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<div class="titlepage"><div><div><h4 class="title">
<a name="asio.reference.basic_signal_set.async_wait"></a><a class="link" href="async_wait.html" title="basic_signal_set::async_wait">basic_signal_set::async_wait</a>
</h4></div></div></div>
<p>
<a class="indexterm" name="asio.indexterm.basic_signal_set.async_wait"></a>
Start
an asynchronous operation to wait for a signal to be delivered.
</p>
<pre class="programlisting">template<
typename <a class="link" href="../SignalHandler.html" title="Signal handler requirements">SignalHandler</a> = <a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>>
<a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_wait(
SignalHandler && handler = <a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>);
</pre>
<p>
This function may be used to initiate an asynchronous wait against the
signal set. It always returns immediately.
</p>
<p>
For each call to <code class="computeroutput">async_wait()</code>, the supplied handler will be
called exactly once. The handler will be called when:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
One of the registered signals in the signal set occurs; or
</li>
<li class="listitem">
The signal set was cancelled, in which case the handler is passed the
error code <code class="computeroutput">asio::error::operation_aborted</code>.
</li>
</ul></div>
<h6>
<a name="asio.reference.basic_signal_set.async_wait.h0"></a>
<span><a name="asio.reference.basic_signal_set.async_wait.parameters"></a></span><a class="link" href="async_wait.html#asio.reference.basic_signal_set.async_wait.parameters">Parameters</a>
</h6>
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<p class="title"><b></b></p>
<dl>
<dt><span class="term">handler</span></dt>
<dd>
<p>
The handler to be called when the signal occurs. Copies will be made
of the handler as required. The function signature of the handler
must be:
</p>
<pre class="programlisting">void handler(
const asio::error_code& error, // Result of operation.
int signal_number // Indicates which signal occurred.
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M.
Kohlhoff<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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