NAME

       aio_cancel - cancel an asynchronous I/O request (REALTIME)

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 to the calling process 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

       The aio_cancel() function is part of the Asynchronous Input and Output option and need not
       be available on all implementations.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       aio_read() , aio_write() , the Base Definitions volume of IEEE Std 1003.1-2001, <aio.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .