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BASH(1)			    General Commands Manual		       BASH(1)

NAME
       bash - GNU Bourne-Again SHell

SYNOPSIS
       bash [options] [command_string |	file]

COPYRIGHT
       Bash is Copyright (C) 1989-2013 by the Free Software Foundation,	Inc.

DESCRIPTION
       Bash  is	 an  sh-compatible  command language interpreter that executes
       commands	read from the standard input or	from a file.  Bash also	incor-
       porates useful features from the	Korn and C shells (ksh and csh).

       Bash  is	 intended  to  be a conformant implementation of the Shell and
       Utilities portion  of  the  IEEE	 POSIX	specification  (IEEE  Standard
       1003.1).	 Bash can be configured	to be POSIX-conformant by default.

OPTIONS
       All  of	the  single-character shell options documented in the descrip-
       tion of the set builtin command can be used as options when  the	 shell
       is invoked.  In addition, bash interprets the following options when it
       is invoked:

       -c	 If the	-c option is present, then commands are	read from  the
		 first non-option argument command_string.  If there are argu-
		 ments after the command_string, they are assigned to the  po-
		 sitional parameters, starting with $0.
       -i	 If the	-i option is present, the shell	is interactive.
       -l	 Make bash act as if it	had been invoked as a login shell (see
		 INVOCATION below).
       -r	 If the	-r option is present,  the  shell  becomes  restricted
		 (see RESTRICTED SHELL below).
       -s	 If  the -s 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.
       -D	 A list	of all double-quoted strings preceded by $ is  printed
		 on  the standard output.  These are the strings that are sub-
		 ject to language translation when the current locale is not C
		 or  POSIX.   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  (see	SHELL  BUILTIN	COMMANDS  below).   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 file-
		 names and arguments.  An argument of -	is equivalent to --.

       Bash also interprets a number of	multi-character	 options.   These  op-
       tions  must  appear on the command line before the single-character op-
       tions to	be recognized.

       --debugger
	      Arrange for the debugger profile to be executed before the shell
	      starts.	Turns  on extended debugging mode (see the description
	      of the extdebug option to	the shopt builtin below).
       --dump-po-strings
	      Equivalent to -D,	but the	output is in the GNU gettext po	 (por-
	      table object) file format.
       --dump-strings
	      Equivalent to -D.
       --help Display  a  usage	 message  on standard output and exit success-
	      fully.
       --init-file file
       --rcfile	file
	      Execute commands from file instead of the	system	wide  initial-
	      ization file /etc/bash.bashrc and	the standard personal initial-
	      ization file ~/.bashrc if	the shell is interactive (see  INVOCA-
	      TION below).

       --login
	      Equivalent to -l.

       --noediting
	      Do  not  use the GNU readline library to read command lines when
	      the shell	is interactive.

       --noprofile
	      Do not read either the system-wide startup file /etc/profile  or
	      any   of	the  personal  initialization  files  ~/.bash_profile,
	      ~/.bash_login, or	~/.profile.   By  default,  bash  reads	 these
	      files  when  it  is invoked as a login shell (see	INVOCATION be-
	      low).

       --norc Do not read and execute  the  system  wide  initialization  file
	      /etc/bash.bashrc	and the	personal initialization	file ~/.bashrc
	      if the shell is interactive.  This option	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 (posix mode).  See
	      SEE  ALSO	 below	for a reference	to a document that details how
	      posix mode affects bash's	behavior.

       --restricted
	      The shell	becomes	restricted (see	RESTRICTED SHELL below).

       --verbose
	      Equivalent to  -v.

       --version
	      Show version information for this	instance of bash on the	 stan-
	      dard output and exit successfully.

ARGUMENTS
       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.  If bash is invoked in this
       fashion,	$0 is set to the name of the file, and the positional  parame-
       ters  are set to	the remaining arguments.  Bash reads and executes com-
       mands from this file, then exits.  Bash's exit status is	the exit  sta-
       tus of the last command executed	in the script.	If no commands are ex-
       ecuted, the exit	status is 0.  An attempt is first  made	 to  open  the
       file in the current directory, and, if no file is found,	then the shell
       searches	the directories	in PATH	for the	script.

INVOCATION
       A login shell is	one whose first	character of argument zero is a	-,  or
       one started with	the --login option.

       An  interactive	shell  is one started without non-option arguments and
       without the -c option whose standard input and error are	both connected
       to  terminals  (as determined by	isatty(3)), or one started with	the -i
       option.	PS1 is set and $- includes i if	bash is	interactive,  allowing
       a shell script or a startup file	to test	this state.

       The  following paragraphs describe 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 below under Tilde	Expan-
       sion in the EXPANSION section.

       When bash is invoked as an interactive login shell, or as a  non-inter-
       active  shell with the --login option, it first reads and executes com-
       mands 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 a login shell exits, bash reads and	 executes  commands  from  the
       file ~/.bash_logout, if it exists.

       When  an	 interactive  shell that is not	a login	shell is started, bash
       reads and executes commands from	 /etc/bash.bashrc  and	~/.bashrc,  if
       these  files  exist.  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 /etc/bash.bashrc and ~/.bashrc.

       When  bash is started non-interactively,	to run a shell script, for ex-
       ample, 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  com-
       mand were executed:
	      if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
       but  the	value of the PATH variable is not used to search for the file-
       name.

       If bash is invoked with the name	sh, it tries to	mimic the startup  be-
       havior  of historical versions of sh as closely as possible, while con-
       forming to the POSIX standard as	well.  When invoked as an  interactive
       login  shell,  or  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 in-
       hibit 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 exe-
       cute commands from any other startup files, the --rcfile	option has  no
       effect.	 A non-interactive shell invoked with the name sh does not at-
       tempt to	read any other startup files.  When invoked as sh, bash	enters
       posix mode after	the startup files are read.

       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.

       Bash attempts to	determine when it is being run with its	standard input
       connected to a network connection, as when executed by the remote shell
       daemon,	usually	rshd, or the secure shell daemon sshd.	If bash	deter-
       mines it	is being run in	this fashion, it reads and  executes  commands
       from  ~/.bashrc	and  ~/.bashrc,	if these files exist and are 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 an-
       other file to be	read, but neither rshd nor sshd	generally  invoke  the
       shell with those	options	or allow them to be specified.

       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, no startup
       files are read, shell functions are not inherited from the environment,
       the SHELLOPTS, BASHOPTS,	CDPATH,	and GLOBIGNORE variables, if they  ap-
       pear  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.

DEFINITIONS
       The  following  definitions  are	used throughout	the rest of this docu-
       ment.
       blank  A	space or tab.
       word   A	sequence of characters considered as  a	 single	 unit  by  the
	      shell.  Also known as a token.
       name   A	 word  consisting  only	 of alphanumeric characters and	under-
	      scores, and beginning with an alphabetic character or an	under-
	      score.  Also referred to as an identifier.
       metacharacter
	      A	 character  that,  when	unquoted, separates words.  One	of the
	      following:
	      |	 & ; ( ) < > space tab
       control operator
	      A	token that performs a control function.	 It is one of the fol-
	      lowing symbols:
	      || & && ;	;; ( ) | |& <newline>

RESERVED WORDS
       Reserved	words are words	that have a special meaning to the shell.  The
       following words are recognized as reserved when unquoted	and either the
       first  word  of a simple	command	(see SHELL GRAMMAR below) or the third
       word of a case or for command:

       ! case  coproc  do done elif else esac fi for  function	if  in	select
       then until while	{ } time [[ ]]

SHELL GRAMMAR
   Simple Commands
       A  simple  command  is a	sequence of optional variable assignments fol-
       lowed by	blank-separated	words and redirections,	and  terminated	 by  a
       control operator.  The first word specifies the command to be executed,
       and is passed as	argument zero.	The remaining words are	passed as  ar-
       guments to the invoked command.

       The  return  value  of a	simple command is its exit status, or 128+n if
       the command is terminated by signal n.

   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]] [ ! ]	command	[ [|||&] command2 ... ]

       The  standard output of command is connected via	a pipe to the standard
       input of	command2.  This	connection is performed	 before	 any  redirec-
       tions specified by the command (see REDIRECTION below).	If |& is used,
       command's standard error, in addition to	its standard output,  is  con-
       nected  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 the
       command.

       The return status of a pipeline is the exit status of the last command,
       unless  the  pipefail  option  is enabled.  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 success-
       fully.  If the reserved word !  precedes	a pipeline, the	exit status of
       that  pipeline  is the logical negation of the exit status as described
       above.  The shell waits for all commands	in the pipeline	 to  terminate
       before returning	a value.

       If  the	time reserved word precedes a pipeline,	the elapsed as well as
       user and	system time consumed by	its execution are  reported  when  the
       pipeline	 terminates.   The -p option changes the output	format to that
       specified by POSIX.  When the shell is in posix mode, it	does not  rec-
       ognize  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;	see the	description of
       TIMEFORMAT under	Shell Variables	below.

       When the	shell is in 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.

       Each  command in	a pipeline is executed as a separate process (i.e., in
       a subshell).

   Lists
       A list is a sequence of one or more pipelines separated by one  of  the
       operators ;, &, &&, or ||, and optionally terminated by one of ;, &, or
       <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 instead of a
       semicolon to delimit commands.

       If a command is terminated by the control operator &,  the  shell  exe-
       cutes  the command in the background in a subshell.  The	shell does not
       wait for	the command to finish, and the return status is	 0.   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	of more	pipelines separated by
       the && and || control operators,	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.

       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.

   Compound Commands
       A compound command is one of the	following.  In most cases a list in  a
       command's  description may be separated from the	rest of	the command by
       one or more newlines, and may be	followed by a newline in  place	 of  a
       semicolon.

       (list) list  is	executed in a subshell environment (see	COMMAND	EXECU-
	      TION ENVIRONMENT below).	Variable assignments and builtin  com-
	      mands  that  affect the shell's environment do not remain	in ef-
	      fect after the command completes.	 The return status is the exit
	      status of	list.

       { list; }
	      list  is simply executed in the current shell environment.  list
	      must be terminated with a	newline	or semicolon.  This  is	 known
	      as  a  group  command.   The return status is the	exit status of
	      list.  Note that unlike the metacharacters ( and ), { and	}  are
	      reserved words and must occur where a reserved word is permitted
	      to be recognized.	 Since they do not cause a  word  break,  they
	      must  be	separated  from	 list  by  whitespace or another shell
	      metacharacter.

       ((expression))
	      The expression is	evaluated according to the rules described be-
	      low under	ARITHMETIC EVALUATION.	If the value of	the expression
	      is non-zero, the return status is	0; otherwise the return	status
	      is 1.  This is exactly equivalent	to let "expression".

       [[ 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	under CONDITIONAL EXPRESSIONS.
	      Word splitting and pathname expansion are	not performed  on  the
	      words  between  the  [[  and  ]];	tilde expansion, parameter and
	      variable expansion, arithmetic expansion,	command	 substitution,
	      process  substitution,  and quote	removal	are performed.	Condi-
	      tional operators such as -f must be unquoted to be recognized as
	      primaries.

	      When  used with [[, the <	and > operators	sort lexicographically
	      using the	current	locale.

       See the description of the test builtin command (section	SHELL  BUILTIN
       COMMANDS	 below)	 for the handling of parameters	(i.e.  missing parame-
       ters).

       When the	== and != operators are	used, the string to the	right  of  the
       operator	is considered a	pattern	and matched according to the rules de-
       scribed below under Pattern Matching, as	if the	extglob	 shell	option
       were enabled.  The = operator is	equivalent to ==.  If the shell	option
       nocasematch 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.   Any
       part  of	 the  pattern  may be quoted to	force the quoted portion to be
       matched as a string.

       An additional binary operator, =~, is available,	with the  same	prece-
       dence  as  ==  and !=.  When it is used,	the string to the right	of the
       operator	is considered an extended regular expression and  matched  ac-
       cordingly  (as  in  regex(3)).	The  return  value  is 0 if the	string
       matches the pattern, and	1 otherwise.  If  the  regular	expression  is
       syntactically  incorrect,  the conditional expression's return value is
       2.  If the shell	option nocasematch is enabled, the match is  performed
       without	regard	to the case of alphabetic characters.  Any part	of the
       pattern may be quoted to	force the quoted portion to be	matched	 as  a
       string.	 Bracket  expressions  in  regular expressions must be treated
       carefully, since	normal quoting characters lose their meanings  between
       brackets.   If  the  pattern is stored in a shell variable, quoting the
       variable	expansion forces the entire pattern to be matched as a string.
       Substrings  matched  by parenthesized subexpressions within the regular
       expression are saved in the array variable BASH_REMATCH.	  The  element
       of  BASH_REMATCH	with index 0 is	the portion of the string matching the
       entire regular expression.  The element of BASH_REMATCH with index n is
       the portion of the string matching the nth parenthesized	subexpression.

       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.

       for name	[ [ in [ word ... ] ] ;	] do list ; done
	      The list of words	following in is	expanded, generating a list of
	      items.  The variable name	is set to each element of this list in
	      turn,  and  list is executed each	time.  If the in word is omit-
	      ted, the for command executes list once for each positional  pa-
	      rameter  that  is	set (see PARAMETERS below).  The return	status
	      is the exit status of the	last command that  executes.   If  the
	      expansion	of the items following in results in an	empty list, no
	      commands are executed, and the return status is 0.

       for (( expr1 ; expr2 ; expr3 )) ; do list ; done
	      First, the arithmetic expression expr1 is	evaluated according to
	      the  rules  described  below  under  ARITHMETIC EVALUATION.  The
	      arithmetic expression expr2 is then evaluated  repeatedly	 until
	      it  evaluates  to	zero.  Each time expr2 evaluates to a non-zero
	      value, list is 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 list that is executed,	or false if any	of the expres-
	      sions is invalid.

       select name [ in	word ] ; do list ; done
	      The list of words	following in is	expanded, generating a list of
	      items.  The set of expanded words	is printed on the standard er-
	      ror, each	preceded by a number.  If the in word is omitted,  the
	      positional  parameters  are printed (see PARAMETERS below).  The
	      PS3 prompt is then displayed and a line read from	 the  standard
	      input.  If the line consists of a	number corresponding to	one of
	      the displayed words, then	the value of name is set to that word.
	      If  the line is empty, the words and prompt are displayed	again.
	      If EOF is	read, the command completes.   Any  other  value  read
	      causes  name  to	be set to null.	 The line read is saved	in the
	      variable REPLY.  The list	is executed after each selection until
	      a	 break	command	is executed.  The exit status of select	is the
	      exit status of the last command executed in list,	or zero	if  no
	      commands were executed.

       case word in [ [(] pattern [ | pattern ]	... ) list ;; ]	... esac
	      A	case command first expands word, and tries to match it against
	      each pattern in turn, using the same matching rules as for path-
	      name  expansion (see Pathname Expansion below).  The word	is ex-
	      panded using tilde expansion, parameter and variable  expansion,
	      arithmetic substitution, command substitution, process substitu-
	      tion and quote removal.  Each pattern examined is	expanded using
	      tilde  expansion,	 parameter  and	variable expansion, arithmetic
	      substitution, command substitution,  and	process	 substitution.
	      If  the  shell  option nocasematch is enabled, the match is per-
	      formed without regard to	the  case  of  alphabetic  characters.
	      When  a  match is	found, the corresponding list is executed.  If
	      the ;; operator is used, no subsequent matches are attempted af-
	      ter the first pattern match.  Using ;& in	place of ;; causes ex-
	      ecution to continue with the list	associated with	the  next  set
	      of  patterns.  Using ;;& in place	of ;; causes the shell to test
	      the next pattern list in the statement, if any, and execute  any
	      associated  list on a successful match.  The exit	status is zero
	      if no pattern matches.  Otherwise, it is the exit	status of  the
	      last command executed in list.

       if list;	then list; [ elif list;	then list; ] ... [ else	list; ]	fi
	      The  if  list is executed.  If its exit status is	zero, the then
	      list is executed.	 Otherwise, each  elif	list  is  executed  in
	      turn,  and  if  its  exit	status is zero,	the corresponding then
	      list is executed and the command completes.  Otherwise, the else
	      list  is executed, if present.  The exit status is the exit sta-
	      tus of the last command executed,	or zero	if no condition	tested
	      true.

       while list-1; do	list-2;	done
       until list-1; do	list-2;	done
	      The  while command continuously executes the list	list-2 as long
	      as the last command in the list list-1 returns an	exit status of
	      zero.   The until	command	is identical to	the while command, ex-
	      cept that	the test is negated; list-2 is executed	as long	as the
	      last command in list-1 returns a non-zero	exit status.  The exit
	      status of	the while and until commands is	the exit status	of the
	      last command executed in list-2, or zero if none was executed.

   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 format for a	coprocess is:

	      coproc [NAME] command [redirections]

       This creates a coprocess	named NAME.  If	NAME is	not supplied, the  de-
       fault name is COPROC.  NAME must	not be supplied	if command is a	simple
       command (see above); otherwise, it is interpreted as the	first word  of
       the  simple command.  When the coprocess	is executed, the shell creates
       an array	variable (see Arrays below) 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  de-
       scriptor	is assigned to NAME[0].	 The standard input of command is con-
       nected via a pipe to a file descriptor in the executing shell, and that
       file  descriptor	 is assigned to	NAME[1].  This pipe is established be-
       fore any	redirections specified by the command (see REDIRECTION below).
       The file	descriptors can	be utilized as arguments to shell commands and
       redirections using standard word	expansions.  The file descriptors  are
       not available in	subshells.  The	process	ID of the shell	spawned	to ex-
       ecute 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 ter-
       minate.

       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.

   Shell Function Definitions
       A shell function	is an object that is called like a simple command  and
       executes	 a  compound  command with a new set of	positional parameters.
       Shell functions are declared as follows:

       name () compound-command	[redirection]
       function	name [()] compound-command [redirection]
	      This defines a function named name.  The reserved	word  function
	      is  optional.   If  the  function	reserved word is supplied, the
	      parentheses are optional.	 The body of the function is the  com-
	      pound  command  compound-command	(see Compound Commands above).
	      That command is usually a	list of	commands between { and },  but
	      may  be  any command listed under	Compound Commands above.  com-
	      pound-command is executed	whenever name is specified as the name
	      of  a  simple  command.  When in posix mode, name	may not	be the
	      name of one of the POSIX	special	 builtins.   Any  redirections
	      (see REDIRECTION below) specified	when a function	is defined are
	      performed	when the function is executed.	The exit status	 of  a
	      function	definition  is	zero unless a syntax error occurs or a
	      readonly function	with the same name already exists.  When  exe-
	      cuted,  the  exit	status of a function is	the exit status	of the
	      last command executed in the body.  (See FUNCTIONS below.)

COMMENTS
       In a non-interactive shell, or an interactive shell in which the	inter-
       active_comments	option	to  the	 shopt	builtin	 is enabled (see SHELL
       BUILTIN COMMANDS	below),	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 interac-
       tive shells.

QUOTING
       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 metacharacters listed above under 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 (see  HIS-
       TORY EXPANSION below), the history expansion character, usually !, must
       be quoted to prevent history expansion.

       There are  three	 quoting  mechanisms:  the  escape  character,	single
       quotes, and double quotes.

       A  non-quoted  backslash	(\) is the 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 is not it-
       self quoted, the	\<newline> is treated as a line	continuation (that is,
       it is removed from the input stream and effectively ignored).

       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.

       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, !.	 The characters	$ and `	retain
       their special meaning within double quotes.  The	backslash retains  its
       special	meaning	only when followed by one of the following characters:
       $, `, ",	\, or <newline>.  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 (see PARAMETERS below).

       Words of	the form $'string' are treated specially.  The word expands to
       string,	with backslash-escaped characters 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
	      \f     form feed
	      \n     new line
	      \r     carriage return
	      \t     horizontal	tab
	      \v     vertical tab
	      \\     backslash
	      \'     single quote
	      \"     double quote
	      \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)
	      \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.

       A double-quoted string preceded by a dollar sign	($"string") will cause
       the  string  to	be translated according	to the current locale.	If the
       current locale is C or POSIX, the  dollar  sign	is  ignored.   If  the
       string is translated and	replaced, the replacement is double-quoted.

PARAMETERS
       A  parameter is an entity that stores values.  It can be	a name,	a num-
       ber, or one of the special characters listed below under	Special	Param-
       eters.	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 declare below in SHELL BUILTIN COMMANDS).

       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 (see SHELL BUILTIN COMMANDS below).

       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,  com-
       mand  substitution, arithmetic expansion, and quote removal (see	EXPAN-
       SION below).  If	the variable has its integer attribute set, then value
       is evaluated as an arithmetic expression	even if	the $((...)) expansion
       is not used (see	Arithmetic Expansion below).  Word  splitting  is  not
       performed,  with	the exception of "$@" as explained below under Special
       Parameters.  Pathname expansion is not  performed.   Assignment	state-
       ments  may also appear as arguments to the alias, declare, typeset, ex-
       port, readonly, and local builtin commands.  When in 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, the += operator can be used to append to
       or add to the variable's	previous value.	 When += is applied to a vari-
       able  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 (see	Arrays below), the variable's value is not un-
       set  (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  ap-
       pended to the variable's	value.

       A variable can be assigned the nameref attribute	using the -n option to
       the declare or local builtin commands (see the descriptions of  declare
       and  local  below) to create a nameref, or a reference to another vari-
       able.  This allows variables to be  manipulated	indirectly.   Whenever
       the nameref variable is referenced or assigned to, the operation	is ac-
       tually 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  in-
       stance,	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 are treated as references	and assignments	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
       -n attribute.  However, nameref variables can reference array variables
       and subscripted array variables.	 Namerefs can be unset	using  the  -n
       option  to the unset builtin.  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.

   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 parameters may not be assigned  to
       with  assignment	statements.  The positional parameters are temporarily
       replaced	when a shell function is executed (see FUNCTIONS below).

       When a positional parameter consisting of more than a single  digit  is
       expanded, it must be enclosed in	braces (see EXPANSION below).

   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 pa-
	      rameter expands to a separate word.  In  contexts	 where	it  is
	      performed, those words are subject to further word splitting and
	      pathname expansion.  When	the  expansion	occurs	within	double
	      quotes,  it  expands to a	single word with the value of each pa-
	      rameter separated	by the first  character	 of  the  IFS  special
	      variable.	  That	is, "$*" is equivalent to "$1c$2c...", where c
	      is the first character of	the value of the IFS variable.	If IFS
	      is  unset,  the  parameters  are separated by spaces.  If	IFS is
	      null, the	parameters are joined without intervening separators.
       @      Expands to the positional	parameters, starting from  one.	  When
	      the  expansion  occurs  within double quotes, each parameter ex-
	      pands to a separate word.	 That is, "$@" is equivalent  to  "$1"
	      "$2"  ...	  If the double-quoted expansion occurs	within a word,
	      the expansion of the first parameter is joined with  the	begin-
	      ning  part  of  the original word, and the expansion of the last
	      parameter	is joined with the last	part  of  the  original	 word.
	      When  there  are no positional parameters, "$@" 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	 fore-
	      ground pipeline.
       -      Expands  to  the	current	option flags as	specified upon invoca-
	      tion, by the set builtin command,	or those set by	the shell  it-
	      self (such as the	-i option).
       $      Expands  to  the	process	ID of the shell.  In a () subshell, it
	      expands to the process ID	of the current	shell,	not  the  sub-
	      shell.
       !      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 (see	JOB CONTROL below).
       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 com-
	      mands,  $0  is set to the	name of	that file.  If bash is started
	      with the -c option, 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.
       _      At  shell	 startup,  set to the absolute pathname	used to	invoke
	      the shell	or shell script	being executed as passed in the	 envi-
	      ronment or argument list.	 Subsequently, expands to the last ar-
	      gument to	the previous command, after expansion.	 Also  set  to
	      the  full	 pathname  used	 to  invoke  each command executed and
	      placed in	the environment	exported to that command.  When	check-
	      ing  mail,  this	parameter holds	the name of the	mail file cur-
	      rently being checked.

   Shell Variables
       The following variables are set by the shell:

       BASH   Expands to the full filename used	to  invoke  this  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 (see SHELL BUILTIN COMMANDS below).  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 read-only.
       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.
       BASH_ALIASES
	      An  associative  array  variable whose members correspond	to the
	      internal list of aliases as maintained  by  the  alias  builtin.
	      Elements added to	this array appear in the alias list; unsetting
	      array elements cause aliases to be removed from the alias	list.
       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 the description of the extdebug op-
	      tion to the shopt	builtin	below)
       BASH_ARGV
	      An  array	 variable containing all of the	parameters in the cur-
	      rent 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 exe-
	      cuted,  the  parameters supplied are pushed onto BASH_ARGV.  The
	      shell sets BASH_ARGV only	when in	extended debugging  mode  (see
	      the  description of the extdebug option to the shopt builtin be-
	      low)
       BASH_CMDS
	      An associative array variable whose members  correspond  to  the
	      internal	hash  table  of	 commands  as  maintained  by the hash
	      builtin.	Elements added to this array appear in the hash	table;
	      unsetting	 array	elements cause commands	to be removed from the
	      hash table.
       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.
       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 func-
	      tion).  Use LINENO to obtain the current line number.
       BASH_REMATCH
	      An array variable	whose members are assigned by  the  =~	binary
	      operator	to the [[ conditional command.	The element with index
	      0	is the portion of the string matching the entire  regular  ex-
	      pression.	 The element with index	n is the portion of the	string
	      matching the nth parenthesized subexpression.  This variable  is
	      read-only.
       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 de-
	      fined  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  ini-
	      tial value is 0.
       BASH_VERSINFO
	      A	readonly array variable	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
	      Expands  to  a string describing the version of this instance of
	      bash.
       COMP_CWORD
	      An index into ${COMP_WORDS} of the word containing  the  current
	      cursor position.	This variable is available only	in shell func-
	      tions invoked by the  programmable  completion  facilities  (see
	      Programmable Completion below).
       COMP_KEY
	      The key (or final	key of a key sequence) used to invoke the cur-
	      rent completion function.
       COMP_LINE
	      The current command line.	 This variable is  available  only  in
	      shell  functions	and  external commands invoked by the program-
	      mable completion facilities (see Programmable Completion below).
       COMP_POINT
	      The index	of the current cursor position relative	to the	begin-
	      ning  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  program-
	      mable completion facilities (see Programmable Completion below).
       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 succes-
	      sive tabs, !, for	listing	alternatives on	partial	 word  comple-
	      tion,  @,	 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 program-
	      mable completion facilities (see Programmable Completion below).
       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	subse-
	      quently reset.
       COMP_WORDS
	      An  array	variable (see Arrays below) consisting of the individ-
	      ual words	in the current command line.  The line is  split  into
	      words  as	 readline would	split it, using	COMP_WORDBREAKS	as de-
	      scribed above.  This variable is available only in  shell	 func-
	      tions  invoked  by  the  programmable completion facilities (see
	      Programmable Completion below).
       COPROC An array variable	(see Arrays below) created to  hold  the  file
	      descriptors  for	output	from and input to an unnamed coprocess
	      (see Coprocesses above).
       DIRSTACK
	      An array variable	(see Arrays below) containing the current con-
	      tents  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 directo-
	      ries already in the stack, but the pushd and popd	builtins  must
	      be used to add and remove	directories.  Assignment to this vari-
	      able will	not change the current directory.  If DIRSTACK is  un-
	      set, it loses its	special	properties, even if it is subsequently
	      reset.
       EUID   Expands to the effective user ID of the current  user,  initial-
	      ized at shell startup.  This variable is readonly.
       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 bot-
	      tom-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 and return	an error  sta-
	      tus.   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 in-
	      stance,	 ${FUNCNAME[$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	infor-
	      mation.
       GROUPS An array variable	containing the list of	groups	of  which  the
	      current  user is a member.  Assignments to GROUPS	have no	effect
	      and return an error status.  If GROUPS is	unset,	it  loses  its
	      special properties, even if it is	subsequently reset.
       HISTCMD
	      The history number, or index in the history list,	of the current
	      command.	If HISTCMD is unset, it	loses its special  properties,
	      even if it is subsequently reset.
       HOSTNAME
	      Automatically set	to the name of the current host.
       HOSTTYPE
	      Automatically  set  to a string that uniquely describes the type
	      of machine on which bash is executing.  The default  is  system-
	      dependent.
       LINENO Each  time this parameter	is referenced, the shell substitutes a
	      decimal number representing the current sequential  line	number
	      (starting	 with  1)  within a script or function.	 When not in a
	      script or	function, the value substituted	is not	guaranteed  to
	      be meaningful.  If LINENO	is unset, it loses its special proper-
	      ties, even if it is subsequently reset.
       MACHTYPE
	      Automatically set	to a string that fully	describes  the	system
	      type  on	which  bash is executing, in the standard GNU cpu-com-
	      pany-system format.  The default is system-dependent.
       MAPFILE
	      An array variable	(see Arrays below) 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 command.
       OPTARG The  value  of the last option argument processed	by the getopts
	      builtin command (see SHELL BUILTIN COMMANDS below).
       OPTIND The index	of the next argument to	be processed  by  the  getopts
	      builtin command (see SHELL BUILTIN COMMANDS below).
       OSTYPE Automatically  set to a string that describes the	operating sys-
	      tem on which bash	is executing.  The  default  is	 system-depen-
	      dent.
       PIPESTATUS
	      An  array	 variable (see Arrays below) containing	a list of exit
	      status values from the processes in  the	most-recently-executed
	      foreground pipeline (which may contain only a single command).
       PPID   The  process  ID	of the shell's parent.	This variable is read-
	      only.
       PWD    The current working directory as set by the cd command.
       RANDOM Each time	this parameter is referenced, a	random integer between
	      0	and 32767 is generated.	 The sequence of random	numbers	may be
	      initialized by assigning a value to RANDOM.  If RANDOM is	unset,
	      it  loses	its special properties,	even if	it is subsequently re-
	      set.
       READLINE_LINE
	      The contents of the readline line	buffer,	for use	with "bind -x"
	      (see SHELL BUILTIN COMMANDS below).
       READLINE_POINT
	      The position of the insertion point in the readline line buffer,
	      for use with "bind -x" (see SHELL	BUILTIN	COMMANDS below).
       REPLY  Set to the line of input read by the read	builtin	 command  when
	      no arguments are supplied.
       SECONDS
	      Each  time  this	parameter is referenced, the number of seconds
	      since shell invocation is	returned.  If a	value is  assigned  to
	      SECONDS,	the  value  returned upon subsequent references	is the
	      number of	seconds	since the assignment plus the value  assigned.
	      If SECONDS is unset, it loses its	special	properties, even if it
	      is subsequently reset.
       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 (see SHELL BUILTIN COMMANDS below).  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 read-only.
       SHLVL  Incremented by one each time an instance of bash is started.
       UID    Expands to the user ID of	the current user, initialized at shell
	      startup.	This variable is readonly.

       The following variables are used	by the shell.  In some cases, bash as-
       signs a default value to	a variable; these cases	are noted below.

       BASH_COMPAT
	      The value	is used	to set the shell's compatibility  level.   See
	      the  description	of the shopt builtin below under SHELL BUILTIN
	      COMMANDS 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  com-
	      patibility  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 compatibility	levels	correspond  to
	      the  compatibility  options  accepted  by	 the shopt builtin de-
	      scribed below (for example, compat42 means that 4.2 and  42  are
	      valid values).  The current version is also a valid value.
       BASH_ENV
	      If  this parameter is set	when bash is executing a shell script,
	      its value	is interpreted as a filename  containing  commands  to
	      initialize the shell, as in ~/.bashrc.  The value	of BASH_ENV is
	      subjected	to  parameter  expansion,  command  substitution,  and
	      arithmetic  expansion  before  being  interpreted	as a filename.
	      PATH is not used to search for the resultant filename.
       BASH_XTRACEFD
	      If set to	an integer corresponding to a valid  file  descriptor,
	      bash  will  write	 the trace output generated when set -x	is en-
	      abled to that file descriptor.  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.
       CDPATH The  search  path	for the	cd command.  This is a colon-separated
	      list of directories in which the shell looks for destination di-
	      rectories	 specified  by	the  cd	 command.   A  sample value is
	      ".:~:/usr".
       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	 (cur-
	      rently  8192)  that  this	 may not exceed.  The minimum value is
	      system-dependent.
       COLUMNS
	      Used by the select compound command to  determine	 the  terminal
	      width  when  printing selection lists.  Automatically set	if the
	      checkwinsize option is enabled or	in an interactive  shell  upon
	      receipt of a SIGWINCH.
       COMPREPLY
	      An array variable	from which bash	reads the possible completions
	      generated	by a shell function invoked by the  programmable  com-
	      pletion  facility	(see Programmable Completion below).  Each ar-
	      ray element contains one possible	completion.
       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    Similar to BASH_ENV; used	when the shell	is  invoked  in	 POSIX
	      mode.
       FCEDIT The default editor for the fc builtin command.
       FIGNORE
	      A	 colon-separated  list	of  suffixes to	ignore when performing
	      filename completion (see READLINE	below).	 A filename whose suf-
	      fix  matches  one	of the entries in FIGNORE is excluded from the
	      list of matched filenames.  A sample value is ".o:~" (Quoting is
	      needed  when  assigning a	value to this variable,	which contains
	      tildes).
       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 filenames
	      to be ignored by pathname	expansion.  If a filename matched by a
	      pathname expansion pattern also matches one of the  patterns  in
	      GLOBIGNORE, it is	removed	from the list of matches.
       HISTCONTROL
	      A	 colon-separated  list	of values controlling how commands are
	      saved on the history list.  If the list of values	 includes  ig-
	      norespace,  lines	 which	begin  with  a space character are not
	      saved in the history list.  A value of ignoredups	 causes	 lines
	      matching 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 in which command history is saved (see HIS-
	      TORY  below).   The default value	is ~/.bash_history.  If	unset,
	      the command history is not saved when a shell exits.
       HISTFILESIZE
	      The maximum number of lines contained in the history file.  When
	      this  variable  is  assigned  a value, the history file is trun-
	      cated, 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 an-
	      chored 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 char-
	      acters, `&' matches the previous history line.  `&' may  be  es-
	      caped  using  a  backslash;  the backslash is removed before at-
	      tempting a match.	 The second and	subsequent lines of  a	multi-
	      line  compound command are not tested, and are added to the his-
	      tory regardless of the value of HISTIGNORE.
       HISTSIZE
	      The number of commands to	remember in the	command	 history  (see
	      HISTORY  below).	 If  the value is 0, commands are not saved in
	      the history list.	 Numeric values	less than zero result in every
	      command  being  saved  on	 the history list (there is no limit).
	      The shell	sets the  default  value  to  500  after  reading  any
	      startup files.
       HISTTIMEFORMAT
	      If  this	variable  is  set and not null,	its value is used as a
	      format string for	strftime(3) 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.
       HOME   The home directory of the	current	user; the default argument for
	      the cd builtin command.  The value of this variable is also used
	      when performing tilde expansion.
       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  at-
	      tempted  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  comple-
	      tions.  When HOSTFILE is unset, the hostname list	is cleared.
       IFS    The Internal Field Separator that	is used	for word splitting af-
	      ter expansion and	to  split  lines  into	words  with  the  read
	      builtin  command.	  The  default	value  is  ``<space><tab><new-
	      line>''.
       IGNOREEOF
	      Controls the action of an	interactive shell on receipt of	an EOF
	      character	as the sole input.  If set, the	value is the number of
	      consecutive EOF characters which must  be	 typed	as  the	 first
	      characters  on an	input line before bash exits.  If the variable
	      exists but does not have a numeric value,	or has no  value,  the
	      default  value  is  10.  If it does not exist, EOF signifies the
	      end of input to the shell.
       INPUTRC
	      The filename for the readline startup file, overriding  the  de-
	      fault of ~/.inputrc (see READLINE	below).
       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 pathname expansion, and determines	 the  behavior
	      of  range	 expressions,  equivalence  classes, and collating se-
	      quences within pathname expansion	and pattern matching.
       LC_CTYPE
	      This variable determines the interpretation  of  characters  and
	      the  behavior of character classes within	pathname expansion and
	      pattern matching.
       LC_MESSAGES
	      This variable determines the locale used	to  translate  double-
	      quoted strings preceded by a $.
       LC_NUMERIC
	      This  variable  determines  the  locale category used for	number
	      formatting.
       LINES  Used by the select compound  command  to	determine  the	column
	      length  for  printing selection lists.  Automatically set	if the
	      checkwinsize option is enabled or	in an interactive  shell  upon
	      receipt of a SIGWINCH.
       MAIL   If  this	parameter  is  set to a	file or	directory name and the
	      MAILPATH variable	is not set, bash informs the user of  the  ar-
	      rival of mail in the specified file or Maildir-format directory.
       MAILCHECK
	      Specifies	 how often (in seconds)	bash checks for	mail.  The de-
	      fault 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.
       MAILPATH
	      A	colon-separated	list of	filenames to be	checked	for mail.  The
	      message to be printed when mail arrives in a particular file may
	      be  specified by separating the filename from the	message	with a
	      `?'.  When used in the text of the message, $_  expands  to  the
	      name of the current mailfile.  Example:
	      MAILPATH='/var/mail/bfox?"You  have  mail":~/shell-mail?"$_  has
	      mail!"'
	      Bash supplies a default value for	this variable, but  the	 loca-
	      tion  of	the  user  mail	files that it uses is system dependent
	      (e.g., /var/mail/$USER).
       OPTERR If set to	the value 1, bash displays error messages generated by
	      the  getopts builtin command (see	SHELL BUILTIN COMMANDS below).
	      OPTERR is	initialized to 1 each time the shell is	invoked	 or  a
	      shell script is executed.
       PATH   The  search  path	for commands.  It is a colon-separated list of
	      directories in which the shell looks for commands	 (see  COMMAND
	      EXECUTION	 below).   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.  The default path	is  system-dependent,  and  is
	      set  by  the administrator who installs bash.  A common value is
	      ``/usr/local/bin:/usr/lo-
	      cal/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
       POSIXLY_CORRECT
	      If  this	variable  is  in the environment when bash starts, the
	      shell enters 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.
       PROMPT_COMMAND
	      If set, the value	is executed as a command prior to issuing each
	      primary prompt.
       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  (see  PROMPTING  below).
	      Characters removed are replaced with an ellipsis.
       PS1    The  value  of  this parameter is	expanded (see PROMPTING	below)
	      and used as the primary prompt string.   The  default  value  is
	      ``\s-\v\$	''.
       PS2    The  value of this parameter is expanded as with PS1 and used as
	      the secondary prompt string.  The	default	is ``> ''.
       PS3    The value	of this	parameter is used as the prompt	for the	select
	      command (see SHELL GRAMMAR above).
       PS4    The  value  of  this  parameter  is expanded as with PS1 and the
	      value is printed before each command bash	displays during	an ex-
	      ecution  trace.  The first character of PS4 is replicated	multi-
	      ple times, as necessary, to indicate multiple levels of indirec-
	      tion.  The default is ``+	''.
       SHELL  The full pathname	to the shell is	kept in	this environment vari-
	      able.  If	it is not set when the shell starts, bash  assigns  to
	      it the full pathname of the current user's login shell.
       TIMEFORMAT
	      The  value of this parameter is used as a	format string specify-
	      ing how the timing information for pipelines prefixed  with  the
	      time  reserved word should be displayed.	The % character	intro-
	      duces 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 de-
	      fault  timeout  for the read builtin.  The select	command	termi-
	      nates 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.
       auto_resume
	      This variable controls how the shell interacts with the user and
	      job  control.   If this variable is set, single word simple com-
	      mands without redirections are treated as	candidates for resump-
	      tion of an existing stopped job.	There is no ambiguity allowed;
	      if there is more than one	job beginning with the	string	typed,
	      the  job	most  recently	accessed  is  selected.	 The name of a
	      stopped job, in this context, is the command line	used to	 start
	      it.   If	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	analo-
	      gous  to the %?  job identifier (see JOB CONTROL below).	If set
	      to any other value, the supplied string must be a	 prefix	 of  a
	      stopped job's name; this provides	functionality analogous	to the
	      %string job identifier.
       histchars
	      The two or three characters which	control	history	expansion  and
	      tokenization (see	HISTORY	EXPANSION below).  The first character
	      is the history expansion character, the character	which  signals
	      the  start  of  a	 history  expansion, normally `!'.  The	second
	      character	is the quick substitution character, which is used  as
	      shorthand	 for  re-running the previous command entered, substi-
	      tuting one string	for another in the command.   The  default  is
	      `^'.   The optional third	character is the character which indi-
	      cates that the remainder of the line is a	comment	when found  as
	      the  first  character of a word, normally	`#'.  The history com-
	      ment 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.

   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 con-
       tiguously.  Indexed arrays are  referenced  using  integers  (including
       arithmetic  expressions)	  and  are  zero-based;	associative arrays are
       referenced using	arbitrary strings.  Unless  otherwise  noted,  indexed
       array indices must be non-negative integers.

       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 indexed array, use declare -a	name (see SHELL	 BUILTIN  COM-
       MANDS  below).	declare	 -a name[subscript] is also accepted; the sub-
       script 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 ...	valuen),  where	 each  value  is  of  the  form	 [sub-
       script]=string.	 Indexed array assignments do not require anything but
       string.	When assigning to indexed arrays, if the optional brackets and
       subscript  are supplied,	that index is assigned to; otherwise the index
       of the element assigned is the last index assigned to by	the  statement
       plus one.  Indexing starts at zero.

       When assigning to an associative	array, the subscript is	required.

       This  syntax is also accepted by	the declare builtin.  Individual array
       elements	may be assigned	to using the name[subscript]=value syntax  in-
       troduced	 above.	  When	assigning to an	indexed	array, if name is sub-
       scripted	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.

       Any  element  of	 an  array may be referenced using ${name[subscript]}.
       The braces are required to avoid	conflicts with pathname	expansion.  If
       subscript  is  @	 or *, the word	expands	to all members of 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
       special variable, and ${name[@]}	expands	each element of	name to	a sep-
       arate word.  When there are no array  members,  ${name[@]}  expands  to
       nothing.	  If the double-quoted expansion occurs	within a word, the ex-
       pansion 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  @ (see Special Parameters above).
       ${#name[subscript]} expands to the length  of  ${name[subscript]}.   If
       subscript is * or @, the	expansion is the number	of elements in the ar-
       ray.  Referencing an array variable without a subscript	is  equivalent
       to  referencing the array with a	subscript of 0.	 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 maxi-
       mum index of the	array, so negative indices count back from the end  of
       the array, and an index of -1 references	the last element.

       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] de-
       stroys the array	element	at index subscript.   Negative	subscripts  to
       indexed	arrays are interpreted as described above.  Care must be taken
       to avoid	unwanted side effects caused  by  pathname  expansion.	 unset
       name, where name	is an array, or	unset name[subscript], where subscript
       is * or @, removes the entire array.

       The declare, local, and readonly	builtins each accept a	-a  option  to
       specify	an indexed array and a -A option to specify an associative ar-
       ray.  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.  The	set and	declare	builtins display array
       values in a way that allows them	to be reused as	assignments.

EXPANSION
       Expansion is performed on the command line after	it has been split into
       words.  There are seven kinds of	expansion performed: brace  expansion,
       tilde  expansion,  parameter  and variable expansion, command substitu-
       tion, arithmetic	expansion, word	splitting, and pathname	expansion.

       The order of expansions is: brace expansion; tilde expansion, parameter
       and  variable expansion,	arithmetic expansion, and command substitution
       (done in	a left-to-right	fashion); word splitting; and pathname	expan-
       sion.

       On systems that can support it, there is	an additional expansion	avail-
       able: process substitution.  This is performed  at  the	same  time  as
       tilde,  parameter,  variable, and arithmetic expansion and command sub-
       stitution.

       Only brace expansion, word splitting, and pathname expansion can	change
       the  number of words of the expansion; other expansions expand a	single
       word to a single	word.  The only	exceptions to this are the  expansions
       of "$@" and "${name[@]}"	as explained above (see	PARAMETERS).

   Brace Expansion
       Brace expansion is a mechanism by which arbitrary strings may be	gener-
       ated.  This mechanism is	similar	to pathname expansion, but  the	 file-
       names generated need not	exist.	Patterns to be brace expanded take the
       form of an optional preamble, followed by either	a series of comma-sep-
       arated  strings or a sequence expression	between	a pair of braces, fol-
       lowed 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,
       a{d,c,b}e expands into `ade ace abe'.

       A sequence expression takes the form {x..y[..incr]}, where x and	y  are
       either  integers	or single characters, 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 pre-
       fixed 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	neces-
       sary.   When  characters	 are  supplied,	the expression expands to each
       character lexicographically between x and y, inclusive, using  the  de-
       fault C locale.	Note that both x and y must be of the same type.  When
       the increment is	supplied, it is	used as	the  difference	 between  each
       term.  The default increment is 1 or -1 as appropriate.

       Brace expansion is performed before any other expansions, and any char-
       acters 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 ex-
       pression.  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	expan-
       sion, the string	${ is not considered eligible for brace	expansion.

       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}}

       Brace expansion introduces a  slight  incompatibility  with  historical
       versions	 of sh.	 sh does not treat opening or closing braces specially
       when they appear	as part	of a word, and preserves them in  the  output.
       Bash  removes  braces  from  words as a consequence of brace expansion.
       For example, a word entered to sh as file{1,2} appears  identically  in
       the  output.  The same word is output as	file1 file2 after expansion by
       bash.  If strict	compatibility with sh is desired, start	bash with  the
       +B option or disable brace expansion with the +B	option to the set com-
       mand (see SHELL BUILTIN COMMANDS	below).

   Tilde Expansion
       If a word begins	with an	unquoted tilde character  (`~'),  all  of  the
       characters  preceding  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 shell parameter HOME.  If HOME is unset, the  home	direc-
       tory  of	 the  user executing the shell is substituted instead.	Other-
       wise, the tilde-prefix is replaced with the home	 directory  associated
       with the	specified login	name.

       If  the tilde-prefix is a `~+', the value of the	shell variable PWD re-
       places the tilde-prefix.	 If the	tilde-prefix is	a `~-',	the  value  of
       the  shell variable OLDPWD, if it is set, is substituted.  If the char-
       acters 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 tilde-prefix as an argu-
       ment.  If the characters	following the tilde in the  tilde-prefix  con-
       sist of a number	without	a leading `+' or `-', `+' is assumed.

       If the login name is invalid, or	the tilde expansion fails, the word is
       unchanged.

       Each variable assignment	is checked for unquoted	tilde-prefixes immedi-
       ately following a : or the first	=.  In these cases, tilde expansion is
       also performed.	Consequently, one may use filenames with tildes	in as-
       signments  to PATH, MAILPATH, and CDPATH, and the shell assigns the ex-
       panded value.

   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 em-
       bedded arithmetic expansion, command substitution, or parameter	expan-
       sion.

       ${parameter}
	      The  value of parameter is substituted.  The braces are required
	      when parameter is	a positional  parameter	 with  more  than  one
	      digit, or	when parameter is followed by a	character which	is not
	      to be interpreted	as part	of its name.  The parameter is a shell
	      parameter	 as  described above PARAMETERS) or an array reference
	      (Arrays).

       If the first character of parameter is an exclamation point (!),	it in-
       troduces	 a  level of variable indirection.  Bash uses the value	of the
       variable	formed from the	rest of	parameter as the name of the variable;
       this  variable  is  then	expanded and that value	is used	in the rest of
       the substitution, rather	than the value of parameter itself.   This  is
       known as	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 indirec-
       tion.

       In each of the cases below, word	is subject to tilde expansion, parame-
       ter expansion, command substitution, and	arithmetic expansion.

       When not	performing substring expansion,	using the forms	documented be-
       low (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 un-
       set.

       ${parameter:-word}
	      Use Default Values.  If parameter	is unset or null,  the	expan-
	      sion  of word is substituted.  Otherwise,	the value of parameter
	      is substituted.
       ${parameter:=word}
	      Assign Default Values.  If parameter is unset or null,  the  ex-
	      pansion  of word is assigned to parameter.  The value of parame-
	      ter is then substituted.	Positional parameters and special  pa-
	      rameters may not be assigned to in this way.
       ${parameter:?word}
	      Display  Error if	Null or	Unset.	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.
       ${parameter:+word}
	      Use  Alternate Value.  If	parameter is null or unset, nothing is
	      substituted, otherwise the expansion of word is substituted.
       ${parameter:offset}
       ${parameter:offset:length}
	      Substring	Expansion.  Expands to up to length characters of  the
	      value  of	 parameter starting at the character specified by off-
	      set.  If parameter is @, an indexed array	subscripted by @ or *,
	      or  an  associative  array name, the results differ as described
	      below.  If length	is omitted, 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 (see ARITHMETIC EVALUATION	below).

	      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 pa-
	      rameter.	 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	expan-
	      sion 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.

	      If parameter is @, 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	expan-
	      sion error if length evaluates to	a number less than zero.

	      If parameter is an indexed array name subscripted	by @ or	*, the
	      result  is  the length members of	the array beginning with ${pa-
	      rameter[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.

	      Substring	expansion applied to an	associative array produces un-
	      defined results.

	      Substring	 indexing  is zero-based unless	the positional parame-
	      ters are used, in	which case the indexing	starts	at  1  by  de-
	      fault.   If offset is 0, and the positional parameters are used,
	      $0 is prefixed to	the list.

       ${!prefix*}
       ${!prefix@}
	      Names matching 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[*]}
	      List of array keys.  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}
	      Parameter	length.	 The length in characters of the value of  pa-
	      rameter  is substituted.	If parameter is	* or @,	the value sub-
	      stituted 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 in-
	      terpreted	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}
	      Remove matching prefix pattern.  The word	is expanded to produce
	      a	pattern	just as	in pathname expansion.	If the pattern matches
	      the beginning of the 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  pat-
	      tern  (the  ``##''  case)	 deleted.  If parameter	is @ or	*, the
	      pattern removal operation	is applied to each positional  parame-
	      ter in turn, and the expansion is	the resultant list.  If	param-
	      eter 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}
	      Remove matching suffix pattern.  The word	is expanded to produce
	      a	pattern	just as	in pathname expansion.	If the pattern matches
	      a	trailing portion 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	 posi-
	      tional  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}
	      Pattern substitution.  The pattern is expanded to	produce	a pat-
	      tern  just  as in	pathname expansion.  Parameter is expanded and
	      the longest match	of pattern against its value is	replaced  with
	      string.	If  pattern  begins with /, all	matches	of pattern are
	      replaced with string.  Normally only  the	 first	match  is  re-
	      placed.	If  pattern begins with	#, it must match at the	begin-
	      ning of the expanded value of parameter.	If pattern begins with
	      %,  it must match	at the end of the expanded value of parameter.
	      If string	is null, matches of pattern are	deleted	and the	/ fol-
	      lowing pattern may be omitted.  If parameter is @	or *, the sub-
	      stitution	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  op-
	      eration  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}
	      Case modification.  This expansion modifies the case  of	alpha-
	      betic  characters	in parameter.  The pattern is expanded to pro-
	      duce a pattern just as in	pathname 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 ^ op-
	      erator 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	 omit-
	      ted,  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.

   Command Substitution
       Command substitution allows the output of a command to replace the com-
       mand name.  There are two forms:

	      $(command)
       or
	      `command`

       Bash performs the expansion by executing	command	and replacing the com-
       mand  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 sub-
       stitution.   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
       pathname	expansion are not performed on the results.

   Arithmetic Expansion
       Arithmetic expansion allows the evaluation of an	arithmetic  expression
       and  the	 substitution of the result.  The format for arithmetic	expan-
       sion is:

	      $((expression))

       The old format $[expression] is deprecated and will be removed  in  up-
       coming versions of bash.

       The  expression	is  treated  as	if it were within double quotes, but a
       double quote inside the parentheses is not treated specially.  All  to-
       kens  in	 the expression	undergo	parameter and variable expansion, com-
       mand 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	 under
       ARITHMETIC EVALUATION.  If expression is	invalid, bash prints a message
       indicating failure and no substitution occurs.

   Process Substitution
       Process substitution is supported on systems that support  named	 pipes
       (FIFOs)	or the /dev/fd method of naming	open files.  It	takes the form
       of <(list) or >(list).  The process list	is run with its	input or  out-
       put connected to	a FIFO or some file in /dev/fd.	 The name of this file
       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 pro-
       vide input for list.  If	the <(list) form is used, the file  passed  as
       an argument should be read to obtain the	output of list.

       When  available,	 process substitution is performed simultaneously with
       parameter and variable expansion, command substitution, and  arithmetic
       expansion.

   Word	Splitting
       The  shell  scans the results of	parameter expansion, command substitu-
       tion, 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 and
       tab  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  charac-
       ter).   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.   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.

       Note that if no expansion occurs, no splitting is performed.

   Pathname Expansion
       After  word  splitting,	unless	the -f option has been set, bash scans
       each word for the characters *, ?, and [.  If one of  these  characters
       appears,	 then  the word	is regarded as a pattern, and replaced with an
       alphabetically sorted list of filenames matching	the pattern (see  Pat-
       tern  Matching  below).	 If  no	 matching filenames are	found, and the
       shell option nullglob is	not enabled, the word is left  unchanged.   If
       the  nullglob  option is	set, and no matches are	found, the word	is re-
       moved.  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  re-
       gard  to	the case of alphabetic characters.  Note that when using range
       expressions like	[a-z] (see below), letters of the other	 case  may  be
       included,  depending  on	 the setting of	LC_COLLATE.  When a pattern is
       used for	pathname expansion, the	character ``.''	 at  the  start	 of  a
       name  or	 immediately following a slash must be matched explicitly, un-
       less the	shell option dotglob is	set.  When matching  a	pathname,  the
       slash character must always be matched explicitly.  In other cases, the
       ``.''  character	is not treated	specially.   See  the  description  of
       shopt  below  under SHELL BUILTIN COMMANDS for a	description of the no-
       caseglob, nullglob, failglob, and dotglob shell options.

       The GLOBIGNORE shell variable may be used to restrict the set of	 file-
       names matching a	pattern.  If GLOBIGNORE	is set,	each matching filename
       that also matches one of	the patterns in	GLOBIGNORE is removed from the
       list  of	 matches.  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.

       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
		     pathname  expansion  context,  two	 adjacent *s used as a
		     single pattern will match all files and zero or more  di-
		     rectories	and  subdirectories.   If followed by a	/, two
		     adjacent *s will match only directories  and  subdirecto-
		     ries.
	      ?	     Matches any single	character.
	      [...]  Matches  any  one	of the enclosed	characters.  A pair of
		     characters	separated by a hyphen denotes a	range  expres-
		     sion;  any	character that falls between those two charac-
		     ters, inclusive, using the	current	locale's collating se-
		     quence and	character set, is matched.  If the first char-
		     acter following the [ is a	!  or a	^ then	any  character
		     not enclosed is matched.  The sorting order of characters
		     in	range expressions is determined	by the current	locale
		     and  the  values  of the LC_COLLATE or LC_ALL shell vari-
		     ables, if set.  To	obtain the traditional	interpretation
		     of	 range	expressions,  where  [a-d]  is	equivalent  to
		     [abcd], set value of the LC_ALL shell variable to	C,  or
		     enable  the  globasciiranges  shell  option.   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.

		     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 us-
		     ing the syntax [=c=], which matches all  characters  with
		     the  same collation weight	(as defined by the current lo-
		     cale) as the character c.

		     Within [ and ], the syntax	[.symbol.] matches the collat-
		     ing symbol	symbol.

       If the extglob shell option is enabled using the	shopt builtin, several
       extended	pattern	matching operators are recognized.  In	the  following
       description, a pattern-list is a	list of	one or more patterns separated
       by a |.	Composite patterns may be formed using one or more of the fol-
       lowing 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

   Quote Removal
       After the preceding expansions, all unquoted occurrences	of the charac-
       ters \, ', and "	that did not result from one of	the  above  expansions
       are removed.

REDIRECTION
       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	opera-
       tors may	precede	or appear anywhere within a simple command or may fol-
       low 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 or equal to	10 and assign it  to  varname.
       If  >&-	or  <&-	is preceded by {varname}, the value of varname defines
       the file	descriptor to close.

       In the following	descriptions, if the file descriptor number  is	 omit-
       ted,  and the first character of	the redirection	operator is <, the re-
       direction 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  descrip-
       tions,  unless  otherwise noted,	is subjected to	brace expansion, tilde
       expansion, parameter  and  variable  expansion,	command	 substitution,
       arithmetic  expansion,  quote  removal,	pathname  expansion,  and word
       splitting.  If it expands to more than one word,	bash reports an	error.

       Note that the order of redirections is significant.  For	 example,  the
       command

	      ls > dirlist 2>&1

       directs	both  standard	output and standard error to the file dirlist,
       while the command

	      ls 2>&1 >	dirlist

       directs only the	standard output	to file	dirlist, because the  standard
       error  was duplicated from the standard output before the standard out-
       put was redirected to dirlist.

       Bash handles several filenames specially	when they are used in redirec-
       tions, as described in the following table:

	      /dev/fd/fd
		     If	 fd  is	 a valid integer, file descriptor fd is	dupli-
		     cated.
	      /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	inter-
       nally.

       Note that the exec builtin command can make redirections	take effect in
       the current shell.

   Redirecting Input
       Redirection of input causes the file whose name results from the	expan-
       sion 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

   Redirecting Output
       Redirection  of	output causes the file whose name results from the ex-
       pansion 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 to the set builtin command is not enabled, the re-
       direction is attempted even if the file named by	word exists.

   Appending Redirected	Output
       Redirection of output in	this fashion causes the	file  whose  name  re-
       sults from the expansion	of word	to be opened for appending on file de-
       scriptor	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

   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 er-
       ror:

	      &>word
       and
	      >&word

       Of the two forms, the first is preferred.  This is semantically equiva-
       lent 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  De-
       scriptors below)	for compatibility reasons.

   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).

   Here	Documents
       This  type  of  redirection  instructs the shell	to read	input from the
       current source until a line containing only delimiter (with no trailing
       blanks)	is seen.  All of the lines read	up to that point are then used
       as the standard input for a command.

       The format of here-documents is:

	      <<[-]word
		      here-document
	      delimiter

       No parameter and	variable expansion, command  substitution,  arithmetic
       expansion,  or pathname expansion is performed on word.	If any charac-
       ters in word are	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 charac-
       ter 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  al-
       lows  here-documents  within  shell scripts to be indented in a natural
       fashion.

   Here	Strings
       A variant of here documents, the	format is:

	      <<<word

       The word	undergoes brace	 expansion,  tilde  expansion,	parameter  and
       variable	 expansion,  command  substitution,  arithmetic	expansion, and
       quote removal.  Pathname	expansion and  word  splitting	are  not  per-
       formed.	 The  result  is supplied as a single string to	the command on
       its standard input.

   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  de-
       scriptor	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 re-
       direction 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.

   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.

   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.

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	 (see  SHELL  BUILTIN COMMANDS below).	The first word of each
       simple command, if unquoted, is checked to see if it has	an alias.   If
       so,  that word is replaced by the text of the alias.  The characters /,
       $, `, and = 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.  If
       arguments are needed, a shell function should be	 used  (see  FUNCTIONS
       below).

       Aliases	are not	expanded when the shell	is not interactive, unless the
       expand_aliases shell option is set using	shopt (see the description  of
       shopt under SHELL BUILTIN COMMANDS below).

