One good way of accomplishing this is for the script to create a blank "configuration file":

• The 1st time the script runs, it sees the file doesn't exist, creates it, and runs command1.


• The 2nd time the script runs, it sees the file does exist, deletes it, and runs command2.


• The 3rd time the script runs, it sees the file doesn't exist, creates it, and runs command1.


• The 4th time the script runs, it sees the file does exist, deletes it, and runs command2.

And so forth.

Here's a script that does that:

#!/bin/sh

# This shell script is PUBLIC DOMAIN. You may do whatever you want with it.



TOGGLE=$HOME/.toggle



if [ ! -e $TOGGLE ]; then

    touch $TOGGLE

    command1

else

    rm $TOGGLE

    command2

fi