title: How can I find duplicate lines in a text file and print them?
body: <p>I have a text file with some 1,200 rows. Some of them are duplicates.</p>
  
  <p>How could I find the duplicate lines in the file (but not worrying about case) and then print out the line's text on the screen, so I can go off and find it? I don't want to delete them or anything, just find which lines they might be.</p>