title: C++ do OS X or Linux headers vary
body: <p>I am making a program that I want to run on both Lubuntu (linux) and Tiger (mac os x). I am including some header functions like "termios", "sys/select" and "unistd" that I have never heard of before. Which leads me to the question: Are there any built-in libraries in Linux that are not included in OS X, or vice versa? Can someone explain which ones they are? I think this would be a good thing for me to know if/when porting programs.</p>
  
  <p>Thanks.</p>