Return_Values

   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.