserted text and
|
|
activates the region.</p>
|
|
|
|
<p style="margin-left:6%;"><b>transpose-chars (C-t)</b></p>
|
|
|
|
<p style="margin-left:15%;">Drag the character before point
|
|
forward over the character at point, moving point forward as
|
|
well. If point is at the end of the line, then this
|
|
transposes the two characters before point. Negative
|
|
arguments have no effect.</p>
|
|
|
|
<p style="margin-left:6%;"><b>transpose-words (M-t)</b></p>
|
|
|
|
<p style="margin-left:15%;">Drag the word before point past
|
|
the word after point, moving point past that word as well.
|
|
If point is at the end of the line, this transposes the last
|
|
two words on the line.</p>
|
|
|
|
<p style="margin-left:6%;"><b>shell-transpose-words
|
|
(M-C-t)</b></p>
|
|
|
|
<p style="margin-left:15%;">Drag the word before point past
|
|
the word after point, moving point past that word as well.
|
|
If the insertion point is at the end of the line, this
|
|
transposes the last two words on the line. Word boundaries
|
|
are the same as <b>shell-forward-word</b> and
|
|
<b>shell-backward-word</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>upcase-word (M-u)</b></p>
|
|
|
|
<p style="margin-left:15%;">Uppercase the current (or
|
|
following) word. With a negative argument, uppercase the
|
|
previous word, but do not move point.</p>
|
|
|
|
<p style="margin-left:6%;"><b>downcase-word (M-l)</b></p>
|
|
|
|
<p style="margin-left:15%;">Lowercase the current (or
|
|
following) word. With a negative argument, lowercase the
|
|
previous word, but do not move point.</p>
|
|
|
|
<p style="margin-left:6%;"><b>capitalize-word (M-c)</b></p>
|
|
|
|
<p style="margin-left:15%;">Capitalize the current (or
|
|
following) word. With a negative argument, capitalize the
|
|
previous word, but do not move point.</p>
|
|
|
|
<p style="margin-left:6%;"><b>overwrite-mode</b></p>
|
|
|
|
<p style="margin-left:15%;">Toggle overwrite mode. With an
|
|
explicit positive numeric argument, switches to overwrite
|
|
mode. With an explicit non-positive numeric argument,
|
|
switches to insert mode. This command affects only
|
|
<b>emacs</b> mode; <b>vi</b> mode does overwrite
|
|
differently. Each call to <i>readline()</i> starts in insert
|
|
mode. <br>
|
|
In overwrite mode, characters bound to <b>self-insert</b>
|
|
replace the text at point rather than pushing the text to
|
|
the right. Characters bound to <b>backward-delete-char</b>
|
|
replace the character before point with a space. By default,
|
|
this command is unbound, but may be bound to the Insert key
|
|
on some keyboards.</p>
|
|
|
|
<h3>Killing and Yanking
|
|
<a name="Killing and Yanking"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>kill-line
|
|
(C-k)</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill the text from point to the
|
|
end of the current line. With a negative numeric argument,
|
|
kill backward from the cursor to the beginning of the
|
|
line.</p>
|
|
|
|
<p style="margin-left:6%;"><b>backward-kill-line (C-x
|
|
Rubout)</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill backward to the beginning
|
|
of the current line. With a negative numeric argument, kill
|
|
forward from the cursor to the end of the line.</p>
|
|
|
|
<p style="margin-left:6%;"><b>unix-line-discard
|
|
(C-u)</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill backward from point to the
|
|
beginning of the line, saving the killed text on the
|
|
kill-ring.</p>
|
|
|
|
<p style="margin-left:6%;"><b>kill-whole-line</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill all characters on the
|
|
current line, no matter where point is.</p>
|
|
|
|
<p style="margin-left:6%;"><b>kill-word (M-d)</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill from point to the end of
|
|
the current word, or if between words, to the end of the
|
|
next word. Word boundaries are the same as those used by
|
|
<b>forward-word</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>backward-kill-word
|
|
(M-Rubout)</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill the word behind point.
|
|
Word boundaries are the same as those used by
|
|
<b>backward-word</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>shell-kill-word
|
|
(M-C-d)</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill from point to the end of
|
|
the current word, or if between words, to the end of the
|
|
next word. Word boundaries are the same as those used by
|
|
<b>shell-forward-word</b>.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>shell-backward-kill-word</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill the word behind point.
|
|
Word boundaries are the same as those used by
|
|
<b>shell-backward-word</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>unix-word-rubout
|
|
(C-w)</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill the word behind point,
|
|
using white space as a word boundary, saving the killed text
|
|
on the kill-ring.</p>
|
|
|
|
<p style="margin-left:6%;"><b>unix-filename-rubout</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill the word behind point,
|
|
using white space and the slash character as the word
|
|
boundaries, saving the killed text on the kill-ring.</p>
|
|
|
|
<p style="margin-left:6%;"><b>delete-horizontal-space
|
|
(M-\)</b></p>
|
|
|
|
<p style="margin-left:15%;">Delete all spaces and tabs
|
|
around point.</p>
|
|
|
|
<p style="margin-left:6%;"><b>kill-region</b></p>
|
|
|
|
<p style="margin-left:15%;">Kill the text in the current
|
|
region.</p>
|
|
|
|
<p style="margin-left:6%;"><b>copy-region-as-kill</b></p>
|
|
|
|
<p style="margin-left:15%;">Copy the text in the region to
|
|
the kill buffer, so it can be yanked immediately.</p>
|
|
|
|
<p style="margin-left:6%;"><b>copy-backward-word</b></p>
|
|
|
|
<p style="margin-left:15%;">Copy the word before point to
|
|
the kill buffer. The word boundaries are the same as
|
|
<b>backward-word</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>copy-forward-word</b></p>
|
|
|
|
<p style="margin-left:15%;">Copy the word following point
|
|
to the kill buffer. The word boundaries are the same as
|
|
<b>forward-word</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>yank (C-y)</b></p>
|
|
|
|
<p style="margin-left:15%;">Yank the top of the kill ring
|
|
into the buffer at point.</p>
|
|
|
|
<p style="margin-left:6%;"><b>yank-pop (M-y)</b></p>
|
|
|
|
<p style="margin-left:15%;">Rotate the kill ring, and yank
|
|
the new top. Only works following <b>yank</b> or
|
|
<b>yank-pop</b>.</p>
|
|
|
|
<h3>Numeric Arguments
|
|
<a name="Numeric Arguments"></a>
|
|
</h3>
|
|
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>digit-argument
|
|
(M-0, M-1,</b> ...<b>, M--)</b></p>
|
|
|
|
<p style="margin-left:15%;">Add this digit to the argument
|
|
already accumulating, or start a new argument. M-- starts a
|
|
negative argument.</p>
|
|
|
|
<p style="margin-left:6%;"><b>universal-argument</b></p>
|
|
|
|
<p style="margin-left:15%;">This is another way to specify
|
|
an argument. If this command is followed by one or more
|
|
digits, optionally with a leading minus sign, those digits
|
|
define the argument. If the command is followed by digits,
|
|
executing <b>universal-argument</b> again ends the numeric
|
|
argument, but is otherwise ignored. As a special case, if
|
|
this command is immediately followed by a character that is
|
|
neither a digit nor minus sign, the argument count for the
|
|
next command is multiplied by four. The argument count is
|
|
initially one, so executing this function the first time
|
|
makes the argument count four, a second time makes the
|
|
argument count sixteen, and so on.</p>
|
|
|
|
<h3>Completing
|
|
<a name="Completing"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>complete
|
|
(TAB)</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt to perform completion
|
|
on the text before point. <b>Bash</b> attempts completion by
|
|
first checking for any programmable completions for the
|
|
command word (see <b>Programmable Completion</b> below),
|
|
otherwise treating the text as a variable (if the text
|
|
begins with <b>$</b>), username (if the text begins with
|
|
<b>~</b>), hostname (if the text begins with <b>@</b>), or
|
|
command (including aliases, functions, and builtins) in
|
|
turn. If none of these produces a match, it falls back to
|
|
filename completion.</p>
|
|
|
|
<p style="margin-left:6%;"><b>possible-completions
|
|
(M-?)</b></p>
|
|
|
|
<p style="margin-left:15%;">List the possible completions
|
|
of the text before point. When displaying completions,
|
|
<b>readline</b> sets the number of columns used for display
|
|
to the value of <b>completion-display-width</b>, the value
|
|
of the shell variable <b>COLUMNS</b>, or the screen width,
|
|
in that order.</p>
|
|
|
|
<p style="margin-left:6%;"><b>insert-completions
|
|
(M-*)</b></p>
|
|
|
|
<p style="margin-left:15%;">Insert all completions of the
|
|
text before point that would have been generated by
|
|
<b>possible-completions</b>, separated by a space.</p>
|
|
|
|
<p style="margin-left:6%;"><b>menu-complete</b></p>
|
|
|
|
<p style="margin-left:15%;">Similar to <b>complete</b>, but
|
|
replaces the word to be completed with a single match from
|
|
the list of possible completions. Repeatedly executing
|
|
<b>menu-complete</b> steps through the list of possible
|
|
completions, inserting each match in turn. At the end of the
|
|
list of completions, <b>menu-complete</b> rings the bell
|
|
(subject to the setting of <b>bell-style</b>) and restores
|
|
the original text. An argument of <i>n</i> moves <i>n</i>
|
|
positions forward in the list of matches; a negative
|
|
argument moves backward through the list. This command is
|
|
intended to be bound to <b>TAB</b>, but is unbound by
|
|
default.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>menu-complete-backward</b></p>
|
|
|
|
<p style="margin-left:15%;">Identical to
|
|
<b>menu-complete</b>, but moves backward through the list of
|
|
possible completions, as if <b>menu-complete</b> had been
|
|
given a negative argument. This command is unbound by
|
|
default.</p>
|
|
|
|
<p style="margin-left:6%;"><b>export-completions</b></p>
|
|
|
|
<p style="margin-left:15%;">Perform completion on the word
|
|
before point as described above and write the list of
|
|
possible completions to <b>readline</b>’s output
|
|
stream using the following format, writing information on
|
|
separate lines:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>the number of matches <i>N</i>;</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">the word being completed;</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em"><i>S</i>:<i>E</i>, where
|
|
<i>S</i> and <i>E</i> are the start and end offsets of the
|
|
word in the <b>readline</b> line buffer; then</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">each match, one per line</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If there are no
|
|
matches, the first line will be “0”, and this
|
|
command does not print any output after the
|
|
<i>S</i>:<i>E</i>. If there is only a single match, this
|
|
prints a single line containing it. If there is more than
|
|
one match, this prints the common prefix of the matches,
|
|
which may be empty, on the first line after the
|
|
<i>S</i>:<i>E</i>, then the matches on subsequent lines. In
|
|
this case, <i>N</i> will include the first line with the
|
|
common prefix.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The user or
|
|
application should be able to accommodate the possibility of
|
|
a blank line. The intent is that the user or application
|
|
reads <i>N</i> lines after the line containing
|
|
<i>S</i>:<i>E</i> to obtain the match list. This command is
|
|
unbound by default.</p>
|
|
|
|
<p style="margin-left:6%;"><b>delete-char-or-list</b></p>
|
|
|
|
<p style="margin-left:15%;">Deletes the character under the
|
|
cursor if not at the beginning or end of the line (like
|
|
<b>delete-char</b>). At the end of the line, it behaves
|
|
identically to <b>possible-completions</b>. This command is
|
|
unbound by default.</p>
|
|
|
|
<p style="margin-left:6%;"><b>complete-filename
|
|
(M-/)</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt filename completion on
|
|
the text before point.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>possible-filename-completions
|
|
(C-x /)</b></p>
|
|
|
|
<p style="margin-left:15%;">List the possible completions
|
|
of the text before point, treating it as a filename.</p>
|
|
|
|
<p style="margin-left:6%;"><b>complete-username
|
|
(M-~)</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt completion on the text
|
|
before point, treating it as a username.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>possible-username-completions
|
|
(C-x ~)</b></p>
|
|
|
|
<p style="margin-left:15%;">List the possible completions
|
|
of the text before point, treating it as a username.</p>
|
|
|
|
<p style="margin-left:6%;"><b>complete-variable
|
|
(M-$)</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt completion on the text
|
|
before point, treating it as a shell variable.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>possible-variable-completions
|
|
(C-x $)</b></p>
|
|
|
|
<p style="margin-left:15%;">List the possible completions
|
|
of the text before point, treating it as a shell
|
|
variable.</p>
|
|
|
|
<p style="margin-left:6%;"><b>complete-hostname
|
|
(M-@)</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt completion on the text
|
|
before point, treating it as a hostname.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>possible-hostname-completions
|
|
(C-x @)</b></p>
|
|
|
|
<p style="margin-left:15%;">List the possible completions
|
|
of the text before point, treating it as a hostname.</p>
|
|
|
|
<p style="margin-left:6%;"><b>complete-command
|
|
(M-!)</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt completion on the text
|
|
before point, treating it as a command name. Command
|
|
completion attempts to match the text against aliases,
|
|
reserved words, shell functions, shell builtins, and finally
|
|
executable filenames, in that order.</p>
|
|
|
|
<p style="margin-left:6%;"><b>possible-command-completions
|
|
(C-x !)</b></p>
|
|
|
|
<p style="margin-left:15%;">List the possible completions
|
|
of the text before point, treating it as a command name.</p>
|
|
|
|
<p style="margin-left:6%;"><b>dynamic-complete-history
|
|
(M-TAB)</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt completion on the text
|
|
before point, comparing the text against history list
|
|
entries for possible completion matches.</p>
|
|
|
|
<p style="margin-left:6%;"><b>dabbrev-expand</b></p>
|
|
|
|
<p style="margin-left:15%;">Attempt menu completion on the
|
|
text before point, comparing the text against lines from the
|
|
history list for possible completion matches.</p>
|
|
|
|
<p style="margin-left:6%;"><b>complete-into-braces
|
|
(M-{)</b></p>
|
|
|
|
<p style="margin-left:15%;">Perform filename completion and
|
|
insert the list of possible completions enclosed within
|
|
braces so the list is available to the shell (see <b>Brace
|
|
Expansion</b> above).</p>
|
|
|
|
<h3>Keyboard Macros
|
|
<a name="Keyboard Macros"></a>
|
|
</h3>
|
|
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>start-kbd-macro
|
|
(C-x ()</b></p>
|
|
|
|
<p style="margin-left:15%;">Begin saving the characters
|
|
typed into the current keyboard macro.</p>
|
|
|
|
<p style="margin-left:6%;"><b>end-kbd-macro (C-x ))</b></p>
|
|
|
|
<p style="margin-left:15%;">Stop saving the characters
|
|
typed into the current keyboard macro and store the
|
|
definition.</p>
|
|
|
|
<p style="margin-left:6%;"><b>call-last-kbd-macro (C-x
|
|
e)</b></p>
|
|
|
|
<p style="margin-left:15%;">Re-execute the last keyboard
|
|
macro defined, by making the characters in the macro appear
|
|
as if typed at the keyboard.</p>
|
|
|
|
<p style="margin-left:6%;"><b>print-last-kbd-macro
|
|
()</b></p>
|
|
|
|
<p style="margin-left:15%;">Print the last keyboard macro
|
|
defined in a format suitable for the <i>inputrc</i>
|
|
file.</p>
|
|
|
|
<h3>Miscellaneous
|
|
<a name="Miscellaneous"></a>
|
|
</h3>
|
|
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><b>re-read-init-file
|
|
(C-x C-r)</b></p>
|
|
|
|
<p style="margin-left:15%;">Read in the contents of the
|
|
<i>inputrc</i> file, and incorporate any bindings or
|
|
variable assignments found there.</p>
|
|
|
|
<p style="margin-left:6%;"><b>abort (C-g)</b></p>
|
|
|
|
<p style="margin-left:15%;">Abort the current editing
|
|
command and ring the terminal’s bell (subject to the
|
|
setting of <b>bell-style</b>).</p>
|
|
|
|
<p style="margin-left:6%;"><b>do-lowercase-version (M-A,
|
|
M-B, M-</b><i>x</i><b>,</b> ...<b>)</b></p>
|
|
|
|
<p style="margin-left:15%;">If the metafied character
|
|
<i>x</i> is uppercase, run the command that is bound to the
|
|
corresponding metafied lowercase character. The behavior is
|
|
undefined if <i>x</i> is already lowercase.</p>
|
|
|
|
<p style="margin-left:6%;"><b>prefix-meta (ESC)</b></p>
|
|
|
|
<p style="margin-left:15%;">Metafy the next character
|
|
typed. <b>ESC f</b> is equivalent to <b>Meta-f</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>undo (C-_, C-x C-u)</b></p>
|
|
|
|
<p style="margin-left:15%;">Incremental undo, separately
|
|
remembered for each line.</p>
|
|
|
|
<p style="margin-left:6%;"><b>revert-line (M-r)</b></p>
|
|
|
|
<p style="margin-left:15%;">Undo all changes made to this
|
|
line. This is like executing the <b>undo</b> command enough
|
|
times to return the line to its initial state.</p>
|
|
|
|
<p style="margin-left:6%;"><b>tilde-expand
|
|
(M-&)</b></p>
|
|
|
|
<p style="margin-left:15%;">Perform tilde expansion on the
|
|
current word.</p>
|
|
|
|
<p style="margin-left:6%;"><b>set-mark (C-@,
|
|
M-<space>)</b></p>
|
|
|
|
<p style="margin-left:15%;">Set the mark to the point. If a
|
|
numeric argument is supplied, set the mark to that
|
|
position.</p>
|
|
|
|
<p style="margin-left:6%;"><b>exchange-point-and-mark (C-x
|
|
C-x)</b></p>
|
|
|
|
<p style="margin-left:15%;">Swap the point with the mark.
|
|
Set the current cursor position to the saved position, then
|
|
set the mark to the old cursor position.</p>
|
|
|
|
<p style="margin-left:6%;"><b>character-search
|
|
(C-])</b></p>
|
|
|
|
<p style="margin-left:15%;">Read a character and move point
|
|
to the next occurrence of that character. A negative
|
|
argument searches for previous occurrences.</p>
|
|
|
|
<p style="margin-left:6%;"><b>character-search-backward
|
|
(M-C-])</b></p>
|
|
|
|
<p style="margin-left:15%;">Read a character and move point
|
|
to the previous occurrence of that character. A negative
|
|
argument searches for subsequent occurrences.</p>
|
|
|
|
<p style="margin-left:6%;"><b>skip-csi-sequence</b></p>
|
|
|
|
<p style="margin-left:15%;">Read enough characters to
|
|
consume a multi-key sequence such as those defined for keys
|
|
like Home and End. CSI sequences begin with a Control
|
|
Sequence Indicator (CSI), usually <i>ESC [</i>. If this
|
|
sequence is bound to “\e[”, keys producing CSI
|
|
sequences have no effect unless explicitly bound to a
|
|
<b>readline</b> command, instead of inserting stray
|
|
characters into the editing buffer. This is unbound by
|
|
default, but usually bound to <i>ESC [</i>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>insert-comment (M-#)</b></p>
|
|
|
|
<p style="margin-left:15%;">Without a numeric argument,
|
|
insert the value of the <b>readline comment-begin</b>
|
|
variable at the beginning of the current line. If a numeric
|
|
argument is supplied, this command acts as a toggle: if the
|
|
characters at the beginning of the line do not match the
|
|
value of <b>comment-begin</b>, insert the value; otherwise
|
|
delete the characters in <b>comment-begin</b> from the
|
|
beginning of the line. In either case, the line is accepted
|
|
as if a newline had been typed. The default value of
|
|
<b>comment-begin</b> causes this command to make the current
|
|
line a shell comment. If a numeric argument causes the
|
|
comment character to be removed, the line will be executed
|
|
by the shell.</p>
|
|
|
|
<p style="margin-left:6%;"><b>spell-correct-word (C-x
|
|
s)</b></p>
|
|
|
|
<p style="margin-left:15%;">Perform spelling correction on
|
|
the current word, treating it as a directory or filename, in
|
|
the same way as the <b>cdspell</b> shell option. Word
|
|
boundaries are the same as those used by
|
|
<b>shell-forward-word</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>glob-complete-word
|
|
(M-g)</b></p>
|
|
|
|
<p style="margin-left:15%;">Treat the word before point as
|
|
a pattern for pathname expansion, with an asterisk
|
|
implicitly appended, then use the pattern to generate a list
|
|
of matching file names for possible completions.</p>
|
|
|
|
<p style="margin-left:6%;"><b>glob-expand-word (C-x
|
|
*)</b></p>
|
|
|
|
<p style="margin-left:15%;">Treat the word before point as
|
|
a pattern for pathname expansion, and insert the list of
|
|
matching file names, replacing the word. If a numeric
|
|
argument is supplied, append a <b>*</b> before pathname
|
|
expansion.</p>
|
|
|
|
<p style="margin-left:6%;"><b>glob-list-expansions (C-x
|
|
g)</b></p>
|
|
|
|
<p style="margin-left:15%;">Display the list of expansions
|
|
that would have been generated by <b>glob-expand-word</b>
|
|
and redisplay the line. If a numeric argument is supplied,
|
|
append a <b>*</b> before pathname expansion.</p>
|
|
|
|
<p style="margin-left:6%;"><b>dump-functions</b></p>
|
|
|
|
<p style="margin-left:15%;">Print all of the functions and
|
|
their key bindings to the <b>readline</b> output stream. If
|
|
a numeric argument is supplied, the output is formatted in
|
|
such a way that it can be made part of an <i>inputrc</i>
|
|
file.</p>
|
|
|
|
<p style="margin-left:6%;"><b>dump-variables</b></p>
|
|
|
|
<p style="margin-left:15%;">Print all of the settable
|
|
<b>readline</b> variables and their values to the
|
|
<b>readline</b> output stream. If a numeric argument is
|
|
supplied, the output is formatted in such a way that it can
|
|
be made part of an <i>inputrc</i> file.</p>
|
|
|
|
<p style="margin-left:6%;"><b>dump-macros</b></p>
|
|
|
|
<p style="margin-left:15%;">Print all of the
|
|
<b>readline</b> key sequences bound to macros and the
|
|
strings they output to the <b>readline</b> output stream. If
|
|
a numeric argument is supplied, the output is formatted in
|
|
such a way that it can be made part of an <i>inputrc</i>
|
|
file.</p>
|
|
|
|
<p style="margin-left:6%;"><b>execute-named-command
|
|
(M-x)</b></p>
|
|
|
|
<p style="margin-left:15%;">Read a bindable <b>readline</b>
|
|
command name from the input and execute the function to
|
|
which it’s bound, as if the key sequence to which it
|
|
was bound appeared in the input. If this function is
|
|
supplied with a numeric argument, it passes that argument to
|
|
the function it executes.</p>
|
|
|
|
<p style="margin-left:6%;"><b>display-shell-version (C-x
|
|
C-v)</b></p>
|
|
|
|
<p style="margin-left:15%;">Display version information
|
|
about the current instance of <b>bash</b>.</p>
|
|
|
|
<h3>Programmable Completion
|
|
<a name="Programmable Completion"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a user
|
|
attempts word completion for a command or an argument to a
|
|
command for which a completion specification (a
|
|
<i>compspec</i>) has been defined using the <b>complete</b>
|
|
builtin (see <b>SHELL BUILTIN COMMANDS</b> below),
|
|
<b>readline</b> invokes the programmable completion
|
|
facilities.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">First,
|
|
<b>bash</b> identifies the command name. If a compspec has
|
|
been defined for that command, the compspec is used to
|
|
generate the list of possible completions for the word. If
|
|
the command word is the empty string (completion attempted
|
|
at the beginning of an empty line), <b>bash</b> uses any
|
|
compspec defined with the <b>-E</b> option to
|
|
<b>complete</b>. The <b>-I</b> option to <b>complete</b>
|
|
indicates that the command word is the first non-assignment
|
|
word on the line, or after a command delimiter such as
|
|
<b>;</b> or <b>|</b>. This usually indicates command name
|
|
completion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the command
|
|
word is a full pathname, <b>bash</b> searches for a compspec
|
|
for the full pathname first. If there is no compspec for the
|
|
full pathname, <b>bash</b> attempts to find a compspec for
|
|
the portion following the final slash. If those searches do
|
|
not result in a compspec, or if there is no compspec for the
|
|
command word, <b>bash</b> uses any compspec defined with the
|
|
<b>-D</b> option to <b>complete</b> as the default. If there
|
|
is no default compspec, <b>bash</b> performs alias expansion
|
|
on the command word as a final resort, and attempts to find
|
|
a compspec for the command word resulting from any
|
|
successful expansion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a compspec is
|
|
not found, <b>bash</b> performs its default completion as
|
|
described above under <b>Completing</b>. Otherwise, once a
|
|
compspec has been found, <b>bash</b> uses it to generate the
|
|
list of matching words.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">First,
|
|
<b>bash</b> performs the <i>actions</i> specified by the
|
|
compspec. This only returns matches which are prefixes of
|
|
the word being completed. When the <b>-f</b> or <b>-d</b>
|
|
option is used for filename or directory name completion,
|
|
<b>bash</b> uses the shell variable <b>FIGNORE</b> to filter
|
|
the matches.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Next,
|
|
programmable completion generates matches specified by a
|
|
pathname expansion pattern supplied as an argument to the
|
|
<b>-G</b> option. The words generated by the pattern need
|
|
not match the word being completed. <b>Bash</b> uses the
|
|
<b>FIGNORE</b> variable to filter the matches, but does not
|
|
use the <b>GLOBIGNORE</b> shell variable.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Next, completion
|
|
considers the string specified as the argument to the
|
|
<b>-W</b> option. The string is first split using the
|
|
characters in the <b>IFS</b> special variable as delimiters.
|
|
This honors shell quoting within the string, in order to
|
|
provide a mechanism for the words to contain shell
|
|
metacharacters or characters in the value of <b>IFS</b>.
|
|
Each word is then expanded using brace expansion, tilde
|
|
expansion, parameter and variable expansion, command
|
|
substitution, and arithmetic expansion, as described above
|
|
under <b>EXPANSION</b>. The results are split using the
|
|
rules described above under <b>Word Splitting</b>. The
|
|
results of the expansion are prefix-matched against the word
|
|
being completed, and the matching words become possible
|
|
completions.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">After these
|
|
matches have been generated, <b>bash</b> executes any shell
|
|
function or command specified with the <b>-F</b> and
|
|
<b>-C</b> options. When the command or function is invoked,
|
|
<b>bash</b> assigns values to the <b>COMP_LINE</b>,
|
|
<b>COMP_POINT</b>, <b>COMP_KEY</b>, and <b>COMP_TYPE</b>
|
|
variables as described above under <b>Shell Variables</b>.
|
|
If a shell function is being invoked, <b>bash</b> also sets
|
|
the <b>COMP_WORDS</b> and <b>COMP_CWORD</b> variables. When
|
|
the function or command is invoked, the first argument
|
|
(<b>$1</b>) is the name of the command whose arguments are
|
|
being completed, the second argument (<b>$2</b>) is the word
|
|
being completed, and the third argument (<b>$3</b>) is the
|
|
word preceding the word being completed on the current
|
|
command line. There is no filtering of the generated
|
|
completions against the word being completed; the function
|
|
or command has complete freedom in generating the matches
|
|
and they do not need to match a prefix of the word.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Any function
|
|
specified with <b>-F</b> is invoked first. The function may
|
|
use any of the shell facilities, including the
|
|
<b>compgen</b> and <b>compopt</b> builtins described below,
|
|
to generate the matches. It must put the possible
|
|
completions in the <b>COMPREPLY</b> array variable, one per
|
|
array element.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Next, any
|
|
command specified with the <b>-C</b> option is invoked in an
|
|
environment equivalent to command substitution. It should
|
|
print a list of completions, one per line, to the standard
|
|
output. Backslash will escape a newline, if necessary. These
|
|
are added to the set of possible completions.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">External
|
|
commands that are invoked to generate completions (
|
|
“external completers”) receive the word
|
|
preceding the completion word as an argument, as described
|
|
above. This provides context that is sometimes useful, but
|
|
may include information that is considered sensitive or part
|
|
of a word expansion that will not appear in the command line
|
|
after expansion. That word may be visible in process
|
|
listings or in audit logs. This may be a concern to users
|
|
and completion specification authors if there is sensitive
|
|
information on the command line before expansion, since
|
|
completion takes place before words are expanded. If this is
|
|
an issue, completion authors should use functions as
|
|
wrappers around external commands and pass context
|
|
information to the external command in a different way.
|
|
External completers can infer context from the
|
|
<b>COMP_LINE</b> and <b>COMP_POINT</b> environment
|
|
variables, but they need to ensure they break words in the
|
|
same way <b>readline</b> does, using the
|
|
<b>COMP_WORDBREAKS</b> variable.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">After generating
|
|
all of the possible completions, <b>bash</b> applies any
|
|
filter specified with the <b>-X</b> option to the
|
|
completions in the list. The filter is a pattern as used for
|
|
pathname expansion; a <b>&</b> in the pattern is
|
|
replaced with the text of the word being completed. A
|
|
literal <b>&</b> may be escaped with a backslash; the
|
|
backslash is removed before attempting a match. Any
|
|
completion that matches the pattern is removed from the
|
|
list. A leading <b>!</b> negates the pattern; in this case
|
|
<b>bash</b> removes any completion that does not match the
|
|
pattern. If the <b>nocasematch</b> shell option is enabled,
|
|
<b>bash</b> performs the match without regard to the case of
|
|
alphabetic characters.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Finally,
|
|
programmable completion adds any prefix and suffix specified
|
|
with the <b>-P</b> and <b>-S</b> options, respectively, to
|
|
each completion, and returns the result to <b>readline</b>
|
|
as the list of possible completions.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
previously-applied actions do not generate any matches, and
|
|
the <b>-o dirnames</b> option was supplied to
|
|
<b>complete</b> when the compspec was defined, <b>bash</b>
|
|
attempts directory name completion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the <b>-o
|
|
plusdirs</b> option was supplied to <b>complete</b> when the
|
|
compspec was defined, <b>bash</b> attempts directory name
|
|
completion and adds any matches to the set of possible
|
|
completions.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">By default, if a
|
|
compspec is found, whatever it generates is returned to the
|
|
completion code as the full set of possible completions. The
|
|
default <b>bash</b> completions and the <b>readline</b>
|
|
default of filename completion are disabled. If the <b>-o
|
|
bashdefault</b> option was supplied to <b>complete</b> when
|
|
the compspec was defined, and the compspec generates no
|
|
matches, <b>bash</b> attempts its default completions. If
|
|
the compspec and, if attempted, the default <b>bash</b>
|
|
completions generate no matches, and the <b>-o default</b>
|
|
option was supplied to <b>complete</b> when the compspec was
|
|
defined, programmable completion performs
|
|
<b>readline</b>’s default completion.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The options
|
|
supplied to <b>complete</b> and <b>compopt</b> can control
|
|
how <b>readline</b> treats the completions. For instance,
|
|
the <b>-o fullquote</b> option tells <b>readline</b> to
|
|
quote the matches as if they were filenames. See the
|
|
description of <b>complete</b> below for details.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a compspec
|
|
indicates that it wants directory name completion, the
|
|
programmable completion functions force <b>readline</b> to
|
|
append a slash to completed names which are symbolic links
|
|
to directories, subject to the value of the
|
|
<b>mark-directories readline</b> variable, regardless of the
|
|
setting of the <b>mark-symlinked-directories readline</b>
|
|
variable.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There is some
|
|
support for dynamically modifying completions. This is most
|
|
useful when used in combination with a default completion
|
|
specified with <b>complete -D</b>. It’s possible for
|
|
shell functions executed as completion functions to indicate
|
|
that completion should be retried by returning an exit
|
|
status of 124. If a shell function returns 124, and changes
|
|
the compspec associated with the command on which completion
|
|
is being attempted (supplied as the first argument when the
|
|
function is executed), programmable completion restarts from
|
|
the beginning, with an attempt to find a new compspec for
|
|
that command. This can be used to build a set of completions
|
|
dynamically as completion is attempted, rather than loading
|
|
them all at once.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">For instance,
|
|
assuming that there is a library of compspecs, each kept in
|
|
a file corresponding to the name of the command, the
|
|
following default completion function would load completions
|
|
dynamically:</p>
|
|
|
|
<p style="margin-left:15%;">_completion_loader() <br>
|
|
{ <br>
|
|
. "/etc/bash_completion.d/$1.sh" >/dev/null
|
|
2>&1 && return 124 <br>
|
|
} <br>
|
|
complete -D -F _completion_loader -o bashdefault -o
|
|
default</p>
|
|
|
|
<h2>HISTORY
|
|
<a name="HISTORY"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the <b>-o
|
|
history</b> option to the <b>set</b> builtin is enabled, the
|
|
shell provides access to the <i>command history</i>, the
|
|
list of commands previously typed. The value of the
|
|
<b>HISTSIZE</b> variable is used as the number of commands
|
|
to save in a history list: the shell saves the text of the
|
|
last <b>HISTSIZE</b> commands (default 500). The shell
|
|
stores each command in the history list prior to parameter
|
|
and variable expansion (see <b>EXPANSION</b> above) but
|
|
after history expansion is performed, subject to the values
|
|
of the shell variables <b>HISTIGNORE</b> and
|
|
<b>HISTCONTROL</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">On startup,
|
|
<b>bash</b> initializes the history list by reading history
|
|
entries from the file named by the <b>HISTFILE</b> variable
|
|
(default <A HREF="file:~/.bash_history"><i>~/.bash_history</i></A>). That file is referred to
|
|
as the <i>history file</i>. The history file is truncated,
|
|
if necessary, to contain no more than the number of history
|
|
entries specified by the value of the <b>HISTFILESIZE</b>
|
|
variable. If <b>HISTFILESIZE</b> is unset, or set to null, a
|
|
non-numeric value, or a numeric value less than zero, the
|
|
history file is not truncated.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When the history
|
|
file is read, lines beginning with the history comment
|
|
character followed immediately by a digit are interpreted as
|
|
timestamps for the following history line. These timestamps
|
|
are optionally displayed depending on the value of the
|
|
<b>HISTTIMEFORMAT</b> variable. When present, history
|
|
timestamps delimit history entries, making multi-line
|
|
entries possible.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a shell
|
|
with history enabled exits, <b>bash</b> copies the last
|
|
<b>$HISTSIZE</b> entries from the history list to
|
|
<b>$HISTFILE</b>. If the <b>histappend</b> shell option is
|
|
enabled (see the description of <b>shopt</b> under <b>SHELL
|
|
BUILTIN COMMANDS</b> below), <b>bash</b> appends the entries
|
|
to the history file, otherwise it overwrites the history
|
|
file. If <b>HISTFILE</b> is unset or null, or if the history
|
|
file is unwritable, the history is not saved. After saving
|
|
the history, <b>bash</b> truncates the history file to
|
|
contain no more than <b>HISTFILESIZE</b> lines as described
|
|
above.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If the
|
|
<b>HISTTIMEFORMAT</b> variable is set, the shell writes the
|
|
timestamp information associated with each history entry to
|
|
the history file, marked with the history comment character,
|
|
so timestamps are preserved across shell sessions. This uses
|
|
the history comment character to distinguish timestamps from
|
|
other history lines. As above, when using
|
|
<b>HISTTIMEFORMAT</b>, the timestamps delimit multi-line
|
|
history entries.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <b>fc</b>
|
|
builtin command (see <b>SHELL BUILTIN COMMANDS</b> below)
|
|
will list or edit and re-execute a portion of the history
|
|
list. The <b>history</b> builtin can display or modify the
|
|
history list and manipulate the history file. When using
|
|
command-line editing, search commands are available in each
|
|
editing mode that provide access to the history list.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell allows
|
|
control over which commands are saved on the history list.
|
|
The <b>HISTCONTROL</b> and <b>HISTIGNORE</b> variables are
|
|
used to save only a subset of the commands entered. If the
|
|
<b>cmdhist</b> shell option is enabled, the shell attempts
|
|
to save each line of a multi-line command in the same
|
|
history entry, adding semicolons where necessary to preserve
|
|
syntactic correctness. The <b>lithist</b> shell option
|
|
modifies <b>cmdhist</b> by saving the command with embedded
|
|
newlines instead of semicolons. See the description of the
|
|
<b>shopt</b> builtin below under <b>SHELL BUILTIN
|
|
COMMANDS</b> for information on setting and unsetting shell
|
|
options.</p>
|
|
|
|
<h2>HISTORY EXPANSION
|
|
<a name="HISTORY EXPANSION"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell
|
|
supports a history expansion feature that is similar to the
|
|
history expansion in <b>csh</b>. This section describes what
|
|
syntax features are available.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">History
|
|
expansion is enabled by default for interactive shells, and
|
|
can be disabled using the <b>+H</b> option to the <b>set</b>
|
|
builtin command (see <b>SHELL BUILTIN COMMANDS</b> below).
|
|
Non-interactive shells do not perform history expansion by
|
|
default, but it can be enabled with “set
|
|
-H”.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">History
|
|
expansions introduce words from the history list into the
|
|
input stream, making it easy to repeat commands, insert the
|
|
arguments to a previous command into the current input line,
|
|
or fix errors in previous commands quickly.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">History
|
|
expansion is performed immediately after a complete line is
|
|
read, before the shell breaks it into words, and is
|
|
performed on each line individually. The shell attempts to
|
|
inform the history expansion functions about quoting still
|
|
in effect from previous lines.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">It takes place
|
|
in two parts. The first is to determine which history list
|
|
entry to use during substitution. The second is to select
|
|
portions of that entry to include into the current one.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The entry
|
|
selected from the history is the <i>event</i>, and the
|
|
portions of that entry that are acted upon are <i>words</i>.
|
|
Various <i>modifiers</i> are available to manipulate the
|
|
selected words. The entry is split into words in the same
|
|
fashion as when reading input, so that several
|
|
<i>metacharacter</i>-separated words surrounded by quotes
|
|
are considered one word. The <i>event designator</i> selects
|
|
the event, the optional <i>word designator</i> selects words
|
|
from the event, and various optional <i>modifiers</i> are
|
|
available to manipulate the selected words.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">History
|
|
expansions are introduced by the appearance of the history
|
|
expansion character, which is <b>!</b> by default. History
|
|
expansions may appear anywhere in the input, but do not
|
|
nest.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Only backslash
|
|
(<b>\</b>) and single quotes can quote the history expansion
|
|
character, but the history expansion character is also
|
|
treated as quoted if it immediately precedes the closing
|
|
double quote in a double-quoted string.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Several
|
|
characters inhibit history expansion if found immediately
|
|
following the history expansion character, even if it is
|
|
unquoted: space, tab, newline, carriage return, <b>=</b>,
|
|
and the other shell metacharacters defined above.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There is a
|
|
special abbreviation for substitution, active when the
|
|
<i>quick substitution</i> character (described above under
|
|
<b>histchars</b>) is the first character on the line. It
|
|
selects the previous history list entry, using an event
|
|
designator equivalent to <b>!!</b>, and substitutes one
|
|
string for another in that entry. It is described below
|
|
under <b>Event Designators</b>. This is the only history
|
|
expansion that does not begin with the history expansion
|
|
character.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Several shell
|
|
options settable with the <b>shopt</b> builtin will modify
|
|
history expansion behavior (see the description of the
|
|
<b>shopt</b> builtin below).and If the <b>histverify</b>
|
|
shell option is enabled, and <b>readline</b> is being used,
|
|
history substitutions are not immediately passed to the
|
|
shell parser. Instead, the expanded line is reloaded into
|
|
the <b>readline</b> editing buffer for further modification.
|
|
If <b>readline</b> is being used, and the <b>histreedit</b>
|
|
shell option is enabled, a failed history substitution is
|
|
reloaded into the <b>readline</b> editing buffer for
|
|
correction.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The <b>-p</b>
|
|
option to the <b>history</b> builtin command shows what a
|
|
history expansion will do before using it. The <b>-s</b>
|
|
option to the <b>history</b> builtin will add commands to
|
|
the end of the history list without actually executing them,
|
|
so that they are available for subsequent recall.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The shell allows
|
|
control of the various characters used by the history
|
|
expansion mechanism (see the description of <b>histchars</b>
|
|
above under <b>Shell Variables</b>). The shell uses the
|
|
history comment character to mark history timestamps when
|
|
writing the history file.</p>
|
|
|
|
<h3>Event Designators
|
|
<a name="Event Designators"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">An event
|
|
designator is a reference to an entry in the history list.
|
|
The event designator consists of the portion of the word
|
|
beginning with the history expansion character and ending
|
|
with the word designator if present, or the end of the word.
|
|
Unless the reference is absolute, events are relative to the
|
|
current position in the history list.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p><b>!</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Start a history substitution, except when followed by a
|
|
<b>blank</b>, newline, carriage return, =, or, when the
|
|
<b>extglob</b> shell option is enabled using the
|
|
<b>shopt</b> builtin, (.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>!</b><i>n</i></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Refer to history list entry
|
|
<i>n</i>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>!-</b><i>n</i></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Refer to the current entry minus
|
|
<i>n</i>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>!!</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Refer to the previous entry.
|
|
This is a synonym for “!-1”.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>!</b><i>string</i></p>
|
|
|
|
<p style="margin-left:15%;">Refer to the most recent
|
|
command preceding the current position in the history list
|
|
starting with <i>string</i>.</p>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>!?</b><i>string</i><b>[?]</b></p>
|
|
|
|
<p style="margin-left:15%;">Refer to the most recent
|
|
command preceding the current position in the history list
|
|
containing <i>string</i>. The trailing <b>?</b> may be
|
|
omitted if <i>string</i> is followed immediately by a
|
|
newline. If <i>string</i> is missing, this uses the string
|
|
from the most recent search; it is an error if there is no
|
|
previous search string.</p>
|
|
|
|
<p style="margin-left:6%;"><b><big>^</big></b>
|
|
<i>string1</i> <b><big>^</big></b> <i>string2</i>
|
|
<b><big>^</big></b></p>
|
|
|
|
<p style="margin-left:15%;">Quick substitution. Repeat the
|
|
previous command, replacing <i>string1</i> with
|
|
<i>string2</i>. Equivalent to “!!:s <big>^</big>
|
|
<i>string1</i> <big>^</big> <i>string2</i> <big>^</big>
|
|
” (see <b>Modifiers</b> below).</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>!#</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="46%">
|
|
|
|
|
|
<p>The entire command line typed so far.</p></td>
|
|
<td width="39%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<h3>Word Designators
|
|
<a name="Word Designators"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Word designators
|
|
are used to select desired words from the event. They are
|
|
optional; if the word designator isn’t supplied, the
|
|
history expansion uses the entire event. A <b>:</b>
|
|
separates the event specification from the word designator.
|
|
It may be omitted if the word designator begins with a
|
|
<b>^</b>, <b>$</b>, <b>*</b>, <b>-</b>, or <b>%</b>. Words
|
|
are numbered from the beginning of the line, with the first
|
|
word being denoted by 0 (zero). Words are inserted into the
|
|
current line separated by single spaces. <b><br>
|
|
0 (zero)</b></p>
|
|
|
|
<p style="margin-left:15%;">The zeroth word. For the shell,
|
|
this is the command word.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p><i>n</i></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>The <i>n</i>th word.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>^</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The first argument: word 1.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>$</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The last word. This is usually
|
|
the last argument, but will expand to the zeroth word if
|
|
there is only one word in the line.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>%</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">The first word matched by the
|
|
most recent “?<i>string</i>?” search, if the
|
|
search string begins with a character that is part of a
|
|
word. By default, searches begin at the end of each line and
|
|
proceed to the beginning, so the first word matched is the
|
|
one closest to the end of the line.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><i>x</i><b>-</b><i>y</i></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">A range of words;
|
|
“-<i>y</i>” abbreviates
|
|
“0-<i>y</i>”.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>*</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">All of the words but the zeroth.
|
|
This is a synonym for “<i>1-$</i>”. It is not an
|
|
error to use <b>*</b> if there is just one word in the
|
|
event; it expands to the empty string in that case.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>x*</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Abbreviates <i>x-$</i>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>x-</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Abbreviates <i>x-$</i> like
|
|
<b>x*</b>, but omits the last word. If <b>x</b> is missing,
|
|
it defaults to 0.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a word
|
|
designator is supplied without an event specification, the
|
|
previous command is used as the event, equivalent to
|
|
<b>!!</b>.</p>
|
|
|
|
<h3>Modifiers
|
|
<a name="Modifiers"></a>
|
|
</h3>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">After the
|
|
optional word designator, the expansion may include a
|
|
sequence of one or more of the following modifiers, each
|
|
preceded by a “:”. These modify, or edit, the
|
|
word or words selected from the history event.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>h</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Remove a trailing pathname
|
|
component, leaving only the head.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>t</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Remove all leading pathname
|
|
components, leaving the tail.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>r</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Remove a trailing suffix of the
|
|
form <i>.xxx</i>, leaving the basename.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>e</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Remove all but the trailing
|
|
suffix.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>p</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Print the new command but do not
|
|
execute it.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>q</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Quote the substituted words,
|
|
escaping further substitutions.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>x</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Quote the substituted words as
|
|
with <b>q</b>, but break into words at <b>blanks</b> and
|
|
newlines. The <b>q</b> and <b>x</b> modifiers are mutually
|
|
exclusive; expansion uses the last one supplied.</p></td></tr>
|
|
</table>
|
|
|
|
|
|
<p style="margin-left:6%;"><b>s/</b><i>old</i><b>/</b><i>new</i><b>/</b></p>
|
|
|
|
<p style="margin-left:15%;">Substitute <i>new</i> for the
|
|
first occurrence of <i>old</i> in the event line. Any
|
|
character may be used as the delimiter in place of /. The
|
|
final delimiter is optional if it is the last character of
|
|
the event line. A single backslash quotes the delimiter in
|
|
<i>old</i> and <i>new</i>. If & appears in <i>new</i>,
|
|
it is replaced with <i>old</i>. A single backslash quotes
|
|
the &. If <i>old</i> is null, it is set to the last
|
|
<i>old</i> substituted, or, if no previous history
|
|
substitutions took place, the last <i>string</i> in a
|
|
<b>!?</b><i>string</i><b>[?]</b> search. If <i>new</i> is
|
|
null, each matching <i>old</i> is deleted.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p><b>&</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Repeat the previous substitution.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>g</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Cause changes to be applied over
|
|
the entire event line. This is used in conjunction with
|
|
“<b>:s</b>” (e.g.,
|
|
“<b>:gs/</b><i>old</i><b>/</b><i>new</i><b>/</b>”)
|
|
or “<b>:&</b>”. If used with
|
|
“<b>:s</b>”, any delimiter can be used in place
|
|
of /, and the final delimiter is optional if it is the last
|
|
character of the event line. An <b>a</b> may be used as a
|
|
synonym for <b>g</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>G</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Apply the following
|
|
“<b>s</b>” or “<b>&</b>”
|
|
modifier once to each word in the event line.</p></td></tr>
|
|
</table>
|
|
|
|
<h2>SHELL BUILTIN COMMANDS
|
|
<a name="SHELL BUILTIN COMMANDS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Unless otherwise
|
|
noted, each builtin command documented in this section as
|
|
accepting options preceded by <b>-</b> accepts <b>--</b> to
|
|
signify the end of the options. The <b>:</b>, <b>true</b>,
|
|
<b>false</b>, and <b>test</b>/<b>[</b> builtins do not
|
|
accept options and do not treat <b>--</b> specially. The
|
|
<b>exit</b>, <b>logout</b>, <b>return</b>, <b>break</b>,
|
|
<b>continue</b>, <b>let</b>, and <b>shift</b> builtins
|
|
accept and process arguments beginning with <b>-</b> without
|
|
requiring <b>--</b>. Other builtins that accept arguments
|
|
but are not specified as accepting options interpret
|
|
arguments beginning with <b>-</b> as invalid options and
|
|
require <b>--</b> to prevent this interpretation.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">All builtins
|
|
except <b>:</b>, <b>true</b>, <b>false</b>, <b>echo</b>, and
|
|
<b>test</b>/<b>[</b> accept <b>--help</b> as a special
|
|
option. If <b>--help</b> is supplied, these builtins output
|
|
a help message and exit with a status of 0. <b><br>
|
|
:</b> [<i>arguments</i>]</p>
|
|
|
|
<p style="margin-left:15%;">No effect; the command does
|
|
nothing beyond expanding <i>arguments</i> and performing any
|
|
specified redirections. The return status is zero.</p>
|
|
|
|
<p style="margin-left:6%;"><b>.</b> [<b>-p</b> <i>path</i>]
|
|
<i>filename</i> [<i>arguments</i>] <b><br>
|
|
source</b> [<b>-p</b> <i>path</i>] <i>filename</i>
|
|
[<i>arguments</i>]</p>
|
|
|
|
<p style="margin-left:15%;">The <b>.</b> command
|
|
(<b>source</b>) reads and execute commands from
|
|
<i>filename</i> in the current shell environment and returns
|
|
the exit status of the last command executed from
|
|
<i>filename</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>filename</i> does not contain a slash, <b>.</b> searches
|
|
for it. If the <b>-p</b> option is supplied, <b>.</b> treats
|
|
<i>path</i> as a colon-separated list of directories in
|
|
which to find <i>filename</i>; otherwise, <b>.</b> uses the
|
|
entries in <b>PATH</b> to find the directory containing
|
|
<i>filename</i>. <i>filename</i> does not need to be
|
|
executable. When <b>bash</b> is not in posix mode, it
|
|
searches the current directory if <i>filename</i> is not
|
|
found in <b>PATH</b>, but does not search the current
|
|
directory if <b>-p</b> is supplied. If the <b>sourcepath</b>
|
|
option to the <b>shopt</b> builtin command is turned off,
|
|
<b>.</b> does not search <b>PATH</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If any
|
|
<i>arguments</i> are supplied, they become the positional
|
|
parameters when <i>filename</i> is executed. Otherwise the
|
|
positional parameters are unchanged.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-T</b> option is enabled, <b>.</b> inherits any trap on
|
|
<b>DEBUG</b>; if it is not, any <b>DEBUG</b> trap string is
|
|
saved and restored around the call to <b>.</b>, and <b>.</b>
|
|
unsets the <b>DEBUG</b> trap while it executes. If <b>-T</b>
|
|
is not set, and the sourced file changes the <b>DEBUG</b>
|
|
trap, the new value persists after <b>.</b> completes. The
|
|
return status is the status of the last command executed
|
|
from <i>filename</i> (0 if no commands are executed), and
|
|
non-zero if <i>filename</i> is not found or cannot be
|
|
read.</p>
|
|
|
|
<p style="margin-left:6%;"><b>alias</b> [<b>-p</b>]
|
|
[<i>name</i>[=<i>value</i>] ...]</p>
|
|
|
|
<p style="margin-left:15%;">With no arguments or with the
|
|
<b>-p</b> option, <b>alias</b> prints the list of aliases in
|
|
the form <b>alias</b> <i>name</i>=<i>value</i> on standard
|
|
output. When arguments are supplied, define an alias for
|
|
each <i>name</i> whose <i>value</i> is given. A trailing
|
|
space in <i>value</i> causes the next word to be checked for
|
|
alias substitution when the alias is expanded during command
|
|
parsing. For each <i>name</i> in the argument list for which
|
|
no <i>value</i> is supplied, print the name and value of the
|
|
alias <i>name</i>. <b>alias</b> returns true unless a
|
|
<i>name</i> is given (without a corresponding =<i>value</i>)
|
|
for which no alias has been defined.</p>
|
|
|
|
<p style="margin-left:6%;"><b>bg</b> [<i>jobspec</i>
|
|
...]</p>
|
|
|
|
<p style="margin-left:15%;">Resume each suspended job
|
|
<i>jobspec</i> in the background, as if it had been started
|
|
with <b>&</b>. If <i>jobspec</i> is not present, the
|
|
shell uses its notion of the <i>current job</i>. <b>bg</b>
|
|
<i>jobspec</i> returns 0 unless run when job control is
|
|
disabled or, when run with job control enabled, any
|
|
specified <i>jobspec</i> was not found or was started
|
|
without job control.</p>
|
|
|
|
<p style="margin-left:6%;"><b>bind</b> [<b>-m</b>
|
|
<i>keymap</i>] [<b>-lsvSVX</b>] <b><br>
|
|
bind</b> [<b>-m</b> <i>keymap</i>] [<b>-q</b>
|
|
<i>function</i>] [<b>-u</b> <i>function</i>] [<b>-r</b>
|
|
<i>keyseq</i>] <b><br>
|
|
bind</b> [<b>-m</b> <i>keymap</i>] <b>-f</b> <i>filename</i>
|
|
<b><br>
|
|
bind</b> [<b>-m</b> <i>keymap</i>] <b>-x</b>
|
|
<i>keyseq</i>[:] <i>shell-command</i> <b><br>
|
|
bind</b> [<b>-m</b> <i>keymap</i>]
|
|
<i>keyseq</i>:<i>function-name</i> <b><br>
|
|
bind</b> [<b>-m</b> <i>keymap</i>] <b>-p</b>|<b>-P</b>
|
|
[<i>readline-command</i>] <b><br>
|
|
bind</b> [<b>-m</b> <i>keymap</i>]
|
|
<i>keyseq</i>:<i>readline-command</i> <b><br>
|
|
bind</b> <i>readline-command-line</i></p>
|
|
|
|
<p style="margin-left:15%;">Display current <b>readline</b>
|
|
key and function bindings, bind a key sequence to a
|
|
<b>readline</b> function or macro or to a shell command, or
|
|
set a <b>readline</b> variable. Each non-option argument is
|
|
a key binding or command as it would appear in a
|
|
<b>readline</b> initialization file such as <i>.inputrc</i>,
|
|
but each binding or command must be passed as a separate
|
|
argument; e.g., '"\C-x\C-r": re-read-init-file'.
|
|
In the following descriptions, output available to be
|
|
re-read is formatted as commands that would appear in a
|
|
<b>readline</b> initialization file or that would be
|
|
supplied as individual arguments to a <b>bind</b> command.
|
|
Options, if supplied, have the following meanings: <b><br>
|
|
-m</b> <i>keymap</i></p>
|
|
|
|
<p style="margin-left:24%;">Use <i>keymap</i> as the keymap
|
|
to be affected by the subsequent bindings. Acceptable
|
|
<i>keymap</i> names are <i>emacs, emacs-standard,
|
|
emacs-meta, emacs-ctlx, vi, vi-move, vi-command</i>, and
|
|
<i>vi-insert</i>. <i>vi</i> is equivalent to
|
|
<i>vi-command</i> (<i>vi-move</i> is also a synonym);
|
|
<i>emacs</i> is equivalent to <i>emacs-standard</i>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-l</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>List the names of all <b>readline</b> functions.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-p</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display <b>readline</b> function
|
|
names and bindings in such a way that they can be used as an
|
|
argument to a subsequent <b>bind</b> command or in a
|
|
<b>readline</b> initialization file. If arguments remain
|
|
after option processing, <b>bind</b> treats them as
|
|
<b>readline</b> command names and restricts output to those
|
|
names.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-P</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">List current <b>readline</b>
|
|
function names and bindings. If arguments remain after
|
|
option processing, <b>bind</b> treats them as
|
|
<b>readline</b> command names and restricts output to those
|
|
names.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-s</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display <b>readline</b> key
|
|
sequences bound to macros and the strings they output in
|
|
such a way that they can be used as an argument to a
|
|
subsequent <b>bind</b> command or in a <b>readline</b>
|
|
initialization file.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-S</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display <b>readline</b> key
|
|
sequences bound to macros and the strings they output.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-v</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display <b>readline</b> variable
|
|
names and values in such a way that they can be used as an
|
|
argument to a subsequent <b>bind</b> command or in a
|
|
<b>readline</b> initialization file.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-V</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">List current <b>readline</b>
|
|
variable names and values.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>-f</b> <i>filename</i></p>
|
|
|
|
<p style="margin-left:24%;">Read key bindings from
|
|
<i>filename</i>.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-q</b> <i>function</i></p>
|
|
|
|
<p style="margin-left:24%;">Display key sequences that
|
|
invoke the named <b>readline</b> <i>function</i>.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-u</b> <i>function</i></p>
|
|
|
|
<p style="margin-left:24%;">Unbind all key sequences bound
|
|
to the named <b>readline</b> <i>function</i>.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-r</b> <i>keyseq</i></p>
|
|
|
|
<p style="margin-left:24%;">Remove any current binding for
|
|
<i>keyseq</i>.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-x</b> <i>keyseq</i><b>[:
|
|
]</b><i>shell-command</i></p>
|
|
|
|
<p style="margin-left:24%;">Cause <i>shell-command</i> to
|
|
be executed whenever <i>keyseq</i> is entered. The separator
|
|
between <i>keyseq</i> and <i>shell-command</i> is either
|
|
whitespace or a colon optionally followed by whitespace. If
|
|
the separator is whitespace, <i>shell-command</i> must be
|
|
enclosed in double quotes and <b>readline</b> expands any of
|
|
its special backslash-escapes in <i>shell-command</i> before
|
|
saving it. If the separator is a colon, any enclosing double
|
|
quotes are optional, and <b>readline</b> does not expand the
|
|
command string before saving it. Since the entire key
|
|
binding expression must be a single argument, it should be
|
|
enclosed in single quotes. When <i>shell-command</i> is
|
|
executed, the shell sets the <b>READLINE_LINE</b> variable
|
|
to the contents of the <b>readline</b> line buffer and the
|
|
<b>READLINE_POINT</b> and <b>READLINE_MARK</b> variables to
|
|
the current location of the insertion point and the saved
|
|
insertion point (the mark), respectively. The shell assigns
|
|
any numeric argument the user supplied to the
|
|
<b>READLINE_ARGUMENT</b> variable. If there was no argument,
|
|
that variable is not set. If the executed command changes
|
|
the value of any of <b>READLINE_LINE</b>,
|
|
<b>READLINE_POINT</b>, or <b>READLINE_MARK</b>, those new
|
|
values will be reflected in the editing state.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-X</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>List all key sequences bound to shell commands and the
|
|
associated commands in a format that can be reused as an
|
|
argument to a subsequent <b>bind</b> command.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is 0 unless an unrecognized option is supplied or an
|
|
error occurred.</p>
|
|
|
|
<p style="margin-left:6%;"><b>break</b> [<i>n</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Exit from within a <b>for</b>,
|
|
<b>while</b>, <b>until</b>, or <b>select</b> loop. If
|
|
<i>n</i> is specified, <b>break</b> exits <i>n</i> enclosing
|
|
loops. <i>n</i> must be ≥ 1. If <i>n</i> is greater than
|
|
the number of enclosing loops, all enclosing loops are
|
|
exited. The return value is 0 unless <i>n</i> is not greater
|
|
than or equal to 1.</p>
|
|
|
|
<p style="margin-left:6%;"><b>builtin</b>
|
|
<i>shell-builtin</i> [<i>arguments</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Execute the specified shell
|
|
builtin <i>shell-builtin</i>, passing it <i>arguments</i>,
|
|
and return its exit status. This is useful when defining a
|
|
function whose name is the same as a shell builtin,
|
|
retaining the functionality of the builtin within the
|
|
function. The <b>cd</b> builtin is commonly redefined this
|
|
way. The return status is false if <i>shell-builtin</i> is
|
|
not a shell builtin command.</p>
|
|
|
|
<p style="margin-left:6%;"><b>caller</b> [<i>expr</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Returns the context of any
|
|
active subroutine call (a shell function or a script
|
|
executed with the <b>.</b> or <b>source</b> builtins).</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Without
|
|
<i>expr</i>, <b>caller</b> displays the line number and
|
|
source filename of the current subroutine call. If a
|
|
non-negative integer is supplied as <i>expr</i>,
|
|
<b>caller</b> displays the line number, subroutine name, and
|
|
source file corresponding to that position in the current
|
|
execution call stack. This extra information may be used,
|
|
for example, to print a stack trace. The current frame is
|
|
frame 0.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is 0 unless the shell is not executing a subroutine
|
|
call or <i>expr</i> does not correspond to a valid position
|
|
in the call stack.</p>
|
|
|
|
<p style="margin-left:6%;"><b>cd</b> [<b>-L</b>]
|
|
[<b>-@</b>] [<i>dir</i>] <b><br>
|
|
cd -P</b> [<b>-e</b>] [<b>-@</b>] [<i>dir</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Change the current directory to
|
|
<i>dir</i>. if <i>dir</i> is not supplied, the value of the
|
|
<b>HOME</b> shell variable is used as <i>dir</i>. If
|
|
<i>dir</i> is the empty string, <b>cd</b> treats it as an
|
|
error. The variable <b>CDPATH</b> exists, and <i>dir</i>
|
|
does not begin with a slash (/), <b>cd</b> uses it as a
|
|
search path: the shell searches each directory name in
|
|
<b>CDPATH</b> for <i>dir</i>. Alternative directory names in
|
|
<b>CDPATH</b> are separated by a colon (:). A null directory
|
|
name in <b>CDPATH</b> is the same as the current directory,
|
|
i.e., “.”.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-P</b>
|
|
option causes <b>cd</b> to use the physical directory
|
|
structure by resolving symbolic links while traversing
|
|
<i>dir</i> and before processing instances of <i>..</i> in
|
|
<i>dir</i> (see also the <b>-P</b> option to the <b>set</b>
|
|
builtin command).</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-L</b>
|
|
option forces <b>cd</b> to follow symbolic links by
|
|
resolving the link after processing instances of <i>..</i>
|
|
in <i>dir</i>. If <i>..</i> appears in <i>dir</i>, <b>cd</b>
|
|
processes it by removing the immediately previous pathname
|
|
component from <i>dir</i>, back to a slash or the beginning
|
|
of <i>dir</i>, and verifying that the portion of <i>dir</i>
|
|
it has processed to that point is still a valid directory
|
|
name after removing the pathname component. If it is not a
|
|
valid directory name, <b>cd</b> returns a non-zero status.
|
|
If neither <b>-L</b> nor <b>-P</b> is supplied, <b>cd</b>
|
|
behaves as if <b>-L</b> had been supplied.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-e</b> option is supplied with <b>-P</b>, and <b>cd</b>
|
|
cannot successfully determine the current working directory
|
|
after a successful directory change, it returns a non-zero
|
|
status.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">On systems that
|
|
support it, the <b>-@</b> option presents the extended
|
|
attributes associated with a file as a directory.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">An argument of
|
|
<b>-</b> is converted to <b>$OLDPWD</b> before attempting
|
|
the directory change.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If <b>cd</b>
|
|
uses a non-empty directory name from <b>CDPATH</b>, or if
|
|
<b>-</b> is the first argument, and the directory change is
|
|
successful, <b>cd</b> writes the absolute pathname of the
|
|
new working directory to the standard output.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
directory change is successful, <b>cd</b> sets the value of
|
|
the <b>PWD</b> environment variable to the new directory
|
|
name, and sets the <b>OLDPWD</b> environment variable to the
|
|
value of the current working directory before the
|
|
change.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is true if the directory was successfully changed;
|
|
false otherwise.</p>
|
|
|
|
<p style="margin-left:6%;"><b>command</b> [<b>-pVv</b>]
|
|
<i>command</i> [<i>arg</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">The <b>command</b> builtin runs
|
|
<i>command</i> with <i>args</i> suppressing the normal shell
|
|
function lookup for <i>command</i>. Only builtin commands or
|
|
commands found in the <b>PATH</b> named <i>command</i> are
|
|
executed. If the <b>-p</b> option is supplied, the search
|
|
for <i>command</i> is performed using a default value for
|
|
<b>PATH</b> that is guaranteed to find all of the standard
|
|
utilities.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If either the
|
|
<b>-V</b> or <b>-v</b> option is supplied, <b>command</b>
|
|
prints a description of <i>command</i>. The <b>-v</b> option
|
|
displays a single word indicating the command or filename
|
|
used to invoke <i>command</i>; the <b>-V</b> option produces
|
|
a more verbose description.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-V</b> or <b>-v</b> option is supplied, the exit status
|
|
is zero if <i>command</i> was found, and non-zero if not. If
|
|
neither option is supplied and an error occurred or
|
|
<i>command</i> cannot be found, the exit status is 127.
|
|
Otherwise, the exit status of the <b>command</b> builtin is
|
|
the exit status of <i>command</i>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>compgen</b> [<b>-V</b>
|
|
<i>varname</i>] [<i>option</i>] [<i>word</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Generate possible completion
|
|
matches for <i>word</i> according to the <i>option</i>s,
|
|
which may be any option accepted by the <b>complete</b>
|
|
builtin with the exceptions of <b>-p</b>, <b>-r</b>,
|
|
<b>-D</b>, <b>-E</b>, and <b>-I</b>, and write the matches
|
|
to the standard output.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-V</b> option is supplied, <b>compgen</b> stores the
|
|
generated completions into the indexed array variable
|
|
<i>varname</i> instead of writing them to the standard
|
|
output.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When using the
|
|
<b>-F</b> or <b>-C</b> options, the various shell variables
|
|
set by the programmable completion facilities, while
|
|
available, will not have useful values.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The matches
|
|
will be generated in the same way as if the programmable
|
|
completion code had generated them directly from a
|
|
completion specification with the same flags. If <i>word</i>
|
|
is specified, only those completions matching <i>word</i>
|
|
will be displayed or stored.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is true unless an invalid option is supplied, or no
|
|
matches were generated.</p>
|
|
|
|
<p style="margin-left:6%;"><b>complete</b>
|
|
[<b>-abcdefgjksuv</b>] [<b>-o</b> <i>comp-option</i>]
|
|
[<b>-DEI</b>] [<b>-A</b> <i>action</i>]</p>
|
|
|
|
<p style="margin-left:15%;">[<b>-G</b> <i>globpat</i>]
|
|
[<b>-W</b> <i>wordlist</i>] [<b>-F</b> <i>function</i>]
|
|
[<b>-C</b> <i>command</i>] <br>
|
|
[<b>-X</b> <i>filterpat</i>] [<b>-P</b> <i>prefix</i>]
|
|
[<b>-S</b> <i>suffix</i>] <i>name</i> [<i>name</i> ...]</p>
|
|
|
|
<p style="margin-left:6%;"><b>complete -pr</b>
|
|
[<b>-DEI</b>] [<i>name</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Specify how arguments to each
|
|
<i>name</i> should be completed.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-p</b> option is supplied, or if no options or
|
|
<i>name</i>s are supplied, print existing completion
|
|
specifications in a way that allows them to be reused as
|
|
input. The <b>-r</b> option removes a completion
|
|
specification for each <i>name</i>, or, if no <i>name</i>s
|
|
are supplied, all completion specifications.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-D</b>
|
|
option indicates that other supplied options and actions
|
|
should apply to the “default” command
|
|
completion; that is, completion attempted on a command for
|
|
which no completion has previously been defined. The
|
|
<b>-E</b> option indicates that other supplied options and
|
|
actions should apply to “empty” command
|
|
completion; that is, completion attempted on a blank line.
|
|
The <b>-I</b> option indicates that other supplied options
|
|
and actions should apply to completion on the initial
|
|
non-assignment word on the line, or after a command
|
|
delimiter such as <b>;</b> or <b>|</b>, which is usually
|
|
command name completion. If multiple options are supplied,
|
|
the <b>-D</b> option takes precedence over <b>-E</b>, and
|
|
both take precedence over <b>-I</b>. If any of <b>-D</b>,
|
|
<b>-E</b>, or <b>-I</b> are supplied, any other <i>name</i>
|
|
arguments are ignored; these completions only apply to the
|
|
case specified by the option.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The process of
|
|
applying these completion specifications when attempting
|
|
word completion is described above under <b>Programmable
|
|
Completion</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Other options,
|
|
if specified, have the following meanings. The arguments to
|
|
the <b>-G</b>, <b>-W</b>, and <b>-X</b> options (and, if
|
|
necessary, the <b>-P</b> and <b>-S</b> options) should be
|
|
quoted to protect them from expansion before the
|
|
<b>complete</b> builtin is invoked. <b><br>
|
|
-o</b> <i>comp-option</i></p>
|
|
|
|
<p style="margin-left:25%;">The <i>comp-option</i> controls
|
|
several aspects of the compspec’s behavior beyond the
|
|
simple generation of completions. <i>comp-option</i> may be
|
|
one of: <b><br>
|
|
bashdefault</b></p>
|
|
|
|
<p style="margin-left:35%;">Perform the rest of the default
|
|
<b>bash</b> completions if the compspec generates no
|
|
matches.</p>
|
|
|
|
<p style="margin-left:25%;"><b>default</b></p>
|
|
|
|
<p style="margin-left:35%;">Use <b>readline</b>’s
|
|
default filename completion if the compspec generates no
|
|
matches.</p>
|
|
|
|
<p style="margin-left:25%;"><b>dirnames</b></p>
|
|
|
|
<p style="margin-left:35%;">Perform directory name
|
|
completion if the compspec generates no matches.</p>
|
|
|
|
<p style="margin-left:25%;"><b>filenames</b></p>
|
|
|
|
<p style="margin-left:35%;">Tell <b>readline</b> that the
|
|
compspec generates filenames, so it can perform any
|
|
filename-specific processing (such as adding a slash to
|
|
directory names, quoting special characters, or suppressing
|
|
trailing spaces). This is intended to be used with shell
|
|
functions.</p>
|
|
|
|
<p style="margin-left:25%;"><b>fullquote</b></p>
|
|
|
|
<p style="margin-left:35%;">Tell <b>readline</b> to quote
|
|
all the completed words even if they are not filenames.</p>
|
|
|
|
<p style="margin-left:25%;"><b>noquote</b></p>
|
|
|
|
<p style="margin-left:35%;">Tell <b>readline</b> not to
|
|
quote the completed words if they are filenames (quoting
|
|
filenames is the default).</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p><b>nosort</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p>Tell <b>readline</b> not to sort the list of possible
|
|
completions alphabetically.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>nospace</b></p>
|
|
|
|
<p style="margin-left:35%;">Tell <b>readline</b> not to
|
|
append a space (the default) to words completed at the end
|
|
of the line.</p>
|
|
|
|
<p style="margin-left:25%;"><b>plusdirs</b></p>
|
|
|
|
<p style="margin-left:35%;">After generating any matches
|
|
defined by the compspec, attempt directory name completion
|
|
and add any matches to the results of the other actions.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-A</b> <i>action</i></p>
|
|
|
|
<p style="margin-left:25%;">The <i>action</i> may be one of
|
|
the following to generate a list of possible
|
|
completions:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p><b>alias</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="53%">
|
|
|
|
|
|
<p>Alias names. May also be specified as <b>-a</b>.</p></td>
|
|
<td width="12%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>arrayvar</b></p>
|
|
|
|
<p style="margin-left:35%;">Array variable names.</p>
|
|
|
|
<p style="margin-left:25%;"><b>binding</b></p>
|
|
|
|
<p style="margin-left:35%;"><b>Readline</b> key binding
|
|
names.</p>
|
|
|
|
<p style="margin-left:25%;"><b>builtin</b></p>
|
|
|
|
<p style="margin-left:35%;">Names of shell builtin
|
|
commands. May also be specified as <b>-b</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>command</b></p>
|
|
|
|
<p style="margin-left:35%;">Command names. May also be
|
|
specified as <b>-c</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>directory</b></p>
|
|
|
|
<p style="margin-left:35%;">Directory names. May also be
|
|
specified as <b>-d</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>disabled</b></p>
|
|
|
|
<p style="margin-left:35%;">Names of disabled shell
|
|
builtins.</p>
|
|
|
|
<p style="margin-left:25%;"><b>enabled</b></p>
|
|
|
|
<p style="margin-left:35%;">Names of enabled shell
|
|
builtins.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p><b>export</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p>Names of exported shell variables. May also be specified
|
|
as <b>-e</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>file</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p style="margin-top: 1em">File and directory names,
|
|
similar to <b>readline</b>’s filename completion. May
|
|
also be specified as <b>-f</b>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>function</b></p>
|
|
|
|
<p style="margin-left:35%;">Names of shell functions.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p><b>group</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="53%">
|
|
|
|
|
|
<p>Group names. May also be specified as <b>-g</b>.</p></td>
|
|
<td width="12%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>helptopic</b></p>
|
|
|
|
<p style="margin-left:35%;">Help topics as accepted by the
|
|
<b>help</b> builtin.</p>
|
|
|
|
<p style="margin-left:25%;"><b>hostname</b></p>
|
|
|
|
<p style="margin-left:35%;">Hostnames, as taken from the
|
|
file specified by the <b>HOSTFILE</b> shell variable.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p><b>job</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p>Job names, if job control is active. May also be
|
|
specified as <b>-j</b>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>keyword</b></p>
|
|
|
|
<p style="margin-left:35%;">Shell reserved words. May also
|
|
be specified as <b>-k</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>running</b></p>
|
|
|
|
<p style="margin-left:35%;">Names of running jobs, if job
|
|
control is active.</p>
|
|
|
|
<p style="margin-left:25%;"><b>service</b></p>
|
|
|
|
<p style="margin-left:35%;">Service names. May also be
|
|
specified as <b>-s</b>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p><b>setopt</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p>Valid arguments for the <b>-o</b> option to the
|
|
<b>set</b> builtin.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>shopt</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p style="margin-top: 1em">Shell option names as accepted
|
|
by the <b>shopt</b> builtin.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>signal</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p style="margin-top: 1em">Signal names.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>stopped</b></p>
|
|
|
|
<p style="margin-left:35%;">Names of stopped jobs, if job
|
|
control is active.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>user</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="51%">
|
|
|
|
|
|
<p>User names. May also be specified as <b>-u</b>.</p></td>
|
|
<td width="14%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>variable</b></p>
|
|
|
|
<p style="margin-left:35%;">Names of all shell variables.
