This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding Linux
manual page for details of Linux behavior), or the interface may not be
implemented on Linux.
aio_cancel — cancel an asynchronous I/O request
int aio_cancel(int fildes, struct aiocb *aiocbp);
The aio_cancel() function shall attempt to cancel one or more
asynchronous I/O requests currently outstanding against file descriptor
fildes. The aiocbp argument points to the asynchronous I/O
control block for a particular request to be canceled. If aiocbp is
NULL, then all outstanding cancelable asynchronous I/O requests against
fildes shall be canceled.
Normal asynchronous notification shall occur for asynchronous I/O
operations that are successfully canceled. If there are requests that cannot
be canceled, then the normal asynchronous completion process shall take
place for those requests when they are completed.
For requested operations that are successfully canceled, the
associated error status shall be set to [ECANCELED] and the return
status shall be -1. For requested operations that are not successfully
canceled, the aiocbp shall not be modified by
If aiocbp is not NULL, then if fildes does not have
the same value as the file descriptor with which the asynchronous operation
was initiated, unspecified results occur.
Which operations are cancelable is implementation-defined.
The aio_cancel() function shall return the value AIO_CANCELED if the
requested operation(s) were canceled. The value AIO_NOTCANCELED shall be
returned if at least one of the requested operation(s) cannot be canceled
because it is in progress. In this case, the state of the other operations, if
any, referenced in the call to aio_cancel() is not indicated by the
return value of aio_cancel(). The application may determine the state
of affairs for these operations by using aio_error(). The value
AIO_ALLDONE is returned if all of the operations have already completed.
Otherwise, the function shall return -1 and set errno to indicate the
The aio_cancel() function shall fail if:
- The fildes argument is not a valid file descriptor.
The following sections are informative.
The Base Definitions volume of POSIX.1‐2017,
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1-2017, Standard for Information Technology -- Portable Operating
System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018
Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html .
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