read man page on CentOS

Man page or keyword search:  
man Server   8420 pages
apropos Keyword Search (all sections)
Output format
CentOS logo
[printable version]

BASH_BUILTINS(1)					      BASH_BUILTINS(1)

NAME
       bash,  :,  ., [, alias, bg, bind, break, builtin, cd, command, compgen,
       complete, continue, declare, dirs, disown, echo,	 enable,  eval,	 exec,
       exit,  export,  fc,  fg, getopts, hash, help, history, jobs, kill, let,
       local, logout, popd, printf, pushd, pwd, read, readonly,	 return,  set,
       shift,  shopt,  source,	suspend,  test,	 times,	 trap,	type, typeset,
       ulimit, umask, unalias, unset,  wait  -	bash  built-in	commands,  see
       bash(1)

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.	  For  example,	 the  :, true, false, and test builtins do not
       accept options.	Also, please note that while executing in non-interac‐
       tive  mode  and	while  in  posix mode, any special builtin (like ., :,
       break, continue, eval,  exec,  exit,  export,  readonly,	 return,  set,
       shift,  source,	times,	trap,  unset)  exiting	with a non-zero status
       causes the shell to stop execution.
       : [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.

	      Note  aliases  are  not  expanded	 by default in non-interactive
	      shell, and it can be enabled by setting the expand_aliases shell
	      option using shopt.

       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  readline	 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 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  non-zero when n is ≤ 0; Otherwise, break
	      returns 0 value.

       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 [-L|-P] [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.   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  success‐
	      fully changed; false otherwise.

       caller [expr]
	      Returns the context of any active subroutine call (a shell func‐
	      tion or a script executed with the . or source builtins.	 With‐
	      out expr, caller displays the line number and source filename of
	      the current subroutine call.  If a non-negative integer is  sup‐
	      plied as expr, caller displays the line number, subroutine name,
	      and source file corresponding to that position  in  the  current
	      execution	 call  stack.  This extra information may be used, for
	      example, to print a stack trace.	The current frame is frame  0.
	      The  return  value is 0 unless the shell is not executing a sub‐
	      routine call or expr does not correspond to a valid position  in
	      the call stack.

       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 [-abcdefgjksuv] [-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:
		      bashdefault
			      Perform the rest of the default bash completions
			      if the compspec generates no matches.
		      default Use readline's default  filename	completion  if
			      the compspec generates no matches.
		      dirnames
			      Perform  directory  name completion if the comp‐
			      spec generates no matches.
		      filenames
			      Tell readline that the compspec generates	 file‐
			      names,  so  it can perform any filename-specific
			      processing (like adding  a  slash	 to  directory
			      names or suppressing trailing spaces).  Intended
			      to be used with shell functions.
		      nospace Tell  readline  not  to  append  a  space	  (the
			      default)	to  words  completed at the end of the
			      line.
		      plusdirs
			      After any matches defined by  the	 compspec  are
			      generated,    directory	name   completion   is
			      attempted and  any  matches  are	added  to  the
			      results of the other actions.
	      -A action
		      The  action  may	be  one of the following to generate a
		      list of possible completions:
		      alias   Alias names.  May also be specified as -a.
		      arrayvar
			      Array variable names.
		      binding Readline key binding names.
		      builtin Names of shell builtin commands.	 May  also  be
			      specified as -b.
		      command Command names.  May also be specified as -c.
		      directory
			      Directory names.	May also be specified as -d.
		      disabled
			      Names of disabled shell builtins.
		      enabled Names of enabled shell builtins.
		      export  Names  of exported shell variables.  May also be
			      specified as -e.
		      file    File names.  May also be specified as -f.
		      function
			      Names of shell functions.
		      group   Group names.  May also be specified as -g.
		      helptopic
			      Help topics as accepted by the help builtin.
		      hostname
			      Hostnames, as taken from the file	 specified  by
			      the HOSTFILE shell variable.
		      job     Job  names,  if job control is active.  May also
			      be specified as -j.
		      keyword Shell reserved words.  May also be specified  as
			      -k.
		      running Names of running jobs, if job control is active.
		      service Service names.  May also be specified as -s.
		      setopt  Valid  arguments	for  the  -o option to the set
			      builtin.
		      shopt   Shell option names  as  accepted	by  the	 shopt
			      builtin.
		      signal  Signal names.
		      stopped Names of stopped jobs, if job control is active.
		      user    User names.  May also be specified as -u.
		      variable
			      Names of all shell variables.  May also be spec‐
			      ified as -v.
	      -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.	 When continue is executed inside of loop, the
	      return  value  is	 non-zero  when	 n is ≤ 0; Otherwise, continue
	      returns 0 value.	When continue is executed outside of loop, the
	      return value is 0.

