aio_read(3) — Linux manual page


AIO_READ(3)               Linux Programmer's Manual              AIO_READ(3)

NAME         top

       aio_read - asynchronous read

SYNOPSIS         top

       #include <aio.h>

       int aio_read(struct aiocb *aiocbp);

       Link with -lrt.

DESCRIPTION         top

       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 position
       aiocbp->aio_offset, regardless of the file offset.  After the call,
       the value of the 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         top

       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         top

       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

       ENOSYS aio_read() is not implemented.

              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         top

       The aio_read() function is available since glibc 2.1.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface  Attribute     Value   │
       │aio_read() │ Thread safety │ MT-Safe │

CONFORMING TO         top

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

NOTES         top

       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.

EXAMPLES         top

       See aio(7).

SEE ALSO         top

       aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3),
       aio_suspend(3), aio_write(3), lio_listio(3), aio(7)

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

                                 2020-06-09                      AIO_READ(3)

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