# writeAll(_:) Writes a sequence of bytes to the current offset and then updates the offset. ``` @discardableResult func writeAll(_ sequence: S) throws -> Int where S : Sequence, S.Element == UInt8 ``` ## Parameters `sequence` The bytes to write. ## Return Value The number of bytes written, equal to the number of elements in `sequence`. ## Discussion This method either writes the entire contents of `sequence`, or throws an error if only part of the content was written. Writes to the position associated with this file descriptor, and increments that position by the number of bytes written. See also [`seek(offset:from:)`](/documentation/System/FileDescriptor/seek(offset:from:)). If `sequence` doesn’t implement the method, temporary space will be allocated as needed. --- 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)