$ sudo jgem install nokogiri
Building native extensions.  This could take a while...
/usr/local/jruby-1.1.5/lib/ruby/1.8/mkmf.rb:7: JRuby does not support native extensions. Check wiki.jruby.org for alternatives. (NotImplementedError)
	from /usr/local/jruby-1.1.5/lib/ruby/1.8/mkmf.rb:3:in `require'
	from extconf.rb:3
ERROR:  Error installing nokogiri:
	ERROR: Failed to build gem native extension.

/usr/local/jruby-1.1.5/bin/jruby extconf.rb install nokogiri


Gem files will remain installed in /usr/local/jruby-1.1.5/lib/ruby/gems/1.8/gems/nokogiri-1.1.0 for inspection.
Results logged to /usr/local/jruby-1.1.5/lib/ruby/gems/1.8/gems/nokogiri-1.1.0/ext/nokogiri/gem_make.out