sudo apt-get install xdotool

nano /home/user/fullscreen.sh


#!/bin/bash
export DISPLAY=:0
windowname=$(xdotool getactivewindow getwindowname | cut -d "-" -f 2)
if [[ $windowname != *"Chromium"* ]]
then
xdotool keydown Ctrl keydown Alt key 1 keyup Alt keyup Ctrl
else
xdotool search --onlyvisible --class "Chromium" windowfocus
sleep 0.2
xdotool key F11
fi