of the option.
It shall begin with a lower-case letter and a full stop (<code>.</code>) shall be
omitted at the end.</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_option_callbacks">Option Callbacks</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The function must be defined in this form:</p>
</div>
<div class="literalblock">
<div class="content">
<pre>int func(const struct option *opt, const char *arg, int unset)</pre>
</div>
</div>
<div class="paragraph">
<p>The callback mecha