Change keyboard brightness on linux on Mac Book Pro

change_brightness.sh

#!/bin/bash

file=/sys/devices/platform/applesmc.768/leds/smc::kbd_backlight/brightness
max_file=/sys/devices/platform/applesmc.768/leds/smc::kbd_backlight/max_brightness

level=$(cat $file)

changement_level=10

function change_brightness
{
    echo $1
    echo $1 > $file
}

# Command line handler
case $1 in

    up)
        level=$((level+changement_level))
    ;;

    down)
        level=$((level-changement_level))
    ;;

    disable) level=0
    ;;
   *)
      echo "Usage: $0 { up | down | disable }"
      exit
      ;;

esac

max=$(cat $max_file)

if [ $level -gt $max ]; then
    level=$max
fi
if [ $level -lt 0 ]; then
    level=0
fi
change_brightness $level

#END