MKSH(1)			FreeBSD	General	Commands Manual		       MKSH(1)

     mksh, sh -- MirBSD	Korn shell

     mksh [-+abCefhiklmnprUuvXx] [-T [!]tty | -] [-+o option] [-c string | -s
	  | file [argument ...]]
     builtin-name [argument ...]

     mksh is a command interpreter intended for	both interactive and shell
     script use.  Its command language is a superset of	the sh(C) shell	lan-
     guage and largely compatible to the original Korn shell.  At times, this
     manual page may give scripting advice; while it sometimes does take por-
     table shell scripting or various standards	into account all information
     is	first and foremost presented with mksh in mind and should be taken as

   I use Android, OS/2,	etc. so	what...?
     Please refer to:

     Most builtins can be called directly, for example if a link points	from
     its name to the shell; not	all make sense,	have been tested or work at
     all though.

     The options are as	follows:

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

     -i		Interactive shell.  A shell that reads commands	from standard
		input is "interactive" if this option is used or if both stan-
		dard 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).	 It also processes the
		ENV parameter or the mkshrc file (see below).  For non-inter-
		active shells, the trackall option is on by default (see the
		set command below).

     -l		Login shell.  If the name or basename the shell	is called with
		(i.e. argv[0]) starts with `-' or if this option is used, the
		shell is assumed to be a login shell; see Startup files	below.

     -p		Privileged shell.  A shell is "privileged" if the real user ID
		or group ID does not match the effective user ID or group ID
		(see getuid(2) and getgid(2)).	Clearing the privileged	option
		causes the shell to set	its effective user ID (group ID) to
		its initial real user ID (group	ID).  For further implica-
		tions, see Startup files.  If the shell	is privileged and this
		flag is	not explicitly set, the	"privileged" option is cleared
		automatically after processing the startup files.

     -r		Restricted shell.  A shell is "restricted" if the basename the
		shell is called	with, after `-'	processing, starts with	`r' or
		if this	option is used.	 The following restrictions come into
		effect after the shell processes any profile and ENV files:

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

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

     -T	name	Spawn mksh on the tty(4) device	given.	The paths name,
		/dev/ttyCname and /dev/ttyname are attempted in	order.	Unless
		name begins with an exclamation	mark (`!'), this is done in a
		subshell and returns immediately.  If name is a	dash (`-'),
		detach from controlling	terminal (daemonise) instead.

     In	addition to the	above, the options described in	the set	built-in com-
     mand 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 de-
     termined as follows: if the -c option is used and there is	a non-option
     argument, it is used as the name; if commands are being read from a file,
     the file is used as the name; otherwise, the name the shell was called
     with (i.e.	argv[0]) is used.

     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 oc-
     curred 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 com-
     mand is executed.

   Startup files
     For the actual location of	these files, see FILES.	 A login shell pro-
     cesses the	system profile first.  A privileged shell then processes the
     suid profile.  A non-privileged login shell processes the user profile
     next.  A non-privileged interactive shell checks the value	of the ENV pa-
     rameter after subjecting it to parameter, command,	arithmetic and tilde
     (`~') substitution; if unset or empty, the	user mkshrc profile is pro-
     cessed; otherwise,	if a file whose	name is	the substitution result	ex-
     ists, it is processed; non-existence is silently ignored.	A privileged
     shell then	drops privileges if neither was	the -p option given on the
     command line nor set during execution of the startup files.

   Command syntax
     The shell begins parsing its input	by removing any	backslash-newline com-
     binations,	then breaking it into words.  Words (which are sequences of
     characters) are delimited by unquoted whitespace characters (space, tab
     and newline) or meta-characters (`<', `>',	`|', `;', `(', `)' and `&').
     Aside from	delimiting words, spaces and tabs are ignored, while newlines
     usually delimit commands.	The meta-characters are	used in	building the
     following tokens: "<", "<&", "<<",	"<<<", ">", ">&", ">>",	"&>", etc. are
     used to specify redirections (see Input/output redirection	below);	"|" is
     used to create pipelines; "|&" is used to create co-processes (see
     Co-processes below); ";" is used to separate commands; "&"	is used	to
     create asynchronous pipelines; "&&" and "||" are used to specify condi-
     tional execution; ";;", ";&" and ";|" are used in case statements;	"((
     ... ))" is	used in	arithmetic expressions;	and lastly, "( ... )" is used
     to	create subshells.

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

     As	words and tokens are parsed, the shell builds commands,	of which there
     are two basic types: simple-commands, typically programmes	that are exe-
     cuted, 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 pa-
     rameter 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	com-
     mand (i.e.	a separate executable file that	is located using the PATH pa-
     rameter; see Command execution below).  Note that all command constructs
     have an exit status: for external commands, this is related to the	status
     returned by wait(2) (if the command could not be found, the exit status
     is	127; if	it could not be	executed, the exit status is 126); the exit
     status of other command constructs	(built-in commands, functions, com-
     pound-commands, pipelines,	lists, etc.) are all well-defined and are de-
     scribed where the construct is described.	The exit status	of a command
     consisting	only of	parameter assignments is that of the last command sub-
     stitution performed during	the parameter assignment or 0 if there were no
     command substitutions.

     Commands can be chained together using the	"|" token to form pipelines,
     in	which the standard output of each command but the last is piped	(see
     pipe(2)) to the standard input of the following command.  The exit	status
     of	a pipeline is that of its last command,	unless the pipefail option is
     set (see there).  All commands of a pipeline are executed in separate
     subshells;	this is	allowed	by POSIX but differs from both variants	of
     AT&T UNIX ksh, where all but the last command were	executed in subshells;
     see the read builtin's description	for implications and workarounds.  A
     pipeline may be prefixed by the "!" reserved word which causes the	exit
     status of the pipeline to be logically complemented: if the original sta-
     tus 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: "&&", "||", "&",	"|&" and ";".  The first two are for
     conditional execution: "cmd1 && cmd2" executes cmd2 only if the exit sta-
     tus of cmd1 is zero; "||" is the opposite - cmd2 is executed only if the
     exit status of cmd1 is non-zero.  "&&" and	"||" have equal	precedence
     which is higher than that of "&", "|&" and	";", which also	have equal
     precedence.  Note that the	"&&" and "||" operators	are
     "left-associative".  For example, both of these commands will print only

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

     The "&" token causes the preceding	command	to be executed asynchronously;
     that is, the shell	starts the command but does not	wait for it to com-
     plete (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 "|&" operator starts a co-process which is a spe-
     cial kind of asynchronous process (see Co-processes below).  Note that a
     command must follow the "&&" and "||" operators, while it need not	follow
     "&", "|&" or ";".	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 recognised 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 as-
     signments or redirections):

	   case	    else     function	  then	    !	    (
	   do	    esac     if		  time	    [[	    ((
	   done	    fi	     in		  until	    {
	   elif	    for	     select	  while	    }

     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 }

     case word in [[(] pattern [| pattern] ...)	list <terminator>] ... 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 `.' and `/' 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 pa-
	   rameter, command and	arithmetic substitution, as well as tilde sub-

	   For historical reasons, open	and close braces may be	used instead
	   of in and esac, for example:	"case $foo { (ba[rz]|blah) date	;; }"

	   The list <terminator>s are:

	   ";;"	 Terminate after the list.

	   ";&"	 Fall through into the next list.

	   ";|"	 Evaluate the remaining	pattern-list tuples.

	   The exit status of a	case statement is that of the executed list;
	   if no list is executed, the exit status is zero.

     for name [in word ...] ; do list; done
	   For each word in the	specified word list, the parameter name	is set
	   to the word and list	is executed.  The exit status of a for state-
	   ment	is the last exit status	of list; if list is never executed,
	   the exit status is zero.  If	in is not used to specify a word list,
	   the positional parameters ($1, $2, etc.) are	used instead; in this
	   case, use a newline instead of the semicolon	(`;') for portability.
	   For historical reasons, open	and close braces may be	used instead
	   of do and done, as in "for i; { echo	$i; }" (not portable).

     function name { list; }
	   Defines the function	name (see Functions below).  All 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 above and Functions	below).	 Most
	   amounts of space and	tab after name will be ignored.

     function name() { list; }
	   bashism for name() {	list; }	(the function keyword is ignored).

     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	exe-
	   cuted 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 whatever non-conditional (not the	first) 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 words is printed on standard error, followed by a prompt
	   (PS3: normally "#? ").  A number corresponding to one of the	enu-
	   merated 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 and trailing space is stripped), and
	   list	is executed.  If a blank line (i.e. zero or more IFS octets)
	   is entered, the menu	is reprinted without executing list.

	   When	list completes,	the enumerated list is printed if REPLY	is
	   empty, 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.  The exit status of a	select
	   statement is	zero if	a break	statement is used to exit the loop,
	   non-zero otherwise.	If "in word ..." is omitted, the positional
	   parameters are used.	 For historical	reasons, open and close	braces
	   may be used instead of do and done, as in: "select i; { echo	$i; }"

     time [-p] [pipeline]
	   The Command execution section describes the time reserved word.

     until list; do list; done
	   This	works like while (see below), except that the body list	is ex-
	   ecuted 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 list is executed as	often
	   as the exit status of the first list	is zero.  The exit status of a
	   while statement is the last exit status of the list in the body of
	   the loop; if	the body is not	executed, the exit status is zero.

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

	      Field splitting and globbing are	not performed on arguments.

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

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

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

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

	      The second operand of the "=" and "!=" expressions is a pattern
	       (e.g. the comparison [[ foobar =	f*r ]] succeeds).  This	even
	       works indirectly, while quoting forces literal interpretation:

		     $ bar=foobar; baz='f*r'	     # or: baz='f+(o)b?r'
		     $ [[ $bar = $baz ]]; echo $?    # 0
		     $ [[ $bar = "$baz"	]]; echo $?  # 1

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

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

     ((	expression ))
	   The arithmetic expression expression	is evaluated; equivalent to
	   `let	"expression"' in a compound construct.
	   See the let command and Arithmetic expressions below.

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

     If	a single-quoted	string is preceded by an unquoted `$', C style back-
     slash expansion (see below) is applied (even single quote characters in-
     side can be escaped and do	not terminate the string then);	the expanded
     result is treated as any other single-quoted string.  If a	double-quoted
     string is preceded	by an unquoted `$', the	`$' is simply ignored.

   Backslash expansion
     In	places where backslashes are expanded, certain C and AT&T UNIX ksh or
     GNU bash style escapes are	translated.  These include "\a", "\b", "\f",
     "\n", "\r", "\t", "\U########", "\u####" and "\v".	 For "\U########" and
     "\u####", `#' means a hexadecimal digit (up to 4 or 8); these translate a
     Universal Coded Character Set codepoint to	UTF-8 (see CAVEATS on UCS lim-
     itations).	 Furthermore, "\E" and "\e" expand to the escape character.

     In	the print builtin mode,	octal sequences	must have the optional up to
     three octal digits	`#' prefixed with the digit zero ("\0###"); hexadeci-
     mal sequences "\x##" are limited to up to two hexadecimal digits `#';
     both octal	and hexadecimal	sequences convert to raw octets; "\%", where
     `%' is none of the	above, translates to \%	(backslashes are retained).

     In	C style	mode, raw octet-yielding octal sequences "\###"	must not have
     the one up	to three octal digits prefixed with the	digit zero; hexadeci-
     mal sequences "\x##" greedily eat up as many hexadecimal digits `#' as
     they can and terminate with the first non-xdigit; below \x100 these pro-
     duce raw octets; above, they are equivalent to "\U#".  The	sequence
     "\c%", where `%' is any octet, translates to Ctrl-%, that is, "\c?" be-
     comes DEL,	everything else	is bitwise ANDed with 0x9F.  "\%", where `%'
     is	none of	the above, translates to %: backslashes	are trimmed even be-
     fore newlines.

     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	com-
     mand 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.	 Aliases are specifically an
     interactive feature: while	they do	happen to work in scripts and on the
     command line in some cases, aliases are expanded during lexing, so	their
     use must be in a separate command tree from their definition; otherwise,
     the alias will not	be found.  Noticeably, command lists (separated	by
     semicolon,	in command substitutions also by newline) may be one same
     parse tree.

     The following command aliases are defined automatically by	the shell:

	   autoload='\\builtin typeset -fu'
	   functions='\\builtin	typeset	-f'
	   hash='\\builtin alias -t'
	   history='\\builtin fc -l'
	   integer='\\builtin typeset -i'
	   local='\\builtin typeset'
	   login='\\builtin exec login'
	   nameref='\\builtin typeset -n'
	   nohup='nohup	'
	   r='\\builtin	fc -e -'
	   type='\\builtin whence -v'

     Tracked aliases allow the shell to	remember where it found	a particular
     command.  The first time the shell	does a path search for a command that
     is	marked as a tracked alias, it saves the	full path of the command.  The
     next time the command is executed,	the shell checks the saved path	to see
     that it is	still valid, and if so,	avoids repeating the path search.
     Tracked aliases can be listed and created using alias -t.	Note that
     changing the PATH parameter clears	the saved paths	for all	tracked
     aliases.  If the trackall option is set (i.e. set -o trackall or set -h),
     the shell tracks all commands.  This option is set	automatically for non-
     interactive shells.  For interactive shells, only the following commands
     are automatically tracked:	cat(1),	cc(1), chmod(1), cp(1),	date(1),
     ed(1), emacs(1), grep(1), ls(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	per-
     form substitutions	on the words of	the command.  There are	three kinds of
     substitution: parameter, command and arithmetic.  Parameter substitu-
     tions, which are described	in detail in the next section, take the	form
     $name or ${...}; command substitutions take the form $(command) or	(dep-
     recated) `command`	or (executed in	the current environment) ${ command;}
     and strip trailing	newlines; and arithmetic substitutions take the	form
     $((expression)).  Parsing the current-environment command substitution
     requires a	space, tab or newline after the	opening	brace and that the
     closing brace be recognised as a keyword (i.e. is preceded	by a newline
     or	semicolon).  They are also called funsubs (function substitutions) and
     behave like functions in that local and return work, and in that exit
     terminates	the parent shell; shell	options	are shared.

     Another variant of	substitution are the valsubs (value substitutions)
     ${|command;} which	are also executed in the current environment, like
     funsubs, but share	their I/O with the parent; instead, they evaluate to
     whatever the, initially empty, expression-local variable REPLY is set to
     within the	commands.

     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 octets which are used to break a string up	into several words;
     any octets	from the set space, tab	and newline that appear	in the IFS
     octets are	called "IFS whitespace".  Sequences of one or more IFS white-
     space octets, in combination with zero or one non-IFS whitespace octets,
     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 or	trailing non-IFS whitespace does create	an empty field.

     Example: If IFS is	set to "<space>:" and VAR is set to
     "<space>A<space>:<space><space>B::D", the substitution for	$VAR results
     in	four fields: "A", "B", "" (an empty field) and "D".  Note that if the
     IFS parameter is set to the empty string, no field	splitting is done; if
     it	is unset, the default value of space, tab and newline is used.

     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: "A",	"B", ""	and "D:E", not "A", "B", "",
     "D" and "E".  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 de-

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

     A command substitution is replaced	by the output generated	by the speci-
     fied command which	is run in a subshell.  For $(command) and ${|command;}
     and ${ command;} substitutions, normal quoting rules are used when
     command is	parsed;	however, for the deprecated `command` form, a `\' fol-
     lowed by any of `$', ``' or `\' is	stripped (as is	`"' when the substitu-
     tion is part of a double-quoted string); a	backslash `\' followed by any
     other character is	unchanged.  As a special case in command substitu-
     tions, 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).

     Note that some shells do not use a	recursive parser for command substitu-
     tions, leading to failure for certain constructs; to be portable, use as
     workaround	"x=$(cat) <<\EOF" (or the newline-keeping "x=<<\EOF" exten-
     sion) instead to merely slurp the string.	IEEE Std 1003.1	("POSIX.1")
     recommends	using case statements of the form x=$(case $foo	in (bar) echo
     $bar ;; (*) echo $baz ;; esac) instead, which would work but not serve as
     example for this portability issue.

	   x=$(case $foo in bar) echo $bar ;; *) echo $baz ;; esac)
	   # above fails to parse on old shells; below is the workaround
	   x=$(eval $(cat)) <<\EOF
	   case	$foo in	bar) echo $bar ;; *) echo $baz ;; esac

     Arithmetic	substitutions are replaced by the value	of the specified ex-
     pression.	For example, the command print $((2+3*4)) displays 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	param-
     eters described below, or a letter	followed by zero or more letters or
     digits (`_' counts	as a letter).  The latter form can be treated as ar-
     rays by appending an array	index of the form [expr] where expr is an
     arithmetic	expression.  Array indices in mksh are limited to the range 0
     through 4294967295, inclusive.  That is, they are a 32-bit	unsigned inte-

     Parameter substitutions take the form $name, ${name} or ${name[expr]}
     where name	is a parameter name.  Substitutions of an array	in scalar con-
     text, i.e.	without	an expr	in the latter form mentioned above, expand the
     element with the key "0".	Substitution of	all array elements with
     ${name[*]}	and ${name[@]} works equivalent	to $* and $@ for positional
     parameters.  If substitution is performed on a parameter (or an array pa-
     rameter element) that is not set, an empty	string is substituted unless
     the nounset option	(set -u) is set, in which case an error	occurs.

     Parameters	can be assigned	values in a number of ways.  First, the	shell
     implicitly	sets some parameters like "#", "PWD" and "$"; this is the only
     way the special single character parameters are set.  Second, parameters
     are imported from the shell's environment at startup.  Third, parameters
     can be assigned values on the command line: for example, FOO=bar sets the
     parameter "FOO" to	"bar"; multiple	parameter assignments can be given on
     a single command line and they can	be followed by a simple-command, in
     which case	the assignments	are in effect only for the duration of the
     command (such assignments are also	exported; see below for	the implica-
     tions of this).  Note that	both the parameter name	and the	`=' must be
     unquoted for the shell to recognise a parameter assignment.  The con-
     struct FOO+=baz is	also recognised; the old and new values	are string-
     concatenated with no separator.  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 parame-
     ters as well as the getopts, read and set -A commands.  Lastly, parame-
     ters 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 environ-
     ment 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 empty, it is substituted; otherwise, word
	     is	substituted.

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

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

	     If	name is	set and	not empty, it is substituted; otherwise, word
	     is	printed	on standard error (preceded by name:) and an error oc-
	     curs (normally causing termination	of a shell script, function,
	     or	a script sourced using the "." built-in).  If word is omitted,
	     the string	"parameter null	or not set" is used instead.

     Note that,	for all	of the above, word is actually considered quoted, and
     special parsing rules apply.  The parsing rules also differ on whether
     the expression is double-quoted: word then	uses double-quoting rules, ex-
     cept for the double quote itself (`"') and	the closing brace, which, if
     backslash escaped,	gets quote removal applied.

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

     The following forms of parameter substitution can also be used:

	     The number	of positional parameters if name is "*", "@" or	not
	     specified;	otherwise the length (in characters) of	the string
	     value of parameter	name.

	     The number	of elements in the array name.

	     The width (in screen columns) of the string value of parameter
	     name, or -1 if ${name} contains a control character.

	     The name of the variable referred to by name.  This will be name
	     except when name is a name	reference (bound variable), created by
	     the nameref command (which	is an alias for	typeset	-n).  name
	     cannot be one of most special parameters (see below).

	     The names of indices (keys) 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 `#'	results	in the shortest	match, and two of them result
	     in	the longest match.

	     Like ${...#...} but deletes from the end of the value.

	     The longest match of pattern in the value of parameter name is
	     replaced with string (deleted if string is	empty; the trailing
	     slash (`/') may be	omitted	in that	case).	A leading slash	fol-
	     lowed by `#' or `%' causes	the pattern to be anchored at the be-
	     ginning or	end of the value, respectively;	empty unanchored
	     patterns cause no replacement; a single leading slash or use of a
	     pattern that matches the empty string causes the replacement to
	     happen only once; two leading slashes cause all occurrences of
	     matches in	the value to be	replaced.  May be slow on long

	     The same as ${name//pattern/string}, except that both pattern and
	     string are	expanded anew for each iteration.  Use with KSH_MATCH.

	     The first len characters of name, starting	at position pos, are
	     substituted.  Both	pos and	:len are optional.  If pos is nega-
	     tive, counting starts at the end of the string; if	it is omitted,
	     it	defaults to 0.	If len is omitted or greater than the length
	     of	the remaining string, all of it	is substituted.	 Both pos and
	     len are evaluated as arithmetic expressions.

	     The hash (using the BAFH algorithm) of the	expansion of name.
	     This is also used internally for the shell's hashtables.

	     A quoted expression safe for re-entry, whose value	is the value
	     of	the name parameter, is substituted.

     Note that pattern may need	extended globbing pattern (@(...)), single
     ('...') or	double ("...") quote escaping unless -o	sh is set.

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

     !	     Process ID	of the last background process started.	 If no back-
	     ground processes have been	started, the parameter is not set.

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

     $	     The PID of	the shell or, if it is a subshell, the PID of the
	     original shell.  Do NOT use this mechanism	for generating tempo-
	     rary 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,	but at most 255.

     0	     The name of the shell, determined as follows: the first argument
	     to	mksh if	it was invoked with the	-c option and arguments	were
	     given; otherwise the file argument, if it was supplied; or	else
	     the name the shell	was invoked with (i.e. argv[0]).  $0 is	also
	     set to the	name of	the current script, or to the name of the cur-
	     rent 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 "." built-in.	 Fur-
	     ther positional parameters	may be accessed	using ${number}.

     *	     All positional parameters (except 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 unset.

     @	     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 empty
	     arguments or splitting arguments with spaces (IFS,	actually).

     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.

     BASHPID	  The PID of the shell or subshell.

     CDPATH	  Like PATH, but used to resolve the argument to the cd	built-
		  in command.  Note that if CDPATH is set and does not contain
		  "." or an empty string element, 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.  If
		  never	unset and not imported,	always set dynamically;	unless
		  the value as reported	by stty(1) is non-zero and sane	enough
		  (minimum is 12x3), defaults to 80; similar for LINES.	 This
		  parameter is used by the interactive line editing modes and
		  by the select, set -o	and kill -l commands to	format infor-
		  mation columns.  Importing from the environment or unsetting
		  this parameter removes the binding to	the actual terminal
		  size in favour of the	provided value.

     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.

		  Time since the epoch,	as returned by gettimeofday(2),	for-
		  matted as decimal tv_sec followed by a dot (`.') and tv_usec
		  padded to exactly six	decimal	digits.

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

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

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

     HISTFILE	  The name of the file used to store command history.  When
		  assigned to or unset,	the file is opened, history is trun-
		  cated	then loaded from the file; subsequent new commands
		  (possibly consisting of several lines) are appended once
		  they successfully compiled.  Also, several invocations of
		  the shell will share history if their	HISTFILE parameters
		  all point to the same	file.

		  Note:	If HISTFILE is unset or	empty, no history file is
		  used.	 This is different from	AT&T UNIX ksh.

     HISTSIZE	  The number of	commands normally stored for history.  The de-
		  fault	is 2047.  The maximum is 65535.

     HOME	  The default directory	for the	cd command and the value sub-
		  stituted 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.

     KSHEGID	  The effective	group id of the	shell at startup.

     KSHGID	  The real group id of the shell at startup.

     KSHUID	  The real user	id of the shell	at startup.

     KSH_MATCH	  The last matched string.  In a future	version, this will be
		  an indexed array, with indexes 1 and up capturing matching
		  groups.  Set by string comparisons (=	and !=)	in double-
		  bracket test expressions when	a match	is found (when != re-
		  turns	false),	by case	when a match is	encountered, and by
		  the substitution operations ${x#pat},	${x##pat}, ${x%pat},
		  ${x%%pat}, ${x/pat/rpl}, ${x/#pat/rpl}, ${x/%pat/rpl},
		  ${x//pat/rpl}, and ${x@/pat/rpl}.  See the end of the	Emacs
		  editing mode documentation for an example.

     KSH_VERSION  The name (self-identification) and version of	the shell
		  (read-only).	See also the version commands in Emacs editing
		  mode and Vi editing mode sections, below.

     LINENO	  The line number of the function or shell script that is cur-
		  rently being executed.

