ACANCEL(2-SVR3)     RISC/os Reference Manual      ACANCEL(2-SVR3)



NAME
     acancel - cancel asynchronous I/O request

SYNOPSIS
     #include <sys/aio.h>

     int acancel(int fildes, aiohandlet handle);


DESCRIPTION
     acancel cancels one or more asynchronous I/O requests
     currently outstanding against file descriptor fildes.  The
     handle argument specifies the particular request to be can-
     celed.  If handle is NULL, then all outstanding asynchronous
     I/O requests against fildes are canceled.

     A signal is not delivered when an asynchronous I/O operation
     is successfully canceled.  If there are requests which can-
     not be canceled, then the normal asynchronous completion
     process takes place for those requests when they are com-
     pleted.

     For requests operation that are successfully canceled, the
     associated aio_errno in the completion block is set to ECAN-
     CELLED and aio_nbytes is set to the actual number of bytes
     transferred.

RETURNS
     acancel returns the value AIO_CANCELLED to the calling pro-
     cess if the requested operation(s) were canceled.  The value
     of AIO_NOTCANCELLED is returned if at least one of the
     requested operation(s) cannot be canceled because it is in
     progress.  The value AIO_ALLDONE is returned if all of the
     operations are not queued and are not in progress.  Other-
     wise, the function returns -1, and sets errno to indicate
     the error.

ERRORS
     If any of the following conditions occur, the acancel
     returns -1 and sets errno to the corresponding value:

     [EBADF]        The fildes argument is not a valid file
                    descriptor.

     [EINVAL]       The handle argument is not a valid asynchro-
                    nous I/O handle.

SEE ALSO
     aread(2), areadv(2), astatus(2), await(2), awrite(2), awri-
     tev(2), listio(2), aio(5).





                        Printed 11/19/92                   Page 1