ksh - Unix, Linux Command
Advertisements
NAME
sh, rsh, pfsh - shell, the standard/restricted command and programming language
ksh, rksh, pfksh - KornShell, a standard/restricted command and programming language
ksh93, rksh93, pfksh93 - KornShell, a standard/restricted command and programming language
SYNOPSIS
sh
ksh
ksh93
[
±abcefhiknoprstuvxBCDP ] [
-R file ] [
±o option ] ... [
- ] [ arg ... ]
DESCRIPTION
is a command and programming language
that executes commands read from a terminal
or a file.
is a restricted version of the
command interpreter
it is used to set up login names and execution environments whose
capabilities are more controlled than those of the standard shell.
is a profile shell version of the
command interpreter
it is used to to execute commands with the attributes specified by
the users profiles (see
pfexec(1)).
See
Invocation below
for the meaning of arguments to the shell.
NOTE: Pfksh, Rpfksh and pfexec parts are not related to Linux systems. Rksh can be used as rksh symlink to ksh93 or as ksh -r.
Definitions.
A
metacharacter is one of the following characters:
; & ( ) | < > 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
|. 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
;, &, |&, &&, or
||, and optionally terminated by
;, &, or
|&. Of these five symbols,
;, &, and
|& have equal precedence,
which is lower than that of
&& and
||. The symbols
&& and
|| also have equal precedence.
A semicolon
(;) causes sequential execution of the preceding pipeline; an ampersand
(&) causes asynchronous execution of the preceding pipeline (i.e., the shell does
not wait for that pipeline to finish).
The symbol
|& causes asynchronous execution of the preceding pipeline
with a two-way pipe established to the parent shell;
the standard input and output of the spawned pipeline
can be written to and read from by the parent shell
by applying
the redirection operators
<& and
>& with arg
p to commands and by using
-p option of
the built-in commands
read and
print described later.
The symbol
&& (||) 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.
Tag | Description |
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.)
|
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:
Tag | Description |
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 =.
An assign_list can be one of the following:
Tag | Description |
|
Tag | Description |
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
list 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,
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:
Tag | Description |
autoload='typeset -fu'
command='command '
compound='typeset -C'
fc=hist
float='typeset -lE'
functions='typeset -f'
hash='alias -t --'
history='hist -l'
integer='typeset -li'
nameref='typeset -n'
nohup='nohup '
r='hist -s'
redirect='command exec'
source='command .'
stop='kill -s STOP'
suspend='kill -s STOP $$'
times='{ { time;} 2>&1;}'
type='whence -v' | |
|
Tilde Substitution.
After alias substitution is performed, each word
is checked to see if it begins with an unquoted
~. 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
~ and the matched login name are replaced by the
login directory of the matched user.
If no match is found, the original text is left unchanged.
A
~ by itself, or in front of a
/, is replaced by
$HOME. A
~ followed by a
+ or
- is replaced by the value of
$PWD and
$OLDPWD respectively.
In addition,
when expanding a
variable assignment, tilde substitution is attempted when
the value of the assignment
begins with a
~, and when a
~ appears after a
:. The
: also terminates a
~ 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.
This feature is only available on
versions of the UNIX operating system that support the
/dev/fd directory for naming open files.
Each command argument of the form
<(list)
or
>(list)
will run process
list asynchronously connected to some file in
/dev/fd. 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
*, @, #, ?, -, $, 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
=.
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.
Tag | Description |
${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
* or
@, then all the positional
parameters, starting with
$1, are substituted
(separated by a field separator character).
If an array
vname with subscript
* @, or of the form
sub1 .. sub2. is used,
then the value
for each of the
elements between
sub1 and
sub2 inclusive (or all elements for
* and
@) is substituted,
separated by
the first character of
the value of
IFS. |
${#parameter}
| |
If
parameter is
* or
@, the number of positional parameters is substituted.
Otherwise, the length of the value of the
parameter is substituted.
|
${#vname[*]}
${#vname[@]}
| |
The number of elements in the array
vname is substituted.
|
${@vname}
| |
Expands to the type name (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
* or
@, or is an array name indexed by
* or
@, then
offset and
length refer to the array index and number
of elements respectively.
A negative
offset is taken relative to one greater than the highest subscript
for indexed arrays.
The order for 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:
|
|
Tag | Description |
# |
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 number of the last background command invoked or
the most recent job put in the background with the
bg built-in command.
|
.sh.command | |
When processing a
DEBUG trap, this variable contains the current command line
that is about to run.
|
.sh.edchar | |
This variable contains the value of the keyboard character
(or sequence of characters if the first character is an ESC, ascii
033) that has
been entered when processing a
KEYBD trap
(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.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.
|
.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:
|
|
Tag | Description |
|
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 $HOME/.kshrc.
