Homebrew cask option not recognized?

I am following an online resource for installing two Mac utilities

http://www.economyofeffort.com/2014/08/11/beyond-ctrl-remap-make-that-caps-lock-key-useful/

Here is the pertinent section:

Install both Karabiner and Seil. (Here again, if you use Homebrew Cask, you can do this with

$ brew cask install karabiner and

$ brew cask install seil

But the cask option is not recognized?

06:51:35/shared $brew cask install seil
Error: Unknown command: cask

Then, just for laughs I tried the command without the cask:

06:55:01/shared $brew install seil
Error: No available formula for seil
Searching formulae...
Searching taps...
Caskroom/cask/seil

It is not clear what the last line of output even means: nothing seems to have happened on the system.

I am on Yosemite.

Solution 1:

As of 2021, the answer to this question for me was that instead of

brew cask install myprogram

I should run:

brew install --cask myprogram

Solution 2:

As of 2021 use this command instead:

brew install cask your-package

Solution 3:

UPD: since the command brew install caskroom/cask/brew-cask gives you the following error Error: caskroom/cask was moved. Tap homebrew/cask instead. please run brew install homebrew/cask

To use brew cask you should have it installed, this is a extension of brew, is not native.

To install it you need to run brew install caskroom/cask/brew-cask from your command line

Homebrew Cask Github