1、 用C语言写一个程序名字为procs4，该程序运行过程中共有4个进程，procs4程序（父进程）创建2个子进程p1和p2，p1子进程再创建一个子进程p3。4个进程完成如下工作: 父进程并打印字符串“I am main process”；p1子进程打印“I am child process p1”字符串；p2子进程打印“I am child process p2”；子进程p3打印字符串“I am child process p3”，然后使用exec（族）系统调用打印当前目录下文件和子目录下

父进程创建两个子进程，并通过管道向两个子进程分别传递数据，子进程得到数据后进行计算，并将结果传回给父进程。-Parent process creates two child processes, and through pipes to the two sub-processes to transfer data, respectively, after the child process data are calculated, and the results back to the pare

本程序采用了特征线法计算管道阀门关闭时的水锤-This program uses a water hammer characteristic line method to calculate the pipe when the valve is closed