bash

BASH(1)                     General Commands Manual                    BASH(1)



NAME
       bash - GNU Bourne-Again SHell

SYNOPSIS
       bash [options] [file]

COPYRIGHT
       Bash is Copyright (C) 1989, 1991 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
       incorporates useful features from the Korn and C shells (ksh and csh).

       Bash is ultimately intended to be a conformant implementation of the
       IEEE Posix Shell and Tools specification (IEEE Working Group 1003.2).

OPTIONS
       In addition to the single-character shell options documented in the
       description of the set builtin command, bash interprets the following
       flags when it is invoked:

       -c string If the -c flag 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 flag is present, the shell is interactive.
       -s        If the -s flag 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.
       -         A single - signals the end of options and disables further
                 option processing.  Any arguments after the - are treated as
                 filenames and arguments.  An argument of -- is equivalent to
                 an argument of -.

       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.

       -norc     Do not read and execute the personal initialization file
                 ~/.bashrc if the shell is interactive.  This option is on by
                 default if the shell is invoked as sh.
       -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 normally
                 reads these files when it is invoked as a login shell (see
                 INVOCATION below).
       -rcfile file
                 Execute commands from file instead of the standard personal
                 initialization file ~/.bashrc, if the shell is interactive
                 (see INVOCATION below).
       -version  Show the version number of this instance of bash when
                 starting.
       -quiet    Do not be verbose when starting up (do not show the shell
                 version or any other information).  This is the default.
       -login    Make bash act as if it had been invoked as a login shell.
       -nobraceexpansion
                 Do not perform curly brace expansion (see Brace Expansion
                 below).
       -nolineediting
                 Do not use the GNU readline library to read command lines if
                 interactive.
       -posix    Change the behavior of bash where the default operation
                 differs from the Posix 1003.2 standard to match the standard

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
       parameters are set to the remaining arguments.  Bash reads and executes
       commands from this file, then exits.  Bash's exit status is the exit
       status of the last command executed in the script.

DEFINITIONS
       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
              underscores, and beginning with an alphabetic character or an
              underscore.  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
              following 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 { }

SHELL GRAMMAR
   Simple Commands
       A simple command is a sequence of optional variable assignments
       followed by blank-separated words and redirections, and terminated by a
       control operator.  The first word specifies the command to be executed.
       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 the
       character |.  The format for a pipeline is:

              [ ! ] command [ | command2 ... ]

       The standard output of command is connected to the standard input of
       command2.  This connection is performed before any redirections
       specified by the command (see REDIRECTION below).

       If the reserved word !  precedes a pipeline, the exit status of that
       pipeline is the logical NOT of the exit status of the last command.
       Otherwise, the status of the pipeline is the exit status of the last
       command.  The shell waits for all commands in the pipeline to terminate
       before returning a value.

       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 terminated by one of ;, &, or <newline>.

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

       If a command is terminated by the control operator &, the shell
       executes 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.

       The control operators && and ⎪⎪ denote AND lists and OR lists,
       respectively.  An AND list has the form

              command && command2

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

       An OR list has the form

              command ⎪⎪ command2

       command2 is executed if and only if command 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.  Variable assignments and
              builtin commands 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.  This
              is known as a group command.  The return status is the exit
              status of list.

       for name [ in word; ] do list ; done
              The list of words following in is expanded, generating a list of
              items.  The variable name is set to each element of this list in
              turn, and list is executed each time.  If the in word is
              omitted, the for command executes list once for each positional
              parameter that is set (see PARAMETERS below).

       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
              standard input.  If the line consists of the number
              corresponding to one of the displayed words, then the value of
              name is set to that word.  If the line is empty, the words and
              prompt are displayed again.  If EOF is read, the command
              completes.  Any other value read causes name to be set to null.
              The line read is saved in the variable REPLY.  The list is
              executed after each selection until a break or return 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
              pathname expansion (see Pathname Expansion below).  When a match
              is found, the corresponding list is executed.  After the first
              match, no subsequent matches are attempted.  The exit status is
              zero if no patterns are matches.  Otherwise, it is the exit
              status of the last command executed in list.

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

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

       [ function ] name () { list; }
              This defines a function named name.  The body of the function is
              the list of commands between { and }.  This list is executed
              whenever name is specified as the name of a simple command.  The
              exit status of a function is the exit status of the last command
              executed in the body.  (See FUNCTIONS below.)

COMMENTS
       In a non-interactive shell, or an interactive shell in which the -o
       interactive-comments option to the set builtin is enabled, a word
       beginning with # causes that word and all remaining characters on that
       line to be ignored.  An interactive shell without the -o
       interactive-comments option enabled does not allow comments.

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

       Each of the metacharacters listed above under DEFINITIONS has special
       meaning to the shell and must be quoted if they are to represent
       themselves.  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
       quoted, the \<newline> is treated as a line continuation (that is, it
       is 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 \.
       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.

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

PARAMETERS
       A parameter is an entity that stores values, somewhat like a variable
       in a conventional programming language.  It can be a name, a number, or
       one of the special characters listed below under Special Parameters.
       For the shell's purposes, a variable is a parameter denoted by a name.

       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,
       command substitution, arithmetic expansion, and quote removal.  If the
       variable has its -i attribute set (see declare below in SHELL BUILTIN
       COMMANDS) then value is subject to arithmetic expansion even if the
       $[...] syntax does not appear.  Word splitting is not performed, with
       the exception of "$@" as explained below under Special Parameters.
       Pathname expansion is not performed.

   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
              single word with the value of each parameter separated by the
              first character of the IFS special variable.  That is, ``$*'' is
              equivalent to ``$1c$2c...'', where c is the first character of
              the value of the IFS variable.  If IFS is null or unset, the
              parameters are separated by spaces.
       @      Expands to the positional parameters, starting from one.  When
              the expansion occurs within double quotes, each parameter
              expands as a separate word.  That is, `` $@'' is equivalent to
              ``$1'' ``$2'' ...  When there are no positional parameters,
              ``$@'' and $@ expand to nothing (i.e., they are removed).
       #      Expands to the number of positional parameters in decimal.
       ?      Expands to the status of the most recently executed foreground
              pipeline.
       -      Expands to the current option flags as specified upon
              invocation, by the set builtin command, or those set by the
              shell itself (such as the -i flag).
       $      Expands to the process ID of the shell.  In a () subshell, it
              expands to the process ID of the current shell, not the
              subshell.
       !      Expands to the process ID of the most recently executed
              background (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
              commands, $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 pathname used to invoke bash, as given by
              argument zero.
       _      Expands to the last argument to the previous command, after
              expansion.  Also set to the full pathname of each command
              executed and placed in the environment exported to that command.

   Shell Variables
       The following variables are set by the shell:

       PPID   The process ID of the shell's parent.
       PWD    The current working directory as set by the cd command.
       OLDPWD The previous working directory as set by the cd command.
       REPLY  Set to the line of input read by the read builtin command when
              no arguments are supplied.
       UID    Expands to the user ID of the current user, initialized at shell
              startup.
       EUID   Expands to the effective user ID of the current user,
              initialized at shell startup.
       BASH   Expands to the full pathname used to invoke this instance of
              bash.
       BASH_VERSION
              Expands to the version number of this instance of bash.
       SHLVL  Incremented by one each time an instance of bash is started.
       RANDOM Each time this parameter is referenced, a random integer 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.
       SECONDS
              Each time this parameter is referenced, the number of seconds
              since shell invocation is returned.  If a value is assigned to
              SECONDS, the value returned upon subsequent references is the
              number of seconds since the assignment plus the value assigned.
              If SECONDS is unset, it loses its special properties, even if it
              is subsequently reset.
       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.  When in a function, the value is not the number
              of the source line that the command appears on (that information
              has been lost by the time the function is executed), but is an
              approximation of the number of simple commands executed in the
              current function.  If LINENO is unset, it loses its special
              properties, even if it is subsequently reset.
       HISTCMD
              The history number, or index in the history list, of the current
              command.  If HISTCMD is unset, it loses its special properties,
              even if it is subsequently reset.
       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).
       HOSTTYPE
              Automatically set to a string that uniquely describes the type
              of machine on which bash is executing.  The default is system-
              dependent.
       OSTYPE Automatically set to a string that describes the operating
              system on which bash is executing.  The default is system-
              dependent.

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

       IFS    The Internal Field Separator that is used for word splitting
              after expansion and to split lines into words with the read
              builtin command.  The default value is
              ``<space><tab><newline>''.
       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).  The default path is system-dependent, and is
              set by the administrator who installs bash.  A common value is
              ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''.
       HOME   The home directory of the current user; the default argument for
              the cd builtin command.
       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''.
       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 ENV is
              subjected to parameter expansion, command substitution, and
              arithmetic expansion before being interpreted as a pathname.
              PATH is not used to search for the resultant pathname.
       MAIL   If this parameter is set to a filename and the MAILPATH variable
              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 prompting.  If this variable is unset, the
              shell disables mail checking.
       MAILPATH
              A colon-separated list of pathnames to be checked for mail.  The
              message to be printed may be specified by separating the
              pathname from the message with a `?'.  $_ stands for the name of
              the current mailfile.  Example:
              MAILPATH='/usr/spool/mail/bfox?"You have mail":~/shell-mail?"$_
              has mail!"'
              Bash supplies a default value for this variable, but the
              location of the user mail files that it uses is system dependent
              (e.g., /usr/spool/mail/$USER).
       MAIL_WARNING
              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 printed.
       PS1    The value of this parameter is expanded (see PROMPTING below)
              and used as the primary prompt string.  The default value is
              ``bash\$ ''.
       PS2    The value of this parameter is expanded 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 and the value is printed
              before each command bash displays during an execution trace.
              The first character of PS4 is replicated multiple times, as
              necessary, to indicate multiple levels of indirection.  The
              default is ``+ ''.
       HISTSIZE
              The number of commands to remember in the command history (see
              HISTORY below).  The default value is 500.
       HISTFILE
              The name of the file in which command history is saved.  (See
              HISTORY 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
              truncated, if necessary, to contain no more than that number of
              lines.  The default value is 500.
       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.
       PROMPT_COMMAND
              If set, the value is executed as a command prior to issuing each
              primary prompt.
       IGNOREEOF
              Controls the action of the shell on receipt of an EOF character
              as the sole input.  If set, the value is the number of
              consecutive EOF characters typed as the first characters on an
              input line before bash exits.  If the variable exists but does
              not have a numeric value, or has no value, the default value is
              10.  If it does not exist, EOF signifies the end of input to the
              shell.  This is only in effect for interactive shells.
       TMOUT  If set to a value greater than zero, 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.
       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
              suffix matches one of the entries in FIGNORE is excluded from
              the list of matched filenames.  A sample value is ``.o:~''.
       INPUTRC
              The filename for the readline startup file, overriding the
              default of ~/.inputrc (see READLINE below).
       notify If set, bash reports terminated background jobs immediately,
              rather than waiting until before printing the next primary
              prompt (see also the -b option to the set builtin command).
       history_control
       HISTCONTROL
              If set to a value of ignorespace, lines which begin with a space
              character are not entered on the history list.  If set to a
              value of ignoredups, lines matching the last history line are
              not entered.  A value of ignoreboth combines the two options.
              If unset, or if set to any other value than those above, all
              lines read by the parser are saved on the history list.

       command_oriented_history
              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.

       glob_dot_filenames
              If set, bash includes filenames beginning with a `.' in the
              results of pathname expansion.

       allow_null_glob_expansion
              If set, bash allows pathname patterns which match no files (see
              Pathname Expansion below) to expand to a null string, rather
              than themselves.

       histchars
              The two or three characters which control history expansion and
              tokenization (see HISTORY EXPANSION below).  The first character
              is the history expansion character, that is, 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,
              substituting one string for another in the command.  The default
              is `^'.  The optional third character is the character which
              signifies that the remainder of the line is a comment, when
              found as the first character of a word, normally `#'.  The
              history comment 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.

       nolinks
              If set, the shell does not follow symbolic links when executing
              commands 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, such as cd.  See also the
              description of the -P option to the set builtin ( SHELL BUILTIN
              COMMANDS below).
       hostname_completion_file
       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 file may be changed interactively; the next time hostname
              completion is attempted bash adds the contents of the new file
              to the already existing database.

       noclobber
              If set, bash does not overwrite an existing file with the >, >&,
              and <> redirection operators.  This variable may be overridden
              when creating output files by using the redirection operator >|
              instead of > (see also the -C option to the set builtin
              command).

       auto_resume
              This variable controls how the shell interacts with the user and
              job control.  If this variable is set, single word simple
              commands without redirections are treated as candidates for
              resumption of an existing stopped job.  There is no ambiguity
              allowed; if there is more than one job beginning with the string
              typed, the job most recently accessed is selected.  The name of
              a stopped job, in this context, is the command line used to
              start it.  If set to the value exact, the string supplied must
              match the name of a stopped job exactly; if set to substring,
              the string supplied needs to match a substring of the name of a
              stopped job.  The substring value provides functionality
              analogous to the %?  job id (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
              % job id.

       no_exit_on_failed_exec
              If this variable exists, a non-interactive shell will not exit
              if it cannot execute the file specified in the exec builtin
              command.  An interactive shell does not exit if exec fails.

       cdable_vars
              If this is 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.

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
       substitution, arithmetic expansion, word splitting, and pathname
       expansion.

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

       On systems that can support it, there is an additional expansion
       available: 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 single exception to this is the expansion
       of ``$@'' as explained above (see PARAMETERS).

   Brace Expansion
       Brace expansion is a mechanism by which arbitrary strings may be
       generated.  This mechanism is similar to pathname expansion, but the
       filenames generated need not exist.  Patterns to be brace expanded take
       the form of an optional preamble, followed by a series of comma-
       separated strings between a pair of braces, followed by an optional
       postamble.  The preamble is prepended to each string contained within
       the braces, and the postamble is then appended to each resulting
       string, expanding left to right.

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

       Brace expansion is performed before any other expansions, and any
       characters 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.  Any incorrectly
       formed brace expansion is left unchanged.

       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 traditional
       versions of sh, the Bourne shell.  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 -nobraceexpansion flag (see OPTIONS above)
       or disable brace expansion with the +o braceexpand option to the set
       command (see SHELL BUILTIN COMMANDS below).

   Tilde Expansion
       If a word begins with a tilde character (`~'), all of the characters
       preceding the first slash (or all characters, if there is no slash) are
       treated as a possible login name. If this login name is the null
       string, the tilde is replaced with the value of the parameter HOME.  If
       HOME is unset, the home directory of the user executing the shell is
       substituted instead.

       If a `+' follows the tilde, the value of PWD replaces the tilde and
       `+'.  If a `-' follows, the value of OLDPWD is substituted.  If the
       value following the tilde is a valid login name, the tilde and login
       name are replaced with the home directory associated with that name.
       If the name is invalid, or the tilde expansion fails, the word is
       unchanged.

       Each variable assignment is checked for unquoted instances of tildes
       following a : or =.  In these cases, tilde substitution is also
       performed.  Consequently, one may use pathnames with tildes in
       assignments to PATH, MAILPATH, and CDPATH, and the shell assigns the
       expanded value.

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

       ${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.

       In each of the cases below, word is subject to tilde expansion,
       parameter expansion, command substitution, and arithmetic expansion.
       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
              expansion 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
              parameter 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}
              The length in characters of the value of parameter is
              substituted.  If parameter is * or @, the length substituted is
              the length of * expanded within double quotes.
       ${parameter#word}
       ${parameter##word}
              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 expansion is the value of parameter with the
              shortest matching pattern deleted (the ``#'' case) or the
              longest matching pattern deleted (the ``##'' case).

       ${parameter%word}
       ${parameter%%word}
              The word is expanded to produce a pattern just as in pathname
              expansion.  If the pattern matches a trailing portion of the
              value of parameter, then the expansion is the value of parameter
              with the shortest matching pattern deleted (the ``%'' case) or
              the longest matching pattern deleted (the ``%%'' case).

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

              $(command)
       or
              `command`

       Bash performs the expansion by executing command and replacing the
       command substitution with the standard output of the command, with any
       trailing newlines deleted.

       When the old-style backquote form of substitution is used, backslash
       retains its literal meaning except when followed by $, `, or \.  When
       using the $(command) form, all characters between the parentheses make
       up the command; none are treated specially.

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

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

   Arithmetic Expansion
       Arithmetic expansion allows the evaluation of an arithmetic expression
       and the substitution of the result.  There are two formats for
       arithmetic expansion:

              $[expression]

              $((expression))

       The expression is treated as if it were within double quotes, but a
       double quote inside the braces or parentheses is not treated specially.
       All tokens in the expression undergo parameter expansion, command
       substitution, and quote removal.  Arithmetic substitutions 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
       output 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
       provide input for list.  If the <(list) form is used, the file passed
       as an argument should be read to obtain the output of list.

       On systems that support it, 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
       substitution, 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 the
       value of IFS is exactly <space><tab><newline>, the default, then any
       sequence of IFS characters 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.  IFS cannot be
       unset.

       Explicit null arguments ("" or '') are retained.  Implicit null
       arguments, resulting from the expansion of parameters that have no
       values, are removed.

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

   Pathname Expansion
       After word splitting, unless the -f option has been set, bash scans
       each word for the characters *, ?, and [.  If one of these characters
       appears, then the word is regarded as a pattern, and replaced with an
       alphabetically sorted list of pathnames matching the pattern.  If no
       matching pathnames are found, and the shell variable
       allow_null_glob_expansion is unset, the word is left unchanged.  If the
       variable is set, and no matches are found, the word is removed.  When a
       pattern is used for pathname generation, the character ``.''  at the
       start of a name or immediately following a slash must be matched
       explicitly, unless the shell variable glob_dot_filenames is set.  The
       slash character must always be matched explicitly.  In other cases, the
       ``.''  character is not treated specially.

       The special pattern characters have the following meanings:

       *      Matches any string, including the null string.
       ?      Matches any single character.
       [...]  Matches any one of the enclosed characters.  A pair of
              characters separated by a minus sign denotes a range; any
              character lexically between those two characters, inclusive, is
              matched.  If the first character following the [ is a !  or a ^
              then any character not enclosed is matched.  A - or ] may be
              matched by including it as the first or last character in the
              set.

   Quote Removal
       After the preceding expansions, all unquoted occurrences of the
       characters \, `, and " 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.

       In the following descriptions, if the file descriptor number is
       omitted, and the first character of the redirection operator is <, the
       redirection 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 that follows the redirection operator in the following
       descriptions is subjected to brace expansion, tilde expansion,
       parameter expansion, command substitution, arithmetic expansion, quote
       removal, and pathname expansion.  If it expands to more than one word,
       bash reports an error.

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

              ls > dirlist 2>&1

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

              ls 2>&1 > dirlist

       directs only the standard output to file dirlist, because the standard
       error was duplicated as standard output before the standard output was
       redirected to dirlist.

   Redirecting Input
       Redirection of input causes the file whose name results from the
       expansion 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 >|, then the value of the -C option to
       the set builtin command is not tested, and file creation is attempted.
       (See also the description of noclobber under Shell Variables above.)

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

       The general format for appending output is:

              [n]>>word

   Redirecting Standard Output and Standard Error
       Bash 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 with this construct.

       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
       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 word (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 as follows:

              <<[-]word
                      here-document
              delimiter

       No parameter expansion, command substitution, pathname expansion, or
       arithmetic 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.  Otherwise, all lines
       of the here-document are subjected to parameter expansion, command
       substitution, and arithmetic expansion.  In the latter case, the pair
       \<newline> is ignored, and \ must be used to quote the characters \, $,
       and `.

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

   Duplicating File Descriptors
       The redirection operator

              [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 word evaluates 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.  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.

   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 as the standard input
       and standard output if n is not specified.  If the file does not exist,
       it is created.

FUNCTIONS
       A shell function, defined as described above under SHELL GRAMMAR,
       stores a series of commands for later execution.  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.  Positional parameter 0 is unchanged.

       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
       function call.  When a function completes, the values of the positional
       parameters and the special parameter # are restored to the values they
       had prior to function execution.

       Function names and definitions may be listed with the -f option to the
       declare or typeset builtin commands.  Functions may be exported so that
       subshells automatically have them defined with the -f option to the
       export builtin.

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

ALIASES
       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 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 alias name and the replacement text may contain any valid
       shell input, including the metacharacters listed above, with the
       exception that the alias name may not contain =.  The first word of the
       replacement text is tested for aliases, but a word that is identical to
       an alias being expanded is not expanded a second time.  This means that
       one may alias ls to ls -F, for instance, and bash does not try to
       recursively expand the replacement text.  If the last character of the
       alias value is a blank, then the next command word following the alias
       is also checked for alias expansion.

       Aliases are created and listed with the alias command, and removed with
       the unalias command.

       There is no mechanism for using arguments in the replacement text, as
       in csh.  If arguments are needed, a shell function should be used.

       Aliases are not expanded when the shell is not interactive.

       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.  This means that
       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 the function
       definition is read, not when the function is executed, because a
       function definition is itself a compound 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 compound commands.

       Note that for almost every purpose, aliases are superseded by shell
       functions.

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 system'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 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-
       generated signals.  Only foreground processes are allowed to read from
       or write to the terminal.  Background processes which attempt to read
       from (write to) the terminal are sent a SIGTTIN (SIGTTOU) signal by the
       terminal driver, which, unless caught, suspends the process.

       If the operating system on which bash is running supports job control,
       bash allows you to use it.  Typing the suspend character (typically ^Z,
       Control-Z) while a process is running causes that process to be stopped
       and returns you to bash.  Typing the delayed suspend character
       (typically ^Y, Control-Y) causes the process to be stopped when it
       attempts to read input from the terminal, and control to be returned to
       bash.  You may then manipulate the state of this job, using the bg
       command to continue it in the background, the fg command to continue it
       in the foreground, or the kill command to kill it.  A ^Z takes effect
       immediately, and has the additional side effect of causing pending
       output and typeahead to be discarded.

       There are a number of ways to refer to a job in the shell.  The
       character % introduces a job name.  Job number n may be referred to as
       %n.  A job may also be referred to using a prefix of the 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 current job, which
       is the last job stopped while it was in the foreground.  The previous
       job may be referenced using %-.  In output pertaining to jobs (e.g.,
       the output of the jobs command), the current job is always flagged with
       a +, and the previous job with a -.

       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 set, bash reports such changes
       immediately.  (See also the description of notify variable under Shell
       Variables above.)

       If you attempt to exit bash while jobs are stopped, the shell prints a
       message warning you.  You may then use the jobs command to inspect
       their status.  If you do this, or try to exit again immediately, you
       are not warned again, and the stopped jobs are terminated.

SIGNALS
       When bash is interactive, it ignores SIGTERM (so that kill 0 does not
       kill an interactive shell), and SIGINT is caught and handled (so that
       the wait builtin is interruptible).  In all cases, bash ignores
       SIGQUIT.  If job control is in effect, bash ignores SIGTTIN, SIGTTOU,
       and SIGTSTP.

       Synchronous jobs started by bash have signals set to the values
       inherited by the shell from its parent.  When job control is not in
       effect, background jobs (jobs started with &) ignore SIGINT and
       SIGQUIT.  Commands run as a result of command substitution ignore the
       keyboard-generated job control signals SIGTTIN, SIGTTOU, and SIGTSTP.

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
       containing an executable file by that name.  If the search is
       unsuccessful, the shell prints an error message and returns a nonzero
       exit status.

       If the search is successful, or if the command name contains one or
       more slashes, the shell executes the named program.  Argument 0 is set
       to the name given, and the remaining 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
       executable 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.

ENVIRONMENT
       When a program is invoked it is given an array of strings called the
       environment.  This is a list of name-value pairs, of the form
       name=value.

       The shell allows you to manipulate the environment in several ways.  On
       invocation, the shell scans its own environment and creates a parameter
       for each name found, automatically marking it for export to child
       processes.  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
       environment 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
       modified 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
       environment seen by that command.

       If the -k flag 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 path name of the command and passed to that command in its
       environment.

EXIT STATUS
       For the purposes of the shell, 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, bash uses the value of 128+signal 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.

       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.

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:
              \t     the current time in HH:MM:SS format
              \d     the date in "Weekday Month Date" format (e.g., "Tue May
                     26")
              \n     newline
              \s     the name of the shell, the basename of $0 (the portion
                     following the final slash)
              \w     the current working directory
              \W     the basename of the current working directory
              \u     the username of the current user
              \h     the hostname
              \#     the command number of this command
              \!     the history 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
       substitution, arithmetic expansion, and word splitting.

READLINE
       This is the library that handles reading input when using an
       interactive shell, unless the -nolineediting option is given.  By
       default, the line editing commands are similar to those of emacs.  A
       vi-style line editing interface is also available.

       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.
       Similarly, meta keys are denoted by M-key, so M-x means Meta-X.  (On
       keyboards 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.)

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

       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
       specified 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.

              "\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 escape
       sequences is

              \C-    control prefix

              \M-    meta prefix

              \e     an escape character

              \\     backslash

              \"     literal "

              \'     literal '

       When entering the text of a macro, single or double quotes should be
       used to indicate a macro definition.  Unquoted text is assumed to be a
       function name.  Backslash will quote any character in the macro text,
       including " and '.

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

       Readline has variables that can be used to further customize its
       behavior.  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.
       The variables and their default values are:

       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.
       editing-mode (emacs)
              Controls whether readline begins with a set of key bindings
              similar to emacs or vi.  editing-mode can be set to either emacs
              or vi.
       mark-modified-lines (Off)
              If set to On, history lines that have been modified are
              displayed with a preceding asterisk (*).
       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.
       comment-begin (``#'')
              The string that is inserted in vi mode when the vi-comment
              command is executed.
       meta-flag (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.
       convert-meta (On)
              If set to On, readline will convert characters with the eighth
              bit set to an ASCII key sequence by stripping the eighth bit and
              prepending an escape character (in effect, using escape as the
              meta prefix).
       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.
       completion-query-items (100)
              This determines when the user is queried about viewing the
              number of possible completions generated by the
              possible-completions command.  It may be set to any integer
              value greater than or equal to zero.  If the number of possible
              completions is greater than or equal to the value of this
              variable, the user is asked whether or not he wishes to view
              them; otherwise they are simply listed on the terminal.
       keymap (emacs)
              Set the current readline keymap.  The set of legal keymap names
              is emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi-move,
              vi-command, and vi-insert.  vi is equivalent to vi-command;
              emacs is equivalent to emacs-standard.  The default value is
              emacs; the value of editing-mode also affects the default
              keymap.
       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.
       expand-tilde (Off)
              If set to on, tilde expansion is performed when readline
              attempts word completion.

       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 three parser directives used.

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

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

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

              application
                     The application construct is used to include
                     application-specific settings.  Each program using the
                     readline library sets the application name, and an
                     initialization file can test for a particular value.
                     This could be used to bind key sequences to functions
                     useful for a specific program.  For instance, the
                     following command adds a key sequence that quotes the
                     current or previous word in Bash:
                     $if Bash
                     # Quote the current or previous word
                     "\C-xq": "\eb\"\ef\""
                     $endif

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

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

       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.

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

       The following is a list of the names of the commands and the default
       key sequences to which they are bound.

   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 this, or the previous, word.  Words
              are composed of alphanumeric characters (letters and digits).
       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.  By default, this is unbound.

   Commands for Manipulating the History
       accept-line (Newline, Return)
              Accept the line regardless of where the cursor is.  If this line
              is non-empty, add it to the history list according to the state
              of the HISTCONTROL variable.  If the line is a modified history
              line, then restore the history line to its original state.
       previous-history (C-p)
              Fetch the previous command from the history list, moving back in
              the list.
       next-history (C-n)
              Fetch the next command from the history list, moving forward in
              the list.
       beginning-of-history (M-<)
              Move to the first line in the history.
       end-of-history (M->)
              Move to the end of the input history, i.e., the line currently
              being entered.
       reverse-search-history (C-r)
              Search backward starting at the current line and moving `up'
              through the history as necessary.  This is an incremental
              search.
       forward-search-history (C-s)
              Search forward starting at the current line and moving `down'
              through the history as necessary.  This is an incremental
              search.
       non-incremental-reverse-search-history (M-p)
              Search backward through the history starting at the current line
              using a non-incremental search for a string supplied by the
              user.
       non-incremental-forward-search-history (M-n)
              Search forward through the history using a non-incremental
              search for a string supplied by the user.
       history-search-forward
              Search forward through the history for the string of characters
              between the start of the current line and the current point.
              This is a non-incremental search.  By default, this command is
              unbound.
       history-search-backward
              Search backward through the history for the string of characters
              between the start of the current line and the current point.
              This is a non-incremental search.  By default, this command is
              unbound.
       yank-nth-arg (M-C-y)
              Insert the first argument to the previous command (usually the
              second word on the previous line) at point (the current cursor
              position).  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.
       yank-last-arg (M-., M-_)
              Insert the last argument to the previous command (the last word
              on the previous line).  With an argument, behave exactly like
              yank-nth-arg.
       shell-expand-line (M-C-e)
              Expand the line the way the shell does when it reads it.  This
              performs alias and history 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.
       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.

   Commands for Changing Text
       delete-char (C-d)
              Delete the character under the cursor.  If point is at the
              beginning of the line, there are no characters in the line, and
              the last character typed was not C-d, then return EOF.
       backward-delete-char (Rubout)
              Delete the character behind the cursor.  When given a numeric
              argument, save the deleted text on the kill-ring.
       quoted-insert (C-q, C-v)
              Add the next character that you type to the line verbatim.  This
              is how to insert characters like C-q, for example.
       tab-insert (C-v TAB)
              Insert a tab character.
       self-insert (a, b, A, 1, !, ...)
              Insert the character typed.
       transpose-chars (C-t)
              Drag the character before point forward over the character at
              point.  Point moves forward as well.  If point is at the end of
              the line, then transpose the two characters before point.
              Negative arguments don't work.
       transpose-words (M-t)
              Drag the word behind the cursor past the word in front of the
              cursor moving the cursor over that word as well.
       upcase-word (M-u)
              Uppercase the current (or following) word.  With a negative
              argument, do the previous word, but do not move point.
       downcase-word (M-l)
              Lowercase the current (or following) word.  With a negative
              argument, do the previous word, but do not move point.
       capitalize-word (M-c)
              Capitalize the current (or following) word.  With a negative
              argument, do the previous word, but do not move point.

   Killing and Yanking
       kill-line (C-k)
              Kill the text from the current cursor position to the end of the
              line.
       backward-kill-line (C-x C-Rubout)
              Kill backward to the beginning of the line.
       unix-line-discard (C-u)
              Kill backward from point to the beginning of the line.
       kill-whole-line
              Kill all characters on the current line, no matter where the
              cursor is.  By default, this is unbound.
       kill-word (M-d)
              Kill from the cursor 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 the cursor.  Word boundaries are the same
              as those used by backward-word.
       unix-word-rubout (C-w)
              Kill the word behind the cursor, using white space as a word
              boundary.  The word boundaries are different from
              backward-kill-word.
       delete-horizontal-space
              Delete all spaces and tabs around point.  By default, this is
              unbound.
       yank (C-y)
              Yank the top of the kill ring into the buffer at the cursor.
       yank-pop (M-y)
              Rotate the kill-ring, and yank the new top.  Only works
              following 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
              Each time this is executed, the argument count is multiplied by
              four.  The argument count is initially one, so executing this
              function the first time makes the argument count four.  By
              default, this is not bound to a key.

