I get this message when I try "sudo gem install sqlite3-ruby":

Building native extensions. This could take a while...
ERROR: Error installing sqlite3-ruby:
ERROR: Failed to build gem native extension.

/usr/local/bin/ruby extconf.rb install sqlite3-ruby
checking for fdatasync() in -lrt... yes
checking for sqlite3.h... no

make: *** No rule to make target `ruby.h', needed by `sqlite3_api_wrap.o'. Stop.

I'm relatively new to linux. Any suggestions? Thanks.