# .env
USERNAME="username"
DATABASE_URL="postgres://${USERNAME}@localhost/my_database"
```
```js
// index.js
console.log('DATABASE_URL', process.env.DATABASE_URL)
```
```sh
$ dotenvx run --debug -- node index.js
[dotenvx@0.14.1] injecting env (2) from .env
DATABASE_URL postgres://username@localhost/my_database
```

</details>
<details><summary>Command Substitution</summary><br>

Add the output of a command to one of your variables in your .env file.

```ini