MQ_GETATTR(2)

💖 mq_getattr — get message queue attributes (REALTIME) 💖

okay so bestie, we're in section 2 of the System Calls Manual today and this one is literally the "tell me everything about my message queue" call 🎀 it's giving peek-behind-the-curtain, and honestly? iconic.

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🌸 LIBRARY 🌸

POSIX Real-time Library (librt, -lrt) — yeah you gotta link the real-time lib, no cap 💅

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✨ SYNOPSIS ✨

#include <mqueue.h>

int
mq_getattr(mqd_t mqdes, struct mq_attr *mqstat);

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🦋 DESCRIPTION 🦋

so the mq_getattr() system call obtains status information and attributes of the message queue and the open message queue description associated with the message queue descriptor. two things at once, she's multitasking, we love her 🫶

the mqdes argument specifies a message queue descriptor.

the results are returned in the mq_attr structure referenced by the mqstat argument.

upon return, the following members will have the values associated with the open message queue description — as set when the message queue was opened, and as modified by subsequent mq_setattr() calls: mq_flags.

the following attributes of the message queue will be returned as set at message queue creation: mq_maxmsg, mq_msgsize.

and upon return, the following members within the mq_attr structure referenced by the mqstat argument will be set to the current state of the message queue:

• mq_curmsgs — the number of messages currently on the queue. that's the live count bestie, it's giving real-time 👑

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💜 RETURN VALUES 💜

upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error. zero means slay, negative one means go check errno 😭

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🔥 ERRORS 🔥

the mq_getattr() system call will fail if:

• [EBADF] — the mqdes argument is not a valid message queue descriptor.

fr fr, that's the whole list. one error. she's low maintenance 💀

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🌈 SEE ALSO 🌈

mq_open(2), mq_send(2), mq_setattr(2), mq_timedsend(2)

like, go read the whole friend group, they all hang out together ✨

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⭐ STANDARDS ⭐

the mq_getattr() system call conforms to IEEE Std 1003.1-2004 (“POSIX.1”). certified standards girlie 💅

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🎀 HISTORY 🎀

support for POSIX message queues first appeared in FreeBSD 7.0. so she's been serving looks since way back 🫶

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👑 COPYRIGHT 👑

portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 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.

ngl that's a lot of legalese but we keep it because it's the law, periodt 🧚

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and that's the page bestie!! this one's from Debian, dated February 21, 2014 — mwah, go read your queue attributes responsibly 💖🌸💅