rksh93(1)
NAME
ksh, rksh, ksh93, rksh93 - KornShell, a standard/restricted command and programming language
SYNOPSIS
ksh [ ±abcefhikmnoprstuvxBCDP ] [ -R file ] [ ±o option ] ... [ - ] [ arg ... ] rksh [ ±abcefhikmnoprstuvxBCD ] [ -R file ] [ ±o option ] ... [ - ] [ arg ... ]
DESCRIPTION
Ksh is a command and programming language that executes commands read
from a terminal or a file. Rksh is a restricted version of the command
interpreter ksh; command interpreter ksh; See Invocation below for the
meaning of arguments to the shell.
Definitions.
A metacharacter is one of the following characters:
; & ( ) âŽâŽª < > new-line 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 . and optionally
preceded by a .. 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 here. Built-ins that cause side
effects in the shell environment and built-ins that are found before
performing a path search (see Execution below) are documented here.
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 below) or a sequence of blank separated words which may be
preceded by a list of variable assignments (see Environment below).
The first word specifies the name of the command to be executed.
Except as specified below, 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; 0-255 if
it terminates normally; 256+signum if it terminates abnormally (the
name of the signal corresponding to the exit status can be obtained via
the -l option of the kill built-in utility).
A pipeline is a sequence of one or more commands separated by âŽâŽª. 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 ! which 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 ;, &, âŽâŽª&,
&&, or âŽâŽªâŽâŽª, and optionally terminated by ;, &, or âŽâŽª&. Of these five
symbols, ;, &, and âŽâŽª& have equal precedence, which is lower than that
of && and âŽâŽªâŽâŽª. The symbols && and âŽâŽªâŽâŽª also have equal precedence. A
semicolon (;) causes sequential execution of the preceding pipeline; an
ampersand (&) causes asynchronous execution of the preceding pipeline
(i.e., the shell does not wait for that pipeline to finish). The
symbol âŽâŽª& 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 described later. The symbol && (âŽâŽªâŽâŽª) causes the list following it
to be executed only if the preceding pipeline returns a zero (non-zero)
value. One or more new-lines may 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 below.
A command is either a simple-command or one of the following. 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,
then the for command executes the do list once for each
positional parameter that is set starting from 1 (see Parameter
Expansion below). Execution ends when there are no more words
in the list.
for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
The arithmetic expression expr1 is evaluated first (see
Arithmetic evaluation below). The arithmetic expression expr2
is repeatedly evaluated until it evaluates to zero and when non-
zero, list is executed and the arithmetic expression expr3
evaluated. If any expression is omitted, then it behaves as if
it evaluated to 1.
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, then the positional parameters starting from 1 are used
instead (see Parameter Expansion below). 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 end-of-file is encountered. If the
REPLY variable is set to null by the execution of list, then 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
below). 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 may be used in place of while to negate the
loop termination test.
((expression))
The expression is evaluated using the rules for arithmetic
evaluation described below. 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. Note, that if two
adjacent open parentheses are needed for nesting, a space must
be inserted to avoid evaluation as an arithmetic command as
described above.
{ list;}
list is simply executed. Note that unlike the metacharacters (
and ), { and } are reserved words and must occur at the
beginning of a line or after a ; in order to be recognized.
[[ expression ]]
Evaluates expression and returns a zero exit status when
expression is true. See Conditional Expressions below, for a
description of expression.
function varname { list ;}
varname () { list ;}
Define a function which is referenced by varname. A function
whose varname contains a . is called a discipline function and
the portion of the varname preceding the last . must refer to
an existing variable. The body of the function is the list of
commands between { and }. A function defined with the function
varname syntax can also be used as an argument to the . special
built-in command to get the equivalent behavior as if the
varname() syntax were used to define it. (See Functions below.)
namespace identifier { list ;}
Defines or uses the name space identifier and runs the commands
in list in this name space. (See Name Spaces below.)
& [ name [ arg... ] ]
Causes subsequent list commands terminated by & to be placed in
the background job pool name. If name is omitted a default
unnamed pool is used. Commands in a named background pool may
be executed remotely.
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 may be set to a format string that
specifies how the timing information should be displayed. See
Shell Variables below 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:
if then else elif fi case esac for while until do done { } function
select time [[ ]] !
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 as well as to other declaration commands created as types.
The syntax for an assignment is of the form:
varname=word
varname[word]=word
No space is permitted between varname and the = or between = and
word.
varname=(assign_list)
No space is permitted between varname and the =. The variable
varname is unset before the assignment. An assign_list can be
one of the following:
word ...
Indexed array assignment.
[word]=word ...
Associative array assignment. If preceded by
typeset -a this will create 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 will
contain all the assignment elements. Additional
assignments made to sub-variables of varname will
also be displayed as part of the value of
varname. If no assignments are specified,
varname will be 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. Other declaration commands such as
readonly, enum, and other declaration commands
can be used in place of typeset.
. 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 new-line to be 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 and command substitution
characters, the characters / and =. The replacement string can contain
any valid shell script including the metacharacters listed above. The
first word of each command in the replaced text, other than any that
are in the process of being replaced, will be tested for aliases. If
the last character of the alias value is a blank then the word
following the alias will also be checked for alias substitution.
Aliases can be used to redefine built-in commands but cannot be used to
redefine the reserved words listed above. 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. Therefore, 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=â€â€²typeset -fuâ€â€²
command=â€â€²command â€â€²
compound=â€â€²typeset -Câ€â€²
fc=hist
float=â€â€²typeset -lEâ€â€²
functions=â€â€²typeset -fâ€â€²
hash=â€â€²alias -t --â€â€²
history=â€â€²hist -lâ€â€²
integer=â€â€²typeset -liâ€â€²
nameref=â€â€²typeset -nâ€â€²
nohup=â€â€²nohup â€â€²
r=â€â€²hist -sâ€â€²
redirect=â€â€²command execâ€â€²
source=â€â€²command .â€â€²
stop=â€â€²kill -s STOPâ€â€²
suspend=â€â€²kill -s STOP $$â€â€²
times=â€â€²{ { time;} 2>&1;}â€â€²
type=â€â€²whence -vâ€â€²
Tilde Substitution.
After alias substitution is performed, each word is checked to see if
it begins with an unquoted âˆâˆ¼. For tilde substitution, word also refers
to the word portion of parameter expansion (see Parameter Expansion
below). If it does, then the word up to a / is checked to see if it
matches a user name in the password database (See getpwname(3).) If a
match is found, the âˆâˆ¼ 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 âˆâˆ¼ by itself, or in front of a /, is
replaced by $HOME. A âˆâˆ¼ 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 âˆâˆ¼, and when
a âˆâˆ¼ appears after a :. The : also terminates a âˆâˆ¼ login name.
Command Substitution.
The standard output from a command list 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 (``) may be
used as part or all of a word; trailing new-lines 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 below). The command substitution $(cat file)
can be replaced by the equivalent but faster $(<file). The command
substitution $(n<#) will expand 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 ( $(()) ) is replaced by the value of the arithmetic
expression within the double parentheses.
Process Substitution.
Each command argument of the form <(list) or >(list) will run process
list asynchronously connected to some file in /dev/fd if this directory
exists, or else a fifo a temporary directory. The name of this file
will become the argument to the command. If the form with > is
selected then writing on this file will provide input for list. If <
is used, then the file passed as an argument will contain 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, as well as putting it onto the standard output. Note that
the file, which is passed as an argument to the command, is a UNIX
pipe(2) so programs that expect to lseek(2) on the file will 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
âˆâˆ—, @, #, ?, -, $, 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 below) between a [ and a ]. To assign values to an indexed
array, use vname=(value ...) or set -A vname value ... . The value of
all non-negative subscripts must be in the range of 0 through
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 may be assigned by writing:
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
will be referenced whenever the nameref variable is used. The name of
a nameref cannot contain a .. When a variable or function name
contains a ., and the portion of the name up to the first . matches the
name of a nameref, the variable referred to is obtained by replacing
the nameref portion with the name of the variable referenced by the
nameref. If a nameref is used as the index of a for loop, a name
reference is established for each item in the list. A nameref provides
a convenient way to refer to the variable inside a function whose name
is passed as an argument to a function. For example, if the name of a
variable is passed as the first argument to a function, the command
typeset -n var=$1
inside the function causes references and assignments to var to be
references and assignments to the variable whose name has been passed
to the function.
If 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 below.
Positional parameters, parameters denoted by a number, may be assigned
values with the set special built-in command. Parameter $0 is set from
argument zero when the shell is invoked.
The character $ is used to introduce substitutable parameters.
${parameter}
The shell reads all the characters from ${ to the matching } as
part of the same word even if it contains braces or
metacharacters. The value, if any, of the parameter is
substituted. The braces are required when parameter is followed
by a letter, digit, or underscore that is not to be interpreted
as part of its name, when the variable name contains a .. 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 âˆâˆ— or @, then
all the positional parameters, starting with $1, are substituted
(separated by a field separator character). If an array vname
with last subscript âˆâˆ— @, 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 âˆâˆ— and @) is
substituted, separated by the first character of the value of
IFS.
${#parameter}
If parameter is âˆâˆ— 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 (See Type Variables below) or
attributes of the variable referred to by vname.
${!vname}
Expands to the name of the variable referred to by vname. This
will be vname except when vname is a name reference.
${!vname[subscript]}
Expands to name of the subscript unless subscript is *, @. 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 @, same as above, 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 then set it to word; the
value of the parameter is then substituted. Positional
parameters may not be assigned to in this way.
${parameter:?word}
If parameter is set and is non-null then substitute its value;
otherwise, print word and exit from the shell (if not
interactive). If word is omitted then a standard message is
printed.
${parameter:+word}
If parameter is set and is non-null then substitute word;
otherwise substitute nothing.
In the above, word is not evaluated unless it is to be used as the
substituted string, so that, 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 above expressions, then 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. If A
negative offset counts backwards from the end of parameter.
Note that one or more blanks is required in front of a minus
sign to prevent the shell from interpreting the operator as :-.
If parameter is âˆâˆ— or @, or is an array name indexed by âˆâˆ— 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 associate 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 given string. Each occurrence of \n in string is replaced
by the portion of parameter that matches the n-th sub-pattern.
In the first form, only the first occurrence of pattern is
replaced. In the second form, each match for pattern is
replaced by the given string. The third form restricts the
pattern match to the beginning of the string while the fourth
form restricts the pattern match to the end of the string. When
string is null, the pattern will be deleted and the / in front
of string may 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 will be re-evaluated for each element.
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 an absolute pathname of the
shell or script being executed as passed in the
environment. Subsequently it is 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. While defining a compound
variable or a type, _ is initialized as a reference to
the compound variable or type. When a discipline
function is invoked, _ is initialized as a reference to
the variable associated with the call to this function.
Finally when _ is used as the name of the first variable
of a type definition, the new type is derived from the
type of the first variable (See Type Variables below.).
! 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 will 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 (see Key Bindings below).
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.
.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. (See Vi Editing Mode below.)
Otherwise, .sh.edmode is null when processing a KEYBD
trap.
.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.level
Set to the current function depth. This can be changed
inside a DEBUG trap and will set the context to the
specified level.
.sh.lineno
Set during a DEBUG trap to the line number for the caller
of each function.
.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 0-th element stores the
complete match and the i-th. element stores the i-th
submatch. The .sh.match variable becomes unset when the
variable that has expanded is assigned a new value.
.sh.math
Used for defining arithmetic functions (see Arithmetic
evaluation below). 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 subshells 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.
KSH_VERSION
A name reference to .sh.version.
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 will be 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 The search path for the cd command.
COLUMNS
If this variable is set, the value is used to define 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 will be checked for the patterns as described
with VISUAL below and the corresponding editing option
(see Special Command set below) will be turned on.
ENV If this variable is set, then parameter expansion,
command substitution, and arithmetic substitution are
performed on the value to generate the pathname of the
script that will be executed when the shell is invoked
interactively (see Invocation below). This file is
typically used for alias and function definitions. The
default value is $HOME/.kshrc. On systems that support a
system wide /etc/ksh.kshrc initialization file, if the
filename generated by the expansion of ENV begins with
/./ or ././ the system wide initialization file will not
be executed.
FCEDIT Obsolete name for the default editor name for the hist
command. FCEDIT is not used when HISTEDIT is set.
FIGNORE
A pattern that defines the set of filenames that will be
ignored when performing filename matching.
FPATH The search path for function definitions. The
directories in this path are searched for a file with the
same name as the function or command when a function with
the -u attribute is referenced and when a command is not
found. If an executable file with the name of that
command is found, then it is read and executed in the
current environment. Unlike PATH, the current directory
must be represented explicitly by . rather than by
adjacent : characters or a beginning or ending :.
HISTCMD
Number of the current command in the history file.
HISTEDIT
Name for the default editor name for the hist command.
HISTFILE
If this variable is set when the shell is invoked, then
the value is the pathname of the file that will be used
to store the command history (see Command Re-entry
below).
HISTSIZE
If this variable is set when the shell is invoked, then
the number of previously entered commands that are
accessible by this shell will be greater than or equal to
this number. The default is 512.
HOME The default argument (home directory) for the cd command.
IFS Internal field separators, normally space, tab, and new-
line that are used to separate the results of command
substitution or parameter expansion and to separate
fields with the built-in command read. The first
character of the IFS variable is used to separate
arguments for the "$âˆâˆ—" substitution (see Quoting below).
Each single occurrence of an IFS character in the string
to be split, that is not in the isspace character class,
and any adjacent characters in IFS that are in the
isspace character class, delimit a field. One or more
characters in IFS that belong to the isspace character
class, delimit a field. In addition, if the same isspace
character appears consecutively inside IFS, this
character is treated as if it were not in the isspace
class, so that if IFS consists of two tab characters,
then two adjacent tab characters delimit a null field.
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 staring 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 File Name
Generation below).
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 will print 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.
MAILCHECK
This variable specifies how often (in seconds) the shell
will check 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 will check before issuing the next
prompt.
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 will be printed. The
message will undergo 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 $_.
PATH The search path for commands (see Execution below). The
user may not change PATH if executing under rksh (except
in .profile).
PS1 The value of this variable is expanded for parameter
expansion, command substitution, and arithmetic
substitution to define the primary prompt string which by
default is ``$''. The character ! in the primary prompt
string is replaced by the command number (see Command Re-
entry below). Two successive occurrences of ! will
produce a single ! when the prompt string is printed.
PS2 Secondary prompt string, by default ``> ''.
PS3 Selection prompt string used within a select loop, by
default ``#? ''.
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 ``+ ''. In addition when PS4
is unset, the execution trace prompt is also ``+ ''.
SHELL The pathname of the shell is kept in the environment. At
invocation, if the basename of this variable is rsh,
rksh, or krsh, then the shell becomes restricted.
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 brackets 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 will be the
default timeout value for the read built-in command. The
select compound command terminates after TMOUT seconds
when input is from a terminal. Otherwise, the shell will
terminate if a line is not entered within the prescribed
number of seconds while reading from a terminal. (Note
that the shell can be compiled with a maximum bound for
this value which cannot be exceeded.)
VISUAL If the value of this variable matches the pattern
*[Vv][Ii]*, then the vi option (see Special Command set
below) is turned on. If the value matches the pattern
*gmacs* , the gmacs option is turned on. If the value
matches the pattern *macs*, then the emacs option will be
turned on. The value of VISUAL overrides the value of
EDITOR.
The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set at
all by the shell (although HOME is set by login(1)). On some systems
MAIL and SHELL are also set by login(1).
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 â€â€²â€â€²) 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 then each of the fields resulting
from IFS are checked to see if they contain one or more of the brace
patterns {*,*}, {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} ,
or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are
letters and n1,n2,n3 are signed numbers and fmt is a format specified
as used by printf. In each case, fields are created by prepending the
characters before the { and appending the characters after the } to
each of the strings generated by the characters between the { and }.
The resulting fields are checked to see if they have any brace
patterns.
In the first form, a field is created for each string between { and ,,
between , and ,, and between , and }. The string represented by * can
contain embedded matching { and } without quoting. Otherwise, each {
and } with * must be quoted.
In the seconds 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 thru l2.
In the remaining forms, a field is created for each number starting at
n1 and continuing until it reaches n2 incrementing n1 by n3. The cases
where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1
otherwise. If forms which specify %fmt any format flags, widths and
precisions can be specified and fmt can end in any of the specifiers
cdiouxX. For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8
fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z4cx.
File Name Generation.
Following splitting, each field is scanned for the characters âˆâˆ—, ?, (,
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 filename is left unchanged unless the
pattern is prefixed with âˆâˆ¼(N) in which case it is removed as described
below. 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 filenames. The names . and .. are also ignored. If
FIGNORE is not set, the character . at the start of each file name
component will be ignored unless the first character of the pattern
corresponding to this component is the character . itself. Note, that
for other uses of pattern matching the / and . are not treated
specially.
âˆâˆ— Matches any string, including the null string. When used
for filename expansion, if the globstar option is on, two
adjacent âˆâˆ—'s by itself will match all files and zero or
more directories and subdirectories. If followed by a /
then only directories and subdirectories will match.
? Matches any single character.
[...] Matches 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 ^ then 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: (Note that word
is equivalent to alnum plus the character _.)
alnum alpha blank cntrl digit graph lower print punct
space upper word xdigit
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 a & or âŽâŽª. A & signifies that all patterns must be matched
whereas âŽâŽª 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 given patterns.
*(pattern-list)
Matches zero or more occurrences of the given patterns.
+(pattern-list)
Matches one or more occurrences of the given patterns.
{n}(pattern-list)
Matches n occurrences of the given patterns.
{m,n}(pattern-list)
Matches from m to n occurrences of the given patterns.
If m is omitted, 0 will be used. If n is omitted at
least m occurrences will be matched.
@(pattern-list)
Matches exactly one of the given patterns.
!(pattern-list)
Matches anything except one of the given patterns.
By default, each pattern, or sub-pattern will match 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 will be chosen. However, for each of the above 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-pair(s)) 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 âŽâŽª. 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 will be skipped over when counting starting and
ending character matches. The behavior is unspecified when the first
character of a pattern-pair is alpha-numeric 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.
Thus, %({}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 n-th. sub-pattern, matches the
same string as the sub-pattern itself.
Finally a pattern can contain sub-patterns of the form
âˆâˆ¼(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 The remainder of the pattern uses basic regular
expression syntax like the grep(1) command.
K The remainder of the pattern uses shell pattern syntax.
This is the default.
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.
X The remainder of the pattern uses augmented regular
expression syntax like the xgrep(1) command.
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.
i Treat the match as case insensitive.
g File the longest match (greedy). This is the default.
l Left anchor the pattern. This is the default for K style
patterns.
r Right anchor the pattern. This is the default for K
style patterns.
If both options and :pattern-list are specified, then the options apply
only to pattern-list. Otherwise, these options remain in effect until
they are disabled by a subsequent âˆâˆ¼(...) or at the end of the sub-
pattern containing âˆâˆ¼(...).
Quoting.
Each of the metacharacters listed earlier (see Definitions above) has a
special meaning to the shell and causes termination of a word unless
quoted. A character may be quoted (i.e., made to stand for itself) by
preceding it with a \. The pair \new-line is removed. All characters
enclosed between a pair of single quote marks (â€â€²â€â€²) 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.
\E Equivalent to the escape character (ascii 033),
\e Equivalent to the escape character (ascii 033),
\cx Expands to the character control-x.
\C[.name.]
Expands to the collating element name.
Inside double quote marks (""), parameter and command substitution
occur and \ quotes the characters \, `, ", and $. A $ in front of a
double quoted string will be ignored in the "C" or "POSIX" locale, and
may cause the string to be replaced by a locale specific string
otherwise. The meaning of $âˆâˆ— and $@ is identical when not quoted or
when used as a variable assignment value or as a file name. However,
when used as a command argument, "$âˆâˆ—" 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 listed below 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. 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 use 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. In addition 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 above 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. In
addition, when the value of an arithmetic variable or sub-expression
can be represented as a long integer, all C language integer arithmetic
operations can be performed. Variables can be referenced by name
within an arithmetic expression without using the parameter expansion
syntax. When a variable is referenced, its value is evaluated as an
arithmetic expression.
Any of the following math library functions that are in the C math
library can be used within an arithmetic expression:
abs acos acosh asin asinh atan atan2 atanh cbrt 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 define 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 identifier, 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] option of the
typeset special built-in command. The -E option causes the expansion
of the value to be represented using scientific notation when it is
expanded. The optional option argument n defines the number of
significant figures. The -F option causes the expansion to be
represented as a floating decimal number when it is expanded. The -X
option cause 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 will be used.
Arithmetic evaluation is performed on the value of each assignment to a
variable with the -E, -F, -X, or -i attribute. Assigning a floating
point number to a variable whose type is an integer causes the
fractional part to be truncated.
Prompting.
When used interactively, the shell prompts with the value of PS1 after
expanding it for parameter expansion, command substitution, and
arithmetic substitution, before reading a command. In addition, each
single ! in the prompt is replaced by the command number. A !! is
required to place ! in the prompt. If at any time a new-line is typed
and further input is needed to complete a command, then the secondary
prompt (i.e., 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:
string True, if string is not null.
-a file
Same as -e below. This 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.
-k file
True, if file exists and it has its sticky bit set.
-n string
True, if length of string is non-zero.
-o ?option
True, if option named option is a valid option name.
-o option
True, if option named option is on.
-p file
True, if file exists and is a fifo special file or a pipe.
-r file
True, if file exists and is readable by current process.
-s file
True, if file exists and has size greater than zero.
-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.
-L file
True, if file exists and is a symbolic link.
-h file
True, if file exists and is a symbolic link.
-N file
True, if file exists and the modification time is greater than
the last access time.
-O file
True, if file exists and is owned by the effective user id of
this process.
-G file
True, if file exists and its group matches the effective group
id of this process.
-R name
True if variable name is a name reference.
-S file
True, if file exists and is a socket.
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.
file1 -ef file2
True, if file1 and file2 exist and refer to the same file.
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 a pattern, the .sh.match array variable will contain
the match and sub-pattern matches.
string = pattern
Same as == above, but is obsolete.
string != pattern
True, if string does not match pattern. When the string matches
the pattern the .sh.match array variable will contain the match
and sub-pattern matches.
string =âˆâˆ¼ ere
True if string matches the pattern âˆâˆ¼(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.
The following obsolete arithmetic comparisons are also permitted:
exp1 -eq exp2
True, if exp1 is equal to exp2.
exp1 -ne exp2
True, if exp1 is not equal to exp2.
exp1 -lt exp2
True, if exp1 is less than 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 -ge exp2
True, if exp1 is greater than or equal to exp2.
In each of the above expressions, if file is of the form /dev/fd/n,
where n is an integer, then the test is applied to the open file whose
descriptor number is n.
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 âŽâŽªâŽâŽª expression2
True, if either expression1 or expression2 is true.
Input/Output.
Before a command is executed, its input and output may be redirected
using a special notation interpreted by the shell. The following may
appear anywhere in a simple-command or may 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 below. 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 given 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
output.
<>;word The same as <>word except that if the command completes
successfully, word is truncated to the offset at command
completion. <>;word cannot be used with the exec(2).
built-in.
<<[-]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, \new-line is ignored, and \ must be
used to quote the characters \, $, `. If - is appended
to <<, then all leading tabs are stripped from word and
from the document. If # is appended to <<, then leading
spaces and tabs will be stripped off the first line of
the document and up to an equivalent indentation will be
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 (see dup(2)). Similarly for the standard output
using >&digit.
<&digit- The file descriptor given 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.
>#((offset)) The same as <# except applies to file descriptor 1.
<#pattern Seeks 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 above 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 above, other than
>&- and the ># and <# forms, is preceded by {varname} with no
intervening space, then a file descriptor number > 10 will be 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 named 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 (i.e.
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, then 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/output
specifications.
Environment.
The environment (see environ(7)) is a list of name-value pairs that is
passed to an executed program in the same way as a normal argument
list. 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 may 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 may 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 above execution of cmd is concerned
except for special built-in commands listed below - 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 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. It is likely to disappear someday.
Functions.
For historical reasons, there are two ways to define functions, the
name() syntax and the function name syntax, described in the Commands
section above. 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 Execution below.)
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, will
also be 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 may 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 can be added when defining new types. 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
given variable is referenced. If the variable .sh.value is assigned a
value inside the discipline function, the referenced variable will
evaluate to this value instead. If the set discipline is defined for a
variable, it is invoked whenever the given variable is assigned a
value. If the append discipline is defined for a variable, it is
invoked whenever a value is appended to the given variable. The
variable .sh.value is given the value of the variable before invoking
the discipline, and the variable will be 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 given variable is
unset. The variable will not be 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 will contain the value being assigned inside
the set discipline function. 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 .. 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 a ..
