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

NAME
     mksh, sh -- MirBSD	Korn shell

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

DESCRIPTION
     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
     such.

   I use Android, OS/2,	etc. so	what...?
     Please see	the FAQ	at the end of this document.

   Invocation
     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
		standard input and standard error are attached to a tty(4).
		An interactive shell has job control enabled, ignores the
		SIGINT,	SIGQUIT	and SIGTERM signals, and prints	prompts	before
		reading	input (see the PS1 and PS2 parameters).	 It also pro-
		cesses the ENV parameter or the	mkshrc file (see below).  For
		non-interactive	shells,	the trackall option is on by default
		(see the set command below).

     -l		Login shell.  If the basename the shell	is called with (i.e.
		argv[0]) starts	with `-' 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 real	user ID	(group ID).  For further implications,
		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	this option is
		used.  The following restrictions come into effect after the
		shell processes	any profile and	ENV files:

		+o   The	cd (and	chdir) command is disabled.
		+o   The	SHELL, ENV and PATH parameters cannot be changed.
		+o   Command names can't	be specified with absolute or relative
		    paths.
		+o   The	-p option of the built-in command command can't	be
		    used.
		+o   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
     determined	as follows: if the -c option is	used and there is a non-option
     argument, it is used as the name; if commands are being read from a file,
     the file is used as the name; otherwise, the basename the shell was
     called with (i.e. argv[0])	is used.

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

   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
     parameter 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
     exists, 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	conditional 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
     parameter assignments come	before any command words.  The command words,
     if	any, define the	command	that is	to be executed and its arguments.  The
     command may be a shell built-in command, a	function or an external	com-
     mand (i.e.	a separate executable file that	is located using the PATH
     parameter;	see Command execution below).  Note that all command con-
     structs 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, func-
     tions, compound-commands, pipelines, lists, etc.) are all well-defined
     and are described where the construct is described.  The exit status of a
     command consisting	only of	parameter assignments is that of the last com-
     mand substitution 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 status of cmd1 is zero; ``||'' is the	opposite - cmd2	is executed
     only if the exit status of	cmd1 is	non-zero.  ``&&'' and ``||'' have
     equal precedence which is higher than that	of ``&'', ``|&'' and ``;'',
     which also	have equal precedence.	Note that the ``&&'' and ``||''	opera-
     tors are "left-associative".  For example,	both of	these commands will
     print only	"bar":

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

     The ``&'' token causes the	preceding command to be	executed asyn-
     chronously; that is, the shell starts the command but does	not wait for
     it	to complete (the shell does keep track of the status of	asynchronous
     commands; see Job control below).	When an	asynchronous command is
     started when job control is disabled (i.e.	in most	scripts), the command
     is	started	with signals SIGINT and	SIGQUIT	ignored	and with input redi-
     rected from /dev/null (however, redirections specified in the asynchro-
     nous command have precedence).  The ``|&''	operator starts	a co-process
     which is a	special	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
     assignments 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 }

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

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

     case word in [[(] pattern [| pattern] ...)	list 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
	   parameter, command and arithmetic substitution, as well as tilde
	   substitution.

	   For historical reasons, open	and close braces may be	used instead
	   of in and esac e.g. case $foo { *) echo bar ;; }.

	   The list terminators	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.  If in is not used	to specify a
	   word	list, the positional parameters	($1, $2, etc.) are used
	   instead.  For historical reasons, open and close braces may be used
	   instead of do and done e.g. for i; {	echo $i; }.  The exit status
	   of a	for statement is the last exit status of list; if list is
	   never executed, the exit status is zero.

     if	list; then list; [elif list; then list;] ... [else list;] fi
	   If the exit status of the first list	is zero, the second list is
	   executed; otherwise,	the list following the elif, if	any, is	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 non-conditional list that	is executed; if	no non-conditional
	   list	is executed, the exit status is	zero.

     select name [in word ...];	do list; done
	   The select statement	provides an automatic method of	presenting the
	   user	with a menu and	selecting from it.  An enumerated list of the
	   specified word(s) is	printed	on standard error, followed by a
	   prompt (PS3:	normally ``#? '').  A number corresponding to one of
	   the enumerated words	is then	read from standard input, name is set
	   to the selected word	(or unset if the selection is not valid),
	   REPLY is set	to what	was read (leading/trailing space is stripped),
	   and list is executed.  If a blank line (i.e.	zero or	more IFS
	   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.  If ``in word	...'' is omit-
	   ted,	the positional parameters are used (i.e. $1, $2, etc.).	 For
	   historical reasons, open and	close braces may be used instead of do
	   and done e.g. select	i; { echo $i; }.  The exit status of a select
	   statement is	zero if	a break	statement is used to exit the loop,
	   non-zero otherwise.

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

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

     function name { list; }
	   Defines the function	name (see Functions below).  Note that redi-
	   rections specified after a function definition are performed	when-
	   ever	the function is	executed, not when the function	definition is
	   executed.

     name() command
	   Mostly the same as function (see Functions below).  Whitespace
	   (space or tab) after	name will be ignored most of the time.

     function name() { list; }
	   The same as name() (bashism).  The function keyword is ignored.

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

     ((	expression ))
	   The arithmetic expression expression	is evaluated; equivalent to
	   ``let "expression"''	(see Arithmetic	expressions and	the let	com-
	   mand, below)	in a compound construct.

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

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

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

	   +o   Operators (e.g. ``-f'', ``='', ``!'') must be unquoted.

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

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

	   +o   The second operand of the ``!=''	and ``='' expressions are a
	       subset of patterns (e.g.	the comparison [[ foobar = f*r ]] suc-
	       ceeds).	This even works	indirectly:

		     $ bar=foobar; baz='f*r'
		     $ [[ $bar = $baz ]]; echo $?
		     $ [[ $bar = "$baz"	]]; echo $?

	       Perhaps surprisingly, the first comparison succeeds, whereas
	       the second doesn't.  This does not apply	to all extglob
	       metacharacters, currently.

