aio_read


SYNOPSIS
       #include <aio.h>

       int aio_read(struct aiocb *aiocbp);

       Link with -lrt.

DESCRIPTION
       The  aio_read() function queues the I/O request described by the buffer
       pointed to by aiocbp.  This function  is  the  asynchronous  analog  of
       read(2).  The arguments of the call

           read(fd, buf, count)

       correspond (in order) to the fields aio_fildes, aio_buf, and aio_nbytes
       of the structure pointed to by aiocbp.  (See aio(7) for  a  description
       of the aiocb structure.)

       The  data is read starting at the absolute file offset aiocbp->aio_off-
       set, regardless of the current file offset.  After the call, the  value
       of the current file offset 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).  The return sta-
       tus of a completed I/O operation can be obtained aio_return(3).   Asyn-
       chronous  notification  of  I/O  completion  can be obtained by setting
       aiocbp->aio_sigevent appropriately; see sigevent(7) for details.

       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 only 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,  or  aio_nbytes  are
              invalid.

       ENOSYS This function is not supported.

NOTES
       It  is  a good idea to zero out the control block before use.  The 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 opera-
       tion or undefined results may occur.  The memory  areas  involved  must
       remain valid.

       Simultaneous I/O operations specifying the same aiocb structure produce
       undefined results.

EXAMPLE
       See aio(7).

SEE ALSO
       aio_cancel(3),  aio_error(3),  aio_fsync(3),  aio_return(3),   aio_sus-
       pend(3), aio_write(3), lio_listio(3), aio(7)

COLOPHON
       This  page  is  part of release 3.35 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://man7.org/linux/man-pages/.



                                  2010-10-03                       AIO_READ(3)
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