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.
-s, --signal signal
-l, --list [number]
-q, --queue value
--timeout milliseconds signal
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:
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 <firstname.lastname@example.org>, Karel Zak <email@example.com>
The original version was taken from BSD 4.4.
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/.