KILL(1) User Commands KILL(1)

NAME

kill - terminate or signal processes

SYNOPSIS

/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...

DESCRIPTION

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
the super-user.


See NOTES for descriptions of the shell built-in versions of kill.

OPTIONS

The following options are supported:

-l
(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 written.
Otherwise, the results are unspecified.


-s signal_name
Specifies the signal to send, using one of the symbolic
names defined in the <signal.h> description. Values of
signal_name is recognized in a case-independent
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.


-signal_name
Equivalent to -s signal_name.


-signal_number
Specifies a non-negative decimal integer,
signal_number, representing the signal to be used
instead of SIGTERM, as the sig argument in the
effective call to kill(2).

OPERANDS

The following operands are supported:

pid
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 option.

2. A job control job ID that identifies a
background process group to be signaled. The
job control job ID notation is applicable only
for invocations of kill in the current shell
execution environment.
The job control job ID type of pid is available only on
systems supporting the job control option.


exit_status
A decimal integer specifying a signal number or the exit
status of a process terminated by a signal.

USAGE

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.

OUTPUT

When the -l option is not specified, the standard output is not be used.


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
symbolic name of the corresponding signal is written in the following
format:

"%s\n", <signal_name>

EXAMPLES

Example 1: Sending the kill signal

Any of the commands:


example% kill -9 100 -165
example% kill -s kill 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 the
following:


example% kill -TERM -123
example% kill -- -123

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment variables
that affect the execution of kill: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES,
and NLSPATH.

EXIT STATUS

The following exit values are returned:

0
At least one matching process was found for each pid operand, and
the specified signal was successfully processed for at least one
matching process.


>0
An error occurred.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:

/usr/bin/kill, csh, ksh, sh


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|CSI | Enabled |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|Standard | See standards(7). |
+--------------------+-------------------+

ksh93


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|CSI | Enabled |
+--------------------+-----------------+
|Interface Stability | Uncommitted |
+--------------------+-----------------+

SEE ALSO

csh(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(7), environ(7), standards(7)

NOTES

/usr/bin/kill
The number of realtime signals supported is defined by the getconf(1)
value _POSIX_RTSIG_MAX.

sh
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 ]...
kill -l


csh
The C-shell, csh, also has a built-in kill command, whose syntax is:

kill [-sig][pid][%job]...
kill -l


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.

-l
Lists the signal names that can be sent.


ksh
The syntax of the ksh kill is:

kill [-sig][pid][%job]...
kill -l


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.

ksh93
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:

number
The process id of job.


-number
The process group id of job.


%number
The job number.


%string
The job whose name begins with string.


%?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 specified the
corresponding signal number is written to standard output. If a number is
specified the corresponding signal name is written to standard output.

-l
List signal names or signal numbers rather than sending
signals as described above. The -n and -s options cannot be
specified.


-n signum
Specify a signal number to send. Signal numbers are not
portable across platforms, except for the following:

0
No signal.


1
HUP


2
INT


3
QUIT


6
ABRT


9
KILL


14
ALRM


15
TERM


-s signame
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:

0
At least one matching process was found for each job operand, and
the specified signal was successfully sent to at least one matching
process.


>0
An error occurred.


August 11, 2009 KILL(1)