如何使用函数freopen_s [英] How to use function freopen_s

问题描述

为了从一个文本文件中读取输入，我写了下面code：

In order to read input from a text file, I wrote the following code:

int main(){
    int x;
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
#endif
    scanf("%d", &x);
    printf("%d\n", x);
    system("pause");
    return 0;
}

它的工作原理相当不错的。

It works quite good.

然而，在Visual Studio中，编译器给我的，因为freopen函数的错误，并建议我使用freopen_s来代替。我试着去了解函数如何freopen_s的作品，但我不能。我的code：

However, in visual studio, the compiler gives me an error because of freopen and suggests me to use freopen_s instead. I try to understand how function freopen_s works, but I can't. My code:

int main(){
    int x;
#ifndef ONLINE_JUDGE
    FILE *stream;
    freopen_s(&stream, "input.txt", "r", stdin);
#endif
    scanf("%d", &x);
    printf("%d\n", x);
    system("pause");
    return 0;
}

这不输出任何东西，甚至是暂停不起作用。在CMD消失在程序完成没有任何印刷之后。我不知道为什么流，在freopen_s使用。谢谢你回答我的问题。

It does not output anything, and even the "pause" does not work. The cmd disappears right after the program finishes without anything printed. I don't know why the "stream" is used in freopen_s. Thank you for answering my question.

推荐答案

我建议您避免使用C风格的I / O库，并使用iostream库。它更安全，更清洁的解决方案。这里是打开一个文件并读取每行到控制台上的标准::字符串对象，并打印出样品code。

I would suggest you to avoid using the C style I/O library and use IOSTREAM Library. Its more safe and clean solution. Here is the sample code which opens a file and reads each line into the "std::string" object and prints on the console.

int main() 
{

std::string  file =  "input.txt";
std::string line;
std::ifstream  text_filestream(file.c_str());

while(std::getline(text_filestream, line)) {
 std::cout<<line<<std::endl;
 }
}    

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