Doing Nothing

Occasionally you will write a script and need to insert a command to do nothing.  The Null command (:) can be used to do this.

if [ -d dir1 ]
then
:
else
mkdir dir1
fi

Exiting a Script

You can use the exit command to exit a script.  If you follow it with a number from 0 to 255, that will be the exit code for the script.