[Important Note] Move to https://github.com/DriftwoodJP/bcupgrade

brew-cask-upgrade.rb

#!/usr/bin/ruby
require 'readline'

# Create cask list
puts "\nCreate cask list...\n"
list = `brew cask list`
casks = list.delete(' (!)').split("\n")
puts "#{casks}\n"

# Check update cask
puts "\nCheck update cask...\n"
update_casks = []
casks.each do |cask|
  info = `brew cask info #{cask}`
  update_casks.push(cask) if info.include?('Not installed')
end
puts "#{update_casks}\n"

# Upgrade cask
if update_casks.any?
  update_casks.each do |cask|
    input = Readline.readline("\nUpgrade #{cask}? [y/n] ")
    next unless input == 'y'
    puts "remove #{cask}"
    system "rm -rf /usr/local/Caskroom/#{cask}"
    puts "install #{cask}"
    system "brew cask install --force #{cask}"
  end
else
  puts "\nAlready up-to-date."
end