“can’t find headers file for ruby” while installing gems

02 January 2010

I just reinstall my old MacBook and had a problem I got each time I install a Mac OSX.

$ sudo gem install RedCloth
Password:
Building native extensions.  This could take a while...
ERROR:  Error installing RedCloth:
	ERROR: Failed to build gem native extension.

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb
can't find header files for ruby.


Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/RedCloth-4.2.2 for inspection.
Results logged to /Library/Ruby/Gems/1.8/gems/RedCloth-4.2.2/ext/redcloth_scan/gem_make.out

And the solution is really simple but I always forget it :

Install Xcode here.