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io_uring_prep_send_zc(3) — Linux manual page

io_uring_prep_send_zc(3)     liburing Manualio_uring_prep_send_zc(3)

NAME        top

       io_uring_prep_send_zc - prepare a zerocopy send request

SYNOPSIS        top

#include <liburing.h>void io_uring_prep_send_zc(struct io_uring_sqe *sqe,intsockfd,const void *buf,size_tlen,intflags,unsignedzc_flags);void io_uring_prep_send_zc_fixed(struct io_uring_sqe *sqe,intsockfd,const void *buf,size_tlen,intflags,unsignedzc_flags);unsignedbuf_index);

DESCRIPTION        top

       Theio_uring_prep_send_zc(3) function prepares a zerocopy send       request. The submission queue entrysqe is setup to use the file       descriptorsockfd to start sending the data frombuf of sizelen       bytes with send modifier flagsflags and zerocopy modifier flagszc_flags.       Theio_uring_prep_send_zc_fixed(3) works just likeio_uring_prep_send_zc(3) except it requires the use of buffers       that have been registered withio_uring_register_buffers(3).  Thebuf andlen arguments must fall within a region specified bybuf_index in the previously registered buffer. The buffer need not       be aligned with the start of the registered buffer.       Seeio_uring_prep_send(3) for a description of flags that can be       set in the SQEioprio field. In addition to those, the zero-copy       send also supports settingIORING_SEND_ZC_REPORT_USAGE .If set,       the notification CQEres field will report the number of bytes       that were copied rather than sent with zero copy. A value of0       indicates success. If the value isIORING_NOTIF_USAGE_ZC_COPIED ,       then data was copied.       Note that usingIOSQE_IO_LINKwith this request type requires the       setting ofMSG_WAITALLin theflags argument, as a short send       isn't considered an error condition without that being set.       These functions prepare an async zerocopysend(2) request. See       that man page for details. For details on the zerocopy nature of       it, seeio_uring_enter(2).

RETURN VALUE        top

       None

ERRORS        top

       The CQEres 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-1on failure and seterrno to the actual error value, io_uring never useserrno.       Instead it returns the negatederrno directly in the CQEres       field.

SEE ALSO        top

io_uring_get_sqe(3),io_uring_submit(3),io_uring_prep_send(3),io_uring_enter(2),send(2)

COLOPHON        top

       This page is part of theliburing (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 2025-08-11.  (At that time,       the date of the most recent commit that was found in the       repository was 2025-08-02.)  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 isnot part of the original manual page), send a mail to       man-pages@man7.orgliburing-2.3                September 6, 2022io_uring_prep_send_zc(3)

Pages that refer to this page:io_uring_prep_send_set_addr(3), io_uring_prep_send_zc(3), io_uring_prep_send_zc_fixed(3)

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