How to wait until all child processes called by fork() complete?

Question

I am forking a number of processes and I want to measure how long it takes to complete the whole task, that is when all processes forked are completed. Please advise how to

Answer 1

The simplest method is to do

while(wait() > 0) { /* no-op */ ; }

This will not work if wait() fails for some reason other than the fact that there are no children left. So with some error checking, this becomes

int status;
[...]
do {
    status = wait();
    if(status == -1 && errno != ECHILD) {
        perror("Error during wait()");
        abort();
    }
} while (status > 0);

See also the manual page wait(2).