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13<b>DbEnv::set_msgcall</b>
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21<b><pre>
22#include &lt;db_cxx.h&gt;
23<p>
24void DbEnv::set_msgcall(void (*db_msgcall_fcn)(const DbEnv *dbenv, const char *msg));
25</pre></b>
26<hr size=1 noshade>
27<b>Description: DbEnv::set_msgcall</b>
28<p>There are interfaces in the Berkeley DB library which either directly output
29informational messages or statistical information, or configure the
30library to output such messages when performing other operations, for
31example, <a href="../api_cxx/env_set_verbose.html">DbEnv::set_verbose</a> and <a href="../api_cxx/env_stat.html">DbEnv::stat_print</a>.</p>
32<p>The DbEnv::set_msgcall and Db::set_msgcall methods are used to
33pass these messages to the application, and Berkeley DB will call
34<b>db_msgcall_fcn</b> with each message.  It is up to the
35<b>db_msgcall_fcn</b> function to display the message in an appropriate
36manner.</p>
37<p>Setting <b>db_msgcall_fcn</b> to NULL unconfigures the callback interface.</p>
38<p>Alternatively, you can use the <a href="../api_cxx/env_set_msg_stream.html">DbEnv::set_message_stream</a> and
39<a href="../api_cxx/db_set_msg_stream.html">Db::set_message_stream</a> methods to display the messages via an output
40stream, or the <a href="../api_cxx/db_set_msgfile.html">Db::set_msgfile</a> or <a href="../api_cxx/env_set_msgfile.html">DbEnv::set_msgfile</a> methods
41to display the messages via a C library FILE *.</p>
42<p>The DbEnv::set_msgcall method configures operations performed using the specified
43<a href="../api_cxx/env_class.html">DbEnv</a> handle, not all operations performed on the underlying
44database environment.</p>
45<p>The DbEnv::set_msgcall method may be called at any time during the life of the
46application.</p>
47<b>Parameters</b> <br>
48 <b>db_msgcall_fcn</b><ul compact><li>The <b>db_msgcall_fcn</b> parameter is the application-specified message
49reporting function.  The function takes two parameters:
50<br>
51<b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment.</ul>
52<b><b>msg</b></b><ul compact><li>The <b>msg</b> parameter is the message string.</ul>
53<br></ul>
54<p>Berkeley DB is not re-entrant.  Callback functions should not attempt to make
55library calls (for example, to release locks or close open handles).
56Re-entering Berkeley DB is not guaranteed to work correctly, and the results
57are undefined.</p>
58<br>
59<hr size=1 noshade>
60<br><b>Class</b>
61<a href="../api_cxx/env_class.html">DbEnv</a>
62<br><b>See Also</b>
63<a href="../api_cxx/env_list.html">Database Environments and Related Methods</a>
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