Return_Values

   x                  Pointer to the retrieved message.
   s                  Pointer to the default message string.
                      Indicates that the function is not able
                      to retrieve the requested message from
                      the catalog. This condition can arise if
                      the requested pair (set_d, msg_id) does
                      not represent an existing message from the
                      open catalog, or it indicates that an error
                      occurred. If an error occurred, the function
                      sets errno to one of the following values:

                      o  EBADF - The catalog descriptor is not
                         valid.

                      o  EVMSRR - An OpenVMS I/O read error;
                         the OpenVMS error code can be found in
                         vaxc$errno.