bash(1)



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
       invoked.  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
                 assigned  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 mes-
                 sages.
       -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.
       -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
       options must appear on the command  line  before  the  single-character
       options 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
              below).

       --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
       executed,  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
       (unless -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
       example, 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
       behavior of historical versions of sh as  closely  as  possible,  while
       conforming  to the POSIX standard as well.  When invoked as an interac-
       tive 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
       inhibit  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
       attempt  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
       another 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
       appear 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
       arguments 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
              effect 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
              below  under ARITHMETIC EVALUATION.  If the value of the expres-
              sion 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
       described 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
       accordingly  (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
              parameter 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
              error, 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  stan-
              dard  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 dis-
              played 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
              expanded using tilde expansion, parameter  and  variable  expan-
              sion,  arithmetic  expansion, command substitution, process sub-
              stitution and quote removal.  Each pattern examined is  expanded
              using  tilde expansion, parameter and variable expansion, arith-
              metic expansion, command substitution, and process substitution.
              If  the  nocasematch  shell option is enabled, the match is per-
              formed 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  patterns.  Using ;;& in place of ;; causes the shell to test
              the next pattern list in the statement, if any, and execute  any
              associated  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,
              except 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 exe-
              cuted.

   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
       default name is COPROC.  NAME must not be supplied if command is a sim-
       ple command (see above); otherwise, it is interpreted as the first word
       of the simple command.  When the coprocess is executed, the shell  cre-
       ates  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
       descriptor is assigned to NAME[0].  The standard input  of  command  is
       connected  via  a pipe to a file descriptor in the executing shell, and
       that file descriptor is assigned to NAME[1].  This pipe is  established
       before  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 execute 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 terminate.

       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
       itself  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,
       export,  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
       expression and added to the variable's current  value,  which  is  also
       evaluated.   When  +=  is  applied  to an array variable using compound
       assignment (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
       applied 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
       attributes 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,
       assignments, 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
              parameter 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
              parameter separated by the first character of  the  IFS  special
              variable.   That  is, "$*" is equivalent to "$1c$2c...", where c
              is the first character of the value of the IFS variable.  If IFS
              is  unset,  the  parameters  are separated by spaces.  If IFS is
              null, the parameters are joined without intervening separators.
       @      Expands to the positional parameters, starting from  one.   When
              the  expansion  occurs  within  double  quotes,  each  parameter
              expands to a separate word.  That is, "$@" 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
              itself (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
              argument 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
              option 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
              below)
       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
              expression.   The  element  with  index  n is the portion of the
              string matching the nth parenthesized subexpression.  This vari-
              able 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
              defined  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
              described 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
              unset,  it  loses  its  special properties, even if it is subse-
              quently 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
              reset.

              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
              instance,    ${FUNCNAME[$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
              reset.
       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
       assigns 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
              described 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
              enabled 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
              directories  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
              array 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
              ignorespace, 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
              anchored  at  the  beginning of the line and must match the com-
              plete line (no implicit  `*'  is  appended).   Each  pattern  is
              tested  against  the line after the checks specified by HISTCON-
              TROL are applied.  In  addition  to  the  normal  shell  pattern
              matching characters, `&' matches the previous history line.  `&'
              may be escaped using  a  backslash;  the  backslash  is  removed
              before attempting a match.  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 HISTIGNORE.  The pattern
              matching 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
              attempted  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
              after 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
              default 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
              sequences 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
              arrival of mail in the specified file or  Maildir-format  direc-
              tory.
       MAILCHECK
              Specifies  how  often  (in  seconds)  bash checks for mail.  The
              default 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
              execution trace.  The first character of PS4 is replicated  mul-
              tiple  times, as necessary, to indicate multiple levels of indi-
              rection.  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
              default 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
       introduced 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
       expansion  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[sub-
       script]}.  If subscript is * or @, the expansion is the number of  ele-
       ments  in  the array.  If the subscript used to reference an element of
       an indexed array evaluates to a number less than  zero,  it  is  inter-
       preted  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]
       destroys  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
       array.   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
       default 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
       expression.   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
       replaces 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
       assignments to PATH, MAILPATH, and CDPATH, and the  shell  assigns  the
       expanded 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
       embedded  arithmetic  expansion,  command  substitution,  or  parameter
       expansion.

       ${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
       parameter 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
       below  (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
       unset.

       ${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
              expansion of word is assigned to parameter.  The value of param-
              eter  is  then  substituted.   Positional parameters and special
              parameters 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
              parameter.  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
              expansion  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 :- expan-
              sion.

              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
              ${parameter[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
              undefined results.

              Substring indexing is zero-based unless the  positional  parame-
              ters  are  used,  in  which  case  the  indexing  starts at 1 by
              default.  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
              parameter is substituted.  If parameter is *  or  @,  the  value
              substituted  is the number of positional parameters.  If parame-
              ter is an array name subscripted by * or @,  the  value  substi-
              tuted  is  the number of elements in the array.  If parameter is
              an indexed array name subscripted by  a  negative  number,  that
              number  is interpreted as relative to one greater than the maxi-
              mum index of parameter, so negative indices count back from  the
              end  of  the  array, and an index of -1 references the last ele-
              ment.

       ${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
              replaced.  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 ^
              operator converts lowercase letters matching pattern  to  upper-
              case; the , operator converts matching uppercase letters to low-
              ercase.  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
              omitted,  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  sub-
              scripted 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
       upcoming 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
       tokens 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
       results 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
       removed.  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
       regard  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,
       unless 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
       nocaseglob, 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
       beginning with a ``.''  will match.  To get the old behavior of  ignor-
       ing  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
                     directories 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
                     sequence and character set, is  matched.   If  the  first
                     character following the [ is a !  or a ^ then any charac-
                     ter not enclosed is matched.  The sorting order of  char-
                     acters  in range expressions is determined by the current
                     locale and the values of the LC_COLLATE or  LC_ALL  shell
                     variables, if set.  To obtain the traditional interpreta-
                     tion 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
                     using the syntax [=c=], which matches all characters with
                     the same collation weight  (as  defined  by  the  current
                     locale) 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
       expansion 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
       results  from  the expansion of word to be opened for appending 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.

       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
       error:

              &>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
       Descriptors 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
       unquoted,  all  lines  of  the here-document are subjected to parameter
       expansion, command substitution, and arithmetic expansion, the  charac-
       ter  sequence  \<newline>  is  ignored, and \ must be used to quote the
       characters \, $, and `.

       If the redirection operator is <<-, then all leading tab characters are
       stripped  from  input  lines  and  the line containing delimiter.  This
       allows 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
                     inserted 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
       below),  while  the  command  number is the position in the sequence of
       commands executed during the current shell session.  After  the  string
       is  decoded,  it is expanded via parameter expansion, command substitu-
       tion, 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
       ~/.inputrc.  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
              arrow 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
              attempts 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),
              regardless 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
              received 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-directories).
       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
              instead of ringing the bell.
       show-mode-in-prompt (Off)
              If  set  to  On,  add a character to the beginning of the prompt
              indicating the editing mode: emacs (@), vi  command  (:)  or  vi
              insertion (+).
       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
              sequences 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
              sequences 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
                     instance,  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
                     library  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
              inserts 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
              EXPANSION 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,
              $EDITOR, 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
              argument, uppercase the previous word, but do not move point.
       downcase-word (M-l)
              Lowercase  the  current  (or  following)  word.  With a negative
              argument, lowercase the previous word, but do not move point.
       capitalize-word (M-c)
              Capitalize the current (or following)  word.   With  a  negative
              argument, 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
              numeric argument, but is otherwise ignored.  As a special  case,
              if  this  command is immediately followed by a character that is
              neither 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
              argument  may  be  used to move backward through the list.  This
              command 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
              removed, the line will be executed by the shell.
       glob-complete-word (M-g)
              The  word  before  point  is  treated  as a pattern for pathname
              expansion, with an asterisk implicitly appended.   This  pattern
              is  used  to  generate a list of matching filenames for possible
              completions.
       glob-expand-word (C-x *)
              The word before point is  treated  as  a  pattern  for  pathname
              expansion,  and  the  list  of  matching  filenames is inserted,
              replacing 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
       option 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
       being 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
       defined, 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
       default 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
       unwritable,  the  history is not saved.  If the HISTTIMEFORMAT variable
       is set, time stamps are written to the history file,  marked  with  the
       history  comment  character, so they may be preserved across shell ses-
       sions.  This uses the history comment character  to  distinguish  time-
       stamps from other history lines.  After saving the history, the history
       file is truncated to contain no more than HISTFILESIZE lines.  If HIST-
       FILESIZE  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
       manipulate  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
       options.

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
       default.   Only  backslash  (\) and single quotes can quote the history
       expansion character,  but  the  history  expansion  character  is  also
       treated  as  quoted if it immediately precedes the closing double quote
       in a double-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
       option 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
              expand 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
              delimiter 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
              environment  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
              positional 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
              returns  true unless a name is given for which no alias has been
              defined.

       bg [jobspec ...]
              Resume each suspended job jobspec in the background,  as  if  it
              had been started with &.  If jobspec is not present, the shell's
              notion of the current job is used.  bg jobspec returns 0  unless
              run  when  job control is disabled or, when run with job control
              enabled, any specified jobspec was  not  found  or  was  started
              without job control.

       bind [-m keymap] [-lpsvPSVX]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] -x keyseq:shell-command
       bind [-m keymap] keyseq:function-name
       bind [-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
              appear in .inputrc, but each binding or command must  be  passed
              as  a  separate argument; e.g., '"\C-x\C-r": re-read-init-file'.
              Options, if supplied, have the following meanings:
              -m keymap
                     Use keymap as the keymap to be affected by the subsequent
                     bindings.  Acceptable keymap names are emacs, emacs-stan-
                     dard, emacs-meta, emacs-ctlx,  vi,  vi-move,  vi-command,
                     and  vi-insert.   vi is equivalent to vi-command (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
                     entered.   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
                     input.

              The  return value is 0 unless an unrecognized option is given or
              an error occurred.

       break [n]
              Exit from within a for, while, until, or select loop.  If  n  is
              specified,  break  n  levels.   n must be >= 1.  If n is greater
              than the number of enclosing  loops,  all  enclosing  loops  are
              exited.   The  return value is 0 unless n is not greater than or
              equal to 1.

       builtin shell-builtin [arguments]
              Execute the specified shell builtin, passing it  arguments,  and
              return its exit status.  This is useful when defining a function
              whose name is the same as a shell builtin, retaining  the  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
              directory names in CDPATH are separated by a colon (:).  A  null
              directory  name  in CDPATH is the same as the current directory,
              i.e., ``.''.  If dir begins with a slash (/), then CDPATH is not
              used.   The  -P  option  causes cd to use the physical directory
              structure by resolving symbolic links while traversing  dir  and
              before processing instances of .. in dir (see also the -P option
              to the set builtin command); the -L option forces symbolic links
              to  be followed by resolving the link after processing instances
              of .. in dir.  If .. appears in dir, it is processed by removing
              the  immediately previous pathname component from dir, back to a
              slash or the beginning of dir.  If the  -e  option  is  supplied
              with  -P,  and  the current working directory cannot be 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
              option is supplied, a description of command is printed.  The -v
              option  causes  a single word indicating the command or filename
              used to invoke command to be displayed; the -V option produces a
              more  verbose  description.  If the -V or -v option is supplied,
              the exit status is 0 if command was found, and  1  if  not.   If
              neither option is supplied and an error occurred or command can-
              not be found, the exit status is 127.  Otherwise, the exit  sta-
              tus of the command builtin is the exit status of command.

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

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

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

       complete [-abcdefgjksuv] [-o comp-option] [-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
              remaining  options  and  actions should apply to the ``default''
              command completion; that is, completion attempted on  a  command
              for  which  no  completion  has previously been defined.  The -E
              option indicates that the remaining options and  actions  should
              apply  to  ``empty''  command  completion;  that  is, completion
              attempted on a blank line.

              The process of applying  these  completion  specifications  when
              word  completion  is attempted is described above under 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
                              default)  to  words  completed at the end of the
                              line.
                      plusdirs
                              After any matches defined by  the  compspec  are
                              generated,    directory   name   completion   is
                              attempted and  any  matches  are  added  to  the
                              results of the other actions.
              -A action
                      The  action  may  be  one of the following to generate a
                      list of possible completions:
                      alias   Alias names.  May also be specified as -a.
                      arrayvar
                              Array variable names.
                      binding Readline key binding names.
                      builtin Names of shell builtin commands.   May  also  be
                              specified as -b.
                      command Command names.  May also be specified as -c.
                      directory
                              Directory names.  May also be specified as -d.
                      disabled
                              Names of disabled shell builtins.
                      enabled Names of enabled shell builtins.
                      export  Names  of exported shell variables.  May also be
                              specified as -e.
                      file    File names.  May also be specified as -f.
                      function
                              Names of shell functions.
                      group   Group names.  May also be specified as -g.
                      helptopic
                              Help topics as accepted by the help builtin.
                      hostname
                              Hostnames, as taken from the file  specified  by
                              the HOSTFILE shell variable.
                      job     Job  names,  if job control is active.  May also
                              be specified as -j.
                      keyword Shell reserved words.  May also be specified  as
                              -k.
                      running Names of running jobs, if job control is active.
                      service Service names.  May also be specified as -s.
                      setopt  Valid  arguments  for  the  -o option to the set
                              builtin.
                      shopt   Shell option names  as  accepted  by  the  shopt
                              builtin.
                      signal  Signal names.
                      stopped Names of stopped jobs, if job control is active.
                      user    User names.  May also be specified as -u.
                      variable
                              Names of all shell variables.  May also be spec-
                              ified as -v.
              -C command
                      command is executed in a subshell environment,  and  its
                      output is used as the possible completions.
              -F function
                      The  shell  function function is executed in the current
                      shell environment.  When the function is  executed,  the
                      first  argument  ($1)  is  the name of the command whose
                      arguments are being completed, the second argument  ($2)
                      is the word being completed, and the third argument ($3)
                      is the word preceding the word being  completed  on  the
                      current  command  line.   When it finishes, the possible
                      completions are retrieved from the value of the  COMPRE-
                      PLY 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
              options, or for the currently-executing completion if  no  names
              are  supplied.   If no options are given, display the completion
              options for each name or the current completion.   The  possible
              values  of  option  are  those  valid  for  the complete builtin
              described above.  The -D option  indicates  that  the  remaining
              options should apply to the ``default'' command completion; that
              is, completion attempted on a command for  which  no  completion
              has  previously  been defined.  The -E option indicates that the
              remaining options should apply to ``empty'' command  completion;
              that is, completion attempted on a blank line.

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

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

       declare [-aAfFgilnrtux] [-p] [name[=value] ...]
       typeset [-aAfFgilnrtux] [-p] [name[=value] ...]
              Declare variables and/or give them attributes.  If no names  are
              given  then display the values of variables.  The -p option will
              display the attributes and values of each name.  When -p is used
              with  name  arguments, additional options, other than -f and -F,
              are ignored.  When -p is supplied  without  name  arguments,  it
              will  display  the attributes and values of all variables having
              the attributes specified by the additional options.  If no other
              options   are   supplied  with  -p,  declare  will  display  the
              attributes and values of all shell  variables.   The  -f  option
              will  restrict  the  display  to shell functions.  The -F option
              inhibits the display of function definitions; only the  function
              name  and  attributes are printed.  If the extdebug shell option
              is enabled using shopt, the source file  name  and  line  number
              where 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 function.  It is ignored in all other cases.  The  follow-
              ing 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
                     inherit the DEBUG  and  RETURN  traps  from  the  calling
                     shell.   The  trace  attribute has no special meaning for
                     variables.
              -u     When the variable is assigned  a  value,  all  lower-case
                     characters  are  converted to upper-case.  The lower-case
                     attribute is disabled.
              -x     Mark names for export  to  subsequent  commands  via  the
                     environment.

