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NOM

       bash-builtins - Commandes internes de bash, consultez bash(1)

SYNOPSIS

       bash  définit les commandes internes suivantes : :, ., [, 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,
       suspend,  test,  times,  trap,  type, typeset, ulimit, umask, unalias, unset, until, wait,
       while.

COMMANDES INTERNES DE BASH

       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,  filenames  in  PATH  are  used to find the directory containing
              filename. The file searched for in PATH need not be executable. When bash is not in
              posix  mode,  the current directory is searched if no file is found in PATH. If the
              sourcepath option to the shopt builtin command is  turned  off,  the  PATH  is  not
              searched. If any arguments are supplied, they become the 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] [-lpsvPSVX]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] -x keyseq:shell-command
       bind [-m keymap] keyseq:function-name
       bind readline-command
              Display current readline key and function  bindings,  bind  a  key  sequence  to  a
              readline function or macro, or set a readline variable. Each non-option argument is
              a command as it would 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-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.
              -X     List  all  key sequences bound to shell commands and the associated commands
                     in a format that can be reused as input.

              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
              status. 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
              integer 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
              current 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. if dir is not supplied, the value of the  HOME
              shell  variable is the default. Any additional arguments following dir are ignored.
              The variable CDPATH defines the search path for the directory containing dir:  each
              directory name in CDPATH is searched for dir. Alternative 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 causes cd to use the physical directory structure by  resolving
              symbolic  links  while  traversing dir and before processing instances of .. in dir
              (see also the -P option to the set builtin command); the -L option forces  symbolic
              links to be followed by resolving the link after processing instances of .. in dir.
              If .. appears in dir, it is processed by removing the immediately previous pathname
              component  from  dir,  back to a slash or the beginning of dir. If the -e option is
              supplied with  -P,  and  the  current  working  directory  cannot  be  successfully
              determined  after  a  successful  directory  change, cd will return an unsuccessful
              status. On systems that support it, the -@ option presents the extended  attributes
              associated  with  a  file  as a directory. An argument of - is converted to $OLDPWD
              before the directory change is attempted. If a non-empty 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  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  filename  used  to  invoke command to be displayed; the -V option
              produces a more verbose description. If the -V or -v option is supplied,  the  exit
              status  is  0 if command was found, and 1 if not. If neither option is supplied and
              an error occurred or command 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
              available, 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
              displayed.

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

       complete [-abcdefgjksuv] [-o comp-option] [-DE] [-A action] [-G 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
              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  specification  for  each  name,  or,  if  no  names  are  supplied, all
              completion 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
                              generates no matches.
                      dirnames
                              Perform directory name completion  if  the  compspec  generates  no
                              matches.
                      filenames
                              Tell  readline  that  the  compspec  generates filenames, so it can
                              perform any filename-specific processing (like adding  a  slash  to
                              directory   names,   quoting  special  characters,  or  suppressing
                              trailing spaces). Intended to be used with shell functions.
                      noquote Tell readline  not  to  quote  the  completed  words  if  they  are
                              filenames (quoting filenames is the default).
                      nospace Tell  readline  not  to  append  a  space  (the  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 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 the function is executed, the first argument ($1) is the name  of  the
                      command  whose  arguments  are being completed, the second argument ($2) is
                      the word being completed, and the third argument ($3) is the word preceding
                      the word being completed on the current command line. 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
              completion specification for a name for which no specification exists, or an  error
              occurs adding a completion specification.

       compopt [-o option] [-DE] [+o option] [name]
              Modify  completion  options  for  each  name  according  to the options, or for the
              currently-executing completion if no names are supplied. If no options  are  given,
              display  the  completion  options  for  each  name  or  the current completion. The
              possible 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''
              command completion; that is,  completion  attempted  on  a  command  for  which  no
              completion  has previously been defined. The -E option indicates that the remaining
              options should apply to ``empty'' command completion; that is, completion attempted
              on a blank line.

