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<title>6.9.1 Popen3 and Popen4 Objects </title>
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<H2><A NAME="SECTION008910000000000000000"></A><A NAME="popen3-objects"></A>
<BR>
6.9.1 Popen3 and Popen4 Objects
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<P>
Instances of the <tt class="class">Popen3</tt> and <tt class="class">Popen4</tt> classes have the
following methods:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1849' xml:id='l2h-1849' class="method">poll</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns <code>-1</code> if child process hasn't completed yet, or its return
code otherwise.
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  <td><nobr><b><tt id='l2h-1850' xml:id='l2h-1850' class="method">wait</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Waits for and returns the status code of the child process.  The
status code encodes both the return code of the process and
information about whether it exited using the <tt class="cfunction">exit()</tt>
system call or died due to a signal.  Functions to help interpret the
status code are defined in the <tt class="module"><a href="module-os.html">os</a></tt> module; see section
<A href="os-process.html#os-process">6.1.5</A> for the <tt class="function">W<var>*</var>()</tt> family of functions.
</dl>

<P>
The following attributes are also available:

<P>
<dl><dt><b><tt id='l2h-1851' xml:id='l2h-1851' class="member">fromchild</tt></b></dt>
<dd>
A file object that provides output from the child process.  For
<tt class="class">Popen4</tt> instances, this will provide both the standard output
and standard error streams.
</dl>

<P>
<dl><dt><b><tt id='l2h-1852' xml:id='l2h-1852' class="member">tochild</tt></b></dt>
<dd>
A file object that provides input to the child process.
</dl>

<P>
<dl><dt><b><tt id='l2h-1853' xml:id='l2h-1853' class="member">childerr</tt></b></dt>
<dd>
A file object that provides error output from the child process, if
<var>capturestderr</var> was true for the constructor, otherwise
<code>None</code>.  This will always be <code>None</code> for <tt class="class">Popen4</tt>
instances.
</dl>

<P>
<dl><dt><b><tt id='l2h-1854' xml:id='l2h-1854' class="member">pid</tt></b></dt>
<dd>
The process ID of the child process.
</dl>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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