MQUEUEFS(4)

💌 mqueuefs(4) 💌

okay so real talk — this is mqueuefs(4), straight out of the Kernel Interfaces Manual (section 4, kernel interfaces, iykyk), and it's genuinely one of the slayest little modules in the FreeBSD kernel. sit down, grab a strawberry drink 🍓, and let me tell you about POSIX message queues.

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✨ NAME ✨

mqueuefs — the POSIX message queue file system 🎀

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🦋 SYNOPSIS 🦋

so there's two ways to get this baby into your life, bestie:

to link it into the kernel (the permanent, main-character way):

options P1003_1B_MQUEUE

to load it as a kernel loadable module (the lowkey, on-demand way):

kldload mqueuefs

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🌸 DESCRIPTION 🌸

okay so the mqueuefs module is what lets the FreeBSD kernel support POSIX message queues. periodt. 💅

the module contains system calls to manipulate POSIX message queues — that's the whole point — and it also contains a file system that gives you a view of all the message queues on the system. the way that this helps users keep track of their message queues… iconic. it makes them way easier to use without you having to invent a bunch of additional tools yourself. no cap, that's actually such a gift. 🫶

the most common usage is literally just this:

mount -t mqueuefs null /mnt/mqueue

where /mnt/mqueue is a mount point.

you can also define an entry in /etc/fstab that looks similar to:

null    /mnt/mqueue     mqueuefs        rw      0       0

which will mount mqueuefs at the /mnt/mqueue mount point during system boot. 🧚

⚠️ vibe check / heads up: using /mnt/mqueue as a permanent mount point is not advised — its intention has always been to be a temporary mount point. see hier(7) for more info on the FreeBSD directory layout. don't do it, bestie, I'm begging 🙈

some common tools work just fine on the file system, e.g.: cat(1), chmod(1), chown(8), ls(1), rm(1), etc. all your faves, all invited to the party 🌈

and here's the thing — to use only the message queue system calls, it is not necessary for the user to mount the file system at all. just load the module or compile it into the kernel. that's it. that's the whole requirement. 😌

manually creating a file, for example, “touch /mnt/mqueue/myqueue”, will create a message queue named myqueue in the kernel, and default message queue attributes will be applied to the queue. but ngl…

💀 it is not advised to use this method to create a queue. it is better to use the mq_open(2) system call to create a queue, because that way the user can actually specify different attributes. let mq_open(2) cook 🔥

and to see the queue's attributes? just read the file. that's it. that's the trick:

cat /mnt/mqueue/myqueue

ate and left no crumbs 🎀

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🎀 SEE ALSO 🎀

• mq_open(2)
• nmount(2)
• unmount(2)
• mount(8)
• umount(8)

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👑 AUTHORS 👑

this manual page was written by David Xu <davidxu@FreeBSD.org>. we stan a documentation icon 💜

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and that's the whole page, bestie! 🌟 this lovely little number comes to you from Debian, dated November 30, 2005 — yes, she's been serving these facts since 2005 and she still looks flawless. mwah 💋✨