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Massive README overhaul (#1433)

Browse source 
rbenv is now the most popular Ruby version manager, so we don't need to
sell it so hard. Instead, help the reader find installation and usage
instructions more easily.

The installation instructions are now simpler and pointing out that
ruby-build needs a separate install is now done in the "Installing Ruby
versions" section.

Finally, link to a wiki doc about potential downsides of rbenv along
with the comparison of different version manager tools.
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@ -1,127 +1,33 @@
# Seamlessly manage 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](http://bundler.io/) 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](https://github.com/basecamp/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](https://github.com/rbenv/rbenv/wiki/Understanding-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](https://github.com/rbenv/rbenv-vars).
See more [plugins on the
wiki](https://github.com/rbenv/rbenv/wiki/Plugins).
[**Why choose rbenv over
RVM?**](https://github.com/rbenv/rbenv/wiki/Why-rbenv%3F)
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.
## 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.
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/`.
### Understanding PATH
You can choose the Ruby version for your project with, for example:
```sh
cd myproject
# choose Ruby version 3.1.2:
rbenv local 3.1.2
```
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:
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.
/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`](#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`](#rbenv-local) command.
4. The global `~/.rbenv/version` file. You can modify this file using
the [`rbenv global`](#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`.
The simplicity of rbenv has its benefits, but also some downsides. See the [comparison of version managers][alternatives] for more details and some alternatives.
## 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.
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.
<details>
<summary>
### Using Package Managers
</summary>
1. Install rbenv using one of the following approaches.
#### Homebrew
@ -136,7 +42,7 @@ Version names to rbenv are simply the names of the directories in
Note that the version of rbenv that is packaged and maintained in the
Debian and Ubuntu repositories is _out of date_. To install the latest
version, it is recommended to [install rbenv using git](#basic-github-checkout).
version, it is recommended to [install rbenv using git](#basic-git-checkout).
```sh
sudo apt install rbenv
@ -148,48 +54,30 @@ Version names to rbenv are simply the names of the directories in
rbenv and you can install it from the AUR using the instructions from this
[wiki page](https://wiki.archlinux.org/index.php/Arch_User_Repository#Installing_and_upgrading_packages).
2. Set up rbenv in your shell.
2. Learn how to load rbenv in your shell.
```sh
# run this and follow the printed instructions:
rbenv init
```
Follow the printed instructions to [set up rbenv shell integration](#how-rbenv-hooks-into-your-shell).
3. Close your Terminal window and open a new one so your changes take effect.
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](#installing-ruby-versions).
4. Verify that rbenv is properly set up using this
[rbenv-doctor](https://github.com/rbenv/rbenv-installer/blob/main/bin/rbenv-doctor) script:
</details>
```sh
curl -fsSL https://github.com/rbenv/rbenv-installer/raw/main/bin/rbenv-doctor | bash
```
<details>
<summary>
```sh
Checking for `rbenv' in PATH: /usr/local/bin/rbenv
Checking for rbenv shims in PATH: OK
Checking `rbenv install' support: /usr/local/bin/rbenv-install (ruby-build 20170523)
Counting installed Ruby versions: none
There aren't any Ruby versions installed under `~/.rbenv/versions'.
You can install Ruby versions like so: rbenv install 2.2.4
Checking RubyGems settings: OK
Auditing installed plugins: OK
```
### Basic Git Checkout
5. That's it! Installing rbenv includes ruby-build, so now you're ready to
[install some Ruby versions](#installing-ruby-versions) using
`rbenv install`.
</summary>
> **Note**
> 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.
### Basic GitHub Checkout
For a more automated install, you can use
[rbenv-installer](https://github.com/rbenv/rbenv-installer#rbenv-installer).
If you prefer a manual approach, follow the steps below.
This will get you going with the latest version of rbenv without needing
a systemwide install.
This will get you going with the latest version of rbenv without needing a system-wide install.
