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<H2><A NAME="SECTION008120000000000000000"> </A>
<BR>
6.1.2 File Object Creation
</H2>
<P>
These functions create new file objects.
<P>
<dl><dt><b><a name="l2h-1129"><tt class="function">fdopen</tt></a></b>(<var>fd</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><big>]</big>)
<dd>
Return an open file object connected to the file descriptor <var>fd</var>.
<a name="l2h-1135"> </a>The <var>mode</var> and <var>bufsize</var> arguments have the same meaning as
the corresponding arguments to the built-in <tt class="function">open()</tt>
function.
Availability: Macintosh, Unix, Windows.
</dl>
<P>
<dl><dt><b><a name="l2h-1130"><tt class="function">popen</tt></a></b>(<var>command</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><big>]</big>)
<dd>
Open a pipe to or from <var>command</var>. The return value is an open
file object connected to the pipe, which can be read or written
depending on whether <var>mode</var> is <code>'r'</code> (default) or <code>'w'</code>.
The <var>bufsize</var> argument has the same meaning as the corresponding
argument to the built-in <tt class="function">open()</tt> function. The exit status of
the command (encoded in the format specified for <tt class="function">wait()</tt>) is
available as the return value of the <tt class="method">close()</tt> method of the file
object, except that when the exit status is zero (termination without
errors), <code>None</code> is returned.
Availability: Unix, Windows.
<P>
<span class="versionnote">Changed in version 2.0:
This function worked unreliably under Windows in
earlier versions of Python. This was due to the use of the
<tt class="cfunction">_popen()</tt> function from the libraries provided with
Windows. Newer versions of Python do not use the broken
implementation from the Windows libraries.</span>
</dl>
<P>
<dl><dt><b><a name="l2h-1131"><tt class="function">tmpfile</tt></a></b>()
<dd>
Return a new file object opened in update mode ("<tt class="samp">w+</tt>"). The file
has no directory entries associated with it and will be automatically
deleted once there are no file descriptors for the file.
Availability: Unix, Windows.
</dl>
<P>
For each of these <tt class="function">popen()</tt> variants, if <var>bufsize</var> is
specified, it specifies the buffer size for the I/O pipes.
<var>mode</var>, if provided, should be the string <code>'b'</code> or
<code>'t'</code>; on Windows this is needed to determine whether the file
objects should be opened in binary or text mode. The default value
for <var>mode</var> is <code>'t'</code>.
<P>
These methods do not make it possible to retrieve the return code from
the child processes. The only way to control the input and output
streams and also retrieve the return codes is to use the
<tt class="class">Popen3</tt> and <tt class="class">Popen4</tt> classes from the <tt class="module"><a href="module-popen2.html">popen2</a></tt>
module; these are only available on Unix.
<P>
<dl><dt><b><a name="l2h-1132"><tt class="function">popen2</tt></a></b>(<var>cmd</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><big>]</big>)
<dd>
Executes <var>cmd</var> as a sub-process. Returns the file objects
<code>(<var>child_stdin</var>, <var>child_stdout</var>)</code>.
Availability: Unix, Windows.
<span class="versionnote">New in version 2.0.</span>
</dl>
<P>
<dl><dt><b><a name="l2h-1133"><tt class="function">popen3</tt></a></b>(<var>cmd</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><big>]</big>)
<dd>
Executes <var>cmd</var> as a sub-process. Returns the file objects
<code>(<var>child_stdin</var>, <var>child_stdout</var>, <var>child_stderr</var>)</code>.
Availability: Unix, Windows.
<span class="versionnote">New in version 2.0.</span>
</dl>
<P>
<dl><dt><b><a name="l2h-1134"><tt class="function">popen4</tt></a></b>(<var>cmd</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><big>]</big>)
<dd>
Executes <var>cmd</var> as a sub-process. Returns the file objects
<code>(<var>child_stdin</var>, <var>child_stdout_and_stderr</var>)</code>.
Availability: Unix, Windows.
<span class="versionnote">New in version 2.0.</span>
</dl>
<P>
This functionality is also available in the <tt class="module"><a href="module-popen2.html">popen2</a></tt> module
using functions of the same names, but the return values of those
functions have a different order.
<P>
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<span class="release-info">Release 2.2, documentation updated on December 21, 2001.</span>
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