Sets same brightness on all displays

light.sh

#!/bin/sh
set -e
lvl="$(brightnessctl -p -e -m s "$@" | cut -d, -f4)"
for i in $(brightnessctl -l -c 'backlight' -m | cut -d, -f1); do
	echo "adjusting $i"
	brightnessctl -e -d "$i" s "$lvl" &
done
wait