Error Installing Ferret on Mac OS X 10.8.5



I try to install Ferret on my Mac (OS X 10.8.5) using the command “sudo
gem install ferret” and get the error message, shown below.

The Mac does have Ruby installed on it and I use Ruby frequently to
successfully build informatics scripts. When I run “ruby -v” I get…
“ruby 1.8.7 (2012-02-08 patchlevel 358) [universal-darwin12.0]”

Any idea as to what the error message means (in English) and how best to

Thanks for any help you can offer.

Building native extensions. This could take a while…
ERROR: Error installing ferret:
ERROR: Failed to build gem native extension.

mkmf.rb can’t find header files for ruby at

Gem files will remain installed in
/Library/Ruby/Gems/1.8/gems/ferret- for inspection.
Results logged to