This tutorial explains Linux “kill” command, options and its usage with examples.
DESCRIPTION
Even on Linux it sometimes happens that processes wear out their welcome and stick around longer than you would like them to. They simply ignore your request to close up and go away. Fortunately you have a powerful gun at your disposal that will clean out anything that doesn’t get a hint: The Arnold Schwarzenegger equivalent among the Linux commands is the kill command.
There are many different signals that can be sent , although the signals in which users are generally most interested are SIGTERM and SIGKILL. The default signal sent is SIGTERM. Programs that handle this signal can do useful cleanup operations (such as saving configuration information to a file) before quitting. However, many programs do not implement a special handler for this signal, and so a default signal handler is called instead. Other times, even a process that has a special handler has gone awry in a way that prevents it from properly handling the signal.
SYNOPSIS
kill [options] […]
OPTIONS
[…]
Send signal to every listed.
–,-s ,–signal
Specify the signal to be sent. The signal can be specified by using name or number.
-l, –list [signal]
List signal names. This option has optional argument, which will convert signal number to signal name, or other way round.
-L, –table
List signal names in a nice table.
Common UNIX Signal Names and Numbers
| 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 |
Alternate signals may be specified in three ways: -9,-SIGKILL or -KILL. Negative PID values may be used to choose whole process groups; see the PGID column in ps command output. A PID of -1 is special; it indicates all processes except the kill process itself and init.
EXAMPLES
1. Send a Kill Single To Process ID 1414
$ kill 4242
To find pid of any job or command use ps command:
$ ps | grep command $ ps aux | grep command $ ps aux | grep apache
2. Forcefully kill 1414 process
$ kill -s SIGKILL 1414
OR
$ kill -s KILL 1414
OR
$ kill -s 9 1414
OR
$ kill -SIGKILL 1414
OR
$ kill -KILL 1414
3. To stop all of your processes and log yourself off, enter the following command
$ kill -kill 0
This sends signal 9, the SIGKILL signal, to all processes that have a process group ID equal to the senders process group ID. Because the shell cannot ignore the SIGKILL signal, this command also stops the login shell and logs you off.
4. To stop all processes that you own, enter the following command
$ kill -9 -1
This sends signal 9, the SIGKILL signal, to all processes owned by the effective user
5. Display ginal names
# kill -L 1 HUP 2 INT 3 QUIT 4 ILL 5 TRAP 6 ABRT 7 BUS 8 FPE 9 KILL 10 USR1 11 SEGV 12 USR2 13 PIPE 14 ALRM 15 TERM 16 STKFLT 17 CHLD 18 CONT 19 STOP 20 TSTP 21 TTIN 22 TTOU 23 URG 24 XCPU 25 XFSZ 26 VTALRM 27 PROF 28 WINCH 29 POLL 30 PWR 31 SYS