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

I use oneliner @ the very beginning of script:

#!/bin/bash

if [[ $(pgrep -afc "$(basename "$0")") -gt "1" ]]; then echo "Another instance of "$0" has already been started!" && exit; fi
.
the_beginning_of_actual_script

It is good to see the presence of process in the memory (no matter what the status of process is); but it does the job for me.