# process.env

## Function

Set a child process environment variable.

## Syntax

```bt
process(program).env(key, value)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| key | Any | Yes | None | Environment variable name. |
| value | Any | No | '' | Environment variable value. |

## Return value

| Type | Description |
| ------ | ------ |
| Process | Returns the new process builder. |

## Example

```bt
cmd = process('cmd').env('BT_ENV', '1')
result = cmd.get_envs()

// Output: {"BT_ENV":"1"}
print result
```

## Notes

- An error will be reported when the key is missing.