#!/bin/bash

# Need brightness-udev for non root users to access file

file=$(find -L /sys/class/backlight/ -maxdepth 2 -name brightness 2> /dev/null)

function inc_brightness() {
    inc=$1
    current=$(cat $file)
    echo $((current + inc)) > $file
    exit
}

function dec_brightness() {
    dec=$1
    current=$(cat $file)
    echo $((current - dec)) > $file
    exit
}


function main ()
{
    while [[ $# -ne 0 ]]; do
        arg="$1"; shift
        case "$arg" in
            --inc) val=$1; inc_brightness $val ;;
            --dec) val=$1; dec_brightness $val ;;
            * ) [[ $arg =~ \-+.* ]] && echo "$arg unknown"
        esac
    done
}

main "$@"