docs: def main():
      """
      Main Entry Point
      """
      args = parser.parse_args()
      filehandle = args.filename
      delim = args.delimiter
      columns = args.columns[0]
  
      if not columns:
          for line in filehandle:
              print line,
          exit(0)
  
      cs = list(chain.from_iterable(columns))
      fields = (extract_fields(line, delim, cs) for line in filehandle)
  
      for line in fields:
          print ' '.join(line)
  
      args.filename.close()