title: Order of /usr/bin and /usr/local/bin and more in $PATH
body: <p>On my Mac I used bash a lot. For my environment settings I added <code>/usr/bin</code> and <code>/usr/local/bin</code> into <code>$PATH</code> as I normally did.</p>
  
  <p>While I do know what <code>/usr/bin</code> and <code>/usr/local/bin</code> are about, I am curious which should go before another, by convention? And is there a specific reason for that?</p>
  
  <p>Similar is for <code>/usr/lib</code> and <code>/usr/local/lib</code> -- hopefully the answer is the same or similar.</p>
  
  <p> a bit more --
  Just an extension of the original question, how would you order the following in $PATH following the convention and why?</p>
  
  <pre><code>/bin
  /sbin
  /usr/bin
  /usr/sbin
  /usr/local/bin
  /usr/local/sbin
  /opt/local/bin
  /opt/local/sbin
  </code></pre>