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KSH(1)                           User commands                          KSH(1)



NAME
       ksh - Public domain Korn shell

SYNOPSIS
       ksh [+-abCefhikmnprsuvxX] [+-o option] [ [ -c command-string [command-
       name] | -s | file ] [argument ...] ]

DESCRIPTION
       ksh is a command interpreter that is intended for both interactive and
       shell script use.  Its command language is a superset of the sh(1)
       shell language.

   Shell Startup
       The following options can be specified only on the command line:

       -c command-string
              the shell executes the command(s) contained in command-string

       -i     interactive mode -- see below

       -l     login shell -- see below interactive mode -- see below

       -s     the shell reads commands from standard input; all non-option
              arguments are positional parameters

       -r     restricted mode -- see below

       In addition to the above, the options described in the set built-in
       command can also be used on the command line.

       If neither the -c nor the -s options are specified, the first non-
       option argument specifies the name of a file the shell reads commands
       from; if there are no non-option arguments, the shell reads commands
       from standard input.  The name of the shell (i.e., the contents of the
       $0) parameter is determined as follows: if the -c option is used and
       there is a non-option argument, it is used as the name; if commands are
       being read from a file, the file is used as the name; otherwise the
       name the shell was called with (i.e., argv[0]) is used.

       A shell is interactive if the -i option is used or if both standard
       input and standard error are attached to a tty.  An interactive shell
       has job control enabled (if available), ignores the INT, QUIT and TERM
       signals, and prints prompts before reading input (see PS1 and PS2
       parameters).  For non-interactive shells, the trackall option is on by
       default (see set command below).

       A shell is restricted if the -r option is used or if either the
       basename of the name the shell is invoked with or the SHELL parameter
       match the pattern *r*sh (e.g., rsh, rksh, rpdksh, etc.).  The following
       restrictions come into effect after the shell processes any profile and
       $ENV files:

         o    the cd command is disabled

         o    the SHELL, ENV and PATH parameters can't be changed

         o    command names can't be specified with absolute or relative paths

         o    the -p option of the command built-in can't be used

         o    redirections that create files can't be used (i.e., >, >|, >>,
              <>)

       A shell is privileged if the -p option is used or if the real user-id
       or group-id does not match the effective user-id or group-id (see
       getuid(2), getgid(2)).  A privileged shell does not process
       $HOME/.profile nor the ENV parameter (see below), instead the file
       /etc/suid_profile is processed.  Clearing the privileged option causes
       the shell to set its effective user-id (group-id) to its real user-id
       (group-id).

       If the basename of the name the shell is called with (i.e., argv[0])
       starts with - or if the -l option is used, the shell is assumed to be a
       login shell and the shell reads and executes the contents of
       /etc/profile, $HOME/.profile and $ENV if they exist and are readable.

       If the ENV parameter is set when the shell starts (or, in the case of
       login shells, after any profiles are processed), its value is subjected
       to parameter, command, arithmetic and tilde substitution and the
       resulting file (if any) is read and executed.  If the ENV parameter is
       not set (and not null) the file $HOME/.kshrc is included (after the
       above mentioned substitutions have been performed).

       The exit status of the shell is 127 if the command file specified on
       the command line could not be opened, or non-zero if a fatal syntax
       error occurred during the execution of a script.  In the absence of
       fatal errors, the exit status is that of the last command executed, or
       zero, if no command is executed.

   Command Syntax
       The shell begins parsing its input by breaking it into words.  Words,
       which are sequences of characters, are delimited by unquoted white-
       space characters (space, tab and newline) or meta-characters (<, >, |,
       ;, &, ( and )).  Aside from delimiting words, spaces and tabs are
       ignored, while newlines usually delimit commands.  The meta-characters
       are used in building the following tokens: <, <&, <<, >, >&, >>, etc.
       are used to specify redirections (see Input/Output Redirection below);
       | is used to create pipelines; |& is used to create co-processes (see
       Co-Processes below); ; is used to separate commands; & is used to
       create asynchronous pipelines; && and || are used to specify
       conditional execution; ;; is used in case statements; (( .. )) are used
       in arithmetic expressions; and lastly, ( .. ) are used to create
       subshells.

       White-space and meta-characters can be quoted individually using
       backslash (\), or in groups using double (") or single (') quotes.
       Note that the following characters are also treated specially by the
       shell and must be quoted if they are to represent themselves: \, ", ',
       #, $, `, ~, {, }, *, ? and [.  The first three of these are the above
       mentioned quoting characters (see Quoting below); #, if used at the
       beginning of a word, introduces a comment -- everything after the # up
       to the nearest newline is ignored; $ is used to introduce parameter,
       command and arithmetic substitutions (see Substitution below); `
       introduces an old-style command substitution (see Substitution below);
       ~ begins a directory expansion (see Tilde Expansion below); { and }
       delimit csh(1) style alternations (see Brace Expansion below); and,
       finally, *, ? and [ are used in file name generation (see File Name
       Patterns below).

       As words and tokens are parsed, the shell builds commands, of which
       there are two basic types: simple-commands, typically programs that are
       executed, and compound-commands, such as for and if statements,
       grouping constructs and function definitions.

       A simple-command consists of some combination of parameter assignments
       (see Parameters below), input/output redirections (see Input/Output
       Redirections below), and command words; the only restriction is that
       parameter assignments come before any command words.  The command
       words, if any, define the command that is to be executed and its
       arguments.  The command may be a shell built-in command, a function or
       an external command, i.e., a separate executable file that is located
       using the PATH parameter (see Command Execution below).  Note that all
       command constructs have an exit status: for external commands, this is
       related to the status returned by wait(2) (if the command could not be
       found, the exit status is 127, if it could not be executed, the exit
       status is 126); the exit status of other command constructs (built-in
       commands, functions, compound-commands, pipelines, lists, etc.) are all
       well defined and are described where the construct is described.  The
       exit status of a command consisting only of parameter assignments is
       that of the last command substitution performed during the parameter
       assignment or zero if there were no command substitutions.

       Commands can be chained together using the | token to form pipelines,
       in which the standard output of each command but the last is piped (see
       pipe(2)) to the standard input of the following command.  The exit
       status of a pipeline is that of its last command.  A pipeline may be
       prefixed by the ! reserved word which causes the exit status of the
       pipeline to be logically complemented: if the original status was 0 the
       complemented status will be 1, and if the original status was not 0,
       then the complemented status will be 0.

       Lists of commands can be created by separating pipelines by any of the
       following tokens: &&, ||, &, |& and ;.  The first two are for
       conditional execution: cmd1 && cmd2 executes cmd2 only if the exit
       status of cmd1 is zero; || is the opposite -- cmd2 is executed only if
       the exit status of cmd1 is non-zero.  && and || have equal precedence
       which is higher than that of &, |& and ;, which also have equal
       precedence.  The & token causes the preceding command to be executed
       asynchronously, that is, the shell starts the command, but does not
       wait for it to complete (the shell does keep track of the status of
       asynchronous commands -- see Job Control below).  When an asynchronous
       command is started when job control is disabled (i.e., in most
       scripts), the command is started with signals INT and QUIT ignored and
       with input redirected from /dev/null (however, redirections specified
       in the asynchronous command have precedence).  The |& operator starts a
       co-process which is special kind of asynchronous process (see Co-
       Processes below).  Note that a command must follow the && and ||
       operators, while a command need not follow &, |& and ;.  The exit
       status of a list is that of the last command executed, with the
       exception of asynchronous lists, for which the exit status is 0.

       Compound commands are created using the following reserved words --
       these words are only recognized if they are unquoted and if they are
       used as the first word of a command (i.e., they can't be preceded by
       parameter assignments or redirections):

       case   else   function   then    !
       do     esac   if         time    [[
       done   fi     in         until   {
       elif   for    select     while   }
       Note: Some shells (but not this one) execute control structure commands
       in a subshell when one or more of their file descriptors are
       redirected, so any environment changes inside them may fail.  To be
       portable, the exec statement should be used instead to redirect file
       descriptors before the control structure.

       In the following compound command descriptions, command lists (denoted
       as list) that are followed by reserved words must end with a semi-
       colon, a newline or a (syntactically correct) reserved word.  For
       example,
              { echo foo; echo bar; }
              { echo foo; echo bar<newline>}
              { { echo foo; echo bar; } }
       are all valid, but
              { echo foo; echo bar }
       is not.

       ( list )
              Execute list in a subshell.  There is no implicit way to pass
              environment changes from a subshell back to its parent.

       { list }
              Compound construct; list is executed, but not in a subshell.
              Note that { and } are reserved words, not meta-characters.

       case word in [ [(] pattern [| pattern] ... ) list ;; ] ... esac
              The case statement attempts to match word against the specified
              patterns; the list associated with the first successfully
              matched pattern is executed.  Patterns used in case statements
              are the same as those used for file name patterns except that
              the restrictions regarding . and / are dropped.  Note that any
              unquoted space before and after a pattern is stripped; any space
              with a pattern must be quoted.  Both the word and the patterns
              are subject to parameter, command, and arithmetic substitution
              as well as tilde substitution.  For historical reasons, open and
              close braces may be used instead of in and esac (e.g., case $foo
              { *) echo bar; }).  The exit status of a case statement is that
              of the executed list; if no list is executed, the exit status is
              zero.

       for name [ in word ... term ] do list done
              where term is either a newline or a ;.  For each word in the
              specified word list, the parameter name is set to the word and
              list is executed.  If in is not used to specify a word list, the
              positional parameters ("$1", "$2", etc.) are used instead.  For
              historical reasons, open and close braces may be used instead of
              do and done (e.g., for i; { echo $i; }).  The exit status of a
              for statement is the last exit status of list; if list is never
              executed, the exit status is zero.

       if list then list [elif list then list] ... [else list] fi
              If the exit status of the first list is zero, the second list is
              executed; otherwise the list following the elif, if any, is
              executed with similar consequences.  If all the lists following
              the if and elifs fail (i.e., exit with non-zero status), the
              list following the else is executed.  The exit status of an if
              statement is that of non-conditional list that is executed; if
              no non-conditional list is executed, the exit status is zero.

       select name [ in word ... term ] do list done
              where term is either a newline or a ;.  The select statement
              provides an automatic method of presenting the user with a menu
              and selecting from it.  An enumerated list of the specified
              words is printed on standard error, followed by a prompt (PS3,
              normally `#? ').  A number corresponding to one of the
              enumerated words is then read from standard input, name is set
              to the selected word (or is unset if the selection is not
              valid), REPLY is set to what was read (leading/trailing space is
              stripped), and list is executed.  If a blank line (i.e., zero or
              more IFS characters) is entered, the menu is re-printed without
              executing list.  When list completes, the enumerated list is
              printed if REPLY is null, the prompt is printed and so on.  This
              process is continues until an end-of-file is read, an interrupt
              is received or a break statement is executed inside the loop.
              If in word ... is omitted, the positional parameters are used
              (i.e., "$1", "$2", etc.).  For historical reasons, open and
              close braces may be used instead of do and done (e.g., select i;
              { echo $i; }).  The exit status of a select statement is zero if
              a break statement is used to exit the loop, non-zero otherwise.

       until list do list done
              This works like while, except that the body is executed only
              while the exit status of the first list is non-zero.

       while list do list done
              A while is a prechecked loop.  Its body is executed as often as
              the exit status of the first list is zero.  The exit status of a
              while statement is the last exit status of the list in the body
              of the loop; if the body is not executed, the exit status is
              zero.

       function name { list }
              Defines the function name.  See Functions below.  Note that
              redirections specified after a function definition are performed
              whenever the function is executed, not when the function
              definition is executed.

       name () command
              Mostly the same as function.  See Functions below.

       time [ -p ] [ pipeline ]
              The time reserved word is described in the Command Execution
              section.

       (( expression ))
              The arithmetic expression expression is evaluated; equivalent to
              let "expression".  See Arithmetic Expressions and the let
              command below.

       [[ expression ]]
              Similar to the test and [ ... ] commands (described later), with
              the following exceptions:

                o    Field splitting and file name generation are not
                     performed on arguments.

                o    The -a (and) and -o (or) operators are replaced with &&
                     and ||, respectively.

                o    Operators (e.g., -f, =, !, etc.) must be unquoted.

                o    The second operand of != and = expressions are patterns
                     (e.g., the comparison in [[ foobar = f*r ]] succeeds).

                o    There are two additional binary operators: < and > which
                     return true if their first string operand is less than,
                     or greater than, their second string operand,
                     respectively.

                o    The single argument form of test, which tests if the
                     argument has non-zero length, is not valid - explicit
                     operators must always be used, e.g., instead of [ str ]
                     use [[ -n str ]]

                o    Parameter, command and arithmetic substitutions are
                     performed as expressions are evaluated and lazy
                     expression evaluation is used for the && and ||
                     operators.  This means that in the statement [[ -r foo &&
                     $(< foo) = b*r ]] the $(< foo) is evaluated if and only
                     if the file foo exists and is readable.

   Quoting
       Quoting is used to prevent the shell from treating characters or words
       specially.  There are three methods of quoting: First, \ quotes the
       following character, unless it is at the end of a line, in which case
       both the \ and the newline are stripped.  Second, a single quote (')
       quotes everything up to the next single quote (this may span lines).
       Third, a double quote (") quotes all characters, except $, ` and \, up
       to the next unquoted double quote.  $ and ` inside double quotes have
       their usual meaning (i.e., parameter, command or arithmetic
       substitution) except no field splitting is carried out on the results
       of double-quoted substitutions.  If a \ inside a double-quoted string
       is followed by \, $, ` or ", it is replaced by the second character; if
       it is followed by a newline, both the \ and the newline are stripped;
       otherwise, both the \ and the character following are unchanged.

       Note: An earlier version of ksh(1) changed the interpretation of
       sequences of the form "...`...\"...`.." according to whether or not
       POSIX mode was in effect.  In the current implementation, the backslash
       in \" is seen and removed by the outer "...", so the backslash is not
       seen by the inner `...`.

   Aliases
       There are two types of aliases: normal command aliases and tracked
       aliases.  Command aliases are normally used as a short hand for a long
       or often used command.  The shell expands command aliases (i.e.,
       substitutes the alias name for its value) when it reads the first word
       of a command.  An expanded alias is re-processed to check for more
       aliases.  If a command alias ends in a space or tab, the following word
       is also checked for alias expansion.  The alias expansion process stops
       when a word that is not an alias is found, when a quoted word is found
       or when an alias word that is currently being expanded is found.

       The following command aliases are defined automatically by the shell:
              autoload='typeset -fu'
              functions='typeset -f'
              hash='alias -t'
              history='fc -l'
              integer='typeset -i'
              local='typeset'
              login='exec login'
              nohup='nohup '
              r='fc -e -'
              stop='kill -STOP'
              suspend='kill -STOP $$'
              type='whence -v'

       Tracked aliases allow the shell to remember where it found a particular
       command.  The first time the shell does a path search for a command
       that is marked as a tracked alias, it saves the full path of the
       command.  The next time the command is executed, the shell checks the
       saved path to see that it is still valid, and if so, avoids repeating
       the path search.  Tracked aliases can be listed and created using alias
       -t.  Note that changing the PATH parameter clears the saved paths for
       all tracked aliases.  If the trackall option is set (i.e., set -o
       trackall or set -h), the shell tracks all commands.  This option is set
       automatically for non-interactive shells.  For interactive shells, only
       the following commands are automatically tracked: cat, cc, chmod, cp,
       date, ed, emacs, grep, ls, mail, make, mv, pr, rm, sed, sh, vi and who.

   Substitution
       The first step the shell takes in executing a simple-command is to
       perform substitutions on the words of the command.  There are three
       kinds of substitution: parameter, command and arithmetic.  Parameter
       substitutions, which are described in detail in the next section, take
       the form $name or ${...}; command substitutions take the form
       $(command) or `command`; and arithmetic substitutions take the form
       $((expression)).

       If a substitution appears outside of double quotes, the results of the
       substitution are generally subject to word or field splitting according
       to the current value of the IFS parameter.  The IFS parameter specifies
       a list of characters which are used to break a string up into several
       words; any characters from the set space, tab and newline that appear
       in the IFS characters are called IFS white space.  Sequences of one or
       more IFS white space characters, in combination with zero or one non-
       IFS white space characters delimit a field.  As a special case, leading
       and trailing IFS white space is stripped (i.e., no leading or trailing
       empty field is created by it); leading or trailing non-IFS white space
       does create an empty field.  Example: if IFS is set to `<space>:', the
       sequence of characters `<space>A<space>:<space><space>B::D' contains
       four fields: `A', `B', `' and `D'.  Note that if the IFS parameter is
       set to the null string, no field splitting is done; if the parameter is
       unset, the default value of space, tab and newline is used.

       The results of substitution are, unless otherwise specified, also
       subject to brace expansion and file name expansion (see the relevant
       sections below).

       A command substitution is replaced by the output generated by the
       specified command, which is run in a subshell.  For $(command)
       substitutions, normal quoting rules are used when command is parsed,
       however, for the `command` form, a \ followed by any of $, ` or \ is
       stripped (a \ followed by any other character is unchanged).  As a
       special case in command substitutions, a command of the form < file is
       interpreted to mean substitute the contents of file ($(< foo) has the
       same effect as $(cat foo), but it is carried out more efficiently
       because no process is started).
       NOTE: $(command) expressions are currently parsed by finding the
       matching parenthesis, regardless of quoting.  This will hopefully be
       fixed soon.

       Arithmetic substitutions are replaced by the value of the specified
       expression.  For example, the command echo $((2+3*4)) prints 14.  See
       Arithmetic Expressions for a description of an expression.

   Parameters
       Parameters are shell variables; they can be assigned values and their
       values can be accessed using a parameter substitution.  A parameter
       name is either one of the special single punctuation or digit character
       parameters described below, or a letter followed by zero or more
       letters or digits (`_' counts as a letter).  The later form can be
       treated as arrays by appending an array index of the form: [expr] where
       expr is an arithmetic expression.  Array indices are currently limited
       to the range 0 through 1023, inclusive.  Parameter substitutions take
       the form $name, ${name} or ${name[expr]}, where name is a parameter
       name.  If substitution is performed on a parameter (or an array
       parameter element) that is not set, a null string is substituted unless
       the nounset option (set -o nounset or set -u) is set, in which case an
       error occurs.

       Parameters can be assigned values in a number of ways.  First, the
       shell implicitly sets some parameters like #, PWD, etc.; this is the
       only way the special single character parameters are set.  Second,
       parameters are imported from the shell's environment at startup.
       Third, parameters can be assigned values on the command line, for
       example, `FOO=bar' sets the parameter FOO to bar; multiple parameter
       assignments can be given on a single command line and they can be
       followed by a simple-command, in which case the assignments are in
       effect only for the duration of the command (such assignments are also
       exported, see below for implications of this).  Note that both the
       parameter name and the = must be unquoted for the shell to recognize a
       parameter assignment.  The fourth way of setting a parameter is with
       the export, readonly and typeset commands; see their descriptions in
       the Command Execution section.  Fifth, for and select loops set
       parameters as well as the getopts, read and set -A commands.  Lastly,
       parameters can be assigned values using assignment operators inside
       arithmetic expressions (see Arithmetic Expressions below) or using the
       ${name=value} form of parameter substitution (see below).

       Parameters with the export attribute (set using the export or typeset
       -x commands, or by parameter assignments followed by simple commands)
       are put in the environment (see environ(7)) of commands run by the
       shell as name=value pairs.  The order in which parameters appear in the
       environment of a command is unspecified.  When the shell starts up, it
       extracts parameters and their values from its environment and
       automatically sets the export attribute for those parameters.

       Modifiers can be applied to the ${name} form of parameter substitution:

       ${name:-word}
              if name is set and not null, it is substituted, otherwise word
              is substituted.

       ${name:+word}
              if name is set and not null, word is substituted, otherwise
              nothing is substituted.

       ${name:=word}
              if name is set and not null, it is substituted, otherwise it is
              assigned word and the resulting value of name is substituted.

       ${name:?word}
              if name is set and not null, it is substituted, otherwise word
              is printed on standard error (preceded by name:) and an error
              occurs (normally causing termination of a shell script, function
              or .-script).  If word is omitted the string `parameter null or
              not set' is used instead.

       In the above modifiers, the : can be omitted, in which case the
       conditions only depend on name being set (as opposed to set and not
       null).  If word is needed, parameter, command, arithmetic and tilde
       substitution are performed on it; if word is not needed, it is not
       evaluated.

       The following forms of parameter substitution can also be used:

       ${#name}
              The number of positional parameters if name is *, @ or is not
              specified, or the length of the string value of parameter name.

       ${#name[*]}, ${#name[@]}
              The number of elements in the array name.

       ${name#pattern}, ${name##pattern}
              If pattern matches the beginning of the value of parameter name,
              the matched text is deleted from the result of substitution.  A
              single # results in the shortest match, two #'s results in the
              longest match.

       ${name%pattern}, ${name%%pattern}
              Like ${..#..} substitution, but it deletes from the end of the
              value.

       The following special parameters are implicitly set by the shell and
       cannot be set directly using assignments:

       !      Process id of the last background process started.  If no
              background processes have been started, the parameter is not
              set.

       #      The number of positional parameters (i.e., $1, $2, etc.).

       $      The process ID of the shell, or the PID of the original shell if
              it is a subshell.

       -      The concatenation of the current single letter options (see set
              command below for list of options).

       ?      The exit status of the last non-asynchronous command executed.
              If the last command was killed by a signal, $? is set to 128
              plus the signal number.

       0      The name the shell was invoked with (i.e., argv[0]), or the
              command-name if it was invoked with the -c option and the
              command-name was supplied, or the file argument, if it was
              supplied.  If the posix option is not set, $0 is the name of the
              current function or script.

       1 ... 9
              The first nine positional parameters that were supplied to the
              shell, function or .-script.  Further positional parameters may
              be accessed using ${number}.

       *      All positional parameters (except parameter 0), i.e., $1 $2
              $3....  If used outside of double quotes, parameters are
              separate words (which are subjected to word splitting); if used
              within double quotes, parameters are separated by the first
              character of the IFS parameter (or the empty string if IFS is
              null).

       @      Same as $*, unless it is used inside double quotes, in which
              case a separate word is generated for each positional parameter
              - if there are no positional parameters, no word is generated
              ("$@" can be used to access arguments, verbatim, without losing
              null arguments or splitting arguments with spaces).

       The following parameters are set and/or used by the shell:

       _ (underscore)
              When an external command is executed by the shell, this
              parameter is set in the environment of the new process to the
              path of the executed command.  In interactive use, this
              parameter is also set in the parent shell to the last word of
              the previous command.  When MAILPATH messages are evaluated,
              this parameter contains the name of the file that changed (see
              MAILPATH parameter below).

       CDPATH Search path for the cd built-in command.  Works the same way as
              PATH for those directories not beginning with / in cd commands.
              Note that if CDPATH is set and does not contain . nor an empty
              path, the current directory is not searched.

       COLUMNS
              Set to the number of columns on the terminal or window.
              Currently set to the cols value as reported by stty(1) if that
              value is non-zero.  This parameter is used by the interactive
              line editing modes, and by select, set -o and kill -l commands
              to format information in columns.

       EDITOR If the VISUAL parameter is not set, this parameter controls the
              command line editing mode for interactive shells.  See VISUAL
              parameter below for how this works.

       ENV    If this parameter is found to be set after any profile files are
              executed, the expanded value is used as a shell start-up file.
              It typically contains function and alias definitions.

       ERRNO  Integer value of the shell's errno variable -- indicates the
              reason the last system call failed.

              Not implemented yet.

       EXECSHELL
              If set, this parameter is assumed to contain the shell that is
              to be used to execute commands that execve(2) fails to execute
              and which do not start with a `#! shell' sequence.

       FCEDIT The editor used by the fc command (see below).

       FPATH  Like PATH, but used when an undefined function is executed to
              locate the file defining the function.  It is also searched when
              a command can't be found using PATH.  See Functions below for
              more information.

       HISTFILE
              The name of the file used to store history.  When assigned to,
              history is loaded from the specified file.  Also, several
              invocations of the shell running on the same machine will share
              history if their HISTFILE parameters all point at the same file.
              NOTE: if HISTFILE isn't set, no history file is used.  This is
              different from the original Korn shell, which uses
              $HOME/.sh_history; in future, pdksh may also use a default
              history file.

       HISTSIZE
              The number of commands normally stored for history, default 128.

       HOME   The default directory for the cd command and the value
              substituted for an unqualified ~ (see Tilde Expansion below).

       IFS    Internal field separator, used during substitution and by the
              read command, to split values into distinct arguments; normally
              set to space, tab and newline.  See Substitution above for
              details.
              Note: this parameter is not imported from the environment when
              the shell is started.