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

       continue [n]
              Resume  the next iteration of the enclosing for, while, until, or select loop. If n
              is specified, resume at the nth enclosing loop. n must be ≥ 1. If n is greater than
              the  number of 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 [-aAfFgilnrtux] [-p] [name[=value] ...]
       typeset [-aAfFgilnrtux] [-p] [name[=value] ...]
              Declare variables and/or give them attributes. If no names are given  then  display
              the  values  of  variables. The -p option will display the attributes and values of
              each name. When -p is used with name arguments, additional options, other  than  -f
              and  -F,  are  ignored. When -p is supplied without name arguments, it will display
              the attributes and values of all variables having the attributes specified  by  the
              additional  options. If no other options are supplied with -p, declare will display
              the attributes and values of all shell variables. The -f option will  restrict  the
              display  to  shell  functions.  The  -F  option  inhibits  the  display of function
              definitions; only the function name and attributes are  printed.  If  the  extdebug
              shell option is enabled using shopt, the source file name and line number where the
              function is defined are displayed as well. The -F option 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
                     converted to lower-case. The upper-case attribute is disabled.
              -n     Give each name the nameref attribute, making it a name reference to  another
                     variable.  That  other  variable  is  defined  by  the  value  of  name. All
                     references and assignments to name, except for  changing  the  -n  attribute
                     itself,  are  performed  on  the variable referenced by name's value. The -n
                     attribute cannot be applied to array variables.
              -r     Make  names  readonly.  These  names  cannot  then  be  assigned  values  by
                     subsequent assignment statements or unset.
              -t     Give  each  name the trace attribute. Traced functions 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
                     converted 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, declare and typeset make each  name  local,  as
              with  the  local  command,  unless the -g option is supplied. If a variable name is
              followed by =value, the value of the variable is set to value. When using -a or  -A
              and the compound assignment syntax to create array variables, additional attributes
              do not take effect until subsequent assignments. The return value is  0  unless  an
              invalid  option  is encountered, an attempt is made to define a function using ``-f
              foo=bar'', an attempt is made to assign a value to a readonly variable, an  attempt
              is  made  to  assign  a  value  to  an  array  variable  without using the compound
              assignment syntax (see Arrays above), one  of  the  names  is  not  a  valid  shell
              variable  name,  an  attempt  is  made  to  turn off readonly status for a 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.
              -c     Clears the directory stack by deleting all of the entries.
              -l     Produces a listing using full pathnames; the default listing format  uses  a
                     tilde to denote the home directory.
              -p     Print the directory stack with one entry per line.
              -v     Print the directory stack with one entry per line, prefixing each entry with
                     its index in the stack.
              +n     Displays the nth entry counting from the left of the list shown by dirs when
                     invoked without options, starting with zero.
              -n     Displays  the  nth  entry  counting from the right of the list shown by dirs
                     when invoked without options, starting with zero.

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

       disown [-ar] [-h] [jobspec ...]
              Without  options,  remove each jobspec from the table of active jobs. If jobspec is
              not present, and neither the -a nor the -r option is supplied, the current  job  is
              used. If the -h option is given, each jobspec is not removed from the table, but is
              marked so that SIGHUP is not sent to the job if the shell receives a SIGHUP. If  no
              jobspec  is supplied, the -a option means to remove or mark all jobs; the -r option
              without a jobspec 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 0
              unless a  write  error  occurs.  If  -n  is  specified,  the  trailing  newline  is
              suppressed.  If  the -e option is given, interpretation of the following backslash-
              escaped characters is enabled. The -E option disables the 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 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 further output
              \e
              \E     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\     backslash
              \0nnn  the eight-bit character whose value is the octal value nnn  (zero  to  three
                     octal digits)
              \xHH   the  eight-bit character whose value is the hexadecimal value HH (one or two
                     hex digits)
              \uHHHH the Unicode (ISO/IEC 10646) character whose value is the  hexadecimal  value
                     HHHH (one to four hex digits)
              \UHHHHHHHH
                     the  Unicode  (ISO/IEC 10646) character whose value is the hexadecimal value
                     HHHHHHHH (one to eight hex digits)

       enable [-a] [-dnps] [-f filename] [name ...]
              Enable and disable builtin shell  commands.  Disabling  a  builtin  allows  a  disk
              command  which  has  the  same  name  as  a  shell  builtin  to be executed without
              specifying a full pathname, even though the shell normally  searches  for  builtins
              before  disk  commands.  If -n is used, each name is disabled; otherwise, names are
              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 arguments, the list consists of all enabled shell
              builtins. If -n is supplied, only disabled builtins are printed. If -a is supplied,
              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-interactive
              shell exits, unless the execfail shell option is enabled. In that case, it  returns
              failure.  An  interactive  shell returns failure if the file cannot be executed. If
              command is not specified, any 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
              subsequently executed commands. If the -f option  is  given,  the  names  refer  to
              functions.  If no names are given, or if the -p option is supplied, a list of names
              of all exported variables is printed. The -n option causes the export  property  to
              be  removed  from  each name. If a variable name is followed by =word, the value of
              the variable is set to word. export returns an exit status of 0 unless  an  invalid
              option  is  encountered, one of the names is not a valid shell variable name, or -f
              is supplied with a name that is not a function.

       fc [-e ename] [-lnr] [first] [last]
       fc -s [pat=rep] [cmd]
              The first form selects a range of commands from first to last from the history list
              and  displays  or  edits and re-executes them. First and last may be specified as a
              string (to locate the last command beginning with that string) or as a  number  (an
              index  into the history list, where a negative number is used as an offset from the
              current command number). If last is not specified it is set to the current  command
              for  listing  (so  that  ``fc  -l  -10''  prints the last 10 commands) and to first
              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
              containing those commands. If ename is not given, the value of the FCEDIT  variable
              is  used, and the value of EDITOR if FCEDIT is not set. If neither variable is set,
              vi is used. When editing is 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.  Command is intepreted the same as first above. A useful alias to use with
              this is ``r="fc -s"'', so that typing ``r cc'' runs the last command beginning with
              ``cc'' and typing ``r'' re-executes the last command.

              If  the  first  form  is  used,  the  return value is 0 unless an 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
              contains  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 argument,
              getopts places that argument into the variable OPTARG. The  shell  does  not  reset
              OPTIND  automatically;  it must be manually reset between multiple calls to getopts
              within the same shell invocation if a new set of parameters is to be used.

              When the end of options is encountered, getopts exits with a 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
              pathname  is  discarded. If the -p option is supplied, no path search is performed,
              and filename is used as the full filename of the command. The -r option causes  the
              shell  to forget all remembered locations. The -d 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 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
                     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 append them to the current history
                     list.
              -w     Write  the current history list 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
              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 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     Display only running jobs.
              -s     Display only stopped jobs.

              If jobspec is given, output is restricted to information about that job. The return
              status is 0 unless an invalid option  is  encountered  or  an  invalid  jobspec  is
              supplied.

              If  the  -x  option is supplied, jobs replaces any jobspec found in command or args
              with the corresponding process group ID, and  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  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 variables
              to the standard output. It is an error to use local when not within a function. The
              return status is 0 unless local is used outside a  function,  an  invalid  name  is
              supplied, or name is a readonly variable.

       logout Exit a login shell.

       mapfile [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
       readarray  [-n  count]  [-O  origin]  [-s  count]  [-t] [-u fd] [-C callback] [-c quantum]
       [array]
              Read lines from the standard input into the indexed array 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
              evaluated, it is supplied the index of the next array element to  be  assigned  and
              the  line  to  be  assigned  to  that  element as additional arguments. callback is
              evaluated after the line is read but before the array element is assigned.

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

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

       popd [-n] [+n] [-n]
              Removes entries from the directory  stack.  With  no  arguments,  removes  the  top
              directory from the stack, and performs a cd to the new top directory. Arguments, if
              supplied, have the 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
              status 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
              format.  The  -v option causes the output to be assigned to the variable var rather
              than being printed to the standard output.

