gistfile1.txt

#!/usr/bin/bash

#source: https://gist.github.com/Blaradox/030f06d165a82583ae817ee954438f2e

id=5555

function get_brightness {
  xbacklight -get | cut -d '.' -f 1
}

function send_notification {
  icon="preferences-system-brightness-lock"
  brightness=$(get_brightness)
  # Make the bar with the special character ─ (it's not dash -)
  # https://en.wikipedia.org/wiki/Box-drawing_character
  #bar=$(seq -s "█" 0 $((brightness / 5)) | sed 's/[0-9]//g')
  # Send the notification
  dunstify -t 1000 -i "$icon" -r $id -u normal "BRIGHTNESS: $brightness%   "
}

case $1 in
  up)
    # increase the backlight by 5%
    xbacklight -inc 5
    send_notification
    ;;
  down)
    # decrease the backlight by 5%
    xbacklight -dec 5
    send_notification
    ;;
esac