CentOSにgem hprocotを入れたかったんですが下記エラー。
Installing hpricot (0.8.6)
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/bin/ruby1.9 extconf.rb
mkmf.rb can't find header files for ruby at /usr/share/ruby/include/ruby.h
Gem files will remain installed in /home/ec2-user/.gem/ruby/1.9.1/gems/hpricot-0.8.6 for inspection.
Results logged to /home/ec2-user/.gem/ruby/1.9.1/gems/hpricot-0.8.6/ext/fast_xs/gem_make.out
上記にある通り
mkmf.rb can't find header files for ruby at /usr/share/ruby/include/ruby.h
なので、
下記コマンドで解決しました。
sudo yum install ruby-devel ruby19-devel