Install Ruby 1.9 on Ubuntu 12.04

install-ruby-1.9-ubuntu.sh

#!/bin/sh

# Make sure we have the latest package info
apt-get update

# Install ruby 1.9 and some other useful related packages
apt-get install -y ruby1.9.3 build-essential libssl-dev zlib1g-dev

# Let "update-alternatives" know about the new ruby
update-alternatives \
    --install /usr/bin/ruby ruby /usr/bin/ruby1.9.1 400 \
    --slave   /usr/share/man/man1/ruby.1.gz ruby.1.gz \
              /usr/share/man/man1/ruby1.9.1.1.gz \
    --slave   /usr/bin/ri ri /usr/bin/ri1.9.1 \
    --slave   /usr/bin/irb irb /usr/bin/irb1.9.1 \
    --slave   /usr/bin/rdoc rdoc /usr/bin/rdoc1.9.1

# Make 1.9 the default
update-alternatives --config ruby
update-alternatives --config gem