title: waitpid, wnohang, wuntraced. How do I use these
body: <p>I am a bit confused.  As I understand, waitpid with a pid of -1 means that I wait for all child's to finish but if I add an option to the waitpid of WNOHANG, that options says to exit immediately if none have finished...These seems extremely confusing.</p>
  
  <p>Why would I tell the computer to wait for child processes to finish and then immediately afterwards tell it to exit immediately if none of the childs have finished?</p>
  
  <p>Can someone explain this option and the WUNTRACED options?  I don't know what it means to be traced.</p>