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2006-09-07 11:22:38

BASH_BUILTINS(1)          BASH_BUILTINS(1)
 
NAME
       bash,  :, ., [, alias, bg, bind, break, builtin, cd, command, compgen,
       complete, continue, declare, dirs, disown, echo, enable,  eval, exec,
       exit,  export,  fc, fg, getopts, hash, help, history, jobs, kill, let,
       local, logout, popd, printf, pushd, pwd, read, readonly, return,  set,
       shift,  shopt,  source, suspend,  test,  times,  trap, type, typeset,
       ulimit, umask, unalias, unset, wait  -  bash  built-in  commands,  see
       bash(1)
BASH BUILTIN COMMANDS
       Unless  otherwise  noted, each builtin command documented in this sec-
       tion as accepting options preceded by - accepts -- to signify the  end
       of the options.
       : [arguments]
       No  effect; the command does nothing beyond expanding arguments
       and performing any specified redirections.  A zero exit code is
       returned.
 .  filename [arguments]
       source filename [arguments]
       Read  and  execute  commands from filename in the current shell
       environment and return the exit status of the last command exe-
       cuted  from  filename.   If  filename does not contain a slash,
       file names in PATH are used to find  the directory  containing
       filename.   The  file  searched  for  in PATH need not be exe-
       cutable. 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 the suspended job jobspec in the background,  as  if  it
       had  been  started  with &.   If  jobspec  is not present, the
       shell's notion of the current job is used.  bg jobspec  returns
       0 unless run when job control is disabled or, when run with job
       control enabled, if jobspec was not found  or  started  without
       job control.
       bind [-m keymap] [-lpsvPSV]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] -x keyseq:shell-command
       bind [-m keymap] keyseq:function-name
       bind readline-command
       Display  current readline key and function bindings, bind a key
       sequence to a readline function or macro,  or  set  a  readline
       variable.   Each non-option  argument is a command as it would
       appear in .inputrc, but each binding or command must be  passed
       as  a separate argument; e.g., '"\C-x\C-r": re-read-init-file'.
       Options, if supplied, have the following meanings:
       -m keymap
       Use keymap as the keymap to be affected  by  the  subse-
       quent  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-com-
       mand; emacs is equivalent to emacs-standard.
       -l     List the names of all readline functions.
       -p     Display readline function names and bindings in  such  a
       way that they can be re-read.
       -P     List current readline function names and bindings.
       -v     Display readline variable names and values in such a way
       that they can be re-read.
       -V     List current readline variable names and values.
       -s     Display readline key sequences bound to macros  and  the
       strings  they  output in such a way that they can be re-
       read.
       -S     Display readline key sequences bound to macros  and  the
       strings they output.
       -f filename
       Read key bindings from filename.
       -q function
       Query about which keys invoke the named function.
       -u function
       Unbind all keys bound to the named function.
       -r keyseq
       Remove any current binding for keyseq.
       -x keyseq:shell-command
       Cause  shell-command  to  be executed whenever keyseq is
       entered.
       The return value is 0 unless an unrecognized option is given or
       an error occurred.
       break [n]
       Exit  from within a for, while, until, or select loop.  If n is
       specified, break n levels.  n must be >= 1.   If n  is  greater
       than  the  number  of  enclosing loops, all enclosing loops are
       exited.  The return value is 0 unless the shell is not  execut-
       ing a loop when break is executed.
       builtin shell-builtin [arguments]
       Execute  the specified shell builtin, passing it arguments, and
       return its exit status.  This is useful when defining  a func-
       tion  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.
       cd [-L|-P] [dir]
       Change the current directory to dir.  The variable HOME is  the
       default  dir.   The variable CDPATH defines the search path for
       the directory containing dir.  Alternative directory  names  in
       CDPATH  are separated by a colon (:).  A null directory name in
       CDPATH is the same as the current directory, i.e.,  ''.''.   If
       dir  begins  with  a slash (/), then CDPATH is not used. The -P
       option says to use the physical directory structure instead  of
       following  symbolic  links  (see also the -P option to the set
       builtin command); the -L option forces  symbolic links  to  be
       followed.   An  argument of  - is equivalent to $OLDPWD.  If a
       non-empty directory name from CDPATH is used, or if  -  is  the
       first  argument, and  the  directory change is successful, the
       absolute pathname of the new working directory  is  written  to
       the standard output.  The return value is true if the directory
       was successfully changed; false otherwise.
       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 file-
       name of the current subroutine call.  If a non-negative integer
       is supplied as expr, caller displays the line  number,  subrou-
       tine  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.
       command [-pVv] command [arg ...]
       Run command with args suppressing  the  normal  shell  function
       lookup. Only builtin commands or commands found in the PATH are
       executed.  If the -p option is given, the search for command is
       performed  using a default value for PATH that is guaranteed to
       find all of the standard utilities.  If either  the  -V  or  -v
       option  is  supplied, a description of command is printed.  The
       -v option causes a single word indicating the command  or  file
       name used to invoke command to be displayed; the -V option pro-
       duces 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  pro-
       grammable  completion  code  had generated them directly from a
       completion specification with the same flags.  If word is spec-
       ified,  only those completions matching word will be displayed.
