Question

我是C ++的新手，我遇到了管道问题。我正在尝试在循环中生成随机数列表，通过管道将它们发送到子进程，对它们进行排序，然后将它们返回给父进程。我能够正确地获得第一个号码，但它永远不会更新到我发送的第二个号码。我觉得有一些基本的东西我忽略了，并且想知道是否有人可以指出我的错误。这是我的代码的相关部分：

if (pid == 0){  // child process---------------------------------
    close(pipe1[1]);    // close write end of pipe1
    close(pipe2[0]);    // close read end of pipe2
    dup2(pipe1[0], STDIN_FILENO);
    dup2(pipe2[1], STDOUT_FILENO);
    execlp("sort", "sort", "-nr", NULL);    // sort incoming data
    close(pipe1[0]);    // close read end of pipe1
    close(pipe2[1]);    // close write end of pipe2
}
else{   // parent process----------------------------------------
    double range = sleepMax-sleepMin;
    double randNum;
    double randNum2;
    char randNumSend[15];
    char randNumRet[15];
    if (randSeed==0){
        srand(NULL);
    }
    else{
        srand(randSeed);
    }
    close(pipe1[0]);    // close read end of pipe1
    close(pipe2[1]);    // close write end of pipe2
    for(int i=0; i<nWorkers; i++){
        randNum = sleepMin + (((double) rand()) /RAND_MAX)*range;   // generate random number within range
        cout<<randNum<<" outbound" <<endl;      // display value beore sending off to child process
        sprintf(randNumSend, "%f", randNum);    // convert double to string
        write(pipe1[1],&randNumSend,sizeof(randNum));   // pass randNum through pipe1 to child process
        close(pipe1[1]);    // close write end of pipe1
    }
    for (int i=0; i<nWorkers; i++){ // loop to read back sorted values from child process
        read(pipe2[0],&randNumRet,sizeof(randNum2));    // read back data
        randNum2 = atof(randNumRet);    // convert back from string to double
        cout<<randNum2<<" inbound" <<endl;  // display results
        close(pipe2[0]);    // close read end of pipe2
    }
}

我的控制台输出是：

1.20022 outbound

4.97513 outbound

2.38587 outbound

2.06326 outbound

1.20023入境

C ++管道只返回第一个值

0 个答案: