The rewinddir function resets the position of the specified
    directory stream to the beginning of the directory. It also
    causes the directory stream to refer to the current state of the
    corresponding directory, the same as using the opendir function.
    If the dir_pointer argument does not refer to a directory stream,
    the effect is undefined.

    The type DIR, defined in the <dirent.h> header file, represents
    a directory stream. A directory stream is an ordered sequence of
    all the directory entries in a particular directory. Directory
    entries represent files.

    See also opendir.