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README.md

Groom your app’s Ruby environment with rbenv.

Use rbenv to pick a Ruby version for your application and guarantee that your development environment matches production. Put rbenv to work with Bundler for painless Ruby upgrades and bulletproof deployments.

Powerful in development. Specify your app's Ruby version once, in a single file. Keep all your teammates on the same page. No headaches running apps on different versions of Ruby. Just Works™ from the command line and with app servers like Pow. Override the Ruby version anytime: just set an environment variable.

Rock-solid in production. Your application's executables are its interface with ops. With rbenv and Bundler binstubs you'll never again need to cd in a cron job or Chef recipe to ensure you've selected the right runtime. The Ruby version dependency lives in one place—your app—so upgrades and rollbacks are atomic, even when you switch versions.

One thing well. rbenv is concerned solely with switching Ruby versions. It's simple and predictable. A rich plugin ecosystem lets you tailor it to suit your needs. Compile your own Ruby versions, or use the ruby-build plugin to automate the process. Specify per-application environment variables with rbenv-vars. See more plugins on the wiki.

Why choose rbenv over RVM?

Table of Contents

How It Works

At a high level, rbenv intercepts Ruby commands using shim executables injected into your PATH, determines which Ruby version has been specified by your application, and passes your commands along to the correct Ruby installation.

Understanding PATH

When you run a command like ruby or rake, your operating system searches through a list of directories to find an executable file with that name. This list of directories lives in an environment variable called PATH, with each directory in the list separated by a colon:

/usr/local/bin:/usr/bin:/bin

Directories in PATH are searched from left to right, so a matching executable in a directory at the beginning of the list takes precedence over another one at the end. In this example, the /usr/local/bin directory will be searched first, then /usr/bin, then /bin.

Understanding Shims

rbenv works by inserting a directory of shims at the front of your PATH:

~/.rbenv/shims:/usr/local/bin:/usr/bin:/bin

Through a process called rehashing, rbenv maintains shims in that directory to match every Ruby command across every installed version of Ruby—irb, gem, rake, rails, ruby, and so on.

Shims are lightweight executables that simply pass your command along to rbenv. So with rbenv installed, when you run, say, rake, your operating system will do the following:

  • Search your PATH for an executable file named rake
  • Find the rbenv shim named rake at the beginning of your PATH
  • Run the shim named rake, which in turn passes the command along to rbenv

Choosing the Ruby Version

When you execute a shim, rbenv determines which Ruby version to use by reading it from the following sources, in this order:

  1. The RBENV_VERSION environment variable, if specified. You can use the rbenv shell command to set this environment variable in your current shell session.

  2. The first .ruby-version file found by searching the directory of the script you are executing and each of its parent directories until reaching the root of your filesystem.

  3. The first .ruby-version file found by searching the current working directory and each of its parent directories until reaching the root of your filesystem. You can modify the .ruby-version file in the current working directory with the rbenv local command.

  4. The global ~/.rbenv/version file. You can modify this file using the rbenv global command. If the global version file is not present, rbenv assumes you want to use the "system" Ruby—i.e. whatever version would be run if rbenv weren't in your path.

Locating the Ruby Installation

Once rbenv has determined which version of Ruby your application has specified, it passes the command along to the corresponding Ruby installation.

Each Ruby version is installed into its own directory under ~/.rbenv/versions. For example, you might have these versions installed:

  • ~/.rbenv/versions/1.8.7-p371/
  • ~/.rbenv/versions/1.9.3-p327/
  • ~/.rbenv/versions/jruby-1.7.1/

Version names to rbenv are simply the names of the directories in ~/.rbenv/versions.

Installation

Compatibility note: rbenv is incompatible with RVM. Please make sure to fully uninstall RVM and remove any references to it from your shell initialization files before installing rbenv.

If you're on Mac OS X, consider installing with Homebrew.

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.

    $ git clone https://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

    Ubuntu Desktop note: Modify your ~/.bashrc instead of ~/.bash_profile.

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

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

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

    Same as in previous step, use ~/.bashrc on Ubuntu, or ~/.zshrc for Zsh.

  4. Restart your shell so that PATH changes take effect. (Opening a new terminal tab will usually do it.) Now check if rbenv was set up:

    $ type rbenv
    #=> "rbenv is a function"
  5. (Optional) Install ruby-build, which provides the rbenv install command that simplifies the process of installing new Ruby versions.

Upgrading

If you've installed rbenv manually using git, you can upgrade your installation to the cutting-edge version at any time.

$ cd ~/.rbenv
$ git pull

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

$ cd ~/.rbenv
$ git fetch
$ git checkout v0.3.0

If you've installed via Homebrew, then upgrade via its brew command:

$ brew update
$ brew upgrade rbenv ruby-build

Homebrew on Mac OS X

As an alternative to installation via GitHub checkout, you can install rbenv and ruby-build using the Homebrew package manager on Mac OS X:

$ brew update
$ brew install rbenv ruby-build

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.

How rbenv hooks into your shell

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 automatically 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.

Installing Ruby Versions

The rbenv install command doesn't ship with rbenv out of the box, but is provided by the ruby-build project. If you installed it either as part of GitHub checkout process outlined above or via Homebrew, you should be able to:

# list all available versions:
$ rbenv install -l

# install a Ruby version:
$ rbenv install 2.0.0-p247

Alternatively to the install command, you can download and compile Ruby manually as a subdirectory of ~/.rbenv/versions/. An entry in that directory can also be a symlink to a Ruby version installed elsewhere on the filesystem. rbenv doesn't care; it will simply treat any entry in the versions/ directory as a separate Ruby version.

Uninstalling Ruby Versions

As time goes on, Ruby versions you install will accumulate in your ~/.rbenv/versions directory.

To remove old Ruby versions, simply rm -rf the directory of the version you want to remove. You can find the directory of a particular Ruby version with the rbenv prefix command, e.g. rbenv prefix 1.8.7-p357.

The ruby-build plugin provides an rbenv uninstall command to automate the removal process.

Uninstalling rbenv

The simplicity of rbenv makes it easy to temporarily disable it, or uninstall from the system.

  1. To disable rbenv managing your Ruby versions, simply remove the rbenv init line from your shell startup configuration. This will remove rbenv shims directory from PATH, and future invocations like ruby will execute the system Ruby version, as before rbenv.

    rbenv will still be accessible on the command line, but your Ruby apps won't be affected by version switching.

  2. To completely uninstall rbenv, perform step (1) and then remove its root directory. This will delete all Ruby versions that were installed under `rbenv root`/versions/ directory:

    rm -rf `rbenv root`
    

    If you've installed rbenv using a package manager, as a final step perform the rbenv package removal. For instance, for Homebrew:

    brew uninstall rbenv
    

Command Reference

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

rbenv local

Sets a local application-specific Ruby version by writing the version name to a .ruby-version file in the current directory. This version overrides the global version, and can be overridden itself by setting the RBENV_VERSION environment variable or with the rbenv shell command.

$ rbenv local 1.9.3-p327

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

$ rbenv local --unset

Previous versions of rbenv stored local version specifications in a file named .rbenv-version. For backwards compatibility, rbenv will read a local version specified in an .rbenv-version file, but a .ruby-version file in the same directory will take precedence.

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 an application-specific .ruby-version file, or by setting the RBENV_VERSION environment variable.

$ rbenv global 1.8.7-p352

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.

rbenv shell

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

$ rbenv shell jruby-1.7.1

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-1.7.1

rbenv 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-p327 (set by /Users/sam/.rbenv/version)
  jruby-1.7.1
  rbx-1.2.4
  ree-1.8.7-2011.03

rbenv version

Displays the currently active Ruby version, along with information on how it was set.

$ rbenv version
1.9.3-p327 (set by /Users/sam/.rbenv/version)

rbenv rehash

Installs shims for all Ruby executables 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 commands.

$ rbenv rehash

rbenv which

Displays the full path to the executable that rbenv will invoke when you run the given command.

$ rbenv which irb
/Users/sam/.rbenv/versions/1.9.3-p327/bin/irb

rbenv whence

Lists all Ruby versions with the given command installed.

$ rbenv whence rackup
1.9.3-p327
jruby-1.7.1
ree-1.8.7-2011.03

Environment variables

You can affect how rbenv operates with the following settings:

name default description
RBENV_VERSION Specifies the Ruby version to be used.
Also see rbenv shell
RBENV_ROOT ~/.rbenv Defines the directory under which Ruby versions and shims reside.
Also see rbenv root
RBENV_DEBUG Outputs debug information.
Also as: rbenv --debug <subcommand>
RBENV_HOOK_PATH see wiki Colon-separated list of paths searched for rbenv hooks.
RBENV_DIR $PWD Directory to start searching for .ruby-version files.

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.

Tests are executed using Bats:

$ bats test
$ bats test/<file>.bats

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

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