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Chet Ramey
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@@ -1,9 +1,9 @@
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- This text is a brief description of the features that are present in
the Bash shell (version 5.0, 15 March 2018).
the Bash shell (version 5.0, 7 August 2018).
This is Edition 5.0, last updated 15 March 2018,
This is Edition 5.0, last updated 7 August 2018,
of The GNU Bash Reference Manual,
for Bash, Version 5.0.
@@ -284,10 +284,10 @@ Next: <a href="#Introduction" accesskey="n" rel="next">Introduction</a>, Previou
<h1 class="top">Bash Features</h1>
<p>This text is a brief description of the features that are present in
the Bash shell (version 5.0, 15 March 2018).
the Bash shell (version 5.0, 7 August 2018).
The Bash home page is <a href="http://www.gnu.org/software/bash/">http://www.gnu.org/software/bash/</a>.
</p>
<p>This is Edition 5.0, last updated 15 March 2018,
<p>This is Edition 5.0, last updated 7 August 2018,
of <cite>The GNU Bash Reference Manual</cite>,
for <code>Bash</code>, Version 5.0.
</p>
@@ -1297,7 +1297,9 @@ zero if no condition tested true.
<p>The syntax of the <code>case</code> command is:
</p>
<div class="example">
<pre class="example">case <var>word</var> in [ [(] <var>pattern</var> [| <var>pattern</var>]&hellip;) <var>command-list</var> ;;]&hellip; esac
<pre class="example">case <var>word</var> in
[ [(] <var>pattern</var> [| <var>pattern</var>]&hellip;) <var>command-list</var> ;;]&hellip;
esac
</pre></div>
<p><code>case</code> will selectively execute the <var>command-list</var> corresponding to
@@ -1443,14 +1445,15 @@ If the <code>nocasematch</code> 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 (&lsquo;<samp>==</samp>&rsquo;) or does not
match (&lsquo;<samp>!=</samp>&rsquo;)the pattern, and 1 otherwise.
match (&lsquo;<samp>!=</samp>&rsquo;) the pattern, and 1 otherwise.
Any part of the pattern may be quoted to force the quoted portion
to be matched as a string.
</p>
<p>An additional binary operator, &lsquo;<samp>=~</samp>&rsquo;, is available, with the same
precedence as &lsquo;<samp>==</samp>&rsquo; and &lsquo;<samp>!=</samp>&rsquo;.
When it is used, the string to the right of the operator is considered
an extended regular expression and matched accordingly (as in <i>regex</i>3)).
a <small>POSIX</small> extended regular expression and matched accordingly
(as 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
@@ -1722,7 +1725,8 @@ from a file (in this case, filenames listed one per line):
<p>with a more compact syntax reminiscent of lambdas:
</p><div class="example">
<pre class="example">cat list | parallel &quot;do-something1 {} config-{} ; do-something2 &lt; {}&quot; | process-output
<pre class="example">cat list | parallel &quot;do-something1 {} config-{} ; do-something2 &lt; {}&quot; |
process-output
</pre></div>
<p>Parallel provides a built-in mechanism to remove filename extensions, which
@@ -1744,12 +1748,20 @@ written as
<p>If a command generates output, you may want to preserve the input order in
the output. For instance, the following command
</p><div class="example">
<pre class="example">{ echo foss.org.my ; echo debian.org; echo freenetproject.org; } | parallel traceroute
<pre class="example">{
echo foss.org.my ;
echo debian.org ;
echo freenetproject.org ;
} | parallel traceroute
</pre></div>
<p>will display as output the traceroute invocation that finishes first.
Adding the <samp>-k</samp> option
</p><div class="example">
<pre class="example">{ echo foss.org.my ; echo debian.org; echo freenetproject.org; } | parallel -k traceroute
<pre class="example">{
echo foss.org.my ;
echo debian.org ;
echo freenetproject.org ;
} | parallel -k traceroute
</pre></div>
<p>will ensure that the output of <code>traceroute foss.org.my</code> is displayed first.
</p>
@@ -2126,8 +2138,16 @@ separators.
<a name="index-_0040"></a>
</dt>
<dd><a name="index-_0024_0040"></a>
<p>($@) Expands to the positional parameters, starting from one. When the
expansion occurs within double quotes, each parameter expands to a
<p>($@) 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,
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, <code>&quot;$@&quot;</code> is equivalent to
<code>&quot;$1&quot; &quot;$2&quot; &hellip;</code>.
If the double-quoted expansion occurs within a word, the expansion of
@@ -2446,6 +2466,12 @@ and the shell assigns the expanded value.
</p></dd>
</dl>
<p>Bash also performs tilde expansion on words satisfying the conditions of
variable assignments (see <a href="#Shell-Parameters">Shell Parameters</a>)
when they appear as arguments to simple commands.
Bash does not do this, except for the <var>declaration</var> commands listed
above, when in <small>POSIX</small> mode.
</p>
<hr>
<a name="Shell-Parameter-Expansion"></a>
<div class="header">
@@ -2480,11 +2506,11 @@ interpreted as part of its name.
</p>
<p>If the first character of <var>parameter</var> is an exclamation point (!),
and <var>parameter</var> is not a <var>nameref</var>,
it introduces a level of variable indirection.
Bash uses the value of the variable formed from the rest of
<var>parameter</var> as the name of the variable; this variable is then
expanded and that value is used in the rest of the substitution, rather
than the value of <var>parameter</var> itself.
it introduces a level of indirection.
Bash uses the value formed by expanding the rest of
<var>parameter</var> as the new <var>parameter</var>; this is then
expanded and that value is used in the rest of the expansion, rather
than the expansion of the original <var>parameter</var>.
This is known as <code>indirect expansion</code>.
The value is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
@@ -5078,8 +5104,8 @@ parent.
<dt><code>mapfile</code></dt>
<dd><a name="index-mapfile"></a>
<div class="example">
<pre class="example">mapfile [-d <var>delim</var>] [-n <var>count</var>] [-O <var>origin</var>] [-s <var>count</var>] [-t] [-u <var>fd</var>]
[-C <var>callback</var>] [-c <var>quantum</var>] [<var>array</var>]
<pre class="example">mapfile [-d <var>delim</var>] [-n <var>count</var>] [-O <var>origin</var>] [-s <var>count</var>]
[-t] [-u <var>fd</var>] [-C <var>callback</var>] [-c <var>quantum</var>] [<var>array</var>]
</pre></div>
<p>Read lines from the standard input into the indexed array variable <var>array</var>,
@@ -5309,8 +5335,8 @@ The exit status is greater than 128 if the timeout is exceeded.
<dt><code>readarray</code></dt>
<dd><a name="index-readarray"></a>
<div class="example">
<pre class="example">readarray [-d <var>delim</var>] [-n <var>count</var>] [-O <var>origin</var>] [-s <var>count</var>] [-t] [-u <var>fd</var>]
[-C <var>callback</var>] [-c <var>quantum</var>] [<var>array</var>]
<pre class="example">readarray [-d <var>delim</var>] [-n <var>count</var>] [-O <var>origin</var>] [-s <var>count</var>]
[-t] [-u <var>fd</var>] [-C <var>callback</var>] [-c <var>quantum</var>] [<var>array</var>]
</pre></div>
<p>Read lines from the standard input into the indexed array variable <var>array</var>,
@@ -6574,7 +6600,8 @@ The shell sets <code>BASH_ARGC</code> only when in extended debugging mode
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>
for a description of the <code>extdebug</code> option to the <code>shopt</code>
builtin).
Setting <code>extdebug</code> after the shell has started to execute a script
Setting <code>extdebug</code> after the shell has started to execute a script,
or referencing this variable when <code>extdebug</code> is not set,
may result in inconsistent values.
</p>
</dd>
@@ -6590,7 +6617,8 @@ The shell sets <code>BASH_ARGV</code> only when in extended debugging mode
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>
for a description of the <code>extdebug</code> option to the <code>shopt</code>
builtin).
Setting <code>extdebug</code> after the shell has started to execute a script
Setting <code>extdebug</code> after the shell has started to execute a script,
or referencing this variable when <code>extdebug</code> is not set,
may result in inconsistent values.
</p>
</dd>
@@ -7180,7 +7208,7 @@ as the sole input. If set, the value denotes the number
of consecutive <code>EOF</code> characters that can be read as the
first character on an input line
before the shell will exit. If the variable exists but does not
have a numeric value (or has no value) then the default is 10.
have a numeric value, or has no value, then the default is 10.
If the variable does not exist, then <code>EOF</code> signifies the end of
input to the shell. This is only in effect for interactive shells.
</p>
@@ -7192,6 +7220,14 @@ input to the shell. This is only in effect for interactive shells.
of <samp>~/.inputrc</samp>.
</p>
</dd>
<dt><code>INSIDE_EMACS</code>
<a name="index-INSIDE_005fEMACS"></a>
</dt>
<dd><p>If Bash finds this variable in the environment when the shell
starts, it assumes that the shell is running in an Emacs shell buffer
and may disable line editing depending on the value of <code>TERM</code>.
</p>
</dd>
<dt><code>LANG</code>
<a name="index-LANG"></a>
</dt>
@@ -7324,7 +7360,9 @@ as if the command
</p><div class="example">
<pre class="example"><code>set -o posix</code>
</pre></div>
<p>had been executed.
<p>had been executed.
When the shell enters <small>POSIX</small> mode, it sets this variable if it was
not already set.
</p>
</dd>
<dt><code>PPID</code>
@@ -7583,9 +7621,12 @@ Next: <a href="#Bash-Startup-Files" accesskey="n" rel="next">Bash Startup Files<
<h3 class="section">6.1 Invoking Bash</h3>
<div class="example">
<pre class="example">bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o <var>option</var>] [-O <var>shopt_option</var>] [<var>argument</var> &hellip;]
bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o <var>option</var>] [-O <var>shopt_option</var>] -c <var>string</var> [<var>argument</var> &hellip;]
bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o <var>option</var>] [-O <var>shopt_option</var>] [<var>argument</var> &hellip;]
<pre class="example">bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o <var>option</var>]
[-O <var>shopt_option</var>] [<var>argument</var> &hellip;]
bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o <var>option</var>]
[-O <var>shopt_option</var>] -c <var>string</var> [<var>argument</var> &hellip;]
bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o <var>option</var>]
[-O <var>shopt_option</var>] [<var>argument</var> &hellip;]
</pre></div>
<p>All of the single-character options used with the <code>set</code> builtin
@@ -8014,7 +8055,7 @@ when a shell with history enabled exits.
(see <a href="#Signals">Signals</a>).
</li><li> In the absence of any traps, <code>SIGINT</code> is caught and handled
((see <a href="#Signals">Signals</a>).
(see <a href="#Signals">Signals</a>).
<code>SIGINT</code> will interrupt some shell builtins.
</li><li> An interactive login shell sends a <code>SIGHUP</code> to all jobs on exit
@@ -8843,7 +8884,7 @@ shell session.
<p>After the string is decoded, it is expanded via
parameter expansion, command substitution, arithmetic
expansion, and quote removal, subject to the value of the
<code>promptvars</code> shell option (see <a href="#Bash-Builtins">Bash Builtins</a>).
<code>promptvars</code> shell option (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>).
</p>
<hr>
<a name="The-Restricted-Shell"></a>
@@ -8913,7 +8954,9 @@ startup files.
<p>The following list is what&rsquo;s changed when &lsquo;<small>POSIX</small> mode&rsquo; is in effect:
</p>
<ol>
<li> When a command in the hash table no longer exists, Bash will re-search
<li> Bash ensures that the <code>POSIXLY_CORRECT</code> variable is set.
</li><li> When a command in the hash table no longer exists, Bash will re-search
<code>$PATH</code> to find the new location. This is also available with
&lsquo;<samp>shopt -s checkhash</samp>&rsquo;.
@@ -10004,6 +10047,7 @@ The default value is &lsquo;<samp>off</samp>&rsquo;.
<p>If set to &lsquo;<samp>on</samp>&rsquo;, and <var>completion-ignore-case</var> is enabled, Readline
treats hyphens (&lsquo;<samp>-</samp>&rsquo;) and underscores (&lsquo;<samp>_</samp>&rsquo;) as equivalent when
performing case-insensitive filename matching and completion.
