---
title: "fd_datasync()"
description: "The fd_datasync() function is used to synchronize the file data associated with a file descriptor to disk. It ensures that any modified data for the file is written to the underlying storage device."
url: "https://wasix.org/docs/api-reference/wasi/fd_datasync/"
markdown: "https://wasix.org/docs/api-reference/wasi/fd_datasync.md"
---

# `fd_datasync()`

Synchronize the file data to disk.

## Description

The `fd_datasync()` function is used to synchronize the file data associated with a file descriptor to disk. It ensures that any modified data for the file is written to the underlying storage device.

## Syntax

```ebnf
  ;;; Note: This is similar to `fdatasync` in POSIX.
  ;;; Synchronize the data of a file to disk.
  (@interface func (export "fd_datasync")
    (param $fd $fd)
    (result $error (expected (error $errno)))
  )
```

## Parameters

- `ctx`: A mutable reference to the function environment.
- `fd`: The file descriptor to synchronize.

## Return Value

The function returns a `Result` containing an `Errno` value indicating the success or failure of the operation. An `Errno::Success` value indicates successful synchronization.

## Logging

This function has been instrumented with debug-level logging. It will log the following information:

- `%fd`: The file descriptor being synchronized.
- `err`: Any encountered error during the synchronization process.

## Note

The `fd_datasync()` function is used to synchronize the file data associated with a file descriptor to disk. It ensures that any modified data for the file is written to the underlying storage device. Only file descriptors with the appropriate `Rights::FD_DATASYNC` permission can be synchronized.

---

[Documentation index](https://wasix.org/llms.txt) · [HTML version](https://wasix.org/docs/api-reference/wasi/fd_datasync/)