rbenv

rbenv is a lightweight Ruby version management tool that lets developers install and switch between different Ruby interpreters. It aims to be minimally opinionated and non-intrusive, in contrast to more feature-rich tools like RVM.

rbenv uses a shim-based approach. The actual Ruby interpreters are installed under ~/.rbenv/versions, while small shim executables reside in ~/.rbenv/shims. When a Ruby command such as ruby, gem, rake, or bundle is run, the shim forwards the call to the appropriate Ruby version according to the current configuration.

To select versions, you can set a global default with rbenv global, a per-project version with rbenv local, or place a .ruby-version file in a project directory. The active version is determined by walking up the directory tree to locate the nearest .ruby-version.

Installation of new Ruby versions is provided by the ruby-build plugin. After installing or adding new executables, you typically run rbenv rehash to refresh the shims so new commands are recognized.

rbenv requires an initialization step in the shell, usually by adding eval "$(rbenv init -)" to the startup script. This ensures the shims are available early in PATH and enables proper command resolution.

It is designed to be lightweight and does not manage gemsets; gem dependencies are typically handled by Bundler. It is primarily used on Unix-like systems and enjoys broad community support.