       The return value is true unless an invalid option is  supplied,
       or no matches were generated.
       complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W
       wordlist] [-P prefix] [-S suffix]
       [-X filterpat] [-F function] [-C command] name [name ...]
       complete -pr [name ...]
       Specify how arguments to each name should be completed.  If the
       -p option is supplied, or if no options are supplied,  existing
       completion specifications are printed in a way that allows them
       to be reused as input.  The  -r  option  removes a  completion
       specification  for each name, or, if no names are supplied, all
       completion specifications.
       The process of applying these  completion  specifications  when
       word  completion is  attempted  is  described above under Pro-
       grammable 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 comp-
        spec's behavior beyond the simple generation of comple-
        tions.  comp-option may be one of:
        bashdefault
         Perform  the  rest  of the default bash comple-
         tions if the compspec generates no matches.
        default Use readline's default filename  completion  if
         the compspec generates no matches.
        dirnames
         Perform  directory name completion if the comp-
         spec generates no matches.
        filenames
         Tell readline that the compspec generates file-
         names,  so it can perform any filename-specific
         processing (like adding a  slash to  directory
         names    or   suppressing   trailing   spaces).
         Intended to be used with shell functions.
        nospace Tell  readline  not  to  append  a  space  (the
         default) to  words completed at the end of the
         line.
       -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.
       -G globpat
        The filename expansion pattern globpat is  expanded  to
        generate the possible completions.
       -W wordlist
        The  wordlist  is split using the characters in the IFS
        special variable as delimiters, and each resultant word
        is  expanded.  The possible completions are the members
        of the resultant list which match the word  being  com-
        pleted.
       -C command
        command  is executed in a subshell environment, and its
        output is used as the possible completions.
       -F function
        The shell function function is executed in the  current
        shell environment.  When it finishes, the possible com-
        pletions are retrieved from the value of the  COMPREPLY
        array variable.
       -X filterpat
        filterpat  is a pattern as used for filename expansion.
        It is applied to the list of possible completions  gen-
        erated by the preceding options and arguments, and each
        completion matching filterpat is removed from the list.
        A  leading  ! in filterpat negates the pattern; in this
        case, any completion not matching filterpat is removed.
       -P prefix
        prefix  is added at the beginning of each possible com-
        pletion after all other options have been applied.
       -S suffix
        suffix is appended to each  possible  completion after
        all other options have been applied.
       The  return value is true unless an invalid option is supplied,
       an option other than -p or -r is supplied without a name argu-
       ment,  an  attempt is made to remove a completion specification
       for a name for which  no specification  exists, or  an error
       occurs adding a completion specification.
       continue [n]
       Resume  the  next iteration of the enclosing for, while, until,
       or select loop.  If n is specified, resume at the nth enclosing
       loop.   n  must  be  >=  1.   If n is greater than the number of
       enclosing loops, the last  enclosing  loop  (the ''top-level''
       loop)  is  resumed.   The return value is 0 unless the shell is
       not executing a loop when continue is executed.
       declare [-afFirtx] [-p] [name[=value] ...]
       typeset [-afFirtx] [-p] [name[=value] ...]
       Declare variables and/or give them attributes.  If no names are
       given then display the values of variables.  The -p option will
       display the attributes and values of each  name.  When  -p  is
       used,  additional  options are ignored.  The -F option inhibits
       the display of function definitions; only the function name and
       attributes  are  printed.   If  the  extdebug  shell  option is
       enabled using shopt, the source file name and line number where
       the  function  is defined are displayed as well. The -F option
       implies -f.  The following options can be used to restrict out-
       put  to variables with the specified attribute or to give vari-
       ables attributes:
       -a     Each name is an array variable (see Arrays above).
       -f     Use function names only.
       -i     The variable is treated as an integer; arithmetic evalu-
       ation (see ARITHMETIC EVALUATION ) is performed when the
       variable is assigned a value.
       -r     Make  names  readonly.   These  names  cannot  then   be
       assigned  values  by subsequent assignment statements or
       unset.
       -t     Give each name the trace  attribute.   Traced  functions
       inherit  the  DEBUG  trap from  the calling shell.  The
       trace attribute has no special meaning for variables.
       -x     Mark names for export to  subsequent  commands  via  the
       environment.
       Using  '+' instead of '-' turns off the attribute instead, with
       the exception that +a may not be used to destroy an array vari-
       able.   When used in a function, makes each name local, as with
       the local command.  If a variable name is followed  by  =value,
       the value of the variable is set to value.  The return value is
       0 unless an invalid option is encountered, an attempt  is  made
       to  define  a function using ''-f foo=bar'', an attempt is made
       to assign a value to a readonly variable, an attempt is made to
       assign  a value to an array variable without using the compound
       assignment syntax (see Arrays above), one of the names is not a
       valid shell variable name, an attempt is made to turn off read-
       only status for a readonly variable, an attempt is made to turn
       off  array  status for an array variable, or an attempt is made
       to display a non-existent function with -f.
       dirs [-clpv] [+n] [-n]
       Without options, displays  the  list  of currently  remembered
       directories.   The  default  display  is on a single line with
       directory names separated by spaces.  Directories are added  to
       the  list  with  the  pushd  command;  the popd command removes
       entries from the list.
       +n     Displays the nth entry counting from  the left  of  the
       list  shown by dirs when invoked without options, start-
       ing with zero.
       -n     Displays the nth entry counting from the  right  of  the
       list  shown by dirs when invoked without options, start-
       ing with zero.
       -c     Clears the  directory  stack  by  deleting  all  of  the
       entries.
       -l     Produces  a  longer  listing; the default listing format
       uses a tilde to denote the home directory.
       -p     Print the directory stack with one entry per line.
       -v     Print the directory stack with one entry per line,  pre-
       fixing each entry with its index in the stack.
       The return value is 0 unless an invalid option is supplied or n
       indexes beyond the end of the directory stack.
       disown [-ar] [-h] [jobspec ...]
       Without options, each jobspec is removed  from  the  table  of
       active  jobs.   If  the -h option is given, each jobspec is not
       removed from the table, but is marked so that  SIGHUP  is  not
       sent  to the job if the shell receives a SIGHUP. If no jobspec
       is present, and neither the -a nor the -r option is  supplied,
       the  current  job  is  used.  If no jobspec is supplied, the -a
       option means to remove or mark all jobs; the -r option  without
       a  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 always 0.  If -n is specified, the  trail-
       ing  newline  is suppressed.  If the -e option is given, inter-
       pretation 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 dynami-
       cally determine whether or not echo expands these escape char-
       acters  by default.  echo does not interpret -- to mean the end
       of options.  echo interprets the following escape sequences:
       \a     alert (bell)
       \b     backspace
       \c     suppress trailing newline
       \e     an escape character
       \f     form feed
       \n     new line
       \r     carriage return
       \t     horizontal tab
       \v     vertical tab
       \\     backslash
       \0nnn  the eight-bit character whose value is the  octal value
       nnn (zero to three octal digits)
       \nnn   the  eight-bit  character whose value is the octal value
       nnn (one to three octal digits)
       \xHH   the eight-bit character whose value is  the  hexadecimal
       value HH (one or two hex digits)
       enable [-adnps] [-f filename] [name ...]
       Enable and disable builtin shell commands.  Disabling a builtin
       allows a disk command which  has the  same  name  as  a shell
       builtin to be executed without specifying a full pathname, even
       though the shell normally searches  for  builtins  before  disk
       commands.   If  -n  is  used, each name is disabled; otherwise,
       names are enabled.  For example, to use the test binary found
       via the PATH instead of the shell builtin version, run ''enable
       -n test''.  The -f option means to load the new builtin command
       name  from  shared  object  filename,  on  systems that support
       dynamic loading. The -d option will delete  a  builtin  previ-
       ously  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  com-
       mand.  This command is then read and executed by the shell, and
       its exit status is returned as the value of eval.  If there are
       no args, or only null arguments, eval returns 0.
       exec [-cl] [-a name] [command [arguments]]
       If command is specified, it replaces the shell.  No new process
       is created.  The arguments become the arguments to command.  If
       the  -l  option  is  supplied,  the  shell places a dash at the
       beginning of the zeroth arg passed to command.   This  is  what
       login(1) does. The  -c  option causes command to be executed
       with an empty environment.  If -a is supplied, the shell passes
       name  as the zeroth argument to the executed command.  If com-
       mand cannot be executed  for  some  reason,  a  non-interactive
       shell  exits,  unless  the shell option execfail is enabled, in
       which case it returns failure.  An  interactive  shell  returns
       failure  if  the file  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 envi-
       ronment of subsequently executed commands.  If the -f option is
       given, the names refer to functions.  If no names are given, or
       if  the  -p  option  is  supplied, a list of all names that are
       exported in this shell is printed.  The -n  option  causes  the
       export  property to  be removed from each name. If a variable
       name is followed by =word, the value of the variable is set  to
       word.   export  returns  an  exit status of 0 unless an invalid
       option is encountered, one of the names is not  a  valid shell
       variable name,  or  -f  is  supplied with a name that is not a
       function.
       fc [-e ename] [-nlr] [first] [last]
       fc -s [pat=rep] [cmd]
       Fix Command.  In the first form, a range of commands from first
       to  last is selected from the history list.  First and last may
       be specified as a string (to locate the last command  beginning
       with  that  string)  or  as a number (an index into the history
       list, where a negative number is used as an  offset  from  the
       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.  Other-
       wise, the editor given by ename is invoked on a file containing
       those commands.  If ename is not given, the value of the FCEDIT
       variable is used, and the value of EDITOR if FCEDIT is not set.
       If neither variable is set, is used.  When editing is complete,
       the edited commands are echoed and executed.
       In the second form, command is re-executed after each  instance
       of  pat is replaced by rep.  A useful alias to use with this is
       ''r="fc -s"'', so that typing ''r cc'' runs  the last  command
       beginning  with  ''cc''  and  typing ''r'' re-executes the last
       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 dis-
       abled  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 parame-
       ters.  optstring contains the option characters  to  be  recog-
       nized;  if  a  character is followed by a colon, the option is
       expected to have an argument, which should be separated from it
       by white space.  The colon and question mark characters may not
       be used as option characters.  Each time it is invoked, getopts
       places the next option in the shell variable name, initializing
       name if it does not exist, and the index of the  next  argument
       to  be  processed into the variable OPTIND.  OPTIND is initial-
       ized to 1 each time the shell or a  shell  script  is  invoked.
