10740 lines
242 KiB
HTML
10740 lines
242 KiB
HTML
<HTML><HEAD>
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<TITLE>BASH(1) Manual Page</TITLE>
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</HEAD>
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<BODY><TABLE WIDTH=100%>
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<TH ALIGN=LEFT>BASH(1)<TH ALIGN=CENTER>2001 November 13<TH ALIGN=RIGHT>BASH(1)
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</TABLE>
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<BR><A HREF="#index">Index</A>
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<HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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bash - GNU Bourne-Again SHell
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>bash</B>
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[options]
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[file]
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<A NAME="lbAD"> </A>
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<H2>COPYRIGHT</H2>
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Bash is Copyright © 1989-2001 by the Free Software Foundation, Inc.
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<A NAME="lbAE"> </A>
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<H2>DESCRIPTION</H2>
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<B>Bash</B>
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is an <B>sh</B>-compatible command language interpreter that
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executes commands read from the standard input or from a file.
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<B>Bash</B>
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also incorporates useful features from the <I>Korn</I> and <I>C</I>
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shells (<B>ksh</B> and <B>csh</B>).
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<P>
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<B>Bash</B>
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is intended to be a conformant implementation of the IEEE
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POSIX Shell and Tools specification (IEEE Working Group 1003.2).
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<A NAME="lbAF"> </A>
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<H2>OPTIONS</H2>
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In addition to the single-character shell options documented in the
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description of the <B>set</B> builtin command, <B>bash</B>
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interprets the following options when it is invoked:
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<P>
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<DL COMPACT>
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<DT><B>-c</B><I> string</I>
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<DD>
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If the
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<B>-c</B>
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option is present, then commands are read from
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<I>string</I>.
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If there are arguments after the
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||
<I>string</I>,
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they are assigned to the positional parameters, starting with
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<B>$0</B>.
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<DT><B>-r</B>
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<DD>
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If the
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<B>-r</B>
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option is present, the shell becomes
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<I>restricted</I>
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(see
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<FONT SIZE=-1><B>RESTRICTED SHELL</B>
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</FONT>
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below).
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<DT><B>-i</B>
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<DD>
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If the
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<B>-i</B>
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option is present, the shell is
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<I>interactive</I>.
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<DT><B>-s</B>
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<DD>
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If the
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<B>-s</B>
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option is present, or if no arguments remain after option
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processing, then commands are read from the standard input.
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This option allows the positional parameters to be set
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when invoking an interactive shell.
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<DT><B>-D</B>
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<DD>
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A list of all double-quoted strings preceded by <B>$</B>
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is printed on the standard ouput.
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These are the strings that
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are subject to language translation when the current locale
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is not <B>C</B> or <B>POSIX</B>.
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||
This implies the <B>-n</B> option; no commands will be executed.
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<DT><B>[-+]O [</B><I>shopt_option</I>]
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<DD>
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<I>shopt_option</I> is one of the shell options accepted by the
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<B>shopt</B> builtin (see
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<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
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||
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||
</FONT>
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||
below).
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If <I>shopt_option</I> is present, <B>-O</B> sets the value of that option;
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||
<B>+O</B> unsets it.
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||
If <I>shopt_option</I> is not supplied, the names and values of the shell
|
||
options accepted by <B>shopt</B> are printed on the standard output.
|
||
If the invocation option is <B>+O</B>, the output is displayed in a format
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||
that may be reused as input.
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||
<DT><B>--</B>
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<DD>
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A
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<B>--</B>
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signals the end of options and disables further option processing.
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||
Any arguments after the
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||
<B>--</B>
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are treated as filenames and arguments. An argument of
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<B>-</B>
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is equivalent to <B>--</B>.
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</DL>
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<P>
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<B>Bash</B>
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also interprets a number of multi-character options.
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These options must appear on the command line before the
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single-character options in order for them to be recognized.
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<P>
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<DL COMPACT>
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<DT><B>--dump-po-strings</B>
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||
<DD>
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||
Equivalent to <B>-D</B>, but the output is in the GNU <I>gettext</I>
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||
<B>po</B> (portable object) file format.
|
||
<DT><B>--dump-strings</B>
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||
|
||
<DD>
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||
Equivalent to <B>-D</B>.
|
||
<DT><B>--help</B>
|
||
|
||
<DD>
|
||
Display a usage message on standard output and exit successfully.
|
||
<DT>
|
||
<DD>
|
||
<B>--init-file</B> <I>file</I>
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||
<DT><B>--rcfile</B> <I>file</I><DD>
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||
|
||
Execute commands from
|
||
<I>file</I>
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||
|
||
instead of the standard personal initialization file
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||
<A HREF="file:~/.bashrc"><I>~/.bashrc</I></A>
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||
|
||
if the shell is interactive (see
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<FONT SIZE=-1><B>INVOCATION</B>
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||
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||
</FONT>
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||
below).
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<DT><B>--login</B>
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||
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||
<DD>
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||
Make
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<B>bash</B>
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act as if it had been invoked as a login shell (see
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<FONT SIZE=-1><B>INVOCATION</B>
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||
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||
</FONT>
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||
below).
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<DT><B>--noediting</B>
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||
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<DD>
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||
Do not use the GNU
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<B>readline</B>
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||
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||
library to read command lines when the shell is interactive.
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<DT><B>--noprofile</B>
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||
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<DD>
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Do not read either the system-wide startup file
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<A HREF="file:/etc/profile"><I>/etc/profile</I></A>
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||
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||
or any of the personal initialization files
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<A HREF="file:~/.bash_profile"><I>~/.bash_profile</I></A>,
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||
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<A HREF="file:~/.bash_login"><I>~/.bash_login</I></A>,
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or
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<A HREF="file:~/.profile"><I>~/.profile</I></A>.
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By default,
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<B>bash</B>
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reads these files when it is invoked as a login shell (see
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<FONT SIZE=-1><B>INVOCATION</B>
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||
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||
</FONT>
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||
below).
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||
<DT><B>--norc</B>
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||
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<DD>
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Do not read and execute the personal initialization file
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||
<A HREF="file:~/.bashrc"><I>~/.bashrc</I></A>
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||
|
||
if the shell is interactive.
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||
This option is on by default if the shell is invoked as
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<B>sh</B>.
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||
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<DT><B>--posix</B>
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||
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||
<DD>
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||
Change the behavior of <B>bash</B> where the default operation differs
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||
from the POSIX 1003.2 standard to match the standard (<I>posix mode</I>).
|
||
<DT><B>--restricted</B>
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||
|
||
<DD>
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The shell becomes restricted (see
|
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<FONT SIZE=-1><B>RESTRICTED SHELL</B>
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||
|
||
</FONT>
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||
below).
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||
<DT><B>--verbose</B>
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||
|
||
<DD>
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||
Equivalent to <B>-v</B>.
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||
<DT><B>--version</B>
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||
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||
<DD>
|
||
Show version information for this instance of
|
||
<B>bash</B>
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||
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||
on the standard output and exit successfully.
|
||
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||
</DL>
|
||
<A NAME="lbAG"> </A>
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||
<H2>ARGUMENTS</H2>
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||
|
||
If arguments remain after option processing, and neither the
|
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<B>-c</B>
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||
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||
nor the
|
||
<B>-s</B>
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||
|
||
option has been supplied, the first argument is assumed to
|
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be the name of a file containing shell commands.
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||
If
|
||
<B>bash</B>
|
||
|
||
is invoked in this fashion,
|
||
<B>$0</B>
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||
|
||
is set to the name of the file, and the positional parameters
|
||
are set to the remaining arguments.
|
||
<B>Bash</B>
|
||
|
||
reads and executes commands from this file, then exits.
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||
<B>Bash</B>'s exit status is the exit status of the last command
|
||
executed in the script.
|
||
If no commands are executed, the exit status is 0.
|
||
An attempt is first made to open the file in the current directory, and,
|
||
if no file is found, then the shell searches the directories in
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
for the script.
|
||
<A NAME="lbAH"> </A>
|
||
<H2>INVOCATION</H2>
|
||
|
||
A <I>login shell</I> is one whose first character of argument zero is a
|
||
<B>-</B>,
|
||
|
||
or one started with the
|
||
<B>--login</B>
|
||
|
||
option.
|
||
<P>
|
||
|
||
An <I>interactive</I> shell is one started without non-option arguments
|
||
and without the
|
||
<B>-c</B>
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||
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||
option
|
||
whose standard input and output are
|
||
both connected to terminals (as determined by
|
||
<I>isatty</I>(3)),
|
||
|
||
or one started with the
|
||
<B>-i</B>
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||
|
||
option.
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||
<FONT SIZE=-1><B>PS1</B>
|
||
|
||
</FONT>
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||
is set and
|
||
<B>$-</B>
|
||
|
||
includes
|
||
<B>i</B>
|
||
|
||
if
|
||
<B>bash</B>
|
||
|
||
is interactive,
|
||
allowing a shell script or a startup file to test this state.
|
||
<P>
|
||
|
||
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 are expanded in file names as described below under
|
||
<B>Tilde Expansion</B>
|
||
|
||
in the
|
||
<FONT SIZE=-1><B>EXPANSION</B>
|
||
|
||
</FONT>
|
||
section.
|
||
<P>
|
||
|
||
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>
|
||
|
||
When a login shell exits,
|
||
<B>bash</B>
|
||
|
||
reads and executes commands from the file <A HREF="file:~/.bash_logout"><I>~/.bash_logout</I></A>, if it
|
||
exists.
|
||
<P>
|
||
|
||
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.
|
||
This may be inhibited by using the
|
||
<B>--norc</B>
|
||
|
||
option.
|
||
The <B>--rcfile</B> <I>file</I> option will force
|
||
<B>bash</B>
|
||
|
||
to read and execute commands from <I>file</I> instead of <A HREF="file:~/.bashrc"><I>~/.bashrc</I></A>.
|
||
<P>
|
||
|
||
When
|
||
<B>bash</B>
|
||
|
||
is started non-interactively, to run a shell script, for example, it
|
||
looks for the variable
|
||
<FONT SIZE=-1><B>BASH_ENV</B>
|
||
|
||
</FONT>
|
||
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>
|
||
<DL COMPACT><DT><DD>
|
||
<TT>if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi</TT>
|
||
|
||
</DL>
|
||
|
||
<P>
|
||
but the value of the
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
variable is not used to search for the file name.
|
||
<P>
|
||
|
||
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 may be used to inhibit this behavior.
|
||
When invoked as an interactive shell with the name
|
||
<B>sh</B>,
|
||
|
||
<B>bash</B>
|
||
|
||
looks for the variable
|
||
<FONT SIZE=-1><B>ENV</B>,
|
||
|
||
</FONT>
|
||
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.
|
||
When invoked as
|
||
<B>sh</B>,
|
||
|
||
<B>bash</B>
|
||
|
||
enters
|
||
<I>posix</I>
|
||
|
||
mode after the startup files are read.
|
||
<P>
|
||
|
||
When
|
||
<B>bash</B>
|
||
|
||
is started in
|
||
<I>posix</I>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>ENV</B>
|
||
|
||
</FONT>
|
||
variable and commands are read and executed from the file
|
||
whose name is the expanded value.
|
||
No other startup files are read.
|
||
<P>
|
||
|
||
<B>Bash</B>
|
||
|
||
attempts to determine when it is being run by the remote shell
|
||
daemon, usually <I>rshd</I>.
|
||
If
|
||
<B>bash</B>
|
||
|
||
determines it is being run by <I>rshd</I>, it reads and executes
|
||
commands from <A HREF="file:~/.bashrc"><I>~/.bashrc</I></A>, if that file exists and is readable.
|
||
It will not do this if invoked as <B>sh</B>.
|
||
The
|
||
<B>--norc</B>
|
||
|
||
option may be used to inhibit this behavior, and the
|
||
<B>--rcfile</B>
|
||
|
||
option may be used to force another file to be read, but
|
||
<I>rshd</I> does not generally invoke the shell with those options
|
||
or allow them to be specified.
|
||
<P>
|
||
|
||
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, no startup
|
||
files are read, shell functions are not inherited from the environment, the
|
||
<FONT SIZE=-1><B>SHELLOPTS</B>
|
||
|
||
</FONT>
|
||
variable, if it appears in the environment, is ignored,
|
||
and the effective user id is set to the real user id.
|
||
If the <B>-p</B> option is supplied at invocation, the startup behavior is
|
||
the same, but the effective user id is not reset.
|
||
<A NAME="lbAI"> </A>
|
||
<H2>DEFINITIONS</H2>
|
||
|
||
<P>
|
||
|
||
The following definitions are used throughout the rest of this
|
||
document.
|
||
|
||
<DL COMPACT>
|
||
<DT><B>blank </B>
|
||
|
||
<DD>
|
||
A space or tab.
|
||
<DT><B>word</B>
|
||
|
||
<DD>
|
||
A sequence of characters considered as a single unit by the shell.
|
||
Also known as a
|
||
<B>token</B>.
|
||
|
||
<DT><B>name</B>
|
||
|
||
<DD>
|
||
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>.
|
||
|
||
<DT><B>metacharacter</B>
|
||
|
||
<DD>
|
||
A character that, when unquoted, separates words. One of the following:
|
||
<BR>
|
||
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<B>| & ; ( ) < > space tab</B>
|
||
|
||
</DL>
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>control operator</B>
|
||
|
||
<DD>
|
||
A <I>token</I> that performs a control function. It is one of the following
|
||
symbols:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<B>|| & && ; ;; ( ) | <newline></B>
|
||
|
||
</DL>
|
||
|
||
|
||
</DL>
|
||
<A NAME="lbAJ"> </A>
|
||
<H2>RESERVED WORDS</H2>
|
||
|
||
<I>Reserved words</I> are words that have a special meaning to the shell.
|
||
The following words are recognized as reserved when unquoted and either
|
||
the first word of a simple command (see
|
||
<FONT SIZE=-1><B>SHELL GRAMMAR</B>
|
||
|
||
</FONT>
|
||
below) or the third word of a
|
||
<B>case </B>
|
||
|
||
or
|
||
<B>for</B>
|
||
|
||
command:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<P>
|
||
|
||
<B>
|
||
</B>
|
||
|
||
! case do done elif else esac fi for function if in select then until while { } time [[ ]]
|
||
</DL>
|
||
|
||
|
||
|
||
<A NAME="lbAK"> </A>
|
||
<H2>SHELL GRAMMAR</H2>
|
||
|
||
<A NAME="lbAL"> </A>
|
||
<H3>Simple Commands</H3>
|
||
|
||
<P>
|
||
|
||
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>
|
||
|
||
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>.
|
||
|
||
<A NAME="lbAM"> </A>
|
||
<H3>Pipelines</H3>
|
||
|
||
<P>
|
||
|
||
A <I>pipeline</I> is a sequence of one or more commands separated by
|
||
the character
|
||
<B>|</B>.
|
||
|
||
The format for a pipeline is:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
[<B>time</B> [<B>-p</B>]] [ ! ] <I>command</I> [ <B>|</B> <I>command2</I> ... ]
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
The standard output of
|
||
<I>command</I>
|
||
|
||
is connected via a pipe to the standard input of
|
||
<I>command2</I>.
|
||
|
||
This connection is performed before any redirections specified by the
|
||
command (see
|
||
<FONT SIZE=-1><B>REDIRECTION</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<P>
|
||
|
||
If the reserved word
|
||
<B>!</B>
|
||
|
||
precedes a pipeline, the exit status of that
|
||
pipeline is the logical NOT of the exit status of the last command.
|
||
Otherwise, the status of the pipeline is the exit status of the last
|
||
command.
|
||
The shell waits for all commands in the pipeline to
|
||
terminate before returning a value.
|
||
<P>
|
||
|
||
If the
|
||
<B>time</B>
|
||
|
||
reserved word precedes a pipeline, the elapsed as well as user and
|
||
system time consumed by its execution are reported when the pipeline
|
||
terminates.
|
||
The <B>-p</B> option changes the output format to that specified by POSIX.
|
||
The
|
||
<FONT SIZE=-1><B>TIMEFORMAT</B>
|
||
|
||
</FONT>
|
||
variable may be set to a format string that specifies how the timing
|
||
information should be displayed; see the description of
|
||
<FONT SIZE=-1><B>TIMEFORMAT</B>
|
||
|
||
</FONT>
|
||
under
|
||
<B>Shell Variables</B>
|
||
|
||
below.
|
||
<P>
|
||
|
||
Each command in a pipeline is executed as a separate process (i.e., in a
|
||
subshell).
|
||
<A NAME="lbAN"> </A>
|
||
<H3>Lists</H3>
|
||
|
||
<P>
|
||
|
||
A <I>list</I> is a sequence of one or more pipelines separated by one
|
||
of the operators
|
||
<B>;</B>,
|
||
|
||
<B>&</B>,
|
||
|
||
<B>&&</B>,
|
||
|
||
or
|
||
<B>||</B>,
|
||
|
||
and optionally terminated by one of
|
||
<B>;</B>,
|
||
|
||
<B>&</B>,
|
||
|
||
or
|
||
<B><newline></B>.
|
||
|
||
<P>
|
||
|
||
Of these list operators,
|
||
<B>&&</B>
|
||
|
||
and
|
||
<B>||</B>
|
||
|
||
have equal precedence, followed by
|
||
<B>;</B>
|
||
|
||
and
|
||
<B>&,</B>
|
||
|
||
which have equal precedence.
|
||
<P>
|
||
|
||
If a command is terminated by the control operator
|
||
<B>&</B>,
|
||
|
||
the shell executes the command in the <I>background</I>
|
||
in a subshell. The shell does not wait for the command to
|
||
finish, and the return status is 0. Commands separated by a
|
||
<B>;</B>
|
||
|
||
are executed sequentially; the shell waits for each
|
||
command to terminate in turn. The return status is the
|
||
exit status of the last command executed.
|
||
<P>
|
||
|
||
The control operators
|
||
<B>&&</B>
|
||
|
||
and
|
||
<B>||</B>
|
||
|
||
denote AND lists and OR lists, respectively.
|
||
An AND list has the form
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<I>command1</I> <B>&&</B> <I>command2</I>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
<I>command2</I>
|
||
|
||
is executed if, and only if,
|
||
<I>command1</I>
|
||
|
||
returns an exit status of zero.
|
||
<P>
|
||
|
||
An OR list has the form
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<I>command1</I> <B>||</B> <I>command2</I>
|
||
<P>
|
||
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
<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.
|
||
<A NAME="lbAO"> </A>
|
||
<H3>Compound Commands</H3>
|
||
|
||
<P>
|
||
|
||
A <I>compound command</I> is one of the following:
|
||
<DL COMPACT>
|
||
<DT>(<I>list</I>)<DD>
|
||
<I>list</I> is executed in a subshell. 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>.
|
||
<DT>{ <I>list</I>; }<DD>
|
||
<I>list</I> is simply 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>.
|
||
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.
|
||
<DT>((<I>expression</I>))<DD>
|
||
The <I>expression</I> is evaluated according to the rules described
|
||
below under
|
||
<FONT SIZE=-1><B>ARITHMETIC</B>EVALUATION<B>.</B>
|
||
|
||
</FONT>
|
||
If the value of the expression is non-zero, the return status is 0;
|
||
otherwise the return status is 1. This is exactly equivalent to
|
||
<B>let "</B><I>expression</I>".
|
||
<DT><B>[[</B> <I>expression</I> <B>]]</B><DD>
|
||
Return a status of 0 or 1 depending on the evaluation of
|
||
the conditional expression <I>expression</I>.
|
||
Expressions are composed of the primaries described below under
|
||
<FONT SIZE=-1><B>CONDITIONAL</B>EXPRESSIONS<B>.</B>
|
||
|
||
</FONT>
|
||
Word splitting and pathname expansion are not performed on the words
|
||
between the <B>[[</B> and <B>]]</B>; tilde expansion, parameter and
|
||
variable expansion, arithmetic expansion, command substitution, process
|
||
substitution, and quote removal are performed.
|
||
<P>
|
||
|
||
|
||
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>.
|
||
The return value is 0 if the string matches or does not match
|
||
the pattern, respectively, and 1 otherwise.
|
||
Any part of the pattern may be quoted to force it to be matched as a
|
||
string.
|
||
<P>
|
||
|
||
|
||
Expressions may be combined using the following operators, listed
|
||
in decreasing order of precedence:
|
||
<P>
|
||
|
||
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>( </B><I>expression</I> )
|
||
|
||
<DD>
|
||
Returns the value of <I>expression</I>.
|
||
This may be used to override the normal precedence of operators.
|
||
<DT><B>! </B><I>expression</I>
|
||
|
||
<DD>
|
||
True if
|
||
<I>expression</I>
|
||
|
||
is false.
|
||
<DT><I>expression1</I> <B>&&</B> <I>expression2</I><DD>
|
||
True if both
|
||
<I>expression1</I>
|
||
|
||
and
|
||
<I>expression2</I>
|
||
|
||
are true.
|
||
<DT><I>expression1</I> <B>||</B> <I>expression2</I>
|
||
<DD>
|
||
|
||
True if either
|
||
<I>expression1</I>
|
||
|
||
or
|
||
<I>expression2</I>
|
||
|
||
is true.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
The <B>&&</B> and
|
||
<B>||</B>
|
||
|
||
operators do not execute <I>expression2</I> if the value of
|
||
<I>expression1</I> is sufficient to determine the return value of
|
||
the entire conditional expression.
|
||
</DL>
|
||
|
||
<DT><B>for</B> <I>name</I> [ <B>in</B> <I>word</I> ] ; <B>do</B> <I>list</I> ; <B>done</B><DD>
|
||
The list of words following <B>in</B> is expanded, generating a list
|
||
of items.
|
||
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
|
||
<FONT SIZE=-1><B>PARAMETERS</B>
|
||
|
||
</FONT>
|
||
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.
|
||
<DT><B>for</B> (( <I>expr1</I> ; <I>expr2</I> ; <I>expr3</I> )) ; <B>do</B> <I>list</I> ; <B>done</B><DD>
|
||
First, the arithmetic expression <I>expr1</I> is evaluated according
|
||
to the rules described below under
|
||
<FONT SIZE=-1><B>ARITHMETIC</B>EVALUATION<B>.</B>
|
||
|
||
</FONT>
|
||
The arithmetic expression <I>expr2</I> is then evaluated repeatedly
|
||
until it evaluates to zero.
|
||
Each time <I>expr2</I> evaluates to a non-zero value, <I>list</I> is
|
||
executed and the arithmetic expression <I>expr3</I> is evaluated.
|
||
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 false if any of the expressions is invalid.
|
||
<DT><B>select</B> <I>name</I> [ <B>in</B> <I>word</I> ] ; <B>do</B> <I>list</I> ; <B>done</B><DD>
|
||
The list of words following <B>in</B> is expanded, generating a list
|
||
of items. The set of expanded words is printed on the standard
|
||
error, each preceded by a number. If the <B>in</B>
|
||
<I>word</I> is omitted, the positional parameters are printed (see
|
||
<FONT SIZE=-1><B>PARAMETERS</B>
|
||
|
||
</FONT>
|
||
below). The
|
||
<B>PS3</B>
|
||
|
||
prompt is then displayed and a line read from the standard input.
|
||
If the line consists of a number corresponding to one of
|
||
the displayed words, then the value of
|
||
<I>name</I>
|
||
|
||
is set to that word. If the line is empty, the words and prompt
|
||
are displayed again. If EOF is read, the command completes. Any
|
||
other value read causes
|
||
<I>name</I>
|
||
|
||
to be set 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.
|
||
<DT><B>case</B> <I>word</I> <B>in</B> [ [(] <I>pattern</I> [ <B>|</B> <I>pattern</I> ]
|
||
<DD>
|
||
A <B>case</B> command first expands <I>word</I>, and tries to match
|
||
it against each <I>pattern</I> in turn, using the same matching rules
|
||
as for pathname expansion (see
|
||
<B>Pathname Expansion</B>
|
||
|
||
below). When a match is found, the
|
||
corresponding <I>list</I> is executed. After the first match, no
|
||
subsequent matches are attempted. The exit status is zero if no
|
||
pattern matches. Otherwise, it is the exit status of the
|
||
last command executed in <I>list</I>.
|
||
<DT><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><DD>
|
||
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.
|
||
<DT>
|
||
<DD>
|
||
<B>while</B> <I>list</I>; <B>do</B> <I>list</I>; <B>done</B>
|
||
<DT><B>until</B> <I>list</I>; <B>do</B> <I>list</I>; <B>done</B><DD>
|
||
|
||
The <B>while</B> command continuously executes the <B>do</B>
|
||
<I>list</I> as long as the last command in <I>list</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;
|
||
the
|
||
<B>do</B>
|
||
|
||
<I>list</I>
|
||
|
||
is executed as long as the last command in
|
||
<I>list</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 <B>do</B> <I>list</I> command executed, or zero if
|
||
none was executed.
|
||
<DT>[ <B>function</B> ] <I>name</I> () { <I>list</I>; }<DD>
|
||
This defines a function named <I>name</I>. The <I>body</I> of the
|
||
function is the
|
||
<I>list</I>
|
||
|
||
of commands between { and }. This list
|
||
is executed whenever <I>name</I> is specified as the
|
||
name of a simple command. The exit status of a function is
|
||
the exit status of the last command executed in the body. (See
|
||
<FONT SIZE=-1><B>FUNCTIONS</B>
|
||
|
||
</FONT>
|
||
below.)
|
||
</DL>
|
||
<A NAME="lbAP"> </A>
|
||
<H2>COMMENTS</H2>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below), a word beginning with
|
||
<B>#</B>
|
||
|
||
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 on by default in interactive shells.
|
||
<A NAME="lbAQ"> </A>
|
||
<H2>QUOTING</H2>
|
||
|
||
<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>
|
||
|
||
Each of the <I>metacharacters</I> listed above under
|
||
<FONT SIZE=-1><B>DEFINITIONS</B>
|
||
|
||
</FONT>
|
||
has special meaning to the shell and must be quoted if it is to
|
||
represent itself.
|
||
<P>
|
||
|
||
When the command history expansion facilities are being used, the
|
||
<I>history expansion</I> character, usually <B>!</B>, must be quoted
|
||
to prevent history expansion.
|
||
<P>
|
||
|
||
There are three quoting mechanisms: the
|
||
<I>escape character</I>,
|
||
|
||
single quotes, and double quotes.
|
||
<P>
|
||
|
||
A non-quoted backslash (<B>\</B>) is the
|
||
<I>escape character</I>.
|
||
|
||
It preserves the literal value of the next character that follows,
|
||
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>
|
||
|
||
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>
|
||
|
||
Enclosing characters in double quotes preserves the literal value
|
||
of all characters within the quotes, with the exception of
|
||
<B>$</B>,
|
||
|
||
<B>`</B>,
|
||
|
||
and
|
||
<B>\</B>.
|
||
|
||
The characters
|
||
<B>$</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>$</B>,
|
||
|
||
<B>`</B>,
|
||
|
||
<B>"</B>,
|
||
<B>\</B>,
|
||
|
||
or
|
||
<B><newline></B>.
|
||
|
||
A double quote may be quoted within double quotes by preceding it with
|
||
a backslash.
|
||
<P>
|
||
|
||
The special parameters
|
||
<B>*</B>
|
||
|
||
and
|
||
<B>@</B>
|
||
|
||
have special meaning when in double
|
||
quotes (see
|
||
<FONT SIZE=-1><B>PARAMETERS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<P>
|
||
|
||
Words of the form <B>$</B>'<I>string</I>' are treated specially. The
|
||
word expands to <I>string</I>, with backslash-escaped characters replaced
|
||
as specifed by the ANSI C standard. Backslash escape sequences, if
|
||
present, are decoded as follows:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>\a</B>
|
||
|
||
<DD>
|
||
alert (bell)
|
||
<DT><B>\b</B>
|
||
|
||
<DD>
|
||
backspace
|
||
<DT><B>\e</B>
|
||
|
||
<DD>
|
||
an escape character
|
||
<DT><B>\f</B>
|
||
|
||
<DD>
|
||
form feed
|
||
<DT><B>\n</B>
|
||
|
||
<DD>
|
||
new line
|
||
<DT><B>\r</B>
|
||
|
||
<DD>
|
||
carriage return
|
||
<DT><B>\t</B>
|
||
|
||
<DD>
|
||
horizontal tab
|
||
<DT><B>\v</B>
|
||
|
||
<DD>
|
||
vertical tab
|
||
<DT><B>\\</B>
|
||
|
||
<DD>
|
||
backslash
|
||
<DT><B>\'</B>
|
||
|
||
<DD>
|
||
single quote
|
||
<DT><B>\</B><I>nnn</I>
|
||
|
||
<DD>
|
||
the eight-bit character whose value is the octal value <I>nnn</I>
|
||
(one to three digits)
|
||
<DT><B>\x</B><I>HH</I>
|
||
|
||
<DD>
|
||
the eight-bit character whose value is the hexadecimal value <I>HH</I>
|
||
(one or two hex digits)
|
||
|
||
</DL></DL>
|
||
|
||
<P>
|
||
|
||
The expanded result is single-quoted, as if the dollar sign had
|
||
not been present.
|
||
<P>
|
||
|
||
A double-quoted string preceded by a dollar sign (<B>$</B>) will cause
|
||
the string to be translated according to the current locale.
|
||
If the current locale is <B>C</B> or <B>POSIX</B>, the dollar sign
|
||
is ignored.
|
||
If the string is translated and replaced, the replacement is
|
||
double-quoted.
|
||
<A NAME="lbAR"> </A>
|
||
<H2>PARAMETERS</H2>
|
||
|
||
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>.
|
||
|
||
For the shell's purposes, 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
|
||
<FONT SIZE=-1><B>SHELL</B>BUILTIN<B>COMMANDS</B>).
|
||
|
||
</FONT>
|
||
<P>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<P>
|
||
|
||
A
|
||
<I>variable</I>
|
||
|
||
may be assigned to by a statement of the form
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<I>name</I>=[<I>value</I>]
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>EXPANSION</B>
|
||
|
||
</FONT>
|
||
below). If the variable has its
|
||
<B>integer</B>
|
||
|
||
attribute set, then
|
||
<I>value</I>
|
||
|
||
is subject to arithmetic expansion even if the $((...)) expansion is
|
||
not used (see
|
||
<B>Arithmetic Expansion</B>
|
||
|
||
below).
|
||
Word splitting is not performed, with the exception
|
||
of <B>"$@"</B> as explained below under
|
||
<B>Special Parameters</B>.
|
||
|
||
Pathname expansion is not performed.
|
||
Assignment statements may also appear as arguments to the
|
||
<B>declare</B>,
|
||
|
||
<B>typeset</B>,
|
||
|
||
<B>export</B>,
|
||
|
||
<B>readonly</B>,
|
||
|
||
and
|
||
<B>local</B>
|
||
|
||
builtin commands.
|
||
<A NAME="lbAS"> </A>
|
||
<H3>Positional Parameters</H3>
|
||
|
||
<P>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>FUNCTIONS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<P>
|
||
|
||
When a positional parameter consisting of more than a single
|
||
digit is expanded, it must be enclosed in braces (see
|
||
<FONT SIZE=-1><B>EXPANSION</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<A NAME="lbAT"> </A>
|
||
<H3>Special Parameters</H3>
|
||
|
||
<P>
|
||
|
||
The shell treats several parameters specially. These parameters may
|
||
only be referenced; assignment to them is not allowed.
|
||
|
||
<DL COMPACT>
|
||
<DT><B>*</B>
|
||
|
||
<DD>
|
||
Expands to the positional parameters, starting from one. 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
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
special variable. That is, "<B>$*</B>" is equivalent
|
||
to "<B>$1</B><I>c</I><B>$2</B><I>c</I><B>...</B>", where
|
||
<I>c</I>
|
||
|
||
is the first character of the value of the
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
variable. If
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
is unset, the parameters are separated by spaces.
|
||
If
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
is null, the parameters are joined without intervening separators.
|
||
<DT><B>@</B>
|
||
|
||
<DD>
|
||
Expands to the positional parameters, starting from one. When the
|
||
expansion occurs within double quotes, each parameter expands to a
|
||
separate word. That is, "<B>$@</B>" is equivalent to
|
||
"<B>$1</B>" "<B>$2</B>" ...
|
||
When there are no positional parameters, "<B>$@</B>" and
|
||
<B>$@</B>
|
||
|
||
expand to nothing (i.e., they are removed).
|
||
<DT><B>#</B>
|
||
|
||
<DD>
|
||
Expands to the number of positional parameters in decimal.
|
||
<DT><B>?</B>
|
||
|
||
<DD>
|
||
Expands to the status of the most recently executed foreground
|
||
pipeline.
|
||
<DT><B>-</B>
|
||
|
||
<DD>
|
||
Expands to the current option flags as specified upon invocation,
|
||
by the
|
||
<B>set</B>
|
||
|
||
builtin command, or those set by the shell itself
|
||
(such as the
|
||
<B>-i</B>
|
||
|
||
option).
|
||
<DT><B>$</B>
|
||
|
||
<DD>
|
||
Expands to the process ID of the shell. In a () subshell, it
|
||
expands to the process ID of the current shell, not the
|
||
subshell.
