x                  Pointer to a valid group structure containing
                       a matching entry.
    NULL               An error occurred.

                       Note: The return value points to a static area
                       that is overwritten by subsequent calls to
                       getgrent, getgrgid, or getgrnam.

                       On error, the function sets errno to one of
                       the following values:

                       o  EACCES - The user process does not have
                          appropriate privileges enabled to access
                          the user authorization file.

                       o  EIO - An I/O error has occurred.

                       o  EINTR - A signal was intercepted during
                          getgrgid.

                       o  EMFILE - OPEN_MAX file descriptors are
                          currently open in the calling process.

                       o  ENFILE - The maximum allowable number of
                          files is currently open in the system.

                       Applications checking for error situations
                       must set errno to 0 before calling getgrgid.
                       If errno is set on return, an error has
                       occurred.