Install rbenv and use it

ruby, rbenv, installation

03 May 2018 by Paul Mesnilgrente

I. What is rbenv

Rbenv is a tool to manage your ruby versions. It works in collaboration with bundler which manage your development libraries versions. You can find more information on their github page.

II. Why I prefer rbenv to RVM

One reason can be found in the article on RVM: there is a bug. But actually, rbenv themselves are explaining it well here. The main reason is that I don’t like to change my shell (RVM overrides cd!) only to have a ruby version manager. I think it is an overkill in comparison of rbenv and this is dangerous as well.

Another point is, python has used the same mechanism as Ruby, the project is called pyenv. So it will be very easy to understand how pyenv works if you have understood how rbenv works. Even if python includes the concept of virtual environemnts.

III. Install and use rbenv

III.1. Install rbenv

Rbenv provides an installation script which include a plugin to facilitate the ruby installation. You can find the repository on github. To summarize it in a bash script:

# prepare the installation to avoid warnings from rbenv-doctor
curl -fsSL https://github.com/rbenv/rbenv-installer/raw/master/bin/rbenv-installer | bash
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
# if you want to be sure that rbenv is correctly installed:
#     - close the terminal and open a new one, or
#     - source your ~/.bashrc
#     - check that everything is OK in the result of the following command:
curl -fsSL https://github.com/rbenv/rbenv-installer/raw/master/bin/rbenv-doctor | bash

III.2. Use rbenv to install ruby

When you wan to install Ruby on your OS, you have the choice. You can install ruby from your package manager (sudo apt install ruby), rbenv will take it into account. Or you can install a specific ruby version (for development maybe) with: rbenv install 2.4.2.

After installing a new version with rbenv, you should execute rbenv rehash to install/update the shims in your new version. More information about shims here.

III.3. Use rbenv to develop your jekyll website

One powerfull feature of rbenv is to set default (global) and local ruby versions easily. For example, if you want to let your default ruby version to be the one installed by the package manager, run rbenv global system. But if you want to develop your jekyll website and make it work on github, you will need to:

  • set a ruby version for the development
  • manage jekyll dependencies

Here is a script to retrieve your jekyll website, install everything and begin to write articles:

# install the currently ruby version supported by github-pages
rbenv install 2.5.3
rbenv rehash
# retrieve your website
git clone git@github.com:/user/project.github.io
# set your ruby environment to 2.4.2 in this folder
cd project.github.io
rbenv local 2.5.3
# install bundler, the ruby library package manager
gem install bundler
bundle install --path vendor
# add vendor to .gitignore if not already done
[ `grep -c vendor .gitignore` -eq 0 ] && echo vendor >> .gitignore
# star the jekyll built-in server
bundle exec jekyll serve
# if you want to show the drafts
bundle exec jekyll serve --drafts

Note: You should update your packages versions in Gemfile to make it match the one from github-pages. You can check github-pages package versions here.

Sources