# write(_:retryOnInterrupt:) Writes the contents of a buffer at the current file offset. ``` func write(_ buffer: UnsafeRawBufferPointer, retryOnInterrupt: Bool = true) throws -> Int ``` ## Parameters `buffer` The region of memory that contains the data being written. `retryOnInterrupt` Whether to retry the write operation if it throws [`interrupted`](/documentation/System/Errno/interrupted). The default is `true`. Pass `false` to try only once and throw an error upon interruption. ## Return Value The number of bytes that were written. ## Discussion After writing, this method increments the file’s offset by the number of bytes written. To change the file’s offset, call the [`seek(offset:from:)`](/documentation/System/FileDescriptor/seek(offset:from:)) method. The corresponding C function is `write`. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)