screen-backlight

#!/bin/sh
val_in=$1
val=$(cat /sys/class/backlight/nv_backlight/brightness)

case $val_in in
        "dec") let val=${val}-10;;
        "inc") let val=${val}+10;;
        *) echo "ERROR" 1>&2 && exit 1
esac

if [ $val -lt 10 ]
then
        let val=10
elif [ $val -gt 90 ]
then
        let val=90
fi

echo $val | sudo tee /sys/class/backlight/nv_backlight/brightness