   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 $), username (if the text begins with ~), hostname
              (if the text begins with @), or command (including aliases and
              functions) in turn.  If none of these produces a match, filename
              completion is attempted.
       possible-completions (M-?)
              List the possible completions of the text before point.
       insert-completions
              Insert all completions of the text before point that would have
              been generated by possible-completions.  By default, this is not
              bound to a key.
       complete-filename (M-/)
              Attempt filename completion on the text before point.
       possible-filename-completions (C-x /)
              List the possible completions of the text before point, treating
              it as a filename.
       complete-username (M-~)
              Attempt completion on the text before point, treating it as a
              username.
       possible-username-completions (C-x ~)
              List the possible completions of the text before point, treating
              it as a username.
       complete-variable (M-$)
              Attempt completion on the text before point, treating it as a
              shell variable.
       possible-variable-completions (C-x $)
              List the possible completions of the text before point, treating
              it as a shell variable.
       complete-hostname (M-@)
              Attempt completion on the text before point, treating it as a
              hostname.
       possible-hostname-completions (C-x @)
              List the possible completions of the text before point, treating
              it as a hostname.
       complete-command (M-!)
              Attempt completion on the text before point, treating it as a
              command name.  Command completion attempts to match the text
              against aliases, reserved words, shell functions, 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.
       complete-into-braces (M-{)
              Perform filename completion and return the list of possible
              completions 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 save the definition.
       call-last-kbd-macro (C-x e)
              Re-execute the last keyboard macro defined, by making the
              characters in the macro appear as if typed at the keyboard.

   Miscellaneous
       re-read-init-file (C-x C-r)
              Read in the contents of your init file, and incorporate any
              bindings or variable assignments found there.
       abort (C-g)
              Abort the current editing command and ring the terminal's bell
              (subject to the setting of bell-style).
       do-uppercase-version (M-a, M-b, ...)
              Run the command that is bound to the corresponding uppercase
              character.
       prefix-meta (ESC)
              Metafy the next character typed.  ESC f is equivalent to Meta-f.
       undo (C-_, C-x C-u)
              Incremental undo, separately remembered for each line.
       revert-line (M-r)
              Undo all changes made to this line.  This is like typing the
              undo command enough times to return the line to its initial
              state.
       tilde-expand (M-~)
              Perform tilde expansion on the current word.
       dump-functions
              Print all of the functions and their key bindings to the
              readline output stream.  If a numeric argument is supplied, the
              output is formatted in such a way that it can be made part of an
              inputrc file.
       display-shell-version (C-x C-v)
              Display version information about the current instance of bash.

HISTORY
       When interactive, the shell provides access to the command history, the
       list of commands previously typed.  The text of the last HISTSIZE
       commands (default 500) is saved in a history list.  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
       command_oriented_history and HISTCONTROL.  On startup, the history is
       initialized from the file named by the variable HISTFILE (default
       ~/.bash_history).  HISTFILE is truncated, if necessary, to contain no
       more than HISTFILESIZE lines.  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 history builtin can be used to
       display the history list and manipulate the history file.  When using
       the command-line editing, search commands are available in each editing
       mode that provide access to the history list.  When an interactive
       shell exits, the last HISTSIZE lines are copied from the history list
       to HISTFILE.  If HISTFILE is unset, or if the history file is
       unwritable, the history is not saved.

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

       History expansion is performed immediately after a complete line is
       read, before the shell breaks it into words.  It takes place in two
       parts.  The first is to determine which line from the previous history
       to use during substitution.  The second is to select portions of that
       line for inclusion into the current one.  The line selected from the
       previous history is the event, and the portions of that line that are
       acted upon are words.  The line is broken into words in the same
       fashion as when reading input, so that several metacharacter-separated
       words surrounded by quotes are considered as one word.  Only backslash
       (\) and single quotes can quote the history escape character, which is
       ! by default.

       The shell allows control of the various characters used by the history
       expansion mechanism (see the description of histchars above under Shell
       Variables).

   Event Designators
       An event designator is a reference to a command line entry in the
       history list.

       !      Start a history substitution, except when followed by a blank,
              newline, = or (.
       !!     Refer to the previous command.  This is a synonym for `!-1'.
       !n     Refer to command line n.
       !-n    Refer to the current command line minus n.
       !string
              Refer to the most recent command starting with string.
       !?string[?]
              Refer to the most recent command containing string.
       ^string1^string2^
              Quick substitution.  Repeat the last command, replacing string1
              with string2.  Equivalent to ``!!:s/string1/string2/'' (see
              Modifiers below).
       !#     The entire command line typed so far.

   Word Designators
       A : separates the event specification from the word designator.  It can
       be omitted if the word designator begins with a ^, $, *, or %.  Words
       are numbered from the beginning of the line, with the first word being
       denoted by a 0 (zero).

       0 (zero)
              The zeroth word.  For the shell, this is the command word.
       n      The nth word.
       ^      The first argument.  That is, word 1.
       $      The last 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.

   Modifiers
       After the optional word designator, you can add a sequence of one or
       more of the following modifiers, each preceded by a `:'.

       h      Remove a trailing pathname component, leaving only the head.
       r      Remove a trailing suffix of the form .xxx, leaving the basename.
       e      Remove all but the trailing suffix.
       t      Remove all leading pathname components, leaving the tail.
       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
              single backslash will quote the &.
       &      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.

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

       - +    unary minus and plus
       ! ~    logical and bitwise negation
       * / %  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
       = *= /= %= += -= <<= >>= &= ^= |=
              assignment

       Shell variables are allowed as operands; parameter expansion is
       performed before the expression is evaluated.  The value of a parameter
       is coerced to a long integer within an expression.  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
       0x or 0X denotes hexadecimal.  Otherwise, numbers take the form
       [base#]n, where base is a decimal number between 2 and 36 representing
       the arithmetic base, and n is a number in that base.  If base is
       omitted, then base 10 is used.

       Operators are evaluated in order of precedence.  Sub-expressions in
       parentheses are evaluated first and may override the precedence rules
       above.

SHELL BUILTIN COMMANDS
       : [arguments]
              No effect; the command does nothing beyond expanding arguments
              and performing any specified redirections.  A zero exit code is
              returned.

        .  filename [arguments]
       source filename [arguments]
              Read and execute commands from filename in the current shell
              environment and return the exit status of the last command
              executed from filename.  If filename does not contain a slash,
              pathnames in PATH are used to find the directory containing
              filename.  The file searched for in PATH need not be executable.
              The current directory is searched if no file is found in PATH.
              If any arguments are supplied, they become the positional
              parameters when file 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.

