管道实现进程间通信：写linux下的用户程序，其中一个为父进程，它创建了另外2个子进程，这2个子进程通过管道机制实现进程间通信。-To achieve inter-process communication pipe: write the user program under linux, one of the parent process, it creates the other two sub-process, the two sub-process through the pipeline mechanism to achieve inter-process communication.