#!/bin/bash
small=HDMI-0
big=DP-1

small_used=`xrandr --listactivemonitors | grep "$small"`
small_used_len=${#small_used}
echo $small_used_len

current=$small
next=$big
if [[ small_used_len -eq 0 ]]; then 
    current=$big
    next=$small
fi

xrandr --output "$current" --off --output "$next" --auto