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Linux 2.6 - man page for aio_read (linux section 3posix)

AIO_READ(P)			    POSIX Programmer's Manual			      AIO_READ(P)

NAME
       aio_read - asynchronous read from a file (REALTIME)

SYNOPSIS
       #include <aio.h>

       int aio_read(struct aiocb *aiocbp);

DESCRIPTION
       The  aio_read()	function  shall  read  aiocbp->aio_nbytes  from  the file associated with
       aiocbp->aio_fildes into the buffer pointed to by aiocbp->aio_buf.  The function call shall
       return when the read request has been initiated or queued to the file or device (even when
       the data cannot be delivered immediately).

       If prioritized I/O is supported for this file, then the asynchronous  operation	shall  be
       submitted   at  a  priority  equal  to  the  scheduling	priority  of  the  process  minus
       aiocbp->aio_reqprio.

       The aiocbp value may be used as an argument to aio_error() and aio_return()  in	order  to
       determine  the error status and return status, respectively, of the asynchronous operation
       while it is proceeding. If an error condition is encountered during queuing, the  function
       call  shall return without having initiated or queued the request. The requested operation
       takes place at the absolute position in the file as given by  aio_offset,  as  if  lseek()
       were  called  immediately  prior to the operation with an offset equal to aio_offset and a
       whence equal to SEEK_SET. After a successful call to enqueue an	asynchronous  I/O  opera-
       tion, the value of the file offset for the file is unspecified.

       The aiocbp->aio_lio_opcode field shall be ignored by aio_read().

       The  aiocbp  argument  points  to  an  aiocb  structure.  If  the  buffer  pointed  to  by
       aiocbp->aio_buf or the control block pointed to by aiocbp becomes an illegal address prior
       to asynchronous I/O completion, then the behavior is undefined.

       Simultaneous asynchronous operations using the same aiocbp produce undefined results.

       If  synchronized I/O is enabled on the file associated with aiocbp->aio_fildes, the behav-
       ior of this function shall be according	to  the  definitions  of  synchronized	I/O  data
       integrity completion and synchronized I/O file integrity completion.

       For  any  system action that changes the process memory space while an asynchronous I/O is
       outstanding to the address range being changed, the result of that action is undefined.

       For regular files, no data transfer shall occur past the offset maximum established in the
       open file description associated with aiocbp->aio_fildes.

RETURN VALUE
       The  aio_read()	function  shall  return  the value zero to the calling process if the I/O
       operation is successfully queued; otherwise, the function shall return the  value  -1  and
       set errno to indicate the error.

ERRORS
       The aio_read() function shall fail if:

       EAGAIN The requested asynchronous I/O operation was not queued due to system resource lim-
	      itations.

       Each of the following conditions may be detected synchronously at the time of the call  to
       aio_read(), or asynchronously.  If any of the conditions below are detected synchronously,
       the aio_read() function shall return -1 and set errno to the corresponding value.  If  any
       of the conditions below are detected asynchronously, the return status of the asynchronous
       operation is set to -1, and the error status of the asynchronous operation is set  to  the
       corresponding value.

       EBADF  The aiocbp->aio_fildes argument is not a valid file descriptor open for reading.

       EINVAL The   file   offset   value   implied   by  aiocbp->aio_offset  would  be  invalid,
	      aiocbp->aio_reqprio is not a valid  value,  or  aiocbp->aio_nbytes  is  an  invalid
	      value.

       In the case that the aio_read() successfully queues the I/O operation but the operation is
       subsequently canceled or encounters an error, the return status of the asynchronous opera-
       tion  is one of the values normally returned by the read() function call. In addition, the
       error status of the asynchronous operation is set to one of the	error  statuses  normally
       set by the read() function call, or one of the following values:

       EBADF  The aiocbp->aio_fildes argument is not a valid file descriptor open for reading.

       ECANCELED
	      The requested I/O was canceled before the I/O completed due to an explicit aio_can-
	      cel() request.

       EINVAL The file offset value implied by aiocbp->aio_offset would be invalid.

       The following condition may be detected synchronously or asynchronously:

       EOVERFLOW
	      The file is a regular file, aiobcp->aio_nbytes is greater than 0, and the  starting
	      offset in aiobcp->aio_offset is before the end-of-file and is at or beyond the off-
	      set maximum in the open file description associated with aiocbp->aio_fildes.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The aio_read() 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_cancel()  , aio_error() , lio_listio() , aio_return() , aio_write() , close() , exec()
       ,  exit()  ,  fork()  ,	lseek()   ,   read()   ,   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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				      AIO_READ(P)


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