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NAME | SYNOPSIS | DESCRIPTION | ARGUMENTS | OPTIONS | EXIT STATUS | NOTES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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KILL(1) User Commands KILL(1)
kill - terminate a process
kill [-signal|-s signal|-p] [-q value] [-a] [--timeout
milliseconds signal] [--] pid|name...
kill -l [number|0xsigmask] | -L
kill -d pid
The command kill sends the specified signal to the specified
processes or process groups.
If no signal is specified, the TERM signal is sent. The default
action for this signal is to terminate the process. This signal
should be used in preference to the KILL signal (number 9), since
a process may install a handler for the TERM signal in order to
perform clean-up steps before terminating in an orderly fashion.
If a process does not terminate after a TERM signal has been sent,
then the KILL signal may be used; be aware that the latter signal
cannot be caught, and so does not give the target process the
opportunity to perform any clean-up before terminating.
Most modern shells have a builtin kill command, with a usage
rather similar to that of the command described here. The --all,
--pid, and --queue options, and the possibility to specify
processes by command name, are local extensions.
If signal is 0, then no actual signal is sent, but error checking
is still performed.
The list of processes to be signaled can be a mixture of names and
PIDs.
pid
Each pid can be expressed in one of the following ways:
n
where n is larger than 0. The process with PID n is
signaled.
0
All processes in the current process group are signaled.
-1
All processes with a PID larger than 1 are signaled.
-n
where n is larger than 1. All processes in process group n
are signaled. When an argument of the form '-n' is given,
and it is meant to denote a process group, either a signal
must be specified first, or the argument must be preceded
by a '--' option, otherwise it will be taken as the signal
to send.
name
All processes invoked using this name will be signaled.
-s, --signal signal
The signal to send. It may be given as a name or a number.
-l, --list [number|0xsigmask]
Print a list of signal names, convert the given signal number
to a name, or convert the given signal mask to names. The
signals can be found in /usr/include/linux/signal.h.
$ ps s $$
UID PID PENDING BLOCKED IGNORED CAUGHT STAT TTY TIME COMMAND
1000 1608069 0000000000000000 0000000000000002 0000000000384000 0000000008013003 Ss pts/44 0:02 zsh
$ kill -l 0x0000000000384000
TERM
TSTP
TTIN
TTOU
-L, --table
Similar to -l, but it will print signal names and their
corresponding numbers.
-a, --all
Do not restrict the command-name-to-PID conversion to
processes with the same UID as the present process.
-p, --pid
Only print the process ID (PID) of the named processes, do not
send any signals.
-r, --require-handler
Do not send the signal if it is not caught in userspace by the
signalled process.
--verbose
Print PID(s) that will be signaled with kill along with the
signal.
-q, --queue value
Send the signal using sigqueue(3) rather than kill(2). The
value argument is an integer that is sent along with the
signal. If the receiving process has installed a handler for
this signal using the SA_SIGINFO flag to sigaction(2), then it
can obtain this data via the si_sigval field of the siginfo_t
structure.
--timeout milliseconds signal
Send a signal defined in the usual way to a process, followed
by an additional signal after a specified delay. The --timeout
option causes kill to wait for a period defined in
milliseconds before sending a follow-up signal to the process.
This feature is implemented using the Linux kernel PID file
descriptor feature in order to guarantee that the follow-up
signal is sent to the same process or not sent if the process
no longer exists.
Note that the operating system may re-use PIDs and
implementing an equivalent feature in a shell using kill and
sleep would be subject to races whereby the follow-up signal
might be sent to a different process that used a recycled PID.
The --timeout option can be specified multiple times: the
signals are sent sequentially with the specified timeouts. The
--timeout option can be combined with the --queue option.
As an example, the following command sends the signals QUIT,
TERM and KILL in sequence and waits for 1000 milliseconds
between sending the signals:
kill --verbose --timeout 1000 TERM --timeout 1000 KILL \
--signal QUIT 12345
-d, --show-process-state pid
Decode signal related fields in /proc/pid/status.
$ kill -d $$
Blocked: INT
Ignored: TERM TSTP TTIN TTOU
Caught: HUP INT PIPE ALRM CHLD WINCH
kill has the following exit status values:
0
success
1
failure
64
partial success (when more than one process specified)
Although it is possible to specify the TID (thread ID, see
gettid(2)) of one of the threads in a multithreaded process as the
argument of kill, the signal is nevertheless directed to the
process (i.e., the entire thread group). In other words, it is not
possible to send a signal to an explicitly selected thread in a
multithreaded process. The signal will be delivered to an
arbitrarily selected thread in the target process that is not
blocking the signal. For more details, see signal(7) and the
description of CLONE_THREAD in clone(2).
Various shells provide a builtin kill command that is preferred in
relation to the kill(1) executable described by this manual. The
easiest way to ensure one is executing the command described in
this page is to use the full path when calling the command, for
example: /bin/kill --version
Salvatore Valente <svalente@mit.edu>, Karel Zak <kzak@redhat.com>
The original version was taken from BSD 4.4.
bash(1), tcsh(1), sigaction(2), kill(2), sigqueue(3), signal(7)
proc(5) proc_pid_status(5)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The kill command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-02-02. (At that time, the date of the most recent commit that
was found in the repository was 2025-01-30.) If you discover any
rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
util-linux 2.41.devel-938-0a... 2025-01-15 KILL(1)
Pages that refer to this page: fuser(1), kill(1), killall(1), pgrep(1), pmsignal(1), skill(1), tcpdump(1), timeout(1), xargs(1), kill(2), sigaction(2), signal(2), posix_spawn(3), signal(7), ldattach(8), lsof(8), systemd-coredump(8), tcpdump(8)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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