linux 共享内存 信号量

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

int main() {
    key_t key = ftok("shmfile", 65);
    int shmid = shmget(key, 1024, 0666|IPC_CREAT);
    char *str = (char*) shmat(shmid, (void*)0, 0);

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

    shmdt(str);
    return 0;
}

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

int main() {
    int shm_fd = shm_open("/my_shm", O_CREAT | O_RDWR, 0666);
    ftruncate(shm_fd, 1024);
    char *str = (char*) mmap(0, 1024, PROT_WRITE, MAP_SHARED, shm_fd, 0);

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

    munmap(str, 1024);
    close(shm_fd);
    shm_unlink("/my_shm");
    return 0;
}

#include <sys/ipc.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("semfile", 65);
    int semid = semget(key, 1, 0666|IPC_CREAT);
    union semun arg;
    arg.val = 1;
    semctl(semid, 0, SETVAL, arg);

    struct sembuf sb = {0, -1, SEM_UNDO};
    semop(semid, &sb, 1);

    printf("Critical Section\n");

    sb.sem_op = 1;
    semop(semid, &sb, 1);

    return 0;
}