doc/html/boost_asio/overview/posix/stream_descriptor.html

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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="boost_asio.overview.posix.stream_descriptor"></a><a class="link" href="stream_descriptor.html" title="Stream-Oriented File Descriptors">Stream-Oriented
  28         File Descriptors</a>
  29 </h4></div></div></div>
  30 <p>
  31           Boost.Asio includes classes added to permit synchronous and asynchronous
  32           read and write operations to be performed on POSIX file descriptors, such
  33           as pipes, standard input and output, and various devices.
  34         </p>
  35 <p>
  36           These classes also provide limited support for regular files. This support
  37           assumes that the underlying read and write operations provided by the operating
  38           system never fail with <code class="computeroutput"><span class="identifier">EAGAIN</span></code>
  39           or <code class="computeroutput"><span class="identifier">EWOULDBLOCK</span></code>. (This assumption
  40           normally holds for buffered file I/O.) Synchronous and asynchronous read
  41           and write operations on file descriptors will succeed but the I/O will
  42           always be performed immediately. Wait operations, and operations involving
  43           <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">null_buffers</span></code>, are not portably supported.
  44         </p>
  45 <p>
  46           For example, to perform read and write operations on standard input and
  47           output, the following objects may be created:
  48         </p>
  49 <pre class="programlisting"><span class="identifier">posix</span><span class="special">::</span><span class="identifier">stream_descriptor</span> <span class="identifier">in</span><span class="special">(</span><span class="identifier">my_io_service</span><span class="special">,</span> <span class="special">::</span><span class="identifier">dup</span><span class="special">(</span><span class="identifier">STDIN_FILENO</span><span class="special">));</span>
  50 <span class="identifier">posix</span><span class="special">::</span><span class="identifier">stream_descriptor</span> <span class="identifier">out</span><span class="special">(</span><span class="identifier">my_io_service</span><span class="special">,</span> <span class="special">::</span><span class="identifier">dup</span><span class="special">(</span><span class="identifier">STDOUT_FILENO</span><span class="special">));</span>
  51 </pre>
  52 <p>
  53           These are then used as synchronous or asynchronous read and write streams.
  54           This means the objects can be used with any of the <a class="link" href="../../reference/read.html" title="read">read()</a>,
  55           <a class="link" href="../../reference/async_read.html" title="async_read">async_read()</a>, <a class="link" href="../../reference/write.html" title="write">write()</a>, <a class="link" href="../../reference/async_write.html" title="async_write">async_write()</a>,
  56           <a class="link" href="../../reference/read_until.html" title="read_until">read_until()</a> or
  57           <a class="link" href="../../reference/async_read_until.html" title="async_read_until">async_read_until()</a>
  58           free functions.
  59         </p>
  60 <h6>
  61 <a name="boost_asio.overview.posix.stream_descriptor.h0"></a>
  62           <span class="phrase"><a name="boost_asio.overview.posix.stream_descriptor.see_also"></a></span><a class="link" href="stream_descriptor.html#boost_asio.overview.posix.stream_descriptor.see_also">See Also</a>
  63         </h6>
  64 <p>
  65           <a class="link" href="../../reference/posix__stream_descriptor.html" title="posix::stream_descriptor">posix::stream_descriptor</a>,
  66           <a class="link" href="../../reference/posix__basic_stream_descriptor.html" title="posix::basic_stream_descriptor">posix::basic_stream_descriptor</a>,
  67           <a class="link" href="../../reference/posix__stream_descriptor_service.html" title="posix::stream_descriptor_service">posix::stream_descriptor_service</a>,
  68           <a class="link" href="../../examples/cpp03_examples.html#boost_asio.examples.cpp03_examples.chat">Chat example (C++03)</a>,
  69           <a class="link" href="../../examples/cpp11_examples.html#boost_asio.examples.cpp11_examples.chat">Chat example (C++11)</a>.
  70         </p>
  71 <h6>
  72 <a name="boost_asio.overview.posix.stream_descriptor.h1"></a>
  73           <span class="phrase"><a name="boost_asio.overview.posix.stream_descriptor.notes"></a></span><a class="link" href="stream_descriptor.html#boost_asio.overview.posix.stream_descriptor.notes">Notes</a>
  74         </h6>
  75 <p>
  76           POSIX stream descriptors are only available at compile time if supported
  77           by the target operating system. A program may test for the macro <code class="computeroutput"><span class="identifier">BOOST_ASIO_HAS_POSIX_STREAM_DESCRIPTOR</span></code>
  78           to determine whether they are supported.
  79         </p>
  80 </div>
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  83 <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2017 Christopher M. Kohlhoff<p>
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  85         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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