一次只有一个程序

Question

我有一种情况，我需要同时运行一个程序的一个实例。

这将是微不足道的：

class OneAtATimePlease
{
  static void Main()
  {
    // Naming a Mutex makes it available computer-wide. Use a name that's
    // unique to your company and application (e.g., include your URL).

    using (var mutex = new Mutex (false, "oreilly.com OneAtATimeDemo"))
    {
      // Wait a few seconds if contended, in case another instance
      // of the program is still in the process of shutting down.

      if (!mutex.WaitOne (TimeSpan.FromSeconds (3), false))
      {
        Console.WriteLine ("Another app instance is running. Bye!");
        return;
      }
      RunProgram();
    }
  }

  static void RunProgram()
  {
    Console.WriteLine ("Running. Press Enter to exit");
    Console.ReadLine();
  }
}

除了小细节，我需要终止现有进程，而不是新进程。

我尝试制作一个信号量，在获取上述互斥锁后，现有进程可以监听，但是因为我希望它等待信号量，所以我最终可能会遇到信号量总是发出信号的情况，因此它不会工作。

谁知道如何解决这个问题？

Answer 1

您需要进程间通信，以向现有应用程序发送信号。对于 C#，请参阅 IPC Mechanisms in C# - Usage and Best Practices。

Answer 2

Cine，我编写了两个互斥体逻辑。第一个是“执行锁”，第二个是“监控锁”。 当第一个进程无法获取监控锁时，它会退出并为新进程释放执行锁。

我不确定这是否是最佳解决方案，欢迎提供任何反馈。

C#：

class Program
    {
        private static string processName = DateTime.Now.ToString("hh.mm.ss");
        private static bool exitProcess;

        private static Mutex firstLock
        {
            get
            {
                return new Mutex(false, "stackoverflow.com/questions/11304052/");
            }
        }

        private static Mutex secondLock
        {
            get
            {
                return new Mutex(false, "stackoverflow.com/questions/11304052/ #2");
            }
        }


        static void Main(string[] args)
        {
            Console.WriteLine(string.Format("Process {0} starting", processName));

            exitProcess = false;

            while (true)
            {
                using (firstLock)
                {
                    Console.WriteLine(string.Format("Process {0} trying to get #1 mutex", processName));

                    if (!firstLock.WaitOne(TimeSpan.FromSeconds(1), false))
                    {
                        Console.WriteLine(string.Format("Process {0} #1 mutex in use, waiting for release", processName));

                        bool killFirstApp = false;

                        while (!killFirstApp)
                        {
                            killFirstApp = LockSecondMutex();
                        }

                        continue;
                    }

                    new Thread(MonitorSecondMutex).Start();

                    RunProgram();

                    firstLock.ReleaseMutex();

                    break;
                }
            }
        }

        static void RunProgram()
        {
            while (!exitProcess)
            {
                Console.WriteLine(string.Format("Process {0} running", processName));

                Thread.Sleep(1000);
            }
        }

        static void MonitorSecondMutex()
        {
            while (true)
            {
                using (secondLock)
                {
                    if (!secondLock.WaitOne(TimeSpan.FromSeconds(2), false))
                    {
                        Console.WriteLine(string.Format("Process {0} lost second mutex. Will now exit.", processName));

                        exitProcess = true;

                        break;
                    }

                    secondLock.ReleaseMutex();
                }

                Thread.Sleep(500);
            }
        }

        static bool LockSecondMutex()
        {
            while (true)
            {
                using (secondLock)
                {
                    if (!secondLock.WaitOne(TimeSpan.FromSeconds(2), false))
                    {
                        continue;
                    }

                    Thread.Sleep(5000);

                    secondLock.ReleaseMutex();
                }

                return true;
            }
        }
    }

Answer 3

您可以通过请求访问某些有限的系统范围资源（例如端口）来完成此操作。您的应用程序可以在启动时将套接字绑定到特定端口。如果绑定失败，向正在运行的实例发送终止信号，然后重试。