bash


SYNOPSIS
       bash [options] [file]

COPYRIGHT
       Bash is Copyright (C) 1989-2009 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
       In  addition  to  the  single-character shell options documented in the
       description of the set builtin command, bash interprets  the  following
       options when it is invoked:

       -c string If  the  -c  option  is  present, then commands are read from
                 string.  If there are arguments after the  string,  they  are
                 assigned to the positional parameters, starting with $0.
       -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.

              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).

       --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
       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 a login shell exits, 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 a network connection, as if by the remote shell  daemon,
       usually  rshd,  or the secure shell daemon sshd.  If bash determines it
       is being run in this fashion,  it  reads  and  executes  commands  from
       ~/.bashrc  and  ~/.bashrc,  if  these files exist and are readable.  It
       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
       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  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,
       the standard error of command is connected to command2's standard input
       through the pipe; it is shorthand for 2>&1 |.  This implicit  redirect-
       ion of the standard error is performed after any redirections specified
       by the command.

       specified by POSIX.  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.

       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 of 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:

       (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

       [[ 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.

              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.  If the  shell
              option  nocasematch  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 pat-
              tern, and 1 otherwise.  Any part of the pattern may be quoted to
              force it to be matched as a string.

              An  additional  binary operator, =~, is available, with the same
              precedence as == and !=.  When it is used,  the  string  to  the
              right  of the operator is considered an extended regular expres-
              sion 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 shell option nocasematch
              is enabled, the match is performed without regard to the case of
              alphabetic characters.  Any part of the pattern may be quoted to
              force it 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 parenthe-
              sized 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.

              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  substitution,  command  substitution,  process
              substitution  and  quote  removal.   Each  pattern  examined  is
              expanded using tilde expansion, parameter  and  variable  expan-
              sion, arithmetic substitution, command substitution, and process
              substitution.  If the shell option nocasematch is  enabled,  the
              match  is  performed  without  regard  to the case of alphabetic
              characters.  When a match is found, the  corresponding  list  is
              executed.  If the ;; operator is used, no subsequent matches are
              attempted after the first pattern match.  Using ;& in  place  of
              ;;  causes  execution  to continue with the list associated with
              the next set of 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
              of  the  while and until commands is the exit status of the last
              do list command executed, or zero if none was executed.

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

       The format for a coprocess is:

              coproc [NAME] command [redirections]

       This  creates  a  coprocess  named  NAME.  If NAME is not supplied, the
       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 coproc is executed, the shell  creates
       an  array  variable (see Arrays below) named NAME in the context of the
       executing shell.  The standard output of command  is  connected  via  a
       pipe  to  a  file  descriptor  in  the  executing  shell, and that file
       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 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.

       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:

       [ 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.  com-
              pound-command is executed whenever name is specified as the name
              of  a  simple command.  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 executed, the exit status of
              a function is the exit status of the last  command  executed  in
              the body.  (See FUNCTIONS below.)

COMMENTS
       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, !.  The characters $  and  `  retain
       their  special meaning within double quotes.  The backslash retains its
       special meaning 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
              \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

       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.

       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.  When += is applied to a vari-
       able 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.

   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 occurs within double quotes, it expands to a  sin-
              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 most recently executed back-
              ground (asynchronous) command.
       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 file name 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 file name 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 Ele-
              ments added to this array appear in the  alias  list;  unsetting
              array elements cause aliases to be removed from the alias list.
       BASH_ARGC
              An  array  variable whose values are the number of parameters in
              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;
              unsetting array elements cause commands to be removed  from  the
              hash table.
       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    corresponding    to    each    member    of   FUNCNAME.
              ${BASH_LINENO[$i]} is the line number in the source  file  where
              ${FUNCNAME[$i]}  was  called  (or ${BASH_LINENO[$i-1]} if refer-
              enced within another shell function).  The corresponding  source
              file  name is ${BASH_SOURCE[$i]}.  Use LINENO to obtain the cur-
              rent line number.
       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 corre-
              sponding to the elements in the FUNCNAME array variable.
       BASH_SUBSHELL
              Incremented by one each time a subshell or subshell  environment
              is spawned.  The initial 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
              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).

       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 is "main".  This variable exists  only  when  a
              shell  function  is  executing.  Assignments to FUNCNAME have no

       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.

       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.

       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
              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_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  file  name.
              PATH is not used to search for the resultant file name.
       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".
       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.
       COLUMNS
              Used  by  the  select  builtin command to determine the terminal
              width when printing selection  lists.   Automatically  set  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).
       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.
       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).
       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
              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  an  interactive  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, by removing the oldest entries, to contain
              no more than that number of lines.  The default  value  is  500.
              The history file is also truncated to this size after writing it
              when an interactive shell exits.
       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.
       HISTSIZE
              The number of commands to remember in the command  history  (see
              HISTORY below).  The default value is 500.
       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
              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.
       LINES  Used by the select  builtin  command  to  determine  the  column
              length  for  printing  selection  lists.  Automatically set upon
              receipt of a SIGWINCH.
       MAIL   If this parameter is set to a file name and the  MAILPATH  vari-
              able is not set, bash informs the user of the arrival of mail in
              the specified file.
       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 file names to  be  checked  for  mail.
              The message to be printed when mail arrives in a particular file
              may be specified by separating the file name  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  supplies  a default value for this variable, but the loca-
              tion 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
              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.
       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%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  input  after
              issuing  the  primary prompt.  Bash terminates after waiting for
              that number of seconds if input does not arrive.
              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
       referenced using arbitrary strings.

       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 greater than or
       equal to zero.  To explicitly declare an indexed array, use declare  -a
       name (see SHELL BUILTIN COMMANDS below).  declare -a name[subscript] is
       also accepted; the subscript 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 the bracket
       and subscript.  When assigning  to  indexed  arrays,  if  the  optional
       brackets  and subscript are supplied, that index is assigned to; other-
       wise 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.
       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.  Referencing an array variable without a  subscript
       is equivalent to referencing the array with a subscript of 0.

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

       The unset builtin is used to  destroy  arrays.   unset  name[subscript]
       destroys  the  array element at index subscript.  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.  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  assign-
       ments.

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,  parame-
       ter,  variable  and arithmetic expansion and command substitution (done
       in a left-to-right fashion), word splitting, and pathname expansion.

       On systems that can support it, there is an additional expansion avail-
       able: process substitution.

       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.
       sary.  When characters are supplied, the  expression  expands  to  each
       character lexicographically between x and y, inclusive.  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-

   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.

       If  the  first  character  of  parameter is an exclamation point (!), a
       level of variable indirection is introduced.  Bash uses  the  value  of
       the variable formed from the rest of parameter as the name of the vari-
       able; 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.  The exceptions to this are the  expan-
       sions  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,  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}
              length  positional parameters beginning at offset.  If parameter
              is an indexed array name subscripted by @ or *,  the  result  is
              the  length members of the array beginning with ${parameter[off-
              set]}.  A negative offset is taken relative to one greater  than
              the  maximum  index of the specified array.  Substring expansion
              applied to an  associative  array  produces  undefined  results.
              Note  that a negative offset must be separated from the colon by
              at least one space to avoid being confused with  the  :-  expan-
              sion.   Substring  indexing  is zero-based unless the positional
              parameters 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.

       ${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
              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 parameter is @ or *, the sub-
              stitution 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.   The  ^  operator
              converts  lowercase letters matching pattern to uppercase; the ,
              operator converts matching uppercase letters to lowercase.   The
              ^^  and  ,,  expansions  convert  each  matched character in the
              expanded value; the ^ and , expansions match  and  convert  only
              the first character in the expanded value..  If pattern is omit-
              ted, it is treated like a ?, which matches every character.   If
              parameter  is @ or *, the case modification operation is applied
              to each positional parameter in turn, and the expansion  is  the
              resultant  list.   If parameter is an array variable subscripted
              with @ or *, the case modification operation is applied to  each
              member  of the array in turn, and the expansion is the resultant
              list.

   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 and replacing the com-
       mand 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 command  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.
              $((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 expansion, string expansion,
       command  substitution, and quote removal.  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 is supported on systems that support  named  pipes
       (FIFOs)  or the /dev/fd method of naming open files.  It takes the form
       of <(list) or >(list).  The process list is run with its input or  out-
       put connected to a FIFO or some file in /dev/fd.  The name of this file
       is passed as an argument to the current command as the  result  of  the
       expansion.   If the >(list) form is used, writing to the file will pro-
       vide input for list.  If the <(list) form is used, the file  passed  as
       an argument should be read to obtain the output of list.

       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 on these characters.  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 and tab are ignored at the
       beginning  and  end of the word, as long as the whitespace character is
       in the value of IFS (an IFS whitespace 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.   Unquoted  implicit
       null arguments, resulting from the expansion of parameters that have no
       values, are removed.  If a parameter with no value is  expanded  within
       double quotes, a null argument results and is retained.

       enabled, the match is performed without regard to the  case  of  alpha-
       betic  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 expan-
       sion, the character ``.''  at the start of a name or  immediately  fol-
       lowing a slash must be matched explicitly, unless the shell option dot-
       glob 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, fail-
       glob, 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 file
       name that also matches one of the patterns  in  GLOBIGNORE  is  removed
       from the list of matches.  The file names ``.''  and ``..''  are always
       ignored when GLOBIGNORE is set and not null.  However, setting  GLOBIG-
       NORE  to  a non-null value has the effect of enabling the dotglob shell
       option, so all other file names beginning with a ``.''  will match.  To
       get  the  old  behavior  of ignoring file names beginning with a ``.'',
       make ``.*''  one of the patterns in GLOBIGNORE.  The dotglob option  is
       disabled when GLOBIGNORE is unset.

       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 glob-
              star shell option is enabled, and * is used in a pathname expan-
              sion  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 subdirectories.
       ?      Matches any single character.
       [...]  Matches any one of the enclosed characters.  A pair  of  charac-
              ters separated by a hyphen denotes a range expression; any char-
              acter that sorts between those two characters, 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  character not enclosed is matched.  The sorting order
              of characters in range expressions is determined by the  current
              locale  and  the value of the LC_COLLATE shell variable, if set.
              A - may be matched by including it as the first or last  charac-
              ter 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
              Within [ and ], the syntax [.symbol.] matches the collating sym-
              bol 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  may
       also  be  used  to open and close files for the current shell execution
       environment.  The following redirection operators may precede or appear
       anywhere within a simple command or may follow 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 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 expansion, command substitution, arithmetic expan-
       sion, 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
       Bash handles several filenames specially when they are used in redirec-
       tions, as described in the following table:

              /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 a TCP connection to the corresponding 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 a UDP connection to the corresponding 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

   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

   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

   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 for a command.

       The format of here-documents is:

              <<[-]word
                      here-document
              delimiter

       No  parameter expansion, command substitution, arithmetic expansion, or
       pathname expansion is performed on word.  If any characters in word are
       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, com-
       mand substitution, and arithmetic expansion.  In the latter  case,  the
       character  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

              [n]<&word

       is used to duplicate input file descriptors.  If word expands to one or
       more digits, the file descriptor denoted by n is made to be a  copy  of
       that  file  descriptor.   If  the  digits in word do not specify a file
       descriptor open for input, a redirection error occurs.  If word  evalu-
       ates  to  -,  file  descriptor n is closed.  If n is not specified, the
       standard input (file descriptor 0) is used.

       The operator

              [n]>&word

       is used similarly to duplicate output file descriptors.  If  n  is  not
       specified,  the  standard  output  (file descriptor 1) is used.  If the
       digits in word do not specify a file descriptor open for output, a  re-
       direction  error  occurs.  As a special case, if n is omitted, and word
       does not expand to one or more digits, the standard output and standard
       error are redirected as described previously.

   Moving File Descriptors
       The redirection operator

              [n]<&digit-

       moves  the  file descriptor digit to file descriptor n, or the standard
       input (file descriptor 0) if n is not specified.  digit is closed after
       being duplicated to n.

       Similarly, the redirection operator

              [n]>&digit-

       moves  the  file descriptor digit to file descriptor n, or the standard
       output (file descriptor 1) if n is not specified.

   Opening File Descriptors for Reading and Writing
       The redirection operator

              [n]<>word

       causes the file whose name is the expansion of word to  be  opened  for
       both  reading and writing on file descriptor n, or on file descriptor 0
       if n is not specified.  If the file does not exist, it is created.

ALIASES
       Aliases allow a string to be substituted for a word when it is used  as
       the  first  word  of  a  simple command.  The shell maintains a list of
       aliases that may be set and unset with the alias  and  unalias  builtin
       commands  (see  SHELL  BUILTIN COMMANDS below).  The first word of each
       simple command, if unquoted, is checked to see if it has an alias.   If
       so,  that word is replaced by the text of the alias.  The characters /,
       $, `, and = and any of the shell metacharacters or  quoting  characters
       There  is no mechanism for using arguments in the replacement text.  If
       arguments are needed, a shell function should be  used  (see  FUNCTIONS
       below).

       Aliases  are not expanded when the shell is not interactive, unless the
       expand_aliases shell option is set using shopt (see the description  of
       shopt under SHELL BUILTIN COMMANDS below).

       The  rules  concerning  the  definition and use of aliases are somewhat
       confusing.  Bash always reads at  least  one  complete  line  of  input
       before  executing  any  of  the  commands  on  that  line.  Aliases are
       expanded when a command is read, not when it is  executed.   Therefore,
       an  alias definition appearing on the same line as another command does
       not take effect until the next line of input  is  read.   The  commands
       following the alias definition on that line are not affected by the new
       alias.  This behavior is also an issue  when  functions  are  executed.
       Aliases  are  expanded when a function definition is read, not when the
       function is executed, because a function definition is  itself  a  com-
       pound command.  As a consequence, aliases defined in a function are not
       available until after that function is executed.  To  be  safe,  always
       put  alias definitions on a separate line, and do not use alias in com-
       pound commands.

       For almost every purpose, aliases are superseded by shell functions.

FUNCTIONS
       A shell function, defined  as  described  above  under  SHELL  GRAMMAR,
       stores  a  series  of commands for later execution.  When the name of a
       shell function is used as a simple command name, the list  of  commands
       associated with that function name is executed.  Functions are executed
       in the context of the current shell;  no  new  process  is  created  to
       interpret  them  (contrast  this with the execution of a shell script).
       When a function is executed, the arguments to the function  become  the
       positional parameters during its execution.  The special parameter # is
       updated to reflect the change.  Special parameter 0 is unchanged.   The
       first  element of the FUNCNAME variable is set to the name of the func-
       tion while the function is executing.

       All other aspects of the  shell  execution  environment  are  identical
       between a function and its caller with these exceptions:  the DEBUG and
       RETURN traps (see the description  of  the  trap  builtin  under  SHELL
       BUILTIN  COMMANDS below) are not inherited unless the function has been
       given the trace attribute (see the description of the  declare  builtin
       below)  or  the -o functrace shell option has been enabled with the set
       builtin (in which case all  functions  inherit  the  DEBUG  and  RETURN
       traps),  and the ERR trap is not inherited unless the -o errtrace shell
       option has been enabled.

       Variables local to the function may be declared with the local  builtin
       command.  Ordinarily, variables and their values are shared between the
       function and its caller.

       If the builtin command return is executed in a function,  the  function
       completes  and  execution resumes with the next command after the func-
       functions and variables with the same name may result in multiple iden-
       tically-named  entries  in  the environment passed to the shell's chil-
       dren.  Care should be taken in cases where this may cause a problem.

       Functions may be recursive.  No limit  is  imposed  on  the  number  of
       recursive calls.

ARITHMETIC EVALUATION
       The  shell allows arithmetic expressions to be evaluated, under certain
       circumstances (see the let and declare builtin commands and  Arithmetic
       Expansion).   Evaluation  is done in fixed-width integers with no check
       for overflow, though division by 0 is trapped and flagged as an  error.
       The  operators  and their precedence, associativity, and values are the
       same as in the C language.  The following list of operators is  grouped
       into  levels  of  equal-precedence operators.  The levels are listed in
       order of decreasing precedence.

       id++ id--
              variable post-increment and post-decrement
       ++id --id
              variable pre-increment and pre-decrement
       - +    unary minus and plus
       ! ~    logical and bitwise negation
       **     exponentiation
       * / %  multiplication, division, remainder
       + -    addition, subtraction
       << >>  left and right bitwise shifts
       <= >= < >
              comparison
       == !=  equality and inequality
       &      bitwise AND
       ^      bitwise exclusive OR
       |      bitwise OR
       &&     logical AND
       ||     logical OR
       expr?expr:expr
              conditional operator
       = *= /= %= += -= <<= >>= &= ^= |=
              assignment
       expr1 , expr2
              comma

       Shell variables are allowed as operands; parameter  expansion  is  per-
       formed before the expression is evaluated.  Within an expression, shell
       variables may also be referenced by name without  using  the  parameter
       expansion  syntax.  A shell variable that is null or unset evaluates to
       0 when referenced by name without using the parameter expansion syntax.
       The  value  of a variable is evaluated as an arithmetic expression when
       it is referenced, or when a variable which has been given  the  integer
       attribute using declare -i is assigned a value.  A null value evaluates
       to 0.  A shell variable need not have its integer attribute  turned  on
       to be used in an expression.

       Constants with a leading 0 are interpreted as octal numbers.  A leading

CONDITIONAL EXPRESSIONS
       Conditional  expressions  are  used  by the [[ compound command and the
       test and [ builtin commands to test file attributes and perform  string
       and  arithmetic comparisons.  Expressions are formed from the following
       unary or binary primaries.  If any file argument to  one  of  the  pri-
       maries is of the form /dev/fd/n, then file descriptor n is checked.  If
       the file argument to  one  of  the  primaries  is  one  of  /dev/stdin,
       /dev/stdout,  or /dev/stderr, file descriptor 0, 1, or 2, respectively,
       is checked.

       Unless otherwise specified, primaries that operate on files follow sym-
       bolic links and operate on the target of the link, rather than the link
       itself.

       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).

       -a file
              True if file exists.
       -b file
              True if file exists and is a block special file.
       -c file
              True if file exists and is a character special file.
       -d file
              True if file exists and is a directory.
       -e file
              True if file exists.
       -f file
              True if file exists and is a regular file.
       -g file
              True if file exists and is set-group-id.
       -h file
              True if file exists and is a symbolic link.
       -k file
              True if file exists and its ``sticky'' bit is set.
       -p file
              True if file exists and is a named pipe (FIFO).
       -r file
              True if file exists and is readable.
       -s file
              True if file exists and has a size greater than zero.
       -t fd  True if file descriptor fd is open and refers to a terminal.
       -u file
              True if file exists and its set-user-id bit is set.
       -w file
              True if file exists and is writable.
       -x file
              True if file exists and is executable.
       -O file
              file2, or if file1 exists and file2 does not.
       file1 -ot file2
              True  if file1 is older than file2, or if file2 exists and file1
              does not.
       file1 -ef file2
              True if file1 and file2 refer to the same device and inode  num-
              bers.
       -o optname
              True  if  shell  option  optname  is  enabled.   See the list of
              options under the description  of  the  -o  option  to  the  set
              builtin below.
       -z string
              True if the length of string is zero.
       string
       -n string
              True if the length of string is non-zero.

       string1 == string2
       string1 = string2
              True  if  the strings are equal.  = should be used with the test
              command for POSIX conformance.

       string1 != string2
              True if the strings are not equal.

       string1 < string2
              True if string1 sorts before string2 lexicographically.

       string1 > string2
              True if string1 sorts after string2 lexicographically.

       arg1 OP arg2
              OP is one of -eq, -ne, -lt, -le, -gt, or -ge.  These  arithmetic
              binary  operators return true if arg1 is equal to, not equal to,
              less than, less than or equal to, greater than, or greater  than
              or  equal  to arg2, respectively.  Arg1 and arg2 may be positive
              or negative integers.

SIMPLE COMMAND EXPANSION
       When a simple command is executed, the  shell  performs  the  following
       expansions, assignments, and redirections, from left to right.

       1.     The  words  that  the  parser has marked as variable assignments
              (those preceding the command name) and  redirections  are  saved
              for later processing.

       2.     The  words that are not variable assignments or redirections are
              expanded.  If any words remain after expansion, the  first  word
              is  taken  to be the name of the command and the remaining words
              are the arguments.

       3.     Redirections are performed as described above under REDIRECTION.

       4.     The text after the = in each variable assignment undergoes tilde
       affect  the  current shell environment.  A redirection error causes the
       command to exit with a non-zero status.

       If there is a command name left after expansion, execution proceeds  as
       described  below.   Otherwise, the command exits.  If one of the expan-
       sions contained a command substitution, the exit status of the  command
       is  the  exit  status  of  the last command substitution performed.  If
       there were no command substitutions, the command exits with a status of
       zero.

COMMAND EXECUTION
       After  a  command  has been split into words, if it results in a simple
       command and an optional list of arguments, the  following  actions  are
       taken.

       If  the  command name contains no slashes, the shell attempts to locate
       it.  If there exists a shell function by that name,  that  function  is
       invoked  as described above in FUNCTIONS.  If the name does not match a
       function, the shell searches for it in the list of shell builtins.   If
       a match is found, that builtin is invoked.

       If  the name is neither a shell function nor a builtin, and contains no
       slashes, bash searches each element of the PATH for  a  directory  con-
       taining  an  executable  file  by that name.  Bash uses a hash table to
       remember the full pathnames of executable files (see hash  under  SHELL
       BUILTIN  COMMANDS  below).  A full search of the directories in PATH is
       performed only if the command is not found in the hash table.   If  the
       search is unsuccessful, the shell searches for a defined shell function
       named command_not_found_handle.  If that function exists, it is invoked
       with  the  original command and the original command's arguments as its
       arguments, and the function's exit status becomes the  exit  status  of
       the  shell.  If that function is not defined, the shell prints an error
       message and returns an exit status of 127.

       If the search is successful, or if the command  name  contains  one  or
       more slashes, the shell executes the named program in a separate execu-
       tion environment.  Argument 0 is set to the name given, and the remain-
       ing arguments to the command are set to the arguments given, if any.

       If  this  execution fails because the file is not in executable format,
       and the file is not a directory, it is assumed to be a shell script,  a
       file  containing  shell commands.  A subshell is spawned to execute it.
       This subshell reinitializes itself, so that the effect is as if  a  new
       shell  had  been  invoked to handle the script, with the exception that
       the locations of commands remembered by  the  parent  (see  hash  below
       under SHELL BUILTIN COMMANDS) are retained by the child.

       If  the program is a file beginning with #!, the remainder of the first
       line specifies an interpreter for the program.  The shell executes  the
       specified interpreter on operating systems that do not handle this exe-
       cutable format themselves.  The arguments to the interpreter consist of
       a  single optional argument following the interpreter name on the first
       line of the program, followed by the name of the program,  followed  by
       the command arguments, if any.
       o      the file creation mode mask as set by umask  or  inherited  from
              the shell's parent

       o      current traps set by trap

       o      shell parameters that are set by variable assignment or with set
              or inherited from the shell's parent in the environment

       o      shell functions defined during execution or inherited  from  the
              shell's parent in the environment

       o      options  enabled  at  invocation (either by default or with com-
              mand-line arguments) or by set

       o      options enabled by shopt

       o      shell aliases defined with alias

       o      various process IDs, including those  of  background  jobs,  the
              value of $$, and the value of PPID

       When  a  simple command other than a builtin or shell function is to be
       executed, it is invoked in a separate execution environment  that  con-
       sists  of the following.  Unless otherwise noted, the values are inher-
       ited from the shell.


       o      the shell's open files, plus  any  modifications  and  additions
              specified by redirections to the command

       o      the current working directory

       o      the file creation mode mask

       o      shell  variables  and  functions  marked  for export, along with
              variables exported for the command, passed in the environment

       o      traps caught by the shell are reset to the values inherited from
              the shell's parent, and traps ignored by the shell are ignored

       A  command  invoked  in  this  separate  environment  cannot affect the
       shell's execution environment.

       Command substitution, commands grouped with parentheses, and  asynchro-
       nous commands are invoked in a subshell environment that is a duplicate
       of the shell environment, except that traps caught  by  the  shell  are
       reset to the values that the shell inherited from its parent at invoca-
       tion.  Builtin commands that are invoked as part of a pipeline are also
       executed in a subshell environment.  Changes made to the subshell envi-
       ronment cannot affect the shell's execution environment.