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

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

       bind [-m keymap] [-lvd] [-q name]
       bind [-m keymap] -f filename
       bind [-m keymap] keyseq:function-name
              Display current readline key and function bindings, or bind a
              key sequence to a readline function or macro.  The binding
              syntax accepted is identical to that of .inputrc, but each
              binding must be passed as a separate argument; e.g., '"\C-x\C-
              r": re-read-init-file'.  Options, if supplied, have the
              following meanings:
              -m keymap
                     Use keymap as the keymap to be affected by the subsequent
                     bindings.  Acceptable keymap names are emacs, emacs-
                     standard, emacs-meta, emacs-ctlx, vi, vi-move, vi-
                     command, and vi-insert.  vi is equivalent to vi-command;
                     emacs is equivalent to emacs-standard.
              -l     List the names of all readline functions
              -v     List current function names and bindings
              -d     Dump function names and bindings in such a way that they
                     can be re-read
              -f filename
                     Read key bindings from filename
              -q function
                     Query about which keys invoke the named function

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

       break [n]
              Exit from within a for, while, or until loop.  If n is
              specified, break n levels.  n must be ≥ 1.  If n is greater than
              the number of enclosing loops, all enclosing loops are exited.
              The return value is 0 unless the shell is not executing a loop
              when break is executed.

       builtin shell-builtin [arguments]
              Execute the specified shell builtin, passing it arguments, and
              return its exit status.  This is useful when you wish to define
              a function whose name is the same as a shell builtin, but need
              the functionality of the builtin within the function itself.
              The cd builtin is commonly redefined this way.  The return
              status is false if shell-builtin is not a shell builtin command.

       cd [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 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.  An argument of - is
              equivalent to $OLDPWD.  The return value is true if the
              directory was successfully changed; false otherwise.

       command [-pVv] command [arg ...]
              Run command with args suppressing the normal shell function
              lookup. Only builtin commands or commands found in the PATH are
              executed.  If the -p option is given, the search for command is
              performed using a default value for PATH that is guaranteed to
              find all of the standard utilities.  If either the -V or -v
              option is supplied, a description of command is printed.  The -v
              option causes a single word indicating the command or pathname
              used to invoke command to be printed; the -V option produces a
              more verbose description.  An argument of -- disables option
              checking for the rest of the arguments.  If the -V or -v option
              is supplied, the exit status is 0 if command was found, and 1 if
              not.  If neither option is supplied and an error occurred or
              command cannot be found, the exit status is 127.  Otherwise, the
              exit status of the command builtin is the exit status of
              command.

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

       declare [-frxi] [name[=value]]
       typeset [-frxi] [name[=value]]
              Declare variables and/or give them attributes.  If no names are
              given, then display the values of variables instead.  The
              options can be used to restrict output to variables with the
              specified attribute.
              -f     Use function names only
              -r     Make names readonly.  These names cannot then be assigned
                     values by subsequent assignment statements.
              -x     Mark names for export to subsequent commands via the
                     environment.
              -i     The variable is treated as an integer; arithmetic
                     evaluation (see ARITHMETIC EVALUATION ) is performed when
                     the variable is assigned a value.

              Using `+' instead of `-' turns off the attribute instead.  When
              used in a function, makes names local, as with the local
              command.  The return value is 0 unless an illegal option is
              encountered, an attempt is made to define a function using "-f
              foo=bar", one of the names is not a legal shell variable name,
              an attempt is made to turn off readonly status for a readonly
              variable, or an attempt is made to display a non-existant
              function with -f.

       dirs [-l] [+/-n]
              Display the list of currently remembered directories.
              Directories are added to the list with the pushd command; the
              popd command moves back up through 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.
              -l     produces a longer listing; the default listing format
                     uses a tilde to denote the home directory.

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

       echo [-neE] [arg ...]
              Output the args, separated by spaces.  The return status is
              always 0.  If -n is specified, the trailing newline is
              suppressed.  If the -e option is given, interpretation of the
              following backslash-escaped characters is enabled.  The -E
              option disables the interpretation of these escape characters,
              even on systems where they are interpreted by default.
              \a     alert (bell)
              \b     backspace
              \c     suppress trailing newline
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\     backslash
              \nnn   the character whose ASCII code is nnn (octal)

       enable [-n] [-all] [name ...]
              Enable and disable builtin shell commands.  This allows the
              execution of a disk command which has the same name as a shell
              builtin without specifying a full pathname.  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, type ``enable -n test''.  If no arguments are
              given, a list of all enabled shell builtins is printed.  If only
              -n is supplied, a list of all disabled builtins is printed.  If
              only -all is supplied, the list printed includes all builtins,
              with an indication of whether or not each is enabled.  enable
              accepts -a as a synonym for -all.  The return value is 0 unless
              a name is not a shell builtin.

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

       exec [[-] command [arguments]]
              If command is specified, it replaces the shell.  No new process
              is created.  The arguments become the arguments to command.  If
              the first argument is -, the shell places a dash in the zeroth
              arg passed to command.  This is what login does.  If the file
              cannot be executed for some reason, a non-interactive shell
              exits, unless the shell variable no_exit_on_failed_exec exists,
              in which case it returns failure.  An interactive shell returns
              failure if the file cannot be executed.  If command is not
              specified, any redirections take effect in the current shell,
              and the return status is 0.

       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 [-nf] [name[=word]] ...
       export -p
              The supplied names are marked for automatic export to the
              environment of subsequently executed commands.  If the -f option
              is given, the names refer to functions.  If no names are given,
              or if the -p option is supplied, a list of all names that are
              exported in this shell is printed.  The -n option causes the
              export property to be removed from the named variables.  An
              argument of -- disables option checking for the rest of the
              arguments.  export returns an exit status of 0 unless an illegal
              option is encountered, one of the names is not a legal shell
              variable name, or -f is supplied with a name that is not a
              function.

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

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

              In the second form, command is re-executed after each instance
              of pat is replaced by rep.  A useful alias to use with this is
              ``r=fc -s'', so that typing ``r cc'' runs the last command
              beginning with ``cc'' and typing ``r'' re-executes the last
              command.

              If the first form is used, the return value is 0 unless an
              illegal option is encountered or first or last specify history
              lines out of range.  If the -e option is supplied, the return
              value is the value of the last command executed or failure if an
              error occurs with the temporary file of commands.  If the second
              form is used, the return status is that of the command re-
              executed, unless cmd does not specify a valid history line, in
              which case fc returns failure.

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

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

              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 illegal
              options or missing option arguments are encountered.  If the
              variable OPTERR is set to 0, no error message will be displayed,
              even if the first character of optstring is not a colon.

              If an illegal 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 normally parses the positional parameters, but if more
              arguments are given in args, getopts parses those instead.
              getopts returns true if an option, specified or unspecified, is
              found.  It returns false if the end of options is encountered or
              an error occurs.

       hash [-r] [name]
              For each name, the full pathname of the command is determined
              and remembered.  The -r option causes the shell to forget all
              remembered locations.  If no arguments are given, information
              about remembered commands is printed.  An argument of --
              disables option checking for the rest of the arguments.  The
              return status is true unless a name is not found or an illegal
              option is supplied.

       help [pattern]
              Display helpful information about builtin commands.  If pattern
              is specified, help gives detailed help on all commands matching
              pattern; otherwise a list of the builtins is printed.  The
              return status is 0 unless no command matches pattern.

       history [n]
       history -rwan [filename]
              With no options, display the command history list with line
              numbers.  Lines listed with a * have been modified.  An argument
              of n lists only the last n lines.  If a non-option argument 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:
              -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,
                     overwriting the history file's contents.

              The return value is 0 unless an illegal option is encountered or
              an error occurs while reading or writing the history file.

       jobs [-lnp] [ jobspec ... ]
       jobs -x command [ args ... ]
              The first form lists the active jobs.  The -l option lists
              process IDs in addition to the normal information; the -p option
              lists only the process ID of the job's process group leader.
              The -n option displays only jobs that have changed status since
              last notified.  If jobspec is given, output is restricted to
              information about that job.  The return status is 0 unless an
              illegal option is encountered or an illegal 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 | -sigspec] [pid | jobspec] ...
       kill -l [signum]
              Send the signal named by sigspec to the processes named by pid
              or jobspec.  sigspec is either a signal name such as SIGKILL or
              a signal number.  If sigspec is a signal name, the name is case
              insensitive and may be given with or without the SIG prefix.  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 specified signals are listed, and
              the return status is 0.  An argument of -- disables option
              checking for the rest of the arguments.  kill returns true if at
              least one signal was successfully sent, or false if an error
              occurs or an illegal option is encountered.

       let arg [arg ...]
              Each arg is an arithmetic expression to be evaluated (see
              ARITHMETIC EVALUATION).  If the last arg evaluates to 0, let
              returns 1; 0 is returned otherwise.

