# Environment Variables

## Shell environment

Environment variables which are available from the shell environment get passed into the command before execution.

{% code title=".hammerkit.yaml" %}

```yaml
tasks:
  example:
    envs:
      VERSION: $VERSION
    cmds:
      - echo $VERSION
```

{% endcode %}

{% hint style="info" %}
Each environment variable that is used, should be specified in the `envs` of the task. Hammerkit ensures that the environment variable is defined, otherwise will throw an error to prevent undesired behavior.
{% endhint %}

## .env file

Environment variables can be defined in the .env file. Those are recommended for secret values that should not be committed nor public.

{% code title=".env" %}

```
NPM_TOKEN=abc
```

{% endcode %}

{% code title=".hammerkit.yaml" %}

```yaml
tasks:
  example:
    envs:
      NPM_TOKEN: $NPM_TOKEN
    cmds:
      - npm publish
```

{% endcode %}

## Defined values in the build file

Environment variables can be defined in the build file itself. They can be defined for the entire build file or only for specific tasks.

{% code title=".hammerkit.yaml" %}

```yaml
envs:
  NODE_VERSION: 14.16.0
  
tasks:
  example:
    cmds:
      - echo $NODE_VERSION
      
  override_example:
    envs:
      NODE_VERSION: 14.0.0
    cmds:
      - echo $NODE_VERSION
```

{% endcode %}

{% hint style="warning" %}
The scope of the defined environment variables are fixed to the build file they are defined in. Neither [referenced](/hammerkit/build-file/references.md) nor [included](/hammerkit/build-file/includes.md) tasks will have access to those.
{% endhint %}


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