该函数创建的管道的两端处于一个进程中间，在实际应 用中没有太大意义，因此，一个进程在由pipe()创建管道后，一般再fork一个子进程，然后通过管道实现父子进程间的通信-The function at the two ends of the pipeline to create a process in the middle, in practical applications is not much significance, therefore, a process by the pipe () to create pipeline, the general re-fork a child process, and then through the pipeline between the process of the realization of his son Communications