|
|
May also be specified as <b>-v</b>.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-C</b> <i>command</i></p>
|
|
|
|
<p style="margin-left:25%;"><i>command</i> is executed in a
|
|
subshell environment, and its output is used as the possible
|
|
completions. Arguments are passed as with the <b>-F</b>
|
|
option.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-F</b> <i>function</i></p>
|
|
|
|
<p style="margin-left:25%;">The shell function
|
|
<i>function</i> is executed in the current shell
|
|
environment. When the function is executed, the first
|
|
argument (<b>$1</b>) is the name of the command whose
|
|
arguments are being completed, the second argument
|
|
(<b>$2</b>) is the word being completed, and the third
|
|
argument (<b>$3</b>) is the word preceding the word being
|
|
completed on the current command line. When <i>function</i>
|
|
finishes, programmable completion retrieves the possible
|
|
completions from the value of the <b>COMPREPLY</b> array
|
|
variable.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-G</b> <i>globpat</i></p>
|
|
|
|
<p style="margin-left:25%;">Expand the pathname expansion
|
|
pattern <i>globpat</i> to generate the possible
|
|
completions.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-P</b> <i>prefix</i></p>
|
|
|
|
<p style="margin-left:25%;">Add <i>prefix</i> to the
|
|
beginning of each possible completion after all other
|
|
options have been applied.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-S</b> <i>suffix</i></p>
|
|
|
|
<p style="margin-left:25%;">Append <i>suffix</i> to each
|
|
possible completion after all other options have been
|
|
applied.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-W</b> <i>wordlist</i></p>
|
|
|
|
<p style="margin-left:25%;">Split the <i>wordlist</i> using
|
|
the characters in the <b>IFS</b> special variable as
|
|
delimiters, and expand each resulting word. Shell quoting is
|
|
honored within <i>wordlist</i>, in order to provide a
|
|
mechanism for the words to contain shell metacharacters or
|
|
characters in the value of <b>IFS</b>. The possible
|
|
completions are the members of the resultant list which
|
|
match a prefix of the word being completed.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-X</b> <i>filterpat</i></p>
|
|
|
|
<p style="margin-left:25%;"><i>filterpat</i> is a pattern
|
|
as used for pathname expansion. It is applied to the list of
|
|
possible completions generated by the preceding options and
|
|
arguments, and each completion matching <i>filterpat</i> is
|
|
removed from the list. A leading <b>!</b> in
|
|
<i>filterpat</i> negates the pattern; in this case, any
|
|
completion not matching <i>filterpat</i> is removed.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is true unless an invalid option is supplied, an
|
|
option other than <b>-p</b>, <b>-r</b>, <b>-D</b>,
|
|
<b>-E</b>, or <b>-I</b> is supplied without a <i>name</i>
|
|
argument, an attempt is made to remove a completion
|
|
specification for a <i>name</i> for which no specification
|
|
exists, or an error occurs adding a completion
|
|
specification.</p>
|
|
|
|
<p style="margin-left:6%;"><b>compopt</b> [<b>-o</b>
|
|
<i>option</i>] [<b>-DEI</b>] [<b>+o</b> <i>option</i>]
|
|
[<i>name</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Modify completion options for
|
|
each <i>name</i> according to the <i>option</i>s, or for the
|
|
currently-executing completion if no <i>name</i>s are
|
|
supplied. If no <i>option</i>s are supplied, display the
|
|
completion options for each <i>name</i> or the current
|
|
completion. The possible values of <i>option</i> are those
|
|
valid for the <b>complete</b> builtin described above.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-D</b>
|
|
option indicates that other supplied options should apply to
|
|
the “default” command completion; the <b>-E</b>
|
|
option indicates that other supplied options should apply to
|
|
“empty” command completion; and the <b>-I</b>
|
|
option indicates that other supplied options should apply to
|
|
completion on the initial word on the line. These are
|
|
determined in the same way as the <b>complete</b>
|
|
builtin.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If multiple
|
|
options are supplied, the <b>-D</b> option takes precedence
|
|
over <b>-E</b>, and both take precedence over <b>-I</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is true unless an invalid option is supplied, an
|
|
attempt is made to modify the options for a <i>name</i> for
|
|
which no completion specification exists, or an output error
|
|
occurs.</p>
|
|
|
|
<p style="margin-left:6%;"><b>continue</b> [<i>n</i>]</p>
|
|
|
|
<p style="margin-left:15%;"><b>continue</b> resumes the
|
|
next iteration of the enclosing <b>for</b>, <b>while</b>,
|
|
<b>until</b>, or <b>select</b> loop. If <i>n</i> is
|
|
specified, <b>bash</b> resumes the <i>n</i>th enclosing
|
|
loop. <i>n</i> must be ≥ 1. If <i>n</i> is greater than
|
|
the number of enclosing loops, the shell resumes the last
|
|
enclosing loop (the “top-level” loop). The
|
|
return value is 0 unless <i>n</i> is not greater than or
|
|
equal to 1.</p>
|
|
|
|
<p style="margin-left:6%;"><b>declare</b>
|
|
[<b>-aAfFgiIlnrtux</b>] [<b>-p</b>]
|
|
[<i>name</i>[=<i>value</i>] ...] <b><br>
|
|
typeset</b> [<b>-aAfFgiIlnrtux</b>] [<b>-p</b>]
|
|
[<i>name</i>[=<i>value</i>] ...]</p>
|
|
|
|
<p style="margin-left:15%;">Declare variables and/or give
|
|
them attributes. If no <i>name</i>s are given then display
|
|
the values of variables or functions. The <b>-p</b> option
|
|
will display the attributes and values of each <i>name</i>.
|
|
When <b>-p</b> is used with <i>name</i> arguments,
|
|
additional options, other than <b>-f</b> and <b>-F</b>, are
|
|
ignored.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When <b>-p</b>
|
|
is supplied without <i>name</i> arguments, <b>declare</b>
|
|
will display the attributes and values of all variables
|
|
having the attributes specified by the additional options.
|
|
If no other options are supplied with <b>-p</b>,
|
|
<b>declare</b> will display the attributes and values of all
|
|
shell variables. The <b>-f</b> option restricts the display
|
|
to shell functions.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-F</b>
|
|
option inhibits the display of function definitions; only
|
|
the function name and attributes are printed. If the
|
|
<b>extdebug</b> shell option is enabled using <b>shopt</b>,
|
|
the source file name and line number where each <i>name</i>
|
|
is defined are displayed as well. The <b>-F</b> option
|
|
implies <b>-f</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-g</b>
|
|
option forces variables to be created or modified at the
|
|
global scope, even when <b>declare</b> is executed in a
|
|
shell function. It is ignored when <b>declare</b> is not
|
|
executed in a shell function.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-I</b>
|
|
option causes local variables to inherit the attributes
|
|
(except the <i>nameref</i> attribute) and value of any
|
|
existing variable with the same <i>name</i> at a surrounding
|
|
scope. If there is no existing variable, the local variable
|
|
is initially unset.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The following
|
|
options can be used to restrict output to variables with the
|
|
specified attribute or to give variables attributes:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-a</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Each <i>name</i> is an indexed array variable (see
|
|
<b>Arrays</b> above).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-A</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Each <i>name</i> is an
|
|
associative array variable (see <b>Arrays</b> above).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-f</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Each <i>name</i> refers to a
|
|
shell function.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-i</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The variable is treated as an
|
|
integer; arithmetic evaluation (see <b>ARITHMETIC
|
|
EVALUATION</b> above) is performed when the variable is
|
|
assigned a value.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-l</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">When the variable is assigned a
|
|
value, all upper-case characters are converted to
|
|
lower-case. The upper-case attribute is disabled.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-n</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Give each <i>name</i> the
|
|
<i>nameref</i> attribute, making it a name reference to
|
|
another variable. That other variable is defined by the
|
|
value of <i>name</i>. All references, assignments, and
|
|
attribute modifications to <i>name</i>, except those using
|
|
or changing the <b>-n</b> attribute itself, are performed on
|
|
the variable referenced by <i>name</i>’s value. The
|
|
nameref attribute cannot be applied to array variables.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-r</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Make <i>name</i>s readonly.
|
|
These names cannot then be assigned values by subsequent
|
|
assignment statements or unset.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-t</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Give each <i>name</i> the
|
|
<i>trace</i> attribute. Traced functions inherit the
|
|
<b>DEBUG</b> and <b>RETURN</b> traps from the calling shell.
|
|
The trace attribute has no special meaning for
|
|
variables.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-u</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">When the variable is assigned a
|
|
value, all lower-case characters are converted to
|
|
upper-case. The lower-case attribute is disabled.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-x</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Mark each <i>name</i> for export
|
|
to subsequent commands via the environment.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Using
|
|
“+” instead of “-” turns off the
|
|
specified attribute instead, with the exceptions that
|
|
<b>+a</b> and <b>+A</b> may not be used to destroy array
|
|
variables and <b>+r</b> will not remove the readonly
|
|
attribute.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When used in a
|
|
function, <b>declare</b> and <b>typeset</b> make each
|
|
<i>name</i> local, as with the <b>local</b> command, unless
|
|
the <b>-g</b> option is supplied. If a variable name is
|
|
followed by =<i>value</i>, the value of the variable is set
|
|
to <i>value</i>. When using <b>-a</b> or <b>-A</b> and the
|
|
compound assignment syntax to create array variables,
|
|
additional attributes do not take effect until subsequent
|
|
assignments.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is 0 unless an invalid option is encountered, an
|
|
attempt is made to define a function using “-f
|
|
foo=bar”, an attempt is made to assign a value to a
|
|
readonly variable, an attempt is made to assign a value to
|
|
an array variable without using the compound assignment
|
|
syntax (see <b>Arrays</b> above), one of the <i>names</i> is
|
|
not a valid shell variable name, an attempt is made to turn
|
|
off readonly status for a readonly variable, an attempt is
|
|
made to turn off array status for an array variable, or an
|
|
attempt is made to display a non-existent function with
|
|
<b>-f</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>dirs [-clpv]
|
|
[+</b><i>n</i><b>] [-</b><i>n</i><b>]</b></p>
|
|
|
|
<p style="margin-left:15%;">Without options, display the
|
|
list of currently remembered directories. The default
|
|
display is on a single line with directory names separated
|
|
by spaces. Directories are added to the list with the
|
|
<b>pushd</b> command; the <b>popd</b> command removes
|
|
entries from the list. The current directory is always the
|
|
first directory in the stack.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Options, if
|
|
supplied, have the following meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-c</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Clears the directory stack by deleting all of the
|
|
entries.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-l</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Produces a listing using full
|
|
pathnames; the default listing format uses a tilde to denote
|
|
the home directory.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-p</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Print the directory stack with
|
|
one entry per line.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-v</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Print the directory stack with
|
|
one entry per line, prefixing each entry with its index in
|
|
the stack.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>+</b><i>n</i></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Displays the <i>n</i>th entry
|
|
counting from the left of the list shown by <b>dirs</b> when
|
|
invoked without options, starting with zero.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-</b><i>n</i></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Displays the <i>n</i>th entry
|
|
counting from the right of the list shown by <b>dirs</b>
|
|
when invoked without options, starting with zero.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is 0 unless an invalid option is supplied or <i>n</i>
|
|
indexes beyond the end of the directory stack.</p>
|
|
|
|
<p style="margin-left:6%;"><b>disown</b> [<b>-ar</b>]
|
|
[<b>-h</b>] [<i>id</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Without options, remove each
|
|
<i>id</i> from the table of active jobs. Each <i>id</i> may
|
|
be a job specification <i>jobspec</i> or a process ID
|
|
<i>pid</i>; if <i>id</i> is a <i>pid</i>, <b>disown</b> uses
|
|
the job containing <i>pid</i> as <i>jobspec</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-h</b> option is supplied, <b>disown</b> does not remove
|
|
the jobs corresponding to each <i>id</i> from the jobs
|
|
table, but rather marks them so the shell does not send
|
|
<b>SIGHUP</b> to the job if the shell receives a
|
|
<b>SIGHUP</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If no <i>id</i>
|
|
is supplied, the <b>-a</b> option means to remove or mark
|
|
all jobs; the <b>-r</b> option without an <i>id</i> argument
|
|
removes or marks running jobs. If no <i>id</i> is supplied,
|
|
and neither the <b>-a</b> nor the <b>-r</b> option is
|
|
supplied, <b>disown</b> removes or marks the current
|
|
job.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is 0 unless an <i>id</i> does not specify a valid
|
|
job.</p>
|
|
|
|
<p style="margin-left:6%;"><b>echo</b> [<b>-neE</b>]
|
|
[<i>arg</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Output the <i>arg</i>s,
|
|
separated by spaces, followed by a newline. The return
|
|
status is 0 unless a write error occurs. If <b>-n</b> is
|
|
specified, the trailing newline is not printed.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-e</b> option is given, <b>echo</b> interprets the
|
|
following backslash-escaped characters. The <b>-E</b> option
|
|
disables interpretation of these escape characters, even on
|
|
systems where they are interpreted by default. The
|
|
<b>xpg_echo</b> shell option determines whether or not
|
|
<b>echo</b> interprets any options and expands these escape
|
|
characters. <b>echo</b> does not interpret <b>--</b> to mean
|
|
the end of options.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>echo</b>
|
|
interprets the following escape sequences:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p><b>\a</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>alert (bell)</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\b</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">backspace</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\c</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">suppress further output</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\e</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\E</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">an escape character</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\f</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">form feed</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\n</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">new line</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\r</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">carriage return</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\t</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">horizontal tab</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\v</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">vertical tab</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\\</b></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">backslash</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\0</b><i>nnn</i></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The eight-bit character whose
|
|
value is the octal value <i>nnn</i> (zero to three octal
|
|
digits).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>\x</b><i>HH</i></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The eight-bit character whose
|
|
value is the hexadecimal value <i>HH</i> (one or two hex
|
|
digits).</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>\u</b><i>HHHH</i></p>
|
|
|
|
<p style="margin-left:24%;">The Unicode (ISO/IEC 10646)
|
|
character whose value is the hexadecimal value <i>HHHH</i>
|
|
(one to four hex digits).</p>
|
|
|
|
<p style="margin-left:15%;"><b>\U</b><i>HHHHHHHH</i></p>
|
|
|
|
<p style="margin-left:24%;">The Unicode (ISO/IEC 10646)
|
|
character whose value is the hexadecimal value
|
|
<i>HHHHHHHH</i> (one to eight hex digits).</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>echo</b>
|
|
writes any unrecognized backslash-escaped characters
|
|
unchanged.</p>
|
|
|
|
<p style="margin-left:6%;"><b>enable</b> [<b>-a</b>]
|
|
[<b>-dnps</b>] [<b>-f</b> <i>filename</i>] [<i>name</i>
|
|
...]</p>
|
|
|
|
<p style="margin-left:15%;">Enable and disable builtin
|
|
shell commands. Disabling a builtin allows an executable
|
|
file which has the same name as a shell builtin to be
|
|
executed without specifying a full pathname, even though the
|
|
shell normally searches for builtins before files.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If <b>-n</b> is
|
|
supplied, each <i>name</i> is disabled; otherwise,
|
|
<i>name</i>s are enabled. For example, to use the
|
|
<b>test</b> binary found using <b>PATH</b> instead of the
|
|
shell builtin version, run “enable -n test”.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If no
|
|
<i>name</i> arguments are supplied, or if the <b>-p</b>
|
|
option is supplied, print a list of shell builtins. With no
|
|
other option arguments, the list consists of all enabled
|
|
shell builtins. If <b>-n</b> is supplied, print only
|
|
disabled builtins. If <b>-a</b> is supplied, the list
|
|
printed includes all builtins, with an indication of whether
|
|
or not each is enabled. The <b>-s</b> option means to
|
|
restrict the output to the POSIX <i>special</i>
|
|
builtins.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-f</b>
|
|
option means to load the new builtin command <i>name</i>
|
|
from shared object <i>filename</i>, on systems that support
|
|
dynamic loading. If <i>filename</i> does not contain a
|
|
slash, <b>Bash</b> will use the value of the
|
|
<b>BASH_LOADABLES_PATH</b> variable as a colon-separated
|
|
list of directories in which to search for <i>filename</i>.
|
|
The default for <b>BASH_LOADABLES_PATH</b> is
|
|
system-dependent, and may include “.” to force a
|
|
search of the current directory. The <b>-d</b> option will
|
|
delete a builtin previously loaded with <b>-f</b>. If
|
|
<b>-s</b> is used with <b>-f</b>, the new builtin becomes a
|
|
POSIX special builtin.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If no options
|
|
are supplied and a <i>name</i> is not a shell builtin,
|
|
<b>enable</b> will attempt to load <i>name</i> from a shared
|
|
object named <i>name</i>, as if the command were
|
|
“enable -f <i>name name</i>”.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is 0 unless a <i>name</i> is not a shell builtin or
|
|
there is an error loading a new builtin from a shared
|
|
object.</p>
|
|
|
|
<p style="margin-left:6%;"><b>eval</b> [<i>arg</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Concatenate the <i>arg</i>s
|
|
together into a single command, separating them with spaces.
|
|
<b>Bash</b> then reads and execute this command, and returns
|
|
its exit status as the return status of <b>eval</b>. If
|
|
there are no <i>args</i>, or only null arguments,
|
|
<b>eval</b> returns 0.</p>
|
|
|
|
<p style="margin-left:6%;"><b>exec</b> [<b>-cl</b>]
|
|
[<b>-a</b> <i>name</i>] [<i>command</i>
|
|
[<i>arguments</i>]]</p>
|
|
|
|
<p style="margin-left:15%;">If <i>command</i> is specified,
|
|
it replaces the shell without creating a new process.
|
|
<i>command</i> cannot be a shell builtin or function. The
|
|
<i>arguments</i> become the arguments to <i>command</i>. If
|
|
the <b>-l</b> option is supplied, the shell places a dash at
|
|
the beginning of the zeroth argument passed to
|
|
<i>command</i>. This is what <i>login</i>(1) does. The
|
|
<b>-c</b> option causes <i>command</i> to be executed with
|
|
an empty environment. If <b>-a</b> is supplied, the shell
|
|
passes <i>name</i> as the zeroth argument to the executed
|
|
command.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>command</i> cannot be executed for some reason, a
|
|
non-interactive shell exits, unless the <b>execfail</b>
|
|
shell option is enabled. In that case, it returns a non-zero
|
|
status. An interactive shell returns a non-zero status if
|
|
the file cannot be executed. A subshell exits
|
|
unconditionally if <b>exec</b> fails.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>command</i> is not specified, any redirections take
|
|
effect in the current shell, and the return status is 0. If
|
|
there is a redirection error, the return status is 1.</p>
|
|
|
|
<p style="margin-left:6%;"><b>exit</b> [<i>n</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Cause the shell to exit with a
|
|
status of <i>n</i>. If <i>n</i> is omitted, the exit status
|
|
is that of the last command executed. Any trap on
|
|
<b>EXIT</b> is executed before the shell terminates.</p>
|
|
|
|
<p style="margin-left:6%;"><b>export</b> [<b>-fn</b>]
|
|
[<i>name</i>[=<i>value</i>]] ... <b><br>
|
|
export -p [-f]</b></p>
|
|
|
|
<p style="margin-left:15%;">The supplied <i>names</i> are
|
|
marked for automatic export to the environment of
|
|
subsequently executed commands. If the <b>-f</b> option is
|
|
given, the <i>names</i> refer to functions.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-n</b>
|
|
option unexports, or removes the export attribute, from each
|
|
<i>name</i>. If no <i>names</i> are given, or if only the
|
|
<b>-p</b> option is supplied, <b>export</b> displays a list
|
|
of names of all exported variables on the standard output.
|
|
Using <b>-p</b> and <b>-f</b> together displays exported
|
|
functions. The <b>-p</b> option displays output in a form
|
|
that may be reused as input.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>export</b>
|
|
allows the value of a variable to be set when it is exported
|
|
or unexported by following the variable name with
|
|
=<i>value</i>. This sets the value of the variable to
|
|
<i>value</i> while modifying the export attribute.
|
|
<b>export</b> returns an exit status of 0 unless an invalid
|
|
option is encountered, one of the <i>names</i> is not a
|
|
valid shell variable name, or <b>-f</b> is supplied with a
|
|
<i>name</i> that is not a function.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>false</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="50%">
|
|
|
|
|
|
<p>Does nothing; returns a non-zero status.</p></td>
|
|
<td width="35%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>fc</b> [<b>-e</b>
|
|
<i>ename</i>] [<b>-D</b>] [<b>-lnr</b>] [<i>first</i>]
|
|
[<i>last</i>] <b><br>
|
|
fc -s</b> [<i>pat</i>=<i>rep</i>] [<i>cmd</i>]</p>
|
|
|
|
<p style="margin-left:15%;">The first form selects a range
|
|
of commands from <i>first</i> to <i>last</i> from the
|
|
history list and displays or edits and re-executes them.
|
|
<i>First</i> and <i>last</i> may be specified as a string
|
|
(to locate the last command beginning with that string) or
|
|
as a number (an index into the history list, where a
|
|
negative number is used as an offset from the current
|
|
command number).</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When listing, a
|
|
<i>first</i> or <i>last</i> of 0 is equivalent to -1 and -0
|
|
is equivalent to the current command (usually the <b>fc</b>
|
|
command); otherwise 0 is equivalent to -1 and -0 is invalid.
|
|
If <i>last</i> is not specified, it is set to the current
|
|
command for listing (so that “fc -l -10” prints
|
|
the last 10 commands) and to <i>first</i> otherwise. If
|
|
<i>first</i> is not specified, it is set to the previous
|
|
command for editing and -16 for listing.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-l</b> option is supplied, the commands are listed on the
|
|
standard output. The <b>-n</b> option suppresses the command
|
|
numbers when listing. The <b>-r</b> option reverses the
|
|
order of the commands.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Otherwise,
|
|
<b>fc</b> invokes the editor named by <i>ename</i> on a file
|
|
containing those commands. If <i>ename</i> is not supplied,
|
|
<b>fc</b> uses the value of the <b>FCEDIT</b> variable, and
|
|
the value of <b>EDITOR</b> if <b>FCEDIT</b> is not set. If
|
|
neither variable is set, <b>fc</b> uses <i>vi.</i> When
|
|
editing is complete, <b>fc</b> reads the file containing the
|
|
edited commands and echoes and executes them. The <b>-D</b>
|
|
option, if supplied, causes <b>fc</b> to remove the selected
|
|
commands from the history list before executing the file of
|
|
edited commands. <b>-D</b> is only effective when <b>fc</b>
|
|
is invoked in this way.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">In the second
|
|
form, <b>fc</b> re-executes <i>command</i> after replacing
|
|
each instance of <i>pat</i> with <i>rep</i>. <i>Command</i>
|
|
is interpreted the same as <i>first</i> above.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">A useful alias
|
|
to use with <b>fc</b> is “r="fc -s"”,
|
|
so that typing “r cc” runs the last command
|
|
beginning with “cc” and typing “r”
|
|
re-executes the last command.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the first
|
|
form is used, the return value is zero unless an invalid
|
|
option is encountered or <i>first</i> or <i>last</i> specify
|
|
history lines out of range. When editing and re-executing a
|
|
file of commands, the return value is the value of the last
|
|
command executed or failure if an error occurs with the
|
|
temporary file. If the second form is used, the return
|
|
status is that of the re-executed command, unless <i>cmd</i>
|
|
does not specify a valid history entry, in which case
|
|
<b>fc</b> returns a non-zero status.</p>
|
|
|
|
<p style="margin-left:6%;"><b>fg</b> [<i>jobspec</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Resume <i>jobspec</i> in the
|
|
foreground, and make it the current job. If <i>jobspec</i>
|
|
is not present, <b>fg</b> uses the shell’s notion of
|
|
the <i>current job</i>. The return value is that of the
|
|
command placed into the foreground, or failure if run when
|
|
job control is disabled or, when run with job control
|
|
enabled, if <i>jobspec</i> does not specify a valid job or
|
|
<i>jobspec</i> specifies a job that was started without job
|
|
control.</p>
|
|
|
|
<p style="margin-left:6%;"><b>getopts</b> <i>optstring
|
|
name</i> [<i>arg</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;"><b>getopts</b> is used by shell
|
|
scripts and functions to parse positional parameters and
|
|
obtain options and their arguments. <i>optstring</i>
|
|
contains the option characters to be recognized; if a
|
|
character is followed by a colon, the option is expected to
|
|
have an argument, which should be separated from it by white
|
|
space. The colon and question mark characters may not be
|
|
used as option characters.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Each time it is
|
|
invoked, <b>getopts</b> places the next option in the shell
|
|
variable <i>name</i>, initializing <i>name</i> if it does
|
|
not exist, and the index of the next argument to be
|
|
processed into the variable <b>OPTIND</b>. <b>OPTIND</b> is
|
|
initialized to 1 each time the shell or a shell script is
|
|
invoked. When an option requires an argument, <b>getopts</b>
|
|
places that argument into the variable <b>OPTARG</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The shell does
|
|
not reset <b>OPTIND</b> automatically; it must be manually
|
|
reset between multiple calls to <b>getopts</b> within the
|
|
same shell invocation to use a new set of parameters.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When it reaches
|
|
the end of options, <b>getopts</b> exits with a return value
|
|
greater than zero. <b>OPTIND</b> is set to the index of the
|
|
first non-option argument, and <i>name</i> is set to ?.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>getopts</b>
|
|
normally parses the positional parameters, but if more
|
|
arguments are supplied as <i>arg</i> values, <b>getopts</b>
|
|
parses those instead.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>getopts</b>
|
|
can report errors in two ways. If the first character of
|
|
<i>optstring</i> is a colon, <b>getopts</b> uses
|
|
<i>silent</i> error reporting. In normal operation,
|
|
<b>getopts</b> prints diagnostic messages when it encounters
|
|
invalid options or missing option arguments. If the variable
|
|
<b>OPTERR</b> is set to 0, <b>getopts</b> does not display
|
|
any error messages, even if the first character of
|
|
<i>optstring</i> is not a colon.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<b>getopts</b> detects an invalid option, it places ? into
|
|
<i>name</i> and, if not silent, prints an error message and
|
|
unsets <b>OPTARG</b>. If <b>getopts</b> is silent, it
|
|
assigns the option character found to <b>OPTARG</b> and does
|
|
not print a diagnostic message.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If a required
|
|
argument is not found, and <b>getopts</b> is not silent, it
|
|
sets the value of <i>name</i> to a question mark (<b>?</b>),
|
|
unsets <b>OPTARG</b>, and prints a diagnostic message. If
|
|
<b>getopts</b> is silent, it sets the value of <i>name</i>
|
|
to a colon (<b>:</b>) and sets <b>OPTARG</b> to the option
|
|
character found.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>getopts</b>
|
|
returns true if an option, specified or unspecified, is
|
|
found. It returns false if the end of options is encountered
|
|
or an error occurs.</p>
|
|
|
|
<p style="margin-left:6%;"><b>hash</b> [<b>-lr</b>]
|
|
[<b>-p</b> <i>filename</i>] [<b>-dt</b>] [<i>name</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Each time <b>hash</b> is
|
|
invoked, it remembers the full pathname of the command
|
|
<i>name</i> as determined by searching the directories in
|
|
<b>$PATH</b>. Any previously-remembered pathname associated
|
|
with <i>name</i> is discarded. If the <b>-p</b> option is
|
|
supplied, <b>hash</b> uses <i>filename</i> as the full
|
|
pathname of the command.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-r</b>
|
|
option causes the shell to forget all remembered locations.
