<!--
{
  "availability" : [
    "iOS: 13.0.0 -",
    "iPadOS: 13.0.0 -",
    "macCatalyst: 13.1.0 -",
    "macOS: 10.15.0 -",
    "tvOS: 13.0.0 -",
    "visionOS: 1.0.0 -",
    "watchOS: 6.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Foundation",
  "identifier" : "/documentation/Foundation/FileHandle/truncate(atOffset:)",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Method",
  "symbol" : {
    "kind" : "Instance Method",
    "modules" : [
      "Foundation"
    ],
    "preciseIdentifier" : "c:objc(cs)NSFileHandle(im)truncateAtOffset:error:"
  },
  "title" : "truncate(atOffset:)"
}
-->

# truncate(atOffset:)

Truncates or extends the file represented by the file handle to a specified offset within the file and puts the file pointer at that position.

```
func truncate(atOffset offset: UInt64) throws
```

## Parameters

`offset`

The offset within the file that marks the new end of the file.

## Discussion

If the file is extended (if `offset` is beyond the current end of file), the added characters are null bytes.

---

Copyright &copy; 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)