title: Delete lines from file with SED or AWK
body: <p>Ive seen many variations, very confused on how to solve these 3 problems.</p>
  
  <ol>
  <li>deleting all rows except the first from a file</li>
  <li>deleting a row from file with a line number</li>
  <li>deleting rows from a file with a range of line numbers</li>
  </ol>