chruby vs elan

chruby is a free, MIT-licensed shell utility for changing the Ruby version used in a session. Selecting a Ruby updates PATH and sets GEM_HOME and GEM_PATH for that installation. It can match installed Ruby names fuzzily and uses the system Ruby when no selection is made. Optional automatic switching checks the current and parent directories for a .ruby-version file. chruby supports bash 3 or later and zsh on Linux and macOS. Installation instructions cover a release tarball, Homebrew, Arch Linux AUR, Fedora Copr, and FreeBSD ports. Additional Ruby implementations can be installed with ruby-install or ruby-build. The project provides guidance for integrations including Capistrano, Chef, Cron, Emacs, Pow, Puppet, Sudo, Vim, and Fish. Releases are PGP signed, with verification instructions, and the codebase is described as about 100 lines with tests.

elan manages installations of the Lean theorem prover on Linux, macOS and Windows. Its `lean` and `lake` binaries use a project’s `lean-toolchain` file to select the specified Lean version and download it when needed. The separate `elan` command provides manual control to install, select, run or uninstall Lean versions. The project supports version pinning, lockfiles, automatic switching, shell integration and CI/CD use. Installation options include shell instructions for Linux and macOS, a PowerShell method for Windows, and release downloads for supported platforms. The README recommends the Nixpkgs version on NixOS because toolchains downloaded by elan require patching there. Lake needs git to download dependencies. The project describes itself as a fork of rustup adapted for Lean infrastructure. elan is free at free, and the repository lists Apache-2.0 and MIT licenses. The releases page identifies v4.2.4 as the latest release.