Error Installing Gem 'devise' ruby on rails - ruby-on-rails

Question

I'm working on my first ruby on rails course, building an application. Below is the error I am getting in the terminal when running the bundle install command. I am trying to add the gem 'devise'. I have no idea how to get past this error. Thanks!
Installing bcrypt (3.1.7) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/local/rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb
checking for ruby/util.h... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/usr/local/rvm/rubies/ruby-1.9.3-p194/bin/ruby
/usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:931:in `block in have_header'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
from /usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:930:in `have_header'
from extconf.rb:14:in `<main>'
Gem files will remain installed in /usr/local/rvm/gems/ruby-1.9.3-p194/gems/bcrypt-3.1.7 for inspection.
Results logged to /usr/local/rvm/gems/ruby-1.9.3-p194/gems/bcrypt-3.1.7/ext/mri/gem_make.out
An error occured while installing bcrypt (3.1.7), and Bundler cannot continue.
Make sure that `gem install bcrypt -v '3.1.7'` succeeds before bundling.

Answer 1

you missing gcc if you use homebrew
brew tap homebrew/dupes
then
brew install apple-gcc42
on linux centos/fedora:
yum install gcc
on linux ubuntu:
apt-get install build-essential
Please update if it helps you.