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/`.
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.
The simplicity of rbenv has its benefits, but also some downsides. See the [comparison of version managers][alternatives] 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.
> For a more automated install, you can use [rbenv-installer](https://github.com/rbenv/rbenv-installer#rbenv-installer). If you do not want to execute scripts downloaded from a web URL or simply prefer a manual approach, follow the steps below.
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](https://github.com/rbenv/ruby-build/wiki#suggested-build-environment) has the necessary tools and libraries**. Then:
For troubleshooting `BUILD FAILED` scenarios, check the [ruby-build Discussions section](https://github.com/rbenv/ruby-build/discussions/categories/build-failures).
Set a Ruby version to finish installation and start using Ruby:
```sh
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.
> You _should not use sudo_ to install gems. Typically, the Ruby versions will be installed under your home directory and thus writeable by your user. If you get the “you don't have write permissions” error when installing gems, it's likely that your "system" Ruby version is still a global default. Change that with `rbenv global <version>` and try again.
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 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:
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 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.
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`
