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BASH(1)								       BASH(1)

NAME
       bash - GNU Bourne-Again SHell

SYNOPSIS
       bash [options] [file]

COPYRIGHT
       Bash is Copyright (C) 1989-2001 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 IEEE POSIX
       Shell and Tools specification (IEEE Working Group 1003.2).

OPTIONS
       In addition to the single-character shell  options  documented  in  the
       description  of	the set builtin command, bash interprets the following
       options when it is invoked:

       -c string If the -c option is present,  then  commands  are  read  from
		 string.   If  there  are arguments after the string, they are
		 assigned to the positional parameters, starting with $0.
       -r	 If the -r option is present,  the  shell  becomes  restricted
		 (see RESTRICTED SHELL below).
       -i	 If the -i option is present, the shell is interactive.
       -s	 If  the -s option is present, or if no arguments remain after
		 option processing, then commands are read from	 the  standard
		 input.	  This	option	allows the positional parameters to be
		 set when invoking an interactive shell.
       -D	 A list of all double-quoted strings preceded by $ is  printed
		 on  the  standard ouput.  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.
       --	 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
       options	must  appear  on  the command line before the single-character
       options in order for them to be recognized.

       --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
	      INVOCATION below).

       --login
	      Make bash act as if it had been invoked as a  login  shell  (see
	      INVOCATION below).

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

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

       --norc Do  not  read  and  execute  the	personal  initialization  file
	      ~/.bashrc	 if  the  shell	 is interactive.  This option is on by
	      default if the shell is invoked as sh.

       --posix
	      Change the behavior of bash where the default operation  differs
	      from  the	 POSIX	1003.2	standard  to match the standard (posix
	      mode).

       --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
       executed, the exit status is 0.

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

       An  interactive	shell  is one started without non-option arguments and
       without the -c option whose standard input and  output  are  both  con‐
       nected  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 file names as described below under Tilde Expan‐
       sion in the EXPANSION section.

       When bash is invoked as an interactive login shell, or as a  non-inter‐
       active  shell with the --login option, it first reads and executes com‐
       mands from the file /etc/profile, if that file exists.	After  reading
       that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile,
       in that order, and reads and executes commands from the first one  that
       exists  and  is	readable.  The --noprofile option may be used when the
       shell is started to inhibit this behavior.

       When a login shell exits, bash reads and	 executes  commands  from  the
       file ~/.bash_logout, if it exists.

       When  an	 interactive  shell that is not a login shell is started, bash
       reads and executes commands from ~/.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
       example, it looks for the variable BASH_ENV in the environment, expands
       its  value if it appears there, and uses the expanded value as the name
       of a file to read and execute.  Bash behaves as if the  following  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
       behavior	 of  historical	 versions  of sh as closely as possible, while
       conforming to the POSIX standard as well.  When invoked as an  interac‐
       tive  login  shell, or a non-interactive shell with the --login option,
       it first attempts to read and execute commands  from  /etc/profile  and
       ~/.profile,  in	that  order.   The  --noprofile	 option may be used to
       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
       attempt 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 by the remote shell
       daemon, usually rshd.  If bash determines it is being run by  rshd,  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 rshd does	not  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 variable, if it appears in the environment,  is  ignored,
       and the effective user id is set to the real user id.  If the -p option
       is supplied at invocation, the startup behavior is the  same,  but  the
       effective user id is not reset.

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

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

       ! case  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.
       The remaining words are passed as arguments 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 the char‐
       acter |.	 The format for a pipeline is:

	      [time [-p]] [ ! ] command [ | command2 ... ]

       The standard output of command is connected to the  standard  input  of
       command2.   This connection is performed before any redirections speci‐
       fied by the command (see REDIRECTION below).

       If the reserved word !  precedes a pipeline, the exit  status  of  that
       pipeline	 is  the  logical  NOT of the exit status of the last command.
       Otherwise, the status of the pipeline is the exit status	 of  the  last
       command.	 The shell waits for all commands in the pipeline to terminate
       before returning a value.

       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.   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.

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

   Lists
       A list is a sequence of one or more pipelines separated by one  of  the
       operators ;, &, &&, or ⎪⎪, and optionally terminated by one of ;, &, or
       <newline>.

       Of these list operators, && and ⎪⎪ have equal precedence, followed by ;
       and &, which have equal precedence.

       If  a  command  is terminated by the control operator &, the shell exe‐
       cutes the command in the background in a subshell.  The shell does  not
       wait  for  the command to finish, and the return status is 0.  Commands
       separated by a ; are executed sequentially; the shell  waits  for  each
       command	to terminate in turn.  The return status is the exit status of
       the last command executed.

       The control operators && and ⎪⎪ denote AND lists and OR lists,  respec‐
       tively.	An AND list has the form

	      command1 && command2

       command2	 is  executed if, and only if, command1 returns an exit status
       of zero.

       An OR list has the form

	      command1 ⎪⎪ command2

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

   Compound Commands
       A compound command is one of the following:

       (list) list is  executed	 in  a	subshell.   Variable  assignments  and
	      builtin  commands	 that  affect  the  shell's environment do not
	      remain in effect after the command completes.  The return status
	      is the exit status of 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.

       ((expression))
	      The expression is evaluated according  to	 the  rules  described
	      below  under ARITHMETIC EVALUATION.  If the value of the expres‐
	      sion 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.

	      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.  The return
	      value is 0 if the string matches or does not match the  pattern,
	      respectively,  and  1 otherwise.	Any part of the pattern may be
	      quoted to force it to be matched as a string.

	      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 execute  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
	      parameter 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
	      error,  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 stan‐
	      dard 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  dis‐
	      played 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 or return command is executed.  The exit
	      status of select is the exit status of the last command executed
	      in list, or zero if no commands were executed.

       case word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac
	      A case command first expands word, and tries to match it against
	      each pattern in turn, using the same matching rules as for path‐
	      name expansion (see Pathname Expansion below).  When a match  is
	      found,  the  corresponding  list	is  executed.  After the first
	      match, no subsequent matches are attempted.  The exit status  is
	      zero if no pattern matches.  Otherwise, it is the exit status of
	      the last command executed in 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; do list; done
       until list; do list; done
	      The while command continuously executes the do list as  long  as
	      the  last	 command  in list returns an exit status of zero.  The
	      until command is identical to the while command, except that the
	      test  is	negated;  the  do list is executed as long as the last
	      command in list returns a non-zero exit status.  The exit status
	      of  the  while and until commands is the exit status of the last
	      do list command executed, or zero if none was executed.

       [ function ] name () { list; }
	      This defines a function named name.  The body of the function is
	      the  list	 of  commands  between { and }.	 This list is executed
	      whenever name is specified as the name of a simple command.  The
	      exit status of a function is the exit status of the last command
	      executed in the body.  (See 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, the  his‐
       tory  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
       itself 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  \.
       The  characters	$  and	`  retain  their special meaning within double
       quotes.	The backslash retains its special meaning only	when  followed
       by one of the following characters: $, `, ", \, or <newline>.  A double
       quote may be quoted within double quotes by preceding it with  a	 back‐
       slash.

       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 specifed by the
       ANSI C standard.	 Backslash escape sequences, if present,  are  decoded
       as follows:
	      \a     alert (bell)
	      \b     backspace
	      \e     an escape character
	      \f     form feed
	      \n     new line
	      \r     carriage return
	      \t     horizontal tab
	      \v     vertical tab
	      \\     backslash
	      \'     single quote
	      \nnn   the  character  whose  ASCII  code is the octal value nnn
		     (one to three digits)
	      \xnnn  the character whose ASCII code is the  hexadecimal	 value
		     nnn (one to three digits)

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

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

PARAMETERS
       A  parameter is an entity that stores values.  It can be a name, a num‐
       ber, or one of the special characters listed below under Special Param‐
       eters.	For the shell's purposes, a variable is a parameter denoted by
       a name.

       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 (see
       declare below in SHELL BUILTIN  COMMANDS)  then	value  is  subject  to
       arithmetic  expansion  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.	 Path‐
       name expansion is not performed.

   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 occurs within double quotes, it expands to a  sin‐
	      gle word with the value of each parameter separated by the first
	      character of the IFS special variable.  That is, "$*" is equiva‐
	      lent to "$1c$2c...", where c is the first character of the value
	      of the IFS variable.  If IFS is unset, the parameters are	 sepa‐
	      rated  by	 spaces.   If  IFS  is null, the parameters are joined
	      without intervening separators.
       @      Expands to the positional parameters, starting from  one.	  When
	      the  expansion  occurs  within  double  quotes,  each  parameter
	      expands to a separate word.  That is, "$@" is equivalent to "$1"
	      "$2"  ...	  When there are no positional parameters, "$@" and $@
	      expand to nothing (i.e., they are removed).
       #      Expands to the number of positional parameters in decimal.
       ?      Expands to the status of the most recently  executed  foreground
	      pipeline.
       -      Expands  to  the	current option flags as specified upon invoca‐
	      tion, by the set builtin command, or  those  set	by  the	 shell
	      itself (such as the -i option).
       $      Expands  to  the	process ID of the shell.  In a () subshell, it
	      expands to the process ID of the current	shell,	not  the  sub‐
	      shell.
       !      Expands  to  the	process ID of the most recently executed back‐
	      ground (asynchronous) command.
       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 file name used to invoke bash, as given by argument
	      zero.
       _      At shell startup, set to the absolute file name of the shell  or
	      shell  script  being  executed  as  passed in the argument list.
	      Subsequently, expands to the last argument to the previous  com‐
	      mand,  after  expansion.	Also set to the full file name of each
	      command executed and placed in the environment exported to  that
	      command.	 When  checking mail, this parameter holds the name of
	      the mail file currently being checked.

   Shell Variables
       The following variables are set by the shell:

       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.
       OLDPWD The previous working directory as set by the cd command.
       REPLY  Set  to  the line of input read by the read builtin command when
	      no arguments are supplied.
       UID    Expands to the user ID of the current user, initialized at shell
	      startup.	This variable is readonly.
       EUID   Expands  to  the effective user ID of the current user, initial‐
	      ized at shell startup.  This variable is readonly.
       GROUPS An array variable containing the list of	groups	of  which  the
	      current  user is a member.  Assignments to GROUPS have no effect
	      and return an error status.  If GROUPS is unset,	it  loses  its
	      special properties, even if it is subsequently reset.
       BASH   Expands  to  the	full file name used to invoke this instance of
	      bash.
       BASH_VERSION
	      Expands to a string describing the version of this  instance  of
	      bash.
       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.

       SHLVL  Incremented by one each time an instance of bash is started.

       RANDOM Each time this parameter is referenced, a random integer between
	      0 and 32767 is generated.	 The sequence of random numbers may be
	      initialized by assigning a value to RANDOM.  If RANDOM is unset,
	      it loses its special properties,	even  if  it  is  subsequently
	      reset.

       SECONDS
	      Each  time  this	parameter is referenced, the number of seconds
	      since shell invocation is returned.  If a value is  assigned  to
	      SECONDS,	the  value  returned upon subsequent references is the
	      number of seconds since the assignment plus the value  assigned.
	      If SECONDS is unset, it loses its special properties, even if it
	      is subsequently reset.

       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.

       HISTCMD
	      The history number, or index in the history list, of the current
	      command.	If HISTCMD is unset, it loses its special  properties,
	      even if it is subsequently reset.

       FUNCNAME
	      The  name of any currently-executing shell function.  This vari‐
	      able exists only when a shell function  is  executing.   Assign‐
	      ments to FUNCNAME have no effect and return an error status.  If
	      FUNCNAME is unset, it loses its special properties, even	if  it
	      is subsequently reset.

       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
	      unset, it loses its special properties, even  if	it  is	subse‐
	      quently reset.

       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).

       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).

       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.

       OSTYPE Automatically  set to a string that describes the operating sys‐
	      tem on which bash is executing.  The  default  is	 system-depen‐
	      dent.

       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.

       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.

       COMP_WORDS
	      An  array variable (see Arrays below) consisting of the individ‐
	      ual words in the current command line.  This variable is	avail‐
	      able only in shell functions invoked by the programmable comple‐
	      tion facilities (see Programmable Completion below).

       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_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).

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

       IFS    The  Internal  Field  Separator  that is used for word splitting
	      after expansion and to split lines  into	words  with  the  read
	      builtin  command.	  The  default	value  is  ``<space><tab><new‐
	      line>''.
       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).	 The default path is system-dependent, and  is
	      set  by  the administrator who installs bash.  A common value is
	      ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''.
       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.
       CDPATH The search path for the cd command.  This is  a  colon-separated
	      list  of	directories  in	 which the shell looks for destination
	      directories specified by the cd  command.	  A  sample  value  is
	      ``.:~:/usr''.
       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 file name.
	      PATH is not used to search for the resultant file name.
       MAIL   If this parameter is set to a file name and the  MAILPATH	 vari‐
	      able is not set, bash informs the user of the arrival of mail in
	      the specified file.
       MAILCHECK
	      Specifies how often (in seconds)	bash  checks  for  mail.   The
	      default  is  60 seconds.	When it is time to check for mail, the
	      shell does so before displaying the  primary  prompt.   If  this
	      variable	is  unset,  or	set  to	 a  value that is not a number
	      greater than or equal to zero, the shell disables mail checking.
       MAILPATH
	      A colon-separated list of file names to  be  checked  for	 mail.
	      The message to be printed when mail arrives in a particular file
	      may be specified by separating the file name  from  the  message
	      with a `?'.  When used in the text of the message, $_ expands to
	      the name of the current mailfile.	 Example:
	      MAILPATH='/var/mail/bfox?"You  have  mail":~/shell-mail?"$_  has
	      mail!"'
	      Bash  supplies  a default value for this variable, but the loca‐
	      tion of the user mail files that it  uses	 is  system  dependent
	      (e.g., /var/mail/$USER).
       PS1    The  value  of  this parameter is expanded (see PROMPTING below)
	      and used as the primary prompt string.   The  default  value  is
	      ``\s-\v\$ ''.
       PS2    The  value of this parameter is expanded as with PS1 and used as
	      the secondary prompt string.  The default is ``> ''.
       PS3    The value of this parameter is used as the prompt for the select
	      command (see SHELL GRAMMAR above).
       PS4    The  value  of  this  parameter  is expanded as with PS1 and the
	      value is printed before each command  bash  displays  during  an
	      execution	 trace.	 The first character of PS4 is replicated mul‐
	      tiple times, as necessary, to indicate multiple levels of	 indi‐
	      rection.	The default is ``+ ''.
       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%3lS'.  If the value is null,  no
	      timing  information  is  displayed.  A trailing newline is added
	      when the format string is displayed.

       HISTSIZE
	      The number of commands to remember in the command	 history  (see
	      HISTORY below).  The default value is 500.

       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 an interactive 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.   The  default  value  is	500.  The history file is also
	      truncated to this size after  writing  it	 when  an  interactive
	      shell exits.

       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.

       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
	      sequences within pathname expansion and pattern matching.

       LC_CTYPE
	      This  variable  determines  the interpretation of characters and
	      the behavior of character classes within pathname expansion  and
	      pattern matching.

       LC_MESSAGES
	      This  variable  determines  the locale used to translate double-
	      quoted strings preceded by a $.

       LC_NUMERIC
	      This variable determines the locale  category  used  for	number
	      formatting.

       LINES  Used  by	the  select  builtin  command  to determine the column
	      length for printing selection  lists.   Automatically  set  upon
	      receipt of a SIGWINCH.

       COLUMNS
	      Used  by	the  select  builtin command to determine the terminal
	      width when printing selection  lists.   Automatically  set  upon
	      receipt of a SIGWINCH.

       PROMPT_COMMAND
	      If set, the value is executed as a command prior to issuing each
	      primary prompt.

       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.

       TMOUT  If set to a value greater than zero, the value is interpreted as
	      the  number  of seconds to wait for input after issuing the pri‐
	      mary prompt.  Bash terminates after waiting for that  number  of
	      seconds if input does not arrive.

       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:~''.

       GLOBIGNORE
	      A colon-separated list of patterns defining the set of filenames
	      to be ignored by pathname expansion.  If a filename matched by a
	      pathname expansion pattern also matches one of the  patterns  in
	      GLOBIGNORE, it is removed from the list of matches.

       INPUTRC
	      The  filename  for  the  readline	 startup  file, overriding the
	      default of ~/.inputrc (see READLINE below).

       HISTCONTROL
	      If set to a value of ignorespace, lines which begin with a space
	      character	 are  not  entered  on	the history list.  If set to a
	      value of ignoredups, lines matching the last  history  line  are
	      not  entered.   A	 value of ignoreboth combines the two options.
	      If unset, or if set to any other value  than  those  above,  all
	      lines  read by the parser are saved on the history list, subject
	      to the value of HISTIGNORE.  This variable's function is	super‐
	      seded  by	 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.

       HISTIGNORE
	      A	 colon-separated list of patterns used to decide which command
	      lines should be saved on the  history  list.   Each  pattern  is
	      anchored	at  the	 beginning of the line and must match the com‐
	      plete line (no implicit  `*'  is	appended).   Each  pattern  is
	      tested  against  the line after the checks specified by HISTCON‐
	      TROL are applied.	 In  addition  to  the	normal	shell  pattern
	      matching characters, `&' matches the previous history line.  `&'
	      may be escaped using  a  backslash;  the	backslash  is  removed
	      before attempting a match.  The second and subsequent lines of a
	      multi-line compound command are not tested, and are added to the
	      history regardless of the value of HISTIGNORE.

       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.

       HOSTFILE
	      Contains	the  name  of  a file in the same format as /etc/hosts
	      that should be read when the shell needs to complete a hostname.
	      The  list	 of possible hostname completions may be changed while
	      the shell is running;  the  next	time  hostname	completion  is
	      attempted	 after the value is changed, bash adds the contents of
	      the new file to the existing list.  If HOSTFILE is set, but  has
	      no value, bash attempts to read /etc/hosts to obtain the list of
	      possible hostname completions.   When  HOSTFILE  is  unset,  the
	      hostname list is cleared.

       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
	      % job identifier.

       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).

   Arrays
       Bash  provides  one-dimensional	array  variables.  Any variable may be
       used as an array; the declare builtin will explicitly declare an array.
       There  is no maximum limit on the size of an array, nor any requirement
       that members be indexed or assigned contiguously.  Arrays  are  indexed
       using integers and are zero-based.

       An  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 greater than or
       equal to zero.  To explicitly declare an array,	use  declare  -a  name
       (see SHELL BUILTIN COMMANDS below).  declare -a name[subscript] is also
       accepted; the subscript is ignored.  Attributes may be specified for an
       array variable using the declare and readonly builtins.	Each attribute
       applies to all members of an array.

       Arrays  are  assigned  to  using	 compound  assignments	of  the	  form
       name=(value1  ...  valuen),  where  each	 value	is  of	the form [sub‐
       script]=string.	Only string is required.  If the optional brackets and
       subscript  are supplied, that index is assigned to; otherwise the index
       of the element assigned is the last index assigned to by the  statement
       plus  one.   Indexing  starts at zero.  This syntax is also accepted by
       the declare builtin.  Individual array  elements	 may  be  assigned  to
       using the name[subscript]=value syntax introduced above.

       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.	  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 expan‐
       sion is the number of elements in  the  array.	Referencing  an	 array
       variable without a subscript is equivalent to referencing element zero.

       The  unset  builtin  is	used to destroy arrays.	 unset name[subscript]
       destroys the array element at index subscript.  unset name, where  name
       is  an  array,  or  unset  name[subscript],  where subscript is * or @,
       removes the entire array.

       The declare, local, and readonly builtins each accept a	-a  option  to
       specify	an  array.   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, parame‐
       ter, variable and arithmetic expansion and command  substitution	 (done
       in a left-to-right fashion), word splitting, and pathname expansion.

       On systems that can support it, there is an additional expansion avail‐
       able: process substitution.

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

   Brace Expansion
       Brace expansion is a mechanism by which arbitrary strings may be gener‐
       ated.  This mechanism is similar to pathname expansion, but  the	 file‐
       names generated need not exist.	Patterns to be brace expanded take the
       form of an optional preamble, followed by a series  of  comma-separated
       strings	between	 a pair of braces, followed by an optional postscript.
       The preamble is prefixed to each string contained  within  the  braces,
       and the postscript is then appended to each resulting string, expanding
       left to right.

       Brace expansions may be nested.	The results of	each  expanded	string
       are  not	 sorted;  left	to  right  order  is  preserved.  For example,
       a{d,c,b}e expands into `ade ace abe'.

       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.   Any  incorrectly
       formed  brace expansion is left unchanged.  A { or , may be quoted with
       a backslash to prevent its being considered part of a brace expression.
       To  avoid conflicts with parameter expansion, the string ${ is not con‐
       sidered eligible for brace expansion.

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

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

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

   Tilde Expansion
       If  a  word  begins  with an unquoted tilde character (`~'), all of the
       characters preceding the first unquoted slash (or  all  characters,  if
       there  is no unquoted slash) are considered a tilde-prefix.  If none of
       the characters in the tilde-prefix are quoted, the  characters  in  the
       tilde-prefix  following the tilde are treated as a possible login name.
       If this login name is the null string, the tilde is replaced  with  the
       value  of  the shell parameter HOME.  If HOME is unset, the home direc‐
       tory of the user executing the shell is	substituted  instead.	Other‐
       wise,  the  tilde-prefix is replaced with the home directory associated
       with the specified login name.

       If the tilde-prefix is a `~+', the value	 of  the  shell	 variable  PWD
       replaces 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 =.  In these cases, tilde expansion is also per‐
       formed.	 Consequently,	one  may use file names with tildes in assign‐
       ments to PATH, MAILPATH, and CDPATH, and the shell assigns the expanded
       value.

   Parameter Expansion
       The `$' character introduces parameter expansion, command substitution,
       or arithmetic expansion.	 The parameter name or symbol to  be  expanded
       may  be enclosed in braces, which are optional but serve to protect the
       variable to be expanded from characters immediately following it	 which
       could be interpreted as part of the name.

       When  braces  are  used, the matching ending brace is the first `}' not
       escaped by a backslash or within a quoted string,  and  not  within  an
       embedded arithmetic expansion, command substitution, or paramter 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.

       If the first character of parameter is an exclamation point, a level of
       variable indirection is introduced.  Bash uses the value of  the	 vari‐
       able  formed  from  the	rest of parameter as the name of the variable;
       this variable is then expanded and that value is used in	 the  rest  of
       the  substitution,  rather than the value of parameter itself.  This is
       known as indirect expansion.  The exception to this is the expansion of
       ${!prefix*} described below.

       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, bash tests for a parameter that is
       unset or null; omitting the colon results in a test only for a  parame‐
       ter that is unset.

       ${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
	      expansion of word is assigned to parameter.  The value of param‐
	      eter  is	then  substituted.   Positional parameters and special
	      parameters 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
	      parameter starting at the character  specified  by  offset.   If
	      length  is omitted, expands to the substring of parameter start‐
	      ing at the character specified by offset.	 length and offset are
	      arithmetic   expressions	 (see  ARITHMETIC  EVALUATION  below).
	      length must evaluate to a number greater than or equal to	 zero.
	      If  offset  evaluates  to	 a number less than zero, the value is
	      used as an offset from the end of the value  of  parameter.   If
	      parameter	 is  @,	 the  result  is  length positional parameters
	      beginning at offset.  If parameter is an array name indexed by @
	      or  *,  the  result is the length members of the array beginning
	      with ${parameter[offset]}.   Substring  indexing	is  zero-based
	      unless  the  positional  parameters  are used, in which case the
	      indexing starts at 1.

       ${!prefix*}
	      Expands to the names of variables whose names begin with prefix,
	      separated by the first character of the IFS special variable.

       ${#parameter}
	      The  length  in  characters of the value of parameter is substi‐
	      tuted.  If parameter is * or @, the  value  substituted  is  the
	      number  of positional parameters.	 If parameter is an array name
	      subscripted by * or @, the value substituted is  the  number  of
	      elements in the array.

       ${parameter#word}
       ${parameter##word}
	      The  word	 is  expanded to produce a pattern just as in pathname
	      expansion.  If the pattern matches the beginning of the value of
	      parameter,  then	the  result  of	 the expansion is the expanded
	      value of parameter with the shortest matching pattern (the ``#''
	      case) or the longest matching pattern (the ``##'' case) deleted.
	      If parameter is @ or *, the pattern removal operation is applied
	      to  each	positional parameter in turn, and the expansion is the
	      resultant list.  If parameter is an array	 variable  subscripted
	      with  @  or  *, the pattern removal operation is applied to each
	      member of the array in turn, and the expansion is the  resultant
	      list.

       ${parameter%word}
       ${parameter%%word}
	      The  word	 is  expanded to produce a pattern just as in pathname
	      expansion.  If the pattern matches a  trailing  portion  of  the
	      expanded value of parameter, then the result of the expansion is
	      the expanded value of parameter with the shortest matching  pat‐
	      tern  (the  ``%''	 case)	or  the	 longest matching pattern (the
	      ``%%'' case) deleted.  If parameter  is  @  or  *,  the  pattern
	      removal  operation  is  applied  to each positional parameter in
	      turn, and the expansion is the resultant list.  If parameter  is
	      an  array	 variable subscripted with @ or *, the pattern removal
	      operation is applied to each member of the array	in  turn,  and
	      the expansion is the resultant list.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
	      The pattern is expanded to produce a pattern just as in pathname
	      expansion.  Parameter is expanded and the longest match of  pat‐
	      tern  against  its  value is replaced with string.  In the first
	      form, only the first match is replaced.  The second form	causes
	      all  matches  of pattern to be replaced with string.  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 parameter is @ or *, the substitution  operation
	      is  applied to each positional parameter in turn, and the expan‐
	      sion is the resultant list.  If parameter is an  array  variable
	      subscripted  with	 @ or *, the substitution operation is applied
	      to each member of the array in turn, and the  expansion  is  the
	      resultant list.

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

	      $(command)
       or
	      `command`

       Bash performs the expansion by executing command and replacing the com‐
       mand  substitution  with	 the  standard output of the command, with any
       trailing newlines deleted.  Embedded newlines are not deleted, but they
       may  be	removed during word splitting.	The command substitution $(cat
       file) can be replaced by the equivalent but faster $(< file).

       When the old-style backquote form of substitution  is  used,  backslash
       retains	its  literal  meaning except when followed by $, `, or \.  The
       first backquote not preceded by a backslash terminates the command sub‐
       stitution.   When using the $(command) form, all characters between the
       parentheses make up the command; none are treated specially.

       Command substitutions may be nested.  To nest when using the backquoted
       form, escape the inner backquotes with backslashes.

       If  the	substitution  appears within double quotes, word splitting and
       pathname expansion are not performed on the results.

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

	      $((expression))

       The expression is treated as if it were within  double  quotes,	but  a
       double  quote  inside  the  parentheses	is not treated specially.  All
       tokens in the expression undergo parameter expansion, string expansion,
       command	substitution, and quote removal.  Arithmetic substitutions may
       be nested.

       The evaluation is performed according to the rules listed  below	 under
       ARITHMETIC EVALUATION.  If expression is invalid, bash prints a message
       indicating failure and no substitution occurs.

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

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

   Word Splitting
       The  shell  scans the results of parameter expansion, command substitu‐
       tion, and arithmetic expansion that did not occur within double	quotes
       for word splitting.

       The  shell  treats each character of IFS as a delimiter, and splits the
       results of the other expansions into words on these characters.	If IFS
       is  unset,  or its value is exactly <space><tab><newline>, the default,
       then any sequence of IFS characters serves to delimit  words.   If  IFS
       has  a  value  other than the default, then sequences of the whitespace
       characters space and tab are ignored at the beginning and  end  of  the
       word,  as  long	as the whitespace character is in the value of IFS (an
       IFS whitespace character).  Any character in IFS that is not IFS white‐
       space,  along  with  any adjacent IFS whitespace characters, delimits a
       field.  A sequence of IFS whitespace characters is also	treated	 as  a
       delimiter.  If the value of IFS is null, no word splitting occurs.

       Explicit	 null  arguments  (""  or '') are retained.  Unquoted implicit
       null arguments, resulting from the expansion of parameters that have no
       values,	are  removed.  If a parameter with no value is expanded within
       double quotes, a null argument results and is retained.

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

   Pathname Expansion
       After word splitting, unless the -f option has  been  set,  bash	 scans
       each  word  for the characters *, ?, and [.  If one of these characters
       appears, then the word is regarded as a pattern, and replaced  with  an
       alphabetically  sorted  list of file names matching the pattern.	 If no
       matching file names are found, and the shell option  nullglob  is  dis‐
       abled,  the word is left unchanged.  If the nullglob option is set, and
       no matches are found, the word is removed.  If the shell option nocase‐
       glob  is	 enabled, the match is performed 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 explicitly, unless the shell  option  dotglob  is
       set.   When  matching  a	 pathname,  the slash character must always be
       matched explicitly.  In	other  cases,  the  ``.''   character  is  not
       treated	specially.   See  the  description  of shopt below under SHELL
       BUILTIN COMMANDS for a description of  the  nocaseglob,	nullglob,  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.  The file names ``.''	and ``..''  are always
       ignored,	 even when GLOBIGNORE is set.  However, setting GLOBIGNORE has
       the effect of enabling the dotglob shell	 option,  so  all  other  file
       names  beginning	 with a ``.''  will match.  To get the old behavior of
       ignoring file names beginning with a ``.'', make	 ``.*''	  one  of  the
       patterns in GLOBIGNORE.	The dotglob option is disabled when GLOBIGNORE
       is unset.

       Pattern Matching

       Any character that appears in a pattern, other than the special pattern
       characters  described below, matches itself.  The NUL character may not
       occur in a pattern.  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.
       ?      Matches any single character.
       [...]  Matches  any  one of the enclosed characters.  A pair of charac‐
	      ters separated by a hyphen denotes a range expression; any char‐
	      acter  that sorts between those two characters, inclusive, using
	      the current locale's collating sequence and  character  set,  is
	      matched.	 If the first character following the [ 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 value of the LC_COLLATE shell variable,  if  set.
	      A	 - may be matched by including it as the first or last charac‐
	      ter 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.2 standard:
	      alnum  alpha  ascii  blank  cntrl	 digit graph lower print punct
	      space upper xdigit
	      A character class matches any character belonging to that class.

	      Within [ and ], an equivalence class can be specified using  the
	      syntax  [=c=], which matches all characters with the same colla‐
	      tion weight (as defined by the current locale) as the  character
	      c.

	      Within [ and ], the syntax [.symbol.] matches the collating sym‐
	      bol 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 exactly one of the given patterns
	      !(pattern-list)
		     Matches anything except one of the given patterns

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

REDIRECTION
       Before a command is executed, its input and output  may	be  redirected
       using  a	 special  notation  interpreted by the shell.  Redirection may
       also be used to open and close files for the  current  shell  execution
       environment.  The following redirection operators may precede or appear
       anywhere within a simple command or may follow a command.  Redirections
       are processed in the order they appear, from left to right.

       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 expansion, command substitution, arithmetic expan‐
       sion, 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 as standard output before the standard output  was
       redirected to dirlist.

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

	      /dev/fd/fd
		     If fd is a valid integer, file descriptor	fd  is	dupli‐
		     cated.
	      /dev/stdin
		     File descriptor 0 is duplicated.
	      /dev/stdout
		     File descriptor 1 is duplicated.
	      /dev/stderr
		     File descriptor 2 is duplicated.
	      /dev/tcp/host/port
		     If host is a valid hostname or Internet address, and port
		     is an integer port number, bash attempts to  open	a  TCP
		     connection to the corresponding socket.
	      /dev/udp/host/port
		     If host is a valid hostname or Internet address, and port
		     is an integer port number, bash attempts to  open	a  UDP
		     connection to the corresponding socket.

       A failure to open or create a file causes the redirection to fail.

   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
       expansion of word to be opened for writing on file descriptor n, or the
       standard output (file descriptor 1) if n is not specified.  If the file
       does not exist it is created; if it does exist it is truncated to  zero
       size.

       The general format for redirecting output is:

	      [n]>word

       If  the	redirection operator is >, and the noclobber option to the set
       builtin has been enabled, the redirection will fail if the  file	 whose
       name  results  from the expansion of word exists and is a regular file.
       If the redirection operator is >|, or the redirection operator is > and
       the noclobber option 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
       results	from  the expansion of word to be opened for appending on file
       descriptor n, or the standard output (file descriptor 1) if  n  is  not
       specified.  If the file does not exist it is created.

       The general format for appending output is:

	      [n]>>word

   Redirecting Standard Output and Standard Error
       Bash  allows both the standard output (file descriptor 1) and the stan‐
       dard error output (file descriptor 2) to	 be  redirected	 to  the  file
       whose name is the expansion of word with this construct.

       There  are  two	formats	 for  redirecting standard output and standard
       error:

	      &>word
       and
	      >&word

       Of the two forms, the first is preferred.  This is semantically equiva‐
       lent to

	      >word 2>&1

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

       The format of here-documents is as follows:

	      <<[-]word
		      here-document
	      delimiter

       No parameter expansion, command substitution, arithmetic expansion,  or
       pathname expansion is performed on word.	 If any characters in word are
       quoted, the delimiter is the result of quote removal on word,  and  the
       lines  in the here-document are not expanded.  If word is unquoted, all
       lines of the here-document are subjected to parameter  expansion,  com‐
       mand  substitution,  and arithmetic expansion.  In the latter case, the
       character sequence \<newline> is ignored, and \ must be used  to	 quote
       the characters \, $, and `.

       If the redirection operator is <<-, then all leading tab characters are
       stripped from input lines and  the  line	 containing  delimiter.	  This
       allows  here-documents within shell scripts to be indented in a natural
       fashion.

   Duplicating File Descriptors
       The redirection operator

	      [n]<&word

       is used to duplicate input file descriptors.  If word expands to one or
       more  digits,  the file descriptor denoted by n is made to be a copy of
       that file descriptor.  If the digits in word  do	 not  specify  a  file
       descriptor  open for input, a redirection error occurs.	If word evalu‐
       ates 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.	As a special case, if n is omitted,  and  word
       does not expand to one or more digits, the standard output and standard
       error are redirected as described previously.

   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
       command, if unquoted, is checked to see if it has  an  alias.   If  so,
       that word is replaced by the text of the alias.	The alias name and the
       replacement text may contain  any  valid	 shell	input,	including  the
       metacharacters listed above, with the exception that the alias name may
       not contain =.  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 expan‐
       sion.

