The seekdir function sets the position of the next readdir
    operation on the directory stream specified by dir_pointer to
    the position specified by location. The value of location should
    be returned from an earlier call to telldir.

    If the value of location was not returned by a call to the
    telldir function, or if there was an intervening call to the
    rewinddir function on this directory stream, the effect is
    unspecified.

    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. You can remove files from or add files
    to a directory asynchronously to the operation of the readdir
    function.

    See readdir, rewinddir, and telldir.