path: root/usr/src/man/man1/ksh93.1

'\" te
.\" Copyright (c) 1982-2007 AT&T Knowledge Ventures
.\" To view license terms, see http://www.opensource.org/licenses/cpl1.0.txt
.\" Portions Copyright (c) 2009, Sun Microsystems, Inc.
.TH KSH93 1 "Sep 10, 2013"
.SH NAME
ksh93, rksh93 \- Korn Shell, a standard and restricted command and programming
language
.SH SYNOPSIS
.LP
.nf
\fBksh93\fR [\fB\(+-abcefhikmnoprstuvxBCD\fR] [\fB-R\fR \fIfile\fR] [ \fB\(+-o\fR \fIoption\fR] ...
       [-] [\fIarg\fR ...]
.fi

.LP
.nf
\fBrksh93\fR [\fB\(+-abcefhikmnoprstuvxBCD\fR] [\fB-R\fR \fIfile\fR] [\fB\(+-o\fR \fIoption\fR] ...
       [-] [\fIarg\fR ...]
.fi

.SH DESCRIPTION
.sp
.LP
\fBksh93\fR is a command and programming language that executes commands read
from a terminal or a file. \fBrksh93\fR is a restricted version of the command
interpreter \fBksh93\fR. \fBrksh93\fR is used to set up login names and
execution environments whose capabilities are more controlled than those of the
standard shell.
.sp
.LP
See \fBInvocation\fR for the meaning of arguments to the shell.
.SS "Definitions"
.sp
.LP
A \fImetacharacter\fR is defined as one of the following characters:
.sp
.in +2
.nf
; & ( ) | < > NEWLINE SPACE TAB
.fi
.in -2
.sp

.sp
.LP
A \fIblank\fR is a \fBTAB\fR or a \fBSPACE\fR.
.sp
.LP
An \fIidentifier\fR is a sequence of letters, digits, or underscores starting
with a letter or underscore. Identifiers are used as components of \fIvariable
names\fR.
.sp
.LP
A \fIvname\fR is a sequence of one or more identifiers separated by a period
(\fB\&.\fR) and optionally preceded by a period (\fB\&.\fR). \fIvnames\fR are
used as function and variable names.
.sp
.LP
A \fIword\fR is a sequence of \fIcharacters\fR from the character set defined
by the current locale, excluding non-quoted \fImetacharacters\fR.
.sp
.LP
A \fIcommand\fR is a sequence of characters in the syntax of the shell
language. The shell reads each command and carries out the desired action
either directly or by invoking separate utilities. A built-in command is a
command that is carried out by the shell itself without creating a separate
process. Some commands are built-in purely for convenience and are not
documented in this manual page. Built-ins that cause side effects in the shell
environment and built-ins that are found before performing a path search (see
\fBExecution\fR) are documented in this manual page. For historical reasons,
some of these built-ins behave differently than other built-ins and are called
special built-ins.
.SS "Commands"
.sp
.LP
A \fIsimple-command\fR is a list of variable assignments (see \fBVariable
Assignments\fR) or a sequence of \fIblank\fR-separated words which can be
preceded by a list of variable assignments. See the \fBEnvironment\fR section
of this manual page.
.sp
.LP
The first word specifies the name of the command to be executed. Except as
specified in this section, the remaining words are passed as arguments to the
invoked command. The command name is passed as argument 0. See \fBexec\fR(2).
The \fIvalue\fR of a simple-command is its exit status. If it terminates
normally, its value is \fB0\fR-\fB255\fR. If it terminates abnormally, its
value is \fB256+\fR\fIsignum\fR. The name of the signal corresponding to the
exit status can be obtained by way of the \fB-l\fR option of the kill built-in
utility.
.sp
.LP
A \fIpipeline\fR is a sequence of one or more commands separated by \fB|\fR.
The standard output of each command but the last is connected by a
\fBpipe\fR(2) to the standard input of the next command. Each command, except
possibly the last, is run as a separate process. The shell waits for the last
command to terminate. The exit status of a pipeline is the exit status of the
last command unless the \fBpipefail\fR option is enabled. Each pipeline can be
preceded by the reserved word\fB!\fR. This causes the exit status of the
pipeline to become \fB0\fR if the exit status of the last command is
\fBnon-zero\fR, and \fB1\fR if the exit status of the last command is \fB0\fR.
.sp
.LP
A \fIlist\fR is a sequence of one or more pipelines separated by \fB;, &, |&,
&&, or |\fR, and optionally terminated by \fB;, &,\fR or \fB|&\fR. Of these
five symbols, \fB;, &\fR, and \fB|&\fR have equal precedence, which is lower
than that of \fB&&\fR and \fB||\fR. The symbols \fB&&\fR and \fB||\fR also have
equal precedence.
.sp
.LP
A semicolon (\fB;\fR) causes sequential execution of the preceding pipeline. An
ampersand (\fB&\fR) causes asynchronous execution of the preceding pipeline,
that is, the shell does \fInot\fR wait for that pipeline to finish. The symbol
\fB|&\fR causes asynchronous execution of the preceding pipeline with a two-way
pipe established to the parent shell. The standard input and output of the
spawned pipeline can be written to and read from by the parent shell by
applying the redirection operators \fB<&\fR and \fB>&\fR with \fBarg p\fR to
commands and by using \fB-p\fR option of the built-in commands \fBread\fR and
\fBprint\fR. The symbol \fB&&\fR (\fB||\fR) causes the \fIlist\fR following it
to be executed only if the preceding pipeline returns a zero (\fBnon-zero\fR)
value. One or more NEWLINEs can appear in a \fIlist\fR instead of a semicolon,
to delimit a command. The first \fIitem\fR of the first \fIpipeline\fR of a
\fIlist\fR that is a simple command not beginning with a redirection, and not
occurring within a \fBwhile\fR, \fBuntil\fR, or \fBif\fR \fIlist\fR , can be
preceded by a semicolon. This semicolon is ignored unless the \fBshowme\fR
option is enabled as described with the \fBset\fR built-in.
.sp
.LP
A \fIcommand\fR is either a simple-command or one of commands in the following
list. Unless otherwise stated, the value returned by a command is that of the
last simple-command executed in the command.
.sp
.ne 2
.na
\fB\fBfor\fR \fIvname\fR \fB[ in\fR \fIword\fR \fB\&... ] ;do\fR \fIlist\fR
\fB;done\fR\fR
.ad
.sp .6
.RS 4n
Each time a \fBfor\fR command is executed, \fIvname\fR is set to the next
\fIword\fR taken from the \fBin\fR \fIword\fR list. If \fBin\fR \fIword ...\fR
is omitted, the \fBfor\fR command executes the \fBdo\fR \fIlist\fR once for
each positional parameter that is set starting from 1. Execution ends when
there are no more words in the list. See \fBParameter Expansion\fR.
.RE

.sp
.ne 2
.na
\fB\fB(( [\fR\fIexpr1\fR\fB] ; [\fR\fIexpr2\fR] ; [\fIexpr3\fR\fB] )) ;do\fR
\fIlist\fR \fB;done\fR\fR
.ad
.sp .6
.RS 4n
The arithmetic expression \fIexpr1\fR is evaluated first. The arithmetic
expression \fIexpr2\fR is repeatedly evaluated until it evaluates to \fBzero\fR
and when \fBnon-zero\fR, \fIlist\fR is executed and the arithmetic expression
\fIexpr3\fR evaluated. If any expression is omitted, then it behaves as if it
evaluated to \fB1\fR. See \fBArithmetic Evaluation\fR.
.RE

.sp
.ne 2
.na
\fB\fBselect\fR \fIvname\fR [ in \fIword\fR \fB\&... ] ;do\fR \fIlist\fR
\fB;done\fR\fR
.ad
.sp .6
.RS 4n
A \fBselect\fR command prints on standard error (file descriptor 2) the set of
\fIwords\fR, each preceded by a number. If \fBin\fR \fIword...\fR is omitted,
the positional parameters starting from \fB1\fR are used instead. See
\fBParameter Expansion\fR. The \fBPS3\fR prompt is printed and a line is read
from the standard input. If this line consists of the number of one of the
listed \fIword\fRs, then the value of the variable \fIvname\fR is set to the
\fIword\fR corresponding to this number. If this line is empty, the selection
list is printed again. Otherwise the value of the variable \fIvname\fR is set
to \fBnull\fR. The contents of the line read from standard input is saved in
the variable \fBREPLY\fR. The \fIlist\fR is executed for each selection until a
break or \fBEOF\fR is encountered. If the \fBREPLY\fR variable is set to
\fBnull\fR by the execution of \fIlist\fR, the selection list is printed before
displaying the \fBPS3\fR prompt for the next selection.
.RE

.sp
.ne 2
.na
\fB\fBcase\fR \fIword\fR \fBin [ [(]\fR \fIpattern\fR \fB[ |\fR \fIpattern\fR
\fB] ... )\fR \fIlist\fR \fB;; ] ... esac\fR\fR
.ad
.sp .6
.RS 4n
A \fBcase\fR command executes the \fIlist\fR associated with the first
\fIpattern\fR that matches \fIword\fR. The form of the patterns is the same as
that used for file name generation. See \fBFile Name Generation\fR.
.sp
The \fB;;\fR operator causes execution of \fBcase\fR to terminate. If \fB;&\fR
is used in place of \fB;;\fR the next subsequent list, if any, is executed.
.RE

.sp
.ne 2
.na
\fB\fBif\fR \fIlist\fR \fB;then\fR \fIlist\fR \fB[ ;elif\fR \fIlist\fR
\fB;then\fR \fIlist\fR ] \fB\&... [ ;else\fR \fIlist\fR \fB]\fR \fB;fi\fR\fR
.ad
.sp .6
.RS 4n
The \fIlist\fR following \fBif\fR is executed and, if it returns a \fBzero\fR
exit status, the \fIlist\fR following the first \fBthen\fR is executed.
Otherwise, the \fIlist\fR following \fBelif\fR is executed, and, if its value
is \fBzero\fR, the \fIlist\fR following the next \fBthen\fR is executed.
Failing each successive \fBelif\fR \fIlist\fR, the \fBelse\fR \fIlist\fR is
executed. If the \fBif\fR \fIlist\fR has \fBnon-zero\fR exit status and there
is no \fBelse\fR \fIlist\fR, then the \fBif\fR command returns a \fBzero\fR
exit status.
.RE

.sp
.ne 2
.na
\fB\fBwhile\fR \fIlist\fR \fB;do\fR \fIlist\fR \fB;done\fR\fR
.ad
.br
.na
\fBuntil \fIlist\fR \fB;do\fR \fIlist\fR \fB;done\fR\fR
.ad
.sp .6
.RS 4n
A \fBwhile\fR command repeatedly executes the while \fIlist\fR and, if the exit
status of the last command in the list is zero, executes the \fBdo\fR
\fIlist\fR, otherwise the loop terminates. If no commands in the \fBdo\fR
\fIlist\fR are executed, then the \fBwhile\fR command returns a \fBzero\fR exit
status, \fBuntil\fR can be used in place of \fBwhile\fR to negate the loop
termination test.
.RE

.sp
.ne 2
.na
\fB\fB((\fR\fIexpression\fR\fB))\fR\fR
.ad
.sp .6
.RS 4n
The \fIexpression\fR is evaluated using the rules for arithmetic evaluation
described in this manual page. If the value of the arithmetic expression is
\fBnon-zero\fR, the exit status is \fB0\fR. Otherwise the exit status is
\fB1\fR.
.RE

.sp
.ne 2
.na
\fB\fB(\fR\fIlist\fR\fB;)\fR\fR
.ad
.sp .6
.RS 4n
Execute list in a separate environment. If two adjacent open parentheses are
needed for nesting, a SPACE must be inserted to avoid evaluation as an
arithmetic command as described in this section.
.sp
\fIlist\fR is simply executed. Unlike the metacharacters, \fB(\fR and \fB)\fR,
\fB{\fR and \fB}\fR are \fIreserved words\fR and must occur at the beginning of
a line or after a \fB;\fR to be recognized.
.RE

.sp
.ne 2
.na
\fB\fB[[\fR \fIexpression\fR \fB]]\fR\fR
.ad
.sp .6
.RS 4n
Evaluates \fIexpression\fR and returns a \fBzero\fR exit status when
\fIexpression\fR is true. See \fBConditional Expressions\fR for a description
of \fIexpression\fR.
.RE

.sp
.ne 2
.na
\fB\fBfunction\fR \fIvarname\fR \fB{\fR \fIlist\fR \fB;}\fR\fR
.ad
.br
.na
\fB\fIvarname\fR \fB() {\fR \fIlist\fR \fB;}\fR\fR
.ad
.sp .6
.RS 4n
Define a function which is referenced by \fIvarname\fR. A function whose
\fIvarname\fR contains a \fB\&.\fR is called a discipline function and the
portion of the \fIvarname\fR preceding the last \fB\&.\fR must refer to an
existing variable.
.sp
The body of the function is the \fIlist\fR of commands between \fB{\fR and
\fB}\fR. A function defined with the function \fIvarname\fR syntax can also be
used as an argument to the \fB\&.\fR special built-in command to get the
equivalent behavior as if the \fIvarname\fR\fB()\fR syntax were used to define
it. See \fBFunctions\fR.
.RE

.sp
.ne 2
.na
\fB\fBtime [\fR \fIpipeline\fR \fB]\fR\fR
.ad
.sp .6
.RS 4n
If \fIpipeline\fR is omitted, the user and system time for the current shell
and completed child processes is printed on standard error. Otherwise,
\fIpipeline\fR is executed and the elapsed time as well as the user and system
time are printed on standard error. The \fBTIMEFORMAT\fR variable can be set to
a format string that specifies how the timing information should be displayed.
See \fBShell Variables\fR for a description of the \fBTIMEFORMAT\fR variable.
.RE

.sp
.LP
The following reserved words are recognized as reserved only when they are the
first word of a command and are not quoted:
.br
.in +2
\fBcase\fR
.in -2
.br
.in +2
\fBdo\fR
.in -2
.br
.in +2
\fBdone\fR
.in -2
.br
.in +2
\fBelse\fR
.in -2
.br
.in +2
\fBelif\fR
.in -2
.br
.in +2
\fBesac\fR
.in -2
.br
.in +2
\fBfor\fR
.in -2
.br
.in +2
\fBfi\fR
.in -2
.br
.in +2
\fBfunction\fR
.in -2
.br
.in +2
\fBif\fR
.in -2
.br
.in +2
\fBselect\fR
.in -2
.br
.in +2
\fBthen\fR
.in -2
.br
.in +2
\fBtime\fR
.in -2
.br
.in +2
\fBuntil\fR
.in -2
.br
.in +2
\fBwhile\fR
.in -2
.br
.in +2
\fB{ }\fR
.in -2
.br
.in +2
\fB[[ ]]\fR
.in -2
.br
.in +2
\fB!\fR
.in -2
.SS "Variable Assignments"
.sp
.LP
One or more variable assignments can start a simple command or can be arguments
to the \fBtypeset\fR, \fBexport\fR, or \fBreadonly\fR special built-in
commands. The syntax for an \fIassignment\fR is of the form:
.sp
.ne 2
.na
\fB\fIvarname\fR\fB=\fR\fIword\fR\fR
.ad
.br
.na
\fB\fIvarname\fR\fB[\fR\fIword\fR\fB]=\fR\fIword\fR\fR
.ad
.sp .6
.RS 4n
No space is permitted between \fIvarname\fR and the \fB=\fR or between \fB=\fR
and \fIword\fR.
.RE

.sp
.ne 2
.na
\fB\fIvarname\fR\fB=(\fR\fIassignlist\fR\fB)\fR\fR
.ad
.sp .6
.RS 4n
No space is permitted between \fIvarname\fR and the \fB=\fR. An
\fIassignlist\fR can be one of the following:
.sp
.ne 2
.na
\fB\fIword ...\fR\fR
.ad
.sp .6
.RS 4n
Indexed array assignment.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIword\fR\fB]=\fR\fIword ...\fR\fR
.ad
.sp .6
.RS 4n
Associative array assignment. If prefixed by \fBtypeset\fR \fB-a\fR, creates an
indexed array instead.
.RE

.sp
.ne 2
.na
\fB\fIassignment ...\fR\fR
.ad
.sp .6
.RS 4n
Compound variable assignment. This creates a compound variable \fIvarname\fR
with sub-variables of the form \fIvarname.name\fR, where \fIname\fR is the name
portion of assignment. The value of \fIvarname\fR contains all the assignment
elements. Additional assignments made to sub-variables of \fIvarname\fR are
also displayed as part of the value of \fIvarname\fR. If no \fIassignment\fRs
are specified, \fIvarname\fR is a compound variable allowing subsequence child
elements to be defined.
.RE

.sp
.ne 2
.na
\fB\fBtypeset [\fR\fIoptions\fR] \fIassignment\fR \fB\&...\fR\fR
.ad
.sp .6
.RS 4n
Nested variable assignment. Multiple assignments can be specified by separating
each of them with a \fB;\fR. The previous value is unset before the assignment.
.RE

In addition, a \fB+=\fR can be used in place of the \fB=\fR to signify adding
to or appending to the previous value. When \fB+=\fR is applied to an
arithmetic type, \fIword\fR is evaluated as an arithmetic expression and added
to the current value. When applied to a string variable, the value defined by
\fIword\fR is appended to the value. For compound assignments, the previous
value is not unset and the new values are appended to the current ones provided
that the types are compatible.
.RE

.SS "Comments"
.sp
.LP
A word beginning with \fB#\fR causes that word and all the following characters
up to a NEWLINE to be commented, or ignored.
.SS "Aliasing"
.sp
.LP
The first word of each command is replaced by the text of an alias if an alias
for this word has been defined. An alias name consists of any number of
characters excluding metacharacters, quoting characters, file expansion
characters, parameter expansion characters, command substitution characters,
and \fB=\fR. The replacement string can contain any valid shell script
including the metacharacters listed in the \fBCommands\fR section. The first
word of each command in the replaced text, other than any that are in the
process of being replaced, are tested for aliases. If the last character of the
alias value is a BLANK then the word following the alias is also checked for
alias substitution.
.sp
.LP
Aliases can be used to redefine built-in commands but cannot be used to
redefine the reserved words listed in the \fBCommands\fR section. Aliases can
be created and listed with the alias command and can be removed with the
\fBunalias\fR command.
.sp
.LP
Aliasing is performed when scripts are read, not while they are executed. For
an alias to take effect, the \fBalias\fR definition command has to be executed
before the command which references the alias is read. The following aliases
are compiled into the shell but can be unset or redefined:
.sp
.in +2
.nf
autoload='typeset -fu'
command='command '
fc=hist
float='typeset -lE'
functions='typeset -f'
hash='alias -t --'
history='hist -l'
integer='typeset -li'
nameref='typeset -n'
nohup='nohup '
r='hist -s'
redirect='command exec'
source='command .'
stop='kill -s STOP'
suspend='kill -s STOP $$'
times='{ { time;} 2>&1;}'
type='whence -v'
.fi
.in -2
.sp

.SS "Tilde Substitution"
.sp
.LP
After alias substitution is performed, each word is checked to see if it begins
with an unquoted tilde (\fB~\fR). For tilde substitution, \fIword\fR also
refers to the \fIword\fR portion of parameter expansion. See \fBParameter
Expansion\fR.
.sp
.LP
If it does, the word up to a \fB/\fR is checked to see if it matches a user
name in the password database. If a match is found, the \fB~\fR and the matched
login name are replaced by the login directory of the matched user. If no match
is found, the original text is left unchanged. A \fB~\fR by itself, or in front
of a \fB/\fR, is replaced by \fB$HOME\fR. A \fB~\fR followed by a \fB+\fR or
\fB-\fR is replaced by the value of \fB$PWD\fR and \fB$OLDPWD\fR respectively.
.sp
.LP
In addition, when expanding a \fIvariable assignment\fR, tilde substitution is
attempted when the value of the assignment begins with a \fB~\fR, and when a
\fB~\fR appears after a colon (\fB:\fR). The \fB:\fR also terminates a \fB~\fR
login name.
.SS "Command Substitution"
.sp
.LP
The standard output from a command enclosed in parentheses preceded by a dollar
sign (\fB$\fR) or a pair of grave accents (\fB``\fR) can be used as part or all
of a word. Trailing NEWLINEs are removed. In the second (obsolete) form, the
string between the quotes is processed for special quoting characters before
the command is executed. See \fBQuoting\fR.
.sp
.LP
The command substitution \fB$(cat file)\fR can be replaced by the equivalent
but faster \fB$(<file)\fR. The command substitution \fB$(\fR\fIn\fR\fB<#)\fR
expands to the current byte offset for file descriptor \fIn\fR.
.SS "Arithmetic Substitution"
.sp
.LP
An arithmetic expression enclosed in double parentheses preceded by a dollar
sign ( \fB$((\fR\fIarithmetic_expression\fR\fB))\fR) is replaced by the value
of the arithmetic expression within the double parentheses.
.SS "Process Substitution"
.sp
.LP
Process substitution is only available on versions of the UNIX operating system
that support the \fB/dev/fd\fR directory for naming open files.
.sp
.LP
Each command argument of the form \fB<(\fR\fIlist\fR\fB)\fR or
\fB>(\fR\fIlist\fR\fB)\fR runs process \fIlist\fR asynchronously connected to
some file in \fB/dev/fd\fR. The name of this file becomes the argument to the
command. If the form with \fB>\fR is selected then writing on this file
provides input for \fIlist\fR. If \fB<\fR is used, then the file passed as an
argument contains the output of the \fIlist\fR process.
.sp
.LP
For example,
.sp
.in +2
.nf
paste <(cut -f1 \fIfile1\fR) <(cut -f3 \fIfile2\fR) | tee \e
     >(\fIprocess1\fR) >(\fIprocess2\fR)
.fi
.in -2
.sp

.sp
.LP
\fBcut\fRs fields 1 and 3 from the files \fIfile1\fR and \fIfile2\fR
respectively, \fBpaste\fRs the results together, and sends it to the processes
\fIprocess1\fR and \fIprocess2\fR. It also displays the results to the standard
output. The file, which is passed as an argument to the command, is a UNIX
\fBpipe\fR(2). Programs that expect to \fBlseek\fR(2) on the file do not work.
.SS "Parameter Expansion"
.sp
.LP
A parameter is a variable, one or more digits, or any of the characters
\fB*\fR, \fB@\fR, \fB#\fR, \fB?\fR, \fB-\fR, \fB$\fR, and \fB!\fR. A variable
is denoted by a \fIvname\fR. To create a variable whose \fIvname\fR contains a
\fB\&.\fR, a variable whose \fBvname\fR consists of everything before the
last . must already exist. A variable has a value and zero or more attributes.
Variables can be assigned values and attributes by using the \fBtypeset\fR
special built-in command. The attributes supported by the shell are described
later with the \fBtypeset\fR special built-in command. Exported variables pass
values and attributes to the environment.
.sp
.LP
The shell supports both indexed and associative arrays. An element of an array
variable is referenced by a subscript. A subscript for an indexed array is
denoted by an arithmetic expression, (see \fBArithmetic Evaluation\fR), between
a \fB[\fR and a \fB]\fR. Use \fBset -A\fR \fIvname value ...\fR to assign
values to an indexed array. The value of all subscripts must be in the range of
\fB0\fR through \fB1,048,575\fR. Indexed arrays do not need to be declared. Any
reference to a variable with a valid subscript is legal and an array is created
if necessary.
.sp
.LP
An associative array is created with the \fB-A\fR option to \fBtypeset\fR. A
subscript for an associative array is denoted by a string enclosed between
\fB[\fR and \fB]\fR.
.sp
.LP
Referencing any array without a subscript is equivalent to referencing the
array with subscript \fB0\fR.
.sp
.LP
The value of a variable can be assigned by:
.sp
.in +2
.nf
\fIvname\fR=\fIvalue\fR [\fIvname\fR=\fIvalue\fR] ...
.fi
.in -2
.sp

.sp
.LP
or
.sp
.in +2
.nf
\fIvname\fR[\fIsubscript\fR]=\fIvalue\fR [\fIvname\fR[\fIsubscript\fR]=\fIvalue\fR] ...
.fi
.in -2
.sp

.sp
.LP
No space is allowed before or after the \fB=\fR. A \fInameref\fR is a variable
that is a reference to another variable. A \fInameref\fR is created with the
\fB-n\fR attribute of \fBtypeset\fR. The value of the variable at the time of
the \fBtypeset\fR command becomes the variable that is referenced whenever the
\fInameref\fR variable is used. The name of a \fInameref\fR cannot contain a
dot (\fI\&.\fR). When a variable or function name contains a \fB\&.,\fR and the
portion of the name up to the first \fB\&.\fR matches the name of a
\fInameref\fR, the variable referred to is obtained by replacing the
\fInameref\fR portion with the name of the variable referenced by the
\fInameref\fR. If a \fInameref\fR is used as the index of a \fBfor\fR loop, a
name reference is established for each item in the list. A \fInameref\fR
provides a convenient way to refer to the variable inside a function whose name
is passed as an argument to a function. For example, if the name of a variable
is passed as the first argument to a function, the command
.sp
.in +2
.nf
 typeset -n var=$1
.fi
.in -2
.sp

.sp
.LP
inside the function causes references and assignments to \fIvar\fR to be
references and assignments to the variable whose name has been passed to the
function. If either of the floating point attributes, \fB-E\fR, or \fB-F\fR, or
the integer attribute, \fB-i\fR, is set for \fIvname\fR, then the \fIvalue\fR
is subject to arithmetic evaluation as described in this manual page.
Positional parameters, parameters denoted by a number, can be assigned values
with the \fBset\fR special built-in command. Parameter \fB$0\fR is set from
argument zero when the shell is invoked. The character \fB$\fR is used to
introduce substitutable parameters.
.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
The shell reads all the characters from \fB${\fR to the matching \fB}\fR as
part of the same word even if it contains braces or metacharacters. The value,
if any, of the parameter is substituted. The braces are required when
\fIparameter\fR is followed by a letter, digit, or underscore that is not to be
interpreted as part of its name, when the variable name contains a \fB\&.\fR,
or when a variable is subscripted. If \fIparameter\fR is one or more digits
then it is a positional parameter. A positional parameter of more than one
digit must be enclosed in braces. If \fIparameter\fR is \fB*\fR or \fB@\fR,
then all the positional parameters, starting with \fB$1\fR, are substituted and
separated by a field separator character. If an array \fIvname\fR with
subscript \fB*\fR or \fB@\fR is used, then the value for each of the elements
is substituted, separated by the first character of the value of \fBIFS\fR.
.RE

.sp
.ne 2
.na
\fB\fB${#\fR\fIparameter\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If \fIparameter\fR is \fB*\fR or \fB@\fR, the number of positional parameters
is substituted. Otherwise, the length of the value of the \fIparameter\fR is
substituted.
.RE

.sp
.ne 2
.na
\fB\fB${#\fR\fIvname\fR\fB[*]}\fR\fR
.ad
.br
.na
\fB\fB${#\fR\fIvname\fR\fB[@]}\fR\fR
.ad
.sp .6
.RS 4n
The number of elements in the array \fIvname\fR is substituted.
.RE

.sp
.ne 2
.na
\fB\fB${!\fR\fIvname\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
Expands to the name of the variable referred to by \fIvname\fR. This is
\fIvname\fR except when \fIvname\fR is a name reference.
.RE

.sp
.ne 2
.na
\fB\fB${!\fR\fIvname\fR\fB[\fR\fIsubscript\fR\fB]}\fR\fR
.ad
.sp .6
.RS 4n
Expands to name of the subscript unless \fIsubscript\fR is \fB*\fR or \fB@\fR.
When \fIsubscript\fR is \fB*\fR, the list of array subscripts for \fIvname\fR
is generated. For a variable that is not an array, the value is \fB0\fR if the
variable is set. Otherwise it is \fBnull\fR. When \fIsubscript\fR is \fB@\fR,
it is the same as \fB$ {\fR\fIvname\fR\fB[\fR\fI*\fR\fB]}\fR, except that when
used in double quotes, each array subscript yields a separate argument.
.RE

.sp
.ne 2
.na
\fB\fB${!\fR\fIprefix\fR\fB*}\fR\fR
.ad
.sp .6
.RS 4n
Expands to the names of the variables whose names begin with \fIprefix\fR.
.RE

.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB:-\fR\fIword\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If \fIparameter\fR is set and is non-null then substitute its value. Otherwise
substitute \fIword\fR.
.sp
\fIword\fR is not evaluated unless it is to be used as the substituted string.
.sp
In the following example, \fBpwd\fR is executed only if \fBd\fR is not set or
is NULL:
.sp
.in +2
.nf
print ${d:-$(pwd)}
.fi
.in -2
.sp

If the colon (\fB:\fR ) is omitted from the expression, the shell only checks
whether \fIparameter\fR is set or not.
.RE

.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB:=\fR\fIword\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If \fIparameter\fR is not set or is \fBnull\fR, set it to \fIword\fR. The value
of the parameter is then substituted. Positional parameters cannot be assigned
to in this way.
.sp
\fIword\fR is not evaluated unless it is to be used as the substituted string.
.sp
In the following example, \fBpwd\fR is executed only if \fBd\fR is not set or
is NULL:
.sp
.in +2
.nf
print ${d:-$(pwd)}
.fi
.in -2
.sp

If the colon (\fB:\fR) is omitted from the expression, the shell only checks
whether \fIparameter\fR is set or not.
.RE

.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB:?\fR\fIword\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If \fIparameter\fR is set and is non-null, substitute its value. Otherwise,
print \fIword\fR and exit from the shell , if the shell is not interactive. If
\fIword\fR is omitted then a standard message is printed.
.sp
\fIword\fR is not evaluated unless it is to be used as the substituted string.
.sp
In the following example, \fBpwd\fR is executed only if \fBd\fR is not set or
is NULL:
.sp
.in +2
.nf
print ${d:-$(pwd)}
.fi
.in -2
.sp

If the colon (\fB:\fR ) is omitted from the expression, the shell only checks
whether \fIparameter\fR is set or not.
.RE

.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB:+\fR\fIword\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If \fIparameter\fR is set and is non-null, substitute \fIword\fR. Otherwise
substitute nothing.
.sp
\fIword\fR is not evaluated unless it is to be used as the substituted string.
.sp
In the following example, \fBpwd\fR is executed only if \fBd\fR is not set or
is NULL:
.sp
.in +2
.nf
print ${d:-$(pwd)}
.fi
.in -2
.sp

If the colon (\fB:\fR) is omitted from the expression, the shell only checks
whether \fIparameter\fR is set or not.
.RE

.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB:\fR\fIoffset\fR:\fIlength\fR}\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB:\fR\fIoffset\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
Expands to the portion of the value of \fIparameter\fR starting at the
character (counting from \fB0\fR) determined by expanding offset as an
arithmetic expression and consisting of the number of characters determined by
the arithmetic expression defined by \fIlength\fR.
.sp
In the second form, the remainder of the value is used. A negative offset
counts backwards from the end of \fIparameter\fR.
.sp
One or more BLANKs is required in front of a minus sign to prevent the shell
from interpreting the operator as \fB:-\fR. If parameter is \fB*\fR or \fB@\fR,
or is an array name indexed by \fB*\fR or \fB@\fR, then \fIoffset\fR and
\fIlength\fR refer to the array index and number of elements respectively. A
negative \fIoffset\fR is taken relative to one greater than the highest
subscript for indexed arrays. The order for associative arrays is unspecified.
.RE

.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB#\fR\fIpattern\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB##\fR\fIpattern\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If the shell \fIpattern\fR matches the beginning of the value of
\fIparameter\fR, then the value of this expansion is the value of the
\fIparameter\fR with the matched portion deleted. Otherwise the value of this
\fIparameter\fR is substituted. In the first form the smallest matching
\fIpattern\fR is deleted and in the second form the largest matching
\fIpattern\fR is deleted. When \fIparameter\fR is \fB@\fR, \fB*\fR, or an array
variable with subscript \fB@\fR or \fB*\fR, the substring operation is applied
to each element in turn.
.RE

.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB%\fR\fIpattern\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB%%\fR\fIpattern\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If the shell \fIpattern\fR matches the end of the value of \fIparameter\fR,
then the value of this expansion is the value of the parameter with the matched
part deleted. Otherwise substitute the value of \fIparameter\fR. In the first
form the smallest matching pattern is deleted, and in the second form the
largest matching pattern is deleted. When parameter is \fB@\fR, \fB*\fR, or an
array variable with subscript \fB@\fR or \fB*\fR, the substring operation is
applied to each element in turn.
.RE

.sp
.ne 2
.na
\fB\fB${\fR\fIparameter\fR\fB/\fR\fIpattern\fR\fB/\fR\fIstring\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB//\fR\fIpattern\fR\fB/\fR\fIstring\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB/#\fR\fIpattern\fR\fB/\fR\fIstring\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB/%\fR\fIpattern\fR\fB/\fR\fIstring\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
Expands \fIparameter\fR and replaces the longest match of \fIpattern\fR with
the specified \fIstring\fR. Each occurrence of \fB\e\fR\fIn\fR in \fIstring\fR
is replaced by the portion of \fIparameter\fR that matches the \fIn\fR\fBth\fR
sub-pattern.
.sp
When \fIstring\fR is null, the \fIpattern\fR is deleted and the \fB/\fR in
front of string can be omitted. When \fIparameter\fR is \fB@\fR, \fB*\fR, or an
array variable with subscript \fB@\fR or \fB*\fR, the substitution operation is
applied to each element in turn. In this case, the \fIstring\fR portion of
\fIword\fR is re-evaluated for each element.
.sp
In the first form, only the first occurrence of \fIpattern\fR is replaced.
.sp
In the second form, each match for \fIpattern\fR is replaced by the specified
\fIstring\fR.
.sp
The third form restricts the pattern match to the beginning of the
\fIstring\fR.
.sp
The fourth form restricts the pattern match to the end of the \fIstring\fR.
.RE

.sp
.LP
The following parameters are automatically set by the shell:
.sp
.ne 2
.na
\fB\fB#\fR\fR
.ad
.RS 19n
The number of positional parameters in decimal.
.RE

.sp
.ne 2
.na
\fB\fB-\fR\fR
.ad
.RS 19n
Options supplied to the shell on invocation or by the \fBset\fR command.
.RE

.sp
.ne 2
.na
\fB\fB?\fR\fR
.ad
.RS 19n
The decimal value returned by the last executed command.
.RE

.sp
.ne 2
.na
\fB\fB$\fR\fR
.ad
.RS 19n
The process number of this shell.
.RE

.sp
.ne 2
.na
\fB\fB_\fR\fR
.ad
.RS 19n
Initially, the value of \fB_\fR is the absolute pathname of the shell or script
being executed as passed in the environment. It is subsequently assigned the
last argument of the previous command.
.sp
This parameter is not set for commands which are asynchronous. This parameter
is also used to hold the name of the matching \fBMAIL\fR file when checking for
mail.
.RE

.sp
.ne 2
.na
\fB\fB!\fR\fR
.ad
.RS 19n
The process number of the last background command invoked or the most recent
job put in the background with the \fBbg\fR built-in command.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.command\fR\fR
.ad
.RS 19n
When processing a \fBDEBUG\fR trap, this variable contains the current command
line that is about to run.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.edchar\fR\fR
.ad
.RS 19n
This variable contains the value of the keyboard character (or sequence of
characters if the first character is an ESC, \fBASCII 033\fR) that has been
entered when processing a \fBKEYBD\fR trap. If the value is changed as part of
the trap action, then the new value replaces the key (or key sequence) that
caused the trap. See the \fBKey Bindings\fR section of this manual page.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.edcol\fR\fR
.ad
.RS 19n
The character position of the cursor at the time of the most recent \fBKEYBD\fR
trap.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.edmode\fR\fR
.ad
.RS 19n
The value is set to ESC when processing a \fBKEYBD\fR trap while in \fBvi\fR
insert mode. Otherwise, \fB\&.sh.edmode\fR is null when processing a
\fBKEYBD\fR trap. See the \fBvi Editing Mode\fR section of this manual page.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.edtext\fR\fR
.ad
.RS 19n
The characters in the input buffer at the time of the most recent \fBKEYBD\fR
trap. The value is null when not processing a \fBKEYBD\fR trap.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.file\fR\fR
.ad
.RS 19n
The pathname of the file than contains the current command.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.fun\fR\fR
.ad
.RS 19n
The name of the current function that is being executed.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.match\fR\fR
.ad
.RS 19n
An indexed array which stores the most recent match and sub-pattern matches
after conditional pattern matches that match and after variables expansions
using the operators \fB#\fR, \fB%\fR, or \fB/\fR. The \fB0\fRth element stores
the complete match and the \fIi\fRth element stores the \fIi\fRth sub-match.
The \fB\&.sh.match\fR variable is unset when the variable that has expanded is
assigned a new value.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.name\fR\fR
.ad
.RS 19n
Set to the name of the variable at the time that a discipline function is
invoked.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.subscript\fR\fR
.ad
.RS 19n
Set to the name subscript of the variable at the time that a discipline
function is invoked.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.subshell\fR\fR
.ad
.RS 19n
The current depth for sub-shells and command substitution.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.value\fR\fR
.ad
.RS 19n
Set to the value of the variable at the time that the set or append discipline
function is invoked.
.RE

.sp
.ne 2
.na
\fB\fB\&.sh.version\fR\fR
.ad
.RS 19n
Set to a value that identifies the version of this shell.
.RE

.sp
.ne 2
.na
\fB\fBLINENO\fR\fR
.ad
.RS 19n
The current line number within the script or function being executed.
.RE

.sp
.ne 2
.na
\fB\fBOLDPWD\fR\fR
.ad
.RS 19n
The previous working directory set by the \fBcd\fR command.
.RE

.sp
.ne 2
.na
\fB\fBOPTARG\fR\fR
.ad
.RS 19n
The value of the last option argument processed by the \fBgetopts\fR built-in
command.
.RE

.sp
.ne 2
.na
\fB\fBOPTIND\fR\fR
.ad
.RS 19n
The index of the last option argument processed by the \fBgetopts\fR built-in
command.
.RE

.sp
.ne 2
.na
\fB\fBPPID\fR\fR
.ad
.RS 19n
The process number of the parent of the shell.
.RE

.sp
.ne 2
.na
\fB\fBPWD\fR\fR
.ad
.RS 19n
The present working directory set by the \fBcd\fR command.
.RE

.sp
.ne 2
.na
\fB\fBRANDOM\fR\fR
.ad
.RS 19n
Each time this variable is referenced, a random integer, uniformly distributed
between \fB0\fR and \fB32767\fR, is generated. The sequence of random numbers
can be initialized by assigning a numeric value to \fBRANDOM\fR.
.RE

.sp
.ne 2
.na
\fB\fBREPLY\fR\fR
.ad
.RS 19n
This variable is set by the \fBselect\fR statement and by the \fBread\fR
built-in command when no arguments are supplied.
.RE

.sp
.ne 2
.na
\fB\fBSECONDS\fR\fR
.ad
.RS 19n
Each time this variable is referenced, the number of seconds since shell
invocation is returned. If this variable is assigned a value, then the value
returned upon reference is the value that was assigned plus the number of
seconds since the assignment.
.RE

.sp
.LP
The following variables are used by the shell:
.sp
.ne 2
.na
\fB\fBCDPATH\fR\fR
.ad
.RS 14n
Defines the search path for the \fBcd\fR command.
.RE

.sp
.ne 2
.na
\fB\fBCOLUMNS\fR\fR
.ad
.RS 14n
Defines the width of the edit window for the shell edit modes and for printing
select lists.
.RE

.sp
.ne 2
.na
\fB\fBEDITOR\fR\fR
.ad
.RS 14n
If the \fBVISUAL\fR variable is not set, the value of this variable is checked
for the patterns as described with \fBVISUAL\fR and the corresponding editing
option is turned on.
.sp
See the \fBset\fR command in the \fBSpecial Command\fR section of this manual
page.
.RE

.sp
.ne 2
.na
\fB\fBENV\fR\fR
.ad
.RS 14n
Performs parameter expansion, command substitution, and arithmetic substitution
on the value to generate the pathname of the script that is executed when the
shell is invoked. This file is typically used for alias and function
definitions. The default value is \fB$HOME/.kshrc\fR.
.sp
See the \fBInvocation\fR section of this manual page.
.sp
\fBENV\fR is not set by the shell.
.RE

.sp
.ne 2
.na
\fB\fBFCEDIT\fR\fR
.ad
.RS 14n
Obsolete name for the default editor name for the \fBhist\fR command.
\fBFCEDIT\fR is not used when \fBHISTEDIT\fR is set.
.sp
The shell specifies a default value to \fBFCEDIT\fR.
.RE

.sp
.ne 2
.na
\fB\fBFIGNORE\fR\fR
.ad
.RS 14n
A pattern that defines the set of file names that is ignored when performing
file name matching.
.RE

.sp
.ne 2
.na
\fB\fBFPATH\fR\fR
.ad
.RS 14n
The search path for function definitions. The directories in this path are
searched for a file with the same name as the function or command when a
function with the \fB-u\fR attribute is referenced and when a command is not
found. If an executable file with the name of that command is found, then it is
read and executed in the current environment. Unlike \fBPATH\fR, the current
directory must be represented explicitly by dot (\fB\&.\fR) rather than by
adjacent colon (\fB:\fR) characters or a beginning or ending colon (\fB:\fR).
.RE

.sp
.ne 2
.na
\fB\fBHISTCMD\fR\fR
.ad
.RS 14n
The number of the current command in the history file.
.RE

.sp
.ne 2
.na
\fB\fBHISTEDIT\fR\fR
.ad
.RS 14n
The name for the default editor name for the \fBhist\fR command.
.RE

.sp
.ne 2
.na
\fB\fBHISTFILE\fR\fR
.ad
.RS 14n
If this variable is set when the shell is invoked, the value is the pathname of
the file that is used to store the command history. See the \fBCommand
Re-entry\fR section of this manual page.
.RE

.sp
.ne 2
.na
\fB\fBHISTSIZE\fR\fR
.ad
.RS 14n
If this variable is set when the shell is invoked, then the number of
previously entered commands that are accessible by this shell is greater than
or equal to this number. The default is \fB512\fR.
.RE

.sp
.ne 2
.na
\fB\fBHOME\fR\fR
.ad
.RS 14n
The default argument (home directory) for the \fBcd\fR command.
.sp
\fBHOME\fR is not set by the shell. \fBHOME\fR is set by \fBlogin\fR(1).
.RE

.sp
.ne 2
.na
\fB\fBIFS\fR\fR
.ad
.RS 14n
Internal field separators, normally SPACE, TAB, and NEWLINE that are used to
separate the results of command substitution or parameter expansion and to
separate fields with the built-in command read. The first character of the
\fBIFS\fR variable is used to separate arguments for the \fB"$*"\fR
substitution. See the \fBQuoting\fR section of this manual page.
.sp
Each single occurrence of an \fBIFS\fR character in the string to be split,
that is not in the \fBissspace\fR character class, and any adjacent characters
in \fBIFS\fR that are in the \fBissspace\fR character class, delimit a field.
One or more characters in IFS that belong to the \fBissspace\fR character
class, delimit a field. In addition, if the same \fBissspace\fR character
appears consecutively inside \fBIFS\fR, this character is treated as if it were
not in the \fBissspace\fR class, so that if \fBIFS\fR consists of two tab
characters, then two adjacent tab characters delimit a null field.
.sp
The shell specifies a default value to \fBIFS\fR.
.RE

.sp
.ne 2
.na
\fB\fBLANG\fR\fR
.ad
.RS 14n
This variable determines the locale category for any category not specifically
selected with a variable starting with \fBLC_\fR or \fBLANG\fR.
.RE

.sp
.ne 2
.na
\fB\fBLC_ALL\fR\fR
.ad
.RS 14n
This variable overrides the value of the \fBLANG\fR variable and any other
\fBLC_\fR variable.
.RE

.sp
.ne 2
.na
\fB\fBLC_COLLATE\fR\fR
.ad
.RS 14n
This variable determines the locale category for character collation
information.
.RE

.sp
.ne 2
.na
\fB\fBLC_CTYPE\fR\fR
.ad
.RS 14n
This variable determines the locale category for character handling functions.
It determines the character classes for pattern matching. See the \fBFile Name
Generation\fR section of this manual page.
.RE

.sp
.ne 2
.na
\fB\fBLC_NUMERIC\fR\fR
.ad
.RS 14n
This variable determines the locale category for the decimal point character.
.RE

.sp
.ne 2
.na
\fB\fBLINES\fR\fR
.ad
.RS 14n
If this variable is set, the value is used to determine the column length for
printing select lists. Select lists prints vertically until about two-thirds of
\fBLINES\fR lines are filled.
.RE

.sp
.ne 2
.na
\fB\fBMAIL\fR\fR
.ad
.RS 14n
If this variable is set to the name of a mail file \fBand\fR the \fBMAILPATH\fR
variable is not set, then the shell informs the user of arrival of mail in the
specified file.
.sp
\fBMAIL\fR is not set by the shell. On some systems, \fBMAIL\fR is set by
\fBlogin\fR(1).
.RE

.sp
.ne 2
.na
\fB\fBMAILCHECK\fR\fR
.ad
.RS 14n
Specifies how often in seconds the shell checks for changes in the modification
time of any of the files specified by the \fBMAILPATH\fR or \fBMAIL\fR
variables. The default value is \fB600\fR seconds. When the time has elapsed
the shell checks before issuing the next prompt.
.sp
The shell specifies a default value to \fBMAILCHECK\fR.
.RE

.sp
.ne 2
.na
\fB\fBMAILPATH\fR\fR
.ad
.RS 14n
A colon ( \fB:\fR ) separated list of file names. If this variable is set, then
the shell informs the user of any modifications to the specified files that
have occurred within the last \fBMAILCHECK\fR seconds. Each file name can be
followed by a \fB?\fR and a message that is printed. The message undergoes
parameter expansion, command substitution, and arithmetic substitution with the
variable \fB$_\fR defined as the name of the file that has changed. The default
message is \fByou have mail in $_\fR.
.RE

.sp
.ne 2
.na
\fB\fBPATH\fR\fR
.ad
.RS 14n
The search path for commands. Except in \fB\&.profile\fR, users cannot change
\fBPATH\fR if executing under \fBrksh93\fR. See the \fBExecution\fR section of
this manual page.
.sp
The shell specifies a default value to \fBPATH\fR.
.RE

.sp
.ne 2
.na
\fB\fBPS1\fR\fR
.ad
.RS 14n
The value of this variable is expanded for parameter expansion, command
substitution, and arithmetic substitution to define the primary prompt string
which by default is \fB$\fR. The character \fB!\fR in the primary prompt string
is replaced by the command number. Two successive occurrences of \fB!\fR
produces a single \fB!\fR when the prompt string is printed. See the \fBCommand
Re-entry\fR section of this manual page.
.sp
The shell specifies a default value to \fBPS1\fR.
.RE

.sp
.ne 2
.na
\fB\fBPS2\fR\fR
.ad
.RS 14n
Secondary prompt string, by default, \fB>\fR.
.sp
The shell specifies a default value to \fBPS2\fR.
.RE

.sp
.ne 2
.na
\fB\fBPS3\fR\fR
.ad
.RS 14n
Selection prompt string used within a select loop, by default \fB#?\fR.
.sp
The shell specifies a default value to \fBPS3\fR.
.RE

.sp
.ne 2
.na
\fB\fBPS4\fR\fR
.ad
.RS 14n
The value of this variable is expanded for parameter evaluation, command
substitution, and arithmetic substitution and precedes each line of an
execution trace. By default, \fBPS4\fR is \fB+\fR. When \fBPS4\fR is unset, the
execution trace prompt is also \fB+\fR .
.sp
The shell specifies a default value to \fBPS4\fR.
.RE

.sp
.ne 2
.na
\fB\fBSHELL\fR\fR
.ad
.RS 14n
The pathname of the shell is kept in the environment. At invocation, if the
basename of this variable is \fBrsh\fR, \fBrksh\fR, \fBrksh93\fR, or
\fBkrsh\fR, the shell becomes restricted.
.sp
\fBSHELL\fR is not set by the shell. On some systems, \fBSHELL\fR is set by
\fBlogin\fR(1).
.RE

.sp
.ne 2
.na
\fB\fBTIMEFORMAT\fR\fR
.ad
.RS 14n
The value of this parameter is used as a format string specifying how the
timing information for pipelines prefixed with the \fBtime\fR reserved word
should be displayed. The \fB%\fR character introduces a format sequence that is
expanded to a time value or other information.
.sp
The format sequences and their meanings are as follows.
.sp
.ne 2
.na
\fB\fB%%\fR\fR
.ad
.sp .6
.RS 4n
A literal \fB%\fR.
.RE

.sp
.ne 2
.na
\fB\fB%[\fIp\fR][l]R\fR\fR
.ad
.sp .6
.RS 4n
The elapsed time in seconds.
.RE

.sp
.ne 2
.na
\fB\fB%[\fIp\fR][l]U\fR\fR
.ad
.sp .6
.RS 4n
The number of CPU seconds spent in user mode.
.RE

.sp
.ne 2
.na
\fB\fB%[\fIp\fR][l]S\fR\fR
.ad
.sp .6
.RS 4n
The number of CPU seconds spent in system mode.
.RE

.sp
.ne 2
.na
\fB\fB%P\fR\fR
.ad
.sp .6
.RS 4n
The CPU percentage, computed as \fB(U + S) / R\fR.
.RE

The braces denote optional portions. The optional \fIp\fR is a digit specifying
the \fIprecision\fR, the number of fractional digits after a decimal point. A
value of \fB0\fR causes no decimal point or fraction to be output. At most
three places after the decimal point can be displayed. Values of \fIp\fR
greater than \fB3\fR are treated as \fB3\fR. If \fIp\fR is not specified, the
value \fB3\fR is used.
.sp
The optional \fBl\fR specifies a longer format, including hours if greater than
zero, minutes, and seconds of the form \fIHHhMMmSS.FFs\fR. The value of \fIp\fR
determines whether or not the fraction is included.
.sp
All other characters are output without change and a trailing NEWLINE is added.
If unset, the default value, \fB$'\enreal\t%2lR\nuser\t%2lU\nsys%2lS'\fR, is
used. If the value is null, no timing information is displayed.
.RE

.sp
.ne 2
.na
\fB\fBTMOUT\fR\fR
.ad
.RS 14n
If set to a value greater than zero, \fBTMOUT\fR is the default time-out value
for the \fBread\fR built-in command. The \fBselect\fR compound command
terminates after \fBTMOUT\fR seconds when input is from a terminal. Otherwise,
the shell terminates if a line is not entered within the prescribed number of
seconds while reading from a terminal. The shell can be compiled with a maximum
bound for this value which cannot be exceeded.
.sp
The shell specifies a default value to \fBTMOUT\fR.
.RE

.sp
.ne 2
.na
\fB\fBVISUAL\fR\fR
.ad
.RS 14n
If the value of this variable matches the pattern \fB*[Vv][Ii]*\fR, then the
\fBvi\fR option is turned on. See \fBSpecial Commands\fR. If the value matches
the pattern \fB*gmacs*\fR , the \fBgmacs\fR option is turned on. If the value
matches the pattern \fB*macs*\fR, then the \fBemacs\fR option is turned on. The
value of \fBVISUAL\fR overrides the value of \fBEDITOR\fR.
.RE

.SS "Field Splitting"
.sp
.LP
After parameter expansion and command substitution, the results of
substitutions are scanned for the field separator characters (those found in
\fBIFS\fR) and split into distinct fields where such characters are found.
Explicit null fields (\fB""\fR or \fB\&''\fR) are retained. Implicit null
fields, those resulting from parameters that have no values or command
substitutions with no output, are removed.
.sp
.LP
If the \fBbraceexpand\fR (\fB-B\fR) option is set, each of the fields resulting
from \fBIFS\fR are checked to see if they contain one or more of the brace
patterns. Valid brace patterns: \fB{*\fR,\fB*}\fR,
\fB{\fR\fIl1\fR\fB\&..\fR\fIl2\fR\fB}\fR ,
\fB{\fR\fIn1\fR\fB\&..\fR\fIn2\fR\fB}\fR,
\fB{\fR\fIn1\fR\fB\&..\fR\fIn2\fR\fB%\fR\fIfmt\fR\fB}
{\fR\fIn1\fR\fB\&..\fR\fIn2\fR \fB\&..\fR\fIn3\fR\fB}\fR, or
\fB{\fR\fIn1\fR\fB\&..\fR\fIn2\fR \fB\&..\fR\fIn3\fR\fB%\fR\fIfmt\fR\fB}\fR ,
where \fB*\fR represents any character, \fIl1\fR,\fIl2\fR are letters and
\fIn1\fR,\fIn2\fR,\fIn3\fR are signed numbers and \fIfmt\fR is a format
specified as used by \fBprintf\fR. In each case, fields are created by
prepending the characters before the \fB{\fR and appending the characters after
the } to each of the strings generated by the characters between the \fB{\fR
and \fB}\fR. The resulting fields are checked to see if they have any brace
patterns.
.sp
.LP
In the first form, a field is created for each string between \fB{\fR and
\fB,,\fR between \fB,\fR and \fB,,\fR and between , and \fB}\fR. The string
represented by \fB*\fR can contain embedded matching { and } without quoting.
Otherwise, each \fB{\fR and \fB}\fR with \fB*\fR must be quoted.
.sp
.LP
In the second form, \fIl1\fR and \fIl2\fR must both be either upper case or
both be lower case characters in the C locale. In this case a field is created
for each character from \fIl1\fR through \fIl2\fR.
.sp
.LP
In the remaining forms, a field is created for each number starting at
\fIn1\fR. This continues until it reaches \fIn2\fR and increments \fIn1\fR by
\fIn3\fR. The cases where \fIn3\fR is not specified behave as if \fIn3\fR were
1 if \fIn1\fR\fB<=\fR\fIn2\fR, and \fB-1\fR otherwise. In forms which specify
\fB%\fR\fIfmt\fR, any format flags, widths and precisions can be specified and
\fIfmt\fR can end in any of the specifiers \fBcdiouxX\fR. For example,
\fB{a,z}{1..5..3%02d}{b..c}x\fR expands to the 8 fields, \fBa01bx, a01cx,
a04bx, a04cx, z01bx, z01cx, z04bx,\fR and \fBz4cx\fR.
.SS "File Name Generation"
.sp
.LP
Following splitting, each field is scanned for the characters \fB*\fR, \fB?\fR,
\fB(\fR, and \fB[\fR, unless the \fB-f\fR option has been set. If one of these
characters appears, then the word is regarded as a pattern.
.sp
.LP
Each file name component that contains any pattern character is replaced with a
lexicographically sorted set of names that matches the pattern from that
directory. If no file name is found that matches the pattern, then that
component of the file name is left unchanged unless the pattern is prefixed
with \fB~(N)\fR in which case it is removed. If \fBFIGNORE\fR is set, then each
file name component that matches the pattern defined by the value of
\fBFIGNORE\fR is ignored when generating the matching file names. The names
\fB\&.\fR and \fB\&..\fR are also ignored. If \fBFIGNORE\fR is not set, the
character \fB\&.\fR at the start of each file name component is ignored unless
the first character of the pattern corresponding to this component is the
character \fB\&.\fR itself. For other uses of pattern matching the \fB/\fR and
\fB\&.\fR are not specially treated.
.sp
.ne 2
.na
\fB\fB*\fR\fR
.ad
.RS 11n
Match any string, including the null string. When used for file name expansion,
if the \fBglobstar\fR option is on, two adjacent \fB*\fRs by themselves match
all files and zero or more directories and subdirectories. If the two adjacent
\fB*\fRs are followed by a \fB/\fR, only directories and subdirectories match.
.RE

.sp
.ne 2
.na
\fB\fB?\fR\fR
.ad
.RS 11n
Matches any single character.
.RE

.sp
.ne 2
.na
\fB[\fB\&...\fR]\fR
.ad
.RS 11n
Match any one of the enclosed characters. A pair of characters separated by
\fB-\fR matches any character lexically between the pair, inclusive. If the
first character following the opening \fB[\fR is a \fB!\fR, any character not
enclosed is matched. A \fB-\fR can be included in the character set by putting
it as the first or last character. Within \fB[\fR and \fB]\fR, character
classes can be specified with the syntax \fB[:\fR\fIclass\fR\fB:]\fR where
\fIclass\fR is one of the following classes defined in the \fBANSI-C\fR
standard:
.sp
.in +2
.nf
\fIalnum alpha blank cntrl digit graph
lower print punct space upper
word xdigit\fR
.fi
.in -2
.sp

\fIword\fR is equivalent to \fIalnum\fR plus the character \fB_\fR. Within
\fB[\fR and \fB]\fR, an equivalence class can be specified with the syntax
\fB[=\fR\fIc\fR\fB=]\fR which matches all characters with the same primary
collation weight (as defined by the current locale) as the character \fIc\fR.
Within \fB[\fR and \fB]\fR, [\fI\&.symbol.\fR] matches the collating symbol
\fIsymbol\fR.
.RE

.sp
.LP
A \fIpattern-list\fR is a list of one or more patterns separated from each
other with an \fB&\fR or \fB|\fR. An \fB&\fR signifies that all patterns must
be matched whereas \fB|\fR requires that only one pattern be matched. Composite
patterns can be formed with one or more of the following sub-patterns:
.sp
.ne 2
.na
\fB\fB?(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 22n
Optionally matches any one of the specified patterns.
.RE

.sp
.ne 2
.na
\fB\fB*(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 22n
Matches zero or more occurrences of the specified patterns.
.RE

.sp
.ne 2
.na
\fB\fB+(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 22n
Matches one or more occurrences of the specified patterns.
.RE

.sp
.ne 2
.na
\fB\fB{\fR\fIn\fR\fB(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 22n
Matches \fIn\fR occurrences of the specified patterns.
.RE

.sp
.ne 2
.na
\fB\fB{\fR\fIm\fR\fB,\fR\fIn\fR\fB(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 22n
Matches from \fIm\fR to \fIn\fR occurrences of the specified patterns. If
\fIm\fR is omitted, \fB0\fR is used. If \fIn\fR is omitted at least \fIm\fR
occurrences are matched.
.RE

.sp
.ne 2
.na
\fB\fB@(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 22n
Matches exactly one of the specified patterns.
.RE

.sp
.ne 2
.na
\fB\fB!(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 22n
Matches anything except one of the specified patterns.
.RE

.sp
.LP
By default, each pattern, or sub-pattern matches the longest string possible
consistent with generating the longest overall match. If more than one match is
possible, the one starting closest to the beginning of the string is chosen.
However, for each of the compound patterns a \fB-\fR can be inserted in front
of the \fB(\fR to cause the shortest match to the specified \fIpattern-list\fR
to be used.
.sp
.LP
When \fIpattern-list\fR is contained within parentheses, the backslash
character \fB\e\fR is treated specially even when inside a character class. All
\fBANSI-C\fR character escapes are recognized and match the specified
character. In addition the following escape sequences are recognized:
.sp
.ne 2
.na
\fB\fB\ed\fR\fR
.ad
.RS 7n
Matches any character in the digit class.
.RE

.sp
.ne 2
.na
\fB\fB\eD\fR\fR
.ad
.RS 7n
Matches any character not in the digit class.
.RE

.sp
.ne 2
.na
\fB\fB\es\fR\fR
.ad
.RS 7n
Matches any character in the space class.
.RE

.sp
.ne 2
.na
\fB\fB\eS\fR\fR
.ad
.RS 7n
Matches any character not in the space class.
.RE

.sp
.ne 2
.na
\fB\fB\ew\fR\fR
.ad
.RS 7n
Matches any character in the word class.
.RE

.sp
.ne 2
.na
\fB\fB\eW\fR\fR
.ad
.RS 7n
Matches any character not in the word class.
.RE

.sp
.LP
A pattern of the form \fB%(\fR\fIpattern-pairs\fR\fB)\fR is a sub-pattern that
can be used to match nested character expressions. Each \fIpattern-pair\fR is a
two character sequence which cannot contain \fB&\fR or \fB|\fR. The first
\fIpattern-pair\fR specifies the starting and ending characters for the match.
Each subsequent \fIpattern-pair\fR represents the beginning and ending
characters of a nested group that is skipped over when counting starting and
ending character matches. The behavior is unspecified when the first character
of a \fIpattern-pair\fR is alphanumeric except for the following:
.sp
.ne 2
.na
\fB\fBD\fR\fR
.ad
.RS 5n
Causes the ending character to terminate the search for this pattern without
finding a match.
.RE

.sp
.ne 2
.na
\fB\fBE\fR\fR
.ad
.RS 5n
Causes the ending character to be interpreted as an escape character.
.RE

.sp
.ne 2
.na
\fB\fBL\fR\fR
.ad
.RS 5n
Causes the ending character to be interpreted as a quote character causing all
characters to be ignored when looking for a match.
.RE

.sp
.ne 2
.na
\fB\fBQ\fR\fR
.ad
.RS 5n
Causes the ending character to be interpreted as a quote character causing all
characters other than any escape character to be ignored when looking for a
match.
.RE

.sp
.LP
\fB%({}Q"E\e)\fR, matches characters starting at \fB{\fR until the matching
\fB}\fR is found not counting any \fB{\fR or \fB}\fR that is inside a double
quoted string or preceded by the escape character \fB\e\fR\&. Without the
\fB{}\fR this pattern matches any C language string.
.sp
.LP
Each sub-pattern in a composite pattern is numbered, starting at \fB1\fR, by
the location of the \fB(\fR within the pattern. The sequence \fB\e\fR\fIn\fR,
where \fIn\fR is a single digit and \fB\e\fR\fIn\fR comes after the \fIn\fRth.
sub-pattern, matches the same string as the sub-pattern itself.
.sp
.LP
A pattern can contain sub-patterns of the form
\fB~(\fR\fIoptions\fR\fB:\fR\fIpattern-list\fR\fB)\fR, where either
\fIoptions\fR or \fB:\fR\fIpattern-list\fR can be omitted. Unlike the other
compound patterns, these sub-patterns are not counted in the numbered
sub-patterns. If \fIoptions\fR is present, it can consist of one or more of the
following:
.sp
.ne 2
.na
\fB\fB+\fR\fR
.ad
.RS 5n
Enable the following options. This is the default.
.RE

.sp
.ne 2
.na
\fB\fB-\fR\fR
.ad
.RS 5n
Disable the following options.
.RE

.sp
.ne 2
.na
\fB\fBE\fR\fR
.ad
.RS 5n
The remainder of the pattern uses extended regular expression syntax like the
\fBegrep\fR(1) command.
.RE

.sp
.ne 2
.na
\fB\fBF\fR\fR
.ad
.RS 5n
The remainder of the pattern uses \fBfgrep\fR(1) expression syntax.
.RE

.sp
.ne 2
.na
\fB\fBg\fR\fR
.ad
.RS 5n
File the longest match (greedy).
.sp
This is the default.
.RE

.sp
.ne 2
.na
\fB\fBG\fR\fR
.ad
.RS 5n
The remainder of the pattern uses basic regular expression syntax like the
\fBgrep\fR(1) command.
.RE

.sp
.ne 2
.na
\fB\fBi\fR\fR
.ad
.RS 5n
Treat the match as case insensitive.
.RE

.sp
.ne 2
.na
\fB\fBK\fR\fR
.ad
.RS 5n
The remainder of the pattern uses shell pattern syntax.
.sp
This is the default.
.RE

.sp
.ne 2
.na
\fB\fBl\fR\fR
.ad
.RS 5n
Left anchor the pattern.
.sp
This is the default for \fBK\fR style patterns.
.RE

.sp
.ne 2
.na
\fB\fBN\fR\fR
.ad
.RS 5n
This is ignored. However, when it is the first letter and is used with file
name generation, and no matches occur, the file pattern expands to the empty
string.
.RE

.sp
.ne 2
.na
\fB\fBr\fR\fR
.ad
.RS 5n
Right anchor the pattern.
.sp
This is the default for \fBK\fR style patterns.
.RE

.sp
.LP
If both \fIoptions\fR and \fB:\fR\fIpattern-list\fR are specified, then the
options apply only to \fIpattern-list\fR. Otherwise, these options remain in
effect until they are disabled by a subsequent \fB~(...)\fR or at the end of
the sub-pattern containing \fB~(...)\fR.
.SS "Quoting"
.sp
.LP
Each of the metacharacters listed in the \fBDefinitions\fR has a special
meaning to the shell.
.sp
.ne 2
.na
\fB\fBg\fR\fR
.ad
.RS 5n
File the longest match (greedy). This is the default.
.RE

.sp
.ne 2
.na
\fB\fBi\fR\fR
.ad
.RS 5n
Treat the match as case insensitive.
.RE

.sp
.LP
If both \fIoptions\fR and \fB:\fR\fIpattern-list\fR are specified, then the
options apply only to \fIpattern-list\fR. Otherwise, the options remain in
effect until they are disabled by a subsequent \fB~(...)\fR or at the end of
the sub-pattern containing \fB~(...)\fR.
.sp
.LP
Each of the metacharacters listed in the \fBDefinitions\fR section of this
manual page has a special meaning to the shell and causes termination of a word
unless quoted. A character can be quoted, that is, made to stand for itself, by
preceding it with a backslash (\fB\e\fR). The pair \fB\e\fRNEWLINE is removed.
All characters enclosed between a pair of single quote marks (\fB\&''\fR) that
is not preceded by a \fB$\fR are quoted. A single quote cannot appear within
the single quotes. A single quoted string preceded by an unquoted \fB$\fR is
processed as an \fBANSI-C\fR string except for the following:
.sp
.ne 2
.na
\fB\fB\e0\fR\fR
.ad
.RS 19n
Causes the remainder of the string to be ignored.
.RE

.sp
.ne 2
.na
\fB\fB\ec\fR\fIx\fR\fR
.ad
.RS 19n
Expands to the character CTRL-x.
.RE

.sp
.ne 2
.na
\fB\fB\eC\fR[\fB\&.\fR\fIname\fR\fB\&.\fR]\fR
.ad
.RS 19n
Expands to the collating element \fIname\fR.
.RE

.sp
.ne 2
.na
\fB\fB\ee\fR\fR
.ad
.RS 19n
Equivalent to the escape character (\fBASCII\fR 033),
.RE

.sp
.ne 2
.na
\fB\fB\eE\fR\fR
.ad
.RS 19n
Equivalent to the escape character (\fBASCII\fR 033),
.RE

.sp
.LP
Inside double quote marks (\fB""\fR), parameter and command substitution occur
and \fB\e\fR quotes the characters \fB\e\fR, \fB`\fR, \fB"\fR, and \fB$\fR. A
\fB$\fR in front of a double quoted string is ignored in the \fBC\fR or
\fBPOSIX\fR locale, and might cause the string to be replaced by a locale
specific string otherwise. The meaning of \fB$*\fR and \fB$@\fR is identical
when not quoted or when used as a variable assignment value or as a file name.
However, when used as a command argument, \fB"$*"\fR is equivalent to
\fB"$1\fId\fR$2\fId\fR..."\fR, where \fId\fR is the first character of the IFS
variable, whereas \fB"$@"\fR is equivalent to \fB"$1" "$2" ....\fR Inside grave
quote marks (\fB``\fR), \fB\\fR quotes the characters \fB\e\fR, \fB`\fR, and
\fB$\fR. If the grave quotes occur within double quotes, then \fB\e\fR also
quotes the character \fB"\fR.
.sp
.LP
The special meaning of reserved words or aliases can be removed by quoting any
character of the reserved word. The recognition of function names or built-in
command names cannot be altered by quoting them.
.SS "Arithmetic Evaluation"
.sp
.LP
The shell performs arithmetic evaluation for arithmetic substitution, to
evaluate an arithmetic command, to evaluate an indexed array subscript, and to
evaluate arguments to the built-in commands \fBshift\fR and \fBlet\fR.
Arithmetic evaluation is also performed on argument operands of the built-in
command printf that correspond to numeric format specifiers in the format
operand. See \fBprintf\fR(1). Evaluations are performed using double precision
floating point arithmetic or long double precision floating point for systems
that provide this data type. Floating point constants follow the \fBANSI-C\fR
programming language floating point conventions. Integer constants follow the
\fBANSI-C\fR programming language integer constant conventions although only
single byte character constants are recognized and character casts are not
recognized. Constants can be of the form \fB[\fR\fIbase#\fR\fB]\fR\fIn\fR where
\fIbase\fR is a decimal number between two and sixty-four representing the
arithmetic base and \fIn\fR is a number in that base. The digits greater than
\fB9\fR are represented by the lower case letters, the upper case letters,
\fB@\fR, and \fB_\fR respectively. For bases less than or equal to \fB36\fR,
upper and lower case characters can be used interchangeably.
.sp
.LP
An arithmetic expression uses the same syntax, precedence, and associativity of
expression as the C language. All the C language operators that apply to
floating point quantities can be used. In addition, the operator \fB**\fR can
be used for exponentiation. It has higher precedence than multiplication and is
left associative. When the value of an arithmetic variable or subexpression can
be represented as a long integer, all C language integer arithmetic operations
can be performed. Variables can be referenced by name within an arithmetic
expression without using the parameter expansion syntax. When a variable is
referenced, its value is evaluated as an arithmetic expression.
.sp
.LP
Any of the following math library functions that are in the C math library can
be used within an arithmetic expression:
.sp
.in +2
.nf
abs acos acosh asin asinh atan atan2 atanh cbrt
copysign cos cosh erf erfc exp exp2 expm1 fabs
fdim finite floor fma fmax fmod hypot ilogb
int isinf isnan lgamma log log2 logb
nearbyint nextafter nexttoward pow remainder
rint round sin sinh sqrt tan tanh tgamma trunc
.fi
.in -2
.sp

.sp
.LP
An internal representation of a \fIvariable\fR as a double precision floating
point can be specified with the \fB-E [\fR\fIn\fR\fB]\fR or \fB-F
[\fR\fIn\fR\fB]\fR option of the \fBtypeset\fR special built-in command. The
\fB-E\fR option causes the expansion of the value to be represented using
scientific notation when it is expanded. The optional option argument \fIn\fR
defines the number of significant figures. The \fB-F\fR option causes the
expansion to be represented as a floating decimal number when it is expanded.
The optional option argument \fIn\fR defines the number of places after the
decimal point in this case.
.sp
.LP
An internal integer representation of a \fIvariable\fR can be specified with
the \fB-i\fR \fB[\fR\fIn\fR\fB]\fR option of the \fBtypeset\fR special built-in
command. The optional option argument \fIn\fR specifies an arithmetic base to
be used when expanding the variable. If you do not specify an arithmetic base,
base 10 is used.
.sp
.LP
Arithmetic evaluation is performed on the value of each assignment to a
variable with the \fB-E\fR, \fB-F\fR, or \fB-i\fR option. Assigning a floating
point number to a variable whose type is an integer causes the fractional part
to be truncated.
.SS "Prompting"
.sp
.LP
When used interactively, the shell prompts with the value of \fBPS1\fR after
expanding it for parameter expansion, command substitution, and arithmetic
substitution, before reading a command. In addition, each single \fB!\fR in the
prompt is replaced by the command number. A \fB!!\fR is required to place
\fB!\fR in the prompt. If at any time a NEWLINE is typed and further input is
needed to complete a command, then the secondary prompt, that is, the value of
\fBPS2\fR, is issued.
.SS "Conditional Expressions"
.sp
.LP
A \fBconditional expression\fR is used with the \fB[[\fR compound command to
test attributes of files and to compare strings. Field splitting and file name
generation are not performed on the words between \fB[[\fR and \fB]]\fR.
.sp
.LP
Each expression can be constructed from one or more of the following unary or
binary expressions:
.sp
.ne 2
.na
\fB\fB-a\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists.
.sp
This option is the same as \fB-e\fR. This option is obsolete.
.RE

.sp
.ne 2
.na
\fB\fB-b\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is a block special file.
.RE

.sp
.ne 2
.na
\fB\fB-c\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is a character special file.
.RE

.sp
.ne 2
.na
\fB\fB-d\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is a directory.
.RE

.sp
.ne 2
.na
\fB\fB-e\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists.
.RE

.sp
.ne 2
.na
\fB\fB-f\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is an ordinary file.
.RE

.sp
.ne 2
.na
\fB\fB-g\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and it has its \fBsetgid\fR bit set.
.RE

.sp
.ne 2
.na
\fB\fB-G\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and its group matches the effective group id of this
process.
.RE

.sp
.ne 2
.na
\fB\fB-h\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is a symbolic link.
.RE

.sp
.ne 2
.na
\fB\fB-k\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and it has its sticky bit set.
.RE

.sp
.ne 2
.na
\fB\fB-L\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is a symbolic link.
.RE

.sp
.ne 2
.na
\fB\fB-n\fR \fIstring\fR\fR
.ad
.RS 21n
True, if length of \fIstring\fR is \fBnon-zero\fR.
.RE

.sp
.ne 2
.na
\fB\fB-N\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and the modification time is greater than the last
access time.
.RE

.sp
.ne 2
.na
\fB\fB-o\fR \fIoption\fR\fR
.ad
.RS 21n
True, if option named \fIoption\fR is on.
.RE

.sp
.ne 2
.na
\fB\fB-o\fR \fI?option\fR\fR
.ad
.RS 21n
True, if option named \fIoption\fR is a valid option name.
.RE

.sp
.ne 2
.na
\fB\fB-O\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is owned by the effective user id of this
process.
.RE

.sp
.ne 2
.na
\fB\fB-p\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is a \fBFIFO\fR special file or a pipe.
.RE

.sp
.ne 2
.na
\fB\fB-r\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is readable by current process.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and has size greater than zero.
.RE

.sp
.ne 2
.na
\fB\fB-S\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is a socket.
.RE

.sp
.ne 2
.na
\fB\fB-t\fR \fIfildes\fR\fR
.ad
.RS 21n
True, if file descriptor number \fIfildes\fR is open and associated with a
terminal device.
.RE

.sp
.ne 2
.na
\fB\fB-u\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and it has its \fBsetuid\fR bit set.
.RE

.sp
.ne 2
.na
\fB\fB-w\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is writable by current process.
.RE

.sp
.ne 2
.na
\fB\fB-x\fR \fIfile\fR\fR
.ad
.RS 21n
True, if \fIfile\fR exists and is executable by current process. If \fIfile\fR
exists and is a directory, then true if the current process has permission to
search in the directory.
.RE

.sp
.ne 2
.na
\fB\fB-z\fR \fIstring\fR\fR
.ad
.RS 21n
True, if length of \fIstring\fR is zero.
.RE

.sp
.ne 2
.na
\fB\fIfile1\fR \fB-ef\fR \fIfile2\fR\fR
.ad
.RS 21n
True, if \fIfile1\fR and \fIfile2\fR exist and refer to the same file.
.RE

.sp
.ne 2
.na
\fB\fIfile1\fR \fB-nt\fR \fIfile2\fR\fR
.ad
.RS 21n
True, if \fIfile1\fR exists and \fIfile2\fR does not, or \fIfile1\fR is newer
than \fIfile2\fR.
.RE

.sp
.ne 2
.na
\fB\fIfile1\fR \fB-ot\fR \fIfile2\fR\fR
.ad
.RS 21n
True, if \fIfile2\fR exists and \fIfile1\fR does not, or \fIfile1\fR is older
than \fIfile2\fR.
.RE

.sp
.ne 2
.na
\fB\fIstring\fR\fR
.ad
.RS 21n
True, if \fIstring\fR is not null.
.RE

.sp
.ne 2
.na
\fB\fIstring\fR \fB==\fR \fIpattern\fR\fR
.ad
.RS 21n
True, if \fIstring\fR matches \fIpattern\fR. Any part of \fIpattern\fR can be
quoted to cause it to be matched as a string. With a successful match to
\fIpattern\fR, the \fB\&.sh.match\fR array variable contains the match and
sub-pattern matches.
.RE

.sp
.ne 2
.na
\fB\fIstring\fR \fB=\fR \fIpattern\fR\fR
.ad
.RS 21n
Same as \fB==\fR, but is obsolete.
.RE

.sp
.ne 2
.na
\fB\fIstring\fR \fB!=\fR \fIpattern\fR\fR
.ad
.RS 21n
True, if \fIstring\fR does not match \fIpattern\fR. When the \fIstring\fR
matches the \fIpattern\fR the \fB\&.sh.match\fR array variable contains the
match and sub-pattern matches.
.RE

.sp
.ne 2
.na
\fB\fIstring\fR \fB=~\fR \fIere\fR\fR
.ad
.RS 21n
True if \fIstring\fR matches the pattern \fB~(E)\fR\fIere\fR where \fIere\fR is
an extended regular expression.
.RE

.sp
.ne 2
.na
\fB\fIstring1\fR \fB<\fR \fIstring2\fR\fR
.ad
.RS 21n
True, if \fIstring1\fR comes before \fIstring2\fR based on \fBASCII\fR value of
their characters.
.RE

.sp
.ne 2
.na
\fB\fIstring1\fR \fB>\fR \fIstring2\fR\fR
.ad
.RS 21n
True, if \fIstring1\fR comes after \fIstring2\fR based on \fBASCII\fR value of
their characters.
.RE

.sp
.LP
In each of the following expressions, if \fIfile\fR is of the form
\fB/dev/fd/\fR\fIn\fR, where \fIn\fR is an integer, the test is applied to the
open file whose descriptor number is \fIn\fR. The following obsolete arithmetic
comparisons are supported:
.sp
.ne 2
.na
\fB\fIexp1\fR \fB-eq\fR \fIexp2\fR\fR
.ad
.RS 17n
True, if \fIexp1\fR is equal to \fIexp2\fR.
.RE

.sp
.ne 2
.na
\fB\fIexp1\fR \fB-ge\fR \fIexp2\fR\fR
.ad
.RS 17n
True, if \fIexp1\fR is greater than or equal to \fIexp2\fR.
.RE

.sp
.ne 2
.na
\fB\fIexp1\fR \fB-gt\fR \fIexp2\fR\fR
.ad
.RS 17n
True, if \fIexp1\fR is greater than \fIexp2\fR.
.RE

.sp
.ne 2
.na
\fB\fIexp1\fR \fB-le\fR \fIexp2\fR\fR
.ad
.RS 17n
True, if \fIexp1\fR is less than or equal to \fIexp2\fR.
.RE

.sp
.ne 2
.na
\fB\fIexp1\fR \fB-lt\fR \fIexp2\fR\fR
.ad
.RS 17n
True, if \fIexp1\fR is less than \fIexp2\fR.
.RE

.sp
.ne 2
.na
\fB\fIexp1\fR \fB-ne\fR \fIexp2\fR\fR
.ad
.RS 17n
True, if \fIexp1\fR is not equal to \fIexp2\fR.
.RE

.sp
.LP
A compound expression can be constructed from these primitives by using any of
the following, listed in decreasing order of precedence:
.sp
.ne 2
.na
\fB\fB(\fR\fIexpression\fR\fB)\fR\fR
.ad
.RS 30n
True, if \fIexpression\fR is true. Used to group expressions.
.RE

.sp
.ne 2
.na
\fB\fB!\fR \fIexpression\fR\fR
.ad
.RS 30n
True, if \fIexpression\fR is false.
.RE

.sp
.ne 2
.na
\fB\fIexpression1\fR \fB&&\fR \fIexpression2\fR\fR
.ad
.RS 30n
True, if \fIexpression1\fR and \fIexpression2\fR are both true.
.RE

.sp
.ne 2
.na
\fB\fIexpression1\fR \fB||\fR \fIexpression2\fR\fR
.ad
.RS 30n
True, if either \fIexpression1\fR or \fIexpression2\fR is true.
.RE

.SS "Input and Output"
.sp
.LP
Before a command is executed, its input and output can be redirected using a
special notation interpreted by the shell. The following can appear anywhere in
a simple command or can precede or follow a command and are \fBnot\fR passed on
to the invoked command. Command substitution, parameter expansion, and
arithmetic substitution occur before \fIword\fR or \fIdigit\fR is used except
as noted in this section. File name generation occurs only if the shell is
interactive and the pattern matches a single file. Field splitting is not
performed.
.sp
.LP
In each of the following redirections, if \fIfile\fR is of the form
\fB/dev/sctp/\fR\fIhost\fR\fB/\fR\fIport\fR,
\fB/dev/tcp/\fR\fIhost\fR\fB/\fR\fIport\fR, or
\fB/dev/udp/\fR\fIhost\fR\fB/\fR\fIport\fR, where \fIhost\fR is a hostname or
host address, and \fIport\fR is a service specified by name or an integer port
number, then the redirection attempts to make a \fBtcp\fR, \fBsctp\fR or
\fBudp\fR connection to the corresponding socket.
.sp
.LP
No intervening space is allowed between the characters of redirection
operators.
.sp
.ne 2
.na
\fB\fB<\fR\fIword\fR\fR
.ad
.RS 14n
Use file \fIword\fR as standard input (file descriptor 0).
.RE

.sp
.ne 2
.na
\fB\fB>\fR\fIword\fR\fR
.ad
.RS 14n
Use file \fIword\fR as standard output (file descriptor 1). If the file does
not exist then it is created. If the file exists, and the \fBnoclobber\fR
option is on, this causes an error. Otherwise, it is truncated to zero length.
.RE

.sp
.ne 2
.na
\fB\fB>|\fR\fIword\fR\fR
.ad
.RS 14n
Same as \fB>\fR, except that it overrides the \fBnoclobber\fR option.
.RE

.sp
.ne 2
.na
\fB\fB>>\fR\fIword\fR\fR
.ad
.RS 14n
Use file \fIword\fR as standard output. If the file exists, then output is
appended to it (by first seeking to the end-of-file). Otherwise, the file is
created.
.RE

.sp
.ne 2
.na
\fB\fB<>\fR\fIword\fR\fR
.ad
.RS 14n
Open file \fIword\fR for reading and writing as standard input.
.RE

.sp
.ne 2
.na
\fB\fB<<\fR\fB[-]\fR\fIword\fR\fR
.ad
.RS 14n
The shell input is read up to a line that is the same as \fIword\fR after any
quoting has been removed, or to an end-of-file. No parameter substitution,
command substitution, arithmetic substitution or file name generation is
performed on \fIword\fR. The resulting document, called a \fBhere-document\fR,
becomes the standard input. If any character of \fIword\fR is quoted, then no
interpretation is placed upon the characters of the document. Otherwise,
parameter expansion, command substitution, and arithmetic substitution occur,
\fB\e\fRNEWLINE is ignored, and \fB\e\fR must be used to quote the characters
\fB\e\fR, \fB$\fR, \fB`\fR\&. If \fB-\fR is appended to \fB<<\fR, then all
leading tabs are stripped from \fIword\fR and from the document. If \fB#\fR is
appended to \fB<<\fR, then leading SPACEs and TABs are stripped off the first
line of the document and up to an equivalent indentation is stripped from the
remaining lines and from \fIword\fR. A tab stop is assumed to occur at every 8
columns for the purposes of determining the indentation.
.RE

.sp
.ne 2
.na
\fB\fB<<<\fR\fIword\fR\fR
.ad
.RS 14n
A short form of here document in which \fIword\fR becomes the contents of the
here-document after any parameter expansion, command substitution, and
arithmetic substitution occur.
.RE

.sp
.ne 2
.na
\fB\fB<&\fR\fIdigit\fR\fR
.ad
.RS 14n
The standard input is duplicated from file descriptor \fIdigit\fR, and
similarly for the standard output using \fB>&\fR\fIdigit\fR. See \fBdup\fR(2).
.RE

.sp
.ne 2
.na
\fB\fB<&\fR\fIdigit\fR\fB-\fR\fR
.ad
.RS 14n
The file descriptor specified by \fIdigit\fR is moved to standard input.
Similarly for the standard output using \fB>&\fR\fIdigit\fR\fB-\fR.
.RE

.sp
.ne 2
.na
\fB\fB<&-\fR\fR
.ad
.RS 14n
The standard input is closed. Similarly for the standard output using
\fB>&-\fR.
.RE

.sp
.ne 2
.na
\fB\fB<&p\fR\fR
.ad
.RS 14n
The input from the co-process is moved to standard input.
.RE

.sp
.ne 2
.na
\fB\fB>&p\fR\fR
.ad
.RS 14n
The output to the co-process is moved to standard output.
.RE

.sp
.ne 2
.na
\fB\fB<#((\fR\fIexpr\fR\fB))\fR\fR
.ad
.RS 14n
Evaluate arithmetic expression \fIexpr\fR and position file descriptor 0 to the
resulting value bytes from the start of the file. The variables \fBCUR\fR and
\fBEOF\fR evaluate to the current offset and end-of-file offset respectively
when evaluating \fIexpr\fR.
.RE

.sp
.ne 2
.na
\fB\fB>#((\fR\fIexpr\fR\fB))\fR\fR
.ad
.RS 14n
The same as \fB<#\fR except applies to file descriptor 1.
.RE

.sp
.ne 2
.na
\fB\fB<#\fR\fIpattern\fR\fR
.ad
.RS 14n
Seek forward to the beginning of the next line containing pattern.
.RE

.sp
.ne 2
.na
\fB\fB<##\fR\fIpattern\fR\fR
.ad
.RS 14n
The same as \fB<#\fR, except that the portion of the file that is skipped is
copied to standard output.
.RE

.sp
.LP
If one of the redirection operators is preceded by a digit, with no intervening
space, then the file descriptor number referred to is that specified by the
digit (instead of the default 0 or 1). If one of the redirection operators
other than \fB>&-\fR and the \fB>#\fR and \fB<#\fR forms, is preceded by
\fB{\fR\fIvarname\fR\fB}\fR with no intervening space, then a file descriptor
number \fB> 10\fR is selected by the shell and stored in the variable
\fIvarname\fR. If \fB>&-\fR or the any of the \fB>#\fR and \fB<#\fR forms is
preceded by \fB{\fR\fIvarname\fR\fB}\fR the value of \fIvarname\fR defines the
file descriptor to close or position. For example:
.sp
.in +2
.nf
\&... 2>&1
.fi
.in -2
.sp

.sp
.LP
means file descriptor 2 is to be opened for writing as a duplicate of file
descriptor 1 and
.sp
.in +2
.nf
exec [\fIn\fR]<\fIfile\fR
.fi
.in -2
.sp

.sp
.LP
means open \fIfile\fR for reading and store the file descriptor number in
variable \fIn\fR. The order in which redirections are specified is significant.
The shell evaluates each redirection in terms of the (\fIfile_descriptor\fR,
\fIfile\fR) association at the time of evaluation. For example:
.sp
.in +2
.nf
\&... 1>\fIfname\fR 2>&1
.fi
.in -2
.sp

.sp
.LP
first associates file descriptor 1 with file \fIfname\fR. It then associates
file descriptor 2 with the file associated with file descriptor 1, that is,
\fIfname\fR. If the order of redirections were reversed, file descriptor 2
would be associated with the terminal (assuming file descriptor 1 had been) and
then file descriptor 1 would be associated with file \fIfname\fR. If a command
is followed by \fB&\fR and job control is not active, the default standard
input for the command is the empty file \fB/dev/null\fR. Otherwise, the
environment for the execution of a command contains the file descriptors of the
invoking shell as modified by input and output specifications.
.SS "Environment"
.sp
.LP
The \fIenvironment\fR is a list of name-value pairs that is passed to an
executed program in the same way as a normal argument list. See
\fBenviron\fR(5).
.sp
.LP
The names must be \fIidentifiers\fR and the values are character strings. The
shell interacts with the environment in several ways. On invocation, the shell
scans the environment and creates a variable for each name found, giving it the
corresponding value and attributes and marking it \fBexport\fR. Executed
commands inherit the environment. If the user modifies the values of these
variables or creates new ones, using the \fBexport\fR or \fBtypeset\fR \fB-x\fR
commands, they become part of the environment. The environment seen by any
executed command is thus composed of any name-value pairs originally inherited
by the shell, whose values can be modified by the current shell, plus any
additions which must be noted in \fBexport\fR or \fBtypeset\fR \fB-x\fR
commands. The environment for any simple-command or function can be augmented
by prefixing it with one or more variable assignments. A variable assignment
argument is a word of the form \fIidentifier\fR\fB=\fR\fIvalue\fR. Thus:
.sp
.in +2
.nf
TERM=450 cmd args
.fi
.in -2
.sp

.sp
.LP
and
.sp
.in +2
.nf
(export TERM; TERM=450; cmd args)
.fi
.in -2
.sp

.sp
.LP
are equivalent (as far as the execution of \fIcmd\fR is concerned except for
special built-in commands listed in the \fBBuilt-Ins\fR section, those that are
preceded with a dagger. If the obsolete \fB-k\fR option is set, all variable
assignment arguments are placed in the environment, even if they occur after
the command name.
.sp
.LP
The following example first prints \fBa=b c\fR and then \fBc\fR:
.sp
.in +2
.nf
echo a=b c
set -k
echo a=b c
.fi
.in -2
.sp

.sp
.LP
This feature is intended for use with scripts written for early versions of the
shell and its use in new scripts is strongly discouraged.
.SS "Functions"
.sp
.LP
For historical reasons, there are two ways to define functions, the
\fBname()\fR syntax and the \fBfunction\fR \fBname\fR syntax. These are
described in the \fBCommands\fR section of this manual page.
.sp
.LP
Shell functions are read in and stored internally. Alias names are resolved
when the function is read. Functions are executed like commands with the
arguments passed as positional parameters. See the \fBExecution\fR section of
this manual page for details.
.sp
.LP
Functions defined by the \fBfunction\fR \fBname\fR syntax and called by name
execute in the same process as the caller and share all files and present
working directory with the caller. Traps caught by the caller are reset to
their default action inside the function. A trap condition that is not caught
or ignored by the function causes the function to terminate and the condition
to be passed on to the caller. A trap on \fBEXIT\fR set inside a function is
executed in the environment of the caller after the function completes.
Ordinarily, variables are shared between the calling program and the function.
However, the \fBtypeset\fR special built-in command used within a function
defines local variables whose scope includes the current function. They can be
passed to functions that they call in the variable assignment list that
precedes the call or as arguments passed as name references. Errors within
functions return control to the caller.
.sp
.LP
Functions defined with the \fBname()\fR syntax and functions defined with the
\fBfunction\fR \fBname\fR syntax that are invoked with the \fB\&.\fR special
built-in are executed in the caller's environment and share all variables and
traps with the caller. Errors within these function executions cause the script
that contains them to abort.
.sp
.LP
The special built-in command \fBreturn\fR is used to return from function
calls.
.sp
.LP
Function names can be listed with the \fB-f\fR or \fB+f\fR option of the
\fBtypeset\fR special built-in command. The text of functions, when available,
is also listed with \fB-f\fR. Functions can be undefined with the \fB-f\fR
option of the \fBunset\fR special built-in command.
.sp
.LP
Ordinarily, functions are unset when the shell executes a shell script.
Functions that need to be defined across separate invocations of the shell
should be placed in a directory and the \fBFPATH\fR variable should contain the
name of this directory. They can also be specified in the \fBENV\fR file.
.SS "Discipline Functions"
.sp
.LP
Each variable can have zero or more discipline functions associated with it.
The shell initially understands the discipline names \fBget\fR, \fBset\fR,
\fBappend\fR, and \fBunset\fR but on most systems others can be added at run
time via the C programming interface extension provided by the \fBbuiltin\fR
built-in utility. If the \fBget\fR discipline is defined for a variable, it is
invoked whenever the specified variable is referenced. If the variable
\fB\&.sh.value\fR is assigned a value inside the discipline function, the
referenced variable is evaluated to this value instead. If the \fBset\fR
discipline is defined for a variable, it is invoked whenever the specified
variable is assigned a value. If the \fBappend\fR discipline is defined for a
variable, it is invoked whenever a value is appended to the specified variable.
The variable \fB\&.sh.value\fR is specified the value of the variable before
invoking the discipline, and the variable is assigned the value of
\fB\&.sh.value\fR after the discipline completes. If .\fBsh.value\fR is
\fBunset\fR inside the discipline, then that value is unchanged. If the
\fBunset\fR discipline is defined for a variable, it is invoked whenever the
specified variable is unset. The variable is not unset unless it is unset
explicitly from within this discipline function.
.sp
.LP
The variable \fB\&.sh.name\fR contains the name of the variable for which the
discipline function is called, \fB\&.sh.subscript\fR is the subscript of the
variable, and \fB\&.sh.value\fR contains the value being assigned inside the
\fBset\fR discipline function. For the \fBset\fR discipline, changing
\fB\&.sh.value\fR changes the value that gets assigned.
.SS "Jobs"
.sp
.LP
If the monitor option of the \fBset\fR command is turned on, an interactive
shell associates a job with each pipeline. It keeps a table of current jobs,
printed by the \fBjobs\fR command, and assigns them small integer numbers. When
a job is started asynchronously with \fB&\fR, the shell prints a line which
looks like:
.sp
.in +2
.nf
[1] 1234
.fi
.in -2
.sp

.sp
.LP
indicating that the job which was started asynchronously was job number 1 and
had one (top-level) process, whose process id was \fB1234\fR.
.sp
.LP
If you are running a job and wish to stop it, CTRL-z sends a \fBSTOP\fR signal
to the current job. The shell normally displays a message that the job has been
stopped, and displays another prompt. You can then manipulate the state of this
job, putting it in the background with the \fBbg\fR command, or run some other
commands and then eventually bring the job back into the foreground with the
foreground command \fBfg\fR. A CTRL-z takes effect immediately and is like an
interrupt in that pending output and unread input are discarded when it is
typed.
.sp
.LP
A job being run in the background stops if it tries to read from the terminal.
Background jobs are normally allowed to produce output, but this can be
disabled by giving the command \fBsttytostop\fR. If you set this \fBtty\fR
option, then background jobs stop when they try to produce output like they do
when they try to read input.
.sp
.LP
There are several ways to refer to jobs in the shell. A job can be referred to
by the process id of any process of the job or by one of the following:
.sp
.ne 2
.na
\fB\fB%\fR\fInumber\fR\fR
.ad
.RS 12n
The job with the specified number.
.RE

.sp
.ne 2
.na
\fB\fB%\fR\fIstring\fR\fR
.ad
.RS 12n
Any job whose command line begins with \fIstring\fR.
.RE

.sp
.ne 2
.na
\fB\fB%?\fR\fIstring\fR\fR
.ad
.RS 12n
Any job whose command line contains \fIstring\fR.
.RE

.sp
.ne 2
.na
\fB\fB%%\fR\fR
.ad
.RS 12n
Current job.
.RE

.sp
.ne 2
.na
\fB\fB%+\fR\fR
.ad
.RS 12n
Equivalent to \fB%%\fR.
.RE

.sp
.ne 2
.na
\fB\fB%-\fR\fR
.ad
.RS 12n
Previous job.
.RE

.sp
.LP
The shell learns immediately whenever a process changes state. It normally
informs you whenever a job becomes blocked so that no further progress is
possible, but only just before it prints a prompt. This is done so that it does
not otherwise disturb your work. The notify option of the \fBset\fR command
causes the shell to print these job change messages as soon as they occur.
.sp
.LP
When the \fBmonitor\fR option is on, each background job that completes
triggers any trap set for \fBCHLD\fR.
.sp
.LP
When you try to leave the shell while jobs are running or stopped, you are
warned that \fBYou have stopped(running) jobs.\fR You can use the \fBjobs\fR
command to see what they are. If you immediately try to exit again, the shell
does not warn you a second time, and the stopped jobs are terminated. When a
login shell receives a \fBHUP\fR signal, it sends a \fBHUP\fR signal to each
job that has not been disowned with the \fBdisown\fR built-in command.
.SS "Signals"
.sp
.LP
The \fBINT\fR and \fBQUIT\fR signals for an invoked command are ignored if the
command is followed by \fB&\fR and the \fBmonitor\fR option is not active.
Otherwise, signals have the values inherited by the shell from its parent. See
the \fBtrap\fR built-in command.
.SS "Execution"
.sp
.LP
Each time a command is read, the substitutions are carried out. If the command
name matches one of the ones in the \fBSpecial Built-in Commands\fR section of
this manual page, it is executed within the current shell process. Next, the
command name is checked to see if it matches a user defined function. If it
does, the positional parameters are saved and then reset to the arguments of
the function call. A function is also executed in the current shell process.
When the function completes or issues a return, the positional parameter list
is restored. For functions defined with the \fBfunction\fR \fBname\fR syntax,
any trap set on \fBEXIT\fR within the function is executed. The exit value of a
function is the value of the last command executed. If a command name is not a
special built-in command or a user defined function, but it is one of the
built-in commands, it is executed in the current shell process.
.sp
.LP
The shell variable \fBPATH\fR defines the search path for the directory
containing the command. Alternative directory names are separated by a colon
(\fB:\fR). The default path is \fB/bin:/usr/bin:\fR, specifying \fB/bin\fR,
\fB/usr/bin\fR, and the current directory in that order. The current directory
can be specified by two or more adjacent colons, or by a colon at the beginning
or end of the path list. If the command name contains a slash (\fB/\fR), the
search path is not used. Otherwise, each directory in the path is searched for
an executable file of the specified name that is not a directory. If found, and
if the shell determines that there is a built-in version of a command
corresponding to a specified pathname, this built-in is invoked in the current
process. If found, and this directory is also contained in the value of the
\fBFPATH\fR variable, then this file is loaded into the current shell
environment as if it were the argument to the . command except that only preset
aliases are expanded, and a function of the specified name is executed as
described in this manual page. If not found, and the file \fB\&.paths\fR is
found, and this file contains a line of the form \fBFPATH=\fR\fIpath\fR where
\fIpath\fR is an existing directory, and this directory contains a file of the
specified name, then this file is loaded into the current shell environment as
if it were the argument to the \fB\&. special\fR built-in command and a
function of the specified name is executed. Otherwise, if found, a process is
created and an attempt is made to execute the command using \fBexec\fR(2).
.sp
.LP
When an executable is found, the directory where it is found in is searched for
a file named \fB\&.paths\fR. If this file is found and it contains a line of
the form \fBBUILTIN_LIB=\fR\fIvalue\fR, the library named by \fIvalue\fR is
searched for as if it were an option argument to \fBbuiltin -f\fR, and if it
contains a built-in of the specified name this is executed instead of a command
by this name. Otherwise, if this file is found and it contains a line of the
form \fIname\fR\fB=\fR\fIvalue\fR in the first or second line, then the
environment variable \fIname\fR is modified by prepending the directory
specified by \fIvalue\fR to the directory list. If \fIvalue\fR is not an
absolute directory, then it specifies a directory relative to the directory
that the executable was found. If the environment variable \fIname\fR does not
already exist it is added to the environment list for the specified command.
.sp
.LP
If the file has execute permission but is not an \fBa.out\fR file, it is
assumed to be a file containing shell commands. A separate shell is spawned to
read it. All non-exported variables are removed in this case. If the shell
command file doesn't have read permission, and/or if the \fBsetuid\fR and
\fBsetgid\fR bits are set on the file, then the shell executes an agent whose
job it is to set up the permissions and execute the shell with the shell
command file passed down as an open file. A parenthesized command is executed
in a sub-shell without removing non-exported variables.
.SS "Command Re-entry"
.sp
.LP
The text of the last \fBHISTSIZE\fR (default 512) commands entered from a
terminal device is saved in a history file. The file \fB$HOME/.sh_history\fR is
used if the \fBHISTFILE\fR variable is not set or if the file it names is not
writable. A shell can access the commands of all interactive shells which use
the same named \fBHISTFILE\fR. The built-in command \fBhist\fR is used to list
or edit a portion of this file. The portion of the file to be edited or listed
can be selected by number or by giving the first character or characters of the
command. A single command or range of commands can be specified. If you do not
specify an editor program as an argument to \fBhist\fR then the value of the
variable \fBHISTEDIT\fR is used. If \fBHISTEDIT\fR is unset, the obsolete
variable \fBFCEDIT\fR is used. If \fBFCEDIT\fR is not defined, then
\fB/bin/ed\fR is used. The edited commands are printed and executed again upon
leaving the editor unless you quit without writing. The \fB-s\fR option (and in
obsolete versions, the editor name \fB-\fR) is used to skip the editing phase
and to re-execute the command. In this case a substitution parameter of the
form \fIold\fR\fB=\fR\fInew\fRcan be used to modify the command before
execution. For example, with the preset alias \fBr\fR, which is aliased to
\fB\&'hist -s'\fR, typing \fB`r bad=good c'\fR re-executes the most recent
command which starts with the letter \fBc\fR, replacing the first occurrence of
the string bad with the string good.
.SS "Inline Editing Options"
.sp
.LP
Normally, each command line entered from a terminal device is simply typed
followed by a NEWLINE (RETURN or LINE FEED). If either the \fBemacs\fR,
\fBgmacs\fR, or \fBvi\fR option is active, the user can edit the command line.
To be in either of these edit modes set the corresponding option. An editing
option is automatically selected each time the \fBVISUAL\fR or \fBEDITOR\fR
variable is assigned a value ending in either of these option names.
.sp
.LP
The editing features require that the user's terminal accept RETURN as carriage
return without line feed and that a SPACE must overwrite the current character
on the screen.
.sp
.LP
Unless the \fBmultiline\fR option is on, the editing modes implement a concept
where the user is looking through a window at the current line. The window
width is the value of \fBCOLUMNS\fR if it is defined, otherwise \fB80\fR. If
the window width is too small to display the prompt and leave at least 8
columns to enter input, the prompt is truncated from the left. If the line is
longer than the window width minus two, a mark is displayed at the end of the
window to notify the user. As the cursor moves and reaches the window
boundaries the window is centered about the cursor. The mark is a \fB>\fR
(\fB<, *\fR) if the line extends on the right , left, or both sides of the
window.
.sp
.LP
The search commands in each edit mode provide access to the history file. Only
strings are matched, not patterns, although a leading \fB^\fR in the string
restricts the match to begin at the first character in the line.
.sp
.LP
Each of the edit modes has an operation to list the files or commands that
match a partially entered word. When applied to the first word on the line, or
the first word after a \fB;\fR, \fB|\fR, \fB&\fR, or \fB(\fR, and the word does
not begin with \fB~\fR or contain a \fB/\fR, the list of aliases, functions,
and executable commands defined by the \fBPATH\fR variable that could match the
partial word is displayed. Otherwise, the list of files that match the
specified word is displayed. If the partially entered word does not contain any
file expansion characters, a \fB*\fR is appended before generating these lists.
After displaying the generated list, the input line is redrawn. These
operations are called command name listing and file name listing, respectively.
There are additional operations, referred to as command name completion and
file name completion, which compute the list of matching commands or files, but
instead of printing the list, replace the current word with a complete or
partial match. For file name completion, if the match is unique, a \fB/\fR is
appended if the file is a directory and a space is appended if the file is not
a directory. Otherwise, the longest common prefix for all the matching files
replaces the word. For command name completion, only the portion of the file
names after the last \fB/\fR are used to find the longest command prefix. If
only a single name matches this prefix, then the word is replaced with the
command name followed by a space. When using a \fBTAB\fR for completion that
does not yield a unique match, a subsequent TAB provides a numbered list of
matching alternatives. A specific selection can be made by entering the
selection number followed by a TAB.
.SS "Key Bindings"
.sp
.LP
The \fBKEYBD\fR trap can be used to intercept keys as they are typed and change
the characters that are actually seen by the shell. This trap is executed after
each character (or sequence of characters when the first character is ESC) is
entered while reading from a terminal.
.sp
.LP
The variable \fB\&.sh.edchar\fR contains the character or character sequence
which generated the trap. Changing the value of \fB\&.sh.edchar\fR in the trap
action causes the shell to behave as if the new value were entered from the
keyboard rather than the original value. The variable \fB\&.sh.edcol\fR is set
to the input column number of the cursor at the time of the input. The variable
\fB\&.sh.edmode\fR is set to \fBESC\fR when in \fBvi\fR insert mode and is null
otherwise. By prepending \fB${.sh.editmode}\fR to a value assigned to
\fB\&.sh.edchar\fR it causes the shell to change to control mode if it is not
already in this mode.
.sp
.LP
This trap is not invoked for characters entered as arguments to editing
directives, or while reading input for a character search.
.SS "\fBemacs\fR Editing Mode"
.sp
.LP
This mode is entered by enabling either the \fBemacs\fR or \fBgmacs\fR option.
The only difference between these two modes is the way they handle \fB^T\fR. To
edit, the user moves the cursor to the point needing correction and then
inserts or deletes characters or words as needed. All the editing commands are
control characters or escape sequences. The notation for control characters is
caret (\fB^\fR) followed by the character.
.sp
.LP
For example, \fB^F\fR is the notation for CTRL/F. This is entered by depressing
\fBf\fR while holding down the CTRL (control) key. The SHIFT key is not
depressed. (The notation \fB^?\fR indicates the DEL (delete) key.)
.sp
.LP
The notation for escape sequences is \fBM-\fR followed by a character. For
example, \fBM-f\fR (pronounced \fBMeta f\fR) is entered by depressing ESC
(\fBASCII 033\fR) followed by \fBf\fR. \fBM-F\fR is the notation for ESC
followed by \fBF\fR.
.sp
.LP
All edit commands operate from any place on the line, not just at the
beginning. The RETURN or the LINE FEED key is not entered after edit commands
except when noted.
.sp
.ne 2
.na
\fB\fB^F\fR\fR
.ad
.RS 13n
Move the cursor forward (right) one character.
.RE

.sp
.ne 2
.na
\fB\fBM-[C\fR\fR
.ad
.RS 13n
Move the cursor forward (right) one character.
.RE

.sp
.ne 2
.na
\fB\fBM-f\fR\fR
.ad
.RS 13n
Move the cursor forward one word. The \fBemacs\fR editor's idea of a word is a
string of characters consisting of only letters, digits and underscores.
.RE

.sp
.ne 2
.na
\fB\fB^B\fR\fR
.ad
.RS 13n
Move the cursor backward (left) one character.
.RE

.sp
.ne 2
.na
\fB\fBM-[D\fR\fR
.ad
.RS 13n
Move the cursor backward (left) one character.
.RE

.sp
.ne 2
.na
\fB\fBM-b\fR\fR
.ad
.RS 13n
Move the cursor backward one word.
.RE

.sp
.ne 2
.na
\fB\fB^A\fR\fR
.ad
.RS 13n
Move the cursor to the beginning of the line.
.RE

.sp
.ne 2
.na
\fB\fBM-[H\fR\fR
.ad
.RS 13n
Move the cursor to the beginning of the line.
.RE

.sp
.ne 2
.na
\fB\fB^E\fR\fR
.ad
.RS 13n
Move the cursor to the end of the line.
.RE

.sp
.ne 2
.na
\fB\fBM-[Y\fR\fR
.ad
.RS 13n
Move the cursor to the end of line.
.RE

.sp
.ne 2
.na
\fB\fB^]\fR\fIchar\fR\fR
.ad
.RS 13n
Move the cursor forward to the character \fIchar\fR on the current line.
.RE

.sp
.ne 2
.na
\fB\fBM-^]\fR\fIchar\fR\fR
.ad
.RS 13n
Move the cursor backwards to the character \fIchar\fR on the current line.
.RE

.sp
.ne 2
.na
\fB\fB^X^X\fR\fR
.ad
.RS 13n
Interchange the cursor and the mark.
.RE

.sp
.ne 2
.na
\fB\fIerase\fR\fR
.ad
.RS 13n
Delete the previous character. The user-defined erase character is defined by
the \fBstty\fR(1) command, and is usually \fB^H\fR or \fB#\fR.
.RE

.sp
.ne 2
.na
\fB\fIlnext\fR\fR
.ad
.RS 13n
Removes the next character's editing features. The user-defined literal next
character is defined by the \fBstty\fR(1) command, or is \fB^V\fR if not
defined.
.RE

.sp
.ne 2
.na
\fB\fB^D\fR\fR
.ad
.RS 13n
Delete the current character.
.RE

.sp
.ne 2
.na
\fB\fBM-d\fR\fR
.ad
.RS 13n
Delete the current word.
.RE

.sp
.ne 2
.na
\fB\fBM-^H\fR\fR
.ad
.RS 13n
MetaBACKSPACE. Delete the previous word.
.RE

.sp
.ne 2
.na
\fB\fBM-h\fR\fR
.ad
.RS 13n
Delete the previous word.
.RE

.sp
.ne 2
.na
\fB\fBM-^?\fR\fR
.ad
.RS 13n
MetaDEL. Delete the previous word. If your interrupt character is \fB^?\fR
(DEL, the default), this command does not work.
.RE

.sp
.ne 2
.na
\fB\fB^T\fR\fR
.ad
.RS 13n
Transpose the current character with the previous character, and advance the
cursor in \fBemacs\fR mode. Transpose two previous characters in \fBgmacs\fR
mode.
.RE

.sp
.ne 2
.na
\fB\fB^C\fR\fR
.ad
.RS 13n
Capitalize the current character.
.RE

.sp
.ne 2
.na
\fB\fBM-c\fR\fR
.ad
.RS 13n
Capitalize the current word.
.RE

.sp
.ne 2
.na
\fB\fBM-l\fR\fR
.ad
.RS 13n
Change the current word to lower case.
.RE

.sp
.ne 2
.na
\fB\fB^K\fR\fR
.ad
.RS 13n
Delete from the cursor to the end of the line. If preceded by a numerical
parameter whose value is less than the current cursor position, delete from
specified position up to the cursor. If preceded by a numerical parameter whose
value is greater than the current cursor position, then delete from cursor up
to specified cursor position.
.RE

.sp
.ne 2
.na
\fB\fB^W\fR\fR
.ad
.RS 13n
Kill from the cursor to the mark.
.RE

.sp
.ne 2
.na
\fB\fBM-p\fR\fR
.ad
.RS 13n
Push the region from the cursor to the mark on the stack.
.RE

.sp
.ne 2
.na
\fB\fIkill\fR\fR
.ad
.RS 13n
Kill the entire current line. The user-defined kill character is defined by the
\fBstty\fR(1) command, usually a \fB^G\fR or \fB@\fR. If two kill characters
are entered in succession, all kill characters from then on cause a line feed.
This is useful when using paper terminals.
.RE

.sp
.ne 2
.na
\fB\fB^Y\fR\fR
.ad
.RS 13n
Restore the last item removed from line. Yank the item back to the line.
.RE

.sp
.ne 2
.na
\fB\fB^L\fR\fR
.ad
.RS 13n
Line feed and print the current line.
.RE

.sp
.ne 2
.na
\fB\fBM-^L\fR\fR
.ad
.RS 13n
Clear the screen.
.RE

.sp
.ne 2
.na
\fB\fB^@\fR\fR
.ad
.RS 13n
Null character. Set mark.
.RE

.sp
.ne 2
.na
\fB\fBM-\fR\fIspace\fR\fR
.ad
.RS 13n
MetaSPACE. Set the mark.
.RE

.sp
.ne 2
.na
\fB\fB^J\fR\fR
.ad
.RS 13n
New line. Execute the current line.
.RE

.sp
.ne 2
.na
\fB\fB^M\fR\fR
.ad
.RS 13n
Return. Execute the current line.
.RE

.sp
.ne 2
.na
\fB\fBEOF\fR\fR
.ad
.RS 13n
End-of-file character, normally \fB^D\fR, is processed as an \fBend-of-file\fR
only if the current line is null.
.RE

.sp
.ne 2
.na
\fB\fB^P\fR\fR
.ad
.RS 13n
Fetch the previous command. Each time \fB^P\fR is entered the previous command
back in time is accessed. Moves back one line when it is not on the first line
of a multi-line command.
.RE

.sp
.ne 2
.na
\fB\fBM-[A\fR\fR
.ad
.RS 13n
Equivalent to \fB^P\fR.
.RE

.sp
.ne 2
.na
\fB\fBM-<\fR\fR
.ad
.RS 13n
Fetch the least recent (oldest) history line.
.RE

.sp
.ne 2
.na
\fB\fBM->\fR\fR
.ad
.RS 13n
Fetch the most recent (youngest) history line.
.RE

.sp
.ne 2
.na
\fB\fB^N\fR\fR
.ad
.RS 13n
Fetch the next command line. Each time \fB^N\fR is entered the next command
line forward in time is accessed.
.RE

.sp
.ne 2
.na
\fB\fBM-[B\fR\fR
.ad
.RS 13n
Equivalent to \fB^N\fR.
.RE

.sp
.ne 2
.na
\fB\fB^R\fR\fIstring\fR\fR
.ad
.RS 13n
Reverse search history for a previous command line containing \fIstring\fR. If
a parameter of zero is specified, the search is forward. \fIstring\fR is
terminated by a RETURN or NEWLINE. If string is preceded by a \fB^\fR, the
matched line must begin with \fIstring\fR. If \fIstring\fR is omitted, then the
next command line containing the most recent \fIstring\fR is accessed. In this
case a parameter of zero reverses the direction of the search.
.RE

.sp
.ne 2
.na
\fB\fB^O\fR\fR
.ad
.RS 13n
Operate. Execute the current line and fetch the next line relative to current
line from the history file.
.RE

.sp
.ne 2
.na
\fB\fBM-\fR\fIdigits\fR\fR
.ad
.RS 13n
Escape. Define numeric parameter. The digits are taken as a parameter to the
next command. The commands that accept a parameter are: \fB^F\fR, \fB^B\fR,
\fBERASE\fR, \fB^C\fR, \fB^D\fR, \fB^K\fR, \fB^R\fR, \fB^P\fR, \fB^N\fR,
\fB^]\fR, \fBM-.\fR, \fBM-\fR, \fBM-^]\fR, \fBM-_\fR, \fBM-=\fR, \fBM-b\fR,
\fBM-c\fR, \fBM-d\fR, \fBM-f\fR, \fBM-h\fR, \fBM-l\fR, and \fBM-^H\fR.
.RE

.sp
.ne 2
.na
\fB\fBM-\fR\fIletter\fR\fR
.ad
.RS 13n
Soft-key. Search the alias list for an alias by the name \fIletter\fR. If an
alias of \fIletter\fR is defined, insert its value on the input queue.
\fIletter\fR must not be one of the metafunctions in this section.
.RE

.sp
.ne 2
.na
\fB\fBM-[\fR\fIletter\fR\fR
.ad
.RS 13n
Soft key. Search the alias list for an alias by the name \fIletter\fR. If an
alias of this name is defined, insert its value on the input queue. This can be
used to program function keys on many terminals.
.RE

.sp
.ne 2
.na
\fB\fBM-.\fR\fR
.ad
.RS 13n
The last word of the previous command is inserted on the line. If preceded by a
numeric parameter, the value of this parameter determines which word to insert
rather than the last word.
.RE

.sp
.ne 2
.na
\fB\fBM-_\fR\fR
.ad
.RS 13n
Same as \fBM-.\fR.
.RE

.sp
.ne 2
.na
\fB\fBM-*\fR\fR
.ad
.RS 13n
Attempt filename generation on the current word. As asterisk is appended if the
word does not match any file or contain any special pattern characters.
.RE

.sp
.ne 2
.na
\fB\fBM-\fRESC\fR
.ad
.RS 13n
Command or file name completion as described in this manual page.
.RE

.sp
.ne 2
.na
\fB\fB^I\fRTAB\fR
.ad
.RS 13n
Attempts command or file name completion as described in this manual page. If a
partial completion occurs, repeating this behaves as if \fBM-=\fR were entered.
If no match is found or entered after SPACE, a TAB is inserted.
.RE

.sp
.ne 2
.na
\fB\fBM-=\fR\fR
.ad
.RS 13n
If not preceded by a numeric parameter, generates the list of matching commands
or file names as described in this manual page. Otherwise, the word under the
cursor is replaced by the item corresponding to the value of the numeric
parameter from the most recently generated command or file list. If the cursor
is not on a word, the word is inserted instead.
.RE

.sp
.ne 2
.na
\fB\fB^U\fR\fR
.ad
.RS 13n
Multiply parameter of next command by \fB4\fR.
.RE

.sp
.ne 2
.na
\fB\fB\e\fR\fR
.ad
.RS 13n
Escape the next character. Editing characters, the user's erase, kill and
interrupt (normally \fB^?\fR) characters can be entered in a command line or in
a search string if preceded by a \fB\e\fR\&. The \fB\e\fR removes the next
character's editing features, if any.
.RE

.sp
.ne 2
.na
\fB\fBM-^V\fR\fR
.ad
.RS 13n
Display the version of the shell.
.RE

.sp
.ne 2
.na
\fB\fBM-#\fR\fR
.ad
.RS 13n
If the line does not begin with a \fB#\fR, a \fB#\fR is inserted at the
beginning of the line and after each NEWLINE, and the line is entered. This
causes a comment to be inserted in the history file. If the line begins with a
\fB#\fR, the \fB#\fR is deleted and one \fB#\fR after each NEWLINE is also
deleted.
.RE

.SS "\fBvi\fR Editing Mode"
.sp
.LP
There are two typing modes. Initially, when you enter a command you are in the
input mode. To edit, the user enters control mode by typing ESC (033) and moves
the cursor to the point needing correction and then inserts or deletes
characters or words as needed. Most control commands accept an optional repeat
\fIcount\fR prior to the command.
.sp
.LP
When in vi mode on most systems, canonical processing is initially enabled and
the command is echoed again if the speed is 1200 baud or greater and it
contains any control characters or less than one second has elapsed since the
prompt was printed. The ESC character terminates canonical processing for the
remainder of the command and the user can then modify the command line. This
scheme has the advantages of canonical processing with the type-ahead echoing
of raw mode.
.sp
.LP
If the option \fBviraw\fR is also set, the terminal is always have canonical
processing disabled. This mode is implicit for systems that do not support two
alternate end of line delimiters, and might be helpful for certain terminals.
.SS "Input Edit Commands"
.sp
.LP
By default the editor is in input mode.
.sp
.LP
The following input edit commands are supported:
.sp
.ne 2
.na
\fBERASE\fR
.ad
.RS 10n
User defined erase character as defined by the \fBstty\fR command, usually
\fB^H\fR or \fB#\fR. Delete previous character.
.RE

.sp
.ne 2
.na
\fB\fB^W\fR\fR
.ad
.RS 10n
Delete the previous blank separated word. On some systems the \fBviraw\fR
option might be required for this to work.
.RE

.sp
.ne 2
.na
\fBEOF\fR
.ad
.RS 10n
As the first character of the line causes the shell to terminate unless the
\fBignoreeof\fR option is set. Otherwise this character is ignored.
.RE

.sp
.ne 2
.na
\fB\fIlnext\fR\fR
.ad
.RS 10n
User defined literal next character as defined by the \fBstty\fR(1) or \fB^V\fR
if not defined. Removes the next character's editing features, if any. On some
systems the \fBviraw\fR option might be required for this to work.
.RE

.sp
.ne 2
.na
\fB\fB\e\fR\fR
.ad
.RS 10n
Escape the next ERASE or KILL character.
.RE

.sp
.ne 2
.na
\fB\fB^I\fR TAB\fR
.ad
.RS 10n
Attempts command or file name completion as described in this manual page and
returns to input mode. If a partial completion occurs, repeating this behaves
as if \fB=\fR were entered from control mode. If no match is found or entered
after SPACE, a TAB is inserted.
.RE

.SS "Motion Edit Commands"
.sp
.LP
The motion edit commands move the cursor.
.sp
.LP
The following motion edit commands are supported:
.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]l\fR\fR
.ad
.RS 13n
Move the cursor forward (right) one character.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB][C\fR\fR
.ad
.RS 13n
Move the cursor forward (right) one character.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]w\fR\fR
.ad
.RS 13n
Move the cursor forward one alphanumeric word.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]W\fR\fR
.ad
.RS 13n
Move the cursor to the beginning of the next word that follows a blank.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]e\fR\fR
.ad
.RS 13n
Move the cursor to the end of the word.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]E\fR\fR
.ad
.RS 13n
Move the cursor to the end of the current blank delimited word.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]h\fR\fR
.ad
.RS 13n
Move the cursor backward (left) one character.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB][D\fR\fR
.ad
.RS 13n
Move the cursor backward (left) one character.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]b\fR\fR
.ad
.RS 13n
Move the cursor backward one word.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]B\fR\fR
.ad
.RS 13n
Move the cursor to the preceding blank separated word.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]|\fR\fR
.ad
.RS 13n
Move the cursor to column \fIcount\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]f\fR\fIc\fR\fR
.ad
.RS 13n
Find the next character \fIc\fR in the current line.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]F\fR\fIc\fR\fR
.ad
.RS 13n
Find the previous character \fIc\fR in the current line.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]t\fR\fIC\fR\fR
.ad
.RS 13n
Equivalent to \fBf\fR followed by \fBh\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]T\fR\fIc\fR\fR
.ad
.RS 13n
Equivalent to \fBF\fR followed by \fBl\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB];\fR\fR
.ad
.RS 13n
Repeat \fIcount\fR times the last single character find command: \fBf\fR,
\fBF\fR, \fBt,\fR or \fBT\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB],\fR\fR
.ad
.RS 13n
Reverse the last single character find command \fIcount\fR times.
.RE

.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 13n
Move the cursor to the start of line.
.RE

.sp
.ne 2
.na
\fB\fB^\fR\fR
.ad
.RS 13n
Move the cursor to start of line.
.RE

.sp
.ne 2
.na
\fB\fB[H\fR\fR
.ad
.RS 13n
Move the cursor to the first non-blank character in the line.
.RE

.sp
.ne 2
.na
\fB\fB$\fR\fR
.ad
.RS 13n
Move the cursor to the end of the line.
.RE

.sp
.ne 2
.na
\fB\fB[Y\fR\fR
.ad
.RS 13n
Move the cursor to the end of the line.
.RE

.sp
.ne 2
.na
\fB\fB%\fR\fR
.ad
.RS 13n
Moves to balancing \fB(\fR, \fB)\fR, \fB{\fR, \fB}\fR, \fB[\fR, or \fB]\fR. If
cursor is not on one of the characters described in this section, the remainder
of the line is searched for the first occurrence of one of the characters
first.
.RE

.SS "Search Edit Commands"
.sp
.LP
The search edit commands access your command history.
.sp
.LP
The following search edit commands are supported:
.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]k\fR\fR
.ad
.RS 13n
Fetch the previous command. Each time \fBk\fR is entered, the previous command
back in time is accessed.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]-\fR\fR
.ad
.RS 13n
Fetch the previous command. Each time \fBk\fR is entered, the previous command
back in time is accessed.
.sp
Equivalent to \fBk\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB][A\fR\fR
.ad
.RS 13n
Fetch the previous command. Each time \fBk\fR is entered, the previous command
back in time is accessed.
.sp
Equivalent to \fBk\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]j\fR\fR
.ad
.RS 13n
Fetch the next command. Each time \fBj\fR is entered, the next command forward
in time is accessed.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]+\fR\fR
.ad
.RS 13n
Fetch the next command. Each time \fBj\fR is entered, the next command forward
in time is accessed.
.sp
Equivalent to \fBj\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB][B\fR\fR
.ad
.RS 13n
Fetch the next command. Each time \fBj\fR is entered, the next command forward
in time is accessed.
.sp
Equivalent to \fBj\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]G\fR\fR
.ad
.RS 13n
Fetch command number \fIcount\fR. The default is the least recent history
command.
.RE

.sp
.ne 2
.na
\fB\fB/\fR\fIstring\fR\fR
.ad
.RS 13n
Search backward through history for a previous command containing \fIstring\fR.
\fIstring\fR is terminated by a RETURN or NEWLINE. If string is preceded by a
\fB^\fR, the matched line must begin with \fIstring\fR. If \fIstring\fR is
null, the previous string is used.
.RE

.sp
.ne 2
.na
\fB\fB?\fR\fIstring\fR\fR
.ad
.RS 13n
Search forward through history for a previous command containing \fIstring\fR.
\fIstring\fR is terminated by a RETURN or NEWLINE. If string is preceded by a
\fB^\fR, the matched line must begin with \fIstring\fR. If \fIstring\fR is
null, the previous string is used.
.sp
Same as \fI/\fR except that search is in the forward direction.
.RE

.sp
.ne 2
.na
\fB\fBn\fR\fR
.ad
.RS 13n
Search in the backwards direction for the next match of the last pattern to
\fI/\fR or \fI?\fR commands.
.RE

.sp
.ne 2
.na
\fB\fBN\fR\fR
.ad
.RS 13n
Search in the forward direction for next match of the last pattern to \fI/\fR
or \fI?\fR.
.RE

.SS "Text Modification Edit Commands"
.sp
.LP
The following commands modify the line:
.sp
.ne 2
.na
\fB\fBa\fR\fR
.ad
.RS 19n
Enter input mode and enter text after the current character.
.RE

.sp
.ne 2
.na
\fB\fBA\fR\fR
.ad
.RS 19n
Append text to the end of the line. Equivalent to \fB$a\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]c\fR\fImotion\fR\fR
.ad
.br
.na
\fB\fBc[\fR\fIcount\fR\fB]\fR\fImotion\fR\fR
.ad
.RS 19n
Delete current character through the character that \fImotion\fR would move the
cursor to and enter input mode. If \fImotion\fR is \fBc\fR, the entire line is
deleted and input mode entered.
.RE

.sp
.ne 2
.na
\fB\fBC\fR\fR
.ad
.RS 19n
Delete the current character through the end of line and enter input mode.
Equivalent to \fBc$\fR.
.RE

.sp
.ne 2
.na
\fB\fBS\fR\fR
.ad
.RS 19n
Equivalent to \fBcc\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]s\fR\fR
.ad
.RS 19n
Replace characters under the cursor in input mode.
.RE

.sp
.ne 2
.na
\fB\fBD[\fR\fIcount\fR\fB]d\fR\fImotion\fR\fR
.ad
.RS 19n
Delete the current character through the end of line. Equivalent to d$.
.RE

.sp
.ne 2
.na
\fB\fBd[\fR\fIcount\fR\fB]\fR\fImotion\fR\fR
.ad
.RS 19n
Delete current character through the character that \fImotion\fR would move to.
If \fImotion\fR is d , the entire line is deleted.
.RE

.sp
.ne 2
.na
\fB\fBi\fR\fR
.ad
.RS 19n
Enter input mode and insert text before the current character.
.RE

.sp
.ne 2
.na
\fB\fBI\fR\fR
.ad
.RS 19n
Insert text before the beginning of the line. Equivalent to \fB0i\fR.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]P\fR\fR
.ad
.RS 19n
Place the previous text modification before the cursor.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]p\fR\fR
.ad
.RS 19n
Place the previous text modification after the cursor.
.RE

.sp
.ne 2
.na
\fB\fBR\fR\fR
.ad
.RS 19n
Enter input mode and replace characters on the screen with characters you type
overlay fashion.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]r\fR\fIc\fR\fR
.ad
.RS 19n
Replace the \fIcount\fR characters starting at the current cursor position with
\fIc\fR, and advance the cursor.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]x\fR\fR
.ad
.RS 19n
Delete current character.
.RE

.sp
.ne 2
.na
\fB\fB[\fIcount\fR]X\fR\fR
.ad
.RS 19n
Delete preceding character.
.RE

.sp
.ne 2
.na
\fB\fB[\fIcount\fR].\fR\fR
.ad
.RS 19n
Repeat the previous text modification command.
.RE

.sp
.ne 2
.na
\fB\fB[\fIcount\fR]~\fR\fR
.ad
.RS 19n
Invert the case of the \fIcount\fR characters starting at the current cursor
position and advance the cursor.
.RE

.sp
.ne 2
.na
\fB\fB[\fIcount\fR]_\fR\fR
.ad
.RS 19n
Causes the \fIcount\fR word of the previous command to be appended and input
mode entered. The last word is used if \fIcount\fR is omitted.
.RE

.sp
.ne 2
.na
\fB\fB*\fR\fR
.ad
.RS 19n
Causes an \fB*\fR to be appended to the current word and file name generation
attempted. If no match is found, it rings the bell. Otherwise, the word is
replaced by the matching pattern and input mode is entered.
.RE

.sp
.ne 2
.na
\fB\fB\e\fR\fR
.ad
.RS 19n
Command or file name completion as described in this manual page.
.RE

.SS "Other Edit Commands"
.sp
.LP
The following miscellaneous edit commands are supported:
.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]y\fR\fImotion\fR\fR
.ad
.br
.na
\fB\fBy[\fR\fIcount\fR\fB]\fR\fImotion\fR\fR
.ad
.RS 18n
Yank the current character through the character to which \fImotion\fR would
move the cursor. Put the yanked characters in the delete buffer. The text and
cursor position are unchanged.
.RE

.sp
.ne 2
.na
\fB\fByy\fR\fR
.ad
.RS 18n
Yank the current line.
.RE

.sp
.ne 2
.na
\fB\fBY\fR\fR
.ad
.RS 18n
Yank the current line from the current cursor location to the end of the line.
Equivalent to \fBy$\fR.
.RE

.sp
.ne 2
.na
\fB\fBu\fR\fR
.ad
.RS 18n
Undo the last text modifying command.
.RE

.sp
.ne 2
.na
\fB\fBU\fR\fR
.ad
.RS 18n
Undo all the text modifying commands performed on current line.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]V\fR\fR
.ad
.RS 18n
Return the command :
.sp
.in +2
.nf
hist -e ${VISUAL:-${EDITOR:-vi}} \fIcount\fR
.fi
.in -2
.sp

in the input buffer. If \fIcount\fR is omitted, the current line is used.
.RE

.sp
.ne 2
.na
\fB\fB^L\fR\fR
.ad
.RS 18n
Line feed and print the current line. This command only works in control mode.
.RE

.sp
.ne 2
.na
\fB\fB^J\fR\fR
.ad
.RS 18n
New line. Execute the current line, regardless of mode.
.RE

.sp
.ne 2
.na
\fB\fB^M\fR\fR
.ad
.RS 18n
Return. Execute the current line, regardless of mode.
.RE

.sp
.ne 2
.na
\fB\fB#\fR\fR
.ad
.RS 18n
If the first character of the command is a \fB#\fR , delete this \fB#\fR and
each \fB#\fR that follows a NEWLINE.
.sp
Otherwise, send the line after inserting a \fB#\fR in front of each line in the
command.
.sp
This is command is useful for causing the current line to be inserted in the
history as a comment and un-commenting previously commented commands in the
history file.
.RE

.sp
.ne 2
.na
\fB\fB[\fR\fIcount\fR\fB]=\fR\fR
.ad
.RS 18n
If \fIcount\fR is not specified, generate the list of matching commands or file
names as described in this manual page.
.sp
Otherwise, replace the word at the current cursor location with the \fIcount\fR
item from the most recently generated command or file list. If the cursor is
not on a word, it is inserted after the current cursor location.
.RE

.sp
.ne 2
.na
\fB\fB@\fR\fIletter\fR\fR
.ad
.RS 18n
Search your alias list for an alias by the name \fIletter\fR. If an alias of
this name is defined, insert its value on the input queue for processing.
.RE

.sp
.ne 2
.na
\fB\fB^V\fR\fR
.ad
.RS 18n
Display version of the shell.
.RE

.SS "Built-in Commands"
.sp
.LP
The following simple-commands are executed in the shell process. Input and
output redirection is permitted. Unless otherwise indicated, the output is
written on file descriptor \fB1\fR and the exit status, when there is no syntax
error, is \fB0\fR. Except for \fB:\fR, \fBtrue\fR, \fBfalse\fR, \fBecho\fR,
\fBnewgrp\fR, and \fBlogin\fR, all built-in commands accept \fB--\fR to
indicate the end of options. They also interpret the option \fB--man\fR as a
request to display the manual page onto standard error and \fB-?\fR as a help
request which prints a usage message on standard error.
.sp
.LP
Commands that are preceded by one or two \fB++\fR symbols are special built-in
commands and are treated specially in the following ways:
.RS +4
.TP
1.
Variable assignment lists preceding the command remain in effect when the
command completes.
.RE
.RS +4
.TP
2.
I/O redirections are processed after variable assignments.
.RE
.RS +4
.TP
3.
Errors cause a script that contains them to abort.
.RE
.RS +4
.TP
4.
They are not valid function names.
.RE
.RS +4
.TP
5.
Words following a command preceded by \fB++\fR that are in the format of a
variable assignment are expanded with the same rules as a variable assignment.
This means that tilde substitution is performed after the \fB=\fR sign and
field splitting and file name generation are not performed.
.RE
.sp
.ne 2
.na
\fB\fB+ : [\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The command only expands parameters.
.RE

.sp
.ne 2
.na
\fB\fB+ .\fR \fIname\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
If \fIname\fR is a function defined with the \fBfunction\fR \fBname\fR reserved
word syntax, the function is executed in the current environment (as if it had
been defined with the \fIname()\fR syntax.) Otherwise if \fIname\fR refers to a
file, the file is read in its entirety and the commands are executed in the
current shell environment. The search path specified by PATH is used to find
the directory containing the file. If any arguments \fIarg\fR are specified,
they become the positional parameters while processing the . command and the
original positional parameters are restored upon completion. Otherwise the
positional parameters are unchanged. The exit status is the exit status of the
last command executed.
.RE

.sp
.ne 2
.na
\fB\fB++ alias [\fR\fB-ptx\fR\fB] [\fR\fIname\fR\fB[
=\fR\fIvalue\fR\fB]] ...\fR\fR
.ad
.sp .6
.RS 4n
\fBalias\fR with no arguments prints the list of aliases in the form
\fIname\fR\fB=\fR\fIvalue\fR on standard output. The \fB-p\fR option causes the
word alias to be inserted before each one. When one or more arguments are
specified, an \fIalias\fR is defined for each \fIname\fR whose \fIvalue\fR is
specified. A trailing space in \fIvalue\fR causes the next word to be checked
for alias substitution. The obsolete \fB-t\fR option is used to set and list
tracked aliases. The value of a tracked alias is the full pathname
corresponding to the specified \fIname\fR. The value becomes undefined when the
value of \fBPATH\fR is reset but the alias remains tracked. Without the
\fB-t\fR option, for each \fIname\fR in the argument list for which no
\fIvalue\fR is specified, the name and value of the alias is printed. The
obsolete -x option has no effect. The exit status is \fBnon-zero\fR if a
\fIname\fR is specified, but no value, and no alias has been defined for the
\fIname\fR.
.RE

.sp
.ne 2
.na
\fB\fBbg [\fR \fIjob\fR\fB\&...]\fR\fR
.ad
.sp .6
.RS 4n
This command is only on systems that support job control. Puts each specified
\fIjob\fR into the background. The current job is put in the background if
\fIjob\fR is not specified. See the \fBJobs\fR section of this manual page for
a description of the format of \fIjob\fR.
.RE

.sp
.ne 2
.na
\fB\fB+ break [\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Exit from the enclosing \fBfor\fR, \fBwhile\fR, \fBuntil\fR, or \fBselect\fR
loop, if any. If \fIn\fR is specified, then break \fIn\fR levels.
.RE

.sp
.ne 2
.na
\fB\fBbuiltin [\fR\fB-ds\fR \fB] [\fR\fB-f\fR \fIfile\fR\fB]
[\fR\fIname ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
If \fIname\fR is not specified, and no \fB-f\fR option is specified, the
built-ins are printed on standard output. The \fB-s\fR option prints only the
special built-ins. Otherwise, each \fIname\fR represents the pathname whose
basename is the name of the built-in. The entry point function name is
determined by prepending \fIb\fR to the built-in name. The ISO C/C++ prototype
is \fBb\fR\fImycommand(int argc, char *argv[], void *context)\fR for the
built-in command \fImycommand\fR where \fIargv\fR is an array of \fIargc\fR
elements and \fIcontext\fR is an optional pointer to a \fBShell_t\fR structure
as described in \fB<ast/shell.h>\fR Special built-ins cannot be bound to a
pathname or deleted. The \fB-d\fR option deletes each of the specified
built-ins. On systems that support dynamic loading, the \fB-f\fR option names a
shared library containing the code for built-ins. The shared library prefix
and/or suffix, which depend on the system, can be omitted. Once a library is
loaded, its symbols become available for subsequent invocations of
\fBbuiltin\fR. Multiple libraries can be specified with separate invocations of
the \fBbuiltin\fR command. Libraries are searched in the reverse order in which
they are specified. When a library is loaded, it looks for a function in the
library whose name is \fBlib_init()\fR and invokes this function with an
argument of \fB0\fR.
.RE

.sp
.ne 2
.na
\fB\fBcd\fR \fB[\fR\fB-LP\fR\fB] [\fR\fIarg\fR\fB]\fR\fR
.ad
.br
.na
\fB\fBcd\fR \fB[\fR\fB-LP\fR\fB]\fR \fIold\fR \fInew\fR\fR
.ad
.sp .6
.RS 4n
This command has two forms.
.sp
In the first form it changes the current directory to \fIarg\fR. If \fIarg\fR
is a \fB-\fR, the directory is changed to the previous directory. The shell
variable \fBHOME\fR is the default \fIarg\fR. The variable \fBPWD\fR is set to
the current directory. The shell variable \fBCDPATH\fR defines the search path
for the directory containing \fIarg\fR. Alternative directory names are
separated by a colon (\fB:\fR). The default path is \fBNULL\fR (specifying the
current directory). The current directory is specified by a null path name,
which can appear immediately after the equal sign or between the colon
delimiters anywhere else in the path list. If \fIarg\fR begins with a \fB/\fR,
the search path is not used. Otherwise, each directory in the path is searched
for \fIarg\fR.
.sp
The second form of \fBcd\fR substitutes the string \fInew\fR for the string
\fIold\fR in the current directory name, \fBPWD\fR, and tries to change to this
new directory. By default, symbolic link names are treated literally when
finding the directory name. This is equivalent to the \fB-L\fR option. The
\fB-P\fR option causes symbolic links to be resolved when determining the
directory. The last instance of \fB-L\fR or \fB-P\fR on the command line
determines which method is used. The \fBcd\fR command cannot be executed by
\fBrksh93\fR.
.RE

.sp
.ne 2
.na
\fB\fBcommand\fR \fB[\fR\fB-pvVx\fR\fB]\fR \fIname\fR
\fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Without the \fB-v\fR or \fB-V\fR options, executes \fIname\fR with the
arguments specified by \fIarg\fR.
.sp
The \fB-p\fR option causes a default path to be searched rather than the one
defined by the value of \fBPATH\fR. Functions are not searched when finding
\fIname\fR. In addition, if \fIname\fR refers to a special built-in, none of
the special properties associated with the leading daggers are honored. For
example, the predefined alias \fBredirect='command exec'\fR prevents a script
from terminating when an invalid redirection is specified.
.sp
With the \fB-x\fR option, if command execution would result in a failure
because there are too many arguments, \fBerrno E2BIG\fR, the shell invokes
command \fIname\fR multiple times with a subset of the arguments on each
invocation. Arguments that occur prior to the first word that expands to
multiple arguments and after the last word that expands to multiple arguments
are passed on each invocation. The exit status is the maximum invocation exit
status.
.sp
With the \fB-v\fR option, \fBcommand\fR is equivalent to the built-in
\fBwhence\fR command described in this section. The \fB-V\fR option causes
\fBcommand\fR to act like \fBwhence -v\fR.
.RE

.sp
.ne 2
.na
\fB\fB+continue\fR \fB[\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Resumes the next iteration of the enclosing \fBfor\fR, \fBwhile\fR,
\fBuntil\fR, or \fBselect\fR loop. If \fIn\fR is specified, then resume at the
\fIn\fRth enclosing loop.
.RE

.sp
.ne 2
.na
\fB\fBdisown\fR \fB[\fR\fIjob...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Causes the shell not to send a \fBHUP\fR signal to each specified \fIjob\fR, or
all active jobs if \fIjob\fR is omitted, when a login shell terminates.
.RE

.sp
.ne 2
.na
\fB\fBecho\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
When the first \fIarg\fR does not begin with a \fB-\fR, and none of the
arguments contain a backslash (\fB\e\fR), prints each of its arguments
separated by a SPACE and terminated by a NEWLINE. Otherwise, the behavior of
\fBecho\fR is system dependent and \fBprint\fR or \fBprintf\fR described in
this section should be used. See \fBecho\fR(1) for usage and description.
.RE

.sp
.ne 2
.na
\fB\fB+eval\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The arguments are read as input to the shell and the resulting commands are
executed.
.RE

.sp
.ne 2
.na
\fB\fB+exec\fR [\fB-c\fR] [\fB-a\fR \fIname ...\fR]
\fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
If \fIarg\fR is specified, the command specified by the arguments is executed
in place of this shell without creating a new process. The \fB-c\fR option
causes the environment to be cleared before applying variable assignments
associated with the exec invocation. The \fB-a\fR option causes \fIname\fR
rather than the first \fIarg\fR, to become \fBargv[0]\fR for the new process.
Input and output arguments can appear and affect the current process. If
\fIarg\fR is not specified, the effect of this command is to modify file
descriptors as prescribed by the input/output redirection list. In this case,
any file descriptor numbers greater than \fB2\fR that are opened with this
mechanism are closed when invoking another program.
.RE

.sp
.ne 2
.na
\fB\fB+exit\fR \fB[\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Causes the shell to exit with the exit status specified by \fIn\fR. The value
is the least significant 8 bits of the specified status. If \fIn\fR is omitted,
then the exit status is that of the last command executed. An end-of-file also
causes the shell to exit except for a shell which has the \fBignoreeof\fR
option turned on. See \fBset\fR.
.RE

.sp
.ne 2
.na
\fB\fB++export\fR \fB[\fR\fB-p\fR\fB]\fR
\fB[\fR\fIname\fR\fB[=\fR\fIvalue\fR\fB]] ...\fR\fR
.ad
.sp .6
.RS 4n
If \fIname\fR is not specified, the names and values of each variable with the
export attribute are printed with the values quoted in a manner that allows
them to be re-entered. The \fB-p\fR option causes the word export to be
inserted before each one. Otherwise, the specified \fIname\fRs are marked for
automatic export to the environment of subsequently-executed commands.
.RE

.sp
.ne 2
.na
\fB\fBfalse\fR\fR
.ad
.sp .6
.RS 4n
Does nothing, and exits \fB1\fR. Used with \fBuntil\fR for infinite loops.
.RE

.sp
.ne 2
.na
\fB\fBfg\fR \fB[\fR\fIjob ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
This command is only on systems that support job control. Each \fIjob\fR
specified is brought to the foreground and waited for in the specified order.
Otherwise, the current job is brought into the foreground. See \fBJobs\fR for a
description of the format of \fIjob\fR.
.RE

.sp
.ne 2
.na
\fB\fBgetconf\fR \fB[\fR\fIname\fR \fB[\fR\fIpathname\fR\fB]]\fR\fR
.ad
.sp .6
.RS 4n
Prints the current value of the configuration parameter specified by
\fIname\fR. The configuration parameters are defined by the IEEE POSIX 1003.1
and IEEE POSIX 1003.2 standards. See \fBpathconf\fR(2) and \fBsysconf\fR(3C).
.sp
The \fIpathname\fR argument is required for parameters whose value depends on
the location in the file system. If no arguments are specified, \fBgetconf\fR
prints the names and values of the current configuration parameters. The
pathname \fB/\fR is used for each of the parameters that requires
\fIpathname\fR.
.RE

.sp
.ne 2
.na
\fB\fBgetopts\fR \fB[\fR \fB-a\fR \fIname\fR\fB]\fR \fIoptstring\fR \fIvname\fR
\fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Checks \fIarg\fR for legal options. If \fIarg\fR is omitted, the positional
parameters are used. An option argument begins with a \fB+\fR or a \fB-\fR. An
option that does not begin with \fB+\fR or \fB-\fR or the argument \fB--\fR
ends the options. Options beginning with \fB+\fR are only recognized when
\fIoptstring\fR begins with a \fB+\fR. \fIoptstring\fR contains the letters
that \fBgetopts\fR recognizes. If a letter is followed by a \fB:\fR, that
option is expected to have an argument. The options can be separated from the
argument by blanks. The option \fB-?\fRcauses \fBgetopts\fR to generate a usage
message on standard error. The \fB-a\fR option can be used to specify the name
to use for the usage message, which defaults to $0. \fBgetopts\fR places the
next option letter it finds inside variable \fIvname\fR each time it is
invoked. The option letter is prepended with a \fB+\fR when \fIarg\fR begins
with a \fB+\fR. The index of the next \fIarg\fR is stored in \fBOPTIND\fR. The
option argument, if any, gets stored in \fBOPTARG\fR. A leading : in
\fIoptstring\fR causes \fBgetopts\fR to store the letter of an invalid option
in \fBOPTARG\fR, and to set \fIvname\fR to \fB?\fR for an unknown option and
to: when a required option argument is missing. Otherwise, \fBgetopts\fR prints
an error message. The exit status is \fBnon-zero\fR when there are no more
options. There is no way to specify any of the options \fB:\fR, \fB+\fR,
\fB-\fR, \fB?\fR, \fB[\fR, and \fB]\fR. The option \fB#\fR can only be
specified as the first option.
.RE

.sp
.ne 2
.na
\fB\fBhist\fR \fB[\fR \fB-e\fR \fIename\fR\fB]\fR\fB[\fR\fB-nlr\fR\fB]\fR
\fB[\fR \fIfirst\fR\fB[\fR\fIlast\fR \fB] ]\fR\fR
.ad
.br
.na
\fB\fR
.ad
.br
.na
\fB\fBhist\fR \fB-s\fR \fB[\fR \fIold\fR\fB=\fR\fInew\fR \fB] [\fR
\fIcommand\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
In the first form, a range of commands from \fIfirst\fR to \fIlast\fR is
selected from the last \fBHISTSIZE\fR commands that were typed at the terminal.
The arguments \fIfirst\fR and \fIlast\fR can be specified as a number or as a
string. A string is used to locate the most recent command starting with the
specified string. A negative number is used as an offset to the current command
number. If the -l option is selected, the commands are listed on standard
output. Otherwise, the editor program \fIename\fR is invoked on a file
containing these keyboard commands. If \fIename\fR is not supplied, then the
value of the variable \fBHISTEDIT\fR is used. If \fBHISTEDIT\fR is not set,
then \fBFCEDIT\fR (default \fB/bin/ed\fR) is used as the editor. When editing
is complete, the edited command(s) is executed if the changes have been saved.
If \fIlast\fR is not specified, then it is set to \fIfirst\fR. If \fIfirst\fR
is not specified, the default is the previous command for editing and \fB-16\fR
for listing. The option \fB-r\fR reverses the order of the commands and the
option \fB-n\fR suppresses command numbers when listing. In the second form,
\fIcommand\fR is interpreted as \fIfirst\fR described in this section and
defaults to the last command executed. The resulting command is executed after
the optional substitution \fIold\fR\fB=\fR\fInew\fR is performed.
.RE

.sp
.ne 2
.na
\fB\fBjobs\fR \fB-lnp\fR \fB[\fR\fIjob ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Lists information about each specified job, or all active jobs if \fIjob\fR is
omitted. The \fB-l\fR option lists process ids in addition to the normal
information. The \fB-n\fR option only displays jobs that have stopped or exited
since last notified. The \fB-p\fR option causes only the process group to be
listed. See \fBJobs\fR for a description of the format of \fIjob\fR.
.RE

.sp
.ne 2
.na
\fB\fBkill\fR \fB[\fR\fB-s\fR \fIsigname\fR\fB]\fR \fIjob ...\fR\fR
.ad
.br
.na
\fB\fBkill\fR \fB[\fR\fB-n\fR \fIsignum\fR\fB]\fR \fIjob ...\fR\fR
.ad
.br
.na
\fB\fBkill\fR \fB-l\fR \fB[\fR\fIsig ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Sends either the \fBTERM\fR (terminate) signal or the specified signal to the
specified jobs or processes. Signals are either specified by number with the
\fB-n\fR option or by name with the \fB-s\fR option (as specified in
\fB<signal.h\fR>, stripped of the prefix `\fBSIG\fR with the exception that
\fBSIGCLD\fR is named \fBCHLD\fR). For backward compatibility, the \fBn\fR and
\fBs\fR can be omitted and the number or name placed immediately after the
\fB-\fR. If the signal being sent is \fBTERM\fR (terminate) or \fBHUP\fR (hang
up), then the job or process is sent a \fBCONT\fR (continue) signal if it is
stopped. The argument \fIjob\fR can be the process id of a process that is not
a member of one of the active jobs. See \fBJobs\fR for a description of the
format of \fIjob\fR. In the third form, \fBkill -l\fR, if \fIsig\fR is not
specified, the signal names are listed. Otherwise, for each \fIsig\fR that is a
name, the corresponding signal number is listed. For each \fIsig\fR that is a
number, the signal name corresponding to the least significant 8 bits of
\fIsig\fR is listed.
.RE

.sp
.ne 2
.na
\fB\fBlet\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Each \fIarg\fR is a separate arithmetic expression to be evaluated. See the
\fBArithmetic Evaluation\fR section of this manual page for a description of
arithmetic expression evaluation. The exit status is \fB0\fR if the value of
the last expression is \fBnon-zero\fR, and \fB1\fR otherwise.
.RE

.sp
.ne 2
.na
\fB\fB+newgrp\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Equivalent to \fBexec\fR \fB/bin/newgrp\fR \fIarg ...\fR
.RE

.sp
.ne 2
.na
\fB\fBprint\fR [\fB-Renprs\fR] \fB[\fR \fB-u\fR \fIunit\fR\fB] [\fR \fB-f\fR
\fIformat\fR \fB] [\fR \fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
With no options or with option \fB-\fR or \fB--\fR, each \fIarg\fR is printed
on standard output. The \fB-f\fR option causes the arguments to be printed as
described by \fBprintf\fR. In this case, any \fBe\fR, \fBn\fR, \fBr\fR, or
\fBR\fR options are ignored. Otherwise, unless the \fB-R\fR or \fB-r,\fR are
specified, the following escape conventions are applied:
.sp
.ne 2
.na
\fB\fB\ea\fR\fR
.ad
.RS 8n
Alert character (\fBASCII\fR 07)
.RE

.sp
.ne 2
.na
\fB\fB\eb\fR\fR
.ad
.RS 8n
Backspace character (\fBASCII\fR 010)
.RE

.sp
.ne 2
.na
\fB\fB\ec\fR\fR
.ad
.RS 8n
Causes print to end without processing more arguments and not adding a NEWLINE
.RE

.sp
.ne 2
.na
\fB\fB\ef\fR\fR
.ad
.RS 8n
Form-feed character (\fBASCII\fR 014)
.RE

.sp
.ne 2
.na
\fB\fB\en\fR\fR
.ad
.RS 8n
NEWLINE character (\fBASCII\fR 012)
.RE

.sp
.ne 2
.na
\fB\fB\er\fR\fR
.ad
.RS 8n
RETURN character (\fBASCII\fR 015)
.RE

.sp
.ne 2
.na
\fB\fB\et\fR\fR
.ad
.RS 8n
TAB character (\fBASCII\fR 011)
.RE

.sp
.ne 2
.na
\fB\fB\ev\fR\fR
.ad
.RS 8n
Vertical TAB character (\fBASCII\fR 013)
.RE

.sp
.ne 2
.na
\fB\fB\eE\fR\fR
.ad
.RS 8n
Escape character (\fBASCII\fR 033)
.RE

.sp
.ne 2
.na
\fB\fB\e\e\fR\fR
.ad
.RS 8n
Backslash character \fB\e\fR
.RE

.sp
.ne 2
.na
\fB\fB\e0\fR\fIx\fR\fR
.ad
.RS 8n
Character defined by the 1, 2, or 3-digit octal string specified by \fIx\fR
.RE

The \fB-R\fR option prints all subsequent arguments and options other than
\fB-n\fR. The \fB-e\fR causes the escape conventions to be applied This is the
default behavior. It reverses the effect of an earlier \fB-r\fR. The \fB-p\fR
option causes the arguments to be written onto the pipe of the process spawned
with \fB|&\fR instead of standard output. The \fB-s\fR option causes the
arguments to be written onto the history file instead of standard output. The
\fB-u\fR option can be used to specify a one digit file descriptor unit number
\fIunit\fR on which the output is placed. The default is \fB1\fR. If the option
\fB-n\fR is used, no NEWLINE is added to the output.
.RE

.sp
.ne 2
.na
\fB\fBprintf\fR \fIformat\fR\fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The arguments \fIarg\fR are printed on standard output in accordance with the
\fBANSI-C\fR formatting rules associated with the format string \fIformat\fR.
If the number of arguments exceeds the number of format specifications, the
format string is reused to format remaining arguments. The following extensions
can also be used: A \fB%b\fR format can be used instead of \fB%s\fR to cause
escape sequences in the corresponding \fIarg\fR to be expanded as described in
\fBprint\fR. A \fB%B\fR option causes each of the arguments to be treated as
variable names and the binary value of the variables is printed. This is most
useful for variables with an attribute of b. A \fB%H\fR format can be used
instead of \fB%s\fR to cause characters in \fIarg\fR that are special in
\fBHTML\fR and \fBXML\fR to be output as their entity name. A \fB%P\fR format
can be used instead of \fB%s\fR to cause \fIarg\fR to be interpreted as an
extended regular expression and be printed as a shell pattern. A \fB%R\fR
format can be used instead of \fB%s\fR to cause \fIarg\fR to be interpreted as
a shell pattern and to be printed as an extended regular expression. A \fB%q\fR
format can be used instead of \fB%\fRs to cause the resulting string to be
quoted in a manner than can be input again to the shell. A
\fB%(\fR\fIdate-format\fR\fB)T\fR format can be use to treat an argument as a
date/time string and to format the date/time according to the \fIdate-format\fR
as defined for the \fBdate\fR(1) command. A \fB%Z\fR format outputs a byte
whose value is 0. The precision field of the %d format can be followed by a .
and the output base. In this case, the \fB#\fR flag character causes
\fBbase\fR\fI#\fR to be prepended. The \fB#\fR flag when used with the \fBd\fR
specifier without an output base, causes the output to be displayed in
thousands units with one of the suffixes \fBk\fR \fBM\fR \fBG\fR \fBT\fR
\fBP\fR \fBE\fR to indicate the unit. The \fB#\fR flag when used with the i
specifier causes the output to be displayed in \fB1024\fR with one of the
suffixes \fBKi\fR \fBMi\fR \fBGi\fR \fBTi\fR \fBPi\fR \fBEi\fR to indicate the
unit. The \fB=\fR flag has been added to center the output within the specified
field width.
.RE

.sp
.ne 2
.na
\fB\fBpwd\fR [\fB-LP\fR]\fR
.ad
.sp .6
.RS 4n
Outputs the value of the current working directory. The \fB-L\fR option is the
default. It prints the logical name of the current directory. If the \fB-P\fR
option is specified, all symbolic links are resolved from the name. The last
instance of \fB-L\fR or \fB-P\fR on the command line determines which method is
used.
.RE

.sp
.ne 2
.na
\fB\fBread\fR \fB[\fR\fB-Aprs\fR\fB] [\fR\fB-d\fR \fIdelim\fR\fB] [\fR \fB-n\fR
\fIn\fR\fB] [[\fR \fB-N\fR \fIn\fR\fB] [[\fR\fB-t\fR \fItimeout\fR\fB]
[\fR\fB-u\fR \fIunit\fR\fB] [\fR\fIvname\fR\fB?\fR\fIprompt\fR\fB] [\fR
\fIvname ...\fR \fB]\fR\fR
.ad
.sp .6
.RS 4n
The shell input mechanism. One line is read and is broken up into fields using
the characters in IFS as separators. The escape character, \fB\e\fR, is used to
remove any special meaning for the next character and for line continuation.
The \fB-d\fR option causes the read to continue to the first character of
\fIdelim\fR rather than \fBNEWLINE\fR. The \fB-n\fR option causes at most
\fIn\fR bytes to read rather a full line but returns when reading from a slow
device as soon as any characters have been read. The \fB-N\fR option causes
exactly \fIn\fR to be read unless an end-of-file has been encountered or the
read times out because of the \fB-t\fR option. In raw mode, \fB-r\fR, the
\fB\e\fR character is not treated specially. The first field is assigned to the
first \fIvname\fR, the second field to the second \fIvname\fR, etc., with
leftover fields assigned to the last \fIvname\fR. When \fIvname\fR has the
binary attribute and \fB-n\fR or \fB-N\fR is specified, the bytes that are read
are stored directly into the variable. If the -v is specified, then the value
of the first \fIvname\fR is used as a default value when reading from a
terminal device. The \fB-A\fR option causes the variable \fIvname\fR to be
unset and each field that is read to be stored in successive elements of the
indexed array \fIvname\fR. The \fB-p\fR option causes the input line to be
taken from the input pipe of a process spawned by the shell using \fB|&\fR. If
the \fB-s\fR option is present, the input is saved as a command in the history
file. The option \fB-u\fR can be used to specify a one digit file descriptor
unit \fIunit\fR to read from. The file descriptor can be opened with the
\fBexec\fR special built-in command. The default value of unit \fIn\fR is
\fB0\fR. The option \fB-t\fR is used to specify a time out in seconds when
reading from a terminal or pipe. If \fIvname\fR is omitted, then REPLY is used
as the default \fIvname\fR. An end-of-file with the \fB-p\fR option causes
cleanup for this process so that another can be spawned. If the first argument
contains a \fB?\fR, the remainder of this word is used as a prompt on standard
error when the shell is interactive. The exit status is \fB0\fR unless an
end-of-file is encountered or read has timed out.
.RE

.sp
.ne 2
.na
\fB\fB++readonly\fR \fB[\fR\fB-p\fR\fB] [\fR
\fIvname\fR\fB[=\fR\fIvalue\fR\fB]] ...\fR\fR
.ad
.sp .6
.RS 4n
If \fIvname\fR is not specified, the names and values of each variable with the
read-only attribute is printed with the values quoted in a manner that allows
them to be input again. The \fB-p\fR option causes the word \fBreadonly\fR to
be inserted before each one. Otherwise, the specified \fIvname\fRs are marked
\fBreadonly\fR and these names cannot be changed by subsequent assignment.
.RE

.sp
.ne 2
.na
\fB\fB+return\fR \fB[\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Causes a shell function or script to return to the invoking script with the
exit status specified by \fIn\fR. The value is the least significant 8 bits of
the specified status. If \fBn\fR is omitted, then the return status is that of
the last command executed. If return is invoked while not in a function or a
script, then it behaves the same as exit.
.RE

.sp
.ne 2
.na
\fB\fB+set [ \(+-BCGabefhkmnoprstuvx] [\(+-o [\fR \fIoption\fR \fB] ] ... [
\(+-A\fR \fIvname\fR\fB]\fR \fB[\fR\fIarg...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The \fBset\fR command supports the following options:
.sp
.ne 2
.na
\fB\fB-a\fR\fR
.ad
.sp .6
.RS 4n
All subsequent variables that are defined are automatically exported.
.RE

.sp
.ne 2
.na
\fB\fB-A\fR\fR
.ad
.sp .6
.RS 4n
Array assignment. Unset the variable \fIvname\fR and assign values sequentially
from the \fIarg\fR list. If \fB+A\fR is used, the variable \fIvname\fR is not
unset first.
.RE

.sp
.ne 2
.na
\fB\fB-b\fR\fR
.ad
.sp .6
.RS 4n
Prints job completion messages as soon as a background job changes state rather
than waiting for the next prompt.
.RE

.sp
.ne 2
.na
\fB\fB-B\fR\fR
.ad
.sp .6
.RS 4n
Enable brace pattern field generation. This is the default behavior.
.RE

.sp
.ne 2
.na
\fB\fB-C\fR\fR
.ad
.sp .6
.RS 4n
Prevents redirection (\fB>\fR) from truncating existing files. Files that are
created are opened with the \fBO_EXCL\fR mode. Requires \fB>|\fR to truncate a
file when turned on.
.RE

.sp
.ne 2
.na
\fB\fB-e\fR\fR
.ad
.sp .6
.RS 4n
If a command has a \fBnon-zero\fR exit status, execute the \fBERR\fR trap, if
set, and exit. This mode is disabled while reading profiles.
.RE

.sp
.ne 2
.na
\fB\fB-f\fR\fR
.ad
.sp .6
.RS 4n
Disables file name generation.
.RE

.sp
.ne 2
.na
\fB\fB-G\fR\fR
.ad
.sp .6
.RS 4n
Causes the pattern \fB**\fR by itself to match files and zero or more
directories and subdirectories when used for file name generation. If followed
by a \fB/\fR only directories and subdirectories are matched.
.RE

.sp
.ne 2
.na
\fB\fB-h\fR\fR
.ad
.sp .6
.RS 4n
Each command becomes a tracked alias when first encountered.
.RE

.sp
.ne 2
.na
\fB\fB-k\fR\fR
.ad
.sp .6
.RS 4n
Obsolete. All variable assignment arguments are placed in the environment for a
command, not just those that precede the command name.
.RE

.sp
.ne 2
.na
\fB\fB-m\fR\fR
.ad
.sp .6
.RS 4n
Background jobs run in a separate process group and a line prints upon
completion. The exit status of background jobs is reported in a completion
message. On systems with job control, this option is turned on automatically
for interactive shells.
.RE

.sp
.ne 2
.na
\fB\fB-n\fR\fR
.ad
.sp .6
.RS 4n
Read commands and check them for syntax errors, but do not execute them.
Ignored for interactive shells.
.RE

.sp
.ne 2
.na
\fB\fB-o\fR\fR
.ad
.sp .6
.RS 4n
If no option name is supplied, the list of options and their current settings
are written to standard output. When invoked with a \fB+\fR, the options are
written in a format that can be input again to the shell to restore the
settings. This option can be repeated to enable or disable multiple options.
.sp
The following argument can be one of the following option names:
.sp
.ne 2
.na
\fB\fBallexport\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-a\fR.
.RE

.sp
.ne 2
.na
\fB\fBbgnice\fR\fR
.ad
.sp .6
.RS 4n
All background jobs are run at a lower priority. This is the default mode.
.RE

.sp
.ne 2
.na
\fB\fBbraceexpand\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-\fRB.
.RE

.sp
.ne 2
.na
\fB\fBemacs\fR\fR
.ad
.sp .6
.RS 4n
Puts you in an \fBemacs\fR style inline editor for command entry.
.RE

.sp
.ne 2
.na
\fB\fBerrexit\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-e\fR.
.RE

.sp
.ne 2
.na
\fB\fBglobstar\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-G\fR.
.RE

.sp
.ne 2
.na
\fB\fBgmacs\fR\fR
.ad
.sp .6
.RS 4n
Puts you in a \fBgmacs\fR style inline editor for command entry.
.RE

.sp
.ne 2
.na
\fB\fBignoreeof\fR\fR
.ad
.sp .6
.RS 4n
The shell does not exit on end-of-file. The command \fBexit\fR must be used.
.RE

.sp
.ne 2
.na
\fB\fBkeyword\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-k\fR.
.RE

.sp
.ne 2
.na
\fB\fBmarkdirs\fR\fR
.ad
.sp .6
.RS 4n
All directory names resulting from file name generation have a trailing /
appended.
.RE

.sp
.ne 2
.na
\fB\fBmonitor\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-m\fR.
.RE

.sp
.ne 2
.na
\fB\fBmultiline\fR\fR
.ad
.sp .6
.RS 4n
The built-in editors use multiple lines on the screen for lines that are longer
than the width of the screen. This might not work for all terminals.
.RE

.sp
.ne 2
.na
\fB\fBnoclobber\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-C\fR.
.RE

.sp
.ne 2
.na
\fB\fBnoexec\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-n\fR.
.RE

.sp
.ne 2
.na
\fB\fBnoglob\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-f\fR.
.RE

.sp
.ne 2
.na
\fB\fBnolog\fR\fR
.ad
.sp .6
.RS 4n
Do not save function definitions in the history file.
.RE

.sp
.ne 2
.na
\fB\fBnotify\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-b\fR.
.RE

.sp
.ne 2
.na
\fB\fBnounset\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-u\fR.
.RE

.sp
.ne 2
.na
\fB\fBpipefail\fR\fR
.ad
.sp .6
.RS 4n
A pipeline does not complete until all components of the pipeline have
completed, and the return value is the value of the last \fBnon-zero\fR command
to fail or zero if no command has failed.
.RE

.sp
.ne 2
.na
\fB\fBprivileged\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-p\fR.
.RE

.sp
.ne 2
.na
\fB\fBshowme\fR\fR
.ad
.sp .6
.RS 4n
When enabled, simple commands or pipelines preceded by a a semicolon (\fB;\fR)
is displayed as if the \fBxtrace\fR option were enabled but is not executed.
Otherwise, the leading \fB;\fR is ignored.
.RE

.sp
.ne 2
.na
\fB\fBtrackall\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-h\fR.
.RE

.sp
.ne 2
.na
\fB\fBverbose\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-v\fR.
.RE

.sp
.ne 2
.na
\fB\fBvi\fR\fR
.ad
.sp .6
.RS 4n
Puts you in insert mode of a \fBvi\fR style inline editor until you hit the
escape character 033. This puts you in control mode. A return sends the line.
.RE

.sp
.ne 2
.na
\fB\fBviraw\fR\fR
.ad
.sp .6
.RS 4n
Each character is processed as it is typed in \fBvi\fR mode.
.RE

.sp
.ne 2
.na
\fB\fBxtrace\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-x\fR.
.sp
If no option name is supplied, the current options settings are printed.
.RE

.RE

.sp
.ne 2
.na
\fB\fB-p\fR\fR
.ad
.sp .6
.RS 4n
Disables processing of the \fB$HOME/.profile\fR file and uses the file
\fB/etc/suid_profile\fR instead of the \fBENV\fR file. This mode is on whenever
the effective \fBuid\fR (\fBgid\fR) is not equal to the real \fBuid\fR
(\fBgid\fR). Turning this off causes the effective \fBuid\fR and \fBgid\fR to
be set to the real \fBuid\fR and \fBgid\fR.
.RE

.sp
.ne 2
.na
\fB\fB-r\fR\fR
.ad
.sp .6
.RS 4n
Enables the restricted shell. This option cannot be unset once set.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR\fR
.ad
.sp .6
.RS 4n
Sort the positional parameters lexicographically.
.RE

.sp
.ne 2
.na
\fB\fB-t\fR\fR
.ad
.sp .6
.RS 4n
Obsolete. Exit after reading and executing one command.
.RE

.sp
.ne 2
.na
\fB\fB-u\fR\fR
.ad
.sp .6
.RS 4n
Treat \fBunset\fR parameters as an error when substituting.
.RE

.sp
.ne 2
.na
\fB\fB-v\fR\fR
.ad
.sp .6
.RS 4n
Print shell input lines as they are read.
.RE

.sp
.ne 2
.na
\fB\fB-x\fR\fR
.ad
.sp .6
.RS 4n
Print commands and their arguments as they are executed.
.RE

.sp
.ne 2
.na
\fB\fB--\fR\fR
.ad
.sp .6
.RS 4n
Do not change any of the options. This is useful in setting \fB$1\fR to a value
beginning with \fB-\fR. If no arguments follow this option then the positional
parameters are unset.
.RE

As an obsolete feature, if the first \fIarg\fR is - then the \fB-x\fR and
\fB-v\fR options are turned off and the next \fIarg\fR is treated as the first
argument. Using \fB+\fR rather than \fB-\fR causes these options to be turned
off. These options can also be used upon invocation of the shell. The current
set of options can be found in \fB$-\fR. Unless \fB-A\fR is specified, the
remaining arguments are positional parameters and are assigned, in order, to
\fB$1 $2 \&....\fR If no arguments are specified, then the names and values of
all variables are printed on the standard output.
.RE

.sp
.ne 2
.na
\fB\fB+shift\fR \fB[\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The positional parameters from \fB$\fR\fIn\fR\fB+1 ...\fR are renamed
\fB$1 ...\fR, the default \fIn\fR is \fB1\fR. The parameter \fIn\fR can be any
arithmetic expression that evaluates to a non-negative number less than or
equal to \fB$#\fR.
.RE

.sp
.ne 2
.na
\fB\fBsleep\fR \fIseconds\fR\fR
.ad
.sp .6
.RS 4n
Suspends execution for the number of decimal seconds or fractions of a second
specified by \fIseconds\fR.
.RE

