c - C 中的共享内存 : Shmget Issues

Question

int shmid;
int* locat;

//create shared memory segment
shmid = shmget(6666, size, 0666);
if (shmid < 0) {
    perror("shmget");
    exit(1);
}

locat = (int *) shmat(shmid, NULL, 0);
if (locat == (int *) -1) {
    perror("shmat");
    exit(1);
}

我正在这样设置共享内存，但我一直收到此错误:shmget: No such file or directory

这段代码工作正常，不知道为什么现在会这样。

Answer 1

As the man says

IPC_CREAT

Create a new segment. If this flag is not used, then shmget() will find the segment associated with key and check to see if the user has permission to access the segment.

您必须将 IPC_CREAT 添加到您的 shmget 调用

shmid = shmget(6666, size, IPC_CREAT | 0666);

您还可以使用IPC_EXCL 来确保该段是新创建的

IPC_EXCL

This flag is used with IPC_CREAT to ensure that this call creates the segment. If the segment already exists, the call fails.