io_uring_prep_tee(3)

✨ io_uring_prep_tee(3) ✨

okay bestie, welcome to the liburing Manual 💖 this one's about io_uring_prep_tee, and no, we're not talking about your favorite oversized t-shirt. we're talking about duplicating pipe data. iconic behavior tbh 🫶

🌸 NAME 🌸

io_uring_prep_tee — prepare a tee request 💅

🦋 SYNOPSIS 🦋

#include <fcntl.h>
#include <liburing.h>

void io_uring_prep_tee(struct io_uring_sqe *sqe,
                       int fd_in,
                       int fd_out,
                       unsigned int nbytes,
                       unsigned int splice_flags);

look at her. five whole arguments. main character energy fr fr 👑

💜 DESCRIPTION 💜

so the io_uring_prep_tee(3) function prepares a tee request. she sets up the submission queue entry sqe so that it uses the file descriptor fd_in as input and the file descriptor fd_out as output, duplicating nbytes bytes worth of data. and then splice_flags? those are the modifier flags for the operation, bestie. if you wanna know the generic splice flags, go check tee(2), she has the lore 📖✨

now here's the tea on the fd_out descriptor — IOSQE_FIXED_FILE can be set in the SQE to indicate that it's a fixed file. and for the input file, the io_uring specific SPLICE_F_FD_IN_FIXED can be set, and fd_in gets given as a registered file descriptor offset. yes, that's a mouthful. yes, it's giving very specific. slay 💅

this function prepares an async tee(2) request. see that man page for the deets, i'm not about to gatekeep you from the source 🌈

🎀 RETURN VALUE 🎀

None. that's it. that's the whole section. she returns nothing and she's unbothered 💀

⭐ ERRORS ⭐

the CQE res field will contain the result of the operation. see the related man page for details on the possible values 👀

⚠️ okay important thing, listen up: where synchronous system calls will return -1 on failure and set errno to the actual error value, io_uring never uses errno. instead it returns the negated errno directly in the CQE res field. not me being dramatic but this trips people UP. note it. remember it. periodt 💅

🔥 SEE ALSO 🔥

• io_uring_get_sqe(3)
• io_uring_submit(3)
• io_uring_register(2)
• splice(2)
• tee(2)

and that's the whole page bestie!! this was brought to you by liburing-2.2, dated March 13, 2022 — yeah she's a lil vintage but she still eats 💖 go forth and duplicate your pipe data responsibly, mwah 🎀✨🦋