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  26 <div class="refentry">
  27 <a name="boost.process.extend.posix_executor"></a><div class="titlepage"></div>
  28 <div class="refnamediv">
  29 <h2><span class="refentrytitle">Struct template posix_executor</span></h2>
  30 <p>boost::process::extend::posix_executor &#8212; The posix executor type. </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: &lt;<a class="link" href="../../../process/reference.html#header.boost.process.extend_hpp" title="Header &lt;boost/process/extend.hpp&gt;">boost/process/extend.hpp</a>&gt;
  34
  35 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Sequence<span class="special">&gt;</span>
  36 <span class="keyword">struct</span> <a class="link" href="posix_executor.html" title="Struct template posix_executor">posix_executor</a> <span class="special">{</span>
  37
  38   <span class="comment">// <a class="link" href="posix_executor.html#idm45170604831472-bb">public member functions</a></span>
  39   <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&amp;</span> <a class="link" href="posix_executor.html#idm45170604830912-bb"><span class="identifier">error</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  40   <span class="keyword">void</span> <a class="link" href="posix_executor.html#idm45170604829440-bb"><span class="identifier">set_error</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  41   <span class="keyword">void</span> <a class="link" href="posix_executor.html#idm45170604825872-bb"><span class="identifier">set_error</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="special">)</span><span class="special">;</span>
  42
  43   <span class="comment">// public data members</span>
  44   <span class="identifier">Sequence</span> <span class="special">&amp;</span> <span class="identifier">seq</span><span class="special">;</span>  <span class="comment">// A reference to the actual initializer-sequence. </span>
  45   <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span> <span class="identifier">exe</span><span class="special">;</span>  <span class="comment">// A pointer to the name of the executable. </span>
  46   <span class="keyword">char</span> <span class="special">*</span><span class="keyword">const</span>  <span class="special">*</span> <span class="identifier">cmd_line</span><span class="special">;</span>  <span class="comment">// A pointer to the argument-vector. </span>
  47   <span class="keyword">char</span> <span class="special">*</span><span class="special">*</span> <span class="identifier">env</span><span class="special">;</span>  <span class="comment">// A pointer to the environment variables, as default it is set to <a href="http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html" target="_top">environ</a></span>
  48   <span class="identifier">pid_t</span> <span class="identifier">pid</span><span class="special">;</span>  <span class="comment">// The pid of the process - it will be -1 before invoking <a href="http://pubs.opengroup.org/onlinepubs/009695399/functions/fork.html" target="_top">fork</a>, and after forking either 0 for the new process or a positive value if in the current process. */. </span>
  49   <span class="identifier">std</span><span class="special">::</span><span class="identifier">shared_ptr</span><span class="special">&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">atomic</span><span class="special">&lt;</span> <span class="keyword">int</span> <span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">exit_status</span><span class="special">;</span>  <span class="comment">// This shared-pointer holds the exit code. It's done this way, so it can be shared between an <code class="computeroutput">asio::io_context</code> and <a class="link" href="../child.html" title="Class child">child</a>. </span>
  50 <span class="special">}</span><span class="special">;</span></pre></div>
  51 <div class="refsect1">
  52 <a name="id-1.3.31.9.13.7.4"></a><h2>Description</h2>
  53 <p>This type represents the posix executor and can be used for overloading in a custom handler. </p>
  54 <div class="note"><table border="0" summary="Note">
  55 <tr>
  56 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
  57 <th align="left">Note</th>
  58 </tr>
  59 <tr><td align="left" valign="top"><p>It is an alias for the implementation on posix, and a forward-declaration on windows.</p></td></tr>
  60 </table></div>
  61 <p>
  62
  63
  64 As information for extension development, here is the structure of the process launching (in pseudo-code and uml)
  65 </p>
  66 <pre class="programlisting">
  67 <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
  68     <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604907072-bb">on_setup</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">)</span><span class="special">;</span>
  69
  70 <span class="keyword">if</span> <span class="special">(</span><a class="link" href="posix_executor.html#idm45170604830912-bb">error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span>
  71 <span class="special">{</span>
  72     <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
  73        <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604903088-bb">on_error</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">,</span> <a class="link" href="posix_executor.html#idm45170604830912-bb">error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
  74     <span class="keyword">return</span> <a class="link" href="../child.html" title="Class child">child</a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  75 <span class="special">}</span>
