path: root/bin/ksh/sh.1

'\" t
.\"	$OpenBSD: sh.1,v 1.6 1998/07/24 20:50:04 deraadt Exp $
.\"{{{}}}
.\"{{{  Notes about man page
.\"     - use the pseudo-macros .sh( and .sh) to begin and end sh-specific
.\"       text and .ksh( and .ksh) for ksh specific text.
.\"     - put i.e., e.g. and etc. in italics
.\"}}}
.\"{{{  To do
.\" todo: Things not covered that should be:
.\"	- distinguish (POSIX) special built-in's, (POSIX) regular built-in's,
.\"	  and sh/ksh weirdo built-in's (put S,R,X superscripts after command
.\"	  name in built-in commands section?)
.\"	- need to be consistent about notation for `See section-name', `
.\"	  See description of foobar command', `See section section-name', etc.
.\"	- need to use the term `external command' meaning `a command that is 
.\"       executed using execve(2)' (as opposed to a built-in command or 
.\"       function) for more clear description.
.\"}}}
.\"{{{  Title
.TH SH 1 "August 19, 1996" "" "User commands"
.\"}}}
.\"{{{  Name
.SH NAME
sh \- Public domain Bourne shell
.\"}}}
.\"{{{  Synopsis
.SH SYNOPSIS
.ad l
\fBsh\fP
[\fB\(+-abCefhikmnprsuvxX\fP] [\fB\(+-o\fP \fIoption\fP] [ [ \fB\-c\fP \fIcommand-string\fP [\fIcommand-name\fP] | \fB\-s\fP | \fIfile\fP ] [\fIargument\fP ...] ]
.ad b
.\"}}}
.\"{{{  Description
.SH DESCRIPTION
\fBsh\fP is a reimplementation of the Bourne shell, a command
interpreter for both interactive and script use.
.\"{{{  Shell Startup
.SS "Shell Startup"
The following options can be specified only on the command line:
.IP "\fB\-c\fP \fIcommand-string\fP"
the shell executes the command(s) contained in \fIcommand-string\fP
.IP \fB\-i\fP
interactive mode \(em see below
.IP \fB\-l\fP
login shell \(em see below
interactive mode \(em see below
.IP \fB\-s\fP
the shell reads commands from standard input; all non-option arguments
are positional parameters
.IP \fB\-r\fP
restricted mode \(em see below
.PP
In addition to the above, the options described in the \fBset\fP built-in
command can also be used on the command line.
.PP
If neither the \fB\-c\fP nor the \fB\-s\fP options are specified, the
first non-option argument specifies the name of a file the shell reads
commands from; if there are no non-option arguments, the shell reads
commands from standard input.
The name of the shell (\fIi.e.\fP, the contents of the \fB$0\fP) parameter
is determined as follows: if the \fB\-c\fP option is used and there is
a non-option argument, it is used as the name; if commands are being
read from a file, the file is used as the name; otherwise the name
the shell was called with (\fIi.e.\fP, argv[0]) is used.
.PP
A shell is \fBinteractive\fP if the \fB\-i\fP option is used or
if both standard input and standard error are attached to a tty.
An interactive shell has job control enabled (if available),
ignores the INT, QUIT and TERM signals, and prints prompts before
reading input (see \fBPS1\fP and \fBPS2\fP parameters).
For non-interactive shells, the \fBtrackall\fP option is on by default
(see \fBset\fP command below).
.PP
A shell is \fBrestricted\fP if the \fB\-r\fP option is used or if either
the basename of the name the shell is invoked with or the \fBSHELL\fP
parameter match the pattern *r*sh (\fIe.g.\fP, rsh, rksh, rpdksh, \fIetc.\fP).
The following restrictions come into effect after the shell processes
any profile and \fB$ENV\fP files:
.nr P2 \n(PD
.nr PD 0
.IP \ \ \(bu
the \fBcd\fP command is disabled
.IP \ \ \(bu
the \fBSHELL\fP, \fBENV\fP and \fBPATH\fP parameters can't be changed
.IP \ \ \(bu
command names can't be specified with absolute or relative paths
.IP \ \ \(bu
the \fB\-p\fP option of the \fBcommand\fP built-in can't be used
.IP \ \ \(bu
redirections that create files can't be used (\fIi.e.\fP, \fB>\fP,
\fB>|\fP, \fB>>\fP, \fB<>\fP)
.nr PD \n(P2
.PP
A shell is \fBprivileged\fP if the \fB\-p\fP option is used or if
the real user-id or group-id does not match the effective user-id
or group-id (see \fIgetuid\fP(2), \fIgetgid\fP(2)).
A privileged shell does not process $HOME/.profile nor the \fBENV\fP
parameter (see below), instead the file /etc/suid_profile is processed.
Clearing the privileged option causes the shell to set its effective
user-id (group-id) to its real user-id (group-id).
.PP
If the basename of the name the shell is called with (\fIi.e.\fP, argv[0])
starts with \fB\-\fP or if the \fB\-l\fP option is used, the shell is assumed
to be a login shell and the shell reads and executes the contents of
\fB/etc/profile\fP and \fB$HOME/.profile\fP if they exist and are readable.
.PP
If the \fBENV\fP parameter is set when the shell starts (or, in the
case of login shells, after any profiles are processed), its value
is subjected to parameter, command, arithmetic and tilde substitution and
the resulting file (if any) is read and executed.
If \fBENV\fP parameter is not set (and not null) and pdksh was compiled
with the \fBDEFAULT_ENV\fP macro defined, the file named in that macro
is included (after the above mentioned substitutions have been performed).
.PP
The exit status of the shell is 127 if the command file specified
on the command line could not be opened, or non-zero if a fatal syntax
error occurred during the execution of a script.
In the absence of fatal errors, the exit status is that of the last
command executed, or zero, if no command is executed.
.\"}}}
.\"{{{  Command Syntax
.SS "Command Syntax"
.\"{{{  words and tokens
The shell begins parsing its input by breaking it into \fIword\fPs.
Words, which are sequences of characters, are delimited by unquoted
\fIwhite-space\fP characters (space, tab and newline) or \fImeta-characters\fP
(\fB<\fP, \fB>\fP, \fB|\fP, \fB;\fP, \fB&\fP, \fB(\fP and \fB)\fP).
Aside from delimiting words, spaces and tabs are ignored, while
newlines usually delimit commands.
The meta-characters are used in building the following tokens:
\fB<\fP, \fB<&\fP, \fB<<\fP, \fB>\fP, \fB>&\fP, \fB>>\fP, \fIetc.\fP are
used to specify redirections (see Input/Output Redirection below);
\fB|\fP is used to create pipelines;
\fB;\fP is used to separate commands;
\fB&\fP is used to create asynchronous pipelines;
\fB&&\fP and \fB||\fP are used to specify conditional execution;
\fB;;\fP is used in \fBcase\fP statements;
and lastly,
\fB(\fP .. \fB)\fP are used to create subshells.
.PP
White-space and meta-characters can be quoted individually using
backslash (\fB\e\fP), or in groups using double (\fB"\fP) or single (\fB'\fP)
quotes.
Note that the following characters are also treated specially by the shell and
must be quoted if they are to represent themselves:
\fB\e\fP, \fB"\fP, \fB'\fP, \fB#\fP, \fB$\fP, \fB`\fP, \fB~\fP, \fB{\fP,
\fB}\fP, \fB*\fP, \fB?\fP and \fB[\fP.
The first three of these are the above mentioned quoting characters
(see Quoting below);
\fB#\fP, if used at the beginning of a word, introduces a comment \(em everything
after the \fB#\fP up to the nearest newline is ignored;
\fB$\fP is used to introduce parameter, command and arithmetic substitutions
(see Substitution below);
\fB`\fP introduces an old-style command substitution
(see Substitution below);
\fB~\fP begins a directory expansion (see Tilde Expansion below);
\fB{\fP and \fB}\fP delimit \fIcsh\fP(1) style alternations
(see Brace Expansion below);
and, finally, \fB*\fP, \fB?\fP and \fB[\fP are used in file name generation
(see File Name Patterns below).
.\"}}}
.\"{{{  simple-command
.PP
As words and tokens are parsed, the shell builds commands, of which
there are two basic types: \fIsimple-commands\fP, typically programs
that are executed, and \fIcompound-commands\fP, such as \fBfor\fP and
\fBif\fP statements, grouping constructs and function definitions.
.PP
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 \fIexternal
command\fP, \fIi.e.\fP, a separate executable file that is located using the
\fBPATH\fP parameter (see Command Execution below).
Note that all command constructs have an \fIexit status\fP: for external
commands, this is related to the status returned by \fIwait\fP(2) (if the
command could not be found, the exit status is 127, if it could not be
executed, the exit status is 126);
the exit status of other command constructs (built-in commands, functions,
compound-commands, pipelines, lists, \fIetc.\fP) are all well defined and are
described where the construct is described.
The exit status of a command consisting only of parameter assignments is that
of the last command substitution performed during the parameter assignment
or zero if there were no command substitutions.
.\"}}}
.\"{{{  pipeline
.PP
Commands can be chained together using the \fB|\fP token to
form \fIpipelines\fP, in which the standard output of each command but
the last is piped (see \fIpipe\fP(2)) to the standard input of the following
command.
The exit status of a pipeline is that of its last command.
A pipeline may be prefixed by the \fB!\fP reserved word which
causes the exit status of the pipeline to be logically
complemented: if the original status was 0 the complemented status will
be 1, and if the original status was not 0, then the complemented
status will be 0.
.\"}}}
.\"{{{  lists
.PP
\fILists\fP of commands can be created by separating pipelines by
any of the following tokens: \fB&&\fP, \fB||\fP, \fB&\fP, \fB|&\fP and \fB;\fP.
The first two are for conditional execution: \fIcmd1\fP \fB&&\fP \fIcmd2\fP
executes \fIcmd2\fP only if the exit status of \fIcmd1\fP is zero;
\fB||\fP is the opposite \(em \fIcmd2\fP is executed only if the exit status
of \fIcmd1\fP is non-zero.
\fB&&\fP and \fB||\fP have equal precedence which is higher than that of
\fB&\fP, \fB|&\fP and \fB;\fP, which also have equal precedence.
The \fB&\fP token causes the preceding command to be executed asynchronously,
that is, the shell starts the command, but does not wait for it to complete
(the shell does keep track of the status of asynchronous commands \(em see
Job Control below).
When an asynchronous command is started when job control is disabled
(\fIi.e.\fP, in most scripts), the command is started with signals INT
and QUIT ignored and with input redirected from /dev/null
(however, redirections specified in the asynchronous command have precedence).
Note that a command must follow the \fB&&\fP and \fB||\fP operators, while
a command need not follow \fB&\fP, \fB|&\fP and \fB;\fP.
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
.PP
Compound commands are created using the following reserved words \(em these
words are only recognized if they are unquoted and if they are used as
the first word of a command (\fIi.e.\fP, they can't be preceded by parameter
assignments or redirections):
.TS
center;
lfB lfB lfB lfB lfB .
case	else	function	then	!
do	esac	if	time	[[
done	fi	in	until	{
elif	for	select	while	}
.TE
\fBNote:\fP Some shells (but not this one) execute control structure commands
in a subshell when one or more of their file descriptors are redirected, so
any environment changes inside them may fail.
To be portable, the \fBexec\fP statement should be used instead to redirect
file descriptors before the control structure.
.PP
In the following compound command descriptions, command lists (denoted as
\fIlist\fP) that are followed by reserved words must end with a
semi-colon, a newline or a (syntactically correct) reserved word.
For example,
.RS
\fB{ echo foo; echo bar; }\fP
.br
\fB{ echo foo; echo bar<newline>}\fP
.br
\fB{ { echo foo; echo bar; } }\fP
.RE
are all valid, but
.RS
\fB{ echo foo; echo bar }\fP
.RE
is not.
.\"{{{  ( list )
.IP "\fB(\fP \fIlist\fP \fB)\fP"
Execute \fIlist\fP in a subshell.  There is no implicit way to pass
environment changes from a subshell back to its parent.
.\"}}}
.\"{{{  { list }
.IP "\fB{\fP \fIlist\fP \fB}\fP"
Compound construct; \fIlist\fP is executed, but not in a subshell.
Note that \fB{\fP and \fB}\fP are reserved words, not meta-characters.
.\"}}}
.\"{{{  case word in [ [ ( ] pattern [ | pattern ] ... ) list ;; ] ... esac
.IP "\fBcase\fP \fIword\fP \fBin\fP [ [\fB(\fP] \fIpattern\fP [\fB|\fP \fIpattern\fP] ... \fB)\fP \fIlist\fP \fB;;\fP ] ... \fBesac\fP"
The \fBcase\fP statement attempts to match \fIword\fP against the specified
\fIpattern\fPs; the \fIlist\fP associated with the first successfully matched
pattern is executed.  Patterns used in \fBcase\fP statements are the same as
those used for file name patterns except that the restrictions regarding
\fB\&.\fP and \fB/\fP are dropped.  Note that any unquoted space before and
after a pattern is stripped; any space with a pattern must be quoted.  Both the
word and the patterns are subject to parameter, command, and arithmetic
substitution as well as tilde substitution.
For historical reasons, open and close braces may be used instead
of \fBin\fP and \fBesac\fP (\fIe.g.\fP, \fBcase $foo { *) echo bar; }\fP).
The exit status of a \fBcase\fP statement is that of the executed \fIlist\fP;
if no \fIlist\fP is executed, the exit status is zero.
.\"}}}
.\"{{{  for name [ in word ... term ] do list done
.IP "\fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ... \fIterm\fP ] \fBdo\fP \fIlist\fP \fBdone\fP"
where \fIterm\fP is either a newline or a \fB;\fP.
For each \fIword\fP in the specified word list, the parameter \fIname\fP is
set to the word and \fIlist\fP is executed.  If \fBin\fP is not used to
specify a word list, the positional parameters (\fB"$1"\fP, \fB"$2"\fP,
\fIetc.\fP) are used instead.
For historical reasons, open and close braces may be used instead
of \fBdo\fP and \fBdone\fP (\fIe.g.\fP, \fBfor i; { echo $i; }\fP).
The exit status of a \fBfor\fP statement is the last exit status
of \fIlist\fP; if \fIlist\fP is never executed, the exit status is zero.
.\"}}}
.\"{{{  if list then list [ elif list then list ] ... [ else list ] fi
.IP "\fBif\fP \fIlist\fP \fBthen\fP \fIlist\fP [\fBelif\fP \fIlist\fP \fBthen\fP \fIlist\fP] ... [\fBelse\fP \fIlist\fP] \fBfi\fP"
If the exit status of the first \fIlist\fP is zero, the second \fIlist\fP
is executed; otherwise the \fIlist\fP following the \fBelif\fP, if any, is
executed with similar consequences.  If all the lists following the \fBif\fP
and \fBelif\fPs fail (\fIi.e.\fP, exit with non-zero status), the \fIlist\fP
following the \fBelse\fP is executed.
The exit status of an \fBif\fP statement is that
of non-conditional \fIlist\fP that is executed; if no non-conditional
\fIlist\fP is executed, the exit status is zero.
.\"}}}
.\"{{{  select name [ in word ... ] do list done
.\"}}}
.\"{{{  until list do list done
.IP "\fBuntil\fP \fIlist\fP \fBdo\fP \fIlist\fP \fBdone\fP"
This works like \fBwhile\fP, except that the body is executed only while the
exit status of the first \fIlist\fP is non-zero.
.\"}}}
.\"{{{  while list do list done
.IP "\fBwhile\fP \fIlist\fP \fBdo\fP \fIlist\fP \fBdone\fP"
A \fBwhile\fP is a prechecked loop.  Its body is executed as often
as the exit status of the first \fIlist\fP is zero.
The exit status of a \fBwhile\fP statement is the last exit status
of the \fIlist\fP in the body of the loop; if the body is not executed,
the exit status is zero.
.\"}}}
.\"{{{  function name { list }
.IP "\fBfunction\fP \fIname\fP \fB{\fP \fIlist\fP \fB}\fP"
Defines the function \fIname\fP.
See Functions below.
Note that redirections specified after a function definition are
performed whenever the function is executed, not when the function
definition is executed.
.\"}}}
.\"{{{  name () command
.IP "\fIname\fP \fB()\fP \fIcommand\fP"
Mostly the same as \fBfunction\fP.
See Functions below.
.\"}}}
.\"{{{  (( expression ))
.\"}}}
.\"{{{  [[ expression ]]
.\"}}}
.\"}}}
.\"}}}
.\"{{{  Quoting
.SS Quoting
Quoting is used to prevent the shell from treating characters or words
specially.
There are three methods of quoting: First, \fB\e\fP quotes
the following character, unless it is at the end of a line, in which
case both the \fB\e\fP and the newline are stripped.
Second, a single quote (\fB'\fP) quotes everything up to the next single
quote (this may span lines).
Third, a double quote (\fB"\fP) quotes all characters,
except \fB$\fP, \fB`\fP and \fB\e\fP, up to the next unquoted double quote.
\fB$\fP and \fB`\fP inside double quotes have their usual meaning (\fIi.e.\fP,
parameter, command or arithmetic substitution) except no field splitting
is carried out on the results of double-quoted substitutions.
If a \fB\e\fP inside a double-quoted string is followed by \fB\e\fP, \fB$\fP,
\fB`\fP or \fB"\fP, it is replaced by the second character; if it is
followed by a newline, both the \fB\e\fP and the newline are stripped;
otherwise, both the \fB\e\fP and the character following are unchanged.
.PP
Note: see POSIX Mode below for a special rule regarding sequences
of the form \fB"\fP...\fB`\fP...\fB\e"\fP...\fB`\fP..\fB"\fP.
.\"}}}
.\"{{{  Aliases
.SS "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 (\fIi.e.\fP,
substitutes the alias name for its value) when it reads the first word
of a command.  An expanded alias is re-processed to check for more
aliases.  If a command alias ends in a space or tab, the following word
is also checked for alias expansion.  The alias expansion process stops
when a word that is not an alias is found, when a quoted word is found
or when an alias word that is currently being expanded is found.
.PP
The following command aliases are defined automatically by the shell:
.ft B
.RS
hash='alias \-t'
.br
type='whence \-v'
.RE
.ft P
.PP
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 \fBalias
\-t\fP.  Note that changing the \fBPATH\fP parameter clears the saved
paths for all tracked aliases.  If the \fBtrackall\fP option is set (\fIi.e.\fP,
\fBset \-o trackall\fP or \fBset \-h\fP), the shell tracks all
commands.  This option is set automatically for non-interactive shells.
For interactive shells, only the following commands are automatically
tracked: \fBcat\fP, \fBcc\fP, \fBchmod\fP, \fBcp\fP, \fBdate\fP, \fBed\fP,
\fBemacs\fP, \fBgrep\fP, \fBls\fP, \fBmail\fP, \fBmake\fP, \fBmv\fP,
\fBpr\fP, \fBrm\fP, \fBsed\fP, \fBsh\fP, \fBvi\fP and \fBwho\fP.
.\"}}}
.\"{{{  Substitution
.SS "Substitution"
The first step the shell takes in executing a simple-command is to
perform substitutions on the words of the command.
There are three kinds of substitution: parameter, command and arithmetic.
Parameter substitutions, which are described in detail in the next section,
take the form \fB$name\fP or \fB${\fP...\fB}\fP; command substitutions take
the form \fB$(\fP\fIcommand\fP\fB)\fP or \fB`\fP\fIcommand\fP\fB`\fP;
and arithmetic substitutions take the form \fB$((\fP\fIexpression\fP\fB))\fP.
.PP
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 \fBIFS\fP parameter.
The \fBIFS\fP parameter specifies a list of characters which 
are used to break a string up into several words;
any characters from the set space, tab and newline that appear in the
IFS characters are called \fIIFS white space\fP.
Sequences of one or more IFS white space characters, in combination with
zero or one non-IFS white space characters delimit a field.
As a special case, leading and trailing IFS white space is stripped (\fIi.e.\fP,
no leading or trailing empty field is created by it); leading or trailing
non-IFS white space does create an empty field.
.PP
Example: if \fBIFS\fP 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', `' and `D'.
Note that if the \fBIFS\fP parameter is set to the null string, no
field splitting is done; if the parameter is unset, the default value
of space, tab and newline is used.
.PP
Also, note that the field splitting applies only to immediate result of
the substitution.  Using the previous example, the substitution for $VAR:E
results in the fields: `A', `B', `' and `D:E', not `A', `B', `', `D' and `E'.
This behavior is POSIX compliant, but incompatible with some other shell
implementations which do field splitting on the word which contained the
substitution or use \fBIFS\fP\ as a general whitespace delimiter.
.PP
The results of substitution are, unless otherwise specified, also subject
to brace expansion and file name expansion (see the relevant sections
below).
.PP
A command substitution is replaced by the output generated by the specified
command, which is run in a subshell.
For \fB$(\fP\fIcommand\fP\fB)\fP substitutions, normal quoting rules
are used when \fIcommand\fP is parsed, however, for the
\fB`\fP\fIcommand\fP\fB`\fP form, a \fB\e\fP followed by any of
\fB$\fP, \fB`\fP or \fB\e\fP is stripped (a \fB\e\fP followed by any other
character is unchanged).
As a special case in command substitutions, a command of the form
\fB<\fP \fIfile\fP is interpreted to mean substitute the contents
of \fIfile\fP ($(< foo) has the same effect as $(cat foo), but it
is carried out more efficiently because no process is started).
.br
.\"todo: fix this( $(..) parenthesis counting).
NOTE: \fB$(\fP\fIcommand\fP\fB)\fP expressions are currently parsed by
finding the matching parenthesis, regardless of quoting.  This will hopefully
be fixed soon.
.PP
Arithmetic substitutions are replaced by the value of the specified
expression.
For example, the command \fBecho $((2+3*4))\fP prints 14.
See Arithmetic Expressions for a description of an \fIexpression\fP.
.\"}}}
.\"{{{  Parameters
.SS "Parameters"
Parameters are shell variables; they can be assigned values and
their values can be accessed using a parameter substitution.
A parameter name is either one of the special single punctuation or digit
character parameters described below, or a letter followed by zero or more
letters or digits (`_' counts as a letter).
Parameter substitutions take the form \fB$\fP\fIname\fP or
\fB${\fP\fIname\fP\fB}\fP, where \fIname\fP is a parameter name.
If substitution is performed on a parameter that is not set, a null
string is substituted unless the \fBnounset\fP option (\fBset \-o nounset\fP
or \fBset \-u\fP) is set, in which case an error occurs.
.PP
.\"{{{  parameter assignment
Parameters can be assigned values in a number of ways.
First, the shell implicitly sets some parameters like \fB#\fP, \fBPWD\fP,
etc.; this is the only way the special single character parameters are
set.
Second, parameters are imported from the shell's environment at startup.
Third, parameters can be assigned values on the command line, for example,
`\fBFOO=bar\fP' sets the parameter FOO to bar; multiple parameter
assignments can be given on a single command line and they can
be followed by a simple-command, in which case the assignments are
in effect only for the duration of the command (such assignments are
also exported, see below for implications of this).
Note that both the parameter name and the \fB=\fP must be unquoted for
the shell to recognize a parameter assignment.
The fourth way of setting a parameter is with the \fBexport\fP, \fBreadonly\fP
and \fBtypeset\fP commands; see their descriptions in the Command Execution
section.
Fifth, \fBfor\fP and \fBselect\fP loops set parameters as well as
the \fBgetopts\fP, \fBread\fP and \fBset \-A\fP commands.
Lastly, parameters can be assigned values using assignment operators
inside arithmetic expressions (see Arithmetic Expressions below) or
using the \fB${\fP\fIname\fP\fB=\fP\fIvalue\fP\fB}\fP form
of parameter substitution (see below).
.\"}}}
.PP
.\"{{{  environment
Parameters with the export attribute (set using the \fBexport\fP or
\fBtypeset \-x\fP commands, or by parameter assignments followed by simple
commands) are put in the environment (see \fIenviron\fP(5)) of commands
run by the shell as \fIname\fP\fB=\fP\fIvalue\fP pairs.
The order in which parameters appear in the environment of a command
is unspecified.
When the shell starts up, it extracts parameters and their values from its
environment and automatically sets the export attribute for those parameters.
.\"}}}
.\"{{{  ${name[:][-+=?]word}
.PP
Modifiers can be applied to the \fB${\fP\fIname\fP\fB}\fP form of parameter
substitution:
.IP \fB${\fP\fIname\fP\fB:-\fP\fIword\fP\fB}\fP
if \fIname\fP is set and not null, it is substituted, otherwise \fIword\fP is
substituted.
.IP \fB${\fP\fIname\fP\fB:+\fP\fIword\fP\fB}\fP
if \fIname\fP is set and not null, \fIword\fP is substituted, otherwise nothing is substituted.
.IP \fB${\fP\fIname\fP\fB:=\fP\fIword\fP\fB}\fP
if \fIname\fP is set and not null, it is substituted, otherwise it is
assigned \fIword\fP and the resulting value of \fIname\fP is substituted.
.IP \fB${\fP\fIname\fP\fB:?\fP\fIword\fP\fB}\fP
if \fIname\fP is set and not null, it is substituted, otherwise \fIword\fP
is printed on standard error (preceded by \fIname\fP:) and an error occurs
(normally causing termination of a shell script, function or \&.-script).
If word is omitted the string `parameter null or not set' is used instead.
.PP
In the above modifiers, the \fB:\fP can be omitted, in which case the
conditions only depend on \fIname\fP being set (as opposed to set and
not null).
If \fIword\fP is needed, parameter, command, arithmetic and tilde substitution
are performed on it; if \fIword\fP is not needed, it is not evaluated.
.\"}}}
.PP
The following forms of parameter substitution can also be used:
.\"{{{  ${#name}
.IP \fB${#\fP\fIname\fP\fB}\fP
The number of positional parameters if \fIname\fP is \fB*\fP, \fB@\fP or
is not specified,
or the length of the string value of parameter \fIname\fP.
.\"}}}
.\"{{{  ${#name[*]}, ${#name[@]}
.IP "\fB${#\fP\fIname\fP\fB[*]}\fP, \fB${#\fP\fIname\fP\fB[@]}\fP"
The number of elements in the array \fIname\fP.
.\"}}}
.\"{{{  ${name#pattern}, ${name##pattern}
.IP "\fB${\fP\fIname\fP\fB#\fP\fIpattern\fP\fB}\fP, \fB${\fP\fIname\fP\fB##\fP\fIpattern\fP\fB}\fP"
If \fIpattern\fP matches the beginning of the value of parameter \fIname\fP,
the matched text is deleted from the result of substitution.  A single
\fB#\fP results in the shortest match, two \fB#\fP's results in the
longest match.
.\"}}}
.\"{{{  ${name%pattern}, ${name%%pattern}
.IP "\fB${\fP\fIname\fP\fB%\fP\fIpattern\fP\fB}\fP, \fB${\fP\fIname\fP\fB%%\fP\fIpattern\fP\fB}\fP"
Like \fB${\fP..\fB#\fP..\fB}\fP substitution, but it deletes from the end of the
value.
.\"}}}
.\"{{{  special shell parameters
.PP
The following special parameters are implicitly set by the shell and cannot be
set directly using assignments:
.\"{{{  !
.IP \fB!\fP
Process id of the last background process started.  If no background
processes have been started, the parameter is not set.
.\"}}}
.\"{{{  #
.IP \fB#\fP
The number of positional parameters (\fIi.e.\fP, \fB$1\fP, \fB$2\fP,
\fIetc.\fP).
.\"}}}
.\"{{{  $
.IP \fB$\fP
The process ID of the shell, or the PID of the original shell if
it is a subshell.
.\"}}}
.\"{{{  -
.IP \fB\-\fP
The concatenation of the current single letter options
(see \fBset\fP command below for list of options).
.\"}}}
.\"{{{  ?
.IP \fB?\fP
The exit status of the last non-asynchronous command executed.
If the last command was killed by a signal, \fB$?\fP is set to 128 plus
the signal number.
.\"}}}
.\"{{{  0
.IP "\fB0\fP"
The name the shell was invoked with (\fIi.e.\fP, \fBargv[0]\fP), or the
\fBcommand-name\fP if it was invoked with the \fB\-c\fP option and the
\fBcommand-name\fP was supplied, or the \fIfile\fP argument, if it was
supplied.
If the \fBposix\fP option is not set, \fB$0\fP is the name of the current
function or script.
.\"}}}
.\"{{{  1-9
.IP "\fB1\fP ... \fB9\fP"
The first nine positional parameters that were supplied to the shell,
function or \fB.\fP-script.
Further positional parameters may be accessed using
\fB${\fP\fInumber\fP\fB}\fP.
.\"}}}
.\"{{{  *
.IP \fB*\fP
All positional parameters (except parameter 0), 
\fIi.e.\fP, \fB$1 $2 $3\fP....
If used outside of double quotes, parameters are separate words
(which are subjected to word splitting); if used within double quotes,
parameters are separated by the first character of the \fBIFS\fP parameter
(or the empty string if \fBIFS\fP is null).
.\"}}}
.\"{{{  @
.IP \fB@\fP
Same as \fB$*\fP, 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 loosing null arguments or
splitting arguments with spaces).
.\"}}}
.\"}}}
.\"{{{  general shell parameters
.PP
The following parameters are set and/or used by the shell:
.\"{{{  CDPATH
.IP \fBCDPATH\fP
Search path for the \fBcd\fP built-in command.  Works the same way as
\fBPATH\fP for those directories not beginning with \fB/\fP in \fBcd\fP
commands.
Note that if CDPATH is set and does not contain \fB.\fP nor an empty path,
the current directory is not searched.  Also, the \fBcd\fP built-in command
will display the resulting directory when a match is found in any search path
other than the than the empty path.
.\"}}}
.\"{{{  COLUMNS
.IP \fBCOLUMNS\fP
Set to the number of columns on the terminal or window.
Currently set to the \fBcols\fP value as reported by \fIstty\fP(1) if that
value is non-zero.
This parameter is used by the interactive line editing modes, and by
\fBselect\fP, \fBset \-o\fP and \fBkill \-l\fP commands
to format information in columns.
.\"}}}
.\"{{{  EDITOR
.\"}}}
.\"{{{  ENV
.IP \fBENV\fP
If this parameter is found to be set after any profile files are
executed, the expanded value is used as a shell start-up file.  It
typically contains function and alias definitions.
.\"}}}
.\"{{{  ERRNO
.IP \fBERRNO\fP
Integer value of the shell's errno variable \(em indicates the reason
the last system call failed.
.\" todo: ERRNO variable
.sp
Not implemented yet.
.\"}}}
.\"{{{  EXECSHELL
.IP \fBEXECSHELL\fP
If set, this parameter is assumed to contain the shell that is to be
used to execute commands that \fIexecve\fP(2) fails to execute and
which do not start with a `\fB#!\fP \fIshell\fP' sequence.
.\"}}}
.\"{{{  FCEDIT
.IP \fBFCEDIT\fP
The editor used by the \fBfc\fP command (see below).
.\"}}}
.\"{{{  FPATH
.IP \fBFPATH\fP
Like \fBPATH\fP, 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 \fBPATH\fP.
See Functions below for more information.
.\"}}}
.\"{{{  HISTFILE
.\"}}}
.\"{{{  HISTSIZE
.\"}}}
.\"{{{  HOME
.IP \fBHOME\fP
The default directory for the \fBcd\fP command and the value
substituted for an unqualified \fB~\fP (see Tilde Expansion below).
.\"}}}
.\"{{{  IFS
.IP \fBIFS\fP
Internal field separator, used during substitution and by the \fBread\fP
command, to split values into distinct arguments; normally set to
space, tab and newline.  See Substitution above for details.
.br
\fBNote:\fP this parameter is not imported from the environment
when the shell is started.
.\"}}}
.\"{{{  KSH_VERSION
.\"}}}
.\"{{{  SH_VERSION
.IP \fBSH_VERSION\fP
The version of shell and the date the version was created (readonly).
.\"}}}
.\"{{{  LINENO
.IP \fBLINENO\fP
The line number of the function or shell script that is currently being
executed.
.\" todo: LINENO variable
.sp
Not implemented yet.
.\"}}}
.\"{{{  LINES
.IP \fBLINES\fP
Set to the number of lines on the terminal or window.
.\"Currently set to the \fBrows\fP value as reported by \fIstty\fP(1) if that
.\"value is non-zero.
.\" todo: LINES variable
.sp
Not implemented yet.
.\"}}}
.\"{{{  MAIL
.\"}}}
.\"{{{  MAILCHECK
.\"}}}
.\"{{{  MAILPATH
.\"}}}
.\"{{{  OLDPWD
.IP \fBOLDPWD\fP
The previous working directory.
Unset if \fBcd\fP has not successfully changed directories since the
shell started, or if the shell doesn't know where it is.
.\"}}}
.\"{{{  OPTARG
.IP \fBOPTARG\fP
When using \fBgetopts\fP, it contains the argument for a parsed option,
if it requires one.
.\"}}}
.\"{{{  OPTIND
.IP \fBOPTIND\fP
The index of the last argument processed when using \fBgetopts\fP.
Assigning 1 to this parameter causes \fBgetopts\fP to
process arguments from the beginning the next time it is invoked.
.\"}}}
.\"{{{  PATH
.IP \fBPATH\fP
A colon separated list of directories that are searched when looking
for commands and \fB.\fP'd files.
An empty string resulting from a leading or trailing colon, or two adjacent
colons is treated as a `.', the current directory.
.\"}}}
.\"{{{  POSIXLY_CORRECT
.IP \fBPOSIXLY_CORRECT\fP
If set, this parameter causes the \fBposix\fP option to be enabled.
See POSIX Mode below.
.\"}}}
.\"{{{  PPID
.IP \fBPPID\fP
The process ID of the shell's parent (readonly).
.\"}}}
.\"{{{  PS1
.IP \fBPS1\fP
\fBPS1\fP is the primary prompt for interactive shells.
The prompt is printed verbatim (\fIi.e.\fP, no substitutions are done).
Default is `\fB$\ \fP' for non-root users, `\fB#\ \fP' for root..
.\"}}}
.\"{{{  PS2
.IP \fBPS2\fP
Secondary prompt string, by default `\fB>\fP ', used when more input is
needed to complete a command.
.\"}}}
.\"{{{  PS3
.\"}}}
.\"{{{  PS4
.IP \fBPS4\fP
Used to prefix commands that are printed during execution tracing
(see \fBset \-x\fP command below).
The prompt is printed verbatim (\fIi.e.\fP, no substitutions are done).
Default is `\fB+\ \fP'.
.\"}}}
.\"{{{  PWD
.IP \fBPWD\fP
The current working directory.  Maybe unset or null if shell doesn't
know where it is.
.\"}}}
.\"{{{  RANDOM
.\"}}}
.\"{{{  REPLY
.IP \fBREPLY\fP
Default parameter for the \fBread\fP command if no names are given.
Also used in \fBselect\fP loops to store the value that is read from
standard input.
.\"}}}
.\"{{{  SECONDS
.\"}}}
.\"{{{  TMOUT
.\"}}}
.\"{{{  TMPDIR
.IP \fBTMPDIR\fP
The directory shell temporary files are created in.  If this parameter
is not set, or does not contain the absolute path of a writable
directory, temporary files are created in \fB/tmp\fP.
.\"}}}
.\"{{{  VISUAL
.\"}}}
.\"}}}
.\"}}}
.\"{{{  Tilde Expansion
.SS "Tilde Expansion"
Tilde expansion, which is done in parallel with parameter substitution,
is done on words starting with an unquoted \fB~\fP.  The characters
following the tilde, up to the first \fB/\fP, if any, are assumed to be
a login name.  If the login name is empty, \fB+\fP or \fB\-\fP, the
value of the \fBHOME\fP, \fBPWD\fP, or \fBOLDPWD\fP parameter is
substituted, respectively.  Otherwise, the password file is searched for
the login name, and the tilde expression is substituted with the
user's home directory.  If the login name is not found in the password
file or if any quoting or parameter substitution occurs in the login name,
no substitution is performed.
.PP
In parameter assignments (those preceding a simple-command or those
occurring in the arguments of \fBalias\fP, \fBexport\fP, \fBreadonly\fP,
and \fBtypeset\fP), tilde expansion is done after any unquoted colon
(\fB:\fP), and login names are also delimited by colons.
.PP
The home directory of previously expanded login names are cached and
re-used.  The \fBalias \-d\fP command may be used to list, change and
add to this cache (\fIe.g.\fP, `alias \-d fac=/usr/local/facilities; cd
~fac/bin').
.\"}}}
.\"{{{  Brace Expansion
.\"}}}
.\"{{{  File Name Patterns
.SS "File Name Patterns"
.PP
A file name pattern is a word containing one or more unquoted \fB?\fP or
\fB*\fP characters or \fB[\fP..\fB]\fP sequences.  Once brace expansion has
been performed, the shell replaces file name patterns with the sorted names
of all the files that match the pattern (if no files match, the word is
left unchanged).  The pattern elements have the following meaning:
.IP \fB?\fP
matches any single character.
.IP \fB*\fP
matches any sequence of characters.
.IP \fB[\fP..\fB]\fP
matches any of the characters inside the brackets.  Ranges of characters
can be specified by separating two characters by a \fB\-\fP, \fIe.g.\fP,
\fB[a0\-9]\fP matches the letter \fBa\fP or any digit.
In order to represent itself, a
\fB\-\fP must either be quoted or the first or last character in the character
list.  Similarly, a \fB]\fP must be quoted or the first character in the list
if it is represent itself instead of the end of the list.  Also, a \fB!\fP
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.
.IP \fB[!\fP..\fB]\fP
like \fB[\fP..\fB]\fP, except it matches any character not inside the brackets.
.PP
Note that pdksh currently never matches \fB.\fP and \fB..\fP, but the original
ksh, Bourne sh and bash do, so this may have to change (too bad).
.PP
Note that none of the above pattern elements match either a period (\fB.\fP)
at the start of a file name or a slash (\fB/\fP), even if they are explicitly
used in a \fB[\fP..\fB]\fP sequence; also, the names \fB.\fP and \fB..\fP
are never matched, even by the pattern \fB.*\fP.
.PP
If the \fBmarkdirs\fP option is set, any directories that result from
file name generation are marked with a trailing \fB/\fP.
.PP
.\" todo: implement this ([[:alpha:]], \fIetc.\fP)
The POSIX character classes (\fIi.e.\fP,
\fB[:\fP\fIclass-name\fP\fB:]\fP inside a \fB[\fP..\fB]\fP expression)
are not yet implemented.
.\"}}}
.\"{{{  Input/Output Redirection
.SS "Input/Output Redirection"
When a command is executed, its standard input, standard output and
standard error (file descriptors 0, 1 and 2, respectively) are normally
inherited from the shell.
Three exceptions to this are commands in pipelines, for which standard input
and/or standard output are those set up by the pipeline, asynchronous commands
created when job control is disabled, for which standard input is initially
set to be from \fB/dev/null\fP, and commands for which any of the following
redirections have been specified:
.IP "\fB>\fP \fIfile\fP"
standard output is redirected to \fIfile\fP.  If \fIfile\fP does not exist,
it is created; if it does exist, is a regular file and the \fBnoclobber\fP
option is set, an error occurs, otherwise the file is truncated.
Note that this means the command \fIcmd < foo > foo\fP will open
\fIfoo\fP for reading and then truncate it when it opens it for writing,
before \fIcmd\fP gets a chance to actually read \fIfoo\fP.
.IP "\fB>|\fP \fIfile\fP"
same as \fB>\fP, except the file is truncated, even if the \fBnoclobber\fP
option is set.
.IP "\fB>>\fP \fIfile\fP"
same as \fB>\fP, except the file an existing file is appended to instead
of being truncated.  Also, the file is opened in append mode, so writes
always go to the end of the file (see \fIopen\fP(2)).
.IP "\fB<\fP \fIfile\fP"
standard input is redirected from \fIfile\fP, which is opened for reading.
.IP "\fB<>\fP \fIfile\fP"
same as \fB<\fP, except the file is opened for reading and writing.
.IP "\fB<<\fP \fImarker\fP"
after reading the command line containing this kind of redirection (called a
here document), the shell copies lines from the command source into a temporary
file until a line matching \fImarker\fP is read.
When the command is executed, standard input is redirected from the temporary
file.
If \fImarker\fP 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 (\fB\e\fP) escapes for
\fB$\fP, \fB`\fP, \fB\e\fP and \fB\enewline\fP.
If multiple here documents are used on the same command line, they are
saved in order.
.IP "\fB<<-\fP \fImarker\fP"
same as \fB<<\fP, except leading tabs are stripped from lines in the
here document.
.IP "\fB<&\fP \fIfd\fP"
standard input is duplicated from file descriptor \fIfd\fP.
\fIfd\fP can be a single digit, indicating the number of an existing
file descriptor, the letter \fBp\fP, indicating the file descriptor
associated with the output of the current co-process, or
the character \fB\-\fP, indicating standard input is to be closed.
.IP "\fB>&\fP \fIfd\fP"
same as \fB<&\fP, except the operation is done on standard output.
.PP
In any of the above redirections, the file descriptor that is redirected
(\fIi.e.\fP, standard input or standard output) can be explicitly given by
preceding the redirection with a single digit.
Parameter, command and arithmetic substitutions, tilde substitutions and
file name generation are all performed on the \fIfile\fP, \fImarker\fP and
\fIfd\fP arguments of redirections.
Note however, that the results of any file name generation are only used
if a single file is matched; if multiple files match, the word with the
unexpanded file name generation characters is used.
Note that in restricted shells, redirections which can create files cannot
be used.
.PP
For simple-commands, redirections may appear anywhere in the command, for
compound-commands (\fBif\fP statements, \fIetc.\fP), any redirections must
appear at the end.
Redirections are processed after pipelines are created and in the order they
are given, so
.RS
\fBcat /foo/bar 2>&1 > /dev/null | cat \-n\fP
.RE
will print an error with a line number prepended to it.
.\"}}}
.\"{{{  Arithmetic Expressions
.SS "Arithmetic Expressions"
Integer arithmetic expressions can be used
inside \fB$((\fP..\fB))\fP expressions,
inside array references (\fIe.g.\fP, \fIname\fP\fB[\fP\fIexpr\fP\fB]\fP),
as numeric arguments to the \fBtest\fP command,
and as the value of an assignment to an integer parameter.
.PP
Expression may contain alpha-numeric parameter identifiers, array
references, and integer constants and may be combined with the
following C operators (listed and grouped in increasing order of precedence).
.TP
Unary operators:
\fB+ \- ! ~ ++ --\fP
.TP
Binary operators:
\fB,\fP
.br
\fB= *= /= %= += \-= <<= >>= &= ^= |=\fP
.br
\fB||\fP
.br
\fB&&\fP
.br
\fB|\fP
.br
\fB^\fP
.br
\fB&\fP
.br
\fB== !=\fP
.br
\fB< <= >= >\fP
.br
\fB<< >>\fP
.br
\fB+ \-\fP
.br
\fB* / %\fP
.TP
Ternary operator:
\fB?:\fP (precedence is immediately higher than assignment)
.TP
Grouping operators:
\fB( )\fP
.PP
Integer constants may be specified with arbitrary bases using the notation
\fIbase\fP\fB#\fP\fInumber\fP, where \fIbase\fP is a decimal integer specifying
the base, and \fInumber\fP is a number in the specified base.
.LP
The operators are evaluated as follows:
.RS
.IP "unary \fB+\fP"
result is the argument (included for completeness).
.IP "unary \fB\-\fP"
negation.
.IP "\fB!\fP"
logical not; the result is 1 if argument is zero, 0 if not.
.IP "\fB~\fP"
arithmetic (bit-wise) not.
.IP "\fB++\fP"
increment; must be applied to a parameter (not a literal or other
expression) - the parameter is incremented by 1.
When used as a prefix operator, the result is the incremented value of
the parameter, when used as a postfix operator, the result is the
original value of the parameter.
.IP "\fB++\fP"
similar to \fB++\fP, except the paramter is decremented by 1.
.IP "\fB,\fP"
separates two arithmetic expressions; the left hand side is evaluated first,
then the right.  The result is value of the expression on the right hand side.
.IP "\fB=\fP"
assignment; variable on the left is set to the value on the right.
.IP "\fB*= /= %= += \-= <<= >>= &= ^= |=\fP"
assignment operators; \fI<var> <op>\fP\fB=\fP \fI<expr>\fP is the same as
\fI<var>\fP \fB=\fP \fI<var> <op>\fP \fB(\fP \fI<expr>\fP \fB)\fP.
.IP "\fB||\fP"
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.
.IP "\fB&&\fP"
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.
.IP "\fB|\fP"
arithmetic (bit-wise) or.
.IP "\fB^\fP"
arithmetic (bit-wise) exclusive-or.
.IP "\fB&\fP"
arithmetic (bit-wise) and.
.IP "\fB==\fP"
equal; the result is 1 if both arguments are equal, 0 if not.
.IP "\fB!=\fP"
not equal; the result is 0 if both arguments are equal, 1 if not.
.IP "\fB<\fP"
less than; the result is 1 if the left argument is less than the right,
0 if not.
.IP "\fB<= >= >\fP"
less than or equal, greater than or equal, greater than.  See <.
.IP "\fB<< >>\fP"
shift left (right); the result is the left argument with its bits shifted
left (right) by the amount given in the right argument.
.IP "\fB+ - * /\fP"
addition, subtraction, multiplication, and division.
.IP "\fB%\fP"
remainder; the result is the remainder of the division of the left argument
by the right.  The sign of the result is unspecified if either argument
is negative.
.IP "\fI<arg1>\fP \fB?\fP \fI<arg2>\fP \fB:\fP \fI<arg3>\fP"
if \fI<arg1>\fP is non-zero, the result is \fI<arg2>\fP,
otherwise \fI<arg3>\fP.
.RE
.\"}}}
.\"{{{  Co-Processes
.\"}}}
.\"{{{  Functions
.SS "Functions"
Functions are defined using either Korn shell \fBfunction\fP \fIname\fP
syntax or the Bourne/POSIX shell \fIname\fP\fB()\fP syntax
(see below for the difference between the two forms).
Functions are like \fB.\fP-scripts in that they are executed in
the current environment, however, unlike \fB.\fP-scripts, shell arguments
(\fIi.e.\fP, positional parameters, \fB$1\fP, \fIetc.\fP) are never visible
inside them.
When the shell is determining the location of a command, functions are
searched after special built-in commands, and before regular and non-regular
built-ins, and before the \fBPATH\fP is searched.
.PP
An existing function may be deleted using \fBunset \-f\fP \fIfunction-name\fP.
A list of functions can be obtained using \fBtypeset +f\fP and the
function definitions can be listed using \fBtypeset \-f\fP.
\fBautoload\fP (which is an alias for \fBtypeset \-fu\fP) may be used to
create undefined functions; when an undefined function is executed, the
shell searches the path specified in the \fBFPATH\fP 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
(\fIi.e.\fP, the shell searches the regular built-in command table
and \fBPATH\fP).
Note that if a command is not found using \fBPATH\fP, an attempt is
made to autoload a function using \fBFPATH\fP (this is an undocumented
feature of the original Korn shell).
.PP
Functions can have two attributes, trace and export, which can be set
with \fBtypeset \-ft\fP and \fBtypeset \-fx\fP, respectively.
When a traced function is executed, the shell's \fBxtrace\fP option is turned
on for the functions duration, otherwise the \fBxtrace\fP option is turned off.
The export attribute of functions is currently not used.  In the original
Korn shell, exported functions are visible to shell scripts that are executed.
.PP
Since functions are executed in the current shell environment, parameter
assignments made inside functions are visible after the function completes.
If this is not the desired effect, the \fBtypeset\fP command can be used
inside a function to create a local parameter.
Note that special parameters (\fIe.g.\fP, \fB$$\fP, \fB$!\fP) can't be
scoped in this way.
.PP
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 \fBreturn\fP command;
this may also be used to explicitly specify the exit status.
.PP
Functions defined with the \fBfunction\fP reserved word are
treated differently in the following ways from functions defined with
the \fB()\fP notation:
.nr P2 \n(PD
.nr PD 0
.IP \ \ \(bu
the \fB$0\fP parameter is set to the name of the function
(Bourne-style functions leave \fB$0\fP untouched).
.IP \ \ \(bu
parameter assignments preceeding function calls are not kept in
the shell environment
(executing Bourne-style functions will keep assignments).
.IP \ \ \(bu
\fBOPTIND\fP is saved/reset and restored on entry and exit from the function
so \fBgetopts\fP can be used properly both inside and outside the function
(Bourne-style functions leave \fBOPTIND\fP untouched, so using \fBgetopts\fP
inside a function interferes with using \fBgetopts\fP outside the function).
.nr PD \n(P2
In the future, the following differences will also be added:
.nr P2 \n(PD
.nr PD 0
.IP \ \ \(bu
A separate trap/signal environment will be used during the execution of
functions.
This will mean that traps set inside a function will not affect the shell's
traps and signals that are not ignored in the shell (but may be trapped) will
have their default effect in a function.
.IP \ \ \(bu
The EXIT trap, if set in a function, will be executed after the function
returns.
.nr PD \n(P2
.\"}}}
.\"{{{  POSIX mode
.SS "POSIX Mode"
The shell is intended to be POSIX compliant, however, in some cases, POSIX
behaviour is contrary either to the original Korn shell behaviour or to
user convenience.
How the shell behaves in these cases is determined by the state of
the posix option (\fBset \-o posix\fP) \(em if it is on, the POSIX behaviour
is followed, otherwise it is not.
The \fBposix\fP option is set automatically when the shell starts up
if the environment contains the \fBPOSIXLY_CORRECT\fP parameter.
(The shell can also be compiled so that it is in POSIX mode by default,
however this is usually not desirable).
.PP
The following is a list of things that are affected by the state of
the \fBposix\fP option:
.nr P2 \n(PD
.nr PD 0
.IP \ \ \(bu
reading of \fB$ENV\fP: if not in posix mode, the \fBENV\fP parameter
is not expanded and included when the shell starts.
.IP \ \ \(bu
\fB\e"\fP inside double quoted \fB`\fP..\fB`\fP command substitutions:
in posix mode, the \fB\e"\fP is interpreted when the command is interpreted;
in non-posix mode, the backslash is stripped before the command substitution
is interpreted.  For example, \fBecho "`echo \e"hi\e"`"\fP produces `"hi"' in
posix mode, `hi' in non-posix mode.  To avoid problems, use the \fB$(...\fP)
form of command substitution.
.IP \ \ \(bu
\fBkill \-l\fP output: in posix mode, signal names are listed one a single line;
in non-posix mode, signal numbers, names and descriptions are printed in
columns.
In future, a new option (\fB\-v\fP perhaps) will be added to distinguish
the two behaviours.
.IP \ \ \(bu
\fBfg\fP exit status: in posix mode, the exit status is 0 if no errors occur;
in non-posix mode, the exit status is that of the last foregrounded job.
.IP \ \ \(bu
\fBgetopts\fP: in posix mode, options must start with a \fB\-\fP; in non-posix
mode, options can start with either \fB\-\fP or \fB+\fP.
.IP \ \ \(bu
brace expansion (also known as alternation): in posix mode, brace expansion
is disabled; in non-posix mode, brace expansion enabled.
Note that \fBset \-o posix\fP (or setting the \fBPOSIXLY_CORRECT\fP parameter)
automatically turns the \fBbraceexpand\fP option off, however it can be
explicitly turned on later.
.IP \ \ \(bu
\fBset \-\fP: in posix mode, this does not clear the \fBverbose\fP or
\fBxtrace\fP options; in non-posix mode, it does.
.IP \ \ \(bu
\fBset\fP exit status: in posix mode, the exit status of set is 0
if there are no errors; in non-posix mode, the exit status is that of
any command substitutions performed in generating the set command.
For example, `\fBset \-\- `false`; echo $?\fP' prints 0 in posix mode,
1 in non-posix mode.  This construct is used in most shell scripts that
use the old \fIgetopt\fP(1) command.
.IP \ \ \(bu
argument expansion of \fBalias\fP, \fBexport\fP, \fBreadonly\fP, and
\fBtypeset\fP commands: in posix mode, normal argument expansion done;
in non-posix mode, field splitting, file globing, brace expansion and
(normal) tilde expansion are turned off, and assignment tilde expansion
is turned on.
.IP \ \ \(bu
signal specification: in posix mode, signals can be specified as digits only
if signal numbers match POSIX values (\fIi.e.\fP, HUP=1, INT=2, QUIT=3, ABRT=6,
KILL=9, ALRM=14, and TERM=15); in non-posix mode, signals can be always digits.
.IP \ \ \(bu
alias expansion: in posix mode, alias expansion is only carried out when
reading command words; in non-posix mode, alias expansion is carried out
on any word following an alias that ended in a space.
For example, the following for loop
.RS
.ft B
alias a='for ' i='j'
.br
a i in 1 2; do echo i=$i j=$j; done
.ft P
.RE
uses parameter \fBi\fP in posix mode, \fBj\fP in non-posix mode.
.IP \ \ \(bu
test: in posix mode, the expression "\fB-t\fP" (preceded by
some number of "\fB!\fP" arguments) is always true as it is a non-zero length
string; in non-posix mode, it tests if file descriptor 1 is a tty (\fIi.e.\fP,
the \fIfd\fP argument to the \fB-t\fP test may be left out and defaults to 1).
.nr PD \n(P2
.\"}}}
.\"{{{  Command Execution (built-in commands)
.SS "Command Execution"
After evaluation of command line arguments, redirections and parameter
assignments, the type of command is determined: a special built-in,
a function, a regular built-in or the name of a file to execute found
using the \fBPATH\fP parameter.
The checks are made in the above order.
Special built-in commands differ from other commands in that 
the \fBPATH\fP parameter is not used to find them, an error
during their execution can cause a non-interactive shell to exit and
parameter assignments that are specified before the command are
kept after the command completes.
Just to confuse things, if the posix option is turned off (see \fBset\fP
command below) some special commands are very special in that
no field splitting, file globing, brace expansion nor tilde expansion
is preformed on arguments that look like assignments.
Regular built-in commands are different only in that the \fBPATH\fP
parameter is not used to find them.
.PP
The original ksh and POSIX differ somewhat in which commands are considered
special or regular:
.IP "POSIX special commands"
.TS
lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB .
\&.	continue	exit	return	trap
:	eval	export	set	unset
break	exec	readonly	shift
.TE
.IP "Additional ksh special commands"
.TS
lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB .
builtin	times	typeset		
.TE
.IP "Very special commands (non-posix mode)"
.TS
lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB .
alias	readonly	set	typeset	
.TE
.IP "POSIX regular commands"
.TS
lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB .
alias	command	fg	kill	umask
bg	false	getopts	read	unalias
cd	fc	jobs	true	wait
.TE
.IP "Additional ksh regular commands"
.TS
lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB .
[	let	pwd	ulimit	
echo	print	test	whence	
.TE
.PP
In the future, the additional ksh special and regular commands may
be treated differently from the POSIX special and regular commands.
.PP
Once the type of the command has been determined, any command line parameter
assignments are performed and exported for the duration of the command.
.PP
The following describes the special and regular built-in commands:
.\"{{{  . file [ arg1 ... ]
.IP "\fB\&.\fP \fIfile\fP [\fIarg1\fP ...]"
Execute the commands in \fIfile\fP in the current environment.
The file is searched for in the directories of \fBPATH\fP.
If arguments are given, the positional parameters may be used to
access them while \fIfile\fP is being executed.
If no arguments are given, the positional parameters are those of the
environment the command is used in.
.\"}}}
.\"{{{  : [ ... ]
.IP "\fB:\fP [ ... ]"
The null command.
Exit status is set to zero.
.\"}}}
.\"{{{  alias [ -d | +-t [ -r ] ] [+-px] [+-] [name1[=value1] ...]
.IP "\fBalias\fP [ \fB\-d\fP | \fB\(+-t\fP [\fB\-r\fP] ] [\fB\(+-px\fP] [\fB\(+-\fP] [\fIname1\fP[\fB=\fP\fIvalue1\fP] ...]"
Without arguments, \fBalias\fP 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).
.sp
When listing aliases, one of two formats is used: 
normally, aliases are listed as \fIname\fP\fB=\fP\fIvalue\fP, where
\fIvalue\fP is quoted; if options were preceded with \fB+\fP 
or a lone \fB+\fP is given on the command line, only \fIname\fP
is printed.
In addition, if the \fB\-p\fP option is used, each alias
is prefixed with the string "\fBalias\fP\ ".
.sp
The \fB\-x\fP option sets (\fB+x\fP clears) the export attribute of an alias,
or, if no names are given, lists the aliases with the export attribute
(exporting an alias has no affect).
.sp
The \fB\-x\fP option sets the export attribute of an alias, or, if no
names are given, lists the aliases with the export attribute
(exporting an alias currently has no affect).
.sp
The \fB\-t\fP option indicates that tracked aliases are to be listed/set
(values specified on the command line are ignored for tracked aliases).
The \fB\-r\fP option indicates that all tracked aliases are to be reset.
.sp
The \fB\-d\fP causes directory aliases, which are used in tilde expansion,
to be listed or set (see Tilde Expansion above).
.\"}}}
.\"{{{  bg [job ...]
.IP "\fBbg\fP [\fIjob\fP ...]"
Resume the specified stopped job(s) in the background.
If no jobs are specified, \fB%+\fP is assumed.
This command is only available on systems which support job control.
See Job Control below for more information.
.\"}}}
.\"{{{  bind [-l] [-m] [key[=editing-command] ...]
.IP "\fBbind\fP [\fB\-m\fP] [\fIkey\fP[\fB=\fP\fIediting-command\fP] ...]"
Set or view the current emacs command editing key bindings/macros.
See Emacs Interactive Input Line Editing below for a complete description.
.\"}}}
.\"{{{  break [level]
.IP "\fBbreak\fP [\fIlevel\fP]"
\fBbreak\fP exits the \fIlevel\fPth inner most for, select, until, or while
loop.
\fIlevel\fP defaults to 1.
.\"}}}
.\"{{{  builtin command [arg1 ...]
.IP "\fBbuiltin\fP \fIcommand\fP [\fIarg1\fP ...]"
Execute the built-in command \fIcommand\fP.
.\"}}}
.\"{{{  cd [-LP] [dir]
.IP "\fBcd\fP [\fB\-LP\fP] [\fIdir\fP]"
Set the working directory to \fIdir\fP.  If the parameter \fBCDPATH\fP
is set, it lists the search path for the directory containing \fIdir\fP.  A
null path means the current directory. If \fIdir\fP is found in any
component of the \fBCDPATH\fP search path other than the null path the name
of the new working directory will be written to standard output. If
\fIdir\fP is missing, the home directory \fB$HOME\fP is used.  If \fIdir\fP
is \fB\-\fP, the previous working directory is used (see OLDPWD parameter).
If \fB\-L\fP option (logical path) is used or if the \fBphysical\fP option
(see \fBset\fP command below) isn't set, references to \fB..\fP in \fIdir\fP
are relative to the path used get to the directory.
If \fB\-P\fP option (physical path) is used or if the \fBphysical\fP option
is set, \fB..\fP is relative to the filesystem directory tree.
The \fBPWD\fP and \fBOLDPWD\fP parameters are updated to reflect the
current and old wording directory, respectively.
.\"}}}
.\"{{{  cd [-LP] old new
.IP "\fBcd\fP [\fB\-LP\fP] \fIold new\fP"
The string \fInew\fP is substituted for \fIold\fP in the current
directory, and the shell attempts to change to the new directory.
.\"}}}
.\"{{{  command [ -pvV ] cmd [arg1 ...]
.IP "\fBcommand\fP [\fB\-p\fP] \fIcmd\fP [\fIarg1\fP ...]"
\fIcmd\fP
is executed exactly as if the \fBcommand\fP had not been specified,
with two exceptions: first, \fIcmd\fP cannot be a shell function, and
second, special built-in commands lose their specialness (\fIi.e.\fP,
redirection and utility errors do not cause the shell to exit, and command
assignments are not permanent).
If the \fB\-p\fP option is given, a default search path is used instead of
the current value of \fBPATH\fP (the actual value of the default path is
system dependent: on POSIXish systems, it is the value returned by
.ce
\fBgetconf CS_PATH\fP
).
.sp
.\"}}}
.\"{{{  continue [levels]
.IP "\fBcontinue\fP [\fIlevels\fP]"
\fBcontinue\fP jumps to the beginning of the \fIlevel\fPth inner most for,
select, until, or while loop.
\fIlevel\fP defaults to 1.
.\"}}}
.\"{{{  echo [-neE] [arg ...]
.IP "\fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]"
Prints its arguments (separated by spaces) followed by a newline, to
standard out.
The newline is suppressed if any of the arguments contain the backslash
sequence \fB\ec\fP.
See \fBprint\fP command below for a list of other backslash sequences
that are recognized.
.sp
The options are provided for compatibility with BSD shell scripts:
\fB\-n\fP suppresses the trailing newline, \fB\-e\fP enables backslash
interpretation (a no-op, since this is normally done), and \fB\-E\fP which
suppresses backslash interpretation.
.\"}}}
.\"{{{  eval command ...
.IP "\fBeval\fP \fIcommand ...\fP"
The arguments are concatenated (with spaces between them) to form
a single string which the shell then parses and executes
in the current environment.
.\"}}}
.\"{{{  exec [command [arg ...]]
.IP "\fBexec\fP [\fIcommand\fP [\fIarg\fP ...]]"
The command is executed without forking, replacing the shell process.
.sp
If no arguments are given, any IO redirection is permanent and the shell
is not replaced.
Any file descriptors which are opened or \fIdup\fP(2)-ed
in this way are made available to other executed commands
(note that the Korn shell differs here: it does not pass on
file descriptors greater than 2).
.\"}}}
.\"{{{  exit [status]
.IP "\fBexit\fP [\fIstatus\fP]"
The shell exits with the specified exit status.
If \fIstatus\fP is not specified, the exit status is the current
value of the \fB?\fP parameter.
.\"}}}
.\"{{{  export [-p] [parameter[=value] ...]
.IP "\fBexport\fP [\fB\-p\fP] [\fIparameter\fP[\fB=\fP\fIvalue\fP]] ..."
Sets the export attribute of the named parameters.
Exported parameters are passed in the environment to executed commands.
If values are specified, the named parameters also assigned.
.sp
If no parameters are specified, the names of all parameters with the export
attribute are printed one per line, unless the \fB\-p\fP option is used,
in which case \fBexport\fP commands defining all exported
parameters, including their values, are printed.
.\"}}}
.\"{{{  false
.IP "\fBfalse\fP"
A command that exits with a non-zero status.
.\"}}}
.\"{{{  fc [-e editor | -l [-n]] [-r] [first [ last ]]
.\"}}}
.\"{{{  fc [-e - | -s] [-g] [old=new] [prefix]
.IP "\fBfc\fP [\fB\-e \-\fP | \fB\-s\fP] [\fB\-g\fP] [\fIold\fP\fB=\fP\fInew\fP] [\fIprefix\fP]"
Re-execute the selected command (the previous command by default) after
performing the optional substitution of \fIold\fP with \fInew\fP.  If
\fB\-g\fP is specified, all occurrences of \fIold\fP are replaced with
\fInew\fP.  This command is usually accessed with the predefined alias
\fBr='fc \-e \-'\fP.
.\"}}}
.\"{{{  fg [job ...]
.IP "\fBfg\fP [\fIjob\fP ...]"
Resume the specified job(s) in the foreground.
If no jobs are specified, \fB%+\fP is assumed.
This command is only available on systems which support job control.
See Job Control below for more information.
.\"}}}
.\"{{{  getopts optstring name [arg ...]
.IP "\fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIarg\fP ...]"
\fBgetopts\fP is used by shell procedures to parse the specified arguments
(or positional parameters, if no arguments are given) and to check for legal
options.
\fIoptstring\fP contains the option letters that
\fBgetopts\fP is to recognize.  If a letter is followed by a colon, the
option is expected to have an argument.
Options that do not take arguments may be grouped in a single argument.
If an option takes an argument and the option character is not the last
character of the argument it is found in, the remainder of the argument
is taken to be the option's argument, otherwise, the next argument is
the option's argument.
.sp
Each time \fBgetopts\fP is invoked, it places the next option in
the shell parameter \fIname\fP and the index of the next argument to be
processed in the shell parameter \fBOPTIND\fP.
If the option was introduced with a \fB+\fP, the option placed in
\fIname\fP is prefixed with a \fB+\fP.
When an option requires an argument, \fBgetopts\fP places it in the
shell parameter \fBOPTARG\fP.
When an illegal option or a missing option argument is
encountered a question mark or a colon is placed in \fIname\fP
(indicating an illegal option or missing argument, respectively)
and \fBOPTARG\fP is set to the option character that caused the problem.
An error message is also printed to standard error if \fIoptstring\fP
does not begin with a colon.
.sp
When the end of the options is encountered, \fBgetopts\fP exits with a
non-zero exit status.
Options end at the first (non-option argument) argument that does not
start with a \-, or when a \fB\-\-\fP argument is encountered.
.sp
Option parsing can be reset by setting \fBOPTIND\fP to 1 (this is done
automatically whenever the shell or a shell procedure is invoked).
.sp
Warning: Changing the value of the shell parameter \fBOPTIND\fP to
a value other than 1, or parsing different sets of arguments without
resetting \fBOPTIND\fP may lead to unexpected results.
.\"}}}
.\"{{{  hash [-r] [name ...]
.IP "\fBhash\fP [\fB\-r\fP] [\fIname ...\fP]"
Without arguments, any hashed executable command pathnames are listed.
The \fB\-r\fP option causes all hashed commands to be removed
from the hash table.
Each \fIname\fP is searched as if it where a command name and added to the
hash table if it is an executable command.
.\"}}}
.\"{{{  jobs [-lpn] [job ...]
.IP "\fBjobs\fP [\fB\-lpn\fP] [\fIjob\fP ...]"
Display information about the specified jobs; if no jobs are specified,
all jobs are displayed.
The \fB\-n\fP option causes information to be displayed only for jobs
that have changed state since the last notification.
If the \fB\-l\fP option is used, the process-id of each process in a job
is also listed.
The \fB\-p\fP option causes only the process group of each job to be printed.
See Job Control below for the format of \fIjob\fP and the displayed job.
.\"}}}
.\"{{{  kill [-s signame | -signum | -signame] { job | pid | -pgrp } ...
.IP "\fBkill\fP [\fB\-s\fP \fIsigname\fP | \fB\-signum\fP | \fB\-signame\fP ] { \fIjob\fP | \fIpid\fP | \fB\-\fP\fIpgrp\fP } ..."
Send the specified signal to the specified jobs, process ids, or process groups.
If no signal is specified, the signal TERM is sent.
If a job is specified, the signal is sent to the job's process group.
See Job Control below for the format of \fIjob\fP.
.\"}}}
.\"{{{  kill -l [exit-status ...]
.IP "\fBkill \-l\fP [\fIexit-status\fP ...]"
Print the name of the signal that killed a process which exited with
the specified \fIexit-status\fPes.
If no arguments are specified, a list of all the signals, their numbers and
a short description of them are printed.
.\"}}}
.\"{{{  let [expression ...]
.\"}}}
.\"{{{  print [-nprsun | -R [-en]] [argument ...]
.IP "\fBprint\fP [\fB\-nprsu\fP\fIn\fP | \fB\-R\fP [\fB\-en\fP]] [\fIargument ...\fP]"
\fBPrint\fP prints its arguments on the standard output, separated by
spaces, and terminated with a newline.  The \fB\-n\fP option suppresses
the newline.  By default, certain C escapes are translated.  These
include \eb, \ef, \en, \er, \et, \ev, and \e0### (# is an octal digit, of
which there may be 0 to 3).
\ec is equivalent to using the \fB\-n\fP option.  \e expansion may be
inhibited with the \fB\-r\fP option.
The \fB\-s\fP option prints to the history file instead of standard output,
the \fB\-u\fP option prints to file descriptor \fIn\fP (\fIn\fP
defaults to 1 if omitted), and the \fB\-p\fP option prints to the co-process
(see Co-Processes above).
.sp
The \fB\-R\fP option is used to emulate, to some degree, the BSD echo
command, which does not process \e sequences unless the \fB\-e\fP option
is given.
As above, the \fB\-n\fP option suppresses the trailing newline.
.\"}}}
.\"{{{  pwd [-LP]
.IP "\fBpwd\fP [\fB\-LP\fP]"
Print the present working directory.
If \fB\-L\fP option is used or if the \fBphysical\fP option
(see \fBset\fP command below) isn't set, the logical path is printed
(\fIi.e.\fP, the path used to \fBcd\fP to the current directory).
If \fB\-P\fP option (physical path) is used or if the \fBphysical\fP option
is set, the path determined from the filesystem (by following \fB..\fP
directories to the root directory) is printed.
.\"}}}
.\"{{{  read [-prsun] [parameter ...]
.IP "\fBread\fP [\fB\-prsu\fP\fIn\fP] [\fIparameter ...\fP]"
Reads a line of input from standard input, separate the line into fields using
the \fBIFS\fP parameter (see Substitution above), and assign each field to the
specified parameters.
If there are more parameters than fields, the extra parameters are set to null,
or alternatively, if there are more fields than parameters, the last parameter
is assigned the remaining fields (inclusive of any separating spaces).
If no parameters are specified, the \fBREPLY\fP parameter is used.
If the input line ends in a backslash and the \fB\-r\fP option was not used, the
backslash and newline are stripped and more input is read.
If no input is read, \fBread\fP exits with a non-zero status.
.sp
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
(\fIe.g.\fP, \fBread nfoo?'number of foos: '\fP).
.sp
The \fB\-u\fP\fIn\fP and \fB\-p\fP options cause input to be read
from file descriptor \fIn\fP or the current co-process (see Co-Processes above
for comments on this), respectively.
If the \fB\-s\fP option is used, input is saved to the history file.
.\"}}}
.\"{{{  readonly [-p] [parameter[=value] ...]
.IP "\fBreadonly\fP [\fB\-p\fP] [\fIparameter\fP[\fB=\fP\fIvalue\fP]] ..."
Sets the readonly attribute of the named parameters.  If values are given,
parameters are set to them before setting the attribute.
Once a parameter is made readonly, it cannot be unset and its value cannot
be changed.
.sp
If no parameters are specified, the names of all parameters with the readonly
attribute are printed one per line, unless the \fB\-p\fP option is used,
in which case \fBreadonly\fP commands defining all readonly
parameters, including their values, are printed.
.\"}}}
.\"{{{  return [status]
.IP "\fBreturn\fP [\fIstatus\fP]"
Returns from a function or \fB.\fP script, with exit status \fIstatus\fP.
If no \fIstatus\fP is given, the exit status of the last executed command
is used.
If used outside of a function or \fB.\fP script, it has the same effect
as \fBexit\fP.
Note that pdksh treats both profile and \fB$ENV\fP files as \fB.\fP scripts,
while the original Korn shell only treats profiles as \fB.\fP scripts.
.\"}}}
.\"{{{  set [+-abCefhkmnpsuvxX] [+-o [option]] [+-A name] [--] [arg ...]
.IP "\fBset\fP [\fB\(+-abCefhkmnpsuvxX\fP] [\fB\(+-o\fP [\fIoption\fP]] [\fB\(+-A\fP \fIname\fP] [\fB\-\-\fP] [\fIarg\fP ...]"
The set command can be used to set (\fB\-\fP) or clear (\fB+\fP) shell options,
set the positional parameters, or set an array parameter.
Options can be changed using the \fB\(+-o\fP \fIoption\fP syntax,
where \fIoption\fP is the long name of an option, or using
the \fB\(+-\fP\fIletter\fP syntax, where \fIletter\fP 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.
.sp
.TS
expand;
afB lfB lw(3i).
\-A		T{
Sets the elements of the array parameter \fIname\fP to \fIarg\fP ...;
If \fB\-A\fP is used, the array is reset (\fIi.e.\fP, emptied) first;
if \fB+A\fP is used, the first N elements are set (where N is the number
of \fIarg\fPs), the rest are left untouched.
T}
\-a	allexport	T{
all new parameters are created with the export attribute
T}
\-b	notify	T{
Print job notification messages asynchronously, instead of just before the
prompt.
Only used if job control is enabled (\fB\-m\fP).
T}
\-C	noclobber	T{
Prevent \fB>\fP redirection from overwriting existing files (\fB>|\fP must
be used to force an overwrite).
T}
\-e	errexit	T{
Exit (after executing the \fBERR\fP trap) as soon as an error occurs or
a command fails (\fIi.e.\fP, exits with a non-zero status).
This does not apply to commands whose exit status is explicitly tested by a
shell construct such as \fBif\fP, \fBuntil\fP, \fBwhile\fP, \fB&&\fP or
\fB||\fP statements.
T}
\-f	noglob	T{
Do not expand file name patterns.
T}
\-h	trackall	T{
Create tracked aliases for all executed commands (see Aliases above).
On by default for non-interactive shells.
T}
\-i	interactive	T{
Enable interactive mode \- this can only be set/unset when the shell is
invoked.
T}
\-k	keyword	T{
Parameter assignments are recognized anywhere in a command.
T}
\-l	login	T{
The shell is a login shell \- this can only be set/unset when the shell is
invoked (see Shell Startup above).
T}
\-m	monitor	T{
Enable job control (default for interactive shells).
T}
\-n	noexec	T{
Do not execute any commands \- useful for checking the syntax of scripts
(ignored if interactive).
T}
\-p	privileged	T{
Set automatically if, when the shell starts, the read uid or gid does not
match the effective uid or gid, respectively.
See Shell Startup above for a description of what this
means.
T}
-r	restricted	T{
Enable restricted mode \(em this option can only be used when the shell is
invoked.  See Shell Startup above for a description of what this
means.
T}
\-s	stdin	T{
If used when the shell is invoked, commands are read from standard input.
Set automatically if the shell is invoked with no arguments.
.sp
When \fB\-s\fP is used in the \fBset\fP command, it causes the specified
arguments to be sorted before assigning them to the positional parameters
(or to array \fIname\fP, if \fB\-A\fP is used).
T}
\-u	nounset	T{
Referencing of an unset parameter is treated as an error, unless
one of the \fB\-\fP, \fB+\fP or \fB=\fP modifiers is used.
T}
\-v	verbose	T{
Write shell input to standard error as it is read.
T}
\-x	xtrace	T{
Print commands and parameter assignments when they are executed,
preceded by the value of \fBPS4\fP.
T}
\-X	markdirs	T{
Mark directories with a trailing \fB/\fP during file name generation.
T}
	bgnice	T{
Background jobs are run with lower priority.
T}
	ignoreeof	T{
The shell will not exit on when end-of-file is read, \fBexit\fP must be used.
T}
	nohup	T{
Do not kill running jobs with a \fBHUP\fP signal when a login shell exists.
Currently set by default, but this will change in the future to be compatible
with the original Korn shell (which doesn't have this option, but does
send the \fBHUP\fP signal).
T}
	nolog	T{
No effect \- in the original Korn shell, this prevents function definitions
from being stored in the history file.
T}
	physical	T{
Causes the \fBcd\fP and \fBpwd\fP commands to use `physical'
(\fIi.e.\fP, the filesystem's) \fB..\fP directories instead of `logical'
directories (\fIi.e.\fP,  the shell handles \fB..\fP, which allows the user
to be obliveous of symlink links to directories).
Clear by default.  Note that setting
this option does not effect the current value of the \fBPWD\fP parameter;
only the \fBcd\fP command changes \fBPWD\fP.
See the \fBcd\fP and \fBpwd\fP commands above for more details.
T}
	posix	T{
Enable posix mode.  See POSIX Mode above.
T}
	vi	T{
Enable vi-like command line editing (interactive shells only).
T}
	viraw	T{
No effect \- in the original Korn shell, unless viraw was set, the vi command
line mode would let the tty driver do the work until ESC (^[) was entered.
pdksh is always in viraw mode.
T}
	vi-esccomplete	T{
In vi command line editing, do command / file name completion when
escape (^[) is entered in command mode.
T}
	vi-show8	T{
Prefix characters with the eighth bit set with `M-'.
If this option is not set, characters in the range
128-160 are printed as is, which may cause problems.
T}
	vi-tabcomplete	T{
In vi command line editing, do command / file name completion when
tab (^I) is entered in insert mode.
T}
.TE
.sp
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 \fB\-\fP.
\fBset -o\fP with no option name will list all the options and whether each
is on or off; \fBset +o\fP will print the long names of all options that
are currently on.
.sp
Remaining arguments, if any, are positional parameters and are assigned,
in order, to the
positional parameters (\fIi.e.\fP, \fB1\fP, \fB2\fP, \fIetc.\fP).
If options are ended with \fB\-\-\fP and there are no remaining arguments,
all positional parameters are cleared.
If no options or arguments are given, then the values of all names are printed.
For unknown historical reasons, a lone \fB\-\fP option is treated specially:
it clears both the \fB\-x\fP and \fB\-v\fP options.
.\"}}}
.\"{{{  shift [number]
.IP "\fBshift\fP [\fInumber\fP]"
The positional parameters \fInumber\fP+1, \fInumber\fP+2 \fIetc.\fP\& are
renamed to \fB1\fP, \fB2\fP, \fIetc.\fP
\fInumber\fP defaults to 1.
.\"}}}
.\"{{{  test expression, [ expression ]
.IP "\fBtest\fP \fIexpression\fP"
.IP "\fB[\fP \fIexpression\fP \fB]\fP"
\fBtest\fP evaluates the \fIexpression\fP and returns zero status if
true, and 1 status if false and greater than 1 if there was an error.
It is normally used as the
condition command of \fBif\fP and \fBwhile\fP statements.
The following basic expressions are available:
.sp
.TS
afB ltw(2.8i).
\fIstr\fP	T{
\fIstr\fP has non-zero length.  Note that there is the potential
for problems if \fIstr\fP turns out to be an operator (\fIe.g.\fP, \fB-r\fP)
- it is generally better to use a test like
.RS
\fB[ X"\fP\fIstr\fP\fB" != X ]\fP
.RE
instead (double quotes are used in case \fIstr\fP contains spaces or file
globing characters).
T}
\-r \fIfile\fP	T{
\fIfile\fP exists and is readable
T}
\-w \fIfile\fP	T{
\fIfile\fP exists and is writable
T}
\-x \fIfile\fP	T{
\fIfile\fP exists and is executable
T}
\-a \fIfile\fP	T{
\fIfile\fP exists
T}
\-e \fIfile\fP	T{
\fIfile\fP exists
T}
\-f \fIfile\fP	T{
\fIfile\fP is a regular file
T}
\-d \fIfile\fP	T{
\fIfile\fP is a directory
T}
\-c \fIfile\fP	T{
\fIfile\fP is a character special device
T}
\-b \fIfile\fP	T{
\fIfile\fP is a block special device
T}
\-p \fIfile\fP	T{
\fIfile\fP is a named pipe
T}
\-u \fIfile\fP	T{
\fIfile\fP's mode has setuid bit set
T}
\-g \fIfile\fP	T{
\fIfile\fP's mode has setgid bit set
T}
\-k \fIfile\fP	T{
\fIfile\fP's mode has sticky bit set
T}
\-s \fIfile\fP	T{
\fIfile\fP is not empty
T}
\-O \fIfile\fP	T{
\fIfile\fP's owner is the shell's effective user-ID
T}
\-G \fIfile\fP	T{
\fIfile\fP's group is the shell's effective group-ID
T}
\-h \fIfile\fP	T{
\fIfile\fP is a symbolic link
T}
\-H \fIfile\fP	T{
\fIfile\fP is a context dependent directory (only useful on HP-UX)
T}
\-L \fIfile\fP	T{
\fIfile\fP is a symbolic link
T}
\-S \fIfile\fP	T{
\fIfile\fP is a socket
T}
\-o \fIoption\fP	T{
shell \fIoption\fP is set (see \fBset\fP command above for list of options).
As a non-standard extension, if the option starts with a \fB!\fP, the test
is negated; the test always fails if option doesn't exist (thus
.RS
\fB[ -o \fP\fIfoo\fP \fB-o -o !\fP\fIfoo\fP \fB]\fP
.RE
returns true if and only if option \fIfoo\fP exists).
T}
\fIfile\fP \-nt \fIfile\fP	T{
first \fIfile\fP is newer than second \fIfile\fP
T}
\fIfile\fP \-ot \fIfile\fP	T{
first \fIfile\fP is older than second \fIfile\fP
T}
\fIfile\fP \-ef \fIfile\fP	T{
first \fIfile\fP is the same file as second \fIfile\fP
T}
\-t\ [\fIfd\fP]	T{
file descriptor is a tty device.
If the posix option (\fBset \-o posix\fP, see POSIX Mode above) is not
set, \fIfd\fP may be left out, in which case it is taken to be 1
(the behaviour differs due to the special POSIX rules described below).
T}
\fIstring\fP	T{
\fIstring\fP is not empty
T}
\-z\ \fIstring\fP	T{
\fIstring\fP is empty
T}
\-n\ \fIstring\fP	T{
\fIstring\fP is not empty
T}
\fIstring\fP\ =\ \fIstring\fP	T{
strings are equal
T}
\fIstring\fP\ !=\ \fIstring\fP	T{
strings are not equal
T}
\fInumber\fP\ \-eq\ \fInumber\fP	T{
numbers compare equal
T}
\fInumber\fP\ \-ne\ \fInumber\fP	T{
numbers compare not equal
T}
\fInumber\fP\ \-ge\ \fInumber\fP	T{
numbers compare greater than or equal
T}
\fInumber\fP\ \-gt\ \fInumber\fP	T{
numbers compare greater than
T}
\fInumber\fP\ \-le\ \fInumber\fP	T{
numbers compare less than or equal
T}
\fInumber\fP\ \-lt\ \fInumber\fP	T{
numbers compare less than
T}
.TE
.sp
The above basic expressions, in which unary operators have precedence over
binary operators, may be combined with the following operators
(listed in increasing order of precedence):
.sp
.TS
afB l.
\fIexpr\fP \-o \fIexpr\fP	logical or
\fIexpr\fP \-a \fIexpr\fP	logical and
! \fIexpr\fP	logical not
( \fIexpr\fP )	grouping
.TE
.sp
On operating systems not supporting \fB/dev/fd/\fP\fIn\fP devices
(where \fIn\fP is a file descriptor number),
the \fBtest\fP command will attempt to fake it for all tests that
operate on files (except the \fB-e\fP test).
I.e., \fB[ -w /dev/fd/2 ]\fP tests if file descriptor 2 is writable.
.sp
Note that some special rules are applied (courtesy of POSIX) if the
number of arguments to \fBtest\fP or \fB[\fP \&... \fB]\fP is less than
five: if leading \fB!\fP arguments can be stripped such that only one
argument remains then a string length test is performed (again, even if
the argument is a unary operator);
if leading \fB!\fP arguments can be stripped such that three
arguments remain and the second argument is a binary operator, then the
binary operation is performed (even if first argument is a unary
operator, including an unstripped \fB!\fP).
.sp
\fBNote:\fP A common mistake is to use \fBif [ $foo = bar ]\fP which
fails if parameter \fBfoo\fP is null or unset, if it has embedded spaces
(\fIi.e.\fP, \fBIFS\fP characters), or if it is a unary operator like \fB!\fP or
\fB\-n\fP.  Use tests like \fBif [ "X$foo" = Xbar ]\fP instead.
.\"}}}
.\"{{{  times
.IP \fBtimes\fP
Print the accumulated user and system times used by the shell and by
processes which have exited that the shell started.
.\"}}}
.\"{{{  trap [handler signal ...]
.IP "\fBtrap\fP [\fIhandler\fP \fIsignal ...\fP]"
Sets trap handler that is to be executed when any of the specified signals
are received.
\fBHandler\fP is either a null string, indicating the signals are to
be ignored, a minus (\fB\-\fP), indicating that the default action is to
be taken for the signals (see signal(2 or 3)), or a string containing shell
commands to be evaluated and executed at the first opportunity (\fIi.e.\fP,
when the current command completes, or before printing the next \fBPS1\fP
prompt) after receipt of one of the signals.
\fBSignal\fP is the name of a signal (\fIe.g.\fP, PIPE or ALRM) or the number
of the signal (see \fBkill \-l\fP command above).
There are two special signals: \fBEXIT\fP (also known as \fB0\fP), which
is executed when the shell is about to exit, and \fBERR\fP which is
executed after an error occurs (an error is something that would cause
the shell to exit if the \fB\-e\fP or \fBerrexit\fP option were set \(em
see \fBset\fP command above).
\fBEXIT\fP 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.
.sp
With no arguments, \fBtrap\fP lists, as a series of \fBtrap\fP commands,
the current state of the traps that have been set since the shell started.
.sp
.\" todo: add these features (trap DEBUG, trap ERR/EXIT in function)
The original Korn shell's \fBDEBUG\fP trap and the handling of \fBERR\fP and
\fBEXIT\fP traps in functions are not yet implemented.
.\"}}}
.\"{{{  true
.IP \fBtrue\fP
A command that exits with a zero value.
.\"}}}
.\"{{{  typeset [[+-Ulprtux] [-L[n]] [-R[n]] [-Z[n]] [-i[n]] | -f [-tux]] [name[=value] ...]
.IP "\fBtypeset\fP [[\(+-Ulprtux] [\fB\-L\fP[\fIn\fP]] [\fB\-R\fP[\fIn\fP]] [\fB\-Z\fP[\fIn\fP]] [\fB\-i\fP[\fIn\fP]] | \fB\-f\fP [\fB\-tux\fP]] [\fIname\fP[\fB=\fP\fIvalue\fP] ...]"
Display or set parameter attributes.
With no \fIname\fP arguments, parameter attributes are displayed: if no options
arg used, the current attributes of all parameters are printed as typeset
commands; if an option is given (or \fB\-\fP with no option letter)
all parameters and their values with the specified attributes are printed;
if options are introduced with \fB+\fP, parameter values are not printed.
.sp
If \fIname\fP arguments are given, the attributes of the named parameters
are set (\fB\-\fP) or cleared (\fB+\fP).
Values for parameters may optionally be specified.
If typeset is used inside a function, any newly created parameters are local
to the function.
.sp
When \fB\-f\fP is used, typeset operates on the attributes of functions.
As with parameters, if no \fIname\fPs are given, functions are listed
with their values (\fIi.e.\fP, definitions) unless options are introduced with
\fB+\fP, in which case only the function names are reported.
.sp
.TS
expand;
afB lw(4.5i).
\-L\fIn\fP	T{
Left justify attribute: \fIn\fP specifies the field width.
If \fIn\fP is not specified, the current width of a parameter (or the
width of its first assigned value) is used.
Leading white space (and zeros, if used with the \fB\-Z\fP option) is stripped.
If necessary, values are either truncated or space padded to fit the
field width.
T}
\-R\fIn\fP	T{
Right justify attribute: \fIn\fP specifies the field width.
If \fIn\fP is not specified, the current width of a parameter (or the
width of its first assigned value) is used.
Trailing white space are stripped.
If necessary, values are either stripped of leading characters
or space padded to make them fit the field width.
T}
\-Z\fIn\fP	T{
Zero fill attribute: if not combined with \fB\-L\fP, this is the
same as \fB\-R\fP, except zero padding is used instead of space padding.
T}
\-i\fIn\fP	T{
integer attribute:
\fIn\fP specifies the base to use when displaying the integer
(if not specified, the base given in the first assignment is used).
Parameters with this attribute may be assigned values containing
arithmetic expressions.
T}
\-U	T{
unsigned integer attribute: integers are printed as unsigned values
(only useful when combined with the \fB\-i\fP option).
This option is not in the original Korn shell.
T}
\-f	T{
Function mode: display or set functions and their attributes, instead of
parameters.
T}
\-l	T{
Lower case attribute: all  upper case characters in values are converted to
lower case.
(In the original Korn shell, this parameter meant `long integer' when used
with the \fB\-i\fP option).
T}
\-p	T{
Print complete typeset commands that can be used to re-create the
attributes (but not the values) of parameters.
This is the default action (option exists for ksh93 compatability).
T}
\-r	T{
Readonly attribute: parameters with the this attribute may not be assigned to
or unset.
Once this attribute is set, it can not be turned off.
T}
\-t	T{
Tag attribute: has no meaning to the shell; provided for application use.
.sp
For functions, \fB\-t\fP is the trace attribute.
When functions with the trace attribute are executed, the \fBxtrace\fP (\fB\-x\fP) shell option is temporarily turned on.
T}
\-u	T{
Upper case attribute: all lower case characters in values are converted to
upper case.
(In the original Korn shell, this parameter meant `unsigned integer' when used
with the \fB\-i\fP option, which meant upper case letters would never be used
for bases greater than 10.  See the \fB\-U\fP option).
.sp
For functions, \fB\-u\fP is the undefined attribute.  See Functions above
for the implications of this.
T}
\-x	T{
Export attribute: parameters (or functions) are placed in the environment of
any executed commands.  Exported functions are not implemented yet.
T}
.TE
.\"}}}
.\"{{{  ulimit [-acdfHlmnpsStvw] [value]
.IP "\fBulimit\fP [\fB\-acdfHlmnpsStvw\fP] [\fIvalue\fP]"
Display or set process limits.
If no options are used, the file size limit (\fB\-f\fP) is assumed.
\fBvalue\fP, if specified, may be either be an arithmetic expression or the
word \fBunlimited\fP.
The limits affect the shell and any processes created by the shell after
a limit is imposed.
Note that some systems may not allow limits to be increased once they
are set.
Also note that the types of limits available are system dependent \- some
systems have only the \fB\-f\fP limit.
.RS
.IP \fB\-a\fP
Displays all limits; unless \fB\-H\fP is used, soft limits are displayed.
.IP \fB\-H\fP
Set the hard limit only (default is to set both hard and soft limits).
.IP \fB\-S\fP
Set the soft limit only (default is to set both hard and soft limits).
.IP \fB\-c\fP
Impose a size limit of \fIn\fP blocks on the size of core dumps.
.IP \fB\-d\fP
Impose a size limit of \fIn\fP kbytes on the size of the data area.
.IP \fB\-f\fP
Impose a size limit of \fIn\fP blocks on files written by the shell and
its child processes (files of any size may be read).
.IP \fB\-l\fP
Impose a limit of \fIn\fP kbytes on the amount of locked (wired) physical
memory.
.IP \fB\-m\fP
Impose a limit of \fIn\fP kbytes on the amount of physical memory used.
.IP \fB\-n\fP
Impose a limit of \fIn\fP file descriptors that can be open at once.
.IP \fB\-p\fP
Impose a limit of \fIn\fP processes that can be run by the user at any one
time.
.IP \fB\-s\fP
Impose a size limit of \fIn\fP kbytes on the size of the stack area.
.IP \fB\-t\fP
Impose a time limit of \fIn\fP cpu seconds to be used by each process.
.IP \fB\-v\fP
Impose a limit of \fIn\fP kbytes on the amount of virtual memory used;
on some systems this is the maximum allowable virtual address (in bytes,
not kbytes).
.IP \fB\-w\fP
Impose a limit of \fIn\fP kbytes on the amount of swap space used.
.PP
As far as \fBulimit\fP is concerned, a block is 512 bytes.
.RE
.\"}}}
.\"{{{  umask [-S] [mask]
.IP "\fBumask\fP [\fB\-S\fP] [\fImask\fP]"
.RS
Display or set the file permission creation mask, or umask (see \fIumask\fP(2)).
If the \fB\-S\fP option is used, the mask displayed or set is symbolic,
otherwise it is an octal number.
.sp
Symbolic masks are like those used by \fIchmod\fP(1):
.RS
[\fBugoa\fP]{{\fB=+-\fP}{\fBrwx\fP}*}+[\fB,\fP...]
.RE
in which the first group of characters is the \fIwho\fP part, the second
group is the \fIop\fP part, and the last group is the \fIperm\fP part.
The \fIwho\fP part specifies which part of the umask is to be modified.
The letters mean:
.RS
.IP \fBu\fP
the user permissions
.IP \fBg\fP
the group permissions
.IP \fBo\fP
the other permissions (non-user, non-group)
.IP \fBa\fP
all permissions (user, group and other)
.RE
.sp
The \fIop\fP part indicates how the \fIwho\fP permissions are to be modified:
.RS
.IP \fB=\fP
set
.IP \fB+\fP
added to
.IP \fB\-\fP
removed from
.RE
.sp
The \fIperm\fP part specifies which permissions are to be set, added or removed:
.RS
.IP \fBr\fP
read permission
.IP \fBw\fP
write permission
.IP \fBx\fP
execute permission
.RE
.sp
When symbolic masks are used, they describe what permissions may
be made available (as opposed to octal masks in which a set bit means
the corresponding bit is to be cleared).
Example: `ug=rwx,o=' sets the mask so files will not be readable, writable
or executable by `others', and is equivalent (on most systems) to the octal
mask `07'.
.RE
.\"}}}
.\"{{{  unalias [-adt] name ...
.IP "\fBunalias\fP [\fB\-adt\fP] [\fIname1\fP ...]"
The aliases for the given names are removed.
If the \fB\-a\fP option is used, all aliases are removed.
If the \fB\-t\fP or \fB\-d\fP options are used, the indicated operations
are carried out on tracked or directory aliases, respectively.
.\"}}}
.\"{{{  unset [-fv] parameter ...
.IP "\fBunset\fP [\fB\-fv\fP] \fIparameter\fP ..."
Unset the named parameters (\fB\-v\fP, the default) or functions (\fB\-f\fP).
The exit status is non-zero if any of the parameters were already unset,
zero otherwise.
.\"}}}
.\"{{{  wait [job]
.IP "\fBwait\fP [\fIjob\fP]"
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 \fBkill \-l\fP \fIexit-status\fP 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 \fIjob\fP.
\fBWait\fP will return if a signal for which a trap has been set is received,
or if a HUP, INT or QUIT signal is received.
.sp
If no jobs are specified, \fBwait\fP waits for all currently running jobs
(if any) to finish and exits with a zero status.
If job monitoring is enabled, the completion status of jobs is
printed (this is not the case when jobs are explicitly specified).
.\"}}}
.\"{{{  whence [-pv] [name ...]
.IP "\fBwhence\fP [\fB\-pv\fP] [name ...]"
For each name, the type of command is listed (reserved word, built-in, alias,
function, tracked alias or executable).
If the \fB\-p\fP option is used, a path search done even if \fIname\fP
is a reserved word, alias, \fIetc.\fP
Without the \fB\-v\fP option, \fBwhence\fP is similar to \fBcommand \-v\fP
except that \fBwhence\fP will find reserved words and won't print aliases
as alias commands;
with the \fB\-v\fP option, \fBwhence\fP is the same as \fBcommand \-V\fP.
Note that for \fBwhence\fP, the \fB\-p\fP option does not affect the search
path used, as it does for \fBcommand\fP.
If the type of one or more of the names could not be determined, the
exit status is non-zero.
.\"}}}
.\"}}}
.\"{{{  job control (and its built-in commands)
.SS "Job Control"
Job control refers to the shell's ability to monitor and control \fBjobs\fP,
which are processes or groups of processes created for commands or pipelines.
At a minimum, the shell keeps track of the status of the background
(\fIi.e.\fP, asynchronous) jobs that currently exist; this information can be
displayed using the \fBjobs\fP command.
If job control is fully enabled (using \fBset \-m\fP or
\fBset \-o monitor\fP), 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 \fBfg\fP and \fBbg\fP commands, respectively,
and the state of the terminal is saved or restored when a foreground
job is stopped or restarted, respectively.
.sp
Note that only commands that create processes (\fIe.g.\fP,
asynchronous commands, subshell commands, and non-built-in,
non-function commands) can be stopped; commands like \fBread\fP cannot be.
.sp
When a job is created, it is assigned a job-number.
For interactive shells, this number is printed inside \fB[\fP..\fB]\fP,
followed by the process-ids of the processes in the job when an asynchronous
command is run.
A job may be referred to in \fBbg\fP, \fBfg\fP, \fBjobs\fP, \fBkill\fP and
\fBwait\fP commands either by the process id of the last process in the
command pipeline (as stored in the \fB$!\fP parameter) or by prefixing the
job-number with a percent sign (\fB%\fP).
Other percent sequences can also be used to refer to jobs:
.sp
.TS
expand;
afB lw(4.5i).
%+	T{
The most recently stopped job, or, if there are no stopped jobs, the oldest
running job.
T}
%%\fR, \fP%	T{
Same as \fB%+\fP.
T}
%\-	T{
The job that would be the \fB%+\fP job, if the later did not exist.
T}
%\fIn\fP	T{
The job with job-number \fIn\fP.
T}
%?\fIstring\fP	T{
The job containing the string \fIstring\fP (an error occurs if multiple jobs
are matched).
T}
%\fIstring\fP	T{
The job starting with string \fIstring\fP (an error occurs if multiple jobs
are matched).
T}
.TE
.sp
When a job changes state (\fIe.g.\fP, a background job finishes or foreground
job is stopped), the shell prints the following status information:
.RS
\fB[\fP\fInumber\fP\fB]\fP \fIflag status command\fP
.RE
where
.IP "\ \fInumber\fP"
is the job-number of the job.
.IP "\ \fIflag\fP"
is \fB+\fP or \fB-\fP if the job is the \fB%+\fP or \fB%-\fP job,
respectively, or space if it is neither.
.IP "\ \fIstatus\fP"
indicates the current state of the job and can be
.RS
.IP "\fBRunning\fP"
the job has neither stopped or exited (note that running does not
necessarily mean consuming CPU time \(em the process could be blocked waiting
for some event).
.IP "\fBDone\fP [\fB(\fP\fInumber\fP\fB)\fP]"
the job exited. \fInumber\fP is the exit status of the job, which is
omitted if the status is zero.
.IP "\fBStopped\fP [\fB(\fP\fIsignal\fP\fB)\fP]"
the job was stopped by the indicated \fIsignal\fP (if no signal is given,
the job was stopped by SIGTSTP).
.IP "\fIsignal-description\fP [\fB(core dumped)\fP]"
the job was killed by a signal (\fIe.g.\fP, Memory\ fault,
Hangup, \fIetc.\fP \(em use
\fBkill \-l\fP for a list of signal descriptions).
The \fB(core\ dumped)\fP message indicates the process created a core file.
.RE
.IP "\ \fIcommand\fP"
is the command that created the process.
If there are multiple processes in the job, then each process will
have a line showing its \fIcommand\fP and possibly its \fIstatus\fP,
if it is different from the status of the previous process.
.PP
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 \fBHUP\fP signal and the shell exits.
Similarly, if the \fBnohup\fP 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 \fBHUP\fP signal and the shell exits.
.\"}}}
.\"{{{  Emacs Interactive Input Line Editing
.\"}}}
.\"{{{  Vi Interactive Input Line Editing
.\"}}}
.\"}}}
.\"{{{  Files
.SH FILES
~/.profile
.br
/etc/profile
.br
/etc/suid_profile
.\"}}}
.\"{{{  Notes
.SH NOTES
Sh is implemented as a runtime option of pdksh, with only those ksh features
whose syntax or semantics are incompatible with a traditional Bourne
shell disabled.  Since this leaves some ksh extensions exposed, caution
should be used where backwards compatibility with traditional Bourne or
POSIX compliant shells is an issue.
.\"}}}
.\"{{{  Bugs
.SH BUGS
Any bugs in pdksh should be reported to pdksh@cs.mun.ca.  Please
include the version of pdksh (echo $KSH_VERSION shows it), the machine,
operating system and compiler you are using and a description of how to
repeat the bug (a small shell script that demonstrates the bug is
best).  The following, if relevant (if you are not sure, include them),
can also helpful: options you are using (both options.h options and set
\-o options) and a copy of your config.h (the file generated by the
configure script).  New versions of pdksh can be obtained from
ftp.cs.mun.ca:pub/pdksh/.
.\"}}}
.\"{{{  Authors
.SH AUTHORS
This shell is based on the public domain 7th edition Bourne shell clone by
Charles Forsyth and parts of the BRL shell by Doug A.\& Gwyn, Doug Kingston,
Ron Natalie, Arnold Robbins, Lou Salkind and others.  The first release
of pdksh was created by Eric Gisin, and it was subsequently maintained by
John R.\& MacMillan (chance!john@sq.sq.com), and
Simon J.\& Gerraty (sjg@zen.void.oz.au).  The current maintainer is
Michael Rendell (michael@cs.mun.ca).
The CONTRIBUTORS file in the source distribution contains a more complete
list of people and their part in the shell's development.
.\"}}}
.\"{{{  See also
.SH "SEE ALSO"
awk(1), 
ksh(1),
csh(1), ed(1), getconf(1), getopt(1), sed(1), stty(1), vi(1),
dup(2), execve(2), getgid(2), getuid(2), open(2), pipe(2), wait(2),
getopt(3), rand(3), signal(3), system(3),
environ(5)
.PP
.IR "The KornShell Command and Programming Language" ,
Morris Bolsky and David Korn, 1989, ISBN 0-13-516972-0.
.PP
.\" XXX ISBN missing
.IR "UNIX Shell Programming" ,
Stephen G.\& Kochan, Patrick H.\& Wood, Hayden.
.PP
.IR "IEEE Standard for information Technology \- Portable Operating System Interface (POSIX) \- Part 2: Shell and Utilities" ,
IEEE Inc, 1993, ISBN 1-55937-255-9.
.\"}}}