              The format is a character string which  contains  three  types  of  objects:  plain
              characters, which are simply copied to standard output, character escape sequences,
              which are converted and copied to the standard output, and  format  specifications,
              each  of  which causes printing of the next successive argument. In addition to the
              standard  printf(1)  format  specifications,  printf   interprets   the   following
              extensions:
              %b     causes  printf  to  expand  backslash  escape sequences in the corresponding
                     argument (except that \c terminates output, backslashes in \',  \",  and  \?
                     are  not removed, and octal escapes beginning with \0 may contain up to four
                     digits).
              %q     causes printf to output the corresponding argument in a format that  can  be
                     reused as shell input.
              %(datefmt)T
                     causes printf to output the date-time string resulting from using datefmt as
                     a format string for strftime(3). The corresponding argument  is  an  integer
                     representing  the  number  of  seconds since the epoch. Two special argument
                     values may be used: -1 represents the current time, and  -2  represents  the
                     time  the shell was invoked. If no argument is specified, conversion behaves
                     as if -1 had been given. This is an exception to the usual printf behavior.

              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
                     working directory as if it had been supplied  as  the  argument  to  the  cd
                     builtin.

              If  the pushd command is successful, a dirs is performed as well. If the first form
              is used, pushd returns 0 unless the cd to dir fails. With the  second  form,  pushd
              returns  0  unless  the  directory  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]  [-a  aname]  [-d  delim]  [-i  text] [-n nchars] [-N nchars] [-p prompt] [-t
       timeout] [-u fd] [name ...]
              One line is read from the standard input, or from the file 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
              intervening  separators  assigned  to  the last name. If there are fewer words read
              from the input stream than names, the remaining names are  assigned  empty  values.
              The  characters  in  IFS are used to split the line into words using the same rules
              the shell uses for expansion (described above under Word Splitting). The  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
                     complete  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
                     coming 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 (or a
                     specified number of characters) is not read within timeout seconds.  timeout
                     may  be  a  decimal  number  with a fractional 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 read times out, read saves any partial input read into the
                     specified  variable name. If timeout is 0, read returns immediately, without
                     trying to read any data. The exit status is 0 if input is available  on  the
                     specified  file  descriptor,  non-zero otherwise. The exit status is greater
                     than 128 if the timeout is exceeded.
              -u fd  Read input from file descriptor fd.

              If no names are supplied, the line read is assigned  to  the  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), a variable  assignment  error  (such  as
              assigning to a readonly variable) occurs, or an invalid file descriptor is supplied
              as the argument to -u.

       readonly [-aAf] [-p] [name[=word] ...]
              The given names are marked readonly; the values of these names may not  be  changed
              by subsequent assignment. If the -f option is supplied, the functions corresponding
              to the names are so marked. The  -a  option  restricts  the  variables  to  indexed
              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  stop  executing and return the value specified by n to its
              caller. If n is omitted, the return status is that of the last command executed  in
              the  function body. If return is used outside a function, but during execution of a
              script by the . (source) command, it causes the shell to stop executing that script
              and  return  either  n  or  the exit status of the last command executed within the
              script as the exit status of the script. If n is supplied, the return value is  its
              least  significant  8  bits.  The return status is non-zero if return is supplied a
              non-numeric argument, or is used outside a function and not during execution  of  a
              script  by  .  or  source.  Any command associated with the RETURN trap is executed
              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
              format  that  can  be  reused  as  input for setting or resetting the currently-set
              variables. 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
                      command), a list, or a compound command (see SHELL GRAMMAR  above),   exits
                      with  a  non-zero status. The shell does not exit if the command that fails
                      is part of the command list immediately following a while or until keyword,
                      part  of  the  test  following  the  if or elif reserved words, part of any
                      command executed in a && or || list except the command following the  final
                      &&  or  ||,  any  command  in  a pipeline but the last, or if the command's
                      return value is being inverted with !. If a compound command other  than  a
                      subshell  returns  a  non-zero status because a command failed while -e was
                      being ignored, the shell does not exit. A trap on ERR, if set, is  executed
                      before  the  shell  exits. This option applies to the shell environment and
                      each subshell environment separately  (see  COMMAND  EXECUTION  ENVIRONMENT
                      above),  and  may cause subshells to exit before executing all the commands
                      in the subshell.

