linux共享内存 实例

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

// 定义共享内存键值和大小
#define SHM_KEY 1234
#define SHM_SIZE 1024

// 定义信号量键值
#define SEM_KEY 5678

union semun {
    int val;
    struct semid_ds *buf;
    unsigned short *array;
};

int main() {
    int shmid, semid;
    char *shmaddr;
    struct sembuf sem_op;

    // 创建共享内存段
    shmid = shmget(SHM_KEY, SHM_SIZE, IPC_CREAT | 0666);
    if (shmid < 0) {
        perror("shmget");
        return -1;
    }

    // 将共享内存附加到进程地址空间
    shmaddr = (char *)shmat(shmid, NULL, 0);
    if (shmaddr == (char *)( - 1)) {
        perror("shmat");
        return -1;
    }

    // 创建信号量集
    semid = semget(SEM_KEY, 1, IPC_CREAT | 0666);
    if (semid < 0) {
        perror("semget");
        return -1;
    }

    union semun arg;
    arg.val = 1;
    if (semctl(semid, 0, SETVAL, arg)!= 0) {
        perror("semctl");
        return -1;
    }

    // 进程1写入数据示例（假设是写操作）
    sem_op.sem_num = 0;
    sem_op.sem_op=-1;
    sem_op.sem_flg = 0;
    if (semop(semid, &sem_op, 1)!= 0) {
        perror("semop write lock");
        return -1;
    }
    sprintf(shmaddr, "Hello from process 1");
    sem_op.sem_op = 1;
    if (semop(semid, &sem_op, 1)!= 0) {
        perror("semop write unlock");
        return -1;
    }


    // 进程2读取数据示例（假设是读操作）
    sem_op.sem_num = 0;
    sem_op.sem_op=-1;
    sem_op.sem_flg = 0;
    if (semop(semid, &sem_op, 1)!= 0) {
        perror("semop read lock");
        return -1;
    }
    printf("Read from shared memory: %s
", shmaddr);
    sem_op.sem_op = 1;
    if (semop(semid, &sem_op, 1)!= 0) {
        perror("semop read unlock");
        return -1;
    }


    // 分离共享内存
    if (shmdt(shmaddr)<0) {
        perror("shmdt");
        return -1;
    }


    return 0;
}