# Inject runtime variables

You can set [runtime variables (ENV)](https://docs.docker.com/engine/reference/builder/#env) to be passed to the Docker container at runtime. You can set runtime variables in individual resources, or [create a secret group](https://northflank.com/docs/v1/application/secure/manage-secret-groups) so that multiple resources in a project can inherit the same secrets.

You can also upload [secret files](#add-a-secret-file-to-a-deployment) to make certificates, configuration files, and other data available in your containers.

![Editing runtime variables in the Northflank application](https://assets.northflank.com/documentation/v1/application/run/inject-runtime-variables/environment-variables.png)

Runtime variables can be set as key-value pairs, or as JSON in the following format:

```JSON
{
    "KEY_1": "value1",
    "KEY_2": "value2"
}
```

An `.env` file can also be uploaded and edited using the following format:

```ENV
KEY_1=value1
KEY_2=value2
```

## Access environment variables in your code

Your runtime variables can be accessed via the process environment, for example in a Node environment a variable set as `ENV_VALUE=Northflank` can be accessed within the container by referring to `process.env.ENV_VALUE`.

| Runtime environment | Environment variable accessor | Required import |
| --- | --- | --- |
| Node | `process.env.ENV_KEY` | none |
| Deno | `Deno.env.get("ENV_KEY")` | none |
| Bun | `Bun.env.ENV_KEY` OR `process.env.ENV_KEY` | none |
| Python | `os.environ.get("ENV_KEY")` | `import os` |
| Java | `System.getenv("ENV_KEY")` | none |
| Kotlin | `System.getenv("ENV_KEY")` | none |
| Ruby on Rails | `ENV["ENV_KEY"]` | none |
| Rust | `env::var("ENV_KEY")` | `use std::env` |
| Go | `os.Getenv("ENV_KEY")` | `import ( "os" )` |
| C# / .NET | `Environment.GetEnvironmentVariable("ENV_KEY")` | `using System;` |
| C++ | `std::getenv("ENV_KEY")` | `#include <cstdlib>` |
| C | `getenv("ENV_KEY")` | `#include <stdlib.h>` |
| PHP | `getenv("ENV_KEY")` | none |
| Lua | `os.getenv("ENV_KEY")` | none |
| Shell / Bash | `${ENV_KEY}` | none |
| PowerShell | `$Env:ENV_KEY` OR `[Environment]::GetEnvironmentVariable('ENV_KEY')` | none |

## Add a secret file to a deployment

You can include secret files which can be accessed in your container's file system. This can be useful to provide certificates, secrets, or configuration files that must are required by your application, but which should not be included in your repository.

To add a secret file, paste or upload the content in the secret file editor on the environment page of a deployment service, combined service, or a job. You can also upload secret files to [secret groups](https://northflank.com/docs/v1/application/secure/manage-secret-groups) to make them available to multiple resources in the same project.

## Next steps

- [Inject secrets: Set build arguments and inject runtime variables into running deployments.](/v1/application/secure/inject-secrets)
- [Manage groups of secrets: Create and manage groups of secrets that can be inherited throughout an entire project or by specific services and jobs.](/v1/application/secure/manage-secret-groups)
- [Upload a secret file: Add secret files that will be mounted in your container.](/v1/application/secure/upload-secret-files)