How to check in a bash script if something is running and exit if it is

Question

I have a script that runs every 15 minutes but sometimes if the box is busy it hangs and the next process will start before the first one is finished creating a snowball effect.

Answer 1

For a method that does not suffer from parsing bugs and race conditions, check out:

• BashFAQ/045 - How can I ensure that only one instance of a script is running at a time (mutual exclusion)?