     LINES	  Set to the number of lines on	the terminal or	window.	 De-
		  faults to 24;	always set, unless imported or unset.  See

     OLDPWD	  The previous working directory.  Unset if cd has not suc-
		  cessfully 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 in-

     PATH	  A colon (semicolon on	OS/2) separated	list of	directories
		  that are searched when looking for commands and files
		  sourced using	the "."	command	(see below).  An empty string
		  resulting from a leading or trailing (semi)colon, or two ad-
		  jacent ones, is treated as a "." (the	current	directory).

     PATHSEP	  A colon (semicolon on	OS/2), for the user's convenience.

     PGRP	  The process ID of the	shell's	process	group leader.

     PIPESTATUS	  An array containing the errorlevel (exit status) codes, one
		  by one, of the last pipeline run in the foreground.

     PPID	  The process ID of the	shell's	parent.

     PS1	  The primary prompt for interactive shells.  Parameter, com-
		  mand and arithmetic substitutions are	performed, and `!' is
		  replaced with	the current command number (see	the fc command
		  below).  A literal `!' can be	put in the prompt by placing
		  "!!" in PS1.

		  The default prompt is	"$ " for non-root users, "# " for
		  root.	 If mksh is invoked by root and	PS1 does not contain a
		  `#' character, the default value will	be used	even if	PS1
		  already exists in the	environment.

		  The mksh distribution	comes with a sample dot.mkshrc con-
		  taining a sophisticated example, but you might like the fol-
		  lowing one (note that	${HOSTNAME:=$(hostname)} and the root-
		  vs-user distinguishing clause	are (in	this example) executed
		  at PS1 assignment time, while	the $USER and $PWD are escaped
		  and thus will	be evaluated each time a prompt	is displayed):

		  PS1='${USER:=$(id -un)}'"@${HOSTNAME:=$(hostname)}:\$PWD $(
			  if ((	USER_ID	)); then print \$; else	print \#; fi) "

		  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 se-
		  quences (such	as escape codes) by prefixing your prompt with
		  a character (such as Ctrl-A) followed	by a carriage return
		  and then delimiting the escape codes with this character.
		  Any occurrences of that character in the prompt are not
		  printed.  By the way,	don't blame me for this	hack; it's de-
		  rived	from the original ksh88(1), which did print the	delim-
		  iter character so you	were out of luck if you	did not	have
		  any non-printing characters.

		  Since	backslashes and	other special characters may be	inter-
		  preted by the	shell, to set PS1 either escape	the backslash
		  itself or use	double quotes.	The latter is more practical.
		  This is a more complex example, avoiding to directly enter
		  special characters (for example with ^V in the emacs editing
		  mode), which embeds the current working directory, in	re-
		  verse	video (colour would work, too),	in the prompt string:

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

		  Due to a strong suggestion from David	G. Korn, mksh now also
		  supports the following form:

			PS1=$'\1\r\1\e[7m\1$PWD\1\e[0m\1> '

     PS2	  Secondary prompt string, by default "> ", used when more in-
		  put is needed	to complete a command.

     PS3	  Prompt used by the select statement when reading a menu se-
		  lection.  The	default	is "#? ".

     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 "+ ".  You may want to set it to
		  "[$EPOCHREALTIME] " instead, to include timestamps.

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

     RANDOM	  Each time RANDOM is referenced, it is	assigned a number be-
		  tween	0 and 32767 from a Linear Congruential PRNG first.

     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 pa-
		  rameter has been assigned an integer value, the number of
		  seconds since	the assignment plus the	value that was as-

     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

     USER_ID	  The effective	user id	of the shell at	startup.

   Tilde expansion
     Tilde expansion, which is done in parallel	with parameter substitution,
     is	applied	to words starting with an unquoted `~'.	 In parameter assign-
     ments (such as those preceding a simple-command or	those occurring	in the
     arguments of a declaration	utility), tilde	expansion is done after	any
     assignment	(i.e. after the	equals sign) or	after an unquoted colon	(`:');
     login names are also delimited by colons.	The Korn shell,	except in
     POSIX mode, always	expands	tildes after unquoted equals signs, not	just
     in	assignment context (see	below),	and enables tab	completion for tildes
     after all unquoted	colons during command line editing.

     The characters following the tilde, up to the first `/', if any, are as-
     sumed to be a login name.	If the login name is empty, `+'	or `-',	the
     simplified	value of the HOME, PWD or OLDPWD parameter is substituted, re-
     spectively.  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 per-

     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 concatena-
     tion of prefix, stri and suffix (e.g. "a{c,b{X,Y},d}e" expands to four
     words: "ace", "abXe", "abYe" and "ade").  As noted	in the example,	brace
     expressions can be	nested and the resulting words are not sorted.	Brace
     expressions must contain an unquoted comma	(`,') for expansion to occur
     (e.g. {} and {foo}	are not	expanded).  Brace expansion is carried out af-
     ter parameter substitution	and before file	name generation.

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

     ?	     Matches any single	character.

     *	     Matches any sequence of octets.

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

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

	     Matches any string	of octets that matches zero or more occur-
	     rences of the specified patterns.	Example: The pattern
	     *(foo|bar)	matches	the strings "",	"foo", "bar", "foobarfoo",

	     Matches any string	of octets that matches one or more occurrences
	     of	the specified patterns.	 Example: The pattern +(foo|bar)
	     matches the strings "foo",	"bar", "foobar", etc.

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

	     Matches a string that matches one of the specified	patterns.  Ex-
	     ample: The	pattern	@(foo|bar) only	matches	the strings "foo" and

	     Matches any string	that does not match one	of the specified pat-
	     terns.  Examples: The pattern !(foo|bar) matches all strings ex-
	     cept "foo"	and "bar"; the pattern !(*) matches no strings;	the
	     pattern !(?)* matches all strings (think about it).

     Note that complicated globbing, especially	with alternatives, is slow;
     using separate comparisons	may (or	may not) be faster.

     Note that mksh (and pdksh)	never matches "." and "..", but	AT&T UNIX ksh,
     Bourne sh and GNU bash do.

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

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

   Input/output	redirection
     When a command is executed, its standard input, standard output and stan-
     dard error	(file descriptors 0, 1 and 2, respectively) are	normally in-
     herited from the shell.  Three exceptions to this are commands in pipe-
     lines, for	which standard input and/or standard output are	those set up
     by	the pipeline, asynchronous commands created when job control is	dis-
     abled, for	which standard input is	initially set to /dev/null, and	com-
     mands for which any of the	following redirections have been specified:

     >file	 Standard output is redirected to file.	 If file does not ex-
		 ist, 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	redi-
		 rection (called a "here document"), the shell copies lines
		 from the command source into a	temporary file until a line
		 matching marker is read.  When	the command is executed, stan-
		 dard 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 (`\') es-
		 capes for `$',	``', `\' and "\newline", but not for `"'.  If
		 multiple here documents are used on the same command line,
		 they are saved	in order.

		 If no marker is given,	the here document ends at the next <<
		 and substitution will be performed.  If marker	is only	a set
		 of either single "''" or double `""' quotes with nothing in
		 between, the here document ends at the	next empty line	and
		 substitution will not be performed.

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

     <<<word	 Same as <<, except that word is the here document.  This is
		 called	a here string.

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

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

     &>file	 Same as >file 2>&1.  This is a	deprecated (legacy) GNU	bash
		 extension supported by	mksh which also	supports the preceding
		 explicit fd digit, for	example, 3&>file is the	same as	3>file
		 2>&3 in mksh but a syntax error in GNU	bash.

     &>|file, &>>file, &>&fd
		 Same as >|file, >>file	or >&fd, followed by 2>&1, as above.
		 These are mksh	extensions.

     In	any of the above redirections, the file	descriptor that	is redirected
     (i.e. standard input or standard output) can be explicitly	given by pre-
     ceding the	redirection with a single digit.  Parameter, command and
     arithmetic	substitutions, tilde substitutions, and, if the	shell is in-
     teractive,	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	multi-
     ple files match, the word with the	expanded file name generation charac-
     ters 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 | pr -n -t

     File descriptors created by I/O redirections are private to the shell.

   Arithmetic expressions
     Integer arithmetic	expressions can	be used	with the let command, inside
     $((...)) expressions, inside array	references (e.g. name[expr]), as nu-
     meric arguments to	the test command, and as the value of an assignment to
     an	integer	parameter.  Warning: This also affects implicit	conversion to
     integer, for example as done by the let command.  Never use unchecked
     user input, e.g. from the environment, in an arithmetic context!

     Expressions are calculated	using signed arithmetic	and the	mksh_ari_t
     type (a 32-bit signed integer), unless they begin with a sole `#' charac-
     ter, in which case	they use mksh_uari_t (a	32-bit unsigned	integer).

     Expressions may contain alpha-numeric parameter identifiers, array	refer-
     ences and integer constants and may be combined with the following	C op-
     erators (listed and grouped in increasing order of	precedence):

     Unary operators:

	   + - ! ~ ++ --

     Binary operators:

	   = +=	-= *= /= %= <<=	>>= ^<=	^>= &= ^= |=
	   == !=
	   < <=	> >=
	   << >> ^< ^>
	   + -
	   * / %

     Ternary operators:

	   ?: (precedence is immediately higher	than assignment)

     Grouping operators:

	   ( )

     Integer constants and expressions are calculated using an exactly 32-bit
     wide, signed or unsigned, type with silent	wraparound on integer over-
     flow.  Integer constants may be specified with arbitrary bases using the
     notation base#number, where base is a decimal integer specifying the base
     (up to 36), and number is a number	in the specified base.	Additionally,
     base-16 integers may be specified by prefixing them with "0x"
     (case-insensitive)	in all forms of	arithmetic expressions,	except as nu-
     meric arguments to	the test built-in utility.  Prefixing numbers with a
     sole digit	zero ("0") does	not cause interpretation as octal (except in
     POSIX mode, as required by	the standard), as that's unsafe	to do.

     As	a special mksh extension, numbers to the base of one are treated as
     either (8-bit transparent)	ASCII or Universal Coded Character Set code-
     points, depending on the shell's utf8-mode	flag (current setting).	 The
     AT&T UNIX ksh93 syntax of "'x'" instead of	"1#x" is also supported.  Note
     that NUL bytes (integral value of zero) cannot be used.  An unset or
     empty parameter evaluates to 0 in integer context.	 If `x'	isn't com-
     prised of exactly one valid character, the	behaviour is undefined (usu-
     ally, the shell aborts with a parse error,	but rarely, it succeeds, e.g.
     on	the sequence C2	20); users of this feature (as opposed to read -a)
     must validate the input first.  See CAVEATS for UTF-8 mode	handling.

     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 incre-
		   mented value	of the parameter; when used as a postfix oper-
		   ator, the result is the original value of the parameter.

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

	   ,	   Separates two arithmetic expressions; the left-hand side is
		   evaluated first, then the right.  The result	is 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, "var1 *= 5 +	3" is the same
		   as specifying "var1 = var1 *	(5 + 3)".

	   ||	   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, greater than or equal.
		   See <.

	   << >>   Shift left (right); the result is the left argument with
		   its bits arithmetically (signed operation) or logically
		   (unsigned expression) shifted left (right) by the amount
		   given in the	right argument.

	   ^< ^>   Rotate left (right);	the result is similar to shift,	except
		   that	the bits shifted out at	one end	are shifted in at the
		   other end, instead of zero or sign bits.

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

	   %	   Remainder; the result is the	symmetric remainder of the di-
		   vision of the left argument by the right.  To get the math-
		   ematical modulus of "a mod b", use the formula "(a %	b + b)
		   % b".

		   If <arg1> is	non-zero, the result is	<arg2>;	otherwise the
		   result is <arg3>.  The non-result argument is not evalu-

     A co-process (which is a pipeline created with the	"|&" operator) is an
     asynchronous process that the shell can both write	to (using print	-p)
     and read from (using read -p).  The input and output of the co-process
     can also be manipulated using >&p and <&p redirections, respectively.
     Once a co-process has been	started, another can't be started until	the
     co-process	exits, or until	the co-process's input has been	redirected us-
     ing 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:

     	 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 descrip-
	 tor and then close that file descriptor: exec 3>&p; exec 3>&-

     	 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.

     	 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 in-
	 put has been duplicated to another file descriptor and	print -un is

     Functions are defined using either	Korn shell function function-name syn-
     tax 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 "." 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 builtins and the PATH is

     An	existing function may be deleted using unset -f	function-name.	A list
     of	functions can be obtained using	typeset	+f and the function defini-
     tions 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,	"trace"	and "export", which can	be set
     with typeset -ft and typeset -fx, respectively.  When a traced function
     is	executed, the shell's xtrace option is turned on for the function's
     duration.	The "export" attribute of functions is currently not used.

     Since functions are executed in the current shell environment, parameter
     assignments made inside functions are visible after the function com-
     pletes.  If this is not the desired effect, the typeset command can be
     used inside a function to create a	local parameter.  Note that AT&T UNIX
     ksh93 uses	static scoping (one global scope, one local scope per func-
     tion) and allows local variables only on Korn style functions, whereas
     mksh uses dynamic scoping (nested scopes of varying locality).  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.
     Note that when called in a	subshell, return will only exit	that subshell
     and will not cause	the original shell to exit a running function (see the loop FAQ).

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

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

     	 OPTIND	is saved/reset and restored on entry and exit from the func-
	 tion 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

     	 Shell options (set -o)	have local scope, i.e. changes inside a	func-
	 tion are reset	upon its exit.

     In	the future, the	following differences may also be added:

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

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

   Command execution
     After evaluation of command-line arguments, redirections and parameter
     assignments, the type of command is determined: a special built-in	com-
     mand, a function, a normal	builtin	or the name of a file to execute found
     using the PATH parameter.	The checks are made in the above order.	 Spe-
     cial built-in commands differ from	other commands in that the PATH	param-
     eter is not used to find them, an error during their execution can	cause
     a non-interactive shell to	exit, and parameter assignments	that are spec-
     ified before the command are kept after the command completes.  Regular
     built-in commands are different only in that the PATH parameter is	not
     used to find them.

     POSIX special built-in utilities:

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

     Additional	mksh commands keeping assignments:

     source, typeset

     All other builtins	are not	special; these are at least:

     [,	alias, bg, bind, builtin, cat, cd, command, echo, false, fc, fg,
     getopts, jobs, kill, let, print, pwd, read, realpath, rename, sleep,
     suspend, test, true, ulimit, umask, unalias, wait,	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 and
     builtin-like reserved words, as well as some optional utilities:

     . file [arg ...]
	    (keeps assignments,	special) This is called	the "dot" command.
	    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.

     : [...]
	    (keeps assignments,	special) The null command.
	    Exit status	is set to zero.

     Lb64decode	[string]
	    (dot.mkshrc	function) Decode string	or standard input to binary.

     Lb64encode	[string]
	    (dot.mkshrc	function) Encode string	or standard input as base64.

     Lbafh_add [string]
	    (dot.mkshrc	functions) Implement the Better	Avalance for the Jenk-
	    ins	Hash.  This is the same	hash mksh currently uses internally.
	    After calling Lbafh_init, call Lbafh_add multiple times until all
	    input is read, then	call Lbafh_finish, which writes	the result to
	    the	unsigned integer Lbafh_v variable for your consumption.

     Lstripcom [file ...]
	    (dot.mkshrc	function) Same as cat but strips any empty lines and
	    comments (from any `#' character onwards, no escapes) and reduces
	    any	amount of whitespace to	one space character.

     [ expression ]
	    (regular) See test.

     alias [-d | -t [-r] | -+x]	[-p] [+] [name [=value]	...]
	    (regular) 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.
	    [][A-Za-z0-9_!%+,.@:-] are valid in	names, except they may not be-
	    gin	with a plus or hyphen-minus, and [[ is not a valid alias name.

	    When listing aliases, one of two formats is	used.  Normally,
	    aliases are	listed as name=value, where value is quoted as neces-
	    sary.  If options were preceded with `+', or a lone	`+' is given
	    on the command line, only name is printed.

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

	    With -p, each alias	is listed with the string "alias " prefixed.

	    The	-t option indicates that tracked aliases are to	be listed/set
	    (values given with the command 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 at-
	    tribute (exporting an alias	has no effect).

	    (built-in alias) See Functions above.

     bg	[job ...]
	    (regular, needs job	control) 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
	    (regular) The names	of editing commands strings can	be bound to
	    are	listed.	 See Emacs editing mode	for more information.

     bind [string ...]
	    The	current	bindings, for string, if given,	else all, are listed.
	    Note: Default prefix bindings (1=Esc, 2=^X,	3=NUL) assumed.

     bind string=[editing-command] [...]
     bind -m string=substitute [...]
	    To string, which should consist of a control character optionally
	    preceded by	one of the three prefix	characters and optionally suc-
	    ceeded by a	tilde character, the editing-command is	bound so that
	    future input of the	string will immediately	invoke that editing
	    command.  If a tilde postfix is given, a tilde trailing the	con-
	    trol character is ignored.	If -m (macro) is given,	future input
	    of the string will be replaced by the given	NUL-terminated
	    substitute string, wherein prefix/control/tilde characters mapped
	    to editing commands	(but not those mapped to other macros) will be

	    Prefix and control characters may be written using caret notation,
	    i.e. ^Z represents Ctrl-Z.	Use a backslash	to escape the caret,
	    an equals sign or another backslash.  Note that, although only
	    three prefix characters (usually Esc, ^X and NUL) are supported,
	    some multi-character sequences can be supported.

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

     builtin [--] command [arg ...]
	    (regular) Execute the built-in command command.

     \builtin command [arg ...]
	    (regular, decl-forwarder) Same as builtin.	Additionally acts as
	    declaration	utility	forwarder, i.e.	this is	a declaration utility
	    (see Tilde expansion) iff command is a declaration utility.

     cat [-u] [file ...]
	    (defer with	flags) Copy files in command line order	to standard
	    output.  If	a file is a single dash	("-") or absent, read from
	    standard input.  For direct	builtin	calls, the POSIX -u option is
	    supported as a no-op.  For calls from shell, if any	options	are
	    given, an external cat(1) utility is preferred over	the builtin.

     cd	[-L] [dir]
     cd	-P [-e]	[dir]
     chdir [-eLP] [dir]
	    (regular) Set the working directory	to dir.	 If the	parameter
	    CDPATH is set, it lists the	search path for	the directory contain-
	    ing	dir.  An unset or empty	path means the current directory.  If
	    dir	is found in any	component of the CDPATH	search path other than
	    an unset or	empty path, the	name of	the new	working	directory will
	    be written to standard output.  If dir is missing, the home	direc-
	    tory HOME is used.	If dir is "-", 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 ".." 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,
	    ".." is relative to	the filesystem directory tree.	The PWD	and
	    OLDPWD parameters are updated to reflect the current and old work-
	    ing	directory, respectively.  If the -e option is set for physical
	    filesystem traversal and PWD could not be set, the exit code is 1;
	    greater than 1 if an error occurred, 0 otherwise.

     cd	[-eLP] old new
     chdir [-eLP] old new
	    (regular) The string new is	substituted for	old in the current di-
	    rectory, and the shell attempts to change to the new directory.

     cls    (dot.mkshrc	alias) Reinitialise the	display	(hard reset).

     command [-pVv] cmd	[arg ...]
	    (regular, decl-forwarder) If neither the -v	nor -V option is
	    given, cmd is executed exactly as if command had not been speci-
	    fied, with two exceptions: firstly,	cmd cannot be a	shell func-
	    tion; and secondly,	special	built-in commands lose their special-
	    ness (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, whose actual
	    value is system-dependent, is used instead of the current PATH.

	    If the -v option is	given, instead of executing cmd, information
	    about what would be	executed is given for each argument.  For
	    builtins, functions	and keywords, their names are simply printed;
	    for	aliases, a command that	defines	them is	printed; for utilities
	    found by searching the PATH	parameter, the full path of the	com-
	    mand is printed.  If no command is found (i.e. the path search
	    fails), nothing is printed and command exits with a	non-zero sta-
	    tus.  The -V option	is like	the -v option, but more	verbose.

     continue [level]
	    (keeps assignments,	special) Jumps to the beginning	of the levelth
	    inner-most for, select, until or while loop.  level	defaults to 1.

     dirs [-lnv]
	    (dot.mkshrc	function) Print	the directory stack.  -l causes	tilde
	    expansion to occur in the output.  -n causes line wrapping before
	    80 columns,	whereas	-v causes numbered vertical output.

     doch   (dot.mkshrc	alias) Execute the last	command	with sudo(8).

     echo [-Een] [arg ...]
	    (regular) Warning: this utility is not portable; use the standard
	    Korn shell built-in	utility	print in new code instead.

	    Print arguments, separated by spaces, followed by a	newline, to
	    standard output.  The newline is suppressed	if any of the argu-
	    ments contain the backslash	sequence "\c".	See the	print command
	    below for a	list of	other backslash	sequences that are recognised.

	    The	options	are provided for compatibility with BSD	shell scripts.
	    The	-E option suppresses backslash interpretation, -e enables it
	    (normally default),	-n suppresses the trailing newline, and	any-
	    thing else causes the word to be printed as	argument instead.

	    If the posix or sh option is set or	this is	a direct builtin call
	    or print -R, only the first	argument is treated as an option, and
	    only if it is exactly "-n".	 Backslash interpretation is disabled.

     enable [-anps] [name ...]
	    (dot.mkshrc	function) Hide and unhide built-in utilities, aliases
	    and	functions and those defined in dot.mkshrc.

	    If no name is given	or the -p option is used, builtins are printed
	    (behind the	string "enable ", followed by "-n " if the builtin is
	    currently disabled), otherwise, they are disabled (if -n is	given)
	    or re-enabled.

	    When printing, only	enabled	builtins are printed by	default; the
	    -a options prints all builtins, while -n prints only disabled
	    builtins instead; -s limits	the list to POSIX special builtins.

     eval command ...
	    (keeps assignments,	special) The arguments are concatenated, with
	    a space between each, to form a single string which	the shell then
	    parses and executes	in the current execution environment.

     exec [-a argv0] [-c] [command [arg	...]]
	    (keeps assignments,	special) The command (with arguments) is exe-
	    cuted without forking, fully replacing the shell process; this is
	    absolute, i.e. exec	never returns, even if the command is not
	    found.  The	-a option permits setting a different argv[0] value,
	    and	-c clears the environment before executing the child process,
	    except for the _ parameter and direct assignments.

	    If no command is given except for I/O redirection, the I/O redi-
	    rection is permanent and the shell is not replaced.	 Any file de-
	    scriptors 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 on.

     exit [status]
	    (keeps assignments,	special) The shell or subshell exits with the
	    specified errorlevel (or the current value of the $? parameter).

     export [-p] [parameter[=value]]
	    (keeps assignments,	special, decl-util) 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.	 This is a declaration util-

	    If no parameters are specified, all	parameters with	the export at-
	    tribute set	are printed one	per line: either their names, or, if a
	    "-"	with no	option letter is specified, name=value pairs, or, with
	    the	-p option, export commands suitable for	re-entry.

	    (OS/2) Null	command	required for shebang-like functionality.

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

     fc	[-e editor | -l	[-n]] [-r] [first [last]]
	    (regular) first and	last select commands from the history.	Com-
	    mands can be selected by history number (negative numbers go back-
	    wards from the current, most recent, line) 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 speci-
	    fied 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 the result is	executed by the	shell.

     fc	-e - | -s [-g] [old=new] [prefix]
	    (regular) Re-execute the selected command (the previous command by
	    default) after performing the optional substitution	of old with
	    new.  If -g	is specified, all occurrences of old are replaced with
	    new.  The meaning of -e - and -s is	identical: re-execute the se-
	    lected command without invoking an editor.	This command is	usu-
	    ally accessed with the predefined: alias r='fc -e -'

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

     functions [name ...]
	    (built-in alias) Display the function definition commands corre-
	    sponding to	the listed, or all defined, functions.

     getopts optstring name [arg ...]
	    (regular) Used by shell procedures to parse	the specified argu-
	    ments (or positional parameters, if	no arguments are given)	and to
	    check for legal options.  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 word it
	    is found in, the remainder of the word is taken to be the option's
	    argument; otherwise, the next word is the option's argument.

	    optstring contains the option letters to be	recognised.  If	a let-
	    ter	is followed by a colon,	the option takes an argument.

	    Each time getopts is invoked, it places the	next option in the
	    shell parameter name.  If the option was introduced	with a `+',
	    the	character placed in name is prefixed with a `+'.  If the op-
	    tion takes an argument, it is placed in the	shell parameter

	    When an illegal option or a	missing	option argument	is encoun-
	    tered, 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 letter that caused the problem.  Furthermore,
	    unless optstring begins with a colon, a question mark is placed in
	    name, OPTARG is unset and a	diagnostic is shown on standard	error.

	    getopts records the	index of the argument to be processed by the
	    next call in OPTIND.  When the end of the options is encountered,
	    getopts returns a non-zero exit status.  Options end at the	first
	    argument that does not start with a	`-' (non-option	argument) or
	    when a "--"	argument is encountered.

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

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

     hash [-r] [name ...]
	    (built-in alias) Without arguments,	any hashed executable command
	    paths are listed.  The -r option causes all	hashed commands	to be
	    removed from the cache.  Each name is searched as if it were a
	    command name and added to the cache	if it is an executable com-

     hd	[file ...]
	    (dot.mkshrc	alias or function) Hexdump stdin or arguments legibly.

     history [-nr] [first [last]]
	    (built-in alias) Same as fc	-l (see	above).

     integer [flags] [name [=value] ...]
	    (built-in alias) Same as typeset -i	(see below).

     jobs [-lnp] [job ...]
	    (regular) 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 job.

     kill [-s signame |	-signum	| -signame] { job | pid	| pgrp } ...
	    (regular) 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 ...]
	    (regular) Print the	signal name corresponding to exit-status.  If
	    no arguments are specified,	a list of all the signals with their
	    numbers and	a short	description of each are	printed.

     let [expression ...]
	    (regular) Each expression is evaluated (see	Arithmetic expressions
	    above).  If	all expressions	evaluate successfully, 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:
		  { \\builtin let 'expr'; }

     local [flags] [name [=value] ...]
	    (built-in alias) Same as typeset (see below).

     mknod [-m mode] name b|c major minor
     mknod [-m mode] name p
	    (optional) Create a	device special file.  The file type may	be one
	    of b (block	type device), c	(character type	device)	or p (named
	    pipe, FIFO).  The file created may be modified according to	its
	    mode (via the -m option), major (major device number), and minor
	    (minor device number).  This is not	normally part of mksh; how-
	    ever, distributors may have	added this as builtin as a speed hack.

     nameref [flags] [name [=value] ...]
	    (built-in alias) Same as typeset -n	(see below).

     popd [-lnv] [+n]
	    (dot.mkshrc	function) Pops the directory stack and returns to the
	    new	top directory.	The flags are as in dirs (see above).  A nu-
	    meric argument +n selects the entry	in the stack to	discard.

     print [-AcelNnprsu[n] | -R	[-n]] [argument	...]
	    (regular) Print the	specified argument(s) on the standard output,
	    separated by spaces, terminated with a newline.  The escapes men-
	    tioned in Backslash	expansion above, as well as "\c", which	is
	    equivalent to using	the -n option, are interpreted.

	    The	options	are as follows:

	    -A	   Each	argument is arithmetically evaluated; the character
		   corresponding to the	resulting value	is printed.  Empty
		   arguments separate input words.

	    -c	   The output is printed columnised, line by line, similar to
		   how the rs(1) utility, tab completion, the kill -l built-in
		   utility and the select statement do.

	    -e	   Restore backslash expansion after a previous	-r.

	    -l	   Change the output word separator to newline.

	    -N	   Change the output word and line separator to	ASCII NUL.

	    -n	   Do not print	the trailing line separator.

	    -p	   Print to the	co-process (see	Co-processes above).

	    -r	   Inhibit backslash expansion.

	    -s	   Print to the	history	file instead of	standard output.

	    -u[n]  Print to the	file descriptor	n (defaults to 1 if omitted)
		   instead of standard output.

	    The	-R option mostly emulates the BSD echo(1) command which	does
	    not	expand backslashes and interprets its first argument as	option
	    only if it is exactly "-n" (to suppress the	trailing newline).

     printf format [arguments ...]
	    (optional, defer always) If	compiled in, format and	print the ar-
	    guments, supporting	the bare POSIX-mandated	minimum.  If an	exter-
	    nal	utility	of the same name is found, it is deferred to, unless
	    run	as direct builtin call or from the builtin utility.

     pushd [-lnv]
	    (dot.mkshrc	function) Rotate the top two elements of the directory
	    stack.  The	options	are the	same as	for dirs (see above), and
	    pushd changes to the topmost directory stack entry after acting.

     pushd [-lnv] +n
	    (dot.mkshrc	function) Rotate the element number n to the top.

     pushd [-lnv] name
	    (dot.mkshrc	function) Push name on top of the stack.

     pwd [-LP]
	    (regular) Print the	present	working	directory.  If no options are
	    given, pwd behaves as if the -P option (print physical path) was
	    used if the	physical shell option is set, the -L option (print
	    logical path) otherwise.  The logical path is the path used	to cd
	    to the current directory; the physical path	is determined from the
	    filesystem (by following ".." directories to the root directory).

     r [-g] [old=new] [prefix]
	    (built-in alias) Same as fc	-e - (see above).

     read [-A |	-a] [-d	x] [-N z | -n z] [-p | -u[n]] [-t n] [-rs] [p ...]
	    (regular) Reads a line of input, separates the input into fields
	    using the IFS parameter (see Substitution above) or	other speci-
	    fied means,	and assigns each field to the specified	parameters p.
	    If no parameters are specified, the	REPLY parameter	is used	to
	    store the result.  If there	are more parameters than fields, the
	    extra parameters are set to	the empty string or 0; if there	are
	    more fields	than parameters, the last parameter is assigned	the
	    remaining fields (including	the word separators).

	    The	options	are as follows:

	    -A	   Store the result into the parameter p (or REPLY) as array
		   of words.  Only no or one parameter is accepted.

	    -a	   Store the result, without applying IFS word splitting, into
		   the parameter p (or REPLY) as array of characters (wide
		   characters if the utf8-mode option is enacted, octets oth-
		   erwise); the	codepoints are encoded as decimal numbers by
		   default.  Only no or	one parameter is accepted.

	    -d x   Use the first byte of x, NUL	if empty, instead of the ASCII
		   newline character to	delimit	input lines.

	    -N z   Instead of reading till end-of-line,	read exactly z bytes.
		   Upon	EOF, a partial read is returned	with exit status 1.
		   After timeout, a partial read is returned with an exit sta-
		   tus as if SIGALRM were caught.

	    -n z   Instead of reading till end-of-line,	read up	to z bytes but
		   return as soon as any bytes are read, e.g. from a slow ter-
		   minal device, or if EOF or a	timeout	occurs.

	    -p	   Read	from the currently active co-process (see Co-processes
		   above for details) instead of from a	file descriptor.

	    -u[n]  Read	from the file descriptor number	n (defaults to 0, i.e.
		   standard input).
		   The argument	must immediately follow	the option character.

	    -t n   Interrupt reading after n seconds (specified	as positive
		   decimal value with an optional fractional part).  The exit
		   status of read is the same as if SIGALRM were caught	if the
		   timeout occurred, but partial reads may still be returned.

	    -r	   Normally, read strips backslash-newline sequences and any
		   remaining backslashes from input.  This option enables raw
		   mode, in which backslashes are retained and ignored.

	    -s	   The input line is saved to the history.

	    If the input is a terminal,	both the -N and	-n options set it into
	    raw	mode; they read	an entire file if -1 is	passed as z argument.

	    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: ').

	    If no input	is read	or a timeout occurred, read exits with a non-
	    zero status.

     readonly [-p] [parameter [=value] ...]
	    (keeps assignments,	special, decl-util) Sets the read-only attri-
	    bute of the	named parameters.  If values are given,	parameters are
	    assigned these before disallowing writes.  Once a parameter	is
	    made read-only, it cannot be unset and its value cannot be

	    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.

     realpath [--] name
	    (defer with	flags) Resolves	an absolute pathname corresponding to
	    name.  If the resolved pathname either exists or can be created
	    immediately, realpath returns 0 and	prints the resolved pathname,
	    otherwise or if an error occurs, it	issues a diagnostic and	re-
	    turns nonzero.  If name ends with a	slash (`/'), resolving to an
	    extant non-directory is also treated as error.

     rename [--] from to
	    (defer always) Renames the file from to to.	 Both must be complete
	    pathnames and on the same device.  Intended	for emergency situa-
	    tions (where /bin/mv becomes unusable); directly calls rename(2).

     return [status]
	    (keeps assignments,	special) Returns from a	function or . script
	    with errorlevel 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 mksh
	    treats both	profile	and ENV	files as . scripts, while the original
	    Korn shell only treated profiles as	. scripts.

     rot13  (dot.mkshrc	alias) ROT13-encrypts/-decrypts	stdin to stdout.

     set [-+abCefhiklmnprsUuvXx] [-+o option] [-+A name] [--] [arg ...]
	    (keeps assignments,	special) The set command can be	used to	show
	    all	shell parameters (like typeset -), set (-) or clear (+)	shell
	    options, set an array parameter or the positional parameters.

	    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 short (if extant)
	    and	long names along with a	description of what each 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.  If name ends
		 with a	`+', the array is appended to instead.

		 An alternative	syntax for the command set -A foo -- a b c;
		 set -A	foo+ --	d e which is compatible	to GNU bash and	also
		 supported by AT&T UNIX	ksh93 is: foo=(a b c); foo+=(d e)

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

	    -b | -o notify
		 Print job notification	messages asynchronously	instead	of
		 just before the prompt.  Only used with job control (-m).

	    -C | -o noclobber
		 Prevent > redirection from overwriting	existing files.	 In-
		 stead,	>| must	be used	to force an overwrite.	Note: This is
		 not safe to use for creation of temporary files or lockfiles
		 due to	a TOCTOU in a check allowing one to redirect output to
		 /dev/null or other device files even in noclobber mode.

	    -e | -o errexit
		 Exit (after executing the ERR trap) as	soon as	an error oc-
		 curs or a command fails (i.e. exits with a non-zero status).
		 This does not apply to	commands whose exit status is explic-
		 itly tested by	a shell	construct such as !, if, until or
		 while statements.  For	&&, || and pipelines (but mind -o
		 pipefail), only the status of the last	command	is tested.

	    -f | -o noglob
		 Do not	expand file name patterns.

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

	    -i | -o interactive
		 The shell is an interactive shell.  This option can only be
		 used when the shell is	invoked.  See above for	details.

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

	    -l | -o login
		 The shell is a	login shell.  This option can only be used
		 when the shell	is invoked.  See above for what	this means.

	    -m | -o monitor
		 Enable	job control (default for interactive shells).

	    -n | -o noexec
		 Do not	execute	any commands.  Useful for checking the syntax
		 of scripts.  Ignored if reading commands from a tty.

	    -p | -o 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.

		 If the	shell is privileged, setting this flag after startup
		 files have been processed let it go full setuid and/or	set-
		 gid.  Clearing	this flag makes	the shell drop privileges.
		 Changing this flag resets the groups vector.

	    -r | -o restricted
		 The shell is a	restricted shell.  This	option can only	be
		 used when the shell is	invoked.  See above for	what this

	    -s | -o 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	ASCIIbetically before assigning	them
		 to the	positional parameters (or to array name, with -A).

	    -U | -o utf8-mode
		 Enable	UTF-8 support in the Emacs editing mode	and internal
		 string	handling functions.  This flag is disabled by default,
		 but can be enabled by setting it on the shell command line;
		 is enabled automatically for interactive shells if requested
		 at compile time, your system supports setlocale(LC_CTYPE, "")
		 and optionally	nl_langinfo(CODESET), or the LC_ALL, LC_CTYPE
		 or LANG environment variables,	and at least one of these re-
		 turns something that matches "UTF-8" or "utf8"	case-insensi-
		 tively; for direct builtin calls depending on the aforemen-
		 tioned	environment variables; or for stdin or scripts,	if the
		 input begins with a UTF-8 Byte	Order Mark.

		 In near future, locale	tracking will be implemented, which
		 means that set	-+U is changed whenever	one of the POSIX lo-
		 cale-related environment variables changes.

	    -u | -o nounset
		 Referencing of	an unset parameter, other than "$@" or "$*",
		 is treated as an error, unless	one of the `-',	`+' or `='
		 modifiers is used.

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

	    -X | -o markdirs
		 Mark directories with a trailing `/' during globbing.

	    -x | -o xtrace
		 Print commands	when they are executed,	preceded by PS4.

	    -o bgnice
		 Background jobs are run with lower priority.

	    -o braceexpand
		 Enable	brace expansion.  This is enabled by default.

	    -o emacs
		 Enable	BRL emacs-like command-line editing (interactive
		 shells	only); see Emacs editing mode.	Enabled	by default.

	    -o gmacs
		 Enable	gmacs-like command-line	editing	(interactive shells
		 only).	 Currently identical to	emacs editing except that
		 transpose-chars (^T) acts slightly differently.

	    -o 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.

	    -o inherit-xtrace
		 Do not	reset -o xtrace	upon entering functions	(default).

	    -o nohup
		 Do not	kill running jobs with a SIGHUP	signal when a login
		 shell exits.  Currently set by	default, but this may change
		 in the	future to be compatible	with AT&T UNIX ksh, which
		 doesn't have this option, but does send the SIGHUP signal.

	    -o nolog
		 No effect.  In	the original Korn shell, this prevented	func-
		 tion definitions from being stored in the history file.

	    -o physical
		 Causes	the cd and pwd commands	to use "physical" (i.e.	the
		 filesystem's) ".." directories	instead	of "logical" directo-
		 ries (i.e. the	shell handles "..", which allows the user to
		 be oblivious of symbolic links	to directories).  Clear	by de-
		 fault.	 Note that setting this	option does not	affect the
		 current value of the PWD parameter; only the cd command
		 changes PWD.  See cd and pwd above for	more details.

	    -o pipefail
		 Make the exit status of a pipeline the	rightmost non-zero er-
		 rorlevel, or zero if all commands exited with zero.

	    -o posix
		 Behave	closer to the standards	(see POSIX mode	for details).
		 Automatically enabled if the shell invocation basename, after
		 `-' and `r' processing, begins	with "sh" and (often used for
		 the lksh binary) this autodetection feature is	compiled in.
		 As a side effect, setting this	flag turns off the braceexpand
		 and utf8-mode flags, which can	be turned back on manually,
		 and (unless both are set in the same command) sh mode.

	    -o sh
		 Enable	kludge /bin/sh compatibility mode (see SH mode below
		 for details).	Automatically enabled if the basename of the
		 shell invocation, after `-' and `r' processing, begins	with
		 "sh" and this autodetection feature is	compiled in (rather
		 uncommon).  As	a side effect, setting this flag turns off the
		 braceexpand flag, which can be	turned back on manually, and
		 posix mode (unless both are set in the	same command).

	    -o vi
		 Enable	vi(1)-like command-line	editing	(interactive shells
		 only).	 See Vi	editing	mode for documentation and limita-

	    -o vi-esccomplete
		 In vi command-line editing, do	command	and file name comple-
		 tion when Esc (^[) is entered in command mode.

	    -o vi-tabcomplete
		 In vi command-line editing, do	command	and file name comple-
		 tion when Tab (^I) is entered in insert mode (default).

	    -o 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.  mksh 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 "$-".	 set -o	with no	option name will list all the
	    options and	whether	each is	on or off; set +o prints a command to
	    restore the	current	option set, using the internal set -o .reset
	    construct, which is	an implementation detail; these	commands are
	    transient (only valid within the current shell session).

	    Remaining arguments, if any, are positional	parameters and are as-
	    signed, in order, to the positional	parameters (i.e. $1, $2,
	    etc.).  If options end with	"--" and there are no remaining	argu-
	    ments, all positional parameters are cleared.  For unknown histor-
	    ical reasons, a lone "-" option is treated specially - it clears
	    both the -v	and -x options.	 If no options or arguments are	given,
	    the	values of all parameters are printed (suitably quoted).

     setenv [name [value]]
	    (dot.mkshrc	function) Without arguments, display the names and
	    values of all exported parameters.	Otherwise, set name's export
	    attribute, and its value to	value (empty string if none given).

     shift [number]
	    (keeps assignments,	special) The positional	parameters number+1,
	    number+2, etc.  (number defaults to	1) are renamed to 1, 2,	etc.

     sleep seconds
	    (regular, needs select(2)) Suspends	execution for a	minimum	of the
	    seconds (specified as positive decimal value with an optional
	    fractional part).  Signal delivery may continue execution earlier.

     smores [file ...]
	    (dot.mkshrc	function) Simple pager:	<Enter>	next; `q'+<Enter> quit

     source file [arg ...]
	    (keeps assignments)	Like . ("dot"),	except that the	current	work-
	    ing	directory is appended to the search path.  (GNU	bash

	    (needs job control and getsid(2)) Stops the	shell as if it had re-
	    ceived 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 suspended.

     test expression
     [ expression ]
	    (regular) test evaluates the expression and	exits with status code
	    0 if true, 1 if false, or greater than 1 if	there was an error.
	    It is often	used as	the condition command of if and	while state-
	    ments.  All	file expressions, except -h and	-L, follow symbolic

	    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 ID.

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

	    -H file	       file is a context dependent directory (only
			       useful on HP-UX).

	    -h file	       file is a symbolic link.

	    -k file	       file's mode has the sticky(7) bit set.

	    -L file	       file is a symbolic link.

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

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

	    -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.

	    -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.

	    -v name	       The shell parameter name	is set.

	    -o option	       Shell option is set (see	the set	command	above
			       for a list of options).	As a non-standard ex-
			       tension,	if the option starts with a `!', 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 exists).
			       The same	can be achieved	with [ -o ?foo ] like
			       in AT&T UNIX ksh93.  option can also be the
			       short flag prefixed with	either `-' or `+' (no
			       logical negation), for example "-x" or "+x" in-
			       stead of	"xtrace".

	    string = string    Strings are equal.  In double brackets, pattern
			       matching	(R59+ using extglobs) occurs if	the
			       right-hand string isn't quoted.

	    string == string   Same as `=' (deprecated).

	    string != string   Strings are not equal.  See `=' regarding pat-
			       tern matching.

	    string > string    First string operand is greater than second
			       string operand.

	    string < string    First string operand is less than second	string

	    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 prece-
	    dence 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.

	    Note that a	number actually	may be an arithmetic expression, such
	    as a mathematical term or the name of an integer variable:

		  x=1; [ "x" -eq 1 ]	  evaluates to true

	    Note that some special rules are applied (courtesy of POSIX) if
	    the	number of arguments to test or inside the brackets [ ... ] is
	    less than five: if leading "!" arguments can be stripped such that
	    only one to	three arguments	remain,	then the lowered comparison is
	    executed; (thanks to XSI) parentheses \( ... \) lower four-	and
	    three-argument forms to two- and one-argument forms, respectively;
	    three-argument forms ultimately prefer binary operations, followed
	    by negation	and parenthesis	lowering; two- and four-argument forms
	    prefer negation followed by	parenthesis; the one-argument form al-
	    ways implies -n.  To assume	this is	not necessarily	portable.

	    Note: A common mistake is to use "if [ $foo	= bar ]" which fails
	    if parameter "foo" is empty	or unset, if it	has embedded spaces
	    (i.e. IFS octets) or if it is a unary operator like	"!" or "-n".
	    Use	tests like "if [ x"$foo" = x"bar" ]" instead, or the double-
	    bracket operator (see [[ above): "if [[ $foo = bar ]]" or, to
	    avoid pattern matching, "if	[[ $foo	= "$bar" ]]"; the [[ ... ]]
	    construct is not only more secure to use but also often faster.

     time [-p] [pipeline]
	    (reserved word) 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:

		  0m0.03s real	   0m0.02s user	    0m0.01s system

	    If the -p option is	given (which is	only permitted if pipeline is
	    a simple command), the output is slightly longer:

		  real	   0.03
		  user	   0.02
		  sys	   0.01

	    Simple redirections	of standard error do not affect	time's output:

		  $ time sleep 1 2>afile
		  $ { time sleep 1; } 2>afile

	    Times for the first	command	do not go to "afile", but those	of the
	    second command do.

     times  (keeps assignments,	special) Print the accumulated user and	system
	    times (see above) used both	by the shell and by processes that the
	    shell started which	have exited.  The format of the	output is:

		  0m0.01s 0m0.00s
		  0m0.04s 0m0.02s

     trap n [signal ...]
	    (keeps assignments,	special) If the	first operand is a decimal un-
	    signed integer, this resets	all specified signals to the default
	    action, i.e. is the	same as	calling	trap with a dash ("-") as
	    handler, followed by the arguments (interpreted as signals).

     trap [handler signal ...]
	    (keeps assignments,	special) Sets a	trap handler that is to	be ex-
	    ecuted when	any of the specified signals are received.  handler is
	    either an empty string, indicating the signals are to be ignored,
	    a dash ("-"), indicating that the default action is	to be taken
	    for	the signals (see signal(3)), or	a string comprised of shell
	    commands to	be 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, possibly
	    prefixed with "SIG", of a signal (e.g. PIPE, ALRM or SIGINT) 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	exe-
	    cuted after	an error occurs; an error is something that would
	    cause the shell to exit if the set -e or set -o errexit option
	    were set.  EXIT handlers are executed in the environment of	the
	    last executed command.  The	original Korn shell's DEBUG trap and
	    handling of	ERR and	EXIT in	functions are not yet implemented.

	    Note that, for non-interactive shells, the trap handler cannot be
	    changed for	signals	that were ignored when the shell started.

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

     true   (regular) A	command	that exits with	a zero status.

     type name ...
	    (built-in alias) Reveal how	name would be interpreted as command.

     typeset [-+aglpnrtUux] [-L[n] | -R[n] | -Z[n]] [-i[n]] [name [=value]
     typeset -f	[-tux] [name ...]
	    (keeps assignments,	decl-util) Display or set attributes of	shell
	    parameters or functions.  With no name arguments, parameter	at-
	    tributes are shown;	if no options are used,	the current attributes
	    of all parameters are printed as typeset commands; if an option is
	    given (or "-" with no option letter), all parameters and their
	    values with	the specified attributes are printed; if options are
	    introduced with `+'	(or "+"	alone),	only names are printed.

	    If any name	arguments are given, the attributes of the so named
	    parameters are set (-) or cleared (+); inside a function, this
	    will cause the parameters to be created (and set to	"" if no value
	    is given) in the local scope (except if -g is used).  Values for
	    parameters may optionally be specified.  For name[*], the change
	    affects all	elements of the	array, and no value may	be specified.

	    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 in-
	    troduced with `+', in which	case only the names are	displayed.

	    -a	    Indexed array attribute.

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

	    -g	    "global" mode.  Do not cause named parameters to be	cre-
		    ated in the	local scope when called	inside a function.

	    -i[n]   Integer attribute.	n specifies the	base to	use when
		    stringifying the integer (if not specified,	the base given
		    in the first assignment is used).  Parameters with this
		    attribute may be assigned arithmetic expressions for val-

	    -L[n]   Left justify attribute.  n specifies the field width.  If
		    n is not specified,	the current width of the parameter (or
		    the	width of its first assigned value) is used.  Leading
		    whitespace (and digit zeros, if used with the -Z option)
		    is stripped.  If necessary,	values are either truncated or
		    padded with	space to fit the field width.

	    -l	    Lower case attribute.  All upper case ASCII	characters in
		    values are converted to lower case.	 (In the original Korn
		    shell, this	parameter meant	"long integer" when used with
		    the	-i option.)

	    -n	    Create a bound variable (name reference): any access to
		    the	variable name will access the variable value in	the
		    current scope (this	is different from AT&T UNIX ksh93!)
		    instead.  Also different from AT&T UNIX ksh93 is that
		    value is lazily evaluated at the time name is accessed.
		    This can be	used by	functions to access variables whose
		    names are passed as	parameters, instead of resorting to

	    -p	    Print complete typeset commands that can be	used to	re-
		    create the attributes and values of	parameters.

	    -R[n]   Right justify attribute.  n	specifies the field width.  If
		    n is not specified,	the current width of the 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 padded with space	to 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.  This attribute has no meaning to the shell
		    for	parameters and is provided for application use.

		    For	functions, -t is the trace attribute.  When functions
		    with the trace attribute are executed, the -o xtrace (-x)
		    shell option is temporarily	turned on.

	    -U	    Unsigned integer attribute.	 Integers are printed as un-
		    signed values (combined with the -i	option).

	    -u	    Upper case attribute.  All lower case ASCII	characters in
		    values are converted to upper case.	 (In the original Korn
		    shell, this	parameter meant	"unsigned integer" when	used
		    with the -i	option which meant upper case letters would
		    never be used for bases greater than 10.  See -U above.)

		    For	functions, -u is the undefined attribute, used with
		    FPATH.  See	Functions above	for the	implications of	this.

	    -x	    Export attribute.  Parameters are placed in	the environ-
		    ment of any	executed commands.  Functions cannot be	ex-
		    ported for security	reasons	("shellshock").

	    -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.  For integers, the	number is padded, not the

	    If any of the -i, -L, -l, -R, -U, -u or -Z options are changed,
	    all	others from this set are cleared, unless they are also given
	    on the same	command	line.

     ulimit [-aBCcdefHilMmnOPpqrSsTtVvwx] [value]
	    (regular) 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 or the word	"unlimited".  The lim-
	    its	affect the shell and any processes created by the shell	after
	    a limit is imposed.	 Note that systems may not allow some limits
	    to be increased once they are set.	Also note that the types of
	    limits available are system	dependent - some systems have only the
	    -f limit, or not even that,	or can set only	the soft limits, etc.

	    -a	   Display all limits (soft limits unless -H is	used).

	    -B n   Set the socket buffer size to n kibibytes.

	    -C n   Set the number of cached threads to n.

	    -c n   Impose a size limit of n blocks on the size of core dumps.
		   Silently ignored if the system does not support this	limit.

	    -d n   Limit the size of the data area to n	kibibytes.
		   On some systems, read-only maximum brk(2) size minus	etext.

	    -e n   Set the maximum niceness to n.

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

	    -H	   Set the hard	limit only (the	default	is to set both hard
		   and soft limits).  With -a, display all hard	limits.

	    -i n   Set the number of pending signals to	n.

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

	    -M n   Set the AIO locked memory to	n kibibytes.

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

	    -n n   Impose a limit of n file descriptors	that can be open at
		   once.  On some systems attempts to set are silently ig-

	    -O n   Set the number of AIO operations to n.

	    -P n   Limit the number of threads per process to n.

		   This	option mostly matches AT&T UNIX	ksh93's	-T;
		   on AIX, see -r as used by its ksh though.

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

	    -q n   Limit the size of POSIX message queues to n bytes.

	    -r n   (AIX) Limit the number of threads per process to n.
		   (Linux) Set the maximum real-time priority to n.

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

	    -s n   Limit the size of the stack area to n kibibytes.

	    -T n   Impose a time limit of n real seconds ("humantime") to be
		   used	by each	process.

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

	    -V n   Set the number of vnode monitors on Haiku to	n.

	    -v n   Impose a limit of n kibibytes on the	amount of virtual mem-
		   ory (address	space) used.

	    -w n   Limit the amount of swap space used to at most n kibibytes.

	    -x n   Set the maximum number of file locks	to n.

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

     umask [-S]	[mask]
	    (regular) Display or set the file permission creation mask or
	    umask (see umask(2)).  If the -S option is used, the mask dis-
	    played 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 oc-
	    tal	masks in which a set bit means the corresponding bit is	to be
	    cleared).  For example, "ug=rwx,o="	sets the mask so files will
	    not	be readable, writable or executable by "others", and is	equiv-
	    alent (on most systems) to the octal mask "007".

     unalias [-adt] [name ...]
	    (regular) 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 ...
	    (keeps assignments,	special) Unset the named parameters (-v, the
	    default) or	functions (-f).	 With parameter[*], attributes are re-
	    tained, only values	are unset.  The	exit status is non-zero	if any
	    of the parameters are read-only, zero otherwise (not portable).

     wait [job ...]
	    (regular) Wait for the specified job(s) to finish.	The exit sta-
	    tus	of wait	is that	of the last specified job; if the last job is
	    killed by a	signal,	the exit status	is 128 + the signal number
	    (see kill -l exit-status above); if	the last specified job cannot
	    be found (because it never existed or had already finished), the
	    exit status	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 re-
	    ceived or if a SIGHUP, SIGINT or SIGQUIT signal is received.

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

     whence [-pv] [name	...]
	    (regular) Without the -v option, it	is the same as command -v, ex-
	    cept aliases are printed as	their definition only.	With the -v
	    option, it is exactly identical to command -V.  In either case,
	    with the -p	option the search is restricted	to the (current) PATH.

     which [-a]	[name ...]
	    (dot.mkshrc	function) Without -a, behaves like whence -p (does a
	    PATH search	for each name printing the resulting pathname if
	    found); with -a, matches in	all PATH components are	printed, i.e.
	    the	search is not stopped after a match.  If no name was matched,
	    the	exit status is 2; if every name	was matched, it	is zero, oth-
	    erwise it is 1.  No	diagnostics are	produced on failure to match.

   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	pipe-
     lines.  At	a minimum, the shell keeps track of the	status of the back-
     ground (i.e. asynchronous)	jobs that currently exist; this	information
     can be displayed using the	jobs commands.	If job control is fully	en-
     abled (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 back-
     ground using the commands fg and bg.

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

     When a job	is created, it is assigned a job number.  For interactive
     shells, this number is printed inside "[...]", followed by	the process
     IDs of the	processes in the job when an asynchronous command is run.  A
     job may be	referred to in 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
     (`%').  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 ex-

     %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 `+' or `-'	character if the job is	the %+ or %- job, re-
	      spectively, 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 ["core	dumped"]
			 The job was killed by a signal	(e.g. memory fault,
			 hangup); use kill -l for a list of signal descrip-
			 tions.	 The "core dumped" message indicates the
			 process created a core	file.

     command  is the command that created the process.	If there are multiple
	      processes	in the job, 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.  Simi-
     larly, 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.

   Terminal state
     The state of the controlling terminal can be modified by a	command	exe-
     cuted in the foreground, whether or not job control is enabled, but the
     modified terminal state is	only kept past the job's lifetime and used for
     later command invocations if the command exits successfully (i.e. with an
     exit status of 0).	 When such a job is momentarily	stopped	or restarted,
     the terminal state	is saved and restored, respectively, but it will not
     be	kept afterwards.  In interactive mode, when line editing is enabled,
     the terminal state	is saved before	being reconfigured by the shell	for
     the line editor, then restored before running a command.

   POSIX mode
     Entering set -o posix mode	will cause mksh	to behave even more POSIX com-
     pliant in places where the	defaults or opinions differ.  Note that	mksh
     will still	operate	with unsigned 32-bit arithmetic; use lksh if arith-
     metic on the host long data type, complete	with ISO C Undefined Behav-
     iour, is required;	refer to the lksh(1) manual page for details.  Most
     other historic, AT&T UNIX ksh-compatible or opinionated differences can
     be	disabled by using this mode; these are:

     	 The incompatible GNU bash I/O redirection &>file is not supported.

     	 File descriptors created by I/O redirections are inherited by child

     	 Numbers with a	leading	digit zero are interpreted as octal.

     	 The echo builtin does not interpret backslashes and only supports the
	 exact option -n.

     	 Alias expansion with a	trailing space only reruns on command words.

     	 Tilde expansion follows POSIX instead of Korn shell rules.

     	 The exit status of fg is always 0.

     	 kill -l only lists signal names, all in one line.

     	 getopts does not accept options with a	leading	`+'.

     	 exec skips builtins, functions	and other commands and uses a PATH
	 search	to determine the utility to execute.

   SH mode
     Compatibility mode; intended for use with legacy scripts that cannot eas-
     ily be fixed; the changes are as follows:

     	 The incompatible GNU bash I/O redirection &>file is not supported.

     	 File descriptors created by I/O redirections are inherited by child

     	 The echo builtin does not interpret backslashes and only supports the
	 exact option -n, unless built with -DMKSH_MIDNIGHTBSD01ASH_COMPAT.

     	 The substitution operations ${x#pat}, ${x##pat}, ${x%pat}, and
	 ${x%%pat} wrongly do not require a parenthesis	to be escaped and do
	 not parse extglobs.

     	 The getopt construct from lksh(1) passes through the errorlevel.

     	 sh -c eats a leading -- if built with -DMKSH_MIDNIGHTBSD01ASH_COMPAT.

   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.  If none of these op-
     tions 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 al-
     lows 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 `>', `+'	or `<' character is displayed in the
     last column indicating that there are more	characters after, before and
     after, or before the current position, respectively.  The line is
     scrolled horizontally as necessary.

     Completed lines are pushed	into the history, unless they begin with an
     IFS octet or IFS white space or are the same as the previous line.

   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 orig-
     inal Korn shell.  In this mode, various editing commands (typically bound
     to	one or more control characters)	cause immediate	actions	without	wait-
     ing for a newline.	 Several editing commands are bound to particular con-
     trol 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 ^[.  These	control	sequences are not case sensi-
     tive.  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 user's tty(4)	characters (e.g. ERASE)	are bound to
     reasonable	substitutes and	override the default bindings; their customary
     values are	shown in parentheses below.  The default bindings were chosen
     to	resemble corresponding Emacs key bindings:

     abort: INTR (^C), ^G
	     Abort the current command,	save it	to the history,	empty the line
	     buffer and	set the	exit state to interrupted.

     auto-insert: [n]
	     Simply causes the character to appear as literal input.  Most or-
	     dinary characters are bound to this.

     backward-char: [n]	^B, ^XD, ANSI-CurLeft, PC-CurLeft
	     Moves the cursor backward n characters.

     backward-word: [n]	^[b, ANSI-Ctrl-CurLeft,	ANSI-Alt-CurLeft
	     Moves the cursor backward to the beginning	of the word; words
	     consist of	alphanumerics, underscore (`_')	and dollar sign	(`$')

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

     beginning-of-line:	^A, ANSI-Home, PC-Home
	     Moves the cursor to the beginning of the edited input line.

     capitalise-word: [n] ^[C, ^[c
	     Uppercase the first ASCII character in the	next n words, leaving
	     the cursor	past the end of	the last word.

     clear-screen: ^[^L
	     Prints a compile-time configurable	sequence to clear the screen
	     and home the cursor, redraws the last line	of the prompt string
	     and the currently edited input line.  The default sequence	works
	     for almost	all standard terminals.

     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 com-
	     pletion, unless it	is a directory name in which case `/' is ap-
	     pended.  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).

     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.  Note that	^I is usually
	     generated by the Tab (tabulator) key.

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

     delete-char-forward: [n] ANSI-Del,	PC-Del
	     Deletes n characters after	the cursor.

     delete-word-backward: [n] Pfx1+ERASE (^[^H), WERASE (^W), ^[^?, ^[^H, ^[h
	     Deletes n words before the	cursor.

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

     down-history: [n] ^N, ^XB,	ANSI-CurDown, PC-CurDown
	     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, search-history-up or up-history has been per-

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

     edit-line:	[n] ^Xe
	     Internally	run the	command	fc -e "${VISUAL:-${EDITOR:-vi}}" -- n
	     on	a temporary script file	to interactively edit line n (if n is
	     not specified, the	current	line); then, unless the	editor invoked
	     exits nonzero but even if the script was not changed, execute the
	     resulting script as if typed on the command line; both the	edited
	     (resulting) and original lines are	added onto history.

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

     end-of-line: ^E, ANSI-End,	PC-End
	     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 canonicalisation.

     eot-or-delete: [n]	EOF (^D)
	     If	alone on a line, same as eot, otherwise, delete-char-forward.

     error: (not bound)
	     Error (ring the bell).

     evaluate-region: ^[^E
	     Evaluates the text	between	the mark and the cursor	position (the
	     entire line if no mark is set) as function	substitution (if it
	     cannot be parsed, the editing state is unchanged and the bell is
	     rung to signal an error); $? is updated accordingly.

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

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

     forward-char: [n] ^F, ^XC,	ANSI-CurRight, PC-CurRight
	     Moves the cursor forward n	characters.

     forward-word: [n] ^[f, ANSI-Ctrl-CurRight,	ANSI-Alt-CurRight
	     Moves the cursor forward to the end of the	nth word.

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

     kill-line:	KILL (^U)
	     Deletes the entire	input line.

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

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

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

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

     list-file:	^X^Y
	     Prints a sorted, columnated list of file names (if	any) that can
	     complete the partial word containing the cursor.  File type indi-
	     cators 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, search-history or

     no-op: QUIT (^\)
	     This does nothing.

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

     prefix-2: ^X, ^[[,	^[O
	     Introduces	a multi-character command sequence.

     prev-hist-word: [n] ^[., ^[_
	     The last word or, if given, the nth word (zero-based) of the pre-
	     vious (on repeated	execution, second-last,	third-last, etc.) com-
	     mand is inserted at the cursor.  Use of this editing command
	     trashes the mark.

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

     quote-region: ^[Q
	     Escapes the text between the mark and the cursor position (the
	     entire line if no mark is set) into a shell command argument.

     redraw: ^L
	     Reprints the last line of the prompt string and the current input
	     line on a new line.

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

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

     search-history: ^R
	     Enter incremental search mode.  The internal history list is
	     searched backwards	for commands matching the input.  An initial
	     `^' in the	search string anchors the search.  The escape key will
	     leave search mode.	 Other commands, including sequences of	escape
	     as	prefix-1 followed by a prefix-1	or prefix-2 key	will be	exe-
	     cuted after leaving search	mode.  The abort (^G) command will re-
	     store the input line before search	started.  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	neces-

     search-history-up:	ANSI-PgUp, PC-PgUp
	     Search backwards through the history buffer for commands whose
	     beginning match the portion of the	input line before the cursor.
	     When used on an empty line, this has the same effect as

     search-history-down: ANSI-PgDn, PC-PgDn
	     Search forwards through the history buffer	for commands whose be-
	     ginning match the portion of the input line before	the cursor.
	     When used on an empty line, this has the same effect as
	     down-history.  This is only useful	after an up-history,
	     search-history or search-history-up.

     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	ex-
	     changes the two previous characters; otherwise, it	exchanges the
	     previous and current characters and moves the cursor one charac-
	     ter to the	right.

     up-history: [n] ^P, ^XA, ANSI-CurUp, PC-CurUp
	     Scrolls the history buffer	backward n lines (earlier).

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

     version: ^[^V
	     Display the version of mksh.  The current edit buffer is restored
	     as	soon as	a key is pressed.  The restoring keypress is pro-
	     cessed, unless it is a space.

     yank: ^Y
	     Inserts the most recently killed text string at the current cur-
	     sor position.

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

     The tab completion	escapes	characters the same way	as the following code:

     print -nr -- "${x@/[\"-\$\&-*:-?[\\\`\{-\}${IFS-$'	\t\n'}]/\\$KSH_MATCH}"

   Vi editing mode
     Note: The vi command-line editing mode has	not yet	been brought up	to the
     same quality and feature set as the emacs mode.  It is 8-bit clean	but
     specifically does not support UTF-8 or MBCS.

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

     	 You start out in insert mode.

     	 There are file	name and command completion commands: =, \, *, ^X, ^E,
	 ^F and, optionally, <Tab> and <Esc>.

     	 The _ command is different (in	mksh, it is the	last argument command;
	 in vi(1) it goes to the start of the current line).

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

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

     Like vi(1), there are two modes: "insert" mode and	"command" mode.	 In
     insert mode, most characters are simply put in the	buffer at the current
     cursor position as	they are typed;	however, some characters are treated
     specially.	 In particular,	the following characters are taken from	cur-
     rent 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 charac-
     ters 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.

     ^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),	en-
	      abled 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 fol-
     lowing 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 "current
     position" refers to the position between the cursor and the character
     preceding the cursor.  A "word" is	a sequence of letters, digits and un-
     derscore characters or a sequence of non-letter, non-digit, non-under-
     score and non-whitespace characters (e.g. "ab2*&^"	contains two words)
     and a "big-word" is a sequence of non-whitespace characters.

     Special mksh 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 in-
		 sert mode; if n is not	specified, the last word is inserted.

     #		 Insert	the comment character (`#') at the start of the	cur-
		 rent 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 re-
		 cent remembered line.

     [n]v	 Internally run	the command fc -e "${VISUAL:-${EDITOR:-vi}}"
		 -- n
		 on a temporary	script file to interactively edit line n (if n
		 is not	specified, the current line); then, unless the editor
		 invoked exits nonzero but even	if the script was not changed,
		 execute the resulting script as if typed on the command line;
		 both the edited (resulting) and original lines	are added onto

     * and ^X	 Command or file name expansion	is applied to the current big-
		 word (with an appended	`*' if the word	contains no file glob-
		 bing characters) - the	big-word is replaced with the result-
		 ing words.  If	the current big-word is	the first on the line
		 or follows one	of the characters `;', `|', `&', `(' or	`)'
		 and does not contain a	slash (`/'), then command expansion is
		 done; otherwise file name expansion is	done.  Command expan-
		 sion 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 com-
		 mand and file name expansion.	<Tab> is only recognised if
		 the vi-tabcomplete option is set, while <Esc> is only recog-
		 nised if the vi-esccomplete option is set (see	set -o).  If n
		 is specified, the nth possible	completion is selected (as re-
		 ported	by the command/file name enumeration command).

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

     ^V		 Display the version of	mksh.  The current edit	buffer is re-
		 stored	as soon	as a key is pressed.  The restoring keypress
		 is ignored.

     @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 parenthe-
	     sis, 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 `^',	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 di-
	     rection of	the search is the same as the last search.

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

     ANSI-CurUp, PC-PgUp
	     Take the characters from the beginning of the line	to the current
	     cursor position as	search string and do a history search, back-
	     wards, for	lines beginning	with this string; keep the cursor po-
	     sition.  This works only in insert	mode and keeps it enabled.

     ANSI-CurDown, PC-PgDn
	     Take the characters from the beginning of the line	to the current
	     cursor position as	search string and do a history search, for-
	     wards, for	lines beginning	with this string; keep the cursor po-
	     sition.  This works only in insert	mode and keeps it enabled.

     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 posi-
	     tion.  The	insertion is only replicated if	command	mode is	re-en-
	     tered 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 in-
	     stead 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 po-
	     sition, 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	and ^R
	     Redraw the	current	line.

     [n].    Redo the last edit	command	n times.

     u	     Undo the last edit	command.

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

     PC	Home, End, Del and cursor keys
	     They move as expected, both in insert and command mode.

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

     ~/.mkshrc		User mkshrc profile (non-privileged interactive
			shells); see Startup files. The	location can be
			changed	at compile time	(e.g. for embedded systems);
			AOSP Android builds use	/system/etc/mkshrc.
     ~/.profile		User profile (non-privileged login shells); see
			Startup	files near the top of this manual.
     /etc/profile	System profile (login shells); see Startup files.
     /etc/shells	Shell database.
     /etc/suid_profile	Privileged shells' profile (sugid); see	Startup	files.

     Note: On Android, /system/etc/ contains the system	and suid profile.

     awk(1), cat(1), ed(1), getopt(1), lksh(1),	sed(1),	sh(1), stty(1),
     dup(2), execve(2),	getgid(2), getuid(2), mknod(2),	mkfifo(2), open(2),
     pipe(2), rename(2), wait(2), getopt(3), nl_langinfo(3), setlocale(3),
     signal(3),	system(3), tty(4), shells(5), environ(7), script(7), utf-8(7),

     The FAQ at or in the mksh.faq file.

     Morris Bolsky, The	KornShell Command and Programming Language, Prentice
     Hall PTR, xvi + 356 pages,	1989, ISBN 978-0-13-516972-8 (0-13-516972-0).

     Morris I. Bolsky and David	G. Korn, The New KornShell Command and
     Programming Language (2nd Edition), Prentice Hall PTR, xvi	+ 400 pages,
     1995, ISBN	978-0-13-182700-4 (0-13-182700-6).

     Stephen G.	Kochan and Patrick H. Wood, UNIX Shell Programming, Sams, 3rd
     Edition, xiii + 437 pages,	2003, ISBN 978-0-672-32490-1 (0-672-32490-3).

     IEEE Inc.,	IEEE Standard for Information Technology - Portable Operating
     System Interface (POSIX), IEEE Press, Part	2: Shell and Utilities,
     xvii + 1195 pages,	1993, ISBN 978-1-55937-255-8 (1-55937-255-9).

     Bill Rosenblatt, Learning the Korn	Shell, O'Reilly, 360 pages, 1993, ISBN
     978-1-56592-054-5 (1-56592-054-6).

     Bill Rosenblatt and Arnold	Robbins, Learning the Korn Shell, Second
     Edition, O'Reilly,	432 pages, 2002, ISBN 978-0-596-00195-7

     Barry Rosenberg, KornShell	Programming Tutorial, Addison-Wesley
     Professional, xxi + 324 pages, 1991, ISBN 978-0-201-56324-5

     The MirBSD	Korn Shell is developed	by mirabilos <> as part of
     The MirOS Project.	 This shell is based on	the public domain 7th edition
     Bourne shell clone	by Charles Forsyth, who	kindly agreed to, in countries
     where the Public Domain status of the work	may not	be valid, grant	a
     copyright licence to the general public to	deal in	the work without re-
     striction and permission to sublicence derivatives	under the terms	of any
     (OSI approved) Open Source	licence, 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 subse-
     quently maintained	by John	R. MacMillan, Simon J. Gerraty and Michael
     Rendell.  The effort of several projects, such as Debian and OpenBSD, and
     other contributors	including our users, to	improve	the shell is appreci-
     ated.  See	the documentation, website and source code (CVS) for details.

     mksh-os2 is developed by KO Myung-Hun <>.

     mksh-w32 is developed by Michael Langguth <>.

     mksh/z/OS is contributed by Daniel	Richard	G. <skunk@iSKUNK.ORG>.

     The BSD daemon is Copyright (C) Marshall Kirk McKusick.  The complete
     legalese is at:

     mksh provides a consistent, clear interface normally.  This may deviate
     from POSIX	in historic or opinionated places.  set	-o posix (see POSIX
     mode for details) will make the shell more	conformant, but	mind the FAQ
     (see SEE ALSO), especially	regarding locales.  mksh (but not lksh)	pro-
     vides a consistent	32-bit integer arithmetic implementation, both signed
     and unsigned, with	sign of	the result of a	remainder operation and	wrap-
     around defined, even (defying POSIX) on 36-bit and	64-bit systems.

     mksh currently uses OPTU-16 internally, which is the same as UTF-8	and
     CESU-8 with 0000..FFFD being valid	codepoints; raw	octets are mapped into
     the PUA range EF80..EFFF, which is	assigned by CSUR for this purpose.

     Suspending	(using ^Z) pipelines like the one below	will only suspend the
     currently running part of the pipeline; in	this example, "fubar" is imme-
     diately printed on	suspension (but	not later after	an fg).

	   $ /bin/sleep	666 && echo fubar

     The truncation process involved when changing HISTFILE does not free old
     history entries (leaks memory) and	leaks old entries into the new history
     if	their line numbers are not overwritten by same-number entries from the
     persistent	history	file; truncating the on-disc file to HISTSIZE lines
     has always	been broken and	prone to history file corruption when multiple
     shells are	accessing the file; the	rollover process for the in-memory
     portion of	the history is slow, should use	memmove(3).

     This document attempts to describe	mksh R59c and up, compiled without any
     options impacting functionality, such as MKSH_SMALL, when not called as
     /bin/sh which, on some systems only, enables set -o posix or set -o sh
     automatically (whose behaviour differs across targets), for an operating
     environment supporting all	of its advanced	needs.

     Please report bugs	in mksh	to the public development mailing list at
     <> (please note the EU-DSGVO/GDPR notice on and in	the SMTP banner!) or in	the
     #!/bin/mksh (or #ksh) IRC channel at (Port 6697 SSL,
     6667 unencrypted),	or at:

MirBSD				October	1, 2020				MirBSD