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BASH-BUILTINS(7)								 BASH-BUILTINS(7)

NAME
       bash-builtins - bash built-in commands, see bash(1)

SYNOPSIS
       bash  defines  the  following built-in commands: :, ., [, alias, bg, bind, break, builtin,
       case, cd, command, compgen, complete, continue, declare, dirs, disown, echo, enable, eval,
       exec,  exit,  export,  fc,  fg,	getopts, hash, help, history, if, jobs, kill, let, local,
       logout, popd, printf, pushd, pwd, read, readonly, return, set, shift, shopt, source,  sus-
       pend, test, times, trap, type, typeset, ulimit, umask, unalias, unset, until, wait, while.

BASH BUILTIN COMMANDS
       Unless  otherwise  noted,  each	builtin  command  documented in this section as accepting
       options preceded by - accepts -- to signify the end of the options.  The :,  true,  false,
       and  test builtins do not accept options and do not treat -- specially.	The exit, logout,
       break, continue, let, and shift builtins accept and process  arguments  beginning  with	-
       without	requiring  --.	 Other	builtins  that	accept arguments but are not specified as
       accepting options interpret arguments beginning with - as invalid options and  require  --
       to prevent this interpretation.
       : [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 executed 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  positional  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 supplied, 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 each suspended job jobspec in the background, as if it had been started with
	      &.  If jobspec is not present, the shell's notion of the current job is  used.   bg
	      jobspec  returns	0  unless  run when job control is disabled or, when run with job
	      control enabled, any specified jobspec was not found or  was  started  without  job
	      control.

       bind [-m keymap] [-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
       bind readline-command
	      Display  current readline key and function bindings, bind a key sequence to a read-
	      line function or macro, or set a readline variable.  Each non-option argument is	a
	      command  as it would appear in .inputrc, but each binding or command must be passed
	      as a separate argument; e.g., '"\C-x\C-r": re-read-init-file'.   Options,  if  sup-
	      plied, have the following meanings:
	      -m keymap
		     Use keymap as the keymap to be affected by the subsequent bindings.  Accept-
		     able keymap names are emacs,  emacs-standard,  emacs-meta,  emacs-ctlx,  vi,
		     vi-move,  vi-command,  and vi-insert.  vi is equivalent to vi-command; emacs
		     is equivalent to emacs-standard.
	      -l     List the names of all readline functions.
	      -p     Display readline function names and bindings in such a way that they can  be
		     re-read.
	      -P     List current readline function names and bindings.
	      -s     Display  readline	key sequences bound to macros and the strings they output
		     in such a way that they can be re-read.
	      -S     Display readline key sequences bound to macros and the strings they output.
	      -v     Display readline variable names and values in such a way that  they  can  be
		     re-read.
	      -V     List current readline variable names and values.
	      -f filename
		     Read key bindings from filename.
	      -q function
		     Query about which keys invoke the named function.
	      -u function
		     Unbind all keys bound to the named function.
	      -r keyseq
		     Remove any current binding for keyseq.
	      -x keyseq:shell-command
		     Cause  shell-command  to  be  executed  whenever  keyseq  is  entered.  When
		     shell-command is executed, the shell sets the READLINE_LINE variable to  the
		     contents  of the readline line buffer and the READLINE_POINT variable to the
		     current location of the insertion point.  If the  executed  command  changes
		     the  value  of  READLINE_LINE  or	READLINE_POINT,  those new values will be
		     reflected in the editing state.

	      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 n is not greater than  or
	      equal to 1.

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

       caller [expr]
	      Returns  the  context  of  any active subroutine call (a shell function or a script
	      executed with the . or source builtins).	Without expr, caller  displays	the  line
	      number and source filename of the current subroutine call.  If a non-negative inte-
	      ger is supplied as expr, caller displays the  line  number,  subroutine  name,  and
	      source  file  corresponding  to  that position in the current execution call stack.
	      This extra information may be used, for example, to print a stack trace.	The  cur-
	      rent  frame  is frame 0.	The return value is 0 unless the shell is not executing a
	      subroutine call or expr does not correspond to a valid position in the call stack.

       cd [-L|[-P [-e]]] [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.  Alterna-
	      tive 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  direc-
	      tory  structure  instead of following symbolic links (see also the -P option to the
	      set builtin command); the -L option forces symbolic links to be followed.   If  the
	      -e option is supplied with -P, and the current working directory cannot be success-
	      fully determined after a successful directory change, cd will return an  unsuccess-
	      ful  status.   An argument of - is equivalent to $OLDPWD.  If a non-empty directory
	      name from CDPATH is used, or if - is the first argument, and the	directory  change
	      is successful, the absolute pathname of the new working directory is written to the
	      standard output.	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 guaran-
	      teed to find all of the standard utilities.  If either the -V or -v option is  sup-
	      plied,  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 sup-
	      plied  and  an  error  occurred or command cannot be found, the exit status is 127.
	      Otherwise, the exit status 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 avail-
	      able, will not have useful values.

	      The matches will be generated in the same way as	if  the  programmable  completion
	      code  had  generated  them  directly  from a completion specification with the same
	      flags.  If word is specified, only those completions matching  word  will  be  dis-
	      played.

	      The  return  value is true unless an invalid option is supplied, or no matches were
	      generated.

       complete [-abcdefgjksuv] [-o comp-option] [-DE] [-A action] [-G globpat] [-W wordlist] [-F
       function] [-C command]
	      [-X filterpat] [-P prefix] [-S suffix] name [name ...]
       complete -pr [-DE] [name ...]
	      Specify  how  arguments to each name should be completed.  If the -p option is sup-
	      plied, or if no  options	are  supplied,	existing  completion  specifications  are
	      printed  in  a way that allows them to be reused as input.  The -r option removes a
	      completion specification for each name, or, if no names are supplied,  all  comple-
	      tion  specifications.   The  -D  option  indicates  that	the remaining options and
	      actions should apply to the ``default'' command  completion;  that  is,  completion
	      attempted on a command for which no completion has previously been defined.  The -E
	      option indicates that the remaining options and actions should apply  to	``empty''
	      command completion; that is, completion attempted on a blank line.

