sh

     dash [-aCefnuvxIimqVEb] [+aCefnuvxIimqVEb] [-o option_name]
          [+o option_name] [command_file [argument ...]]
     dash -c [-aCefnuvxIimqVEb] [+aCefnuvxIimqVEb] [-o option_name]
          [+o option_name] command_string [command_name [argument ...]]
     dash -s [-aCefnuvxIimqVEb] [+aCefnuvxIimqVEb] [-o option_name]
          [+o option_name] [argument ...]

DESCRIPTION
     dash is the standard command interpreter for the system.  The current
     version of dash is in the process of being changed to conform with the
     POSIX 1003.2 and 1003.2a specifications for the shell.  This version has
     many features which make it appear similar in some respects to the Korn
     shell, but it is not a Korn shell clone (see ksh(1)).  Only features des-
     ignated by POSIX, plus a few Berkeley extensions, are being incorporated
     into this shell.  This man page is not intended to be a tutorial or a
     complete specification of the shell.

   Overview
     The shell is a command that reads lines from either a file or the termi-
     nal, interprets them, and generally executes other commands.  It is the
     program that is running when a user logs into the system (although a user
     can select a different shell with the chsh(1) command).  The shell imple-
     ments a language that has flow control constructs, a macro facility that
     provides a variety of features in addition to data storage, along with
     built in history and line editing capabilities.  It incorporates many
     features to aid interactive use and has the advantage that the interpre-
     tative language is common to both interactive and non-interactive use
     (shell scripts).  That is, commands can be typed directly to the running
     shell or can be put into a file and the file can be executed directly by
     the shell.

   Invocation
     If no args are present and if the standard input of the shell is con-
     nected to a terminal (or if the -i flag is set), and the -c option is not
     present, the shell is considered an interactive shell.  An interactive
     shell generally prompts before each command and handles programming and
     command errors differently (as described below).  When first starting,
     the shell inspects argument 0, and if it begins with a dash '-', the
     shell is also considered a login shell.  This is normally done automati-
     cally by the system when the user first logs in.  A login shell first
     reads commands from the files /etc/profile and .profile if they exist.
     If the environment variable ENV is set on entry to an interactive shell,
     or is set in the .profile of a login shell, the shell next reads commands
     from the file named in ENV.  Therefore, a user should place commands that
     are to be executed only at login time in the .profile file, and commands
     that are executed for every interactive shell inside the ENV file.  To
     set the ENV variable to some file, place the following line in your
     .profile of your home directory

           ENV=$HOME/.shinit; export ENV

     substituting for ``.shinit'' any filename you wish.

     If command line arguments besides the options have been specified, then

           -a allexport     Export all variables assigned to.

           -c               Read commands from the command_string operand
                            instead of from the standard input.  Special
                            parameter 0 will be set from the command_name op-
                            erand and the positional parameters ($1, $2, etc.)
                            set from the remaining argument operands.

           -C noclobber     Don't overwrite existing files with ``>''.

           -e errexit       If not interactive, exit immediately if any
                            untested command fails.  The exit status of a com-
                            mand is considered to be explicitly tested if the
                            command is used to control an if, elif, while, or
                            until; or if the command is the left hand operand
                            of an ``&&'' or ``||'' operator.

           -f noglob        Disable pathname expansion.

           -n noexec        If not interactive, read commands but do not exe-
                            cute them.  This is useful for checking the syntax
                            of shell scripts.

           -u nounset       Write a message to standard error when attempting
                            to expand a variable that is not set, and if the
                            shell is not interactive, exit immediately.

           -v verbose       The shell writes its input to standard error as it
                            is read.  Useful for debugging.

           -x xtrace        Write each command to standard error (preceded by
                            a '+ ') before it is executed.  Useful for debug-
                            ging.

           -I ignoreeof     Ignore EOF's from input when interactive.

           -i interactive   Force the shell to behave interactively.

           -l               Make dash act as if it had been invoked as a login
                            shell.

           -m monitor       Turn on job control (set automatically when inter-
                            active).

           -s stdin         Read commands from standard input (set automati-
                            cally if no file arguments are present).  This
                            option has no effect when set after the shell has
                            already started running (i.e. with set).

           -V vi            Enable the built-in vi(1) command line editor
                            (disables -E if it has been set).

           -E emacs         Enable the built-in emacs(1) command line editor
           Control operators:
                 & && ( ) ; ;; | || <newline>

           Redirection operators:
                 < > >| << >> <& >& <<- <>

   Quoting
     Quoting is used to remove the special meaning of certain characters or
     words to the shell, such as operators, whitespace, or keywords.  There
     are three types of quoting: matched single quotes, matched double quotes,
     and backslash.

   Backslash
     A backslash preserves the literal meaning of the following character,
     with the exception of <newline>.  A backslash preceding a <newline> is
     treated as a line continuation.

   Single Quotes
     Enclosing characters in single quotes preserves the literal meaning of
     all the characters (except single quotes, making it impossible to put
     single-quotes in a single-quoted string).

   Double Quotes
     Enclosing characters within double quotes preserves the literal meaning
     of all characters except dollarsign ($), backquote (`), and backslash
     (\).  The backslash inside double quotes is historically weird, and
     serves to quote only the following characters:
           $ ` " \ <newline>.
     Otherwise it remains literal.

   Reserved Words
     Reserved words are words that have special meaning to the shell and are
     recognized at the beginning of a line and after a control operator.  The
     following are reserved words:

           !       elif    fi      while   case
           else    for     then    {       }
           do      done    until   if      esac

     Their meaning is discussed later.

   Aliases
     An alias is a name and corresponding value set using the alias(1) builtin
     command.  Whenever a reserved word may occur (see above), and after
     checking for reserved words, the shell checks the word to see if it
     matches an alias.  If it does, it replaces it in the input stream with
     its value.  For example, if there is an alias called ``lf'' with the
     value ``ls -F'', then the input:

           lf foobar <return>

     would become

           ls -F foobar <return>

     Otherwise, a complex command or some other special construct may have
     been recognized.

   Simple Commands
     If a simple command has been recognized, the shell performs the following
     actions:

           1.   Leading words of the form ``name=value'' are stripped off and
                assigned to the environment of the simple command.  Redirect-
                ion operators and their arguments (as described below) are
                stripped off and saved for processing.

           2.   The remaining words are expanded as described in the section
                called ``Expansions'', and the first remaining word is consid-
                ered the command name and the command is located.  The remain-
                ing words are considered the arguments of the command.  If no
                command name resulted, then the ``name=value'' variable
                assignments recognized in item 1 affect the current shell.

           3.   Redirections are performed as described in the next section.

   Redirections
     Redirections are used to change where a command reads its input or sends
     its output.  In general, redirections open, close, or duplicate an exist-
     ing reference to a file.  The overall format used for redirection is:

           [n] redir-op file

     where redir-op is one of the redirection operators mentioned previously.
     Following is a list of the possible redirections.  The [n] is an optional
     number, as in '3' (not '[3]'), that refers to a file descriptor.

           [n]> file   Redirect standard output (or n) to file.

           [n]>| file  Same, but override the -C option.

           [n]>> file  Append standard output (or n) to file.

           [n]< file   Redirect standard input (or n) from file.

           [n1]<&n2    Duplicate standard input (or n1) from file descriptor
                       n2.

           [n]<&-      Close standard input (or n).

           [n1]>&n2    Duplicate standard output (or n1) to n2.

           [n]>&-      Close standard output (or n).

           [n]<> file  Open file for reading and writing on standard input (or
                       n).

     The following redirection is often called a ``here-document''.


   Search and Execution
     There are three types of commands: shell functions, builtin commands, and
     normal programs -- and the command is searched for (by name) in that
     order.  They each are executed in a different way.

     When a shell function is executed, all of the shell positional parameters
     (except $0, which remains unchanged) are set to the arguments of the
     shell function.  The variables which are explicitly placed in the envi-
     ronment of the command (by placing assignments to them before the func-
     tion name) are made local to the function and are set to the values
     given.  Then the command given in the function definition is executed.
     The positional parameters are restored to their original values when the
     command completes.  This all occurs within the current shell.

     Shell builtins are executed internally to the shell, without spawning a
     new process.

     Otherwise, if the command name doesn't match a function or builtin, the
     command is searched for as a normal program in the file system (as
     described in the next section).  When a normal program is executed, the
     shell runs the program, passing the arguments and the environment to the
     program.  If the program is not a normal executable file (i.e., if it
     does not begin with the "magic number" whose ASCII representation is
     "#!", so execve(2) returns ENOEXEC then) the shell will interpret the
     program in a subshell.  The child shell will reinitialize itself in this
     case, so that the effect will be as if a new shell had been invoked to
     handle the ad-hoc shell script, except that the location of hashed com-
     mands located in the parent shell will be remembered by the child.

     Note that previous versions of this document and the source code itself
     misleadingly and sporadically refer to a shell script without a magic
     number as a "shell procedure".

   Path Search
     When locating a command, the shell first looks to see if it has a shell
     function by that name.  Then it looks for a builtin command by that name.
     If a builtin command is not found, one of two things happen:

     1.   Command names containing a slash are simply executed without per-
          forming any searches.

     2.   The shell searches each entry in PATH in turn for the command.  The
          value of the PATH variable should be a series of entries separated
          by colons.  Each entry consists of a directory name.  The current
          directory may be indicated implicitly by an empty directory name, or
          explicitly by a single period.

   Command Exit Status
     Each command has an exit status that can influence the behaviour of other
     shell commands.  The paradigm is that a command exits with zero for nor-
     mal or success, and non-zero for failure, error, or a false indication.
     The man page for each command should indicate the various exit codes and
     what they mean.  Additionally, the builtin commands return exit codes, as

     o   pipeline

     o   list or compound-list

     o   compound command

     o   function definition

     Unless otherwise stated, the exit status of a command is that of the last
     simple command executed by the command.

   Pipelines
     A pipeline is a sequence of one or more commands separated by the control
     operator |.  The standard output of all but the last command is connected
     to the standard input of the next command.  The standard output of the
     last command is inherited from the shell, as usual.

     The format for a pipeline is:

           [!] command1 [| command2 ...]

     The standard output of command1 is connected to the standard input of
     command2.  The standard input, standard output, or both of a command is
     considered to be assigned by the pipeline before any redirection speci-
     fied by redirection operators that are part of the command.

     If the pipeline is not in the background (discussed later), the shell
     waits for all commands to complete.

     If the reserved word ! does not precede the pipeline, the exit status is
     the exit status of the last command specified in the pipeline.  Other-
     wise, the exit status is the logical NOT of the exit status of the last
     command.  That is, if the last command returns zero, the exit status is
     1; if the last command returns greater than zero, the exit status is
     zero.

     Because pipeline assignment of standard input or standard output or both
     takes place before redirection, it can be modified by redirection.  For
     example:

           $ command1 2>&1 | command2

     sends both the standard output and standard error of command1 to the
     standard input of command2.

     A ; or <newline> terminator causes the preceding AND-OR-list (described
     next) to be executed sequentially; a & causes asynchronous execution of
     the preceding AND-OR-list.

     Note that unlike some other shells, each process in the pipeline is a
     child of the invoking shell (unless it is a shell builtin, in which case
     it executes in the current shell -- but any effect it has on the environ-
     ment is wiped).

   Lists -- Generally Speaking
     A list is a sequence of zero or more commands separated by newlines,
     semicolons, or ampersands, and optionally terminated by one of these
     three characters.  The commands in a list are executed in the order they
     are written.  If command is followed by an ampersand, the shell starts
     the command and immediately proceed onto the next command; otherwise it
     waits for the command to terminate before proceeding to the next one.

   Short-Circuit List Operators
     ``&&'' and ``||'' are AND-OR list operators.  ``&&'' executes the first
     command, and then executes the second command iff the exit status of the
     first command is zero.  ``||'' is similar, but executes the second com-
     mand iff the exit status of the first command is nonzero.  ``&&'' and
     ``||'' both have the same priority.

   Flow-Control Constructs -- if, while, for, case
     The syntax of the if command is

           if list
           then list
           [ elif list
           then    list ] ...
           [ else list ]
           fi

     The syntax of the while command is

           while list
           do   list
           done

     The two lists are executed repeatedly while the exit status of the first
     list is zero.  The until command is similar, but has the word until in
     place of while, which causes it to repeat until the exit status of the
     first list is zero.

     The syntax of the for command is

           for variable [ in [ word ... ] ]
           do   list
           done

     The words following in are expanded, and then the list is executed
     repeatedly with the variable set to each word in turn.  Omitting in word
     ... is equivalent to in "$@".

     The syntax of the break and continue command is

           break [ num ]
           continue [ num ]

     Break terminates the num innermost for or while loops.  Continue contin-
     ues with the next iteration of the innermost loop.  These are implemented

   Grouping Commands Together
     Commands may be grouped by writing either

           (list)

     or

           { list; }

     The first of these executes the commands in a subshell.  Builtin commands
     grouped into a (list) will not affect the current shell.  The second form
     does not fork another shell so is slightly more efficient.  Grouping com-
     mands together this way allows you to redirect their output as though
     they were one program:

           { printf " hello " ; printf " world\n" ; } > greeting

     Note that ``}'' must follow a control operator (here, ``;'') so that it
     is recognized as a reserved word and not as another command argument.

   Functions
     The syntax of a function definition is

           name () command

     A function definition is an executable statement; when executed it
     installs a function named name and returns an exit status of zero.  The
     command is normally a list enclosed between ``{'' and ``}''.

     Variables may be declared to be local to a function by using a local com-
     mand.  This should appear as the first statement of a function, and the
     syntax is

           local [variable | -] ...

     Local is implemented as a builtin command.

     When a variable is made local, it inherits the initial value and exported
     and readonly flags from the variable with the same name in the surround-
     ing scope, if there is one.  Otherwise, the variable is initially unset.
     The shell uses dynamic scoping, so that if you make the variable x local
     to function f, which then calls function g, references to the variable x
     made inside g will refer to the variable x declared inside f, not to the
     global variable named x.

     The only special parameter that can be made local is ``-''.  Making ``-''
     local any shell options that are changed via the set command inside the
     function to be restored to their original values when the function
     returns.

     The syntax of the return command is

           return [exitstatus]

     ics, numerics, and underscores - the first of which must not be numeric.
     A parameter can also be denoted by a number or a special character as
     explained below.

   Positional Parameters
     A positional parameter is a parameter denoted by a number (n > 0).  The
     shell sets these initially to the values of its command line arguments
     that follow the name of the shell script.  The set builtin can also be
     used to set or reset them.

   Special Parameters
     A special parameter is a parameter denoted by one of the following spe-
     cial characters.  The value of the parameter is listed next to its char-
     acter.

     *            Expands to the positional parameters, starting from one.
                  When the expansion occurs within a double-quoted string it
                  expands to a single field with the value of each parameter
                  separated by the first character of the IFS variable, or by
                  a <space> if IFS is unset.

     @            Expands to the positional parameters, starting from one.
                  When the expansion occurs within double-quotes, each posi-
                  tional parameter expands as a separate argument.  If there
                  are no positional parameters, the expansion of @ generates
                  zero arguments, even when @ is double-quoted.  What this
                  basically means, for example, is if $1 is ``abc'' and $2 is
                  ``def ghi'', then "$@" expands to the two arguments:

                        "abc" "def ghi"

     #            Expands to the number of positional parameters.

     ?            Expands to the exit status of the most recent pipeline.

     - (Hyphen.)  Expands to the current option flags (the single-letter
                  option names concatenated into a string) as specified on
                  invocation, by the set builtin command, or implicitly by the
                  shell.

     $            Expands to the process ID of the invoked shell.  A subshell
                  retains the same value of $ as its parent.

     !            Expands to the process ID of the most recent background com-
                  mand executed from the current shell.  For a pipeline, the
                  process ID is that of the last command in the pipeline.

     0 (Zero.)    Expands to the name of the shell or shell script.

   Word Expansions
     This clause describes the various expansions that are performed on words.
     Not all expansions are performed on every word, as explained later.

     Tilde expansions, parameter expansions, command substitutions, arithmetic
          the IFS variable is null.

     3.   Pathname Expansion (unless set -f is in effect).

     4.   Quote Removal.

     The $ character is used to introduce parameter expansion, command substi-
     tution, or arithmetic evaluation.

   Tilde Expansion (substituting a user's home directory)
     A word beginning with an unquoted tilde character (~) is subjected to
     tilde expansion.  All the characters up to a slash (/) or the end of the
     word are treated as a username and are replaced with the user's home
     directory.  If the username is missing (as in ~/foobar), the tilde is
     replaced with the value of the HOME variable (the current user's home
     directory).

   Parameter Expansion
     The format for parameter expansion is as follows:

           ${expression}

     where expression consists of all characters until the matching ``}''.
     Any ``}'' escaped by a backslash or within a quoted string, and charac-
     ters in embedded arithmetic expansions, command substitutions, and vari-
     able expansions, are not examined in determining the matching ``}''.

     The simplest form for parameter expansion is:

           ${parameter}

     The value, if any, of parameter is substituted.

     The parameter name or symbol can be enclosed in braces, which are
     optional except for positional parameters with more than one digit or
     when parameter is followed by a character that could be interpreted as
     part of the name.  If a parameter expansion occurs inside double-quotes:

     1.   Pathname expansion is not performed on the results of the expansion.

     2.   Field splitting is not performed on the results of the expansion,
          with the exception of @.

     In addition, a parameter expansion can be modified by using one of the
     following formats.

     ${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 parame-
                           ter.  In all cases, the final value of parameter is
                           substituted.  Only variables, not positional param-
                           null, null is substituted; otherwise, the expansion
                           of word is substituted.

     In the parameter expansions shown previously, use of the colon in the
     format results in a test for a parameter that is unset or null; omission
     of the colon results in a test for a parameter that is only unset.

     ${#parameter}         String Length.  The length in characters of the
                           value of parameter.

     The following four varieties of parameter expansion provide for substring
     processing.  In each case, pattern matching notation (see Shell
     Patterns), rather than regular expression notation, is used to evaluate
     the patterns.  If parameter is * or @, the result of the expansion is
     unspecified.  Enclosing the full parameter expansion string in double-
     quotes does not cause the following four varieties of pattern characters
     to be quoted, whereas quoting characters within the braces has this
     effect.

     ${parameter%word}     Remove Smallest Suffix Pattern.  The word is
                           expanded to produce a pattern.  The parameter
                           expansion then results in parameter, with the
                           smallest portion of the suffix matched by the pat-
                           tern deleted.

     ${parameter%%word}    Remove Largest Suffix Pattern.  The word is
                           expanded to produce a pattern.  The parameter
                           expansion then results in parameter, with the
                           largest portion of the suffix matched by the pat-
                           tern deleted.

     ${parameter#word}     Remove Smallest Prefix Pattern.  The word is
                           expanded to produce a pattern.  The parameter
                           expansion then results in parameter, with the
                           smallest portion of the prefix matched by the pat-
                           tern deleted.

     ${parameter##word}    Remove Largest Prefix Pattern.  The word is
                           expanded to produce a pattern.  The parameter
                           expansion then results in parameter, with the
                           largest portion of the prefix matched by the pat-
                           tern deleted.

   Command Substitution
     Command substitution allows the output of a command to be substituted in
     place of the command name itself.  Command substitution occurs when the
     command is enclosed as follows:

           $(command)

     or (``backquoted'' version):

           `command`


           $((expression))

     The expression is treated as if it were in double-quotes, except that a
     double-quote inside the expression is not treated specially.  The shell
     expands all tokens in the expression for parameter expansion, command
     substitution, and quote removal.

     Next, the shell treats this as an arithmetic expression and substitutes
     the value of the expression.

   White Space Splitting (Field Splitting)
     After parameter expansion, command substitution, and arithmetic expansion
     the shell scans the results of expansions and substitutions that did not
     occur in double-quotes for field splitting and multiple fields can
     result.

     The shell treats each character of the IFS as a delimiter and uses the
     delimiters to split the results of parameter expansion and command sub-
     stitution into fields.

   Pathname Expansion (File Name Generation)
     Unless the -f flag is set, file name generation is performed after word
     splitting is complete.  Each word is viewed as a series of patterns, sep-
     arated by slashes.  The process of expansion replaces the word with the
     names of all existing files whose names can be formed by replacing each
     pattern with a string that matches the specified pattern.  There are two
     restrictions on this: first, a pattern cannot match a string containing a
     slash, and second, a pattern cannot match a string starting with a period
     unless the first character of the pattern is a period.  The next section
     describes the patterns used for both Pathname Expansion and the case com-
     mand.

   Shell Patterns
     A pattern consists of normal characters, which match themselves, and
     meta-characters.  The meta-characters are ``!'', ``*'', ``?'', and ``[''.
     These characters lose their special meanings if they are quoted.  When
     command or variable substitution is performed and the dollar sign or back
     quotes are not double quoted, the value of the variable or the output of
     the command is scanned for these characters and they are turned into
     meta-characters.

     An asterisk (``*'') matches any string of characters.  A question mark
     matches any single character.  A left bracket (``['') introduces a char-
     acter class.  The end of the character class is indicated by a (``]'');
     if the ``]'' is missing then the ``['' matches a ``['' rather than intro-
     ducing a character class.  A character class matches any of the charac-
     ters between the square brackets.  A range of characters may be specified
     using a minus sign.  The character class may be complemented by making an
     exclamation point the first character of the character class.

     To include a ``]'' in a character class, make it the first character
     listed (after the ``!'', if any).  To include a minus sign, make it the
     first or last character listed.
            The commands in the specified file are read and executed by the
            shell.

     alias [name[=string ...]]
            If name=string is specified, the shell defines the alias name with
            value string.  If just name is specified, the value of the alias
            name is printed.  With no arguments, the alias builtin prints the
            names and values of all defined aliases (see unalias).

     bg [job] ...
            Continue the specified jobs (or the current job if no jobs are
            given) in the background.

     command [-p] [-v] [-V] command [arg ...]
            Execute the specified command but ignore shell functions when
            searching for it.  (This is useful when you have a shell function
            with the same name as a builtin command.)

            -p     search for command using a PATH that guarantees to find all
                   the standard utilities.

            -V     Do not execute the command but search for the command and
                   print the resolution of the command search.  This is the
                   same as the type builtin.

            -v     Do not execute the command but search for the command and
                   print the absolute pathname of utilities, the name for
                   builtins or the expansion of aliases.

     cd -

     cd [-LP] [directory]
            Switch to the specified directory (default HOME).  If an entry for
            CDPATH appears in the environment of the cd command or the shell
            variable CDPATH is set and the directory name does not begin with
            a slash, then the directories listed in CDPATH will be searched
            for the specified directory.  The format of CDPATH is the same as
            that of PATH.  If a single dash is specified as the argument, it
            will be replaced by the value of OLDPWD.  The cd command will
            print out the name of the directory that it actually switched to
            if this is different from the name that the user gave.  These may
            be different either because the CDPATH mechanism was used or
            because the argument is a single dash.  The -P option causes the
            physical directory structure to be used, that is, all symbolic
            links are resolved to their respective values.  The -L option
            turns off the effect of any preceding -P options.

     echo [-n] args...
            Print the arguments on the standard output, separated by spaces.
            Unless the -n option is present, a newline is output following the
            arguments.

            If any of the following sequences of characters is encountered
            during output, the sequence is not output.  Instead, the specified
            \r      Output a carriage return.

            \t      Output a (horizontal) tab character.

            \v      Output a vertical tab.

            \0digits
                    Output the character whose value is given by zero to three
                    octal digits.  If there are zero digits, a nul character
                    is output.

            \\      Output a backslash.

            All other backslash sequences elicit undefined behaviour.

     eval string ...
            Concatenate all the arguments with spaces.  Then re-parse and exe-
            cute the command.

     exec [command arg ...]
            Unless command is omitted, the shell process is replaced with the
            specified program (which must be a real program, not a shell
            builtin or function).  Any redirections on the exec command are
            marked as permanent, so that they are not undone when the exec
            command finishes.

     exit [exitstatus]
            Terminate the shell process.  If exitstatus is given it is used as
            the exit status of the shell; otherwise the exit status of the
            preceding command is used.

     export name ...

     export -p
            The specified names are exported so that they will appear in the
            environment of subsequent commands.  The only way to un-export a
            variable is to unset it.  The shell allows the value of a variable
            to be set at the same time it is exported by writing

                  export name=value

            With no arguments the export command lists the names of all
            exported variables.  With the -p option specified the output will
            be formatted suitably for non-interactive use.

     fc [-e editor] [first [last]]

     fc -l [-nr] [first [last]]

     fc -s [old=new] [first]
            The fc builtin lists, or edits and re-executes, commands previ-
            ously entered to an interactive shell.

            -e editor

            -n     Suppress command numbers when listing with -l.

            -r     Reverse the order of the commands listed (with -l) or
                   edited (with neither -l nor -s).

            -s     Re-execute the command without invoking an editor.

            first

            last   Select the commands to list or edit.  The number of previ-
                   ous commands that can be accessed are determined by the
                   value of the HISTSIZE variable.  The value of first or last
                   or both are one of the following:

                   [+]number
                          A positive number representing a command number;
                          command numbers can be displayed with the -l option.

                   -number
                          A negative decimal number representing the command
                          that was executed number of commands previously.
                          For example, -1 is the immediately previous command.

            string
                   A string indicating the most recently entered command that
                   begins with that string.  If the old=new operand is not
                   also specified with -s, the string form of the first oper-
                   and cannot contain an embedded equal sign.

            The following environment variables affect the execution of fc:

            FCEDIT    Name of the editor to use.

            HISTSIZE  The number of previous commands that are accessible.

     fg [job]
            Move the specified job or the current job to the foreground.

     getopts optstring var
            The POSIX getopts command, not to be confused with the Bell Labs
            -derived getopt(1).

            The first argument should be a series of letters, each of which
            may be optionally followed by a colon to indicate that the option
            requires an argument.  The variable specified is set to the parsed
            option.

            The getopts command deprecates the older getopt(1) utility due to
            its handling of arguments containing whitespace.

            The getopts builtin may be used to obtain options and their argu-
            ments from a list of parameters.  When invoked, getopts places the
            value of the next option from the option string in the list in the
            specifying a colon as the first character of optstring all errors
            will be ignored.

            A nonzero value is returned when the last option is reached.  If
            there are no remaining arguments, getopts will set var to the spe-
            cial option, ``--'', otherwise, it will set var to ``?''.

            The following code fragment shows how one might process the argu-
            ments for a command that can take the options [a] and [b], and the
            option [c], which requires an argument.

                  while getopts abc: f
                  do
                          case $f in
                          a | b)  flag=$f;;
                          c)      carg=$OPTARG;;
                          \?)     echo $USAGE; exit 1;;
                          esac
                  done
                  shift `expr $OPTIND - 1`

            This code will accept any of the following as equivalent:

                  cmd -acarg file file
                  cmd -a -c arg file file
                  cmd -carg -a file file
                  cmd -a -carg -- file file

     hash -rv command ...
            The shell maintains a hash table which remembers the locations of
            commands.  With no arguments whatsoever, the hash command prints
            out the contents of this table.  Entries which have not been
            looked at since the last cd command are marked with an asterisk;
            it is possible for these entries to be invalid.

            With arguments, the hash command removes the specified commands
            from the hash table (unless they are functions) and then locates
            them.  With the -v option, hash prints the locations of the com-
            mands as it finds them.  The -r option causes the hash command to
            delete all the entries in the hash table except for functions.

     pwd [-LP]
            builtin command remembers what the current directory is rather
            than recomputing it each time.  This makes it faster.  However, if
            the current directory is renamed, the builtin version of pwd will
            continue to print the old name for the directory.  The -P option
            causes the physical value of the current working directory to be
            shown, that is, all symbolic links are resolved to their respec-
            tive values.  The -L option turns off the effect of any preceding
            -P options.

     read [-p prompt] [-r] variable [...]
            The prompt is printed if the -p option is specified and the stan-
            dard input is a terminal.  Then a line is read from the standard
            treated literally.  If a backslash is followed by a newline, the
            backslash and the newline will be deleted.

     readonly name ...

     readonly -p
            The specified names are marked as read only, so that they cannot
            be subsequently modified or unset.  The shell allows the value of
            a variable to be set at the same time it is marked read only by
            writing

                  readonly name=value

            With no arguments the readonly command lists the names of all read
            only variables.  With the -p option specified the output will be
            formatted suitably for non-interactive use.

     printf format [arguments ...]
            printf formats and prints its arguments, after the first, under
            control of the format.  The format is a character string which
            contains three types of objects: plain characters, which are sim-
            ply copied to standard output, character escape sequences which
            are converted and copied to the standard output, and format speci-
            fications, each of which causes printing of the next successive
            argument.

            The arguments after the first are treated as strings if the corre-
            sponding format is either b, c or s; otherwise it is evaluated as
            a C constant, with the following extensions:

                  o   A leading plus or minus sign is allowed.
                  o   If the leading character is a single or double quote,
                      the value is the ASCII code of the next character.

            The format string is reused as often as necessary to satisfy the
            arguments.  Any extra format specifications are evaluated with
            zero or the null string.

            Character escape sequences are in backslash notation as defined in
            ANSI X3.159-1989 (``ANSI C89'').  The characters and their mean-
            ings are as follows:

                  \a      Write a <bell> character.

                  \b      Write a <backspace> character.

                  \f      Write a <form-feed> character.

                  \n      Write a <new-line> character.

                  \r      Write a <carriage return> character.

                  \t      Write a <tab> character.


                    #       A `#' character specifying that the value should
                            be printed in an ``alternative form''.  For b, c,
                            d, and s formats, this option has no effect.  For
                            the o format the precision of the number is
                            increased to force the first character of the out-
                            put string to a zero.  For the x (X) format, a
                            non-zero result has the string 0x (0X) prepended
                            to it.  For e, E, f, g, and G formats, the result
                            will always contain a decimal point, even if no
                            digits follow the point (normally, a decimal point
                            only appears in the results of those formats if a
                            digit follows the decimal point).  For g and G
                            formats, trailing zeros are not removed from the
                            result as they would otherwise be.

                    -       A minus sign `-' which specifies left adjustment
                            of the output in the indicated field;

                    +       A `+' character specifying that there should
                            always be a sign placed before the number when
                            using signed formats.

