02shmunlink.cpp

//
// Created by jxq on 19-8-14.
//

// p35 poxis共享内存

#include <errno.h>
#include <unistd.h>
#include <iostream>
#include <stdio.h>
#include <cstring>

#include <fcntl.h>           /* For O_* constants */
#include <sys/stat.h>        /* For mode constants */
#include <mqueue.h>
#include <sys/mman.h>

using namespace std;

#define ERR_EXIT(m) \
        do  \
        {   \
            perror(m);  \
            exit(EXIT_FAILURE); \
        } while (0);

struct student
{
    char name[32];
    int age;
};

int main(int argc, char** argv)
{
    int shmid;
    shmid = shm_open("/xyz", O_CREAT | O_RDWR, 0666);
    //shmid = shm_open("/xyz", O_RDWR, S_IRUSR);
    if (shmid == -1)
    {
        ERR_EXIT("shmid");
    }
    printf("shmopen success\n");

    student stu;
    strcpy(stu.name , "hello");
    stu.age = 20;

    if (ftruncate(shmid, sizeof(stu)) == -1)
    {
        ERR_EXIT("ftruncate");
    }
    printf("truncate succ\n");

    struct stat buf;
    if (fstat(shmid, &buf) == -1)
    {
        ERR_EXIT("fstat");
    }

    printf("mode: %o, size: %ld\n", buf.st_mode & 07777, buf.st_size);

    close(shmid);
    if (shm_unlink("/xyz") == -1)
    {
        ERR_EXIT("shmunlink");
    }
    printf("shm_unlink succ\n");


    return 0;
}