Check to see if a message is in a POSIX message queue w/o removing it from the queue?

Question

POSIX provides a way to read a message queue using its mq_receive function. This function also removes it from the queue. I need to find a way to check to see if a message is in the queue without removing it.

Answer 1

From the Linux mq_overview(7) man page:

Polling message queue descriptors

On Linux, a message queue descriptor is actually a file descriptor, and can be monitored using select(2), poll(2), or epoll(7). This is not portable.