共享内存使用举例

查看共享内存使用情况
ipcs   -m

删除指定key的共享内存
ipcrm -m shmid

 

例一：

server.c (创建共享内存并写入数据)

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

// 定义学生结构体
typedef struct
{
    int id;
    char name[32];
    float score;
} Student;

// 定义班级结构体（包含多个学生）
typedef struct
{
    int count;
    Student students[10]; // 假设班级最多10人
} Classroom;

int main()
{
    // 1. 创建共享内存
    int shmid = shmget((key_t)12345, 1024, 0666 | IPC_CREAT);
    if (shmid == -1)
    {
        perror("shmget failed");
        exit(EXIT_FAILURE);
    }

    // 2. 映射共享内存
    Classroom *shared_class = (Classroom *)shmat(shmid, NULL, 0);
    if (shared_class == (void *)-1)
    {
        perror("shmat failed");
        exit(EXIT_FAILURE);
    }

    // 3. 写入班级数据
    shared_class->count = 3; // 班级有3名学生

    // 学生1
    shared_class->students[0].id = 1001;
    strcpy(shared_class->students[0].name, "张三");
    shared_class->students[0].score = 89.5f;

    // 学生2
    shared_class->students[1].id = 1002;
    strcpy(shared_class->students[1].name, "李四");
    shared_class->students[1].score = 92.0f;

    // 学生3
    shared_class->students[2].id = 1003;
    strcpy(shared_class->students[2].name, "王五");
    shared_class->students[2].score = 78.5f;

    printf("数据已写入共享内存，按任意键释放资源...\n");
    getchar();

    // 4. 断开映射
    if (shmdt(shared_class) == -1)
    {
        perror("shmdt failed");
    }

    // 5. 删除共享内存
    if (shmctl(shmid, IPC_RMID, 0) == -1)
    {
        perror("shmctl failed");
    }

    return 0;
}

client.c (读取共享内存数据)

#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/shm.h>
 
// 必须与server.c中的定义一致
typedef struct {
    int id;
    char name[32];
    float score;
} Student;
 
typedef struct {
    int count;
    Student students[10];
} Classroom;
 
int main() {
    // 1. 获取共享内存
    int shmid = shmget((key_t)12345, 0, 0666);
    if(shmid == -1) {
        perror("shmget failed");
        exit(EXIT_FAILURE);
    }
 
    // 2. 映射共享内存
    Classroom *shared_class = (Classroom *)shmat(shmid, NULL, 0);
    if(shared_class == (void *)-1) {
        perror("shmat failed");
        exit(EXIT_FAILURE);
    }
 
    // 3. 读取并显示数据 
    printf("班级人数: %d\n", shared_class->count);
    for(int i = 0; i < shared_class->count; i++) {
        printf("学生%d: ID=%d, 姓名=%s, 分数=%.1f\n",
               i+1,
               shared_class->students[i].id,
               shared_class->students[i].name,
               shared_class->students[i].score);
    }
 
    // 4. 断开映射
    if(shmdt(shared_class) == -1) {
        perror("shmdt failed");
    }
 
    return 0;
}

输出结果：

 

 

 

例二：

server.c

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

int main()
{
    int shm_id = shmget((key_t)1234, 1024, 0666 | IPC_CREAT);
    if (shm_id == -1)
    {
        perror("shmget failed");
        exit(EXIT_FAILURE);
    }

    void *shm = shmat(shm_id, NULL, 0);
    if (shm == (void *)-1)
    {
        perror("shmat failed");
        exit(EXIT_FAILURE);
    }

    char *shared_memory = (char *)shm;
    strcpy(shared_memory, "Hello, World!");

    if (shmdt(shm) == -1)
    {
        perror("shmdt failed");
        exit(EXIT_FAILURE);
    }

    return 0;
}

client.c

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

int main()
{
    int shm_id = shmget((key_t)1234, 1024, 0666 | IPC_CREAT);
    if (shm_id == -1)
    {
        perror("shmget failed");
        exit(EXIT_FAILURE);
    }

    void *shm = shmat(shm_id, NULL, 0);
    if (shm == (void *)-1)
    {
        perror("shmat failed");
        exit(EXIT_FAILURE);
    }

    char *shared_memory = (char *)shm;
    printf("Read from shared memory: %s\n", shared_memory);

    if (shmdt(shm) == -1)
    {
        perror("shmdt failed");
        exit(EXIT_FAILURE);
    }

    return 0;
}