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<h2 class="title" style="clear: both"><a id="dbset_msgcall"></a>Db::set_msgcall()</h2>
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<pre class="programlisting">#include <db_cxx.h>
void Db::set_msgcall(void (*db_msgcall_fcn)(const DbEnv *dbenv, char *msg));</pre>
<p>
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, <a class="xref" href="envset_verbose.html" title="DbEnv::set_verbose()">DbEnv::set_verbose()</a> and
<a class="xref" href="envstat.html" title="DbEnv::stat_print()">DbEnv::stat_print()</a>.
</p>
<p>
The <a class="xref" href="envset_msgcall.html" title="DbEnv::set_msgcall()">DbEnv::set_msgcall()</a> and
<code class="methodname">Db::set_msgcall()</code> methods are used to
pass these messages to the application, and Berkeley DB will call
<span class="bold"><strong>db_msgcall_fcn</strong></span> with each message. It
is up to the <span class="bold"><strong>db_msgcall_fcn</strong></span> function
to display the message in an appropriate manner.
</p>
<p>
Setting <span class="bold"><strong>db_msgcall_fcn</strong></span> to NULL
unconfigures the callback interface.
</p>
<p>
Alternatively, you can use the
<span>
<a class="xref" href="envset_error_stream.html" title="DbEnv::set_error_stream()">DbEnv::set_error_stream()</a>
and
<a class="xref" href="dbset_error_stream.html" title="Db::set_error_stream()">Db::set_error_stream()</a>
methods to display the messages via an output stream, or the
</span>
<a class="xref" href="dbset_msgfile.html" title="Db::set_msgfile()">Db::set_msgfile()</a> or
<a class="xref" href="envset_msgfile.html" title="DbEnv::set_msgfile()">Db::set_msgfile()</a>
methods to display the messages via a C library FILE *.
<span>You should not mix these approaches.</span>
</p>
<p>
For <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> handles opened
inside of Berkeley DB environments, calling the <code class="methodname">Db::set_msgcall()</code>
method affects the entire environment and is equivalent to calling the
<code class="methodname">DbEnv::set_msgcall()</code> method.
</p>
<p>
The <code class="methodname">Db::set_msgcall()</code> method configures operations performed using
the specified <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> handle,
not all operations performed on the underlying database.
</p>
<p>
The <code class="methodname">Db::set_msgcall()</code> method may be called at any time during the
life of the application.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
Berkeley DB is not re-entrant. Callback functions should not attempt to make
library calls (for example, to release locks or close open handles). Re-entering
Berkeley DB is not guaranteed to work correctly, and the results are undefined.
</p>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="id1649522"></a>Parameters</h3>
</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div>
<h4 class="title"><a id="id1649510"></a>db_msgcall_fcn</h4>
</div>
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</div>
<p>
The <span class="bold"><strong>db_msgcall_fcn</strong></span> parameter is the
application-specified message reporting function. The function takes
two parameters:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">dbenv</code>
</p>
<p>
The <span class="bold"><strong>dbenv</strong></span> parameter is the enclosing
database environment.
</p>
</li>
<li>
<p>
<code class="literal">msg</code>
</p>
<p>
The <span class="bold"><strong>msg</strong></span> parameter is the message
string.
</p>
</li>
</ul>
</div>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="id1649700"></a>Class</h3>
</div>
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<p>
<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a>
</p>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="id1649626"></a>See Also</h3>
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<p>
<a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a>
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