c 共享內存demo

一個進程寫數據，一個進程讀數據

寫進程：

1. shmget()獲取共享內存

2. shmat()共享內存映射到進程空間

3. 寫數據

讀進程：

1. shmget()獲取共享內存

2. shmat()共享內存映射到進程空間

3. 讀數據

4. shmdt()共享內存從進程空間解除映射

5. shmctl()刪除共享內存
讀進程

//
// Created by gxf on 2020/2/10.
//

#ifndef UNTITLED_MAIN_H
#define UNTITLED_MAIN_H

char *ftokFilePath = "/Users/gxf/CLionProjects/untitled/main.c";
int project_id = 10;

typedef struct {
    int age;
    char name[50];
}person;

#endif //UNTITLED_MAIN_H

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

#include "main.h"


int main() {
    key_t ftokRes = ftok(ftokFilePath, project_id);
    person *zhangsan;
    person lisi = {10, "lisi"};

    int shmid = shmget(ftokRes, sizeof(person), IPC_CREAT | 0777);
    printf("shamid :%d\n", shmid);
    zhangsan = (person *)shmat(shmid, NULL, SHM_W);
    zhangsan->age = 20;
    strcpy(zhangsan->name, "zhangsan1111");


    return 0;
}

//
// Created by gxf on 2020/2/10.
//
#include <stdlib.h>
#include <stdio.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <string.h>

#include  "main.h"

int main() {
    key_t ftokRes = ftok(ftokFilePath, project_id);
    printf("%d\n", ftokRes);
    person *zhangsan = malloc(sizeof(person));
    int shmid = shmget(ftokRes, sizeof(person), IPC_CREAT);
    person *shmaddr = shmat(shmid, NULL, SHM_R);
    memcpy(zhangsan, shmaddr, sizeof(person));
    printf("age:%d, name:%s\n", zhangsan->age, zhangsan->name);
    int res = shmdt(shmaddr);
    if (res)
        fprintf(stderr, "shmdt fail");
    res = shmctl(shmid, IPC_RMID, NULL);
    if (res)
        fprintf(stderr, "rm ipcs -m fail");


    return 0;
}