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

     If	a single-quoted	string is preceded by an unquoted `$', C style back-
     slash expansion (see below) is applied (even single quote characters
     inside can	be escaped and do not terminate	the string then); the expanded
     result is treated as any other single-quoted string.  If a	double-quoted
     string is preceded	by an unquoted `$', 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, of
     which there may be	none up	to four	or eight; these	escapes	translate a
     Unicode codepoint to UTF-8.  Furthermore, ``\E'' and ``\e'' expand	to the
     escape character.

     In	the print builtin mode,	``\"'',	``\''' and ``\?'' are explicitly
     excluded; octal sequences must have the none up to	three octal digits
     ``#'' prefixed with the digit zero	(``\0###''); hexadecimal sequences
     ``\x##'' are limited to none 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).

     Backslash expansion in the	C style	mode slightly differs: octal sequences
     ``\###'' must have	no digit zero prefixing	the one	up to three octal dig-
     its ``#'' and yield raw octets; hexadecimal sequences ``\x#*'' greedily
     eat up as many hexadecimal	digits ``#'' as	they can and terminate with
     the first non-hexadecimal digit; these translate a	Unicode	codepoint to
     UTF-8.  The sequence ``\c#'', where ``#'' is any octet, translates	to
     Ctrl-# (which basically means, ``\c?'' becomes DEL, everything else is
     bitwise ANDed with	0x1F).	Finally, ``\#'', where # is none of the	above,
     translates	to # (has the backslash	trimmed), even if it is	a newline.

   Aliases
     There are two types of aliases: normal command aliases and	tracked
     aliases.  Command aliases are normally used as a short hand for a long or
     often used	command.  The shell expands command aliases (i.e. substitutes
     the alias name for	its value) when	it reads the first word	of a command.
     An	expanded alias is re-processed to check	for more aliases.  If a	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).

   Substitution
     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
     whitespace	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	cre-
     ated 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 split-
     ting on the word which contained the substitution or use IFS as a general
     whitespace	delimiter.

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

     A command substitution is replaced	by the output generated	by the 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=$(cat) <<\EOF'' (or	the newline-keeping ``x=<<\EOF''
     extension)	instead	to merely slurp	the string.  IEEE Std 1003.1
     (``POSIX.1'') recommends using case statements of the form	x=$(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
	   EOF

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

   Parameters
     Parameters	are shell variables; they can be assigned values and their
     values can	be accessed using a parameter substitution.  A parameter name
     is	either one of the special single punctuation or	digit character	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
     arrays 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-
     ger.

     Parameter substitutions take the form $name, ${name} or ${name[expr]}
     where name	is a parameter name.  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
     parameter 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 assign-
     ments can be given	on a single command line and they can be followed by a
     simple-command, in	which case the assignments are in effect only for the
     duration of the command (such assignments are also	exported; see below
     for the implications of this).  Note that both the	parameter name and the
     `=' must be unquoted for the shell	to recognise a parameter assignment.
     The construct FOO+=baz is also recognised;	the old	and new	values are
     immediately concatenated.	The fourth way of setting a parameter is with
     the export, global, readonly and typeset commands;	see their descriptions
     in	the Command execution section.	Fifth, for and select loops set	param-
     eters 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:

     ${name:-word}
	     If	name is	set and	not empty, it is substituted; otherwise, word
	     is	substituted.

     ${name:+word}
	     If	name is	set and	not empty, word	is substituted;	otherwise,
	     nothing is	substituted.

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

     ${name:?word}
	     If	name is	set and	not empty, it is substituted; otherwise, word
	     is	printed	on standard error (preceded by name:) and an error
	     occurs (normally causing termination of a shell script, function,
	     or	a script sourced using the ``.'' built-in).  If	word is	omit-
	     ted, 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,
     except 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 (if	name
     is	an array, the element with the key ``0'' will be substituted in	scalar
     context):

     ${#name}
	     The number	of positional parameters if name is ``*'', ``@'' or
	     not specified; otherwise the length (in characters) of the	string
	     value of parameter	name.

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

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

     ${!name}
	     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).

     ${!name[*]}
     ${!name[@]}
	     The names of indices (keys) in the	array name.

     ${name#pattern}
     ${name##pattern}
	     If	pattern	matches	the beginning of the value of parameter	name,
	     the matched text is deleted from the result of substitution.  A
	     single `#'	results	in the shortest	match, and two of them result
	     in	the longest match.  Cannot be applied to a vector (${*}	or
	     ${@} or ${array[*]} or ${array[@]}).

     ${name%pattern}
     ${name%%pattern}
	     Like ${...#...} substitution, but it deletes from the end of the
	     value.  Cannot be applied to a vector.

     ${name/pattern/string}
     ${name/#pattern/string}
     ${name/%pattern/string}
     ${name//pattern/string}
	     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
	     beginning 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.  Cannot be applied to	a vec-
	     tor.  Inefficiently implemented, may be slow.

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

     ${name:pos:len}
	     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.  Currently, pos must
	     start with	a space, opening parenthesis or	digit to be recog-
	     nised.  Cannot be applied to a vector.

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

     ${name@Q}
	     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 basename the shell was	invoked	with (i.e. argv[0]).  $0 is
	     also set to the name of the current script	or the name of the
	     current function, if it was defined with the function keyword
	     (i.e. a Korn shell	style function).

     1 .. 9  The first nine positional parameters that were supplied to	the
	     shell, function, or script	sourced	using the ``.''	built-in.
	     Further 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.
		  Always set, defaults to 80, unless the value as reported by
		  stty(1) is non-zero and sane enough (minimum is 12x3); simi-
		  lar for LINES.  This parameter is used by the	interactive
		  line editing modes and by the	select,	set -o and kill	-l
		  commands to format information 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.

     EPOCHREALTIME
		  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
		  default is 2047.  Do not set this value to insanely high
		  values such as 1000000000 because mksh can then not allocate
		  enough memory	for the	history	and will not start.

     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.

     KSHGID	  The real group id of the shell.

     KSHUID	  The real user	id of the shell.

     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 !=
		  returns 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 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.
		  Always set, defaults to 24.  See COLUMNS.

     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
		  invoked.

     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 adjacent ones, is	treated	as a ``.'' (the	current	direc-
		  tory).

     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
		  sequences (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	char-
		  acter.  Any occurrences of that character in the prompt are
		  not printed.	By the way, don't blame	me for this hack; it's
		  derived from the original ksh88(1), which did	print the
		  delimiter 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
		  reverse video	(colour	would work, too), in the prompt
		  string:

			x=$(print \\001)
			PS1="$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
		  input	is needed to complete a	command.

     PS3	  Prompt used by the select statement when reading a menu
		  selection.  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
		  between 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
		  parameter has	been assigned an integer value,	the number of
		  seconds since	the assignment plus the	value that was
		  assigned.

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

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

     USER_ID	  The effective	user id	of the shell.

   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
     assumed to	be a login name.  If the login name is empty, `+' or `-', the
     simplified	value of the HOME, PWD or OLDPWD parameter is substituted,
     respectively.  Otherwise, the password file is searched for the login
     name, and the tilde expression is substituted with	the user's home	direc-
     tory.  If the login name is not found in the password file	or if any
     quoting or	parameter substitution occurs in the login name, no substitu-
     tion is performed.

     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:

	   prefix{str1,...,strN}suffix

     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 exam-
     ple, 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 after parameter substitution and before file name genera-
     tion.

   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-
     ing:

     ?	     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 itself, 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.

     *(pattern|...|pattern)
	     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'', etc.

     +(pattern|...|pattern)
	     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.

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

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

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

     Note that 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
     inherited 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
		 exist,	it is created; if it does exist, is a regular file,
		 and the noclobber option is set, an error occurs; otherwise,
		 the file is truncated.	 Note that this	means the command cmd
		 <foo >foo will	open foo for reading and then truncate it when
		 it opens it for writing, before cmd gets a chance to actually
		 read foo.

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

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

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

     <>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 (`\')
		 escapes 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
     interactive, file name generation are all performed on the	file, marker
     and fd arguments of redirections.	Note, however, that the	results	of any
     file name generation are only used	if a single file is matched; if	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
     numeric 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
     operators (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
     numeric 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 Unicode codepoints, 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	(inte-
     gral value	of zero) cannot	be used.  An unset or empty parameter evalu-
     ates to 0 in integer context.  In Unicode mode, raw octets	are mapped
     into the range EF80..EFFF as in OPTU-8, which is in the PUA and has been
     assigned by CSUR for this use.  If	more than one octet in ASCII mode, or
     a sequence	of more	than one octet not forming a valid and minimal CESU-8
     sequence is passed, the behaviour is undefined (usually, the shell	aborts
     with a parse error, but rarely, it	succeeds, e.g. on the sequence C2 20).
     That's why	you should always use ASCII mode unless	you know that the
     input is well-formed UTF-8	in the range of	0000..FFFD if you use this
     feature, as opposed to read -a.

     The operators are evaluated as follows:

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

	   unary -
		   Negation.

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

	   ~	   Arithmetic (bit-wise) NOT.

	   ++	   Increment; must be applied to a parameter (not a literal or
		   other expression).  The parameter is	incremented by 1.
		   When	used as	a prefix operator, the result is the 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.

	   !=	   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
		   division of the left	argument by the	right.	To get the
		   mathematical	modulus	of ``a mod b'',	use the	formula	``(a %
		   b + b) % b''.

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

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

     Some notes	concerning co-processes:

     +o	 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>&-

     +o	 In order for co-processes to share a common output, the shell must
	 keep the write	portion	of the output pipe open.  This means that end-
	 of-file will not be detected until all	co-processes sharing the co-
	 process'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.

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

   Functions
     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
     searched.

     An	existing function may be deleted using unset -f	function-name.	A list
     of	functions can be obtained using	typeset	+f and the function 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	func-
     tion is executed, the shell's xtrace option is turned on for the func-
     tion's duration.  The ``export'' attribute	of functions is	currently not
     used.  In the original Korn shell,	exported functions are visible to
     shell scripts that	are executed.

     Since functions are executed in the current shell environment, parameter
     assignments made inside functions are visible after the function 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
     while...read loop FAQ below).

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

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

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

     +o	 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
	 function).

     +o	 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:

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

     +o	 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.

     The original ksh and POSIX	differ somewhat	in which commands are consid-
     ered special or regular.

     POSIX special built-in utilities:

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

     Additional	mksh commands keeping assignments:

     global, source, typeset

     Builtins that are not special:

     [,	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:

     . file [arg ...]
	    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 exe-
	    cuted.  If no arguments are	given, the positional parameters are
	    those of the environment the command is used in.

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

     [ expression ]
	    See	test.

     alias [-d | -t [-r] | +-x]	[-p] [+] [name [=value]	...]
	    Without arguments, alias lists all aliases.	 For any name without
	    a value, the existing alias	is listed.  Any	name with a value
	    defines an alias (see Aliases above).  [A-Za-z0-9_!%,@-] are valid
	    in names except they may not begin with a hyphen-minus.

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

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

	    If the -p option is	used, each alias is prefixed with the string
	    ``alias ''.

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

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

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

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

     bind [-m] string=[substitute] ...
     bind string=[editing-command] ...
	    The	specified editing command is bound to the given	string,	which
	    should consist of a	control	character optionally preceded by one
	    of the two prefix characters and optionally	succeeded by a tilde
	    character.	Future input of	the string will	cause the editing com-
	    mand to be immediately invoked.  If	the -m flag is given, the
	    specified input string will	afterwards be immediately replaced by
	    the	given substitute string	which may contain editing commands but
	    not	other macros.  If a tilde postfix is given, a tilde trailing
	    the	one or two prefices and	the control character is ignored, any
	    other trailing character will be processed afterwards.

	    Control characters may be written using caret notation i.e.	^X
	    represents Ctrl-X.	Note that although only	two prefix characters
	    (usually ESC and ^X) are supported,	some multi-character sequences
	    can	be supported.

	    The	following default bindings show	how the	arrow keys, the	home,
	    end	and delete key on a BSD	wsvt25,	xterm-xfree86 or GNU screen
	    terminal are bound (of course some escape sequences	won't work out
	    quite this nicely):

		  bind '^X'=prefix-2
		  bind '^[['=prefix-2
		  bind '^XA'=up-history
		  bind '^XB'=down-history
		  bind '^XC'=forward-char
		  bind '^XD'=backward-char
		  bind '^X1~'=beginning-of-line
		  bind '^X7~'=beginning-of-line
		  bind '^XH'=beginning-of-line
		  bind '^X4~'=end-of-line
		  bind '^X8~'=end-of-line
		  bind '^XF'=end-of-line
		  bind '^X3~'=delete-char-forward

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

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

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

     cat [-u] [file ...]
	    Read files sequentially, in	command	line order, and	write them 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]
	    Set	the working directory to dir.  If the parameter	CDPATH is set,
	    it lists the search	path for the directory containing 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 directory 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
	    The	string new is substituted for old in the current directory,
	    and	the shell attempts to change to	the new	directory.

     command [-pVv] cmd	[arg ...]
	    If neither the -v nor -V option is given, cmd is executed exactly
	    as if command had not been specified, with two exceptions:
	    firstly, cmd cannot	be a shell function; and secondly, special
	    built-in commands lose their specialness (i.e. redirection and
	    utility errors do not cause	the shell to exit, and command assign-
	    ments are not permanent).  The declaration utility property	is not
	    reset.

	    If the -p option is	given, a default search	path is	used instead
	    of the current value of PATH, the actual value of which is system
	    dependent.

	    If the -v option is	given, instead of executing cmd, information
	    about what would be	executed is given (and the same	is done	for
	    arg	...).  For 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 command is	printed.  If no	command	is found (i.e.
	    the	path search fails), nothing is printed and command exits with
	    a non-zero status.	The -V option is like the -v option, except it
	    is more verbose.

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

     echo [-Een] [arg ...]
	    Warning: this utility is not portable; use the Korn	shell builtin
	    print instead.

	    Prints its arguments (separated by spaces) followed	by a newline,
	    to the standard output.  The newline is suppressed if any of the
	    arguments contain the backslash sequence ``\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	-n option suppresses the trailing newline, -e enables back-
	    slash interpretation (a no-op, since this is normally done), and
	    -E suppresses backslash interpretation.

	    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 dis-
	    abled.

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

     exec [-a argv0] [-c] [command [arg	...]]
	    The	command	is executed without forking, replacing the shell
	    process.  This is currently	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 exe-
	    cuting the child process, except for the _ variable	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
	    descriptors	greater	than 2 which are opened	or dup(2)'d in this
	    way	are not	made available to other	executed commands (i.e.	com-
	    mands that are not built-in	to the shell).	Note that the Bourne
	    shell differs here;	it does	pass these file	descriptors on.

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

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

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

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

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

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

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

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

	    Each time getopts is invoked, it places the	next option in the
	    shell parameter name and the index of the argument to be processed
	    by the next	call to	getopts	in the shell parameter OPTIND.	If the
	    option was introduced with a `+', the option placed	in name	is
	    prefixed with a `+'.  When an option requires an argument, getopts
	    places it in the shell parameter OPTARG.

	    When an illegal option or a	missing	option argument	is 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 character	that caused the	problem.  Furthermore,
	    if optstring does not begin	with a colon, a	question mark is
	    placed in name, OPTARG is unset, and an error message is printed
	    to standard	error.

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

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

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

     global [+-aglpnrtUux] [-L[n] | -R[n] | -Z[n]] [-i[n]] [name [=value] ...]
	    See	typeset	-g.  Deprecated, will be removed from a	future version
	    of mksh.

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

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

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

     kill -l [exit-status ...]
	    Print the signal name corresponding	to exit-status.	 If no argu-
	    ments are specified, a list	of all the signals with	their numbers
	    and	a short	description of each are	printed.

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

     mknod [-m mode] name b|c major minor
     mknod [-m mode] name p
	    Create a device special file.  The file type may be	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 num-
	    ber).  This	is not normally	part of	mksh; however, distributors
	    may	have added this	as builtin as a	speed hack.

     print [-AcelNnprsu[n] | -R	[-n]] [argument	...]
	    Print the specified	argument(s) on the standard output, separated
	    by spaces, terminated with a newline.  The escapes mentioned 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).

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

     read [-A |	-a] [-d	x] [-N z | -n z] [-p | -u[n]] [-t n] [-rs] [p ...]
	    Reads a line of input, separates the input into fields using the
	    IFS	parameter (see Substitution above), and	assigns	each field to
	    the	specified parameters p.	 If no parameters are specified, the
	    REPLY parameter is used to store the result.  With the -A and -a
	    options, only no or	one parameter is accepted.  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.

	    -a	   Store the result without word splitting into	the parameter
		   p (or REPLY)	as array of characters (wide characters	if the
		   utf8-mode option is enacted,	octets otherwise); the code-
		   points are encoded as decimal numbers by default.

	    -d x   Use the first byte of x, NUL	if empty, instead of the ASCII
		   newline character as	input line delimiter.

	    -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 on	this.

	    -u[n]  Read	from the file descriptor n (defaults to	0, i.e.	stan-
		   dard	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, the ASCII backslash character escapes the special
		   meaning of the following character and is stripped from the
		   input; read does not	stop when encountering a backslash-
		   newline sequence and	does not store that newline in the
		   result.  This option	enables	raw mode, in which backslashes
		   are not processed.

	    -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] ...]
	    Sets the read-only attribute of the	named parameters.  This	is a
	    declaration	utility.  If values are	given, parameters are set to
	    them before	setting	the attribute.	Once a parameter is made read-
	    only, it cannot be unset and its value cannot be changed.

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

     realpath [--] name
	    Prints the resolved	absolute pathname corresponding	to name.  If
	    name ends with a slash (`/'), it's also checked for	existence and
	    whether it is a directory; otherwise, realpath returns 0 if	the
	    pathname either exists or can be created immediately, i.e. all but
	    the	last component exist and are directories.  For calls from the
	    shell, if any options are given, an	external realpath(1) utility
	    is preferred over the builtin.

     rename [--] from to
	    Renames the	file from to to.  Both must be complete	pathnames and
	    on the same	device.	 An external utility is	preferred over this
	    builtin, which is intended for emergency situations	(where /bin/mv
	    becomes unusable) and directly calls rename(2).

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

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

	    -A name
		 Sets the elements of the array	parameter name to arg ... If
		 -A is used, the array is reset	(i.e. emptied) first; if +A is
		 used, the first N elements are	set (where N is	the number of
		 arguments); the rest are left untouched.

		 An alternative	syntax for the command set -A foo -- a b c
		 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 if job control is enabled
		 (-m).

	    -C | -o noclobber
		 Prevent > redirection from overwriting	existing files.
		 Instead, >| must be used to force an overwrite.  Note that
		 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
		 occurs	or a command fails (i.e. exits with a non-zero sta-
		 tus).	This does not apply to commands	whose exit status is
		 explicitly tested by a	shell construct	such as	if, until,
		 while or ! statements.	 For &&	or ||, only the	status of the
		 last command is tested.

	    -f | -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	a description
		 of what this means.

	    -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 a description of
		 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	interactive).

	    -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.

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

	    -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	before assigning them to the posi-
		 tional	parameters (or to array	name, if -A is used).

	    -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
		 returns something that	matches	``UTF-8'' or ``utf8'' case-
		 insensitively;	for direct builtin calls depending on the
		 aforementioned	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
		 locale-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 file name genera-
		 tion.

	    -x | -o xtrace
		 Print command trees when they are executed, preceded by the
		 value of PS4.

	    -o bgnice
		 Background jobs are run with lower priority.

	    -o braceexpand
		 Enable	brace expansion	(a.k.a.	alternation).  This is enabled
		 by default.

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

	    -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.  This is
		 enabled by 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 prevents 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''
		 directories (i.e. the shell handles ``..'', which allows the
		 user to be oblivious of symbolic links	to directories).
		 Clear by default.  Note that setting this option does not
		 affect	the current value of the PWD parameter;	only the cd
		 command changes PWD.  See the cd and pwd commands above for
		 more details.

	    -o pipefail
		 Make the exit status of a pipeline (before logically comple-
		 menting) the rightmost	non-zero errorlevel, or	zero if	all
		 commands exited with zero.

	    -o posix
		 Behave	closer to the standards	(see POSIX mode	for details).
		 Automatically enabled if the basename of the shell invocation
		 begins	with ``sh'' and	this autodetection feature is compiled
		 in (not in MirBSD).  As a side	effect,	setting	this flag
		 turns off braceexpand mode, which can be turned back on manu-
		 ally, and sh mode (unless both	are enabled at the same	time).

	    -o sh
		 Enable	/bin/sh	(kludge) mode (see SH mode).  Automatically
		 enabled if the	basename of the	shell invocation begins	with
		 ``sh''	and this autodetection feature is compiled in (not in
		 MirBSD).  As a	side effect, setting this flag turns off
		 braceexpand mode, which can be	turned back on manually, and
		 posix mode (unless both are enabled at	the same time).

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

	    -o vi-esccomplete
		 In vi command-line editing, do	command	and file name comple-
		 tion when escape (^[) 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.	This is	the
		 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 will print the
	    long names of all options that are currently on.  In a future ver-
	    sion, set +o will behave POSIX compliant and print commands	to
	    restore the	current	options	instead.

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

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

     sleep seconds
	    Suspends execution for a minimum of	the seconds specified as posi-
	    tive decimal value with an optional	fractional part.  Signal
	    delivery may continue execution earlier.

     source file [arg ...]
	    Like . (``dot''), except that the current working directory	is
	    appended to	the search path	(GNU bash extension).

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

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

	    The	following basic	expressions are	available:

	    -a file	       file exists.

	    -b file	       file is a block special device.

	    -c file	       file is a character special device.

	    -d file	       file is a directory.

	    -e file	       file exists.

	    -f file	       file is a regular file.

	    -G file	       file's group is the shell's effective group 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(8) 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
			       extension, 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 led by either	`-' or `+' (no logical
			       negation), for example ``-x'' or	``+x'' instead
			       of ``xtrace''.

	    string = string    Strings are equal.

	    string == string   Strings are equal.

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

	    string < string    First string operand is less than second	string
			       operand.

	    string != string   Strings are not equal.

	    number -eq number  Numbers compare equal.

	    number -ne number  Numbers compare not equal.

	    number -ge number  Numbers compare greater than or equal.

	    number -gt number  Numbers compare greater than.

	    number -le number  Numbers compare less than or equal.

	    number -lt number  Numbers compare less than.

	    The	above basic expressions, in which unary	operators have 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 compari-
	    son	is executed; (thanks to	XSI) parentheses \( ...	\) lower four-
	    and	three-argument forms to	two- and one-argument forms, respec-
	    tively; three-argument forms ultimately prefer binary operations,
	    followed by	negation and parenthesis lowering; two-	and four-argu-
	    ment forms prefer negation followed	by parenthesis;	the one-argu-
	    ment form always implies -n.

	    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	``if [[	$foo = bar ]]''	or, to avoid
	    pattern matching (see [[ above): ``if [[ $foo = "$bar" ]]''

	    The	[[ ... ]] construct is not only	more secure to use but also
	    often faster.

     time [-p] [pipeline]
	    If a pipeline is given, the	times used to execute the pipeline are
	    reported.  If no pipeline is given,	then the user and system time
	    used by the	shell itself, and all the commands it has run since it
	    was	started, are reported.	The times reported are the real	time
	    (elapsed time from start to	finish), the user CPU time (time spent
	    running in user mode), and the system CPU time (time spent running
	    in kernel mode).  Times are	reported to standard error; the	format
	    of the output is:

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

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

		  real	   0.00
		  user	   0.00
		  sys	   0.00

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

	    Simple redirections	of standard error do not affect	the output of
	    the	time command:

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

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

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

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

     trap n [signal ...]
	    If the first operand is a decimal unsigned 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 argu-
	    ments (n [signal ...]), all	of which are treated as	signals.

     trap [handler signal ...]
	    Sets a trap	handler	that is	to be executed when any	of the speci-
	    fied signals are received.	handler	is either an empty string,
	    indicating the signals are to be ignored, a	dash (``-''), indicat-
	    ing	that the default action	is to be taken for the signals (see
	    signal(3)),	or a string containing 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 of	a signal (e.g. PIPE or ALRM)
	    or the number of the signal	(see the kill -l command above).

	    There are two special signals: EXIT	(also known as 0), which is
	    executed when the shell is about to	exit, and ERR, which is	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.

	    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 piped to another
	    process (an	artifact of the	fact that traps	are cleared when sub-
	    processes are created).

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

     true   A command that exits with a	zero value.

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

	    If name arguments are given, the attributes	of the named parame-
	    ters are set (-) or	cleared	(+); inside a function,	this will
	    cause the parameters to be created (with no	value) in the local
	    scope (but see -g).	 Values	for parameters may optionally be spec-
	    ified.  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
	    introduced with `+', in which case only the	function names are
	    reported.

	    -a	    Indexed array attribute.

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

	    -g	    Do not cause named parameters to be	created	in the local
		    scope when called inside a function.

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

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

	    -l	    Lower case attribute.  All upper case 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 using eval.

	    -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 a parameter (or
		    the	width of its first assigned value) is used.  Trailing
		    whitespace is stripped.  If	necessary, values are either
		    stripped of	leading	characters or space padded to make
		    them fit the field width.

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

	    -t	    Tag	attribute.  Has	no meaning to the shell; provided for
		    application	use.

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

	    -U	    Unsigned integer attribute.	 Integers are printed as
		    unsigned values (combine with the -i option).  This	option
		    is not in the original Korn	shell.

	    -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 the -U
		    option.)

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

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

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

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

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

	    -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.

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

	    -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 (files	of any size may	be
		   read).

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

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

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

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

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

	    -r n   Set the maximum real-time priority to n.

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

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

	    -T n   Impose a time limit of n real seconds 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   Impose a limit of n kibibytes on the	amount of swap space
		   used.

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

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

	    Symbolic masks are like those used by chmod(1).  When used,	they
	    describe what permissions may be made available (as	opposed	to
	    octal masks	in which a set bit means the corresponding bit is to
	    be cleared).  For example, ``ug=rwx,o='' sets the mask so files
	    will not be	readable, writable or executable by ``others'',	and is
	    equivalent (on most	systems) to the	octal mask ``007''.

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

     unset [-fv] parameter ...
	    Unset the named parameters (-v, the	default) or functions (-f).
	    With parameter[*], attributes are kept, only values	are unset.

	    The	exit status is non-zero	if any of the parameters have the
	    read-only attribute	set, zero otherwise.

     wait [job ...]
	    Wait for the specified job(s) to finish.  The exit status of wait
	    is that of the last	specified job; if the last job is killed by a
	    signal, the	exit status is 128 + the number	of the signal (see
	    kill -l exit-status	above);	if the last specified job can't	be
	    found (because it never existed or had already finished), the exit
	    status of wait is 127.  See	Job control below for the format of
	    job.  wait will return if a	signal for which a trap	has been set
	    is received	or if a	SIGHUP,	SIGINT or SIGQUIT signal is 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	...]
	    Without the	-v option, it is the same as command -v, except
	    aliases are	not printed as alias command.  With the	-v option, it
	    is exactly the same	as command -V.	In either case,	the -p option
	    differs: the search	path is	not affected in	whence,	but the	search
	    is restricted to the path.

   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
     enabled (using set	-m or set -o monitor), as it is	for interactive
     shells, the processes of a	job are	placed in their	own process group.
     Foreground	jobs can be stopped by typing the suspend character from the
     terminal (normally	^Z), jobs can be restarted in either the foreground or
     background	using the fg and bg commands, and the state of the terminal is
     saved or restored when a foreground job is	stopped	or restarted, respec-
     tively.

     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
		    exist.

     %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

     where...

     number   is the job number	of the job;

     flag     is the `+' or `-'	character if the job is	the %+ or %- job,
	      respectively, or space if	it is neither;

     status   indicates	the current state of the job and can be:

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

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

	      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.

   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:

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

     +o	 File descriptors created by I/O redirections are inherited by child
	 processes.

     +o	 Numbers with a	leading	digit zero are interpreted as octal.

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

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

     +o	 Tilde expansion follows POSIX instead of Korn shell rules.

     +o	 The exit status of fg is always 0.

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

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

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

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

     +o	 File descriptors created by I/O redirections are inherited by child
	 processes.

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

     +o	 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.

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

     +o	 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
     options are enabled, the shell simply reads lines using the normal	tty(4)
     driver.  If the emacs or gmacs option is set, the shell allows emacs-like
     editing of	the command; similarly,	if the vi option is set, the shell
     allows vi-like editing of the command.  These modes are described in
     detail in the following sections.

     In	these editing modes, if	a line is longer than the screen width (see
     the COLUMNS parameter), a `>', `+'	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,	empty the line buffer and set the exit
	     state to interrupted.

     auto-insert: [n]
	     Simply causes the character to appear as literal input.  Most
	     ordinary 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	(`$')
	     characters.

     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 entire prompt 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
	     appended.	If there is no command or file name with the current
	     partial word as its prefix, a bell	character is output (usually
	     causing a beep to be sounded).

     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-
	     formed.

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

     edit-line:	[n] ^Xe
	     Edit line n or the	current	line, if not specified,	interactively.
	     The actual	command	executed is fc -e ${VISUAL:-${EDITOR:-vi}} n.

     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
	     search-history-up.

     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.

     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
	     restore 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-
	     sary.

     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
	     up-history.

     search-history-down: ANSI-PgDn, PC-PgDn
	     Search forwards 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
	     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
	     exchanges the two previous	characters; otherwise, it exchanges
	     the previous and current characters and moves the cursor one
	     character to the right.

     up-history: [n] ^P, ^XA, 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 is orphaned, yet still functional.
     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:

     +o	 You start out in insert mode.

     +o	 There are file	name and command completion commands: =, \, *, ^X, ^E,
	 ^F and, optionally, <tab> and <esc>.

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

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

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

     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 cur-
     rent cursor position as they are typed; however, some characters are
     treated specially.	 In particular,	the following characters are taken
     from current tty(4) settings (see stty(1))	and have their usual meaning
     (normal values are	in parentheses): kill (^U), erase (^?),	werase (^W),
     eof (^D), intr (^C) and quit (^\).	 In addition to	the above, the follow-
     ing characters are	also treated specially in insert mode:

     ^E	      Command and file name enumeration	(see below).

     ^F	      Command and file name completion (see below).  If	used twice in
	      a	row, the list of possible completions is displayed; if used a
	      third time, the completion is undone.

     ^H	      Erases previous character.

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

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

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

     <esc>    Puts the editor in command mode (see below).

     <tab>    Optional file name and command completion	(see ^F	above),
	      enabled with set -o vi-tabcomplete.

     In	command	mode, each character is	interpreted as a command.  Characters
     that don't	correspond to commands,	are illegal combinations of commands,
     or	are commands that can't	be carried out,	all cause beeps.  In the 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	underscore characters or a sequence of non-letter, non-digit,
     non-underscore 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
		 insert	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
		 I#^J).

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

     [n]v	 Edit line n using the vi(1) editor; if	n is not specified,
		 the current line is edited.  The actual command executed is
		 fc -e ${VISUAL:-${EDITOR:-vi}}	n.

     * and ^X	 Command or file name expansion	is applied to the current big-
		 word (with an appended	`*' 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
		 reported by the command/file name enumeration command).

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

     ^V		 Display the version of	mksh.  The current edit	buffer is
		 restored 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
	     c.

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

     [n];    Repeats the last f, F, t or T command.

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

     Inter-line	movement commands:

     [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.

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

     [n]?string
	     Same as /,	except it searches forward through the history.

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

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

     ANSI-CurUp, PC-PgUp
	     Take the characters from the beginning of the line	to the current
	     cursor position as	search string and do a backwards history
	     search for	lines beginning	with this string; keep the cursor
	     position.	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-
	     entered i.e. <esc>	is used.

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

     [n]s    Substitute	the next n characters (i.e. delete the characters and
	     go	into insert mode).

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

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

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

     [n]x    Delete the	next n characters.

     [n]X    Delete the	previous n characters.

     D	     Delete to the end of the line.

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

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

     [n]R    Replace.  Enter insert mode but overwrite existing	characters
	     instead of	inserting before existing characters.  The replacement
	     is	repeated n times.

     [n]~    Change the	case of	the next n characters.

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

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

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

     [n]P    Same as p,	except the buffer is pasted at the current position.

     Miscellaneous vi commands

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

     ^L	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 deleted and a new prompt to be printed.

FILES
     ~/.mkshrc		User mkshrc profile (non-privileged interactive
			shells); see Startup files. The	location can be
			changed	at compile time	(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	Suid profile (privileged shells); see Startup files.

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

SEE ALSO
     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),
     mknod(8)

     http://www.mirbsd.org/ksh-chan.htm

     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
     (0-596-00195-9).

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

AUTHORS
     The MirBSD	Korn Shell is developed	by mirabilos <m@mirbsd.org> 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
     restriction 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
     subsequently 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	appreciated.  See the documentation, web site and CVS for details.

     mksh-os2 is developed by KO Myung-Hun <komh@chollian.net>.

     mksh-w32 is developed by Michael Langguth <lan@scalaris.com>.

     The BSD daemon is Copyright (C) Marshall Kirk McKusick.  The complete
     legalese is at: http://www.mirbsd.org/TaC-mksh.txt

CAVEATS
     mksh provides a consistent	32-bit integer arithmetic implementation, both
     signed and	unsigned, with sign of the result of a remainder operation and
     wraparound	defined, even (defying POSIX) on 36-bit	and 64-bit systems.

     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 cause the shell to behave more conformant.

     For the purpose of	POSIX, mksh supports only the ``C'' locale.  mksh's
     utf8-mode only supports the Unicode BMP (Basic Multilingual Plane)	and
     maps raw octets into the U+EF80..U+EFFF wide character range; compare
     Arithmetic	expressions.  The following POSIX sh code toggles the
     utf8-mode option dependent	on the current POSIX locale for	mksh to	allow
     using the UTF-8 mode, within the constraints outlined above, in code por-
     table across various shell	implementations:

	   case	${KSH_VERSION:-} in
	   *MIRBSD KSH*|*LEGACY	KSH*)
		   case	${LC_ALL:-${LC_CTYPE:-${LANG:-}}} in
		   *[Uu][Tt][Ff]8*|*[Uu][Tt][Ff]-8*) set -U ;;
		   *) set +U ;;
		   esac	;;
	   esac
     In	near future, (Unicode) locale tracking will be implemented though.

     See also the FAQ below.

