1io_uring_prep_read(3)           liburing Manual          io_uring_prep_read(3)
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NAME

6       io_uring_prep_read_fixed  -  prepare  I/O  read request with registered
7       buffer
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SYNOPSIS

10       #include <liburing.h>
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12       void io_uring_prep_read_fixed(struct io_uring_sqe *sqe,
13                               int fd,
14                               void *buf,
15                               unsigned nbytes,
16                               __u64 offset,
17                               int buf_index);
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DESCRIPTION

20       The io_uring_prep_read_fixed(3) prepares an IO read request with a pre‐
21       viously  registered  IO buffer. The submission queue entry sqe is setup
22       to use the file descriptor fd to start reading nbytes into  the  buffer
23       buf  at  the  specified offset, and with the buffer matching the regis‐
24       tered index of buf_index.
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26       This works just like io_uring_prep_read(3) except it requires  the  use
27       of buffers that have been registered with io_uring_register_buffers(3).
28       The buf and nbytes arguments must fall within  a  region  specified  by
29       buf_index  in  the previously registered buffer. The buffer need not be
30       aligned with the start of the registered buffer.
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32       After the read has been prepared it can be submitted with  one  of  the
33       submit functions.
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RETURN VALUE

37       None
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ERRORS

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

47       io_uring_prep_read(3), io_uring_register_buffers(3)
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51liburing-2.1                   February 13, 2022         io_uring_prep_read(3)