Basic usage

Install using yarn add @rhangai/env-builder

Create a template.env

APP_NAME=example-app
APP_PASSWORD={{util.random(16)}}
APP_HOST=myapp.example.com
APP_CONNECTION_URL=http://${APP_HOST}/data

Create a .env.local

APP_HOST=myapp.localhost

Configure it using:

yarn run env-builder generate -t template.env -i .env.local -o .env

The generated output will be

APP_NAME=example-app
APP_PASSWORD=somerandomdata12
APP_HOST=myapp.example.com
APP_CONNECTION_URL=http://myapp.localhost/data

Guide

Now that you know what this library does, let's explain what each flag of the following command

yarn run env-builder generate -t template.env -i .env.local -o .env

The -t/--template [file] flag is the template option, it will use it as a base file to generate your .env, it will be also considered the first input file to set the environment variable values

The -i/--input [file] flag may be used to read and override the variables on the template, it can also have additional variables. You can use this flag multiple times on the same command.

The -o/--output [file] flag is used to write the environment file generated by this command.

The --env-override-prefix <prefix> flag is usually combined when using CI. It allows the variables to be overwritten by environment variables of the same name, but prefixed with prefix.

• Example: When using --env-override-prefix CI_OVERRIDE_ you can set the env CI_OVERRIDE_APP_NAME=my-ci-app to override the variable APP_NAME

package.json mode

You can simplify the usage of the scripts simply by creating the env-builder entry on the package.json file

{
	"devDependencies": {
		"@rhangai/env-builder": "^0.4.0"
	},
	"scripts": {
		"env": "env-builder generate --package --",
		"env:ci": "env-builder generate --package --env-override-prefix CI_OVERRIDE_ --"
	},
	"env-builder": {
		"template": "env/template.env",
		"output": ".env", // Or array [".env", "output/.env"]
		"local": ".env.local",
		"modes": {
			"dev": ["env/development.env"],
			"prod": ["env/production.env"]
		}
	}
}

And the running yarn env

Context

The default context contains two main variables util and env

You can use it in an expression like:

MY_ENV={{ env.OTHER_ENV + util.random(64) }}

Util:

• util.random(n, alphabet = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFHIJKLMNOPQRSTUVXYZ_'): Generates a random string of length n
• util.randomBase64(n): N random bytes, base64 encoded
• util.randomUrlSafeBase64(n): N random bytes, base64 encoded url safe
• util.randomHex(n): N random bytes, hex encoded