                    ' '     A space specifying that a blank should be left
                            before a positive number for a signed format.  A
                            `+' overrides a space if both are used;

                    0       A zero `0' character indicating that zero-padding
                            should be used rather than blank-padding.  A `-'
                            overrides a `0' if both are used;

            Field Width:
                    An optional digit string specifying a field width; if the
                    output string has fewer characters than the field width it
                    will be blank-padded on the left (or right, if the left-
                    adjustment indicator has been given) to make up the field
                    width (note that a leading zero is a flag, but an embedded
                    zero is part of a field width);

            Precision:
                    An optional period, '.', followed by an optional digit
                    string giving a precision which specifies the number of
                    digits to appear after the decimal point, for e and f for-
                    mats, or the maximum number of characters to be printed
                    from a string (b and s formats); if the digit string is
                    missing, the precision is treated as zero;

            Format:
                    A character which indicates the type of format to use (one
                    of diouxXfwEgGbcs).

            A field width or precision may be '*' instead of a digit string.
            In this case an argument supplies the field width or precision.


            eE          The argument is printed in the style [-]d.ddde+-dd
                        where there is one digit before the decimal point and
                        the number after is equal to the precision specifica-
                        tion for the argument; when the precision is missing,
                        6 digits are produced.  An upper-case E is used for an
                        `E' format.

            gG          The argument is printed in style f or in style e (E)
                        whichever gives full precision in minimum space.

            b           Characters from the string argument are printed with
                        backslash-escape sequences expanded.
                        The following additional backslash-escape sequences
                        are supported:

                        \c      Causes dash to ignore any remaining characters
                                in the string operand containing it, any
                                remaining string operands, and any additional
                                characters in the format operand.

                        \0num   Write an 8-bit character whose ASCII value is
                                the 1-, 2-, or 3-digit octal number num.

            c           The first character of argument is printed.

            s           Characters from the string argument are printed until
                        the end is reached or until the number of characters
                        indicated by the precision specification is reached;
                        if the precision is omitted, all characters in the
                        string are printed.

            %           Print a `%'; no argument is used.

            In no case does a non-existent or small field width cause trunca-
            tion of a field; padding takes place only if the specified field
            width exceeds the actual width.

     set [{ -options | +options | -- }] arg ...
            The set command performs three different functions.

            With no arguments, it lists the values of all shell variables.

            If options are given, it sets the specified option flags, or
            clears them as described in the section called Argument List
            Processing.  As a special case, if the option is -o or +o and no
            argument is supplied, the shell prints the settings of all its
            options.  If the option is -o, the settings are printed in a
            human-readable format; if the option is +o, the settings are
            printed in a format suitable for reinput to the shell to affect
            the same option settings.

            The third use of the set command is to set the values of the
            shell's positional parameters to the specified args.  To change

     test expression

     [ expression ]
            The test utility evaluates the expression and, if it evaluates to
            true, returns a zero (true) exit status; otherwise it returns 1
            (false).  If there is no expression, test also returns 1 (false).

            All operators and flags are separate arguments to the test util-
            ity.

            The following primaries are used to construct expression:

            -b file       True if file exists and is a block special file.

            -c file       True if file exists and is a character special file.

            -d file       True if file exists and is a directory.

            -e file       True if file exists (regardless of type).

            -f file       True if file exists and is a regular file.

            -g file       True if file exists and its set group ID flag is
                          set.

            -h file       True if file exists and is a symbolic link.

            -k file       True if file exists and its sticky bit is set.

            -n string     True if the length of string is nonzero.

            -p file       True if file is a named pipe (FIFO).

            -r file       True if file exists and is readable.

            -s file       True if file exists and has a size greater than
                          zero.

            -t file_descriptor
                          True if the file whose file descriptor number is
                          file_descriptor is open and is associated with a
                          terminal.

            -u file       True if file exists and its set user ID flag is set.

            -w file       True if file exists and is writable.  True indicates
                          only that the write flag is on.  The file is not
                          writable on a read-only file system even if this
                          test indicates true.

            -x file       True if file exists and is executable.  True indi-
                          cates only that the execute flag is on.  If file is
                          a directory, true indicates that file can be
                          searched.
                          tive group id of this process.

            -S file       True if file exists and is a socket.

            file1 -nt file2
                          True if file1 and file2 exist and file1 is newer
                          than file2.

            file1 -ot file2
                          True if file1 and file2 exist and file1 is older
                          than file2.

            file1 -ef file2
                          True if file1 and file2 exist and refer to the same
                          file.

            string        True if string is not the null string.

            s1 = s2       True if the strings s1 and s2 are identical.

            s1 != s2      True if the strings s1 and s2 are not identical.

            s1 < s2       True if string s1 comes before s2 based on the ASCII
                          value of their characters.

            s1 > s2       True if string s1 comes after s2 based on the ASCII
                          value of their characters.

            n1 -eq n2     True if the integers n1 and n2 are algebraically
                          equal.

            n1 -ne n2     True if the integers n1 and n2 are not algebraically
                          equal.

            n1 -gt n2     True if the integer n1 is algebraically greater than
                          the integer n2.

            n1 -ge n2     True if the integer n1 is algebraically greater than
                          or equal to the integer n2.

            n1 -lt n2     True if the integer n1 is algebraically less than
                          the integer n2.

            n1 -le n2     True if the integer n1 is algebraically less than or
                          equal to the integer n2.

