title: Getting an image source with sed
body: <p>If I have a line of text which looks like...</p>
  
  <pre><code>[garbage] &lt;img src="[some url]" [garbage] /&gt; [garbage]
  </code></pre>
  
  <p>Using sed, how can I get the URL that the image is pointing to? There are no other instances of <code>src=</code> on that line.</p>