例1：
#include <stdio.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ipc.h>
int main ()
{
int segment_id;
char* shared_memory;
struct shmid_ds shmbuffer;
int segment_size;
key_t keys;
const int shared_segment_size = 0x6400;
keys= ftok("/usr", 'a');
/* Allocate a shared memory segment. */
segment_id = shmget (keys, 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 ("shared memory attached at address %p\n", shared_memory);
/* Determine the segment’s size. */
shmctl (segment_id, IPC_STAT, &shmbuffer);
segment_size = shmbuffer.shm_segsz;
printf ("segment size: %d\n", segment_size);
/* Write a string to the shared memory segment. */
sprintf (shared_memory, "Hello, world.");
/* 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 ("shared memory reattached at address %p\n", shared_memory);
/* Print out the string from shared memory. */
printf ("%s\n", shared_memory);
/* Detach the shared memory segment. */
shmdt (shared_memory);
sleep(10);
/* Deallocate the shared memory segment. */
shmctl (segment_id, IPC_RMID, 0);
return 0;
}
例2：
#include <stdio.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ipc.h>
int main ()
{
int segment_id;
char* shared_memory;
struct shmid_ds shmbuffer;
int segment_size;
key_t keys;
const int shared_segment_size = 0x6400;
keys= ftok("/usr", 'a');
/* Allocate a shared memory segment. */
segment_id = shmget (keys, shared_segment_size, S_IRUSR | S_IWUSR);
/* Attach the shared memory segment. */
if (segment_id < 0)
{
printf("Cannot get share memory\n");
return -1;
}
shared_memory = (char*) shmat (segment_id, 0, 0);
printf ("shared memory attached at address %p\n", shared_memory);
/* Determine the segment’s size. */
shmctl (segment_id, IPC_STAT, &shmbuffer);
segment_size = shmbuffer.shm_segsz;
printf ("segment size: %d\n", segment_size);
/* Print out the string from shared memory. */
printf ("shared_memory: %s\n", shared_memory);
/* Detach the shared memory segment. */
shmdt (shared_memory);
return 0;
}
