title: Checking the stdin buffer if it's empty
body: <p>I am trying to read a number character with character, but I don't know if the stdin buffer is empty or not.</p>
  <p>My first solution whas to look for <code>\n</code> character in stdin buffer, but this is no good if I what to enter multiple numbers separated by <code>&quot; &quot;</code>.</p>
  <p>How can I know if in stdin buffer I have characters or not?</p>
  <p>I need to do it in C and to be portable.</p>