require 'formula' class GnupgInstalled < Requirement fatal true satisfy { which('gpg') || which('gpg2') } def message; <<-EOS.undent Gnupg is required to use these tools. You can install Gnupg or Gnupg2 with Homebrew: brew install gnupg brew install gnupg2 Or you can use one of several different prepackaged installers that are available. EOS end end class Pius < Formula homepage 'http://www.phildev.net/pius/' url 'http://downloads.sourceforge.net/project/pgpius/pius/2.0.10/pius-2.0.10.tar.bz2' sha1 '47dadf604cb1eac7ad2ee6594745b0ecc4af4ede' depends_on GnupgInstalled def install # Replace hardcoded gpg path: https://sourceforge.net/p/pgpius/bugs/12/ inreplace 'pius', '/usr/bin/gpg', HOMEBREW_PREFIX/'bin/gpg' bin.install 'pius' bin.install 'pius-keyring-mgr' bin.install 'pius-party-worksheet' end end