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 .