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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) 1989-2020 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 description
       of the set builtin command, including -o, can be	used as	 options  when
       the  shell  is invoked.	In addition, bash interprets the following op-
       tions 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, the  first  argument  is  as-
		 signed	 to $0 and any remaining arguments are assigned	to the
		 positional parameters.	 The assignment	to $0 sets the name of
		 the shell, which is used in warning and error messages.
       -i	 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	or when	reading	 input
		 through a pipe.
       -D	 A  list of all	double-quoted strings preceded by $ is printed
		 on the	standard output.  These	are the	strings	that are  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	standard personal ini-
	      tialization file ~/.bashrc if the	shell is interactive (see  IN-
	      VOCATION 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  /usr/lo-
	      cal/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 INVO-
	      CATION below).

       --norc Do  not  read  and  execute  the	personal  initialization  file
	      ~/.bashrc	if the shell is	interactive.  This option is on	by de-
	      fault 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  (un-
       less  -s	 is  specified)	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 /usr/local/etc/profile, if that file	exists.	 After
       reading	that  file,  it	 looks for ~/.bash_profile, ~/.bash_login, and
       ~/.profile, in that order, and reads and	 executes  commands  from  the
       first  one  that	exists and is readable.	 The --noprofile option	may be
       used when the shell is started to inhibit this behavior.

       When an interactive login shell exits, or a non-interactive login shell
       executes	 the  exit  builtin  command, bash reads and executes commands
       from the	file ~/.bash_logout, if	it exists.

       When an interactive shell that is not a login shell  is	started,  bash
       reads  and executes commands from ~/.bashrc, if that file exists.  This
       may be inhibited	by using the --norc option.  The --rcfile file	option
       will  force  bash  to  read  and	 execute commands from file instead of
       ~/.bashrc.

       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	/usr/local/etc/profile
       and ~/.profile, in that order.  The --noprofile option may be  used  to
       inhibit	this  behavior.	 When invoked as an interactive	shell with the
       name sh,	bash looks for the variable ENV, expands its value  if	it  is
       defined,	 and uses the expanded value as	the name of a file to read and
       execute.	 Since a shell invoked as sh does not attempt to read and 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, if that file exists and is readable.  It	 will  not  do
       this  if	 invoked as sh.	 The --norc option may be used to inhibit this
       behavior, and the --rcfile option may be	used to	force another file  to
       be  read,  but  neither	rshd  nor sshd generally invoke	the shell with
       those options or	allow them to be specified.

       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 newline
       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 command (see SHELL GRAMMAR below), the third word of  a
       case  or	 select	command	(only in is valid), or the third word of a for
       command (only in	and do are valid):

       ! 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).  See COMMAND EXECUTION ENVIRONMENT for a description of  a
       subshell	 environment.	If  the	 lastpipe  option is enabled using the
       shopt builtin (see the description of shopt below), the last element of
       a pipeline may be run by	the shell process.

   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.  These are
       referred	to as asynchronous commands.  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  exe-
       cuted.

       AND  and	 OR  lists are sequences of one	or 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 (success).

       An OR list has the form

	      command1 || command2

       command2	is executed if,	and only if, command1 returns a	non-zero  exit
       status.	 The  return  status of	AND and	OR lists is the	exit status of
       the last	command	executed in the	list.

   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.

	      When the == and != operators are used, the string	to  the	 right
	      of the operator is considered a pattern and matched according to
	      the rules	described below	under Pattern Matching,	as if the ext-
	      glob shell option	were enabled.  The = operator is equivalent to
	      ==.  If the nocasematch shell option is enabled,	the  match  is
	      performed	 without  regard to the	case of	alphabetic characters.
	      The return value is 0 if the string matches  (==)	 or  does  not
	      match  (!=)  the pattern,	and 1 otherwise.  Any part of the pat-
	      tern may be quoted to force the quoted portion to	be matched  as
	      a	string.

	      An  additional  binary operator, =~, is available, with the same
	      precedence as == and !=.	When it	is used,  the  string  to  the
	      right of the operator is considered a POSIX extended regular ex-
	      pression and matched accordingly (using the  POSIX  regcomp  and
	      regexec  interfaces  usually described in	regex(3)).  The	return
	      value is 0 if the	string matches the pattern, and	 1  otherwise.
	      If the regular expression	is syntactically incorrect, the	condi-
	      tional expression's return value is 2.  If the nocasematch shell
	      option  is enabled, the match is performed without regard	to the
	      case of alphabetic characters.  Any part of the pattern  may  be
	      quoted  to  force	 the quoted portion to be matched as a string.
	      Bracket expressions in regular expressions must be treated care-
	      fully,  since  normal quoting characters lose their meanings be-
	      tween brackets.  If the pattern is stored	in a  shell  variable,
	      quoting  the  variable expansion forces the entire pattern to be
	      matched as a string.

	      The pattern will match if	it matches any	part  of  the  string.
	      Anchor  the  pattern using the ^ and $ regular expression	opera-
	      tors to force it to match	the entire string.  The	array variable
	      BASH_REMATCH  records which parts	of the string matched the pat-
	      tern.  The element of BASH_REMATCH with  index  0	 contains  the
	      portion  of  the	string matching	the entire regular expression.
	      Substrings matched by parenthesized  subexpressions  within  the
	      regular  expression  are saved in	the remaining BASH_REMATCH in-
	      dices. 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 matching rules  described	 under
	      Pattern Matching below.  The word	is expanded using tilde	expan-
	      sion, parameter and variable  expansion,	arithmetic  expansion,
	      command  substitution,  process  substitution and	quote removal.
	      Each pattern examined is expanded	using tilde expansion, parame-
	      ter  and	variable expansion, arithmetic expansion, command sub-
	      stitution, and process substitution.  If the  nocasematch	 shell
	      option  is enabled, the match is performed without regard	to the
	      case of alphabetic characters.  When a match is found, the  cor-
	      responding  list	is  executed.	If the ;; operator is used, no
	      subsequent matches are attempted after the first pattern	match.
	      Using  ;&	 in  place of ;; causes	execution to continue with the
	      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 suc-
	      cessful match, continuing	the case statement execution as	if the
	      pattern list had not matched.  The exit status  is  zero	if  no
	      pattern  matches.	  Otherwise, it	is the exit status of the last
	      command executed in 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.  Other than those created
       to execute command and process substitutions, the file descriptors  are
       not available in	subshells.  The	process	ID of the shell	spawned	to 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:

       fname ()	compound-command [redirection]
       function	fname [()] compound-command [redirection]
	      This defines a function named fname.  The	reserved word function
	      is  optional.   If  the  function	reserved word is supplied, the
	      parentheses are optional.	 The body of the function is the  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, with
	      one exception: If	the function reserved word is  used,  but  the
	      parentheses  are	not  supplied,	the braces are required.  com-
	      pound-command is executed	whenever fname	is  specified  as  the
	      name  of	a simple command.  When	in posix mode, fname must be a
	      valid shell name and may not be the name of  one	of  the	 POSIX
	      special  builtins.   In default mode, a function name can	be any
	      unquoted shell word that does not	contain	$.   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, !.  When the shell is	in posix mode,
       the ! has no special meaning within double quotes,  even	 when  history
       expansion  is  enabled.	 The  characters  $ and	` retain their special
       meaning within double quotes.  The backslash retains its	special	 mean-
       ing  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
	      \?     question mark
	      \nnn   the  eight-bit  character	whose value is the octal value
		     nnn (one to three octal digits)
	      \xHH   the eight-bit character whose value  is  the  hexadecimal
		     value HH (one or two hex digits)
	      \uHHHH the  Unicode (ISO/IEC 10646) character whose value	is the
		     hexadecimal value HHHH (one to four hex digits)
	      \UHHHHHHHH
		     the Unicode (ISO/IEC 10646) character whose value is  the
		     hexadecimal value HHHHHHHH	(one to	eight hex digits)
	      \cx    a control-x character

       The  expanded  result  is  single-quoted, as if the dollar sign had not
       been present.

       A double-quoted string preceded by a dollar sign	($"string") will cause
       the  string to be translated according to the current locale.  The get-
       text infrastructure performs the	message	catalog	 lookup	 and  transla-
       tion,  using  the  LC_MESSAGES  and TEXTDOMAIN shell variables.	If the
       current locale is C or POSIX, or	if there are  no  translations	avail-
       able,  the dollar sign is ignored.  If the string is translated and re-
       placed, 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 (declaration 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.	 This  includes	 arguments  to
       builtin	commands  such	as  declare  that accept assignment statements
       (declaration commands).	When +=	is applied to a	variable for which the
       integer attribute has been set, value is	evaluated as an	arithmetic ex-
       pression	and added to the variable's current value, which is also eval-
       uated.	When +=	is applied to an array variable	using compound assign-
       ment (see Arrays	below),	the variable's value is	not unset  (as	it  is
       when  using  =),	 and new values	are appended to	the array beginning at
       one greater than	the array's maximum  index  (for  indexed  arrays)  or
       added  as additional key-value pairs in an associative array.  When ap-
       plied to	a string-valued	variable, value	is expanded  and  appended  to
       the variable's value.

       A variable can be assigned the nameref attribute	using the -n option to
       the declare or local builtin commands (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, assigned to, unset,	or has its at-
       tributes	modified (other	than using or changing the  nameref  attribute
       itself),	 the operation is actually performed on	the variable specified
       by the nameref variable's value.	 A nameref  is	commonly  used	within
       shell functions to refer	to a variable whose name is passed as an argu-
       ment to the function.  For instance, if a variable name is passed to  a
       shell function as its first argument, running
	      declare -n ref=$1
       inside  the  function creates a nameref variable	ref whose value	is the
       variable	name passed as the first argument.  References and assignments
       to  ref,	 and changes to	its attributes,	are treated as references, as-
       signments, and attribute	modifications to the variable whose  name  was
       passed  as  $1.	 If the	control	variable in a for loop has the nameref
       attribute, the list of words can	be a list of shell  variables,	and  a
       name  reference will be established for each word in the	list, in turn,
       when the	loop is	executed.  Array variables cannot be given the nameref
       attribute.   However,  nameref  variables can reference array variables
       and subscripted array variables.	 Namerefs can be unset	using  the  -n
       option  to the unset builtin.  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$2c...", where c
	      is the first character of	the value of the IFS variable.	If IFS
	      is  unset,  the  parameters  are separated by spaces.  If	IFS is
	      null, the	parameters are joined without intervening separators.
       @      Expands to the positional	parameters,  starting  from  one.   In
	      contexts	where  word  splitting is performed, this expands each
	      positional parameter to a	separate word; if  not	within	double
	      quotes,  these words are subject to word splitting.  In contexts
	      where word splitting is not performed, this expands to a	single
	      word  with each positional parameter separated by	a space.  When
	      the expansion occurs within double quotes,  each	parameter  ex-
	      pands  to	 a separate word.  That	is, "$@" 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.

   Shell Variables
       The following variables are set by the shell:

       _      At shell startup,	set to the pathname used to invoke  the	 shell
	      or  shell	 script	being executed as passed in the	environment or
	      argument list.  Subsequently, expands to the  last  argument  to
	      the  previous  simple  command executed in the foreground, after
	      expansion.  Also set to the full pathname	used  to  invoke  each
	      command  executed	and placed in the environment exported to that
	      command.	When checking mail, this parameter holds the  name  of
	      the mail file currently being checked.
       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.   Assignments  to
	      BASHPID  have no effect.	If BASHPID is unset, it	loses its spe-
	      cial properties, even if it is subsequently reset.
       BASH_ALIASES
	      An associative array variable whose members  correspond  to  the
	      internal	list  of  aliases  as maintained by the	alias builtin.
	      Elements added to	this array appear in the alias list;  however,
	      unsetting	 array elements	currently does not cause aliases to be
	      removed from the alias list.  If BASH_ALIASES is unset, it loses
	      its special properties, even if it is subsequently reset.
       BASH_ARGC
	      An  array	 variable whose	values are the number of parameters in
	      each frame of the	current	bash execution call stack.  The	number
	      of  parameters  to  the  current	subroutine  (shell function or
	      script executed with . or	source)	is at the top  of  the	stack.
	      When  a  subroutine is executed, the number of parameters	passed
	      is pushed	onto BASH_ARGC.	 The shell sets	BASH_ARGC only when in
	      extended debugging mode (see the description of the extdebug op-
	      tion to the shopt	builtin	below).	 Setting  extdebug  after  the
	      shell has	started	to execute a script, or	referencing this vari-
	      able when	extdebug is not	set, may result	in  inconsistent  val-
	      ues.
       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).  Setting extdebug after the	shell has started to execute a
	      script,  or  referencing this variable when extdebug is not set,
	      may result in inconsistent values.
       BASH_ARGV0
	      When referenced, this variable expands to	the name of the	 shell
	      or shell script (identical to $0;	see the	description of special
	      parameter	0 above).  Assignment to BASH_ARGV0 causes  the	 value
	      assigned	to also	be assigned to $0.  If BASH_ARGV0 is unset, it
	      loses its	special	properties, even if it is subsequently reset.
       BASH_CMDS
	      An associative array variable whose members  correspond  to  the
	      internal	hash  table  of	 commands  as  maintained  by the hash
	      builtin.	Elements added to this array appear in the hash	table;
	      however,	unsetting array	elements currently does	not cause com-
	      mand names to be removed from the	hash table.  If	 BASH_CMDS  is
	      unset,  it  loses	 its  special properties, even if it is	subse-
	      quently reset.
       BASH_COMMAND
	      The command currently being executed or about  to	 be  executed,
	      unless the shell is executing a command as the result of a trap,
	      in which case it is the command executing	at  the	 time  of  the
	      trap.   If  BASH_COMMAND	is unset, it loses its special proper-
	      ties, even if it is subsequently reset.
       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_LOADABLES_PATH
	      A	 colon-separated  list of directories in which the shell looks
	      for dynamically loadable builtins	specified by the  enable  com-
	      mand.
       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.
       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.  If BASH_SUBSHELL is unset, it	loses its spe-
	      cial properties, even if it is subsequently reset.
       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.
       EPOCHREALTIME
	      Each time	this parameter is referenced, it expands to the	number
	      of seconds since the Unix	Epoch  (see  time(3))  as  a  floating
	      point  value  with  micro-second	granularity.   Assignments  to
	      EPOCHREALTIME are	ignored.  If EPOCHREALTIME is unset, it	 loses
	      its special properties, even if it is subsequently reset.
       EPOCHSECONDS
	      Each time	this parameter is referenced, it expands to the	number
	      of seconds since the Unix	Epoch (see time(3)).   Assignments  to
	      EPOCHSECONDS  are	 ignored.   If EPOCHSECONDS is unset, 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.  If FUNCNAME  is	unset,
	      it  loses	its special properties,	even if	it is subsequently re-
	      set.

	      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.
	      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.	Assignments to HISTCMD are ignored.  If	HISTCMD	is un-
	      set, 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,	it expands to a	random
	      integer between 0	and 32767.  Assigning a	value to  RANDOM  ini-
	      tializes	(seeds)	 the sequence of random	numbers.  If RANDOM is
	      unset, it	loses its special properties, even  if	it  is	subse-
	      quently reset.
       READLINE_LINE
	      The contents of the readline line	buffer,	for use	with "bind -x"
	      (see SHELL BUILTIN COMMANDS below).
       READLINE_MARK
	      The position of the mark (saved insertion	point) in the readline
	      line  buffer, for	use with "bind -x" (see	SHELL BUILTIN COMMANDS
	      below).  The characters between the insertion point and the mark
	      are often	called the region.
       READLINE_POINT
	      The position of the insertion point in the readline line buffer,
	      for use with "bind -x" (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.
	      The  number  of seconds at shell invocation and the current time
	      is always	determined by querying the system clock.   If  SECONDS
	      is  unset, it loses its special properties, even if it is	subse-
	      quently 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.
       SRANDOM
	      This variable expands to a 32-bit	pseudo-random number each time
	      it  is  referenced. The random number generator is not linear on
	      systems that support /dev/urandom	or  arc4random,	 so  each  re-
	      turned  number  has no relationship to the numbers preceding it.
	      The random number	generator cannot be seeded, so assignments  to
	      this variable have no effect.  If	SRANDOM	is unset, it loses its
	      special properties, even if it is	subsequently reset.
       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
	      SHELL  COMPATIBILITY MODE	below for a description	of the various
	      compatibility levels and their effects.  The value may be	a dec-
	      imal  number  (e.g., 4.2)	or an integer (e.g., 42) corresponding
	      to the desired compatibility level.  If BASH_COMPAT is unset  or
	      set  to  the empty string, the compatibility level is set	to the
	      default for the current version.	If BASH_COMPAT	is  set	 to  a
	      value  that  is  not  one	of the valid compatibility levels, the
	      shell prints an error message and	sets the  compatibility	 level
	      to the default for the current version.  The valid values	corre-
	      spond to the compatibility levels	described below	under  BSHELL-
	      COMPATIBILITYMODE.   For	example,  4.2  and 42 are valid	values
	      that correspond to the compat42 shopt option and set the compat-
	      ibility level to 42.  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    Expanded and executed  similarly	to  BASH_ENV  (see  INVOCATION
	      above) when an interactive shell is invoked in posix mode.
       EXECIGNORE
	      A	 colon-separated list of shell patterns	(see Pattern Matching)
	      defining the list	of filenames to	be ignored by  command	search
	      using  PATH.  Files whose	full pathnames match one of these pat-
	      terns are	not considered executable files	for  the  purposes  of
	      completion and command execution via PATH	lookup.	 This does not
	      affect the behavior of the [, test, and [[ commands.  Full path-
	      names  in	 the command hash table	are not	subject	to EXECIGNORE.
	      Use this variable	to ignore shared library files that  have  the
	      executable  bit  set, but	are not	executable files.  The pattern
	      matching honors the setting of the extglob shell option.
       FCEDIT The 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:~".
       FUNCNEST
	      If  set  to  a  numeric  value greater than 0, defines a maximum
	      function nesting level.  Function	invocations that  exceed  this
	      nesting level will cause the current command to abort.
       GLOBIGNORE
	      A	 colon-separated  list	of  patterns  defining the set of file
	      names to be ignored by  pathname	expansion.   If	 a  file  name
	      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.  The	pattern	match-
	      ing honors the setting of	the extglob shell option.
       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).
       INSIDE_EMACS
	      If  this	variable  appears  in  the  environment	when the shell
	      starts, bash assumes that	it is running inside  an  Emacs	 shell
	      buffer  and  may disable line editing, depending on the value of
	      TERM.
       LANG   Used to determine	the  locale  category  for  any	 category  not
	      specifically selected with a variable starting with LC_.
       LC_ALL This  variable  overrides	 the  value  of	LANG and any other LC_
	      variable specifying a locale category.
       LC_COLLATE
	      This variable determines the collation order used	 when  sorting
	      the  results  of 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.
       LC_TIME
	      This  variable  determines the locale category used for data and
	      time 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 can be configured to	supply a default value for this	 vari-
	      able  (there  is	no  value by default), but the location	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.  When the	 shell	enters
	      posix mode, it sets this variable	if it was not already set.
       PROMPT_COMMAND
	      If  this variable	is set,	and is an array, the value of each set
	      element is executed as a command prior to	issuing	 each  primary
	      prompt.	If this	is set but not an array	variable, its value is
	      used as a	command	to execute instead.
       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.
       PS0    The  value  of  this parameter is	expanded (see PROMPTING	below)
	      and displayed by interactive shells after	reading	a command  and
	      before the command is executed.
       PS1    The  value  of  this parameter is	expanded (see PROMPTING	below)
	      and used as the primary prompt string.   The  default  value  is
	      ``\u@\h\$	''.
       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 the expanded value	of PS4
	      is replicated multiple times, as necessary, to indicate multiple
	      levels of	indirection.  The default is ``+ ''.
       SHELL  This  variable expands to	the full pathname to the shell.	 If it
	      is not set when the shell	starts,	bash assigns to	 it  the  full
	      pathname of the current user's login shell.
       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 ref-
       erenced 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 may be  of  the  form	 [sub-
       script]=string.	 Indexed array assignments do not require anything but
       string.	Each value in the list is expanded using all the shell	expan-
       sions  described	 below under EXPANSION.	 When assigning	to indexed ar-
       rays, 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 words in a compound assign-
       ment  may  be  either assignment	statements, for	which the subscript is
       required, or a list of words that is interpreted	as a sequence  of  al-
       ternating  keys and values: name=( key1 value1 key2 value2 ...).	 These
       are treated identically to  name=(  [key1]=value1  [key2]=value2	 ...).
       The  first  word	in the list determines how the remaining words are in-
       terpreted; all assignments in a list must be of the  same  type.	  When
       using  key/value	 pairs,	 the keys may not be missing or	empty; a final
       missing value is	treated	like the empty string.

       This syntax is also accepted by the declare builtin.  Individual	 array
       elements	 may be	assigned to using the name[subscript]=value syntax 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.  If	the subscript used to reference	an element of an indexed array
       evaluates to a number less than zero, it	is interpreted as relative  to
       one  greater  than  the maximum index of	the array, so negative indices
       count back from the end of the array, and an index of -1	references the
       last element.

       Referencing an array variable without a subscript is equivalent to ref-
       erencing	the array with a subscript of 0.  Any reference	to a  variable
       using a valid subscript is legal, and bash will create an array if nec-
       essary.

       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, for	both indexed and asso-
       ciative arrays.	Negative subscripts to indexed arrays are  interpreted
       as  described  above.   Unsetting the last element of an	array variable
       does not	unset the variable.  unset name, where name is	an  array,  or
       unset  name[subscript],	where  subscript is * or @, removes the	entire
       array.

       When using a variable name with a subscript as an argument  to  a  com-
       mand,  such  as with unset, without using the word expansion syntax de-
       scribed above, the argument is subject to pathname expansion.  If path-
       name expansion is not desired, the argument should be quoted.

       The  declare,  local,  and readonly builtins each accept	a -a option to
       specify an indexed array	and a -A option	to specify an associative  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.

       After  these  expansions	are performed, quote characters	present	in the
       original	word are removed  unless  they	have  been  quoted  themselves
       (quote removal).

       Only  brace  expansion,	word splitting,	and pathname expansion can in-
       crease the number of words of the expansion; other expansions expand  a
       single  word to a single	word.  The only	exceptions to this are the ex-
       pansions	 of  "$@"  and	"${name[@]}",  and,  in	 most  cases,  $*  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, and
       inhibits	brace expansion	until the closing }.

       This construct is typically used	as shorthand when the common prefix of
       the strings to be generated is longer than in the above example:

	      mkdir /usr/local/src/bash/{old,new,dist,bugs}
       or
	      chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}

       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.

       Bash  also  performs tilde expansion on words satisfying	the conditions
       of variable assignments (as described above under PARAMETERS) when they
       appear  as arguments to simple commands.	 Bash does not do this,	except
       for the declaration commands listed above, when in posix	mode.

   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  (!),  and
       parameter is not	a nameref, it introduces a level of indirection.  Bash
       uses the	value formed by	expanding the rest of parameter	as the new pa-
       rameter;	 this  is  then	expanded and that value	is used	in the rest of
       the expansion, rather than the expansion	 of  the  original  parameter.
       This is known as	indirect expansion.  The value is subject to tilde ex-
       pansion,	parameter expansion, command substitution, and arithmetic  ex-
       pansion.	  If  parameter	 is a nameref, this expands to the name	of the
       parameter referenced by parameter instead of  performing	 the  complete
       indirect	 expansion.   The  exceptions  to  this	 are the expansions of
       ${!prefix*} and ${!name[@]} described  below.   The  exclamation	 point
       must  immediately  follow the left brace	in order to introduce 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, and matched against the
	      expanded value of	parameter using	the rules described under Pat-
	      tern  Matching  below.   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	 pattern  (the	``##''
	      case)  deleted.  If parameter is @ or *, the pattern removal op-
	      eration is applied to each positional parameter in turn, and the
	      expansion	is the resultant list.	If parameter is	an array vari-
	      able 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, and matched against the
	      expanded value of	parameter using	the rules described under Pat-
	      tern  Matching below.  If	the pattern matches a trailing portion
	      of the expanded value of parameter, then the result of  the  ex-
	      pansion  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/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.	The match is performed using the rules described under
	      Pattern Matching below.  If pattern begins with /,  all  matches
	      of  pattern  are	replaced with string.  Normally	only the first
	      match is replaced.  If pattern begins with #, it must  match  at
	      the  beginning  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 /	following pattern may be omitted.  If the  nocasematch
	      shell  option  is	enabled, the match is performed	without	regard
	      to the case of alphabetic	characters.  If	parameter is @	or  *,
	      the substitution operation is applied to each positional parame-
	      ter in turn, and the expansion is	the resultant list.  If	param-
	      eter is an array variable	subscripted with @ or *, the substitu-
	      tion operation is	applied	to each	member of the array  in	 turn,
	      and the expansion	is the resultant list.

       ${parameter^pattern}
       ${parameter^^pattern}
       ${parameter,pattern}
       ${parameter,,pattern}
	      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.

       ${parameter@operator}
	      Parameter	transformation.	 The expansion is either a transforma-
	      tion  of	the  value of parameter	or information about parameter
	      itself, depending	on the value of	operator.  Each	operator is  a
	      single letter:

	      U	     The  expansion is a string	that is	the value of parameter
		     with lowercase alphabetic characters converted to	upper-
		     case.
	      u	     The  expansion is a string	that is	the value of parameter
		     with the first character converted	to uppercase, if it is
		     alphabetic.
	      L	     The  expansion is a string	that is	the value of parameter
		     with uppercase alphabetic characters converted to	lower-
		     case.
	      Q	     The  expansion is a string	that is	the value of parameter
		     quoted in a format	that can be reused as input.
	      E	     The expansion is a	string that is the value of  parameter
		     with  backslash  escape  sequences	 expanded  as with the
		     $'...' quoting mechanism.
	      P	     The expansion is a	string that is the result of expanding
		     the value of parameter as if it were a prompt string (see
		     PROMPTING below).
	      A	     The expansion is a	string in the form  of	an  assignment
		     statement	or  declare  command  that, if evaluated, will
		     recreate parameter	with its attributes and	value.
	      K	     Produces a	possibly-quoted	version	of the value of	param-
		     eter, except that it prints the values of indexed and as-
		     sociative arrays as a sequence of quoted key-value	 pairs
		     (see Arrays above).
	      a	     The  expansion is a string	consisting of flag values rep-
		     resenting parameter's attributes.

	      If parameter is @	or *, the 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 operation is applied to each member of the	array in turn,
	      and the expansion	is the resultant list.

	      The result of the	expansion is subject  to  word	splitting  and
	      pathname expansion as described below.

   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	in a subshell environ-
       ment and	replacing the command substitution with	the standard output of
       the command, with any trailing newlines deleted.	 Embedded newlines are
       not  deleted,  but they may be removed during word splitting.  The com-
       mand 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  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 allows a process's input or	output to be  referred
       to  using  a  filename.	 It takes the form of <(list) or >(list).  The
       process list is run asynchronously, and its input or output appears  as
       a filename.  This filename is passed as an argument to the current com-
       mand as the result of the expansion.  If	 the  >(list)  form  is	 used,
       writing	to  the	file will provide input	for list.  If the <(list) form
       is used,	the file passed	as an argument should be read  to  obtain  the
       output of list.	Process	substitution is	supported on systems that sup-
       port named pipes	(FIFOs)	or the /dev/fd method of naming	open files.

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

   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,
       tab, and	newline	are ignored at the beginning and end of	the  word,  as
       long  as	the whitespace character is in the value of IFS	(an IFS	white-
       space character).  Any character	in IFS that  is	 not  IFS  whitespace,
       along with any adjacent IFS whitespace characters, delimits a field.  A
       sequence	of IFS whitespace characters is	also treated as	 a  delimiter.
       If the value of IFS is null, no word splitting occurs.

       Explicit	 null arguments	("" or '') are retained	and passed to commands
       as empty	strings.  Unquoted implicit null arguments, resulting from the
       expansion of parameters that have no values, are	removed.  If a parame-
       ter with	no value is expanded within double quotes, a null argument re-
       sults and is retained and passed	to a command as	an empty string.  When
       a quoted	null argument appears as part of a  word  whose	 expansion  is
       non-null, the null argument is removed.	That is, the word -d'' becomes
       -d after	word splitting and null	argument removal.

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

   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,	and is not quoted, then	the word is regarded as	a pattern, and
       replaced	 with  an alphabetically sorted	list of	filenames matching the
       pattern (see Pattern 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  removed.	 If  the  failglob shell option	is set,	and no
       matches are found, an error message is printed and the command  is  not
       executed.  If the shell option nocaseglob is enabled, the match is per-
       formed without regard to	the case of  alphabetic	 characters.   When  a
       pattern	is  used  for  pathname	expansion, the character ``.''	at the
       start of	a name or immediately following	a slash	must  be  matched  ex-
       plicitly,  unless the shell option dotglob is set.  The filenames ``.''
       and ``..''  must	always be matched explicitly, even if dotglob is  set.
       In  other  cases,  the ``.''  character is not treated specially.  When
       matching	a pathname, the	slash character	must always be matched explic-
       itly  by	 a slash in the	pattern, but in	other matching contexts	it can
       be matched by a special pattern character as described below under Pat-
       tern  Matching.	See the	description of shopt below under SHELL BUILTIN
       COMMANDS	for a description of the nocaseglob, 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  file
       name  that  also	 matches  one of the patterns in GLOBIGNORE is removed
       from the	list of	matches.  If the nocaseglob option is set, the	match-
       ing  against  the patterns in GLOBIGNORE	is performed without regard to
       case.  The filenames ``.''  and ``..''  are always ignored when GLOBIG-
       NORE  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.  The pattern matching honors the setting of the extglob shell
       option.

       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

       Complicated extended pattern matching against long strings is slow, es-
       pecially	when the patterns contain alternations and the strings contain
       multiple	 matches.   Using separate matches against shorter strings, or
       using arrays of strings instead of a single long	string,	may be faster.

   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.  If {varname} is supplied, the redirect-
       ion persists beyond the scope of	the command, allowing the  shell  pro-
       grammer to manage the file descriptor himself.

       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.  If the operating system on
       which bash is running provides these special files, bash	will use them;
       otherwise it will emulate them internally with the  behavior  described
       below.

	      /dev/fd/fd
		     If	 fd  is	 a valid integer, file descriptor fd is	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.

   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	(or file descriptor n if n is specified) for a
       command.

       The format of here-documents is:

	      [n]<<[-]word
		      here-document
	      delimiter

       No parameter and	variable expansion, command  substitution,  arithmetic
       expansion,  or pathname expansion is performed on word.	If any part of
       word is quoted, the delimiter is	the result of quote removal  on	 word,
       and  the	 lines	in the here-document are not expanded.	If word	is un-
       quoted, all lines of the	here-document are subjected to	parameter  ex-
       pansion,	 command substitution, and arithmetic expansion, the character
       sequence	\<newline> is ignored, and \ must be used to quote the charac-
       ters \, $, 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:

	      [n]<<<word

       The word	undergoes tilde	expansion, parameter and  variable  expansion,
       command	substitution,  arithmetic expansion, and quote removal.	 Path-
       name expansion and word splitting are not  performed.   The  result  is
       supplied	as a single string, with a newline appended, to	the command on
       its standard input (or file descriptor n	if n is	specified).

   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,  and
       all  lines that make up a compound command, before executing any	of the
       commands	on that	line or	the compound command.	Aliases	 are  expanded
       when  a	command	is read, not when it is	executed.  Therefore, an alias
       definition appearing on the same	line as	another	command	does not  take
       effect  until  the  next	line of	input is read.	The commands following
       the alias definition on that line are not affected by  the  new	alias.
       This  behavior  is  also	an issue when functions	are executed.  Aliases
       are expanded when a function definition is read,	not when the  function
       is  executed,  because a	function definition is itself a	command.  As a
       consequence, aliases defined in a function are not available until  af-
       ter  that  function  is executed.  To be	safe, always put alias defini-
       tions 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.	 If a variable is declared  local,  the	 vari-
       able's  visible	scope  is restricted to	that function and its children
       (including the functions	it calls).  Local variables "shadow" variables
       with  the same name declared at previous	scopes.	 For instance, a local
       variable	declared in a function hides a global  variable	 of  the  same
       name:  references  and assignments refer	to the local variable, leaving
       the global variable unmodified.	When the function returns, the	global
       variable	is once	again visible.

       The  shell  uses	 dynamic  scoping  to  control a variable's visibility
       within functions.  With dynamic scoping,	visible	 variables  and	 their
       values  are a result of the sequence of function	calls that caused exe-
       cution to reach the current function.  The value	of a variable  that  a
       function	 sees  depends on its value within its caller, if any, whether
       that caller is the "global" scope or another shell function.   This  is
       also  the  value	 that  a local variable	declaration "shadows", and the
       value that is restored when the function	returns.

       For example, if a variable var is declared as local in function	func1,
       and  func1  calls  another  function func2, references to var made from
       within func2 will resolve to the	local variable var from	func1, shadow-
       ing any global variable named var.

       The unset builtin also acts using the same dynamic scope: if a variable
       is local	to the current scope, unset will unset it; otherwise the unset
       will  refer  to	the  variable  found in	any calling scope as described
       above.  If a variable at	the current local scope	is unset, it will  re-
       main  so	until it is reset in that scope	or until the function returns.
       Once the	function returns, any instance of the variable at  a  previous
       scope will become visible.  If the unset	acts on	a variable at a	previ-
       ous scope, any instance of a variable with  that	 name  that  had  been
       shadowed	will become visible.

       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.

       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,	 the  ((  com-
       pound command, 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  fol-
       lowing list of operators	is grouped into	levels of equal-precedence op-
       erators.	 The levels are	listed in order	of decreasing precedence.

       id++ id--
	      variable post-increment and post-decrement
       - +    unary minus and plus
       ++id --id
	      variable pre-increment and pre-decrement
       ! ~    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.

       Integer constants follow	the C language definition, without suffixes or
       character constants.  Constants with a leading 0	are interpreted	as oc-
       tal  numbers.  A	leading	0x or 0X denotes hexadecimal.  Otherwise, num-
       bers take the form [base#]n, where the optional base is a decimal  num-
       ber  between 2 and 64 representing the arithmetic base, and n is	a num-
       ber in that base.  If base# is omitted, then base  10  is  used.	  When
       specifying n, if	a non-digit is required, the digits greater than 9 are
       represented by the lowercase letters, the uppercase letters, @, and  _,
       in  that	order.	If base	is less	than or	equal to 36, lowercase and up-
       percase letters may be used interchangeably to  represent  numbers  be-
       tween 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.   The test	and [ commands determine their
       behavior	based on the number of	arguments;  see	 the  descriptions  of
       those commands for any other command-specific actions.

       Expressions  are	 formed	 from the following unary or binary primaries.
       Bash handles several filenames specially	when they are used in  expres-
       sions.  If the operating	system on which	bash is	running	provides these
       special files, bash will	use them; otherwise it will emulate  them  in-
       ternally	 with  this  behavior: 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.  When used with the [[ command, Arg1 and
	      Arg2 are evaluated as  arithmetic	 expressions  (see  ARITHMETIC
	      EVALUATION above).

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

       1.     The  words  that	the  parser has	marked as variable assignments
	      (those preceding the command name) and  redirections  are	 saved
	      for later	processing.

       2.     The  words that are not variable assignments or redirections are
	      expanded.	 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
       in  a  separate execution environment with the original command and the
       original	command's arguments as its arguments, and the function's  exit
       status  becomes	the exit status	of that	subshell.  If that function is
       not defined, the	shell prints an	error message and returns an exit sta-
       tus 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,	generally  in-
       valid options or	missing	arguments.

       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 job whose command name  be-
       gins  with  ce.	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 error.  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 previous job with a	-.  A single % (with  no  accompanying
       job specification) 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.

       When  the shell is waiting for a	job or process using the wait builtin,
       and job control is enabled, wait	 will  return  when  the  job  changes
       state.  The -f option causes wait to wait until the job or process ter-
       minates before returning.

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  displays	PS0  after  it
       reads  a	 command  but  before  executing it.  Bash displays PS4	as de-
       scribed above before tracing each command when the  -x  option  is  en-
       abled.	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).	This can have unwanted side effects if
       escaped portions	of the string appear within  command  substitution  or
       contain characters special to word expansion.

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.	If  that  file	does not exist or cannot be read, the ultimate
       default is /etc/inputrc.	 When a	program	which uses  the	 readline  li-
       brary  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  constructs.	  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
       or using	the bind builtin command (see SHELL BUILTIN COMMANDS below).

       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.
       blink-matching-paren (Off)
	      If set to	On, readline attempts to briefly move the cursor to an
	      opening parenthesis when a closing parenthesis is	inserted.
       colored-completion-prefix (Off)
	      If set to	On, when listing completions,  readline	 displays  the
	      common prefix of the set of possible completions using a differ-
	      ent color.  The color definitions	are taken from	the  value  of
	      the LS_COLORS environment	variable.
       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-display-width	(-1)
	      The number of screen columns used	to  display  possible  matches
	      when  performing completion.  The	value is ignored if it is less
	      than 0 or	greater	than the terminal screen width.	 A value of  0
	      will  cause  matches  to be displayed one	per line.  The default
	      value is -1.
       completion-ignore-case (Off)
	      If set to	On, readline performs filename matching	and completion
	      in a case-insensitive fashion.
       completion-map-case (Off)
	      If  set  to  On, and completion-ignore-case is enabled, readline
	      treats hyphens (-) and underscores (_) as	equivalent  when  per-
	      forming case-insensitive filename	matching and completion.
       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, readline
	      will ask whether or not the user 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).  The default is On,	but readline will  set	it  to
	      Off if the locale	contains eight-bit characters.
       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.
       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.
       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.
       emacs-mode-string (@)
	      If  the  show-mode-in-prompt variable is enabled,	this string is
	      displayed	immediately before the last line of the	primary	prompt
	      when emacs editing mode is active.  The value is expanded	like a
	      key binding, so the standard set of meta-	and  control  prefixes
	      and  backslash escape sequences is available.  Use the \1	and \2
	      escapes to begin and end sequences of  non-printing  characters,
	      which  can be used to embed a terminal control sequence into the
	      mode string.
       enable-bracketed-paste (On)
	      When set to On, readline will configure the terminal  in	a  way
	      that will	enable it to insert each paste into the	editing	buffer
	      as a single string of characters,	instead	of treating each char-
	      acter  as	 if it had been	read from the keyboard.	 This can pre-
	      vent pasted characters from being	interpreted  as	 editing  com-
	      mands.
       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 (unset)
	      Set the maximum number of	history	entries	saved in  the  history
	      list.   If set to	zero, any existing history entries are deleted
	      and no new entries are saved.  If	set to a value less than zero,
	      the  number  of history entries is not limited.  By default, the
	      number of	history	entries	is set to the value  of	 the  HISTSIZE
	      shell  variable.	If an attempt is made to set history-size to a
	      non-numeric value, the maximum number of history entries will be
	      set to 500.
       horizontal-scroll-mode (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.	 This setting is automatically enabled	for  terminals
	      of height	1.
       input-meta (Off)
	      If  set to On, readline will enable eight-bit input (that	is, it
	      will not strip the eighth	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.	 The default  is  Off,
	      but  readline will set it	to On if the locale contains eight-bit
	      characters.
       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.
	      The default is Off, but readline will set	it to On if the	locale
	      contains eight-bit characters.
       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 string to the	beginning of the prompt	 indi-
	      cating  the  editing  mode:  emacs, vi command, or vi insertion.
	      The mode strings are user-settable (e.g.,	emacs-mode-string).
       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.
       vi-cmd-mode-string ((cmd))
	      If  the  show-mode-in-prompt variable is enabled,	this string is
	      displayed	immediately before the last line of the	primary	prompt
	      when  vi	editing	mode is	active and in command mode.  The value
	      is expanded like a key binding, so the standard set of meta- and
	      control  prefixes	 and  backslash	escape sequences is available.
	      Use the \1 and \2	escapes	to begin and  end  sequences  of  non-
	      printing	characters, which can be used to embed a terminal con-
	      trol sequence into the mode string.
       vi-ins-mode-string ((ins))
	      If the show-mode-in-prompt variable is enabled, this  string  is
	      displayed	immediately before the last line of the	primary	prompt
	      when vi editing mode is active and in insertion mode.  The value
	      is expanded like a key binding, so the standard set of meta- and
	      control prefixes and backslash escape  sequences	is  available.
	      Use  the	\1  and	 \2 escapes to begin and end sequences of non-
	      printing characters, which can be	used to	embed a	terminal  con-
	      trol sequence into the mode string.
       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, after any comparison operator,
	       extends to the end of the  line;	 unless	 otherwise  noted,  no
	      characters are required to isolate it.

	      mode   The  mode=	 form  of  the	$if  directive is used to test
		     whether readline is in emacs or vi	 mode.	 This  may  be
		     used  in conjunction with the set keymap command, for 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	both the 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.

	      version
		     The version test  may  be	used  to  perform  comparisons
		     against  specific readline	versions.  The version expands
		     to	the current readline version.  The set	of  comparison
		     operators	includes  =,  (and  ==), !=, <=, >=, <,	and >.
		     The version number	supplied on the	right side of the  op-
		     erator  consists  of  a major version number, an optional
		     decimal point, and	an optional minor version (e.g., 7.1).
		     If	 the  minor version is omitted,	it is assumed to be 0.
		     The operator may be separated from	the string version and
		     from the version number argument by whitespace.

	      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

	      variable
		     The variable construct provides simple equality tests for
		     readline  variables and values.  The permitted comparison
		     operators are =, ==, and !=.  The variable	name  must  be
		     separated from the	comparison operator by whitespace; the
		     operator may be separated from the	 value	on  the	 right
		     hand  side	 by whitespace.	 Both string and boolean vari-
		     ables may be tested. Boolean  variables  must  be	tested
		     against the values	on and off.

       $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.
       previous-screen-line
	      Attempt to move point to the same	physical screen	column on  the
	      previous	physical  screen  line.	This will not have the desired
	      effect if	the current Readline line does not take	up  more  than
	      one  physical line or if point is	not greater than the length of
	      the prompt plus the screen width.
       next-screen-line
	      Attempt to move point to the same	physical screen	column on  the
	      next physical screen line. This will not have the	desired	effect
	      if the current Readline line does	not  take  up  more  than  one
	      physical	line  or if the	length of the current Readline line is
	      not greater than the length of the prompt	plus the screen	width.
       clear-display (M-C-l)
	      Clear the	screen and, if	possible,  the	terminal's  scrollback
	      buffer,  then  redraw the	current	line, leaving the current line
	      at the top of the	screen.
       clear-screen (C-l)
	      Clear the	screen,	then redraw the	current	line, leaving the cur-
	      rent  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.
       history-substring-search-backward
	      Search backward through the history for the string of characters
	      between the start	of the current line and	the current cursor po-
	      sition  (the  point).  The search	string may match anywhere in a
	      history line.  This is a non-incremental search.
       history-substring-search-forward
	      Search forward through the history for the string	of  characters
	      between the start	of the current line and	the point.  The	search
	      string may match anywhere	in a history line.  This is a  non-in-
	      cremental	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.   A
	      numeric  argument,  if  supplied,	specifies the history entry to
	      use instead of the current line.
       edit-and-execute-command	(C-x C-e)
	      Invoke an	editor on the current command line,  and  execute  the
	      result as	shell commands.	 Bash attempts to invoke $VISUAL, $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
	      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
	      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 nor minus sign, the argument	 count	for  the  next
	      command  is multiplied by	four.  The argument count is initially
	      one, so executing	this function the first	time makes  the	 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-lowercase-version (M-A, M-B, M-x, ...)
	      If the metafied character	x is uppercase,	run the	 command  that
	      is bound to the corresponding metafied lowercase character.  The
	      behavior is undefined if x is already lowercase.
       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.	If there is no
       default compspec, bash attempts alias expansion on the command word  as
       a  final	 resort,  and attempts to find a compspec for the command word
       from any	successful expansion.

       Once a compspec has been	found, it is used  to  generate	 the  list  of
       matching	 words.	  If a compspec	is not found, the default bash 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.	 If the	nocasematch  shell  option  is
       enabled,	 the  match  is	performed without regard to the	case of	alpha-
       betic characters.

       Finally,	any prefix and suffix specified	with the -P and	-S options are
       added to	each member of the completion list, and	the result is returned
       to the readline completion code as the list of possible completions.

       If the previously-applied actions do not	generate any matches, and  the
       -o  dirnames  option was	supplied to complete when the compspec was 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 fol-
       lowing 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, and	is performed  on  each
       line  individually  without  taking  quoting on previous	lines into ac-
       count.  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	avail-
       able  to	 manipulate the	selected words.	 The line is broken into words
       in the same fashion as when reading input, so that several  metacharac-
       ter-separated words surrounded by quotes	are considered one word.  His-
       tory expansions are introduced by the appearance	of the history	expan-
       sion  character,	 which is ! by default.	 Only backslash	(\) and	single
       quotes can quote	the history expansion character, but the  history  ex-
       pansion	character is also treated as quoted if it immediately precedes
       the closing double quote	in a double-quoted string.

       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.  If
	      string is	missing, the string from the  most  recent  search  is
	      used; it is an error if there is no previous search string.
       ^string1^string2^
	      Quick  substitution.   Repeat  the  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  first word matched by the most recent `?string?' search, if
	      the search string	begins with a character	 that  is  part	 of  a
	      word.
       x-y    A	range of words;	`-y' abbreviates `0-y'.
       *      All  of  the words 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 x is miss-
	      ing, it defaults to 0.

       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 `:'.  These mod-
       ify, or edit, the word or words selected	from the history event.

       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.  The	q and x	modifiers are mutually	exclu-
	      sive; the	last one supplied is used.
       s/old/new/
	      Substitute  new  for  the	 first	occurrence of old in the event
	      line.  Any character may be used as the delimiter	in place of /.
	      The  final  delimiter 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	single backslash will quote the	&.  If old is null, it is  set
	      to  the last old substituted, or,	if no previous history substi-
	      tutions took place, the last string in  a	 !?string[?]   search.
	      If new is	null, each matching old	is deleted.
       &      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' or `&' 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, return, break, con-
       tinue, let, and shift builtins accept and process  arguments  beginning
       with  - without requiring --.  Other builtins that accept arguments but
       are not specified as accepting options  interpret  arguments  beginning
       with  -	as  invalid options and	require	-- to prevent this interpreta-
       tion.
       : [arguments]
	      No effect; the command does nothing beyond  expanding  arguments
	      and performing any specified redirections.  The return status is
	      zero.

	.  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.  If the -T option is enabled,
	      source  inherits any trap	on DEBUG; if it	is not,	any DEBUG trap
	      string is	saved and restored around  the	call  to  source,  and
	      source  unsets  the  DEBUG trap while it executes.  If -T	is not
	      set, and the sourced file	changes	the DEBUG trap,	the new	 value
	      is  retained  when  source  completes.  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 [-m	keymap]	keyseq: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 (vi-move
		     is	also a synonym); emacs is  equivalent  to  emacs-stan-
		     dard.
	      -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 and READLINE_MARK
		     variables to the current location of the insertion	 point
		     and  the  saved insertion point (the mark), respectively.
		     If	the executed command changes the value of any of READ-
		     LINE_LINE,	 READLINE_POINT,  or  READLINE_MARK, those new
		     values will be reflected in the editing state.
	      -X     List all key sequences bound to shell  commands  and  the
		     associated	commands in a format that can be reused	as 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] [-DEI] [-A action] [-G glob-
       pat] [-W	wordlist]
	      [-F function] [-C	command] [-X filterpat]	[-P prefix]  [-S  suf-
	      fix] name	[name ...]
       complete	-pr [-DEI] [name ...]
	      Specify  how arguments to	each name should be completed.	If the
	      -p option	is supplied, or	if no options are  supplied,  existing
	      completion  specifications are printed in	a way that allows them
	      to be reused as input.  The -r option removes a completion spec-
	      ification	 for each name,	or, if no names	are supplied, all com-
	      pletion specifications.  The -D option indicates that other sup-
	      plied  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 other supplied options and	actions	 should	 apply
	      to  ``empty''  command completion; that is, completion attempted
	      on a blank line.	The -I option indicates	 that  other  supplied
	      options  and  actions  should apply to completion	on the initial
	      non-assignment word on the line, or after	 a  command  delimiter
	      such  as	;  or |, which is usually command name completion.  If
	      multiple options are supplied, the -D  option  takes  precedence
	      over -E, and both	take precedence	over -I.  If any of -D,	-E, or
	      -I are supplied, any other name  arguments  are  ignored;	 these
	      completions only apply to	the case specified by the option.

	      The  process  of	applying  these	completion specifications when
	      word completion is attempted is described	above  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).
		      nosort  Tell readline not	to sort	the list  of  possible
			      completions alphabetically.
		      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.  Shell quoting is honored within wordlist,
		      in order to provide a mechanism for the words to contain
		      shell  metacharacters or characters in the value of IFS.
		      The possible completions are the members of  the	resul-
		      tant list	which match the	word being completed.
	      -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] [-DEI] [+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 other supplied 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 other
	      supplied	options	 should	apply to ``empty'' command completion;
	      that is, completion attempted on a blank line.   The  -I	option
	      indicates	that other supplied options should apply to completion
	      on the initial non-assignment word on the	line, or after a  com-
	      mand  delimiter  such  as	 ; or |, which is usually command name
	      completion.

	      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 [-aAfFgiIlnrtux]	[-p] [name[=value] ...]
       typeset [-aAfFgiIlnrtux]	[-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 each
	      name is defined are displayed as well.  The  -F  option  implies
	      -f.  The -g option forces	variables to be	created	or modified at
	      the global scope,	even when declare is executed in a shell func-
	      tion.   It  is ignored in	all other cases.  The -I option	causes
	      local variables to inherit the attributes	 (except  the  nameref
	      attribute) and value of any existing variable with the same name
	      at a surrounding scope.  If there	is no existing	variable,  the
	      local variable is	initially unset.  The following	options	can be
	      used to restrict output to variables with	the  specified	attri-
	      bute 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, assign-
		     ments, and	attribute modifications	to name, except	 those
		     using  or changing	the -n attribute itself, are performed
		     on	the variable referenced	by name's value.  The  nameref
		     attribute cannot be applied to array variables.
	      -r     Make names	readonly.  These names cannot then be assigned
		     values by subsequent assignment statements	or unset.
	      -t     Give each name the	trace attribute.  Traced functions 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 and +A may	not be used to	destroy	 array
	      variables	 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
	      variable name is followed	by =value, the value of	 the  variable
	      is  set  to value.  When using -a	or -A and the compound assign-
	      ment 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.  The current directory is always the first	direc-
	      tory in the stack.
	      -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 ... |	pid ...	]
	      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.	A subshell  exits  unconditionally  if
	      exec  fails.  If command is not specified, any redirections take
	      effect in	the current shell, and the return  status  is  0.   If
	      there is a redirection error, the	return status is 1.

       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).  When listing, a
	      first or last of 0 is equivalent to -1 and -0 is	equivalent  to
	      the  current  command  (usually  the fc command);	otherwise 0 is
	      equivalent to -1 and -0 is invalid.  If last is  not  specified,
	      it  is  set  to the current command for listing (so that ``fc -l
	      -10'' prints the last 10 commands) and to	first  otherwise.   If
	      first  is	 not  specified, it is set to the previous command 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 interpreted 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 [arg ...]
	      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  supplied as arg values, getopts parses those in-
	      stead.

