bash

BASH(1)                     General Commands Manual                    BASH(1)

NAME
       bash - GNU Bourne-Again SHell

SYNOPSIS
       bash [options] [command_string | file]

COPYRIGHT
       Bash is Copyright (C) 1989-2016 by the Free Software Foundation, Inc.

DESCRIPTION
       Bash  is  an  sh-compatible  command language interpreter that executes
       commands read from the standard input or from a file.  Bash also incor-
       porates useful features from the Korn and C shells (ksh and csh).

       Bash  is  intended  to  be a conformant implementation of the Shell and
       Utilities portion  of  the  IEEE  POSIX  specification  (IEEE  Standard
       1003.1).  Bash can be configured to be POSIX-conformant by default.

OPTIONS
       All of the single-character shell options documented in the description
       of the set builtin command can be used as options when the shell is in-
       voked.   In  addition, bash interprets the following options when it is
       invoked:

       -c        If the -c option is present, then commands are read from  the
                 first non-option argument command_string.  If there are argu-
                 ments after the command_string, the  first  argument  is  as-
                 signed  to $0 and any remaining arguments are assigned to the
                 positional parameters.  The assignment to $0 sets the name of
                 the shell, which is used in warning and error messages.
       -i        If the -i option is present, the shell is interactive.
       -l        Make bash act as if it had been invoked as a login shell (see
                 INVOCATION below).
       -r        If the -r option is present,  the  shell  becomes  restricted
                 (see RESTRICTED SHELL below).
       -s        If  the -s option is present, or if no arguments remain after
                 option processing, then commands are read from  the  standard
                 input.   This  option  allows the positional parameters to be
                 set when invoking an interactive shell.
       -v        Print shell input lines as they are read.
       -x        Print commands and their arguments as they are executed.
       -D        A list of all double-quoted strings preceded by $ is  printed
                 on  the standard output.  These are the strings that are sub-
                 ject to language translation when the current locale is not C
                 or  POSIX.   This  implies the -n option; no commands will be
                 executed.
       [-+]O [shopt_option]
                 shopt_option is one of the  shell  options  accepted  by  the
                 shopt   builtin  (see  SHELL  BUILTIN  COMMANDS  below).   If
                 shopt_option is present, -O sets the value of that option; +O
                 unsets  it.   If  shopt_option is not supplied, the names and
                 values of the shell options accepted by shopt are printed  on
                 the  standard  output.   If  the invocation option is +O, the
                 output is displayed in a format that may be reused as input.
       --        A -- signals the end of options and disables  further  option
                 processing.   Any arguments after the -- are treated as file-
                 names and arguments.  An argument of - is equivalent to --.

       Bash also interprets a number of multi-character  options.   These  op-
       tions  must  appear on the command line before the single-character op-
       tions to be recognized.

       --debugger
              Arrange for the debugger profile to be executed before the shell
              starts.   Turns  on extended debugging mode (see the description
              of the extdebug option to the shopt builtin below).
       --dump-po-strings
              Equivalent to -D, but the output is in the GNU gettext po  (por-
              table object) file format.
       --dump-strings
              Equivalent to -D.
       --help Display  a  usage  message  on standard output and exit success-
              fully.
       --init-file file
       --rcfile file
              Execute commands from file instead of the system  wide  initial-
              ization file /etc/bash.bashrc and the standard personal initial-
              ization file ~/.bashrc if the shell is interactive (see  INVOCA-
              TION below).

       --login
              Equivalent to -l.

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

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

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

       --posix
              Change  the behavior of bash where the default operation differs
              from the POSIX 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.

       --restricted
              The shell becomes restricted (see RESTRICTED SHELL below).

       --verbose
              Equivalent to -v.

       --version
              Show version information for this instance of bash on the  stan-
              dard output and exit successfully.

ARGUMENTS
       If arguments remain after option processing, and neither the -c nor the
       -s option has been supplied, the first argument is assumed  to  be  the
       name  of  a file containing shell commands.  If bash is invoked in this
       fashion, $0 is set to the name of the file, and the positional  parame-
       ters  are set to the remaining arguments.  Bash reads and executes com-
       mands from this file, then exits.  Bash's exit status is the exit  sta-
       tus of the last command executed in the script.  If no commands are ex-
       ecuted, the exit status is 0.  An attempt is first  made  to  open  the
       file in the current directory, and, if no file is found, then the shell
       searches the directories in PATH for the script.

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

       An  interactive  shell is one started without non-option arguments (un-
       less -s is specified) and without the -c option  whose  standard  input
       and error are both connected to terminals (as determined by isatty(3)),
       or one started with the -i option.  PS1 is set and  $-  includes  i  if
       bash  is interactive, allowing a shell script or a startup file to test
       this state.

       The following paragraphs describe how bash executes its startup  files.
       If  any  of  the files exist but cannot be read, bash reports an error.
       Tildes are expanded in filenames as described below under Tilde  Expan-
       sion in the EXPANSION section.

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

       When an interactive login shell exits, or a non-interactive login shell
       executes the exit builtin command, bash  reads  and  executes  commands
       from the file ~/.bash_logout, if it exists.

       When  an  interactive  shell that is not a login shell is started, bash
       reads and executes commands from  /etc/bash.bashrc  and  ~/.bashrc,  if
       these  files  exist.  This may be inhibited by using the --norc option.
       The --rcfile file option will force bash to read and  execute  commands
       from file instead of /etc/bash.bashrc and ~/.bashrc.

       When  bash is started non-interactively, to run a shell script, for ex-
       ample, it looks for the variable BASH_ENV in the  environment,  expands
       its  value if it appears there, and uses the expanded value as the name
       of a file to read and execute.  Bash behaves as if the  following  com-
       mand were executed:
              if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
       but  the value of the PATH variable is not used to search for the file-
       name.

       If bash is invoked with the name sh, it tries to mimic the startup  be-
       havior  of historical versions of sh as closely as possible, while con-
       forming to the POSIX standard as well.  When invoked as an  interactive
       login  shell,  or  a  non-interactive shell with the --login option, it
       first attempts to read  and  execute  commands  from  /etc/profile  and
       ~/.profile,  in  that order.  The --noprofile option may be used to in-
       hibit this behavior.  When invoked as an  interactive  shell  with  the
       name  sh,  bash  looks for the variable ENV, expands its value if it is
       defined, and uses the expanded value as the name of a file to read  and
       execute.  Since a shell invoked as sh does not attempt to read and exe-
       cute commands from any other startup files, the --rcfile option has  no
       effect.   A non-interactive shell invoked with the name sh does not at-
       tempt to read any other startup files.  When invoked as sh, bash enters
       posix mode after the startup files are read.

       When  bash  is  started in posix mode, as with the --posix command line
       option, it follows the POSIX standard for startup files.  In this mode,
       interactive  shells  expand  the ENV variable and commands are read and
       executed from the file whose name is  the  expanded  value.   No  other
       startup files are read.

       Bash attempts to determine when it is being run with its standard input
       connected to a network connection, as when executed by the remote shell
       daemon,  usually rshd, or the secure shell daemon sshd.  If bash deter-
       mines it is being run in this fashion, it reads and  executes  commands
       from  ~/.bashrc  and  ~/.bashrc, if these files exist and are readable.
       It will not do this if invoked as sh.  The --norc option may be used to
       inhibit this behavior, and the --rcfile option may be used to force an-
       other file to be read, but neither rshd nor sshd generally  invoke  the
       shell with those options or allow them to be specified.

       If the shell is started with the effective user (group) id not equal to
       the real user (group) id, and the -p option is not supplied, no startup
       files are read, shell functions are not inherited from the environment,
       the SHELLOPTS, BASHOPTS, CDPATH, and GLOBIGNORE variables, if they  ap-
       pear  in the environment, are ignored, and the effective user id is set
       to the real user id.  If the -p option is supplied at  invocation,  the
       startup behavior is the same, but the effective user id is not reset.

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

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

       ! case  coproc  do done elif else esac fi for  function  if  in  select
       then until while { } time [[ ]]

SHELL GRAMMAR
   Simple Commands
       A  simple  command  is a sequence of optional variable assignments fol-
       lowed by blank-separated words and redirections, and  terminated  by  a
       control operator.  The first word specifies the command to be executed,
       and is passed as argument zero.  The remaining words are passed as  ar-
       guments to the invoked command.

       The  return  value  of a simple command is its exit status, or 128+n if
       the command is terminated by signal n.

   Pipelines
       A pipeline is a sequence of one or more commands separated  by  one  of
       the control operators | or |&.  The format for a pipeline is:

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

       The  standard output of command is connected via a pipe to the standard
       input of command2.  This connection is performed  before  any  redirec-
       tions specified by the command (see REDIRECTION below).  If |& is used,
       command's standard error, in addition to its standard output,  is  con-
       nected  to  command2's standard input through the pipe; it is shorthand
       for 2>&1 |.  This implicit redirection of the  standard  error  to  the
       standard  output  is  performed after any redirections specified by the
       command.

       The return status of a pipeline is the exit status of the last command,
       unless  the  pipefail  option  is enabled.  If pipefail is enabled, the
       pipeline's return status is the value of the last  (rightmost)  command
       to  exit  with a non-zero status, or zero if all commands exit success-
       fully.  If the reserved word !  precedes a pipeline, the exit status of
       that  pipeline  is the logical negation of the exit status as described
       above.  The shell waits for all commands in the pipeline  to  terminate
       before returning a value.

       If  the  time reserved word precedes a pipeline, the elapsed as well as
       user and system time consumed by its execution are  reported  when  the
       pipeline  terminates.   The -p option changes the output format to that
       specified by POSIX.  When the shell is in posix mode, it does not  rec-
       ognize  time  as  a  reserved word if the next token begins with a `-'.
       The TIMEFORMAT variable may be set to a format  string  that  specifies
       how  the timing information should be displayed; see the description of
       TIMEFORMAT under Shell Variables below.

       When the shell is in posix mode, time may be followed by a newline.  In
       this  case,  the shell displays the total user and system time consumed
       by the shell and its children.  The TIMEFORMAT variable may be used  to
       specify the format of the time information.

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

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

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

       A  sequence  of  one or more newlines may appear in a list instead of a
       semicolon to delimit commands.

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

       AND  and  OR  lists are sequences of one or more pipelines separated by
       the && and || control operators, respectively.  AND and  OR  lists  are
       executed with left associativity.  An AND list has the form

              command1 && command2

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

       An OR list has the form

              command1 || command2

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

   Compound Commands
       A compound command is one of the following.  In most cases a list in  a
       command's  description may be separated from the rest of the command by
       one or more newlines, and may be followed by a newline in  place  of  a
       semicolon.

       (list) list  is  executed in a subshell environment (see COMMAND EXECU-
              TION ENVIRONMENT below).  Variable assignments and builtin  com-
              mands  that  affect the shell's environment do not remain in ef-
              fect after the command completes.  The return status is the exit
              status of list.

       { list; }
              list  is simply executed in the current shell environment.  list
              must be terminated with a newline or semicolon.  This  is  known
              as  a  group  command.   The return status is the exit status of
              list.  Note that unlike the metacharacters ( and ), { and }  are
              reserved words and must occur where a reserved word is permitted
              to be recognized.  Since they do not cause a  word  break,  they
              must  be  separated  from  list  by  whitespace or another shell
              metacharacter.

       ((expression))
              The expression is evaluated according to the rules described be-
              low under ARITHMETIC EVALUATION.  If the value of the expression
              is non-zero, the return status is 0; otherwise the return status
              is 1.  This is exactly equivalent to let "expression".

       [[ expression ]]
              Return  a  status  of  0 or 1 depending on the evaluation of the
              conditional expression expression.  Expressions are composed  of
              the  primaries  described  below  under CONDITIONAL EXPRESSIONS.
              Word splitting and pathname expansion are not performed  on  the
              words  between  the  [[  and  ]]; tilde expansion, parameter and
              variable expansion, arithmetic expansion, command  substitution,
              process  substitution,  and quote removal are performed.  Condi-
              tional operators such as -f must be unquoted to be recognized as
              primaries.

              When  used with [[, the < and > operators sort lexicographically
              using the current locale.

       See the description of the test builtin command (section SHELL  BUILTIN
       COMMANDS  below)  for the handling of parameters (i.e.  missing parame-
       ters).

       When the == and != operators are used, the string to the right  of  the
       operator is considered a pattern and matched according to the rules de-
       scribed below under Pattern Matching, as if the  extglob  shell  option
       were  enabled.  The = operator is equivalent to ==.  If the nocasematch
       shell option is enabled, the match is performed without regard  to  the
       case  of  alphabetic  characters.   The return value is 0 if the string
       matches (==) or does not match (!=) the pattern, and 1 otherwise.   Any
       part  of  the  pattern  may be quoted to force the quoted portion to be
       matched as a string.

       An additional binary operator, =~, is available, with the  same  prece-
       dence  as  ==  and !=.  When it is used, the string to the right of the
       operator is considered an extended regular expression and  matched  ac-
       cordingly  (as  in  regex(3)).   The  return  value  is 0 if the string
       matches the pattern, and 1 otherwise.  If  the  regular  expression  is
       syntactically  incorrect,  the conditional expression's return value is
       2.  If the nocasematch shell option is enabled, the match is  performed
       without  regard  to the case of alphabetic characters.  Any part of the
       pattern may be quoted to force the quoted portion to be  matched  as  a
       string.   Bracket  expressions  in  regular expressions must be treated
       carefully, since normal quoting characters lose their meanings  between
       brackets.   If  the  pattern is stored in a shell variable, quoting the
       variable expansion forces the entire pattern to be matched as a string.
       Substrings  matched  by parenthesized subexpressions within the regular
       expression are saved in the array variable BASH_REMATCH.   The  element
       of  BASH_REMATCH with index 0 is the portion of the string matching the
       entire regular expression.  The element of BASH_REMATCH with index n is
       the portion of the string matching the nth parenthesized subexpression.

       Expressions  may  be  combined using the following operators, listed in
       decreasing order of precedence:

              ( expression )
                     Returns the value of expression.  This  may  be  used  to
                     override the normal precedence of operators.
              ! expression
                     True if expression is false.
              expression1 && expression2
                     True if both expression1 and expression2 are true.
              expression1 || expression2
                     True if either expression1 or expression2 is true.

              The && and || operators do not evaluate expression2 if the value
              of expression1 is sufficient to determine the  return  value  of
              the entire conditional expression.

       for name [ [ in [ word ... ] ] ; ] do list ; done
              The list of words following in is expanded, generating a list of
              items.  The variable name is set to each element of this list in
              turn,  and  list is executed each time.  If the in word is omit-
              ted, the for command executes list once for each positional  pa-
              rameter  that  is set (see PARAMETERS below).  The return status
              is the exit status of the last command that  executes.   If  the
              expansion of the items following in results in an empty list, no
              commands are executed, and the return status is 0.

       for (( expr1 ; expr2 ; expr3 )) ; do list ; done
              First, the arithmetic expression expr1 is evaluated according to
              the  rules  described  below  under  ARITHMETIC EVALUATION.  The
              arithmetic expression expr2 is then evaluated  repeatedly  until
              it  evaluates  to zero.  Each time expr2 evaluates to a non-zero
              value, list is executed and the arithmetic expression  expr3  is
              evaluated.   If  any  expression is omitted, it behaves as if it
              evaluates to 1.  The return value is the exit status of the last
              command in list that is executed, or false if any of the expres-
              sions is invalid.

       select name [ in word ] ; do list ; done
              The list of words following in is expanded, generating a list of
              items.  The set of expanded words is printed on the standard er-
              ror, each preceded by a number.  If the in word is omitted,  the
              positional  parameters  are printed (see PARAMETERS below).  The
              PS3 prompt is then displayed and a line read from  the  standard
              input.  If the line consists of a number corresponding to one of
              the displayed words, then the value of name is set to that word.
              If  the line is empty, the words and prompt are displayed again.
              If EOF is read, the command completes.   Any  other  value  read
              causes  name  to  be set to null.  The line read is saved in the
              variable REPLY.  The list is executed after each selection until
              a  break  command is executed.  The exit status of select is the
              exit status of the last command executed in list, or zero if  no
              commands were executed.

       case word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac
              A case command first expands word, and tries to match it against
              each pattern in turn, using the same matching rules as for path-
              name  expansion (see Pathname Expansion below).  The word is ex-
              panded using tilde expansion, parameter and variable  expansion,
              arithmetic expansion, command substitution, process substitution
              and quote removal.  Each  pattern  examined  is  expanded  using
              tilde  expansion,  parameter  and variable expansion, arithmetic
              expansion, command substitution, and process  substitution.   If
              the  nocasematch shell option is enabled, the match is performed
              without regard to the case of  alphabetic  characters.   When  a
              match  is  found, the corresponding list is executed.  If the ;;
              operator is used, no subsequent matches are attempted after  the
              first  pattern  match.  Using ;& in place of ;; causes execution
              to continue with the list associated with the next set  of  pat-
              terns.   Using  ;;&  in place of ;; causes the shell to test the
              next pattern list in the statement, if any, and execute any  as-
              sociated list on a successful match.  The exit status is zero if
              no pattern matches.  Otherwise, it is the  exit  status  of  the
              last command executed in list.

       if list; then list; [ elif list; then list; ] ... [ else list; ] fi
              The  if  list is executed.  If its exit status is zero, the then
              list is executed.  Otherwise, each  elif  list  is  executed  in
              turn,  and  if  its  exit status is zero, the corresponding then
              list is executed and the command completes.  Otherwise, the else
              list  is executed, if present.  The exit status is the exit sta-
              tus of the last command executed, or zero if no condition tested
              true.

       while list-1; do list-2; done
       until list-1; do list-2; done
              The  while command continuously executes the list list-2 as long
              as the last command in the list list-1 returns an exit status of
              zero.   The until command is identical to the while command, ex-
              cept that the test is negated: list-2 is executed as long as the
              last command in list-1 returns a non-zero exit status.  The exit
              status of the while and until commands is the exit status of the
              last command executed in list-2, or zero if none was executed.

   Coprocesses
       A coprocess is a shell command preceded by the coproc reserved word.  A
       coprocess is executed asynchronously in a subshell, as if  the  command
       had  been  terminated  with the & control operator, with a two-way pipe
       established between the executing shell and the coprocess.

       The format for a coprocess is:

              coproc [NAME] command [redirections]

       This creates a coprocess named NAME.  If NAME is not supplied, the  de-
       fault name is COPROC.  NAME must not be supplied if command is a simple
       command (see above); otherwise, it is interpreted as the first word  of
       the  simple command.  When the coprocess is executed, the shell creates
       an array variable (see Arrays below) named NAME in the context  of  the
       executing  shell.   The  standard  output of command is connected via a
       pipe to a file descriptor in the executing shell,  and  that  file  de-
       scriptor is assigned to NAME[0].  The standard input of command is con-
       nected via a pipe to a file descriptor in the executing shell, and that
       file  descriptor  is assigned to NAME[1].  This pipe is established be-
       fore any redirections specified by the command (see REDIRECTION below).
       The file descriptors can be utilized as arguments to shell commands and
       redirections using standard word expansions.  The file descriptors  are
       not available in subshells.  The process ID of the shell spawned to ex-
       ecute the coprocess is available as the value of the variable NAME_PID.
       The  wait builtin command may be used to wait for the coprocess to ter-
       minate.

       Since the coprocess is created as an asynchronous command,  the  coproc
       command  always  returns  success.  The return status of a coprocess is
       the exit status of command.

   Shell Function Definitions
       A shell function is an object that is called like a simple command  and
       executes  a  compound  command with a new set of positional parameters.
       Shell functions are declared as follows:

       name () compound-command [redirection]
       function name [()] compound-command [redirection]
              This defines a function named name.  The reserved word  function
              is  optional.   If  the  function reserved word is supplied, the
              parentheses are optional.  The body of the function is the  com-
              pound  command  compound-command  (see Compound Commands above).
              That command is usually a list of commands between { and },  but
              may  be  any  command listed under Compound Commands above, with
              one exception: If the function reserved word is  used,  but  the
              parentheses  are  not  supplied,  the braces are required.  com-
              pound-command is executed whenever name is specified as the name
              of  a  simple  command.  When in posix mode, name may not be the
              name of one of the POSIX  special  builtins.   Any  redirections
              (see REDIRECTION below) specified when a function is defined are
              performed when the function is executed.  The exit status  of  a
              function  definition  is  zero unless a syntax error occurs or a
              readonly function with the same name already exists.  When  exe-
              cuted,  the  exit status of a function is the exit status of the
              last command executed in the body.  (See FUNCTIONS below.)

COMMENTS
       In a non-interactive shell, or an interactive shell in which the inter-
       active_comments  option  to  the  shopt  builtin  is enabled (see SHELL
       BUILTIN COMMANDS below), a word beginning with # causes that  word  and
       all  remaining  characters  on that line to be ignored.  An interactive
       shell without the interactive_comments option enabled  does  not  allow
       comments.  The interactive_comments option is on by default in interac-
       tive shells.

QUOTING
       Quoting is used to remove the special meaning of certain characters  or
       words  to  the shell.  Quoting can be used to disable special treatment
       for special characters, to prevent reserved words from being recognized
       as such, and to prevent parameter expansion.

       Each  of  the metacharacters listed above under DEFINITIONS has special
       meaning to the shell and must be quoted if it is to represent itself.

       When the command history expansion facilities are being used (see  HIS-
       TORY EXPANSION below), the history expansion character, usually !, must
       be quoted to prevent history expansion.

       There are  three  quoting  mechanisms:  the  escape  character,  single
       quotes, and double quotes.

       A  non-quoted  backslash (\) is the escape character.  It preserves the
       literal value of the next character that follows, with the exception of
       <newline>.   If a \<newline> pair appears, and the backslash is not it-
       self quoted, the \<newline> is treated as a line continuation (that is,
       it is removed from the input stream and effectively ignored).

       Enclosing  characters  in  single quotes preserves the literal value of
       each character within the quotes.  A single quote may not occur between
       single quotes, even when preceded by a backslash.

       Enclosing  characters  in  double quotes preserves the literal value of
       all characters within the quotes, with the exception of $, `,  \,  and,
       when history expansion is enabled, !.  When the shell is in posix mode,
       the ! has no special meaning within double quotes,  even  when  history
       expansion  is  enabled.   The  characters  $ and ` retain their special
       meaning within double quotes.  The backslash retains its special  mean-
       ing  only when followed by one of the following characters: $, `, ", \,
       or <newline>.  A double quote may be quoted  within  double  quotes  by
       preceding  it  with a backslash.  If enabled, history expansion will be
       performed unless an !  appearing in double quotes is  escaped  using  a
       backslash.  The backslash preceding the !  is not removed.

       The  special  parameters  *  and  @ have special meaning when in double
       quotes (see PARAMETERS below).

       Words of the form $'string' are treated specially.  The word expands to
       string,  with backslash-escaped characters replaced as specified by the
       ANSI C standard.  Backslash escape sequences, if present,  are  decoded
       as follows:
              \a     alert (bell)
              \b     backspace
              \e
              \E     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\     backslash
              \'     single quote
              \"     double quote
              \?     question mark
              \nnn   the  eight-bit  character  whose value is the octal value
                     nnn (one to three 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)
              \cx    a control-x character

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

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

PARAMETERS
       A  parameter is an entity that stores values.  It can be a name, a num-
       ber, or one of the special characters listed below under Special Param-
       eters.   A variable is a parameter denoted by a name.  A variable has a
       value and zero or more attributes.  Attributes are assigned  using  the
       declare builtin command (see declare below in SHELL BUILTIN COMMANDS).

       A parameter is set if it has been assigned a value.  The null string is
       a valid value.  Once a variable is set, it may be unset only  by  using
       the unset builtin command (see SHELL BUILTIN COMMANDS below).

       A variable may be assigned to by a statement of the form

              name=[value]

       If  value  is not given, the variable is assigned the null string.  All
       values undergo tilde expansion, parameter and variable expansion,  com-
       mand  substitution, arithmetic expansion, and quote removal (see EXPAN-
       SION below).  If the variable has its integer attribute set, then value
       is evaluated as an arithmetic expression even if the $((...)) expansion
       is not used (see Arithmetic Expansion below).  Word  splitting  is  not
       performed,  with the exception of "$@" as explained below under Special
       Parameters.  Pathname expansion is not  performed.   Assignment  state-
       ments  may also appear as arguments to the alias, declare, typeset, ex-
       port, readonly, and  local  builtin  commands  (declaration  commands).
       When in posix mode, these builtins may appear in a command after one or
       more instances of the  command  builtin  and  retain  these  assignment
       statement properties.

       In  the context where an assignment statement is assigning a value to a
       shell variable or array index, the += operator can be used to append to
       or  add  to  the variable's previous value.  This includes arguments to
       builtin commands such as  declare  that  accept  assignment  statements
       (declaration commands).  When += is applied to a variable for which the
       integer attribute has been set, value is evaluated as an arithmetic ex-
       pression and added to the variable's current value, which is also eval-
       uated.  When += is applied to an array variable using compound  assign-
       ment  (see  Arrays  below), the variable's value is not unset (as it is
       when using =), and new values are appended to the  array  beginning  at
       one  greater  than  the  array's  maximum index (for indexed arrays) or
       added as additional key-value pairs in an associative array.  When  ap-
       plied  to  a  string-valued variable, value is expanded and appended to
       the variable's value.

       A variable can be assigned the nameref attribute using the -n option to
       the  declare or local builtin commands (see the descriptions of declare
       and local below) to create a nameref, or a reference to  another  vari-
       able.   This  allows  variables to be manipulated indirectly.  Whenever
       the nameref variable is referenced, assigned to, unset, or has its  at-
       tributes  modified  (other than using or changing the nameref attribute
       itself), the operation is actually performed on the variable  specified
       by  the  nameref  variable's  value.  A nameref is commonly used within
       shell functions to refer to a variable whose name is passed as an argu-
       ment  to the function.  For instance, if a variable name is passed to a
       shell function as its first argument, running
              declare -n ref=$1
       inside the function creates a nameref variable ref whose value  is  the
       variable name passed as the first argument.  References and assignments
       to ref, and changes to its attributes, are treated as  references,  as-
       signments,  and  attribute modifications to the variable whose name was
       passed as $1.  If the control variable in a for loop  has  the  nameref
       attribute,  the  list  of words can be a list of shell variables, and a
       name reference will be established for each word in the list, in  turn,
       when the loop is executed.  Array variables cannot be given the nameref
       attribute.  However, nameref variables can  reference  array  variables
       and  subscripted  array  variables.  Namerefs can be unset using the -n
       option to the unset builtin.  Otherwise, if unset is executed with  the
       name  of  a nameref variable as an argument, the variable referenced by
       the nameref variable will be unset.

   Positional Parameters
       A positional parameter is a parameter denoted by one  or  more  digits,
       other than the single digit 0.  Positional parameters are assigned from
       the shell's arguments when it is invoked, and may be  reassigned  using
       the  set builtin command.  Positional parameters may not be assigned to
       with assignment statements.  The positional parameters are  temporarily
       replaced when a shell function is executed (see FUNCTIONS below).

       When  a  positional parameter consisting of more than a single digit is
       expanded, it must be enclosed in braces (see EXPANSION below).

   Special Parameters
       The shell treats several parameters specially.   These  parameters  may
       only be referenced; assignment to them is not allowed.
       *      Expands  to  the positional parameters, starting from one.  When
              the expansion is not within double quotes, each  positional  pa-
              rameter  expands  to  a  separate word.  In contexts where it is
              performed, those words are subject to further word splitting and
              pathname  expansion.   When  the  expansion occurs within double
              quotes, it expands to a single word with the value of  each  pa-
              rameter  separated  by  the  first  character of the IFS special
              variable.  That is, "$*" is equivalent to "$1c$2c...",  where  c
              is the first character of the value of the IFS variable.  If IFS
              is unset, the parameters are separated by  spaces.   If  IFS  is
              null, the parameters are joined without intervening separators.
       @      Expands  to  the positional parameters, starting from one.  When
              the expansion occurs within double quotes,  each  parameter  ex-
              pands  to  a separate word.  That is, "$@" is equivalent to "$1"
              "$2" ...  If the double-quoted expansion occurs within  a  word,
              the  expansion  of the first parameter is joined with the begin-
              ning part of the original word, and the expansion  of  the  last
              parameter  is  joined  with  the last part of the original word.
              When there are no positional parameters, "$@" and $@  expand  to
              nothing (i.e., they are removed).
       #      Expands to the number of positional parameters in decimal.
       ?      Expands  to  the exit status of the most recently executed fore-
              ground pipeline.
       -      Expands to the current option flags as  specified  upon  invoca-
              tion,  by the set builtin command, or those set by the shell it-
              self (such as the -i option).
       $      Expands to the process ID of the shell.  In a  ()  subshell,  it
              expands  to  the  process  ID of the current shell, not the sub-
              shell.
       !      Expands to the process ID of the job most recently  placed  into
              the  background,  whether executed as an asynchronous command or
              using the bg builtin (see JOB CONTROL below).
       0      Expands to the name of the shell or shell script.  This  is  set
              at shell initialization.  If bash is invoked with a file of com-
              mands, $0 is set to the name of that file.  If bash  is  started
              with  the  -c option, then $0 is set to the first argument after
              the string to be executed, if one is present.  Otherwise, it  is
              set  to  the  filename used to invoke bash, as given by argument
              zero.
       _      At shell startup, set to the absolute pathname  used  to  invoke
              the  shell or shell script being executed as passed in the envi-
              ronment or argument list.  Subsequently, expands to the last ar-
              gument  to  the  previous command, after expansion.  Also set to
              the full pathname used  to  invoke  each  command  executed  and
              placed in the environment exported to that command.  When check-
              ing mail, this parameter holds the name of the  mail  file  cur-
              rently being checked.

   Shell Variables
       The following variables are set by the shell:

       BASH   Expands  to  the  full  filename used to invoke this instance of
              bash.
       BASHOPTS
              A colon-separated list of enabled shell options.  Each  word  in
              the  list  is  a  valid  argument for the -s option to the shopt
              builtin command (see SHELL BUILTIN COMMANDS below).  The options
              appearing  in  BASHOPTS  are  those reported as on by shopt.  If
              this variable is in the environment when bash  starts  up,  each
              shell  option  in  the  list  will be enabled before reading any
              startup files.  This variable is read-only.
       BASHPID
              Expands to the process ID of the  current  bash  process.   This
              differs  from  $$ under certain circumstances, such as subshells
              that do not require bash to be re-initialized.
       BASH_ALIASES
              An associative array variable whose members  correspond  to  the
              internal  list  of  aliases  as maintained by the alias builtin.
              Elements added to this array appear in the alias list;  however,
              unsetting  array elements currently does not cause aliases to be
              removed from the alias list.  If BASH_ALIASES is unset, it loses
              its special properties, even if it is subsequently reset.
       BASH_ARGC
              An  array  variable whose values are the number of parameters in
              each frame of the current bash execution call stack.  The number
              of  parameters  to  the  current  subroutine  (shell function or
              script executed with . or source) is at the top  of  the  stack.
              When  a  subroutine is executed, the number of parameters passed
              is pushed onto BASH_ARGC.  The shell sets BASH_ARGC only when in
              extended debugging mode (see the description of the extdebug op-
              tion to the shopt builtin below)
       BASH_ARGV
              An array variable containing all of the parameters in  the  cur-
              rent bash execution call stack.  The final parameter of the last
              subroutine call is at the top of the stack; the first  parameter
              of the initial call is at the bottom.  When a subroutine is exe-
              cuted, the parameters supplied are pushed onto  BASH_ARGV.   The
              shell  sets  BASH_ARGV only when in extended debugging mode (see
              the description of the extdebug option to the shopt builtin  be-
              low)
       BASH_CMDS
              An  associative  array  variable whose members correspond to the
              internal hash table  of  commands  as  maintained  by  the  hash
              builtin.  Elements added to this array appear in the hash table;
              however, unsetting array elements currently does not cause  com-
              mand  names  to be removed from the hash table.  If BASH_CMDS is
              unset, it loses its special properties, even  if  it  is  subse-
              quently reset.
       BASH_COMMAND
              The  command  currently  being executed or about to be executed,
              unless the shell is executing a command as the result of a trap,
              in  which  case  it  is the command executing at the time of the
              trap.
       BASH_EXECUTION_STRING
              The command argument to the -c invocation option.
       BASH_LINENO
              An array variable whose members are the line numbers  in  source
              files  where  each corresponding member of FUNCNAME was invoked.
              ${BASH_LINENO[$i]}  is  the  line  number  in  the  source  file
              (${BASH_SOURCE[$i+1]})  where  ${FUNCNAME[$i]}  was  called  (or
              ${BASH_LINENO[$i-1]} if referenced within  another  shell  func-
              tion).  Use LINENO to obtain the current line number.
       BASH_LOADABLES_PATH
              A  colon-separated  list of directories in which the shell looks
              for dynamically loadable builtins specified by the  enable  com-
              mand.
       BASH_REMATCH
              An  array  variable  whose members are assigned by the =~ binary
              operator to the [[ conditional command.  The element with  index
              0  is  the portion of the string matching the entire regular ex-
              pression.  The element with index n is the portion of the string
              matching  the nth parenthesized subexpression.  This variable is
              read-only.
       BASH_SOURCE
              An array variable whose members are the source  filenames  where
              the  corresponding  shell  function  names in the FUNCNAME array
              variable are defined.  The shell function ${FUNCNAME[$i]} is de-
              fined   in   the   file   ${BASH_SOURCE[$i]}   and  called  from
              ${BASH_SOURCE[$i+1]}.
       BASH_SUBSHELL
              Incremented by one within each subshell or subshell  environment
              when  the  shell begins executing in that environment.  The ini-
              tial value is 0.
       BASH_VERSINFO
              A readonly array variable whose members hold version information
              for  this  instance  of  bash.  The values assigned to the array
              members are as follows:
              BASH_VERSINFO[0]        The major version number (the release).
              BASH_VERSINFO[1]        The minor version number (the version).
              BASH_VERSINFO[2]        The patch level.
              BASH_VERSINFO[3]        The build version.
              BASH_VERSINFO[4]        The release status (e.g., beta1).
              BASH_VERSINFO[5]        The value of MACHTYPE.
       BASH_VERSION
              Expands to a string describing the version of this  instance  of
              bash.
       COMP_CWORD
              An  index  into ${COMP_WORDS} of the word containing the current
              cursor position.  This variable is available only in shell func-
              tions  invoked  by  the  programmable completion facilities (see
              Programmable Completion below).
       COMP_KEY
              The key (or final key of a key sequence) used to invoke the cur-
              rent completion function.
       COMP_LINE
              The  current  command  line.  This variable is available only in
              shell functions and external commands invoked  by  the  program-
              mable completion facilities (see Programmable Completion below).
       COMP_POINT
              The  index of the current cursor position relative to the begin-
              ning of the current command.  If the current cursor position  is
              at the end of the current command, the value of this variable is
              equal to ${#COMP_LINE}.  This  variable  is  available  only  in
              shell  functions  and  external commands invoked by the program-
              mable completion facilities (see Programmable Completion below).
       COMP_TYPE
              Set to an integer value corresponding to the type of  completion
              attempted  that  caused a completion function to be called: TAB,
              for normal completion, ?, for listing completions after  succes-
              sive  tabs,  !, for listing alternatives on partial word comple-
              tion, @, to list completions if the word is not  unmodified,  or
              %,  for  menu  completion.   This  variable is available only in
              shell functions and external commands invoked  by  the  program-
              mable completion facilities (see Programmable Completion below).
       COMP_WORDBREAKS
              The  set  of characters that the readline library treats as word
              separators when performing word completion.  If  COMP_WORDBREAKS
              is  unset, it loses its special properties, even if it is subse-
              quently reset.
       COMP_WORDS
              An array variable (see Arrays below) consisting of the  individ-
              ual  words  in the current command line.  The line is split into
              words as readline would split it, using COMP_WORDBREAKS  as  de-
              scribed  above.   This variable is available only in shell func-
              tions invoked by the  programmable  completion  facilities  (see
              Programmable Completion below).
       COPROC An  array  variable  (see Arrays below) created to hold the file
              descriptors for output from and input to  an  unnamed  coprocess
              (see Coprocesses above).
       DIRSTACK
              An array variable (see Arrays below) containing the current con-
              tents of the directory stack.  Directories appear in  the  stack
              in  the order they are displayed by the dirs builtin.  Assigning
              to members of this array variable may be used to modify directo-
              ries  already in the stack, but the pushd and popd builtins must
              be used to add and remove directories.  Assignment to this vari-
              able  will not change the current directory.  If DIRSTACK is un-
              set, it loses its special properties, even if it is subsequently
              reset.
       EUID   Expands  to  the effective user ID of the current user, initial-
              ized at shell startup.  This variable is readonly.
       FUNCNAME
              An array variable containing the names of  all  shell  functions
              currently in the execution call stack.  The element with index 0
              is the name of any currently-executing shell function.  The bot-
              tom-most  element  (the  one  with the highest index) is "main".
              This variable exists only when a shell  function  is  executing.
              Assignments  to  FUNCNAME have no effect.  If FUNCNAME is unset,
              it loses its special properties, even if it is subsequently  re-
              set.

              This  variable  can  be  used  with BASH_LINENO and BASH_SOURCE.
              Each  element  of  FUNCNAME  has   corresponding   elements   in
              BASH_LINENO and BASH_SOURCE to describe the call stack.  For in-
              stance,   ${FUNCNAME[$i]}   was    called    from    the    file
              ${BASH_SOURCE[$i+1]}  at  line  number  ${BASH_LINENO[$i]}.  The
              caller builtin displays the current call stack using this infor-
              mation.
       GROUPS An  array  variable  containing  the list of groups of which the
              current user is a member.  Assignments to GROUPS have no effect.
              If  GROUPS is unset, it loses its special properties, even if it
              is subsequently reset.
       HISTCMD
              The history number, or index in the history list, of the current
              command.   If HISTCMD is unset, it loses its special properties,
              even if it is subsequently reset.
       HOSTNAME
              Automatically set to the name of the current host.
       HOSTTYPE
              Automatically set to a string that uniquely describes  the  type
              of  machine  on which bash is executing.  The default is system-
              dependent.
       LINENO Each time this parameter is referenced, the shell substitutes  a
              decimal  number  representing the current sequential line number
              (starting with 1) within a script or function.  When  not  in  a
              script  or  function, the value substituted is not guaranteed to
              be meaningful.  If LINENO is unset, it loses its special proper-
              ties, even if it is subsequently reset.
       MACHTYPE
              Automatically  set  to  a string that fully describes the system
              type on which bash is executing, in the  standard  GNU  cpu-com-
              pany-system format.  The default is system-dependent.
       MAPFILE
              An  array  variable  (see Arrays below) created to hold the text
              read by the mapfile builtin when no variable name is supplied.
       OLDPWD The previous working directory as set by the cd command.
       OPTARG The value of the last option argument processed by  the  getopts
              builtin command (see SHELL BUILTIN COMMANDS below).
       OPTIND The  index  of  the next argument to be processed by the getopts
              builtin command (see SHELL BUILTIN COMMANDS below).
       OSTYPE Automatically set to a string that describes the operating  sys-
              tem  on  which  bash is executing.  The default is system-depen-
              dent.
       PIPESTATUS
              An array variable (see Arrays below) containing a list  of  exit
              status  values  from the processes in the most-recently-executed
              foreground pipeline (which may contain only a single command).
       PPID   The process ID of the shell's parent.  This  variable  is  read-
              only.
       PWD    The current working directory as set by the cd command.
       RANDOM Each time this parameter is referenced, a random integer between
              0 and 32767 is generated.  The sequence of random numbers may be
              initialized by assigning a value to RANDOM.  If RANDOM is unset,
              it loses its special properties, even if it is subsequently  re-
              set.
       READLINE_LINE
              The contents of the readline line buffer, for use with "bind -x"
              (see SHELL BUILTIN COMMANDS below).
       READLINE_POINT
              The position of the insertion point in the readline line buffer,
              for use with "bind -x" (see SHELL BUILTIN COMMANDS below).
       REPLY  Set  to  the line of input read by the read builtin command when
              no arguments are supplied.
       SECONDS
              Each time this parameter is referenced, the  number  of  seconds
              since  shell  invocation is returned.  If a value is assigned to
              SECONDS, the value returned upon subsequent  references  is  the
              number  of seconds since the assignment plus the value assigned.
              If SECONDS is unset, it loses its special properties, even if it
              is subsequently reset.
       SHELLOPTS
              A  colon-separated  list of enabled shell options.  Each word in
              the list is a valid argument  for  the  -o  option  to  the  set
              builtin command (see SHELL BUILTIN COMMANDS below).  The options
              appearing in SHELLOPTS are those reported as on by set  -o.   If
              this  variable  is  in the environment when bash starts up, each
              shell option in the list will  be  enabled  before  reading  any
              startup files.  This variable is read-only.
       SHLVL  Incremented by one each time an instance of bash is started.
       UID    Expands to the user ID of the current user, initialized at shell
              startup.  This variable is readonly.

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

       BASH_COMPAT
              The  value  is used to set the shell's compatibility level.  See
              the description of the shopt builtin below under  SHELL  BUILTIN
              COMMANDS  for  a description of the various compatibility levels
              and their effects.  The value may be  a  decimal  number  (e.g.,
              4.2)  or an integer (e.g., 42) corresponding to the desired com-
              patibility level.  If BASH_COMPAT is unset or set to  the  empty
              string,  the  compatibility  level is set to the default for the
              current version.  If BASH_COMPAT is set to a value that  is  not
              one of the valid compatibility levels, the shell prints an error
              message and sets the compatibility level to the default for  the
              current  version.   The valid compatibility levels correspond to
              the compatibility options accepted  by  the  shopt  builtin  de-
              scribed  below  (for example, compat42 means that 4.2 and 42 are
              valid values).  The current version is also a valid value.
       BASH_ENV
              If this parameter is set when bash is executing a shell  script,
              its  value  is  interpreted as a filename containing commands to
              initialize the shell, as in ~/.bashrc.  The value of BASH_ENV is
              subjected  to  parameter  expansion,  command  substitution, and
              arithmetic expansion before being  interpreted  as  a  filename.
              PATH is not used to search for the resultant filename.
       BASH_XTRACEFD
              If  set  to an integer corresponding to a valid file descriptor,
              bash will write the trace output generated when set  -x  is  en-
              abled  to  that  file descriptor.  The file descriptor is closed
              when BASH_XTRACEFD is unset or assigned a new value.   Unsetting
              BASH_XTRACEFD  or assigning it the empty string causes the trace
              output to be sent to the  standard  error.   Note  that  setting
              BASH_XTRACEFD to 2 (the standard error file descriptor) and then
              unsetting it will result in the standard error being closed.
       CDPATH The search path for the cd command.  This is  a  colon-separated
              list of directories in which the shell looks for destination di-
              rectories specified by  the  cd  command.   A  sample  value  is
              ".:~:/usr".
       CHILD_MAX
              Set  the  number  of exited child status values for the shell to
              remember.  Bash will not allow this value to be decreased  below
              a  POSIX-mandated  minimum,  and  there is a maximum value (cur-
              rently 8192) that this may not exceed.   The  minimum  value  is
              system-dependent.
       COLUMNS
              Used  by  the  select compound command to determine the terminal
              width when printing selection lists.  Automatically set  if  the
              checkwinsize  option  is enabled or in an interactive shell upon
              receipt of a SIGWINCH.
       COMPREPLY
              An array variable from which bash reads the possible completions
              generated  by  a shell function invoked by the programmable com-
              pletion facility (see Programmable Completion below).  Each  ar-
              ray element contains one possible completion.
       EMACS  If  bash  finds  this variable in the environment when the shell
              starts with value "t", it assumes that the shell is  running  in
              an Emacs shell buffer and disables line editing.
       ENV    Similar  to  BASH_ENV;  used  when the shell is invoked in POSIX
              mode.
       EXECIGNORE
              A colon-separated list of shell patterns (see Pattern  Matching)
              defining  the  list of filenames to be ignored by command search
              using PATH.  Files whose full pathnames match one of these  pat-
              terns  are  not  considered executable files for the purposes of
              completion and command execution via PATH lookup.  This does not
              affect the behavior of the [, test, and [[ commands.  Full path-
              names in the command hash table are not subject  to  EXECIGNORE.
              Use  this  variable to ignore shared library files that have the
              executable bit set, but are not executable files.   The  pattern
              matching honors the setting of the extglob shell option.
       FCEDIT The default editor for the fc builtin command.
       FIGNORE
              A  colon-separated  list  of  suffixes to ignore when performing
              filename completion (see READLINE below).  A filename whose suf-
              fix  matches  one of the entries in FIGNORE is excluded from the
              list of matched filenames.  A sample value is ".o:~" (Quoting is
              needed  when  assigning a value to this variable, which contains
              tildes).
       FUNCNEST
              If set to a numeric value greater  than  0,  defines  a  maximum
              function  nesting  level.  Function invocations that exceed this
              nesting level will cause the current command to abort.
       GLOBIGNORE
              A colon-separated list of patterns defining the set of filenames
              to be ignored by pathname expansion.  If a filename matched by a
              pathname expansion pattern also matches one of the  patterns  in
              GLOBIGNORE, it is removed from the list of matches.
       HISTCONTROL
              A  colon-separated  list  of values controlling how commands are
              saved on the history list.  If the list of values  includes  ig-
              norespace,  lines  which  begin  with  a space character are not
              saved in the history list.  A value of ignoredups  causes  lines
              matching the previous history entry to not be saved.  A value of
              ignoreboth is shorthand for ignorespace and ignoredups.  A value
              of erasedups causes all previous lines matching the current line
              to be removed from the history list before that line  is  saved.
              Any  value  not in the above list is ignored.  If HISTCONTROL is
              unset, or does not include a valid value, all lines read by  the
              shell parser are saved on the history list, subject to the value
              of HISTIGNORE.  The second and subsequent lines of a  multi-line
              compound  command  are  not tested, and are added to the history
              regardless of the value of HISTCONTROL.
       HISTFILE
              The name of the file in which command history is saved (see HIS-
              TORY  below).   The default value is ~/.bash_history.  If unset,
              the command history is not saved when a shell exits.
       HISTFILESIZE
              The maximum number of lines contained in the history file.  When
              this  variable  is  assigned  a value, the history file is trun-
              cated, if necessary, to contain no  more  than  that  number  of
              lines  by removing the oldest entries.  The history file is also
              truncated to this size after writing it when a shell exits.   If
              the  value  is  0,  the  history file is truncated to zero size.
              Non-numeric values and numeric values  less  than  zero  inhibit
              truncation.   The  shell  sets the default value to the value of
              HISTSIZE after reading any startup files.
       HISTIGNORE
              A colon-separated list of patterns used to decide which  command
              lines  should be saved on the history list.  Each pattern is an-
              chored at the beginning of the line and must match the  complete
              line  (no  implicit  `*'  is  appended).  Each pattern is tested
              against the line after the checks specified by  HISTCONTROL  are
              applied.  In addition to the normal shell pattern matching char-
              acters, `&' matches the previous history line.  `&' may  be  es-
              caped  using  a  backslash;  the backslash is removed before at-
              tempting a match.  The second and subsequent lines of  a  multi-
              line  compound command are not tested, and are added to the his-
              tory regardless of the value of HISTIGNORE.  The pattern  match-
              ing honors the setting of the extglob shell option.
       HISTSIZE
              The  number  of commands to remember in the command history (see
              HISTORY below).  If the value is 0, commands are  not  saved  in
              the history list.  Numeric values less than zero result in every
              command being saved on the history list  (there  is  no  limit).
              The  shell  sets  the  default  value  to  500 after reading any
              startup files.
       HISTTIMEFORMAT
              If this variable is set and not null, its value  is  used  as  a
              format string for strftime(3) to print the time stamp associated
              with each history entry displayed by the  history  builtin.   If
              this  variable  is  set,  time stamps are written to the history
              file so they may be preserved across shell sessions.  This  uses
              the  history  comment  character  to distinguish timestamps from
              other history lines.
       HOME   The home directory of the current user; the default argument for
              the cd builtin command.  The value of this variable is also used
              when performing tilde expansion.
       HOSTFILE
              Contains the name of a file in the  same  format  as  /etc/hosts
              that should be read when the shell needs to complete a hostname.
              The list of possible hostname completions may be  changed  while
              the  shell  is running; the next time hostname completion is at-
              tempted after the value is changed, bash adds  the  contents  of
              the  new file to the existing list.  If HOSTFILE is set, but has
              no value, or does not name a readable  file,  bash  attempts  to
              read  /etc/hosts to obtain the list of possible hostname comple-
              tions.  When HOSTFILE is unset, the hostname list is cleared.
       IFS    The Internal Field Separator that is used for word splitting af-
              ter  expansion  and  to  split  lines  into  words with the read
              builtin  command.   The  default  value  is  ``<space><tab><new-
              line>''.
       IGNOREEOF
              Controls the action of an interactive shell on receipt of an EOF
              character as the sole input.  If set, the value is the number of
              consecutive  EOF  characters  which  must  be typed as the first
              characters on an input line before bash exits.  If the  variable
              exists  but  does not have a numeric value, or has no value, the
              default value is 10.  If it does not exist,  EOF  signifies  the
              end of input to the shell.
       INPUTRC
              The  filename  for the readline startup file, overriding the de-
              fault of ~/.inputrc (see READLINE below).
       LANG   Used to determine the  locale  category  for  any  category  not
              specifically selected with a variable starting with LC_.
       LC_ALL This  variable  overrides  the  value  of LANG and any other LC_
              variable specifying a locale category.
       LC_COLLATE
              This variable determines the collation order used  when  sorting
              the  results  of pathname expansion, and determines the behavior
              of range expressions, equivalence  classes,  and  collating  se-
              quences within pathname expansion and pattern matching.
       LC_CTYPE
              This  variable  determines  the interpretation of characters and
              the behavior of character classes within pathname expansion  and
              pattern matching.
       LC_MESSAGES
              This  variable  determines  the locale used to translate double-
              quoted strings preceded by a $.
       LC_NUMERIC
              This variable determines the locale  category  used  for  number
              formatting.
       LC_TIME
              This  variable  determines the locale category used for data and
              time formatting.
       LINES  Used by the select compound  command  to  determine  the  column
              length  for  printing selection lists.  Automatically set if the
              checkwinsize option is enabled or in an interactive  shell  upon
              receipt of a SIGWINCH.
       MAIL   If  this  parameter  is  set to a file or directory name and the
              MAILPATH variable is not set, bash informs the user of  the  ar-
              rival of mail in the specified file or Maildir-format directory.
       MAILCHECK
              Specifies  how often (in seconds) bash checks for mail.  The de-
              fault is 60 seconds.  When it is time to  check  for  mail,  the
              shell  does  so  before  displaying the primary prompt.  If this
              variable is unset, or set to  a  value  that  is  not  a  number
              greater than or equal to zero, the shell disables mail checking.
       MAILPATH
              A colon-separated list of filenames to be checked for mail.  The
              message to be printed when mail arrives in a particular file may
              be  specified by separating the filename from the message with a
              `?'.  When used in the text of the message, $_  expands  to  the
              name of the current mailfile.  Example:
              MAILPATH='/var/mail/bfox?"You  have  mail":~/shell-mail?"$_  has
              mail!"'
              Bash can be configured to supply a default value for this  vari-
              able  (there  is  no  value by default), but the location of the
              user  mail  files  that  it  uses  is  system  dependent  (e.g.,
              /var/mail/$USER).
       OPTERR If set to the value 1, bash displays error messages generated by
              the getopts builtin command (see SHELL BUILTIN COMMANDS  below).
              OPTERR  is  initialized to 1 each time the shell is invoked or a
              shell script is executed.
       PATH   The search path for commands.  It is a colon-separated  list  of
              directories  in  which the shell looks for commands (see COMMAND
              EXECUTION below).  A zero-length (null) directory  name  in  the
              value of PATH indicates the current directory.  A null directory
              name may appear as two adjacent colons,  or  as  an  initial  or
              trailing  colon.   The  default path is system-dependent, and is
              set by the administrator who installs bash.  A common value is
              ``/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:
              /sbin''.
       POSIXLY_CORRECT
              If this variable is in the environment  when  bash  starts,  the
              shell  enters posix mode before reading the startup files, as if
              the --posix invocation option had been supplied.  If it  is  set
              while  the  shell is running, bash enables posix mode, as if the
              command set -o posix had been executed.
       PROMPT_COMMAND
              If set, the value is executed as a command prior to issuing each
              primary prompt.

       PROMPT_DIRTRIM
              If  set  to a number greater than zero, the value is used as the
              number of trailing directory components to retain when expanding
              the  \w  and  \W  prompt  string  escapes (see PROMPTING below).
              Characters removed are replaced with an ellipsis.
       PS0    The value of this parameter is expanded  (see  PROMPTING  below)
              and  displayed by interactive shells after reading a command and
              before the command is executed.
       PS1    The value of this parameter is expanded  (see  PROMPTING  below)
              and  used  as  the  primary prompt string.  The default value is
              ``\s-\v\$ ''.
       PS2    The value of this parameter is expanded as with PS1 and used  as
              the secondary prompt string.  The default is ``> ''.
       PS3    The value of this parameter is used as the prompt for the select
              command (see SHELL GRAMMAR above).
       PS4    The value of this parameter is expanded  as  with  PS1  and  the
              value is printed before each command bash displays during an ex-
              ecution trace.  The first character of PS4 is replicated  multi-
              ple times, as necessary, to indicate multiple levels of indirec-
              tion.  The default is ``+ ''.
       SHELL  The full pathname to the shell is kept in this environment vari-
              able.   If  it is not set when the shell starts, bash assigns to
              it the full pathname of the current user's login shell.
       TIMEFORMAT
              The value of this parameter is used as a format string  specify-
              ing  how  the timing information for pipelines prefixed with the
              time reserved word should be displayed.  The % character  intro-
              duces  an  escape  sequence  that is expanded to a time value or
              other information.  The escape sequences and their meanings  are
              as follows; the braces denote optional portions.
              %%        A literal %.
              %[p][l]R  The elapsed time in seconds.
              %[p][l]U  The number of CPU seconds spent in user mode.
              %[p][l]S  The number of CPU seconds spent in system mode.
              %P        The CPU percentage, computed as (%U + %S) / %R.

              The  optional  p is a digit specifying the precision, the number
              of fractional digits after a decimal point.  A value of 0 causes
              no decimal point or fraction to be output.  At most three places
              after the decimal point may be specified; values  of  p  greater
              than  3 are changed to 3.  If p is not specified, the value 3 is
              used.

              The optional l specifies a longer format, including minutes,  of
              the  form  MMmSS.FFs.   The value of p determines whether or not
              the fraction is included.

              If this variable is not set, bash acts as if it  had  the  value
              $'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'.   If  the value is null,
              no timing information is displayed.  A trailing newline is added
              when the format string is displayed.
       TMOUT  If set to a value greater than zero, TMOUT is treated as the de-
              fault timeout for the read builtin.  The select  command  termi-
              nates if input does not arrive after TMOUT seconds when input is
              coming from a terminal.  In an interactive shell, the  value  is
              interpreted as the number of seconds to wait for a line of input
              after issuing the primary prompt.  Bash terminates after waiting
              for  that number of seconds if a complete line of input does not
              arrive.
       TMPDIR If set, bash uses its value as the name of a directory in  which
              bash creates temporary files for the shell's use.
       auto_resume
              This variable controls how the shell interacts with the user and
              job control.  If this variable is set, single word  simple  com-
              mands without redirections are treated as candidates for resump-
              tion of an existing stopped job.  There is no ambiguity allowed;
              if  there  is more than one job beginning with the string typed,
              the job most recently accessed  is  selected.   The  name  of  a
              stopped  job, in this context, is the command line used to start
              it.  If set to the value exact, the string supplied  must  match
              the  name  of  a  stopped  job exactly; if set to substring, the
              string supplied needs to match a substring  of  the  name  of  a
              stopped  job.  The substring value provides functionality analo-
              gous to the %?  job identifier (see JOB CONTROL below).  If  set
              to  any  other  value, the supplied string must be a prefix of a
              stopped job's name; this provides functionality analogous to the
              %string job identifier.
       histchars
              The  two or three characters which control history expansion and
              tokenization (see HISTORY EXPANSION below).  The first character
              is  the history expansion character, the character which signals
              the start of a history  expansion,  normally  `!'.   The  second
              character  is the quick substitution character, which is used as
              shorthand for re-running the previous command  entered,  substi-
              tuting  one  string  for another in the command.  The default is
              `^'.  The optional third character is the character which  indi-
              cates  that the remainder of the line is a comment when found as
              the first character of a word, normally `#'.  The  history  com-
              ment character causes history substitution to be skipped for the
              remaining words on the line.  It does not necessarily cause  the
              shell parser to treat the rest of the line as a comment.

   Arrays
       Bash  provides one-dimensional indexed and associative array variables.
       Any variable may be used as an indexed array; the declare builtin  will
       explicitly  declare an array.  There is no maximum limit on the size of
       an array, nor any requirement that members be indexed or assigned  con-
       tiguously.   Indexed  arrays  are  referenced using integers (including
       arithmetic expressions) and are zero-based; associative arrays are ref-
       erenced using arbitrary strings.  Unless otherwise noted, indexed array
       indices must be non-negative integers.

       An indexed array is created automatically if any variable  is  assigned
       to using the syntax name[subscript]=value.  The subscript is treated as
       an arithmetic expression that must evaluate to a number.  To explicitly
       declare  an  indexed array, use declare -a name (see SHELL BUILTIN COM-
       MANDS below).  declare -a name[subscript] is also  accepted;  the  sub-
       script is ignored.

       Associative arrays are created using declare -A name.

       Attributes may be specified for an array variable using the declare and
       readonly builtins.  Each attribute applies to all members of an array.

       Arrays  are  assigned  to  using  compound  assignments  of  the   form
       name=(value1  ...  valuen),  where  each  value  is  of  the form [sub-
       script]=string.  Indexed array assignments do not require anything  but
       string.  When assigning to indexed arrays, if the optional brackets and
       subscript are supplied, that index is assigned to; otherwise the  index
       of  the element assigned is the last index assigned to by the statement
       plus one.  Indexing starts at zero.

       When assigning to an associative array, the subscript is required.

       This syntax is also accepted by the declare builtin.  Individual  array
       elements  may be assigned to using the name[subscript]=value syntax in-
       troduced above.  When assigning to an indexed array, if  name  is  sub-
       scripted  by  a negative number, that number is interpreted as relative
       to one greater than the maximum index  of  name,  so  negative  indices
       count back from the end of the array, and an index of -1 references the
       last element.