       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
       before  executing  any  of  the	commands  on  that  line.  Aliases are
       expanded when a command is read, not when it is	executed.   Therefore,
       an  alias definition appearing on the same line as another command does
       not take effect until the next line of input  is	 read.	 The  commands
       following the alias definition on that line are not affected by the new
       alias.  This behavior is also an issue  when  functions	are  executed.
       Aliases	are  expanded when a function definition is read, not when the
       function is executed, because a function definition is  itself  a  com‐
       pound command.  As a consequence, aliases defined in a function are not
       available until after that function is executed.	 To  be	 safe,	always
       put  alias definitions on a separate line, and do not use alias in com‐
       pound 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
       interpret  them	(contrast  this with the execution of a shell script).
       When a function is executed, the arguments to the function  become  the
       positional parameters during its execution.  The special parameter # is
       updated to reflect the change.  Positional parameter  0	is  unchanged.
       The  FUNCNAME  variable	is  set	 to the name of the function while the
       function is executing.  All other aspects of the shell execution	 envi‐
       ronment are identical between a function and its caller with the excep‐
       tion that the DEBUG trap (see the description of the trap builtin under
       SHELL BUILTIN COMMANDS below) is not inherited.

       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  the	builtin command return is executed in a function, the function
       completes and execution resumes with the next command after  the	 func‐
       tion  call.   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.  Functions may be exported so
       that subshells automatically have them defined with the	-f  option  to
       the export builtin.

       Functions  may  be  recursive.	No  limit  is imposed on the number of
       recursive calls.

ARITHMETIC EVALUATION
       The shell allows arithmetic expressions to be evaluated, under  certain
       circumstances  (see  the let builtin command and Arithmetic Expansion).
       Evaluation is done in long integers with no check for overflow,	though
       division	 by  0	is trapped and flagged as an error.  The operators and
       their precedence and associativity are the same as in the  C  language.
       The  following list of operators is grouped into levels of equal-prece‐
       dence operators.	 The levels are listed in order of  decreasing	prece‐
       dence.

       id++ id--
	      variable post-increment and post-decrement
       ++id --id
	      variable pre-increment and pre-decrement
       - +    unary minus and plus
       ! ~    logical and bitwise negation
       **     exponentiation
       * / %  multiplication, division, remainder
       + -    addition, subtraction
       << >>  left and right bitwise shifts
       <= >= < >
	      comparison
       == !=  equality and inequality
       &      bitwise AND
       ^      bitwise exclusive OR
       |      bitwise OR
       &&     logical AND
       ||     logical OR
       expr?expr:expr
	      conditional evaluation
       = *= /= %= += -= <<= >>= &= ^= |=
	      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.  The value of a variable is evaluated	as  an	arith‐
       metic expression when it is referenced.	A shell variable need not have
       its integer attribute turned on to be used in an expression.

       Constants with a leading 0 are interpreted as octal numbers.  A leading
       0x  or  0X  denotes  hexadecimal.   Otherwise,  numbers	take  the form
       [base#]n, where base is a decimal number between 2 and 64  representing
       the arithmetic base, and n is a number in that base.  If base# is omit‐
       ted, then base 10 is used.  The digits greater than 9  are  represented
       by  the	lowercase  letters,  the  uppercase letters, _, and @, in that
       order.  If base is less than or equal to 36,  lowercase	and  uppercase
       letters	may be used interchangably to represent numbers between 10 and
       35.

       Operators are evaluated in order	 of  precedence.   Sub-expressions  in
       parentheses  are	 evaluated first and may override the precedence rules
       above.

CONDITIONAL EXPRESSIONS
       Conditional expressions are used by the [[  compound  command  and  the
       test  and [ builtin commands to test file attributes and perform string
       and arithmetic comparisons.  Expressions are formed from the  following
       unary  or  binary  primaries.   If any file argument to one of the pri‐
       maries is of the form /dev/fd/n, then file descriptor n is checked.  If
       the  file  argument  to	one  of	 the  primaries	 is one of /dev/stdin,
       /dev/stdout, or /dev/stderr, file descriptor 0, 1, or 2,	 respectively,
       is checked.

       -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.
       -O file
	      True if file exists and is owned by the effective user id.
       -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.
       -S file
	      True if file exists and is a socket.
       -N file
	      True  if	file  exists  and  has been modified since it was last
	      read.
       file1 -nt file2
	      True if file1 is newer (according	 to  modification  date)  than
	      file2.
       file1 -ot file2
	      True if file1 is older than file2.
       file1 -ef file2
	      True if file1 and file2 have the same device and inode numbers.
       -o optname
	      True  if	shell  option  optname	is  enabled.   See the list of
	      options under the description  of	 the  -o  option  to  the  set
	      builtin below.
       -z string
	      True if the length of string is zero.
       -n string
       string True if the length of string is non-zero.
       string1 == string2
	      True if the strings are equal.  = may be used in place of ==.
       string1 != string2
	      True if the strings are not equal.
       string1 < string2
	      True  if	string1	 sorts before string2 lexicographically in the
	      current locale.
       string1 > string2
	      True if string1 sorts after  string2  lexicographically  in  the
	      current locale.
       arg1 OP arg2
	      OP  is one of -eq, -ne, -lt, -le, -gt, or -ge.  These arithmetic
	      binary operators return true if arg1 is equal to, not equal  to,
	      less  than, less than or equal to, greater than, or greater than
	      or equal to arg2, respectively.  Arg1 and arg2 may  be  positive
	      or negative integers.

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

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

       2.     The words that are not variable assignments or redirections  are
	      expanded.	  If  any words remain after expansion, the first word
	      is taken to be the name of the command and the  remaining	 words
	      are the arguments.

       3.     Redirections are performed as described above under REDIRECTION.

       4.     The text after the = in each variable assignment undergoes tilde
	      expansion, parameter expansion, command substitution, arithmetic
	      expansion,  and quote removal before being assigned to the vari‐
	      able.

       If no command name results, the variable assignments affect the current
       shell  environment.  Otherwise, the variables are added to the environ‐
       ment of the executed command and do not affect the current shell	 envi‐
       ronment.	  If  any  of  the assignments attempts to assign a value to a
       readonly variable, an error occurs, and the command exits with  a  non-
       zero status.

       If  no  command	name  results,	redirections are performed, but do not
       affect the current shell environment.  A redirection error  causes  the
       command to exit with a non-zero status.

       If  there is a command name left after expansion, execution proceeds as
       described below.	 Otherwise, the command exits.	If one of  the	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
       remember	 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 prints an error message  and  returns
       an exit status of 127.

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

       If this execution fails because the file is not in  executable  format,
       and  the file is not a directory, it is assumed to be a shell script, a
       file containing shell commands.	A subshell is spawned to  execute  it.
       This  subshell  reinitializes itself, so that the effect is as if a new
       shell had been invoked to handle the script, with  the  exception  that
       the  locations  of  commands  remembered	 by the parent (see hash below
       under 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:

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

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

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

       ·      current traps set by trap

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

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

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

       ·      options enabled by shopt

       ·      shell aliases defined with alias

       ·      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.

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

       ·      the current working directory

       ·      the file creation mode mask

       ·      shell variables marked for export, along with variables exported
	      for the command, passed in the environment

       ·      traps  caught by the shell are reset to the values the inherited
	      from the shell's parent, and traps  ignored  by  the  shell  are
	      ignored

       A  command  invoked  in	this  separate	environment  cannot affect the
       shell's execution environment.

       Command substitution and asynchronous commands are invoked  in  a  sub‐
       shell  environment that is a duplicate of the shell environment, except
       that traps caught by the shell are reset to the values that  the	 shell
       inherited  from	its  parent  at invocation.  Builtin commands that are
       invoked as part of a pipeline are also executed in a subshell  environ‐
       ment.   Changes	made  to  the  subshell	 environment cannot affect the
       shell's execution environment.

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
       invocation, 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
       declare -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,
       replacing  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 file name of the command and passed to that command in  its	 envi‐
       ronment.

EXIT STATUS
       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
       returns	a status of 127.  If a command is found but is not executable,
       the return status is 126.

       If a command fails because of an error during expansion or redirection,
       the exit status is greater than zero.

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

       Bash  itself  returns  the  exit	 status	 of the last command executed,
       unless 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
       ignores SIGTTIN, SIGTTOU, and SIGTSTP.

       Synchronous jobs started by bash have signal handlers set to the values
       inherited by the shell from its parent.	When job  control  is  not  in
       effect,	asynchronous commands ignore SIGINT and SIGQUIT as well.  Com‐
       mands run as a result of command substitution ignore the	 keyboard-gen‐
       erated job control signals SIGTTIN, SIGTTOU, and SIGTSTP.

       The  shell  exits by default upon receipt of a SIGHUP.  Before exiting,
       it 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 using 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.

       When bash receives a signal for which a trap has been set while waiting
       for a command to complete, the trap will not be executed until the 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
       execution of processes and continue (resume) their execution at a later
       point.  A user typically	 employs  this	facility  via  an  interactive
       interface supplied jointly by the system'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
       write to the terminal.  Background processes which attempt to read from
       (write to) the terminal are sent a SIGTTIN (SIGTTOU) signal by the ter‐
       minal 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
       returned	 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 name.  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	 exam‐
       ple, %ce refers to a stopped ce job.  If a prefix matches more than one
       job, bash reports an error.  Using %?ce, on the other hand,  refers  to
       any job containing the string ce in its command line.  If the substring
       matches more than one job, bash reports an 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	 back‐
       ground.	 The  previous job may be referenced using %-.	In output per‐
       taining to jobs (e.g., the output of the jobs command), the current job
       is always flagged with a +, and the previous job with a -.

       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.

       If an attempt to exit bash is made while jobs are  stopped,  the	 shell
       prints a warning message.  The jobs command may then be used to inspect
       their status.  If a second attempt to exit is made without an interven‐
       ing  command, the shell does not print another warning, and the stopped
       jobs are terminated.

PROMPTING
       When executing interactively, bash displays the primary prompt PS1 when
       it  is  ready  to  read a command, and the secondary prompt PS2 when it
       needs more input to complete  a	command.   Bash	 allows	 these	prompt
       strings	to  be	customized  by inserting a number of backslash-escaped
       special characters that are decoded as follows:
	      \a     an ASCII bell character (07)
	      \d     the date in "Weekday Month Date" format (e.g.,  "Tue  May
		     26")
	      \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
	      \u     the username of the current user
	      \v     the version of bash (e.g., 2.00)
	      \V     the release of bash, version + patchlevel (e.g., 2.00.0)
	      \w     the current working directory
	      \W     the basename of the current working directory
	      \!     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
       below),	while  the  command  number is the position in the sequence of
       commands executed during the current shell session.  After  the	string
       is  decoded,  it is expanded via parameter expansion, command substitu‐
       tion, arithmetic expansion, and quote removal, subject to the value  of
       the  promptvars	shell option (see the description of the shopt command
       under SHELL BUILTIN COMMANDS below).

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

   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
       ~/.inputrc.   When a program which uses the readline library starts up,
       the initialization file is read, and the key bindings and variables are
       set.   There  are  only	a few basic constructs allowed in the readline
       initialization file.  Blank lines are ignored.  Lines beginning with  a
       #  are  comments.   Lines  beginning with a $ indicate conditional con‐
       structs.	 Other lines denote key bindings and variable settings.

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

       For example, placing

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

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

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

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

       When using the form keyname:function-name or macro, keyname is the name
       of a key spelled out in English.	 For example:

	      Control-u: universal-argument
	      Meta-Rubout: backward-kill-word
	      Control-o: "> output"

       In  the above example, C-u is bound to the function universal-argument,
       M-DEL is bound to the function backward-kill-word, and C-o is bound  to
       run  the macro expressed on the right hand side (that is, to insert the
       text ``> output'' into the line).

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

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

       In this example, C-u is again bound to the function universal-argument.
       C-x  C-r is bound to the function re-read-init-file, and ESC [ 1 1 ~ is
       bound to insert the text ``Function Key 1''.

       The full set of GNU Emacs style escape sequences is
	      \C-    control prefix
	      \M-    meta prefix
	      \e     an escape character
	      \\     backslash
	      \"     literal "
	      \'     literal '

       In addition to the GNU Emacs style escape sequences, a  second  set  of
       backslash escapes is available:
	      \a     alert (bell)
	      \b     backspace
	      \d     delete
	      \f     form feed
	      \n     newline
	      \r     carriage return
	      \t     horizontal tab
	      \v     vertical tab
	      \nnn   the  character  whose  ASCII  code is the octal value nnn
		     (one to three digits)
	      \xnnn  the character whose ASCII code is the  hexadecimal	 value
		     nnn (one to three digits)

       When entering the text of a macro, single or double quotes must be used
       to indicate a macro definition.	Unquoted text is assumed to be a func‐
       tion  name.   In	 the macro body, the backslash escapes described above
       are expanded.  Backslash will quote any other character	in  the	 macro
       text, including " and '.

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

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

	      set variable-name value

       Except where noted, readline variables can take the values On  or  Off.
       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.
       comment-begin (``#'')
	      The string that is inserted  when	 the  readline	insert-comment
	      command is executed.  This command is bound to M-# in emacs mode
	      and to # in vi command mode.
       completion-ignore-case (Off)
	      If set to On, readline performs filename matching and completion
	      in a case-insensitive fashion.
       completion-query-items (100)
	      This  determines when the user is queried about viewing the num‐
	      ber of possible completions generated  by	 the  possible-comple‐
	      tions  command.  It may be set to any integer value greater than
	      or equal to zero.	 If the	 number	 of  possible  completions  is
	      greater than or equal to the value of this variable, the user is
	      asked whether or not he wishes to view them; otherwise they  are
	      simply listed on the terminal.
       convert-meta (On)
	      If  set  to On, readline will convert characters with the eighth
	      bit set to an ASCII key sequence by stripping the eighth bit and
	      prefixing	 an  escape  character (in effect, using escape as the
	      meta prefix).
       disable-completion (Off)
	      If set to On, readline will inhibit word completion.  Completion
	      characters  will	be  inserted into the line as if they had been
	      mapped to self-insert.
       editing-mode (emacs)
	      Controls whether readline begins with a set of key bindings sim‐
	      ilar to emacs or vi.  editing-mode can be set to either emacs or
	      vi.
       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
	      arrow keys.
       expand-tilde (Off)
	      If set  to  on,  tilde  expansion	 is  performed	when  readline
	      attempts word completion.
       horizontal-scroll-mode (Off)
	      When  set	 to  On, makes readline use a single line for display,
	      scrolling the input horizontally on a single screen line when it
	      becomes  longer  than the screen width rather than wrapping to a
	      new line.
       input-meta (Off)
	      If set to On, readline will enable eight-bit input (that is,  it
	      will  not	 strip	the  high  bit	from the characters it reads),
	      regardless of what the terminal claims it can support.  The name
	      meta-flag is a synonym for this variable.
       isearch-terminators (``C-[C-J'')
	      The  string  of  characters that should terminate an incremental
	      search without subsequently executing the character  as  a  com‐
	      mand.   If this variable has not been given a value, the charac‐
	      ters ESC and C-J will terminate an incremental search.
       keymap (emacs)
	      Set the current readline keymap.	The set of valid keymap	 names
	      is  emacs,  emacs-standard,  emacs-meta, emacs-ctlx, vi, vi-com‐
	      mand, and vi-insert.  vi is equivalent to vi-command;  emacs  is
	      equivalent  to  emacs-standard.  The default value is emacs; the
	      value of editing-mode also affects the default keymap.
       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 (*).
       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.
       print-completions-horizontally (Off)
	      If set to On, readline will  display  completions	 with  matches
	      sorted  horizontally in alphabetical order, rather than down the
	      screen.
       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.
       visible-stats (Off)
	      If  set to On, a character denoting a file's type as reported by
	      stat(2) is appended to the filename when listing	possible  com‐
	      pletions.

   Readline Conditional Constructs
       Readline	 implements  a	facility  similar in spirit to the conditional
       compilation features of the C preprocessor which	 allows	 key  bindings
       and  variable  settings	to be performed as the result of tests.	 There
       are four parser directives used.

       $if    The $if construct allows bindings to be made based on the	 edit‐
	      ing  mode,  the  terminal	 being	used, or the application using
	      readline.	 The text of the test extends to the end of the	 line;
	      no characters are required to isolate it.

	      mode   The  mode=	 form  of  the	$if  directive is used to test
		     whether readline is in emacs or vi	 mode.	 This  may  be
		     used  in  conjunction  with  the  set keymap command, for
		     instance, to  set	bindings  in  the  emacs-standard  and
		     emacs-ctlx	 keymaps  only	if readline is starting out in
		     emacs mode.

	      term   The term= form may be used to  include  terminal-specific
		     key bindings, perhaps to bind the key sequences output by
		     the terminal's function keys.  The word on the right side
		     of the = is tested against the both full name of the ter‐
		     minal and the portion of the  terminal  name  before  the
		     first  -.	This allows sun to match both sun and sun-cmd,
		     for instance.

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

		     $if Bash
		     # Quote the current or previous word
		     "\C-xq": "\eb\"\ef\""
		     $endif

       $endif This command, as seen in the previous example, terminates an $if
	      command.

       $else  Commands in this branch of the $if directive are executed if the
	      test fails.

       $include
	      This  directive takes a single filename as an argument and reads
	      commands and bindings from that file.  For example, the  follow‐
	      ing directive would read /etc/inputrc:

	      $include	/etc/inputrc

   Searching
       Readline	 provides  commands  for searching through the command history
       (see HISTORY below) for lines containing a specified string.  There are
       two search modes: incremental and non-incremental.

       Incremental  searches  begin  before  the  user has finished typing the
       search string.  As each character of the search string is typed,	 read‐
       line displays the next entry from the history matching the string typed
       so far.	An incremental search requires	only  as  many	characters  as
       needed  to  find	 the desired history entry.  The characters present in
       the value of the isearch-terminators variable are used to terminate  an
       incremental search.  If that variable has not been assigned a value the
       Escape and Control-J characters will terminate an  incremental  search.
       Control-G  will	abort  an  incremental search and restore the original
       line.  When the search is terminated, the history entry containing  the
       search string becomes the current line.

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

       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).
       clear-screen (C-l)
	      Clear the screen leaving the current line	 at  the  top  of  the
	      screen.	With  an  argument,  refresh  the current line without
	      clearing the screen.
       redraw-current-line
	      Refresh the current line.

   Commands for Manipulating the History
       accept-line (Newline, Return)
	      Accept the line regardless of where the cursor is.  If this line
	      is  non-empty, add it to the history list according to the state
	      of the HISTCONTROL variable.  If the line is a modified  history
	      line, then restore the history line to its original state.
       previous-history (C-p)
	      Fetch the previous command from the history list, moving back in
	      the list.
       next-history (C-n)
	      Fetch the next command from the history list, moving forward  in
	      the list.
       beginning-of-history (M-<)
	      Move to the first line in the history.
       end-of-history (M->)
	      Move  to	the end of the input history, i.e., the line currently
	      being entered.
       reverse-search-history (C-r)
	      Search backward starting at the current  line  and  moving  `up'
	      through  the  history  as	 necessary.   This  is	an incremental
	      search.
       forward-search-history (C-s)
	      Search forward starting at the current line  and	moving	`down'
	      through  the  history  as	 necessary.   This  is	an incremental
	      search.
       non-incremental-reverse-search-history (M-p)
	      Search backward through the history starting at the current line
	      using  a	non-incremental	 search	 for  a string supplied by the
	      user.
       non-incremental-forward-search-history (M-n)
	      Search forward  through  the  history  using  a  non-incremental
	      search for a string supplied by the user.
       history-search-forward
	      Search  forward through the history for the string of characters
	      between the start of the current line and the point.  This is  a
	      non-incremental search.
       history-search-backward
	      Search backward through the history for the string of characters
	      between the start of the current line and the point.  This is  a
	      non-incremental search.
       yank-nth-arg (M-C-y)
	      Insert  the  first argument to the previous command (usually the
	      second word on the previous line) at point.  With an argument n,
	      insert  the nth word from the previous command (the words in the
	      previous command	begin  with  word  0).	 A  negative  argument
	      inserts the nth word from the end of the previous command.
       yank-last-arg (M-., M-_)
	      Insert  the last argument to the previous command (the last word
	      of the  previous	history	 entry).   With	 an  argument,	behave
	      exactly  like  yank-nth-arg.   Successive calls to yank-last-arg
	      move back through the history list, inserting the last  argument
	      of each line in turn.
       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
	      EXPANSION below for a description of history expansion.
       magic-space
	      Perform history expansion on  the	 current  line	and  insert  a
	      space.  See HISTORY EXPANSION below for a description of history
	      expansion.
       alias-expand-line
	      Perform alias expansion on the current line.  See ALIASES	 above
	      for a description of alias expansion.
       history-and-alias-expand-line
	      Perform history and alias expansion on the current line.
       insert-last-argument (M-., M-_)
	      A synonym for yank-last-arg.
       operate-and-get-next (C-o)
	      Accept  the  current  line for execution and fetch the next line
	      relative to the current line from the history for editing.   Any
	      argument is ignored.

   Commands for Changing Text
       delete-char (C-d)
	      Delete  the character at point.  If point is at the beginning of
	      the line, there are no characters in  the	 line,	and  the  last
	      character typed was not bound to delete-char, then return EOF.
       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.  By default, this is not bound to a key.
       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.
       upcase-word (M-u)
	      Uppercase	 the  current  (or  following)	word.  With a negative
	      argument, uppercase the previous word, but do not move point.
       downcase-word (M-l)
	      Lowercase the current (or	 following)  word.   With  a  negative
	      argument, lowercase the previous word, but do not move point.
       capitalize-word (M-c)
	      Capitalize  the  current	(or  following) word.  With a negative
	      argument, capitalize the previous word, but do not move point.

   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.
       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.
       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
	      numeric argument, but is otherwise ignored.  As a special	 case,
	      if  this	command is immediately followed by a character that is
	      neither a digit or minus sign, the argument count for  the  next
	      command  is multiplied by four.  The argument count is initially
	      one, so executing this function the first time makes  the	 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 $), username (if the text begins with	 ~),  hostname
	      (if  the	text begins with @), or command (including aliases and
	      functions) in turn.  If none of these produces a match, filename
	      completion is attempted.
       possible-completions (M-?)
	      List the possible completions of the text before point.
       insert-completions (M-*)
	      Insert  all completions of the text before point that would have
	      been generated by possible-completions.
       menu-complete
	      Similar to complete, but replaces the word to be completed  with
	      a	 single match from the list of possible completions.  Repeated
	      execution of menu-complete steps through the  list  of  possible
	      completions,  inserting  each  match in turn.  At the end of the
	      list of completions, the bell is rung (subject to the setting of
	      0	 and  the original text is restored.  An argument of n moves n
	      positions forward in the list of matches;	 a  negative  argument
	      may  be used to move backward through the list.  This command is
	      intended to be bound to TAB, but is unbound by default.
       delete-char-or-list
	      Deletes the character under the cursor if not at	the  beginning
	      or  end  of  the	line (like delete-char).  If at the end of the
	      line, behaves identically to possible-completions.  This command
	      is unbound by default.
       complete-filename (M-/)
	      Attempt filename completion on the text before point.
       possible-filename-completions (C-x /)
	      List the possible completions of the text before point, treating
	      it as a filename.
       complete-username (M-~)
	      Attempt completion on the text before point, treating  it	 as  a
	      username.
       possible-username-completions (C-x ~)
	      List the possible completions of the text before point, treating
	      it as a username.
       complete-variable (M-$)
	      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.
       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.

