title: How to update Xcode to install "UNIX Development Support"?
body: <p>I installed Xcode a long time ago.</p>
  
  <p>Apparently I didn't check back then the "UNIX Development Support" checkbox.</p>
  
  <p>Now I want to have them but when I click on the installation this is what appears:</p>
  
  <p><img src="https://i.stack.imgur.com/fKJ4z.png" alt="disabled"> </p>
  
  <p>The <em>UNIX Development Support</em> check box is disabled</p>
  
  <p><strong>Q:</strong> How can I install the UNIX Development Support?  Is there a way to run some script that creates all the needed links from <code>/Developer/</code> to <code>/usr/bin</code> ?</p>
  
  <p><strong>EDIT:</strong>
  Note: This is for old Xcode 3. Screens and tool names differ for Xcode 4 ("Unix Command Line Tools")</p>