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+This is bashref.info, produced by makeinfo version 6.8 from
+bashref.texi.
+
+This text is a brief description of the features that are present in the
+Bash shell (version 5.2, 19 September 2022).
+
+   This is Edition 5.2, last updated 19 September 2022, of 'The GNU Bash
+Reference Manual', for 'Bash', Version 5.2.
+
+   Copyright (C) 1988-2022 Free Software Foundation, Inc.
+
+     Permission is granted to copy, distribute and/or modify this
+     document under the terms of the GNU Free Documentation License,
+     Version 1.3 or any later version published by the Free Software
+     Foundation; with no Invariant Sections, no Front-Cover Texts, and
+     no Back-Cover Texts.  A copy of the license is included in the
+     section entitled "GNU Free Documentation License".
+INFO-DIR-SECTION Basics
+START-INFO-DIR-ENTRY
+* Bash: (bash).                     The GNU Bourne-Again SHell.
+END-INFO-DIR-ENTRY
+
+
+File: bashref.info,  Node: Top,  Next: Introduction,  Prev: (dir),  Up: (dir)
+
+Bash Features
+*************
+
+This text is a brief description of the features that are present in the
+Bash shell (version 5.2, 19 September 2022).  The Bash home page is
+<http://www.gnu.org/software/bash/>.
+
+   This is Edition 5.2, last updated 19 September 2022, of 'The GNU Bash
+Reference Manual', for 'Bash', Version 5.2.
+
+   Bash contains features that appear in other popular shells, and some
+features that only appear in Bash.  Some of the shells that Bash has
+borrowed concepts from are the Bourne Shell ('sh'), the Korn Shell
+('ksh'), and the C-shell ('csh' and its successor, 'tcsh').  The
+following menu breaks the features up into categories, noting which
+features were inspired by other shells and which are specific to Bash.
+
+   This manual is meant as a brief introduction to features found in
+Bash.  The Bash manual page should be used as the definitive reference
+on shell behavior.
+
+* Menu:
+
+* Introduction::		An introduction to the shell.
+* Definitions::			Some definitions used in the rest of this
+				manual.
+* Basic Shell Features::	The shell "building blocks".
+* Shell Builtin Commands::	Commands that are a part of the shell.
+* Shell Variables::		Variables used or set by Bash.
+* Bash Features::		Features found only in Bash.
+* Job Control::			What job control is and how Bash allows you
+				to use it.
+* Command Line Editing::	Chapter describing the command line
+				editing features.
+* Using History Interactively::	Command History Expansion
+* Installing Bash::		How to build and install Bash on your system.
+* Reporting Bugs::		How to report bugs in Bash.
+* Major Differences From The Bourne Shell::	A terse list of the differences
+						between Bash and historical
+						versions of /bin/sh.
+* GNU Free Documentation License::	Copying and sharing this documentation.
+* Indexes::			Various indexes for this manual.
+
+
+File: bashref.info,  Node: Introduction,  Next: Definitions,  Up: Top
+
+1 Introduction
+**************
+
+* Menu:
+
+* What is Bash?::		A short description of Bash.
+* What is a shell?::		A brief introduction to shells.
+
+
+File: bashref.info,  Node: What is Bash?,  Next: What is a shell?,  Up: Introduction
+
+1.1 What is Bash?
+=================
+
+Bash is the shell, or command language interpreter, for the GNU
+operating system.  The name is an acronym for the 'Bourne-Again SHell',
+a pun on Stephen Bourne, the author of the direct ancestor of the
+current Unix shell 'sh', which appeared in the Seventh Edition Bell Labs
+Research version of Unix.
+
+   Bash is largely compatible with 'sh' and incorporates useful features
+from the Korn shell 'ksh' and the C shell 'csh'.  It is intended to be a
+conformant implementation of the IEEE POSIX Shell and Tools portion of
+the IEEE POSIX specification (IEEE Standard 1003.1).  It offers
+functional improvements over 'sh' for both interactive and programming
+use.
+
+   While the GNU operating system provides other shells, including a
+version of 'csh', Bash is the default shell.  Like other GNU software,
+Bash is quite portable.  It currently runs on nearly every version of
+Unix and a few other operating systems - independently-supported ports
+exist for MS-DOS, OS/2, and Windows platforms.
+
+
+File: bashref.info,  Node: What is a shell?,  Prev: What is Bash?,  Up: Introduction
+
+1.2 What is a shell?
+====================
+
+At its base, a shell is simply a macro processor that executes commands.
+The term macro processor means functionality where text and symbols are
+expanded to create larger expressions.
+
+   A Unix shell is both a command interpreter and a programming
+language.  As a command interpreter, the shell provides the user
+interface to the rich set of GNU utilities.  The programming language
+features allow these utilities to be combined.  Files containing
+commands can be created, and become commands themselves.  These new
+commands have the same status as system commands in directories such as
+'/bin', allowing users or groups to establish custom environments to
+automate their common tasks.
+
+   Shells may be used interactively or non-interactively.  In
+interactive mode, they accept input typed from the keyboard.  When
+executing non-interactively, shells execute commands read from a file.
+
+   A shell allows execution of GNU commands, both synchronously and
+asynchronously.  The shell waits for synchronous commands to complete
+before accepting more input; asynchronous commands continue to execute
+in parallel with the shell while it reads and executes additional
+commands.  The "redirection" constructs permit fine-grained control of
+the input and output of those commands.  Moreover, the shell allows
+control over the contents of commands' environments.
+
+   Shells also provide a small set of built-in commands ("builtins")
+implementing functionality impossible or inconvenient to obtain via
+separate utilities.  For example, 'cd', 'break', 'continue', and 'exec'
+cannot be implemented outside of the shell because they directly
+manipulate the shell itself.  The 'history', 'getopts', 'kill', or 'pwd'
+builtins, among others, could be implemented in separate utilities, but
+they are more convenient to use as builtin commands.  All of the shell
+builtins are described in subsequent sections.
+
+   While executing commands is essential, most of the power (and
+complexity) of shells is due to their embedded programming languages.
+Like any high-level language, the shell provides variables, flow control
+constructs, quoting, and functions.
+
+   Shells offer features geared specifically for interactive use rather
+than to augment the programming language.  These interactive features
+include job control, command line editing, command history and aliases.
+Each of these features is described in this manual.
+
+
+File: bashref.info,  Node: Definitions,  Next: Basic Shell Features,  Prev: Introduction,  Up: Top
+
+2 Definitions
+*************
+
+These definitions are used throughout the remainder of this manual.
+
+'POSIX'
+     A family of open system standards based on Unix.  Bash is primarily
+     concerned with the Shell and Utilities portion of the POSIX 1003.1
+     standard.
+
+'blank'
+     A space or tab character.
+
+'builtin'
+     A command that is implemented internally by the shell itself,
+     rather than by an executable program somewhere in the file system.
+
+'control operator'
+     A 'token' that performs a control function.  It is a 'newline' or
+     one of the following: '||', '&&', '&', ';', ';;', ';&', ';;&', '|',
+     '|&', '(', or ')'.
+
+'exit status'
+     The value returned by a command to its caller.  The value is
+     restricted to eight bits, so the maximum value is 255.
+
+'field'
+     A unit of text that is the result of one of the shell expansions.
+     After expansion, when executing a command, the resulting fields are
+     used as the command name and arguments.
+
+'filename'
+     A string of characters used to identify a file.
+
+'job'
+     A set of processes comprising a pipeline, and any processes
+     descended from it, that are all in the same process group.
+
+'job control'
+     A mechanism by which users can selectively stop (suspend) and
+     restart (resume) execution of processes.
+
+'metacharacter'
+     A character that, when unquoted, separates words.  A metacharacter
+     is a 'space', 'tab', 'newline', or one of the following characters:
+     '|', '&', ';', '(', ')', '<', or '>'.
+
+'name'
+     A 'word' consisting solely of letters, numbers, and underscores,
+     and beginning with a letter or underscore.  'Name's are used as
+     shell variable and function names.  Also referred to as an
+     'identifier'.
+
+'operator'
+     A 'control operator' or a 'redirection operator'.  *Note
+     Redirections::, for a list of redirection operators.  Operators
+     contain at least one unquoted 'metacharacter'.
+
+'process group'
+     A collection of related processes each having the same process
+     group ID.
+
+'process group ID'
+     A unique identifier that represents a 'process group' during its
+     lifetime.
+
+'reserved word'
+     A 'word' that has a special meaning to the shell.  Most reserved
+     words introduce shell flow control constructs, such as 'for' and
+     'while'.
+
+'return status'
+     A synonym for 'exit status'.
+
+'signal'
+     A mechanism by which a process may be notified by the kernel of an
+     event occurring in the system.
+
+'special builtin'
+     A shell builtin command that has been classified as special by the
+     POSIX standard.
+
+'token'
+     A sequence of characters considered a single unit by the shell.  It
+     is either a 'word' or an 'operator'.
+
+'word'
+     A sequence of characters treated as a unit by the shell.  Words may
+     not include unquoted 'metacharacters'.
+
+
+File: bashref.info,  Node: Basic Shell Features,  Next: Shell Builtin Commands,  Prev: Definitions,  Up: Top
+
+3 Basic Shell Features
+**********************
+
+Bash is an acronym for 'Bourne-Again SHell'.  The Bourne shell is the
+traditional Unix shell originally written by Stephen Bourne.  All of the
+Bourne shell builtin commands are available in Bash, The rules for
+evaluation and quoting are taken from the POSIX specification for the
+'standard' Unix shell.
+
+   This chapter briefly summarizes the shell's 'building blocks':
+commands, control structures, shell functions, shell parameters, shell
+expansions, redirections, which are a way to direct input and output
+from and to named files, and how the shell executes commands.
+
+* Menu:
+
+* Shell Syntax::		What your input means to the shell.
+* Shell Commands::		The types of commands you can use.
+* Shell Functions::		Grouping commands by name.
+* Shell Parameters::		How the shell stores values.
+* Shell Expansions::		How Bash expands parameters and the various
+				expansions available.
+* Redirections::		A way to control where input and output go.
+* Executing Commands::		What happens when you run a command.
+* Shell Scripts::		Executing files of shell commands.
+
+
+File: bashref.info,  Node: Shell Syntax,  Next: Shell Commands,  Up: Basic Shell Features
+
+3.1 Shell Syntax
+================
+
+* Menu:
+
+* Shell Operation::	The basic operation of the shell.
+* Quoting::		How to remove the special meaning from characters.
+* Comments::		How to specify comments.
+
+When the shell reads input, it proceeds through a sequence of
+operations.  If the input indicates the beginning of a comment, the
+shell ignores the comment symbol ('#'), and the rest of that line.
+
+   Otherwise, roughly speaking, the shell reads its input and divides
+the input into words and operators, employing the quoting rules to
+select which meanings to assign various words and characters.
+
+   The shell then parses these tokens into commands and other
+constructs, removes the special meaning of certain words or characters,
+expands others, redirects input and output as needed, executes the
+specified command, waits for the command's exit status, and makes that
+exit status available for further inspection or processing.
+
+
+File: bashref.info,  Node: Shell Operation,  Next: Quoting,  Up: Shell Syntax
+
+3.1.1 Shell Operation
+---------------------
+
+The following is a brief description of the shell's operation when it
+reads and executes a command.  Basically, the shell does the following:
+
+  1. Reads its input from a file (*note Shell Scripts::), from a string
+     supplied as an argument to the '-c' invocation option (*note
+     Invoking Bash::), or from the user's terminal.
+
+  2. Breaks the input into words and operators, obeying the quoting
+     rules described in *note Quoting::.  These tokens are separated by
+     'metacharacters'.  Alias expansion is performed by this step (*note
+     Aliases::).
+
+  3. Parses the tokens into simple and compound commands (*note Shell
+     Commands::).
+
+  4. Performs the various shell expansions (*note Shell Expansions::),
+     breaking the expanded tokens into lists of filenames (*note
+     Filename Expansion::) and commands and arguments.
+
+  5. Performs any necessary redirections (*note Redirections::) and
+     removes the redirection operators and their operands from the
+     argument list.
+
+  6. Executes the command (*note Executing Commands::).
+
+  7. Optionally waits for the command to complete and collects its exit
+     status (*note Exit Status::).
+
+
+File: bashref.info,  Node: Quoting,  Next: Comments,  Prev: Shell Operation,  Up: Shell Syntax
+
+3.1.2 Quoting
+-------------
+
+* Menu:
+
+* Escape Character::	How to remove the special meaning from a single
+			character.
+* Single Quotes::	How to inhibit all interpretation of a sequence
+			of characters.
+* Double Quotes::	How to suppress most of the interpretation of a
+			sequence of characters.
+* ANSI-C Quoting::	How to expand ANSI-C sequences in quoted strings.
+* Locale Translation::	How to translate strings into different languages.
+
+Quoting 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.
+
+   Each of the shell metacharacters (*note Definitions::) has special
+meaning to the shell and must be quoted if it is to represent itself.
+When the command history expansion facilities are being used (*note
+History Interaction::), the "history expansion" character, usually '!',
+must be quoted to prevent history expansion.  *Note Bash History
+Facilities::, for more details concerning history expansion.
+
+   There are three quoting mechanisms: the "escape character", single
+quotes, and double quotes.
+
+
+File: bashref.info,  Node: Escape Character,  Next: Single Quotes,  Up: Quoting
+
+3.1.2.1 Escape Character
+........................
+
+A non-quoted backslash '\' is the Bash escape character.  It preserves
+the literal value of the next character that follows, with the exception
+of 'newline'.  If a '\newline' pair appears, and the backslash itself is
+not quoted, the '\newline' is treated as a line continuation (that is,
+it is removed from the input stream and effectively ignored).
+
+
+File: bashref.info,  Node: Single Quotes,  Next: Double Quotes,  Prev: Escape Character,  Up: Quoting
+
+3.1.2.2 Single Quotes
+.....................
+
+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.
+
+
+File: bashref.info,  Node: Double Quotes,  Next: ANSI-C Quoting,  Prev: Single Quotes,  Up: Quoting
+
+3.1.2.3 Double Quotes
+.....................
+
+Enclosing characters in double quotes ('"') preserves the literal value
+of all characters within the quotes, with the exception of '$', '`',
+'\', and, when history expansion is enabled, '!'.  When the shell is in
+POSIX mode (*note Bash POSIX Mode::), the '!' has no special meaning
+within double quotes, even when history expansion is enabled.  The
+characters '$' and '`' retain their special meaning within double quotes
+(*note Shell Expansions::).  The backslash retains its special meaning
+only when followed by one of the following characters: '$', '`', '"',
+'\', or 'newline'.  Within double quotes, backslashes that are followed
+by one of these characters are removed.  Backslashes preceding
+characters without a special meaning are left unmodified.  A double
+quote may be quoted within double quotes by preceding it with a
+backslash.  If enabled, history expansion will be performed unless an
+'!' appearing in double quotes is escaped using a backslash.  The
+backslash preceding the '!' is not removed.
+
+   The special parameters '*' and '@' have special meaning when in
+double quotes (*note Shell Parameter Expansion::).
+
+
+File: bashref.info,  Node: ANSI-C Quoting,  Next: Locale Translation,  Prev: Double Quotes,  Up: Quoting
+
+3.1.2.4 ANSI-C Quoting
+......................
+
+Character sequences of the form $'STRING' are treated as a special kind
+of single quotes.  The sequence expands to STRING, with
+backslash-escaped characters in STRING replaced as specified by the ANSI
+C standard.  Backslash escape sequences, if present, are decoded as
+follows:
+
+'\a'
+     alert (bell)
+'\b'
+     backspace
+'\e'
+'\E'
+     an escape character (not ANSI C)
+'\f'
+     form feed
+'\n'
+     newline
+'\r'
+     carriage return
+'\t'
+     horizontal tab
+'\v'
+     vertical tab
+'\\'
+     backslash
+'\''
+     single quote
+'\"'
+     double quote
+'\?'
+     question mark
+'\NNN'
+     the eight-bit character whose value is the octal value NNN (one to
+     three octal digits)
+'\xHH'
+     the eight-bit character whose value is the hexadecimal value HH
+     (one or two hex digits)
+'\uHHHH'
+     the Unicode (ISO/IEC 10646) character whose value is the
+     hexadecimal value HHHH (one to four hex digits)
+'\UHHHHHHHH'
+     the Unicode (ISO/IEC 10646) character whose value is the
+     hexadecimal value HHHHHHHH (one to eight hex digits)
+'\cX'
+     a control-X character
+
+The expanded result is single-quoted, as if the dollar sign had not been
+present.
+
+
+File: bashref.info,  Node: Locale Translation,  Prev: ANSI-C Quoting,  Up: Quoting
+
+3.1.2.5 Locale-Specific Translation
+...................................
+
+* Menu:
+
+* Creating Internationalized Scripts::	How to use translations and different
+					languages in your scripts.
+
+Prefixing a double-quoted string with a dollar sign ('$'), such as
+$"hello, world", will cause the string to be translated according to the
+current locale.  The 'gettext' infrastructure performs the lookup and
+translation, using the 'LC_MESSAGES', 'TEXTDOMAINDIR', and 'TEXTDOMAIN'
+shell variables, as explained below.  See the gettext documentation for
+additional details not covered here.  If the current locale is 'C' or
+'POSIX', if there are no translations available, of if the string is not
+translated, the dollar sign is ignored.  Since this is a form of double
+quoting, the string remains double-quoted by default, whether or not it
+is translated and replaced.  If the 'noexpand_translation' option is
+enabled using the 'shopt' builtin (*note The Shopt Builtin::),
+translated strings are single-quoted instead of double-quoted.
+
+   The rest of this section is a brief overview of how you use gettext
+to create translations for strings in a shell script named SCRIPTNAME.
+There are more details in the gettext documentation.
+
+
+File: bashref.info,  Node: Creating Internationalized Scripts,  Up: Locale Translation
+
+Once you've marked the strings in your script that you want to translate
+using $"...", you create a gettext "template" file using the command
+
+     bash --dump-po-strings SCRIPTNAME > DOMAIN.pot
+
+The DOMAIN is your "message domain".  It's just an arbitrary string
+that's used to identify the files gettext needs, like a package or
+script name.  It needs to be unique among all the message domains on
+systems where you install the translations, so gettext knows which
+translations correspond to your script.  You'll use the template file to
+create translations for each target language.  The template file
+conventionally has the suffix '.pot'.
+
+   You copy this template file to a separate file for each target
+language you want to support (called "PO" files, which use the suffix
+'.po').  PO files use various naming conventions, but when you are
+working to translate a template file into a particular language, you
+first copy the template file to a file whose name is the language you
+want to target, with the '.po' suffix.  For instance, the Spanish
+translations of your strings would be in a file named 'es.po', and to
+get started using a message domain named "example," you would run
+
+     cp example.pot es.po
+
+Ultimately, PO files are often named DOMAIN.po and installed in
+directories that contain multiple translation files for a particular
+language.
+
+   Whichever naming convention you choose, you will need to translate
+the strings in the PO files into the appropriate languages.  This has to
+be done manually.
+
+   When you have the translations and PO files complete, you'll use the
+gettext tools to produce what are called "MO" files, which are compiled
+versions of the PO files the gettext tools use to look up translations
+efficiently.  MO files are also called "message catalog" files.  You use
+the 'msgfmt' program to do this.  For instance, if you had a file with
+Spanish translations, you could run
+
+     msgfmt -o es.mo es.po
+
+to produce the corresponding MO file.
+
+   Once you have the MO files, you decide where to install them and use
+the 'TEXTDOMAINDIR' shell variable to tell the gettext tools where they
+are.  Make sure to use the same message domain to name the MO files as
+you did for the PO files when you install them.
+
+   Your users will use the 'LANG' or 'LC_MESSAGES' shell variables to
+select the desired language.
+
+   You set the 'TEXTDOMAIN' variable to the script's message domain.  As
+above, you use the message domain to name your translation files.
+
+   You, or possibly your users, set the 'TEXTDOMAINDIR' variable to the
+name of a directory where the message catalog files are stored.  If you
+install the message files into the system's standard message catalog
+directory, you don't need to worry about this variable.
+
+   The directory where the message catalog files are stored varies
+between systems.  Some use the message catalog selected by the
+'LC_MESSAGES' shell variable.  Others create the name of the message
+catalog from the value of the 'TEXTDOMAIN' shell variable, possibly
+adding the '.mo' suffix.  If you use the 'TEXTDOMAIN' variable, you may
+need to set the 'TEXTDOMAINDIR' variable to the location of the message
+catalog files, as above.  It's common to use both variables in this
+fashion: '$TEXTDOMAINDIR'/'$LC_MESSAGES'/LC_MESSAGES/'$TEXTDOMAIN'.mo.
+
+   If you used that last convention, and you wanted to store the message
+catalog files with Spanish (es) and Esperanto (eo) translations into a
+local directory you use for custom translation files, you could run
+
+     TEXTDOMAIN=example
+     TEXTDOMAINDIR=/usr/local/share/locale
+
+     cp es.mo ${TEXTDOMAINDIR}/es/LC_MESSAGES/${TEXTDOMAIN}.mo
+     cp eo.mo ${TEXTDOMAINDIR}/eo/LC_MESSAGES/${TEXTDOMAIN}.mo
+
+   When all of this is done, and the message catalog files containing
+the compiled translations are installed in the correct location, your
+users will be able to see translated strings in any of the supported
+languages by setting the 'LANG' or 'LC_MESSAGES' environment variables
+before running your script.
+
+
+File: bashref.info,  Node: Comments,  Prev: Quoting,  Up: Shell Syntax
+
+3.1.3 Comments
+--------------
+
+In a non-interactive shell, or an interactive shell in which the
+'interactive_comments' option to the 'shopt' builtin is enabled (*note
+The Shopt Builtin::), a word beginning with '#' causes that word and all
+remaining characters on that line to be ignored.  An interactive shell
+without the 'interactive_comments' option enabled does not allow
+comments.  The 'interactive_comments' option is on by default in
+interactive shells.  *Note Interactive Shells::, for a description of
+what makes a shell interactive.
+
+
+File: bashref.info,  Node: Shell Commands,  Next: Shell Functions,  Prev: Shell Syntax,  Up: Basic Shell Features
+
+3.2 Shell Commands
+==================
+
+A simple shell command such as 'echo a b c' consists of the command
+itself followed by arguments, separated by spaces.
+
+   More complex shell commands are composed of simple commands arranged
+together in a variety of ways: in a pipeline in which the output of one
+command becomes the input of a second, in a loop or conditional
+construct, or in some other grouping.
+
+* Menu:
+
+* Reserved Words::		Words that have special meaning to the shell.
+* Simple Commands::		The most common type of command.
+* Pipelines::			Connecting the input and output of several
+				commands.
+* Lists::			How to execute commands sequentially.
+* Compound Commands::		Shell commands for control flow.
+* Coprocesses::			Two-way communication between commands.
+* GNU Parallel::		Running commands in parallel.
+
+
+File: bashref.info,  Node: Reserved Words,  Next: Simple Commands,  Up: Shell Commands
+
+3.2.1 Reserved Words
+--------------------
+
+Reserved words are words that have special meaning to the shell.  They
+are used to begin and end the shell's compound commands.
+
+   The following words are recognized as reserved when unquoted and the
+first word of a command (see below for exceptions):
+
+'if'    'then'  'elif'  'else'  'fi'      'time'
+'for'   'in'    'until' 'while' 'do'      'done'
+'case'  'esac'  'coproc''select''function'
+'{'     '}'     '[['    ']]'    '!'
+
+'in' is recognized as a reserved word if it is the third word of a
+'case' or 'select' command.  'in' and 'do' are recognized as reserved
+words if they are the third word in a 'for' command.
+
+
+File: bashref.info,  Node: Simple Commands,  Next: Pipelines,  Prev: Reserved Words,  Up: Shell Commands
+
+3.2.2 Simple Commands
+---------------------
+
+A simple command is the kind of command encountered most often.  It's
+just a sequence of words separated by 'blank's, terminated by one of the
+shell's control operators (*note Definitions::).  The first word
+generally specifies a command to be executed, with the rest of the words
+being that command's arguments.
+
+   The return status (*note Exit Status::) of a simple command is its
+exit status as provided by the POSIX 1003.1 'waitpid' function, or 128+N
+if the command was terminated by signal N.
+
+
+File: bashref.info,  Node: Pipelines,  Next: Lists,  Prev: Simple Commands,  Up: Shell Commands
+
+3.2.3 Pipelines
+---------------
+
+A 'pipeline' is a sequence of one or more commands separated by one of
+the control operators '|' or '|&'.
+
+   The format for a pipeline is
+     [time [-p]] [!] COMMAND1 [ | or |& COMMAND2 ] ...
+
+The output of each command in the pipeline is connected via a pipe to
+the input of the next command.  That is, each command reads the previous
+command's output.  This connection is performed before any redirections
+specified by COMMAND1.
+
+   If '|&' is used, COMMAND1's standard error, in addition to its
+standard output, is connected to COMMAND2's standard input through the
+pipe; it is shorthand for '2>&1 |'.  This implicit redirection of the
+standard error to the standard output is performed after any
+redirections specified by COMMAND1.
+
+   The reserved word 'time' causes timing statistics to be printed for
+the pipeline once it finishes.  The statistics currently consist of
+elapsed (wall-clock) time and user and system time consumed by the
+command's execution.  The '-p' option changes the output format to that
+specified by POSIX.  When the shell is in POSIX mode (*note Bash POSIX
+Mode::), it does not recognize 'time' as a reserved word if the next
+token begins with a '-'.  The 'TIMEFORMAT' variable may be set to a
+format string that specifies how the timing information should be
+displayed.  *Note Bash Variables::, for a description of the available
+formats.  The use of 'time' as a reserved word permits the timing of
+shell builtins, shell functions, and pipelines.  An external 'time'
+command cannot time these easily.
+
+   When the shell is in POSIX mode (*note Bash POSIX Mode::), 'time' 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
+'TIMEFORMAT' variable may be used to specify the format of the time
+information.
+
+   If the pipeline is not executed asynchronously (*note Lists::), the
+shell waits for all commands in the pipeline to complete.
+
+   Each command in a multi-command pipeline, where pipes are created, is
+executed in its own "subshell", which is a separate process (*note
+Command Execution Environment::).  If the 'lastpipe' option is enabled
+using the 'shopt' builtin (*note The Shopt Builtin::), the last element
+of a pipeline may be run by the shell process when job control is not
+active.
+
+   The exit status of a pipeline is the exit status of the last command
+in the pipeline, unless the 'pipefail' option is enabled (*note The Set
+Builtin::).  If 'pipefail' 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
+'!' precedes the pipeline, the exit status 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.
+
+
+File: bashref.info,  Node: Lists,  Next: Compound Commands,  Prev: Pipelines,  Up: Shell Commands
+
+3.2.4 Lists of Commands
+-----------------------
+
+A 'list' is a sequence of one or more pipelines separated by one of the
+operators ';', '&', '&&', or '||', and optionally terminated by one of
+';', '&', or a 'newline'.
+
+   Of these list operators, '&&' and '||' have equal precedence,
+followed by ';' and '&', which have equal precedence.
+
+   A sequence of one or more newlines may appear in a 'list' to delimit
+commands, equivalent to a semicolon.
+
+   If a command is terminated by the control operator '&', the shell
+executes the command asynchronously in a subshell.  This is known as
+executing the command in the "background", and these are referred to as
+"asynchronous" commands.  The shell does not wait for the command to
+finish, and the return status is 0 (true).  When job control is not
+active (*note Job Control::), the standard input for asynchronous
+commands, in the absence of any explicit redirections, is redirected
+from '/dev/null'.
+
+   Commands separated by a ';' 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.
+
+   AND and OR lists are sequences of one or more pipelines separated by
+the control operators '&&' and '||', respectively.  AND and OR lists are
+executed with left associativity.
+
+   An AND list has the form
+     COMMAND1 && COMMAND2
+
+COMMAND2 is executed if, and only if, COMMAND1 returns an exit status of
+zero (success).
+
+   An OR list has the form
+     COMMAND1 || COMMAND2
+
+COMMAND2 is executed if, and only if, COMMAND1 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.
+
+
+File: bashref.info,  Node: Compound Commands,  Next: Coprocesses,  Prev: Lists,  Up: Shell Commands
+
+3.2.5 Compound Commands
+-----------------------
+
+* Menu:
+
+* Looping Constructs::		Shell commands for iterative action.
+* Conditional Constructs::	Shell commands for conditional execution.
+* Command Grouping::		Ways to group commands.
+
+Compound commands are the shell programming language constructs.  Each
+construct begins with a reserved word or control operator and is
+terminated by a corresponding reserved word or operator.  Any
+redirections (*note Redirections::) associated with a compound command
+apply to all commands within that compound command unless explicitly
+overridden.
+
+   In most cases a list of commands in a compound 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.
+
+   Bash provides looping constructs, conditional commands, and
+mechanisms to group commands and execute them as a unit.
+
+
+File: bashref.info,  Node: Looping Constructs,  Next: Conditional Constructs,  Up: Compound Commands
+
+3.2.5.1 Looping Constructs
+..........................
+
+Bash supports the following looping constructs.
+
+   Note that wherever a ';' appears in the description of a command's
+syntax, it may be replaced with one or more newlines.
+
+'until'
+     The syntax of the 'until' command is:
+
+          until TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
+
+     Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
+     status which is not zero.  The return status is the exit status of
+     the last command executed in CONSEQUENT-COMMANDS, or zero if none
+     was executed.
+
+'while'
+     The syntax of the 'while' command is:
+
+          while TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
+
+     Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
+     status of zero.  The return status is the exit status of the last
+     command executed in CONSEQUENT-COMMANDS, or zero if none was
+     executed.
+
+'for'
+     The syntax of the 'for' command is:
+
+          for NAME [ [in [WORDS ...] ] ; ] do COMMANDS; done
+
+     Expand WORDS (*note Shell Expansions::), and execute COMMANDS once
+     for each member in the resultant list, with NAME bound to the
+     current member.  If 'in WORDS' is not present, the 'for' command
+     executes the COMMANDS once for each positional parameter that is
+     set, as if 'in "$@"' had been specified (*note Special
+     Parameters::).
+
+     The return status is the exit status of the last command that
+     executes.  If there are no items in the expansion of WORDS, no
+     commands are executed, and the return status is zero.
+
+     An alternate form of the 'for' command is also supported:
+
+          for (( EXPR1 ; EXPR2 ; EXPR3 )) ; do COMMANDS ; done
+
+     First, the arithmetic expression EXPR1 is evaluated according to
+     the rules described below (*note Shell Arithmetic::).  The
+     arithmetic expression EXPR2 is then evaluated repeatedly until it
+     evaluates to zero.  Each time EXPR2 evaluates to a non-zero value,
+     COMMANDS are executed and the arithmetic expression EXPR3 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 COMMANDS that is executed, or false if any of the
+     expressions is invalid.
+
+   The 'break' and 'continue' builtins (*note Bourne Shell Builtins::)
+may be used to control loop execution.
+
+
+File: bashref.info,  Node: Conditional Constructs,  Next: Command Grouping,  Prev: Looping Constructs,  Up: Compound Commands
+
+3.2.5.2 Conditional Constructs
+..............................
+
+'if'
+     The syntax of the 'if' command is:
+
+          if TEST-COMMANDS; then
+            CONSEQUENT-COMMANDS;
+          [elif MORE-TEST-COMMANDS; then
+            MORE-CONSEQUENTS;]
+          [else ALTERNATE-CONSEQUENTS;]
+          fi
+
+     The TEST-COMMANDS list is executed, and if its return status is
+     zero, the CONSEQUENT-COMMANDS list is executed.  If TEST-COMMANDS
+     returns a non-zero status, each 'elif' list is executed in turn,
+     and if its exit status is zero, the corresponding MORE-CONSEQUENTS
+     is executed and the command completes.  If 'else
+     ALTERNATE-CONSEQUENTS' is present, and the final command in the
+     final 'if' or 'elif' clause has a non-zero exit status, then
+     ALTERNATE-CONSEQUENTS is executed.  The return status is the exit
+     status of the last command executed, or zero if no condition tested
+     true.
+
+'case'
+     The syntax of the 'case' command is:
+
+          case WORD in
+              [ [(] PATTERN [| PATTERN]...) COMMAND-LIST ;;]...
+          esac
+
+     'case' will selectively execute the COMMAND-LIST corresponding to
+     the first PATTERN that matches WORD.  The match is performed
+     according to the rules described below in *note Pattern Matching::.
+     If the 'nocasematch' shell option (see the description of 'shopt'
+     in *note The Shopt Builtin::) is enabled, the match is performed
+     without regard to the case of alphabetic characters.  The '|' is
+     used to separate multiple patterns, and the ')' operator terminates
+     a pattern list.  A list of patterns and an associated command-list
+     is known as a CLAUSE.
+
+     Each clause must be terminated with ';;', ';&', or ';;&'.  The WORD
+     undergoes tilde expansion, parameter expansion, command
+     substitution, arithmetic expansion, and quote removal (*note Shell
+     Parameter Expansion::) before matching is attempted.  Each PATTERN
+     undergoes tilde expansion, parameter expansion, command
+     substitution, arithmetic expansion, process substitution, and quote
+     removal.
+
+     There may be an arbitrary number of 'case' clauses, each terminated
+     by a ';;', ';&', or ';;&'.  The first pattern that matches
+     determines the command-list that is executed.  It's a common idiom
+     to use '*' as the final pattern to define the default case, since
+     that pattern will always match.
+
+     Here is an example using 'case' in a script that could be used to
+     describe one interesting feature of an animal:
+
+          echo -n "Enter the name of an animal: "
+          read ANIMAL
+          echo -n "The $ANIMAL has "
+          case $ANIMAL in
+            horse | dog | cat) echo -n "four";;
+            man | kangaroo ) echo -n "two";;
+            *) echo -n "an unknown number of";;
+          esac
+          echo " legs."
+
+
+     If the ';;' operator is used, no subsequent matches are attempted
+     after the first pattern match.  Using ';&' in place of ';;' causes
+     execution to continue with the COMMAND-LIST associated with the
+     next clause, if any.  Using ';;&' in place of ';;' causes the shell
+     to test the patterns in the next clause, if any, and execute any
+     associated COMMAND-LIST on a successful match, continuing the case
+     statement execution as if the pattern list had not matched.
+
+     The return status is zero if no PATTERN is matched.  Otherwise, the
+     return status is the exit status of the COMMAND-LIST executed.
+
+'select'
+
+     The 'select' construct allows the easy generation of menus.  It has
+     almost the same syntax as the 'for' command:
+
+          select NAME [in WORDS ...]; do COMMANDS; done
+
+     The list of words following 'in' is expanded, generating a list of
+     items, and the set of expanded words is printed on the standard
+     error output stream, each preceded by a number.  If the 'in WORDS'
+     is omitted, the positional parameters are printed, as if 'in "$@"'
+     had been specified.  'select' then displays the 'PS3' prompt and
+     reads a line from the standard input.  If the line consists of a
+     number corresponding to one of the displayed words, then the value
+     of NAME is set to that word.  If the line is empty, the words and
+     prompt are displayed again.  If 'EOF' is read, the 'select' command
+     completes and returns 1.  Any other value read causes NAME to be
+     set to null.  The line read is saved in the variable 'REPLY'.
+
+     The COMMANDS are executed after each selection until a 'break'
+     command is executed, at which point the 'select' command completes.
+
+     Here is an example that allows the user to pick a filename from the
+     current directory, and displays the name and index of the file
+     selected.
+
+          select fname in *;
+          do
+          	echo you picked $fname \($REPLY\)
+          	break;
+          done
+
+'((...))'
+          (( EXPRESSION ))
+
+     The arithmetic EXPRESSION is evaluated according to the rules
+     described below (*note Shell Arithmetic::).  The EXPRESSION
+     undergoes the same expansions as if it were within double quotes,
+     but double quote characters in EXPRESSION are not treated specially
+     are removed.  If the value of the expression is non-zero, the
+     return status is 0; otherwise the return status is 1.
+
+'[[...]]'
+          [[ EXPRESSION ]]
+
+     Return a status of 0 or 1 depending on the evaluation of the
+     conditional expression EXPRESSION.  Expressions are composed of the
+     primaries described below in *note Bash Conditional Expressions::.
+     The words between the '[[' and ']]' do not undergo word splitting
+     and filename expansion.  The shell performs tilde expansion,
+     parameter and variable expansion, arithmetic expansion, command
+     substitution, process substitution, and quote removal on those
+     words (the expansions that would occur if the words were enclosed
+     in double quotes).  Conditional operators such as '-f' must be
+     unquoted to be recognized as primaries.
+
+     When used with '[[', the '<' and '>' operators sort
+     lexicographically using the current locale.
+
+     When the '==' and '!=' operators are used, the string to the right
+     of the operator is considered a pattern and matched according to
+     the rules described below in *note Pattern Matching::, as if the
+     'extglob' shell option were enabled.  The '=' operator is identical
+     to '=='.  If the 'nocasematch' shell option (see the description of
+     'shopt' in *note The Shopt Builtin::) is enabled, the match is
+     performed without regard to the case of alphabetic characters.  The
+     return value is 0 if the string matches ('==') or does not match
+     ('!=') the pattern, and 1 otherwise.
+
+     If you quote any part of the pattern, using any of the shell's
+     quoting mechanisms, the quoted portion is matched literally.  This
+     means every character in the quoted portion matches itself, instead
+     of having any special pattern matching meaning.
+
+     An additional binary operator, '=~', is available, with the same
+     precedence as '==' and '!='.  When you use '=~', the string to the
+     right of the operator is considered a POSIX extended regular
+     expression pattern and matched accordingly (using the POSIX
+     'regcomp' and 'regexec' interfaces usually described in regex(3)).
+     The return value is 0 if the string matches the pattern, and 1 if
+     it does not.  If the regular expression is syntactically incorrect,
+     the conditional expression returns 2.  If the 'nocasematch' shell
+     option (see the description of 'shopt' in *note The Shopt
+     Builtin::) is enabled, the match is performed without regard to the
+     case of alphabetic characters.
+
+     You can quote any part of the pattern to force the quoted portion
+     to be matched literally instead of as a regular expression (see
+     above).  If the pattern is stored in a shell variable, quoting the
+     variable expansion forces the entire pattern to be matched
+     literally.
+
+     The pattern will match if it matches any part of the string.  If
+     you want to force the pattern to match the entire string, anchor
+     the pattern using the '^' and '$' regular expression operators.
+
+     For example, the following will match a line (stored in the shell
+     variable 'line') if there is a sequence of characters anywhere in
+     the value consisting of any number, including zero, of characters
+     in the 'space' character class, immediately followed by zero or one
+     instances of 'a', then a 'b':
+
+          [[ $line =~ [[:space:]]*(a)?b ]]
+
+     That means values for 'line' like 'aab', ' aaaaaab', 'xaby', and '
+     ab' will all match, as will a line containing a 'b' anywhere in its
+     value.
+
+     If you want to match a character that's special to the regular
+     expression grammar ('^$|[]()\.*+?'), it has to be quoted to remove
+     its special meaning.  This means that in the pattern 'xxx.txt', the
+     '.' matches any character in the string (its usual regular
+     expression meaning), but in the pattern '"xxx.txt"', it can only
+     match a literal '.'.
+
+     Likewise, if you want to include a character in your pattern that
+     has a special meaning to the regular expression grammar, you must
+     make sure it's not quoted.  If you want to anchor a pattern at the
+     beginning or end of the string, for instance, you cannot quote the
+     '^' or '$' characters using any form of shell quoting.
+
+     If you want to match 'initial string' at the start of a line, the
+     following will work:
+          [[ $line =~ ^"initial string" ]]
+     but this will not:
+          [[ $line =~ "^initial string" ]]
+     because in the second example the '^' is quoted and doesn't have
+     its usual special meaning.
+
+     It is sometimes difficult to specify a regular expression properly
+     without using quotes, or to keep track of the quoting used by
+     regular expressions while paying attention to shell quoting and the
+     shell's quote removal.  Storing the regular expression in a shell
+     variable is often a useful way to avoid problems with quoting
+     characters that are special to the shell.  For example, the
+     following is equivalent to the pattern used above:
+
+          pattern='[[:space:]]*(a)?b'
+          [[ $line =~ $pattern ]]
+
+     Shell programmers should take special care with backslashes, since
+     backslashes are used by both the shell and regular expressions to
+     remove the special meaning from the following character.  This
+     means that after the shell's word expansions complete (*note Shell
+     Expansions::), any backslashes remaining in parts of the pattern
+     that were originally not quoted can remove the special meaning of
+     pattern characters.  If any part of the pattern is quoted, the
+     shell does its best to ensure that the regular expression treats
+     those remaining backslashes as literal, if they appeared in a
+     quoted portion.
+
+     The following two sets of commands are _not_ equivalent:
+
+          pattern='\.'
+
+          [[ . =~ $pattern ]]
+          [[ . =~ \. ]]
+
+          [[ . =~ "$pattern" ]]
+          [[ . =~ '\.' ]]
+
+     The first two matches will succeed, but the second two will not,
+     because in the second two the backslash will be part of the pattern
+     to be matched.  In the first two examples, the pattern passed to
+     the regular expression parser is '\.'.  The backslash removes the
+     special meaning from '.', so the literal '.' matches.  In the
+     second two examples, the pattern passed to the regular expression
+     parser has the backslash quoted (e.g., '\\\.'), which will not
+     match the string, since it does not contain a backslash.  If the
+     string in the first examples were anything other than '.', say 'a',
+     the pattern would not match, because the quoted '.' in the pattern
+     loses its special meaning of matching any single character.
+
+     Bracket expressions in regular expressions can be sources of errors
+     as well, since characters that are normally special in regular
+     expressions lose their special meanings between brackets.  However,
+     you can use bracket expressions to match special pattern characters
+     without quoting them, so they are sometimes useful for this
+     purpose.
+
+     Though it might seem like a strange way to write it, the following
+     pattern will match a '.' in the string:
+
+          [[ . =~ [.] ]]
+
+     The shell performs any word expansions before passing the pattern
+     to the regular expression functions, so you can assume that the
+     shell's quoting takes precedence.  As noted above, the regular
+     expression parser will interpret any unquoted backslashes remaining
+     in the pattern after shell expansion according to its own rules.
+     The intention is to avoid making shell programmers quote things
+     twice as much as possible, so shell quoting should be sufficient to
+     quote special pattern characters where that's necessary.
+
+     The array variable 'BASH_REMATCH' records which parts of the string
+     matched the pattern.  The element of 'BASH_REMATCH' 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
+     'BASH_REMATCH' indices.  The element of 'BASH_REMATCH' with index N
+     is the portion of the string matching the Nth parenthesized
+     subexpression.
+
+     Bash sets 'BASH_REMATCH' in the global scope; declaring it as a
+     local variable will lead to unexpected results.
+
+     Expressions may be combined using the following operators, listed
+     in decreasing order of precedence:
+
+     '( EXPRESSION )'
+          Returns the value of EXPRESSION.  This may be used to override
+          the normal precedence of operators.
+
+     '! EXPRESSION'
+          True if EXPRESSION is false.
+
+     'EXPRESSION1 && EXPRESSION2'
+          True if both EXPRESSION1 and EXPRESSION2 are true.
+
+     'EXPRESSION1 || EXPRESSION2'
+          True if either EXPRESSION1 or EXPRESSION2 is true.
+
+     The '&&' and '||' operators do not evaluate EXPRESSION2 if the
+     value of EXPRESSION1 is sufficient to determine the return value of
+     the entire conditional expression.
+
+
+File: bashref.info,  Node: Command Grouping,  Prev: Conditional Constructs,  Up: Compound Commands
+
+3.2.5.3 Grouping Commands
+.........................
+
+Bash provides two ways to group a list of commands to be executed as a
+unit.  When commands are grouped, redirections may be applied to the
+entire command list.  For example, the output of all the commands in the
+list may be redirected to a single stream.
+
+'()'
+          ( LIST )
+
+     Placing a list of commands between parentheses forces the shell to
+     create a subshell (*note Command Execution Environment::), and each
+     of the commands in LIST is executed in that subshell environment.
+     Since the LIST is executed in a subshell, variable assignments do
+     not remain in effect after the subshell completes.
+
+'{}'
+          { LIST; }
+
+     Placing a list of commands between curly braces causes the list to
+     be executed in the current shell context.  No subshell is created.
+     The semicolon (or newline) following LIST is required.
+
+   In addition to the creation of a subshell, there is a subtle
+difference between these two constructs due to historical reasons.  The
+braces are reserved words, so they must be separated from the LIST by
+'blank's or other shell metacharacters.  The parentheses are operators,
+and are recognized as separate tokens by the shell even if they are not
+separated from the LIST by whitespace.
+
+   The exit status of both of these constructs is the exit status of
+LIST.
+
+
+File: bashref.info,  Node: Coprocesses,  Next: GNU Parallel,  Prev: Compound Commands,  Up: Shell Commands
+
+3.2.6 Coprocesses
+-----------------
+
+A 'coprocess' is a shell command preceded by the 'coproc' reserved word.
+A coprocess is executed asynchronously in a subshell, as if the command
+had been terminated with the '&' control operator, with a two-way pipe
+established between the executing shell and the coprocess.
+
+   The syntax for a coprocess is:
+
+     coproc [NAME] COMMAND [REDIRECTIONS]
+
+This creates a coprocess named NAME.  COMMAND may be either a simple
+command (*note Simple Commands::) or a compound command (*note Compound
+Commands::).  NAME is a shell variable name.  If NAME is not supplied,
+the default name is 'COPROC'.
+
+   The recommended form to use for a coprocess is
+
+     coproc NAME { COMMAND; }
+
+This form is recommended because simple commands result in the coprocess
+always being named 'COPROC', and it is simpler to use and more complete
+than the other compound commands.
+
+   There are other forms of coprocesses:
+
+     coproc NAME COMPOUND-COMMAND
+     coproc COMPOUND-COMMAND
+     coproc SIMPLE-COMMAND
+
+If COMMAND is a compound command, NAME is optional.  The word following
+'coproc' determines whether that word is interpreted as a variable name:
+it is interpreted as NAME if it is not a reserved word that introduces a
+compound command.  If COMMAND is a simple command, NAME is not allowed;
+this is to avoid confusion between NAME and the first word of the simple
+command.
+
+   When the coprocess is executed, the shell creates an array variable
+(*note Arrays::) named NAME in the context of the executing shell.  The
+standard output of COMMAND is connected via a pipe to a file descriptor
+in the executing shell, and that file descriptor is assigned to NAME[0].
+The standard input of COMMAND is connected via a pipe to a file
+descriptor in the executing shell, and that file descriptor is assigned
+to NAME[1].  This pipe is established before any redirections specified
+by the command (*note Redirections::).  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 'NAME_PID'.  The 'wait' builtin
+command may be used to wait for the coprocess to terminate.
+
+   Since the coprocess is created as an asynchronous command, the
+'coproc' command always returns success.  The return status of a
+coprocess is the exit status of COMMAND.
+
+
+File: bashref.info,  Node: GNU Parallel,  Prev: Coprocesses,  Up: Shell Commands
+
+3.2.7 GNU Parallel
+------------------
+
+There are ways to run commands in parallel that are not built into Bash.
+GNU Parallel is a tool to do just that.
+
+   GNU Parallel, as its name suggests, can be used to build and run
+commands in parallel.  You may run the same command with different
+arguments, whether they are filenames, usernames, hostnames, or lines
+read from files.  GNU Parallel provides shorthand references to many of
+the most common operations (input lines, various portions of the input
+line, different ways to specify the input source, and so on).  Parallel
+can replace 'xargs' or feed commands from its input sources to several
+different instances of Bash.
+
+   For a complete description, refer to the GNU Parallel documentation,
+which is available at
+<https://www.gnu.org/software/parallel/parallel_tutorial.html>.
+
+
+File: bashref.info,  Node: Shell Functions,  Next: Shell Parameters,  Prev: Shell Commands,  Up: Basic Shell Features
+
+3.3 Shell Functions
+===================
+
+Shell functions are a way to group commands for later execution using a
+single name for the group.  They are executed just like a "regular"
+command.  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.  Shell functions are executed in the current shell context; no
+new process is created to interpret them.
+
+   Functions are declared using this syntax:
+     FNAME () COMPOUND-COMMAND [ REDIRECTIONS ]
+
+   or
+
+     function FNAME [()] COMPOUND-COMMAND [ REDIRECTIONS ]
+
+   This defines a shell function named FNAME.  The reserved word
+'function' is optional.  If the 'function' reserved word is supplied,
+the parentheses are optional.  The "body" of the function is the
+compound command COMPOUND-COMMAND (*note Compound Commands::).  That
+command is usually a LIST enclosed between { and }, but may be any
+compound command listed above.  If the 'function' reserved word is used,
+but the parentheses are not supplied, the braces are recommended.
+COMPOUND-COMMAND is executed whenever FNAME is specified as the name of
+a simple command.  When the shell is in POSIX mode (*note Bash POSIX
+Mode::), FNAME must be a valid shell name and may not be the same as one
+of the special builtins (*note Special Builtins::).  In default mode, a
+function name can be any unquoted shell word that does not contain '$'.
+Any redirections (*note Redirections::) associated with the shell
+function are performed when the function is executed.  A function
+definition may be deleted using the '-f' option to the 'unset' builtin
+(*note Bourne Shell Builtins::).
+
+   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.
+
+   Note that for historical reasons, in the most common usage the curly
+braces that surround the body of the function must be separated from the
+body by 'blank's or newlines.  This is because the braces are reserved
+words and are only recognized as such when they are separated from the
+command list by whitespace or another shell metacharacter.  Also, when
+using the braces, the LIST must be terminated by a semicolon, a '&', or
+a newline.
+
+   When a function is executed, the arguments to the function become the
+positional parameters during its execution (*note Positional
+Parameters::).  The special parameter '#' that expands to the number of
+positional parameters is updated to reflect the change.  Special
+parameter '0' is unchanged.  The first element of the 'FUNCNAME'
+variable is set to the name of the function while the function is
+executing.
+
+   All other aspects of the shell execution environment are identical
+between a function and its caller with these exceptions: the 'DEBUG' and
+'RETURN' traps are not inherited unless the function has been given the
+'trace' attribute using the 'declare' builtin or the '-o functrace'
+option has been enabled with the 'set' builtin, (in which case all
+functions inherit the 'DEBUG' and 'RETURN' traps), and the 'ERR' trap is
+not inherited unless the '-o errtrace' shell option has been enabled.
+*Note Bourne Shell Builtins::, for the description of the 'trap'
+builtin.
+
+   The 'FUNCNEST' 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.
+
+   If the builtin command 'return' is executed in a function, the
+function completes and execution resumes with the next command after the
+function call.  Any command associated with the 'RETURN' trap is
+executed before execution resumes.  When a function completes, the
+values of the positional parameters and the special parameter '#' are
+restored to the values they had prior to the function's execution.  If a
+numeric argument is given to 'return', that is the function's return
+status; otherwise the function's return status is the exit status of the
+last command executed before the 'return'.
+
+   Variables local to the function may be declared with the 'local'
+builtin ("local variables").  Ordinarily, variables and their values are
+shared between a function and its caller.  These variables are visible
+only to the function and the commands it invokes.  This is particularly
+important when a shell function calls other functions.
+
+   In the following description, the "current scope" is a currently-
+executing function.  Previous scopes consist of that function's caller
+and so on, back to the "global" scope, where the shell is not executing
+any shell function.  Consequently, a local variable at the current local
+scope is a variable declared using the 'local' or 'declare' builtins in
+the function that is currently executing.
+
+   Local variables "shadow" 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.
+
+   The shell uses "dynamic scoping" to control a variable's visibility
+within functions.  With dynamic scoping, visible variables and their
+values are a result of the sequence of function calls that caused
+execution to reach the current function.  The value of a variable that a
+function sees depends on its value within its caller, if any, whether
+that caller is the "global" scope or another shell function.  This is
+also the value that a local variable declaration "shadows", and the
+value that is restored when the function returns.
+
+   For example, if a variable 'var' is declared as local in function
+'func1', and 'func1' calls another function 'func2', references to 'var'
+made from within 'func2' will resolve to the local variable 'var' from
+'func1', shadowing any global variable named 'var'.
+
+   The following script demonstrates this behavior.  When executed, the
+script displays
+
+     In func2, var = func1 local
+
+     func1()
+     {
+         local var='func1 local'
+         func2
+     }
+
+     func2()
+     {
+         echo "In func2, var = $var"
+     }
+
+     var=global
+     func1
+
+   The 'unset' builtin also acts using the same dynamic scope: if a
+variable is local to the current scope, 'unset' 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 (appearing as unset) until it is reset in that scope or
+until the function returns.  Once the function returns, any instance of
+the variable at a previous scope 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 (see below how
+'localvar_unset'shell option changes this behavior).
+
+   Function names and definitions may be listed with the '-f' option to
+the 'declare' ('typeset') builtin command (*note Bash Builtins::).  The
+'-F' option to 'declare' or 'typeset' will list the function names only
+(and optionally the source file and line number, if the 'extdebug' shell
+option is enabled).  Functions may be exported so that child shell
+processes (those created when executing a separate shell invocation)
+automatically have them defined with the '-f' option to the 'export'
+builtin (*note Bourne Shell Builtins::).
+
+   Functions may be recursive.  The 'FUNCNEST' 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 placed on the number of
+recursive calls.
+
+
+File: bashref.info,  Node: Shell Parameters,  Next: Shell Expansions,  Prev: Shell Functions,  Up: Basic Shell Features
+
+3.4 Shell Parameters
+====================
+
+* Menu:
+
+* Positional Parameters::	The shell's command-line arguments.
+* Special Parameters::		Parameters denoted by special characters.
+
+A "parameter" is an entity that stores values.  It can be a 'name', a
+number, or one of the special characters listed below.  A "variable" is
+a parameter denoted by a 'name'.  A variable has a 'value' and zero or
+more 'attributes'.  Attributes are assigned using the 'declare' builtin
+command (see the description of the 'declare' builtin in *note Bash
+Builtins::).
+
+   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 'unset' builtin command.
+
+   A variable may be assigned to by a statement of the form
+     NAME=[VALUE]
+If VALUE is not given, the variable is assigned the null string.  All
+VALUEs undergo tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal (*note
+Shell Parameter Expansion::).  If the variable has its 'integer'
+attribute set, then VALUE is evaluated as an arithmetic expression even
+if the '$((...))' expansion is not used (*note Arithmetic Expansion::).
+Word splitting and filename expansion are not performed.  Assignment
+statements may also appear as arguments to the 'alias', 'declare',
+'typeset', 'export', 'readonly', and 'local' builtin commands
+("declaration" commands).  When in POSIX mode (*note Bash POSIX Mode::),
+these builtins may appear in a command after one or more instances of
+the 'command' builtin and retain these assignment statement properties.
+
+   In the context where an assignment statement is assigning a value to
+a shell variable or array index (*note Arrays::), the '+=' operator can
+be used to append to or add to the variable's previous value.  This
+includes arguments to builtin commands such as 'declare' that accept
+assignment statements (declaration commands).  When '+=' is applied to a
+variable for which the 'integer' attribute has been set, VALUE 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 (*note Arrays::), 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, VALUE is expanded and appended to the variable's value.
+
+   A variable can be assigned the 'nameref' attribute using the '-n'
+option to the 'declare' or 'local' builtin commands (*note Bash
+Builtins::) to create a "nameref", 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 nameref 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
+     declare -n ref=$1
+inside the function creates a nameref variable 'ref' whose value is the
+variable name passed as the first argument.  References and assignments
+to 'ref', and changes to its attributes, are treated as references,
+assignments, and attribute modifications to the variable whose name was
+passed as '$1'.
+
+   If the control variable in a 'for' loop has the nameref attribute,
+the list of words can be a list of shell variables, and a name reference
+will be established for each word in the list, in turn, when the loop is
+executed.  Array variables cannot be given the nameref attribute.
+However, nameref variables can reference array variables and subscripted
+array variables.  Namerefs can be unset using the '-n' option to the
+'unset' builtin (*note Bourne Shell Builtins::).  Otherwise, if 'unset'
+is executed with the name of a nameref variable as an argument, the
+variable referenced by the nameref variable will be unset.
+
+
+File: bashref.info,  Node: Positional Parameters,  Next: Special Parameters,  Up: Shell Parameters
+
+3.4.1 Positional Parameters
+---------------------------
+
+A "positional parameter" is a parameter denoted by one or more digits,
+other than the single digit '0'.  Positional parameters are assigned
+from the shell's arguments when it is invoked, and may be reassigned
+using the 'set' builtin command.  Positional parameter 'N' may be
+referenced as '${N}', or as '$N' when 'N' consists of a single digit.
+Positional parameters may not be assigned to with assignment statements.
+The 'set' and 'shift' builtins are used to set and unset them (*note
+Shell Builtin Commands::).  The positional parameters are temporarily
+replaced when a shell function is executed (*note Shell Functions::).
+
+   When a positional parameter consisting of more than a single digit is
+expanded, it must be enclosed in braces.
+
+
+File: bashref.info,  Node: Special Parameters,  Prev: Positional Parameters,  Up: Shell Parameters
+
+3.4.2 Special Parameters
+------------------------
+
+The shell treats several parameters specially.  These parameters may
+only be referenced; assignment to them is not allowed.
+
+'*'
+     ($*) 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
+     filename 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 'IFS' special
+     variable.  That is, '"$*"' is equivalent to '"$1C$2C..."', where C
+     is the first character of the value of the 'IFS' variable.  If
+     'IFS' is unset, the parameters are separated by spaces.  If 'IFS'
+     is null, the parameters are joined without intervening separators.
+
+'@'
+     ($@) Expands to the positional parameters, starting from one.  In
+     contexts where word splitting is performed, this expands each
+     positional parameter to a separate word; if not within double
+     quotes, these words are subject to word splitting.  In contexts
+     where word splitting is not performed, this expands to a single
+     word with each positional parameter separated by a space.  When the
+     expansion occurs within double quotes, and word splitting is
+     performed, each parameter expands to a separate word.  That is,
+     '"$@"' is equivalent to '"$1" "$2" ...'.  If the double-quoted
+     expansion occurs within a word, the expansion of the first
+     parameter is joined with the beginning part of the original word,
+     and the expansion of the last parameter is joined with the last
+     part of the original word.  When there are no positional
+     parameters, '"$@"' and '$@' expand to nothing (i.e., they are
+     removed).
+
+'#'
+     ($#) Expands to the number of positional parameters in decimal.
+
+'?'
+     ($?)  Expands to the exit status of the most recently executed
+     foreground pipeline.
+
+'-'
+     ($-, a hyphen.)  Expands to the current option flags as specified
+     upon invocation, by the 'set' builtin command, or those set by the
+     shell itself (such as the '-i' option).
+
+'$'
+     ($$) Expands to the process ID of the shell.  In a subshell, it
+     expands to the process ID of the invoking shell, not the subshell.
+
+'!'
+     ($!)  Expands to the process ID of the job most recently placed
+     into the background, whether executed as an asynchronous command or
+     using the 'bg' builtin (*note Job Control Builtins::).
+
+'0'
+     ($0) Expands to the name of the shell or shell script.  This is set
+     at shell initialization.  If Bash is invoked with a file of
+     commands (*note Shell Scripts::), '$0' is set to the name of that
+     file.  If Bash is started with the '-c' option (*note Invoking
+     Bash::), then '$0' 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 Bash, as given by argument zero.
+
+
+File: bashref.info,  Node: Shell Expansions,  Next: Redirections,  Prev: Shell Parameters,  Up: Basic Shell Features
+
+3.5 Shell Expansions
+====================
+
+Expansion is performed on the command line after it has been split into
+'token's.  There are seven kinds of expansion performed:
+
+   * brace expansion
+   * tilde expansion
+   * parameter and variable expansion
+   * command substitution
+   * arithmetic expansion
+   * word splitting
+   * filename expansion
+
+* Menu:
+
+* Brace Expansion::		Expansion of expressions within braces.
+* Tilde Expansion::		Expansion of the ~ character.
+* Shell Parameter Expansion::	How Bash expands variables to their values.
+* Command Substitution::	Using the output of a command as an argument.
+* Arithmetic Expansion::	How to use arithmetic in shell expansions.
+* Process Substitution::	A way to write and read to and from a
+				command.
+* Word Splitting::	How the results of expansion are split into separate
+			arguments.
+* Filename Expansion::	A shorthand for specifying filenames matching patterns.
+* Quote Removal::	How and when quote characters are removed from
+			words.
+
+   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
+filename expansion.
+
+   On systems that can support it, there is an additional expansion
+available: "process substitution".  This is performed at the same time
+as tilde, parameter, variable, and arithmetic expansion and command
+substitution.
+
+   After these expansions are performed, quote characters present in the
+original word are removed unless they have been quoted themselves
+("quote removal").
+
+   Only brace expansion, word splitting, and filename 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 '"$@"' and '$*' (*note Special Parameters::), and
+'"${NAME[@]}"' and '${NAME[*]}' (*note Arrays::).
+
+   After all expansions, 'quote removal' (*note Quote Removal::) is
+performed.
+
+
+File: bashref.info,  Node: Brace Expansion,  Next: Tilde Expansion,  Up: Shell Expansions
+
+3.5.1 Brace Expansion
+---------------------
+
+Brace expansion is a mechanism by which arbitrary strings may be
+generated.  This mechanism is similar to "filename expansion" (*note
+Filename Expansion::), but the filenames generated need not exist.
+Patterns to be brace expanded take the form of an optional PREAMBLE,
+followed by either a series of comma-separated strings or a sequence
+expression between a pair of braces, followed by an optional POSTSCRIPT.
+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.
+
+   Brace expansions may be nested.  The results of each expanded string
+are not sorted; left to right order is preserved.  For example,
+     bash$ echo a{d,c,b}e
+     ade ace abe
+
+   A sequence expression takes the form '{X..Y[..INCR]}', where X and Y
+are either integers or letters, and INCR, an optional increment, is an
+integer.  When integers are supplied, the expression expands to each
+number between X and Y, inclusive.  Supplied integers may be prefixed
+with '0' to force each term to have the same width.  When either X 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
+letters are supplied, the expression expands to each character
+lexicographically between X and Y, inclusive, using the default C
+locale.  Note that both X and Y must be of the same type (integer or
+letter).  When the increment is supplied, it is used as the difference
+between each term.  The default increment is 1 or -1 as appropriate.
+
+   Brace expansion is performed before any other expansions, and any
+characters special to other expansions are preserved in the result.  It
+is strictly textual.  Bash does not apply any syntactic interpretation
+to the context of the expansion or the text between the braces.
+
+   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 { or ',' may be quoted with a backslash to prevent its being
+considered part of a brace expression.  To avoid conflicts with
+parameter expansion, the string '${' is not considered eligible for
+brace expansion, and inhibits brace expansion until the closing '}'.
+
+   This construct is typically used as shorthand when the common prefix
+of the strings to be generated is longer than in the above example:
+     mkdir /usr/local/src/bash/{old,new,dist,bugs}
+   or
+     chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
+
+
+File: bashref.info,  Node: Tilde Expansion,  Next: Shell Parameter Expansion,  Prev: Brace Expansion,  Up: Shell Expansions
+
+3.5.2 Tilde Expansion
+---------------------
+
+If a word begins with an unquoted tilde character ('~'), all of the
+characters up to the first unquoted slash (or all characters, if there
+is no unquoted slash) are considered a "tilde-prefix".  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 "login name".
+If this login name is the null string, the tilde is replaced with the
+value of the 'HOME' shell variable.  If 'HOME' 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.
+
+   If the tilde-prefix is '~+', the value of the shell variable 'PWD'
+replaces the tilde-prefix.  If the tilde-prefix is '~-', the value of
+the shell variable 'OLDPWD', if it is set, is substituted.
+
+   If the characters following the tilde in the tilde-prefix consist of
+a number N, 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 'dirs' builtin invoked with the characters
+following tilde in the tilde-prefix as an argument (*note The Directory
+Stack::).  If the tilde-prefix, sans the tilde, consists of a number
+without a leading '+' or '-', '+' is assumed.
+
+   If the login name is invalid, or the tilde expansion fails, the word
+is left unchanged.
+
+   Each variable assignment is checked for unquoted tilde-prefixes
+immediately following a ':' or the first '='.  In these cases, tilde
+expansion is also performed.  Consequently, one may use filenames with
+tildes in assignments to 'PATH', 'MAILPATH', and 'CDPATH', and the shell
+assigns the expanded value.
+
+   The following table shows how Bash treats unquoted tilde-prefixes:
+
+'~'
+     The value of '$HOME'
+'~/foo'
+     '$HOME/foo'
+
+'~fred/foo'
+     The subdirectory 'foo' of the home directory of the user 'fred'
+
+'~+/foo'
+     '$PWD/foo'
+
+'~-/foo'
+     '${OLDPWD-'~-'}/foo'
+
+'~N'
+     The string that would be displayed by 'dirs +N'
+
+'~+N'
+     The string that would be displayed by 'dirs +N'
+
+'~-N'
+     The string that would be displayed by 'dirs -N'
+
+   Bash also performs tilde expansion on words satisfying the conditions
+of variable assignments (*note Shell Parameters::) when they appear as
+arguments to simple commands.  Bash does not do this, except for the
+declaration commands listed above, when in POSIX mode.
+
+
+File: bashref.info,  Node: Shell Parameter Expansion,  Next: Command Substitution,  Prev: Tilde Expansion,  Up: Shell Expansions
+
+3.5.3 Shell Parameter Expansion
+-------------------------------
+
+The '$' 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.
+
+   When braces are used, the matching ending brace is the first '}' not
+escaped by a backslash or within a quoted string, and not within an
+embedded arithmetic expansion, command substitution, or parameter
+expansion.
+
+   The basic form of parameter expansion is ${PARAMETER}.  The value of
+PARAMETER is substituted.  The PARAMETER is a shell parameter as
+described above (*note Shell Parameters::) or an array reference (*note
+Arrays::).  The braces are required when PARAMETER is a positional
+parameter with more than one digit, or when PARAMETER is followed by a
+character that is not to be interpreted as part of its name.
+
+   If the first character of PARAMETER is an exclamation point (!), and
+PARAMETER is not a nameref, it introduces a level of indirection.  Bash
+uses the value formed by expanding the rest of PARAMETER as the new
+PARAMETER; this is then expanded and that value is used in the rest of
+the expansion, rather than the expansion of the original PARAMETER.
+This is known as 'indirect expansion'.  The value is subject to tilde
+expansion, parameter expansion, command substitution, and arithmetic
+expansion.  If PARAMETER is a nameref, this expands to the name of the
+variable referenced by PARAMETER instead of performing the complete
+indirect expansion.  The exceptions to this are the expansions of
+${!PREFIX*} and ${!NAME[@]} described below.  The exclamation point must
+immediately follow the left brace in order to introduce indirection.
+
+   In each of the cases below, WORD is subject to tilde expansion,
+parameter expansion, command substitution, and arithmetic expansion.
+
+   When not performing substring expansion, using the form described
+below (e.g., ':-'), Bash tests for a parameter that is unset or null.
+Omitting the colon results in a test only for a parameter that is unset.
+Put another way, if the colon is included, the operator tests for both
+PARAMETER's existence and that its value is not null; if the colon is
+omitted, the operator tests only for existence.
+
+'${PARAMETER:-WORD}'
+     If PARAMETER is unset or null, the expansion of WORD is
+     substituted.  Otherwise, the value of PARAMETER is substituted.
+
+          $ v=123
+          $ echo ${v-unset}
+          123
+
+'${PARAMETER:=WORD}'
+     If PARAMETER is unset or null, the expansion of WORD is assigned to
+     PARAMETER.  The value of PARAMETER is then substituted.  Positional
+     parameters and special parameters may not be assigned to in this
+     way.
+
+          $ var=
+          $ : ${var:=DEFAULT}
+          $ echo $var
+          DEFAULT
+
+'${PARAMETER:?WORD}'
+     If PARAMETER is null or unset, the expansion of WORD (or a message
+     to that effect if WORD is not present) is written to the standard
+     error and the shell, if it is not interactive, exits.  Otherwise,
+     the value of PARAMETER is substituted.
+
+          $ var=
+          $ : ${var:?var is unset or null}
+          bash: var: var is unset or null
+
+'${PARAMETER:+WORD}'
+     If PARAMETER is null or unset, nothing is substituted, otherwise
+     the expansion of WORD is substituted.
+
+          $ var=123
+          $ echo ${var:+var is set and not null}
+          var is set and not null
+
+'${PARAMETER:OFFSET}'
+'${PARAMETER:OFFSET:LENGTH}'
+     This is referred to as Substring Expansion.  It expands to up to
+     LENGTH characters of the value of PARAMETER starting at the
+     character specified by OFFSET.  If PARAMETER is '@' or '*', an
+     indexed array subscripted by '@' or '*', or an associative array
+     name, the results differ as described below.  If LENGTH is omitted,
+     it expands to the substring of the value of PARAMETER starting at
+     the character specified by OFFSET and extending to the end of the
+     value.  LENGTH and OFFSET are arithmetic expressions (*note Shell
+     Arithmetic::).
+
+     If OFFSET evaluates to a number less than zero, the value is used
+     as an offset in characters from the end of the value of PARAMETER.
+     If LENGTH evaluates to a number less than zero, it is interpreted
+     as an offset in characters from the end of the value of PARAMETER
+     rather than a number of characters, and the expansion is the
+     characters between OFFSET 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 ':-' expansion.
+
+     Here are some examples illustrating substring expansion on
+     parameters and subscripted arrays:
+
+     $ string=01234567890abcdefgh
+     $ echo ${string:7}
+     7890abcdefgh
+     $ echo ${string:7:0}
+     
+     $ echo ${string:7:2}
+     78
+     $ echo ${string:7:-2}
+     7890abcdef
+     $ echo ${string: -7}
+     bcdefgh
+     $ echo ${string: -7:0}
+     
+     $ echo ${string: -7:2}
+     bc
+     $ echo ${string: -7:-2}
+     bcdef
+     $ set -- 01234567890abcdefgh
+     $ echo ${1:7}
+     7890abcdefgh
+     $ echo ${1:7:0}
+     
+     $ echo ${1:7:2}
+     78
+     $ echo ${1:7:-2}
+     7890abcdef
+     $ echo ${1: -7}
+     bcdefgh
+     $ echo ${1: -7:0}
+     
+     $ echo ${1: -7:2}
+     bc
+     $ echo ${1: -7:-2}
+     bcdef
+     $ array[0]=01234567890abcdefgh
+     $ echo ${array[0]:7}
+     7890abcdefgh
+     $ echo ${array[0]:7:0}
+     
+     $ echo ${array[0]:7:2}
+     78
+     $ echo ${array[0]:7:-2}
+     7890abcdef
+     $ echo ${array[0]: -7}
+     bcdefgh
+     $ echo ${array[0]: -7:0}
+     
+     $ echo ${array[0]: -7:2}
+     bc
+     $ echo ${array[0]: -7:-2}
+     bcdef
+
+     If PARAMETER is '@' or '*', the result is LENGTH positional
+     parameters beginning at OFFSET.  A negative OFFSET 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 LENGTH evaluates to a number less than zero.
+
+     The following examples illustrate substring expansion using
+     positional parameters:
+
+     $ set -- 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+     $ echo ${@:7}
+     7 8 9 0 a b c d e f g h
+     $ echo ${@:7:0}
+     
+     $ echo ${@:7:2}
+     7 8
+     $ echo ${@:7:-2}
+     bash: -2: substring expression < 0
+     $ echo ${@: -7:2}
+     b c
+     $ echo ${@:0}
+     ./bash 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+     $ echo ${@:0:2}
+     ./bash 1
+     $ echo ${@: -7:0}
+     
+
+     If PARAMETER is an indexed array name subscripted by '@' or '*',
+     the result is the LENGTH members of the array beginning with
+     '${PARAMETER[OFFSET]}'.  A negative OFFSET is taken relative to one
+     greater than the maximum index of the specified array.  It is an
+     expansion error if LENGTH evaluates to a number less than zero.
+
+     These examples show how you can use substring expansion with
+     indexed arrays:
+
+     $ array=(0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h)
+     $ echo ${array[@]:7}
+     7 8 9 0 a b c d e f g h
+     $ echo ${array[@]:7:2}
+     7 8
+     $ echo ${array[@]: -7:2}
+     b c
+     $ echo ${array[@]: -7:-2}
+     bash: -2: substring expression < 0
+     $ echo ${array[@]:0}
+     0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+     $ echo ${array[@]:0:2}
+     0 1
+     $ echo ${array[@]: -7:0}
+     
+
+     Substring expansion applied to an associative array produces
+     undefined results.
+
+     Substring indexing is zero-based unless the positional parameters
+     are used, in which case the indexing starts at 1 by default.  If
+     OFFSET is 0, and the positional parameters are used, '$0' is
+     prefixed to the list.
+
+'${!PREFIX*}'
+'${!PREFIX@}'
+     Expands to the names of variables whose names begin with PREFIX,
+     separated by the first character of the 'IFS' special variable.
+     When '@' is used and the expansion appears within double quotes,
+     each variable name expands to a separate word.
+
+'${!NAME[@]}'
+'${!NAME[*]}'
+     If NAME is an array variable, expands to the list of array indices
+     (keys) assigned in NAME.  If NAME is not an array, expands to 0 if
+     NAME is set and null otherwise.  When '@' is used and the expansion
+     appears within double quotes, each key expands to a separate word.
+
+'${#PARAMETER}'
+     The length in characters of the expanded value of PARAMETER is
+     substituted.  If PARAMETER is '*' or '@', the value substituted is
+     the number of positional parameters.  If PARAMETER is an array name
+     subscripted by '*' or '@', the value substituted is the number of
+     elements in the array.  If PARAMETER is an indexed array name
+     subscripted by a negative number, that number is interpreted as
+     relative to one greater than the maximum index of PARAMETER, so
+     negative indices count back from the end of the array, and an index
+     of -1 references the last element.
+
+'${PARAMETER#WORD}'
+'${PARAMETER##WORD}'
+     The WORD is expanded to produce a pattern and matched according to
+     the rules described below (*note Pattern Matching::).  If the
+     pattern matches the beginning of the expanded value of PARAMETER,
+     then the result of the expansion is the expanded value of PARAMETER
+     with the shortest matching pattern (the '#' case) or the longest
+     matching pattern (the '##' case) deleted.  If PARAMETER is '@' or
+     '*', the pattern removal operation is applied to each positional
+     parameter in turn, and the expansion is the resultant list.  If
+     PARAMETER is an array variable subscripted with '@' or '*', the
+     pattern removal operation is applied to each member of the array in
+     turn, and the expansion is the resultant list.
+
+'${PARAMETER%WORD}'
+'${PARAMETER%%WORD}'
+     The WORD is expanded to produce a pattern and matched according to
+     the rules described below (*note Pattern Matching::).  If the
+     pattern matches a trailing portion of the expanded value of
+     PARAMETER, then the result of the expansion is the value of
+     PARAMETER with the shortest matching pattern (the '%' case) or the
+     longest matching pattern (the '%%' case) deleted.  If PARAMETER is
+     '@' or '*', the pattern removal operation is applied to each
+     positional parameter in turn, and the expansion is the resultant
+     list.  If PARAMETER is an array variable subscripted with '@' or
+     '*', the pattern removal operation is applied to each member of the
+     array in turn, and the expansion is the resultant list.
+
+'${PARAMETER/PATTERN/STRING}'
+'${PARAMETER//PATTERN/STRING}'
+'${PARAMETER/#PATTERN/STRING}'
+'${PARAMETER/%PATTERN/STRING}'
+     The PATTERN is expanded to produce a pattern just as in filename
+     expansion.  PARAMETER is expanded and the longest match of PATTERN
+     against its value is replaced with STRING.  STRING undergoes tilde
+     expansion, parameter and variable expansion, arithmetic expansion,
+     command and process substitution, and quote removal.  The match is
+     performed according to the rules described below (*note Pattern
+     Matching::).
+
+     In the first form above, only the first match is replaced.  If
+     there are two slashes separating PARAMETER and PATTERN (the second
+     form above), all matches of PATTERN are replaced with STRING.  If
+     PATTERN is preceded by '#' (the third form above), it must match at
+     the beginning of the expanded value of PARAMETER.  If PATTERN is
+     preceded by '%' (the fourth form above), it must match at the end
+     of the expanded value of PARAMETER.  If the expansion of STRING is
+     null, matches of PATTERN are deleted.  If STRING is null, matches
+     of PATTERN are deleted and the '/' following PATTERN may be
+     omitted.
+
+     If the 'patsub_replacement' shell option is enabled using 'shopt',
+     any unquoted instances of '&' in STRING are replaced with the
+     matching portion of PATTERN.  This is intended to duplicate a
+     common 'sed' idiom.
+
+     Quoting any part of STRING inhibits replacement in the expansion of
+     the quoted portion, including replacement strings stored in shell
+     variables.  Backslash will escape '&' in STRING; the backslash is
+     removed in order to permit a literal '&' in the replacement string.
+     Users should take care if STRING is double-quoted to avoid unwanted
+     interactions between the backslash and double-quoting, since
+     backslash has special meaning within double quotes.  Pattern
+     substitution performs the check for unquoted '&' after expanding
+     STRING, so users should ensure to properly quote any occurrences of
+     '&' they want to be taken literally in the replacement and ensure
+     any instances of '&' they want to be replaced are unquoted.
+
+     For instance,
+
+          var=abcdef
+          rep='& '
+          echo ${var/abc/& }
+          echo "${var/abc/& }"
+          echo ${var/abc/$rep}
+          echo "${var/abc/$rep}"
+
+     will display four lines of "abc def", while
+
+          var=abcdef
+          rep='& '
+          echo ${var/abc/\& }
+          echo "${var/abc/\& }"
+          echo ${var/abc/"& "}
+          echo ${var/abc/"$rep"}
+
+     will display four lines of "& def".  Like the pattern removal
+     operators, double quotes surrounding the replacement string quote
+     the expanded characters, while double quotes enclosing the entire
+     parameter substitution do not, since the expansion is performed in
+     a context that doesn't take any enclosing double quotes into
+     account.
+
+     Since backslash can escape '&', it can also escape a backslash in
+     the replacement string.  This means that '\\' will insert a literal
+     backslash into the replacement, so these two 'echo' commands
+
+          var=abcdef
+          rep='\\&xyz'
+          echo ${var/abc/\\&xyz}
+          echo ${var/abc/$rep}
+
+     will both output '\abcxyzdef'.
+
+     It should rarely be necessary to enclose only STRING in double
+     quotes.
+
+     If the 'nocasematch' shell option (see the description of 'shopt'
+     in *note The Shopt Builtin::) is enabled, the match is performed
+     without regard to the case of alphabetic characters.  If PARAMETER
+     is '@' or '*', the substitution operation is applied to each
+     positional parameter in turn, and the expansion is the resultant
+     list.  If PARAMETER is an array variable subscripted with '@' or
+     '*', the substitution operation is applied to each member of the
+     array in turn, and the expansion is the resultant list.
+
+'${PARAMETER^PATTERN}'
+'${PARAMETER^^PATTERN}'
+'${PARAMETER,PATTERN}'
+'${PARAMETER,,PATTERN}'
+     This expansion modifies the case of alphabetic characters in
+     PARAMETER.  The PATTERN is expanded to produce a pattern just as in
+     filename expansion.  Each character in the expanded value of
+     PARAMETER is tested against PATTERN, and, if it matches the
+     pattern, its case is converted.  The pattern should not attempt to
+     match more than one character.
+
+     The '^' operator converts lowercase letters matching PATTERN to
+     uppercase; the ',' operator converts matching uppercase letters to
+     lowercase.  The '^^' and ',,' expansions convert each matched
+     character in the expanded value; the '^' and ',' expansions match
+     and convert only the first character in the expanded value.  If
+     PATTERN is omitted, it is treated like a '?', which matches every
+     character.
+
+     If PARAMETER is '@' or '*', the case modification operation is
+     applied to each positional parameter in turn, and the expansion is
+     the resultant list.  If PARAMETER is an array variable subscripted
+     with '@' or '*', the case modification operation is applied to each
+     member of the array in turn, and the expansion is the resultant
+     list.
+
+'${PARAMETER@OPERATOR}'
+     The expansion is either a transformation of the value of PARAMETER
+     or information about PARAMETER itself, depending on the value of
+     OPERATOR.  Each OPERATOR is a single letter:
+
+     'U'
+          The expansion is a string that is the value of PARAMETER with
+          lowercase alphabetic characters converted to uppercase.
+     'u'
+          The expansion is a string that is the value of PARAMETER with
+          the first character converted to uppercase, if it is
+          alphabetic.
+     'L'
+          The expansion is a string that is the value of PARAMETER with
+          uppercase alphabetic characters converted to lowercase.
+     'Q'
+          The expansion is a string that is the value of PARAMETER
+          quoted in a format that can be reused as input.
+     'E'
+          The expansion is a string that is the value of PARAMETER with
+          backslash escape sequences expanded as with the '$'...''
+          quoting mechanism.
+     'P'
+          The expansion is a string that is the result of expanding the
+          value of PARAMETER as if it were a prompt string (*note
+          Controlling the Prompt::).
+     'A'
+          The expansion is a string in the form of an assignment
+          statement or 'declare' command that, if evaluated, will
+          recreate PARAMETER with its attributes and value.
+     'K'
+          Produces a possibly-quoted version of the value of PARAMETER,
+          except that it prints the values of indexed and associative
+          arrays as a sequence of quoted key-value pairs (*note
+          Arrays::).
+     'a'
+          The expansion is a string consisting of flag values
+          representing PARAMETER's attributes.
+     'k'
+          Like the 'K' transformation, but expands the keys and values
+          of indexed and associative arrays to separate words after word
+          splitting.
+
+     If PARAMETER is '@' or '*', the operation is applied to each
+     positional parameter in turn, and the expansion is the resultant
+     list.  If PARAMETER is an array variable subscripted with '@' or
+     '*', the operation is applied to each member of the array in turn,
+     and the expansion is the resultant list.
+
+     The result of the expansion is subject to word splitting and
+     filename expansion as described below.
+
+
+File: bashref.info,  Node: Command Substitution,  Next: Arithmetic Expansion,  Prev: Shell Parameter Expansion,  Up: Shell Expansions
+
+3.5.4 Command Substitution
+--------------------------
+
+Command substitution allows the output of a command to replace the
+command itself.  Command substitution occurs when a command is enclosed
+as follows:
+     $(COMMAND)
+or
+     `COMMAND`
+
+Bash performs the expansion by executing COMMAND 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 '$(cat FILE)' can be replaced by the equivalent
+but faster '$(< FILE)'.
+
+   When the old-style backquote form of substitution is used, backslash
+retains its literal meaning except when followed by '$', '`', or '\'.
+The first backquote not preceded by a backslash terminates the command
+substitution.  When using the '$(COMMAND)' form, all characters between
+the parentheses make up the command; none are treated specially.
+
+   Command substitutions may be nested.  To nest when using the
+backquoted form, escape the inner backquotes with backslashes.
+
+   If the substitution appears within double quotes, word splitting and
+filename expansion are not performed on the results.
+
+
+File: bashref.info,  Node: Arithmetic Expansion,  Next: Process Substitution,  Prev: Command Substitution,  Up: Shell Expansions
+
+3.5.5 Arithmetic Expansion
+--------------------------
+
+Arithmetic expansion allows the evaluation of an arithmetic expression
+and the substitution of the result.  The format for arithmetic expansion
+is:
+
+     $(( EXPRESSION ))
+
+   The EXPRESSION undergoes the same expansions as if it were within
+double quotes, but double quote characters in EXPRESSION are not treated
+specially and are removed.  All tokens in the expression undergo
+parameter and variable expansion, command substitution, and quote
+removal.  The result is treated as the arithmetic expression to be
+evaluated.  Arithmetic expansions may be nested.
+
+   The evaluation is performed according to the rules listed below
+(*note Shell Arithmetic::).  If the expression is invalid, Bash prints a
+message indicating failure to the standard error and no substitution
+occurs.
+
+
+File: bashref.info,  Node: Process Substitution,  Next: Word Splitting,  Prev: Arithmetic Expansion,  Up: Shell Expansions
+
+3.5.6 Process Substitution
+--------------------------
+
+Process substitution allows a process's input or output to be referred
+to using a filename.  It takes the form of
+     <(LIST)
+or
+     >(LIST)
+The process LIST 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 '>(LIST)' form is used,
+writing to the file will provide input for LIST.  If the '<(LIST)' form
+is used, the file passed as an argument should be read to obtain the
+output of LIST.  Note that no space may appear between the '<' or '>'
+and the left parenthesis, otherwise the construct would be interpreted
+as a redirection.  Process substitution is supported on systems that
+support named pipes (FIFOs) or the '/dev/fd' method of naming open
+files.
+
+   When available, process substitution is performed simultaneously with
+parameter and variable expansion, command substitution, and arithmetic
+expansion.
+
+
+File: bashref.info,  Node: Word Splitting,  Next: Filename Expansion,  Prev: Process Substitution,  Up: Shell Expansions
+
+3.5.7 Word Splitting
+--------------------
+
+The shell scans the results of parameter expansion, command
+substitution, and arithmetic expansion that did not occur within double
+quotes for word splitting.
+
+   The shell treats each character of '$IFS' as a delimiter, and splits
+the results of the other expansions into words using these characters as
+field terminators.  If 'IFS' is unset, or its value is exactly
+'<space><tab><newline>', the default, then sequences of ' <space>',
+'<tab>', and '<newline>' at the beginning and end of the results of the
+previous expansions are ignored, and any sequence of 'IFS' characters
+not at the beginning or end serves to delimit words.  If 'IFS' has a
+value other than the default, then sequences of the whitespace
+characters 'space', 'tab', and 'newline' are ignored at the beginning
+and end of the word, as long as the whitespace character is in the value
+of 'IFS' (an 'IFS' whitespace character).  Any character in 'IFS' that
+is not 'IFS' whitespace, along with any adjacent 'IFS' whitespace
+characters, delimits a field.  A sequence of 'IFS' whitespace characters
+is also treated as a delimiter.  If the value of 'IFS' is null, no word
+splitting occurs.
+
+   Explicit null arguments ('""' or '''') 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
+'-d''' becomes '-d' after word splitting and null argument removal.
+
+   Note that if no expansion occurs, no splitting is performed.
+
+
+File: bashref.info,  Node: Filename Expansion,  Next: Quote Removal,  Prev: Word Splitting,  Up: Shell Expansions
+
+3.5.8 Filename Expansion
+------------------------
+
+* Menu:
+
+* Pattern Matching::	How the shell matches patterns.
+
+After word splitting, unless the '-f' option has been set (*note The Set
+Builtin::), Bash scans each word for the characters '*', '?', and '['.
+If one of these characters appears, and is not quoted, then the word is
+regarded as a PATTERN, and replaced with an alphabetically sorted list
+of filenames matching the pattern (*note Pattern Matching::).  If no
+matching filenames are found, and the shell option 'nullglob' is
+disabled, the word is left unchanged.  If the 'nullglob' option is set,
+and no matches are found, the word is removed.  If the 'failglob' shell
+option is set, and no matches are found, an error message is printed and
+the command is not executed.  If the shell option 'nocaseglob' is
+enabled, the match is performed without regard to the case of alphabetic
+characters.
+
+   When a pattern is used for filename expansion, the character '.' at
+the start of a filename or immediately following a slash must be matched
+explicitly, unless the shell option 'dotglob' is set.  In order to match
+the filenames '.' and '..', the pattern must begin with '.' (for
+example, '.?'), even if 'dotglob' is set.  If the 'globskipdots' shell
+option is enabled, the filenames '.' and '..' are never matched, even if
+the pattern begins with a '.'.  When not matching filenames, the '.'
+character is not treated specially.
+
+   When matching a filename, 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 (*note
+Pattern Matching::).
+
+   See the description of 'shopt' in *note The Shopt Builtin::, for a
+description of the 'nocaseglob', 'nullglob', 'globskipdots', 'failglob',
+and 'dotglob' options.
+
+   The 'GLOBIGNORE' shell variable may be used to restrict the set of
+file names matching a pattern.  If 'GLOBIGNORE' is set, each matching
+file name that also matches one of the patterns in 'GLOBIGNORE' is
+removed from the list of matches.  If the 'nocaseglob' option is set,
+the matching against the patterns in 'GLOBIGNORE' is performed without
+regard to case.  The filenames '.' and '..' are always ignored when
+'GLOBIGNORE' is set and not null.  However, setting 'GLOBIGNORE' to a
+non-null value has the effect of enabling the 'dotglob' shell option, so
+all other filenames beginning with a '.' will match.  To get the old
+behavior of ignoring filenames beginning with a '.', make '.*' one of
+the patterns in 'GLOBIGNORE'.  The 'dotglob' option is disabled when
+'GLOBIGNORE' is unset.
+
+
+File: bashref.info,  Node: Pattern Matching,  Up: Filename Expansion
+
+3.5.8.1 Pattern Matching
+........................
+
+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.
+
+   The special pattern characters have the following meanings:
+'*'
+     Matches any string, including the null string.  When the 'globstar'
+     shell option is enabled, and '*' is used in a filename expansion
+     context, two adjacent '*'s used as a single pattern will match all
+     files and zero or more directories and subdirectories.  If followed
+     by a '/', two adjacent '*'s will match only directories and
+     subdirectories.
+'?'
+     Matches any single character.
+'[...]'
+     Matches any one of the enclosed characters.  A pair of characters
+     separated by a hyphen denotes a RANGE EXPRESSION; 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 '[' is a '!' or a '^' then any
+     character not enclosed is matched.  A '-' may be matched by
+     including it as the first or last character in the set.  A ']' may
+     be matched by including it as the first character in the set.  The
+     sorting order of characters in range expressions, and the
+     characters included in the range, are determined by the current
+     locale and the values of the 'LC_COLLATE' and 'LC_ALL' shell
+     variables, if set.
+
+     For example, in the default C locale, '[a-dx-z]' is equivalent to
+     '[abcdxyz]'.  Many locales sort characters in dictionary order, and
+     in these locales '[a-dx-z]' is typically not equivalent to
+     '[abcdxyz]'; it might be equivalent to '[aBbCcDdxYyZz]', for
+     example.  To obtain the traditional interpretation of ranges in
+     bracket expressions, you can force the use of the C locale by
+     setting the 'LC_COLLATE' or 'LC_ALL' environment variable to the
+     value 'C', or enable the 'globasciiranges' shell option.
+
+     Within '[' and ']', "character classes" can be specified using the
+     syntax '[:'CLASS':]', where CLASS is one of the following classes
+     defined in the POSIX standard:
+          alnum   alpha   ascii   blank   cntrl   digit   graph   lower
+          print   punct   space   upper   word    xdigit
+     A character class matches any character belonging to that class.
+     The 'word' character class matches letters, digits, and the
+     character '_'.
+
+     Within '[' and ']', an "equivalence class" can be specified using
+     the syntax '[='C'=]', which matches all characters with the same
+     collation weight (as defined by the current locale) as the
+     character C.
+
+     Within '[' and ']', the syntax '[.'SYMBOL'.]' matches the collating
+     symbol SYMBOL.
+
+   If the 'extglob' shell option is enabled using the 'shopt' builtin,
+the shell recognizes several extended pattern matching operators.  In
+the following description, a PATTERN-LIST is a list of one or more
+patterns separated by a '|'.  When matching filenames, the 'dotglob'
+shell option determines the set of filenames that are tested, as
+described above.  Composite patterns may be formed using one or more of
+the following sub-patterns:
+
+'?(PATTERN-LIST)'
+     Matches zero or one occurrence of the given patterns.
+
+'*(PATTERN-LIST)'
+     Matches zero or more occurrences of the given patterns.
+
+'+(PATTERN-LIST)'
+     Matches one or more occurrences of the given patterns.
+
+'@(PATTERN-LIST)'
+     Matches one of the given patterns.
+
+'!(PATTERN-LIST)'
+     Matches anything except one of the given patterns.
+
+   The 'extglob' option changes the behavior of the parser, since the
+parentheses are normally treated as operators with syntactic meaning.
+To ensure that extended matching patterns are parsed correctly, make
+sure that 'extglob' is enabled before parsing constructs containing the
+patterns, including shell functions and command substitutions.
+
+   When matching filenames, the 'dotglob' shell option determines the
+set of filenames that are tested: when 'dotglob' is enabled, the set of
+filenames includes all files beginning with '.', but the filenames '.'
+and '..' must be matched by a pattern or sub-pattern that begins with a
+dot; when it is disabled, the set does not include any filenames
+beginning with "."  unless the pattern or sub-pattern begins with a '.'.
+As above, '.' only has a special meaning when matching filenames.
+
+   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.
+
+
+File: bashref.info,  Node: Quote Removal,  Prev: Filename Expansion,  Up: Shell Expansions
+
+3.5.9 Quote Removal
+-------------------
+
+After the preceding expansions, all unquoted occurrences of the
+characters '\', ''', and '"' that did not result from one of the above
+expansions are removed.
+
+
+File: bashref.info,  Node: Redirections,  Next: Executing Commands,  Prev: Shell Expansions,  Up: Basic Shell Features
+
+3.6 Redirections
+================
+
+Before a command is executed, its input and output may be "redirected"
+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 simple command or may
+follow a command.  Redirections are processed in the order they appear,
+from left to right.
+
+   Each redirection that may be preceded by a file descriptor number may
+instead be preceded by a word of the form {VARNAME}.  In this case, for
+each redirection operator except >&- and <&-, the shell will allocate a
+file descriptor greater than 10 and assign it to {VARNAME}.  If >&- or
+<&- is preceded by {VARNAME}, the value of VARNAME defines the file
+descriptor to close.  If {VARNAME} is supplied, the redirection persists
+beyond the scope of the command, allowing the shell programmer to manage
+the file descriptor's lifetime manually.  The 'varredir_close' shell
+option manages this behavior (*note The Shopt Builtin::).
+
+   In the following descriptions, if the file descriptor number is
+omitted, and the first character of the redirection operator is '<', the
+redirection refers to the standard input (file descriptor 0).  If the
+first character of the redirection operator is '>', the redirection
+refers to the standard output (file descriptor 1).
+
+   The word following the redirection operator in the following
+descriptions, unless otherwise noted, is subjected to brace expansion,
+tilde expansion, parameter expansion, command substitution, arithmetic
+expansion, quote removal, filename expansion, and word splitting.  If it
+expands to more than one word, Bash reports an error.
+
+   Note that the order of redirections is significant.  For example, the
+command
+     ls > DIRLIST 2>&1
+directs both standard output (file descriptor 1) and standard error
+(file descriptor 2) to the file DIRLIST, while the command
+     ls 2>&1 > DIRLIST
+directs only the standard output to file DIRLIST, because the standard
+error was made a copy of the standard output before the standard output
+was redirected to DIRLIST.
+
+   Bash handles several filenames specially when they are used in
+redirections, as described in the following table.  If the operating
+system on which Bash is running provides these special files, bash will
+use them; otherwise it will emulate them internally with the behavior
+described below.
+
+'/dev/fd/FD'
+     If FD is a valid integer, file descriptor FD is duplicated.
+
+'/dev/stdin'
+     File descriptor 0 is duplicated.
+
+'/dev/stdout'
+     File descriptor 1 is duplicated.
+
+'/dev/stderr'
+     File descriptor 2 is duplicated.
+
+'/dev/tcp/HOST/PORT'
+     If HOST is a valid hostname or Internet address, and PORT is an
+     integer port number or service name, Bash attempts to open the
+     corresponding TCP socket.
+
+'/dev/udp/HOST/PORT'
+     If HOST is a valid hostname or Internet address, and PORT is an
+     integer port number or service name, Bash attempts to open the
+     corresponding UDP socket.
+
+   A failure to open or create a file causes the redirection to fail.
+
+   Redirections using file descriptors greater than 9 should be used
+with care, as they may conflict with file descriptors the shell uses
+internally.
+
+3.6.1 Redirecting Input
+-----------------------
+
+Redirection of input causes the file whose name results from the
+expansion of WORD to be opened for reading on file descriptor 'n', or
+the standard input (file descriptor 0) if 'n' is not specified.
+
+   The general format for redirecting input is:
+     [N]<WORD
+
+3.6.2 Redirecting Output
+------------------------
+
+Redirection of output causes the file whose name results from the
+expansion of WORD to be opened for writing on file descriptor N, or the
+standard output (file descriptor 1) if N is not specified.  If the file
+does not exist it is created; if it does exist it is truncated to zero
+size.
+
+   The general format for redirecting output is:
+     [N]>[|]WORD
+
+   If the redirection operator is '>', and the 'noclobber' option to the
+'set' builtin has been enabled, the redirection will fail if the file
+whose name results from the expansion of WORD exists and is a regular
+file.  If the redirection operator is '>|', or the redirection operator
+is '>' and the 'noclobber' option is not enabled, the redirection is
+attempted even if the file named by WORD exists.
+
+3.6.3 Appending Redirected Output
+---------------------------------
+
+Redirection of output in this fashion causes the file whose name results
+from the expansion of WORD to be opened for appending on file descriptor
+N, or the standard output (file descriptor 1) if N is not specified.  If
+the file does not exist it is created.
+
+   The general format for appending output is:
+     [N]>>WORD
+
+3.6.4 Redirecting Standard Output and Standard Error
+----------------------------------------------------
+
+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 WORD.
+
+   There are two formats for redirecting standard output and standard
+error:
+     &>WORD
+and
+     >&WORD
+Of the two forms, the first is preferred.  This is semantically
+equivalent to
+     >WORD 2>&1
+   When using the second form, WORD may not expand to a number or '-'.
+If it does, other redirection operators apply (see Duplicating File
+Descriptors below) for compatibility reasons.
+
+3.6.5 Appending Standard Output and Standard Error
+--------------------------------------------------
+
+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 WORD.
+
+   The format for appending standard output and standard error is:
+     &>>WORD
+This is semantically equivalent to
+     >>WORD 2>&1
+   (see Duplicating File Descriptors below).
+
+3.6.6 Here Documents
+--------------------
+
+This type of redirection instructs the shell to read input from the
+current source until a line containing only WORD (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 N if N is specified) for a
+command.
+
+   The format of here-documents is:
+     [N]<<[-]WORD
+             HERE-DOCUMENT
+     DELIMITER
+
+   No parameter and variable expansion, command substitution, arithmetic
+expansion, or filename expansion is performed on WORD.  If any part of
+WORD is quoted, the DELIMITER is the result of quote removal on WORD,
+and the lines in the here-document are not expanded.  If WORD is
+unquoted, all lines of the here-document are subjected to parameter
+expansion, command substitution, and arithmetic expansion, the character
+sequence '\newline' is ignored, and '\' must be used to quote the
+characters '\', '$', and '`'.
+
+   If the redirection operator is '<<-', then all leading tab characters
+are stripped from input lines and the line containing DELIMITER.  This
+allows here-documents within shell scripts to be indented in a natural
+fashion.
+
+3.6.7 Here Strings
+------------------
+
+A variant of here documents, the format is:
+     [N]<<< WORD
+
+   The WORD undergoes tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal.  Filename
+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 N if N is specified).
+
+3.6.8 Duplicating File Descriptors
+----------------------------------
+
+The redirection operator
+     [N]<&WORD
+is used to duplicate input file descriptors.  If WORD expands to one or
+more digits, the file descriptor denoted by N is made to be a copy of
+that file descriptor.  If the digits in WORD do not specify a file
+descriptor open for input, a redirection error occurs.  If WORD
+evaluates to '-', file descriptor N is closed.  If N is not specified,
+the standard input (file descriptor 0) is used.
+
+   The operator
+     [N]>&WORD
+is used similarly to duplicate output file descriptors.  If N is not
+specified, the standard output (file descriptor 1) is used.  If the
+digits in WORD do not specify a file descriptor open for output, a
+redirection error occurs.  If WORD evaluates to '-', file descriptor N
+is closed.  As a special case, if N is omitted, and WORD does not expand
+to one or more digits or '-', the standard output and standard error are
+redirected as described previously.
+
+3.6.9 Moving File Descriptors
+-----------------------------
+
+The redirection operator
+     [N]<&DIGIT-
+moves the file descriptor DIGIT to file descriptor N, or the standard
+input (file descriptor 0) if N is not specified.  DIGIT is closed after
+being duplicated to N.
+
+   Similarly, the redirection operator
+     [N]>&DIGIT-
+moves the file descriptor DIGIT to file descriptor N, or the standard
+output (file descriptor 1) if N is not specified.
+
+3.6.10 Opening File Descriptors for Reading and Writing
+-------------------------------------------------------
+
+The redirection operator
+     [N]<>WORD
+causes the file whose name is the expansion of WORD to be opened for
+both reading and writing on file descriptor N, or on file descriptor 0
+if N is not specified.  If the file does not exist, it is created.
+
+
+File: bashref.info,  Node: Executing Commands,  Next: Shell Scripts,  Prev: Redirections,  Up: Basic Shell Features
+
+3.7 Executing Commands
+======================
+
+* Menu:
+
+* Simple Command Expansion::	How Bash expands simple commands before
+				executing them.
+* Command Search and Execution::	How Bash finds commands and runs them.
+* Command Execution Environment::	The environment in which Bash
+					executes commands that are not
+					shell builtins.
+* Environment::		The environment given to a command.
+* Exit Status::		The status returned by commands and how Bash
+			interprets it.
+* Signals::		What happens when Bash or a command it runs
+			receives a signal.
+
+
+File: bashref.info,  Node: Simple Command Expansion,  Next: Command Search and Execution,  Up: Executing Commands
+
+3.7.1 Simple Command Expansion
+------------------------------
+
+When a simple command is executed, the shell performs the following
+expansions, assignments, and redirections, from left to right, in the
+following order.
+
+  1. The words that the parser has marked as variable assignments (those
+     preceding the command name) and redirections are saved for later
+     processing.
+
+  2. The words that are not variable assignments or redirections are
+     expanded (*note Shell Expansions::).  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.
+
+  3. Redirections are performed as described above (*note
+     Redirections::).
+
+  4. The text after the '=' in each variable assignment undergoes tilde
+     expansion, parameter expansion, command substitution, arithmetic
+     expansion, and quote removal before being assigned to the variable.
+
+   If no command name results, the variable assignments affect the
+current shell environment.  In the case of such a command (one that
+consists only of assignment statements and redirections), assignment
+statements are performed before redirections.  Otherwise, the variables
+are added to the environment of the executed command and do not affect
+the current shell environment.  If any of the assignments attempts to
+assign a value to a readonly variable, an error occurs, and the command
+exits with a non-zero status.
+
+   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.
+
+   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.
+
+
+File: bashref.info,  Node: Command Search and Execution,  Next: Command Execution Environment,  Prev: Simple Command Expansion,  Up: Executing Commands
+
+3.7.2 Command Search and Execution
+----------------------------------
+
+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.
+
+  1. 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 in *note Shell Functions::.
+
+  2. 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.
+
+  3. If the name is neither a shell function nor a builtin, and contains
+     no slashes, Bash searches each element of '$PATH' for a directory
+     containing an executable file by that name.  Bash uses a hash table
+     to remember the full pathnames of executable files to avoid
+     multiple 'PATH' searches (see the description of 'hash' in *note
+     Bourne Shell Builtins::).  A full search of the directories in
+     '$PATH' 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 'command_not_found_handle'.  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.
+
+  4. 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
+     supplied, if any.
+
+  5. 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
+     "shell script" and the shell executes it as described in *note
+     Shell Scripts::.
+
+  6. If the command was not begun asynchronously, the shell waits for
+     the command to complete and collects its exit status.
+
+
+File: bashref.info,  Node: Command Execution Environment,  Next: Environment,  Prev: Command Search and Execution,  Up: Executing Commands
+
+3.7.3 Command Execution Environment
+-----------------------------------
+
+The shell has an "execution environment", which consists of the
+following:
+
+   * open files inherited by the shell at invocation, as modified by
+     redirections supplied to the 'exec' builtin
+
+   * the current working directory as set by 'cd', 'pushd', or 'popd',
+     or inherited by the shell at invocation
+
+   * the file creation mode mask as set by 'umask' or inherited from the
+     shell's parent
+
+   * current traps set by 'trap'
+
+   * shell parameters that are set by variable assignment or with 'set'
+     or inherited from the shell's parent in the environment
+
+   * shell functions defined during execution or inherited from the
+     shell's parent in the environment
+
+   * options enabled at invocation (either by default or with
+     command-line arguments) or by 'set'
+
+   * options enabled by 'shopt' (*note The Shopt Builtin::)
+
+   * shell aliases defined with 'alias' (*note Aliases::)
+
+   * various process IDs, including those of background jobs (*note
+     Lists::), the value of '$$', and the value of '$PPID'
+
+   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.
+
+   * the shell's open files, plus any modifications and additions
+     specified by redirections to the command
+
+   * the current working directory
+
+   * the file creation mode mask
+
+   * shell variables and functions marked for export, along with
+     variables exported for the command, passed in the environment
+     (*note Environment::)
+
+   * traps caught by the shell are reset to the values inherited from
+     the shell's parent, and traps ignored by the shell are ignored
+
+   A command invoked in this separate environment cannot affect the
+shell's execution environment.
+
+   A "subshell" is a copy of the shell process.
+
+   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.
+
+   Subshells spawned to execute command substitutions inherit the value
+of the '-e' option from the parent shell.  When not in POSIX mode, Bash
+clears the '-e' option in such subshells.
+
+   If a command is followed by a '&' and job control is not active, the
+default standard input for the command is the empty file '/dev/null'.
+Otherwise, the invoked command inherits the file descriptors of the
+calling shell as modified by redirections.
+
+
+File: bashref.info,  Node: Environment,  Next: Exit Status,  Prev: Command Execution Environment,  Up: Executing Commands
+
+3.7.4 Environment
+-----------------
+
+When a program is invoked it is given an array of strings called the
+"environment".  This is a list of name-value pairs, of the form
+'name=value'.
+
+   Bash 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 'export' to child
+processes.  Executed commands inherit the environment.  The 'export' and
+'declare -x' 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 'unset' and 'export
+-n' commands, plus any additions via the 'export' and 'declare -x'
+commands.
+
+   The environment for any simple command or function may be augmented
+temporarily by prefixing it with parameter assignments, as described in
+*note Shell Parameters::.  These assignment statements affect only the
+environment seen by that command.
+
+   If the '-k' option is set (*note The Set Builtin::), then all
+parameter assignments are placed in the environment for a command, not
+just those that precede the command name.
+
+   When Bash invokes an external command, the variable '$_' is set to
+the full pathname of the command and passed to that command in its
+environment.
+
+
+File: bashref.info,  Node: Exit Status,  Next: Signals,  Prev: Environment,  Up: Executing Commands
+
+3.7.5 Exit Status
+-----------------
+
+The exit status of an executed command is the value returned by the
+'waitpid' 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.
+
+   For the shell's purposes, a command which exits with a zero exit
+status has succeeded.  A non-zero exit status indicates failure.  This
+seemingly counter-intuitive scheme is used so there is one well-defined
+way to indicate success and a variety of ways to indicate various
+failure modes.  When a command terminates on a fatal signal whose number
+is N, Bash uses the value 128+N as the exit status.
+
+   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.
+
+   If a command fails because of an error during expansion or
+redirection, the exit status is greater than zero.
+
+   The exit status is used by the Bash conditional commands (*note
+Conditional Constructs::) and some of the list constructs (*note
+Lists::).
+
+   All of the Bash builtins return an exit status of zero if they
+succeed and a non-zero status on failure, so they may be used by the
+conditional and list constructs.  All builtins return an exit status of
+2 to indicate incorrect usage, generally invalid options or missing
+arguments.
+
+   The exit status of the last command is available in the special
+parameter $?  (*note Special Parameters::).
+
+
+File: bashref.info,  Node: Signals,  Prev: Exit Status,  Up: Executing Commands
+
+3.7.6 Signals
+-------------
+
+When Bash is interactive, in the absence of any traps, it ignores
+'SIGTERM' (so that 'kill 0' does not kill an interactive shell), and
+'SIGINT' is caught and handled (so that the 'wait' builtin is
+interruptible).  When Bash receives a 'SIGINT', it breaks out of any
+executing loops.  In all cases, Bash ignores 'SIGQUIT'.  If job control
+is in effect (*note Job Control::), Bash ignores 'SIGTTIN', 'SIGTTOU',
+and 'SIGTSTP'.
+
+   Non-builtin commands started by Bash have signal handlers set to the
+values inherited by the shell from its parent.  When job control is not
+in effect, asynchronous commands ignore 'SIGINT' and 'SIGQUIT' in
+addition to these inherited handlers.  Commands run as a result of
+command substitution ignore the keyboard-generated job control signals
+'SIGTTIN', 'SIGTTOU', and 'SIGTSTP'.
+
+   The shell exits by default upon receipt of a 'SIGHUP'.  Before
+exiting, an interactive shell resends the 'SIGHUP' to all jobs, running
+or stopped.  Stopped jobs are sent 'SIGCONT' to ensure that they receive
+the 'SIGHUP'.  To prevent the shell from sending the 'SIGHUP' signal to
+a particular job, it should be removed from the jobs table with the
+'disown' builtin (*note Job Control Builtins::) or marked to not receive
+'SIGHUP' using 'disown -h'.
+
+   If the 'huponexit' shell option has been set with 'shopt' (*note The
+Shopt Builtin::), Bash sends a 'SIGHUP' to all jobs when an interactive
+login shell exits.
+
+   If Bash 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 Bash is waiting for an asynchronous command via
+the 'wait' builtin, the reception of a signal for which a trap has been
+set will cause the 'wait' builtin to return immediately with an exit
+status greater than 128, immediately after which the trap is executed.
+
+   When job control is not enabled, and Bash is waiting for a foreground
+command to complete, the shell receives keyboard-generated signals such
+as 'SIGINT' (usually generated by '^C') that users commonly intend to
+send to that command.  This happens because the shell and the command
+are in the same process group as the terminal, and '^C' sends 'SIGINT'
+to all processes in that process group.  See *note Job Control::, for a
+more in-depth discussion of process groups.
+
+   When Bash is running without job control enabled and receives
+'SIGINT' while waiting for a foreground command, it waits until that
+foreground command terminates and then decides what to do about the
+'SIGINT':
+
+  1. If the command terminates due to the 'SIGINT', Bash concludes that
+     the user meant to end the entire script, and acts on the 'SIGINT'
+     (e.g., by running a 'SIGINT' trap or exiting itself);
+
+  2. If the pipeline does not terminate due to 'SIGINT', the program
+     handled the 'SIGINT' itself and did not treat it as a fatal signal.
+     In that case, Bash does not treat 'SIGINT' as a fatal signal,
+     either, instead assuming that the 'SIGINT' was used as part of the
+     program's normal operation (e.g., 'emacs' uses it to abort editing
+     commands) or deliberately discarded.  However, Bash will run any
+     trap set on 'SIGINT', as it does with any other trapped signal it
+     receives while it is waiting for the foreground command to
+     complete, for compatibility.
+
+
+File: bashref.info,  Node: Shell Scripts,  Prev: Executing Commands,  Up: Basic Shell Features
+
+3.8 Shell Scripts
+=================
+
+A shell script is a text file containing shell commands.  When such a
+file is used as the first non-option argument when invoking Bash, and
+neither the '-c' nor '-s' option is supplied (*note Invoking Bash::),
+Bash reads and executes commands from the file, then exits.  This mode
+of operation creates a non-interactive shell.  The shell first searches
+for the file in the current directory, and looks in the directories in
+'$PATH' if not found there.
+
+   When Bash runs a shell script, it sets the special parameter '0' to
+the name of the file, rather than the name of the shell, and the
+positional parameters are set to the remaining arguments, if any are
+given.  If no additional arguments are supplied, the positional
+parameters are unset.
+
+   A shell script may be made executable by using the 'chmod' command to
+turn on the execute bit.  When Bash finds such a file while searching
+the '$PATH' for a command, it creates a new instance of itself to
+execute it.  In other words, executing
+     filename ARGUMENTS
+is equivalent to executing
+     bash filename ARGUMENTS
+
+if 'filename' is an executable shell script.  This subshell
+reinitializes itself, so that the effect is as if a new shell had been
+invoked to interpret the script, with the exception that the locations
+of commands remembered by the parent (see the description of 'hash' in
+*note Bourne Shell Builtins::) are retained by the child.
+
+   Most versions of Unix make this a part of the operating system's
+command execution mechanism.  If the first line of a script begins with
+the two characters '#!', the remainder of the line specifies an
+interpreter for the program and, depending on the operating system, one
+or more optional arguments for that interpreter.  Thus, you can specify
+Bash, 'awk', Perl, or some other interpreter and write the rest of the
+script file in that language.
+
+   The arguments to the interpreter consist of one or more optional
+arguments following the interpreter name on the first line of the script
+file, followed by the name of the script file, followed by the rest of
+the arguments supplied to the script.  The details of how the
+interpreter line is split into an interpreter name and a set of
+arguments vary across systems.  Bash will perform this action on
+operating systems that do not handle it themselves.  Note that some
+older versions of Unix limit the interpreter name and a single argument
+to a maximum of 32 characters, so it's not portable to assume that using
+more than one argument will work.
+
+   Bash scripts often begin with '#! /bin/bash' (assuming that Bash has
+been installed in '/bin'), since this ensures that Bash will be used to
+interpret the script, even if it is executed under another shell.  It's
+a common idiom to use 'env' to find 'bash' even if it's been installed
+in another directory: '#!/usr/bin/env bash' will find the first
+occurrence of 'bash' in '$PATH'.
+
+
+File: bashref.info,  Node: Shell Builtin Commands,  Next: Shell Variables,  Prev: Basic Shell Features,  Up: Top
+
+4 Shell Builtin Commands
+************************
+
+* Menu:
+
+* Bourne Shell Builtins::	Builtin commands inherited from the Bourne
+				Shell.
+* Bash Builtins::		Table of builtins specific to Bash.
+* Modifying Shell Behavior::	Builtins to modify shell attributes and
+				optional behavior.
+* Special Builtins::		Builtin commands classified specially by
+				POSIX.
+
+Builtin commands are contained within the shell itself.  When the name
+of a builtin command is used as the first word of a simple command
+(*note Simple Commands::), the shell executes the command directly,
+without invoking another program.  Builtin commands are necessary to
+implement functionality impossible or inconvenient to obtain with
+separate utilities.
+
+   This section briefly describes the builtins which Bash inherits from
+the Bourne Shell, as well as the builtin commands which are unique to or
+have been extended in Bash.
+
+   Several builtin commands are described in other chapters: builtin
+commands which provide the Bash interface to the job control facilities
+(*note Job Control Builtins::), the directory stack (*note Directory
+Stack Builtins::), the command history (*note Bash History Builtins::),
+and the programmable completion facilities (*note Programmable
+Completion Builtins::).
+
+   Many of the builtins have been extended by POSIX or Bash.
+
+   Unless otherwise noted, each builtin command documented as accepting
+options preceded by '-' accepts '--' to signify the end of the options.
+The ':', 'true', 'false', and 'test'/'[' builtins do not accept options
+and do not treat '--' specially.  The 'exit', 'logout', 'return',
+'break', 'continue', 'let', and 'shift' builtins accept and process
+arguments beginning with '-' without requiring '--'.  Other builtins
+that accept arguments but are not specified as accepting options
+interpret arguments beginning with '-' as invalid options and require
+'--' to prevent this interpretation.
+
+
+File: bashref.info,  Node: Bourne Shell Builtins,  Next: Bash Builtins,  Up: Shell Builtin Commands
+
+4.1 Bourne Shell Builtins
+=========================
+
+The following shell builtin commands are inherited from the Bourne
+Shell.  These commands are implemented as specified by the POSIX
+standard.
+
+': (a colon)'
+          : [ARGUMENTS]
+
+     Do nothing beyond expanding ARGUMENTS and performing redirections.
+     The return status is zero.
+
+'. (a period)'
+          . FILENAME [ARGUMENTS]
+
+     Read and execute commands from the FILENAME argument in the current
+     shell context.  If FILENAME does not contain a slash, the 'PATH'
+     variable is used to find FILENAME, but FILENAME does not need to be
+     executable.  When Bash is not in POSIX mode, it searches the
+     current directory if FILENAME is not found in '$PATH'.  If any
+     ARGUMENTS are supplied, they become the positional parameters when
+     FILENAME is executed.  Otherwise the positional parameters are
+     unchanged.  If the '-T' option is enabled, '.' inherits any trap on
+     'DEBUG'; if it is not, any 'DEBUG' trap string is saved and
+     restored around the call to '.', and '.' unsets the 'DEBUG' trap
+     while it executes.  If '-T' is not set, and the sourced file
+     changes the 'DEBUG' trap, the new value is retained when '.'
+     completes.  The return status is the exit status of the last
+     command executed, or zero if no commands are executed.  If FILENAME
+     is not found, or cannot be read, the return status is non-zero.
+     This builtin is equivalent to 'source'.
+
+'break'
+          break [N]
+
+     Exit from a 'for', 'while', 'until', or 'select' loop.  If N is
+     supplied, the Nth enclosing loop is exited.  N must be greater than
+     or equal to 1.  The return status is zero unless N is not greater
+     than or equal to 1.
+
+'cd'
+          cd [-L|[-P [-e]] [-@] [DIRECTORY]
+
+     Change the current working directory to DIRECTORY.  If DIRECTORY is
+     not supplied, the value of the 'HOME' shell variable is used.  If
+     the shell variable 'CDPATH' exists, it is used as a search path:
+     each directory name in 'CDPATH' is searched for DIRECTORY, with
+     alternative directory names in 'CDPATH' separated by a colon (':').
+     If DIRECTORY begins with a slash, 'CDPATH' is not used.
+
+     The '-P' option means to not follow symbolic links: symbolic links
+     are resolved while 'cd' is traversing DIRECTORY and before
+     processing an instance of '..' in DIRECTORY.
+
+     By default, or when the '-L' option is supplied, symbolic links in
+     DIRECTORY are resolved after 'cd' processes an instance of '..' in
+     DIRECTORY.
+
+     If '..' appears in DIRECTORY, it is processed by removing the
+     immediately preceding pathname component, back to a slash or the
+     beginning of DIRECTORY.
+
+     If the '-e' option is supplied with '-P' and the current working
+     directory cannot be successfully determined after a successful
+     directory change, 'cd' will return an unsuccessful status.
+
+     On systems that support it, the '-@' option presents the extended
+     attributes associated with a file as a directory.
+
+     If DIRECTORY is '-', it is converted to '$OLDPWD' before the
+     directory change is attempted.
+
+     If a non-empty directory name from 'CDPATH' is used, or if '-' is
+     the first argument, and the directory change is successful, the
+     absolute pathname of the new working directory is written to the
+     standard output.
+
+     If the directory change is successful, 'cd' sets the value of the
+     'PWD' environment variable to the new directory name, and sets the
+     'OLDPWD' environment variable to the value of the current working
+     directory before the change.
+
+     The return status is zero if the directory is successfully changed,
+     non-zero otherwise.
+
+'continue'
+          continue [N]
+
+     Resume the next iteration of an enclosing 'for', 'while', 'until',
+     or 'select' loop.  If N is supplied, the execution of the Nth
+     enclosing loop is resumed.  N must be greater than or equal to 1.
+     The return status is zero unless N is not greater than or equal to
+     1.
+
+'eval'
+          eval [ARGUMENTS]
+
+     The arguments are concatenated together into a single command,
+     which is then read and executed, and its exit status returned as
+     the exit status of 'eval'.  If there are no arguments or only empty
+     arguments, the return status is zero.
+
+'exec'
+          exec [-cl] [-a NAME] [COMMAND [ARGUMENTS]]
+
+     If COMMAND is supplied, it replaces the shell without creating a
+     new process.  If the '-l' option is supplied, the shell places a
+     dash at the beginning of the zeroth argument passed to COMMAND.
+     This is what the 'login' program does.  The '-c' option causes
+     COMMAND to be executed with an empty environment.  If '-a' is
+     supplied, the shell passes NAME as the zeroth argument to COMMAND.
+     If COMMAND cannot be executed for some reason, a non-interactive
+     shell exits, unless the 'execfail' 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 'exec' fails.  If no COMMAND is specified,
+     redirections may be used to affect the current shell environment.
+     If there are no redirection errors, the return status is zero;
+     otherwise the return status is non-zero.
+
+'exit'
+          exit [N]
+
+     Exit the shell, returning a status of N to the shell's parent.  If
+     N is omitted, the exit status is that of the last command executed.
+     Any trap on 'EXIT' is executed before the shell terminates.
+
+'export'
+          export [-fn] [-p] [NAME[=VALUE]]
+
+     Mark each NAME to be passed to child processes in the environment.
+     If the '-f' option is supplied, the NAMEs refer to shell functions;
+     otherwise the names refer to shell variables.  The '-n' option
+     means to no longer mark each NAME for export.  If no NAMEs are
+     supplied, or if the '-p' option is given, a list of names of all
+     exported variables is displayed.  The '-p' option displays output
+     in a form that may be reused as input.  If a variable name is
+     followed by =VALUE, the value of the variable is set to VALUE.
+
+     The return status is zero unless an invalid option is supplied, one
+     of the names is not a valid shell variable name, or '-f' is
+     supplied with a name that is not a shell function.
+
+'getopts'
+          getopts OPTSTRING NAME [ARG ...]
+
+     'getopts' is used by shell scripts to parse positional parameters.
+     OPTSTRING 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 whitespace.  The
+     colon (':') and question mark ('?') may not be used as option
+     characters.  Each time it is invoked, 'getopts' places the next
+     option in the shell variable NAME, initializing NAME if it does not
+     exist, and the index of the next argument to be processed into the
+     variable 'OPTIND'.  'OPTIND' is initialized to 1 each time the
+     shell or a shell script is invoked.  When an option requires an
+     argument, 'getopts' places that argument into the variable
+     'OPTARG'.  The shell does not reset 'OPTIND' automatically; it must
+     be manually reset between multiple calls to 'getopts' within the
+     same shell invocation if a new set of parameters is to be used.
+
+     When the end of options is encountered, 'getopts' exits with a
+     return value greater than zero.  'OPTIND' is set to the index of
+     the first non-option argument, and NAME is set to '?'.
+
+     'getopts' normally parses the positional parameters, but if more
+     arguments are supplied as ARG values, 'getopts' parses those
+     instead.
+
+     'getopts' can report errors in two ways.  If the first character of
+     OPTSTRING is a colon, SILENT error reporting is used.  In normal
+     operation, diagnostic messages are printed when invalid options or
+     missing option arguments are encountered.  If the variable 'OPTERR'
+     is set to 0, no error messages will be displayed, even if the first
+     character of 'optstring' is not a colon.
+
+     If an invalid option is seen, 'getopts' places '?' into NAME and,
+     if not silent, prints an error message and unsets 'OPTARG'.  If
+     'getopts' is silent, the option character found is placed in
+     'OPTARG' and no diagnostic message is printed.
+
+     If a required argument is not found, and 'getopts' is not silent, a
+     question mark ('?') is placed in NAME, 'OPTARG' is unset, and a
+     diagnostic message is printed.  If 'getopts' is silent, then a
+     colon (':') is placed in NAME and 'OPTARG' is set to the option
+     character found.
+
+'hash'
+          hash [-r] [-p FILENAME] [-dt] [NAME]
+
+     Each time 'hash' is invoked, it remembers the full pathnames of the
+     commands specified as NAME arguments, so they need not be searched
+     for on subsequent invocations.  The commands are found by searching
+     through the directories listed in '$PATH'.  Any
+     previously-remembered pathname is discarded.  The '-p' option
+     inhibits the path search, and FILENAME is used as the location of
+     NAME.  The '-r' option causes the shell to forget all remembered
+     locations.  The '-d' option causes the shell to forget the
+     remembered location of each NAME.  If the '-t' option is supplied,
+     the full pathname to which each NAME corresponds is printed.  If
+     multiple NAME arguments are supplied with '-t', the NAME is printed
+     before the hashed full pathname.  The '-l' option causes output to
+     be displayed in a format that may be reused as input.  If no
+     arguments are given, or if only '-l' is supplied, information about
+     remembered commands is printed.  The return status is zero unless a
+     NAME is not found or an invalid option is supplied.
+
+'pwd'
+          pwd [-LP]
+
+     Print the absolute pathname of the current working directory.  If
+     the '-P' option is supplied, the pathname printed will not contain
+     symbolic links.  If the '-L' option is supplied, the pathname
+     printed may contain symbolic links.  The return status is zero
+     unless an error is encountered while determining the name of the
+     current directory or an invalid option is supplied.
+
+'readonly'
+          readonly [-aAf] [-p] [NAME[=VALUE]] ...
+
+     Mark each NAME as readonly.  The values of these names may not be
+     changed by subsequent assignment.  If the '-f' option is supplied,
+     each NAME refers to a shell function.  The '-a' option means each
+     NAME refers to an indexed array variable; the '-A' option means
+     each NAME refers to an associative array variable.  If both options
+     are supplied, '-A' takes precedence.  If no NAME arguments are
+     given, or if the '-p' 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 '-p' option
+     causes output to be displayed in a format that may be reused as
+     input.  If a variable name is followed by =VALUE, the value of the
+     variable is set to VALUE.  The return status is zero unless an
+     invalid option is supplied, one of the NAME arguments is not a
+     valid shell variable or function name, or the '-f' option is
+     supplied with a name that is not a shell function.
+
+'return'
+          return [N]
+
+     Cause a shell function to stop executing and return the value N to
+     its caller.  If N is not supplied, the return value is the exit
+     status of the last command executed in the function.  If 'return'
+     is executed by a trap handler, the last command used to determine
+     the status is the last command executed before the trap handler.
+     If 'return' is executed during a 'DEBUG' trap, the last command
+     used to determine the status is the last command executed by the
+     trap handler before 'return' was invoked.  'return' may also be
+     used to terminate execution of a script being executed with the '.'
+     ('source') builtin, returning either N or the exit status of the
+     last command executed within the script as the exit status of the
+     script.  If N is supplied, the return value is its least
+     significant 8 bits.  Any command associated with the 'RETURN' trap
+     is executed before execution resumes after the function or script.
+     The return status is non-zero if 'return' is supplied a non-numeric
+     argument or is used outside a function and not during the execution
+     of a script by '.' or 'source'.
+
+'shift'
+          shift [N]
+
+     Shift the positional parameters to the left by N.  The positional
+     parameters from N+1 ... '$#' are renamed to '$1' ... '$#'-N.
+     Parameters represented by the numbers '$#' down to '$#'-N+1 are
+     unset.  N must be a non-negative number less than or equal to '$#'.
+     If N is zero or greater than '$#', the positional parameters are
+     not changed.  If N is not supplied, it is assumed to be 1.  The
+     return status is zero unless N is greater than '$#' or less than
+     zero, non-zero otherwise.
+
+'test'
+'['
+          test EXPR
+
+     Evaluate a conditional expression EXPR and return a status of 0
+     (true) or 1 (false).  Each operator and operand must be a separate
+     argument.  Expressions are composed of the primaries described
+     below in *note Bash Conditional Expressions::.  'test' does not
+     accept any options, nor does it accept and ignore an argument of
+     '--' as signifying the end of options.
+
+     When the '[' form is used, the last argument to the command must be
+     a ']'.
+
+     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.
+
+     '! EXPR'
+          True if EXPR is false.
+
+     '( EXPR )'
+          Returns the value of EXPR.  This may be used to override the
+          normal precedence of operators.
+
+     'EXPR1 -a EXPR2'
+          True if both EXPR1 and EXPR2 are true.
+
+     'EXPR1 -o EXPR2'
+          True if either EXPR1 or EXPR2 is true.
+
+     The 'test' and '[' builtins evaluate conditional expressions using
+     a set of rules based on the number of arguments.
+
+     0 arguments
+          The expression is false.
+
+     1 argument
+          The expression is true if, and only if, the argument is not
+          null.
+
+     2 arguments
+          If the first argument is '!', the expression is true if and
+          only if the second argument is null.  If the first argument is
+          one of the unary conditional operators (*note Bash Conditional
+          Expressions::), the expression is true if the unary test is
+          true.  If the first argument is not a valid unary operator,
+          the expression is false.
+
+     3 arguments
+          The following conditions are applied in the order listed.
+
+            1. If the second argument is one of the binary conditional
+               operators (*note Bash Conditional Expressions::), the
+               result of the expression is the result of the binary test
+               using the first and third arguments as operands.  The
+               '-a' and '-o' operators are considered binary operators
+               when there are three arguments.
+            2. If the first argument is '!', the value is the negation
+               of the two-argument test using the second and third
+               arguments.
+            3. If the first argument is exactly '(' and the third
+               argument is exactly ')', the result is the one-argument
+               test of the second argument.
+            4. Otherwise, the expression is false.
+
+     4 arguments
+          The following conditions are applied in the order listed.
+
+            1. If the first argument is '!', the result is the negation
+               of the three-argument expression composed of the
+               remaining arguments.
+            2. If the first argument is exactly '(' and the fourth
+               argument is exactly ')', the result is the two-argument
+               test of the second and third arguments.
+            3. Otherwise, the expression is parsed and evaluated
+               according to precedence using the rules listed above.
+
+     5 or more arguments
+          The expression is parsed and evaluated according to precedence
+          using the rules listed above.
+
+     When used with 'test' or '[', the '<' and '>' operators sort
+     lexicographically using ASCII ordering.
+
+'times'
+          times
+
+     Print out the user and system times used by the shell and its
+     children.  The return status is zero.
+
+'trap'
+          trap [-lp] [ARG] [SIGSPEC ...]
+
+     The commands in ARG are to be read and executed when the shell
+     receives signal SIGSPEC.  If ARG is absent (and there is a single
+     SIGSPEC) or equal to '-', each specified signal's disposition is
+     reset to the value it had when the shell was started.  If ARG is
+     the null string, then the signal specified by each SIGSPEC is
+     ignored by the shell and commands it invokes.  If ARG is not
+     present and '-p' has been supplied, the shell displays the trap
+     commands associated with each SIGSPEC.  If no arguments are
+     supplied, or only '-p' is given, 'trap' prints the list of commands
+     associated with each signal number in a form that may be reused as
+     shell input.  The '-l' option causes the shell to print a list of
+     signal names and their corresponding numbers.  Each SIGSPEC is
+     either a signal name or a signal number.  Signal names are case
+     insensitive and the 'SIG' prefix is optional.
+
+     If a SIGSPEC is '0' or 'EXIT', ARG is executed when the shell
+     exits.  If a SIGSPEC is 'DEBUG', the command ARG is executed before
+     every simple command, 'for' command, 'case' command, 'select'
+     command, every arithmetic 'for' command, and before the first
+     command executes in a shell function.  Refer to the description of
+     the 'extdebug' option to the 'shopt' builtin (*note The Shopt
+     Builtin::) for details of its effect on the 'DEBUG' trap.  If a
+     SIGSPEC is 'RETURN', the command ARG is executed each time a shell
+     function or a script executed with the '.' or 'source' builtins
+     finishes executing.
+
+     If a SIGSPEC is 'ERR', the command ARG 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 'ERR' trap is not executed if the failed
+     command is part of the command list immediately following an
+     'until' or 'while' keyword, part of the test following the 'if' or
+     'elif' reserved words, part of a command executed in a '&&' or '||'
+     list except the command following the final '&&' or '||', any
+     command in a pipeline but the last, or if the command's return
+     status is being inverted using '!'.  These are the same conditions
+     obeyed by the 'errexit' ('-e') option.
+
+     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 zero unless a SIGSPEC does not specify a valid
+     signal.
+
+'umask'
+          umask [-p] [-S] [MODE]
+
+     Set the shell process's file creation mask to MODE.  If MODE begins
+     with a digit, it is interpreted as an octal number; if not, it is
+     interpreted as a symbolic mode mask similar to that accepted by the
+     'chmod' command.  If MODE is omitted, the current value of the mask
+     is printed.  If the '-S' option is supplied without a MODE
+     argument, the mask is printed in a symbolic format.  If the '-p'
+     option is supplied, and MODE is omitted, the output is in a form
+     that may be reused as input.  The return status is zero if the mode
+     is successfully changed or if no MODE argument is supplied, and
+     non-zero otherwise.
+
+     Note that when the mode is interpreted as an octal number, each
+     number of the umask is subtracted from '7'.  Thus, a umask of '022'
+     results in permissions of '755'.
+
+'unset'
+          unset [-fnv] [NAME]
+
+     Remove each variable or function NAME.  If the '-v' option is
+     given, each NAME refers to a shell variable and that variable is
+     removed.  If the '-f' option is given, the NAMEs refer to shell
+     functions, and the function definition is removed.  If the '-n'
+     option is supplied, and NAME is a variable with the 'nameref'
+     attribute, NAME will be unset rather than the variable it
+     references.  '-n' has no effect if the '-f' option is supplied.  If
+     no options are supplied, each NAME refers to a variable; if there
+     is no variable by that name, a function with that name, if any, is
+     unset.  Readonly variables and functions may not be unset.  Some
+     shell variables lose their special behavior if they are unset; such
+     behavior is noted in the description of the individual variables.
+     The return status is zero unless a NAME is readonly or may not be
+     unset.
+
+
+File: bashref.info,  Node: Bash Builtins,  Next: Modifying Shell Behavior,  Prev: Bourne Shell Builtins,  Up: Shell Builtin Commands
+
+4.2 Bash Builtin Commands
+=========================
+
+This section describes builtin commands which are unique to or have been
+extended in Bash.  Some of these commands are specified in the POSIX
+standard.
+
+'alias'
+          alias [-p] [NAME[=VALUE] ...]
+
+     Without arguments or with the '-p' option, 'alias' prints the list
+     of aliases on the standard output in a form that allows them to be
+     reused as input.  If arguments are supplied, an alias is defined
+     for each NAME whose VALUE is given.  If no VALUE is given, the name
+     and value of the alias is printed.  Aliases are described in *note
+     Aliases::.
+
+'bind'
+          bind [-m KEYMAP] [-lpsvPSVX]
+          bind [-m KEYMAP] [-q FUNCTION] [-u FUNCTION] [-r KEYSEQ]
+          bind [-m KEYMAP] -f FILENAME
+          bind [-m KEYMAP] -x KEYSEQ:SHELL-COMMAND
+          bind [-m KEYMAP] KEYSEQ:FUNCTION-NAME
+          bind [-m KEYMAP] KEYSEQ:READLINE-COMMAND
+          bind READLINE-COMMAND-LINE
+
+     Display current Readline (*note Command Line Editing::) key and
+     function bindings, bind a key sequence to a Readline function or
+     macro, or set a Readline variable.  Each non-option argument is a
+     command as it would appear in a Readline initialization file (*note
+     Readline Init File::), but each binding or command must be passed
+     as a separate argument; e.g., '"\C-x\C-r":re-read-init-file'.
+
+     Options, if supplied, have the following meanings:
+
+     '-m KEYMAP'
+          Use KEYMAP as the keymap to be affected by the subsequent
+          bindings.  Acceptable KEYMAP names are 'emacs',
+          'emacs-standard', 'emacs-meta', 'emacs-ctlx', 'vi', 'vi-move',
+          'vi-command', and 'vi-insert'.  'vi' is equivalent to
+          'vi-command' ('vi-move' is also a synonym); 'emacs' is
+          equivalent to 'emacs-standard'.
+
+     '-l'
+          List the names of all Readline functions.
+
+     '-p'
+          Display Readline function names and bindings in such a way
+          that they can be used as input or in a Readline initialization
+          file.
+
+     '-P'
+          List current Readline function names and bindings.
+
+     '-v'
+          Display Readline variable names and values in such a way that
+          they can be used as input or in a Readline initialization
+          file.
+
+     '-V'
+          List current Readline variable names and values.
+
+     '-s'
+          Display Readline key sequences bound to macros and the strings
+          they output in such a way that they can be used as input or in
+          a Readline initialization file.
+
+     '-S'
+          Display Readline key sequences bound to macros and the strings
+          they output.
+
+     '-f FILENAME'
+          Read key bindings from FILENAME.
+
+     '-q FUNCTION'
+          Query about which keys invoke the named FUNCTION.
+
+     '-u FUNCTION'
+          Unbind all keys bound to the named FUNCTION.
+
+     '-r KEYSEQ'
+          Remove any current binding for KEYSEQ.
+
+     '-x KEYSEQ:SHELL-COMMAND'
+          Cause SHELL-COMMAND to be executed whenever KEYSEQ is entered.
+          When SHELL-COMMAND is executed, the shell sets the
+          'READLINE_LINE' variable to the contents of the Readline line
+          buffer and the 'READLINE_POINT' and 'READLINE_MARK' variables
+          to the current location of the insertion point and the saved
+          insertion point (the MARK), respectively.  The shell assigns
+          any numeric argument the user supplied to the
+          'READLINE_ARGUMENT' variable.  If there was no argument, that
+          variable is not set.  If the executed command changes the
+          value of any of 'READLINE_LINE', 'READLINE_POINT', or
+          'READLINE_MARK', those new values will be reflected in the
+          editing state.
+
+     '-X'
+          List all key sequences bound to shell commands and the
+          associated commands in a format that can be reused as input.
+
+     The return status is zero unless an invalid option is supplied or
+     an error occurs.
+
+'builtin'
+          builtin [SHELL-BUILTIN [ARGS]]
+
+     Run a shell builtin, passing it ARGS, and return its exit status.
+     This is useful when defining a shell function with the same name as
+     a shell builtin, retaining the functionality of the builtin within
+     the function.  The return status is non-zero if SHELL-BUILTIN is
+     not a shell builtin command.
+
+'caller'
+          caller [EXPR]
+
+     Returns the context of any active subroutine call (a shell function
+     or a script executed with the '.' or 'source' builtins).
+
+     Without EXPR, 'caller' displays the line number and source filename
+     of the current subroutine call.  If a non-negative integer is
+     supplied as EXPR, 'caller' 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 EXPR does not correspond to a valid position in
+     the call stack.
+
+'command'
+          command [-pVv] COMMAND [ARGUMENTS ...]
+
+     Runs COMMAND with ARGUMENTS ignoring any shell function named
+     COMMAND.  Only shell builtin commands or commands found by
+     searching the 'PATH' are executed.  If there is a shell function
+     named 'ls', running 'command ls' within the function will execute
+     the external command 'ls' instead of calling the function
+     recursively.  The '-p' option means to use a default value for
+     'PATH' that is guaranteed to find all of the standard utilities.
+     The return status in this case is 127 if COMMAND cannot be found or
+     an error occurred, and the exit status of COMMAND otherwise.
+
+     If either the '-V' or '-v' option is supplied, a description of
+     COMMAND is printed.  The '-v' option causes a single word
+     indicating the command or file name used to invoke COMMAND to be
+     displayed; the '-V' option produces a more verbose description.  In
+     this case, the return status is zero if COMMAND is found, and
+     non-zero if not.
+
+'declare'
+          declare [-aAfFgiIlnrtux] [-p] [NAME[=VALUE] ...]
+
+     Declare variables and give them attributes.  If no NAMEs are given,
+     then display the values of variables instead.
+
+     The '-p' option will display the attributes and values of each
+     NAME.  When '-p' is used with NAME arguments, additional options,
+     other than '-f' and '-F', are ignored.
+
+     When '-p' is supplied without NAME arguments, 'declare' will
+     display the attributes and values of all variables having the
+     attributes specified by the additional options.  If no other
+     options are supplied with '-p', 'declare' will display the
+     attributes and values of all shell variables.  The '-f' option will
+     restrict the display to shell functions.
+
+     The '-F' option inhibits the display of function definitions; only
+     the function name and attributes are printed.  If the 'extdebug'
+     shell option is enabled using 'shopt' (*note The Shopt Builtin::),
+     the source file name and line number where each NAME is defined are
+     displayed as well.  '-F' implies '-f'.
+
+     The '-g' option forces variables to be created or modified at the
+     global scope, even when 'declare' is executed in a shell function.
+     It is ignored in all other cases.
+
+     The '-I' option causes local variables to inherit the attributes
+     (except the 'nameref' attribute) and value of any existing variable
+     with the same NAME 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 attributes or to give variables attributes:
+
+     '-a'
+          Each NAME is an indexed array variable (*note Arrays::).
+
+     '-A'
+          Each NAME is an associative array variable (*note Arrays::).
+
+     '-f'
+          Use function names only.
+
+     '-i'
+          The variable is to be treated as an integer; arithmetic
+          evaluation (*note Shell Arithmetic::) is performed when the
+          variable is assigned a value.
+
+     '-l'
+          When the variable is assigned a value, all upper-case
+          characters are converted to lower-case.  The upper-case
+          attribute is disabled.
+
+     '-n'
+          Give each NAME the 'nameref' attribute, making it a name
+          reference to another variable.  That other variable is defined
+          by the value of NAME.  All references, assignments, and
+          attribute modifications to NAME, except for those using or
+          changing the '-n' attribute itself, are performed on the
+          variable referenced by NAME's value.  The nameref attribute
+          cannot be applied to array variables.
+
+     '-r'
+          Make NAMEs readonly.  These names cannot then be assigned
+          values by subsequent assignment statements or unset.
+
+     '-t'
+          Give each NAME the 'trace' attribute.  Traced functions
+          inherit the 'DEBUG' and 'RETURN' traps from the calling shell.
+          The trace attribute has no special meaning for variables.
+
+     '-u'
+          When the variable is assigned a value, all lower-case
+          characters are converted to upper-case.  The lower-case
+          attribute is disabled.
+
+     '-x'
+          Mark each NAME for export to subsequent commands via the
+          environment.
+
+     Using '+' instead of '-' turns off the attribute instead, with the
+     exceptions that '+a' and '+A' may not be used to destroy array
+     variables and '+r' will not remove the readonly attribute.  When
+     used in a function, 'declare' makes each NAME local, as with the
+     'local' command, unless the '-g' option is used.  If a variable
+     name is followed by =VALUE, the value of the variable is set to
+     VALUE.
+
+     When using '-a' or '-A' and the compound assignment syntax to
+     create array variables, additional attributes do not take effect
+     until subsequent assignments.
+
+     The return status is zero unless an invalid option is encountered,
+     an attempt is made to define a function using '-f foo=bar', an
+     attempt is made to assign a value to a readonly variable, an
+     attempt is made to assign a value to an array variable without
+     using the compound assignment syntax (*note Arrays::), one of the
+     NAMEs 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 '-f'.
+
+'echo'
+          echo [-neE] [ARG ...]
+
+     Output the ARGs, separated by spaces, terminated with a newline.
+     The return status is 0 unless a write error occurs.  If '-n' is
+     specified, the trailing newline is suppressed.  If the '-e' option
+     is given, interpretation of the following backslash-escaped
+     characters is enabled.  The '-E' option disables the interpretation
+     of these escape characters, even on systems where they are
+     interpreted by default.  The 'xpg_echo' shell option may be used to
+     dynamically determine whether or not 'echo' expands these escape
+     characters by default.  'echo' does not interpret '--' to mean the
+     end of options.
+
+     'echo' interprets the following escape sequences:
+     '\a'
+          alert (bell)
+     '\b'
+          backspace
+     '\c'
+          suppress further output
+     '\e'
+     '\E'
+          escape
+     '\f'
+          form feed
+     '\n'
+          new line
+     '\r'
+          carriage return
+     '\t'
+          horizontal tab
+     '\v'
+          vertical tab
+     '\\'
+          backslash
+     '\0NNN'
+          the eight-bit character whose value is the octal value NNN
+          (zero to three octal digits)
+     '\xHH'
+          the eight-bit character whose value is the hexadecimal value
+          HH (one or two hex digits)
+     '\uHHHH'
+          the Unicode (ISO/IEC 10646) character whose value is the
+          hexadecimal value HHHH (one to four hex digits)
+     '\UHHHHHHHH'
+          the Unicode (ISO/IEC 10646) character whose value is the
+          hexadecimal value HHHHHHHH (one to eight hex digits)
+
+'enable'
+          enable [-a] [-dnps] [-f FILENAME] [NAME ...]
+
+     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 '-n'
+     is used, the NAMEs become disabled.  Otherwise NAMEs are enabled.
+     For example, to use the 'test' binary found via '$PATH' instead of
+     the shell builtin version, type 'enable -n test'.
+
+     If the '-p' option is supplied, or no NAME arguments appear, a list
+     of shell builtins is printed.  With no other arguments, the list
+     consists of all enabled shell builtins.  The '-a' option means to
+     list each builtin with an indication of whether or not it is
+     enabled.
+
+     The '-f' option means to load the new builtin command NAME from
+     shared object FILENAME, on systems that support dynamic loading.
+     Bash will use the value of the 'BASH_LOADABLES_PATH' variable as a
+     colon-separated list of directories in which to search for
+     FILENAME.  The default is system-dependent.  The '-d' option will
+     delete a builtin loaded with '-f'.
+
+     If there are no options, a list of the shell builtins is displayed.
+     The '-s' option restricts 'enable' to the POSIX special builtins.
+     If '-s' is used with '-f', the new builtin becomes a special
+     builtin (*note Special Builtins::).
+
+     If no options are supplied and a NAME is not a shell builtin,
+     'enable' will attempt to load NAME from a shared object named NAME,
+     as if the command were 'enable -f NAME NAME'.
+
+     The return status is zero unless a NAME is not a shell builtin or
+     there is an error loading a new builtin from a shared object.
+
+'help'
+          help [-dms] [PATTERN]
+
+     Display helpful information about builtin commands.  If PATTERN is
+     specified, 'help' gives detailed help on all commands matching
+     PATTERN, otherwise a list of the builtins is printed.
+
+     Options, if supplied, have the following meanings:
+
+     '-d'
+          Display a short description of each PATTERN
+     '-m'
+          Display the description of each PATTERN in a manpage-like
+          format
+     '-s'
+          Display only a short usage synopsis for each PATTERN
+
+     The return status is zero unless no command matches PATTERN.
+
+'let'
+          let EXPRESSION [EXPRESSION ...]
+
+     The 'let' builtin allows arithmetic to be performed on shell
+     variables.  Each EXPRESSION is evaluated according to the rules
+     given below in *note Shell Arithmetic::.  If the last EXPRESSION
+     evaluates to 0, 'let' returns 1; otherwise 0 is returned.
+
+'local'
+          local [OPTION] NAME[=VALUE] ...
+
+     For each argument, a local variable named NAME is created, and
+     assigned VALUE.  The OPTION can be any of the options accepted by
+     'declare'.  'local' can only be used within a function; it makes
+     the variable NAME have a visible scope restricted to that function
+     and its children.  If NAME is '-', the set of shell options is made
+     local to the function in which 'local' is invoked: shell options
+     changed using the 'set' builtin inside the function are restored to
+     their original values when the function returns.  The restore is
+     effected as if a series of 'set' commands were executed to restore
+     the values that were in place before the function.  The return
+     status is zero unless 'local' is used outside a function, an
+     invalid NAME is supplied, or NAME is a readonly variable.
+
+'logout'
+          logout [N]
+
+     Exit a login shell, returning a status of N to the shell's parent.
+
+'mapfile'
+          mapfile [-d DELIM] [-n COUNT] [-O ORIGIN] [-s COUNT]
+              [-t] [-u FD] [-C CALLBACK] [-c QUANTUM] [ARRAY]
+
+     Read lines from the standard input into the indexed array variable
+     ARRAY, or from file descriptor FD if the '-u' option is supplied.
+     The variable 'MAPFILE' is the default ARRAY.  Options, if supplied,
+     have the following meanings:
+
+     '-d'
+          The first character of DELIM is used to terminate each input
+          line, rather than newline.  If DELIM is the empty string,
+          'mapfile' will terminate a line when it reads a NUL character.
+     '-n'
+          Copy at most COUNT lines.  If COUNT is 0, all lines are
+          copied.
+     '-O'
+          Begin assigning to ARRAY at index ORIGIN.  The default index
+          is 0.
+     '-s'
+          Discard the first COUNT lines read.
+     '-t'
+          Remove a trailing DELIM (default newline) from each line read.
+     '-u'
+          Read lines from file descriptor FD instead of the standard
+          input.
+     '-C'
+          Evaluate CALLBACK each time QUANTUM lines are read.  The '-c'
+          option specifies QUANTUM.
+     '-c'
+          Specify the number of lines read between each call to
+          CALLBACK.
+
+     If '-C' is specified without '-c', the default quantum is 5000.
+     When CALLBACK 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.  CALLBACK is evaluated after the
+     line is read but before the array element is assigned.
+
+     If not supplied with an explicit origin, 'mapfile' will clear ARRAY
+     before assigning to it.
+
+     'mapfile' returns successfully unless an invalid option or option
+     argument is supplied, ARRAY is invalid or unassignable, or ARRAY is
+     not an indexed array.
+
+'printf'
+          printf [-v VAR] FORMAT [ARGUMENTS]
+
+     Write the formatted ARGUMENTS to the standard output under the
+     control of the FORMAT.  The '-v' option causes the output to be
+     assigned to the variable VAR rather than being printed to the
+     standard output.
+
+     The FORMAT 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 ARGUMENT.  In addition to
+     the standard 'printf(1)' formats, 'printf' interprets the following
+     extensions:
+
+     '%b'
+          Causes 'printf' to expand backslash escape sequences in the
+          corresponding ARGUMENT in the same way as 'echo -e' (*note
+          Bash Builtins::).
+     '%q'
+          Causes 'printf' to output the corresponding ARGUMENT in a
+          format that can be reused as shell input.
+     '%Q'
+          like '%q', but applies any supplied precision to the ARGUMENT
+          before quoting it.
+     '%(DATEFMT)T'
+          Causes 'printf' to output the date-time string resulting from
+          using DATEFMT as a format string for 'strftime'(3).  The
+          corresponding ARGUMENT 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 'printf' behavior.
+
+     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.
+
+     Arguments to non-string format specifiers are treated as C language
+     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.
+
+     The FORMAT is reused as necessary to consume all of the ARGUMENTS.
+     If the FORMAT requires more ARGUMENTS 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.
+
+'read'
+          read [-ers] [-a ANAME] [-d DELIM] [-i TEXT] [-n NCHARS]
+              [-N NCHARS] [-p PROMPT] [-t TIMEOUT] [-u FD] [NAME ...]
+
+     One line is read from the standard input, or from the file
+     descriptor FD supplied as an argument to the '-u' option, split
+     into words as described above in *note Word Splitting::, and the
+     first word is assigned to the first NAME, the second word to the
+     second NAME, and so on.  If there are more words than names, the
+     remaining words and their intervening delimiters are assigned to
+     the last NAME.  If there are fewer words read from the input stream
+     than names, the remaining names are assigned empty values.  The
+     characters in the value of the 'IFS' variable are used to split the
+     line into words using the same rules the shell uses for expansion
+     (described above in *note Word Splitting::).  The backslash
+     character '\' may be used to remove any special meaning for the
+     next character read and for line continuation.
+
+     Options, if supplied, have the following meanings:
+
+     '-a ANAME'
+          The words are assigned to sequential indices of the array
+          variable ANAME, starting at 0.  All elements are removed from
+          ANAME before the assignment.  Other NAME arguments are
+          ignored.
+
+     '-d DELIM'
+          The first character of DELIM is used to terminate the input
+          line, rather than newline.  If DELIM is the empty string,
+          'read' will terminate a line when it reads a NUL character.
+
+     '-e'
+          Readline (*note Command Line Editing::) 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.
+
+     '-i TEXT'
+          If Readline is being used to read the line, TEXT is placed
+          into the editing buffer before editing begins.
+
+     '-n NCHARS'
+          'read' returns after reading NCHARS characters rather than
+          waiting for a complete line of input, but honors a delimiter
+          if fewer than NCHARS characters are read before the delimiter.
+
+     '-N NCHARS'
+          'read' returns after reading exactly NCHARS characters rather
+          than waiting for a complete line of input, unless EOF is
+          encountered or 'read' times out.  Delimiter characters
+          encountered in the input are not treated specially and do not
+          cause 'read' to return until NCHARS characters are read.  The
+          result is not split on the characters in 'IFS'; the intent is
+          that the variable is assigned exactly the characters read
+          (with the exception of backslash; see the '-r' option below).
+
+     '-p PROMPT'
+          Display PROMPT, without a trailing newline, before attempting
+          to read any input.  The prompt is displayed only if input is
+          coming from a terminal.
+
+     '-r'
+          If this option is given, 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.
+
+     '-s'
+          Silent mode.  If input is coming from a terminal, characters
+          are not echoed.
+
+     '-t TIMEOUT'
+          Cause 'read' to time out and return failure if a complete line
+          of input (or a specified number of characters) is not read
+          within TIMEOUT seconds.  TIMEOUT may be a decimal number with
+          a fractional portion following the decimal point.  This option
+          is only effective if 'read' is reading input from a terminal,
+          pipe, or other special file; it has no effect when reading
+          from regular files.  If 'read' times out, 'read' saves any
+          partial input read into the specified variable NAME.  If
+          TIMEOUT is 0, 'read' returns immediately, without trying to
+          read any data.  The exit status is 0 if input is available on
+          the specified file descriptor, or the read will return EOF,
+          non-zero otherwise.  The exit status is greater than 128 if
+          the timeout is exceeded.
+
+     '-u FD'
+          Read input from file descriptor FD.
+
+     If no NAMEs are supplied, the line read, without the ending
+     delimiter but otherwise unmodified, is assigned to the variable
+     'REPLY'.  The exit status is zero, unless end-of-file is
+     encountered, 'read' 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 '-u'.
+
+'readarray'
+          readarray [-d DELIM] [-n COUNT] [-O ORIGIN] [-s COUNT]
+              [-t] [-u FD] [-C CALLBACK] [-c QUANTUM] [ARRAY]
+
+     Read lines from the standard input into the indexed array variable
+     ARRAY, or from file descriptor FD if the '-u' option is supplied.
+
+     A synonym for 'mapfile'.
+
+'source'
+          source FILENAME
+
+     A synonym for '.' (*note Bourne Shell Builtins::).
+
+'type'
+          type [-afptP] [NAME ...]
+
+     For each NAME, indicate how it would be interpreted if used as a
+     command name.
+
+     If the '-t' option is used, 'type' prints a single word which is
+     one of 'alias', 'function', 'builtin', 'file' or 'keyword', if NAME
+     is an alias, shell function, shell builtin, disk file, or shell
+     reserved word, respectively.  If the NAME is not found, then
+     nothing is printed, and 'type' returns a failure status.
+
+     If the '-p' option is used, 'type' either returns the name of the
+     disk file that would be executed, or nothing if '-t' would not
+     return 'file'.
+
+     The '-P' option forces a path search for each NAME, even if '-t'
+     would not return 'file'.
+
+     If a command is hashed, '-p' and '-P' print the hashed value, which
+     is not necessarily the file that appears first in '$PATH'.
+
+     If the '-a' option is used, 'type' returns all of the places that
+     contain an executable named FILE.  This includes aliases and
+     functions, if and only if the '-p' option is not also used.
+
+     If the '-f' option is used, 'type' does not attempt to find shell
+     functions, as with the 'command' builtin.
+
+     The return status is zero if all of the NAMEs are found, non-zero
+     if any are not found.
+
+'typeset'
+          typeset [-afFgrxilnrtux] [-p] [NAME[=VALUE] ...]
+
+     The 'typeset' command is supplied for compatibility with the Korn
+     shell.  It is a synonym for the 'declare' builtin command.
+
+'ulimit'
+          ulimit [-HS] -a
+          ulimit [-HS] [-bcdefiklmnpqrstuvxPRT] [LIMIT]
+
+     'ulimit' provides control over the resources available to processes
+     started by the shell, on systems that allow such control.  If an
+     option is given, it is interpreted as follows:
+
+     '-S'
+          Change and report the soft limit associated with a resource.
+
+     '-H'
+          Change and report the hard limit associated with a resource.
+
+     '-a'
+          All current limits are reported; no limits are set.
+
+     '-b'
+          The maximum socket buffer size.
+
+     '-c'
+          The maximum size of core files created.
+
+     '-d'
+          The maximum size of a process's data segment.
+
+     '-e'
+          The maximum scheduling priority ("nice").
+
+     '-f'
+          The maximum size of files written by the shell and its
+          children.
+
+     '-i'
+          The maximum number of pending signals.
+
+     '-k'
+          The maximum number of kqueues that may be allocated.
+
+     '-l'
+          The maximum size that may be locked into memory.
+
+     '-m'
+          The maximum resident set size (many systems do not honor this
+          limit).
+
+     '-n'
+          The maximum number of open file descriptors (most systems do
+          not allow this value to be set).
+
+     '-p'
+          The pipe buffer size.
+
+     '-q'
+          The maximum number of bytes in POSIX message queues.
+
+     '-r'
+          The maximum real-time scheduling priority.
+
+     '-s'
+          The maximum stack size.
+
+     '-t'
+          The maximum amount of cpu time in seconds.
+
+     '-u'
+          The maximum number of processes available to a single user.
+
+     '-v'
+          The maximum amount of virtual memory available to the shell,
+          and, on some systems, to its children.
+
+     '-x'
+          The maximum number of file locks.
+
+     '-P'
+          The maximum number of pseudoterminals.
+
+     '-R'
+          The maximum time a real-time process can run before blocking,
+          in microseconds.
+
+     '-T'
+          The maximum number of threads.
+
+     If LIMIT is given, and the '-a' option is not used, LIMIT is the
+     new value of the specified resource.  The special LIMIT values
+     'hard', 'soft', and 'unlimited' stand for the current hard limit,
+     the current soft limit, and no limit, respectively.  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.  Otherwise, the
+     current value of the soft limit for the specified resource is
+     printed, unless the '-H' option is supplied.  When more than one
+     resource is specified, the limit name and unit, if appropriate, are
+     printed before the value.  When setting new limits, if neither '-H'
+     nor '-S' is supplied, both the hard and soft limits are set.  If no
+     option is given, then '-f' is assumed.  Values are in 1024-byte
+     increments, except for '-t', which is in seconds; '-R', which is in
+     microseconds; '-p', which is in units of 512-byte blocks; '-P',
+     '-T', '-b', '-k', '-n' and '-u', which are unscaled values; and,
+     when in POSIX Mode (*note Bash POSIX Mode::), '-c' and '-f', which
+     are in 512-byte increments.
+
+     The return status is zero unless an invalid option or argument is
+     supplied, or an error occurs while setting a new limit.
+
+'unalias'
+          unalias [-a] [NAME ... ]
+
+     Remove each NAME from the list of aliases.  If '-a' is supplied,
+     all aliases are removed.  Aliases are described in *note Aliases::.
+
+
+File: bashref.info,  Node: Modifying Shell Behavior,  Next: Special Builtins,  Prev: Bash Builtins,  Up: Shell Builtin Commands
+
+4.3 Modifying Shell Behavior
+============================
+
+* Menu:
+
+* The Set Builtin::		Change the values of shell attributes and
+				positional parameters.
+* The Shopt Builtin::		Modify shell optional behavior.
+
+
+File: bashref.info,  Node: The Set Builtin,  Next: The Shopt Builtin,  Up: Modifying Shell Behavior
+
+4.3.1 The Set Builtin
+---------------------
+
+This builtin is so complicated that it deserves its own section.  'set'
+allows you to change the values of shell options and set the positional
+parameters, or to display the names and values of shell variables.
+
+'set'
+          set [-abefhkmnptuvxBCEHPT] [-o OPTION-NAME] [--] [-] [ARGUMENT ...]
+          set [+abefhkmnptuvxBCEHPT] [+o OPTION-NAME] [--] [-] [ARGUMENT ...]
+
+     If no options or arguments are supplied, 'set' displays the names
+     and values of all shell variables and functions, sorted according
+     to the current locale, in a format that may be reused as input for
+     setting or resetting the currently-set variables.  Read-only
+     variables cannot be reset.  In POSIX mode, only shell variables are
+     listed.
+
+     When options are supplied, they set or unset shell attributes.
+     Options, if specified, have the following meanings:
+
+     '-a'
+          Each variable or function that is created or modified is given
+          the export attribute and marked for export to the environment
+          of subsequent commands.
+
+     '-b'
+          Cause the status of terminated background jobs to be reported
+          immediately, rather than before printing the next primary
+          prompt.
+
+     '-e'
+          Exit immediately if a pipeline (*note Pipelines::), which may
+          consist of a single simple command (*note Simple Commands::),
+          a list (*note Lists::), or a compound command (*note Compound
+          Commands::) returns a non-zero status.  The shell does not
+          exit if the command that fails is part of the command list
+          immediately following a 'while' or 'until' keyword, part of
+          the test in an 'if' statement, part of any command executed in
+          a '&&' or '||' list except the command following the final
+          '&&' or '||', any command in a pipeline but the last, or if
+          the command's return status is being inverted with '!'.  If a
+          compound command other than a subshell returns a non-zero
+          status because a command failed while '-e' was being ignored,
+          the shell does not exit.  A trap on 'ERR', if set, is executed
+          before the shell exits.
+
+          This option applies to the shell environment and each subshell
+          environment separately (*note Command Execution
+          Environment::), and may cause subshells to exit before
+          executing all the commands in the subshell.
+
+          If a compound command or shell function executes in a context
+          where '-e' is being ignored, none of the commands executed
+          within the compound command or function body will be affected
+          by the '-e' setting, even if '-e' is set and a command returns
+          a failure status.  If a compound command or shell function
+          sets '-e' while executing in a context where '-e' is ignored,
+          that setting will not have any effect until the compound
+          command or the command containing the function call completes.
+
+     '-f'
+          Disable filename expansion (globbing).
+
+     '-h'
+          Locate and remember (hash) commands as they are looked up for
+          execution.  This option is enabled by default.
+
+     '-k'
+          All arguments in the form of assignment statements are placed
+          in the environment for a command, not just those that precede
+          the command name.
+
+     '-m'
+          Job control is enabled (*note Job Control::).  All processes
+          run in a separate process group.  When a background job
+          completes, the shell prints a line containing its exit status.
+
+     '-n'
+          Read commands but do not execute them.  This may be used to
+          check a script for syntax errors.  This option is ignored by
+          interactive shells.
+
+     '-o OPTION-NAME'
+
+          Set the option corresponding to OPTION-NAME:
+
+          'allexport'
+               Same as '-a'.
+
+          'braceexpand'
+               Same as '-B'.
+
+          'emacs'
+               Use an 'emacs'-style line editing interface (*note
+               Command Line Editing::).  This also affects the editing
+               interface used for 'read -e'.
+
+          'errexit'
+               Same as '-e'.
+
+          'errtrace'
+               Same as '-E'.
+
+          'functrace'
+               Same as '-T'.
+
+          'hashall'
+               Same as '-h'.
+
+          'histexpand'
+               Same as '-H'.
+
+          'history'
+               Enable command history, as described in *note Bash
+               History Facilities::.  This option is on by default in
+               interactive shells.
+
+          'ignoreeof'
+               An interactive shell will not exit upon reading EOF.
+
+          'keyword'
+               Same as '-k'.
+
+          'monitor'
+               Same as '-m'.
+
+          'noclobber'
+               Same as '-C'.
+
+          'noexec'
+               Same as '-n'.
+
+          'noglob'
+               Same as '-f'.
+
+          'nolog'
+               Currently ignored.
+
+          'notify'
+               Same as '-b'.
+
+          'nounset'
+               Same as '-u'.
+
+          'onecmd'
+               Same as '-t'.
+
+          'physical'
+               Same as '-P'.
+
+          'pipefail'
+               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.
+
+          'posix'
+               Change the behavior of Bash where the default operation
+               differs from the POSIX standard to match the standard
+               (*note Bash POSIX Mode::).  This is intended to make Bash
+               behave as a strict superset of that standard.
+
+          'privileged'
+               Same as '-p'.
+
+          'verbose'
+               Same as '-v'.
+
+          'vi'
+               Use a 'vi'-style line editing interface.  This also
+               affects the editing interface used for 'read -e'.
+
+          'xtrace'
+               Same as '-x'.
+
+     '-p'
+          Turn on privileged mode.  In this mode, the '$BASH_ENV' and
+          '$ENV' files are not processed, shell functions are not
+          inherited from the environment, and the 'SHELLOPTS',
+          'BASHOPTS', 'CDPATH' and 'GLOBIGNORE' 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 '-p' option is not supplied,
+          these actions are taken and the effective user id is set to
+          the real user id.  If the '-p' 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.
+
+     '-r'
+          Enable restricted shell mode.  This option cannot be unset
+          once it has been set.
+
+     '-t'
+          Exit after reading and executing one command.
+
+     '-u'
+          Treat unset variables and parameters other than the special
+          parameters '@' or '*', or array variables subscripted with '@'
+          or '*', as an error when performing parameter expansion.  An
+          error message will be written to the standard error, and a
+          non-interactive shell will exit.
+
+     '-v'
+          Print shell input lines as they are read.
+
+     '-x'
+          Print a trace of simple commands, 'for' commands, 'case'
+          commands, 'select' commands, and arithmetic 'for' commands and
+          their arguments or associated word lists after they are
+          expanded and before they are executed.  The value of the 'PS4'
+          variable is expanded and the resultant value is printed before
+          the command and its expanded arguments.
+
+     '-B'
+          The shell will perform brace expansion (*note Brace
+          Expansion::).  This option is on by default.
+
+     '-C'
+          Prevent output redirection using '>', '>&', and '<>' from
+          overwriting existing files.
+
+     '-E'
+          If set, any trap on 'ERR' is inherited by shell functions,
+          command substitutions, and commands executed in a subshell
+          environment.  The 'ERR' trap is normally not inherited in such
+          cases.
+
+     '-H'
+          Enable '!' style history substitution (*note History
+          Interaction::).  This option is on by default for interactive
+          shells.
+
+     '-P'
+          If set, do not resolve symbolic links when performing commands
+          such as 'cd' which change the current directory.  The physical
+          directory is used instead.  By default, Bash follows the
+          logical chain of directories when performing commands which
+          change the current directory.
+
+          For example, if '/usr/sys' is a symbolic link to
+          '/usr/local/sys' then:
+               $ cd /usr/sys; echo $PWD
+               /usr/sys
+               $ cd ..; pwd
+               /usr
+
+          If 'set -P' is on, then:
+               $ cd /usr/sys; echo $PWD
+               /usr/local/sys
+               $ cd ..; pwd
+               /usr/local
+
+     '-T'
+          If set, any trap on 'DEBUG' and 'RETURN' are inherited by
+          shell functions, command substitutions, and commands executed
+          in a subshell environment.  The 'DEBUG' and 'RETURN' traps are
+          normally not inherited in such cases.
+
+     '--'
+          If no arguments follow this option, then the positional
+          parameters are unset.  Otherwise, the positional parameters
+          are set to the ARGUMENTS, even if some of them begin with a
+          '-'.
+
+     '-'
+          Signal the end of options, cause all remaining ARGUMENTS to be
+          assigned to the positional parameters.  The '-x' and '-v'
+          options are turned off.  If there are no arguments, the
+          positional parameters remain unchanged.
+
+     Using '+' rather than '-' causes these options to be turned off.
+     The options can also be used upon invocation of the shell.  The
+     current set of options may be found in '$-'.
+
+     The remaining N ARGUMENTS are positional parameters and are
+     assigned, in order, to '$1', '$2', ... '$N'.  The special parameter
+     '#' is set to N.
+
+     The return status is always zero unless an invalid option is
+     supplied.
+
+
+File: bashref.info,  Node: The Shopt Builtin,  Prev: The Set Builtin,  Up: Modifying Shell Behavior
+
+4.3.2 The Shopt Builtin
+-----------------------
+
+This builtin allows you to change additional shell optional behavior.
+
+'shopt'
+          shopt [-pqsu] [-o] [OPTNAME ...]
+
+     Toggle the values of settings controlling optional shell behavior.
+     The settings can be either those listed below, or, if the '-o'
+     option is used, those available with the '-o' option to the 'set'
+     builtin command (*note The Set Builtin::).  With no options, or
+     with the '-p' option, a list of all settable options is displayed,
+     with an indication of whether or not each is set; if OPTNAMEs are
+     supplied, the output is restricted to those options.  The '-p'
+     option causes output to be displayed in a form that may be reused
+     as input.  Other options have the following meanings:
+
+     '-s'
+          Enable (set) each OPTNAME.
+
+     '-u'
+          Disable (unset) each OPTNAME.
+
+     '-q'
+          Suppresses normal output; the return status indicates whether
+          the OPTNAME is set or unset.  If multiple OPTNAME arguments
+          are given with '-q', the return status is zero if all OPTNAMEs
+          are enabled; non-zero otherwise.
+
+     '-o'
+          Restricts the values of OPTNAME to be those defined for the
+          '-o' option to the 'set' builtin (*note The Set Builtin::).
+
+     If either '-s' or '-u' is used with no OPTNAME arguments, 'shopt'
+     shows only those options which are set or unset, respectively.
+
+     Unless otherwise noted, the 'shopt' options are disabled (off) by
+     default.
+
+     The return status when listing options is zero if all OPTNAMEs are
+     enabled, non-zero otherwise.  When setting or unsetting options,
+     the return status is zero unless an OPTNAME is not a valid shell
+     option.
+
+     The list of 'shopt' options is:
+
+     'assoc_expand_once'
+          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.
+
+     'autocd'
+          If set, a command name that is the name of a directory is
+          executed as if it were the argument to the 'cd' command.  This
+          option is only used by interactive shells.
+
+     'cdable_vars'
+          If this is set, an argument to the 'cd' builtin command that
+          is not a directory is assumed to be the name of a variable
+          whose value is the directory to change to.
+
+     'cdspell'
+          If set, minor errors in the spelling of a directory component
+          in a 'cd' command will be corrected.  The errors checked for
+          are transposed characters, a missing character, and a
+          character too many.  If a correction is found, the corrected
+          path is printed, and the command proceeds.  This option is
+          only used by interactive shells.
+
+     'checkhash'
+          If this is set, Bash 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.
+
+     'checkjobs'
+          If set, Bash 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 (*note Job
+          Control::).  The shell always postpones exiting if any jobs
+          are stopped.
+
+     'checkwinsize'
+          If set, Bash checks the window size after each external
+          (non-builtin) command and, if necessary, updates the values of
+          'LINES' and 'COLUMNS'.  This option is enabled by default.
+
+     'cmdhist'
+          If set, Bash 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
+          (*note Bash History Facilities::).
+
+     'compat31'
+     'compat32'
+     'compat40'
+     'compat41'
+     'compat42'
+     'compat43'
+     'compat44'
+          These control aspects of the shell's compatibility mode (*note
+          Shell Compatibility Mode::).
+
+     'complete_fullquote'
+          If set, Bash quotes all shell metacharacters in filenames and
+          directory names when performing completion.  If not set, Bash
+          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.
+
+     'direxpand'
+          If set, Bash 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, Bash
+          attempts to preserve what the user typed.
+
+     'dirspell'
+          If set, Bash attempts spelling correction on directory names
+          during word completion if the directory name initially
+          supplied does not exist.
+
+     'dotglob'
+          If set, Bash includes filenames beginning with a '.'  in the
+          results of filename expansion.  The filenames '.' and '..'
+          must always be matched explicitly, even if 'dotglob' is set.
+
+     'execfail'
+          If this is set, a non-interactive shell will not exit if it
+          cannot execute the file specified as an argument to the 'exec'
+          builtin command.  An interactive shell does not exit if 'exec'
+          fails.
+
+     'expand_aliases'
+          If set, aliases are expanded as described below under Aliases,
+          *note Aliases::.  This option is enabled by default for
+          interactive shells.
+
+     'extdebug'
+          If set at shell invocation, or in a shell startup file,
+          arrange to execute the debugger profile before the shell
+          starts, identical to the '--debugger' option.  If set after
+          invocation, behavior intended for use by debuggers is enabled:
+
+            1. The '-F' option to the 'declare' builtin (*note Bash
+               Builtins::) displays the source file name and line number
+               corresponding to each function name supplied as an
+               argument.
+
+            2. If the command run by the 'DEBUG' trap returns a non-zero
+               value, the next command is skipped and not executed.
+
+            3. If the command run by the 'DEBUG' trap returns a value of
+               2, and the shell is executing in a subroutine (a shell
+               function or a shell script executed by the '.' or
+               'source' builtins), the shell simulates a call to
+               'return'.
+
+            4. 'BASH_ARGC' and 'BASH_ARGV' are updated as described in
+               their descriptions (*note Bash Variables::).
+
+            5. Function tracing is enabled: command substitution, shell
+               functions, and subshells invoked with '( COMMAND )'
+               inherit the 'DEBUG' and 'RETURN' traps.
+
+            6. Error tracing is enabled: command substitution, shell
+               functions, and subshells invoked with '( COMMAND )'
+               inherit the 'ERR' trap.
+
+     'extglob'
+          If set, the extended pattern matching features described above
+          (*note Pattern Matching::) are enabled.
+
+     'extquote'
+          If set, '$'STRING'' and '$"STRING"' quoting is performed
+          within '${PARAMETER}' expansions enclosed in double quotes.
+          This option is enabled by default.
+
+     'failglob'
+          If set, patterns which fail to match filenames during filename
+          expansion result in an expansion error.
+
+     'force_fignore'
+          If set, the suffixes specified by the 'FIGNORE' shell variable
+          cause words to be ignored when performing word completion even
+          if the ignored words are the only possible completions.  *Note
+          Bash Variables::, for a description of 'FIGNORE'.  This option
+          is enabled by default.
+
+     'globasciiranges'
+          If set, range expressions used in pattern matching bracket
+          expressions (*note Pattern Matching::) 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' will not collate between 'A' and 'B', and
+          upper-case and lower-case ASCII characters will collate
+          together.
+
+     'globskipdots'
+          If set, filename expansion will never match the filenames '.'
+          and '..', even if the pattern begins with a '.'.  This option
+          is enabled by default.
+
+     'globstar'
+          If set, the pattern '**' used in a filename expansion context
+          will match all files and zero or more directories and
+          subdirectories.  If the pattern is followed by a '/', only
+          directories and subdirectories match.
+
+     'gnu_errfmt'
+          If set, shell error messages are written in the standard GNU
+          error message format.
+
+     'histappend'
+          If set, the history list is appended to the file named by the
+          value of the 'HISTFILE' variable when the shell exits, rather
+          than overwriting the file.
+
+     'histreedit'
+          If set, and Readline is being used, a user is given the
+          opportunity to re-edit a failed history substitution.
+
+     'histverify'
+          If set, and Readline is being used, the results of history
+          substitution are not immediately passed to the shell parser.
+          Instead, the resulting line is loaded into the Readline
+          editing buffer, allowing further modification.
+
+     'hostcomplete'
+          If set, and Readline is being used, Bash will attempt to
+          perform hostname completion when a word containing a '@' is
+          being completed (*note Commands For Completion::).  This
+          option is enabled by default.
+
+     'huponexit'
+          If set, Bash will send 'SIGHUP' to all jobs when an
+          interactive login shell exits (*note Signals::).
+
+     'inherit_errexit'
+          If set, command substitution inherits the value of the
+          'errexit' option, instead of unsetting it in the subshell
+          environment.  This option is enabled when POSIX mode is
+          enabled.
+
+     'interactive_comments'
+          Allow a word beginning with '#' to cause that word and all
+          remaining characters on that line to be ignored in an
+          interactive shell.  This option is enabled by default.
+
+     'lastpipe'
+          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.
+
+     'lithist'
+          If enabled, and the 'cmdhist' option is enabled, multi-line
+          commands are saved to the history with embedded newlines
+          rather than using semicolon separators where possible.
+
+     'localvar_inherit'
+          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.
+
+     'localvar_unset'
+          If set, calling 'unset' 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.
+
+     'login_shell'
+          The shell sets this option if it is started as a login shell
+          (*note Invoking Bash::).  The value may not be changed.
+
+     'mailwarn'
+          If set, and a file that Bash is checking for mail has been
+          accessed since the last time it was checked, the message '"The
+          mail in MAILFILE has been read"' is displayed.
+
+     'no_empty_cmd_completion'
+          If set, and Readline is being used, Bash will not attempt to
+          search the 'PATH' for possible completions when completion is
+          attempted on an empty line.
+
+     'nocaseglob'
+          If set, Bash matches filenames in a case-insensitive fashion
+          when performing filename expansion.
+
+     'nocasematch'
+          If set, Bash matches patterns in a case-insensitive fashion
+          when performing matching while executing 'case' or '[['
+          conditional commands (*note Conditional Constructs::, when
+          performing pattern substitution word expansions, or when
+          filtering possible completions as part of programmable
+          completion.
+
+     'noexpand_translation'
+          If set, Bash encloses the translated results of $"..."
+          quoting in single quotes instead of double quotes.  If the
+          string is not translated, this has no effect.
+
+     'nullglob'
+          If set, Bash allows filename patterns which match no files to
+          expand to a null string, rather than themselves.
+
+     'patsub_replacement'
+          If set, Bash expands occurrences of '&' in the replacement
+          string of pattern substitution to the text matched by the
+          pattern, as described above (*note Shell Parameter
+          Expansion::).  This option is enabled by default.
+
+     'progcomp'
+          If set, the programmable completion facilities (*note
+          Programmable Completion::) are enabled.  This option is
+          enabled by default.
+
+     'progcomp_alias'
+          If set, and programmable completion is enabled, Bash treats a
+          command name that doesn't have any completions as a possible
+          alias and attempts alias expansion.  If it has an alias, Bash
+          attempts programmable completion using the command word
+          resulting from the expanded alias.
+
+     'promptvars'
+          If set, prompt strings undergo parameter expansion, command
+          substitution, arithmetic expansion, and quote removal after
+          being expanded as described below (*note Controlling the
+          Prompt::).  This option is enabled by default.
+
+     'restricted_shell'
+          The shell sets this option if it is started in restricted mode
+          (*note The Restricted Shell::).  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.
+
+     'shift_verbose'
+          If this is set, the 'shift' builtin prints an error message
+          when the shift count exceeds the number of positional
+          parameters.
+
+     'sourcepath'
+          If set, the '.' ('source') builtin uses the value of 'PATH' to
+          find the directory containing the file supplied as an
+          argument.  This option is enabled by default.
+
+     'varredir_close'
+          If set, the shell automatically closes file descriptors
+          assigned using the '{varname}' redirection syntax (*note
+          Redirections::) instead of leaving them open when the command
+          completes.
+
+     'xpg_echo'
+          If set, the 'echo' builtin expands backslash-escape sequences
+          by default.
+
+
+File: bashref.info,  Node: Special Builtins,  Prev: Modifying Shell Behavior,  Up: Shell Builtin Commands
+
+4.4 Special Builtins
+====================
+
+For historical reasons, the POSIX standard has classified several
+builtin commands as _special_.  When Bash is executing in POSIX mode,
+the special builtins differ from other builtin commands in three
+respects:
+
+  1. Special builtins are found before shell functions during command
+     lookup.
+
+  2. If a special builtin returns an error status, a non-interactive
+     shell exits.
+
+  3. Assignment statements preceding the command stay in effect in the
+     shell environment after the command completes.
+
+   When Bash is not executing in POSIX mode, these builtins behave no
+differently than the rest of the Bash builtin commands.  The Bash POSIX
+mode is described in *note Bash POSIX Mode::.
+
+   These are the POSIX special builtins:
+     break : . continue eval exec exit export readonly return set
+     shift trap unset
+
+
+File: bashref.info,  Node: Shell Variables,  Next: Bash Features,  Prev: Shell Builtin Commands,  Up: Top
+
+5 Shell Variables
+*****************
+
+* Menu:
+
+* Bourne Shell Variables::	Variables which Bash uses in the same way
+				as the Bourne Shell.
+* Bash Variables::		List of variables that exist in Bash.
+
+This chapter describes the shell variables that Bash uses.  Bash
+automatically assigns default values to a number of variables.
+
+
+File: bashref.info,  Node: Bourne Shell Variables,  Next: Bash Variables,  Up: Shell Variables
+
+5.1 Bourne Shell Variables
+==========================
+
+Bash uses certain shell variables in the same way as the Bourne shell.
+In some cases, Bash assigns a default value to the variable.
+
+'CDPATH'
+     A colon-separated list of directories used as a search path for the
+     'cd' builtin command.
+
+'HOME'
+     The current user's home directory; the default for the 'cd' builtin
+     command.  The value of this variable is also used by tilde
+     expansion (*note Tilde Expansion::).
+
+'IFS'
+     A list of characters that separate fields; used when the shell
+     splits words as part of expansion.
+
+'MAIL'
+     If this parameter is set to a filename or directory name and the
+     'MAILPATH' variable is not set, Bash informs the user of the
+     arrival of mail in the specified file or Maildir-format directory.
+
+'MAILPATH'
+     A colon-separated list of filenames which the shell periodically
+     checks for new mail.  Each list entry can specify the message that
+     is printed when new mail arrives in the mail file by separating the
+     filename from the message with a '?'.  When used in the text of the
+     message, '$_' expands to the name of the current mail file.
+
+'OPTARG'
+     The value of the last option argument processed by the 'getopts'
+     builtin.
+
+'OPTIND'
+     The index of the last option argument processed by the 'getopts'
+     builtin.
+
+'PATH'
+     A colon-separated list of directories in which the shell looks for
+     commands.  A zero-length (null) directory name in the value of
+     'PATH' indicates the current directory.  A null directory name may
+     appear as two adjacent colons, or as an initial or trailing colon.
+
+'PS1'
+     The primary prompt string.  The default value is '\s-\v\$ '.  *Note
+     Controlling the Prompt::, for the complete list of escape sequences
+     that are expanded before 'PS1' is displayed.
+
+'PS2'
+     The secondary prompt string.  The default value is '> '.  'PS2' is
+     expanded in the same way as 'PS1' before being displayed.
+
+
+File: bashref.info,  Node: Bash Variables,  Prev: Bourne Shell Variables,  Up: Shell Variables
+
+5.2 Bash Variables
+==================
+
+These variables are set or used by Bash, but other shells do not
+normally treat them specially.
+
+   A few variables used by Bash are described in different chapters:
+variables for controlling the job control facilities (*note Job Control
+Variables::).
+
+'_'
+     ($_, an underscore.)  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.
+
+'BASH'
+     The full pathname used to execute the current instance of Bash.
+
+'BASHOPTS'
+     A colon-separated list of enabled shell options.  Each word in the
+     list is a valid argument for the '-s' option to the 'shopt' builtin
+     command (*note The Shopt Builtin::).  The options appearing in
+     'BASHOPTS' are those reported as 'on' by 'shopt'.  If this variable
+     is in the environment when Bash starts up, each shell option in the
+     list will be enabled before reading any startup files.  This
+     variable is readonly.
+
+'BASHPID'
+     Expands to the process ID of the current Bash process.  This
+     differs from '$$' under certain circumstances, such as subshells
+     that do not require Bash to be re-initialized.  Assignments to
+     'BASHPID' have no effect.  If 'BASHPID' is unset, it loses its
+     special properties, even if it is subsequently reset.
+
+'BASH_ALIASES'
+     An associative array variable whose members correspond to the
+     internal list of aliases as maintained by the 'alias' builtin.
+     (*note Bourne Shell Builtins::).  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 'BASH_ALIASES' is unset, it loses its special properties, even
+     if it is subsequently reset.
+
+'BASH_ARGC'
+     An array variable whose values are the number of parameters in each
+     frame of the current bash execution call stack.  The number of
+     parameters to the current subroutine (shell function or script
+     executed with '.' or 'source') is at the top of the stack.  When a
+     subroutine is executed, the number of parameters passed is pushed
+     onto 'BASH_ARGC'.  The shell sets 'BASH_ARGC' only when in extended
+     debugging mode (see *note The Shopt Builtin:: for a description of
+     the 'extdebug' option to the 'shopt' builtin).  Setting 'extdebug'
+     after the shell has started to execute a script, or referencing
+     this variable when 'extdebug' is not set, may result in
+     inconsistent values.
+
+'BASH_ARGV'
+     An array variable containing all of the parameters in the current
+     bash 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 'BASH_ARGV'.  The shell
+     sets 'BASH_ARGV' only when in extended debugging mode (see *note
+     The Shopt Builtin:: for a description of the 'extdebug' option to
+     the 'shopt' builtin).  Setting 'extdebug' after the shell has
+     started to execute a script, or referencing this variable when
+     'extdebug' is not set, may result in inconsistent values.
+
+'BASH_ARGV0'
+     When referenced, this variable expands to the name of the shell or
+     shell script (identical to '$0'; *Note Special Parameters::, for
+     the description of special parameter 0).  Assignment to
+     'BASH_ARGV0' causes the value assigned to also be assigned to '$0'.
+     If 'BASH_ARGV0' is unset, it loses its special properties, even if
+     it is subsequently reset.
+
+'BASH_CMDS'
+     An associative array variable whose members correspond to the
+     internal hash table of commands as maintained by the 'hash' builtin
+     (*note Bourne Shell Builtins::).  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 'BASH_CMDS' is unset, it loses its special properties,
+     even if it is subsequently reset.
+
+'BASH_COMMAND'
+     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
+     'BASH_COMMAND' is unset, it loses its special properties, even if
+     it is subsequently reset.
+
+'BASH_COMPAT'
+     The value is used to set the shell's compatibility level.  *Note
+     Shell Compatibility Mode::, 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 'BASH_COMPAT' is unset or set to
+     the empty string, the compatibility level is set to the default for
+     the current version.  If 'BASH_COMPAT' 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 (*note Shell Compatibility
+     Mode::).  For example, 4.2 and 42 are valid values that correspond
+     to the 'compat42' 'shopt' option and set the compatibility level to
+     42.  The current version is also a valid value.
+
+'BASH_ENV'
+     If this variable is set when Bash is invoked to execute a shell
+     script, its value is expanded and used as the name of a startup
+     file to read before executing the script.  *Note Bash Startup
+     Files::.
+
+'BASH_EXECUTION_STRING'
+     The command argument to the '-c' invocation option.
+
+'BASH_LINENO'
+     An array variable whose members are the line numbers in source
+     files where each corresponding member of 'FUNCNAME' was invoked.
+     '${BASH_LINENO[$i]}' is the line number in the source file
+     ('${BASH_SOURCE[$i+1]}') where '${FUNCNAME[$i]}' was called (or
+     '${BASH_LINENO[$i-1]}' if referenced within another shell
+     function).  Use 'LINENO' to obtain the current line number.
+
+'BASH_LOADABLES_PATH'
+     A colon-separated list of directories in which the shell looks for
+     dynamically loadable builtins specified by the 'enable' command.
+
+'BASH_REMATCH'
+     An array variable whose members are assigned by the '=~' binary
+     operator to the '[[' conditional command (*note Conditional
+     Constructs::).  The element with index 0 is the portion of the
+     string matching the entire regular expression.  The element with
+     index N is the portion of the string matching the Nth parenthesized
+     subexpression.
+
+'BASH_SOURCE'
+     An array variable whose members are the source filenames where the
+     corresponding shell function names in the 'FUNCNAME' array variable
+     are defined.  The shell function '${FUNCNAME[$i]}' is defined in
+     the file '${BASH_SOURCE[$i]}' and called from
+     '${BASH_SOURCE[$i+1]}'
+
+'BASH_SUBSHELL'
+     Incremented by one within each subshell or subshell environment
+     when the shell begins executing in that environment.  The initial
+     value is 0.  If 'BASH_SUBSHELL' is unset, it loses its special
+     properties, even if it is subsequently reset.
+
+'BASH_VERSINFO'
+     A readonly array variable (*note Arrays::) whose members hold
+     version information for this instance of Bash.  The values assigned
+     to the array members are as follows:
+
+     'BASH_VERSINFO[0]'
+          The major version number (the "release").
+
+     'BASH_VERSINFO[1]'
+          The minor version number (the "version").
+
+     'BASH_VERSINFO[2]'
+          The patch level.
+
+     'BASH_VERSINFO[3]'
+          The build version.
+
+     'BASH_VERSINFO[4]'
+          The release status (e.g., 'beta1').
+
+     'BASH_VERSINFO[5]'
+          The value of 'MACHTYPE'.
+
+'BASH_VERSION'
+     The version number of the current instance of Bash.
+
+'BASH_XTRACEFD'
+     If set to an integer corresponding to a valid file descriptor, Bash
+     will write the trace output generated when 'set -x' is enabled to
+     that file descriptor.  This allows tracing output to be separated
+     from diagnostic and error messages.  The file descriptor is closed
+     when 'BASH_XTRACEFD' is unset or assigned a new value.  Unsetting
+     'BASH_XTRACEFD' or assigning it the empty string causes the trace
+     output to be sent to the standard error.  Note that setting
+     'BASH_XTRACEFD' to 2 (the standard error file descriptor) and then
+     unsetting it will result in the standard error being closed.
+
+'CHILD_MAX'
+     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.
+
+'COLUMNS'
+     Used by the 'select' command to determine the terminal width when
+     printing selection lists.  Automatically set if the 'checkwinsize'
+     option is enabled (*note The Shopt Builtin::), or in an interactive
+     shell upon receipt of a 'SIGWINCH'.
+
+'COMP_CWORD'
+     An index into '${COMP_WORDS}' of the word containing the current
+     cursor position.  This variable is available only in shell
+     functions invoked by the programmable completion facilities (*note
+     Programmable Completion::).
+
+'COMP_LINE'
+     The current command line.  This variable is available only in shell
+     functions and external commands invoked by the programmable
+     completion facilities (*note Programmable Completion::).
+
+'COMP_POINT'
+     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
+     '${#COMP_LINE}'.  This variable is available only in shell
+     functions and external commands invoked by the programmable
+     completion facilities (*note Programmable Completion::).
+
+'COMP_TYPE'
+     Set to an integer value corresponding to the type of completion
+     attempted that caused a completion function to be called: <TAB>,
+     for normal completion, '?', for listing completions after
+     successive tabs, '!', for listing alternatives on partial word
+     completion, '@', to list completions if the word is not unmodified,
+     or '%', for menu completion.  This variable is available only in
+     shell functions and external commands invoked by the programmable
+     completion facilities (*note Programmable Completion::).
+
+'COMP_KEY'
+     The key (or final key of a key sequence) used to invoke the current
+     completion function.
+
+'COMP_WORDBREAKS'
+     The set of characters that the Readline library treats as word
+     separators when performing word completion.  If 'COMP_WORDBREAKS'
+     is unset, it loses its special properties, even if it is
+     subsequently reset.
+
+'COMP_WORDS'
+     An array variable consisting of the individual words in the current
+     command line.  The line is split into words as Readline would split
+     it, using 'COMP_WORDBREAKS' as described above.  This variable is
+     available only in shell functions invoked by the programmable
+     completion facilities (*note Programmable Completion::).
+
+'COMPREPLY'
+     An array variable from which Bash reads the possible completions
+     generated by a shell function invoked by the programmable
+     completion facility (*note Programmable Completion::).  Each array
+     element contains one possible completion.
+
+'COPROC'
+     An array variable created to hold the file descriptors for output
+     from and input to an unnamed coprocess (*note Coprocesses::).
+
+'DIRSTACK'
+     An array variable containing the current contents of the directory
+     stack.  Directories appear in the stack in the order they are
+     displayed by the 'dirs' builtin.  Assigning to members of this
+     array variable may be used to modify directories already in the
+     stack, but the 'pushd' and 'popd' builtins must be used to add and
+     remove directories.  Assignment to this variable will not change
+     the current directory.  If 'DIRSTACK' is unset, it loses its
+     special properties, even if it is subsequently reset.
+
+'EMACS'
+     If Bash finds this variable in the environment when the shell
+     starts with value 't', it assumes that the shell is running in an
+     Emacs shell buffer and disables line editing.
+
+'ENV'
+     Expanded and executed similarly to 'BASH_ENV' (*note Bash Startup
+     Files::) when an interactive shell is invoked in POSIX Mode (*note
+     Bash POSIX Mode::).
+
+'EPOCHREALTIME'
+     Each time this parameter is referenced, it expands to the number of
+     seconds since the Unix Epoch as a floating point value with
+     micro-second granularity (see the documentation for the C library
+     function 'time' for the definition of Epoch).  Assignments to
+     'EPOCHREALTIME' are ignored.  If 'EPOCHREALTIME' is unset, it loses
+     its special properties, even if it is subsequently reset.
+
+'EPOCHSECONDS'
+     Each time this parameter is referenced, it expands to the number of
+     seconds since the Unix Epoch (see the documentation for the C
+     library function 'time' for the definition of Epoch).  Assignments
+     to 'EPOCHSECONDS' are ignored.  If 'EPOCHSECONDS' is unset, it
+     loses its special properties, even if it is subsequently reset.
+
+'EUID'
+     The numeric effective user id of the current user.  This variable
+     is readonly.
+
+'EXECIGNORE'
+     A colon-separated list of shell patterns (*note Pattern Matching::)
+     defining the list of filenames to be ignored by command search
+     using 'PATH'.  Files whose full pathnames match one of these
+     patterns are not considered executable files for the purposes of
+     completion and command execution via 'PATH' lookup.  This does not
+     affect the behavior of the '[', 'test', and '[[' commands.  Full
+     pathnames in the command hash table are not subject to
+     'EXECIGNORE'.  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 'extglob' shell
+     option.
+
+'FCEDIT'
+     The editor used as a default by the '-e' option to the 'fc' builtin
+     command.
+
+'FIGNORE'
+     A colon-separated list of suffixes to ignore when performing
+     filename completion.  A filename whose suffix matches one of the
+     entries in 'FIGNORE' is excluded from the list of matched
+     filenames.  A sample value is '.o:~'
+
+'FUNCNAME'
+     An array variable containing the names of all shell functions
+     currently in the execution call stack.  The element with index 0 is
+     the name of any currently-executing shell function.  The
+     bottom-most element (the one with the highest index) is '"main"'.
+     This variable exists only when a shell function is executing.
+     Assignments to 'FUNCNAME' have no effect.  If 'FUNCNAME' is unset,
+     it loses its special properties, even if it is subsequently reset.
+
+     This variable can be used with 'BASH_LINENO' and 'BASH_SOURCE'.
+     Each element of 'FUNCNAME' has corresponding elements in
+     'BASH_LINENO' and 'BASH_SOURCE' to describe the call stack.  For
+     instance, '${FUNCNAME[$i]}' was called from the file
+     '${BASH_SOURCE[$i+1]}' at line number '${BASH_LINENO[$i]}'.  The
+     'caller' builtin displays the current call stack using this
+     information.
+
+'FUNCNEST'
+     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.
+
+'GLOBIGNORE'
+     A colon-separated list of patterns defining the set of file names
+     to be ignored by filename expansion.  If a file name matched by a
+     filename expansion pattern also matches one of the patterns in
+     'GLOBIGNORE', it is removed from the list of matches.  The pattern
+     matching honors the setting of the 'extglob' shell option.
+
+'GROUPS'
+     An array variable containing the list of groups of which the
+     current user is a member.  Assignments to 'GROUPS' have no effect.
+     If 'GROUPS' is unset, it loses its special properties, even if it
+     is subsequently reset.
+
+'histchars'
+     Up to three characters which control history expansion, quick
+     substitution, and tokenization (*note History Interaction::).  The
+     first character is the "history expansion" character, that is, the
+     character which signifies the start of a history expansion,
+     normally '!'.  The second character is the character which
+     signifies 'quick substitution' when seen as the first character on
+     a line, normally '^'.  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, usually '#'.
+     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.
+
+'HISTCMD'
+     The history number, or index in the history list, of the current
+     command.  Assignments to 'HISTCMD' are ignored.  If 'HISTCMD' is
+     unset, it loses its special properties, even if it is subsequently
+     reset.
+
+'HISTCONTROL'
+     A colon-separated list of values controlling how commands are saved
+     on the history list.  If the list of values includes 'ignorespace',
+     lines which begin with a space character are not saved in the
+     history list.  A value of 'ignoredups' causes lines which match the
+     previous history entry to not be saved.  A value of 'ignoreboth' is
+     shorthand for 'ignorespace' and 'ignoredups'.  A value of
+     'erasedups' 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 'HISTCONTROL' 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
+     'HISTIGNORE'.  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 'HISTCONTROL'.
+
+'HISTFILE'
+     The name of the file to which the command history is saved.  The
+     default value is '~/.bash_history'.
+
+'HISTFILESIZE'
+     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 'HISTSIZE' after reading any
+     startup files.
+
+'HISTIGNORE'
+     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 '*' is appended).  Each pattern is tested against
+     the line after the checks specified by 'HISTCONTROL' are applied.
+     In addition to the normal shell pattern matching characters, '&'
+     matches the previous history line.  '&' 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
+     'HISTIGNORE'.  The pattern matching honors the setting of the
+     'extglob' shell option.
+
+     'HISTIGNORE' subsumes the function of 'HISTCONTROL'.  A pattern of
+     '&' is identical to 'ignoredups', and a pattern of '[ ]*' is
+     identical to 'ignorespace'.  Combining these two patterns,
+     separating them with a colon, provides the functionality of
+     'ignoreboth'.
+
+'HISTSIZE'
+     The maximum number of commands to remember on the history list.  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.
+
+'HISTTIMEFORMAT'
+     If this variable is set and not null, its value is used as a format
+     string for 'strftime' to print the time stamp associated with each
+     history entry displayed by the 'history' 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.
+
+'HOSTFILE'
+     Contains the name of a file in the same format as '/etc/hosts' 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, Bash adds the contents of the new file
+     to the existing list.  If 'HOSTFILE' is set, but has no value, or
+     does not name a readable file, Bash attempts to read '/etc/hosts'
+     to obtain the list of possible hostname completions.  When
+     'HOSTFILE' is unset, the hostname list is cleared.
+
+'HOSTNAME'
+     The name of the current host.
+
+'HOSTTYPE'
+     A string describing the machine Bash is running on.
+
+'IGNOREEOF'
+     Controls the action of the shell on receipt of an 'EOF' character
+     as the sole input.  If set, the value denotes the number of
+     consecutive 'EOF' characters that can be read as the first
+     character on an input line before the shell will exit.  If the
+     variable exists but does not have a numeric value, or has no value,
+     then the default is 10.  If the variable does not exist, then 'EOF'
+     signifies the end of input to the shell.  This is only in effect
+     for interactive shells.
+
+'INPUTRC'
+     The name of the Readline initialization file, overriding the
+     default of '~/.inputrc'.
+
+'INSIDE_EMACS'
+     If Bash finds this variable in the environment when the shell
+     starts, it assumes that the shell is running in an Emacs shell
+     buffer and may disable line editing depending on the value of
+     'TERM'.
+
+'LANG'
+     Used to determine the locale category for any category not
+     specifically selected with a variable starting with 'LC_'.
+
+'LC_ALL'
+     This variable overrides the value of 'LANG' and any other 'LC_'
+     variable specifying a locale category.
+
+'LC_COLLATE'
+     This variable determines the collation order used when sorting the
+     results of filename expansion, and determines the behavior of range
+     expressions, equivalence classes, and collating sequences within
+     filename expansion and pattern matching (*note Filename
+     Expansion::).
+
+'LC_CTYPE'
+     This variable determines the interpretation of characters and the
+     behavior of character classes within filename expansion and pattern
+     matching (*note Filename Expansion::).
+
+'LC_MESSAGES'
+     This variable determines the locale used to translate double-quoted
+     strings preceded by a '$' (*note Locale Translation::).
+
+'LC_NUMERIC'
+     This variable determines the locale category used for number
+     formatting.
+
+'LC_TIME'
+     This variable determines the locale category used for data and time
+     formatting.
+
+'LINENO'
+     The line number in the script or shell function currently
+     executing.  If 'LINENO' is unset, it loses its special properties,
+     even if it is subsequently reset.
+
+'LINES'
+     Used by the 'select' command to determine the column length for
+     printing selection lists.  Automatically set if the 'checkwinsize'
+     option is enabled (*note The Shopt Builtin::), or in an interactive
+     shell upon receipt of a 'SIGWINCH'.
+
+'MACHTYPE'
+     A string that fully describes the system type on which Bash is
+     executing, in the standard GNU CPU-COMPANY-SYSTEM format.
+
+'MAILCHECK'
+     How often (in seconds) that the shell should check for mail in the
+     files specified in the 'MAILPATH' or 'MAIL' variables.  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.
+
+'MAPFILE'
+     An array variable created to hold the text read by the 'mapfile'
+     builtin when no variable name is supplied.
+
+'OLDPWD'
+     The previous working directory as set by the 'cd' builtin.
+
+'OPTERR'
+     If set to the value 1, Bash displays error messages generated by
+     the 'getopts' builtin command.
+
+'OSTYPE'
+     A string describing the operating system Bash is running on.
+
+'PIPESTATUS'
+     An array variable (*note Arrays::) containing a list of exit status
+     values from the processes in the most-recently-executed foreground
+     pipeline (which may contain only a single command).
+
+'POSIXLY_CORRECT'
+     If this variable is in the environment when Bash starts, the shell
+     enters POSIX mode (*note Bash POSIX Mode::) before reading the
+     startup files, as if the '--posix' invocation option had been
+     supplied.  If it is set while the shell is running, Bash enables
+     POSIX mode, as if the command
+          set -o posix
+     had been executed.  When the shell enters POSIX mode, it sets this
+     variable if it was not already set.
+
+'PPID'
+     The process ID of the shell's parent process.  This variable is
+     readonly.
+
+'PROMPT_COMMAND'
+     If this variable is set, and is an array, the value of each set
+     element is interpreted as a command to execute before printing the
+     primary prompt ('$PS1').  If this is set but not an array variable,
+     its value is used as a command to execute instead.
+
+'PROMPT_DIRTRIM'
+     If set to a number greater than zero, the value is used as the
+     number of trailing directory components to retain when expanding
+     the '\w' and '\W' prompt string escapes (*note Controlling the
+     Prompt::).  Characters removed are replaced with an ellipsis.
+
+'PS0'
+     The value of this parameter is expanded like 'PS1' and displayed by
+     interactive shells after reading a command and before the command
+     is executed.
+
+'PS3'
+     The value of this variable is used as the prompt for the 'select'
+     command.  If this variable is not set, the 'select' command prompts
+     with '#? '
+
+'PS4'
+     The value of this parameter is expanded like 'PS1' and the expanded
+     value is the prompt printed before the command line is echoed when
+     the '-x' option is set (*note The Set Builtin::).  The first
+     character of the expanded value is replicated multiple times, as
+     necessary, to indicate multiple levels of indirection.  The default
+     is '+ '.
+
+'PWD'
+     The current working directory as set by the 'cd' builtin.
+
+'RANDOM'
+     Each time this parameter is referenced, it expands to a random
+     integer between 0 and 32767.  Assigning a value to this variable
+     seeds the random number generator.  If 'RANDOM' is unset, it loses
+     its special properties, even if it is subsequently reset.
+
+'READLINE_ARGUMENT'
+     Any numeric argument given to a Readline command that was defined
+     using 'bind -x' (*note Bash Builtins:: when it was invoked.
+
+'READLINE_LINE'
+     The contents of the Readline line buffer, for use with 'bind -x'
+     (*note Bash Builtins::).
+
+'READLINE_MARK'
+     The position of the "mark" (saved insertion point) in the Readline
+     line buffer, for use with 'bind -x' (*note Bash Builtins::).  The
+     characters between the insertion point and the mark are often
+     called the "region".
+
+'READLINE_POINT'
+     The position of the insertion point in the Readline line buffer,
+     for use with 'bind -x' (*note Bash Builtins::).
+
+'REPLY'
+     The default variable for the 'read' builtin.
+
+'SECONDS'
+     This variable expands to the number of seconds since the shell was
+     started.  Assignment to this variable resets the count to the value
+     assigned, and the expanded value becomes the value assigned plus
+     the number of seconds since the assignment.  The number of seconds
+     at shell invocation and the current time are always determined by
+     querying the system clock.  If 'SECONDS' is unset, it loses its
+     special properties, even if it is subsequently reset.
+
+'SHELL'
+     This environment variable expands to the full pathname to the
+     shell.  If it is not set when the shell starts, Bash assigns to it
+     the full pathname of the current user's login shell.
+
+'SHELLOPTS'
+     A colon-separated list of enabled shell options.  Each word in the
+     list is a valid argument for the '-o' option to the 'set' builtin
+     command (*note The Set Builtin::).  The options appearing in
+     'SHELLOPTS' are those reported as 'on' by 'set -o'.  If this
+     variable is in the environment when Bash starts up, each shell
+     option in the list will be enabled before reading any startup
+     files.  This variable is readonly.
+
+'SHLVL'
+     Incremented by one each time a new instance of Bash is started.
+     This is intended to be a count of how deeply your Bash shells are
+     nested.
+
+'SRANDOM'
+     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 '/dev/urandom' or 'arc4random', 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 'SRANDOM' is unset, it loses its
+     special properties, even if it is subsequently reset.
+
+'TIMEFORMAT'
+     The value of this parameter is used as a format string specifying
+     how the timing information for pipelines prefixed with the 'time'
+     reserved word should be displayed.  The '%' 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.
+
+     '%%'
+          A literal '%'.
+
+     '%[P][l]R'
+          The elapsed time in seconds.
+
+     '%[P][l]U'
+          The number of CPU seconds spent in user mode.
+
+     '%[P][l]S'
+          The number of CPU seconds spent in system mode.
+
+     '%P'
+          The CPU percentage, computed as (%U + %S) / %R.
+
+     The optional P is a digit specifying the precision, 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 P greater than 3 are
+     changed to 3.  If P is not specified, the value 3 is used.
+
+     The optional 'l' specifies a longer format, including minutes, of
+     the form MMmSS.FFs.  The value of P determines whether or not the
+     fraction is included.
+
+     If this variable is not set, Bash acts as if it had the value
+          $'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'
+     If the value is null, no timing information is displayed.  A
+     trailing newline is added when the format string is displayed.
+
+'TMOUT'
+     If set to a value greater than zero, 'TMOUT' is treated as the
+     default timeout for the 'read' builtin (*note Bash Builtins::).
+     The 'select' command (*note Conditional Constructs::) terminates if
+     input does not arrive after 'TMOUT' 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.  Bash terminates after waiting for that number of seconds
+     if a complete line of input does not arrive.
+
+'TMPDIR'
+     If set, Bash uses its value as the name of a directory in which
+     Bash creates temporary files for the shell's use.
+
+'UID'
+     The numeric real user id of the current user.  This variable is
+     readonly.
+
+
+File: bashref.info,  Node: Bash Features,  Next: Job Control,  Prev: Shell Variables,  Up: Top
+
+6 Bash Features
+***************
+
+This chapter describes features unique to Bash.
+
+* Menu:
+
+* Invoking Bash::		Command line options that you can give
+				to Bash.
+* Bash Startup Files::		When and how Bash executes scripts.
+* Interactive Shells::		What an interactive shell is.
+* Bash Conditional Expressions::	Primitives used in composing expressions for
+				the 'test' builtin.
+* Shell Arithmetic::		Arithmetic on shell variables.
+* Aliases::			Substituting one command for another.
+* Arrays::			Array Variables.
+* The Directory Stack::		History of visited directories.
+* Controlling the Prompt::	Customizing the various prompt strings.
+* The Restricted Shell::	A more controlled mode of shell execution.
+* Bash POSIX Mode::		Making Bash behave more closely to what
+				the POSIX standard specifies.
+* Shell Compatibility Mode::	How Bash supports behavior that was present
+				in earlier versions and has changed.
+
+
+File: bashref.info,  Node: Invoking Bash,  Next: Bash Startup Files,  Up: Bash Features
+
+6.1 Invoking Bash
+=================
+
+     bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o OPTION]
+         [-O SHOPT_OPTION] [ARGUMENT ...]
+     bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o OPTION]
+         [-O SHOPT_OPTION] -c STRING [ARGUMENT ...]
+     bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o OPTION]
+         [-O SHOPT_OPTION] [ARGUMENT ...]
+
+   All of the single-character options used with the 'set' builtin
+(*note The Set Builtin::) can be used as options when the shell is
+invoked.  In addition, there are several multi-character options that
+you can use.  These options must appear on the command line before the
+single-character options to be recognized.
+
+'--debugger'
+     Arrange for the debugger profile to be executed before the shell
+     starts.  Turns on extended debugging mode (see *note The Shopt
+     Builtin:: for a description of the 'extdebug' option to the 'shopt'
+     builtin).
+
+'--dump-po-strings'
+     A list of all double-quoted strings preceded by '$' is printed on
+     the standard output in the GNU 'gettext' PO (portable object) file
+     format.  Equivalent to '-D' except for the output format.
+
+'--dump-strings'
+     Equivalent to '-D'.
+
+'--help'
+     Display a usage message on standard output and exit successfully.
+
+'--init-file FILENAME'
+'--rcfile FILENAME'
+     Execute commands from FILENAME (instead of '~/.bashrc') in an
+     interactive shell.
+
+'--login'
+     Equivalent to '-l'.
+
+'--noediting'
+     Do not use the GNU Readline library (*note Command Line Editing::)
+     to read command lines when the shell is interactive.
+
+'--noprofile'
+     Don't load the system-wide startup file '/etc/profile' or any of
+     the personal initialization files '~/.bash_profile',
+     '~/.bash_login', or '~/.profile' when Bash is invoked as a login
+     shell.
+
+'--norc'
+     Don't read the '~/.bashrc' initialization file in an interactive
+     shell.  This is on by default if the shell is invoked as 'sh'.
+
+'--posix'
+     Change the behavior of Bash where the default operation differs
+     from the POSIX standard to match the standard.  This is intended to
+     make Bash behave as a strict superset of that standard.  *Note Bash
+     POSIX Mode::, for a description of the Bash POSIX mode.
+
+'--restricted'
+     Make the shell a restricted shell (*note The Restricted Shell::).
+
+'--verbose'
+     Equivalent to '-v'.  Print shell input lines as they're read.
+
+'--version'
+     Show version information for this instance of Bash on the standard
+     output and exit successfully.
+
+   There are several single-character options that may be supplied at
+invocation which are not available with the 'set' builtin.
+
+'-c'
+     Read and execute commands from the first non-option argument
+     COMMAND_STRING, then exit.  If there are arguments after the
+     COMMAND_STRING, the first argument is assigned to '$0' and any
+     remaining arguments are assigned to the positional parameters.  The
+     assignment to '$0' sets the name of the shell, which is used in
+     warning and error messages.
+
+'-i'
+     Force the shell to run interactively.  Interactive shells are
+     described in *note Interactive Shells::.
+
+'-l'
+     Make this shell act as if it had been directly invoked by login.
+     When the shell is interactive, this is equivalent to starting a
+     login shell with 'exec -l bash'.  When the shell is not
+     interactive, the login shell startup files will be executed.  'exec
+     bash -l' or 'exec bash --login' will replace the current shell with
+     a Bash login shell.  *Note Bash Startup Files::, for a description
+     of the special behavior of a login shell.
+
+'-r'
+     Make the shell a restricted shell (*note The Restricted Shell::).
+
+'-s'
+     If this option is present, or if no arguments remain after option
+     processing, then commands are read from the standard input.  This
+     option allows the positional parameters to be set when invoking an
+     interactive shell or when reading input through a pipe.
+
+'-D'
+     A list of all double-quoted strings preceded by '$' is printed on
+     the standard output.  These are the strings that are subject to
+     language translation when the current locale is not 'C' or 'POSIX'
+     (*note Locale Translation::).  This implies the '-n' option; no
+     commands will be executed.
+
+'[-+]O [SHOPT_OPTION]'
+     SHOPT_OPTION is one of the shell options accepted by the 'shopt'
+     builtin (*note The Shopt Builtin::).  If SHOPT_OPTION is present,
+     '-O' sets the value of that option; '+O' unsets it.  If
+     SHOPT_OPTION is not supplied, the names and values of the shell
+     options accepted by 'shopt' are printed on the standard output.  If
+     the invocation option is '+O', the output is displayed in a format
+     that may be reused as input.
+
+'--'
+     A '--' signals the end of options and disables further option
+     processing.  Any arguments after the '--' are treated as filenames
+     and arguments.
+
+   A _login_ shell is one whose first character of argument zero is '-',
+or one invoked with the '--login' option.
+
+   An _interactive_ shell is one started without non-option arguments,
+unless '-s' is specified, without specifying the '-c' option, and whose
+input and output are both connected to terminals (as determined by
+'isatty(3)'), or one started with the '-i' option.  *Note Interactive
+Shells::, for more information.
+
+   If arguments remain after option processing, and neither the '-c' nor
+the '-s' option has been supplied, the first argument is assumed to be
+the name of a file containing shell commands (*note Shell Scripts::).
+When Bash is invoked in this fashion, '$0' is set to the name of the
+file, and the positional parameters are set to the remaining arguments.
+Bash reads and executes commands from this file, then exits.  Bash'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.
+
+
+File: bashref.info,  Node: Bash Startup Files,  Next: Interactive Shells,  Prev: Invoking Bash,  Up: Bash Features
+
+6.2 Bash Startup Files
+======================
+
+This section describes how Bash executes its startup files.  If any of
+the files exist but cannot be read, Bash reports an error.  Tildes are
+expanded in filenames as described above under Tilde Expansion (*note
+Tilde Expansion::).
+
+   Interactive shells are described in *note Interactive Shells::.
+
+Invoked as an interactive login shell, or with '--login'
+........................................................
+
+When Bash is invoked as an interactive login shell, or as a
+non-interactive shell with the '--login' option, it first reads and
+executes commands from the file '/etc/profile', if that file exists.
+After reading that file, it looks for '~/.bash_profile',
+'~/.bash_login', and '~/.profile', in that order, and reads and executes
+commands from the first one that exists and is readable.  The
+'--noprofile' option may be used when the shell is started to inhibit
+this behavior.
+
+   When an interactive login shell exits, or a non-interactive login
+shell executes the 'exit' builtin command, Bash reads and executes
+commands from the file '~/.bash_logout', if it exists.
+
+Invoked as an interactive non-login shell
+.........................................
+
+When an interactive shell that is not a login shell is started, Bash
+reads and executes commands from '~/.bashrc', if that file exists.  This
+may be inhibited by using the '--norc' option.  The '--rcfile FILE'
+option will force Bash to read and execute commands from FILE instead of
+'~/.bashrc'.
+
+   So, typically, your '~/.bash_profile' contains the line
+     if [ -f ~/.bashrc ]; then . ~/.bashrc; fi
+after (or before) any login-specific initializations.
+
+Invoked non-interactively
+.........................
+
+When Bash is started non-interactively, to run a shell script, for
+example, it looks for the variable 'BASH_ENV' 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.  Bash behaves as if the
+following command were executed:
+     if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
+but the value of the 'PATH' variable is not used to search for the
+filename.
+
+   As noted above, if a non-interactive shell is invoked with the
+'--login' option, Bash attempts to read and execute commands from the
+login shell startup files.
+
+Invoked with name 'sh'
+......................
+
+If Bash is invoked with the name 'sh', it tries to mimic the startup
+behavior of historical versions of 'sh' as closely as possible, while
+conforming to the POSIX standard as well.
+
+   When invoked as an interactive login shell, or as a non-interactive
+shell with the '--login' option, it first attempts to read and execute
+commands from '/etc/profile' and '~/.profile', in that order.  The
+'--noprofile' option may be used to inhibit this behavior.  When invoked
+as an interactive shell with the name 'sh', Bash looks for the variable
+'ENV', 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
+'sh' does not attempt to read and execute commands from any other
+startup files, the '--rcfile' option has no effect.  A non-interactive
+shell invoked with the name 'sh' does not attempt to read any other
+startup files.
+
+   When invoked as 'sh', Bash enters POSIX mode after the startup files
+are read.
+
+Invoked in POSIX mode
+.....................
+
+When Bash is started in POSIX mode, as with the '--posix' command line
+option, it follows the POSIX standard for startup files.  In this mode,
+interactive shells expand the 'ENV' variable and commands are read and
+executed from the file whose name is the expanded value.  No other
+startup files are read.
+
+Invoked by remote shell daemon
+..............................
+
+Bash attempts to determine when it is being run with its standard input
+connected to a network connection, as when executed by the historical
+remote shell daemon, usually 'rshd', or the secure shell daemon 'sshd'.
+If Bash determines it is being run non-interactively in this fashion, it
+reads and executes commands from '~/.bashrc', if that file exists and is
+readable.  It will not do this if invoked as 'sh'.  The '--norc' option
+may be used to inhibit this behavior, and the '--rcfile' option may be
+used to force another file to be read, but neither 'rshd' nor 'sshd'
+generally invoke the shell with those options or allow them to be
+specified.
+
+Invoked with unequal effective and real UID/GIDs
+................................................
+
+If Bash is started with the effective user (group) id not equal to the
+real user (group) id, and the '-p' option is not supplied, no startup
+files are read, shell functions are not inherited from the environment,
+the 'SHELLOPTS', 'BASHOPTS', 'CDPATH', and 'GLOBIGNORE' variables, if
+they appear in the environment, are ignored, and the effective user id
+is set to the real user id.  If the '-p' option is supplied at
+invocation, the startup behavior is the same, but the effective user id
+is not reset.
+
+
+File: bashref.info,  Node: Interactive Shells,  Next: Bash Conditional Expressions,  Prev: Bash Startup Files,  Up: Bash Features
+
+6.3 Interactive Shells
+======================
+
+* Menu:
+
+* What is an Interactive Shell?::	What determines whether a shell is Interactive.
+* Is this Shell Interactive?::	How to tell if a shell is interactive.
+* Interactive Shell Behavior::	What changes in an interactive shell?
+
+
+File: bashref.info,  Node: What is an Interactive Shell?,  Next: Is this Shell Interactive?,  Up: Interactive Shells
+
+6.3.1 What is an Interactive Shell?
+-----------------------------------
+
+An interactive shell is one started without non-option arguments (unless
+'-s' is specified) and without specifying the '-c' option, whose input
+and error output are both connected to terminals (as determined by
+'isatty(3)'), or one started with the '-i' option.
+
+   An interactive shell generally reads from and writes to a user's
+terminal.
+
+   The '-s' invocation option may be used to set the positional
+parameters when an interactive shell is started.
+
+
+File: bashref.info,  Node: Is this Shell Interactive?,  Next: Interactive Shell Behavior,  Prev: What is an Interactive Shell?,  Up: Interactive Shells
+
+6.3.2 Is this Shell Interactive?
+--------------------------------
+
+To determine within a startup script whether or not Bash is running
+interactively, test the value of the '-' special parameter.  It contains
+'i' when the shell is interactive.  For example:
+
+     case "$-" in
+     *i*)	echo This shell is interactive ;;
+     *)	echo This shell is not interactive ;;
+     esac
+
+   Alternatively, startup scripts may examine the variable 'PS1'; it is
+unset in non-interactive shells, and set in interactive shells.  Thus:
+
+     if [ -z "$PS1" ]; then
+             echo This shell is not interactive
+     else
+             echo This shell is interactive
+     fi
+
+
+File: bashref.info,  Node: Interactive Shell Behavior,  Prev: Is this Shell Interactive?,  Up: Interactive Shells
+
+6.3.3 Interactive Shell Behavior
+--------------------------------
+
+When the shell is running interactively, it changes its behavior in
+several ways.
+
+  1. Startup files are read and executed as described in *note Bash
+     Startup Files::.
+
+  2. Job Control (*note Job Control::) is enabled by default.  When job
+     control is in effect, Bash ignores the keyboard-generated job
+     control signals 'SIGTTIN', 'SIGTTOU', and 'SIGTSTP'.
+
+  3. Bash expands and displays 'PS1' before reading the first line of a
+     command, and expands and displays 'PS2' before reading the second
+     and subsequent lines of a multi-line command.  Bash expands and
+     displays 'PS0' after it reads a command but before executing it.
+     See *note Controlling the Prompt::, for a complete list of prompt
+     string escape sequences.
+
+  4. Bash executes the values of the set elements of the
+     'PROMPT_COMMAND' array variable as commands before printing the
+     primary prompt, '$PS1' (*note Bash Variables::).
+
+  5. Readline (*note Command Line Editing::) is used to read commands
+     from the user's terminal.
+
+  6. Bash inspects the value of the 'ignoreeof' option to 'set -o'
+     instead of exiting immediately when it receives an 'EOF' on its
+     standard input when reading a command (*note The Set Builtin::).
+
+  7. Command history (*note Bash History Facilities::) and history
+     expansion (*note History Interaction::) are enabled by default.
+     Bash will save the command history to the file named by '$HISTFILE'
+     when a shell with history enabled exits.
+
+  8. Alias expansion (*note Aliases::) is performed by default.
+
+  9. In the absence of any traps, Bash ignores 'SIGTERM' (*note
+     Signals::).
+
+  10. In the absence of any traps, 'SIGINT' is caught and handled (*note
+     Signals::).  'SIGINT' will interrupt some shell builtins.
+
+  11. An interactive login shell sends a 'SIGHUP' to all jobs on exit if
+     the 'huponexit' shell option has been enabled (*note Signals::).
+
+  12. The '-n' invocation option is ignored, and 'set -n' has no effect
+     (*note The Set Builtin::).
+
+  13. Bash will check for mail periodically, depending on the values of
+     the 'MAIL', 'MAILPATH', and 'MAILCHECK' shell variables (*note Bash
+     Variables::).
+
+  14. Expansion errors due to references to unbound shell variables
+     after 'set -u' has been enabled will not cause the shell to exit
+     (*note The Set Builtin::).
+
+  15. The shell will not exit on expansion errors caused by VAR being
+     unset or null in '${VAR:?WORD}' expansions (*note Shell Parameter
+     Expansion::).
+
+  16. Redirection errors encountered by shell builtins will not cause
+     the shell to exit.
+
+  17. When running in POSIX mode, a special builtin returning an error
+     status will not cause the shell to exit (*note Bash POSIX Mode::).
+
+  18. A failed 'exec' will not cause the shell to exit (*note Bourne
+     Shell Builtins::).
+
+  19. Parser syntax errors will not cause the shell to exit.
+
+  20. If the 'cdspell' shell option is enabled, the shell will attempt
+     simple spelling correction for directory arguments to the 'cd'
+     builtin (see the description of the 'cdspell' option to the 'shopt'
+     builtin in *note The Shopt Builtin::).  The 'cdspell' option is
+     only effective in interactive shells.
+
+  21. The shell will check the value of the 'TMOUT' variable and exit if
+     a command is not read within the specified number of seconds after
+     printing '$PS1' (*note Bash Variables::).
+
+
+File: bashref.info,  Node: Bash Conditional Expressions,  Next: Shell Arithmetic,  Prev: Interactive Shells,  Up: Bash Features
+
+6.4 Bash Conditional Expressions
+================================
+
+Conditional expressions are used by the '[[' compound command (*note
+Conditional Constructs::) and the 'test' and '[' builtin commands (*note
+Bourne Shell Builtins::).  The 'test' and '[' commands determine their
+behavior based on the number of arguments; see the descriptions of those
+commands for any other command-specific actions.
+
+   Expressions may be unary or binary, and are formed from the following
+primaries.  Unary expressions are often used to examine the status of a
+file.  There are string operators and numeric comparison operators as
+well.  Bash handles several filenames specially when they are used in
+expressions.  If the operating system on which Bash is running provides
+these special files, Bash will use them; otherwise it will emulate them
+internally with this behavior: If the FILE argument to one of the
+primaries is of the form '/dev/fd/N', then file descriptor N is checked.
+If the FILE argument to one of the primaries is one of '/dev/stdin',
+'/dev/stdout', or '/dev/stderr', file descriptor 0, 1, or 2,
+respectively, is checked.
+
+   When used with '[[', the '<' and '>' operators sort lexicographically
+using the current locale.  The 'test' command uses ASCII ordering.
+
+   Unless otherwise specified, primaries that operate on files follow
+symbolic links and operate on the target of the link, rather than the
+link itself.
+
+'-a FILE'
+     True if FILE exists.
+
+'-b FILE'
+     True if FILE exists and is a block special file.
+
+'-c FILE'
+     True if FILE exists and is a character special file.
+
+'-d FILE'
+     True if FILE exists and is a directory.
+
+'-e FILE'
+     True if FILE exists.
+
+'-f FILE'
+     True if FILE exists and is a regular file.
+
+'-g FILE'
+     True if FILE exists and its set-group-id bit is set.
+
+'-h FILE'
+     True if FILE exists and is a symbolic link.
+
+'-k FILE'
+     True if FILE exists and its "sticky" bit is set.
+
+'-p FILE'
+     True if FILE exists and is a named pipe (FIFO).
+
+'-r FILE'
+     True if FILE exists and is readable.
+
+'-s FILE'
+     True if FILE exists and has a size greater than zero.
+
+'-t FD'
+     True if file descriptor FD is open and refers to a terminal.
+
+'-u FILE'
+     True if FILE exists and its set-user-id bit is set.
+
+'-w FILE'
+     True if FILE exists and is writable.
+
+'-x FILE'
+     True if FILE exists and is executable.
+
+'-G FILE'
+     True if FILE exists and is owned by the effective group id.
+
+'-L FILE'
+     True if FILE exists and is a symbolic link.
+
+'-N FILE'
+     True if FILE exists and has been modified since it was last read.
+
+'-O FILE'
+     True if FILE exists and is owned by the effective user id.
+
+'-S FILE'
+     True if FILE exists and is a socket.
+
+'FILE1 -ef FILE2'
+     True if FILE1 and FILE2 refer to the same device and inode numbers.
+
+'FILE1 -nt FILE2'
+     True if FILE1 is newer (according to modification date) than FILE2,
+     or if FILE1 exists and FILE2 does not.
+
+'FILE1 -ot FILE2'
+     True if FILE1 is older than FILE2, or if FILE2 exists and FILE1
+     does not.
+
+'-o OPTNAME'
+     True if the shell option OPTNAME is enabled.  The list of options
+     appears in the description of the '-o' option to the 'set' builtin
+     (*note The Set Builtin::).
