KILL(1) General Commands Manual KILL(1)

kill — terminate or signal a process

kill [-signal_number | -signal_name | -s signal_name] pid ...

kill -l [exit_status]

The kill utility sends a signal to the process(es) specified by the pid operand(s). If no signal is specified, the TERM signal is used.

Only the superuser may send signals to other users' processes.

The options are as follows:

[exit_status]
Display the name of the signal corresponding to exit_status. exit_status may be the exit status of a command killed by a signal (see the special sh(1) parameter ‘?’) or a signal number.

If no operand is given, display the names of all the signals.

-signal_number | -signal_name | signal_name
A non-negative decimal integer or a symbolic name specifying the signal to be sent instead of the default TERM.

The following PIDs have special meanings:

-1
If superuser, broadcast the signal to all processes; otherwise, broadcast to all processes belonging to the user.
0
Send the signal to all processes whose group ID is equal to the process group ID of the sender, and for which the process has permission.
-pgid
Send the signal to all processes within the specified process group.

Some of the more commonly used signals:

1 (hang up)
2 (interrupt)
3 (quit)
6 (abort)
9 (non-catchable, non-ignorable kill)
14 (alarm clock)
15 (software termination signal)

For a complete list, consult the signal(3) manual page.

A signal number of 0 (kill -0 pid) does not send a signal, but only checks the validity of a certain PID. It succeeds if pid exists or raises an error otherwise.

The kill utility exits 0 on success, and >0 if an error occurs.

Forcibly terminate process ID 1234:

$ kill -9 1234

Send the init(8) process the hangup signal, instructing it to re-read ttys(5):

# kill -HUP 1

csh(1), ksh(1), pkill(1), ps(1), kill(2), signal(3)

The kill utility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification.

The -signal_name and -signal_number syntax is marked by IEEE Std 1003.1-2008 (“POSIX.1”) as being an X/Open System Interfaces option.

kill also exists as a built-in to csh(1) and ksh(1), though with a different syntax.

A kill command appeared in Version 3 AT&T UNIX.

April 24, 2025 Debian