rbenv: new cheatsheet

rbenv.md

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+---
+title: rbenv
+category: Ruby
+layout: 2017/sheet
+updated: 2017-10-11
+description: |
+  A one-page guide to rbenv Ruby version manager, with usage examples and more.
+intro: |
+  [rbenv](https://github.com/rbenv/rbenv) lets you manage installations of multiple Ruby versions.
+---
+
+### Installation
+
+#### Install rbenv and ruby-build
+
+```bash
+git clone https://github.com/sstephenson/rbenv.git ~/.rbenv
+git clone https://github.com/sstephenson/ruby-build.git ~/.rbenv/plugins/ruby-build
+```
+
+#### Install rbenv and ruby-build
+
+```bash
+echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile
+echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
+```
+
+#### Verify installation
+
+```bash
+type rbenv   # → "rbenv is a function"
+```
+
+These are generic instructions; there may be rbenv packages available for your OS.
+
+See: [Installation](https://github.com/rbenv/rbenv#installation)
+
+### Managing versions
+
+| Command                 | Description                 |
+| ---                     | ---                         |
+| `rbenv install -l`      | List all available versions |
+| ---                     | ---                         |
+| `rbenv install 2.2.1`   | Install Ruby _2.2.1_        |
+| `rbenv uninstall 2.2.1` | Uninstall Ruby _2.2.1_      |
+| ---                     | ---                         |
+| `rbenv versions`        | See installed versions      |
+| `rbenv version`         | See current version         |
+| ---                     | ---                         |
+| `rbenv which <NAME>`    | Display path to executable  |
+| `rbenv rehash`          | Re-write binstubs           |
+
+## Using versions
+{: .-three-column}
+
+### Locally
+
+| `rbenv local 2.2.2`   | Use Ruby _2.2.2_ in project |
+| `rbenv local --unset` | Undo above                  |
+
+Application-specific version numbers are stored in `.ruby-version`.
+
+### Globally
+
+| `rbenv global 2.2.2`   | Use Ruby _2.2.2_ globally |
+| `rbenv global --unset` | Undo above                  |
+
+Global version numbers are stored in `~/.rbenv/version`.
+
+### Shell
+
+| `rbenv shell 2.2.2`   | Use Ruby _2.2.2_ in shell |
+| `rbenv shell --unset` | Undo above                |
+
+Shell-local version numbers are stored as environment variables.
+
+## References
+
+- [rbenv project page](https://github.com/rbenv/rbenv) _(github.com)_
+- [rbenv ubuntu server cheatsheet](https://gist.github.com/rahul286/7160839f4425a3b7e718) _(gist.github.com)_