	      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 -d start-end
       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.  If	offset
		     is	negative, it is	interpreted as relative	to one greater
		     than the last history position, so	negative indices count
		     back from the end of the history,	and  an	 index	of  -1
		     refers to the current history -d command.
	      -d start-end
		     Delete  the  history  entries between positions start and
		     end, inclusive.  Positive and negative values  for	 start
		     and end are interpreted as	described above.
	      -a     Append  the  ``new''  history  lines to the history file.
		     These are history lines entered since  the	 beginning  of
		     the current bash session, but not already appended	to the
		     history file.
	      -n     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 following history entry.  The return value is
	      0	unless an invalid option is encountered, an error occurs while
	      reading  or  writing the history file, an	invalid	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|-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.  The -L option is
	      equivalent to -l.	 kill returns true if at least one signal  was
	      successfully sent, or false if an	error occurs or	an invalid op-
	      tion 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.  If name is -, the	set of	shell  options
	      is  made	local to the function in which local is	invoked: shell
	      options changed using the	set builtin inside  the	 function  are
	      restored	to  their  original  values when the function returns.
	      The restore is effected as if a series of	set commands were exe-
	      cuted  to	restore	the values that	were in	place before the func-
	      tion.  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 [-d delim] [-n count] [-O origin] [-s count] [-t] [-u  fd]  [-C
       callback] [-c quantum] [array]
       readarray [-d delim] [-n	count] [-O origin] [-s count] [-t] [-u fd] [-C
       callback] [-c quantum] [array]
	      Read lines from the standard input into the indexed array	 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:
	      -d     The  first	 character  of delim is	used to	terminate each
		     input line, rather	than newline.  If delim	is  the	 empty
		     string, mapfile will terminate a line when	it reads a NUL
		     character.
	      -n     Copy at most count	lines.	If count is 0, all  lines  are
		     copied.
	      -O     Begin  assigning  to  array at index origin.  The default
		     index is 0.
	      -s     Discard the first count lines read.
	      -t     Remove a trailing delim (default newline) from each  line
		     read.
	      -u     Read  lines  from file descriptor fd instead of the 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 in the same	way as echo -e.
	      %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.

	      The %b, %q, and %T directives all	use the	field width and	preci-
	      sion arguments from the format specification and write that many
	      bytes from (or use that wide a field for)	the expanded argument,
	      which usually contains more characters than the original.

	      Arguments	 to non-string format specifiers are treated as	C 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, pushd exchanges the top  two  di-
	      rectories	 and  returns  0, unless the directory stack is	empty.
	      Arguments, if supplied, have the following meanings:
	      -n     Suppresses	the normal change of directory	when  rotating
		     or	 adding	 directories  to  the  stack, so that only the
		     stack is manipulated.
	      +n     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, split into
	      words as described above under Word  Splitting,  and  the	 first
	      word  is assigned	to the first name, the second word to the sec-
	      ond name,	and so on.  If there are more words  than  names,  the
	      remaining	words and their	intervening delimiters are assigned to
	      the last name.  If there are fewer words	read  from  the	 input
	      stream  than  names, the remaining names are assigned empty val-
	      ues.  The	characters in IFS are used  to	split  the  line  into
	      words  using  the	 same  rules the shell uses for	expansion (de-
	      scribed above under Word Splitting).   The  backslash  character
	      (\) may be used to remove	any special meaning for	the next char-
	      acter 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.	 If delim is the empty
		     string, read will terminate a line	when it	 reads	a  NUL
		     character.
	      -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, but  uses	 Read-
		     line's default filename completion.
	      -i text
		     If	 readline  is  being  used  to	read the line, text is
		     placed into the editing buffer before editing begins.
	      -n nchars
		     read returns after	reading	nchars characters rather  than
		     waiting for a complete line of input, but honors a	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.	The result is not split	on the	characters  in
		     IFS;  the intent is that the variable is assigned exactly
		     the characters read (with the exception of	backslash; see
		     the -r option below).
	      -p prompt
		     Display prompt 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 then 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,	without	the ending de-
	      limiter but otherwise unmodified,	is assigned  to	 the  variable
	      REPLY.   The  exit status	is zero, unless	end-of-file is encoun-
	      tered, read times	out (in	which case the status is greater  than
	      128),  a variable	assignment error (such as assigning to a read-
	      only variable) occurs, or	an invalid file	descriptor 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 executed by a trap handler, the last command used	to de-
	      termine  the status is the last command executed before the trap
	      handler.	If return is executed during a DEBUG  trap,  the  last
	      command  used  to	 determine the status is the last command exe-
	      cuted by the trap	handler	before return was invoked.  If	return
	      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 signif-
	      icant 8 bits.  The return	status is non-zero if return  is  sup-
	      plied  a non-numeric argument, or	is used	outside	a function and
	      not during execution of a	script by . or	source.	  Any  command
	      associated with the RETURN trap is executed before execution re-
	      sumes 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      Each variable or function	that is	created	or modified is
		      given the	export attribute and marked for	export to  the
		      environment of subsequent	commands.
	      -b      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 status.
		      The shell	does not exit if the  command  that  fails  is
		      part  of	the command list immediately following a while
		      or until keyword,	part of	the test following the	if  or
		      elif  reserved  words, part of any command executed in a
		      && or || list except the command following the final  &&
		      or ||, any command in a pipeline but the last, or	if the
		      command's	return 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; if optnames are supplied, the	output
	      is restricted to those options.  The -p option causes output  to
	      be  displayed  in	a form that may	be reused as input.  Other op-
	      tions 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:

	      assoc_expand_once
		      If  set, the shell suppresses multiple evaluation	of as-
		      sociative	array subscripts during	arithmetic  expression
		      evaluation,  while  executing  builtins that can perform
		      variable assignments, and	while executing	builtins  that
		      perform array dereferencing.
	      autocd  If  set,	a command name that is the name	of a directory
		      is executed as if	it were	the argument to	 the  cd  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 external
		      (non-builtin) command and,  if  necessary,  updates  the
		      values  of LINES and COLUMNS.  This option is enabled by
		      default.
	      cmdhist If set, bash attempts to save all	lines of  a  multiple-
		      line  command  in	 the  same history entry.  This	allows
		      easy re-editing of multi-line commands.  This option  is
		      enabled  by  default,  but only has an effect if command
		      history is enabled, as described above under HISTORY.
	      compat31
	      compat32
	      compat40
	      compat41
	      compat42
	      compat43
	      compat44
		      These control aspects of the shell's compatibility  mode
		      (see SHELL COMPATIBILITY MODE below).

	      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.  The filenames	 ``.''
		      and  ``..''   must always	be matched explicitly, even if
		      dotglob is set.

	      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 at shell invocation, or in a shell startup file,
		      arrange to execute the debugger profile before the shell
		      starts,  identical to the	--debugger option.  If set af-
		      ter invocation, behavior intended	for use	 by  debuggers
		      is enabled:

		      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),  the	 shell
			     simulates a call to return.

		      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.

	      inherit_errexit
		      If set, command substitution inherits the	value  of  the
		      errexit  option, instead of unsetting it in the subshell
		      environment.  This option	is enabled when	posix mode  is
		      enabled.

	      interactive_comments
		      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.

	      localvar_inherit
		      If set, local variables inherit the value	and attributes
		      of a variable of the same	name that exists at a previous
		      scope before any new value is assigned.  The nameref at-
		      tribute is not inherited.

	      localvar_unset
		      If  set,	calling	 unset	on local variables in previous
		      function scopes marks them so  subsequent	 lookups  find
		      them  unset until	that function returns. This is identi-
		      cal to the behavior of unsetting local variables at  the
		      current function scope.

	      login_shell
		      The  shell  sets this option if it is started as a login
		      shell (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, when performing pattern substi-
		      tution  word expansions, or when filtering possible com-
		      pletions as part of programmable completion.

	      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.

	      progcomp_alias
		      If set, and programmable	completion  is	enabled,  bash
		      treats  a	command	name that doesn't have any completions
		      as a possible alias and attempts alias expansion.	If  it
		      has  an alias, bash attempts programmable	completion us-
		      ing the command word resulting from the expanded alias.

	      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
	      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 [-HS] -a
       ulimit [-HS] [-bcdefiklmnpqrstuvxPRT [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, if appropriate, are	printed	before the value.   Other  op-
	      tions are	interpreted as follows:
	      -a     All current limits	are reported; no limits	are set
	      -b     The maximum socket	buffer size
	      -c     The maximum size of core files created
	      -d     The maximum size of a process's data segment
	      -e     The maximum scheduling priority ("nice")
	      -f     The  maximum  size	 of files written by the shell and its
		     children
	      -i     The maximum number	of pending signals
	      -k     The maximum number	of kqueues that	may be allocated
	      -l     The maximum size that may be locked into memory
	      -m     The maximum resident set size (many systems do not	 honor
		     this limit)
	      -n     The maximum number	of open	file descriptors (most systems
		     do	not allow this value to	be set)
	      -p     The pipe 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
	      -P     The maximum number	of pseudoterminals
	      -R     The maximum time  a  real-time  process  can  run	before
		     blocking, in microseconds
	      -T     The maximum number	of threads

	      If  limit	 is given, and the -a option is	not used, limit	is the
	      new value	of the specified resource.  If	no  option  is	given,
	      then  -f is assumed.  Values are in 1024-byte increments,	except
	      for -t, which is in seconds; -R, which is	in  microseconds;  -p,
	      which  is	 in  units of 512-byte blocks; -P, -T, -b, -k, -n, and
	      -u, which	are unscaled values; and, when in posix	mode,  -c  and
	      -f,  which  are  in 512-byte increments.	The return status is 0
	      unless an	invalid	option or argument is supplied,	 or  an	 error
	      occurs while setting a new limit.

