linux fork 共享内存

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

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

int main() {
    key_t key = ftok("/tmp", 'R');
    int shmid = shmget(key, 1024, 0644 | IPC_CREAT);
    char *str = (char*) shmat(shmid, (void*)0, 0);

    int semid = semget(key, 1, 0644 | IPC_CREAT);
    union semun arg;
    arg.val = 1;
    semctl(semid, 0, SETVAL, arg);

    struct sembuf sb = {0, -1, SEM_UNDO};
    semop(semid, &sb, 1); // 获取信号量

    strcpy(str, "Hello, World!");
    printf("Data written in memory: %s\n", str);

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

    shmdt(str);
    return 0;
}

#include <fcntl.h>
#include <unistd.h>
#include <sys/shm.h>
#include <stdio.h>

int main() {
    key_t key = ftok("/tmp", 'R');
    int shmid = shmget(key, 1024, 0644 | IPC_CREAT);
    char *str = (char*) shmat(shmid, (void*)0, 0);

    int fd = open("/tmp/shared_memory.lock", O_RDWR | O_CREAT, 0644);
    flock(fd, LOCK_EX); // 获取文件锁

    strcpy(str, "Hello, World!");
    printf("Data written in memory: %s\n", str);

    flock(fd, LOCK_UN); // 释放文件锁
    close(fd);

    shmdt(str);
    return 0;
}