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Chet Ramey
2017-03-28 11:32:59 -04:00
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doc/bashref.html
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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 4.4, 1 February 2017).
the Bash shell (version 4.4, 22 March 2017).
This is Edition 4.4, last updated 1 February 2017,
This is Edition 4.4, last updated 22 March 2017,
of The GNU Bash Reference Manual,
for Bash, Version 4.4.
@@ -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 4.4, 1 February 2017).
the Bash shell (version 4.4, 22 March 2017).
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 4.4, last updated 1 February 2017,
<p>This is Edition 4.4, last updated 22 March 2017,
of <cite>The GNU Bash Reference Manual</cite>,
for <code>Bash</code>, Version 4.4.
</p>
@@ -1865,8 +1865,56 @@ before the <code>return</code>.
</p>
<p>Variables local to the function may be declared with the
<code>local</code> builtin. These variables are visible only to
the function and the commands it invokes.
the function and the commands it invokes. This is particularly
important when a shell function calls other functions.
</p>
<p>Local variables &quot;shadow&quot; variables with the same name declared at
previous scopes. For instance, a local variable declared in a function
hides a global variable of the same name: references and assignments
refer to the local variable, leaving the global variable unmodified.
When the function returns, the global variable is once again visible.
</p>
<p>The shell uses <var>dynamic scoping</var> to control a variable&rsquo;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 &quot;global&quot; scope or another shell function.
This is also the value that a local variable
declaration &quot;shadows&quot;, and the value that is restored when the function
returns.
</p>
<p>For example, if a variable <var>var</var> is declared as local in function
<var>func1</var>, and <var>func1</var> calls another function <var>func2</var>,
references to <var>var</var> made from within <var>func2</var> will resolve to the
local variable <var>var</var> from <var>func1</var>, shadowing any global variable
named <var>var</var>.
</p>
<p>The following script demonstrates this behavior.
When executed, the script displays
</p>
<div class="example">
<pre class="example">In func2, var = func1 local
</pre></div>
<div class="example">
<pre class="example">func1()
{
local var='func1 local'
func2
}
func2()
{
echo &quot;In func2, var = $var&quot;
}
var=global
func1
</pre></div>
<p>Function names and definitions may be listed with the
<samp>-f</samp> option to the <code>declare</code> (<code>typeset</code>)
builtin command (see <a href="#Bash-Builtins">Bash Builtins</a>).
@@ -3370,7 +3418,7 @@ natural fashion.
</pre></div>
<p>The <var>word</var> undergoes
brace expansion, tilde expansion, parameter and variable expansion,
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,
@@ -6392,6 +6440,8 @@ sequences that are expanded before <code>PS1</code> is displayed.
<a name="index-PS2"></a>
</dt>
<dd><p>The secondary prompt string. The default value is &lsquo;<samp>&gt; </samp>&rsquo;.
<code>PS2</code> is expanded in the same way as <code>PS1</code> before being
displayed.
</p>
</dd>
</dl>
@@ -7262,10 +7312,11 @@ and before the command is executed.
<dt><code>PS4</code>
<a name="index-PS4"></a>
</dt>
<dd><p>The value is the prompt printed before the command line is echoed
when the <samp>-x</samp> option is set (see <a href="#The-Set-Builtin">The Set Builtin</a>).
The first character of <code>PS4</code> is replicated multiple times, as
necessary, to indicate multiple levels of indirection.
<dd><p>The value of this parameter is expanded like <var>PS1</var>
and the expanded value is the prompt printed before the command line
is echoed when the <samp>-x</samp> option is set (see <a href="#The-Set-Builtin">The Set Builtin</a>).
The first character of the expanded value is replicated multiple times,
as necessary, to indicate multiple levels of indirection.
The default is &lsquo;<samp>+ </samp>&rsquo;.
</p>
</dd>
@@ -7877,7 +7928,10 @@ signals <code>SIGTTIN</code>, <code>SIGTTOU</code>, and <code>SIGTSTP</code>.
</li><li> Bash expands and displays <code>PS1</code> before reading the first line
of a command, and expands and displays <code>PS2</code> before reading the
second and subsequent lines of a multi-line command.
Bash displays <code>PS0</code> after it reads a command but before executing it.
Bash expands and displays <code>PS0</code> after it reads a command but before
executing it.
