Brightness control with Intel chipsets (ThinkPad etc.)

brightness.sh

#!/bin/bash
#
# Shows and optionally adjusts Intel screen brightness
#
# Run from command line or bind to shortcut keys
#
# Usage: brightness [up|down]
#
# by: Runar Balstad Jensen
# url: https://gist.github.com/emning/5d3301a3f3c9420414f7
# ref: http://askubuntu.com/q/428237
#

DEV=/sys/class/backlight/intel_backlight

STEPS=17        # 17 * 50 = 850, and 851 is the max for my Intel device
FUDGE=3         # round up or down if within this much of 0 or MAX 

sudo_if_needed()
{
        test $UID = 0 || echo sudo
}

get_brightness()
{
        CUR=$(cat $DEV/brightness)
        MAX=$(cat $DEV/max_brightness)
}

set_brightness()
{
        val=$1

        if [[ $val -le $FUDGE ]]
        then
                val=0
        fi

        if [[ $val -ge $((MAX - FUDGE)) ]]
        then
                val=$MAX
        fi

        $(sudo_if_needed) tee $DEV/brightness <<< $val > /dev/null
}

print_brightness()
{
        echo "$CUR/$MAX ($(((CUR * 100) / MAX)) %)"
}

if [[ $# -eq 1 ]]
then
        get_brightness

        case "$1" in
                up)
                        set_brightness $((CUR + (MAX / STEPS)))
                        ;;
                down)
                        set_brightness $((CUR - (MAX / STEPS)))
                        ;;
        esac
fi

get_brightness
print_brightness