       local [name[=value] ...]
              For each argument, create a local variable named name, and
              assign it value.  When local is used within a function, it
              causes the variable name to have a visible scope restricted to
              that function and its children.  With no operands, local writes
              a list of local variables to the standard output.  It is an
              error to use local when not within a function.  The return
              status is 0 unless local is used outside a function, or an
              illegal name is supplied.

       logout Exit a login shell.

       popd [+/-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.
              +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 illegal
              option is encountered, the directory stack is empty, a non-
              existent directory stack entry is specified, or the directory
              change fails.

       pushd [dir]
       pushd +/-n
              Adds a directory to the top of the directory stack, or rotates
              the stack, making the new top of the stack the current working
              directory.  With no arguments, exchanges the top two directories
              and returns 0, unless the directory stack is empty.
              +n     Rotates the stack so that the nth directory (counting
                     from the left of the list shown by dirs) is at the top.
              -n     Rotates the stack so that the nth directory (counting
                     from the right) 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
              directory stack is empty, a non-existant directory stack element
              is specified, or the directory change to the specified new
              current directory fails.

       pwd    Print the absolute pathname of the current working directory.
              The path printed contains no symbolic links if the -P option to
              the set builtin command is set.  See also the description of
              nolinks under Shell Variables above).  The return status is 0
              unless an error occurs while reading the pathname of the current
              directory.

       read [-r] [name ...]
              One line is read from the standard input, and the first word is
              assigned to the first name, the second word to the second name,
              and so on, with leftover words assigned to the last name.  Only
              the characters in IFS are recognized as word delimiters.  If no
              names are supplied, the line read is assigned to the variable
              REPLY.  The return code is zero, unless end-of-file is
              encountered.  If the -r option is given, a backslash-newline
              pair is not ignored, and the backslash is considered to be part
              of the line.

       readonly [-f] [name ...]
       readonly -p
              The given names are marked readonly and 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.  If no arguments are given, or if the -p option is
              supplied, a list of all readonly names is printed.  An argument
              of -- disables option checking for the rest of the arguments.
              The return status is 0 unless an illegal option is encountered,
              one of the names is not a legal shell variable name, or -f is
              supplied with a name that is not a function.

       return [n]
              Causes a function to exit with the return value specified by n.
              If n is omitted, the return status is that of the last command
              executed in the function body.  If used outside a function, but
              during execution of a script by the .  (source) command, it
              causes the shell to stop executing that script and return either
              n or the exit status of the last command executed within the
              script as the exit status of the script.  If used outside a
              function and not during execution of a script by ., the return
              status is false.

       set [--abefhkmnptuvxldCHP] [-o option] [arg ...]
              -a      Automatically mark variables which are modified or
                      created for export to the environment of subsequent
                      commands.
              -b      Cause the status of terminated background jobs to be
                      reported immediately, rather than before the next
                      primary prompt.  (Also see notify under Shell Variables
                      above).
              -e      Exit immediately if a simple-command (see SHELL GRAMMAR
                      above) exits with a non-zero status.  The shell does not
                      exit if the command that fails is part of an until or
                      while loop, part of an if statement, part of a && or ⎪⎪
                      list, or if the command's return value is being inverted
                      via !.
              -f      Disable pathname expansion.
              -h      Locate and remember function commands as functions are
                      defined.  Function commands are normally looked up when
                      the function is executed.
              -k      All keyword arguments are placed in the environment for
                      a command, not just those that precede the command name.
              -m      Monitor mode.  Job control is enabled.  This flag is on
                      by default for interactive shells on systems that
                      support it (see JOB CONTROL above).  Background
                      processes run in a separate process group and a line
                      containing their exit status is printed upon their
                      completion.
              -n      Read commands but do not execute them.  This may be used
                      to check a shell script for syntax errors.  This is
                      ignored for interactive shells.
              -o option-name
                      The option-name can be one of the following:
                      allexport
                              Same as -a.
                      braceexpand
                              The shell performs brace expansion (see Brace
                              Expansion above).  This is on by default.
                      emacs   Use an emacs-style command line editing
                              interface.  This is enabled by default when the
                              shell is interactive, unless the shell is
                              started with the -nolineediting option.
                      errexit Same as -e.
                      histexpand
                              Same as -H.
                      ignoreeof
                              The effect is as if the shell command
                              `IGNOREEOF=10' had been executed (see Shell
                              Variables above).
                      interactive-comments
                              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).
                      monitor Same as -m.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nohash  Same as -d.
                      notify  Same as -b.
                      nounset Same as -u.
                      physical
                              Same as -P.
                      posix   Change the behavior of bash where the default
                              operation differs from the Posix 1003.2 standard
                              to match the standard.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      vi      Use a vi-style command line editing interface.
                      xtrace  Same as -x.
                      If no option-name is supplied, the values of the current
                      options are printed.
              -p      Turn on privileged mode.  In this mode, the $ENV file is
                      not processed, and shell functions are not inherited
                      from the environment.  This is enabled automatically on
                      startup if the effective user (group) id is not equal to
                      the real user (group) id.  Turning this option off
                      causes the effective user and group ids to be set to the
                      real user and group ids.
              -t      Exit after reading and executing one command.
              -u      Treat unset variables as an error when performing
                      parameter expansion.  If expansion is attempted on an
                      unset variable, the shell prints an error message, and,
                      if not interactive, exits with a non-zero status.
              -v      Print shell input lines as they are read.
              -x      After expanding each simple-command, bash displays the
                      expanded value of PS4, followed by the command and its
                      expanded arguments.
              -l      Save and restore the binding of name in a for name [in
                      word] command (see SHELL GRAMMAR above).
              -d      Disable the hashing of commands that are looked up for
                      execution.  Normally, commands are remembered in a hash
                      table, and once found, do not have to be looked up
                      again.
              -C      The effect is as if the shell command `noclobber=' had
                      been executed (see Shell Variables above).
              -H      Enable !  style history substitution.  This flag is on
                      by default when the shell is interactive.
              -P      If set, do not follow symbolic links when performing
                      commands such as cd which change the current directory.
                      The physical directory is used instead.
              --      If no arguments follow this flag, then the positional
                      parameters are unset.  Otherwise, the positional
                      parameters are set to the args, even if some of them
                      begin with a -.
              -       Signal the end of options, cause all remaining args to
                      be assigned to the positional parameters.  The -x and -v
                      options are turned off.  If there are no args, the
                      positional parameters remain unchanged.

              The flags are off by default unless otherwise noted.  Using +
              rather than - causes these flags to be turned off.  The flags
              can also be specified as options to an invocation of the shell.
              The current set of flags may be found in $-.  After the option
              arguments are processed, the remaining n args are treated as
              values for the positional parameters and are assigned, in order,
              to $1, $2, ...  $n.  If no options or args are supplied, all
              shell variables are printed.  The return status is always true
              unless an illegal option is encountered.

