Macintosh Terminal Pocket Guide

Name

kill — stdin  stdout  - file  -- opt  --help  --version

Synopsis

kill [options] [process_ids]

The kill command sends a signal to a process, given its process ID (PID). This can terminate a process (the default action), interrupt it, suspend it, crash it, and so on. You must own the process, or be the superuser, to affect it. Remember our story in the introduction about terminating a hung Microsoft Word? We used a kill command (actually killall, described shortly) for this purpose, since it can succeed when other more common methods have failed.

To terminate the process with PID 13243, for example, run:

➜ kill 13243

You can also terminate a shell job (see Shell Job Control) by its job number, preceded by a percent sign to distinguish it from a PID:

➜ kill %2

If kill does not work—some programs catch this signal without terminating—add the option -KILL or (equivalently) -9:

➜ kill -KILL 13243

which is virtually guaranteed to work. However, this is not a clean exit for the program, which may leave system resources allocated (or cause other inconsistencies) upon its death.

If you don’t know the PID of a process, run ps and examine the output:

➜ ps -ax | grep emacs

or even better, try the killall command, which looks up all processes for a given program by its name and kills them:

➜ killall less
[1]+  Terminated: 15          less -c myfile

In addition to the kill program in the filesystem (usually /bin/kill), most shells have built-in kill commands, but their syntax and behavior differ. However, they all ...