title: How to keep just lines contain specific string in grep?
body: <p>I have text file. I need print just these lines which contain one of specific string for example:
  Text file:</p>
  
  <pre><code>Car, bold 231212 /Fds
  House pen 232123 /RYF
  game kon 342442 /ksgj
  mess three 42424 /UTR
  </code></pre>
  
  <p>And I need just keep lines contain Fds or UTR</p>
  
  <p>Output:</p>
  
  <pre><code>Car, bold 231212 /Fds
  mess three 42424 /UTR
  </code></pre>
  
  <p>How to do these in grep?</p>
  
  <p>Thank you</p>