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+<HTML><HEAD>
+<TITLE>BASH(1) Manual Page</TITLE>
+</HEAD>
+<BODY><TABLE WIDTH=100%>
+<TR>
+<TH ALIGN=LEFT width=33%>BASH(1)<TH ALIGN=CENTER width=33%>2020 October 29<TH ALIGN=RIGHT width=33%>BASH(1)
+</TR>
+</TABLE>
+<BR><A HREF="#index">Index</A>
+<HR>
+
+
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+
+<A NAME="lbAB">&nbsp;</A>
+<H3>NAME</H3>
+
+bash - GNU Bourne-Again SHell
+<A NAME="lbAC">&nbsp;</A>
+<H3>SYNOPSIS</H3>
+
+<B>bash</B>
+
+[options]
+[command_string | file]
+<A NAME="lbAD">&nbsp;</A>
+<H3>COPYRIGHT</H3>
+
+
+Bash is Copyright &#169; 1989-2020 by the Free Software Foundation, Inc.
+<A NAME="lbAE">&nbsp;</A>
+<H3>DESCRIPTION</H3>
+
+<B>Bash</B>
+
+is an <B>sh</B>-compatible command language interpreter that
+executes commands read from the standard input or from a file.
+<B>Bash</B>
+
+also incorporates useful features from the <I>Korn</I> and <I>C</I>
+shells (<B>ksh</B> and <B>csh</B>).
+<P>
+
+<B>Bash</B>
+
+is intended to be a conformant implementation of the
+Shell and Utilities portion of the IEEE POSIX specification
+(IEEE Standard 1003.1).
+<B>Bash</B>
+
+can be configured to be POSIX-conformant by default.
+<A NAME="lbAF">&nbsp;</A>
+<H3>OPTIONS</H3>
+
+All of the single-character shell options documented in the
+description of the <B>set</B> builtin command, including <B>-o</B>,
+can be used as options when the shell is invoked.
+In addition, <B>bash</B>
+interprets the following options when it is invoked:
+<P>
+
+
+<DL COMPACT>
+<DT><B>-c</B>
+
+<DD>
+If the
+<B>-c</B>
+
+option is present, then commands are read from the first non-option argument
+<I>command_string</I>.
+
+If there are arguments after the
+<I>command_string</I>,
+
+the first argument is assigned to
+<B>$0</B>
+
+and any remaining arguments are assigned to the positional parameters.
+The assignment to
+<B>$0</B>
+
+sets the name of the shell, which is used in warning and error messages.
+<DT><B>-i</B>
+
+<DD>
+If the
+<B>-i</B>
+
+option is present, the shell is
+<I>interactive</I>.
+
+<DT><B>-l</B>
+
+<DD>
+Make
+<B>bash</B>
+
+act as if it had been invoked as a login shell (see
+<FONT SIZE=-1><B>INVOCATION</B>
+
+</FONT>
+below).
+<DT><B>-r</B>
+
+<DD>
+If the
+<B>-r</B>
+
+option is present, the shell becomes
+<I>restricted</I>
+
+(see
+<FONT SIZE=-1><B>RESTRICTED SHELL</B>
+
+</FONT>
+below).
+<DT><B>-s</B>
+
+<DD>
+If the
+<B>-s</B>
+
+option is present, or if no arguments remain after option
+processing, then commands are read from the standard input.
+This option allows the positional parameters to be set
+when invoking an interactive shell or when reading input
+through a pipe.
+<DT><B>-D</B>
+
+<DD>
+A list of all double-quoted strings preceded by <B>$</B>
+is printed on the standard output.
+These are the strings that
+are subject to language translation when the current locale
+is not <B>C</B> or <B>POSIX</B>.
+This implies the <B>-n</B> option; no commands will be executed.
+<DT><B>[-+]O [</B><I>shopt_option</I>]
+
+<DD>
+<I>shopt_option</I> is one of the shell options accepted by the
+<B>shopt</B> builtin (see
+<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
+
+</FONT>
+below).
+If <I>shopt_option</I> is present, <B>-O</B> sets the value of that option;
+<B>+O</B> unsets it.
+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
+that may be reused as input.
+<DT><B>--</B>
+
+<DD>
+A
+<B>--</B>
+
+signals the end of options and disables further option processing.
+Any arguments after the
+<B>--</B>
+
+are treated as filenames and arguments. An argument of
+<B>-</B>
+
+is equivalent to <B>--</B>.
+
+</DL>
+<P>
+
+<B>Bash</B>
+
+also interprets a number of multi-character options.
+These options must appear on the command line before the
+single-character options to be recognized.
+<P>
+
+
+<DL COMPACT>
+<DT><B>--debugger</B>
+
+<DD>
+Arrange for the debugger profile to be executed before the shell
+starts.
+Turns on extended debugging mode (see the description of the
+<B>extdebug</B>
+
+option to the
+<B>shopt</B>
+
+builtin below).
+<DT><B>--dump-po-strings</B>
+
+<DD>
+Equivalent to <B>-D</B>, but the output is in the GNU <I>gettext</I>
+<B>po</B> (portable object) file format.
+<DT><B>--dump-strings</B>
+
+<DD>
+Equivalent to <B>-D</B>.
+<DT><B>--help</B>
+
+<DD>
+Display a usage message on standard output and exit successfully.
+<DT><B>--init-file</B> <I>file</I><DD>
+
+<DT><B>--rcfile</B> <I>file</I><DD>
+
+Execute commands from
+<I>file</I>
+
+instead of the standard personal initialization file
+<A HREF="file:~/.bashrc"><I>~/.bashrc</I></A>
+
+if the shell is interactive (see
+<FONT SIZE=-1><B>INVOCATION</B>
+
+</FONT>
+below).
+<DT><B>--login</B>
+
+<DD>
+Equivalent to <B>-l</B>.
+<DT><B>--noediting</B>
+
+<DD>
+Do not use the GNU
+<B>readline</B>
+
+library to read command lines when the shell is interactive.
+<DT><B>--noprofile</B>
+
+<DD>
+Do not read either the system-wide startup file
+
+<A HREF="file:/etc/profile"><I>/etc/profile</I></A>
+
+or any of the personal initialization files
+<A HREF="file:~/.bash_profile"><I>~/.bash_profile</I></A>,
+
+<A HREF="file:~/.bash_login"><I>~/.bash_login</I></A>,
+
+or
+<A HREF="file:~/.profile"><I>~/.profile</I></A>.
+
+By default,
+<B>bash</B>
+
+reads these files when it is invoked as a login shell (see
+<FONT SIZE=-1><B>INVOCATION</B>
+
+</FONT>
+below).
+<DT><B>--norc</B>
+
+<DD>
+Do not read and execute the personal initialization file
+<A HREF="file:~/.bashrc"><I>~/.bashrc</I></A>
+
+if the shell is interactive.
+This option is on by default if the shell is invoked as
+<B>sh</B>.
+
+<DT><B>--posix</B>
+
+<DD>
+Change the behavior of <B>bash</B> where the default operation differs
+from the POSIX standard to match the standard (<I>posix mode</I>).
+See
+<FONT SIZE=-1><B>SEE ALSO</B>
+
+</FONT>
+below for a reference to a document that details how posix mode affects
+bash's behavior.
+<DT><B>--restricted</B>
+
+<DD>
+The shell becomes restricted (see
+<FONT SIZE=-1><B>RESTRICTED SHELL</B>
+
+</FONT>
+below).
+<DT><B>--verbose</B>
+
+<DD>
+Equivalent to <B>-v</B>.
+<DT><B>--version</B>
+
+<DD>
+Show version information for this instance of
+<B>bash</B>
+
+on the standard output and exit successfully.
+
+</DL>
+<A NAME="lbAG">&nbsp;</A>
+<H3>ARGUMENTS</H3>
+
+If arguments remain after option processing, and neither the
+<B>-c</B>
+
+nor the
+<B>-s</B>
+
+option has been supplied, the first argument is assumed to
+be the name of a file containing shell commands.
+If
+<B>bash</B>
+
+is invoked in this fashion,
+<B>$0</B>
+
+is set to the name of the file, and the positional parameters
+are set to the remaining arguments.
+<B>Bash</B>
+
+reads and executes commands from this file, then exits.
+<B>Bash</B>'s exit status is the exit status of the last command
+executed in the script.
+If no commands are executed, the exit status is 0.
+An attempt is first made to open the file in the current directory, and,
+if no file is found, then the shell searches the directories in
+<FONT SIZE=-1><B>PATH</B>
+
+</FONT>
+for the script.
+<A NAME="lbAH">&nbsp;</A>
+<H3>INVOCATION</H3>
+
+A <I>login shell</I> is one whose first character of argument zero is a
+<B>-</B>,
+
+or one started with the
+<B>--login</B>
+
+option.
+<P>
+
+An <I>interactive</I> shell is one started without non-option arguments
+(unless <B>-s</B> is specified)
+and without the
+<B>-c</B>
+
+option
+whose standard input and error are
+both connected to terminals (as determined by
+<I>isatty</I>(3)),
+
+or one started with the
+<B>-i</B>
+
+option.
+<FONT SIZE=-1><B>PS1</B>
+
+</FONT>
+is set and
+<B>$-</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 filenames 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 an interactive login shell exits,
+or a non-interactive login shell executes the <B>exit</B> builtin command,
+<B>bash</B>
+
+reads and executes commands from the file <A HREF="file:~/.bash_logout"><I>~/.bash_logout</I></A>, if it
+exists.
+<P>
+
+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 &quot;$BASH_ENV&quot; ]; then . &quot;$BASH_ENV&quot;; fi</TT>
+
+</DL>
+
+<P>
+but the value of the
+<FONT SIZE=-1><B>PATH</B>
+
+</FONT>
+variable is not used to search for the filename.
+<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 with its standard input
+connected to a network connection, as when executed by the remote shell
+daemon, usually <I>rshd</I>, or the secure shell daemon <I>sshd</I>.
+If
+<B>bash</B>
+
+determines it is being run in this fashion, 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 neither
+<I>rshd</I> nor <I>sshd</I> 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>
+<FONT SIZE=-1><B>BASHOPTS</B>,
+
+</FONT>
+<FONT SIZE=-1><B>CDPATH</B>,
+
+</FONT>
+and
+<FONT SIZE=-1><B>GLOBIGNORE</B>
+
+</FONT>
+variables, if they appear in the environment, are 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">&nbsp;</A>
+<H3>DEFINITIONS</H3>
+
+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>| &amp; ; ( ) &lt; &gt; space tab newline</B>
+
+</DL>
+
+<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>|| &amp; &amp;&amp; ; ;; ;&amp; ;;&amp; ( ) | |&amp; &lt;newline&gt;</B>
+
+</DL>
+
+
+</DL>
+<A NAME="lbAJ">&nbsp;</A>
+<H3>RESERVED WORDS</H3>
+
+<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 command (see
+<FONT SIZE=-1><B>SHELL GRAMMAR</B>
+
+</FONT>
+below), the third word of a
+<B>case</B>
+
+or
+<B>select</B>
+
+command
+(only <B>in</B> is valid), or the third word of a
+<B>for</B>
+
+command (only <B>in</B> and <B>do</B> are valid):
+<DL COMPACT><DT><DD>
+
+<P>
+
+<B>
+</B>
+
+! case coproc do done elif else esac fi for function if in select then until while { } time [[ ]]
+</DL>
+
+
+<A NAME="lbAK">&nbsp;</A>
+<H3>SHELL GRAMMAR</H3>
+
+<A NAME="lbAL">&nbsp;</A>
+<H4>Simple Commands</H4>
+
+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">&nbsp;</A>
+<H4>Pipelines</H4>
+
+A <I>pipeline</I> is a sequence of one or more commands separated by
+one of the control operators
+<B>|</B>
+
+or <B>|&amp;</B>.
+The format for a pipeline is:
+<DL COMPACT><DT><DD>
+<P>
+
+[<B>time</B> [<B>-p</B>]] [ ! ] <I>command</I> [ [<B>|</B>|<B>|&amp;</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).
+If <B>|&amp;</B> is used, <I>command</I>'s standard error, in addition to its
+standard output, is connected to
+<I>command2</I>'s standard input through the pipe;
+it is shorthand for <B>2&gt;&amp;1 |</B>.
+This implicit redirection of the standard error to the standard output is
+performed after any redirections specified by the command.
+<P>
+
+The return status of a pipeline is the exit status of the last
+command, unless the <B>pipefail</B> option is enabled.
+If <B>pipefail</B> is enabled, the pipeline's return status is the
+value of the last (rightmost) command to exit with a non-zero status,
+or zero if all commands exit successfully.
+If the reserved word
+<B>!</B>
+
+precedes a pipeline, the exit status of that pipeline is the logical
+negation of the exit status as described above.
+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.
+When the shell is in <I>posix mode</I>, it does not recognize
+<B>time</B> as a reserved word if the next token begins with a `-'.
+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>
+
+When the shell is in <I>posix mode</I>, <B>time</B>
+may be followed by a newline. In this case, the shell displays the
+total user and system time consumed by the shell and its children.
+The
+<FONT SIZE=-1><B>TIMEFORMAT</B>
+
+</FONT>
+variable may be used to specify the format of
+the time information.
+<P>
+
+Each command in a pipeline is executed as a separate process (i.e., in a
+subshell).
+See
+<FONT SIZE=-1><B>COMMAND EXECUTION ENVIRONMENT</B></FONT>
+for a description of a subshell environment.
+If the <B>lastpipe</B> option is enabled using the <B>shopt</B> builtin
+(see the description of <B>shopt</B> below),
+the last element of a pipeline may be run by the shell process.
+<A NAME="lbAN">&nbsp;</A>
+<H4>Lists</H4>
+
+A <I>list</I> is a sequence of one or more pipelines separated by one
+of the operators
+<B>;</B>,
+
+<B>&amp;</B>,
+
+<B>&amp;&amp;</B>,
+
+or
+<B>||</B>,
+
+and optionally terminated by one of
+<B>;</B>,
+
+<B>&amp;</B>,
+
+or
+<B>&lt;newline&gt;</B>.
+
+<P>
+
+Of these list operators,
+<B>&amp;&amp;</B>
+
+and
+<B>||</B>
+
+have equal precedence, followed by
+<B>;</B>
+
+and
+<B>&amp;</B>,
+
+which have equal precedence.
+<P>
+
+A sequence of one or more newlines may appear in a <I>list</I> instead
+of a semicolon to delimit commands.
+<P>
+
+If a command is terminated by the control operator
+<B>&amp;</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.
+These are referred to as <I>asynchronous</I> commands.
+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>
+
+AND and OR lists are sequences of one or more pipelines separated by the
+<B>&amp;&amp;</B> and <B>||</B> control operators, respectively.
+AND and OR lists are executed with left associativity.
+An AND list has the form
+<DL COMPACT><DT><DD>
+<P>
+
+<I>command1</I> <B>&amp;&amp;</B> <I>command2</I>
+</DL>
+
+<P>
+
+<I>command2</I>
+
+is executed if, and only if,
+<I>command1</I>
+
+returns an exit status of zero (success).
+<P>
+
+An OR 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 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">&nbsp;</A>
+<H4>Compound Commands</H4>
+
+A <I>compound command</I> is one of the following.
+In most cases a <I>list</I> in a command's description may be separated from
+the rest of the command by one or more newlines, and may be followed by a
+newline in place of a semicolon.
+<DL COMPACT>
+<DT>(<I>list</I>)<DD>
+<I>list</I> is executed in a subshell environment (see
+<FONT SIZE=-1><B>COMMAND EXECUTION ENVIRONMENT</B></FONT>
+below).
+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 or another
+shell metacharacter.
+<DT>((<I>expression</I>))<DD>
+The <I>expression</I> is evaluated according to the rules described
+below under
+<FONT SIZE=-1><B>ARITHMETIC EVALUATION</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 &quot;</B><I>expression</I>&quot;.
+<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 EXPRESSIONS</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.
+Conditional operators such as <B>-f</B> must be unquoted to be recognized
+as primaries.
+<P>
+
+
+When used with <B>[[</B>, the <B>&lt;</B> and <B>&gt;</B> operators sort
+lexicographically using the current locale.
+<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>,
+as if the <B>extglob</B> shell option were enabled.
+The <B>=</B> operator is equivalent to <B>==</B>.
+If the
+<B>nocasematch</B>
+
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+The return value is 0 if the string matches (<B>==</B>) or does not match
+(<B>!=</B>) the pattern, and 1 otherwise.
+Any part of the pattern may be quoted to force the quoted portion
+to be matched as a string.
+<P>
+
+
+An additional binary operator, <B>=~</B>, is available, with the same
+precedence as <B>==</B> and <B>!=</B>.
+When it is used, the string to the right of the operator is considered
+a POSIX extended regular expression and matched accordingly
+(using the POSIX <I>regcomp</I> and <I>regexec</I> interfaces
+usually described in <I>regex</I>(3)).
+The return value is 0 if the string matches
+the pattern, and 1 otherwise.
+If the regular expression is syntactically incorrect, the conditional
+expression's return value is 2.
+If the
+<B>nocasematch</B>
+
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+Any part of the pattern may be quoted to force the quoted portion
+to be matched as a string.
+Bracket expressions in regular expressions must be treated carefully,
+since normal quoting characters lose their meanings between brackets.
+If the pattern is stored in a shell variable, quoting the variable
+expansion forces the entire pattern to be matched as a string.
+<P>
+
+
+The pattern will match if it matches any part of the string.
+Anchor the pattern using the <B>^</B> and <B>$</B> regular expression
+operators to force it to match the entire string.
+The array variable
+<FONT SIZE=-1><B>BASH_REMATCH</B>
+
+</FONT>
+records which parts of the string matched the pattern.
+The element of
+<FONT SIZE=-1><B>BASH_REMATCH</B>
+
+</FONT>
+with index 0 contains the portion of
+the string matching the entire regular expression.
+Substrings matched by parenthesized subexpressions within the regular
+expression are saved in the remaining
+<FONT SIZE=-1><B>BASH_REMATCH</B>
+
+</FONT>
+indices. The element of
+<FONT SIZE=-1><B>BASH_REMATCH</B>
+
+</FONT>
+with index <I>n</I> is the portion of the
+string matching the <I>n</I>th parenthesized subexpression.
+<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>&amp;&amp;</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>&amp;&amp;</B> and <B>||</B>
+operators do not evaluate <I>expression2</I> if the value of
+<I>expression1</I> is sufficient to determine the return value of
+the entire conditional expression.
+</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 EVALUATION</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
+<FONT SIZE=-1><B>PS3</B>
+
+</FONT>
+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
+<FONT SIZE=-1><B>REPLY</B>.
+
+</FONT>
+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 matching rules
+described under
+<B>Pattern Matching</B>
+
+below.
+The <I>word</I> is expanded using tilde
+expansion, parameter and variable expansion, arithmetic expansion,
+command substitution, process substitution and quote removal.
+Each <I>pattern</I> examined is expanded using tilde
+expansion, parameter and variable expansion, arithmetic expansion,
+command substitution, and process substitution.
+If the
+<B>nocasematch</B>
+
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+When a match is found, the corresponding <I>list</I> is executed.
+If the <B>;;</B> operator is used, no subsequent matches are attempted after
+the first pattern match.
+Using <B>;&amp;</B> in place of <B>;;</B> causes execution to continue with
+the <I>list</I> associated with the next set of patterns.
+Using <B>;;&amp;</B> in place of <B>;;</B> causes the shell to test the next
+pattern list in the statement, if any, and execute any associated <I>list</I>
+on a successful match,
+continuing the case statement execution as if the pattern list had not matched.
+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><B>while</B> <I>list-1</I>; <B>do</B> <I>list-2</I>; <B>done</B><DD>
+
+<DT><B>until</B> <I>list-1</I>; <B>do</B> <I>list-2</I>; <B>done</B><DD>
+
+The <B>while</B> command continuously executes the list
+<I>list-2</I> as long as the last command in the list <I>list-1</I> returns
+an exit status of zero. The <B>until</B> command is identical
+to the <B>while</B> command, except that the test is negated:
+<I>list-2</I>
+
+is executed as long as the last command in
+<I>list-1</I>
+
+returns a non-zero exit status.
+The exit status of the <B>while</B> and <B>until</B> commands
+is the exit status
+of the last command executed in <I>list-2</I>, or zero if
+none was executed.
+</DL>
+<A NAME="lbAP">&nbsp;</A>
+<H4>Coprocesses</H4>
+
+A <I>coprocess</I> is a shell command preceded by the <B>coproc</B> reserved
+word.
+A coprocess is executed asynchronously in a subshell, as if the command
+had been terminated with the <B>&amp;</B> control operator, with a two-way pipe
+established between the executing shell and the coprocess.
+<P>
+
+The format for a coprocess is:
+<DL COMPACT><DT><DD>
+<P>
+
+<B>coproc</B> [<I>NAME</I>] <I>command</I> [<I>redirections</I>]
+</DL>
+
+<P>
+
+This creates a coprocess named <I>NAME</I>.
+If <I>NAME</I> is not supplied, the default name is <B>COPROC</B>.
+<I>NAME</I> must not be supplied if <I>command</I> is a <I>simple
+command</I> (see above); otherwise, it is interpreted as the first word
+of the simple command.
+When the coprocess is executed, the shell creates an array variable (see
+<B>Arrays</B>
+
+below) named <I>NAME</I> in the context of the executing shell.
+The standard output of
+<I>command</I>
+
+is connected via a pipe to a file descriptor in the executing shell,
+and that file descriptor is assigned to <I>NAME</I>[0].
+The standard input of
+<I>command</I>
+
+is connected via a pipe to a file descriptor in the executing shell,
+and that file descriptor is assigned to <I>NAME</I>[1].
+This pipe is established before any redirections specified by the
+command (see
+<FONT SIZE=-1><B>REDIRECTION</B>
+
+</FONT>
+below).
+The file descriptors can be utilized as arguments to shell commands
+and redirections using standard word expansions.
+Other than those created to execute command and process substitutions,
+the file descriptors are not available in subshells.
+The process ID of the shell spawned to execute the coprocess is
+available as the value of the variable <I>NAME</I>_PID.
+The <B>wait</B>
+builtin command may be used to wait for the coprocess to terminate.
+<P>
+
+Since the coprocess is created as an asynchronous command,
+the <B>coproc</B> command always returns success.
+The return status of a coprocess is the exit status of <I>command</I>.
+<A NAME="lbAQ">&nbsp;</A>
+<H4>Shell Function Definitions</H4>
+
+A shell function is an object that is called like a simple command and
+executes a compound command with a new set of positional parameters.
+Shell functions are declared as follows:
+<DL COMPACT>
+<DT><I>fname</I> () <I>compound-command</I> [<I>redirection</I>]<DD>
+
+<DT><B>function</B> <I>fname</I> [()] <I>compound-command</I> [<I>redirection</I>]<DD>
+
+This defines a function named <I>fname</I>.
+The reserved word <B>function</B> is optional.
+If the <B>function</B> reserved word is supplied, the parentheses are optional.
+The <I>body</I> of the function is the compound command
+<I>compound-command</I>
+
+(see <B>Compound Commands</B> above).
+That command is usually a <I>list</I> of commands between { and }, but
+may be any command listed under <B>Compound Commands</B> above,
+with one exception: If the <B>function</B> reserved word is used, but the
+parentheses are not supplied, the braces are required.
+<I>compound-command</I> is executed whenever <I>fname</I> is specified as the
+name of a simple command.
+When in <I>posix mode</I>, <I>fname</I> must be a valid shell <I>name</I>
+and may not be the name of one of the
+POSIX <I>special builtins</I>.
+In default mode, a function name can be any unquoted shell word that does
+not contain <B>$</B>.
+Any redirections (see
+<FONT SIZE=-1><B>REDIRECTION</B>
+
+</FONT>
+below) specified when a function is defined are performed
+when the function is executed.
+The exit status of a function definition is zero unless a syntax error
+occurs or a readonly function with the same name already exists.
+When executed, the exit status of a function is the exit status of the
+last command executed in the body. (See
+<FONT SIZE=-1><B>FUNCTIONS</B>
+
+</FONT>
+below.)
+</DL>
+<A NAME="lbAR">&nbsp;</A>
+<H3>COMMENTS</H3>
+
+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="lbAS">&nbsp;</A>
+<H3>QUOTING</H3>
+
+<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
+(see
+<FONT SIZE=-1><B>HISTORY EXPANSION</B>
+
+</FONT>
+below), 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 &lt;newline&gt;. If a <B>\</B>&lt;newline&gt; pair
+appears, and the backslash is not itself quoted, the <B>\</B>&lt;newline&gt;
+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>$</B>,
+
+<B>`</B>,
+
+<B>\</B>,
+
+and, when history expansion is enabled,
+<B>!</B>.
+
+When the shell is in <I>posix mode</I>, the <B>!</B> has no special meaning
+within double quotes, even when history expansion is enabled.
+The characters
+<B>$</B>
+
+and
+<B>`</B>
+
+retain their special meaning within double quotes. The backslash
+retains its special meaning only when followed by one of the following
+characters:
+<B>$</B>,
+
+<B>`</B>,
+
+<B>&quot;</B>,
+<B>\</B>,
+
+or
+<B>&lt;newline&gt;</B>.
+
+A double quote may be quoted within double quotes by preceding it with
+a backslash.
+If enabled, history expansion will be performed unless an
+<B>!</B>
+
+appearing in double quotes is escaped using a backslash.
+The backslash preceding the
+<B>!</B>
+
+is not removed.
+<P>
+
+The special parameters
+<B>*</B>
+
+and
+<B>@</B>
+
+have special meaning when in double
+quotes (see
+<FONT SIZE=-1><B>PARAMETERS</B>
+
+</FONT>
+below).
+<P>
+
+Words of the form <B>$</B>aq<I>string</I>aq are treated specially. The
+word expands to <I>string</I>, with backslash-escaped characters replaced
+as specified 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>
+<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>\aq</B>
+
+<DD>
+single quote
+<DT><B>\dq</B>
+
+<DD>
+double quote
+<DT><B>\?</B>
+
+<DD>
+question mark
+<DT><B>\</B><I>nnn</I>
+
+<DD>
+the eight-bit character whose value is the octal value <I>nnn</I>
+(one to three octal 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)
+<DT><B>\u</B><I>HHHH</I>
+
+<DD>
+the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
+<I>HHHH</I> (one to four hex digits)
+<DT><B>\U</B><I>HHHHHHHH</I>
+
+<DD>
+the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
+<I>HHHHHHHH</I> (one to eight hex digits)
+<DT><B>\c</B><I>x</I>
+
+<DD>
+a control-<I>x</I> character
+
+</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>dq<I>string</I>dq)
+will cause the string to be translated according to the current locale.
+The <I>gettext</I> infrastructure performs the message catalog lookup and
+translation, using the <B>LC_MESSAGES</B> and <B>TEXTDOMAIN</B> shell
+variables.
+If the current locale is <B>C</B> or <B>POSIX</B>,
+or if there are no translations available,
+the dollar sign is ignored.
+If the string is translated and replaced, the replacement is
+double-quoted.
+<A NAME="lbAT">&nbsp;</A>
+<H3>PARAMETERS</H3>
+
+A
+<I>parameter</I>
+
+is an entity that stores values.
+It can be a
+<I>name</I>,
+
+a number, or one of the special characters listed below under
+<B>Special Parameters</B>.
+
+A
+<I>variable</I>
+
+is a parameter denoted by a
+<I>name</I>.
+
+A variable has a <I>value</I> and zero or more <I>attributes</I>.
+Attributes are assigned using the
+<B>declare</B>
+
+builtin command (see
+<B>declare</B>
+
+below in
+<FONT SIZE=-1><B>SHELL BUILTIN 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 evaluated as an arithmetic expression even if the $((...)) expansion is
+not used (see
+<B>Arithmetic Expansion</B>
+
+below).
+Word splitting is not performed, with the exception
+of <B>&quot;$@&quot;</B> as explained below under
+<B>Special Parameters</B>.
+
+Pathname expansion is not performed.
+Assignment statements may also appear as arguments to the
+<B>alias</B>,
+
+<B>declare</B>,
+
+<B>typeset</B>,
+
+<B>export</B>,
+
+<B>readonly</B>,
+
+and
+<B>local</B>
+
+builtin commands (<I>declaration</I> commands).
+When in <I>posix mode</I>, these builtins may appear in a command after
+one or more instances of the <B>command</B> builtin and retain these
+assignment statement properties.
+<P>
+
+In the context where an assignment statement is assigning a value
+to a shell variable or array index, the += operator can be used to
+append to or add to the variable's previous value.
+This includes arguments to builtin commands such as <B>declare</B> that
+accept assignment statements (<I>declaration</I> commands).
+When += is applied to a variable for which the <I>integer</I> attribute has been
+set, <I>value</I> is evaluated as an arithmetic expression and added to the
+variable's current value, which is also evaluated.
+When += is applied to an array variable using compound assignment (see
+<B>Arrays</B>
+
+below), the
+variable's value is not unset (as it is when using =), and new values are
+appended to the array beginning at one greater than the array's maximum index
+(for indexed arrays) or added as additional key-value pairs in an
+associative array.
+When applied to a string-valued variable, <I>value</I> is expanded and
+appended to the variable's value.
+<P>
+
+A variable can be assigned the <I>nameref</I> attribute using the
+<B>-n</B> option to the <B>declare</B> or <B>local</B> builtin commands
+(see the descriptions of <B>declare</B> and <B>local</B> below)
+to create a <I>nameref</I>, or a reference to another variable.
+This allows variables to be manipulated indirectly.
+Whenever the nameref variable is referenced, assigned to, unset, or has
+its attributes modified (other than using or changing the <I>nameref</I>
+attribute itself), the
+operation is actually performed on the variable specified by the nameref
+variable's value.
+A nameref is commonly used within shell functions to refer to a variable
+whose name is passed as an argument to the function.
+For instance, if a variable name is passed to a shell function as its first
+argument, running
+<P>
+<DL COMPACT><DT><DD>
+<TT>declare -n ref=$1</TT>
+
+</DL>
+
+<P>
+inside the function creates a nameref variable <B>ref</B> whose value is
+the variable name passed as the first argument.
+References and assignments to <B>ref</B>, and changes to its attributes,
+are treated as references, assignments, and attribute modifications
+to the variable whose name was passed as <B>$1</B>.
+If the control variable in a <B>for</B> loop has the nameref attribute,
+the list of words can be a list of shell variables, and a name reference
+will be established for each word in the list, in turn, when the loop is
+executed.
+Array variables cannot be given the <B>nameref</B> attribute.
+However, nameref variables can reference array variables and subscripted
+array variables.
+Namerefs can be unset using the <B>-n</B> option to the <B>unset</B> builtin.
+Otherwise, if <B>unset</B> is executed with the name of a nameref variable
+as an argument, the variable referenced by the nameref variable will be unset.
+<A NAME="lbAU">&nbsp;</A>
+<H4>Positional Parameters</H4>
+
+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="lbAV">&nbsp;</A>
+<H4>Special Parameters</H4>
+
+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 is not within double quotes, each positional parameter
+expands to a separate word.
+In contexts where it is performed, those words
+are subject to further word splitting and pathname expansion.
+When the expansion occurs within double quotes, it expands to a single word
+with the value of each parameter separated by the first character of the
+<FONT SIZE=-1><B>IFS</B>
+
+</FONT>
+special variable. That is, &quot;<B>$*</B>&quot; is equivalent
+to &quot;<B>$1</B><I>c</I><B>$2</B><I>c</I><B>...</B>&quot;, where
+<I>c</I>
+
+is the first character of the value of the
+<FONT SIZE=-1><B>IFS</B>
+
+</FONT>
+variable. If
+<FONT SIZE=-1><B>IFS</B>
+
+</FONT>
+is unset, the parameters are separated by spaces.
+If
+<FONT SIZE=-1><B>IFS</B>
+
+</FONT>
+is null, the parameters are joined without intervening separators.
+<DT><B>@</B>
+
+<DD>
+Expands to the positional parameters, starting from one.
+In contexts where word splitting is performed, this expands each
+positional parameter to a separate word; if not within double
+quotes, these words are subject to word splitting.
+In contexts where word splitting is not performed,
+this expands to a single word
+with each positional parameter separated by a space.
+When the
+expansion occurs within double quotes, each parameter expands to a
+separate word. That is, &quot;<B>$@</B>&quot; is equivalent to
+&quot;<B>$1</B>&quot; &quot;<B>$2</B>&quot; ...
+If the double-quoted expansion occurs within a word, the expansion of
+the first parameter is joined with the beginning part of the original
+word, and the expansion of the last parameter is joined with the last
+part of the original word.
+When there are no positional parameters, &quot;<B>$@</B>&quot; and
+<B>$@</B>
+
+expand to nothing (i.e., they are removed).
+<DT><B>#</B>
+
+<DD>
+Expands to the number of positional parameters in decimal.
+<DT><B>?</B>
+
+<DD>
+Expands to the exit status of the most recently executed foreground
+pipeline.
+<DT><B>-</B>
+
+<DD>
+Expands to the current option flags as specified upon invocation,
+by the
+<B>set</B>
+
+builtin command, or those set by the shell itself
+(such as the
+<B>-i</B>
+
+option).
+<DT><B>$</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 job most recently placed into the
+background, whether executed as an asynchronous command or using
+the <B>bg</B> builtin (see
+<FONT SIZE=-1><B>JOB CONTROL</B>
+
+</FONT>
+below).
+<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 filename used to invoke
+<B>bash</B>,
+
+as given by argument zero.
+
+</DL>
+<A NAME="lbAW">&nbsp;</A>
+<H4>Shell Variables</H4>
+
+The following variables are set by the shell:
+<P>
+
+
+<DL COMPACT>
+<DT><B>_</B>
+
+<DD>
+At shell startup, set to the pathname used to invoke the
+shell or shell script being executed as passed in the environment
+or argument list.
+Subsequently, expands to the last argument to the previous simple
+command executed in the foreground, after expansion.
+Also set to the full pathname used to invoke 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.
+<DT><B>BASH</B>
+
+<DD>
+Expands to the full filename used to invoke this instance of
+<B>bash</B>.
+
+<DT><B>BASHOPTS</B>
+
+<DD>
+A colon-separated list of enabled shell options. Each word in
+the list is a valid argument for the
+<B>-s</B>
+
+option to the
+<B>shopt</B>
+
+builtin command (see
+<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
+
+</FONT>
+below). The options appearing in
+<FONT SIZE=-1><B>BASHOPTS</B>
+
+</FONT>
+are those reported as
+<I>on</I>
+
+by <B>shopt</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>BASHPID</B>
+
+<DD>
+Expands to the process ID of the current <B>bash</B> process.
+This differs from <B>$$</B> under certain circumstances, such as subshells
+that do not require <B>bash</B> to be re-initialized.
+Assignments to
+<FONT SIZE=-1><B>BASHPID</B>
+
+</FONT>
+have no effect.
+If
+<B>BASHPID</B>
+
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<DT><B>BASH_ALIASES</B>
+
+<DD>
+An associative array variable whose members correspond to the internal
+list of aliases as maintained by the <B>alias</B> builtin.
+Elements added to this array appear in the alias list; however,
+unsetting array elements currently does not cause aliases to be removed
+from the alias list.
+If
+<B>BASH_ALIASES</B>
+
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<DT><B>BASH_ARGC</B>
+
+<DD>
+An array variable whose values are the number of parameters in each
+frame of the current <B>bash</B> execution call stack.
+The number of
+parameters to the current subroutine (shell function or script executed
+with <B>.</B> or <B>source</B>) is at the top of the stack.
+When a subroutine is executed, the number of parameters passed is pushed onto
+<FONT SIZE=-1><B>BASH_ARGC</B>.
+
+</FONT>
+The shell sets
+<FONT SIZE=-1><B>BASH_ARGC</B>
+
+</FONT>
+only when in extended debugging mode (see the description of the
+<B>extdebug</B>
+
+option to the
+<B>shopt</B>
+
+builtin below).
+Setting <B>extdebug</B> after the shell has started to execute a script,
+or referencing this variable when <B>extdebug</B> is not set,
+may result in inconsistent values.
+<DT><B>BASH_ARGV</B>
+
+<DD>
+An array variable containing all of the parameters in the current <B>bash</B>
+execution call stack. The final parameter of the last subroutine call
+is at the top of the stack; the first parameter of the initial call is
+at the bottom. When a subroutine is executed, the parameters supplied
+are pushed onto
+<FONT SIZE=-1><B>BASH_ARGV</B>.
+
+</FONT>
+The shell sets
+<FONT SIZE=-1><B>BASH_ARGV</B>
+
+</FONT>
+only when in extended debugging mode
+(see the description of the
+<B>extdebug</B>
+
+option to the
+<B>shopt</B>
+
+builtin below).
+Setting <B>extdebug</B> after the shell has started to execute a script,
+or referencing this variable when <B>extdebug</B> is not set,
+may result in inconsistent values.
+<DT><B>BASH_ARGV0</B>
+
+<DD>
+When referenced, this variable expands to the name of the shell or shell
+script (identical to
+<B>$0</B>;
+
+see the description of special parameter 0 above).
+Assignment to
+<B>BASH_ARGV0</B>
+
+causes the value assigned to also be assigned to <B>$0</B>.
+If
+<B>BASH_ARGV0</B>
+
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<DT><B>BASH_CMDS</B>
+
+<DD>
+An associative array variable whose members correspond to the internal
+hash table of commands as maintained by the <B>hash</B> builtin.
+Elements added to this array appear in the hash table; however,
+unsetting array elements currently does not cause command names to be removed
+from the hash table.
+If
+<B>BASH_CMDS</B>
+
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<DT><B>BASH_COMMAND</B>
+
+<DD>
+The command currently being executed or about to be executed, unless the
+shell is executing a command as the result of a trap,
+in which case it is the command executing at the time of the trap.
+If
+<B>BASH_COMMAND</B>
+
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<DT><B>BASH_EXECUTION_STRING</B>
+
+<DD>
+The command argument to the <B>-c</B> invocation option.
+<DT><B>BASH_LINENO</B>
+
+<DD>
+An array variable whose members are the line numbers in source files
+where each corresponding member of
+<FONT SIZE=-1><B>FUNCNAME</B>
+
+</FONT>
+was invoked.
+<B>${BASH_LINENO[</B><I>$i</I><B>]}</B> is the line number in the source
+file (<B>${BASH_SOURCE[</B><I>$i+1</I><B>]}</B>) where
+<B>${FUNCNAME[</B><I>$i</I><B>]}</B> was called
+(or <B>${BASH_LINENO[</B><I>$i-1</I><B>]}</B> if referenced within another
+shell function).
+Use
+<FONT SIZE=-1><B>LINENO</B>
+
+</FONT>
+to obtain the current line number.
+<DT><B>BASH_LOADABLES_PATH</B>
+
+<DD>
+A colon-separated list of directories in which the shell looks for
+dynamically loadable builtins specified by the
+<B>enable</B>
+
+command.
+<DT><B>BASH_REMATCH</B>
+
+<DD>
+An array variable whose members are assigned by the <B>=~</B> binary
+operator to the <B>[[</B> conditional command.
+The element with index 0 is the portion of the string
+matching the entire regular expression.
+The element with index <I>n</I> is the portion of the
+string matching the <I>n</I>th parenthesized subexpression.
+<DT><B>BASH_SOURCE</B>
+
+<DD>
+An array variable whose members are the source filenames
+where the corresponding shell function names in the
+<FONT SIZE=-1><B>FUNCNAME</B>
+
+</FONT>
+array variable are defined.
+The shell function
+<B>${FUNCNAME[</B><I>$i</I><B>]}</B> is defined in the file
+<B>${BASH_SOURCE[</B><I>$i</I><B>]}</B> and called from
+<B>${BASH_SOURCE[</B><I>$i+1</I><B>]}</B>.
+<DT><B>BASH_SUBSHELL</B>
+
+<DD>
+Incremented by one within each subshell or subshell environment when
+the shell begins executing in that environment.
+The initial value is 0.
+If
+<B>BASH_SUBSHELL</B>
+
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<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
+<FONT SIZE=-1><B>MACHTYPE</B>.
+
+</FONT>
+</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_KEY</B>
+
+<DD>
+The key (or final key of a key sequence) used to invoke the current
+completion function.
+<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_TYPE</B>
+
+<DD>
+Set to an integer value corresponding to the type of completion attempted
+that caused a completion function to be called:
+<I>TAB</I>, for normal completion,
+<I>?</I>, for listing completions after successive tabs,
+<I>!</I>, for listing alternatives on partial word completion,
+<I>@</I>, to list completions if the word is not unmodified,
+or
+<I>%</I>, for menu completion.
+This variable is available only in shell functions and external
+commands invoked by the
+programmable completion facilities (see <B>Programmable Completion</B>
+below).
+<DT><B>COMP_WORDBREAKS</B>
+
+<DD>
+The set of characters that the <B>readline</B> library treats as word
+separators when performing word completion.
+If
+<FONT SIZE=-1><B>COMP_WORDBREAKS</B>
+
+</FONT>
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<DT><B>COMP_WORDS</B>
+
+<DD>
+An array variable (see <B>Arrays</B> below) consisting of the individual
+words in the current command line.
+The line is split into words as <B>readline</B> would split it, using
+<FONT SIZE=-1><B>COMP_WORDBREAKS</B>
+
+</FONT>
+as described above.
+This variable is available only in shell functions invoked by the
+programmable completion facilities (see <B>Programmable Completion</B>
+below).
+<DT><B>COPROC</B>
+
+<DD>
+An array variable (see <B>Arrays</B> below) created to hold the file descriptors
+for output from and input to an unnamed coprocess (see <B>Coprocesses</B>
+above).
+<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>EPOCHREALTIME</B>
+
+<DD>
+Each time this parameter is referenced, it expands to the number of seconds
+since the Unix Epoch (see <I>time</I>(3)) as a floating point value
+with micro-second granularity.
+Assignments to
+<FONT SIZE=-1><B>EPOCHREALTIME</B>
+
+</FONT>
+are ignored.
+If
+<FONT SIZE=-1><B>EPOCHREALTIME</B>
+
+</FONT>
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<DT><B>EPOCHSECONDS</B>
+
+<DD>
+Each time this parameter is referenced, it expands to the number of seconds
+since the Unix Epoch (see <I>time</I>(3)).
+Assignments to
+<FONT SIZE=-1><B>EPOCHSECONDS</B>
+
+</FONT>
+are ignored.
+If
+<FONT SIZE=-1><B>EPOCHSECONDS</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>
+An array variable containing the names of all shell functions
+currently in the execution call stack.
+The element with index 0 is the name of any currently-executing
+shell function.
+The bottom-most element (the one with the highest index) is
+<TT>&quot;main&quot;</TT>.
+
+This variable exists only when a shell function is executing.
+Assignments to
+<FONT SIZE=-1><B>FUNCNAME</B>
+
+</FONT>
+have no effect.
+If
+<FONT SIZE=-1><B>FUNCNAME</B>
+
+</FONT>
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<P>
+
+
+This variable can be used with <B>BASH_LINENO</B> and <B>BASH_SOURCE</B>.
+Each element of <B>FUNCNAME</B> has corresponding elements in
+<B>BASH_LINENO</B> and <B>BASH_SOURCE</B> to describe the call stack.
+For instance, <B>${FUNCNAME[</B><I>$i</I><B>]}</B> was called from the file
+<B>${BASH_SOURCE[</B><I>$i+1</I><B>]}</B> at line number
+<B>${BASH_LINENO[</B><I>$i</I><B>]}</B>.
+The <B>caller</B> builtin displays the current call stack using this
+information.
+<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.
+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.
+Assignments to
+<FONT SIZE=-1><B>HISTCMD</B>
+
+</FONT>
+are ignored.
+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>MAPFILE</B>
+
+<DD>
+An array variable (see <B>Arrays</B> below) created to hold the text
+read by the <B>mapfile</B> builtin when no variable name is supplied.
+<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, it expands to a random integer
+between 0 and 32767.
+Assigning
+a value to
+<FONT SIZE=-1><B>RANDOM</B>
+
+</FONT>
+initializes (seeds) the sequence of random numbers.
+If
+<FONT SIZE=-1><B>RANDOM</B>
+
+</FONT>
+is unset, it loses its special properties, even if it is
+subsequently reset.
+<DT><B>READLINE_LINE</B>
+
+<DD>
+The contents of the
+<B>readline</B>
+
+line buffer, for use with
+<TT>bind -x</TT>
+
+(see
+<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
+
+</FONT>
+below).
+<DT><B>READLINE_MARK</B>
+
+<DD>
+The position of the mark (saved insertion point) in the
+<B>readline</B>
+
+line buffer, for use with
+<TT>bind -x</TT>
+
+(see
+<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
+
+</FONT>
+below).
+The characters between the insertion point and the mark are often
+called the <I>region</I>.
+<DT><B>READLINE_POINT</B>
+
+<DD>
+The position of the insertion point in the
+<B>readline</B>
+
+line buffer, for use with
+<TT>bind -x</TT>
+
+(see
+<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
+
+</FONT>
+below).
+<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.
+The number of seconds at shell invocation and the current time is always
+determined by querying the system clock.
+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>SRANDOM</B>
+
+<DD>
+This variable expands to a 32-bit pseudo-random number each time it is
+referenced. The random number generator is not linear on systems that
+support <TT>/dev/urandom</TT> or <I>arc4random</I>, so each returned number
+has no relationship to the numbers preceding it.
+The random number generator cannot be seeded, so assignments to this
+variable have no effect.
+If
+<FONT SIZE=-1><B>SRANDOM</B>
+
+</FONT>
+is unset, it loses its special properties,
+even if it is subsequently reset.
+<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_COMPAT</B>
+
+<DD>
+The value is used to set the shell's compatibility level.
+See
+<FONT SIZE=-1><B>SHELL COMPATIBILITY MODE</B>
+
+</FONT>
+below for a description of the various compatibility
+levels and their effects.
+The value may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
+corresponding to the desired compatibility level.
+If <B>BASH_COMPAT</B> is unset or set to the empty string, the compatibility
+level is set to the default for the current version.
+If <B>BASH_COMPAT</B> is set to a value that is not one of the valid
+compatibility levels, the shell prints an error message and sets the
+compatibility level to the default for the current version.
+The valid values correspond to the compatibility levels
+described below under
+<FONT SIZE=-1><B>BSHELL</B>COMPATIBILITY<B>MODE</B>.
+
+</FONT>
+For example, 4.2 and 42 are valid values that correspond
+to the <B>compat42</B> <B>shopt</B> option
+and set the compatibility level to 42.
+The current version is also a valid value.
+<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 filename.
+<FONT SIZE=-1><B>PATH</B>
+
+</FONT>
+is not used to search for the resultant filename.
+<DT><B>BASH_XTRACEFD</B>
+
+<DD>
+If set to an integer corresponding to a valid file descriptor, <B>bash</B>
+will write the trace output generated when
+<TT>set -x</TT>
+
+is enabled to that file descriptor.
+The file descriptor is closed when
+<FONT SIZE=-1><B>BASH_XTRACEFD</B>
+
+</FONT>
+is unset or assigned a new value.
+Unsetting
+<FONT SIZE=-1><B>BASH_XTRACEFD</B>
+
+</FONT>
+or assigning it the empty string causes the
+trace output to be sent to the standard error.
+Note that setting
+<FONT SIZE=-1><B>BASH_XTRACEFD</B>
+
+</FONT>
+to 2 (the standard error file
+descriptor) and then unsetting it will result in the standard error
+being closed.
+<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
+<TT>&quot;.:~:/usr&quot;</TT>.
+
+<DT><B>CHILD_MAX</B>
+
+<DD>
+Set the number of exited child status values for the shell to remember.
+Bash will not allow this value to be decreased below a POSIX-mandated
+minimum, and there is a maximum value (currently 8192) that this may
+not exceed.
+The minimum value is system-dependent.
+<DT><B>COLUMNS</B>
+
+<DD>
+Used by the <B>select</B> compound command to determine the terminal width
+when printing selection lists.
+Automatically set if the
+<B>checkwinsize</B>
+
+option is enabled or in an interactive shell upon receipt of a
+<FONT SIZE=-1><B>SIGWINCH</B>.
+
+</FONT>
+<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).
+Each array element contains one possible completion.
+<DT><B>EMACS</B>
+
+<DD>
+If <B>bash</B> finds this variable in the environment when the shell starts
+with value
+<TT>t</TT>,
+
+it assumes that the shell is running in an Emacs shell buffer and disables
+line editing.
+<DT><B>ENV</B>
+
+<DD>
+Expanded and executed similarly to
+<FONT SIZE=-1><B>BASH_ENV</B>
+
+</FONT>
+(see <B>INVOCATION</B> above)
+when an interactive shell is invoked in <I>posix mode</I>.
+<DT><B>EXECIGNORE</B>
+
+<DD>
+A colon-separated list of shell patterns (see <B>Pattern Matching</B>)
+defining the list of filenames to be ignored by command search using
+<B>PATH</B>.
+Files whose full pathnames match one of these patterns are not considered
+executable files for the purposes of completion and command execution
+via <B>PATH</B> lookup.
+This does not affect the behavior of the <B>[</B>, <B>test</B>, and <B>[[</B>
+commands.
+Full pathnames in the command hash table are not subject to <B>EXECIGNORE</B>.
+Use this variable to ignore shared library files that have the executable
+bit set, but are not executable files.
+The pattern matching honors the setting of the <B>extglob</B> shell
+option.
+<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
+<TT>&quot;.o:~&quot;</TT>.
+
+<DT><B>FUNCNEST</B>
+
+<DD>
+If set to a numeric value greater than 0, defines a maximum function
+nesting level. Function invocations that exceed this nesting level
+will cause the current command to abort.
+<DT><B>GLOBIGNORE</B>
+
+<DD>
+A colon-separated list of patterns defining the set of file names to
+be ignored by pathname expansion.
+If a file name matched by a pathname expansion pattern also matches one
+of the patterns in
+<FONT SIZE=-1><B>GLOBIGNORE</B>,
+
+</FONT>
+it is removed from the list of matches.
+<DT><B>HISTCONTROL</B>
+
+<DD>
+A colon-separated list of values controlling how commands are saved on
+the history list.
+If the list of values includes
+<I>ignorespace</I>,
+
+lines which begin with a
+<B>space</B>
+
+character are not saved in the history list.
+A value of
+<I>ignoredups</I>
+
+causes lines matching the previous history entry to not be saved.
+A value of
+<I>ignoreboth</I>
+
+is shorthand for <I>ignorespace</I> and <I>ignoredups</I>.
+A value of
+<I>erasedups</I>
+
+causes all previous lines matching the current line to be removed from
+the history list before that line is saved.
+Any value not in the above list is ignored.
+If
+<FONT SIZE=-1><B>HISTCONTROL</B>
+
+</FONT>
+is unset, or does not include a valid value,
+all lines read by the shell parser are saved on the history list,
+subject to the value of
+<FONT SIZE=-1><B>HISTIGNORE</B>.
+
+</FONT>
+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
+<FONT SIZE=-1><B>HISTCONTROL</B>.
+
+</FONT>
+<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 a 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 by removing the oldest entries.
+The history file is also truncated to this size after
+writing it when a shell exits.
+If the value is 0, the history file is truncated to zero size.
+Non-numeric values and numeric values less than zero inhibit truncation.
+The shell sets the default value to the value of <B>HISTSIZE</B>
+after reading any startup files.
+<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
+<FONT SIZE=-1><B>HISTCONTROL</B>
+
+</FONT>
+are applied.
+In addition to the normal shell pattern matching characters, `<B>&amp;</B>'
+matches the previous history line. `<B>&amp;</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
+<FONT SIZE=-1><B>HISTIGNORE</B>.
+
+</FONT>
+The pattern matching honors the setting of the <B>extglob</B> shell
+option.
+<DT><B>HISTSIZE</B>
+
+<DD>
+The number of commands to remember in the command history (see
+<FONT SIZE=-1><B>HISTORY</B>
+
+</FONT>
+below).
+If the value is 0, commands are not saved in the history list.
+Numeric values less than zero result in every command being saved
+on the history list (there is no limit).
+The shell sets the default value to 500 after reading any startup files.
+<DT><B>HISTTIMEFORMAT</B>
+
+<DD>
+If this variable is set and not null, its value is used as a format string
+for <I>strftime</I>(3) to print the time stamp associated with each history
+entry displayed by the <B>history</B> builtin.
+If this variable is set, time stamps are written to the history file so
+they may be preserved across shell sessions.
+This uses the history comment character to distinguish timestamps from
+other history lines.
+<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, or does not name a readable file,
+<B>bash</B> attempts to read
+
+<I>/etc/hosts</I>
+
+to obtain the list of possible hostname completions.
+When
+<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
+``&lt;space&gt;&lt;tab&gt;&lt;newline&gt;''.
+<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>INSIDE_EMACS</B>
+
+<DD>
+If this variable appears in the environment when the shell starts,
+<B>bash</B> assumes that it is running inside an Emacs shell buffer
+and may disable line editing, depending on the value of <B>TERM</B>.
+<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
+<FONT SIZE=-1><B>LANG</B>
+
+</FONT>
+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>LC_TIME</B>
+
+<DD>
+This variable determines the locale category used for data and time
+formatting.
+<DT><B>LINES</B>
+
+<DD>
+Used by the <B>select</B> compound command to determine the column length
+for printing selection lists.
+Automatically set if the
+<B>checkwinsize</B>
+
+option is enabled or in an interactive shell upon receipt of a
+<FONT SIZE=-1><B>SIGWINCH</B>.
+
+</FONT>
+<DT><B>MAIL</B>
+
+<DD>
+If this parameter is set to a file or directory 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 or
+Maildir-format directory.
+<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 filenames to be checked for mail.
+The message to be printed when mail arrives in a particular file
+may be specified by separating the filename from the message with a `?'.
+When used in the text of the message, <B>$_</B> expands to the name of
+the current mailfile.
+Example:
+<DL COMPACT><DT><DD>
+<P>
+
+<B>MAILPATH</B>=aq/var/mail/bfox?&quot;You have mail&quot;:~/shell-mail?&quot;$_ has mail!&quot;aq
+<P>
+
+<B>Bash</B>
+
+can be configured to supply
+a default value for this variable (there is no value by default),
+but the location of the user
+mail files that it uses is system dependent (e.g., /var/mail/<B>$USER</B>).
+</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).
+A zero-length (null) directory name in the value of
+<FONT SIZE=-1><B>PATH</B>
+
+</FONT>
+indicates the current directory.
+A null directory name may appear as two adjacent colons, or as an initial
+or trailing colon.
+The default path is system-dependent,
+and is set by the administrator who installs
+<B>bash</B>.
+
+A common value is
+
+<TT>/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin</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.
+When the shell enters <I>posix mode</I>, it sets this variable if it was
+not already set.
+<DT><B>PROMPT_COMMAND</B>
+
+<DD>
+If this variable is set, and is an array,
+the value of each set element is executed as a command
+prior to issuing each primary prompt.
+If this is set but not an array variable,
+its value is used as a command to execute instead.
+<DT><B>PROMPT_DIRTRIM</B>
+
+<DD>
+If set to a number greater than zero, the value is used as the number of
+trailing directory components to retain when expanding the <B>\w</B> and
+<B>\W</B> prompt string escapes (see
+<FONT SIZE=-1><B>PROMPTING</B>
+
+</FONT>
+below). Characters removed are replaced with an ellipsis.
+<DT><B>PS0</B>
+
+<DD>
+The value of this parameter is expanded (see
+<FONT SIZE=-1><B>PROMPTING</B>
+
+</FONT>
+below) and displayed by interactive shells after reading a command
+and before the command is executed.
+<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
+<FONT SIZE=-1><B>PS1</B>
+
+</FONT>
+and used as the secondary prompt string. The default is
+``<B>&gt; </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
+<FONT SIZE=-1><B>PS1</B>
+
+</FONT>
+and the value is printed before each command
+<B>bash</B>
+
+displays during an execution trace. The first character of
+the expanded value 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>SHELL</B>
+
+<DD>
+This variable expands to the full pathname to the shell.
+If it is not set when the shell starts,
+<B>bash</B>
+
+assigns to it the full pathname of the current user's login shell.
+<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>$aq\nreal\t%3lR\nuser\t%3lU\nsys\t%3lSaq</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,
+<FONT SIZE=-1><B>TMOUT</B>
+
+</FONT>
+is treated as the
+default timeout for the <B>read</B> builtin.
+The <B>select</B> command terminates if input does not arrive
+after
+<FONT SIZE=-1><B>TMOUT</B>
+
+</FONT>
+seconds when input is coming from a terminal.
+In an interactive shell, the value is interpreted as the
+number of seconds to wait for a line of input after issuing the
+primary prompt.
+<B>Bash</B>
+
+terminates after waiting for that number of seconds if a complete
+line of input does not arrive.
+<DT><B>TMPDIR</B>
+
+<DD>
+If set, <B>bash</B> uses its value as the name of a directory in which
+<B>bash</B> creates temporary files for the shell's use.
+<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><I>string</I> 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="lbAX">&nbsp;</A>
+<H4>Arrays</H4>
+
+<B>Bash</B>
+
+provides one-dimensional indexed and associative array variables.
+Any variable may be used as an indexed array; the
+<B>declare</B>
+
+builtin 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.
+Indexed arrays are referenced using integers (including arithmetic
+expressions) and are zero-based; associative arrays are referenced
+using arbitrary strings.
+Unless otherwise noted, indexed array indices must be non-negative integers.
+<P>
+
+An indexed 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.
+To explicitly declare an indexed 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.
+<P>
+
+Associative arrays are created using
+<B>declare -A </B><I>name</I>.
+
+<P>
+
+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> may be of the form [<I>subscript</I>]=<I>string</I>.
+Indexed array assignments do not require anything but <I>string</I>.
+Each <I>value</I> in the list is expanded using all the shell expansions
+described below under
+<FONT SIZE=-1><B>EXPANSION</B>.
+
+</FONT>
+When assigning to indexed arrays, if the optional brackets and subscript
+are supplied, that index is assigned to;
+otherwise the index of the element assigned is the last index assigned
+to by the statement plus one. Indexing starts at zero.
+<P>
+
+When assigning to an associative array, the words in a compound assignment
+may be either assignment statements, for which the subscript is required,
+or a list of words that is interpreted as a sequence of alternating keys
+and values:
+<I>name</I>=<B>( </B><I>key1 value1 key2 value2</I> ...<B>)</B>.
+These are treated identically to
+<I>name</I>=<B>(</B> [<I>key1</I>]=<I>value1</I> [<I>key2</I>]=<I>value2</I> ...<B>)</B>.
+The first word in the list determines how the remaining words
+are interpreted; all assignments in a list must be of the same type.
+When using key/value pairs, the keys may not be missing or empty;
+a final missing value is treated like the empty string.
+<P>
+
+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.
+When assigning to an indexed array, if
+<I>name</I>
+
+is subscripted by a negative number, that number is
+interpreted as relative to one greater than the maximum index of
+<I>name</I>, so negative indices count back from the end of the
+array, and an index of -1 references the last element.
+<P>
+
+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.
+If the double-quoted expansion occurs within a word, the expansion of
+the first parameter is joined with the beginning part of the original
+word, and the expansion of the last parameter is joined with the last
+part of the original word.
+This is analogous to the expansion
+of the special parameters <B>*</B> and <B>@</B> (see
+<B>Special Parameters</B>
+
+above). ${#<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.
+If the
+<I>subscript</I>
+
+used to reference an element of an indexed array
+evaluates to a number less than zero, it is
+interpreted as relative to one greater than the maximum index of the array,
+so negative indices count back from the end of the
+array, and an index of -1 references the last element.
+<P>
+
+Referencing an array variable without a subscript is equivalent to
+referencing the array with a subscript of 0.
+Any reference to a variable using a valid subscript is legal, and
+<B>bash</B>
+
+will create an array if necessary.
+<P>
+
+An array variable is considered set if a subscript has been assigned a
+value. The null string is a valid value.
+<P>
+
+It is possible to obtain the keys (indices) of an array as well as the values.
+${<B>!</B><I>name</I>[<I>@</I>]} and ${<B>!</B><I>name</I>[<I>*</I>]}
+expand to the indices assigned in array variable <I>name</I>.
+The treatment when in double quotes is similar to the expansion of the
+special parameters <I>@</I> and <I>*</I> within double quotes.
+<P>
+
+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>,
+for both indexed and associative arrays.
+Negative subscripts to indexed arrays are interpreted as described above.
+Unsetting the last element of an array variable does not unset the variable.
+<B>unset</B> <I>name</I>, where <I>name</I> is an array, 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>
+
+When using a variable name with a subscript as an argument to a command,
+such as with <B>unset</B>, without using the word expansion syntax
+described above, the argument is subject to pathname expansion.
+If pathname expansion is not desired, the argument should be quoted.
+<P>
+
+The
+<B>declare</B>,
+
+<B>local</B>,
+
+and
+<B>readonly</B>
+
+builtins each accept a
+<B>-a</B>
+
+option to specify an indexed array and a
+<B>-A</B>
+
+option to specify an associative array.
+If both options are supplied,
+<B>-A</B>
+
+takes precedence.
+The
+<B>read</B>
+
+builtin accepts a
+<B>-a</B>
+
+option to assign a list of words read from the standard input
+to an array. The
+<B>set</B>
+
+and
+<B>declare</B>
+
+builtins display array values in a way that allows them to be
+reused as assignments.
+<A NAME="lbAY">&nbsp;</A>
+<H3>EXPANSION</H3>
+
+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 and variable expansion, 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>.
+This is performed at the
+same time as tilde, parameter, variable, and arithmetic expansion and
+command substitution.
+<P>
+
+After these expansions are performed, quote characters present in the
+original word are removed unless they have been quoted themselves
+(<I>quote removal</I>).
+<P>
+
+Only brace expansion, word splitting, and pathname expansion
+can increase the number of words of the expansion; other expansions
+expand a single word to a single word.
+The only exceptions to this are the expansions of
+&quot;<B>$@</B>&quot; and &quot;<B>${</B><I>name</I><B>[@]}</B>&quot;,
+and, in most cases, <B>$*</B> and <B>${</B><I>name</I><B>[*]}</B>
+as explained above (see
+<FONT SIZE=-1><B>PARAMETERS</B>).
+
+</FONT>
+<A NAME="lbAZ">&nbsp;</A>
+<H4>Brace Expansion</H4>
+
+<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 either a series of comma-separated strings or
+a sequence expression between a pair of braces, followed by
+an optional
+<I>postscript</I>.
+
+The preamble is prefixed to each string contained
+within the braces, and the postscript is then appended
+to each resulting string, expanding left to right.
+<P>
+
+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>
+
+A sequence expression takes the form
+<B>{</B><I>x</I><B>..</B><I>y</I><B>[..</B><I>incr</I><B>]}</B>,
+where <I>x</I> and <I>y</I> are either integers or single characters,
+and <I>incr</I>, an optional increment, is an integer.
+When integers are supplied, the expression expands to each number between
+<I>x</I> and <I>y</I>, inclusive.
+Supplied integers may be prefixed with <I>0</I> to force each term to have the
+same width.
+When either <I>x</I> or y begins with a zero, the shell
+attempts to force all generated terms to contain the same number of digits,
+zero-padding where necessary.
+When characters are supplied, the expression expands to each character
+lexicographically between <I>x</I> and <I>y</I>, inclusive,
+using the default C locale.
+Note that both <I>x</I> and <I>y</I> must be of the same type.
+When the increment is supplied, it is used as the difference between
+each term. The default increment is 1 or -1 as appropriate.
+<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 or a valid
+sequence expression.
+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, and inhibits brace
+expansion until the closing <B>}</B>.
+<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="lbBA">&nbsp;</A>
+<H4>Tilde Expansion</H4>
+
+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 the first
+<B>=</B>.
+
+In these cases, tilde expansion is also performed.
+Consequently, one may use filenames 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.
+<P>
+
+Bash also performs tilde expansion on words satisfying the conditions of
+variable assignments (as described above under
+<FONT SIZE=-1><B>PARAMETERS</B>)
+
+</FONT>
+when they appear as arguments to simple commands.
+Bash does not do this, except for the <I>declaration</I> commands listed
+above, when in <I>posix mode</I>.
+<A NAME="lbBB">&nbsp;</A>
+<H4>Parameter Expansion</H4>
+
+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 parameter
+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.
+The <I>parameter</I> is a shell parameter as described above
+<B>PARAMETERS</B>) or an array reference (<B>Arrays</B>).
+
+</DL>
+<P>
+
+If the first character of <I>parameter</I> is an exclamation point (<B>!</B>),
+and <I>parameter</I> is not a <I>nameref</I>,
+it introduces a level of indirection.
+<B>Bash</B> uses the value formed by expanding the rest of
+<I>parameter</I> as the new <I>parameter</I>; this is then
+expanded and that value is used in the rest of the expansion, rather
+than the expansion of the original <I>parameter</I>.
+This is known as <I>indirect expansion</I>.
+The value is subject to tilde expansion,
+parameter expansion, command substitution, and arithmetic expansion.
+If <I>parameter</I> is a nameref, this expands to the name of the
+parameter referenced by <I>parameter</I> instead of performing the
+complete indirect expansion.
+The exceptions to this are the expansions of ${<B>!</B><I>prefix</I><B>*</B>} and
+${<B>!</B><I>name</I>[<I>@</I>]} described below.
+The exclamation point must immediately follow the left brace in order to
+introduce indirection.
+<P>
+
+In each of the cases below, <I>word</I> is subject to tilde expansion,
+parameter expansion, command substitution, and arithmetic expansion.
+<P>
+
+When not performing substring expansion, using the forms documented below
+(e.g., <B>:-</B>),
+<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>${<I>parameter</I><B>:</B><I>offset</I>}<DD>
+
+<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 the value of <I>parameter</I>
+starting at the character specified by <I>offset</I>.
+If <I>parameter</I> is <B>@</B>, an indexed array subscripted by
+<B>@</B> or <B>*</B>, or an associative array name, the results differ as
+described below.
+If <I>length</I> is omitted, expands to the substring of the value of
+<I>parameter</I> starting at the character specified by <I>offset</I>
+and extending to the end of the value.
+<I>length</I> and <I>offset</I> are arithmetic expressions (see
+<FONT SIZE=-1><B>ARITHMETIC EVALUATION</B>
+
+</FONT>
+below).
+<P>
+If <I>offset</I> evaluates to a number less than zero, the value
+is used as an offset in characters
+from the end of the value of <I>parameter</I>.
+If <I>length</I> evaluates to a number less than zero,
+it is interpreted as an offset in characters
+from the end of the value of <I>parameter</I> rather than
+a number of characters, and the expansion is the characters between
+<I>offset</I> and that result.
+Note that a negative offset must be separated from the colon by at least
+one space to avoid being confused with the <B>:-</B> expansion.
+<P>
+If <I>parameter</I> is <B>@</B>, the result is <I>length</I> positional
+parameters beginning at <I>offset</I>.
+A negative <I>offset</I> is taken relative to one greater than the greatest
+positional parameter, so an offset of -1 evaluates to the last positional
+parameter.
+It is an expansion error if <I>length</I> evaluates to a number less than
+zero.
+<P>
+If <I>parameter</I> is an indexed array name subscripted by @ or *,
+the result is the <I>length</I>
+members of the array beginning with ${<I>parameter</I>[<I>offset</I>]}.
+A negative <I>offset</I> is taken relative to one greater than the maximum
+index of the specified array.
+It is an expansion error if <I>length</I> evaluates to a number less than
+zero.
+<P>
+Substring expansion applied to an associative array produces undefined
+results.
+<P>
+Substring indexing is zero-based unless the positional parameters
+are used, in which case the indexing starts at 1 by default.
+If <I>offset</I> is 0, and the positional parameters are used, <B>$0</B> is
+prefixed to the list.
+<DT>${<B>!</B><I>prefix</I><B>*</B>}<DD>
+
+<DT>${<B>!</B><I>prefix</I><B>@</B>}<DD>
+
+<B>Names matching prefix</B>.
+Expands to the names of variables whose names begin with <I>prefix</I>,
+separated by the first character of the
+<FONT SIZE=-1><B>IFS</B>
+
+</FONT>
+special variable.
+When <I>@</I> is used and the expansion appears within double quotes, each
+variable name expands to a separate word.
+<DT>${<B>!</B><I>name</I>[<I>@</I>]}<DD>
+
+<DT>${<B>!</B><I>name</I>[<I>*</I>]}<DD>
+
+<B>List of array keys</B>.
+If <I>name</I> is an array variable, expands to the list of array indices
+(keys) assigned in <I>name</I>.
+If <I>name</I> is not an array, expands to 0 if <I>name</I> is set and null
+otherwise.
+When <I>@</I> is used and the expansion appears within double quotes, each
+key expands to a separate word.
+<DT>${<B>#</B><I>parameter</I>}<DD>
+<B>Parameter length</B>.
+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.
+If
+<I>parameter</I>
+
+is an indexed array name subscripted by a negative number, that number is
+interpreted as relative to one greater than the maximum index of
+<I>parameter</I>, so negative indices count back from the end of the
+array, and an index of -1 references the last element.
+<DT>${<I>parameter</I><B>#</B><I>word</I>}<DD>
+
+<DT>${<I>parameter</I><B>##</B><I>word</I>}<DD>
+
+<B>Remove matching prefix pattern</B>.
+The
+<I>word</I>
+
+is expanded to produce a pattern just as in pathname
+expansion, and matched against the expanded value of
+<I>parameter</I>
+
+using the rules described under
+<B>Pattern Matching</B>
+
+below.
+If the pattern matches the beginning of
+the value of
+<I>parameter</I>,
+
+then the result of the expansion is the expanded value of
+<I>parameter</I>
+
+with the shortest matching pattern (the ``<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>${<I>parameter</I><B>%</B><I>word</I>}<DD>
+
+<DT>${<I>parameter</I><B>%%</B><I>word</I>}<DD>
+
+<B>Remove matching suffix pattern</B>.
+The <I>word</I> is expanded to produce a pattern just as in
+pathname expansion, and matched against the expanded value of
+<I>parameter</I>
+
+using the rules described under
+<B>Pattern Matching</B>
+
+below.
+If the pattern matches a trailing portion of the expanded value of
+<I>parameter</I>,
+
+then the result of the expansion is the expanded value of
+<I>parameter</I>
+
+with the shortest matching pattern (the ``<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>${<I>parameter</I><B>/</B><I>pattern</I><B>/</B><I>string</I>}<DD>
+<B>Pattern substitution</B>.
+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>.
+The match is performed using the rules described under
+<B>Pattern Matching</B>
+
+below.
+If <I>pattern</I> begins with <B>/</B>, all matches of <I>pattern</I> are
+replaced with <I>string</I>. Normally only the first match is replaced.
+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 the
+<B>nocasematch</B>
+
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+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.
+<DT>${<I>parameter</I><B>^</B><I>pattern</I>}<DD>
+
+<DT>${<I>parameter</I><B>^^</B><I>pattern</I>}<DD>
+<DT>${<I>parameter</I><B>,</B><I>pattern</I>}<DD>
+<DT>${<I>parameter</I><B>,,</B><I>pattern</I>}<DD>
+
+<B>Case modification</B>.
+This expansion modifies the case of alphabetic characters in <I>parameter</I>.
+The <I>pattern</I> is expanded to produce a pattern just as in
+pathname expansion.
+Each character in the expanded value of <I>parameter</I> is tested against
+<I>pattern</I>, and, if it matches the pattern, its case is converted.
+The pattern should not attempt to match more than one character.
+The <B>^</B> operator converts lowercase letters matching <I>pattern</I>
+to uppercase; the <B>,</B> operator converts matching uppercase letters
+to lowercase.
+The <B>^^</B> and <B>,,</B> expansions convert each matched character in the
+expanded value; the <B>^</B> and <B>,</B> expansions match and convert only
+the first character in the expanded value.
+If <I>pattern</I> is omitted, it is treated like a <B>?</B>, which matches
+every character.
+If
+<I>parameter</I>
+
+is
+<B>@</B>
+
+or
+<B>*</B>,
+
+the case modification operation is applied to each positional
+parameter in turn, and the expansion is the resultant list.
+If
+<I>parameter</I>
+
+is an array variable subscripted with
+<B>@</B>
+
+or
+<B>*</B>,
+
+the case modification operation is applied to each member of the
+array in turn, and the expansion is the resultant list.
+<DT>${<I>parameter</I><B>@</B><I>operator</I>}<DD>
+<B>Parameter transformation</B>.
+The expansion is either a transformation of the value of <I>parameter</I>
+or information about <I>parameter</I> itself, depending on the value of
+<I>operator</I>. Each <I>operator</I> is a single letter:
+<P>
+<DL COMPACT><DT><DD>
+
+<DL COMPACT>
+<DT><B>U</B>
+
+<DD>
+The expansion is a string that is the value of <I>parameter</I> with lowercase
+alphabetic characters converted to uppercase.
+<DT><B>u</B>
+
+<DD>
+The expansion is a string that is the value of <I>parameter</I> with the first
+character converted to uppercase, if it is alphabetic.
+<DT><B>L</B>
+
+<DD>
+The expansion is a string that is the value of <I>parameter</I> with uppercase
+alphabetic characters converted to lowercase.
+<DT><B>Q</B>
+
+<DD>
+The expansion is a string that is the value of <I>parameter</I> quoted in a
+format that can be reused as input.
+<DT><B>E</B>
+
+<DD>
+The expansion is a string that is the value of <I>parameter</I> with backslash
+escape sequences expanded as with the <B>$'...'</B> quoting mechanism.
+<DT><B>P</B>
+
+<DD>
+The expansion is a string that is the result of expanding the value of
+<I>parameter</I> as if it were a prompt string (see <B>PROMPTING</B> below).
+<DT><B>A</B>
+
+<DD>
+The expansion is a string in the form of
+an assignment statement or <B>declare</B> command that, if
+evaluated, will recreate <I>parameter</I> with its attributes and value.
+<DT><B>K</B>
+
+<DD>
+Produces a possibly-quoted version of the value of <I>parameter</I>,
+except that it prints the values of
+indexed and associative arrays as a sequence of quoted key-value pairs
+(see <B>Arrays</B> above).
+<DT><B>a</B>
+
+<DD>
+The expansion is a string consisting of flag values representing
+<I>parameter</I>'s attributes.
+
+</DL>
+<P>
+
+If
+<I>parameter</I>
+
+is
+<B>@</B>
+
+or
+<B>*</B>,
+
+the operation is applied to each positional
+parameter in turn, and the expansion is the resultant list.
+If
+<I>parameter</I>
+
+is an array variable subscripted with
+<B>@</B>
+
+or
+<B>*</B>,
+
+the operation is applied to each member of the
+array in turn, and the expansion is the resultant list.
+<P>
+The result of the expansion is subject to word splitting and pathname
+expansion as described below.
+</DL>
+
+</DL>
+<A NAME="lbBC">&nbsp;</A>
+<H4>Command Substitution</H4>
+
+<I>Command substitution</I> allows the output of a command to replace
+the command name. There are two forms:
+<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> in a subshell environment
+and replacing the command substitution with the standard output of the
+command, with any trailing newlines deleted.
+Embedded newlines are not deleted, but they may be removed during
+word splitting.
+The command substitution <B>$(cat </B><I>file</I>) can be replaced by
+the equivalent but faster <B>$(&lt; </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="lbBD">&nbsp;</A>
+<H4>Arithmetic Expansion</H4>
+
+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 and variable expansion,
+command substitution, and quote removal.
+The result is treated as the arithmetic expression to be evaluated.
+Arithmetic expansions may be nested.
+<P>
+
+The evaluation is performed according to the rules listed below under
+<FONT SIZE=-1><B>ARITHMETIC EVALUATION</B>.
+
+</FONT>
+If
+<I>expression</I>
+
+is invalid,
+<B>bash</B>
+
+prints a message indicating failure and no substitution occurs.
+<A NAME="lbBE">&nbsp;</A>
+<H4>Process Substitution</H4>
+
+<I>Process substitution</I> allows a process's input or output to be
+referred to using a filename.
+It takes the form of
+<B>&lt;(</B><I>list</I><B>)</B>
+or
+<B>&gt;(</B><I>list</I><B>)</B>.
+The process <I>list</I> is run asynchronously, and its input or output
+appears as a filename.
+This filename is
+passed as an argument to the current command as the result of the
+expansion.
+If the <B>&gt;(</B><I>list</I><B>)</B> form is used, writing to
+the file will provide input for <I>list</I>. If the
+<B>&lt;(</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>.
+Process substitution is supported on systems that support named
+pipes (<I>FIFOs</I>) or the <B>/dev/fd</B> method of naming open files.
+<P>
+
+When available, process substitution is performed
+simultaneously with parameter and variable expansion,
+command substitution,
+and arithmetic expansion.
+<A NAME="lbBF">&nbsp;</A>
+<H4>Word Splitting</H4>
+
+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 using these characters as field terminators.
+If
+<FONT SIZE=-1><B>IFS</B>
+
+</FONT>
+is unset, or its
+value is exactly
+<B>&lt;space&gt;&lt;tab&gt;&lt;newline&gt;</B>,
+
+the default, then
+sequences of
+<B>&lt;space&gt;</B>,
+
+<B>&lt;tab&gt;</B>,
+
+and
+<B>&lt;newline&gt;</B>
+
+at the beginning and end of the results of the previous
+expansions are ignored, and
+any sequence of
+<FONT SIZE=-1><B>IFS</B>
+
+</FONT>
+characters not at the beginning or end 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>,
+
+<B>tab</B>,
+
+and
+<B>newline</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>&quot;&quot;</B> or <B>aqaq</B>) are retained
+and passed to commands as empty strings.
+Unquoted implicit null arguments, resulting from the expansion of
+parameters that have no values, are removed.
+If a parameter with no value is expanded within double quotes, a
+null argument results and is retained
+and passed to a command as an empty string.
+When a quoted null argument appears as part of a word whose expansion is
+non-null, the null argument is removed.
+That is, the word
+<TT>-daqaq</TT> becomes <TT>-d</TT> after word splitting and
+null argument removal.
+<P>
+
+Note that if no expansion occurs, no splitting
+is performed.
+<A NAME="lbBG">&nbsp;</A>
+<H4>Pathname Expansion</H4>
+
+After word splitting,
+unless the
+<B>-f</B>
+
+option has been set,
+<B>bash</B>
+
+scans each word for the characters
+<B>*</B>,
+
+<B>?</B>,
+
+and
+<B>[</B>.
+
+If one of these characters appears, and is not quoted, then the word is
+regarded as a
+<I>pattern</I>,
+
+and replaced with an alphabetically sorted list of
+filenames matching the pattern
+(see
+<FONT SIZE=-1><B>Pattern Matching</B>
+
+</FONT>
+below).
+If no matching filenames are found,
+and the shell option
+<B>nullglob</B>
+
+is not enabled, the word is left unchanged.
+If the
+<B>nullglob</B>
+
+option is set, and no matches are found,
+the word is removed.
+If the
+<B>failglob</B>
+
+shell option is set, and no matches are found, an error message
+is printed and the command is not executed.
+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.
+The filenames
+<B>``.''</B>
+
+and
+<B>``..''</B>
+
+must always be matched explicitly, even if
+<B>dotglob</B>
+
+is set.
+In other cases, the
+<B>``.''</B>
+
+character is not treated specially.
+When matching a pathname, the slash character must always be
+matched explicitly by a slash in the pattern, but in other matching
+contexts it can be matched by a special pattern character as described
+below under
+<FONT SIZE=-1><B>Pattern Matching</B>.
+
+</FONT>
+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>,
+
+<B>failglob</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.
+If the <B>nocaseglob</B> option is set, the matching against the patterns in
+<FONT SIZE=-1><B>GLOBIGNORE</B>
+
+</FONT>
+is performed without regard to case.
+The filenames
+<B>``.''</B>
+
+and
+<B>``..''</B>
+
+are always ignored when
+<FONT SIZE=-1><B>GLOBIGNORE</B>
+
+</FONT>
+is set and not null. However, setting
+<FONT SIZE=-1><B>GLOBIGNORE</B>
+
+</FONT>
+to a non-null value has the effect of enabling the
+<B>dotglob</B>
+
+shell option, so all other filenames beginning with a
+<B>``.''</B>
+
+will match.
+To get the old behavior of ignoring filenames 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.
+The pattern matching honors the setting of the <B>extglob</B> shell
+option.
+<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. A backslash escapes the following character; the
+escaping backslash is discarded when matching.
+The special pattern characters must be quoted if
+they are to be matched literally.
+<P>
+
+The special pattern characters have the following meanings:
+<P>
+
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT><B>*</B>
+
+<DD>
+Matches any string, including the null string.
+When the <B>globstar</B> shell option is enabled, and <B>*</B> is used in
+a pathname expansion context, two adjacent <B>*</B>s used as a single
+pattern will match all files and zero or more directories and
+subdirectories.
+If followed by a <B>/</B>, two adjacent <B>*</B>s will match only directories
+and subdirectories.
+<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 falls 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 values of the
+<FONT SIZE=-1><B>LC_COLLATE</B>
+
+</FONT>
+or
+<FONT SIZE=-1><B>LC_ALL</B>
+
+</FONT>
+shell variables, if set.
+To obtain the traditional interpretation of range expressions, where
+<B>[a-d]</B>
+
+is equivalent to
+<B>[abcd]</B>,
+
+set value of the
+<B>LC_ALL</B>
+
+shell variable to
+<B>C</B>,
+
+or enable the
+<B>globasciiranges</B>
+
+shell option.
+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 standard:
+</DL>
+<P>
+
+<DL COMPACT><DT><DD>
+<B>
+</B>
+
+alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
+<BR>
+
+A character class matches any character belonging to that class.
+The <B>word</B> character class matches letters, digits, and the character _.
+<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>
+
+</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 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>
+
+
+<P>
+
+Complicated extended pattern matching against long strings is slow,
+especially when the patterns contain alternations and the strings
+contain multiple matches.
+Using separate matches against shorter strings, or using arrays of
+strings instead of a single long string, may be faster.
+<A NAME="lbBH">&nbsp;</A>
+<H4>Quote Removal</H4>
+
+After the preceding expansions, all unquoted occurrences of the
+characters
+<B>\</B>,
+
+<B>aq</B>,
+
+and <B>&quot;</B> that did not result from one of the above
+expansions are removed.
+<A NAME="lbBI">&nbsp;</A>
+<H3>REDIRECTION</H3>
+
+Before a command is executed, its input and output
+may be
+<I>redirected</I>
+
+using a special notation interpreted by the shell.
+Redirection allows commands' file handles to be
+duplicated, opened, closed,
+made to refer to different files,
+and can change the files the command reads from and writes to.
+Redirection may also be used to modify file handles in the
+current shell execution environment.
+The following redirection
+operators may precede or appear anywhere within a
+<I>simple command</I>
+
+or may follow a
+<I>command</I>.
+
+Redirections are processed in the order they appear, from
+left to right.
+<P>
+
+Each redirection that may be preceded by a file descriptor number
+may instead be preceded by a word of the form {<I>varname</I>}.
+In this case, for each redirection operator except
+&gt;&amp;- and &lt;&amp;-, the shell will allocate a file descriptor greater
+than or equal to 10 and assign it to <I>varname</I>.
+If &gt;&amp;- or &lt;&amp;- is preceded
+by {<I>varname</I>}, the value of <I>varname</I> defines the file
+descriptor to close.
+If {<I>varname</I>} is supplied, the redirection persists beyond
+the scope of the command, allowing the shell programmer to manage
+the file descriptor himself.
+<P>
+
+In the following descriptions, if the file descriptor number is
+omitted, and the first character of the redirection operator is
+<B>&lt;</B>,
+
+the redirection refers to the standard input (file descriptor
+0). If the first character of the redirection operator is
+<B>&gt;</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 and variable expansion,
+command substitution, arithmetic expansion, quote removal,
+pathname expansion, and word splitting.
+If it expands to more than one word,
+<B>bash</B>
+
+reports an error.
+<P>
+
+Note that the order of redirections is significant. For example,
+the command
+<DL COMPACT><DT><DD>
+<P>
+
+ls <B>&gt;</B> dirlist 2<B>&gt;&amp;</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>&gt;&amp;</B>1 <B>&gt;</B> dirlist
+</DL>
+
+<P>
+
+directs only the standard output to file
+<I>dirlist</I>,
+
+because the standard error was duplicated from the 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.
+If the operating system on which <B>bash</B> is running provides these
+special files, bash will use them; otherwise it will emulate them
+internally with the behavior described below.
+<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
+the corresponding TCP 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
+the corresponding UDP socket.
+
+</DL></DL>
+
+<P>
+
+A failure to open or create a file causes the redirection to fail.
+<P>
+
+Redirections using file descriptors greater than 9 should be used with
+care, as they may conflict with file descriptors the shell uses
+internally.
+<A NAME="lbBJ">&nbsp;</A>
+<H4>Redirecting Input</H4>
+
+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>&lt;</B><I>word</I>
+</DL>
+
+<A NAME="lbBK">&nbsp;</A>
+<H4>Redirecting Output</H4>
+
+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>&gt;</B><I>word</I>
+</DL>
+
+<P>
+
+If the redirection operator is
+<B>&gt;</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>&gt;|</B>,
+
+or the redirection operator is
+<B>&gt;</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="lbBL">&nbsp;</A>
+<H4>Appending Redirected Output</H4>
+
+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>&gt;&gt;</B><I>word</I>
+</DL>
+
+<A NAME="lbBM">&nbsp;</A>
+<H4>Redirecting Standard Output and Standard Error</H4>
+
+This construct 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>.
+
+<P>
+
+There are two formats for redirecting standard output and
+standard error:
+<DL COMPACT><DT><DD>
+<P>
+
+<B>&amp;&gt;</B><I>word</I>
+</DL>
+
+and
+<DL COMPACT><DT><DD>
+<B>&gt;&amp;</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>&gt;</B><I>word</I> 2<B>&gt;&amp;</B>1
+</DL>
+
+<P>
+
+When using the second form, <I>word</I> may not expand to a number or
+<B>-</B>. If it does, other redirection operators apply
+(see <B>Duplicating File Descriptors</B> below) for compatibility
+reasons.
+<A NAME="lbBN">&nbsp;</A>
+<H4>Appending Standard Output and Standard Error</H4>
+
+This construct allows both the
+standard output (file descriptor 1) and
+the standard error output (file descriptor 2)
+to be appended to the file whose name is the
+expansion of
+<I>word</I>.
+
+<P>
+
+The format for appending standard output and standard error is:
+<DL COMPACT><DT><DD>
+<P>
+
+<B>&amp;&gt;&gt;</B><I>word</I>
+</DL>
+
+<P>
+
+This is semantically equivalent to
+<DL COMPACT><DT><DD>
+<P>
+
+<B>&gt;&gt;</B><I>word</I> 2<B>&gt;&amp;</B>1
+</DL>
+
+<P>
+
+(see <B>Duplicating File Descriptors</B> below).
+<A NAME="lbBO">&nbsp;</A>
+<H4>Here Documents</H4>
+
+This type of redirection instructs the shell to read input from the
+current source until a line containing only
+<I>delimiter</I>
+
+(with no trailing blanks)
+is seen. All of
+the lines read up to that point are then used as the standard
+input (or file descriptor <I>n</I> if <I>n</I> is specified) for a command.
+<P>
+
+The format of here-documents is:
+<DL COMPACT><DT><DD>
+<P>
+
+<PRE>
+[<I>n</I>]<B>&lt;&lt;</B>[<B>-</B>]<I>word</I>
+ <I>here-document</I>
+<I>delimiter</I>
+</PRE>
+
+</DL>
+
+<P>
+
+No parameter and variable expansion, command substitution,
+arithmetic expansion, or pathname expansion is performed on
+<I>word</I>.
+
+If any part of
+<I>word</I>
+
+is quoted, the
+<I>delimiter</I>
+
+is the result of quote removal on
+<I>word</I>,
+
+and the lines in the here-document are not expanded.
+If <I>word</I> is unquoted,
+all lines of the here-document are subjected to
+parameter expansion, command substitution, and arithmetic expansion,
+the character sequence
+<B>\&lt;newline&gt;</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>&lt;&lt;-</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="lbBP">&nbsp;</A>
+<H4>Here Strings</H4>
+
+A variant of here documents, the format is:
+<DL COMPACT><DT><DD>
+<P>
+
+<PRE>
+[<I>n</I>]<B>&lt;&lt;&lt;</B><I>word</I>
+</PRE>
+
+</DL>
+
+<P>
+
+The <I>word</I> undergoes
+tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal.
+Pathname expansion and word splitting are not performed.
+The result is supplied as a single string, with a newline appended,
+to the command on its
+standard input (or file descriptor <I>n</I> if <I>n</I> is specified).
+<A NAME="lbBQ">&nbsp;</A>
+<H4>Duplicating File Descriptors</H4>
+
+The redirection operator
+<DL COMPACT><DT><DD>
+<P>
+
+[<I>n</I>]<B>&lt;&amp;</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>&gt;&amp;</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.
+If
+<I>word</I>
+
+evaluates to
+<B>-</B>,
+
+file descriptor
+<I>n</I>
+
+is closed.
+As a special case, if <I>n</I> is omitted, and <I>word</I> does not
+expand to one or more digits or <B>-</B>, the standard output and standard
+error are redirected as described previously.
+<A NAME="lbBR">&nbsp;</A>
+<H4>Moving File Descriptors</H4>
+
+The redirection operator
+<DL COMPACT><DT><DD>
+<P>
+
+[<I>n</I>]<B>&lt;&amp;</B><I>digit</I><B>-</B>
+</DL>
+
+<P>
+
+moves the file descriptor <I>digit</I> to file descriptor
+<I>n</I>,
+
+or the standard input (file descriptor 0) if <I>n</I> is not specified.
+<I>digit</I> is closed after being duplicated to <I>n</I>.
+<P>
+
+Similarly, the redirection operator
+<DL COMPACT><DT><DD>
+<P>
+
+[<I>n</I>]<B>&gt;&amp;</B><I>digit</I><B>-</B>
+</DL>
+
+<P>
+
+moves the file descriptor <I>digit</I> to file descriptor
+<I>n</I>,
+
+or the standard output (file descriptor 1) if <I>n</I> is not specified.
+<A NAME="lbBS">&nbsp;</A>
+<H4>Opening File Descriptors for Reading and Writing</H4>
+
+The redirection operator
+<DL COMPACT><DT><DD>
+<P>
+
+[<I>n</I>]<B>&lt;&gt;</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="lbBT">&nbsp;</A>
+<H3>ALIASES</H3>
+
+<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 simple 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 characters <B>/</B>, <B>$</B>, <B>`</B>, and <B>=</B> and
+any of the shell <I>metacharacters</I> or quoting characters
+listed above may not appear in an alias name.
+The replacement text may contain any valid shell input,
+including shell metacharacters.
+The first word of the replacement text is tested
+for aliases, but a word that is identical to an alias being expanded
+is not expanded a second time.
+This means that one may alias
+<B>ls</B>
+
+to
+<B>ls -F</B>,
+
+for instance, and
+<B>bash</B>
+
+does not try to recursively expand the replacement text.
+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,
+and all lines that make up a compound command,
+before executing any of the commands on that line or the compound command.
+Aliases are expanded when a
+command is read, not when it is executed. Therefore, an
+alias definition appearing on the same line as another
+command does not take effect until the 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 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="lbBU">&nbsp;</A>
+<H3>FUNCTIONS</H3>
+
+A shell function, defined as described above under
+<FONT SIZE=-1><B>SHELL GRAMMAR</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. Special parameter <B>0</B>
+is unchanged.
+The first element of the
+<FONT SIZE=-1><B>FUNCNAME</B>
+
+</FONT>
+variable is set to the name of the function while the function
+is executing.
+<P>
+
+All other aspects of the shell execution
+environment are identical between a function and its caller
+with these exceptions: the
+<FONT SIZE=-1><B>DEBUG</B>
+
+</FONT>
+and
+<B>RETURN</B>
+
+traps (see the description of the
+<B>trap</B>
+
+builtin under
+<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
+
+</FONT>
+below) are not inherited unless the function has been given the
+<B>trace</B> attribute (see the description of the
+<FONT SIZE=-1><B>declare</B>
+
+</FONT>
+builtin below) or the
+<B>-o functrace</B> shell option has been enabled with
+the <B>set</B> builtin
+(in which case all functions inherit the <B>DEBUG</B> and <B>RETURN</B> traps),
+and the
+<FONT SIZE=-1><B>ERR</B>
+
+</FONT>
+trap is not inherited unless the <B>-o errtrace</B> shell option has
+been enabled.
+<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.
+If a variable is declared <B>local</B>, the variable's visible scope
+is restricted to that function and its children (including the functions
+it calls).
+Local variables &quot;shadow&quot; variables with the same name declared at
+previous scopes.
+For instance, a local variable declared in a function
+hides a global variable of the same name: references and assignments
+refer to the local variable, leaving the global variable unmodified.
+When the function returns, the global variable is once again visible.
+<P>
+
+The shell uses <I>dynamic scoping</I> to control a variable's visibility
+within functions.
+With dynamic scoping, visible variables and their values
+are a result of the sequence of function calls that caused execution
+to reach the current function.
+The value of a variable that a function sees depends
+on its value within its caller, if any, whether that caller is
+the &quot;global&quot; scope or another shell function.
+This is also the value that a local variable
+declaration &quot;shadows&quot;, and the value that is restored when the function
+returns.
+<P>
+
+For example, if a variable <I>var</I> is declared as local in function
+<I>func1</I>, and <I>func1</I> calls another function <I>func2</I>,
+references to <I>var</I> made from within <I>func2</I> will resolve to the
+local variable <I>var</I> from <I>func1</I>, shadowing any global variable
+named <I>var</I>.
+<P>
+
+The <B>unset</B> builtin also acts using the same dynamic scope: if a
+variable is local to the current scope, <B>unset</B> will unset it;
+otherwise the unset will refer to the variable found in any calling scope
+as described above.
+If a variable at the current local scope is unset, it will remain so
+until it is reset in that scope or until the function returns.
+Once the function returns, any instance of the variable at a previous
+scope will become visible.
+If the unset acts on a variable at a previous scope, any instance of a
+variable with that name that had been shadowed will become visible.
+<P>
+
+The <B>FUNCNEST</B> variable, if set to a numeric value greater
+than 0, defines a maximum function nesting level. Function
+invocations that exceed the limit cause the entire command to
+abort.
+<P>
+
+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.
+Any command associated with the <B>RETURN</B> trap is executed
+before execution resumes.
+When a function completes, the values of the
+positional parameters and the special parameter
+<B>#</B>
+
+are restored to the values they had prior to the function's
+execution.
+<P>
+
+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
+(and optionally the source file and line number, if the <B>extdebug</B>
+shell option is enabled).
+Functions may be exported so that subshells
+automatically have them defined with the
+<B>-f</B>
+
+option to the
+<B>export</B>
+
+builtin.
+A function definition may be deleted using the <B>-f</B> option to
+the
+<B>unset</B>
+
+builtin.
+<P>
+
+Functions may be recursive.
+The <B>FUNCNEST</B> variable may be used to limit the depth of the
+function call stack and restrict the number of function invocations.
+By default, no limit is imposed on the number of recursive calls.
+<A NAME="lbBV">&nbsp;</A>
+<H3>ARITHMETIC EVALUATION</H3>
+
+The shell allows arithmetic expressions to be evaluated, under
+certain circumstances (see the <B>let</B> and <B>declare</B> builtin
+commands, the <B>((</B> compound command, and <B>Arithmetic Expansion</B>).
+Evaluation is done in fixed-width integers with no check for overflow,
+though division by 0 is trapped and flagged as an error.
+The operators and their precedence, associativity, and values
+are the same as in the C language.
+The following list of operators is grouped into levels of
+equal-precedence operators.
+The levels are listed in order of decreasing precedence.
+<P>
+
+
+<DL COMPACT>
+<DT><B></B><I>id</I>++ <I>id</I>--
+
+<DD>
+variable post-increment and post-decrement
+<DT><B>- +</B>
+
+<DD>
+unary minus and plus
+<DT><B>++</B><I>id</I> --<I>id</I>
+
+<DD>
+variable pre-increment and pre-decrement
+<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>&lt;&lt; &gt;&gt;</B>
+
+<DD>
+left and right bitwise shifts
+<DT><B>&lt;= &gt;= &lt; &gt;</B>
+
+<DD>
+comparison
+<DT><B>== !=</B>
+
+<DD>
+equality and inequality
+<DT><B>&amp;</B>
+
+<DD>
+bitwise AND
+<DT><B>^</B>
+
+<DD>
+bitwise exclusive OR
+<DT><B>|</B>
+
+<DD>
+bitwise OR
+<DT><B>&amp;&amp;</B>
+
+<DD>
+logical AND
+<DT><B>||</B>
+
+<DD>
+logical OR
+<DT><B></B><I>expr</I>?<I>expr</I>:<I>expr</I>
+
+<DD>
+conditional operator
+<DT><B>= *= /= %= += -= &lt;&lt;= &gt;&gt;= &amp;= ^= |=</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.
+A shell variable that is null or unset evaluates to 0 when referenced
+by name without using the parameter expansion syntax.
+The value of a variable is evaluated as an arithmetic expression
+when it is referenced, or when a variable which has been given the
+<I>integer</I> attribute using <B>declare -i</B> is assigned a value.
+A null value evaluates to 0.
+A shell variable need not have its <I>integer</I> attribute
+turned on to be used in an expression.
+<P>
+
+Integer constants follow the C language definition, without suffixes or
+character constants.
+Constants with a leading 0 are interpreted as octal numbers.
+A leading 0x or 0X denotes hexadecimal.
+Otherwise, numbers take the form [<I>base#</I>]n, where the optional <I>base</I>
+is a decimal number between 2 and 64 representing the arithmetic
+base, and <I>n</I> is a number in that base.
+If <I>base#</I> is omitted, then base 10 is used.
+When specifying <I>n</I>,
+if a non-digit is required,
+the digits greater than 9 are represented by the lowercase letters,
+the uppercase letters, @, and _, in that order.
+If <I>base</I> is less than or equal to 36, lowercase and uppercase
+letters may be used interchangeably to represent numbers between 10
+and 35.
+<P>
+
+Operators are evaluated in order of precedence. Sub-expressions in
+parentheses are evaluated first and may override the precedence
+rules above.
+<A NAME="lbBW">&nbsp;</A>
+<H3>CONDITIONAL EXPRESSIONS</H3>
+
+Conditional expressions are used by the <B>[[</B> compound command and
+the <B>test</B> and <B>[</B> builtin commands to test file attributes
+and perform string and arithmetic comparisons.
+The <B>test</B> and <B>[</B> commands determine their behavior based on
+the number of arguments; see the descriptions of those commands for any
+other command-specific actions.
+<P>
+
+Expressions are formed from the following unary or binary primaries.
+<B>Bash</B> handles several filenames specially when they are used in
+expressions.
+If the operating system on which <B>bash</B> is running provides these
+special files, bash will use them; otherwise it will emulate them
+internally with this behavior:
+If any <I>file</I> argument to one of the primaries is of the form
+<I>/dev/fd/n</I>, then 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>
+
+Unless otherwise specified, primaries that operate on files follow symbolic
+links and operate on the target of the link, rather than the link itself.
+<P>
+
+
+When used with <B>[[</B>, the <B>&lt;</B> and <B>&gt;</B> operators sort
+lexicographically using the current locale.
+The <B>test</B> command sorts using ASCII ordering.
+<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>-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>-N </B><I>file</I>
+
+<DD>
+True if <I>file</I> exists and has been modified since it was last read.
+<DT><B>-O </B><I>file</I>
+
+<DD>
+True if <I>file</I> exists and is owned by the effective user id.
+<DT><B>-S </B><I>file</I>
+
+<DD>
+True if <I>file</I> exists and is a socket.
+<DT><I>file1</I> <B>-ef</B> <I>file2</I><DD>
+True if <I>file1</I> and <I>file2</I> refer to the same device and
+inode numbers.
+<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>,
+or if <I>file1</I> exists and file2 does not.
+<DT><I>file1</I> -<B>ot</B> <I>file2</I><DD>
+True if <I>file1</I> is older than <I>file2</I>, or if <I>file2</I> exists
+and <I>file1</I> does not.
+<DT><B>-o </B><I>optname</I>
+
+<DD>
+True if the shell option
+<I>optname</I>
+
+is enabled.
+See the list of options under the description of the
+<B>-o</B>
+
+option to the
+<B>set</B>
+
+builtin below.
+<DT><B>-v </B><I>varname</I>
+
+<DD>
+True if the shell variable
+<I>varname</I>
+
+is set (has been assigned a value).
+<DT><B>-R </B><I>varname</I>
+
+<DD>
+True if the shell variable
+<I>varname</I>
+
+is set and is a name reference.
+<DT><B>-z </B><I>string</I>
+
+<DD>
+True if the length of <I>string</I> is zero.
+<DT><I>string</I><DD>
+
+<DT><B>-n </B><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>
+
+<DT><I>string1</I> <B>=</B> <I>string2</I><DD>
+
+True if the strings are equal. <B>=</B> should be used
+with the <B>test</B> command for POSIX conformance.
+When used with the <B>[[</B> command, this performs pattern matching as
+described above (<B>Compound Commands</B>).
+<DT><I>string1</I> <B>!=</B> <I>string2</I><DD>
+True if the strings are not equal.
+<DT><I>string1</I> <B>&lt;</B> <I>string2</I><DD>
+True if <I>string1</I> sorts before <I>string2</I> lexicographically.
+<DT><I>string1</I> <B>&gt;</B> <I>string2</I><DD>
+True if <I>string1</I> sorts after <I>string2</I> lexicographically.
+<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.
+When used with the <B>[[</B> command,
+<I>Arg1</I>
+
+and
+<I>Arg2</I>
+
+are evaluated as arithmetic expressions (see
+<FONT SIZE=-1><B>ARITHMETIC EVALUATION</B>
+
+</FONT>
+above).
+
+</DL>
+<A NAME="lbBX">&nbsp;</A>
+<H3>SIMPLE COMMAND EXPANSION</H3>
+
+When a simple command is executed, the shell performs the following
+expansions, assignments, and redirections, from left to right, in
+the following order.
+<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="lbBY">&nbsp;</A>
+<H3>COMMAND EXECUTION</H3>
+
+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 searches for a defined shell
+function named <B>command_not_found_handle</B>.
+If that function exists, it is invoked in a separate execution environment
+with the original command and
+the original command's arguments as its arguments, and the function's
+exit status becomes the exit status of that subshell.
+If that function is not defined, the shell prints an error
+message and returns an exit status of 127.
+<P>
+
+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="lbBZ">&nbsp;</A>
+<H3>COMMAND EXECUTION ENVIRONMENT</H3>
+
+The shell has an <I>execution environment</I>, which consists of the
+following:
+<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
+<FONT SIZE=-1><B>PPID</B>
+
+</FONT>
+</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.
+
+<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 and functions 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 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, commands grouped with parentheses,
+and asynchronous commands are invoked in a
+subshell environment that is a duplicate of the shell environment,
+except that traps caught by the shell are reset to the values
+that the shell inherited from its parent at invocation. Builtin
+commands that are invoked as part of a pipeline are also executed in a
+subshell environment. Changes made to the subshell environment
+cannot affect the shell's execution environment.
+<P>
+
+Subshells spawned to execute command substitutions inherit the value of
+the <B>-e</B> option from the parent shell. When not in <I>posix mode</I>,
+<B>bash</B> clears the <B>-e</B> option in such subshells.
+<P>
+
+If a command is followed by a <B>&amp;</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="lbCA">&nbsp;</A>
+<H3>ENVIRONMENT</H3>
+
+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 filename of the command and passed to that
+command in its environment.
+<A NAME="lbCB">&nbsp;</A>
+<H3>EXIT STATUS</H3>
+
+The exit status of an executed command is the value returned by the
+<I>waitpid</I> system call or equivalent function. Exit statuses
+fall between 0 and 255, though, as explained below, the shell may
+use values above 125 specially. Exit statuses from shell builtins and
+compound commands are also limited to this range. Under certain
+circumstances, the shell will use special values to indicate specific
+failure modes.
+<P>
+
+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,
+generally invalid options or missing arguments.
+<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="lbCC">&nbsp;</A>
+<H3>SIGNALS</H3>
+
+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>
+
+Non-builtin commands run 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>
+in addition to these inherited handlers.
+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>
+
+If <B>bash</B> is waiting for a command to complete and receives a signal
+for which a trap has been set, 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="lbCD">&nbsp;</A>
+<H3>JOB CONTROL</H3>
+
+<I>Job control</I>
+
+refers to the ability to selectively stop (<I>suspend</I>)
+the execution of processes and continue (<I>resume</I>)
+their execution at a later point. A user typically employs
+this facility via an interactive interface supplied jointly
+by the operating system kernel's terminal driver and
+<B>bash</B>.
+
+<P>
+
+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, if the
+user so specifies with <TT>stty tostop</TT>, write to the
+terminal.
+Background processes which attempt to read from (write to when
+<TT>stty tostop</TT> is in effect) the
+terminal are sent a
+<FONT SIZE=-1><B>SIGTTIN (SIGTTOU)</B>
+
+</FONT>
+signal by the kernel's 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 specification (<I>jobspec</I>). 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
+job whose command name begins with
+<B>ce</B>.
+
+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>.
+
+If there is only a single job, <B>%+</B> and <B>%-</B> can both be used
+to refer to that job.
+In output pertaining to jobs (e.g., the output of the
+<B>jobs</B>
+
+command), the current job is always flagged with a
+<B>+</B>,
+
+and the previous job with a
+<B>-</B>.
+
+A single % (with no accompanying job specification) also refers to the
+current job.
+<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 &amp;''</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 (or, if the <B>checkjobs</B> shell option has
+been enabled using the <B>shopt</B> builtin, running), the shell prints a
+warning message, and, if the <B>checkjobs</B> option is enabled, lists the
+jobs and their statuses.
+The
+<B>jobs</B>
+
+command may then be used to inspect their status.
+If a second attempt to exit is made without an intervening command,
+the shell does not print another warning, and any stopped
+jobs are terminated.
+<P>
+
+When the shell is waiting for a job or process using the <B>wait</B>
+builtin, and job control is enabled, <B>wait</B> will return when the
+job changes state. The <B>-f</B> option causes <B>wait</B> to wait
+until the job or process terminates before returning.
+<A NAME="lbCE">&nbsp;</A>
+<H3>PROMPTING</H3>
+
+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>
+
+displays
+<FONT SIZE=-1><B>PS0</B>
+
+</FONT>
+after it reads a command but before executing it.
+<B>Bash</B>
+
+displays
+<FONT SIZE=-1><B>PS4</B>
+
+</FONT>
+as described above
+before tracing each command when the <B>-x</B> option is enabled.
+<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 &quot;Weekday Month Date&quot; format (e.g., &quot;Tue May 26&quot;)
+<DT><B>\D{</B><I>format</I>}
+
+<DD>
+the <I>format</I> is passed to <I>strftime</I>(3) and the result is inserted
+into the prompt string; an empty <I>format</I> results in a locale-specific
+time representation. The braces are required
+<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>$0</B>
+
+(the portion following the final slash)
+<DT><B>\t</B>
+
+<DD>
+the current time in 24-hour HH:MM:SS format
+<DT><B>\T</B>
+
+<DD>
+the current time in 12-hour HH:MM:SS format
+<DT><B>\@</B>
+
+<DD>
+the current time in 12-hour am/pm format
+<DT><B>\A</B>
+
+<DD>
+the current time in 24-hour HH:MM format
+<DT><B>\u</B>
+
+<DD>
+the username of the current user
+<DT><B>\v</B>
+
+<DD>
+the version of <B>bash</B> (e.g., 2.00)
+<DT><B>\V</B>
+
+<DD>
+the release of <B>bash</B>, version + patch level (e.g., 2.00.0)
+<DT><B>\w</B>
+
+<DD>
+the current working directory, with
+<FONT SIZE=-1><B>$HOME</B>
+
+</FONT>
+abbreviated with a tilde
+(uses the value of the
+<FONT SIZE=-1><B>PROMPT_DIRTRIM</B>
+
+</FONT>
+variable)
+<DT><B>\W</B>
+
+<DD>
+the basename of the current working directory, with
+<FONT SIZE=-1><B>$HOME</B>
+
+</FONT>
+abbreviated with a tilde
+<DT><B>\!</B>
+
+<DD>
+the history number of this command
+<DT><B>\#</B>
+
+<DD>
+the command number of this command
+<DT><B>\$</B>
+
+<DD>
+if the effective UID is 0, a
+<B>#</B>,
+
+otherwise a
+<B>$</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).
+This can have unwanted side effects if escaped portions of the string
+appear within command substitution or contain characters special to
+word expansion.
+<A NAME="lbCF">&nbsp;</A>
+<H3>READLINE</H3>
+
+This is the library that handles reading input when using an interactive
+shell, unless the
+<B>--noediting</B>
+
+option is given at shell invocation.
+Line editing is also used when using the <B>-e</B> option to the
+<B>read</B> builtin.
+By default, the line editing commands are similar to those of Emacs.
+A vi-style line editing interface is also available.
+Line editing can be enabled at any time using the
+<B>-o emacs</B>
+
+or
+<B>-o vi</B>
+
+options to the
+<B>set</B>
+
+builtin (see
+<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
+
+</FONT>
+below).
+To turn off line editing after the shell is running, use the
+<B>+o emacs</B>
+
+or
+<B>+o vi</B>
+
+options to the
+<B>set</B>
+
+builtin.
+<A NAME="lbCG">&nbsp;</A>
+<H4>Readline Notation</H4>
+
+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="lbCH">&nbsp;</A>
+<H4>Readline Initialization</H4>
+
+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>.
+
+If that file does not exist or cannot be read, the ultimate default is
+<A HREF="file:/etc/inputrc"><I>/etc/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="lbCI">&nbsp;</A>
+<H4>Readline Key Bindings</H4>
+
+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: &quot;&gt; output&quot;
+</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>&gt; output</TT>
+
+into the line).
+<P>
+
+In the second form, <B>&quot;keyseq&quot;</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>
+&quot;\C-u&quot;: universal-argument
+<BR>
+
+&quot;\C-x\C-r&quot;: re-read-init-file
+<BR>
+
+&quot;\e[11~&quot;: &quot;Function Key 1&quot;
+</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 &quot;
+<DT><B>\aq</B>
+
+<DD>
+literal aq
+</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 &quot; and aq.
+<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="lbCJ">&nbsp;</A>
+<H4>Readline Variables</H4>
+
+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>
+
+or using the <B>bind</B> builtin command (see
+<FONT SIZE=-1><B>SHELL BUILTIN COMMANDS</B>
+
+</FONT>
+below).
+<P>
+
+Except where noted, readline variables can take the values
+<B>On</B>
+
+or
+<B>Off</B>
+
+(without regard to case).
+Unrecognized variable names are ignored.
+When a variable value is read, empty or null values, &quot;on&quot; (case-insensitive),
+and &quot;1&quot; are equivalent to <B>On</B>. All other values are equivalent to
+<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>bind-tty-special-chars (On)</B>
+
+<DD>
+If set to <B>On</B>, readline attempts to bind the control characters
+treated specially by the kernel's terminal driver to their readline
+equivalents.
+<DT><B>blink-matching-paren (Off)</B>
+
+<DD>
+If set to <B>On</B>, readline attempts to briefly move the cursor to an
+opening parenthesis when a closing parenthesis is inserted.
+<DT><B>colored-completion-prefix (Off)</B>
+
+<DD>
+If set to <B>On</B>, when listing completions, readline displays the
+common prefix of the set of possible completions using a different color.
+The color definitions are taken from the value of the <B>LS_COLORS</B>
+environment variable.
+<DT><B>colored-stats (Off)</B>
+
+<DD>
+If set to <B>On</B>, readline displays possible completions using different
+colors to indicate their file type.
+The color definitions are taken from the value of the <B>LS_COLORS</B>
+environment variable.
+<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-display-width (-1)</B>
+
+<DD>
+The number of screen columns used to display possible matches
+when performing completion.
+The value is ignored if it is less than 0 or greater than the terminal
+screen width.
+A value of 0 will cause matches to be displayed one per line.
+The default value is -1.
+<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-map-case (Off)</B>
+
+<DD>
+If set to <B>On</B>, and <B>completion-ignore-case</B> is enabled, readline
+treats hyphens (<I>-</I>) and underscores (<I>_</I>) as equivalent when
+performing case-insensitive filename matching and completion.
+<DT><B>completion-prefix-display-length (0)</B>
+
+<DD>
+The length in characters of the common prefix of a list of possible
+completions that is displayed without modification. When set to a
+value greater than zero, common prefixes longer than this value are
+replaced with an ellipsis when displaying possible completions.
+<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,
+readline will ask whether or not the user 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>).
+The default is <I>On</I>, but readline will set it to <I>Off</I> if the
+locale contains eight-bit characters.
+<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>echo-control-characters (On)</B>
+
+<DD>
+When set to <B>On</B>, on operating systems that indicate they support it,
+readline echoes a character corresponding to a signal generated from the
+keyboard.
+<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>emacs-mode-string (@)</B>
+
+<DD>
+If the <I>show-mode-in-prompt</I> variable is enabled,
+this string is displayed immediately before the last line of the primary
+prompt when emacs editing mode is active. The value is expanded like a
+key binding, so the standard set of meta- and control prefixes and
+backslash escape sequences is available.
+Use the \1 and \2 escapes to begin and end sequences of
+non-printing characters, which can be used to embed a terminal control
+sequence into the mode string.
+<DT><B>enable-bracketed-paste (On)</B>
+
+<DD>
+When set to <B>On</B>, readline will configure the terminal in a way
+that will enable it to insert each paste into the editing buffer as a
+single string of characters, instead of treating each character as if
+it had been read from the keyboard. This can prevent pasted characters
+from being interpreted as editing commands.
+<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>enable-meta-key (On)</B>
+
+<DD>
+When set to <B>On</B>, readline will try to enable any meta modifier
+key the terminal claims to support when it is called. On many terminals,
+the meta key is used to send eight-bit characters.
+<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 (Off)</B>
+
+<DD>
+If set to <B>On</B>, the history code attempts to place point at the
+same location on each history line retrieved with <B>previous-history</B>
+or <B>next-history</B>.
+<DT><B>history-size (unset)</B>
+
+<DD>
+Set the maximum number of history entries saved in the history list.
+If set to zero, any existing history entries are deleted and no new entries
+are saved.
+If set to a value less than zero, the number of history entries is not
+limited.
+By default, the number of history entries is set to the value of the
+<B>HISTSIZE</B> shell variable.
+If an attempt is made to set <I>history-size</I> to a non-numeric value,
+the maximum number of history entries will be set to 500.
+<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.
+This setting is automatically enabled for terminals of height 1.
+<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 eighth 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.
+The default is <I>Off</I>, but readline will set it to <I>On</I> if the
+locale contains eight-bit characters.
+<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>keyseq-timeout (500)</B>
+
+<DD>
+Specifies the duration <I>readline</I> will wait for a character when reading an
+ambiguous key sequence (one that can form a complete key sequence using
+the input read so far, or can take additional input to complete a longer
+key sequence).
+If no input is received within the timeout, <I>readline</I> will use the shorter
+but complete key sequence.
+The value is specified in milliseconds, so a value of 1000 means that
+<I>readline</I> will wait one second for additional input.
+If this variable is set to a value less than or equal to zero, or to a
+non-numeric value, <I>readline</I> will wait until another key is pressed to
+decide which key sequence to complete.
+<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>mark-symlinked-directories (Off)</B>
+
+<DD>
+If set to <B>On</B>, completed names which are symbolic links to directories
+have a slash appended (subject to the value of
+<B>mark-directories</B>).
+<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.
+If set to <B>Off</B>, the leading `.' must be
+supplied by the user in the filename to be completed.
+<DT><B>menu-complete-display-prefix (Off)</B>
+
+<DD>
+If set to <B>On</B>, menu completion displays the common prefix of the
+list of possible completions (which may be empty) before cycling through
+the list.
+<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.
+The default is <I>Off</I>, but readline will set it to <I>On</I> if the
+locale contains eight-bit characters.
+<DT><B>page-completions (On)</B>
+
+<DD>
+If set to <B>On</B>, readline uses an internal <I>more</I>-like pager
+to display a screenful of possible completions at a time.
+<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>revert-all-at-newline (Off)</B>
+
+<DD>
+If set to <B>On</B>, readline will undo all changes to history lines
+before returning when <B>accept-line</B> is executed. By default,
+history lines may be modified and retain individual undo lists across
+calls to <B>readline</B>.
+<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>show-all-if-unmodified (Off)</B>
+
+<DD>
+This alters the default behavior of the completion functions in
+a fashion similar to <B>show-all-if-ambiguous</B>.
+If set to
+<B>On</B>,
+
+words which have more than one possible completion without any
+possible partial completion (the possible completions don't share
+a common prefix) cause the matches to be listed immediately instead
+of ringing the bell.
+<DT><B>show-mode-in-prompt (Off)</B>
+
+<DD>
+If set to <B>On</B>, add a string to the beginning of the prompt
+indicating the editing mode: emacs, vi command, or vi insertion.
+The mode strings are user-settable (e.g., <I>emacs-mode-string</I>).
+<DT><B>skip-completed-text (Off)</B>
+
+<DD>
+If set to <B>On</B>, this alters the default completion behavior when
+inserting a single match into the line. It's only active when
+performing completion in the middle of a word. If enabled, readline
+does not insert characters from the completion that match characters
+after point in the word being completed, so portions of the word
+following the cursor are not duplicated.
+<DT><B>vi-cmd-mode-string ((cmd))</B>
+
+<DD>
+If the <I>show-mode-in-prompt</I> variable is enabled,
+this string is displayed immediately before the last line of the primary
+prompt when vi editing mode is active and in command mode.
+The value is expanded like a
+key binding, so the standard set of meta- and control prefixes and
+backslash escape sequences is available.
+Use the \1 and \2 escapes to begin and end sequences of
+non-printing characters, which can be used to embed a terminal control
+sequence into the mode string.
+<DT><B>vi-ins-mode-string ((ins))</B>
+
+<DD>
+If the <I>show-mode-in-prompt</I> variable is enabled,
+this string is displayed immediately before the last line of the primary
+prompt when vi editing mode is active and in insertion mode.
+The value is expanded like a
+key binding, so the standard set of meta- and control prefixes and
+backslash escape sequences is available.
+Use the \1 and \2 escapes to begin and end sequences of
+non-printing characters, which can be used to embed a terminal control
+sequence into the mode string.
+<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="lbCK">&nbsp;</A>
+<H4>Readline Conditional Constructs</H4>
+
+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>$if</B>
+
+construct allows bindings to be made based on the
+editing mode, the terminal being used, or the application using
+readline. The text of the test, after any comparison operator,
+<BR>&nbsp;extends&nbsp;to&nbsp;the&nbsp;end&nbsp;of&nbsp;the&nbsp;line;
+unless otherwise noted, no characters are required to isolate it.
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT><B>mode</B><DD>
+The <B>mode=</B> form of the <B>$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 both the 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>version</B><DD>
+The <B>version</B> test may be used to perform comparisons against
+specific readline versions.
+The <B>version</B> expands to the current readline version.
+The set of comparison operators includes
+<B>=</B>,
+
+(and
+<B>==</B>),
+
+<B>!=</B>,
+
+<B>&lt;=</B>,
+
+<B>&gt;=</B>,
+
+<B>&lt;</B>,
+
+and
+<B>&gt;</B>.
+
+The version number supplied on the right side of the operator consists
+of a major version number, an optional decimal point, and an optional
+minor version (e.g., <B>7.1</B>). If the minor version is omitted, it
+is assumed to be <B>0</B>.
+The operator may be separated from the string <B>version</B>
+and from the version number argument by whitespace.
+<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 <B>bash</B>:
+<P>
+<DL COMPACT><DT><DD>
+<PRE>
+<B>$if</B> Bash
+# Quote the current or previous word
+&quot;\C-xq&quot;: &quot;\eb\&quot;\ef\&quot;&quot;
+<B>$endif</B>
+</PRE>
+
+</DL>
+
+<DT><I>variable</I><DD>
+The <I>variable</I> construct provides simple equality tests for readline
+variables and values.
+The permitted comparison operators are <I>=</I>, <I>==</I>, and <I>!=</I>.
+The variable name must be separated from the comparison operator by
+whitespace; the operator may be separated from the value on the right hand
+side by whitespace.
+Both string and boolean variables may be tested. Boolean variables must be
+tested against the values <I>on</I> and <I>off</I>.
+</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="lbCL">&nbsp;</A>
+<H4>Searching</H4>
+
+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="lbCM">&nbsp;</A>
+<H4>Readline Command Names</H4>
+
+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="lbCN">&nbsp;</A>
+<H4>Commands for Moving</H4>
+
+
+<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>shell-forward-word</B>
+
+<DD>
+Move forward to the end of the next word.
+Words are delimited by non-quoted shell metacharacters.
+<DT><B>shell-backward-word</B>
+
+<DD>
+Move back to the start of the current or previous word.
+Words are delimited by non-quoted shell metacharacters.
+<DT><B>previous-screen-line</B>
+
+<DD>
+Attempt to move point to the same physical screen column on the previous
+physical screen line. This will not have the desired effect if the current
+Readline line does not take up more than one physical line or if point is not
+greater than the length of the prompt plus the screen width.
+<DT><B>next-screen-line</B>
+
+<DD>
+Attempt to move point to the same physical screen column on the next
+physical screen line. This will not have the desired effect if the current
+Readline line does not take up more than one physical line or if the length
+of the current Readline line is not greater than the length of the prompt
+plus the screen width.
+<DT><B>clear-display (M-C-l)</B>
+
+<DD>
+Clear the screen and, if possible, the terminal's scrollback buffer,
+then redraw the current line,
+leaving the current line at the top of the screen.
+<DT><B>clear-screen (C-l)</B>
+
+<DD>
+Clear the screen,
+then redraw the current line,
+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="lbCO">&nbsp;</A>
+<H4>Commands for Manipulating the History</H4>
+
+
+<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-&lt;)</B>
+
+<DD>
+Move to the first line in the history.
+<DT><B>end-of-history (M-&gt;)</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>history-substring-search-backward</B>
+
+<DD>
+Search backward through the history for the string of characters
+between the start of the current line and the current cursor
+position (the <I>point</I>).
+The search string may match anywhere in a history line.
+This is a non-incremental search.
+<DT><B>history-substring-search-forward</B>
+
+<DD>
+Search forward through the history for the string of characters
+between the start of the current line and the point.
+The search string may match anywhere in a history line.
+This is a non-incremental search.
+<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.
+Once the argument <I>n</I> is computed, the argument is extracted
+as if the &quot;!<I>n</I>&quot; history expansion had been specified.
+<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 a numeric argument, behave exactly like <B>yank-nth-arg</B>.
+Successive calls to <B>yank-last-arg</B> move back through the history
+list, inserting the last word (or the word specified by the argument to
+the first call) of each line in turn.
+Any numeric argument supplied to these successive calls determines
+the direction to move through the history. A negative argument switches
+the direction through the history (back or forward).
+The history expansion facilities are used to extract the last word,
+as if the &quot;!$&quot; history expansion had been specified.
+<DT><B>shell-expand-line (M-C-e)</B>
+
+<DD>
+Expand the line as the shell does. This
+performs alias and history expansion as well as all of the shell
+word expansions. See
+<FONT SIZE=-1><B>HISTORY EXPANSION</B>
+
+</FONT>
+below for a description of history expansion.
+<DT><B>history-expand-line (M-^)</B>
+
+<DD>
+Perform history expansion on the current line.
+See
+<FONT SIZE=-1><B>HISTORY EXPANSION</B>
+
+</FONT>
+below for a description of history expansion.
+<DT><B>magic-space</B>
+
+<DD>
+Perform history expansion on the current line and insert a space.
+See
+<FONT SIZE=-1><B>HISTORY EXPANSION</B>
+
+</FONT>
+below for a description of history expansion.
+<DT><B>alias-expand-line</B>
+
+<DD>
+Perform alias expansion on the current line.
+See
+<FONT SIZE=-1><B>ALIASES</B>
+
+</FONT>
+above for a description of alias expansion.
+<DT><B>history-and-alias-expand-line</B>
+
+<DD>
+Perform history and alias expansion on the current line.
+<DT><B>insert-last-argument (M-., M-_)</B>
+
+<DD>
+A synonym for <B>yank-last-arg</B>.
+<DT><B>operate-and-get-next (C-o)</B>
+
+<DD>
+Accept the current line for execution and fetch the next line
+relative to the current line from the history for editing.
+A numeric argument, if supplied, specifies the history entry to use instead
+of the current line.
+<DT><B>edit-and-execute-command (C-x C-e)</B>
+
+<DD>
+Invoke an editor on the current command line, and execute the result as shell
+commands.
+<B>Bash</B> attempts to invoke
+<FONT SIZE=-1><B>$VISUAL</B>,
+
+</FONT>
+<FONT SIZE=-1><B>$EDITOR</B>,
+
+</FONT>
+and <I>emacs</I> as the editor, in that order.
+
+</DL>
+<A NAME="lbCP">&nbsp;</A>
+<H4>Commands for Changing Text</H4>
+
+
+<DL COMPACT>
+<DT><B></B><I>end-of-file</I> (usually C-d)
+
+<DD>
+The character indicating end-of-file as set, for example, by
+<TT>stty</TT>.
+
+If this character is read when there are no characters
+on the line, and point is at the beginning of the line, Readline
+interprets it as the end of input and returns
+<FONT SIZE=-1><B>EOF</B>.
+
+</FONT>
+<DT><B>delete-char (C-d)</B>
+
+<DD>
+Delete the character at point.
+If this function is bound to the
+same character as the tty <B>EOF</B> character, as <B>C-d</B>
+commonly is, see above for the effects.
+<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,&nbsp;b,&nbsp;A,&nbsp;1,&nbsp;!,&nbsp;...)</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.
+<DT><B>overwrite-mode</B>
+
+<DD>
+Toggle overwrite mode. With an explicit positive numeric argument,
+switches to overwrite mode. With an explicit non-positive numeric
+argument, switches to insert mode. This command affects only
+<B>emacs</B> mode; <B>vi</B> mode does overwrite differently.
+Each call to <I>readline()</I> starts in insert mode.
+In overwrite mode, characters bound to <B>self-insert</B> replace
+the text at point rather than pushing the text to the right.
+Characters bound to <B>backward-delete-char</B> replace the character
+before point with a space. By default, this command is unbound.
+
+</DL>
+<A NAME="lbCQ">&nbsp;</A>
+<H4>Killing and Yanking</H4>
+
+
+<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>shell-kill-word</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>shell-forward-word</B>.
+<DT><B>shell-backward-kill-word</B>
+
+<DD>
+Kill the word behind point.
+Word boundaries are the same as those used by <B>shell-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>unix-filename-rubout</B>
+
+<DD>
+Kill the word behind point, using white space and the slash character
+as the word boundaries.
+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="lbCR">&nbsp;</A>
+<H4>Numeric Arguments</H4>
+
+
+<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 nor minus sign, the argument count
+for the next command is multiplied by four.
+The argument count is initially one, so executing this function the
+first time makes the argument count four, a second time makes the
+argument count sixteen, and so on.
+
+</DL>
+<A NAME="lbCS">&nbsp;</A>
+<H4>Completing</H4>
+
+
+<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>menu-complete-backward</B>
+
+<DD>
+Identical to <B>menu-complete</B>, but moves backward through the list
+of possible completions, as if <B>menu-complete</B> had been given a
+negative argument. This command is unbound by default.
+<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>dabbrev-expand</B>
+
+<DD>
+Attempt menu 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="lbCT">&nbsp;</A>
+<H4>Keyboard Macros</H4>
+
+
+<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.
+<DT><B>print-last-kbd-macro ()</B>
+
+<DD>
+Print the last keyboard macro defined in a format suitable for the
+<I>inputrc</I> file.
+
+</DL>
+<A NAME="lbCU">&nbsp;</A>
+<H4>Miscellaneous</H4>
+
+
+<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-lowercase-version (M-A, M-B, M-</B><I>x</I>, ...)
+
+<DD>
+If the metafied character <I>x</I> is uppercase, run the command
+that is bound to the corresponding metafied lowercase character.
+The behavior is undefined if <I>x</I> is already lowercase.
+<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-&amp;)</B>
+
+<DD>
+Perform tilde expansion on the current word.
+<DT><B>set-mark (C-@, M-&lt;space&gt;)</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>skip-csi-sequence</B>
+
+<DD>
+Read enough characters to consume a multi-key sequence such as those
+defined for keys like Home and End. Such sequences begin with a
+Control Sequence Indicator (CSI), usually ESC-[. If this sequence is
+bound to &quot;\[&quot;, keys producing such sequences will have no effect
+unless explicitly bound to a readline command, instead of inserting
+stray characters into the editing buffer. This is unbound by default,
+but usually bound to ESC-[.
+<DT><B>insert-comment (M-#)</B>
+
+<DD>
+Without a numeric argument, the value of the readline
+<B>comment-begin</B>
+
+variable is inserted at the beginning of the current line.
+If a numeric argument is supplied, this command acts as a toggle: if
+the characters at the beginning of the line do not match the value
+of <B>comment-begin</B>, the value is inserted, otherwise
+the characters in <B>comment-begin</B> are deleted from the beginning of
+the line.
+In either case, the line is accepted as if a newline had been typed.
+The default value of
+<B>comment-begin</B> causes this command to make the current line
+a shell comment.
+If a numeric argument causes the comment character to be removed, the line
+will be executed by the shell.
+<DT><B>glob-complete-word (M-g)</B>
+
+<DD>
+The word before point is treated as a pattern for pathname expansion,
+with an asterisk implicitly appended. This pattern is used to
+generate a list of matching filenames for possible completions.
+<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 filenames is inserted, replacing the word.
+If a numeric argument is supplied, an asterisk is appended before
+pathname expansion.
+<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.
+If a numeric argument is supplied, an asterisk is appended before
+pathname expansion.
+<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 output. 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="lbCV">&nbsp;</A>
+<H4>Programmable Completion</H4>
+
+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 the command word is the empty string (completion attempted at the
+beginning of an empty line), any compspec defined with
+the <B>-E</B> option to <B>complete</B> is used.
+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.
+If those searches do not result in a compspec, any compspec defined with
+the <B>-D</B> option to <B>complete</B> is used as the default.
+If there is no default compspec, <B>bash</B> attempts alias expansion
+on the command word as a final resort, and attempts to find a compspec
+for the command word from any successful expansion.
+<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 pathname 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, and arithmetic 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>
+<FONT SIZE=-1><B>COMP_POINT</B>,
+
+</FONT>
+<FONT SIZE=-1><B>COMP_KEY</B>,
+
+</FONT>
+and
+<FONT SIZE=-1><B>COMP_TYPE</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 (<B>$1</B>) is the name of the command whose arguments are
+being completed,
+the second argument (<B>$2</B>) is the word being completed,
+and the third argument (<B>$3</B>) is the word preceding the word being
+completed on the current command line.
+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, one per array element.
+<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>&amp;</B>
+in the pattern is replaced with the text of the word being completed.
+A literal <B>&amp;</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.
+If the
+<B>nocasematch</B>
+
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+<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>
+
+If the <B>-o plusdirs</B> option was supplied to <B>complete</B> when the
+compspec was defined, directory name completion is attempted and any
+matches are added to the results of the other actions.
+<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 bashdefault</B> option was supplied to <B>complete</B> when
+the compspec was defined, the <B>bash</B> default completions are attempted
+if the compspec generates no matches.
+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 (and, if attempted, the default <B>bash</B> completions)
+generate no matches.
+<P>
+
+When a compspec indicates that directory name completion is desired,
+the programmable completion functions force readline to append a slash
+to completed names which are symbolic links to directories, subject to
+the value of the <B>mark-directories</B> readline variable, regardless
+of the setting of the <B>mark-symlinked-directories</B> readline variable.
+<P>
+
+There is some support for dynamically modifying completions. This is
+most useful when used in combination with a default completion specified
+with <B>complete -D</B>.
+It's possible for shell functions executed as completion
+handlers to indicate that completion should be retried by returning an
+exit status of 124. If a shell function returns 124, and changes
+the compspec associated with the command on which completion is being
+attempted (supplied as the first argument when the function is executed),
+programmable completion restarts from the beginning, with an
+attempt to find a new compspec for that command. This allows a set of
+completions to be built dynamically as completion is attempted, rather than
+being loaded all at once.
+<P>
+
+For instance, assuming that there is a library of compspecs, each kept in a
+file corresponding to the name of the command, the following default
+completion function would load completions dynamically:
+<P>
+
+<TT>_completion_loader()
+<BR>
+
+{
+<BR>
+
+<TT>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</TT>. &quot;/etc/bash_completion.d/$1.sh&quot; &gt;/dev/null 2&gt;&amp;1 &amp;&amp; return 124<BR>
+<BR>
+
+}
+<BR>
+
+complete -D -F _completion_loader -o bashdefault -o default
+<BR>
+
+</TT>
+<A NAME="lbCW">&nbsp;</A>
+<H3>HISTORY</H3>
+
+When the
+<B>-o history</B>
+
+option to the
+<B>set</B>
+
+builtin is enabled, the shell provides access to the
+<I>command history</I>,
+the list of commands previously typed.
+The value of the
+<FONT SIZE=-1><B>HISTSIZE</B>
+
+</FONT>
+variable is used as the
+number of commands to save in a history list.
+The text of the last
+<FONT SIZE=-1><B>HISTSIZE</B>
+
+</FONT>
+commands (default 500) is saved. The shell
+stores each command in the history list prior to parameter and
+variable expansion (see
+<FONT SIZE=-1><B>EXPANSION</B>
+
+</FONT>
+above) but after history expansion is performed, subject to the
+values of the shell variables
+<FONT SIZE=-1><B>HISTIGNORE</B>
+
+</FONT>
+and
+<FONT SIZE=-1><B>HISTCONTROL</B>.
+
+</FONT>
+<P>
+
+On startup, the history is initialized from the file named by
+the variable
+<FONT SIZE=-1><B>HISTFILE</B>
+
+</FONT>
+(default <A HREF="file:~/.bash_history"><I>~/.bash_history</I></A>).
+The file named by the value of
+<FONT SIZE=-1><B>HISTFILE</B>
+
+</FONT>
+is truncated, if necessary, to contain no more than
+the number of lines specified by the value of
+<FONT SIZE=-1><B>HISTFILESIZE</B>.
+
+</FONT>
+If <B>HISTFILESIZE</B> is unset, or set to null, a non-numeric value,
+or a numeric value less than zero, the history file is not truncated.
+When the history file is read,
+lines beginning with the history comment character followed immediately
+by a digit are interpreted as timestamps for the following history line.
+These timestamps are optionally displayed depending on the value of the
+<FONT SIZE=-1><B>HISTTIMEFORMAT</B>
+
+</FONT>
+variable.
+When a shell with history enabled exits, the last
+<FONT SIZE=-1><B>$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.
+If the
+<FONT SIZE=-1><B>HISTTIMEFORMAT</B>
+
+</FONT>
+variable is set, time stamps are written to the history file, marked
+with the history comment character, so
+they may be preserved across shell sessions.
+This uses the history comment character to distinguish timestamps from
+other history lines.
+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 unset, or set to null, a non-numeric value,
+or a numeric value less than zero, the history file is not truncated.
+<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="lbCX">&nbsp;</A>
+<H3>HISTORY EXPANSION</H3>
+
+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, and is performed
+on each line individually without taking quoting on previous lines into
+account.
+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, but the history expansion character is
+also treated as quoted if it immediately precedes the closing double quote
+in a double-quoted string.
+<P>
+
+Several characters inhibit history expansion if found immediately
+following the history expansion character, even if it is unquoted:
+space, tab, newline, carriage return, and <B>=</B>.
+If the <B>extglob</B> shell option is enabled, <B>(</B> will also
+inhibit expansion.
+<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 below), 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>).
+
+The shell uses
+the history comment character to mark history timestamps when
+writing the history file.
+<A NAME="lbCY">&nbsp;</A>
+<H4>Event Designators</H4>
+
+An event designator is a reference to a command line entry in the
+history list.
+Unless the reference is absolute, events are relative to the current
+position in the history list.
+<P>
+
+
+<DL COMPACT>
+<DT><B>!</B>
+
+<DD>
+Start a history substitution, except when followed by a
+<B>blank</B>,
+
+newline, carriage return, =
+or ( (when the <B>extglob</B> shell option is enabled using
+the <B>shopt</B> builtin).
+<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 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 preceding the current position in the
+history list starting with
+<I>string</I>.
+
+<DT><B>!?</B><I>string</I><B>[?]</B>
+
+<DD>
+Refer to the most recent command preceding the current position in the
+history list containing
+<I>string</I>.
+
+The trailing <B>?</B> may be omitted if
+<I>string</I>
+
+is followed immediately by a newline.
+If <I>string</I> is missing, the string from the most recent search is used;
+it is an error if there is no previous search string.
+<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 previous command, replacing
+<I>string1</I>
+
+with
+<I>string2</I>.
+
+Equivalent to
+``!!:s<FONT SIZE=+2>^</FONT><I>string1</I><FONT SIZE=+2>^</FONT><I>string2</I><FONT SIZE=+2>^</FONT>''
+(see <B>Modifiers</B> below).
+<DT><B>!#</B>
+
+<DD>
+The entire command line typed so far.
+
+</DL>
+<A NAME="lbCZ">&nbsp;</A>
+<H4>Word Designators</H4>
+
+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>$</B>
+
+<DD>
+The last word. This is usually the last argument, but will expand to the
+zeroth word if there is only one word in the line.
+<DT><B>%</B>
+
+<DD>
+The first word matched by the most recent `?<I>string</I>?' search,
+if the search string begins with a character that is part of a word.
+<DT><I>x</I><B>-</B>y
+
+<DD>
+A range of words; `-<I>y</I>' abbreviates `0-<I>y</I>'.
+<DT><B>*</B>
+
+<DD>
+All of the words but the zeroth. This is a synonym
+for `<I>1-$</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.
+If <B>x</B> is missing, it defaults to 0.
+
+</DL>
+<P>
+
+If a word designator is supplied without an event specification, the
+previous command is used as the event.
+<A NAME="lbDA">&nbsp;</A>
+<H4>Modifiers</H4>
+
+After the optional word designator, there may appear a sequence of
+one or more of the following modifiers, each preceded by a `:'.
+These modify, or edit, the word or words selected from the history event.
+<P>
+
+
+<DL COMPACT>
+<DT><B>h</B>
+
+<DD>
+Remove a trailing filename component, leaving only the head.
+<DT><B>t</B>
+
+<DD>
+Remove all leading filename 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.
+The <B>q</B> and <B>x</B> modifiers are mutually exclusive; the last one
+supplied is used.
+<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 character may be used as the delimiter in place of /.
+The final delimiter is optional if it is the last character of the
+event line.
+The delimiter may be quoted in
+<I>old</I>
+
+and
+<I>new</I>
+
+with a single backslash. If &amp; appears in
+<I>new</I>,
+
+it is replaced by
+<I>old</I>.
+
+A single backslash will quote the &amp;.
+If
+<I>old</I>
+
+is null, it is set to the last
+<I>old</I>
+
+substituted, or, if no previous history substitutions took place,
+the last
+<I>string</I>
+
+in a
+<B>!?</B><I>string</I><B>[?]</B>
+
+search.
+If
+<I>new</I>
+
+is null, each matching
+<I>old</I>
+
+is deleted.
+<DT><B>&amp;</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>:&amp;</B>'. If used with
+`<B>:s</B>', any delimiter can be used
+in place of /, and the final delimiter is optional
+if it is the last character of the event line.
+An <B>a</B> may be used as a synonym for <B>g</B>.
+<DT><B>G</B>
+
+<DD>
+Apply the following `<B>s</B>' or `<B>&amp;</B>' modifier once to each word
+in the event line.
+
+</DL>
+<A NAME="lbDB">&nbsp;</A>
+<H3>SHELL BUILTIN COMMANDS</H3>
+
+
+
+<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.
+The <B>:</B>, <B>true</B>, <B>false</B>, and <B>test</B>/<B>[</B> builtins
+do not accept options and do not treat <B>--</B> specially.
+The <B>exit</B>, <B>logout</B>, <B>return</B>,
+<B>break</B>, <B>continue</B>, <B>let</B>,
+and <B>shift</B> builtins accept and process arguments beginning with
+<B>-</B> without requiring <B>--</B>.
+Other builtins that accept arguments but are not specified as accepting
+options interpret arguments beginning with <B>-</B> as invalid options and
+require <B>--</B> to prevent this interpretation.
+<P>
+
+<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.
+The return status is zero.
+<DT><B> . </B> <I>filename</I> [<I>arguments</I>]<DD>
+
+<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, filenames 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.
+If the <B>-T</B> option is enabled, <B>source</B> inherits any trap on
+<B>DEBUG</B>; if it is not, any <B>DEBUG</B> trap string is saved and
+restored around the call to <B>source</B>, and <B>source</B> unsets the
+<B>DEBUG</B> trap while it executes.
+If <B>-T</B> is not set, and the sourced file changes
+the <B>DEBUG</B> trap, the new value is retained when <B>source</B> completes.
+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 each suspended job <I>jobspec</I> in the background, as if it
+had been started with
+<B>&amp;</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, any specified <I>jobspec</I> was not found
+or was started without job control.
+<DT><B>bind</B> [<B>-m</B> <I>keymap</I>] [<B>-lpsvPSVX</B>]<DD>
+
+<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>
+<DT><B>bind</B> [<B>-m</B> <I>keymap</I>] <I>keyseq</I>:<I>readline-command</I><DD>
+
+Display current
+<B>readline</B>
+
+key and function bindings, bind a key sequence to a
+<B>readline</B>
+
+function or macro, or set a
+<B>readline</B>
+
+variable.
+Each non-option argument is a command as it would appear in
+<I>.inputrc</I>,
+
+but each binding or command must be passed as a separate argument;
+e.g., '&quot;\C-x\C-r&quot;: 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>vi-move</I> is also
+a synonym); <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>-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>-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>-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.
+When <I>shell-command</I> is executed, the shell sets the
+<FONT SIZE=-1><B>READLINE_LINE</B>
+
+</FONT>
+variable to the contents of the <B>readline</B> line buffer and the
+<FONT SIZE=-1><B>READLINE_POINT</B>
+
+</FONT>
+and
+<FONT SIZE=-1><B>READLINE_MARK</B>
+
+</FONT>
+variables to the current location of the insertion point and the saved
+insertion point (the mark), respectively.
+If the executed command changes the value of any of
+<FONT SIZE=-1><B>READLINE_LINE</B>,
+
+</FONT>
+<FONT SIZE=-1><B>READLINE_POINT</B>,
+
+</FONT>
+or
+<FONT SIZE=-1><B>READLINE_MARK</B>,
+
+</FONT>
+those new values will be reflected in the editing state.
+<DT><B>-X</B>
+
+<DD>
+List all key sequences bound to shell commands and the associated commands
+in a format that can be reused as input.
+
+</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 <I>n</I> is not greater than or equal to 1.
+<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>caller</B> [<I>expr</I>]<DD>
+Returns the context of any active subroutine call (a shell function or
+a script executed with the <B>.</B> or <B>source</B> builtins).
+Without <I>expr</I>, <B>caller</B> displays the line number and source
+filename of the current subroutine call.
+If a non-negative integer is supplied as <I>expr</I>, <B>caller</B>
+displays the line number, subroutine name, and source file corresponding
+to that position in the current execution call stack. This extra
+information may be used, for example, to print a stack trace. The
+current frame is frame 0.
+The return value is 0 unless the shell is not executing a subroutine
+call or <I>expr</I> does not correspond to a valid position in the
+call stack.
+<DT><B>cd</B> [<B>-L</B>|[<B>-P</B> [<B>-e</B>]] [-@]] [<I>dir</I>]<DD>
+Change the current directory to <I>dir</I>.
+if <I>dir</I> is not supplied, the value of the
+<FONT SIZE=-1><B>HOME</B>
+
+</FONT>
+shell variable is the default.
+Any additional arguments following <I>dir</I> are ignored.
+The variable
+<FONT SIZE=-1><B>CDPATH</B>
+
+</FONT>
+defines the search path for the directory containing
+<I>dir</I>:
+
+each directory name in
+<FONT SIZE=-1><B>CDPATH</B>
+
+</FONT>
+is searched for <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 causes <B>cd</B> to use the physical directory structure
+by resolving symbolic links while traversing <I>dir</I> and
+before processing instances of <I>..</I> in <I>dir</I> (see also the
+<B>-P</B>
+
+option to the
+<B>set</B>
+
+builtin command); the
+<B>-L</B>
+
+option forces symbolic links to be followed by resolving the link
+after processing instances of <I>..</I> in <I>dir</I>.
+If <I>..</I> appears in <I>dir</I>, it is processed by removing the
+immediately previous pathname component from <I>dir</I>, back to a slash
+or the beginning of <I>dir</I>.
+If the
+<B>-e</B>
+
+option is supplied with
+<B>-P</B>,
+
+and the current working directory cannot be successfully determined
+after a successful directory change, <B>cd</B> will return an unsuccessful
+status.
+On systems that support it, the <B>-@</B> option presents the extended
+attributes associated with a file as a directory.
+An argument of
+<B>-</B>
+
+is converted to
+<FONT SIZE=-1><B>$OLDPWD</B>
+
+</FONT>
+before the directory change is attempted.
+If a non-empty directory name from
+<FONT SIZE=-1><B>CDPATH</B>
+
+</FONT>
+is used, or if
+<B>-</B> is the first argument, and the directory change is
+successful, the absolute pathname of the new working directory is
+written to the standard output.
+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
+<FONT SIZE=-1><B>PATH</B>
+
+</FONT>
+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 filename
+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><B>complete</B> [<B>-abcdefgjksuv</B>] [<B>-o</B> <I>comp-option</I>] [<B>-DEI</B>] [<B>-A</B> <I>action</I>] [<B>-G</B> <I>globpat</I>] [<B>-W</B> <I>wordlist</I>]<DD>
+<BR>
+
+[<B>-F</B> <I>function</I>] [<B>-C</B> <I>command</I>] [<B>-X</B> <I>filterpat</I>] [<B>-P</B> <I>prefix</I>] [<B>-S</B> <I>suffix</I>] <I>name</I> [<I>name ...</I>]
+
+<DT><B>complete</B> <B>-pr</B> [<B>-DEI</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.
+The <B>-D</B> option indicates that other supplied options and actions should
+apply to the ``default'' command completion; that is, completion attempted
+on a command for which no completion has previously been defined.
+The <B>-E</B> option indicates that other supplied options and actions should
+apply to ``empty'' command completion; that is, completion attempted on a
+blank line.
+The <B>-I</B> option indicates that other supplied options and actions should
+apply to completion on the initial non-assignment word on the line, or after
+a command delimiter such as <B>;</B> or <B>|</B>, which is usually command
+name completion.
+If multiple options are supplied, the <B>-D</B> option takes precedence
+over <B>-E</B>, and both take precedence over <B>-I</B>.
+If any of <B>-D</B>, <B>-E</B>, or <B>-I</B> are supplied, any other
+<I>name</I> arguments are ignored; these completions only apply to the case
+specified by the option.
+<P>
+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>bashdefault</B>
+
+<DD>
+Perform the rest of the default <B>bash</B> completions if the compspec
+generates no matches.
+<DT><B>default</B>
+
+<DD>
+Use readline's default filename 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,
+quoting special characters, or suppressing trailing spaces).
+Intended to be used with shell functions.
+<DT><B>noquote</B>
+
+<DD>
+Tell readline not to quote the completed words if they are filenames
+(quoting filenames is the default).
+<DT><B>nosort</B>
+
+<DD>
+Tell readline not to sort the list of possible completions alphabetically.
+<DT><B>nospace</B>
+
+<DD>
+Tell readline not to append a space (the default) to words completed at
+the end of the line.
+<DT><B>plusdirs</B>
+
+<DD>
+After any matches defined by the compspec are generated,
+directory name completion is attempted and any
+matches are added to the results of the other actions.
+</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>service</B>
+
+<DD>
+Service names. May also be specified as <B>-s</B>.
+<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>-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 the function is executed,
+the first argument (<B>$1</B>) is the name of the command whose arguments are
+being completed,
+the second argument (<B>$2</B>) is the word being completed,
+and the third argument (<B>$3</B>) is the word preceding the word being
+completed on the current command line.
+When it finishes, the possible completions are retrieved from the value
+of the
+<FONT SIZE=-1><B>COMPREPLY</B>
+
+</FONT>
+array variable.
+<DT><B>-G</B> <I>globpat</I><DD>
+The pathname expansion pattern <I>globpat</I> is expanded to generate
+the possible completions.
+<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.
+<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.
+Shell quoting is honored within <I>wordlist</I>,
+in order to provide a
+mechanism for the words to contain shell metacharacters or characters
+in the value of
+<FONT SIZE=-1><B>IFS</B>.
+
+</FONT>
+The possible completions are the members of the resultant list which
+match the word being completed.
+<DT><B>-X</B> <I>filterpat</I><DD>
+<I>filterpat</I> is a pattern as used for pathname expansion.
+It is applied to the list of possible completions generated by the
+preceding options and arguments, and each completion matching
+<I>filterpat</I> is removed from the list.
+A leading <B>!</B> in <I>filterpat</I> negates the pattern; in this
+case, any completion not matching <I>filterpat</I> is removed.
+
+</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>compopt</B> [<B>-o</B> <I>option</I>] [<B>-DEI</B>] [<B>+o</B> <I>option</I>] [<I>name</I>]<DD>
+Modify completion options for each <I>name</I> according to the
+<I>option</I>s, or for the
+currently-executing completion if no <I>name</I>s are supplied.
+If no <I>option</I>s are given, display the completion options for each
+<I>name</I> or the current completion.
+The possible values of <I>option</I> are those valid for the <B>complete</B>
+builtin described above.
+The <B>-D</B> option indicates that other supplied options should
+apply to the ``default'' command completion; that is, completion attempted
+on a command for which no completion has previously been defined.
+The <B>-E</B> option indicates that other supplied options should
+apply to ``empty'' command completion; that is, completion attempted on a
+blank line.
+The <B>-I</B> option indicates that other supplied options should
+apply to completion on the initial non-assignment word on the line,
+or after a command delimiter such as <B>;</B> or <B>|</B>, which is usually
+command name completion.
+<P>
+The return value is true unless an invalid option is supplied, an attempt
+is made to modify the options for a <I>name</I> for which no completion
+specification exists, or an output error occurs.
+<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 <I>n</I> is not greater than or equal to 1.
+<DT><B>declare</B> [<B>-aAfFgiIlnrtux</B>] [<B>-p</B>] [<I>name</I>[=<I>value</I>] ...]<DD>
+
+<DT><B>typeset</B> [<B>-aAfFgiIlnrtux</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 with <I>name</I> arguments, additional options,
+other than <B>-f</B> and <B>-F</B>, are ignored.
+When
+<B>-p</B>
+
+is supplied without <I>name</I> arguments, it will display the attributes
+and values of all variables having the attributes specified by the
+additional options.
+If no other options are supplied with <B>-p</B>, <B>declare</B> will display
+the attributes and values of all shell variables. The <B>-f</B> option
+will restrict the display to shell functions.
+The
+<B>-F</B>
+
+option inhibits the display of function definitions; only the
+function name and attributes are printed.
+If the <B>extdebug</B> shell option is enabled using <B>shopt</B>,
+the source file name and line number where each <I>name</I>
+is defined are displayed as well. The
+<B>-F</B>
+
+option implies
+<B>-f</B>.
+
+The
+<B>-g</B>
+
+option forces variables to be created or modified at the global scope,
+even when <B>declare</B> is executed in a shell function.
+It is ignored in all other cases.
+The
+<B>-I</B>
+
+option causes local variables to inherit the attributes
+(except the <I>nameref</I> attribute)
+and value of any existing variable with the same
+<I>name</I> at a surrounding scope.
+If there is no existing variable, the local variable is initially unset.
+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 indexed array variable (see
+<B>Arrays</B>
+
+above).
+<DT><B>-A</B>
+
+<DD>
+Each <I>name</I> is an associative 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>
+above) is performed when the variable is assigned a value.
+<DT><B>-l</B>
+
+<DD>
+When the variable is assigned a value, all upper-case characters are
+converted to lower-case.
+The upper-case attribute is disabled.
+<DT><B>-n</B>
+
+<DD>
+Give each <I>name</I> the <I>nameref</I> attribute, making
+it a name reference to another variable.
+That other variable is defined by the value of <I>name</I>.
+All references, assignments, and attribute modifications
+to <I>name</I>, except those using or changing the
+<B>-n</B> attribute itself, are performed on the variable referenced by
+<I>name</I>'s value.
+The nameref attribute cannot be applied to array variables.
+<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>-t</B>
+
+<DD>
+Give each <I>name</I> the <I>trace</I> attribute.
+Traced functions inherit the <B>DEBUG</B> and <B>RETURN</B> traps from
+the calling shell.
+The trace attribute has no special meaning for variables.
+<DT><B>-u</B>
+
+<DD>
+When the variable is assigned a value, all lower-case characters are
+converted to upper-case.
+The lower-case attribute is disabled.
+<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 exceptions that <B>+a</B> and <B>+A</B>
+may not be used to destroy array variables and <B>+r</B> will not
+remove the readonly attribute.
+When used in a function,
+<B>declare</B>
+
+and
+<B>typeset</B>
+
+make each
+<I>name</I> local, as with the
+<B>local</B>
+
+command,
+unless the <B>-g</B> option is supplied.
+If a variable name is followed by =<I>value</I>, the value of
+the variable is set to <I>value</I>.
+When using <B>-a</B> or <B>-A</B> and the compound assignment syntax to
+create array variables, additional attributes do not take effect until
+subsequent assignments.
+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.
+The current directory is always the first directory in the stack.
+<DL COMPACT><DT><DD>
+
+<DL COMPACT>
+<DT><B>-c</B>
+
+<DD>
+Clears the directory stack by deleting all of the entries.
+<DT><B>-l</B>
+
+<DD>
+Produces a listing using full pathnames;
+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.
+<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.
+
+</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> ... | <I>pid</I> ... ]<DD>
+Without options, remove each
+<I>jobspec</I>
+
+from the table of active jobs.
+If
+<I>jobspec</I>
+
+is not present, and neither the <B>-a</B> nor the <B>-r</B> option
+is supplied, the <I>current job</I> is used.
+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 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 0 unless a write error occurs.
+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 further output
+<DT><B>\e</B>
+
+<DD>
+<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>\0</B><I>nnn</I>
+
+<DD>
+the eight-bit character whose value is the octal value <I>nnn</I>
+(zero to three octal 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)
+<DT><B>\u</B><I>HHHH</I>
+
+<DD>
+the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
+<I>HHHH</I> (one to four hex digits)
+<DT><B>\U</B><I>HHHHHHHH</I>
+
+<DD>
+the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
+<I>HHHHHHHH</I> (one to eight hex digits)
+
+</DL></DL>
+
+<DT><B>enable</B> [<B>-a</B>] [<B>-dnps</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 argument passed to
+<I>command</I>.
+
+This is what
+<I>login</I>(1)
+
+does. The
+<B>-c</B>
+
+option causes
+<I>command</I>
+
+to be executed with an empty environment. If
+<B>-a</B>
+
+is supplied, the shell passes
+<I>name</I>
+
+as the zeroth argument to the executed command.
+If
+<I>command</I>
+
+cannot be executed for some reason, a non-interactive shell exits,
+unless the
+<B>execfail</B>
+
+shell option
+is enabled. In that case, it returns failure.
+An interactive shell returns failure if the file cannot be executed.
+A subshell exits unconditionally if <B>exec</B> fails.
+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><B>export</B> [<B>-fn</B>] [<I>name</I>[=<I>word</I>]] ...<DD>
+
+<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 names of all exported variables is printed.
+The
+<B>-n</B>
+
+option causes the export property to be removed from each
+<I>name</I>.
+If a variable name is followed by =<I>word</I>, the value of
+the variable is set to <I>word</I>.
+<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><B>fc</B> [<B>-e</B> <I>ename</I>] [<B>-lnr</B>] [<I>first</I>] [<I>last</I>]<DD>
+
+<DT><B>fc</B> <B>-s</B> [<I>pat</I>=<I>rep</I>] [<I>cmd</I>]<DD>
+
+The first form selects a range of commands from
+<I>first</I>
+
+to
+<I>last</I>
+
+from the history list and displays or edits and re-executes them.
+<I>First</I>
+
+and
+<I>last</I>
+
+may be specified as a string (to locate the last command beginning
+with that string) or as a number (an index into the history list,
+where a negative number is used as an offset from the current
+command number).
+When listing, a <I>first</I> or <I>last</I> of
+0 is equivalent to -1 and -0 is equivalent to the current
+command (usually the <B>fc</B> command); otherwise 0 is equivalent to -1
+and -0 is invalid.
+If
+<I>last</I>
+
+is not specified, it is set to
+the current command for listing (so that
+
+<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>.
+<I>Command</I> is interpreted the same as <I>first</I> above.
+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>arg ...</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.
+<FONT SIZE=-1><B>OPTIND</B>
+
+</FONT>
+is set to the index of the first non-option argument,
+and <I>name</I> is set to ?.
+<P>
+<B>getopts</B>
+
+normally parses the positional parameters, but if more arguments are
+supplied as
+<I>arg</I>
+
+values,
+<B>getopts</B>
+
+parses those instead.
+<P>
+<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>-lr</B>] [<B>-p</B> <I>filename</I>] [<B>-dt</B>] [<I>name</I>]<DD>
+Each time <B>hash</B> is invoked,
+the full pathname of the command
+<I>name</I>
+
+is determined by searching
+the directories in
+<B>$PATH</B>
+
+and remembered. Any previously-remembered pathname is discarded.
+If the
+<B>-p</B>
+
+option is supplied, no path search is performed, and
+<I>filename</I>
+
+is used as the full filename of the command.
+The
+<B>-r</B>
+
+option causes the shell to forget all
+remembered locations.
+The
+<B>-d</B>
+
+option causes the shell to forget the remembered location of each <I>name</I>.
+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.
+The
+<B>-l</B>
+
+option causes output to be displayed in a format that may be reused as input.
+If no arguments are given, or if only <B>-l</B> is supplied,
+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>-dms</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.
+<DL COMPACT><DT><DD>
+
+<DL COMPACT>
+<DT><B>-d</B>
+
+<DD>
+Display a short description of each <I>pattern</I>
+<DT><B>-m</B>
+
+<DD>
+Display the description of each <I>pattern</I> in a manpage-like format
+<DT><B>-s</B>
+
+<DD>
+Display only a short usage synopsis for each <I>pattern</I>
+
+</DL>
+<P>
+
+The return status is 0 unless no command matches
+<I>pattern</I>.
+
+</DL>
+
+<DT><B>history [</B><I>n</I>]<DD>
+
+<DT><B>history</B> <B>-c</B><DD>
+<DT><B>history -d</B> <I>offset</I><DD>
+<DT><B>history -d</B> <I>start</I>-<I>end</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 the shell variable
+<FONT SIZE=-1><B>HISTTIMEFORMAT</B>
+
+</FONT>
+is set and not null,
+it is used as a format string for <I>strftime</I>(3) to display
+the time stamp associated with each displayed history entry.
+No intervening blank is printed between the formatted time stamp
+and the history line.
+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>.
+If <I>offset</I> is negative, it is interpreted as relative to one greater
+than the last history position, so negative indices count back from the
+end of the history, and an index of -1 refers to the current
+<B>history -d</B> command.
+<DT><B>-d</B> <I>start</I>-<I>end</I><DD>
+Delete the history entries between positions <I>start</I> and <I>end</I>,
+inclusive. Positive and negative values for <I>start</I> and <I>end</I>
+are interpreted as described above.
+<DT><B>-a</B>
+
+<DD>
+Append the ``new'' history lines to the history file.
+These are history lines entered since the beginning of the current
+<B>bash</B> session, but not already appended to the history file.
+<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 append them to the current history list.
+<DT><B>-w</B>
+
+<DD>
+Write the current history list 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>
+
+If the
+<FONT SIZE=-1><B>HISTTIMEFORMAT</B>
+
+</FONT>
+variable is set, the time stamp information
+associated with each history entry is written to the history file,
+marked with the history comment character.
+When the history file is read, lines beginning with the history
+comment character followed immediately by a digit are interpreted
+as timestamps for the following history entry.
+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><B>jobs</B> [<B>-lnprs</B>] [ <I>jobspec</I> ... ]<DD>
+
+<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>-n</B>
+
+<DD>
+Display information only about jobs that have changed status since
+the user was last notified of their status.
+<DT><B>-p</B>
+
+<DD>
+List only the process ID of the job's process group
+leader.
+<DT><B>-r</B>
+
+<DD>
+Display only running jobs.
+<DT><B>-s</B>
+
+<DD>
+Display only 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><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>] ...<DD>
+
+<DT><B>kill</B> <B>-l</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 case-insensitive signal name such as
+<FONT SIZE=-1><B>SIGKILL</B>
+
+</FONT>
+(with or without the
+<FONT SIZE=-1><B>SIG</B>
+
+</FONT>
+prefix) or a signal number;
+<I>signum</I>
+
+is a signal number.
+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.
+The
+<B>-L</B>
+
+option is equivalent to <B>-l</B>.
+<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 EVALUATION</B>
+
+</FONT>
+above).
+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.
+If <I>name</I> is -, the set of shell options is made local to the function
+in which <B>local</B> is invoked: shell options changed using the
+<B>set</B> builtin inside the function are restored to their original values
+when the function returns.
+The restore is effected as if a series of <B>set</B> commands were executed
+to restore the values that were in place before the function.
+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>mapfile</B> [<B>-d</B> <I>delim</I>] [<B>-n</B> <I>count</I>] [<B>-O</B> <I>origin</I>] [<B>-s</B> <I>count</I>] [<B>-t</B>] [<B>-u</B> <I>fd</I>] [<B>-C</B> <I>callback</I>] [<B>-c</B> <I>quantum</I>] [<I>array</I>]<DD>
+
+<DT><B>readarray</B> [<B>-d</B> <I>delim</I>] [<B>-n</B> <I>count</I>] [<B>-O</B> <I>origin</I>] [<B>-s</B> <I>count</I>] [<B>-t</B>] [<B>-u</B> <I>fd</I>] [<B>-C</B> <I>callback</I>] [<B>-c</B> <I>quantum</I>] [<I>array</I>]<DD>
+
+Read lines from the standard input into the indexed array variable
+<I>array</I>,
+
+or from file descriptor
+<I>fd</I>
+
+if the
+<B>-u</B>
+
+option is supplied.
+The variable
+<FONT SIZE=-1><B>MAPFILE</B>
+
+</FONT>
+is the default <I>array</I>.
+Options, if supplied, have the following meanings:
+<DL COMPACT><DT><DD>
+
+<DL COMPACT>
+<DT><B>-d</B>
+
+<DD>
+The first character of <I>delim</I> is used to terminate each input line,
+rather than newline.
+If <I>delim</I> is the empty string, <B>mapfile</B> will terminate a line
+when it reads a NUL character.
+<DT><B>-n</B>
+
+<DD>
+Copy at most
+<I>count</I>
+
+lines. If <I>count</I> is 0, all lines are copied.
+<DT><B>-O</B>
+
+<DD>
+Begin assigning to
+<I>array</I>
+
+at index
+<I>origin</I>.
+
+The default index is 0.
+<DT><B>-s</B>
+
+<DD>
+Discard the first <I>count</I> lines read.
+<DT><B>-t</B>
+
+<DD>
+Remove a trailing <I>delim</I> (default newline) from each line read.
+<DT><B>-u</B>
+
+<DD>
+Read lines from file descriptor <I>fd</I> instead of the standard input.
+<DT><B>-C</B>
+
+<DD>
+Evaluate
+<I>callback</I>
+
+each time <I>quantum</I> lines are read. The <B>-c</B> option specifies
+<I>quantum</I>.
+
+<DT><B>-c</B>
+
+<DD>
+Specify the number of lines read between each call to
+<I>callback</I>.
+
+
+</DL>
+<P>
+
+If
+<B>-C</B>
+
+is specified without
+<B>-c</B>,
+
+the default quantum is 5000.
+When <I>callback</I> is evaluated, it is supplied the index of the next
+array element to be assigned and the line to be assigned to that element
+as additional arguments.
+<I>callback</I> is evaluated after the line is read but before the
+array element is assigned.
+<P>
+
+If not supplied with an explicit origin, <B>mapfile</B> will clear <I>array</I>
+before assigning to it.
+<P>
+
+<B>mapfile</B> returns successfully unless an invalid option or option
+argument is supplied, <I>array</I> is invalid or unassignable, or if
+<I>array</I> is not an indexed array.
+</DL>
+
+<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>-n</B>
+
+<DD>
+Suppresses the normal change of directory when removing directories
+from the stack, so that only the stack is manipulated.
+<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.
+
+</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> [<B>-v</B> <I>var</I>] <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 <B>-v</B> option causes the output to be assigned to the variable
+<I>var</I> rather than being printed to the standard output.
+<P>
+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) format specifications,
+<B>printf</B> interprets the following extensions:
+<DL COMPACT><DT><DD>
+
+<DL COMPACT>
+<DT><B>%b</B>
+
+<DD>
+causes
+<B>printf</B> to expand backslash escape sequences in the corresponding
+<I>argument</I>
+in the same way as <B>echo -e</B>.
+<DT><B>%q</B>
+
+<DD>
+causes <B>printf</B> to output the corresponding
+<I>argument</I> in a format that can be reused as shell input.
+<DT><B>%(</B><I>datefmt</I>)T
+
+<DD>
+causes <B>printf</B> to output the date-time string resulting from using
+<I>datefmt</I> as a format string for <I>strftime</I>(3).
+The corresponding <I>argument</I> is an integer representing the number of
+seconds since the epoch.
+Two special argument values may be used: -1 represents the current
+time, and -2 represents the time the shell was invoked.
+If no argument is specified, conversion behaves as if -1 had been given.
+This is an exception to the usual <B>printf</B> behavior.
+
+</DL>
+<P>
+
+The %b, %q, and %T directives all use the field width and precision
+arguments from the format specification and write that many bytes from
+(or use that wide a field for) the expanded argument, which usually
+contains more characters than the original.
+<P>
+
+Arguments to non-string format specifiers are treated as C constants,
+except that a leading plus or minus sign is allowed, and if the leading
+character is a single or double quote, the value is the ASCII value of
+the following character.
+<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.
+</DL>
+
+<DT><B>pushd</B> [<B>-n</B>] [+<I>n</I>] [-<I>n</I>]<DD>
+
+<DT><B>pushd</B> [<B>-n</B>] [<I>dir</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, <B>pushd</B> 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>-n</B>
+
+<DD>
+Suppresses the normal change of directory when rotating or
+adding directories to the stack, so that only the stack is manipulated.
+<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><I>dir</I>
+
+<DD>
+Adds
+<I>dir</I>
+
+to the directory stack at the top, making it the
+new current working directory as if it had been supplied as the argument
+to the <B>cd</B> builtin.
+
+</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>-a</B> <I>aname</I>] [<B>-d</B> <I>delim</I>] [<B>-i</B> <I>text</I>] [<B>-n</B> <I>nchars</I>] [<B>-N</B> <I>nchars</I>] [<B>-p</B> <I>prompt</I>] [<B>-t</B> <I>timeout</I>] [<B>-u</B> <I>fd</I>] [<I>name</I> ...]<DD>
+One line is read from the standard input, or from the file descriptor
+<I>fd</I> supplied as an argument to the <B>-u</B> option,
+split into words as described above under <B>Word Splitting</B>,
+and the first word
+is assigned to the first
+<I>name</I>,
+
+the second word to the second
+<I>name</I>,
+
+and so on.
+If there are more words than names, the remaining words and their
+intervening delimiters are assigned to the last
+<I>name</I>.
+
+If there are fewer words read from the input stream than names,
+the remaining names are assigned empty values.
+The characters in
+<FONT SIZE=-1><B>IFS</B>
+
+</FONT>
+are used to split the line into words using the same rules the shell
+uses for expansion (described above under <B>Word Splitting</B>).
+The backslash character (<B>\</B>) 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.
+If <I>delim</I> is the empty string, <B>read</B> will terminate a line
+when it reads a NUL character.
+<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.
+Readline uses the current (or default, if line editing was not previously
+active) editing settings, but uses Readline's default filename completion.
+<DT><B>-i </B><I>text</I>
+
+<DD>
+If
+<B>readline</B>
+
+is being used to read the line, <I>text</I> is placed into the editing
+buffer before editing begins.
+<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, but honors a delimiter if fewer
+than <I>nchars</I> characters are read before the delimiter.
+<DT><B>-N </B><I>nchars</I>
+
+<DD>
+<B>read</B> returns after reading exactly <I>nchars</I> characters rather
+than waiting for a complete line of input, unless EOF is encountered or
+<B>read</B> times out.
+Delimiter characters encountered in the input are
+not treated specially and do not cause <B>read</B> to return until
+<I>nchars</I> characters are read.
+The result is not split on the characters in <B>IFS</B>; the intent is
+that the variable is assigned exactly the characters read
+(with the exception of backslash; see the <B>-r</B> option below).
+<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 then 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 (or a specified number of characters)
+is not read within <I>timeout</I> seconds.
+<I>timeout</I> may be a decimal number with a fractional portion following
+the decimal point.
+This option is only effective if <B>read</B> is reading input from a
+terminal, pipe, or other special file; it has no effect when reading
+from regular files.
+If <B>read</B> times out, <B>read</B> saves any partial input read into
+the specified variable <I>name</I>.
+If <I>timeout</I> is 0, <B>read</B> returns immediately, without trying to
+read any data. The exit status is 0 if input is available on
+the specified file descriptor, non-zero otherwise.
+The exit status is greater than 128 if the timeout is exceeded.
+<DT><B>-u </B><I>fd</I>
+
+<DD>
+Read input from file descriptor <I>fd</I>.
+
+</DL>
+<P>
+
+If no
+<I>names</I>
+
+are supplied, the line read,
+without the ending delimiter but otherwise unmodified,
+is assigned to the variable
+<FONT SIZE=-1><B>REPLY</B>.
+
+</FONT>
+The exit status is zero, unless end-of-file is encountered, <B>read</B>
+times out (in which case the status is greater than 128),
+a variable assignment error (such as assigning to a readonly variable) occurs,
+or an invalid file descriptor is supplied as the argument to <B>-u</B>.
+</DL>
+
+<DT><B>readonly</B> [<B>-aAf</B>] [<B>-p</B>] [<I>name</I>[=<I>word</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 indexed arrays; the
+<B>-A</B>
+
+option restricts the variables to associative arrays.
+If both options are supplied,
+<B>-A</B>
+
+takes precedence.
+If no
+<I>name</I>
+
+arguments are given, or if the
+<B>-p</B>
+
+option is supplied, a list of all readonly names is printed.
+The other options may be used to restrict the output to a subset of
+the set of readonly names.
+The
+<B>-p</B>
+
+option causes output to be displayed in a format that
+may be reused as input.
+If a variable name is followed by =<I>word</I>, the value of
+the variable is set to <I>word</I>.
+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 stop executing and return the value specified by
+<I>n</I>
+
+to its caller.
+If
+<I>n</I>
+
+is omitted, the return status is that of the last command
+executed in the function body.
+If <B>return</B> is executed by a trap handler, the last command used to
+determine the status is the last command executed before the trap handler.
+If <B>return</B> is executed during a <B>DEBUG</B> trap, the last command
+used to determine the status is the last command executed by the trap
+handler before <B>return</B> was invoked.
+If
+<B>return</B>
+
+is 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 <I>n</I> is supplied, the return value is its least significant
+8 bits.
+The return status is non-zero if
+<B>return</B>
+
+is supplied a non-numeric argument, or
+is used outside a
+function and not during execution of a script by <B>.</B> or <B>source</B>.
+Any command associated with the <B>RETURN</B> trap is executed
+before execution resumes after the function or script.
+<DT><B>set</B> [<B>--abefhkmnptuvxBCEHPT</B>] [<B>-o</B> <I>option-name</I>] [<I>arg</I> ...]<DD>
+
+<DT><B>set</B> [<B>+abefhkmnptuvxBCEHPT</B>] [<B>+o</B> <I>option-name</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
+for setting or resetting the currently-set variables.
+Read-only variables cannot be reset.
+In <I>posix mode</I>, only shell variables are listed.
+The output is sorted according to the current locale.
+When options are specified, they set or unset shell attributes.
+Any arguments remaining after option processing are treated
+as values for the positional parameters and are assigned, in order, to
+<B>$1</B>,
+
+<B>$2</B>,
+
+<B>...</B>
+
+<B>$</B><I>n</I>.
+
+Options, if specified, have the following meanings:
+<DL COMPACT><DT><DD>
+
+<DL COMPACT>
+<DT><B>-a</B>
+
+<DD>
+Each variable or function that is created or modified is given the
+export attribute and marked 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>pipeline</I> (which may consist of a single <I>simple command</I>),
+a <I>list</I>,
+or a <I>compound 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 the command list immediately following a
+<B>while</B>
+
+or
+<B>until</B>
+
+keyword,
+part of the test following the
+<B>if</B>
+
+or
+<B>elif</B>
+
+reserved words, part of any command executed in a
+<B>&amp;&amp;</B>
+
+or
+<B>||</B>
+
+list except the command following the final <B>&amp;&amp;</B> or <B>||</B>,
+any command in a pipeline but the last,
+or if the command's return value is
+being inverted with
+<B>!</B>.
+
+If a compound command other than a subshell
+returns a non-zero status because a command failed
+while <B>-e</B> was being ignored, the shell does not exit.
+A trap on <B>ERR</B>, if set, is executed before the shell exits.
+This option applies to the shell environment and each subshell environment
+separately (see
+<FONT SIZE=-1><B>COMMAND EXECUTION ENVIRONMENT</B>
+
+</FONT>
+above), and may cause
+subshells to exit before executing all the commands in the subshell.
+<P>
+
+
+If a compound command or shell function executes in a context
+where <B>-e</B> is being ignored,
+none of the commands executed within the compound command or function body
+will be affected by the <B>-e</B> setting, even if <B>-e</B> is set
+and a command returns a failure status.
+If a compound command or shell function sets <B>-e</B> while executing in
+a context where <B>-e</B> is ignored, that setting will not have any
+effect until the compound command or the command containing the function
+call completes.
+<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).
+All processes run in a separate process group.
+When a background job completes, the shell prints a line
+containing its exit status.
+<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.
+This also affects the editing interface used for <B>read -e</B>.
+<DT><B>errexit</B>
+
+<DD>
+Same as
+<B>-e</B>.
+
+<DT><B>errtrace</B>
+
+<DD>
+Same as
+<B>-E</B>.
+
+<DT><B>functrace</B>
+
+<DD>
+Same as
+<B>-T</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>.
+
+<DT><B>nolog</B>
+
+<DD>
+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>pipefail</B>
+
+<DD>
+If set, the return value of a pipeline is the value of the last
+(rightmost) command to exit with a non-zero status, or zero if all
+commands in the pipeline exit successfully.
+This option is disabled by default.
+<DT><B>posix</B>
+
+<DD>
+Change the behavior of
+<B>bash</B>
+
+where the default operation differs
+from the POSIX standard to match the standard (<I>posix mode</I>).
+See
+<FONT SIZE=-1><B>SEE ALSO</B>
+
+</FONT>
+below for a reference to a document that details how posix mode affects
+bash's behavior.
+<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.
+This also affects the editing interface used for <B>read -e</B>.
+<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>
+<FONT SIZE=-1><B>BASHOPTS</B>,
+
+</FONT>
+<FONT SIZE=-1><B>CDPATH</B>,
+
+</FONT>
+and
+<FONT SIZE=-1><B>GLOBIGNORE</B>
+
+</FONT>
+variables, if they appear in the environment, are 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 and parameters other than the special
+parameters &quot;@&quot; and &quot;*&quot; as an error when performing
+parameter expansion. If expansion is attempted on an
+unset variable or parameter, the shell prints an error message, and,
+if not interactive, exits with a non-zero status.
+<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>,
+<B>for</B> command, <B>case</B> command, <B>select</B> command, or
+arithmetic <B>for</B> command, display the expanded value of
+<FONT SIZE=-1><B>PS4</B>,
+
+</FONT>
+followed by the command and its expanded arguments
+or associated word list.
+<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>&gt;</B>,
+
+<B>&gt;&amp;</B>,
+
+and
+<B>&lt;&gt;</B>
+
+redirection operators. This may be overridden when
+creating output files by using the redirection operator
+<B>&gt;|</B>
+
+instead of
+<B>&gt;</B>.
+
+<DT><B>-E</B>
+
+<DD>
+If set, any trap on <B>ERR</B> is inherited by shell functions, command
+substitutions, and commands executed in a subshell environment.
+The <B>ERR</B> trap is normally not inherited in such cases.
+<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 resolve symbolic links when executing
+commands such as
+<B>cd</B>
+
+that change the current working directory. It uses the
+physical directory structure instead. By default,
+<B>bash</B>
+
+follows the logical chain of directories when performing commands
+which change the current directory.
+<DT><B>-T</B>
+
+<DD>
+If set, any traps on <B>DEBUG</B> and <B>RETURN</B> are inherited by shell
+functions, command substitutions, and commands executed in a
+subshell environment.
+The <B>DEBUG</B> and <B>RETURN</B> traps are normally not inherited
+in such cases.
+<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 settings controlling optional shell behavior.
+The settings can be either those listed below, or, if the
+<B>-o</B>
+
+option is used, those available with the
+<B>-o</B>
+
+option to the <B>set</B> builtin command.
+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;
+if <I>optnames</I> are supplied, the output is restricted to those options.
+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,
+<B>shopt</B>
+
+shows only those options which are set or unset, respectively.
+Unless otherwise noted, the <B>shopt</B> options are disabled (unset)
+by default.
+<P>
+
+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>assoc_expand_once</B>
+
+<DD>
+If set, the shell suppresses multiple evaluation of associative array
+subscripts during arithmetic expression evaluation, while executing
+builtins that can perform variable assignments,
+and while executing builtins that perform array dereferencing.
+<DT><B>autocd</B>
+
+<DD>
+If set, a command name that is the name of a directory is executed as if
+it were the argument to the <B>cd</B> command.
+This option is only used by interactive shells.
+<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 filename 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>checkjobs</B>
+
+<DD>
+If set, <B>bash</B> lists the status of any stopped and running jobs before
+exiting an interactive shell. If any jobs are running, this causes
+the exit to be deferred until a second exit is attempted without an
+intervening command (see
+<FONT SIZE=-1><B>JOB CONTROL</B>
+
+</FONT>
+above). The shell always
+postpones exiting if any jobs are stopped.
+<DT><B>checkwinsize</B>
+
+<DD>
+If set, <B>bash</B> checks the window size after each external (non-builtin)
+command and, if necessary, updates the values of
+<FONT SIZE=-1><B>LINES</B>
+
+</FONT>
+and
+<FONT SIZE=-1><B>COLUMNS</B>.
+
+</FONT>
+This option is enabled by default.
+<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.
+This option is enabled by default, but only has an effect if command
+history is enabled, as described above under
+<FONT SIZE=-1><B>HISTORY</B>.
+
+</FONT>
+
+<DT><B>compat31</B>
+
+<DD>
+<DT><B>compat32</B>
+
+<DD>
+<DT><B>compat40</B>
+
+<DD>
+<DT><B>compat41</B>
+
+<DD>
+<DT><B>compat42</B>
+
+<DD>
+<DT><B>compat43</B>
+
+<DD>
+<DT><B>compat44</B>
+
+<DD>
+
+These control aspects of the shell's compatibility mode
+(see
+<FONT SIZE=-1><B>SHELL COMPATIBILITY MODE</B>
+
+</FONT>
+below).
+<DT><B>complete_fullquote</B>
+
+<DD>
+If set,
+<B>bash</B>
+
+quotes all shell metacharacters in filenames and directory names when
+performing completion.
+If not set,
+<B>bash</B>
+
+removes metacharacters such as the dollar sign from the set of
+characters that will be quoted in completed filenames
+when these metacharacters appear in shell variable references in words to be
+completed.
+This means that dollar signs in variable names that expand to directories
+will not be quoted;
+however, any dollar signs appearing in filenames will not be quoted, either.
+This is active only when bash is using backslashes to quote completed
+filenames.
+This variable is set by default, which is the default bash behavior in
+versions through 4.2.
+<DT><B>direxpand</B>
+
+<DD>
+If set,
+<B>bash</B>
+
+replaces directory names with the results of word expansion when performing
+filename completion. This changes the contents of the readline editing
+buffer.
+If not set,
+<B>bash</B>
+
+attempts to preserve what the user typed.
+<DT><B>dirspell</B>
+
+<DD>
+If set,
+<B>bash</B>
+
+attempts spelling correction on directory names during word completion
+if the directory name initially supplied does not exist.
+<DT><B>dotglob</B>
+
+<DD>
+If set,
+<B>bash</B>
+
+includes filenames beginning with a `.' in the results of pathname
+expansion.
+The filenames
+<B>``.''</B>
+
+and
+<B>``..''</B>
+
+must always be matched explicitly, even if
+<B>dotglob</B>
+
+is set.
+<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>extdebug</B>
+
+<DD>
+If set at shell invocation,
+or in a shell startup file,
+arrange to execute the debugger profile
+before the shell starts, identical to the <B>--debugger</B> option.
+If set after invocation, behavior intended for use by debuggers is enabled:
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT><B>1.</B>
+
+<DD>
+The <B>-F</B> option to the <B>declare</B> builtin displays the source
+file name and line number corresponding to each function name supplied
+as an argument.
+<DT><B>2.</B>
+
+<DD>
+If the command run by the <B>DEBUG</B> trap returns a non-zero value, the
+next command is skipped and not executed.
+<DT><B>3.</B>
+
+<DD>
+If the command run by the <B>DEBUG</B> trap returns a value of 2, and the
+shell is executing in a subroutine (a shell function or a shell script
+executed by the <B>.</B> or <B>source</B> builtins), the shell simulates
+a call to <B>return</B>.
+<DT><B>4.</B>
+
+<DD>
+<FONT SIZE=-1><B>BASH_ARGC</B>
+
+</FONT>
+and
+<FONT SIZE=-1><B>BASH_ARGV</B>
+
+</FONT>
+are updated as described in their descriptions above.
+<DT><B>5.</B>
+
+<DD>
+Function tracing is enabled: command substitution, shell functions, and
+subshells invoked with <B>(</B> <I>command</I> <B>)</B> inherit the
+<B>DEBUG</B> and <B>RETURN</B> traps.
+<DT><B>6.</B>
+
+<DD>
+Error tracing is enabled: command substitution, shell functions, and
+subshells invoked with <B>(</B> <I>command</I> <B>)</B> inherit the
+<B>ERR</B> trap.
+</DL></DL>
+
+<DT><B>extglob</B>
+
+<DD>
+If set, the extended pattern matching features described above under
+<B>Pathname Expansion</B> are enabled.
+<DT><B>extquote</B>
+
+<DD>
+If set, <B>$</B>aq<I>string</I>aq and <B>$</B>&quot;<I>string</I>&quot; quoting is
+performed within <B>${</B><I>parameter</I><B>}</B> expansions
+enclosed in double quotes. This option is enabled by default.
+<DT><B>failglob</B>
+
+<DD>
+If set, patterns which fail to match filenames during pathname expansion
+result in an expansion error.
+<DT><B>force_fignore</B>
+
+<DD>
+If set, the suffixes specified by the
+<FONT SIZE=-1><B>FIGNORE</B>
+
+</FONT>
+shell variable
+cause words to be ignored when performing word completion even if
+the ignored words are the only possible completions.
+See
+<FONT SIZE=-1><B>SHELL VARIABLES</B></FONT>
+above for a description of
+<FONT SIZE=-1><B>FIGNORE</B>.
+
+</FONT>
+This option is enabled by default.
+<DT><B>globasciiranges</B>
+
+<DD>
+If set, range expressions used in pattern matching bracket expressions (see
+<FONT SIZE=-1><B>Pattern Matching</B>
+
+</FONT>
+above) behave as if in the traditional C locale when performing
+comparisons. That is, the current locale's collating sequence
+is not taken into account, so
+<B>b</B>
+
+will not collate between
+<B>A</B>
+
+and
+<B>B</B>,
+
+and upper-case and lower-case ASCII characters will collate together.
+<DT><B>globstar</B>
+
+<DD>
+If set, the pattern <B>**</B> used in a pathname expansion context will
+match all files and zero or more directories and subdirectories.
+If the pattern is followed by a <B>/</B>, only directories and
+subdirectories match.
+<DT><B>gnu_errfmt</B>
+
+<DD>
+If set, shell error messages are written in the standard GNU error
+message format.
+<DT><B>histappend</B>
+
+<DD>
+If set, the history list is appended to the file named by the value
+of the
+<FONT SIZE=-1><B>HISTFILE</B>
+
+</FONT>
+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>inherit_errexit</B>
+
+<DD>
+If set, command substitution inherits the value of the <B>errexit</B> option,
+instead of unsetting it in the subshell environment.
+This option is enabled when <I>posix mode</I> is enabled.
+<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>lastpipe</B>
+
+<DD>
+If set, and job control is not active, the shell runs the last command of
+a pipeline not executed in the background in the current shell environment.
+<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>localvar_inherit</B>
+
+<DD>
+If set, local variables inherit the value and attributes of a variable of
+the same name that exists at a previous scope before any new value is
+assigned. The nameref attribute is not inherited.
+<DT><B>localvar_unset</B>
+
+<DD>
+If set, calling <B>unset</B> on local variables in previous function scopes
+marks them so subsequent lookups find them unset until that function
+returns. This is identical to the behavior of unsetting local variables
+at the current function scope.
+<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
+<FONT SIZE=-1><B>PATH</B>
+
+</FONT>
+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>nocasematch</B>
+
+<DD>
+If set,
+<B>bash</B>
+
+matches patterns in a case-insensitive fashion when performing matching
+while executing <B>case</B> or <B>[[</B> conditional commands,
+when performing pattern substitution word expansions,
+or when filtering possible completions as part of programmable completion.
+<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>progcomp_alias</B>
+
+<DD>
+If set, and programmable completion is enabled, <B>bash</B> treats a command
+name that doesn't have any completions as a possible alias and attempts
+alias expansion. If it has an alias, <B>bash</B> attempts programmable
+completion using the command word resulting from the expanded alias.
+<DT><B>promptvars</B>
+
+<DD>
+If set, prompt strings undergo
+parameter expansion, command substitution, arithmetic
+expansion, and quote removal 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. A login shell cannot be suspended; the
+<B>-f</B>
+
+option can be used to override this and force the suspension.
+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><B>test</B> <I>expr</I><DD>
+
+<DT><B>[</B> <I>expr</I> <B>]</B><DD>
+Return a status of 0 (true) or 1 (false) depending on
+the evaluation of the conditional expression
+<I>expr</I>.
+
+Each operator and operand must be a separate argument.
+Expressions are composed of the primaries described above under
+
+<FONT SIZE=-1><B>CONDITIONAL EXPRESSIONS</B>.
+
+</FONT>
+<B>test</B> does not accept any options, nor does it accept and ignore
+an argument of <B>--</B> as signifying the end of options.
+<P>
+
+
+Expressions may be combined using the following operators, listed
+in decreasing order of precedence.
+The evaluation depends on the number of arguments; see below.
+Operator precedence is used when there are five or more arguments.
+<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 EXPRESSIONS</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>
+The following conditions are applied in the order listed.
+If the second argument is one of the binary conditional operators listed above
+under
+<FONT SIZE=-1><B>CONDITIONAL EXPRESSIONS</B>,
+
+</FONT>
+the result of the expression is the result of the binary test using
+the first and third arguments as operands.
+The <B>-a</B> and <B>-o</B> operators are considered binary operators
+when there are three arguments.
+If the first argument is <B>!</B>, the value is the negation of
+the two-argument test using the second and third arguments.
+If the first argument is exactly <B>(</B> and the third argument is
+exactly <B>)</B>, the result is the one-argument test of the second
+argument.
+Otherwise, the expression is false.
+<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.
+<P>
+
+
+</DL>
+<P>
+
+When used with <B>test</B> or <B>[</B>, the <B>&lt;</B> and <B>&gt;</B> operators
+sort lexicographically using ASCII ordering.
+</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 (and there is a single <I>sigspec</I>) or
+<B>-</B>,
+
+each specified signal is
+reset to its original disposition (the value it 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.
+The
+<B>-l</B>
+
+option causes the shell to print a list of signal names and
+their corresponding numbers.
+Each
+<I>sigspec</I>
+
+is either
+a signal name defined in &lt;<I>signal.h</I>&gt;, or a signal number.
+Signal names are case insensitive and the
+<FONT SIZE=-1><B>SIG</B>
+
+</FONT>
+prefix is optional.
+<P>
+
+
+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 before every <I>simple command</I>, <I>for</I> command,
+<I>case</I> command, <I>select</I> command, every arithmetic <I>for</I>
+command, and before the first command executes in a shell function (see
+<FONT SIZE=-1><B>SHELL GRAMMAR</B>
+
+</FONT>
+above).
+Refer to the description of the <B>extdebug</B> option to the
+<B>shopt</B> builtin for details of its effect on the <B>DEBUG</B> trap.
+If a
+<I>sigspec</I>
+
+is
+<FONT SIZE=-1><B>RETURN</B>,
+
+</FONT>
+the command
+<I>arg</I>
+
+is executed each time a shell function or a script executed with
+the <B>.</B> or <B>source</B> builtins finishes executing.
+<P>
+
+
+If a
+<I>sigspec</I>
+
+is
+<FONT SIZE=-1><B>ERR</B>,
+
+</FONT>
+the command
+<I>arg</I>
+
+is executed whenever
+a pipeline (which may consist of a single simple
+command), a list, or a compound command returns a
+non-zero exit status,
+subject to the following conditions.
+The
+<FONT SIZE=-1><B>ERR</B>
+
+</FONT>
+trap is not executed if the failed
+command is part of the command list immediately following a
+<B>while</B>
+
+or
+<B>until</B>
+
+keyword,
+part of the test in an
+<I>if</I>
+
+statement, part of a command executed in a
+<B>&amp;&amp;</B>
+
+or
+<B>||</B>
+
+list except the command following the final <B>&amp;&amp;</B> or <B>||</B>,
+any command in a pipeline but the last,
+or if the command's return value is
+being inverted using
+<B>!</B>.
+
+These are the same conditions obeyed by the <B>errexit</B> (<B>-e</B>) option.
+<P>
+
+
+Signals ignored upon entry to the shell cannot be trapped or reset.
+Trapped signals that are not being ignored are reset to their original
+values in a subshell or subshell environment when one is created.
+The return status is false if any
+<I>sigspec</I>
+
+is invalid; otherwise
+<B>trap</B>
+
+returns true.
+<DT><B>type</B> [<B>-aftpP</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>.
+
+The
+<B>-P</B>
+
+option forces a
+<FONT SIZE=-1><B>PATH</B>
+
+</FONT>
+search for each <I>name</I>, even if
+<TT>type -t name</TT>
+
+would not return
+<I>file</I>.
+
+If a command is hashed,
+<B>-p</B>
+
+and
+<B>-P</B>
+
+print the hashed value, which is 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>.
+
+The
+<B>-f</B>
+
+option suppresses shell function lookup, as with the <B>command</B> builtin.
+<B>type</B>
+
+returns true if all of the arguments are found, false if
+any are not found.
+<DT><B>ulimit</B> [<B>-HS</B>] <B>-a</B><DD>
+
+<DT><B>ulimit</B> [<B>-HS</B>] [<B>-bcdefiklmnpqrstuvxPRT</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 by a non-root user once it is set;
+a soft limit may be increased up to the value of the hard limit.
+If neither <B>-H</B> nor <B>-S</B> is specified, 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, if appropriate,
+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; no limits are set
+<DT><B>-b</B>
+
+<DD>
+The maximum socket buffer size
+<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>-e</B>
+
+<DD>
+The maximum scheduling priority (&quot;nice&quot;)
+<DT><B>-f</B>
+
+<DD>
+The maximum size of files written by the shell and its children
+<DT><B>-i</B>
+
+<DD>
+The maximum number of pending signals
+<DT><B>-k</B>
+
+<DD>
+The maximum number of kqueues that may be allocated
+<DT><B>-l</B>
+
+<DD>
+The maximum size that may be locked into memory
+<DT><B>-m</B>
+
+<DD>
+The maximum resident set size (many systems do not honor this limit)
+<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>-q</B>
+
+<DD>
+The maximum number of bytes in POSIX message queues
+<DT><B>-r</B>
+
+<DD>
+The maximum real-time scheduling priority
+<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 and, on
+some systems, to its children
+<DT><B>-x</B>
+
+<DD>
+The maximum number of file locks
+<DT><B>-P</B>
+
+<DD>
+The maximum number of pseudoterminals
+<DT><B>-R</B>
+
+<DD>
+The maximum time a real-time process can run before blocking, in microseconds
+<DT><B>-T</B>
+
+<DD>
+The maximum number of threads
+
+</DL>
+<P>
+
+If
+<I>limit</I>
+
+is given, and the
+<B>-a</B>
+
+option is not used,
+<I>limit</I> is the new value of the specified resource.
+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>-R</B>,
+
+which is in microseconds;
+<B>-p</B>,
+
+which is in units of 512-byte blocks;
+<B>-P</B>,
+
+<B>-T</B>,
+
+<B>-b</B>,
+
+<B>-k</B>,
+
+<B>-n</B>,
+
+and
+<B>-u</B>,
+
+which are unscaled values;
+and, when in posix mode,
+<B>-c</B>
+
+and
+<B>-f</B>,
+
+which are in 512-byte increments.
+The return status is 0 unless an invalid option or argument is supplied,
+or an error occurs while setting a new limit.
+</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>] [-<B>n</B>] [<I>name</I> ...]<DD>
+For each
+<I>name</I>,
+
+remove the corresponding variable or function.
+If the
+<B>-v</B>
+
+option is given, each
+<I>name</I>
+
+refers to a shell variable, and that variable is removed.
+Read-only variables may not be unset.
+If
+<B>-f</B>
+
+is specified, each
+<I>name</I>
+
+refers to a shell function, and the function definition
+is removed.
+If the
+<B>-n</B>
+
+option is supplied, and <I>name</I> is a variable with the <I>nameref</I>
+attribute, <I>name</I> will be unset rather than the variable it
+references.
+<B>-n</B> has no effect if the <B>-f</B> option is supplied.
+If no options are supplied, each <I>name</I> refers to a variable; if
+there is no variable by that name, a function with that name, if any, is
+unset.
+Each unset variable or function is removed from the environment
+passed to subsequent commands.
+If any of
+<FONT SIZE=-1><B>BASH_ALIASES</B>,
+
+</FONT>
+<FONT SIZE=-1><B>BASH_ARGV0</B>,
+
+</FONT>
+<FONT SIZE=-1><B>BASH_CMDS</B>,
+
+</FONT>
+<FONT SIZE=-1><B>BASH_COMMAND</B>,
+
+</FONT>
+<FONT SIZE=-1><B>BASH_SUBSHELL</B>,
+
+</FONT>
+<FONT SIZE=-1><B>BASHPID</B>,
+
+</FONT>
+<FONT SIZE=-1><B>COMP_WORDBREAKS</B>,
+
+</FONT>
+<FONT SIZE=-1><B>DIRSTACK</B>,
+
+</FONT>
+<FONT SIZE=-1><B>EPOCHREALTIME</B>,
+
+</FONT>
+<FONT SIZE=-1><B>EPOCHSECONDS</B>,
+
+</FONT>
+<FONT SIZE=-1><B>FUNCNAME</B>,
+
+</FONT>
+<FONT SIZE=-1><B>GROUPS</B>,
+
+</FONT>
+<FONT SIZE=-1><B>HISTCMD</B>,
+
+</FONT>
+<FONT SIZE=-1><B>LINENO</B>,
+
+</FONT>
+<FONT SIZE=-1><B>RANDOM</B>,
+
+</FONT>
+<FONT SIZE=-1><B>SECONDS</B>,
+
+</FONT>
+or
+<FONT SIZE=-1><B>SRANDOM</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>
+
+is readonly.
+<DT><B>wait</B> [<B>-fn</B>] [-p <I>varname</I>] [<I>id ...</I>]<DD>
+Wait for each specified child process and return its termination status.
+Each
+<I>id</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>id</I>
+
+is not given,
+<B>wait</B> waits for all running background jobs and
+the last-executed process substitution, if its process id is the same as
+<B>$!</B>,
+and the return status is zero.
+If the <B>-n</B> option is supplied,
+<B>wait</B> waits for a single job
+from the list of <I>id</I>s or, if no <I>id</I>s are supplied, any job,
+to complete and returns its exit status.
+If none of the supplied arguments is a child of the shell, or if no arguments
+are supplied and the shell has no unwaited-for children, the exit status
+is 127.
+If the <B>-p</B> option is supplied, the process or job identifier of the job
+for which the exit status is returned is assigned to the variable
+<I>varname</I> named by the option argument.
+The variable will be unset initially, before any assignment.
+This is useful only when the <B>-n</B> option is supplied.
+Supplying the <B>-f</B> option, when job control is enabled,
+forces <B>wait</B> to wait for <I>id</I> to terminate before returning
+its status, instead of returning when it changes status.
+If
+<I>id</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="lbDC">&nbsp;</A>
+<H3>SHELL COMPATIBILITY MODE</H3>
+
+Bash-4.0 introduced the concept of a `shell compatibility level', specified
+as a set of options to the shopt builtin
+<B>compat31</B>,
+
+<B>compat32</B>,
+
+<B>compat40</B>,
+
+<B>compat41</B>,
+
+and so on).
+There is only one current
+compatibility level -- each option is mutually exclusive.
+The compatibility level is intended to allow users to select behavior
+from previous versions that is incompatible with newer versions
+while they migrate scripts to use current features and
+behavior. It's intended to be a temporary solution.
+<P>
+
+This section does not mention behavior that is standard for a particular
+version (e.g., setting <B>compat32</B> means that quoting the rhs of the regexp
+matching operator quotes special regexp characters in the word, which is
+default behavior in bash-3.2 and above).
+<P>
+
+If a user enables, say, <B>compat32</B>, it may affect the behavior of other
+compatibility levels up to and including the current compatibility level.
+The idea is that each compatibility level controls behavior that changed
+in that version of <B>bash</B>,
+but that behavior may have been present in earlier versions.
+For instance, the change to use locale-based comparisons with the <B>[[</B>
+command came in bash-4.1, and earlier versions used ASCII-based comparisons,
+so enabling <B>compat32</B> will enable ASCII-based comparisons as well.
+That granularity may not be sufficient for
+all uses, and as a result users should employ compatibility levels carefully.
+Read the documentation for a particular feature to find out the
+current behavior.
+<P>
+
+Bash-4.3 introduced a new shell variable:
+<FONT SIZE=-1><B>BASH_COMPAT</B>.
+
+</FONT>
+The value assigned
+to this variable (a decimal version number like 4.2, or an integer
+corresponding to the <B>compat</B><I>NN</I> option, like 42) determines the
+compatibility level.
+<P>
+
+Starting with bash-4.4, Bash has begun deprecating older compatibility
+levels.
+Eventually, the options will be removed in favor of
+<FONT SIZE=-1><B>BASH_COMPAT</B>.
+
+</FONT>
+<P>
+
+Bash-5.0 is the final version for which there will be an individual shopt
+option for the previous version. Users should use
+<FONT SIZE=-1><B>BASH_COMPAT</B>
+
+</FONT>
+on bash-5.0 and later versions.
+<P>
+
+The following table describes the behavior changes controlled by each
+compatibility level setting.
+The <B>compat</B><I>NN</I> tag is used as shorthand for setting the
+compatibility level
+to <I>NN</I> using one of the following mechanisms.
+For versions prior to bash-5.0, the compatibility level may be set using
+the corresponding <B>compat</B><I>NN</I> shopt option.
+For bash-4.3 and later versions, the
+<FONT SIZE=-1><B>BASH_COMPAT</B>
+
+</FONT>
+variable is preferred,
+and it is required for bash-5.1 and later versions.
+<DL COMPACT>
+<DT><B>compat31</B><DD>
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT>*<DD>
+quoting the rhs of the <B>[[</B> command's regexp matching operator (=~)
+has no special effect
+</DL></DL>
+
+
+<DT><B>compat32</B><DD>
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT>*<DD>
+interrupting a command list such as &quot;a ; b ; c&quot; causes the execution
+of the next command in the list (in bash-4.0 and later versions,
+the shell acts as if it received the interrupt, so
+interrupting one command in a list aborts the execution of the
+entire list)
+</DL></DL>
+
+
+<DT><B>compat40</B><DD>
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT>*<DD>
+the <B>&lt;</B> and <B>&gt;</B> operators to the <B>[[</B> command do not
+consider the current locale when comparing strings; they use ASCII
+ordering.
+Bash versions prior to bash-4.1 use ASCII collation and
+<I>strcmp</I>(3);
+
+bash-4.1 and later use the current locale's collation sequence and
+<I>strcoll</I>(3).
+
+</DL></DL>
+
+
+<DT><B>compat41</B><DD>
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT>*<DD>
+in <I>posix</I> mode, <B>time</B> may be followed by options and still be
+recognized as a reserved word (this is POSIX interpretation 267)
+<DT>*<DD>
+in <I>posix</I> mode, the parser requires that an even number of single
+quotes occur in the <I>word</I> portion of a double-quoted
+parameter expansion and treats them specially, so that characters within
+the single quotes are considered quoted
+(this is POSIX interpretation 221)
+</DL></DL>
+
+
+<DT><B>compat42</B><DD>
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT>*<DD>
+the replacement string in double-quoted pattern substitution does not
+undergo quote removal, as it does in versions after bash-4.2
+<DT>*<DD>
+in posix mode, single quotes are considered special when expanding
+the <I>word</I> portion of a double-quoted parameter expansion
+and can be used to quote a closing brace or other special character
+(this is part of POSIX interpretation 221);
+in later versions, single quotes
+are not special within double-quoted word expansions
+</DL></DL>
+
+
+<DT><B>compat43</B><DD>
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT>*<DD>
+the shell does not print a warning message if an attempt is made to
+use a quoted compound assignment as an argument to declare
+(declare -a foo='(1 2)'). Later versions warn that this usage is
+deprecated
+<DT>*<DD>
+word expansion errors are considered non-fatal errors that cause the
+current command to fail, even in posix mode
+(the default behavior is to make them fatal errors that cause the shell
+to exit)
+<DT>*<DD>
+when executing a shell function, the loop state (while/until/etc.)
+is not reset, so <B>break</B> or <B>continue</B> in that function will break
+or continue loops in the calling context. Bash-4.4 and later reset
+the loop state to prevent this
+</DL></DL>
+
+
+<DT><B>compat44</B><DD>
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT>*<DD>
+the shell sets up the values used by
+<FONT SIZE=-1><B>BASH_ARGV</B>
+
+</FONT>
+and
+<FONT SIZE=-1><B>BASH_ARGC</B>
+
+</FONT>
+so they can expand to the shell's positional parameters even if extended
+debugging mode is not enabled
+<DT>*<DD>
+a subshell inherits loops from its parent context, so <B>break</B>
+or <B>continue</B> will cause the subshell to exit.
+Bash-5.0 and later reset the loop state to prevent the exit
+<DT>*<DD>
+variable assignments preceding builtins like <B>export</B> and <B>readonly</B>
+that set attributes continue to affect variables with the same
+name in the calling environment even if the shell is not in posix
+mode
+</DL></DL>
+
+
+<DT><B>compat50</B><DD>
+
+<DL COMPACT><DT><DD>
+<DL COMPACT>
+<DT>*<DD>
+Bash-5.1 changed the way
+<FONT SIZE=-1><B>$RANDOM</B>
+
+</FONT>
+is generated to introduce slightly
+more randomness. If the shell compatibility level is set to 50 or
+lower, it reverts to the method from bash-5.0 and previous versions,
+so seeding the random number generator by assigning a value to
+<FONT SIZE=-1><B>RANDOM</B>
+
+</FONT>
+will produce the same sequence as in bash-5.0
+<DT>*<DD>
+If the command hash table is empty, bash versions prior to bash-5.1
+printed an informational message to that effect, even when producing
+output that can be reused as input. Bash-5.1 suppresses that message
+when the <B>-l</B> option is supplied.
+</DL></DL>
+
+
+
+
+</DL>
+<A NAME="lbDD">&nbsp;</A>
+<H3>RESTRICTED SHELL</H3>
+
+
+
+<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
+<FONT SIZE=-1><B>SHELL</B>,
+
+</FONT>
+<FONT SIZE=-1><B>PATH</B>,
+
+</FONT>
+<FONT SIZE=-1><B>HISTFILE</B>,
+
+</FONT>
+<FONT SIZE=-1><B>ENV</B>,
+
+</FONT>
+or
+<FONT SIZE=-1><B>BASH_ENV</B>
+
+</FONT>
+<DT>*<DD>
+specifying command names containing
+<B>/</B>
+
+<DT>*<DD>
+specifying a filename 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>history</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
+<FONT SIZE=-1><B>SHELLOPTS</B>
+
+</FONT>
+from the shell environment at startup
+<DT>*<DD>
+redirecting output using the &gt;, &gt;|, &lt;&gt;, &gt;&amp;, &amp;&gt;, and &gt;&gt; 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>
+using the <B>enable</B> builtin command to enable disabled shell builtins
+<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="lbDE">&nbsp;</A>
+<H3>SEE ALSO</H3>
+
+
+<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>
+<A HREF="http://pubs.opengroup.org/onlinepubs/9699919799/">http://pubs.opengroup.org/onlinepubs/9699919799/</A>
+<DT><A HREF="http://tiswww.case.edu/~chet/bash/POSIX">http://tiswww.case.edu/~chet/bash/POSIX</A> -- a description of posix mode<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="lbDF">&nbsp;</A>
+<H3>FILES</H3>
+
+
+<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="lbDG">&nbsp;</A>
+<H3>AUTHORS</H3>
+
+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.ramey@case.edu">chet.ramey@case.edu</A>
+<A NAME="lbDH">&nbsp;</A>
+<H3>BUG REPORTS</H3>
+
+If you find a bug in
+<B>bash,</B>
+
+you should report it. But first, you should
+make sure that it really is a bug, and that it appears in the latest
+version of
+<B>bash</B>.
+
+The latest version is always available from
+<I><A HREF="ftp://ftp.gnu.org/pub/gnu/bash/">ftp://ftp.gnu.org/pub/gnu/bash/</A></I>.
+<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.ramey@case.edu">chet.ramey@case.edu</A></I>.
+
+<A NAME="lbDI">&nbsp;</A>
+<H3>BUGS</H3>
+
+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>
+
+Array variables may not (yet) be exported.
+<P>
+
+There may be only one active coprocess at a time.
+
+
+
+<HR>
+<TABLE WIDTH=100%>
+<TR>
+<TH ALIGN=LEFT width=33%>GNU Bash 5.1<TH ALIGN=CENTER width=33%>2020 October 29<TH ALIGN=RIGHT width=33%>BASH(1)
+</TR>
+</TABLE>
+<HR>
+<A NAME="index">&nbsp;</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>
+<DT><A HREF="#lbAP">Coprocesses</A><DD>
+<DT><A HREF="#lbAQ">Shell Function Definitions</A><DD>
+</DL>
+<DT><A HREF="#lbAR">COMMENTS</A><DD>
+<DT><A HREF="#lbAS">QUOTING</A><DD>
+<DT><A HREF="#lbAT">PARAMETERS</A><DD>
+<DL>
+<DT><A HREF="#lbAU">Positional Parameters</A><DD>
+<DT><A HREF="#lbAV">Special Parameters</A><DD>
+<DT><A HREF="#lbAW">Shell Variables</A><DD>
+<DT><A HREF="#lbAX">Arrays</A><DD>
+</DL>
+<DT><A HREF="#lbAY">EXPANSION</A><DD>
+<DL>
+<DT><A HREF="#lbAZ">Brace Expansion</A><DD>
+<DT><A HREF="#lbBA">Tilde Expansion</A><DD>
+<DT><A HREF="#lbBB">Parameter Expansion</A><DD>
+<DT><A HREF="#lbBC">Command Substitution</A><DD>
+<DT><A HREF="#lbBD">Arithmetic Expansion</A><DD>
+<DT><A HREF="#lbBE">Process Substitution</A><DD>
+<DT><A HREF="#lbBF">Word Splitting</A><DD>
+<DT><A HREF="#lbBG">Pathname Expansion</A><DD>
+<DT><A HREF="#lbBH">Quote Removal</A><DD>
+</DL>
+<DT><A HREF="#lbBI">REDIRECTION</A><DD>
+<DL>
+<DT><A HREF="#lbBJ">Redirecting Input</A><DD>
+<DT><A HREF="#lbBK">Redirecting Output</A><DD>
+<DT><A HREF="#lbBL">Appending Redirected Output</A><DD>
+<DT><A HREF="#lbBM">Redirecting Standard Output and Standard Error</A><DD>
+<DT><A HREF="#lbBN">Appending Standard Output and Standard Error</A><DD>
+<DT><A HREF="#lbBO">Here Documents</A><DD>
+<DT><A HREF="#lbBP">Here Strings</A><DD>
+<DT><A HREF="#lbBQ">Duplicating File Descriptors</A><DD>
+<DT><A HREF="#lbBR">Moving File Descriptors</A><DD>
+<DT><A HREF="#lbBS">Opening File Descriptors for Reading and Writing</A><DD>
+</DL>
+<DT><A HREF="#lbBT">ALIASES</A><DD>
+<DT><A HREF="#lbBU">FUNCTIONS</A><DD>
+<DT><A HREF="#lbBV">ARITHMETIC EVALUATION</A><DD>
+<DT><A HREF="#lbBW">CONDITIONAL EXPRESSIONS</A><DD>
+<DT><A HREF="#lbBX">SIMPLE COMMAND EXPANSION</A><DD>
+<DT><A HREF="#lbBY">COMMAND EXECUTION</A><DD>
+<DT><A HREF="#lbBZ">COMMAND EXECUTION ENVIRONMENT</A><DD>
+<DT><A HREF="#lbCA">ENVIRONMENT</A><DD>
+<DT><A HREF="#lbCB">EXIT STATUS</A><DD>
+<DT><A HREF="#lbCC">SIGNALS</A><DD>
+<DT><A HREF="#lbCD">JOB CONTROL</A><DD>
+<DT><A HREF="#lbCE">PROMPTING</A><DD>
+<DT><A HREF="#lbCF">READLINE</A><DD>
+<DL>
+<DT><A HREF="#lbCG">Readline Notation</A><DD>
+<DT><A HREF="#lbCH">Readline Initialization</A><DD>
+<DT><A HREF="#lbCI">Readline Key Bindings</A><DD>
+<DT><A HREF="#lbCJ">Readline Variables</A><DD>
+<DT><A HREF="#lbCK">Readline Conditional Constructs</A><DD>
+<DT><A HREF="#lbCL">Searching</A><DD>
+<DT><A HREF="#lbCM">Readline Command Names</A><DD>
+<DT><A HREF="#lbCN">Commands for Moving</A><DD>
+<DT><A HREF="#lbCO">Commands for Manipulating the History</A><DD>
+<DT><A HREF="#lbCP">Commands for Changing Text</A><DD>
+<DT><A HREF="#lbCQ">Killing and Yanking</A><DD>
+<DT><A HREF="#lbCR">Numeric Arguments</A><DD>
+<DT><A HREF="#lbCS">Completing</A><DD>
+<DT><A HREF="#lbCT">Keyboard Macros</A><DD>
+<DT><A HREF="#lbCU">Miscellaneous</A><DD>
+<DT><A HREF="#lbCV">Programmable Completion</A><DD>
+</DL>
+<DT><A HREF="#lbCW">HISTORY</A><DD>
+<DT><A HREF="#lbCX">HISTORY EXPANSION</A><DD>
+<DL>
+<DT><A HREF="#lbCY">Event Designators</A><DD>
+<DT><A HREF="#lbCZ">Word Designators</A><DD>
+<DT><A HREF="#lbDA">Modifiers</A><DD>
+</DL>
+<DT><A HREF="#lbDB">SHELL BUILTIN COMMANDS</A><DD>
+<DT><A HREF="#lbDC">SHELL COMPATIBILITY MODE</A><DD>
+<DT><A HREF="#lbDD">RESTRICTED SHELL</A><DD>
+<DT><A HREF="#lbDE">SEE ALSO</A><DD>
+<DT><A HREF="#lbDF">FILES</A><DD>
+<DT><A HREF="#lbDG">AUTHORS</A><DD>
+<DT><A HREF="#lbDH">BUG REPORTS</A><DD>
+<DT><A HREF="#lbDI">BUGS</A><DD>
+</DL>
+<HR>
+This document was created by man2html from bash.1.<BR>
+Time: 18 November 2020 15:13:09 EST
+</BODY>
+</HTML>