linux修改共享内存大小生效

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

int main() {
    key_t key = ftok("/tmp/shmfile", 65);
    int shmid = shmget(key, 1024, 0666 | IPC_CREAT);

    if (shmid == -1) {
        perror("shmget");
        exit(EXIT_FAILURE);
    }

    // 分离共享内存段
    if (shmdt(shmat(shmid, NULL, 0)) == (void *) -1) {
        perror("shmdt");
        exit(EXIT_FAILURE);
    }

    // 修改共享内存大小
    if (shmctl(shmid, IPC_RESIZE, (struct shmid_ds *) &(struct shmid_ds){.shm_segsz = 2048}) == -1) {
        perror("shmctl");
        exit(EXIT_FAILURE);
    }

    // 重新附加共享内存段
    void *shmaddr = shmat(shmid, NULL, 0);
    if (shmaddr == (void *) -1) {
        perror("shmat");
        exit(EXIT_FAILURE);
    }

    printf("Shared memory resized and reattached successfully.\n");

    // 清理资源
    shmdt(shmaddr);
    shmctl(shmid, IPC_RMID, NULL);

    return 0;
}