                      If a compound command or shell function executes in a context where  -e  is
                      being ignored, none of the commands executed within the compound command or
                      function body will be affected by the -e setting, even if -e is set  and  a
                      command  returns  a failure status. If a compound command or shell function
                      sets -e while executing in a context where -e is ignored, that setting will
                      not  have  any  effect until the compound command or the command containing
                      the function call completes.
              -f      Disable pathname expansion.
              -h      Remember the location of commands as they are looked up for execution. This
                      is enabled by default.
              -k      All  arguments  in  the  form  of  assignment  statements are placed in the
                      environment for a command, not just those that precede the command name.
              -m      Monitor mode. Job control is enabled. This option  is  on  by  default  for
                      interactive  shells on systems that support it (see JOB CONTROL above). All
                      processes run in a separate process group. When a background job completes,
                      the shell prints a line containing its exit status.
              -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 disabled
                              by default.
                      posix   Change the behavior of bash where  the  default  operation  differs
                              from the POSIX standard to match the standard (posix mode). See SEE
                              ALSO below for a reference to a document  that  details  how  posix
                              mode affects bash's behavior.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      vi      Use  a  vi-style  command line editing interface. This also affects
                              the editing interface used for read -e.
                      xtrace  Same as -x.
                      If -o is supplied with no option-name, the values of  the  current  options
                      are  printed.  If  +o  is  supplied  with  no  option-name, a series of set
                      commands to recreate the  current  option  settings  is  displayed  on  the
                      standard output.
              -p      Turn on privileged mode. In this mode, the $ENV and $BASH_ENV files are not
                      processed, shell functions are not inherited from the environment, and  the
                      SHELLOPTS,  BASHOPTS,  CDPATH,  and GLOBIGNORE variables, if they appear in
                      the environment, are ignored. If the shell is started  with  the  effective
                      user (group) id not equal to the real user (group) id, and the -p option is
                      not 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 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
                      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,  display 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 redirection operator >| instead of >.
              -E      If  set,  any  trap  on  ERR  is  inherited  by  shell  functions,  command
                      substitutions, 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 resolve symbolic links when  executing  commands
                      such  as cd that change the current working directory. It uses the physical
                      directory structure instead. By default, bash follows the logical chain  of
                      directories when performing commands which change the current directory.
              -T      If  set,  any  traps  on DEBUG and RETURN are inherited by shell functions,
                      command substitutions, and commands 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  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 encountered.

       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 settings controlling optional shell behavior. The settings can
              be either those listed below, or, if the -o option is used,  those  available  with
              the -o option to the set builtin command. With no options, or with the -p option, a
              list of all settable options is displayed, with an indication  of  whether  or  not
              each  is  set.  The  -p  option causes output to be displayed in a form that may be
              reused as input. Other options have the following meanings:
              -s     Enable (set) each optname.
              -u     Disable (unset) each optname.
              -q     Suppresses normal output (quiet mode); the return status  indicates  whether
                     the  optname  is  set or unset. If multiple optname arguments are given with
                     -q, the return  status  is  zero  if  all  optnames  are  enabled;  non-zero
                     otherwise.
              -o     Restricts the values of optname to be those defined for the -o option to the
                     set builtin.

              If either -s or -u is used with  no  optname  arguments,  shopt  shows  only  those
              options  which  are  set  or unset, respectively. Unless otherwise noted, the shopt
              options are disabled (unset) by default.

