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# dotenv-expand
<img src="https://raw.githubusercontent.com/motdotla/dotenv-expand/master/dotenv-expand.png" alt="dotenv-expand" align="right" />
Dotenv-expand adds variable expansion on top of
[dotenv](http://github.com/motdotla/dotenv). If you find yourself needing to
expand environment variables already existing on your machine, then
dotenv-expand is your tool.
[](https://travis-ci.org/motdotla/dotenv-expand)
[](https://www.npmjs.com/package/dotenv-expand)
[](https://github.com/feross/standard)
## Install
```bash
# Install locally (recommended)
npm install dotenv-expand --save
```
Or installing with yarn? `yarn add dotenv-expand`
## Usage
Create a `.env` file in the root of your project:
```dosini
PASSWORD="s1mpl3"
DB_PASS=$PASSWORD
```
As early as possible in your application, import and configure dotenv and then expand dotenv:
```javascript
var dotenv = require('dotenv')
var dotenvExpand = require('dotenv-expand')
var myEnv = dotenv.config()
dotenvExpand.expand(myEnv)
console.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](https://nodejs.org/api/cli.html#cli_r_require_module) 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`.
```bash
$ 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`
```bash
$ 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.
```bash
$ DOTENV_CONFIG_<OPTION>=value node -r dotenv-expand/config your_script.js
```
```bash
$ DOTENV_CONFIG_ENCODING=latin1 node -r dotenv-expand/config your_script.js dotenv_config_path=/custom/path/to/.env
```
## Examples
See [tests/.env](https://github.com/motdotla/dotenv-expand/blob/master/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.
```js
const dotenv = {
parsed: {
BASIC: 'basic',
BASIC_EXPAND: '${BASIC}',
BASIC_EXPAND_SIMPLE: '$BASIC'
}
}
const obj = dotenvExpand.expand(dotenv)
console.log(obj)
```
#### Options
##### ignoreProcessEnv
Default: `false`
Turn off writing to `process.env`.
```js
const dotenv = {
ignoreProcessEnv: true,
parsed: {
SHOULD_NOT_EXIST: 'testing'
}
}
const obj = dotenvExpand.expand(dotenv).parsed
console.log(obj.SHOULD_NOT_EXIST) // testing
console.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](https://github.com/motdotla/dotenv-expand/blob/master/tests/.env).
## Contributing Guide
See [CONTRIBUTING.md](CONTRIBUTING.md)
## CHANGELOG
See [CHANGELOG.md](CHANGELOG.md)
## Who's using dotenv-expand?
[These npm modules depend on it.](https://www.npmjs.com/browse/depended/dotenv-expand)