       Any element of an array may  be  referenced  using  ${name[subscript]}.
       The braces are required to avoid conflicts with pathname expansion.  If
       subscript is @ or *, the word expands to all members  of  name.   These
       subscripts  differ only when the word appears within double quotes.  If
       the word is double-quoted, ${name[*]} expands to a single word with the
       value  of each array member separated by the first character of the IFS
       special variable, and ${name[@]} expands each element of name to a sep-
       arate  word.   When  there  are no array members, ${name[@]} expands to
       nothing.  If the double-quoted expansion occurs within a word, the  ex-
       pansion of the first parameter is joined with the beginning part of the
       original word, and the expansion of the last parameter is  joined  with
       the last part of the original word.  This is analogous to the expansion
       of the special parameters *  and  @  (see  Special  Parameters  above).
       ${#name[subscript]}  expands  to  the length of ${name[subscript]}.  If
       subscript is * or @, the expansion is the number of elements in the ar-
       ray.  If the subscript used to reference an element of an indexed array
       evaluates to a number less than zero, it is interpreted as relative  to
       one  greater  than  the maximum index of the array, so negative indices
       count back from the end of the array, and an index of -1 references the
       last element.

       Referencing an array variable without a subscript is equivalent to ref-
       erencing the array with a subscript of 0.  Any reference to a  variable
       using a valid subscript is legal, and bash will create an array if nec-
       essary.

       An array variable is considered set if a subscript has been assigned  a
       value.  The null string is a valid value.

       It  is possible to obtain the keys (indices) of an array as well as the
       values.  ${!name[@]} and ${!name[*]} expand to the indices assigned  in
       array variable name.  The treatment when in double quotes is similar to
       the expansion of the special parameters @ and * within double quotes.

       The unset builtin is used to destroy arrays.  unset name[subscript] de-
       stroys  the  array  element at index subscript.  Negative subscripts to
       indexed arrays are interpreted as described above.  Care must be  taken
       to  avoid  unwanted  side  effects caused by pathname expansion.  unset
       name, where name is an array, or unset name[subscript], where subscript
       is * or @, removes the entire array.

       The  declare,  local,  and readonly builtins each accept a -a option to
       specify an indexed array and a -A option to specify an associative  ar-
       ray.   If  both  options  are  supplied, -A takes precedence.  The read
       builtin accepts a -a option to assign a list of  words  read  from  the
       standard input to an array.  The set and declare builtins display array
       values in a way that allows them to be reused as assignments.

EXPANSION
       Expansion is performed on the command line after it has been split into
       words.   There are seven kinds of expansion performed: brace expansion,
       tilde expansion, parameter and variable  expansion,  command  substitu-
       tion, arithmetic expansion, word splitting, and pathname expansion.

       The order of expansions is: brace expansion; tilde expansion, parameter
       and variable expansion, arithmetic expansion, and command  substitution
       (done  in a left-to-right fashion); word splitting; and pathname expan-
       sion.

       On systems that can support it, there is an additional expansion avail-
       able:  process  substitution.   This  is  performed at the same time as
       tilde, parameter, variable, and arithmetic expansion and  command  sub-
       stitution.

       After  these  expansions are performed, quote characters present in the
       original word are removed  unless  they  have  been  quoted  themselves
       (quote removal).

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

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

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

       A  sequence expression takes the form {x..y[..incr]}, where x and y are
       either integers or single characters, and incr, an optional  increment,
       is  an  integer.  When integers are supplied, the expression expands to
       each number between x and y, inclusive.  Supplied integers may be  pre-
       fixed  with 0 to force each term to have the same width.  When either x
       or y begins with a zero, the shell  attempts  to  force  all  generated
       terms  to  contain the same number of digits, zero-padding where neces-
       sary.  When characters are supplied, the  expression  expands  to  each
       character  lexicographically  between x and y, inclusive, using the de-
       fault C locale.  Note that both x and y must be of the same type.  When
       the  increment  is  supplied, it is used as the difference between each
       term.  The default increment is 1 or -1 as appropriate.

       Brace expansion is performed before any other expansions, and any char-
       acters  special to other expansions are preserved in the result.  It is
       strictly textual.  Bash does not apply any syntactic interpretation  to
       the context of the expansion or the text between the braces.

       A  correctly-formed  brace  expansion must contain unquoted opening and
       closing braces, and at least one unquoted comma or a valid sequence ex-
       pression.  Any incorrectly formed brace expansion is left unchanged.  A
       { or , may be quoted with a backslash to prevent its  being  considered
       part  of  a brace expression.  To avoid conflicts with parameter expan-
       sion, the string ${ is not considered eligible for brace expansion.

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

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

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

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

       If the tilde-prefix is a `~+', the value of the shell variable PWD  re-
       places  the  tilde-prefix.  If the tilde-prefix is a `~-', the value of
       the shell variable OLDPWD, if it is set, is substituted.  If the  char-
       acters  following  the tilde in the tilde-prefix consist of a number N,
       optionally prefixed by a `+' or a `-',  the  tilde-prefix  is  replaced
       with the corresponding element from the directory stack, as it would be
       displayed by the dirs builtin invoked with the tilde-prefix as an argu-
       ment.   If  the characters following the tilde in the tilde-prefix con-
       sist of a number without a leading `+' or `-', `+' is assumed.

       If the login name is invalid, or the tilde expansion fails, the word is
       unchanged.

       Each variable assignment is checked for unquoted tilde-prefixes immedi-
       ately following a : or the first =.  In these cases, tilde expansion is
       also performed.  Consequently, one may use filenames with tildes in as-
       signments to PATH, MAILPATH, and CDPATH, and the shell assigns the  ex-
       panded value.

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

       When  braces  are  used, the matching ending brace is the first `}' not
       escaped by a backslash or within a quoted string, and not within an em-
       bedded  arithmetic expansion, command substitution, or parameter expan-
       sion.

       ${parameter}
              The value of parameter is substituted.  The braces are  required
              when  parameter  is  a  positional  parameter with more than one
              digit, or when parameter is followed by a character which is not
              to be interpreted as part of its name.  The parameter is a shell
              parameter as described above PARAMETERS) or an  array  reference
              (Arrays).

       If  the  first  character of parameter is an exclamation point (!), and
       parameter is not a nameref, it introduces a level of variable  indirec-
       tion.   Bash uses the value of the variable formed from the rest of pa-
       rameter as the name of the variable; this variable is then expanded and
       that  value  is  used  in the rest of the substitution, rather than the
       value of parameter itself.  This is known as  indirect  expansion.   If
       parameter is a nameref, this expands to the name of the variable refer-
       enced by parameter instead of performing the complete  indirect  expan-
       sion.   The  exceptions  to  this are the expansions of ${!prefix*} and
       ${!name[@]} described below.  The exclamation  point  must  immediately
       follow the left brace in order to introduce indirection.

       In each of the cases below, word is subject to tilde expansion, parame-
       ter expansion, command substitution, and arithmetic expansion.

       When not performing substring expansion, using the forms documented be-
       low  (e.g.,  :-),  bash  tests  for  a parameter that is unset or null.
       Omitting the colon results in a test only for a parameter that  is  un-
       set.

       ${parameter:-word}
              Use  Default  Values.  If parameter is unset or null, the expan-
              sion of word is substituted.  Otherwise, the value of  parameter
              is substituted.
       ${parameter:=word}
              Assign  Default  Values.  If parameter is unset or null, the ex-
              pansion of word is assigned to parameter.  The value of  parame-
              ter  is then substituted.  Positional parameters and special pa-
              rameters may not be assigned to in this way.
       ${parameter:?word}
              Display Error if Null or Unset.  If parameter is null or  unset,
              the  expansion  of  word (or a message to that effect if word is
              not present) is written to the standard error and the shell,  if
              it is not interactive, exits.  Otherwise, the value of parameter
              is substituted.
       ${parameter:+word}
              Use Alternate Value.  If parameter is null or unset, nothing  is
              substituted, otherwise the expansion of word is substituted.
       ${parameter:offset}
       ${parameter:offset:length}
              Substring  Expansion.  Expands to up to length characters of the
              value of parameter starting at the character specified  by  off-
              set.  If parameter is @, an indexed array subscripted by @ or *,
              or an associative array name, the results  differ  as  described
              below.   If  length  is omitted, expands to the substring of the
              value of parameter starting at the character specified by offset
              and  extending  to  the end of the value.  length and offset are
              arithmetic expressions (see ARITHMETIC EVALUATION below).

              If offset evaluates to a number less than  zero,  the  value  is
              used as an offset in characters from the end of the value of pa-
              rameter.  If length evaluates to a number less than zero, it  is
              interpreted as an offset in characters from the end of the value
              of parameter rather than a number of characters, and the  expan-
              sion  is  the  characters  between offset and that result.  Note
              that a negative offset must be separated from the  colon  by  at
              least one space to avoid being confused with the :- expansion.

              If  parameter  is  @, the result is length positional parameters
              beginning at offset.  A negative offset is taken relative to one
              greater  than the greatest positional parameter, so an offset of
              -1 evaluates to the last positional parameter.  It is an  expan-
              sion error if length evaluates to a number less than zero.

              If parameter is an indexed array name subscripted by @ or *, the
              result is the length members of the array beginning  with  ${pa-
              rameter[offset]}.   A  negative  offset is taken relative to one
              greater than the maximum index of the specified array.  It is an
              expansion error if length evaluates to a number less than zero.

              Substring expansion applied to an associative array produces un-
              defined results.

              Substring indexing is zero-based unless the  positional  parame-
              ters  are  used,  in  which case the indexing starts at 1 by de-
              fault.  If offset is 0, and the positional parameters are  used,
              $0 is prefixed to the list.

       ${!prefix*}
       ${!prefix@}
              Names  matching prefix.  Expands to the names of variables whose
              names begin with prefix, separated by the first character of the
              IFS  special variable.  When @ is used and the expansion appears
              within double quotes, each variable name expands to  a  separate
              word.

       ${!name[@]}
       ${!name[*]}
              List  of  array  keys.  If name is an array variable, expands to
              the list of array indices (keys) assigned in name.  If  name  is
              not  an  array,  expands to 0 if name is set and null otherwise.
              When @ is used and the expansion appears within  double  quotes,
              each key expands to a separate word.

       ${#parameter}
              Parameter  length.  The length in characters of the value of pa-
              rameter is substituted.  If parameter is * or @, the value  sub-
              stituted  is  the number of positional parameters.  If parameter
              is an array name subscripted by * or @, the value substituted is
              the number of elements in the array.  If parameter is an indexed
              array name subscripted by a negative number, that number is  in-
              terpreted  as  relative to one greater than the maximum index of
              parameter, so negative indices count back from the  end  of  the
              array, and an index of -1 references the last element.

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

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

       ${parameter/pattern/string}
              Pattern substitution.  The pattern is expanded to produce a pat-
              tern just as in pathname expansion.  Parameter is  expanded  and
              the  longest match of pattern against its value is replaced with
              string.  If pattern begins with /, all matches  of  pattern  are
              replaced  with  string.   Normally  only  the first match is re-
              placed.  If pattern begins with #, it must match at  the  begin-
              ning of the expanded value of parameter.  If pattern begins with
              %, it must match at the end of the expanded value of  parameter.
              If string is null, matches of pattern are deleted and the / fol-
              lowing pattern may be omitted.  If the nocasematch shell  option
              is enabled, the match is performed without regard to the case of
              alphabetic characters.  If parameter is @ or *, the substitution
              operation  is  applied to each positional parameter in turn, and
              the expansion is the resultant list.  If parameter is  an  array
              variable  subscripted with @ or *, the substitution operation is
              applied to each member of the array in turn, and  the  expansion
              is the resultant list.

       ${parameter^pattern}
       ${parameter^^pattern}
       ${parameter,pattern}
       ${parameter,,pattern}
              Case  modification.   This expansion modifies the case of alpha-
              betic characters in parameter.  The pattern is expanded to  pro-
              duce a pattern just as in pathname expansion.  Each character in
              the expanded value of parameter is tested against pattern,  and,
              if  it  matches the pattern, its case is converted.  The pattern
              should not attempt to match more than one character.  The ^  op-
              erator converts lowercase letters matching pattern to uppercase;
              the , operator converts matching uppercase letters to lowercase.
              The  ^^  and ,, expansions convert each matched character in the
              expanded value; the ^ and , expansions match  and  convert  only
              the  first character in the expanded value.  If pattern is omit-
              ted, it is treated like a ?, which matches every character.   If
              parameter  is @ or *, the case modification operation is applied
              to each positional parameter in turn, and the expansion  is  the
              resultant  list.   If parameter is an array variable subscripted
              with @ or *, the case modification operation is applied to  each
              member  of the array in turn, and the expansion is the resultant
              list.

       ${parameter@operator}
              Parameter transformation.  The expansion is either a transforma-
              tion  of  the  value of parameter or information about parameter
              itself, depending on the value of operator.  Each operator is  a
              single letter:

              Q      The  expansion is a string that is the value of parameter
                     quoted in a format that can be reused as input.
              E      The expansion is a string that is the value of  parameter
                     with  backslash  escape  sequences  expanded  as with the
                     $'...' quoting mechansim.
              P      The expansion is a string that is the result of expanding
                     the value of parameter as if it were a prompt string (see
                     PROMPTING below).
              A      The expansion is a string in the form  of  an  assignment
                     statement  or  declare  command  that, if evaluated, will
                     recreate parameter with its attributes and value.
              a      The expansion is a string consisting of flag values  rep-
                     resenting parameter's attributes.

              If  parameter  is @ or *, the operation is applied to each posi-
              tional parameter in turn, and the  expansion  is  the  resultant
              list.   If  parameter is an array variable subscripted with @ or
              *, the case modification operation is applied to each member  of
              the array in turn, and the expansion is the resultant list.

              The  result  of  the  expansion is subject to word splitting and
              pathname expansion as described below.

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

              $(command)
       or
              `command`

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

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

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

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

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

              $((expression))

       The old format $[expression] is deprecated and will be removed  in  up-
       coming versions of bash.

       The  expression  is  treated  as if it were within double quotes, but a
       double quote inside the parentheses is not treated specially.  All  to-
       kens  in  the expression undergo parameter and variable expansion, com-
       mand substitution, and quote removal.  The result  is  treated  as  the
       arithmetic  expression  to  be evaluated.  Arithmetic expansions may be
       nested.

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

   Process Substitution
       Process substitution allows a process's input or output to be  referred
       to  using  a  filename.   It takes the form of <(list) or >(list).  The
       process list is run asynchronously, and its input or output appears  as
       a filename.  This filename is passed as an argument to the current com-
       mand as the result of the expansion.  If  the  >(list)  form  is  used,
       writing  to  the file will provide input for list.  If the <(list) form
       is used, the file passed as an argument should be read  to  obtain  the
       output of list.  Process substitution is supported on systems that sup-
       port named pipes (FIFOs) or the /dev/fd method of naming open files.

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

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

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

       Explicit  null arguments ("" or '') are retained and passed to commands
       as empty strings.  Unquoted implicit null arguments, resulting from the
       expansion of parameters that have no values, are removed.  If a parame-
       ter with no value is expanded within double quotes, a null argument re-
       sults and is retained and passed to a command as an empty string.  When
       a quoted null argument appears as part of a  word  whose  expansion  is
       non-null, the null argument is removed.  That is, the word -d'' becomes
       -d after word splitting and null argument removal.

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

   Pathname Expansion
       After word splitting, unless the -f option has  been  set,  bash  scans
       each  word  for the characters *, ?, and [.  If one of these characters
       appears, then the word is regarded as a pattern, and replaced  with  an
       alphabetically  sorted list of filenames matching the pattern (see Pat-
       tern Matching below).  If no matching  filenames  are  found,  and  the
       shell  option  nullglob is not enabled, the word is left unchanged.  If
       the nullglob option is set, and no matches are found, the word  is  re-
       moved.   If the failglob shell option is set, and no matches are found,
       an error message is printed and the command is not  executed.   If  the
       shell  option nocaseglob is enabled, the match is performed without re-
       gard to the case of alphabetic characters.  Note that when using  range
       expressions  like  [a-z]  (see below), letters of the other case may be
       included, depending on the setting of LC_COLLATE.  When  a  pattern  is
       used  for  pathname  expansion,  the character ``.''  at the start of a
       name or immediately following a slash must be matched  explicitly,  un-
       less  the  shell  option dotglob is set.  When matching a pathname, the
       slash character must always be matched explicitly.  In other cases, the
       ``.''   character  is  not  treated  specially.  See the description of
       shopt below under SHELL BUILTIN COMMANDS for a description of  the  no-
       caseglob, nullglob, failglob, and dotglob shell options.

       The  GLOBIGNORE shell variable may be used to restrict the set of file-
       names matching a pattern.  If GLOBIGNORE is set, each matching filename
       that also matches one of the patterns in GLOBIGNORE is removed from the
       list of matches.  If the nocaseglob option is set, the matching against
       the  patterns  in  GLOBIGNORE is performed without regard to case.  The
       filenames ``.''  and ``..''  are always ignored when GLOBIGNORE is  set
       and  not null.  However, setting GLOBIGNORE to a non-null value has the
       effect of enabling the dotglob shell option, so all other filenames be-
       ginning  with a ``.''  will match.  To get the old behavior of ignoring
       filenames beginning with a ``.'', make ``.*''  one of the  patterns  in
       GLOBIGNORE.   The  dotglob option is disabled when GLOBIGNORE is unset.
       The pattern matching honors the setting of the extglob shell option.

       Pattern Matching

       Any character that appears in a pattern, other than the special pattern
       characters  described below, matches itself.  The NUL character may not
       occur in a pattern.  A backslash escapes the following  character;  the
       escaping  backslash  is  discarded  when matching.  The special pattern
       characters must be quoted if they are to be matched literally.

       The special pattern characters have the following meanings:

              *      Matches any string, including the null string.  When  the
                     globstar  shell  option  is  enabled,  and * is used in a
                     pathname expansion context, two adjacent  *s  used  as  a
                     single  pattern will match all files and zero or more di-
                     rectories and subdirectories.  If followed by  a  /,  two
                     adjacent  *s  will match only directories and subdirecto-
                     ries.
              ?      Matches any single character.
              [...]  Matches any one of the enclosed characters.   A  pair  of
                     characters  separated by a hyphen denotes a range expres-
                     sion; any character that falls between those two  charac-
                     ters, inclusive, using the current locale's collating se-
                     quence and character set, is matched.  If the first char-
                     acter  following  the [ is a !  or a ^ then any character
                     not enclosed is matched.  The sorting order of characters
                     in  range expressions is determined by the current locale
                     and the values of the LC_COLLATE or  LC_ALL  shell  vari-
                     ables,  if set.  To obtain the traditional interpretation
                     of  range  expressions,  where  [a-d]  is  equivalent  to
                     [abcd],  set  value of the LC_ALL shell variable to C, or
                     enable the globasciiranges shell  option.   A  -  may  be
                     matched by including it as the first or last character in
                     the set.  A ] may be matched by including it as the first
                     character in the set.

                     Within  [ and ], character classes can be specified using
                     the syntax [:class:], where class is one of the following
                     classes defined in the POSIX standard:
                     alnum  alpha  ascii  blank  cntrl digit graph lower print
                     punct space upper word xdigit
                     A character class matches any character belonging to that
                     class.  The word character class matches letters, digits,
                     and the character _.

                     Within [ and ], an equivalence class can be specified us-
                     ing  the  syntax [=c=], which matches all characters with
                     the same collation weight (as defined by the current  lo-
                     cale) as the character c.

                     Within [ and ], the syntax [.symbol.] matches the collat-
                     ing symbol symbol.

       If the extglob shell option is enabled using the shopt builtin, several
       extended  pattern  matching operators are recognized.  In the following
       description, a pattern-list is a list of one or more patterns separated
       by a |.  Composite patterns may be formed using one or more of the fol-
       lowing sub-patterns:

              ?(pattern-list)
                     Matches zero or one occurrence of the given patterns
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns
              +(pattern-list)
                     Matches one or more occurrences of the given patterns
              @(pattern-list)
                     Matches one of the given patterns
              !(pattern-list)
                     Matches anything except one of the given patterns

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

REDIRECTION
       Before a command is executed, its input and output  may  be  redirected
       using  a special notation interpreted by the shell.  Redirection allows
       commands' file handles to be duplicated, opened, closed, made to  refer
       to different files, and can change the files the command reads from and
       writes to.  Redirection may also be used to modify file handles in  the
       current  shell execution environment.  The following redirection opera-
       tors may precede or appear anywhere within a simple command or may fol-
       low  a  command.   Redirections are processed in the order they appear,
       from left to right.

