Script already running - bash

For scripts with long execution time it can be a good idea to check if the script is already running. This to avoid mess and unnecessary load on server caused by multiple instances of the same script.

Add the following code to the script header:

already=`ps -ef | grep "$0" | grep -v grep|wc -l`
if [ $already -gt 1 ]
then
   echo "$0 already running"
   exit 1
fi