dbus-read-battery.go

package main

import (
	"fmt"
	"maps"
	"slices"
	"sort"

	"github.com/godbus/dbus/v5"
)

const (
	intf = "org.freedesktop.UPower.Device"
	path = "/org/freedesktop/UPower/devices/battery_BAT0"
	meta = "org.freedesktop.DBus.Properties"
)

var props = []string{
	"NativePath",       // string
	"Vendor",           // string
	"Model",            // string
	"Serial",           // string
	"UpdateTime",       // uint64
	"Type",             // uint32
	"PowerSupply",      // bool
	"HasHistory",       // bool
	"HasStatistics",    // bool
	"Online",           // bool
	"Energy",           // float64
	"EnergyEmpty",      // float64
	"EnergyFull",       // float64
	"EnergyFullDesign", // float64
	"EnergyRate",       // float64
	"Voltage",          // float64
	"ChargeCycles",     // int32
	"Luminosity",       // float64
	"TimeToEmpty",      // int64
	"TimeToFull",       // int64
	"Percentage",       // float64
	"Temperature",      // float64
	"IsPresent",        // bool
	"State",            // uint32
	"IsRechargeable",   // bool
	"Capacity",         // float64
	"Technology",       // uint32
	"WarningLevel",     // uint32
	"BatteryLevel",     // uint32
	"IconName",         // string
}

func main() {
	bus := must(dbus.ConnectSystemBus())
	defer bus.Close()

	var bat map[string]dbus.Variant
	obj := bus.Object(intf[:22], path)
	throw(obj.Call(meta+".GetAll", 0, intf).Store(&bat))
	show(bat)

	throw(bus.AddMatchSignal(
		dbus.WithMatchInterface(meta),
		dbus.WithMatchMember("PropertiesChanged"),
		dbus.WithMatchObjectPath(path),
		dbus.WithMatchArg(0, intf),
	))

	ch := make(chan *dbus.Signal, 10)
	bus.Signal(ch)
	for sig := range ch {
		diff := sig.Body[1].(map[string]dbus.Variant)
		maps.Copy(bat, diff)
		show(diff)
	}
}

func show(dic map[string]dbus.Variant) {
	var keys []string
	for key, _ := range dic {
		if slices.Contains(props, key) {
			keys = append(keys, key)
		}
	}
	sort.Strings(keys)
	for _, key := range keys {
		fmt.Printf("%s = %v\n", key, dic[key].Value())
	}
	fmt.Println()
}

func throw(err error) {
	if err != nil {
		panic(err)
	}
}

func must[T any](val T, err error) T {
	throw(err)
	return val
}