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# NSFileManagerUnmountDissentingProcessIdentifierErrorKey

The process identifier of the process that prevented a volume from unmounting.

```
let NSFileManagerUnmountDissentingProcessIdentifierErrorKey: String
```

## Discussion

If [`unmountVolume(at:options:completionHandler:)`](/documentation/Foundation/FileManager/unmountVolume(at:options:completionHandler:)) fails, the error sent to its completion handler will contain a `userInfo` dictionary with this string as one of its keys. The value is the process identifier of the process that prevented the unmounting, as an [`NSNumber`](/documentation/Foundation/NSNumber).

---

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