       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, a function with that name, if	any, is	unset.
	      Each unset variable or function is removed from the  environment
	      passed   to   subsequent	commands.   If	any  of	 BASH_ALIASES,
	      BASH_ARGV0,  BASH_CMDS,  BASH_COMMAND,  BASH_SUBSHELL,  BASHPID,
	      COMP_WORDBREAKS,	DIRSTACK,  EPOCHREALTIME,  EPOCHSECONDS, FUNC-
	      NAME, GROUPS, HISTCMD, LINENO, RANDOM, SECONDS, or  SRANDOM  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 [-fn] [-p varname] [id ...]
	      Wait for each specified child process and	return its termination
	      status.  Each id 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 id is not	given,	wait  waits  for  all  running
	      background  jobs	and the	last-executed process substitution, if
	      its process id is	the same as $!,	and the	return status is zero.
	      If  the  -n option is supplied, wait waits for a single job from
	      the list of ids or, if no	ids are	supplied, any job, to complete
	      and  returns its exit status.  If	none of	the supplied arguments
	      is a child of the	shell, or if no	arguments are supplied and the
	      shell  has no unwaited-for children, the exit status is 127.  If
	      the -p option is supplied, the process or	job identifier of  the
	      job  for	which  the  exit status	is returned is assigned	to the
	      variable varname named by	the  option  argument.	 The  variable
	      will  be unset initially,	before any assignment.	This is	useful
	      only when	the -n option is supplied.  Supplying the  -f  option,
	      when  job	control	is enabled, forces wait	to wait	for id to ter-
	      minate before returning its status, instead of returning when it
	      changes  status.	If id 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.

SHELL COMPATIBILITY MODE
       Bash-4.0	introduced the concept of a `shell compatibility level', spec-
       ified as	a set of options to the	shopt builtin compat31,	compat32, com-
       pat40,  compat41,  and so on).  There is	only one current compatibility
       level --	each option is mutually	exclusive.  The	compatibility level is
       intended	 to allow users	to select behavior from	previous versions that
       is incompatible with newer versions while they migrate scripts  to  use
       current	features  and  behavior. It's intended to be a temporary solu-
       tion.

       This section does not mention behavior that is standard for a  particu-
       lar  version  (e.g., setting compat32 means that	quoting	the rhs	of the
       regexp matching operator	quotes special regexp characters in the	 word,
       which is	default	behavior in bash-3.2 and above).

       If  a  user enables, say, compat32, it may affect the behavior of other
       compatibility levels up to  and	including  the	current	 compatibility
       level.	The  idea  is  that each compatibility level controls behavior
       that changed in that version of bash, but that behavior may  have  been
       present	in  earlier versions.  For instance, the change	to use locale-
       based comparisons with the [[ command came  in  bash-4.1,  and  earlier
       versions	used ASCII-based comparisons, so enabling compat32 will	enable
       ASCII-based comparisons as well.	 That granularity may  not  be	suffi-
       cient  for  all uses, and as a result users should employ compatibility
       levels carefully.  Read the documentation for a particular  feature  to
       find out	the current behavior.

       Bash-4.3	 introduced  a new shell variable: BASH_COMPAT.	 The value as-
       signed to this variable (a decimal version number like 4.2, or an inte-
       ger  corresponding to the compatNN option, like 42) determines the com-
       patibility level.

       Starting	with bash-4.4, Bash has	begun deprecating older	 compatibility
       levels.	 Eventually, the options will be removed in favor of BASH_COM-
       PAT.

       Bash-5.0	is the final version for which there  will  be	an  individual
       shopt  option for the previous version. Users should use	BASH_COMPAT on
       bash-5.0	and later versions.

       The following table describes the behavior changes controlled  by  each
       compatibility level setting.  The compatNN tag is used as shorthand for
       setting the compatibility level to NN using one of the following	mecha-
       nisms.	For versions prior to bash-5.0,	the compatibility level	may be
       set using the corresponding compatNN shopt option.   For	 bash-4.3  and
       later  versions,	 the  BASH_COMPAT variable is preferred, and it	is re-
       quired for bash-5.1 and later versions.

       compat31
	      o	     quoting the rhs of	the [[ command's regexp	matching oper-
		     ator (=~) has no special effect

       compat32
	      o	     interrupting  a  command  list such as "a ; b ; c"	causes
		     the execution  of	the  next  command  in	the  list  (in
		     bash-4.0  and later versions, the shell acts as if	it re-
		     ceived the	interrupt, so interrupting one	command	 in  a
		     list aborts the execution of the entire list)

       compat40
	      o	     the  <  and > operators to	the [[ command do not consider
		     the current locale	when comparing strings;	they use ASCII
		     ordering.	Bash versions prior to bash-4.1	use ASCII col-
		     lation and	strcmp(3); bash-4.1 and	later use the  current
		     locale's collation	sequence and strcoll(3).

       compat41
	      o	     in	 posix mode, time may be followed by options and still
		     be	recognized as a	reserved word (this is POSIX interpre-
		     tation 267)
	      o	     in	posix mode, the	parser requires	that an	even number of
		     single quotes occur in the	 word  portion	of  a  double-
		     quoted  parameter expansion and treats them specially, so
		     that characters within the	single quotes  are  considered
		     quoted (this is POSIX interpretation 221)

       compat42
	      o	     the replacement string in double-quoted pattern substitu-
		     tion does not undergo quote removal, as it	does  in  ver-
		     sions after bash-4.2
	      o	     in	 posix mode, single quotes are considered special when
		     expanding the word	portion	of a  double-quoted  parameter
		     expansion	and  can  be  used to quote a closing brace or
		     other special character (this is part of POSIX  interpre-
		     tation  221);  in	later  versions, single	quotes are not
		     special within double-quoted word expansions

       compat43
	      o	     the shell does not	print a	warning	message	if an  attempt
		     is	 made  to use a	quoted compound	assignment as an argu-
		     ment to declare (declare -a foo='(1 2)'). Later  versions
		     warn that this usage is deprecated
	      o	     word  expansion  errors  are  considered non-fatal	errors
		     that cause	the current command to	fail,  even  in	 posix
		     mode  (the	 default behavior is to	make them fatal	errors
		     that cause	the shell to exit)
	      o	     when  executing  a	 shell	function,   the	  loop	 state
		     (while/until/etc.)	 is not	reset, so break	or continue in
		     that function will	break or continue loops	in the calling
		     context.  Bash-4.4	and later reset	the loop state to pre-
		     vent this

       compat44
	      o	     the shell sets  up	 the  values  used  by	BASH_ARGV  and
		     BASH_ARGC	so  they  can expand to	the shell's positional
		     parameters	even if	extended debugging mode	is not enabled
	      o	     a subshell	inherits loops from  its  parent  context,  so
		     break  or	continue  will	cause  the  subshell  to exit.
		     Bash-5.0 and later	reset the loop state  to  prevent  the
		     exit
	      o	     variable  assignments  preceding builtins like export and
		     readonly that set attributes continue to affect variables
		     with the same name	in the calling environment even	if the
		     shell is not in posix mode

       compat50
	      o	     Bash-5.1 changed the way $RANDOM is generated  to	intro-
		     duce slightly more	randomness. If the shell compatibility
		     level is set to 50	or lower, it  reverts  to  the	method
		     from  bash-5.0 and	previous versions, so seeding the ran-
		     dom number	generator by assigning a value to RANDOM  will
		     produce the same sequence as in bash-5.0
	      o	     If	 the  command hash table is empty, bash	versions prior
		     to	bash-5.1 printed an informational message to that  ef-
		     fect,  even  when	producing output that can be reused as
		     input. Bash-5.1 suppresses	that message when the  -l  op-
		     tion is supplied.

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,	HISTFILE, 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
	      history 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
       /usr/local/bin/bash
	      The bash executable
       /usr/local/etc/profile
	      The systemwide initialization file, executed for login shells
       ~/.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 5.1			2020 October 29			       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 | SHELL COMPATIBILITY MODE | RESTRICTED SHELL | SEE ALSO | FILES | AUTHORS | BUG REPORTS | BUGS

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