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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);

       Link with -lrt.

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_offset, regardless of the current file posi-
       tion.  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  appropri-
       ately.   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.

       ENOSYS This function is not supported.

       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.

CONFORMING TO
       POSIX.1-2001.

NOTES
       It  is  a good idea to zero out the control block before use.  This control 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.

SEE ALSO
       aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3), aio_suspend(3), aio_write(3)

COLOPHON
       This  page  is part of release 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                  2003-11-14                       AIO_READ(3)