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 comple-
       tion using aio_return(3).

       The data is read starting at the absolute file offset aiocbp->aio_offset, 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 prior-
       ity 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.

       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 posi-
              tion 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 opera-
       tion 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 3.25 of the Linux man-pages project.  A description of the project, and information about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                                           2003-11-14                                                AIO_READ(3)