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<h2 class="title" style="clear: both"><a id="envset_msgcall"></a>DbEnv::set_msgcall()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db_cxx.h>
void DbEnv::set_msgcall(void (*db_msgcall_fcn)(const DbEnv *dbenv,
const 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 <code class="methodname">DbEnv::set_msgcall()</code> and
<a class="xref" href="dbset_msgcall.html" title="Db::set_msgcall()">Db::set_msgcall()</a>
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>
The <code class="methodname">DbEnv::set_msgcall()</code> method configures operations performed
using the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle, not all
operations performed on the underlying database environment.
</p>
<p>
The <code class="methodname">DbEnv::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>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
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<div>
<h3 class="title"><a id="idp7569320"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp7569512"></a>db_msgcall_fcn</h4>
</div>
</div>
</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>
</div>
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<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
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<h3 class="title"><a id="idp7573112"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
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<div>
<h3 class="title"><a id="idp7565376"></a>See Also</h3>
</div>
</div>
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<p>
<a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a>
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