OKSH(1)                 FreeBSD General Commands Manual                OKSH(1)

     oksh, rksh â<“ public domain Korn shell

     oksh [-+abCefhiklmnpruvXx] [-+o option]
          [-c string | -s | file [argument ...]]

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

     The options are as follows:

     -c string
             oksh will execute the command(s) contained in string.

     -i      Interactive shell.  A shell is â<œinteractiveâ< if this option is
             used or if both standard input and standard error are attached to
             a tty(4).  An interactive shell has job control enabled, ignores
             the SIGINT, SIGQUIT, and SIGTERM signals, and prints prompts
             before reading input (see the PS1 and PS2 parameters).  For non-
             interactive shells, the trackall option is on by default (see the
             set command below).

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

     -p      Privileged shell.  A shell is â<œprivilegedâ< if this 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) and 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).

     -r      Restricted shell.  A shell is â<œrestrictedâ< if this option is
             used; if the basename the shell was invoked with was â<œrkshâ<; or
             if the SHELL parameter is set to â<œrkshâ<.  The following
             restrictions come into effect after the shell processes any
             profile and ENV files:

             â<¢<¢   The cd command is disabled.
             â<¢<¢   The SHELL, ENV, and PATH parameters cannot be changed.
             â<¢<¢   Command names can't be specified with absolute or relative
             â<¢<¢   The -p option of the built-in command command can't be used.
             â<¢<¢   Redirections that create files can't be used (i.e. â<˜>â<™, â<˜>|â<™,
                 â<˜>>â<™, â<˜<>â<™).

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

     In addition to the above, the options described in the set built-in
     command can also be used on the command line: both [-+abCefhkmnuvXx] and
     [-+o option] can be used for single letter or long options, respectively.

     If neither the -c nor the -s option is 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 the
     standard input.  The name of the shell (i.e. the contents of $0) 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 basename the shell was
     called with (i.e. argv[0]) is used.

     If the ENV parameter is set when an interactive shell starts (or, in the
     case of login shells, after any profiles are processed), its value is
     subjected to parameter, command, arithmetic, and tilde (â<˜~â<™) substitution
     and the resulting file (if any) is read and executed.  In order to have
     an interactive (as opposed to login) shell process a startup file, ENV
     may be set and exported (see below) in $HOME/.profile - future
     interactive shell invocations will process any file pointed to by $ENV:

           export ENV=$HOME/.kshrc

     $HOME/.kshrc is then free to specify instructions for interactive shells.
     For example, the global configuration file may be sourced:

           . /etc/ksh.kshrc

     The above strategy may be employed to keep setup procedures for login
     shells in $HOME/.profile and setup procedures for interactive shells in
     $HOME/.kshrc.  Of course, since login shells are also interactive, any
     commands placed in $HOME/.kshrc will be executed by login shells too.

     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 whitespace
     characters (space, tab, and newline) or meta-characters (â<˜<â<™, â<˜>â<™, â<˜|â<™,
     â<˜;â<™, â<˜(â<™, â<˜)â<™, and â<˜&â<™).  Aside from delimiting words, spaces and tabs
     are ignored, while newlines usually delimit commands.  The meta-
     characters are used in building the following tokens: â<˜<â<™, â<˜<&â<™, â<˜<<â<™,
     â<˜>â<™, â<˜>&â<™, â<˜>>â<™, etc. are used to specify redirections (see Input/output
     redirection below); â<˜|â<™ is used to create pipelines; â<˜|&â<™ is used to
     create co-processes (see Co-processes below); â<˜;â<™ is used to separate
     commands; â<˜&â<™ is used to create asynchronous pipelines; â<˜&&â<™ and â<˜||â<™ are
     used to specify conditional execution; â<˜;;â<™ is used in case statements;
     â<˜(( .. ))â<™ is used in arithmetic expressions; and lastly, â<˜( .. )â<™ is
     used to create subshells.

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

     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 0 if there were no command substitutions.

     Commands can be chained together using the â<˜|â<™ 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, unless the pipefail option is
     set.  A pipeline may be prefixed by the â<˜!â<™ 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; if the original
     status was not 0, the complemented status will be 0.

     Lists of commands can be created by separating pipelines by any of the
     following tokens: â<˜&&â<™, â<˜||â<™, â<˜&â<™, â<˜|&â<™, and â<˜;â<™.  The first two are for
     conditional execution: â<œcmd1 && cmd2â< executes cmd2 only if the exit
     status of cmd1 is zero; â<˜||â<™ is the opposite â<” cmd2 is executed only if
     the exit status of cmd1 is non-zero.  â<˜&&â<™ and â<˜||â<™ have equal precedence
     which is higher than that of â<˜&â<™, â<˜|&â<™, and â<˜;â<™, which also have equal
     precedence.  The â<˜&&â<™ and â<˜||â<™ operators are "left-associative".  For
     example, both of these commands will print only "bar":

           $ false && echo foo || echo bar
           $ true || echo foo && echo bar

     The â<˜&â<™ 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 SIGINT and SIGQUIT ignored and with input
     redirected from /dev/null (however, redirections specified in the
     asynchronous command have precedence).  The â<˜|&â<™ operator starts a co-
     process which is a special kind of asynchronous process (see Co-processes
     below).  A command must follow the â<˜&&â<™ and â<˜||â<™ operators, while it need
     not follow â<˜&â<™, â<˜|&â<™, or â<˜;â<™.  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   esac       in       until   ((   }
           do     fi         name     while   ))
           done   for        select   !       [[
           elif   function   then     (       ]]
           else   if         time     )       {

     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 semicolon, a
     newline, or a (syntactically correct) reserved word.  For example, the
     following are all valid:

           $ { echo foo; echo bar; }
           $ { echo foo; echo bar<newline> }
           $ { { echo foo; echo bar; } }

     This is not valid:

           $ { echo foo; echo bar }

     (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 â<˜{â<™ and â<˜}â<™ are reserved words, not meta-characters.

     case word in [[(] pattern [| pattern] ...) list ;; ] ... esac
             The case statement attempts to match word against a specified
             pattern; 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 â<˜.â<™ and â<˜/â<™ are dropped.  Note that any
             unquoted space before and after a pattern is stripped; any space
             within 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

     for name [in [word ...]]; do list; done
             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 there are no items, list is not executed and 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 ...]; do list; done
             The select statement provides an automatic method of presenting
             the user with a menu and selecting from it.  An enumerated list
             of the specified word(s) is printed on standard error, followed
             by a prompt (PS3: normally â<˜#? â<™).  A number corresponding to one
             of the enumerated words is then read from standard input, name is
             set to the selected word (or 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 reprinted without
             executing list.

