ksh(1)
ksh --
KornShell, a standard/restricted command and programming language
Synopsis
/u95/bin/ksh [±abcefhikmnoprstuvxCD] [-R file] [±o option] ... [-] [arg ...]
/u95/bin/sh [±abcefhikmnoprstuvxCD] [-R file] [±o option] ... [-] [arg ...]
Description
This manual page describes the version of the Korn Shell that complies
with X/Open Interface Definitions, Version 4 Issue 2 (sometimes
called ``ksh-93'') and is found in /bin/ksh.
In an X/Open-compliant execution environment, this is the standard shell
(see
profile(4)).
See
``ksh-93 vs. ksh-88'' in Differences for SCO OpenServer and SCO UnixWare 1 and 2 users
for a list of the major differences between the ``ksh-93'' shell and
the earlier version of the Korn Shell (
ksh88(1))
used in previous releases.
Also see ``Compatibility'', below.
The Korn Shell utility
is a command and programming language
that executes commands read from a terminal
or a file.
A restricted version of this utility can be run with the -r
option; it is used to set up login names and execution environments whose
capabilities are more controlled than those of the non-restricted shell.
See
``Invocation''
and
``Rsh Only''
for the meaning of arguments to the shell.
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 . (period) and optionally preceded
by a . (period).
Vnames are used as function and variable names.
A
word
is a sequence of
characters
from the character set defined by the current locale,
excluding non-quoted metacharacters.
A
command
is a sequence of characters in the syntax
of the shell language.
The shell reads each command and
carries out the desired action either directly or by invoking
separate utilities.
A built-in command is a command that is carried out by the
shell itself without creating a separate process.
Some commands are built-in purely for convenience
and are not documented 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'')
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.
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.
A
command
is either a simple-command
or one of the following.
Unless otherwise stated,
the value returned by a command is that of the
last simple-command executed in the command.
for vname [ in word ... ] ;do list ;done-
Each time a
for
command is executed,
vname
is set to the next
word
taken from the
in
word
list.
If
in word
...
is omitted, then
the
for
command executes the do list once for each positional parameter
that is set starting from 1
(see
``Parameter Expansion'').
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'').
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'').
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'').
The
;;
operator causes execution of
case
to terminate.
If
;&
is used in place of
;;
the 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''
for a description of
expression.
function varname { list ;}-
varname () { list ;}-
Define a function which is referenced by
varname.
A function whose
varname
contains a
.
is called a discipline function and the portion
of the
varname
preceding the last
.
must refer to an existing variable.
The body of the function is the
list
of commands between
{
and
}.
A function defined with the function varname
syntax can also be used as an argument to the .
special built-in command to get the equivalent behavior
as if the varname() syntax were used to define it.
(See
``Functions'').
time [ pipeline ]-
If pipeline is omitted the user and system time for
the current shell and completed child processes is printed
on standard error.
Otherwise,
pipeline
is executed and the elapsed time as well as
the user and system time are printed on standard error.
The following reserved words
are recognized as reserved only when they serve as 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 ,
export ,
or
readonly
special built-in commands.
The syntax for an assignment is of the form:
varname=word
varname[word]=word
No space is permitted between varname and the = or
between = and word.
varname=(assign_list)
No space is permitted between varname and the =.
An assign_list can be one of the following:
word ...-
Indexed array assignment.
[word]=word ...-
Associative array assignment.
assignment ...-
Nested variable assignment.
typeset [options] assignment ...-
Nested variable assignment. Multiple assignments
can be specified by separating each of them with a ;.
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
exported aliases
are compiled into the shell
but can be unset or redefined:
autoload='typeset -fu'-
command='command '-
fc=hist-
float='typeset -E'-
functions='typeset -f'-
hash='alias -t --'-
history='hist -l'-
integer='typeset -i'-
nameref='typeset -n'-
nohup='nohup '-
r='hist -s'-
redirect='command exec'-
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'').
If it does, then the word up to a
``/''
is checked to see if it matches a user name in the
password database (often the
/etc/passwd
file).
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
$OLDPWD
respectively.
In addition,
when expanding a
variable assignment,
tilde substitution is attempted when
the value of the assignment
begins with a
``~'',
and when a
``~''
appears after a
``:''.
The
``:''
also terminates a
``~''
login name.
Command substitution.
The standard output from a command enclosed in
parentheses preceded by a dollar sign ($)
or a pair of grave accents (``)
may be used as part or all
of a word;
trailing new-lines are removed.
In the second (obsolete) form, the string between the quotes is processed
for special quoting characters before the command is executed (see
``Quoting'').
The command substitution
$(cat file)
can be replaced by the equivalent but faster
$(<file).
Arithmetic substitution.
An arithmetic expression enclosed in double
parentheses preceded by a dollar sign ($(()))
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 -f4 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.
Parameter expansion.
A
parameter
is a
variable,
one or more digits,
or any of the characters
``'',
``@'',
``#'',
``?'',
``-'',
``$'',
and
``!\^''.
A
variable
is denoted by a vname.
To create a variable whose
vname
contains a ``.'',
a variable whose
vname
consists of everything before the last ``.'' must already exist.
A
variable
has a
value
and zero or more
attributes.
Variables
can be assigned
values
and
attributes
by using the
typeset
special built-in command.
The attributes supported by the shell are described
later with the
typeset
special built-in command.
Exported variables pass values and attributes to
the environment.
The shell supports both indexed and associative arrays.
An element of an array variable is referenced by a
subscript.
A
subscript
for an indexed array is denoted by
an
arithmetic expression
(see
``Arithmetic evaluation'')
between a
``[''
and a
``]''.
To assign values to an indexed array, use
set -A vname value ... .
The value of all
subscripts must be in the
range of
0 through 4095.
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 period (.).
When a variable or function name contains a period, and the portion
of the name up to the first period 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.
A nameref provides a convenient way to refer to the variable
inside a function whose name is passed as an argument to a function.
For example, if the name of a variable is passed as the first
argument to a function, the command
typeset -n var=$1
inside the function causes references and assignments to
var
to be references and assignments to the variable whose
name has been passed to the function.
If either of the floating point attributes,
-E,
or
-F,
or the integer attribute,
-i,
is set for
vname,
then the
value
is subject to arithmetic evaluation as described below.
Positional parameters,
parameters denoted by a number,
may be assigned values with the
set
special built-in command.
Parameter
$0
is set from argument zero when the shell
is invoked.
The character
``$''
is used to introduce substitutable
parameters.
${parameter}-
The shell
reads all the characters from
${
to the matching
}
as part of the same word even if it contains
braces or metacharacters.
The value, if any, of the parameter is substituted.
The braces are required when
parameter
is followed by a letter, digit, or underscore
that is not to be interpreted as part of its name,
when the variable name contains a ``.'',
or when a variable is subscripted.
If
parameter
is one or more digits then it is a positional parameter.
A positional parameter of more than one digit must be
enclosed in braces.
If
parameter
is
or
@,
then all the positional
parameters, starting with
$1,
are substituted
(separated by a field separator character).
If an array
vname
with subscript
or
@
is used,
then the value
for each of the
elements
is substituted,
separated by
the first character of
the value of
IFS.
${#parameter}-
If
parameter
is
or
@,
the number of positional parameters is substituted.
Otherwise, the length of the value of the
parameter is substituted.
${#vname[*]}-
${#vname[@]}-
The number of elements in the array
vname
is substituted.
${!vname}-
Expands to the name of the variable referred to by
vname.
This will be
vname
except when
vname
is a name reference.
${!vname[subscript]}-
Expands to name of the subscript unless
subscript
is
*
or
@.
When
subscript
is
*,
the list of array subscripts for vname
is generated.
For a variable that is not an array, the value is 0 if the variable
is set. Otherwise it is null.
When
subscript
is
@,
same as above, except that when used in double quotes,
each array subscript yields a separate
argument.
${!prefix*}-
Expands to the names of the variables whose names begin with
prefix.
${parameter:-word}-
If
parameter
is set and is non-null then substitute its value;
otherwise substitute
word.
${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.
${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
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.
${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
@,
*,
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 nth 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 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.
The following
parameters
are automatically set by the shell:
#-
The number of positional parameters in decimal.
--
Options supplied to the shell on invocation or by
the
set
command.
?-
The decimal value returned by the last executed command.
$-
The process number of this shell.
_-
Initially, the value of
_
is an absolute pathname of the shell or script being executed
as passed in the environment.
Subsequently it is assigned the last argument of the previous command.
This parameter is not set for commands which are asynchronous.
This parameter is also used to hold the name of the matching
MAIL
file when checking for mail.
!-
The process number of the last background command invoked.
.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'').
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'').
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.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.value-
Set to the value of the variable at the time that the
set
discipline function is invoked.
