掌握系统调用shmget()、shmat()、shmdtshmctl()的使用方法及其功能，理解共享存储区通信原理；

系统理解linux 的三种通信机制。

-Master the system call shmget (), shmat (), shmdtshmctl () to use its functions, understanding, communication principle of shared storage area　system to understand the linux three communication mechanisms.