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<head><title>GETENV$.html -- ACL2 Version 3.1</title></head>
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<h2>GETENV$</h2>read an environment variable
<pre>Major Section: <a href="PROGRAMMING.html">PROGRAMMING</a>
</pre><p>
<code>(Getenv$ str)</code>, where <code>str</code> is a string, reads the value of
environment variable <code>str</code>, returning <code>nil</code> if none is found or if the
read fails. The formal story is that <code>getenv$</code> reads its value from the
<code>oracle</code> field of the ACL2 <code><a href="STATE.html">state</a></code>. The return value is thus a triple
of the form <code>(mv erp val state)</code>, where <code>erp</code> will always be <code>nil</code> in
practice, <code>val</code> is the value that has been read, and <code>state</code> is the new
state, which is obtained by popping <code>val</code> from the top of the state's
oracle.
<pre>
Example:
(getenv$ "PWD") ==> (mv nil "/u/joe/work" state)
</pre>
Also see <a href="SETENV$.html">setenv$</a>.
<p>
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