一个完整的linux daemon示例

csharp_daemon_demo.cs

using System;
using System.Threading;
using System.Timers;
using System.Runtime.InteropServices;
using System.IO;
using System.Text;


/********************************************
 * 一个完整的linux daemon示例，作者宇内流云 *
 ********************************************/

namespace daemon
{
    class Program
    {

        const string DaemonTag = "--daemon.";
        static void Main(string[] args)
        {
            // 如果已经是daemon后台服务，就直接执行后台主函数
            if (string.IsNullOrEmpty(Environment.GetEnvironmentVariable(DaemonTag)) == false)
            {
                Environment.SetEnvironmentVariable(DaemonTag, null);
                DaemonMain(args);
                return;
            }


            // 如果还不是daemon状态，就作daemon处理
            ///////////////////////////////////////////////

            int pid = fork();
            if (pid != 0) exit(0);
            setsid();
            pid = fork();
            if (pid != 0) exit(0);
            umask(0);


            // 这儿已经进入“守护进程”工作状态了!

            //关闭所有打开的文件描述符
            int max = open("/dev/null", 0);
            for (var i = 0; i <= max; i++) { close(i); }


            // 设置标记，防止重复运行
            Environment.SetEnvironmentVariable(DaemonTag,"yes");


            //为execp重组参数
                var args1 = args == null ? new string[2] : new string[args.Length + 2];

                args1[0] = "mono";
                args1[1] = Path.Combine(Environment.CurrentDirectory, Thread.GetDomain().FriendlyName);

                //复制参数
                if (args1.Length > 2)
                {
                    for (var i = 0; i < args.Length; i++)
                    { args1[i + 2] = args[i]; }
                }


                //守护状态下重新加载和运行本程序
                execvp("mono", args1);

        }


        /// <summary>
        /// Daemon工作状态的主方法
        /// </summary>
        /// <param name="aargs"></param>
        static void DaemonMain(string[] aargs)
        {
            //启动一个线程去处理一些事情
            (new Thread(DaemonWorkFunct) { IsBackground = true }).Start();


            //daemon时，控制台输入、输出流已经关闭
            //请不要再用Console.Write/Read等方法

            //阻止daemon进程退出
            (new AutoResetEvent(false)).WaitOne();

        }


        static FileStream fs;
        static int count = 0;
        static void DaemonWorkFunct() {
            fs = File.Open("/tmp/daemon.txt", FileMode.OpenOrCreate);
            var t = new System.Timers.Timer() { Interval = 1000 };
            t.Elapsed += OnElapsed;
            t.Start();
        }
        private static void OnElapsed(object sender, ElapsedEventArgs e)
        {
            var s = DateTime.Now.ToString("yyy-MM-dd HH:mm:ss") + "\n";
            var b = Encoding.ASCII.GetBytes(s);
            fs.Write(b, 0, b.Length);
            fs.Flush();

            count++;
            if (count > 100) {
                fs.Close();
                fs.Dispose();
                exit(0);
            }

        }



        [DllImport("libc", SetLastError = true)]
        static extern int fork();

        [DllImport("libc", SetLastError = true)]
        static extern int setsid();

        [DllImport("libc", SetLastError = true)]
        static extern int umask(int mask);

        [DllImport("libc", SetLastError = true)]
        static extern int open([MarshalAs(UnmanagedType.LPStr)]string pathname, int flags);

        [DllImport("libc", SetLastError = true)]
        static extern int close(int fd);

        [DllImport("libc", SetLastError = true)]
        static extern int exit(int code);

        [DllImport("libc", SetLastError = true)]
        static extern int execvp([MarshalAs(UnmanagedType.LPStr)]string file, string[] argv);


    }

}