说明：  多进程的有名管道通信实例，在pc中linux环境下测试通过，测试中使用2个有名管道实现全双工通信，test_fifo_rw用于写管道，并读取另一个管道内容，test_fifo_echo将读管道的数据简单处理后回送到另一个管道中，
(Examples of well-known multi-process communication named pipe, in the pc linux environment tested, the test used in two well-known pipeline to achieve full-duplex communication, test_fifo_rw writing for a pipeline, and read the contents of another pipeline, test_fifo_echo read data pipeline after a simple treatment write back to another pipeline,)