A quick search reveals that I’m not the only one who’s had difficulty installing the nokogiri Ruby gem on Mac OS X. The official docs recommend installing the fink or macports versions of libxml2, and so does this nokogiri tutorial over on the Engine Yard blog. I like macports. It’s a good way to stay up to date with the latest and greatest versions of everything, but I have this thing about trying to make things work with the libraries that come as standard on Mac OS X. I don’t know, maybe it’s that it reduces dependencies, or maybe I’m just strange.
Anyway, here’s how I got nokogiri to install under Snow Leopard without resorting to macports or fink:
sudo gem install nokogiri -- --with-xml2-include=/usr/include/libxml2 --with-xml2-lib=/usr/lib --with-xslt-dir=/usr
What’s weird is that, unless I’m mistaken, those paths are exactly where nokogiri should be looking for the relevant libxml2 files in the first place! I’m still to find out whether it all works as it’s supposed to. But installation is the first step! Let me know if it works for you.