Linux in a Nutshell, 6th Edition

Name

kill

Synopsis

kill [options] [pids]

Send a signal to terminate one or more process IDs. You must own the process or be a privileged user. If no signal is specified, TERM is sent.

This entry describes the /bin/kill command. There are also built-in shell commands of the same name; the bash version is described in Chapter 6.

In some Linux distributions, /bin/kill allows you to specify a command name, such as gcc or xpdf, instead of a process ID (PID). All processes running that command with the same UID as the process issuing /bin/kill are sent the signal.

If /bin/kill is issued with a pid of 0, it sends the signal to all processes of its own process group. If /bin/kill is issued with a pid of −1, it sends the signal to all processes except process 1 (the system’s init process).

Options

-a

Kill all processes of the given name (if privileges allow), not just processes with the same UID. To use this option, specify the full path (e.g., /bin/kill -a gcc).

-l

List all signals.

-p

Print the process ID of the named process, but don’t send it a signal. To use this option, specify the full path (e.g., /bin/kill -p).

-s SIGNAL, -SIGNAL

The signal number (from /usr/include/sys/signal.h) or name (from kill -l). With a signal number of 9 (KILL), the kill cannot be caught by the process; use this to kill a process that a plain kill doesn’t terminate. The default signal is TERM. The letter flag itself is optional: both kill −9 1024 and kill -s 9 1024 terminate process 1024.