100% CPU usage during wait

[raypulver]

I have found waitpid very useful for my project but have recently discovered that it uses the entire CPU while it waits. Is there any change that could be made to the code so that it blocks execution without consuming resources during the wait? The problem is with this loop

do {
  r = waitpid(child, &status, WNOHANG);
} while (r != -1);

[raypulver]

I took out the loop and replaced it with

waitpid(child, &status, 0);

This seems to work. WNOHANG makes it so the call is non-blocking. If you pass no flags to waitpid instead, it blocks without need for the do while loop. I wonder why WNOHANG was passed in though?

[raypulver]

I had problems with my original solution, finding out that you definitely have to loop over waitpid to use it correctly. I eventually ended up using the loop

while (waitpid(child, &status, 0) == - 1) {
  if (errno != EINTR) {
    perror("waitpid");
    exit(1);
  }
}

This seems to work perfectly, without the 100% CPU problem.