Shell中管道的作业控制

Question

I am writing a shell in C. I am trying to set up a new process group for each job. The first process of each pipeline becomes the leader of the job's process group, the other processes join the leader's process group.

So in this case, cat somefile | wc cat somefile | wc , the cat process will be the process leader.

How can I achieve this behaviour using setpgid ? If I am looping over each process, do I need to store the value of the pid of the first fork and use that as the group ID for subsequent iterations of the loop to set the appropriate process group ID in the child class?

Answer 1

If I were you, I'd take the fork() pid that the parent recieves and do setpgid(child_pid,your_gid);. getpgid(0) can be used to return your group id. Use those two pieces of information to do setpgid().