Pipe vs msg queue

Question

What is the difference between message queues and a pipe in Linux?

Answer 1

Off the top of my head and assuming you talk about posix message queues (not the SysV ones):

• Pipes aren't limited in size, message queues are.
• Pipes can be integrated in systems using file descriptors, message queues have their own set of functions, though linux supports select(), poll(), epoll() and friends on the mqd_t.
• Pipes, once closed, require some amount of cooperation on both sides to reestablish them, message queues can be closed and reopened on either side without the coorporation of the other side.
• Pipes are flat, much like a stream, to impose a message structure you would have to implement a protocol on both sides, message queues are message oriented already, no care has to be taken to get, say, the fifth message in the queue.