waybar, display brightness value of external screen using ddcutil

config

    "custom/ddcutil": {
    "format": "{percentage}% {icon}",
    "interval": 1,
    "format-icons": ["", "", ""],
    "exec": "/path/to/waybar-ddcutil.py",
    "return-type": "json"
    },

style.css

#custom-ddcutil {
    background-color: #f1c40f;
    color: #000000;
}

waybar-ddcutil.py

#!/usr/bin/env python

import subprocess
import json

data = {}
cmd = ["ddcutil", "getvcp", "10", "--bus", "1"]
value = subprocess.run(cmd, stdout=subprocess.PIPE).stdout.decode('utf8')
# output looks like this in my case: VCP code 0x10 (Brightness                    ): current value =    20, max value =   100
percentage = value.split(":")[1].split(",")[0].split("=")[1].strip(" ")
data['percentage'] = int(percentage)
print(json.dumps(data))

Here is my implementation of the script, I am caching the value because many times when changing the brightness ddcutil wouldn't be able to get the value so it would break for a second and look really janky.

#!/bin/bash

output=$(ddcutil -t getvcp 10 2>/dev/null)

if [ $? -eq 0 ]; then
    trimmed=${output#* * * }
    value=${trimmed%% *}

    cached_value=$(cat /tmp/waybar_ddcutil_value 2>/dev/null)
    if [ "$cached_value" != "$value" ]; then
        echo $value > /tmp/waybar_ddcutil_value
    fi
    echo {\"percentage\": $value}
else
    echo {\"percentage\": $(cat /tmp/waybar_ddcutil_value 2>/dev/null || echo 0)}
fi