写入管道总是失败

Question

我试图通过尝试将文本文件中的数据读取到第一个管道并在另一个管道上读取它来在 2 个进程之间进行通信，但写入函数总是失败：

主要：

int main(int argc, char* argv[])
{
    int readerPip[2], writerPip[2], reader, writer;

    if (pipe(readerPip))
    {
      fprintf (stderr, "Pipe failed.\n");
      return EXIT_FAILURE;
    }

    if(pipe(writerPip))
    {
      fprintf (stderr, "Pipe failed.\n");
      return EXIT_FAILURE;
    }

    close(readerPip[1]); // closing reader writing side pipe for main thread
    reader = fork();
    if (reader < 0)
    {
        perror("Cannot fork()");
        exit(EXIT_FAILURE);
    }
    else if (reader == 0)
    {
        do_reader(readerPip);
    }

    wait(NULL);
    close(writerPip[0]); // closing writer reader side pipe for main thread
    do_father(readerPip, writerPip);
    close(readerPip[0]); // closing reader reader side pipe for main thread
    close(writerPip[1]); // closing writer writing side pipe for main thread
    writer = fork();

    if (writer < 0)
    {
        perror("Cannot fork()");
        exit(EXIT_FAILURE);
    }
    else if (writer == 0)
    {
        do_writer(writerPip);
    }

    return 1;
}// main

do_Reader：

void do_reader(int readerPipe[])
{
    char stringCommand[17];
    long long unsigned command;

    close(readerPipe[0]);
    while (1)
    {
        scanf("%s", stringCommand);
        command = convertStringToPolygon(stringCommand);

        if ((command & 0xFFFFFFFF) == 0xFFFFFFFF)
        {
            break;
        }

        if (write(readerPipe[1], stringCommand, strlen(stringCommand) ) == -1)
        {
            printf("writing falied");
        }
        else
        {
            printf("success");
        }

        printf("\n");
    }

    close(readerPipe[1]);
    exit(0);
}

do_father

void do_father(int readerPipe[], int writerPipe[])
{
    long long unsigned nbytes;
    char currentPolygon[17];
    currentPolygon[16] = '\0';
    while (1)
    {
        nbytes = read(readerPipe[0], currentPolygon, sizeof(currentPolygon));
        if (nbytes == 0)
        {
            printf("done");
            break;
        }

        manageProgram(readerPipe, writerPipe,        convertStringToCommand(currentPolygon));
    }
}

do_writer

void do_writer(int pip[])
{
    close(pip[1]);
    long long unsigned command, nbytes;

    while (1)
    {
    nbytes = read(pip[0], &command, sizeof(command));
        if (nbytes == 0)
        {
            break;
        }
        if ((((command & THIRD_BIT_MASK) != FALSE) || ((command & FORTH_BIT_MASK) 
!= FALSE) ||
            ((command & FIFTH_BIT_MASK) != FALSE)) != FALSE)
            generateOutputDependsOnBits(command);
    }

    close(pip[0]);
    exit(0);
}

其余代码无关紧要，因为为阅读器管道编写代码不起作用。 文本文件如下所示：

3a 0000050000050505 3e 003cc40000c43c3c 巴 000088ec9c32ce32 f8 抄送 3a 000085ec9a32cd32 4c 8c 5c 交流 fd FFFFFFFFFFFFFFFF

Answer 1

您在main 中关闭readpipe[1]（之前 fork）并在do_reader 中关闭readpipe[0]，所以管道的两边封闭在孩子身上。

将main 中的close(readpipe[1]) 向下移动（例如，在wait 之前）。

但是，你可能不想在那里wait。您可能希望在do_father 之后执行此操作，因为这将依赖于内核管道缓冲区足够大以容纳 所有 子级在父级甚至尝试获取第一个字节之前发送给父级的数据.