Linux进程通信-有名管道

有名管道

博文

https://www.cnblogs.com/fangshenghui/archive/2004/01/13/4039805.html

编程步骤：

步骤	进程1	进程2	使用函数
1	建立管道文件		mfifo
2	打开管道	打开管道	open
3	读写数据	读写数据	write/read
4	关闭管道	关闭管道	close
5	删除管道	删除管道	unlink

使用实例

进程1：写管道

    const char *fifo_name = "/tmp/my_fifo";
    int pipe_fd = -1;
    int data_fd = -1;
    int res = 0;
    const int open_mode = O_WRONLY;
    int bytes_sent = 0;
    char buffer[PIPE_BUF + 1];
    int bytes_read = 0;
    if(access(fifo_name, F_OK) == -1)
    {
        printf ("Create the fifo pipe.\n");
        //建立管道
        res = mkfifo(fifo_name, 0777);
        if(res != 0)
        {
            fprintf(stderr, "Could not create fifo %s\n", fifo_name);
            exit(EXIT_FAILURE);
        }
    }

    printf("Process %d opening FIFO O_WRONLY\n", getpid());
    //打开管道
    pipe_fd = open(fifo_name, open_mode);
    printf("Process %d result %d\n", getpid(), pipe_fd);

    if(pipe_fd != -1)
    {
        bytes_read = 0;
        data_fd = open("Data.txt", O_RDONLY);
        if (data_fd == -1)
        {
            close(pipe_fd);
            fprintf (stderr, "Open file[Data.txt] failed\n");
            return -1;
        }
        bytes_read = read(data_fd, buffer, PIPE_BUF);
        buffer[bytes_read] = '\0';
        while(bytes_read > 0)
        {
            //写管道
            res = write(pipe_fd, buffer, bytes_read);
            if(res == -1)
            {
                fprintf(stderr, "Write error on pipe\n");
                exit(EXIT_FAILURE);
            }

            bytes_sent += res;
            bytes_read = read(data_fd, buffer, PIPE_BUF);
            buffer[bytes_read] = '\0';
        }
        //关闭管道
        close(pipe_fd);
        close(data_fd);
    }

进程2：读管道

    const char *fifo_name = "/tmp/my_fifo";
    int pipe_fd = -1;
    int data_fd = -1;
    int res = 0;
    int open_mode = O_RDONLY;
    char buffer[PIPE_BUF + 1];
    int bytes_read = 0;
    int bytes_write = 0;

    memset(buffer, '\0', sizeof(buffer));

    printf("Process %d opening FIFO O_RDONLY\n", getpid());
    //打开管道
    pipe_fd = open(fifo_name, open_mode);
    data_fd = open("DataFormFIFO.txt", O_WRONLY|O_CREAT, 0644);
        if (data_fd == -1)
    {
        fprintf(stderr, "Open file[DataFormFIFO.txt] failed\n");
        close(pipe_fd);
        return -1;
    }

    printf("Process %d result %d\n",getpid(), pipe_fd);
    if(pipe_fd != -1)
    {
        do
        {
            //读管道
            res = read(pipe_fd, buffer, PIPE_BUF);
            bytes_write = write(data_fd, buffer, res);
            bytes_read += res;
        }while(res > 0);
        //关闭管道
        close(pipe_fd);
        close(data_fd);
    }