File=/sys/class/backlight/intel_backlight/brightness
Brightness=$1
MaxBrightness=$(cat /sys/class/backlight/intel_backlight/max_brightness)
PercentBrightness=$(($MaxBrightness / 100))
NewBrightness=$(($Brightness * $PercentBrightness))

sudo chown $USER $File
echo $NewBrightness > $File