       KSH_VERSION
              The version of shell and the date the version was created
              (readonly).  See also the version commands in Emacs Editing Mode
              and Vi Editing Mode sections, below.

       LINENO The line number of the function or shell script that is
              currently being executed.

       LINES  Set to the number of lines on the terminal or window.

              Not implemented yet.

       MAIL   If set, the user will be informed of the arrival of mail in the
              named file.  This parameter is ignored if the MAILPATH parameter
              is set.

       MAILCHECK
              How often, in seconds, the shell will check for mail in the
              file(s) specified by MAIL or MAILPATH.  If 0, the shell checks
              before each prompt.  The default is 600 (10 minutes).

       MAILPATH
              A list of files to be checked for mail.  The list is colon
              separated, and each file may be followed by a ? and a message to
              be printed if new mail has arrived.  Command, parameter and
              arithmetic substitution is performed on the message, and, during
              substitution, the parameter $_ contains the name of the file.
              The default message is you have mail in $_.

       OLDPWD The previous working directory.  Unset if cd has not
              successfully changed directories since the shell started, or if
              the shell doesn't know where it is.

       OPTARG When using getopts, it contains the argument for a parsed
              option, if it requires one.

       OPTIND The index of the last argument processed when using getopts.
              Assigning 1 to this parameter causes getopts to process
              arguments from the beginning the next time it is invoked.

       PATH   A colon separated list of directories that are searched when
              looking for commands and .'d files.  An empty string resulting
              from a leading or trailing colon, or two adjacent colons is
              treated as a `.', the current directory.

       POSIXLY_CORRECT
              If set, this parameter causes the posix option to be enabled.
              See POSIX Mode below.

       PPID   The process ID of the shell's parent (readonly).

       PS1    PS1 is the primary prompt for interactive shells.  Parameter,
              command and arithmetic substitutions are performed, and ! is
              replaced with the current command number (see fc command below).
              A literal ! can be put in the prompt by placing !! in PS1.  Note
              that since the command line editors try to figure out how long
              the prompt is (so they know how far it is to edge of the
              screen), escape codes in the prompt tend to mess things up.  You
              can tell the shell not to count certain sequences (such as
              escape codes) by prefixing your prompt with a non-printing
              character (such as control-A) followed by a carriage return and
              then delimiting the escape codes with this non-printing
              character.  If you don't have any non-printing characters,
              you're out of luck...  BTW, don't blame me for this hack; it's
              in the original ksh.  Default is `$ ' for non-root users, `# '
              for root.

       PS2    Secondary prompt string, by default `> ', used when more input
              is needed to complete a command.

       PS3    Prompt used by select statement when reading a menu selection.
              Default is `#? '.

       PS4    Used to prefix commands that are printed during execution
              tracing (see set -x command below).  Parameter, command and
              arithmetic substitutions are performed before it is printed.
              Default is `+ '.

       PWD    The current working directory.  Maybe unset or null if shell
              doesn't know where it is.

       RANDOM A simple random number generator.  Every time RANDOM is
              referenced, it is assigned the next number in a random number
              series.  The point in the series can be set by assigning a
              number to RANDOM (see rand(3)).

       REPLY  Default parameter for the read command if no names are given.
              Also used in select loops to store the value that is read from
              standard input.

       SECONDS
              The number of seconds since the shell started or, if the
              parameter has been assigned an integer value, the number of
              seconds since the assignment plus the value that was assigned.

       TMOUT  If set to a positive integer in an interactive shell, it
              specifies the maximum number of seconds the shell will wait for
              input after printing the primary prompt (PS1).  If the time is
              exceeded, the shell exits.

       TMPDIR The directory shell temporary files are created in.  If this
              parameter is not set, or does not contain the absolute path of a
              writable directory, temporary files are created in /tmp.

       VISUAL If set, this parameter controls the command line editing mode
              for interactive shells.  If the last component of the path
              specified in this parameter contains the string vi, emacs or
              gmacs, the vi, emacs or gmacs (Gosling emacs) editing mode is
              enabled, respectively.

   Tilde Expansion
       Tilde expansion, which is done in parallel with parameter substitution,
       is done on words starting with an unquoted ~.  The characters following
       the tilde, up to the first /, if any, are assumed to be a login name.
       If the login name is empty, + or -, the value of the HOME, PWD, or
       OLDPWD parameter is substituted, respectively.  Otherwise, the password
       file is searched for the login name, and the tilde expression is
       substituted with the user's home directory.  If the login name is not
       found in the password file or if any quoting or parameter substitution
       occurs in the login name, no substitution is performed.

       In parameter assignments (those preceding a simple-command or those
       occurring in the arguments of alias, export, readonly, and typeset),
       tilde expansion is done after any unquoted colon (:), and login names
       are also delimited by colons.

       The home directory of previously expanded login names are cached and
       re-used.  The alias -d command may be used to list, change and add to
       this cache (e.g., `alias -d fac=/usr/local/facilities; cd ~fac/bin').

   Brace Expansion (alternation)
       Brace expressions, which take the form
              prefix{str1,...,strN}suffix
       are expanded to N words, each of which is the concatenation of prefix,
       stri and suffix (e.g., `a{c,b{X,Y},d}e' expands to four word: ace,
       abXe, abYe, and ade).  As noted in the example, brace expressions can
       be nested and the resulting words are not sorted.  Brace expressions
       must contain an unquoted comma (,) for expansion to occur (i.e., {} and
       {foo} are not expanded).  Brace expansion is carried out after
       parameter substitution and before file name generation.

   File Name Patterns
       A file name pattern is a word containing one or more unquoted ? or *
       characters or [..] sequences.  Once brace expansion has been performed,
       the shell replaces file name patterns with the sorted names of all the
       files that match the pattern (if no files match, the word is left
       unchanged).  The pattern elements have the following meaning:

       ?      matches any single character.

       *      matches any sequence of characters.

       [..]   matches any of the characters inside the brackets.  Ranges of
              characters can be specified by separating two characters by a -,
              e.g., [a0-9] matches the letter a or any digit.  In order to
              represent itself, a - must either be quoted or the first or last
              character in the character list.  Similarly, a ] must be quoted
              or the first character in the list if it is represent itself
              instead of the end of the list.  Also, a ! appearing at the
              start of the list has special meaning (see below), so to
              represent itself it must be quoted or appear later in the list.

       [!..]  like [..], except it matches any character not inside the
              brackets.

       *(pattern| ... |pattern)
              matches any string of characters that matches zero or more
              occurrences of the specified patterns.  Example: the pattern
              *(foo|bar) matches the strings `', `foo', `bar', `foobarfoo',
              etc..

       +(pattern| ... |pattern)
              matches any string of characters that matches one or more
              occurrences of the specified patterns.  Example: the pattern
              +(foo|bar) matches the strings `foo', `bar', `foobarfoo', etc..

       ?(pattern| ... |pattern)
              matches the empty string or a string that matches one of the
              specified patterns.  Example: the pattern ?(foo|bar) only
              matches the strings `', `foo' and `bar'.

       @(pattern| ... |pattern)
              matches a string that matches one of the specified patterns.
              Example: the pattern @(foo|bar) only matches the strings `foo'
              and `bar'.

       !(pattern| ... |pattern)
              matches any string that does not match one of the specified
              patterns.  Examples: the pattern !(foo|bar) matches all strings
              except `foo' and `bar'; the pattern !(*) matches no strings; the
              pattern !(?)* matches all strings (think about it).

       Note that pdksh currently never matches . and .., but the original ksh,
       Bourne sh and bash do, so this may have to change (too bad).

       Note that none of the above pattern elements match either a period (.)
       at the start of a file name or a slash (/), even if they are explicitly
       used in a [..] sequence; also, the names . and .. are never matched,
       even by the pattern .*.

       If the markdirs option is set, any directories that result from file
       name generation are marked with a trailing /.

       The POSIX character classes (i.e., [:class-name:] inside a [..]
       expression) are not yet implemented.

   Input/Output Redirection
       When a command is executed, its standard input, standard output and
       standard error (file descriptors 0, 1 and 2, respectively) are normally
       inherited from the shell.  Three exceptions to this are commands in
       pipelines, for which standard input and/or standard output are those
       set up by the pipeline, asynchronous commands created when job control
       is disabled, for which standard input is initially set to be from
       /dev/null, and commands for which any of the following redirections
       have been specified:

       > file standard output is redirected to file.  If file does not exist,
              it is created; if it does exist, is a regular file and the
              noclobber option is set, an error occurs, otherwise the file is
              truncated.  Note that this means the command cmd < foo > foo
              will open foo for reading and then truncate it when it opens it
              for writing, before cmd gets a chance to actually read foo.

       >| file
              same as >, except the file is truncated, even if the noclobber
              option is set.

       >> file
              same as >, except the file an existing file is appended to
              instead of being truncated.  Also, the file is opened in append
              mode, so writes always go to the end of the file (see open(2)).

       < file standard input is redirected from file, which is opened for
              reading.

       <> file
              same as <, except the file is opened for reading and writing.

       << marker
              after reading the command line containing this kind of
              redirection (called a here document), the shell copies lines
              from the command source into a temporary file until a line
              matching marker is read.  When the command is executed, standard
              input is redirected from the temporary file.  If marker contains
              no quoted characters, the contents of the temporary file are
              processed as if enclosed in double quotes each time the command
              is executed, so parameter, command and arithmetic substitutions
              are performed, along with backslash (\) escapes for $, `, \ and
              \newline.  If multiple here documents are used on the same
              command line, they are saved in order.

       <<- marker
              same as <<, except leading tabs are stripped from lines in the
              here document.

       <& fd  standard input is duplicated from file descriptor fd.  fd can be
              a single digit, indicating the number of an existing file
              descriptor, the letter p, indicating the file descriptor
              associated with the output of the current co-process, or the
              character -, indicating standard input is to be closed.

       >& fd  same as <&, except the operation is done on standard output.

       In any of the above redirections, the file descriptor that is
       redirected (i.e., standard input or standard output) can be explicitly
       given by preceding the redirection with a single digit.  Parameter,
       command and arithmetic substitutions, tilde substitutions and (if the
       shell is interactive) file name generation are all performed on the
       file, marker and fd arguments of redirections.  Note however, that the
       results of any file name generation are only used if a single file is
       matched; if multiple files match, the word with the unexpanded file
       name generation characters is used.  Note that in restricted shells,
       redirections which can create files cannot be used.

       For simple-commands, redirections may appear anywhere in the command,
       for compound-commands (if statements, etc.), any redirections must
       appear at the end.  Redirections are processed after pipelines are
       created and in the order they are given, so
              cat /foo/bar 2>&1 > /dev/null | cat -n
       will print an error with a line number prepended to it.

   Arithmetic Expressions
       Integer arithmetic expressions can be used with the let command, inside
       $((..)) expressions, inside array references (e.g., name[expr]), as
       numeric arguments to the test command, and as the value of an
       assignment to an integer parameter.

       Expression may contain alpha-numeric parameter identifiers, array
       references, and integer constants and may be combined with the
       following C operators (listed and grouped in increasing order of
       precedence).

       Unary operators:
              + - ! ~ ++ --

       Binary operators:
              ,
              = *= /= %= += -= <<= >>= &= ^= |=
              ||
              &&
              |
              ^
              &
              == !=
              < <= >= >
              << >>
              + -
              * / %

       Ternary operator:
              ?: (precedence is immediately higher than assignment)

       Grouping operators:
              ( )

       Integer constants may be specified with arbitrary bases using the
       notation base#number, where base is a decimal integer specifying the
       base, and number is a number in the specified base.

       The operators are evaluated as follows:

              unary +
                     result is the argument (included for completeness).

              unary -
                     negation.

              !      logical not; the result is 1 if argument is zero, 0 if
                     not.

              ~      arithmetic (bit-wise) not.

              ++     increment; must be applied to a parameter (not a literal
                     or other expression) - the parameter is incremented by 1.
                     When used as a prefix operator, the result is the
                     incremented value of the parameter, when used as a
                     postfix operator, the result is the original value of the
                     parameter.

              --     similar to ++, except the parameter is decremented by 1.

              ,      separates two arithmetic expressions; the left hand side
                     is evaluated first, then the right.  The result is value
                     of the expression on the right hand side.

              =      assignment; variable on the left is set to the value on
                     the right.

              *= /= %= += -= <<= >>= &= ^= |=
                     assignment operators; <var> <op>= <expr> is the same as
                     <var> = <var> <op> ( <expr> ).

              ||     logical or; the result is 1 if either argument is non-
                     zero, 0 if not.  The right argument is evaluated only if
                     the left argument is zero.

              &&     logical and; the result is 1 if both arguments are non-
                     zero, 0 if not.  The right argument is evaluated only if
                     the left argument is non-zero.

              |      arithmetic (bit-wise) or.

              ^      arithmetic (bit-wise) exclusive-or.

              &      arithmetic (bit-wise) and.

              ==     equal; the result is 1 if both arguments are equal, 0 if
                     not.

              !=     not equal; the result is 0 if both arguments are equal, 1
                     if not.

              <      less than; the result is 1 if the left argument is less
                     than the right, 0 if not.

              <= >= >
                     less than or equal, greater than or equal, greater than.
                     See <.

              << >>  shift left (right); the result is the left argument with
                     its bits shifted left (right) by the amount given in the
                     right argument.

              + - * /
                     addition, subtraction, multiplication, and division.

              %      remainder; the result is the remainder of the division of
                     the left argument by the right.  The sign of the result
                     is unspecified if either argument is negative.

              <arg1> ? <arg2> : <arg3>
                     if <arg1> is non-zero, the result is <arg2>, otherwise
                     <arg3>.

   Co-Processes
       A co-process, which is a pipeline created with the |& operator, is an
       asynchronous process that the shell can both write to (using print -p)
       and read from (using read -p).  The input and output of the co-process
       can also be manipulated using >&p and <&p redirections, respectively.
       Once a co-process has been started, another can't be started until the
       co-process exits, or until the co-process input has been redirected
       using an exec n>&p redirection.  If a co-process's input is redirected
       in this way, the next co-process to be started will share the output
       with the first co-process, unless the output of the initial co-process
       has been redirected using an exec n<&p redirection.

       Some notes concerning co-processes:

         o    the only way to close the co-process input (so the co-process
              reads an end-of-file) is to redirect the input to a numbered
              file descriptor and then close that file descriptor (e.g., exec
              3>&p;exec 3>&-).

         o    in order for co-processes to share a common output, the shell
              must keep the write portion of the output pipe open.  This means
              that end of file will not be detected until all co-processes
              sharing the co-process output have exited (when they all exit,
              the shell closes its copy of the pipe).  This can be avoided by
              redirecting the output to a numbered file descriptor (as this
              also causes the shell to close its copy).  Note that this
              behaviour is slightly different from the original Korn shell
              which closes its copy of the write portion of the co-processes'
              output when the most recently started co-process (instead of
              when all sharing co-processes) exits.

         o    print -p will ignore SIGPIPE signals during writes if the signal
              is not being trapped or ignored; the same is not true if the co-
              process input has been duplicated to another file descriptor and
              print -un is used.

   Functions
       Functions are defined using either Korn shell function name syntax or
       the Bourne/POSIX shell name() syntax (see below for the difference
       between the two forms).  Functions are like .-scripts in that they are
       executed in the current environment, however, unlike .-scripts, shell
       arguments (i.e., positional parameters, $1, etc.) are never visible
       inside them.  When the shell is determining the location of a command,
       functions are searched after special built-in commands, and before
       regular and non-regular built-ins, and before the PATH is searched.

       An existing function may be deleted using unset -f function-name.  A
       list of functions can be obtained using typeset +f and the function
       definitions can be listed using typeset -f.  autoload (which is an
       alias for typeset -fu) may be used to create undefined functions; when
       an undefined function is executed, the shell searches the path
       specified in the FPATH parameter for a file with the same name as the
       function, which, if found is read and executed.  If after executing the
       file, the named function is found to be defined, the function is
       executed, otherwise, the normal command search is continued (i.e., the
       shell searches the regular built-in command table and PATH).  Note that
       if a command is not found using PATH, an attempt is made to autoload a
       function using FPATH (this is an undocumented feature of the original
       Korn shell).

       Functions can have two attributes, trace and export, which can be set
       with typeset -ft and typeset -fx, respectively.  When a traced function
       is executed, the shell's xtrace option is turned on for the functions
       duration, otherwise the xtrace option is turned off.  The export
       attribute of functions is currently not used.  In the original Korn
       shell, exported functions are visible to shell scripts that are
       executed.

       Since functions are executed in the current shell environment,
       parameter assignments made inside functions are visible after the
       function completes.  If this is not the desired effect, the typeset
       command can be used inside a function to create a local parameter.
       Note that special parameters (e.g., $$, $!) can't be scoped in this
       way.

       The exit status of a function is that of the last command executed in
       the function.  A function can be made to finish immediately using the
       return command; this may also be used to explicitly specify the exit
       status.

       Functions defined with the function reserved word are treated
       differently in the following ways from functions defined with the ()
       notation:

         o    the $0 parameter is set to the name of the function (Bourne-
              style functions leave $0 untouched).

         o    parameter assignments preceding function calls are not kept in
              the shell environment (executing Bourne-style functions will
              keep assignments).

         o    OPTIND is saved/reset and restored on entry and exit from the
              function so getopts can be used properly both inside and outside
              the function (Bourne-style functions leave OPTIND untouched, so
              using getopts inside a function interferes with using getopts
              outside the function).  In the future, the following differences
              will also be added:

         o    A separate trap/signal environment will be used during the
              execution of functions.  This will mean that traps set inside a
              function will not affect the shell's traps and signals that are
              not ignored in the shell (but may be trapped) will have their
              default effect in a function.

         o    The EXIT trap, if set in a function, will be executed after the
              function returns.

   POSIX Mode
       The shell is intended to be POSIX compliant, however, in some cases,
       POSIX behaviour is contrary either to the original Korn shell behaviour
       or to user convenience.  How the shell behaves in these cases is
       determined by the state of the posix option (set -o posix) -- if it is
       on, the POSIX behaviour is followed, otherwise it is not.  The posix
       option is set automatically when the shell starts up if the environment
       contains the POSIXLY_CORRECT parameter.  (The shell can also be
       compiled so that it is in POSIX mode by default, however this is
       usually not desirable).

       The following is a list of things that are affected by the state of the
       posix option:

         o    kill -l output: in posix mode, signal names are listed one a
              single line; in non-posix mode, signal numbers, names and
              descriptions are printed in columns.  In future, a new option
              (-v perhaps) will be added to distinguish the two behaviours.

         o    fg exit status: in posix mode, the exit status is 0 if no errors
              occur; in non-posix mode, the exit status is that of the last
              foregrounded job.

         o    eval exit status: if eval gets to see an empty command (e.g.,
              eval "`false`"), its exit status in posix mode will be 0.  In
              non-posix mode, it will be the exit status of the last command
              substitution that was done in the processing of the arguments to
              eval (or 0 if there were no command substitutions).

         o    getopts: in posix mode, options must start with a -; in non-
              posix mode, options can start with either - or +.

         o    brace expansion (also known as alternation): in posix mode,
              brace expansion is disabled; in non-posix mode, brace expansion
              enabled.  Note that set -o posix (or setting the POSIXLY_CORRECT
              parameter) automatically turns the braceexpand option off,
              however it can be explicitly turned on later.

         o    set -: in posix mode, this does not clear the verbose or xtrace
              options; in non-posix mode, it does.

         o    set exit status: in posix mode, the exit status of set is 0 if
              there are no errors; in non-posix mode, the exit status is that
              of any command substitutions performed in generating the set
              command.  For example, `set -- `false`; echo $?' prints 0 in
              posix mode, 1 in non-posix mode.  This construct is used in most
              shell scripts that use the old getopt(1) command.

         o    argument expansion of alias, export, readonly, and typeset
              commands: in posix mode, normal argument expansion done; in non-
              posix mode, field splitting, file globing, brace expansion and
              (normal) tilde expansion are turned off, and assignment tilde
              expansion is turned on.

         o    signal specification: in posix mode, signals can be specified as
              digits only if signal numbers match POSIX values (i.e., HUP=1,
              INT=2, QUIT=3, ABRT=6, KILL=9, ALRM=14, and TERM=15); in non-
              posix mode, signals can be always digits.

         o    alias expansion: in posix mode, alias expansion is only carried
              out when reading command words; in non-posix mode, alias
              expansion is carried out on any word following an alias that
              ended in a space.  For example, the following for loop
              alias a='for ' i='j'
              a i in 1 2; do echo i=$i j=$j; done
       uses parameter i in posix mode, j in non-posix mode.

         o    test: in posix mode, the expression "-t" (preceded by some
              number of "!" arguments) is always true as it is a non-zero
              length string; in non-posix mode, it tests if file descriptor 1
              is a tty (i.e., the fd argument to the -t test may be left out
              and defaults to 1).

   Command Execution
       After evaluation of command line arguments, redirections and parameter
       assignments, the type of command is determined: a special built-in, a
       function, a regular built-in or the name of a file to execute found
       using the PATH parameter.  The checks are made in the above order.
       Special built-in commands differ from other commands in that the PATH
       parameter is not used to find them, an error during their execution can
       cause a non-interactive shell to exit and parameter assignments that
       are specified before the command are kept after the command completes.
       Just to confuse things, if the posix option is turned off (see set
       command below) some special commands are very special in that no field
       splitting, file globing, brace expansion nor tilde expansion is
       performed on arguments that look like assignments.  Regular built-in
       commands are different only in that the PATH parameter is not used to
       find them.

       The original ksh and POSIX differ somewhat in which commands are
       considered special or regular:
       POSIX special commands

              .       continue   exit       return   trap
              :       eval       export     set      unset
              break   exec       readonly   shift
       Additional ksh special commands

              builtin   times   typeset
       Very special commands (non-posix mode)

              alias   readonly   set   typeset
       POSIX regular commands

              alias   command   fg        kill   umask
              bg      false     getopts   read   unalias
              cd      fc        jobs      true   wait
       Additional ksh regular commands

              [      let     pwd    ulimit
              echo   print   test   whence

       In the future, the additional ksh special and regular commands may be
       treated differently from the POSIX special and regular commands.

       Once the type of the command has been determined, any command line
       parameter assignments are performed and exported for the duration of
       the command.

       The following describes the special and regular built-in commands:

       . file [arg1 ...]
              Execute the commands in file in the current environment.  The
              file is searched for in the directories of PATH.  If arguments
              are given, the positional parameters may be used to access them
              while file is being executed.  If no arguments are given, the
              positional parameters are those of the environment the command
              is used in.

       : [ ... ]
              The null command.  Exit status is set to zero.

       alias [ -d | +-t [-r] ] [+-px] [+-] [name1[=value1] ...]
              Without arguments, alias lists all aliases.  For any name
              without a value, the existing alias is listed.  Any name with a
              value defines an alias (see Aliases above).

              When listing aliases, one of two formats is used: normally,
              aliases are listed as name=value, where value is quoted; if
              options were preceded with + or a lone + is given on the command
              line, only name is printed.  In addition, if the -p option is
              used, each alias is prefixed with the string "alias ".

              The -x option sets (+x clears) the export attribute of an alias,
              or, if no names are given, lists the aliases with the export
              attribute (exporting an alias has no affect).

              The -t option indicates that tracked aliases are to be
              listed/set (values specified on the command line are ignored for
              tracked aliases).  The -r option indicates that all tracked
              aliases are to be reset.

              The -d causes directory aliases, which are used in tilde
              expansion, to be listed or set (see Tilde Expansion above).

       bg [job ...]
              Resume the specified stopped job(s) in the background.  If no
              jobs are specified, %+ is assumed.  This command is only
              available on systems which support job control.  See Job Control
              below for more information.

       bind [-l] [-m] [key[=editing-command] ...]
              Set or view the current emacs command editing key
              bindings/macros.  See Emacs Editing Mode below for a complete
              description.

       break [level]
              break exits the levelth inner most for, select, until, or while
              loop.  level defaults to 1.

       builtin command [arg1 ...]
              Execute the built-in command command.

       cd [-LP] [dir]
              Set the working directory to dir.  If the parameter CDPATH is
              set, it lists directories to search in for dir.  An empty entry
              in the CDPATH entry means the current directory.  If a non-empty
              directory from CDPATH is used, the resulting full path is
              printed to standard output.  If dir is missing, the home
              directory $HOME is used.  If dir is -, the previous working
              directory is used (see OLDPWD parameter).  If -L option (logical
              path) is used or if the physical option (see set command below)
              isn't set, references to .. in dir are relative to the path used
              get to the directory.  If -P option (physical path) is used or
              if the physical option is set, .. is relative to the filesystem
              directory tree.  The PWD and OLDPWD parameters are updated to
              reflect the current and old wording directory, respectively.

       cd [-LP] old new
              The string new is substituted for old in the current directory,
              and the shell attempts to change to the new directory.

       command [-pvV] cmd [arg1 ...]
              If neither the -v nor -V options are given, cmd is executed
              exactly as if the command had not been specified, with two
              exceptions: first, cmd cannot be a shell function, and second,
              special built-in commands lose their specialness (i.e.,
              redirection and utility errors do not cause the shell to exit,
              and command assignments are not permanent).  If the -p option is
              given, a default search path is used instead of the current
              value of PATH (the actual value of the default path is system
              dependent: on POSIXish systems, it is the value returned by
              getconf CS_PATH ).

