Homebrew

Homebrew Primer / Glossary

This section is llm-generated

Core Concepts

• Homebrew (“brew”)
  The actual package manager CLI (brew install foo). Manages where software comes from and how it’s installed.
• Formula (plural: formulae)
  A recipe (written in Ruby) describing how to download, compile, and install a piece of software.
  • Example: brew install wget pulls the wget formula, builds it (or fetches a prebuilt binary), and installs it.
  • Stored in GitHub repos like homebrew-core.
• Cask
  A type of formula, but specifically for macOS applications packaged as binaries (usually .app, .dmg, .pkg).
  • Example: brew install --cask google-chrome downloads the dmg and installs Chrome into /Applications.
  • Lives in homebrew-cask.
• Tap
  A Git repo containing formulae or casks. Think of it as an extra “source of packages”.
  • The default is homebrew/core and homebrew/cask.
  • Anyone can make a tap: e.g. brew tap hashicorp/tap gives access to brew install hashicorp/terraform.
• Keg
  The installed copy of a formula in Homebrew’s cellar.
  • Stored under /usr/local/Cellar/<formula>/<version> (Intel macs) or /opt/homebrew/Cellar/... (Apple Silicon).
• Cellar
  The folder containing all kegs. It’s the “wine cellar” for your software.
• Prefix
  The “root directory” under which Homebrew is installed.
  • /usr/local (Intel macs) or /opt/homebrew (Apple Silicon).
  • Symlinks from bin/, lib/, etc. point into the Cellar so software is on your PATH.

Supporting Concepts

• Bottle
  A precompiled binary of a formula (so you don’t have to compile from source).
  • brew install wget usually installs a bottle.
  • If no bottle is available, it falls back to building from source.
• Head formula
  Formula that installs from the latest commit of the project’s repo (not a release).
  • Example: brew install --HEAD neovim.
• Taproom (rarely used term)
  Just a nickname for the collection of taps.
• Bundle
  A Brewfile system (brew bundle) — like a lockfile or manifest. Lets you declare all the formulae, casks, and taps you want and restore them on a new machine.

Mental Model

• Brew is the waiter.
• Formulae are the recipes.
• Casks are pre-boxed takeout meals (apps).
• Taps are extra cookbooks from other chefs.
• Cellar is the wine cellar where all bottles (installations) are stored.
• Kegs are the actual bottles of wine (specific software versions).
• Prefix is the front-of-house restaurant entrance (where symlinks make software available).