       When  an option requires an argument, getopts places that argu-
       ment 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  dis-
       played,  even  if  the  first  character of optstring is not a
       colon.
       If an invalid option is seen, getopts places ? into  name  and,
       if  not  silent, prints an error message and unsets OPTARG.  If
       getopts is silent, the option  character found  is  placed  in
       OPTARG and no diagnostic message is printed.
       If a required argument is not found, and getopts is not silent,
       a question mark (?) is placed in name, OPTARG is unset,  and  a
       diagnostic  message  is  printed.  If getopts is silent, then a
       colon (:) is placed in name and OPTARG is  set  to  the  option
       character found.
       getopts returns true if an option, specified or unspecified, is
       found.  It returns false if the end of options  is  encountered
       or an error occurs.
       hash [-lr] [-p filename] [-dt] [name]
       For  each name, the full file name of the command is determined
       by searching the directories in $PATH and remembered.   If  the
       -p  option  is supplied, no path search is performed, and file-
       name is used as the full file name  of  the  command.   The  -r
       option  causes  the  shell  to forget all remembered locations.
       The -d option causes the shell to forget the  remembered loca-
       tion  of each  name.   If  the -t option is supplied, the full
       pathname to which each name corresponds is printed.  If  multi-
       ple  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  sup-
       plied.
       help [-s] [pattern]
       Display helpful information about builtin commands.  If pattern
       is specified, help gives detailed help on all commands matching
       pattern; otherwise help for all the builtins and shell control
       structures is printed.  The -s option restricts the information
       displayed  to  a short usage synopsis.  The return status is 0
       unless no command matches pattern.
       history [n]
       history -c
       history -d offset
       history -anrw [filename]
       history -p arg [arg ...]
       history -s arg [arg ...]
       With no options, display the command  history  list  with  line
       numbers.  Lines listed with a * have been modified.  An argu-
       ment 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  sup-
       plied, have the following meanings:
       -c     Clear the history list by deleting all the entries.
       -d offset
       Delete the history entry at position offset.
       -a     Append  the ''new'' history lines (history lines entered
       since the beginning of the current bash session) to  the
       history file.
       -n     Read the history lines not already read from the history
       file into the current history  list.   These  are lines
       appended  to the history file since the beginning of the
       current bash session.
       -r     Read the contents of the history file and use  them  as
       the current history.
       -w     Write the current history to the history file, overwrit-
       ing the history file's contents.
       -p     Perform history substitution on the following  args  and
       display  the  result  on  the standard output.  Does not
       store the results in the history list.  Each arg must be
       quoted to disable normal history expansion.
       -s     Store  the  args  in the history list as a single entry.
       The last command in the history list is  removed  before
       the args are added.
       If  the HISTTIMEFORMAT is set, the time stamp information asso-
       ciated with each history entry is written to the history file.
       The  return value is 0 unless an invalid option is encountered,
       an error occurs while reading or writing the history  file,  an
       invalid offset is supplied as an argument to -d, or the history
       expansion supplied as an argument to -p fails.
       jobs [-lnprs] [ jobspec ... ]
       jobs -x command [ args ... ]
       The first form lists the active jobs.   The  options  have  the
       following meanings:
       -l     List  process IDs in addition to the normal information.
       -p     List only the process ID  of  the job's  process group
       leader.
       -n     Display  information  only  about jobs that have changed
       status since the user was last notified of their status.
       -r     Restrict output to running jobs.
       -s     Restrict output to stopped jobs.
       If  jobspec is given, output is restricted to information about
       that job.  The return status is 0 unless an invalid  option  is
       encountered or an invalid jobspec is supplied.
       If  the  -x option is supplied, jobs replaces any jobspec found
       in command or args with the corresponding process group ID, and
       executes command passing it args, returning its exit status.
       kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...
       kill -l [sigspec | exit_status]
       Send  the  signal  named by sigspec or signum to the processes
       named by pid or jobspec. sigspec is either a  case-insensitive
       signal name such as SIGKILL (with or without the SIG prefix) or
       a signal number; signum is a signal number.  If sigspec is  not
       present, then SIGTERM is assumed.  An argument of -l lists the
       signal names.  If any arguments are supplied when -l is  given,
       the  names  of  the  signals corresponding to the arguments are
       listed, and the return status is 0.  The exit_status  argument
       to -l is a number specifying either a signal number or the exit
       status of a process terminated by a signal.  kill returns  true
       if  at  least  one signal was successfully sent, or false if an
       error occurs or an invalid option is encountered.
       let arg [arg ...]
       Each arg is an  arithmetic  expression  to  be  evaluated  (see
       ARITHMETIC  EVALUATION).  If  the last arg evaluates to 0, let
       returns 1; 0 is returned otherwise.
       local [option] [name[=value] ...]
       For each argument, a local variable named name is created,  and
       assigned value. The option can be any of the options accepted
       by declare.  When local is used within a function,  it  causes
       the  variable  name  to have a visible scope restricted to that
       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.
       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  fol-
       lowing meanings:
       +n     Removes the nth entry counting from the left of the list
       shown by dirs, starting with zero.  For example:  ''popd
       +0''  removes  the first directory, ''popd +1'' the sec-
       ond.