1. Clone rbenv into `~/.rbenv`.
@ -197,121 +85,41 @@ a systemwide install.
git clone https://github.com/rbenv/rbenv.git ~/.rbenv
```
2. Add `~/.rbenv/bin` to your `$PATH` for access to the `rbenv`
command-line utility.
2. Configure your shell to load rbenv:
* For **bash**:
Ubuntu Desktop users should configure `~/.bashrc`:
_Ubuntu Desktop_ users should configure `~/.bashrc`:
```bash
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(~/.rbenv/bin/rbenv init - bash)"' >> ~/.bashrc
```
On other platforms, bash is usually configured via `~/.bash_profile`:
On _other platforms_, bash is usually configured via `~/.bash_profile`:
```bash
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile
echo 'eval "$(~/.rbenv/bin/rbenv init - bash)"' >> ~/.bash_profile
```
* For **Zsh**:
```zsh
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.zshrc
echo 'eval "$(~/.rbenv/bin/rbenv init - zsh)"' >> ~/.zshrc
```
* For **Fish shell**:
```fish
set -Ux fish_user_paths $HOME/.rbenv/bin $fish_user_paths
echo 'status --is-interactive; and ~/.rbenv/bin/rbenv init - fish | source' >> ~/.config/fish/config.fish
```
3. Set up rbenv in your shell.
If you are curious, see here to [understand what `init` does](#how-rbenv-hooks-into-your-shell).
```sh
~/.rbenv/bin/rbenv init
```
Follow the printed instructions to [set up rbenv shell integration](#how-rbenv-hooks-into-your-shell).
3. Restart your shell so that these changes take effect. (Opening a new terminal tab will usually do it.)
4. Restart your shell so that PATH changes take effect. (Opening a new
terminal tab will usually do it.)
5. Verify that rbenv is properly set up using this
[rbenv-doctor](https://github.com/rbenv/rbenv-installer/blob/main/bin/rbenv-doctor) script:
```sh
curl -fsSL https://github.com/rbenv/rbenv-installer/raw/main/bin/rbenv-doctor | bash
```
```sh
Checking for `rbenv' in PATH: /usr/local/bin/rbenv
Checking for rbenv shims in PATH: OK
Checking `rbenv install' support: /usr/local/bin/rbenv-install (ruby-build 20170523)
Counting installed Ruby versions: none
There aren't any Ruby versions installed under `~/.rbenv/versions'.
You can install Ruby versions like so: rbenv install 2.2.4
Checking RubyGems settings: OK
Auditing installed plugins: OK
```
6. _(Optional)_ Install [ruby-build][], which provides the
`rbenv install` command that simplifies the process of
[installing new Ruby versions](#installing-ruby-versions).
#### Upgrading with Git
If you've installed rbenv manually using Git, you can upgrade to the
latest version by pulling from GitHub:
```sh
cd ~/.rbenv
git pull
```
#### Updating the list of available Ruby versions
If you're using the `rbenv install` command, then the list of available Ruby versions is not automatically updated when pulling from the rbenv repo. To do this manually:
```sh
cd ~/.rbenv/plugins/ruby-build
git pull
```
### 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 invasive 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.
</details>
### 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:
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:
```sh
# list latest stable versions:
@ -321,41 +129,43 @@ rbenv install -l
rbenv install -L
# install a Ruby version:
rbenv install 2.0.0-p247
rbenv install 3.1.2
```
Set a Ruby version to finish installation and start using commands `rbenv global 2.0.0-p247` or `rbenv local 2.0.0-p247`
> **Note**
> If the `rbenv install` command wasn't found, you can install ruby-build as a plugin:
> ```sh
> git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ruby-build
> ```
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.
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.
#### Installing Ruby gems
Once you've installed some Ruby versions, you'll want to install gems.
First, ensure that the target version for your project is the one you want by
checking `rbenv version` (see [Command Reference](#command-reference)). Select
another version using `rbenv local 2.0.0-p247`, for example. Then, proceed to
install gems as you normally would:
Select a Ruby version for your project using `rbenv local 3.1.2`, for example. Then, proceed to install gems as you normally would:
```sh
gem install bundler
```
**You don't need sudo** to install gems. Typically, the Ruby versions will be
installed and writeable by your user. No extra privileges are required to
install gems.
