Bash variable change doesn't persist

Question

I have a short bash script to check to see if a Python program is running. The program writes out a PID file when it runs, so comparing this to the current list of running p

Answer 1

Commands after a pipe | are run in a subshell. Changes to variable values in a subshell do not propagate to the parent shell.

Solution: change your loop to

while read PID; do
    # ...
done < $PIDFILE