       -n     Removes the nth entry counting from  the  right  of  the
       list  shown  by  dirs, starting with zero.  For example:
       ''popd -0'' removes the last directory, ''popd -1''  the
       next to last.
       -n     Suppresses  the normal change of directory when removing
       directories from the stack, so that only  the  stack  is
       manipulated.
       If the popd command is successful, a dirs is performed as well,
       and the return status is 0.  popd returns false if  an  invalid
       option  is  encountered, the  directory stack is empty, a non-
       existent directory stack entry is specified, or  the  directory
       change fails.
       printf format [arguments]
       Write  the formatted arguments to the standard output under the
       control of the format.  The format is a character string which
       contains three  types  of objects: plain characters, which are
       simply copied to standard output, character  escape  sequences,
       which are converted and copied to the standard output, and for-
       mat specifications, each of which causes printing of  the  next
       successive  argument.   In  addition  to the standard printf(1)
       formats, %b causes printf to expand backslash escape  sequences
       in  the  corresponding  argument (except  that  \c  terminates
       output, backslashes in \', \", and  \?  are  not removed,  and
       octal escapes beginning with \0 may contain up to four digits),
       and %q causes printf to output the corresponding argument in  a
       format that can be reused as shell input.
       The  format  is reused as necessary to consume all of the argu-
       ments.  If the format requires more  arguments  than  are  sup-
       plied,  the  extra  format  specifications  behave as if a zero
       value or null string, as appropriate, had been  supplied.   The
       return value is zero on success, non-zero on failure.
       pushd [-n] [dir]
       pushd [-n] [+n] [-n]
       Adds  a directory to the top of the directory stack, or rotates
       the stack, making the new top of the stack the current  working
       directory.   With  no arguments, exchanges the top two directo-
       ries and returns 0, unless the directory stack is empty. Argu-
       ments, if supplied, have the following meanings:
       +n     Rotates  the  stack  so that the nth directory (counting
       from the left of the list shown by dirs,  starting  with
       zero) is at the top.
       -n     Rotates  the  stack  so that the nth directory (counting
       from the right of the list shown by dirs, starting  with
       zero) is at the top.
       -n     Suppresses  the  normal  change of directory when adding
       directories to the stack, so  that  only  the  stack  is
       manipulated.
       dir    Adds  dir to  the directory stack at the top, making it
       the new current working directory.
       If the pushd command is successful,  a  dirs  is performed  as
       well.  If the first form is used, pushd returns 0 unless the cd
       to dir fails.  With the second form, pushd returns 0 unless the
       directory  stack is empty, a non-existent directory stack ele-
       ment is specified, or the directory change to the specified new
       current directory fails.
       pwd [-LP]
       Print  the  absolute pathname of the current working directory.
       The pathname printed contains  no  symbolic  links  if  the  -P
       option is supplied or the -o physical option to the set builtin
       command is enabled.  If the -L option  is  used, the  pathname
       printed  may  contain  symbolic  links.  The return status is 0
       unless an error occurs while reading the name  of  the  current
       directory or an invalid option is supplied.
       read  [-ers]  [-u  fd] [-t timeout] [-a aname] [-p prompt] [-n nchars]
       [-d delim] [name ...]
       One  line  is  read  from  the standard input, or from the file
       descriptor fd supplied as an argument to the -u option, and the
       first  word  is  assigned to the first name, the second word to
       the second name, and so  on,  with  leftover  words  and their
       intervening separators assigned to the last name.  If there are
       fewer words read from the input stream than names, the  remain-
       ing names are assigned empty values.  The characters in IFS are
       used to split the line into words.  The backslash character (\)
       may  be used to remove any special meaning for the next charac-
       ter 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 argu-
       ments 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, read-
       line (see READLINE above) is used to obtain the line.
       -n nchars
       read returns after reading nchars characters rather than
       waiting for a complete line of input.
       -p prompt
       Display  prompt  on  standard  error, without a trailing
       newline, before  attempting  to  read  any  input.   The
       prompt  is displayed only if input is coming from a ter-
       minal.
       -r     Backslash does not act  as  an  escape  character.   The
       backslash is considered to be part of the line.  In par-
       ticular, a backslash-newline pair may not be used as  a
       line continuation.
       -s     Silent  mode.  If input is coming from a terminal, char-
       acters are not echoed.
       -t timeout
       Cause read to time out and return failure if a  complete
       line  of input is not read within timeout seconds.  This
       option has no effect if read is not reading  input  from
       the terminal or a pipe.
       -u fd  Read input from file descriptor fd.
       If  no  names  are  supplied,  the line read is assigned to the
       variable REPLY.  The return code is zero, unless end-of-file is
       encountered,  read  times out, or an invalid file descriptor is
       supplied as the argument to -u.
       readonly [-apf] [name[=word] ...]
       The given names are marked readonly; the values of these names
       may  not be changed by subsequent assignment.  If the -f option
       is supplied, the functions corresponding to the  names  are  so
       marked. The  -a option restricts the variables to arrays.  If
       no name arguments are given, or if the -p option is supplied, a
       list  of all  readonly names is printed.  The -p option causes
       output to be displayed in a format that may be reused as input.
       If a variable name is followed by =word, the value of the vari-
       able is set to word.  The return status is 0 unless an  invalid
       option  is  encountered, one of the names is not a valid shell
       variable name, or -f is supplied with a  name  that  is  not  a
       function.
       return [n]
       Causes a function to exit with the return value specified by n.
