Mastering Embedded Linux Programming - Second Edition

Using mmap to share memory

As we saw in Chapter 12, Learning About Processes and Threads, POSIX shared memory requires mmap to access the memory segment. In this case, you set the MAP_SHARED flag and use the file descriptor from shm_open():

int shm_fd; char *shm_p;  shm_fd = shm_open("/myshm", O_CREAT | O_RDWR, 0666); ftruncate(shm_fd, 65536); shm_p = mmap(NULL, 65536, PROT_READ | PROT_WRITE,              MAP_SHARED, shm_fd, 0);