io_uring_prep_ftruncate(3)

✨ io_uring_prep_ftruncate — prepare an ftruncate request ✨

okay so bestie, this is page 3 of the liburing Manual for io_uring_prep_ftruncate, and I am so ready to tell you about it 💖

🎀 NAME 🎀

io_uring_prep_ftruncate — prepare an ftruncate request

like. that's it. that's the whole job. and she does it flawlessly 💅

🌸 SYNOPSIS 🌸

#include <liburing.h>

void io_uring_prep_ftruncate(struct io_uring_sqe *sqe,
                             int fd,
                             loff_t len);

🦋 DESCRIPTION 🦋

so the io_uring_prep_ftruncate(3) function prepares an ftruncate request, no cap. The submission queue entry sqe gets set up to use the file descriptor fd — that's the one that should get truncated — down (or up, we don't judge) to the length indicated by the len argument. iconic behaviour honestly ✨

🚨 important bestie alert 🚨 Applications must define _GNU_SOURCE to obtain the definition of this helper, because loff_t will not be defined without it. and if loff_t isn't defined, nothing compiles, and we simply cannot have that 😭

💜 RETURN VALUE 💜

None. she returns nothing. she's mysterious like that 🙈

🔥 ERRORS 🔥

The CQE res field will contain the result of the operation. See the related man page for the details on possible values, fr fr — I'm not about to make up numbers that aren't in the original, that's not the vibe. 💀

Now here's the part you need to know: where synchronous system calls will return -1 on failure and set errno to the actual error value, io_uring never uses errno. periodt. Instead it returns the negated errno directly in the CQE res field. so like, negative number = your error code, just flipped. remember that or you'll be debugging for three business days 🫶

🌈 SEE ALSO 🌈

• io_uring_get_sqe(3)
• io_uring_submit(3)
• ftruncate(2)

and that's the whole page!! go truncate something responsibly, bestie 💖✨🌸🦋🎀💅

this was page io_uring_prep_ftruncate(3) from liburing-2.6, dated January 23, 2024 — ty for coming to my ted talk, mwah 😘