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<title>6.9.1 Popen3 and Popen4 Objects
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<H2><A NAME=
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6.9.1 Popen3 and Popen4 Objects
Instances of the
<tt class=
"class">Popen3
</tt> and
<tt class=
"class">Popen4
</tt> classes have the
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<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>
Returns
<code>-
1</code> if child process hasn't completed yet, or its return
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"0"><tr valign=
"baseline">
<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>
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.
The following attributes are also available:
<dl><dt><b><tt id='l2h-
1851' xml:id='l2h-
1851'
class=
"member">fromchild
</tt></b></dt>
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><dt><b><tt id='l2h-
1852' xml:id='l2h-
1852'
class=
"member">tochild
</tt></b></dt>
A file object that provides input to the child process.
<dl><dt><b><tt id='l2h-
1853' xml:id='l2h-
1853'
class=
"member">childerr
</tt></b></dt>
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>
<dl><dt><b><tt id='l2h-
1854' xml:id='l2h-
1854'
class=
"member">pid
</tt></b></dt>
The process ID of the child process.
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<span class=
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2.4.2, documentation updated on
28 September
2005.
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