Toggle Laptop and Monitor Display automatically

toggle_displays.sh

#!/bin/bash
# Use this script if you have an external monitor (HDMI) and want that as primary display
# but switch to the laptop monitor (eDP) when the external monitor is off (power off or otherwise)
# Guess if you have the external monitor attached to a UPS device, you don't need this script...!

# Detect when monitor is powered off and switch the laptop display back on
# and vice-versa, keeping the external monitor as primary display whenever
# possible.

function get_laptop_display() {
	# Should work for most laptops - if it doesn't
	# check the output of `xrandr -q` and get the
	# correct string instead of "edp"
	xrandr -q | grep -i edp | awk '{print $1}'
}

function get_hdmi_display() {
	# Should work for most HDMI monitors - if it doesn't
	# check the output of `xrandr -q` and get the
	# correct string instead of "hdmi"
	xrandr -q | grep -i hdmi | awk '{print $1}'
}

function toggle_edp_on() {
	xrandr --output $1 --auto
}

function toggle_edp_off() {
	xrandr --output $1 --off
}

function toggle_displays() {
	# Detect if HDMI (external monitor) goes off and then
	# switch back to laptop display and vice-verza.
	display_name=$1
	result=`sudo ddcutil getvcp d6 --terse 2>/dev/null| awk '{print $NF}'`
	# echo "Result => $result"
	case $result in
		"x05"|"ERR"|"") toggle_edp_on $display_name ;; # Monitor is off. Power on laptop display
		"x01") toggle_edp_off $display_name ;; # Monitor is on. Power off laptop display
	esac
	
}

display_name=`get_laptop_display`

# Run in background
while true
	  do
		  toggle_displays $display_name
		  sleep 2
	  done&

Required software - ddcutil

$ sudo apt install ddcutil -y

Reference and thank you - https://bbs.archlinux.org/viewtopic.php?pid=1919724#p1919724