掌握系统调用pipe()的使用方法及其功能，理解管道通信原理；

（２）掌握利用系统调用exit()和wait()实现父进程与子进程之间的同步，理解同步的含义。

-Master the system call pipe () to use its functions, to understand the pipeline communication theory　(2) master system call exit () and wait () synchronization between the parent process and child process, understanding the meaning of synchronization.