  76
  77 <span class="identifier">pid</span> <span class="special">=</span> <a href="http://pubs.opengroup.org/onlinepubs/009695399/functions/fork.html" target="_top"><span class="identifier">fork</span><span class="special">(</span><span class="special">)</span></a>
  78 <a class="link" href="handler.html#idm45170604907072-bb">on_setup</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">)</span><span class="special">;</span>
  79
  80 <span class="keyword">if</span> <span class="special">(</span><span class="identifier">pid</span> <span class="special">==</span> <span class="special">-</span><span class="number">1</span><span class="special">)</span> <span class="comment">//fork error </span>
  81 <span class="special">{</span>
  82     <a class="link" href="posix_executor.html#idm45170604829440-bb">set_error</a><span class="special">(</span><a class="link" href="../../../process/reference.html#boost.process.extend.get_last_error">get_last_error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
  83     <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
  84         <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604894640-bb">on_fork_error</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">,</span> <a class="link" href="posix_executor.html#idm45170604830912-bb">error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
  85     <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
  86         <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604903088-bb">on_error</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">,</span> <a class="link" href="posix_executor.html#idm45170604830912-bb">error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
  87     <span class="keyword">return</span> <a class="link" href="../child.html" title="Class child">child</a><span class="special">(</span><span class="special">)</span>
  88 <span class="special">}</span>
  89 <span class="keyword">else</span> <span class="keyword">if</span> <span class="special">(</span><span class="identifier">pid</span> <span class="special">==</span> <span class="number">0</span><span class="special">)</span> <span class="comment">//child process</span>
  90 <span class="special">{</span>
  91     <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
  92         <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604889616-bb">on_exec_setup</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">)</span><span class="special">;</span>
  93     <a href="http://pubs.opengroup.org/onlinepubs/009695399/functions/exec.html" target="_top"><span class="identifier">execve</span></a><span class="special">(</span><span class="identifier">exe</span><span class="special">,</span> <span class="identifier">cmd_line</span><span class="special">,</span> <span class="identifier">env</span><span class="special">)</span><span class="special">;</span>
  94     <span class="keyword">auto</span> <span class="identifier">ec</span> <span class="special">=</span> <a class="link" href="../../../process/reference.html#boost.process.extend.get_last_error">get_last_error</a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  95     <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
  96         <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604884064-bb">on_exec_error</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">)</span><span class="special">;</span>
  97
  98     <span class="emphasis"><em><span class="identifier">unspecified</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></em></span><span class="comment">//here the error is send to the father process interally</span>
  99
 100     <a href="http://en.cppreference.com/w/cpp/utility/program/exit" target="_top"><span class="identifier">std</span><span class="special">::</span><span class="identifier">exit</span></a><span class="special">(</span><a href="http://en.cppreference.com/w/c/program/EXIT_status" target="_top"><span class="identifier">EXIT_FAILURE</span></a><span class="special">)</span><span class="special">;</span>
 101     <span class="keyword">return</span> <a class="link" href="../child.html" title="Class child">child</a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="comment">//for C++ compliance</span>
 102 <span class="special">}</span>
 103
 104 <a class="link" href="../child.html" title="Class child">child</a> <span class="identifier">c</span><span class="special">(</span><span class="identifier">pid</span><span class="special">,</span> <span class="identifier">exit_code</span><span class="special">)</span><span class="special">;</span>
 105
 106 <span class="emphasis"><em><span class="identifier">unspecified</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></em></span><span class="comment">//here, we read the the error from the child process</span>
 107
 108 <span class="keyword">if</span> <span class="special">(</span><a class="link" href="posix_executor.html#idm45170604830912-bb">error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span>
 109     <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
 110         <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604903088-bb">on_error</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">,</span> <a class="link" href="posix_executor.html#idm45170604830912-bb">error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
 111 <span class="keyword">else</span>
 112     <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
