如何将cin和cout重定向到文件?
2021-12-01 00:00:00
c++
如何将 cin
重定向到 in.txt
并将 cout
重定向到 out.txt
?
How can I redirect cin
to in.txt
and cout
to out.txt
?
推荐答案
这是您想要执行的操作的示例.阅读注释以了解代码中每一行的作用.我已经在我的电脑上用 gcc 4.6.1 测试过它;它工作正常.
Here is an working example of what you want to do. Read the comments to know what each line in the code does. I've tested it on my pc with gcc 4.6.1; it works fine.
#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 << "
"; //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
}
您可以在一行中保存和重定向:
auto cinbuf = std::cin.rdbuf(in.rdbuf()); //save and redirect
此处 std::cin.rdbuf(in.rdbuf())
将 std::cin's
缓冲区设置为 in.rdbuf()
然后返回与 std::cin
关联的旧缓冲区.使用 std::cout
也可以做到同样的事情 —或任何流.
Here std::cin.rdbuf(in.rdbuf())
sets std::cin's
buffer to in.rdbuf()
and then returns the old buffer associated with std::cin
. The very same can be done with std::cout
— or any stream for that matter.
希望有所帮助.
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