              Using  `+'  instead of `-' turns off the attribute instead, with
              the exceptions that +a may not be used to destroy an array 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
              assign  a  value to an array variable without using the compound
              assignment syntax (see Arrays above), one of the names is not  a
              valid  shell variable name, an attempt is made to turn off read-
              only status for a readonly variable, an attempt is made to  turn
              off array status for an array variable, or an attempt is made to
              display a non-existent function with -f.

       dirs [-clpv] [+n] [-n]
              Without options,  displays  the  list  of  currently  remembered
              directories.   The  default  display  is  on  a single line with
              directory names separated by spaces.  Directories are  added  to
              the  list  with  the  pushd  command;  the  popd command removes
              entries from the list.  The  current  directory  is  always  the
              first directory in the stack.
              -c     Clears  the  directory  stack  by  deleting  all  of  the
                     entries.
              -l     Produces a listing  using  full  pathnames;  the  default
                     listing format uses a tilde to denote the home directory.
              -p     Print the directory stack with one entry per line.
              -v     Print  the  directory stack with one entry per line, 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
              receives a SIGHUP.  If no jobspec is  supplied,  the  -a  option
              means  to  remove or mark all jobs; the -r option without a job-
              spec argument restricts operation to running jobs.   The  return
              value is 0 unless a jobspec does not specify a valid job.

       echo [-neE] [arg ...]
              Output  the  args,  separated  by spaces, followed by a newline.
              The return status is 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
              escape  characters  by  default.   echo does not interpret -- to
              mean the end of options.  echo interprets the  following  escape
              sequences:
              \a     alert (bell)
              \b     backspace
              \c     suppress further output
              \e
              \E     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\     backslash
              \0nnn  the  eight-bit  character  whose value is the octal value
                     nnn (zero to three octal digits)
              \xHH   the eight-bit character whose value  is  the  hexadecimal
                     value HH (one or two hex digits)
              \uHHHH the  Unicode (ISO/IEC 10646) character whose value is the
                     hexadecimal value HHHH (one to four hex digits)
              \UHHHHHHHH
                     the Unicode (ISO/IEC 10646) character whose value is  the
                     hexadecimal value HHHHHHHH (one to eight hex digits)

       enable [-a] [-dnps] [-f filename] [name ...]
              Enable  and disable builtin shell commands.  Disabling a builtin
              allows a disk command which has the same name as a shell builtin
              to  be  executed without specifying a full pathname, even though
              the shell normally searches for builtins before  disk  commands.
              If  -n  is  used,  each  name  is disabled; otherwise, names are
              enabled.  For example, to use the test binary found via the PATH
              instead  of  the  shell builtin version, run ``enable -n test''.
              The -f option means to load the new builtin  command  name  from
              shared object filename, on systems that support dynamic loading.
              The -d option will delete a builtin previously loaded  with  -f.
              If no name arguments are given, or if the -p option is supplied,
              a list of shell builtins is printed.  With no other option 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
              login(1) does.  The -c option causes command to be executed with
              an  empty environment.  If -a is supplied, the shell passes name
              as the zeroth argument to the executed command.  If command 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
              invalid option is encountered or first or last  specify  history
              lines  out  of  range.  If the -e option is supplied, the return
              value is the value of the last command executed or failure if an
              error occurs with the temporary file of commands.  If the second
              form is used, the return status is that of the  command  re-exe-
              cuted,  unless  cmd  does  not  specify a valid history line, in
              which case fc returns failure.