 113         <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604903088-bb">on_success</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">)</span><span class="special">;</span>
 114
 115 <span class="comment">//now we check again, because a on_success handler might've errored.</span>
 116 <span class="keyword">if</span> <span class="special">(</span><a class="link" href="posix_executor.html#idm45170604830912-bb">error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span>
 117 <span class="special">{</span>
 118     <span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span> <span class="special">&amp;</span> <span class="identifier">s</span> <span class="special">:</span> <span class="identifier">seq</span><span class="special">)</span>
 119         <span class="identifier">s</span><span class="special">.</span><a class="link" href="handler.html#idm45170604903088-bb">on_error</a><span class="special">(</span><span class="special">*</span><span class="keyword">this</span><span class="special">,</span> <a class="link" href="posix_executor.html#idm45170604830912-bb">error</a><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
 120     <span class="keyword">return</span> <a class="link" href="../child.html" title="Class child">child</a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
 121 <span class="special">}</span>
 122 <span class="keyword">else</span>
 123     <span class="keyword">return</span> <span class="identifier">c</span><span class="special">;</span>
 124 </pre>
 125 <p>
 126
 127 </p>
 128 <div class="mediaobject">
 129 <img src="../../../boost_process/posix_success.svg"><div class="caption"><p>The sequence if when no error occurs.</p></div>
 130 </div>
 131 <p>
 132
 133 </p>
 134 <div class="mediaobject">
 135 <img src="../../../boost_process/posix_exec_err.svg"><div class="caption"><p>The sequence if the execution fails.</p></div>
 136 </div>
 137 <p>
 138
 139 </p>
 140 <div class="mediaobject">
 141 <img src="../../../boost_process/posix_fork_err.svg"><div class="caption"><p>The sequence if the fork fails.</p></div>
 142 </div>
 143 <p>
 144
 145 </p>
 146 <div class="note"><table border="0" summary="Note">
 147 <tr>
 148 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
 149 <th align="left">Note</th>
 150 </tr>
 151 <tr><td align="left" valign="top"><p>Error handling if execve fails is done through a pipe, unless ignore_error is used. </p></td></tr>
 152 </table></div>
 153 <p>
 154 </p>
 155 <div class="refsect2">
 156 <a name="id-1.3.31.9.13.7.4.4"></a><h3>Template Parameters</h3>
 157 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
 158 <pre class="literallayout"><span class="keyword">typename</span> Sequence</pre>
 159 <p>The used initializer-sequence, it is fulfills the boost.fusion <a href="http://www.boost.org/doc/libs/master/libs/fusion/doc/html/fusion/sequence.html" target="_top">sequence</a> concept.</p>
 160 </li></ol></div>
 161 </div>
 162 <div class="refsect2">
 163 <a name="id-1.3.31.9.13.7.4.5"></a><h3>
 164 <a name="idm45170604831472-bb"></a><code class="computeroutput">posix_executor</code> public member functions</h3>
 165 <div class="orderedlist"><ol class="orderedlist" type="1">
 166 <li class="listitem">
 167 <pre class="literallayout"><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&amp;</span> <a name="idm45170604830912-bb"></a><span class="identifier">error</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>This function returns a const reference to the error state of the executor. </li>
 168 <li class="listitem">
 169 <pre class="literallayout"><span class="keyword">void</span> <a name="idm45170604829440-bb"></a><span class="identifier">set_error</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&amp;</span> ec<span class="special">,</span> <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&amp;</span> msg<span class="special">)</span><span class="special">;</span></pre>
 170 <p>This function can be used to report an error to the executor. This will be handled according to the configuration of the executor, i.e. it might throw an exception. </p>
 171 <div class="note"><table border="0" summary="Note">
 172 <tr>
 173 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
 174 <th align="left">Note</th>
 175 </tr>
 176 <tr><td align="left" valign="top"><p>This is the required way to handle errors in initializers. </p></td></tr>
 177 </table></div>
 178 <p>
 179 </p>
 180 </li>
 181 <li class="listitem">
 182 <pre class="literallayout"><span class="keyword">void</span> <a name="idm45170604825872-bb"></a><span class="identifier">set_error</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&amp;</span> ec<span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span> msg<span class="special">)</span><span class="special">;</span></pre>
 183 <p>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </p>
 184 </li>
 185 </ol></div>
 186 </div>
 187 </div>
 188 </div>
 189 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 190 <td align="left"></td>
 191 <td align="right"><div class="copyright-footer">Copyright &#169; 2006-2012 Julio M. Merino Vidal, Ilya Sokolov,
 192       Felipe Tanus, Jeff Flinn, Boris Schaeling<br>Copyright &#169; 2016 Klemens D. Morgenstern<p>
 193         Distributed under the Boost Software License, Version 1.0. (See accompanying
 194         file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 195       </p>
 196 </div></td>
 197 </tr></table>
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