The default value is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt><code>completion-prefix-display-length</code></dt>
@@ -10365,7 +10409,7 @@ Meta-Rubout: backward-kill-word
Control-o: &quot;&gt; output&quot;
</pre></div>
<p>In the above example, <kbd>C-u</kbd> is bound to the function
<p>In the example above, <kbd>C-u</kbd> is bound to the function
<code>universal-argument</code>,
<kbd>M-DEL</kbd> is bound to the function <code>backward-kill-word</code>, and
<kbd>C-o</kbd> is bound to run the macro
@@ -11068,7 +11112,7 @@ how to insert key sequences like <kbd>C-q</kbd>, for example.
sequence sent by some terminals, and such a binding is assigned by default.
It allows Readline to insert the pasted text as a single unit without treating
each character as if it had been read from the keyboard. The characters
are inserted as if each one was bound to <code>self-insert</code>) instead of
are inserted as if each one was bound to <code>self-insert</code> instead of
executing any editing commands.
</p>
</dd>
@@ -11973,10 +12017,10 @@ matches were generated.
<dt><code>complete</code></dt>
<dd><a name="index-complete"></a>
<div class="example">
<pre class="example"><code>complete [-abcdefgjksuv] [-o <var>comp-option</var>] [-DE] [-A <var>action</var>] [-G <var>globpat</var>] [-W <var>wordlist</var>]
[-F <var>function</var>] [-C <var>command</var>] [-X <var>filterpat</var>]
<pre class="example"><code>complete [-abcdefgjksuv] [-o <var>comp-option</var>] [-DEI] [-A <var>action</var>] [-G <var>globpat</var>]
[-W <var>wordlist</var>] [-F <var>function</var>] [-C <var>command</var>] [-X <var>filterpat</var>]
[-P <var>prefix</var>] [-S <var>suffix</var>] <var>name</var> [<var>name</var> &hellip;]</code>
<code>complete -pr [-DE] [<var>name</var> &hellip;]</code>
<code>complete -pr [-DEI] [<var>name</var> &hellip;]</code>
</pre></div>
<p>Specify how arguments to each <var>name</var> should be completed.
@@ -11986,16 +12030,24 @@ reused as input.
The <samp>-r</samp> option removes a completion specification for
each <var>name</var>, or, if no <var>name</var>s are supplied, all
completion specifications.
The <samp>-D</samp> option indicates that the remaining options and actions should
The <samp>-D</samp> option indicates that other supplied options and actions should
apply to the &ldquo;default&rdquo; command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The <samp>-E</samp> option indicates that the remaining options and actions should
The <samp>-E</samp> option indicates that other supplied options and actions should
apply to &ldquo;empty&rdquo; command completion; that is, completion attempted on a
blank line.
The <samp>-I</samp> option indicates that other supplied options and actions should
apply to completion on the inital non-assignment word on the line, or after a
command delimiter such as &lsquo;<samp>;</samp>&rsquo; or &lsquo;<samp>|</samp>&rsquo;, which is usually command
name completion.
If multiple options are supplied, the <samp>-D</samp> option takes precedence
over <samp>-E</samp>, and both take precedence over <samp>-I</samp>.
If any of <samp>-D</samp>, <samp>-E</samp>, or <samp>-I</samp> are supplied, any other
<var>name</var> arguments are ignored; these completions only apply to the case
specified by the option.
</p>
<p>The process of applying these completion specifications when word completion
is attempted is described above (see <a href="#Programmable-Completion">Programmable Completion</a>). The
<samp>-D</samp> option takes precedence over <samp>-E</samp>.
is attempted is described above (see <a href="#Programmable-Completion">Programmable Completion</a>).
</p>
<p>Other options, if specified, have the following meanings.
The arguments to the <samp>-G</samp>, <samp>-W</samp>, and <samp>-X</samp> options
@@ -12027,7 +12079,7 @@ no matches.
</dd>
<dt><code>filenames</code></dt>
<dd><p>Tell Readline that the compspec generates filenames, so it can perform any
filename-specific processing (like adding a slash to directory names
filename-specific processing (like adding a slash to directory names,
quoting special characters, or suppressing trailing spaces).
This option is intended to be used with shell functions specified
with <samp>-F</samp>.
@@ -12221,7 +12273,7 @@ an error occurs adding a completion specification.