.sh.version-
Set to a value that identifies the version of this shell.
LINENO-
The current line number within the script or
function being executed.
OLDPWD-
The previous working directory set by the
cd
command.
OPTARG-
The value of the last option argument processed by the
getopts
built-in command.
OPTIND-
The index of the last option argument processed by the
getopts
built-in command.
PPID-
The process number of the parent of the shell.
PWD-
The present working directory set by the
cd
command.
RANDOM-
Each time this variable is referenced, a random integer,
uniformly distributed between 0 and 32767, is generated.
The sequence of random numbers can be initialized by assigning
a numeric value to
RANDOM.
REPLY-
This variable is set by the
select
statement and by
the
read
built-in command when no arguments are supplied.
SECONDS-
Each time this variable is referenced, the number of
seconds since shell invocation is returned.
If this variable is
assigned a value, then the value returned upon reference will
be the value that was assigned plus the number of seconds since the assignment.
The following
variables
are used by the shell:
CDPATH-
The search path for the
cd
command.
COLUMNS-
If this variable is set,
the value is used to define the width of the edit window
for the shell edit modes and for printing
select
lists.
EDITOR-
If the value of this variable ends in
``emacs'',
``gmacs'',
or
``vi''
and the
VISUAL
variable is not set,
then the corresponding 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
(see
``Invocation'').
This file is typically used for
alias
and
function
definitions.
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.
This path is searched when a function with the
-u
attribute is referenced and when a command is not found.
If an executable file is found, then it is read and executed
in the current environment.
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'').
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 128.
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'').
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.
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'').
LC_MESSAGES-
Determines the locale that should be used to affect the format
and contents of diagnostic messages written to standard error.
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'').
The user may not change
PATH
if executing under
the restricted (-r) shell
(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'').
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.
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 ends in
``emacs'',
``gmacs'',
or
``vi''
then the corresponding option
(see special command
set
below)
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).
On some systems
MAIL
and
SHELL
are also
set by
login.
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.
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.
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.
-
Matches any string, including the null string.
?-
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:
alnum alpha blank cntrl digit graph
lower print punct space upper 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:
?(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.
@(pattern-list)-
Matches exactly one of the given patterns.
!(pattern-list)-
Matches anything except one of the given patterns.
Each sub-pattern in a composite pattern is numbered,
starting at 1, by the location of the ( within
the pattern.
The sequence \n, where n
is a single digit and \n comes after
the nth sub-pattern,
matches the same string as the sub-pattern itself.
Quoting.
Each of the
metacharacters
listed earlier (see
``Definitions'')
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 that
\0
within the string causes the remainder of the
string to be ignored and
\E
is equivalent to the escape character
(ASCII 033).
Inside double quote marks
(``""''),
parameter and command substitution occur and
\
quotes the characters
``\'',
```'',
``"'',
and
``$''.
A
$
in front of a double quoted string 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.
Floating point constants follow the ANSI-C programming language
conventions.
Integer constants are 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.
If
base
is omitted,
then base 10 is used.
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, 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.
The following math library functions can be used with an arithmetic
expression:
abs acos asin atan cos cosh exp
int log sin sinh sqrt tan tanh
An internal representation of a
variable
as a double precision floating point can be specified with the
-E [n]
or
-F [n]
option of the
typeset
special built-in command.
The
-E
option causes the expansion of the value to be represented using
scientific notation when it is expanded.
The optional option argument
n
defines the number of significant figures.
The
-F
option causes the expansion to be represented as a floating decimal number
when it is expanded.
The optional option argument
n
defines the number of places after the decimal point in this case.
An internal integer representation of a
variable
can be specified with the
-i [n]
option of the
typeset
special built-in command.
The optional option argument
n
specifies an arithmetic base to be used when expanding the variable.
If you do not specify an arithmetic base,
the first assignment to the
variable determines the arithmetic base.
Arithmetic evaluation is performed on the value of each
assignment to a variable with the
-E,
-F,
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
(that is, the value of
PS2)
is issued.
Conditional expressions.
A
conditional expression
is used with the
[[
compound command to test attributes of files and to compare
strings.
Field splitting and file name generation are
not performed on the words between
[[
and
]].
Each expression can be constructed from one or more
of the following unary or binary expressions:
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 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.
-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.
string = pattern-
Same as == above, but is obsolete.
string != pattern-
True, if
string
does not match
pattern.
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.
< word-
Use file
word
as standard input (file descriptor 0).
