Shell Script to Toggle Between Two Commands

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

(As a complement to the main answer)

To make it display a message after running the commands, and also showing an icon - example for toggling touchpad off and on (source, also here):

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

TOGGLE=$HOME/.toggle_touchpad

if [ ! -e $TOGGLE ]; then
    touch $TOGGLE
    xinput disable 14
    notify-send -u low -i mouse --icon=/usr/share/icons/HighContrast/256x256/status/touchpad-disabled.png "Trackpad disabled"
else
    rm $TOGGLE
    xinput enable 14
    notify-send -u low -i mouse --icon=/usr/share/icons/HighContrast/256x256/devices/input-touchpad.png "Trackpad enabled"
fi

(in the above commands 14 is a variable to be identified with xinput list)

You can write a file with your last command. Then when it is run again you read the file, and see which command was executed.