See <a href="#Controlling-the-Prompt">Controlling the Prompt</a>, for a complete list of prompt
string escape sequences.
</li><li> Bash executes the value of the <code>PROMPT_COMMAND</code> variable as a command
before printing the primary prompt, <code>$PS1</code>
@@ -8130,6 +8184,8 @@ is equal to, not equal to, less than, less than or equal to,
greater than, or greater than or equal to <var>arg2</var>,
respectively. <var>Arg1</var> and <var>arg2</var>
may be positive or negative integers.
When used with the <code>[[</code> command, <var>Arg1</var> and <var>Arg2</var>
are evaluated as arithmetic expressions (see <a href="#Shell-Arithmetic">Shell Arithmetic</a>).
</p></dd>
</dl>
@@ -8623,7 +8679,8 @@ has a non-null value, then the
value is executed just as if it had been typed on the command line.
</p>
<p>In addition, the following table describes the special characters which
can appear in the prompt variables <code>PS1</code> to <code>PS4</code>:
can appear in the prompt variables <code>PS0</code>, <code>PS1</code>, <code>PS2</code>, and
<code>PS4</code>:
</p>
<dl compact="compact">
<dt><code>\a</code></dt>
@@ -10659,6 +10716,25 @@ Words are delimited by non-quoted shell metacharacters.
Words are delimited by non-quoted shell metacharacters.
</p>
</dd>
<dt><code>previous-screen-line ()</code>
<a name="index-previous_002dscreen_002dline-_0028_0029"></a>
</dt>
<dd><p>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
Readline 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>
</dd>
<dt><code>next-screen-line ()</code>
<a name="index-next_002dscreen_002dline-_0028_0029"></a>
</dt>
<dd><p>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
Readline line does not take up more than one physical line or if the length
of the current Readline line is not greater than the length of the prompt
plus the screen width.
</p>
</dd>
<dt><code>clear-screen (C-l)</code>
<a name="index-clear_002dscreen-_0028C_002dl_0029"></a>
</dt>
@@ -13258,7 +13334,7 @@ If Readline is not enabled, this option has no effect.
</dd>
<dt><code>--enable-prompt-string-decoding</code></dt>
<dd><p>Turn on the interpretation of a number of backslash-escaped characters
in the <code>$PS1</code>, <code>$PS2</code>, <code>$PS3</code>, and <code>$PS4</code> prompt
in the <code>$PS0</code>, <code>$PS1</code>, <code>$PS2</code>, and <code>$PS4</code> prompt
strings. See <a href="#Controlling-the-Prompt">Controlling the Prompt</a>, for a complete list of prompt
string escape sequences.
</p>
@@ -15066,6 +15142,7 @@ Next: <a href="#Concept-Index" accesskey="n" rel="next">Concept Index</a>, Previ
<tr><td colspan="4"> <hr></td></tr>
<tr><th><a name="Function-Index_fn_letter-N">N</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-next_002dhistory-_0028C_002dn_0029"><code>next-history (C-n)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-next_002dscreen_002dline-_0028_0029"><code>next-screen-line ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-non_002dincremental_002dforward_002dsearch_002dhistory-_0028M_002dn_0029"><code>non-incremental-forward-search-history (M-n)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-non_002dincremental_002dreverse_002dsearch_002dhistory-_0028M_002dp_0029"><code>non-incremental-reverse-search-history (M-p)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
@@ -15082,6 +15159,7 @@ Next: <a href="#Concept-Index" accesskey="n" rel="next">Concept Index</a>, Previ
<tr><td></td><td valign="top"><a href="#index-possible_002dvariable_002dcompletions-_0028C_002dx-_0024_0029"><code>possible-variable-completions (C-x $)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-prefix_002dmeta-_0028ESC_0029"><code>prefix-meta (<span class="key">ESC</span>)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-previous_002dhistory-_0028C_002dp_0029"><code>previous-history (C-p)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-previous_002dscreen_002dline-_0028_0029"><code>previous-screen-line ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-print_002dlast_002dkbd_002dmacro-_0028_0029"><code>print-last-kbd-macro ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Keyboard-Macros">Keyboard Macros</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th><a name="Function-Index_fn_letter-Q">Q</a></th><td></td><td></td></tr>