title: Close the stdin of boost::process child
body: <p>I'm trying to call a process with a string to its stdin, with Boost-1.64.0.
  The current code is :</p>
  
  <pre><code>  bp::opstream inStream ;
    bp::ipstream outStream;
    bp::ipstream errStream;
  
    bp::child child(
      command, // the command line
      bp::shell,
      bp::std_out &gt; outStream,
      bp::std_err &gt; errStream,
      bp::std_in  &lt; inStream);
  
  
    // read the outStream/errStream in threads
  
    child.wait();
  </code></pre>
  
  <p>The problem is that the child executable is waiting for its stdin EOF. Here child.wait() is hanging indefinitely… </p>
  
  <p>I tried to used asio::buffer, std_in.close(),… But no luck.
  The only hack I found was to delete() the inStream… And that's not really reliable.</p>
  
  <p>How am I supposed to "notify" the child process and close its stdin with the new boost::process library ?</p>
  
  <p>Thanks !</p>