              If the -v option is given, instead of executing cmd, information
              about what would be executed is given (and the same is done for
              arg1 ...): for special and regular built-in commands and
              functions, their names are simply printed, for aliases, a
              command that defines them is printed, and for commands found by
              searching the PATH parameter, the full path of the command is
              printed.  If no command is found, (i.e., the path search fails),
              nothing is printed and command exits with a non-zero status.
              The -V option is like the -v option, except it is more verbose.

       continue [levels]
              continue jumps to the beginning of the levelth inner most for,
              select, until, or while loop.  level defaults to 1.

       echo [-neE] [arg ...]
              Prints its arguments (separated by spaces) followed by a
              newline, to standard out.  The newline is suppressed if any of
              the arguments contain the backslash sequence \c.  See print
              command below for a list of other backslash sequences that are
              recognized.

              The options are provided for compatibility with BSD shell
              scripts: -n suppresses the trailing newline, -e enables
              backslash interpretation (a no-op, since this is normally done),
              and -E suppresses backslash interpretation.

       eval command ...
              The arguments are concatenated (with spaces between them) to
              form a single string which the shell then parses and executes in
              the current environment.

       exec [command [arg ...]]
              The command is executed without forking, replacing the shell
              process.

              If no arguments are given, any IO redirection is permanent and
              the shell is not replaced.  Any file descriptors greater than 2
              which are opened or dup(2)-ed in this way are not made available
              to other executed commands (i.e., commands that are not built-in
              to the shell).  Note that the Bourne shell differs here: it does
              pass these file descriptors on.

       exit [status]
              The shell exits with the specified exit status.  If status is
              not specified, the exit status is the current value of the ?
              parameter.

       export [-p] [parameter[=value]] ...
              Sets the export attribute of the named parameters.  Exported
              parameters are passed in the environment to executed commands.
              If values are specified, the named parameters also assigned.

              If no parameters are specified, the names of all parameters with
              the export attribute are printed one per line, unless the -p
              option is used, in which case export commands defining all
              exported parameters, including their values, are printed.

       false  A command that exits with a non-zero status.

       fc [-e editor | -l [-n]] [-r] [first [last]]
              first and last select commands from the history.  Commands can
              be selected by history number, or a string specifying the most
              recent command starting with that string.  The -l option lists
              the command on stdout, and -n inhibits the default command
              numbers.  The -r option reverses the order of the list.  Without
              -l, the selected commands are edited by the editor specified
              with the -e option, or if no -e is specified, the editor
              specified by the FCEDIT parameter (if this parameter is not set,
              /bin/ed is used), and then executed by the shell.

       fc [-e - | -s] [-g] [old=new] [prefix]
              Re-execute the selected command (the previous command by
              default) after performing the optional substitution of old with
              new.  If -g is specified, all occurrences of old are replaced
              with new.  This command is usually accessed with the predefined
              alias r='fc -e -'.

       fg [job ...]
              Resume the specified job(s) in the foreground.  If no jobs are
              specified, %+ is assumed.  This command is only available on
              systems which support job control.  See Job Control below for
              more information.

       getopts optstring name [arg ...]
              getopts is used by shell procedures to parse the specified
              arguments (or positional parameters, if no arguments are given)
              and to check for legal options.  optstring contains the option
              letters that getopts is to recognize.  If a letter is followed
              by a colon, the option is expected to have an argument.  Options
              that do not take arguments may be grouped in a single argument.
              If an option takes an argument and the option character is not
              the last character of the argument it is found in, the remainder
              of the argument is taken to be the option's argument, otherwise,
              the next argument is the option's argument.

              Each time getopts is invoked, it places the next option in the
              shell parameter name and the index of the next argument to be
              processed in the shell parameter OPTIND.  If the option was
              introduced with a +, the option placed in name is prefixed with
              a +.  When an option requires an argument, getopts places it in
              the shell parameter OPTARG.  When an illegal option or a missing
              option argument is encountered a question mark or a colon is
              placed in name (indicating an illegal option or missing
              argument, respectively) and OPTARG is set to the option
              character that caused the problem.  An error message is also
              printed to standard error if optstring does not begin with a
              colon.

              When the end of the options is encountered, getopts exits with a
              non-zero exit status.  Options end at the first (non-option)
              argument that does not start with a -, or when a -- argument is
              encountered.

              Option parsing can be reset by setting OPTIND to 1 (this is done
              automatically whenever the shell or a shell procedure is
              invoked).

              Warning: Changing the value of the shell parameter OPTIND to a
              value other than 1, or parsing different sets of arguments
              without resetting OPTIND may lead to unexpected results.

       hash [-r] [name ...]
              Without arguments, any hashed executable command pathnames are
              listed.  The -r option causes all hashed commands to be removed
              from the hash table.  Each name is searched as if it where a
              command name and added to the hash table if it is an executable
              command.

       jobs [-lpn] [job ...]
              Display information about the specified jobs; if no jobs are
              specified, all jobs are displayed.  The -n option causes
              information to be displayed only for jobs that have changed
              state since the last notification.  If the -l option is used,
              the process-id of each process in a job is also listed.  The -p
              option causes only the process group of each job to be printed.
              See Job Control below for the format of job and the displayed
              job.

       kill [-s signame | -signum | -signame ] { job | pid | -pgrp } ...
              Send the specified signal to the specified jobs, process ids, or
              process groups.  If no signal is specified, the signal TERM is
              sent.  If a job is specified, the signal is sent to the job's
              process group.  See Job Control below for the format of job.

       kill -l [exit-status ...]
              Print the name of the signal that killed a process which exited
              with the specified exit-statuses.  If no arguments are
              specified, a list of all the signals, their numbers and a short
              description of them are printed.

       let [expression ...]
              Each expression is evaluated, see Arithmetic Expressions above.
              If all expressions are successfully evaluated, the exit status
              is 0 (1) if the last expression evaluated to non-zero (zero).
              If an error occurs during the parsing or evaluation of an
              expression, the exit status is greater than 1.  Since
              expressions may need to be quoted, (( expr )) is syntactic sugar
              for let "expr".

       print [-nprsun | -R [-en]] [argument ...]
              Print prints its arguments on the standard output, separated by
              spaces, and terminated with a newline.  The -n option suppresses
              the newline.  By default, certain C escapes are translated.
              These include \b, \f, \n, \r, \t, \v, and \0### (# is an octal
              digit, of which there may be 0 to 3).  \c is equivalent to using
              the -n option.  \ expansion may be inhibited with the -r option.
              The -s option prints to the history file instead of standard
              output, the -u option prints to file descriptor n (n defaults to
              1 if omitted), and the -p option prints to the co-process (see
              Co-Processes above).

              The -R option is used to emulate, to some degree, the BSD echo
              command, which does not process \ sequences unless the -e option
              is given.  As above, the -n option suppresses the trailing
              newline.

       pwd [-LP]
              Print the present working directory.  If -L option is used or if
              the physical option (see set command below) isn't set, the
              logical path is printed (i.e., the path used to cd to the
              current directory).  If -P option (physical path) is used or if
              the physical option is set, the path determined from the
              filesystem (by following .. directories to the root directory)
              is printed.

       read [-prsun] [parameter ...]
              Reads a line of input from standard input, separate the line
              into fields using the IFS parameter (see Substitution above),
              and assign each field to the specified parameters.  If there are
              more parameters than fields, the extra parameters are set to
              null, or alternatively, if there are more fields than
              parameters, the last parameter is assigned the remaining fields
              (inclusive of any separating spaces).  If no parameters are
              specified, the REPLY parameter is used.  If the input line ends
              in a backslash and the -r option was not used, the backslash and
              newline are stripped and more input is read.  If no input is
              read, read exits with a non-zero status.

              The first parameter may have a question mark and a string
              appended to it, in which case the string is used as a prompt
              (printed to standard error before any input is read) if the
              input is a tty (e.g., read nfoo?'number of foos: ').

              The -un and -p options cause input to be read from file
              descriptor n or the current co-process (see Co-Processes above
              for comments on this), respectively.  If the -s option is used,
              input is saved to the history file.

       readonly [-p] [parameter[=value]] ...
              Sets the readonly attribute of the named parameters.  If values
              are given, parameters are set to them before setting the
              attribute.  Once a parameter is made readonly, it cannot be
              unset and its value cannot be changed.

              If no parameters are specified, the names of all parameters with
              the readonly attribute are printed one per line, unless the -p
              option is used, in which case readonly commands defining all
              readonly parameters, including their values, are printed.

       return [status]
              Returns from a function or . script, with exit status status.
              If no status is given, the exit status of the last executed
              command is used.  If used outside of a function or . script, it
              has the same effect as exit.  Note that pdksh treats both
              profile and $ENV files as . scripts, while the original Korn
              shell only treats profiles as . scripts.

       set [+-abCefhkmnpsuvxX] [+-o [option]] [+-A name] [--] [arg ...]
              The set command can be used to set (-) or clear (+) shell
              options, set the positional parameters, or set an array
              parameter.  Options can be changed using the +-o option syntax,
              where option is the long name of an option, or using the
              +-letter syntax, where letter is the option's single letter name
              (not all options have a single letter name).  The following
              table lists both option letters (if they exist) and long names
              along with a description of what the option does.


               -A                    Sets the elements of the array parameter name to arg ...; If -A is used, the array is reset (i.e., emptied) first; if +A is used, the first N elements are set (where N is the number of args), the rest are left untouched.
               -a   allexport        all new parameters are created with the export attribute
               -b   notify           Print job notification messages asynchronously, instead of just before the prompt. Only used if job control is enabled (-m).
               -C   noclobber        Prevent > redirection from overwriting existing files (>| must be used to force an overwrite).
               -e   errexit          Exit (after executing the ERR trap) as soon as an error occurs or a command fails (i.e., exits with a non-zero status). This does not apply to commands whose exit status is explicitly tested by a shell construct such as if, until, while, && or || statements.
               -f   noglob           Do not expand file name patterns.
               -h   trackall         Create tracked aliases for all executed commands (see Aliases above). On by default for non-interactive shells.
               -i   interactive      Enable interactive mode - this can only be set/unset when the shell is invoked.
               -k   keyword          Parameter assignments are recognized anywhere in a command.
               -l   login            The shell is a login shell - this can only be set/unset when the shell is invoked (see Shell Startup above).
               -m   monitor          Enable job control (default for interactive shells).
               -n   noexec           Do not execute any commands - useful for checking the syntax of scripts (ignored if interactive).
               -p   privileged       Set automatically if, when the shell starts, the real uid or gid does not match the effective uid or gid, respectively. See Shell Startup above for a description of what this means.
               -r   restricted       Enable restricted mode -- this option can only be used when the shell is invoked. See Shell Startup above for a description of what this means.
               -s   stdin            If used when the shell is invoked, commands are read from standard input. Set automatically if the shell is invoked with no arguments. When -s is used in the set command, it causes the specified arguments to be sorted before assigning them to the positional parameters (or to array name, if -A is used).

               -u   nounset          Referencing of an unset parameter is treated as an error, unless one of the -, + or = modifiers is used.
               -v   verbose          Write shell input to standard error as it is read.
               -x   xtrace           Print commands and parameter assignments when they are executed, preceded by the value of PS4.
               -X   markdirs         Mark directories with a trailing / during file name generation.
                   bgnice           Background jobs are run with lower priority.
                   braceexpand      Enable brace expansion (aka, alternation).
                   emacs            Enable BRL emacs-like command line editing (interactive shells only); see Emacs Editing Mode.
                   emacs-usemeta    In emacs command-line editing, use the 8th bit as meta (^[) prefix.  This is the default if  LC_CTYPE is unset or POSIX respectively C. 8
                   gmacs            Enable gmacs-like (Gosling emacs) command line editing (interactive shells only); currently identical to emacs editing except that transpose (^T) acts slightly differently.
                   ignoreeof        The shell will not (easily) exit on when end-of-file is read, exit must be used. To avoid infinite loops, the shell will exit if eof is read 13 times in a row.
                   nohup            Do not kill running jobs with a HUP signal when a login shell exists. Currently set by default, but this will change in the future to be compatible with the original Korn shell (which doesn't have this option, but does send the HUP signal).
                   nolog            No effect - in the original Korn shell, this prevents function definitions from being stored in the history file.
                   physical         Causes the cd and pwd commands to use `physical' (i.e., the filesystem's) .. directories instead of `logical' directories (i.e.,  the shell handles .., which allows the user to be oblivious of symlink links to directories). Clear by default. Note that setting this option does not effect the current value of the PWD parameter; only the cd command changes PWD. See the cd and pwd commands above for more details.
                   posix            Enable posix mode. See POSIX Mode above.
                   vi               Enable vi-like command line editing (interactive shells only).
                   viraw            No effect - in the original Korn shell, unless viraw was set, the vi command line mode would let the tty driver do the work until ESC (^[) was entered. pdksh is always in viraw mode.
                   vi-esccomplete   In vi command line editing, do command / file name completion when escape (^[) is entered in command mode.
                   vi-show8         Prefix characters with the eighth bit set with `M-'. If this option is not set, characters in the range 128-160 are printed as is, which may cause problems.
                   vi-tabcomplete   In vi command line editing, do command / file name completion when tab (^I) is entered in insert mode.  This is the default.

              These options can also be used upon invocation of the shell.
              The current set of options (with single letter names) can be
              found in the parameter -.  set -o with no option name will list
              all the options and whether each is on or off; set +o will print
              the long names of all options that are currently on.

              Remaining arguments, if any, are positional parameters and are
              assigned, in order, to the positional parameters (i.e., 1, 2,
              etc.).  If options are ended with -- and there are no remaining
              arguments, all positional parameters are cleared.  If no options
              or arguments are given, then the values of all names are
              printed.  For unknown historical reasons, a lone - option is
              treated specially: it clears both the -x and -v options.

       shift [number]
              The positional parameters number+1, number+2 etc. are renamed to
              1, 2, etc. number defaults to 1.

       test expression

       [ expression ]
              test evaluates the expression and returns zero status if true, 1
              if false, and greater than 1 if there was an error.  It is
              normally used as the condition command of if and while
              statements.  The following basic expressions are available:


               str                str has non-zero length. Note that there is the potential for problems if str turns out to be an operator (e.g., -r) - it is generally better to use a test like [ X"str" != X ] instead (double quotes are used in case str contains spaces or file globing characters).
               -r file            file exists and is readable.
               -w file            file exists and is writable.
               -x file            file exists and is executable.
               -a file            file exists.
               -e file            file exists.
               -f file            file is a regular file.
               -d file            file is a directory.
               -c file            file is a character special device.
               -b file            file is a block special device.
               -p file            file is a named pipe.
               -u file            file's mode has setuid bit set.
               -g file            file's mode has setgid bit set.
               -k file            file's mode has sticky bit set.
               -s file            file is not empty.
               -O file            file's owner is the shell's effective user-ID.
               -G file            file's group is the shell's effective group-ID.
               -h file            file is a symbolic link.
               -H file            file is a context dependent directory (only useful on HP-UX).
               -L file            file is a symbolic link.
               -S file            file is a socket.
               -o option          shell option is set (see set command above for list of options). As a non-standard extension, if the option starts with a !, the test is negated; the test always fails if option doesn't exist (thus [ -o foo -o -o !foo ] returns true if and only if option foo exists).
               file -nt file      first file is newer than second file or first file exists and the second file does not.
               file -ot file      first file is older than second file or second file exists and the first file does not.
               file -ef file      first file is the same file as second file.
               -t [fd]            file descriptor is a tty device. If the posix option (set -o posix, see POSIX Mode above) is not set, fd may be left out, in which case it is taken to be 1 (the behaviour differs due to the special POSIX rules described below).
               string             string is not empty.
               -z string          string is empty.
               -n string          string is not empty.
               string = string    strings are equal.
               string == string   strings are equal.
               string != string   strings are not equal.
               number -eq number   numbers compare equal.
               number -ne number   numbers compare not equal.
               number -ge number   numbers compare greater than or equal.
               number -gt number   numbers compare greater than.
               number -le number   numbers compare less than or equal.
               number -lt number   numbers compare less than.

              The above basic expressions, in which unary operators have
              precedence over binary operators, may be combined with the
              following operators (listed in increasing order of precedence):


               expr -o expr   logical or
               expr -a expr   logical and
               ! expr        logical not
               ( expr )      grouping

              On operating systems not supporting /dev/fd/n devices (where n
              is a file descriptor number), the test command will attempt to
              fake it for all tests that operate on files (except the -e
              test).  I.e., [ -w /dev/fd/2 ] tests if file descriptor 2 is
              writable.

              Note that some special rules are applied (courtesy of POSIX) if
              the number of arguments to test or [ ... ] is less than five: if
              leading ! arguments can be stripped such that only one argument
              remains then a string length test is performed (again, even if
              the argument is a unary operator); if leading ! arguments can be
              stripped such that three arguments remain and the second
              argument is a binary operator, then the binary operation is
              performed (even if first argument is a unary operator, including
              an unstripped !).

              Note: A common mistake is to use if [ $foo = bar ] which fails
              if parameter foo is null or unset, if it has embedded spaces
              (i.e., IFS characters), or if it is a unary operator like ! or
              -n.  Use tests like if [ "X$foo" = Xbar ] instead.

       time [-p] [ pipeline ]
              If a pipeline is given, the times used to execute the pipeline
              are reported.  If no pipeline is given, then the user and system
              time used by the shell itself, and all the commands it has run
              since it was started, are reported.  The times reported are the
              real time (elapsed time from start to finish), the user CPU time
              (time spent running in user mode) and the system CPU time (time
              spent running in kernel mode).  Times are reported to standard
              error; the format of the output is:
                  0.00s real     0.00s user     0.00s system
              unless the -p option is given (only possible if pipeline is a
              simple command), in which case the output is slightly longer:
                  real   0.00
                  user   0.00
                  sys    0.00
              (the number of digits after the decimal may vary from system to
              system).  Note that simple redirections of standard error do not
              effect the output of the time command: time sleep 1 2> afile {
              time sleep 1; } 2> afile times for the first command do not go
              to afile, but those of the second command do.

       times  Print the accumulated user and system times used by the shell
              and by processes which have exited that the shell started.

       trap [handler signal ...]
              Sets trap handler that is to be executed when any of the
              specified signals are received.  Handler is either a null
              string, indicating the signals are to be ignored, a minus (-),
              indicating that the default action is to be taken for the
              signals (see signal(3)), or a string containing shell commands
              to be evaluated and executed at the first opportunity (i.e.,
              when the current command completes, or before printing the next
              PS1 prompt) after receipt of one of the signals.  Signal is the
              name of a signal (e.g., PIPE or ALRM) or the number of the
              signal (see kill -l command above).  There are two special
              signals: EXIT (also known as 0), which is executed when the
              shell is about to exit, and ERR which is executed after an error
              occurs (an error is something that would cause the shell to exit
              if the -e or errexit option were set -- see set command above).
              EXIT handlers are executed in the environment of the last
              executed command.  Note that for non-interactive shells, the
              trap handler cannot be changed for signals that were ignored
              when the shell started.

              With no arguments, trap lists, as a series of trap commands, the
              current state of the traps that have been set since the shell
              started.  Note that the output of trap can not be usefully piped
              to another process (an artifact of the fact that traps are
              cleared when subprocesses are created).

              The original Korn shell's DEBUG trap and the handling of ERR and
              EXIT traps in functions are not yet implemented.

       true   A command that exits with a zero value.

       typeset [[+-Ulprtux] [-L[n]] [-R[n]] [-Z[n]] [-i[n]] | -f [-tux]]
              [name[=value] ...]
              Display or set parameter attributes.  With no name arguments,
              parameter attributes are displayed: if no options arg used, the
              current attributes of all parameters are printed as typeset
              commands; if an option is given (or - with no option letter) all
              parameters and their values with the specified attributes are
              printed; if options are introduced with +, parameter values are
              not printed.

              If name arguments are given, the attributes of the named
              parameters are set (-) or cleared (+).  Values for parameters
              may optionally be specified.  If typeset is used inside a
              function, any newly created parameters are local to the
              function.

              When -f is used, typeset operates on the attributes of
              functions.  As with parameters, if no names are given, functions
              are listed with their values (i.e., definitions) unless options
              are introduced with +, in which case only the function names are
              reported.


               -Ln   Left justify attribute: n specifies the field width. If n is not specified, the current width of a parameter (or the width of its first assigned value) is used. Leading white space (and zeros, if used with the -Z option) is stripped. If necessary, values are either truncated or space padded to fit the field width.
               -Rn   Right justify attribute: n specifies the field width. If n is not specified, the current width of a parameter (or the width of its first assigned value) is used. Trailing white space are stripped. If necessary, values are either stripped of leading characters or space padded to make them fit the field width.
               -Zn   Zero fill attribute: if not combined with -L, this is the same as -R, except zero padding is used instead of space padding.
               -in   integer attribute: n specifies the base to use when displaying the integer (if not specified, the base given in the first assignment is used). Parameters with this attribute may be assigned values containing arithmetic expressions.
               -U   unsigned integer attribute: integers are printed as unsigned values (only useful when combined with the -i option). This option is not in the original Korn shell.
               -f   Function mode: display or set functions and their attributes, instead of parameters.
               -l   Lower case attribute: all  upper case characters in values are converted to lower case. (In the original Korn shell, this parameter meant `long integer' when used with the -i option).
               -p   Print complete typeset commands that can be used to re-create the attributes (but not the values) of parameters. This is the default action (option exists for ksh93 compatibility).
               -r   Readonly attribute: parameters with the this attribute may not be assigned to or unset. Once this attribute is set, it can not be turned off.
               -t   Tag attribute: has no meaning to the shell; provided for application use. For functions, -t is the trace attribute. When functions with the trace attribute are executed, the xtrace (-x) shell option is temporarily turned on.

               -u   Upper case attribute: all lower case characters in values are converted to upper case. (In the original Korn shell, this parameter meant `unsigned integer' when used with the -i option, which meant upper case letters would never be used for bases greater than 10. See the -U option). For functions, -u is the undefined attribute. See Functions above for the implications of this.

               -x   Export attribute: parameters (or functions) are placed in the environment of any executed commands. Exported functions are not implemented yet.

       ulimit [-abcdfHlmnpsStvw] [value]
              Display or set process limits.  If no options are used, the file
              size limit (-f) is assumed.  value, if specified, may be either
              be an arithmetic expression or the word unlimited.  The limits
              affect the shell and any processes created by the shell after a
              limit is imposed.  Note that some systems may not allow limits
              to be increased once they are set.  Also note that the types of
              limits available are system dependent - some systems have only
              the -f limit.

              -a     Displays all limits; unless -H is used, soft limits are
                     displayed.

              -H     Set the hard limit only (default is to set both hard and
                     soft limits).

              -S     Set the soft limit only (default is to set both hard and
                     soft limits).

              -b     Impose a size limit of n bytes on the size of socket
                     buffers.

              -c     Impose a size limit of n blocks on the size of core
                     dumps.

              -d     Impose a size limit of n kbytes on the size of the data
                     area.

              -f     Impose a size limit of n blocks on files written by the
                     shell and its child processes (files of any size may be
                     read).

              -l     Impose a limit of n kbytes on the amount of locked
                     (wired) physical memory.

              -m     Impose a limit of n kbytes on the amount of physical
                     memory used.

              -n     Impose a limit of n file descriptors that can be open at
                     once.

              -p     Impose a limit of n processes that can be run by the user
                     at any one time.

              -s     Impose a size limit of n kbytes on the size of the stack
                     area.

              -t     Impose a time limit of n CPU seconds to be used by each
                     process.

              -v     Impose a limit of n kbytes on the amount of virtual
                     memory used; on some systems this is the maximum
                     allowable virtual address (in bytes, not kbytes).

              -w     Impose a limit of n kbytes on the amount of swap space
                     used.

              As far as ulimit is concerned, a block is 512 bytes.

       umask [-S] [mask]
              Display or set the file permission creation mask, or umask (see
              umask(2)).  If the -S option is used, the mask displayed or set
              is symbolic, otherwise it is an octal number.

              Symbolic masks are like those used by chmod(1):
                     [ugoa]{{=+-}{rwx}*}+[,...]
              in which the first group of characters is the who part, the
              second group is the op part, and the last group is the perm
              part.  The who part specifies which part of the umask is to be
              modified.  The letters mean:

                     u      the user permissions

                     g      the group permissions

                     o      the other permissions (non-user, non-group)

                     a      all permissions (user, group and other)

              The op part indicates how the who permissions are to be
              modified:

                     =      set

                     +      added to

                     -      removed from

              The perm part specifies which permissions are to be set, added
              or removed:

                     r      read permission

                     w      write permission

                     x      execute permission

              When symbolic masks are used, they describe what permissions may
              be made available (as opposed to octal masks in which a set bit
              means the corresponding bit is to be cleared).  Example:
              `ug=rwx,o=' sets the mask so files will not be readable,
              writable or executable by `others', and is equivalent (on most
              systems) to the octal mask `07'.

       unalias [-adt] [name1 ...]
              The aliases for the given names are removed.  If the -a option
              is used, all aliases are removed.  If the -t or -d options are
              used, the indicated operations are carried out on tracked or
              directory aliases, respectively.

       unset [-fv] parameter ...
              Unset the named parameters (-v, the default) or functions (-f).
              The exit status is non-zero if any of the parameters were
              already unset, zero otherwise.

       wait [job]
              Wait for the specified job(s) to finish.  The exit status of
              wait is that of the last specified job: if the last job is
              killed by a signal, the exit status is 128 + the number of the
              signal (see kill -l exit-status above); if the last specified
              job can't be found (because it never existed, or had already
              finished), the exit status of wait is 127.  See Job Control
              below for the format of job.  Wait will return if a signal for
              which a trap has been set is received, or if a HUP, INT or QUIT
              signal is received.

              If no jobs are specified, wait waits for all currently running
              jobs (if any) to finish and exits with a zero status.  If job
              monitoring is enabled, the completion status of jobs is printed
              (this is not the case when jobs are explicitly specified).

       whence [-pv] [name ...]
              For each name, the type of command is listed (reserved word,
              built-in, alias, function, tracked alias or executable).  If the
              -p option is used, a path search done even if name is a reserved
              word, alias, etc. Without the -v option, whence is similar to
              command -v except that whence will find reserved words and won't
              print aliases as alias commands; with the -v option, whence is
              the same as command -V.  Note that for whence, the -p option
              does not affect the search path used, as it does for command.
              If the type of one or more of the names could not be determined,
              the exit status is non-zero.

   Job Control
       Job control refers to the shell's ability to monitor and control jobs,
       which are processes or groups of processes created for commands or
       pipelines.  At a minimum, the shell keeps track of the status of the
       background (i.e., asynchronous) jobs that currently exist; this
       information can be displayed using the jobs command.  If job control is
       fully enabled (using set -m or set -o monitor), as it is for
       interactive shells, the processes of a job are placed in their own
       process group, foreground jobs can be stopped by typing the suspend
       character from the terminal (normally ^Z), jobs can be restarted in
       either the foreground or background, using the fg and bg commands,
       respectively, and the state of the terminal is saved or restored when a
       foreground job is stopped or restarted, respectively.

       Note that only commands that create processes (e.g., asynchronous
       commands, subshell commands, and non-built-in, non-function commands)
       can be stopped; commands like read cannot be.

       When a job is created, it is assigned a job-number.  For interactive
       shells, this number is printed inside [..], followed by the process-ids
       of the processes in the job when an asynchronous command is run.  A job
       may be referred to in bg, fg, jobs, kill and wait commands either by
       the process id of the last process in the command pipeline (as stored
       in the $! parameter) or by prefixing the job-number with a percent sign
       (%).  Other percent sequences can also be used to refer to jobs:


        %+        The most recently stopped job, or, if there are no stopped jobs, the oldest running job.
        %%, %     Same as %+.
        %-        The job that would be the %+ job, if the later did not exist.
        %n        The job with job-number n.
        %?string   The job containing the string string (an error occurs if multiple jobs are matched).
        %string   The job starting with string string (an error occurs if multiple jobs are matched).

       When a job changes state (e.g., a background job finishes or foreground
       job is stopped), the shell prints the following status information:
              [number] flag status command
       where

        number
              is the job-number of the job.

        flag  is + or - if the job is the %+ or %- job, respectively, or space
              if it is neither.

        status
              indicates the current state of the job and can be

              Running
                     the job has neither stopped or exited (note that running
                     does not necessarily mean consuming CPU time -- the
                     process could be blocked waiting for some event).

              Done [(number)]
                     the job exited.  number is the exit status of the job,
                     which is omitted if the status is zero.

              Stopped [(signal)]
                     the job was stopped by the indicated signal (if no signal
                     is given, the job was stopped by SIGTSTP).

              signal-description [(core dumped)]
                     the job was killed by a signal (e.g., Memory fault,
                     Hangup, etc. -- use kill -l for a list of signal
                     descriptions).  The (core dumped) message indicates the
                     process created a core file.

        command
              is the command that created the process.  If there are multiple
              processes in the job, then each process will have a line showing
              its command and possibly its status, if it is different from the
              status of the previous process.

       When an attempt is made to exit the shell while there are jobs in the
       stopped state, the shell warns the user that there are stopped jobs and
       does not exit.  If another attempt is immediately made to exit the
       shell, the stopped jobs are sent a HUP signal and the shell exits.
       Similarly, if the nohup option is not set and there are running jobs
       when an attempt is made to exit a login shell, the shell warns the user
       and does not exit.  If another attempt is immediately made to exit the
       shell, the running jobs are sent a HUP signal and the shell exits.

   Interactive Input Line Editing
       The shell supports three modes of reading command lines from a tty in
       an interactive session.  Which is used is controlled by the emacs,
       gmacs and vi set options (at most one of these can be set at once).  If
       none of these options is enabled, the shell simply reads lines using
       the normal tty driver.  If the emacs or gmacs option is set, the shell
       allows emacs like editing of the command; similarly, if the vi option
       is set, the shell allows vi like editing of the command.  These modes
       are described in detail in the following sections.

       In these editing modes, if a line is longer that the screen width (see
       COLUMNS parameter), a >, + or < character is displayed in the last
       column indicating that there are more characters after, before and
       after, or before the current position, respectively.  The line is
       scrolled horizontally as necessary.

   Emacs Editing Mode
       When the emacs option is set, interactive input line editing is
       enabled.  Warning: This mode is slightly different from the emacs mode
       in the original Korn shell and the 8th bit is stripped in emacs mode.
       In this mode various editing commands (typically bound to one or more
       control characters) cause immediate actions without waiting for a new-
       line.  Several editing commands are bound to particular control
       characters when the shell is invoked; these bindings can be changed
       using the following commands:

       bind   The current bindings are listed.

       bind string=[editing-command]
              The specified editing command is bound to the given string,
              which should consist of a control character (which may be
              written using caret notation ^X), optionally preceded by one of
              the two prefix characters.  Future input of the string will
              cause the editing command to be immediately invoked.  Note that
              although only two prefix characters (usually ESC and ^X) are
              supported, some multi-character sequences can be supported.  The
              following binds the arrow keys on an ANSI terminal, or xterm
              (these are in the default bindings).  Of course some escape
              sequences won't work out quite this nicely:

              bind '^[['=prefix-2
              bind '^XA'=up-history
              bind '^XB'=down-history
              bind '^XC'=forward-char
              bind '^XD'=backward-char

       bind -l
              Lists the names of the functions to which keys may be bound.

       bind -m string=[substitute]
              The specified input string will afterwards be immediately
              replaced by the given substitute string, which may contain
              editing commands.

       The following is a list of editing commands available.  Each
       description starts with the name of the command, a n, if the command
       can be prefixed with a count, and any keys the command is bound to by
       default (written using caret notation, e.g., ASCII ESC character is
       written as ^[).  A count prefix for a command is entered using the
       sequence ^[n, where n is a sequence of 1 or more digits; unless
       otherwise specified, if a count is omitted, it defaults to 1.  Note
       that editing command names are used only with the bind command.
       Furthermore, many editing commands are useful only on terminals with a
       visible cursor.  The default bindings were chosen to resemble
       corresponding EMACS key bindings.  The users tty characters (e.g.,
       ERASE) are bound to reasonable substitutes and override the default
       bindings.

       abort ^G
              Useful as a response to a request for a search-history pattern
              in order to abort the search.

       auto-insert n
              Simply causes the character to appear as literal input.  Most
              ordinary characters are bound to this.

       backward-char  n ^B
              Moves the cursor backward n characters.

       backward-word  n ^[B
              Moves the cursor backward to the beginning of a word; words
              consist of alphanumerics, underscore (_) and dollar ($).

       beginning-of-history ^[<
              Moves to the beginning of the history.

       beginning-of-line ^A
              Moves the cursor to the beginning of the edited input line.

       capitalize-word n ^[c, ^[C
              Uppercase the first character in the next n words, leaving the
              cursor past the end of the last word.  If the current line does
              not begin with a comment character, one is added at the
              beginning of the line and the line is entered (as if return had
              been pressed), otherwise the existing comment characters are
              removed and the cursor is placed at the beginning of the line.

       complete ^[^[

       complete ^I
              Automatically completes as much as is unique of the command name
              or the file name containing the cursor.  If the entire remaining
              command or file name is unique a space is printed after its
              completion, unless it is a directory name in which case / is
              appended.  If there is no command or file name with the current
              partial word as its prefix, a bell character is output (usually
              causing a audio beep).

       complete-command ^X^[
              Automatically completes as much as is unique of the command name
              having the partial word up to the cursor as its prefix, as in
              the complete command described above.

       complete-file ^[^X
              Automatically completes as much as is unique of the file name
              having the partial word up to the cursor as its prefix, as in
              the complete command described above.

       complete-list ^[=
              List the possible completions for the current word.

       delete-char-backward n ERASE, ^?, ^H
              Deletes n characters before the cursor.

       delete-char-forward n
              Deletes n characters after the cursor.

       delete-word-backward n ^[ERASE, ^[^?, ^[^H, ^[h
              Deletes n words before the cursor.

       delete-word-forward n ^[d
              Deletes characters after the cursor up to the end of n words.

       down-history n ^N
              Scrolls the history buffer forward n lines (later).  Each input
              line originally starts just after the last entry in the history
              buffer, so down-history is not useful until either search-
              history or up-history has been performed.

       downcase-word n ^[L, ^[l
              Lowercases the next n words.

       end-of-history ^[>
              Moves to the end of the history.

       end-of-line ^E
              Moves the cursor to the end of the input line.

       eot ^_ Acts as an end-of-file; this is useful because edit-mode input
              disables normal terminal input canonicalization.

       eot-or-delete n ^D
              Acts as eot if alone on a line; otherwise acts as delete-char-
              forward.

       error  Error (ring the bell).

       exchange-point-and-mark ^X^X
              Places the cursor where the mark is, and sets the mark to where
              the cursor was.

       expand-file ^[*
              Appends a * to the current word and replaces the word with the
              result of performing file globbing on the word.  If no files
              match the pattern, the bell is rung.

       forward-char n ^F
              Moves the cursor forward n characters.

       forward-word n ^[f
              Moves the cursor forward to the end of the nth word.

       goto-history n ^[g
              Goes to history number n.

       kill-line KILL
              Deletes the entire input line.

       kill-region ^W
              Deletes the input between the cursor and the mark.

       kill-to-eol n ^K
              Deletes the input from the cursor to the end of the line if n is
              not specified, otherwise deletes characters between the cursor
              and column n.

       list ^[?
              Prints a sorted, columnated list of command names or file names
              (if any) that can complete the partial word containing the
              cursor.  Directory names have / appended to them.

       list-command ^X?
              Prints a sorted, columnated list of command names (if any) that
              can complete the partial word containing the cursor.

       list-file ^X^Y
              Prints a sorted, columnated list of file names (if any) that can
              complete the partial word containing the cursor.  File type
              indicators are appended as described under list above.

       newline ^J, ^M
              Causes the current input line to be processed by the shell.  The
              current cursor position may be anywhere on the line.

       newline-and-next ^O
              Causes the current input line to be processed by the shell, and
              the next line from history becomes the current line.  This is
              only useful after an up-history or search-history.

       no-op QUIT
              This does nothing.

       prefix-1 ^[
              Introduces a 2-character command sequence.

       prefix-2 ^X

       prefix-2 ^[[
              Introduces a 2-character command sequence.

       prev-hist-word n ^[., ^[_
              The last (nth) word of the previous command is inserted at the
              cursor.

       quote ^^
              The following character is taken literally rather than as an
              editing command.

       redraw ^L
              Reprints the prompt string and the current input line.

       search-character-backward n ^[^]
              Search backward in the current line for the nth occurrence of
              the next character typed.

       search-character-forward n ^]
              Search forward in the current line for the nth occurrence of the
              next character typed.

       search-history ^R
              Enter incremental search mode.  The internal history list is
              searched backwards for commands matching the input.  An initial
              ^ in the search string anchors the search.  The abort key will
              leave search mode.  Other commands will be executed after
              leaving search mode.  Successive search-history commands
              continue searching backward to the next previous occurrence of
              the pattern.  The history buffer retains only a finite number of
              lines; the oldest are discarded as necessary.

       set-mark-command ^[<space>
              Set the mark at the cursor position.

       stuff  On systems supporting it, pushes the bound character back onto
              the terminal input where it may receive special processing by
              the terminal handler.  This is useful for the BRL ^T mini-systat
              feature, for example.

       stuff-reset
              Acts like stuff, then aborts input the same as an interrupt.

       transpose-chars ^T
              If at the end of line, or if the gmacs option is set, this
              exchanges the two previous characters; otherwise, it exchanges
              the previous and current characters and moves the cursor one
              character to the right.

       up-history n ^P
              Scrolls the history buffer backward n lines (earlier).

       upcase-word n ^[U, ^[u
              Uppercases the next n words.

       version ^V
              Display the version of ksh.  The current edit buffer is restored
              as soon as any key is pressed (the key is then processed, unless
              it is a space).

       yank ^Y
              Inserts the most recently killed text string at the current
              cursor position.

       yank-pop ^[y
              Immediately after a yank, replaces the inserted text string with
              the next previous killed text string.

   Vi Editing Mode
       The vi command line editor in ksh has basically the same commands as
       the vi editor (see vi(1)), with the following exceptions:

         o    you start out in insert mode,

         o    there are file name and command completion commands (=, \, *,
              ^X, ^E, ^F and, optionally, <tab>),

         o    the _ command is different (in ksh it is the last argument
              command, in vi it goes to the start of the current line),

         o    the / and G commands move in the opposite direction as the j
              command

         o    and commands which don't make sense in a single line editor are
              not available (e.g., screen movement commands, ex : commands,
              etc.).

       Note that the ^X stands for control-X; also <esc>, <space> and <tab>
       are used for escape, space and tab, respectively (no kidding).

       Like vi, there are two modes: insert mode and command mode.  In insert
       mode, most characters are simply put in the buffer at the current
       cursor position as they are typed, however, some characters are treated
       specially.  In particular, the following characters are taken from
       current tty settings (see stty(1)) and have their usual meaning (normal
       values are in parentheses): kill (^U), erase (^?), werase (^W), eof
       (^D), intr (^C) and quit (^\).  In addition to the above, the following
       characters are also treated specially in insert mode:

        ^H     erases previous character
        ^V     literal next: the next character typed is not treated specially (can be used to insert the characters being described here)
        ^J ^M   end of line: the current line is read, parsed and executed by the shell
        <esc>   puts the editor in command mode (see below)
        ^E     command and file name enumeration (see below)
        ^F     command and file name completion (see below). If used twice in a row, the list of possible completions is displayed; if used a third time, the completion is undone.
        ^X     command and file name expansion (see below)
        <tab>   optional file name and command completion (see ^F above), enabled with set -o vi-tabcomplete

       In command mode, each character is interpreted as a command.
       Characters that don't correspond to commands, are illegal combinations
       of commands or are commands that can't be carried out all cause beeps.
       In the following command descriptions, a n indicates the command may be
       prefixed by a number (e.g., 10l moves right 10 characters); if no
       number prefix is used, n is assumed to be 1 unless otherwise specified.
       The term `current position' refers to the position between the cursor
       and the character preceding the cursor.  A `word' is a sequence of
       letters, digits and underscore characters or a sequence of non-letter,
       non-digit, non-underscore, non-white-space characters (e.g., ab2*&^
       contains two words) and a `big-word' is a sequence of non-white-space
       characters.

       Special ksh vi commands
              The following commands are not in, or are different from, the
              normal vi file editor:

              n_     insert a space followed by the nth big-word from the last
                     command in the history at the current position and enter
                     insert mode; if n is not specified, the last word is
                     inserted.

              #      insert the comment character (#) at the start of the
                     current line and return the line to the shell (equivalent
                     to I#^J).

              ng     like G, except if n is not specified, it goes to the most
                     recent remembered line.

              nv     edit line n using the vi editor; if n is not specified,
                     the current line is edited.  The actual command executed
                     is `fc -e ${VISUAL:-${EDITOR:-vi}} n'.

              * and ^X
                     command or file name expansion is applied to the current
                     big-word (with an appended *, if the word contains no
                     file globing characters) - the big-word is replaced with
                     the resulting words.  If the current big-word is the
                     first on the line (or follows one of the following
                     characters: ;, |, &, (, )) and does not contain a slash
                     (/) then command expansion is done, otherwise file name
                     expansion is done.  Command expansion will match the big-
                     word against all aliases, functions and built-in commands
                     as well as any executable files found by searching the
                     directories in the PATH parameter.  File name expansion
                     matches the big-word against the files in the current
                     directory.  After expansion, the cursor is placed just
                     past the last word and the editor is in insert mode.

              n\, n^F, n<tab> and n<esc>
                     command/file name completion: replace the current big-
                     word with the longest unique match obtained after
                     performing command/file name expansion.  <tab> is only
                     recognized if the vi-tabcomplete option is set, while
                     <esc> is only recognized if the vi-esccomplete option is
                     set (see set -o).  If n is specified, the nth possible
                     completion is selected (as reported by the command/file
                     name enumeration command).

              = and ^E
                     command/file name enumeration: list all the commands or
                     files that match the current big-word.

              ^V     display the version of pdksh; it is displayed until
                     another key is pressed (this key is ignored).

              @c     macro expansion: execute the commands found in the alias
                     _c.

       Intra-line movement commands

              nh and n^H
                     move left n characters.

              nl and n<space>
                     move right n characters.

              0      move to column 0.

              ^      move to the first non white-space character.

              n|     move to column n.

              $      move to the last character.

              nb     move back n words.

              nB     move back n big-words.

              ne     move forward to the end the word, n times.

              nE     move forward to the end the big-word, n times.

              nw     move forward n words.

              nW     move forward n big-words.

              %      find match: the editor looks forward for the nearest
                     parenthesis, bracket or brace and then moves the to the
                     matching parenthesis, bracket or brace.

              nfc    move forward to the nth occurrence of the character c.

              nFc    move backward to the nth occurrence of the character c.

              ntc    move forward to just before the nth occurrence of the
                     character c.

              nTc    move backward to just before the nth occurrence of the
                     character c.

              n;     repeats the last f, F, t or T command.

              n,     repeats the last f, F, t or T command, but moves in the
                     opposite direction.

       Inter-line movement commands

              nj and n+ and n^N
                     move to the nth next line in the history.

              nk and n- and n^P
                     move to the nth previous line in the history.

              nG     move to line n in the history; if n is not specified, the
                     number first remembered line is used.

              ng     like G, except if n is not specified, it goes to the most
                     recent remembered line.

              n/string
                     search backward through the history for the nth line
                     containing string; if string starts with ^, the remainder
                     of the string must appear at the start of the history
                     line for it to match.

              n?string
                     same as /, except it searches forward through the
                     history.

              nn     search for the nth occurrence of the last search string;
                     the direction of the search is the same as the last
                     search.

              nN     search for the nth occurrence of the last search string;
                     the direction of the search is the opposite of the last
                     search.

       Edit commands

              na     append text n times: goes into insert mode just after the
                     current position.  The append is only replicated if
                     command mode is re-entered (i.e., <esc> is used).

              nA     same as a, except it appends at the end of the line.

              ni     insert text n times: goes into insert mode at the current
                     position.  The insertion is only replicated if command
                     mode is re-entered (i.e., <esc> is used).

              nI     same as i, except the insertion is done just before the
                     first non-blank character.

              ns     substitute the next n characters (i.e., delete the
                     characters and go into insert mode).

              S      substitute whole line: all characters from the first non-
                     blank character to the end of line are deleted and insert
                     mode is entered.

              ncmove-cmd
                     change from the current position to the position
                     resulting from n move-cmds (i.e., delete the indicated
                     region and go into insert mode); if move-cmd is c, the
                     line starting from the first non-blank character is
                     changed.

              C      change from the current position to the end of the line
                     (i.e., delete to the end of the line and go into insert
                     mode).

              nx     delete the next n characters.

              nX     delete the previous n characters.

              D      delete to the end of the line.

              ndmove-cmd
                     delete from the current position to the position
                     resulting from n move-cmds; move-cmd is a movement
                     command (see above) or d, in which case the current line
                     is deleted.

              nrc    replace the next n characters with the character c.

              nR     replace: enter insert mode but overwrite existing
                     characters instead of inserting before existing
                     characters.  The replacement is repeated n times.

              n~     change the case of the next n characters.

              nymove-cmd
                     yank from the current position to the position resulting
                     from n move-cmds into the yank buffer; if move-cmd is y,
                     the whole line is yanked.

              Y      yank from the current position to the end of the line.

              np     paste the contents of the yank buffer just after the
                     current position, n times.

              nP     same as p, except the buffer is pasted at the current
                     position.

       Miscellaneous vi commands

              ^J and ^M
                     the current line is read, parsed and executed by the
                     shell.

              ^L and ^R
                     redraw the current line.

              n.     redo the last edit command n times.

              u      undo the last edit command.

              U      undo all changes that have been made to the current line.

              intr and quit
                     the interrupt and quit terminal characters cause the
                     current line to be deleted and a new prompt to be
                     printed.

FILES
       ~/.kshrc
       ~/.profile
       /etc/profile
       /etc/suid_profile

BUGS
       Any bugs in pdksh should be reported to pdksh@cs.mun.ca.  Please
       include the version of pdksh (echo $KSH_VERSION shows it), the machine,
       operating system and compiler you are using and a description of how to
       repeat the bug (a small shell script that demonstrates the bug is
       best).  The following, if relevant (if you are not sure, include them),
       can also helpful: options you are using (both options.h options and set
       -o options) and a copy of your config.h (the file generated by the
       configure script).  New versions of pdksh can be obtained from
       ftp://ftp.cs.mun.ca/pub/pdksh/.

       BTW, the most frequently reported bug is
               echo hi | read a; echo $a   # Does not print hi
       I'm aware of this and there is no need to report it.

VERSION
       This page documents version
        @(#)PD KSH v5.2.14 99/07/13.2 of the public domain korn shell.

AUTHORS
       This shell is based on the public domain 7th edition Bourne shell clone
       by Charles Forsyth and parts of the BRL shell by Doug A. Gwyn, Doug
       Kingston, Ron Natalie, Arnold Robbins, Lou Salkind and others.  The
       first release of pdksh was created by Eric Gisin, and it was
       subsequently maintained by John R. MacMillan (chance!john@sq.sq.com),
       and Simon J. Gerraty (sjg@zen.void.oz.au).  The current maintainer is
       Michael Rendell (michael@cs.mun.ca).  The CONTRIBUTORS file in the
       source distribution contains a more complete list of people and their
       part in the shell's development.

SEE ALSO
       awk(1), sh(1), csh(1), ed(1), getconf(1), getopt(1), sed(1), stty(1),
       vi(1), dup(2), execve(2), getgid(2), getuid(2), open(2), pipe(2),
       wait(2), getopt(3), rand(3), signal(3), system(3), environ(7)

       The KornShell Command and Programming Language, Morris Bolsky and David
       Korn, 1989, ISBN 0-13-516972-0.

       UNIX Shell Programming, Stephen G. Kochan, Patrick H. Wood, Hayden.

       IEEE Standard for information Technology - Portable Operating System
       Interface (POSIX) - Part 2: Shell and Utilities, IEEE Inc, 1993, ISBN
       1-55937-255-9.



                                August 19, 1996                         KSH(1)