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

       getopts optstring name [args]
              getopts is used by shell procedures to parse positional  parame-
              ters.   optstring  contains  the  option characters to be recog-
              nized; if a character is followed by  a  colon,  the  option  is
              expected  to have an argument, which should be separated from it
              by white space.  The colon and question mark characters may  not
              be  used as option characters.  Each time it is invoked, getopts
              places the next option in the shell variable name,  initializing
              name if it does not exist, and the index of the next argument to
              be processed into the variable OPTIND.  OPTIND is initialized to
              1  each  time  the  shell or a shell script is invoked.  When an
              option requires an argument, getopts places that  argument  into
              the  variable OPTARG.  The shell does not reset OPTIND automati-
              cally; it must be  manually  reset  between  multiple  calls  to
              getopts within the same shell invocation if a new set of parame-
              ters is to be used.

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

              getopts normally parses the positional parameters, but  if  more
              arguments are given in args, getopts parses those instead.

              getopts  can  report errors in two ways.  If the first character
              of optstring is a colon, silent error  reporting  is  used.   In
              normal  operation,  diagnostic messages are printed when invalid
              options or missing option arguments  are  encountered.   If  the
              variable  OPTERR  is  set  to  0, no error messages will be dis-
              played, even if the first character of optstring is not a colon.

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

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

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

       hash [-lr] [-p filename] [-dt] [name]
              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
              option  causes  the  shell  to forget the remembered location of
              each name.  If the -t option is supplied, the full  pathname  to
              which  each name corresponds is printed.  If multiple name argu-
              ments are supplied with -t,  the  name  is  printed  before  the
              hashed  full  pathname.   The -l option causes output to be dis-
              played in a format that may be reused as input.  If no arguments
              are  given,  or if only -l is supplied, information about remem-
              bered 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
                     appended  to  the history file since the beginning of the
                     current bash session.
              -r     Read the contents of the history file and append them  to
                     the current history list.
              -w     Write the current history list to the history file, 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
              executes 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
              option 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
              array before assigning to it.

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

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

              If the popd command is successful, a dirs is performed as  well,
              and  the  return  status is 0.  popd returns false if an invalid
              option is encountered, the directory stack is empty, a non-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
                     argument  is  specified,  conversion behaves as if -1 had
                     been given.  This is an exception  to  the  usual  printf
                     behavior.

              Arguments  to non-string format specifiers are treated as C 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
              directories  and returns 0, unless the directory stack is empty.
              Arguments, if supplied, have the following meanings:
              -n     Suppresses the normal change of directory  when  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
              invalid option is supplied.

       read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p
       prompt] [-t timeout] [-u fd] [name ...]
              One line is read from the  standard  input,  or  from  the  file
              descriptor  fd  supplied  as an argument to the -u option, split
              into words as described above  under  Word  Splitting,  and  the
              first word is assigned to the first name, the second word to the
              second 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
              (described 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
                     ignored.
              -d delim
                     The first character of delim is  used  to  terminate  the
                     input line, rather than newline.
              -e     If the standard input is coming from a terminal, readline
                     (see READLINE above) is used to obtain the  line.   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
                     returns  immediately,  without  trying  to read any data.
                     The exit status is 0 if input is available on the  speci-
                     fied  file descriptor, non-zero otherwise.  The exit sta-
                     tus 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
              encountered, 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
              arrays;  the  -A  option  restricts the variables to associative
              arrays.  If both options are supplied, -A takes precedence.   If
              no  name arguments are given, or if the -p option is supplied, a
              list of all readonly names is printed.  The other options may be
              used  to  restrict the output to a subset of the set of readonly
              names.  The -p option causes output to be displayed in a  format
              that  may be reused as input.  If a variable name is followed by
              =word, the value of the variable is set  to  word.   The  return
              status  is 0 unless an invalid option is encountered, one of the
              names is not a valid shell variable name, or -f is supplied with
              a name that is not a function.

       return [n]
              Causes  a function to stop executing and return the value 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
              return is executed by a trap handler, the last command  used  to
              determine  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
              executed 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
              significant 8 bits.  The return status is non-zero if return  is
              supplied  a  non-numeric argument, or is used outside a function
              and not during execution of a script by . or source.   Any  com-
              mand  associated  with the RETURN trap is executed before execu-
              tion resumes after the function or script.