   Miscellaneous
       re-read-init-file (C-x C-r)
	      Read  in	the  contents of the inputrc file, and incorporate any
	      bindings or variable assignments found there.
       abort (C-g)
	      Abort the current editing command and ring the  terminal's  bell
	      (subject to the setting of bell-style).
       do-uppercase-version (M-a, M-b, M-x, ...)
	      If  the  metafied character x is lowercase, run the command that
	      is bound to the corresponding uppercase character.
       prefix-meta (ESC)
	      Metafy the next character typed.	ESC f is equivalent to Meta-f.
       undo (C-_, C-x C-u)
	      Incremental undo, separately remembered for each line.
       revert-line (M-r)
	      Undo all changes made to this line.  This is like executing  the
	      undo  command  enough  times  to	return the line to its initial
	      state.
       tilde-expand (M-&)
	      Perform tilde expansion on the current word.
       set-mark (C-@, M-<space>)
	      Set the mark to the point.  If a numeric argument	 is  supplied,
	      the mark is set to that position.
       exchange-point-and-mark (C-x C-x)
	      Swap  the	 point	with the mark.	The current cursor position is
	      set to the saved position, and the old cursor position is	 saved
	      as the mark.
       character-search (C-])
	      A character is read and point is moved to the next occurrence of
	      that character.  A negative count searches for  previous	occur‐
	      rences.
       character-search-backward (M-C-])
	      A	 character  is	read and point is moved to the previous occur‐
	      rence of that character.	A negative count searches  for	subse‐
	      quent occurrences.
       insert-comment (M-#)
	      The  value of the readline comment-begin variable is inserted at
	      the beginning of the current line, and the line is  accepted  as
	      if a newline had been typed.  The default value of comment-begin
	      causes this command to make the current line a shell comment.
       glob-expand-word (C-x *)
	      The word before point is	treated	 as  a	pattern	 for  pathname
	      expansion,  and  the  list  of  matching file names is inserted,
	      replacing the word.
       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.
       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 ouput.  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.
       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 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.

       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 filename expansion pattern to the -G
       option are generated next.  The words generated by the pattern need not
       match  the  word being completed.  The GLOBIGNORE shell variable is not
       used to filter the matches, but the FIGNORE 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,  arithmetic  expansion,  and
       pathname	 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 com‐
       pleted, 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  and  COMP_POINT	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
       is the name of the command whose arguments  are	being  completed,  the
       second  argument is the word being completed, and the third argument is
       the word preceding the word being  completed  on	 the  current  command
       line.  No filtering of the generated completions against the word being
       completed is performed; the function or command has complete freedom in
       generating the matches.

       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.

       Next, any command specified with the -C option is invoked in  an	 envi‐
       ronment	equivalent to command substitution.  It should print a list of
       completions, one per line, to the standard output.   Backslash  may  be
       used to escape a newline, if necessary.

       After  all of the possible completions are generated, any filter speci‐
       fied with the -X option is applied to the list.	The filter is  a  pat‐
       tern  as	 used  for  pathname expansion; a & in the pattern is replaced
       with the text of the word being completed.  A literal & may be  escaped
       with  a	backslash; the backslash is removed before attempting a match.
       Any completion that matches the pattern will be removed from the	 list.
       A leading ! negates the pattern; in this case any completion not match‐
       ing the pattern will be removed.

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

       If the previously-applied actions do not generate any matches, and  the
       -o  dirnames  option  was  supplied  to	complete when the compspec was
       defined, directory name completion is attempted.

       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 default option was supplied
       to complete when the compspec was defined, readline's  default  comple‐
       tion will be performed if the compspec generates no matches.

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.	When an inter‐
       active shell exits, the last $HISTSIZE lines are copied from  the  his‐
       tory 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 over‐
       written.	 If HISTFILE is unset, or if the history file  is  unwritable,
       the  history  is not saved.  After saving the history, the history file
       is truncated to contain no more than HISTFILESIZE lines.	 If  HISTFILE‐
       SIZE is not set, no truncation is performed.

       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
       manipulate 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
       options.

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

       History expansions introduce words from the history list into the input
       stream,	making	it  easy to repeat commands, insert the arguments to a
       previous command into the current input line, or fix errors in previous
       commands quickly.

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

       Several	shell  options	settable with the shopt builtin may be used to
       tailor the behavior of history  expansion.   If	the  histverify	 shell
       option is enabled (see the description of the shopt builtin), and read‐
       line 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 sub‐
       stitution will be reloaded into the readline editing buffer for correc‐
       tion.   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).

   Event Designators
       An  event designator is a reference to a command line entry in the his‐
       tory list.

       !      Start a history substitution, except when followed by  a	blank,
	      newline, = or (.
       !n     Refer to command line n.
       !-n    Refer to the current command line minus n.
       !!     Refer to the previous command.  This is a synonym for `!-1'.
       !string
	      Refer to the most recent command starting with string.
       !?string[?]
	      Refer  to the most recent command containing string.  The trail‐
	      ing ? may be omitted if string is followed immediately by a new‐
	      line.
       ^string1^string2^
	      Quick  substitution.  Repeat the last command, replacing string1
	      with string2.  Equivalent to ``!!:s/string1/string2/'' (see Mod‐
	      ifiers 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 argument.
       %      The word matched by the most recent `?string?' search.
       x-y    A range of words; `-y' abbreviates `0-y'.
       *      All of the words but the zeroth.	This is a synonym  for	`1-$'.
	      It  is  not  an  error to use * if there is just one word in the
	      event; the empty string is returned in that case.
       x*     Abbreviates x-$.
       x-     Abbreviates x-$ like x*, but omits the last word.

       If a word designator is supplied without an  event  specification,  the
       previous command is used as the event.

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

       h      Remove a trailing file name component, leaving only the head.
       t      Remove all leading file name components, leaving the tail.
       r      Remove a trailing suffix of the form .xxx, leaving the basename.
       e      Remove all but the trailing suffix.
       p      Print the new command but do not execute it.
       q      Quote the substituted words, escaping further substitutions.
       x      Quote the substituted words as with q, but break into  words  at
	      blanks and newlines.
       s/old/new/
	      Substitute  new  for  the	 first	occurrence of old in the event
	      line.  Any delimiter can be used	in  place  of  /.   The	 final
	      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 sin‐
	      gle backslash will quote the &.  If old is null, it  is  set  to
	      the  last	 old substituted, or, if no previous history substitu‐
	      tions took place, the last string in a !?string[?]  search.
       &      Repeat the previous substitution.
       g      Cause changes to be applied over the entire event line.  This is
	      used  in	conjunction  with `:s' (e.g., `:gs/old/new/') or `:&'.
	      If used with `:s', any delimiter can be used in place of /,  and
	      the  final  delimiter is optional if it is the last character of
	      the event line.

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.
       : [arguments]
	      No effect; the command does nothing beyond  expanding  arguments
	      and  performing any specified redirections.  A zero exit code is
	      returned.

	.  filename [arguments]
       source filename [arguments]
	      Read and execute commands from filename  in  the	current	 shell
	      environment  and return the exit status of the last command exe‐
	      cuted from filename.  If filename does not contain a slash, file
	      names  in	 PATH  are used to find the directory containing file‐
	      name.  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
	      positional parameters are unchanged.  The return status  is  the
	      status  of  the  last  command exited within the script (0 if no
	      commands are executed), and false if 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
	      returns true unless a name is given for which no alias has  been
	      defined.

       bg [jobspec]
	      Resume the 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,	if  jobspec  was not found or started without job con‐
	      trol.

       bind [-m keymap] [-lpsvPSV]
       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
	      Display current readline key and function bindings,  or  bind  a
	      key  sequence to a readline function or macro.  The binding syn‐
	      tax accepted is identical to that of .inputrc, but each  binding
	      must  be	passed	as  a  separate	 argument;  e.g., '"\C-x\C-r":
	      re-read-init-file'.  Options, if supplied,  have	the  following
	      meanings:
	      -m keymap
		     Use keymap as the keymap to be affected by the subsequent
		     bindings.	Acceptable keymap names are emacs, emacs-stan‐
		     dard,  emacs-meta,	 emacs-ctlx,  vi, vi-move, vi-command,
		     and vi-insert.  vi is equivalent to vi-command; emacs  is
		     equivalent to emacs-standard.
	      -l     List the names of all readline functions.
	      -p     Display  readline	function  names and bindings in such a
		     way that they can be re-read.
	      -P     List current readline function names and bindings.
	      -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.
	      -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.
	      -f filename
		     Read key bindings from filename.
	      -q function
		     Query about which keys invoke the named function.
	      -u function
		     Unbind all keys bound to the named function.
	      -r keyseq
		     Remove any current binding for keyseq.
	      -x keyseq:shell-command
		     Cause shell-command to be	executed  whenever  keyseq  is
		     entered.

	      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  exited.
	      The  return  value is 0 unless the shell is not executing a loop
	      when break is executed.

       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.

       cd [-LP] [dir]
	      Change  the  current directory to dir.  The variable HOME is the
	      default dir.  The variable CDPATH defines the  search  path  for
	      the  directory  containing  dir.	Alternative directory 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  says  to use the physical directory structure instead of
	      following symbolic links (see also the  -P  option  to  the  set
	      builtin command); the -L option forces symbolic links to be fol‐
	      lowed.  An argument of - is equivalent to $OLDPWD.   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
	      option is supplied, a description of command is printed.	The -v
	      option causes a single word indicating the command or file  name
	      used to invoke command to be displayed; the -V option produces a
	      more verbose description.	 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
	      facilities, 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	 [-abcdefjkvu]	[-o  comp-option] [-A action] [-G globpat] [-W
       wordlist] [-P prefix] [-S suffix]
	      [-X filterpat] [-F function] [-C command] name [name ...]
       complete -pr [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  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:
		      default Use readline's default completion if  the	 comp‐
			      spec 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 or suppressing trailing spaces).  Intended
			      to be used with shell functions.
	      -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.
		      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.
		      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.
	      -G globpat
		      The  filename  expansion	pattern globpat is expanded to
		      generate the possible completions.
	      -W wordlist
		      The wordlist is split using the characters  in  the  IFS
		      special  variable as delimiters, and each resultant word
		      is expanded.  The possible completions are  the  members
		      of  the  resultant  list which match the word being com‐
		      pleted.
	      -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 it finishes, the possible  com‐
		      pletions	are  retrieved from the value of the COMPREPLY
		      array variable.
	      -X filterpat
		      filterpat is a pattern as used for  filename  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.
	      -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.

	      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.

       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
	      enclosing loops, the  last  enclosing  loop  (the	 ``top-level''
	      loop) is resumed.	 The return value is 0 unless the shell is not
	      executing a loop when continue is executed.

       declare [-afFirx] [-p] [name[=value]]
       typeset [-afFirx] [-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,  additional	 options  are ignored.	The -F option inhibits
	      the display of function definitions; only the function name  and
	      attributes  are printed.	The -F option implies -f.  The follow‐
	      ing options can be used to restrict output to variables with the
	      specified attribute or to give variables attributes:
	      -a     Each name is an array variable (see Arrays above).
	      -f     Use function names only.
	      -i     The variable is treated as an integer; arithmetic evalua‐
		     tion (see ARITHMETIC EVALUATION ) is performed  when  the
		     variable is assigned a value.
	      -r     Make names readonly.  These names cannot then be assigned
		     values by subsequent assignment statements or unset.
	      -x     Mark names for export  to	subsequent  commands  via  the
		     environment.

	      Using  `+'  instead of `-' turns off the attribute instead, with
	      the exception that +a may not be used to destroy an array	 vari‐
	      able.   When  used in a function, makes each name local, as with
	      the local command.  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 assign a value to an
	      array variable without using the compound assignment syntax (see
	      Arrays  above),  one  of the names is not a valid shell variable
	      name, an attempt is made to turn off readonly status for a read‐
	      only  variable,  an attempt is made to turn off array status for
	      an array variable, or an attempt is made to display a  non-exis‐
	      tent function with -f.

       dirs [-clpv] [+n] [-n]
	      Without  options,	 displays  the	list  of  currently remembered
	      directories.  The default display	 is  on	 a  single  line  with
	      directory	 names	separated by spaces.  Directories are added to
	      the list with  the  pushd	 command;  the	popd  command  removes
	      entries from the list.
	      +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.
	      -c     Clears  the  directory  stack  by	deleting  all  of  the
		     entries.
	      -l     Produces a longer listing;	 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.

