KSH93(1) User Commands KSH93(1)


NAME


ksh93, rksh93 - Korn Shell, a standard and restricted command and
programming language

SYNOPSIS


ksh93 [+-abcefhikmnoprstuvxBCD] [-R file] [ +-o option] ...
[-] [arg ...]


rksh93 [+-abcefhikmnoprstuvxBCD] [-R file] [+-o option] ...
[-] [arg ...]


DESCRIPTION


ksh93 is a command and programming language that executes commands read
from a terminal or a file. rksh93 is a restricted version of the command
interpreter ksh93. rksh93 is used to set up login names and execution
environments whose capabilities are more controlled than those of the
standard shell.


See Invocation for the meaning of arguments to the shell.

Definitions


A metacharacter is defined as one of the following characters:

; & ( ) | < > NEWLINE SPACE TAB


A blank is a TAB or a SPACE.


An identifier is a sequence of letters, digits, or underscores starting
with a letter or underscore. Identifiers are used as components of
variable names.


A vname is a sequence of one or more identifiers separated by a period
(.) and optionally preceded by a period (.). vnames are used as function
and variable names.


A word is a sequence of characters from the character set defined by the
current locale, excluding non-quoted metacharacters.


A command 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 Execution) 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.

Commands


A simple-command is a list of variable assignments (see Variable
Assignments) or a sequence of blank-separated words which can be preceded
by a list of variable assignments. See the Environment section of this
manual page.


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
exec(2). The value of a simple-command is its exit status. If it
terminates normally, its value is 0-255. If it terminates abnormally, its
value is 256+signum. The name of the signal corresponding to the exit
status can be obtained by way of the -l option of the kill built-in
utility.


A pipeline is a sequence of one or more commands separated by |. The
standard output of each command but the last is connected by a pipe(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 pipefail option is enabled. Each pipeline can be
preceded by the reserved word!. This causes the exit status of the
pipeline to become 0 if the exit status of the last command is non-zero,
and 1 if the exit status of the last command is 0.


A list is a sequence of one or more pipelines separated by ;, &, |&, &&,
or |, and optionally terminated by ;, &, or |&. Of these five symbols, ;,
&, and |& have equal precedence, which is lower than that of && and ||.
The symbols && and || also have equal precedence.


A semicolon (;) causes sequential execution of the preceding pipeline. An
ampersand (&) causes asynchronous execution of the preceding pipeline,
that is, the shell does not wait for that pipeline to finish. The symbol
|& 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 <& and >& with arg p to commands
and by using -p option of the built-in commands read and print. The
symbol && (||) causes the list following it to be executed only if the
preceding pipeline returns a zero (non-zero) value. One or more NEWLINEs
can appear in a list instead of a semicolon, to delimit a command. The
first item of the first pipeline of a list that is a simple command not
beginning with a redirection, and not occurring within a while, until, or
if list , can be preceded by a semicolon. This semicolon is ignored
unless the showme option is enabled as described with the set built-in.


A command 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.

for vname [ in word ... ] ;do list ;done

Each time a for command is executed, vname is set to the next word
taken from the in word list. If in word ... is omitted, the for
command executes the do list once for each positional parameter that
is set starting from 1. Execution ends when there are no more words
in the list. See Parameter Expansion.


(( [expr1] ; [expr2] ; [expr3] )) ;do list ;done

The arithmetic expression expr1 is evaluated first. The arithmetic
expression expr2 is repeatedly evaluated until it evaluates to zero
and when non-zero, list is executed and the arithmetic expression
expr3 evaluated. If any expression is omitted, then it behaves as if
it evaluated to 1. See Arithmetic Evaluation.


select vname [ in word ... ] ;do list ;done

A select command prints on standard error (file descriptor 2) the set
of words, each preceded by a number. If in word... is omitted, the
positional parameters starting from 1 are used instead. See Parameter
Expansion. The PS3 prompt is printed and a line is read from the
standard input. If this line consists of the number of one of the
listed words, then the value of the variable vname is set to the word
corresponding to this number. If this line is empty, the selection
list is printed again. Otherwise the value of the variable vname is
set to null. The contents of the line read from standard input is
saved in the variable REPLY. The list is executed for each selection
until a break or EOF is encountered. If the REPLY variable is set to
null by the execution of list, the selection list is printed before
displaying the PS3 prompt for the next selection.


case word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac

A case command executes the list associated with the first pattern
that matches word. The form of the patterns is the same as that used
for file name generation. See File Name Generation.

The ;; operator causes execution of case to terminate. If ;& is used
in place of ;; the next subsequent list, if any, is executed.


if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi

The list following if is executed and, if it returns a zero exit
status, the list following the first then is executed. Otherwise,
the list following elif is executed, and, if its value is zero, the
list following the next then is executed. Failing each successive
elif list, the else list is executed. If the if list has non-zero
exit status and there is no else list, then the if command returns a
zero exit status.


while list ;do list ;done
until list ;do list ;done

A while command repeatedly executes the while list and, if the exit
status of the last command in the list is zero, executes the do list,
otherwise the loop terminates. If no commands in the do list are
executed, then the while command returns a zero exit status, until
can be used in place of while to negate the loop termination test.


((expression))

The expression is evaluated using the rules for arithmetic evaluation
described in this manual page. If the value of the arithmetic
expression is non-zero, the exit status is 0. Otherwise the exit
status is 1.


(list;)

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.

list is simply executed. Unlike the metacharacters, ( and ), { and }
are reserved words and must occur at the beginning of a line or after
a ; to be recognized.


[[ expression ]]

Evaluates expression and returns a zero exit status when expression
is true. See Conditional Expressions for a description of expression.


function varname { list ;}
varname () { list ;}

Define a function which is referenced by varname. A function whose
varname contains a . is called a discipline function and the portion
of the varname preceding the last . must refer to an existing
variable.

The body of the function is the list of commands between { and }. A
function defined with the function varname syntax can also be used as
an argument to the . special built-in command to get the equivalent
behavior as if the varname() syntax were used to define it. See
Functions.


time [ pipeline ]

If pipeline is omitted, the user and system time for the current
shell and completed child processes is printed on standard error.
Otherwise, pipeline is executed and the elapsed time as well as the
user and system time are printed on standard error. The TIMEFORMAT
variable can be set to a format string that specifies how the timing
information should be displayed. See Shell Variables for a
description of the TIMEFORMAT variable.


The following reserved words are recognized as reserved only when they
are the first word of a command and are not quoted:
case
do
done
else
elif
esac
for
fi
function
if
select
then
time
until
while
{ }
[[ ]]
!

Variable Assignments


One or more variable assignments can start a simple command or can be
arguments to the typeset, export, or readonly special built-in commands.
The syntax for an assignment is of the form:

varname=word
varname[word]=word

No space is permitted between varname and the = or between = and
word.


varname=(assignlist)

No space is permitted between varname and the =. An assignlist can be
one of the following:

word ...

Indexed array assignment.


[word]=word ...

Associative array assignment. If prefixed by typeset -a, creates
an indexed array instead.


assignment ...

Compound variable assignment. This creates a compound variable
varname with sub-variables of the form varname.name, where name
is the name portion of assignment. The value of varname contains
all the assignment elements. Additional assignments made to sub-
variables of varname are also displayed as part of the value of
varname. If no assignments are specified, varname is a compound
variable allowing subsequence child elements to be defined.


typeset [options] assignment ...

Nested variable assignment. Multiple assignments can be specified
by separating each of them with a ;. The previous value is unset
before the assignment.

In addition, a += can be used in place of the = to signify adding to
or appending to the previous value. When += is applied to an
arithmetic type, word is evaluated as an arithmetic expression and
added to the current value. When applied to a string variable, the
value defined by word 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.


Comments


A word beginning with # causes that word and all the following characters
up to a NEWLINE to be commented, or ignored.

Aliasing


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 =. The replacement string can contain any
valid shell script including the metacharacters listed in the Commands
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.


Aliases can be used to redefine built-in commands but cannot be used to
redefine the reserved words listed in the Commands section. Aliases can
be created and listed with the alias command and can be removed with the
unalias command.


Aliasing is performed when scripts are read, not while they are executed.
For an alias to take effect, the alias 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:

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'


Tilde Substitution


After alias substitution is performed, each word is checked to see if it
begins with an unquoted tilde (~). For tilde substitution, word also
refers to the word portion of parameter expansion. See Parameter
Expansion.


If it does, the word up to a / is checked to see if it matches a user
name in the password database. If a match is found, the ~ 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 ~ by itself, or in
front of a /, is replaced by $HOME. A ~ followed by a + or - is replaced
by the value of $PWD and $OLDPWD respectively.


In addition, when expanding a variable assignment, tilde substitution is
attempted when the value of the assignment begins with a ~, and when a ~
appears after a colon (:). The : also terminates a ~ login name.

Command Substitution


The standard output from a command enclosed in parentheses preceded by a
dollar sign ($) or a pair of grave accents (``) 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 Quoting.


The command substitution $(cat file) can be replaced by the equivalent
but faster $(<file). The command substitution $(n<#) expands to the
current byte offset for file descriptor n.

Arithmetic Substitution


An arithmetic expression enclosed in double parentheses preceded by a
dollar sign ( $((arithmetic_expression))) is replaced by the value of the
arithmetic expression within the double parentheses.

Process Substitution


Process substitution is only available on versions of the UNIX operating
system that support the /dev/fd directory for naming open files.


Each command argument of the form <(list) or >(list) runs process list
asynchronously connected to some file in /dev/fd. The name of this file
becomes the argument to the command. If the form with > is selected then
writing on this file provides input for list. If < is used, then the file
passed as an argument contains the output of the list process.


For example,

paste <(cut -f1 file1) <(cut -f3 file2) | tee \
>(process1) >(process2)


cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
the results together, and sends it to the processes process1 and
process2. It also displays the results to the standard output. The file,
which is passed as an argument to the command, is a UNIX pipe(2).
Programs that expect to lseek(2) on the file do not work.

Parameter Expansion


A parameter is a variable, one or more digits, or any of the characters
*, @, #, ?, -, $, and !. A variable is denoted by a vname. To create a
variable whose vname contains a ., a variable whose vname 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 typeset special built-in command. The attributes
supported by the shell are described later with the typeset special
built-in command. Exported variables pass values and attributes to the
environment.


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 Arithmetic
Evaluation), between a [ and a ]. Use set -A vname value ... to assign
values to an indexed array. The value of all subscripts must be in the
range of 0 through 1,048,575. 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.


An associative array is created with the -A option to typeset. A
subscript for an associative array is denoted by a string enclosed
between [ and ].


Referencing any array without a subscript is equivalent to referencing
the array with subscript 0.


The value of a variable can be assigned by:

vname=value [vname=value] ...


or

vname[subscript]=value [vname[subscript]=value] ...


No space is allowed before or after the =. A nameref is a variable that
is a reference to another variable. A nameref is created with the -n
attribute of typeset. The value of the variable at the time of the
typeset command becomes the variable that is referenced whenever the
nameref variable is used. The name of a nameref cannot contain a dot (.).
When a variable or function name contains a ., and the portion of the
name up to the first . matches the name of a nameref, the variable
referred to is obtained by replacing the nameref portion with the name of
the variable referenced by the nameref. If a nameref is used as the index
of a for loop, a name reference is established for each item in the list.
A nameref 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

typeset -n var=$1


inside the function causes references and assignments to var to be
references and assignments to the variable whose name has been passed to
the function. If either of the floating point attributes, -E, or -F, or
the integer attribute, -i, is set for vname, then the value is subject to
arithmetic evaluation as described in this manual page. Positional
parameters, parameters denoted by a number, can be assigned values with
the set special built-in command. Parameter $0 is set from argument zero
when the shell is invoked. The character $ is used to introduce
substitutable parameters.

${parameter}

The shell reads all the characters from ${ to the matching } 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 parameter 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 ., or when a variable is subscripted. If parameter 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
parameter is * or @, then all the positional parameters, starting
with $1, are substituted and separated by a field separator
character. If an array vname with subscript * or @ is used, then the
value for each of the elements is substituted, separated by the first
character of the value of IFS.


${#parameter}

If parameter is * or @, the number of positional parameters is
substituted. Otherwise, the length of the value of the parameter is
substituted.


${#vname[*]}
${#vname[@]}

The number of elements in the array vname is substituted.


${!vname}

Expands to the name of the variable referred to by vname. This is
vname except when vname is a name reference.


${!vname[subscript]}

Expands to name of the subscript unless subscript is * or @. When
subscript is *, the list of array subscripts for vname is generated.
For a variable that is not an array, the value is 0 if the variable
is set. Otherwise it is null. When subscript is @, it is the same as
$ {vname[*]}, except that when used in double quotes, each array
subscript yields a separate argument.


${!prefix*}

Expands to the names of the variables whose names begin with prefix.


${parameter:-word}

If parameter is set and is non-null then substitute its value.
Otherwise substitute word.

word is not evaluated unless it is to be used as the substituted
string.

In the following example, pwd is executed only if d is not set or is
NULL:

print ${d:-$(pwd)}


If the colon (: ) is omitted from the expression, the shell only
checks whether parameter is set or not.


${parameter:=word}

If parameter is not set or is null, set it to word. The value of the
parameter is then substituted. Positional parameters cannot be
assigned to in this way.

word is not evaluated unless it is to be used as the substituted
string.

In the following example, pwd is executed only if d is not set or is
NULL:

print ${d:-$(pwd)}


If the colon (:) is omitted from the expression, the shell only
checks whether parameter is set or not.


${parameter:?word}

If parameter is set and is non-null, substitute its value. Otherwise,
print word and exit from the shell , if the shell is not interactive.
If word is omitted then a standard message is printed.

word is not evaluated unless it is to be used as the substituted
string.

In the following example, pwd is executed only if d is not set or is
NULL:

print ${d:-$(pwd)}


If the colon (: ) is omitted from the expression, the shell only
checks whether parameter is set or not.


${parameter:+word}

If parameter is set and is non-null, substitute word. Otherwise
substitute nothing.

word is not evaluated unless it is to be used as the substituted
string.

In the following example, pwd is executed only if d is not set or is
NULL:

print ${d:-$(pwd)}


If the colon (:) is omitted from the expression, the shell only
checks whether parameter is set or not.


${parameter:offset:length}
${parameter:offset}

Expands to the portion of the value of parameter starting at the
character (counting from 0) determined by expanding offset as an
arithmetic expression and consisting of the number of characters
determined by the arithmetic expression defined by length.

In the second form, the remainder of the value is used. A negative
offset counts backwards from the end of parameter.

One or more BLANKs is required in front of a minus sign to prevent
the shell from interpreting the operator as :-. If parameter is * or
@, or is an array name indexed by * or @, then offset and length
refer to the array index and number of elements respectively. A
negative offset is taken relative to one greater than the highest
subscript for indexed arrays. The order for associative arrays is
unspecified.


${parameter#pattern}
${parameter##pattern}

If the shell pattern matches the beginning of the value of parameter,
then the value of this expansion is the value of the parameter with
the matched portion deleted. Otherwise the value of this parameter is
substituted. In the first form the smallest matching pattern is
deleted and in the second form the largest matching pattern is
deleted. When parameter is @, *, or an array variable with subscript
@ or *, the substring operation is applied to each element in turn.


${parameter%pattern}
${parameter%%pattern}

If the shell pattern matches the end of the value of parameter, then
the value of this expansion is the value of the parameter with the
matched part deleted. Otherwise substitute the value of parameter. In
the first form the smallest matching pattern is deleted, and in the
second form the largest matching pattern is deleted. When parameter
is @, *, or an array variable with subscript @ or *, the substring
operation is applied to each element in turn.


${parameter/pattern/string}
${parameter//pattern/string}
${parameter/#pattern/string}
${parameter/%pattern/string}

Expands parameter and replaces the longest match of pattern with the
specified string. Each occurrence of \n in string is replaced by the
portion of parameter that matches the nth sub-pattern.

When string is null, the pattern is deleted and the / in front of
string can be omitted. When parameter is @, *, or an array variable
with subscript @ or *, the substitution operation is applied to each
element in turn. In this case, the string portion of word is re-
evaluated for each element.

In the first form, only the first occurrence of pattern is replaced.

In the second form, each match for pattern is replaced by the
specified string.

The third form restricts the pattern match to the beginning of the
string.

The fourth form restricts the pattern match to the end of the string.


The following parameters are automatically set by the shell:

#
The number of positional parameters in decimal.


-
Options supplied to the shell on invocation or by the
set command.


?
The decimal value returned by the last executed
command.


$
The process number of this shell.


_
Initially, the value of _ 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.

This parameter is not set for commands which are
asynchronous. This parameter is also used to hold the
name of the matching MAIL file when checking for mail.


!
The process number of the last background command
invoked or the most recent job put in the background
with the bg built-in command.


.sh.command
When processing a DEBUG trap, this variable contains
the current command line that is about to run.


.sh.edchar
This variable contains the value of the keyboard
character (or sequence of characters if the first
character is an ESC, ASCII 033) that has been entered
when processing a KEYBD 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 Key Bindings section of this manual
page.


.sh.edcol
The character position of the cursor at the time of
the most recent KEYBD trap.


.sh.edmode
The value is set to ESC when processing a KEYBD trap
while in vi insert mode. Otherwise, .sh.edmode is null
when processing a KEYBD trap. See the vi Editing Mode
section of this manual page.


.sh.edtext
The characters in the input buffer at the time of the
most recent KEYBD trap. The value is null when not
processing a KEYBD trap.


.sh.file
The pathname of the file than contains the current
command.


.sh.fun
The name of the current function that is being
executed.


.sh.match
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 #, %, or /. The 0th element stores
the complete match and the ith element stores the ith
sub-match. The .sh.match variable is unset when the
variable that has expanded is assigned a new value.


.sh.name
Set to the name of the variable at the time that a
discipline function is invoked.


.sh.subscript
Set to the name subscript of the variable at the time
that a discipline function is invoked.


.sh.subshell
The current depth for sub-shells and command
substitution.


.sh.value
Set to the value of the variable at the time that the
set or append discipline function is invoked.


.sh.version
Set to a value that identifies the version of this
shell.


LINENO
The current line number within the script or function
being executed.


OLDPWD
The previous working directory set by the cd command.


OPTARG
The value of the last option argument processed by the
getopts built-in command.


OPTIND
The index of the last option argument processed by the
getopts built-in command.


PPID
The process number of the parent of the shell.


PWD
The present working directory set by the cd command.


RANDOM
Each time this variable is referenced, a random
integer, uniformly distributed between 0 and 32767, is
generated. The sequence of random numbers can be
initialized by assigning a numeric value to RANDOM.


REPLY
This variable is set by the select statement and by
the read built-in command when no arguments are
supplied.


SECONDS
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.


The following variables are used by the shell:

CDPATH
Defines the search path for the cd command.


COLUMNS
Defines the width of the edit window for the shell edit
modes and for printing select lists.


EDITOR
If the VISUAL variable is not set, the value of this
variable is checked for the patterns as described with
VISUAL and the corresponding editing option is turned on.

See the set command in the Special Command section of this
manual page.


ENV
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 $HOME/.kshrc.

See the Invocation section of this manual page.

ENV is not set by the shell.


FCEDIT
Obsolete name for the default editor name for the hist
command. FCEDIT is not used when HISTEDIT is set.

The shell specifies a default value to FCEDIT.


FIGNORE
A pattern that defines the set of file names that is
ignored when performing file name matching.


FPATH
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 -u
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 PATH, the current directory must be represented
explicitly by dot (.) rather than by adjacent colon (:)
characters or a beginning or ending colon (:).


HISTCMD
The number of the current command in the history file.


HISTEDIT
The name for the default editor name for the hist command.


HISTFILE
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 Command Re-entry section of this
manual page.


HISTSIZE
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 512.


HOME
The default argument (home directory) for the cd command.

HOME is not set by the shell. HOME is set by login(1).


IFS
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
IFS variable is used to separate arguments for the "$*"
substitution. See the Quoting section of this manual page.

Each single occurrence of an IFS character in the string to
be split, that is not in the issspace character class, and
any adjacent characters in IFS that are in the issspace
character class, delimit a field. One or more characters
in IFS that belong to the issspace character class, delimit
a field. In addition, if the same issspace character
appears consecutively inside IFS, this character is treated
as if it were not in the issspace class, so that if IFS
consists of two tab characters, then two adjacent tab
characters delimit a null field.

The shell specifies a default value to IFS.


LANG
This variable determines the locale category for any
category not specifically selected with a variable starting
with LC_ or LANG.


LC_ALL
This variable overrides the value of the LANG variable and
any other LC_ variable.


LC_COLLATE
This variable determines the locale category for character
collation information.


LC_CTYPE
This variable determines the locale category for character
handling functions. It determines the character classes
for pattern matching. See the File Name Generation section
of this manual page.


LC_NUMERIC
This variable determines the locale category for the
decimal point character.


LINES
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 LINES lines are
filled.


MAIL
If this variable is set to the name of a mail file and the
MAILPATH variable is not set, then the shell informs the
user of arrival of mail in the specified file.

MAIL is not set by the shell. On some systems, MAIL is set
by login(1).


MAILCHECK
Specifies how often in seconds the shell checks for changes
in the modification time of any of the files specified by
the MAILPATH or MAIL variables. The default value is 600
seconds. When the time has elapsed the shell checks before
issuing the next prompt.

The shell specifies a default value to MAILCHECK.


MAILPATH
A colon ( : ) 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 MAILCHECK seconds. Each file name can be
followed by a ? and a message that is printed. The message
undergoes parameter expansion, command substitution, and
arithmetic substitution with the variable $_ defined as the
name of the file that has changed. The default message is
you have mail in $_.


