Systemd wrapper for Minecraft servers.

MinecraftSystemdWrapper.go

// MIT License <https://opensource.org/licenses/MIT> - Copyright (c) 2020 Miguel Dorta
package main

import (
	"fmt"
	"golang.org/x/sys/unix"
	"io"
	"os"
	"os/exec"
	"os/signal"
)

const programName = "MinecraftSystemdWrapper"

func main() {
	if len(os.Args) < 2 {
		fmt.Println("Usage:    " + programName + " [command]")
		os.Exit(1)
	}

	cmd := exec.Command(os.Args[1], os.Args[2:]...)
	cmd.SysProcAttr = &unix.SysProcAttr{Setpgid:true}
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	stdin, err := cmd.StdinPipe()
	if err != nil {
		printError("error getting process stdin pipe: %s", err)
		os.Exit(1)
	}

	exited := make(chan bool, 1)
	quit := make(chan os.Signal, 2)
	signal.Notify(quit, unix.SIGINT, unix.SIGTERM)

	go func() {
		if err := cmd.Run(); err != nil {
			printError("minecraft process returned an error: %s", err)
			os.Exit(1)
		}
		exited <- true
	}()

	select {
	case <-exited:
		os.Exit(0)
	case <-quit:
	}

	if _, err := io.WriteString(stdin, "stop\n"); err != nil {
		printError("error writing stop command to minecraft process: %s", err)
		if err := cmd.Process.Kill(); err != nil {
			printError("error killing minecraft process: %s", err)
		}
		os.Exit(1)
	}

	<- exited
	os.Exit(0)
}

func printError(format string, a ...interface{}) {
	format = fmt.Sprintf("%s: %s\n", programName, format)
	_, _ = fmt.Fprintf(os.Stderr, format, a...)
}