NAME

       aio_read - asynchronous 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_offset, 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
       status of a completed I/O operation can be obtained by aio_return(3).  Asynchronous 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 detected only 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 aio_read() is not implemented.

       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.

VERSIONS

       The aio_read() function is available since glibc 2.1.

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008.

NOTES

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

       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_suspend(3), aio_write(3), lio_listio(3),
       aio(7)

COLOPHON

       This page is part of release 3.54 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/.

                                                   2012-05-08                                        AIO_READ(3)