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 between 0 and 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 || 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.

for (( [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 is 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;}

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 dot (.) 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.

namespace identifier { list };

Defines or uses the name space identifier and runs the commands
in list in this name space. See Name Spaces.

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, enum, 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. The variable varname is unset before the assignment.

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.

. filename

Include the assignment commands contained in filename.

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. The right
hand side of a variable assignment undergoes all the expansion
listed below except word splitting, brace expansion, and file
name generation. When the left hand side is an assignment is a
compound variable and the right hand is the name of a compound
variable, the compound variable on the right will be copied or
appended to the compound variable on the left.

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, the 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 '
compound='typeset -C'
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 - $(list) - or in a brace group preceded by a dollar sign
- ${ list;}, - or in a pair of grave accents - `` - can be used as part
or all of a word. Trailing NEWLINEs are removed. In the second case,
the { and } are treated as a reserved words so that { must be followed
by a blank and } must appear at the beginning of the line or follow a
;. In the third (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. Except for the second form,
the command list is run in a subshell so that no side effects are
possible. For the second form, the final } will be recognized as a
reserved word after any token.

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

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.

Process substitution of the form <(list) can also be used with the <
redirection operator which causes the output of list to be standard
input or the input for whatever file descriptor is specified.

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 ]. To assign values to an indexed
array, use vname=(value ...) or set -A vname value .... The value of
all subscripts must be in the range of 0 to 4,194,303. A negative
subscript is treated as an offset from the maximum current index +1 so
that -1 refers to the last element. Indexed arrays can be declared
with the -a option to typeset. Indexed arrays need not be declared.
Any reference to a variable with a valid subscript is legal and an
array will be 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] ...

Note that no space is allowed before or after the =.

Attributes assigned by the typeset special built-in command apply to
all elements of the array. An array element can be a simple variable,
a compound variable or an array variable. An element of an indexed
array can be either an indexed array or an associative array. An
element of an associative array can also be either. To refer to an
array element that is part of an array element, concatenate the
subscript in brackets. For example, to refer to the foobar element of
an associative array that is defined as the third element of the
indexed array, use ${vname[3][foobar]}.

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 dot (.) 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 any of the floating point attributes, -E, -F or
-X, 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 or when the variable name
contains a dot (.). The braces are also required when a
variable is subscripted unless it is part of an Arithmetic
Expression or a Conditional Expression. 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 last subscript *
or @ is used, or for index arrays of the form sub1..sub2 is
used, then the value for each of the elements between sub1 and
sub2 inclusive (or all elements for * and @) 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 type name or attributes of the variable referred
to by vname. See Type Variables.

${!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 @, or
of the form sub1..sub2. 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. When subscript is of the form
sub1..sub2 it expands to the list of subscripts between sub1
and sub2 inclusive using the same quoting rules as @.

${!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.

${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.

${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.

${parameter:+word}
If parameter is set and is non-null, substitute word.
Otherwise substitute nothing.

In the above, 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 id or the pool name and job number of the last
background command invoked or the most recent job put in the
background with the bg built-in command. Background jobs
started in a named pool with be in the form pool.number where
pool is the pool name and number is the job number within that
pool.

.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.math
Used for defining arithmetic functions (see Arithmetic
evaluation) and stores the list of user-defined arithmetic
functions.

.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. When a user-defined
arithmetic function is invoked, the value of .sh.value is saved
and .sh.value is set to long double precision floating point.
.sh.value is restored when the function returns.

.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.

SHLVL An integer variable the is incremented each time the shell is
invoked and is exported. If SHLVL is not in the environment
when the shell is invoked, it is set to 1.

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 Commands 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.

JOBMAX This variable defines the maximum number running background
jobs that can run at a time. When this limit is reached, the
shell will wait for a job to complete before starting a new
job.

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 are:

{*,*[,*]...}
{l1..l2}
{n1..n2}
{n1..n2%fmt}
{n1..n2..n3}
{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 the
first comma (`,'), between a pair of commas (`,') and between the last
comma (`,') and the terminating }. The string represented by * can
contain embedded matching { and } without quoting. Otherwise, each {
and } within * 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 to l2 inclusive.

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 z04cx.

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 ! or ^, 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. :pattern-list must be omitted for options F, G, N and V
below. 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.

X The remainder of the pattern uses augmented regular expression
syntax.

P The remainder of the pattern uses perl(1) regular expression
syntax. Not all perl regular expression syntax is currently
implemented.

V The remainder of the pattern uses System V regular expression
syntax.

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 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 (``), \ 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. The floating point constants Nan and Inf
can be used to represent "not a number" and infinity respectively.
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:

rint round sin sinh sqrt tan tanh tgamma trunc abs
acos acosh asin asinh atan atan2 atanh cbrt ceil copysign
cos cosh erf erfc exp exp2 expm1 fabs fpclassify fdim
finite floor fma fmax fmin fmod hypot ilogb int isfinite
sinf isnan isnormal issubnormal issubordered iszero j0
j1 jn lgamma log log10 log2 logb nearbyint nextafter
nexttoward pow remainder rint round scanb signbit sin sinh
sqrt tan tanh tgamma trunc y0 y1 yn

In addition, arithmetic functions can be defined as shell functions
with a variant of the function name syntax:

function .sh.math.name ident { list ;}

where name is the function name used in the arithmetic expression and
each identified ident is a name reference to the long double precision
floating point argument. The value of .sh.value when the function
returns is the value of this function. User defined functions can take
up to 3 arguments and override C math library functions.

An internal representation of a variable as a double precision floating
point can be specified with the -E[n], -F[n], or -X[n] options 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. The -X option causes the expansion to be
represented using the %a format defined by ISO C-99. The optional
option argument n defines the number of places after the decimal (or
radix) 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, -X 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 a literal ! 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.

-R name True if variable name is a name reference.

-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.

-v name True, if variable name is a valid variable name and is
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 above 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 also 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 Write output to a temporary file. If the command
completes successfully rename it to word, otherwise,
delete the temporary file. >;word cannot be used with
the exec(2) built-in.

>>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 \, $ and `. 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(7).

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. The variable _ is a reference to
the variable including the subscript if any. For the set discipline,
changing .sh.value will change the value that gets assigned. Finally,
the expansion ${var.name}, when name is the name of a discipline, and
there is no variable of this name, is equivalent to the command
substitution ${var.name;}.

Name Spaces

Commands and functions that are executed as part of the list of a
namespace command that modify variables or create new ones, create a
new variable whose name is the name of the name space as given by
identifier preceded by two dots (..). When a variable whose name is
name is referenced, it is first searched for using .identifier.name.
Similarly, a function defined by a command in the namespace list is
created using the name space name preceded by two dots (..).

When the list of a namespace command contains a namespace command, the
names of variables and functions that are created consist of the
variable or function name preceded by the list of identifiers, each
preceded by two dots (..).

Outside of a name space, a variable or function created inside a name
space can be referenced by preceding it with the name space name.

By default, variables staring with .sh are in the sh name space.

Typed Variables

Typed variables provide a way to create data structure and objects. A
type can be defined either by a shared library, by the enum built-in
command described below, or by using the -T option of the typeset
built-in command. With the -T option of typeset, the type name,
specified as an option argument to -T, is set with a compound variable
assignment that defines the type. Function definitions can appear
inside the compound variable assignment and these become discipline
functions for this type and can be invoked or redefined by each
instance of the type. The function name create is treated specially.
It is invoked for each instance of the type that is created but is not
inherited and cannot be redefined for each instance.

When a type is defined a special built-in command of that name is
added. These built-ins are declaration commands and follow the same
expansion rules as all the special built-in commands defined below that
are preceded by a dot (.). These commands can subsequently be used
inside further type definitions. The man page for these commands can
be generated by using the --man option or any of the other -- options
described with getopts. The -r, -a, -A, -h and -S options of typeset
are permitted with each of these new built-ins.

An instance of a type is created by invoking the type name followed by
one or more instance names. Each instance of the type is initialized
with a copy of the sub-variables except for sub-variables that are
defined with the -s option. Variables defined with -S are shared by
all instances of the type. Each instance can change the value of any
sub-variable and can also define new discipline functions of the same
names as those defined by the type definition as well as any standard
discipline names. No additional sub-variables can be defined for any
instance.

When defining a type, if the value of a sub-variable is not set and the
-r attribute is specified, it causes the sub-variable to be a required
sub-variable. Whenever an instance of a type is created, all required
sub-variables must be specified. These sub-variables become readonly
in each instance.

When unset is invoked on a sub-variable within a type, and the -r
attribute has not been specified for this field, the value is reset to
the default value associative with the type. Invoking unset on a type
instance not contained within another type deletes all sub-variables
and the variable itself. A type definition can be derived from another
type definition by defining the first sub-variable name as _ and
defining its type as the base type. Any remaining definitions will be
additions and modifications that apply to the new type. If the new
type name is the same is that of the base type, the type will be
replaced and the original type will no longer be accessible.

The typeset command with -T and no option argument or operands will
write all the type definitions to standard output in a form that that
can be read in to create all the types.

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 stty tostop. 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.

A job pool is a collection of jobs started with list & associated with
a name.

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.

pool All the jobs in the job pool named by pool.

pool.number The job number number in the pool named by pool.

%string Any job whose command line begins with string.

%?string Any job whose command line contains string.

%% Current job.

%+ Equivalent to %%.

%- Previous job.

In addition, unless noted otherwise, wherever a job can be specified,
the name of a background job pool can be used to represent all the jobs
in that pool.

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 variables PATH and FPATH define 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 list of directories defined by PATH and FPATH is
checked in order. If the directory being searched is contained in the
value of the FPATH variable and contains a file whose name matches the
command being searched, 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 this directory is not in FPATH, the shell first determines whether
there is a built-in version of a command corresponding to a given
pathname and, if so, it is invoked in the current process. If no
built-in is found, the shell checks for a file named .paths in this
directory. If found and there is a line of the form:

FPATH=path

where path is an existing directory, then that directory is searched
immediately after the current directory as if it were found in the
FPATH variable. If path does not begin with /, it is checked for
relative to the directory being searched.

The .paths file is then checked for a line of the form:

PLUGIN_LIB=libname[:libname]...

Each library named by libname will be 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.

Any built-in loaded from a library found this way will be associated
with the directory containing the .paths file so it will only execute
if not found in an earlier directory.

Finally, the directory will be checked for a file of the given name.
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. If
the .paths 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 in which the executable
was found. If the environment variable name does not already exist it
will be added to the environment list for the specified command. 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=new can 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.

^I (TAB) 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(1) 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 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]fc 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 (zero) Move the cursor to the start of line.

^ Move the cursor to the first non-blank character in the
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 the 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 - is entered, the
previous command back in time is accessed. Equivalent to
k.

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

[count][B Fetch the next command. Each time [B 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 ? commands.

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 to 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
is entered.

C Delete the current character through to 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 to the end of line.
Equivalent to d$.

d [count]motion
Delete current character through to 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 to 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.

In the list below, 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. A built-in specified by a pathname will only be
executed when that pathname would be found during the path
search. Built-ins found in libraries loaded via the .paths
file will be associated with the pathname of the directory
containing the .paths file.

The ISO C/C++ prototype is int b_mycommand(int argc,
char **argv, Shbltin_t *context) for the built-in command
mycommand where argv is an array of argc elements and context
is an optional pointer to a Shbltin_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 literal -, 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, 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.

++ enum [-i] type[=(value ...)]
Creates a declaration command named type that is an integer
type that allows one of the specified values as enumeration
names. If =(value ...) is omitted, then type must be an
indexed array variable with at least two elements and the
values are taken from this array variable. If -i is specified
the values are case insensitive.

+ 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 export command
is the same as typeset -x except that if you use export within
a function, no local variable is created. The -p option causes
the word export to be inserted before each one. Otherwise, the
specified name s 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 -Ll [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
backwards 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 or kill -L,
if sig is not specified, the signal names are listed. The -l
option lists only the signal names whereas -L lists each signal
name and corresponding number. 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.
let only recognizes octal constants starting with 0 when the
set option letoctal is on. 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 [-CRenprsv] [-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
options are specified, the following escape conventions are
applied:

\a Alert character (ASCII 007)

\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 -v option treats each arg as a variable
name and writes the value in the printf %B format. The -C
option treats each arg as a variable name and writes the values
in the printf %#B format. 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:

%b A %b format can be used instead of %s to cause escape
sequences in the corresponding arg to be expanded as
described in print.

%B 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.

%H 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. The alternate flag #
formats the output for use as a URI.

%P 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.

%R 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.

%q 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. When q is preceded by the
alternative format specifier, #, the string is quoted
in manner suitable for a field in a .csv format file.

%[(date-format)]T
A %[(date-format)]T format can be used 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. For example, `printf '%(%s)T'
now' would print the current time in UNIX timestamp
format (seconds since 00:00:00 UTC, January 1, 1970).

%Z A %Z format outputs a byte whose value is 0.

