io_uring_prep_writev(3) — Linux manual page

io_uring_prep_writev(3)      liburing Manual     io_uring_prep_writev(3)

NAME

       io_uring_prep_writev - prepare vector I/O write request

SYNOPSIS

       #include <sys/uio.h>
       #include <liburing.h>

       void io_uring_prep_writev(struct io_uring_sqe *sqe,
                                 int fd,
                                 const struct iovec *iovecs,
                                 unsigned nr_vecs,
                                 __u64 offset);

DESCRIPTION

       The io_uring_prep_writev(3) prepares a vectored IO write request.
       The submission queue entry sqe is setup to use the file
       descriptor fd to start writing nr_vecs from the iovecs array at
       the specified offset.

       On files that support seeking, if the offset is set to -1, the
       write operation commences at the file offset, and the file offset
       is incremented by the number of bytes written. See write(2) for
       more details. Note that for an async API, reading and updating
       the current file offset may result in unpredictable behavior,
       unless access to the file is serialized. It is not encouraged to
       use this feature if it's possible to provide the desired IO
       offset from the application or library.

       On files that are not capable of seeking, the offset must be 0 or
       -1.

       After the write has been prepared it can be submitted with one of
       the submit functions.

RETURN VALUE

       None

ERRORS

       The CQE res field will contain the result of the operation. See
       the related man page for details on possible values. Note that
       where synchronous system calls will return -1 on failure and set
       errno to the actual error value, io_uring never uses errno.
       Instead it returns the negated errno directly in the CQE res
       field.

NOTES

       Unless an application explicitly needs to pass in more than one
       iovec, it is more efficient to use io_uring_prep_write(3) rather
       than this function, as no state has to be maintained for a non-
       vectored IO request.  As with any request that passes in data in
       a struct, that data must remain valid until the request has been
       successfully submitted. It need not remain valid until
       completion. Once a request has been submitted, the in-kernel
       state is stable. Very early kernels (5.4 and earlier) required
       state to be stable until the completion occurred. Applications
       can test for this behavior by inspecting the
       IORING_FEAT_SUBMIT_STABLE flag passed back from
       io_uring_queue_init_params(3).

SEE ALSO

       io_uring_get_sqe(3), io_uring_prep_write(3),
       io_uring_prep_writev2(3), io_uring_submit(3)

COLOPHON

       This page is part of the liburing (A library for io_uring)
       project.  Information about the project can be found at 
       ⟨https://github.com/axboe/liburing⟩.  If you have a bug report for
       this manual page, send it to io-uring@vger.kernel.org.  This page
       was obtained from the project's upstream Git repository
       ⟨https://github.com/axboe/liburing⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-03.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

liburing-2.1                November 15, 2021    io_uring_prep_writev(3)

Pages that refer to this page: io_uring_prep_writev2(3), io_uring_prep_writev(3)

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