|
||
<DT><B>!</B>
|
||
|
||
<DD>
|
||
Expands to the process ID of the most recently executed background
|
||
(asynchronous) command.
|
||
<DT><B>0</B>
|
||
|
||
<DD>
|
||
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 file name used to invoke
|
||
<B>bash</B>,
|
||
|
||
as given by argument zero.
|
||
<DT><B>_</B>
|
||
|
||
<DD>
|
||
At shell startup, set to the absolute file name of the shell or shell
|
||
script being executed as passed in the argument list.
|
||
Subsequently, expands to the last argument to the previous command,
|
||
after expansion.
|
||
Also set to the full file name of each command executed and placed in
|
||
the environment exported to that command.
|
||
When checking mail, this parameter holds the name of the mail file
|
||
currently being checked.
|
||
|
||
</DL>
|
||
<A NAME="lbAU"> </A>
|
||
<H3>Shell Variables</H3>
|
||
|
||
<P>
|
||
|
||
The following variables are set by the shell:
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>BASH</B>
|
||
|
||
<DD>
|
||
Expands to the full file name used to invoke this instance of
|
||
<B>bash</B>.
|
||
|
||
<DT><B>BASH_VERSINFO</B>
|
||
|
||
<DD>
|
||
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>
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>BASH_VERSINFO[</B>0]
|
||
|
||
<DD>
|
||
The major version number (the <I>release</I>).
|
||
<DT><B>BASH_VERSINFO[</B>1]
|
||
|
||
<DD>
|
||
The minor version number (the <I>version</I>).
|
||
<DT><B>BASH_VERSINFO[</B>2]
|
||
|
||
<DD>
|
||
The patch level.
|
||
<DT><B>BASH_VERSINFO[</B>3]
|
||
|
||
<DD>
|
||
The build version.
|
||
<DT><B>BASH_VERSINFO[</B>4]
|
||
|
||
<DD>
|
||
The release status (e.g., <I>beta1</I>).
|
||
<DT><B>BASH_VERSINFO[</B>5]
|
||
|
||
<DD>
|
||
The value of <B>MACHTYPE</B>.
|
||
|
||
</DL></DL>
|
||
|
||
<DT><B>BASH_VERSION</B>
|
||
|
||
<DD>
|
||
Expands to a string describing the version of this instance of
|
||
<B>bash</B>.
|
||
|
||
<DT><B>COMP_CWORD</B>
|
||
|
||
<DD>
|
||
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).
|
||
<DT><B>COMP_LINE</B>
|
||
|
||
<DD>
|
||
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).
|
||
<DT><B>COMP_POINT</B>
|
||
|
||
<DD>
|
||
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).
|
||
<DT><B>COMP_WORDS</B>
|
||
|
||
<DD>
|
||
An array variable (see <B>Arrays</B> below) consisting of the individual
|
||
words in the current command line.
|
||
This variable is available only in shell functions invoked by the
|
||
programmable completion facilities (see <B>Programmable Completion</B>
|
||
below).
|
||
<DT><B>DIRSTACK</B>
|
||
|
||
<DD>
|
||
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.
|
||
Assignment to this variable will not change the current directory.
|
||
If
|
||
<FONT SIZE=-1><B>DIRSTACK</B>
|
||
|
||
</FONT>
|
||
is unset, it loses its special properties, even if it is
|
||
subsequently reset.
|
||
<DT><B>EUID</B>
|
||
|
||
<DD>
|
||
Expands to the effective user ID of the current user, initialized at
|
||
shell startup. This variable is readonly.
|
||
<DT><B>FUNCNAME</B>
|
||
|
||
<DD>
|
||
The name of any currently-executing shell function.
|
||
This variable exists only when a shell function is executing.
|
||
Assignments to
|
||
<FONT SIZE=-1><B>FUNCNAME</B>
|
||
|
||
</FONT>
|
||
have no effect and return an error status.
|
||
If
|
||
<FONT SIZE=-1><B>FUNCNAME</B>
|
||
|
||
</FONT>
|
||
is unset, it loses its special properties, even if it is
|
||
subsequently reset.
|
||
<DT><B>GROUPS</B>
|
||
|
||
<DD>
|
||
An array variable containing the list of groups of which the current
|
||
user is a member.
|
||
Assignments to
|
||
<FONT SIZE=-1><B>GROUPS</B>
|
||
|
||
</FONT>
|
||
have no effect and return an error status.
|
||
If
|
||
<FONT SIZE=-1><B>GROUPS</B>
|
||
|
||
</FONT>
|
||
is unset, it loses its special properties, even if it is
|
||
subsequently reset.
|
||
<DT><B>HISTCMD</B>
|
||
|
||
<DD>
|
||
The history number, or index in the history list, of the current
|
||
command.
|
||
If
|
||
<FONT SIZE=-1><B>HISTCMD</B>
|
||
|
||
</FONT>
|
||
is unset, it loses its special properties, even if it is
|
||
subsequently reset.
|
||
<DT><B>HOSTNAME</B>
|
||
|
||
<DD>
|
||
Automatically set to the name of the current host.
|
||
<DT><B>HOSTTYPE</B>
|
||
|
||
<DD>
|
||
Automatically set to a string that uniquely
|
||
describes the type of machine on which
|
||
<B>bash</B>
|
||
|
||
is executing.
|
||
The default is system-dependent.
|
||
<DT><B>LINENO</B>
|
||
|
||
<DD>
|
||
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
|
||
<FONT SIZE=-1><B>LINENO</B>
|
||
|
||
</FONT>
|
||
is unset, it loses its special properties, even if it is
|
||
subsequently reset.
|
||
<DT><B>MACHTYPE</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>OLDPWD</B>
|
||
|
||
<DD>
|
||
The previous working directory as set by the
|
||
<B>cd</B>
|
||
|
||
command.
|
||
<DT><B>OPTARG</B>
|
||
|
||
<DD>
|
||
The value of the last option argument processed by the
|
||
<B>getopts</B>
|
||
|
||
builtin command (see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<DT><B>OPTIND</B>
|
||
|
||
<DD>
|
||
The index of the next argument to be processed by the
|
||
<B>getopts</B>
|
||
|
||
builtin command (see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<DT><B>OSTYPE</B>
|
||
|
||
<DD>
|
||
Automatically set to a string that
|
||
describes the operating system on which
|
||
<B>bash</B>
|
||
|
||
is executing.
|
||
The default is system-dependent.
|
||
<DT><B>PIPESTATUS</B>
|
||
|
||
<DD>
|
||
An array variable (see
|
||
<B>Arrays</B>
|
||
|
||
below) containing a list of exit status values from the processes
|
||
in the most-recently-executed foreground pipeline (which may
|
||
contain only a single command).
|
||
<DT><B>PPID</B>
|
||
|
||
<DD>
|
||
The process ID of the shell's parent. This variable is readonly.
|
||
<DT><B>PWD</B>
|
||
|
||
<DD>
|
||
The current working directory as set by the
|
||
<B>cd</B>
|
||
|
||
command.
|
||
<DT><B>RANDOM</B>
|
||
|
||
<DD>
|
||
Each time this parameter is referenced, a random integer between
|
||
0 and 32767 is
|
||
generated. The sequence of random numbers may be initialized by assigning
|
||
a value to
|
||
<FONT SIZE=-1><B>RANDOM</B>.
|
||
|
||
</FONT>
|
||
If
|
||
<FONT SIZE=-1><B>RANDOM</B>
|
||
|
||
</FONT>
|
||
is unset, it loses its special properties, even if it is
|
||
subsequently reset.
|
||
<DT><B>REPLY</B>
|
||
|
||
<DD>
|
||
Set to the line of input read by the
|
||
<B>read</B>
|
||
|
||
builtin command when no arguments are supplied.
|
||
<DT><B>SECONDS</B>
|
||
|
||
<DD>
|
||
Each time this parameter is
|
||
referenced, the number of seconds since shell invocation is returned. If a
|
||
value is assigned to
|
||
<FONT SIZE=-1><B>SECONDS</B>,
|
||
|
||
</FONT>
|
||
the value returned upon subsequent
|
||
references is
|
||
the number of seconds since the assignment plus the value assigned.
|
||
If
|
||
<FONT SIZE=-1><B>SECONDS</B>
|
||
|
||
</FONT>
|
||
is unset, it loses its special properties, even if it is
|
||
subsequently reset.
|
||
<DT><B>SHELLOPTS</B>
|
||
|
||
<DD>
|
||
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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below). The options appearing in
|
||
<FONT SIZE=-1><B>SHELLOPTS</B>
|
||
|
||
</FONT>
|
||
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, each shell option in the list will be enabled before
|
||
reading any startup files.
|
||
This variable is read-only.
|
||
<DT><B>SHLVL</B>
|
||
|
||
<DD>
|
||
Incremented by one each time an instance of
|
||
<B>bash</B>
|
||
|
||
is started.
|
||
<DT><B>UID</B>
|
||
|
||
<DD>
|
||
Expands to the user ID of the current user, initialized at shell startup.
|
||
This variable is readonly.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
The following variables are used by the shell. In some cases,
|
||
<B>bash</B>
|
||
|
||
assigns a default value to a variable; these cases are noted
|
||
below.
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>BASH_ENV</B>
|
||
|
||
<DD>
|
||
If this parameter is set when <B>bash</B> is executing a shell script,
|
||
its value is interpreted as a filename containing commands to
|
||
initialize the shell, as in
|
||
<A HREF="file:~/.bashrc"><I>~/.bashrc</I></A>.
|
||
|
||
The value of
|
||
<FONT SIZE=-1><B>BASH_ENV</B>
|
||
|
||
</FONT>
|
||
is subjected to parameter expansion, command substitution, and arithmetic
|
||
expansion before being interpreted as a file name.
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
is not used to search for the resultant file name.
|
||
<DT><B>CDPATH</B>
|
||
|
||
<DD>
|
||
The search path for the
|
||
<B>cd</B>
|
||
|
||
command.
|
||
This is a colon-separated list of directories in which the shell looks
|
||
for destination directories specified by the
|
||
<B>cd</B>
|
||
|
||
command.
|
||
A sample value is ``.:~:/usr''.
|
||
<DT><B>COLUMNS</B>
|
||
|
||
<DD>
|
||
Used by the <B>select</B> builtin command to determine the terminal width
|
||
when printing selection lists. Automatically set upon receipt of a SIGWINCH.
|
||
<DT><B>COMPREPLY</B>
|
||
|
||
<DD>
|
||
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).
|
||
<DT><B>FCEDIT</B>
|
||
|
||
<DD>
|
||
The default editor for the
|
||
<B>fc</B>
|
||
|
||
builtin command.
|
||
<DT><B>FIGNORE</B>
|
||
|
||
<DD>
|
||
A colon-separated list of suffixes to ignore when performing
|
||
filename completion (see
|
||
<FONT SIZE=-1><B>READLINE</B>
|
||
|
||
</FONT>
|
||
below).
|
||
A filename whose suffix matches one of the entries in
|
||
<FONT SIZE=-1><B>FIGNORE</B>
|
||
|
||
</FONT>
|
||
is excluded from the list of matched filenames.
|
||
A sample value is ``.o:~''.
|
||
<DT><B>GLOBIGNORE</B>
|
||
|
||
<DD>
|
||
A colon-separated list of patterns defining the set of filenames to
|
||
be ignored by pathname expansion.
|
||
If a filename matched by a pathname expansion pattern also matches one
|
||
of the patterns in
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>,
|
||
|
||
</FONT>
|
||
it is removed from the list of matches.
|
||
<DT><B>HISTCONTROL</B>
|
||
|
||
<DD>
|
||
If set to a value of
|
||
<I>ignorespace</I>,
|
||
|
||
lines which begin with a
|
||
<B>space</B>
|
||
|
||
character are not entered on the history list.
|
||
If set to a value of
|
||
<I>ignoredups</I>,
|
||
|
||
lines matching the last history line are not entered.
|
||
A value of
|
||
<I>ignoreboth</I>
|
||
|
||
combines the two options.
|
||
If unset, or if set to any other value than those above,
|
||
all lines read
|
||
by the parser are saved on the history list, subject to the value
|
||
of
|
||
<B>HISTIGNORE</B>.
|
||
|
||
This variable's function is superseded by
|
||
<B>HISTIGNORE</B>.
|
||
|
||
The second and subsequent lines of a multi-line compound command are
|
||
not tested, and are added to the history regardless of the value of
|
||
<B>HISTCONTROL</B>.
|
||
|
||
<DT><B>HISTFILE</B>
|
||
|
||
<DD>
|
||
The name of the file in which command history is saved (see
|
||
<FONT SIZE=-1><B>HISTORY</B>
|
||
|
||
</FONT>
|
||
below). The default value is <A HREF="file:~/.bash_history"><I>~/.bash_history</I></A>. If unset, the
|
||
command history is not saved when an interactive shell exits.
|
||
<DT><B>HISTFILESIZE</B>
|
||
|
||
<DD>
|
||
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 that number of lines. The default
|
||
value is 500. The history file is also truncated to this size after
|
||
writing it when an interactive shell exits.
|
||
<DT><B>HISTIGNORE</B>
|
||
|
||
<DD>
|
||
A colon-separated list of patterns used to decide which command lines
|
||
should be saved on the history list. Each pattern is anchored at the
|
||
beginning of the line and must match the complete line (no implicit
|
||
`<B>*</B>' is appended). 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. `<B>&</B>' may be escaped using a
|
||
backslash; the backslash is removed before attempting a match.
|
||
The second and subsequent lines of a multi-line compound command are
|
||
not tested, and are added to the history regardless of the value of
|
||
<B>HISTIGNORE</B>.
|
||
|
||
<DT><B>HISTSIZE</B>
|
||
|
||
<DD>
|
||
The number of commands to remember in the command history (see
|
||
<FONT SIZE=-1><B>HISTORY</B>
|
||
|
||
</FONT>
|
||
below). The default value is 500.
|
||
<DT><B>HOME</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>HOSTFILE</B>
|
||
|
||
<DD>
|
||
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
|
||
<FONT SIZE=-1><B>HOSTFILE</B>
|
||
|
||
</FONT>
|
||
is set, but has no value, <B>bash</B> attempts to read
|
||
|
||
<I>/etc/hosts</I>
|
||
|
||
to obtain the list of possible hostname completions.
|
||
When
|
||
<FONT SIZE=-1><B>HOSTFILE</B>
|
||
|
||
</FONT>
|
||
is unset, the hostname list is cleared.
|
||
<DT><B>IFS</B>
|
||
|
||
<DD>
|
||
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. The default value is
|
||
``<space><tab><newline>''.
|
||
<DT><B>IGNOREEOF</B>
|
||
|
||
<DD>
|
||
Controls the
|
||
action of an interactive shell on receipt of an
|
||
<FONT SIZE=-1><B>EOF</B>
|
||
|
||
</FONT>
|
||
character as the sole input. If set, the value is the number of
|
||
consecutive
|
||
<FONT SIZE=-1><B>EOF</B>
|
||
|
||
</FONT>
|
||
characters which must be
|
||
typed as the first characters on an input line before
|
||
<B>bash</B>
|
||
|
||
exits. If the variable exists but does not have a numeric value, or
|
||
has no value, the default value is 10. If it does not exist,
|
||
<FONT SIZE=-1><B>EOF</B>
|
||
|
||
</FONT>
|
||
signifies the end of input to the shell.
|
||
<DT><B>INPUTRC</B>
|
||
|
||
<DD>
|
||
The filename for the
|
||
<B>readline</B>
|
||
|
||
startup file, overriding the default of
|
||
|
||
<A HREF="file:~/.inputrc"><I>~/.inputrc</I></A>
|
||
|
||
(see
|
||
<FONT SIZE=-1><B>READLINE</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<DT><B>LANG</B>
|
||
|
||
<DD>
|
||
Used to determine the locale category for any category not specifically
|
||
selected with a variable starting with <B>LC_</B>.
|
||
<DT><B>LC_ALL</B>
|
||
|
||
<DD>
|
||
This variable overrides the value of <B>LANG</B> and any other
|
||
<B>LC_</B> variable specifying a locale category.
|
||
<DT><B>LC_COLLATE</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>LC_CTYPE</B>
|
||
|
||
<DD>
|
||
This variable determines the interpretation of characters and the
|
||
behavior of character classes within pathname expansion and pattern
|
||
matching.
|
||
<DT><B>LC_MESSAGES</B>
|
||
|
||
<DD>
|
||
This variable determines the locale used to translate double-quoted
|
||
strings preceded by a <B>$</B>.
|
||
<DT><B>LC_NUMERIC</B>
|
||
|
||
<DD>
|
||
This variable determines the locale category used for number formatting.
|
||
<DT><B>LINES</B>
|
||
|
||
<DD>
|
||
Used by the <B>select</B> builtin command to determine the column length
|
||
for printing selection lists. Automatically set upon receipt of a SIGWINCH.
|
||
<DT><B>MAIL</B>
|
||
|
||
<DD>
|
||
If this parameter is set to a file name and the
|
||
<FONT SIZE=-1><B>MAILPATH</B>
|
||
|
||
</FONT>
|
||
variable is not set,
|
||
<B>bash</B>
|
||
|
||
informs the user of the arrival of mail in the specified file.
|
||
<DT><B>MAILCHECK</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>MAILPATH</B>
|
||
|
||
<DD>
|
||
A colon-separated list of file names to be checked for mail.
|
||
The message to be printed when mail arrives in a particular file
|
||
may be specified by separating the file name from the message with a `?'.
|
||
When used in the text of the message, <B>$_</B> expands to the name of
|
||
the current mailfile.
|
||
Example:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<B>MAILPATH</B>='/var/mail/bfox?"You have mail":~/shell-mail?"$_ has mail!"'
|
||
<P>
|
||
|
||
<B>Bash</B>
|
||
|
||
supplies a default value for this variable, but the location of the user
|
||
mail files that it uses is system dependent (e.g., /var/mail/<B>$USER</B>).
|
||
</DL>
|
||
|
||
<DT><B>OPTERR</B>
|
||
|
||
<DD>
|
||
If set to the value 1,
|
||
<B>bash</B>
|
||
|
||
displays error messages generated by the
|
||
<B>getopts</B>
|
||
|
||
builtin command (see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<FONT SIZE=-1><B>OPTERR</B>
|
||
|
||
</FONT>
|
||
is initialized to 1 each time the shell is invoked or a shell
|
||
script is executed.
|
||
<DT><B>PATH</B>
|
||
|
||
<DD>
|
||
The search path for commands. It
|
||
is a colon-separated list of directories in which
|
||
the shell looks for commands (see
|
||
<FONT SIZE=-1><B>COMMAND EXECUTION</B>
|
||
|
||
</FONT>
|
||
below). The default path is system-dependent,
|
||
and is set by the administrator who installs
|
||
<B>bash</B>.
|
||
|
||
A common value is
|
||
<TT>/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.</TT>.
|
||
|
||
<DT><B>POSIXLY_CORRECT</B>
|
||
|
||
<DD>
|
||
If this variable is in the environment when <B>bash</B> starts, the shell
|
||
enters <I>posix mode</I> 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 <I>posix mode</I>, as if the command
|
||
<TT>set -o posix</TT>
|
||
|
||
had been executed.
|
||
<DT><B>PROMPT_COMMAND</B>
|
||
|
||
<DD>
|
||
If set, the value is executed as a command prior to issuing each primary
|
||
prompt.
|
||
<DT><B>PS1</B>
|
||
|
||
<DD>
|
||
The value of this parameter is expanded (see
|
||
<FONT SIZE=-1><B>PROMPTING</B>
|
||
|
||
</FONT>
|
||
below) and used as the primary prompt string. The default value is
|
||
``<B>\s-\v\$ </B>''.
|
||
<DT><B>PS2</B>
|
||
|
||
<DD>
|
||
The value of this parameter is expanded as with
|
||
<B>PS1</B>
|
||
|
||
and used as the secondary prompt string. The default is
|
||
``<B>> </B>''.
|
||
<DT><B>PS3</B>
|
||
|
||
<DD>
|
||
The value of this parameter is used as the prompt for the
|
||
<B>select</B>
|
||
|
||
command (see
|
||
<FONT SIZE=-1><B>SHELL GRAMMAR</B>
|
||
|
||
</FONT>
|
||
above).
|
||
<DT><B>PS4</B>
|
||
|
||
<DD>
|
||
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
|
||
<FONT SIZE=-1><B>PS4</B>
|
||
|
||
</FONT>
|
||
is replicated multiple times, as necessary, to indicate multiple
|
||
levels of indirection. The default is ``<B>+ </B>''.
|
||
<DT><B>TIMEFORMAT</B>
|
||
|
||
<DD>
|
||
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
|
||
braces denote optional portions.
|
||
<P>
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>%%</B>
|
||
|
||
<DD>
|
||
A literal <B>%</B>.
|
||
<DT><B>%[</B><I>p</I>][l]R
|
||
|
||
<DD>
|
||
The elapsed time in seconds.
|
||
<DT><B>%[</B><I>p</I>][l]U
|
||
|
||
<DD>
|
||
The number of CPU seconds spent in user mode.
|
||
<DT><B>%[</B><I>p</I>][l]S
|
||
|
||
<DD>
|
||
The number of CPU seconds spent in system mode.
|
||
<DT><B>%P</B>
|
||
|
||
<DD>
|
||
The CPU percentage, computed as (%U + %S) / %R.
|
||
|
||
</DL></DL>
|
||
|
||
<DT><DD>
|
||
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.
|
||
At most three places after the decimal point may be specified;
|
||
values of <I>p</I> greater than 3 are changed to 3.
|
||
If <I>p</I> is not specified, the value 3 is used.
|
||
<DT><DD>
|
||
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.
|
||
<DT><DD>
|
||
If this variable is not set, <B>bash</B> acts as if it had the
|
||
value <B>$'\nreal\t%3lR\nuser\t%3lU\nsys %3lS'</B>.
|
||
If the value is null, no timing information is displayed.
|
||
A trailing newline is added when the format string is displayed.
|
||
<DT><B>TMOUT</B>
|
||
|
||
<DD>
|
||
If set to a value greater than zero, the value is interpreted as the
|
||
number of seconds to wait for input after issuing the primary prompt.
|
||
<B>Bash</B>
|
||
|
||
terminates after waiting for that number of seconds if input does
|
||
not arrive.
|
||
<DT><B>auto_resume</B>
|
||
|
||
<DD>
|
||
This variable controls how the shell interacts with the user and
|
||
job control. If this variable is set, single word simple
|
||
commands 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 the string typed, the job most recently
|
||
accessed is selected. The
|
||
<I>name</I>
|
||
|
||
of a stopped job, in this context, is the command line used to
|
||
start it.
|
||
If set to the value
|
||
<I>exact</I>,
|
||
|
||
the string supplied must match the name of a stopped job exactly;
|
||
if set to
|
||
<I>substring</I>,
|
||
|
||
the string supplied 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
|
||
<FONT SIZE=-1><B>JOB CONTROL</B>
|
||
|
||
</FONT>
|
||
below). If set to any other value, the supplied string must
|
||
be a prefix of a stopped job's name; this provides functionality
|
||
analogous to the
|
||
<B>%</B>
|
||
|
||
job identifier.
|
||
<DT><B>histchars</B>
|
||
|
||
<DD>
|
||
The two or three characters which control history expansion
|
||
and tokenization (see
|
||
<FONT SIZE=-1><B>HISTORY EXPANSION</B>
|
||
|
||
</FONT>
|
||
below). The first character is the <I>history expansion</I> character,
|
||
the character which signals the start of a history
|
||
expansion, normally `<B>!</B>'.
|
||
The second character is the <I>quick substitution</I>
|
||
character, which is used as shorthand for re-running the previous
|
||
command entered, substituting one string for another in the command.
|
||
The default is `<B>^</B>'.
|
||
The optional third character is the character
|
||
which indicates that the remainder of the line is a comment when found
|
||
as the first character of a word, normally `<B>#</B>'. The history
|
||
comment character causes history substitution to be skipped 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.
|
||
|
||
</DL>
|
||
<A NAME="lbAV"> </A>
|
||
<H3>Arrays</H3>
|
||
|
||
<B>Bash</B>
|
||
|
||
provides one-dimensional array variables. Any variable may be used as
|
||
an array; the
|
||
<B>declare</B>
|
||
|
||
builtin will explicitly declare an array. There is no maximum
|
||
limit on the size of an array, nor any requirement that members
|
||
be indexed or assigned contiguously. Arrays are indexed using
|
||
integers and are zero-based.
|
||
<P>
|
||
|
||
An array is created automatically if any variable is assigned to using
|
||
the syntax <I>name</I>[<I>subscript</I>]=<I>value</I>. 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 array, use
|
||
<B>declare -a </B><I>name</I>
|
||
|
||
(see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<B>declare -a </B><I>name</I>[<I>subscript</I>]
|
||
|
||
is also accepted; the <I>subscript</I> is ignored. 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>
|
||
|
||
Arrays are assigned to 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> is of the form [<I>subscript</I>]=<I>string</I>. Only
|
||
<I>string</I> is required. 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.
|
||
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>
|
||
|
||
Any element of an array may be 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>. 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
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
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. This is analogous to the expansion
|
||
of the special parameters <B>*</B> and <B>@</B> (see
|
||
<B>Special Parameters</B>
|
||
|
||
above). ${#<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.
|
||
Referencing an array variable without a subscript is equivalent to
|
||
referencing element zero.
|
||
<P>
|
||
|
||
The
|
||
<B>unset</B>
|
||
|
||
builtin is used to destroy arrays. <B>unset</B> <I>name</I>[<I>subscript</I>]
|
||
destroys the array element at index <I>subscript</I>.
|
||
<B>unset</B> <I>name</I>, where <I>name</I> is an array, or
|
||
<B>unset</B> <I>name</I>[<I>subscript</I>], where
|
||
<I>subscript</I> is <B>*</B> or <B>@</B>, removes the entire array.
|
||
<P>
|
||
|
||
The
|
||
<B>declare</B>,
|
||
|
||
<B>local</B>,
|
||
|
||
and
|
||
<B>readonly</B>
|
||
|
||
builtins each accept a
|
||
<B>-a</B>
|
||
|
||
option to specify an array. 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.
|
||
<A NAME="lbAW"> </A>
|
||
<H2>EXPANSION</H2>
|
||
|
||
Expansion is performed on the command line after it has been split into
|
||
words. There are seven kinds of expansion performed:
|
||
<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>,
|
||
|
||
and
|
||
<I>pathname expansion</I>.
|
||
|
||
<P>
|
||
|
||
The order of expansions is: brace expansion, tilde expansion,
|
||
parameter, variable and arithmetic expansion and
|
||
command substitution
|
||
(done in a left-to-right fashion), word splitting, and pathname
|
||
expansion.
|
||
<P>
|
||
|
||
On systems that can support it, there is an additional expansion
|
||
available: <I>process substitution</I>.
|
||
<P>
|
||
|
||
Only brace expansion, word splitting, and pathname expansion
|
||
can change 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>${</B><I>name</I><B>[@]}</B>"
|
||
as explained above (see
|
||
<FONT SIZE=-1><B>PARAMETERS</B>).
|
||
|
||
</FONT>
|
||
<A NAME="lbAX"> </A>
|
||
<H3>Brace Expansion</H3>
|
||
|
||
<P>
|
||
|
||
<I>Brace expansion</I>
|
||
|
||
is a mechanism by which arbitrary strings
|
||
may be generated. This mechanism is similar to
|
||
<I>pathname expansion</I>, but the filenames generated
|
||
need not exist. Patterns to be brace expanded take
|
||
the form of an optional
|
||
<I>preamble</I>,
|
||
|
||
followed by a series of comma-separated strings
|
||
between a pair of braces, followed by an optional
|
||
<I>postscript</I>.
|
||
|
||
The preamble is prefixed to each string contained
|
||
within the braces, and the postscript is then appended
|
||
to each resulting string, expanding left to right.
|
||
<P>
|
||
|
||
Brace expansions may be nested. The results of each expanded
|
||
string are not sorted; left to right order is preserved.
|
||
For example, a<B>{</B>d,c,b<B>}</B>e expands into `ade ace abe'.
|
||
<P>
|
||
|
||
Brace expansion is performed before any other expansions,
|
||
and any characters special to other expansions are preserved
|
||
in the result. It is strictly textual.
|
||
<B>Bash</B>
|
||
|
||
does not apply any syntactic interpretation to the context of the
|
||
expansion or the text between the braces.
|
||
<P>
|
||
|
||
A correctly-formed brace expansion must contain unquoted opening
|
||
and closing braces, and at least one unquoted comma.
|
||
Any incorrectly formed brace expansion is left unchanged.
|
||
A <B>{</B> or <B>,</B> may be quoted with a backslash to prevent its
|
||
being considered part of a brace expression.
|
||
To avoid conflicts with parameter expansion, the string <B>${</B>
|
||
is not considered eligible for brace expansion.
|
||
<P>
|
||
|
||
This construct is typically used as shorthand when the common
|
||
prefix of the strings to be generated is longer than in the
|
||
above example:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
mkdir /usr/local/src/bash/{old,new,dist,bugs}
|
||
</DL>
|
||
|
||
or
|
||
<DL COMPACT><DT><DD>
|
||
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
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 <I>file{1,2}</I>
|
||
appears identically in the output. The same word is
|
||
output as
|
||
<I>file1 file2</I>
|
||
|
||
after expansion by
|
||
<B>bash</B>.
|
||
|
||
If strict compatibility with
|
||
<B>sh</B>
|
||
|
||
is desired, 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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<A NAME="lbAY"> </A>
|
||
<H3>Tilde Expansion</H3>
|
||
|
||
<P>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>HOME</B>.
|
||
|
||
</FONT>
|
||
If
|
||
<FONT SIZE=-1><B>HOME</B>
|
||
|
||
</FONT>
|
||
is unset, the home directory of the user executing the shell is
|
||
substituted instead.
|
||
Otherwise, the tilde-prefix is replaced with the home directory
|
||
associated with the specified login name.
|
||
<P>
|
||
|
||
If the tilde-prefix is a `~+', the value of the shell variable
|
||
<FONT SIZE=-1><B>PWD</B>
|
||
|
||
</FONT>
|
||
replaces the tilde-prefix.
|
||
If the tilde-prefix is a `~-', the value of the shell variable
|
||
<FONT SIZE=-1><B>OLDPWD</B>,
|
||
|
||
</FONT>
|
||
if it is set, is substituted.
|
||
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 tilde-prefix as an argument.
|
||
If the characters following the tilde in the tilde-prefix consist of a
|
||
number without a leading `+' or `-', `+' is assumed.
|
||
<P>
|
||
|
||
If the login name is invalid, or the tilde expansion fails, the word
|
||
is unchanged.
|
||
<P>
|
||
|
||
Each variable assignment is checked for unquoted tilde-prefixes immediately
|
||
following a
|
||
<B>:</B>
|
||
|
||
or
|
||
<B>=</B>.
|
||
|
||
In these cases, tilde expansion is also performed.
|
||
Consequently, one may use file names with tildes in assignments to
|
||
<FONT SIZE=-1><B>PATH</B>,
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>MAILPATH</B>,
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>CDPATH</B>,
|
||
|
||
</FONT>
|
||
and the shell assigns the expanded value.
|
||
<A NAME="lbAZ"> </A>
|
||
<H3>Parameter Expansion</H3>
|
||
|
||
<P>
|
||
|
||
The `<B>$</B>' character introduces parameter expansion,
|
||
command substitution, or arithmetic expansion. The parameter name
|
||
or symbol to be expanded may be enclosed in braces, which
|
||
are optional but serve to protect the variable to be expanded from
|
||
characters immediately following it which could be
|
||
interpreted as part of the name.
|
||
<P>
|
||
|
||
When braces are used, the matching ending brace is the first `<B>}</B>'
|
||
not escaped by a backslash or within a quoted string, and not within an
|
||
embedded arithmetic expansion, command substitution, or paramter
|
||
expansion.
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT>${<I>parameter</I>}<DD>
|
||
The value of <I>parameter</I> is substituted. 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.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
If the first character of <I>parameter</I> is an exclamation point,
|
||
a level of variable indirection is introduced.
|
||
<B>Bash</B> uses the value of the variable formed from the rest of
|
||
<I>parameter</I> 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 <I>parameter</I> itself.
|
||
This is known as <I>indirect expansion</I>.
|
||
The exception to this is the expansion of ${!<I>prefix</I>*}
|
||
described below.
|
||
<P>
|
||
|
||
In each of the cases below, <I>word</I> is subject to tilde expansion,
|
||
parameter expansion, command substitution, and arithmetic expansion.
|
||
When not performing substring expansion, <B>bash</B> tests for a parameter
|
||
that is unset or null; omitting the colon results in a test only for a
|
||
parameter that is unset.
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT>${<I>parameter</I><B>:-</B><I>word</I>}<DD>
|
||
<B>Use Default Values</B>. If
|
||
<I>parameter</I>
|
||
|
||
is unset or null, the expansion of
|
||
<I>word</I>
|
||
|
||
is substituted. Otherwise, the value of
|
||
<I>parameter</I>
|
||
|
||
is substituted.
|
||
<DT>${<I>parameter</I><B>:=</B><I>word</I>}<DD>
|
||
<B>Assign Default Values</B>.
|
||
If
|
||
<I>parameter</I>
|
||
|
||
is unset or null, the expansion of
|
||
<I>word</I>
|
||
|
||
is assigned to
|
||
<I>parameter</I>.
|
||
|
||
The value of
|
||
<I>parameter</I>
|
||
|
||
is then substituted. Positional parameters and special parameters may
|
||
not be assigned to in this way.
|
||
<DT>${<I>parameter</I><B>:?</B><I>word</I>}<DD>
|
||
<B>Display Error if Null or Unset</B>.
|
||
If
|
||
<I>parameter</I>
|
||
|
||
is null or unset, the expansion of <I>word</I> (or a message to that effect
|
||
if
|
||
<I>word</I>
|
||
|
||
is not present) is written to the standard error and the shell, if it
|
||
is not interactive, exits. Otherwise, the value of <I>parameter</I> is
|
||
substituted.
|
||
<DT>${<I>parameter</I><B>:+</B><I>word</I>}<DD>
|
||
<B>Use Alternate Value</B>.
|
||
If
|
||
<I>parameter</I>
|
||
|
||
is null or unset, nothing is substituted, otherwise the expansion of
|
||
<I>word</I>
|
||
|
||
is substituted.
|
||
<DT>
|
||
<DD>
|
||
${<I>parameter</I><B>:</B><I>offset</I>}
|
||
<DT>${<I>parameter</I><B>:</B><I>offset</I><B>:</B><I>length</I>}<DD>
|
||
|
||
<B>Substring Expansion.</B>
|
||
Expands to up to <I>length</I> characters of <I>parameter</I>
|
||
starting at the character specified by <I>offset</I>.
|
||
If <I>length</I> is omitted, expands to the substring of
|
||
<I>parameter</I> starting at the character specified by <I>offset</I>.
|
||
<I>length</I> and <I>offset</I> are arithmetic expressions (see
|
||
<FONT SIZE=-1><B>ARITHMETIC EVALUATION</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<I>length</I> must evaluate to a number greater than or equal to zero.
|
||
If <I>offset</I> evaluates to a number less than zero, the value
|
||
is used as an offset from the end of the value of <I>parameter</I>.
|
||
If <I>parameter</I> is <B>@</B>, the result is <I>length</I> positional
|
||
parameters beginning at <I>offset</I>.
|
||
If <I>parameter</I> is an array name indexed by @ or *,
|
||
the result is the <I>length</I>
|
||
members of the array beginning with ${<I>parameter</I>[<I>offset</I>]}.
|
||
Substring indexing is zero-based unless the positional parameters
|
||
are used, in which case the indexing starts at 1.
|
||
<DT>${<B>!</B><I>prefix</I><B>*</B>}<DD>
|
||
Expands to the names of variables whose names begin with <I>prefix</I>,
|
||
separated by the first character of the
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
special variable.
|
||
<DT>${<B>#</B><I>parameter</I>}<DD>
|
||
The length in characters of the value of <I>parameter</I> is substituted.
|
||
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.
|
||
<DT>
|
||
<DD>
|
||
${<I>parameter</I><B>#</B><I>word</I>}
|
||
<DT>${<I>parameter</I><B>##</B><I>word</I>}<DD>
|
||
|
||
The
|
||
<I>word</I>
|
||
|
||
is expanded to produce a pattern just as in pathname
|
||
expansion. 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 ``<B>#</B>'' case) or the
|
||
longest matching pattern (the ``<B>##</B>'' 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.
|
||
<DT>
|
||
<DD>
|
||
${<I>parameter</I><B>%</B><I>word</I>}
|
||
<DT>${<I>parameter</I><B>%%</B><I>word</I>}<DD>
|
||
|
||
The <I>word</I> is expanded to produce a pattern just as in
|
||
pathname expansion.
|
||
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 ``<B>%</B>'' case) or the
|
||
longest matching pattern (the ``<B>%%</B>'' 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.
|
||
<DT>
|
||
<DD>
|
||
${<I>parameter</I><B>/</B><I>pattern</I><B>/</B><I>string</I>}
|
||
<DT>${<I>parameter</I><B>//</B><I>pattern</I><B>/</B><I>string</I>}<DD>
|
||
|
||
The <I>pattern</I> is expanded to produce a pattern just as in
|
||
pathname expansion.
|
||
<I>Parameter</I> is expanded and the longest match of <I>pattern</I>
|
||
against its value is replaced with <I>string</I>.
|
||
In the first form, only the first match is replaced.
|
||
The second form causes all matches of <I>pattern</I> to be
|
||
replaced with <I>string</I>.
|
||
If <I>pattern</I> begins with <B>#</B>, it must match at the beginning
|
||
of the expanded value of <I>parameter</I>.
|
||
If <I>pattern</I> begins with <B>%</B>, it must match at the end
|
||
of the expanded value of <I>parameter</I>.
|
||
If <I>string</I> is null, matches of <I>pattern</I> are deleted
|
||
and the <B>/</B> following <I>pattern</I> may be omitted.
|
||
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.
|
||
</DL>
|
||
<A NAME="lbBA"> </A>
|
||
<H3>Command Substitution</H3>
|
||
|
||
<P>
|
||
|
||
<I>Command substitution</I> allows the output of a command to replace
|
||
the command name. There are two forms:
|
||
<P>
|
||
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<B>$(</B><I>command</I><B>)</B>
|
||
</DL>
|
||
|
||
or
|
||
<DL COMPACT><DT><DD>
|
||
<B>`</B><I>command</I><B>`</B>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
<B>Bash</B>
|
||
|
||
performs the expansion by executing <I>command</I> and
|
||
replacing the command substitution with the standard output of the
|
||
command, with any trailing newlines deleted.
|
||
Embedded newlines are not deleted, but they may be removed during
|
||
word splitting.
|
||
The command substitution <B>$(cat </B><I>file</I>) can be replaced by
|
||
the equivalent but faster <B>$(< </B><I>file</I>).
|
||
<P>
|
||
|
||
When the old-style backquote form of substitution is used,
|
||
backslash retains its literal meaning except when followed by
|
||
<B>$</B>,
|
||
|
||
<B>`</B>,
|
||
|
||
or
|
||
<B>\</B>.
|
||
|
||
The first backquote not preceded by a backslash terminates the
|
||
command substitution.
|
||
When using the $(<I>command</I>) form, all characters between the
|
||
parentheses make up the command; none are treated specially.
|
||
<P>
|
||
|
||
Command substitutions may be nested. To nest when using the backquoted form,
|
||
escape the inner backquotes with backslashes.
|
||
<P>
|
||
|
||
If the substitution appears within double quotes, word splitting and
|
||
pathname expansion are not performed on the results.
|
||
<A NAME="lbBB"> </A>
|
||
<H3>Arithmetic Expansion</H3>
|
||
|
||
<P>
|
||
|
||
Arithmetic expansion allows the evaluation of an arithmetic expression
|
||
and the substitution of the result. The format for arithmetic expansion is:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<B>$((</B><I>expression</I><B>))</B>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
The
|
||
<I>expression</I>
|
||
|
||
is treated as if it were within double quotes, but a double quote
|
||
inside the parentheses is not treated specially.
|
||
All tokens in the expression undergo parameter expansion, string
|
||
expansion, command substitution, and quote removal.
|
||
Arithmetic substitutions may be nested.
|
||
<P>
|
||
|
||
The evaluation is performed according to the rules listed below under
|
||
<FONT SIZE=-1><B>ARITHMETIC</B>EVALUATION<B>.</B>
|
||
|
||
</FONT>
|
||
If
|
||
<I>expression</I>
|
||
|
||
is invalid,
|
||
<B>bash</B>
|
||
|
||
prints a message indicating failure and no substitution occurs.
|
||
<A NAME="lbBC"> </A>
|
||
<H3>Process Substitution</H3>
|
||
|
||
<P>
|
||
|
||
<I>Process substitution</I> is supported on systems that support named
|
||
pipes (<I>FIFOs</I>) or the <B>/dev/fd</B> method of naming open files.
|
||
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> is run with its input or output connected to a
|
||
<I>FIFO</I> or some file in <B>/dev/fd</B>. The name of this file is
|
||
passed as an argument to the current command as the result of the
|
||
expansion. If the <B>>(</B><I>list</I><B>)</B> form is used, writing to
|
||
the file will provide input for <I>list</I>. If the
|
||
<B><(</B><I>list</I><B>)</B> form is used, the file passed as an
|
||
argument should be read to obtain the output of <I>list</I>.
|
||
<P>
|
||
|
||
When available, process substitution is performed
|
||
simultaneously with parameter and variable expansion,
|
||
command substitution,
|
||
and arithmetic expansion.
|
||
<A NAME="lbBD"> </A>
|
||
<H3>Word Splitting</H3>
|
||
|
||
<P>
|
||
|
||
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>.
|
||
|
||
<P>
|
||
|
||
The shell treats each character of
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
as a delimiter, and splits the results of the other
|
||
expansions into words on these characters. If
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
is unset, or its
|
||
value is exactly
|
||
<B><space><tab><newline></B>,
|
||
|
||
the default, then
|
||
any sequence of
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
characters serves to delimit words. If
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
has a value other than the default, then sequences of
|
||
the whitespace characters
|
||
<B>space</B>
|
||
|
||
and
|
||
<B>tab</B>
|
||
|
||
are ignored at the beginning and end of the
|
||
word, as long as the whitespace character is in the
|
||
value of
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
(an
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
whitespace character).
|
||
Any character in
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
that is not
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
whitespace, along with any adjacent
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
whitespace characters, delimits a field.
|
||
A sequence of
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
whitespace characters is also treated as a delimiter.
|
||
If the value of
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
is null, no word splitting occurs.
|
||
<P>
|
||
|
||
Explicit null arguments (<B>""</B> or <B>''</B>) are retained.
|
||
Unquoted implicit null arguments, resulting from the expansion of
|
||
parameters that have no values, are removed.
|
||
If a parameter with no value is expanded within double quotes, a
|
||
null argument results and is retained.
|
||
<P>
|
||
|
||
Note that if no expansion occurs, no splitting
|
||
is performed.
|
||
<A NAME="lbBE"> </A>
|
||
<H3>Pathname Expansion</H3>
|
||
|
||
<P>
|
||
|
||
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, then the word is
|
||
regarded as a
|
||
<I>pattern</I>,
|
||
|
||
and replaced with an alphabetically sorted list of
|
||
file names matching the pattern.
|
||
If no matching file names are found,
|
||
and the shell option
|
||
<B>nullglob</B>
|
||
|
||
is disabled, the word is left unchanged.
|
||
If the
|
||
<B>nullglob</B>
|
||
|
||
option is set, and no matches are found,
|
||
the word is removed.
|
||
If the shell option
|
||
<B>nocaseglob</B>
|
||
|
||
is enabled, the match is performed without regard to the case
|
||
of alphabetic characters.
|
||
When a pattern is used for pathname expansion,
|
||
the character
|
||
<B>``.''</B>
|
||
|
||
at the start of a name or immediately following a slash
|
||
must be matched explicitly, unless the shell option
|
||
<B>dotglob</B>
|
||
|
||
is set.
|
||
When matching a pathname, the slash character must always be
|
||
matched explicitly.
|
||
In other cases, the
|
||
<B>``.''</B>
|
||
|
||
character is not treated specially.
|
||
See the description of
|
||
<B>shopt</B>
|
||
|
||
below under
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
for a description of the
|
||
<B>nocaseglob</B>,
|
||
|
||
<B>nullglob</B>,
|
||
|
||
and
|
||
<B>dotglob</B>
|
||
|
||
shell options.
|
||
<P>
|
||
|
||
The
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>
|
||
|
||
</FONT>
|
||
shell variable may be used to restrict the set of file names matching a
|
||
<I>pattern</I>.
|
||
|
||
If
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>
|
||
|
||
</FONT>
|
||
is set, each matching file name that also matches one of the patterns in
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>
|
||
|
||
</FONT>
|
||
is removed from the list of matches.
|
||
The file names
|
||
<B>``.''</B>
|
||
|
||
and
|
||
<B>``..''</B>
|
||
|
||
are always ignored, even when
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>
|
||
|
||
</FONT>
|
||
is set. However, setting
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>
|
||
|
||
</FONT>
|
||
has the effect of enabling the
|
||
<B>dotglob</B>
|
||
|
||
shell option, so all other file names beginning with a
|
||
<B>``.''</B>
|
||
|
||
will match.
|
||
To get the old behavior of ignoring file names beginning with a
|
||
<B>``.''</B>,
|
||
|
||
make
|
||
<B>``.*''</B>
|
||
|
||
one of the patterns in
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>.
|
||
|
||
</FONT>
|
||
The
|
||
<B>dotglob</B>
|
||
|
||
option is disabled when
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>
|
||
|
||
</FONT>
|
||
is unset.
|
||
<P>
|
||
|
||
<B>Pattern Matching</B>
|
||
<P>
|
||
|
||
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. The special pattern characters must be quoted if
|
||
they are to be matched literally.
|
||
<P>
|
||
|
||
The special pattern characters have the following meanings:
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>*</B>
|
||
|
||
<DD>
|
||
Matches any string, including the null string.
|
||
<DT><B>?</B>
|
||
|
||
<DD>
|
||
Matches any single character.
|
||
<DT><B>[...]</B>
|
||
|
||
<DD>
|
||
Matches any one of the enclosed characters. A pair of characters
|
||
separated by a hyphen denotes a
|
||
<I>range expression</I>;
|
||
any character that sorts between those two characters, inclusive,
|
||
using the current locale's collating sequence and character set,
|
||
is matched. If the first character following the
|
||
<B>[</B>
|
||
|
||
is a
|
||
<B>!</B>
|
||
|
||
or a
|
||
<B>^</B>
|
||
|
||
then any character not enclosed is matched.
|
||
The sorting order of characters in range expressions is determined by
|
||
the current locale and the value of the <B>LC_COLLATE</B> shell variable,
|
||
if set.
|
||
A
|
||
<B>-</B>
|
||
|
||
may be matched by including it as the first or last character
|
||
in the set.
|
||
A
|
||
<B>]</B>
|
||
|
||
may be matched by including it as the first character
|
||
in the set.
|
||
<BR>
|
||
|
||
<P>
|
||
|
||
|
||
Within
|
||
<B>[</B>
|
||
|
||
and
|
||
<B>]</B>,
|
||
|
||
<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.2 standard:
|
||
</DL>
|
||
<P>
|
||
|
||
<DL COMPACT><DT><DD>
|
||
<B>
|
||
</B>
|
||
|
||
alnum alpha ascii blank cntrl digit graph lower print punct space upper xdigit
|
||
<BR>
|
||
|
||
A character class matches any character belonging to that class.
|
||
<BR>
|
||
|
||
<P>
|
||
|
||
|
||
Within
|
||
<B>[</B>
|
||
|
||
and
|
||
<B>]</B>,
|
||
|
||
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>.
|
||
<BR>
|
||
|
||
<P>
|
||
|
||
|
||
Within
|
||
<B>[</B>
|
||
|
||
and
|
||
<B>]</B>,
|
||
|
||
the syntax <B>[.</B><I>symbol</I><B>.]</B> matches the collating symbol
|
||
<I>symbol</I>.
|
||
</DL>
|
||
|
||
|
||
<P>
|
||
|
||
If the <B>extglob</B> shell option is enabled using the <B>shopt</B>
|
||
builtin, several extended pattern matching operators are recognized.
|
||
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>
|
||
|
||
<DL COMPACT><DT><DD>
|
||
<DL COMPACT>
|
||
<DT><B>?(</B><I>pattern-list</I><B>)</B><DD>
|
||
Matches zero or one occurrence of the given patterns
|
||
<DT><B>*(</B><I>pattern-list</I><B>)</B><DD>
|
||
Matches zero or more occurrences of the given patterns
|
||
<DT><B>+(</B><I>pattern-list</I><B>)</B><DD>
|
||
Matches one or more occurrences of the given patterns
|
||
<DT><B>@(</B><I>pattern-list</I><B>)</B><DD>
|
||
Matches exactly one of the given patterns
|
||
<DT><B>!(</B><I>pattern-list</I><B>)</B><DD>
|
||
Matches anything except one of the given patterns
|
||
</DL></DL>
|
||
|
||
|
||
<A NAME="lbBF"> </A>
|
||
<H3>Quote Removal</H3>
|
||
|
||
<P>
|
||
|
||
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.
|
||
<A NAME="lbBG"> </A>
|
||
<H2>REDIRECTION</H2>
|
||
|
||
Before a command is executed, its input and output
|
||
may be
|
||
<I>redirected</I>
|
||
|
||
using a special notation interpreted by the shell.
|
||
Redirection may also be used to open and close files for 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>
|
||
|
||
In the following descriptions, if the file descriptor number is
|
||
omitted, and the first character of the redirection operator is
|
||
<B><</B>,
|
||
|
||
the redirection refers to the standard input (file descriptor
|
||
0). If the first character of the redirection operator is
|
||
<B>></B>,
|
||
|
||
the redirection refers to the standard output (file descriptor
|
||
1).
|
||
<P>
|
||
|
||
The word following the redirection operator in the following
|
||
descriptions, unless otherwise noted, is subjected to brace expansion,
|
||
tilde expansion, parameter 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>
|
||
|
||
Note that the order of redirections is significant. For example,
|
||
the command
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
ls <B>></B> dirlist 2<B>>&</B>1
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
directs both standard output and standard error to the file
|
||
<I>dirlist</I>,
|
||
|
||
while the command
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
ls 2<B>>&</B>1 <B>></B> dirlist
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
directs only the standard output to file
|
||
<I>dirlist</I>,
|
||
|
||
because the standard error was duplicated as standard output
|
||
before the standard output was redirected to
|
||
<I>dirlist</I>.
|
||
|
||
<P>
|
||
|
||
<B>Bash</B> handles several filenames specially when they are used in
|
||
redirections, as described in the following table:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>/dev/fd/</B><I>fd</I>
|
||
|
||
<DD>
|
||
If <I>fd</I> is a valid integer, file descriptor <I>fd</I> is duplicated.
|
||
<DT><B>/dev/stdin</B>
|
||
|
||
<DD>
|
||
File descriptor 0 is duplicated.
|
||
<DT><B>/dev/stdout</B>
|
||
|
||
<DD>
|
||
File descriptor 1 is duplicated.
|
||
<DT><B>/dev/stderr</B>
|
||
|
||
<DD>
|
||
File descriptor 2 is duplicated.
|
||
<DT><B>/dev/tcp/</B><I>host</I>/<I>port</I>
|
||
|
||
<DD>
|
||
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
|
||
a TCP connection to the corresponding socket.
|
||
<DT><B>/dev/udp/</B><I>host</I>/<I>port</I>
|
||
|
||
<DD>
|
||
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
|
||
a UDP connection to the corresponding socket.
|
||
|
||
</DL></DL>
|
||
|
||
<P>
|
||
|
||
A failure to open or create a file causes the redirection to fail.
|
||
<A NAME="lbBH"> </A>
|
||
<H3>Redirecting Input</H3>
|
||
|
||
<P>
|
||
|
||
Redirection of input causes the file whose name results from
|
||
the expansion of
|
||
<I>word</I>
|
||
|
||
to be opened for reading on file descriptor
|
||
<I>n</I>,
|
||
|
||
or the standard input (file descriptor 0) if
|
||
<I>n</I>
|
||
|
||
is not specified.
|
||
<P>
|
||
|
||
The general format for redirecting input is:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
[<I>n</I>]<B><</B><I>word</I>
|
||
</DL>
|
||
|
||
<A NAME="lbBI"> </A>
|
||
<H3>Redirecting Output</H3>
|
||
|
||
<P>
|
||
|
||
Redirection of output causes the file whose name results from
|
||
the expansion of
|
||
<I>word</I>
|
||
|
||
to be opened 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>
|
||
|
||
The general format for redirecting output is:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
[<I>n</I>]<B>></B><I>word</I>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
If the redirection operator is
|
||
<B>></B>,
|
||
|
||
and the
|
||
<B>noclobber</B>
|
||
|
||
option to the
|
||
<B>set</B>
|
||
|
||
builtin has been enabled, the redirection will fail 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 command is not enabled, the redirection is attempted even
|
||
if the file named by <I>word</I> exists.
|
||
<A NAME="lbBJ"> </A>
|
||
<H3>Appending Redirected Output</H3>
|
||
|
||
<P>
|
||
|
||
Redirection of output in this fashion
|
||
causes the file whose name results from
|
||
the expansion of
|
||
<I>word</I>
|
||
|
||
to be opened 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>
|
||
|
||
The general format for appending output is:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
[<I>n</I>]<B>>></B><I>word</I>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
<A NAME="lbBK"> </A>
|
||
<H3>Redirecting Standard Output and Standard Error</H3>
|
||
|
||
<P>
|
||
|
||
<B>Bash</B>
|
||
|
||
allows both the
|
||
standard output (file descriptor 1) and
|
||
the standard error output (file descriptor 2)
|
||
to be redirected to the file whose name is the
|
||
expansion of
|
||
<I>word</I>
|
||
|
||
with this construct.
|
||
<P>
|
||
|
||
There are two formats for redirecting standard output and
|
||
standard error:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<B>&></B><I>word</I>
|
||
</DL>
|
||
|
||
and
|
||
<DL COMPACT><DT><DD>
|
||
<B>>&</B><I>word</I>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
Of the two forms, the first is preferred.
|
||
This is semantically equivalent to
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<B>></B><I>word</I> 2<B>>&</B>1
|
||
</DL>
|
||
|
||
<A NAME="lbBL"> </A>
|
||
<H3>Here Documents</H3>
|
||
|
||
<P>
|
||
|
||
This type of redirection instructs the shell to read input from the
|
||
current source until a line containing only
|
||
<I>word</I>
|
||
|
||
(with no trailing blanks)
|
||
is seen. All of
|
||
the lines read up to that point are then used as the standard
|
||
input for a command.
|
||
<P>
|
||
|
||
The format of here-documents is as follows:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<PRE>
|
||
<B><<</B>[<B>-</B>]<I>word</I>
|
||
<I>here-document</I>
|
||
<I>delimiter</I>
|
||
</PRE>
|
||
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
No parameter expansion, command substitution, arithmetic expansion,
|
||
or pathname expansion is performed on
|
||
<I>word</I>.
|
||
|
||
If any characters in
|
||
<I>word</I>
|
||
|
||
are 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,
|
||
all lines of the here-document are subjected to parameter expansion,
|
||
command substitution, and arithmetic expansion. In the latter
|
||
case, the character sequence
|
||
<B>\<newline></B>
|
||
|
||
is ignored, and
|
||
<B>\</B>
|
||
|
||
must be used to quote the characters
|
||
<B>\</B>,
|
||
|
||
<B>$</B>,
|
||
|
||
and
|
||
<B>`</B>.
|
||
|
||
<P>
|
||
|
||
If the redirection operator is
|
||
<B><<-</B>,
|
||
|
||
then all leading tab characters are stripped from input lines and the
|
||
line containing
|
||
<I>delimiter</I>.
|
||
|
||
This allows
|
||
here-documents within shell scripts to be indented in a
|
||
natural fashion.
|
||
<A NAME="lbBM"> </A>
|
||
<H3>Duplicating File Descriptors</H3>
|
||
|
||
<P>
|
||
|
||
The redirection operator
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
[<I>n</I>]<B><&</B><I>word</I>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
is used to duplicate input file descriptors.
|
||
If
|
||
<I>word</I>
|
||
|
||
expands to one or more digits, the file descriptor denoted by
|
||
<I>n</I>
|
||
|
||
is made to be a copy of that file descriptor.
|
||
If the digits in
|
||
<I>word</I>
|
||
|
||
do not specify a file descriptor open for input, a redirection error occurs.
|
||
If
|
||
<I>word</I>
|
||
|
||
evaluates to
|
||
<B>-</B>,
|
||
|
||
file descriptor
|
||
<I>n</I>
|
||
|
||
is closed. If
|
||
<I>n</I>
|
||
|
||
is not specified, the standard input (file descriptor 0) is used.
|
||
<P>
|
||
|
||
The operator
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
[<I>n</I>]<B>>&</B><I>word</I>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
is used similarly to duplicate output file descriptors. If
|
||
<I>n</I>
|
||
|
||
is not specified, the standard output (file descriptor 1) is used.
|
||
If the digits in
|
||
<I>word</I>
|
||
|
||
do not specify a file descriptor open for output, a redirection error occurs.
|
||
As a special case, if <I>n</I> is omitted, and <I>word</I> does not
|
||
expand to one or more digits, the standard output and standard
|
||
error are redirected as described previously.
|
||
<A NAME="lbBN"> </A>
|
||
<H3>Opening File Descriptors for Reading and Writing</H3>
|
||
|
||
<P>
|
||
|
||
The redirection operator
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
[<I>n</I>]<B><></B><I>word</I>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
causes the file whose name is the expansion of
|
||
<I>word</I>
|
||
|
||
to be opened 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.
|
||
<A NAME="lbBO"> </A>
|
||
<H2>ALIASES</H2>
|
||
|
||
<I>Aliases</I> allow a string to be substituted for a word when it is used
|
||
as the first word of a simple command.
|
||
The shell maintains a list of aliases that may be set and unset with the
|
||
<B>alias</B>
|
||
|
||
and
|
||
<B>unalias</B>
|
||
|
||
builtin commands (see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
The first word of each command, if unquoted,
|
||
is checked to see if it has an
|
||
alias. If so, that word is replaced by the text of the alias.
|
||
The alias name and the replacement text may contain any valid
|
||
shell input, including the
|
||
<I>metacharacters</I>
|
||
|
||
listed above, with the exception that the alias name may not
|
||
contain <I>=</I>. 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.
|
||
If the last character of the alias value is a
|
||
<I>blank</I>,
|
||
|
||
then the next command
|
||
word following the alias is also checked for alias expansion.
|
||
<P>
|
||
|
||
Aliases are created and listed with the
|
||
<B>alias</B>
|
||
|
||
command, and removed with the
|
||
<B>unalias</B>
|
||
|
||
command.
|
||
<P>
|
||
|
||
There is no mechanism for using arguments in the replacement text.
|
||
If arguments are needed, a shell function should be used (see
|
||
<FONT SIZE=-1><B>FUNCTIONS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<P>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B></FONT>
|
||
below).
|
||
<P>
|
||
|
||
The rules concerning the definition and use of aliases are
|
||
somewhat confusing.
|
||
<B>Bash</B>
|
||
|
||
always reads at least one complete line
|
||
of input before executing any
|
||
of the commands on that line. 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 next line of input is read.
|
||
The commands following the alias definition
|
||
on that line 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 compound 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>
|
||
|
||
For almost every purpose, aliases are superseded by
|
||
shell functions.
|
||
<A NAME="lbBP"> </A>
|
||
<H2>FUNCTIONS</H2>
|
||
|
||
A shell function, defined as described above under
|
||
<FONT SIZE=-1><B>SHELL</B>GRAMMAR<B>,</B>
|
||
|
||
</FONT>
|
||
stores a series of commands for later execution.
|
||
When the name of a shell function is used as a simple command name,
|
||
the list of commands associated with that function name is executed.
|
||
Functions are executed in the context of the
|
||
current shell; no new process is created to interpret
|
||
them (contrast this with the execution of a shell script).
|
||
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 change. Positional parameter 0
|
||
is unchanged.
|
||
The
|
||
<FONT SIZE=-1><B>FUNCNAME</B>
|
||
|
||
</FONT>
|
||
variable is set to the name of the function while the function
|
||
is executing.
|
||
All other aspects of the shell execution
|
||
environment are identical between a function and its caller
|
||
with the exception that the
|
||
<FONT SIZE=-1><B>DEBUG</B>
|
||
|
||
</FONT>
|
||
trap (see the description of the
|
||
<B>trap</B>
|
||
|
||
builtin under
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below) is not inherited.
|
||
<P>
|
||
|
||
Variables local to the function may be declared with the
|
||
<B>local</B>
|
||
|
||
builtin command. Ordinarily, variables and their values
|
||
are shared between the function and its caller.
|
||
<P>
|
||
|
||
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. 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>
|
||
|
||
Function names and definitions may be listed with the
|
||
<B>-f</B>
|
||
|
||
option to the
|
||
<B>declare</B>
|
||
|
||
or
|
||
<B>typeset</B>
|
||
|
||
builtin commands. The
|
||
<B>-F</B>
|
||
|
||
option to
|
||
<B>declare</B>
|
||
|
||
or
|
||
<B>typeset</B>
|
||
|
||
will list the function names only.
|
||
Functions may be exported so that subshells
|
||
automatically have them defined with the
|
||
<B>-f</B>
|
||
|
||
option to the
|
||
<B>export</B>
|
||
|
||
builtin.
|
||
<P>
|
||
|
||
Functions may be recursive. No limit is imposed on the number
|
||
of recursive calls.
|
||
<A NAME="lbBQ"> </A>
|
||
<H2>ARITHMETIC EVALUATION</H2>
|
||
|
||
The shell allows arithmetic expressions to be evaluated, under
|
||
certain circumstances (see the <B>let</B> builtin command and
|
||
<B>Arithmetic Expansion</B>).
|
||
Evaluation is done in long integers with no check for overflow,
|
||
though division by 0 is trapped and flagged as an error.
|
||
The operators and their precedence and associativity 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.
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B></B><I>id</I>++ <I>id</I>--
|
||
|
||
<DD>
|
||
variable post-increment and post-decrement
|
||
<DT><B>++</B><I>id</I> --<I>id</I>
|
||
|
||
<DD>
|
||
variable pre-increment and pre-decrement
|
||
<DT><B>- +</B>
|
||
|
||
<DD>
|
||
unary minus and plus
|
||
<DT><B>! ~</B>
|
||
|
||
<DD>
|
||
logical and bitwise negation
|
||
<DT><B>**</B>
|
||
|
||
<DD>
|
||
exponentiation
|
||
<DT><B>* / %</B>
|
||
|
||
<DD>
|
||
multiplication, division, remainder
|
||
<DT><B>+ -</B>
|
||
|
||
<DD>
|
||
addition, subtraction
|
||
<DT><B><< >></B>
|
||
|
||
<DD>
|
||
left and right bitwise shifts
|
||
<DT><B><= >= < ></B>
|
||
|
||
<DD>
|
||
comparison
|
||
<DT><B>== !=</B>
|
||
|
||
<DD>
|
||
equality and inequality
|
||
<DT><B>&</B>
|
||
|
||
<DD>
|
||
bitwise AND
|
||
<DT><B>^</B>
|
||
|
||
<DD>
|
||
bitwise exclusive OR
|
||
<DT><B>|</B>
|
||
|
||
<DD>
|
||
bitwise OR
|
||
<DT><B>&&</B>
|
||
|
||
<DD>
|
||
logical AND
|
||
<DT><B>||</B>
|
||
|
||
<DD>
|
||
logical OR
|
||
<DT><B></B><I>expr</I>?<I>expr</I>:<I>expr</I>
|
||
|
||
<DD>
|
||
conditional evaluation
|
||
<DT><B>= *= /= %= += -= <<= >>= &= ^= |=</B>
|
||
|
||
<DD>
|
||
assignment
|
||
<DT><B></B><I>expr1</I> , <I>expr2</I>
|
||
|
||
<DD>
|
||
comma
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
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.
|
||
The value of a variable is evaluated as an arithmetic expression
|
||
when it is referenced.
|
||
A shell variable need not have its integer attribute
|
||
turned on to be used in an expression.
|
||
<P>
|
||
|
||
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 <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.
|
||
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 interchangably to represent numbers between 10
|
||
and 35.
|
||
<P>
|
||
|
||
Operators are evaluated in order of precedence. Sub-expressions in
|
||
parentheses are evaluated first and may override the precedence
|
||
rules above.
|
||
<A NAME="lbBR"> </A>
|
||
<H2>CONDITIONAL EXPRESSIONS</H2>
|
||
|
||
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.
|
||
Expressions are formed from the following unary or binary primaries.
|
||
If any <I>file</I> argument to one of the primaries is of the form
|
||
<I>/dev/fd/n</I>, then file descriptor <I>n</I> is checked.
|
||
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>, file
|
||
descriptor 0, 1, or 2, respectively, is checked.
|
||
<P>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-a </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists.
|
||
<DT><B>-b </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is a block special file.
|
||
<DT><B>-c </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is a character special file.
|
||
<DT><B>-d </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is a directory.
|
||
<DT><B>-e </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists.
|
||
<DT><B>-f </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is a regular file.
|
||
<DT><B>-g </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is set-group-id.
|
||
<DT><B>-h </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is a symbolic link.
|
||
<DT><B>-k </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and its ``sticky'' bit is set.
|
||
<DT><B>-p </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is a named pipe (FIFO).
|
||
<DT><B>-r </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is readable.
|
||
<DT><B>-s </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and has a size greater than zero.
|
||
<DT><B>-t </B><I>fd</I>
|
||
|
||
<DD>
|
||
True if file descriptor
|
||
<I>fd</I>
|
||
|
||
is open and refers to a terminal.
|
||
<DT><B>-u </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and its set-user-id bit is set.
|
||
<DT><B>-w </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is writable.
|
||
<DT><B>-x </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is executable.
|
||
<DT><B>-O </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is owned by the effective user id.
|
||
<DT><B>-G </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is owned by the effective group id.
|
||
<DT><B>-L </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is a symbolic link.
|
||
<DT><B>-S </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and is a socket.
|
||
<DT><B>-N </B><I>file</I>
|
||
|
||
<DD>
|
||
True if <I>file</I> exists and has been modified since it was last read.
|
||
<DT><I>file1</I> -<B>nt</B> <I>file2</I><DD>
|
||
True if <I>file1</I> is newer (according to
|
||
modification date) than <I>file2</I>.
|
||
<DT><I>file1</I> -<B>ot</B> <I>file2</I><DD>
|
||
True if <I>file1</I> is older than <I>file2</I>.
|
||
<DT><I>file1</I> <B>-ef</B> <I>file2</I><DD>
|
||
True if <I>file1</I> and <I>file2</I> have the same device and
|
||
inode numbers.
|
||
<DT><B>-o </B><I>optname</I>
|
||
|
||
<DD>
|
||
True if 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.
|
||
<DT><B>-z </B><I>string</I>
|
||
|
||
<DD>
|
||
True if the length of <I>string</I> is zero.
|
||
<DT><B>-n </B><I>string</I>
|
||
|
||
<DD>
|
||
<DT><I>string</I><DD>
|
||
True if the length of
|
||
<I>string</I>
|
||
|
||
is non-zero.
|
||
<DT><I>string1</I> <B>==</B> <I>string2</I><DD>
|
||
True if the strings are equal. <B>=</B> may be used in place of
|
||
<B>==</B>.
|
||
<DT><I>string1</I> <B>!=</B> <I>string2</I><DD>
|
||
True if the strings are not equal.
|
||
<DT><I>string1</I> <B><</B> <I>string2</I><DD>
|
||
True if <I>string1</I> sorts before <I>string2</I> lexicographically
|
||
in the current locale.
|
||
<DT><I>string1</I> <B>></B> <I>string2</I><DD>
|
||
True if <I>string1</I> sorts after <I>string2</I> lexicographically
|
||
in the current locale.
|
||
<DT><I>arg1</I> <B>OP</B> <I>arg2</I>
|
||
|
||
<DD>
|
||
<FONT SIZE=-1><B>OP</B>
|
||
|
||
</FONT>
|
||
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.
|
||
|
||
</DL>
|
||
<A NAME="lbBS"> </A>
|
||
<H2>SIMPLE COMMAND EXPANSION</H2>
|
||
|
||
When a simple command is executed, the shell performs the following
|
||
expansions, assignments, and redirections, from left to right.
|
||
<DL COMPACT>
|
||
<DT>1.<DD>
|
||
The words that the parser has marked as variable assignments (those
|
||
preceding the command name) and redirections are saved for later
|
||
processing.
|
||
<DT>2.<DD>
|
||
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.
|
||
<DT>3.<DD>
|
||
Redirections are performed as described above under
|
||
<FONT SIZE=-1><B>REDIRECTION</B>.
|
||
|
||
</FONT>
|
||
<DT>4.<DD>
|
||
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.
|
||
</DL>
|
||
<P>
|
||
|
||
If no command name results, the variable assignments affect the current
|
||
shell environment. 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>
|
||
|
||
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>
|
||
|
||
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 status of zero.
|
||
<A NAME="lbBT"> </A>
|
||
<H2>COMMAND EXECUTION</H2>
|
||
|
||
After a command has been split into words, if it results in a
|
||
simple command and an optional list of arguments, the following
|
||
actions are taken.
|
||
<P>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>FUNCTIONS</B>.
|
||
|
||
</FONT>
|
||
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>
|
||
|
||
If the name is neither a shell function nor a builtin,
|
||
and contains no slashes,
|
||
<B>bash</B>
|
||
|
||
searches each element of the
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
A full search of the directories in
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
is performed only if the command is not found in the hash table.
|
||
If the search is unsuccessful, the shell prints an error
|
||
message and returns an exit status of 127.
|
||
<P>
|
||
|
||
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>
|
||
|
||
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. A subshell is spawned to execute
|
||
it. 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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>)</FONT>
|
||
are retained by the child.
|
||
<P>
|
||
|
||
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.
|
||
<A NAME="lbBU"> </A>
|
||
<H2>COMMAND EXECUTION ENVIRONMENT</H2>
|
||
|
||
The shell has an <I>execution environment</I>, which consists of the
|
||
following:
|
||
<P>
|
||
<DL COMPACT>
|
||
<DT>*<DD>
|
||
open files inherited by the shell at invocation, as modified by
|
||
redirections supplied to the <B>exec</B> builtin
|
||
<DT>*<DD>
|
||
the current working directory as set by <B>cd</B>, <B>pushd</B>, or
|
||
<B>popd</B>, or inherited by the shell at invocation
|
||
<DT>*<DD>
|
||
the file creation mode mask as set by <B>umask</B> or inherited from
|
||
the shell's parent
|
||
<DT>*<DD>
|
||
current traps set by <B>trap</B>
|
||
<DT>*<DD>
|
||
shell parameters that are set by variable assignment or with <B>set</B>
|
||
or inherited from the shell's parent in the environment
|
||
<DT>*<DD>
|
||
shell functions defined during execution or inherited from the shell's
|
||
parent in the environment
|
||
<DT>*<DD>
|
||
options enabled at invocation (either by default or with command-line
|
||
arguments) or by <B>set</B>
|
||
<DT>*<DD>
|
||
options enabled by <B>shopt</B>
|
||
<DT>*<DD>
|
||
shell aliases defined with <B>alias</B>
|
||
<DT>*<DD>
|
||
various process IDs, including those of background jobs, the value
|
||
of <B>$$</B>, and the value of <B>$PPID</B>
|
||
</DL>
|
||
<P>
|
||
|
||
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>
|
||
<DL COMPACT>
|
||
<DT>*<DD>
|
||
the shell's open files, plus any modifications and additions specified
|
||
by redirections to the command
|
||
<DT>*<DD>
|
||
the current working directory
|
||
<DT>*<DD>
|
||
the file creation mode mask
|
||
<DT>*<DD>
|
||
shell variables marked for export, along with variables exported for
|
||
the command, passed in the environment
|
||
<DT>*<DD>
|
||
traps caught by the shell are reset to the values the inherited
|
||
from the shell's parent, and traps ignored by the shell are ignored
|
||
</DL>
|
||
<P>
|
||
|
||
A command invoked in this separate environment cannot affect the
|
||
shell's execution environment.
|
||
<P>
|
||
|
||
Command substitution 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 are also executed in a
|
||
subshell environment. Changes made to the subshell environment
|
||
cannot affect the shell's execution environment.
|
||
<P>
|
||
|
||
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>.
|
||
Otherwise, the invoked command inherits the file descriptors of the calling
|
||
shell as modified by redirections.
|
||
<A NAME="lbBV"> </A>
|
||
<H2>ENVIRONMENT</H2>
|
||
|
||
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>=value.
|
||
|
||
<P>
|
||
|
||
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>
|
||
|
||
and
|
||
<B>declare -x</B>
|
||
|
||
commands allow parameters and functions to be added to and
|
||
deleted from the environment. If the value of a parameter
|
||
in the environment is modified, the new value 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>
|
||
|
||
command, plus any additions via the
|
||
<B>export</B>
|
||
|
||
and
|
||
<B>declare -x</B>
|
||
|
||
commands.
|
||
<P>
|
||
|
||
The environment for any
|
||
<I>simple command</I>
|
||
|
||
or function may be augmented temporarily by prefixing it with
|
||
parameter assignments, as described above in
|
||
<FONT SIZE=-1><B>PARAMETERS</B>.
|
||
|
||
</FONT>
|
||
These assignment statements affect only the environment seen
|
||
by that command.
|
||
<P>
|
||
|
||
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>
|
||
|
||
When
|
||
<B>bash</B>
|
||
|
||
invokes an external command, the variable
|
||
<B>_</B>
|
||
|
||
is set to the full file name of the command and passed to that
|
||
command in its environment.
|
||
<A NAME="lbBW"> </A>
|
||
<H2>EXIT STATUS</H2>
|
||
|
||
For the shell's purposes, a command which exits with a
|
||
zero exit status has succeeded. An exit status of zero
|
||
indicates success. A non-zero exit status indicates failure.
|
||
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>
|
||
|
||
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>
|
||
|
||
If a command fails because of an error during expansion or redirection,
|
||
the exit status is greater than zero.
|
||
<P>
|
||
|
||
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.
|
||
<P>
|
||
|
||
<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.
|
||
<A NAME="lbBX"> </A>
|
||
<H2>SIGNALS</H2>
|
||
|
||
When <B>bash</B> is interactive, in the absence of any traps, it ignores
|
||
<FONT SIZE=-1><B>SIGTERM</B>
|
||
|
||
</FONT>
|
||
(so that <B>kill 0</B> does not kill an interactive shell),
|
||
and
|
||
<FONT SIZE=-1><B>SIGINT</B>
|
||
|
||
</FONT>
|
||
is caught and handled (so that the <B>wait</B> builtin is interruptible).
|
||
In all cases, <B>bash</B> ignores
|
||
<FONT SIZE=-1><B>SIGQUIT</B>.
|
||
|
||
</FONT>
|
||
If job control is in effect,
|
||
<B>bash</B>
|
||
|
||
ignores
|
||
<FONT SIZE=-1><B>SIGTTIN</B>,
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>SIGTTOU</B>,
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>SIGTSTP</B>.
|
||
|
||
</FONT>
|
||
<P>
|
||
|
||
Synchronous jobs started by <B>bash</B> have signal handlers
|
||
set to the values inherited by the shell from its parent.
|
||
When job control is not in effect, asynchronous commands
|
||
ignore
|
||
<FONT SIZE=-1><B>SIGINT</B>
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>SIGQUIT</B>
|
||
|
||
</FONT>
|
||
as well.
|
||
Commands run as a result of command substitution ignore the
|
||
keyboard-generated job control signals
|
||
<FONT SIZE=-1><B>SIGTTIN</B>,
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>SIGTTOU</B>,
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>SIGTSTP</B>.
|
||
|
||
</FONT>
|
||
<P>
|
||
|
||
The shell exits by default upon receipt of a
|
||
<FONT SIZE=-1><B>SIGHUP</B>.
|
||
|
||
</FONT>
|
||
Before exiting, an interactive shell resends the
|
||
<FONT SIZE=-1><B>SIGHUP</B>
|
||
|
||
</FONT>
|
||
to all jobs, running or stopped.
|
||
Stopped jobs are sent
|
||
<FONT SIZE=-1><B>SIGCONT</B>
|
||
|
||
</FONT>
|
||
to ensure that they receive the
|
||
<FONT SIZE=-1><B>SIGHUP</B>.
|
||
|
||
</FONT>
|
||
To prevent the shell from
|
||
sending the signal to a particular job, it should be removed from the
|
||
jobs table with the
|
||
<B>disown</B>
|
||
|
||
builtin (see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below) or marked
|
||
to not receive
|
||
<FONT SIZE=-1><B>SIGHUP</B>
|
||
|
||
</FONT>
|
||
using
|
||
<B>disown -h</B>.
|
||
|
||
<P>
|
||
|
||
If the
|
||
<B>huponexit</B>
|
||
|
||
shell option has been set with
|
||
<B>shopt</B>,
|
||
|
||
<B>bash</B>
|
||
|
||
sends a
|
||
<FONT SIZE=-1><B>SIGHUP</B>
|
||
|
||
</FONT>
|
||
to all jobs when an interactive login shell exits.
|
||
<P>
|
||
|
||
When <B>bash</B> receives a signal for which a trap has been set while
|
||
waiting for a command to complete, the trap will not be executed until
|
||
the command completes.
|
||
When <B>bash</B> is waiting for an asynchronous command via the <B>wait</B>
|
||
builtin, the reception of a signal for which a trap has been set will
|
||
cause the <B>wait</B> builtin to return immediately with an exit status
|
||
greater than 128, immediately after which the trap is executed.
|
||
<A NAME="lbBY"> </A>
|
||
<H2>JOB CONTROL</H2>
|
||
|
||
<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 system's terminal driver and
|
||
<B>bash</B>.
|
||
|
||
<P>
|
||
|
||
The shell associates a
|
||
<I>job</I>
|
||
|
||
with each pipeline. It keeps a table of currently executing
|
||
jobs, which may be listed with the
|
||
<B>jobs</B>
|
||
|
||
command. When
|
||
<B>bash</B>
|
||
|
||
starts a job asynchronously (in the
|
||
<I>background</I>),
|
||
|
||
it prints a line that looks like:
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
[1] 25647
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
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>
|
||
|
||
To facilitate the implementation of the user interface to job
|
||
control, the operating system maintains the notion of a <I>current terminal
|
||
process group ID</I>. Members of this process group (processes whose
|
||
process group ID is equal to the current terminal process group ID)
|
||
receive keyboard-generated signals such as
|
||
<FONT SIZE=-1><B>SIGINT</B>.
|
||
|
||
</FONT>
|
||
These processes are said to be in the
|
||
<I>foreground</I>.
|
||
|
||
<I>Background</I>
|
||
|
||
processes are those whose process group ID differs from the terminal's;
|
||
such processes are immune to keyboard-generated signals.
|
||
Only foreground processes are allowed to read from or write to the
|
||
terminal. Background processes which attempt to read from (write to) the
|
||
terminal are sent a
|
||
<FONT SIZE=-1><B>SIGTTIN (SIGTTOU)</B>
|
||
|
||
</FONT>
|
||
signal by the terminal driver,
|
||
which, unless caught, suspends the process.
|
||
<P>
|
||
|
||
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
|
||
causes that process to be stopped and returns control to
|
||
<B>bash</B>.
|
||
|
||
Typing the
|
||
<I>delayed suspend</I>
|
||
|
||
character (typically
|
||
<B>^Y</B>,
|
||
|
||
Control-Y) causes the process to be stopped when it
|
||
attempts to read input from the terminal, and control to
|
||
be returned to
|
||
<B>bash</B>.
|
||
|
||
The user may then manipulate 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. A <B>^Z</B> takes effect immediately,
|
||
and has the additional side effect of causing pending output
|
||
and typeahead to be discarded.
|
||
<P>
|
||
|
||
There are a number of ways to refer to a job in the shell.
|
||
The character
|
||
<B>%</B>
|
||
|
||
introduces a job name. 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 stopped
|
||
<B>ce</B>
|
||
|
||
job. If a prefix matches more than one job,
|
||
<B>bash</B>
|
||
|
||
reports an error. Using
|
||
<B>%?ce</B>,
|
||
|
||
on the other hand, refers to any job containing the string
|
||
<B>ce</B>
|
||
|
||
in its command line. If the substring matches more than one job,
|
||
<B>bash</B>
|
||
|
||
reports an error. The symbols
|
||
<B>%%</B>
|
||
|
||
and
|
||
<B>%+</B>
|
||
|
||
refer to the shell's notion of the
|
||
<I>current job</I>,
|
||
|
||
which is the last job stopped while it was in
|
||
the foreground or started in the background.
|
||
The
|
||
<I>previous job</I>
|
||
|
||
may be referenced using
|
||
<B>%-</B>.
|
||
|
||
In output pertaining to jobs (e.g., the output of the
|
||
<B>jobs</B>
|
||
|
||
command), the current job is always flagged with a
|
||
<B>+</B>,
|
||
|
||
and the previous job with a
|
||
<B>-</B>.
|
||
|
||
<P>
|
||
|
||
Simply naming a job can be used to bring it into the
|
||
foreground:
|
||
<B>%1</B>
|
||
|
||
is a synonym for
|
||
<B>``fg %1''</B>,
|
||
bringing job 1 from the background into the foreground.
|
||
Similarly,
|
||
<B>``%1 &''</B>
|
||
|
||
resumes job 1 in the background, equivalent to
|
||
<B>``bg %1''</B>.
|
||
<P>
|
||
|
||
The shell learns immediately whenever a job changes state.
|
||
Normally,
|
||
<B>bash</B>
|
||
|
||
waits until it is about to print a prompt before reporting
|
||
changes in a job's status so as to not interrupt
|
||
any other output. If the
|
||
<B>-b</B>
|
||
|
||
option to the
|
||
<B>set</B>
|
||
|
||
builtin command
|
||
is enabled,
|
||
<B>bash</B>
|
||
|
||
reports such changes immediately.
|
||
Any trap on
|
||
<FONT SIZE=-1><B>SIGCHLD</B>
|
||
|
||
</FONT>
|
||
is executed for each child that exits.
|
||
<P>
|
||
|
||
If an attempt to exit
|
||
<B>bash</B>
|
||
|
||
is made while jobs are stopped, the shell prints a warning message. The
|
||
<B>jobs</B>
|
||
|
||
command may then be used to inspect their status.
|
||
If a second attempt to exit is made without an intervening command,
|
||
the shell does not print another warning, and the stopped
|
||
jobs are terminated.
|
||
<A NAME="lbBZ"> </A>
|
||
<H2>PROMPTING</H2>
|
||
|
||
When executing interactively,
|
||
<B>bash</B>
|
||
|
||
displays the primary prompt
|
||
<FONT SIZE=-1><B>PS1</B>
|
||
|
||
</FONT>
|
||
when it is ready to read a command, and the secondary prompt
|
||
<FONT SIZE=-1><B>PS2</B>
|
||
|
||
</FONT>
|
||
when it needs more input to complete a command.
|
||
<B>Bash</B>
|
||
|
||
allows these prompt strings to be customized by inserting a number of
|
||
backslash-escaped special characters that are decoded as follows:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>\a</B>
|
||
|
||
<DD>
|
||
an ASCII bell character (07)
|
||
<DT><B>\d</B>
|
||
|
||
<DD>
|
||
the date in "Weekday Month Date" format (e.g., "Tue May 26")
|
||
<DT><B>\e</B>
|
||
|
||
<DD>
|
||
an ASCII escape character (033)
|
||
<DT><B>\h</B>
|
||
|
||
<DD>
|
||
the hostname up to the first `.'
|
||
<DT><B>\H</B>
|
||
|
||
<DD>
|
||
the hostname
|
||
<DT><B>\j</B>
|
||
|
||
<DD>
|
||
the number of jobs currently managed by the shell
|
||
<DT><B>\l</B>
|
||
|
||
<DD>
|
||
the basename of the shell's terminal device name
|
||
<DT><B>\n</B>
|
||
|
||
<DD>
|
||
newline
|
||
<DT><B>\r</B>
|
||
|
||
<DD>
|
||
carriage return
|
||
<DT><B>\s</B>
|
||
|
||
<DD>
|
||
the name of the shell, the basename of
|
||
<B>$0</B>
|
||
|
||
(the portion following the final slash)
|
||
<DT><B>\t</B>
|
||
|
||
<DD>
|
||
the current time in 24-hour HH:MM:SS format
|
||
<DT><B>\T</B>
|
||
|
||
<DD>
|
||
the current time in 12-hour HH:MM:SS format
|
||
<DT><B>\@</B>
|
||
|
||
<DD>
|
||
the current time in 12-hour am/pm format
|
||
<DT><B>\A</B>
|
||
|
||
<DD>
|
||
the current time in 24-hour HH:MM format
|
||
<DT><B>\u</B>
|
||
|
||
<DD>
|
||
the username of the current user
|
||
<DT><B>\v</B>
|
||
|
||
<DD>
|
||
the version of <B>bash</B> (e.g., 2.00)
|
||
<DT><B>\V</B>
|
||
|
||
<DD>
|
||
the release of <B>bash</B>, version + patchelvel (e.g., 2.00.0)
|
||
<DT><B>\w</B>
|
||
|
||
<DD>
|
||
the current working directory
|
||
<DT><B>\W</B>
|
||
|
||
<DD>
|
||
the basename of the current working directory
|
||
<DT><B>\!</B>
|
||
|
||
<DD>
|
||
the history number of this command
|
||
<DT><B>\#</B>
|
||
|
||
<DD>
|
||
the command number of this command
|
||
<DT><B>\$</B>
|
||
|
||
<DD>
|
||
if the effective UID is 0, a
|
||
<B>#</B>,
|
||
|
||
otherwise a
|
||
<B>$</B>
|
||
|
||
<DT><B>\</B><I>nnn</I>
|
||
|
||
<DD>
|
||
the character corresponding to the octal number <I>nnn</I>
|
||
<DT><B>\\</B>
|
||
|
||
<DD>
|
||
a backslash
|
||
<DT><B>\[</B>
|
||
|
||
<DD>
|
||
begin a sequence of non-printing characters, which could be used to
|
||
embed a terminal control sequence into the prompt
|
||
<DT><B>\]</B>
|
||
|
||
<DD>
|
||
end a sequence of non-printing characters
|
||
|
||
</DL></DL>
|
||
|
||
<P>
|
||
|
||
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
|
||
<FONT SIZE=-1><B>HISTORY</B>
|
||
|
||
</FONT>
|
||
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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<A NAME="lbCA"> </A>
|
||
<H2>READLINE</H2>
|
||
|
||
This is the library that handles reading input when using an interactive
|
||
shell, unless the
|
||
<B>--noediting</B>
|
||
|
||
option is given at shell invocation.
|
||
By default, the line editing commands are similar to those of emacs.
|
||
A vi-style line editing interface is also available.
|
||
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 (see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<A NAME="lbCB"> </A>
|
||
<H3>Readline Notation</H3>
|
||
|
||
<P>
|
||
|
||
In this section, the emacs-style notation is used to denote
|
||
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. (On keyboards
|
||
without a
|
||
<I>meta</I>
|
||
|
||
key, M-<I>x</I> means ESC <I>x</I>, i.e., press the Escape key
|
||
then the
|
||
<I>x</I>
|
||
|
||
key. This makes ESC the <I>meta prefix</I>.
|
||
The combination M-C-<I>x</I> means ESC-Control-<I>x</I>,
|
||
or press the Escape key
|
||
then hold the Control key while pressing the
|
||
<I>x</I>
|
||
|
||
key.)
|
||
<P>
|
||
|
||
Readline 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>) causes that command to act in a
|
||
backward direction.
|
||
Commands whose behavior with arguments deviates from this are noted
|
||
below.
|
||
<P>
|
||
|
||
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 cause the text to be
|
||
accumulated 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.
|
||
<A NAME="lbCC"> </A>
|
||
<H3>Readline Initialization</H3>
|
||
|
||
<P>
|
||
|
||
Readline 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
|
||
<FONT SIZE=-1><B>INPUTRC</B>
|
||
|
||
</FONT>
|
||
variable. If that variable is unset, the default is
|
||
<A HREF="file:~/.inputrc"><I>~/.inputrc</I></A>.
|
||
|
||
When a program which uses the readline library starts up, the
|
||
initialization file is read, and the key bindings and variables
|
||
are set.
|
||
There are only a few basic constructs allowed in the
|
||
readline initialization 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>
|
||
|
||
The default key-bindings may be changed with an
|
||
<I>inputrc </I>
|
||
|
||
file.
|
||
Other programs that use this library may add their own commands
|
||
and bindings.
|
||
<P>
|
||
|
||
For example, placing
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
M-Control-u: universal-argument
|
||
</DL>
|
||
|
||
or
|
||
<DL COMPACT><DT><DD>
|
||
C-Meta-u: universal-argument
|
||
</DL>
|
||
|
||
into the
|
||
<I>inputrc</I>
|
||
|
||
would make M-C-u execute the readline command
|
||
<I>universal-argument</I>.
|
||
|
||
<P>
|
||
|
||
The following symbolic character names are recognized:
|
||
<I>RUBOUT</I>,
|
||
|
||
<I>DEL</I>,
|
||
|
||
<I>ESC</I>,
|
||
|
||
<I>LFD</I>,
|
||
|
||
<I>NEWLINE</I>,
|
||
|
||
<I>RET</I>,
|
||
|
||
<I>RETURN</I>,
|
||
|
||
<I>SPC</I>,
|
||
|
||
<I>SPACE</I>,
|
||
|
||
and
|
||
<I>TAB</I>.
|
||
|
||
<P>
|
||
|
||
In addition to command names, readline allows keys to be bound
|
||
to a string that is inserted when the key is pressed (a <I>macro</I>).
|
||
<A NAME="lbCD"> </A>
|
||
<H3>Readline Key Bindings</H3>
|
||
|
||
<P>
|
||
|
||
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 name 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.
|
||
<P>
|
||
|
||
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>
|
||
<DL COMPACT><DT><DD>
|
||
Control-u: universal-argument
|
||
<BR>
|
||
|
||
Meta-Rubout: backward-kill-word
|
||
<BR>
|
||
|
||
Control-o: "> output"
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
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
|
||
<TT>> output</TT>
|
||
|
||
into the line).
|
||
<P>
|
||
|
||
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 the symbolic character names
|
||
are not recognized.
|
||
<P>
|
||
<DL COMPACT><DT><DD>
|
||
"\C-u": universal-argument
|
||
<BR>
|
||
|
||
"\C-x\C-r": re-read-init-file
|
||
<BR>
|
||
|
||
"\e[11~": "Function Key 1"
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
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
|
||
<TT>Function Key 1</TT>.
|
||
|
||
<P>
|
||
|
||
The full set of GNU Emacs style escape sequences is
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>\C-</B>
|
||
|
||
<DD>
|
||
control prefix
|
||
<DT><B>\M-</B>
|
||
|
||
<DD>
|
||
meta prefix
|
||
<DT><B>\e</B>
|
||
|
||
<DD>
|
||
an escape character
|
||
<DT><B>\\</B>
|
||
|
||
<DD>
|
||
backslash
|
||
<DT><B>\</B>
|
||
|
||
<DD>
|
||
literal "
|
||
<DT><B>\'</B>
|
||
|
||
<DD>
|
||
literal '
|
||
</DL></DL>
|
||
|
||
|
||
<P>
|
||
|
||
In addition to the GNU Emacs style escape sequences, a second
|
||
set of backslash escapes is available:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>\a</B>
|
||
|
||
<DD>
|
||
alert (bell)
|
||
<DT><B>\b</B>
|
||
|
||
<DD>
|
||
backspace
|
||
<DT><B>\d</B>
|
||
|
||
<DD>
|
||
delete
|
||
<DT><B>\f</B>
|
||
|
||
<DD>
|
||
form feed
|
||
<DT><B>\n</B>
|
||
|
||
<DD>
|
||
newline
|
||
<DT><B>\r</B>
|
||
|
||
<DD>
|
||
carriage return
|
||
<DT><B>\t</B>
|
||
|
||
<DD>
|
||
horizontal tab
|
||
<DT><B>\v</B>
|
||
|
||
<DD>
|
||
vertical tab
|
||
<DT><B>\</B><I>nnn</I>
|
||
|
||
<DD>
|
||
the eight-bit character whose value is the octal value <I>nnn</I>
|
||
(one to three digits)
|
||
<DT><B>\x</B><I>HH</I>
|
||
|
||
<DD>
|
||
the eight-bit character whose value is the hexadecimal value <I>HH</I>
|
||
(one or two hex digits)
|
||
</DL></DL>
|
||
|
||
|
||
<P>
|
||
|
||
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.
|
||
In the macro body, the backslash escapes described above are expanded.
|
||
Backslash will quote any other character in the macro text,
|
||
including " and '.
|
||
<P>
|
||
|
||
<B>Bash</B>
|
||
|
||
allows the current readline key bindings to be displayed or modified
|
||
with the
|
||
<B>bind</B>
|
||
|
||
builtin command. The editing mode may be switched during interactive
|
||
use by using the
|
||
<B>-o</B>
|
||
|
||
option to the
|
||
<B>set</B>
|
||
|
||
builtin command (see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below).
|
||
<A NAME="lbCE"> </A>
|
||
<H3>Readline Variables</H3>
|
||
|
||
<P>
|
||
|
||
Readline 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
|
||
<DL COMPACT><DT><DD>
|
||
<P>
|
||
|
||
<B>set</B> <I>variable-name</I> <I>value</I>
|
||
</DL>
|
||
|
||
<P>
|
||
|
||
Except where noted, readline variables can take the values
|
||
<B>On</B>
|
||
|
||
or
|
||
<B>Off</B>.
|
||
|
||
The variables and their default values are:
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>bell-style (audible)</B>
|
||
|
||
<DD>
|
||
Controls what happens when readline wants to ring the terminal bell.
|
||
If set to <B>none</B>, readline never rings the bell. If set to
|
||
<B>visible</B>, readline uses a visible bell if one is available.
|
||
If set to <B>audible</B>, readline attempts to ring the terminal's bell.
|
||
<DT><B>comment-begin (``#'')</B>
|
||
|
||
<DD>
|
||
The string that is inserted when the readline
|
||
<B>insert-comment</B>
|
||
|
||
command is executed.
|
||
This command is bound to
|
||
<B>M-#</B>
|
||
|
||
in emacs mode and to
|
||
<B>#</B>
|
||
|
||
in vi command mode.
|
||
<DT><B>completion-ignore-case (Off)</B>
|
||
|
||
<DD>
|
||
If set to <B>On</B>, readline performs filename matching and completion
|
||
in a case-insensitive fashion.
|
||
<DT><B>completion-query-items (100)</B>
|
||
|
||
<DD>
|
||
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, the user is asked whether
|
||
or not he wishes to view them; otherwise they are simply listed
|
||
on the terminal.
|
||
<DT><B>convert-meta (On)</B>
|
||
|
||
<DD>
|
||
If set to <B>On</B>, readline will convert characters with the
|
||
eighth bit set to an ASCII key sequence
|
||
by stripping the eighth bit and prefixing an
|
||
escape character (in effect, using escape as the <I>meta prefix</I>).
|
||
<DT><B>disable-completion (Off)</B>
|
||
|
||
<DD>
|
||
If set to <B>On</B>, readline will inhibit word completion. Completion
|
||
characters will be inserted into the line as if they had been
|
||
mapped to <B>self-insert</B>.
|
||
<DT><B>editing-mode (emacs)</B>
|
||
|
||
<DD>
|
||
Controls whether readline begins with 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>.
|
||
|
||
<DT><B>enable-keypad (Off)</B>
|
||
|
||
<DD>
|
||
When set to <B>On</B>, readline will try to enable the application
|
||
keypad when it is called. Some systems need this to enable the
|
||
arrow keys.
|
||
<DT><B>expand-tilde (Off)</B>
|
||
|
||
<DD>
|
||
If set to <B>on</B>, tilde expansion is performed when readline
|
||
attempts word completion.
|
||
<DT><B>history-preserve-point</B>
|
||
|
||
<DD>
|
||
If set to <B>on</B>, the history code attempts to place point at the
|
||
same location on each history line retrived with <B>previous-history</B>
|
||
or <B>next-history</B>.
|
||
<DT><B>horizontal-scroll-mode (Off)</B>
|
||
|
||
<DD>
|
||
When set to <B>On</B>, makes readline 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.
|
||
<DT><B>input-meta (Off)</B>
|
||
|
||
<DD>
|
||
If set to <B>On</B>, readline will enable eight-bit input (that is,
|
||
it will not strip the high bit from the characters it reads),
|
||
regardless of what the terminal claims it can support. The name
|
||
<B>meta-flag</B>
|
||
|
||
is a synonym for this variable.
|
||
<DT><B>isearch-terminators (``C-[C-J'')</B>
|
||
|
||
<DD>
|
||
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 <I>C-J</I> will terminate an incremental search.
|
||
<DT><B>keymap (emacs)</B>
|
||
|
||
<DD>
|
||
Set the current readline 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.
|
||
<DT><B>mark-directories (On)</B>
|
||
|
||
<DD>
|
||
If set to <B>On</B>, completed directory names have a slash
|
||
appended.
|
||
<DT><B>mark-modified-lines (Off)</B>
|
||
|
||
<DD>
|
||
If set to <B>On</B>, history lines that have been modified are displayed
|
||
with a preceding asterisk (<B>*</B>).
|
||
<DT><B>match-hidden-files (On)</B>
|
||
|
||
<DD>
|
||
This variable, when set to <B>On</B>, causes readline to match files whose
|
||
names begin with a `.' (hidden files) when performing filename
|
||
completion, unless the leading `.' is
|
||
supplied by the user in the filename to be completed.
|
||
<DT><B>output-meta (Off)</B>
|
||
|
||
<DD>
|
||
If set to <B>On</B>, readline will display characters with the
|
||
eighth bit set directly rather than as a meta-prefixed escape
|
||
sequence.
|
||
<DT><B>print-completions-horizontally (Off)</B>
|
||
|
||
<DD>
|
||
If set to <B>On</B>, readline will display completions with matches
|
||
sorted horizontally in alphabetical order, rather than down the screen.
|
||
<DT><B>show-all-if-ambiguous (Off)</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>visible-stats (Off)</B>
|
||
|
||
<DD>
|
||
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.
|
||
|
||
</DL>
|
||
<A NAME="lbCF"> </A>
|
||
<H3>Readline Conditional Constructs</H3>
|
||
|
||
<P>
|
||
|
||
Readline 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 used.
|
||
<DL COMPACT>
|
||
<DT><B>$if</B><DD>
|
||
The
|
||
<B>$if</B>
|
||
|
||
construct allows bindings to be made based on the
|
||
editing mode, the terminal being used, or the application using
|
||
readline. The text of the test extends to the end of the line;
|
||
no characters are required to isolate it.
|
||
<DL COMPACT><DT><DD>
|
||
<DL COMPACT>
|
||
<DT><B>mode</B><DD>
|
||
The <B>mode=</B> form of the <B>$if</B> directive is used to test
|
||
whether readline 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
|
||
readline is starting out in emacs mode.
|
||
<DT><B>term</B><DD>
|
||
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 the both full name of the terminal and the portion
|
||
of the terminal name before the first <B>-</B>. This allows
|
||
<I>sun</I>
|
||
|
||
to match both
|
||
<I>sun</I>
|
||
|
||
and
|
||
<I>sun-cmd</I>,
|
||
|
||
for instance.
|
||
<DT><B>application</B><DD>
|
||
The <B>application</B> construct is used to include
|
||
application-specific settings. Each program using the readline
|
||
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 Bash:
|
||
<P>
|
||
<DL COMPACT><DT><DD>
|
||
<PRE>
|
||
<B>$if</B> Bash
|
||
# Quote the current or previous word
|
||
"\C-xq": "\eb\"\ef\""
|
||
<B>$endif</B>
|
||
</PRE>
|
||
|
||
</DL>
|
||
|
||
</DL></DL>
|
||
|
||
<DT><B>$endif</B><DD>
|
||
This command, as seen in the previous example, terminates an
|
||
<B>$if</B> command.
|
||
<DT><B>$else</B><DD>
|
||
Commands in this branch of the <B>$if</B> directive are executed if
|
||
the test fails.
|
||
<DT><B>$include</B><DD>
|
||
This directive takes a single filename as an argument and reads commands
|
||
and bindings from that file. For example, the following directive
|
||
would read <A HREF="file:/etc/inputrc"><I>/etc/inputrc</I></A>:
|
||
<P>
|
||
<DL COMPACT><DT><DD>
|
||
<PRE>
|
||
<B>$include</B> <A HREF="file:/etc/inputrc"><I>/etc/inputrc</I></A>
|
||
</PRE>
|
||
|
||
</DL>
|
||
|
||
</DL>
|
||
<A NAME="lbCG"> </A>
|
||
<H3>Searching</H3>
|
||
|
||
<P>
|
||
|
||
Readline provides commands for searching through the command history
|
||
(see
|
||
<FONT SIZE=-1><B>HISTORY</B>
|
||
|
||
</FONT>
|
||
below) for lines containing a specified string.
|
||
There are two search modes:
|
||
<I>incremental</I>
|
||
|
||
and
|
||
<I>non-incremental</I>.
|
||
|
||
<P>
|
||
|
||
Incremental searches begin before the user has finished typing the
|
||
search string.
|
||
As each character of the search string is typed, readline 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.
|
||
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 the Escape and
|
||
Control-J characters will terminate an incremental search.
|
||
Control-G will abort an incremental search and restore the original
|
||
line.
|
||
When the search is terminated, the history entry containing the
|
||
search string becomes the current line.
|
||
<P>
|
||
|
||
To find other matching entries in the history list, type Control-S or
|
||
Control-R as appropriate.
|
||
This will search backward or forward in the history for the next
|
||
entry matching the search string typed so far.
|
||
Any other key sequence bound to a readline command will terminate
|
||
the search and execute that command.
|
||
For instance, a <I>newline</I> will terminate the search and accept
|
||
the line, thereby executing the command from the history list.
|
||
<P>
|
||
|
||
Readline remembers the last incremental search string. If two
|
||
Control-Rs are typed without any intervening characters defining a
|
||
new search string, any remembered search string is used.
|
||
<P>
|
||
|
||
Non-incremental searches read the entire search string before starting
|
||
to search for matching history lines. The search string may be
|
||
typed by the user or be part of the contents of the current line.
|
||
<A NAME="lbCH"> </A>
|
||
<H3>Readline Command Names</H3>
|
||
|
||
<P>
|
||
|
||
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.
|
||
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>.
|
||
<A NAME="lbCI"> </A>
|
||
<H3>Commands for Moving</H3>
|
||
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>beginning-of-line (C-a)</B>
|
||
|
||
<DD>
|
||
Move to the start of the current line.
|
||
<DT><B>end-of-line (C-e)</B>
|
||
|
||
<DD>
|
||
Move to the end of the line.
|
||
<DT><B>forward-char (C-f)</B>
|
||
|
||
<DD>
|
||
Move forward a character.
|
||
<DT><B>backward-char (C-b)</B>
|
||
|
||
<DD>
|
||
Move back a character.
|
||
<DT><B>forward-word (M-f)</B>
|
||
|
||
<DD>
|
||
Move forward to the end of the next word. Words are composed of
|
||
alphanumeric characters (letters and digits).
|
||
<DT><B>backward-word (M-b)</B>
|
||
|
||
<DD>
|
||
Move back to the start of the current or previous word. Words are
|
||
composed of alphanumeric characters (letters and digits).
|
||
<DT><B>clear-screen (C-l)</B>
|
||
|
||
<DD>
|
||
Clear the screen leaving the current line at the top of the screen.
|
||
With an argument, refresh the current line without clearing the
|
||
screen.
|
||
<DT><B>redraw-current-line</B>
|
||
|
||
<DD>
|
||
Refresh the current line.
|
||
|
||
</DL>
|
||
<A NAME="lbCJ"> </A>
|
||
<H3>Commands for Manipulating the History</H3>
|
||
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>accept-line (Newline, Return)</B>
|
||
|
||
<DD>
|
||
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
|
||
<FONT SIZE=-1><B>HISTCONTROL</B>
|
||
|
||
</FONT>
|
||
variable. If the line is a modified history
|
||
line, then restore the history line to its original state.
|
||
<DT><B>previous-history (C-p)</B>
|
||
|
||
<DD>
|
||
Fetch the previous command from the history list, moving back in
|
||
the list.
|
||
<DT><B>next-history (C-n)</B>
|
||
|
||
<DD>
|
||
Fetch the next command from the history list, moving forward in the
|
||
list.
|
||
<DT><B>beginning-of-history (M-<)</B>
|
||
|
||
<DD>
|
||
Move to the first line in the history.
|
||
<DT><B>end-of-history (M->)</B>
|
||
|
||
<DD>
|
||
Move to the end of the input history, i.e., the line currently being
|
||
entered.
|
||
<DT><B>reverse-search-history (C-r)</B>
|
||
|
||
<DD>
|
||
Search backward starting at the current line and moving `up' through
|
||
the history as necessary. This is an incremental search.
|
||
<DT><B>forward-search-history (C-s)</B>
|
||
|
||
<DD>
|
||
Search forward starting at the current line and moving `down' through
|
||
the history as necessary. This is an incremental search.
|
||
<DT><B>non-incremental-reverse-search-history (M-p)</B>
|
||
|
||
<DD>
|
||
Search backward through the history starting at the current line
|
||
using a non-incremental search for a string supplied by the user.
|
||
<DT><B>non-incremental-forward-search-history (M-n)</B>
|
||
|
||
<DD>
|
||
Search forward through the history using a non-incremental search for
|
||
a string supplied by the user.
|
||
<DT><B>history-search-forward</B>
|
||
|
||
<DD>
|
||
Search forward through the history for the string of characters
|
||
between the start of the current line and the point.
|
||
This is a non-incremental search.
|
||
<DT><B>history-search-backward</B>
|
||
|
||
<DD>
|
||
Search backward through the history for the string of characters
|
||
between the start of the current line and the point.
|
||
This is a non-incremental search.
|
||
<DT><B>yank-nth-arg (M-C-y)</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>yank-last-arg (M-., M-_)</B>
|
||
|
||
<DD>
|
||
Insert the last argument to the previous command (the last word of
|
||
the previous history entry). With an 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 argument of each line in turn.
|
||
<DT><B>shell-expand-line (M-C-e)</B>
|
||
|
||
<DD>
|
||
Expand the line as the shell does. This
|
||
performs alias and history expansion as well as all of the shell
|
||
word expansions. See
|
||
<FONT SIZE=-1><B>HISTORY EXPANSION</B>
|
||
|
||
</FONT>
|
||
below for a description of history expansion.
|
||
<DT><B>history-expand-line (M-^)</B>
|
||
|
||
<DD>
|
||
Perform history expansion on the current line.
|
||
See
|
||
<FONT SIZE=-1><B>HISTORY EXPANSION</B>
|
||
|
||
</FONT>
|
||
below for a description of history expansion.
|
||
<DT><B>magic-space</B>
|
||
|
||
<DD>
|
||
Perform history expansion on the current line and insert a space.
|
||
See
|
||
<FONT SIZE=-1><B>HISTORY EXPANSION</B>
|
||
|
||
</FONT>
|
||
below for a description of history expansion.
|
||
<DT><B>alias-expand-line</B>
|
||
|
||
<DD>
|
||
Perform alias expansion on the current line.
|
||
See
|
||
<FONT SIZE=-1><B>ALIASES</B>
|
||
|
||
</FONT>
|
||
above for a description of alias expansion.
|
||
<DT><B>history-and-alias-expand-line</B>
|
||
|
||
<DD>
|
||
Perform history and alias expansion on the current line.
|
||
<DT><B>insert-last-argument (M-., M-_)</B>
|
||
|
||
<DD>
|
||
A synonym for <B>yank-last-arg</B>.
|
||
<DT><B>operate-and-get-next (C-o)</B>
|
||
|
||
<DD>
|
||
Accept the current line for execution and fetch the next line
|
||
relative to the current line from the history for editing. Any
|
||
argument is ignored.
|
||
|
||
</DL>
|
||
<A NAME="lbCK"> </A>
|
||
<H3>Commands for Changing Text</H3>
|
||
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>delete-char (C-d)</B>
|
||
|
||
<DD>
|
||
Delete the character at point. If point is at the
|
||
beginning of the line, there are no characters in the line, and
|
||
the last character typed was not bound to <B>delete-char</B>,
|
||
then return
|
||
<FONT SIZE=-1><B>EOF</B>.
|
||
|
||
</FONT>
|
||
<DT><B>backward-delete-char (Rubout)</B>
|
||
|
||
<DD>
|
||
Delete the character behind the cursor. When given a numeric argument,
|
||
save the deleted text on the kill ring.
|
||
<DT><B>forward-backward-delete-char</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>quoted-insert (C-q, C-v)</B>
|
||
|
||
<DD>
|
||
Add the next character typed to the line verbatim. This is
|
||
how to insert characters like <B>C-q</B>, for example.
|
||
<DT><B>tab-insert (C-v TAB)</B>
|
||
|
||
<DD>
|
||
Insert a tab character.
|
||
<DT><B>self-insert (a, b, A, 1, !, ...)</B>
|
||
|
||
<DD>
|
||
Insert the character typed.
|
||
<DT><B>transpose-chars (C-t)</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>transpose-words (M-t)</B>
|
||
|
||
<DD>
|
||
Drag the word before point past the word after point,
|
||
moving point over that word as well.
|
||
If point is at the end of the line, this transposes
|
||
the last two words on the line.
|
||
<DT><B>upcase-word (M-u)</B>
|
||
|
||
<DD>
|
||
Uppercase the current (or following) word. With a negative argument,
|
||
uppercase the previous word, but do not move point.
|
||
<DT><B>downcase-word (M-l)</B>
|
||
|
||
<DD>
|
||
Lowercase the current (or following) word. With a negative argument,
|
||
lowercase the previous word, but do not move point.
|
||
<DT><B>capitalize-word (M-c)</B>
|
||
|
||
<DD>
|
||
Capitalize the current (or following) word. With a negative argument,
|
||
capitalize the previous word, but do not move point.
|
||
|
||
</DL>
|
||
<A NAME="lbCL"> </A>
|
||
<H3>Killing and Yanking</H3>
|
||
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>kill-line (C-k)</B>
|
||
|
||
<DD>
|
||
Kill the text from point to the end of the line.
|
||
<DT><B>backward-kill-line (C-x Rubout)</B>
|
||
|
||
<DD>
|
||
Kill backward to the beginning of the line.
|
||
<DT><B>unix-line-discard (C-u)</B>
|
||
|
||
<DD>
|
||
Kill backward from point to the beginning of the line.
|
||
The killed text is saved on the kill-ring.
|
||
|
||
<DT><B>kill-whole-line</B>
|
||
|
||
<DD>
|
||
Kill all characters on the current line, no matter where point is.
|
||
<DT><B>kill-word (M-d)</B>
|
||
|
||
<DD>
|
||
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>.
|
||
<DT><B>backward-kill-word (M-Rubout)</B>
|
||
|
||
<DD>
|
||
Kill the word behind point.
|
||
Word boundaries are the same as those used by <B>backward-word</B>.
|
||
<DT><B>unix-word-rubout (C-w)</B>
|
||
|
||
<DD>
|
||
Kill the word behind point, using white space as a word boundary.
|
||
The killed text is saved on the kill-ring.
|
||
<DT><B>delete-horizontal-space (M-\)</B>
|
||
|
||
<DD>
|
||
Delete all spaces and tabs around point.
|
||
<DT><B>kill-region</B>
|
||
|
||
<DD>
|
||
Kill the text in the current region.
|
||
<DT><B>copy-region-as-kill</B>
|
||
|
||
<DD>
|
||
Copy the text in the region to the kill buffer.
|
||
<DT><B>copy-backward-word</B>
|
||
|
||
<DD>
|
||
Copy the word before point to the kill buffer.
|
||
The word boundaries are the same as <B>backward-word</B>.
|
||
<DT><B>copy-forward-word</B>
|
||
|
||
<DD>
|
||
Copy the word following point to the kill buffer.
|
||
The word boundaries are the same as <B>forward-word</B>.
|
||
<DT><B>yank (C-y)</B>
|
||
|
||
<DD>
|
||
Yank the top of the kill ring into the buffer at point.
|
||
<DT><B>yank-pop (M-y)</B>
|
||
|
||
<DD>
|
||
Rotate the kill ring, and yank the new top. Only works following
|
||
<B>yank</B>
|
||
|
||
or
|
||
<B>yank-pop</B>.
|
||
|
||
|
||
</DL>
|
||
<A NAME="lbCM"> </A>
|
||
<H3>Numeric Arguments</H3>
|
||
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>digit-argument (M-0, M-1, ..., M--)</B>
|
||
|
||
<DD>
|
||
Add this digit to the argument already accumulating, or start a new
|
||
argument. M-- starts a negative argument.
|
||
<DT><B>universal-argument</B>
|
||
|
||
<DD>
|
||
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 or 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.
|
||
|
||
</DL>
|
||
<A NAME="lbCN"> </A>
|
||
<H3>Completing</H3>
|
||
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>complete (TAB)</B>
|
||
|
||
<DD>
|
||
Attempt to perform completion on the text before point.
|
||
<B>Bash</B>
|
||
|
||
attempts completion 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 and functions) in turn. If none
|
||
of these produces a match, filename completion is attempted.
|
||
<DT><B>possible-completions (M-?)</B>
|
||
|
||
<DD>
|
||
List the possible completions of the text before point.
|
||
<DT><B>insert-completions (M-*)</B>
|
||
|
||
<DD>
|
||
Insert all completions of the text before point
|
||
that would have been generated by
|
||
<B>possible-completions</B>.
|
||
<DT><B>menu-complete</B>
|
||
|
||
<DD>
|
||
Similar to <B>complete</B>, but replaces the word to be completed
|
||
with a single match from the list of possible completions.
|
||
Repeated execution of <B>menu-complete</B> steps through the list
|
||
of possible completions, inserting each match in turn.
|
||
At the end of the list of completions, the bell is rung
|
||
(subject to the setting of <B>bell-style</B>)
|
||
and the original text is restored.
|
||
An argument of <I>n</I> moves <I>n</I> positions forward in the list
|
||
of matches; a negative argument may be used to move backward
|
||
through the list.
|
||
This command is intended to be bound to <B>TAB</B>, but is unbound
|
||
by default.
|
||
<DT><B>delete-char-or-list</B>
|
||
|
||
<DD>
|
||
Deletes the character under the cursor if not at the beginning or
|
||
end of the line (like <B>delete-char</B>).
|
||
If at the end of the line, behaves identically to
|
||
<B>possible-completions</B>.
|
||
This command is unbound by default.
|
||
<DT><B>complete-filename (M-/)</B>
|
||
|
||
<DD>
|
||
Attempt filename completion on the text before point.
|
||
<DT><B>possible-filename-completions (C-x /)</B>
|
||
|
||
<DD>
|
||
List the possible completions of the text before point,
|
||
treating it as a filename.
|
||
<DT><B>complete-username (M-~)</B>
|
||
|
||
<DD>
|
||
Attempt completion on the text before point, treating
|
||
it as a username.
|
||
<DT><B>possible-username-completions (C-x ~)</B>
|
||
|
||
<DD>
|
||
List the possible completions of the text before point,
|
||
treating it as a username.
|
||
<DT><B>complete-variable (M-$)</B>
|
||
|
||
<DD>
|
||
Attempt completion on the text before point, treating
|
||
it as a shell variable.
|
||
<DT><B>possible-variable-completions (C-x $)</B>
|
||
|
||
<DD>
|
||
List the possible completions of the text before point,
|
||
treating it as a shell variable.
|
||
<DT><B>complete-hostname (M-@)</B>
|
||
|
||
<DD>
|
||
Attempt completion on the text before point, treating
|
||
it as a hostname.
|
||
<DT><B>possible-hostname-completions (C-x @)</B>
|
||
|
||
<DD>
|
||
List the possible completions of the text before point,
|
||
treating it as a hostname.
|
||
<DT><B>complete-command (M-!)</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>possible-command-completions (C-x !)</B>
|
||
|
||
<DD>
|
||
List the possible completions of the text before point,
|
||
treating it as a command name.
|
||
<DT><B>dynamic-complete-history (M-TAB)</B>
|
||
|
||
<DD>
|
||
Attempt completion on the text before point, comparing
|
||
the text against lines from the history list for possible
|
||
completion matches.
|
||
<DT><B>complete-into-braces (M-{)</B>
|
||
|
||
<DD>
|
||
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).
|
||
|
||
</DL>
|
||
<A NAME="lbCO"> </A>
|
||
<H3>Keyboard Macros</H3>
|
||
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>start-kbd-macro (C-x ()</B>
|
||
|
||
<DD>
|
||
Begin saving the characters typed into the current keyboard macro.
|
||
<DT><B>end-kbd-macro (C-x ))</B>
|
||
|
||
<DD>
|
||
Stop saving the characters typed into the current keyboard macro
|
||
and store the definition.
|
||
<DT><B>call-last-kbd-macro (C-x e)</B>
|
||
|
||
<DD>
|
||
Re-execute the last keyboard macro defined, by making the characters
|
||
in the macro appear as if typed at the keyboard.
|
||
|
||
</DL>
|
||
<A NAME="lbCP"> </A>
|
||
<H3>Miscellaneous</H3>
|
||
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>re-read-init-file (C-x C-r)</B>
|
||
|
||
<DD>
|
||
Read in the contents of the <I>inputrc</I> file, and incorporate
|
||
any bindings or variable assignments found there.
|
||
<DT><B>abort (C-g)</B>
|
||
|
||
<DD>
|
||
Abort the current editing command and
|
||
ring the terminal's bell (subject to the setting of
|
||
<B>bell-style</B>).
|
||
|
||
<DT><B>do-uppercase-version (M-a, M-b, M-</B><I>x</I>, ...)
|
||
|
||
<DD>
|
||
If the metafied character <I>x</I> is lowercase, run the command
|
||
that is bound to the corresponding uppercase character.
|
||
<DT><B>prefix-meta (ESC)</B>
|
||
|
||
<DD>
|
||
Metafy the next character typed.
|
||
<FONT SIZE=-1><B>ESC</B>
|
||
|
||
</FONT>
|
||
<B>f</B>
|
||
|
||
is equivalent to
|
||
<B>Meta-f</B>.
|
||
|
||
<DT><B>undo (C-_, C-x C-u)</B>
|
||
|
||
<DD>
|
||
Incremental undo, separately remembered for each line.
|
||
<DT><B>revert-line (M-r)</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>tilde-expand (M-&)</B>
|
||
|
||
<DD>
|
||
Perform tilde expansion on the current word.
|
||
<DT><B>set-mark (C-@, M-<space>)</B>
|
||
|
||
<DD>
|
||
Set the mark to the point. If a
|
||
numeric argument is supplied, the mark is set to that position.
|
||
<DT><B>exchange-point-and-mark (C-x C-x)</B>
|
||
|
||
<DD>
|
||
Swap the point with the mark. The current cursor position is set to
|
||
the saved position, and the old cursor position is saved as the mark.
|
||
<DT><B>character-search (C-])</B>
|
||
|
||
<DD>
|
||
A character is read and point is moved to the next occurrence of that
|
||
character. A negative count searches for previous occurrences.
|
||
<DT><B>character-search-backward (M-C-])</B>
|
||
|
||
<DD>
|
||
A character is read and point is moved to the previous occurrence of that
|
||
character. A negative count searches for subsequent occurrences.
|
||
<DT><B>insert-comment (M-#)</B>
|
||
|
||
<DD>
|
||
The value of the readline
|
||
<B>comment-begin</B>
|
||
|
||
variable is inserted at the beginning of the current line, and 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.
|
||
<DT><B>glob-expand-word (C-x *)</B>
|
||
|
||
<DD>
|
||
The word before point is treated as a pattern for pathname expansion,
|
||
and the list of matching file names is inserted, replacing the word.
|
||
<DT><B>glob-list-expansions (C-x g)</B>
|
||
|
||
<DD>
|
||
The list of expansions that would have been generated by
|
||
<B>glob-expand-word</B>
|
||
|
||
is displayed, and the line is redrawn.
|
||
<DT><B>dump-functions</B>
|
||
|
||
<DD>
|
||
Print all of the functions and their key bindings to the
|
||
readline 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.
|
||
<DT><B>dump-variables</B>
|
||
|
||
<DD>
|
||
Print all of the settable readline variables and their values to the
|
||
readline 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.
|
||
<DT><B>dump-macros</B>
|
||
|
||
<DD>
|
||
Print all of the readline key sequences bound to macros and the
|
||
strings they ouput. 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.
|
||
<DT><B>display-shell-version (C-x C-v)</B>
|
||
|
||
<DD>
|
||
Display version information about the current instance of
|
||
<B>bash</B>.
|
||
|
||
|
||
</DL>
|
||
<A NAME="lbCQ"> </A>
|
||
<H3>Programmable Completion</H3>
|
||
|
||
<P>
|
||
|
||
When word completion is attempted for an argument to a command for
|
||
which a completion specification (a <I>compspec</I>) has been defined
|
||
using the <B>complete</B> builtin (see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below), the programmable completion facilities are invoked.
|
||
<P>
|
||
|
||
First, the command name is identified.
|
||
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 a full pathname, a compspec for the full
|
||
pathname is searched for first.
|
||
If no compspec is found for the full pathname, an attempt is made to
|
||
find a compspec for the portion following the final slash.
|
||
<P>
|
||
|
||
Once a compspec has been found, it is used to generate the list of
|
||
matching words.
|
||
If a compspec is not found, the default <B>bash</B> completion as
|
||
described above under <B>Completing</B> is performed.
|
||
<P>
|
||
|
||
First, the actions specified by the compspec are used.
|
||
Only matches which are prefixed by the word being completed are
|
||
returned.
|
||
When the
|
||
<B>-f</B>
|
||
|
||
or
|
||
<B>-d</B>
|
||
|
||
option is used for filename or directory name completion, the shell
|
||
variable
|
||
<FONT SIZE=-1><B>FIGNORE</B>
|
||
|
||
</FONT>
|
||
is used to filter the matches.
|
||
<P>
|
||
|
||
Any completions specified by a filename expansion pattern to the
|
||
<B>-G</B> option are generated next.
|
||
The words generated by the pattern need not match the word
|
||
being completed.
|
||
The
|
||
<FONT SIZE=-1><B>GLOBIGNORE</B>
|
||
|
||
</FONT>
|
||
shell variable is not used to filter the matches, but the
|
||
<FONT SIZE=-1><B>FIGNORE</B>
|
||
|
||
</FONT>
|
||
variable is used.
|
||
<P>
|
||
|
||
Next, the string specified as the argument to the <B>-W</B> option
|
||
is considered.
|
||
The string is first split using the characters in the
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
special variable as delimiters.
|
||
Shell quoting is honored.
|
||
Each word is then expanded using
|
||
brace expansion, tilde expansion, parameter and variable expansion,
|
||
command substitution, arithmetic expansion, and pathname expansion,
|
||
as described above under
|
||
<FONT SIZE=-1><B>EXPANSION</B>.
|
||
|
||
</FONT>
|
||
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 the possible completions.
|
||
<P>
|
||
|
||
After these matches have been generated, any shell function or command
|
||
specified with the <B>-F</B> and <B>-C</B> options is invoked.
|
||
When the command or function is invoked, the
|
||
<FONT SIZE=-1><B>COMP_LINE</B>
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>COMP_POINT</B>
|
||
|
||
</FONT>
|
||
variables are assigned values as described above under
|
||
<B>Shell Variables</B>.
|
||
If a shell function is being invoked, the
|
||
<FONT SIZE=-1><B>COMP_WORDS</B>
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>COMP_CWORD</B>
|
||
|
||
</FONT>
|
||
variables are also set.
|
||
When the function or command is invoked, the first argument is the
|
||
name of the command whose arguments are being completed, the
|
||
second argument is the word being completed, and the third argument
|
||
is the word preceding the word being completed on the current command line.
|
||
No filtering of the generated completions against the word being completed
|
||
is performed; the function or command has complete freedom in generating
|
||
the matches.
|
||
<P>
|
||
|
||
Any function specified with <B>-F</B> is invoked first.
|
||
The function may use any of the shell facilities, including the
|
||
<B>compgen</B> builtin described below, to generate the matches.
|
||
It must put the possible completions in the
|
||
<FONT SIZE=-1><B>COMPREPLY</B>
|
||
|
||
</FONT>
|
||
array variable.
|
||
<P>
|
||
|
||
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 may be used to escape a newline, if necessary.
|
||
<P>
|
||
|
||
After all of the possible completions are generated, any filter
|
||
specified with the <B>-X</B> option is applied to 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 will be removed from the list.
|
||
A leading <B>!</B> negates the pattern; in this case any completion
|
||
not matching the pattern will be removed.
|
||
<P>
|
||
|
||
Finally, any prefix and suffix specified with the <B>-P</B> and <B>-S</B>
|
||
options are added to each member of the completion list, and the result is
|
||
returned to the readline completion code as the list of possible
|
||
completions.
|
||
<P>
|
||
|
||
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, directory name completion is attempted.
|
||
<P>
|
||
|
||
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 are not attempted, and the readline
|
||
default of filename completion is disabled.
|
||
If the <B>-o default</B> option was supplied to <B>complete</B> when the
|
||
compspec was defined, readline's default completion will be performed
|
||
if the compspec generates no matches.
|
||
<A NAME="lbCR"> </A>
|
||
<H2>HISTORY</H2>
|
||
|
||
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 text of the last
|
||
<FONT SIZE=-1><B>HISTSIZE</B>
|
||
|
||
</FONT>
|
||
commands (default 500) is saved. The shell
|
||
stores each command in the history list prior to parameter and
|
||
variable expansion (see
|
||
<FONT SIZE=-1><B>EXPANSION</B>
|
||
|
||
</FONT>
|
||
above) but after history expansion is performed, subject to the
|
||
values of the shell variables
|
||
<FONT SIZE=-1><B>HISTIGNORE</B>
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>HISTCONTROL</B>.
|
||
|
||
</FONT>
|
||
<P>
|
||
|
||
On startup, the history is initialized from the file named by
|
||
the variable
|
||
<FONT SIZE=-1><B>HISTFILE</B>
|
||
|
||
</FONT>
|
||
(default <A HREF="file:~/.bash_history"><I>~/.bash_history</I></A>).
|
||
The file named by the value of
|
||
<FONT SIZE=-1><B>HISTFILE</B>
|
||
|
||
</FONT>
|
||
is truncated, if necessary, to contain no more than
|
||
the number of lines specified by the value of
|
||
<FONT SIZE=-1><B>HISTFILESIZE</B>.
|
||
|
||
</FONT>
|
||
When an interactive shell exits, the last
|
||
<FONT SIZE=-1><B>$HISTSIZE</B>
|
||
|
||
</FONT>
|
||
lines are copied from the history list to
|
||
<FONT SIZE=-1><B>$HISTFILE</B>.
|
||
|
||
</FONT>
|
||
If the
|
||
<B>histappend</B>
|
||
|
||
shell option is enabled
|
||
(see the description of
|
||
<B>shopt</B>
|
||
|
||
under
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below), the lines are appended to the history file,
|
||
otherwise the history file is overwritten.
|
||
If
|
||
<FONT SIZE=-1><B>HISTFILE</B>
|
||
|
||
</FONT>
|
||
is unset, or if the history file is unwritable, the history is
|
||
not saved. After saving the history, the history file is truncated
|
||
to contain no more than
|
||
<FONT SIZE=-1><B>HISTFILESIZE</B>
|
||
|
||
</FONT>
|
||
lines. If
|
||
<FONT SIZE=-1><B>HISTFILESIZE</B>
|
||
|
||
</FONT>
|
||
is not set, no truncation is performed.
|
||
<P>
|
||
|
||
The builtin command
|
||
<B>fc</B>
|
||
|
||
(see
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below) may be used to list or edit and re-execute a portion of
|
||
the history list.
|
||
The
|
||
<B>history</B>
|
||
|
||
builtin may be used to 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>
|
||
|
||
The shell allows control over which commands are saved on the history
|
||
list. The
|
||
<FONT SIZE=-1><B>HISTCONTROL</B>
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>HISTIGNORE</B>
|
||
|
||
</FONT>
|
||
variables may be set to cause the shell to save only a subset of the
|
||
commands entered.
|
||
The
|
||
<B>cmdhist</B>
|
||
|
||
shell option, if enabled, causes the shell to attempt 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 causes the shell to save the command with embedded newlines
|
||
instead of semicolons. See the description of the
|
||
<B>shopt</B>
|
||
|
||
builtin below under
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
for information on setting and unsetting shell options.
|
||
<A NAME="lbCS"> </A>
|
||
<H2>HISTORY EXPANSION</H2>
|
||
|
||
<P>
|
||
|
||
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. This
|
||
feature 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
|
||
<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
|
||
|
||
</FONT>
|
||
below). Non-interactive shells do not perform history expansion
|
||
by default.
|
||
<P>
|
||
|
||
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>
|
||
|
||
History expansion is performed immediately after a complete line
|
||
is read, before the shell breaks it into words.
|
||
It takes place in two parts.
|
||
The first is to determine which line from the history list
|
||
to use during substitution.
|
||
The second is to select portions of that line for inclusion into
|
||
the current one.
|
||
The line selected from the history is the <I>event</I>,
|
||
and the portions of that line that are acted upon are <I>words</I>.
|
||
Various <I>modifiers</I> are available to manipulate the selected words.
|
||
The line is broken 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.
|
||
History expansions are introduced by the appearance of the
|
||
history expansion character, which is <B>!</B> by default.
|
||
Only backslash (<B>\</B>) and single quotes can quote
|
||
the history expansion character.
|
||
<P>
|
||
|
||
Several shell options settable with the
|
||
<B>shopt</B>
|
||
|
||
builtin may be used to tailor the behavior of history expansion.
|
||
If the
|
||
<B>histverify</B>
|
||
|
||
shell option is enabled (see the description of the
|
||
<B>shopt</B>
|
||
|
||
builtin), 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 will be reloaded
|
||
into the
|
||
<B>readline</B>
|
||
|
||
editing buffer for correction.
|
||
The
|
||
<B>-p</B>
|
||
|
||
option to the
|
||
<B>history</B>
|
||
|
||
builtin command may be used to see what a history expansion will
|
||
do before using it.
|
||
The
|
||
<B>-s</B>
|
||
|
||
option to the
|
||
<B>history</B>
|
||
|
||
builtin may be used to add commands to the end of the history list
|
||
without actually executing them, so that they are available for
|
||
subsequent recall.
|
||
<P>
|
||
|
||
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>).
|
||
|
||
<A NAME="lbCT"> </A>
|
||
<H3>Event Designators</H3>
|
||
|
||
<P>
|
||
|
||
An event designator is a reference to a command line entry in the
|
||
history list.
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>!</B>
|
||
|
||
<DD>
|
||
Start a history substitution, except when followed by a
|
||
<B>blank</B>,
|
||
|
||
newline, = or (.
|
||
<DT><B>!</B><I>n</I>
|
||
|
||
<DD>
|
||
Refer to command line
|
||
<I>n</I>.
|
||
|
||
<DT><B>!-</B><I>n</I>
|
||
|
||
<DD>
|
||
Refer to the current command line minus
|
||
<I>n</I>.
|
||
|
||
<DT><B>!!</B>
|
||
|
||
<DD>
|
||
Refer to the previous command. This is a synonym for `!-1'.
|
||
<DT><B>!</B><I>string</I>
|
||
|
||
<DD>
|
||
Refer to the most recent command starting with
|
||
<I>string</I>.
|
||
|
||
<DT><B>!?</B><I>string</I><B>[?]</B>
|
||
|
||
<DD>
|
||
Refer to the most recent command containing
|
||
<I>string</I>.
|
||
|
||
The trailing <B>?</B> may be omitted if
|
||
<I>string</I>
|
||
|
||
is followed immediately by a newline.
|
||
<DT><B></B><FONT SIZE=+2><B>^</B></FONT><B></B><I>string1</I><FONT SIZE=+2>^</FONT><I>string2</I><FONT SIZE=+2>^</FONT>
|
||
|
||
<DD>
|
||
Quick substitution. Repeat the last command, replacing
|
||
<I>string1</I>
|
||
|
||
with
|
||
<I>string2</I>.
|
||
|
||
Equivalent to
|
||
``!!:s/<I>string1</I>/<I>string2</I>/''
|
||
(see <B>Modifiers</B> below).
|
||
<DT><B>!#</B>
|
||
|
||
<DD>
|
||
The entire command line typed so far.
|
||
|
||
</DL>
|
||
<A NAME="lbCU"> </A>
|
||
<H3>Word Designators</H3>
|
||
|
||
<P>
|
||
|
||
Word designators are used to select desired words from the 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.
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>0 (zero)</B>
|
||
|
||
<DD>
|
||
The zeroth word. For the shell, this is the command
|
||
word.
|
||
<DT><I>n</I>
|
||
|
||
<DD>
|
||
The <I>n</I>th word.
|
||
<DT><B>^</B>
|
||
|
||
<DD>
|
||
The first argument. That is, word 1.
|
||
<DT><B>$</B>
|
||
|
||
<DD>
|
||
The last argument.
|
||
<DT><B>%</B>
|
||
|
||
<DD>
|
||
The word matched by the most recent `?<I>string</I>?' search.
|
||
<DT><I>x</I><B>-</B>y
|
||
|
||
<DD>
|
||
A range of words; `-<I>y</I>' abbreviates `0-<I>y</I>'.
|
||
<DT><B>*</B>
|
||
|
||
<DD>
|
||
All of the words but the zeroth. This is a synonym
|
||
for `<I>1-$</I>'. It is not an error to use
|
||
<B>*</B>
|
||
|
||
if there is just one
|
||
word in the event; the empty string is returned in that case.
|
||
<DT><B>x*</B>
|
||
|
||
<DD>
|
||
Abbreviates <I>x-$</I>.
|
||
<DT><B>x-</B>
|
||
|
||
<DD>
|
||
Abbreviates <I>x-$</I> like <B>x*</B>, but omits the last word.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
If a word designator is supplied without an event specification, the
|
||
previous command is used as the event.
|
||
<A NAME="lbCV"> </A>
|
||
<H3>Modifiers</H3>
|
||
|
||
<P>
|
||
|
||
After the optional word designator, there may appear a sequence of
|
||
one or more of the following modifiers, each preceded by a `:'.
|
||
<P>
|
||
|
||
|
||
<P>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>h</B>
|
||
|
||
<DD>
|
||
Remove a trailing file name component, leaving only the head.
|
||
<DT><B>t</B>
|
||
|
||
<DD>
|
||
Remove all leading file name components, leaving the tail.
|
||
<DT><B>r</B>
|
||
|
||
<DD>
|
||
Remove a trailing suffix of the form <I>.xxx</I>, leaving the
|
||
basename.
|
||
<DT><B>e</B>
|
||
|
||
<DD>
|
||
Remove all but the trailing suffix.
|
||
<DT><B>p</B>
|
||
|
||
<DD>
|
||
Print the new command but do not execute it.
|
||
<DT><B>q</B>
|
||
|
||
<DD>
|
||
Quote the substituted words, escaping further substitutions.
|
||
<DT><B>x</B>
|
||
|
||
<DD>
|
||
Quote the substituted words as with
|
||
<B>q</B>,
|
||
|
||
but break into words at
|
||
<B>blanks</B>
|
||
|
||
and newlines.
|
||
<DT><B>s/</B><I>old</I>/<I>new</I>/
|
||
|
||
<DD>
|
||
Substitute
|
||
<I>new</I>
|
||
|
||
for the first occurrence of
|
||
<I>old</I>
|
||
|
||
in the event line. Any delimiter can be used in place of /. The
|
||
final delimiter is optional if it is the last character of the
|
||
event line. The delimiter may be quoted in
|
||
<I>old</I>
|
||
|
||
and
|
||
<I>new</I>
|
||
|
||
with a single backslash. If & appears in
|
||
<I>new</I>,
|
||
|
||
it is replaced by
|
||
<I>old</I>.
|
||
|
||
A single backslash will quote 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.
|
||
<DT><B>&</B>
|
||
|
||
<DD>
|
||
Repeat the previous substitution.
|
||
<DT><B>g</B>
|
||
|
||
<DD>
|
||
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>/<I>new</I>/')
|
||
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.
|
||
|
||
</DL>
|
||
<A NAME="lbCW"> </A>
|
||
<H2>SHELL BUILTIN COMMANDS</H2>
|
||
|
||
|
||
|
||
<P>
|
||
|
||
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.
|
||
<P>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>:</B> [<I>arguments</I>]<DD>
|
||
|
||
No effect; the command does nothing beyond expanding
|
||
<I>arguments</I>
|
||
|
||
and performing any specified
|
||
redirections. A zero exit code is returned.
|
||
<DT>
|
||
<DD>
|
||
<B> . </B> <I>filename</I> [<I>arguments</I>]
|
||
<DT><B>source</B> <I>filename</I> [<I>arguments</I>]<DD>
|
||
|
||
Read and execute commands from
|
||
<I>filename</I>
|
||
|
||
in the current
|
||
shell environment and return the exit status of the last command
|
||
executed from
|
||
<I>filename</I>.
|
||
|
||
If
|
||
<I>filename</I>
|
||
|
||
does not contain a slash, file names in
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
are used to find the directory containing
|
||
<I>filename</I>.
|
||
|
||
The file searched for in
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
need not be executable.
|
||
When <B>bash</B> is not in <I>posix mode</I>, the current directory is
|
||
searched if no file is found in
|
||
<FONT SIZE=-1><B>PATH</B>.
|
||
|
||
</FONT>
|
||
If the
|
||
<B>sourcepath</B>
|
||
|
||
option to the
|
||
<B>shopt</B>
|
||
|
||
builtin command is turned off, the
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
is not searched.
|
||
If any <I>arguments</I> are supplied, they become the positional
|
||
parameters when <I>filename</I> is executed. Otherwise the positional
|
||
parameters are unchanged.
|
||
The return status is the status of the last command exited within
|
||
the script (0 if no commands are executed), and false if
|
||
<I>filename</I>
|
||
|
||
is not found or cannot be read.
|
||
<DT><B>alias</B> [<B>-p</B>] [<I>name</I>[=<I>value</I>] ...]<DD>
|
||
<B>Alias</B> with no arguments or with the
|
||
<B>-p</B>
|
||
|
||
option prints the list of aliases in the form
|
||
<B>alias</B> <I>name</I>=<I>value</I> on standard output.
|
||
When arguments are supplied, an alias is defined 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.
|
||
For each <I>name</I> in the argument list for which no <I>value</I>
|
||
is supplied, the name and value of the alias is printed.
|
||
<B>Alias</B> returns true unless a <I>name</I> is given for which
|
||
no alias has been defined.
|
||
<DT><B>bg</B> [<I>jobspec</I>]<DD>
|
||
Resume the 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's notion of the
|
||
<I>current job</I> is used.
|
||
<B>bg</B>
|
||
|
||
<I>jobspec</I>
|
||
|
||
returns 0 unless run when job control is disabled or, when run with
|
||
job control enabled, if <I>jobspec</I> was not found or started without
|
||
job control.
|
||
<DT>
|
||
<DD>
|
||
<B>bind</B> [<B>-m</B> <I>keymap</I>] [<B>-lpsvPSV</B>]
|
||
<DT><B>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>]<DD>
|
||
<DT><B>bind</B> [<B>-m</B> <I>keymap</I>] <B>-f</B> <I>filename</I><DD>
|
||
<DT><B>bind</B> [<B>-m</B> <I>keymap</I>] <B>-x</B> <I>keyseq</I>:<I>shell-command</I><DD>
|
||
<DT><B>bind</B> [<B>-m</B> <I>keymap</I>] <I>keyseq</I>:<I>function-name</I><DD>
|
||
|
||
Display current
|
||
<B>readline</B>
|
||
|
||
key and function bindings, or bind a key sequence to a
|
||
<B>readline</B>
|
||
|
||
function or macro. The binding syntax accepted is identical to that of
|
||
<I>.inputrc</I>,
|
||
|
||
but each binding must be passed as a separate argument;
|
||
e.g., '"\C-x\C-r": re-read-init-file'. Options, if supplied, have the
|
||
following meanings:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-m </B><I>keymap</I>
|
||
|
||
<DD>
|
||
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>emacs</I> is
|
||
equivalent to <I>emacs-standard</I>.
|
||
<DT><B>-l</B>
|
||
|
||
<DD>
|
||
List the names of all <B>readline</B> functions.
|
||
<DT><B>-p</B>
|
||
|
||
<DD>
|
||
Display <B>readline</B> function names and bindings in such a way
|
||
that they can be re-read.
|
||
<DT><B>-P</B>
|
||
|
||
<DD>
|
||
List current <B>readline</B> function names and bindings.
|
||
<DT><B>-v</B>
|
||
|
||
<DD>
|
||
Display <B>readline</B> variable names and values in such a way that they
|
||
can be re-read.
|
||
<DT><B>-V</B>
|
||
|
||
<DD>
|
||
List current <B>readline</B> variable names and values.
|
||
<DT><B>-s</B>
|
||
|
||
<DD>
|
||
Display <B>readline</B> key sequences bound to macros and the strings
|
||
they output in such a way that they can be re-read.
|
||
<DT><B>-S</B>
|
||
|
||
<DD>
|
||
Display <B>readline</B> key sequences bound to macros and the strings
|
||
they output.
|
||
<DT><B>-f </B><I>filename</I>
|
||
|
||
<DD>
|
||
Read key bindings from <I>filename</I>.
|
||
<DT><B>-q </B><I>function</I>
|
||
|
||
<DD>
|
||
Query about which keys invoke the named <I>function</I>.
|
||
<DT><B>-u </B><I>function</I>
|
||
|
||
<DD>
|
||
Unbind all keys bound to the named <I>function</I>.
|
||
<DT><B>-r </B><I>keyseq</I>
|
||
|
||
<DD>
|
||
Remove any current binding for <I>keyseq</I>.
|
||
<DT><B>-x </B><I>keyseq</I>:<I>shell-command</I>
|
||
|
||
<DD>
|
||
Cause <I>shell-command</I> to be executed whenever <I>keyseq</I> is
|
||
entered.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
The return value is 0 unless an unrecognized option is given or an
|
||
error occurred.
|
||
</DL>
|
||
|
||
<DT><B>break</B> [<I>n</I>]<DD>
|
||
Exit from within a
|
||
<B>for</B>,
|
||
|
||
<B>while</B>,
|
||
|
||
<B>until</B>,
|
||
|
||
or
|
||
<B>select</B>
|
||
|
||
loop. If <I>n</I> is specified, break <I>n</I> levels.
|
||
<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 the shell is not executing
|
||
a loop when
|
||
<B>break</B>
|
||
|
||
is executed.
|
||
<DT><B>builtin</B> <I>shell-builtin</I> [<I>arguments</I>]<DD>
|
||
Execute the specified shell builtin, 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.
|
||
<DT><B>cd</B> [<B>-LP</B>] [<I>dir</I>]<DD>
|
||
Change the current directory to <I>dir</I>. The variable
|
||
<FONT SIZE=-1><B>HOME</B>
|
||
|
||
</FONT>
|
||
is the
|
||
default
|
||
<I>dir</I>.
|
||
|
||
The variable
|
||
<FONT SIZE=-1><B>CDPATH</B>
|
||
|
||
</FONT>
|
||
defines the search path for the directory containing
|
||
<I>dir</I>.
|
||
|
||
Alternative directory names in
|
||
<FONT SIZE=-1><B>CDPATH</B>
|
||
|
||
</FONT>
|
||
are separated by a colon (:). A null directory name in
|
||
<FONT SIZE=-1><B>CDPATH</B>
|
||
|
||
</FONT>
|
||
is the same as the current directory, i.e., ``<B>.</B>''. If
|
||
<I>dir</I>
|
||
|
||
begins with a slash (/),
|
||
then
|
||
<FONT SIZE=-1><B>CDPATH</B>
|
||
|
||
</FONT>
|
||
is not used. The
|
||
<B>-P</B>
|
||
|
||
option says to use the physical directory structure instead of
|
||
following symbolic links (see also the
|
||
<B>-P</B>
|
||
|
||
option to the
|
||
<B>set</B>
|
||
|
||
builtin command); the
|
||
<B>-L</B>
|
||
|
||
option forces symbolic links to be followed. An argument of
|
||
<B>-</B>
|
||
|
||
is equivalent to
|
||
<FONT SIZE=-1><B>$OLDPWD</B>.
|
||
|
||
</FONT>
|
||
The return value is true if the directory was successfully changed;
|
||
false otherwise.
|
||
<DT><B>command</B> [<B>-pVv</B>] <I>command</I> [<I>arg</I> ...]<DD>
|
||
Run
|
||
<I>command</I>
|
||
|
||
with
|
||
<I>args</I>
|
||
|
||
suppressing the normal shell function lookup. Only builtin
|
||
commands or commands found in the
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
are executed. If the
|
||
<B>-p</B>
|
||
|
||
option is given, 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.
|
||
If either the
|
||
<B>-V</B>
|
||
|
||
or
|
||
<B>-v</B>
|
||
|
||
option is supplied, a description of
|
||
<I>command</I>
|
||
|
||
is printed. The
|
||
<B>-v</B>
|
||
|
||
option causes a single word indicating the command or file name
|
||
used to invoke
|
||
<I>command</I>
|
||
|
||
to be displayed; the
|
||
<B>-V</B>
|
||
|
||
option produces a more verbose description.
|
||
If the
|
||
<B>-V</B>
|
||
|
||
or
|
||
<B>-v</B>
|
||
|
||
option is supplied, the exit status is 0 if
|
||
<I>command</I>
|
||
|
||
was found, and 1 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>.
|
||
|
||
<DT><B>compgen</B> [<I>option</I>] [<I>word</I>]<DD>
|
||
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 exception of <B>-p</B> and <B>-r</B>, and write
|
||
the matches to the standard output.
|
||
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>
|
||
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.
|
||
<P>
|
||
The return value is true unless an invalid option is supplied, or no
|
||
matches were generated.
|
||
<DT>
|
||
<DD>
|
||
<B>complete</B> [<B>-abcdefgjkvu</B>] [<B>-o</B> <I>comp-option</I>] [<B>-A</B> <I>action</I>] [<B>-G</B> <I>globpat</I>] [<B>-W</B> <I>wordlist</I>] [<B>-P</B> <I>prefix</I>] [<B>-S</B> <I>suffix</I>]
|
||
<BR>
|
||
|
||
[<B>-X</B> <I>filterpat</I>] [<B>-F</B> <I>function</I>] [<B>-C</B> <I>command</I>] <I>name</I> [<I>name ...</I>]
|
||
<DT><B>complete</B> <B>-pr</B> [<I>name</I> ...]<DD>
|
||
|
||
Specify how arguments to each <I>name</I> should be completed.
|
||
If the <B>-p</B> option is supplied, or if no options are supplied,
|
||
existing completion specifications are printed 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>
|
||
The process of applying these completion specifications when word completion
|
||
is attempted is described above under <B>Programmable Completion</B>.
|
||
<P>
|
||
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.
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-o</B> <I>comp-option</I><DD>
|
||
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:
|
||
<DL COMPACT><DT><DD>
|
||
<DL COMPACT>
|
||
<DT><B>default</B>
|
||
|
||
<DD>
|
||
Use readline's default completion if the compspec generates no matches.
|
||
<DT><B>dirnames</B>
|
||
|
||
<DD>
|
||
Perform directory name completion if the compspec generates no matches.
|
||
<DT><B>filenames</B>
|
||
|
||
<DD>
|
||
Tell readline that the compspec generates filenames, so it can perform any
|
||
filename-specific processing (like adding a slash to directory names or
|
||
suppressing trailing spaces). Intended to be used with shell functions.
|
||
</DL></DL>
|
||
|
||
<DT><B>-A</B> <I>action</I><DD>
|
||
The <I>action</I> may be one of the following to generate a list of possible
|
||
completions:
|
||
<DL COMPACT><DT><DD>
|
||
<DL COMPACT>
|
||
<DT><B>alias</B>
|
||
|
||
<DD>
|
||
Alias names. May also be specified as <B>-a</B>.
|
||
<DT><B>arrayvar</B>
|
||
|
||
<DD>
|
||
Array variable names.
|
||
<DT><B>binding</B>
|
||
|
||
<DD>
|
||
<B>Readline</B> key binding names.
|
||
<DT><B>builtin</B>
|
||
|
||
<DD>
|
||
Names of shell builtin commands. May also be specified as <B>-b</B>.
|
||
<DT><B>command</B>
|
||
|
||
<DD>
|
||
Command names. May also be specified as <B>-c</B>.
|
||
<DT><B>directory</B>
|
||
|
||
<DD>
|
||
Directory names. May also be specified as <B>-d</B>.
|
||
<DT><B>disabled</B>
|
||
|
||
<DD>
|
||
Names of disabled shell builtins.
|
||
<DT><B>enabled</B>
|
||
|
||
<DD>
|
||
Names of enabled shell builtins.
|
||
<DT><B>export</B>
|
||
|
||
<DD>
|
||
Names of exported shell variables. May also be specified as <B>-e</B>.
|
||
<DT><B>file</B>
|
||
|
||
<DD>
|
||
File names. May also be specified as <B>-f</B>.
|
||
<DT><B>function</B>
|
||
|
||
<DD>
|
||
Names of shell functions.
|
||
<DT><B>group</B>
|
||
|
||
<DD>
|
||
Group names. May also be specified as <B>-g</B>.
|
||
<DT><B>helptopic</B>
|
||
|
||
<DD>
|
||
Help topics as accepted by the <B>help</B> builtin.
|
||
<DT><B>hostname</B>
|
||
|
||
<DD>
|
||
Hostnames, as taken from the file specified by the
|
||
<FONT SIZE=-1><B>HOSTFILE</B>
|
||
|
||
</FONT>
|
||
shell variable.
|
||
<DT><B>job</B>
|
||
|
||
<DD>
|
||
Job names, if job control is active. May also be specified as <B>-j</B>.
|
||
<DT><B>keyword</B>
|
||
|
||
<DD>
|
||
Shell reserved words. May also be specified as <B>-k</B>.
|
||
<DT><B>running</B>
|
||
|
||
<DD>
|
||
Names of running jobs, if job control is active.
|
||
<DT><B>setopt</B>
|
||
|
||
<DD>
|
||
Valid arguments for the <B>-o</B> option to the <B>set</B> builtin.
|
||
<DT><B>shopt</B>
|
||
|
||
<DD>
|
||
Shell option names as accepted by the <B>shopt</B> builtin.
|
||
<DT><B>signal</B>
|
||
|
||
<DD>
|
||
Signal names.
|
||
<DT><B>stopped</B>
|
||
|
||
<DD>
|
||
Names of stopped jobs, if job control is active.
|
||
<DT><B>user</B>
|
||
|
||
<DD>
|
||
User names. May also be specified as <B>-u</B>.
|
||
<DT><B>variable</B>
|
||
|
||
<DD>
|
||
Names of all shell variables. May also be specified as <B>-v</B>.
|
||
</DL></DL>
|
||
|
||
<DT><B>-G</B> <I>globpat</I><DD>
|
||
The filename expansion pattern <I>globpat</I> is expanded to generate
|
||
the possible completions.
|
||
<DT><B>-W</B> <I>wordlist</I><DD>
|
||
The <I>wordlist</I> is split using the characters in the
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
special variable as delimiters, and each resultant word is expanded.
|
||
The possible completions are the members of the resultant list which
|
||
match the word being completed.
|
||
<DT><B>-C</B> <I>command</I><DD>
|
||
<I>command</I> is executed in a subshell environment, and its output is
|
||
used as the possible completions.
|
||
<DT><B>-F</B> <I>function</I><DD>
|
||
The shell function <I>function</I> is executed in the current shell
|
||
environment.
|
||
When it finishes, the possible completions are retrieved from the value
|
||
of the
|
||
<FONT SIZE=-1><B>COMPREPLY</B>
|
||
|
||
</FONT>
|
||
array variable.
|
||
<DT><B>-X</B> <I>filterpat</I><DD>
|
||
<I>filterpat</I> is a pattern as used for filename 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.
|
||
<DT><B>-P</B> <I>prefix</I><DD>
|
||
<I>prefix</I> is added at the beginning of each possible completion
|
||
after all other options have been applied.
|
||
<DT><B>-S</B> <I>suffix</I><DD>
|
||
<I>suffix</I> is appended to each possible completion
|
||
after all other options have been applied.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
The return value is true unless an invalid option is supplied, an option
|
||
other than <B>-p</B> or <B>-r</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.
|
||
</DL>
|
||
|
||
<DT><B>continue</B> [<I>n</I>]<DD>
|
||
Resume 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, resume at 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 last enclosing loop
|
||
(the ``top-level'' loop) is resumed. The return value is 0 unless the
|
||
shell is not executing a loop when
|
||
<B>continue</B>
|
||
|
||
is executed.
|
||
<DT>
|
||
<DD>
|
||
<B>declare</B> [<B>-afFirx</B>] [<B>-p</B>] [<I>name</I>[=<I>value</I>]]
|
||
<DT><B>typeset</B> [<B>-afFirx</B>] [<B>-p</B>] [<I>name</I>[=<I>value</I>]]<DD>
|
||
|
||
Declare variables and/or give them attributes.
|
||
If no <I>name</I>s are given then display the values of variables.
|
||
The
|
||
<B>-p</B>
|
||
|
||
option will display the attributes and values of each
|
||
<I>name</I>.
|
||
|
||
When
|
||
<B>-p</B>
|
||
|
||
is used, additional options are ignored.
|
||
The
|
||
<B>-F</B>
|
||
|
||
option inhibits the display of function definitions; only the
|
||
function name and attributes are printed.
|
||
The
|
||
<B>-F</B>
|
||
|
||
option implies
|
||
<B>-f</B>.
|
||
|
||
The following options can
|
||
be used to restrict output to variables with the specified attribute or
|
||
to give variables attributes:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-a</B>
|
||
|
||
<DD>
|
||
Each <I>name</I> is an array variable (see
|
||
<B>Arrays</B>
|
||
|
||
above).
|
||
<DT><B>-f</B>
|
||
|
||
<DD>
|
||
Use function names only.
|
||
<DT><B>-i</B>
|
||
|
||
<DD>
|
||
The variable is treated as an integer; arithmetic evaluation (see
|
||
<FONT SIZE=-1><B>ARITHMETIC EVALUATION ) </B>
|
||
|
||
</FONT>
|
||
is performed when the variable is assigned a value.
|
||
<DT><B>-r</B>
|
||
|
||
<DD>
|
||
Make <I>name</I>s readonly. These names cannot then be assigned values
|
||
by subsequent assignment statements or unset.
|
||
<DT><B>-x</B>
|
||
|
||
<DD>
|
||
Mark <I>name</I>s for export to subsequent commands via the environment.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
Using `+' instead of `-'
|
||
turns off the attribute instead, with the exception that <B>+a</B>
|
||
may not be used to destroy an array variable. When used in a function,
|
||
makes each
|
||
<I>name</I> local, as with the
|
||
<B>local</B>
|
||
|
||
command. The return value is 0 unless an invalid option is encountered,
|
||
an attempt is made to define a function using
|
||
|
||
<TT>-f foo=bar</TT>,
|
||
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>.
|
||
</DL>
|
||
|
||
<DT><B>dirs [-clpv</B>] [+<I>n</I>] [-<I>n</I>]
|
||
|
||
<DD>
|
||
Without options, displays 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.
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>+</B><I>n</I><DD>
|
||
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.
|
||
<DT><B>-</B><I>n</I><DD>
|
||
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.
|
||
<DT><B>-c</B>
|
||
|
||
<DD>
|
||
Clears the directory stack by deleting all of the entries.
|
||
<DT><B>-l</B>
|
||
|
||
<DD>
|
||
Produces a longer listing; the default listing format uses a
|
||
tilde to denote the home directory.
|
||
<DT><B>-p</B>
|
||
|
||
<DD>
|
||
Print the directory stack with one entry per line.
|
||
<DT><B>-v</B>
|
||
|
||
<DD>
|
||
Print the directory stack with one entry per line,
|
||
prefixing each entry with its index in the stack.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
The return value is 0 unless an
|
||
invalid option is supplied or <I>n</I> indexes beyond the end
|
||
of the directory stack.
|
||
</DL>
|
||
|
||
<DT><B>disown</B> [<B>-ar</B>] [<B>-h</B>] [<I>jobspec</I> ...]<DD>
|
||
Without options, each
|
||
<I>jobspec</I>
|
||
|
||
is removed from the table of active jobs.
|
||
If the <B>-h</B> option is given, each
|
||
<I>jobspec</I>
|
||
|
||
is not removed from the table, but is marked so that
|
||
<FONT SIZE=-1><B>SIGHUP</B>
|
||
|
||
</FONT>
|
||
is not sent to the job if the shell receives a
|
||
<FONT SIZE=-1><B>SIGHUP</B>.
|
||
|
||
</FONT>
|
||
If no
|
||
<I>jobspec</I>
|
||
|
||
is present, and neither the
|
||
<B>-a</B>
|
||
|
||
nor the
|
||
<B>-r</B>
|
||
|
||
option is supplied, the <I>current job</I> is used.
|
||
If no
|
||
<I>jobspec</I>
|
||
|
||
is supplied, the
|
||
<B>-a</B>
|
||
|
||
option means to remove or mark all jobs; the
|
||
<B>-r</B>
|
||
|
||
option without a
|
||
<I>jobspec</I>
|
||
|
||
argument restricts operation to running jobs.
|
||
The return value is 0 unless a
|
||
<I>jobspec</I>
|
||
|
||
does not specify a valid job.
|
||
<DT><B>echo</B> [<B>-neE</B>] [<I>arg</I> ...]<DD>
|
||
Output the <I>arg</I>s, separated by spaces, followed by a newline.
|
||
The return status is always 0.
|
||
If <B>-n</B> is specified, the trailing newline is
|
||
suppressed. If the <B>-e</B> option is given, interpretation of
|
||
the following backslash-escaped characters is enabled. The
|
||
<B>-E</B>
|
||
|
||
option disables the interpretation of these escape characters,
|
||
even on systems where they are interpreted by default.
|
||
The <B>xpg_echo</B> shell option may be used to
|
||
dynamically determine whether or not <B>echo</B> expands these
|
||
escape characters by default.
|
||
<B>echo</B>
|
||
|
||
does not interpret
|
||
<B>--</B>
|
||
|
||
to mean the end of options.
|
||
<B>echo</B>
|
||
|
||
interprets the following escape sequences:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>\a</B>
|
||
|
||
<DD>
|
||
alert (bell)
|
||
<DT><B>\b</B>
|
||
|
||
<DD>
|
||
backspace
|
||
<DT><B>\c</B>
|
||
|
||
<DD>
|
||
suppress trailing newline
|
||
<DT><B>\e</B>
|
||
|
||
<DD>
|
||
an escape character
|
||
<DT><B>\f</B>
|
||
|
||
<DD>
|
||
form feed
|
||
<DT><B>\n</B>
|
||
|
||
<DD>
|
||
new line
|
||
<DT><B>\r</B>
|
||
|
||
<DD>
|
||
carriage return
|
||
<DT><B>\t</B>
|
||
|
||
<DD>
|
||
horizontal tab
|
||
<DT><B>\v</B>
|
||
|
||
<DD>
|
||
vertical tab
|
||
<DT><B>\\</B>
|
||
|
||
<DD>
|
||
backslash
|
||
<DT><B>\</B><I>nnn</I>
|
||
|
||
<DD>
|
||
the eight-bit character whose value is the octal value <I>nnn</I>
|
||
(one to three digits)
|
||
<DT><B>\x</B><I>HH</I>
|
||
|
||
<DD>
|
||
the eight-bit character whose value is the hexadecimal value <I>HH</I>
|
||
(one or two hex digits)
|
||
|
||
</DL></DL>
|
||
|
||
<DT><B>enable</B> [<B>-adnps</B>] [<B>-f</B> <I>filename</I>] [<I>name</I> ...]<DD>
|
||
Enable and disable builtin shell commands.
|
||
Disabling a builtin allows a disk command 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 disk commands.
|
||
If <B>-n</B> is used, each <I>name</I>
|
||
is disabled; otherwise,
|
||
<I>names</I> are enabled. For example, to use the
|
||
<B>test</B>
|
||
|
||
binary found via the
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
instead of the shell builtin version, run
|
||
<TT>enable -n test</TT>.
|
||
|
||
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. The
|
||
<B>-d</B>
|
||
|
||
option will delete a builtin previously loaded with
|
||
<B>-f</B>.
|
||
|
||
If no <I>name</I> arguments are given, or if the
|
||
<B>-p</B>
|
||
|
||
option is supplied, a list of shell builtins is printed.
|
||
With no other option arguments, the list consists of all enabled
|
||
shell builtins.
|
||
If <B>-n</B> is supplied, only disabled builtins are printed.
|
||
If <B>-a</B> is supplied, the list printed includes all builtins, with an
|
||
indication of whether or not each is enabled.
|
||
If <B>-s</B> is supplied, the output is restricted to the POSIX
|
||
<I>special</I> builtins.
|
||
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.
|
||
<DT><B>eval</B> [<I>arg</I> ...]<DD>
|
||
The <I>arg</I>s are read and concatenated together into a single
|
||
command. This command is then read and executed by the shell, and
|
||
its exit status is returned as the value of
|
||
<B>eval</B>.
|
||
|
||
If there are no
|
||
<I>args</I>,
|
||
|
||
or only null arguments,
|
||
<B>eval</B>
|
||
|
||
returns 0.
|
||
<DT><B>exec</B> [<B>-cl</B>] [<B>-a</B> <I>name</I>] [<I>command</I> [<I>arguments</I>]]<DD>
|
||
If
|
||
<I>command</I>
|
||
|
||
is specified, it replaces the shell.
|
||
No new process is created. 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 arg 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. If
|
||
<I>command</I>
|
||
|
||
cannot be executed for some reason, a non-interactive shell exits,
|
||
unless the shell option
|
||
<B>execfail</B>
|
||
|
||
is enabled, in which case it returns failure.
|
||
An interactive shell returns failure if the file cannot be executed.
|
||
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.
|
||
<DT><B>exit</B> [<I>n</I>]<DD>
|
||
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.
|
||
A trap on
|
||
<FONT SIZE=-1><B>EXIT</B>
|
||
|
||
</FONT>
|
||
is executed before the shell terminates.
|
||
<DT>
|
||
<DD>
|
||
<B>export</B> [<B>-fn</B>] [<I>name</I>[=<I>word</I>]] ...
|
||
<DT><B>export -p</B>
|
||
|
||
<DD>
|
||
|
||
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.
|
||
If no
|
||
<I>names</I>
|
||
|
||
are given, or if the
|
||
<B>-p</B>
|
||
|
||
option is supplied, a list
|
||
of all names that are exported in this shell is printed.
|
||
The
|
||
<B>-n</B>
|
||
|
||
option causes the export property to be removed from the
|
||
named variables.
|
||
<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.
|
||
<DT>
|
||
<DD>
|
||
<B>fc</B> [<B>-e</B> <I>ename</I>] [<B>-nlr</B>] [<I>first</I>] [<I>last</I>]
|
||
<DT><B>fc</B> <B>-s</B> [<I>pat</I>=<I>rep</I>] [<I>cmd</I>]<DD>
|
||
|
||
Fix Command. In the first form, a range of commands from
|
||
<I>first</I>
|
||
|
||
to
|
||
<I>last</I>
|
||
|
||
is selected from the history list.
|
||
<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). If
|
||
<I>last</I>
|
||
|
||
is not specified it is set to
|
||
the current command for listing (so that
|
||
|
||
<TT>fc -l -10</TT>
|
||
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>
|
||
The
|
||
<B>-n</B>
|
||
|
||
option suppresses
|
||
the command numbers when listing. The
|
||
<B>-r</B>
|
||
|
||
option reverses the order of
|
||
the commands. If the
|
||
<B>-l</B>
|
||
|
||
option is given,
|
||
the commands are listed on
|
||
standard output. Otherwise, the editor given by
|
||
<I>ename</I>
|
||
|
||
is invoked
|
||
on a file containing those commands. If
|
||
<I>ename</I>
|
||
|
||
is not given, the
|
||
value of the
|
||
<FONT SIZE=-1><B>FCEDIT</B>
|
||
|
||
</FONT>
|
||
variable is used, and
|
||
the value of
|
||
<FONT SIZE=-1><B>EDITOR</B>
|
||
|
||
</FONT>
|
||
if
|
||
<FONT SIZE=-1><B>FCEDIT</B>
|
||
|
||
</FONT>
|
||
is not set. If neither variable is set,
|
||
|
||
<I>vi</I>
|
||
|
||
is used. When editing is complete, the edited commands are
|
||
echoed and executed.
|
||
<P>
|
||
In the second form, <I>command</I> is re-executed after each instance
|
||
of <I>pat</I> is replaced by <I>rep</I>.
|
||
A useful alias to use with this is
|
||
|
||
<TT>r='fc -s'</TT>,
|
||
so that typing
|
||
|
||
<TT>r cc</TT>
|
||
runs the last command beginning with
|
||
|
||
<TT>cc</TT>
|
||
and typing
|
||
|
||
<TT>r</TT>
|
||
re-executes the last command.
|
||
<P>
|
||
If the first form is used, the return value is 0 unless an invalid
|
||
option is encountered or
|
||
<I>first</I>
|
||
|
||
or
|
||
<I>last</I>
|
||
|
||
specify history lines out of range.
|
||
If the
|
||
<B>-e</B>
|
||
|
||
option is supplied, the return value is the value of the last
|
||
command executed or failure if an error occurs with the temporary
|
||
file of commands. If the second form is used, the return status
|
||
is that of the command re-executed, unless
|
||
<I>cmd</I>
|
||
|
||
does not specify a valid history line, in which case
|
||
<B>fc</B>
|
||
|
||
returns failure.
|
||
<DT><B>fg</B> [<I>jobspec</I>]<DD>
|
||
Resume
|
||
<I>jobspec</I>
|
||
|
||
in the foreground, and make it the current job.
|
||
If
|
||
<I>jobspec</I>
|
||
|
||
is not present, the shell's notion of the <I>current job</I> is used.
|
||
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.
|
||
<DT><B>getopts</B> <I>optstring</I> <I>name</I> [<I>args</I>]<DD>
|
||
<B>getopts</B>
|
||
|
||
is used by shell procedures to parse positional parameters.
|
||
<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.
|
||
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
|
||
<FONT SIZE=-1><B>OPTIND</B>.
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>OPTIND</B>
|
||
|
||
</FONT>
|
||
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
|
||
<FONT SIZE=-1><B>OPTARG</B>.
|
||
|
||
</FONT>
|
||
The shell does not reset
|
||
<FONT SIZE=-1><B>OPTIND</B>
|
||
|
||
</FONT>
|
||
automatically; it must be manually reset between multiple
|
||
calls to
|
||
<B>getopts</B>
|
||
|
||
within the same shell invocation if a new set of parameters
|
||
is to be used.
|
||
<P>
|
||
When the end of options is encountered, <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 <B>name</B> is set to ?.
|
||
<P>
|
||
<B>getopts</B>
|
||
|
||
normally parses the positional parameters, but if more arguments are
|
||
given in
|
||
<I>args</I>,
|
||
|
||
<B>getopts</B>
|
||
|
||
parses those instead.
|
||
<P>
|
||
<B>getopts</B>
|
||
|
||
can report errors in two ways. If the first character of
|
||
<I>optstring</I>
|
||
|
||
is a colon,
|
||
<I>silent</I>
|
||
|
||
error reporting is used. In normal operation diagnostic messages
|
||
are printed when invalid options or missing option arguments are
|
||
encountered.
|
||
If the variable
|
||
<FONT SIZE=-1><B>OPTERR</B>
|
||
|
||
</FONT>
|
||
is set to 0, no error messages will be displayed, even if the first
|
||
character of
|
||
<I>optstring</I>
|
||
|
||
is not a colon.
|
||
<P>
|
||
If an invalid option is seen,
|
||
<B>getopts</B>
|
||
|
||
places ? into
|
||
<I>name</I>
|
||
|
||
and, if not silent,
|
||
prints an error message and unsets
|
||
<FONT SIZE=-1><B>OPTARG</B>.
|
||
|
||
</FONT>
|
||
If
|
||
<B>getopts</B>
|
||
|
||
is silent,
|
||
the option character found is placed in
|
||
<FONT SIZE=-1><B>OPTARG</B>
|
||
|
||
</FONT>
|
||
and no diagnostic message is printed.
|
||
<P>
|
||
If a required argument is not found, and
|
||
<B>getopts</B>
|
||
|
||
is not silent,
|
||
a question mark (<B>?</B>) is placed in
|
||
<I>name</I>,
|
||
|
||
<FONT SIZE=-1><B>OPTARG</B>
|
||
|
||
</FONT>
|
||
is unset, and a diagnostic message is printed.
|
||
If
|
||
<B>getopts</B>
|
||
|
||
is silent, then a colon (<B>:</B>) is placed in
|
||
<I>name</I>
|
||
|
||
and
|
||
<FONT SIZE=-1><B>OPTARG</B>
|
||
|
||
</FONT>
|
||
is set to the option character found.
|
||
<P>
|
||
<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.
|
||
<DT><B>hash</B> [<B>-r</B>] [<B>-p</B> <I>filename</I>] [<B>-t</B>] [<I>name</I>]<DD>
|
||
For each
|
||
<I>name</I>,
|
||
|
||
the full file name of the command is determined by searching
|
||
the directories in
|
||
<B>$PATH</B>
|
||
|
||
and remembered.
|
||
If the
|
||
<B>-p</B>
|
||
|
||
option is supplied, no path search is performed, and
|
||
<I>filename</I>
|
||
|
||
is used as the full file name of the command.
|
||
The
|
||
<B>-r</B>
|
||
|
||
option causes the shell to forget all
|
||
remembered locations.
|
||
If the
|
||
<B>-t</B>
|
||
|
||
option is supplied, the full pathname to which each <I>name</I> corresponds
|
||
is printed. If multiple <I>name</I> arguments are supplied with <B>-t</B>,
|
||
the <I>name</I> is printed before the hashed full pathname.
|
||
If no arguments are given, information about remembered commands is printed.
|
||
The return status is true unless a
|
||
<I>name</I>
|
||
|
||
is not found or an invalid option is supplied.
|
||
<DT><B>help</B> [<B>-s</B>] [<I>pattern</I>]<DD>
|
||
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>;
|
||
|
||
otherwise help for all the builtins and shell control structures
|
||
is printed.
|
||
The <B>-s</B> option restricts the information displayed to a short
|
||
usage synopsis.
|
||
The return status is 0 unless no command matches
|
||
<I>pattern</I>.
|
||
|
||
<DT>
|
||
<DD>
|
||
<B>history [</B><I>n</I>]
|
||
<DT><B>history</B> <B>-c</B><DD>
|
||
<DT><B>history -d</B> <I>offset</I><DD>
|
||
<DT><B>history</B> <B>-anrw</B> [<I>filename</I>]<DD>
|
||
<DT><B>history</B> <B>-p</B> <I>arg</I> [<I>arg ...</I>]<DD>
|
||
<DT><B>history</B> <B>-s</B> <I>arg</I> [<I>arg ...</I>]<DD>
|
||
|
||
With no options, display the command
|
||
history list with line numbers. Lines listed
|
||
with a
|
||
<B>*</B>
|
||
|
||
have been modified. An argument of
|
||
<I>n</I>
|
||
|
||
lists only the last
|
||
<I>n</I>
|
||
|
||
lines. If <I>filename</I> is supplied, it is used as the
|
||
name of the history file; if not, the value of
|
||
<FONT SIZE=-1><B>HISTFILE</B>
|
||
|
||
</FONT>
|
||
is used. Options, if supplied, have the following meanings:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-c</B>
|
||
|
||
<DD>
|
||
Clear the history list by deleting all the entries.
|
||
<DT><B>-d</B> <I>offset</I><DD>
|
||
Delete the history entry at position <I>offset</I>.
|
||
<DT><B>-a</B>
|
||
|
||
<DD>
|
||
Append the ``new'' history lines (history lines entered since the
|
||
beginning of the current <B>bash</B> session) to the history file.
|
||
<DT><B>-n</B>
|
||
|
||
<DD>
|
||
Read the history lines not already read from the history
|
||
file into the current history list. These are lines
|
||
appended to the history file since the beginning of the
|
||
current <B>bash</B> session.
|
||
<DT><B>-r</B>
|
||
|
||
<DD>
|
||
Read the contents of the history file
|
||
and use them as the current history.
|
||
<DT><B>-w</B>
|
||
|
||
<DD>
|
||
Write the current history to the history file, overwriting the
|
||
history file's contents.
|
||
<DT><B>-p</B>
|
||
|
||
<DD>
|
||
Perform history substitution on the following <I>args</I> and display
|
||
the result on the standard output.
|
||
Does not store the results in the history list.
|
||
Each <I>arg</I> must be quoted to disable normal history expansion.
|
||
<DT><B>-s</B>
|
||
|
||
<DD>
|
||
Store the
|
||
<I>args</I>
|
||
|
||
in the history list as a single entry. The last command in the
|
||
history list is removed before the
|
||
<I>args</I>
|
||
|
||
are added.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
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> is supplied as an argument to <B>-d</B>, or the
|
||
history expansion supplied as an argument to <B>-p</B> fails.
|
||
</DL>
|
||
|
||
<DT>
|
||
<DD>
|
||
<B>jobs</B> [<B>-lnprs</B>] [ <I>jobspec</I> ... ]
|
||
<DT><B>jobs</B> <B>-x</B> <I>command</I> [ <I>args</I> ... ]<DD>
|
||
|
||
The first form lists the active jobs. The options have the following
|
||
meanings:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-l</B>
|
||
|
||
<DD>
|
||
List process IDs
|
||
in addition to the normal information.
|
||
<DT><B>-p</B>
|
||
|
||
<DD>
|
||
List only the process ID of the job's process group
|
||
leader.
|
||
<DT><B>-n</B>
|
||
|
||
<DD>
|
||
Display information only about jobs that have changed status since
|
||
the user was last notified of their status.
|
||
<DT><B>-r</B>
|
||
|
||
<DD>
|
||
Restrict output to running jobs.
|
||
<DT><B>-s</B>
|
||
|
||
<DD>
|
||
Restrict output to stopped jobs.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
If
|
||
<I>jobspec</I>
|
||
|
||
is given, output is restricted 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>
|
||
|
||
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.
|
||
</DL>
|
||
|
||
<DT>
|
||
<DD>
|
||
<B>kill</B> [<B>-s</B> <I>sigspec</I> | <B>-n</B> <I>signum</I> | <B>-</B><I>sigspec</I>] [<I>pid</I> | <I>jobspec</I>] ...
|
||
<DT><B>kill</B> <B>-l</B> [<I>sigspec</I> | <I>exit_status</I>]<DD>
|
||
|
||
Send the signal named by
|
||
<I>sigspec</I>
|
||
|
||
or
|
||
<I>signum</I>
|
||
|
||
to the processes named by
|
||
<I>pid</I>
|
||
|
||
or
|
||
<I>jobspec</I>.
|
||
|
||
<I>sigspec</I>
|
||
|
||
is either a signal name such as
|
||
<FONT SIZE=-1><B>SIGKILL</B>
|
||
|
||
</FONT>
|
||
or a signal number;
|
||
<I>signum</I>
|
||
|
||
is a signal number. If
|
||
<I>sigspec</I>
|
||
|
||
is a signal name, the name may be
|
||
given with or without the
|
||
<FONT SIZE=-1><B>SIG</B>
|
||
|
||
</FONT>
|
||
prefix.
|
||
If
|
||
<I>sigspec</I>
|
||
|
||
is not present, then
|
||
<FONT SIZE=-1><B>SIGTERM</B>
|
||
|
||
</FONT>
|
||
is assumed.
|
||
An argument of
|
||
<B>-l</B>
|
||
|
||
lists the signal names.
|
||
If any arguments are supplied when
|
||
<B>-l</B>
|
||
|
||
is given, the names of the signals corresponding to the arguments are
|
||
listed, 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.
|
||
<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.
|
||
<DT><B>let</B> <I>arg</I> [<I>arg</I> ...]<DD>
|
||
Each
|
||
<I>arg</I>
|
||
|
||
is an arithmetic expression to be evaluated (see
|
||
<FONT SIZE=-1><B>ARITHMETIC</B>EVALUATION<B>).</B>
|
||
|
||
</FONT>
|
||
If the last
|
||
<I>arg</I>
|
||
|
||
evaluates to 0,
|
||
<B>let</B>
|
||
|
||
returns 1; 0 is returned otherwise.
|
||
<DT><B>local</B> [<I>option</I>] [<I>name</I>[=<I>value</I>] ...]<DD>
|
||
For each argument, a local variable named
|
||
<I>name </I>
|
||
|
||
is created, and assigned
|
||
<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.
|
||
With no operands,
|
||
<B>local</B>
|
||
|
||
writes a list of local variables to the standard output. It is
|
||
an error to use
|
||
<B>local</B>
|
||
|
||
when not within a function. 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.
|
||
<DT><B>logout</B>
|
||
|
||
<DD>
|
||
Exit a login shell.
|
||
<DT><B>popd</B> [-<B>n</B>] [+<I>n</I>] [-<I>n</I>]<DD>
|
||
Removes entries from the directory stack. With no arguments,
|
||
removes the top directory from the stack, and performs a
|
||
<B>cd</B>
|
||
|
||
to the new top directory.
|
||
Arguments, if supplied, have the following meanings:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>+</B><I>n</I><DD>
|
||
Removes the <I>n</I>th entry counting from the left of the list
|
||
shown by
|
||
<B>dirs</B>,
|
||
|
||
starting with zero. For example:
|
||
|
||
<TT>popd +0</TT>
|
||
removes the first directory,
|
||
|
||
<TT>popd +1</TT>
|
||
the second.
|
||
<DT><B>-</B><I>n</I><DD>
|
||
Removes the <I>n</I>th entry counting from the right of the list
|
||
shown by
|
||
<B>dirs</B>,
|
||
|
||
starting with zero. For example:
|
||
|
||
<TT>popd -0</TT>
|
||
removes the last directory,
|
||
|
||
<TT>popd -1</TT>
|
||
the next to last.
|
||
<DT><B>-n</B>
|
||
|
||
<DD>
|
||
Suppresses the normal change of directory when removing directories
|
||
from the stack, so that only the stack is manipulated.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
If the
|
||
<B>popd</B>
|
||
|
||
command is successful, a
|
||
<B>dirs</B>
|
||
|
||
is performed as well, and the return status is 0.
|
||
<B>popd</B>
|
||
|
||
returns false if an invalid option is encountered, the directory stack
|
||
is empty, a non-existent directory stack entry is specified, or the
|
||
directory change fails.
|
||
</DL>
|
||
|
||
<DT><B>printf</B> <I>format</I> [<I>arguments</I>]<DD>
|
||
Write the formatted <I>arguments</I> to the standard output under the
|
||
control of the <I>format</I>.
|
||
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>(1) formats, <B>%b</B> causes
|
||
<B>printf</B> to expand backslash escape sequences in the corresponding
|
||
<I>argument</I>, and <B>%q</B> causes <B>printf</B> to output the corresponding
|
||
<I>argument</I> in a format that can be reused as shell input.
|
||
<P>
|
||
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. The return value is zero on success,
|
||
non-zero on failure.
|
||
<DT>
|
||
<DD>
|
||
<B>pushd</B> [<B>-n</B>] [<I>dir</I>]
|
||
<DT><B>pushd</B> [<B>-n</B>] [+<I>n</I>] [-<I>n</I>]<DD>
|
||
|
||
Adds a directory to the top of the directory stack, or rotates
|
||
the stack, making the new top of the stack the current working
|
||
directory. With no arguments, exchanges the top two directories
|
||
and returns 0, unless the directory stack is empty.
|
||
Arguments, if supplied, have the following meanings:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>+</B><I>n</I><DD>
|
||
Rotates 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.
|
||
<DT><B>-</B><I>n</I><DD>
|
||
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.
|
||
<DT><B>-n</B>
|
||
|
||
<DD>
|
||
Suppresses the normal change of directory when adding directories
|
||
to the stack, so that only the stack is manipulated.
|
||
<DT><I>dir</I>
|
||
|
||
<DD>
|
||
Adds
|
||
<I>dir</I>
|
||
|
||
to the directory stack at the top, making it the
|
||
new current working directory.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
If the
|
||
<B>pushd</B>
|
||
|
||
command is successful, a
|
||
<B>dirs</B>
|
||
|
||
is performed as well.
|
||
If the first form is used,
|
||
<B>pushd</B>
|
||
|
||
returns 0 unless the cd to
|
||
<I>dir</I>
|
||
|
||
fails. With the second form,
|
||
<B>pushd</B>
|
||
|
||
returns 0 unless the directory stack is empty,
|
||
a non-existent directory stack element is specified,
|
||
or the directory change to the specified new current directory
|
||
fails.
|
||
</DL>
|
||
|
||
<DT><B>pwd</B> [<B>-LP</B>]<DD>
|
||
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.
|
||
<DT><B>read</B> [<B>-ers</B>] [<B>-t</B> <I>timeout</I>] [<B>-a</B> <I>aname</I>] [<B>-p</B> <I>prompt</I>] [<B>-n</B> <I>nchars</I>] [<B>-d</B> <I>delim</I>] [<I>name</I> ...]<DD>
|
||
One line is read from the standard input, and the first word
|
||
is assigned to the first
|
||
<I>name</I>,
|
||
|
||
the second word to the second
|
||
<I>name</I>,
|
||
|
||
and so on, with leftover words and their intervening separators assigned
|
||
to the last
|
||
<I>name</I>.
|
||
|
||
If there are fewer words read from the standard input than names,
|
||
the remaining names are assigned empty values.
|
||
The characters in
|
||
<FONT SIZE=-1><B>IFS</B>
|
||
|
||
</FONT>
|
||
are used to split the line into words.
|
||
The backslash character (<B>\</B>) may be used to remove any special
|
||
meaning for the next character read and for line continuation.
|
||
Options, if supplied, have the following meanings:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-a </B><I>aname</I>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>-d </B><I>delim</I>
|
||
|
||
<DD>
|
||
The first character of <I>delim</I> is used to terminate the input line,
|
||
rather than newline.
|
||
<DT><B>-e</B>
|
||
|
||
<DD>
|
||
If the standard input
|
||
is coming from a terminal,
|
||
<B>readline</B>
|
||
|
||
(see
|
||
<FONT SIZE=-1><B>READLINE</B>
|
||
|
||
</FONT>
|
||
above) is used to obtain the line.
|
||
<DT><B>-n </B><I>nchars</I>
|
||
|
||
<DD>
|
||
<B>read</B> returns after reading <I>nchars</I> characters rather than
|
||
waiting for a complete line of input.
|
||
<DT><B>-p </B><I>prompt</I>
|
||
|
||
<DD>
|
||
Display <I>prompt</I> on standard error, without a
|
||
trailing newline, before attempting to read any input. The prompt
|
||
is displayed only if input is coming from a terminal.
|
||
<DT><B>-r</B>
|
||
|
||
<DD>
|
||
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 be used as a line
|
||
continuation.
|
||
<DT><B>-s</B>
|
||
|
||
<DD>
|
||
Silent mode. If input is coming from a terminal, characters are
|
||
not echoed.
|
||
<DT><B>-t </B><I>timeout</I>
|
||
|
||
<DD>
|
||
Cause <B>read</B> to time out and return failure if a complete line of
|
||
input is not read within <I>timeout</I> seconds.
|
||
This option has no effect if <B>read</B> is not reading input from the
|
||
terminal or a pipe.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
If no
|
||
<I>names</I>
|
||
|
||
are supplied, the line read is assigned to the variable
|
||
<FONT SIZE=-1><B>REPLY</B>.
|
||
|
||
</FONT>
|
||
The return code is zero, unless end-of-file is encountered or <B>read</B>
|
||
times out.
|
||
</DL>
|
||
|
||
<DT><B>readonly</B> [<B>-apf</B>] [<I>name</I> ...]<DD>
|
||
|
||
The given
|
||
<I>names</I> are marked readonly; the values of these
|
||
<I>names</I>
|
||
|
||
may not be changed by subsequent assignment.
|
||
If the
|
||
<B>-f</B>
|
||
|
||
option is supplied, the functions corresponding to the
|
||
<I>names</I> are so
|
||
marked.
|
||
The
|
||
<B>-a</B>
|
||
|
||
option restricts the variables to arrays.
|
||
If no
|
||
<I>name</I>
|
||
|
||
arguments are given, or if the
|
||
<B>-p</B>
|
||
|
||
option is supplied, a list of all readonly names is printed.
|
||
The
|
||
<B>-p</B>
|
||
|
||
option causes output to be displayed in a format that
|
||
may be reused as input.
|
||
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.
|
||
<DT><B>return</B> [<I>n</I>]<DD>
|
||
Causes a function to exit with the return value specified by
|
||
<I>n</I>.
|
||
|
||
If
|
||
<I>n</I>
|
||
|
||
is omitted, the return status is that of the last command
|
||
executed in the function body. If used outside a function,
|
||
but during execution of a script 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 used outside a
|
||
function and not during execution of a script by <B>.</B>,
|
||
the return status is false.
|
||
<DT><B>set</B> [<B>--abefhkmnptuvxBCHP</B>] [<B>-o</B> <I>option</I>] [<I>arg</I> ...]<DD>
|
||
Without options, the name and value of each shell variable are displayed
|
||
in a format that can be reused as input.
|
||
The output is sorted according to the current locale.
|
||
When options are specified, they set or unset shell attributes.
|
||
Any arguments remaining after the options are processed are treated
|
||
as values for the positional parameters and are assigned, in order, to
|
||
<B>$1</B>,
|
||
|
||
<B>$2</B>,
|
||
|
||
<B>...</B>
|
||
|
||
<B>$</B><I>n</I>.
|
||
|
||
Options, if specified, have the following meanings:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-a</B>
|
||
|
||
<DD>
|
||
Automatically mark variables and functions which are modified or created
|
||
for export to the environment of subsequent commands.
|
||
<DT><B>-b</B>
|
||
|
||
<DD>
|
||
Report the status of terminated background jobs
|
||
immediately, rather than before the next primary prompt. This is
|
||
effective only when job control is enabled.
|
||
<DT><B>-e</B>
|
||
|
||
<DD>
|
||
Exit immediately if a <I>simple command</I> (see
|
||
<FONT SIZE=-1><B>SHELL GRAMMAR</B>
|
||
|
||
</FONT>
|
||
above) exits with a non-zero status. The shell does not exit if the
|
||
command that fails is part of an
|
||
<I>until</I>
|
||
|
||
or
|
||
<I>while</I>
|
||
|
||
loop,
|
||
part of an
|
||
<I>if</I>
|
||
|
||
statement, part of a
|
||
<B>&&</B>
|
||
|
||
or
|
||
<B>||</B>
|
||
|
||
list, or if the command's return value is
|
||
being inverted via
|
||
<B>!</B>.
|
||
|
||
A trap on <B>ERR</B>, if set, is executed before the shell exits.
|
||
<DT><B>-f</B>
|
||
|
||
<DD>
|
||
Disable pathname expansion.
|
||
<DT><B>-h</B>
|
||
|
||
<DD>
|
||
Remember the location of commands as they are looked up for execution.
|
||
This is enabled by default.
|
||
<DT><B>-k</B>
|
||
|
||
<DD>
|
||
All arguments in the form of assignment statements
|
||
are placed in the environment for a command, not just
|
||
those that precede the command name.
|
||
<DT><B>-m</B>
|
||
|
||
<DD>
|
||
Monitor mode. Job control is enabled. This option is on
|
||
by default for interactive shells on systems that support
|
||
it (see
|
||
<FONT SIZE=-1><B>JOB CONTROL</B>
|
||
|
||
</FONT>
|
||
above). Background processes run in a separate process
|
||
group and a line containing their exit status is printed
|
||
upon their completion.
|
||
<DT><B>-n</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>-o </B><I>option-name</I>
|
||
|
||
<DD>
|
||
The <I>option-name</I> can be one of the following:
|
||
<DL COMPACT><DT><DD>
|
||
<DL COMPACT>
|
||
<DT><B>allexport</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-a</B>.
|
||
|
||
<DT><B>braceexpand</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-B</B>.
|
||
|
||
<DT><B>emacs</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>errexit</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-e</B>.
|
||
|
||
<DT><B>hashall</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-h</B>.
|
||
|
||
<DT><B>histexpand</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-H</B>.
|
||
|
||
<DT><B>history</B>
|
||
|
||
<DD>
|
||
Enable command history, as described above under
|
||
<FONT SIZE=-1><B>HISTORY</B>.
|
||
|
||
</FONT>
|
||
This option is on by default in interactive shells.
|
||
<DT><B>ignoreeof</B>
|
||
|
||
<DD>
|
||
The effect is as if the shell command
|
||
<TT>IGNOREEOF=10</TT>
|
||
|
||
had been executed
|
||
(see
|
||
<B>Shell Variables</B>
|
||
|
||
above).
|
||
<DT><B>keyword</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-k</B>.
|
||
|
||
<DT><B>monitor</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-m</B>.
|
||
|
||
<DT><B>noclobber</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-C</B>.
|
||
|
||
<DT><B>noexec</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-n</B>.
|
||
|
||
<DT><B>noglob</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-f</B>.
|
||
|
||
<B>nolog</B>
|
||
|
||
Currently ignored.
|
||
<DT><B>notify</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-b</B>.
|
||
|
||
<DT><B>nounset</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-u</B>.
|
||
|
||
<DT><B>onecmd</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-t</B>.
|
||
|
||
<DT><B>physical</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-P</B>.
|
||
|
||
<DT><B>posix</B>
|
||
|
||
<DD>
|
||
Change the behavior of
|
||
<B>bash</B>
|
||
|
||
where the default operation differs
|
||
from the POSIX 1003.2 standard to match the standard (<I>posix mode</I>).
|
||
<DT><B>privileged</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-p</B>.
|
||
|
||
<DT><B>verbose</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-v</B>.
|
||
|
||
<DT><B>vi</B>
|
||
|
||
<DD>
|
||
Use a vi-style command line editing interface.
|
||
<DT><B>xtrace</B>
|
||
|
||
<DD>
|
||
Same as
|
||
<B>-x</B>.
|
||
|
||
<P>
|
||
</DL>
|
||
<P>
|
||
|
||
If
|
||
<B>-o</B>
|
||
|
||
is supplied with no <I>option-name</I>, the values of the current options are
|
||
printed.
|
||
If
|
||
<B>+o</B>
|
||
|
||
is supplied with no <I>option-name</I>, a series of
|
||
<B>set</B>
|
||
|
||
commands to recreate the current option settings is displayed on
|
||
the standard output.
|
||
</DL>
|
||
|
||
<DT><B>-p</B>
|
||
|
||
<DD>
|
||
Turn on
|
||
<I>privileged</I>
|
||
|
||
mode. In this mode, the
|
||
<FONT SIZE=-1><B>$ENV</B>
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>$BASH_ENV</B>
|
||
|
||
</FONT>
|
||
files are not processed, shell functions are not inherited from the
|
||
environment, and the
|
||
<FONT SIZE=-1><B>SHELLOPTS</B>
|
||
|
||
</FONT>
|
||
variable, if it appears in the environment, is ignored.
|
||
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.
|
||
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.
|
||
<DT><B>-t</B>
|
||
|
||
<DD>
|
||
Exit after reading and executing one command.
|
||
<DT><B>-u</B>
|
||
|
||
<DD>
|
||
Treat unset variables as an error when performing
|
||
parameter expansion. If expansion is attempted on an
|
||
unset variable, the shell prints an error message, and,
|
||
if not interactive, exits with a non-zero status.
|
||
<DT><B>-v</B>
|
||
|
||
<DD>
|
||
Print shell input lines as they are read.
|
||
<DT><B>-x</B>
|
||
|
||
<DD>
|
||
After expanding each <I>simple command</I>,
|
||
display the expanded value of
|
||
<FONT SIZE=-1><B>PS4</B>,
|
||
|
||
</FONT>
|
||
followed by the command and its expanded arguments.
|
||
<DT><B>-B</B>
|
||
|
||
<DD>
|
||
The shell performs brace expansion (see
|
||
<B>Brace Expansion</B>
|
||
|
||
above). This is on by default.
|
||
<DT><B>-C</B>
|
||
|
||
<DD>
|
||
If set,
|
||
<B>bash</B>
|
||
|
||
does not overwrite an existing file with the
|
||
<B>></B>,
|
||
|
||
<B>>&</B>,
|
||
|
||
and
|
||
<B><></B>
|
||
|
||
redirection operators. This may be overridden when
|
||
creating output files by using the redirection operator
|
||
<B>>|</B>
|
||
|
||
instead of
|
||
<B>></B>.
|
||
|
||
<DT><B>-H</B>
|
||
|
||
<DD>
|
||
Enable
|
||
<B>!</B>
|
||
|
||
style history substitution. This option is on by
|
||
default when the shell is interactive.
|
||
<DT><B>-P</B>
|
||
|
||
<DD>
|
||
If set, the shell does not follow 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.
|
||
<DT><B>--</B>
|
||
|
||
<DD>
|
||
If no arguments follow this option, then the positional parameters are
|
||
unset. Otherwise, the positional parameters are set to the
|
||
<I>arg</I>s, even if some of them begin with a
|
||
<B>-</B>.
|
||
|
||
<DT><B>-</B>
|
||
|
||
<DD>
|
||
Signal the end of options, cause all remaining <I>arg</I>s to be
|
||
assigned 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.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
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 true unless an invalid option is encountered.
|
||
</DL>
|
||
|
||
<DT><B>shift</B> [<I>n</I>]<DD>
|
||
The positional parameters from <I>n</I>+1 ... are renamed to
|
||
<B>$1</B>
|
||
|
||
<B>....</B>
|
||
|
||
Parameters represented by the numbers <B>$#</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.
|
||
<DT><B>shopt</B> [<B>-pqsu</B>] [<B>-o</B>] [<I>optname</I> ...]<DD>
|
||
Toggle the values of variables controlling optional shell behavior.
|
||
With no options, or with the
|
||
<B>-p</B>
|
||
|
||
option, a list of all settable options is displayed, with
|
||
an indication of whether or not each is set.
|
||
The <B>-p</B> option causes output to be displayed in a form that
|
||
may be reused as input.
|
||
Other options have the following meanings:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-s</B>
|
||
|
||
<DD>
|
||
Enable (set) each <I>optname</I>.
|
||
<DT><B>-u</B>
|
||
|
||
<DD>
|
||
Disable (unset) each <I>optname</I>.
|
||
<DT><B>-q</B>
|
||
|
||
<DD>
|
||
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 given with
|
||
<B>-q</B>,
|
||
|
||
the return status is zero if all <I>optnames</I> are enabled; non-zero
|
||
otherwise.
|
||
<DT><B>-o</B>
|
||
|
||
<DD>
|
||
Restricts the values of <I>optname</I> to be those defined for the
|
||
<B>-o</B>
|
||
|
||
option to the
|
||
<B>set</B>
|
||
|
||
builtin.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
If either
|
||
<B>-s</B>
|
||
|
||
or
|
||
<B>-u</B>
|
||
|
||
is used with no <I>optname</I> arguments, the display is limited to
|
||
those options which are set or unset, respectively.
|
||
Unless otherwise noted, the <B>shopt</B> options are disabled (unset)
|
||
by default.
|
||
<P>
|
||
|
||
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>
|
||
|
||
The list of <B>shopt</B> options is:
|
||
<P>
|
||
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><B>cdable_vars</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>cdspell</B>
|
||
|
||
<DD>
|
||
If set, minor errors in the spelling of a directory component in a
|
||
<B>cd</B>
|
||
|
||
command will be corrected.
|
||
The errors checked for are transposed characters,
|
||
a missing character, and one character too many.
|
||
If a correction is found, the corrected file name is printed,
|
||
and the command proceeds.
|
||
This option is only used by interactive shells.
|
||
<DT><B>checkhash</B>
|
||
|
||
<DD>
|
||
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, a normal path search is performed.
|
||
<DT><B>checkwinsize</B>
|
||
|
||
<DD>
|
||
If set, <B>bash</B> checks the window size after each command
|
||
and, if necessary, updates the values of
|
||
<FONT SIZE=-1><B>LINES</B>
|
||
|
||
</FONT>
|
||
and
|
||
<FONT SIZE=-1><B>COLUMNS</B>.
|
||
|
||
</FONT>
|
||
<DT><B>cmdhist</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>dotglob</B>
|
||
|
||
<DD>
|
||
If set,
|
||
<B>bash</B>
|
||
|
||
includes filenames beginning with a `.' in the results of pathname
|
||
expansion.
|
||
<DT><B>execfail</B>
|
||
|
||
<DD>
|
||
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 command. An interactive shell does not exit if
|
||
<B>exec</B>
|
||
|
||
fails.
|
||
<DT><B>expand_aliases</B>
|
||
|
||
<DD>
|
||
If set, aliases are expanded as described above under
|
||
<FONT SIZE=-1><B>ALIASES</B>.
|
||
|
||
</FONT>
|
||
This option is enabled by default for interactive shells.
|
||
<DT><B>extglob</B>
|
||
|
||
<DD>
|
||
If set, the extended pattern matching features described above under
|
||
<B>Pathname Expansion</B> are enabled.
|
||
<DT><B>histappend</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>histreedit</B>
|
||
|
||
<DD>
|
||
If set, and
|
||
<B>readline</B>
|
||
|
||
is being used, a user is given the opportunity to re-edit a
|
||
failed history substitution.
|
||
<DT><B>histverify</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>hostcomplete</B>
|
||
|
||
<DD>
|
||
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
|
||
<FONT SIZE=-1><B>READLINE</B>
|
||
|
||
</FONT>
|
||
above).
|
||
This is enabled by default.
|
||
<DT><B>huponexit</B>
|
||
|
||
<DD>
|
||
If set, <B>bash</B> will send
|
||
<FONT SIZE=-1><B>SIGHUP</B>
|
||
|
||
</FONT>
|
||
to all jobs when an interactive login shell exits.
|
||
<DT><B>interactive_comments</B>
|
||
|
||
<DD>
|
||
If set, allow a word beginning with
|
||
<B>#</B>
|
||
|
||
to cause that word and all remaining characters on that
|
||
line to be ignored in an interactive shell (see
|
||
<FONT SIZE=-1><B>COMMENTS</B>
|
||
|
||
</FONT>
|
||
above). This option is enabled by default.
|
||
<DT><B>lithist</B>
|
||
|
||
<DD>
|
||
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.
|
||
<DT><B>login_shell</B>
|
||
|
||
<DD>
|
||
The shell sets this option if it is started as a login shell (see
|
||
<FONT SIZE=-1><B>INVOCATION</B>
|
||
|
||
</FONT>
|
||
above).
|
||
The value may not be changed.
|
||
<DT><B>mailwarn</B>
|
||
|
||
<DD>
|
||
If set, and a file that <B>bash</B> is checking for mail has been
|
||
accessed since the last time it was checked, the message ``The mail in
|
||
<I>mailfile</I> has been read'' is displayed.
|
||
<DT><B>no_empty_cmd_completion</B>
|
||
|
||
<DD>
|
||
If set, and
|
||
<B>readline</B>
|
||
|
||
is being used,
|
||
<B>bash</B>
|
||
|
||
will not attempt to search the <B>PATH</B> for possible completions when
|
||
completion is attempted on an empty line.
|
||
<DT><B>nocaseglob</B>
|
||
|
||
<DD>
|
||
If set,
|
||
<B>bash</B>
|
||
|
||
matches filenames in a case-insensitive fashion when performing pathname
|
||
expansion (see
|
||
<B>Pathname Expansion</B>
|
||
|
||
above).
|
||
<DT><B>nullglob</B>
|
||
|
||
<DD>
|
||
If set,
|
||
<B>bash</B>
|
||
|
||
allows patterns which match no
|
||
files (see
|
||
<B>Pathname Expansion</B>
|
||
|
||
above)
|
||
to expand to a null string, rather than themselves.
|
||
<DT><B>progcomp</B>
|
||
|
||
<DD>
|
||
If set, the programmable completion facilities (see
|
||
<B>Programmable Completion</B> above) are enabled.
|
||
This option is enabled by default.
|
||
<DT><B>promptvars</B>
|
||
|
||
<DD>
|
||
If set, prompt strings undergo variable and parameter expansion after
|
||
being expanded as described in
|
||
<FONT SIZE=-1><B>PROMPTING</B>
|
||
|
||
</FONT>
|
||
above. This option is enabled by default.
|
||
<DT><B>restricted_shell</B>
|
||
|
||
<DD>
|
||
The shell sets this option if it is started in restricted mode (see
|
||
<FONT SIZE=-1><B>RESTRICTED SHELL</B>
|
||
|
||
</FONT>
|
||
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.
|
||
<DT><B>shift_verbose</B>
|
||
|
||
<DD>
|
||
If set, the
|
||
<B>shift</B>
|
||
|
||
builtin prints an error message when the shift count exceeds the
|
||
number of positional parameters.
|
||
<DT><B>sourcepath</B>
|
||
|
||
<DD>
|
||
If set, the
|
||
<B>source</B> (<B>.</B>) builtin uses the value of
|
||
<FONT SIZE=-1><B>PATH</B>
|
||
|
||
</FONT>
|
||
to find the directory containing the file supplied as an argument.
|
||
This option is enabled by default.
|
||
<DT><B>xpg_echo</B>
|
||
|
||
<DD>
|
||
If set, the <B>echo</B> builtin expands backslash-escape sequences
|
||
by default.
|
||
</DL></DL>
|
||
|
||
<DT><B>suspend</B> [<B>-f</B>]<DD>
|
||
Suspend the execution of this shell until it receives a
|
||
<FONT SIZE=-1><B>SIGCONT</B>
|
||
|
||
</FONT>
|
||
signal. The
|
||
<B>-f</B>
|
||
|
||
option says not to complain if this is
|
||
a login shell; just suspend anyway. The return status is 0 unless
|
||
the shell is a login shell and
|
||
<B>-f</B>
|
||
|
||
is not supplied, or if job control is not enabled.
|
||
<DT>
|
||
<DD>
|
||
<B>test</B> <I>expr</I>
|
||
<DT><B>[</B> <I>expr</I> <B>]</B><DD>
|
||
Return a status of 0 or 1 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
|
||
<FONT SIZE=-1><B>CONDITIONAL</B>EXPRESSIONS<B>.</B>
|
||
|
||
</FONT>
|
||
<P>
|
||
|
||
|
||
Expressions may be combined using the following operators, listed
|
||
in decreasing order of precedence.
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>! </B><I>expr</I>
|
||
|
||
<DD>
|
||
True if
|
||
<I>expr</I>
|
||
|
||
is false.
|
||
<DT><B>( </B><I>expr</I> )
|
||
|
||
<DD>
|
||
Returns the value of <I>expr</I>.
|
||
This may be used to override the normal precedence of operators.
|
||
<DT><I>expr1</I> -<B>a</B> <I>expr2</I><DD>
|
||
True if both
|
||
<I>expr1</I>
|
||
|
||
and
|
||
<I>expr2</I>
|
||
|
||
are true.
|
||
<DT><I>expr1</I> -<B>o</B> <I>expr2</I><DD>
|
||
True if either
|
||
<I>expr1</I>
|
||
|
||
or
|
||
<I>expr2</I>
|
||
|
||
is true.
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
<B>test</B> and <B>[</B> evaluate conditional
|
||
expressions using a set of rules based on the number of arguments.
|
||
<P>
|
||
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT>0 arguments<DD>
|
||
The expression is false.
|
||
<DT>1 argument<DD>
|
||
The expression is true if and only if the argument is not null.
|
||
<DT>2 arguments<DD>
|
||
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
|
||
<FONT SIZE=-1><B>CONDITIONAL</B>EXPRESSIONS<B>,</B>
|
||
|
||
</FONT>
|
||
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.
|
||
<DT>3 arguments<DD>
|
||
If the second argument is one of the binary conditional operators listed above
|
||
under
|
||
<FONT SIZE=-1><B>CONDITIONAL</B>EXPRESSIONS<B>,</B>
|
||
|
||
</FONT>
|
||
the result of the expression is the result of the binary test using
|
||
the first and third arguments as operands.
|
||
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.
|
||
The <B>-a</B> and <B>-o</B> operators are considered binary operators
|
||
in this case.
|
||
<DT>4 arguments<DD>
|
||
If the first argument is <B>!</B>, the result is the negation of
|
||
the three-argument expression composed of the remaining arguments.
|
||
Otherwise, the expression is parsed and evaluated according to
|
||
precedence using the rules listed above.
|
||
<DT>5 or more arguments<DD>
|
||
The expression is parsed and evaluated according to precedence
|
||
using the rules listed above.
|
||
</DL></DL>
|
||
|
||
|
||
<DT><B>times</B>
|
||
|
||
<DD>
|
||
Print the accumulated user and system times for the shell and
|
||
for processes run from the shell. The return status is 0.
|
||
<DT><B>trap</B> [<B>-lp</B>] [<I>arg</I>] [<I>sigspec</I> ...]<DD>
|
||
The command
|
||
<I>arg</I>
|
||
|
||
is to be read and executed when the shell receives
|
||
signal(s)
|
||
<I>sigspec</I>.
|
||
|
||
If
|
||
<I>arg</I>
|
||
|
||
is absent or
|
||
<B>-</B>,
|
||
|
||
all specified signals are
|
||
reset to their original values (the values they had
|
||
upon entrance to the shell).
|
||
If
|
||
<I>arg</I>
|
||
|
||
is the null string the signal specified by each
|
||
<I>sigspec</I>
|
||
|
||
is ignored by the shell and by the commands it invokes.
|
||
If
|
||
<I>arg</I>
|
||
|
||
is not present and
|
||
<B>-p</B>
|
||
|
||
has been supplied, then the trap commands associated with each
|
||
<I>sigspec</I>
|
||
|
||
are displayed.
|
||
If no arguments are supplied or if only
|
||
<B>-p</B>
|
||
|
||
is given,
|
||
<B>trap</B>
|
||
|
||
prints the list of commands associated with each signal number.
|
||
Each
|
||
<I>sigspec</I>
|
||
|
||
is either
|
||
a signal name defined in <<I>signal.h</I>>, or a signal number.
|
||
If a
|
||
<I>sigspec</I>
|
||
|
||
is
|
||
<FONT SIZE=-1><B>EXIT</B>
|
||
|
||
</FONT>
|
||
(0) the command
|
||
<I>arg</I>
|
||
|
||
is executed on exit from the shell.
|
||
If a
|
||
<I>sigspec</I>
|
||
|
||
is
|
||
<FONT SIZE=-1><B>DEBUG</B>,
|
||
|
||
</FONT>
|
||
the command
|
||
<I>arg</I>
|
||
|
||
is executed after every <I>simple command</I> (see
|
||
<FONT SIZE=-1><B>SHELL GRAMMAR</B>
|
||
|
||
</FONT>
|
||
above).
|
||
If a
|
||
<I>sigspec</I>
|
||
|
||
is
|
||
<FONT SIZE=-1><B>ERR</B>,
|
||
|
||
</FONT>
|
||
the command
|
||
<I>arg</I>
|
||
|
||
is executed whenever a simple command has a non-zero exit status.
|
||
The
|
||
<FONT SIZE=-1><B>ERR</B>
|
||
|
||
</FONT>
|
||
trap is not executed if the failed command is part of an
|
||
<I>until</I>
|
||
|
||
or
|
||
<I>while</I>
|
||
|
||
loop,
|
||
part of an
|
||
<I>if</I>
|
||
|
||
statement, part of a
|
||
<B>&&</B>
|
||
|
||
or
|
||
<B>||</B>
|
||
|
||
list, or if the command's return value is
|
||
being inverted via
|
||
<B>!</B>.
|
||
|
||
The
|
||
<B>-l</B>
|
||
|
||
option causes the shell to print a list of signal names and
|
||
their corresponding numbers.
|
||
Signals ignored upon entry to the shell cannot be trapped or reset.
|
||
Trapped signals are reset to their original values in a child
|
||
process when it is created.
|
||
The return status is false if any
|
||
<I>sigspec</I>
|
||
|
||
is invalid; otherwise
|
||
<B>trap</B>
|
||
|
||
returns true.
|
||
<DT><B>type</B> [<B>-atp</B>] <I>name</I> [<I>name</I> ...]<DD>
|
||
With no options,
|
||
indicate how each
|
||
<I>name</I>
|
||
|
||
would be interpreted if used as a command name.
|
||
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 disk file,
|
||
respectively.
|
||
If the
|
||
<I>name</I>
|
||
|
||
is not found, then nothing is printed, and an exit status of false
|
||
is returned.
|
||
If the
|
||
<B>-p</B>
|
||
|
||
option is used,
|
||
<B>type</B>
|
||
|
||
either returns the name of the disk file
|
||
that would be executed if
|
||
<I>name</I>
|
||
|
||
were specified as a command name,
|
||
or nothing if
|
||
<TT>type -t name</TT>
|
||
|
||
would not return
|
||
<I>file</I>.
|
||
|
||
If a command is hashed,
|
||
<B>-p</B>
|
||
|
||
prints the hashed value, not necessarily the file that appears
|
||
first in
|
||
<FONT SIZE=-1><B>PATH</B>.
|
||
|
||
</FONT>
|
||
If the
|
||
<B>-a</B>
|
||
|
||
option is used,
|
||
<B>type</B>
|
||
|
||
prints all of the places that contain
|
||
an executable named
|
||
<I>name</I>.
|
||
|
||
This includes aliases and functions,
|
||
if and only if the
|
||
<B>-p</B>
|
||
|
||
option is not also used.
|
||
The table of hashed commands is not consulted
|
||
when using
|
||
<B>-a</B>.
|
||
|
||
<B>type</B>
|
||
|
||
returns true if any of the arguments are found, false if
|
||
none are found.
|
||
<DT><B>ulimit</B> [<B>-SHacdflmnpstuv</B> [<I>limit</I>]]<DD>
|
||
Provides control over the resources available to the shell and to
|
||
processes started by it, on systems that allow such control.
|
||
The <B>-H</B> and <B>-S</B> options specify that the hard or soft limit is
|
||
set for the given resource. A hard limit cannot be increased 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, both the soft and hard
|
||
limits are set.
|
||
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, the current value of the soft limit of the resource is
|
||
printed, unless the <B>-H</B> option is given. When more than one
|
||
resource is specified, the limit name and unit are printed before the value.
|
||
Other options are interpreted as follows:
|
||
<DL COMPACT><DT><DD>
|
||
|
||
<DL COMPACT>
|
||
<DT><B>-a</B>
|
||
|
||
<DD>
|
||
All current limits are reported
|
||
<DT><B>-c</B>
|
||
|
||
<DD>
|
||
The maximum size of core files created
|
||
<DT><B>-d</B>
|
||
|
||
<DD>
|
||
The maximum size of a process's data segment
|
||
<DT><B>-f</B>
|
||
|
||
<DD>
|
||
The maximum size of files created by the shell
|
||
<DT><B>-l</B>
|
||
|
||
<DD>
|
||
The maximum size that may be locked into memory
|
||
<DT><B>-m</B>
|
||
|
||
<DD>
|
||
The maximum resident set size
|
||
<DT><B>-n</B>
|
||
|
||
<DD>
|
||
The maximum number of open file descriptors (most systems do not
|
||
allow this value to be set)
|
||
<DT><B>-p</B>
|
||
|
||
<DD>
|
||
The pipe size in 512-byte blocks (this may not be set)
|
||
<DT><B>-s</B>
|
||
|
||
<DD>
|
||
The maximum stack size
|
||
<DT><B>-t</B>
|
||
|
||
<DD>
|
||
The maximum amount of cpu time in seconds
|
||
<DT><B>-u</B>
|
||
|
||
<DD>
|
||
The maximum number of processes available to a single user
|
||
<DT><B>-v</B>
|
||
|
||
<DD>
|
||
The maximum amount of virtual memory available to the shell
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
If
|
||
<I>limit</I>
|
||
|
||
is given, it is the new value of the specified resource (the
|
||
<B>-a</B>
|
||
|
||
option is display only).
|
||
If no option is given, then
|
||
<B>-f</B>
|
||
|
||
is assumed. Values are in 1024-byte increments, except for
|
||
<B>-t</B>,
|
||
|
||
which is in seconds,
|
||
<B>-p</B>,
|
||
|
||
which is in units of 512-byte blocks,
|
||
and
|
||
<B>-n</B>
|
||
|
||
and
|
||
<B>-u</B>,
|
||
|
||
which are unscaled values.
|
||
The return status is 0 unless an invalid option or argument is supplied,
|
||
or an error occurs while setting a new limit.
|
||
</DL>
|
||
|
||
<DT><B>umask</B> [<B>-p</B>] [<B>-S</B>] [<I>mode</I>]<DD>
|
||
The user file-creation mask is set 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, the current value of the mask is printed.
|
||
The
|
||
<B>-S</B>
|
||
|
||
option causes the mask to be printed in symbolic form; 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 0 if the mode was successfully changed or if
|
||
no <I>mode</I> argument was supplied, and false otherwise.
|
||
<DT><B>unalias</B> [-<B>a</B>] [<I>name</I> ...]<DD>
|
||
Remove each <I>name</I> from the list of defined aliases. If
|
||
<B>-a</B>
|
||
|
||
is supplied, all alias definitions are removed. The return
|
||
value is true unless a supplied
|
||
<I>name</I>
|
||
|
||
is not a defined alias.
|
||
<DT><B>unset</B> [-<B>fv</B>] [<I>name</I> ...]<DD>
|
||
For each
|
||
<I>name</I>,
|
||
|
||
remove the corresponding variable or function.
|
||
If no options are supplied, or the
|
||
<B>-v</B>
|
||
|
||
option is given, each
|
||
<I>name</I>
|
||
|
||
refers to a shell variable.
|
||
Read-only variables may not be unset.
|
||
If
|
||
<B>-f</B>
|
||
|
||
is specifed,
|
||
each
|
||
<I>name</I>
|
||
|
||
refers to a shell function, and the function definition
|
||
is removed.
|
||
Each unset variable or function is removed from the environment
|
||
passed to subsequent commands.
|
||
If any of
|
||
<FONT SIZE=-1><B>RANDOM</B>,
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>SECONDS</B>,
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>LINENO</B>,
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>HISTCMD</B>,
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>FUNCNAME</B>,
|
||
|
||
</FONT>
|
||
<FONT SIZE=-1><B>GROUPS</B>,
|
||
|
||
</FONT>
|
||
or
|
||
<FONT SIZE=-1><B>DIRSTACK</B>
|
||
|
||
</FONT>
|
||
are unset, they lose their special properties, even if they are
|
||
subsequently reset. The exit status is true unless a
|
||
<I>name</I>
|
||
|
||
does not exist or is readonly.
|
||
<DT><B>wait</B> [<I>n</I>]<DD>
|
||
Wait for the specified process and return its termination
|
||
status.
|
||
<I>n</I>
|
||
|
||
may be a process
|
||
ID or a job specification; if a job spec is given, all processes
|
||
in that job's pipeline are waited for. If
|
||
<I>n</I>
|
||
|
||
is not given, all currently active child processes
|
||
are waited for, and the return status is zero. If
|
||
<I>n</I>
|
||
|
||
specifies a non-existent process or job, the return status is
|
||
127. Otherwise, the return status is the exit status of the last
|
||
process or job waited for.
|
||
|
||
|
||
</DL>
|
||
<A NAME="lbCX"> </A>
|
||
<H2>RESTRICTED SHELL</H2>
|
||
|
||
|
||
|
||
<P>
|
||
|
||
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 restricted.
|
||
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:
|
||
<DL COMPACT>
|
||
<DT>*<DD>
|
||
changing directories with <B>cd</B>
|
||
<DT>*<DD>
|
||
setting or unsetting the values of
|
||
<B>SHELL</B>,
|
||
|
||
<B>PATH</B>,
|
||
|
||
<B>ENV</B>,
|
||
|
||
or
|
||
<B>BASH_ENV</B>
|
||
|
||
<DT>*<DD>
|
||
specifying command names containing
|
||
<B>/</B>
|
||
|
||
<DT>*<DD>
|
||
specifying a file name containing a
|
||
<B>/</B>
|
||
|
||
as an argument to the
|
||
<B>.</B>
|
||
|
||
builtin command
|
||
<DT>*<DD>
|
||
Specifying a filename containing a slash as an argument to the
|
||
<B>-p</B>
|
||
|
||
option to the
|
||
<B>hash</B>
|
||
|
||
builtin command
|
||
<DT>*<DD>
|
||
importing function definitions from the shell environment at startup
|
||
<DT>*<DD>
|
||
parsing the value of <B>SHELLOPTS</B> from the shell environment at startup
|
||
<DT>*<DD>
|
||
redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
|
||
<DT>*<DD>
|
||
using the
|
||
<B>exec</B>
|
||
|
||
builtin command to replace the shell with another command
|
||
<DT>*<DD>
|
||
adding or deleting builtin commands with the
|
||
<B>-f</B>
|
||
|
||
and
|
||
<B>-d</B>
|
||
|
||
options to the
|
||
<B>enable</B>
|
||
|
||
builtin command
|
||
<DT>*<DD>
|
||
specifying the
|
||
<B>-p</B>
|
||
|
||
option to the
|
||
<B>command</B>
|
||
|
||
builtin command
|
||
<DT>*<DD>
|
||
turning off restricted mode with
|
||
<B>set +r</B> or <B>set +o restricted</B>.
|
||
</DL>
|
||
<P>
|
||
|
||
These restrictions are enforced after any startup files are read.
|
||
<P>
|
||
|
||
When a command that is found to be a shell script is executed (see
|
||
<FONT SIZE=-1><B>COMMAND EXECUTION</B>
|
||
|
||
</FONT>
|
||
above),
|
||
<B>rbash</B>
|
||
|
||
turns off any restrictions in the shell spawned to execute the
|
||
script.
|
||
|
||
|
||
<A NAME="lbCY"> </A>
|
||
<H2>SEE ALSO</H2>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT><I>Bash Reference Manual</I>, Brian Fox and Chet Ramey<DD>
|
||
<DT><I>The Gnu Readline Library</I>, Brian Fox and Chet Ramey<DD>
|
||
<DT><I>The Gnu History Library</I>, Brian Fox and Chet Ramey<DD>
|
||
<DT><I>Portable Operating System Interface (POSIX) Part 2: Shell and Utilities</I>, IEEE<DD>
|
||
<DT><I>sh</I>(1), <I>ksh</I>(1), <I>csh</I>(1)<DD>
|
||
<DT><I>emacs</I>(1), <I>vi</I>(1)<DD>
|
||
<DT><I>readline</I>(3)<DD>
|
||
|
||
</DL>
|
||
<A NAME="lbCZ"> </A>
|
||
<H2>FILES</H2>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT>
|
||
<A HREF="file:/bin/bash"><I>/bin/bash</I></A>
|
||
|
||
<DD>
|
||
The <B>bash</B> executable
|
||
<DT>
|
||
<A HREF="file:/etc/profile"><I>/etc/profile</I></A>
|
||
|
||
<DD>
|
||
The systemwide initialization file, executed for login shells
|
||
<DT>
|
||
<A HREF="file:~/.bash_profile"><I>~/.bash_profile</I></A>
|
||
|
||
<DD>
|
||
The personal initialization file, executed for login shells
|
||
<DT>
|
||
<A HREF="file:~/.bashrc"><I>~/.bashrc</I></A>
|
||
|
||
<DD>
|
||
The individual per-interactive-shell startup file
|
||
<DT>
|
||
<A HREF="file:~/.bash_logout"><I>~/.bash_logout</I></A>
|
||
|
||
<DD>
|
||
The individual login shell cleanup file, executed when a login shell exits
|
||
<DT>
|
||
<A HREF="file:~/.inputrc"><I>~/.inputrc</I></A>
|
||
|
||
<DD>
|
||
Individual <I>readline</I> initialization file
|
||
|
||
</DL>
|
||
<A NAME="lbDA"> </A>
|
||
<H2>AUTHORS</H2>
|
||
|
||
Brian Fox, Free Software Foundation
|
||
<BR>
|
||
|
||
<A HREF="mailto:bfox@gnu.org">bfox@gnu.org</A>
|
||
<P>
|
||
|
||
Chet Ramey, Case Western Reserve University
|
||
<BR>
|
||
|
||
<A HREF="mailto:chet@ins.CWRU.Edu">chet@ins.CWRU.Edu</A>
|
||
<A NAME="lbDB"> </A>
|
||
<H2>BUG REPORTS</H2>
|
||
|
||
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>
|
||
|
||
that you have.
|
||
<P>
|
||
|
||
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!
|
||
Suggestions and `philosophical' bug reports may be mailed
|
||
to <I><A HREF="mailto:bug-bash@gnu.org">bug-bash@gnu.org</A></I> or posted to the Usenet
|
||
newsgroup
|
||
<A HREF="news:gnu.bash.bug">gnu.bash.bug</A>.
|
||
|
||
<P>
|
||
|
||
ALL bug reports should include:
|
||
<P>
|
||
|
||
|
||
<DL COMPACT>
|
||
<DT>The version number of <B>bash</B><DD>
|
||
<DT>The hardware and operating system<DD>
|
||
<DT>The compiler used to compile<DD>
|
||
<DT>A description of the bug behaviour<DD>
|
||
<DT>A short script or `recipe' which exercises the bug<DD>
|
||
|
||
</DL>
|
||
<P>
|
||
|
||
<I>bashbug</I>
|
||
|
||
inserts the first three items automatically into the template
|
||
it provides for filing a bug report.
|
||
<P>
|
||
|
||
Comments and bug reports concerning
|
||
this manual page should be directed to
|
||
<I><A HREF="mailto:chet@ins.CWRU.Edu">chet@ins.CWRU.Edu</A></I>.
|
||
|
||
<A NAME="lbDC"> </A>
|
||
<H2>BUGS</H2>
|
||
|
||
<P>
|
||
|
||
It's too big and too slow.
|
||
<P>
|
||
|
||
There are some subtle differences between
|
||
<B>bash</B>
|
||
|
||
and traditional versions of
|
||
<B>sh</B>,
|
||
|
||
mostly because of the
|
||
<FONT SIZE=-1><B>POSIX</B>
|
||
|
||
</FONT>
|
||
specification.
|
||
<P>
|
||
|
||
Aliases are confusing in some uses.
|
||
<P>
|
||
|
||
Shell builtin commands and functions are not stoppable/restartable.
|
||
<P>
|
||
|
||
Compound commands and command sequences of the form `a ; b ; c'
|
||
are not handled gracefully when process suspension is attempted.
|
||
When a process is stopped, the shell immediately executes the next
|
||
command in the sequence.
|
||
It suffices to place the sequence of commands between
|
||
parentheses to force it into a subshell, which may be stopped as
|
||
a unit.
|
||
<P>
|
||
|
||
Commands inside of <B>$(</B>...<B>)</B> command substitution are not
|
||
parsed until substitution is attempted. This will delay error
|
||
reporting until some time after the command is entered.
|
||
<P>
|
||
|
||
Array variables may not (yet) be exported.
|
||
|
||
|
||
|
||
<HR>
|
||
<A NAME="index"> </A><H2>Index</H2>
|
||
<DL>
|
||
<DT><A HREF="#lbAB">NAME</A><DD>
|
||
<DT><A HREF="#lbAC">SYNOPSIS</A><DD>
|
||
<DT><A HREF="#lbAD">COPYRIGHT</A><DD>
|
||
<DT><A HREF="#lbAE">DESCRIPTION</A><DD>
|
||
<DT><A HREF="#lbAF">OPTIONS</A><DD>
|
||
<DT><A HREF="#lbAG">ARGUMENTS</A><DD>
|
||
<DT><A HREF="#lbAH">INVOCATION</A><DD>
|
||
<DT><A HREF="#lbAI">DEFINITIONS</A><DD>
|
||
<DT><A HREF="#lbAJ">RESERVED WORDS</A><DD>
|
||
<DT><A HREF="#lbAK">SHELL GRAMMAR</A><DD>
|
||
<DL>
|
||
<DT><A HREF="#lbAL">Simple Commands</A><DD>
|
||
<DT><A HREF="#lbAM">Pipelines</A><DD>
|
||
<DT><A HREF="#lbAN">Lists</A><DD>
|
||
<DT><A HREF="#lbAO">Compound Commands</A><DD>
|
||
</DL>
|
||
<DT><A HREF="#lbAP">COMMENTS</A><DD>
|
||
<DT><A HREF="#lbAQ">QUOTING</A><DD>
|
||
<DT><A HREF="#lbAR">PARAMETERS</A><DD>
|
||
<DL>
|
||
<DT><A HREF="#lbAS">Positional Parameters</A><DD>
|
||
<DT><A HREF="#lbAT">Special Parameters</A><DD>
|
||
<DT><A HREF="#lbAU">Shell Variables</A><DD>
|
||
<DT><A HREF="#lbAV">Arrays</A><DD>
|
||
</DL>
|
||
<DT><A HREF="#lbAW">EXPANSION</A><DD>
|
||
<DL>
|
||
<DT><A HREF="#lbAX">Brace Expansion</A><DD>
|
||
<DT><A HREF="#lbAY">Tilde Expansion</A><DD>
|
||
<DT><A HREF="#lbAZ">Parameter Expansion</A><DD>
|
||
<DT><A HREF="#lbBA">Command Substitution</A><DD>
|
||
<DT><A HREF="#lbBB">Arithmetic Expansion</A><DD>
|
||
<DT><A HREF="#lbBC">Process Substitution</A><DD>
|
||
<DT><A HREF="#lbBD">Word Splitting</A><DD>
|
||
<DT><A HREF="#lbBE">Pathname Expansion</A><DD>
|
||
<DT><A HREF="#lbBF">Quote Removal</A><DD>
|
||
</DL>
|
||
<DT><A HREF="#lbBG">REDIRECTION</A><DD>
|
||
<DL>
|
||
<DT><A HREF="#lbBH">Redirecting Input</A><DD>
|
||
<DT><A HREF="#lbBI">Redirecting Output</A><DD>
|
||
<DT><A HREF="#lbBJ">Appending Redirected Output</A><DD>
|
||
<DT><A HREF="#lbBK">Redirecting Standard Output and Standard Error</A><DD>
|
||
<DT><A HREF="#lbBL">Here Documents</A><DD>
|
||
<DT><A HREF="#lbBM">Duplicating File Descriptors</A><DD>
|
||
<DT><A HREF="#lbBN">Opening File Descriptors for Reading and Writing</A><DD>
|
||
</DL>
|
||
<DT><A HREF="#lbBO">ALIASES</A><DD>
|
||
<DT><A HREF="#lbBP">FUNCTIONS</A><DD>
|
||
<DT><A HREF="#lbBQ">ARITHMETIC EVALUATION</A><DD>
|
||
<DT><A HREF="#lbBR">CONDITIONAL EXPRESSIONS</A><DD>
|
||
<DT><A HREF="#lbBS">SIMPLE COMMAND EXPANSION</A><DD>
|
||
<DT><A HREF="#lbBT">COMMAND EXECUTION</A><DD>
|
||
<DT><A HREF="#lbBU">COMMAND EXECUTION ENVIRONMENT</A><DD>
|
||
<DT><A HREF="#lbBV">ENVIRONMENT</A><DD>
|
||
<DT><A HREF="#lbBW">EXIT STATUS</A><DD>
|
||
<DT><A HREF="#lbBX">SIGNALS</A><DD>
|
||
<DT><A HREF="#lbBY">JOB CONTROL</A><DD>
|
||
<DT><A HREF="#lbBZ">PROMPTING</A><DD>
|
||
<DT><A HREF="#lbCA">READLINE</A><DD>
|
||
<DL>
|
||
<DT><A HREF="#lbCB">Readline Notation</A><DD>
|
||
<DT><A HREF="#lbCC">Readline Initialization</A><DD>
|
||
<DT><A HREF="#lbCD">Readline Key Bindings</A><DD>
|
||
<DT><A HREF="#lbCE">Readline Variables</A><DD>
|
||
<DT><A HREF="#lbCF">Readline Conditional Constructs</A><DD>
|
||
<DT><A HREF="#lbCG">Searching</A><DD>
|
||
<DT><A HREF="#lbCH">Readline Command Names</A><DD>
|
||
<DT><A HREF="#lbCI">Commands for Moving</A><DD>
|
||
<DT><A HREF="#lbCJ">Commands for Manipulating the History</A><DD>
|
||
<DT><A HREF="#lbCK">Commands for Changing Text</A><DD>
|
||
<DT><A HREF="#lbCL">Killing and Yanking</A><DD>
|
||
<DT><A HREF="#lbCM">Numeric Arguments</A><DD>
|
||
<DT><A HREF="#lbCN">Completing</A><DD>
|
||
<DT><A HREF="#lbCO">Keyboard Macros</A><DD>
|
||
<DT><A HREF="#lbCP">Miscellaneous</A><DD>
|
||
<DT><A HREF="#lbCQ">Programmable Completion</A><DD>
|
||
</DL>
|
||
<DT><A HREF="#lbCR">HISTORY</A><DD>
|
||
<DT><A HREF="#lbCS">HISTORY EXPANSION</A><DD>
|
||
<DL>
|
||
<DT><A HREF="#lbCT">Event Designators</A><DD>
|
||
<DT><A HREF="#lbCU">Word Designators</A><DD>
|
||
<DT><A HREF="#lbCV">Modifiers</A><DD>
|
||
</DL>
|
||
<DT><A HREF="#lbCW">SHELL BUILTIN COMMANDS</A><DD>
|
||
<DT><A HREF="#lbCX">RESTRICTED SHELL</A><DD>
|
||
<DT><A HREF="#lbCY">SEE ALSO</A><DD>
|
||
<DT><A HREF="#lbCZ">FILES</A><DD>
|
||
<DT><A HREF="#lbDA">AUTHORS</A><DD>
|
||
<DT><A HREF="#lbDB">BUG REPORTS</A><DD>
|
||
<DT><A HREF="#lbDC">BUGS</A><DD>
|
||
</DL>
|
||
<HR>
|
||
This document was created by man2html
|
||
using the manual pages.<BR>
|
||
Time: 17:56:16 GMT, November 13, 2001
|
||
</BODY>
|
||
</HTML>
|