how to reap some child processes (but not all) with waitpid function

Question

I am working on the task of writing myshell on systemprogramming class. I have a question because I am having a hard time writing Sigchld_handler that handles multiple processes through pipes(eg. ls | grep .c)

This question is based on my understanding as follows.

• Signal is not queued.
• However, the list of terminated children is queued to the parent process.

At first, I wrote sigchld handler of myshell as follows.

reaped_id[reap_count] = Waitpid(pid[reap_count], NULL, 0); 

The problem with the initial Sigchld_handler is that because the Sigchld signal is not queued, when there are multiple terminated child processes, they fail to reap the second process and a zombie process is created.

So, the textbook says to write the program as below when reaping the child processes with sigchld_handler.

while((pid=waitpid(-1, NULL,0)) > 0){
    Sigprocmask(SIG_BLOCK, &mask_all, &prev_all); 
    deletejob(pid); 
    Sigprocmask(SIG_BLOCK, &prev_all, NULL); 
}

But I think the problem with this code is that the parents are blocked until all the child processes are terminated. (Because waitpid returns -1 when the child process no longer exists)

My myshell's Sigchld_handler wants all terminated child processes(not all child processes) to be reaped, but both the running child process and the parent process(myshell) should be executed concurrently. I wish Parent process doesn't wait until the whole child process is over.

How should I write sigchld_handler?

Thank you.