              The return status when listing options is zero if all optnames  are  enabled,  non-
              zero otherwise. When setting or unsetting 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
                      interactive shells.
              cdable_vars
                      If set, an argument to the cd builtin command that is not  a  directory  is
                      assumed to be the name of a variable whose value is the directory to change
                      to.
              cdspell If set, minor errors in the spelling of  a  directory  component  in  a  cd
                      command   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 filename 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
                      exiting an interactive shell. If any jobs are running, this causes the exit
                      to be deferred until a second exit  is  attempted  without  an  intervening
                      command  (see JOB CONTROL above). The shell always postpones 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 and 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).
              compat32
                      If  set,  bash  changes its behavior to that of version 3.2 with respect to
                      locale-specific string comparison when using the [[ conditional command's <
                      and > operators (see previous item).
              compat40
                      If  set,  bash  changes its behavior to that of version 4.0 with respect to
                      locale-specific string comparison when using the [[ conditional command's <
                      and   >   operators  (see  description  of  compat31)  and  the  effect  of
                      interrupting a command list. Bash versions 4.0 and later interrupt the list
                      as if the shell received the interrupt; previous versions continue with the
                      next command in the list.
              compat41
                      If set, bash, when in posix mode, treats a single quote in a  double-quoted
                      parameter  expansion  as  a special character. The single quotes must match
                      (an  even  number)  and  the  characters  between  the  single  quotes  are
                      considered  quoted. This is the behavior of posix mode through version 4.1.
                      The default bash behavior remains as in previous versions.
              compat42
                      If set, bash does  not  process  the  replacement  string  in  the  pattern
                      substitution word expansion using quote removal.
              complete_fullquote
                      If  set,  bash  quotes  all shell metacharacters in filenames and directory
                      names when performing completion. If not set, bash  removes  metacharacters
                      such  as  the dollar sign from the set of characters that will be quoted in
                      completed filenames when these  metacharacters  appear  in  shell  variable
                      references  in  words  to  be  completed.  This  means that dollar signs in
                      variable names that expand to directories will not be quoted; however,  any
                      dollar  signs  appearing  in  filenames will not be quoted, either. This is
                      active only when bash is using backslashes to  quote  completed  filenames.
                      This  variable  is  set  by  default, which is the default bash behavior in
                      versions through 4.2.
              direxpand
                      If set, bash replaces directory names with the results  of  word  expansion
                      when  performing  filename  completion.  This  changes  the contents of the
                      readline editing buffer. If not set, bash attempts  to  preserve  what  the
                      user typed.
              dirspell
                      If  set,  bash  attempts spelling correction on directory names during word
                      completion if the directory name 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
                             descriptions 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
                      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 possible completions. See SHELL VARIABLES above for a description
                      of FIGNORE. This option is enabled by default.
              globasciiranges
                      If set, range expressions used in pattern matching bracket expressions (see
                      Pattern  Matching  above)  behave  as  if  in the traditional C locale when
                      performing comparisons. That is, the current locale's collating sequence is
                      not  taken  into account, so b will not collate between A and B, and upper-
                      case and lower-case ASCII characters will collate together.
              globstar
                      If set, the pattern ** used in a pathname expansion 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
                      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 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
                      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 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  (true)  or  1  (false) 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. 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
                     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 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
                     conditional operator, the expression is false.
              3 arguments
                     The  following  conditions  are  applied  in the order listed. If the second
                     argument is one of the  binary  conditional  operators  listed  above  under
                     CONDITIONAL  EXPRESSIONS,  the result of the expression is the result of the
                     binary test using the first and third arguments as operands. The -a  and  -o
                     operators are considered binary operators when there are three arguments. If
                     the first argument is !, the value is the negation of the two-argument  test
                     using the second and third arguments. If the first argument is exactly ( and
                     the third argument is exactly ), the result is the one-argument test of  the
                     second argument. 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
              command, case command, select command, every arithmetic for command, and before the
              first  command executes in a shell function (see SHELL GRAMMAR above). Refer to the
              description of the extdebug option to the shopt builtin for details of  its  effect
              on  the DEBUG trap. If a sigspec is RETURN, the command arg is executed each time a
              shell function or a  script  executed  with  the  .  or  source  builtins  finishes
              executing.

