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| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_asio.overview.posix.fork"></a><a class="link" href="fork.html" title="Fork">Fork</a> |
| </h4></div></div></div> |
| <p> |
| Boost.Asio supports programs that utilise the <code class="computeroutput"><span class="identifier">fork</span><span class="special">()</span></code> system call. Provided the program calls |
| <code class="computeroutput"><span class="identifier">io_service</span><span class="special">.</span><span class="identifier">notify_fork</span><span class="special">()</span></code> |
| at the appropriate times, Boost.Asio will recreate any internal file descriptors |
| (such as the "self-pipe trick" descriptor used for waking up |
| a reactor). The notification is usually performed as follows: |
| </p> |
| <pre class="programlisting"><span class="identifier">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> |
| <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> |
| <span class="special">{</span> |
| <span class="identifier">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> |
| <span class="special">...</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> |
| <span class="special">{</span> |
| <span class="identifier">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> |
| <span class="special">...</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| User-defined services can also be made fork-aware by overriding the <code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">service</span><span class="special">::</span><span class="identifier">fork_service</span><span class="special">()</span></code> |
| virtual function. |
| </p> |
| <p> |
| Note that any file descriptors accessible via Boost.Asio's public API (e.g. |
| the descriptors underlying <code class="computeroutput"><span class="identifier">basic_socket</span><span class="special"><></span></code>, <code class="computeroutput"><span class="identifier">posix</span><span class="special">::</span><span class="identifier">stream_descriptor</span></code>, |
| etc.) are not altered during a fork. It is the program's responsibility |
| to manage these as required. |
| </p> |
| <h6> |
| <a name="boost_asio.overview.posix.fork.h0"></a> |
| <span class="phrase"><a name="boost_asio.overview.posix.fork.see_also"></a></span><a class="link" href="fork.html#boost_asio.overview.posix.fork.see_also">See |
| Also</a> |
| </h6> |
| <p> |
| <a class="link" href="../../reference/io_service/notify_fork.html" title="io_service::notify_fork">io_service::notify_fork()</a>, |
| <a class="link" href="../../reference/io_service/fork_event.html" title="io_service::fork_event">io_service::fork_event</a>, |
| <a class="link" href="../../reference/io_service__service/fork_service.html" title="io_service::service::fork_service">io_service::service::fork_service()</a>, |
| <a class="link" href="../../examples/cpp03_examples.html#boost_asio.examples.cpp03_examples.fork">Fork examples</a>. |
| </p> |
| </div> |
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| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2003-2015 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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