Return_Values

   x                  A pointer to an object of type DIR.
   NULL               Indicates an error; errno is set to one of the
                      following values:

                      o  EACCES - Search permission is denied
                         for any component of dir_name or read
                         permission is denied for dir_name.

                      o  ENAMETOOLONG - The length of the dir_name
                         string exceeds PATH_MAX, or a pathname
                         component is longer than NAME_MAX.

                      o  ENOENT - The dir_name argument points to
                         the name of a file that does not exist, or
                         is an empty string.