       Subshells spawned to execute command substitutions inherit the value of
       the  -e  option  from  the  parent shell.  When not in posix mode, Bash
       clears the -e option in such subshells.
       invocation, the shell scans its own environment and creates a parameter
       for  each name found, automatically marking it for export to child pro-
       cesses.  Executed commands inherit the  environment.   The  export  and
       declare  -x  commands allow parameters and functions to be added to and
       deleted from the environment.  If the value of a parameter in the envi-
       ronment  is  modified,  the  new value becomes part of the environment,
       replacing the old.  The environment inherited by any  executed  command
       consists  of the shell's initial environment, whose values may be modi-
       fied in the shell, less any pairs removed by the  unset  command,  plus
       any additions via the export and declare -x commands.

       The  environment  for  any  simple command or function may be augmented
       temporarily by prefixing it with parameter  assignments,  as  described
       above in PARAMETERS.  These assignment statements affect only the envi-
       ronment seen by that command.

       If the -k option is set (see the set builtin command below),  then  all
       parameter  assignments are placed in the environment for a command, not
       just those that precede the command name.

       When bash invokes an external command, the variable _  is  set  to  the
       full  file  name of the command and passed to that command in its envi-
       ronment.

EXIT STATUS
       The exit status of an executed command is the  value  returned  by  the
       waitpid system call or equivalent function.  Exit statuses fall between
       0 and 255, though, as explained below, the shell may use  values  above
       125 specially.  Exit statuses from shell builtins and compound commands
       are also limited to this range. Under certain circumstances, the  shell
       will use special values to indicate specific failure modes.

       For the shell's purposes, a command which exits with a zero exit status
       has succeeded.  An exit status of zero indicates success.   A  non-zero
       exit  status  indicates  failure.  When a command terminates on a fatal
       signal N, bash uses the value of 128+N as the exit status.

       If a command is not found, the child  process  created  to  execute  it
       returns  a status of 127.  If a command is found but is not executable,
       the return status is 126.

       If a command fails because of an error during expansion or redirection,
       the exit status is greater than zero.

       Shell  builtin  commands return a status of 0 (true) if successful, and
       non-zero (false) if an error occurs while they execute.   All  builtins
       return an exit status of 2 to indicate incorrect usage.

       Bash  itself  returns  the  exit  status  of the last command executed,
       unless a syntax error occurs, in which case it exits  with  a  non-zero
       value.  See also the exit builtin command below.

SIGNALS
       When  bash  is  interactive,  in  the  absence of any traps, it ignores
       The shell exits by default upon receipt of a SIGHUP.   Before  exiting,
       an  interactive  shell  resends  the  SIGHUP  to  all  jobs, running or
       stopped.  Stopped jobs are sent SIGCONT to ensure that they receive the
       SIGHUP.   To  prevent the shell from sending the signal to a particular
       job, it should be removed from the jobs table with the  disown  builtin
       (see  SHELL  BUILTIN  COMMANDS  below)  or marked to not receive SIGHUP
       using disown -h.

       If the huponexit shell option has been set with  shopt,  bash  sends  a
       SIGHUP to all jobs when an interactive login shell exits.

       If  bash is waiting for a command to complete and receives a signal for
       which a trap has been set, the trap will not be executed until the com-
       mand  completes.   When bash is waiting for an asynchronous command via
       the wait builtin, the reception of a signal for which a trap  has  been
       set will cause the wait builtin to return immediately with an exit sta-
       tus greater than 128, immediately after which the trap is executed.

JOB CONTROL
       Job control refers to the ability to  selectively  stop  (suspend)  the
       execution of processes and continue (resume) their execution at a later
       point.  A user typically  employs  this  facility  via  an  interactive
       interface  supplied  jointly  by the operating system kernel's terminal
       driver and bash.

       The shell associates a job with each pipeline.  It  keeps  a  table  of
       currently  executing  jobs,  which may be listed with the jobs command.
       When bash starts a job asynchronously (in the background), it prints  a
       line that looks like:

              [1] 25647

       indicating that this job is job number 1 and that the process ID of the
       last process in the pipeline associated with this job is 25647.  All of
       the  processes  in a single pipeline are members of the same job.  Bash
       uses the job abstraction as the basis for job control.

       To facilitate the implementation of the user interface to job  control,
       the operating system maintains the notion of a current terminal process
       group ID.  Members of this process group (processes whose process group
       ID is equal to the current terminal process group ID) receive keyboard-
       generated signals such as SIGINT.  These processes are said  to  be  in
       the  foreground.  Background processes are those whose process group ID
       differs from the terminal's; such processes are immune to keyboard-gen-
       erated signals.  Only foreground processes are allowed to read from or,
       if the user so specifies with  stty  tostop,  write  to  the  terminal.
       Background  processes  which  attempt  to read from (write to when stty
       tostop is in effect) the terminal are sent a SIGTTIN  (SIGTTOU)  signal
       by  the  kernel's  terminal  driver, which, unless caught, suspends the
       process.

       If the operating system on which bash is running supports job  control,
       bash contains facilities to use it.  Typing the suspend character (typ-
       ically ^Z, Control-Z) while a process is running causes that process to
       name used to start it, or using a substring that appears in its command
       line.  For example, %ce refers to  a  stopped  ce  job.   If  a  prefix
       matches  more  than one job, bash reports an error.  Using %?ce, on the
       other hand, refers to any job containing the string ce in  its  command
       line.   If  the  substring  matches  more than one job, bash reports an
       error.  The symbols %% and %+ refer to the shell's notion of  the  cur-
       rent  job, which is the last job stopped while it was in the foreground
       or started in the background.  The previous job may be referenced using
       %-.  If there is only a single job, %+ and %- can both be used to refer
       to that job.  In output pertaining to jobs (e.g.,  the  output  of  the
       jobs command), the current job is always flagged with a +, and the pre-
       vious job with a -.  A single % (with no  accompanying  job  specifica-
       tion) also refers to the current job.

       Simply  naming a job can be used to bring it into the foreground: %1 is
       a synonym for ``fg %1'', bringing job 1 from the  background  into  the
       foreground.   Similarly,  ``%1  &''  resumes  job  1 in the background,
       equivalent to ``bg %1''.

       The shell learns immediately whenever a job changes  state.   Normally,
       bash waits until it is about to print a prompt before reporting changes
       in a job's status so as to not interrupt any other output.  If  the  -b
       option to the set builtin command is enabled, bash reports such changes
       immediately.  Any trap on SIGCHLD  is  executed  for  each  child  that
       exits.

       If  an  attempt to exit bash is made while jobs are stopped (or, if the
       checkjobs shell option has been enabled using the shopt  builtin,  run-
       ning), the shell prints a warning message, and, if the checkjobs option
       is enabled, lists the jobs and their statuses.  The  jobs  command  may
       then  be  used to inspect their status.  If a second attempt to exit is
       made without an intervening command, the shell does not  print  another
       warning, and any stopped jobs are terminated.

PROMPTING
       When executing interactively, bash displays the primary prompt PS1 when
       it is ready to read a command, and the secondary  prompt  PS2  when  it
       needs  more  input  to  complete  a  command.  Bash allows these prompt
       strings to be customized by inserting  a  number  of  backslash-escaped
       special characters that are decoded as follows:
              \a     an ASCII bell character (07)
              \d     the  date  in "Weekday Month Date" format (e.g., "Tue May
                     26")
              \D{format}
                     the format is passed to 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
                     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

       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
              \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.
       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-ignore-case (Off)
              If set to On, readline performs filename matching and completion
              in a case-insensitive fashion.
       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.
              meta prefix).
       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.
       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.
       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.
       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 (0)
              Set the maximum number of history entries saved in  the  history
              list.  If set to zero, the number of entries in the history list
              is not limited.
       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 high  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.
       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.
       mark-directories (On)
              user in the filename to be completed.
       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.
       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.
       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.
       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

              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-
       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'
              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  an  argument,  behave
              exactly  like  yank-nth-arg.   Successive calls to yank-last-arg
              move back through the history list, inserting the last  argument
              of each line in turn.  The history expansion facilities are used
              to extract the last argument, 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
       delete-char (C-d)
              Delete  the character at point.  If point is at the beginning of
              the line, there are no characters in  the  line,  and  the  last
              character typed was not bound to delete-char, then return EOF.
       backward-delete-char (Rubout)
              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 (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 shell-forward-word.
       shell-backward-kill-word (M-Rubout)
              Kill the word behind point.  Word boundaries  are  the  same  as

       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 or 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

       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.

   Miscellaneous
              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 file names  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  file  names  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
              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  to  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.
       in the COMPREPLY array variable.

       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.

       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 compspec for that command.  This allows a set of com-
       pletions  to  be  built  dynamically as completion is attempted, rather

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.  When the  his-
       tory  file  is read, lines beginning with the history comment character
       followed immediately by a digit are interpreted as timestamps  for  the
       preceding  history  line.   These  timestamps  are optionally displayed
       depending on the value of the HISTTIMEFORMAT variable.  When an  inter-
       active  shell  exits, the last $HISTSIZE lines are copied from the his-
       tory 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  over-
       written.   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 sessions.   This  uses
       the history comment character to distinguish timestamps from other his-
       tory lines.  After saving the history, the history file is truncated to
       contain  no  more than HISTFILESIZE lines.  If HISTFILESIZE is not set,
       no truncation is performed.

       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
       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.

       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.

       !      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 line minus n.
       !!     Refer to the previous command.  This is a synonym for `!-1'.
       !string
              Refer to the most recent command starting with string.
       !?string[?]
              Refer  to the most recent command containing string.  The trail-
              ing ? may be omitted if string is followed immediately by a new-
              line.
       ^string1^string2^
              Quick  substitution.  Repeat the last command, replacing string1
              with string2.  Equivalent to ``!!:s/string1/string2/'' (see Mod-
              The zeroth word.  For the shell, this is the command word.
       n      The nth word.
       ^      The first argument.  That is, word 1.
       $      The last argument.
       %      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 file name component, leaving only the head.
       t      Remove all leading file name 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, break, continue, let,
       and  shift builtins accept and process arguments beginning with - with-
       out requiring --.  Other builtins that accept  arguments  but  are  not
       specified  as accepting options interpret arguments beginning with - as
       invalid options and require -- to prevent this interpretation.
              When  bash  is  not  in  posix  mode,  the  current directory is
              searched if no file is found in PATH.  If the sourcepath  option
              to  the  shopt  builtin  command  is turned off, the PATH is not
              searched.  If any arguments are supplied, they become the  posi-
              tional  parameters  when  filename  is  executed.  Otherwise the
              positional parameters are unchanged.  The return status  is  the
              status  of  the  last  command exited within the script (0 if no
              commands are executed), and false if filename is  not  found  or
              cannot be read.

       alias [-p] [name[=value] ...]
              Alias with no arguments or with the -p option prints the list of
              aliases in the form alias name=value on standard  output.   When
              arguments  are supplied, an alias is defined for each name whose
              value is given.  A trailing space in  value causes the next word
              to be checked for alias substitution when the alias is expanded.
              For each name in the argument list for which no  value  is  sup-
              plied,  the  name  and  value  of  the  alias is printed.  Alias
              returns true unless a name is given for which no alias has  been
              defined.

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

       bind [-m keymap] [-lpsvPSV]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] -x keyseq:shell-command
       bind [-m keymap] keyseq:function-name
       bind readline-command
              Display current readline key and function bindings, bind  a  key
              sequence  to  a  readline  function  or macro, or set a readline
              variable.  Each non-option argument is a  command  as  it  would
              appear  in  .inputrc, but each binding or command must be passed
              as a separate argument; e.g.,  '"\C-x\C-r":  re-read-init-file'.
              Options, if supplied, have the following meanings:
              -m keymap
                     Use keymap as the keymap to be affected by the subsequent
                     bindings.  Acceptable keymap names are emacs, emacs-stan-
                     dard,  emacs-meta,  emacs-ctlx,  vi, vi-move, vi-command,
                     and vi-insert.  vi is equivalent to vi-command; emacs  is
                     equivalent to emacs-standard.
              -l     List the names of all readline functions.
              -p     Display  readline  function  names and bindings in such a
                     way that they can be re-read.
              -P     List current readline function names and bindings.
              -s     Display readline key sequences bound to  macros  and  the
                     strings  they  output  in such a way that they can be re-
                     read.
                     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.

              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] [dir]
              Change  the  current directory to dir.  The variable HOME is the
              default dir.  The variable CDPATH defines the  search  path  for
              the  directory  containing  dir.  Alternative directory names in
              CDPATH are separated by a colon (:).  A null directory  name  in
              CDPATH  is  the  same as the current directory, i.e., ``.''.  If
              dir begins with a slash (/), then CDPATH is  not  used.  The  -P
              option  says  to use the physical directory structure instead of
              following symbolic links (see also the  -P  option  to  the  set
              builtin command); the -L option forces symbolic links to be fol-
              lowed.  An argument of - is equivalent to $OLDPWD.   If  a  non-
              empty  directory  name from CDPATH is used, or if - is the first
              option  causes a single word indicating the command or file name
              used to invoke command to be displayed; the -V option produces a
              more  verbose  description.  If the -V or -v option is supplied,
              the exit status is 0 if command was found, and  1  if  not.   If
              neither option is supplied and an error occurred or command can-
              not be found, the exit status is 127.  Otherwise, the exit  sta-
              tus of the command builtin is the exit status of command.

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

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

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

       complete [-abcdefgjksuv] [-o comp-option] [-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
                              ing trailing spaces).  Intended to be used  with
                              shell functions.
                      nospace Tell   readline  not  to  append  a  space  (the
                              default) to words completed at the  end  of  the
                              line.
                      plusdirs
                              After  any  matches  defined by the compspec are
                              generated,   directory   name   completion    is
                              attempted  and  any  matches  are  added  to the
                              results of the other actions.
              -A action
                      The action may be one of the  following  to  generate  a
                      list of possible completions:
                      alias   Alias names.  May also be specified as -a.
                      arrayvar
                              Array variable names.
                      binding Readline key binding names.
                      builtin Names  of  shell  builtin commands.  May also be
                              specified as -b.
                      command Command names.  May also be specified as -c.
                      directory
                              Directory names.  May also be specified as -d.
                      disabled
                              Names of disabled shell builtins.
                      enabled Names of enabled shell builtins.
                      export  Names of exported shell variables.  May also  be
                              specified as -e.
                      file    File names.  May also be specified as -f.
                      function
                              Names of shell functions.
                      group   Group names.  May also be specified as -g.
                      helptopic
                              Help topics as accepted by the help builtin.
                      hostname
                              Hostnames,  as  taken from the file specified by
                              the HOSTFILE shell variable.
                      job     Job names, if job control is active.   May  also
                              be specified as -j.
                      keyword Shell  reserved words.  May also be specified as
                              -k.
                      running Names of running jobs, if job control is active.
                      service Service names.  May also be specified as -s.
                      setopt  Valid arguments for the -o  option  to  the  set
                              builtin.
                      shopt   Shell  option  names  as  accepted  by the shopt
                              builtin.
                      signal  Signal names.
                      stopped Names of stopped jobs, if job control is active.
                      user    User names.  May also be specified as -u.
                      variable
                              Names of all shell variables.  May also be spec-
                              ified as -v.
              -G globpat
                      The  pathname  expansion  pattern globpat is expanded to
                      shell environment.  When it finishes, the possible  com-
                      pletions  are  retrieved from the value of the COMPREPLY
                      array variable.
              -X filterpat
                      filterpat is a pattern as used for  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.
              -P prefix
                      prefix  is  added at the beginning of each possible com-
                      pletion after all other options have been applied.
              -S suffix
                      suffix is appended to each possible completion after all
                      other options have been applied.

              The  return  value is true unless an invalid option is supplied,
              an option other than -p or -r is supplied without a  name  argu-
              ment,  an  attempt  is made to remove a completion specification
              for a name for which no specification exists, or an error occurs
              adding a completion specification.

       compopt [-o option] [-DE] [+o option] [name]
              Modify  completion  options  for  each  name  according  to  the
              options, or for the currently-execution 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  comple-
       tion 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 [-aAfFilrtux] [-p] [name[=value] ...]
       typeset [-aAfFilrtux] [-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 are ignored.  When -p is
              -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.
              -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, makes each name local, as with the local command.
              If a variable name is followed by =value, the value of the vari-
              able  is  set to value.  The return value is 0 unless an invalid
              option is encountered, an attempt is made to define  a  function
              using  ``-f foo=bar'', an attempt is made to assign a value to a
              readonly variable, an attempt is made to assign a  value  to  an
              array variable without using the compound assignment syntax (see
              Arrays above), one of the names is not a  valid  shell  variable
              name, an attempt is made to turn off readonly status for a read-
              only variable, an attempt is made to turn off array  status  for
              an  array variable, or an attempt is made to display a non-exis-
              tent function with -f.

       dirs [+n] [-n] [-cplv]
              Without options,  displays  the  list  of  currently  remembered
              directories.   The  default  display  is  on  a single line with
              directory names separated by spaces.  Directories are  added  to
              the  list  with  the  pushd  command;  the  popd command removes
              entries from the list.
              +n     Displays the nth entry counting from the left of the list
                     shown by dirs when invoked without options, starting with
                     zero.
              -n     Displays the nth entry counting from  the  right  of  the
                     list shown by dirs when invoked without options, starting
                     with zero.
              -c     Clears  the  directory  stack  by  deleting  all  of  the
                     entries.
              -l     Produces  a  longer  listing;  the default listing format
              the -h option is given, each jobspec is not removed from the ta-
              ble, but is marked so that SIGHUP is not sent to the job if  the
              shell  receives a SIGHUP.  If no jobspec is present, and neither
              the -a nor the -r option is supplied, the current job  is  used.
              If no jobspec is supplied, the -a option means to remove or mark
              all jobs; the -r option without  a  jobspec  argument  restricts
              operation  to running jobs.  The return value is 0 unless a job-
              spec does not specify a valid job.

       echo [-neE] [arg ...]
              Output the args, separated by spaces,  followed  by  a  newline.
              The return status is always 0.  If -n is specified, the trailing
              newline is suppressed.  If the -e option is  given,  interpreta-
              tion  of  the following backslash-escaped characters is enabled.
              The -E option disables the interpretation of these escape  char-
              acters,  even  on systems where they are interpreted by default.
              The xpg_echo shell option may be used to  dynamically  determine
              whether  or not echo expands these escape characters by default.
              echo does not interpret -- to mean the  end  of  options.   echo
              interprets the following escape sequences:
              \a     alert (bell)
              \b     backspace
              \c     suppress further output
              \e     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\     backslash
              \0nnn  the  eight-bit  character  whose value is the octal value
                     nnn (zero to three octal digits)
              \xHH   the eight-bit character whose value  is  the  hexadecimal
                     value HH (one or two hex digits)

       enable [-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
              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 shell option execfail is enabled, in  which  case  it
              returns  failure.   An  interactive shell returns failure if the
              file cannot be executed.  If command is not specified, any 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 all names that are
              exported in this shell is printed.  The  -n  option  causes  the
              export  property  to  be  removed from each name.  If a variable
              name is followed by =word, the value of the variable is  set  to
              word.   export  returns  an  exit  status of 0 unless an invalid
              option is encountered, one of the names is  not  a  valid  shell
              variable name, or -f is supplied with a name that is not a func-
              tion.

       fc [-e ename] [-lnr] [first] [last]
       fc -s [pat=rep] [cmd]
              Fix Command.  In the first form, a range of commands from  first
              to  last  is selected from the history list.  First and last may
              be specified as a string (to locate the last  command  beginning
              with  that  string)  or  as  a number (an index into the history
              list, where a negative number is used as an offset from the cur-
              rent command number).  If last is not specified it is set to the
              current command for listing (so that ``fc -l  -10''  prints  the
              last 10 commands) and to first otherwise.  If first is not spec-
              ified it is set to the previous command for editing and -16  for
              listing.

              The  -n option suppresses the command numbers when listing.  The
              -r option reverses the order of the commands.  If the -l  option
              is  given,  the  commands are listed on standard output.  Other-
              wise, the editor given by ename is invoked on a file  containing
              those  commands.  If ename is not given, the value of the FCEDIT
              variable is used, and the value of EDITOR if FCEDIT is not  set.
              If  neither  variable  is set, 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.  A useful alias to use with this is

       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
              pathname.  The -l option causes output to be displayed in a for-
              mat that may be reused as input.  If no arguments are given,  or
              if only -l is supplied, information about remembered commands is
              printed.  The return status is true unless a name is  not  found
              or an invalid option is supplied.

       help [-dms] [pattern]
              Display  helpful information about builtin commands.  If pattern
              is specified, help gives detailed help on all commands  matching
              pattern;  otherwise  help for all the builtins and shell control
              structures is printed.
              -d     Display a short description of each pattern
              -m     Display the description of each pattern in a manpage-like
                     format
              -s     Display only a short usage synopsis for each pattern
       The return status is 0 unless no command matches pattern.

       history [n]
       history -c
       history -d offset
       history -anrw [filename]
       history -p arg [arg ...]
       history -s arg [arg ...]
              With no options, display the command history list with line num-
              bers.  Lines listed with a * have been modified.  An argument of
              n  lists only the last n lines.  If the shell variable HISTTIME-
              FORMAT is set and not null, it is used as a  format  string  for
              strftime(3)  to display the time stamp associated with each dis-
              played history entry.  No intervening blank is  printed  between
              the  formatted  time stamp and the history line.  If filename is
              supplied, it is used as the name of the history  file;  if  not,
              the  value  of HISTFILE is used.  Options, if supplied, have the
              following meanings:
              -c     Clear the history list by deleting all the entries.
              -d offset
                     Delete the history entry at position offset.
              -a     Append the ``new'' history lines (history  lines  entered
                     since  the  beginning of the current bash session) to the
                     history file.
              -n     Read the history lines not already read from the  history
                     file  into  the  current  history  list.  These are lines
                     appended to the history file since the beginning  of  the
                     current bash session.
              -r     Read the contents of the history file and use them as the
                     current history.
              -w     Write the current history to the history file,  overwrit-
                     ing the history file's contents.
              -p     Perform  history  substitution  on the following args and
                     display the result on  the  standard  output.   Does  not
                     store  the results in the history list.  Each arg must be
                     quoted to disable normal history expansion.
              -s     Store the args in the history list  as  a  single  entry.
                     The  last  command  in the history list is removed before
                     the args are added.

       jobs [-lnprs] [ jobspec ... ]
       jobs -x command [ args ... ]
              The first form lists the active jobs.  The options have the fol-
              lowing meanings:
              -l     List process IDs in addition to the normal information.
              -p     List only the process  ID  of  the  job's  process  group
                     leader.
              -n     Display  information  only  about  jobs that have changed
                     status since the user was last notified of their status.
              -r     Restrict output to running jobs.
              -s     Restrict output to stopped jobs.

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

              If the -x option is supplied, jobs replaces any jobspec found in
              command  or  args  with  the corresponding process group ID, and
              executes command passing it args, returning its exit status.

       kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...
       kill -l [sigspec | exit_status]
              Send the signal named by sigspec  or  signum  to  the  processes
              named  by  pid or jobspec.  sigspec is either a case-insensitive
              signal name such as SIGKILL (with or without the SIG prefix)  or
              a  signal  number; signum is a signal number.  If sigspec is not
              present, then SIGTERM is assumed.  An argument of -l  lists  the
              signal  names.   If any arguments are supplied when -l is given,
              the names of the signals  corresponding  to  the  arguments  are
              listed, and the return status is 0.  The exit_status argument to
              -l is a number specifying either a signal  number  or  the  exit
              status  of  a process terminated by a signal.  kill returns true
              if at least one signal was successfully sent,  or  false  if  an
              error occurs or an invalid option is encountered.

       let arg [arg ...]
              Each arg is an arithmetic expression to be evaluated (see ARITH-
              METIC EVALUATION 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.  With no operands, local writes a list of
              local variables to the standard output.  It is an error  to  use
              local when not within a function.  The return status is 0 unless
              local is used outside a function, an invalid name  is  supplied,
              or name is a readonly variable.

       logout Exit a login shell.

       mapfile  [-n  count]  [-O origin] [-s count] [-t] [-u fd] [-C callback]
              -t     Remove a trailing 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 as an additional argument.  call-
              back 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 format is a character string which
              contains three types of objects:  plain  characters,  which  are
              simply  copied  to  standard output, character escape sequences,
              which are converted and copied to the standard output, and  for-
              mat  specifications,  each  of which causes printing of the next
              successive argument.  In addition to the standard printf(1) for-
              mats,  %b  causes printf to expand backslash escape sequences in
              the corresponding argument (except that  \c  terminates  output,
              backslashes in \', \", and \? are not removed, and octal escapes

       pushd [-n] [+n] [-n]
       pushd [-n] [dir]
              Adds  a  directory to the top of the directory stack, or rotates
              the stack, making the new top of the stack the  current  working
              directory.  With no arguments, exchanges the top two directories
              and returns 0, unless the directory stack is empty.   Arguments,
              if supplied, have the following meanings:
              -n     Suppresses  the  normal  change  of directory when adding
                     directories to the stack,  so  that  only  the  stack  is
                     manipulated.
              +n     Rotates  the  stack  so  that the nth directory (counting
                     from the left of the list shown by  dirs,  starting  with
                     zero) is at the top.
              -n     Rotates  the  stack  so  that the nth directory (counting
                     from the right of the list shown by dirs,  starting  with
                     zero) is at the top.
              dir    Adds dir to the directory stack at the top, making it the
                     new current working directory.

              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, and the
              first word is assigned to the first name, the second word to the
              second  name, and so on, with leftover words and their interven-
              ing separators assigned to the last name.  If  there  are  fewer
              words read from the input stream than names, the remaining names
              are assigned empty values.  The characters in IFS  are  used  to
              split  the  line into words.  The backslash character (\) may be
              used to remove any special meaning for the next  character  read
              and  for line continuation.  Options, if supplied, have the fol-
              lowing meanings:
              -a aname
                     The words are assigned to sequential indices of the array
                     variable aname, starting at 0.  aname is unset before any
                     new  values  are  assigned.   Other  name  arguments  are
                     ignored.
                     waiting  for a complete line of input, but honor 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.
              -p prompt
                     Display prompt on standard error, without a trailing new-
                     line, before attempting to read any input.  The prompt is
                     displayed only if input is coming from a terminal.
              -r     Backslash does not act as an escape character.  The back-
                     slash  is considered to be part of the line.  In particu-
                     lar, a backslash-newline pair may not be used as  a  line
                     continuation.
              -s     Silent mode.  If input is coming from a terminal, charac-
                     ters are not echoed.
              -t timeout
                     Cause read to time out and return failure if  a  complete
                     line  of input is not read within timeout seconds.  time-
                     out may be a decimal number  with  a  fractional  portion
                     following  the decimal point.  This option is only effec-
                     tive if read is reading input from a terminal,  pipe,  or
                     other  special  file;  it has no effect when reading from
                     regular files.  If timeout is 0, read returns success  if
                     input  is  available  on  the  specified file descriptor,
                     failure otherwise.  The exit status is greater  than  128
                     if the timeout is exceeded.
              -u fd  Read input from file descriptor fd.

              If no names are supplied, the line read is assigned to the vari-
              able REPLY.  The return code  is  zero,  unless  end-of-file  is
              encountered,  read  times  out (in which case the return code is
              greater than 128), or an invalid file descriptor is supplied  as
              the argument to -u.

       readonly [-aApf] [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 no name arguments are given, or if the -p option  is
              supplied,  a  list  of  all  readonly  names is printed.  The -p
              option causes output to be displayed in a  format  that  may  be
              reused  as  input.  If a variable name is followed by =word, the
              value of the 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.

       set [--abefhkmnptuvxBCEHPT] [-o option] [arg ...]
       set [+abefhkmnptuvxBCEHPT] [+o option] [arg ...]
              Without options, the name and value of each shell  variable  are
              displayed in a format that can be reused as input for setting or
              resetting the currently-set variables.  Read-only variables can-
              not  be  reset.  In posix mode, only shell variables are listed.
              The output is sorted according  to  the  current  locale.   When
              options  are specified, they set or unset shell attributes.  Any
              arguments remaining after 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      Automatically  mark  variables  and  functions which are
                      modified or created for export  to  the  environment  of
                      subsequent commands.
              -b      Report  the status of terminated background jobs immedi-
                      ately, rather than before the next primary prompt.  This
                      is effective only when job control is enabled.
              -e      Exit  immediately  if a pipeline (which may consist of a
                      single simple command),  a subshell command enclosed  in
                      parentheses,  or one of the commands executed as part of
                      a command list enclosed by  braces  (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 !.  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.
              -f      Disable pathname expansion.
              -h      Remember  the location of commands as they are looked up
                      for execution.  This is enabled by default.
              -k      All arguments in the form of assignment  statements  are
                      placed  in the environment for a command, not just those
                      that precede the command name.
              -m      Monitor mode.  Job control is enabled.  This  option  is
                      on  by  default  for  interactive shells on systems that
                      support it (see JOB  CONTROL  above).   Background  pro-
                      cesses  run  in a separate process group and a line con-
                      taining their exit status is printed upon their  comple-
                      tion.
              -n      Read commands but do not execute them.  This may be used
                      to check a shell script  for  syntax  errors.   This  is
                      ignored by interactive shells.
              -o option-name
                      The option-name can be one of the following:
                      allexport
                              Same as -a.

                      hashall Same as -h.
                      histexpand
                              Same as -H.
                      history Enable command history, as described above under
                              HISTORY.  This option is on by default in inter-
                              active shells.
                      ignoreeof
                              The   effect   is   as   if  the  shell  command
                              ``IGNOREEOF=10'' had been  executed  (see  Shell
                              Variables above).
                      keyword Same as -k.
                      monitor Same as -m.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Currently ignored.
                      notify  Same as -b.
                      nounset Same as -u.
                      onecmd  Same as -t.
                      physical
                              Same as -P.
                      pipefail
                              If  set,  the  return value of a pipeline is the
                              value of the last (rightmost)  command  to  exit
                              with  a non-zero status, or zero if all commands
                              in the pipeline exit successfully.  This  option
                              is disabled by default.
                      posix   Change  the  behavior  of bash where the default
                              operation differs from  the  POSIX  standard  to
                              match the standard (posix mode).
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      vi      Use  a  vi-style command line editing interface.
                              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
                      and its expanded arguments or associated word list.
              -B      The shell performs brace expansion (see Brace  Expansion
                      above).  This is on by default.
              -C      If  set,  bash  does not overwrite an existing file with
                      the >, >&, and <> redirection operators.   This  may  be
                      overridden when creating output files by using the redi-
                      rection operator >| instead of >.
              -E      If set, any trap on ERR is inherited by shell functions,
                      command  substitutions,  and commands executed in a sub-
                      shell environment.  The ERR trap is normally not  inher-
                      ited in such cases.
              -H      Enable !  style history substitution.  This option is on
                      by default when the shell is interactive.
              -P      If set, the shell does not follow  symbolic  links  when
                      executing  commands  such  as cd that change the current
                      working  directory.   It  uses  the  physical  directory
                      structure instead.  By default, bash follows the logical
                      chain of  directories  when  performing  commands  which
                      change the current directory.
              -T      If  set,  any traps on DEBUG and RETURN are inherited by
                      shell functions,  command  substitutions,  and  commands
                      executed  in  a  subshell  environment.   The  DEBUG and
                      RETURN traps are normally not inherited in such cases.
              --      If no arguments follow this option, then the  positional
                      parameters are unset.  Otherwise, the positional parame-
                      ters are set to the args, even if  some  of  them  begin
                      with a -.
              -       Signal  the  end of options, cause all remaining args to
                      be assigned to the positional parameters.  The -x and -v
                      options are turned off.  If there are no args, the posi-
                      tional parameters remain unchanged.

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

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

       shopt [-pqsu] [-o] [optname ...]
              Toggle the values of variables controlling optional shell behav-
              ior.  With no options, or with the -p option, a list of all set-
              table options is displayed, with an indication of whether or not
              each is set.  The -p option causes output to be displayed  in  a
              form  that  may be reused as input.  Other options have the fol-
              play is limited to those options which are set or unset, respec-
              tively.   Unless otherwise noted, the shopt options are disabled
              (unset) by default.

              The return status when listing options is zero if  all  optnames
              are  enabled,  non-zero  otherwise.   When  setting or unsetting
              options, the return status is zero unless an optname  is  not  a
              valid shell option.

