---
name: "io_cancel"
section: "3"
platform: "linux"
package: "libaio"
version: "0.3.113-5"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/io_cancel/3"
---

# io\_cancel(3)

Cancel io requests

## NAME

io\_cancel - Cancel io requests

## SYNOPSIS

```
#include <errno.h>

#include <libaio.h>

int io_cancel(io_context_t ctx, struct iocb *iocb);

struct iocb {
	void		*data; /* Return in the io completion event */
	unsigned	key;	/* For use in identifying io requests */
	short		aio_lio_opcode;
	short		aio_reqprio; 	/* Not used */
	int		aio_fildes;
};
```

## DESCRIPTION

Attempts to cancel an *iocb* previously passed to [**io\_submit**(3)](/io_submit/3.md). If the operation is successfully cancelled, the resulting event is copied into the memory pointed to by result without being placed into the completion queue.

When one or more requests are asynchronously processed, it might be useful in some situations to cancel a selected operation, e.g., if it becomes obvious that the written data is no longer accurate and would have to be overwritten soon.  As an example, assume an application, which writes data in files in a situation where new incoming data would have to be written in a file which will be updated by an enqueued request.

## RETURN VALUES

*0* is returned on success, otherwise returns *errno*.

## ERRORS

- **EFAULT**

  If any of the data structures pointed to are invalid.

- **EINVAL**

  If *aio\_context* specified by *ctx* is invalid.

- **EAGAIN**

  If the *iocb* specified was not cancelled.

- **ENOSYS**

  If not implemented.

## SEE ALSO

[**io**(3)](/io/3.md), [**io\_fsync**(3)](/io_fsync/3.md), [**io\_getevents**(3)](/io_getevents/3.md), [**io\_prep\_fsync**(3)](/io_prep_fsync/3.md), [**io\_prep\_pread**(3)](/io_prep_pread/3.md), [**io\_prep\_pwrite**(3)](/io_prep_pwrite/3.md), [**io\_queue\_init**(3)](/io_queue_init/3.md), [**io\_queue\_release**(3)](/io_queue_release/3.md), [**io\_queue\_run**(3)](/io_queue_run/3.md), [**io\_queue\_wait**(3)](/io_queue_wait/3.md), [**io\_set\_callback**(3)](/io_set_callback/3.md), [**io\_submit**(3)](/io_submit/3.md), [**errno**(3)](/errno/3.md).