dotenv-expand

Dotenv-expand adds variable expansion on top of dotenv. If you find yourself needing to expand environment variables already existing on your machine, then dotenv-expand is your tool.

Install

1# Install locally (recommended)
2npm install dotenv-expand --save

Or installing with yarn? yarn add dotenv-expand

Usage

Create a .env file in the root of your project:

1PASSWORD="s1mpl3"
2DB_PASS=$PASSWORD
3

As early as possible in your application, import and configure dotenv and then expand dotenv:

1var dotenv = require('dotenv')
2var dotenvExpand = require('dotenv-expand')
3
4var myEnv = dotenv.config()
5dotenvExpand.expand(myEnv)
6
7console.log(process.env)

That's it. process.env now has the expanded keys and values you defined in your .env file.

Preload

You can use the --require (-r) command line option to preload dotenv & dotenv- . By doing this, you do not need to require and load dotenv or dotenv-expand in your application code. This is the preferred approach when using import instead of require.

1$ node -r dotenv-expand/config your_script.js

The configuration options below are supported as command line arguments in the format dotenv_config_<option>=value

1$ node -r dotenv-expand/config your_script.js dotenv_config_path=/custom/path/to/your/env/vars

Additionally, you can use environment variables to set configuration options. Command line arguments will precede these.

1$ DOTENV_CONFIG_<OPTION>=value node -r dotenv-expand/config your_script.js

1$ DOTENV_CONFIG_ENCODING=latin1 node -r dotenv-expand/config your_script.js dotenv_config_path=/custom/path/to/.env

Examples

See tests/.env for simple and complex examples of variable expansion in your .env file.

Documentation

DotenvExpand exposes one function:

• expand

Expand

expand will expand your environment variables.

1const dotenv = {
2  parsed: {
3    BASIC: 'basic',
4    BASIC_EXPAND: '${BASIC}',
5    BASIC_EXPAND_SIMPLE: '$BASIC'
6  }
7}
8
9const obj = dotenvExpand.expand(dotenv)
10
11console.log(obj)

Options

ignoreProcessEnv

Default: false

Turn off writing to process.env.

1const dotenv = {
2  ignoreProcessEnv: true,
3  parsed: {
4    SHOULD_NOT_EXIST: 'testing'
5  }
6}
7const obj = dotenvExpand.expand(dotenv).parsed
8
9console.log(obj.SHOULD_NOT_EXIST) // testing
10console.log(process.env.SHOULD_NOT_EXIST) // undefined

FAQ

What rules does the expansion engine follow?

The expansion engine roughly has the following rules:

• $KEY will expand any env with the name KEY
• ${KEY} will expand any env with the name KEY
• \$KEY will escape the $KEY rather than expand
• ${KEY:-default} will first attempt to expand any env with the name KEY. If not one, then it will return default

You can see a full list of examples here.

Contributing Guide

See CONTRIBUTING.md

CHANGELOG

See CHANGELOG.md

Who's using dotenv-expand?

These npm modules depend on it.