+
+'-v VARNAME'
+     True if the shell variable VARNAME is set (has been assigned a
+     value).
+
+'-R VARNAME'
+     True if the shell variable VARNAME is set and is a name reference.
+
+'-z STRING'
+     True if the length of STRING is zero.
+
+'-n STRING'
+'STRING'
+     True if the length of STRING is non-zero.
+
+'STRING1 == STRING2'
+'STRING1 = STRING2'
+     True if the strings are equal.  When used with the '[[' command,
+     this performs pattern matching as described above (*note
+     Conditional Constructs::).
+
+     '=' should be used with the 'test' command for POSIX conformance.
+
+'STRING1 != STRING2'
+     True if the strings are not equal.
+
+'STRING1 < STRING2'
+     True if STRING1 sorts before STRING2 lexicographically.
+
+'STRING1 > STRING2'
+     True if STRING1 sorts after STRING2 lexicographically.
+
+'ARG1 OP ARG2'
+     'OP' is one of '-eq', '-ne', '-lt', '-le', '-gt', or '-ge'.  These
+     arithmetic binary operators return true if ARG1 is equal to, not
+     equal to, less than, less than or equal to, greater than, or
+     greater than or equal to ARG2, respectively.  ARG1 and ARG2 may be
+     positive or negative integers.  When used with the '[[' command,
+     ARG1 and ARG2 are evaluated as arithmetic expressions (*note Shell
+     Arithmetic::).
+
+
+File: bashref.info,  Node: Shell Arithmetic,  Next: Aliases,  Prev: Bash Conditional Expressions,  Up: Bash Features
+
+6.5 Shell Arithmetic
+====================
+
+The shell allows arithmetic expressions to be evaluated, as one of the
+shell expansions or by using the '((' compound command, the 'let'
+builtin, or the '-i' option to the 'declare' builtin.
+
+   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.
+
+'ID++ ID--'
+     variable post-increment and post-decrement
+
+'++ID --ID'
+     variable pre-increment and pre-decrement
+
+'- +'
+     unary minus and plus
+
+'! ~'
+     logical and bitwise negation
+
+'**'
+     exponentiation
+
+'* / %'
+     multiplication, division, remainder
+
+'+ -'
+     addition, subtraction
+
+'<< >>'
+     left and right bitwise shifts
+
+'<= >= < >'
+     comparison
+
+'== !='
+     equality and inequality
+
+'&'
+     bitwise AND
+
+'^'
+     bitwise exclusive OR
+
+'|'
+     bitwise OR
+
+'&&'
+     logical AND
+
+'||'
+     logical OR
+
+'expr ? expr : expr'
+     conditional operator
+
+'= *= /= %= += -= <<= >>= &= ^= |='
+     assignment
+
+'expr1 , expr2'
+     comma
+
+   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 'integer' attribute using 'declare -i' is assigned a value.  A
+null value evaluates to 0.  A shell variable need not have its 'integer'
+attribute turned on to be used in an expression.
+
+   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 [BASE'#']N, where the optional BASE is a decimal
+number between 2 and 64 representing the arithmetic base, and N is a
+number in that base.  If BASE'#' is omitted, then base 10 is used.  When
+specifying N, 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 BASE is less than or equal to 36, lowercase and
+uppercase letters may be used interchangeably to represent numbers
+between 10 and 35.
+
+   Operators are evaluated in order of precedence.  Sub-expressions in
+parentheses are evaluated first and may override the precedence rules
+above.
+
+
+File: bashref.info,  Node: Aliases,  Next: Arrays,  Prev: Shell Arithmetic,  Up: Bash Features
+
+6.6 Aliases
+===========
+
+"Aliases" 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 'alias' and 'unalias' builtin
+commands.
+
+   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 '/', '$', '`', '=' and any of the shell
+metacharacters 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
+'ls' to '"ls -F"', for instance, and Bash does not try to recursively
+expand the replacement text.  If the last character of the alias value
+is a 'blank', then the next command word following the alias is also
+checked for alias expansion.
+
+   Aliases are created and listed with the 'alias' command, and removed
+with the 'unalias' command.
+
+   There is no mechanism for using arguments in the replacement text, as
+in 'csh'.  If arguments are needed, use a shell function (*note Shell
+Functions::).
+
+   Aliases are not expanded when the shell is not interactive, unless
+the 'expand_aliases' shell option is set using 'shopt' (*note The Shopt
+Builtin::).
+
+   The rules concerning the definition and use of aliases are somewhat
+confusing.  Bash 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 'alias' in compound commands.
+
+   For almost every purpose, shell functions are preferred over aliases.
+
+
+File: bashref.info,  Node: Arrays,  Next: The Directory Stack,  Prev: Aliases,  Up: Bash Features
+
+6.7 Arrays
+==========
+
+Bash provides one-dimensional indexed and associative array variables.
+Any variable may be used as an indexed array; the 'declare' 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 (*note Shell Arithmetic::)) and are zero-based;
+associative arrays use arbitrary strings.  Unless otherwise noted,
+indexed array indices must be non-negative integers.
+
+   An indexed array is created automatically if any variable is assigned
+to using the syntax
+     NAME[SUBSCRIPT]=VALUE
+
+The SUBSCRIPT is treated as an arithmetic expression that must evaluate
+to a number.  To explicitly declare an array, use
+     declare -a NAME
+The syntax
+     declare -a NAME[SUBSCRIPT]
+is also accepted; the SUBSCRIPT is ignored.
+
+Associative arrays are created using
+     declare -A NAME
+
+   Attributes may be specified for an array variable using the 'declare'
+and 'readonly' builtins.  Each attribute applies to all members of an
+array.
+
+   Arrays are assigned to using compound assignments of the form
+     NAME=(VALUE1 VALUE2 ... )
+where each VALUE may be of the form '[SUBSCRIPT]='STRING.  Indexed array
+assignments do not require anything but STRING.  When assigning to
+indexed arrays, if the optional subscript is 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.
+
+   Each VALUE in the list undergoes all the shell expansions described
+above (*note Shell Expansions::).
+
+   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: NAME=(KEY1 VALUE1 KEY2 VALUE2 ... ).  These
+are treated identically to NAME=( [KEY1]=VALUE1 [KEY2]=VALUE2 ... ).
+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.
+
+   This syntax is also accepted by the 'declare' builtin.  Individual
+array elements may be assigned to using the 'NAME[SUBSCRIPT]=VALUE'
+syntax introduced above.
+
+   When assigning to an indexed array, if NAME is subscripted by a
+negative number, that number is interpreted as relative to one greater
+than the maximum index of NAME, so negative indices count back from the
+end of the array, and an index of -1 references the last element.
+
+   The '+=' operator will append to an array variable when assigning
+using the compound assignment syntax; see *note Shell Parameters::
+above.
+
+   Any element of an array may be referenced using '${NAME[SUBSCRIPT]}'.
+The braces are required to avoid conflicts with the shell's filename
+expansion operators.  If the SUBSCRIPT is '@' or '*', the word expands
+to all members of the array NAME.  These subscripts differ only when the
+word appears within double quotes.  If the word is double-quoted,
+'${NAME[*]}' expands to a single word with the value of each array
+member separated by the first character of the 'IFS' variable, and
+'${NAME[@]}' expands each element of NAME to a separate word.  When
+there are no array members, '${NAME[@]}' 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 '@' and '*'.  '${#NAME[SUBSCRIPT]}' expands to the length of
+'${NAME[SUBSCRIPT]}'.  If SUBSCRIPT is '@' or '*', the expansion is the
+number of elements in the array.  If the SUBSCRIPT 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 refers to the last element.
+
+   Referencing an array variable without a subscript is equivalent to
+referencing with a subscript of 0.  Any reference to a variable using a
+valid subscript is legal, and 'bash' will create an array if necessary.
+
+   An array variable is considered set if a subscript has been assigned
+a value.  The null string is a valid value.
+
+   It is possible to obtain the keys (indices) of an array as well as
+the values.  ${!NAME[@]} and ${!NAME[*]} expand to the indices assigned
+in array variable NAME.  The treatment when in double quotes is similar
+to the expansion of the special parameters '@' and '*' within double
+quotes.
+
+   The 'unset' builtin is used to destroy arrays.  'unset
+NAME[SUBSCRIPT]' destroys the array element at index SUBSCRIPT.
+Negative subscripts to indexed arrays are interpreted as described
+above.  Unsetting the last element of an array variable does not unset
+the variable.  'unset NAME', where NAME is an array, removes the entire
+array.  'unset NAME[SUBSCRIPT]' behaves differently depending on the
+array type when given a subscript of '*' or '@'.  When NAME is an
+associative array, it removes the element with key '*' or '@'.  If NAME
+is an indexed array, 'unset' removes all of the elements, but does not
+remove the array itself.
+
+   When using a variable name with a subscript as an argument to a
+command, such as with 'unset', without using the word expansion syntax
+described above, the argument is subject to the shell's filename
+expansion.  If filename expansion is not desired, the argument should be
+quoted.
+
+   The 'declare', 'local', and 'readonly' builtins each accept a '-a'
+option to specify an indexed array and a '-A' option to specify an
+associative array.  If both options are supplied, '-A' takes precedence.
+The 'read' builtin accepts a '-a' option to assign a list of words read
+from the standard input to an array, and can read values from the
+standard input into individual array elements.  The 'set' and 'declare'
+builtins display array values in a way that allows them to be reused as
+input.
+
+
+File: bashref.info,  Node: The Directory Stack,  Next: Controlling the Prompt,  Prev: Arrays,  Up: Bash Features
+
+6.8 The Directory Stack
+=======================
+
+* Menu:
+
+* Directory Stack Builtins::		Bash builtin commands to manipulate
+					the directory stack.
+
+The directory stack is a list of recently-visited directories.  The
+'pushd' builtin adds directories to the stack as it changes the current
+directory, and the 'popd' builtin removes specified directories from the
+stack and changes the current directory to the directory removed.  The
+'dirs' builtin displays the contents of the directory stack.  The
+current directory is always the "top" of the directory stack.
+
+   The contents of the directory stack are also visible as the value of
+the 'DIRSTACK' shell variable.
+
+
+File: bashref.info,  Node: Directory Stack Builtins,  Up: The Directory Stack
+
+6.8.1 Directory Stack Builtins
+------------------------------
+
+'dirs'
+          dirs [-clpv] [+N | -N]
+
+     Display the list of currently remembered directories.  Directories
+     are added to the list with the 'pushd' command; the 'popd' command
+     removes directories from the list.  The current directory is always
+     the first directory in the stack.
+
+     '-c'
+          Clears the directory stack by deleting all of the elements.
+     '-l'
+          Produces a listing using full pathnames; the default listing
+          format uses a tilde to denote the home directory.
+     '-p'
+          Causes 'dirs' to print the directory stack with one entry per
+          line.
+     '-v'
+          Causes 'dirs' to print the directory stack with one entry per
+          line, prefixing each entry with its index in the stack.
+     '+N'
+          Displays the Nth directory (counting from the left of the list
+          printed by 'dirs' when invoked without options), starting with
+          zero.
+     '-N'
+          Displays the Nth directory (counting from the right of the
+          list printed by 'dirs' when invoked without options), starting
+          with zero.
+
+'popd'
+          popd [-n] [+N | -N]
+
+     Removes elements from the directory stack.  The elements are
+     numbered from 0 starting at the first directory listed by 'dirs';
+     that is, 'popd' is equivalent to 'popd +0'.
+
+     When no arguments are given, 'popd' removes the top directory from
+     the stack and changes to the new top directory.
+
+     Arguments, if supplied, have the following meanings:
+
+     '-n'
+          Suppresses the normal change of directory when removing
+          directories from the stack, so that only the stack is
+          manipulated.
+     '+N'
+          Removes the Nth directory (counting from the left of the list
+          printed by 'dirs'), starting with zero, from the stack.
+     '-N'
+          Removes the Nth directory (counting from the right of the list
+          printed by 'dirs'), starting with zero, from the stack.
+
+     If the top element of the directory stack is modified, and the '-n'
+     option was not supplied, 'popd' uses the 'cd' builtin to change to
+     the directory at the top of the stack.  If the 'cd' fails, 'popd'
+     returns a non-zero value.
+
+     Otherwise, 'popd' returns an unsuccessful status if an invalid
+     option is encountered, the directory stack is empty, or a
+     non-existent directory stack entry is specified.
+
+     If the 'popd' command is successful, Bash runs 'dirs' to show the
+     final contents of the directory stack, and the return status is 0.
+
+'pushd'
+          pushd [-n] [+N | -N | DIR]
+
+     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, 'pushd' exchanges the top two
+     elements of the directory stack.
+
+     Arguments, if supplied, have the following meanings:
+
+     '-n'
+          Suppresses the normal change of directory when rotating or
+          adding directories to the stack, so that only the stack is
+          manipulated.
+     '+N'
+          Brings the Nth directory (counting from the left of the list
+          printed by 'dirs', starting with zero) to the top of the list
+          by rotating the stack.
+     '-N'
+          Brings the Nth directory (counting from the right of the list
+          printed by 'dirs', starting with zero) to the top of the list
+          by rotating the stack.
+     'DIR'
+          Makes DIR be the top of the stack.
+
+     After the stack has been modified, if the '-n' option was not
+     supplied, 'pushd' uses the 'cd' builtin to change to the directory
+     at the top of the stack.  If the 'cd' fails, 'pushd' returns a
+     non-zero value.
+
+     Otherwise, if no arguments are supplied, 'pushd' returns 0 unless
+     the directory stack is empty.  When rotating the directory stack,
+     'pushd' returns 0 unless the directory stack is empty or a
+     non-existent directory stack element is specified.
+
+     If the 'pushd' command is successful, Bash runs 'dirs' to show the
+     final contents of the directory stack.
+
+
+File: bashref.info,  Node: Controlling the Prompt,  Next: The Restricted Shell,  Prev: The Directory Stack,  Up: Bash Features
+
+6.9 Controlling the Prompt
+==========================
+
+Bash examines the value of the array variable 'PROMPT_COMMAND' just
+before printing each primary prompt.  If any elements in
+'PROMPT_COMMAND' are set and non-null, Bash executes each value, in
+numeric order, just as if it had been typed on the command line.
+
+   In addition, the following table describes the special characters
+which can appear in the prompt variables 'PS0', 'PS1', 'PS2', and 'PS4':
+
+'\a'
+     A bell character.
+'\d'
+     The date, in "Weekday Month Date" format (e.g., "Tue May 26").
+'\D{FORMAT}'
+     The FORMAT is passed to 'strftime'(3) and the result is inserted
+     into the prompt string; an empty FORMAT results in a
+     locale-specific time representation.  The braces are required.
+'\e'
+     An escape character.
+'\h'
+     The hostname, up to the first '.'.
+'\H'
+     The hostname.
+'\j'
+     The number of jobs currently managed by the shell.
+'\l'
+     The basename of the shell's terminal device name.
+'\n'
+     A newline.
+'\r'
+     A carriage return.
+'\s'
+     The name of the shell, the basename of '$0' (the portion following
+     the final slash).
+'\t'
+     The time, in 24-hour HH:MM:SS format.
+'\T'
+     The time, in 12-hour HH:MM:SS format.
+'\@'
+     The time, in 12-hour am/pm format.
+'\A'
+     The time, in 24-hour HH:MM format.
+'\u'
+     The username of the current user.
+'\v'
+     The version of Bash (e.g., 2.00)
+'\V'
+     The release of Bash, version + patchlevel (e.g., 2.00.0)
+'\w'
+     The value of the 'PWD' shell variable ('$PWD'), with '$HOME'
+     abbreviated with a tilde (uses the '$PROMPT_DIRTRIM' variable).
+'\W'
+     The basename of '$PWD', with '$HOME' abbreviated with a tilde.
+'\!'
+     The history number of this command.
+'\#'
+     The command number of this command.
+'\$'
+     If the effective uid is 0, '#', otherwise '$'.
+'\NNN'
+     The character whose ASCII code is the octal value NNN.
+'\\'
+     A backslash.
+'\['
+     Begin a sequence of non-printing characters.  This could be used to
+     embed a terminal control sequence into the prompt.
+'\]'
+     End a sequence of non-printing characters.
+
+   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 (*note Bash History
+Facilities::), 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 'promptvars' shell option (*note The Shopt
+Builtin::).  This can have unwanted side effects if escaped portions of
+the string appear within command substitution or contain characters
+special to word expansion.
+
+
+File: bashref.info,  Node: The Restricted Shell,  Next: Bash POSIX Mode,  Prev: Controlling the Prompt,  Up: Bash Features
+
+6.10 The Restricted Shell
+=========================
+
+If Bash is started with the name 'rbash', or the '--restricted' or '-r'
+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.  A restricted shell behaves identically to 'bash'
+with the exception that the following are disallowed or not performed:
+
+   * Changing directories with the 'cd' builtin.
+   * Setting or unsetting the values of the 'SHELL', 'PATH', 'HISTFILE',
+     'ENV', or 'BASH_ENV' variables.
+   * Specifying command names containing slashes.
+   * Specifying a filename containing a slash as an argument to the '.'
+     builtin command.
+   * Specifying a filename containing a slash as an argument to the
+     'history' builtin command.
+   * Specifying a filename containing a slash as an argument to the '-p'
+     option to the 'hash' builtin command.
+   * Importing function definitions from the shell environment at
+     startup.
+   * Parsing the value of 'SHELLOPTS' from the shell environment at
+     startup.
+   * Redirecting output using the '>', '>|', '<>', '>&', '&>', and '>>'
+     redirection operators.
+   * Using the 'exec' builtin to replace the shell with another command.
+   * Adding or deleting builtin commands with the '-f' and '-d' options
+     to the 'enable' builtin.
+   * Using the 'enable' builtin command to enable disabled shell
+     builtins.
+   * Specifying the '-p' option to the 'command' builtin.
+   * Turning off restricted mode with 'set +r' or 'shopt -u
+     restricted_shell'.
+
+   These restrictions are enforced after any startup files are read.
+
+   When a command that is found to be a shell script is executed (*note
+Shell Scripts::), 'rbash' turns off any restrictions in the shell
+spawned to execute the script.
+
+   The restricted shell mode is only one component of a useful
+restricted environment.  It should be accompanied by setting 'PATH' to a
+value that allows execution of only a few verified commands (commands
+that allow shell escapes are particularly vulnerable), changing the
+current directory to a non-writable directory other than '$HOME' after
+login, not allowing the restricted shell to execute shell scripts, and
+cleaning the environment of variables that cause some commands to modify
+their behavior (e.g., 'VISUAL' or 'PAGER').
+
+   Modern systems provide more secure ways to implement a restricted
+environment, such as 'jails', 'zones', or 'containers'.
+
+
+File: bashref.info,  Node: Bash POSIX Mode,  Next: Shell Compatibility Mode,  Prev: The Restricted Shell,  Up: Bash Features
+
+6.11 Bash POSIX Mode
+====================
+
+Starting Bash with the '--posix' command-line option or executing 'set
+-o posix' while Bash is running will cause Bash to conform more closely
+to the POSIX standard by changing the behavior to match that specified
+by POSIX in areas where the Bash default differs.
+
+   When invoked as 'sh', Bash enters POSIX mode after reading the
+startup files.
+
+   The following list is what's changed when 'POSIX mode' is in effect:
+
+  1. Bash ensures that the 'POSIXLY_CORRECT' variable is set.
+
+  2. When a command in the hash table no longer exists, Bash will
+     re-search '$PATH' to find the new location.  This is also available
+     with 'shopt -s checkhash'.
+
+  3. Bash will not insert a command without the execute bit set into the
+     command hash table, even if it returns it as a (last-ditch) result
+     from a '$PATH' search.
+
+  4. The message printed by the job control code and builtins when a job
+     exits with a non-zero status is 'Done(status)'.
+
+  5. The message printed by the job control code and builtins when a job
+     is stopped is 'Stopped(SIGNAME)', where SIGNAME is, for example,
+     'SIGTSTP'.
+
+  6. Alias expansion is always enabled, even in non-interactive shells.
+
+  7. Reserved words appearing in a context where reserved words are
+     recognized do not undergo alias expansion.
+
+  8. Alias expansion is performed when initially parsing a command
+     substitution.  The default mode generally defers it, when enabled,
+     until the command substitution is executed.  This means that
+     command substitution will not expand aliases that are defined after
+     the command substitution is initially parsed (e.g., as part of a
+     function definition).
+
+  9. The POSIX 'PS1' and 'PS2' expansions of '!' to the history number
+     and '!!' to '!' are enabled, and parameter expansion is performed
+     on the values of 'PS1' and 'PS2' regardless of the setting of the
+     'promptvars' option.
+
+  10. The POSIX startup files are executed ('$ENV') rather than the
+     normal Bash files.
+
+  11. Tilde expansion is only performed on assignments preceding a
+     command name, rather than on all assignment statements on the line.
+
+  12. The default history file is '~/.sh_history' (this is the default
+     value of '$HISTFILE').
+
+  13. Redirection operators do not perform filename expansion on the
+     word in the redirection unless the shell is interactive.
+
+  14. Redirection operators do not perform word splitting on the word in
+     the redirection.
+
+  15. Function names must be valid shell 'name's.  That is, they may not
+     contain characters other than letters, digits, and underscores, and
+     may not start with a digit.  Declaring a function with an invalid
+     name causes a fatal syntax error in non-interactive shells.
+
+  16. Function names may not be the same as one of the POSIX special
+     builtins.
+
+  17. POSIX special builtins are found before shell functions during
+     command lookup.
+
+  18. When printing shell function definitions (e.g., by 'type'), Bash
+     does not print the 'function' keyword.
+
+  19. Literal tildes that appear as the first character in elements of
+     the 'PATH' variable are not expanded as described above under *note
+     Tilde Expansion::.
+
+  20. The 'time' reserved word may be used by itself as a command.  When
+     used in this way, it displays timing statistics for the shell and
+     its completed children.  The 'TIMEFORMAT' variable controls the
+     format of the timing information.
+
+  21. When parsing and expanding a ${...} expansion that appears within
+     double quotes, single quotes are no longer special and cannot be
+     used to quote a closing brace or other special character, unless
+     the operator is one of those defined to perform pattern removal.
+     In this case, they do not have to appear as matched pairs.
+
+  22. The parser does not recognize 'time' as a reserved word if the
+     next token begins with a '-'.
+
+  23. The '!' character does not introduce history expansion within a
+     double-quoted string, even if the 'histexpand' option is enabled.
+
+  24. If a POSIX special builtin returns an error status, a
+     non-interactive shell exits.  The fatal errors are those listed in
+     the POSIX standard, and include things like passing incorrect
+     options, redirection errors, variable assignment errors for
+     assignments preceding the command name, and so on.
+
+  25. A non-interactive shell exits with an error status if a variable
+     assignment error occurs when no command name follows the assignment
+     statements.  A variable assignment error occurs, for example, when
+     trying to assign a value to a readonly variable.
+
+  26. A non-interactive shell exits with an error status if a variable
+     assignment error occurs in an assignment statement preceding a
+     special builtin, but not with any other simple command.  For any
+     other simple command, the shell aborts execution of that command,
+     and execution continues at the top level ("the shell shall not
+     perform any further processing of the command in which the error
+     occurred").
+
+  27. A non-interactive shell exits with an error status if the
+     iteration variable in a 'for' statement or the selection variable
+     in a 'select' statement is a readonly variable.
+
+  28. Non-interactive shells exit if FILENAME in '.'  FILENAME is not
+     found.
+
+  29. Non-interactive shells exit if a syntax error in an arithmetic
+     expansion results in an invalid expression.
+
+  30. Non-interactive shells exit if a parameter expansion error occurs.
+
+  31. Non-interactive shells exit if there is a syntax error in a script
+     read with the '.' or 'source' builtins, or in a string processed by
+     the 'eval' builtin.
+
+  32. While variable indirection is available, it may not be applied to
+     the '#' and '?' special parameters.
+
+  33. Expanding the '*' special parameter in a pattern context where the
+     expansion is double-quoted does not treat the '$*' as if it were
+     double-quoted.
+
+  34. Assignment statements preceding POSIX special builtins persist in
+     the shell environment after the builtin completes.
+
+  35. The 'command' builtin does not prevent builtins that take
+     assignment statements as arguments from expanding them as
+     assignment statements; when not in POSIX mode, assignment builtins
+     lose their assignment statement expansion properties when preceded
+     by 'command'.
+
+  36. The 'bg' builtin uses the required format to describe each job
+     placed in the background, which does not include an indication of
+     whether the job is the current or previous job.
+
+  37. The output of 'kill -l' prints all the signal names on a single
+     line, separated by spaces, without the 'SIG' prefix.
+
+  38. The 'kill' builtin does not accept signal names with a 'SIG'
+     prefix.
+
+  39. The 'export' and 'readonly' builtin commands display their output
+     in the format required by POSIX.
+
+  40. The 'trap' builtin displays signal names without the leading
+     'SIG'.
+
+  41. The 'trap' builtin doesn't check the first argument for a possible
+     signal specification and revert the signal handling to the original
+     disposition if it is, unless that argument consists solely of
+     digits and is a valid signal number.  If users want to reset the
+     handler for a given signal to the original disposition, they should
+     use '-' as the first argument.
+
+  42. 'trap -p' displays signals whose dispositions are set to SIG_DFL
+     and those that were ignored when the shell started.
+
+  43. The '.' and 'source' builtins do not search the current directory
+     for the filename argument if it is not found by searching 'PATH'.
+
+  44. Enabling POSIX mode has the effect of setting the
+     'inherit_errexit' option, so subshells spawned to execute command
+     substitutions inherit the value of the '-e' option from the parent
+     shell.  When the 'inherit_errexit' option is not enabled, Bash
+     clears the '-e' option in such subshells.
+
+  45. Enabling POSIX mode has the effect of setting the 'shift_verbose'
+     option, so numeric arguments to 'shift' that exceed the number of
+     positional parameters will result in an error message.
+
+  46. When the 'alias' builtin displays alias definitions, it does not
+     display them with a leading 'alias ' unless the '-p' option is
+     supplied.
+
+  47. When the 'set' builtin is invoked without options, it does not
+     display shell function names and definitions.
+
+  48. When the 'set' builtin is invoked without options, it displays
+     variable values without quotes, unless they contain shell
+     metacharacters, even if the result contains nonprinting characters.
+
+  49. When the 'cd' builtin is invoked in logical mode, and the pathname
+     constructed from '$PWD' and the directory name supplied as an
+     argument does not refer to an existing directory, 'cd' will fail
+     instead of falling back to physical mode.
+
+  50. When the 'cd' builtin cannot change a directory because the length
+     of the pathname constructed from '$PWD' and the directory name
+     supplied as an argument exceeds 'PATH_MAX' when all symbolic links
+     are expanded, 'cd' will fail instead of attempting to use only the
+     supplied directory name.
+
+  51. The 'pwd' builtin verifies that the value it prints is the same as
+     the current directory, even if it is not asked to check the file
+     system with the '-P' option.
+
+  52. When listing the history, the 'fc' builtin does not include an
+     indication of whether or not a history entry has been modified.
+
+  53. The default editor used by 'fc' is 'ed'.
+
+  54. The 'type' and 'command' builtins will not report a non-executable
+     file as having been found, though the shell will attempt to execute
+     such a file if it is the only so-named file found in '$PATH'.
+
+  55. The 'vi' editing mode will invoke the 'vi' editor directly when
+     the 'v' command is run, instead of checking '$VISUAL' and
+     '$EDITOR'.
+
+  56. When the 'xpg_echo' option is enabled, Bash does not attempt to
+     interpret any arguments to 'echo' as options.  Each argument is
+     displayed, after escape characters are converted.
+
+  57. The 'ulimit' builtin uses a block size of 512 bytes for the '-c'
+     and '-f' options.
+
+  58. The arrival of 'SIGCHLD' when a trap is set on 'SIGCHLD' does not
+     interrupt the 'wait' builtin and cause it to return immediately.
+     The trap command is run once for each child that exits.
+
+  59. The 'read' builtin may be interrupted by a signal for which a trap
+     has been set.  If Bash receives a trapped signal while executing
+     'read', the trap handler executes and 'read' returns an exit status
+     greater than 128.
+
+  60. The 'printf' builtin uses 'double' (via 'strtod') to convert
+     arguments corresponding to floating point conversion specifiers,
+     instead of 'long double' if it's available.  The 'L' length
+     modifier forces 'printf' to use 'long double' if it's available.
+
+  61. Bash removes an exited background process's status from the list
+     of such statuses after the 'wait' builtin is used to obtain it.
+
+   There is other POSIX behavior that Bash does not implement by default
+even when in POSIX mode.  Specifically:
+
+  1. The 'fc' builtin checks '$EDITOR' as a program to edit history
+     entries if 'FCEDIT' is unset, rather than defaulting directly to
+     'ed'.  'fc' uses 'ed' if 'EDITOR' is unset.
+
+  2. As noted above, Bash requires the 'xpg_echo' option to be enabled
+     for the 'echo' builtin to be fully conformant.
+
+   Bash can be configured to be POSIX-conformant by default, by
+specifying the '--enable-strict-posix-default' to 'configure' when
+building (*note Optional Features::).
+
+
+File: bashref.info,  Node: Shell Compatibility Mode,  Prev: Bash POSIX Mode,  Up: Bash Features
+
+6.12 Shell Compatibility Mode
+=============================
+
+Bash-4.0 introduced the concept of a "shell compatibility level",
+specified as a set of options to the shopt builtin ('compat31',
+'compat32', 'compat40', 'compat41', 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.
+
+   This section does not mention behavior that is standard for a
+particular version (e.g., setting 'compat32' 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 subsequent versions).
+
+   If a user enables, say, 'compat32', 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 Bash, but that behavior may have been present
+in earlier versions.  For instance, the change to use locale-based
+comparisons with the '[[' command came in bash-4.1, and earlier versions
+used ASCII-based comparisons, so enabling 'compat32' 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.
+
+   Bash-4.3 introduced a new shell variable: 'BASH_COMPAT'.  The value
+assigned to this variable (a decimal version number like 4.2, or an
+integer corresponding to the 'compat'NN option, like 42) determines the
+compatibility level.
+
+   Starting with bash-4.4, Bash has begun deprecating older
+compatibility levels.  Eventually, the options will be removed in favor
+of 'BASH_COMPAT'.
+
+   Bash-5.0 is the final version for which there will be an individual
+shopt option for the previous version.  Users should use 'BASH_COMPAT'
+on bash-5.0 and later versions.
+
+   The following table describes the behavior changes controlled by each
+compatibility level setting.  The 'compat'NN tag is used as shorthand
+for setting the compatibility level to NN using one of the following
+mechanisms.  For versions prior to bash-5.0, the compatibility level may
+be set using the corresponding 'compat'NN shopt option.  For bash-4.3
+and later versions, the 'BASH_COMPAT' variable is preferred, and it is
+required for bash-5.1 and later versions.
+
+'compat31'
+        * quoting the rhs of the '[[' command's regexp matching operator
+          (=~) has no special effect
+
+'compat32'
+        * interrupting a command list such as "a ; b ; c" 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)
+
+'compat40'
+        * the '<' and '>' operators to the '[[' 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 strcmp(3); bash-4.1 and later use the current locale's
+          collation sequence and strcoll(3).
+
+'compat41'
+        * in posix mode, 'time' may be followed by options and still be
+          recognized as a reserved word (this is POSIX interpretation
+          267)
+        * in posix mode, the parser requires that an even number of
+          single quotes occur in the WORD 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)
+
+'compat42'
+        * the replacement string in double-quoted pattern substitution
+          does not undergo quote removal, as it does in versions after
+          bash-4.2
+        * in posix mode, single quotes are considered special when
+          expanding the WORD portion of a double-quoted ${...} parameter
+          expansion and can be used to quote a closing brace or other
+          special character (this is part of POSIX interpretation 221);
+          in later versions, single quotes are not special within
+          double-quoted word expansions
+
+'compat43'
+        * the shell does not print a warning message if an attempt is
+          made to use a quoted compound assignment as an argument to
+          declare (e.g., declare -a foo='(1 2)').  Later versions warn
+          that this usage is deprecated
+        * word expansion errors are considered non-fatal errors that
+          cause the current command to fail, even in posix mode (the
+          default behavior is to make them fatal errors that cause the
+          shell to exit)
+        * when executing a shell function, the loop state
+          (while/until/etc.)  is not reset, so 'break' or 'continue' in
+          that function will break or continue loops in the calling
+          context.  Bash-4.4 and later reset the loop state to prevent
+          this
+
+'compat44'
+        * the shell sets up the values used by 'BASH_ARGV' and
+          'BASH_ARGC' so they can expand to the shell's positional
+          parameters even if extended debugging mode is not enabled
+        * a subshell inherits loops from its parent context, so 'break'
+          or 'continue' will cause the subshell to exit.  Bash-5.0 and
+          later reset the loop state to prevent the exit
+        * variable assignments preceding builtins like 'export' and
+          'readonly' that set attributes continue to affect variables
+          with the same name in the calling environment even if the
+          shell is not in posix mode
+
+'compat50 (set using BASH_COMPAT)'
+        * Bash-5.1 changed the way '$RANDOM' 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 'RANDOM' will produce the same sequence
+          as in bash-5.0
+        * 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 '-l' option is supplied.
+
+'compat51 (set using BASH_COMPAT)'
+        * The 'unset' builtin will unset the array 'a' given an argument
+          like 'a[@]'.  Bash-5.2 will unset an element with key '@'
+          (associative arrays) or remove all the elements without
+          unsetting the array (indexed arrays)
+        * arithmetic commands ( ((...))  )  and the expressions in an
+          arithmetic for statement can be expanded more than once
+        * expressions used as arguments to arithmetic operators in the
+          '[[' conditional command can be expanded more than once
+        * the expressions in substring parameter brace expansion can be
+          expanded more than once
+        * the expressions in the $(( ...  ))  word expansion can be
+          expanded more than once
+        * arithmetic expressions used as indexed array subscripts can be
+          expanded more than once
+        * 'test -v', when given an argument of 'A[@]', where A is an
+          existing associative array, will return true if the array has
+          any set elements.  Bash-5.2 will look for and report on a key
+          named '@'
+        * the ${PARAMETER[:]=VALUE} word expansion will return VALUE,
+          before any variable-specific transformations have been
+          performed (e.g., converting to lowercase).  Bash-5.2 will
+          return the final value assigned to the variable.
+        * Parsing command substitutions will behave as if extended glob
+          (*note The Shopt Builtin::) is enabled, so that parsing a
+          command substitution containing an extglob pattern (say, as
+          part of a shell function) will not fail.  This assumes the
+          intent is to enable extglob before the command is executed and
+          word expansions are performed.  It will fail at word expansion
+          time if extglob hasn't been enabled by the time the command is
+          executed.
+
+
+File: bashref.info,  Node: Job Control,  Next: Command Line Editing,  Prev: Bash Features,  Up: Top
+
+7 Job Control
+*************
+
+This chapter discusses what job control is, how it works, and how Bash
+allows you to access its facilities.
+
+* Menu:
+
+* Job Control Basics::		How job control works.
+* Job Control Builtins::	Bash builtin commands used to interact
+				with job control.
+* Job Control Variables::	Variables Bash uses to customize job
+				control.
+
+
+File: bashref.info,  Node: Job Control Basics,  Next: Job Control Builtins,  Up: Job Control
+
+7.1 Job Control Basics
+======================
+
+Job control refers to the ability to selectively stop (suspend) the
+execution of processes and continue (resume) 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 Bash.
+
+   The shell associates a JOB with each pipeline.  It keeps a table of
+currently executing jobs, which may be listed with the 'jobs' command.
+When Bash starts a job asynchronously, it prints a line that looks like:
+     [1] 25647
+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.  Bash
+uses the JOB abstraction as the basis for job control.
+
+   To facilitate the implementation of the user interface to job
+control, the operating system maintains the notion of a current terminal
+process group ID.  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 'SIGINT'.  These processes
+are said to be in the foreground.  Background 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 'stty tostop', write to the
+terminal.  Background processes which attempt to read from (write to
+when 'stty tostop' is in effect) the terminal are sent a 'SIGTTIN'
+('SIGTTOU') signal by the kernel's terminal driver, which, unless
+caught, suspends the process.
+
+   If the operating system on which Bash is running supports job
+control, Bash contains facilities to use it.  Typing the "suspend"
+character (typically '^Z', Control-Z) while a process is running causes
+that process to be stopped and returns control to Bash.  Typing the
+"delayed suspend" character (typically '^Y', Control-Y) causes the
+process to be stopped when it attempts to read input from the terminal,
+and control to be returned to Bash.  The user then manipulates the state
+of this job, using the 'bg' command to continue it in the background,
+the 'fg' command to continue it in the foreground, or the 'kill' command
+to kill it.  A '^Z' takes effect immediately, and has the additional
+side effect of causing pending output and typeahead to be discarded.
+
+   There are a number of ways to refer to a job in the shell.  The
+character '%' introduces a job specification ("jobspec").
+
+   Job number 'n' may be referred to as '%n'.  The symbols '%%' and '%+'
+refer to the shell's notion of the current job, which is the last job
+stopped while it was in the foreground or started in the background.  A
+single '%' (with no accompanying job specification) also refers to the
+current job.  The previous job may be referenced using '%-'.  If there
+is only a single job, '%+' and '%-' can both be used to refer to that
+job.  In output pertaining to jobs (e.g., the output of the 'jobs'
+command), the current job is always flagged with a '+', and the previous
+job with a '-'.
+
+   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, '%ce' refers to a stopped job whose command name begins with
+'ce'.  Using '%?ce', on the other hand, refers to any job containing the
+string 'ce' in its command line.  If the prefix or substring matches
+more than one job, Bash reports an error.
+
+   Simply naming a job can be used to bring it into the foreground: '%1'
+is a synonym for 'fg %1', bringing job 1 from the background into the
+foreground.  Similarly, '%1 &' resumes job 1 in the background,
+equivalent to 'bg %1'
+
+   The shell learns immediately whenever a job changes state.  Normally,
+Bash 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'
+option to the 'set' builtin is enabled, Bash reports such changes
+immediately (*note The Set Builtin::).  Any trap on 'SIGCHLD' is
+executed for each child process that exits.
+
+   If an attempt to exit Bash is made while jobs are stopped, (or
+running, if the 'checkjobs' option is enabled - see *note The Shopt
+Builtin::), the shell prints a warning message, and if the 'checkjobs'
+option is enabled, lists the jobs and their statuses.  The 'jobs'
+command may then be used to inspect their status.  If a second attempt
+to exit is made without an intervening command, Bash does not print
+another warning, and any stopped jobs are terminated.
+
+   When the shell is waiting for a job or process using the 'wait'
+builtin, and job control is enabled, 'wait' will return when the job
+changes state.  The '-f' option causes 'wait' to wait until the job or
+process terminates before returning.
+
+
+File: bashref.info,  Node: Job Control Builtins,  Next: Job Control Variables,  Prev: Job Control Basics,  Up: Job Control
+
+7.2 Job Control Builtins
+========================
+
+'bg'
+          bg [JOBSPEC ...]
+
+     Resume each suspended job JOBSPEC in the background, as if it had
+     been started with '&'.  If JOBSPEC is not supplied, the current job
+     is used.  The return status is zero unless it is run when job
+     control is not enabled, or, when run with job control enabled, any
+     JOBSPEC was not found or specifies a job that was started without
+     job control.
+
+'fg'
+          fg [JOBSPEC]
+
+     Resume the job JOBSPEC in the foreground and make it the current
+     job.  If JOBSPEC is not supplied, the current job is used.  The
+     return status is that of the command placed into the foreground, or
+     non-zero if run when job control is disabled or, when run with job
+     control enabled, JOBSPEC does not specify a valid job or JOBSPEC
+     specifies a job that was started without job control.
+
+'jobs'
+          jobs [-lnprs] [JOBSPEC]
+          jobs -x COMMAND [ARGUMENTS]
+
+     The first form lists the active jobs.  The options have the
+     following meanings:
+
+     '-l'
+          List process IDs in addition to the normal information.
+
+     '-n'
+          Display information only about jobs that have changed status
+          since the user was last notified of their status.
+
+     '-p'
+          List only the process ID of the job's process group leader.
+
+     '-r'
+          Display only running jobs.
+
+     '-s'
+          Display only stopped jobs.
+
+     If JOBSPEC is given, output is restricted to information about that
+     job.  If JOBSPEC is not supplied, the status of all jobs is listed.
+
+     If the '-x' option is supplied, 'jobs' replaces any JOBSPEC found
+     in COMMAND or ARGUMENTS with the corresponding process group ID,
+     and executes COMMAND, passing it ARGUMENTs, returning its exit
+     status.
+
+'kill'
+          kill [-s SIGSPEC] [-n SIGNUM] [-SIGSPEC] JOBSPEC or PID
+          kill -l|-L [EXIT_STATUS]
+
+     Send a signal specified by SIGSPEC or SIGNUM to the process named
+     by job specification JOBSPEC or process ID PID.  SIGSPEC is either
+     a case-insensitive signal name such as 'SIGINT' (with or without
+     the 'SIG' prefix) or a signal number; SIGNUM is a signal number.
+     If SIGSPEC and SIGNUM are not present, 'SIGTERM' is used.  The '-l'
+     option lists the signal names.  If any arguments are supplied when
+     '-l' is given, the names of the signals corresponding to the
+     arguments are listed, and the return status is zero.  EXIT_STATUS
+     is a number specifying a signal number or the exit status of a
+     process terminated by a signal.  The '-L' option is equivalent to
+     '-l'.  The return status is zero if at least one signal was
+     successfully sent, or non-zero if an error occurs or an invalid
+     option is encountered.
+
+'wait'
+          wait [-fn] [-p VARNAME] [JOBSPEC or PID ...]
+
+     Wait until the child process specified by each process ID PID or
+     job specification JOBSPEC exits and return the exit status of the
+     last command waited for.  If a job spec is given, all processes in
+     the job are waited for.  If no arguments are given, 'wait' waits
+     for all running background jobs and the last-executed process
+     substitution, if its process id is the same as $!, and the return
+     status is zero.  If the '-n' option is supplied, 'wait' waits for a
+     single job from the list of PIDs or JOBSPECs or, if no arguments
+     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 '-p' option is supplied, the
+     process or job identifier of the job for which the exit status is
+     returned is assigned to the variable VARNAME named by the option
+     argument.  The variable will be unset initially, before any
+     assignment.  This is useful only when the '-n' option is supplied.
+     Supplying the '-f' option, when job control is enabled, forces
+     'wait' to wait for each PID or JOBSPEC to terminate before
+     returning its status, instead of returning when it changes status.
+     If neither JOBSPEC nor PID specifies an active child process of the
+     shell, the return status is 127.  If 'wait' is interrupted by a
+     signal, the return status will be greater than 128, as described
+     above (*note Signals::).  Otherwise, the return status is the exit
+     status of the last process or job waited for.
+
+'disown'
+          disown [-ar] [-h] [JOBSPEC ... | PID ... ]
+
+     Without options, remove each JOBSPEC from the table of active jobs.
+     If the '-h' option is given, the job is not removed from the table,
+     but is marked so that 'SIGHUP' is not sent to the job if the shell
+     receives a 'SIGHUP'.  If JOBSPEC is not present, and neither the
+     '-a' nor the '-r' option is supplied, the current job is used.  If
+     no JOBSPEC is supplied, the '-a' option means to remove or mark all
+     jobs; the '-r' option without a JOBSPEC argument restricts
+     operation to running jobs.
+
+'suspend'
+          suspend [-f]
+
+     Suspend the execution of this shell until it receives a 'SIGCONT'
+     signal.  A login shell, or a shell without job control enabled,
+     cannot be suspended; the '-f' option can be used to override this
+     and force the suspension.  The return status is 0 unless the shell
+     is a login shell or job control is not enabled and '-f' is not
+     supplied.
+
+   When job control is not active, the 'kill' and 'wait' builtins do not
+accept JOBSPEC arguments.  They must be supplied process IDs.
+
+
+File: bashref.info,  Node: Job Control Variables,  Prev: Job Control Builtins,  Up: Job Control
+
+7.3 Job Control Variables
+=========================
+
+'auto_resume'
+     This variable controls how the shell interacts with the user and
+     job control.  If this variable exists then single word simple
+     commands without redirections are treated as candidates for
+     resumption of an existing job.  There is no ambiguity allowed; if
+     there is more than one job beginning with the string typed, then
+     the most recently accessed job will be selected.  The name of a
+     stopped job, in this context, is the command line used to start it.
+     If this variable is set to the value 'exact', the string supplied
+     must match the name of a stopped job exactly; if set to
+     'substring', the string supplied needs to match a substring of the
+     name of a stopped job.  The 'substring' value provides
+     functionality analogous to the '%?' job ID (*note Job Control
+     Basics::).  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 '%' job ID.
+
+
+File: bashref.info,  Node: Command Line Editing,  Next: Using History Interactively,  Prev: Job Control,  Up: Top
+
+8 Command Line Editing
+**********************
+
+This chapter describes the basic features of the GNU command line
+editing interface.  Command line editing is provided by the Readline
+library, which is used by several different programs, including Bash.
+Command line editing is enabled by default when using an interactive
+shell, unless the '--noediting' option is supplied at shell invocation.
+Line editing is also used when using the '-e' option to the 'read'
+builtin command (*note Bash Builtins::).  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 '-o emacs' or '-o vi' options to the 'set' builtin command
+(*note The Set Builtin::), or disabled using the '+o emacs' or '+o vi'
+options to 'set'.
+
+* Menu:
+
+* Introduction and Notation::	Notation used in this text.
+* Readline Interaction::	The minimum set of commands for editing a line.
+* Readline Init File::		Customizing Readline from a user's view.
+* Bindable Readline Commands::	A description of most of the Readline commands
+				available for binding
+* Readline vi Mode::		A short description of how to make Readline
+				behave like the vi editor.
+* Programmable Completion::	How to specify the possible completions for
+				a specific command.
+* Programmable Completion Builtins::	Builtin commands to specify how to
+				complete arguments for a particular command.
+* A Programmable Completion Example::	An example shell function for
+				generating possible completions.
+
+
+File: bashref.info,  Node: Introduction and Notation,  Next: Readline Interaction,  Up: Command Line Editing
+
+8.1 Introduction to Line Editing
+================================
+
+The following paragraphs describe the notation used to represent
+keystrokes.
+
+   The text 'C-k' is read as 'Control-K' and describes the character
+produced when the <k> key is pressed while the Control key is depressed.
+
+   The text 'M-k' is read as 'Meta-K' and describes the character
+produced when the Meta key (if you have one) is depressed, and the <k>
+key is pressed.  The Meta key is labeled <ALT> on many keyboards.  On
+keyboards with two keys labeled <ALT> (usually to either side of the
+space bar), the <ALT> on the left side is generally set to work as a
+Meta key.  The <ALT> key on the right may also be configured to work as
+a Meta key or may be configured as some other modifier, such as a
+Compose key for typing accented characters.
+
+   If you do not have a Meta or <ALT> key, or another key working as a
+Meta key, the identical keystroke can be generated by typing <ESC>
+_first_, and then typing <k>.  Either process is known as "metafying"
+the <k> key.
+
+   The text 'M-C-k' is read as 'Meta-Control-k' and describes the
+character produced by "metafying" 'C-k'.
+
+   In addition, several keys have their own names.  Specifically, <DEL>,
+<ESC>, <LFD>, <SPC>, <RET>, and <TAB> all stand for themselves when seen
+in this text, or in an init file (*note Readline Init File::).  If your
+keyboard lacks a <LFD> key, typing <C-j> will produce the desired
+character.  The <RET> key may be labeled <Return> or <Enter> on some
+keyboards.
+
+
+File: bashref.info,  Node: Readline Interaction,  Next: Readline Init File,  Prev: Introduction and Notation,  Up: Command Line Editing
+
+8.2 Readline Interaction
+========================
+
+Often during an interactive session you type in a long line of text,
+only to notice that the first word on the line is misspelled.  The
+Readline library gives you a set of commands for manipulating the text
+as you type it in, allowing you to just fix your typo, and not forcing
+you to retype the majority of the line.  Using these editing commands,
+you move the cursor to the place that needs correction, and delete or
+insert the text of the corrections.  Then, when you are satisfied with
+the line, you simply press <RET>.  You do not have to be at the end of
+the line to press <RET>; the entire line is accepted regardless of the
+location of the cursor within the line.
+
+* Menu:
+
+* Readline Bare Essentials::	The least you need to know about Readline.
+* Readline Movement Commands::	Moving about the input line.
+* Readline Killing Commands::	How to delete text, and how to get it back!
+* Readline Arguments::		Giving numeric arguments to commands.
+* Searching::			Searching through previous lines.
+
+
+File: bashref.info,  Node: Readline Bare Essentials,  Next: Readline Movement Commands,  Up: Readline Interaction
+
+8.2.1 Readline Bare Essentials
+------------------------------
+
+In order to enter characters into the line, simply type them.  The typed
+character appears where the cursor was, and then the cursor moves one
+space to the right.  If you mistype a character, you can use your erase
+character to back up and delete the mistyped character.
+
+   Sometimes you may mistype a character, and not notice the error until
+you have typed several other characters.  In that case, you can type
+'C-b' to move the cursor to the left, and then correct your mistake.
+Afterwards, you can move the cursor to the right with 'C-f'.
+
+   When you add text in the middle of a line, you will notice that
+characters to the right of the cursor are 'pushed over' to make room for
+the text that you have inserted.  Likewise, when you delete text behind
+the cursor, characters to the right of the cursor are 'pulled back' to
+fill in the blank space created by the removal of the text.  A list of
+the bare essentials for editing the text of an input line follows.
+
+'C-b'
+     Move back one character.
+'C-f'
+     Move forward one character.
+<DEL> or <Backspace>
+     Delete the character to the left of the cursor.
+'C-d'
+     Delete the character underneath the cursor.
+Printing characters
+     Insert the character into the line at the cursor.
+'C-_' or 'C-x C-u'
+     Undo the last editing command.  You can undo all the way back to an
+     empty line.
+
+(Depending on your configuration, the <Backspace> key might be set to
+delete the character to the left of the cursor and the <DEL> key set to
+delete the character underneath the cursor, like 'C-d', rather than the
+character to the left of the cursor.)
+
+
+File: bashref.info,  Node: Readline Movement Commands,  Next: Readline Killing Commands,  Prev: Readline Bare Essentials,  Up: Readline Interaction
+
+8.2.2 Readline Movement Commands
+--------------------------------
+
+The above table describes the most basic keystrokes that you need in
+order to do editing of the input line.  For your convenience, many other
+commands have been added in addition to 'C-b', 'C-f', 'C-d', and <DEL>.
+Here are some commands for moving more rapidly about the line.
+
+'C-a'
+     Move to the start of the line.
+'C-e'
+     Move to the end of the line.
+'M-f'
+     Move forward a word, where a word is composed of letters and
+     digits.
+'M-b'
+     Move backward a word.
+'C-l'
+     Clear the screen, reprinting the current line at the top.
+
+   Notice how 'C-f' moves forward a character, while 'M-f' moves forward
+a word.  It is a loose convention that control keystrokes operate on
+characters while meta keystrokes operate on words.
+
+
+File: bashref.info,  Node: Readline Killing Commands,  Next: Readline Arguments,  Prev: Readline Movement Commands,  Up: Readline Interaction
+
+8.2.3 Readline Killing Commands
+-------------------------------
+
+"Killing" text means to delete the text from the line, but to save it
+away for later use, usually by "yanking" (re-inserting) it back into the
+line.  ('Cut' and 'paste' are more recent jargon for 'kill' and 'yank'.)
+
+   If the description for a command says that it 'kills' text, then you
+can be sure that you can get the text back in a different (or the same)
+place later.
+
+   When you use a kill command, the text is saved in a "kill-ring".  Any
+number of consecutive kills save all of the killed text together, so
+that when you yank it back, you get it all.  The kill ring is not line
+specific; the text that you killed on a previously typed line is
+available to be yanked back later, when you are typing another line.
+
+   Here is the list of commands for killing text.
+
+'C-k'
+     Kill the text from the current cursor position to the end of the
+     line.
+
+'M-d'
+     Kill from the cursor 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 'M-f'.
+
+'M-<DEL>'
+     Kill from the cursor to the start of the current word, or, if
+     between words, to the start of the previous word.  Word boundaries
+     are the same as those used by 'M-b'.
+
+'C-w'
+     Kill from the cursor to the previous whitespace.  This is different
+     than 'M-<DEL>' because the word boundaries differ.
+
+   Here is how to "yank" the text back into the line.  Yanking means to
+copy the most-recently-killed text from the kill buffer.
+
+'C-y'
+     Yank the most recently killed text back into the buffer at the
+     cursor.
+
+'M-y'
+     Rotate the kill-ring, and yank the new top.  You can only do this
+     if the prior command is 'C-y' or 'M-y'.
+
+
+File: bashref.info,  Node: Readline Arguments,  Next: Searching,  Prev: Readline Killing Commands,  Up: Readline Interaction
+
+8.2.4 Readline Arguments
+------------------------
+
+You can pass numeric arguments to Readline commands.  Sometimes the
+argument acts as a repeat count, other times it is the sign of the
+argument that is significant.  If you pass a negative argument to a
+command which normally acts in a forward direction, that command will
+act in a backward direction.  For example, to kill text back to the
+start of the line, you might type 'M-- C-k'.
+
+   The general way to pass numeric arguments to a command is to type
+meta digits before the command.  If the first 'digit' typed is a minus
+sign ('-'), then the sign of the argument will be negative.  Once you
+have typed one meta digit to get the argument started, you can type the
+remainder of the digits, and then the command.  For example, to give the
+'C-d' command an argument of 10, you could type 'M-1 0 C-d', which will
+delete the next ten characters on the input line.
+
+
+File: bashref.info,  Node: Searching,  Prev: Readline Arguments,  Up: Readline Interaction
+
+8.2.5 Searching for Commands in the History
+-------------------------------------------
+
+Readline provides commands for searching through the command history
+(*note Bash History Facilities::) for lines containing a specified
+string.  There are two search modes: "incremental" and
+"non-incremental".
+
+   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.  To search backward in the
+history for a particular string, type 'C-r'.  Typing 'C-s' searches
+forward through the history.  The characters present in the value of the
+'isearch-terminators' variable are used to terminate an incremental
+search.  If that variable has not been assigned a value, the <ESC> and
+'C-J' characters will terminate an incremental search.  'C-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.
+
+   To find other matching entries in the history list, type 'C-r' or
+'C-s' 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 <RET> will terminate the
+search and accept the line, thereby executing the command from the
+history list.  A movement command will terminate the search, make the
+last line found the current line, and begin editing.
+
+   Readline remembers the last incremental search string.  If two 'C-r's
+are typed without any intervening characters defining a new search
+string, any remembered search string is used.
+
+   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.
+
+
+File: bashref.info,  Node: Readline Init File,  Next: Bindable Readline Commands,  Prev: Readline Interaction,  Up: Command Line Editing
+
+8.3 Readline Init File
+======================
+
+Although the Readline library comes with a set of Emacs-like keybindings
+installed by default, it is possible to use a different set of
+keybindings.  Any user can customize programs that use Readline by
+putting commands in an "inputrc" file, conventionally in their home
+directory.  The name of this file is taken from the value of the shell
+variable 'INPUTRC'.  If that variable is unset, the default is
+'~/.inputrc'.  If that file does not exist or cannot be read, the
+ultimate default is '/etc/inputrc'.  The 'bind' builtin command can also
+be used to set Readline keybindings and variables.  *Note Bash
+Builtins::.
+
+   When a program which uses the Readline library starts up, the init
+file is read, and the key bindings are set.
+
+   In addition, the 'C-x C-r' command re-reads this init file, thus
+incorporating any changes that you might have made to it.
+
+* Menu:
+
+* Readline Init File Syntax::	Syntax for the commands in the inputrc file.
+
+* Conditional Init Constructs::	Conditional key bindings in the inputrc file.
+
+* Sample Init File::		An example inputrc file.
+
+
+File: bashref.info,  Node: Readline Init File Syntax,  Next: Conditional Init Constructs,  Up: Readline Init File
+
+8.3.1 Readline Init File Syntax
+-------------------------------
+
+There are only a few basic constructs allowed in the Readline init file.
+Blank lines are ignored.  Lines beginning with a '#' are comments.
+Lines beginning with a '$' indicate conditional constructs (*note
+Conditional Init Constructs::).  Other lines denote variable settings
+and key bindings.
+
+Variable Settings
+     You can modify the run-time behavior of Readline by altering the
+     values of variables in Readline using the 'set' command within the
+     init file.  The syntax is simple:
+
+          set VARIABLE VALUE
+
+     Here, for example, is how to change from the default Emacs-like key
+     binding to use 'vi' line editing commands:
+
+          set editing-mode vi
+
+     Variable names and values, where appropriate, are recognized
+     without regard to case.  Unrecognized variable names are ignored.
+
+     Boolean variables (those that can be set to on or off) are set to
+     on if the value is null or empty, ON (case-insensitive), or 1.  Any
+     other value results in the variable being set to off.
+
+     The 'bind -V' command lists the current Readline variable names and
+     values.  *Note Bash Builtins::.
+
+     A great deal of run-time behavior is changeable with the following
+     variables.
+
+     'active-region-start-color'
+          A string variable that controls the text color and background
+          when displaying the text in the active region (see the
+          description of 'enable-active-region' below).  This string
+          must not take up any physical character positions on the
+          display, so it should consist only of terminal escape
+          sequences.  It is output to the terminal before displaying the
+          text in the active region.  This variable is reset to the
+          default value whenever the terminal type changes.  The default
+          value is the string that puts the terminal in standout mode,
+          as obtained from the terminal's terminfo description.  A
+          sample value might be '\e[01;33m'.
+
+     'active-region-end-color'
+          A string variable that "undoes" the effects of
+          'active-region-start-color' and restores "normal" terminal
+          display appearance after displaying text in the active region.
+          This string must not take up any physical character positions
+          on the display, so it should consist only of terminal escape
+          sequences.  It is output to the terminal after displaying the
+          text in the active region.  This variable is reset to the
+          default value whenever the terminal type changes.  The default
+          value is the string that restores the terminal from standout
+          mode, as obtained from the terminal's terminfo description.  A
+          sample value might be '\e[0m'.
+
+     'bell-style'
+          Controls what happens when Readline wants to ring the terminal
+          bell.  If set to 'none', Readline never rings the bell.  If
+          set to 'visible', Readline uses a visible bell if one is
+          available.  If set to 'audible' (the default), Readline
+          attempts to ring the terminal's bell.
+
+     'bind-tty-special-chars'
+          If set to 'on' (the default), Readline attempts to bind the
+          control characters treated specially by the kernel's terminal
+          driver to their Readline equivalents.
+
+     'blink-matching-paren'
+          If set to 'on', Readline attempts to briefly move the cursor
+          to an opening parenthesis when a closing parenthesis is
+          inserted.  The default is 'off'.
+
+     'colored-completion-prefix'
+          If set to 'on', 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 'LS_COLORS' environment variable.  If there is a
+          color definition in 'LS_COLORS' for the custom suffix
+          'readline-colored-completion-prefix', Readline uses this color
+          for the common prefix instead of its default.  The default is
+          'off'.
+
+     'colored-stats'
+          If set to 'on', Readline displays possible completions using
+          different colors to indicate their file type.  The color
+          definitions are taken from the value of the 'LS_COLORS'
+          environment variable.  The default is 'off'.
+
+     'comment-begin'
+          The string to insert at the beginning of the line when the
+          'insert-comment' command is executed.  The default value is
+          '"#"'.
+
+     'completion-display-width'
+          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.
+
+     'completion-ignore-case'
+          If set to 'on', Readline performs filename matching and
+          completion in a case-insensitive fashion.  The default value
+          is 'off'.
+
+     'completion-map-case'
+          If set to 'on', and COMPLETION-IGNORE-CASE is enabled,
+          Readline treats hyphens ('-') and underscores ('_') as
+          equivalent when performing case-insensitive filename matching
+          and completion.  The default value is 'off'.
+
+     'completion-prefix-display-length'
+          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.
+
+     'completion-query-items'
+          The number of possible completions that determines when the
+          user is asked whether the list of possibilities should be
+          displayed.  If the number of possible completions is greater
+          than or equal to this value, Readline will ask whether or not
+          the user wishes to view them; otherwise, they are simply
+          listed.  This variable must be set to an integer value greater
+          than or equal to zero.  A zero value means Readline should
+          never ask; negative values are treated as zero.  The default
+          limit is '100'.
+
+     'convert-meta'
+          If set to 'on', Readline will convert characters with the
+          eighth bit set to an ASCII key sequence by stripping the
+          eighth bit and prefixing an <ESC> character, converting them
+          to a meta-prefixed key sequence.  The default value is 'on',
+          but will be set to 'off' if the locale is one that contains
+          eight-bit characters.  This variable is dependent on the
+          'LC_CTYPE' locale category, and may change if the locale is
+          changed.
+
+     'disable-completion'
+          If set to 'On', Readline will inhibit word completion.
+          Completion characters will be inserted into the line as if
+          they had been mapped to 'self-insert'.  The default is 'off'.
+
+     'echo-control-characters'
+          When set to 'on', on operating systems that indicate they
+          support it, Readline echoes a character corresponding to a
+          signal generated from the keyboard.  The default is 'on'.
+
+     'editing-mode'
+          The 'editing-mode' variable controls which default set of key
+          bindings is used.  By default, Readline starts up in Emacs
+          editing mode, where the keystrokes are most similar to Emacs.
+          This variable can be set to either 'emacs' or 'vi'.
+
+     'emacs-mode-string'
+          If the SHOW-MODE-IN-PROMPT 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.  The default is '@'.
+
+     'enable-active-region'
+          The "point" is the current cursor position, and "mark" refers
+          to a saved cursor position (*note Commands For Moving::).  The
+          text between the point and mark is referred to as the
+          "region".  When this variable is set to 'On', Readline allows
+          certain commands to designate the region as "active".  When
+          the region is active, Readline highlights the text in the
+          region using the value of the 'active-region-start-color',
+          which defaults to the string that enables the terminal's
+          standout mode.  The active region shows the text inserted by
+          bracketed-paste and any matching text found by incremental and
+          non-incremental history searches.  The default is 'On'.
+
+     'enable-bracketed-paste'
+          When set to 'On', Readline configures the terminal to insert
+          each paste into the editing buffer as a single string of
+          characters, instead of treating each character as if it had
+          been read from the keyboard.  This is called putting the
+          terminal into "bracketed paste mode"; it prevents Readline
+          from executing any editing commands bound to key sequences
+          appearing in the pasted text.  The default is 'On'.
+
+     'enable-keypad'
+          When set to 'on', Readline will try to enable the application
+          keypad when it is called.  Some systems need this to enable
+          the arrow keys.  The default is 'off'.
+
+     'enable-meta-key'
+          When set to 'on', 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.  The default is 'on'.
+
+     'expand-tilde'
+          If set to 'on', tilde expansion is performed when Readline
+          attempts word completion.  The default is 'off'.
+
+     'history-preserve-point'
+          If set to 'on', the history code attempts to place the point
+          (the current cursor position) at the same location on each
+          history line retrieved with 'previous-history' or
+          'next-history'.  The default is 'off'.
+
+     'history-size'
+          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 not limited.  If an
+          attempt is made to set HISTORY-SIZE to a non-numeric value,
+          the maximum number of history entries will be set to 500.
+
+     'horizontal-scroll-mode'
+          This variable can be set to either 'on' or 'off'.  Setting it
+          to 'on' means that the text of the lines being edited will
+          scroll horizontally on a single screen line when they are
+          longer than the width of the screen, instead of wrapping onto
+          a new screen line.  This variable is automatically set to 'on'
+          for terminals of height 1.  By default, this variable is set
+          to 'off'.
+
+     'input-meta'
+          If set to 'on', Readline will enable eight-bit input (it will
+          not clear the eighth bit in the characters it reads),
+          regardless of what the terminal claims it can support.  The
+          default value is 'off', but Readline will set it to 'on' if
+          the locale contains eight-bit characters.  The name
+          'meta-flag' is a synonym for this variable.  This variable is
+          dependent on the 'LC_CTYPE' locale category, and may change if
+          the locale is changed.
+
+     'isearch-terminators'
+          The string of characters that should terminate an incremental
+          search without subsequently executing the character as a
+          command (*note Searching::).  If this variable has not been
+          given a value, the characters <ESC> and 'C-J' will terminate
+          an incremental search.
+
+     'keymap'
+          Sets Readline's idea of the current keymap for key binding
+          commands.  Built-in 'keymap' names are 'emacs',
+          'emacs-standard', 'emacs-meta', 'emacs-ctlx', 'vi', 'vi-move',
+          'vi-command', and 'vi-insert'.  'vi' is equivalent to
+          'vi-command' ('vi-move' is also a synonym); 'emacs' is
+          equivalent to 'emacs-standard'.  Applications may add
+          additional names.  The default value is 'emacs'.  The value of
+          the 'editing-mode' variable also affects the default keymap.
+
+     'keyseq-timeout'
+          Specifies the duration Readline 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, Readline will use the
+          shorter but complete key sequence.  Readline uses this value
+          to determine whether or not input is available on the current
+          input source ('rl_instream' by default).  The value is
+          specified in milliseconds, so a value of 1000 means that
+          Readline 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, Readline will wait until another key is
+          pressed to decide which key sequence to complete.  The default
+          value is '500'.
+
+     'mark-directories'
+          If set to 'on', completed directory names have a slash
+          appended.  The default is 'on'.
+
+     'mark-modified-lines'
+          This variable, when set to 'on', causes Readline to display an
+          asterisk ('*') at the start of history lines which have been
+          modified.  This variable is 'off' by default.
+
+     'mark-symlinked-directories'
+          If set to 'on', completed names which are symbolic links to
+          directories have a slash appended (subject to the value of
+          'mark-directories').  The default is 'off'.
+
+     'match-hidden-files'
+          This variable, when set to 'on', causes Readline to match
+          files whose names begin with a '.' (hidden files) when
+          performing filename completion.  If set to 'off', the leading
+          '.' must be supplied by the user in the filename to be
+          completed.  This variable is 'on' by default.
+
+     'menu-complete-display-prefix'
+          If set to 'on', menu completion displays the common prefix of
+          the list of possible completions (which may be empty) before
+          cycling through the list.  The default is 'off'.
+
+     'output-meta'
+          If set to 'on', Readline will display characters with the
+          eighth bit set directly rather than as a meta-prefixed escape
+          sequence.  The default is 'off', but Readline will set it to
+          'on' if the locale contains eight-bit characters.  This
+          variable is dependent on the 'LC_CTYPE' locale category, and
+          may change if the locale is changed.
+
+     'page-completions'
+          If set to 'on', Readline uses an internal 'more'-like pager to
+          display a screenful of possible completions at a time.  This
+          variable is 'on' by default.
+
+     'print-completions-horizontally'
+          If set to 'on', Readline will display completions with matches
+          sorted horizontally in alphabetical order, rather than down
+          the screen.  The default is 'off'.
+
+     'revert-all-at-newline'
+          If set to 'on', Readline will undo all changes to history
+          lines before returning when 'accept-line' is executed.  By
+          default, history lines may be modified and retain individual
+          undo lists across calls to 'readline()'.  The default is
+          'off'.
+
+     'show-all-if-ambiguous'
+          This alters the default behavior of the completion functions.
+          If set to 'on', words which have more than one possible
+          completion cause the matches to be listed immediately instead
+          of ringing the bell.  The default value is 'off'.
+
+     'show-all-if-unmodified'
+          This alters the default behavior of the completion functions
+          in a fashion similar to SHOW-ALL-IF-AMBIGUOUS.  If set to
+          'on', 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.  The
+          default value is 'off'.
+
+     'show-mode-in-prompt'
+          If set to 'on', 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.,
+          EMACS-MODE-STRING).  The default value is 'off'.
+
+     'skip-completed-text'
+          If set to 'on', 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.  For instance, if this is enabled, attempting
+          completion when the cursor is after the 'e' in 'Makefile' will
+          result in 'Makefile' rather than 'Makefilefile', assuming
+          there is a single possible completion.  The default value is
+          'off'.
+
+     'vi-cmd-mode-string'
+          If the SHOW-MODE-IN-PROMPT 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.  The
+          default is '(cmd)'.
+
+     'vi-ins-mode-string'
+          If the SHOW-MODE-IN-PROMPT 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.  The
+          default is '(ins)'.
+
+     'visible-stats'
+          If set to 'on', a character denoting a file's type is appended
+          to the filename when listing possible completions.  The
+          default is 'off'.
+
+Key Bindings
+     The syntax for controlling key bindings in the init file is simple.
+     First you need to find the name of the command that you want to
+     change.  The following sections contain tables of the command name,
+     the default keybinding, if any, and a short description of what the
+     command does.
+
+     Once you know the name of the command, simply place on a line in
+     the init file the name of the key you wish to bind the command to,
+     a colon, and then the name of the command.  There can be no space
+     between the key name and the colon - that will be interpreted as
+     part of the key name.  The name of the key can be expressed in
+     different ways, depending on what you find most comfortable.
+
+     In addition to command names, Readline allows keys to be bound to a
+     string that is inserted when the key is pressed (a MACRO).
+
+     The 'bind -p' command displays Readline function names and bindings
+     in a format that can be put directly into an initialization file.
+     *Note Bash Builtins::.
+
+     KEYNAME: FUNCTION-NAME or MACRO
+          KEYNAME is the name of a key spelled out in English.  For
+          example:
+               Control-u: universal-argument
+               Meta-Rubout: backward-kill-word
+               Control-o: "> output"
+
+          In the example above, 'C-u' is bound to the function
+          'universal-argument', 'M-DEL' is bound to the function
+          'backward-kill-word', and 'C-o' is bound to run the macro
+          expressed on the right hand side (that is, to insert the text
+          '> output' into the line).
+
+          A number of symbolic character names are recognized while
+          processing this key binding syntax: DEL, ESC, ESCAPE, LFD,
+          NEWLINE, RET, RETURN, RUBOUT, SPACE, SPC, and TAB.
+
+     "KEYSEQ": FUNCTION-NAME or MACRO
+          KEYSEQ differs from KEYNAME above in that strings denoting an
+          entire key sequence can be specified, by placing the key
+          sequence in double quotes.  Some GNU Emacs style key escapes
+          can be used, as in the following example, but the special
+          character names are not recognized.
+
+               "\C-u": universal-argument
+               "\C-x\C-r": re-read-init-file
+               "\e[11~": "Function Key 1"
+
+          In the above example, 'C-u' is again bound to the function
+          'universal-argument' (just as it was in the first example),
+          ''C-x' 'C-r'' is bound to the function 're-read-init-file',
+          and '<ESC> <[> <1> <1> <~>' is bound to insert the text
+          'Function Key 1'.
+
+     The following GNU Emacs style escape sequences are available when
+     specifying key sequences:
+
+     '\C-'
+          control prefix
+     '\M-'
+          meta prefix
+     '\e'
+          an escape character
+     '\\'
+          backslash
+     '\"'
+          <">, a double quotation mark
+     '\''
+          <'>, a single quote or apostrophe
+
+     In addition to the GNU Emacs style escape sequences, a second set
+     of backslash escapes is available:
+
+     '\a'
+          alert (bell)
+     '\b'
+          backspace
+     '\d'
+          delete
+     '\f'
+          form feed
+     '\n'
+          newline
+     '\r'
+          carriage return
+     '\t'
+          horizontal tab
+     '\v'
+          vertical tab
+     '\NNN'
+          the eight-bit character whose value is the octal value NNN
+          (one to three digits)
+     '\xHH'
+          the eight-bit character whose value is the hexadecimal value
+          HH (one or two hex digits)
+
+     When entering the text of a macro, single or double quotes must be
+     used to indicate a macro definition.  Unquoted text is assumed to
+     be a function name.  In the macro body, the backslash escapes
+     described above are expanded.  Backslash will quote any other
+     character in the macro text, including '"' and '''.  For example,
+     the following binding will make ''C-x' \' insert a single '\' into
+     the line:
+          "\C-x\\": "\\"
+
+
+File: bashref.info,  Node: Conditional Init Constructs,  Next: Sample Init File,  Prev: Readline Init File Syntax,  Up: Readline Init File
+
+8.3.2 Conditional Init Constructs
+---------------------------------
+
+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.
+
+'$if'
+     The '$if' 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, extends to the
+     end of the line; unless otherwise noted, no characters are required
+     to isolate it.
+
+     'mode'
+          The 'mode=' form of the '$if' directive is used to test
+          whether Readline is in 'emacs' or 'vi' mode.  This may be used
+          in conjunction with the 'set keymap' command, for instance, to
+          set bindings in the 'emacs-standard' and 'emacs-ctlx' keymaps
+          only if Readline is starting out in 'emacs' mode.
+
+     'term'
+          The 'term=' 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
+          '=' is tested against both the full name of the terminal and
+          the portion of the terminal name before the first '-'.  This
+          allows 'sun' to match both 'sun' and 'sun-cmd', for instance.
+
+     'version'
+          The 'version' test may be used to perform comparisons against
+          specific Readline versions.  The 'version' expands to the
+          current Readline version.  The set of comparison operators
+          includes '=' (and '=='), '!=', '<=', '>=', '<', and '>'.  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., '7.1').  If the minor
+          version is omitted, it is assumed to be '0'.  The operator may
+          be separated from the string 'version' and from the version
+          number argument by whitespace.  The following example sets a
+          variable if the Readline version being used is 7.0 or newer:
+               $if version >= 7.0
+               set show-mode-in-prompt on
+               $endif
+
+     'application'
+          The APPLICATION construct is used to include
+          application-specific settings.  Each program using the
+          Readline library sets the APPLICATION NAME, and you can test
+          for a particular value.  This could be used to bind key
+          sequences to functions useful for a specific program.  For
+          instance, the following command adds a key sequence that
+          quotes the current or previous word in Bash:
+               $if Bash
+               # Quote the current or previous word
+               "\C-xq": "\eb\"\ef\""
+               $endif
+
+     'variable'
+          The VARIABLE construct provides simple equality tests for
+          Readline variables and values.  The permitted comparison
+          operators are '=', '==', and '!='.  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
+          ON and OFF.  The following example is equivalent to the
+          'mode=emacs' test described above:
+               $if editing-mode == emacs
+               set show-mode-in-prompt on
+               $endif
+
+'$endif'
+     This command, as seen in the previous example, terminates an '$if'
+     command.
+
+'$else'
+     Commands in this branch of the '$if' directive are executed if the
+     test fails.
+
+'$include'
+     This directive takes a single filename as an argument and reads
+     commands and bindings from that file.  For example, the following
+     directive reads from '/etc/inputrc':
+          $include /etc/inputrc
+
+
+File: bashref.info,  Node: Sample Init File,  Prev: Conditional Init Constructs,  Up: Readline Init File
+
+8.3.3 Sample Init File
+----------------------
+
+Here is an example of an INPUTRC file.  This illustrates key binding,
+variable assignment, and conditional syntax.
+
+     # This file controls the behaviour of line input editing for
+     # programs that use the GNU Readline library.  Existing
+     # programs include FTP, Bash, and GDB.
+     #
+     # You can re-read the inputrc file with C-x C-r.
+     # Lines beginning with '#' are comments.
+     #
+     # First, include any system-wide bindings and variable
+     # assignments from /etc/Inputrc
+     $include /etc/Inputrc
+
+     #
+     # Set various bindings for emacs mode.
+
+     set editing-mode emacs
+
+     $if mode=emacs
+
+     Meta-Control-h:	backward-kill-word	Text after the function name is ignored
+
+     #
+     # Arrow keys in keypad mode
+     #
+     #"\M-OD":        backward-char
+     #"\M-OC":        forward-char
+     #"\M-OA":        previous-history
+     #"\M-OB":        next-history
+     #
+     # Arrow keys in ANSI mode
+     #
+     "\M-[D":        backward-char
+     "\M-[C":        forward-char
+     "\M-[A":        previous-history
+     "\M-[B":        next-history
+     #
+     # Arrow keys in 8 bit keypad mode
+     #
+     #"\M-\C-OD":       backward-char
+     #"\M-\C-OC":       forward-char
+     #"\M-\C-OA":       previous-history
+     #"\M-\C-OB":       next-history
+     #
+     # Arrow keys in 8 bit ANSI mode
+     #
+     #"\M-\C-[D":       backward-char
+     #"\M-\C-[C":       forward-char
+     #"\M-\C-[A":       previous-history
+     #"\M-\C-[B":       next-history
+
+     C-q: quoted-insert
+
+     $endif
+
+     # An old-style binding.  This happens to be the default.
+     TAB: complete
+
+     # Macros that are convenient for shell interaction
+     $if Bash
+     # edit the path
+     "\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
+     # prepare to type a quoted word --
+     # insert open and close double quotes
+     # and move to just after the open quote
+     "\C-x\"": "\"\"\C-b"
+     # insert a backslash (testing backslash escapes
+     # in sequences and macros)
+     "\C-x\\": "\\"
+     # Quote the current or previous word
+     "\C-xq": "\eb\"\ef\""
+     # Add a binding to refresh the line, which is unbound
+     "\C-xr": redraw-current-line
+     # Edit variable on current line.
+     "\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
+     $endif
+
+     # use a visible bell if one is available
+     set bell-style visible
+
+     # don't strip characters to 7 bits when reading
+     set input-meta on
+
+     # allow iso-latin1 characters to be inserted rather
+     # than converted to prefix-meta sequences
+     set convert-meta off
+
+     # display characters with the eighth bit set directly
+     # rather than as meta-prefixed characters
+     set output-meta on
+
+     # if there are 150 or more possible completions for a word,
+     # ask whether or not the user wants to see all of them
+     set completion-query-items 150
+
+     # For FTP
+     $if Ftp
+     "\C-xg": "get \M-?"
+     "\C-xt": "put \M-?"
+     "\M-.": yank-last-arg
+     $endif
+
+
+File: bashref.info,  Node: Bindable Readline Commands,  Next: Readline vi Mode,  Prev: Readline Init File,  Up: Command Line Editing
+
+8.4 Bindable Readline Commands
+==============================
+
+* Menu:
+
+* Commands For Moving::		Moving about the line.
+* Commands For History::	Getting at previous lines.
+* Commands For Text::		Commands for changing text.
+* Commands For Killing::	Commands for killing and yanking.
+* Numeric Arguments::		Specifying numeric arguments, repeat counts.
+* Commands For Completion::	Getting Readline to do the typing for you.
+* Keyboard Macros::		Saving and re-executing typed characters
+* Miscellaneous Commands::	Other miscellaneous commands.
+
+This section describes Readline commands that may be bound to key
+sequences.  You can list your key bindings by executing 'bind -P' or,
+for a more terse format, suitable for an INPUTRC file, 'bind -p'.
+(*Note Bash Builtins::.)  Command names without an accompanying key
+sequence are unbound by default.
+
+   In the following descriptions, "point" refers to the current cursor
+position, and "mark" refers to a cursor position saved by the 'set-mark'
+command.  The text between the point and mark is referred to as the
+"region".
+
+
+File: bashref.info,  Node: Commands For Moving,  Next: Commands For History,  Up: Bindable Readline Commands
+
+8.4.1 Commands For Moving
+-------------------------
+
+'beginning-of-line (C-a)'
+     Move to the start of the current line.
+
+'end-of-line (C-e)'
+     Move to the end of the line.
+
+'forward-char (C-f)'
+     Move forward a character.
+
+'backward-char (C-b)'
+     Move back a character.
+
+'forward-word (M-f)'
+     Move forward to the end of the next word.  Words are composed of
+     letters and digits.
+
+'backward-word (M-b)'
+     Move back to the start of the current or previous word.  Words are
+     composed of letters and digits.
+
+'shell-forward-word (M-C-f)'
+     Move forward to the end of the next word.  Words are delimited by
+     non-quoted shell metacharacters.
+
+'shell-backward-word (M-C-b)'
+     Move back to the start of the current or previous word.  Words are
+     delimited by non-quoted shell metacharacters.
+
+'previous-screen-line ()'
+     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.
+
+'next-screen-line ()'
+     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.
+
+'clear-display (M-C-l)'
+     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.
+
+'clear-screen (C-l)'
+     Clear the screen, then redraw the current line, leaving the current
+     line at the top of the screen.
+
+'redraw-current-line ()'
+     Refresh the current line.  By default, this is unbound.
+
+
+File: bashref.info,  Node: Commands For History,  Next: Commands For Text,  Prev: Commands For Moving,  Up: Bindable Readline Commands
+
+8.4.2 Commands For Manipulating The History
+-------------------------------------------
+
+'accept-line (Newline or Return)'
+     Accept the line regardless of where the cursor is.  If this line is
+     non-empty, add it to the history list according to the setting of
+     the 'HISTCONTROL' and 'HISTIGNORE' variables.  If this line is a
+     modified history line, then restore the history line to its
+     original state.
+
+'previous-history (C-p)'
+     Move 'back' through the history list, fetching the previous
+     command.
+
+'next-history (C-n)'
+     Move 'forward' through the history list, fetching the next command.
+
+'beginning-of-history (M-<)'
+     Move to the first line in the history.
+
+'end-of-history (M->)'
+     Move to the end of the input history, i.e., the line currently
+     being entered.
+
+'reverse-search-history (C-r)'
+     Search backward starting at the current line and moving 'up'
+     through the history as necessary.  This is an incremental search.
+     This command sets the region to the matched text and activates the
+     mark.
+
+'forward-search-history (C-s)'
+     Search forward starting at the current line and moving 'down'
+     through the history as necessary.  This is an incremental search.
+     This command sets the region to the matched text and activates the
+     mark.
+
+'non-incremental-reverse-search-history (M-p)'
+     Search backward starting at the current line and moving 'up'
+     through the history as necessary using a non-incremental search for
+     a string supplied by the user.  The search string may match
+     anywhere in a history line.
+
+'non-incremental-forward-search-history (M-n)'
+     Search forward starting at the current line and moving 'down'
+     through the history as necessary using a non-incremental search for
+     a string supplied by the user.  The search string may match
+     anywhere in a history line.
+
+'history-search-forward ()'
+     Search forward through the history for the string of characters
+     between the start of the current line and the point.  The search
+     string must match at the beginning of a history line.  This is a
+     non-incremental search.  By default, this command is unbound.
+
+'history-search-backward ()'
+     Search backward through the history for the string of characters
+     between the start of the current line and the point.  The search
+     string must match at the beginning of a history line.  This is a
+     non-incremental search.  By default, this command is unbound.
+
+'history-substring-search-forward ()'
+     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.  By default, this command is unbound.
+
+'history-substring-search-backward ()'
+     Search backward through the history for the string of characters
+     between the start of the current line and the point.  The search
+     string may match anywhere in a history line.  This is a
+     non-incremental search.  By default, this command is unbound.
+
+'yank-nth-arg (M-C-y)'
+     Insert the first argument to the previous command (usually the
+     second word on the previous line) at point.  With an argument N,
+     insert the Nth word from the previous command (the words in the
+     previous command begin with word 0).  A negative argument inserts
+     the Nth word from the end of the previous command.  Once the
+     argument N is computed, the argument is extracted as if the '!N'
+     history expansion had been specified.
+
+'yank-last-arg (M-. or M-_)'
+     Insert last argument to the previous command (the last word of the
+     previous history entry).  With a numeric argument, behave exactly
+     like 'yank-nth-arg'.  Successive calls to 'yank-last-arg' 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 argument,
+     as if the '!$' history expansion had been specified.
+
+'operate-and-get-next (C-o)'
+     Accept the current line for return to the calling application as if
+     a newline had been entered, and fetch the next line relative to the
+     current line from the history for editing.  A numeric argument, if
+     supplied, specifies the history entry to use instead of the current
+     line.
+
+'fetch-history ()'
+     With a numeric argument, fetch that entry from the history list and
+     make it the current line.  Without an argument, move back to the
+     first entry in the history list.
+
+
+File: bashref.info,  Node: Commands For Text,  Next: Commands For Killing,  Prev: Commands For History,  Up: Bindable Readline Commands
+
+8.4.3 Commands For Changing Text
+--------------------------------
+
+'end-of-file (usually C-d)'
+     The character indicating end-of-file as set, for example, by
+     'stty'.  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 EOF.
+
+'delete-char (C-d)'
+     Delete the character at point.  If this function is bound to the
+     same character as the tty EOF character, as 'C-d' commonly is, see
+     above for the effects.
+
+'backward-delete-char (Rubout)'
+     Delete the character behind the cursor.  A numeric argument means
+     to kill the characters instead of deleting them.
+
+'forward-backward-delete-char ()'
+     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.  By default, this is not bound to a key.
+
+'quoted-insert (C-q or C-v)'
+     Add the next character typed to the line verbatim.  This is how to
+     insert key sequences like 'C-q', for example.
+
+'self-insert (a, b, A, 1, !, ...)'
+     Insert yourself.
+
+'bracketed-paste-begin ()'
+     This function is intended to be bound to the "bracketed paste"
+     escape sequence sent by some terminals, and such a binding is
+     assigned by default.  It allows Readline to insert the pasted text
+     as a single unit without treating each character as if it had been
+     read from the keyboard.  The characters are inserted as if each one
+     was bound to 'self-insert' instead of executing any editing
+     commands.
+
+     Bracketed paste sets the region (the characters between point and
+     the mark) to the inserted text.  It uses the concept of an _active
+     mark_: when the mark is active, Readline redisplay uses the
+     terminal's standout mode to denote the region.
+
+'transpose-chars (C-t)'
+     Drag the character before the cursor forward over the character at
+     the cursor, moving the cursor forward as well.  If the insertion
+     point is at the end of the line, then this transposes the last two
+     characters of the line.  Negative arguments have no effect.
+
+'transpose-words (M-t)'
+     Drag the word before point past the word after point, moving point
+     past that word as well.  If the insertion point is at the end of
+     the line, this transposes the last two words on the line.
+
+'upcase-word (M-u)'
+     Uppercase the current (or following) word.  With a negative
+     argument, uppercase the previous word, but do not move the cursor.
+
+'downcase-word (M-l)'
+     Lowercase the current (or following) word.  With a negative
+     argument, lowercase the previous word, but do not move the cursor.
+
+'capitalize-word (M-c)'
+     Capitalize the current (or following) word.  With a negative
+     argument, capitalize the previous word, but do not move the cursor.
+
+'overwrite-mode ()'
+     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
+     'emacs' mode; 'vi' mode does overwrite differently.  Each call to
+     'readline()' starts in insert mode.
+
+     In overwrite mode, characters bound to 'self-insert' replace the
+     text at point rather than pushing the text to the right.
+     Characters bound to 'backward-delete-char' replace the character
+     before point with a space.
+
+     By default, this command is unbound.
+
+
+File: bashref.info,  Node: Commands For Killing,  Next: Numeric Arguments,  Prev: Commands For Text,  Up: Bindable Readline Commands
+
+8.4.4 Killing And Yanking
+-------------------------
+
+'kill-line (C-k)'
+     Kill the text from point to the end of the line.  With a negative
+     numeric argument, kill backward from the cursor to the beginning of
+     the current line.
+
+'backward-kill-line (C-x Rubout)'
+     Kill backward from the cursor to the beginning of the current line.
+     With a negative numeric argument, kill forward from the cursor to
+     the end of the current line.
+
+'unix-line-discard (C-u)'
+     Kill backward from the cursor to the beginning of the current line.
+
+'kill-whole-line ()'
+     Kill all characters on the current line, no matter where point is.
+     By default, this is unbound.
+
+'kill-word (M-d)'
+     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 'forward-word'.
+
+'backward-kill-word (M-<DEL>)'
+     Kill the word behind point.  Word boundaries are the same as
+     'backward-word'.
+
+'shell-kill-word (M-C-d)'
+     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 'shell-forward-word'.
+
+'shell-backward-kill-word ()'
+     Kill the word behind point.  Word boundaries are the same as
+     'shell-backward-word'.
+
+'shell-transpose-words (M-C-t)'
+     Drag the word before point past the word after point, moving point
+     past that word as well.  If the insertion point is at the end of
+     the line, this transposes the last two words on the line.  Word
+     boundaries are the same as 'shell-forward-word' and
+     'shell-backward-word'.
+
+'unix-word-rubout (C-w)'
+     Kill the word behind point, using white space as a word boundary.
+     The killed text is saved on the kill-ring.
+
+'unix-filename-rubout ()'
+     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.
+
+'delete-horizontal-space ()'
+     Delete all spaces and tabs around point.  By default, this is
+     unbound.
+
+'kill-region ()'
+     Kill the text in the current region.  By default, this command is
+     unbound.
+
+'copy-region-as-kill ()'
+     Copy the text in the region to the kill buffer, so it can be yanked
+     right away.  By default, this command is unbound.
+
+'copy-backward-word ()'
+     Copy the word before point to the kill buffer.  The word boundaries
+     are the same as 'backward-word'.  By default, this command is
+     unbound.
+
+'copy-forward-word ()'
+     Copy the word following point to the kill buffer.  The word
+     boundaries are the same as 'forward-word'.  By default, this
+     command is unbound.
+
+'yank (C-y)'
+     Yank the top of the kill ring into the buffer at point.
+
+'yank-pop (M-y)'
+     Rotate the kill-ring, and yank the new top.  You can only do this
+     if the prior command is 'yank' or 'yank-pop'.
+
+
+File: bashref.info,  Node: Numeric Arguments,  Next: Commands For Completion,  Prev: Commands For Killing,  Up: Bindable Readline Commands
+
+8.4.5 Specifying Numeric Arguments
+----------------------------------
+
+'digit-argument (M-0, M-1, ... M--)'
+     Add this digit to the argument already accumulating, or start a new
+     argument.  'M--' starts a negative argument.
+
+'universal-argument ()'
+     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 'universal-argument' 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.
+     By default, this is not bound to a key.
+
+
+File: bashref.info,  Node: Commands For Completion,  Next: Keyboard Macros,  Prev: Numeric Arguments,  Up: Bindable Readline Commands
+
+8.4.6 Letting Readline Type For You
+-----------------------------------
+
+'complete (<TAB>)'
+     Attempt to perform completion on the text before point.  The actual
+     completion performed is application-specific.  Bash attempts
+     completion treating the text as a variable (if the text begins with
+     '$'), username (if the text begins with '~'), hostname (if the text
+     begins with '@'), or command (including aliases and functions) in
+     turn.  If none of these produces a match, filename completion is
+     attempted.
+
+'possible-completions (M-?)'
+     List the possible completions of the text before point.  When
+     displaying completions, Readline sets the number of columns used
+     for display to the value of 'completion-display-width', the value
+     of the environment variable 'COLUMNS', or the screen width, in that
+     order.
+
+'insert-completions (M-*)'
+     Insert all completions of the text before point that would have
+     been generated by 'possible-completions'.
+
+'menu-complete ()'
+     Similar to 'complete', but replaces the word to be completed with a
+     single match from the list of possible completions.  Repeated
+     execution of 'menu-complete' 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
+     'bell-style') and the original text is restored.  An argument of N
+     moves N 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 <TAB>, but is unbound by
+     default.
+
+'menu-complete-backward ()'
+     Identical to 'menu-complete', but moves backward through the list
+     of possible completions, as if 'menu-complete' had been given a
+     negative argument.
+
+'delete-char-or-list ()'
+     Deletes the character under the cursor if not at the beginning or
+     end of the line (like 'delete-char').  If at the end of the line,
+     behaves identically to 'possible-completions'.  This command is
+     unbound by default.
+
+'complete-filename (M-/)'
+     Attempt filename completion on the text before point.
+
+'possible-filename-completions (C-x /)'
+     List the possible completions of the text before point, treating it
+     as a filename.
+
+'complete-username (M-~)'
+     Attempt completion on the text before point, treating it as a
+     username.
+
+'possible-username-completions (C-x ~)'
+     List the possible completions of the text before point, treating it
+     as a username.
+
+'complete-variable (M-$)'
+     Attempt completion on the text before point, treating it as a shell
+     variable.
+
+'possible-variable-completions (C-x $)'
+     List the possible completions of the text before point, treating it
+     as a shell variable.
+
+'complete-hostname (M-@)'
+     Attempt completion on the text before point, treating it as a
+     hostname.
+
+'possible-hostname-completions (C-x @)'
+     List the possible completions of the text before point, treating it
+     as a hostname.
+
+'complete-command (M-!)'
+     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.
+
+'possible-command-completions (C-x !)'
+     List the possible completions of the text before point, treating it
+     as a command name.
+
+'dynamic-complete-history (M-<TAB>)'
+     Attempt completion on the text before point, comparing the text
+     against lines from the history list for possible completion
+     matches.
+
+'dabbrev-expand ()'
+     Attempt menu completion on the text before point, comparing the
+     text against lines from the history list for possible completion
+     matches.
+
+'complete-into-braces (M-{)'
+     Perform filename completion and insert the list of possible
+     completions enclosed within braces so the list is available to the
+     shell (*note Brace Expansion::).
+
+
+File: bashref.info,  Node: Keyboard Macros,  Next: Miscellaneous Commands,  Prev: Commands For Completion,  Up: Bindable Readline Commands
+
+8.4.7 Keyboard Macros
+---------------------
+
+'start-kbd-macro (C-x ()'
+     Begin saving the characters typed into the current keyboard macro.
+
+'end-kbd-macro (C-x ))'
+     Stop saving the characters typed into the current keyboard macro
+     and save the definition.
+
+'call-last-kbd-macro (C-x e)'
+     Re-execute the last keyboard macro defined, by making the
+     characters in the macro appear as if typed at the keyboard.
+
+'print-last-kbd-macro ()'
+     Print the last keyboard macro defined in a format suitable for the
+     INPUTRC file.
+
+
+File: bashref.info,  Node: Miscellaneous Commands,  Prev: Keyboard Macros,  Up: Bindable Readline Commands
+
+8.4.8 Some Miscellaneous Commands
+---------------------------------
+
+'re-read-init-file (C-x C-r)'
+     Read in the contents of the INPUTRC file, and incorporate any
+     bindings or variable assignments found there.
+
+'abort (C-g)'
+     Abort the current editing command and ring the terminal's bell
+     (subject to the setting of 'bell-style').
+
+'do-lowercase-version (M-A, M-B, M-X, ...)'
+     If the metafied character X is upper case, run the command that is
+     bound to the corresponding metafied lower case character.  The
+     behavior is undefined if X is already lower case.
+
+'prefix-meta (<ESC>)'
+     Metafy the next character typed.  This is for keyboards without a
+     meta key.  Typing '<ESC> f' is equivalent to typing 'M-f'.
+
+'undo (C-_ or C-x C-u)'
+     Incremental undo, separately remembered for each line.
+
+'revert-line (M-r)'
+     Undo all changes made to this line.  This is like executing the
+     'undo' command enough times to get back to the beginning.
+
+'tilde-expand (M-&)'
+     Perform tilde expansion on the current word.
+
+'set-mark (C-@)'
+     Set the mark to the point.  If a numeric argument is supplied, the
+     mark is set to that position.
+
+'exchange-point-and-mark (C-x C-x)'
+     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.
+
+'character-search (C-])'
+     A character is read and point is moved to the next occurrence of
+     that character.  A negative argument searches for previous
+     occurrences.
+
+'character-search-backward (M-C-])'
+     A character is read and point is moved to the previous occurrence
+     of that character.  A negative argument searches for subsequent
+     occurrences.
+
+'skip-csi-sequence ()'
+     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 "\e[", 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-[.
+
+'insert-comment (M-#)'
+     Without a numeric argument, the value of the 'comment-begin'
+     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
+     'comment-begin', the value is inserted, otherwise the characters in
+     'comment-begin' 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 'comment-begin' 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.
+
+'dump-functions ()'
+     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 INPUTRC
+     file.  This command is unbound by default.
+
+'dump-variables ()'
+     Print all of the settable 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
+     INPUTRC file.  This command is unbound by default.
+
+'dump-macros ()'
+     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 INPUTRC
+     file.  This command is unbound by default.
+
+'spell-correct-word (C-x s)'
+     Perform spelling correction on the current word, treating it as a
+     directory or filename, in the same way as the 'cdspell' shell
+     option.  Word boundaries are the same as those used by
+     'shell-forward-word'.
+
+'glob-complete-word (M-g)'
+     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 file names for possible
+     completions.
+
+'glob-expand-word (C-x *)'
+     The word before point is treated as a pattern for pathname
+     expansion, and the list of matching file names is inserted,
+     replacing the word.  If a numeric argument is supplied, a '*' is
+     appended before pathname expansion.
+
+'glob-list-expansions (C-x g)'
+     The list of expansions that would have been generated by
+     'glob-expand-word' is displayed, and the line is redrawn.  If a
+     numeric argument is supplied, a '*' is appended before pathname
+     expansion.
+
+'display-shell-version (C-x C-v)'
+     Display version information about the current instance of Bash.
+
+'shell-expand-line (M-C-e)'
+     Expand the line as the shell does.  This performs alias and history
+     expansion as well as all of the shell word expansions (*note Shell
+     Expansions::).
+
+'history-expand-line (M-^)'
+     Perform history expansion on the current line.
+
+'magic-space ()'
+     Perform history expansion on the current line and insert a space
+     (*note History Interaction::).
+
+'alias-expand-line ()'
+     Perform alias expansion on the current line (*note Aliases::).
+
+'history-and-alias-expand-line ()'
+     Perform history and alias expansion on the current line.
+
+'insert-last-argument (M-. or M-_)'
+     A synonym for 'yank-last-arg'.
+
+'edit-and-execute-command (C-x C-e)'
+     Invoke an editor on the current command line, and execute the
+     result as shell commands.  Bash attempts to invoke '$VISUAL',
+     '$EDITOR', and 'emacs' as the editor, in that order.
+
+
+File: bashref.info,  Node: Readline vi Mode,  Next: Programmable Completion,  Prev: Bindable Readline Commands,  Up: Command Line Editing
+
+8.5 Readline vi Mode
+====================
+
+While the Readline library does not have a full set of 'vi' editing
+functions, it does contain enough to allow simple editing of the line.
+The Readline 'vi' mode behaves as specified in the POSIX standard.
+
+   In order to switch interactively between 'emacs' and 'vi' editing
+modes, use the 'set -o emacs' and 'set -o vi' commands (*note The Set
+Builtin::).  The Readline default is 'emacs' mode.
+
+   When you enter a line in 'vi' mode, you are already placed in
+'insertion' mode, as if you had typed an 'i'.  Pressing <ESC> switches
+you into 'command' mode, where you can edit the text of the line with
+the standard 'vi' movement keys, move to previous history lines with 'k'
+and subsequent lines with 'j', and so forth.
+
+
+File: bashref.info,  Node: Programmable Completion,  Next: Programmable Completion Builtins,  Prev: Readline vi Mode,  Up: Command Line Editing
+
+8.6 Programmable Completion
+===========================
+
+When word completion is attempted for an argument to a command for which
+a completion specification (a COMPSPEC) has been defined using the
+'complete' builtin (*note Programmable Completion Builtins::), the
+programmable completion facilities are invoked.
+
+   First, the command name is identified.  If a compspec has been
+defined for that command, the compspec is used to generate the list of
+possible completions for the word.  If the command word is the empty
+string (completion attempted at the beginning of an empty line), any
+compspec defined with the '-E' option to 'complete' is used.  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 '-D' option to 'complete' is used as the default.  If
+there is no default compspec, Bash 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
+
+   Once a compspec has been found, it is used to generate the list of
+matching words.  If a compspec is not found, the default Bash completion
+described above (*note Commands For Completion::) is performed.
+
+   First, the actions specified by the compspec are used.  Only matches
+which are prefixed by the word being completed are returned.  When the
+'-f' or '-d' option is used for filename or directory name completion,
+the shell variable 'FIGNORE' is used to filter the matches.  *Note Bash
+Variables::, for a description of 'FIGNORE'.
+
+   Any completions specified by a filename expansion pattern to the '-G'
+option are generated next.  The words generated by the pattern need not
+match the word being completed.  The 'GLOBIGNORE' shell variable is not
+used to filter the matches, but the 'FIGNORE' shell variable is used.
+
+   Next, the string specified as the argument to the '-W' option is
+considered.  The string is first split using the characters in the 'IFS'
+special variable as delimiters.  Shell quoting is honored within the
+string, in order to provide a mechanism for the words to contain shell
+metacharacters or characters in the value of 'IFS'.  Each word is then
+expanded using brace expansion, tilde expansion, parameter and variable
+expansion, command substitution, and arithmetic expansion, as described
+above (*note Shell Expansions::).  The results are split using the rules
+described above (*note Word Splitting::).  The results of the expansion
+are prefix-matched against the word being completed, and the matching
+words become the possible completions.
+
+   After these matches have been generated, any shell function or
+command specified with the '-F' and '-C' options is invoked.  When the
+command or function is invoked, the 'COMP_LINE', 'COMP_POINT',
+'COMP_KEY', and 'COMP_TYPE' variables are assigned values as described
+above (*note Bash Variables::).  If a shell function is being invoked,
+the 'COMP_WORDS' and 'COMP_CWORD' variables are also set.  When the
+function or command is invoked, the first argument ($1) is the name of
+the command whose arguments are being completed, the second argument
+($2) is the word being completed, and the third argument ($3) 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.
+
+   Any function specified with '-F' is invoked first.  The function may
+use any of the shell facilities, including the 'compgen' and 'compopt'
+builtins described below (*note Programmable Completion Builtins::), to
+generate the matches.  It must put the possible completions in the
+'COMPREPLY' array variable, one per array element.
+
+   Next, any command specified with the '-C' 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.
+
+   After all of the possible completions are generated, any filter
+specified with the '-X' option is applied to the list.  The filter is a
+pattern as used for pathname expansion; a '&' in the pattern is replaced
+with the text of the word being completed.  A literal '&' 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 '!' negates the pattern; in this case any completion not
+matching the pattern will be removed.  If the 'nocasematch' shell option
+(see the description of 'shopt' in *note The Shopt Builtin::) is
+enabled, the match is performed without regard to the case of alphabetic
+characters.
+
+   Finally, any prefix and suffix specified with the '-P' and '-S'
+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.
+
+   If the previously-applied actions do not generate any matches, and
+the '-o dirnames' option was supplied to 'complete' when the compspec
+was defined, directory name completion is attempted.
+
+   If the '-o plusdirs' option was supplied to 'complete' when the
+compspec was defined, directory name completion is attempted and any
+matches are added to the results of the other actions.
+
+   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 Bash completions are not attempted, and the Readline default of
+filename completion is disabled.  If the '-o bashdefault' option was
+supplied to 'complete' when the compspec was defined, the default Bash
+completions are attempted if the compspec generates no matches.  If the
+'-o default' option was supplied to 'complete' when the compspec was
+defined, Readline's default completion will be performed if the compspec
+(and, if attempted, the default Bash completions) generate no matches.
+
+   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 MARK-DIRECTORIES Readline variable, regardless of the
+setting of the MARK-SYMLINKED-DIRECTORIES Readline variable.
+
+   There is some support for dynamically modifying completions.  This is
+most useful when used in combination with a default completion specified
+with '-D'.  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.
+
+   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:
+
+     _completion_loader()
+     {
+         . "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
+     }
+     complete -D -F _completion_loader -o bashdefault -o default
+
+
+File: bashref.info,  Node: Programmable Completion Builtins,  Next: A Programmable Completion Example,  Prev: Programmable Completion,  Up: Command Line Editing
+
+8.7 Programmable Completion Builtins
+====================================
+
+Three builtin commands are available to manipulate the programmable
+completion facilities: one to specify how the arguments to a particular
+command are to be completed, and two to modify the completion as it is
+happening.
+
+'compgen'
+          compgen [OPTION] [WORD]
+
+     Generate possible completion matches for WORD according to the
+     OPTIONs, which may be any option accepted by the 'complete' builtin
+     with the exception of '-p' and '-r', and write the matches to the
+     standard output.  When using the '-F' or '-C' options, the various
+     shell variables set by the programmable completion facilities,
+     while available, will not have useful values.
+
+     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 WORD is
+     specified, only those completions matching WORD will be displayed.
+
+     The return value is true unless an invalid option is supplied, or
+     no matches were generated.
+
+'complete'
+          complete [-abcdefgjksuv] [-o COMP-OPTION] [-DEI] [-A ACTION] [-G GLOBPAT]
+          [-W WORDLIST] [-F FUNCTION] [-C COMMAND] [-X FILTERPAT]
+          [-P PREFIX] [-S SUFFIX] NAME [NAME ...]
+          complete -pr [-DEI] [NAME ...]
+
+     Specify how arguments to each NAME should be completed.  If the
+     '-p' 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 '-r' option removes a completion
+     specification for each NAME, or, if no NAMEs are supplied, all
+     completion specifications.  The '-D' 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 '-E' option indicates
+     that other supplied options and actions should apply to "empty"
+     command completion; that is, completion attempted on a blank line.
+     The '-I' 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 ';' or '|', which is
+     usually command name completion.  If multiple options are supplied,
+     the '-D' option takes precedence over '-E', and both take
+     precedence over '-I'.  If any of '-D', '-E', or '-I' are supplied,
+     any other NAME arguments are ignored; these completions only apply
+     to the case specified by the option.
+
+     The process of applying these completion specifications when word
+     completion is attempted is described above (*note Programmable
+     Completion::).
+
+     Other options, if specified, have the following meanings.  The
+     arguments to the '-G', '-W', and '-X' options (and, if necessary,
+     the '-P' and '-S' options) should be quoted to protect them from
+     expansion before the 'complete' builtin is invoked.
+
+     '-o COMP-OPTION'
+          The COMP-OPTION controls several aspects of the compspec's
+          behavior beyond the simple generation of completions.
+          COMP-OPTION may be one of:
+
+          'bashdefault'
+               Perform the rest of the default Bash completions if the
+               compspec generates no matches.
+
+          'default'
+               Use Readline's default filename completion if the
+               compspec generates no matches.
+
+          'dirnames'
+               Perform directory name completion if the compspec
+               generates no matches.
+
+          'filenames'
+               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).  This option
+               is intended to be used with shell functions specified
+               with '-F'.
+
+          'noquote'
+               Tell Readline not to quote the completed words if they
+               are filenames (quoting filenames is the default).
+
+          'nosort'
+               Tell Readline not to sort the list of possible
+               completions alphabetically.
+
+          'nospace'
+               Tell Readline not to append a space (the default) to
+               words completed at the end of the line.
+
+          'plusdirs'
+               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.
+
+     '-A ACTION'
+          The ACTION may be one of the following to generate a list of
+          possible completions:
+
+          'alias'
+               Alias names.  May also be specified as '-a'.
+
+          'arrayvar'
+               Array variable names.
+
+          'binding'
+               Readline key binding names (*note Bindable Readline
+               Commands::).
+
+          'builtin'
+               Names of shell builtin commands.  May also be specified
+               as '-b'.
+
+          'command'
+               Command names.  May also be specified as '-c'.
+
+          'directory'
+               Directory names.  May also be specified as '-d'.
+
+          'disabled'
+               Names of disabled shell builtins.
+
+          'enabled'
+               Names of enabled shell builtins.
+
+          'export'
+               Names of exported shell variables.  May also be specified
+               as '-e'.
+
+          'file'
+               File names.  May also be specified as '-f'.
+
+          'function'
+               Names of shell functions.
+
+          'group'
+               Group names.  May also be specified as '-g'.
+
+          'helptopic'
+               Help topics as accepted by the 'help' builtin (*note Bash
+               Builtins::).
+
+          'hostname'
+               Hostnames, as taken from the file specified by the
+               'HOSTFILE' shell variable (*note Bash Variables::).
+
+          'job'
+               Job names, if job control is active.  May also be
+               specified as '-j'.
+
+          'keyword'
+               Shell reserved words.  May also be specified as '-k'.
+
+          'running'
+               Names of running jobs, if job control is active.
+
+          'service'
+               Service names.  May also be specified as '-s'.
+
+          'setopt'
+               Valid arguments for the '-o' option to the 'set' builtin
+               (*note The Set Builtin::).
+
+          'shopt'
+               Shell option names as accepted by the 'shopt' builtin
+               (*note Bash Builtins::).
+
+          'signal'
+               Signal names.
+
+          'stopped'
+               Names of stopped jobs, if job control is active.
+
+          'user'
+               User names.  May also be specified as '-u'.
+
+          'variable'
+               Names of all shell variables.  May also be specified as
+               '-v'.
+
+     '-C COMMAND'
+          COMMAND is executed in a subshell environment, and its output
+          is used as the possible completions.  Arguments are passed as
+          with the '-F' option.
+
+     '-F FUNCTION'
+          The shell function FUNCTION is executed in the current shell
+          environment.  When it is executed, $1 is the name of the
+          command whose arguments are being completed, $2 is the word
+          being completed, and $3 is the word preceding the word being
+          completed, as described above (*note Programmable
+          Completion::).  When it finishes, the possible completions are
+          retrieved from the value of the 'COMPREPLY' array variable.
+
+     '-G GLOBPAT'
+          The filename expansion pattern GLOBPAT is expanded to generate
+          the possible completions.
+
+     '-P PREFIX'
+          PREFIX is added at the beginning of each possible completion
+          after all other options have been applied.
+
+     '-S SUFFIX'
+          SUFFIX is appended to each possible completion after all other
+          options have been applied.
+
+     '-W WORDLIST'
+          The WORDLIST is split using the characters in the 'IFS'
+          special variable as delimiters, and each resultant word is
+          expanded.  The possible completions are the members of the
+          resultant list which match the word being completed.
+
+     '-X FILTERPAT'
+          FILTERPAT is a pattern as used for filename expansion.  It is
+          applied to the list of possible completions generated by the
+          preceding options and arguments, and each completion matching
+          FILTERPAT is removed from the list.  A leading '!' in
+          FILTERPAT negates the pattern; in this case, any completion
+          not matching FILTERPAT is removed.
+
+     The return value is true unless an invalid option is supplied, an
+     option other than '-p' or '-r' is supplied without a NAME argument,
+     an attempt is made to remove a completion specification for a NAME
+     for which no specification exists, or an error occurs adding a
+     completion specification.
+
+'compopt'
+          compopt [-o OPTION] [-DEI] [+o OPTION] [NAME]
+     Modify completion options for each NAME according to the OPTIONs,
+     or for the currently-executing completion if no NAMEs are supplied.
+     If no OPTIONs are given, display the completion options for each
+     NAME or the current completion.  The possible values of OPTION are
+     those valid for the 'complete' builtin described above.  The '-D'
+     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
+     '-E' option indicates that other supplied options should apply to
+     "empty" command completion; that is, completion attempted on a
+     blank line.  The '-I' 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 ';' or '|', which is
+     usually command name completion.
+
+     If multiple options are supplied, the '-D' option takes precedence
+     over '-E', and both take precedence over '-I'
+
+     The return value is true unless an invalid option is supplied, an
+     attempt is made to modify the options for a NAME for which no
+     completion specification exists, or an output error occurs.
+
+
+File: bashref.info,  Node: A Programmable Completion Example,  Prev: Programmable Completion Builtins,  Up: Command Line Editing
+
+8.8 A Programmable Completion Example
+=====================================
+
+The most common way to obtain additional completion functionality beyond
+the default actions 'complete' and 'compgen' provide is to use a shell
+function and bind it to a particular command using 'complete -F'.
+
+   The following function provides completions for the 'cd' builtin.  It
+is a reasonably good example of what shell functions must do when used
+for completion.  This function uses the word passed as '$2' to determine
+the directory name to complete.  You can also use the 'COMP_WORDS' array
+variable; the current word is indexed by the 'COMP_CWORD' variable.
+
+   The function relies on the 'complete' and 'compgen' builtins to do
+much of the work, adding only the things that the Bash 'cd' does beyond
+accepting basic directory names: tilde expansion (*note Tilde
+Expansion::), searching directories in $CDPATH, which is described above
+(*note Bourne Shell Builtins::), and basic support for the 'cdable_vars'
+shell option (*note The Shopt Builtin::).  '_comp_cd' modifies the value
+of IFS so that it contains only a newline to accommodate file names
+containing spaces and tabs - 'compgen' prints the possible completions
+it generates one per line.
+
+   Possible completions go into the COMPREPLY array variable, one
+completion per array element.  The programmable completion system
+retrieves the completions from there when the function returns.
+
+     # A completion function for the cd builtin
+     # based on the cd completion function from the bash_completion package
+     _comp_cd()
+     {
+         local IFS=$' \t\n'    # normalize IFS
+         local cur _skipdot _cdpath
+         local i j k
+
+         # Tilde expansion, which also expands tilde to full pathname
+         case "$2" in
+         \~*)    eval cur="$2" ;;
+         *)      cur=$2 ;;
+         esac
+
+         # no cdpath or absolute pathname -- straight directory completion
+         if [[ -z "${CDPATH:-}" ]] || [[ "$cur" == @(./*|../*|/*) ]]; then
+             # compgen prints paths one per line; could also use while loop
+             IFS=$'\n'
+             COMPREPLY=( $(compgen -d -- "$cur") )
+             IFS=$' \t\n'
+         # CDPATH+directories in the current directory if not in CDPATH
+         else
+             IFS=$'\n'
+             _skipdot=false
+             # preprocess CDPATH to convert null directory names to .