> word-
Use file
word
as standard output (file descriptor 1).
If the file does not exist then it is created.
If the file exists, and the
noclobber
option is on,
this causes an error;
otherwise, it is truncated to zero length.
>|word-
Same as
>,
except that it overrides the
noclobber
option.
>>word-
Use file
word
as standard output.
If the file exists, then output is appended to it (by first seeking to the end-of-file);
otherwise, the file is created.
<>word-
Open file
word
for reading and writing
as standard input.
<<[-]word-
The shell input is read up to a line that is the same as
word
after any quoting has been removed,
or to an end-of-file.
No parameter substitution, command substitution, arithmetic substitution or
file name generation is performed on
word.
The resulting document,
called a
here-document,
becomes
the standard input.
If any character of
word
is quoted, then no interpretation
is placed upon the characters of the document;
otherwise, parameter expansion, command substitution, and arithmetic
substitution occur,
\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.
<& 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.
If one of the above is preceded by a digit,
then the
file descriptor number referred to is that specified
by the digit
(instead of the default 0 or 1).
For example:
... 2>&1
means file descriptor 2 is to be opened
for writing as a duplicate
of file descriptor 1.
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(5))
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.
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'').
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 and
all functions it calls.
Errors within functions return control to the caller.
Functions defined with the
name()
syntax and functions defined with the
function
name
syntax that are invoked with the .
special built-in
are executed in the caller's
environment and share all variables
and traps with the caller.
Errors within these function executions cause the script that contains
them to abort.
The special built-in command
return
is used to return
from function calls.
Function names
can be listed with the
-f
or
+f
option of the
typeset
special built-in command.
The text of functions, when available, will also
be listed with
-f.
Functions can be undefined with the
-f
option of the
unset
special built-in command.
Ordinarily, functions are unset when the shell executes a shell script.
Functions that need to be defined across separate
invocations of the shell should
be placed in a directory and the
FPATH
variable should contain the name of this directory.
They may also
be specified in the
ENV
file.
Discipline functions.
Each variable can have zero or more discipline functions
associated with it.
The shell initially understands the discipline names get,
set, and unset but on most systems
others can be added at run time via the
C programming interface extension provided by the
builtin
built-in utility.
If the get discipline is defined for a variable, it is invoked
whenever the 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.
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.
For the set discipline,
changing
.sh.value
will change the value that gets assigned.
Jobs
If the
monitor
option of the
set
command is turned on,
an interactive shell associates a job with each pipeline.
It keeps
a table of current jobs, printed by the
jobs
command, and assigns them small integer numbers.
When a job is started asynchronously with
&,
the shell prints a line which looks
like:
[1] 1234
indicating that the job which was started asynchronously was job number
1 and had one (top-level) process, whose process id was 1234.
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 (<Ctrl>-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.
Background jobs can be re-enabled to produce output by giving the command
stty -tostop.
There are several ways to refer to jobs in the shell.
A job can be referred to by the process id of any process of the job
or by one of the following:
% number-
The job with the given number.
% 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,
it is executed within the
current shell process.
Next, the command name is checked to see if
it matches a user defined function.
If it does,
the positional parameters are saved
and then reset to the arguments of the
function
call.
A function is also executed in the
current shell process.
When the
function
completes or issues a
return,
the positional parameter list is restored.
For functions defined with the
function
name
syntax,
any trap set on
EXIT
within the function is executed.
The exit value of a
function
is the value of the last command executed.
If a command name is not a
special built-in command
or a user defined
function,
but it is one of the built-in commands ,
it is executed in the current shell process.
The shell variable
PATH
defines the search path for
the directory containing the command.
Alternative directory names are separated by
a colon (:).
The default path is
/bin:/usr/bin:
(specifying
/bin,
/usr/bin,
and the current directory
in that order).
The current directory can be specified by
two or more adjacent colons, or by a colon
at the beginning or end of the path list.
If the command name contains a ``/'', then the search path
is not used.
Otherwise, each directory in the path is
searched for an executable file that is not a directory.
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.
A process is created and
an attempt is made to execute the command via
exec(2).
If the file has execute permission but is not an
a.out
file,
it is assumed to be a file containing shell commands.
A separate shell is spawned to read it.
All non-exported variables are removed in this case.
If the shell command
file doesn't have read permission,
or if the
setuid
and/or
setgid
bits are set on the file,
then the shell executes an agent whose job it is to
set up the permissions and execute the shell with the
shell command file passed down as an open file.
A parenthesized command is executed in
a sub-shell without removing non-exported variables.
Command re-entry.
The text of the last
HISTSIZE
(default 128)
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 user's terminal
accept <Return> as carriage return without line feed
and that a space (` ') must overwrite the current character on
the screen.
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.
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 <Ctrl>-F.
This is entered by depressing ``f'' while holding down the
<Ctrl> (control) key.
The <Shift> key is
not
depressed.
(The notation
^?
indicates the <Del> (delete) key.)
The notation for escape sequences is
M-
followed by a
character.
For example,
M-f
(pronounced Meta f)
is entered by depressing <Esc>
(ASCII 033 )
followed by ``f''.
M-F
would be the notation for <Esc> followed by <Shift> (capital) ``F''.)
All edit commands
operate from any place on the line
(not just at the beginning).
Neither the <Return> nor the LINE FEED key is
entered after edit commands except when noted.
^F-
Move cursor forward (right) one character.
M-f-
Move cursor forward one word.
(The
emacs
editor's idea of a word is a string of characters
consisting of only letters, digits and underscores.)
^B-
Move cursor backward (left) one character.
M-b-
Move cursor backward one word.
^A-
Move cursor to start of line.
^E-
Move cursor to end of line.
^]-
Move cursor forward to character
char
on current line.
M-^-
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.
^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.
^@-
(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-<-
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.
^R string-
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-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.
The can be used to program functions keys on many terminals.
M-.-
The last word of the previous command is inserted
on the line.
If preceded by a numeric parameter, the value
of this parameter determines which word to insert rather than
the last word.
M-_-
Same as
M-..
M-*-
Attempt file name generation on the current word.
An asterisk is appended if the word doesn't match any file
or contain any special
pattern characters.
M-<Esc>-
Command or file name completion as described above.
M-=-
Command or file name listing as described above.
^U-
Multiply parameter of next command by 4.
\-
Escape next character.
Editing characters, the user's erase, kill and
interrupt (normally ``^?'')
characters
may be entered
in a command line or in a search string if preceded by a
``\''.
The
``\''
removes the next character's
editing features (if any).
^V-
Display version of the shell.
M-#-
If the line does not begin with a
``#'',
a
``#''
is inserted
at the beginning of the line
and after each new-line,
and the line is entered.
This causes a comment to be inserted in the history file.
If the line begins with a
``#'',
the
``#''
is deleted and one
``#''
after each new-line is also deleted.
Vi editing mode.
There are two typing modes.
Initially, when you enter a command you are in the
input
mode.
To edit, the user enters
control
mode by typing ESC
(033)
and moves the cursor to the point needing correction and
then inserts or deletes characters or words as needed.
Most control commands accept an optional repeat
count
prior to the command.
When in
vi
mode on most systems,
canonical processing is initially enabled and the
command will be echoed again if the speed is 1200 baud or greater and it
contains any control characters or less than one second has elapsed
since the prompt was printed.
The ESC character terminates canonical processing for the remainder of the command
and the user can then modify the command line.
This scheme has the advantages of canonical processing with the type-ahead
echoing of raw mode.
If the option
viraw
is also set, the terminal will always have canonical processing
disabled.
This mode is implicit for systems that do not support two
alternate end of line delimiters,
and may be helpful for certain terminals.
Input edit commands
By default the editor is in input mode.
erase-
(User defined erase character as defined
by the stty command, usually
^H
or
#.)
Delete previous character.
^W-
Delete the previous blank separated word.
On some systems the viraw option
may be required for this to work.
eof-
As the first character of the line causes
the shell to terminate unless the ignoreeof
option is set.
Otherwise this character is ignored.
^V-
Escape next character.
Editing characters and the user's erase or kill
characters may be entered
in a command line or in a search string if preceded by a
^V.
The
^V
removes the next character's
editing features (if any).
On some systems the viraw option
may be required for this to work.
\-
Escape the next
erase
or
kill
character.
Motion edit commands
These commands will move the cursor.
[count]l-
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]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
rhf.
[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 first non-blank character in line.
$-
Cursor to end of line.
%-
Moves to balancing
(,
),
{,
},
[,
or
].
If cursor is not on one of the above characters,
the remainder of the line is searched for the first
occurrence of one of the above characters first.
Search edit commands
These commands access your command history.
[count]k-
Fetch previous command.
Each time
k
is entered
the previous command back in time is accessed.
[count]--
Equivalent to
k.
[count]j-
Fetch next command.
Each time
j
is entered
the next command forward in time is accessed.
[count]+-
Equivalent to
j.
[count]G-
The command number
count
is fetched.
The default is the least recent history command.
/ string-
Search backward through history for a previous command containing
string.
string
is terminated by a <Return> or NEW LINE.
If string is preceded by a
^,
the matched line must begin with
string.
If string is null, the previous string will be used.
? string-
Same as
/
except that search will be in the forward direction.
n-
Search for next match of the last pattern to
/
or
?
commands.
N-
Search for next match of the last pattern to
/
or
?/,
but in reverse direction.
Text modification edit commands
These commands will modify the line.
a-
Enter input mode and enter text after the current character.
A-
Append text to the end of the line.
Equivalent to
$a.
[count]cmotion-
c[count]motion-
Delete current character through the character that
motion
would move the cursor to and enter input mode.
If motion is
c,
the entire line will be deleted and
input mode entered.
C-
Delete the current character through the end of line and enter input mode.
Equivalent to
c$.
S-
Equivalent to
cc.
[count]s-
Replace characters under the cursor in input mode.
D-
Delete the current character through the end of line.
Equivalent to
d$.
[count]dmotion-
d[count]motion-
Delete current character through the character that
motion
would move to.
If motion is
d,
the entire line will be deleted.
i-
Enter input mode and insert text before the current character.
I-
Insert text before the beginning of the line.
Equivalent to
0i .
[count]P-
Place the previous text modification before the cursor.
[count]p-
Place the previous text modification after the cursor.
R-
Enter input mode and
replace characters on the screen with characters you type overlay fashion.
[count]rc-
Replace the
count
character(s) starting at the current cursor position with
c,
and advance the cursor.
[count]x-
Delete current character.
[count]X-
Delete preceding character.
[count].-
Repeat the previous text modification command.
[count]~-
Invert the case of the
count
character(s) starting at the current cursor position and advance the cursor.
[count]_-
Causes the
count
word of the previous command to be appended and
input mode entered.
The last word is used
if
count
is omitted.
*-
Causes an
``*''
to be appended to the current word and file name generation attempted.
If no match is found,
it rings the bell.
Otherwise, the word is replaced
by the matching pattern and input mode is entered.
\-
Command or file name completion as described above.
Other edit commands
Miscellaneous commands.
[count]ymotion-
y[count]motion-
Yank current character through character that
motion
would move the cursor to and puts them into the delete buffer.
The text and cursor are unchanged.
yy-
Yanks the entire line.
Y-
Yanks from current position to end of line.
Equivalent to
y$.
u-
Undo the last text modifying command.
U-
Undo all the text modifying commands performed on the line.
[count]v-
Returns the command
hist -e ${VISUAL:-${EDITOR:-vi}} count
in the input buffer.
If
count
is omitted, then the current line is used.
^L-
Line feed and print current line.
Has effect only in control mode.
^J-
(New line) Execute the current line, regardless of mode.
^M-
(Return) Execute the current line, regardless of mode.
#-
If the first character of the command is a
``#'',
then this command deletes this
``#''
and each
``#''
that follows a newline.
Otherwise,
sends the line after
inserting a
``#''
in front of each line in the command.
Useful for causing the current line to be
inserted in the history as a comment and
uncommenting previously commented commands
in the history file.
=-
Command or file name listing as described above.
@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,
command,
newgrp,
and
login,
all built-in commands accept
--
to indicate end of options.
They also interpret the option
-?
as a help request and print 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:
-
Variable assignment lists preceding the command
remain in effect when the command completes.
-
I/O redirections are processed after variable assignments.
-
Errors
cause a script
that contains them to abort.
-
They are not valid function names.
-
Words
following a command preceded by ++
that are in the format of a variable assignment
are expanded with the same rules as a variable assignment.
This means that
tilde substitution is performed after the
``=''
sign and field splitting and file name generation are not
performed.
+ : [ arg ... ]-
The command only expands parameters.
+ . name [ arg ... ]-
If
name
is a function defined with the
function
name
reserved word syntax,
the function is executed in the current environment
(as if it had been defined with the
name ()
syntax.)
Otherwise if
name
refers to a file, the
file is read in its entirety and the commands are
executed in the current shell environment.
The search path
specified by
PATH
is used to find the directory containing the file.
If any arguments
arg
are 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.
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.
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.