On systems that support a system wide /etc/ksh.kshrc initialization file,
if the filename generated by the expansion of
ENV begins with
/./ or
././ the system wide initialization file will not be executed.
|
|
FCEDIT Obsolete name for
the default editor name for the
hist command.
FCEDIT is not used when
HISTEDIT is set.
|
FIGNORE |
A pattern that defines the set of filenames that will be
ignored when performing filename matching.
|
FPATH |
The search path for function definitions.
The directories in this path are searched for a file with the same name
as the function or command when a function with the
-u attribute is referenced and when a command is not found.
If an executable file with the name of that command is found,
then it is read and executed
in the current environment.
Unlike
PATH, the current directory must be represented
explicitly by
. rather than by adjacent
: characters or a beginning or ending
:. |
|
HISTCMD Number of the current command in the history file.
|
|
HISTEDIT Name for
the default editor name for the
hist command.
|
HISTFILE |
If this variable is set when the shell is invoked, then
the value is the pathname of the file that will be
used to store the command history (see
Command Re-entry below).
|
HISTSIZE |
If this variable is set when the shell is invoked, then
the number of previously entered commands that
are accessible by this shell
will be greater than or equal to this number.
The default is 512.
|
|
HOME The default argument (home directory) for the
cd command.
|
IFS |
Internal field separators,
normally
space, tab, and
new-line that are used to separate the results of
command substitution or parameter expansion
and to separate fields with the built-in command
read. The first character of the
IFS variable is used to separate arguments for the
"$*"
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
(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.
If it is
pfsh or
pfksh, then the shell becomes a profile shell (see
pfexec(1)).
|
TIMEFORMAT |
The value of this parameter is used as a format string specifying
how the timing information for pipelines prefixed with the
time reserved word should be displayed.
The % character introduces a format sequence that is
expanded to a time value or other information.
The format sequences and their meanings are as follows.
Tag | Description |
%% |
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 '') 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
*, ?, (, 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
~(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.
Tag | Description |
* |
Matches any string, including the null string.
When used for filename expansion,
if the
globstar option is on, two adjacent
*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
! 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
|. A
& signifies that all patterns must be matched whereas
| requires that only one pattern be matched.
Composite patterns can be formed with one or more of the following sub-patterns:
Tag | Description |
?(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:
Tag | Description |
\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
|. 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:
Tag | Description |
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
~(options:pattern-list),
where either options or :pattern-list
can be omitted. Unlike the other compound patterns,
these sub-patterns are not counted in the numbered sub-patterns.
If options is present, it can consist of one or more
of the following:
Tag | Description |
+ |
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.
|
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 ~(...) or at the end of
the sub-pattern containing ~(...).
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
('')
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:
Tag | Description |
\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
$* and
$@ is identical when not quoted or when used as a variable assignment value
or as a file name.
However, when used as a command argument,
"$*"
is equivalent to
"$1d$2d...",
where
d is the first character of the
IFS variable, whereas
"$@"
is equivalent to
"$1"
"$2"
....
Inside grave quote marks
(``),
\ quotes the characters
\, `, and
$. If the grave quotes occur within double quotes, then
\ also quotes the character
".
The special meaning of reserved words or aliases can be removed by quoting any
character of the reserved word.
The recognition of function names or built-in command names 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.
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 copysign cos cosh erf erfc exp exp2 expm1 fabs fdim finite floor fma fmax fmod j0 j1 jn hypot ilogb int isinf isnan lgamma log log2 logb nearbyint nextafter nexttoward pow rint round sin sinh sqrt tan tanh tgamma trunc y0 y1 yn
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:
Tag | Description |
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.
|
-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.
|
-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 =~ ere
| |
True if
string matches the pattern
~(E)ere where
ere is an extended regular expression.
|
string1 < string2
| |
True, if
string1 comes before
string2 based on ASCII value of their characters.
|
string1 > string2
| |
True, if
string1 comes after
string2 based on ASCII value of their characters.
|
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 || 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.
Tag | Description |
<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 |
Sames 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 callers
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;}.
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.
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.
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:
Tag | Description |
%number | |
The job with the given number.
|
%string | |
Any job whose command line begins with
string. |
%?string | |
Any job whose command line contains
string. |
%% |
Current job.
|
%+ |
Equivalent to
%%. |
%- |
Previous job.
|
The shell learns immediately whenever a process changes state.
It normally informs you whenever a job becomes blocked so that
no further progress is possible, but only just before it prints
a prompt.
This is done so that it does not otherwise disturb your work.
The
notify option of the
set command causes
the shell to print these job change messages
as soon as they occur.
When the
monitor option is on, each background job that completes
triggers any trap set for
CHLD.
When you try to leave the shell while jobs are running or stopped, you 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 variable
PATH defines the search path for
the directory containing the command.
Alternative directory names are separated by
a colon
(:). The default path is
/bin:/usr/bin: (specifying
/bin, /usr/bin, and the current directory
in that order).
The current directory can be specified by
two or more adjacent colons, or by a colon
at the beginning or end of the path list.
If the command name contains a /, then the search path
is not used.
Otherwise, each directory in the path is
searched for an executable file
of the given name
that is not a directory.
If found, and if the shell
determines that there is a built-in version
of a command corresponding to a given pathname,
this built-in is invoked in the current process.
If found, and this directory is also contained in the value of the
FPATH variable,
then this file is loaded into the current shell environment
as if it were the argument to the . command
except that only preset aliases are expanded,
and a function of the given name is executed
as described above.
If not found, and the file
.paths is found, and this file contains a line of the form
FPATH=path where
path names an
existing directory, and this directory contains
a file of the given name,
then this file is loaded into the current shell environment
as if it were the argument to the . special built-in command
and a function of the given name is executed.
Otherwise, if found,
a process is created and
an attempt is made to execute the command via
exec(2).
When an executable is found, the directory where it is found
in is searched for a file named
.paths. If this file is found and it contains a line of the form
BUILTIN_LIB=value , then the library named by
value 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.
Otherwise, if this file is found and it contains a line of the form
name=value in the first or second line, then the environment variable
name is modified by prepending the directory specified by
value to the directory list.
If
value is not an absolute directory, then it
specifies a directory relative to the directory that the
executable was found.
If the environment variable
name does not already exist it will be added to the environment
list for the specified command.
If the file has execute permission but is not an
a.out file,
it is assumed to be a file containing shell commands.
A separate shell is spawned to read it.
All non-exported variables are removed in this case.
If the shell command
file doesnt 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.
A parenthesized command is executed in
a sub-shell without removing non-exported variables.
Command Re-entry.
The text of the last
HISTSIZE
(default 512)
commands entered from a terminal device
is saved in a
history file.
The file
$HOME/.sh_history is used if the
HISTFILE
variable is not set
or if the file it names is not writable.
A shell can access the commands of
all
interactive shells which use the same named
HISTFILE. The built-in command
hist is used to list or
edit a portion of this file.
The portion of the file to be edited or listed can be selected by
number or by giving the first character or
characters of the command.
A single command or range of commands can be specified.
If you do not specify an editor program as
an argument to
hist then the value of the variable
HISTEDIT is used.
If
HISTEDIT is unset, the obsolete variable
FCEDIT is used.
If
FCEDIT is not defined, then
/bin/ed is used.
The edited 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
'hist -s', 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 users 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
;, |, &, or
(, and the word does not begin with
~ or contain a
/, the list of aliases, functions, and executable commands
defined by the
PATH variable that could match the partial word is displayed.
Otherwise, the list of files that match the 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.
Tag | Description |
^F |
Move cursor forward (right) one character.
|
M-[C |
Move cursor forward (right) one character.
|
M-f |
Move cursor forward one word.
(The
emacs editors 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 characters
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 doesnt 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 users 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 characters
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.
Tag | Description |
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 characters
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.
Tag | Description |
[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]|
|
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.
Tag | Description |
[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.
Tag | Description |
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$. |
[count]dmotion
d[count]motion
| |
Delete current character through the character that
motion would move to.
If motion is
d , the entire line will be deleted.
|
i |
Enter input mode and insert text before the current character.
|
I |
Insert text before the beginning of the line.
Equivalent to
0i. |
[count]P
|
Place the previous text modification before the cursor.
|
[count]p
|
Place the previous text modification after the cursor.
|
R |
Enter input mode and
replace characters on the screen with characters you type overlay fashion.
|
[count]rc
|
Replace the
count character(s) starting at the current cursor position with
c, and advance the cursor.
|
[count]x
|
Delete current character.
|
[count]X
|
Delete preceding character.
|
[count].
|
Repeat the previous text modification command.
|
[count]~
|
Invert the case of the
count character(s) starting at the current cursor position and advance the cursor.
|
[count]_
|
Causes the
count word of the previous command to be appended and
input mode entered.
The last word is used
if
count is omitted.
|
* |
Causes an
* to be appended to the current word and file name generation attempted.
If no match is found,
it rings the bell.
Otherwise, the word is replaced
by the matching pattern and input mode is entered.
|
\ |
Command or file name completion as described above.
|
Other Edit Commands
Miscellaneous commands.
Tag | Description |
[count]ymotion
y[count]motion
| |
Yank current character through character that
motion would move the cursor to and puts them into the delete buffer.
