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How to fix Unknown command: cask on macOS Monterey.

December 03, 2021

Photo by Ken Suarez on Unsplash

I recently bumped into an unknown command error while trying to install the Firefox macOS application using a CLI workflow with Homebrew.

Disclaimer: This post assumes that Homebrew is installed on your machine, if not I suggest that you install it from brew.sh before applying this fix . Also, this fix has been tested to work on macOS Monterey version 12.0.1, but should work fine on other versions. If the issue is still not solved, please leave a comment or check out the references at the bottom.

For starters, Cask is an extension of Homebrew a.k.a brew for installation uninstallation and management of GUI macOS applications such as Discord, Google Chrome and Firefox.

With Cask, you don’t need to “To install, drag this icon…”as you would normally do when installing a new macOS application.

Pre & Post Homebrew Cask migration

Initially, to install a new macOS application with Cask, you first tap (Third-Party Repositories) Homebrew with. $ brew tap homebrew/cask-versions followed by. $ brew cask install <macos-application-name>.

The brew tap command adds more repositories to the list of formulae that Homebrew tracks, updates, and installs from.

In my case;

$ brew cask install firefox 
Error: Unknown command: cask

Turns out, Cask has been moved to Homebrew making it easier to install many macOS applications.

Tapping Cask should now work running the command below:

$ brew tap homebrew/cask-versions
==> Tapping homebrew/cask-versions
Cloning into '/usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask-versions'...
remote: Enumerating objects: 241396, done.
remote: Total 241396 (delta 0), reused 0 (delta 0), pack-reused 241396
Receiving objects: 100% (241396/241396), 61.59 MiB | 7.18 MiB/s, done.
Resolving deltas: 100% (166739/166739), done.
Tapped 205 casks (235 files, 68.3MB).

Now, to install any casks available formulae, simply run this command.

$ brew install <formulae> or $ brew install --cask <formulae>

In my case:

$ brew install firefox
==> Downloading https://download-installer.cdn.mozilla.net/pub/firefox/releases/94.0.2/mac/en-US/Fi
######################################################################## 100.0%
==> Installing Cask firefox
==> Moving App 'Firefox.app' to '/Applications/Firefox.app'
🍺  firefox was successfully installed!

To browse all casks available formulaes the cask tap via the Homebrewcheckout https://formulae.brew.sh/cask/

References:

Written by Ernest Saidu Kamara, a software engineer born in Sierra Leone and raised in Norway - Follow me on my social network. 👇🏿