brightness command line tool using xrandr

xrandr-3.sh

function brightness(){
    if [ $# -gt 0 ]; then
        # set brightnessValue
        brightnessValue=$1
        # get activeDisplay
        activeDisplay=`xrandr -q | grep ' connected' | head -n 1 | cut -d ' ' -f1`
        # change brightness if $activeDisplay is not empty
        if [ "$activeDisplay" != "" ]; then
            xrandr --output $activeDisplay --brightness $brightnessValue
        else
            echo "Could not determine active display, run 'xrandr --verbose' for detailed info"
        fi  
    else
        echo -e "Error!!! Syntax: brightness <value (0.0 to 1.0)>"
    fi  
}

thanks