Stop script when gnome session ends

Question

In Start Script when Gnome Starts Up it was asked how to automatically start a script on gnome login. But how to automatically stop a long running script on logout, that was started on login? In my case there are two processes when I login twice. Interestingly the process started first does not reside under gnome-session anymore.

Answer 1

I would wrap the binary that gets executed in a simple bash script that saves the pid of the started process in a temporary file. If this file already exists it skips the start of the application. Since the file is saved in the /tmp directory everything gets deleted once you restart your computer.

#!/bin/bash

binary="git-cola"
temp_file="/tmp/my_${binary}_instance.pid"

if [[ -f ${temp_file} ]]
then
  echo "PID exists"
else
  exec ${binary} &
  echo $! > ${temp_file}
fi

With a little more effort you can check if the pid of the process is still running and restart it on the login again (for example if the process crashed or the other user closed it).

I actually don't use Gnome, so I can't tell you if there is a more elegant way to kill the process. Like a logout hook. But once you got the pid of the process saved you can kill it with kill -9 PID. (See man kill for more gentle ways to end the process).

This might not be the solution to stop the process. But to prevent it starting twice.