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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="boost_asio.reference.io_service.notify_fork"></a><a class="link" href="notify_fork.html" title="io_service::notify_fork">io_service::notify_fork</a>
  28 </h4></div></div></div>
  29 <p>
  30           <a class="indexterm" name="idp171472736"></a>
  31 Notify the <a class="link" href="../io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> of a fork-related event.
  32         </p>
  33 <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">notify_fork</span><span class="special">(</span>
  34     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">fork_event</span> <span class="identifier">event</span><span class="special">);</span>
  35 </pre>
  36 <p>
  37           This function is used to inform the <a class="link" href="../io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> that the process is
  38           about to fork, or has just forked. This allows the <a class="link" href="../io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>, and the services it
  39           contains, to perform any necessary housekeeping to ensure correct operation
  40           following a fork.
  41         </p>
  42 <p>
  43           This function must not be called while any other <a class="link" href="../io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> function, or any function
  44           on an I/O object associated with the <a class="link" href="../io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>, is being called in
  45           another thread. It is, however, safe to call this function from within
  46           a completion handler, provided no other thread is accessing the <a class="link" href="../io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>.
  47         </p>
  48 <h6>
  49 <a name="boost_asio.reference.io_service.notify_fork.h0"></a>
  50           <span class="phrase"><a name="boost_asio.reference.io_service.notify_fork.parameters"></a></span><a class="link" href="notify_fork.html#boost_asio.reference.io_service.notify_fork.parameters">Parameters</a>
  51         </h6>
  52 <div class="variablelist">
  53 <p class="title"><b></b></p>
  54 <dl class="variablelist">
  55 <dt><span class="term">event</span></dt>
  56 <dd><p>
  57                 A fork-related event.
  58               </p></dd>
  59 </dl>
  60 </div>
  61 <h6>
  62 <a name="boost_asio.reference.io_service.notify_fork.h1"></a>
  63           <span class="phrase"><a name="boost_asio.reference.io_service.notify_fork.exceptions"></a></span><a class="link" href="notify_fork.html#boost_asio.reference.io_service.notify_fork.exceptions">Exceptions</a>
  64         </h6>
  65 <div class="variablelist">
  66 <p class="title"><b></b></p>
  67 <dl class="variablelist">
  68 <dt><span class="term">boost::system::system_error</span></dt>
  69 <dd><p>
  70                 Thrown on failure. If the notification fails the <a class="link" href="../io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> object should
  71                 no longer be used and should be destroyed.
  72               </p></dd>
  73 </dl>
  74 </div>
  75 <h6>
  76 <a name="boost_asio.reference.io_service.notify_fork.h2"></a>
  77           <span class="phrase"><a name="boost_asio.reference.io_service.notify_fork.example"></a></span><a class="link" href="notify_fork.html#boost_asio.reference.io_service.notify_fork.example">Example</a>
  78         </h6>
  79 <p>
  80           The following code illustrates how to incorporate the <code class="computeroutput"><span class="identifier">notify_fork</span><span class="special">()</span></code> function:
  81         </p>
  82 <pre class="programlisting"><span class="identifier">my_io_service</span><span class="special">.</span><span class="identifier">notify_fork</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">fork_prepare</span><span class="special">);</span>
  83 <span class="keyword">if</span> <span class="special">(</span><span class="identifier">fork</span><span class="special">()</span> <span class="special">==</span> <span class="number">0</span><span class="special">)</span>
  84 <span class="special">{</span>
  85   <span class="comment">// This is the child process.</span>
  86   <span class="identifier">my_io_service</span><span class="special">.</span><span class="identifier">notify_fork</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">fork_child</span><span class="special">);</span>
  87 <span class="special">}</span>
  88 <span class="keyword">else</span>
  89 <span class="special">{</span>
  90   <span class="comment">// This is the parent process.</span>
  91   <span class="identifier">my_io_service</span><span class="special">.</span><span class="identifier">notify_fork</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">fork_parent</span><span class="special">);</span>
  92 <span class="special">}</span>
  93 </pre>
  94 <h6>
  95 <a name="boost_asio.reference.io_service.notify_fork.h3"></a>
  96           <span class="phrase"><a name="boost_asio.reference.io_service.notify_fork.remarks"></a></span><a class="link" href="notify_fork.html#boost_asio.reference.io_service.notify_fork.remarks">Remarks</a>
  97         </h6>
  98 <p>
  99           For each service object <code class="computeroutput"><span class="identifier">svc</span></code>
 100           in the <a class="link" href="../io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>
 101           set, performs <code class="computeroutput"><span class="identifier">svc</span><span class="special">-&gt;</span><span class="identifier">fork_service</span><span class="special">();</span></code>.
 102           When processing the fork_prepare event, services are visited in reverse
 103           order of the beginning of service object lifetime. Otherwise, services
 104           are visited in order of the beginning of service object lifetime.
 105         </p>
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