%d 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 format without an
output base, displays the output in powers of 1000
indicated by one of the following suffixes: k M G T P
E, and when used with the %i format displays the output
in powers of 1024 indicated by one of the following
suffixes: Ki Mi Gi Ti Pi Ei.

= The = flag centers the output within the specified
field width.

L The L flag, when used with the %c or %s formats, treats
precision as character width instead of byte count.

, The , flag, when used with the %d or %f formats,
separates groups of digits with the grouping delimiter
(`,' in groups of 3 in the C locale).

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 [-ACSprsv] [-d delim] [-n n | -N n] [-t timeout] [-u unit]
[vname?prompt] [name ...]

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 -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 -C option causes the variable
vname to be read as a compound variable. Blanks will be
ignored when finding the beginning open parenthesis. The -S
option causes the line to be treated like a record in a .csv
format file so that double quotes can be used to allow the
delimiter character and the new-line character to appear within
a field. 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 Unless contained in a || or && command, or the command
following an if, while or until command or in the
pipeline following !, 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.

letoctal The let command allows octal constants
starting with 0.

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 [+-ACHSfblmnprtux] [+-EFLRXZi[n]] [+-M [mapname]]
[-T [tname=(assign_list)]] [-h str] [-a [type]] [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.

-C Causes each vname to be a compound variable. If value
names a compound variable it is copied into vname.
Otherwise, it unsets each vname.

-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 are 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 names refer to function names rather
than variable names. No assignments can be made and
the only other valid options are -S, -t, -u and -x.
The -S option can be used with discipline functions
defined in a type to indicate that the function is
static. For a static function, the same method will be
used by all instances of that type no matter which
instance references it. In addition, it can only use
value of variables from the original type definition.
These discipline functions cannot be redefined in any
type instance. The -t option turns on execution
tracing for this function. The -u option causes this
function to be marked undefined. The FPATH variable
will be searched to find the function definition when
the function is referenced. If no options other than
-f are specified, then the function definition will be
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 exit status can be used to determine
whether the function is defined so that typeset -f
.sh.math.name will return 0 when math function name is
defined and non-zero otherwise.

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 Used within type definitions to add information when
generating information about the sub-variable on the
man page. It is ignored when used outside of a type
definition. When used with -f the information is
associated with the corresponding discipline function.

-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 Used with -i, -E or -F to indicate long integer, or
long float. Otherwise, all upper-case characters are
converted to lower-case. The upper-case option, -u, is
turned off. Equivalent to -M tolower.

-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.

-m moves or renames the variable. The value is the name
of a variable whose value will be moved to vname. The
original variable will be unset. Cannot be used with
any other options.

-M Use the character mapping mapping such as tolower and
toupper when assigning a value to each of the specified
operands. When mapping is specified and there are not
operands, all variables that use this mapping are
written to standard output. When mapping is omitted
and there are no operands, all mapped variables are
written to standard output.

-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.

-p The name, attributes and values for the given vname are
written on standard output in a form that can be used
as shell input. If +p is specified, then the values
are not displayed.

-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.

-S When used within the assign_list of a type definition,
it causes the specified sub-variable to be shared by
all instances of the type. When used inside a function
defined with the function reserved word, the specified
variables will have function static scope. Otherwise,
the variable is unset prior to processing the
assignment list.

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

-T If followed by tname, it creates a type named by tname
using the compound assignment assign_list to tname.
Otherwise, it writes all the type definitions to
standard output.

-u When given along with -i specifies unsigned integer.
Otherwise, all lower-case characters are converted to
upper-case. The lower-case option, -l, is turned off.
Equivalent to -M toupper.

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

-X Declares vname to be a double precision floating point
number and expands using the %a format of ISO-C99. If
n is non-zero, it defines the number of hex digits
after the radix point that is used when expanding
vname. The default is 10.

-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 is specified 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.

-E Reads the file named by the ENV variable or by $HOME/.kshrc if
not defined after the profiles.

-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 rksh93.

USAGE

See largefile(7) for the description of the behavior of ksh93 and
rksh93 when encountering files greater than or equal to 2 Gbyte ( 2^31
bytes).

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.

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.

INTERFACE STABILITY

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), echo(1), egrep(1), env(1),
fgrep(1), grep(1), login(1), newgrp(1), paste(1), perl(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), ulimit(2), umask(2), rand(3C),
sysconf(3C), tcgetattr(3C), wait(3C), a.out(5), profile(5),
attributes(7), environ(7), largefile(7), standards(7)


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.

illumos March 8, 2021 illumos