#!/usr/bin/python3

import os
import sys

if __name__ == "__main__":

  if len(sys.argv) < 4:
    print("Use: %s FILE1 FILE2 DEST_FILE" % sys.argv[0])
    exit(1)

  file1 = sys.argv[1]
  file2 = sys.argv[2]
  dest = sys.argv[3]
  lines = lines_cmp = []
  notfound = []

  with open(file1, 'r') as ff:
    lines = ff.readlines()
  with open(file2, 'r') as ff2:
    lines_cmp = ff2.read()

  for line in lines:
    if not line in lines_cmp:
      notfound.append(line)

  with open(dest, 'w') as f:
    f.write('\n'.join(notfound))