       set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]
       set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg ...]
              Without options, the name and value of each shell  variable  are
              displayed in a format that can be reused as input for setting or
              resetting the currently-set variables.  Read-only variables can-
              not  be  reset.  In posix mode, only shell variables are listed.
              The output is sorted according  to  the  current  locale.   When
              options  are specified, they set or unset shell attributes.  Any
              arguments remaining after 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
                      ignored by interactive shells.
              -o option-name
                      The option-name can be one of the following:
                      allexport
                              Same as -a.
                      braceexpand
                              Same as -B.
                      emacs   Use an emacs-style command line  editing  inter-
                              face.  This is enabled by default when the shell
                              is interactive, unless the shell is started with
                              the  --noediting  option.  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
                              ``IGNOREEOF=10''  had  been  executed (see Shell
                              Variables above).
                      keyword Same as -k.
                      monitor Same as -m.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Currently ignored.
                      notify  Same as -b.
                      nounset Same as -u.
                      onecmd  Same as -t.
                      physical
                              Same as -P.
                      pipefail
                              If set, the return value of a  pipeline  is  the
                              value  of  the  last (rightmost) command to exit
                              with a non-zero status, or zero if all  commands
                              in  the pipeline exit successfully.  This option
                              is disabled by default.
                      posix   Change the behavior of bash  where  the  default
                              operation  differs  from  the  POSIX standard to
                              match the standard (posix mode).  See  SEE  ALSO
                              below for a reference to a document that details
                              how posix mode affects bash's behavior.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      vi      Use a vi-style command line  editing  interface.
                              This also affects the editing interface used for
                              read -e.
                      xtrace  Same as -x.
                      If -o is supplied with no option-name, the values of the
                      current  options are printed.  If +o is supplied with no
                      option-name, a series of set commands  to  recreate  the
                      current  option  settings  is  displayed on the standard
                      output.
              -p      Turn on privileged mode.  In this  mode,  the  $ENV  and
                      $BASH_ENV  files  are not processed, shell functions are
                      not inherited from the environment, and  the  SHELLOPTS,
                      BASHOPTS,  CDPATH,  and  GLOBIGNORE  variables,  if they
                      appear in the environment, are ignored.  If the shell is
                      started  with the effective user (group) id not equal to
                      the real user (group) id, and the -p option is not  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
                      executed in  a  subshell  environment.   The  DEBUG  and
                      RETURN traps are normally not inherited in such cases.
              --      If  no arguments follow this option, then the positional
                      parameters are unset.  Otherwise, the positional parame-
                      ters  are  set  to  the args, even if some of them begin
                      with a -.
              -       Signal the end of options, cause all remaining  args  to
                      be assigned to the positional parameters.  The -x and -v
                      options are turned off.  If there are no args, the posi-
                      tional parameters remain unchanged.

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

       shift [n]
              The positional parameters from n+1 ... are renamed  to  $1  ....
              Parameters  represented  by  the  numbers  $# down to $#-n+1 are
              unset.  n must be a non-negative number less than  or  equal  to
              $#.   If  n is 0, no parameters are changed.  If n is not given,
              it is assumed to be 1.  If n is greater than $#, the  positional
              parameters  are  not changed.  The return status is greater than
              zero if n is greater than $# or less than zero; otherwise 0.

       shopt [-pqsu] [-o] [optname ...]
              Toggle the values of 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
              options,  the  return  status is zero unless an optname is not a
              valid shell option.

              The list of shopt options is:

              autocd  If set, a command name that is the name of  a  directory
                      is  executed  as  if it were the argument to the cd 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
                      exiting if any jobs are stopped.
              checkwinsize
                      If set, bash checks the window size after  each  command
                      and,  if necessary, updates the values of LINES and 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 >
                      operators.  Bash versions prior to  bash-4.1  use  ASCII
                      collation and strcmp(3); bash-4.1 and later use the cur-
                      rent 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
                      interrupt  the  list as if the shell received the inter-
                      rupt; 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
                      removal.
              compat43
                      If  set,  bash  does  not  print a warning message if an
                      attempt is made to use a quoted compound  array  assign-
                      ment  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
                      expand to directories will not be quoted;  however,  any
                      dollar  signs appearing in filenames will not be quoted,
                      either.  This is active only when bash  is  using  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
                      debugger profile before the shell starts,  identical  to
                      the  --debugger option.  If set after invocation, behav-
                      ior 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
                      description  of  FIGNORE.   This  option  is  enabled by
                      default.
              globasciiranges
                      If set,  range  expressions  used  in  pattern  matching
                      bracket  expressions (see Pattern Matching above) behave
                      as if in the traditional C locale when  performing  com-
                      parisons.   That  is,  the  current  locale's  collating
                      sequence is not taken into account, so b will  not  col-
                      late  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
                      exits, rather than overwriting the file.
              histreedit
                      If set, and readline is being used, a user is given  the
                      opportunity to re-edit a failed history substitution.
              histverify
                      If  set, and readline is being used, the results of his-
                      tory substitution are  not  immediately  passed  to  the
                      shell  parser.   Instead,  the  resulting line is loaded
                      into the readline editing buffer, allowing further modi-
                      fication.
              hostcomplete
                      If set, and readline is being used, bash will attempt to
                      perform hostname completion when a word containing  a  @
                      is   being  completed  (see  Completing  under  READLINE
                      above).  This is enabled by default.
              huponexit
                      If set, bash will send SIGHUP to all jobs when an inter-
                      active login shell exits.
              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
                      option is enabled by default.
              lastpipe
                      If  set,  and  job control is not active, the shell runs
                      the last command of a pipeline not executed in the 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
                      attempt to search the PATH for possible completions when
                      completion is attempted on an empty line.
              nocaseglob
                      If set, bash matches  filenames  in  a  case-insensitive
                      fashion when performing pathname expansion (see Pathname
                      Expansion above).
              nocasematch
                      If set, bash  matches  patterns  in  a  case-insensitive
                      fashion when performing matching while executing case or
                      [[ conditional commands, 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
                      removal after being expanded as described  in  PROMPTING
                      above.  This option is enabled by default.
              restricted_shell
                      The   shell  sets  this  option  if  it  is  started  in
                      restricted mode (see RESTRICTED SHELL below).  The value
                      may  not be changed.  This is not reset when the startup
                      files are executed, allowing the startup files  to  dis-
                      cover whether or not a shell is restricted.
              shift_verbose
                      If  set,  the shift builtin prints an error message when
                      the shift count exceeds the number of positional parame-
                      ters.
              sourcepath
                      If set, the source (.) builtin uses the value of PATH to
                      find the directory containing the file  supplied  as  an
                      argument.  This option is enabled by default.
              xpg_echo
                      If   set,  the  echo  builtin  expands  backslash-escape
                      sequences by default.

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

              If a sigspec is EXIT (0) the command arg  is  executed  on  exit
              from  the shell.  If a sigspec is DEBUG, the command arg is 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)
              option.

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

       type [-aftpP] name [name ...]
              With  no options, indicate how each name would be interpreted if
              used as a command name.  If the -t option is used, type prints a
              string  which  is  one  of alias, keyword, function, builtin, or
              file if  name  is  an  alias,  shell  reserved  word,  function,
              builtin,  or disk file, respectively.  If the name is not found,
              then nothing  is  printed,  and  an  exit  status  of  false  is
              returned.   If  the  -p  option is used, type either returns the
              name of the disk file that would be executed if name were speci-
              fied as a command name, or nothing if ``type -t name'' would not
              return file.  The -P option forces a PATH search for each  name,
              even if ``type -t name'' would not return file.  If a command is
              hashed, -p and -P print the hashed value, 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,
              respectively.   If  limit  is  omitted, the current value of the
              soft limit of the resource is printed, unless the -H  option  is
              given.  When more than one resource is specified, the limit name
              and unit are printed before the value.  Other options are 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
              returns  its exit status.  If n specifies a non-existent process
              or job, the return status is 127.  Otherwise, the return  status
              is the exit status of the last process or job waited for.

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)

Man(1) output converted with man2html
list of all man pages