这个是对linux下进程间通信之“信号”的特性进行测试的代码，尤其是对实时信号和非实时信号的排队问题进行的测试和验证。 本代码在redhat linux2.4平台上验证无误 -This is the Inter-Process Communication under linux the signal to test the characteristics of the code, especially for real-time signal and non-real-time si