1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Stream-Oriented File Descriptors</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="../posix.html" title="POSIX-Specific Functionality"> 9<link rel="prev" href="local.html" title="UNIX Domain Sockets"> 10<link rel="next" href="fork.html" title="Fork"> 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="local.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../posix.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="fork.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.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">EAGAIN</code> or <code class="computeroutput">EWOULDBLOCK</code>. 39 (This assumption normally holds for buffered file I/O.) Synchronous and 40 asynchronous read and write operations on file descriptors will succeed 41 but the I/O will always be performed immediately. Wait operations, and 42 operations involving <code class="computeroutput">boost::asio::null_buffers</code>, are not portably 43 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">posix::stream_descriptor in(my_io_context, ::dup(STDIN_FILENO)); 50posix::stream_descriptor out(my_io_context, ::dup(STDOUT_FILENO)); 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="../../examples/cpp03_examples.html#boost_asio.examples.cpp03_examples.chat">Chat example (C++03)</a>, 67 <a class="link" href="../../examples/cpp11_examples.html#boost_asio.examples.cpp11_examples.chat">Chat example (C++11)</a>. 68 </p> 69<h6> 70<a name="boost_asio.overview.posix.stream_descriptor.h1"></a> 71 <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> 72 </h6> 73<p> 74 POSIX stream descriptors are only available at compile time if supported 75 by the target operating system. A program may test for the macro <code class="computeroutput">BOOST_ASIO_HAS_POSIX_STREAM_DESCRIPTOR</code> 76 to determine whether they are supported. 77 </p> 78</div> 79<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 80<td align="left"></td> 81<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 82 Kohlhoff<p> 83 Distributed under the Boost Software License, Version 1.0. (See accompanying 84 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>) 85 </p> 86</div></td> 87</tr></table> 88<hr> 89<div class="spirit-nav"> 90<a accesskey="p" href="local.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../posix.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="fork.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 91</div> 92</body> 93</html> 94
