eyword">const</span> <span class="identifier">string_type</span> <span class="special">&amp;</span> id<span class="special">,</span> <span class="keyword">const</span> <span class="identifier">string_type</span> <span class="special">&amp;</span> value<span class="special">)</span><span class="special">;</span></pre>Emplace an environment variable. </li>
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<pre class="literallayout"><span class="keyword">bool</span> <a name="idp51502400-bb"></a><span class="identifier">empty</span><span 