shared memory demo

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

#define IPCKEY 0x366378

int test_share_mem_write()
{
    int shm_id;
    key_t key;
    void * p_sm = 0;
    int i_ret = 0;


    shm_id = shmget(IPCKEY , 1028, IPC_CREAT | 0640); //obtain a shared memory identifier 
    if (-1 == shm_id)
    {
        printf("shmget error %d\n", shm_id);
        exit(1);
    }

    p_sm = shmat(shm_id, (void*)0, 0); //a process attaches it to its address space
    if (p_sm == (void*)-1)
    {
        printf("shmat error\n");
        exit(1);
    }

    strncpy((char*)p_sm, "aaaaaaaa", sizeof(p_sm));
    strncpy((char*)p_sm, "bbbbb", sizeof(p_sm));


    i_ret = shmdt(p_sm); //detach the shared memory from process
    if (i_ret == -1)
    {
        printf("shmdt error\n");
        exit(1);
    }

    if (-1 == shmctl(shm_id, IPC_RMID, NULL)) // shmctl catchall for various shared memory operations, IPC_RMID is del
    {
        printf("shmctl IPC_RMID error\n");
        exit(1);
    }

    return 0;
}

int main()
{
    printf("hello share_mem_write\n");

    test_share_mem_write();
}