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 first occurrence of 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
the restricted shell (-r)
command [ -pvV ] 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
-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
nth
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 ... ]-
Prints each of its arguments separated by a space
and follows the last argument with a new-line.
The dash character (-) is not treated specially, and a backslash
appearing before the end of the echo line is ignored (unless quoted).
Also see, print or printf, described below.
See
echo(1)
for general usage and description.
+ 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
fpathconf(2)
and
sysconf(3C).)
The
pathname
argument is required for parameters whose value depends on
the location in the file system.
If no arguments are 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.
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 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
C
can only be specified as the first option.
hist [ -e ename ] [ -nlr ] [ first [ last ] ]-
hist -s [ old=new ] [ command ]-
In the first form,
a range of commands from
first
to
last
is selected from the last
HISTSIZE
commands that were typed at the terminal.
The arguments
first
and
last
may be specified as a number or as a string.
A string is used to locate the most recent command starting with
the given string.
A negative number is used as an offset to the current command number.
If the
-l
option
is selected,
the commands are listed on standard output.
Otherwise, the editor program
ename
is invoked on a file containing these
keyboard commands.
If
ename
is not supplied, then the value of the variable
HISTEDIT
is used.
If
HISTEDIT
is not set, then
FCEDIT
(default
/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''
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 [ -Rnprs ] [ -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
n,
r,
R
options are ignored.
Otherwise,
unless the
-R
or
-r,
are specified, the following
escape conventions will be applied:
\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 \.
\0 x-
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
-p
option causes the
arguments to be written onto the pipe
of the process spawned with
|&
instead of standard output.
The
-s
option causes the
arguments to be written onto the history file
instead of standard output.
The
-u
option can be used to specify a one digit
file descriptor unit number
unit
on which the
output 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:
-
A
%b
format can be used instead of
%s
to cause escape sequences in the corresponding
arg
to be expanded as described in
printf(1).
-
A
%P
format can be used instead of
%s
to cause
arg
to be interpreted as an extended regular
expression and be printed as a shell pattern.
-
A
%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.
-
The precision field of the
%d
format can be followed by a
.
and the output base.
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 [-Aprs] [-d delim] [-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.
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.
The
-A
option causes the variable
vname
to be unset and each field that is read to be stored in
successive elements of the indexed array
vname.
The
-p
option causes the input line
to be taken from the input pipe
of a process spawned by the shell
using
``|&''.
If the
-s
option is present,
the input 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.
+ 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 [ ±Cabefhkmnopstuvx ] [ ±o [ option ] ] ... [ ±A vname ] [ arg ... ]-
The options for this command have meaning as follows:
-A-
Array assignment.
Unset the variable
vname
and assign values sequentially from the
arg
list.
If
+A
is used, the variable
vname
is not unset first.
-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.
-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-
If a command has a non-zero exit status,
execute the
ERR
trap, if set,
and exit.
This mode is disabled while reading profiles.
-f-
Disables file name generation.
-h-
Each command
becomes a tracked alias when first encountered.
-k-
(Obsolete). All variable assignment arguments are placed in the environment for a command,
not just those that precede the command name.
-m-
Background jobs will run in a separate process group
and a line will print upon completion.
The exit status of background jobs is reported in a completion message.
On systems with job control,
this option is turned on automatically for
interactive shells.
-n-
Read commands and check them for syntax errors, but do not execute them.
Ignored for interactive shells.
-o-
The following argument can be one of the following option names:
allexport-
Same as
-a.
errexit-
Same as
-e.
bgnice-
All background jobs are run at a lower priority.
This is the default mode.
emacs-
Puts you in an
emacs
style in-line editor for command entry.
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.
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.
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.
-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.
If
sig
is 0 or
EXIT
and the
trap
statement is executed inside the body of a function,
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.
true-
Does nothing, and exits 0. Used with
while
for infinite loops.
++ typeset [ ±AHflnprtux ] [ ±EFLRZi[n] ] [ vname[=value ] ] ...-
Sets attributes and values for shell variables and functions.
When invoked inside a function,
a new instance of the variable
vname
is created.
The variable's value and type are restored
when the function completes.
The following list of attributes may be specified:
-A-
Declares
vname
to be an associative array.
Subscripts are strings rather than arithmetic
expressions.
-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.
-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
-s.
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.
-1-
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.
-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
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
options is specified, the limit applies to both.
The current resource limit is printed when
limit
is omitted.
In this case, the soft limit is printed unless
H
is specified.
When more than one resource is specified, then the limit
name and unit is printed before the value.
