---
title: "fd_fdstat_set_flags()"
description: "Set file descriptor flags for a file descriptor."
url: "https://wasix.org/docs/api-reference/wasi/fd_fdstat_set_flags/"
markdown: "https://wasix.org/docs/api-reference/wasi/fd_fdstat_set_flags.md"
---

# `fd_fdstat_set_flags()`

Set file descriptor flags for a file descriptor.

## Description

The `fd_fdstat_set_flags()` function is used to set the file descriptor flags for a given file descriptor. File descriptor flags modify the behavior and characteristics of the file descriptor, allowing applications to customize its behavior according to specific requirements.

In POSIX systems, file descriptors are associated with a set of flags that control various aspects of their behavior. These flags provide additional control over file descriptor operations, such as non-blocking mode, close-on-exec behavior, or file status flags. The `fd_fdstat_set_flags()` function allows applications to modify these flags for a particular file descriptor, altering its behavior as needed.

## Syntax

```ebnf
  ;;; Note: This is similar to `fcntl(fd, F_SETFL, flags)` in POSIX.
  ;;; Adjust the flags associated with a file descriptor.
  (@interface func (export "fd_fdstat_set_flags")
    (param $fd $fd)
    ;;; The desired values of the file descriptor flags.
    (param $flags $fdflags)
    (result $error (expected (error $errno)))
  )
```

## Parameters

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

## Return Value

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

## POSIX Context

In POSIX-compliant systems, file descriptor flags are crucial for controlling the behavior of file descriptors. They allow applications to customize how file descriptors operate, enabling features such as non-blocking I/O or close-on-exec behavior.

The `fd_fdstat_set_flags()` function corresponds to the POSIX `fcntl()` system call with the `F_SETFL` command. It allows applications to set or modify the flags associated with a file descriptor. By using this function, applications can fine-tune the behavior of file descriptors to suit their specific needs.

## Note

The `fd_fdstat_set_flags()` function is used to modify the flags associated with a file descriptor. By providing the desired flags, applications can customize the behavior and characteristics of the file descriptor to suit their specific requirements.

---

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