Simple Ruby Version Management: rbenv

rbenv lets you easily switch between multiple versions of Ruby. It's simple, unobtrusive, and follows the UNIX tradition of single-purpose tools that do one thing well.

rbenv does…

• Let you change the default Ruby version on a per-user basis.
• Provide support for per-project Ruby versions.
• Allow you to override the Ruby version with an environment variable.

rbenv does not…

• Need to be loaded into your shell. Instead, rbenv's shim approach works by adding a directory to your $PATH.
• Override shell commands like cd. That's just obnoxious!
• Have a configuration file. There's nothing to configure except which version of Ruby you want to use.
• Install Ruby. You can build and install Ruby yourself, or use ruby-build to automate the process.
• Manage gemsets. Bundler is a better way to manage application dependencies. If you have projects that are not yet using Bundler you can install the rbenv-gemset plugin.
• Require changes to Ruby libraries for compatibility. The simplicity of rbenv means as long as it's in your $PATH, nothing else needs to know about it.
• Prompt you with warnings when you switch to a project. Instead of executing arbitrary code, rbenv reads just the version name from each project. There's nothing to "trust."

How It Works

rbenv operates on the per-user directory ~/.rbenv. Version names in rbenv correspond to subdirectories of ~/.rbenv/versions. For example, you might have ~/.rbenv/versions/1.8.7-p354 and ~/.rbenv/versions/1.9.3-preview1.

Each version is a working tree with its own binaries, like ~/.rbenv/versions/1.8.7-p354/bin/ruby and ~/.rbenv/versions/1.9.3-preview1/irb. rbenv makes shim binaries for every such binary across all installed versions of Ruby.

These shims are simple wrapper scripts that live in ~/.rbenv/shims and detect which Ruby version you want to use. They insert the directory for the selected version at the beginning of your $PATH and then execute the corresponding binary.

Because of the simplicity of the shim approach, all you need to use rbenv is ~/.rbenv/shims in your $PATH.

Installation

rbenv is a young project, so for now you must install it from source.

1. Check out rbenv into ~/.rbenv.

    $ cd
    $ git clone git://github.com/sstephenson/rbenv.git .rbenv
   

2. Add ~/.rbenv/bin to your $PATH for access to the rbenv command-line utility.

    $ echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> .bash_profile
   

3. Add rbenv's shims directory to your $PATH and set up Bash autocompletion. (If you prefer not to load rbenv in your shell, you can manually add $HOME/.rbenv/shims to your path in step 2.)

    $ echo 'eval "$(rbenv init -)"' >> .bash_profile
   

4. Restart your shell. You can now begin using rbenv.

    $ exec
   

5. Install Ruby versions into ~/.rbenv/versions. For example, to install Ruby 1.9.2-p290, download and unpack the source, then run:

    $ ./configure --prefix=~/.rbenv/versions/1.9.2-p290
    $ make
    $ make install
   

   The ruby-build project simplifies this process to a single command:

    $ ruby-build 1.9.2-p290 ~/.rbenv/versions/1.9.2-p290
   

6. Rebuild the shim binaries. You should do this any time you install a new Ruby binary (for example, when installing a new Ruby version, or when installing a gem that provides a binary).

    $ rbenv rehash
   

Usage

Like git, the rbenv command delegates to subcommands based on its first argument. The most common subcommands are:

• set-default — sets the default version of Ruby to be used in all shells by writing the version name to the ~/.rbenv/default file. This version can be overridden by a per-project .rbenv-version file, or by setting the RBENV_VERSION environment variable.

    $ rbenv set-default 1.9.2-p290
  

  The special version name system tells rbenv to use the system Ruby (detected by searching your $PATH).

• set-local — sets a local per-project Ruby version by writing the version name to an .rbenv-version file in the current directory. This version overrides the default, and can be overridden itself by setting the RBENV_VERSION environment variable.

    $ rbenv set-local rbx-1.2.4
  

• versions — lists all Ruby versions known to rbenv, and shows an asterisk next to the currently active version.

    $ rbenv versions
      1.8.7-p352
      1.9.2-p290
    * 1.9.3-preview1 (set by /Users/sam/.rbenv/default)
      jruby-1.6.3
      rbx-1.2.4
      ree-1.8.7-2011.03
  

• version — displays the currently active Ruby version, along with information on how it was set.

    $ rbenv version
    1.8.7-p352 (set by /Volumes/37signals/basecamp/.rbenv-version)
  

• rehash — installs shims for all Ruby binaries known to rbenv (i.e., ~/.rbenv/versions/*/bin/*). Run this command after you install a new version of Ruby, or install a gem that provides binaries.

    $ rbenv rehash
  

Contributing

The rbenv source code is hosted on GitHub. It's clean, modular, and easy to understand, even if you're not a shell hacker.

Please feel free to submit pull requests and file bugs on the issue tracker.

License

(The MIT license)

Copyright (c) 2011 Sam Stephenson

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.