1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>basic_signal_set::async_wait</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../boost_asio.html" title="Boost.Asio"> 8<link rel="up" href="../basic_signal_set.html" title="basic_signal_set"> 9<link rel="prev" href="add/overload2.html" title="basic_signal_set::add (2 of 2 overloads)"> 10<link rel="next" href="basic_signal_set.html" title="basic_signal_set::basic_signal_set"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="add/overload2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../basic_signal_set.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="basic_signal_set.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="boost_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> 28</h4></div></div></div> 29<p> 30 <a class="indexterm" name="boost_asio.indexterm.basic_signal_set.async_wait"></a> 31Start 32 an asynchronous operation to wait for a signal to be delivered. 33 </p> 34<pre class="programlisting">template< 35 typename <a class="link" href="../SignalHandler.html" title="Signal handler requirements">SignalHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>> 36<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_wait( 37 SignalHandler && handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>); 38</pre> 39<p> 40 This function may be used to initiate an asynchronous wait against the 41 signal set. It always returns immediately. 42 </p> 43<p> 44 For each call to <code class="computeroutput">async_wait()</code>, the supplied handler will be 45 called exactly once. The handler will be called when: 46 </p> 47<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 48<li class="listitem"> 49 One of the registered signals in the signal set occurs; or 50 </li> 51<li class="listitem"> 52 The signal set was cancelled, in which case the handler is passed the 53 error code <code class="computeroutput">boost::asio::error::operation_aborted</code>. 54 </li> 55</ul></div> 56<h6> 57<a name="boost_asio.reference.basic_signal_set.async_wait.h0"></a> 58 <span class="phrase"><a name="boost_asio.reference.basic_signal_set.async_wait.parameters"></a></span><a class="link" href="async_wait.html#boost_asio.reference.basic_signal_set.async_wait.parameters">Parameters</a> 59 </h6> 60<div class="variablelist"> 61<p class="title"><b></b></p> 62<dl class="variablelist"> 63<dt><span class="term">handler</span></dt> 64<dd> 65<p> 66 The handler to be called when the signal occurs. Copies will be made 67 of the handler as required. The function signature of the handler 68 must be: 69</p> 70<pre class="programlisting">void handler( 71 const boost::system::error_code& error, // Result of operation. 72 int signal_number // Indicates which signal occurred. 73); 74</pre> 75<p> 76 Regardless of whether the asynchronous operation completes immediately 77 or not, the handler will not be invoked from within this function. 78 On immediate completion, invocation of the handler will be performed 79 in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>. 80 </p> 81</dd> 82</dl> 83</div> 84</div> 85<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 86<td align="left"></td> 87<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 88 Kohlhoff<p> 89 Distributed under the Boost Software License, Version 1.0. (See accompanying 90 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>) 91 </p> 92</div></td> 93</tr></table> 94<hr> 95<div class="spirit-nav"> 96<a accesskey="p" href="add/overload2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../basic_signal_set.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="basic_signal_set.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 97</div> 98</body> 99</html> 100
