title: How to wait() only for some child processes and prevent zombies
body: <p>I'm trying to write a mock-shell in c on linux, and got stuck on this problem:</p>
  
  <p>I need to run some processes in the background, and some processes in the foreground.
  To prevent the foreground processes from becoming zombies, I can use wait(), but how do I prevent the background processes from becoming zombies?</p>