Change brightness of Screen

Well, beeing all about scripts here, got a new one:

The script is also a wrapper wether you have (xorg-)xbacklight installed or not, but if not, it requires sudo to be passwordless for the user (if called by a WM/without using terminal).

#!/usr/bin/env  bash
# Description:    Change brightness of laptop lcd
#        This script is part of my AwesomeWM configuration (https://github.com/sri-arjuna/awesome)
#        The most recent version should be available on: https://raw.githubusercontent.com/sri-arjuna/awesome/master/scripts/brightness.sh
# Disclaimer:   This code comes without any warrenty of any kind, use at your own risk!
# GNU General Public License (GPL) 2016 by Simon Arjuna Erat (sea) (erat.simon æ gmail,com)
#
#
#    Variables
#
    BASE=/sys/class/backlight
    ITEM=$(cd $BASE;ls)
    DIR=$BASE/$ITEM
    FILE=$DIR/backlight
    MAX=$(<$DIR/max_backlight)
    STEP_COUNT=20
    STEP_VALUE=$(( $MAX / $STEP_COUNT ))
    CUR=$(<$FILE)
#
#    Action
#
    if which xbacklight 2>/dev/null >&2
    then    # xbacklight is installed
        #cur=$(xbacklight)
        #cur=${cur/\.*}
        case "${1,,}" in
        "")    echo "Usage: brightness.sh up|down"
            exit 1
            ;;
        up)    xbacklight -inc 20
            ;;
        down)    xbacklight -dec 20
            ;;
        esac
    else    # Fallback, dont like the use of sudo in a background script
        # Required/recomend passwordless sudo, but is a security risk!
        case "${1,,}" in
        "")    echo "Usage: brightness.sh up|down"
            exit 1
            ;;
        up)    num=$(( $CUR + $STEP_VALUE ))
            [ $num -ge $MAX ] && num=$MAX
            [ $num -le 0 ] && num=0
            sudo tee $FILE <<< $num
            ;;
        down)
            num=$(( $CUR - $STEP_VALUE ))
            [ $num -ge $MAX ] && num=$MAX
            [ $num -le 0 ] && num=0
            sudo tee $FILE <<< $num
            ;;
        esac
    fi