title: How to insert text after a certain complex string in a file using SED
body: <p>I want to add new line in a html file by using sed command</p>
  <p>The line I  want to add is</p>
  <pre><code>&lt;link href=&quot;https://newvalue.css&quot; rel=&quot;test1&quot; id=&quot;test2&quot;&gt;  
  </code></pre>
  <p>After</p>
  <pre><code>&lt;link href=&quot;test.css&quot; rel=&quot;test1&quot; id=&quot;test2&quot;&gt;
  </code></pre>
  <p>in a html file.</p>
  <p>Can anyone help ?</p>