       declare [-afFirtx] [-p] [name[=value] ...]
       typeset [-afFirtx] [-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.  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 following options can be used to restrict out‐
	      put to variables with the specified attribute or to  give	 vari‐
	      ables 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.
	      -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.
	      -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.   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
	      assignment  syntax (see Arrays above), one of the names is not a
	      valid shell variable name, an attempt is made to turn off	 read‐
	      only  status for a readonly variable, an attempt is made to turn
	      off array status for an array variable, or an attempt is made to
	      display a non-existent function with -f.

       dirs [-clpv] [+n] [-n]
	      Without  options,	 displays  the	list  of  currently remembered
	      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
	      \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)

       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 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 func‐
	      tion.

       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, 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 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 [-lr] [-p filename] [-dt] [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.	 The -d option
	      causes the shell to forget the remembered location of each name.
	      If  the  -t  option is supplied, the full pathname to which each
	      name corresponds is printed.  If	multiple  name	arguments  are
	      supplied	with  -t,  the	name is printed before the hashed full
	      pathname.	 The -l option causes output to be displayed in a for‐
	      mat  that may be reused as input.	 If no arguments are given, or
	      if only -l is supplied, information about remembered commands is
	      printed.	 The  return status is true unless a name is not found
	      or an invalid option is supplied.

       help [-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 the shell variable HISTTIME‐
	      FORMAT is set and not null, it is used as a  format  string  for
	      strftime(3)  to display the time stamp associated with each dis‐
	      played history entry.  No intervening blank is  printed  between
	      the  formatted  time stamp and the history line.	If filename is
	      supplied, it is used as the name of the history  file;  if  not,
	      the  value  of HISTFILE is used.	Options, if supplied, have the
	      following meanings:
	      -c     Clear the history list by deleting all the entries.
	      -d offset
		     Delete the history entry at position offset.
	      -a     Append the ``new'' history lines (history	lines  entered
		     since  the	 beginning of the current bash session) to the
		     history file.
	      -n     Read the history lines not already read from the  history
		     file  into	 the  current  history	list.  These are lines
		     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.

	      If the HISTTIMEFORMAT is set, the time stamp information associ‐
	      ated  with  each	history	 entry is written to the history file.
	      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 case-insensitive
	      signal name such as SIGKILL (with or without the SIG prefix)  or
	      a	 signal	 number; signum is a signal number.  If sigspec is not
	      present, then SIGTERM is assumed.	 An argument of -l  lists  the
	      signal  names.   If any arguments are supplied when -l is given,
	      the names of the signals	corresponding  to  the	arguments  are
	      listed, and the return status is 0.  The exit_status argument to
	      -l is a number specifying either a signal	 number	 or  the  exit
	      status  of  a process terminated by a signal.  kill returns true
	      if at least one signal was successfully sent,  or	 false	if  an
	      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 [-v var] 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  (except that \c terminates output,
	      backslashes in \', \", and \? are not removed, and octal escapes
	      beginning	 with \0 may contain up to four digits), and %q causes
	      printf to output the corresponding argument in a format that can
	      be reused as shell input.

	      The  -v  option causes the output to be assigned to the variable
	      var rather than being printed to the standard output.

	      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] [-u fd] [-t timeout] [-a aname] [-p prompt] [-n nchars] [-d
       delim] [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  interven‐
	      ing  separators  assigned	 to the last name.  If there are fewer
	      words read from the input stream than names, the remaining names
	      are  assigned  empty  values.  The characters in IFS are used to
	      split the line into words.  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  fol‐
	      lowing 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.
	      -n nchars
		     read returns after reading nchars characters rather  than
		     waiting for a complete line of input.
	      -p prompt
		     Display prompt on standard error, without a trailing new‐
		     line, before attempting to read any input.	 The prompt is
		     displayed only if input is coming from a terminal.
	      -r     Backslash does not act as an escape character.  The back‐
		     slash is considered to be part of the line.  In  particu‐
		     lar,  a  backslash-newline pair may not be used as a line
		     continuation.
	      -s     Silent mode.  If input is coming from a terminal, charac‐
		     ters are not echoed.
	      -t timeout
		     Cause  read  to time out and return failure if a complete
		     line of input is not read within timeout  seconds.	  This
		     option  has  no  effect if read is not reading input from
		     the terminal or a pipe.
	      -u fd  Read input from file descriptor fd.

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

       readonly [-apf] [name[=word] ...]
	      The  given  names are marked readonly; the values of these names
	      may not be changed by subsequent assignment.  If the  -f	option
	      is  supplied,  the  functions  corresponding to the names are so
	      marked.  The -a option restricts the variables to 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.
	      If a variable name is followed by =word, the value of the	 vari‐
	      able  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 func‐
	      tion.

       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.	Any command associated with the RETURN trap is
	      executed before execution resumes after the function or script.

       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 for setting or
	      resetting the currently-set variables.  Read-only variables can‐
	      not be reset.  In posix mode, only shell variables  are  listed.
	      The  output  is  sorted  according  to the current locale.  When
	      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 fol‐
	      lowing meanings:
	      -a      Automatically mark variables  and	 functions  which  are
		      modified	or  created  for  export to the environment of
		      subsequent commands.
	      -b      Report the status of terminated background jobs  immedi‐
		      ately, rather than before the next primary prompt.  This
		      is effective only when job control is enabled.
	      -e      Exit immediately if a 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  the  command
		      list  immediately	 following  a  while or until keyword,
		      part of the test in an if statement, part of a && or  ⎪⎪
		      list, or if the command's return value is being inverted
		      via !.  A trap on ERR, if set, is	 executed  before  the
		      shell exits.
	      -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.
		      errtrace
			      Same as -E.
		      functrace
			      Same as -T.
		      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.  nolog Currently ignored.
		      notify  Same as -b.
		      nounset Same as -u.
		      onecmd  Same as -t.
		      physical
			      Same as -P.
		      pipefail
			      If set, the return value of a  pipeline  is  the
			      value  of	 the  last (rightmost) command to exit
			      with a non-zero status, or zero if all  commands
			      in  the pipeline exit successfully.  This option
			      is disabled by default.
		      posix   Change the behavior of bash  where  the  default
			      operation	 differs  from	the  POSIX standard to
			      match the standard (posix mode).
		      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, for	command,  case
		      command, select command, or arithmetic for command, dis‐
		      play the expanded value of PS4, followed by the  command
		      and its expanded arguments or associated word list.
	      -B      The  shell performs brace expansion (see Brace Expansion
		      above).  This is on by default.
	      -C      If set, bash does not overwrite an  existing  file  with
		      the  >,  >&,  and <> redirection operators.  This may be
		      overridden when creating output files by using the redi‐
		      rection operator >| instead of >.
	      -E      If set, any trap on ERR is inherited by shell functions,
		      command substitutions, and commands executed in  a  sub‐
		      shell  environment.  The ERR trap is normally not inher‐
		      ited in such cases.
	      -H      Enable !	style history substitution.  This option is on
		      by default when the shell is interactive.
	      -P      If  set,	the  shell does not 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 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.
	      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 sub‐
			     routine (a shell function or a shell script  exe‐
			     cuted  by	the  .	or source builtins), a call to
			     return is simulated.
		      4.     BASH_ARGC and BASH_ARGV are updated as  described
			     in their descriptions above.
		      5.     Function  tracing	is enabled:  command substitu‐
			     tion, shell functions, and subshells invoked with
			     ( command ) inherit the DEBUG and RETURN traps.
		      6.     Error  tracing is enabled:	 command substitution,
			     shell functions, and  subshells  invoked  with  (
			     command ) inherit the ERROR trap.
	      extglob If set, the extended pattern matching features described
		      above under Pathname Expansion are enabled.
	      extquote
		      If set, $'string' and  $"string"	quoting	 is  performed
		      within   ${parameter}   expansions  enclosed  in	double
		      quotes.  This option is enabled by default.
	      failglob
		      If set, patterns which fail to  match  filenames	during
		      pathname expansion result in an expansion error.
	      force_fignore
		      If  set,	the  suffixes  specified  by the FIGNORE shell
		      variable cause words to be ignored when performing  word
		      completion even if the ignored words are the only possi‐
		      ble  completions.	  See  SHELL  VARIABLES	 above	for  a
		      description  of  FIGNORE.	  This	option	is  enabled by
		      default.
	      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  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.
	      login_shell
		      The  shell  sets this option if it is started as a login
		      shell (see INVOCATION above).   The  value  may  not  be
		      changed.
	      mailwarn
		      If  set,	and  a file that bash is checking for mail has
		      been accessed since the last time it  was	 checked,  the
		      message  ``The  mail in mailfile has been read'' is dis‐
		      played.
	      no_empty_cmd_completion
		      If set, and  readline  is	 being	used,  bash  will  not
		      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).
	      nocasematch
		      If set, bash  matches  patterns  in  a  case-insensitive
		      fashion when performing matching while executing case or
		      [[ conditional commands.
	      nullglob
		      If set, bash allows patterns which match no  files  (see
		      Pathname	Expansion  above)  to expand to a null string,
		      rather than themselves.
	      progcomp
		      If set, the programmable completion facilities (see Pro‐
		      grammable Completion above) are enabled.	This option is
		      enabled by default.
	      promptvars
		      If set, prompt strings undergo parameter expansion, com‐
		      mand   substitution,  arithmetic	expansion,  and	 quote
		      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  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.	When  the  suspended shell is a background process, it
	      can be restarted by the fg command. For more  information,  read
	      the JOB CONTROL section. The suspend command can not suspend the
	      login shell.  However, when -f option is specified, suspend com‐
	      mand  can	 suspend  even	login  shell.	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.   test  does  not
	      accept any options, nor does it accept and ignore an argument of
	      -- as signifying the end of options.

