title: Idiomatic way to chose shared memory or unix semaphore key
body: <p>What is the idiomatic way to choose a key for <code>shmget</code> or <code>semget</code> functions? </p>
  
  <p>How can I be sure that the same key isn't used by some other processes? </p>
  
  <p>Yes. i know that a big random number is most likely not used by anyone else, but is't there a bulletproof way to choose it?</p>