The command kill sends the specified signal to the specified
processes or process groups. If no signal is specified, the TERM
signal is sent. This TERM signal will kill processes that do not
catch it; for other processes it may be necessary to use the KILL
signal (number 9), since this signal cannot be caught.
Most modern shells have a builtin kill function, 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
The list of processes to be signaled can be a mixture of names and
pid Each pid can be one of four things:
n where n is larger than 0. The process with pid n is
0 All processes in the current process group are
-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
Do not restrict the command-name-to-pid conversion to
processes with the same uid as the present process.
Only print the process id (pid) of the named processes, do not
send any signals.
Print pid(s) that will be signaled with kill along with the
-q, --queue value
Use sigqueue(2) 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.
It is not possible to send a signal to an explicitly selected thread
in a multithreaded process using the kill(2) syscall. If kill(2) is
used to send a signal to a thread group, then the kernel selects an
arbitrary member of the thread group that has not blocked the signal.
For more details see clone(2), the CLONE_THREAD description.
The command kill(1) as well as syscall kill(2) accept a TID (thread
ID, see gettid(2)) as an argument. In this case the kill behavior is
not changed and the signal is also delivered to the thread group
rather than to the specified thread.
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
firstname.lastname@example.org. This page was obtained from the
project's upstream Git repository
2016-10-04. If you discover any rendering problems in this HTML ver‐
sion 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 man‐
ual page), send a mail to email@example.com
util-linux July 2014 KILL(1)