# BT.add_path

## Function

 appends or prepends a path to the currently valid PATH.

## Syntax

```bt
BT.add_path(path)
BT.add_path(path, 'prepend')
```

## Parameters

| Parameters | Type | Required | Default | Description |
| ------ | ------ | ------ | ------ | ------ |
| path | String | Yes | None | The path to write to PATH. |
| mode | String | No | append | Writing position; `prepend` means preceding, omitting or `append` means appending. |

## Return Value

| Type | Description |
| ------ | ------ |
| Bool | Returns true for actual writing; returns false when the path already exists and is not added repeatedly. |

## Examples

```bt
BT.add_path('@/bin')
result = BT.has_path('@/bin')

// Output: true
print result
```

## Notes

- The path will be parsed first according to BT path rules, `@` and `@/...` are based on the project root.
- This method only writes the BT runtime environment variable overlay and does not modify the system's permanent PATH.