battery.go

package main

import (
	"fmt"
	"os/exec"
	"regexp"
	"strconv"
	"strings"
	"time"
)

func Watch() {
	percentagePattern := regexp.MustCompile(`(\d+)%`)
	prev := int64(0)
	for {
		cmd := exec.Command("acpi")
		out_bytes, err := cmd.Output()
		if err != nil {
			fmt.Println(err)
			time.Sleep(time.Minute)
			continue
		}

		out := string(out_bytes)
		p := percentagePattern.FindStringSubmatch(out)
		i, _ := strconv.ParseInt(p[1], 10, 8)
		if strings.Contains(out, "Discharging") &&
			i != prev && i <= 15 {
			exec.Command("notify-send", "Battery low alert").Run()
		}
		prev = i
		time.Sleep(time.Minute)
	}
}

func main() {
	Watch()
}