+             _cdpath=${CDPATH/#:/.:}
+             _cdpath=${_cdpath//::/:.:}
+             _cdpath=${_cdpath/%:/:.}
+             for i in ${_cdpath//:/$'\n'}; do
+                 if [[ $i -ef . ]]; then _skipdot=true; fi
+                 k="${#COMPREPLY[@]}"
+                 for j in $( compgen -d -- "$i/$cur" ); do
+                     COMPREPLY[k++]=${j#$i/}        # cut off directory
+                 done
+             done
+             $_skipdot || COMPREPLY+=( $(compgen -d -- "$cur") )
+             IFS=$' \t\n'
+         fi
+
+         # variable names if appropriate shell option set and no completions
+         if shopt -q cdable_vars && [[ ${#COMPREPLY[@]} -eq 0 ]]; then
+             COMPREPLY=( $(compgen -v -- "$cur") )
+         fi
+
+         return 0
+     }
+
+   We install the completion function using the '-F' option to
+'complete':
+
+     # Tell readline to quote appropriate and append slashes to directories;
+     # use the bash default completion for other arguments
+     complete -o filenames -o nospace -o bashdefault -F _comp_cd cd
+
+Since we'd like Bash and Readline to take care of some of the other
+details for us, we use several other options to tell Bash and Readline
+what to do.  The '-o filenames' option tells Readline that the possible
+completions should be treated as filenames, and quoted appropriately.
+That option will also cause Readline to append a slash to filenames it
+can determine are directories (which is why we might want to extend
+'_comp_cd' to append a slash if we're using directories found via
+CDPATH: Readline can't tell those completions are directories).  The '-o
+nospace' option tells Readline to not append a space character to the
+directory name, in case we want to append to it.  The '-o bashdefault'
+option brings in the rest of the "Bash default" completions - possible
+completions that Bash adds to the default Readline set.  These include
+things like command name completion, variable completion for words
+beginning with '$' or '${', completions containing pathname expansion
+patterns (*note Filename Expansion::), and so on.
+
+   Once installed using 'complete', '_comp_cd' will be called every time
+we attempt word completion for a 'cd' command.
+
+   Many more examples - an extensive collection of completions for most
+of the common GNU, Unix, and Linux commands - are available as part of
+the bash_completion project.  This is installed by default on many
+GNU/Linux distributions.  Originally written by Ian Macdonald, the
+project now lives at <https://github.com/scop/bash-completion/>.  There
+are ports for other systems such as Solaris and Mac OS X.
+
+   An older version of the bash_completion package is distributed with
+bash in the 'examples/complete' subdirectory.
+
+
+File: bashref.info,  Node: Using History Interactively,  Next: Installing Bash,  Prev: Command Line Editing,  Up: Top
+
+9 Using History Interactively
+*****************************
+
+This chapter describes how to use the GNU History Library interactively,
+from a user's standpoint.  It should be considered a user's guide.  For
+information on using the GNU History Library in other programs, see the
+GNU Readline Library Manual.
+
+* Menu:
+
+* Bash History Facilities::	How Bash lets you manipulate your command
+				history.
+* Bash History Builtins::	The Bash builtin commands that manipulate
+				the command history.
+* History Interaction::		What it feels like using History as a user.
+
+
+File: bashref.info,  Node: Bash History Facilities,  Next: Bash History Builtins,  Up: Using History Interactively
+
+9.1 Bash History Facilities
+===========================
+
+When the '-o history' option to the 'set' builtin is enabled (*note The
+Set Builtin::), the shell provides access to the "command history", the
+list of commands previously typed.  The value of the 'HISTSIZE' shell
+variable is used as the number of commands to save in a history list.
+The text of the last '$HISTSIZE' commands (default 500) is saved.  The
+shell stores each command in the history list prior to parameter and
+variable expansion but after history expansion is performed, subject to
+the values of the shell variables 'HISTIGNORE' and 'HISTCONTROL'.
+
+   When the shell starts up, the history is initialized from the file
+named by the 'HISTFILE' variable (default '~/.bash_history').  The file
+named by the value of 'HISTFILE' is truncated, if necessary, to contain
+no more than the number of lines specified by the value of the
+'HISTFILESIZE' variable.  When a shell with history enabled exits, the
+last '$HISTSIZE' lines are copied from the history list to the file
+named by '$HISTFILE'.  If the 'histappend' shell option is set (*note
+Bash Builtins::), the lines are appended to the history file, otherwise
+the history file is overwritten.  If 'HISTFILE' is unset, or if the
+history file is unwritable, the history is not saved.  After saving the
+history, the history file is truncated to contain no more than
+'$HISTFILESIZE' lines.  If 'HISTFILESIZE' is unset, or set to null, a
+non-numeric value, or a numeric value less than zero, the history file
+is not truncated.
+
+   If the 'HISTTIMEFORMAT' 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 builtin command 'fc' may be used to list or edit and re-execute a
+portion of the history list.  The 'history' 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 (*note Commands For
+History::).
+
+   The shell allows control over which commands are saved on the history
+list.  The 'HISTCONTROL' and 'HISTIGNORE' variables may be set to cause
+the shell to save only a subset of the commands entered.  The 'cmdhist'
+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 'lithist' shell
+option causes the shell to save the command with embedded newlines
+instead of semicolons.  The 'shopt' builtin is used to set these
+options.  *Note The Shopt Builtin::, for a description of 'shopt'.
+
+
+File: bashref.info,  Node: Bash History Builtins,  Next: History Interaction,  Prev: Bash History Facilities,  Up: Using History Interactively
+
+9.2 Bash History Builtins
+=========================
+
+Bash provides two builtin commands which manipulate the history list and
+history file.
+
+'fc'
+          fc [-e ENAME] [-lnr] [FIRST] [LAST]
+          fc -s [PAT=REP] [COMMAND]
+
+     The first form selects a range of commands from FIRST to LAST from
+     the history list and displays or edits and re-executes them.  Both
+     FIRST and LAST may be specified as a string (to locate the most
+     recent 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 FIRST or LAST of 0 is equivalent to -1 and -0 is
+     equivalent to the current command (usually the 'fc' command);
+     otherwise 0 is equivalent to -1 and -0 is invalid.
+
+     If LAST is not specified, it is set to FIRST.  If FIRST is not
+     specified, it is set to the previous command for editing and -16
+     for listing.  If the '-l' flag is given, the commands are listed on
+     standard output.  The '-n' flag suppresses the command numbers when
+     listing.  The '-r' flag reverses the order of the listing.
+     Otherwise, the editor given by ENAME is invoked on a file
+     containing those commands.  If ENAME is not given, the value of the
+     following variable expansion is used: '${FCEDIT:-${EDITOR:-vi}}'.
+     This says to use the value of the 'FCEDIT' variable if set, or the
+     value of the 'EDITOR' variable if that is set, or 'vi' if neither
+     is set.  When editing is complete, the edited commands are echoed
+     and executed.
+
+     In the second form, COMMAND is re-executed after each instance of
+     PAT in the selected command is replaced by REP.  COMMAND is
+     interpreted the same as FIRST above.
+
+     A useful alias to use with the 'fc' command is 'r='fc -s'', so that
+     typing 'r cc' runs the last command beginning with 'cc' and typing
+     'r' re-executes the last command (*note Aliases::).
+
+'history'
+          history [N]
+          history -c
+          history -d OFFSET
+          history -d START-END
+          history [-anrw] [FILENAME]
+          history -ps ARG
+
+     With no options, display the history list with line numbers.  Lines
+     prefixed with a '*' have been modified.  An argument of N lists
+     only the last N lines.  If the shell variable 'HISTTIMEFORMAT' is
+     set and not null, it is used as a format string for STRFTIME 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.
+
+     Options, if supplied, have the following meanings:
+
+     '-c'
+          Clear the history list.  This may be combined with the other
+          options to replace the history list completely.
+
+     '-d OFFSET'
+          Delete the history entry at position OFFSET.  If OFFSET is
+          positive, it should be specified as it appears when the
+          history is displayed.  If OFFSET 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 'history
+          -d' command.
+
+     '-d START-END'
+          Delete the range of history entries between positions START
+          and END, inclusive.  Positive and negative values for START
+          and END are interpreted as described above.
+
+     '-a'
+          Append the new history lines to the history file.  These are
+          history lines entered since the beginning of the current Bash
+          session, but not already appended to the history file.
+
+     '-n'
+          Append the history lines not already read from the history
+          file to the current history list.  These are lines appended to
+          the history file since the beginning of the current Bash
+          session.
+
+     '-r'
+          Read the history file and append its contents to the history
+          list.
+
+     '-w'
+          Write out the current history list to the history file.
+
+     '-p'
+          Perform history substitution on the ARGs and display the
+          result on the standard output, without storing the results in
+          the history list.
+
+     '-s'
+          The ARGs are added to the end of the history list as a single
+          entry.
+
+     If a FILENAME argument is supplied when any of the '-w', '-r',
+     '-a', or '-n' options is used, Bash uses FILENAME as the history
+     file.  If not, then the value of the 'HISTFILE' variable is used.
+
+     The return value is 0 unless an invalid option is encountered, an
+     error occurs while reading or writing the history file, an invalid
+     OFFSET or range is supplied as an argument to '-d', or the history
+     expansion supplied as an argument to '-p' fails.
+
+
+File: bashref.info,  Node: History Interaction,  Prev: Bash History Builtins,  Up: Using History Interactively
+
+9.3 History Expansion
+=====================
+
+The History library provides a history expansion feature that is similar
+to the history expansion provided by 'csh'.  This section describes the
+syntax used to manipulate the history information.
+
+   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.
+
+   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.  Bash attempts to inform the history expansion
+functions about quoting still in effect from previous lines.
+
+   History expansion takes place in two parts.  The first is to
+determine which line from the history list should be used during
+substitution.  The second is to select portions of that line for
+inclusion into the current one.  The line selected from the history is
+called the "event", and the portions of that line that are acted upon
+are called "words".  Various "modifiers" are available to manipulate the
+selected words.  The line is broken into words in the same fashion that
+Bash does, so that several words surrounded by quotes are considered one
+word.  History expansions are introduced by the appearance of the
+history expansion character, which is '!' by default.
+
+   History expansion implements shell-like quoting conventions: a
+backslash can be used to remove the special handling for the next
+character; single quotes enclose verbatim sequences of characters, and
+can be used to inhibit history expansion; and characters enclosed within
+double quotes may be subject to history expansion, since backslash can
+escape the history expansion character, but single quotes may not, since
+they are not treated specially within double quotes.
+
+   When using the shell, only '\' and ''' may be used to escape the
+history expansion character, but the history expansion character is also
+treated as quoted if it immediately precedes the closing double quote in
+a double-quoted string.
+
+   Several shell options settable with the 'shopt' builtin (*note The
+Shopt Builtin::) may be used to tailor the behavior of history
+expansion.  If the 'histverify' shell option is enabled, and Readline is
+being used, history substitutions are not immediately passed to the
+shell parser.  Instead, the expanded line is reloaded into the Readline
+editing buffer for further modification.  If Readline is being used, and
+the 'histreedit' shell option is enabled, a failed history expansion
+will be reloaded into the Readline editing buffer for correction.  The
+'-p' option to the 'history' builtin command may be used to see what a
+history expansion will do before using it.  The '-s' option to the
+'history' 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.  This is most useful in conjunction with Readline.
+
+   The shell allows control of the various characters used by the
+history expansion mechanism with the 'histchars' variable, as explained
+above (*note Bash Variables::).  The shell uses the history comment
+character to mark history timestamps when writing the history file.
+
+* Menu:
+
+* Event Designators::	How to specify which history line to use.
+* Word Designators::	Specifying which words are of interest.
+* Modifiers::		Modifying the results of substitution.
+
+
+File: bashref.info,  Node: Event Designators,  Next: Word Designators,  Up: History Interaction
+
+9.3.1 Event Designators
+-----------------------
+
+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.
+
+'!'
+     Start a history substitution, except when followed by a space, tab,
+     the end of the line, '=' or '(' (when the 'extglob' shell option is
+     enabled using the 'shopt' builtin).
+
+'!N'
+     Refer to command line N.
+
+'!-N'
+     Refer to the command N lines back.
+
+'!!'
+     Refer to the previous command.  This is a synonym for '!-1'.
+
+'!STRING'
+     Refer to the most recent command preceding the current position in
+     the history list starting with STRING.
+
+'!?STRING[?]'
+     Refer to the most recent command preceding the current position in
+     the history list containing STRING.  The trailing '?' may be
+     omitted if the STRING is followed immediately by a newline.  If
+     STRING is missing, the string from the most recent search is used;
+     it is an error if there is no previous search string.
+
+'^STRING1^STRING2^'
+     Quick Substitution.  Repeat the last command, replacing STRING1
+     with STRING2.  Equivalent to '!!:s^STRING1^STRING2^'.
+
+'!#'
+     The entire command line typed so far.
+
+
+File: bashref.info,  Node: Word Designators,  Next: Modifiers,  Prev: Event Designators,  Up: History Interaction
+
+9.3.2 Word Designators
+----------------------
+
+Word designators are used to select desired words from the event.  A ':'
+separates the event specification from the word designator.  It may be
+omitted if the word designator begins with a '^', '$', '*', '-', or '%'.
+Words are numbered from the beginning of the line, with the first word
+being denoted by 0 (zero).  Words are inserted into the current line
+separated by single spaces.
+
+   For example,
+
+'!!'
+     designates the preceding command.  When you type this, the
+     preceding command is repeated in toto.
+
+'!!:$'
+     designates the last argument of the preceding command.  This may be
+     shortened to '!$'.
+
+'!fi:2'
+     designates the second argument of the most recent command starting
+     with the letters 'fi'.
+
+   Here are the word designators:
+
+'0 (zero)'
+     The '0'th word.  For many applications, this is the command word.
+
+'N'
+     The Nth word.
+
+'^'
+     The first argument; that is, word 1.
+
+'$'
+     The last argument.
+
+'%'
+     The first word matched by the most recent '?STRING?' search, if the
+     search string begins with a character that is part of a word.
+
+'X-Y'
+     A range of words; '-Y' abbreviates '0-Y'.
+
+'*'
+     All of the words, except the '0'th.  This is a synonym for '1-$'.
+     It is not an error to use '*' if there is just one word in the
+     event; the empty string is returned in that case.
+
+'X*'
+     Abbreviates 'X-$'
+
+'X-'
+     Abbreviates 'X-$' like 'X*', but omits the last word.  If 'x' is
+     missing, it defaults to 0.
+
+   If a word designator is supplied without an event specification, the
+previous command is used as the event.
+
+
+File: bashref.info,  Node: Modifiers,  Prev: Word Designators,  Up: History Interaction
+
+9.3.3 Modifiers
+---------------
+
+After the optional word designator, you can add 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.
+
+'h'
+     Remove a trailing pathname component, leaving only the head.
+
+'t'
+     Remove all leading pathname components, leaving the tail.
+
+'r'
+     Remove a trailing suffix of the form '.SUFFIX', leaving the
+     basename.
+
+'e'
+     Remove all but the trailing suffix.
+
+'p'
+     Print the new command but do not execute it.
+
+'q'
+     Quote the substituted words, escaping further substitutions.
+
+'x'
+     Quote the substituted words as with 'q', but break into words at
+     spaces, tabs, and newlines.  The 'q' and 'x' modifiers are mutually
+     exclusive; the last one supplied is used.
+
+'s/OLD/NEW/'
+     Substitute NEW for the first occurrence of OLD in the event line.
+     Any character may be used as the delimiter in place of '/'.  The
+     delimiter may be quoted in OLD and NEW with a single backslash.  If
+     '&' appears in NEW, it is replaced by OLD.  A single backslash will
+     quote the '&'.  If OLD is null, it is set to the last OLD
+     substituted, or, if no previous history substitutions took place,
+     the last STRING in a !?STRING'[?]' search.  If NEW is null, each
+     matching OLD is deleted.  The final delimiter is optional if it is
+     the last character on the input line.
+
+'&'
+     Repeat the previous substitution.
+
+'g'
+'a'
+     Cause changes to be applied over the entire event line.  Used in
+     conjunction with 's', as in 'gs/OLD/NEW/', or with '&'.
+
+'G'
+     Apply the following 's' or '&' modifier once to each word in the
+     event.
+
+
+File: bashref.info,  Node: Installing Bash,  Next: Reporting Bugs,  Prev: Using History Interactively,  Up: Top
+
+10 Installing Bash
+******************
+
+This chapter provides basic instructions for installing Bash on the
+various supported platforms.  The distribution supports the GNU
+operating systems, nearly every version of Unix, and several non-Unix
+systems such as BeOS and Interix.  Other independent ports exist for
+MS-DOS, OS/2, and Windows platforms.
+
+* Menu:
+
+* Basic Installation::	Installation instructions.
+* Compilers and Options::	How to set special options for various
+				systems.
+* Compiling For Multiple Architectures::	How to compile Bash for more
+						than one kind of system from
+						the same source tree.
+* Installation Names::	How to set the various paths used by the installation.
+* Specifying the System Type::	How to configure Bash for a particular system.
+* Sharing Defaults::	How to share default configuration values among GNU
+			programs.
+* Operation Controls::	Options recognized by the configuration program.
+* Optional Features::	How to enable and disable optional features when
+			building Bash.
+
+
+File: bashref.info,  Node: Basic Installation,  Next: Compilers and Options,  Up: Installing Bash
+
+10.1 Basic Installation
+=======================
+
+These are installation instructions for Bash.
+
+   The simplest way to compile Bash is:
+
+  1. 'cd' to the directory containing the source code and type
+     './configure' to configure Bash for your system.  If you're using
+     'csh' on an old version of System V, you might need to type 'sh
+     ./configure' instead to prevent 'csh' from trying to execute
+     'configure' itself.
+
+     Running 'configure' takes some time.  While running, it prints
+     messages telling which features it is checking for.
+
+  2. Type 'make' to compile Bash and build the 'bashbug' bug reporting
+     script.
+
+  3. Optionally, type 'make tests' to run the Bash test suite.
+
+  4. Type 'make install' to install 'bash' and 'bashbug'.  This will
+     also install the manual pages and Info file, message translation
+     files, some supplemental documentation, a number of example
+     loadable builtin commands, and a set of header files for developing
+     loadable builtins.  You may need additional privileges to install
+     'bash' to your desired destination, so 'sudo make install' might be
+     required.  More information about controlling the locations where
+     'bash' and other files are installed is below (*note Installation
+     Names::).
+
+   The 'configure' shell script attempts to guess correct values for
+various system-dependent variables used during compilation.  It uses
+those values to create a 'Makefile' in each directory of the package
+(the top directory, the 'builtins', 'doc', 'po', and 'support'
+directories, each directory under 'lib', and several others).  It also
+creates a 'config.h' file containing system-dependent definitions.
+Finally, it creates a shell script named 'config.status' that you can
+run in the future to recreate the current configuration, a file
+'config.cache' that saves the results of its tests to speed up
+reconfiguring, and a file 'config.log' containing compiler output
+(useful mainly for debugging 'configure').  If at some point
+'config.cache' contains results you don't want to keep, you may remove
+or edit it.
+
+   To find out more about the options and arguments that the 'configure'
+script understands, type
+
+     bash-4.2$ ./configure --help
+
+at the Bash prompt in your Bash source directory.
+
+   If you want to build Bash in a directory separate from the source
+directory - to build for multiple architectures, for example - just use
+the full path to the configure script.  The following commands will
+build bash in a directory under '/usr/local/build' from the source code
+in '/usr/local/src/bash-4.4':
+
+     mkdir /usr/local/build/bash-4.4
+     cd /usr/local/build/bash-4.4
+     bash /usr/local/src/bash-4.4/configure
+     make
+
+   See *note Compiling For Multiple Architectures:: for more information
+about building in a directory separate from the source.
+
+   If you need to do unusual things to compile Bash, please try to
+figure out how 'configure' could check whether or not to do them, and
+mail diffs or instructions to <bash-maintainers@gnu.org> so they can be
+considered for the next release.
+
+   The file 'configure.ac' is used to create 'configure' by a program
+called Autoconf.  You only need 'configure.ac' if you want to change it
+or regenerate 'configure' using a newer version of Autoconf.  If you do
+this, make sure you are using Autoconf version 2.69 or newer.
+
+   You can remove the program binaries and object files from the source
+code directory by typing 'make clean'.  To also remove the files that
+'configure' created (so you can compile Bash for a different kind of
+computer), type 'make distclean'.
+
+
+File: bashref.info,  Node: Compilers and Options,  Next: Compiling For Multiple Architectures,  Prev: Basic Installation,  Up: Installing Bash
+
+10.2 Compilers and Options
+==========================
+
+Some systems require unusual options for compilation or linking that the
+'configure' script does not know about.  You can give 'configure'
+initial values for variables by setting them in the environment.  Using
+a Bourne-compatible shell, you can do that on the command line like
+this:
+
+     CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
+
+   On systems that have the 'env' program, you can do it like this:
+
+     env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
+
+   The configuration process uses GCC to build Bash if it is available.
+
+
+File: bashref.info,  Node: Compiling For Multiple Architectures,  Next: Installation Names,  Prev: Compilers and Options,  Up: Installing Bash
+
+10.3 Compiling For Multiple Architectures
+=========================================
+
+You can compile Bash for more than one kind of computer at the same
+time, by placing the object files for each architecture in their own
+directory.  To do this, you must use a version of 'make' that supports
+the 'VPATH' variable, such as GNU 'make'.  'cd' to the directory where
+you want the object files and executables to go and run the 'configure'
+script from the source directory (*note Basic Installation::).  You may
+need to supply the '--srcdir=PATH' argument to tell 'configure' where
+the source files are.  'configure' automatically checks for the source
+code in the directory that 'configure' is in and in '..'.
+
+   If you have to use a 'make' that does not support the 'VPATH'
+variable, you can compile Bash for one architecture at a time in the
+source code directory.  After you have installed Bash for one
+architecture, use 'make distclean' before reconfiguring for another
+architecture.
+
+   Alternatively, if your system supports symbolic links, you can use
+the 'support/mkclone' script to create a build tree which has symbolic
+links back to each file in the source directory.  Here's an example that
+creates a build directory in the current directory from a source
+directory '/usr/gnu/src/bash-2.0':
+
+     bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
+
+The 'mkclone' script requires Bash, so you must have already built Bash
+for at least one architecture before you can create build directories
+for other architectures.
+
+
+File: bashref.info,  Node: Installation Names,  Next: Specifying the System Type,  Prev: Compiling For Multiple Architectures,  Up: Installing Bash
+
+10.4 Installation Names
+=======================
+
+By default, 'make install' will install into '/usr/local/bin',
+'/usr/local/man', etc.; that is, the "installation prefix" defaults to
+'/usr/local'.  You can specify an installation prefix other than
+'/usr/local' by giving 'configure' the option '--prefix=PATH', or by
+specifying a value for the 'prefix' 'make' variable when running 'make
+install' (e.g., 'make install prefix=PATH').  The 'prefix' variable
+provides a default for 'exec_prefix' and other variables used when
+installing bash.
+
+   You can specify separate installation prefixes for
+architecture-specific files and architecture-independent files.  If you
+give 'configure' the option '--exec-prefix=PATH', 'make install' will
+use PATH as the prefix for installing programs and libraries.
+Documentation and other data files will still use the regular prefix.
+
+   If you would like to change the installation locations for a single
+run, you can specify these variables as arguments to 'make': 'make
+install exec_prefix=/' will install 'bash' and 'bashbug' into '/bin'
+instead of the default '/usr/local/bin'.
+
+   If you want to see the files bash will install and where it will
+install them without changing anything on your system, specify the
+variable 'DESTDIR' as an argument to 'make'.  Its value should be the
+absolute directory path you'd like to use as the root of your sample
+installation tree.  For example,
+
+     mkdir /fs1/bash-install
+     make install DESTDIR=/fs1/bash-install
+
+will install 'bash' into '/fs1/bash-install/usr/local/bin/bash', the
+documentation into directories within
+'/fs1/bash-install/usr/local/share', the example loadable builtins into
+'/fs1/bash-install/usr/local/lib/bash', and so on.  You can use the
+usual 'exec_prefix' and 'prefix' variables to alter the directory paths
+beneath the value of 'DESTDIR'.
+
+   The GNU Makefile standards provide a more complete description of
+these variables and their effects.
+
+
+File: bashref.info,  Node: Specifying the System Type,  Next: Sharing Defaults,  Prev: Installation Names,  Up: Installing Bash
+
+10.5 Specifying the System Type
+===============================
+
+There may be some features 'configure' can not figure out automatically,
+but needs to determine by the type of host Bash will run on.  Usually
+'configure' can figure that out, but if it prints a message saying it
+can not guess the host type, give it the '--host=TYPE' option.  'TYPE'
+can either be a short name for the system type, such as 'sun4', or a
+canonical name with three fields: 'CPU-COMPANY-SYSTEM' (e.g.,
+'i386-unknown-freebsd4.2').
+
+   See the file 'support/config.sub' for the possible values of each
+field.
+
+
+File: bashref.info,  Node: Sharing Defaults,  Next: Operation Controls,  Prev: Specifying the System Type,  Up: Installing Bash
+
+10.6 Sharing Defaults
+=====================
+
+If you want to set default values for 'configure' scripts to share, you
+can create a site shell script called 'config.site' that gives default
+values for variables like 'CC', 'cache_file', and 'prefix'.  'configure'
+looks for 'PREFIX/share/config.site' if it exists, then
+'PREFIX/etc/config.site' if it exists.  Or, you can set the
+'CONFIG_SITE' environment variable to the location of the site script.
+A warning: the Bash 'configure' looks for a site script, but not all
+'configure' scripts do.
+
+
+File: bashref.info,  Node: Operation Controls,  Next: Optional Features,  Prev: Sharing Defaults,  Up: Installing Bash
+
+10.7 Operation Controls
+=======================
+
+'configure' recognizes the following options to control how it operates.
+
+'--cache-file=FILE'
+     Use and save the results of the tests in FILE instead of
+     './config.cache'.  Set FILE to '/dev/null' to disable caching, for
+     debugging 'configure'.
+
+'--help'
+     Print a summary of the options to 'configure', and exit.
+
+'--quiet'
+'--silent'
+'-q'
+     Do not print messages saying which checks are being made.
+
+'--srcdir=DIR'
+     Look for the Bash source code in directory DIR.  Usually
+     'configure' can determine that directory automatically.
+
+'--version'
+     Print the version of Autoconf used to generate the 'configure'
+     script, and exit.
+
+   'configure' also accepts some other, not widely used, boilerplate
+options.  'configure --help' prints the complete list.
+
+
+File: bashref.info,  Node: Optional Features,  Prev: Operation Controls,  Up: Installing Bash
+
+10.8 Optional Features
+======================
+
+The Bash 'configure' has a number of '--enable-FEATURE' options, where
+FEATURE indicates an optional part of Bash.  There are also several
+'--with-PACKAGE' options, where PACKAGE is something like 'bash-malloc'
+or 'purify'.  To turn off the default use of a package, use
+'--without-PACKAGE'.  To configure Bash without a feature that is
+enabled by default, use '--disable-FEATURE'.
+
+   Here is a complete list of the '--enable-' and '--with-' options that
+the Bash 'configure' recognizes.
+
+'--with-afs'
+     Define if you are using the Andrew File System from Transarc.
+
+'--with-bash-malloc'
+     Use the Bash version of 'malloc' in the directory 'lib/malloc'.
+     This is not the same 'malloc' that appears in GNU libc, but an
+     older version originally derived from the 4.2 BSD 'malloc'.  This
+     'malloc' is very fast, but wastes some space on each allocation.
+     This option is enabled by default.  The 'NOTES' file contains a
+     list of systems for which this should be turned off, and
+     'configure' disables this option automatically for a number of
+     systems.
+
+'--with-curses'
+     Use the curses library instead of the termcap library.  This should
+     be supplied if your system has an inadequate or incomplete termcap
+     database.
+
+'--with-gnu-malloc'
+     A synonym for '--with-bash-malloc'.
+
+'--with-installed-readline[=PREFIX]'
+     Define this to make Bash link with a locally-installed version of
+     Readline rather than the version in 'lib/readline'.  This works
+     only with Readline 5.0 and later versions.  If PREFIX is 'yes' or
+     not supplied, 'configure' uses the values of the make variables
+     'includedir' and 'libdir', which are subdirectories of 'prefix' by
+     default, to find the installed version of Readline if it is not in
+     the standard system include and library directories.  If PREFIX is
+     'no', Bash links with the version in 'lib/readline'.  If PREFIX is
+     set to any other value, 'configure' treats it as a directory
+     pathname and looks for the installed version of Readline in
+     subdirectories of that directory (include files in PREFIX/'include'
+     and the library in PREFIX/'lib').
+
+'--with-libintl-prefix[=PREFIX]'
+     Define this to make Bash link with a locally-installed version of
+     the libintl library instead of the version in 'lib/intl'.
+
+'--with-libiconv-prefix[=PREFIX]'
+     Define this to make Bash look for libiconv in PREFIX instead of the
+     standard system locations.  There is no version included with Bash.
+
+'--enable-minimal-config'
+     This produces a shell with minimal features, close to the
+     historical Bourne shell.
+
+   There are several '--enable-' options that alter how Bash is
+compiled, linked, and installed, rather than changing run-time features.
+
+'--enable-largefile'
+     Enable support for large files
+     (http://www.unix.org/version2/whatsnew/lfs20mar.html) if the
+     operating system requires special compiler options to build
+     programs which can access large files.  This is enabled by default,
+     if the operating system provides large file support.
+
+'--enable-profiling'
+     This builds a Bash binary that produces profiling information to be
+     processed by 'gprof' each time it is executed.
+
+'--enable-separate-helpfiles'
+     Use external files for the documentation displayed by the 'help'
+     builtin instead of storing the text internally.
+
+'--enable-static-link'
+     This causes Bash to be linked statically, if 'gcc' is being used.
+     This could be used to build a version to use as root's shell.
+
+   The 'minimal-config' option can be used to disable all of the
+following options, but it is processed first, so individual options may
+be enabled using 'enable-FEATURE'.
+
+   All of the following options except for 'alt-array-implementation',
+'disabled-builtins', 'direxpand-default', 'strict-posix-default', and
+'xpg-echo-default' are enabled by default, unless the operating system
+does not provide the necessary support.
+
+'--enable-alias'
+     Allow alias expansion and include the 'alias' and 'unalias'
+     builtins (*note Aliases::).
+
+'--enable-alt-array-implementation'
+     This builds bash using an alternate implementation of arrays (*note
+     Arrays::) that provides faster access at the expense of using more
+     memory (sometimes many times more, depending on how sparse an array
+     is).
+
+'--enable-arith-for-command'
+     Include support for the alternate form of the 'for' command that
+     behaves like the C language 'for' statement (*note Looping
+     Constructs::).
+
+'--enable-array-variables'
+     Include support for one-dimensional array shell variables (*note
+     Arrays::).
+
+'--enable-bang-history'
+     Include support for 'csh'-like history substitution (*note History
+     Interaction::).
+
+'--enable-brace-expansion'
+     Include 'csh'-like brace expansion ( 'b{a,b}c' ==> 'bac bbc' ).
+     See *note Brace Expansion::, for a complete description.
+
+'--enable-casemod-attributes'
+     Include support for case-modifying attributes in the 'declare'
+     builtin and assignment statements.  Variables with the 'uppercase'
+     attribute, for example, will have their values converted to
+     uppercase upon assignment.
+
+'--enable-casemod-expansion'
+     Include support for case-modifying word expansions.
+
+'--enable-command-timing'
+     Include support for recognizing 'time' as a reserved word and for
+     displaying timing statistics for the pipeline following 'time'
+     (*note Pipelines::).  This allows pipelines as well as shell
+     builtins and functions to be timed.
+
+'--enable-cond-command'
+     Include support for the '[[' conditional command.  (*note
+     Conditional Constructs::).
+
+'--enable-cond-regexp'
+     Include support for matching POSIX regular expressions using the
+     '=~' binary operator in the '[[' conditional command.  (*note
+     Conditional Constructs::).
+
+'--enable-coprocesses'
+     Include support for coprocesses and the 'coproc' reserved word
+     (*note Pipelines::).
+
+'--enable-debugger'
+     Include support for the bash debugger (distributed separately).
+
+'--enable-dev-fd-stat-broken'
+     If calling 'stat' on /dev/fd/N returns different results than
+     calling 'fstat' on file descriptor N, supply this option to enable
+     a workaround.  This has implications for conditional commands that
+     test file attributes.
+
+'--enable-direxpand-default'
+     Cause the 'direxpand' shell option (*note The Shopt Builtin::) to
+     be enabled by default when the shell starts.  It is normally
+     disabled by default.
+
+'--enable-directory-stack'
+     Include support for a 'csh'-like directory stack and the 'pushd',
+     'popd', and 'dirs' builtins (*note The Directory Stack::).
+
+'--enable-disabled-builtins'
+     Allow builtin commands to be invoked via 'builtin xxx' even after
+     'xxx' has been disabled using 'enable -n xxx'.  See *note Bash
+     Builtins::, for details of the 'builtin' and 'enable' builtin
+     commands.
+
+'--enable-dparen-arithmetic'
+     Include support for the '((...))' command (*note Conditional
+     Constructs::).
+
+'--enable-extended-glob'
+     Include support for the extended pattern matching features
+     described above under *note Pattern Matching::.
+
+'--enable-extended-glob-default'
+     Set the default value of the 'extglob' shell option described above
+     under *note The Shopt Builtin:: to be enabled.
+
+'--enable-function-import'
+     Include support for importing function definitions exported by
+     another instance of the shell from the environment.  This option is
+     enabled by default.
+
+'--enable-glob-asciirange-default'
+     Set the default value of the 'globasciiranges' shell option
+     described above under *note The Shopt Builtin:: to be enabled.
+     This controls the behavior of character ranges when used in pattern
+     matching bracket expressions.
+
+'--enable-help-builtin'
+     Include the 'help' builtin, which displays help on shell builtins
+     and variables (*note Bash Builtins::).
+
+'--enable-history'
+     Include command history and the 'fc' and 'history' builtin commands
+     (*note Bash History Facilities::).
+
+'--enable-job-control'
+     This enables the job control features (*note Job Control::), if the
+     operating system supports them.
+
+'--enable-multibyte'
+     This enables support for multibyte characters if the operating
+     system provides the necessary support.
+
+'--enable-net-redirections'
+     This enables the special handling of filenames of the form
+     '/dev/tcp/HOST/PORT' and '/dev/udp/HOST/PORT' when used in
+     redirections (*note Redirections::).
+
+'--enable-process-substitution'
+     This enables process substitution (*note Process Substitution::) if
+     the operating system provides the necessary support.
+
+'--enable-progcomp'
+     Enable the programmable completion facilities (*note Programmable
+     Completion::).  If Readline is not enabled, this option has no
+     effect.
+
+'--enable-prompt-string-decoding'
+     Turn on the interpretation of a number of backslash-escaped
+     characters in the '$PS0', '$PS1', '$PS2', and '$PS4' prompt
+     strings.  See *note Controlling the Prompt::, for a complete list
+     of prompt string escape sequences.
+
+'--enable-readline'
+     Include support for command-line editing and history with the Bash
+     version of the Readline library (*note Command Line Editing::).
+
+'--enable-restricted'
+     Include support for a "restricted shell".  If this is enabled,
+     Bash, when called as 'rbash', enters a restricted mode.  See *note
+     The Restricted Shell::, for a description of restricted mode.
+
+'--enable-select'
+     Include the 'select' compound command, which allows the generation
+     of simple menus (*note Conditional Constructs::).
+
+'--enable-single-help-strings'
+     Store the text displayed by the 'help' builtin as a single string
+     for each help topic.  This aids in translating the text to
+     different languages.  You may need to disable this if your compiler
+     cannot handle very long string literals.
+
+'--enable-strict-posix-default'
+     Make Bash POSIX-conformant by default (*note Bash POSIX Mode::).
+
+'--enable-translatable-strings'
+     Enable support for '$"STRING"' translatable strings (*note Locale
+     Translation::).
+
+'--enable-usg-echo-default'
+     A synonym for '--enable-xpg-echo-default'.
+
+'--enable-xpg-echo-default'
+     Make the 'echo' builtin expand backslash-escaped characters by
+     default, without requiring the '-e' option.  This sets the default
+     value of the 'xpg_echo' shell option to 'on', which makes the Bash
+     'echo' behave more like the version specified in the Single Unix
+     Specification, version 3.  *Note Bash Builtins::, for a description
+     of the escape sequences that 'echo' recognizes.
+
+   The file 'config-top.h' contains C Preprocessor '#define' statements
+for options which are not settable from 'configure'.  Some of these are
+not meant to be changed; beware of the consequences if you do.  Read the
+comments associated with each definition for more information about its
+effect.
+
+
+File: bashref.info,  Node: Reporting Bugs,  Next: Major Differences From The Bourne Shell,  Prev: Installing Bash,  Up: Top
+
+Appendix A Reporting Bugs
+*************************
+
+Please report all bugs you find in Bash.  But first, you should make
+sure that it really is a bug, and that it appears in the latest version
+of Bash.  The latest version of Bash is always available for FTP from
+<ftp://ftp.gnu.org/pub/gnu/bash/> and from
+<http://git.savannah.gnu.org/cgit/bash.git/snapshot/bash-master.tar.gz>.
+
+   Once you have determined that a bug actually exists, use the
+'bashbug' 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 <bug-bash@gnu.org> or posted to the Usenet
+newsgroup 'gnu.bash.bug'.
+
+   All bug reports should include:
+   * The version number of Bash.
+   * The hardware and operating system.
+   * The compiler used to compile Bash.
+   * A description of the bug behaviour.
+   * A short script or 'recipe' which exercises the bug and may be used
+     to reproduce it.
+
+'bashbug' inserts the first three items automatically into the template
+it provides for filing a bug report.
+
+   Please send all reports concerning this manual to <bug-bash@gnu.org>.
+
+
+File: bashref.info,  Node: Major Differences From The Bourne Shell,  Next: GNU Free Documentation License,  Prev: Reporting Bugs,  Up: Top
+
+Appendix B Major Differences From The Bourne Shell
+**************************************************
+
+Bash implements essentially the same grammar, parameter and variable
+expansion, redirection, and quoting as the Bourne Shell.  Bash uses the
+POSIX standard as the specification of how these features are to be
+implemented.  There are some differences between the traditional Bourne
+shell and Bash; this section quickly details the differences of
+significance.  A number of these differences are explained in greater
+depth in previous sections.  This section uses the version of 'sh'
+included in SVR4.2 (the last version of the historical Bourne shell) as
+the baseline reference.
+
+   * Bash is POSIX-conformant, even where the POSIX specification
+     differs from traditional 'sh' behavior (*note Bash POSIX Mode::).
+
+   * Bash has multi-character invocation options (*note Invoking
+     Bash::).
+
+   * Bash has command-line editing (*note Command Line Editing::) and
+     the 'bind' builtin.
+
+   * Bash provides a programmable word completion mechanism (*note
+     Programmable Completion::), and builtin commands 'complete',
+     'compgen', and 'compopt', to manipulate it.
+
+   * Bash has command history (*note Bash History Facilities::) and the
+     'history' and 'fc' builtins to manipulate it.  The Bash history
+     list maintains timestamp information and uses the value of the
+     'HISTTIMEFORMAT' variable to display it.
+
+   * Bash implements 'csh'-like history expansion (*note History
+     Interaction::).
+
+   * Bash has one-dimensional array variables (*note Arrays::), and the
+     appropriate variable expansions and assignment syntax to use them.
+     Several of the Bash builtins take options to act on arrays.  Bash
+     provides a number of built-in array variables.
+
+   * The '$'...'' quoting syntax, which expands ANSI-C backslash-escaped
+     characters in the text between the single quotes, is supported
+     (*note ANSI-C Quoting::).
+
+   * Bash supports the '$"..."' quoting syntax to do locale-specific
+     translation of the characters between the double quotes.  The '-D',
+     '--dump-strings', and '--dump-po-strings' invocation options list
+     the translatable strings found in a script (*note Locale
+     Translation::).
+
+   * Bash implements the '!' keyword to negate the return value of a
+     pipeline (*note Pipelines::).  Very useful when an 'if' statement
+     needs to act only if a test fails.  The Bash '-o pipefail' option
+     to 'set' will cause a pipeline to return a failure status if any
+     command fails.
+
+   * Bash has the 'time' reserved word and command timing (*note
+     Pipelines::).  The display of the timing statistics may be
+     controlled with the 'TIMEFORMAT' variable.
+
+   * Bash implements the 'for (( EXPR1 ; EXPR2 ; EXPR3 ))' arithmetic
+     for command, similar to the C language (*note Looping
+     Constructs::).
+
+   * Bash includes the 'select' compound command, which allows the
+     generation of simple menus (*note Conditional Constructs::).
+
+   * Bash includes the '[[' compound command, which makes conditional
+     testing part of the shell grammar (*note Conditional Constructs::),
+     including optional regular expression matching.
+
+   * Bash provides optional case-insensitive matching for the 'case' and
+     '[[' constructs.
+
+   * Bash includes brace expansion (*note Brace Expansion::) and tilde
+     expansion (*note Tilde Expansion::).
+
+   * Bash implements command aliases and the 'alias' and 'unalias'
+     builtins (*note Aliases::).
+
+   * Bash provides shell arithmetic, the '((' compound command (*note
+     Conditional Constructs::), and arithmetic expansion (*note Shell
+     Arithmetic::).
+
+   * Variables present in the shell's initial environment are
+     automatically exported to child processes.  The Bourne shell does
+     not normally do this unless the variables are explicitly marked
+     using the 'export' command.
+
+   * Bash supports the '+=' assignment operator, which appends to the
+     value of the variable named on the left hand side.
+
+   * Bash includes the POSIX pattern removal '%', '#', '%%' and '##'
+     expansions to remove leading or trailing substrings from variable
+     values (*note Shell Parameter Expansion::).
+
+   * The expansion '${#xx}', which returns the length of '${xx}', is
+     supported (*note Shell Parameter Expansion::).
+
+   * The expansion '${var:'OFFSET'[:'LENGTH']}', which expands to the
+     substring of 'var''s value of length LENGTH, beginning at OFFSET,
+     is present (*note Shell Parameter Expansion::).
+
+   * The expansion '${VAR/[/]'PATTERN'[/'REPLACEMENT']}', which matches
+     PATTERN and replaces it with REPLACEMENT in the value of VAR, is
+     available (*note Shell Parameter Expansion::).
+
+   * The expansion '${!PREFIX*}' expansion, which expands to the names
+     of all shell variables whose names begin with PREFIX, is available
+     (*note Shell Parameter Expansion::).
+
+   * Bash has indirect variable expansion using '${!word}' (*note Shell
+     Parameter Expansion::).
+
+   * Bash can expand positional parameters beyond '$9' using '${NUM}'.
+
+   * The POSIX '$()' form of command substitution is implemented (*note
+     Command Substitution::), and preferred to the Bourne shell's '``'
+     (which is also implemented for backwards compatibility).
+
+   * Bash has process substitution (*note Process Substitution::).
+
+   * Bash automatically assigns variables that provide information about
+     the current user ('UID', 'EUID', and 'GROUPS'), the current host
+     ('HOSTTYPE', 'OSTYPE', 'MACHTYPE', and 'HOSTNAME'), and the
+     instance of Bash that is running ('BASH', 'BASH_VERSION', and
+     'BASH_VERSINFO').  *Note Bash Variables::, for details.
+
+   * The 'IFS' variable is used to split only the results of expansion,
+     not all words (*note Word Splitting::).  This closes a longstanding
+     shell security hole.
+
+   * The filename expansion bracket expression code uses '!' and '^' to
+     negate the set of characters between the brackets.  The Bourne
+     shell uses only '!'.
+
+   * Bash implements the full set of POSIX filename expansion operators,
+     including character classes, equivalence classes, and collating
+     symbols (*note Filename Expansion::).
+
+   * Bash implements extended pattern matching features when the
+     'extglob' shell option is enabled (*note Pattern Matching::).
+
+   * It is possible to have a variable and a function with the same
+     name; 'sh' does not separate the two name spaces.
+
+   * Bash functions are permitted to have local variables using the
+     'local' builtin, and thus useful recursive functions may be written
+     (*note Bash Builtins::).
+
+   * Variable assignments preceding commands affect only that command,
+     even builtins and functions (*note Environment::).  In 'sh', all
+     variable assignments preceding commands are global unless the
+     command is executed from the file system.
+
+   * Bash performs filename expansion on filenames specified as operands
+     to input and output redirection operators (*note Redirections::).
+
+   * Bash contains the '<>' redirection operator, allowing a file to be
+     opened for both reading and writing, and the '&>' redirection
+     operator, for directing standard output and standard error to the
+     same file (*note Redirections::).
+
+   * Bash includes the '<<<' redirection operator, allowing a string to
+     be used as the standard input to a command.
+
+   * Bash implements the '[n]<&WORD' and '[n]>&WORD' redirection
+     operators, which move one file descriptor to another.
+
+   * Bash treats a number of filenames specially when they are used in
+     redirection operators (*note Redirections::).
+
+   * Bash can open network connections to arbitrary machines and
+     services with the redirection operators (*note Redirections::).
+
+   * The 'noclobber' option is available to avoid overwriting existing
+     files with output redirection (*note The Set Builtin::).  The '>|'
+     redirection operator may be used to override 'noclobber'.
+
+   * The Bash 'cd' and 'pwd' builtins (*note Bourne Shell Builtins::)
+     each take '-L' and '-P' options to switch between logical and
+     physical modes.
+
+   * Bash allows a function to override a builtin with the same name,
+     and provides access to that builtin's functionality within the
+     function via the 'builtin' and 'command' builtins (*note Bash
+     Builtins::).
+
+   * The 'command' builtin allows selective disabling of functions when
+     command lookup is performed (*note Bash Builtins::).
+
+   * Individual builtins may be enabled or disabled using the 'enable'
+     builtin (*note Bash Builtins::).
+
+   * The Bash 'exec' builtin takes additional options that allow users
+     to control the contents of the environment passed to the executed
+     command, and what the zeroth argument to the command is to be
+     (*note Bourne Shell Builtins::).
+
+   * Shell functions may be exported to children via the environment
+     using 'export -f' (*note Shell Functions::).
+
+   * The Bash 'export', 'readonly', and 'declare' builtins can take a
+     '-f' option to act on shell functions, a '-p' option to display
+     variables with various attributes set in a format that can be used
+     as shell input, a '-n' option to remove various variable
+     attributes, and 'name=value' arguments to set variable attributes
+     and values simultaneously.
+
+   * The Bash 'hash' builtin allows a name to be associated with an
+     arbitrary filename, even when that filename cannot be found by
+     searching the '$PATH', using 'hash -p' (*note Bourne Shell
+     Builtins::).
+
+   * Bash includes a 'help' builtin for quick reference to shell
+     facilities (*note Bash Builtins::).
+
+   * The 'printf' builtin is available to display formatted output
+     (*note Bash Builtins::).
+
+   * The Bash 'read' builtin (*note Bash Builtins::) will read a line
+     ending in '\' with the '-r' option, and will use the 'REPLY'
+     variable as a default if no non-option arguments are supplied.  The
+     Bash 'read' builtin also accepts a prompt string with the '-p'
+     option and will use Readline to obtain the line when given the '-e'
+     option.  The 'read' builtin also has additional options to control
+     input: the '-s' option will turn off echoing of input characters as
+     they are read, the '-t' option will allow 'read' to time out if
+     input does not arrive within a specified number of seconds, the
+     '-n' option will allow reading only a specified number of
+     characters rather than a full line, and the '-d' option will read
+     until a particular character rather than newline.
+
+   * The 'return' builtin may be used to abort execution of scripts
+     executed with the '.' or 'source' builtins (*note Bourne Shell
+     Builtins::).
+
+   * Bash includes the 'shopt' builtin, for finer control of shell
+     optional capabilities (*note The Shopt Builtin::), and allows these
+     options to be set and unset at shell invocation (*note Invoking
+     Bash::).
+
+   * Bash has much more optional behavior controllable with the 'set'
+     builtin (*note The Set Builtin::).
+
+   * The '-x' ('xtrace') option displays commands other than simple
+     commands when performing an execution trace (*note The Set
+     Builtin::).
+
+   * The 'test' builtin (*note Bourne Shell Builtins::) is slightly
+     different, as it implements the POSIX algorithm, which specifies
+     the behavior based on the number of arguments.
+
+   * Bash includes the 'caller' builtin, which displays the context of
+     any active subroutine call (a shell function or a script executed
+     with the '.' or 'source' builtins).  This supports the Bash
+     debugger.
+
+   * The 'trap' builtin (*note Bourne Shell Builtins::) allows a 'DEBUG'
+     pseudo-signal specification, similar to 'EXIT'.  Commands specified
+     with a 'DEBUG' trap are executed before every simple command, 'for'
+     command, 'case' command, 'select' command, every arithmetic 'for'
+     command, and before the first command executes in a shell function.
+     The 'DEBUG' trap is not inherited by shell functions unless the
+     function has been given the 'trace' attribute or the 'functrace'
+     option has been enabled using the 'shopt' builtin.  The 'extdebug'
+     shell option has additional effects on the 'DEBUG' trap.
+
+     The 'trap' builtin (*note Bourne Shell Builtins::) allows an 'ERR'
+     pseudo-signal specification, similar to 'EXIT' and 'DEBUG'.
+     Commands specified with an 'ERR' trap are executed after a simple
+     command fails, with a few exceptions.  The 'ERR' trap is not
+     inherited by shell functions unless the '-o errtrace' option to the
+     'set' builtin is enabled.
+
+     The 'trap' builtin (*note Bourne Shell Builtins::) allows a
+     'RETURN' pseudo-signal specification, similar to 'EXIT' and
+     'DEBUG'.  Commands specified with a 'RETURN' trap are executed
+     before execution resumes after a shell function or a shell script
+     executed with '.' or 'source' returns.  The 'RETURN' trap is not
+     inherited by shell functions unless the function has been given the
+     'trace' attribute or the 'functrace' option has been enabled using
+     the 'shopt' builtin.
+
+   * The Bash 'type' builtin is more extensive and gives more
+     information about the names it finds (*note Bash Builtins::).
+
+   * The Bash 'umask' builtin permits a '-p' option to cause the output
+     to be displayed in the form of a 'umask' command that may be reused
+     as input (*note Bourne Shell Builtins::).
+
+   * Bash implements a 'csh'-like directory stack, and provides the
+     'pushd', 'popd', and 'dirs' builtins to manipulate it (*note The
+     Directory Stack::).  Bash also makes the directory stack visible as
+     the value of the 'DIRSTACK' shell variable.
+
+   * Bash interprets special backslash-escaped characters in the prompt
+     strings when interactive (*note Controlling the Prompt::).
+
+   * The Bash restricted mode is more useful (*note The Restricted
+     Shell::); the SVR4.2 shell restricted mode is too limited.
+
+   * The 'disown' builtin can remove a job from the internal shell job
+     table (*note Job Control Builtins::) or suppress the sending of
+     'SIGHUP' to a job when the shell exits as the result of a 'SIGHUP'.
+
+   * Bash includes a number of features to support a separate debugger
+     for shell scripts.
+
+   * The SVR4.2 shell has two privilege-related builtins ('mldmode' and
+     'priv') not present in Bash.
+
+   * Bash does not have the 'stop' or 'newgrp' builtins.
+
+   * Bash does not use the 'SHACCT' variable or perform shell
+     accounting.
+
+   * The SVR4.2 'sh' uses a 'TIMEOUT' variable like Bash uses 'TMOUT'.
+
+More features unique to Bash may be found in *note Bash Features::.
+
+B.1 Implementation Differences From The SVR4.2 Shell
+====================================================
+
+Since Bash is a completely new implementation, it does not suffer from
+many of the limitations of the SVR4.2 shell.  For instance:
+
+   * Bash does not fork a subshell when redirecting into or out of a
+     shell control structure such as an 'if' or 'while' statement.
+
+   * Bash does not allow unbalanced quotes.  The SVR4.2 shell will
+     silently insert a needed closing quote at 'EOF' under certain
+     circumstances.  This can be the cause of some hard-to-find errors.
+
+   * The SVR4.2 shell uses a baroque memory management scheme based on
+     trapping 'SIGSEGV'.  If the shell is started from a process with
+     'SIGSEGV' blocked (e.g., by using the 'system()' C library function
+     call), it misbehaves badly.
+
+   * In a questionable attempt at security, the SVR4.2 shell, when
+     invoked without the '-p' option, will alter its real and effective
+     UID and GID if they are less than some magic threshold value,
+     commonly 100.  This can lead to unexpected results.
+
+   * The SVR4.2 shell does not allow users to trap 'SIGSEGV', 'SIGALRM',
+     or 'SIGCHLD'.
+
+   * The SVR4.2 shell does not allow the 'IFS', 'MAILCHECK', 'PATH',
+     'PS1', or 'PS2' variables to be unset.
+
+   * The SVR4.2 shell treats '^' as the undocumented equivalent of '|'.
+
+   * Bash allows multiple option arguments when it is invoked ('-x -v');
+     the SVR4.2 shell allows only one option argument ('-xv').  In fact,
+     some versions of the shell dump core if the second argument begins
+     with a '-'.
+
+   * The SVR4.2 shell exits a script if any builtin fails; Bash exits a
+     script only if one of the POSIX special builtins fails, and only
+     for certain failures, as enumerated in the POSIX standard.
+
+   * The SVR4.2 shell behaves differently when invoked as 'jsh' (it
+     turns on job control).
+
+
+File: bashref.info,  Node: GNU Free Documentation License,  Next: Indexes,  Prev: Major Differences From The Bourne Shell,  Up: Top
+
+Appendix C GNU Free Documentation License
+*****************************************
+
+                     Version 1.3, 3 November 2008
+
+     Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+     <http://fsf.org/>
+
+     Everyone is permitted to copy and distribute verbatim copies
+     of this license document, but changing it is not allowed.
+
+  0. PREAMBLE
+
+     The purpose of this License is to make a manual, textbook, or other
+     functional and useful document "free" in the sense of freedom: to
+     assure everyone the effective freedom to copy and redistribute it,
+     with or without modifying it, either commercially or
+     noncommercially.  Secondarily, this License preserves for the
+     author and publisher a way to get credit for their work, while not
+     being considered responsible for modifications made by others.
+
+     This License is a kind of "copyleft", which means that derivative
+     works of the document must themselves be free in the same sense.
+     It complements the GNU General Public License, which is a copyleft
+     license designed for free software.
+
+     We have designed this License in order to use it for manuals for
+     free software, because free software needs free documentation: a
+     free program should come with manuals providing the same freedoms
+     that the software does.  But this License is not limited to
+     software manuals; it can be used for any textual work, regardless
+     of subject matter or whether it is published as a printed book.  We
+     recommend this License principally for works whose purpose is
+     instruction or reference.
+
+  1. APPLICABILITY AND DEFINITIONS
+
+     This License applies to any manual or other work, in any medium,
+     that contains a notice placed by the copyright holder saying it can
+     be distributed under the terms of this License.  Such a notice
+     grants a world-wide, royalty-free license, unlimited in duration,
+     to use that work under the conditions stated herein.  The
+     "Document", below, refers to any such manual or work.  Any member
+     of the public is a licensee, and is addressed as "you".  You accept
+     the license if you copy, modify or distribute the work in a way
+     requiring permission under copyright law.
+
+     A "Modified Version" of the Document means any work containing the
+     Document or a portion of it, either copied verbatim, or with
+     modifications and/or translated into another language.
+
+     A "Secondary Section" is a named appendix or a front-matter section
+     of the Document that deals exclusively with the relationship of the
+     publishers or authors of the Document to the Document's overall
+     subject (or to related matters) and contains nothing that could
+     fall directly within that overall subject.  (Thus, if the Document
+     is in part a textbook of mathematics, a Secondary Section may not
+     explain any mathematics.)  The relationship could be a matter of
+     historical connection with the subject or with related matters, or
+     of legal, commercial, philosophical, ethical or political position
+     regarding them.
+
+     The "Invariant Sections" are certain Secondary Sections whose
+     titles are designated, as being those of Invariant Sections, in the
+     notice that says that the Document is released under this License.
