#!/bin/sh

export bl_level=0
export pcnt=0
export maxbr=$(cat /sys/class/backlight/backlight/max_brightness)

cat /dev/random > /dev/fb0 2> /dev/null

echo "press:"
echo "   + to increment backlight"
echo "   - to decrement backlight"
echo "   q to exit"
echo ""

while [ true ]; do
        echo "backlight: $bl_level ($pcnt%)"
        echo $bl_level > /sys/class/backlight/backlight/brightness
        cat /sys/class/backlight/backlight/actual_brightness

        read -n1 in

        [ $in == "q" ] && exit;
        [ "$in" == "+" ] && bl_level=$(( bl_level + 1 ))
        [ "$in" == "-" ] && bl_level=$(( bl_level - 1 ))
        if [ "$in" == "n" ] ; then
                read -p "enter value:" val
                bl_level=$val
        fi

        [ $bl_level -lt 0 ] && bl_level=0
        [ $bl_level -gt $maxbr ] && bl_level=$maxbr

        if [ $bl_level -eq 0 ] ; then
            pcnt=0
        else
            pcnt=$(( 100 * $bl_level / $maxbr )) 
        fi
done
