Mastering Embedded Linux Programming - Second Edition

POSIX message queues

Message queues are identified by a name, which must begin with a forward slash / and contain only one / character: message queues are actually kept in a pseudo filesystem of the type mqueue. You create a queue and get a reference to an existing queue through mq_open(3), which returns a file descriptor. Each message has a priority, and messages are read from the queue based on priority and then on the age order. Messages can be up to /proc/sys/kernel/msgmax bytes long.

The default value is 8 KiB, but you can set it to be any size in the range 128 bytes to 1 MiB by writing the value to /proc/sys/kernel/msgmax bytes. Each message has a priority. They are read from the queue based on the priority then the age order. Since ...