Brew Concepts
Internal
Overview
Homebrew is a package management system for Mac. All applications installed with Homebrew are linked from /usr/local/bin which usually takes precedence over /usr/bin:/bin:/usr/sbin:/sbin, where system utilities are installed. For example, if bash is installed with Homebrew, it'll be usually the newest one and take precedence over the one that comes with the system in /bin/bash.
Formula
A formula is a package definition written in Ruby. Conceptually, this is the term for "program managed by brew" (also see cask below). Homebrew comes with a good amount of existing formulae, and they are stored as Ruby files in the default tap named "homebrew/core": /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/<package-name>.rb. The directory where a specific formula is located can be displayed with:
brew formula <formula-name>
The formulae that have already been applied to the system can be listed with:
brew list
An application that has never been installed on the system can be installed with:
brew install <formula-name>
and it can be updated with:
brew update <formula-name>
Common Formulate
bash
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/bash.rb
Custom Formulae
New formulae can be created. Instructions are available here: https://docs.brew.sh/Formula-Cookbook. The sequence is:
brew create <URL>
where <URL> is a zip or tar file, installed with
brew install <formula>
and debugged with:
brew install --debug --verbose <formula>
Formula API: http://www.rubydoc.info/github/Homebrew/brew/master/Formula
Keg
A keg is the installation prefix of a formula. The corresponding directories are stored in cellar.
Example:
/usr/local/Cellar/foo/0.1
Tap
A tap is a Git repository of formulae or casks.
The list of all taps available on the system is provided by:
brew tap
A new repository can be added.
By default, the following taps are available:
- homebrew/core
- homebrew/cask
Cellar
The directory where all kegs are stored:
/usr/local/Cellar
Depending on the brew instance, the location may differ. The actual value can be obtained with:
brew --cellar
The command yields the same result as $(brew --prefix)/Cellar.
Bottle
Cask
A cask is application distributed in binary form, in some cases also including a graphical UI. Examples: google-chrome, docker, corretto11. Brew commands allow for a --cask command line option that changes their semantics to apply to casks, instead of formulae. The difference between formulae and casks is that in case of formulae, source code that will be compiled. Casks are pre-compiled.
The files associated with a cask are stored in the "Caskroom" /usr/local/Caskroom.
To install Homebrew Cask itself:
brew tap caskroom/cask
An example of installing Google Chrome with cask:
brew cask install google-chrome
==> Satisfying dependencies
==> Downloading https://dl.google.com/chrome/mac/stable/GGRO/googlechrome.dmg
######################################################################## 100.0%
==> Verifying checksum for Cask google-chrome
==> Installing Cask google-chrome
==> Moving App 'Google Chrome.app' to '/Applications/Google Chrome.app'.
🍺 google-chrome was successfully installed!
User Space vs. System Space
Install Path
brew --prefix
Displays the brew install path.
--prefix can be used with specific formulas:
brew --prefix python