linux 共享内存 写数据

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

#define SHM_SIZE 1024

int main() {
    key_t key = ftok("/tmp/shmfile", 65); // 生成一个唯一的键
    int shmid = shmget(key, SHM_SIZE, 0666|IPC_CREAT); // 创建共享内存段
    char *str = (char*) shmat(shmid, (void*)0, 0); // 将共享内存连接到当前进程的地址空间

    printf("Writing to shared memory: \"%s\"\n", "Hello, World!");
    strncpy(str, "Hello, World!", SHM_SIZE); // 写入数据

    shmdt(str); // 分离共享内存
    return 0;
}

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

#define SHM_SIZE 1024

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

int main() {
    key_t key = ftok("/tmp/shmfile", 65);
    int shmid = shmget(key, SHM_SIZE, 0666|IPC_CREAT);
    char *str = (char*) shmat(shmid, (void*)0, 0);

    key_t semkey = ftok("/tmp/shmfile", 66);
    int semid = semget(semkey, 1, 0666|IPC_CREAT);
    union semun arg;
    arg.val = 1; // 初始化信号量为1
    semctl(semid, 0, SETVAL, arg);

    struct sembuf sem_op;
    sem_op.sem_num = 0;
    sem_op.sem_op = -1; // 请求信号量
    sem_op.sem_flg = 0;
    semop(semid, &sem_op, 1);

    printf("Writing to shared memory: \"%s\"\n", "Hello, World!");
    strncpy(str, "Hello, World!", SHM_SIZE);

    sem_op.sem_op = 1; // 释放信号量
    semop(semid, &sem_op, 1);

    shmdt(str);
    return 0;
}