如何重定向fork（）创建的子进程的IO并使用exec（）函数？

I am writing a Shell in C language. User should be able to execute various commands and use pipe(|) to redirect input of one command to the other. The main shell process is the parent process and forks new process for each command and in child process the command is called by exec*() function. I am writing a Shell in C language. User should