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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |NOTES |SEE ALSO |COLOPHON | |
io_uring_prep_sendmsg(3) liburing Manualio_uring_prep_sendmsg(3)io_uring_prep_sendmsg - prepare a sendmsg request
#include <sys/types.h>#include <sys/socket.h>#include <liburing.h>void io_uring_prep_sendmsg(struct io_uring_sqe *sqe,intfd,const struct msghdr *msg,unsignedflags);void io_uring_prep_sendmsg_zc(struct io_uring_sqe *sqe,intfd,const struct msghdr *msg,unsignedflags);
Theio_uring_prep_sendmsg(3) function prepares a sendmsg request. The submission queue entrysqe is setup to use the file descriptorfd to start sending the data indicated bymsg with thesendmsg(2) defined flags in theflags argument. Theio_uring_prep_sendmsg_zc(3) accepts the same parameters asio_uring_prep_sendmsg(3) but prepares a zerocopy sendmsg request. 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. This function prepares an asyncsendmsg(2) request. See that man page for details.
None
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.
As with any request that passes in data in a struct, that data must remain valid until the request has been successfully submitted. It need not remain valid until completion. Once a request has been submitted, the in-kernel state is stable. Very early kernels (5.4 and earlier) required state to be stable until the completion occurred. Applications can test for this behavior by inspecting theIORING_FEAT_SUBMIT_STABLEflag passed back fromio_uring_queue_init_params(3).
io_uring_get_sqe(3),io_uring_submit(3),io_uring_buf_ring_init(3),io_uring_buf_ring_add(3),sendmsg(2)
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-2.2 March 12, 2022io_uring_prep_sendmsg(3)Pages that refer to this page:io_uring_prep_sendmsg(3), io_uring_prep_sendmsg_zc(3)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |