Main Entry Point

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()