IO Redirection in C++ (redirect cin/cout to file stream, and restore)

最新推荐文章于 2022-03-26 22:29:24 发布

YuManzi

最新推荐文章于 2022-03-26 22:29:24 发布

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分类专栏： Programming Lauguage 文章标签： c++ cincout redirect

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本文介绍了一个使用C++进行标准输入输出流重定向的例子。通过此方法，程序可以从文件而非键盘读取输入，并将输出写入到文件中。示例展示了如何通过更改std::cin和std::cout的标准缓冲区来实现这一过程。

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Author: YuMaNzI  2014/01/19

#include <iostream>
#include <fstream>
#include <string>

void f()
{
    std::string line;
    while(std::getline(std::cin, line))  //input from the file in.txt
    {
        std::cout << line << "\n";   //output to the file out.txt
    }
}
int main()
{
    std::ifstream in("in.txt");
    std::streambuf *cinbuf = std::cin.rdbuf(); //save old buf
    std::cin.rdbuf(in.rdbuf()); //redirect std::cin to in.txt!

    std::ofstream out("out.txt");
    std::streambuf *coutbuf = std::cout.rdbuf(); //save old buf
    std::cout.rdbuf(out.rdbuf()); //redirect std::cout to out.txt!

    std::string word;
    std::cin >> word;           //input from the file in.txt
    std::cout << word << "  ";  //output to the file out.txt

    f(); //call function


    std::cin.rdbuf(cinbuf);   //reset to standard input again
    std::cout.rdbuf(coutbuf); //reset to standard output again

    std::cin >> word;   //input from the standard input
    std::cout << word;  //output to the standard input
}