	      Expressions may  be  combined  using  the	 following  operators,
	      listed in decreasing order of precedence.
	      ! 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 (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  cor‐
	      responding  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 command, case command, select command, every
	      arithmetic for command, and before the first command executes in
	      a shell function	(see  SHELL  GRAMMAR  above).	Refer  to  the
	      description  of  the  extdebug  option  to the shopt builtin for
	      details of its effect on the DEBUG trap.	If a sigspec  is  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 && or ⎪⎪ list, or
	      if the command's return value is being inverted  via  !.	 These
	      are  the	same  conditions  obeyed  by the errexit option.  If a
	      sigspec is RETURN, the command arg is executed each time a shell
	      function or a script executed with the . or source builtins fin‐
	      ishes executing.	Signals ignored upon entry to the shell cannot
	      be trapped, reset or listed.  Trapped signals that are not being
	      ignored 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 [-aftpP] name [name ...]
	      With no options, indicate how each name would be interpreted  if
	      used as a command name.  If the -t option is used, type prints a
	      string which is one of alias,  keyword,  function,  builtin,  or
	      file  if	name  is  an  alias,  shell  reserved  word, function,
	      builtin, or disk file, respectively.  If the name is not	found,
	      then  nothing  is	 printed,  and	an  exit  status  of  false is
	      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.  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	 func‐
	      tion  lookup, as with the command builtin.  type returns true if
	      any of the arguments are found, false if none are found.

       ulimit [-SHacdefilmnpqrstuvx [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 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 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
	      -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 (has no effect on Linux)
	      -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
	      -x     The maximum number of file locks

	      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 or argument is supplied, or an error
	      occurs while setting a new limit.

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

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

       unset [-fv] [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	 func‐
	      tion,  and the function definition is removed.  Each unset vari‐
	      able or function is removed from the environment passed to  sub‐
	      sequent  commands.   If any of RANDOM, SECONDS, LINENO, HISTCMD,
	      FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their special
	      properties,  even if they are subsequently reset.	 The exit sta‐
	      tus is true unless a name is readonly.

       wait [n ...]
	      Wait for each specified process and return its termination  sta‐
	      tus.   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-existent  process or job, the return status is
	      127.  Otherwise, the return status is the	 exit  status  of  the
	      last process or job waited for.

SEE ALSO
       bash(1), sh(1)

GNU Bash-3.0			  2004 Apr 20		      BASH_BUILTINS(1)
[top]

List of man pages available for CentOS

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net