How to log out of a Linux system from a script

If you run a script using a command like exec myscript and the script includes a logout command, the script will end abruptly and so will the shell from in which it was running.

Using the source builtin

Another way to log out of a system through a script is to use the source builtin to run the script. When you run a command such as source wait4three, the command will read and execute all the commands included in the script just as if you were typing them. In other words, the constraints involved in running a script are removed.

Another benefit of using the source builtin is that you don’t need execute permission to run a script, just read access.

One simple alternative

One very simple alternative to logging out from inside a script is to run both the script and the logout command on one line – separated by a semicolon. This ensures that the logout command will run once the script has finished.

$ wait4three; logout

The script shown earlier could then use exit instead of logout.

#!/bin/bash

while true
do
  sleep 10
  count=`who | wc -l`
  echo $count
  if [ $count -ge 3 ]; then
    exit
  fi
done

Wrap-up

While logging out of a system from a script is rarely required, there may be times when you need to run a lengthy process and want to be sure that you’re logged out when it completes. Running a script that includes the logout command and running with the exec or the source builtin makes this possible.