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# checkCompletionExists

An integer value indicating whether to check for the existence of a completion action.

```
uint32_t checkCompletionExists;
```

## Discussion

If the value of this field is a positive unsigned integer, the [`completion`](/documentation/DriverKit/IOUserClientMethodArguments/completion) field must be set to a valid action. If the value is `0`, the [`completion`](/documentation/DriverKit/IOUserClientMethodArguments/completion) field must be `NULL`. If the value of this field is -1U, the [`completion`](/documentation/DriverKit/IOUserClientMethodArguments/completion) field is ignored.

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