text: #!/usr/bin/env python3
  """ Command line interface to difflib.py providing diffs in four formats:
  
  * ndiff:    lists every line and highlights interline changes.
  * context:  highlights clusters of changes in a before/after format.
  * unified:  highlights clusters of changes in an inline format.
  * html:     generates side by side comparison with change highlights.
  
  """
  
  import sys, os, difflib, argparse
  from datetime import datetime, timezone
  
  def file_mtime(path):
      t = datetime.fromtimestamp(os.stat(path).st_mtime,
                                 timezone.utc)
      return t.astimezone().isoformat()
  
  def main():
  
      parser = argparse.ArgumentParser()
      parser.add_argument('-c', action='store_true', default=False,
                          help='Produce a context format diff (default)')
      parser.add_argument('-u', action='store_true', default=False,
                          help='Produce a unified format diff')
      parser.add_argument('-m', action='store_true', default=False,
                          help='Produce HTML side by side diff '
                               '(can use -c and -l in conjunction)')
      parser.add_argument('-n', action='store_true', default=False,
                          help='Produce a ndiff format diff')
      parser.add_argument('-l', '--lines', type=int, default=3,
                          help='Set number of context lines (default 3)')
      parser.add_argument('fromfile')
      parser.add_argument('tofile')
      options = parser.parse_args()
  
      n = options.lines
      fromfile = options.fromfile
      tofile = options.tofile
  
      fromdate = file_mtime(fromfile)
      todate = file_mtime(tofile)
      with open(fromfile) as ff:
          fromlines = ff.readlines()
      with open(tofile) as tf:
          tolines = tf.readlines()
  
      if options.u:
          diff = difflib.unified_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)
      elif options.n:
          diff = difflib.ndiff(fromlines, tolines)
      elif options.m:
          diff = difflib.HtmlDiff().make_file(fromlines,tolines,fromfile,tofile,context=options.c,numlines=n)
      else:
          diff = difflib.context_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)
  
      sys.stdout.writelines(diff)
  
  if __name__ == '__main__':
      main()
  