+target="${backlight_dir}"/brightness
+if [ "${1}" = "+" -o "${1}" = "-" ]; then
+ fract=$(expr "${max_brightness}" / 20)
+ cur_brightness=$(cat "${backlight_dir}"/brightness)
+ brightness=$(expr "${cur_brightness}" "${1}" "${fract}")
+ if [ "${brightness}" -gt "${max_brightness}" ]; then
+ brightness="${max_brightness}"
+ elif [ "${brightness}" -lt "0" ]; then
+ brightness=0
+ fi
+ sudo sh -c 'echo '"${brightness}"' > '"${target}"
+ exit 0
+fi
+percentage=${1}