I've seen Guard and it's usefulness in web development and would like to install it. Naturally, I expected to be able to use
sudo gem install guard to do so (yes, it is a Ruby Gem). However the installation errors out. Here is what I'm getting:
Building native extensions. This could take a while... ERROR: Error installing guard: ERROR: Failed to build gem native extension. /usr/bin/ruby1.9.1 extconf.rb /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError) from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require' from extconf.rb:4:in `<main>' Gem files will remain installed in /var/lib/gems/1.9.1/gems/ffi-1.9.3 for inspection. Results logged to /var/lib/gems/1.9.1/gems/ffi-1.9.3/ext/ffi_c/gem_make.out
Does anyone know how I can fix this? Thanks for any help.