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.
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 error.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 AIO_CANCEL(3P)