title: Add a line in between two lines in a file from bash
body: <p>I have file named <code>user.rb</code> as like:</p>
  
  <pre><code>class User &lt; ApplicationRecord
  end
  </code></pre>
  
  <p>I want to add a new line and after adding line it will look :</p>
  
  <pre><code>class User &lt; ApplicationRecord
    include Company
  end
  </code></pre>
  
  <p>But I want to add this additional line from bash script or terminal.
   I tried it with this bash code:</p>
  
  <pre><code>sed -i '' 's/end/include Company\n\end/' app/models/user.rb
  </code></pre>
  
  <p>But it does not return new line after adding line.
  Please help me.</p>