Brew cask installation software prompt: error: unknown command: cask

problem

➜ /Users/test > brew cask install mounty
Error: Unknown command: cask

Brew cask installation software prompt: error: unknown command: cask

resolvent:

Use brew install -- cask mount

➜ /Users/test >brew install --cask mounty
Updating Homebrew...

Reference address: install software through brew cask on MAC prompt: error: unknown command: cask?