ibm-information-center/dist/eclipse/plugins/i5OS.ic.apis_5.4.0.1/sigeset.htm

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<title>sigemptyset()--Initialize and Empty Signal Set</title>
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<h2>sigemptyset()--Initialize and Empty Signal Set</h2>
<div class="box" style="width: 60%;">
<br>
&nbsp;&nbsp;Syntax<br>
<pre>
#include &lt;signal.h&gt;
int sigemptyset( sigset_t <em>*set</em> );
</pre>
<br>
&nbsp;&nbsp;Service Program Name: QPOSSRV1<br>
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<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
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<br>
&nbsp;&nbsp;Threadsafe: Yes<br>
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<p>The <strong>sigemptyset()</strong> function is part of a family of functions
that manipulate signal sets. <strong>Signal sets</strong> are data objects that
let a thread keep track of groups of signals. For example, a thread might
create a signal set to record which signals it is blocking, and another signal
set to record which signals are pending. Signal sets are used to manipulate
groups of signals used by other functions (such as <strong>
sigprocmask()</strong>) or to examine signal sets returned by other functions
(such as <strong>sigpending()</strong>).</p>
<p><strong>sigemptyset()</strong> initializes the signal set specified by <em>
set</em> to an empty set. That is, all supported signals are excluded (see <a
href="sigactn.htm#TBLSIGTBL1">Control Signals Table</a>).</p>
<br>
<!-- Please NOTE: DO NOT DELETE THIS SECTION if this API has no authorities and locks. -->
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<h3>Authorities and Locks</h3>
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<p>None.</p>
<br>
<h3>Parameters</h3>
<dl>
<dt><strong><em>*set</em></strong></dt>
<dd>(Input) A pointer to a signal set.</dd>
</dl>
<br>
<h3>Return Value</h3>
<table cellpadding="5">
<!-- cols="5 95" -->
<tr>
<td align="left" valign="top"><em>0</em></td>
<td align="left" valign="top"><strong>sigemptyset()</strong> was
successful.</td>
</tr>
</table>
<br>
<br>
<h3>Error Conditions</h3>
<p>The <strong>sigemptyset()</strong> function does not return an error.</p>
<br>
<h3>Related Information</h3>
<ul>
<li>The &lt;<strong>signal.h</strong>&gt; file (see <a href="unix13.htm">Header
Files for UNIX-Type Functions</a>)<br>
<br>
</li>
<li><a href="sigactn.htm">sigaction()</a>--Examine and Change Signal Action<br>
<br>
</li>
<li><a href="sigaset.htm">sigaddset()</a>--Add Signal to Signal Set<br>
<br>
</li>
<li><a href="sigdset.htm">sigdelset()</a>--Delete Signal from Signal Set<br>
<br>
</li>
<li><a href="sigfset.htm">sigfillset()</a>--Initialize and Fill Signal Set<br>
<br>
</li>
<li><a href="sigismbr.htm">sigismember()</a>--Test for Signal in Signal Set<br>
<br>
</li>
<li><a href="sigpmsk.htm">sigprocmask()</a>--Examine and Change Blocked
Signals<br>
<br>
</li>
<li><a href="sigpend.htm">sigpending()</a>--Examine Pending Signals<br>
<br>
</li>
<li><a href="sigsusp.htm">sigsuspend()</a>--Wait for Signal<br>
<br>
</li>
<li><a href="sigtwait.htm">sigtimedwait()</a>--Synchronously Accept a Signal for
Interval of Time<br>
<br>
</li>
<li><a href="sigwait.htm">sigwait()</a>--Synchronously Accept a Signal<br>
<br>
</li>
<li><a href="sigwaiti.htm">sigwaitinfo()</a>--Synchronously Accept a Signal and
Signal Data</li>
</ul>
<br>
<h3>Example</h3>
<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
for information pertaining to code examples.</p>
<p>The following example initializes a set of signals to the empty set:</p>
<pre>
#include &lt;stdio.h&gt;
#include &lt;unistd.h&gt;
#include &lt;signal.h&gt;
int main( int argc, char *argv[] ) {
struct sigaction sigact;
sigset_t sigset;
sigemptyset( &amp;sigact.sa_mask );
sigact.sa_flags = 0;
sigact.sa_handler = SIG_IGN;
sigaction( SIGUSR2, &amp;sigact, NULL );
/*
* Unblocking all signals ensures that the signal
* handling action will be taken when the signal
* is generated.
*/
sigemptyset( &amp;sigset );
sigprocmask( SIG_SETMASK, &amp;sigset, NULL );
printf( "before kill()\n" );
kill( getpid(), SIGUSR2 );
printf( "after kill()\n" );
return( 0 );
}
</pre>
<br>
<h3>Output:</h3>
<pre>
before kill()
after kill()
</pre>
<br>
<hr>
API introduced: V3R6
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