通过父进程读取数据，并使用c++中的管道将其发送给子进程。

#include <iostream>
#include <unistd.h>

int main() {
    int pipefd[2];
    pid_t pid;
    char buffer[1024];

    // 创建管道
    if (pipe(pipefd) == -1) {
        std::cerr << "Failed to create pipe." << std::endl;
        return 1;
    }

    // 创建子进程
    pid = fork();

    if (pid < 0) {
        std::cerr << "Failed to create child process." << std::endl;
        return 1;
    } else if (pid == 0) {
        // 子进程中读取数据
        close(pipefd[1]);  // 关闭写入端

        // 从管道中读取数据
        ssize_t bytesRead = read(pipefd[0], buffer, sizeof(buffer));
        if (bytesRead > 0) {
            std::cout << "Child process received data: " << buffer << std::endl;
        }

        close(pipefd[0]);  // 关闭读取端
    } else {
        // 父进程中写入数据
        close(pipefd[0]);  // 关闭读取端

        std::string data = "Hello, child process!";
        // 将数据写入管道
        ssize_t bytesWritten = write(pipefd[1], data.c_str(), data.size());
        if (bytesWritten > 0) {
            std::cout << "Parent process sent data: " << data << std::endl;
        }

        close(pipefd[1]);  // 关闭写入端
    }

    return 0;
}