control backlight brightness on linux window manager

brightness.sh

#!/bin/bash
config_file=/sys/class/backlight/intel_backlight/brightness
brightness=$(cat $config_file)
max_brightness=100000
brightness_measure=$(( max_brightness / 10 ))

function get_percentage() {
    percent=$(( $brightness * 100 / $max_brightness  ))
    echo Brightness: $percent/100
}

case "$1" in
    1)
        if [ $brightness -lt $max_brightness ]
        then
            brightness=$(( $brightness + $brightness_measure ))
            sudo tee $config_file <<< "$brightness" > /dev/null 2>&1
        fi
        get_percentage
        ;;
    0)
        if [ $brightness -gt $brightness_measure ]
        then
            brightness=$(( $brightness - $brightness_measure ))
            sudo tee $config_file <<< "$brightness" > /dev/null 2>&1
        fi
        get_percentage
        ;;
    *)
        echo Error: wrong input
        echo $0 1 to increase, 0 to decrease
        ;;
esac