       If n is omitted, the return status is that of the last  command
       executed in the function body.  If used outside a function, but
       during execution of a script by the  .   (source)  command,  it
       causes  the  shell  to  stop  executing  that script and return
       either n or the exit status of the last command executed within
       the script as the exit status of the script.  If used outside a
       function and not during execution of a script by ., the  return
       status  is  false.  Any command associated with the RETURN trap
       is executed before execution  resumes  after  the  function  or
       script.
       set [--abefhkmnptuvxBCHP] [-o option] [arg ...]
       Without  options, the name and value of each shell variable are
       displayed in a format that can be reused as input.  The  output
       is  sorted  according  to the current locale.  When options are
       specified, they set or unset shell attributes.   Any  arguments
       remaining after the options are processed are treated as values
       for the positional parameters and are assigned,  in  order,  to
       $1,  $2, ...   $n.   Options, if specified, have the following
       meanings:
       -a      Automatically mark variables and functions  which  are
        modified or  created  for export to the environment of
        subsequent commands.
       -b      Report the status of terminated background jobs immedi-
        ately,  rather  than  before  the  next primary prompt.
        This is effective only when job control is enabled.
       -e      Exit immediately if a simple command (see SHELL GRAMMAR
        above)  exits  with  a non-zero status.  The shell does
        not exit if the command that fails is part of the  com-
        mand  list  immediately following a while or until key-
        word, part of the test in an if statement, part of a &&
        or  ||  list, or if the command's return value is being
        inverted via !.  A trap on ERR,  if  set,  is  executed
        before the shell exits.
       -f      Disable pathname expansion.
       -h      Remember the location of commands as they are looked up
        for execution.  This is enabled by default.
       -k      All arguments in the form of assignment statements  are
        placed in the environment for a command, not just those
        that precede the command name.
       -m      Monitor mode.  Job control is enabled.  This option  is
        on  by  default  for interactive shells on systems that
        support it (see JOB CONTROL  above).   Background  pro-
        cesses  run in a separate process group and a line con-
        taining their exit status is printed upon their comple-
        tion.
       -n      Read  commands  but  do  not execute them.  This may be
        used to check a shell script for syntax  errors.  This
        is ignored by interactive shells.
       -o option-name
        The option-name can be one of the following:
        allexport
         Same as -a.
        braceexpand
         Same as -B.
        emacs   Use  an emacs-style command line editing inter-
         face.  This is  enabled  by  default  when  the
         shell  is  interactive,  unless  the  shell  is
         started with the --noediting option.
        errtrace
         Same as -E.
        functrace
         Same as -T.
        errexit Same as -e.
        hashall Same as -h.
        histexpand
         Same as -H.
        history Enable  command  history,  as  described above
         under HISTORY.  This option is on by default in
         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 1003.2 stan-
         dard to match the standard ('posix mode).
        privileged
         Same as -p.
        verbose Same as -v.
        vi      Use a vi-style command line editing  interface.
        xtrace  Same as -x.
        If  -o  is  supplied with no option-name, the values of
        the current options are printed.  If  +o  is  supplied
        with no option-name, a series of set commands to recre-
        ate the current option settings  is  displayed  on  the
        standard output.
       -p      Turn  on privileged  mode.  In this mode, the $ENV and
        $BASH_ENV files are not processed, shell functions  are
        not  inherited  from the environment, and the SHELLOPTS
        variable, if it appears in the environment, is ignored.
        If the shell is started with the effective user (group)
        id not equal to the real user (group) id,  and  the  -p
        option is not supplied, these actions are taken and the
        effective user id is set to the real user id.   If  the
        -p option is supplied at startup, the effective user id
        is not reset.   Turning  this  option  off  causes  the
        effective user and group ids to be set to the real user
        and group ids.
       -t      Exit after reading and executing one command.
       -u      Treat unset  variables  as  an  error  when  performing
        parameter  expansion.   If expansion is attempted on an
        unset variable, the shell prints an error message, and,
        if not interactive, exits with a non-zero status.
       -v      Print shell input lines as they are read.
       -x      After  expanding each simple command, for command, case
        command, select command, or  arithmetic for  command,
        display the expanded value of PS4, followed by the com-
        mand 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 func-
        tions, 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 follow symbolic links when
        executing commands such as cd that change  the  current
        working  directory.   It uses  the  physical directory
        structure instead.  By default, bash follows the logi-
        cal chain of directories when performing commands which
        change the current directory.
       -T      If set, any trap on DEBUG is inherited by  shell func-
        tions,  command substitutions, and commands executed in
        a subshell environment.  The DEBUG trap is normally not
        inherited in such cases.
       --      If no arguments follow this option, then the positional
        parameters are unset.  Otherwise, the positional param-
        eters  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  variables  controlling  optional shell
       behavior.   With no  options, or with the -p option, a list of
       all settable  options  is  displayed,  with  an  indication  of
       whether  or not each is set.  The -p option causes output to be
       displayed in a form that may be reused as input. Other options
       have the following meanings:
       -s     Enable (set) each optname.
       -u     Disable (unset) each optname.
