#include <db_cxx.h>
 
void Db::set_msgcall(void (*db_msgcall_fcn)(const DbEnv *dbenv, 
                                            const char *msgpfx,
                                            const char *msg));

There are interfaces in the Berkeley DB library which either directly output informational messages or statistical information, or configure the library to output such messages when performing other operations, for example, DbEnv::set_verbose() and DbEnv::stat_print() .

The DbEnv::set_msgcall() and Db::set_msgcall() methods are used to pass these messages to the application, and Berkeley DB will call db_msgcall_fcn with each message. It is up to the db_msgcall_fcn function to display the message in an appropriate manner.

Setting db_msgcall_fcn to NULL unconfigures the callback interface.

Alternatively, you can use the DbEnv::set_error_stream() and Db::set_error_stream() methods to display the messages via an output stream, or the Db::set_msgfile() or Db::set_msgfile() methods to display the messages via a C library FILE *. You should not mix these approaches.

For Db handles opened inside of Berkeley DB environments, calling the Db::set_msgcall() method affects the entire environment and is equivalent to calling the DbEnv::set_msgcall() method.

The Db::set_msgcall() method configures operations performed using the specified Db handle, not all operations performed on the underlying database.

The Db::set_msgcall() method may be called at any time during the life of the application.