85 lines
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85 lines
4.9 KiB
HTML
<html>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<title>Fork</title>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="boost_asio.overview.posix.fork"></a><a class="link" href="fork.html" title="Fork">Fork</a>
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</h4></div></div></div>
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<p>
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Boost.Asio supports programs that utilise the <code class="computeroutput">fork()</code> system
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call. Provided the program calls <code class="computeroutput">io_context.notify_fork()</code>
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at the appropriate times, Boost.Asio will recreate any internal file descriptors
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(such as the "self-pipe trick" descriptor used for waking up
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a reactor). The notification is usually performed as follows:
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</p>
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<pre class="programlisting">io_context_.notify_fork(boost::asio::io_context::fork_prepare);
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if (fork() == 0)
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{
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io_context_.notify_fork(boost::asio::io_context::fork_child);
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...
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}
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else
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{
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io_context_.notify_fork(boost::asio::io_context::fork_parent);
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...
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}
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</pre>
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<p>
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User-defined services can also be made fork-aware by overriding the <code class="computeroutput">io_context::service::notify_fork()</code>
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virtual function.
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</p>
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<p>
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Note that any file descriptors accessible via Boost.Asio's public API (e.g.
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the descriptors underlying <code class="computeroutput">basic_socket<></code>, <code class="computeroutput">posix::stream_descriptor</code>,
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etc.) are not altered during a fork. It is the program's responsibility
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to manage these as required.
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</p>
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<h6>
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<a name="boost_asio.overview.posix.fork.h0"></a>
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<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
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Also</a>
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</h6>
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<p>
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<a class="link" href="../../reference/io_context/notify_fork.html" title="io_context::notify_fork">io_context::notify_fork()</a>,
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<a class="link" href="../../reference/io_context/fork_event.html" title="io_context::fork_event">io_context::fork_event</a>,
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<a class="link" href="../../reference/execution_context__service/notify_fork.html" title="execution_context::service::notify_fork">io_context::service::notify_fork()</a>,
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<a class="link" href="../../examples/cpp03_examples.html#boost_asio.examples.cpp03_examples.fork">Fork examples</a>.
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</p>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2021 Christopher
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M. Kohlhoff<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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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</p>
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