       The  rules  concerning  the  definition and use of aliases are somewhat
       confusing.  Bash	always reads at	least one complete line	of  input  be-
       fore  executing any of the commands on that line.  Aliases are expanded
       when a command is read, not when	it is executed.	 Therefore,  an	 alias
       definition  appearing on	the same line as another command does not take
       effect until the	next line of input is read.   The  commands  following
       the  alias  definition  on that line are	not affected by	the new	alias.
       This behavior is	also an	issue when functions  are  executed.   Aliases
       are  expanded when a function definition	is read, not when the function
       is executed, because a function definition is itself  a	compound  com-
       mand.   As  a consequence, aliases defined in a function	are not	avail-
       able 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, aliases are superseded	by shell functions.

FUNCTIONS
       A shell function, defined  as  described	 above	under  SHELL  GRAMMAR,
       stores  a  series  of commands for later	execution.  When the name of a
       shell function is used as a simple command name,	the list  of  commands
       associated with that function name is executed.	Functions are executed
       in the context of the current shell; no new process is created  to  in-
       terpret	them  (contrast	 this  with  the execution of a	shell script).
       When a function is executed, the	arguments to the function  become  the
       positional parameters during its	execution.  The	special	parameter # 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 func-
       tion while the function is executing.

       All other aspects of the	shell execution	environment are	identical  be-
       tween  a	 function and its caller with these exceptions:	 the DEBUG and
       RETURN traps (see the description  of  the  trap	 builtin  under	 SHELL
       BUILTIN	COMMANDS below)	are not	inherited unless the function has been
       given the trace attribute (see the description of the  declare  builtin
       below)  or  the -o functrace shell 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.

       Variables local to the function may be declared with the	local  builtin
       command.	 Ordinarily, variables and their values	are shared between the
       function	and its	caller.

       The FUNCNEST variable, if set to	a numeric value	greater	 than  0,  de-
       fines  a	maximum	function nesting level.	 Function invocations that ex-
       ceed 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 func-
       tion call.  Any command associated with the RETURN trap is executed be-
       fore  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.

       Function	 names and definitions may be listed with the -f option	to the
       declare or typeset builtin commands.  The -F option to declare or type-
       set  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	subshells automatically	have them defined with
       the -f option to	the export builtin.   A	 function  definition  may  be
       deleted	using  the  -f	option	to the unset builtin.  Note that shell
       functions and variables with the	same name may result in	multiple iden-
       tically-named  entries  in  the environment passed to the shell's chil-
       dren.  Care should be taken in cases where this may cause a problem.

       Functions may be	recursive.  The	FUNCNEST variable may be used to limit
       the  depth  of the function call	stack and restrict the number of func-
       tion invocations.  By default, no limit is imposed on the number	of re-
       cursive calls.

ARITHMETIC EVALUATION
       The  shell allows arithmetic expressions	to be evaluated, under certain
       circumstances (see the let and declare builtin commands and  Arithmetic
       Expansion).   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  per-
       formed 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.

       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, 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	repre-
       sent 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.

CONDITIONAL EXPRESSIONS
       Conditional  expressions	 are  used  by the [[ compound command and the
       test and	[ builtin commands to test file	attributes and perform	string
       and  arithmetic comparisons.  Expressions are formed from the following
       unary or	binary primaries.  If any file argument	to  one	 of  the  pri-
       maries 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.

       Unless otherwise	specified, primaries that operate on files follow sym-
       bolic links and operate on the target of	the link, rather than the link
       itself.

       When used with [[, the <	and > operators	sort  lexicographically	 using
       the current locale.  The	test command sorts using ASCII ordering.

       -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 is set-group-id.
       -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  num-
	      bers.
       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.  See the list of
	      options under the	description  of	 the  -o  option  to  the  set
	      builtin below.
       -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	refer-
	      ence.
       -z string
	      True if the length of string is zero.
       string
       -n string
	      True if the length of string is non-zero.

       string1 == string2
       string1 = string2
	      True  if	the strings are	equal.	= should be used with the test
	      command for POSIX	conformance.  When used	with the  [[  command,
	      this performs pattern matching as	described above	(Compound Com-
	      mands).

       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.

SIMPLE COMMAND EXPANSION
       When a simple command is	executed, the shell performs the following ex-
       pansions, assignments, and redirections,	from left to right.

       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.	 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 under REDIRECTION.

       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	 vari-
	      able.

       If no command name results, the variable	assignments affect the current
       shell environment.  Otherwise, the variables are	added to the  environ-
       ment  of	the executed command and do not	affect the current shell envi-
       ronment.	 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  af-
       fect  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	expan-
       sions 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.

COMMAND	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.

       If  the	command	name contains no slashes, the shell attempts to	locate
       it.  If there exists a shell function by	that name,  that  function  is
       invoked	as described above in FUNCTIONS.  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.

       If  the name is neither a shell function	nor a builtin, and contains no
       slashes,	bash searches each element of the PATH for  a  directory  con-
       taining an executable file by that name.	 Bash uses a hash table	to re-
       member the full pathnames of executable files  (see  hash  under	 SHELL
       BUILTIN	COMMANDS  below).  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
       with  the  original command and the original command's arguments	as its
       arguments, and the function's exit status becomes the  exit  status  of
       the  shell.  If that function is	not defined, the shell prints an error
       message and returns an exit status of 127.

       If the search is	successful, or if the command  name  contains  one  or
       more slashes, the shell executes	the named program in a separate	execu-
       tion environment.  Argument 0 is	set to the name	given, and the remain-
       ing arguments to	the command are	set to the arguments given, if any.

       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,  a
       file  containing	 shell commands.  A subshell is	spawned	to execute it.
       This subshell reinitializes itself, so that the effect is as if	a  new
       shell  had  been	 invoked to handle the script, with the	exception that
       the locations of	commands remembered by the parent (see hash below  un-
       der SHELL BUILTIN COMMANDS) are retained	by the child.

       If  the program is a file beginning with	#!, the	remainder of the first
       line specifies an interpreter for the program.  The shell executes  the
       specified interpreter on	operating systems that do not handle this exe-
       cutable format themselves.  The arguments to the	interpreter consist of
       a  single optional argument following the interpreter name on the first
       line of the program, followed by	the name of the	program,  followed  by
       the command arguments, if any.

COMMAND	EXECUTION ENVIRONMENT
       The  shell  has an execution environment, which consists	of the follow-
       ing:

       o      open files inherited by the shell	at invocation, as modified  by
	      redirections supplied to the exec	builtin

       o      the  current  working directory as set by	cd, pushd, or popd, or
	      inherited	by the shell at	invocation

       o      the file creation	mode mask as set by umask  or  inherited  from
	      the shell's parent

       o      current traps set	by trap

       o      shell parameters that are	set by variable	assignment or with set
	      or inherited from	the shell's parent in the environment

       o      shell functions defined during execution or inherited  from  the
	      shell's parent in	the environment

       o      options  enabled	at  invocation (either by default or with com-
	      mand-line	arguments) or by set

       o      options enabled by shopt

       o      shell aliases defined with alias

       o      various process IDs, including those  of	background  jobs,  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  con-
       sists  of the following.	 Unless	otherwise noted, the values are	inher-
       ited from the shell.

       o      the shell's open files, plus  any	 modifications	and  additions
	      specified	by redirections	to the command

       o      the current working directory

       o      the file creation	mode mask

       o      shell  variables	and  functions	marked	for export, along with
	      variables	exported for the command, passed in the	environment

       o      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.

       Command substitution, commands grouped with parentheses,	and  asynchro-
       nous commands are invoked in a subshell environment that	is a duplicate
       of the shell environment, except	that traps caught by the shell are re-
       set  to	the values that	the shell inherited from its parent at invoca-
       tion.  Builtin commands that are	invoked	as part	of a pipeline are also
       executed	in a subshell environment.  Changes made to the	subshell envi-
       ronment 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  de-
       fault standard input for	the command is the empty file /dev/null.  Oth-
       erwise, the invoked command inherits the	file descriptors of the	 call-
       ing shell as modified by	redirections.

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.

       The  shell provides several ways	to manipulate the environment.	On in-
       vocation, the shell scans its own environment and creates  a  parameter
       for  each name found, automatically marking it for export to child pro-
       cesses.	Executed commands inherit the environment.  The	export and de-
       clare  -x  commands  allow  parameters and functions to be added	to and
       deleted from the	environment.  If the value of a	parameter in the envi-
       ronment is modified, the	new value becomes part of the environment, re-
       placing the old.	 The environment inherited  by	any  executed  command
       consists	 of the	shell's	initial	environment, whose values may be modi-
       fied in the shell, less any pairs removed by the	 unset	command,  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
       above in	PARAMETERS.  These assignment statements affect	only the envi-
       ronment seen by that command.

       If the -k option	is set (see the	set builtin command below),  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 filename of	the command and	passed to that command in its environ-
       ment.

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.  An exit status of zero indicates	success.   A  non-zero
       exit  status  indicates	failure.  When a command terminates on a fatal
       signal N, bash uses the value of	128+N as the exit status.

       If a command is not found, the child process created to execute it  re-
       turns  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.

       Shell  builtin  commands	return a status	of 0 (true) if successful, and
       non-zero	(false)	if an error occurs while they execute.	 All  builtins
       return an exit status of	2 to indicate incorrect	usage.

       Bash  itself  returns the exit status of	the last command executed, un-
       less a syntax error occurs, in which case  it  exits  with  a  non-zero
       value.  See also	the exit builtin command below.

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).  In
       all cases, bash ignores SIGQUIT.	 If job	control	is in effect, bash ig-
       nores SIGTTIN, SIGTTOU, and SIGTSTP.

       Non-builtin commands run	by bash	have signal handlers set to the	values
       inherited by the	shell from its parent.	When job control is not	in ef-
       fect,  asynchronous  commands  ignore SIGINT and	SIGQUIT	in addition to
       these inherited handlers.  Commands run as a result of command  substi-
       tution ignore the keyboard-generated job	control	signals	SIGTTIN, SIGT-
       TOU, 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	signal to a particular
       job, it should be removed from the jobs table with the  disown  builtin
       (see  SHELL BUILTIN COMMANDS below) or marked to	not receive SIGHUP us-
       ing disown -h.

       If the huponexit	shell option has been set with	shopt,	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 com-
       mand  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 sta-
       tus greater than	128, immediately after which the trap is executed.

JOB CONTROL
       Job control refers to the ability to selectively	stop (suspend) the ex-
       ecution	of  processes and continue (resume) their execution at a later
       point.  A user typically	employs	this facility via an  interactive  in-
       terface	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 (in the background), 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-gen-
       erated 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 (typ-
       ically ^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 re-
       turned to bash.	The user may then manipulate 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 charac-
       ter  %  introduces  a job specification (jobspec).  Job number n	may be
       referred	to as %n.  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  ce  job.	 If  a	prefix
       matches	more  than one job, bash reports an error.  Using %?ce,	on the
       other hand, refers to any job containing	the string ce in  its  command
       line.   If the substring	matches	more than one job, bash	reports	an er-
       ror.  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.  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 pre-
       vious job with a	-.  A single % (with no	 accompanying  job  specifica-
       tion) also refers to the	current	job.

       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 command is enabled, bash reports such changes
       immediately.  Any trap on SIGCHLD is executed for each child  that  ex-
       its.

       If  an  attempt to exit bash is made while jobs are stopped (or,	if the
       checkjobs shell option has been enabled using the shopt	builtin,  run-
       ning), 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, the	shell does not	print  another
       warning,	and any	stopped	jobs are terminated.

PROMPTING
       When executing interactively, bash displays the primary prompt PS1 when
       it is ready to read a command, and the secondary	 prompt	 PS2  when  it
       needs  more  input  to  complete	 a  command.  Bash allows these	prompt
       strings to be customized	by inserting  a	 number	 of  backslash-escaped
       special characters that are decoded as follows:
	      \a     an	ASCII bell character (07)
	      \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 in-
		     serted into the prompt string; an empty format results in
		     a locale-specific time representation.   The  braces  are
		     required
	      \e     an	ASCII escape character (033)
	      \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     newline
	      \r     carriage return
	      \s     the  name	of  the	shell, the basename of $0 (the portion
		     following the final slash)
	      \t     the current time in 24-hour HH:MM:SS format
	      \T     the current time in 12-hour HH:MM:SS format
	      \@     the current time in 12-hour am/pm format
	      \A     the current 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 + patch level	(e.g., 2.00.0)
	      \w     the current working  directory,  with  $HOME  abbreviated
		     with  a tilde (uses the value of the PROMPT_DIRTRIM vari-
		     able)
	      \W     the basename of the current working directory, with $HOME
		     abbreviated with a	tilde
	      \!     the history number	of this	command
	      \#     the command number	of this	command
	      \$     if	the effective UID is 0,	a #, otherwise a $
	      \nnn   the character corresponding to the	octal number nnn
	      \\     a backslash
	      \[     begin  a sequence of non-printing characters, which could
		     be	used to	embed a	terminal  control  sequence  into  the
		     prompt
	      \]     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 (see HISTORY be-
       low), while the command number is the position in the sequence of  com-
       mands  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 (see the	description of the shopt command under
       SHELL BUILTIN COMMANDS below).

READLINE
       This  is	 the library that handles reading input	when using an interac-
       tive shell, unless the --noediting option is given at shell invocation.
       Line editing is also used when using the	-e option to the read builtin.
       By default, the line editing commands are similar to those of Emacs.  A
       vi-style	line editing interface is also available.  Line	editing	can be
       enabled at any time using the -o	emacs or -o  vi	 options  to  the  set
       builtin	(see  SHELL BUILTIN COMMANDS below).  To turn off line editing
       after the shell is running, use the +o emacs or +o vi  options  to  the
       set builtin.

   Readline Notation
       In this section,	the Emacs-style	notation is used to denote keystrokes.
       Control keys are	denoted	by C-key, e.g.,	C-n  means  Control-N.	 Simi-
       larly,  meta  keys are denoted by M-key,	so M-x means Meta-X.  (On key-
       boards without a	meta key, M-x means ESC	x, i.e., press the Escape  key
       then the	x key.	This makes ESC the meta	prefix.	 The combination M-C-x
       means ESC-Control-x, or press the Escape	key then hold the Control  key
       while pressing the x key.)

       Readline	commands may be	given numeric arguments, which normally	act as
       a repeat	count.	Sometimes, however, it is the  sign  of	 the  argument
       that  is	 significant.	Passing	 a negative argument to	a command that
       acts in the forward direction (e.g., kill-line) causes that command  to
       act  in	a  backward direction.	Commands whose behavior	with arguments
       deviates	from this are noted below.

       When a command is described as killing text, the	text deleted is	 saved
       for possible future retrieval (yanking).	 The killed text is saved in a
       kill ring.  Consecutive kills cause the text to be accumulated into one
       unit, which can be yanked all at	once.  Commands	which do not kill text
       separate	the chunks of text on the kill ring.

   Readline Initialization
       Readline	is customized by putting commands in  an  initialization  file
       (the  inputrc  file).  The name of this file is taken from the value of
       the INPUTRC variable.  If that variable is unset, the default is	~/.in-
       putrc.	When  a	program	which uses the readline	library	starts up, the
       initialization file is read, and	the key	 bindings  and	variables  are
       set.   There  are  only	a few basic constructs allowed in the readline
       initialization file.  Blank lines are ignored.  Lines beginning with  a
       #  are  comments.   Lines  beginning with a $ indicate conditional con-
       structs.	 Other lines denote key	bindings and variable settings.

       The default key-bindings	may be changed with an	inputrc	 file.	 Other
       programs	that use this library may add their own	commands and bindings.

       For example, placing

	      M-Control-u: universal-argument
       or
	      C-Meta-u:	universal-argument
       into  the inputrc would make M-C-u execute the readline command univer-
       sal-argument.

       The following symbolic character	names  are  recognized:	 RUBOUT,  DEL,
       ESC, LFD, NEWLINE, RET, RETURN, SPC, SPACE, and TAB.

       In  addition  to	 command  names, readline allows keys to be bound to a
       string that is inserted when the	key is pressed (a macro).

   Readline Key	Bindings
       The syntax for controlling key bindings in the inputrc file is  simple.
       All  that is required is	the name of the	command	or the text of a macro
       and a key sequence to which it should be	bound. The name	may be	speci-
       fied in one of two ways:	as a symbolic key name,	possibly with Meta- or
       Control-	prefixes, or as	a key sequence.

       When using the form 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 above example, 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).

       In the second form, "keyseq":function-name  or  macro,  keyseq  differs
       from  keyname above in that strings denoting an entire key sequence may
       be specified by placing the sequence within double  quotes.   Some  GNU
       Emacs  style  key escapes can be	used, as in the	following example, but
       the symbolic character names are	not recognized.

	      "\C-u": universal-argument
	      "\C-x\C-r": re-read-init-file
	      "\e[11~":	"Function Key 1"

       In this example,	C-u is again bound to the function universal-argument.
       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 full	set of GNU Emacs style escape sequences	is
	      \C-    control prefix
	      \M-    meta prefix
	      \e     an	escape character
	      \\     backslash
	      \"     literal "
	      \'     literal '

       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 func-
       tion  name.   In	 the macro body, the backslash escapes described above
       are expanded.  Backslash	will quote any other character	in  the	 macro
       text, including " and '.

       Bash  allows the	current	readline key bindings to be displayed or modi-
       fied with the bind builtin command.  The	editing	mode may  be  switched
       during  interactive  use	by using the -o	option to the set builtin com-
       mand (see SHELL BUILTIN COMMANDS	below).

   Readline Variables
       Readline	has variables that can be used to further customize its	behav-
       ior.  A variable	may be set in the inputrc file with a statement	of the
       form

	      set variable-name	value

       Except where noted, readline variables can take the values  On  or  Off
       (without	 regard	 to  case).   Unrecognized variable names are ignored.
       When a variable value is	read, empty or null values, "on"  (case-insen-
       sitive),	and "1"	are equivalent to On.  All other values	are equivalent
       to Off.	The variables and their	default	values are:

       bell-style (audible)
	      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, readline attempts	to ring	the terminal's bell.
       bind-tty-special-chars (On)
	      If  set  to On, readline attempts	to bind	the control characters
	      treated specially	by the kernel's	terminal driver	to their read-
	      line equivalents.
       colored-stats (Off)
	      If  set to On, readline displays possible	completions using dif-
	      ferent colors to indicate	their file type.   The	color  defini-
	      tions  are  taken	 from  the  value of the LS_COLORS environment
	      variable.
       comment-begin (``#'')
	      The string that is inserted  when	 the  readline	insert-comment
	      command is executed.  This command is bound to M-# in emacs mode
	      and to # in vi command mode.
       completion-ignore-case (Off)
	      If set to	On, readline performs filename matching	and completion
	      in a case-insensitive fashion.
       completion-prefix-display-length	(0)
	      The  length in characters	of the common prefix of	a list of pos-
	      sible 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	possi-
	      ble completions.
       completion-query-items (100)
	      This  determines when the	user is	queried	about viewing the num-
	      ber of possible completions generated  by	 the  possible-comple-
	      tions  command.  It may be set to	any integer value greater than
	      or equal to zero.	 If the	 number	 of  possible  completions  is
	      greater than or equal to the value of this variable, the user is
	      asked whether or not he wishes to	view them; otherwise they  are
	      simply listed on the terminal.
       convert-meta (On)
	      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  escape  character (in effect, using escape	as the
	      meta prefix).
       disable-completion (Off)
	      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.
       editing-mode (emacs)
	      Controls whether readline	begins with a set of key bindings sim-
	      ilar to Emacs or vi.  editing-mode can be	set to either emacs or
	      vi.
       echo-control-characters (On)
	      When set to On, on operating systems that	indicate they  support
	      it, readline echoes a character corresponding to a signal	gener-
	      ated from	the keyboard.
       enable-keypad (Off)
	      When set to On, readline will try	to enable the application key-
	      pad when it is called.  Some systems need	this to	enable the ar-
	      row keys.
       enable-meta-key (On)
	      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.
       expand-tilde (Off)
	      If set to	On, tilde expansion is	performed  when	 readline  at-
	      tempts word completion.
       history-preserve-point (Off)
	      If  set  to  On, the history code	attempts to place point	at the
	      same location on each history line retrieved with	 previous-his-
	      tory or next-history.
       history-size (0)
	      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.
       horizontal-scroll-mode (Off)
	      When  set	 to  On, makes readline	use a single line for display,
	      scrolling	the input horizontally on a single screen line when it
	      becomes  longer  than the	screen width rather than wrapping to a
	      new line.
       input-meta (Off)
	      If set to	On, readline will enable eight-bit input (that is,  it
	      will  not	 strip the high	bit from the characters	it reads), re-
	      gardless of what the terminal claims it can support.   The  name
	      meta-flag	is a synonym for this variable.
       isearch-terminators (``C-[C-J'')
	      The  string  of  characters that should terminate	an incremental
	      search without subsequently executing the	character  as  a  com-
	      mand.   If this variable has not been given a value, the charac-
	      ters ESC and C-J will terminate an incremental search.
       keymap (emacs)
	      Set the current readline keymap.	The set	of valid keymap	 names
	      is  emacs,  emacs-standard,  emacs-meta, emacs-ctlx, vi, vi-com-
	      mand, and	vi-insert.  vi is equivalent to	vi-command;  emacs  is
	      equivalent  to  emacs-standard.  The default value is emacs; the
	      value of editing-mode also affects the default keymap.
       keyseq-timeout (500)
	      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 re-
	      ceived within the	timeout, readline will	use  the  shorter  but
	      complete	key sequence.  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.
       mark-directories	(On)
	      If set to	On, completed directory	names have a slash appended.
       mark-modified-lines (Off)
	      If set to	On, history lines that have  been  modified  are  dis-
	      played with a preceding asterisk (*).
       mark-symlinked-directories (Off)
	      If set to	On, completed names which are symbolic links to	direc-
	      tories have a slash appended (subject to the value  of  mark-di-
	      rectories).
       match-hidden-files (On)
	      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.
       menu-complete-display-prefix (Off)
	      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.
       output-meta (Off)
	      If set to	On, readline will display characters with  the	eighth
	      bit set directly rather than as a	meta-prefixed escape sequence.
       page-completions	(On)
	      If  set to On, readline uses an internal more-like pager to dis-
	      play a screenful of possible completions at a time.
       print-completions-horizontally (Off)
	      If set to	On, readline will  display  completions	 with  matches
	      sorted  horizontally in alphabetical order, rather than down the
	      screen.
       revert-all-at-newline (Off)
	      If set to	On, readline will undo all changes  to	history	 lines
	      before returning when accept-line	is executed.  By default, his-
	      tory lines may be	modified  and  retain  individual  undo	 lists
	      across calls to readline.
       show-all-if-ambiguous (Off)
	      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.
       show-all-if-unmodified (Off)
	      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	possi-
	      ble  partial  completion (the possible completions don't share a
	      common prefix) cause the matches to be  listed  immediately  in-
	      stead of ringing the bell.
       show-mode-in-prompt (Off)
	      If set to	On, add	a character to the beginning of	the prompt in-
	      dicating the editing mode: emacs (@), vi command (:) or  vi  in-
	      sertion (+).
       skip-completed-text (Off)
	      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.
       visible-stats (Off)
	      If set to	On, a character	denoting a file's type as reported  by
	      stat(2)  is  appended to the filename when listing possible com-
	      pletions.

   Readline Conditional	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 edit-
	      ing mode,	the terminal being  used,  or  the  application	 using
	      readline.	  The text of the test extends to the end of the line;
	      no characters are	required to isolate it.

	      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  in-
		     stance,   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	the both full name of the ter-
		     minal  and	 the  portion  of the terminal name before the
		     first -.  This allows sun to match	both sun and  sun-cmd,
		     for instance.

	      application
		     The application construct is used to include application-
		     specific settings.	 Each program using the	 readline  li-
		     brary  sets  the  application name, and an	initialization
		     file can test for a particular value.  This could be used
		     to	 bind key sequences to functions useful	for a specific
		     program.  For instance, the following command adds	a  key
		     sequence  that  quotes  the  current  or previous word in
		     bash:

		     $if Bash
		     # Quote the current or previous word
		     "\C-xq": "\eb\"\ef\""
		     $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 follow-
	      ing directive would read /etc/inputrc:

	      $include	/etc/inputrc

   Searching
       Readline	provides commands for searching	through	 the  command  history
       (see HISTORY below) 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, read-
       line displays the next entry from the history matching the string typed
       so  far.	  An  incremental  search  requires only as many characters as
       needed to find the desired history entry.  The  characters  present  in
       the  value of the isearch-terminators variable are used to terminate an
       incremental search.  If that variable has not been assigned a value the
       Escape  and  Control-J characters will terminate	an incremental search.
       Control-G will abort an incremental search  and	restore	 the  original
       line.   When the	search is terminated, the history entry	containing the
       search string becomes the current line.

       To find other matching entries in the history list, type	 Control-S  or
       Control-R  as appropriate.  This	will search backward or	forward	in the
       history for the next entry matching the search  string  typed  so  far.
       Any  other  key sequence	bound to a readline command will terminate the
       search and execute that command.	 For instance, a newline  will	termi-
       nate the	search and accept the line, thereby executing the command from
       the history list.

       Readline	remembers the last incremental search string.  If two Control-
       Rs  are	typed without any intervening characters defining a new	search
       string, any remembered search string is used.

       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.

   Readline Command Names
       The following is	a list of the names of the commands  and  the  default
       key sequences to	which they are bound.  Command names without an	accom-
       panying key sequence are	unbound	by default.  In	the following descrip-
       tions,  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.

   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
	      alphanumeric characters (letters and digits).
       backward-word (M-b)
	      Move back	to the start of	the current or previous	 word.	 Words
	      are composed of alphanumeric characters (letters and digits).
       shell-forward-word
	      Move  forward  to	the end	of the next word.  Words are delimited
	      by non-quoted shell metacharacters.
       shell-backward-word
	      Move back	to the start of	the current or previous	 word.	 Words
	      are delimited by non-quoted shell	metacharacters.
       clear-screen (C-l)
	      Clear  the  screen  leaving  the	current	line at	the top	of the
	      screen.  With an argument,  refresh  the	current	 line  without
	      clearing the screen.
       redraw-current-line
	      Refresh the current line.

   Commands for	Manipulating the History
       accept-line (Newline, 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	 state
	      of  the HISTCONTROL variable.  If	the line is a modified history
	      line, then restore the history line to its original state.
       previous-history	(C-p)
	      Fetch the	previous command from the history list,	moving back in
	      the list.
       next-history (C-n)
	      Fetch  the next command from the history list, moving forward in
	      the list.
       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.
       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.
       non-incremental-reverse-search-history (M-p)
	      Search backward through the history starting at the current line
	      using a non-incremental search for  a  string  supplied  by  the
	      user.
       non-incremental-forward-search-history (M-n)
	      Search  forward  through	the  history  using  a non-incremental
	      search for a string supplied by the user.
       history-search-forward
	      Search forward through the history for the string	of  characters
	      between  the start of the	current	line and the point.  This is a
	      non-incremental search.
       history-search-backward
	      Search backward through the history for the string of characters
	      between  the start of the	current	line and the point.  This is a
	      non-incremental search.
       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 in-
	      serts 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-., M-_)
	      Insert the 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 word, as	if the "!$" history expansion had been
	      specified.
       shell-expand-line (M-C-e)
	      Expand the line as the shell does.  This performs	alias and his-
	      tory expansion as	well as	all of the shell word expansions.  See
	      HISTORY EXPANSION	below for a description	of history expansion.
       history-expand-line (M-^)
	      Perform history expansion	on the current line.  See HISTORY  EX-
	      PANSION below for	a description of history expansion.
       magic-space
	      Perform  history	expansion  on  the  current  line and insert a
	      space.  See HISTORY EXPANSION below for a	description of history
	      expansion.
       alias-expand-line
	      Perform  alias expansion on the current line.  See ALIASES above
	      for a description	of alias expansion.
       history-and-alias-expand-line
	      Perform history and alias	expansion on the current line.
       insert-last-argument (M-., M-_)
	      A	synonym	for yank-last-arg.
       operate-and-get-next (C-o)
	      Accept the current line for execution and	fetch  the  next  line
	      relative	to the current line from the history for editing.  Any
	      argument is ignored.
       edit-and-execute-command	(C-xC-e)
	      Invoke an	editor on the current command line,  and  execute  the
	      result as	shell commands.	 Bash attempts to invoke $VISUAL, $ED-
	      ITOR, and	emacs as the editor, in	that order.

   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 charac-
	      ters 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.  When given a numeric
	      argument,	save the deleted text on the kill ring.
       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 cur-
	      sor is deleted.
       quoted-insert (C-q, C-v)
	      Add the next character typed to the line verbatim.  This is  how
	      to insert	characters like	C-q, for example.
       tab-insert (C-v TAB)
	      Insert a tab character.
       self-insert (a, b, A, 1,	!, ...)
	      Insert the character typed.
       transpose-chars (C-t)
	      Drag  the	 character  before point forward over the character at
	      point, moving point forward as well.  If point is	at the end  of
	      the  line, then this transposes the two characters before	point.
	      Negative arguments have no effect.
       transpose-words (M-t)
	      Drag the word before point past the  word	 after	point,	moving
	      point  over  that	 word  as well.	 If point is at	the end	of the
	      line, this transposes the	last two words on the line.
       upcase-word (M-u)
	      Uppercase	the current (or	following) word.  With a negative  ar-
	      gument, uppercase	the previous word, but do not move point.
       downcase-word (M-l)
	      Lowercase	 the current (or following) word.  With	a negative ar-
	      gument, lowercase	the previous word, but do not move point.
       capitalize-word (M-c)
	      Capitalize the current (or following) word.  With	a negative ar-
	      gument, capitalize the previous word, but	do not move point.
       overwrite-mode
	      Toggle  overwrite	mode.  With an explicit	positive numeric argu-
	      ment, 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, charac-
	      ters bound to self-insert	replace	the text at point rather  than
	      pushing  the  text  to  the  right.   Characters	bound to back-
	      ward-delete-char replace	the  character	before	point  with  a
	      space.  By default, this command is unbound.

   Killing and Yanking
       kill-line (C-k)
	      Kill the text from point to the end of the line.
       backward-kill-line (C-x Rubout)
	      Kill backward to the beginning of	the line.
       unix-line-discard (C-u)
	      Kill  backward  from  point  to  the beginning of	the line.  The
	      killed text is saved on the kill-ring.
       kill-whole-line
	      Kill all characters on the current line, no matter  where	 point
	      is.
       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 those used by forward-word.
       backward-kill-word (M-Rubout)
	      Kill  the	 word  behind  point.  Word boundaries are the same as
	      those used by backward-word.
       shell-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 those used by shell-forward-word.
       shell-backward-kill-word	(M-Rubout)
	      Kill the word behind point.  Word	boundaries  are	 the  same  as
	      those used by shell-backward-word.
       unix-word-rubout	(C-w)
	      Kill  the	 word behind point, using white	space as a word	bound-
	      ary.  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 (M-\)
	      Delete all spaces	and tabs around	point.
       kill-region
	      Kill the text in the current region.
       copy-region-as-kill
	      Copy the text in the region to the kill buffer.
       copy-backward-word
	      Copy the word before point to the	kill buffer.  The word	bound-
	      aries are	the same as backward-word.
       copy-forward-word
	      Copy  the	 word  following  point	 to the	kill buffer.  The word
	      boundaries are the same as forward-word.
       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.  Only	works  follow-
	      ing yank or yank-pop.

   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  fol-
	      lowed by digits, executing universal-argument again ends the nu-
	      meric argument, but is otherwise ignored.	 As a special case, if
	      this command is immediately followed by a	character that is nei-
	      ther a digit or minus sign, the argument count for the next com-
	      mand  is	multiplied  by	four.  The argument count is initially
	      one, so executing	this function the first	time makes  the	 argu-
	      ment count four, a second	time makes the argument	count sixteen,
	      and so on.

   Completing
       complete	(TAB)
	      Attempt to perform completion on the text	 before	 point.	  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.
       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 ar-
	      gument may be used to move backward through the list.  This com-
	      mand 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.  This command is unbound by default.
       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 com-
	      pletions	enclosed within	braces so the list is available	to the
	      shell (see Brace Expansion above).

   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 store	the definition.
       call-last-kbd-macro (C-x	e)
	      Re-execute the last keyboard macro defined, by making the	 char-
	      acters 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.

   Miscellaneous
       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-uppercase-version (M-a, M-b, M-x, ...)
	      If the metafied character	x is lowercase,	run the	 command  that
	      is bound to the corresponding uppercase character.
       prefix-meta (ESC)
	      Metafy the next character	typed.	ESC f is equivalent to Meta-f.
       undo (C-_, 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 return  the	line  to  its  initial
	      state.
       tilde-expand (M-&)
	      Perform tilde expansion on the current word.
       set-mark	(C-@, M-<space>)
	      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 count searches for previous	occur-
	      rences.
       character-search-backward (M-C-])
	      A	character is read and point is moved to	 the  previous	occur-
	      rence  of	 that character.  A negative count searches for	subse-
	      quent 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 "\[", 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	readline  com-
	      ment-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,	other-
	      wise the characters in comment-begin are deleted from the	begin-
	      ning 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 re-
	      moved, the line will be executed by the shell.
       glob-complete-word (M-g)
	      The word before point is treated as a pattern for	 pathname  ex-
	      pansion,	with an	asterisk implicitly appended.  This pattern is
	      used to generate a list of matching filenames for	possible  com-
	      pletions.
       glob-expand-word	(C-x *)
	      The  word	 before	point is treated as a pattern for pathname ex-
	      pansion, and the list of matching	filenames is inserted, replac-
	      ing the word.  If	a numeric argument is supplied,	an asterisk 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, an	asterisk  is  appended	before
	      pathname expansion.
       dump-functions
	      Print  all  of the functions and their key bindings to the read-
	      line output stream.  If a	numeric	argument is supplied, the out-
	      put  is  formatted  in such a way	that it	can be made part of an
	      inputrc file.
       dump-variables
	      Print all	of the settable	readline variables and their values to
	      the  readline output stream.  If a numeric argument is supplied,
	      the output is formatted in such a	way that it can	be  made  part
	      of an inputrc file.
       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.
       display-shell-version (C-x C-v)
	      Display version information about	the current instance of	bash.

   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 (see SHELL BUILTIN COMMANDS	below),	 the  program-
       mable completion	facilities are invoked.

       First,  the  command  name  is  identified.  If the command word	is the
       empty string (completion	attempted at the beginning of an empty	line),
       any  compspec  defined  with  the  -E option to complete	is used.  If a
       compspec	has been defined for that command, the	compspec  is  used  to
       generate	the list of possible completions for the word.	If the command
       word is a full pathname,	a compspec for the full	pathname  is  searched
       for  first.   If	no compspec is found for the full pathname, an attempt
       is made to find a compspec for the portion following the	 final	slash.
       If  those  searches  do	not result in a	compspec, any compspec defined
       with the	-D option to complete is used as the default.

       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 comple-
       tion as described above under Completing	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.

       Any completions specified by a pathname expansion pattern to the	-G op-
       tion 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 variable is used.

       Next, the string	specified as the argument to the -W option is  consid-
       ered.   The  string is first split using	the characters in the IFS spe-
       cial variable as	delimiters.  Shell quoting is honored.	Each  word  is
       then  expanded  using  brace  expansion,	tilde expansion, parameter and
       variable	expansion, command substitution, and arithmetic	expansion,  as
       described above under EXPANSION.	 The results are split using the rules
       described above under 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	under Shell 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  be-
       ing  completed,	the  second argument ($2) is the word being completed,
       and the third argument ($3) is the word preceding the word  being  com-
       pleted on the current command line.  No filtering of the	generated com-
       pletions	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  builtin  described
       below,  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	 envi-
       ronment	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	speci-
       fied with the -X	option is applied to the list.	The filter is  a  pat-
       tern  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	match-
       ing the pattern will be removed.

       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 de-
       fined, 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 sup-
       plied to	complete when the compspec was defined,	the bash default  com-
       pletions	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	speci-
       fied with complete -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 de-
       fault 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

HISTORY
       When the	-o history option to the set builtin  is  enabled,  the	 shell
       provides	access to the command history, the list	of commands previously
       typed.  The value of the	HISTSIZE variable is used  as  the  number  of
       commands	to save	in a history list.  The	text of	the last HISTSIZE com-
       mands (default 500) is saved.  The shell	stores	each  command  in  the
       history	list  prior to parameter and variable expansion	(see EXPANSION
       above) but after	history	expansion is performed,	subject	to the	values
       of the shell variables HISTIGNORE and HISTCONTROL.

       On startup, the history is initialized from the file named by the vari-
       able HISTFILE (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 HISTFILESIZE.	 If  HISTFILE-
       SIZE  is	unset, or set to null, a non-numeric value, or a numeric value
       less than zero, the history file	is not truncated.   When  the  history
       file  is	 read, lines beginning with the	history	comment	character fol-
       lowed immediately by a digit are	interpreted as timestamps for the pre-
       ceding history line.  These timestamps are optionally displayed depend-
       ing on the value	of the HISTTIMEFORMAT variable.	  When	a  shell  with
       history	enabled	 exits,	 the  last $HISTSIZE lines are copied from the
       history list to $HISTFILE.  If the histappend shell option  is  enabled
       (see  the description of	shopt under SHELL BUILTIN COMMANDS below), the
       lines are appended to the history file, otherwise the history  file  is
       overwritten.   If  HISTFILE  is	unset,	or  if the history file	is un-
       writable, the history is	not saved.  If the HISTTIMEFORMAT variable  is
       set,  time stamps are written to	the history file, marked with the his-
       tory comment character, so they may be preserved	across shell sessions.
       This  uses the history comment character	to distinguish timestamps from
       other history lines.  After saving the history,	the  history  file  is
       truncated  to contain no	more than 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.

       The  builtin  command fc	(see SHELL BUILTIN COMMANDS below) may be used
       to list or edit and re-execute a	portion	of the history list.  The his-
       tory  builtin may be used to display or modify the history list and ma-
       nipulate	the history file.  When	 using	command-line  editing,	search
       commands	 are available in each editing mode that provide access	to the
       history list.

       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.  See	the description	of the shopt builtin below under SHELL
       BUILTIN COMMANDS	for information	on setting  and	 unsetting  shell  op-
       tions.

HISTORY	EXPANSION
       The  shell  supports a history expansion	feature	that is	similar	to the
       history expansion in csh.  This section describes what syntax  features
       are  available.	 This  feature	is  enabled by default for interactive
       shells, and can be disabled using the +H	option to the set builtin com-
       mand (see SHELL BUILTIN COMMANDS	below).	 Non-interactive shells	do not
       perform history expansion by default.

       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.  It	 takes	place  in  two
       parts.	The  first is to determine which line from the history list to
       use during substitution.	 The second is to select portions of that line
       for inclusion into the current one.  The	line selected from the history
       is the event, and the portions of that line that	 are  acted  upon  are
       words.	Various	 modifiers  are	 available  to manipulate the selected
       words.  The line	is broken into words in	the same fashion as when read-
       ing  input, so that several metacharacter-separated words surrounded by
       quotes are considered one word.	History	expansions are	introduced  by
       the  appearance	of  the	history	expansion character, which is !	by de-
       fault.  Only backslash (\) and single quotes can	quote the history  ex-
       pansion character.

       Several	characters inhibit history expansion if	found immediately fol-
       lowing the history expansion character, even if it is unquoted:	space,
       tab,  newline,  carriage	return,	and =.	If the extglob shell option is
       enabled,	( will also inhibit expansion.

       Several shell options settable with the shopt builtin may  be  used  to
       tailor  the behavior of history expansion.  If the histverify shell op-
       tion is enabled (see the	description of the shopt builtin  below),  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	substitution 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.

       The shell allows	control	of the various characters used by the  history
       expansion mechanism (see	the description	of histchars above under Shell
       Variables).  The	shell uses the history comment character to mark  his-
       tory timestamps when writing the	history	file.

   Event Designators
       An  event designator is a reference to a	command	line entry in the his-
       tory 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	blank,
	      newline, carriage	return,	= or ( (when the extglob shell	option
	      is enabled using the shopt builtin).
       !n     Refer to command line n.
       !-n    Refer to the current command minus n.
       !!     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 string	is followed immediately	by a newline.
       ^string1^string2^
	      Quick substitution.   Repeat  the	 previous  command,  replacing
	      string1  with  string2.  Equivalent to ``!!:s/string1/string2/''
	      (see Modifiers below).
       !#     The entire command line typed so far.

   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	 sepa-
       rated by	single spaces.

       0 (zero)
	      The zeroth word.	For the	shell, this is the command word.
       n      The nth word.
       ^      The first	argument.  That	is, word 1.
       $      The  last	word.  This is usually the last	argument, but will ex-
	      pand to the zeroth word if there is only one word	in the line.
       %      The word matched by the most recent `?string?' search.
       x-y    A	range of words;	`-y' abbreviates `0-y'.
       *      All of the words but the zeroth.	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 a word designator is supplied	without	an  event  specification,  the
       previous	command	is used	as the event.

   Modifiers
       After  the optional word	designator, there may appear a sequence	of one
       or more of the following	modifiers, each	preceded by a `:'.

       h      Remove a trailing	filename component, leaving only the head.
       t      Remove all leading filename components, leaving the tail.
       r      Remove a trailing	suffix of the form .xxx, 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
	      blanks and newlines.
       s/old/new/
	      Substitute  new  for  the	 first	occurrence of old in the event
	      line.  Any delimiter can be used in place	of /.  The  final  de-
	      limiter  is  optional  if	 it is the last	character of the event
	      line.  The delimiter may be quoted in old	and new	with a	single
	      backslash.   If &	appears	in new,	it is replaced by old.	A sin-
	      gle backslash will quote the &.  If old is null, it  is  set  to
	      the  last	 old substituted, or, if no previous history substitu-
	      tions took place,	the last string	in a !?string[?]  search.
       &      Repeat the previous substitution.
       g      Cause changes to be applied over the entire event	line.  This is
	      used  in	conjunction  with `:s' (e.g., `:gs/old/new/') or `:&'.
	      If used with `:s', any delimiter can be used in place of /,  and
	      the  final  delimiter is optional	if it is the last character of
	      the event	line.  An a may	be used	as a synonym for g.
       G      Apply the	following `s' modifier once to each word in the	 event
	      line.

SHELL BUILTIN COMMANDS
       Unless otherwise	noted, each builtin command documented in this section
       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, break,	continue, let,
       and  shift builtins accept and process arguments	beginning with - with-
       out 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.
       : [arguments]
	      No effect; the command does nothing beyond  expanding  arguments
	      and  performing any specified redirections.  A zero exit code is
	      returned.

	.  filename [arguments]
       source filename [arguments]
	      Read and execute commands	from filename in the current shell en-
	      vironment	 and  return  the exit status of the last command exe-
	      cuted from filename.  If filename	 does  not  contain  a	slash,
	      filenames	 in  PATH  are	used  to find the directory containing
	      filename.	 The file searched for in PATH need not	be executable.
	      When  bash  is  not  in  posix  mode,  the  current directory is
	      searched if no file is found in PATH.  If	the sourcepath	option
	      to  the  shopt  builtin  command	is turned off, the PATH	is not
	      searched.	 If any	arguments are supplied,	they become the	 posi-
	      tional  parameters when filename is executed.  Otherwise the po-
	      sitional parameters are unchanged.  The  return  status  is  the
	      status  of  the  last  command exited within the script (0 if no
	      commands are executed), and false	if filename is	not  found  or
	      cannot be	read.

       alias [-p] [name[=value]	...]
	      Alias with no arguments or with the -p option prints the list of
	      aliases in the form alias	name=value on standard	output.	  When
	      arguments	 are supplied, an alias	is defined for each name whose
	      value is given.  A trailing space	in  value causes the next word
	      to be checked for	alias substitution when	the alias is expanded.
	      For each name in the argument list for which no  value  is  sup-
	      plied,  the  name	 and value of the alias	is printed.  Alias re-
	      turns true unless	a name is given	for which no  alias  has  been
	      defined.

       bg [jobspec ...]
	      Resume  each  suspended  job jobspec in the background, as if it
	      had been started with &.	If jobspec is not present, the shell's
	      notion  of the current job is used.  bg jobspec returns 0	unless
	      run when job control is disabled or, when	run with  job  control
	      enabled,	any  specified	jobspec	 was  not found	or was started
	      without job control.

       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 readline-command
	      Display current readline 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 ap-
	      pear  in .inputrc, but each binding or command must be passed as
	      a	separate argument; e.g., '"\C-x\C-r": re-read-init-file'.  Op-
	      tions, 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-stan-
		     dard,  emacs-meta,	 emacs-ctlx,  vi, vi-move, vi-command,
		     and vi-insert.  vi	is equivalent to vi-command; 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 re-read.
	      -P     List current readline function names and bindings.
	      -s     Display readline key sequences bound to  macros  and  the
		     strings  they  output  in such a way that they can	be re-
		     read.
	      -S     Display readline key sequences bound to  macros  and  the
		     strings they output.
	      -v     Display  readline variable	names and values in such a way
		     that they can be re-read.
	      -V     List current readline variable names and values.
	      -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 en-
		     tered.   When  shell-command  is executed,	the shell sets
		     the READLINE_LINE variable	to the contents	of  the	 read-
		     line  line	 buffer	and the	READLINE_POINT variable	to the
		     current location of the insertion point.  If the executed
		     command  changes  the  value  of  READLINE_LINE  or READ-
		     LINE_POINT, 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 in-
		     put.

	      The  return value	is 0 unless an unrecognized option is given or
	      an error occurred.

       break [n]
	      Exit from	within a for, while, until, or select loop.  If	 n  is
	      specified,  break	 n  levels.   n	must be	>= 1.  If n is greater
	      than the number of enclosing loops, all enclosing	loops are  ex-
	      ited.   The  return  value  is 0 unless n	is not greater than or
	      equal to 1.

       builtin shell-builtin [arguments]
	      Execute the specified shell builtin, passing it  arguments,  and
	      return its exit status.  This is useful when defining a function
	      whose name is the	same as	a shell	builtin, retaining  the	 func-
	      tionality	of the builtin within the function.  The cd builtin is
	      commonly redefined this way.  The	 return	 status	 is  false  if
	      shell-builtin is not a shell builtin command.

       caller [expr]
	      Returns the context of any active	subroutine call	(a shell func-
	      tion or a	script executed	with the . or source builtins).	 With-
	      out expr,	caller displays	the line number	and source filename of
	      the current subroutine call.  If a non-negative integer is  sup-
	      plied 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 sub-
	      routine call or expr does	not correspond to a valid position  in
	      the call stack.

       cd [-L|[-P [-e]]	[-@]] [dir]
	      Change  the  current  directory to dir.  if dir is not supplied,
	      the value	of the HOME shell variable is the default.  Any	 addi-
	      tional arguments following dir are ignored.  The variable	CDPATH
	      defines the search path for the directory	containing  dir:  each
	      directory	 name  in CDPATH is searched for dir.  Alternative di-
	      rectory names in CDPATH are separated by a colon	(:).   A  null
	      directory	 name  in CDPATH is the	same as	the current directory,
	      i.e., ``.''.  If dir begins with a slash (/), then CDPATH	is not
	      used.  The  -P  option  causes  cd to use	the physical directory
	      structure	by resolving symbolic links while traversing  dir  and
	      before processing	instances of ..	in dir (see also the -P	option
	      to the set builtin command); the -L option forces	symbolic links
	      to  be followed by resolving the link after processing instances
	      of .. in dir.  If	.. appears in dir, it is processed by removing
	      the  immediately previous	pathname component from	dir, back to a
	      slash or the beginning of	dir.  If the  -e  option  is  supplied
	      with  -P,	 and  the current working directory cannot be success-
	      fully 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.  An argument of - is converted to $OLDPWD
	      before the directory change is attempted.	 If a non-empty	direc-
	      tory  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.
	      The return value is  true	 if  the  directory  was  successfully
	      changed; false otherwise.

       command [-pVv] command [arg ...]
	      Run  command  with  args	suppressing  the normal	shell function
	      lookup. Only builtin commands or commands	found in the PATH  are
	      executed.	  If the -p option is given, the search	for command is
	      performed	using a	default	value for PATH that is	guaranteed  to
	      find  all	of the standard	utilities.  If either the -V or	-v op-
	      tion is supplied,	a description of command is printed.   The  -v
	      option  causes  a	single word indicating the command or filename
	      used to invoke command to	be displayed; the -V option produces a
	      more  verbose  description.  If the -V or	-v option is supplied,
	      the exit status is 0 if command was found, and  1	 if  not.   If
	      neither option is	supplied and an	error occurred or command can-
	      not be found, the	exit status is 127.  Otherwise,	the exit  sta-
	      tus of the command builtin is the	exit status of command.

       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 fa-
	      cilities,	while available, will not have useful values.

	      The matches will be generated in the same	way as if the program-
	      mable completion code had	generated them directly	from a comple-
	      tion 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	[-abcdefgjksuv]	[-o comp-option] [-DE] [-A action]  [-G	 glob-
       pat] [-W	wordlist] [-F function]	[-C command]
	      [-X filterpat] [-P prefix] [-S suffix] name [name	...]
       complete	-pr [-DE] [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 spec-
	      ification	 for each name,	or, if no names	are supplied, all com-
	      pletion specifications.  The -D option indicates	that  the  re-
	      maining options and actions should apply to the ``default'' com-
	      mand completion; that is,	completion attempted on	a command  for
	      which  no	completion has previously been defined.	 The -E	option
	      indicates	that the remaining options and actions should apply to
	      ``empty''	command	completion; that is, completion	attempted on a
	      blank line.

	      The process of applying  these  completion  specifications  when
	      word  completion	is attempted is	described above	under Program-
	      mable 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	expan-
	      sion before the complete builtin is invoked.
	      -o comp-option
		      The  comp-option	controls  several aspects of the comp-
		      spec's behavior beyond the simple	generation of  comple-
		      tions.  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 comp-
			      spec generates no	matches.
		      filenames
			      Tell readline that the compspec generates	 file-
			      names,  so  it can perform any filename-specific
			      processing (like adding  a  slash	 to  directory
			      names,  quoting special characters, or suppress-
			      ing trailing spaces).  Intended to be used  with
			      shell functions.
		      noquote Tell  readline  not to quote the completed words
			      if they are filenames (quoting filenames is  the
			      default).
		      nospace Tell  readline  not  to  append a	space (the de-
			      fault) to	words completed	 at  the  end  of  the
			      line.
		      plusdirs
			      After  any  matches  defined by the compspec are
			      generated,  directory  name  completion  is  at-
			      tempted 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.
		      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.
		      hostname
			      Hostnames,  as  taken from the file specified by
			      the HOSTFILE shell variable.
		      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.
		      shopt   Shell  option  names  as	accepted  by the shopt
			      builtin.
		      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 spec-
			      ified as -v.
	      -C command
		      command  is  executed in a subshell environment, and its
		      output is	used as	the possible completions.
	      -F function
		      The shell	function function is executed in  the  current
		      shell  environment.   When the function is executed, the
		      first argument ($1) is the name of the command whose ar-
		      guments 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 cur-
		      rent command line.  When it finishes, the	possible  com-
		      pletions	are  retrieved from the	value of the COMPREPLY
		      array variable.
	      -G globpat
		      The pathname expansion pattern globpat  is  expanded  to
		      generate the possible completions.
	      -P prefix
		      prefix  is  added	at the beginning of each possible com-
		      pletion 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  com-
		      pleted.
	      -X filterpat
		      filterpat	 is  a pattern as used for pathname expansion.
		      It is applied to the list	of possible completions	gener-
		      ated  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 argu-
	      ment, 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 [-o option] [-DE] [+o option] [name]
	      Modify completion	options	for each name  according  to  the  op-
	      tions, or	for the	currently-executing completion if no names are
	      supplied.	 If no options are given, display the  completion  op-
	      tions  for  each	name  or the current completion.  The possible
	      values of	option are those valid for the	complete  builtin  de-
	      scribed  above.	The -D option indicates	that the remaining op-
	      tions 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  the
	      remaining	 options should	apply to ``empty'' command completion;
	      that is, completion attempted on a blank line.

	      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.

       continue	[n]
	      Resume the next iteration	of the enclosing for, while, until, or
	      select  loop.   If  n  is	specified, resume at the nth enclosing
	      loop.  n must be >= 1.  If n is greater than the number  of  en-
	      closing  loops, the last enclosing loop (the ``top-level'' loop)
	      is resumed.  The return value is 0 unless	n is not greater  than
	      or equal to 1.

       declare [-aAfFgilnrtux] [-p] [name[=value] ...]
       typeset [-aAfFgilnrtux] [-p] [name[=value] ...]
	      Declare  variables and/or	give them attributes.  If no names are
	      given then display the values of variables.  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, it
	      will display the attributes and values of	all  variables	having
	      the attributes specified by the additional options.  If no other
	      options are supplied with	 -p,  declare  will  display  the  at-
	      tributes	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,  the  source  file	name and line number where the
	      function is defined are displayed	as well.  The  -F  option  im-
	      plies -f.	 The -g	option forces variables	to be created or modi-
	      fied at the global scope,	even when declare  is  executed	 in  a
	      shell  function.	It is ignored in all other cases.  The follow-
	      ing options can be used to restrict output to variables with the
	      specified	attribute or to	give variables attributes:
	      -a     Each  name	 is  an	 indexed  array	 variable  (see	Arrays
		     above).
	      -A     Each name is an associative array	variable  (see	Arrays
		     above).
	      -f     Use function names	only.
	      -i     The variable is treated as	an integer; arithmetic evalua-
		     tion (see ARITHMETIC EVALUATION above) 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 and assign-
		     ments to name, except for changing	the -n	attribute  it-
		     self,  are	performed on the variable referenced by	name's
		     value.  The -n attribute cannot be	applied	to array vari-
		     ables.
	      -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 in-
		     herit  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 names	for export to subsequent commands via the  en-
		     vironment.

	      Using  `+'  instead of `-' turns off the attribute instead, with
	      the exceptions that +a may not be	used to	destroy	an array vari-
	      able  and	 +r will not remove the	readonly attribute.  When used
	      in a function, declare and typeset make each name	local, as with
	      the local	command, unless	the -g option is supplied.  If a vari-
	      able 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 value is 0
	      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 as-
	      sign a value to an array variable	without	using the compound as-
	      signment syntax (see Arrays above), one of the names  is	not  a
	      valid  shell variable name, an attempt is	made to	turn off read-
	      only 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.

       dirs [-clpv] [+n] [-n]
	      Without options, displays	the list of currently  remembered  di-
	      rectories.   The default display is on a single line with	direc-
	      tory names separated by spaces.  Directories are	added  to  the
	      list  with  the  pushd command; the popd command removes entries
	      from the list.
	      -c     Clears the	directory stack	by deleting  all  of  the  en-
		     tries.
	      -l     Produces  a  listing  using  full	pathnames; the default
		     listing format uses a tilde to denote the home directory.
	      -p     Print the directory stack with one	entry per line.
	      -v     Print the directory stack with one	entry per  line,  pre-
		     fixing each entry with its	index in the stack.
	      +n     Displays the nth entry counting from the left of the list
		     shown by dirs when	invoked	without	options, starting with
		     zero.
	      -n     Displays  the  nth	 entry	counting from the right	of the
		     list shown	by dirs	when invoked without options, starting
		     with zero.

	      The  return value	is 0 unless an invalid option is supplied or n
	      indexes beyond the end of	the directory stack.

       disown [-ar] [-h] [jobspec ...]
	      Without options, remove each jobspec from	the  table  of	active
	      jobs.   If jobspec is not	present, and neither the -a nor	the -r
	      option is	supplied, the current job is used.  If the  -h	option
	      is  given,  each	jobspec	 is not	removed	from the table,	but is
	      marked so	that SIGHUP is not sent	to the job if  the  shell  re-
	      ceives a SIGHUP.	If no jobspec is supplied, the -a option means
	      to remove	or mark	all jobs; the -r option	without	a jobspec  ar-
	      gument restricts operation to running jobs.  The return value is
	      0	unless a jobspec does not specify a valid job.

       echo [-neE] [arg	...]
	      Output the args, separated by spaces,  followed  by  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  interpreta-
	      tion  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 es-
	      cape characters by default.  echo	does not interpret -- to  mean
	      the  end	of  options.  echo interprets the following escape se-
	      quences:
	      \a     alert (bell)
	      \b     backspace
	      \c     suppress further output
	      \e
	      \E     an	escape character
	      \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 [-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, each name is disabled; otherwise, names  are  en-
	      abled.   For  example, to	use the	test binary found via the PATH
	      instead of the shell builtin version, run	 ``enable  -n  test''.
	      The  -f  option  means to	load the new builtin command name from
	      shared object filename, on systems that support dynamic loading.
	      The  -d  option will delete a builtin previously loaded with -f.
	      If no name arguments are given, or if the	-p option is supplied,
	      a	list of	shell builtins is printed.  With no other option argu-
	      ments, the list consists of all enabled shell builtins.	If  -n
	      is  supplied, only disabled builtins are printed.	 If -a is sup-
	      plied, the list printed includes all builtins, with  an  indica-
	      tion  of whether or not each is enabled.	If -s is supplied, the
	      output is	restricted to the POSIX	special	builtins.  The	return
	      value  is	 0 unless a name is not	a shell	builtin	or there is an
	      error loading a new builtin from a shared	object.

       eval [arg ...]
	      The args are read	and concatenated together into a  single  com-
	      mand.   This command is then read	and executed by	the shell, and
	      its exit status is returned as the value of eval.	 If there  are
	      no args, or only null arguments, eval returns 0.

       exec [-cl] [-a name] [command [arguments]]
	      If  command is specified,	it replaces the	shell.	No new process
	      is created.  The arguments become	the arguments to command.   If
	      the -l option is supplied, the shell places a dash at the	begin-
	      ning of the zeroth argument passed to command.  This is what lo-
	      gin(1)  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	the executed command.  If command can-
	      not 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.	If command is not specified, any redi-
	      rections take effect in the current shell, and the return	status
	      is 0.  If	there is a redirection error, the return status	is 1.

       exit [n]
	      Cause  the  shell	 to exit with a	status of n.  If n is omitted,
	      the exit status is that of the last command executed.  A trap on
	      EXIT is executed before the shell	terminates.

       export [-fn] [name[=word]] ...
       export -p
	      The  supplied names are marked for automatic export to the envi-
	      ronment of subsequently executed commands.  If the -f option  is
	      given,  the names	refer to functions.  If	no names are given, or
	      if the -p	option is supplied, a list of names  of	 all  exported
	      variables	 is printed.  The -n option causes the export property
	      to be removed from each name.  If	a variable name	is followed by
	      =word, the value of the variable is set to word.	export returns
	      an exit status of	0 unless an invalid option is encountered, one
	      of  the  names is	not a valid shell variable name, or -f is sup-
	      plied with a name	that is	not a function.

       fc [-e ename] [-lnr] [first] [last]
       fc -s [pat=rep] [cmd]
	      The first	form selects a range of	commands from  first  to  last
	      from  the	 history  list	and  displays or edits and re-executes
	      them.  First and last may	be specified as	a  string  (to	locate
	      the  last	command	beginning with that string) or as a number (an
	      index into the history list, where a negative number is used  as
	      an  offset  from	the  current  command number).	If last	is not
	      specified	it is set to the current command for listing (so  that
	      ``fc  -l	-10'' prints the last 10 commands) and to first	other-
	      wise.  If	first is not specified it is set to the	previous  com-
	      mand for editing and -16 for listing.

	      The  -n option suppresses	the command numbers when listing.  The
	      -r option	reverses the order of the commands.  If	the -l	option
	      is  given,  the  commands	are listed on standard output.	Other-
	      wise, the	editor given by	ename is invoked on a file  containing
	      those  commands.	If ename is not	given, the value of the	FCEDIT
	      variable is used,	and the	value of EDITOR	if FCEDIT is not  set.
	      If  neither  variable  is	set, vi	is used.  When editing is com-
	      plete, the edited	commands are echoed and	executed.

	      In the second form, command is re-executed after	each  instance
	      of  pat  is  replaced by rep.  Command is	intepreted the same as
	      first above.  A useful alias to use with this is ``r="fc	-s"'',
	      so  that	typing	``r  cc'' runs the last	command	beginning with
	      ``cc'' and typing	``r'' re-executes the last command.

	      If the first form	is used, the return value is 0 unless  an  in-
	      valid  option  is	 encountered  or first or last specify history
	      lines out	of range.  If the -e option is	supplied,  the	return
	      value is the value of the	last command executed or failure if an
	      error occurs with	the temporary file of commands.	 If the	second
	      form  is	used, the return status	is that	of the command re-exe-
	      cuted, unless cmd	does not specify  a  valid  history  line,  in
	      which case fc returns failure.

       fg [jobspec]
	      Resume  jobspec  in the foreground, and make it the current job.
	      If jobspec is not	present, the shell's notion of the current job
	      is  used.	  The  return value is that of the command placed into
	      the foreground, or failure if run	when job control  is  disabled
	      or, when run with	job control enabled, if	jobspec	does not spec-
	      ify a valid job or jobspec specifies  a  job  that  was  started
	      without job control.

       getopts optstring name [args]
	      getopts  is used by shell	procedures to parse positional parame-
	      ters.  optstring contains	the option  characters	to  be	recog-
	      nized;  if a character is	followed by a colon, the option	is ex-
	      pected to	have an	argument, which	should be separated from it by
	      white  space.  The colon and question mark characters may	not be
	      used as option characters.  Each time  it	 is  invoked,  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 op-
	      tion 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 re-
	      turn 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 given in args, 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  dis-
	      played, 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 OP-
	      TARG 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.

	      getopts returns true if an option, specified or unspecified,  is
	      found.  It returns false if the end of options is	encountered or
	      an error occurs.

       hash [-lr] [-p filename]	[-dt] [name]
	      Each time	hash is	invoked, the full pathname of the command name
	      is  determined  by searching the directories in $PATH and	remem-
	      bered.  Any previously-remembered	pathname is discarded.	If the
	      -p option	is supplied, no	path search is performed, and filename
	      is used as the full filename of  the  command.   The  -r	option
	      causes the shell to forget all remembered	locations.  The	-d op-
	      tion 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 for-
	      mat  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 true unless a name is not found
	      or an invalid option is supplied.

       help [-dms] [pattern]
	      Display helpful information about	builtin	commands.  If  pattern
	      is  specified, help gives	detailed help on all commands matching
	      pattern; otherwise help for all the builtins and	shell  control
	      structures is printed.
	      -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 0 unless no command matches pattern.

       history [n]
       history -c
       history -d offset
       history -anrw [filename]
       history -p arg [arg ...]
       history -s arg [arg ...]
	      With no options, display the command history list	with line num-
	      bers.  Lines listed with a * have	been modified.	An argument of
	      n	lists only the last n lines.  If the shell variable  HISTTIME-
	      FORMAT  is  set  and not null, it	is used	as a format string for
	      strftime(3) to display the time stamp associated with each  dis-
	      played  history  entry.  No intervening blank is printed between
	      the formatted time stamp and the history line.  If  filename  is
	      supplied,	 it  is	 used as the name of the history file; if not,
	      the value	of HISTFILE is used.  Options, if supplied,  have  the
	      following	meanings:
	      -c     Clear the history list by deleting	all the	entries.
	      -d offset
		     Delete the	history	entry at position offset.
	      -a     Append  the  ``new'' history lines	(history lines entered
		     since the beginning of the	current	bash session)  to  the
		     history file.
	      -n     Read  the history lines not already read from the history
		     file into the current history list.  These	are lines  ap-
		     pended  to	 the  history  file since the beginning	of the
		     current bash session.
	      -r     Read the contents of the history file and append them  to
		     the current history list.
	      -w     Write the current history list to the history file, over-
		     writing the history file's	contents.
	      -p     Perform history substitution on the  following  args  and
		     display  the  result  on  the  standard output.  Does not
		     store the results in the history list.  Each arg must  be
		     quoted to disable normal history expansion.
	      -s     Store  the	 args  in  the history list as a single	entry.
		     The last command in the history list  is  removed	before
		     the args are added.

	      If  the  HISTTIMEFORMAT variable is set, the time	stamp informa-
	      tion associated with each	history	entry is written to  the  his-
	      tory  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 previous history line.	 The return value is 0
	      unless  an  invalid option is encountered, an error occurs while
	      reading or writing the history file, an invalid offset  is  sup-
	      plied as an argument to -d, or the history expansion supplied as
	      an argument to -p	fails.

       jobs [-lnprs] [ jobspec ... ]
       jobs -x command [ args ... ]
	      The first	form lists the active jobs.  The options have the fol-
	      lowing 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.	 The return status is 0	unless an  invalid  option  is
	      encountered or an	invalid	jobspec	is supplied.

	      If the -x	option is supplied, jobs replaces any jobspec found in
	      command or args with the corresponding process group ID, and ex-
	      ecutes command passing it	args, returning	its exit status.

       kill [-s	sigspec	| -n signum | -sigspec]	[pid | jobspec]	...
       kill -l [sigspec	| exit_status]
	      Send  the	 signal	 named	by  sigspec or signum to the processes
	      named by pid or jobspec.	sigspec	is either  a  case-insensitive
	      signal  name such	as SIGKILL (with or without the	SIG prefix) or
	      a	signal number; signum is a signal number.  If sigspec  is  not
	      present,	then  SIGTERM is assumed.  An argument of -l 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 0.  The exit_status argument to
	      -l  is  a	 number	 specifying either a signal number or the exit
	      status of	a process terminated by	a signal.  kill	 returns  true
	      if at least one signal was successfully sent, or false if	an er-
	      ror occurs or an invalid option is encountered.

       let arg [arg ...]
	      Each arg is an arithmetic	expression to be evaluated (see	ARITH-
	      METIC  EVALUATION	 above).   If the last arg evaluates to	0, let
	      returns 1; 0 is returned otherwise.

       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.  When	local is used within a function, it causes the
	      variable	name  to have a	visible	scope restricted to that func-
	      tion and its children.  With no operands,	local writes a list of
	      local  variables	to the standard	output.	 It is an error	to use
	      local when not within a function.	 The return status is 0	unless
	      local  is	 used outside a	function, an invalid name is supplied,
	      or name is a readonly variable.

       logout Exit a login shell.

       mapfile [-n count] [-O origin] [-s count] [-t] [-u  fd]	[-C  callback]
       [-c quantum] [array]
       readarray  [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback]
       [-c quantum] [array]
	      Read lines from the standard input into the indexed array	 vari-
	      able  array, or from file	descriptor fd if the -u	option is sup-
	      plied.  The variable MAPFILE is the default array.  Options,  if
	      supplied,	have the following meanings:
	      -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 newline from each line read.
	      -u     Read  lines  from file descriptor fd instead of the stan-
		     dard 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  ar-
	      ray before assigning to it.

	      mapfile  returns successfully unless an invalid option or	option
	      argument is supplied, array is invalid or	 unassignable,	or  if
	      array is not an indexed array.

       popd [-n] [+n] [-n]
	      Removes  entries	from  the directory stack.  With no arguments,
	      removes the top directory	from the stack,	and performs a	cd  to
	      the new top directory.  Arguments, if supplied, have the follow-
	      ing meanings:
	      -n     Suppresses	the normal change of directory	when  removing
		     directories from the stack, so that only the stack	is ma-
		     nipulated.
	      +n     Removes the nth entry counting from the left of the  list
		     shown  by	dirs, starting with zero.  For example:	``popd
		     +0'' removes the first directory, ``popd +1'' the second.
	      -n     Removes the nth entry counting from the right of the list
		     shown  by	dirs, starting with zero.  For example:	``popd
		     -0'' removes the last directory, ``popd -1'' the next  to
		     last.

	      If  the popd command is successful, a dirs is performed as well,
	      and the return status is 0.  popd	returns	false  if  an  invalid
	      option is	encountered, the directory stack is empty, a non-exis-
	      tent directory stack entry is specified, or the directory	change
	      fails.

       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) format	specifications,	printf
	      interprets the following extensions:
	      %b     causes printf to expand backslash escape sequences	in the
		     corresponding argument (except that \c terminates output,
		     backslashes in \',	\", and	\? are not removed, and	 octal
		     escapes beginning with \0 may contain up to four digits).
	      %q     causes  printf  to	output the corresponding argument in a
		     format that can be	reused as shell	input.
	      %(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 ar-
		     gument is specified, conversion behaves as	if -1 had been
		     given.   This  is an exception to the usual printf	behav-
		     ior.

	      Arguments	to non-string format specifiers	are treated as C  con-
	      stants, 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 argu-
	      ments.  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.

       pushd [-n] [+n] [-n]
       pushd [-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, exchanges the top two directories
	      and returns 0, unless the	directory stack	is empty.   Arguments,
	      if supplied, have	the following meanings:
	      -n     Suppresses	the normal change of directory when adding di-
		     rectories to the stack, so	that only the stack is manipu-
		     lated.
	      +n     Rotates  the  stack  so  that the nth directory (counting
		     from the left of the list shown by	 dirs,	starting  with
		     zero) is at the top.
	      -n     Rotates  the  stack  so  that the nth directory (counting
		     from the right of the list	shown by dirs,	starting  with
		     zero) is at the top.
	      dir    Adds dir to the directory stack at	the top, making	it the
		     new current working directory as if it had	been  supplied
		     as	the argument to	the cd builtin.

	      If the pushd command is successful, a dirs is performed as well.
	      If the first form	is used, pushd returns 0 unless	the cd to  dir
	      fails.   With the	second form, pushd returns 0 unless the	direc-
	      tory stack is empty, a non-existent directory stack  element  is
	      specified,  or the directory change to the specified new current
	      directory	fails.

       pwd [-LP]
	      Print the	absolute pathname of the  current  working  directory.
	      The pathname printed contains no symbolic	links if the -P	option
	      is supplied or the -o physical option to the set builtin command
	      is  enabled.  If the -L option is	used, the pathname printed may
	      contain symbolic links.  The return status is 0 unless an	 error
	      occurs while reading the name of the current directory or	an in-
	      valid option is supplied.

       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 de-
	      scriptor fd supplied as an argument to the -u  option,  and  the
	      first word is assigned to	the first name,	the second word	to the
	      second name, and so on, with leftover words and their  interven-
	      ing  separators  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 IFS are used to
	      split the	line into words	using the same rules  the  shell  uses
	      for expansion (described above under Word	Splitting).  The back-
	      slash 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.  aname is unset before any
		     new values	are assigned.  Other name  arguments  are  ig-
		     nored.
	      -d delim
		     The first character of delim is used to terminate the in-
		     put line, rather than newline.
	      -e     If	the standard input is coming from a terminal, readline
		     (see  READLINE  above) is used to obtain the line.	 Read-
		     line uses the current (or default,	if  line  editing  was
		     not previously active) editing settings.
	      -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	honor a	delim-
		     iter 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 charac-
		     ters encountered in the input are not  treated  specially
		     and  do  not cause	read to	return until nchars characters
		     are read.
	      -p prompt
		     Display prompt on standard	error, without a trailing new-
		     line, before attempting to	read any input.	 The prompt is
		     displayed only if input is	coming from a terminal.
	      -r     Backslash does not	act as an escape character.  The back-
		     slash  is considered to be	part of	the line.  In particu-
		     lar, a backslash-newline pair may not be used as  a  line
		     continuation.
	      -s     Silent mode.  If input is coming from a terminal, charac-
		     ters 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	 deci-
		     mal  number with a	fractional portion following the deci-
		     mal 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  re-
		     turns  immediately, without trying	to read	any data.  The
		     exit status is 0 if input is available on	the  specified
		     file  descriptor, non-zero	otherwise.  The	exit status is
		     greater than 128 if the timeout is	exceeded.
	      -u fd  Read input	from file descriptor fd.

	      If no names are supplied,	the line read is assigned to the vari-
	      able  REPLY.  The	return code is zero, unless end-of-file	is en-
	      countered, read times out	(in which  case	 the  return  code  is
	      greater  than 128), a variable assignment	error (such as assign-
	      ing to a readonly	variable) occurs, or an	invalid	file  descrip-
	      tor is supplied as the argument to -u.

       readonly	[-aAf] [-p] [name[=word] ...]
	      The  given  names	are marked readonly; the values	of these names
	      may not be changed by subsequent assignment.  If the  -f	option
	      is  supplied,  the  functions  corresponding to the names	are so
	      marked.  The -a option restricts the variables  to  indexed  ar-
	      rays;  the  -A option restricts the variables to associative ar-
	      rays.  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
	      =word, the value of the variable is set  to  word.   The	return
	      status  is 0 unless an invalid option is encountered, one	of the
	      names is not a valid shell variable name,	or -f is supplied with
	      a	name that is not a function.

       return [n]
	      Causes  a	function to stop executing and return the value	speci-
	      fied by n	to its caller.	If n is	omitted, the return status  is
	      that  of the last	command	executed in the	function body.	If re-
	      turn is used outside a  function,	 but  during  execution	 of  a
	      script  by  the .	 (source) command, it causes the shell to stop
	      executing	that script and	return 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.  The	return status is non-zero if return is
	      supplied a non-numeric argument, or is used outside  a  function
	      and  not	during execution of a script by	. or source.  Any com-
	      mand associated with the RETURN trap is executed	before	execu-
	      tion resumes after the function or script.

       set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]
       set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg	...]
	      Without  options,	 the name and value of each shell variable are
	      displayed	in a format that can be	reused as input	for setting or
	      resetting	the currently-set variables.  Read-only	variables can-
	      not be reset.  In	posix mode, only shell variables  are  listed.
	      The  output is sorted according to the current locale.  When op-
	      tions are	specified, they	set or unset  shell  attributes.   Any
	      arguments	 remaining after option	processing are treated as val-
	      ues for the positional parameters	and are	assigned, in order, to
	      $1,  $2,	...   $n.   Options,  if specified, have the following
	      meanings:
	      -a      Automatically mark variables  and	 functions  which  are
		      modified	or  created  for  export to the	environment of
		      subsequent commands.
	      -b      Report the status	of terminated background jobs  immedi-
		      ately, rather than before	the next primary prompt.  This
		      is effective only	when job control is enabled.
	      -e      Exit immediately if a pipeline (which may	consist	 of  a
		      single  simple  command),	 a list, or a compound command
		      (see SHELL GRAMMAR above),  exits	with a	non-zero  sta-
		      tus.   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 following the
		      if or elif reserved words, part of any command  executed
		      in  a && or || list except the command following the fi-
		      nal && or	||, any	command	in a pipeline but the last, or
		      if  the command's	return value 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 envi-
		      ronment  separately  (see	 COMMAND EXECUTION ENVIRONMENT
		      above), 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 pathname expansion.
	      -h      Remember	the location of	commands as they are looked up
		      for execution.  This 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      Monitor mode.  Job control is enabled.  This  option  is
		      on  by  default  for  interactive	shells on systems that
		      support it (see JOB CONTROL above).  All	processes  run
		      in a separate process group.  When a background job com-
		      pletes, the shell	prints a line containing its exit sta-
		      tus.
	      -n      Read commands but	do not execute them.  This may be used
		      to check a shell script for syntax errors.  This is  ig-
		      nored by interactive shells.
	      -o option-name
		      The option-name can be one of the	following:
		      allexport
			      Same as -a.
		      braceexpand
			      Same as -B.
		      emacs   Use  an  emacs-style command line	editing	inter-
			      face.  This is enabled by	default	when the shell
			      is interactive, unless the shell is started with
			      the --noediting option.  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 above under
			      HISTORY.	This option is on by default in	inter-
			      active shells.
		      ignoreeof
			      The  effect  is  as  if  the shell command ``IG-
			      NOREEOF=10'' had been executed (see Shell	 Vari-
			      ables above).
		      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 (posix mode).  See SEE ALSO
			      below for	a reference to a document that details
			      how posix	mode affects bash's behavior.
		      privileged
			      Same as -p.
		      verbose Same as -v.
		      vi      Use  a  vi-style command line editing interface.
			      This also	affects	the editing interface used for
			      read -e.
		      xtrace  Same as -x.
		      If -o is supplied	with no	option-name, the values	of the
		      current options are printed.  If +o is supplied with  no
		      option-name,  a  series  of set commands to recreate the
		      current option settings is  displayed  on	 the  standard
		      output.
	      -p      Turn  on	privileged  mode.   In this mode, the $ENV and
		      $BASH_ENV	files are not processed, shell	functions  are
		      not  inherited  from the environment, and	the SHELLOPTS,
		      BASHOPTS,	CDPATH,	and GLOBIGNORE variables, if they  ap-
		      pear  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 sup-
		      plied, these actions are taken and the effective user id
		      is  set  to  the real user id.  If the -p	option is sup-
		      plied 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.
	      -t      Exit after reading and executing one command.
	      -u      Treat unset variables and	parameters other than the spe-
		      cial  parameters "@" and "*" as an error when performing
		      parameter	expansion.  If expansion is  attempted	on  an
		      unset  variable  or parameter, the shell prints an error
		      message, and, if not interactive,	exits with a  non-zero
		      status.
	      -v      Print shell input	lines as they are read.
	      -x      After  expanding	each simple command, for command, case
		      command, select command, or arithmetic for command, dis-
		      play  the	expanded value of PS4, followed	by the command
		      and its expanded arguments or associated word list.
	      -B      The shell	performs brace expansion (see Brace  Expansion
		      above).  This is on by default.
	      -C      If  set,	bash  does not overwrite an existing file with
		      the >, >&, and <>	redirection operators.	 This  may  be
		      overridden when creating output files by using the redi-
		      rection operator >| instead of >.
	      -E      If set, any trap on ERR is inherited by shell functions,
		      command  substitutions,  and commands executed in	a sub-
		      shell environment.  The ERR trap is normally not	inher-
		      ited in such cases.
	      -H      Enable !	style history substitution.  This option is on
		      by default when the shell	is interactive.
	      -P      If set, the shell	does not resolve symbolic  links  when
		      executing	 commands  such	 as cd that change the current
		      working  directory.   It	uses  the  physical  directory
		      structure	instead.  By default, bash follows the logical
		      chain of	directories  when  performing  commands	 which
		      change the current directory.
	      -T      If  set,	any traps on DEBUG and RETURN are inherited by
		      shell functions, command substitutions, and commands ex-
		      ecuted  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 parame-
		      ters are set to the args,	even if	 some  of  them	 begin
		      with a -.
	      -	      Signal  the  end of options, cause all remaining args to
		      be assigned to the positional parameters.	 The -x	and -v
		      options are turned off.  If there	are no args, the posi-
		      tional parameters	remain unchanged.

	      The options are off by default unless otherwise noted.  Using  +
	      rather  than  -  causes these options to be turned off.  The op-
	      tions can	also be	specified as arguments to an invocation	of the
	      shell.   The current set of options may be found in $-.  The re-
	      turn status is always true unless	an invalid option  is  encoun-
	      tered.

       shift [n]
	      The  positional  parameters  from	n+1 ...	are renamed to $1 ....
	      Parameters represented by	the numbers $# down to $#-n+1 are  un-
	      set.   n must be a non-negative number less than or equal	to $#.
	      If n is 0, no parameters are changed.  If	n is not given,	it  is
	      assumed to be 1.	If n is	greater	than $#, the positional	param-
	      eters are	not changed.  The return status	is greater  than  zero
	      if n is greater than $# or less than zero; otherwise 0.

       shopt [-pqsu] [-o] [optname ...]
	      Toggle  the values of settings controlling optional shell	behav-
	      ior.  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.	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.  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 (quiet mode); the	return	status
		     indicates whether the optname is set or unset.  If	multi-
		     ple optname arguments are given with -q, the return  sta-
		     tus  is zero if all optnames are enabled; non-zero	other-
		     wise.
	      -o     Restricts the values of optname to	be those  defined  for
		     the -o option to 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 (unset)
	      by default.

	      The return status	when listing options is	zero if	 all  optnames
	      are  enabled, non-zero otherwise.	 When setting or unsetting op-
	      tions, the return	status is zero unless  an  optname  is	not  a
	      valid shell option.

	      The list of shopt	options	is:

	      autocd  If  set,	a command name that is the name	of a directory
		      is executed as if	it were	the argument to	 the  cd  com-
		      mand.  This option is only used by interactive shells.
	      cdable_vars
		      If  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 com-
		      ponent in	a cd command will be  corrected.   The	errors
		      checked for are transposed characters, a missing charac-
		      ter, and one character too many.	 If  a	correction  is
		      found,  the  corrected filename is printed, and the com-
		      mand proceeds.  This option is only used by  interactive
		      shells.
	      checkhash
		      If set, bash checks that a command found in the hash ta-
		      ble exists before	trying to execute  it.	 If  a	hashed
		      command  no  longer exists, a normal path	search is per-
		      formed.
	      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
		      (see JOB CONTROL above).	The shell always postpones ex-
		      iting if any jobs	are stopped.
	      checkwinsize
		      If  set,	bash checks the	window size after each command
		      and, if necessary, updates the values of LINES and  COL-
		      UMNS.
	      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.
	      compat31
		      If set, bash changes its behavior	to that	of version 3.1
		      with respect to quoted arguments to the  [[  conditional
		      command's	=~ operator and	locale-specific	string compar-
		      ison when	using the [[ conditional command's < and > op-
		      erators.	Bash versions prior to bash-4.1	use ASCII col-
		      lation and strcmp(3); bash-4.1 and later use the current
		      locale's collation sequence and strcoll(3).
	      compat32
		      If set, bash changes its behavior	to that	of version 3.2
		      with respect to locale-specific string  comparison  when
		      using  the  [[  conditional  command's < and > operators
		      (see previous item).
	      compat40
		      If set, bash changes its behavior	to that	of version 4.0
		      with  respect  to	locale-specific	string comparison when
		      using the	[[ conditional command's  <  and  >  operators
		      (see  description	 of compat31) and the effect of	inter-
		      rupting a	command	list.  Bash versions 4.0 and later in-
		      terrupt the list as if the shell received	the interrupt;
		      previous versions	continue with the next command in  the
		      list.
	      compat41
		      If  set, bash, when in posix mode, treats	a single quote
		      in a double-quoted  parameter  expansion	as  a  special
		      character.   The	single quotes must match (an even num-
		      ber) and the characters between the  single  quotes  are
		      considered  quoted.   This is the	behavior of posix mode
		      through version 4.1.  The	default	bash behavior  remains
		      as in previous versions.
	      compat42
		      If  set, bash does not process the replacement string in
		      the pattern substitution word expansion using quote  re-
		      moval.
	      complete_fullquote
		      If  set,	bash  quotes all shell metacharacters in file-
		      names and	directory names	 when  performing  completion.
		      If not set, bash removes metacharacters such as the dol-
		      lar 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 ex-
		      pand 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	 back-
		      slashes  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 buf-
		      fer.  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  ini-
		      tially supplied does not exist.
	      dotglob If  set, bash includes filenames beginning with a	`.' in
		      the results of pathname expansion.
	      execfail
		      If set, a	non-interactive	shell will not exit if it can-
		      not  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 above under
		      ALIASES.	This option is enabled by default for interac-
		      tive shells.
	      extdebug
		      If  set,	behavior  intended for use by debuggers	is en-
		      abled:
		      1.     The -F option to the declare builtin 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 sub-
			     routine (a	shell function or a shell script  exe-
			     cuted by the . or source builtins), a call	to re-
			     turn is simulated.
		      4.     BASH_ARGC and BASH_ARGV are updated as  described
			     in	their descriptions above.
		      5.     Function  tracing	is enabled:  command substitu-
			     tion, 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 under Pathname Expansion 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
		      pathname 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	possi-
		      ble completions.	See SHELL VARIABLES above  for	a  de-
		      scription	 of  FIGNORE.	This  option is	enabled	by de-
		      fault.
	      globasciiranges
		      If set,  range  expressions  used	 in  pattern  matching
		      bracket  expressions (see	Pattern	Matching above)	behave
		      as if in the traditional C locale	when  performing  com-
		      parisons.	  That	is, the	current	locale's collating se-
		      quence 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.
	      globstar
		      If set, the pattern ** used in a pathname	expansion con-
		      text  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 ex-
		      its, 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 his-
		      tory substitution	are  not  immediately  passed  to  the
		      shell  parser.   Instead,	 the  resulting	line is	loaded
		      into the readline	editing	buffer,	allowing further modi-
		      fication.
	      hostcomplete
		      If set, and readline is being used, bash will attempt to
		      perform hostname completion when a word containing  a  @
		      is   being  completed  (see  Completing  under  READLINE
		      above).  This is enabled by default.
	      huponexit
		      If set, bash will	send SIGHUP to all jobs	when an	inter-
		      active login shell exits.
	      interactive_comments
		      If set, allow a word beginning with # to cause that word
		      and all remaining	characters on that line	to be  ignored
		      in  an interactive shell (see COMMENTS above).  This op-
		      tion 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 back-
		      ground in	the current shell environment.
	      lithist If set, and the cmdhist option  is  enabled,  multi-line
		      commands are saved to the	history	with embedded newlines
		      rather than using	semicolon separators where possible.
	      login_shell
		      The shell	sets this option if it is started as  a	 login
		      shell  (see  INVOCATION  above).	 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  dis-
		      played.
	      no_empty_cmd_completion
		      If  set,	and  readline is being used, bash will not at-
		      tempt 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 pathname expansion (see Pathname
		      Expansion	above).
	      nocasematch
		      If  set,	bash  matches  patterns	 in a case-insensitive
		      fashion when performing matching while executing case or
		      [[ conditional commands.
	      nullglob
		      If  set,	bash allows patterns which match no files (see
		      Pathname Expansion above)	to expand to  a	 null  string,
		      rather than themselves.
	      progcomp
		      If set, the programmable completion facilities (see Pro-
		      grammable	Completion above) are enabled.	This option is
		      enabled by default.
	      promptvars
		      If set, prompt strings undergo parameter expansion, com-
		      mand substitution, arithmetic expansion, and  quote  re-
		      moval  after  being  expanded  as	described in PROMPTING
		      above.  This option is enabled by	default.
	      restricted_shell
		      The shell	sets this option  if  it  is  started  in  re-
		      stricted	mode  (see RESTRICTED SHELL below).  The value
		      may not be changed.  This	is not reset when the  startup
		      files  are  executed, allowing the startup files to dis-
		      cover whether or not a shell is restricted.
	      shift_verbose
		      If set, the shift	builtin	prints an error	 message  when
		      the shift	count exceeds the number of positional parame-
		      ters.
	      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.
	      xpg_echo
		      If set, the echo builtin	expands	 backslash-escape  se-
		      quences by default.

       suspend [-f]
	      Suspend  the execution of	this shell until it receives a SIGCONT
	      signal.  A login shell cannot be suspended; the -f option	can be
	      used to override this and	force the suspension.  The return sta-
	      tus is 0 unless the shell	is a login shell and -f	 is  not  sup-
	      plied, or	if job control is not enabled.

       test expr
       [ expr ]
	      Return a status of 0 (true) or 1 (false) depending on the	evalu-
	      ation of the conditional expression expr.	 Each operator and op-
	      erand  must be a separate	argument.  Expressions are composed of
	      the primaries described  above  under  CONDITIONAL  EXPRESSIONS.
	      test  does not accept any	options, nor does it accept and	ignore
	      an argument of --	as signifying the end of options.

	      Expressions may  be  combined  using  the	 following  operators,
	      listed  in  decreasing  order of precedence.  The	evaluation de-
	      pends on the number of arguments;	see  below.   Operator	prece-
	      dence 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.

	      test and [ 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 argu-
		     ment is one of the	 unary	conditional  operators	listed
		     above  under  CONDITIONAL	EXPRESSIONS, the expression is
		     true if the unary test is true.  If the first argument is
		     not a valid unary conditional operator, the expression is
		     false.
	      3	arguments
		     The following conditions are applied in the order listed.
		     If	 the  second argument is one of	the binary conditional
		     operators listed above under 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.	 If the	first argument	is  !,
		     the  value	is the negation	of the two-argument test using
		     the second	and third arguments.  If the first argument is
		     exactly ( and the third argument is exactly ), the	result
		     is	the one-argument test of the second argument.	Other-
		     wise, the expression is false.
	      4	arguments
		     If	the first argument is !, the result is the negation of
		     the three-argument	expression composed of	the  remaining
		     arguments.	 Otherwise, the	expression is parsed and eval-
		     uated 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  lexico-
	      graphically using	ASCII ordering.

       times  Print  the  accumulated  user and	system times for the shell and
	      for processes run	from the shell.	 The return status is 0.

       trap [-lp] [[arg] sigspec ...]
	      The command arg is to be read and	executed when  the  shell  re-
	      ceives signal(s) sigspec.	 If arg	is absent (and there is	a sin-
	      gle sigspec) or -, each specified	signal is reset	to its	origi-
	      nal  disposition	(the value it had upon entrance	to the shell).
	      If arg is	the null string	the signal specified by	 each  sigspec
	      is  ignored by the shell and by the commands it invokes.	If arg
	      is not present and -p has	been supplied, then the	trap  commands
	      associated with each sigspec are displayed.  If no arguments are
	      supplied or if only -p is	given, trap prints the	list  of  com-
	      mands  associated	 with  each  signal.  The -l option causes the
	      shell to print a list of signal names  and  their	 corresponding
	      numbers.	 Each sigspec is either	a signal name defined in <sig-
	      nal.h>, or a signal number.  Signal names	are  case  insensitive
	      and the SIG prefix is optional.

	      If  a  sigspec  is  EXIT (0) the command arg is executed on exit
	      from the shell.  If a sigspec is DEBUG, the command arg is  exe-
	      cuted  before  every  simple command, for	command, case command,
	      select command, every arithmetic for  command,  and  before  the
	      first  command  executes	in a shell function (see SHELL GRAMMAR
	      above).  Refer to	the description	of the extdebug	option to  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 fin-
	      ishes executing.

	      If a sigspec is ERR, the command arg is executed	whenever  a  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
	      a	 while	or until keyword, part of the test in an if statement,
	      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 value is	being  inverted	 using
	      !.  These	are the	same conditions	obeyed by the errexit (-e) op-
	      tion.

	      Signals ignored upon entry to the	shell cannot be	trapped	or re-
	      set.   Trapped  signals  that are	not being ignored are reset to
	      their original values in a subshell or subshell environment when
	      one  is  created.	  The return status is false if	any sigspec is
	      invalid; otherwise trap returns true.

       type [-aftpP] name [name	...]
	      With no options, indicate	how each name would be interpreted  if
	      used as a	command	name.  If the -t option	is used, type prints a
	      string which is one of alias,  keyword,  function,  builtin,  or
	      file  if	name  is  an  alias,  shell  reserved  word, function,
	      builtin, or disk file, respectively.  If the name	is not	found,
	      then  nothing  is	 printed,  and	an exit	status of false	is re-
	      turned.  If the -p option	is used, type either returns the  name
	      of  the  disk file that would be executed	if name	were specified
	      as a command name, or nothing if ``type -t name''	would not  re-
	      turn  file.   The	 -P option forces a PATH search	for each name,
	      even if ``type -t	name'' would not return	file.  If a command is
	      hashed, -p and -P	print the hashed value,	which is not necessar-
	      ily the file that	appears	first in PATH.	If the	-a  option  is
	      used,  type  prints all of the places that contain an executable
	      named name.  This	includes aliases and functions,	if and only if
	      the -p option is not also	used.  The table of hashed commands is
	      not consulted when using -a.  The	 -f  option  suppresses	 shell
	      function lookup, as with the command builtin.  type returns true
	      if all of	the arguments are found, false if any are not found.

       ulimit [-HSTabcdefilmnpqrstuvx [limit]]
	      Provides control over the	resources available to the  shell  and
	      to  processes started by it, on systems that allow such control.
	      The -H and -S options specify that the hard or soft limit	is set
	      for  the	given resource.	 A hard	limit cannot be	increased by a
	      non-root user once it is set; a soft limit may be	 increased  up
	      to  the value of the hard	limit.	If neither -H nor -S is	speci-
	      fied, both the soft and hard limits are set.  The	value of limit
	      can be a number in the unit specified for	the resource or	one of
	      the special values hard, soft, or	unlimited, which stand for the
	      current  hard  limit,  the current soft limit, and no limit, re-
	      spectively.  If limit is omitted,	the current value of the  soft
	      limit of the resource is printed,	unless the -H option is	given.
	      When more	than one resource is specified,	 the  limit  name  and
	      unit  are	 printed  before  the value.  Other options are	inter-
	      preted as	follows:
	      -a     All current limits	are reported
	      -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
	      -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 size in 512-byte blocks (this may	not be set)
	      -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
	      -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.  If	no  option  is	given,
	      then  -f is assumed.  Values are in 1024-byte increments,	except
	      for -t, which is in seconds; -p, which is	in units  of  512-byte
	      blocks;  and -T, -b, -n, and -u, which are unscaled values.  The
	      return status is 0 unless	an invalid option or argument is  sup-
	      plied, or	an error occurs	while setting a	new limit.

       umask [-p] [-S] [mode]
	      The user file-creation mask is set to mode.  If mode begins with
	      a	digit, it is interpreted as an octal number; otherwise	it  is
	      interpreted  as a	symbolic mode mask similar to that accepted by
	      chmod(1).	 If mode is omitted, the current value of the mask  is
	      printed.	 The  -S  option causes	the mask to be printed in sym-
	      bolic form; the default output is	an octal number.   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 0 if the mode
	      was  successfully	 changed  or if	no mode	argument was supplied,
	      and false	otherwise.

       unalias [-a] [name ...]
	      Remove each name from the	list of	defined	 aliases.   If	-a  is
	      supplied,	 all  alias definitions	are removed.  The return value
	      is true unless a supplied	name is	not a defined alias.

       unset [-fv] [-n]	[name ...]
	      For each name, remove the	corresponding  variable	 or  function.
	      If the -v	option is given, each name refers to a shell variable,
	      and that variable	is removed.  Read-only variables  may  not  be
	      unset.   If  -f  is specified, each name refers to a shell func-
	      tion, 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	 vari-
	      able  by	that name, any function	with that name is unset.  Each
	      unset variable or	 function  is  removed	from  the  environment
	      passed  to subsequent commands.  If any of COMP_WORDBREAKS, RAN-
	      DOM, SECONDS, LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are
	      unset, they lose their special properties, even if they are sub-
	      sequently	reset.	The exit status	is true	unless a name is read-
	      only.

       wait [-n] [n ...]
	      Wait for each specified child process and	return its termination
	      status.  Each n may be a process ID or a job specification; if a
	      job  spec	 is  given,  all  processes in that job's pipeline are
	      waited for.  If n	is not given, all currently active child  pro-
	      cesses are waited	for, and the return status is zero.  If	the -n
	      option is	supplied, wait waits for any job to terminate and  re-
	      turns its	exit status.  If n specifies a non-existent process or
	      job, the return status is	127.  Otherwise, the return status  is
	      the exit status of the last process or job waited	for.

RESTRICTED SHELL
       If bash is started with the name	rbash, or the -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.  It
       behaves identically to bash with	the exception that the	following  are
       disallowed or not performed:

       o      changing directories with	cd

       o      setting or unsetting the values of SHELL,	PATH, ENV, or BASH_ENV

       o      specifying command names containing /

       o      specifying  a  filename  containing  a / as an argument to the .
	      builtin command

       o      specifying a filename containing a slash as an argument  to  the
	      -p option	to the hash builtin command

       o      importing	 function  definitions	from  the shell	environment at
	      startup

       o      parsing the value	of SHELLOPTS from  the	shell  environment  at
	      startup

       o      redirecting output using the >, >|, <>, >&, &>, and >> redirect-
	      ion operators

       o      using the	exec builtin command to	replace	the shell with another
	      command

       o      adding  or  deleting builtin commands with the -f	and -d options
	      to the enable builtin command

       o      using the	 enable	 builtin  command  to  enable  disabled	 shell
	      builtins

       o      specifying the -p	option to the command builtin command

       o      turning off restricted mode with set +r or set +o	restricted.

       These restrictions are enforced after any startup files are read.

       When a command that is found to be a shell script is executed (see COM-
       MAND EXECUTION above), rbash turns off any restrictions	in  the	 shell
       spawned to execute the script.

SEE ALSO
       Bash Reference Manual, Brian Fox	and Chet Ramey
       The Gnu Readline	Library, Brian Fox and Chet Ramey
       The Gnu History Library,	Brian Fox and Chet Ramey
       Portable	 Operating  System  Interface (POSIX) Part 2: Shell and	Utili-
       ties, IEEE --
	      http://pubs.opengroup.org/onlinepubs/9699919799/
       http://tiswww.case.edu/~chet/bash/POSIX -- a description	of posix mode
       sh(1), ksh(1), csh(1)
       emacs(1), vi(1)
       readline(3)

FILES
       /bin/bash
	      The bash executable
       /etc/profile
	      The systemwide initialization file, executed for login shells
       /etc/bash.bashrc
	      The systemwide per-interactive-shell startup file
       /etc/bash.bash.logout
	      The systemwide login shell cleanup file, executed	when  a	 login
	      shell exits
       ~/.bash_profile
	      The personal initialization file,	executed for login shells
       ~/.bashrc
	      The individual per-interactive-shell startup file
       ~/.bash_logout
	      The  individual  login shell cleanup file, executed when a login
	      shell exits
       ~/.inputrc
	      Individual readline initialization file

AUTHORS
       Brian Fox, Free Software	Foundation
       bfox@gnu.org

       Chet Ramey, Case	Western	Reserve	University
       chet.ramey@case.edu

BUG REPORTS
       If you find a bug in bash, you should report it.	 But first, you	should
       make  sure  that	 it really is a	bug, and that it appears in the	latest
       version	of  bash.   The	 latest	 version  is  always  available	  from
       ftp://ftp.gnu.org/pub/gnu/bash/.

       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
       A description of	the bug	behaviour
       A short script or `recipe' which	exercises the bug

       bashbug	inserts	 the first three items automatically into the template
       it provides for filing a	bug report.

       Comments	and bug	reports	concerning this	manual page should be directed
       to chet.ramey@case.edu.

BUGS
       It's too	big and	too slow.

       There are some subtle differences between bash and traditional versions
       of sh, mostly because of	the POSIX specification.

       Aliases are confusing in	some uses.

       Shell builtin commands and functions are	not stoppable/restartable.

       Compound	commands and command sequences of the form `a ;	b ; c' are not
       handled	gracefully  when  process  suspension  is  attempted.	When a
       process is stopped, the shell immediately executes the next command  in
       the  sequence.	It  suffices to	place the sequence of commands between
       parentheses to force it into a subshell,	which  may  be	stopped	 as  a
       unit.

       Array variables may not (yet) be	exported.

       There may be only one active coprocess at a time.

GNU Bash 4.3			2014 February 2			       BASH(1)

NAME | SYNOPSIS | COPYRIGHT | DESCRIPTION | OPTIONS | ARGUMENTS | INVOCATION | DEFINITIONS | RESERVED WORDS | SHELL GRAMMAR | COMMENTS | QUOTING | PARAMETERS | EXPANSION | REDIRECTION | ALIASES | FUNCTIONS | ARITHMETIC EVALUATION | CONDITIONAL EXPRESSIONS | SIMPLE COMMAND EXPANSION | COMMAND EXECUTION | COMMAND EXECUTION ENVIRONMENT | ENVIRONMENT | EXIT STATUS | SIGNALS | JOB CONTROL | PROMPTING | READLINE | HISTORY | HISTORY EXPANSION | SHELL BUILTIN COMMANDS | RESTRICTED SHELL | SEE ALSO | FILES | AUTHORS | BUG REPORTS | BUGS

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