UNIX Kill Command Examples

How do I send a KILL signal to a process under UNIX operating systems?

Use the kill command to send a signal to each process specified by a pid (process identifier). The default signal is SIGTERM (terminate the process).

Syntax

kill PID
kill -s signalName PID
kill -9 PID

Common UNIX Signal Names and Numbers

All available UNIX signals have different names, and are mapped to certain numbers as described below.

Number	Name	Description	Used for
0	SIGNULL	Null	Check access to pid
1	SIGHUP	Hangup	Terminate; can be trapped
2	SIGINT	Interrupt	Terminate; can be trapped
3	SIGQUIT	Quit	Terminate with core dump; can be
9	SIGKILL	Kill	Forced termination; cannot be trapped
15	SIGTERM	Terminate	Terminate; can be trapped
24	SIGSTOP	Stop	Pause the process; cannot be trapped
25	SIGTSTP	Terminal	stop Pause the process; can be
26	SIGCONT	Continue	Run a stopped process

Note the specific mapping between numbers and signals can vary between Unix implementations, please see the manual page entry signal(5), by typing the following command:

man 5 signal

Examples: Send a Kill Single To Process ID 1414

Use the following command to kill pid 4242 and exit gracefully:

kill 4242

To find pid of any job or command use ps command:

ps | grep command
ps aux | grep command
ps aux | grep apache

The following all are equivalent commands with -9 SIGKIL (i.e forcefully kill 1414 process):

kill -s SIGKILL 1414
kill -s KILL 1414
kill -s 9 1414
kill -SIGKILL 1414
kill -KILL 1414