+     If a section does not fit the above definition of Secondary then it
+     is not allowed to be designated as Invariant.  The Document may
+     contain zero Invariant Sections.  If the Document does not identify
+     any Invariant Sections then there are none.
+
+     The "Cover Texts" are certain short passages of text that are
+     listed, as Front-Cover Texts or Back-Cover Texts, in the notice
+     that says that the Document is released under this License.  A
+     Front-Cover Text may be at most 5 words, and a Back-Cover Text may
+     be at most 25 words.
+
+     A "Transparent" copy of the Document means a machine-readable copy,
+     represented in a format whose specification is available to the
+     general public, that is suitable for revising the document
+     straightforwardly with generic text editors or (for images composed
+     of pixels) generic paint programs or (for drawings) some widely
+     available drawing editor, and that is suitable for input to text
+     formatters or for automatic translation to a variety of formats
+     suitable for input to text formatters.  A copy made in an otherwise
+     Transparent file format whose markup, or absence of markup, has
+     been arranged to thwart or discourage subsequent modification by
+     readers is not Transparent.  An image format is not Transparent if
+     used for any substantial amount of text.  A copy that is not
+     "Transparent" is called "Opaque".
+
+     Examples of suitable formats for Transparent copies include plain
+     ASCII without markup, Texinfo input format, LaTeX input format,
+     SGML or XML using a publicly available DTD, and standard-conforming
+     simple HTML, PostScript or PDF designed for human modification.
+     Examples of transparent image formats include PNG, XCF and JPG.
+     Opaque formats include proprietary formats that can be read and
+     edited only by proprietary word processors, SGML or XML for which
+     the DTD and/or processing tools are not generally available, and
+     the machine-generated HTML, PostScript or PDF produced by some word
+     processors for output purposes only.
+
+     The "Title Page" means, for a printed book, the title page itself,
+     plus such following pages as are needed to hold, legibly, the
+     material this License requires to appear in the title page.  For
+     works in formats which do not have any title page as such, "Title
+     Page" means the text near the most prominent appearance of the
+     work's title, preceding the beginning of the body of the text.
+
+     The "publisher" means any person or entity that distributes copies
+     of the Document to the public.
+
+     A section "Entitled XYZ" means a named subunit of the Document
+     whose title either is precisely XYZ or contains XYZ in parentheses
+     following text that translates XYZ in another language.  (Here XYZ
+     stands for a specific section name mentioned below, such as
+     "Acknowledgements", "Dedications", "Endorsements", or "History".)
+     To "Preserve the Title" of such a section when you modify the
+     Document means that it remains a section "Entitled XYZ" according
+     to this definition.
+
+     The Document may include Warranty Disclaimers next to the notice
+     which states that this License applies to the Document.  These
+     Warranty Disclaimers are considered to be included by reference in
+     this License, but only as regards disclaiming warranties: any other
+     implication that these Warranty Disclaimers may have is void and
+     has no effect on the meaning of this License.
+
+  2. VERBATIM COPYING
+
+     You may copy and distribute the Document in any medium, either
+     commercially or noncommercially, provided that this License, the
+     copyright notices, and the license notice saying this License
+     applies to the Document are reproduced in all copies, and that you
+     add no other conditions whatsoever to those of this License.  You
+     may not use technical measures to obstruct or control the reading
+     or further copying of the copies you make or distribute.  However,
+     you may accept compensation in exchange for copies.  If you
+     distribute a large enough number of copies you must also follow the
+     conditions in section 3.
+
+     You may also lend copies, under the same conditions stated above,
+     and you may publicly display copies.
+
+  3. COPYING IN QUANTITY
+
+     If you publish printed copies (or copies in media that commonly
+     have printed covers) of the Document, numbering more than 100, and
+     the Document's license notice requires Cover Texts, you must
+     enclose the copies in covers that carry, clearly and legibly, all
+     these Cover Texts: Front-Cover Texts on the front cover, and
+     Back-Cover Texts on the back cover.  Both covers must also clearly
+     and legibly identify you as the publisher of these copies.  The
+     front cover must present the full title with all words of the title
+     equally prominent and visible.  You may add other material on the
+     covers in addition.  Copying with changes limited to the covers, as
+     long as they preserve the title of the Document and satisfy these
+     conditions, can be treated as verbatim copying in other respects.
+
+     If the required texts for either cover are too voluminous to fit
+     legibly, you should put the first ones listed (as many as fit
+     reasonably) on the actual cover, and continue the rest onto
+     adjacent pages.
+
+     If you publish or distribute Opaque copies of the Document
+     numbering more than 100, you must either include a machine-readable
+     Transparent copy along with each Opaque copy, or state in or with
+     each Opaque copy a computer-network location from which the general
+     network-using public has access to download using public-standard
+     network protocols a complete Transparent copy of the Document, free
+     of added material.  If you use the latter option, you must take
+     reasonably prudent steps, when you begin distribution of Opaque
+     copies in quantity, to ensure that this Transparent copy will
+     remain thus accessible at the stated location until at least one
+     year after the last time you distribute an Opaque copy (directly or
+     through your agents or retailers) of that edition to the public.
+
+     It is requested, but not required, that you contact the authors of
+     the Document well before redistributing any large number of copies,
+     to give them a chance to provide you with an updated version of the
+     Document.
+
+  4. MODIFICATIONS
+
+     You may copy and distribute a Modified Version of the Document
+     under the conditions of sections 2 and 3 above, provided that you
+     release the Modified Version under precisely this License, with the
+     Modified Version filling the role of the Document, thus licensing
+     distribution and modification of the Modified Version to whoever
+     possesses a copy of it.  In addition, you must do these things in
+     the Modified Version:
+
+       A. Use in the Title Page (and on the covers, if any) a title
+          distinct from that of the Document, and from those of previous
+          versions (which should, if there were any, be listed in the
+          History section of the Document).  You may use the same title
+          as a previous version if the original publisher of that
+          version gives permission.
+
+       B. List on the Title Page, as authors, one or more persons or
+          entities responsible for authorship of the modifications in
+          the Modified Version, together with at least five of the
+          principal authors of the Document (all of its principal
+          authors, if it has fewer than five), unless they release you
+          from this requirement.
+
+       C. State on the Title page the name of the publisher of the
+          Modified Version, as the publisher.
+
+       D. Preserve all the copyright notices of the Document.
+
+       E. Add an appropriate copyright notice for your modifications
+          adjacent to the other copyright notices.
+
+       F. Include, immediately after the copyright notices, a license
+          notice giving the public permission to use the Modified
+          Version under the terms of this License, in the form shown in
+          the Addendum below.
+
+       G. Preserve in that license notice the full lists of Invariant
+          Sections and required Cover Texts given in the Document's
+          license notice.
+
+       H. Include an unaltered copy of this License.
+
+       I. Preserve the section Entitled "History", Preserve its Title,
+          and add to it an item stating at least the title, year, new
+          authors, and publisher of the Modified Version as given on the
+          Title Page.  If there is no section Entitled "History" in the
+          Document, create one stating the title, year, authors, and
+          publisher of the Document as given on its Title Page, then add
+          an item describing the Modified Version as stated in the
+          previous sentence.
+
+       J. Preserve the network location, if any, given in the Document
+          for public access to a Transparent copy of the Document, and
+          likewise the network locations given in the Document for
+          previous versions it was based on.  These may be placed in the
+          "History" section.  You may omit a network location for a work
+          that was published at least four years before the Document
+          itself, or if the original publisher of the version it refers
+          to gives permission.
+
+       K. For any section Entitled "Acknowledgements" or "Dedications",
+          Preserve the Title of the section, and preserve in the section
+          all the substance and tone of each of the contributor
+          acknowledgements and/or dedications given therein.
+
+       L. Preserve all the Invariant Sections of the Document, unaltered
+          in their text and in their titles.  Section numbers or the
+          equivalent are not considered part of the section titles.
+
+       M. Delete any section Entitled "Endorsements".  Such a section
+          may not be included in the Modified Version.
+
+       N. Do not retitle any existing section to be Entitled
+          "Endorsements" or to conflict in title with any Invariant
+          Section.
+
+       O. Preserve any Warranty Disclaimers.
+
+     If the Modified Version includes new front-matter sections or
+     appendices that qualify as Secondary Sections and contain no
+     material copied from the Document, you may at your option designate
+     some or all of these sections as invariant.  To do this, add their
+     titles to the list of Invariant Sections in the Modified Version's
+     license notice.  These titles must be distinct from any other
+     section titles.
+
+     You may add a section Entitled "Endorsements", provided it contains
+     nothing but endorsements of your Modified Version by various
+     parties--for example, statements of peer review or that the text
+     has been approved by an organization as the authoritative
+     definition of a standard.
+
+     You may add a passage of up to five words as a Front-Cover Text,
+     and a passage of up to 25 words as a Back-Cover Text, to the end of
+     the list of Cover Texts in the Modified Version.  Only one passage
+     of Front-Cover Text and one of Back-Cover Text may be added by (or
+     through arrangements made by) any one entity.  If the Document
+     already includes a cover text for the same cover, previously added
+     by you or by arrangement made by the same entity you are acting on
+     behalf of, you may not add another; but you may replace the old
+     one, on explicit permission from the previous publisher that added
+     the old one.
+
+     The author(s) and publisher(s) of the Document do not by this
+     License give permission to use their names for publicity for or to
+     assert or imply endorsement of any Modified Version.
+
+  5. COMBINING DOCUMENTS
+
+     You may combine the Document with other documents released under
+     this License, under the terms defined in section 4 above for
+     modified versions, provided that you include in the combination all
+     of the Invariant Sections of all of the original documents,
+     unmodified, and list them all as Invariant Sections of your
+     combined work in its license notice, and that you preserve all
+     their Warranty Disclaimers.
+
+     The combined work need only contain one copy of this License, and
+     multiple identical Invariant Sections may be replaced with a single
+     copy.  If there are multiple Invariant Sections with the same name
+     but different contents, make the title of each such section unique
+     by adding at the end of it, in parentheses, the name of the
+     original author or publisher of that section if known, or else a
+     unique number.  Make the same adjustment to the section titles in
+     the list of Invariant Sections in the license notice of the
+     combined work.
+
+     In the combination, you must combine any sections Entitled
+     "History" in the various original documents, forming one section
+     Entitled "History"; likewise combine any sections Entitled
+     "Acknowledgements", and any sections Entitled "Dedications".  You
+     must delete all sections Entitled "Endorsements."
+
+  6. COLLECTIONS OF DOCUMENTS
+
+     You may make a collection consisting of the Document and other
+     documents released under this License, and replace the individual
+     copies of this License in the various documents with a single copy
+     that is included in the collection, provided that you follow the
+     rules of this License for verbatim copying of each of the documents
+     in all other respects.
+
+     You may extract a single document from such a collection, and
+     distribute it individually under this License, provided you insert
+     a copy of this License into the extracted document, and follow this
+     License in all other respects regarding verbatim copying of that
+     document.
+
+  7. AGGREGATION WITH INDEPENDENT WORKS
+
+     A compilation of the Document or its derivatives with other
+     separate and independent documents or works, in or on a volume of a
+     storage or distribution medium, is called an "aggregate" if the
+     copyright resulting from the compilation is not used to limit the
+     legal rights of the compilation's users beyond what the individual
+     works permit.  When the Document is included in an aggregate, this
+     License does not apply to the other works in the aggregate which
+     are not themselves derivative works of the Document.
+
+     If the Cover Text requirement of section 3 is applicable to these
+     copies of the Document, then if the Document is less than one half
+     of the entire aggregate, the Document's Cover Texts may be placed
+     on covers that bracket the Document within the aggregate, or the
+     electronic equivalent of covers if the Document is in electronic
+     form.  Otherwise they must appear on printed covers that bracket
+     the whole aggregate.
+
+  8. TRANSLATION
+
+     Translation is considered a kind of modification, so you may
+     distribute translations of the Document under the terms of section
+     4.  Replacing Invariant Sections with translations requires special
+     permission from their copyright holders, but you may include
+     translations of some or all Invariant Sections in addition to the
+     original versions of these Invariant Sections.  You may include a
+     translation of this License, and all the license notices in the
+     Document, and any Warranty Disclaimers, provided that you also
+     include the original English version of this License and the
+     original versions of those notices and disclaimers.  In case of a
+     disagreement between the translation and the original version of
+     this License or a notice or disclaimer, the original version will
+     prevail.
+
+     If a section in the Document is Entitled "Acknowledgements",
+     "Dedications", or "History", the requirement (section 4) to
+     Preserve its Title (section 1) will typically require changing the
+     actual title.
+
+  9. TERMINATION
+
+     You may not copy, modify, sublicense, or distribute the Document
+     except as expressly provided under this License.  Any attempt
+     otherwise to copy, modify, sublicense, or distribute it is void,
+     and will automatically terminate your rights under this License.
+
+     However, if you cease all violation of this License, then your
+     license from a particular copyright holder is reinstated (a)
+     provisionally, unless and until the copyright holder explicitly and
+     finally terminates your license, and (b) permanently, if the
+     copyright holder fails to notify you of the violation by some
+     reasonable means prior to 60 days after the cessation.
+
+     Moreover, your license from a particular copyright holder is
+     reinstated permanently if the copyright holder notifies you of the
+     violation by some reasonable means, this is the first time you have
+     received notice of violation of this License (for any work) from
+     that copyright holder, and you cure the violation prior to 30 days
+     after your receipt of the notice.
+
+     Termination of your rights under this section does not terminate
+     the licenses of parties who have received copies or rights from you
+     under this License.  If your rights have been terminated and not
+     permanently reinstated, receipt of a copy of some or all of the
+     same material does not give you any rights to use it.
+
+  10. FUTURE REVISIONS OF THIS LICENSE
+
+     The Free Software Foundation may publish new, revised versions of
+     the GNU Free Documentation License from time to time.  Such new
+     versions will be similar in spirit to the present version, but may
+     differ in detail to address new problems or concerns.  See
+     <http://www.gnu.org/copyleft/>.
+
+     Each version of the License is given a distinguishing version
+     number.  If the Document specifies that a particular numbered
+     version of this License "or any later version" applies to it, you
+     have the option of following the terms and conditions either of
+     that specified version or of any later version that has been
+     published (not as a draft) by the Free Software Foundation.  If the
+     Document does not specify a version number of this License, you may
+     choose any version ever published (not as a draft) by the Free
+     Software Foundation.  If the Document specifies that a proxy can
+     decide which future versions of this License can be used, that
+     proxy's public statement of acceptance of a version permanently
+     authorizes you to choose that version for the Document.
+
+  11. RELICENSING
+
+     "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
+     World Wide Web server that publishes copyrightable works and also
+     provides prominent facilities for anybody to edit those works.  A
+     public wiki that anybody can edit is an example of such a server.
+     A "Massive Multiauthor Collaboration" (or "MMC") contained in the
+     site means any set of copyrightable works thus published on the MMC
+     site.
+
+     "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
+     license published by Creative Commons Corporation, a not-for-profit
+     corporation with a principal place of business in San Francisco,
+     California, as well as future copyleft versions of that license
+     published by that same organization.
+
+     "Incorporate" means to publish or republish a Document, in whole or
+     in part, as part of another Document.
+
+     An MMC is "eligible for relicensing" if it is licensed under this
+     License, and if all works that were first published under this
+     License somewhere other than this MMC, and subsequently
+     incorporated in whole or in part into the MMC, (1) had no cover
+     texts or invariant sections, and (2) were thus incorporated prior
+     to November 1, 2008.
+
+     The operator of an MMC Site may republish an MMC contained in the
+     site under CC-BY-SA on the same site at any time before August 1,
+     2009, provided the MMC is eligible for relicensing.
+
+ADDENDUM: How to use this License for your documents
+====================================================
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and license
+notices just after the title page:
+
+       Copyright (C)  YEAR  YOUR NAME.
+       Permission is granted to copy, distribute and/or modify this document
+       under the terms of the GNU Free Documentation License, Version 1.3
+       or any later version published by the Free Software Foundation;
+       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+       Texts.  A copy of the license is included in the section entitled ``GNU
+       Free Documentation License''.
+
+   If you have Invariant Sections, Front-Cover Texts and Back-Cover
+Texts, replace the "with...Texts."  line with this:
+
+         with the Invariant Sections being LIST THEIR TITLES, with
+         the Front-Cover Texts being LIST, and with the Back-Cover Texts
+         being LIST.
+
+   If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+   If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of free
+software license, such as the GNU General Public License, to permit
+their use in free software.
+
+
+File: bashref.info,  Node: Indexes,  Prev: GNU Free Documentation License,  Up: Top
+
+Appendix D Indexes
+******************
+
+* Menu:
+
+* Builtin Index::		Index of Bash builtin commands.
+* Reserved Word Index::		Index of Bash reserved words.
+* Variable Index::		Quick reference helps you find the
+				variable you want.
+* Function Index::		Index of bindable Readline functions.
+* Concept Index::		General index for concepts described in
+				this manual.
+
+
+File: bashref.info,  Node: Builtin Index,  Next: Reserved Word Index,  Up: Indexes
+
+D.1 Index of Shell Builtin Commands
+===================================
+
+
+* Menu:
+
+* .:                                     Bourne Shell Builtins.
+                                                              (line  17)
+* ::                                     Bourne Shell Builtins.
+                                                              (line  11)
+* [:                                     Bourne Shell Builtins.
+                                                              (line 275)
+* alias:                                 Bash Builtins.       (line  11)
+* bg:                                    Job Control Builtins.
+                                                              (line   7)
+* bind:                                  Bash Builtins.       (line  21)
+* break:                                 Bourne Shell Builtins.
+                                                              (line  37)
+* builtin:                               Bash Builtins.       (line 108)
+* caller:                                Bash Builtins.       (line 117)
+* cd:                                    Bourne Shell Builtins.
+                                                              (line  45)
+* command:                               Bash Builtins.       (line 134)
+* compgen:                               Programmable Completion Builtins.
+                                                              (line  12)
+* complete:                              Programmable Completion Builtins.
+                                                              (line  30)
+* compopt:                               Programmable Completion Builtins.
+                                                              (line 238)
+* continue:                              Bourne Shell Builtins.
+                                                              (line  90)
+* declare:                               Bash Builtins.       (line 154)
+* dirs:                                  Directory Stack Builtins.
+                                                              (line   7)
+* disown:                                Job Control Builtins.
+                                                              (line 104)
+* echo:                                  Bash Builtins.       (line 257)
+* enable:                                Bash Builtins.       (line 306)
+* eval:                                  Bourne Shell Builtins.
+                                                              (line  99)
+* exec:                                  Bourne Shell Builtins.
+                                                              (line 107)
+* exit:                                  Bourne Shell Builtins.
+                                                              (line 125)
+* export:                                Bourne Shell Builtins.
+                                                              (line 132)
+* fc:                                    Bash History Builtins.
+                                                              (line  10)
+* fg:                                    Job Control Builtins.
+                                                              (line  17)
+* getopts:                               Bourne Shell Builtins.
+                                                              (line 148)
+* hash:                                  Bourne Shell Builtins.
+                                                              (line 192)
+* help:                                  Bash Builtins.       (line 342)
+* history:                               Bash History Builtins.
+                                                              (line  46)
+* jobs:                                  Job Control Builtins.
+                                                              (line  27)
+* kill:                                  Job Control Builtins.
+                                                              (line  58)
+* let:                                   Bash Builtins.       (line 361)
+* local:                                 Bash Builtins.       (line 369)
+* logout:                                Bash Builtins.       (line 385)
+* mapfile:                               Bash Builtins.       (line 390)
+* popd:                                  Directory Stack Builtins.
+                                                              (line  35)
+* printf:                                Bash Builtins.       (line 436)
+* pushd:                                 Directory Stack Builtins.
+                                                              (line  69)
+* pwd:                                   Bourne Shell Builtins.
+                                                              (line 212)
+* read:                                  Bash Builtins.       (line 488)
+* readarray:                             Bash Builtins.       (line 585)
+* readonly:                              Bourne Shell Builtins.
+                                                              (line 222)
+* return:                                Bourne Shell Builtins.
+                                                              (line 241)
+* set:                                   The Set Builtin.     (line  11)
+* shift:                                 Bourne Shell Builtins.
+                                                              (line 262)
+* shopt:                                 The Shopt Builtin.   (line   9)
+* source:                                Bash Builtins.       (line 594)
+* suspend:                               Job Control Builtins.
+                                                              (line 116)
+* test:                                  Bourne Shell Builtins.
+                                                              (line 275)
+* times:                                 Bourne Shell Builtins.
+                                                              (line 360)
+* trap:                                  Bourne Shell Builtins.
+                                                              (line 366)
+* type:                                  Bash Builtins.       (line 599)
+* typeset:                               Bash Builtins.       (line 631)
+* ulimit:                                Bash Builtins.       (line 637)
+* umask:                                 Bourne Shell Builtins.
+                                                              (line 415)
+* unalias:                               Bash Builtins.       (line 743)
+* unset:                                 Bourne Shell Builtins.
+                                                              (line 433)
+* wait:                                  Job Control Builtins.
+                                                              (line  76)
+
+
+File: bashref.info,  Node: Reserved Word Index,  Next: Variable Index,  Prev: Builtin Index,  Up: Indexes
+
+D.2 Index of Shell Reserved Words
+=================================
+
+
+* Menu:
+
+* !:                                     Pipelines.           (line   9)
+* [[:                                    Conditional Constructs.
+                                                              (line 126)
+* ]]:                                    Conditional Constructs.
+                                                              (line 126)
+* {:                                     Command Grouping.    (line  21)
+* }:                                     Command Grouping.    (line  21)
+* case:                                  Conditional Constructs.
+                                                              (line  28)
+* do:                                    Looping Constructs.  (line  12)
+* done:                                  Looping Constructs.  (line  12)
+* elif:                                  Conditional Constructs.
+                                                              (line   7)
+* else:                                  Conditional Constructs.
+                                                              (line   7)
+* esac:                                  Conditional Constructs.
+                                                              (line  28)
+* fi:                                    Conditional Constructs.
+                                                              (line   7)
+* for:                                   Looping Constructs.  (line  32)
+* function:                              Shell Functions.     (line  13)
+* if:                                    Conditional Constructs.
+                                                              (line   7)
+* in:                                    Conditional Constructs.
+                                                              (line  28)
+* select:                                Conditional Constructs.
+                                                              (line  84)
+* then:                                  Conditional Constructs.
+                                                              (line   7)
+* time:                                  Pipelines.           (line   9)
+* until:                                 Looping Constructs.  (line  12)
+* while:                                 Looping Constructs.  (line  22)
+
+
+File: bashref.info,  Node: Variable Index,  Next: Function Index,  Prev: Reserved Word Index,  Up: Indexes
+
+D.3 Parameter and Variable Index
+================================
+
+
+* Menu:
+
+* !:                                     Special Parameters.  (line  55)
+* #:                                     Special Parameters.  (line  39)
+* $:                                     Special Parameters.  (line  51)
+* $!:                                    Special Parameters.  (line  56)
+* $#:                                    Special Parameters.  (line  40)
+* $$:                                    Special Parameters.  (line  52)
+* $*:                                    Special Parameters.  (line  10)
+* $-:                                    Special Parameters.  (line  47)
+* $0:                                    Special Parameters.  (line  61)
+* $?:                                    Special Parameters.  (line  43)
+* $@:                                    Special Parameters.  (line  23)
+* $_:                                    Bash Variables.      (line  14)
+* *:                                     Special Parameters.  (line   9)
+* -:                                     Special Parameters.  (line  46)
+* 0:                                     Special Parameters.  (line  60)
+* ?:                                     Special Parameters.  (line  42)
+* @:                                     Special Parameters.  (line  22)
+* _:                                     Bash Variables.      (line  13)
+* active-region-end-color:               Readline Init File Syntax.
+                                                              (line  51)
+* active-region-start-color:             Readline Init File Syntax.
+                                                              (line  38)
+* auto_resume:                           Job Control Variables.
+                                                              (line   6)
+* BASH:                                  Bash Variables.      (line  23)
+* BASHOPTS:                              Bash Variables.      (line  26)
+* BASHPID:                               Bash Variables.      (line  35)
+* BASH_ALIASES:                          Bash Variables.      (line  42)
+* BASH_ARGC:                             Bash Variables.      (line  51)
+* BASH_ARGV:                             Bash Variables.      (line  64)
+* BASH_ARGV0:                            Bash Variables.      (line  76)
+* BASH_CMDS:                             Bash Variables.      (line  84)
+* BASH_COMMAND:                          Bash Variables.      (line  93)
+* BASH_COMPAT:                           Bash Variables.      (line 100)
+* BASH_ENV:                              Bash Variables.      (line 116)
+* BASH_EXECUTION_STRING:                 Bash Variables.      (line 122)
+* BASH_LINENO:                           Bash Variables.      (line 125)
+* BASH_LOADABLES_PATH:                   Bash Variables.      (line 133)
+* BASH_REMATCH:                          Bash Variables.      (line 137)
+* BASH_SOURCE:                           Bash Variables.      (line 145)
+* BASH_SUBSHELL:                         Bash Variables.      (line 152)
+* BASH_VERSINFO:                         Bash Variables.      (line 158)
+* BASH_VERSION:                          Bash Variables.      (line 181)
+* BASH_XTRACEFD:                         Bash Variables.      (line 184)
+* bell-style:                            Readline Init File Syntax.
+                                                              (line  64)
+* bind-tty-special-chars:                Readline Init File Syntax.
+                                                              (line  71)
+* blink-matching-paren:                  Readline Init File Syntax.
+                                                              (line  76)
+* CDPATH:                                Bourne Shell Variables.
+                                                              (line   9)
+* CHILD_MAX:                             Bash Variables.      (line 195)
+* colored-completion-prefix:             Readline Init File Syntax.
+                                                              (line  81)
+* colored-stats:                         Readline Init File Syntax.
+                                                              (line  91)
+* COLUMNS:                               Bash Variables.      (line 202)
+* comment-begin:                         Readline Init File Syntax.
+                                                              (line  97)
+* completion-display-width:              Readline Init File Syntax.
+                                                              (line 102)
+* completion-ignore-case:                Readline Init File Syntax.
+                                                              (line 109)
+* completion-map-case:                   Readline Init File Syntax.
+                                                              (line 114)
+* completion-prefix-display-length:      Readline Init File Syntax.
+                                                              (line 120)
+* completion-query-items:                Readline Init File Syntax.
+                                                              (line 127)
+* COMPREPLY:                             Bash Variables.      (line 254)
+* COMP_CWORD:                            Bash Variables.      (line 208)
+* COMP_KEY:                              Bash Variables.      (line 237)
+* COMP_LINE:                             Bash Variables.      (line 214)
+* COMP_POINT:                            Bash Variables.      (line 219)
+* COMP_TYPE:                             Bash Variables.      (line 227)
+* COMP_WORDBREAKS:                       Bash Variables.      (line 241)
+* COMP_WORDS:                            Bash Variables.      (line 247)
+* convert-meta:                          Readline Init File Syntax.
+                                                              (line 138)
+* COPROC:                                Bash Variables.      (line 260)
+* DIRSTACK:                              Bash Variables.      (line 264)
+* disable-completion:                    Readline Init File Syntax.
+                                                              (line 148)
+* echo-control-characters:               Readline Init File Syntax.
+                                                              (line 153)
+* editing-mode:                          Readline Init File Syntax.
+                                                              (line 158)
+* EMACS:                                 Bash Variables.      (line 274)
+* emacs-mode-string:                     Readline Init File Syntax.
+                                                              (line 164)
+* enable-active-region:                  Readline Init File Syntax.
+                                                              (line 174)
+* enable-bracketed-paste:                Readline Init File Syntax.
+                                                              (line 187)
+* enable-keypad:                         Readline Init File Syntax.
+                                                              (line 196)
+* ENV:                                   Bash Variables.      (line 279)
+* EPOCHREALTIME:                         Bash Variables.      (line 284)
+* EPOCHSECONDS:                          Bash Variables.      (line 292)
+* EUID:                                  Bash Variables.      (line 299)
+* EXECIGNORE:                            Bash Variables.      (line 303)
+* expand-tilde:                          Readline Init File Syntax.
+                                                              (line 207)
+* FCEDIT:                                Bash Variables.      (line 316)
+* FIGNORE:                               Bash Variables.      (line 320)
+* FUNCNAME:                              Bash Variables.      (line 326)
+* FUNCNEST:                              Bash Variables.      (line 343)
+* GLOBIGNORE:                            Bash Variables.      (line 348)
+* GROUPS:                                Bash Variables.      (line 355)
+* histchars:                             Bash Variables.      (line 361)
+* HISTCMD:                               Bash Variables.      (line 376)
+* HISTCONTROL:                           Bash Variables.      (line 382)
+* HISTFILE:                              Bash Variables.      (line 398)
+* HISTFILESIZE:                          Bash Variables.      (line 402)
+* HISTIGNORE:                            Bash Variables.      (line 413)
+* history-preserve-point:                Readline Init File Syntax.
+                                                              (line 211)
+* history-size:                          Readline Init File Syntax.
+                                                              (line 217)
+* HISTSIZE:                              Bash Variables.      (line 433)
+* HISTTIMEFORMAT:                        Bash Variables.      (line 440)
+* HOME:                                  Bourne Shell Variables.
+                                                              (line  13)
+* horizontal-scroll-mode:                Readline Init File Syntax.
+                                                              (line 226)
+* HOSTFILE:                              Bash Variables.      (line 448)
+* HOSTNAME:                              Bash Variables.      (line 459)
+* HOSTTYPE:                              Bash Variables.      (line 462)
+* IFS:                                   Bourne Shell Variables.
+                                                              (line  18)
+* IGNOREEOF:                             Bash Variables.      (line 465)
+* input-meta:                            Readline Init File Syntax.
+                                                              (line 235)
+* INPUTRC:                               Bash Variables.      (line 475)
+* INSIDE_EMACS:                          Bash Variables.      (line 479)
+* isearch-terminators:                   Readline Init File Syntax.
+                                                              (line 245)
+* keymap:                                Readline Init File Syntax.
+                                                              (line 252)
+* LANG:                                  Creating Internationalized Scripts.
+                                                              (line  51)
+* LANG <1>:                              Bash Variables.      (line 485)
+* LC_ALL:                                Bash Variables.      (line 489)
+* LC_COLLATE:                            Bash Variables.      (line 493)
+* LC_CTYPE:                              Bash Variables.      (line 500)
+* LC_MESSAGES:                           Creating Internationalized Scripts.
+                                                              (line  51)
+* LC_MESSAGES <1>:                       Bash Variables.      (line 505)
+* LC_NUMERIC:                            Bash Variables.      (line 509)
+* LC_TIME:                               Bash Variables.      (line 513)
+* LINENO:                                Bash Variables.      (line 517)
+* LINES:                                 Bash Variables.      (line 522)
+* MACHTYPE:                              Bash Variables.      (line 528)
+* MAIL:                                  Bourne Shell Variables.
+                                                              (line  22)
+* MAILCHECK:                             Bash Variables.      (line 532)
+* MAILPATH:                              Bourne Shell Variables.
+                                                              (line  27)
+* MAPFILE:                               Bash Variables.      (line 540)
+* mark-modified-lines:                   Readline Init File Syntax.
+                                                              (line 282)
+* mark-symlinked-directories:            Readline Init File Syntax.
+                                                              (line 287)
+* match-hidden-files:                    Readline Init File Syntax.
+                                                              (line 292)
+* menu-complete-display-prefix:          Readline Init File Syntax.
+                                                              (line 299)
+* meta-flag:                             Readline Init File Syntax.
+                                                              (line 235)
+* OLDPWD:                                Bash Variables.      (line 544)
+* OPTARG:                                Bourne Shell Variables.
+                                                              (line  34)
+* OPTERR:                                Bash Variables.      (line 547)
+* OPTIND:                                Bourne Shell Variables.
+                                                              (line  38)
+* OSTYPE:                                Bash Variables.      (line 551)
+* output-meta:                           Readline Init File Syntax.
+                                                              (line 304)
+* page-completions:                      Readline Init File Syntax.
+                                                              (line 312)
+* PATH:                                  Bourne Shell Variables.
+                                                              (line  42)
+* PIPESTATUS:                            Bash Variables.      (line 554)
+* POSIXLY_CORRECT:                       Bash Variables.      (line 559)
+* PPID:                                  Bash Variables.      (line 569)
+* PROMPT_COMMAND:                        Bash Variables.      (line 573)
+* PROMPT_DIRTRIM:                        Bash Variables.      (line 579)
+* PS0:                                   Bash Variables.      (line 585)
+* PS1:                                   Bourne Shell Variables.
+                                                              (line  48)
+* PS2:                                   Bourne Shell Variables.
+                                                              (line  53)
+* PS3:                                   Bash Variables.      (line 590)
+* PS4:                                   Bash Variables.      (line 595)
+* PWD:                                   Bash Variables.      (line 603)
+* RANDOM:                                Bash Variables.      (line 606)
+* READLINE_ARGUMENT:                     Bash Variables.      (line 612)
+* READLINE_LINE:                         Bash Variables.      (line 616)
+* READLINE_MARK:                         Bash Variables.      (line 620)
+* READLINE_POINT:                        Bash Variables.      (line 626)
+* REPLY:                                 Bash Variables.      (line 630)
+* revert-all-at-newline:                 Readline Init File Syntax.
+                                                              (line 322)
+* SECONDS:                               Bash Variables.      (line 633)
+* SHELL:                                 Bash Variables.      (line 642)
+* SHELLOPTS:                             Bash Variables.      (line 647)
+* SHLVL:                                 Bash Variables.      (line 656)
+* show-all-if-ambiguous:                 Readline Init File Syntax.
+                                                              (line 329)
+* show-all-if-unmodified:                Readline Init File Syntax.
+                                                              (line 335)
+* show-mode-in-prompt:                   Readline Init File Syntax.
+                                                              (line 344)
+* skip-completed-text:                   Readline Init File Syntax.
+                                                              (line 350)
+* SRANDOM:                               Bash Variables.      (line 661)
+* TEXTDOMAIN:                            Creating Internationalized Scripts.
+                                                              (line  51)
+* TEXTDOMAINDIR:                         Creating Internationalized Scripts.
+                                                              (line  51)
+* TIMEFORMAT:                            Bash Variables.      (line 670)
+* TMOUT:                                 Bash Variables.      (line 708)
+* TMPDIR:                                Bash Variables.      (line 720)
+* UID:                                   Bash Variables.      (line 724)
+* vi-cmd-mode-string:                    Readline Init File Syntax.
+                                                              (line 363)
+* vi-ins-mode-string:                    Readline Init File Syntax.
+                                                              (line 374)
+* visible-stats:                         Readline Init File Syntax.
+                                                              (line 385)
+
+
+File: bashref.info,  Node: Function Index,  Next: Concept Index,  Prev: Variable Index,  Up: Indexes
+
+D.4 Function Index
+==================
+
+
+* Menu:
+
+* abort (C-g):                           Miscellaneous Commands.
+                                                              (line  10)
+* accept-line (Newline or Return):       Commands For History.
+                                                              (line   6)
+* alias-expand-line ():                  Miscellaneous Commands.
+                                                              (line 131)
+* backward-char (C-b):                   Commands For Moving. (line  15)
+* backward-delete-char (Rubout):         Commands For Text.   (line  17)
+* backward-kill-line (C-x Rubout):       Commands For Killing.
+                                                              (line  11)
+* backward-kill-word (M-<DEL>):          Commands For Killing.
+                                                              (line  28)
+* backward-word (M-b):                   Commands For Moving. (line  22)
+* beginning-of-history (M-<):            Commands For History.
+                                                              (line  20)
+* beginning-of-line (C-a):               Commands For Moving. (line   6)
+* bracketed-paste-begin ():              Commands For Text.   (line  33)
+* call-last-kbd-macro (C-x e):           Keyboard Macros.     (line  13)
+* capitalize-word (M-c):                 Commands For Text.   (line  66)
+* character-search (C-]):                Miscellaneous Commands.
+                                                              (line  42)
+* character-search-backward (M-C-]):     Miscellaneous Commands.
+                                                              (line  47)
+* clear-display (M-C-l):                 Commands For Moving. (line  48)
+* clear-screen (C-l):                    Commands For Moving. (line  53)
+* complete (<TAB>):                      Commands For Completion.
+                                                              (line   6)
+* complete-command (M-!):                Commands For Completion.
+                                                              (line  80)
+* complete-filename (M-/):               Commands For Completion.
+                                                              (line  49)
+* complete-hostname (M-@):               Commands For Completion.
+                                                              (line  72)
+* complete-into-braces (M-{):            Commands For Completion.
+                                                              (line 100)
+* complete-username (M-~):               Commands For Completion.
+                                                              (line  56)
+* complete-variable (M-$):               Commands For Completion.
+                                                              (line  64)
+* copy-backward-word ():                 Commands For Killing.
+                                                              (line  69)
+* copy-forward-word ():                  Commands For Killing.
+                                                              (line  74)
+* copy-region-as-kill ():                Commands For Killing.
+                                                              (line  65)
+* dabbrev-expand ():                     Commands For Completion.
+                                                              (line  95)
+* delete-char (C-d):                     Commands For Text.   (line  12)
+* delete-char-or-list ():                Commands For Completion.
+                                                              (line  43)
+* delete-horizontal-space ():            Commands For Killing.
+                                                              (line  57)
+* digit-argument (M-0, M-1, ... M--):    Numeric Arguments.   (line   6)
+* display-shell-version (C-x C-v):       Miscellaneous Commands.
+                                                              (line 116)
+* do-lowercase-version (M-A, M-B, M-X, ...): Miscellaneous Commands.
+                                                              (line  14)
+* downcase-word (M-l):                   Commands For Text.   (line  62)
+* dump-functions ():                     Miscellaneous Commands.
+                                                              (line  74)
+* dump-macros ():                        Miscellaneous Commands.
+                                                              (line  86)
+* dump-variables ():                     Miscellaneous Commands.
+                                                              (line  80)
+* dynamic-complete-history (M-<TAB>):    Commands For Completion.
+                                                              (line  90)
+* edit-and-execute-command (C-x C-e):    Miscellaneous Commands.
+                                                              (line 140)
+* end-kbd-macro (C-x )):                 Keyboard Macros.     (line   9)
+* end-of-file (usually C-d):             Commands For Text.   (line   6)
+* end-of-history (M->):                  Commands For History.
+                                                              (line  23)
+* end-of-line (C-e):                     Commands For Moving. (line   9)
+* exchange-point-and-mark (C-x C-x):     Miscellaneous Commands.
+                                                              (line  37)
+* fetch-history ():                      Commands For History.
+                                                              (line 103)
+* forward-backward-delete-char ():       Commands For Text.   (line  21)
+* forward-char (C-f):                    Commands For Moving. (line  12)
+* forward-search-history (C-s):          Commands For History.
+                                                              (line  33)
+* forward-word (M-f):                    Commands For Moving. (line  18)
+* glob-complete-word (M-g):              Miscellaneous Commands.
+                                                              (line  98)
+* glob-expand-word (C-x *):              Miscellaneous Commands.
+                                                              (line 104)
+* glob-list-expansions (C-x g):          Miscellaneous Commands.
+                                                              (line 110)
+* history-and-alias-expand-line ():      Miscellaneous Commands.
+                                                              (line 134)
+* history-expand-line (M-^):             Miscellaneous Commands.
+                                                              (line 124)
+* history-search-backward ():            Commands For History.
+                                                              (line  57)
+* history-search-forward ():             Commands For History.
+                                                              (line  51)
+* history-substring-search-backward ():  Commands For History.
+                                                              (line  69)
+* history-substring-search-forward ():   Commands For History.
+                                                              (line  63)
+* insert-comment (M-#):                  Miscellaneous Commands.
+                                                              (line  61)
+* insert-completions (M-*):              Commands For Completion.
+                                                              (line  22)
+* insert-last-argument (M-. or M-_):     Miscellaneous Commands.
+                                                              (line 137)
+* kill-line (C-k):                       Commands For Killing.
+                                                              (line   6)
+* kill-region ():                        Commands For Killing.
+                                                              (line  61)
+* kill-whole-line ():                    Commands For Killing.
+                                                              (line  19)
+* kill-word (M-d):                       Commands For Killing.
+                                                              (line  23)
+* magic-space ():                        Miscellaneous Commands.
+                                                              (line 127)
+* menu-complete ():                      Commands For Completion.
+                                                              (line  26)
+* menu-complete-backward ():             Commands For Completion.
+                                                              (line  38)
+* next-history (C-n):                    Commands For History.
+                                                              (line  17)
+* next-screen-line ():                   Commands For Moving. (line  41)
+* non-incremental-forward-search-history (M-n): Commands For History.
+                                                              (line  45)
+* non-incremental-reverse-search-history (M-p): Commands For History.
+                                                              (line  39)
+* operate-and-get-next (C-o):            Commands For History.
+                                                              (line  96)
+* overwrite-mode ():                     Commands For Text.   (line  70)
+* possible-command-completions (C-x !):  Commands For Completion.
+                                                              (line  86)
+* possible-completions (M-?):            Commands For Completion.
+                                                              (line  15)
+* possible-filename-completions (C-x /): Commands For Completion.
+                                                              (line  52)
+* possible-hostname-completions (C-x @): Commands For Completion.
+                                                              (line  76)
+* possible-username-completions (C-x ~): Commands For Completion.
+                                                              (line  60)
+* possible-variable-completions (C-x $): Commands For Completion.
+                                                              (line  68)
+* prefix-meta (<ESC>):                   Miscellaneous Commands.
+                                                              (line  19)
+* previous-history (C-p):                Commands For History.
+                                                              (line  13)
+* previous-screen-line ():               Commands For Moving. (line  34)
+* print-last-kbd-macro ():               Keyboard Macros.     (line  17)
+* quoted-insert (C-q or C-v):            Commands For Text.   (line  26)
+* re-read-init-file (C-x C-r):           Miscellaneous Commands.
+                                                              (line   6)
+* redraw-current-line ():                Commands For Moving. (line  57)
+* reverse-search-history (C-r):          Commands For History.
+                                                              (line  27)
+* revert-line (M-r):                     Miscellaneous Commands.
+                                                              (line  26)
+* self-insert (a, b, A, 1, !, ...):      Commands For Text.   (line  30)
+* set-mark (C-@):                        Miscellaneous Commands.
+                                                              (line  33)
+* shell-backward-kill-word ():           Commands For Killing.
+                                                              (line  37)
+* shell-backward-word (M-C-b):           Commands For Moving. (line  30)
+* shell-expand-line (M-C-e):             Miscellaneous Commands.
+                                                              (line 119)
+* shell-forward-word (M-C-f):            Commands For Moving. (line  26)
+* shell-kill-word (M-C-d):               Commands For Killing.
+                                                              (line  32)
+* shell-transpose-words (M-C-t):         Commands For Killing.
+                                                              (line  41)
+* skip-csi-sequence ():                  Miscellaneous Commands.
+                                                              (line  52)
+* spell-correct-word (C-x s):            Miscellaneous Commands.
+                                                              (line  92)
+* start-kbd-macro (C-x ():               Keyboard Macros.     (line   6)
+* tilde-expand (M-&):                    Miscellaneous Commands.
+                                                              (line  30)
+* transpose-chars (C-t):                 Commands For Text.   (line  47)
+* transpose-words (M-t):                 Commands For Text.   (line  53)
+* undo (C-_ or C-x C-u):                 Miscellaneous Commands.
+                                                              (line  23)
+* universal-argument ():                 Numeric Arguments.   (line  10)
+* unix-filename-rubout ():               Commands For Killing.
+                                                              (line  52)
+* unix-line-discard (C-u):               Commands For Killing.
+                                                              (line  16)
+* unix-word-rubout (C-w):                Commands For Killing.
+                                                              (line  48)
+* upcase-word (M-u):                     Commands For Text.   (line  58)
+* yank (C-y):                            Commands For Killing.
+                                                              (line  79)
+* yank-last-arg (M-. or M-_):            Commands For History.
+                                                              (line  84)
+* yank-nth-arg (M-C-y):                  Commands For History.
+                                                              (line  75)
+* yank-pop (M-y):                        Commands For Killing.
+                                                              (line  82)
+
+
+File: bashref.info,  Node: Concept Index,  Prev: Function Index,  Up: Indexes
+
+D.5 Concept Index
+=================
+
+
+* Menu:
+
+* alias expansion:                       Aliases.             (line   6)
+* arithmetic evaluation:                 Shell Arithmetic.    (line   6)
+* arithmetic expansion:                  Arithmetic Expansion.
+                                                              (line   6)
+* arithmetic, shell:                     Shell Arithmetic.    (line   6)
+* arrays:                                Arrays.              (line   6)
+* background:                            Job Control Basics.  (line   6)
+* Bash configuration:                    Basic Installation.  (line   6)
+* Bash installation:                     Basic Installation.  (line   6)
+* Bourne shell:                          Basic Shell Features.
+                                                              (line   6)
+* brace expansion:                       Brace Expansion.     (line   6)
+* builtin:                               Definitions.         (line  17)
+* command editing:                       Readline Bare Essentials.
+                                                              (line   6)
+* command execution:                     Command Search and Execution.
+                                                              (line   6)
+* command expansion:                     Simple Command Expansion.
+                                                              (line   6)
+* command history:                       Bash History Facilities.
+                                                              (line   6)
+* command search:                        Command Search and Execution.
+                                                              (line   6)
+* command substitution:                  Command Substitution.
+                                                              (line   6)
+* command timing:                        Pipelines.           (line   9)
+* commands, compound:                    Compound Commands.   (line   6)
+* commands, conditional:                 Conditional Constructs.
+                                                              (line   6)
+* commands, grouping:                    Command Grouping.    (line   6)
+* commands, lists:                       Lists.               (line   6)
+* commands, looping:                     Looping Constructs.  (line   6)
+* commands, pipelines:                   Pipelines.           (line   6)
+* commands, shell:                       Shell Commands.      (line   6)
+* commands, simple:                      Simple Commands.     (line   6)
+* comments, shell:                       Comments.            (line   6)
+* Compatibility Level:                   Shell Compatibility Mode.
+                                                              (line   6)
+* Compatibility Mode:                    Shell Compatibility Mode.
+                                                              (line   6)
+* completion builtins:                   Programmable Completion Builtins.
+                                                              (line   6)
+* configuration:                         Basic Installation.  (line   6)
+* control operator:                      Definitions.         (line  21)
+* coprocess:                             Coprocesses.         (line   6)
+* directory stack:                       The Directory Stack. (line   6)
+* editing command lines:                 Readline Bare Essentials.
+                                                              (line   6)
+* environment:                           Environment.         (line   6)
+* evaluation, arithmetic:                Shell Arithmetic.    (line   6)
+* event designators:                     Event Designators.   (line   6)
+* execution environment:                 Command Execution Environment.
+                                                              (line   6)
+* exit status:                           Definitions.         (line  26)
+* exit status <1>:                       Exit Status.         (line   6)
+* expansion:                             Shell Expansions.    (line   6)
+* expansion, arithmetic:                 Arithmetic Expansion.
+                                                              (line   6)
+* expansion, brace:                      Brace Expansion.     (line   6)
+* expansion, filename:                   Filename Expansion.  (line   9)
+* expansion, parameter:                  Shell Parameter Expansion.
+                                                              (line   6)
+* expansion, pathname:                   Filename Expansion.  (line   9)
+* expansion, tilde:                      Tilde Expansion.     (line   6)
+* expressions, arithmetic:               Shell Arithmetic.    (line   6)
+* expressions, conditional:              Bash Conditional Expressions.
+                                                              (line   6)
+* field:                                 Definitions.         (line  30)
+* filename:                              Definitions.         (line  35)
+* filename expansion:                    Filename Expansion.  (line   9)
+* foreground:                            Job Control Basics.  (line   6)
+* functions, shell:                      Shell Functions.     (line   6)
+* history builtins:                      Bash History Builtins.
+                                                              (line   6)
+* history events:                        Event Designators.   (line   8)
+* history expansion:                     History Interaction. (line   6)
+* history list:                          Bash History Facilities.
+                                                              (line   6)
+* History, how to use:                   A Programmable Completion Example.
+                                                              (line 113)
+* identifier:                            Definitions.         (line  51)
+* initialization file, readline:         Readline Init File.  (line   6)
+* installation:                          Basic Installation.  (line   6)
+* interaction, readline:                 Readline Interaction.
+                                                              (line   6)
+* interactive shell:                     Invoking Bash.       (line 131)
+* interactive shell <1>:                 Interactive Shells.  (line   6)
+* internationalization:                  Locale Translation.  (line   6)
+* internationalized scripts:             Creating Internationalized Scripts.
+                                                              (line   3)
+* job:                                   Definitions.         (line  38)
+* job control:                           Definitions.         (line  42)
+* job control <1>:                       Job Control Basics.  (line   6)
+* kill ring:                             Readline Killing Commands.
+                                                              (line  18)
+* killing text:                          Readline Killing Commands.
+                                                              (line   6)
+* localization:                          Locale Translation.  (line   6)
+* login shell:                           Invoking Bash.       (line 128)
+* matching, pattern:                     Pattern Matching.    (line   6)
+* metacharacter:                         Definitions.         (line  46)
+* name:                                  Definitions.         (line  51)
+* native languages:                      Locale Translation.  (line   6)
+* notation, readline:                    Readline Bare Essentials.
+                                                              (line   6)
+* operator, shell:                       Definitions.         (line  57)
+* parameter expansion:                   Shell Parameter Expansion.
+                                                              (line   6)
+* parameters:                            Shell Parameters.    (line   6)
+* parameters, positional:                Positional Parameters.
+                                                              (line   6)
+* parameters, special:                   Special Parameters.  (line   6)
+* pathname expansion:                    Filename Expansion.  (line   9)
+* pattern matching:                      Pattern Matching.    (line   6)
+* pipeline:                              Pipelines.           (line   6)
+* POSIX:                                 Definitions.         (line   9)
+* POSIX Mode:                            Bash POSIX Mode.     (line   6)
+* process group:                         Definitions.         (line  62)
+* process group ID:                      Definitions.         (line  66)
+* process substitution:                  Process Substitution.
+                                                              (line   6)
+* programmable completion:               Programmable Completion.
+                                                              (line   6)
+* prompting:                             Controlling the Prompt.
+                                                              (line   6)
+* quoting:                               Quoting.             (line   6)
+* quoting, ANSI:                         ANSI-C Quoting.      (line   6)
+* Readline, how to use:                  Job Control Variables.
+                                                              (line  23)
+* redirection:                           Redirections.        (line   6)
+* reserved word:                         Definitions.         (line  70)
+* reserved words:                        Reserved Words.      (line   6)
+* restricted shell:                      The Restricted Shell.
+                                                              (line   6)
+* return status:                         Definitions.         (line  75)
+* shell arithmetic:                      Shell Arithmetic.    (line   6)
+* shell function:                        Shell Functions.     (line   6)
+* shell script:                          Shell Scripts.       (line   6)
+* shell variable:                        Shell Parameters.    (line   6)
+* shell, interactive:                    Interactive Shells.  (line   6)
+* signal:                                Definitions.         (line  78)
+* signal handling:                       Signals.             (line   6)
+* special builtin:                       Definitions.         (line  82)
+* special builtin <1>:                   Special Builtins.    (line   6)
+* startup files:                         Bash Startup Files.  (line   6)
+* string translations:                   Creating Internationalized Scripts.
+                                                              (line   3)
+* suspending jobs:                       Job Control Basics.  (line   6)
+* tilde expansion:                       Tilde Expansion.     (line   6)
+* token:                                 Definitions.         (line  86)
+* translation, native languages:         Locale Translation.  (line   6)
+* variable, shell:                       Shell Parameters.    (line   6)
+* variables, readline:                   Readline Init File Syntax.
+                                                              (line  37)
+* word:                                  Definitions.         (line  90)
+* word splitting:                        Word Splitting.      (line   6)
+* yanking text:                          Readline Killing Commands.
+                                                              (line   6)
+
+
+
+Tag Table:
+Node: Top899
+Node: Introduction2821
+Node: What is Bash?3037
+Node: What is a shell?4151
+Node: Definitions6689
+Node: Basic Shell Features9640
+Node: Shell Syntax10859
+Node: Shell Operation11885
+Node: Quoting13178
+Node: Escape Character14482
+Node: Single Quotes14967
+Node: Double Quotes15315
+Node: ANSI-C Quoting16593
+Node: Locale Translation17903
+Node: Creating Internationalized Scripts19214
+Node: Comments23331
+Node: Shell Commands23949
+Node: Reserved Words24887
+Node: Simple Commands25643
+Node: Pipelines26297
+Node: Lists29296
+Node: Compound Commands31091
+Node: Looping Constructs32103
+Node: Conditional Constructs34598
+Node: Command Grouping49086
+Node: Coprocesses50564
+Node: GNU Parallel53227
+Node: Shell Functions54144
+Node: Shell Parameters62029
+Node: Positional Parameters66417
+Node: Special Parameters67319
+Node: Shell Expansions70533
+Node: Brace Expansion72660
+Node: Tilde Expansion75394
+Node: Shell Parameter Expansion78015
+Node: Command Substitution96366
+Node: Arithmetic Expansion97721
+Node: Process Substitution98689
+Node: Word Splitting99809
+Node: Filename Expansion101753
+Node: Pattern Matching104502
+Node: Quote Removal109504
+Node: Redirections109799
+Node: Executing Commands119459
+Node: Simple Command Expansion120129
+Node: Command Search and Execution122239
+Node: Command Execution Environment124617
+Node: Environment127652
+Node: Exit Status129315
+Node: Signals131099
+Node: Shell Scripts134548
+Node: Shell Builtin Commands137575
+Node: Bourne Shell Builtins139613
+Node: Bash Builtins161079
+Node: Modifying Shell Behavior191935
+Node: The Set Builtin192280
+Node: The Shopt Builtin202881
+Node: Special Builtins218793
+Node: Shell Variables219772
+Node: Bourne Shell Variables220209
+Node: Bash Variables222313
+Node: Bash Features255128
+Node: Invoking Bash256141
+Node: Bash Startup Files262154
+Node: Interactive Shells267285
+Node: What is an Interactive Shell?267696
+Node: Is this Shell Interactive?268345
+Node: Interactive Shell Behavior269160
+Node: Bash Conditional Expressions272789
+Node: Shell Arithmetic277431
+Node: Aliases280375
+Node: Arrays282988
+Node: The Directory Stack289379
+Node: Directory Stack Builtins290163
+Node: Controlling the Prompt294423
+Node: The Restricted Shell297388
+Node: Bash POSIX Mode299998
+Node: Shell Compatibility Mode311916
+Node: Job Control320483
+Node: Job Control Basics320943
+Node: Job Control Builtins325945
+Node: Job Control Variables331740
+Node: Command Line Editing332896
+Node: Introduction and Notation334567
+Node: Readline Interaction336190
+Node: Readline Bare Essentials337381
+Node: Readline Movement Commands339170
+Node: Readline Killing Commands340130
+Node: Readline Arguments342051
+Node: Searching343095
+Node: Readline Init File345281
+Node: Readline Init File Syntax346542
+Node: Conditional Init Constructs370128
+Node: Sample Init File374324
+Node: Bindable Readline Commands377448
+Node: Commands For Moving378652
+Node: Commands For History380703
+Node: Commands For Text385697
+Node: Commands For Killing389346
+Node: Numeric Arguments392379
+Node: Commands For Completion393518
+Node: Keyboard Macros397709
+Node: Miscellaneous Commands398397
+Node: Readline vi Mode404342
+Node: Programmable Completion405249
+Node: Programmable Completion Builtins413029
+Node: A Programmable Completion Example423781
+Node: Using History Interactively429029
+Node: Bash History Facilities429713
+Node: Bash History Builtins432718
+Node: History Interaction437742
+Node: Event Designators441362
+Node: Word Designators442716
+Node: Modifiers444476
+Node: Installing Bash446284
+Node: Basic Installation447421
+Node: Compilers and Options451143
+Node: Compiling For Multiple Architectures451884
+Node: Installation Names453576
+Node: Specifying the System Type455685
+Node: Sharing Defaults456402
+Node: Operation Controls457075
+Node: Optional Features458033
+Node: Reporting Bugs469252
+Node: Major Differences From The Bourne Shell470527
+Node: GNU Free Documentation License487376
+Node: Indexes512553
+Node: Builtin Index513007
+Node: Reserved Word Index519834
+Node: Variable Index522282
+Node: Function Index539056
+Node: Concept Index552840
+
+End Tag Table
+
+
+Local Variables:
+coding: utf-8
+End: