# writeInt64

`import { writeInt64 } from "destack:bytes";`

Write one signed 64-bit integer.

```ds title="writeInt64"
export function writeInt64(bytes: &'a exclusive [uint8], offset: usize, value: int64, order?: "bigEndian" | "littleEndian"): void
```

[language/library/src/bytes/bytes.ds:133:140](https://github.com/destack-sh/destack/blob/main/language/library/src/bytes/bytes.ds#L133-L140)