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 ..
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.
Type 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 new -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 ††. 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 the -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 the -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 they 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.
This paragraph and the next require features that are not in all
versions of UNIX and may not apply. If you are running a job and wish
to do something else you may hit the key ^Z (control-Z) which sends a
STOP signal to the current job. The shell will then normally indicate
that the job has been `Stopped', and print 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 ^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 will stop 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 will 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 given number.
pool All the jobs in the job pool named by pool.
pool.number
The job number number in the job 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
will be warned that `You have stopped(running) jobs.' You may use the
jobs command to see what they are. If you immediately try to exit
again, the shell will not warn you a second time, and the stopped jobs
will be 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 described below.
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 (but see also the trap built-in command below).
Execution.
Each time a command is read, the above substitutions are carried out.
If the command name matches one of the Special Built-in Commands listed
below, 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
listed below, it is executed in the current shell process.
The shell variables PATH followed by the variable FPATH defines the
list of directories to search for the command name. 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 /, then 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 FPATH 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 given name is
executed as described above.
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 names an existing directory then that directory is searched after
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 will be
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, or if
the setuid and/or 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 that 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 /usr/bin/ex is used. The edited command(s) is
printed and re-executed 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 â€â€²hist -sâ€â€², typing `r bad=good c' will re-
execute the most recent command which starts with the letter c,
replacing the first occurrence of the string bad with the string good.
In-line Editing Options.
Normally, each command line entered from a terminal device is simply
typed followed by a new-line (`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 will be centered
about the cursor. The mark is a > (<, *) if the line extends on the
right (left, both) side(s) 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 ;, âŽâŽª, &, or (, and the word does
not begin with âˆâˆ¼ 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
given 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
will provide 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 (see below) and is null otherwise. By prepending
${.sh.editmode} to a value assigned to .sh.edchar it will cause 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 control 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 would be the notation for ESC followed by
`SHIFT' (capital) `F'.)
All edit commands operate from any place on the line (not just at the
beginning). Neither the `RETURN' nor the `LINE FEED' key is entered
after edit commands except when noted.
^F Move cursor forward (right) one character.
M-[C Move cursor forward (right) one character.
M-f Move 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 cursor backward (left) one character.
M-[D Move cursor backward (left) one character.
M-b Move cursor backward one word.
^A Move cursor to start of line.
M-[H Move cursor to start of line.
^E Move cursor to end of line.
M-[Y Move cursor to end of line.
^]char Move cursor forward to character char on current line.
M-^]char Move cursor backward to character char on current line.
^X^X Interchange the cursor and mark.
erase (User defined erase character as defined by the stty(1)
command, usually ^H or #.) Delete previous character.
lnext (User defined literal next character as defined by the
stty(1) command, or ^V if not defined.) Removes the next
character's editing features (if any).
^D Delete current character.
M-d Delete current word.
M-^H (Meta-backspace) Delete previous word.
M-h Delete previous word.
M-^? (Meta-DEL) Delete previous word (if your interrupt character
is ^? (DEL, the default) then this command will not work).
^T Transpose current character with previous character and
advance the cursor in emacs mode. Transpose two previous
characters in gmacs mode.
^C Capitalize current character.
M-c Capitalize 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, then delete from given 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 given 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 (User defined kill character as defined by the stty command,
usually ^G or @.) Kill the entire current line. If two kill
characters are entered in succession, all kill characters
from then on cause a line feed (useful when using paper
terminals).
^Y Restore last item removed from line. (Yank item back to the
line.)
^L Line feed and print current line.
M-^L Clear the screen.
^@ (Null character) Set mark.
M-space (Meta space) Set 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 previous command. Each time ^P is entered the previous
command back in time is accessed. Moves back one line when
not on the first line of a multi-line command.
M-[A If the cursor is at the end of the line, it is equivalent to
^R with string set to the contents of the current line.
Otherwise, it is equivalent to ^P.
M-< Fetch the least recent (oldest) history line.
M-> Fetch the most recent (youngest) history line.
^N Fetch 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 given, the search is
forward. String is terminated by a `RETURN' or `NEW LINE'.
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-b, M-c, M-d, M-f, M-h, M-l and M-^H.
M-letter Soft-key - Your alias list is searched for an alias by the
name _letter and if an alias of this name is defined, its
value will be inserted on the input queue. The letter must
not be one of the above meta-functions.
M-[letter Soft-key - Your alias list is searched for an alias by the
name __letter and if an alias of this name is defined, its
value will be inserted 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 file name generation on the current word. An
asterisk is appended if the word doesn't match any file or
contain any special pattern characters.
M-ESC Command or file name completion as described above.
^I tab Attempts command or file name completion as described above.
If a partial completion occurs, repeating this will behave 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, it generates the list
of matching commands or file names as described above.
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, it is inserted instead.
^U Multiply parameter of next command by 4.
\ Escape next character. Editing characters, the user's erase,
kill and interrupt (normally ^?) characters may 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 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 new-line, 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 new-line 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 will be 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 will always have
canonical processing disabled. This mode is implicit for systems that
do not support two alternate end of line delimiters, and may be helpful
for certain terminals.
Input Edit Commands
By default the editor is in input mode.
erase (User defined erase character as defined by the stty
command, usually ^H or #.) Delete previous character.
^W Delete the previous blank separated word. On some
systems the viraw option may be required for this to
work.
eof As the first character of the line causes the shell to
terminate unless the ignoreeof option is set.
Otherwise this character is ignored.
lnext (User defined literal next character as defined by the
stty(1) or ^V if not defined.) Removes the next
character's editing features (if any). On some
systems the viraw option may be required for this to
work.
\ Escape the next erase or kill character.
^I tab Attempts command or file name completion as described
above and returns to input mode. If a partial
completion occurs, repeating this will behave as if =
were entered from control mode. If no match is found
or entered after space, a tab is inserted.
Motion Edit Commands
These commands will move the cursor.
[count]l Cursor forward (right) one character.
[count][C Cursor forward (right) one character.
[count]w Cursor forward one alpha-numeric word.
[count]W Cursor to the beginning of the next word that follows
a blank.
[count]e Cursor to end of word.
[count]E Cursor to end of the current blank delimited word.
[count]h Cursor backward (left) one character.
[count][D Cursor backward (left) one character.
[count]b Cursor backward one word.
[count]B Cursor to preceding blank separated word.
[count]âŽâŽª Cursor to column count.
[count]fc Find the next character c in the current line.
[count]Fc Find the previous character c in the current line.
[count]tc Equivalent to f followed by h.
[count]Tc Equivalent to F followed by l.
[count]; Repeats count times, the last single character find
command, f, F, t, or T.
[count], Reverses the last single character find command count
times.
0 Cursor to start of line.
^ Cursor to start of line.
[H Cursor to first non-blank character in line.
$ Cursor to end of line.
[Y Cursor to end of line.
% Moves to balancing (, ), {, }, [, or ]. If cursor is
not on one of the above characters, the remainder of
the line is searched for the first occurrence of one
of the above characters first.
Search Edit Commands
These commands access your command history.
[count]k Fetch previous command. Each time k is entered the
previous command back in time is accessed.
[count]- Equivalent to k.
[count][A If cursor is at the end of the line it is equivalent
to / with string^set to the contents of the current
line. Otherwise, it is equivalent to k.
[count]j Fetch next command. Each time j is entered the next
command forward in time is accessed.
[count]+ Equivalent to j.
[count][B Equivalent to j.
[count]G The command number count is fetched. 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 `NEW LINE'. If string is preceded by a ^, the
matched line must begin with string. If string is
null, the previous string will be used.
?string Same as / except that search will be in the forward
direction.
n Search for next match of the last pattern to / or ?
commands.
N Search for next match of the last pattern to / or ?,
but in reverse direction.
Text Modification Edit Commands
These commands will modify the line.
a Enter input mode and enter text after the current
character.
A Append text to the end of the line. Equivalent to $a.
[count]cmotion
c[count]motion
Delete current character through the character that
motion would move the cursor to and enter input mode.
If motion is c, the entire line will be deleted and
input mode entered.
C Delete the current character through the end of line
and enter input mode. Equivalent to c$.
S Equivalent to cc.
[count]s Replace characters under the cursor in input mode.
D Delete the current character through the end of line.
Equivalent to d$.
[count]dmotion
d[count]motion
Delete current character through the character that
motion would move to. If motion is d , the entire
line will be deleted.
i Enter input mode and insert text before the current
character.
I Insert text before the beginning of the line.
Equivalent to 0i.
[count]P Place the previous text modification before the
cursor.
[count]p Place the previous text modification after the cursor.
R Enter input mode and replace characters on the screen
with characters you type overlay fashion.
[count]rc Replace the count character(s) starting at the current
cursor position with c, and advance the cursor.
[count]x Delete current character.
[count]X Delete preceding character.
[count]. Repeat the previous text modification command.
[count]âˆâˆ¼ Invert the case of the count character(s) starting at
the current cursor position and advance the cursor.
[count]_ Causes the count word of the previous command to be
appended and input mode entered. The last word is
used if count is omitted.
* Causes an * to be appended to the current word and
file name generation attempted. If no match is found,
it rings the bell. Otherwise, the word is replaced by
the matching pattern and input mode is entered.
\ Command or file name completion as described above.
Other Edit Commands
Miscellaneous commands.
[count]ymotion
y[count]motion
Yank current character through character that motion
would move the cursor to and puts them into the delete
buffer. The text and cursor are unchanged.
yy Yanks the entire line.
Y Yanks from current position to end of line.
Equivalent to y$.
u Undo the last text modifying command.
U Undo all the text modifying commands performed on the
line.
[count]v Returns the command hist -e ${VISUAL:-${EDITOR:-vi}}
count in the input buffer. If count is omitted, then
the current line is used.
^L Line feed and print current line. Has effect only 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 #, then
this command deletes this # and each # that follows a
newline. Otherwise, sends the line after inserting a
# in front of each line in the command. Useful for
causing the current line to be inserted in the history
as a comment and uncommenting previously commented
commands in the history file.
[count]= If count is not specified, it generates the list of
matching commands or file names as described above.
Otherwise, the word under the the cursor is replaced
by the count item from the most recently generated
command or file list. If the cursor is not on a word,
it is inserted instead.
@letter Your alias list is searched for an alias by the name
_letter and if an alias of this name is defined, its
value will be inserted 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/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 zero. Except for :, true, false, echo, newgrp,
and login, all built-in commands accept -- to indicate end of options.
They also interpret the option --man as a request to display the man
page onto standard error and -? as a help request which prints a usage
message on standard error. Commands that are preceded by one or two â€
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. These are called declaration
built-ins.
†: [ 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 given, 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 given, an alias is defined for each name whose
value is given. 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 given 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 given, 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 given, 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 Jobs 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 associate with the pathname of the directory containing
the .paths file.
The ISO C/C++ prototype is b_mycommand(int argc, char *argv[], void
*context) for the builtin command mycommand where argv is array an of
argc elements and context is an optional pointer to a Shell_t structure
as described in <ast/shell.h>.
Special built-ins cannot be bound to a pathname or deleted. The -d
option deletes each of the given 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 can be in either of two forms. In the first form
it changes the current directory to arg. If arg is - 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). Note that 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
/ then 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 may not be executed by rksh. rksh93.
command [ -pvxV ] name [ arg ... ]
Without the -v or -V options, command executes name with the
arguments given by arg. The -p option causes a default path to
be searched rather than the one defined by the value of PATH.
Functions will not be searched for when finding name. In
addition, if name refers to a special built-in, none of the
special properties associated with the leading daggers will be
honored. (For example, the predefined alias redirect=â€â€²command
execâ€â€² prevents a script from terminating when an invalid
redirection is given.) With the -x option, if command execution
would result in a failure because there are too many arguments,
errno E2BIG, the shell will invoke 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 will be passed on each invocation. The exit status
will be the maximum invocation exit status. With the -v option,
command is equivalent to the built-in whence command described
below. The -V option causes command to act like whence -v.
†continue [ n ]
Resume the next iteration of the enclosing for, while, until, or
select loop. If n is specified, then resume at the n-th
enclosing loop.
disown [ job... ]
Causes the shell not to send a HUP signal to each given 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 \, then echo prints each of its arguments
separated by a space and terminated by a new-line. Otherwise,
the behavior of echo is system dependent and print or printf
described below 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
command(s) executed.
†exec [ -c ] [ -a name ] [ arg ... ]
If arg is given, 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/output
arguments may appear and affect the current process. If arg is
not given, 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 will be 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 will also cause the shell
to exit except for a shell which has the ignoreeof option (see
set below) turned on.
††export [ -p ] [ name[=value] ] ...
If name is not given, 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-input. 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
given names are marked for automatic export to the environment
of subsequently-executed commands.
false Does nothing, and exits 1. Used with until for infinite loops.
fg [ job... ]
This command is only on systems that support job control. Each
job specified is brought to the foreground and waited for in the
specified order. Otherwise, the current job is brought into the
foreground. See Jobs for a description of the format of job.
getconf [ name [ pathname ] ]
Prints the current value of the configuration parameter given by
name. The configuration parameters are defined by the IEEE
POSIX 1003.1 and IEEE POSIX 1003.2 standards. (See pathconf(2)
and sysconf(2).) The pathname argument is required for
parameters whose value depends on the location in the file
system. If no arguments are given, 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 not beginning 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 argument 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 will be
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 may be specified as a
number or as a string. A string is used to locate the most
recent command starting with the given 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 /usr/bin/ex) 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 will be 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 above 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 given 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 given by
number with the -n option or by name with the -s option (as
given in <signal.h>, stripped of the prefix ``SIG'' with the
exception that SIGCLD is named CHLD). For backward
compatibility, the n and s can be omitted and the number or name
placed immediately after the -. If the signal being sent is
TERM (terminate) or HUP (hangup), then the job or process will
be 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
list only the signal names. -L options 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 Arithmetic Evaluation above, 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, R
options are ignored. Otherwise, unless the -C, -R, -r, or -v
are specified, the following escape conventions will be applied:
The alert character (ascii 07).
The backspace character (ascii 010).
\c Causes print to end without processing more arguments and
not adding a new-line.
\f The formfeed character (ascii 014).
\n The new-line character (ascii 012).
\r The carriage return character (ascii 015).
\t The tab character (ascii 011).
\v The vertical tab character (ascii 013).
\E The escape character (ascii 033).
\\ The backslash character \.
\0x The character defined by the 1, 2, or 3-digit octal
string given by x.
The -R option will print all subsequent arguments and options
other than -n. The -e causes the above 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 âŽâŽª& 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 value
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 will be placed. The
default is 1. If the option -n is used, no new-line 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 variable will be
printed. The alternate flag # causes a compound variable
to be output on a single line. This is most useful for
compound variables and variables whose attribute is -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
reinput to the shell. When q is preceded by the
alternative format specifier, #, the string is quoted in
manner suitable as a field in a .csv format file.
%(date-format)T
A %(date-format)T format can be use to treat an argument
as a date/time string and to format the date/time
according to the date-format as defined for the date(1)
command.
%Z A %Z format will output 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 (,
on 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 given, 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 ] [ vname ... ]
The shell input mechanism. One line is read and is broken up
into fields using the characters in IFS as separators. The
escape character, \, is used to remove any special meaning for
the next character and for line continuation. The -d option
causes the read to continue to the first character of delim
rather than new-line. The -n option causes at most n bytes to
read rather a full line but will return when reading from a slow
device as soon as any characters have been read. The -N option
causes exactly n to be read unless an end-of-file has been
encountered or the read times out because of the -t option. In
raw mode, -r, the \ character is not treated specially. The
first field is assigned to the first vname, the second field to
the second vname, etc., with leftover fields assigned to the
last vname. When vname has the binary attribute and -n or -N is
specified, the bytes that are read are stored directly into the
variable. If the -v is specified, then the value of the first
vname will be 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 âŽâŽª&. If
the -s option is present, the input will be 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 timeout 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 given, the names and values of each variable
with the readonly attribute is printed with the values quoted in
a manner that allows them to be re-inputted. The -p option
causes the word readonly to be inserted before each one.
Otherwise, the given vnames are marked readonly and these names
cannot be changed by subsequent assignment. When defining a
type, if the value of a readonly sub-variable is not defined the
value is required when creating each instance.
†return [ n ]
Causes a shell function or . script to return to the invoking
script with the exit status specified by n. The value will be
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 options for this command have meaning as follows:
-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 Enable brace pattern field generation. This is the
default behavior.
-B Enable brace group expansion. On by default.
-C Prevents redirection > from truncating existing files.
Files that are created are opened with the O_EXCL mode.
Requires >âŽâŽª to truncate a file when turned on.
-G Causes the pattern âˆâˆ—âˆâˆ— by itself to match files and zero
or more directories and sub-directories when used for
file name generation. If followed by a / only
directories and sub-directories are matched.
-a All subsequent variables that are defined are
automatically exported.
-b Prints job completion messages as soon as a background
job changes state rather than waiting for the next
prompt.
-e Unless contained in a âŽâŽªâŽâŽª 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.
-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 will run in a separate process group and
a line will print 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 The following argument can be one of the following
option names:
allexport
Same as -a.
errexit Same as -e.
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 in-line editor for
command entry.
globstar
Same as -G.
gmacs Puts you in a gmacs style in-line editor for
command entry.
ignoreeof
The shell will 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 will use multiple lines on
the screen for lines that are longer than the
width of the screen. This may 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 will not complete until all
components of the pipeline have completed, and
the return value will be the value of the last
non-zero command to fail or zero if no command
has failed.
showme When enabled, simple commands or pipelines
preceded by a semicolon (;) will be displayed as
if the xtrace option were enabled but will not
be executed. Otherwise, the leading ; will be
ignored.
privileged
Same as -p.
verbose Same as -v.
trackall
Same as -h.
vi Puts you in insert mode of a vi style in-line
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, then the current option
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; 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 may 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 given, 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 ... ,
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 given 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 will be processed as if it were an
argument to eval when the shell receives signal(s) sig. Each
sig can be given 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 will be executed whenever a
command has a non-zero exit status. If sig is DEBUG then action
will be executed before each command. The variable .sh.command
will contain the contents of the current command line when
action is running. If the exit status of the trap is 2 the
command will not be executed. If the exit status of the trap is
255 and inside a function or a dot script, the function or dot
script will return. 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 will be 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.
An exit or return without an argument in a trap action will preserve
the exit status of the command that invoked the trap.
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. The following list of attributes may be specified:
-A Declares vname to be an associative array. Subscripts
are strings rather than arithmetic expressions.
-C causes each vname to be a compound variable. value names
a compound variable it is copied into vname. Otherwise,
it unsets each vname.
-a Declares vname to be an indexed array. If type is
specified, it must be the name of an enumeration type
created with the enum command and it allows enumeration
constants to be used as subscripts.
-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 will be used.
-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 will be used.
-H This option provides UNIX to host-name file mapping on
non-UNIX machines.
-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.
-M Use the character mapping mapping defined by wctrans(3).
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.
-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.
-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 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.
-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.
-f 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 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 is 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.
-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
will be determined by the size associated with the -Z.
If the base64 string assigned results in more data, it
will be truncated. Otherwise, it will be 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.
-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.
-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 will be ten.
-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 .
-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.
-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. Cannot be
used with any other options.
-p The name, attributes and values for the given vnames 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 The given vnames are marked readonly and these names
cannot be changed by subsequent assignment.
-t Tags the variables. Tags are user definable and have no
special meaning to the shell.
-u 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 given vnames are marked for automatic export to the
environment of subsequently-executed commands. Variables
whose names contain a . cannot be exported.
The -i attribute cannot be specified along with -R, -L, -Z, or
-f.
Using + rather than - causes these options to be turned off. If
no vname arguments are given, 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 given, only those variables which have all of the
given options are printed. Otherwise, the vnames and attributes
of all variables that have attributes are printed.
ulimit [ -HSacdfmnpstv ] [ limit ]
Set or display a resource limit. The available resource limits
are listed below. 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 below with each resource, or the value unlimited.
The -H and -S options specify whether the hard limit or the soft
limit for the given resource is set. A hard limit cannot be
increased once it is set. 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. When more than one
resource is specified, then the limit name and unit is printed
before the value.
-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 K-bytes 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 may be read).
-m The number of K-bytes 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 K-bytes on the size of the stack area.
-t The number of CPU seconds to be used by each process.
-v The number of K-bytes for virtual memory.
If no option is given, -f is assumed.
umask [ -S ] [ mask ]
The user file-creation mask is set to mask (see umask(2)). mask
can either be an octal number or a symbolic value as described
in chmod(1). If a symbolic value is given, 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.
†unalias [ -a ] name ...
The aliases given 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 given by the list of vnames are unassigned, i.e.,
except for sub-variables within a type, their values and
attributes are erased. For sub-variables of a type, the values
are reset to the default value from the type definition.
Readonly 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 will be 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 given, 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 -p option turns off the -v option. The -a
option is similar to the -v option but causes all
interpretations of the given 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 from the file named by
performing parameter expansion, command substitution, and arithmetic
substitution on the value of the environment variable ENV if the file
exists. If the -s option is not present and arg and a file by the name
of arg exists, then it reads and executes this script. Otherwise, if
the first arg does not contain a /, a path search is performed on the
first arg to determine the name of the script to execute. The script
arg must have execute permission and any setuid and setgid settings
will be 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 below; the following options are interpreted by
the shell when it is invoked:
-D Do not execute the script, but output the set of double quoted
strings preceded by a $. These strings are needed for
localization of the script to different locales.
-E Reads the file named by the ENV variable or by $HOME/.kshrc if
not defined after the profiles.
-c If the -c option is present, then commands are read from the
first arg. Any remaining arguments become positional
parameters starting at 0.
-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 above,
is written to file descriptor 2.
-i If the -i option is present or if the shell input and output
are attached to a terminal (as told by tcgetattr(2)), then
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 ). In all cases, QUIT is
ignored by the shell.
-r If the -r option is present, the shell is a restricted shell.
-D A list of all double quoted strings that are preceded by a $
will be printed on standard output and the shell will exit.
This set of strings will be subject to language translation
when the locale is not C or POSIX. No commands will be
executed.
-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.
The remaining options and arguments are described under the set command
above. An optional - as the first argument is ignored.
Rksh Only.
Rksh is used to set up login names and execution environments whose
capabilities are more controlled than those of the standard shell. The
actions of rksh are identical to those of ksh, except that the
following are disallowed:
Unsetting the restricted option.
changing directory (see cd(1)),
setting or unsetting the value or attributes of SHELL, ENV,
FPATH, or PATH,
specifying path or command names containing /,
redirecting output (>, >|, <>, and >>).
adding or deleting built-in commands.
using command -p to invoke a command.
The restrictions above are enforced after .profile and the ENV files
are interpreted.
When a command to be executed is found to be a shell procedure, rksh
invokes ksh 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 (e.g.,
/usr/rbin) that can be safely invoked by rksh.
EXIT STATUS
Errors detected by the shell, such as syntax errors, cause the shell to return a non-zero exit status. If the shell is being used non- interactively, then execution of the shell file is abandoned unless the error occurs inside a subshell in which case the subshell is abandoned. Otherwise, the shell returns the exit status of the last command executed (see also the exit command above). 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.
FILES
/etc/profile
The system wide initialization file, executed for login shells.
$HOME/.profile
The personal initialization file, executed for login shells
after /etc/profile.
$HOME/.kshrc
Default personal initialization file, executed 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
SEE ALSO
cat(1), cd(1), chmod(1), cut(1), egrep(1), echo(1), emacs(1), env(1), fgrep(1), gmacs(1), grep(1), newgrp(1), stty(1), test(1), umask(1), vi(1), dup(2), exec(2), fork(2), getpwnam(3), ioctl(2), lseek(2), paste(1), pathconf(2), pipe(2), sysconf(2), umask(2), ulimit(2), wait(2), wctrans(3), rand(3), a.out(5), profile(5), environ(7). Morris I. Bolsky and David G. Korn, 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.
CAVEATS
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 will continue to exec the
original command. Use the -t option of the alias command to correct
this situation.
Some very old shell scripts contain a ^ as a synonym for the pipe
character âŽâŽª.
Using the hist built-in command within a compound command will cause
the whole command to disappear from the history file.
The built-in command . file reads the whole file before any commands
are executed. Therefore, alias and unalias commands in the file will
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 won't be 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.
KSH(1)
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