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KILL(1) User Commands KILL(1)
NAME
kill - terminate a process
SYNOPSIS
kill [-signal|-s signal|-p] [-q value] [-a] [--timeout milliseconds
signal] [--] pid|name...
kill -l [number] | -L
DESCRIPTION
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.
ARGUMENTS
The list of processes to be signaled can be a mixture of names and
PIDs.
pid Each pid can be one of four things:
n where n is larger than 0. The process with PID n is sig‐
naled.
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.
OPTIONS
-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/sig‐
nal.h
-L, --table
Similar to -l, but it will print signal names and their corre‐
sponding 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.
--verbose
Print PID(s) that will be signaled with kill along with the sig‐
nal.
-q, --queue value
Use 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 the usual way to a process. --timeout
will make kill to wait for a period defined in milliseconds
before sending follow-up signal to process. This feature is
implemented by PID file-descriptor and guaranties that follow-up
signals are sent to the same process or not sent if the process
no more exist. Note that the operating system may re-use PIDs
and implement the same feature in a shell by kill and sleep com‐
mands sequence may introduce a race. This option can be speci‐
fied more than once than signals are sent sequentially in
defined timeouts. The --timeout option can be combined with
--queue option.
Example. Send signals QUIT, TERM and KILL in sequence and wait
for 1000 milliseconds between the signals
kill --verbose --timeout 1000 TERM --timeout 1000 KILL --signal
QUIT 12345
NOTES
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 have provide an internal kill implementation that is
preferred in relation to the kill(1) executable described by this man‐
ual. Easiest way to ensure one is executing the executable is to use
full path when calling the command, for example: /bin/kill --version
RETURN CODES
kill has the following return codes:
0 success
1 failure
64 partial success (when more than one process specified)
SEE ALSO
bash(1), tcsh(1), sigaction(2), kill(2), sigqueue(3), signal(7)
AUTHORS
Salvatore Valente ⟨svalente@mit.edu⟩
Karel Zak ⟨kzak@redhat.com⟩
The original version was taken from BSD 4.4.
AVAILABILITY
The kill command is part of the util-linux package and is available
from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
linux/⟩.
util-linux November 2019 KILL(1)