              The list of shopt options is:

              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 file name is printed, and the com-
                      mand proceeds.  This option is only used by  interactive
                      shells.
              checkhash
                      If set, bash checks that a command found in the hash ta-
                      ble exists before trying to execute  it.   If  a  hashed
                      command  no  longer exists, a normal path search is per-
                      formed.
              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 com-
                      mand's =~ operator.
              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.
              compat40
                      If set, bash changes its behavior to that of version 4.0
                      exec  builtin  command.   An  interactive shell does not
                      exit if exec fails.
              expand_aliases
                      If set, aliases are expanded as  described  above  under
                      ALIASES.  This option is enabled by default for interac-
                      tive shells.
              extdebug
                      If set,  behavior  intended  for  use  by  debuggers  is
                      enabled:
                      1.     The -F option to the declare builtin displays the
                             source file name and line number corresponding to
                             each function name supplied as an argument.
                      2.     If  the  command  run by the DEBUG trap returns a
                             non-zero value, the next command is  skipped  and
                             not executed.
                      3.     If  the  command  run by the DEBUG trap returns a
                             value of 2, and the shell is executing in a  sub-
                             routine  (a shell function or a shell script exe-
                             cuted by the . or source  builtins),  a  call  to
                             return is simulated.
                      4.     BASH_ARGC  and BASH_ARGV are updated as described
                             in their descriptions above.
                      5.     Function tracing is enabled:   command  substitu-
                             tion, shell functions, and subshells invoked with
                             ( command ) inherit the DEBUG and RETURN traps.
                      6.     Error tracing is enabled:  command  substitution,
                             shell  functions,  and  subshells  invoked with (
                             command ) inherit the ERROR trap.
              extglob If set, the extended pattern matching features described
                      above under Pathname Expansion are enabled.
              extquote
                      If  set,  $'string'  and  $"string" quoting is performed
                      within  ${parameter}  expansions  enclosed   in   double
                      quotes.  This option is enabled by default.
              failglob
                      If  set,  patterns  which fail to match filenames during
                      pathname expansion result in an expansion error.
              force_fignore
                      If set, the suffixes  specified  by  the  FIGNORE  shell
                      variable  cause words to be ignored when performing word
                      completion even if the ignored words are the only possi-
                      ble  completions.   See  SHELL  VARIABLES  above  for  a
                      description of  FIGNORE.   This  option  is  enabled  by
                      default.
              globstar
                      If set, the pattern ** used in a pathname expansion con-
                      text will match a 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
                      If set, and readline is being used, bash will attempt to
                      perform  hostname  completion when a word containing a @
                      is  being  completed  (see  Completing  under   READLINE
                      above).  This is enabled by default.
              huponexit
                      If set, bash will send SIGHUP to all jobs when an inter-
                      active login shell exits.
              interactive_comments
                      If set, allow a word beginning with # to cause that word
                      and  all remaining characters on that line to be ignored
                      in an interactive  shell  (see  COMMENTS  above).   This
                      option is enabled by default.
              lithist If  set,  and  the cmdhist option is enabled, multi-line
                      commands are saved to the history with embedded newlines
                      rather than using semicolon separators where possible.
              login_shell
                      The  shell  sets this option if it is started as a login
                      shell (see INVOCATION above).   The  value  may  not  be
                      changed.
              mailwarn
                      If  set,  and  a file that bash is checking for mail has
                      been accessed since the last time it  was  checked,  the
                      message  ``The  mail in mailfile has been read'' is dis-
                      played.
              no_empty_cmd_completion
                      If set, and  readline  is  being  used,  bash  will  not
                      attempt to search the PATH for possible completions when
                      completion is attempted on an empty line.
              nocaseglob
                      If set, bash matches  filenames  in  a  case-insensitive
                      fashion when performing pathname expansion (see Pathname
                      Expansion above).
              nocasematch
                      If set, bash  matches  patterns  in  a  case-insensitive
                      fashion when performing matching while executing case or
                      [[ conditional commands.
              nullglob
                      If set, bash allows patterns which match no  files  (see
                      Pathname  Expansion  above)  to expand to a null string,
                      rather than themselves.
              progcomp
                      If set, the programmable completion facilities (see Pro-
                      grammable Completion above) are enabled.  This option is
                      enabled by default.
              promptvars
                      If set, prompt strings undergo parameter expansion, com-
                      mand   substitution,  arithmetic  expansion,  and  quote
                      removal after being expanded as described  in  PROMPTING
                      above.  This option is enabled by default.
              restricted_shell
                      The   shell  sets  this  option  if  it  is  started  in
                      restricted mode (see RESTRICTED SHELL below).  The value
                      may  not be changed.  This is not reset when the startup
                      files are executed, allowing the startup files  to  dis-

       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 or 1 depending on  the  evaluation  of  the
              conditional  expression expr.  Each operator and operand must be
              a separate argument.  Expressions are composed of the  primaries
              described  above  under  CONDITIONAL EXPRESSIONS.  test does not
              accept any options, nor does it accept and ignore an argument of
              -- as signifying the end of options.

              Expressions  may  be  combined  using  the  following operators,
              listed  in  decreasing  order  of  precedence.   The  evaluation
              depends on the number of arguments; see below.
              ! expr True if expr is false.
              ( expr )
                     Returns  the value of expr.  This may be used to override
                     the normal precedence of operators.
              expr1 -a expr2
                     True if both expr1 and expr2 are true.
              expr1 -o expr2
                     True if either expr1 or expr2 is true.

              test and [ evaluate conditional expressions using a set of rules
              based on the number of arguments.

              0 arguments
                     The expression is false.
              1 argument
                     The expression is true if and only if the argument is not
                     null.
              2 arguments
                     If the first argument is !, the expression is true if and
                     only  if the second argument is null.  If the first argu-
                     ment is one of the  unary  conditional  operators  listed
                     above  under  CONDITIONAL  EXPRESSIONS, the expression is
                     true if the unary test is true.  If the first argument is
                     not a valid unary conditional operator, the expression is
                     false.
              3 arguments
                     If the second argument is one of the  binary  conditional
                     operators listed above under CONDITIONAL EXPRESSIONS, the
                     result of the expression is the result of the binary test
                     using  the first and third arguments as operands.  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-

              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 sim-
              ple command has a non-zero exit status, subject to the following
              conditions.  The ERR trap is not executed if the failed  command
              is  part  of  the  command list immediately following a while or
              until keyword, part of the test in an if statement,  part  of  a
              command  executed in a && or || list, or if the command's return
              value is being inverted via !.  These are  the  same  conditions
              obeyed by the errexit 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
              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
              -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
              -x     The maximum number of file locks
              -T     The maximum number of threads

              If limit is given, it is the new value of the specified resource
              (the -a option is display only).  If no option is given, then -f
              is assumed.  Values are in 1024-byte increments, except for  -t,
              which  is  in seconds, -p, which is in units of 512-byte blocks,
              and -T, -b, -n, and -u, which are unscaled values.   The  return
              status is 0 unless an invalid option or argument is supplied, or
              an error occurs while setting a new limit.

       umask [-p] [-S] [mode]
              The user file-creation mask is set to mode.  If mode begins with
              a  digit,  it is interpreted as an octal number; otherwise it is
              interpreted as a symbolic mode mask similar to that accepted  by
              chmod(1).   If mode is omitted, the current value of the mask is
              printed.  The -S option causes the mask to be  printed  in  sym-
              For  each  name,  remove the corresponding variable or function.
              If no options are supplied, or the -v option is given, each name
              refers  to  a  shell  variable.   Read-only variables may not be
              unset.  If -f is specified, each name refers to  a  shell  func-
              tion,  and the function definition is removed.  Each unset vari-
              able or function is removed from the environment passed to  sub-
              sequent  commands.   If any of COMP_WORDBREAKS, RANDOM, SECONDS,
              LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are  unset,  they
              lose  their  special  properties,  even if they are subsequently
              reset.  The exit status is true unless a name is readonly.

       wait [n ...]
              Wait for each specified process and return its termination  sta-
              tus.   Each  n  may be a process ID or a job specification; if a
              job spec is given, all processes  in  that  job's  pipeline  are
              waited  for.  If n is not given, all currently active child pro-
              cesses are waited for, and the return  status  is  zero.   If  n
              specifies  a  non-existent  process or job, the return status is
              127.  Otherwise, the return status is the  exit  status  of  the
              last process or job waited for.

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  file  name 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

       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
       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/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
       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-4.1                   2009 December 29                        BASH(1)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2014 Hurricane Electric. All Rights Reserved.