共享内存段权限被拒绝

Question

运行其他文件时，我正在使用共享内存段进行共享数据和更改。

我的代码

#define _XOPEN_SOURCE 700
#include <stdlib.h>    
#include <time.h>      
#include <unistd.h>    
#include <signal.h>    
#include <stdbool.h>   
#include <stdio.h>     
#include <sys/types.h> 
#include <sys/ipc.h>   
#include <sys/shm.h>   
#include <sys/wait.h>  

bool eaten = false;
void onInterruptSignal()
{
    fprintf(stderr, "\nPellet PID is: %d - Died due to the interrupt !-Eaten : %s\n ", getpid(), eaten ? " True " : "False");
    exit(0);
}
void onTerminationSignal()
{
    fprintf(stderr, "\nFish PID: %d - Died due to the termination !-Eaten : %s\n ", getpid(), eaten ? " True " : "False");
    exit(0);
}


int main(int argc, char *argv[])
{
    signal(SIGINT, onInterruptSignal);
    signal(SIGTERM, onTerminationSignal);

    int sharedMemoryID; // Shared memory ID which will be assigned in it when the shared memory segment create successfully
    key_t keyValue = 1337;
    char(*sharedDataArray)[10][10]; 

    // Create shared memory segment which return some value. But it returns -1 if it is not able create shared memory segment
    if ((sharedMemoryID = shmget(keyValue, sizeof(char[10][10]), IPC_CREAT )) < 0)
    {
        perror("Error while creating memory segment.\n");
        exit(1);
    }
    // Add the sharedDataArray in Shared memory so that it can be access by others
    if ((sharedDataArray = (char(*)[10][10])shmat(sharedMemoryID, NULL,0)) == (char(*)[10][10]) - 1)
    {
        perror("Error while attching sharedDataArray to shared memory.\n");
        exit(1);
    }
    srand(time(NULL));
    
    int row = rand() % 10;
    int col = rand() % 10;
    while (*sharedDataArray[row][col] != '#')
    {
        row = rand() % 10;
        col = rand() % 10;
    }
    *sharedDataArray[row][col] = 0x50; // My terminal doesn't support extended ASCII, so we won't be using 0x50.
    while (row < 9)
    {
        *sharedDataArray[row][col] = '#';
        row++;
        if (*sharedDataArray[row][col] == 'F')
        {
            *sharedDataArray[row][col] |= 0x50;
            eaten =
                true;
            sleep(1);
            break;
        }
        *sharedDataArray[row][col] = 0x50;
        sleep(1);
    }
    if (!eaten)
    {
        *sharedDataArray[row][col] = '#';
    }
    else if (*sharedDataArray[row][col] == 0x50)
    {
        *sharedDataArray[row][col] = 'F';
    }
    sleep(1);
    printf("Pellet PID is: %d, X: %d, Y: %d - eaten: %s\n", getpid(), row, col, eaten ? "True" : "False");
    exit(0);
}

在附加共享内存时会遇到错误，它说

Error while attching sharedDataArray to shared memory.
: Permission denied

我尝试了所有命令以清除共享内存段，即ipcrm，然后重新启动也关闭了我的PC。但是，当我再次打开时，它给了我与上面提到的相同的错误。

有人知道我如何摆脱这个错误吗？

编辑

shmget（）通过运行ipcs -m创建共享内存ID，它显示了创建但没有说服力的SHMID。 我如何授予他们允许？

ipcs -m

tia

Answer 1

如果您的程序创建共享内存对象，则创建时的权限设置为 0，即根本没有权限。例如，请参阅 https:// 中的 shmflg 文档pubs.opengroup.org/onlinepubs/9699919799/functions/shmget.html

您可能需要类似的内容

#include <sys/stat.h> // for S_IR*** & S_IW*** macros

shmget(keyValue, sizeof(char[10][10]), IPC_CREAT | S_IRUSR | S_IWUSR);

Your code might have run without error before如果已经存在具有足够权限的共享内存对象。