.sp
.ne 2
.na
\fB\fB+trap\fR \fB-p\fR \fB[\fR\fIaction\fR\fB]\fR
\fB[\fR\fIsig\fR\fB] ...\fR\fR
.ad
.sp .6
.RS 4n
The \fB-p\fR option causes the trap action associated with each trap as
specified by the arguments to be printed with appropriate quoting. Otherwise,
\fIaction\fR is processed as if it were an argument to \fBeval\fR when the
shell receives signal(s) \fIsig\fR. Each \fIsig\fR can be specified as a number
or as the name of the signal. Trap commands are executed in order of signal
number. Any attempt to set a trap on a signal that was ignored on entry to the
current shell is ineffective. If \fIaction\fR is omitted and the first
\fIsig\fR is a number, or if \fIaction\fR is \fB-\fR, then the trap(s) for each
\fIsig\fR are reset to their original values. If \fIaction\fR is the null
string then this signal is ignored by the shell and by the commands it invokes.
If \fIsig\fR is \fBERR\fR then \fIaction\fR is executed whenever a command has
a \fBnon-zero\fR exit status. If \fIsig\fR is \fBDEBUG\fR then \fIaction\fR is
executed before each command. The variable \fB\&.sh.command\fR contains the
contents of the current command line when \fIaction\fR is running. If \fIsig\fR
is \fB0\fR or \fBEXIT\fR and the trap statement is executed inside the body of
a function defined with the \fBfunction\fR \fIname\fR syntax, then the command
\fIaction\fR is executed after the function completes. If \fIsig\fR is \fB0\fR
or \fBEXIT\fR for a trap set outside any function then the command \fIaction\fR
is executed on exit from the shell. If \fIsig\fR is \fBKEYBD\fR, then
\fIaction\fR is executed whenever a key is read while in \fBemacs\fR,
\fBgmacs\fR, or \fBvi\fR mode. The \fBtrap\fR command with no arguments prints
a list of commands associated with each signal number.
.RE

.sp
.ne 2
.na
\fB\fBtrue\fR\fR
.ad
.sp .6
.RS 4n
Does nothing, and exits \fB0\fR. Used with while for infinite loops.
.RE

.sp
.ne 2
.na
\fB\fB++typeset [\(+-AHflabnprtux ] [ \(+-EFLRZi[\fR\fIn\fR\fB] ] [\fR
\fIvname\fR\fB[=\fR\fIvalue\fR \fB] ]\fR\fR
.ad
.sp .6
.RS 4n
Sets attributes and values for shell variables and functions. When invoked
inside a function defined with the \fBfunction\fR \fIname\fR syntax, a new
instance of the variable \fIvname\fR is created, and the variable's value and
type are restored when the function completes.
.sp
Using \fB+\fR rather than \fB-\fR causes these options to be turned off. If no
\fIvname\fR arguments are specified, a list of \fIvname\fRs (and optionally the
\fIvalue\fRs) of the variables is printed. Using \fB+\fR rather than \fB-\fR
keeps the values from being printed.) The \fB-p\fR option causes \fBtypeset\fR
followed by the option letters to be printed before each name rather than the
names of the options. If any option other than \fB-p\fR is specified, only
those variables which have all of the specified options are printed. Otherwise,
the \fIvname\fRs and \fIattributes\fR of all variables that have attributes are
printed.
.sp
The following list of attributes can be specified:
.sp
.ne 2
.na
\fB\fB-a\fR\fR
.ad
.RS 6n
Declares \fIvname\fR to be an indexed array. This is optional unless except for
compound variable assignments.
.RE

.sp
.ne 2
.na
\fB\fB-A\fR\fR
.ad
.RS 6n
Declares \fIvname\fR to be an associative array. Sub-scripts are strings rather
than arithmetic expressions.
.RE

.sp
.ne 2
.na
\fB\fB-b\fR\fR
.ad
.RS 6n
The variable can hold any number of bytes of data. The data can be text or
binary. The value is represented by the \fBbase64\fR encoding of the data. If
\fB-Z\fR is also specified, the size in bytes of the data in the buffer is
determined by the size associated with the \fB-Z\fR. If the \fBbase64\fR string
assigned results in more data, it is truncated. Otherwise, it is filled with
bytes whose value is zero. The \fBprintf\fR format \fB%B\fR can be used to
output the actual data in this buffer instead of the \fBbase64\fR encoding of
the data.
.RE

.sp
.ne 2
.na
\fB\fB-E\fR\fR
.ad
.RS 6n
Declares \fIvname\fR to be a double precision floating point number. If \fIn\fR
is \fBnon-zero\fR, it defines the number of significant figures that are used
when expanding \fIvname\fR. Otherwise, ten significant figures is used.
.RE

.sp
.ne 2
.na
\fB\fB-f\fR\fR
.ad
.RS 6n
The names refer to function names rather than variable names. No assignments
can be made and the only other valid options are \fB-t\fR, \fB-u\fR, and
\fB-x.\fR The \fB-t\fR option turns on execution tracing for this function. The
\fB-u\fR option causes this function to be marked undefined. The \fBFPATH\fR
variable is searched to find the function definition when the function is
referenced. If no options other than \fB-f\fR is specified, then the function
definition is displayed on standard output. If \fB+f\fR is specified, then a
line containing the function name followed by a shell comment containing the
line number and path name of the file where this function was defined, if any,
is displayed.
.sp
The \fB-i\fR attribute cannot be specified with \fB-f\fR.
.RE

.sp
.ne 2
.na
\fB\fB-F\fR\fR
.ad
.RS 6n
Declares \fIvname\fR to be a double precision floating point number. If \fIn\fR
is \fBnon-zero\fR, it defines the number of places after the decimal point that
are used when expanding \fIvname\fR. Otherwise ten places after the decimal
point is used.
.RE

.sp
.ne 2
.na
\fB\fB-H\fR\fR
.ad
.RS 6n
This option provides UNIX to hostname file mapping on non-UNIX machines.
.RE

.sp
.ne 2
.na
\fB\fB-i\fR\fR
.ad
.RS 6n
Declares \fIvname\fR to be represented internally as integer. The right hand
side of an assignment is evaluated as an arithmetic expression when assigning
to an integer. If \fIn\fR is \fBnon-zero\fR, it defines the output arithmetic
base, otherwise the output base is ten.
.sp
The \fB-i\fR attribute cannot be specified along with \fB-R\fR, \fB-L\fR,
\fB-Z\fR, or \fB-f\fR.
.RE

.sp
.ne 2
.na
\fB\fB-l\fR\fR
.ad
.RS 6n
All uppercase characters are converted to lowercase. The uppercase option,
\fB-u\fR, is turned off.
.RE

.sp
.ne 2
.na
\fB\fB-L\fR\fR
.ad
.RS 6n
Left justify and remove leading blanks from \fIvalue\fR. If \fIn\fR is
\fBnon-zero\fR, it defines the width of the field, otherwise it is determined
by the width of the value of first assignment. When the variable is assigned
to, it is filled on the right with blanks or truncated, if necessary, to fit
into the field. The \fB-R\fR option is turned off.
.sp
The \fB-i\fR attribute cannot be specified with \fB-L\fR.
.RE

.sp
.ne 2
.na
\fB\fB-n\fR\fR
.ad
.RS 6n
Declares \fIvname\fR to be a reference to the variable whose name is defined by
the value of variable \fIvname\fR. This is usually used to reference a variable
inside a function whose name has been passed as an argument.
.RE

.sp
.ne 2
.na
\fB\fB-R\fR\fR
.ad
.RS 6n
Right justify and fill with leading blanks. If \fIn\fR is \fBnon-zero\fR, it
defines the width of the field, otherwise it is determined by the width of the
value of first assignment. The field is left filled with blanks or truncated
from the end if the variable is reassigned. The \fB-L\fR option is turned off.
.sp
The \fB-i\fR attribute cannot be specified with \fB-R\fR.
.RE

.sp
.ne 2
.na
\fB\fB-r\fR\fR
.ad
.RS 6n
The specified \fIvname\fRs are marked read-only and these names cannot be
changed by subsequent assignment.
.RE

.sp
.ne 2
.na
\fB\fB-t\fR\fR
.ad
.RS 6n
Tags the variables. Tags are user definable and have no special meaning to the
shell.
.RE

.sp
.ne 2
.na
\fB\fB-u\fR\fR
.ad
.RS 6n
All lowercase characters are converted to uppercase. The lowercase option,
\fB-l\fR, is turned off.
.RE

.sp
.ne 2
.na
\fB\fB-x\fR\fR
.ad
.RS 6n
The specified \fIvname\fRs are marked for automatic export to the environment
of subsequently-executed commands. Variables whose names contain a . cannot be
exported.
.RE

.sp
.ne 2
.na
\fB\fB-Z\fR\fR
.ad
.RS 6n
Right justify and fill with leading zeros if the first non-blank character is a
digit and the \fB-L\fR option has not been set. Remove leading zeros if the
\fB-L\fR option is also set. If \fIn\fR is \fBnon-zero\fR, it defines the width
of the field, otherwise it is determined by the width of the value of first
assignment.
.sp
The \fB-i\fR attribute cannot be specified with \fB-Z\fR.
.RE

.RE

.sp
.ne 2
.na
\fB\fBulimit [\fR\fB-HSacdfmnpstv\fR\fB] [\fR \fIlimit\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Set or display a resource limit. Many systems do not support one or more of
these limits. The limit for a specified resource is set when \fIlimit\fR is
specified. The value of \fIlimit\fR can be a number in the unit specified with
each resource, or the value unlimited. When more than one resource is
specified, then the limit name and unit is printed before the value.
.sp
If no option is specified, \fB-f\fR is assumed.
.sp
The following are the available resource limits:
.sp
.ne 2
.na
\fB\fB-a\fR\fR
.ad
.RS 6n
Lists all of the current resource limits.
.RE

.sp
.ne 2
.na
\fB\fB-c\fR\fR
.ad
.RS 6n
The number of 512-byte blocks on the size of core dumps.
.RE

.sp
.ne 2
.na
\fB\fB-d\fR\fR
.ad
.RS 6n
The number of Kbytes on the size of the data area.
.RE

.sp
.ne 2
.na
\fB\fB-f\fR\fR
.ad
.RS 6n
The number of 512-byte blocks on files that can be written by the current
process or by child processes (files of any size can be read).
.RE

.sp
.ne 2
.na
\fB\fB-H\fR\fR
.ad
.RS 6n
Specifies a hard limit for the specified resource.
.sp
A hard limit cannot be increased once it is set.
.sp
If neither the \fB-H\fR nor \fB-S\fR option is specified, the limit applies to
both. The current resource limit is printed when \fIlimit\fR is omitted. In
this case, the soft limit is printed unless \fB-H\fR is specified.
.RE

.sp
.ne 2
.na
\fB\fB-m\fR\fR
.ad
.RS 6n
The number of Kbytes on the size of physical memory.
.RE

.sp
.ne 2
.na
\fB\fB-n\fR\fR
.ad
.RS 6n
The number of file descriptors plus 1.
.RE

.sp
.ne 2
.na
\fB\fB-p\fR\fR
.ad
.RS 6n
The number of 512-byte blocks for pipe buffering.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR\fR
.ad
.RS 6n
The number of Kbytes on the size of the stack area.
.RE

.sp
.ne 2
.na
\fB\fB-S\fR\fR
.ad
.RS 6n
Specifies a soft limit for the specified resource.
.sp
A soft limit can be increased up to the value of the hard limit.
.sp
If neither the \fB-H\fR nor \fB-S\fR option is specified, the limit applies to
both. The current resource limit is printed when \fIlimit\fR is omitted. In
this case, the soft limit is printed unless \fB-H\fR is specified.
.RE

.sp
.ne 2
.na
\fB\fB-t\fR\fR
.ad
.RS 6n
The number of CPU seconds to be used by each process.
.RE

.sp
.ne 2
.na
\fB\fB-v\fR\fR
.ad
.RS 6n
The number of Kbytes for virtual memory.
.RE

.RE

.sp
.ne 2
.na
\fB\fBumask\fR \fB[\fR\fB-S\fR\fB]\fR\fB[\fR\fImask\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The user file-creation mask is set to \fImask\fR. \fImask\fR can either be an
octal number or a symbolic value as described in \fBchmod\fR(1).
.sp
If a symbolic value is specified, the new \fBumask\fR value is the complement
of the result of applying \fImask\fR to the complement of the previous
\fBumask\fR value. If \fImask\fR is omitted, the current value of the mask is
printed. The \fB-S\fR option causes the mode to be printed as a symbolic value.
Otherwise, the mask is printed in octal.
.sp
See \fBumask\fR(2)
.RE

.sp
.ne 2
.na
\fB\fB+unalias\fR \fB[\fR\fB-a\fR\fB]\fR \fIname\fR\fR
.ad
.sp .6
.RS 4n
The aliases specified by the list of \fIname\fRs are removed from the alias
list. The \fB-a\fR option causes all the aliases to be unset.
.RE

.sp
.ne 2
.na
\fB\fB+unset\fR \fB[\fR\fB-fnv\fR\fB]\fR \fIvname\fR\fR
.ad
.sp .6
.RS 4n
The variables specified by the list of \fIvname\fRs are unassigned, i.e., their
values and attributes are erased. Read-only variables cannot be unset. If the
\fB-f\fR option is set, then the names refer to function names. If the \fB-v\fR
option is set, then the names refer to variable names. The \fB-f\fR option
overrides \fB-v\fR. If \fB-n\fR is set and \fIname\fR is a name reference, then
\fIname\fR is unset rather than the variable that it references. The default is
equivalent to \fB-v\fR. Unsetting \fBLINENO\fR, \fBMAILCHECK\fR, \fBOPTARG\fR,
\fBOPTIND\fR, \fBRANDOM\fR, \fBSECONDS\fR, \fBTMOUT\fR, and \fB_\fR removes
their special meaning even if they are subsequently assigned to.
.RE

.sp
.ne 2
.na
\fB\fBwait\fR \fB[\fR\fIjob\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Wait for the specified job and report its termination status. If \fIjob\fR is
not specified, then all currently active child processes are waited for. The
exit status from this command is that of the last process waited for if
\fIjob\fR is specified; otherwise it is zero. See \fBJobs\fR for a description
of the format of \fIjob\fR.
.RE

.sp
.ne 2
.na
\fB\fBwhence\fR \fB[\fR\fB-afpv\fR\fB]\fR \fIname ...\fR\fR
.ad
.sp .6
.RS 4n
For each \fIname\fR, indicate how it would be interpreted if used as a command
name. The \fB-v\fR option produces a more verbose report. The \fB-f\fR option
skips the search for functions. The \fB-p\fR option does a path search for
\fIname\fR even if name is an alias, a function, or a reserved word. The
\fB-a\fR option is similar to the -v option but causes all interpretations of
the specified name to be reported.
.RE

.SS "Invocation"
.sp
.LP
If the shell is invoked by \fBexec\fR(2), and the first character of argument
zero (\fB$0\fR) is \fB-\fR, then the shell is assumed to be a login shell and
commands are read from \fB/etc/profile\fR and then from either .\fBprofile\fR
in the current directory or \fB$HOME/.profile\fR, if either file exists. Next,
for interactive shells, commands are read first from \fB/etc/ksh.kshrc\fR, and
then from the file named by performing parameter expansion, command
substitution, and arithmetic substitution on the value of the environment
variable \fBENV\fR if the file exists. If the \fB-s\fR option is not present
and \fIarg\fR and a file by the name of \fIarg\fR exists, then it reads and
executes this script. Otherwise, if the first \fIarg\fR does not contain a
\fB/\fR, a path search is performed on the first \fIarg\fR to determine the
name of the script to execute. The script \fIarg\fR must have execute
permission and any \fBsetuid\fR and \fBsetgid\fR settings are ignored. If the
script is not found on the path, \fIarg\fR is processed as if it named a
built-in command or function.
.sp
.LP
Commands are then read as described, and the following options are interpreted
by the shell when it is invoked:
.sp
.ne 2
.na
\fB\fB-c\fR\fR
.ad
.RS 15n
If the \fB-c\fR option is present, then commands are read from the first
\fIarg\fR. Any remaining arguments become positional parameters starting at
\fB0\fR.
.RE

.sp
.ne 2
.na
\fB\fB-D\fR\fR
.ad
.RS 15n
A list of all double quoted strings that are preceded by a \fB$\fR is printed
on standard output and the shell exits. This set of strings is subject to
language translation when the locale is not C or POSIX. No commands are
executed.
.RE

.sp
.ne 2
.na
\fB\fB-i\fR\fR
.ad
.RS 15n
If the \fB-i\fR option is present or if the shell input and output are attached
to a terminal (as told by \fBtcgetattr\fR(3C), this shell is interactive. In
this case \fBTERM\fR is ignored (so that \fBkill 0\fR does not kill an
interactive shell) and \fBINTR\fR is caught and ignored (so that wait is
interruptible). In all cases, \fBQUIT\fR is ignored by the shell.
.RE

.sp
.ne 2
.na
\fB\fB-R\fR \fIfilename\fR\fR
.ad
.RS 15n
The \fB-R\fR \fIfilename\fR option is used to generate a cross reference
database that can be used by a separate utility to find definitions and
references for variables and commands.
.RE

.sp
.ne 2
.na
\fB\fB-r\fR\fR
.ad
.RS 15n
If the \fB-r\fR option is present, the shell is a restricted shell.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR\fR
.ad
.RS 15n
If the \fB-s\fR option is present or if no arguments remain, then commands are
read from the standard input. Shell output, except for the output of the
\fBSpecial Commands\fR listed, is written to file descriptor 2.
.RE

.sp
.LP
The remaining options and arguments are described under the \fBset\fR command.
An optional \fB-\fR as the first argument is ignored.
.SS "\fBrksh93\fR Only"
.sp
.LP
\fBrksh93\fR is used to set up login names and execution environments whose
capabilities are more controlled than those of the standard shell.
.sp
.LP
The actions of \fBrksh93\fR are identical to those of \fBksh93\fR, except that
the following are disallowed:
.RS +4
.TP
.ie t \(bu
.el o
Unsetting the restricted option
.RE
.RS +4
.TP
.ie t \(bu
.el o
Changing directory. See \fBcd\fR(1).
.RE
.RS +4
.TP
.ie t \(bu
.el o
Setting or unsetting the value or attributes of \fBSHELL\fR, \fBENV\fR,
\fBFPATH\fR, or \fBPATH\fR
.RE
.RS +4
.TP
.ie t \(bu
.el o
Specifying path or command names containing \fB/\fR,
.RE
.RS +4
.TP
.ie t \(bu
.el o
Redirecting output (\fB>\fR, \fB>\fR\fB|\fR, \fB<>\fR, and \fB>>\fR).
.RE
.RS +4
.TP
.ie t \(bu
.el o
Adding or deleting built-in commands.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Using \fBcommand\fR \fB-p\fR to invoke a command.
.RE
.sp
.LP
These restrictions are enforced after .\fBprofile\fR and the \fBENV\fR files
are interpreted.
.sp
.LP
When a command to be executed is found to be a shell procedure, \fBrksh93\fR
invokes \fBksh93\fR to execute it. Thus, it is possible to provide to the
end-user shell procedures that have access to the full power of the standard
shell, while imposing a limited menu of commands. This scheme assumes that the
end-user does not have write and execute permissions in the same directory. The
net effect of these rules is that the writer of the .\fBprofile\fR has complete
control over user actions, by performing guaranteed setup actions and leaving
the user in an appropriate directory (probably not the login directory). The
system administrator often sets up a directory of commands, for example,
\fB/usr/rbin\fR, that can be safely invoked by \fBrksh\fR.
.SH USAGE
.sp
.LP
See \fBlargefile\fR(5) for the description of the behavior of \fBksh93\fR and
\fBrksh93\fR when encountering files greater than or equal to 2 Gbyte ( 2^31
bytes).
.SH EXIT STATUS
.sp
.LP
The following exit values are returned:
.sp
.ne 2
.na
\fB\fBnon-zero\fR\fR
.ad
.sp .6
.RS 4n
Returns \fBnon-zero\fR when errors, such as syntax errors, are detected by the
shell.
.sp
If the shell is being used non-interactively, then execution of the shell file
is abandoned unless the error occurs inside a sub-shell in which case the
sub-shell is abandoned.
.RE

.sp
.ne 2
.na
\fB\fIexit status of last command executed\fR\fR
.ad
.sp .6
.RS 4n
Returns the exit status of the last command executed.
.sp
Run time errors detected by the shell are reported by printing the command or
function name and the error condition. If the line number that the error
occurred on is greater than one, then the line number is also printed in square
brackets (\fB[]\fR) after the command or function name.
.sp
See the \fBksh93 exit\fR command for additional details.
.RE

.SH FILES
.sp
.ne 2
.na
\fB\fB/etc/profile\fR\fR
.ad
.sp .6
.RS 4n
The system initialization file, executed for login shells.
.RE

.sp
.ne 2
.na
\fB\fB/etc/ksh.kshrc\fR\fR
.ad
.sp .6
.RS 4n
The system wide startup file, executed for interactive shells.
.RE

.sp
.ne 2
.na
\fB\fB$HOME/.profile\fR\fR
.ad
.sp .6
.RS 4n
The personal initialization file, executed for login shells after
\fB/etc/profile\fR.
.RE

.sp
.ne 2
.na
\fB\fB$HOME/.kshrc\fR\fR
.ad
.sp .6
.RS 4n
Default personal initialization file, executed after \fB/etc/ksh.kshrc\fR, for
interactive shells when \fBENV\fR is not set.
.RE

.sp
.ne 2
.na
\fB\fB/etc/suid-profile\fR\fR
.ad
.sp .6
.RS 4n
Alternative initialization file, executed instead of the personal
initialization file when the real and effective user or group id do not match.
.RE

.sp
.ne 2
.na
\fB\fB/dev/null\fR\fR
.ad
.sp .6
.RS 4n
NULL device.
.RE

.SH AUTHORS
.sp
.LP
David Korn, \fBdgk@research.att.com\fR
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	See below.
.TE

.sp
.LP
The scripting interface is Uncommitted. The environment variables,
\fB\&.paths\fR feature, and editing modes are Volatile.
.SH SEE ALSO
.sp
.LP
\fBcat\fR(1), \fBcd\fR(1), \fBchmod\fR(1), \fBcut\fR(1), \fBdate\fR(1),
\fBegrep\fR(1), \fBecho\fR(1), \fBegrep\fR(1), \fBenv\fR(1), \fBfgrep\fR(1),
\fBgrep\fR(1), \fBlogin\fR(1), \fBnewgrp\fR(1), \fBpaste\fR(1),
\fBprintf\fR(1), \fBstty\fR(1), \fBtest\fR(1), \fBumask\fR(1), \fBvi\fR(1),
\fBdup\fR(2), \fBexec\fR(2), \fBfork\fR(2), \fBioctl\fR(2), \fBlseek\fR(2),
\fBpathconf\fR(2), \fBpipe\fR(2), \fBsysconf\fR(3C), \fBulimit\fR(2),
\fBumask\fR(2), \fBrand\fR(3C)\fBtcgetattr\fR(3C), \fBwait\fR(3C),
\fBa.out\fR(4), \fBprofile\fR(4), \fBattributes\fR(5), \fBenviron\fR(5),
\fBlargefile\fR(5), \fBstandards\fR(5)
.sp
.LP
Bolsky, Morris I. and Korn, David G., \fIThe New KornShell Command and
Programming Language\fR, Prentice Hall, 1995.
.sp
.LP
\fIPOSIX-Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2\fR,
IEEE, 1993.
.SH NOTES
.sp
.LP
\fBksh93\fR scripts should choose shell function names outside the namespace
used by reserved keywords of the ISO C99, C++ and JAVA languages to avoid
collisions with future enhancements to \fBksh93\fR.
.sp
.LP
If a command is executed, and then a command with the same name is installed in
a directory in the search path before the directory where the original command
was found, the shell continues to \fBexec\fR the original command. Use the
\fB-t\fR option of the alias command to correct this situation.
.sp
.LP
Some very old shell scripts contain a caret (\fB^\fR) as a synonym for the pipe
character (\fB|\fR).
.sp
.LP
Using the \fBhist\fR built-in command within a compound command causes the
whole command to disappear from the history file.
.sp
.LP
The built-in command \fB\&.\fR \fIfile\fR reads the whole file before any
commands are executed. \fBalias\fR and \fBunalias\fR commands in the file do
not apply to any commands defined in the file.
.sp
.LP
Traps are not processed while a job is waiting for a foreground process. Thus,
a trap on \fBCHLD\fR is not executed until the foreground job terminates.
.sp
.LP
It is a good idea to leave a space after the comma operator in arithmetic
expressions to prevent the comma from being interpreted as the decimal point
character in certain locales.
.sp
.LP
There might be some restrictions on creating a \fB\&.paths\fR file which is
portable across other operating systems.
.sp
.LP
If the system supports the 64-bit instruction set, \fB/bin/ksh93\fR executes
the 64-bit version of \fBksh93\fR.