       Each redirection that may be preceded by a file descriptor  number  may
       instead be preceded by a word of the form {varname}.  In this case, for
       each redirection operator except >&- and <&-, the shell will allocate a
       file  descriptor  greater than or equal to 10 and assign it to varname.
       If >&- or <&- is preceded by {varname}, the value  of  varname  defines
       the file descriptor to close.

       In  the  following descriptions, if the file descriptor number is omit-
       ted, and the first character of the redirection operator is <, the  re-
       direction  refers  to  the  standard input (file descriptor 0).  If the
       first character of the  redirection  operator  is  >,  the  redirection
       refers to the standard output (file descriptor 1).

       The  word  following the redirection operator in the following descrip-
       tions, unless otherwise noted, is subjected to brace  expansion,  tilde
       expansion,  parameter  and  variable  expansion,  command substitution,
       arithmetic expansion,  quote  removal,  pathname  expansion,  and  word
       splitting.  If it expands to more than one word, bash reports an error.

       Note  that  the order of redirections is significant.  For example, the
       command

              ls > dirlist 2>&1

       directs both standard output and standard error to  the  file  dirlist,
       while the command

              ls 2>&1 > dirlist

       directs  only the standard output to file dirlist, because the standard
       error was duplicated from the standard output before the standard  out-
       put was redirected to dirlist.

       Bash handles several filenames specially when they are used in redirec-
       tions, as described in the following table.  If the operating system on
       which bash is running provides these special files, bash will use them;
       otherwise it will emulate them internally with the  behavior  described
       below.

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

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

       Redirections using file descriptors greater than 9 should be used  with
       care,  as they may conflict with file descriptors the shell uses inter-
       nally.

       Note that the exec builtin command can make redirections take effect in
       the current shell.

   Redirecting Input
       Redirection of input causes the file whose name results from the expan-
       sion of word to be opened for reading on  file  descriptor  n,  or  the
       standard input (file descriptor 0) if n is not specified.

       The general format for redirecting input is:

              [n]<word

   Redirecting Output
       Redirection  of  output causes the file whose name results from the ex-
       pansion of word to be opened for writing on file descriptor n,  or  the
       standard output (file descriptor 1) if n is not specified.  If the file
       does not exist it is created; if it does exist it is truncated to  zero
       size.

       The general format for redirecting output is:

              [n]>word

       If  the  redirection operator is >, and the noclobber option to the set
       builtin has been enabled, the redirection will fail if the  file  whose
       name  results  from the expansion of word exists and is a regular file.
       If the redirection operator is >|, or the redirection operator is > and
       the noclobber option to the set builtin command is not enabled, the re-
       direction is attempted even if the file named by word exists.

   Appending Redirected Output
       Redirection of output in this fashion causes the file  whose  name  re-
       sults from the expansion of word to be opened for appending on file de-
       scriptor n, or the standard output (file descriptor  1)  if  n  is  not
       specified.  If the file does not exist it is created.

       The general format for appending output is:

              [n]>>word

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

       There  are two formats for redirecting standard output and standard er-
       ror:

              &>word
       and
              >&word

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

              >word 2>&1

       When  using  the second form, word may not expand to a number or -.  If
       it does, other redirection operators apply (see  Duplicating  File  De-
       scriptors below) for compatibility reasons.

   Appending Standard Output and Standard Error
       This  construct allows both the standard output (file descriptor 1) and
       the standard error output (file descriptor 2) to  be  appended  to  the
       file whose name is the expansion of word.

       The format for appending standard output and standard error is:

              &>>word

       This is semantically equivalent to

              >>word 2>&1

       (see Duplicating File Descriptors below).

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

       The format of here-documents is:

              [n]<<[-]word
                      here-document
              delimiter

       No  parameter  and variable expansion, command substitution, arithmetic
       expansion, or pathname expansion is performed on word.  If any part  of
       word  is  quoted, the delimiter is the result of quote removal on word,
       and the lines in the here-document are not expanded.  If  word  is  un-
       quoted,  all  lines of the here-document are subjected to parameter ex-
       pansion, command substitution, and arithmetic expansion, the  character
       sequence \<newline> is ignored, and \ must be used to quote the charac-
       ters \, $, and `.

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

   Here Strings
       A variant of here documents, the format is:

              [n]<<strftime(3) and the result is in-
                     serted into the prompt string; an empty format results in
                     a locale-specific time representation.   The  braces  are
                     required
              \e     an ASCII escape character (033)
              \h     the hostname up to the first `.'
              \H     the hostname
              \j     the number of jobs currently managed by the shell
              \l     the basename of the shell's terminal device name
              \n     newline
              \r     carriage return
              \s     the  name  of  the shell, the basename of $0 (the portion
                     following the final slash)
              \t     the current time in 24-hour HH:MM:SS format
              \T     the current time in 12-hour HH:MM:SS format
              \@     the current time in 12-hour am/pm format
              \A     the current time in 24-hour HH:MM format
              \u     the username of the current user
              \v     the version of bash (e.g., 2.00)
              \V     the release of bash, version + patch level (e.g., 2.00.0)
              \w     the current working  directory,  with  $HOME  abbreviated
                     with  a tilde (uses the value of the PROMPT_DIRTRIM vari-
                     able)

              \W     the basename of the current working directory, with $HOME
                     abbreviated with a tilde
              \!     the history number of this command
              \#     the command number of this command
              \$     if the effective UID is 0, a #, otherwise a $
              \nnn   the character corresponding to the octal number nnn
              \\     a backslash
              \[     begin  a sequence of non-printing characters, which could
                     be used to embed a terminal  control  sequence  into  the
                     prompt
              \]     end a sequence of non-printing characters

       The  command  number  and the history number are usually different: the
       history number of a command is its position in the history list,  which
       may  include  commands  restored from the history file (see HISTORY be-
       low), while the command number is the position in the sequence of  com-
       mands  executed  during the current shell session.  After the string is
       decoded, it is expanded via parameter expansion, command  substitution,
       arithmetic  expansion,  and  quote removal, subject to the value of the
       promptvars shell option (see the description of the shopt command under
       SHELL BUILTIN COMMANDS below).

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

   Readline Notation
       In this section, the Emacs-style notation is used to denote keystrokes.
       Control keys are denoted by C-key, e.g., C-n  means  Control-N.   Simi-
       larly,  meta  keys are denoted by M-key, so M-x means Meta-X.  (On key-
       boards without a meta key, M-x means ESC x, i.e., press the Escape  key
       then the x key.  This makes ESC the meta prefix.  The combination M-C-x
       means ESC-Control-x, or press the Escape key then hold the Control  key
       while pressing the x key.)

       Readline commands may be given numeric arguments, which normally act as
       a repeat count.  Sometimes, however, it is the  sign  of  the  argument
       that  is  significant.   Passing  a negative argument to a command that
       acts in the forward direction (e.g., kill-line) causes that command  to
       act  in  a  backward direction.  Commands whose behavior with arguments
       deviates from this are noted below.

       When a command is described as killing text, the text deleted is  saved
       for possible future retrieval (yanking).  The killed text is saved in a
       kill ring.  Consecutive kills cause the text to be accumulated into one
       unit, which can be yanked all at once.  Commands which do not kill text
       separate the chunks of text on the kill ring.

   Readline Initialization
       Readline is customized by putting commands in  an  initialization  file
       (the  inputrc  file).  The name of this file is taken from the value of
       the INPUTRC variable.  If that variable is unset, the default is ~/.in-
       putrc.   When  a program which uses the readline library starts up, the
       initialization file is read, and the key  bindings  and  variables  are
       set.   There  are  only  a few basic constructs allowed in the readline
       initialization file.  Blank lines are ignored.  Lines beginning with  a
       #  are  comments.   Lines  beginning with a $ indicate conditional con-
       structs.  Other lines denote key bindings and variable settings.

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

       For example, placing

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              set variable-name value

       Except where noted, readline variables can take the values  On  or  Off
       (without  regard  to  case).   Unrecognized variable names are ignored.
       When a variable value is read, empty or null values, "on"  (case-insen-
       sitive), and "1" are equivalent to On.  All other values are equivalent
       to Off.  The variables and their default values are:

       bell-style (audible)
              Controls what happens when readline wants to ring  the  terminal
              bell.  If set to none, readline never rings the bell.  If set to
              visible, readline uses a visible bell if one is  available.   If
              set to audible, readline attempts to ring the terminal's bell.
       bind-tty-special-chars (On)
              If  set  to On, readline attempts to bind the control characters
              treated specially by the kernel's terminal driver to their read-
              line equivalents.
       blink-matching-paren (Off)
              If set to On, readline attempts to briefly move the cursor to an
              opening parenthesis when a closing parenthesis is inserted.
       colored-completion-prefix (Off)
              If set to On, when listing completions,  readline  displays  the
              common prefix of the set of possible completions using a differ-
              ent color.  The color definitions are taken from  the  value  of
              the LS_COLORS environment variable.
       colored-stats (Off)
              If  set to On, readline displays possible completions using dif-
              ferent colors to indicate their file type.   The  color  defini-
              tions  are  taken  from  the  value of the LS_COLORS environment
              variable.
       comment-begin (``#'')
              The string that is inserted  when  the  readline  insert-comment
              command is executed.  This command is bound to M-# in emacs mode
              and to # in vi command mode.
       completion-display-width (-1)
              The number of screen columns used to  display  possible  matches
              when  performing completion.  The value is ignored if it is less
              than 0 or greater than the terminal screen width.  A value of  0
              will  cause  matches  to be displayed one per line.  The default
              value is -1.
       completion-ignore-case (Off)
              If set to On, readline performs filename matching and completion
              in a case-insensitive fashion.

       completion-map-case (Off)
              If  set  to  On, and completion-ignore-case is enabled, readline
              treats hyphens (-) and underscores (_) as equivalent  when  per-
              forming case-insensitive filename matching and completion.
       completion-prefix-display-length (0)
              The  length in characters of the common prefix of a list of pos-
              sible completions that is displayed without modification.   When
              set  to  a  value greater than zero, common prefixes longer than
              this value are replaced with an ellipsis when displaying  possi-
              ble completions.
       completion-query-items (100)
              This  determines when the user is queried about viewing the num-
              ber of possible completions generated  by  the  possible-comple-
              tions  command.  It may be set to any integer value greater than
              or equal to zero.  If the  number  of  possible  completions  is
              greater than or equal to the value of this variable, the user is
              asked whether or not he wishes to view them; otherwise they  are
              simply listed on the terminal.
       convert-meta (On)
              If  set  to On, readline will convert characters with the eighth
              bit set to an ASCII key sequence by stripping the eighth bit and
              prefixing  an  escape  character (in effect, using escape as the
              meta prefix).  The default is On, but readline will  set  it  to
              Off if the locale contains eight-bit characters.
       disable-completion (Off)
              If set to On, readline will inhibit word completion.  Completion
              characters will be inserted into the line as if  they  had  been
              mapped to self-insert.
       echo-control-characters (On)
              When  set to On, on operating systems that indicate they support
              it, readline echoes a character corresponding to a signal gener-
              ated from the keyboard.
       editing-mode (emacs)
              Controls whether readline begins with a set of key bindings sim-
              ilar to Emacs or vi.  editing-mode can be set to either emacs or
              vi.
       enable-bracketed-paste (Off)
              When  set  to  On, readline will configure the terminal in a way
              that will enable it to insert each paste into the editing buffer
              as a single string of characters, instead of treating each char-
              acter as if it had been read from the keyboard.  This  can  pre-
              vent  pasted  characters  from being interpreted as editing com-
              mands.
       enable-keypad (Off)
              When set to On, readline will try to enable the application key-
              pad when it is called.  Some systems need this to enable the ar-
              row keys.
       enable-meta-key (On)
              When set to On, readline will try to enable  any  meta  modifier
              key  the  terminal claims to support when it is called.  On many
              terminals, the meta key is used to send eight-bit characters.
       expand-tilde (Off)
              If set to On, tilde expansion is  performed  when  readline  at-
              tempts word completion.
       history-preserve-point (Off)
              If  set  to  On, the history code attempts to place point at the
              same location on each history line retrieved with  previous-his-
              tory or next-history.
       history-size (unset)
              Set  the  maximum number of history entries saved in the history
              list.  If set to zero, any existing history entries are  deleted
              and no new entries are saved.  If set to a value less than zero,
              the number of history entries is not limited.  By  default,  the
              number  of  history  entries is set to the value of the HISTSIZE
              shell variable.  If an attempt is made to set history-size to  a
              non-numeric value, the maximum number of history entries will be
              set to 500.
       horizontal-scroll-mode (Off)
              When set to On, makes readline use a single  line  for  display,
              scrolling the input horizontally on a single screen line when it
              becomes longer than the screen width rather than wrapping  to  a
              new line.
       input-meta (Off)
              If  set to On, readline will enable eight-bit input (that is, it
              will not strip the eighth bit from the characters it reads), re-
              gardless  of  what the terminal claims it can support.  The name
              meta-flag is a synonym for this variable.  The default  is  Off,
              but  readline will set it to On if the locale contains eight-bit
              characters.
       isearch-terminators (``C-[C-J'')
              The string of characters that should  terminate  an  incremental
              search  without  subsequently  executing the character as a com-
              mand.  If this variable has not been given a value, the  charac-
              ters ESC and C-J will terminate an incremental search.
       keymap (emacs)
              Set  the current readline keymap.  The set of valid keymap names
              is emacs, emacs-standard, emacs-meta,  emacs-ctlx,  vi,  vi-com-
              mand,  and  vi-insert.  vi is equivalent to vi-command; emacs is
              equivalent to emacs-standard.  The default value is  emacs;  the
              value of editing-mode also affects the default keymap.
       emacs-mode-string (@)
              This string is displayed immediately before the last line of the
              primary prompt when emacs editing mode is active.  The value  is
              expanded  like  a  key binding, so the standard set of meta- and
              control prefixes and backslash escape  sequences  is  available.
              Use  the  \1  and  \2 escapes to begin and end sequences of non-
              printing characters, which can be used to embed a terminal  con-
              trol sequence into the mode string.
       keyseq-timeout (500)
              Specifies  the  duration readline will wait for a character when
              reading an ambiguous key sequence (one that can form a  complete
              key sequence using the input read so far, or can take additional
              input to complete a longer key sequence).  If no  input  is  re-
              ceived  within  the  timeout,  readline will use the shorter but
              complete key sequence.  The value is specified in  milliseconds,
              so  a value of 1000 means that readline will wait one second for
              additional input.  If this variable is set to a value less  than
              or  equal to zero, or to a non-numeric value, readline will wait
              until another key is pressed to decide  which  key  sequence  to
              complete.
       mark-directories (On)
              If set to On, completed directory names have a slash appended.
       mark-modified-lines (Off)
              If  set  to  On,  history lines that have been modified are dis-
              played with a preceding asterisk (*).
       mark-symlinked-directories (Off)
              If set to On, completed names which are symbolic links to direc-
              tories  have  a slash appended (subject to the value of mark-di-
              rectories).
       match-hidden-files (On)
              This variable, when set to On, causes readline  to  match  files
              whose  names  begin  with  a  `.' (hidden files) when performing
              filename completion.  If set to Off, the  leading  `.'  must  be
              supplied by the user in the filename to be completed.
       menu-complete-display-prefix (Off)
              If  set to On, menu completion displays the common prefix of the
              list of possible completions (which may be empty) before cycling
              through the list.
       output-meta (Off)
              If  set  to On, readline will display characters with the eighth
              bit set directly rather than as a meta-prefixed escape sequence.
              The default is Off, but readline will set it to On if the locale
              contains eight-bit characters.
       page-completions (On)
              If set to On, readline uses an internal more-like pager to  dis-
              play a screenful of possible completions at a time.
       print-completions-horizontally (Off)
              If  set  to  On,  readline will display completions with matches
              sorted horizontally in alphabetical order, rather than down  the
              screen.
       revert-all-at-newline (Off)
              If  set  to  On, readline will undo all changes to history lines
              before returning when accept-line is executed.  By default, his-
              tory  lines  may  be  modified  and retain individual undo lists
              across calls to readline.
       show-all-if-ambiguous (Off)
              This alters the default behavior of  the  completion  functions.
              If set to On, words which have more than one possible completion
              cause the matches to be listed immediately  instead  of  ringing
              the bell.
       show-all-if-unmodified (Off)
              This  alters the default behavior of the completion functions in
              a fashion similar to show-all-if-ambiguous.  If set to On, words
              which  have more than one possible completion without any possi-
              ble partial completion (the possible completions don't  share  a
              common  prefix)  cause  the matches to be listed immediately in-
              stead of ringing the bell.
       show-mode-in-prompt (Off)
              If set to On, add a character to the beginning of the prompt in-
              dicating  the  editing mode: emacs (@), vi command (:) or vi in-
              sertion (+).
       skip-completed-text (Off)
              If set to On, this alters the default completion  behavior  when
              inserting  a  single match into the line.  It's only active when
              performing completion in the middle  of  a  word.   If  enabled,
              readline  does  not  insert  characters from the completion that
              match characters after point in the  word  being  completed,  so
              portions of the word following the cursor are not duplicated.
       vi-cmd-mode-string ((cmd))
              This string is displayed immediately before the last line of the
              primary prompt when vi editing mode is  active  and  in  command
              mode.  The value is expanded like a key binding, so the standard
              set of meta- and control prefixes and backslash escape sequences
              is  available.   Use  the \1 and \2 escapes to begin and end se-
              quences of non-printing characters, which can be used to embed a
              terminal control sequence into the mode string.
       vi-ins-mode-string ((ins))
              This string is displayed immediately before the last line of the
              primary prompt when vi editing mode is active and  in  insertion
              mode.  The value is expanded like a key binding, so the standard
              set of meta- and control prefixes and backslash escape sequences
              is  available.   Use  the \1 and \2 escapes to begin and end se-
              quences of non-printing characters, which can be used to embed a
              terminal control sequence into the mode string.
       visible-stats (Off)
              If  set to On, a character denoting a file's type as reported by
              stat(2) is appended to the filename when listing  possible  com-
              pletions.

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

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

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

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

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

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

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

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

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

              $include  /etc/inputrc

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

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

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

       Readline remembers the last incremental search string.  If two Control-
       Rs are typed without any intervening characters defining a  new  search
       string, any remembered search string is used.

       Non-incremental  searches read the entire search string before starting
       to search for matching history lines.  The search string may  be  typed
       by the user or be part of the contents of the current line.

   Readline Command Names
       The  following  is  a list of the names of the commands and the default
       key sequences to which they are bound.  Command names without an accom-
       panying key sequence are unbound by default.  In the following descrip-
       tions, point refers to the current cursor position, and mark refers  to
       a  cursor position saved by the set-mark command.  The text between the
       point and mark is referred to as the region.

   Commands for Moving
       beginning-of-line (C-a)
              Move to the start of the current line.
       end-of-line (C-e)
              Move to the end of the line.
       forward-char (C-f)
              Move forward a character.
       backward-char (C-b)
              Move back a character.
       forward-word (M-f)
              Move forward to the end of the next word.  Words are composed of
              alphanumeric characters (letters and digits).
       backward-word (M-b)
              Move  back  to the start of the current or previous word.  Words
              are composed of alphanumeric characters (letters and digits).
       shell-forward-word
              Move forward to the end of the next word.  Words  are  delimited
              by non-quoted shell metacharacters.
       shell-backward-word
              Move  back  to the start of the current or previous word.  Words
              are delimited by non-quoted shell metacharacters.
       clear-screen (C-l)
              Clear the screen leaving the current line  at  the  top  of  the
              screen.   With  an  argument,  refresh  the current line without
              clearing the screen.
       redraw-current-line
              Refresh the current line.

   Commands for Manipulating the History
       accept-line (Newline, Return)
              Accept the line regardless of where the cursor is.  If this line
              is  non-empty, add it to the history list according to the state
              of the HISTCONTROL variable.  If the line is a modified  history
              line, then restore the history line to its original state.
       previous-history (C-p)
              Fetch the previous command from the history list, moving back in
              the list.
       next-history (C-n)
              Fetch the next command from the history list, moving forward  in
              the list.
       beginning-of-history (M-<)
              Move to the first line in the history.
       end-of-history (M->)
              Move  to  the end of the input history, i.e., the line currently
              being entered.
       reverse-search-history (C-r)
              Search backward starting at the current  line  and  moving  `up'
              through  the  history  as  necessary.   This  is  an incremental
              search.
       forward-search-history (C-s)
              Search forward starting at the current line  and  moving  `down'
              through  the  history  as  necessary.   This  is  an incremental
              search.
       non-incremental-reverse-search-history (M-p)
              Search backward through the history starting at the current line
              using  a  non-incremental  search  for  a string supplied by the
              user.
       non-incremental-forward-search-history (M-n)
              Search forward  through  the  history  using  a  non-incremental
              search for a string supplied by the user.
       history-search-forward
              Search  forward through the history for the string of characters
              between the start of the current line and the point.  This is  a
              non-incremental search.
       history-search-backward
              Search backward through the history for the string of characters
              between the start of the current line and the point.  This is  a
              non-incremental search.
       yank-nth-arg (M-C-y)
              Insert  the  first argument to the previous command (usually the
              second word on the previous line) at point.  With an argument n,
              insert  the nth word from the previous command (the words in the
              previous command begin with word 0).  A  negative  argument  in-
              serts  the  nth word from the end of the previous command.  Once
              the argument n is computed, the argument is extracted as if  the
              "!n" history expansion had been specified.
       yank-last-arg (M-., M-_)
              Insert  the last argument to the previous command (the last word
              of the previous history entry).  With a numeric argument, behave
              exactly  like  yank-nth-arg.   Successive calls to yank-last-arg
              move back through the history list, inserting the last word  (or
              the  word  specified  by the argument to the first call) of each
              line in turn.  Any numeric argument supplied to these successive
              calls  determines  the direction to move through the history.  A
              negative argument switches the  direction  through  the  history
              (back or forward).  The history expansion facilities are used to
              extract the last word, as if the "!$" history expansion had been
              specified.
       shell-expand-line (M-C-e)
              Expand the line as the shell does.  This performs alias and his-
              tory expansion as well as all of the shell word expansions.  See
              HISTORY EXPANSION below for a description of history expansion.
       history-expand-line (M-^)
              Perform  history expansion on the current line.  See HISTORY EX-
              PANSION below for a description of history expansion.
       magic-space
              Perform history expansion on  the  current  line  and  insert  a
              space.  See HISTORY EXPANSION below for a description of history
              expansion.
       alias-expand-line
              Perform alias expansion on the current line.  See ALIASES  above
              for a description of alias expansion.
       history-and-alias-expand-line
              Perform history and alias expansion on the current line.
       insert-last-argument (M-., M-_)
              A synonym for yank-last-arg.
       operate-and-get-next (C-o)
              Accept  the  current  line for execution and fetch the next line
              relative to the current line from the history for editing.   Any
              argument is ignored.
       edit-and-execute-command (C-xC-e)
              Invoke  an  editor  on the current command line, and execute the
              result as shell commands.  Bash attempts to invoke $VISUAL, $ED-
              ITOR, and emacs as the editor, in that order.

   Commands for Changing Text
       end-of-file (usually C-d)
              The  character  indicating  end-of-file  as set, for example, by
              ``stty''.  If this character is read when there are  no  charac-
              ters  on  the  line,  and point is at the beginning of the line,
              Readline interprets it as the end of input and returns EOF.
       delete-char (C-d)
              Delete the character at point.  If this function is bound to the
              same character as the tty EOF character, as C-d commonly is, see
              above for the effects.
       backward-delete-char (Rubout)
              Delete the character behind the cursor.  When  given  a  numeric
              argument, save the deleted text on the kill ring.
       forward-backward-delete-char
              Delete  the  character under the cursor, unless the cursor is at
              the end of the line, in which case the character behind the cur-
              sor is deleted.
       quoted-insert (C-q, C-v)
              Add  the next character typed to the line verbatim.  This is how
              to insert characters like C-q, for example.
       tab-insert (C-v TAB)
              Insert a tab character.
       self-insert (a, b, A, 1, !, ...)
              Insert the character typed.
       transpose-chars (C-t)
              Drag the character before point forward over  the  character  at
              point,  moving point forward as well.  If point is at the end of
              the line, then this transposes the two characters before  point.
              Negative arguments have no effect.
       transpose-words (M-t)
              Drag  the  word  before  point past the word after point, moving
              point over that word as well.  If point is at  the  end  of  the
              line, this transposes the last two words on the line.
       upcase-word (M-u)
              Uppercase  the current (or following) word.  With a negative ar-
              gument, uppercase the previous word, but do not move point.
       downcase-word (M-l)
              Lowercase the current (or following) word.  With a negative  ar-
              gument, lowercase the previous word, but do not move point.
       capitalize-word (M-c)
              Capitalize the current (or following) word.  With a negative ar-
              gument, capitalize the previous word, but do not move point.
       overwrite-mode
              Toggle overwrite mode.  With an explicit positive numeric  argu-
              ment, switches to overwrite mode.  With an explicit non-positive
              numeric argument, switches to insert mode.  This command affects
              only  emacs mode; vi mode does overwrite differently.  Each call
              to readline() starts in insert mode.  In overwrite mode, charac-
              ters  bound to self-insert replace the text at point rather than
              pushing the text  to  the  right.   Characters  bound  to  back-
              ward-delete-char  replace  the  character  before  point  with a
              space.  By default, this command is unbound.

   Killing and Yanking
       kill-line (C-k)
              Kill the text from point to the end of the line.
       backward-kill-line (C-x Rubout)
              Kill backward to the beginning of the line.
       unix-line-discard (C-u)
              Kill backward from point to the  beginning  of  the  line.   The
              killed text is saved on the kill-ring.
       kill-whole-line
              Kill  all  characters on the current line, no matter where point
              is.
       kill-word (M-d)
              Kill from point to the end of the current word,  or  if  between
              words,  to  the  end  of the next word.  Word boundaries are the
              same as those used by forward-word.
       backward-kill-word (M-Rubout)
              Kill the word behind point.  Word boundaries  are  the  same  as
              those used by backward-word.
       shell-kill-word
              Kill  from  point  to the end of the current word, or if between
              words, to the end of the next word.   Word  boundaries  are  the
              same as those used by shell-forward-word.
       shell-backward-kill-word
              Kill  the  word  behind  point.  Word boundaries are the same as
              those used by shell-backward-word.
       unix-word-rubout (C-w)
              Kill the word behind point, using white space as a  word  bound-
              ary.  The killed text is saved on the kill-ring.
       unix-filename-rubout
              Kill  the  word  behind  point,  using white space and the slash
              character as the word boundaries.  The killed text is  saved  on
              the kill-ring.
       delete-horizontal-space (M-\)
              Delete all spaces and tabs around point.
       kill-region
              Kill the text in the current region.
       copy-region-as-kill
              Copy the text in the region to the kill buffer.
       copy-backward-word
              Copy  the word before point to the kill buffer.  The word bound-
              aries are the same as backward-word.
       copy-forward-word
              Copy the word following point to  the  kill  buffer.   The  word
              boundaries are the same as forward-word.
       yank (C-y)
              Yank the top of the kill ring into the buffer at point.
       yank-pop (M-y)
              Rotate  the kill ring, and yank the new top.  Only works follow-
              ing yank or yank-pop.

   Numeric Arguments
       digit-argument (M-0, M-1, ..., M--)
              Add this digit to the argument already accumulating, or start  a
              new argument.  M-- starts a negative argument.
       universal-argument
              This  is another way to specify an argument.  If this command is
              followed by one or more digits, optionally with a leading  minus
              sign,  those digits define the argument.  If the command is fol-
              lowed by digits, executing universal-argument again ends the nu-
              meric argument, but is otherwise ignored.  As a special case, if
              this command is immediately followed by a character that is nei-
              ther  a  digit  nor  minus sign, the argument count for the next
              command is multiplied by four.  The argument count is  initially
              one,  so  executing this function the first time makes the argu-
              ment count four, a second time makes the argument count sixteen,
              and so on.

   Completing
       complete (TAB)
              Attempt  to  perform  completion on the text before point.  Bash
              attempts completion treating the text as a variable (if the text
              begins  with  $), username (if the text begins with ~), hostname
              (if the text begins with @), or command (including  aliases  and
              functions) in turn.  If none of these produces a match, filename
              completion is attempted.
       possible-completions (M-?)
              List the possible completions of the text before point.
       insert-completions (M-*)
              Insert all completions of the text before point that would  have
              been generated by possible-completions.
       menu-complete
              Similar  to complete, but replaces the word to be completed with
              a single match from the list of possible completions.   Repeated
              execution  of  menu-complete  steps through the list of possible
              completions, inserting each match in turn.  At the  end  of  the
              list of completions, the bell is rung (subject to the setting of
              bell-style) and the original text is restored.  An argument of n
              moves n positions forward in the list of matches; a negative ar-
              gument may be used to move backward through the list.  This com-
              mand is intended to be bound to TAB, but is unbound by default.
       menu-complete-backward
              Identical  to menu-complete, but moves backward through the list
              of possible completions, as if menu-complete had  been  given  a
              negative argument.  This command is unbound by default.
       delete-char-or-list
              Deletes  the  character under the cursor if not at the beginning
              or end of the line (like delete-char).  If at  the  end  of  the
              line, behaves identically to possible-completions.  This command
              is unbound by default.
       complete-filename (M-/)
              Attempt filename completion on the text before point.
       possible-filename-completions (C-x /)
              List the possible completions of the text before point, treating
              it as a filename.
       complete-username (M-~)
              Attempt  completion  on  the text before point, treating it as a
              username.
       possible-username-completions (C-x ~)
              List the possible completions of the text before point, treating
              it as a username.
       complete-variable (M-$)
              Attempt  completion  on  the text before point, treating it as a
              shell variable.
       possible-variable-completions (C-x $)
              List the possible completions of the text before point, treating
              it as a shell variable.
       complete-hostname (M-@)
              Attempt  completion  on  the text before point, treating it as a
              hostname.
       possible-hostname-completions (C-x @)
              List the possible completions of the text before point, treating
              it as a hostname.
       complete-command (M-!)
              Attempt  completion  on  the text before point, treating it as a
              command name.  Command completion attempts  to  match  the  text
              against   aliases,   reserved   words,  shell  functions,  shell
              builtins, and finally executable filenames, in that order.
       possible-command-completions (C-x !)
              List the possible completions of the text before point, treating
              it as a command name.
       dynamic-complete-history (M-TAB)
              Attempt  completion on the text before point, comparing the text
              against lines from the  history  list  for  possible  completion
              matches.
       dabbrev-expand
              Attempt  menu completion on the text before point, comparing the
              text against lines from the history list for possible completion
              matches.
       complete-into-braces (M-{)
              Perform filename completion and insert the list of possible com-
              pletions enclosed within braces so the list is available to  the
              shell (see Brace Expansion above).

   Keyboard Macros
       start-kbd-macro (C-x ()
              Begin  saving  the  characters  typed  into the current keyboard
              macro.
       end-kbd-macro (C-x ))
              Stop saving the characters typed into the current keyboard macro
              and store the definition.
       call-last-kbd-macro (C-x e)
              Re-execute  the last keyboard macro defined, by making the char-
              acters in the macro appear as if typed at the keyboard.
       print-last-kbd-macro ()
              Print the last keyboard macro defined in a format  suitable  for
              the inputrc file.

   Miscellaneous
       re-read-init-file (C-x C-r)
              Read  in  the  contents of the inputrc file, and incorporate any
              bindings or variable assignments found there.
       abort (C-g)
              Abort the current editing command and ring the  terminal's  bell
              (subject to the setting of bell-style).
       do-uppercase-version (M-a, M-b, M-x, ...)
              If  the  metafied character x is lowercase, run the command that
              is bound to the corresponding uppercase character.
       prefix-meta (ESC)
              Metafy the next character typed.  ESC f is equivalent to Meta-f.
       undo (C-_, C-x C-u)
              Incremental undo, separately remembered for each line.
       revert-line (M-r)
              Undo all changes made to this line.  This is like executing  the
              undo  command  enough  times  to  return the line to its initial
              state.
       tilde-expand (M-&)
              Perform tilde expansion on the current word.
       set-mark (C-@, M-<space>)
              Set the mark to the point.  If a numeric argument  is  supplied,
              the mark is set to that position.
       exchange-point-and-mark (C-x C-x)
              Swap  the  point  with the mark.  The current cursor position is
              set to the saved position, and the old cursor position is  saved
              as the mark.
       character-search (C-])
              A character is read and point is moved to the next occurrence of
              that character.  A negative count searches for  previous  occur-
              rences.
       character-search-backward (M-C-])
              A  character  is  read and point is moved to the previous occur-
              rence of that character.  A negative count searches  for  subse-
              quent occurrences.
       skip-csi-sequence
              Read  enough  characters to consume a multi-key sequence such as
              those defined for keys like Home and End.  Such sequences  begin
              with a Control Sequence Indicator (CSI), usually ESC-[.  If this
              sequence is bound to "\[", keys producing  such  sequences  will
              have  no  effect  unless explicitly bound to a readline command,
              instead of inserting stray characters into the  editing  buffer.
              This is unbound by default, but usually bound to ESC-[.
       insert-comment (M-#)
              Without  a  numeric  argument,  the  value  of the readline com-
              ment-begin variable is inserted at the beginning of the  current
              line.  If a numeric argument is supplied, this command acts as a
              toggle: if the characters at the beginning of the  line  do  not
              match  the value of comment-begin, the value is inserted, other-
              wise the characters in comment-begin are deleted from the begin-
              ning  of the line.  In either case, the line is accepted as if a
              newline had been typed.   The  default  value  of  comment-begin
              causes  this  command  to make the current line a shell comment.
              If a numeric argument causes the comment  character  to  be  re-
              moved, the line will be executed by the shell.
       glob-complete-word (M-g)
              The  word  before point is treated as a pattern for pathname ex-
              pansion, with an asterisk implicitly appended.  This pattern  is
              used  to generate a list of matching filenames for possible com-
              pletions.
       glob-expand-word (C-x *)
              The word before point is treated as a pattern for  pathname  ex-
              pansion, and the list of matching filenames is inserted, replac-
              ing the word.  If a numeric argument is supplied, an asterisk is
              appended before pathname expansion.
       glob-list-expansions (C-x g)
              The  list  of  expansions  that  would  have  been  generated by
              glob-expand-word is displayed, and the line is  redrawn.   If  a
              numeric  argument  is  supplied,  an asterisk is appended before
              pathname expansion.
       dump-functions
              Print all of the functions and their key bindings to  the  read-
              line output stream.  If a numeric argument is supplied, the out-
              put is formatted in such a way that it can be made  part  of  an
              inputrc file.
       dump-variables
              Print all of the settable readline variables and their values to
              the readline output stream.  If a numeric argument is  supplied,
              the  output  is formatted in such a way that it can be made part
              of an inputrc file.
       dump-macros
              Print all of the readline key sequences bound to macros and  the
              strings  they  output.   If  a numeric argument is supplied, the
              output is formatted in such a way that it can be made part of an
              inputrc file.
       display-shell-version (C-x C-v)
              Display version information about the current instance of bash.

   Programmable Completion
       When  word  completion  is  attempted  for an argument to a command for
       which a completion specification (a compspec) has  been  defined  using
       the  complete  builtin (see SHELL BUILTIN COMMANDS below), the program-
       mable completion facilities are invoked.

       First, the command name is identified.  If  the  command  word  is  the
       empty  string (completion attempted at the beginning of an empty line),
       any compspec defined with the -E option to  complete  is  used.   If  a
       compspec  has  been  defined  for that command, the compspec is used to
       generate the list of possible completions for the word.  If the command
       word  is  a full pathname, a compspec for the full pathname is searched
       for first.  If no compspec is found for the full pathname,  an  attempt
       is  made  to find a compspec for the portion following the final slash.
       If those searches do not result in a  compspec,  any  compspec  defined
       with the -D option to complete is used as the default.

       Once  a  compspec  has  been  found, it is used to generate the list of
       matching words.  If a compspec is not found, the default  bash  comple-
       tion as described above under Completing is performed.

       First,  the  actions  specified by the compspec are used.  Only matches
       which are prefixed by the word being completed are returned.  When  the
       -f  or -d option is used for filename or directory name completion, the
       shell variable FIGNORE is used to filter the matches.

       Any completions specified by a pathname expansion pattern to the -G op-
       tion  are  generated next.  The words generated by the pattern need not
       match the word being completed.  The GLOBIGNORE shell variable  is  not
       used to filter the matches, but the FIGNORE variable is used.

       Next,  the string specified as the argument to the -W option is consid-
       ered.  The string is first split using the characters in the  IFS  spe-
       cial  variable  as delimiters.  Shell quoting is honored.  Each word is
       then expanded using brace expansion,  tilde  expansion,  parameter  and
       variable  expansion, command substitution, and arithmetic expansion, as
       described above under EXPANSION.  The results are split using the rules
       described above under Word Splitting.  The results of the expansion are
       prefix-matched against the word being completed, and the matching words
       become the possible completions.

       After  these matches have been generated, any shell function or command
       specified with the -F and -C options is invoked.  When the  command  or
       function is invoked, the COMP_LINE, COMP_POINT, COMP_KEY, and COMP_TYPE
       variables are assigned values as described above under Shell Variables.
       If  a  shell  function  is being invoked, the COMP_WORDS and COMP_CWORD
       variables are also set.  When the function or command is  invoked,  the
       first  argument ($1) is the name of the command whose arguments are be-
       ing completed, the second argument ($2) is the  word  being  completed,
       and  the  third argument ($3) is the word preceding the word being com-
       pleted on the current command line.  No filtering of the generated com-
       pletions against the word being completed is performed; the function or
       command has complete freedom in generating the matches.

       Any function specified with -F is invoked first.  The function may  use
       any  of  the  shell facilities, including the compgen builtin described
       below, to generate the matches.  It must put the  possible  completions
       in the COMPREPLY array variable, one per array element.

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

       After all of the possible completions are generated, any filter  speci-
       fied  with  the -X option is applied to the list.  The filter is a pat-
       tern as used for pathname expansion; a & in  the  pattern  is  replaced
       with  the text of the word being completed.  A literal & may be escaped
       with a backslash; the backslash is removed before attempting  a  match.
       Any  completion that matches the pattern will be removed from the list.
       A leading ! negates the pattern; in this case any completion not match-
       ing  the  pattern  will be removed.  If the nocasematch shell option is
       enabled, the match is performed without regard to the  case  of  alpha-
       betic characters.

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

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

       If  the  -o  plusdirs option was supplied to complete when the compspec
       was defined, directory name completion is attempted and any matches are
       added to the results of the other actions.

       By  default,  if a compspec is found, whatever it generates is returned
       to the completion code as the full set of  possible  completions.   The
       default bash completions are not attempted, and the readline default of
       filename completion is disabled.  If the -o bashdefault option was sup-
       plied  to complete when the compspec was defined, the bash default com-
       pletions are attempted if the compspec generates no matches.  If the -o
       default  option was supplied to complete when the compspec was defined,
       readline's default completion will be performed if the  compspec  (and,
       if attempted, the default bash completions) generate no matches.

       When  a  compspec  indicates that directory name completion is desired,
       the programmable completion functions force readline to append a  slash
       to  completed names which are symbolic links to directories, subject to
       the value of the mark-directories readline variable, regardless of  the
       setting of the mark-symlinked-directories readline variable.

       There  is  some support for dynamically modifying completions.  This is
       most useful when used in combination with a default  completion  speci-
       fied  with  complete -D.  It's possible for shell functions executed as
       completion handlers to indicate that completion should  be  retried  by
       returning  an exit status of 124.  If a shell function returns 124, and
       changes the compspec associated with the command on which completion is
       being  attempted  (supplied  as the first argument when the function is
       executed), programmable completion restarts from the beginning, with an
       attempt  to find a new compspec for that command.  This allows a set of
       completions to be built dynamically as completion is attempted,  rather
       than being loaded all at once.

       For  instance, assuming that there is a library of compspecs, each kept
       in a file corresponding to the name of the command, the  following  de-
       fault completion function would load completions dynamically:

       _completion_loader()
       {
            . "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
       }
       complete -D -F _completion_loader -o bashdefault -o default

HISTORY
       When  the  -o  history  option to the set builtin is enabled, the shell
       provides access to the command history, the list of commands previously
       typed.   The  value  of  the HISTSIZE variable is used as the number of
       commands to save in a history list.  The text of the last HISTSIZE com-
       mands  (default  500)  is  saved.  The shell stores each command in the
       history list prior to parameter and variable expansion  (see  EXPANSION
       above)  but after history expansion is performed, subject to the values
       of the shell variables HISTIGNORE and HISTCONTROL.

       On startup, the history is initialized from the file named by the vari-
       able  HISTFILE  (default ~/.bash_history).  The file named by the value
       of HISTFILE is truncated, if necessary, to contain  no  more  than  the
       number  of  lines specified by the value of HISTFILESIZE.  If HISTFILE-
       SIZE is unset, or set to null, a non-numeric value, or a numeric  value
       less  than  zero,  the history file is not truncated.  When the history
       file is read, lines beginning with the history comment  character  fol-
       lowed immediately by a digit are interpreted as timestamps for the pre-
       ceding history line.  These timestamps are optionally displayed depend-
       ing  on  the  value  of the HISTTIMEFORMAT variable.  When a shell with
       history enabled exits, the last $HISTSIZE lines  are  copied  from  the
       history  list  to $HISTFILE.  If the histappend shell option is enabled
       (see the description of shopt under SHELL BUILTIN COMMANDS below),  the
       lines  are  appended to the history file, otherwise the history file is
       overwritten.  If HISTFILE is unset, or  if  the  history  file  is  un-
       writable,  the history is not saved.  If the HISTTIMEFORMAT variable is
       set, time stamps are written to the history file, marked with the  his-
       tory comment character, so they may be preserved across shell sessions.
       This uses the history comment character to distinguish timestamps  from
       other  history  lines.   After  saving the history, the history file is
       truncated to contain no more than HISTFILESIZE lines.  If  HISTFILESIZE
       is  unset, or set to null, a non-numeric value, or a numeric value less
       than zero, the history file is not truncated.

       The builtin command fc (see SHELL BUILTIN COMMANDS below) may  be  used
       to list or edit and re-execute a portion of the history list.  The his-
       tory builtin may be used to display or modify the history list and  ma-
       nipulate  the  history  file.   When using command-line editing, search
       commands are available in each editing mode that provide access to  the
       history list.

       The  shell  allows control over which commands are saved on the history
       list.  The HISTCONTROL and HISTIGNORE variables may be set to cause the
       shell to save only a subset of the commands entered.  The cmdhist shell
       option, if enabled, causes the shell to attempt to save each line of  a
       multi-line  command  in the same history entry, adding semicolons where
       necessary to preserve syntactic correctness.  The lithist shell  option
       causes  the shell to save the command with embedded newlines instead of
       semicolons.  See the description of the shopt builtin below under SHELL
       BUILTIN  COMMANDS  for  information  on setting and unsetting shell op-
       tions.

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

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

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

       Several characters inhibit history expansion if found immediately  fol-
       lowing  the history expansion character, even if it is unquoted: space,
       tab, newline, carriage return, and =.  If the extglob shell  option  is
       enabled, ( will also inhibit expansion.

       Several  shell  options  settable with the shopt builtin may be used to
       tailor the behavior of history expansion.  If the histverify shell  op-
       tion  is  enabled (see the description of the shopt builtin below), and
       readline is being  used,  history  substitutions  are  not  immediately
       passed  to  the  shell  parser.  Instead, the expanded line is reloaded
       into the readline editing buffer for further modification.  If readline
       is  being  used,  and  the histreedit shell option is enabled, a failed
       history substitution will be reloaded into the readline editing  buffer
       for  correction.   The  -p option to the history builtin command may be
       used to see what a history expansion will do before using it.   The  -s
       option to the history builtin may be used to add commands to the end of
       the history list without actually executing  them,  so  that  they  are
       available for subsequent recall.

       The  shell allows control of the various characters used by the history
       expansion mechanism (see the description of histchars above under Shell
       Variables).   The shell uses the history comment character to mark his-
       tory timestamps when writing the history file.

   Event Designators
       An event designator is a reference to a command line entry in the  his-
       tory  list.   Unless  the reference is absolute, events are relative to
       the current position in the history list.

       !      Start a history substitution, except when followed by  a  blank,
              newline,  carriage return, = or ( (when the extglob shell option
              is enabled using the shopt builtin).
       !n     Refer to command line n.
       !-n    Refer to the current command minus n.
       !!     Refer to the previous command.  This is a synonym for `!-1'.
       !string
              Refer to the most recent command preceding the current  position
              in the history list starting with string.
       !?string[?]
              Refer  to the most recent command preceding the current position
              in the history list containing string.  The trailing  ?  may  be
              omitted if string is followed immediately by a newline.
       ^string1^string2^
              Quick  substitution.   Repeat  the  previous  command, replacing
              string1 with string2.  Equivalent  to  ``!!:s/string1/string2/''
              (see Modifiers below).
       !#     The entire command line typed so far.

   Word Designators
       Word  designators are used to select desired words from the event.  A :
       separates the event specification from the word designator.  It may  be
       omitted  if  the word designator begins with a ^, $, *, -, or %.  Words
       are numbered from the beginning of the line, with the first word  being
       denoted  by  0  (zero).  Words are inserted into the current line sepa-
       rated by single spaces.

       0 (zero)
              The zeroth word.  For the shell, this is the command word.
       n      The nth word.
       ^      The first argument.  That is, word 1.
       $      The last word.  This is usually the last argument, but will  ex-
              pand to the zeroth word if there is only one word in the line.
       %      The word matched by the most recent `?string?' search.
       x-y    A range of words; `-y' abbreviates `0-y'.
       *      All  of  the words but the zeroth.  This is a synonym for `1-$'.
              It is not an error to use * if there is just  one  word  in  the
              event; the empty string is returned in that case.
       x*     Abbreviates x-$.
       x-     Abbreviates x-$ like x*, but omits the last word.

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

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

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

SHELL BUILTIN COMMANDS
       Unless otherwise noted, each builtin command documented in this section
       as accepting options preceded by - accepts -- to signify the end of the
       options.  The :, true, false, and test builtins do not  accept  options
       and  do  not treat -- specially.  The exit, logout, return, break, con-
       tinue, 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 interpreta-
       tion.
       : [arguments]
              No effect; the command does nothing beyond  expanding  arguments
              and performing any specified redirections.  The return status is
              zero.

        .  filename [arguments]
       source filename [arguments]
              Read and execute commands from filename in the current shell en-
              vironment  and  return  the exit status of the last command exe-
              cuted 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  posi-
              tional  parameters when filename is executed.  Otherwise the po-
              sitional parameters are unchanged.  If the -T option is enabled,
              source  inherits any trap on DEBUG; if it is not, any DEBUG trap
              string is saved and restored around  the  call  to  source,  and
              source  unsets  the  DEBUG trap while it executes.  If -T is not
              set, and the sourced file changes the DEBUG trap, the new  value
              is  retained  when  source  completes.  The return status is the
              status of the last command exited within the  script  (0  if  no
              commands  are  executed),  and false if filename is not found or
              cannot be read.

       alias [-p] [name[=value] ...]
              Alias with no arguments or with the -p option prints the list of
              aliases  in  the form alias name=value on standard output.  When
              arguments are supplied, an alias is defined for each name  whose
              value  is given.  A trailing space in value causes the next word
              to be checked for alias substitution when the alias is expanded.
              For  each  name  in the argument list for which no value is sup-
              plied, the name and value of the alias is  printed.   Alias  re-
              turns  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 [-m keymap] keyseq: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 ap-
              pear in .inputrc, but each binding or command must be passed  as
              a separate argument; e.g., '"\C-x\C-r": re-read-init-file'.  Op-
              tions, if supplied, have the following meanings:
              -m keymap
                     Use keymap as the keymap to be affected by the subsequent
                     bindings.  Acceptable keymap names are emacs, emacs-stan-
                     dard, emacs-meta, emacs-ctlx,  vi,  vi-move,  vi-command,
                     and  vi-insert.   vi is equivalent to vi-command (vi-move
                     is also a synonym); emacs is  equivalent  to  emacs-stan-
                     dard.
              -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 en-
                     tered.   When  shell-command  is executed, the shell sets
                     the READLINE_LINE variable to the contents of  the  read-
                     line  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 READ-
                     LINE_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 in-
                     put.

              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  ex-
              ited.   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  func-
              tionality of the builtin within the function.  The cd builtin is
              commonly redefined this way.  The  return  status  is  false  if
              shell-builtin is not a shell builtin command.

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

       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  addi-
              tional 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 di-
              rectory 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 success-
              fully 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 direc-
              tory  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 op-
              tion 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 can-
              not be found, the exit status is 127.  Otherwise, the exit  sta-
              tus of the command builtin is the exit status of command.

       compgen [option] [word]
              Generate  possible  completion matches for word according to the
              options, which may  be  any  option  accepted  by  the  complete
              builtin  with  the exception of -p and -r, and write the matches
              to the standard output.  When using the -F or  -C  options,  the
              various  shell  variables set by the programmable completion fa-
              cilities, while available, will not have useful values.

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

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

       complete [-abcdefgjksuv] [-o comp-option] [-DE] [-A action]  [-G  glob-
       pat] [-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 spec-
              ification  for each name, or, if no names are supplied, all com-
              pletion specifications.  The -D option indicates  that  the  re-
              maining options and actions should apply to the ``default'' com-
              mand completion; that is, completion attempted on a command  for
              which  no completion has previously been defined.  The -E option
              indicates that the remaining options 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 Program-
              mable Completion.

              Other options, if specified, have the following  meanings.   The
              arguments  to the -G, -W, and -X options (and, if necessary, the
              -P and -S options) should be quoted to protect them from  expan-
              sion before the complete builtin is invoked.
              -o comp-option
                      The  comp-option  controls  several aspects of the comp-
                      spec's behavior beyond the simple generation of  comple-
                      tions.  comp-option may be one of:
                      bashdefault
                              Perform the rest of the default bash completions
                              if the compspec generates no matches.
                      default Use readline's default  filename  completion  if
                              the compspec generates no matches.
                      dirnames
                              Perform  directory  name completion if the comp-
                              spec generates no matches.
                      filenames
                              Tell readline that the compspec generates  file-
                              names,  so  it can perform any filename-specific
                              processing (like adding  a  slash  to  directory
                              names,  quoting special characters, or suppress-
                              ing 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).
                      nosort  Tell  readline  not to sort the list of possible
                              completions alphabetically.

                      nospace Tell readline not to append  a  space  (the  de-
                              fault)  to  words  completed  at  the end of the
                              line.
                      plusdirs
                              After any matches defined by  the  compspec  are
                              generated,  directory  name  completion  is  at-
                              tempted and any matches are added to the results
                              of the other actions.
              -A action
                      The  action  may  be  one of the following to generate a
                      list of possible completions:
                      alias   Alias names.  May also be specified as -a.
                      arrayvar
                              Array variable names.
                      binding Readline key binding names.
                      builtin Names of shell builtin commands.   May  also  be
                              specified as -b.
                      command Command names.  May also be specified as -c.
                      directory
                              Directory names.  May also be specified as -d.
                      disabled
                              Names of disabled shell builtins.
                      enabled Names of enabled shell builtins.
                      export  Names  of exported shell variables.  May also be
                              specified as -e.
                      file    File names.  May also be specified as -f.
                      function
                              Names of shell functions.
                      group   Group names.  May also be specified as -g.
                      helptopic
                              Help topics as accepted by the help builtin.
                      hostname
                              Hostnames, as taken from the file  specified  by
                              the HOSTFILE shell variable.
                      job     Job  names,  if job control is active.  May also
                              be specified as -j.
                      keyword Shell reserved words.  May also be specified  as
                              -k.
                      running Names of running jobs, if job control is active.
                      service Service names.  May also be specified as -s.
                      setopt  Valid  arguments  for  the  -o option to the set
                              builtin.
                      shopt   Shell option names  as  accepted  by  the  shopt
                              builtin.
                      signal  Signal names.
                      stopped Names of stopped jobs, if job control is active.
                      user    User names.  May also be specified as -u.
                      variable
                              Names of all shell variables.  May also be spec-
                              ified as -v.
              -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 ar-
                      guments 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  cur-
                      rent  command line.  When it finishes, the possible com-
                      pletions 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  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.
              -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.
              -X filterpat
                      filterpat is a pattern as used for  pathname  expansion.
                      It is applied to the list of possible completions gener-
                      ated by the preceding options and  arguments,  and  each
                      completion  matching filterpat is removed from the list.
                      A leading ! in filterpat negates the  pattern;  in  this
                      case, any completion not matching filterpat is removed.

              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.

       compopt [-o option] [-DE] [+o option] [name]
              Modify  completion  options  for  each name according to the op-
              tions, or for the currently-executing completion if no names are
              supplied.   If  no options are given, display the completion op-
              tions for each name or the  current  completion.   The  possible
              values  of  option  are those valid for the complete builtin de-
              scribed above.  The -D option indicates that the  remaining  op-
              tions  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 en-
              closing 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 at-
              tributes 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  each
              name  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 func-
              tion.  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 evalua-
                     tion  (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,  assign-
                     ments,  and attribute modifications to name, except those
                     using or changing the -n attribute itself, are  performed
                     on  the variable referenced by name's value.  The nameref
                     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 in-
                     herit 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 en-
                     vironment.

              Using `+' instead of `-' turns off the attribute  instead,  with
              the exceptions that +a may not be used to destroy an array vari-
              able 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 vari-
              able  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 as-
              sign a value to an array variable without using the compound as-
              signment  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 di-
              rectories.  The default display is on a single line with  direc-
              tory  names  separated  by spaces.  Directories are added to the
              list with the pushd command; the popd  command  removes  entries
              from the list.  The current directory is always the first direc-
              tory in the stack.
              -c     Clears the directory stack by deleting  all  of  the  en-
                     tries.
              -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,  pre-
                     fixing 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 ... | pid ... ]
              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  re-
              ceives a SIGHUP.  If no jobspec is supplied, the -a option means
              to remove or mark all jobs; the -r option without a jobspec  ar-
              gument 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  interpreta-
              tion  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 es-
              cape characters by default.  echo does not interpret -- to  mean
              the  end  of  options.  echo interprets the following escape se-
              quences:
              \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  en-
              abled.   For  example, to use the test binary found via the PATH
              instead of the shell builtin version, run  ``enable  -n  test''.
              The  -f  option  means to load the new builtin command name from
              shared object filename, on systems that support dynamic loading.
              The  -d  option will delete a builtin previously loaded with -f.
              If no name arguments are given, or if the -p option is supplied,
              a list of shell builtins is printed.  With no other option argu-
              ments, the list consists of all enabled shell builtins.   If  -n
              is  supplied, only disabled builtins are printed.  If -a is sup-
              plied, the list printed includes all builtins, with  an  indica-
              tion  of whether or not each is enabled.  If -s is supplied, the
              output is restricted to the POSIX special builtins.  The  return
              value  is  0 unless a name is not a shell builtin or there is an
              error loading a new builtin from a shared object.

       eval [arg ...]
              The args are read and concatenated together into a  single  com-
              mand.   This command is then read and executed by the shell, and
              its exit status is returned as the value of eval.  If there  are
              no args, or only null arguments, eval returns 0.

       exec [-cl] [-a name] [command [arguments]]
              If  command is specified, it replaces the shell.  No new process
              is created.  The arguments become the arguments to command.   If
              the -l option is supplied, the shell places a dash at the begin-
              ning of the zeroth argument passed to command.  This is what lo-
              gin(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 can-
              not 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 redi-
              rections 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 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 sup-
              plied 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 other-
              wise.  If first is not specified it is set to the previous  com-
              mand for editing and -16 for listing.

              The  -n option suppresses the command numbers when listing.  The
              -r option reverses the order of the commands.  If the -l  option
              is  given,  the  commands are listed on standard output.  Other-
              wise, the editor given by ename is invoked on a file  containing
              those  commands.  If ename is not given, the value of the FCEDIT
              variable is used, and the value of EDITOR if FCEDIT is not  set.
              If  neither  variable  is set, vi is used.  When editing is com-
              plete, the edited commands are echoed and executed.

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

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

       getopts optstring name [args]
              getopts  is used by shell procedures to parse positional parame-
              ters.  optstring contains the option  characters  to  be  recog-
              nized;  if a character is followed by a colon, the option is ex-
              pected 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 op-
              tion 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 re-
              turn 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 OP-
              TARG 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 remem-
              bered.  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 op-
              tion causes the shell to forget the remembered location of  each
              name.   If the -t option is supplied, the full pathname to which
              each name corresponds is printed.  If  multiple  name  arguments
              are supplied with -t, the name is printed before the hashed full
              pathname.  The -l option causes output to be displayed in a for-
              mat  that may be reused as input.  If no arguments are given, or
              if only -l is supplied, information about remembered commands is
              printed.   The  return status is true unless a name is not found
              or an invalid option is supplied.

       help [-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 num-
              bers.  Lines listed with a * have been modified.  An argument of
              n lists only the last n lines.  If the shell variable  HISTTIME-
              FORMAT  is  set  and not null, it is used as a format string for
              strftime(3) to display the time stamp associated with each  dis-
              played  history  entry.  No intervening blank is printed between
              the formatted time stamp and the history line.  If  filename  is
              supplied,  it  is  used as the name of the history file; if not,
              the value of HISTFILE is used.  Options, if supplied,  have  the
              following meanings:
              -c     Clear the history list by deleting all the entries.
              -d offset
                     Delete the history entry at position offset.
              -a     Append  the  ``new''  history  lines to the history file.
                     These are history lines entered since  the  beginning  of
                     the current bash session, but not already appended to the
                     history file.
              -n     Read the history lines not already read from the  history
                     file  into the current history list.  These are lines ap-
                     pended 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, over-
                     writing 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  informa-
              tion  associated  with each history entry is written to the his-
              tory 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 following history entry.  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 sup-
              plied as an argument to -d, or the history expansion supplied as
              an argument to -p fails.

       jobs [-lnprs] [ jobspec ... ]
       jobs -x command [ args ... ]
              The first form lists the active jobs.  The options have the fol-
              lowing meanings:
              -l     List process IDs in addition to the normal information.
              -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 ex-
              ecutes command passing it args, returning its exit status.

       kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...
       kill -l|-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.  The -L option is
              equivalent to -l.  kill returns true if at least one signal  was
              successfully sent, or false if an error occurs or an invalid op-
              tion is encountered.

       let arg [arg ...]
              Each arg is an arithmetic expression to be evaluated (see ARITH-
              METIC  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 func-
              tion and its children.  If name is -, the set of  shell  options
              is  made  local to the function in which local is invoked: shell
              options changed using the set builtin inside  the  function  are
              restored  to  their  original  values when the function returns.
              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 [-d delim] [-n count] [-O origin] [-s count] [-t] [-u  fd]  [-C
       callback] [-c quantum] [array]
       readarray [-d delim] [-n count] [-O origin] [-s count] [-t] [-u fd] [-C
       callback] [-c quantum] [array]
              Read lines from the standard input into the indexed array  vari-
              able  array, or from file descriptor fd if the -u option is sup-
              plied.  The variable MAPFILE is the default array.  Options,  if
              supplied, have the following meanings:
              -d     The  first  character  of delim is used to terminate each
                     input line, rather than newline.
              -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 delim (default newline) from each  line
                     read.
              -u     Read  lines  from file descriptor fd instead of the stan-
                     dard 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  ar-
              ray 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 follow-
              ing meanings:
              -n     Suppresses the normal change of directory  when  removing
                     directories from the stack, so that only the stack is ma-
                     nipulated.
              +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-exis-
              tent directory stack entry is specified, or the directory change
              fails.

       printf [-v var] format [arguments]
              Write  the  formatted arguments to the standard output under the
              control of the format.  The -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 in the same way as echo -e.
              %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 ar-
                     gument is specified, conversion behaves as if -1 had been
                     given.   This  is an exception to the usual printf behav-
                     ior.

              Arguments to non-string format specifiers are treated as C  con-
              stants, 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 argu-
              ments.  If the format requires more arguments than are supplied,
              the  extra  format  specifications  behave as if a zero value or
              null string, as appropriate,  had  been  supplied.   The  return
              value is zero on success, non-zero on failure.

       pushd [-n] [+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, pushd exchanges the top two di-
              rectories and returns 0, unless the directory  stack  is  empty.
              Arguments, if supplied, have the following meanings:
              -n     Suppresses  the  normal change of directory when rotating
                     or 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 direc-
              tory stack is empty, a non-existent directory stack  element  is
              specified,  or the directory change to the specified new current
              directory fails.

       pwd [-LP]
              Print the absolute pathname of the  current  working  directory.
              The pathname printed contains no symbolic links if the -P option
              is supplied or the -o physical option to the set builtin command
              is  enabled.  If the -L option is used, the pathname printed may
              contain symbolic links.  The return status is 0 unless an  error
              occurs while reading the name of the current directory or an in-
              valid 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 de-
              scriptor fd supplied as an argument to the -u option, split into
              words  as  described  above  under Word Splitting, and the first
              word is assigned to the first name, the second word to the  sec-
              ond  name,  and  so on.  If there are more words than names, the
              remaining words and their intervening delimiters are assigned to
              the  last  name.   If  there are fewer words read from the input
              stream than names, the remaining names are assigned  empty  val-
              ues.   The  characters  in  IFS  are used to split the line into
              words using the same rules the shell  uses  for  expansion  (de-
              scribed  above  under  Word Splitting).  The backslash character
              (\) may be used to remove any special meaning for the next char-
              acter  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  ig-
                     nored.
              -d delim
                     The first character of delim is used to terminate the in-
                     put line, rather than newline.
              -e     If the standard input is coming from a terminal, readline
                     (see  READLINE  above) is used to obtain the line.  Read-
                     line 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 honors a delim-
                     iter 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 charac-
                     ters encountered in the input are not  treated  specially
                     and  do  not cause read to return until nchars characters
                     are read.  The result is not split on the  characters  in
                     IFS;  the intent is that the variable is assigned exactly
                     the characters read (with the exception of backslash; see
                     the -r option below).
              -p prompt
                     Display prompt on standard error, without a trailing new-
                     line, before attempting to read any input.  The prompt is
                     displayed only if input is coming from a terminal.
              -r     Backslash does not act as an escape character.  The back-
                     slash is considered to be part of the line.  In  particu-
                     lar,  a  backslash-newline pair may not be used as a line
                     continuation.
              -s     Silent mode.  If input is coming from a terminal, charac-
                     ters are not echoed.
              -t timeout
                     Cause  read  to time out and return failure if a complete
                     line of input (or a specified number  of  characters)  is
                     not  read within timeout seconds.  timeout may be a deci-
                     mal number with a fractional portion following the  deci-
                     mal  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 re-
                     turns 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 vari-
              able REPLY.  The exit status is zero, unless end-of-file is  en-
              countered,  read  times out (in which case the status is greater
              than 128), a variable assignment error (such as assigning  to  a
              readonly variable) occurs, or an invalid file descriptor is sup-
              plied as the argument to -u.

       readonly [-aAf] [-p] [name[=word] ...]
              The given names are marked readonly; the values of  these  names
              may  not  be changed by subsequent assignment.  If the -f option
              is supplied, the functions corresponding to  the  names  are  so
              marked.   The  -a  option restricts the variables to indexed ar-
              rays; the -A option restricts the variables to  associative  ar-
              rays.  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  speci-
              fied  by n to its caller.  If n is omitted, the return status is
              that of the last command executed in the function body.  If  re-
              turn is executed by a trap handler, the last command used to de-
              termine the status is the last command executed before the  trap
              handler.   if  return  is executed during a DEBUG trap, the last
              command used to determine the status is the  last  command  exe-
              cuted  by the trap handler before return was invoked.  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 signif-
              icant  8  bits.  The return status is non-zero if return is sup-
              plied 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 re-
              sumes 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 can-
              not be reset.  In posix mode, only shell variables  are  listed.
              The  output is sorted according to the current locale.  When op-
              tions are specified, they set or unset  shell  attributes.   Any
              arguments  remaining after option processing are treated as val-
              ues for the positional parameters and are assigned, in order, to
              $1,  $2,  ...   $n.   Options,  if specified, have the following
              meanings:
              -a      Each variable or function that is created or modified is
                      given  the export attribute and marked 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 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 envi-
                      ronment  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 com-
                      pletes, the shell prints a line containing its exit sta-
                      tus.
              -n      Read commands but do not execute them.  This may be used
                      to check a shell script for syntax errors.  This is  ig-
                      nored 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.  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 inter-
                              active shells.
                      ignoreeof
                              The  effect  is  as  if  the shell command ``IG-
                              NOREEOF=10'' had been executed (see Shell  Vari-
                              ables 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  ap-
                      pear  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 sup-
                      plied, these actions are taken and the effective user id
                      is  set  to  the real user id.  If the -p option is sup-
                      plied 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 spe-
                      cial  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, dis-
                      play  the expanded value of PS4, followed by the command
                      and its expanded arguments or associated word list.
              -B      The shell performs brace expansion (see Brace  Expansion
                      above).  This is on by default.
              -C      If  set,  bash  does not overwrite an existing file with
                      the >, >&, and <> redirection operators.   This  may  be
                      overridden when creating output files by using the redi-
                      rection operator >| instead of >.
              -E      If set, any trap on ERR is inherited by shell functions,
                      command  substitutions,  and commands executed in a sub-
                      shell environment.  The ERR trap is normally not  inher-
                      ited in such cases.
              -H      Enable !  style history substitution.  This option is on
                      by default when the shell is interactive.
              -P      If set, the shell does not 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 ex-
                      ecuted  in a subshell environment.  The DEBUG and RETURN
                      traps are normally not inherited in such cases.
              --      If no arguments follow this option, then the  positional
                      parameters are unset.  Otherwise, the positional parame-
                      ters are set to the args, even if  some  of  them  begin
                      with a -.
              -       Signal  the  end of options, cause all remaining args to
                      be assigned to the positional parameters.  The -x and -v
                      options are turned off.  If there are no args, the posi-
                      tional parameters remain unchanged.

              The options are off by default unless otherwise noted.  Using  +
              rather  than  -  causes these options to be turned off.  The op-
              tions can also be specified as arguments to an invocation of the
              shell.   The current set of options may be found in $-.  The re-
              turn status is always true unless an invalid option  is  encoun-
              tered.

       shift [n]
              The  positional  parameters  from n+1 ... are renamed to $1 ....
              Parameters represented by the numbers $# down to $#-n+1 are  un-
              set.   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 param-
              eters 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 behav-
              ior.  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 multi-
                     ple optname arguments are given with -q, the return  sta-
                     tus  is zero if all optnames are enabled; non-zero other-
                     wise.
              -o     Restricts the values of optname to be those  defined  for
                     the -o option to the set builtin.

              If  either  -s  or  -u  is used with no optname arguments, 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 op-
              tions, 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  com-
                      mand.  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 com-
                      ponent in a cd command will be  corrected.   The  errors
                      checked for are transposed characters, a missing charac-
                      ter, and one character too many.   If  a  correction  is
                      found,  the  corrected filename is printed, and the com-
                      mand proceeds.  This option is only used by  interactive
                      shells.
              checkhash
                      If set, bash checks that a command found in the hash ta-
                      ble exists before trying to execute  it.   If  a  hashed
                      command  no  longer exists, a normal path search is per-
                      formed.
              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 ex-
                      iting 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  COL-
                      UMNS.
              cmdhist If  set,  bash attempts to save all lines of a multiple-
                      line command in the same  history  entry.   This  allows
                      easy re-editing of multi-line commands.
              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 compar-
                      ison when using the [[ conditional command's < and > op-
                      erators.  Bash versions prior to bash-4.1 use ASCII col-
                      lation 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) and the  effect  of  interrupting  a
                      command  list.   Bash  versions 3.2 and earlier continue
                      with the next command in the list after  one  terminates
                      due to an interrupt.
              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  inter-
                      rupting a command list.  Bash versions 4.0 and later in-
                      terrupt 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  num-
                      ber)  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 re-
                      moval.
              compat43
                      If set, bash does not print a warning message if an  at-
                      tempt  is made to use a quoted compound array assignment
                      as an argument to declare, makes word  expansion  errors
                      non-fatal  errors that cause the current command to fail
                      (the default behavior is to make them fatal errors  that
                      cause  the  shell  to exit), and does not reset the loop
                      state when a shell function  is  executed  (this  allows
                      break or continue in a shell function to affect loops in
                      the caller's context).
              complete_fullquote
                      If set, bash quotes all shell  metacharacters  in  file-
                      names  and  directory  names when performing completion.
                      If not set, bash removes metacharacters such as the dol-
                      lar  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  ex-
                      pand  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 back-
                      slashes 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  buf-
                      fer.   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 ini-
                      tially 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 can-
                      not execute the file specified as  an  argument  to  the
                      exec  builtin  command.   An  interactive shell does not
                      exit if exec fails.
              expand_aliases
                      If set, aliases are expanded as  described  above  under
                      ALIASES.  This option is enabled by default for interac-
                      tive shells.
              extdebug
                      If set at shell invocation, arrange to execute  the  de-
                      bugger profile before the shell starts, identical to the
                      --debugger option.  If set  after  invocation,  behavior
                      intended for use by debuggers is enabled:
                      1.     The -F option to the declare builtin displays the
                             source file name and line number corresponding to
                             each function name supplied as an argument.
                      2.     If  the  command  run by the DEBUG trap returns a
                             non-zero value, the next command is  skipped  and
                             not executed.
                      3.     If  the  command  run by the DEBUG trap returns a
                             value of 2, and the shell is executing in a  sub-
                             routine  (a shell function or a shell script exe-
                             cuted by the . or  source  builtins),  the  shell
                             simulates a call to return.
                      4.     BASH_ARGC  and BASH_ARGV are updated as described
                             in their descriptions above.
                      5.     Function tracing is  enabled:  command  substitu-
                             tion, shell functions, and subshells invoked with
                             ( command ) inherit the DEBUG and RETURN traps.
                      6.     Error tracing is enabled:  command  substitution,
                             shell  functions,  and  subshells  invoked with (
                             command ) inherit the 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 possi-
                      ble  completions.   See  SHELL VARIABLES above for a de-
                      scription of FIGNORE.  This option  is  enabled  by  de-
                      fault.
              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 com-
                      parisons.  That is, the current locale's  collating  se-
                      quence  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 con-
                      text 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 ex-
                      its, rather than overwriting the file.
              histreedit
                      If  set, and readline is being used, a user is given the
                      opportunity to re-edit a failed history substitution.
              histverify
                      If set, and readline is being used, the results of  his-
                      tory  substitution  are  not  immediately  passed to the
                      shell parser.  Instead, the  resulting  line  is  loaded
                      into the readline editing buffer, allowing further modi-
                      fication.
              hostcomplete
                      If set, and readline is being used, bash will attempt to
                      perform  hostname  completion when a word containing a @
                      is  being  completed  (see  Completing  under   READLINE
                      above).  This is enabled by default.
              huponexit
                      If set, bash will send SIGHUP to all jobs when an inter-
                      active login shell exits.
              inherit_errexit
                      If set, command substitution inherits the value  of  the
                      errexit  option, instead of unsetting it in the subshell
                      environment.  This option is enabled when posix mode  is
                      enabled.
              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 op-
                      tion 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 back-
                      ground 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  dis-
                      played.
              no_empty_cmd_completion
                      If  set,  and  readline is being used, bash will not at-
                      tempt 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, when performing pattern substi-
                      tution word expansions, or when filtering possible  com-
                      pletions as part of programmable completion.
              nullglob
                      If  set,  bash allows patterns which match no files (see
                      Pathname Expansion above) to expand to  a  null  string,
                      rather than themselves.
              progcomp
                      If set, the programmable completion facilities (see Pro-
                      grammable Completion above) are enabled.  This option is
                      enabled by default.
              promptvars
                      If set, prompt strings undergo parameter expansion, com-
                      mand substitution, arithmetic expansion, and  quote  re-
                      moval  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  re-
                      stricted  mode  (see RESTRICTED SHELL below).  The value
                      may not be changed.  This is not reset when the  startup
                      files  are  executed, allowing the startup files to dis-
                      cover whether or not a shell is restricted.
              shift_verbose
                      If set, the shift builtin prints an error  message  when
                      the shift count exceeds the number of positional parame-
                      ters.
              sourcepath
                      If set, the source (.) builtin uses the value of PATH to
                      find  the  directory  containing the file supplied as an
                      argument.  This option is enabled by default.
              xpg_echo
                      If set, the echo builtin  expands  backslash-escape  se-
                      quences 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 sta-
              tus is 0 unless the shell is a login shell and -f  is  not  sup-
              plied, or if job control is not enabled.

       test expr
       [ expr ]
              Return a status of 0 (true) or 1 (false) depending on the evalu-
              ation of the conditional expression expr.  Each operator and op-
              erand  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 de-
              pends on the number of arguments; see  below.   Operator  prece-
              dence 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 argu-
                     ment is one of the  unary  conditional  operators  listed
                     above  under  CONDITIONAL  EXPRESSIONS, the expression is
                     true if the unary test is true.  If the first argument is
                     not a valid unary conditional operator, the expression is
                     false.
              3 arguments
                     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.   Other-
                     wise, 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 eval-
                     uated according to  precedence  using  the  rules  listed
                     above.
              5 or more arguments
                     The  expression  is  parsed  and  evaluated  according to
                     precedence using the rules listed above.

              When used with test or [, the < and  >  operators  sort  lexico-
              graphically 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  re-
              ceives signal(s) sigspec.  If arg is absent (and there is a sin-
              gle sigspec) or -, each specified signal is reset to its  origi-
              nal  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  com-
              mands  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 <sig-
              nal.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  exe-
              cuted  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 fin-
              ishes executing.

              If a sigspec is ERR, the command  arg  is  executed  whenever  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) op-
              tion.

              Signals ignored upon entry to the shell cannot be trapped or re-
              set.   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 re-
              turned.  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  re-
              turn  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 necessar-
              ily 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 [-HSabcdefiklmnpqrstuvxPT [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 speci-
              fied, 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, re-
              spectively.  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 inter-
              preted 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
              -k     The maximum number of kqueues that may be allocated
              -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
              -P     The maximum number of pseudoterminals
              -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;  -P,  -T, -b, -k, -n, and -u, which are unscaled values;
              and, when in Posix mode, -c and -f, which are in 512-byte incre-
              ments.  The return status is 0 unless an invalid option or argu-
              ment is supplied, or an error occurs while setting a new limit.

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

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

       unset [-fv] [-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  func-
              tion,  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 vari-
              able 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,  RAN-
              DOM, SECONDS, LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are
              unset, they lose their special properties, even if they are sub-
              sequently reset.  The exit status is true unless a name is read-
              only.

       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 pro-
              cesses are waited for, and the return status is zero.  If the -n
              option  is supplied, wait waits for any job to terminate and re-
              turns 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.

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

       o      changing directories with cd

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

       o      specifying command names containing /

       o      specifying a filename containing a / as an  argument  to  the  .
              builtin command

       o      specifying  a  filename containing a slash as an argument to the
              -p option to the hash builtin command

       o      importing function definitions from  the  shell  environment  at
              startup

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

       o      redirecting output using the >, >|, <>, >&, &>, and >> redirect-
              ion operators

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

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

       o      using  the  enable  builtin  command  to  enable  disabled shell
              builtins

       o      specifying the -p option to the command builtin command

       o      turning off restricted mode with set +r or set +o restricted.

       These restrictions are enforced after any startup files are read.

       When a command that is found to be a shell script is executed (see COM-
       MAND  EXECUTION  above),  rbash turns off any restrictions in the shell
       spawned to execute the script.

SEE ALSO
       Bash Reference Manual, Brian Fox and Chet Ramey
       The Gnu Readline Library, Brian Fox and Chet Ramey
       The Gnu History Library, Brian Fox and Chet Ramey
       Portable Operating System Interface (POSIX) Part 2:  Shell  and  Utili-
       ties, IEEE --
              http://pubs.opengroup.org/onlinepubs/9699919799/
       http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
       sh(1), ksh(1), csh(1)
       emacs(1), vi(1)
       readline(3)

FILES
       /bin/bash
              The bash executable
       /etc/profile
              The systemwide initialization file, executed for login shells
       /etc/bash.bashrc
              The systemwide per-interactive-shell startup file

       /etc/bash.bash.logout
              The  systemwide  login shell cleanup file, executed when a login
              shell exits
       ~/.bash_profile
              The personal initialization file, executed for login shells
       ~/.bashrc
              The individual per-interactive-shell startup file
       ~/.bash_logout
              The individual login shell cleanup file, executed when  a  login
              shell exits
       ~/.inputrc
              Individual readline initialization file

AUTHORS
       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet.ramey@case.edu

BUG REPORTS
       If you find a bug in bash, you should report it.  But first, you should
       make sure that it really is a bug, and that it appears  in  the  latest
       version   of  bash.   The  latest  version  is  always  available  from
       ftp://ftp.gnu.org/pub/gnu/bash/.

       Once you have determined that a bug actually exists,  use  the  bashbug
       command  to submit a bug report.  If you have a fix, you are encouraged
       to mail that as well!  Suggestions and `philosophical' bug reports  may
       be  mailed  to  bug-bash@gnu.org  or  posted  to  the  Usenet newsgroup
       gnu.bash.bug.

       ALL bug reports should include:

       The version number of bash
       The hardware and operating system
       The compiler used to compile
       A description of the bug behaviour
       A short script or `recipe' which exercises the bug

       bashbug inserts the first three items automatically into  the  template
       it provides for filing a bug report.

       Comments and bug reports concerning this manual page should be directed
       to chet.ramey@case.edu.

BUGS
       It's too big and too slow.

       There are some subtle differences between bash and traditional versions
       of sh, mostly because of the POSIX specification.

       Aliases are confusing in some uses.

       Shell builtin commands and functions are not stoppable/restartable.

       Compound commands and command sequences of the form `a ; b ; c' are not
       handled gracefully  when  process  suspension  is  attempted.   When  a
       process  is stopped, the shell immediately executes the next command in
       the sequence.  It suffices to place the sequence  of  commands  between
       parentheses  to  force  it  into  a subshell, which may be stopped as a
       unit.

       Array variables may not (yet) be exported.

       There may be only one active coprocess at a time.

GNU Bash 4.4                    2016 August 26                         BASH(1)
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