Question

我有2个程序使用共享内存块相互通信。

第一个程序从命令行获取一个参数并分叉指定的次数，每个子进程的ID和一个随机生成的数字存储在一个2D数组中，然后该数组被传递给第二个程序附加的内存块。问题是我不知道如何做到这一点，并希望得到一些帮助，因为我在这方面有点新手。

以下是目前为止第一个程序的代码，经过全面测试和运行：

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <unistd.h>
#include <time.h>

int main(int argc, char *argv[])
{
    if (argc < 2)
    {
        printf("\nError with command line argument!\n");
        exit(1);
    }

    /* Program is simulation of a printer queue, forked child processes
       act as jobs in the queue with pids being the job number and a
       randomly generated value being the priority order (this comes into
       play in program 2) */

    srand(time(null));
    pid_t pid;

    int amount, i, pID, rNum;

    amount = atoi(argv[1]);

    int procID[amount]; /* 1D array that will hold pid for each process */
    int randNum[amount]; /* 1D array that will hold random number to
                            determine priority level of the print jobs */

    int rows = amount;
    int cols = 2;

    int printDetails[rows][cols]; /* 2D array that will hold the values
                                     from both 1D arrays, displaying all
                                     data from print queue when output */

    printf("\nPrint queue started:");
    getchar();

    for (i = 0; i < amount; i++)
    {
         pid = fork();

         if (pid < 0)
         {
             perror("Error with fork!");
             exit(1);
         }

         if (pid == 0)
         {
             pID = getpid();
             rNum = rand()%50;

             printf("\nPrint Job : %d", pID);
             printf("\nPriority Level : %d\n", rNum);

             procID[i] = pID;
             randNum[i] = rNum;

             sleep(1);
         }

         else
         {
             wait(NULL);
             return 0;
         }
    }

    printf("\n%d successful print jobs created\n", amount);

    printf("\n-----PRINT DETAILS-----\n");
    printf("\nJob No:\tPriority:\n");

    for (i = 0; i < rows; i++)
    {
        printDetails[i][0] = procID[i];
        printDetails[i][1] = randNum[i];

        printf("%d\t%d\n", printDetails[i][0], printDetails[i][1];
    }

    printf("\n-----END OF LIST-----\n");

    /* Create shared memory segment using shmget and shmat,
       how do I insert the array above into this, like I said
       complete noob! */

}

对于巨大的代码墙感到抱歉，只是为了帮助理解我正在使用的内容，就像我说的那样，对于共享内存的任何帮助都会非常感激，因为我有点超出我的深度！

Answer 1

写入机制上的复制将在您在第二个进程上更改它时分配一个新指针...当它死亡时，它将采用带有不同数据的新分配内存...解决方案是分配动态指针...当您更改它的值时，它不会动态分配新值并使用旧值并更改其数据

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <unistd.h>
#include <time.h>

int main(int argc, char *argv[])
{
    if (argc < 2)
    {
        printf("\nError with command line argument!\n");
        exit(1);
    }

    /* Program is simulation of a printer queue, forked child processes
       act as jobs in the queue with pids being the job number and a
       randomly generated value being the priority order (this comes into
       play in program 2) */

    srand(time(NULL)); // null -> NULL
    pid_t pid;

    int amount, i, pID, rNum;

    amount = atoi(argv[1]);

    int* procID =(int*) calloc(amount,sizeof(int)); /* 1D array that will hold pid for each process */
    if(!procID)
    return -1;
    int* randNum =(int*) calloc (amount,sizeof(int)); /* 1D array that will hold random number to
                            determine priority level of the print jobs */
    if(!randNum)
    return -1;
    int rows = amount;
    int cols = 2;
    int k;
    int** printDetails = (int**) calloc (rows, sizeof(int*)); /* 2D array that will hold the values
                                     from both 1D arrays, displaying all
                                     data from print queue when output */
    if(!printDetails)
    return -1;
    for(k=0; k<rows;k++)
    {
        printDetails[k] = (int*) calloc (cols, sizeof(int));
        if(!printDetails[k])
        return -1;
    }
    printf("\nPrint queue started:");
    getchar();

    for (i = 0; i < amount; i++)
    {
         pid = fork();

         if (pid < 0)
         {
             perror("Error with fork!");
             exit(1);
         }

         if (pid == 0)
         {
             pID = getpid();
             rNum = rand()%50;

             printf("\nPrint Job : %d", pID);
             printf("\nPriority Level : %d\n", rNum);

             procID[i] = pID;
             randNum[i] = rNum;

             sleep(1);
         }

         else
         {
             wait(NULL);
             return 0;
         }
    }

    printf("\n%d successful print jobs created\n", amount);

    printf("\n-----PRINT DETAILS-----\n");
    printf("\nJob No:\tPriority:\n");

    for (i = 0; i < rows; i++)
    {
        printDetails[i][0] = procID[i];
        printDetails[i][1] = randNum[i];

        printf("%d\t%d\n", printDetails[i][0], printDetails[i][1]);
    }

    printf("\n-----END OF LIST-----\n");

    /* Create shared memory segment using shmget and shmat,
       how do I insert the array above into this, like I said
       complete noob! */
    for(k=0; k<rows; k++)
        free(printDetails[k]);
    free(printDetails);
    free(randNum);
    free(procID);
}

具有共享内存的二维数组

1 个答案: