Bash find if all env variables are declared, by variable name

I'm having issues with the below script. It should exit only if there is not a variable set by that name.

#!/bin/bash
set -e

echo 'START: env_vars_config'

required_var(){
  VARIABLE=$1
  echo "detecting if $VARIABLE exists"
  echo ${!VARIABLE}
  if [ -z ${!VARIABLE}+x ]; then
    echo "${VARIABLE} was defined"
  else
    echo "Need to set environment var $VARIABLE" && exit 1;
  fi
}

# these are required variables to deploy
required_var MONGO_URL
required_var AWS_REGION
required_var AUTOSCALING_GROUP_NAME
required_var LATEST_STABLE_COMMIT
required_var ENV_FILE
required_var DEPLOY_FILE
required_var POSTMAN_ENVIRONMENT_UID
required_var POSTMAN_COLLECTION_UID
required_var POSTMAN_API_KEY
required_var MANDRILL_KEY
required_var SERVER_SECRET
required_var S3_BUCKET
required_var ELASTIC_URL
required_var ELASTIC_PASSWORD
required_var ELASTIC_PREFIX


echo 'END: env_vars_config'

Right now this script always exits on the first check MONGO_URL however I know this is variable set and is a string.

• What would a check for unset look like?
• What would a check for unset or empty string look like?

FIXED 2 issues, firstly the + symbol at the end of the if statement was a typo. Secondly I had the order of the if statement backwards.

  if [ -z "${!VARIABLE}" ]; then
    echo "Need to set environment var $VARIABLE" && exit 1;
  else
    echo "${VARIABLE} was defined"
  fi