mq_close(3)

✨ mq_close — bestie, let's close that message queue descriptor 💅

okay so first things first: this is mq_close(3) from the Library Functions Manual, and it's lowkey one of the most satisfying lil functions in the whole POSIX lineup. It's giving cleanup era. Let's get into it 🫶

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🌸 LIBRARY 🌸

She lives in the real-time library, aka librt, so when you're linking you're gonna want -lrt. Don't forget it, bestie, or the linker will simply not know her 😭

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✨ SYNOPSIS ✨

#include <mqueue.h>

int mq_close(mqd_t mqdes);

that's it. that's the whole vibe. one include, one function, one descriptor. iconic 🎀

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👑 DESCRIPTION 👑

mq_close() closes the message queue descriptor mqdes. boom. done. you're welcome 💅

But wait, there's lore: if the calling process has attached a notification request to this message queue via mqdes — and the notification request situation is a whole thing, see mq_notify(3) — then that request gets removed, and now another process can attach a notification request of its own. So it's not just closing a door, it's freeing up the door for someone else. very generous of you, fr fr 🌈

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💖 RETURN VALUE 💖

• On success, mq_close() returns 0. clean. slayed. ✨
• On error, it returns -1, and errno is set to tell you what went wrong. rude but informative 💀

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😭 ERRORS 😭

• EBADF — the message queue descriptor specified in mqdes is invalid. like, girl, that descriptor doesn't exist. it's not real. vibe check failed 🙈

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🦋 ATTRIBUTES 🦋

okay so the terms used in this section are explained over in attributes(7) if you wanna go read up, but here's the tea:

• Interface: mq_close() — Attribute: Thread safety — Value: MT-Safe 👑

so yes bestie, she is MT-Safe, multiple threads can call her and it's all fine, no cap 🧚

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🌟 STANDARDS 🌟

POSIX.1-2008. she's standardized, she's official, she's certified main character energy ⭐

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📜 HISTORY 📜

POSIX.1-2001.</purpose> — yeah she's been around. vintage. classic. still serving 💜

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🍓 NOTES 🍓

• All open message queues are automatically closed when the process terminates. so if you forget, the OS handles it. she's got you 🫶
• They're also all automatically closed upon execve(2). surprise cleanup, love that for you ✨

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🌈 SEE ALSO 🌈

• mq_getattr(3)
• mq_notify(3)
• mq_open(3)
• mq_receive(3)
• mq_send(3)
• mq_unlink(3)
• mq_overview(7)

go read those too, they're all part of the mq cinematic universe 🎀

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and that's the whole page, bestie!! this was Linux man-pages 6.20, dated 2026-02-08, and it's the mq_close(3) manual page. go close a descriptor, you absolute legend. mwah 💖💅✨