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Ways to 'kill' With Linux

To kill or not to kill

January 8, 2009

Juliet Kemp
... other than what its name implies.

kill is most often used without an argument or with -9, to kill a process off. But it can also be used to send various other signals to a process. Some are variations on process termination, but you can also get information about or out of processes.

  • kill -0 pid: This doesn't actually kill the process, just returns 0 (success) if the process exists and 1 (failure) if not. The command itself will not give you any output — you have to look at the exit code, using echo $? to get the information. So as a one-liner:
    kill -0 1685; echo $?
    will output 0 if process 1685 exists, and 1 if it doesn't. This can also be useful in shell scripts if you have a process number recorded and wish to check if it's still running.
  • kill -9 pid: You probably already know that you can terminate the process WITH EXTREME PREJUDICE. kill -KILL does the same thing and has the advantage of looking more vicious. The downside is that it is an extra couple of characters to type.
  • kill -HUP pid: Restarts the process.
  • kill -INT pid: Another way of killing the process, this time by interrupting it. It is a useful halfway house between kill and kill -9.
  • kill -ABRT pid: Stops your program and gets it to dump core if possible/appropriate. (kill -6 is a synonym.) This can be useful if a process is misbehaving, as it means that you may get debug information.

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