What is mqueue in linux

Viewed 89k times. How do I use mqueue message queue in a c program on a Linux based system? Improve this question. Johan Johan Add a comment. Active Oldest Votes. Improve this answer. One short remark. I'm sure I'm not understanding something right, but aren't message queues supposed to be asynchronous?

Why does the client barf an error and exits if the server isn't available? As far as my probably wrong understanding goes, the whole point of message queues is to allow clients to write to unattended queues -- or else, what's the real difference between mqueues and FIFO?

What am I misunderstanding here? Have you noticed I'm asking a lot of questions? The queue is always available through the API, the OS will keep it safe until someone consumes that data. Show 2 more comments. There is something very wrong with your implementation.

It is a terrible idea to pass pointers through mqueues, since a pointer is only valid in its own process, while mqueues are intended to be used between processes. But in the end you are passing ints. This is just a synthetic example to show usage of mqueue. It demonstrates the contents of one integer moving through the queue into another integer where both are treated as buffers. After the filesystem has been mounted, the message queues on the system can be viewed and manipulated using the commands usually used for files e.

Linux implementation of message queue descriptors On Linux, a message queue descriptor is actually a file descriptor. POSIX does not require such an implementation.

This means that a message queue descriptor can be monitored using select 2 , poll 2 , or epoll 7. This is not portable. Linux does not currently 2. This ceiling value was removed in Linux 3. Then one or more clients can be run for testing. Figure: Screenshot showing server and two clients run from terminals in Linux. Your email address will not be published. Please click here if you are not redirected within a few seconds.

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FIFOs in Linux. Tags: client communication example interprocess Linux message posix process program queue server. Leave a Reply Cancel reply.