KILL(1)KILL(1)NAMEkill - terminate or signal processes
/usr/bin/kill -s signal_name pid...
/usr/bin/kill -l [exit_status]
/usr/bin/kill [-signal_name] pid...
/usr/bin/kill [-signal_number] pid...
The kill utility sends a signal to the process or processes specified
by each pid operand.
For each pid operand, the kill utility performs actions equivalent to
the kill(2) function called with the following arguments:
1. The value of the pid operand is used as the pid argument.
2. The sig argument is the value specified by the -s option,
the -signal_name option, or the -signal_number option, or,
if none of these options is specified, by SIGTERM.
The signaled process must belong to the current user unless the user is
See NOTES for descriptions of the shell built-in versions of kill.
The following options are supported:
(The letter ell.) Writes all values of signal_name
supported by the implementation, if no operand is
specified. If an exit_status operand is specified and
it is a value of the ? shell special parameter and
wait corresponding to a process that was terminated
by a signal, the signal_name corresponding to the
signal that terminated the process is written. If an
exit_status operand is specified and it is the
unsigned decimal integer value of a signal number,
the signal_name corresponding to that signal is writ‐
ten. Otherwise, the results are unspecified.
Specifies the signal to send, using one of the sym‐
bolic names defined in the <signal.h> description.
Values of signal_name is recognized in a case-inde‐
pendent fashion, without the SIG prefix. In addition,
the symbolic name 0 is recognized, representing the
signal value zero. The corresponding signal is sent
instead of SIGTERM.
Equivalent to -s signal_name.
Specifies a non-negative decimal integer, signal_num‐
ber, representing the signal to be used instead of
SIGTERM, as the sig argument in the effective call to
The following operands are supported:
One of the following:
1. A decimal integer specifying a process or
process group to be signaled. The process or
processes selected by positive, negative and
zero values of the pid operand is as
described for the kill function. If process
number 0 is specified, all processes in the
process group are signaled. If the first pid
operand is negative, it should be preceded by
−− to keep it from being interpreted as an
2. A job control job ID that identifies a back‐
ground process group to be signaled. The job
control job ID notation is applicable only
for invocations of kill in the current shell
The job control job ID type of pid is available only on
systems supporting the job control option.
A decimal integer specifying a signal number or the exit
status of a process terminated by a signal.
Process numbers can be found by using ps(1).
The job control job ID notation is not required to work as expected
when kill is operating in its own utility execution environment. In
either of the following examples:
example% nohup kill %1 &
example% system( "kill %1");
kill operates in a different environment and does not share the shell's
understanding of job numbers.
When the -l option is not specified, the standard output is not be
When the -l option is specified, the symbolic name of each signal is
written in the following format:
"%s%c", <signal_name>, <separator>
where the <signal_name> is in upper-case, without the SIG prefix, and
the <separator> is either a newline character or a space character. For
the last signal written, <separator> is a newline character.
When both the -l option and exit_status operand are specified, the sym‐
bolic name of the corresponding signal is written in the following for‐
Example 1 Sending the kill signal
Any of the commands:
example% kill-9 100 -165
example% kill-skill 100 -165
example% kill-s KILL 100 -165
sends the SIGKILL signal to the process whose process ID is 100 and to
all processes whose process group ID is 165, assuming the sending
process has permission to send that signal to the specified processes,
and that they exist.
Example 2 Avoiding ambiguity with an initial negative number
To avoid an ambiguity of an initial negative number argument specifying
either a signal number or a process group, the former is always be the
case. Therefore, to send the default signal to a process group (for
example, 123), an application should use a command similar to one of
example% kill-TERM -123
example% kill-- -123
See environ(5) for descriptions of the following environment variables
that affect the execution of kill: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES,
The following exit values are returned:
At least one matching process was found for each pid operand, and
the specified signal was successfully processed for at least one
An error occurred.
See attributes(5) for descriptions of the following attributes:
/usr/bin/kill, csh, ksh, sh
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
│CSI │ Enabled │
│Interface Stability │ Committed │
│Standard │ See standards(5). │
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
│CSI │ Enabled │
│Interface Stability │ Uncommitted │
SEE ALSOcsh(1), getconf(1), jobs(1), ksh(1), ksh93(1), ps(1), sh(1),
shell_builtins(1), wait(1), kill(2), signal(3C), signal.h(3HEAD),
attributes(5), environ(5), standards(5)NOTES
The number of realtime signals supported is defined by the getconf(1)
The Bourne shell, sh, has a built-in version of kill to provide the
functionality of the kill command for processes identified with a
jobid. The sh syntax is:
kill [ -sig ] [ pid ] [ %job ]...
The C-shell, csh, also has a built-in kill command, whose syntax is:
The csh kill built-in sends the TERM (terminate) signal, by default, or
the signal specified, to the specified process ID, the job indicated,
or the current job. Signals are either specified by number or by name.
There is no default. Typing kill does not send a signal to the current
job. If the signal being sent is TERM (terminate) or HUP (hangup), then
the job or process is sent a CONT (continue) signal as well.
Lists the signal names that can be sent.
The syntax of the ksh kill is:
The ksh kill sends either the TERM (terminate) signal or the specified
signal to the specified jobs or processes. Signals are either specified
by number or by names (as specified in signal.h(3HEAD) stripped of the
SIG prefix). If the signal being sent is TERM (terminate) or HUP
(hangup), then the job or process is sent a CONT (continue) signal if
it is stopped. The argument job can be the process id of a process that
is not a member of one of the active jobs. In the second form, kill-l,
the signal numbers and names are listed.
The syntax of the ksh93 kill is:
kill [-n signum] [-s signame] job ...
kill [-n signum] [-s signame] -l [arg ...]
With the first form in which -l is not specified, kill sends a signal
to one or more processes specified by job. This normally terminates the
processes unless the signal is being caught or ignored.
Specify job as one of the following:
The process id of job.
The process group id of job.
The job number.
The job whose name begins with string.
The job whose name contains string.
The current job.
The previous job.
If the signal is not specified with either the -n or the -s option, the
SIGTERM signal is used.
If -l is specified, and no arg is specified, then kill writes the list
of signals to standard output. Otherwise, arg can be either a signal
name, or a number representing either a signal number or exit status
for a process that was terminated due to a signal. If a name is speci‐
fied the corresponding signal number is written to standard output. If
a number is specified the corresponding signal name is written to stan‐
List signal names or signal numbers rather than sending
signals as described above. The -n and -s options cannot
Specify a signal number to send. Signal numbers are not
portable across platforms, except for the following:
Specify a signal name to send. The signal names are
derived from their names in <signal.h> without the SIG
prefix and are case insensitive. kill-l generates the
list of signals on the current platform.
kill in ksh93 exits with one of the following values:
At least one matching process was found for each job operand, and
the specified signal was successfully sent to at least one match‐
An error occurred.
Aug 11, 2009 KILL(1)