Waiting for background processes to finish before exiting script

Question

How do I make sure that all my background processes have finished execution before I exit my script (TCL/Bash).

I was thinking of writing all my background process pids to a pidfile. And then at the end pgrep the pidfile to see if any processes are still running before I exit.

Is there some simpler way to do this? And is there a TCL specific way to do this?

Answer 1

If you want to wait for jobs to finish, use wait. This will make the shell wait until all background jobs complete. However, if any of your jobs daemonize themselves, they are no longer children of the shell and wait will have no effect (as far as the shell is concerned, the child is already done. Indeed, when a process daemonizes itself, it does so by terminating and spawning a new process that inherits its role).

#!/bin/sh { sleep 5; echo waking up after 5 seconds; } & { sleep 1; echo waking up after 1 second; } & wait echo all jobs are done! 

Answer 2

You can use kill -0 for checking whether a particular pid is running or not.

Assuming, you have list of pid numbers in a file called pid in pwd

while true; do      if [ -s pid ] ; then         for pid in `cat pid`         do               echo "Checking the $pid"             kill -0 "$pid" 2>/dev/null || sed -i "/^$pid$/d" pid         done     else         echo "All your process completed" ## Do what you want here... here all your pids are in finished stated         break     fi done