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

       disown [-ar] [-h] [jobspec ...]
	      Without  options,	 each  jobspec	is  removed  from the table of
	      active jobs.  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 receives a SIGHUP.   If  no  jobspec  is
	      present,	and  neither the -a nor the -r option is supplied, the
	      current job is used.  If no jobspec is supplied, the  -a	option
	      means  to	 remove or mark all jobs; the -r option without a job‐
	      spec argument 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 always 0.  If -n is specified, the trailing
	      newline  is  suppressed.	If the -e option is given, interpreta‐
	      tion of the following backslash-escaped characters  is  enabled.
	      The  -E option disables the interpretation of these escape char‐
	      acters, even on systems where they are interpreted  by  default.
	      The  xpg_echo  shell option may be used to dynamically determine
	      whether or not echo expands these escape characters by  default.
	      echo  does  not  interpret  -- to mean the end of options.  echo
	      interprets the following escape sequences:
	      \a     alert (bell)
	      \b     backspace
	      \c     suppress trailing newline
	      \e     an escape character
	      \f     form feed
	      \n     new line
	      \r     carriage return
	      \t     horizontal tab
	      \v     vertical tab
	      \\     backslash
	      \nnn   the character whose ASCII code is	the  octal  value  nnn
		     (one to three digits)
	      \xnnn  the  character  whose ASCII code is the hexadecimal value
		     nnn (one to three digits)

       enable [-adnps] [-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
	      enabled.	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 arg passed to command.	 This is what login(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 cannot be
	      executed for some reason, a non-interactive shell exits,	unless
	      the  shell  option execfail is enabled, in which case it returns
	      failure.	An interactive shell returns failure if the file  can‐
	      not  be executed.	 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	 all  names  that  are
	      exported	in  this  shell	 is printed.  The -n option causes the
	      export property to be removed from the named variables.	export
	      returns  an exit status of 0 unless an invalid option is encoun‐
	      tered, one of the names is not a valid shell variable  name,  or
	      -f is supplied with a name that is not a function.

       fc [-e ename] [-nlr] [first] [last]
       fc -s [pat=rep] [cmd]
	      Fix  Command.  In the first form, a range of commands from first
	      to last is selected from the history list.  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 cur‐
	      rent command number).  If last is not specified it is set to the
	      current  command	for  listing (so that ``fc -l -10'' prints the
	      last 10 commands) and to first otherwise.	 If first is not spec‐
	      ified  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.  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 com‐
	      mand.

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

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

       getopts optstring name [args]
	      getopts is used by shell procedures to parse positional  parame‐
	      ters.   optstring	 contains  the	option characters to be recog‐
	      nized; if a character is followed by  a  colon,  the  option  is
	      expected	to have an argument, which should be separated from it
	      by white space.  The colon and question mark characters may  not
	      be  used as option characters.  Each time it is invoked, getopts
	      places the next option in the shell variable name,  initializing
	      name if it does not exist, and the index of the next argument to
	      be processed into the variable OPTIND.  OPTIND is initialized to
	      1	 each  time  the  shell or a shell script is invoked.  When an
	      option requires an argument, getopts places that	argument  into
	      the  variable OPTARG.  The shell does not reset OPTIND automati‐
	      cally; it must be	 manually  reset  between  multiple  calls  to
	      getopts within the same shell invocation if a new set of parame‐
	      ters is to be used.

	      When the end of options is encountered,  getopts	exits  with  a
	      return  value  greater than zero.	 OPTIND is set to the index of
	      the first non-option argument, and name is set to ?.

	      getopts normally parses the positional parameters, but  if  more
	      arguments are given in args, getopts parses those instead.

	      getopts  can  report errors in two ways.	If the first character
	      of optstring is a colon, silent error  reporting	is  used.   In
	      normal  operation	 diagnostic  messages are printed when invalid
	      options or missing option arguments  are	encountered.   If  the
	      variable	OPTERR	is  set	 to  0, no error messages will be dis‐
	      played, even if the first character of optstring is not a colon.

	      If an invalid option is seen, getopts places ? into name and, if
	      not  silent,  prints  an	error  message	and unsets OPTARG.  If
	      getopts is silent, the  option  character	 found	is  placed  in
	      OPTARG and no diagnostic message is printed.

	      If  a required argument is not found, and getopts is not silent,
	      a question mark (?) is placed in name, OPTARG is	unset,	and  a
	      diagnostic  message  is  printed.	  If getopts is silent, then a
	      colon (:) is placed in name and OPTARG  is  set  to  the	option
	      character found.

	      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 [-r] [-p filename] [name]
	      For  each	 name, the full file name of the command is determined
	      by searching the directories in $PATH and remembered.  If the -p
	      option is supplied, no path search is performed, and filename is
	      used as the full file name of the command.  The -r option causes
	      the  shell  to forget all remembered locations.  If no arguments
	      are given, information about  remembered	commands  is  printed.
	      The  return  status  is  true  unless  a name is not found or an
	      invalid option is supplied.

       help [-s] [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.  The -s option restricts the information
	      displayed to a short usage synopsis.  The	 return	 status	 is  0
	      unless no command matches pattern.

       history [n]
       history -c
       history -d offset
       history -anrw [filename]
       history -p arg [arg ...]
       history -s arg [arg ...]
	      With no options, display the command history list with line num‐
	      bers.  Lines listed with a * have been modified.	An argument of
	      n	 lists	only the last n lines.	If filename is supplied, it is
	      used as the name of the history file; if not, the value of HIST‐
	      FILE  is	used.	Options, if supplied, have the following mean‐
	      ings:
	      -c     Clear the history list by deleting all the entries.
	      -d offset
		     Delete the history entry at position offset.
	      -a     Append the ``new'' history lines (history	lines  entered
		     since  the	 beginning of the current bash session) to the
		     history file.
	      -n     Read the history lines not already read from the  history
		     file  into	 the  current  history	list.  These are lines
		     appended to the history file since the beginning  of  the
		     current bash session.
	      -r     Read the contents of the history file and use them as the
		     current history.
	      -w     Write the current history to the history file,  overwrit‐
		     ing 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.

	      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 supplied 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.
	      -p     List only the process  ID	of  the	 job's	process	 group
		     leader.
	      -n     Display  information  only	 about	jobs that have changed
		     status since the user was last notified of their status.
	      -r     Restrict output to running jobs.
	      -s     Restrict output to 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
	      executes command passing it args, returning its exit status.

       kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...
       kill -l [sigspec | exit_status]
	      Send the signal named by sigspec	or  signum  to	the  processes
	      named  by	 pid or jobspec.  sigspec is either a signal name such
	      as SIGKILL or a signal number; signum is a  signal  number.   If
	      sigspec  is a signal name, the name may be given with or without
	      the SIG prefix.  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  sig‐
	      nals  corresponding  to the arguments are listed, and the return
	      status is 0.  The exit_status argument to -l is a number	speci‐
	      fying  either  a	signal	number or the exit status of a process
	      terminated by a signal.  kill returns true if at least one  sig‐
	      nal  was	successfully  sent,  or false if an error occurs or an
	      invalid option is encountered.

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

       local [option] [name[=value] ...]
	      For each argument, a local variable named name is	 created,  and
	      assigned	value.	 The option can be any of the options accepted
	      by declare.  When local is used within a function, it causes the
	      variable	name  to have a visible scope restricted to that func‐
	      tion and its children.  With no operands, local writes a list of
	      local  variables	to the standard output.	 It is an error to use
	      local when not within a function.	 The return status is 0 unless
	      local  is	 used outside a function, an invalid name is supplied,
	      or name is a readonly variable.

       logout Exit a login shell.

       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     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.
	      -n     Suppresses the normal change of directory	when  removing
		     directories  from	the  stack,  so that only the stack is
		     manipulated.

	      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 format [arguments]
	      Write the formatted arguments to the standard output  under  the
	      control  of  the format.	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  for‐
	      mat  specifications,  each  of which causes printing of the next
	      successive argument.  In addition to the standard printf(1) for‐
	      mats,  %b	 causes printf to expand backslash escape sequences in
	      the corresponding argument, and %q causes printf to  output  the
	      corresponding  argument  in a format that can be reused as shell
	      input.

	      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] [dir]
       pushd [-n] [+n] [-n]
	      Adds a directory to the top of the directory stack,  or  rotates
	      the  stack,  making the new top of the stack the current working
	      directory.  With no arguments, exchanges the top two directories
	      and  returns 0, unless the directory stack is empty.  Arguments,
	      if supplied, have the following meanings:
	      +n     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.
	      -n     Suppresses the normal change  of  directory  when	adding
		     directories  to  the  stack,  so  that  only the stack is
		     manipulated.
	      dir    Adds dir to the directory stack at the top, making it the
		     new current working directory.

	      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
	      invalid option is supplied.

       read [-ers] [-t timeout] [-a aname] [-p prompt] [-n nchars] [-d	delim]
       [name ...]
	      One  line is read from the standard input, and the first word is
	      assigned to the first name, the second word to the second	 name,
	      and  so on, with leftover words and their intervening separators
	      assigned to the last name.  If there are fewer words  read  from
	      the  standard input than names, the remaining names are assigned
	      empty values.  The characters in IFS are used to split the  line
	      into  words.   The backslash character (\) may be used to remove
	      any special meaning for the next character  read	and  for  line
	      continuation.   Options,	if  supplied, have the following mean‐
	      ings:
	      -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
		     ignored.
	      -d delim
		     The  first	 character  of	delim is used to terminate the
		     input line, rather than newline.
	      -e     If the standard input is coming from a terminal, readline
		     (see READLINE above) is used to obtain the line.
	      -n nchars
		     read  returns after reading nchars characters rather than
		     waiting for a complete line of input.
	      -p prompt
		     Display  prompt,  without	a  trailing  newline,	before
		     attempting	 to  read  any input.  The prompt is displayed
		     only if input is coming from a terminal.
	      -r     Backslash does not act as an escape character.  The back‐
		     slash  is considered to be part of the line.  In particu‐
		     lar, a backslash-newline pair may not be used as  a  line
		     continuation.
	      -s     Silent mode.  If input is coming from a terminal, charac‐
		     ters are not echoed.
	      -t timeout
		     Cause read to time out and return failure if  a  complete
		     line  of  input is not read within timeout seconds.  This
		     option has no effect if read is not  reading  input  from
		     the terminal or a pipe.