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

       suspend [-f]
              Suspend the execution of this shell until it receives a SIGCONT
              signal.  The -f option says not to complain if this is a login
              shell; just suspend anyway.  The return status is 0 unless the
              shell is a login shell and -f is not supplied, or if job control
              is not enabled.

       test expr
       [ expr ]
              Return a status of 0 (true) or 1 (false) depending on the
              evaluation of the conditional expression expr.  Expressions may
              be unary or binary.  Unary expressions are often used to examine
              the status of a file.  There are string operators and numeric
              comparison operators as well.  Each operator and operand must be
              a separate argument.  If file is of the form /dev/fd/n, then
              file descriptor n is checked.
              -b file
                     True if file exists and is block special.
              -c file
                     True if file exists and is character special.
              -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.
              -k file
                     True if file has its ``sticky'' bit set.
              -L file
                     True if file exists and is a symbolic link.
              -p file
                     True if file exists and is a named pipe.
              -r file
                     True if file exists and is readable.
              -s file
                     True if file exists and has a size greater than zero.
              -S file
                     True if file exists and is a socket.
              -t fd  True if fd is opened on 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
                     True if file exists and is owned by the effective user
                     id.
              -G file
                     True if file exists and is owned by the effective group
                     id.
              file1 -nt file2
                     True if file1 is newer (according to modification date)
                     than file2.
              file1 -ot file2
                     True if file1 is older than file2.
              file1 -ef file
                     True if file1 and file2 have the same device and inode
                     numbers.
              -z string
                     True if the length of string is zero.
              -n string
              string True if the length of string is non-zero.
              string1 = string2
                     True if the strings are equal.
              string1 != string2
                     True if the strings are not equal.
              ! expr True if expr is false.
              expr1 -a expr2
                     True if both expr1 AND expr2 are true.
              expr1 -o expr2
                     True if either expr1 OR expr2 is true.
              arg1 OP arg2
                     OP is one of -eq, -ne, -lt, -le, -gt, or -ge.  These
                     arithmetic binary operators return true if arg1 is equal,
                     not-equal, less-than, less-than-or-equal, greater-than,
                     or greater-than-or-equal than arg2, respectively.  Arg1
                     and arg2 may be positive integers, negative integers, or
                     the special expression -l string, which evaluates to the
                     length of string.

       times  Print the accumulated user and system times for the shell and
              for processes run from the shell.  The return status is 0.

       trap [-l] [arg] [sigspec]
              The command arg is to be read and executed when the shell
              receives signal(s) sigspec.  If arg is absent or -, all
              specified signals are reset to their original values (the values
              they had upon entrance to the shell).  If arg is the null string
              this signal is ignored by the shell and by the commands it
              invokes.  sigspec is either a signal name defined in <signal.h>,
              or a signal number.  If sigspec is EXIT (0) the command arg is
              executed on exit from the shell.  With no arguments, trap prints
              the list of commands associated with each signal number.  The -l
              option causes the shell to print a list of signal names and
              their corresponding numbers.  An argument of -- disables option
              checking for the rest of the arguments.  Signals ignored upon
              entry to the shell cannot be trapped or reset.  Trapped signals
              are reset to their original values in a child process when it is
              created.  The return status is false if either the trap name or
              number is invalid; otherwise trap returns true.

       type [-all] [-type | -path] name [name ...]
              With no options, indicate how each name would be interpreted if
              used as a command name.  If the -type flag is used, type prints
              a phrase 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 -path flag is used, type either returns the
              name of the disk file that would be executed if name were
              specified as a command name, or nothing if -type would not
              return file.  If a command is hashed, -path prints the hashed
              value, not necessarily the file that appears first in PATH.  If
              the -all flag is used, type prints all of the places that
              contain an executable named name.  This includes aliases and
              functions, if and only if the -path flag is not also used.  The
              table of hashed commands is not consulted when using -all.  type
              accepts -a, -t, and -p in place of -all, -type, and -path,
              respectively.  An argument of -- disables option checking for
              the rest of the arguments.  type returns true if any of the
              arguments are found, false if none are found.

       ulimit [-SHacdfmstpnuv [limit]]
              Ulimit provides control over the resources available to the
              shell and to processes started by it, on systems that allow such
              control.  The value of limit can be a number in the unit
              specified for the resource, or the value unlimited.  The H and S
              options specify that the hard or soft limit is set for the given
              resource.  A hard limit cannot be increased once it is set; a
              soft limit may be increased up to the value of the hard limit.
              If neither H nor S is specified, the command applies to the soft
              limit.  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 is
              printed before the value.  Other options are interpreted as
              follows:
              -a     all current limits are reported
              -c     the maximum size of core files created
              -d     the maximum size of a process's data segment
              -f     the maximum size of files created by the shell
              -m     the maximum resident set size
              -s     the maximum stack size
              -t     the maximum amount of cpu time in seconds
              -p     the pipe size in 512-byte blocks (this may not be set)
              -n     the maximum number of open file descriptors (most systems
                     do not allow this value to be set, only displayed)
              -u     the maximum number of processes available to a single
                     user
              -v     The maximum amount of virtual memory available to the
                     shell

              An argument of -- disables option checking for the rest of the
              arguments.  If limit is given, it is the new value of the
              specified resource (the -a option is display only).  If no
              option is given, then -f is assumed.  Values are in 1024-byte
              increments, except for -t, which is in seconds, -p, which is in
              units of 512-byte blocks, and -n and -u, which are unscaled
              values.  The return status is 0 unless an illegal option is
              encountered, a non-numeric argument other than unlimited is
              supplied as limit, or an error occurs while setting a new limit.

       umask [-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, or if the -S option is supplied,
              the current value of the mask is printed.  The -S option causes
              the mask to be printed in symbolic form; the default output is
              an octal number.  An argument of -- disables option checking for
              the rest of the arguments.  The return status is 0 if the mode
              was successfully changed or if no mode argument was supplied,
              and false otherwise.

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

       unset [-fv] [name ...]
              For each name, remove the corresponding variable or, given the
              -f option, function.  An argument of -- disables option checking
              for the rest of the arguments.  Note that PATH, IFS, PPID, PS1,
              PS2, UID, and EUID cannot be unset.  If any of RANDOM, SECONDS,
              LINENO, or HISTCMD are unset, they lose their special
              properties, even if they are subsequently reset.  The exit
              status is true unless a name does not exist or is non-
              unsettable.

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

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

       An interactive shell is one whose standard input and output are both
       connected to terminals (as determined by isatty(3)), or one started
       with the -i option.  PS1 is set and $- includes i if bash is
       interactive, allowing a shell script or a startup file to test this
       state.

       Login shells:
         On login (subject to the -noprofile option):
               if /etc/profile exists, source it.

               if ~/.bash_profile exists, source it,
                 else if ~/.bash_login exists, source it,
                   else if ~/.profile exists, source it.

         On exit:
               if ~/.bash_logout exists, source it.

       Non-login interactive shells:
         On startup (subject to the -norc and -rcfile options):
               if ~/.bashrc exists, source it.

       Non-interactive shells:
         On startup:
               if the environment variable ENV is non-null, expand
               it and source the file it names, as if the command
                       if [ "$ENV" ]; then . $ENV; fi
               had been executed, but do not use PATH to search
               for the pathname.  When not started in Posix mode, bash
               looks for BASH_ENV before ENV.

       If Bash is invoked as sh, it tries to mimic the behavior of sh as
       closely as possible.  For a login shell, it attempts to source only
       /etc/profile and ~/.profile, in that order.  The -noprofile option may
       still be used to disable this behavior.  A shell invoked as sh does not
       attempt to source any other startup files.

       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,
       the ENV variable is expanded and that file sourced; no other startup
       files are read.

SEE ALSO
       Bash Features, Brian Fox and Chet Ramey
       The Gnu Readline Library, Brian Fox and Chet Ramey
       The Gnu History Library, Brian Fox and Chet Ramey
       A System V Compatible Implementation of 4.2BSD Job Control, David
       Lennert
       Portable Operating System Interface (POSIX) Part 2: Shell and
       Utilities, 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
       ~/.bash_profile
              The personal initialization file, executed for login shells
       ~/.bashrc
              The individual per-interactive-shell startup file
       ~/.inputrc
              Individual readline initialization file

AUTHORS
              Brian Fox, Free Software Foundation (primary author)
              bfox@ai.MIT.Edu

              Chet Ramey, Case Western Reserve University
              chet@ins.CWRU.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 that you have.

       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 welcome to
       mail that as well!  Suggestions and `philosophical' bug reports may be
       mailed to bug-bash@prep.ai.MIT.Edu or posted to the Usenet newsgroup
       gnu.bash.bug.

       ALL bug reports should include:

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

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

       Comments and bug reports concerning this manual page should be directed
       to chet@ins.CWRU.Edu.

BUGS
       It's too big and too slow.

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

       Aliases are confusing in some uses.



GNU                               1995 May 5                           BASH(1)