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<h4 class="subsection">18.2.4 setlogmask</h4>

<p>The symbols referred to in this section are declared in the file
<samp><span class="file">syslog.h</span></samp>.

<!-- syslog.h -->
<!-- BSD -->
<div class="defun">
&mdash; Function: int <b>setlogmask</b> (<var>int mask</var>)<var><a name="index-setlogmask-2065"></a></var><br>
<blockquote>
        <p><code>setlogmask</code> sets a mask (the &ldquo;logmask&rdquo;) that determines which
future <code>syslog</code> calls shall be ignored.  If a program has not
called <code>setlogmask</code>, <code>syslog</code> doesn't ignore any calls.  You
can use <code>setlogmask</code> to specify that messages of particular
priorities shall be ignored in the future.

        <p>A <code>setlogmask</code> call overrides any previous <code>setlogmask</code> call.

        <p>Note that the logmask exists entirely independently of opening and
closing of Syslog connections.

        <p>Setting the logmask has a similar effect to, but is not the same as,
configuring Syslog.  The Syslog configuration may cause Syslog to
discard certain messages it receives, but the logmask causes certain
messages never to get submitted to Syslog in the first place.

        <p><var>mask</var> is a bit string with one bit corresponding to each of the
possible message priorities.  If the bit is on, <code>syslog</code> handles
messages of that priority normally.  If it is off, <code>syslog</code>
discards messages of that priority.  Use the message priority macros
described in <a href="syslog_003b-vsyslog.html#syslog_003b-vsyslog">syslog; vsyslog</a> and the <code>LOG_MASK</code> to construct
an appropriate <var>mask</var> value, as in this example:

     <pre class="smallexample">          LOG_MASK(LOG_EMERG) | LOG_MASK(LOG_ERROR)
</pre>
        <p>or

     <pre class="smallexample">          ~(LOG_MASK(LOG_INFO))
</pre>
        <p>There is also a <code>LOG_UPTO</code> macro, which generates a mask with the bits
on for a certain priority and all priorities above it:

     <pre class="smallexample">          LOG_UPTO(LOG_ERROR)
</pre>
        <p>The unfortunate naming of the macro is due to the fact that internally,
higher numbers are used for lower message priorities.

        </blockquote></div>

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