Find the unused ENV variables in your Rails app

search.sh

# All variable names in a nice convenient file, each one in a separate line:
# heroku config --app <app> | awk '{print $1}' | sed s/:$//g >> env_variables.txt
# or
# cat .env | awk -F= '{print $1}' | sed '/^#/ d' | sed s/:$//g | sort >> env_variables.txt

variables=`cat env_variables.txt`

# new array
declare -a zombie_variables

for variable in $variables ;
do

  echo "Searching for usage of $variable"

  # Find occurences of ENV.fetch("foo"), ENV.fetch('foo'), ENV["foo"], ENV['foo']
  # (regex stops at $variable, so it also finds ENV.fetch("foo", fallback))
  # -m 1          stop reading when string is found
  # -ERI          use regex, recursive search in directories, and ignore binary files
  # --exclude-dir let's not search the whole universe
  # --color       put some color in your findings
  if grep -m 1 -ERI --exclude-dir=node_modules --color "ENV(\.fetch\(|\[)[(\"|')+]$variable" . ; then
    echo ""
  else
    echo "$variable NOT FOUND"
    zombie_variables+=($variable)
    echo ""
  fi
done

echo "ZOMBIE VARIABLES:"

# expand and print the array elements in a separate line each
printf "%s\n" "${zombie_variables[@]}"
printf "%s\n" "${zombie_variables[@]}" >> zombie_variables.txt

echo "The end."