#!/bin/sh

path=/sys/class/backlight/acpi_video0

luminance() {
    read -r level < "$path"/actual_brightness
    factor=$((max / 100))
    printf '%d\n' "$((level / factor))"
}

read -r max < "$path"/max_brightness

echo xbacklight -set "$(luminance)"

inotifywait -me modify --format '' "$path"/actual_brightness | while read; do
    echo xbacklight -set "$(luminance)"
done