	      The  process  of	applying  these completion specifications when word completion is
	      attempted is described above under Programmable Completion.

	      Other options, if specified, have the following meanings.  The arguments to the -G,
	      -W,  and	-X options (and, if necessary, the -P and -S options) should be quoted to
	      protect them from expansion before the complete builtin is invoked.
	      -o comp-option
		      The comp-option controls several aspects of the compspec's behavior  beyond
		      the simple generation of completions.  comp-option may be one of:
		      bashdefault
			      Perform  the  rest  of the default bash completions if the compspec
			      generates no matches.
		      default Use readline's default filename completion if the  compspec  gener-
			      ates no matches.
		      dirnames
			      Perform  directory  name	completion  if	the compspec generates no
			      matches.
		      filenames
			      Tell readline that the compspec generates filenames, so it can per-
			      form  any  filename-specific  processing	(like  adding  a slash to
			      directory names, quoting special characters, or suppressing  trail-
			      ing spaces).  Intended to be used with shell functions.
		      nospace Tell  readline  not  to  append a space (the default) to words com-
			      pleted at the end of the line.
		      plusdirs
			      After any matches defined by the compspec are generated,	directory
			      name  completion	is  attempted  and  any  matches are added to the
			      results of the other actions.
	      -A action
		      The action may be one of the following to generate a list of possible  com-
		      pletions:
		      alias   Alias names.  May also be specified as -a.
		      arrayvar
			      Array variable names.
		      binding Readline key binding names.
		      builtin Names of shell builtin commands.	May also be specified as -b.
		      command Command names.  May also be specified as -c.
		      directory
			      Directory names.	May also be specified as -d.
		      disabled
			      Names of disabled shell builtins.
		      enabled Names of enabled shell builtins.
		      export  Names of exported shell variables.  May also be specified as -e.
		      file    File names.  May also be specified as -f.
		      function
			      Names of shell functions.
		      group   Group names.  May also be specified as -g.
		      helptopic
			      Help topics as accepted by the help builtin.
		      hostname
			      Hostnames,  as  taken from the file specified by the HOSTFILE shell
			      variable.
		      job     Job names, if job control is active.  May also be specified as -j.
		      keyword Shell reserved words.  May also be specified as -k.
		      running Names of running jobs, if job control is active.
		      service Service names.  May also be specified as -s.
		      setopt  Valid arguments for the -o option to the set builtin.
		      shopt   Shell option names as accepted by the shopt builtin.
		      signal  Signal names.
		      stopped Names of stopped jobs, if job control is active.
		      user    User names.  May also be specified as -u.
		      variable
			      Names of all shell variables.  May also be specified as -v.
	      -C command
		      command is executed in a subshell environment, and its output  is  used  as
		      the possible completions.
	      -F function
		      The  shell  function function is executed in the current shell environment.
		      When it finishes, the possible completions are retrieved from the value  of
		      the COMPREPLY array variable.
	      -G globpat
		      The pathname expansion pattern globpat is expanded to generate the possible
		      completions.
	      -P prefix
		      prefix is added at the beginning of  each  possible  completion  after  all
		      other options have been applied.
	      -S suffix
		      suffix is appended to each possible completion after all other options have
		      been applied.
	      -W wordlist
		      The wordlist is split using the characters in the IFS special  variable  as
		      delimiters,  and each resultant word is expanded.  The possible completions
		      are the members of the resultant list which match the word being completed.
	      -X filterpat
		      filterpat is a pattern as used for pathname expansion.  It  is  applied  to
		      the  list  of  possible  completions generated by the preceding options and
		      arguments, and each completion matching filterpat is removed from the list.
		      A  leading ! in filterpat negates the pattern; in this case, any completion
		      not matching filterpat is removed.

	      The return value is true unless an invalid option is supplied, an option other than
	      -p  or  -r is supplied without a name argument, an attempt is made to remove a com-
	      pletion specification for a name for which no specification  exists,  or	an  error
	      occurs adding a completion specification.

       compopt [-o option] [-DE] [+o option] [name]
	      Modify  completion  options for each name according to the options, or for the cur-
	      rently-executing completion if no names are supplied.  If  no  options  are  given,
	      display the completion options for each name or the current completion.  The possi-
	      ble values of option are those valid for the complete builtin described above.  The
	      -D option indicates that the remaining options should apply to the ``default'' com-
	      mand completion; that is, completion attempted on a command for which no completion
	      has  previously  been  defined.  The -E option indicates that the remaining options
	      should apply to ``empty'' command completion; that is, completion  attempted  on	a
	      blank line.

	      The  return  value is true unless an invalid option is supplied, an attempt is made
	      to modify the options for a name for which no completion specification  exists,  or
	      an output error occurs.

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

       declare [-aAfFgilrtux] [-p] [name[=value] ...]
       typeset [-aAfFgilrtux] [-p] [name[=value] ...]
	      Declare  variables and/or give them attributes.  If no names are given then display
	      the values of variables.	The -p option will display the attributes and  values  of
	      each  name.   When  -p is used with name arguments, additional options are ignored.
	      When -p is supplied without name arguments, it will display the attributes and val-
	      ues of all variables having the attributes specified by the additional options.  If
	      no other options are supplied with -p, declare will display the attributes and val-
	      ues of all shell variables.  The -f option will restrict the display to shell func-
	      tions.  The -F option inhibits the display of function definitions; only the  func-
	      tion  name  and  attributes  are	printed.  If the extdebug shell option is enabled
	      using shopt, the source file name and line number where the function is defined are
	      displayed as well.  The -F option implies -f.  The -g option forces variables to be
	      created or modified at the global scope, even when declare is executed in  a  shell
	      function.   It is ignored in all other cases.  The following options can be used to
	      restrict output to variables with the specified  attribute  or  to  give	variables
	      attributes:
	      -a     Each name is an indexed array variable (see Arrays above).
	      -A     Each name is an associative array variable (see Arrays above).
	      -f     Use function names only.
	      -i     The variable is treated as an integer; arithmetic evaluation (see ARITHMETIC
		     EVALUATION above) is performed when the variable is assigned a value.
	      -l     When the variable is assigned a value, all upper-case  characters	are  con-
		     verted to lower-case.  The upper-case attribute is disabled.
	      -r     Make  names  readonly.  These names cannot then be assigned values by subse-
		     quent assignment statements or unset.
	      -t     Give each name the trace attribute.  Traced functions inherit the DEBUG  and
		     RETURN  traps  from  the  calling shell.  The trace attribute has no special
		     meaning for variables.
	      -u     When the variable is assigned a value, all lower-case  characters	are  con-
		     verted to upper-case.  The lower-case attribute is disabled.
	      -x     Mark names for export to subsequent commands via the environment.

	      Using  `+' instead of `-' turns off the attribute instead, with the exceptions that
	      +a may not be used to destroy an array variable and +r will not remove the readonly
	      attribute.   When used in a function, makes each name local, as with the local com-
	      mand, unless the -g option is supplied, If a variable name is followed  by  =value,
	      the value of the variable is set to value.  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  assign-
	      ment  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  readonly  variable,  an
	      attempt  is  made  to turn off array status for an array variable, or an attempt is
	      made to display a non-existent function with -f.

       dirs [+n] [-n] [-clpv]
	      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, prefixing 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 jobspec
	      is  not  present, and neither -a nor -r is supplied, the shell's notion of the cur-
	      rent job is used.  If the -h option is given, each jobspec is not removed from  the
	      table,  but is marked so that SIGHUP is not sent to the job if the shell receives a
	      SIGHUP.  If no jobspec is present, and neither the -a nor the  -r  option  is  sup-
	      plied,  the current job is used.	If no jobspec is supplied, the -a option means to
	      remove or mark all jobs; the -r option without a jobspec argument restricts  opera-
	      tion  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, interpretation of the following	backslash-escaped  characters  is
	      enabled.	 The  -E  option  disables the interpretation of these escape characters,
	      even on systems where they are interpreted by default.  The xpg_echo  shell  option
	      may be used to dynamically determine whether or not echo expands these escape char-
	      acters by default.  echo does not interpret -- to mean the end  of  options.   echo
	      interprets the following escape sequences:
	      \a     alert (bell)
	      \b     backspace
	      \c     suppress further output
	      \e
	      \E     an escape character
	      \f     form feed
	      \n     new line
	      \r     carriage return
	      \t     horizontal tab
	      \v     vertical tab
	      \\     backslash
	      \0nnn  the  eight-bit  character	whose value is the octal value nnn (zero to three
		     octal digits)
	      \xHH   the eight-bit character whose value is the hexadecimal value HH (one or  two
		     hex digits)
	      \uHHHH the  Unicode  (ISO/IEC 10646) character whose value is the hexadecimal value
		     HHHH (one to four hex digits)
	      \UHHHHHHHH
		     the Unicode (ISO/IEC 10646) character whose value is the  hexadecimal  value
		     HHHHHHHH (one to eight hex digits)

       enable [-a] [-dnps] [-f filename] [name ...]
	      Enable  and disable builtin shell commands.  Disabling a builtin allows a disk com-
	      mand 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  com-
	      mand  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  argu-
	      ments  are  given,  or  if  the  -p option is supplied, a list of shell builtins is
	      printed.	With no other option arguments, 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 indication 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 command.  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 beginning of the zeroth argument 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-inter-
	      active  shell  exits, unless the shell option execfail is enabled, in which case it
	      returns failure.	An interactive shell returns failure if the file cannot  be  exe-
	      cuted.   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 environment of subse-
	      quently executed commands.  If the -f option is given, the  names  refer	to  func-
	      tions.  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  prop-
	      erty  to	be  removed from each name.  If a variable name is followed by =word, the
	      value of the variable is set to word.  export returns an exit status of 0 unless an
	      invalid option is encountered, one of the names is not a valid shell variable name,
	      or -f is supplied with a name that is not a function.

       fc [-e ename] [-lnr] [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 current command num-
	      ber).  If last is not specified it is set to the current command	for  listing  (so
	      that  ``fc  -l -10'' prints the last 10 commands) and to first otherwise.  If first
	      is not specified it is set to the previous command for editing and -16 for listing.

	      The -n option suppresses the command numbers when listing.  The -r option  reverses
	      the  order  of the commands.  If the -l option is given, the commands are listed on
	      standard output.	Otherwise, the editor given by ename is invoked on  a  file  con-
	      taining 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, is
	      used.  When editing is complete, 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
	      command.

	      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-executed,  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 specify 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 parameters.  optstring con-
	      tains the option characters to be recognized; if	a  character  is  followed  by	a
	      colon,  the  option is expected to have an argument, which should be separated from
	      it by white space.  The colon and question mark  characters  may	not  be  used  as
	      option  characters.  Each time it is invoked, 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 argu-
	      ment,  getopts  places  that argument into the variable OPTARG.  The shell does not
	      reset OPTIND automatically; it must be manually reset  between  multiple	calls  to
	      getopts within the same shell invocation if a new set of parameters is to be used.

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

	      getopts  normally parses the positional parameters, but if more arguments are 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 displayed, even if the first
	      character of optstring is not a colon.

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

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

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

       hash [-lr] [-p filename] [-dt] [name]
	      Each time hash is invoked, the full pathname of the command name is  determined  by
	      searching the directories in $PATH and remembered.  Any previously-remembered path-
	      name is discarded.  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.  The -d option causes the shell to forget
	      the remembered location of each name.  If the -t option is supplied, the full path-
	      name to which each name corresponds is printed.  If  multiple  name  arguments  are
	      supplied	with  -t,  the	name  is printed before the hashed full pathname.  The -l
	      option causes output to be displayed in a format that may be reused as  input.   If
	      no  arguments  are  given,  or if only -l is supplied, information about remembered
	      commands is printed.  The return status is true unless a name is not  found  or  an
	      invalid option is supplied.

       help [-dms] [pattern]
	      Display  helpful information about builtin commands.  If pattern is specified, help
	      gives detailed help on all commands matching pattern; otherwise help  for  all  the
	      builtins and shell control structures is printed.
	      -d     Display a short description of each pattern
	      -m     Display the description of each pattern in a manpage-like format
	      -s     Display only a short usage synopsis for each pattern

	      The return status is 0 unless no command matches pattern.

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

	      If  the  HISTTIMEFORMAT variable is set, the time stamp information associated with
	      each history entry is written to the history file, marked with the history  comment
	      character.  When the history file is read, lines beginning with the history comment
	      character followed immediately by a digit are interpreted  as  timestamps  for  the
	      previous	history  line.	The return value is 0 unless an invalid option is encoun-
	      tered, 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 following meanings:
	      -l     List process IDs in addition to the normal information.
	      -n     Display information only about jobs that have changed status since the  user
		     was last notified of their status.
	      -p     List only the process ID of the job's process group leader.
	      -r     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 job-
	      spec.  sigspec is either a case-insensitive signal name such as  SIGKILL	(with  or
	      without  the SIG prefix) or a signal number; signum is a signal number.  If sigspec
	      is not present, then SIGTERM is assumed.	An argument of -l lists the signal names.
	      If  any  arguments  are  supplied when -l is given, the names of the signals corre-
	      sponding to the arguments are listed, and the return status is 0.  The  exit_status
	      argument	to -l is a number specifying either a signal number or the exit status of
	      a process terminated by a signal.  kill returns true if at  least  one  signal  was
	      successfully sent, or false if an error occurs or an invalid option is encountered.

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

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

       logout Exit a login shell.

       mapfile [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
       readarray [-n count] [-O origin] [-s count]  [-t]  [-u  fd]  [-C  callback]  [-c  quantum]
       [array]
	      Read  lines  from the standard input into the indexed array variable array, or from
	      file descriptor fd if the -u option is  supplied.   The  variable  MAPFILE  is  the
	      default array.  Options, if supplied, have the following meanings:
	      -n     Copy at most count lines.	If count is 0, all lines are copied.
	      -O     Begin assigning to array at index origin.	The default index is 0.
	      -s     Discard the first count lines read.
	      -t     Remove a trailing newline from each line read.
	      -u     Read lines from file descriptor fd instead of the standard input.
	      -C     Evaluate callback each time quantum lines are read.  The -c option specifies
		     quantum.
	      -c     Specify the number of lines read between each call to callback.

	      If -C is specified without -c, the default quantum is 5000.  When callback is eval-
	      uated,  it  is  supplied the index of the next array element to be assigned and the
	      line to be assigned to that element as additional arguments.  callback is evaluated
	      after the line is read but before the array element is assigned.

	      If  not supplied with an explicit origin, mapfile will clear array before assigning
	      to it.

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

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

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

       printf [-v var] format [arguments]
	      Write  the formatted arguments to the standard output under the control of the for-
	      mat.  The -v option causes the output to be assigned to  the  variable  var  rather
	      than being printed to the standard output.

	      The format is a character string which contains three types of objects: plain char-
	      acters, which are simply copied to standard  output,  character  escape  sequences,
	      which  are  converted and copied to the standard output, and format specifications,
	      each of which causes printing of the next successive argument.  In addition to  the
	      standard	printf(1)  format  specifications, printf interprets the following exten-
	      sions:
	      %b     causes printf to expand backslash	escape	sequences  in  the  corresponding
		     argument  (except	that  \c terminates output, backslashes in \', \", and \?
		     are not removed, and octal escapes beginning with \0 may contain up to  four
		     digits).
	      %q     causes  printf  to output the corresponding argument in a format that can be
		     reused as shell input.
	      %(datefmt)T
		     causes printf to output the date-time string resulting from using datefmt as
		     a	format	string for strftime(3).  The corresponding argument is an integer
		     representing the number of seconds since the epoch.   Two	special  argument
		     values  may  be  used: -1 represents the current time, and -2 represents the
		     time the shell was invoked.

	      Arguments to non-string format specifiers are treated as C constants, except that a
	      leading  plus or minus sign is allowed, and if the leading character is a single or
	      double quote, the value is the ASCII value of the following character.

	      The format is reused as necessary to consume all of the arguments.  If  the  format
	      requires	more  arguments than are supplied, the extra format specifications behave
	      as if a zero value or null string, as appropriate, had been supplied.   The  return
	      value is zero on success, non-zero on failure.

       pushd [-n] [+n] [-n]
       pushd [-n] [dir]
	      Adds  a  directory  to the top of the directory stack, or rotates the stack, making
	      the new top of the  stack  the  current  working	directory.   With  no  arguments,
	      exchanges  the  top  two	directories  and returns 0, unless the directory stack is
	      empty.  Arguments, if supplied, have the following meanings:
	      -n     Suppresses the normal change of directory when  adding  directories  to  the
		     stack, so that only the stack is manipulated.
	      +n     Rotates  the  stack so that the nth directory (counting from the left of the
		     list shown by dirs, starting with zero) is at the top.
	      -n     Rotates the stack so that the nth directory (counting from the right of  the
		     list shown by dirs, starting with zero) is at the top.
	      dir    Adds  dir to the directory stack at the top, making it the new current work-
		     ing 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 directory stack is empty, a non-existent directory stack  ele-
	      ment  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] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t  time-
       out] [-u fd] [name ...]
	      One  line  is read from the standard input, or from the file descriptor fd supplied
	      as an argument to the -u option, 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 inter-
	      vening separators assigned to the last name.  If there are fewer	words  read  from
	      the  input  stream  than names, the remaining names are assigned empty values.  The
	      characters in IFS are used to split the line into words.	The  backslash	character
	      (\)  may	be used to remove any special meaning for the next character read and for
	      line continuation.  Options, if supplied, have the following meanings:
	      -a aname
		     The words are assigned to sequential indices of the  array  variable  aname,
		     starting  at  0.	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.  Readline uses the current  (or  default,
		     if line editing was not previously active) editing settings.
	      -i text
		     If  readline is being used to read the line, text is placed into the editing
		     buffer before editing begins.
	      -n nchars
		     read returns after reading nchars characters rather than waiting for a  com-
		     plete  line  of input, but honor a delimiter if fewer than nchars characters
		     are read before the delimiter.
	      -N nchars
		     read returns after reading exactly nchars characters rather than waiting for
		     a	complete  line	of  input,  unless  EOF is encountered or read times out.
		     Delimiter characters encountered in the input are not treated specially  and
		     do not cause read to return until nchars characters are read.
	      -p prompt
		     Display  prompt  on  standard  error,  without  a	trailing  newline, before
		     attempting to read any input.  The prompt is displayed only if input is com-
		     ing from a terminal.
	      -r     Backslash	does not act as an escape character.  The backslash is considered
		     to be part of the line.  In particular, a backslash-newline pair may not  be
		     used as a line continuation.
	      -s     Silent mode.  If input is coming from a terminal, characters are not echoed.
	      -t timeout
		     Cause read to time out and return failure if a complete line of input is not
		     read within timeout seconds.  timeout may be a decimal number with  a  frac-
		     tional  portion  following the decimal point.  This option is only effective
		     if read is reading input from a terminal, pipe, or other  special	file;  it
		     has  no  effect  when  reading  from  regular  files.  If timeout is 0, read
		     returns success if input is available  on	the  specified	file  descriptor,
		     failure  otherwise.   The	exit status is greater than 128 if the timeout is
		     exceeded.
	      -u fd  Read input from file descriptor fd.

	      If no names are supplied, the line read is assigned to  the  variable  REPLY.   The
	      return  code  is	zero, unless end-of-file is encountered, read times out (in which
	      case the return code is greater than 128), or an invalid file  descriptor  is  sup-
	      plied as the argument to -u.

       readonly [-aAf] [-p] [name[=word] ...]
	      The  given  names are marked readonly; the values of these names may not be changed
	      by subsequent assignment.  If the -f option is supplied, the functions  correspond-
	      ing  to  the names are so marked.  The -a option restricts the variables to indexed
	      arrays; the -A option restricts the  variables  to  associative  arrays.	 If  both
	      options  are  supplied, -A takes precedence.  If no name arguments are given, or if
	      the -p option is supplied, a list of all readonly  names	is  printed.   The  other
	      options  may  be	used  to  restrict  the output to a subset of the set of readonly
	      names.  The -p option causes output to be displayed in a format that may be  reused
	      as  input.   If  a variable name is followed by =word, the value of the variable is
	      set to word.  The return status is 0 unless an invalid option is	encountered,  one
	      of the names is not a valid shell variable name, or -f is supplied with a name that
	      is not a function.

       return [n]
	      Causes a function to 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)  com-
	      mand,  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.  Any command associated with the RETURN  trap  is  exe-
	      cuted before execution resumes after the function or script.

