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# metadataWrite(from:startingAt:length:)

Synchronously writes file system metadata from a buffer to the resource.

```
func metadataWrite(from buffer: UnsafeRawBufferPointer, startingAt offset: off_t, length: Int) throws
```

## Parameters

`buffer`

A buffer to provide the data.

`offset`

The offset into the resource from which to start writing.

`length`

The number of bytes to writing.

## Discussion

This method provides access to the Kernel Buffer Cache, which is the primary system cache for file system metadata.
Unlike equivalent kernel APIs, this method doesn’t hold any kernel-level claim to the underlying buffers.

For the write to succeed, requests must conform to any transfer requirements of the underlying resource.
Disk drives typically require sector-addressed operations of one or more sector-aligned offsets, where a sector equals `physicalBlockSize`.

This method doesn’t support partial writing of metadata.

> Throws: Any error encountered while reading data.

---

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