title: Replace a character in Terminal
body: <p>I have a file.</p>
  
  <p>My second line begins with a '#' symbol.</p>
  
  <p>Which command should I use to remove that symbol?</p>
  
  <p>Also on the third line, I have to put a '#' symbol at the beginning of the line.</p>
  
  <p>For example:</p>
  
  <pre><code>line 2: # url: http//192.168.1.1:8000
  line 3:   url: http//example.com
  </code></pre>
  
  <p>when running the command, change the place of that '#'</p>
  
  <p>Alternativly, is there a way to put the local IP in second line automatically?  (So if I restart the router for example, the line will refresh the IP)</p>