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# extension

The extension of this file or directory component.

```
var `extension`: String? { get }
```

## Discussion

If `self` does not contain a `.` anywhere, or only
at the start, returns `nil`. Otherwise, returns everything after the dot.

Examples:

- `foo.txt    => txt`
- `foo.tar.gz => gz`
- `Foo.app    => app`
- `.hidden    => nil`
- `..         => nil`

---

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