             When list completes, the enumerated list is printed if REPLY is
             NULL, the prompt is printed, and so on.  This process continues
             until an end-of-file is read, an interrupt is received, or a
             break statement is executed inside the loop.  If â<œin word ...â< 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 pre-checked 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

     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

     (( expression ))
             The arithmetic expression expression is evaluated; equivalent to
             let expression (see Arithmetic expressions and the let command,

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

                   â<¢<¢   Field splitting and file name generation are not
                       performed on arguments.

                   â<¢<¢   The -a (AND) and -o (OR) operators are replaced with
                       â<˜&&â<™ and â<˜||â<™, respectively.

                   â<¢<¢   Operators (e.g. â<˜-fâ<™, â<˜=â<™, â<˜!â<™) must be unquoted.

                   â<¢<¢   The second operand of the â<˜!=â<™ and â<˜=â<™ expressions are
                       patterns (e.g. the comparison [[ foobar = f*r ]]

                   â<¢<¢   The â<˜<â<™ and â<˜>â<™ binary operators do not need to be
                       quoted with the â<˜\â<™ character.

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

                   â<¢<¢   Parameter, command, and arithmetic substitutions are
                       performed as expressions are evaluated and lazy
                       expression evaluation is used for the â<˜&&â<™ and â<˜||â<™
                       operators.  This means that in the following statement,
                       $(< foo) is evaluated if and only if the file foo
                       exists and is readable:

                             $ [[ -r foo && $(< foo) = b*r ]]

     Quoting is used to prevent the shell from treating characters or words
     specially.  There are three methods of quoting.  First, â<˜\â<™ quotes the
     following character, unless it is at the end of a line, in which case
     both the â<˜\â<™ and the newline are stripped.  Second, a single quote (â<˜'â<™)
     quotes everything up to the next single quote (this may span lines).
     Third, a double quote (â<˜"â<™) quotes all characters, except â<˜$â<™, â<˜`â<™ and
     â<˜\â<™, up to the next unquoted double quote.  â<˜$â<™ and â<˜`â<™ 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 â<˜\â<™ inside a double-quoted string is
     followed by â<˜\â<™, â<˜$â<™, â<˜`â<™, or â<˜"â<™, it is replaced by the second
     character; if it is followed by a newline, both the â<˜\â<™ and the newline
     are stripped; otherwise, both the â<˜\â<™ and the character following are

     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'
           login='exec login'
           nohup='nohup '
           r='fc -s'
           stop='kill -STOP'

     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(1), cc(1), chmod(1), cp(1), date(1),
     ed(1), emacs, grep(1), ls(1), mail(1), make(1), mv(1), pr(1), rm(1),
     sed(1), sh(1), vi(1), and who(1).

     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 â<œIFS whitespaceâ<.  Sequences of one or more
     IFS whitespace characters, in combination with zero or one non-IFS
     whitespace characters, delimit a field.  As a special case, leading and
     trailing IFS whitespace is stripped (i.e. no leading or trailing empty
     field is created by it); leading non-IFS whitespace does create an empty

     Example: If IFS is set to â<œ<space>:â<, and VAR is set to
     â<œ<space>A<space>:<space><space>B::Dâ<, the substitution for $VAR results
     in four fields: â<˜Aâ<™, â<˜Bâ<™, â<˜â<™ (an empty field), and â<˜Dâ<™.  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

     Also, note that the field splitting applies only to the immediate result
     of the substitution.  Using the previous example, the substitution for
     $VAR:E results in the fields: â<˜Aâ<™, â<˜Bâ<™, â<˜â<™, and â<˜D:Eâ<™, not â<˜Aâ<™, â<˜Bâ<™, â<˜â<™,
     â<˜Dâ<™, and â<˜Eâ<™.  This behavior is POSIX compliant, but incompatible with
     some other shell implementations which do field splitting on the word
     which contained the substitution or use IFS as a general whitespace

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

     A command substitution is replaced by the output generated by the
     specified command, which is run in a subshell.  For $(command)
     substitutions, normal quoting rules are used when command is parsed;
     however, for the `command` form, a â<˜\â<™ followed by any of â<˜$â<™, â<˜`â<™, or
     â<˜\â<™ is stripped (a â<˜\â<™ 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.  Note that $(< foo)
     has the same effect as $(cat foo), but it is carried out more efficiently
     because no process is started.

     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 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 (â<˜_â<™ counts as a letter).  The latter form can be treated as
     arrays by appending an array index of the form [expr] where expr is an
     arithmetic expression.  Parameter substitutions take the form $name,
     ${name}, or ${name[expr]} where name is a parameter name.  If expr is a
     literal â<˜@â<™ then the named array is expanded using the same quoting rules
     as â<˜$@â<™, while if expr is a literal â<˜*â<™ then the named array is expanded
     using the same quoting rules as â<˜$*â<™.  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 â<˜#â<™, â<˜PWDâ<™, and â<˜$â<™; 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 â<œFOOâ< to â<œbarâ<; 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 the implications of this).  Note that both the parameter name and the
     â<˜=â<™ 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 the
     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:

             If name is set and not NULL, it is substituted; otherwise, word
             is substituted.

             If name is set and not NULL, word is substituted; otherwise,
             nothing is substituted.

             If name is set and not NULL, it is substituted; otherwise, it is
             assigned word and the resulting value of name is substituted.

             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 sourced using the â<˜.â<™ built-in).  If word is omitted,
             the string â<œparameter null or not setâ< is used instead.

     In the above modifiers, the â<˜:â<™ 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

     The following forms of parameter substitution can also be used:

             The number of positional parameters if name is â<˜*â<™, â<˜@â<™, or not
             specified; otherwise the length of the string value of parameter

             The number of elements in the array name.

             If pattern matches the beginning of the value of parameter name,
             the matched text is deleted from the result of substitution.  A
             single â<˜#â<™ results in the shortest match, and two of them result
             in the longest match.

             Like ${..#..} substitution, but it deletes from the end of the

     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

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

     $        The PID of the shell, or the PID of the original shell if it is
              a subshell.  Do NOT use this mechanism for generating temporary
              file names; see mktemp(1) instead.

     -        The concatenation of the current single letter options (see the
              set command below for a 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 of the shell, determined as follows: the first argument
              to oksh if it was invoked with the -c option and arguments were
              given; otherwise the file argument, if it was supplied; or else
              the basename the shell was invoked with (i.e. argv[0]).  $0 is
              also set to the name of the current script or the name of the
              current function, if it was defined with the function keyword
              (i.e. a Korn shell style function).

     1 ... 9  The first nine positional parameters that were supplied to the
              shell, function, or script sourced using the â<˜.â<™ built-in.
              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
                the MAILPATH parameter, below).

     CDPATH     Search path for the cd built-in command.  It works the same
                way as PATH for those directories not beginning with â<˜/â<™ or
                â<˜.â<™ in cd commands.  Note that if CDPATH is set and does not
                contain â<˜.â<™ or an empty path, the current directory is not
                searched.  Also, the cd built-in command will display the
                resulting directory when a match is found in any search path
                other than the empty path.

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

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

                Note: traditionally, EDITOR was used to specify the name of an
                (old-style) line editor, such as ed(1), and VISUAL was used to
                specify a (new-style) screen editor, such as vi(1).  Hence if
                VISUAL is set, it overrides EDITOR.

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

     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 â<œ#!shellâ< 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.

                A colon separated list of history settings.  If ignoredups is
                present, lines identical to the previous history line will not
                be saved.  If ignorespace is present, lines starting with a
                space will not be saved.  Unknown settings are ignored.

     HISTFILE   The name of the file used to store command 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 to
                the same file.

                Note: If HISTFILE isn't set, no history file is used.  This is
                different from the original Korn shell, which uses

     HISTSIZE   The number of commands normally stored for history.  The
                default is 500.

     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.

                The version of the shell and the date the version was created

     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.

     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 set to 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 â<˜?â<™ 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 â<œyou have mail
                in $_â<.

     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 next argument to be processed when using
                getopts.  Assigning 1 to this parameter causes getopts to
                process arguments from the beginning the next time it is

     PATH       A colon separated list of directories that are searched when
                looking for commands and files sourced using the â<˜.â<™ command
                (see below).  An empty string resulting from a leading or
                trailing colon, or two adjacent colons, is treated as a â<˜.â<™
                (the current directory).

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

     PPID       The process ID of the shell's parent (read-only).

     PS1        The primary prompt for interactive shells.  Parameter,
                command, and arithmetic substitutions are performed, and the
                prompt string can be customised using backslash-escaped
                special characters.

                Note that since the command-line editors try to figure out how
                long the prompt is (so they know how far it is to the 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 using the \[...\] substitution (see
                below) or 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.  By the way, don't blame me for this hack; it's in
                the original oksh.

                The default prompt is the first part of the hostname, followed
                by â<˜$ â<™ for non-root users, â<˜# â<™ for root.

                The following backslash-escaped special characters can be used
                to customise the prompt:

                \a            Insert an ASCII bell character.
                \d            The current date, in the format â<œDay Month Dateâ<
                              for example â<œWed Nov 03â<.
                \D{format}    The current date, with format converted by
                              strftime(3).  The braces must be specified.
                \e            Insert an ASCII escape character.
                \h            The hostname, minus domain name.
                \H            The full hostname, including domain name.
                \j            Current number of jobs running (see Job control
                \l            The controlling terminal.
                \n            Insert a newline character.
                \r            Insert a carriage return character.
                \s            The name of the shell.
                \t            The current time, in 24-hour HH:MM:SS format.
                \T            The current time, in 12-hour HH:MM:SS format.
                \@            The current time, in 12-hour HH:MM:SS AM/PM
                \A            The current time, in 24-hour HH:MM format.
                \u            The current user's username.
                \v            The current version of oksh.
                \V            Like â<˜\vâ<™, but more verbose.
                \w            The current working directory.  $HOME is
                              abbreviated as â<˜~â<™.
                \W            The basename of the current working directory.
                              $HOME is abbreviated as â<˜~â<™.
                \!            The current history number.  An unescaped â<˜!â<™
                              will produce the current history number too, as
                              per the POSIX specification.  A literal â<˜!â<™ can
                              be put in the prompt by placing â<˜!!â<™ in PS1.
                \#            The current command number.  This could be
                              different to the current history number, if
                              HISTFILE contains a history list from a previous
                \$            The default prompt character i.e. â<˜#â<™ if the
                              effective UID is 0, otherwise â<˜$â<™.  Since the
                              shell interprets â<˜$â<™ as a special character
                              within double quotes, it is safer in this case
                              to escape the backslash than to try quoting it.
                \nnn          The octal character nnn.
                \\            Insert a single backslash character.
                \[            Normally the shell keeps track of the number of
                              characters in the prompt.  Use of this sequence
                              turns off that count.
                \]            Use of this sequence turns the count back on.

                Note that the backslash itself may be interpreted by the
                shell.  Hence, to set PS1 either escape the backslash itself,
                or use double quotes.  The latter is more practical:

                      PS1="\u "

                This is a more complex example, which does not rely on the
                above backslash-escaped sequences.  It embeds the current
                working directory, in reverse video, in the prompt string:

                      x=$(print \\001)
                      PS1="$x$(print \\r)$x$(tput so)$x\$PWD$x$(tput se)$x> "

     PS2        Secondary prompt string, by default â<˜> â<™, used when more input
                is needed to complete a command.

     PS3        Prompt used by the select statement when reading a menu
                selection.  The default is â<˜#? â<™.

     PS4        Used to prefix commands that are printed during execution
                tracing (see the set -x command below).  Parameter, command,
                and arithmetic substitutions are performed before it is
                printed.  The default is â<˜+ â<™.

     PWD        The current working directory.  May be unset or NULL if the
                shell doesn't know where it is.

     RANDOM     A random number generator.  Every time RANDOM is referenced,
                it is assigned the next random number in the range 0-32767.
                By default, arc4random(3) is used to produce values.  If the
                variable RANDOM is assigned a value, the value is used as the
                seed to srand_deterministic(3) and subsequent references of
                RANDOM produce a predictable sequence.

     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.

     TERM       The user's terminal type.  If set, it will be used to
                determine the escape sequence used to clear the screen.

     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 temporary shell 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 â<œviâ<, â<œemacsâ<,
                or â<œgmacsâ<, the vi(1), emacs, or gmacs (Gosling emacs) editing
                mode is enabled, respectively.  See also the EDITOR parameter,

   Tilde expansion
     Tilde expansion, which is done in parallel with parameter substitution,
     is done on words starting with an unquoted â<˜~â<™.  The characters following
     the tilde, up to the first â<˜/â<™, if any, are assumed to be a login name.
     If the login name is empty, â<˜+â<™, or â<˜-â<™, 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 (such as those preceding a simple-command or
     those occurring in the arguments of alias, export, readonly, and
     typeset), tilde expansion is done after any assignment (i.e. after the
     equals sign) or after an unquoted colon (â<˜:â<™); 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 take the following form:


     The expressions are expanded to N words, each of which is the
     concatenation of prefix, stri, and suffix (e.g. â<œa{c,b{X,Y},d}eâ< expands
     to four words: â<œaceâ<, â<œabXeâ<, â<œabYeâ<, and â<œadeâ<).  As noted in the
     example, brace expressions can be nested and the resulting words are not
     sorted.  Brace expressions must contain an unquoted comma (â<˜,â<™) for
     expansion to occur (e.g. {} and {foo} are not expanded).  Brace expansion
     is carried out after parameter substitution and before file name

   File name patterns
     A file name pattern is a word containing one or more unquoted â<˜?â<™, â<˜*â<™,
     â<˜+â<™, â<˜@â<™, or â<˜!â<™ characters or â<œ[..]â< 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

     ?       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 â<˜-â<™
             (e.g. â<œ[a0-9]â< matches the letter â<˜aâ<™ or any digit).  In order to
             represent itself, a â<˜-â<™ must either be quoted or the first or
             last character in the character list.  Similarly, a â<˜]â<™ must be
             quoted or the first character in the list if it is to represent
             itself instead of the end of the list.  Also, a â<˜!â<™ 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.