BUGS
     Suspending	(using ^Z) pipelines like the one below	will only suspend the
     currently running part of the pipeline; in	this example, ``fubar''	is
     immediately 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 R55 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 <miros-mksh@mirbsd.org> mailing list or
     in	the #!/bin/mksh	(or #ksh) IRC channel at irc.freenode.net (Port	6697
     SSL, 6667 unencrypted), or	at: https://launchpad.net/mksh

FREQUENTLY ASKED QUESTIONS
     This FAQ attempts to document some	of the questions users of mksh or
     readers of	this manual page may encounter.

   I'm an Android user,	so what's mksh?
     mksh is a UNIX shell / command interpreter, similar to COMMAND.COM	or
     CMD.EXE, which has	been included with Android Open	Source Project for a
     while now.	 Basically, it's a program that	runs in	a terminal (console
     window), takes user input and runs	commands or scripts, which it can also
     be	asked to do by other programs, even in the background.	Any privilege
     pop-ups you might be encountering are thus	not mksh issues	but questions
     by	some other program utilising it.

   I'm an OS/2 user, what do I need to know?
     Unlike the	native command prompt, the current working directory is, for
     security reasons common on	Unix systems which the shell is	designed for,
     not in the	search path at all; if you really need this, run the command
     PATH=.$PATHSEP$PATH or add	that to	a suitable initialisation file.

     There are two different newline modes for mksh-os2: standard (Unix) mode,
     in	which only LF (0A hex) is supported as line separator, and "textmode",
     which also	accepts	ASCII newlines (CR+LF),	like most other	tools on OS/2,
     but creating an incompatibility with standard mksh.  If you compiled mksh
     from source, you will get the standard Unix mode unless -T	is added dur-
     ing compilation; you will most likely have	gotten this shell through
     komh's port on Hobbes, or from his	OS/2 Factory on	eComStation Korea,
     which uses	"textmode", though.  Most OS/2 users will want to use
     "textmode"	unless they need absolute compatibility	with Unix mksh.

   How do I start mksh on a specific terminal?
     Normally:
	   mksh	-T/dev/tty2

     However, if you want for it to return (e.g. for an	embedded system	rescue
     shell), use this on your real console device instead:
	   mksh	-T!/dev/ttyACM0

     mksh can also daemonise (send to the background):
	   mksh	-T- -c 'exec cdio lock'

   POSIX says...
     Run the shell in POSIX mode (and possibly lksh instead of mksh):
	   set -o posix

   My prompt from <some	other shell> does not work!
     Contact us	on the mailing list or on IRC, we'll convert it	for you.

   Something is	going wrong with my while...read loop
     Most likely, you've encountered the problem in which the shell runs all
     parts of a	pipeline as subshell.  The inner loop will be executed in a
     subshell and variable changes cannot be propagated	if run in a pipeline:

	   bar | baz | while read foo; do ...; done

     Note that exit in the inner loop will only	exit the subshell and not the
     original shell.  Likewise,	if the code is inside a	function, return in
     the inner loop will only exit the subshell	and won't terminate the	func-
     tion.

     Use co-processes instead:

	   bar | baz |&
	   while read -p foo; do ...; done
	   exec	3>&p; exec 3>&-

     If	read is	run in a loop such as while read foo; do ...; done then	lead-
     ing whitespace will be removed (IFS) and backslashes processed.  You
     might want	to use while IFS= read -r foo; do ...; done for	pristine I/O.
     Similarly,	when using the -a option, use of the -r	option might be	pru-
     dent (``read -raN-1 arr <file''); the same	applies	for NUL-terminated
     lines:

	   find	. -type	f -print0 |& \
	       while IFS= read -d '' -pr filename; do
		   print -r -- "found <${filename#./}>"
	   done

   What	differences in function-local scopes are there?
     mksh has a	different scope	model from AT&T	UNIX ksh, which	leads to sub-
     tle differences in	semantics for identical	builtins.  This	can cause
     issues with a nameref to suddenly point to	a local	variable by accident.

     GNU bash allows unsetting local variables;	in mksh, doing so in a func-
     tion allows back access to	the global variable (actually the one in the
     next scope	up) with the same name.	 The following code, when run before
     the function definitions, changes the behaviour of	unset to behave	like
     other shells (the alias can be removed after the definitions):

	   case	${KSH_VERSION:-} in
	   *MIRBSD KSH*|*LEGACY	KSH*)
		   function unset_compat {
			   \\builtin typeset unset_compat_x

			   for unset_compat_x in "$@"; do
				   eval	"\\\\builtin unset $unset_compat_x[*]"
			   done
		   }
		   \\builtin alias unset=unset_compat
		   ;;
	   esac

     When a local variable is created (e.g. using local, typeset, integer,
     \\builtin typeset)	it does	not, like in other shells, inherit the value
     from the global (next scope up) variable with the same name; it is	rather
     created without any value (unset but defined).

   I get an error in this regex	comparison
     Use extglobs instead of regexes:
	   [[ foo =~ (foo|bar).*baz ]]	 # becomes
	   [[ foo = *@(foo|bar)*baz* ]]	 # instead

   Are there any extensions to avoid?
     GNU bash supports ``&>'' (and ``|&'') to redirect both stdout and stderr
     in	one go,	but this breaks	POSIX and Korn Shell syntax; use POSIX redi-
     rections instead:
	   foo |& bar |& baz &>log		   # GNU bash
	   foo 2>&1 | bar 2>&1 | baz >log 2>&1	   # POSIX

   ^L (Ctrl-L) does not	clear the screen
     Use ^[^L (Escape+Ctrl-L) or rebind	it:
	   bind	'^L=clear-screen'

   ^U (Ctrl-U) clears the entire line
     If	it should only delete the line up to the cursor, use:
	   bind	-m ^U='^[0^K'

   Cursor Up behaves differently from zsh
     Some shells make Cursor Up	search in the history only for commands	start-
     ing with what was already entered.	 mksh separates	the shortcuts: Cursor
     Up	goes up	one command and	PgUp searches the history as described above.

MirBSD				April 12, 2017				MirBSD

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