1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Global std_in</title> 6<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../../process/reference.html#header.boost.process.io_hpp" title="Header <boost/process/io.hpp>"> 10<link rel="prev" href="null.html" title="Global null"> 11<link rel="next" href="std_out.html" title="Global std_out"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 16<td align="center"><a href="../../../../index.html">Home</a></td> 17<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="null.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../process/reference.html#header.boost.process.io_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="std_out.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="refentry"> 27<a name="boost.process.std_in"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Global std_in</span></h2> 30<p>boost::process::std_in</p> 31</div> 32<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 33<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../process/reference.html#header.boost.process.io_hpp" title="Header <boost/process/io.hpp>">boost/process/io.hpp</a>> 34 35</span><span class="emphasis"><em><span class="identifier">unspecified</span></em></span> std_in<span class="special">;</span></pre></div> 36<div class="refsect1"> 37<a name="id-1.3.30.9.16.18.4"></a><h2>Description</h2> 38<p>This property allows to set the input stream for the child process.</p> 39<div class="sect1"> 40<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 41<a name="namespaceboost_1_1process_1stdin_details"></a>Details</h2></div></div></div> 42<div class="toc"><dl class="toc"> 43<dt><span class="sect2"><a href="std_in.html#namespaceboost_1_1process_1stdin_file">File Input</a></span></dt> 44<dt><span class="sect2"><a href="std_in.html#namespaceboost_1_1process_1stdin_pipe">Pipe Input</a></span></dt> 45<dt><span class="sect2"><a href="std_in.html#namespaceboost_1_1process_1stdin_async_pipe">Asynchronous Pipe Input</a></span></dt> 46<dt><span class="sect2"><a href="std_in.html#namespaceboost_1_1process_1stdin_close">Close</a></span></dt> 47<dt><span class="sect2"><a href="std_in.html#namespaceboost_1_1process_1stdin_null">Null</a></span></dt> 48</dl></div> 49<div class="sect2"> 50<div class="titlepage"><div><div><h3 class="title"> 51<a name="namespaceboost_1_1process_1stdin_file"></a>File Input</h3></div></div></div> 52<p>The file I/O simple redirects the stream to a file, for which the possible types are</p> 53<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 54<li class="listitem"><p><code class="computeroutput">boost::filesystem::path</code></p></li> 55<li class="listitem"><p><code class="computeroutput">std::basic_string<char_type></code></p></li> 56<li class="listitem"><p><code class="computeroutput">const char_type*</code></p></li> 57<li class="listitem"><p><code class="computeroutput">FILE*</code></p></li> 58</ul></div> 59<p> 60</p> 61<p>with <code class="computeroutput">char_type</code> being either <code class="computeroutput">char</code> or <code class="computeroutput">wchar_t</code>.</p> 62<p>FILE* is explicitly added, so the process can easily redirect the output stream of the child to another output stream of the process. That is:</p> 63<pre class="programlisting"><span class="identifier">system</span><span class="special">(</span><span class="string">"ls"</span><span class="special">,</span> <span class="identifier">std_in</span> <span class="special"><</span> <span class="identifier">stdin</span><span class="special">)</span><span class="special">;</span> 64</pre> 65<div class="warning"><table border="0" summary="Warning"> 66<tr> 67<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../doc/src/images/warning.png"></td> 68<th align="left">Warning</th> 69</tr> 70<tr><td align="left" valign="top"><p>If the launching and the child process use the input, this leads to undefined behaviour.</p></td></tr> 71</table></div> 72<p> 73A syntax like <code class="computeroutput">system("ls", std_out > std::cerr)</code> is not possible, due to the C++ implementation not providing access to the handle.</p> 74<p>The valid expressions for this property are</p> 75<pre class="programlisting"><span class="identifier">std_in</span> <span class="special"><</span> <span class="identifier">file</span><span class="special">;</span> 76<span class="identifier">std_in</span> <span class="special">=</span> <span class="identifier">file</span><span class="special">;</span> 77</pre> 78</div> 79<div class="sect2"> 80<div class="titlepage"><div><div><h3 class="title"> 81<a name="namespaceboost_1_1process_1stdin_pipe"></a>Pipe Input</h3></div></div></div> 82<p>As explained in the corresponding section, the boost.process library provides a <a class="link" href="async_pipe.html" title="Class async_pipe">async_pipe</a> class which can be used to communicate with child processes.</p> 83<div class="note"><table border="0" summary="Note"> 84<tr> 85<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../doc/src/images/note.png"></td> 86<th align="left">Note</th> 87</tr> 88<tr><td align="left" valign="top"><p>Technically the <a class="link" href="async_pipe.html" title="Class async_pipe">async_pipe</a> works synchronous here, since no asio implementation is used by the library here. The async-operation will then however not end if the process is finished, since the pipe remains open. You can use the async_close function with on_exit to fix that.</p></td></tr> 89</table></div> 90<p> 91Valid expressions with pipes are these:</p> 92<pre class="programlisting"><span class="identifier">std_in</span> <span class="special"><</span> <span class="identifier">pipe</span><span class="special">;</span> 93<span class="identifier">std_in</span> <span class="special">=</span> <span class="identifier">pipe</span><span class="special">;</span> 94</pre> 95<p>Where the valid types for <code class="computeroutput">pipe</code> are the following:</p> 96<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 97<li class="listitem"><p><code class="computeroutput"><a class="link" href="basic_pipe.html" title="Class template basic_pipe">basic_pipe</a></code></p></li> 98<li class="listitem"><p><code class="computeroutput"><a class="link" href="async_pipe.html" title="Class async_pipe">async_pipe</a></code></p></li> 99<li class="listitem"><p><code class="computeroutput"><a class="link" href="basic_opstream.html" title="Class template basic_opstream">basic_opstream</a></code></p></li> 100<li class="listitem"><p><code class="computeroutput"><a class="link" href="basic_pstream.html" title="Class template basic_pstream">basic_pstream</a></code></p></li> 101</ul></div> 102<p> 103</p> 104<p>Note that the pipe may also be used between several processes, like this:</p> 105<pre class="programlisting"><span class="identifier">pipe</span> <span class="identifier">p</span><span class="special">;</span> 106<span class="identifier">child</span> <span class="identifier">c1</span><span class="special">(</span><span class="string">"nm"</span><span class="special">,</span> <span class="string">"a.out"</span><span class="special">,</span> <span class="identifier">std_out</span><span class="special">></span><span class="identifier">p</span><span class="special">)</span><span class="special">;</span> 107<span class="identifier">child</span> <span class="identifier">c2</span><span class="special">(</span><span class="string">"c++filt"</span><span class="special">,</span> <span class="identifier">std_in</span><span class="special"><</span><span class="identifier">p</span><span class="special">)</span><span class="special">;</span> 108</pre> 109</div> 110<div class="sect2"> 111<div class="titlepage"><div><div><h3 class="title"> 112<a name="namespaceboost_1_1process_1stdin_async_pipe"></a>Asynchronous Pipe Input</h3></div></div></div> 113<p>Asynchronous Pipe I/O classifies communication which has automatically handling of the asynchronous operations by the process library. This means, that a pipe will be constructed, the async_read/-write will be automatically started, and that the end of the child process will also close the pipe.</p> 114<p>Valid types for pipe I/O are the following:</p> 115<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 116<li class="listitem"><p><code class="computeroutput">boost::asio::const_buffer</code> <a href="#ftn.id-1.3.30.9.16.18.4.3.4.4.1.1.1.2" class="footnote" name="id-1.3.30.9.16.18.4.3.4.4.1.1.1.2"><sup class="footnote">[30]</sup></a> </p></li> 117<li class="listitem"><p><code class="computeroutput">boost::asio::mutable_buffer</code> <a href="#ftn.id-1.3.30.9.16.18.4.3.4.4.1.2.1.2" class="footnote" name="id-1.3.30.9.16.18.4.3.4.4.1.2.1.2"><sup class="footnote">[31]</sup></a> </p></li> 118<li class="listitem"><p><code class="computeroutput">boost::asio::streambuf</code></p></li> 119</ul></div> 120<p> 121</p> 122<p>Valid expressions with pipes are these:</p> 123<pre class="programlisting"><span class="identifier">std_in</span> <span class="special"><</span> <span class="identifier">buffer</span><span class="special">;</span> 124<span class="identifier">std_in</span> <span class="special">=</span> <span class="identifier">buffer</span><span class="special">;</span> 125<span class="identifier">std_out</span> <span class="special">></span> <span class="identifier">buffer</span><span class="special">;</span> 126<span class="identifier">std_out</span> <span class="special">=</span> <span class="identifier">buffer</span><span class="special">;</span> 127<span class="identifier">std_err</span> <span class="special">></span> <span class="identifier">buffer</span><span class="special">;</span> 128<span class="identifier">std_err</span> <span class="special">=</span> <span class="identifier">buffer</span><span class="special">;</span> 129<span class="special">(</span><span class="identifier">std_out</span> <span class="special">&</span> <span class="identifier">std_err</span><span class="special">)</span> <span class="special">></span> <span class="identifier">buffer</span><span class="special">;</span> 130<span class="special">(</span><span class="identifier">std_out</span> <span class="special">&</span> <span class="identifier">std_err</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">buffer</span><span class="special">;</span> 131</pre> 132<div class="note"><table border="0" summary="Note"> 133<tr> 134<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../doc/src/images/note.png"></td> 135<th align="left">Note</th> 136</tr> 137<tr><td align="left" valign="top"> 138<p>It is also possible to get a future for std_in, by chaining another <code class="computeroutput">std::future<void></code> onto it, so you can wait for the input to be completed. It looks like this: </p> 139<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">future</span><span class="special"><</span><span class="keyword">void</span><span class="special">></span> <span class="identifier">fut</span><span class="special">;</span> 140<span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_context</span> <span class="identifier">ios</span><span class="special">;</span> 141<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">data</span><span class="special">;</span> 142<span class="identifier">child</span> <span class="identifier">c</span><span class="special">(</span><span class="string">"prog"</span><span class="special">,</span> <span class="identifier">std_in</span> <span class="special"><</span> <span class="identifier">buffer</span><span class="special">(</span><span class="identifier">data</span><span class="special">)</span> <span class="special">></span> <span class="identifier">fut</span><span class="special">,</span> <span class="identifier">ios</span><span class="special">)</span><span class="special">;</span> 143<span class="identifier">fut</span><span class="special">.</span><span class="identifier">get</span><span class="special">(</span><span class="special">)</span><span class="special">;</span> 144</pre> 145</td></tr> 146</table></div> 147<p> 148</p> 149<div class="note"><table border="0" summary="Note"> 150<tr> 151<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../doc/src/images/note.png"></td> 152<th align="left">Note</th> 153</tr> 154<tr><td align="left" valign="top"><p><code class="computeroutput">boost::asio::buffer</code> is also available in the <code class="computeroutput">boost::process</code> namespace.</p></td></tr> 155</table></div> 156<p> 157</p> 158<div class="warning"><table border="0" summary="Warning"> 159<tr> 160<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../doc/src/images/warning.png"></td> 161<th align="left">Warning</th> 162</tr> 163<tr><td align="left" valign="top"><p>This feature requires <code class="computeroutput">boost/process/async.hpp</code> to be included and a reference to <code class="computeroutput">boost::asio::io_context</code> to be passed to the launching function.</p></td></tr> 164</table></div> 165<p> 166</p> 167</div> 168<div class="sect2"> 169<div class="titlepage"><div><div><h3 class="title"> 170<a name="namespaceboost_1_1process_1stdin_close"></a>Close</h3></div></div></div> 171<p>The input stream can be closed, so it cannot be read from. This will lead to an error when attempted.</p> 172<p>This can be achieved by the following syntax.</p> 173<pre class="programlisting"><span class="identifier">std_in</span> <span class="special"><</span> <span class="identifier">close</span><span class="special">;</span> 174<span class="identifier">std_in</span> <span class="special">=</span> <span class="identifier">close</span><span class="special">;</span> 175<span class="identifier">std_in</span><span class="special">.</span><span class="identifier">close</span><span class="special">(</span><span class="special">)</span><span class="special">;</span> 176</pre> 177</div> 178<div class="sect2"> 179<div class="titlepage"><div><div><h3 class="title"> 180<a name="namespaceboost_1_1process_1stdin_null"></a>Null</h3></div></div></div> 181<p>The input stream can be redirected to read from the null-device, which means that only <code class="computeroutput">EOF</code> is read.</p> 182<p>The syntax to achieve that has the following variants:</p> 183<pre class="programlisting"><span class="identifier">std_in</span> <span class="special"><</span> <span class="identifier">null</span><span class="special">;</span> 184<span class="identifier">std_in</span> <span class="special">=</span> <span class="identifier">null</span><span class="special">;</span> 185<span class="identifier">std_in</span><span class="special">.</span><span class="identifier">null</span><span class="special">(</span><span class="special">)</span><span class="special">;</span> 186</pre> 187<p> </p> 188</div> 189</div> 190</div> 191<div class="footnotes"> 192<br><hr style="width:100; text-align:left;margin-left: 0"> 193<div id="ftn.id-1.3.30.9.16.18.4.3.4.4.1.1.1.2" class="footnote"><p><a href="#id-1.3.30.9.16.18.4.3.4.4.1.1.1.2" class="para"><sup class="para">[30] </sup></a> Constructed with <code class="computeroutput">boost::asio::buffer</code></p></div> 194<div id="ftn.id-1.3.30.9.16.18.4.3.4.4.1.2.1.2" class="footnote"><p><a href="#id-1.3.30.9.16.18.4.3.4.4.1.2.1.2" class="para"><sup class="para">[31] </sup></a> Constructed with <code class="computeroutput">boost::asio::buffer</code></p></div> 195</div> 196</div> 197<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 198<td align="left"></td> 199<td align="right"><div class="copyright-footer">Copyright © 2006-2012 Julio M. Merino Vidal, Ilya Sokolov, 200 Felipe Tanus, Jeff Flinn, Boris Schaeling<br>Copyright © 2016 Klemens D. Morgenstern<p> 201 Distributed under the Boost Software License, Version 1.0. (See accompanying 202 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 203 </p> 204</div></td> 205</tr></table> 206<hr> 207<div class="spirit-nav"> 208<a accesskey="p" href="null.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../process/reference.html#header.boost.process.io_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="std_out.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 209</div> 210</body> 211</html> 212
