将标准输出流与文件输出流之间的互相关联

int
main() {
    string file_name = "/home/zhihui/Videos/test";
    ofstream local(file_name,std::ios::binary);
    local << "test file." << endl;           //输出到文件
    local << "try somthing bad." << endl;    //输出到文件
    auto cout_buff = std::cout.rdbuf(); // save pointer to std::cout buffer

    std::cout.rdbuf(local.rdbuf()); // substitute internal std::cout buffer with
    // buffer of 'local' object

    // now std::cout work with 'local' buffer
    // you don't see this message
    std::cout << "some message";        //本来输出到屏幕的标准输出流被关联到文件输出流，会显示到文件里

    // go back to old buffer
    std::cout.rdbuf(cout_buff);         //将标准输出流恢复

    // you will see this message
    std::cout << "back to default buffer\n";

    auto fstream_buf = local.rdbuf();

    local.basic_ios::rdbuf(std::cout.rdbuf());　//文件输出流被关联到标准输出流

    local << "try somthing new." << endl;//这时直接输出到屏幕而不是文件


    return 0;
}

文件中输出的信息

test file.
try somthing bad.
some message

 

屏幕输出的信息

back to default buffer
try somthing new.