文件中第一个方法创建了一个进程的副本，以子进程模式 (由命令行指定) 工作；第二个方法创建一个事件和一个子进程，然后等待子进程在返回前向事件发出信号；第三个方法在子进程模式下被调用，其功能只是向父进程发出终止信号-the first method creates a process s copy to a child process mode (designated by the command line) The second way to create an event and a child process, and then wait for the child process to signal the event before returning The third method is called in the child process mode, its function is to issue a termination signal to the parent process