If stored procedure does not generate result set(s) you can reach output parameters immediately after calling SACommand::Execute:
You can use SAParam () operators for quick accessing values. In this case you can process the result as shown below:
long out_param = cmd.Param("nOutput"); printf("%d\n", out_param);
After the statement has been executed, SQLAPI++ stores the returned values of output parameters in the SAParam objects bound to those parameters. On some servers these returned values are not guaranteed to be set until all results returned by the procedure have been fetched (using SACommand::FetchNext method). See Server specific information on output parameters availability on different DBMSs.
For processing result set(s), if any, see Fetch result set(s).
If you call a function SQLAPI++ library automatically creates SAParam object to represent the function return value. You can refer to this SAParam object using SQLAPI++ predefined name
Returning Long, BLob and CLob data can have some differences (if you need piecewise operations) from other data types. See Handle Long/CLob/BLob to get more information.