# Environment Variable

Specify environment variables (required or optional) used by your script.

==- :icon-code-review: Show Me How
```yaml bashly.yml
environment_variables:
  - name: config_path
    help: Location of the config file
    default: ~/config.ini
  - name: api_key
    help: Your API key
    required: true
  - name: app_env
    help: Application environment
    allowed: [dev, prod, test]
    default: dev
```
===

If an environment variable is defined as required (false by default), the
execution of the script will be halted with a friendly error if it is not set.

In addition, you can specify a default value for the environment variable, which
will be used in case the user has not defined it in their environment.

!!! Note
Most properties are optional, unless specified otherwise.
!!!

[!button variant="primary" icon="code-review" text="Environment Variables Example"](https://github.com/bashly-framework/bashly/tree/master/examples/environment-variables#readme)

## Basic Options

### name

[!badge String] [!badge variant="danger" text="Required"]

The name of the variable. Use a lowercase name, it will be automatically
capitalized wherever needed.

### help

[!badge String]

The message to display when using `--help`. Can have multiple lines.

## Common Options

### default

[!badge String]

The value to use in case it is not provided by the user. Implies that this
environment variable is optional.

### private

[!badge Boolean]

Setting this to `true` on any environment variable, will hide it from the help
text.

!!!success Tip
To allow users to see private environment variables, see
[Settings :icon-chevron-right: private_reveal_key](/usage/settings/#private_reveal_key)
!!!

### required

[!badge Boolean]

Specify if this variable is required.

## Advanced Options

### allowed

[!badge Array of Strings]

Limit the allowed values to a specified whitelist. Can be used in conjunction
with [`default`](#default) or [`required`](#required).

### validate

[!badge String / Array of Strings]

Apply a custom validation function.

[!ref](/advanced/validations)