bat-alert/main.go

package main

import (
    "flag"
    "log"
    "os"
    "os/exec"
    "strconv"
    "strings"
    "time"
)

func notify(msg string) {
    cmd := exec.Command("notify-send", "-t", "5000", "-u", "critical", "bat-alert", msg)
    err := cmd.Run()
    if err != nil {
        log.Println(err)
    }
}

var targetFlag = flag.Int("target", 15, "when to send the alert")

func main() {
    flag.Parse()
    sent := false
    for {
        capacity, err := os.ReadFile("/sys/class/power_supply/BAT0/capacity")
        if err != nil {
            notify("error: " + err.Error())
        }

        numCap, err := strconv.Atoi(strings.Trim(string(capacity), "\n"))
        if err != nil {
            notify("error: " + err.Error())
        }

        if numCap <= *targetFlag {
            if !sent {
                sent = true
                notify("battery running low!")
            }
        } else {
            sent = false
        }

        time.Sleep(time.Second * 10)
    }
}