linux_shmem.c

Linux Shared Memory Sample code

#include <stdio.h> #include <sys/shm.h> #include <sys/stat.h>
int main () { int segment_id;
	  char* shared_memory;
	  struct shmid_ds shmbuffer;
	  int segment_size;
	  const int shared_segment_size = 0x6400;
	  /* Allocate a shared memory segment. */
	  segment_id = shmget (IPC_PRIVATE, shared_segment_size, IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR);
	   /* Attach the shared memory segment. */ shared_memory = (char*) shmat (segment_id, 0, 0);
	  printf (\u201cshared memory attached at address %p\n\u201d, shared_memory);
	  /* Determine the segment\u2019s size. */
	  shmctl (segment_id, IPC_STAT, &shmbuffer);
	  segment_size = shmbuffer.shm_segsz;
	  printf (\u201csegment size: %d\n\u201d, segment_size);
	  /* Write a string to the shared memory segment. */
	  sprintf (shared_memory, \u201cHello, world.\u201d);
	  /* Detach the shared memory segment. */
	  shmdt (shared_memory);
	  /* Reattach the shared memory segment, at a different address. */ shared_memory = (char*) shmat (segment_id, (void*) 0x5000000, 0);
	  printf (\u201cshared memory reattached at address %p\n\u201d, shared_memory);
	  /* Print out the string from shared memory. */
	  printf (\u201c%s\n\u201d, shared_memory);
	  /* Detach the shared memory segment. */
	  shmdt (shared_memory);
	  /* Deallocate the shared memory segment.  */
	  shmctl (segment_id, IPC_RMID, 0);
	  return 0; }