What is ruby-build?

ruby-build is a tool that lets you install different versions of the Ruby programming language on your computer. It is most commonly used as a companion to a popular Ruby management tool called rbenv, adding a simple command that downloads, compiles, and sets up whatever specific version of Ruby you need. At a high level, the software automates the messy work of building Ruby from its raw source code. Instead of manually hunting down the right files, figuring out the correct configuration settings, and running build commands, you just tell it which version you want. It then downloads the necessary code, verifies that the downloaded files are safe and uncorrupted using checksums, compiles everything, and installs it into a specific folder on your machine. This tool is primarily used by Ruby developers who need to manage multiple projects that rely on different versions of the language. For example, a developer might maintain an older application running on Ruby 1.9.3 while simultaneously building a new project that requires a modern version like Ruby 3.2.0. It allows them to switch between these versions seamlessly on the same computer without conflicts. It can also be used without rbenv as a standalone program if someone needs very precise control over exactly where and how Ruby is installed. The project includes several smart features to make builds faster and more reliable. It uses a download mirror sponsored by 37signals to fetch files quickly, automatically falling back to official source websites if the mirror is down. It also supports download caching, meaning if you uninstall and reinstall a particular version later, it can reuse the previously downloaded files instead of fetching them from the internet all over again. For advanced users, it allows for fine-tuning of the build process through environment variables and custom definition files for versions of Ruby that are not officially supported yet.