I know that with ipcs(1) command, one can monitor System V message queues, shared memory and semaphores, but how do I monitor POSIX message queues, shared memory and semaphores. For POSIX message queues, I can mount a pseudo filesystem, as stated in mq_overview(7). Thank you in advance for any help.
ipcs(1) POSIX equivalent to System V
posix;ipc
I don't believe there are any commands that allow you to monitor POSIX message queues specifically. As you mentioned, all of the details are exposed via a pseudo filesystem, usually mounted under /dev/mqueue. Once you've done that, you can then use file management commands like ls, rm, cat, etc. to inspect and manage the queue details.