1io_uring_prep_splice(3)         liburing Manual        io_uring_prep_splice(3)
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NAME

6       io_uring_prep_splice - prepare an splice request
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SYNOPSIS

9       #include <fcntl.h>
10       #include <liburing.h>
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12       void io_uring_prep_splice(struct io_uring_sqe *sqe,
13                                 int fd_in,
14                                 int64_t off_in,
15                                 int fd_out,
16                                 int64_t off_out,
17                                 unsigned int nbytes,
18                                 unsigned int splice_flags);
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DESCRIPTION

21       The  io_uring_prep_splice(3)  function  prepares  a splice request. The
22       submission queue entry sqe is setup to use as input the file descriptor
23       fd_in  at offset off_in, splicing data to the file descriptor at fd_out
24       and at offset off_out.  nbytes bytes of data should be spliced  between
25       the  two  descriptors.   splice_flags are modifier flags for the opera‐
26       tion. See splice(2) for the generic splice flags.
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28       If the fd_out descriptor, IOSQE_FIXED_FILE can be set in the SQE to in‐
29       dicate    that.   For   the   input   file,   the   io_uring   specific
30       SPLICE_F_FD_IN_FIXED can be set in splice_flags and fd_in  given  as  a
31       registered file descriptor offset.
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33       If fd_in refers to a pipe, off_in is ignored and must be set to -1.
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35       If  fd_in  does  not  refer to a pipe and off_in is -1, then nbytes are
36       read from fd_in starting from the file offset, which is incremented  by
37       the number of bytes read.
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39       If fd_in does not refer to a pipe and off_in is not -1, then the start‐
40       ing offset of fd_in will be off_in.
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42       The same rules apply to fd_out and off_out.
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44       This function prepares an async splice(2) request. See  that  man  page
45       for details.
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RETURN VALUE

49       None
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ERRORS

52       The CQE res field will contain the result of the operation. See the re‐
53       lated man page for details on possible values. Note that where synchro‐
54       nous system calls will return -1 on failure and set errno to the actual
55       error value, io_uring never uses errno.  Instead it returns the negated
56       errno directly in the CQE res field.
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SEE ALSO

59       io_uring_get_sqe(3),      io_uring_submit(3),     io_uring_register(2),
60       splice(2)
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NOTES

64       Note that even if fd_in or fd_out refers to a pipe, the  splice  opera‐
65       tion  can  still  fail  with EINVAL if one of the fd doesn't explicitly
66       support splice operation, e.g. reading  from  terminal  is  unsupported
67       from kernel 5.7 to 5.11.
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71liburing-2.2                    March 13, 2022         io_uring_prep_splice(3)
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