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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] | -L
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]
Print a list of signal names, or convert the given signal
number to a name. The signals can be found in
/usr/include/linux/signal.h.
-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
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)
For bug reports, use the issue tracker at
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
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-10.) 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 2.39.594-1e0ad 2023-07-19 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 2024-06-26 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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