              If  a  sigspec is ERR, the command arg is executed whenever a a pipeline (which may
              consist of a single simple command), a  list,  or  a  compound  command  returns  a
              non-zero  exit  status,  subject  to  the following conditions. The ERR trap is not
              executed if the failed command is part of the command list immediately following  a
              while  or  until  keyword,  part  of the test in an if statement, part of a command
              executed in a && or || list except the command following the final &&  or  ||,  any
              command  in  a  pipeline  but  the  last, or if the command's return value is being
              inverted using !. These are the same conditions obeyed by the errexit (-e) option.

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

       type [-aftpP] name [name ...]
              With  no  options, indicate how each name would be interpreted if used as a command
              name. If the -t option is used, type  prints  a  string  which  is  one  of  alias,
              keyword,  function,  builtin,  or  file  if  name is an alias, shell reserved word,
              function, builtin, or disk file, respectively. If  the  name  is  not  found,  then
              nothing  is  printed,  and an exit status of false is 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,
              which is 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
              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 follows:
              -a     All current limits are reported
              -b     The maximum socket buffer size
              -c     The maximum size of core files created
              -d     The maximum size of a process's data segment
              -e     The maximum scheduling priority ("nice")
              -f     The maximum size of files written by the shell and its children
              -i     The maximum number of pending signals
              -l     The maximum size that may be locked into memory
              -m     The maximum resident set size (many systems do not honor this limit)
              -n     The  maximum number of open file descriptors (most systems do not allow this
                     value to be set)
              -p     The pipe size in 512-byte blocks (this may not be set)
              -q     The maximum number of bytes in POSIX message queues
              -r     The maximum real-time scheduling priority
              -s     The maximum stack size
              -t     The maximum amount of cpu time in seconds
              -u     The maximum number of processes available to a single user
              -v     The maximum amount of virtual memory available to the  shell  and,  on  some
                     systems, to its children
              -x     The maximum number of file locks
              -T     The maximum number of threads

              If  limit  is  given,  and the -a option is not used, limit is the new value of the
              specified resource. If no option is given,  then  -f  is  assumed.  Values  are  in
              1024-byte  increments, except for -t, which is in seconds; -p, which is in units of
              512-byte blocks; and -T, -b, -n, and -u, which  are  unscaled  values.  The  return
              status  is  0  unless an invalid option or argument is 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
              omitted,  the output is in a form that may be reused as input. The return status is
              0 if the mode was successfully changed or if no mode  argument  was  supplied,  and
              false otherwise.

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

       unset [-fv] [-n] [name ...]
              For  each  name, remove the corresponding variable or function. If the -v option is
              given, each name refers to a shell variable, and that variable  is  removed.  Read-
              only  variables  may  not be unset. If -f is specified, each name refers to a shell
              function, and the function definition is removed. If the -n option is supplied, and
              name  is  a variable with the nameref attribute, name will be unset rather than the
              variable it references. -n has no effect if  the  -f  option  is  supplied.  If  no
              options  are  supplied,  each name refers to a variable; if there is no variable by
              that name, any function with that name is unset. Each unset variable or function is
              removed   from   the   environment   passed  to  subsequent  commands.  If  any  of
              COMP_WORDBREAKS, 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] [n ...]
              Wait for each specified child process and return its termination status. Each n may
              be  a  process  ID or a job specification; if a job spec is given, all processes in
              that job's pipeline are waited for. If n is not given, all currently  active  child
              processes  are  waited  for,  and  the  return  status is zero. If the -n option is
              supplied, wait waits for any job to terminate and returns its  exit  status.  If  n
              specifies  a  non-existent process or job, the return status is 127. Otherwise, the
              return status is the exit status of the last process or job waited for.

VOIR AUSSI

       bash(1), sh(1)