> **Warning**
> 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.
Check the location where gems are being installed with `gem env`:
```sh
gem env home
# => ~/.rbenv/versions/<ruby-version>/lib/ruby/gems/...
# => ~/.rbenv/versions/<version>/lib/ruby/gems/...
```
### Uninstalling Ruby versions
#### Uninstalling Ruby versions
As time goes on, Ruby versions you install will accumulate in your
`~/.rbenv/versions` directory.
@ -363,41 +173,35 @@ As time goes on, Ruby versions you install will accumulate in your
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`.
2.7.0`.
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.
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
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:
- Homebrew: `brew uninstall rbenv`
- Debian, Ubuntu, and their derivatives: `sudo apt purge rbenv`
- Archlinux and its derivatives: `sudo pacman -R rbenv`
## Command Reference
Like `git`, the `rbenv` command delegates to subcommands based on its
first argument. The most common subcommands are:
The main rbenv commands you need to know are:
### 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 local
@ -407,7 +211,7 @@ 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
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:
@ -421,7 +225,7 @@ 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
rbenv global 3.1.2
The special version name `system` tells rbenv to use the system Ruby
(detected by searching your `$PATH`).
@ -449,34 +253,11 @@ prefer not to use shell integration, you may simply set the
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.
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
rbenv rehash
### rbenv which
@ -488,7 +269,7 @@ you run the given command.
### rbenv whence
Lists all Ruby versions with the given command installed.
Lists all Ruby versions that contain the specified executable name.
$ rbenv whence rackup
1.9.3-p327
@ -507,11 +288,42 @@ name | default | description
`RBENV_HOOK_PATH` | [_see wiki_][hooks] | Colon-separated list of paths searched for rbenv hooks.
`RBENV_DIR` | `$PWD` | Directory to start searching for `.ruby-version` files.
## Development
### How rbenv hooks into your shell
The rbenv source code is [hosted on
GitHub](https://github.com/rbenv/rbenv). It's clean, modular,
and easy to understand, even if you're not a shell hacker.
`rbenv init` is a helper command to bootstrap rbenv into a shell. This helper is part of the recommended installation instructions, but optional, as an advanced user can set up the following tasks manually. Here is what the command does when its output is `eval`'d:
0. Adds `rbenv` executable to PATH if necessary.
1. Prepends `~/.rbenv/shims` directory to PATH. This is basically the only requirement for rbenv to function properly.
2. Installs shell completion for rbenv commands.
3. Regenerates rbenv shims. If this step slows down your shell startup, you can invoke `rbenv init -` with the `--no-rehash` flag.
4. Installs the "sh" dispatcher. This bit is also optional, but allows rbenv and plugins to change variables in your current shell, making commands like `rbenv shell` possible.
You can run `rbenv init -` for yourself to inspect the generated script.
### Uninstalling rbenv
The simplicity of rbenv makes it easy to temporarily disable it, or
uninstall from the system.
1. To **disable** rbenv managing your Ruby versions, simply remove the `rbenv init` line from your shell startup configuration. This will remove rbenv shims directory from PATH, and future invocations like `ruby` will execute the system Ruby version, bypassing rbenv completely.
While disabled, `rbenv` will still be accessible on the command line, but your Ruby apps won't be affected by version switching.
2. To completely **uninstall** rbenv, perform step (1) and then remove the rbenv root directory. This will **delete all Ruby versions** that were installed under `` `rbenv root`/versions/ ``:
rm -rf "$(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`
## Development
Tests are executed using [Bats](https://github.com/sstephenson/bats):
@ -524,3 +336,4 @@ tracker](https://github.com/rbenv/rbenv/issues).
[ruby-build]: https://github.com/rbenv/ruby-build#readme
[hooks]: https://github.com/rbenv/rbenv/wiki/Authoring-plugins#rbenv-hooks
[alternatives]: https://github.com/rbenv/rbenv/wiki/Other-version-managers