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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 global 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.

In contrast with rvm, 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 dangerous and error-prone.
  • 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."

Table of Contents

1 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-rc1.

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-rc1/bin/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.

2 Installation

Compatibility note: rbenv is incompatible with rvm. Things will appear to work until you try to install a gem. The problem is that rvm actually overrides the gem command with a shell function! Please remove any references to rvm before using rbenv.

2.1 Basic GitHub Checkout

This will get you going with the latest version of rbenv and make it easy to fork and contribute any changes back upstream.

  1. Check out rbenv into ~/.rbenv.

     $ cd
     $ git clone 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

    Zsh note: Modify your ~/.zshenv file instead of ~/.bash_profile.

  3. Add rbenv init to your shell to enable shims and autocompletion.

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

    Zsh note: Modify your ~/.zshenv file instead of ~/.bash_profile.

  4. Restart your shell so the path changes take effect. You can now begin using rbenv.

     $ exec $SHELL
  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=$HOME/.rbenv/versions/1.9.2-p290
     $ make
     $ make install

    The ruby-build project provides an rbenv install command that simplifies the process of installing new Ruby versions to:

     $ rbenv install 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

2.1.1 Upgrading

If you've installed rbenv using the instructions above, you can upgrade your installation at any time using git.

To upgrade to the latest development version of rbenv, use git pull:

$ cd ~/.rbenv
$ git pull

To upgrade to a specific release of rbenv, check out the corresponding tag:

$ cd ~/.rbenv
$ git fetch
$ git tag
$ git checkout v0.2.0

2.2 Homebrew on Mac OS X

You can also install rbenv using the Homebrew package manager on Mac OS X.

$ brew update
$ brew install rbenv
$ brew install ruby-build

The same commands can be used for upgrading.

Afterwards you'll still need to add eval "$(rbenv init -)" to your profile as stated in the caveats. You'll only ever have to do this once.

2.3 Neckbeard Configuration

Skip this section unless you must know what every line in your shell profile is doing.

rbenv init is the only command that crosses the line of loading extra commands into your shell. Coming from rvm, some of you might be opposed to this idea. Here's what rbenv init actually does:

  1. Sets up your shims path. This is the only requirement for rbenv to function properly. You can do this by hand by prepending ~/.rbenv/shims to your $PATH.

  2. Installs autocompletion. This is entirely optional but pretty useful. Sourcing ~/.rbenv/completions/rbenv.bash will set that up. There is also a ~/.rbenv/completions/rbenv.zsh for Zsh users.

  3. Rehashes shims. From time to time you'll need to rebuild your shim files. Doing this on init makes sure everything is up to date. You can always run rbenv rehash manually.

  4. Installs the sh dispatcher. This bit is also optional, but allows rbenv and plugins to change variables in your current shell, making commands like rbenv shell possible. The sh dispatcher doesn't do anything crazy like override cd or hack your shell prompt, but if for some reason you need rbenv to be a real script rather than a shell function, you can safely skip it.

Run rbenv init - for yourself to see exactly what happens under the hood.

3 Usage

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

3.1 rbenv global

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

$ rbenv global 1.9.2-p290

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

When run without a version number, rbenv global reports the currently configured global version.

3.2 rbenv 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 global, and can be overridden itself by setting the RBENV_VERSION environment variable or with the rbenv shell command.

$ rbenv local rbx-1.2.4

When run without a version number, rbenv local reports the currently configured local version. You can also unset the local version:

$ rbenv local --unset

3.3 rbenv shell

Sets a shell-specific Ruby version by setting the RBENV_VERSION environment variable in your shell. This version overrides both project-specific versions and the global version.

$ rbenv shell jruby-1.6.4

When run without a version number, rbenv shell reports the current value of RBENV_VERSION. You can also unset the shell version:

$ rbenv shell --unset

Note that you'll need rbenv's shell integration enabled (step 3 of the installation instructions) in order to use this command. If you prefer not to use shell integration, you may simply set the RBENV_VERSION variable yourself:

$ export RBENV_VERSION=jruby-1.6.4

3.4 rbenv versions

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

$ rbenv versions
* 1.9.3-rc1 (set by /Users/sam/.rbenv/global)

3.5 rbenv 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)

3.6 rbenv 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

3.7 rbenv which

Displays the full path to the binary that rbenv will execute when you run the given command.

$ rbenv which irb

3.8 rbenv whence

Lists all Ruby versions with the given command installed.

$ rbenv whence rackup

4 Development

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.

4.1 Version History

0.3.0 (December 25, 2011)

  • Added an rbenv root command which prints the value of $RBENV_ROOT, or the default root directory if it's unset.
  • Clarified Zsh installation instructions in the readme.
  • Removed some redundant code in rbenv rehash.
  • Fixed an issue with calling readlink for paths with spaces.
  • Changed Zsh initialization code to install completion hooks only for interactive shells.
  • Added preliminary support for ksh.
  • rbenv rehash creates or removes shims only when necessary instead of removing and re-creating all shims on each invocation.
  • Fixed that RBENV_DIR, when specified, would be incorrectly expanded to its parent directory.
  • Removed the deprecated set-default and set-local commands.
  • Added a --no-rehash option to rbenv init for skipping the automatic rehash when opening a new shell.

0.2.1 (October 1, 2011)

  • Changed the rbenv command to ensure that RBENV_DIR is always an absolute path. This fixes an issue where Ruby scripts using the ruby-local-exec wrapper would go into an infinite loop when invoked with a relative path from the command line.

0.2.0 (September 28, 2011)

  • Renamed rbenv set-default to rbenv global and rbenv set-local to rbenv local. The set- commands are deprecated and will be removed in the next major release.
  • rbenv now uses greadlink on Solaris.
  • Added a ruby-local-exec command which can be used in shebangs in place of #!/usr/bin/env ruby to properly set the project-specific Ruby version regardless of current working directory.
  • Fixed an issue with rbenv rehash when no binaries are present.
  • Added support for rbenv-sh-* commands, which run inside the current shell instead of in a child process.
  • Added an rbenv shell command for conveniently setting the $RBENV_VERSION environment variable.
  • Added support for storing rbenv versions and shims in directories other than ~/.rbenv with the $RBENV_ROOT environment variable.
  • Added support for debugging rbenv via set -x when the $RBENV_DEBUG environment variable is set.
  • Refactored the autocompletion system so that completions are now built-in to each command and shared between bash and Zsh.
  • Added support for plugin bundles in ~/.rbenv/plugins as documented in issue #102.
  • Added /usr/local/etc/rbenv.d to the list of directories searched for rbenv hooks.
  • Added support for an $RBENV_DIR environment variable which defaults to the current working directory for specifying where rbenv searches for local version files.

0.1.2 (August 16, 2011)

  • Fixed rbenv to be more resilient against nonexistent entries in $PATH.
  • Made the rbenv rehash command operate atomically.
  • Modified the rbenv init script to automatically run rbenv rehash so that shims are recreated whenever a new shell is opened.
  • Added initial support for Zsh autocompletion.
  • Removed the dependency on egrep for reading version files.

0.1.1 (August 14, 2011)

  • Fixed a syntax error in the rbenv help command.
  • Removed -e from the shebang in favor of set -e at the top of each file for compatibility with operating systems that do not support more than one argument in the shebang.

0.1.0 (August 11, 2011)

  • Initial public release.

4.2 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.