Nokogiri is a an HTML, SAX, XML, and Reader parser available on multiple open-source operating systems. Nokogiri also allows you to search document with XPath or CSS3 selectors. You can find out how to download it at the link below.

nokogiri-f91aa2f6
Because Nokogiri needs to be compiled and dynamically linked against both libxml2 and libxslt, it has gained a reputation for being complicated to install.

As of Nokogiri 1.6, libxml2 and libxslt source code is bundled with Nokogiri, and compiled at gem-install-time. The instructions in this document should work for all versions 1.6.4 and later.

(If you need support for installing earlier versions of Nokogiri, you may want to take a look at the git history for this document.)

Get Nokogiri here: http://www.nokogiri.org/tutorials/installing_nokogiri.html#freebsd