#!/bin/sh
brightness_dir="/sys/class/backlight/intel_backlight/brightness"
max_brightness=`cat /sys/class/backlight/intel_backlight/max_brightness`
current_brightness_level=`cat $brightness_dir`
new_brightness_level=`expr $current_brightness_level + $1`

if [ "$1" -ge 0 ]; then
	if [ "$new_brightness_level" -le "$max_brightness" ]; then
		echo $new_brightness_level > $brightness_dir
	else
		echo $max_brightness > $brightness_dir
	fi
else
	if [ "$new_brightness_level" -ge 0 ]; then
		echo $new_brightness_level > $brightness_dir
	else
		echo 0 > $brightness_dir
	fi
fi