---
name: "aio_cancel"
section: "2"
platform: "macos"
package: "xnu"
version: "12377.121.6"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/aio_cancel"
---

# aio\_cancel(2)

cancel an outstanding asynchronous I/O operation (REALTIME)

## NAME

**aio\_cancel** – cancel an outstanding asynchronous I/O operation (REALTIME)

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<aio.h\>**

*int*\

**aio\_cancel**(*int fildes*, *struct aiocb \*aiocbp*);

## DESCRIPTION

The **aio\_cancel**() system call cancels the outstanding asynchronous I/O request for the file descriptor specified in *fildes*. If *aiocbp* is specified, only that specific asynchronous I/O request is cancelled.

Normal asynchronous notification occurs for cancelled requests. Requests complete with an error result of ECANCELED.

## RESTRICTIONS

The **aio\_cancel**() system call does not cancel asynchronous I/O requests for raw disk devices. The **aio\_cancel**() system call will always return AIO\_NOTCANCELED for file descriptors associated with raw disk devices.

## RETURN VALUES

The **aio\_cancel**() system call returns -1 to indicate an error, or one of the following:

- \[AIO\_ALLDONE\]

  All of the requests meeting the criteria have finished.

- \[AIO\_CANCELED\]

  All outstanding requests meeting the criteria specified were cancelled.

- \[AIO\_NOTCANCELED\]

  Some requests were not cancelled, status for the requests should be checked with [aio\_error(2)](/aio_error/2.md).

## ERRORS

An error return from **aio\_cancel**() indicates:

- \[EBADF\]

  The *fildes* argument is not a valid file descriptor.

## SEE ALSO

[aio\_error(2)](/aio_error/2.md), [aio\_read(2)](/aio_read/2.md), [aio\_return(2)](/aio_return/2.md), [aio\_suspend(2)](/aio_suspend/2.md), [aio\_write(2)](/aio_write/2.md), [aio(4)](/aio/4.md)

## STANDARDS

The **aio\_cancel**() system call is expected to conform to the IEEE Std 1003.1 (“POSIX.1”) standard.

## HISTORY

The **aio\_cancel**() system call first appeared in FreeBSD 3.0. The first functional implementation of **aio\_cancel**() appeared in FreeBSD 4.0.

## AUTHORS

This manual page was originally written by Wes Peters ⟨wes@softweyr.com⟩. Christopher M Sedore ⟨cmsedore@maxwell.syr.edu⟩ updated it when **aio\_cancel**() was implemented for FreeBSD 4.0.