PATH
The search path for commands. Except in .profile, users
cannot change PATH if executing under rksh93. See the
Execution section of this manual page.

The shell specifies a default value to PATH.


PS1
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 $. The character ! in the primary prompt string
is replaced by the command number. Two successive
occurrences of ! produces a single ! when the prompt string
is printed. See the Command Re-entry section of this manual
page.

The shell specifies a default value to PS1.


PS2
Secondary prompt string, by default, >.

The shell specifies a default value to PS2.


PS3
Selection prompt string used within a select loop, by
default #?.

The shell specifies a default value to PS3.


PS4
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, PS4 is +. When PS4 is unset, the execution
trace prompt is also + .

The shell specifies a default value to PS4.


SHELL
The pathname of the shell is kept in the environment. At
invocation, if the basename of this variable is rsh, rksh,
rksh93, or krsh, the shell becomes restricted.

SHELL is not set by the shell. On some systems, SHELL is
set by login(1).


TIMEFORMAT
The value of this parameter is used as a format string
specifying how the timing information for pipelines
prefixed with the time reserved word should be displayed.
The % character introduces a format sequence that is
expanded to a time value or other information.

The format sequences and their meanings are as follows.

%%

A literal %.


%[p][l]R

The elapsed time in seconds.


%[p][l]U

The number of CPU seconds spent in user mode.


%[p][l]S

The number of CPU seconds spent in system mode.


%P

The CPU percentage, computed as (U + S) / R.

The braces denote optional portions. The optional p is a
digit specifying the precision, the number of fractional
digits after a decimal point. A value of 0 causes no
decimal point or fraction to be output. At most three
places after the decimal point can be displayed. Values of
p greater than 3 are treated as 3. If p is not specified,
the value 3 is used.

The optional l specifies a longer format, including hours
if greater than zero, minutes, and seconds of the form
HHhMMmSS.FFs. The value of p determines whether or not the
fraction is included.

All other characters are output without change and a
trailing NEWLINE is added. If unset, the default value,
$'\nreal\t%2lR\nuser\t%2lU\nsys%2lS', is used. If the value
is null, no timing information is displayed.


TMOUT
If set to a value greater than zero, TMOUT is the default
time-out value for the read built-in command. The select
compound command terminates after TMOUT 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.

The shell specifies a default value to TMOUT.


VISUAL
If the value of this variable matches the pattern
*[Vv][Ii]*, then the vi option is turned on. See Special
Commands. If the value matches the pattern *gmacs* , the
gmacs option is turned on. If the value matches the pattern
*macs*, then the emacs option is turned on. The value of
VISUAL overrides the value of EDITOR.


Field Splitting


After parameter expansion and command substitution, the results of
substitutions are scanned for the field separator characters (those found
in IFS) and split into distinct fields where such characters are found.
Explicit null fields ("" or '') are retained. Implicit null fields, those
resulting from parameters that have no values or command substitutions
with no output, are removed.


If the braceexpand (-B) option is set, each of the fields resulting from
IFS are checked to see if they contain one or more of the brace patterns.
Valid brace patterns: {*,*}, {l1..l2} , {n1..n2}, {n1..n2%fmt} {n1..n2
..n3}, or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are
letters and n1,n2,n3 are signed numbers and fmt is a format specified as
used by printf. In each case, fields are created by prepending the
characters before the { and appending the characters after the } to each
of the strings generated by the characters between the { and }. The
resulting fields are checked to see if they have any brace patterns.


In the first form, a field is created for each string between { and ,,
between , and ,, and between , and }. The string represented by * can
contain embedded matching { and } without quoting. Otherwise, each { and
} with * must be quoted.


In the second form, l1 and l2 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 l1 through l2.


In the remaining forms, a field is created for each number starting at
n1. This continues until it reaches n2 and increments n1 by n3. The cases
where n3 is not specified behave as if n3 were 1 if n1<=n2, and -1
otherwise. In forms which specify %fmt, any format flags, widths and
precisions can be specified and fmt can end in any of the specifiers
cdiouxX. For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8 fields,
a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx, and z4cx.

File Name Generation


Following splitting, each field is scanned for the characters *, ?, (,
and [, unless the -f option has been set. If one of these characters
appears, then the word is regarded as a pattern.


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 ~(N) in which case it is removed. If FIGNORE is set,
then each file name component that matches the pattern defined by the
value of FIGNORE is ignored when generating the matching file names. The
names . and .. are also ignored. If FIGNORE is not set, the character .
at the start of each file name component is ignored unless the first
character of the pattern corresponding to this component is the character
. itself. For other uses of pattern matching the / and . are not
specially treated.

*
Match any string, including the null string. When used for
file name expansion, if the globstar option is on, two
adjacent *s by themselves match all files and zero or more
directories and subdirectories. If the two adjacent *s are
followed by a /, only directories and subdirectories match.


?
Matches any single character.


[...]
Match any one of the enclosed characters. A pair of characters
separated by - matches any character lexically between the
pair, inclusive. If the first character following the opening
[ is a !, any character not enclosed is matched. A - can be
included in the character set by putting it as the first or
last character. Within [ and ], character classes can be
specified with the syntax [:class:] where class is one of the
following classes defined in the ANSI-C standard:

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


word is equivalent to alnum plus the character _. Within [ and
], an equivalence class can be specified with the syntax [=c=]
which matches all characters with the same primary collation
weight (as defined by the current locale) as the character c.
Within [ and ], [.symbol.] matches the collating symbol
symbol.


A pattern-list is a list of one or more patterns separated from each
other with an & or |. An & signifies that all patterns must be matched
whereas | requires that only one pattern be matched. Composite patterns
can be formed with one or more of the following sub-patterns:

?(pattern-list)
Optionally matches any one of the specified
patterns.


*(pattern-list)
Matches zero or more occurrences of the specified
patterns.


+(pattern-list)
Matches one or more occurrences of the specified
patterns.


{n(pattern-list)
Matches n occurrences of the specified patterns.


{m,n(pattern-list)
Matches from m to n occurrences of the specified
patterns. If m is omitted, 0 is used. If n is
omitted at least m occurrences are matched.


@(pattern-list)
Matches exactly one of the specified patterns.


!(pattern-list)
Matches anything except one of the specified
patterns.


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 - can
be inserted in front of the ( to cause the shortest match to the
specified pattern-list to be used.


When pattern-list is contained within parentheses, the backslash
character \ is treated specially even when inside a character class. All
ANSI-C character escapes are recognized and match the specified
character. In addition the following escape sequences are recognized:

\d
Matches any character in the digit class.


\D
Matches any character not in the digit class.


\s
Matches any character in the space class.


\S
Matches any character not in the space class.


\w
Matches any character in the word class.


\W
Matches any character not in the word class.


A pattern of the form %(pattern-pairs) is a sub-pattern that can be used
to match nested character expressions. Each pattern-pair is a two
character sequence which cannot contain & or |. The first pattern-pair
specifies the starting and ending characters for the match. Each
subsequent pattern-pair 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 pattern-pair is alphanumeric except for the following:

D
Causes the ending character to terminate the search for this pattern
without finding a match.


E
Causes the ending character to be interpreted as an escape
character.


L
Causes the ending character to be interpreted as a quote character
causing all characters to be ignored when looking for a match.


Q
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.


%({}Q"E\), matches characters starting at { until the matching } is found
not counting any { or } that is inside a double quoted string or preceded
by the escape character \. Without the {} this pattern matches any C
language string.


Each sub-pattern in a composite pattern is numbered, starting at 1, by
the location of the ( within the pattern. The sequence \n, where n is a
single digit and \n comes after the nth. sub-pattern, matches the same
string as the sub-pattern itself.


A pattern can contain sub-patterns of the form ~(options:pattern-list),
where either options or :pattern-list can be omitted. Unlike the other
compound patterns, these sub-patterns are not counted in the numbered
sub-patterns. If options is present, it can consist of one or more of the
following:

+
Enable the following options. This is the default.


-
Disable the following options.


E
The remainder of the pattern uses extended regular expression syntax
like the egrep(1) command.


F
The remainder of the pattern uses fgrep(1) expression syntax.


g
File the longest match (greedy).

This is the default.


G
The remainder of the pattern uses basic regular expression syntax
like the grep(1) command.


i
Treat the match as case insensitive.


K
The remainder of the pattern uses shell pattern syntax.

This is the default.


l
Left anchor the pattern.

This is the default for K style patterns.


N
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.


r
Right anchor the pattern.

This is the default for K style patterns.


If both options and :pattern-list are specified, then the options apply
only to pattern-list. Otherwise, these options remain in effect until
they are disabled by a subsequent ~(...) or at the end of the sub-pattern
containing ~(...).

Quoting


Each of the metacharacters listed in the Definitions has a special
meaning to the shell.

g
File the longest match (greedy). This is the default.


i
Treat the match as case insensitive.


If both options and :pattern-list are specified, then the options apply
only to pattern-list. Otherwise, the options remain in effect until they
are disabled by a subsequent ~(...) or at the end of the sub-pattern
containing ~(...).


Each of the metacharacters listed in the Definitions 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 (\). The pair \NEWLINE is
removed. All characters enclosed between a pair of single quote marks
('') that is not preceded by a $ are quoted. A single quote cannot appear
within the single quotes. A single quoted string preceded by an unquoted
$ is processed as an ANSI-C string except for the following:

\0
Causes the remainder of the string to be ignored.


\cx
Expands to the character CTRL-x.


\C[.name.]
Expands to the collating element name.


\e
Equivalent to the escape character (ASCII 033),


\E
Equivalent to the escape character (ASCII 033),


Inside double quote marks (""), parameter and command substitution occur
and \ quotes the characters \, `, ", and $. A $ in front of a double
quoted string is ignored in the C or POSIX locale, and might cause the
string to be replaced by a locale specific string otherwise. The meaning
of $* and $@ is identical when not quoted or when used as a variable
assignment value or as a file name. However, when used as a command
argument, "$*" is equivalent to "$1d$2d...", where d is the first
character of the IFS variable, whereas "$@" is equivalent to "$1" "$2"
.... Inside grave quote marks (``), \fR quotes the characters \, `, and
$. If the grave quotes occur within double quotes, then \ also quotes the
character ".


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.

Arithmetic Evaluation


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 shift and let.
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 printf(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 ANSI-C programming language floating point conventions.
Integer constants follow the ANSI-C 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
[base#]n where base is a decimal number between two and sixty-four
representing the arithmetic base and n is a number in that base. The
digits greater than 9 are represented by the lower case letters, the
upper case letters, @, and _ respectively. For bases less than or equal
to 36, upper and lower case characters can be used interchangeably.


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 ** 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.


Any of the following math library functions that are in the C math
library can be used within an arithmetic expression:

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


An internal representation of a variable as a double precision floating
point can be specified with the -E [n] or -F [n] option of the typeset
special built-in command. The -E option causes the expansion of the value
to be represented using scientific notation when it is expanded. The
optional option argument n defines the number of significant figures. The
-F option causes the expansion to be represented as a floating decimal
number when it is expanded. The optional option argument n defines the
number of places after the decimal point in this case.


An internal integer representation of a variable can be specified with
the -i [n] option of the typeset special built-in command. The optional
option argument n specifies an arithmetic base to be used when expanding
the variable. If you do not specify an arithmetic base, base 10 is used.


Arithmetic evaluation is performed on the value of each assignment to a
variable with the -E, -F, or -i option. Assigning a floating point number
to a variable whose type is an integer causes the fractional part to be
truncated.

Prompting


When used interactively, the shell prompts with the value of PS1 after
expanding it for parameter expansion, command substitution, and
arithmetic substitution, before reading a command. In addition, each
single ! in the prompt is replaced by the command number. A !! is
required to place ! 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 PS2, is issued.

Conditional Expressions


A conditional expression is used with the [[ compound command to test
attributes of files and to compare strings. Field splitting and file name
generation are not performed on the words between [[ and ]].


Each expression can be constructed from one or more of the following
unary or binary expressions:

-a file
True, if file exists.

This option is the same as -e. This option is
obsolete.


-b file
True, if file exists and is a block special file.


-c file
True, if file exists and is a character special
file.


-d file
True, if file exists and is a directory.


-e file
True, if file exists.


-f file
True, if file exists and is an ordinary file.


-g file
True, if file exists and it has its setgid bit set.


-G file
True, if file exists and its group matches the
effective group id of this process.


-h file
True, if file exists and is a symbolic link.


-k file
True, if file exists and it has its sticky bit set.


-L file
True, if file exists and is a symbolic link.


-n string
True, if length of string is non-zero.


-N file
True, if file exists and the modification time is
greater than the last access time.


-o option
True, if option named option is on.


-o ?option
True, if option named option is a valid option name.


-O file
True, if file exists and is owned by the effective
user id of this process.


-p file
True, if file exists and is a FIFO special file or a
pipe.


-r file
True, if file exists and is readable by current
process.


-s file
True, if file exists and has size greater than zero.


-S file
True, if file exists and is a socket.


-t fildes
True, if file descriptor number fildes is open and
associated with a terminal device.


-u file
True, if file exists and it has its setuid bit set.


-w file
True, if file exists and is writable by current
process.


-x file
True, if file exists and is executable by current
process. If file exists and is a directory, then
true if the current process has permission to search
in the directory.


-z string
True, if length of string is zero.


file1 -ef file2
True, if file1 and file2 exist and refer to the same
file.


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


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


string
True, if string is not null.


string == pattern
True, if string matches pattern. Any part of pattern
can be quoted to cause it to be matched as a string.
With a successful match to pattern, the .sh.match
array variable contains the match and sub-pattern
matches.


string = pattern
Same as ==, but is obsolete.


string != pattern
True, if string does not match pattern. When the
string matches the pattern the .sh.match array
variable contains the match and sub-pattern matches.


string =~ ere
True if string matches the pattern ~(E)ere where ere
is an extended regular expression.


string1 < string2
True, if string1 comes before string2 based on ASCII
value of their characters.


string1 > string2
True, if string1 comes after string2 based on ASCII
value of their characters.


In each of the following expressions, if file is of the form /dev/fd/n,
where n is an integer, the test is applied to the open file whose
descriptor number is n. The following obsolete arithmetic comparisons are
supported:

exp1 -eq exp2
True, if exp1 is equal to exp2.


exp1 -ge exp2
True, if exp1 is greater than or equal to exp2.


exp1 -gt exp2
True, if exp1 is greater than exp2.


exp1 -le exp2
True, if exp1 is less than or equal to exp2.


exp1 -lt exp2
True, if exp1 is less than exp2.


exp1 -ne exp2
True, if exp1 is not equal to exp2.


A compound expression can be constructed from these primitives by using
any of the following, listed in decreasing order of precedence:

(expression)
True, if expression is true. Used to group
expressions.


! expression
True, if expression is false.


expression1 && expression2
True, if expression1 and expression2 are
both true.


expression1 || expression2
True, if either expression1 or expression2
is true.


Input and Output


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 not passed on to the invoked command. Command substitution,
parameter expansion, and arithmetic substitution occur before word or
digit 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.


In each of the following redirections, if file is of the form
/dev/sctp/host/port, /dev/tcp/host/port, or /dev/udp/host/port, where
host is a hostname or host address, and port is a service specified by
name or an integer port number, then the redirection attempts to make a
tcp, sctp or udp connection to the corresponding socket.


No intervening space is allowed between the characters of redirection
operators.

<word
Use file word as standard input (file descriptor 0).


>word
Use file word as standard output (file descriptor 1). If
the file does not exist then it is created. If the file
exists, and the noclobber option is on, this causes an
error. Otherwise, it is truncated to zero length.


>|word
Same as >, except that it overrides the noclobber option.


>>word
Use file word 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.


<>word
Open file word for reading and writing as standard input.


<<[-]word
The shell input is read up to a line that is the same as
word 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 word. The resulting document, called a here-
document, becomes the standard input. If any character of
word is quoted, then no interpretation is placed upon the
characters of the document. Otherwise, parameter expansion,
command substitution, and arithmetic substitution occur,
\NEWLINE is ignored, and \ must be used to quote the
characters \, $, `. If - is appended to <<, then all
leading tabs are stripped from word and from the document.
If # is appended to <<, 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 word. A tab stop is assumed to occur at every 8
columns for the purposes of determining the indentation.


<<<word
A short form of here document in which word becomes the
contents of the here-document after any parameter
expansion, command substitution, and arithmetic
substitution occur.


<&digit
The standard input is duplicated from file descriptor
digit, and similarly for the standard output using >&digit.
See dup(2).


<&digit-
The file descriptor specified by digit is moved to standard
input. Similarly for the standard output using >&digit-.


<&-
The standard input is closed. Similarly for the standard
output using >&-.


<&p
The input from the co-process is moved to standard input.


>&p
The output to the co-process is moved to standard output.


<#((expr))
Evaluate arithmetic expression expr and position file
descriptor 0 to the resulting value bytes from the start of
the file. The variables CUR and EOF evaluate to the current
offset and end-of-file offset respectively when evaluating
expr.


>#((expr))
The same as <# except applies to file descriptor 1.


<#pattern
Seek forward to the beginning of the next line containing
pattern.


<##pattern
The same as <#, except that the portion of the file that is
skipped is copied to standard output.


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 >&- and the ># and <# forms, is preceded
by {varname} with no intervening space, then a file descriptor number >
10 is selected by the shell and stored in the variable varname. If >&- or
the any of the ># and <# forms is preceded by {varname} the value of
varname defines the file descriptor to close or position. For example:

... 2>&1


means file descriptor 2 is to be opened for writing as a duplicate of
file descriptor 1 and

exec [n]<file


means open file for reading and store the file descriptor number in
variable n. The order in which redirections are specified is significant.
The shell evaluates each redirection in terms of the (file_descriptor,
file) association at the time of evaluation. For example:

... 1>fname 2>&1


first associates file descriptor 1 with file fname. It then associates
file descriptor 2 with the file associated with file descriptor 1, that
is, fname. 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 fname. If
a command is followed by & and job control is not active, the default
standard input for the command is the empty file /dev/null. Otherwise,
the environment for the execution of a command contains the file
descriptors of the invoking shell as modified by input and output
specifications.

Environment


The environment is a list of name-value pairs that is passed to an
executed program in the same way as a normal argument list. See
environ(5).


The names must be identifiers 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 export.
Executed commands inherit the environment. If the user modifies the
values of these variables or creates new ones, using the export or
typeset -x 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 export or
typeset -x 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 identifier=value.
Thus:

TERM=450 cmd args


and

(export TERM; TERM=450; cmd args)


are equivalent (as far as the execution of cmd is concerned except for
special built-in commands listed in the Built-Ins section, those that are
preceded with a dagger. If the obsolete -k option is set, all variable
assignment arguments are placed in the environment, even if they occur
after the command name.


The following example first prints a=b c and then c:

echo a=b c
set -k
echo a=b c


This feature is intended for use with scripts written for early versions
of the shell and its use in new scripts is strongly discouraged.

Functions


For historical reasons, there are two ways to define functions, the
name() syntax and the function name syntax. These are described in the
Commands section of this manual page.


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 Execution
section of this manual page for details.


Functions defined by the function name 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 EXIT 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 typeset 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.


Functions defined with the name() syntax and functions defined with the
function name syntax that are invoked with the . 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.


The special built-in command return is used to return from function
calls.


Function names can be listed with the -f or +f option of the typeset
special built-in command. The text of functions, when available, is also
listed with -f. Functions can be undefined with the -f option of the
unset special built-in command.


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 FPATH variable should
contain the name of this directory. They can also be specified in the ENV
file.

Discipline Functions


Each variable can have zero or more discipline functions associated with
it. The shell initially understands the discipline names get, set,
append, and unset but on most systems others can be added at run time via
the C programming interface extension provided by the builtin built-in
utility. If the get discipline is defined for a variable, it is invoked
whenever the specified variable is referenced. If the variable .sh.value
is assigned a value inside the discipline function, the referenced
variable is evaluated to this value instead. If the set discipline is
defined for a variable, it is invoked whenever the specified variable is
assigned a value. If the append discipline is defined for a variable, it
is invoked whenever a value is appended to the specified variable. The
variable .sh.value is specified the value of the variable before invoking
the discipline, and the variable is assigned the value of .sh.value after
the discipline completes. If .sh.value is unset inside the discipline,
then that value is unchanged. If the unset 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.


The variable .sh.name contains the name of the variable for which the
discipline function is called, .sh.subscript is the subscript of the
variable, and .sh.value contains the value being assigned inside the set
discipline function. For the set discipline, changing .sh.value changes
the value that gets assigned.

Jobs


If the monitor option of the set command is turned on, an interactive
shell associates a job with each pipeline. It keeps a table of current
jobs, printed by the jobs command, and assigns them small integer
numbers. When a job is started asynchronously with &, the shell prints a
line which looks like:

[1] 1234


indicating that the job which was started asynchronously was job number 1
and had one (top-level) process, whose process id was 1234.


If you are running a job and wish to stop it, CTRL-z sends a STOP 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 bg command,
or run some other commands and then eventually bring the job back into
the foreground with the foreground command fg. A CTRL-z takes effect
immediately and is like an interrupt in that pending output and unread
input are discarded when it is typed.


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 sttytostop. If you set this
tty option, then background jobs stop when they try to produce output
like they do when they try to read input.


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:

%number
The job with the specified number.


%string
Any job whose command line begins with string.


%?string
Any job whose command line contains string.


%%
Current job.


%+
Equivalent to %%.


%-
Previous job.


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 set command causes the shell to print these job change messages as
soon as they occur.


When the monitor option is on, each background job that completes
triggers any trap set for CHLD.


When you try to leave the shell while jobs are running or stopped, you
are warned that You have stopped(running) jobs. You can use the jobs
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 HUP signal, it sends a HUP
signal to each job that has not been disowned with the disown built-in
command.

Signals


The INT and QUIT signals for an invoked command are ignored if the
command is followed by & and the monitor option is not active.
Otherwise, signals have the values inherited by the shell from its
parent. See the trap built-in command.

Execution


Each time a command is read, the substitutions are carried out. If the
command name matches one of the ones in the Special Built-in Commands
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 function name syntax, any trap set on EXIT 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.


The shell variable PATH defines the search path for the directory
containing the command. Alternative directory names are separated by a
colon (:). The default path is /bin:/usr/bin:, specifying /bin, /usr/bin,
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 (/), 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 FPATH 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 .paths is found, and this file contains a line of the
form FPATH=path where path 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 . special
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 exec(2).


When an executable is found, the directory where it is found in is
searched for a file named .paths. If this file is found and it contains a
line of the form BUILTIN_LIB=value, the library named by value is
searched for as if it were an option argument to builtin -f, 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 name=value in the first or second line, then the
environment variable name is modified by prepending the directory
specified by value to the directory list. If value is not an absolute
directory, then it specifies a directory relative to the directory that
the executable was found. If the environment variable name does not
already exist it is added to the environment list for the specified
command.


If the file has execute permission but is not an a.out 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
setuid and setgid 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.

Command Re-entry
The text of the last HISTSIZE (default 512) commands entered from a
terminal device is saved in a history file. The file $HOME/.sh_history is
used if the HISTFILE 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 HISTFILE. The built-in command hist 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 hist
then the value of the variable HISTEDIT is used. If HISTEDIT is unset,
the obsolete variable FCEDIT is used. If FCEDIT is not defined, then
/bin/ed is used. The edited commands are printed and executed again upon
leaving the editor unless you quit without writing. The -s option (and in
obsolete versions, the editor name -) is used to skip the editing phase
and to re-execute the command. In this case a substitution parameter of
the form old=newcan be used to modify the command before execution. For
example, with the preset alias r, which is aliased to 'hist -s', typing
`r bad=good c' re-executes the most recent command which starts with the
letter c, replacing the first occurrence of the string bad with the
string good.

Inline Editing Options


Normally, each command line entered from a terminal device is simply
typed followed by a NEWLINE (RETURN or LINE FEED). If either the emacs,
gmacs, or vi 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 VISUAL or EDITOR variable
is assigned a value ending in either of these option names.


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.


Unless the multiline 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 COLUMNS if it is defined, otherwise 80. 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 > (<, *) if the line extends on the right , left, or both sides of
the window.


The search commands in each edit mode provide access to the history file.
Only strings are matched, not patterns, although a leading ^ in the
string restricts the match to begin at the first character in the line.


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 ;, |, &, or (, and the word does not
begin with ~ or contain a /, the list of aliases, functions, and
executable commands defined by the PATH 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 * 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 / 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 / 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 TAB 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.

Key Bindings


The KEYBD 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.


The variable .sh.edchar contains the character or character sequence
which generated the trap. Changing the value of .sh.edchar 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 .sh.edcol is
set to the input column number of the cursor at the time of the input.
The variable .sh.edmode is set to ESC when in vi insert mode and is null
otherwise. By prepending ${.sh.editmode} to a value assigned to
.sh.edchar it causes the shell to change to control mode if it is not
already in this mode.


This trap is not invoked for characters entered as arguments to editing
directives, or while reading input for a character search.

emacs Editing Mode
This mode is entered by enabling either the emacs or gmacs option. The
only difference between these two modes is the way they handle ^T. 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 (^) followed by the character.


For example, ^F is the notation for CTRL/F. This is entered by depressing
f while holding down the CTRL (control) key. The SHIFT key is not
depressed. (The notation ^? indicates the DEL (delete) key.)


The notation for escape sequences is M- followed by a character. For
example, M-f (pronounced Meta f) is entered by depressing ESC (ASCII 033)
followed by f. M-F is the notation for ESC followed by F.


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.

^F
Move the cursor forward (right) one character.


M-[C
Move the cursor forward (right) one character.


M-f
Move the cursor forward one word. The emacs editor's idea of
a word is a string of characters consisting of only letters,
digits and underscores.


^B
Move the cursor backward (left) one character.


M-[D
Move the cursor backward (left) one character.


M-b
Move the cursor backward one word.


^A
Move the cursor to the beginning of the line.


M-[H
Move the cursor to the beginning of the line.


^E
Move the cursor to the end of the line.


M-[Y
Move the cursor to the end of line.


^]char
Move the cursor forward to the character char on the current
line.


M-^]char
Move the cursor backwards to the character char on the
current line.


^X^X
Interchange the cursor and the mark.


erase
Delete the previous character. The user-defined erase
character is defined by the stty(1) command, and is usually
^H or #.


lnext
Removes the next character's editing features. The user-
defined literal next character is defined by the stty(1)
command, or is ^V if not defined.


^D
Delete the current character.


M-d
Delete the current word.


M-^H
MetaBACKSPACE. Delete the previous word.


M-h
Delete the previous word.


M-^?
MetaDEL. Delete the previous word. If your interrupt
character is ^? (DEL, the default), this command does not
work.


^T
Transpose the current character with the previous character,
and advance the cursor in emacs mode. Transpose two previous
characters in gmacs mode.


^C
Capitalize the current character.


M-c
Capitalize the current word.


M-l
Change the current word to lower case.


^K
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.


^W
Kill from the cursor to the mark.


M-p
Push the region from the cursor to the mark on the stack.


kill
Kill the entire current line. The user-defined kill
character is defined by the stty(1) command, usually a ^G or
@. 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.


^Y
Restore the last item removed from line. Yank the item back
to the line.


^L
Line feed and print the current line.


M-^L
Clear the screen.


^@
Null character. Set mark.


M-space
MetaSPACE. Set the mark.


^J
New line. Execute the current line.


^M
Return. Execute the current line.


EOF
End-of-file character, normally ^D, is processed as an end-
of-file only if the current line is null.


^P
Fetch the previous command. Each time ^P 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.


M-[A
Equivalent to ^P.


M-<
Fetch the least recent (oldest) history line.


M->
Fetch the most recent (youngest) history line.


^N
Fetch the next command line. Each time ^N is entered the
next command line forward in time is accessed.


M-[B
Equivalent to ^N.


^Rstring
Reverse search history for a previous command line
containing string. If a parameter of zero is specified, the
search is forward. string is terminated by a RETURN or
NEWLINE. If string is preceded by a ^, the matched line must
begin with string. If string is omitted, then the next
command line containing the most recent string is accessed.
In this case a parameter of zero reverses the direction of
the search.


^O
Operate. Execute the current line and fetch the next line
relative to current line from the history file.


M-digits
Escape. Define numeric parameter. The digits are taken as a
parameter to the next command. The commands that accept a
parameter are: ^F, ^B, ERASE, ^C, ^D, ^K, ^R, ^P, ^N, ^],
M-., M-, M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l, and
M-^H.


M-letter
Soft-key. Search the alias list for an alias by the name
letter. If an alias of letter is defined, insert its value
on the input queue. letter must not be one of the
metafunctions in this section.


M-[letter
Soft key. Search the alias list for an alias by the name
letter. 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.


M-.
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.


M-_
Same as M-..


M-*
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.


M-ESC
Command or file name completion as described in this manual
page.


^ITAB
Attempts command or file name completion as described in
this manual page. If a partial completion occurs, repeating
this behaves as if M-= were entered. If no match is found
or entered after SPACE, a TAB is inserted.


M-=
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.


^U
Multiply parameter of next command by 4.


\
Escape the next character. Editing characters, the user's
erase, kill and interrupt (normally ^?) characters can be
entered in a command line or in a search string if preceded
by a \. The \ removes the next character's editing features,
if any.


M-^V
Display the version of the shell.


M-#
If the line does not begin with a #, a # 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 #, the # is deleted
and one # after each NEWLINE is also deleted.


vi Editing Mode
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 count prior to the command.


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.


If the option viraw 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.

Input Edit Commands


By default the editor is in input mode.


The following input edit commands are supported:

ERASE
User defined erase character as defined by the stty command,
usually ^H or #. Delete previous character.


^W
Delete the previous blank separated word. On some systems the
viraw option might be required for this to work.


EOF
As the first character of the line causes the shell to
terminate unless the ignoreeof option is set. Otherwise this
character is ignored.


lnext
User defined literal next character as defined by the stty(1)
or ^V if not defined. Removes the next character's editing
features, if any. On some systems the viraw option might be
required for this to work.


\
Escape the next ERASE or KILL character.


^I TAB
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 = were entered from
control mode. If no match is found or entered after SPACE, a
TAB is inserted.


Motion Edit Commands


The motion edit commands move the cursor.


The following motion edit commands are supported:

[count]l
Move the cursor forward (right) one character.


[count][C
Move the cursor forward (right) one character.


[count]w
Move the cursor forward one alphanumeric word.


[count]W
Move the cursor to the beginning of the next word that
follows a blank.


[count]e
Move the cursor to the end of the word.


[count]E
Move the cursor to the end of the current blank delimited
word.


[count]h
Move the cursor backward (left) one character.


[count][D
Move the cursor backward (left) one character.


[count]b
Move the cursor backward one word.


[count]B
Move the cursor to the preceding blank separated word.


[count]|
Move the cursor to column count.


[count]fc
Find the next character c in the current line.


[count]Fc
Find the previous character c in the current line.


[count]tC
Equivalent to f followed by h.


[count]Tc
Equivalent to F followed by l.


[count];
Repeat count times the last single character find command:
f, F, t, or T.


[count],
Reverse the last single character find command count times.


0
Move the cursor to the start of line.


^
Move the cursor to start of line.


[H
Move the cursor to the first non-blank character in the
line.


$
Move the cursor to the end of the line.


[Y
Move the cursor to the end of the line.


%
Moves to balancing (, ), {, }, [, or ]. 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.


Search Edit Commands


The search edit commands access your command history.


The following search edit commands are supported:

[count]k
Fetch the previous command. Each time k is entered, the
previous command back in time is accessed.


[count]-
Fetch the previous command. Each time k is entered, the
previous command back in time is accessed.

Equivalent to k.


[count][A
Fetch the previous command. Each time k is entered, the
previous command back in time is accessed.

Equivalent to k.


[count]j
Fetch the next command. Each time j is entered, the next
command forward in time is accessed.


[count]+
Fetch the next command. Each time j is entered, the next
command forward in time is accessed.

Equivalent to j.


[count][B
Fetch the next command. Each time j is entered, the next
command forward in time is accessed.

Equivalent to j.


[count]G
Fetch command number count. The default is the least recent
history command.


/string
Search backward through history for a previous command
containing string. string is terminated by a RETURN or
NEWLINE. If string is preceded by a ^, the matched line must
begin with string. If string is null, the previous string is
used.


?string
Search forward through history for a previous command
containing string. string is terminated by a RETURN or
NEWLINE. If string is preceded by a ^, the matched line must
begin with string. If string is null, the previous string is
used.

Same as / except that search is in the forward direction.


n
Search in the backwards direction for the next match of the
last pattern to / or ? commands.


N
Search in the forward direction for next match of the last
pattern to / or ?.


Text Modification Edit Commands


The following commands modify the line:

a
Enter input mode and enter text after the current
character.


A
Append text to the end of the line. Equivalent to $a.


[count]cmotion
c[count]motion
Delete current character through the character that
motion would move the cursor to and enter input mode.
If motion is c, the entire line is deleted and input
mode entered.


C
Delete the current character through the end of line
and enter input mode. Equivalent to c$.


S
Equivalent to cc.


[count]s
Replace characters under the cursor in input mode.


D[count]dmotion
Delete the current character through the end of line.
Equivalent to d$.


d[count]motion
Delete current character through the character that
motion would move to. If motion is d , the entire
line is deleted.


i
Enter input mode and insert text before the current
character.


I
Insert text before the beginning of the line.
Equivalent to 0i.


[count]P
Place the previous text modification before the
cursor.


[count]p
Place the previous text modification after the cursor.


R
Enter input mode and replace characters on the screen
with characters you type overlay fashion.


[count]rc
Replace the count characters starting at the current
cursor position with c, and advance the cursor.


[count]x
Delete current character.


[count]X
Delete preceding character.


[count].
Repeat the previous text modification command.


[count]~
Invert the case of the count characters starting at
the current cursor position and advance the cursor.


[count]_
Causes the count word of the previous command to be
appended and input mode entered. The last word is used
if count is omitted.


*
Causes an * 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.


\
Command or file name completion as described in this
manual page.


Other Edit Commands


The following miscellaneous edit commands are supported:

[count]ymotion
y[count]motion
Yank the current character through the character to
which motion would move the cursor. Put the yanked
characters in the delete buffer. The text and cursor
position are unchanged.


yy
Yank the current line.


Y
Yank the current line from the current cursor location
to the end of the line. Equivalent to y$.


u
Undo the last text modifying command.


U
Undo all the text modifying commands performed on
current line.


[count]V
Return the command :

hist -e ${VISUAL:-${EDITOR:-vi}} count


in the input buffer. If count is omitted, the current
line is used.


^L
Line feed and print the current line. This command only
works in control mode.


^J
New line. Execute the current line, regardless of mode.


^M
Return. Execute the current line, regardless of mode.


#
If the first character of the command is a # , delete
this # and each # that follows a NEWLINE.

Otherwise, send the line after inserting a # in front
of each line in the command.

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.


[count]=
If count is not specified, generate the list of
matching commands or file names as described in this
manual page.

Otherwise, replace the word at the current cursor
location with the count 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.


@letter
Search your alias list for an alias by the name letter.
If an alias of this name is defined, insert its value
on the input queue for processing.


^V
Display version of the shell.


Built-in Commands
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 1 and the exit status, when there is
no syntax error, is 0. Except for :, true, false, echo, newgrp, and
login, all built-in commands accept -- to indicate the end of options.
They also interpret the option --man as a request to display the manual
page onto standard error and -? as a help request which prints a usage
message on standard error.


Commands that are preceded by one or two ++ symbols are special built-in
commands and are treated specially in the following ways:

1. Variable assignment lists preceding the command remain in
effect when the command completes.

2. I/O redirections are processed after variable assignments.

3. Errors cause a script that contains them to abort.

4. They are not valid function names.

5. Words following a command preceded by ++ 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 = sign and field splitting
and file name generation are not performed.

+ : [arg ...]

The command only expands parameters.


+ . name [arg ...]

If name is a function defined with the function name reserved word
syntax, the function is executed in the current environment (as if it
had been defined with the name() syntax.) Otherwise if name 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 arg 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.


++ alias [-ptx] [name[ =value]] ...

alias with no arguments prints the list of aliases in the form
name=value on standard output. The -p option causes the word alias to
be inserted before each one. When one or more arguments are
specified, an alias is defined for each name whose value is
specified. A trailing space in value causes the next word to be
checked for alias substitution. The obsolete -t option is used to set
and list tracked aliases. The value of a tracked alias is the full
pathname corresponding to the specified name. The value becomes
undefined when the value of PATH is reset but the alias remains
tracked. Without the -t option, for each name in the argument list
for which no value is specified, the name and value of the alias is
printed. The obsolete -x option has no effect. The exit status is
non-zero if a name is specified, but no value, and no alias has been
defined for the name.


bg [ job...]

This command is only on systems that support job control. Puts each
specified job into the background. The current job is put in the
background if job is not specified. See the Jobs section of this
manual page for a description of the format of job.


+ break [n]

Exit from the enclosing for, while, until, or select loop, if any. If
n is specified, then break n levels.


builtin [-ds ] [-f file] [name ...]

If name is not specified, and no -f option is specified, the built-
ins are printed on standard output. The -s option prints only the
special built-ins. Otherwise, each name represents the pathname whose
basename is the name of the built-in. The entry point function name
is determined by prepending b to the built-in name. The ISO C/C++
prototype is bmycommand(int argc, char *argv[], void *context) for
the built-in command mycommand where argv is an array of argc
elements and context is an optional pointer to a Shell_t structure as
described in <ast/shell.h> Special built-ins cannot be bound to a
pathname or deleted. The -d option deletes each of the specified
built-ins. On systems that support dynamic loading, the -f 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 builtin. Multiple libraries can be
specified with separate invocations of the builtin 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 lib_init() and invokes this function with an argument of 0.


cd [-LP] [arg]
cd [-LP] old new

This command has two forms.

In the first form it changes the current directory to arg. If arg is
a -, the directory is changed to the previous directory. The shell
variable HOME is the default arg. The variable PWD is set to the
current directory. The shell variable CDPATH defines the search path
for the directory containing arg. Alternative directory names are
separated by a colon (:). The default path is NULL (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 arg begins
with a /, the search path is not used. Otherwise, each directory in
the path is searched for arg.

The second form of cd substitutes the string new for the string old
in the current directory name, PWD, 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 -L option. The
-P option causes symbolic links to be resolved when determining the
directory. The last instance of -L or -P on the command line
determines which method is used. The cd command cannot be executed by
rksh93.


command [-pvVx] name [arg ...]

Without the -v or -V options, executes name with the arguments
specified by arg.

The -p option causes a default path to be searched rather than the
one defined by the value of PATH. Functions are not searched when
finding name. In addition, if name refers to a special built-in, none
of the special properties associated with the leading daggers are
honored. For example, the predefined alias redirect='command exec'
prevents a script from terminating when an invalid redirection is
specified.

With the -x option, if command execution would result in a failure
because there are too many arguments, errno E2BIG, the shell invokes
command name 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.

With the -v option, command is equivalent to the built-in whence
command described in this section. The -V option causes command to
act like whence -v.


+continue [n]

Resumes the next iteration of the enclosing for, while, until, or
select loop. If n is specified, then resume at the nth enclosing
loop.


disown [job...]

Causes the shell not to send a HUP signal to each specified job, or
all active jobs if job is omitted, when a login shell terminates.


echo [arg ...]

When the first arg does not begin with a -, and none of the arguments
contain a backslash (\), prints each of its arguments separated by a
SPACE and terminated by a NEWLINE. Otherwise, the behavior of echo is
system dependent and print or printf described in this section should
be used. See echo(1) for usage and description.


+eval [arg ...]

The arguments are read as input to the shell and the resulting
commands are executed.


+exec [-c] [-a name ...] [arg ...]

If arg is specified, the command specified by the arguments is
executed in place of this shell without creating a new process. The
-c option causes the environment to be cleared before applying
variable assignments associated with the exec invocation. The -a
option causes name rather than the first arg, to become argv[0] for
the new process. Input and output arguments can appear and affect
the current process. If arg 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 2 that are opened with this mechanism are closed
when invoking another program.


+exit [n]

Causes the shell to exit with the exit status specified by n. The
value is the least significant 8 bits of the specified status. If n
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 ignoreeof option turned on. See set.


++export [-p] [name[=value]] ...

If name 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 -p option causes the word
export to be inserted before each one. Otherwise, the specified names
are marked for automatic export to the environment of subsequently-
executed commands.


false

Does nothing, and exits 1. Used with until for infinite loops.


fg [job ...]

This command is only on systems that support job control. Each job
specified is brought to the foreground and waited for in the
specified order. Otherwise, the current job is brought into the
foreground. See Jobs for a description of the format of job.


getconf [name [pathname]]

Prints the current value of the configuration parameter specified by
name. The configuration parameters are defined by the IEEE POSIX
1003.1 and IEEE POSIX 1003.2 standards. See pathconf(2) and
sysconf(3C).

The pathname argument is required for parameters whose value depends
on the location in the file system. If no arguments are specified,
getconf prints the names and values of the current configuration
parameters. The pathname / is used for each of the parameters that
requires pathname.


getopts [ -a name] optstring vname [arg ...]

Checks arg for legal options. If arg is omitted, the positional
parameters are used. An option argument begins with a + or a -. An
option that does not begin with + or - or the argument -- ends the
options. Options beginning with + are only recognized when optstring
begins with a +. optstring contains the letters that getopts
recognizes. If a letter is followed by a :, that option is expected
to have an argument. The options can be separated from the argument
by blanks. The option -?causes getopts to generate a usage message on
standard error. The -a option can be used to specify the name to use
for the usage message, which defaults to $0. getopts places the next
option letter it finds inside variable vname each time it is invoked.
The option letter is prepended with a + when arg begins with a +. The
index of the next arg is stored in OPTIND. The option argument, if
any, gets stored in OPTARG. A leading : in optstring causes getopts
to store the letter of an invalid option in OPTARG, and to set vname
to ? for an unknown option and to: when a required option argument is
missing. Otherwise, getopts prints an error message. The exit status
is non-zero when there are no more options. There is no way to
specify any of the options :, +, -, ?, [, and ]. The option # can
only be specified as the first option.


hist [ -e ename][-nlr] [ first[last ] ]
hist -s [ old=new ] [ command]

In the first form, a range of commands from first to last is selected
from the last HISTSIZE commands that were typed at the terminal. The
arguments first and last 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 ename is
invoked on a file containing these keyboard commands. If ename is not
supplied, then the value of the variable HISTEDIT is used. If
HISTEDIT is not set, then FCEDIT (default /bin/ed) is used as the
editor. When editing is complete, the edited command(s) is executed
if the changes have been saved. If last is not specified, then it is
set to first. If first is not specified, the default is the previous
command for editing and -16 for listing. The option -r reverses the
order of the commands and the option -n suppresses command numbers
when listing. In the second form, command is interpreted as first
described in this section and defaults to the last command executed.
The resulting command is executed after the optional substitution
old=new is performed.


jobs -lnp [job ...]

Lists information about each specified job, or all active jobs if job
is omitted. The -l option lists process ids in addition to the normal
information. The -n option only displays jobs that have stopped or
exited since last notified. The -p option causes only the process
group to be listed. See Jobs for a description of the format of job.


kill [-s signame] job ...
kill [-n signum] job ...
kill -l [sig ...]

Sends either the TERM (terminate) signal or the specified signal to
the specified jobs or processes. Signals are either specified by
number with the -n option or by name with the -s option (as specified
in <signal.h>, stripped of the prefix `SIG with the exception that
SIGCLD is named CHLD). For backward compatibility, the n and s can be
omitted and the number or name placed immediately after the -. If the
signal being sent is TERM (terminate) or HUP (hang up), then the job
or process is sent a CONT (continue) signal if it is stopped. The
argument job can be the process id of a process that is not a member
of one of the active jobs. See Jobs for a description of the format
of job. In the third form, kill -l, if sig is not specified, the
signal names are listed. Otherwise, for each sig that is a name, the
corresponding signal number is listed. For each sig that is a number,
the signal name corresponding to the least significant 8 bits of sig
is listed.


let [arg ...]

Each arg is a separate arithmetic expression to be evaluated. See the
Arithmetic Evaluation section of this manual page for a description
of arithmetic expression evaluation. The exit status is 0 if the
value of the last expression is non-zero, and 1 otherwise.


+newgrp [arg ...]

Equivalent to exec /bin/newgrp arg ...


print [-Renprs] [ -u unit] [ -f format ] [ arg ...]

With no options or with option - or --, each arg is printed on
standard output. The -f option causes the arguments to be printed as
described by printf. In this case, any e, n, r, or R options are
ignored. Otherwise, unless the -R or -r, are specified, the following
escape conventions are applied:

\a
Alert character (ASCII 07)


\b
Backspace character (ASCII 010)


\c
Causes print to end without processing more arguments and not
adding a NEWLINE


\f
Form-feed character (ASCII 014)


\n
NEWLINE character (ASCII 012)


\r
RETURN character (ASCII 015)


\t
TAB character (ASCII 011)


\v
Vertical TAB character (ASCII 013)


\E
Escape character (ASCII 033)


\\
Backslash character \


\0x
Character defined by the 1, 2, or 3-digit octal string
specified by x

The -R option prints all subsequent arguments and options other than
-n. The -e causes the escape conventions to be applied This is the
default behavior. It reverses the effect of an earlier -r. The -p
option causes the arguments to be written onto the pipe of the
process spawned with |& instead of standard output. The -s option
causes the arguments to be written onto the history file instead of
standard output. The -u option can be used to specify a one digit
file descriptor unit number unit on which the output is placed. The
default is 1. If the option -n is used, no NEWLINE is added to the
output.


printf format[arg ...]

The arguments arg are printed on standard output in accordance with
the ANSI-C formatting rules associated with the format string format.
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 %b format can
be used instead of %s to cause escape sequences in the corresponding
arg to be expanded as described in print. A %B 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 %H format can be used instead of %s to cause
characters in arg that are special in HTML and XML to be output as
their entity name. A %P format can be used instead of %s to cause arg
to be interpreted as an extended regular expression and be printed as
a shell pattern. A %R format can be used instead of %s to cause arg
to be interpreted as a shell pattern and to be printed as an extended
regular expression. A %q format can be used instead of %s to cause
the resulting string to be quoted in a manner than can be input again
to the shell. A %(date-format)T format can be use to treat an
argument as a date/time string and to format the date/time according
to the date-format as defined for the date(1) command. A %Z 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 # flag
character causes base# to be prepended. The # flag when used with the
d specifier without an output base, causes the output to be displayed
in thousands units with one of the suffixes k M G T P E to indicate
the unit. The # flag when used with the i specifier causes the output
to be displayed in 1024 with one of the suffixes Ki Mi Gi Ti Pi Ei to
indicate the unit. The = flag has been added to center the output
within the specified field width.


pwd [-LP]

Outputs the value of the current working directory. The -L option is
the default. It prints the logical name of the current directory. If
the -P option is specified, all symbolic links are resolved from the
name. The last instance of -L or -P on the command line determines
which method is used.


read [-Aprs] [-d delim] [ -n n] [[ -N n] [[-t timeout] [-u unit]
[vname?prompt] [ vname ... ]

The shell input mechanism. One line is read and is broken up into
fields using the characters in IFS as separators. The escape
character, \, is used to remove any special meaning for the next
character and for line continuation. The -d option causes the read
to continue to the first character of delim rather than NEWLINE. The
-n option causes at most n bytes to read rather a full line but
returns when reading from a slow device as soon as any characters
have been read. The -N option causes exactly n to be read unless an
end-of-file has been encountered or the read times out because of the
-t option. In raw mode, -r, the \ character is not treated specially.
The first field is assigned to the first vname, the second field to
the second vname, etc., with leftover fields assigned to the last
vname. When vname has the binary attribute and -n or -N is specified,
the bytes that are read are stored directly into the variable. If the
-v is specified, then the value of the first vname is used as a
default value when reading from a terminal device. The -A option
causes the variable vname to be unset and each field that is read to
be stored in successive elements of the indexed array vname. The -p
option causes the input line to be taken from the input pipe of a
process spawned by the shell using |&. If the -s option is present,
the input is saved as a command in the history file. The option -u
can be used to specify a one digit file descriptor unit unit to read
from. The file descriptor can be opened with the exec special built-
in command. The default value of unit n is 0. The option -t is used
to specify a time out in seconds when reading from a terminal or
pipe. If vname is omitted, then REPLY is used as the default vname.
An end-of-file with the -p option causes cleanup for this process so
that another can be spawned. If the first argument contains a ?, the
remainder of this word is used as a prompt on standard error when the
shell is interactive. The exit status is 0 unless an end-of-file is
encountered or read has timed out.


++readonly [-p] [ vname[=value]] ...

If vname 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 -p option causes the word
readonly to be inserted before each one. Otherwise, the specified
vnames are marked readonly and these names cannot be changed by
subsequent assignment.


+return [n]

Causes a shell function or script to return to the invoking script
with the exit status specified by n. The value is the least
significant 8 bits of the specified status. If n 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.


+set [ +-BCGabefhkmnoprstuvx] [+-o [ option ] ] ... [ +-A vname] [arg...]

The set command supports the following options:

-a

All subsequent variables that are defined are automatically
exported.


-A

Array assignment. Unset the variable vname and assign values
sequentially from the arg list. If +A is used, the variable vname
is not unset first.


-b

Prints job completion messages as soon as a background job
changes state rather than waiting for the next prompt.


-B

Enable brace pattern field generation. This is the default
behavior.


-C

Prevents redirection (>) from truncating existing files. Files
that are created are opened with the O_EXCL mode. Requires >| to
truncate a file when turned on.


-e

If a command has a non-zero exit status, execute the ERR trap, if
set, and exit. This mode is disabled while reading profiles.


-f

Disables file name generation.


-G

Causes the pattern ** by itself to match files and zero or more
directories and subdirectories when used for file name
generation. If followed by a / only directories and
subdirectories are matched.


-h

Each command becomes a tracked alias when first encountered.


-k

Obsolete. All variable assignment arguments are placed in the
environment for a command, not just those that precede the
command name.


-m

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.


-n

Read commands and check them for syntax errors, but do not
execute them. Ignored for interactive shells.


-o

If no option name is supplied, the list of options and their
current settings are written to standard output. When invoked
with a +, 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.

The following argument can be one of the following option names:

allexport

Same as -a.


bgnice

All background jobs are run at a lower priority. This is the
default mode.


braceexpand

Same as -B.


emacs

Puts you in an emacs style inline editor for command entry.


errexit

Same as -e.


globstar

Same as -G.


gmacs

Puts you in a gmacs style inline editor for command entry.


ignoreeof

The shell does not exit on end-of-file. The command exit must
be used.


keyword

Same as -k.


markdirs

All directory names resulting from file name generation have
a trailing / appended.


monitor

Same as -m.


multiline

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.


noclobber

Same as -C.


noexec

Same as -n.


noglob

Same as -f.


nolog

Do not save function definitions in the history file.


notify

Same as -b.


nounset

Same as -u.


pipefail

A pipeline does not complete until all components of the
pipeline have completed, and the return value is the value of
the last non-zero command to fail or zero if no command has
failed.


privileged

Same as -p.


showme

When enabled, simple commands or pipelines preceded by a a
semicolon (;) is displayed as if the xtrace option were
enabled but is not executed. Otherwise, the leading ; is
ignored.


trackall

Same as -h.


verbose

Same as -v.


vi

Puts you in insert mode of a vi style inline editor until you
hit the escape character 033. This puts you in control mode.
A return sends the line.


viraw

Each character is processed as it is typed in vi mode.


xtrace

Same as -x.

If no option name is supplied, the current options settings
are printed.


-p

Disables processing of the $HOME/.profile file and uses the file
/etc/suid_profile instead of the ENV file. This mode is on
whenever the effective uid (gid) is not equal to the real uid
(gid). Turning this off causes the effective uid and gid to be
set to the real uid and gid.


-r

Enables the restricted shell. This option cannot be unset once
set.


-s

Sort the positional parameters lexicographically.


-t

Obsolete. Exit after reading and executing one command.


-u

Treat unset parameters as an error when substituting.


-v

Print shell input lines as they are read.


-x

Print commands and their arguments as they are executed.


--

Do not change any of the options. This is useful in setting $1 to
a value beginning with -. If no arguments follow this option then
the positional parameters are unset.

As an obsolete feature, if the first arg is - then the -x and -v
options are turned off and the next arg is treated as the first
argument. Using + rather than - 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 $-. Unless -A is specified,
the remaining arguments are positional parameters and are assigned,
in order, to $1 $2 .... If no arguments are specified, then the names
and values of all variables are printed on the standard output.


+shift [n]

The positional parameters from $n+1 ... are renamed $1 ..., the
default n is 1. The parameter n can be any arithmetic expression that
evaluates to a non-negative number less than or equal to $#.


sleep seconds

Suspends execution for the number of decimal seconds or fractions of
a second specified by seconds.


+trap -p [action] [sig] ...

The -p option causes the trap action associated with each trap as
specified by the arguments to be printed with appropriate quoting.
Otherwise, action is processed as if it were an argument to eval when
the shell receives signal(s) sig. Each sig 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 action
is omitted and the first sig is a number, or if action is -, then the
trap(s) for each sig are reset to their original values. If action is
the null string then this signal is ignored by the shell and by the
commands it invokes. If sig is ERR then action is executed whenever
a command has a non-zero exit status. If sig is DEBUG then action is
executed before each command. The variable .sh.command contains the
contents of the current command line when action is running. If sig
is 0 or EXIT and the trap statement is executed inside the body of a
function defined with the function name syntax, then the command
action is executed after the function completes. If sig is 0 or EXIT
for a trap set outside any function then the command action is
executed on exit from the shell. If sig is KEYBD, then action is
executed whenever a key is read while in emacs, gmacs, or vi mode.
The trap command with no arguments prints a list of commands
associated with each signal number.


true

Does nothing, and exits 0. Used with while for infinite loops.


++typeset [+-AHflabnprtux ] [ +-EFLRZi[n] ] [ vname[=value ] ]

Sets attributes and values for shell variables and functions. When
invoked inside a function defined with the function name syntax, a
new instance of the variable vname is created, and the variable's
value and type are restored when the function completes.

Using + rather than - causes these options to be turned off. If no
vname arguments are specified, a list of vnames (and optionally the
values) of the variables is printed. Using + rather than - keeps the
values from being printed.) The -p option causes typeset followed by
the option letters to be printed before each name rather than the
names of the options. If any option other than -p is specified, only
those variables which have all of the specified options are printed.
Otherwise, the vnames and attributes of all variables that have
attributes are printed.

The following list of attributes can be specified:

-a
Declares vname to be an indexed array. This is optional unless
except for compound variable assignments.


-A
Declares vname to be an associative array. Sub-scripts are
strings rather than arithmetic expressions.


-b
The variable can hold any number of bytes of data. The data can
be text or binary. The value is represented by the base64
encoding of the data. If -Z is also specified, the size in
bytes of the data in the buffer is determined by the size
associated with the -Z. If the base64 string assigned results
in more data, it is truncated. Otherwise, it is filled with
bytes whose value is zero. The printf format %B can be used to
output the actual data in this buffer instead of the base64
encoding of the data.


-E
Declares vname to be a double precision floating point number.
If n is non-zero, it defines the number of significant figures
that are used when expanding vname. Otherwise, ten significant
figures is used.


-f
The names refer to function names rather than variable names.
No assignments can be made and the only other valid options are
-t, -u, and -x. The -t option turns on execution tracing for
this function. The -u option causes this function to be marked
undefined. The FPATH variable is searched to find the function
definition when the function is referenced. If no options other
than -f is specified, then the function definition is displayed
on standard output. If +f 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.

The -i attribute cannot be specified with -f.


-F
Declares vname to be a double precision floating point number.
If n is non-zero, it defines the number of places after the
decimal point that are used when expanding vname. Otherwise ten
places after the decimal point is used.


-H
This option provides UNIX to hostname file mapping on non-UNIX
machines.


-i
Declares vname 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 n is non-zero, it
defines the output arithmetic base, otherwise the output base
is ten.

The -i attribute cannot be specified along with -R, -L, -Z, or
-f.


-l
All uppercase characters are converted to lowercase. The
uppercase option, -u, is turned off.


-L
Left justify and remove leading blanks from value. If n is non-
zero, 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
-R option is turned off.

The -i attribute cannot be specified with -L.


-n
Declares vname to be a reference to the variable whose name is
defined by the value of variable vname. This is usually used to
reference a variable inside a function whose name has been
passed as an argument.


-R
Right justify and fill with leading blanks. If n is non-zero,
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 -L option is turned off.

The -i attribute cannot be specified with -R.


-r
The specified vnames are marked read-only and these names
cannot be changed by subsequent assignment.


-t
Tags the variables. Tags are user definable and have no special
meaning to the shell.


-u
All lowercase characters are converted to uppercase. The
lowercase option, -l, is turned off.


-x
The specified vnames are marked for automatic export to the
environment of subsequently-executed commands. Variables whose
names contain a . cannot be exported.


-Z
Right justify and fill with leading zeros if the first non-
blank character is a digit and the -L option has not been set.
Remove leading zeros if the -L option is also set. If n is non-
zero, it defines the width of the field, otherwise it is
determined by the width of the value of first assignment.

The -i attribute cannot be specified with -Z.


ulimit [-HSacdfmnpstv] [ limit]

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
limit is specified. The value of limit 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.

If no option is specified, -f is assumed.

The following are the available resource limits:

-a
Lists all of the current resource limits.


-c
The number of 512-byte blocks on the size of core dumps.


-d
The number of Kbytes on the size of the data area.


-f
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).


-H
Specifies a hard limit for the specified resource.

A hard limit cannot be increased once it is set.

If neither the -H nor -S option is specified, the limit applies
to both. The current resource limit is printed when limit is
omitted. In this case, the soft limit is printed unless -H is
specified.


-m
The number of Kbytes on the size of physical memory.


-n
The number of file descriptors plus 1.


-p
The number of 512-byte blocks for pipe buffering.


-s
The number of Kbytes on the size of the stack area.


-S
Specifies a soft limit for the specified resource.

A soft limit can be increased up to the value of the hard
limit.

If neither the -H nor -S option is specified, the limit applies
to both. The current resource limit is printed when limit is
omitted. In this case, the soft limit is printed unless -H is
specified.


-t
The number of CPU seconds to be used by each process.


-v
The number of Kbytes for virtual memory.


umask [-S][mask]

The user file-creation mask is set to mask. mask can either be an
octal number or a symbolic value as described in chmod(1).

If a symbolic value is specified, the new umask value is the
complement of the result of applying mask to the complement of the
previous umask value. If mask is omitted, the current value of the
mask is printed. The -S option causes the mode to be printed as a
symbolic value. Otherwise, the mask is printed in octal.

See umask(2)


+unalias [-a] name

The aliases specified by the list of names are removed from the alias
list. The -a option causes all the aliases to be unset.


+unset [-fnv] vname

The variables specified by the list of vnames are unassigned, i.e.,
their values and attributes are erased. Read-only variables cannot be
unset. If the -f option is set, then the names refer to function
names. If the -v option is set, then the names refer to variable
names. The -f option overrides -v. If -n is set and name is a name
reference, then name is unset rather than the variable that it
references. The default is equivalent to -v. Unsetting LINENO,
MAILCHECK, OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes
their special meaning even if they are subsequently assigned to.


wait [job]

Wait for the specified job and report its termination status. If job
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 job is specified; otherwise it is zero. See
Jobs for a description of the format of job.


whence [-afpv] name ...

For each name, indicate how it would be interpreted if used as a
command name. The -v option produces a more verbose report. The -f
option skips the search for functions. The -p option does a path
search for name even if name is an alias, a function, or a reserved
word. The -a option is similar to the -v option but causes all
interpretations of the specified name to be reported.


Invocation


If the shell is invoked by exec(2), and the first character of argument
zero ($0) is -, then the shell is assumed to be a login shell and
commands are read from /etc/profile and then from either .profile in the
current directory or $HOME/.profile, if either file exists. Next, for
interactive shells, commands are read first from /etc/ksh.kshrc, and then
from the file named by performing parameter expansion, command
substitution, and arithmetic substitution on the value of the environment
variable ENV if the file exists. If the -s option is not present and arg
and a file by the name of arg exists, then it reads and executes this
script. Otherwise, if the first arg does not contain a /, a path search
is performed on the first arg to determine the name of the script to
execute. The script arg must have execute permission and any setuid and
setgid settings are ignored. If the script is not found on the path, arg
is processed as if it named a built-in command or function.


Commands are then read as described, and the following options are
interpreted by the shell when it is invoked:

-c
If the -c option is present, then commands are read from
the first arg. Any remaining arguments become positional
parameters starting at 0.


-D
A list of all double quoted strings that are preceded by a
$ 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.


-i
If the -i option is present or if the shell input and
output are attached to a terminal (as told by
tcgetattr(3C), this shell is interactive. In this case
TERM is ignored (so that kill 0 does not kill an
interactive shell) and INTR is caught and ignored (so that
wait is interruptible). In all cases, QUIT is ignored by
the shell.


-R filename
The -R filename 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.


-r
If the -r option is present, the shell is a restricted
shell.


-s
If the -s option is present or if no arguments remain,
then commands are read from the standard input. Shell
output, except for the output of the Special Commands
listed, is written to file descriptor 2.


The remaining options and arguments are described under the set command.
An optional - as the first argument is ignored.

rksh93 Only
rksh93 is used to set up login names and execution environments whose
capabilities are more controlled than those of the standard shell.


The actions of rksh93 are identical to those of ksh93, except that the
following are disallowed:

o Unsetting the restricted option

o Changing directory. See cd(1).

o Setting or unsetting the value or attributes of SHELL, ENV,
FPATH, or PATH

o Specifying path or command names containing /,

o Redirecting output (>, >|, <>, and >>).

o Adding or deleting built-in commands.

o Using command -p to invoke a command.


These restrictions are enforced after .profile and the ENV files are
interpreted.


When a command to be executed is found to be a shell procedure, rksh93
invokes ksh93 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
.profile 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, /usr/rbin, that can be safely invoked
by rksh.

USAGE


See largefile(5) for the description of the behavior of ksh93 and rksh93
when encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).

EXIT STATUS


The following exit values are returned:

non-zero

Returns non-zero when errors, such as syntax errors, are detected by
the shell.

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.


exit status of last command executed

Returns the exit status of the last command executed.

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 ([]) after the command or function
name.

See the ksh93 exit command for additional details.


FILES


/etc/profile

The system initialization file, executed for login shells.


/etc/ksh.kshrc

The system wide startup file, executed for interactive shells.


$HOME/.profile

The personal initialization file, executed for login shells after
/etc/profile.


$HOME/.kshrc

Default personal initialization file, executed after /etc/ksh.kshrc,
for interactive shells when ENV is not set.


/etc/suid-profile

Alternative initialization file, executed instead of the personal
initialization file when the real and effective user or group id do
not match.


/dev/null

NULL device.


AUTHORS


David Korn, dgk@research.att.com

ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | See below. |
+--------------------+-----------------+


The scripting interface is Uncommitted. The environment variables, .paths
feature, and editing modes are Volatile.

SEE ALSO


cat(1), cd(1), chmod(1), cut(1), date(1), egrep(1), echo(1), egrep(1),
env(1), fgrep(1), grep(1), login(1), newgrp(1), paste(1), printf(1),
stty(1), test(1), umask(1), vi(1), dup(2), exec(2), fork(2), ioctl(2),
lseek(2), pathconf(2), pipe(2), sysconf(3C), ulimit(2), umask(2),
rand(3C), tcgetattr(3C), wait(3C), a.out(4), profile(4), attributes(5),
environ(5), largefile(5), standards(5)


Bolsky, Morris I. and Korn, David G., The New KornShell Command and
Programming Language, Prentice Hall, 1995.


POSIX-Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2,
IEEE, 1993.

NOTES


ksh93 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 ksh93.


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 exec the original
command. Use the -t option of the alias command to correct this
situation.


Some very old shell scripts contain a caret (^) as a synonym for the pipe
character (|).


Using the hist built-in command within a compound command causes the
whole command to disappear from the history file.


The built-in command . file reads the whole file before any commands are
executed. alias and unalias commands in the file do not apply to any
commands defined in the file.


Traps are not processed while a job is waiting for a foreground process.
Thus, a trap on CHLD is not executed until the foreground job terminates.


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.


There might be some restrictions on creating a .paths file which is
portable across other operating systems.


If the system supports the 64-bit instruction set, /bin/ksh93 executes
the 64-bit version of ksh93.


September 10, 2013 KSH93(1)