Quick-and-dirty way to ensure only one instance of a shell script is running at a time

Question

What\'s a quick-and-dirty way to make sure that only one instance of a shell script is running at a given time?

Answer 1

Create a lock file in a known location and check for existence on script start? Putting the PID in the file might be helpful if someone's attempting to track down an errant instance that's preventing execution of the script.