            These primaries can be combined with the following operators:

            ! expression  True if expression is false.

            expression1 -a expression2
                          True if both expression1 and expression2 are true.

            expression1 -o expression2
            number or as the name of the signal.  If signal is 0, the action
            is executed when the shell exits.  action may be null, which cause
            the specified signals to be ignored.  With action omitted or set
            to `-' the specified signals are set to their default action.
            When the shell forks off a subshell, it resets trapped (but not
            ignored) signals to the default action.  The trap command has no
            effect on signals that were ignored on entry to the shell.  trap
            without any arguments cause it to write a list of signals and
            their associated action to the standard output in a format that is
            suitable as an input to the shell that achieves the same trapping
            results.

            Examples:

                  trap

            List trapped signals and their corresponding action

                  trap '' INT QUIT tstp 30

            Ignore signals INT QUIT TSTP USR1

                  trap date INT

            Print date upon receiving signal INT

     type [name ...]
            Interpret each name as a command and print the resolution of the
            command search.  Possible resolutions are: shell keyword, alias,
            shell builtin, command, tracked alias and not found.  For aliases
            the alias expansion is printed; for commands and tracked aliases
            the complete pathname of the command is printed.

     ulimit [-H | -S] [-a | -tfdscmlpn [value]]
            Inquire about or set the hard or soft limits on processes or set
            new limits.  The choice between hard limit (which no process is
            allowed to violate, and which may not be raised once it has been
            lowered) and soft limit (which causes processes to be signaled but
            not necessarily killed, and which may be raised) is made with
            these flags:

            -H          set or inquire about hard limits

            -S          set or inquire about soft limits.  If neither -H nor
                        -S is specified, the soft limit is displayed or both
                        limits are set.  If both are specified, the last one
                        wins.

            The limit to be interrogated or set, then, is chosen by specifying
            any one of these flags:

            -a          show all the current limits

            -t          show or set the limit on CPU time (in seconds)

            -m          show or set the limit on the total physical memory
                        that can be in use by a process (in kilobytes)

            -l          show or set the limit on how much memory a process can
                        lock with mlock(2) (in kilobytes)

            -p          show or set the limit on the number of processes this
                        user can have at one time

            -n          show or set the limit on the number files a process
                        can have open at once

            If none of these is specified, it is the limit on file size that
            is shown or set.  If value is specified, the limit is set to that
            number; otherwise the current limit is displayed.

            Limits of an arbitrary process can be displayed or set using the
            sysctl(8) utility.

     umask [mask]
            Set the value of umask (see umask(2)) to the specified octal
            value.  If the argument is omitted, the umask value is printed.

     unalias [-a] [name]
            If name is specified, the shell removes that alias.  If -a is
            specified, all aliases are removed.

     unset [-fv] name ...
            The specified variables and functions are unset and unexported.
            If -f or -v is specified, the corresponding function or variable
            is unset, respectively.  If a given name corresponds to both a
            variable and a function, and no options are given, only the vari-
            able is unset.

     wait [job]
            Wait for the specified job to complete and return the exit status
            of the last process in the job.  If the argument is omitted, wait
            for all jobs to complete and the return an exit status of zero.

   Command Line Editing
     When dash is being used interactively from a terminal, the current com-
     mand and the command history (see fc in Builtins) can be edited using vi-
     mode command-line editing.  This mode uses commands, described below,
     similar to a subset of those described in the vi man page.  The command
     'set -o vi' enables vi-mode editing and place sh into vi insert mode.
     With vi-mode enabled, sh can be switched between insert mode and command
     mode.  The editor is not described in full here, but will be in a later
     document.  It's similar to vi: typing <ESC> will throw you into command
     VI command mode.  Hitting <return> while in command mode will pass the
     line to the shell.

EXIT STATUS
     Errors that are detected by the shell, such as a syntax error, will cause
                tion Path Search.

     CDPATH     The search path used with the cd builtin.

     MAIL       The name of a mail file, that will be checked for the arrival
                of new mail.  Overridden by MAILPATH.

     MAILCHECK  The frequency in seconds that the shell checks for the arrival
                of mail in the files specified by the MAILPATH or the MAIL
                file.  If set to 0, the check will occur at each prompt.

     MAILPATH   A colon ``:'' separated list of file names, for the shell to
                check for incoming mail.  This environment setting overrides
                the MAIL setting.  There is a maximum of 10 mailboxes that can
                be monitored at once.

     PS1        The primary prompt string, which defaults to ``$  '', unless
                you are the superuser, in which case it defaults to ``#  ''.

     PS2        The secondary prompt string, which defaults to ``>  ''.

     PS4        Output before each line when execution trace (set -x) is
                enabled, defaults to ``+  ''.

     IFS        Input Field Separators.  This is normally set to <space>,
                <tab>, and <newline>.  See the White Space Splitting section
                for more details.

     TERM       The default terminal setting for the shell.  This is inherited
                by children of the shell, and is used in the history editing
                modes.

     HISTSIZE   The number of lines in the history buffer for the shell.

     PWD        The logical value of the current working directory.  This is
                set by the cd command.

     OLDPWD     The previous logical value of the current working directory.
                This is set by the cd command.

     PPID       The process ID of the parent process of the shell.

FILES
     $HOME/.profile

     /etc/profile

SEE ALSO
     csh(1), echo(1), getopt(1), ksh(1), login(1), printf(1), test(1),
     getopt(3), passwd(5), environ(7), sysctl(8)

HISTORY
     dash is a POSIX-compliant implementation of /bin/sh that aims to be as
     small as possible.  dash is a direct descendant of the NetBSD version of
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