#!/usr/bin/env python3

"""."""

import sys


def usage(retval):
    """Output a usage message."""
    if retval == 0:
        w = sys.stdout.write
    else:
        w = sys.stderr.write

    w(f'Usage: {sys.argv[0]} --help\n')

    sys.exit(retval)


def main():
    """Start the ball rolling."""
    while sys.argv[1:]:
        if sys.argv[1] in ('-h', '--help'):
            usage(0)
        else:
            sys.stderr.write(f'{sys.argv[0]}: unrecognized option: {sys.argv[1]}\n')
            usage(1)
        del sys.argv[1]

    print('Hello world!')


if __name__ == '__main__':
    main()