io_uring_prep_splice(3) — Linux manual page


io_uring_prep_splice(3)      liburing Manual     io_uring_prep_splice(3)

NAME         top

       io_uring_prep_splice - prepare an splice request

SYNOPSIS         top

       #include <fcntl.h>
       #include <liburing.h>

       void io_uring_prep_splice(struct io_uring_sqe *sqe,
                                 int fd_in,
                                 int64_t off_in,
                                 int fd_out,
                                 int64_t off_out,
                                 unsigned int nbytes,
                                 unsigned int splice_flags);

DESCRIPTION         top

       The io_uring_prep_splice(3) function prepares a splice request.
       The submission queue entry sqe is setup to use as input the file
       descriptor fd_in at offset off_in, splicing data to the file
       descriptor at fd_out and at offset off_out.  nbytes bytes of data
       should be spliced between the two descriptors.  splice_flags are
       modifier flags for the operation. See splice(2) for the generic
       splice flags.

       If the fd_out descriptor, IOSQE_FIXED_FILE can be set in the SQE
       to indicate that. For the input file, the io_uring specific
       SPLICE_F_FD_IN_FIXED can be set in splice_flags and fd_in given
       as a registered file descriptor offset.

       If fd_in refers to a pipe, off_in is ignored and must be set to

       If fd_in does not refer to a pipe and off_in is -1, then nbytes
       are read from fd_in starting from the file offset, which is
       incremented by the number of bytes read.

       If fd_in does not refer to a pipe and off_in is not -1, then the
       starting offset of fd_in will be off_in.

       The same rules apply to fd_out and off_out.

       This function prepares an async splice(2) request. See that man
       page for details.

RETURN VALUE         top


ERRORS         top

       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

SEE ALSO         top

       io_uring_get_sqe(3), io_uring_submit(3), io_uring_register(2),

NOTES         top

       Note that even if fd_in or fd_out refers to a pipe, the splice
       operation can still fail with EINVAL if one of the fd doesn't
       explicitly support splice operation, e.g. reading from terminal
       is unsupported from kernel 5.7 to 5.11.

COLOPHON         top

       This page is part of the liburing (A library for io_uring)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report for
       this manual page, send it to  This page
       was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-19.)  If you discover any rendering
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       (which is not part of the original manual page), send a mail to

liburing-2.2                 March 13, 2022      io_uring_prep_splice(3)

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