title: gcc switches - what do these do?
body: <p>I am new with using gcc and so I have a couple of questions.</p>
  
  <p>What do the following switches accomplish:</p>
  
  <pre>
  gcc -v -lm -lfftw3 code.c
  </pre>
  
  <p>I know that <code>lfftw3</code> is an <code>.h</code> file used with <code>code.c</code> but why is it part of the command?</p>
  
  <p>I couldn't find out what <code>-lm</code> does in my search. What does it do?</p>
  
  <p>I think I found out <code>-v</code> causes gcc to display programs invoked by it.</p>