A simple step-by-step to install Ruby and Rails.

ruby-rails.sh

#!/bin/bash 


# update packages
sudo apt-get update

# installing dependencies
sudo apt-get install -y git-core curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libssl-dev mysql-client libmysqlclient-dev

# go to the page ~
cd

# cloning the repo and setting in the PATH
git clone git://github.com/sstephenson/rbenv.git .rbenv
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
exec $SHELL

# cloning the repo
git clone git://github.com/sstephenson/ruby-build.git ~/.rbenv/plugins/ruby-build
echo 'export PATH="$HOME/.rbenv/plugins/ruby-build/bin:$PATH"' >> ~/.bashrc
exec $SHELL

# using rbenv to install the latest version of ruby
rbenv install 2.0.0-p247
rbenv global 2.0.0-p247

# changing to don't install docs for all gems
echo "gem: --no-ri --no-rdoc" > ~/.gemrc

# updating the system and installing rails
gem update --system
gem install rails

# making rails executable
rbenv rehash

# showing the version of rails 
rails -v