             Within a bracket expression, the name of a character class
             enclosed in â<˜[:â<™ and â<˜:]â<™ stands for the list of all characters
             belonging to that class.  Supported character classes:

                   alnum   cntrl   lower   space
                   alpha   digit   print   upper
                   blank   graph   punct   xdigit

             These match characters using the macros specified in isalnum(3),
             isalpha(3), and so on.  A character class may not be used as an
             endpoint of a range.

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

             Matches any string of characters that matches zero or more
             occurrences of the specified patterns.  Example: The pattern
             *(foo|bar) matches the strings â<œâ<, â<œfooâ<, â<œbarâ<, â<œfoobarfooâ<,

             Matches any string of characters that matches one or more
             occurrences of the specified patterns.  Example: The pattern
             +(foo|bar) matches the strings â<œfooâ<, â<œbarâ<, â<œfoobarâ<, etc.

             Matches the empty string or a string that matches one of the
             specified patterns.  Example: The pattern ?(foo|bar) only matches
             the strings â<œâ<, â<œfooâ<, and â<œbarâ<.

             Matches a string that matches one of the specified patterns.
             Example: The pattern @(foo|bar) only matches the strings â<œfooâ<
             and â<œbarâ<.

             Matches any string that does not match one of the specified
             patterns.  Examples: The pattern !(foo|bar) matches all strings
             except â<œfooâ< and â<œbarâ<; the pattern !(*) matches no strings; the
             pattern !(?)* matches all strings (think about it).

     Unlike most shells, ksh never matches â<˜.â<™ and â<˜..â<™.

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

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

   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

     > 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 if file exists it 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

     <> 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 â<œhere documentâ<), 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 (â<˜\â<™) escapes for â<˜$â<™, â<˜`â<™,
             â<˜\â<™, and â<˜\newlineâ<™.  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 â<˜pâ<™, indicating the file descriptor
             associated with the output of the current co-process; or the
             character â<˜-â<™, 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 expanded 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 the following will print an error with a
     line number prepended to it:

           $ cat /foo/bar 2>&1 > /dev/null | cat -n

   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.

     Expressions 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 operators:

           ?: (precedence is immediately higher than assignment)

     Grouping operators:

           ( )

     A parameter that is NULL or unset evaluates to 0.  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.  Additionally, integers may be prefixed with â<˜0Xâ<™ or
     â<˜0xâ<™ (specifying base 16) or â<˜0â<™ (base 8) in all forms of arithmetic
     expressions, except as numeric arguments to the test command.

     The operators are evaluated as follows:

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

           unary -

           !       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

           --      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 the value
                   of the expression on the right-hand side.

           =       Assignment; the 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⟩, with any operator precedence in
                   ⟨expr⟩ preserved.  For example, â<œvar1 *= 5 + 3â< is the same
                   as specifying â<œvar1 = var1 * (5 + 3)â<.

           ||      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) XOR (exclusive-OR).

           &       Arithmetic (bit-wise) AND.

           ==      Equal; the result is 1 if both arguments are equal, 0 if

           !=      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.

                   If ⟨arg1⟩ is non-zero, the result is ⟨arg2⟩; otherwise the
                   result is ⟨arg3⟩.

     A co-process, which is a pipeline created with the â<˜|&â<™ 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's 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:

     â<¢<¢   The only way to close the co-process's 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

     â<¢<¢   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's 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-process output when the most recently started co-process (instead
         of when all sharing co-processes) exits.

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

     Functions are defined using either Korn shell function function-name
     syntax or the Bourne/POSIX shell function-name() syntax (see below for
     the difference between the two forms).  Functions are like .-scripts
     (i.e. scripts sourced using the â<˜.â<™ built-in) in that they are executed
     in the current environment.  However, unlike .-scripts, shell arguments
     (i.e. positional parameters $1, $2, etc.) are never visible inside them.
     When the shell is determining the location of a command, functions are
     searched after special built-in commands, 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.  The autoload command (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, â<œtraceâ< and â<œexportâ<, 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 function's
     duration; otherwise, the xtrace option is turned off.  The â<œexportâ<
     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:

     â<¢<¢   The $0 parameter is set to the name of the function (Bourne-style
         functions leave $0 untouched).

     â<¢<¢   Parameter assignments preceding function calls are not kept in the
         shell environment (executing Bourne-style functions will keep

     â<¢<¢   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

   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:

     â<¢kill -l output.  In POSIX mode, only signal names are listed (in a
         single line); in non-POSIX mode, signal numbers, names, and
         descriptions are printed (in columns).

     â<¢echo options.  In POSIX mode, -e and -E are not treated as options,
         but printed like other arguments; in non-POSIX mode, these options
         control the interpretation of backslash sequences.

     â<¢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.

     â<¢eval exit status.  If eval gets to see an empty command (i.e. 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).

     â<¢getopts.  In POSIX mode, options must start with a â<˜-â<™; in non-POSIX
         mode, options can start with either â<˜-â<™ or â<˜+â<™.

     â<¢<¢   Brace expansion (also known as alternation).  In POSIX mode, brace
         expansion is disabled; in non-POSIX mode, brace expansion is 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.

     â<¢set -.  In POSIX mode, this does not clear the verbose or xtrace
         options; in non-POSIX mode, it does.

     â<¢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.

     â<¢<¢   Argument expansion of the alias, export, readonly, and typeset
         commands.  In POSIX mode, normal argument expansion is done; in non-
         POSIX mode, field splitting, file globbing, brace expansion, and
         (normal) tilde expansion are turned off, while assignment tilde
         expansion is turned on.

     â<¢<¢   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 always be digits.

     â<¢<¢   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 uses parameter â<˜iâ<™ in POSIX mode
         and â<˜jâ<™ in non-POSIX mode:

               alias a='for ' i='j'
               a i in 1 2; do echo i=$i j=$j; done

     â<¢test.  In POSIX mode, the expression â<˜-tâ<™ (preceded by some number of
         â<˜!â<™ 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(4) (i.e. the
         fd argument to the -t test may be left out and defaults to 1).

   Strict Bourne shell mode
     When the sh option is enabled (see the set command), oksh will behave
     like sh(1) in the following ways:

     â<¢<¢   The parameter $_ is not set to:

         -   the expanded alias' full program path after entering commands
             that are tracked aliases
         -   the last argument on the command line after entering external
         -   the file that changed when MAILPATH is set to monitor a mailbox

     â<¢<¢   File descriptors are left untouched when executing exec with no

     â<¢<¢   Backslash-escaped special characters are not substituted in PS1.

     â<¢<¢   Sequences of â<˜((...))â<™ are not interpreted as arithmetic expressions.

   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 the set command
     below), some special commands are very special in that no field
     splitting, file globbing, 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

     ., :, break, continue, eval, exec, exit, export, readonly, return, set,
     shift, times, trap, unset

     Additional oksh special commands

     builtin, typeset

     Very special commands (when POSIX mode is off)

     alias, readonly, set, typeset

     POSIX regular commands

     alias, bg, cd, command, false, fc, fg, getopts, jobs, kill, pwd, read,
     true, umask, unalias, wait

     Additional oksh regular commands

     [, echo, let, print, suspend, test, ulimit, whence

     Once the type of 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 [arg ...]
             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] | +-x] [-p] [+] [name [=value] ...]
             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 â<˜+â<™, or a lone â<˜+â<™ is given on the
             command line, only name is printed.

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

             If the -p option is used, each alias is prefixed with the string
             â<œalias â<.

             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 -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 effect).

     bg [job ...]
             Resume the specified stopped job(s) in the background.  If no
             jobs are specified, %+ is assumed.  See Job control below for
             more information.

     bind [-l]
             The current bindings are listed.  If the -l flag is given, bind
             instead lists the names of the functions to which keys may be
             bound.  See Emacs editing mode for more information.

     bind [-m] string=[substitute] ...
     bind string=[editing-command] ...
             In Emacs editing mode, the specified editing command is bound to
             the given string.  Future input of the string will cause the
             editing command to be immediately invoked.  Bindings have no
             effect in Vi editing mode.

             If the -m flag is given, the specified input string will
             afterwards be immediately replaced by the given substitute
             string, which may contain editing commands.  Control characters
             may be written using caret notation.  For example, ^X represents

             If a certain character occurs as the first character of any bound
             multi-character string sequence, that character becomes a command
             prefix character.  Any character sequence that starts with a
             command prefix character but that is not bound to a command or
             substitute is implicitly considered as bound to the â<˜errorâ<™
             command.  By default, two command prefix characters exist: Escape
             (^[) and Control-X (^X).

             The following default bindings show how the arrow keys on an ANSI
             terminal or xterm are bound (of course some escape sequences
             won't work out quite this nicely):

                   bind '^[[A'=up-history
                   bind '^[[B'=down-history
                   bind '^[[C'=forward-char
                   bind '^[[D'=backward-char

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

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

     cd [-LP] [dir]
             Set the working directory to dir.  If the parameter CDPATH is
             set, it lists the search path for the directory containing dir.
             A NULL path or â<˜.â<™ means the current directory.  If dir is found
             in any component of the CDPATH search path other than the NULL
             path, the name of the new working directory will be written to
             standard output.  If dir is missing, the home directory HOME is
             used.  If dir is â<˜-â<™, the previous working directory is used (see
             the OLDPWD parameter).

             If the -L option (logical path) is used or if the physical option
             isn't set (see the set command below), references to â<˜..â<™ in dir
             are relative to the path used to get to the directory.  If the -P
             option (physical path) is used or if the physical option is set,
             â<˜..â<™ is relative to the filesystem directory tree.  The PWD and
             OLDPWD parameters are updated to reflect the current and old
             working 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 [arg ...]
             If neither the -v nor -V option is given, cmd is executed exactly
             as if command had not been specified, with two exceptions:
             firstly, cmd cannot be an alias or a shell function; and
             secondly, 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 POSIX-ish systems, it is the value
             returned by getconf PATH).  Nevertheless, reserved words,
             aliases, shell functions, and builtin commands are still found
             before external commands.

             If the -v option is given, instead of executing cmd, information
             about what would be executed is given (and the same is done for
             arg ...).  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 [level]
             Jumps to the beginning of the levelth inner-most for, select,
             until, or while loop.  level defaults to 1.

     echo [-Een] [arg ...]
             Prints its arguments (separated by spaces) followed by a newline,
             to the standard output.  The newline is suppressed if any of the
             arguments contain the backslash sequence â<˜\câ<™.  See the print
             command below for a list of other backslash sequences that are

             The options are provided for compatibility with BSD shell
             scripts.  The -n option suppresses the trailing newline, -e
             enables backslash interpretation (a no-op, since this is normally
             done), and -E suppresses backslash interpretation.  If the posix
             option is set, only the first argument is treated as an option,
             and only if it is exactly â<œ-nâ<.

     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

             If no command is given except for I/O redirection, the I/O
             redirection is permanent and the shell is not replaced.  Any file
             descriptors greater than 2 which are opened or dup(2)'d 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

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

     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 are 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]]
             Fix command.  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 standard output, 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 -s [-g] [old=new] [prefix]
             Re-execute the most recent command beginning with prefix, or the
             previous command if no prefix is specified, performing the
             optional substitution of old with new.  If -g is specified, all
             occurrences of old are replaced with new.  The editor is not
             invoked when the -s flag is used.  The obsolescent equivalent â<œ-e
             -â< is also accepted.  This command is usually accessed with the
             predefined alias r='fc -s'.

     fg [job ...]
             Resume the specified job(s) in the foreground.  If no jobs are
             specified, %+ is assumed.  See Job control below for more

     getopts optstring name [arg ...]
             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 argument to be
             processed by the next call to getopts in the shell parameter
             OPTIND.  If the option was introduced with a â<˜+â<™, the option
             placed in name is prefixed with a â<˜+â<™.  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.  Furthermore, if optstring does not begin with a colon,
             a question mark is placed in name, OPTARG is unset, and an error
             message is printed to standard error.

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

             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 were a
             command name and added to the hash table if it is an executable

     jobs [-lnp] [job ...]
             Display information about the specified job(s); 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

     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 TERM signal 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 signal name corresponding to exit-status.  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 [-nprsu[n] | -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 â<˜\bâ<™, â<˜\fâ<™, â<˜\nâ<™, â<˜\râ<™, â<˜\tâ<™, â<˜\vâ<™, and â<˜\0###â<™
             (â<˜#â<™ is an octal digit, of which there may be 0 to 3).  â<˜\câ<™ is
             equivalent to using the -n option.  â<˜\â<™ 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(1)
             command, which does not process â<˜\â<™ sequences unless the -e
             option is given.  As above, the -n option suppresses the trailing

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

     read [-prsu[n]] [parameter ...]
             Reads a line of input from the standard input, separates the line
             into fields using the IFS parameter (see Substitution above), and
             assigns 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 the 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(4) (e.g. read nfoo?'number of foos: ').

             The -un and -p options cause input to be read from file
             descriptor n (n defaults to 0 if omitted) 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 read-only attribute of the named parameters.  If values
             are given, parameters are set to them before setting the
             attribute.  Once a parameter is made read-only, it cannot be
             unset and its value cannot be changed.

             If no parameters are specified, the names of all parameters with
             the read-only attribute are printed one per line, unless the -p
             option is used, in which case readonly commands defining all
             read-only 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 ksh 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 name          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
                              arguments); the rest are left untouched.

             -a | allexport   All new parameters are created with the export

             -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.  Instead, >| must be used to force an

             -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.  For && or ||, only the status
                              of the last command is tested.

             -f | noglob      Do not expand file name patterns.

             -h | trackall    Create tracked aliases for all executed commands
                              (see Aliases above).  Enabled by default for
                              non-interactive shells.

             -k | keyword     Parameter assignments are recognized anywhere in
                              a command.

             -m | monitor     Enable job control (default for interactive

             -n | noexec      Do not execute any commands.  Useful for
                              checking the syntax of scripts (ignored if

             -p | privileged  The shell is a privileged shell.  It is set
                              automatically if, when the shell starts, the
                              real UID or GID does not match the effective UID
                              (EUID) or GID (EGID), respectively.  See 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 with 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 â<˜-â<™, â<˜+â<™, or â<˜=â<™
                              modifiers is used.

             -v | verbose     Write shell input to standard error as it is

             -X | markdirs    Mark directories with a trailing â<˜/â<™ during file
                              name generation.

             -x | xtrace      Print commands and parameter assignments when
                              they are executed, preceded by the value of PS4.

             bgnice           Background jobs are run with lower priority.

             braceexpand      Enable brace expansion (a.k.a. alternation).

             csh-history      Enables a subset of csh(1)-style history editing
                              using the â<˜!â<™ character.

             emacs            Enable BRL emacs-like command-line editing
                              (interactive shells only); see Emacs editing

             gmacs            Enable gmacs-like 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 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.

             interactive      The shell is an interactive shell.  This option
                              can only be used when the shell is invoked.  See
                              above for a description of what this means.

             login            The shell is a login shell.  This option can
                              only be used when the shell is invoked.  See
                              above for a description of what this means.

             nohup            Do not kill running jobs with a SIGHUP signal
                              when a login shell exits.  Currently set by
                              default; this is different from the original
                              Korn shell (which doesn't have this option, but
                              does send the SIGHUP 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 â<œphysicalâ<
                              (i.e. the filesystem's) â<˜..â<™ directories instead
                              of â<œlogicalâ< directories (i.e. the shell handles
                              â<˜..â<™, which allows the user to be oblivious of
                              symbolic links to directories).  Clear by
                              default.  Note that setting this option does not
                              affect the current value of the PWD parameter;
                              only the cd command changes PWD.  See the cd and
                              pwd commands above for more details.

             pipefail         The exit status of a pipeline is the exit status
                              of the rightmost command in the pipeline that
                              doesn't return 0, or 0 if all commands returned
                              a 0 exit status.

             posix            Enable POSIX mode.  See POSIX mode above.

             restricted       The shell is a restricted shell.  This option
                              can only be used when the shell is invoked.  See
                              above for a description of what this means.

             sh               Enable strict Bourne shell mode (see Strict
                              Bourne shell mode above).

             vi               Enable vi(1)-like command-line editing
                              (interactive shells only).

             vi-esccomplete   In vi command-line editing, do command and file
                              name completion when escape (^[) is entered in
                              command mode.

             vi-show8         Prefix characters with the eighth bit set with
                              â<˜M-â<™.  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 and file
                              name completion when tab (^I) is entered in
                              insert mode.  This is the default.

             viraw            No effect.  In the original Korn shell, unless
                              viraw was set, the vi command-line mode would
                              let the tty(4) driver do the work until ESC (^[)
                              was entered.  ksh is always in viraw mode.

             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 â<˜$-â<™.  set -o with no option name will list all the
             options and whether each is on or off; set +o will print the
             current shell options in a form that can be reinput to the shell
             to achieve the same option settings.

             Remaining arguments, if any, are positional parameters and are
             assigned, in order, to the positional parameters (i.e. $1, $2,
             etc.).  If options end with â<˜--â<™ and there are no remaining
             arguments, all positional parameters are cleared.  If no options
             or arguments are given, the values of all names are printed.  For
             unknown historical reasons, a lone â<˜-â<™ 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
             â<˜1â<™, â<˜2â<™, etc.  number defaults to 1.

             Stops the shell as if it had received the suspend character from
             the terminal.  It is not possible to suspend a login shell unless
             the parent process is a member of the same terminal session but
             is a member of a different process group.  As a general rule, if
             the shell was started by another shell or via su(1), it can be

     test expression
     [ expression ]
             test evaluates the expression and returns zero status if true, 1
             if false, or greater than 1 if there was an error.  It is
             normally used as the condition command of if and while
             statements.  Symbolic links are followed for all file expressions
             except -h and -L.

             The following basic expressions are available:

             -a file            file exists.

             -b file            file is a block special device.

             -c file            file is a character special device.

             -d file            file is a directory.

             -e file            file exists.

             -f file            file is a regular file.

             -G file            file's group is the shell's effective group

             -g file            file's mode has the setgid bit set.

             -h file            file is a symbolic link.

             -k file            file's mode has the sticky(8) bit set.

             -L file            file is a symbolic link.

             -O file            file's owner is the shell's effective user ID.

             -o option          Shell option is set (see the set command above
                                for a list of options).  As a non-standard
                                extension, if the option starts with a â<˜!â<™,
                                the test is negated; the test always fails if
                                option doesn't exist (so [ -o foo -o -o !foo ]
                                returns true if and only if option foo

             -p file            file is a named pipe.

             -r file            file exists and is readable.

             -S file            file is a unix(4)-domain socket.

             -s file            file is not empty.

             -t [fd]            File descriptor fd is a tty(4) device.  If the
                                posix option 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 above).

             -u file            file's mode has the setuid bit set.

             -w file            file exists and is writable.

             -x file            file exists and is executable.

             file1 -nt file2    file1 is newer than file2 or file1 exists and
                                file2 does not.

             file1 -ot file2    file1 is older than file2 or file2 exists and
                                file1 does not.

             file1 -ef file2    file1 is the same file as file2.

             string             string has non-zero length.

             -n string          string is not empty.

             -z string          string is empty.

             string = string    Strings are equal.

             string == string   Strings are equal.

             string != string   Strings are not equal.

             string > string    Strings compare greater than based on the
                                ASCII value of their characters.

             string < string    Strings compare less than based on the ASCII
                                value of their characters.

             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).  For
             example, [ -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 â<˜!â<™ 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 â<˜!â<™ 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 the first argument is a unary operator,
             including an unstripped â<˜!â<™).

             Note: A common mistake is to use â<œif [ $foo = bar ]â< which fails
             if parameter â<œfooâ< is NULL or unset, if it has embedded spaces
             (i.e. IFS characters), or if it is a unary operator like â<˜!â<™ or
             â<˜-nâ<™.  Use tests like â<œif [ "X$foo" = Xbar ]â< 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:

                   0m0.00s real     0m0.00s user     0m0.00s system

             If the -p option is given the output is slightly longer:

                   real     0.00
                   user     0.00
                   sys      0.00

             It is an error to specify the -p option unless pipeline is a
             simple command.

             Simple redirections of standard error do not affect 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 â<œafileâ<, but those of
             the second command do.

     times   Print the accumulated user and system times used both by the
             shell and by processes that the shell started which have exited.
             The format of the output is:

                   0m0.00s 0m0.00s
                   0m0.00s 0m0.00s

     trap [handler signal ...]
             Sets a 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 sign (â<˜-â<™),
             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
             the 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 the 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 cannot 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.

     type    Short form of command -V (see above).

     typeset [[+-lprtUux] [-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 are used, the
             current attributes of all parameters are printed as typeset
             commands; if an option is given (or â<˜-â<™ with no option letter),
             all parameters and their values with the specified attributes are
             printed; if options are introduced with â<˜+â<™, 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 name arguments are given, functions are
             listed with their values (i.e. definitions) unless options are
             introduced with â<˜+â<™, in which case only the function names are

             -f      Function mode.  Display or set functions and their
                     attributes, instead of parameters.

             -i[n]   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

             -L[n]   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
                     whitespace (and zeros, if used with the -Z option) is
                     stripped.  If necessary, values are either truncated or
                     space padded to fit the field width.

             -l      Lower case attribute.  All upper case characters in
                     values are converted to lower case.  (In the original
                     Korn shell, this parameter meant â<œlong integerâ< 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

             -R[n]   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 whitespace is stripped.  If necessary, values
                     are either stripped of leading characters or space padded
                     to make them fit the field width.

             -r      Read-only attribute.  Parameters with this attribute may
                     not be assigned to or unset.  Once this attribute is set,
                     it cannot 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      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.

             -u      Upper case attribute.  All lower case characters in
                     values are converted to upper case.  (In the original
                     Korn shell, this parameter meant â<œunsigned integerâ< 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 yet implemented.

             -Z[n]   Zero fill attribute.  If not combined with -L, this is
                     the same as -R, except zero padding is used instead of
                     space padding.

     ulimit [-acdfHlmnpSst [value]] ...
             Display or set process limits.  If no options are used, the file
             size limit (-f) is assumed.  value, if specified, may be either
             an arithmetic expression starting with a number or the word
             â<œunlimitedâ<.  The limits affect the shell and any processes
             created by the shell after a limit is imposed; limits may not be
             increased once they are set.

             -a     Display all limits; unless -H is used, soft limits are

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

             -d n   Impose a size limit of n kilobytes on the size of the data

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

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

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

             -m n   Impose a limit of n kilobytes on the amount of physical
                    memory used.  This limit is not enforced.

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

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

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

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

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

             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).  When 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).  For example, â<œug=rwx,o=â< sets the mask so files
             will not be readable, writable, or executable by â<œothersâ<, and is
             equivalent (on most systems) to the octal mask â<œ007â<.

     unalias [-adt] [name ...]
             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 have the
             read-only attribute set, 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 SIGHUP, SIGINT, or SIGQUIT signal is

             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 is performed even if name is a
             reserved word, alias, etc.  Without the -v option, whence is
             similar to command -v except that whence 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

   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 commands.  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, and the state of the terminal is
     saved or restored when a foreground job is stopped or restarted,

     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 â<œ[..]â<, followed by the process IDs
     of the processes in the job when an asynchronous command is run.  A job
     may be referred to in the 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
     (â<˜%â<™).  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.

     %-             The job that would be the %+ job if the latter did not

     %n             The job with job number n.

     %?string       The job with its command containing the string string (an
                    error occurs if multiple jobs are matched).

     %string        The job with its command starting with the 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


     number   is the job number of the job;

     flag     is the â<˜+â<™ or â<˜-â<™ character 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:

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

              Running    The job has neither stopped nor exited (note that
                         running does not necessarily mean consuming CPU time
                         - the process could be blocked waiting for some

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

              signal-description [â<œcore dumpedâ<]
                         The job was killed by a signal (e.g. memory fault,
                         hangup); use kill -l for a list of signal
                         descriptions.  The â<œcore dumpedâ< message indicates
                         the process created a core file.

     command  is the command that created the process.  If there are multiple
              processes in the job, 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 SIGHUP 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 SIGHUP signal and the shell exits.

   Interactive input line editing
     The shell supports three modes of reading command lines from a tty(4) in
     an interactive session, controlled by the emacs, gmacs, and vi options
     (at most one of these can be set at once).  The default is emacs.
     Editing modes can be set explicitly using the set built-in, or implicitly
     via the EDITOR and VISUAL environment variables.  If none of these
     options are enabled, the shell simply reads lines using the normal tty(4)
     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 than the screen width (see
     the COLUMNS parameter), a â<˜>â<™, â<˜+â<™, or â<˜<â<™ 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.  In this mode, various editing commands (typically
     bound to one or more control characters) cause immediate actions without
     waiting for a newline.  Several editing commands are bound to particular
     control characters when the shell is invoked; these bindings can be
     changed using the bind command.

     The following is a list of available editing commands.  Each description
     starts with the name of the command, suffixed with a colon; an [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. the ASCII ESC
     character is written as ^[.  ^[A-Z] sequences are not case sensitive.  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 user's tty(4) characters (e.g.
     ERASE) are bound to reasonable substitutes and override the default

     abort: ^C, ^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, ^X^D
             Moves the cursor backward n characters.

     backward-word: [n] ^[b
             Moves the cursor backward to the beginning of the word; words
             consist of alphanumerics, underscore (â<˜_â<™), and dollar sign (â<˜$â<™)

     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.

     clear-screen: ^L
             Clears the screen if the TERM parameter is set and the terminal
             supports clearing the screen, then reprints the prompt string and
             the current input line.

     comment: ^[#
             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: ^[^[
             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 â<˜/â<™ 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 beep to be sounded).

             Custom completions may be configured by creating an array named
             â<˜complete_commandâ<™, optionally suffixed with an argument number
             to complete only for a single argument.  So defining an array
             named â<˜complete_killâ<™ provides possible completions for any
             argument to the kill(1) command, but â<˜complete_kill_1â<™ only
             completes the first argument.  For example, the following command
             makes oksh offer a selection of signal names for the first
             argument to kill(1):

                   set -A complete_kill_1 -- -9 -HUP -INFO -KILL -TERM

     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 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: ^I, ^[=
             Complete as much as is possible of the current word, and list the
             possible completions for it.  If only one completion is possible,
             match as in the complete command above.

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

     delete-char-forward: [n] Delete
             Deletes n characters after the cursor.

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

     delete-word-forward: [n] ^[d
             Deletes n words after the cursor.

     down-history: [n] ^N, ^XB
             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

     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 â<˜*â<™ 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, ^XC
             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-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 â<˜/â<™ 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.

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

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

             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
             â<˜^â<™ 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.

     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, ^XA
             Scrolls the history buffer backward n lines (earlier).

     upcase-word: [n] ^[U, ^[u
             Uppercase the next n words.

     quote: ^V
             Synonym for ^^.

     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 previously killed text string.

     The following editing commands lack default bindings but can be used with
     the bind command:

             Deletes the input between the cursor and the mark.

   Vi editing mode
     The vi command-line editor in oksh has basically the same commands as the
     vi(1) editor with the following exceptions:

     â<¢<¢   You start out in insert mode.

     â<¢<¢   There are file name and command completion commands: =, \, *, ^X, ^E,
         ^F, and, optionally, ⟨tab⟩ and ⟨esc⟩.

     â<¢<¢   The _ command is different (in oksh it is the last argument command;
         in vi(1) it goes to the start of the current line).

     â<¢<¢   The / and G commands move in the opposite direction to the j command.

     â<¢<¢   Commands which don't make sense in a single line editor are not
         available (e.g. screen movement commands and ex(1)-style colon (:)

     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(1), there are two modes: â<œinsertâ< mode and â<œcommandâ< 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(4) 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:

     ^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.

     ^H          Erases previous character.

     ^J | ^M     End of line.  The current line is read, parsed, and executed
                 by the shell.

     ^L          Clear the screen (if possible) and redraw the current line.
                 See the clear-screen command in Emacs editing mode for more

     ^R          Redraw the current line.

     ^V          Literal next.  The next character typed is not treated
                 specially (can be used to insert the characters being
                 described here).

     ^X          Command and file name expansion (see below).

     ⟨esc⟩       Puts the editor in command mode (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, an [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 â<œcurrent positionâ< refers to the position between the cursor and the
     character preceding the cursor.  A â<œwordâ< is a sequence of letters,
     digits, and underscore characters or a sequence of non-letter, non-digit,
     non-underscore, and non-whitespace characters (e.g. â<œab2*&^â< contains two
     words) and a â<œbig-wordâ< is a sequence of non-whitespace characters.

     Special oksh 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

     #           Insert the comment character (â<˜#â<™) at the start of the
                 current line and return the line to the shell (equivalent to

     [n]g        Like G, except if n is not specified, it goes to the most
                 recent remembered line.

     [n]v        Edit line n using the vi(1) 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 â<˜*â<™ if the word contains no file
                 globbing 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 characters â<˜;â<™, â<˜|â<™, â<˜&â<™, â<˜(â<™, or
                 â<˜)â<™, and does not contain a slash (â<˜/â<™), 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 and 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.

     @c          Macro expansion.  Execute the commands found in the alias _c.

     Intra-line movement commands:

     [n]h and [n]^H
             Move left n characters.

     [n]l and [n]⟨space⟩
             Move right n characters.

     0       Move to column 0.

     ^       Move to the first non-whitespace character.

     [n]|    Move to column n.

     $       Move to the last character.

     [n]b    Move back n words.

     [n]B    Move back n big-words.

     [n]e    Move forward to the end of the word, n times.

     [n]E    Move forward to the end of the big-word, n times.

     [n]w    Move forward n words.

     [n]W    Move forward n big-words.

     %       Find match.  The editor looks forward for the nearest
             parenthesis, bracket, or brace and then moves the cursor to the
             matching parenthesis, bracket, or brace.

     [n]fc   Move forward to the nth occurrence of the character c.

     [n]Fc   Move backward to the nth occurrence of the character c.

     [n]tc   Move forward to just before the nth occurrence of the character

     [n]Tc   Move backward to just before the nth occurrence of the character

     [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

     Inter-line movement commands:

     [n]j, [n]+, and [n]^N
             Move to the nth next line in the history.

     [n]k, [n]-, and [n]^P
             Move to the nth previous line in the history.

     [n]G    Move to line n in the history; if n is not specified, the number
             of the first remembered line is used.

     [n]g    Like G, except if n is not specified, it goes to the most recent
             remembered line.

             Search backward through the history for the nth line containing
             string; if string starts with â<˜^â<™, the remainder of the string
             must appear at the start of the history line for it to match.

             Same as /, except it searches forward through the history.

     [n]n    Search for the nth occurrence of the last search string; the
             direction of the search is the same as the last search.

     [n]N    Search for the nth occurrence of the last search string; the
             direction of the search is the opposite of the last search.

     Edit commands

     [n]a    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.

     [n]A    Same as a, except it appends at the end of the line.

     [n]i    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.

     [n]I    Same as i, except the insertion is done just before the first
             non-blank character.

     [n]s    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 the line are deleted and insert mode is

             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).

     [n]x    Delete the next n characters.

     [n]X    Delete the previous n characters.

     D       Delete to the end of the line.

             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.

     [n]rc   Replace the next n characters with the character c.

     [n]R    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.

             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.

     [n]p    Paste the contents of the yank buffer just after the current
             position, n times.

     [n]P    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      Clear the screen (if possible) and redraw the current line.

     ^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.

     ~/.profile           User's login profile.
     /etc/ksh.kshrc       Global configuration file.  Not sourced by default.
     /etc/profile         System login profile.
     /etc/shells          Shell database.
     /etc/suid_profile    Privileged shell profile.

     csh(1), ed(1), mg(1), sh(1), stty(1), vi(1), shells(5), environ(7),

     S. R. Bourne, â<œThe UNIX Shellâ<, Bell System Technical Journal, 57:6, pp.
     1971-1990, 1978.

     S. R. Bourne, An Introduction to the UNIX Shell, AT&T Bell Laboratories,
     Computing Science Technical Report, 70, 1978.

     Morris Bolsky and David Korn, The KornShell Command and Programming
     Language, Prentice Hall, First Edition 1989, ISBN 0135169720.

     Stephen G. Kochan and Patrick H. Wood, UNIX Shell Programming, 3rd
     Edition, Sams, 2003, ISBN 0672324903.

     IEEE Inc., IEEE Standard for Information Technology - Portable Operating
     System Interface (POSIX) - Part 2: Shell and Utilities, 1993, ISBN

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

     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 <change!john@sq.sq.com>, Simon J. Gerraty
     <sjg@zen.void.oz.au>, and 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.

     $(command) expressions are currently parsed by finding the closest
     matching (unquoted) parenthesis.  Thus constructs inside $(command) may
     produce an error.  For example, the parenthesis in â<˜x);;â<™ is interpreted
     as the closing parenthesis in â<˜$(case x in x);; *);; esac)â<™.

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