rbenv is a version manager tool for the Ruby programming language on Unix-like systems. It is useful for switching between multiple Ruby versions on the same machine and for ensuring that each project you are working on always runs on the correct Ruby version.

After rbenv injects itself into your PATH at installation time, any invocation of ruby, gem, bundler, or other Ruby-related executable will first activate rbenv. Then, rbenv scans the current project directory for a file named .ruby-version. If found, that file determines the version of Ruby that should be used within that directory. Finally, rbenv looks up that Ruby version among those installed under ~/.rbenv/versions/.

You can choose the Ruby version for your project with, for example:

cd myproject
# choose Ruby version 3.1.2:
rbenv local 3.1.2

Doing so will create or update the .ruby-version file in the current directory with the version that you've chosen. A different project of yours that is another directory might be using a different version of Ruby altogether—rbenv will seamlessly transition from one Ruby version to another when you switch projects.

Finally, almost every aspect of rbenv's mechanism is customizable via plugins written in bash.

The simplicity of rbenv has its benefits, but also some downsides. See the comparison of version managers for more details and some alternatives.

On systems with Homebrew package manager, the “Using Package Managers” method is recommended. On other systems, “Basic Git Checkout” might be the easiest way of ensuring that you are always installing the latest version of rbenv.

1. Install rbenv using one of the following approaches.

   Homebrew

   On macOS or Linux, we recommend installing rbenv with Homebrew.

   brew install rbenv

   Debian, Ubuntu, and their derivatives

   [!CAUTION]
   The version of rbenv that is packaged and maintained in official Debian and Ubuntu repositories is out of date. To install the latest version, it is recommended to install rbenv using git.

   sudo apt install rbenv

   Arch Linux and its derivatives

   Archlinux has an AUR Package for rbenv and you can install it from the AUR using the instructions from this wiki page.

   Fedora

   Fedora has an official package which you can install:

   sudo dnf install rbenv

2. Set up your shell to load rbenv.

   rbenv init

3. Close your Terminal window and open a new one so your changes take effect.

That's it! You are now ready to install some Ruby versions.

This will get you going with the latest version of rbenv without needing a system-wide install.

1. Clone rbenv into ~/.rbenv.

   git clone https://github.com/rbenv/rbenv.git ~/.rbenv

2. Set up your shell to load rbenv.

   ~/.rbenv/bin/rbenv init

   If you are curious, see here to understand what init does.

3. Restart your shell so that these changes take effect. (Opening a new terminal tab will usually do it.)

When manually installing rbenv, it might be useful to note how completion scripts for various shells work. Completion scripts help with typing rbenv commands by expanding partially entered rbenv command names and option flags; typically this is invoked by pressing Tab key in an interactive shell.

• The bash completion script for rbenv ships with the project and gets loaded by the rbenv init mechanism.

• The zsh completion script ships with the project, but needs to be added to FPATH in zsh before it can be discovered by the shell. One way to do this would be to edit ~/.zshrc:

  # assuming that rbenv was installed to `~/.rbenv`
  FPATH=~/.rbenv/completions:"$FPATH"
  
  autoload -U compinit
  compinit

• The fish completion script for rbenv ships with the fish shell itself and is not maintained by the rbenv project.

The rbenv install command does not ship with rbenv out-of-the-box, but is provided by the ruby-build plugin.

Before attempting to install Ruby, check that your build environment has the necessary tools and libraries. Then:

# list latest stable versions:
rbenv install -l

# list all local versions:
rbenv install -L

# install a Ruby version:
rbenv install 3.1.2

For troubleshooting BUILD FAILED scenarios, check the ruby-build Discussions section.

git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ruby-build

Set a Ruby version to finish installation and start using Ruby:

rbenv global 3.1.2   # set the default Ruby version for this machine
# or:
rbenv local 3.1.2    # set the Ruby version for this directory

Alternatively to the rbenv 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.

Select a Ruby version for your project using rbenv local 3.1.2, for example. Then, proceed to install gems as you normally would:

gem install bundler

Check the location where gems are being installed with gem env:

gem env home
# => ~/.rbenv/versions/<version>/lib/ruby/gems/...

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 2.7.0.

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

The main rbenv commands you need to know are:

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

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)

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 3.1.2

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

rbenv local --unset

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 3.1.2

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.

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

Installs shims for all Ruby executables known to rbenv (~/.rbenv/versions/*/bin/*). Typically you do not need to run this command, as it will run automatically after installing gems.

rbenv rehash

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

Lists all Ruby versions that contain the specified executable name.

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

You can affect how rbenv operates with the following settings:

rbenv init is a helper command to bootstrap rbenv into a shell. This helper is part of the recommended installation instructions, but optional, as an advanced user can set up the following tasks manually. Here is what the command does when its output is eval'd by a shell during its startup:

0. Adds rbenv executable to PATH if necessary.

1. Prepends ~/.rbenv/shims directory to PATH. This is basically the only requirement for rbenv to function properly.

2. Installs bash shell completion for rbenv commands.

3. Regenerates rbenv shims. If this step slows down your shell startup, you can invoke rbenv init - with the --no-rehash flag.

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.

You can run rbenv init - for yourself to inspect the generated script.

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 comment or 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, bypassing rbenv completely.

   While disabled, 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 the rbenv root directory. This will delete all Ruby versions that were installed under `rbenv root`/versions/:

   rm -rf "$(rbenv root)"
   

   If you've installed rbenv using a package manager, as a final step perform the rbenv package removal:

   • Homebrew: brew uninstall rbenv
   • Debian, Ubuntu, and their derivatives: sudo apt purge rbenv
   • Archlinux and its derivatives: sudo pacman -R rbenv

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.