I have a message queue from which I am getting messages in a loop. The problem is that I don't know how to exit the loop. msgrcv returns type size_t so it keeps going. What value should I compare the return value so I can exit the loop? while(msgrcv(msqid, &msgreceived, sizeof(msgreceived), BUFFER_CHANGED, 0) != -1){ printf("%d %d %d %d ",msgreceived.value0,msgreceived.value1,msgreceived.value2,msgreceived.value3);