	      If no names are supplied, the line read is assigned to the vari‐
	      able REPLY.  The return code  is	zero,  unless  end-of-file  is
	      encountered or read times out.

       readonly [-apf] [name ...]
	      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 arrays.	 If no
	      name  arguments  are  given,  or if the -p option is supplied, a
	      list of all readonly names is printed.   The  -p	option	causes
	      output  to be displayed in a format that may be reused as input.
	      The return status is 0 unless an invalid option is  encountered,
	      one  of  the  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 exit with the return value specified by  n.
	      If  n  is omitted, the return status is that of the last command
	      executed in the function body.  If used outside a function,  but
	      during  execution	 of  a	script	by the .  (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  used  outside  a
	      function	and  not during execution of a script by ., the return
	      status is false.

       set [--abefhkmnptuvxBCHP] [-o option] [arg ...]
	      Without options, the name and value of each shell	 variable  are
	      displayed	 in  a format that can be reused as input.  The output
	      is sorted according to the current  locale.   When  options  are
	      specified,  they	set  or unset shell attributes.	 Any arguments
	      remaining after the options are processed are treated as	values
	      for the positional parameters and are assigned, in order, to $1,
	      $2, ...  $n.  Options, if specified, have	 the  following	 mean‐
	      ings:
	      -a      Automatically  mark  variables  and  functions which are
		      modified or created for export  to  the  environment  of
		      subsequent commands.
	      -b      Report  the status of terminated background jobs immedi‐
		      ately, rather than before the next primary prompt.  This
		      is effective only when job control is enabled.
	      -e      Exit  immediately if a simple command (see SHELL GRAMMAR
		      above) exits with a non-zero status.  The shell does not
		      exit  if	the  command that fails is part of an until or
		      while loop, part of an if statement, part of a && or  ⎪⎪
		      list, or if the command's return value is being inverted
		      via !.
	      -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).  Background pro‐
		      cesses run in a separate process group and a  line  con‐
		      taining  their exit status is printed upon their comple‐
		      tion.
	      -n      Read commands but do not execute them.  This may be used
		      to  check	 a  shell  script  for syntax errors.  This is
		      ignored by interactive shells.
	      -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.
		      errexit Same as -e.
		      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
			      ``IGNOREEOF=10'' had been	 executed  (see	 Shell
			      Variables above).
		      keyword Same as -k.
		      monitor Same as -m.
		      noclobber
			      Same as -C.
		      noexec  Same as -n.
		      noglob  Same as -f.
		      notify  Same as -b.
		      nounset Same as -u.
		      onecmd  Same as -t.
		      physical
			      Same as -P.
		      posix   Change  the  behavior  of bash where the default
			      operation differs from the POSIX 1003.2 standard
			      to match the standard (posix mode).
		      privileged
			      Same as -p.
		      verbose Same as -v.
		      vi      Use a vi-style command line editing interface.
		      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
		      variable, if it appears in the environment, is  ignored.
		      If  the shell is started with the effective user (group)
		      id not equal to the real user (group)  id,  and  the  -p
		      option  is not supplied, these actions are taken and the
		      effective user id is set to the real user id.  If the -p
		      option  is supplied at startup, the effective user id is
		      not reset.  Turning this option off causes the effective
		      user  and group ids to be set to the real user and group
		      ids.
	      -t      Exit after reading and executing one command.
	      -u      Treat unset variables as an error when performing param‐
		      eter  expansion.	 If expansion is attempted on an unset
		      variable, the shell prints an error message, and, if not
		      interactive, exits with a non-zero status.
	      -v      Print shell input lines as they are read.
	      -x      After   expanding	  each	simple	command,  display  the
		      expanded value of PS4, followed by the command  and  its
		      expanded arguments.
	      -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 >.
	      -H      Enable !	style history substitution.  This option is on
		      by default when the shell is interactive.
	      -P      If set, the shell does not follow	 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.
	      --      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
	      options  can  also be specified as arguments to an invocation of
	      the shell.  The current set of options may be found in $-.   The
	      return 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
	      unset.  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
	      parameters  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 variables controlling optional shell behav‐
	      ior.  With no options, or with the -p option, a list of all set‐
	      table options is displayed, with an indication of whether or not
	      each  is	set.  The -p option causes output to be displayed in a
	      form that may be reused as input.	 Other options have  the  fol‐
	      lowing 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,  the  dis‐
	      play is limited to those options which are set or unset, respec‐
	      tively.  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
	      options,	the  return  status is zero unless an optname is not a
	      valid shell option.

	      The list of shopt options is:

	      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 file name 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.
	      checkwinsize
		      If  set,	bash checks the window size after each command
		      and, if necessary, updates the values of LINES and  COL‐
		      UMNS.
	      cmdhist If  set,	bash attempts to save all lines of a multiple-
		      line command in the same	history	 entry.	  This	allows
		      easy re-editing of multi-line commands.
	      dotglob If  set, bash includes filenames beginning with a `.' in
		      the results of pathname expansion.
	      execfail
		      If set, a non-interactive shell will not exit if it can‐
		      not  execute  the	 file  specified as an argument to the
		      exec builtin command.  An	 interactive  shell  does  not
		      exit if exec fails.
	      expand_aliases
		      If  set,	aliases	 are expanded as described above under
		      ALIASES.	This option is enabled by default for interac‐
		      tive shells.
	      extglob If set, the extended pattern matching features described
		      above under Pathname Expansion are enabled.
	      histappend
		      If set, the history list is appended to the  file	 named
		      by  the  value  of  the HISTFILE variable when the shell
		      exits, rather than overwriting the file.
	      histreedit
		      If set, and readline is being used, a user is given  the
		      opportunity to re-edit a failed history substitution.
	      histverify
		      If  set, and readline is being used, the results of his‐
		      tory substitution are  not  immediately  passed  to  the
		      shell  parser.   Instead,	 the  resulting line is loaded
		      into the readline editing buffer, allowing further modi‐
		      fication.
	      hostcomplete
		      If set, and readline is being used, bash will attempt to
		      perform hostname completion when a word containing  a  @
		      is   being  completed  (see  Completing  under  READLINE
		      above).  This is enabled by default.
	      huponexit
		      If set, bash will send SIGHUP to all jobs when an inter‐
		      active login shell exits.
	      interactive_comments
		      If set, allow a word beginning with # to cause that word
		      and all remaining characters on that line to be  ignored
		      in  an  interactive  shell  (see	COMMENTS above).  This
		      option is enabled by default.
	      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.
	      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
		      attempt to search the PATH for possible completions when
		      completion is attempted on an empty line.
	      nocaseglob
		      If  set,	bash  matches  filenames in a case-insensitive
		      fashion when performing pathname expansion (see Pathname
		      Expansion above).
	      nullglob
		      If  set,	bash allows patterns which match no files (see
		      Pathname Expansion above) to expand to  a	 null  string,
		      rather than themselves.
	      progcomp
		      If set, the programmable completion facilities (see Pro‐
		      grammable Completion above) are enabled.	This option is
		      enabled by default.
	      promptvars
		      If  set,	prompt	strings undergo variable and parameter
		      expansion 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
		      restricted 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
		      sequences by default.
       suspend [-f]
	      Suspend the execution of this shell until it receives a  SIGCONT
	      signal.	The  -f option says not to complain if this is a login
	      shell; just suspend anyway.  The return status is 0  unless  the
	      shell is a login shell and -f is not supplied, or if job control
	      is not enabled.
       test expr
       [ expr ]
	      Return a status of 0 or 1 depending on  the  evaluation  of  the
	      conditional  expression expr.  Each operator and operand must be
	      a separate argument.  Expressions are composed of the  primaries
	      described above under CONDITIONAL EXPRESSIONS.

	      Expressions  may	be  combined  using  the  following operators,
	      listed in decreasing order of precedence.
	      ! 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
		     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.  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.	 Otherwise,  the  expression is false.
		     The -a and -o operators are considered  binary  operators
		     in this case.
	      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.

       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
	      receives signal(s) sigspec.  If arg is absent or -,  all	speci‐
	      fied signals are reset to their original values (the values they
	      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 commands associated with each
	      signal number.  Each sigspec is either a signal name defined  in
	      <signal.h>,  or  a  signal number.  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 executed after every simple command
	      (see SHELL GRAMMAR above).  The -l option causes	the  shell  to
	      print  a	list  of signal names and their corresponding numbers.
	      Signals ignored upon entry to the shell  cannot  be  trapped  or
	      reset.   Trapped signals are reset to their original values in a
	      child process when it is created.	 The return status is false if
	      any sigspec is invalid; otherwise trap returns true.

       type [-atp] 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
	      returned.	  If  the  -p  option is used, type either returns the
	      name of the disk file that would be executed if name were speci‐
	      fied as a command name, or nothing if ``type -t name'' would not
	      return file.  If a command  is  hashed,  -p  prints  the	hashed
	      value,  not necessarily the file that appears first in PATH.  If
	      the -a option is used, type prints all of the places  that  con‐
	      tain  an executable named name.  This includes aliases and func‐
	      tions, if and only if the -p option is not also used.  The table
	      of hashed commands is not consulted when using -a.  type returns
	      true if any of the arguments are found, false if none are found.

       ulimit [-SHacdflmnpstuv [limit]]
	      Provides control over the resources available to the  shell  and
	      to  processes started by it, on systems that allow such control.
	      The value of limit can be a number in the unit specified for the
	      resource, or the value unlimited.	 The -H and -S options specify
	      that the hard or soft limit is set for the  given	 resource.   A
	      hard  limit cannot be increased once it is set; a soft limit may
	      be increased up to the value of the hard limit.  If  neither  -H
	      nor  -S is specified, both the soft and hard limits are set.  If
	      limit is omitted, the current value of the  soft	limit  of  the
	      resource	is  printed, unless the -H option is given.  When more
	      than one resource is specified, the  limit  name	and  unit  are
	      printed before the value.	 Other options are interpreted as fol‐
	      lows:
	      -a     All current limits are reported
	      -c     The maximum size of core files created
	      -d     The maximum size of a process's data segment
	      -f     The maximum size of files created by the shell
	      -l     The maximum size that may be locked into memory
	      -m     The maximum resident set size
	      -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)
	      -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

	      If limit is given, it is the new value of the specified resource
	      (the -a option is display only).	If no option is given, then -f
	      is  assumed.  Values are in 1024-byte increments, except for -t,
	      which is in seconds, -p, which is in units of  512-byte  blocks,
	      and  -n and -u, which are unscaled values.  The return status is
	      0 unless an invalid option is encountered, a  non-numeric	 argu‐
	      ment  other  than	 unlimited  is	supplied as limit, 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] [name ...]
	      For  each	 name,	remove the corresponding variable or function.
	      If no options are supplied, or the -v option is given, each name
	      refers  to  a  shell  variable.	Read-only variables may not be
	      unset.  If -f is specifed, each name refers to a shell function,
	      and  the function definition is removed.	Each unset variable or
	      function is removed from the environment	passed	to  subsequent
	      commands.	 If any of RANDOM, SECONDS, LINENO, HISTCMD, FUNCNAME,
	      GROUPS, or DIRSTACK are unset, they lose their  special  proper‐
	      ties,  even  if they are subsequently reset.  The exit status is
	      true unless a name does not exist or is readonly.

       wait [n]
	      Wait for the specified process and return its  termination  sta‐
	      tus.   n	may  be	 a process ID or a job specification; if a job
	      spec is given, all processes in that job's pipeline  are	waited
	      for.   If	 n  is not given, all currently active child processes
	      are waited for, and the return status is zero.  If n specifies a
	      non-existent  process  or job, the return status is 127.	Other‐
	      wise, the return status is the exit status of the	 last  process
	      or job waited for.

RESTRICTED SHELL
       If bash is started with the name rbash, or the -r option is supplied at
       invocation, the shell becomes restricted.  A restricted shell  is  used
       to  set	up an environment more controlled than the standard shell.  It
       behaves identically to bash with the exception that the	following  are
       disallowed or not performed:

       ·      changing directories with cd

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

       ·      specifying command names containing /

       ·      specifying  a  file  name containing a / as an argument to the .
	      builtin command

       ·      Specifying a filename containing a slash as an argument  to  the
	      -p option to the hash builtin command

       ·      importing	 function  definitions	from  the shell environment at
	      startup

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

       ·      redirecting output using the >, >|, <>, >&, &>, and >> redirect‐
	      ion operators

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

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

       ·      specifying the -p option to the command builtin command

       ·      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
       sh(1), ksh(1), csh(1)
       emacs(1), vi(1)
       readline(3)

FILES
       /bin/bash
	      The bash executable
       /etc/profile
	      The systemwide initialization file, executed for login shells
       ~/.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@ins.CWRU.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 that you have.

       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@ins.CWRU.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.

       Commands inside of $(...) command substitution  are  not	 parsed	 until
       substitution  is attempted.  This will delay error reporting until some
       time after the command is entered.

       Array variables may not (yet) be exported.

GNU Bash-2.05			  2001 Mar 5			       BASH(1)
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