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<H2><A NAME="SECTION0010120000000000000000"></A>
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8.1.2 Module Contents 
</H2>

<P>
Module <tt class=module>posix</tt> defines the following data item:

<P>
<dl><dt><b><a name="l2h-1442"><tt>environ</tt></a></b>
<dd>
A dictionary representing the string environment at the time the
interpreter was started. For example, <tt>environ['HOME']</tt> is the
pathname of your home directory, equivalent to
<tt>getenv("HOME")</tt> in C.

<P>
Modifying this dictionary does not affect the string environment
passed on by <tt class=function>execv()</tt>, <tt class=function>popen()</tt> or
<tt class=function>system()</tt>; if you need to change the environment, pass
<tt>environ</tt> to <tt class=function>execve()</tt> or add variable assignments and
export statements to the command string for <tt class=function>system()</tt> or
<tt class=function>popen()</tt>.

<P>
<b>Note:</b> The <tt class=module><a href="module-os.html">os</a></tt> module provides an alternate
implementation of <tt>environ</tt> which updates the environment on
modification.  Note also that updating <tt>os.environ</tt> will render
this dictionary obsolete.  Use of the <tt class=module><a href="module-os.html">os</a></tt> for this is
recommended over direct access to the <tt class=module>posix</tt> module.
</dl>

<P>
Additional contents of this module should only be accessed via the
<tt class=module><a href="module-os.html">os</a></tt> module; refer to the documentation for that module for
further information.
<p>
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