How do I kill all a user's processes using their UID

Question

I want to kill all running processes of a particular user from either a shell script or native code on a linux system.

Do I have to read the /proc directory and look for these?

Any ideas? Is there a dynamic mapping of the pids under UIDs in linux? Isnt this in the proc?

If no where is this list maintained. Should I read from it? Also where is the static list of all UIDs in the system so I can validate this this user exists and then proceed to kill all processes running under it?

Answer 1

Use either skill -u UID or pkill -u UID.

Skill was a linux-specific and is now outdated, and pkill is more portable (Linux, Solaris, BSD)

I think, both utilites have no access to any list other than full list of processes (or readdir of /proc). I think, they itterate over /proc and check every process for match.

PS: Another tool is killall .

To get list of users, use getpwent (it will get one user per call).

Answer 2

If the pkill function is unavailable on your UNIX / Linux distribution you could run the following command as the root user:

ps -ef | grep username | grep -v grep | awk '{print $2}' | xargs kill

where username is the user who's processes you want to delete

Answer 3

If you pass -1 as the process ID argument to either the kill shell command or the kill C function, then the signal is sent to all the processes it can reach, which in practice means all the processes of the user running the kill command or syscall.

su -c 'kill -TERM -1' bob

In C (error checking omitted):

if (fork() == 0) {
    setuid(uid);
    signal(SIGTERM, SIG_DFL);
    kill(-1, SIGTERM);
}