difference between msgget() and mq_open

Question

I Read about message queue operations such as msgget(), msgsnd() and msgrcv(). But when I was searching for message queue related questions on stack overflow, I came to know there is another set of message queue operations such as mq_open(), mq_send(), mq_receive(). Can any one please let me know what are the differences between these 2 types of message queues and which type of message queues are extensively being used?

Answer 1

The msgXXX family is inherited from SysV. The mq_XXX family was created by POSIX. Both families are however part of POSIX.

The two families have somewhat different feature sets the most important being that the SysV variant allows for the specification of different message types. This provides for flexibility in the way messages are processed and in assigning priorities. The POSIX family in contrast always returns the oldest message with the highest priority.

As a rule the POSIX family is the better choice unless there is something about SysV that you really need to use. The POSIX interface is also less cumbersome. An added bonus (on Linux) is that the POSIX mqd_t type representing a queue identifier is actually a file descriptor. This allows for the extremely convenient use of POSIX queues with select, poll and similar facilities.