|
|
Assigning to the <b>PATH</b> variable also clears all hashed
|
|
filenames. The <b>-d</b> option causes the shell to forget
|
|
the remembered location of each <i>name</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-t</b> option is supplied, <b>hash</b> prints the full
|
|
pathname corresponding to each <i>name</i>. If multiple
|
|
<i>name</i> arguments are supplied with <b>-t</b>,
|
|
<b>hash</b> prints the <i>name</i> before the corresponding
|
|
hashed full pathname. The <b>-l</b> option displays output
|
|
in a format that may be reused as input.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If no arguments
|
|
are given, or if only <b>-l</b> is supplied, <b>hash</b>
|
|
prints information about remembered commands. The <b>-t</b>,
|
|
<b>-d</b>, and <b>-p</b> options (the options that act on
|
|
the <i>name</i> arguments) are mutually exclusive. Only one
|
|
will be active. If more than one is supplied, <b>-t</b> has
|
|
higher priority than <b>-p</b>, and both have higher
|
|
priority than <b>-d</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
status is zero unless a <i>name</i> is not found or an
|
|
invalid option is supplied.</p>
|
|
|
|
<p style="margin-left:6%;"><b>help</b> [<b>-dms</b>]
|
|
[<i>pattern</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Display helpful information
|
|
about builtin commands. If <i>pattern</i> is specified,
|
|
<b>help</b> gives detailed help on all commands matching
|
|
<i>pattern</i> as described below; otherwise it displays a
|
|
list of all the builtins and shell compound commands.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Options, if
|
|
supplied, have the follow meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-d</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Display a short description of each <i>pattern</i></p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-m</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display the description of each
|
|
<i>pattern</i> in a manpage-like format</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-s</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display only a short usage
|
|
synopsis for each <i>pattern</i></p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>pattern</i> contains pattern matching characters (see
|
|
<b>Pattern Matching</b> above) it’s treated as a shell
|
|
pattern and <b>help</b> prints the description of each help
|
|
topic matching <i>pattern</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If not, and
|
|
<i>pattern</i> exactly matches the name of a help topic,
|
|
<b>help</b> prints the description associated with that
|
|
topic. Otherwise, <b>help</b> performs prefix matching and
|
|
prints the descriptions of all matching help topics.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
status is 0 unless no command matches <i>pattern</i>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>history [-H]
|
|
[</b><i>range</i><b>] <br>
|
|
history -c <br>
|
|
history -d</b> <i>range</i> <b><br>
|
|
history -anrw</b> [<i>filename</i>] <b><br>
|
|
history -p</b> <i>arg</i> [<i>arg</i> ...] <b><br>
|
|
history -s</b> <i>arg</i> [<i>arg</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">With no options, or with the
|
|
<b>-H</b> option, display the portion of the command history
|
|
list specified by <i>range</i>, as described below. If
|
|
<i>range</i> is not specified, display the entire history
|
|
list. Without <b>-H</b>, display the list with command
|
|
numbers, prefixing entries that have been modified with a
|
|
“*”.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">A <i>range</i>
|
|
argument is specified in the form of a number <i>offset</i>
|
|
or a range <i>start</i>-<i>end</i>. If <i>offset</i> is
|
|
supplied, it references the history entry at position
|
|
<i>offset</i> in the history list; when listing this
|
|
displays the last <i>offset</i> entries. A negative
|
|
<i>offset</i> counts back from the end of the history list,
|
|
relative to one greater than the last history position. When
|
|
listing, negative and positive <i>offsets</i> have identical
|
|
results. <i>start</i> and <i>end</i>, if supplied, reference
|
|
the portion of the history list beginning at position
|
|
<i>start</i> through position <i>end</i>. If <i>start</i> or
|
|
<i>end</i> are negative, they count back from the end of the
|
|
history list. When listing, if <i>start</i> is greater than
|
|
<i>end</i>, the history entries are displayed in reverse
|
|
order from <i>end</i> to <i>start</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the shell
|
|
variable <b>HISTTIMEFORMAT</b> is set and not null, it is
|
|
used as a format string for <i>strftime</i>(3) to display
|
|
the time stamp associated with each displayed history entry.
|
|
If <b>history</b> uses <b>HISTTIMEFORMAT</b>, it does not
|
|
print an intervening space between the formatted time stamp
|
|
and the history entry.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>filename</i> is supplied, <b>history</b> uses it as the
|
|
name of the history file; if not, it uses the value of
|
|
<b>HISTFILE</b>. If <i>filename</i> is not supplied and
|
|
<b>HISTFILE</b> is unset or null, the <b>-a, -n, -r,</b> and
|
|
<b>-w</b> options have no effect.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Options, if
|
|
supplied, have the following meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-c</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Clear the history list by deleting all the entries. This
|
|
can be used with the other options to replace the history
|
|
list.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>-d</b> <i>range</i></p>
|
|
|
|
<p style="margin-left:24%;">Delete the history entries
|
|
specified by <i>range</i>, as described above. An index of
|
|
-1 refers to the current <b>history -d</b> command.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-H</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Display the selected history entries in the format that
|
|
would be written to the history file, including any time
|
|
stamp information as described below, without prefixing the
|
|
entry with any line number or “*”.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-a</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Append the “new”
|
|
history lines to the history file. These are history lines
|
|
entered since the beginning of the current <b>bash</b>
|
|
session, but not already appended to the history file.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-n</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Read the history lines not
|
|
already read from the history file and add them to the
|
|
current history list. These are lines appended to the
|
|
history file since the beginning of the current <b>bash</b>
|
|
session.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-r</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Read the history file and append
|
|
its contents to the current history list.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-w</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Write the current history list
|
|
to the history file, overwriting the history file.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-p</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Perform history substitution on
|
|
the following <i>args</i> and display the result on the
|
|
standard output, without storing the results in the history
|
|
list. Each <i>arg</i> must be quoted to disable normal
|
|
history expansion.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-s</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Store the <i>args</i> in the
|
|
history list as a single entry. The last command in the
|
|
history list is removed before adding the <i>args</i>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>HISTTIMEFORMAT</b> variable is set, <b>history</b> writes
|
|
the time stamp information associated with each history
|
|
entry to the history file, marked with the history comment
|
|
character as described above. When the history file is read,
|
|
lines beginning with the history comment character followed
|
|
immediately by a digit are interpreted as timestamps for the
|
|
following history entry.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is 0 unless an invalid option is encountered, an error
|
|
occurs while reading or writing the history file, an invalid
|
|
<i>offset</i> or range is supplied as an argument to
|
|
<b>-d</b>, or the history expansion supplied as an argument
|
|
to <b>-p</b> fails.</p>
|
|
|
|
<p style="margin-left:6%;"><b>jobs</b> [<b>-lnprs</b>] [
|
|
<i>jobspec</i> ... ] <b><br>
|
|
jobs -x</b> <i>command</i> [ <i>args</i> ... ]</p>
|
|
|
|
<p style="margin-left:15%;">The first form lists the active
|
|
jobs. The options have the following meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-l</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>List process IDs in addition to the normal
|
|
information.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-n</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display information only about
|
|
jobs that have changed status since the user was last
|
|
notified of their status.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-p</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">List only the process ID of the
|
|
job’s process group leader.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-r</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display only running jobs.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-s</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Display only stopped jobs.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If
|
|
<i>jobspec</i> is supplied, <b>jobs</b> restricts output to
|
|
information about that job. The return status is 0 unless an
|
|
invalid option is encountered or an invalid <i>jobspec</i>
|
|
is supplied.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-x</b> option is supplied, <b>jobs</b> replaces any
|
|
<i>jobspec</i> found in <i>command</i> or <i>args</i> with
|
|
the corresponding process group ID, and executes
|
|
<i>command</i>, passing it <i>args</i>, returning its exit
|
|
status.</p>
|
|
|
|
<p style="margin-left:6%;"><b>kill</b> [<b>-s</b>
|
|
<i>sigspec</i> | <b>-n</b> <i>signum</i> |
|
|
<b>-</b><i>sigspec</i>] <i>id</i> [ ... ] <b><br>
|
|
kill -l</b>|<b>-L</b> [<i>sigspec</i> |
|
|
<i>exit_status</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Send the signal specified by
|
|
<i>sigspec</i> or <i>signum</i> to the processes named by
|
|
each <i>id</i>. Each <i>id</i> may be a job specification
|
|
<i>jobspec</i> or a process ID <i>pid</i>. <i>sigspec</i> is
|
|
either a case-insensitive signal name such as <b>SIGKILL</b>
|
|
(with or without the <b>SIG</b> prefix) or a signal number;
|
|
<i>signum</i> is a signal number. If <i>sigspec</i> is not
|
|
supplied, then <b>kill</b> sends <b>SIGTERM</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-l</b>
|
|
option lists the signal names. If any arguments are supplied
|
|
when <b>-l</b> is given, <b>kill</b> lists the names of the
|
|
signals corresponding to the arguments, and the return
|
|
status is 0. The <i>exit_status</i> argument to <b>-l</b> is
|
|
a number specifying either a signal number or the exit
|
|
status of a process terminated by a signal; if it is
|
|
supplied, <b>kill</b> prints the name of the signal that
|
|
caused the process to terminate. <b>kill</b> assumes that
|
|
process exit statuses are greater than 128; anything less
|
|
than that is a signal number. The <b>-L</b> option is
|
|
equivalent to <b>-l</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>kill</b>
|
|
returns true if at least one signal was successfully sent,
|
|
or false if an error occurs or an invalid option is
|
|
encountered.</p>
|
|
|
|
<p style="margin-left:6%;"><b>let</b> <i>arg</i>
|
|
[<i>arg</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Each <i>arg</i> is evaluated as
|
|
an arithmetic expression (see <b>ARITHMETIC EVALUATION</b>
|
|
above). If the last <i>arg</i> evaluates to 0, <b>let</b>
|
|
returns 1; otherwise <b>let</b> returns 0.</p>
|
|
|
|
<p style="margin-left:6%;"><b>local</b> [<i>option</i>]
|
|
[<i>name</i>[=<i>value</i>] ... | - ]</p>
|
|
|
|
<p style="margin-left:15%;">For each argument, create a
|
|
local variable named <i>name</i> and assign it <i>value</i>.
|
|
The <i>option</i> can be any of the options accepted by
|
|
<b>declare</b>. When <b>local</b> is used within a function,
|
|
it causes the variable <i>name</i> to have a visible scope
|
|
restricted to that function and its children. It is an error
|
|
to use <b>local</b> when not within a function.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If <i>name</i>
|
|
is -, it makes the set of shell options local to the
|
|
function in which <b>local</b> is invoked: any shell options
|
|
changed using the <b>set</b> builtin inside the function
|
|
after the call to <b>local</b> are restored to their
|
|
original values when the function returns. The restore is
|
|
performed as if a series of <b>set</b> commands were
|
|
executed to restore the values that were in place before the
|
|
function.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">With no
|
|
operands, <b>local</b> writes a list of local variables to
|
|
the standard output.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
status is 0 unless <b>local</b> is used outside a function,
|
|
an invalid <i>name</i> is supplied, or <i>name</i> is a
|
|
readonly variable.</p>
|
|
|
|
<p style="margin-left:6%;"><b>logout
|
|
[</b><i>n</i><b>]</b></p>
|
|
|
|
<p style="margin-left:15%;">Exit a login shell, returning a
|
|
status of <i>n</i> to the shell’s parent.</p>
|
|
|
|
<p style="margin-left:6%;"><b>mapfile</b> [<b>-d</b>
|
|
<i>delim</i>] [<b>-n</b> <i>count</i>] [<b>-O</b>
|
|
<i>origin</i>] [<b>-s</b> <i>count</i>] [<b>-t</b>]
|
|
[<b>-u</b> <i>fd</i>] [<b>-C</b> <i><br>
|
|
callback</i>] [<b>-c</b> <i>quantum</i>] [<i>array</i>]
|
|
<b><br>
|
|
readarray</b> [<b>-d</b> <i>delim</i>] [<b>-n</b>
|
|
<i>count</i>] [<b>-O</b> <i>origin</i>] [<b>-s</b>
|
|
<i>count</i>] [<b>-t</b>] [<b>-u</b> <i>fd</i>] [<b>-C</b>
|
|
<i><br>
|
|
callback</i>] [<b>-c</b> <i>quantum</i>] [<i>array</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Read lines from the standard
|
|
input, or from file descriptor <i>fd</i> if the <b>-u</b>
|
|
option is supplied, into the indexed array variable
|
|
<i>array</i>. The variable <b>MAPFILE</b> is the default
|
|
<i>array</i>. Options, if supplied, have the following
|
|
meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-d</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Use the first character of <i>delim</i> to terminate
|
|
each input line, rather than newline. If <i>delim</i> is the
|
|
empty string, <b>mapfile</b> will terminate a line when it
|
|
reads a NUL character.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-n</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Copy at most <i>count</i> lines.
|
|
If <i>count</i> is 0, copy all lines.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-O</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Begin assigning to <i>array</i>
|
|
at index <i>origin</i>. The default index is 0.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-s</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Discard the first <i>count</i>
|
|
lines read.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-t</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Remove a trailing <i>delim</i>
|
|
(default newline) from each line read.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-u</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Read lines from file descriptor
|
|
<i>fd</i> instead of the standard input.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-C</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Evaluate <i>callback</i> each
|
|
time <i>quantum</i> lines are read. The <b>-c</b> option
|
|
specifies <i>quantum</i>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-c</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Specify the number of lines read
|
|
between each call to <i>callback</i>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If <b>-C</b> is
|
|
specified without <b>-c</b>, the default quantum is 5000.
|
|
When <i>callback</i> is evaluated, it is supplied the index
|
|
of the next array element to be assigned and the line to be
|
|
assigned to that element as additional arguments.
|
|
<i>callback</i> is evaluated after the line is read but
|
|
before the array element is assigned.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If not supplied
|
|
with an explicit origin, <b>mapfile</b> will clear
|
|
<i>array</i> before assigning to it.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>mapfile</b>
|
|
returns zero unless an invalid option or option argument is
|
|
supplied, <i>array</i> is invalid or unassignable, or if
|
|
<i>array</i> is not an indexed array.</p>
|
|
|
|
<p style="margin-left:6%;"><b>popd</b> [-<b>n</b>]
|
|
[+<i>n</i>] [-<i>n</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Remove entries from the
|
|
directory stack. The elements are numbered from 0 starting
|
|
at the first directory listed by <b>dirs</b>, so <b>popd</b>
|
|
is equivalent to “popd +0.” With no arguments,
|
|
<b>popd</b> removes the top directory from the stack, and
|
|
changes to the new top directory. Arguments, if supplied,
|
|
have the following meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-n</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Suppress the normal change of directory when removing
|
|
directories from the stack, only manipulate the stack.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>+</b><i>n</i></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Remove the <i>n</i>th entry
|
|
counting from the left of the list shown by <b>dirs</b>,
|
|
starting with zero, from the stack. For example: “popd
|
|
+0” removes the first directory, “popd +1”
|
|
the second.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-</b><i>n</i></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Remove the <i>n</i>th entry
|
|
counting from the right of the list shown by <b>dirs</b>,
|
|
starting with zero. For example: “popd -0”
|
|
removes the last directory, “popd -1” the next
|
|
to last.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the top
|
|
element of the directory stack is modified, and the
|
|
<b>-n</b> option was not supplied, <b>popd</b> uses the
|
|
<b>cd</b> builtin to change to the directory at the top of
|
|
the stack. If the <b>cd</b> fails, <b>popd</b> returns a
|
|
non-zero value.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Otherwise,
|
|
<b>popd</b> returns false if an invalid option is supplied,
|
|
the directory stack is empty, or <i>n</i> specifies a
|
|
non-existent directory stack entry.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>popd</b> command is successful, <b>bash</b> runs
|
|
<b>dirs</b> to show the final contents of the directory
|
|
stack, and the return status is 0.</p>
|
|
|
|
<p style="margin-left:6%;"><b>printf</b> [<b>-v</b>
|
|
<i>var</i>] <i>format</i> [<i>arguments</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Write the formatted
|
|
<i>arguments</i> to the standard output under the control of
|
|
the <i>format</i>. The <b>-v</b> option assigns the output
|
|
to the variable <i>var</i> rather than printing it to the
|
|
standard output.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The
|
|
<i>format</i> is a character string which contains three
|
|
types of objects: plain characters, which are simply copied
|
|
to standard output, character escape sequences, which are
|
|
converted and copied to the standard output, and format
|
|
specifications, each of which causes printing of the next
|
|
successive <i>argument</i>. In addition to the standard
|
|
<i>printf</i>(3) format characters
|
|
<b>cCsSndiouxXeEfFgGaA</b>, <b>printf</b> interprets the
|
|
following additional format specifiers:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>%b</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>causes <b>printf</b> to expand backslash escape
|
|
sequences in the corresponding <i>argument</i> in the same
|
|
way as <b>echo -e</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>%q</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">causes <b>printf</b> to output
|
|
the corresponding <i>argument</i> in a format that can be
|
|
reused as shell input. <b>%q</b> and <b>%Q</b> use the
|
|
<b>$''</b> quoting style if any characters in the argument
|
|
string require it, and backslash quoting otherwise. If the
|
|
format string uses the <i>printf</i> alternate form, these
|
|
two formats quote the argument string using single
|
|
quotes.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>%Q</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">like <b>%q</b>, but applies any
|
|
supplied precision to the <i>argument</i> before quoting
|
|
it.</p> </td></tr>
|
|
</table>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>%(</b><i>datefmt</i><b>)T</b></p>
|
|
|
|
<p style="margin-left:24%;">causes <b>printf</b> to output
|
|
the date-time string resulting from using <i>datefmt</i> as
|
|
a format string for <i>strftime</i>(3). The corresponding
|
|
<i>argument</i> is an integer representing the number of
|
|
seconds since the epoch. This format specifier recognizes
|
|
two special argument values: -1 represents the current time,
|
|
and -2 represents the time the shell was invoked. If no
|
|
argument is specified, conversion behaves as if -1 had been
|
|
supplied. This is an exception to the usual <b>printf</b>
|
|
behavior.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The %b, %q, and
|
|
%T format specifiers all use the field width and precision
|
|
arguments from the format specification and write that many
|
|
bytes from (or use that wide a field for) the expanded
|
|
argument, which usually contains more characters than the
|
|
original.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The %n format
|
|
specifier accepts a corresponding argument that is treated
|
|
as a shell variable name.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The %s and %c
|
|
format specifiers accept an l (long) modifier, which forces
|
|
them to convert the argument string to a wide-character
|
|
string and apply any supplied field width and precision in
|
|
terms of characters, not bytes. The %S and %C format
|
|
specifiers are equivalent to %ls and %lc, respectively.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Arguments to
|
|
non-string format specifiers are treated as C constants,
|
|
except that a leading plus or minus sign is allowed, and if
|
|
the leading character is a single or double quote, the value
|
|
is the numeric value of the following character, using the
|
|
current locale.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Format
|
|
specifiers may apply to the <i>n</i>th argument rather than
|
|
the next sequential argument. In this case, the
|
|
’%’ in the format specifier is replaced by the
|
|
sequence “%<i>n</i>$”, where <i>n</i> is a
|
|
decimal integer greater than 0, giving the argument number
|
|
to use as the operand. The format string should not mix
|
|
numbered and unnumbered argument specifiers, though this is
|
|
allowed. Unnumbered argument specifiers always refer to the
|
|
next argument following the last argument consumed by an
|
|
unnumbered specifier; numbered argument specifiers refer to
|
|
absolute positions in the argument list.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The
|
|
<i>format</i> is reused as necessary to consume all of the
|
|
<i>arguments</i>. If the <i>format</i> requires more
|
|
<i>arguments</i> than are supplied, the extra format
|
|
specifications behave as if a zero value or null string, as
|
|
appropriate, had been supplied. If <i>format</i> is reused,
|
|
a numbered argument specifier “%<i>n</i>$”
|
|
refers to the <i>n</i>th argument following the highest
|
|
numbered argument consumed by the previous use of
|
|
<i>format</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
value is zero on success, non-zero if an invalid option is
|
|
supplied or a write or assignment error occurs.</p>
|
|
|
|
<p style="margin-left:6%;"><b>pushd</b> [<b>-n</b>]
|
|
[+<i>n</i>] [-<i>n</i>] <b><br>
|
|
pushd</b> [<b>-n</b>] [<i>dir</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Add a directory to the top of
|
|
the directory stack, or rotate the stack, making the new top
|
|
of the stack the current working directory. With no
|
|
arguments, <b>pushd</b> exchanges the top two elements of
|
|
the directory stack. Arguments, if supplied, have the
|
|
following meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p><b>-n</b></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Suppress the normal change of directory when rotating or
|
|
adding directories to the stack, only manipulate the
|
|
stack.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>+</b><i>n</i></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Rotate the stack so that the
|
|
<i>n</i>th directory (counting from the left of the list
|
|
shown by <b>dirs</b>, starting with zero) is at the top.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-</b><i>n</i></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Rotates the stack so that the
|
|
<i>n</i>th directory (counting from the right of the list
|
|
shown by <b>dirs</b>, starting with zero) is at the top.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="4%">
|
|
|
|
|
|
<p style="margin-top: 1em"><i>dir</i></p></td>
|
|
<td width="5%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Adds <i>dir</i> to the directory
|
|
stack at the top.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">After the stack
|
|
has been modified, if the <b>-n</b> option was not supplied,
|
|
<b>pushd</b> uses the <b>cd</b> builtin to change to the
|
|
directory at the top of the stack. If the <b>cd</b> fails,
|
|
<b>pushd</b> returns a non-zero value.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Otherwise, if
|
|
no arguments are supplied, <b>pushd</b> returns zero unless
|
|
the directory stack is empty. When rotating the directory
|
|
stack, <b>pushd</b> returns zero unless the directory stack
|
|
is empty or <i>n</i> specifies a non-existent directory
|
|
stack element.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>pushd</b> command is successful, <b>bash</b> runs
|
|
<b>dirs</b> to show the final contents of the directory
|
|
stack.</p>
|
|
|
|
<p style="margin-left:6%;"><b>pwd</b> [<b>-LP</b>]</p>
|
|
|
|
<p style="margin-left:15%;">Print the absolute pathname of
|
|
the current working directory. The pathname printed contains
|
|
no symbolic links if the <b>-P</b> option is supplied or the
|
|
<b>-o physical</b> option to the <b>set</b> builtin command
|
|
is enabled. If the <b>-L</b> option is used, the pathname
|
|
printed may contain symbolic links. The return status is 0
|
|
unless an error occurs while reading the name of the current
|
|
directory or an invalid option is supplied.</p>
|
|
|
|
<p style="margin-left:6%;"><b>read</b> [<b>-Eers</b>]
|
|
[<b>-a</b> <i>aname</i>] [<b>-d</b> <i>delim</i>] [<b>-i</b>
|
|
<i>text</i>] [<b>-n</b> <i>nchars</i>] [<b>-N</b>
|
|
<i>nchars</i>] [<b>-p</b> <i><br>
|
|
prompt</i>] [<b>-t</b> <i>timeout</i>] [<b>-u</b> <i>fd</i>]
|
|
[<i>name</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Read one line from the standard
|
|
input, or from the file descriptor <i>fd</i> supplied as an
|
|
argument to the <b>-u</b> option, split it into words as
|
|
described above under <b>Word Splitting</b>, and assign the
|
|
first word to the first <i>name</i>, the second word to the
|
|
second <i>name</i>, and so on. If there are more words than
|
|
names, the remaining words and their intervening delimiters
|
|
are assigned to the last <i>name</i>. If there are fewer
|
|
words read from the input stream than names, the remaining
|
|
names are assigned empty values. The characters in the value
|
|
of the <b>IFS</b> variable are used to split the line into
|
|
words using the same rules the shell uses for expansion
|
|
(described above under <b>Word Splitting</b>). The backslash
|
|
character (<b>\</b>) removes any special meaning for the
|
|
next character read and is used for line continuation.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Options, if
|
|
supplied, have the following meanings: <b><br>
|
|
-a</b> <i>aname</i></p>
|
|
|
|
<p style="margin-left:24%;">The words are assigned to
|
|
sequential indices of the array variable <i>aname</i>,
|
|
starting at 0. <i>aname</i> is unset before any new values
|
|
are assigned. Other <i>name</i> arguments are ignored.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-d</b> <i>delim</i></p>
|
|
|
|
<p style="margin-left:24%;">The first character of
|
|
<i>delim</i> terminates the input line, rather than newline.
|
|
If <i>delim</i> is the empty string, <b>read</b> will
|
|
terminate a line when it reads a NUL character.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-e</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>If the standard input is coming from a terminal,
|
|
<b>read</b> uses <b>readline</b> (see <b>READLINE</b> above)
|
|
to obtain the line. <b>Readline</b> uses the current (or
|
|
default, if line editing was not previously active) editing
|
|
settings, but uses <b>readline</b>’s default filename
|
|
completion.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-E</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the standard input is coming
|
|
from a terminal, <b>read</b> uses <b>readline</b> (see
|
|
<b>READLINE</b> above) to obtain the line. <b>Readline</b>
|
|
uses the current (or default, if line editing was not
|
|
previously active) editing settings, but uses bash’s
|
|
default completion, including programmable completion.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>-i</b> <i>text</i></p>
|
|
|
|
<p style="margin-left:24%;">If <b>readline</b> is being
|
|
used to read the line, <b>read</b> places <i>text</i> into
|
|
the editing buffer before editing begins.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-n</b> <i>nchars</i></p>
|
|
|
|
<p style="margin-left:24%;"><b>read</b> returns after
|
|
reading <i>nchars</i> characters rather than waiting for a
|
|
complete line of input, unless it encounters EOF or
|
|
<b>read</b> times out, but honors a delimiter if it reads
|
|
fewer than <i>nchars</i> characters before the
|
|
delimiter.</p>
|
|
|
|
<p style="margin-left:15%;"><b>-N</b> <i>nchars</i></p>
|
|
|
|
<p style="margin-left:24%;"><b>read</b> returns after
|
|
reading exactly <i>nchars</i> characters rather than waiting
|
|
for a complete line of input, unless it encounters EOF or
|
|
<b>read</b> times out. Any delimiter characters in the input
|
|
are not treated specially and do not cause <b>read</b> to
|
|
return until it has read <i>nchars</i> characters. The
|
|
result is not split on the characters in <b>IFS</b>; the
|
|
intent is that the variable is assigned exactly the
|
|
characters read (with the exception of backslash; see the
|
|
<b>-r</b> option below).</p>
|
|
|
|
<p style="margin-left:15%;"><b>-p</b> <i>prompt</i></p>
|
|
|
|
<p style="margin-left:24%;">Display <i>prompt</i> on
|
|
standard error, without a trailing newline, before
|
|
attempting to read any input, but only if input is coming
|
|
from a terminal.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-r</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Backslash does not act as an escape character. The
|
|
backslash is considered to be part of the line. In
|
|
particular, a backslash-newline pair may not then be used as
|
|
a line continuation.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-s</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Silent mode. If input is coming
|
|
from a terminal, characters are not echoed.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>-t</b> <i>timeout</i></p>
|
|
|
|
<p style="margin-left:24%;">Cause <b>read</b> to time out
|
|
and return failure if it does not read a complete line of
|
|
input (or a specified number of characters) within
|
|
<i>timeout</i> seconds. <i>timeout</i> may be a decimal
|
|
number with a fractional portion following the decimal
|
|
point. This option is only effective if <b>read</b> is
|
|
reading input from a terminal, pipe, or other special file;
|
|
it has no effect when reading from regular files. If
|
|
<b>read</b> times out, it saves any partial input read into
|
|
the specified variable <i>name</i>, and the exit status is
|
|
greater than 128. If <i>timeout</i> is 0, <b>read</b>
|
|
returns immediately, without trying to read any data. In
|
|
this case, the exit status is 0 if input is available on the
|
|
specified file descriptor, or the read will return EOF,
|
|
non-zero otherwise.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p><b>-u</b> <i>fd</i></p></td>
|
|
<td width="3%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Read input from file descriptor <i>fd</i> instead of the
|
|
standard input.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Other than the
|
|
case where <i>delim</i> is the empty string, <b>read</b>
|
|
ignores any NUL characters in the input.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If no
|
|
<i>names</i> are supplied, <b>read</b> assigns the line
|
|
read, without the ending delimiter but otherwise unmodified,
|
|
to the variable <b>REPLY</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The exit status
|
|
is zero, unless end-of-file is encountered, <b>read</b>
|
|
times out (in which case the status is greater than 128), a
|
|
variable assignment error (such as assigning to a readonly
|
|
variable) occurs, or an invalid file descriptor is supplied
|
|
as the argument to <b>-u</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>readonly</b> [<b>-aAf</b>]
|
|
[<b>-p</b>] [<i>name</i>[=<i>word</i>] ...]</p>
|
|
|
|
<p style="margin-left:15%;">The given <i>names</i> are
|
|
marked readonly; the values of these <i>names</i> may not be
|
|
changed by subsequent assignment or unset. If the <b>-f</b>
|
|
option is supplied, each <i>name</i> refers to a shell
|
|
function. The <b>-a</b> option restricts the variables to
|
|
indexed arrays; the <b>-A</b> option restricts the variables
|
|
to associative arrays. If both options are supplied,
|
|
<b>-A</b> takes precedence. If no <i>name</i> arguments are
|
|
supplied, or if the <b>-p</b> option is supplied, print a
|
|
list of all readonly names. The other options may be used to
|
|
restrict the output to a subset of the set of readonly
|
|
names. The <b>-p</b> option displays output in a format that
|
|
may be reused as input.</p>
|
|
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>readonly</b>
|
|
allows the value of a variable to be set at the same time
|
|
the readonly attribute is changed by following the variable
|
|
name with =<i>value</i>. This sets the value of the variable
|
|
is to <i>value</i> while modifying the readonly
|
|
attribute.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
status is 0 unless an invalid option is encountered, one of
|
|
the <i>names</i> is not a valid shell variable name, or
|
|
<b>-f</b> is supplied with a <i>name</i> that is not a
|
|
function.</p>
|
|
|
|
<p style="margin-left:6%;"><b>return</b> [<i>n</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Stop executing a shell function
|
|
or sourced file and return the value specified by <i>n</i>
|
|
to its caller. If <i>n</i> is omitted, the return status is
|
|
that of the last command executed. If <b>return</b> is
|
|
executed by a trap handler, the last command used to
|
|
determine the status is the last command executed before the
|
|
trap handler. If <b>return</b> is executed during a
|
|
<b>DEBUG</b> trap, the last command used to determine the
|
|
status is the last command executed by the trap handler
|
|
before <b>return</b> was invoked.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When
|
|
<b>return</b> is used to terminate execution of a script
|
|
being executed by the <b>.</b> (<b>source</b>) command, it
|
|
causes the shell to stop executing that script and return
|
|
either <i>n</i> or the exit status of the last command
|
|
executed within the script as the exit status of the script.
|
|
If <i>n</i> is supplied, the return value is its least
|
|
significant 8 bits.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Any command
|
|
associated with the <b>RETURN</b> trap is executed before
|
|
execution resumes after the function or script.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
status is non-zero if <b>return</b> is supplied a
|
|
non-numeric argument, or is used outside a function and not
|
|
during execution of a script by <b>.</b> or
|
|
<b>source</b>.</p>
|
|
|
|
<p style="margin-left:6%;"><b>set</b>
|
|
[<b>-abefhkmnptuvxBCEHPT</b>] [<b>-o</b> <i>option-name</i>]
|
|
[<b>--</b>] [<b>-</b>] [<i>arg</i> ...] <b><br>
|
|
set</b> [<b>+abefhkmnptuvxBCEHPT</b>] [<b>+o</b>
|
|
<i>option-name</i>] [<b>--</b>] [<b>-</b>] [<i>arg</i> ...]
|
|
<b><br>
|
|
set -o <br>
|
|
set +o</b></p>
|
|
|
|
<p style="margin-left:15%;">Without options, display the
|
|
name and value of each shell variable in a format that can
|
|
be reused as input for setting or resetting the
|
|
currently-set variables. Read-only variables cannot be
|
|
reset. In posix mode, only shell variables are listed. The
|
|
output is sorted according to the current locale. When
|
|
options are specified, they set or unset shell attributes.
|
|
Any arguments remaining after option processing are treated
|
|
as values for the positional parameters and are assigned, in
|
|
order, to <b>$1</b>, <b>$2</b>, ..., <b>$</b><i>n</i>.
|
|
Options, if specified, have the following meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-a</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p>Each variable or function that is created or modified is
|
|
given the export attribute and marked for export to the
|
|
environment of subsequent commands.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-b</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Report the status of terminated
|
|
background jobs immediately, rather than before the next
|
|
primary prompt or after a foreground command terminates.
|
|
This is effective only when job control is enabled.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-e</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Exit immediately if a
|
|
<i>pipeline</i> (which may consist of a single <i>simple
|
|
command</i>), a <i>list</i>, or a <i>compound command</i>
|
|
(see <b>SHELL GRAMMAR</b> above), exits with a non-zero
|
|
status. The shell does not exit if the command that fails is
|
|
part of the command list immediately following a
|
|
<b>while</b> or <b>until</b> reserved word, part of the test
|
|
following the <b>if</b> or <b>elif</b> reserved words, part
|
|
of any command executed in a <b>&&</b> or <b>||</b>
|
|
list except the command following the final
|
|
<b>&&</b> or <b>||</b>, any command in a pipeline
|
|
but the last (subject to the state of the <b>pipefail</b>
|
|
shell option), or if the command’s return value is
|
|
being inverted with <b>!</b>. If a compound command other
|
|
than a subshell returns a non-zero status because a command
|
|
failed while <b>-e</b> was being ignored, the shell does not
|
|
exit. A trap on <b>ERR</b>, if set, is executed before the
|
|
shell exits. This option applies to the shell environment
|
|
and each subshell environment separately (see <b>COMMAND
|
|
EXECUTION ENVIRONMENT</b> above), and may cause subshells to
|
|
exit before executing all the commands in the subshell.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%; margin-top: 1em">If a compound
|
|
command or shell function executes in a context where
|
|
<b>-e</b> is being ignored, none of the commands executed
|
|
within the compound command or function body will be
|
|
affected by the <b>-e</b> setting, even if <b>-e</b> is set
|
|
and a command returns a failure status. If a compound
|
|
command or shell function sets <b>-e</b> while executing in
|
|
a context where <b>-e</b> is ignored, that setting will not
|
|
have any effect until the compound command or the command
|
|
containing the function call completes.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-f</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Disable pathname expansion.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-h</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Remember the location of
|
|
commands as they are looked up for execution. This is
|
|
enabled by default.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-k</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">All arguments in the form of
|
|
assignment statements are placed in the environment for a
|
|
command, not just those that precede the command name.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-m</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Monitor mode. Job control is
|
|
enabled. This option is on by default for interactive shells
|
|
on systems that support it (see <b>JOB CONTROL</b> above).
|
|
All processes run in a separate process group. When a
|
|
background job completes, the shell prints a line containing
|
|
its exit status.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-n</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Read commands but do not execute
|
|
them. This may be used to check a shell script for syntax
|
|
errors. This is ignored by interactive shells.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>-o</b>
|
|
<i>option-name</i></p>
|
|
|
|
<p style="margin-left:25%;">The <i>option-name</i> can be
|
|
one of the following: <b><br>
|
|
allexport</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-a</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>braceexpand</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-B</b>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p><b>emacs</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p>Use an emacs-style command line editing interface. This
|
|
is enabled by default when the shell is interactive, unless
|
|
the shell is started with the <b>--noediting</b> option.
|
|
This also affects the editing interface used for <b>read
|
|
-e</b>.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>errexit</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-e</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>errtrace</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-E</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>functrace</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-T</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>hashall</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-h</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>histexpand</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-H</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>history</b></p>
|
|
|
|
<p style="margin-left:35%;">Enable command history, as
|
|
described above under <b>HISTORY</b>. This option is on by
|
|
default in interactive shells.</p>
|
|
|
|
<p style="margin-left:25%;"><b>ignoreeof</b></p>
|
|
|
|
<p style="margin-left:35%;">The effect is as if the shell
|
|
command “IGNOREEOF=10” had been executed (see
|
|
<b>Shell Variables</b> above).</p>
|
|
|
|
<p style="margin-left:25%;"><b>keyword</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-k</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>monitor</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-m</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>noclobber</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-C</b>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p><b>noexec</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="23%">
|
|
|
|
|
|
<p>Same as <b>-n</b>.</p></td>
|
|
<td width="42%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>noglob</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="23%">
|
|
|
|
|
|
<p style="margin-top: 1em">Same as <b>-f</b>.</p></td>
|
|
<td width="42%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>nolog</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="23%">
|
|
|
|
|
|
<p style="margin-top: 1em">Currently ignored.</p></td>
|
|
<td width="42%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>notify</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="23%">
|
|
|
|
|
|
<p style="margin-top: 1em">Same as <b>-b</b>.</p></td>
|
|
<td width="42%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>nounset</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-u</b>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p><b>onecmd</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="14%">
|
|
|
|
|
|
<p>Same as <b>-t</b>.</p></td>
|
|
<td width="51%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>physical</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-P</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>pipefail</b></p>
|
|
|
|
<p style="margin-left:35%;">If set, the return value of a
|
|
pipeline is the value of the last (rightmost) command to
|
|
exit with a non-zero status, or zero if all commands in the
|
|
pipeline exit successfully. This option is disabled by
|
|
default.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="6%">
|
|
|
|
|
|
<p><b>posix</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p>Enable posix mode; change the behavior of <b>bash</b>
|
|
where the default operation differs from the POSIX standard
|
|
to match the standard. See <b>SEE ALSO</b> below for a
|
|
reference to a document that details how posix mode affects
|
|
bash’s behavior.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;"><b>privileged</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-p</b>.</p>
|
|
|
|
<p style="margin-left:25%;"><b>verbose</b></p>
|
|
|
|
<p style="margin-left:35%;">Same as <b>-v</b>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p><b>vi</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p>Use a vi-style command line editing interface. This also
|
|
affects the editing interface used for <b>read -e</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>xtrace</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p style="margin-top: 1em">Same as <b>-x</b>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:25%;">If <b>-o</b> is supplied with
|
|
no <i>option-name</i>, <b>set</b> prints the current shell
|
|
option settings. If <b>+o</b> is supplied with no
|
|
<i>option-name</i>, <b>set</b> prints a series of <b>set</b>
|
|
commands to recreate the current option settings on the
|
|
standard output.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-p</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Turn on <i>privileged</i> mode.
|
|
In this mode, the shell does not read the <b>$ENV</b> and
|
|
<b>$BASH_ENV</b> files, does not inherit shell functions
|
|
from the environment, and ignores the <b>SHELLOPTS</b>,
|
|
<b>BASHOPTS</b>, <b>CDPATH</b>, and <b>GLOBIGNORE</b>
|
|
variables, if they appear in the environment. If the shell
|
|
is started with the effective user (group) id not equal to
|
|
the real user (group) id, and the <b>-p</b> option is not
|
|
supplied, these actions are taken and the effective user id
|
|
is set to the real user id (see <b>INVOCATION</b> above for
|
|
more details). If the <b>-p</b> option is supplied at
|
|
startup, the effective user id is not reset. Turning this
|
|
option off causes the effective user and group ids to be set
|
|
to the real user and group ids.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-r</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Enable restricted shell mode.
|
|
This option cannot be unset once it has been set.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-t</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Exit after reading and executing
|
|
one command.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-u</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Treat unset variables and
|
|
parameters other than the special parameters “@”
|
|
and “*”, or array variables subscripted with
|
|
“@” or “*”, as an error when
|
|
performing parameter expansion. If expansion is attempted on
|
|
an unset variable or parameter, the shell prints an error
|
|
message, and, if not interactive, exits with a non-zero
|
|
status.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-v</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Print shell input lines as they
|
|
are read.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-x</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">After expanding each <i>simple
|
|
command</i>, <b>for</b> command, <b>case</b> command,
|
|
<b>select</b> command, or arithmetic <b>for</b> command,
|
|
display the expanded value of <b>PS4</b>, followed by the
|
|
command and its expanded arguments or associated word list,
|
|
to the standard error.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-B</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">The shell performs brace
|
|
expansion (see <b>Brace Expansion</b> above). This is on by
|
|
default.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-C</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">If set, <b>bash</b> does not
|
|
overwrite an existing file with the <b>></b>,
|
|
<b>>&</b>, and <b><></b> redirection operators.
|
|
Using the redirection operator <b>>|</b> instead of
|
|
<b>></b> will override this and force the creation of an
|
|
output file.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-E</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">If set, any trap on <b>ERR</b>
|
|
is inherited by shell functions, command substitutions, and
|
|
commands executed in a subshell environment. The <b>ERR</b>
|
|
trap is normally not inherited in such cases.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-H</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Enable <b>!</b> style history
|
|
substitution. This option is on by default when the shell is
|
|
interactive.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-P</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">If set, the shell does not
|
|
resolve symbolic links when executing commands such as
|
|
<b>cd</b> that change the current working directory. It uses
|
|
the physical directory structure instead. By default,
|
|
<b>bash</b> follows the logical chain of directories when
|
|
performing commands which change the current directory.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-T</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">If set, any traps on
|
|
<b>DEBUG</b> and <b>RETURN</b> are inherited by shell
|
|
functions, command substitutions, and commands executed in a
|
|
subshell environment. The <b>DEBUG</b> and <b>RETURN</b>
|
|
traps are normally not inherited in such cases.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>--</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">If no arguments follow this
|
|
option, unset the positional parameters. Otherwise, set the
|
|
positional parameters to the <i>arg</i>s, even if some of
|
|
them begin with a <b>-</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-</b></p></td>
|
|
<td width="7%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p style="margin-top: 1em">Signal the end of options, and
|
|
assign all remaining <i>arg</i>s to the positional
|
|
parameters. The <b>-x</b> and <b>-v</b> options are turned
|
|
off. If there are no <i>arg</i>s, the positional parameters
|
|
remain unchanged.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The options are
|
|
off by default unless otherwise noted. Using + rather than -
|
|
causes these options to be turned off. The options can also
|
|
be specified as arguments to an invocation of the shell. The
|
|
current set of options may be found in <b>$-</b>. The return
|
|
status is always zero unless an invalid option is
|
|
encountered.</p>
|
|
|
|
<p style="margin-left:6%;"><b>shift</b> [<i>n</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Rename positional parameters
|
|
from <i>n</i>+1 ... to <b>$1 ....</b> Parameters represented
|
|
by the numbers <b>$#</b> down to <b>$#</b>-<i>n</i>+1 are
|
|
unset. <i>n</i> must be a non-negative number less than or
|
|
equal to <b>$#</b>. If <i>n</i> is 0, no parameters are
|
|
changed. If <i>n</i> is not given, it is assumed to be 1. If
|
|
<i>n</i> is greater than <b>$#</b>, the positional
|
|
parameters are not changed. The return status is greater
|
|
than zero if <i>n</i> is greater than <b>$#</b> or less than
|
|
zero; otherwise 0.</p>
|
|
|
|
<p style="margin-left:6%;"><b>shopt</b> [<b>-pqsu</b>]
|
|
[<b>-o</b>] [<i>optname</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Toggle the values of settings
|
|
controlling optional shell behavior. The settings can be
|
|
either those listed below, or, if the <b>-o</b> option is
|
|
used, those available with the <b>-o</b> option to the
|
|
<b>set</b> builtin command.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">With no
|
|
options, or with the <b>-p</b> option, display a list of all
|
|
settable options, with an indication of whether or not each
|
|
is set; if any <i>optnames</i> are supplied, the output is
|
|
restricted to those options. The <b>-p</b> option displays
|
|
output in a form that may be reused as input.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Other options
|
|
have the following meanings:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-s</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Enable (set) each <i>optname</i>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-u</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Disable (unset) each
|
|
<i>optname</i>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-q</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Suppresses normal output (quiet
|
|
mode); the return status indicates whether the
|
|
<i>optname</i> is set or unset. If multiple <i>optname</i>
|
|
arguments are supplied with <b>-q</b>, the return status is
|
|
zero if all <i>optnames</i> are enabled; non-zero
|
|
otherwise.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-o</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Restricts the values of
|
|
<i>optname</i> to be those defined for the <b>-o</b> option
|
|
to the <b>set</b> builtin.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If either
|
|
<b>-s</b> or <b>-u</b> is used with no <i>optname</i>
|
|
arguments, <b>shopt</b> shows only those options which are
|
|
set or unset, respectively. Unless otherwise noted, the
|
|
<b>shopt</b> options are disabled (unset) by default.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The return
|
|
status when listing options is zero if all <i>optnames</i>
|
|
are enabled, non-zero otherwise. When setting or unsetting
|
|
options, the return status is zero unless an <i>optname</i>
|
|
is not a valid shell option.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The list of
|
|
<b>shopt</b> options is: <b><br>
|
|
array_expand_once</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the shell suppresses
|
|
multiple evaluation of associative and indexed array
|
|
subscripts during arithmetic expression evaluation, while
|
|
executing builtins that can perform variable assignments,
|
|
and while executing builtins that perform array
|
|
dereferencing.</p>
|
|
|
|
<p style="margin-left:15%;"><b>assoc_expand_once</b></p>
|
|
|
|
<p style="margin-left:25%;">Deprecated; a synonym for
|
|
<b>array_expand_once</b>.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="8%">
|
|
|
|
|
|
<p><b>autocd</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="75%">
|
|
|
|
|
|
<p>If set, a command name that is the name of a directory
|
|
is executed as if it were the argument to the <b>cd</b>
|
|
command. This option is only used by interactive shells.</p></td></tr>
|
|
</table>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>bash_source_fullpath</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, filenames added to the
|
|
<b>BASH_SOURCE</b> array variable are converted to full
|
|
pathnames (see <b>Shell Variables</b> above).</p>
|
|
|
|
<p style="margin-left:15%;"><b>cdable_vars</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, an argument to the
|
|
<b>cd</b> builtin command that is not a directory is assumed
|
|
to be the name of a variable whose value is the directory to
|
|
change to.</p>
|
|
|
|
<p style="margin-left:15%;"><b>cdspell</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the <b>cd</b> command
|
|
attempts to correct minor errors in the spelling of a
|
|
directory component. Minor errors include transposed
|
|
characters, a missing character, and one extra character. If
|
|
<b>cd</b> corrects the directory name, it prints the
|
|
corrected filename, and the command proceeds. This option is
|
|
only used by interactive shells.</p>
|
|
|
|
<p style="margin-left:15%;"><b>checkhash</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> checks that
|
|
a command found in the hash table exists before trying to
|
|
execute it. If a hashed command no longer exists,
|
|
<b>bash</b> performs a normal path search.</p>
|
|
|
|
<p style="margin-left:15%;"><b>checkjobs</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> lists the
|
|
status of any stopped and running jobs before exiting an
|
|
interactive shell. If any jobs are running, <b>bash</b>
|
|
defers the exit until a second exit is attempted without an
|
|
intervening command (see <b>JOB CONTROL</b> above). The
|
|
shell always postpones exiting if any jobs are stopped.</p>
|
|
|
|
<p style="margin-left:15%;"><b>checkwinsize</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> checks the
|
|
window size after each external (non-builtin) command and,
|
|
if necessary, updates the values of <b>LINES</b> and
|
|
<b>COLUMNS</b>, using the file descriptor associated with
|
|
the standard error if it is a terminal. This option is
|
|
enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>cmdhist</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> attempts to
|
|
save all lines of a multiple-line command in the same
|
|
history entry. This allows easy re-editing of multi-line
|
|
commands. This option is enabled by default, but only has an
|
|
effect if command history is enabled, as described above
|
|
under <b>HISTORY</b>.</p>
|
|
|
|
<p style="margin-left:15%;"><b>compat31 <br>
|
|
compat32 <br>
|
|
compat40 <br>
|
|
compat41 <br>
|
|
compat42 <br>
|
|
compat43 <br>
|
|
compat44</b></p>
|
|
|
|
<p style="margin-left:25%;">These control aspects of the
|
|
shell’s compatibility mode (see <b>SHELL COMPATIBILITY
|
|
MODE</b> below).</p>
|
|
|
|
<p style="margin-left:15%;"><b>complete_fullquote</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> quotes all
|
|
shell metacharacters in filenames and directory names when
|
|
performing completion. If not set, <b>bash</b> removes
|
|
metacharacters such as the dollar sign from the set of
|
|
characters that will be quoted in completed filenames when
|
|
these metacharacters appear in shell variable references in
|
|
words to be completed. This means that dollar signs in
|
|
variable names that expand to directories will not be
|
|
quoted; however, any dollar signs appearing in filenames
|
|
will not be quoted, either. This is active only when bash is
|
|
using backslashes to quote completed filenames. This
|
|
variable is set by default, which is the default bash
|
|
behavior in versions through 4.2.</p>
|
|
|
|
<p style="margin-left:15%;"><b>direxpand</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> replaces
|
|
directory names with the results of word expansion when
|
|
performing filename completion. This changes the contents of
|
|
the <b>readline</b> editing buffer. If not set, <b>bash</b>
|
|
attempts to preserve what the user typed.</p>
|
|
|
|
<p style="margin-left:15%;"><b>dirspell</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> attempts
|
|
spelling correction on directory names during word
|
|
completion if the directory name initially supplied does not
|
|
exist.</p>
|
|
|
|
<p style="margin-left:15%;"><b>dotglob</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> includes
|
|
filenames beginning with a “.” in the results of
|
|
pathname expansion. The filenames <i>.</i> and <i>..</i>
|
|
must always be matched explicitly, even if <b>dotglob</b> is
|
|
set.</p>
|
|
|
|
<p style="margin-left:15%;"><b>execfail</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, a non-interactive shell
|
|
will not exit if it cannot execute the file specified as an
|
|
argument to the <b>exec</b> builtin. An interactive shell
|
|
does not exit if <b>exec</b> fails.</p>
|
|
|
|
<p style="margin-left:15%;"><b>expand_aliases</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, aliases are expanded as
|
|
described above under <b>ALIASES</b>. This option is enabled
|
|
by default for interactive shells.</p>
|
|
|
|
<p style="margin-left:15%;"><b>extdebug</b></p>
|
|
|
|
<p style="margin-left:25%;">If set at shell invocation, or
|
|
in a shell startup file, arrange to execute the debugger
|
|
profile before the shell starts, identical to the
|
|
<b>--debugger</b> option. If set after invocation, behavior
|
|
intended for use by debuggers is enabled:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>1.</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="66%">
|
|
|
|
|
|
<p>The <b>-F</b> option to the <b>declare</b> builtin
|
|
displays the source file name and line number corresponding
|
|
to each function name supplied as an argument.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>2.</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="66%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the command run by the
|
|
<b>DEBUG</b> trap returns a non-zero value, the next command
|
|
is skipped and not executed.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>3.</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="66%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the command run by the
|
|
<b>DEBUG</b> trap returns a value of 2, and the shell is
|
|
executing in a subroutine (a shell function or a shell
|
|
script executed by the <b>.</b> or <b>source</b> builtins),
|
|
the shell simulates a call to <b>return</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>4.</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="66%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>BASH_ARGC</b> and
|
|
<b>BASH_ARGV</b> are updated as described in their
|
|
descriptions above).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>5.</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="66%">
|
|
|
|
|
|
<p style="margin-top: 1em">Function tracing is enabled:
|
|
command substitution, shell functions, and subshells invoked
|
|
with <b>(</b> <i>command</i> <b>)</b> inherit the
|
|
<b>DEBUG</b> and <b>RETURN</b> traps.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="25%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>6.</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="66%">
|
|
|
|
|
|
<p style="margin-top: 1em">Error tracing is enabled:
|
|
command substitution, shell functions, and subshells invoked
|
|
with <b>(</b> <i>command</i> <b>)</b> inherit the <b>ERR</b>
|
|
trap.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%;"><b>extglob</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, enable the extended
|
|
pattern matching features described above under <b>Pathname
|
|
Expansion</b>.</p>
|
|
|
|
<p style="margin-left:15%;"><b>extquote</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>$</b>'<i>string</i>'
|
|
and <b>$</b>"<i>string</i>" quoting is performed
|
|
within <b>${</b><i>parameter</i><b>}</b> expansions enclosed
|
|
in double quotes. This option is enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>failglob</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, patterns which fail to
|
|
match filenames during pathname expansion result in an
|
|
expansion error.</p>
|
|
|
|
<p style="margin-left:15%;"><b>force_fignore</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the suffixes specified
|
|
by the <b>FIGNORE</b> shell variable cause words to be
|
|
ignored when performing word completion even if the ignored
|
|
words are the only possible completions. See <b>Shell
|
|
Variables</b> above for a description of <b>FIGNORE</b>.
|
|
This option is enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>globasciiranges</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, range expressions used
|
|
in pattern matching bracket expressions (see <b>Pattern
|
|
Matching</b> above) behave as if in the traditional C locale
|
|
when performing comparisons. That is, pattern matching does
|
|
not take the current locale’s collating sequence into
|
|
account, so <b>b</b> will not collate between <b>A</b> and
|
|
<b>B</b>, and upper-case and lower-case ASCII characters
|
|
will collate together.</p>
|
|
|
|
<p style="margin-left:15%;"><b>globskipdots</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, pathname expansion will
|
|
never match the filenames <i>.</i> and <i>..</i>, even if
|
|
the pattern begins with a “.”. This option is
|
|
enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>globstar</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the pattern <b>**</b>
|
|
used in a pathname expansion context will match all files
|
|
and zero or more directories and subdirectories. If the
|
|
pattern is followed by a <b>/</b>, only directories and
|
|
subdirectories match.</p>
|
|
|
|
<p style="margin-left:15%;"><b>gnu_errfmt</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, shell error messages
|
|
are written in the standard GNU error message format.</p>
|
|
|
|
<p style="margin-left:15%;"><b>histappend</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the history list is
|
|
appended to the file named by the value of the
|
|
<b>HISTFILE</b> variable when the shell exits, rather than
|
|
overwriting the file.</p>
|
|
|
|
<p style="margin-left:15%;"><b>histreedit</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, and <b>readline</b> is
|
|
being used, the user is given the opportunity to re-edit a
|
|
failed history substitution.</p>
|
|
|
|
<p style="margin-left:15%;"><b>histverify</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, and <b>readline</b> is
|
|
being used, the results of history substitution are not
|
|
immediately passed to the shell parser. Instead, the
|
|
resulting line is loaded into the <b>readline</b> editing
|
|
buffer, allowing further modification.</p>
|
|
|
|
<p style="margin-left:15%;"><b>hostcomplete</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, and <b>readline</b> is
|
|
being used, <b>bash</b> will attempt to perform hostname
|
|
completion when a word containing a <b>@</b> is being
|
|
completed (see <b>Completing</b> under <b>READLINE</b>
|
|
above). This is enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>huponexit</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> will send
|
|
<b>SIGHUP</b> to all jobs when an interactive login shell
|
|
exits.</p>
|
|
|
|
<p style="margin-left:15%;"><b>inherit_errexit</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, command substitution
|
|
inherits the value of the <b>errexit</b> option, instead of
|
|
unsetting it in the subshell environment. This option is
|
|
enabled when posix mode is enabled.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>interactive_comments</b></p>
|
|
|
|
<p style="margin-left:25%;">In an interactive shell, a word
|
|
beginning with <b>#</b> causes that word and all remaining
|
|
characters on that line to be ignored, as in a
|
|
non-interactive shell (see <b>COMMENTS</b> above). This
|
|
option is enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>lastpipe</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, and job control is not
|
|
active, the shell runs the last command of a pipeline not
|
|
executed in the background in the current shell
|
|
environment.</p>
|
|
|
|
<p style="margin-left:15%;"><b>lithist</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, and the <b>cmdhist</b>
|
|
option is enabled, multi-line commands are saved to the
|
|
history with embedded newlines rather than using semicolon
|
|
separators where possible.</p>
|
|
|
|
<p style="margin-left:15%;"><b>localvar_inherit</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, local variables inherit
|
|
the value and attributes of a variable of the same name that
|
|
exists at a previous scope before any new value is assigned.
|
|
The nameref attribute is not inherited.</p>
|
|
|
|
<p style="margin-left:15%;"><b>localvar_unset</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, calling <b>unset</b> on
|
|
local variables in previous function scopes marks them so
|
|
subsequent lookups find them unset until that function
|
|
returns. This is identical to the behavior of unsetting
|
|
local variables at the current function scope.</p>
|
|
|
|
<p style="margin-left:15%;"><b>login_shell</b></p>
|
|
|
|
<p style="margin-left:25%;">The shell sets this option if
|
|
it is started as a login shell (see <b>INVOCATION</b>
|
|
above). The value may not be changed.</p>
|
|
|
|
<p style="margin-left:15%;"><b>mailwarn</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, and a file that
|
|
<b>bash</b> is checking for mail has been accessed since the
|
|
last time it was checked, <b>bash</b> displays the message
|
|
“The mail in <i>mailfile</i> has been read”.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>no_empty_cmd_completion</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, and <b>readline</b> is
|
|
being used, <b>bash</b> does not search <b>PATH</b> for
|
|
possible completions when completion is attempted on an
|
|
empty line.</p>
|
|
|
|
<p style="margin-left:15%;"><b>nocaseglob</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> matches
|
|
filenames in a case-insensitive fashion when performing
|
|
pathname expansion (see <b>Pathname Expansion</b>
|
|
above).</p>
|
|
|
|
<p style="margin-left:15%;"><b>nocasematch</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> matches
|
|
patterns in a case-insensitive fashion when performing
|
|
matching while executing <b>case</b> or <b>[[</b>
|
|
conditional commands, when performing pattern substitution
|
|
word expansions, or when filtering possible completions as
|
|
part of programmable completion.</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><b>noexpand_translation</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> encloses
|
|
the translated results of <b>$"</b>...<b>"</b>
|
|
quoting in single quotes instead of double quotes. If the
|
|
string is not translated, this has no effect.</p>
|
|
|
|
<p style="margin-left:15%;"><b>nullglob</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, pathname expansion
|
|
patterns which match no files (see <b>Pathname Expansion</b>
|
|
above) expand to nothing and are removed, rather than
|
|
expanding to themselves.</p>
|
|
|
|
<p style="margin-left:15%;"><b>patsub_replacement</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, <b>bash</b> expands
|
|
occurrences of <b>&</b> in the replacement string of
|
|
pattern substitution to the text matched by the pattern, as
|
|
described under <b>Parameter Expansion</b> above. This
|
|
option is enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>progcomp</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, enable the programmable
|
|
completion facilities (see <b>Programmable Completion</b>
|
|
above). This option is enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>progcomp_alias</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, and programmable
|
|
completion is enabled, <b>bash</b> treats a command name
|
|
that doesn’t have any completions as a possible alias
|
|
and attempts alias expansion. If it has an alias,
|
|
<b>bash</b> attempts programmable completion using the
|
|
command word resulting from the expanded alias.</p>
|
|
|
|
<p style="margin-left:15%;"><b>promptvars</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, prompt strings undergo
|
|
parameter expansion, command substitution, arithmetic
|
|
expansion, and quote removal after being expanded as
|
|
described in <b>PROMPTING</b> above. This option is enabled
|
|
by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>restricted_shell</b></p>
|
|
|
|
<p style="margin-left:25%;">The shell sets this option if
|
|
it is started in restricted mode (see <b>RESTRICTED
|
|
SHELL</b> below). The value may not be changed. This is not
|
|
reset when the startup files are executed, allowing the
|
|
startup files to discover whether or not a shell is
|
|
restricted.</p>
|
|
|
|
<p style="margin-left:15%;"><b>shift_verbose</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the <b>shift</b>
|
|
builtin prints an error message when the shift count exceeds
|
|
the number of positional parameters.</p>
|
|
|
|
<p style="margin-left:15%;"><b>sourcepath</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the <b>.</b>
|
|
(<b>source</b>) builtin uses the value of <b>PATH</b> to
|
|
find the directory containing the file supplied as an
|
|
argument when the <b>-p</b> option is not supplied. This
|
|
option is enabled by default.</p>
|
|
|
|
<p style="margin-left:15%;"><b>varredir_close</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the shell automatically
|
|
closes file descriptors assigned using the <i>{varname}</i>
|
|
redirection syntax (see <b>REDIRECTION</b> above) instead of
|
|
leaving them open when the command completes.</p>
|
|
|
|
<p style="margin-left:15%;"><b>xpg_echo</b></p>
|
|
|
|
<p style="margin-left:25%;">If set, the <b>echo</b> builtin
|
|
expands backslash-escape sequences by default. If the
|
|
<b>posix</b> shell option is also enabled, <b>echo</b> does
|
|
not interpret any options.</p>
|
|
|
|
<p style="margin-left:6%;"><b>suspend</b> [<b>-f</b>]</p>
|
|
|
|
<p style="margin-left:15%;">Suspend the execution of this
|
|
shell until it receives a <b>SIGCONT</b> signal. A login
|
|
shell, or a shell without job control enabled, cannot be
|
|
suspended; the <b>-f</b> option will override this and force
|
|
the suspension. The return status is 0 unless the shell is a
|
|
login shell or job control is not enabled and <b>-f</b> is
|
|
not supplied.</p>
|
|
|
|
<p style="margin-left:6%;"><b>test</b> <i>expr</i> <b><br>
|
|
[</b> <i>expr</i> <b>]</b></p>
|
|
|
|
<p style="margin-left:15%;">Return a status of 0 (true) or
|
|
1 (false) depending on the evaluation of the conditional
|
|
expression <i>expr</i>. Each operator and operand must be a
|
|
separate argument. Expressions are composed of the primaries
|
|
described above under <b>CONDITIONAL EXPRESSIONS</b>.
|
|
<b>test</b> does not accept any options, nor does it accept
|
|
and ignore an argument of <b>--</b> as signifying the end of
|
|
options.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Expressions may
|
|
be combined using the following operators, listed in
|
|
decreasing order of precedence. The evaluation depends on
|
|
the number of arguments; see below. <b>test</b> uses
|
|
operator precedence when there are five or more arguments.
|
|
<b><br>
|
|
!</b> <i>expr</i></p>
|
|
|
|
<p style="margin-left:24%;">True if <i>expr</i> is
|
|
false.</p>
|
|
|
|
<p style="margin-left:15%;"><b>(</b> <i>expr</i>
|
|
<b>)</b></p>
|
|
|
|
<p style="margin-left:24%;">Returns the value of
|
|
<i>expr</i>. This may be used to override normal operator
|
|
precedence.</p>
|
|
|
|
<p style="margin-left:15%;"><i>expr1</i> -<b>a</b>
|
|
<i>expr2</i></p>
|
|
|
|
<p style="margin-left:24%;">True if both <i>expr1</i> and
|
|
<i>expr2</i> are true.</p>
|
|
|
|
<p style="margin-left:15%;"><i>expr1</i> -<b>o</b>
|
|
<i>expr2</i></p>
|
|
|
|
<p style="margin-left:24%;">True if either <i>expr1</i> or
|
|
<i>expr2</i> is true.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em"><b>test</b> and
|
|
<b>[</b> evaluate conditional expressions using a set of
|
|
rules based on the number of arguments. <br>
|
|
0 arguments</p>
|
|
|
|
<p style="margin-left:24%;">The expression is false.</p>
|
|
|
|
<p style="margin-left:15%;">1 argument</p>
|
|
|
|
<p style="margin-left:24%;">The expression is true if and
|
|
only if the argument is not null.</p>
|
|
|
|
<p style="margin-left:15%;">2 arguments</p>
|
|
|
|
<p style="margin-left:24%;">If the first argument is
|
|
<b>!</b>, the expression is true if and only if the second
|
|
argument is null. If the first argument is one of the unary
|
|
conditional operators listed above under <b>CONDITIONAL
|
|
EXPRESSIONS</b>, the expression is true if the unary test is
|
|
true. If the first argument is not a valid unary conditional
|
|
operator, the expression is false.</p>
|
|
|
|
<p style="margin-left:15%;">3 arguments</p>
|
|
|
|
<p style="margin-left:24%;">The following conditions are
|
|
applied in the order listed. If the second argument is one
|
|
of the binary conditional operators listed above under
|
|
<b>CONDITIONAL EXPRESSIONS</b>, the result of the expression
|
|
is the result of the binary test using the first and third
|
|
arguments as operands. The <b>-a</b> and <b>-o</b> operators
|
|
are considered binary operators when there are three
|
|
arguments. If the first argument is <b>!</b>, the value is
|
|
the negation of the two-argument test using the second and
|
|
third arguments. If the first argument is exactly <b>(</b>
|
|
and the third argument is exactly <b>)</b>, the result is
|
|
the one-argument test of the second argument. Otherwise, the
|
|
expression is false.</p>
|
|
|
|
<p style="margin-left:15%;">4 arguments</p>
|
|
|
|
<p style="margin-left:24%;">The following conditions are
|
|
applied in the order listed. If the first argument is
|
|
<b>!</b>, the result is the negation of the three-argument
|
|
expression composed of the remaining arguments. If the first
|
|
argument is exactly <b>(</b> and the fourth argument is
|
|
exactly <b>)</b>, the result is the two-argument test of the
|
|
second and third arguments. Otherwise, the expression is
|
|
parsed and evaluated according to precedence using the rules
|
|
listed above.</p>
|
|
|
|
<p style="margin-left:15%;">5 or more arguments</p>
|
|
|
|
<p style="margin-left:24%;">The expression is parsed and
|
|
evaluated according to precedence using the rules listed
|
|
above.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When the shell
|
|
is in posix mode, or if the expression is part of the
|
|
<b>[[</b> command, the <b><</b> and <b>></b> operators
|
|
sort using the current locale. If the shell is not in posix
|
|
mode, the <b>test</b> and <b>[</b> commands sort
|
|
lexicographically using ASCII ordering.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The historical
|
|
operator-precedence parsing with 4 or more arguments can
|
|
lead to ambiguities when it encounters strings that look
|
|
like primaries. The POSIX standard has deprecated the
|
|
<b>-a</b> and <b>-o</b> primaries and enclosing expressions
|
|
within parentheses. Scripts should no longer use them.
|
|
It’s much more reliable to restrict test invocations
|
|
to a single primary, and to replace uses of <b>-a</b> and
|
|
<b>-o</b> with the shell’s <b>&&</b> and
|
|
<b>||</b> list operators.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="7%">
|
|
|
|
|
|
<p><b>times</b></p></td>
|
|
<td width="2%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p>Print the accumulated user and system times for the
|
|
shell and for processes run from the shell. The return
|
|
status is 0.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>trap</b> [<b>-lpP</b>]
|
|
[[<i>action</i>] <i>sigspec</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">The <i>action</i> is a command
|
|
that is read and executed when the shell receives any of the
|
|
signals <i>sigspec</i>. If <i>action</i> is absent (and
|
|
there is a single <i>sigspec</i>) or <b>-</b>, each
|
|
specified <i>sigspec</i> is reset to the value it had when
|
|
the shell was started. If <i>action</i> is the null string
|
|
the signal specified by each <i>sigspec</i> is ignored by
|
|
the shell and by the commands it invokes.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If no arguments
|
|
are supplied, <b>trap</b> displays the actions associated
|
|
with each trapped signal as a set of <b>trap</b> commands
|
|
that can be reused as shell input to restore the current
|
|
signal dispositions. If <b>-p</b> is given, and
|
|
<i>action</i> is not present, then <b>trap</b> displays the
|
|
actions associated with each <i>sigspec</i> or, if none are
|
|
supplied, for all trapped signals, as a set of <b>trap</b>
|
|
commands that can be reused as shell input to restore the
|
|
current signal dispositions. The <b>-P</b> option behaves
|
|
similarly, but displays only the actions associated with
|
|
each <i>sigspec</i> argument. <b>-P</b> requires at least
|
|
one <i>sigspec</i> argument. The <b>-P</b> or <b>-p</b>
|
|
options may be used in a subshell environment (e.g., command
|
|
substitution) and, as long as they are used before
|
|
<b>trap</b> is used to change a signal’s handling,
|
|
will display the state of its parent’s traps.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-l</b>
|
|
option prints a list of signal names and their corresponding
|
|
numbers. Each <i>sigspec</i> is either a signal name defined
|
|
in <<i>signal.h</i>>, or a signal number. Signal names
|
|
are case insensitive and the <b>SIG</b> prefix is optional.
|
|
If <b>-l</b> is supplied with no <i>sigspec</i> arguments,
|
|
it prints a list of valid signal names.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If a
|
|
<i>sigspec</i> is <b>EXIT</b> (0), <i>action</i> is executed
|
|
on exit from the shell. If a <i>sigspec</i> is <b>DEBUG</b>,
|
|
<i>action</i> is executed before every <i>simple
|
|
command</i>, <i>for</i> command, <i>case</i> command,
|
|
<i>select</i> command, (( arithmetic command, [[ conditional
|
|
command, arithmetic <i>for</i> command, and before the first
|
|
command executes in a shell function (see <b>SHELL
|
|
GRAMMAR</b> above). Refer to the description of the
|
|
<b>extdebug</b> shell option (see <b>shopt</b> above) for
|
|
details of its effect on the <b>DEBUG</b> trap. If a
|
|
<i>sigspec</i> is <b>RETURN</b>, <i>action</i> is executed
|
|
each time a shell function or a script executed with the
|
|
<b>.</b> or <b>source</b> builtins finishes executing.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If a
|
|
<i>sigspec</i> is <b>ERR</b>, <i>action</i> is executed
|
|
whenever a pipeline (which may consist of a single simple
|
|
command), a list, or a compound command returns a non-zero
|
|
exit status, subject to the following conditions. The
|
|
<b>ERR</b> trap is not executed if the failed command is
|
|
part of the command list immediately following a
|
|
<b>while</b> or <b>until</b> reserved word, part of the test
|
|
in an <i>if</i> statement, part of a command executed in a
|
|
<b>&&</b> or <b>||</b> list except the command
|
|
following the final <b>&&</b> or <b>||</b>, any
|
|
command in a pipeline but the last (subject to the state of
|
|
the <b>pipefail</b> shell option), or if the command’s
|
|
return value is being inverted using <b>!</b>. These are the
|
|
same conditions obeyed by the <b>errexit</b> (<b>-e</b>)
|
|
option.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">When the shell
|
|
is not interactive, signals ignored upon entry to the shell
|
|
cannot be trapped or reset. Interactive shells permit
|
|
trapping signals ignored on entry. Trapped signals that are
|
|
not being ignored are reset to their original values in a
|
|
subshell or subshell environment when one is created. The
|
|
return status is false if any <i>sigspec</i> is invalid;
|
|
otherwise <b>trap</b> returns true.</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="5%">
|
|
|
|
|
|
<p><b>true</b></p></td>
|
|
<td width="4%"></td>
|
|
<td width="41%">
|
|
|
|
|
|
<p>Does nothing, returns a 0 status.</p></td>
|
|
<td width="44%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>type</b> [<b>-aftpP</b>]
|
|
<i>name</i> [<i>name</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Indicate how each <i>name</i>
|
|
would be interpreted if used as a command name.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-t</b> option is used, <b>type</b> prints a string which
|
|
is one of <i>alias</i>, <i>keyword</i>, <i>function</i>,
|
|
<i>builtin</i>, or <i>file</i> if <i>name</i> is an alias,
|
|
shell reserved word, function, builtin, or executable file,
|
|
respectively. If the <i>name</i> is not found, <b>type</b>
|
|
prints nothing and returns a non-zero exit status.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-p</b> option is used, <b>type</b> either returns the
|
|
pathname of the executable file that would be found by
|
|
searching <b>$PATH</b> for <i>name</i> or nothing if
|
|
“type -t name” would not return <i>file</i>. The
|
|
<b>-P</b> option forces a <b>PATH</b> search for each
|
|
<i>name</i>, even if “type -t name” would not
|
|
return <i>file</i>. If <i>name</i> is present in the table
|
|
of hashed commands, <b>-p</b> and <b>-P</b> print the hashed
|
|
value, which is not necessarily the file that appears first
|
|
in <b>PATH</b>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-a</b> option is used, <b>type</b> prints all of the
|
|
places that contain a command named <i>name</i>. This
|
|
includes aliases, reserved words, functions, and builtins,
|
|
but the path search options (<b>-p</b> and <b>-P</b>) can be
|
|
supplied to restrict the output to executable files.
|
|
<b>type</b> does not consult the table of hashed commands
|
|
when using <b>-a</b> with <b>-p</b>, and only performs a
|
|
<b>PATH</b> search for <i>name</i>.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-f</b>
|
|
option suppresses shell function lookup, as with the
|
|
<b>command</b> builtin. <b>type</b> returns true if all of
|
|
the arguments are found, false if any are not found.</p>
|
|
|
|
<p style="margin-left:6%;"><b>ulimit</b> [<b>-HS</b>] <b>-a
|
|
<br>
|
|
ulimit</b> [<b>-HS</b>] [<b>-bcdefiklmnpqrstuvxPRT</b>
|
|
[<i>limit</i>]]</p>
|
|
|
|
<p style="margin-left:15%;">Provides control over the
|
|
resources available to the shell and to processes it starts,
|
|
on systems that allow such control.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The <b>-H</b>
|
|
and <b>-S</b> options specify whether the hard or soft limit
|
|
is set for the given resource. A hard limit cannot be
|
|
increased by a non-root user once it is set; a soft limit
|
|
may be increased up to the value of the hard limit. If
|
|
neither <b>-H</b> nor <b>-S</b> is specified, <b>ulimit</b>
|
|
sets both the soft and hard limits.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">The value of
|
|
<i>limit</i> can be a number in the unit specified for the
|
|
resource or one of the special values <b>hard</b>,
|
|
<b>soft</b>, or <b>unlimited</b>, which stand for the
|
|
current hard limit, the current soft limit, and no limit,
|
|
respectively. If <i>limit</i> is omitted, <b>ulimit</b>
|
|
prints the current value of the soft limit of the resource,
|
|
unless the <b>-H</b> option is given. When more than one
|
|
resource is specified, the limit name and unit, if
|
|
appropriate, are printed before the value. Other options are
|
|
interpreted as follows:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p><b>-a</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Report all current limits; no limits are set.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-b</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum socket buffer
|
|
size.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-c</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum size of core files
|
|
created.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-d</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum size of a
|
|
process’s data segment.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-e</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum scheduling priority
|
|
(“nice”).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-f</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum size of files
|
|
written by the shell and its children.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-i</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum number of pending
|
|
signals.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-k</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum number of kqueues
|
|
that may be allocated.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-l</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum size that may be
|
|
locked into memory.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-m</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum resident set size
|
|
(many systems do not honor this limit).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-n</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum number of open file
|
|
descriptors (most systems do not allow this value to be
|
|
set).</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-p</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The pipe size in 512-byte blocks
|
|
(this may not be set).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-q</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum number of bytes in
|
|
POSIX message queues.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-r</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum real-time scheduling
|
|
priority.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-s</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum stack size.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-t</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum amount of cpu time
|
|
in seconds.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-u</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum number of processes
|
|
available to a single user.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-v</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum amount of virtual
|
|
memory available to the shell and, on some systems, to its
|
|
children.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-x</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum number of file
|
|
locks.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-P</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum number of
|
|
pseudoterminals.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-R</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum time a real-time
|
|
process can run before blocking, in microseconds.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="3%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>-T</b></p></td>
|
|
<td width="6%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The maximum number of
|
|
threads.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If <i>limit</i>
|
|
is supplied, and the <b>-a</b> option is not used,
|
|
<i>limit</i> is the new value of the specified resource. If
|
|
no option is supplied, then <b>-f</b> is assumed.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Values are in
|
|
1024-byte increments, except for <b>-t</b>, which is in
|
|
seconds; <b>-R</b>, which is in microseconds; <b>-p</b>,
|
|
which is in units of 512-byte blocks; <b>-P</b>, <b>-T</b>,
|
|
<b>-b</b>, <b>-k</b>, <b>-n</b>, and <b>-u</b>, which are
|
|
unscaled values; and, when in posix mode, <b>-c</b> and
|
|
<b>-f</b>, which are in 512-byte increments. The return
|
|
status is 0 unless an invalid option or argument is
|
|
supplied, or an error occurs while setting a new limit.</p>
|
|
|
|
<p style="margin-left:6%;"><b>umask</b> [<b>-p</b>]
|
|
[<b>-S</b>] [<i>mode</i>]</p>
|
|
|
|
<p style="margin-left:15%;">Set the user file-creation mask
|
|
to <i>mode</i>. If <i>mode</i> begins with a digit, it is
|
|
interpreted as an octal number; otherwise it is interpreted
|
|
as a symbolic mode mask similar to that accepted by
|
|
<i>chmod</i>(1). If <i>mode</i> is omitted, <b>umask</b>
|
|
prints the current value of the mask. The <b>-S</b> option
|
|
without a <i>mode</i> argument prints the mask in a symbolic
|
|
format; the default output is an octal number. If the
|
|
<b>-p</b> option is supplied, and <i>mode</i> is omitted,
|
|
the output is in a form that may be reused as input. The
|
|
return status is zero if the mode was successfully changed
|
|
or if no <i>mode</i> argument was supplied, and non-zero
|
|
otherwise.</p>
|
|
|
|
<p style="margin-left:6%;"><b>unalias</b> [-<b>a</b>]
|
|
[<i>name</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Remove each <i>name</i> from
|
|
the list of defined aliases. If <b>-a</b> is supplied,
|
|
remove all alias definitions. The return value is true
|
|
unless a supplied <i>name</i> is not a defined alias.</p>
|
|
|
|
<p style="margin-left:6%;"><b>unset</b> [-<b>fv</b>]
|
|
[-<b>n</b>] [<i>name</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">For each <i>name</i>, remove
|
|
the corresponding variable or function. If the <b>-v</b>
|
|
option is given, each <i>name</i> refers to a shell
|
|
variable, and that variable is removed. If <b>-f</b> is
|
|
specified, each <i>name</i> refers to a shell function, and
|
|
the function definition is removed. If the <b>-n</b> option
|
|
is supplied, and <i>name</i> is a variable with the
|
|
<i>nameref</i> attribute, <i>name</i> will be unset rather
|
|
than the variable it references. <b>-n</b> has no effect if
|
|
the <b>-f</b> option is supplied. Read-only variables and
|
|
functions may not be unset. When variables or functions are
|
|
removed, they are also removed from the environment passed
|
|
to subsequent commands. If no options are supplied, each
|
|
<i>name</i> refers to a variable; if there is no variable by
|
|
that name, a function with that name, if any, is unset. Some
|
|
shell variables may not be unset. If any of
|
|
<b>BASH_ALIASES</b>, <b>BASH_ARGV0</b>, <b>BASH_CMDS</b>,
|
|
<b>BASH_COMMAND</b>, <b>BASH_SUBSHELL</b>, <b>BASHPID</b>,
|
|
<b>COMP_WORDBREAKS</b>, <b>DIRSTACK</b>,
|
|
<b>EPOCHREALTIME</b>, <b>EPOCHSECONDS</b>, <b>FUNCNAME</b>,
|
|
<b>GROUPS</b>, <b>HISTCMD</b>, <b>LINENO</b>, <b>RANDOM</b>,
|
|
<b>SECONDS</b>, or <b>SRANDOM</b> are unset, they lose their
|
|
special properties, even if they are subsequently reset. The
|
|
exit status is true unless a <i>name</i> is readonly or may
|
|
not be unset.</p>
|
|
|
|
<p style="margin-left:6%;"><b>wait</b> [<b>-fn</b>]
|
|
[<b>-p</b> <i>varname</i>] [<i>id</i> ...]</p>
|
|
|
|
<p style="margin-left:15%;">Wait for each specified child
|
|
process <i>id</i> and return the termination status of the
|
|
last <i>id</i>. Each <i>id</i> may be a process ID
|
|
<i>pid</i> or a job specification <i>jobspec</i>; if a
|
|
jobspec is supplied, <b>wait</b> waits for all processes in
|
|
the job.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If no options
|
|
or <i>id</i>s are supplied, <b>wait</b> waits for all
|
|
running background jobs and the last-executed process
|
|
substitution, if its process id is the same as <b>$!</b>,
|
|
and the return status is zero.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-n</b> option is supplied, <b>wait</b> waits for any one
|
|
of the given <i>id</i>s or, if no <i>id</i>s are supplied,
|
|
any job or process substitution, to complete and returns its
|
|
exit status. If none of the supplied <i>id</i>s is a child
|
|
of the shell, or if no <i>id</i>s are supplied and the shell
|
|
has no unwaited-for children, the exit status is 127.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If the
|
|
<b>-p</b> option is supplied, <b>wait</b> assigns the
|
|
process or job identifier of the job for which the exit
|
|
status is returned to the variable <i>varname</i> named by
|
|
the option argument. The variable, which cannot be readonly,
|
|
will be unset initially, before any assignment. This is
|
|
useful only when used with the <b>-n</b> option.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">Supplying the
|
|
<b>-f</b> option, when job control is enabled, forces
|
|
<b>wait</b> to wait for each <i>id</i> to terminate before
|
|
returning its status, instead of returning when it changes
|
|
status. If there are no <i>id</i> arguments, <b>wait</b>
|
|
waits until all background processes have terminated.</p>
|
|
|
|
<p style="margin-left:15%; margin-top: 1em">If none of the
|
|
<i>id</i>s specify one of the shell’s active child
|
|
processes, the return status is 127. If <b>wait</b> is
|
|
interrupted by a signal, any <i>varname</i> will remain
|
|
unset, and the return status will be greater than 128, as
|
|
described under <b>SIGNALS</b> above. Otherwise, the return
|
|
status is the exit status of the last <i>id</i>.</p>
|
|
|
|
<h2>SHELL COMPATIBILITY MODE
|
|
<a name="SHELL COMPATIBILITY MODE"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Bash-4.0
|
|
introduced the concept of a <i>shell compatibility
|
|
level</i>, specified as a set of options to the shopt
|
|
builtin (<b>compat31</b>, <b>compat32</b>, <b>compat40</b>,
|
|
<b>compat41</b>, and so on). There is only one current
|
|
compatibility level — each option is mutually
|
|
exclusive. The compatibility level is intended to allow
|
|
users to select behavior from previous versions that is
|
|
incompatible with newer versions while they migrate scripts
|
|
to use current features and behavior. It’s intended to
|
|
be a temporary solution.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">This section
|
|
does not mention behavior that is standard for a particular
|
|
version (e.g., setting <b>compat32</b> means that quoting
|
|
the right hand side of the regexp matching operator quotes
|
|
special regexp characters in the word, which is default
|
|
behavior in bash-3.2 and subsequent versions).</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If a user
|
|
enables, say, <b>compat32</b>, it may affect the behavior of
|
|
other compatibility levels up to and including the current
|
|
compatibility level. The idea is that each compatibility
|
|
level controls behavior that changed in that version of
|
|
<b>bash</b>, but that behavior may have been present in
|
|
earlier versions. For instance, the change to use
|
|
locale-based comparisons with the <b>[[</b> command came in
|
|
bash-4.1, and earlier versions used ASCII-based comparisons,
|
|
so enabling <b>compat32</b> will enable ASCII-based
|
|
comparisons as well. That granularity may not be sufficient
|
|
for all uses, and as a result users should employ
|
|
compatibility levels carefully. Read the documentation for a
|
|
particular feature to find out the current behavior.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Bash-4.3
|
|
introduced a new shell variable: <b>BASH_COMPAT</b>. The
|
|
value assigned to this variable (a decimal version number
|
|
like 4.2, or an integer corresponding to the
|
|
<b>compat</b><i>NN</i> option, like 42) determines the
|
|
compatibility level.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Starting with
|
|
bash-4.4, <b>bash</b> began deprecating older compatibility
|
|
levels. Eventually, the options will be removed in favor of
|
|
<b>BASH_COMPAT</b>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Bash-5.0 was the
|
|
final version for which there was an individual shopt option
|
|
for the previous version. <b>BASH_COMPAT</b> is the only
|
|
mechanism to control the compatibility level in versions
|
|
newer than bash-5.0.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">The following
|
|
table describes the behavior changes controlled by each
|
|
compatibility level setting. The <b>compat</b><i>NN</i> tag
|
|
is used as shorthand for setting the compatibility level to
|
|
<i>NN</i> using one of the following mechanisms. For
|
|
versions prior to bash-5.0, the compatibility level may be
|
|
set using the corresponding <b>compat</b><i>NN</i> shopt
|
|
option. For bash-4.3 and later versions, the
|
|
<b>BASH_COMPAT</b> variable is preferred, and it is required
|
|
for bash-5.1 and later versions. <b><br>
|
|
compat31</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Quoting the rhs of the <b>[[</b> command’s regexp
|
|
matching operator (=~) has no special effect.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat32</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>The <b><</b> and <b>></b> operators to the
|
|
<b>[[</b> command do not consider the current locale when
|
|
comparing strings; they use ASCII ordering.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat40</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>The <b><</b> and <b>></b> operators to the
|
|
<b>[[</b> command do not consider the current locale when
|
|
comparing strings; they use ASCII ordering. <b>Bash</b>
|
|
versions prior to bash-4.1 use ASCII collation and
|
|
<i>strcmp</i>(3); bash-4.1 and later use the current
|
|
locale’s collation sequence and <i>strcoll</i>(3).</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat41</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>In posix mode, <b>time</b> may be followed by options
|
|
and still be recognized as a reserved word (this is POSIX
|
|
interpretation 267).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">In <i>posix</i> mode, the parser
|
|
requires that an even number of single quotes occur in the
|
|
<i>word</i> portion of a double-quoted parameter expansion
|
|
and treats them specially, so that characters within the
|
|
single quotes are considered quoted (this is POSIX
|
|
interpretation 221).</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat42</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>The replacement string in double-quoted pattern
|
|
substitution does not undergo quote removal, as it does in
|
|
versions after bash-4.2.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">In posix mode, single quotes are
|
|
considered special when expanding the <i>word</i> portion of
|
|
a double-quoted parameter expansion and can be used to quote
|
|
a closing brace or other special character (this is part of
|
|
POSIX interpretation 221); in later versions, single quotes
|
|
are not special within double-quoted word expansions.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat43</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Word expansion errors are considered non-fatal errors
|
|
that cause the current command to fail, even in posix mode
|
|
(the default behavior is to make them fatal errors that
|
|
cause the shell to exit).</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">When executing a shell function,
|
|
the loop state (while/until/etc.) is not reset, so
|
|
<b>break</b> or <b>continue</b> in that function will break
|
|
or continue loops in the calling context. Bash-4.4 and later
|
|
reset the loop state to prevent this.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat44</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>The shell sets up the values used by <b>BASH_ARGV</b>
|
|
and <b>BASH_ARGC</b> so they can expand to the shell’s
|
|
positional parameters even if extended debugging mode is not
|
|
enabled.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">A subshell inherits loops from
|
|
its parent context, so <b>break</b> or <b>continue</b> will
|
|
cause the subshell to exit. Bash-5.0 and later reset the
|
|
loop state to prevent the exit</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Variable assignments preceding
|
|
builtins like <b>export</b> and <b>readonly</b> that set
|
|
attributes continue to affect variables with the same name
|
|
in the calling environment even if the shell is not in posix
|
|
mode.</p> </td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat50</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>Bash-5.1 changed the way <b>$RANDOM</b> is generated to
|
|
introduce slightly more randomness. If the shell
|
|
compatibility level is set to 50 or lower, it reverts to the
|
|
method from bash-5.0 and previous versions, so seeding the
|
|
random number generator by assigning a value to
|
|
<b>RANDOM</b> will produce the same sequence as in
|
|
bash-5.0.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the command hash table is
|
|
empty, bash versions prior to bash-5.1 printed an
|
|
informational message to that effect, even when producing
|
|
output that can be reused as input. Bash-5.1 suppresses that
|
|
message when the <b>-l</b> option is supplied.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat51</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>The <b>unset</b> builtin treats attempts to unset array
|
|
subscripts <b>@</b> and <b>*</b> differently depending on
|
|
whether the array is indexed or associative, and differently
|
|
than in previous versions.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Arithmetic commands (
|
|
<b>((</b>...<b>))</b> ) and the expressions in an arithmetic
|
|
for statement can be expanded more than once.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Expressions used as arguments to
|
|
arithmetic operators in the <b>[[</b> conditional command
|
|
can be expanded more than once.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expressions in substring
|
|
parameter brace expansion can be expanded more than
|
|
once.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The expressions in the
|
|
<b>$((</b>...<b>))</b> word expansion can be expanded more
|
|
than once.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Arithmetic expressions used as
|
|
indexed array subscripts can be expanded more than once.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em"><b>test -v</b>, when given an
|
|
argument of <b>A[@]</b>, where <b>A</b> is an existing
|
|
associative array, will return true if the array has any set
|
|
elements. Bash-5.2 will look for and report on a key named
|
|
<b>@</b>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">The
|
|
${<i>parameter</i><b>[:]=</b><i>value</i>} word expansion
|
|
will return <i>value</i>, before any variable-specific
|
|
transformations have been performed (e.g., converting to
|
|
lowercase). Bash-5.2 will return the final value assigned to
|
|
the variable.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">Parsing command substitutions
|
|
will behave as if extended globbing (see the description of
|
|
the <b>shopt</b> builtin above) is enabled, so that parsing
|
|
a command substitution containing an extglob pattern (say,
|
|
as part of a shell function) will not fail. This assumes the
|
|
intent is to enable extglob before the command is executed
|
|
and word expansions are performed. It will fail at word
|
|
expansion time if extglob hasn’t been enabled by the
|
|
time the command is executed.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%;"><b>compat52</b></p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p>The <b>test</b> builtin uses its historical algorithm to
|
|
parse parenthesized subexpressions when given five or more
|
|
arguments.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="15%"></td>
|
|
<td width="1%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="8%"></td>
|
|
<td width="76%">
|
|
|
|
|
|
<p style="margin-top: 1em">If the <b>-p</b> or <b>-P</b>
|
|
option is supplied to the <b>bind</b> builtin, <b>bind</b>
|
|
treats any arguments remaining after option processing as
|
|
bindable command names, and displays any key sequences bound
|
|
to those commands, instead of treating the arguments as key
|
|
sequences to bind.</p></td></tr>
|
|
</table>
|
|
|
|
<h2>RESTRICTED SHELL
|
|
<a name="RESTRICTED SHELL"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If <b>bash</b>
|
|
is started with the name <b>rbash</b>, or the <b>-r</b>
|
|
option is supplied at invocation, the shell becomes
|
|
<i>restricted</i>. A restricted shell is used to set up an
|
|
environment more controlled than the standard shell. It
|
|
behaves identically to <b>bash</b> with the exception that
|
|
the following are disallowed or not performed:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Changing directories with
|
|
<b>cd</b>.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Setting or unsetting the values
|
|
of <b>SHELL</b>, <b>PATH</b>, <b>HISTFILE</b>, <b>ENV</b>,
|
|
or <b>BASH_ENV</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Specifying command names
|
|
containing <b>/</b>.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Specifying a filename containing
|
|
a <b>/</b> as an argument to the <b>.</b> builtin
|
|
command.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Using the <b>-p</b> option to
|
|
the <b>.</b> builtin command to specify a search path.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Specifying a filename containing
|
|
a slash as an argument to the <b>history</b> builtin
|
|
command.</p> </td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Specifying a filename containing
|
|
a slash as an argument to the <b>-p</b> option to the
|
|
<b>hash</b> builtin command.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Importing function definitions
|
|
from the shell environment at startup.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Parsing the values of
|
|
<b>BASHOPTS</b> and <b>SHELLOPTS</b> from the shell
|
|
environment at startup.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Redirecting output using the
|
|
>, >|, <>, >&, &>, and >>
|
|
redirection operators.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Using the <b>exec</b> builtin
|
|
command to replace the shell with another command.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Adding or deleting builtin
|
|
commands with the <b>-f</b> and <b>-d</b> options to the
|
|
<b>enable</b> builtin command.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Using the <b>enable</b> builtin
|
|
command to enable disabled shell builtins.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Specifying the <b>-p</b> option
|
|
to the <b>command</b> builtin command.</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="7%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">Turning off restricted mode with
|
|
<b>set +r</b> or <b>shopt -u restricted_shell</b>.</p></td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">These
|
|
restrictions are enforced after any startup files are
|
|
read.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">When a command
|
|
that is found to be a shell script is executed (see
|
|
<b>COMMAND EXECUTION</b> above), <b>rbash</b> turns off any
|
|
restrictions in the shell spawned to execute the script.</p>
|
|
|
|
<h2>SEE ALSO
|
|
<a name="SEE ALSO"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>Bash
|
|
Reference Manual</i>, Brian Fox and Chet Ramey <i><br>
|
|
The GNU Readline Library</i>, Brian Fox and Chet Ramey
|
|
<i><br>
|
|
The GNU History Library</i>, Brian Fox and Chet Ramey <br>
|
|
POSIX.1-2024, The IEEE and The Open Group</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><a href="https://pubs.opengroup.org/onlinepubs/9799919799/">https://pubs.opengroup.org/onlinepubs/9799919799/</a></p>
|
|
|
|
<p style="margin-left:6%;">a description of posix mode</p>
|
|
|
|
|
|
<p style="margin-left:15%;"><a href="http://tiswww.case.edu/~chet/bash/POSIX">http://tiswww.case.edu/~chet/bash/POSIX</a></p>
|
|
|
|
<p style="margin-left:6%;"><i>sh</i>(1), <i>ksh</i>(1),
|
|
<i>csh</i>(1) <i><br>
|
|
emacs</i>(1), <i>vi</i>(1) <i><br>
|
|
readline</i>(3)</p>
|
|
|
|
<h2>FILES
|
|
<a name="FILES"></a>
|
|
</h2>
|
|
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><A HREF="file:/bin/bash"><i>/bin/bash</i></A></p>
|
|
|
|
<p style="margin-left:15%;">The <b>bash</b> executable</p>
|
|
|
|
<p style="margin-left:6%;"><A HREF="file:/etc/profile"><i>/etc/profile</i></A></p>
|
|
|
|
<p style="margin-left:15%;">The systemwide initialization
|
|
file, executed for login shells</p>
|
|
|
|
<p style="margin-left:6%;"><A HREF="file:~/.bash_profile"><i>~/.bash_profile</i></A></p>
|
|
|
|
<p style="margin-left:15%;">The personal initialization
|
|
file, executed for login shells</p>
|
|
|
|
<p style="margin-left:6%;"><A HREF="file:~/.bashrc"><i>~/.bashrc</i></A></p>
|
|
|
|
<p style="margin-left:15%;">The individual
|
|
per-interactive-shell startup file</p>
|
|
|
|
<p style="margin-left:6%;"><A HREF="file:~/.bash_logout"><i>~/.bash_logout</i></A></p>
|
|
|
|
<p style="margin-left:15%;">The individual login shell
|
|
cleanup file, executed when a login shell exits</p>
|
|
|
|
<p style="margin-left:6%;"><A HREF="file:~/.bash_history"><i>~/.bash_history</i></A></p>
|
|
|
|
<p style="margin-left:15%;">The default value of
|
|
<b>HISTFILE</b>, the file in which bash saves the command
|
|
history</p>
|
|
|
|
<p style="margin-left:6%;"><A HREF="file:~/.inputrc"><i>~/.inputrc</i></A></p>
|
|
|
|
<p style="margin-left:15%;">Individual <i>readline</i>
|
|
initialization file</p>
|
|
|
|
<h2>AUTHORS
|
|
<a name="AUTHORS"></a>
|
|
</h2>
|
|
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><a href="mailto:bfox@gnu.org">Brian
|
|
Fox, Free Software Foundation</a> <br>
|
|
<a href="mailto:chet.ramey@case.edu">Chet Ramey, Case
|
|
Western Reserve University</a></p>
|
|
|
|
<h2>BUG REPORTS
|
|
<a name="BUG REPORTS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">If you find a
|
|
bug in <b>bash</b>, you should report it. But first, you
|
|
should make sure that it really is a bug, and that it
|
|
appears in the latest version of <b>bash</b>. The latest
|
|
version is always available from
|
|
<a href="ftp://ftp.gnu.org/pub/gnu/bash/">ftp://ftp.gnu.org/pub/gnu/bash/</a>
|
|
and
|
|
<a href="http://git.savannah.gnu.org/cgit/bash.git/snapshot/bash-master.tar.gz">http://git.savannah.gnu.org/cgit/bash.git/snapshot/bash-master.tar.gz</a>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Once you have
|
|
determined that a bug actually exists, use the
|
|
<i>bashbug</i> command to submit a bug report. If you have a
|
|
fix, you are encouraged to mail that as well! You may send
|
|
suggestions and “philosophical” bug reports, as
|
|
well as comments and bug reports concerning this manual
|
|
page, to to
|
|
<a href="mailto:bug-bash@gnu.org">bug-bash@gnu.org</a>.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>All</i> bug
|
|
reports should include:</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p>•</p></td>
|
|
<td width="1%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p>the version number of <b>bash</b> (“echo
|
|
$BASH_VERSION”),</p> </td>
|
|
<td width="26%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="1%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p style="margin-top: 1em">the host platform and operating
|
|
system (“uname -a”),</p></td>
|
|
<td width="26%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="1%"></td>
|
|
<td width="65%">
|
|
|
|
|
|
<p style="margin-top: 1em">either</p></td>
|
|
<td width="26%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:11%; margin-top: 1em">(a)</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="9%"></td>
|
|
<td width="1%"></td>
|
|
<td width="84%">
|
|
|
|
|
|
<p style="margin-top: 1em">if you or an administrator built
|
|
and installed <b>bash</b> from source, the name and version
|
|
of the compiler used to build it, as reported by
|
|
<b>bash</b>’s “configure” script; or</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="9%">
|
|
|
|
|
|
<p style="margin-top: 1em">(b)</p></td>
|
|
<td width="1%"></td>
|
|
<td width="84%">
|
|
|
|
|
|
<p style="margin-top: 1em">if your site uses a
|
|
distributor’s <b>bash</b> package, the version of that
|
|
package (for example, “dpkg -i bash” or
|
|
“rpm -qi bash”),</p></td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="9%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="1%"></td>
|
|
<td width="84%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:9%; margin-top: 1em">a description of
|
|
the behavior <b>bash</b> exhibited,</p>
|
|
|
|
<table width="100%" border="0" rules="none" frame="void"
|
|
cellspacing="0" cellpadding="0">
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="1%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">a description of the behavior
|
|
you expected from <b>bash</b>, and</p></td>
|
|
<td width="6%">
|
|
</td></tr>
|
|
<tr valign="top" align="left">
|
|
<td width="6%"></td>
|
|
<td width="2%">
|
|
|
|
|
|
<p style="margin-top: 1em">•</p></td>
|
|
<td width="1%"></td>
|
|
<td width="85%">
|
|
|
|
|
|
<p style="margin-top: 1em">a short shell script or
|
|
“recipe” exercising the unexpected behavior.</p></td>
|
|
<td width="6%">
|
|
</td></tr>
|
|
</table>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em"><i>bashbug</i>
|
|
inserts the first three items automatically into the
|
|
template it provides for filing a bug report.</p>
|
|
|
|
<h2>BUGS
|
|
<a name="BUGS"></a>
|
|
</h2>
|
|
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">It’s too
|
|
big and too slow.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">There are some
|
|
subtle differences between <b>bash</b> and historical
|
|
versions of <b>sh</b>, due mostly to <b>bash</b>’s
|
|
independent implementation and the evolution of the POSIX
|
|
specification.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Aliases are
|
|
confusing in some uses.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Shell builtin
|
|
commands and functions are not stoppable/restartable.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Compound
|
|
commands and command lists of the form “a ; b ;
|
|
c” are not handled gracefully when combined with
|
|
process suspension. When a process is stopped, the shell
|
|
immediately executes the next command in the list or breaks
|
|
out of any existing loops. It suffices to enclose the
|
|
command in parentheses to force it into a subshell, which
|
|
may be stopped as a unit, or to start the command in the
|
|
background and immediately bring it into the foreground.</p>
|
|
|
|
<p style="margin-left:6%; margin-top: 1em">Array variables
|
|
may not (yet) be exported.</p>
|
|
<hr>
|
|
</body>
|
|
</html>
|