title: How do I extract lines from a file using their line number on unix?
body: <p>Using sed or similar how would you extract lines from a file? If I wanted lines 1, 5, 1010, 20503 from a file, how would I get these 4 lines?</p>
  
  <p>What if I have a fairly large number of lines I need to extract?
  If I had a file with 100 lines, each representing a line number that I wanted to extract from another file, how would I do that?</p>