mqueue.h(7POSIX)

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

🎀 mqueue.h — message queues (REALTIME) 🎀

okay bestie, gather round, because we're doing the POSIX Programmer's Manual thing and this one is mqueue.h(7POSIX). yes it's a header page. yes it's mostly "here are the things this header shall define." no it is not boring, it's the blueprint of message queues and we're gonna stan it. 💅

✨ PROLOG ✨

so first things first, this page is part of the POSIX Programmer's Manual. and like… a heads up, girlies: the Linux implementation of this interface may differ. if you're on Linux, go consult the corresponding Linux manual page for the deets, or honestly the interface might not even be implemented on Linux at all. 😭 so check before you commit, fr fr.

🌸 NAME 🌸

mqueue.h — message queues (REALTIME)

🦋 SYNOPSIS 🦋

#include <mqueue.h>

that's it. that's the whole synopsis. iconic. 🫶

💖 DESCRIPTION 💖

okay so here's everything this header shall define, and I mean every single crumb, no skips:

👑 The types

  • The <mqueue.h> header shall define the mqd_t type, which is used for message queue descriptors. and listen — this is not an array type. not an array. do not come for it. 🙈
  • The <mqueue.h> header shall define the pthread_attr_t, size_t, and ssize_t types as described in <sys/types.h>.
  • The <mqueue.h> header shall define the struct timespec structure as described in <time.h>.
  • The tag sigevent shall be declared as naming an incomplete structure type, the contents of which are described in the <signal.h> header. so like, the vibes are there, the guts live elsewhere. main character mystery energy. ✨

🧚 The mq_attr structure

The <mqueue.h> header shall define the mq_attr structure, which is used in getting and setting the attributes of a message queue. Attributes are initially set when the message queue is created. An mq_attr structure shall have at least the following fields:

long    mq_flags    Message queue flags.
long    mq_maxmsg   Maximum number of messages.
long    mq_msgsize  Maximum message size.
long    mq_curmsgs  Number of messages currently queued.

four longs, four jobs, all of them slaying. 🔥

⭐ The functions

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided. 👇

int      mq_close(mqd_t);
int      mq_getattr(mqd_t, struct mq_attr *);
int      mq_notify(mqd_t, const struct sigevent *);
mqd_t    mq_open(const char *, int, ...);
ssize_t  mq_receive(mqd_t, char *, size_t, unsigned *);
int      mq_send(mqd_t, const char *, size_t, unsigned);
int      mq_setattr(mqd_t, const struct mq_attr *restrict,
             struct mq_attr *restrict);
ssize_t  mq_timedreceive(mqd_t, char *restrict, size_t,
             unsigned *restrict, const struct timespec *restrict);
int      mq_timedsend(mqd_t, const char *, size_t, unsigned,
             const struct timespec *);
int      mq_unlink(const char *);

look at all those restricts. very demure, very mindful, very careful about aliasing. 💜

🌈 One more thing

Inclusion of the <mqueue.h> header may make visible symbols defined in the headers <fcntl.h>, <signal.h>, and <time.h>. surprise guests at the function. 💀

The following sections are informative. (translation: the real requirements are above, these next ones are just vibes and context.)

🍓 APPLICATION USAGE 🍓

None.

she said nothing. silent. mysterious. periodt.

💜 RATIONALE 💜

None.

no thoughts, head empty, still valid. 😌

🎀 FUTURE DIRECTIONS 🎀

None.

the future is… also nothing. which honestly? peaceful.

🌸 SEE ALSO 🌸

  • <fcntl.h>
  • <signal.h>
  • <sys_types.h>
  • <time.h>

and from the System Interfaces volume of POSIX.1‐2017, go read up on these besties:

  • mq_close()
  • mq_getattr()
  • mq_notify()
  • mq_open()
  • mq_receive()
  • mq_send()
  • mq_setattr()
  • mq_unlink()

okay legal corner, but make it cute because we respect the paperwork:

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. (so if they fight, the original wins, no cap.) 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 .

and that's the whole page, bestie 💖 this little love letter to <mqueue.h> was brought to you by IEEE/The Open Group, 2017, filed under mqueue.h(7POSIX). now go open a queue and send something nice. mwah. 🫶✨

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