PROLOG

       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.

NAME

       aio_cancel — cancel an asynchronous I/O request

SYNOPSIS

       #include <aio.h>

       int aio_cancel(int fildes, struct aiocb *aiocbp);

DESCRIPTION

       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 aio_cancel().

       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.

RETURN VALUE

       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.

ERRORS

       The aio_cancel() function shall fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       aio_read(), aio_write()

       The Base Definitions volume of POSIX.1‐2017, <aio.h>

COPYRIGHT

       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 .

       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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .