Snippet that you must start right after a brew update to be notify of what brew cask app need to be updated on your Mac OSX

brewcask-update.sh

#!/usr/bin/env bash
#┌───────────────────────────────┐
#│ Print cask packages thet need │
#│ to be updated                 │
#└───────────────────────────────┘

caskList=( $(brew cask list) )

for i in "${caskList[@]}"; do
   info=( $(brew cask info $i) )
   if [[ " ${info[*]} " == *"Not installed"* ]]; then
     echo ${info[0]%?}
   fi
done