A command-line tool for populating environment variables.

gem install populate-env

Heroku apps can describe which environment variables they need via an app.json manifest:

{
  "env": {
    "BRAND_COLOUR": "smaragdine",
    "AMAZING_WEB_SERVICES_TOKEN": {
      "description": "A required token for interacting with Amazing Web Services."
    },
    "WEB_CONCURRENCY": {
      "description": "The number of processes to run.",
      "value": "5"
    },
    "LEATHER_SEATS": {
      "description": "Optional flag to enable leather seats.",
      "required": false
    },
    "SECRET_TOKEN": {
      "description": "A secret key for verifying the integrity of signed cookies.",
      "generator": "secret"
    }
  },
  "environments": {
    "test": {
      "AMAZING_WEB_SERVICES_TOKEN": "mock"
    }
  }
}

Given this file, running the following command will generate a .env file:

$ populate-env heroku

BRAND_COLOUR: "smaragdine"
  => using default from app.json

AMAZING_WEB_SERVICES_TOKEN: "token-from-heroku-app"
  => using value from detected Heroku remote "dev"

WEB_CONCURRENCY: "5"
  => using default from app.json

LEATHER_SEATS: (skipped)
  => no value available

SECRET_TOKEN: "1d8505..."
  => generated secret (32 chars)

WEB_CONCURRENCY: "5"
  => using default from app.json

The resulting .env file looks like this:

BRAND_COLOUR=smaragdine

# A required token for interacting with Amazing Web Services.
AMAZING_WEB_SERVICES_TOKEN=token-from-heroku-app

# The number of processes to run.
WEB_CONCURRENCY=5

# Optional flag to enable leather seats.
# LEATHER_SEATS=

# A secret key for verifying the integrity of signed cookies.
SECRET_TOKEN=1d8505fa8172fae3b17f5e57568406b8

Any required environment variable not currently in your ENV will be populated by trying each of the following:

1. Using the default value, as specified in your app.json
2. Generating a pseudorandom secret (for environment variables marked with generator: secret)
3. Using the values from your remote Heroku instance
4. Prompting you for a missing, required value

The command above is equivalent to the following options:

populate-env heroku \
    --manifest app.json \
    --manifest-environment production \
    --destination .env \
    --skip-local-env \
    --heroku-config \
    --generate-secrets \
    --prompt-missing

If your project has a git remote with heroku.com in the URL, populate-env will detect it and use it to retrieve remote configuration. If you don't want this behaviour, you can skip it with:

populate-env heroku --no-heroku-config

If you have multiple Heroku remotes or want to specify your Heroku app explicitly, you can use either:

populate-env heroku --heroku-remote staging # or
populate-env heroku --heroku-app spronking-wildebeest-42

For full options, run:

populate-env heroku --help

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/Aupajo/populate-env. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the Populate::Env project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.