Below is a quick little script I threw together to copy config vars from one Heroku app to another, e.g. when trying to create a staging or test app that [largely] mirrors another.
It relies on a Heroku app.json to specify which config vars are required, combined with a dump of your other app’s config vars via heroku config --shell -a <app-name> >foo.env to get the <env-file> input.
#!/usr/bin/env ruby # frozen_string_literal: true require 'json' # Usage: env-setter <app.json> <env-file> [-a <heroku-app-name>] app_json_file = ARGV[0] env_file = ARGV[1] env_var_keys = [] heroku_app_name = nil # parse command line -a switch to get Heroku app name if ARGV.include?('-a') heroku_app_name = ARGV[ARGV.index('-a') + 1] end # Pull required config vars from app.json begin parsed_json = JSON.parse(File.read(app_json_file)) env_var_keys = parsed_json['env'].map {|k,v| k if v.is_a?(Hash) && v['required'] }.compact rescue JSON::ParserError, EOFError puts "Error parsing JSON file: #{app_json_file}" exit 1 end # puts "Required config vars from app.json: #{env_var_keys.join(', ')}" # Pull env vars from env file begin env_vars = Hash[*File.readlines(env_file).map(&:chomp).map { |line| line.split('=', 2) }.flatten] rescue EOFError puts "Error reading env file: #{env_file}" exit 1 end # puts "Loaded env var names from #{env_file}: #{env_vars.keys.join(', ')}" # Check if any required env vars are missing missing_vars = env_var_keys - env_vars.keys if missing_vars.any? puts "Missing required env vars from #{env_file}: #{missing_vars.join(', ')}" exit 1 end # Set config vars on Heroku if app name provided if heroku_app_name puts "Setting config vars on Heroku app #{heroku_app_name}..." system('heroku', 'config:set', '--app', heroku_app_name, *env_vars.map {|k,v| "#{k}=#{v}" }.flatten) end 
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