-a-
Lists all of the current resource limits.
-c-
The number of 512-byte blocks on the size of core dumps.
-d-
The number of K-bytes on the size of the data area.
-f-
The number of 512-byte blocks on files that can be written by the
current process or by child processes (files of any size may be read).
-m-
The number of K-bytes on the size of physical memory.
-n-
The number of file descriptors plus 1.
-p-
The number of 512-byte blocks for pipe buffering.
-s-
The number of K-bytes on the size of the stack area.
-t-
The number of CPU seconds to be used by each process.
-v-
The number of K-bytes for virtual memory.
If no option is given,
-f
is assumed.
umask [ -S ] [ mask ]-
The user file-creation mask is set to
mask
(see
umask(2)).
mask
can either be an octal number or
a symbolic value as described in
chmod(1).
If a symbolic value is given,
the new
umask value is the complement of the result of
applying
mask
to the complement of the previous umask value.
If
mask
is omitted, the current value of the mask is printed.
The
-S
option causes the mode to be printed as a symbolic
value. Otherwise, the
mask is printed in octal.
+ unalias [ -a ] name ...-
The aliases
given by the list of
names
are removed from the alias list.
The
-a
option causes all the
aliases to be unset.
+unset [ -fnv ] vname ...-
The variables given by the list of
vnames
are unassigned,
i.e.,
their values and attributes are erased.
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.
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
options skips the search for functions.
The
-p
option
does a path search for
name
even if name is an alias, a function, or a reserved word.
The
-a
option
is similar to the
-v
option but causes
all interpretations of the 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
is, then a path search is performed on the first
arg
to determine the name of the script to execute.
The script
arg
must have read 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:
-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(3C)),
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.
-R filename-
The
-R
filename
option is used
to generate a cross reference database
that can be used by a separate utility
to find definitions and references for variables and commands.
The remaining options and arguments are described under the
set
command above.
An optional
-
as the first argument is ignored.
Rsh only
The restricted shell utility (invoked by specifying the -r option
on the command line)
is used to set up login names and execution environments whose
capabilities are more controlled than those of the standard shell.
The actions of
the restricted shell
are identical to those of
sh
except that the following are disallowed:
-
changing directory (see
cd(1)),
-
setting or unsetting the value or attributes of
SHELL,
ENV,
or
PATH
-
specifying path or
command names containing
/
-
redirecting output
( ( >,
>|,
<>,
and
>>).
-
adding or deleting built-in commands.
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,
the restricted shell invokes
a non-restricted shell 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
restricted shell users.
Files
/etc/passwd
/etc/suid_profile
$HOME/.profile
/tmp/sh
/dev/null
Exit codes
Errors detected by the shell, such as syntax errors,
cause the shell
to return a non-zero exit status.
Otherwise, the shell returns the exit status of
the last command executed (see also the
exit
command above).
If the shell is being used non-interactively,
then execution of the shell file is abandoned.
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.
Compatibility
Older versions of ksh (and other legacy shells such as
sh) disregard multiple arguments supplied to the test -f
operation, and test only the first argument without returning an error.
This version of ksh returns an error if 2 arguments are specified,
and returns no error when 3 or more are specified.
This may break older shell scripts that depend on using wild card
characters in test -f statements, in cases where the wild
cards happen to resolve to exactly two file names.
See
test(1).
For other compatibility differences between this version of ksh
(ksh-93) and the previous version of ksh (ksh-88), see
``ksh-93 vs. ksh-88'' in Differences for SCO OpenServer and SCO UnixWare 1 and 2 users.
For compatibility with older shell scripts, the previous verison of
ksh is provided as /usr/bin/ksh88.
Putting
#!ksh88
at the top of a ksh scripts will force the script to run with
the older version of ksh.
References
cat(1),
cd(1),
chmod(1),
cut(1),
echo(1),
env(1),
newgrp(1M),
paste(1),
stty(1),
test(1),
umask(1),
vi(1),
dup(2),
exec(2),
fork(2),
ioctl(2),
lseek(2),
fpathconf(2),
pipe(2),
sysconf(3C),
umask(2),
ulimit(2),
wait(2),
rand(3C),
a.out(4),
profile(4),
environ(5).
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.
Notices
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
won't be executed until the foreground job terminates.
It is a good idea to leave a space after the comma operator in
arithmetic expressions to prevent the comma from being interpreted
as the decimal point character in certain locales.
© 2005 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 - 02 June 2005