<option> <name>directory</name> <type>std::string</type> <longopt>directory</longopt> <descr>pathname</descr> <hasvalue /> </option> <option> <name>socket</name> <type>int</type> <longopt>socket</longopt> <descr>socket port</descr> <hasvalue /> </option> <mutex> <name>directory</name> <name>socket</name> </mutex>
A separately-specified mutex contains a list
of mutually exclusive options. The above example allows either
“directory” or “socket”, but not both.