$ git clone https://github.com/sstephenson/rbenv.git ~/.rbenv
$ git clone https://github.com/sstephenson/ruby-build.git ~/.rbenv/plugins/ruby-build
$ echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile
$ echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
$ source ~/.bash_profile
$ which rbenv
~/.rbenv/bin/rbenv
$ rbenv --version
rbenv 1.1.1-6-g2d7cefe

export PATH="$PATH:$HOME/.rbenv/bin"
eval "$(rbenv init - zsh)"

$ rbenv install -l

$ rbenv install 2.4.2
$ rbenv global 2.4.2
$ rbenv rehash

$ ruby -v