title: Difference between SIGUSR1 and SIGUSR2
body: <p>Reading the manuscript for signals, I came across the signal table and saw there are two defined signals for usr SIGUSR1 and SIGUSR2.
  Is there any difference between the two?
  If so when should I choose to use one over the other?
  If there is no difference why are ther two signals serving the same purpose?</p>