       set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]
       set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg ...]
	      Without  options, the name and value of each shell variable are displayed in a for-
	      mat that can be reused as input for setting or resetting	the  currently-set  vari-
	      ables.   Read-only  variables cannot be reset.  In posix mode, only shell variables
	      are listed.  The output is sorted according to the current  locale.   When  options
	      are  specified,  they set or unset shell attributes.  Any arguments remaining after
	      option processing are treated as values  for  the  positional  parameters  and  are
	      assigned,  in order, to $1, $2, ...  $n.	Options, if specified, have the following
	      meanings:
	      -a      Automatically mark variables and functions which are  modified  or  created
		      for export to the environment of subsequent commands.
	      -b      Report  the  status  of terminated background jobs immediately, rather than
		      before the next primary prompt.  This is effective only when job control is
		      enabled.
	      -e      Exit  immediately  if a pipeline (which may consist of a single simple com-
		      mand),  a subshell command enclosed in parentheses, or one of the  commands
		      executed	as  part  of a command list enclosed by braces (see SHELL GRAMMAR
		      above) exits with a non-zero status.  The shell does not exit if	the  com-
		      mand  that  fails is part of the command list immediately following a while
		      or until keyword, part of the test following the if or elif reserved words,
		      part  of any command executed in a && or || list except the command follow-
		      ing the final && or ||, any command in a pipeline but the last, or  if  the
		      command's return value is being inverted with !.	A trap on ERR, if set, is
		      executed before the shell exits.	This option applies to the shell environ-
		      ment  and each subshell environment separately (see COMMAND EXECUTION ENVI-
		      RONMENT above), and may cause subshells to exit before  executing  all  the
		      commands in the subshell.
	      -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  envi-
		      ronment 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  processes run in a separate process group and a line containing
		      their exit status is printed upon their completion.
	      -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 interface.  This is enabled
			      by default when the shell  is  interactive,  unless  the	shell  is
			      started with the --noediting option.  This also affects the editing
			      interface used for read -e.
		      errexit Same as -e.
		      errtrace
			      Same as -E.
		      functrace
			      Same as -T.
		      hashall Same as -h.
		      histexpand
			      Same as -H.
		      history Enable command history, as described  above  under  HISTORY.   This
			      option is on by default in interactive 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.
		      nolog   Currently ignored.
		      notify  Same as -b.
		      nounset Same as -u.
		      onecmd  Same as -t.
		      physical
			      Same as -P.
		      pipefail
			      If set, the return value of a pipeline is the  value  of	the  last
			      (rightmost)  command to exit with a non-zero status, or zero if all
			      commands in the pipeline exit successfully.  This  option  is  dis-
			      abled by default.
		      posix   Change  the  behavior  of  bash where the default operation differs
			      from the POSIX standard to match the standard (posix mode).
		      privileged
			      Same as -p.
		      verbose Same as -v.
		      vi      Use a vi-style command line editing interface.  This  also  affects
			      the editing interface used for read -e.
		      xtrace  Same as -x.
		      If  -o  is  supplied with no option-name, the values of the current options
		      are printed.  If +o is supplied with no option-name, a series of	set  com-
		      mands  to recreate the current option settings is displayed on the standard
		      output.
	      -p      Turn on privileged mode.	In this mode, the $ENV and  $BASH_ENV  files  are
		      not  processed, shell functions are not inherited from the environment, and
		      the SHELLOPTS, BASHOPTS, CDPATH, and GLOBIGNORE variables, if  they  appear
		      in  the  environment, are ignored.  If the shell is started with the effec-
		      tive 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 effec-
		      tive user and group ids to be set to the real user and group ids.
	      -t      Exit after reading and executing one command.
	      -u      Treat unset variables and parameters other than the special parameters  "@"
		      and  "*"	as an error when performing parameter expansion.  If expansion is
		      attempted on an unset variable or parameter, the shell prints an error mes-
		      sage, and, if not interactive, exits with a non-zero status.
	      -v      Print shell input lines as they are read.
	      -x      After expanding each simple command, for command, case command, select com-
		      mand, or arithmetic for command, display the expanded value  of  PS4,  fol-
		      lowed by the command and its expanded arguments or associated word list.
	      -B      The shell performs brace expansion (see Brace Expansion above).  This is on
		      by default.
	      -C      If set, bash does not overwrite an existing file with the >, >&, and <> re-
		      direction  operators.  This may be overridden when creating output files by
		      using the redirection operator >| instead of >.
	      -E      If set, any trap on ERR is inherited by shell functions, command	substitu-
		      tions,  and  commands  executed in a subshell environment.  The ERR trap is
		      normally not inherited in such cases.
	      -H      Enable !	style history substitution.  This option is on	by  default  when
		      the shell is interactive.
	      -P      If  set,	the  shell does not 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.
	      -T      If set, any traps on DEBUG and RETURN are  inherited  by	shell  functions,
		      command  substitutions,  and  commands  executed in a subshell environment.
		      The DEBUG and RETURN traps are normally not inherited in such cases.
	      --      If no arguments follow this option,  then  the  positional  parameters  are
		      unset.   Otherwise,  the positional parameters are set to the 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 positional 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 argu-
	      ments 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 encountered.

       shift [n]
	      The  positional  parameters  from n+1 ... are renamed to $1 ....	Parameters repre-
	      sented 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  behavior.	 With  no
	      options,	or  with the -p option, a list of all settable options is displayed, with
	      an indication of whether or not each is set.  The -p option  causes  output  to  be
	      displayed  in a form that may be reused as input.  Other options have the following
	      meanings:
	      -s     Enable (set) each optname.
	      -u     Disable (unset) each optname.
	      -q     Suppresses normal output (quiet mode); the return status  indicates  whether
		     the  optname  is set or unset.  If multiple optname arguments are given with
		     -q, the return status 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  display  is  limited  to
	      those  options  which  are set or unset, respectively.  Unless otherwise noted, the
	      shopt options are disabled (unset) by default.

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

	      The list of shopt options is:

	      autocd  If set, a command name that is the name of a directory is executed as if it
		      were  the argument to the cd command.  This option is only used by interac-
		      tive shells.
	      cdable_vars
		      If set, an argument to the cd builtin command that is not  a  directory  is
		      assumed to be the name of a variable whose value is the directory to change
		      to.
	      cdspell If set, minor errors in the spelling of a directory component in a cd  com-
		      mand  will be corrected.	The errors checked for are transposed characters,
		      a missing character, and one character too many.	If a correction is found,
		      the  corrected file name is printed, and the command proceeds.  This option
		      is only used by interactive shells.
	      checkhash
		      If set, bash checks that a command found in the hash  table  exists  before
		      trying  to execute it.  If a hashed command no longer exists, a normal path
		      search is performed.
	      checkjobs
		      If set, bash lists the status of any stopped and running jobs before  exit-
		      ing an interactive shell.  If any jobs are running, this causes the exit to
		      be deferred until a second exit is attempted without an intervening command
		      (see  JOB  CONTROL  above).  The shell always postpones exiting if any jobs
		      are stopped.
	      checkwinsize
		      If set, bash checks the window size after each command and,  if  necessary,
		      updates the values of LINES and COLUMNS.
	      cmdhist If  set,	bash attempts to save all lines of a multiple-line command in the
		      same history entry.  This allows easy re-editing of multi-line commands.
	      compat31
		      If set, bash changes its behavior to that of version 3.1	with  respect  to
		      quoted arguments to the [[ conditional command's =~ operator.
	      compat32
		      If  set,	bash  changes its behavior to that of version 3.2 with respect to
		      locale-specific string comparison when using the [[ conditional command's <
		      and  >  operators.  Bash versions prior to bash-4.1 use ASCII collation and
		      strcmp(3); bash-4.1 and later use the current locale's  collation  sequence
		      and strcoll(3).
	      compat40
		      If  set,	bash  changes its behavior to that of version 4.0 with respect to
		      locale-specific string comparison when using the [[ conditional command's <
		      and  >  operators (see previous item) and the effect of interrupting a com-
		      mand list.
	      compat41
		      If set, bash, when in posix mode, treats a single quote in a  double-quoted
		      parameter  expansion  as a special character.  The single quotes must match
		      (an even number) and the characters between the single quotes  are  consid-
		      ered  quoted.  This is the behavior of posix mode through version 4.1.  The
		      default bash behavior remains as in previous versions.
	      dirspell
		      If set, bash attempts spelling correction on directory  names  during  word
		      completion if the directory name initially supplied does not exist.
	      dotglob If  set,	bash  includes	filenames  beginning with a `.' in the results of
		      pathname expansion.
	      execfail
		      If set, a non-interactive shell will not exit if it cannot execute the file
		      specified as an argument to the exec builtin command.  An interactive shell
		      does not exit if exec fails.
	      expand_aliases
		      If set, aliases are expanded as described above under ALIASES.  This option
		      is enabled by default for interactive shells.
	      extdebug
		      If set, behavior intended for use by debuggers is enabled:
		      1.     The  -F  option to the declare builtin displays the source file name
			     and line number corresponding to each function name supplied  as  an
			     argument.
		      2.     If  the  command run by the DEBUG trap returns a non-zero value, the
			     next command is skipped and not executed.
		      3.     If the command run by the DEBUG trap returns a value of 2,  and  the
			     shell  is	executing  in  a  subroutine (a shell function or a shell
			     script executed by the . or source builtins), a call  to  return  is
			     simulated.
		      4.     BASH_ARGC	and  BASH_ARGV are updated as described in their descrip-
			     tions above.
		      5.     Function tracing is enabled:  command substitution, shell functions,
			     and  subshells invoked with ( command ) inherit the DEBUG and RETURN
			     traps.
		      6.     Error tracing is enabled:	command  substitution,	shell  functions,
			     and subshells invoked with ( command ) inherit the ERR trap.
	      extglob If  set, the extended pattern matching features described above under Path-
		      name Expansion are enabled.
	      extquote
		      If set, $'string' and $"string" quoting is  performed  within  ${parameter}
		      expansions enclosed in double quotes.  This option is enabled by default.
	      failglob
		      If  set,	patterns  which fail to match filenames during pathname expansion
		      result in an expansion error.
	      force_fignore
		      If set, the suffixes specified by the FIGNORE shell variable cause words to
		      be  ignored  when  performing word completion even if the ignored words are
		      the only possible completions.  See SHELL VARIABLES above for a description
		      of FIGNORE.  This option is enabled by default.
	      globstar
		      If  set, the pattern ** used in a pathname expansion context will match all
		      files and zero or more directories and subdirectories.  If the  pattern  is
		      followed by a /, only directories and subdirectories match.
	      gnu_errfmt
		      If  set, shell error messages are written in the standard GNU error message
		      format.
	      histappend
		      If set, the history list is appended to the file named by the value of  the
		      HISTFILE variable when the shell exits, rather than overwriting the file.
	      histreedit
		      If  set, and readline is being used, a user is given the opportunity to re-
		      edit a failed history substitution.
	      histverify
		      If set, and readline is being used, the results of history substitution are
		      not immediately passed to the shell parser.  Instead, the resulting line is
		      loaded into the readline editing buffer, allowing further modification.
	      hostcomplete
		      If set, and readline is being used, bash will attempt to	perform  hostname
		      completion  when	a  word containing a @ is being completed (see Completing
		      under READLINE above).  This is enabled by default.
	      huponexit
		      If set, bash will send SIGHUP to all jobs when an interactive  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.
	      lastpipe
		      If set, and job control is not active, the shell runs the last command of a
		      pipeline not executed in the background in the current shell environment.
	      lithist If set, and the cmdhist option is enabled, multi-line commands are saved to
		      the  history  with embedded newlines rather than using semicolon separators
		      where possible.
	      login_shell
		      The shell sets this option if it is started as a login shell  (see  INVOCA-
		      TION above).  The value may not be changed.
	      mailwarn
		      If  set,	and a file that bash is checking for mail has been accessed since
		      the last time it was checked, the message ``The mail in mailfile	has  been
		      read'' is displayed.
	      no_empty_cmd_completion
		      If  set,	and  readline  is being used, bash will not attempt to search the
		      PATH for possible completions when completion  is  attempted  on	an  empty
		      line.
	      nocaseglob
		      If  set, bash matches filenames in a case-insensitive fashion when perform-
		      ing pathname expansion (see Pathname Expansion above).
	      nocasematch
		      If set, bash matches patterns in a case-insensitive fashion when performing
		      matching while executing case or [[ conditional commands.
	      nullglob
		      If  set,	bash allows patterns which match no files (see Pathname Expansion
		      above) to expand to a null string, rather than themselves.
	      progcomp
		      If set, the programmable completion facilities (see Programmable Completion
		      above) are enabled.  This option is enabled by default.
	      promptvars
		      If  set,	prompt strings undergo parameter expansion, command substitution,
		      arithmetic expansion, and quote removal 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 discover
		      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 parameters.
	      sourcepath
		      If set, the source (.) builtin uses the value of PATH to find the directory
		      containing the file supplied as an argument.  This  option  is  enabled  by
		      default.
	      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.  A login
	      shell cannot be suspended; the -f option can be used to override this and force the
	      suspension.  The return status is 0 unless the shell is a login shell 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 com-
	      posed of the primaries described above under CONDITIONAL	EXPRESSIONS.   test  does
	      not accept any options, nor does it accept and ignore an argument of -- as signify-
	      ing the end of options.

	      Expressions may be combined using the following  operators,  listed  in  decreasing
	      order of precedence.  The evaluation depends on the number of arguments; see below.
	      Operator precedence is used when there are five or more arguments.
	      ! expr True if expr is false.
	      ( expr )
		     Returns the value of expr.  This may be used to override the  normal  prece-
		     dence 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 num-
	      ber of arguments.

	      0 arguments
		     The expression is false.
	      1 argument
		     The expression is true if and only if the argument is not null.
	      2 arguments
		     If the first argument is !, the expression is true if and only if the second
		     argument  is  null.   If  the first argument is one of the unary conditional
		     operators listed above under CONDITIONAL EXPRESSIONS, the expression is true
		     if  the unary test is true.  If the first argument is not a valid unary con-
		     ditional operator, the expression is false.
	      3 arguments
		     The following conditions are applied in the order	listed.   If  the  second
		     argument  is one of the binary conditional operators listed above under CON-
		     DITIONAL EXPRESSIONS, the result of the expression  is  the  result  of  the
		     binary  test using the first and third arguments as operands.  The -a and -o
		     operators are considered binary operators when there  are	three  arguments.
		     If  the  first  argument is !, the value is the negation of the two-argument
		     test using the second and third arguments.  If the first argument is exactly
		     (	and  the third argument is exactly ), the result is the one-argument test
		     of the second argument.  Otherwise, the expression is false.
	      4 arguments
		     If the first argument is !, the result is the negation of the three-argument
		     expression  composed  of the remaining arguments.	Otherwise, the expression
		     is parsed and evaluated according	to  precedence	using  the  rules  listed
		     above.
	      5 or more arguments
		     The  expression  is  parsed  and evaluated according to precedence using the
		     rules listed above.

	      When used with test or [, the < and > operators sort lexicographically using  ASCII
	      ordering.

       times  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 (and there is a single sigspec) or -, each specified
	      signal is reset to its original disposition (the value it had upon entrance to  the
	      shell).	If arg is the null string the signal specified by each sigspec is ignored
	      by the shell and by the commands it invokes.  If arg is not present and -p has been
	      supplied, then the trap commands associated with each sigspec are displayed.  If no
	      arguments are supplied or if only -p is given, trap prints  the  list  of  commands
	      associated  with	each  signal.	The -l option causes the shell to print a list of
	      signal names and their corresponding numbers.  Each sigspec is either a signal name
	      defined  in  <signal.h>, or a signal number.  Signal names are case insensitive and
	      the SIG prefix is optional.

	      If a sigspec is EXIT (0) the command arg is executed on exit from the shell.  If	a
	      sigspec is DEBUG, the command arg is executed before every simple command, for com-
	      mand, case command, select command, every arithmetic for command,  and  before  the
	      first command executes in a shell function (see SHELL GRAMMAR above).  Refer to the
	      description of the extdebug option to the shopt builtin for details of  its  effect
	      on the DEBUG trap.  If a sigspec is RETURN, the command arg is executed each time a
	      shell function or a script executed with the . or source builtins finishes  execut-
	      ing.

	      If  a  sigspec  is ERR, the command arg is executed whenever a simple command has a
	      non-zero exit status, subject to the following conditions.  The  ERR  trap  is  not
	      executed	if the failed command is part of the command list immediately following a
	      while or until keyword, part of the test in an if statement, part of a command exe-
	      cuted in a && or || list, or if the command's return value is being inverted via !.
	      These are the same conditions obeyed by the errexit option.

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

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

       ulimit [-HSTabcdefilmnpqrstuvx [limit]]
	      Provides control over the resources available to the shell and to processes started
	      by it, on systems that allow such control.  The -H and -S options specify that  the
	      hard or soft limit is set for the given resource.  A hard limit cannot be increased
	      by a non-root user once it is set; a soft limit may be increased up to the value of
	      the  hard  limit.  If neither -H nor -S is specified, both the soft and hard limits
	      are set.	The value of limit can be a number in the unit specified for the resource
	      or  one of the special values hard, soft, or unlimited, which stand for the current
	      hard limit, the current soft limit, and no limit, respectively.  If limit is  omit-
	      ted,  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 follows:
	      -a     All current limits are reported
	      -b     The maximum socket buffer size
	      -c     The maximum size of core files created
	      -d     The maximum size of a process's data segment
	      -e     The maximum scheduling priority ("nice")
	      -f     The maximum size of files written by the shell and its children
	      -i     The maximum number of pending signals
	      -l     The maximum size that may be locked into memory
	      -m     The maximum resident set size (many systems do not honor this limit)
	      -n     The  maximum number of open file descriptors (most systems do not allow this
		     value to be set)
	      -p     The pipe size in 512-byte blocks (this may not be set)
	      -q     The maximum number of bytes in POSIX message queues
	      -r     The maximum real-time scheduling priority
	      -s     The maximum stack size
	      -t     The maximum amount of cpu time in seconds
	      -u     The maximum number of processes available to a single user
	      -v     The maximum amount of virtual memory available to the  shell  and,  on  some
		     systems, to its children
	      -x     The maximum number of file locks
	      -T     The maximum number of threads

	      If  limit is given, 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 -T, -b, -n, and -u, which are unscaled values.  The return status is	0
	      unless  an invalid option or argument is supplied, or an error occurs while setting
	      a new limit.

       umask [-p] [-S] [mode]
	      The user file-creation mask is set to mode.  If mode begins with	a  digit,  it  is
	      interpreted as an octal number; otherwise it is interpreted as a symbolic mode mask
	      similar to that accepted by chmod(1).  If mode is omitted, the current value of the
	      mask is printed.	The -S option causes the mask to be printed in symbolic form; the
	      default output is an octal number.  If the -p option is supplied, and mode is omit-
	      ted,  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 specified, 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
	      COMP_WORDBREAKS, RANDOM, SECONDS, LINENO, HISTCMD, FUNCNAME,  GROUPS,  or  DIRSTACK
	      are unset, they lose their special properties, even if they are subsequently reset.
	      The exit status is true unless a name is readonly.

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

SEE ALSO
       bash(1), sh(1)

GNU Bash-2.05a				 2001 October 29			 BASH-BUILTINS(7)
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