aio_read

AIO_READ(3)		  Linux Programmer’s Manual		  AIO_READ(3)



NAME
       aio_read - asynchronous read

SYNOPSIS
       #include <aio.h>

       int aio_read(struct aiocb *aiocbp);


DESCRIPTION
       The  aio_read  function	requests  an  asynchronous "n = read(fd, buf,
       count)"	 with	fd,   buf,   count   given   by	  aiocbp->aio_fildes,
       aiocbp->aio_buf, aiocbp->aio_nbytes, respectively. The return status n
       can be retrieved upon completion using aio_return(3).

       The data is read starting at the absolute file offset aiocbp->aio_off-
       set,  regardless of the current file position. After this request, the
       value of the current file position is unspecified.

       The "asynchronous" means that this call returns as soon as the request
       has  been  enqueued;  the  read may or may not have completed when the
       call returns. One tests for completion using aio_error(3).

       If _POSIX_PRIORITIZED_IO is defined, and this file supports  it,	 then
       the asynchronous operation is submitted at a priority equal to that of
       the calling process minus aiocbp->aio_reqprio.

       The field aiocbp->aio_lio_opcode is ignored.

       No data is read from a regular file beyond its maximum offset.

RETURN VALUE
       On success, 0 is returned. On error the request is not enqueued, -1 is
       returned,  and  errno  is  set  appropriately.  If  an  error is first
       detected later, it will be reported via aio_return(3) (returns  status
       -1)  and	 aio_error(3) (error status whatever one would have gotten in
       errno, such as EBADF).

ERRORS
       EAGAIN Out of resources.

       EBADF  aio_fildes is not a valid file descriptor open for reading.

       EINVAL One or more of aio_offset, aio_reqprio, aio_nbytes are invalid.

       EOVERFLOW
	      The file is a regular file, we start reading before end-of-file
	      and want at least one byte, but the starting position  is	 past
	      the maximum offset for this file.

       ENOSYS This function is not supported.


NOTES
       It is a good idea to zero out the control block before use.  This con-
       trol block must	not  be	 changed  while	 the  read  operation  is  in
       progress.  The buffer area being read into must not be accessed during
       the operation  or  undefined  results  may  occur.  The	memory	areas
       involved must remain valid.


CONFORMING TO
       POSIX 1003.1-2003

SEE ALSO
       aio_cancel(3),  aio_error(3),  aio_fsync(3),  aio_return(3),  aio_sus-
       pend(3), aio_write(3)



				  2003-11-14			  AIO_READ(3)