       -q     Suppresses normal output (quiet mode); the return status
       indicates whether the optname is set or unset.  If  mul-
       tiple  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, the  dis-
       play  is limited  to  those  options  which  are set or unset,
       respectively.  Unless otherwise noted, the  shopt  options  are
       disabled (unset) by default.
       The  return status when listing options is zero if all optnames
       are enabled, non-zero otherwise.  When  setting or  unsetting
       options, the  return status is zero unless an optname is not a
       valid shell option.
       The list of shopt options is:
       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 file name is printed,  and  the
        command proceeds.  This option is only used by interac-
        tive 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  per-
        formed.
       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.
       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  inter-
        active 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 correspond-
        ing to each function name supplied as  an argu-
        ment.
        2.     If  the  command run by the DEBUG trap returns a
        non-zero value, the next command is skipped  and
        not executed.
        3.     If  the  command run by the DEBUG trap returns a
        value of 2, and the shell is executing in a sub-
        routine (a shell function or a shell script exe-
        cuted by the . or source builtins),  a  call  to
        return is simulated.
       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 pos-
        sible completions.  See SHELL  VARIABLES above  for  a
        description  of  FIGNORE.   This option is enabled by
        default.
       gnu_errfmt
        If set, shell error messages are written in  the stan-
        dard GNU error message format.
       histappend
        If  set, the history list is appended to the file named
        by the value of the HISTFILE variable  when  the shell
        exits, rather than overwriting the file.
       histreedit
        If set, and readline is being used, a user is given the
        opportunity to re-edit a failed history substitution.
       histverify
        If set, and readline is being used, the results of his-
        tory  substitution  are  not  immediately passed to the
        shell parser.  Instead, the resulting  line  is  loaded
        into the readline editing buffer, allowing further mod-
        ification.
       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.
       lithist If  set, and the cmdhist option is enabled, multi-line
        commands are saved to the history  with  embedded  new-
        lines rather than using semicolon separators where pos-
        sible.
       login_shell
        The shell sets this option if it is started as a login
        shell  (see  INVOCATION  above).  The value may not be
        changed.
       mailwarn
        If set, and a file that bash is checking for  mail  has
        been  accessed  since the last time it was checked, the
        message ''The mail in mailfile has been read'' is  dis-
        played.
       no_empty_cmd_completion
        If  set, and  readline  is  being  used, bash will not
        attempt to search the  PATH  for possible  completions
        when completion is attempted on an empty line.
       nocaseglob
        If  set, bash  matches filenames in a case-insensitive
        fashion when performing pathname expansion  (see Path-
        name Expansion above).
       nullglob
        If  set, bash allows patterns which match no files (see
        Pathname Expansion above) to expand to a null  string,
        rather than themselves.
       progcomp
        If  set, the  programmable  completion facilities (see
        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 param-
        eters.
       sourcepath
        If set, the source (.) builtin uses the value  of  PATH
        to  find the directory containing the file supplied as
        an argument.  This option is enabled by default.
       xpg_echo
        If  set, the  echo  builtin  expands  backslash-escape
        sequences by default.
       suspend [-f]
       Suspend the execution of this shell until it receives a SIGCONT
       signal.  The -f option says not to complain if this is a login
       shell;  just suspend anyway.  The return status is 0 unless the
       shell is a login shell and -f is not supplied, or if  job  con-
       trol is not enabled.
       test expr
       [ expr ]
       Return  a  status  of 0 or 1 depending on the evaluation of the
       conditional expression expr.  Each operator and operand must be
       a separate argument.  Expressions are composed of the primaries
       described above under CONDITIONAL EXPRESSIONS.
       Expressions may be  combined  using  the following  operators,
       listed in decreasing order of precedence.
       ! expr True if expr is false.
       ( expr )
       Returns the value of expr.  This may be used to override
       the normal precedence of operators.
       expr1 -a expr2
       True if both expr1 and expr2 are true.
       expr1 -o expr2
       True if either expr1 or expr2 is true.
       test and [ evaluate conditional  expressions  using  a  set  of
       rules based on the number of arguments.
       0 arguments
       The expression is false.
       1 argument
       The  expression  is  true if and only if the argument is
       not null.
       2 arguments
       If the first argument is !, the expression  is  true  if
       and  only if the second argument is null.  If the first
       argument is  one  of  the unary  conditional  operators
       listed  above under CONDITIONAL EXPRESSIONS, the expres-
       sion is true if the unary test is true.   If  the first
       argument  is not a valid unary conditional operator, the
       expression is false.
       3 arguments
       If the second argument is one of the binary  conditional
       operators listed above  under CONDITIONAL EXPRESSIONS,
       the result of the expression is the result of the binary
       test  using  the  first and third arguments as operands.
       If the first argument is !, the value is the negation of
       the  two-argument test using the second and third argu-
       ments.  If the first argument is exactly ( and the third
       argument  is  exactly  ), the result is the one-argument
       test of the second argument.  Otherwise, the  expression
       is false. The -a and -o operators are considered binary
       operators in this case.
       4 arguments
       If the first argument is !, the result is the  negation
       of the three-argument expression composed of the remain-
       ing 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.
       times  Print  the  accumulated user and system times for the shell and
       for processes run from the shell.  The return status is 0.
       trap [-lp] [[arg] sigspec ...]
       The command arg is to be read  and  executed  when  the shell
       receives signal(s)  sigspec.  If arg is absent (and there is a
       single sigspec) or -, each specified signal  is  reset  to  its
       original disposition  (the  value  it had upon entrance to the
       shell).  If arg is the null string the signal specified by each
       sigspec is ignored by the shell and by the commands it invokes.
       If arg is not present and -p has been supplied, then  the  trap
       commands associated  with  each sigspec are displayed. If no
       arguments are supplied or if only -p is given, trap prints  the
       list  of commands  associated with each signal. The -l option
       causes the shell to print a list of signal names and their cor-
       responding  numbers.   Each  sigspec  is either a signal name
       defined in , 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 exe-
       cutes in a shell function (see SHELL GRAMMAR above).  Refer  to
       the  description of the extglob option to the shopt builtin for
       details of its effect on the DEBUG trap. If a sigspec is  ERR,
       the  command  arg  is  executed whenever a simple command has a
       non-zero exit status, subject to the following conditions.  The
       ERR  trap  is not executed if the failed command is part of the
       command list immediately following a while  or  until  keyword,
       part  of the test in an if statement, part of a && or || list,
       or if the command's return  value  is  being  inverted  via  !.
       These are the same conditions obeyed by the errexit option.  If
       a sigspec is RETURN, the command arg is executed each  time  a
       shell  function  or  a  script  executed with  the . or source
       builtins finishes executing.  Signals ignored upon entry to the
       shell cannot be trapped or reset.  Trapped signals are reset to
       their original values in a child process when  it  is  created.
       The return status is false if any sigspec is invalid; otherwise
       trap returns true.
       type [-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 spec-
       ified as a command name, or nothing if ''type -t name'' would
       not  return  file.  The -P option forces a PATH search for each
       name, even if ''type -t name'' would not return file. If  a
       command is hashed, -p and -P print the hashed value, not neces-
       sarily the file that appears first in PATH.  If the  -a  option
       is  used,  type  prints  all of the places that contain an exe-
       cutable 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 any of the arguments are found,  false  if
       none are found.
       ulimit [-SHacdflmnpstuv [limit]]
       Provides control over the resources available to the shell and
       to processes started by it, on systems that allow such control.
       The  -H  and  -S options specify that the hard or soft limit is
       set for the given resource.  A hard limit cannot be  increased
       once  it is set; a soft limit may be increased up to the value
       of the hard limit.  If neither -H nor -S is specified, both the
       soft and hard limits are set.  The value of limit can be a num-
       ber in the unit specified for the resource or one of  the  spe-
       cial  values hard, soft, or unlimited, which stand for the cur-
       rent hard limit, the current soft limit, and no limit,  respec-
       tively. 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
       -c     The maximum size of core files created
       -d     The maximum size of a process's data segment
       -f     The maximum size of files created by the shell
       -l     The maximum size that may be locked into memory
       -m     The maximum resident set size
       -n     The  maximum  number of open file descriptors (most sys-
       tems do not allow this value to be set)
       -p     The pipe size in 512-byte blocks (this may not be set)
       -s     The maximum stack size
       -t     The maximum amount of cpu time in seconds
       -u     The maximum number of processes available to  a  single
       user
       -v     The  maximum  amount  of virtual memory available to the
       shell
       If limit is given,  it  is  the  new  value  of  the  specified
       resource (the  -a  option  is  display only).  If no option is
       given, then -f is assumed.  Values are in 1024-byte increments,
       except  for  -t, which is in seconds, -p, which is in units of
       512-byte blocks, and -n and -u, which are unscaled values.  The
       return status is 0 unless an invalid option or argument is sup-
       plied, 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 num-
       ber.  If the -p option is supplied, and mode  is omitted,  the
       output  is  in  a form that may be reused as input.  The return
       status is 0 if the mode was successfully changed or if no  mode
       argument was supplied, and false otherwise.
       unalias [-a] [name ...]
       Remove  each  name  from the list of defined aliases.  If -a is
       supplied, all alias definitions are removed.  The return value
       is true unless a supplied name is not a defined alias.
       unset [-fv] [name ...]
       For  each  name, remove the corresponding variable or function.
       If no options are supplied, or the -v  option  is  given,  each
       name  refers  to a shell variable.  Read-only variables may not
       be unset.  If -f is specifed, each name refers to a shell func-
       tion, and the function definition is removed.  Each unset vari-
       able or function is removed from the environment passed to sub-
       sequent  commands.  If any of RANDOM, SECONDS, LINENO, HISTCMD,
       FUNCNAME, GROUPS, or DIRSTACK are unset, they lose  their  spe-
       cial properties, even if they are subsequently reset.  The exit
       status is true unless a name is readonly.
       wait [n]
       Wait for the specified process and return its termination  sta-
       tus.   n may  be a process ID or a job specification; if a job
       spec is given, all processes in that job's pipeline are  waited
       for.   If  n is not given, all currently active child processes
       are waited for, and the return status is zero.  If n  specifies
       a  non-existent process or job, the return status is 127.  Oth-
       erwise, the return status is the exit status of the  last  pro-
       cess or job waited for.
SEE ALSO
       bash(1), sh(1)
 
GNU Bash-3.0    2004 Apr 20       BASH_BUILTINS(1)
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