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<h3 class="section" id="Environment-Variables-1"><span>36.7 Environment Variables<a class="copiable-link" href="#Environment-Variables-1"> ¶</a></span></h3>
<a class="anchor" id="XREFgetenv"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-getenv"><span><code class="def-type"><var class="var">val</var> =</code> <strong class="def-name">getenv</strong> <code class="def-code-arguments">("<var class="var">var</var>")</code><a class="copiable-link" href="#index-getenv"> ¶</a></span></dt>
<dd><p>Return the value of the environment variable <var class="var">var</var>.
</p>
<p>For example,
</p>
<div class="example">
<pre class="example-preformatted">getenv ("PATH")
</pre></div>
<p>returns a string containing the value of your path.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFsetenv">setenv</a>, <a class="ref" href="#XREFunsetenv">unsetenv</a>, <a class="ref" href="#XREFisenv">isenv</a>.
</p></dd></dl>
<a class="anchor" id="XREFisenv"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isenv"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isenv</strong> <code class="def-code-arguments">(<var class="var">var</var>)</code><a class="copiable-link" href="#index-isenv"> ¶</a></span></dt>
<dd><p>Return true if the variable <var class="var">var</var> is an environment variable, and false
otherwise.
</p>
<p>For example,
</p>
<div class="example">
<pre class="example-preformatted">tf = isenv ("PATH")
</pre></div>
<p>will typically return true on UNIX systems because <code class="code">"PATH"</code> is an
environment variable for UNIX.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFgetenv">getenv</a>, <a class="ref" href="#XREFsetenv">setenv</a>, <a class="ref" href="#XREFunsetenv">unsetenv</a>.
</p></dd></dl>
<a class="anchor" id="XREFsetenv"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-setenv"><span><strong class="def-name">setenv</strong> <code class="def-code-arguments">("<var class="var">var</var>", <var class="var">value</var>)</code><a class="copiable-link" href="#index-setenv"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-setenv-1"><span><strong class="def-name">setenv</strong> <code class="def-code-arguments">(<var class="var">var</var>)</code><a class="copiable-link" href="#index-setenv-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-putenv"><span><strong class="def-name">putenv</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-putenv"> ¶</a></span></dt>
<dd><p>Set the value of the environment variable <var class="var">var</var> to <var class="var">value</var>.
</p>
<p>If no <var class="var">value</var> is specified then the variable will be assigned the null
string.
</p>
<p>Programming Note: <code class="code">putenv</code> is an alias for <code class="code">setenv</code> and can be used
interchangeably.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFunsetenv">unsetenv</a>, <a class="ref" href="#XREFgetenv">getenv</a>, <a class="ref" href="#XREFisenv">isenv</a>.
</p></dd></dl>
<a class="anchor" id="XREFunsetenv"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-unsetenv"><span><strong class="def-name">unsetenv</strong> <code class="def-code-arguments">("<var class="var">var</var>")</code><a class="copiable-link" href="#index-unsetenv"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-unsetenv-1"><span><code class="def-type"><var class="var">status</var> =</code> <strong class="def-name">unsetenv</strong> <code class="def-code-arguments">("<var class="var">var</var>")</code><a class="copiable-link" href="#index-unsetenv-1"> ¶</a></span></dt>
<dd><p>Delete the environment variable <var class="var">var</var>.
</p>
<p>Return 0 if the variable was deleted, or did not exist, and -1 if an error
occurred.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFsetenv">setenv</a>, <a class="ref" href="#XREFgetenv">getenv</a>, <a class="ref" href="#XREFisenv">isenv</a>.
</p></dd></dl>
<a class="anchor" id="XREFget_005fhome_005fdirectory"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-get_005fhome_005fdirectory"><span><code class="def-type"><var class="var">homedir</var> =</code> <strong class="def-name">get_home_directory</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-get_005fhome_005fdirectory"> ¶</a></span></dt>
<dd><p>Return the current home directory.
</p>
<p>On most systems, this is equivalent to <code class="code">getenv ("HOME")</code>. On Windows
systems, if the environment variable <code class="env">HOME</code> is not set then it is
equivalent to
<code class="code">fullfile (getenv ("HOMEDRIVE"), getenv ("HOMEPATH"))</code>
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFgetenv">getenv</a>.
</p></dd></dl>
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