Scripting Bits
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Scripting Bits

Per-Environment Configuration

It’s a well-established practice to supply credentials and environment-specific configuration to a web app via environment variables.

By “environment-specific”, I mean specific to a particular instance of the running web app. That could be the web app running on its production server or the web app running on a developer’s laptop.

For Node.js applications, the most common implementations I’ve seen are:

  • Literally using environment variables — usually when deploying to a cloud provider or when running in a Docker container
  • Using a config file that gets automatically translated into environment variables — e.g. via the dotenv tool.

For providing configuration during development on my laptop, I’ve found a config file to be the easiest way.

Recently, I’ve started building a web app, and I needed an easy way to provide an SSL certificate to my code. I naturally reached for dotenv. But, to my surprise, there was no easy way to provide strings with multiple lines.

dotenv has its own homegrown configuration format that looks like:


It resembles BASH, but in reality, only supports simple string keys and string values, with augmentations nailed on over time.

I got to thinking about prior art for configuration files:

  • *nix packages always seem to use fully-featured config formats — many look like TOML.
  • Node.js and npm use JSON.
  • Rails, and many cloud providers use YAML.

I realized that a minimal KEY=VALUE syntax is just not good enough. And, neither is, for that matter, JSON, because it’s lacking that first layer of make-my-life-easier features (like multi-line strings or variables.)

So, I set out to implement as YAML version of dotenv:



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