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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | SEE ALSO | COLOPHON |
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io_uring_pr...sg_zc_fixed(3) liburing Manual io_uring_pr...sg_zc_fixed(3)
io_uring_prep_sendmsg_zc_fixed - prepare a zero-copy sendmsg using
fixed buffers
#include <liburing.h>
void io_uring_prep_sendmsg_zc_fixed(struct io_uring_sqe *sqe,
int fd,
const struct msghdr *msg,
unsigned flags,
unsigned buf_index);
The io_uring_prep_sendmsg_zc_fixed(3) function prepares a zero-
copy sendmsg request using fixed (registered) buffers. The
submission queue entry sqe is setup to send data on the socket
indicated by the file descriptor fd using the message structure
msg.
The flags argument contains flags for the sendmsg operation, as
described in sendmsg(2).
The buf_index specifies the index of the registered buffer set to
use. The buffers in msg must be part of the registered buffer set
previously registered with io_uring_register_buffers(3).
Zero-copy sends avoid copying data from user to kernel space,
improving performance for large transfers. Using fixed buffers
additionally avoids the overhead of mapping buffers for each I/O
operation.
Note that zero-copy sends require the application to wait for a
notification before reusing the buffer. See
io_uring_prep_send_zc(3) for more details on zero-copy semantics.
None
The CQE res field will contain the result of the operation, the
number of bytes sent on success. On error, a negative errno value
is returned.
Despite accepting an array of iovec's with a size_t number of
bytes each, this function can transfer at most INT_MAX bytes per
call (the maximum for the underlying syscall interface).
io_uring_get_sqe(3), io_uring_submit(3),
io_uring_prep_sendmsg_zc(3), io_uring_prep_sendmsg(3),
io_uring_prep_send_zc_fixed(3), io_uring_register_buffers(3),
sendmsg(2)
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 2026-05-24. (At that time,
the date of the most recent commit that was found in the
repository was 2026-05-18.) 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-2.10 January 18, 2025io_uring_pr...sg_zc_fixed(3)
Pages that refer to this page: io_uring_prep_sendmsg_zc_fixed(3)
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HTML rendering created 2026-05-24 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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