Introduction - If you have any usage issues, please Google them yourself
The use of pipeline technology communication between parent and child, the specific process: the parent process to three seconds for the cycle to receive user input sent to the child process, the child process after receiving the information display and returns the parent process receives a return message to be displayed. Parent and child processes used in the communication process interrupt signal processing methods for processing, receiving the " exit" string both parent and child process exits. (Tip, use SIGUSR1 or SIGUSR2 signal)