MQ_SETATTR(3POSIX)

📦 version 2017a, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu resolute, ubuntu stonking

💖 MQ_SETATTR(3POSIX) — the girlies' guide 💖

okay so bestie, welcome to mq_setattr(3POSIX) from the POSIX Programmer's Manual. this is the page where we mess with message queue attributes. grab a strawberry 🍓 and let's go.

🫶 PROLOG 🫶

Real talk first, no cap: this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so like, go consult the corresponding Linux manual page for details on Linux behavior), or honestly the interface may not be implemented on Linux at all. 💀 check before you commit, okay?

✨ NAME ✨

mq_setattr — set message queue attributes (REALTIME)

🌸 SYNOPSIS 🌸

#include <mqueue.h>

int mq_setattr(mqd_t mqdes, const struct mq_attr *restrict mqstat,
    struct mq_attr *restrict omqstat);

💅 DESCRIPTION 💅

So mq_setattr() sets attributes associated with the open message queue description referenced by the message queue descriptor you passed in as mqdes. That's the whole vibe. 💜

The message queue attributes corresponding to the following members defined in the mq_attr structure shall be set to the specified values upon successful completion of mq_setattr():

  • mq_flags — the value of this member is the bitwise-logical OR of zero or more of O_NONBLOCK and any implementation-defined flags. that's it, that's the member, she's the only one invited to the party.

The values of the mq_maxmsg, mq_msgsize, and mq_curmsgs members of the mq_attr structure shall be ignored by mq_setattr(). not me ignoring them, the standard is ignoring them, and honestly? valid.

If omqstat is non-NULL, the mq_setattr() function shall store, in the location referenced by omqstat, the previous message queue attributes and the current queue status. and the plot twist: these values shall be the same as would be returned by a call to mq_getattr() at that point. so it's giving "here's the before photo" 📸

🔥 RETURN VALUE 🔥

Upon successful completion, the function shall return a value of zero and the attributes of the message queue shall have been changed as specified. slay. ✅

Otherwise — and this is the sad part 😭 — the message queue attributes shall be unchanged, and the function shall return a value of -1 and set errno to indicate the error. nothing changes, bestie, we just get an error code and a lesson.

💀 ERRORS 💀

The mq_setattr() function shall fail if:

  • EBADF — the mqdes argument is not a valid message queue descriptor. it's not a queue, girl, it's a fake ID.

The following sections are informative. (translation: the drama is over, this is bonus content 🎀)

🦋 EXAMPLES 🦋

None. literally none. the standard said "no example, figure it out" 😭

🌈 APPLICATION USAGE 🌈

None. again. nothing here. moving on, bestie 🧚

👑 RATIONALE 👑

None. the reasoning stays mysterious. iykyk.

⭐ FUTURE DIRECTIONS ⭐

None. she's not going anywhere, apparently.

💖 SEE ALSO 💖

  • mq_open()
  • mq_send()
  • msgctl()
  • msgget()
  • msgrcv()
  • msgsnd()

Also, from the Base Definitions volume of POSIX.1‐2017: <mqueue.h> 🫶

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

okay that's the whole page, you ate that 💅 and for the record, this came to you courtesy of IEEE/The Open Group, dated 2017 — so like, shoutout to them, this page is their main character moment. periodt. 🌟

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