The text and cursor are unchanged.
|
yy |
Yanks the entire line.
|
Y |
Yanks from current position to end of line.
Equivalent to
y$. |
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 symbols
are special built-in commands and
are treated specially in the following ways:
Tag | Description |
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.
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
|
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='command exec' 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 specifed 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
-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 [ oldnew ] [ 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
/bin/ed) is used as the editor.
When editing is complete, the edited command(s)
is executed if the changes have been saved.
If
last is not specified,
then it 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 -l [ 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, if
sig is not specified,
the signal names are listed.
Otherwise, for each
sig that is a name, the corresponding signal number is listed.
For each
sig that is a number, the signal name corresponding to the
least significant 8 bits of
sig is listed.
|
let arg ...
| |
Each
arg is a separate
arithmetic expression to be evaluated.
See
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:
Tag | Description |
\a |
The alert character (ascii
07). |
\b |
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
|& 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:
Tag | Description |
%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.
|
%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.
|
%(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 specifier without an output base,
causes the output to be displayed in thousands units with one of the suffixes
k M G T P E to indicate the unit.
The
# flag when used with the
i specifier causes the output to be displayed in 1024 with one of the suffixes
Ki Mi Gi Ti Pi Ei to indicate the unit.
|
= |
The
= flag has been added to center the output within the specified field width.
|
|
pwd [ -LP ]
| |
Outputs the value of the current working
directory.
The
-L option is the default; it prints the logical name of the current directory.
If the
-P option is 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 [ -ACprsv ] [ -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
-p option causes the input line
to be taken from the input pipe
of a process spawned by the shell
using
|&. If the
-s option is present,
the input 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:
Tag | Description |
-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
>| to truncate a file when turned on.
|
-G |
Causes the pattern
** 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
|| 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:
Tag | Description |
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. |
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.
|
true
|
Does nothing, and exits 0. Used with
while for infinite loops.
|
typeset [ ±ACHSflbnprtux ] [ ±EFLRXZi[n] ] [ -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 variables value and type are restored
when the function completes.
The following list of attributes may be specified:
Tag | Description |
-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.
|
-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 |
Creates a type named by tname using the compound
assignment
assign_list to tname.
|
-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
-t, -u and
-x. The
-t option
turns on execution tracing for this function.
The
-u option
causes this function to be marked undefined.
The
FPATH variable 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.
|
-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 |
All upper-case characters are
converted to lower-case.
The upper-case option,
-u, is turned off.
|
-n |
Declares
vname to be a reference to the variable whose name is
defined by the value of variable
vname. This is usually used to reference a variable inside
a function whose name has been passed as an argument.
|
-p |
The name, attributes and values for the given
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 |
All lower-case characters are converted
to upper-case.
The lower-case option,
-l, is turned off.
|
-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.
Tag | Description |
-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:
Tag | Description |
-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.
|
Tag | Description |
-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 interruptible).
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.
|
-P |
If
-P or
-o profile is present, the shell is a profile shell (see
pfexec(1)).
|
-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 filename argument specifies the generated database. A script file must be
provided on the command line as well.
|
The remaining options and arguments are described under the
set command above.
An optional
- as the first argument is ignored.
Rsh
Rksh
Rksh93 is used to set up login names and execution environments whose
capabilities are more controlled than those of the standard shell.
The actions of
are identical to those of
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,
invokes
sh
invokes
ksh
invokes
ksh93 to execute it.
Thus, it is possible to provide to the end-user shell procedures
that have access to the full power of
the standard shell,
while imposing a limited menu of commands;
this scheme assumes that the end-user does not have write and
execute permissions in the same directory.
The net effect of these rules is that the writer of the
.profile has complete control over user actions,
by performing guaranteed setup actions
and leaving the user in an appropriate directory
(probably
not the login directory).
The system administrator often sets up a directory
of commands
(e.g.,
/usr/rbin) that can be safely invoked by
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
Tag | Description |
/etc/profile | |
The system wide initialization file, executed for login shells.
|
/etc/ksh.kshrc | |
The system wide startup file, executed for interactive shells.
|
$HOME/.profile | |
The personal initialization file, executed for login shells after /etc/profile.
|
$HOME/..kshrc
| |
Default personal initialization file, executed for interactive shells when
ENV is not set.
|
/etc/suid_profile | |
Alternative initialization file, executed when instead of personal initialization file when the real and effective user or group id do not match.
|
/dev/null | |
NULL device
|
SEE ALSO
cd(1),
chmod(1),
cut(1),
egrep(1),
echo(1),
emacs(1),
env(1),
fgrep(1),
gmacs(1),
grep(1),
newgrp(1),
pfexec(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),
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
|.
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 wont 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.
Advertisements
|