#!/bin/sh

[ ! -d /var/cache/backlight ] && mkdir /var/cache/backlight
[ ! -w /var/cache/backlight ] && chmod 755 /var/cache/backlight

for card in $(find /sys/class/backlight/ -type l); do
    cp "/sys/class/backlight/$(basename "$card")/brightness" "/var/cache/backlight/$(basename "$card")-brightness-old"
done
