title: exit status on incorrect usage
body: <p>I have a check in my program to see if the user supplies the right amount of command line arguments. If they do not, I print a usage message and then exit the program.</p>
  
  <p>However I'm not sure if I should exit with EXIT_SUCCESS or EXIT_FAILURE - it appears that they both have some merit in terms of their english meaning. Is there an important distinction? What should I do?</p>