main_r.c

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#define SHM_SIZE  100

int main(void)
{
    int shmid;
    char buff[SHM_SIZE];
    void
 
 *shmadr;
    int ret;

    shmid = shmget((key_t)12345, SHM_SIZE, 0666|IPC_CREAT);
    if (shmid == -1) {
        printf("creat share memory failed!\n");
        exit(1);
    }

    shmadr = shmat(shmid, 0, 0);
    if (shmadr == (void*)-1) {
        printf("shmat failed!\n");
        exit(1);
    }

    memset
 
(buff, 0, sizeof(buff));
    memcpy(buff, (char*)shmadr, sizeof(buff));
    printf("get: %s\n", buff);

    ret = shmdt(shmadr);
    if (ret == -1) {
        printf("shmdt failed!\n");
        exit(1);
    }

    return 0;
}

main_w.c

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
 

#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#define SHM_SIZE  100

int main(void)
{
    int shmid;
    char buff[SHM_SIZE];
    void *shmadr;
    int ret;

    shmid = shmget((key_t)12345, SHM_SIZE, 0666|IPC_CREAT);
    if (shmid == -1) {
        printf("creat share memory failed!\n");
        exit(1);
    }

    shmadr = shmat(shmid, 0, 0);
    if (shmadr == (void*)-1) {
        printf("shmat failed!\n");
        exit(1);
    }

    strcpy(buff, "hello word!");
    memcpy((char*)shmadr, buff, strlen(buff)+1);

    ret = shmdt(shmadr);
    if (ret == -1) {
        printf("shmdt failed!\n");
        exit(1);
    }

    return 0;
}