#!/bin/bash
DEV=/sys/class/backlight/backlight
BL=$(cat $DEV/brightness)
if [ $BL -eq 0 ]; then
	exit 0
fi
if [ $BL -lt 5 ]; then
	BL=$((BL - 1))
else
	BL=$((BL - ( BL / 4 )))
fi
echo $BL > $DEV/brightness