<dt><code>compopt</code></dt>
<dd><a name="index-compopt"></a>
<div class="example">
<pre class="example"><code>compopt</code> [-o <var>option</var>] [-DE] [+o <var>option</var>] [<var>name</var>]
<pre class="example"><code>compopt</code> [-o <var>option</var>] [-DEI] [+o <var>option</var>] [<var>name</var>]
</pre></div>
<p>Modify completion options for each <var>name</var> according to the
<var>option</var>s, or for the currently-executing completion if no <var>name</var>s
@@ -12230,14 +12282,19 @@ If no <var>option</var>s are given, display the completion options for each
<var>name</var> or the current completion.
The possible values of <var>option</var> are those valid for the <code>complete</code>
builtin described above.
The <samp>-D</samp> option indicates that the remaining options should
The <samp>-D</samp> option indicates that other supplied options should
apply to the &ldquo;default&rdquo; command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The <samp>-E</samp> option indicates that the remaining options should
The <samp>-E</samp> option indicates that other supplied options should
apply to &ldquo;empty&rdquo; command completion; that is, completion attempted on a
blank line.
The <samp>-I</samp> option indicates that other supplied options should
apply to completion on the inital non-assignment word on the line, or after a
command delimiter such as &lsquo;<samp>;</samp>&rsquo; or &lsquo;<samp>|</samp>&rsquo;, which is usually command
name completion.
</p>
<p>The <samp>-D</samp> option takes precedence over <samp>-E</samp>.
<p>If multiple options are supplied, the <samp>-D</samp> option takes precedence
over <samp>-E</samp>, and both take precedence over <samp>-I</samp>
</p>
<p>The return value is true unless an invalid option is supplied, an attempt
is made to modify the options for a <var>name</var> for which no completion
@@ -12291,7 +12348,7 @@ _comp_cd()
local cur _skipdot _cdpath
local i j k
# Tilde expansion, with side effect of expanding tilde to full pathname
# Tilde expansion, which also expands tilde to full pathname
case &quot;$2&quot; in
\~*) eval cur=&quot;$2&quot; ;;
*) cur=$2 ;;
@@ -12626,8 +12683,8 @@ fix errors in previous commands quickly.
</p>
<p>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 without taking quoting on previous lines into
account.
on each line individually. Bash attempts to inform the history
expansion functions about quoting still in effect from previous lines.
</p>
<p>History expansion takes place in two parts. The first is to determine
which line from the history list should be used during substitution.
@@ -12640,8 +12697,18 @@ that Bash does, so that several words
surrounded by quotes are considered one word.
History expansions are introduced by the appearance of the
history expansion character, which is &lsquo;<samp>!</samp>&rsquo; by default.
Only &lsquo;<samp>\</samp>&rsquo; and &lsquo;<samp>'</samp>&rsquo; may be used to escape the history expansion
character, but the history expansion character is
</p>
<p>History expansion implements shell-like quoting conventions:
a backslash can be used to remove the special handling for the next character;
single quotes enclose verbatim sequences of characters, and can be used to
inhibit history expansion;
and characters enclosed within double quotes may be subject to history
expansion, since backslash can escape the history expansion character,
but single quotes may not, since they are not treated specially within
double quotes.
</p>
<p>When using the shell, only &lsquo;<samp>\</samp>&rsquo; and &lsquo;<samp>'</samp>&rsquo; may be used to escape 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>
@@ -13285,7 +13352,7 @@ compiled and linked, rather than changing run-time features.
</p>
<dl compact="compact">
<dt><code>--enable-largefile</code></dt>
<dd><p>Enable support for <a href="http://www.sas.com/standards/large_file/x_open.20Mar96.html">large files</a> if the operating system requires special compiler options
<dd><p>Enable support for <a href="http://www.unix.org/version2/whatsnew/lfs20mar.html">large files</a> if the operating system requires special compiler options
to build programs which can access large files. This is enabled by
default, if the operating system provides large file support.
</p>
@@ -14991,6 +15058,7 @@ Next: <a href="#Function-Index" accesskey="n" rel="next">Function Index</a>, Pre
<tr><td></td><td valign="top"><a href="#index-IGNOREEOF"><code>IGNOREEOF</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-input_002dmeta"><code>input-meta</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-INPUTRC"><code>INPUTRC</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-INSIDE_005fEMACS"><code>INSIDE_EMACS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-isearch_002dterminators"><code>isearch-terminators</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th><a name="Variable-Index_vr_letter-K">K</a></th><td></td><td></td></tr>