Manage Environment Variables in Elixir

I love how the Elixir build tool, Mix, has built-in support for configuration settings. It makes configuring packages much simpler by providing a standard interface for config settings.

I’m currently developing a Twilio API client for Elixir. While I develop and test it, I need to store an “Account SID” and “Auth token” to make requests. Naturally, I turned to Mix config.

Because I needed to have separate configuration files for each environment, so that I could test with different credentials, I set up config/config.exs like this:

use Mix.Config

import_config "#{Mix.env}.exs"

I then created config/development.exs and config/test.exs files to store environment-specific settings.

# config/development.exs
use Mix.Config

config :ex_twilio, account_sid: "SID HERE"
config :ex_twilio, auth_token:  "TOKEN HERE"

But I’m going to be pushing this project to Github when it’s ready, so I don’t want to store my real credentials here. Instead, I want to use ENV variables. So, I update my config/<environment>.exs files to look like this:

use Mix.Config

config :ex_twilio, account_sid: System.get_env("TWILIO_ACCOUNT_SID")
config :ex_twilio, auth_token:  System.get_env("TWILIO_AUTH_TOKEN")

After trying a variety of different solutions, it seems like the best way currently to get these variables to be set is to create a .env file in your project directory:

export TWILIO_ACCOUNT_SID="<SID HERE>"
export TWILIO_AUTH_TOKEN="<TOKEN HERE>"

Then, simply run source .env in your shell before you run any iex or mix commands. Done!