c++ rdbuf流指针重定向

给个例子吧，假如把cin重定向到in.txt，把cout重定向到out.txt

#include <iostream>#include <fstream>#include <string>using namespace std;int main(){ ofstream out("out.txt"); ifstream in("in.txt"); cin.rdbuf(in.rdbuf()); cout.rdbuf(out.rdbuf()); string s; cin>>s; cout<<s<<endl; return 0;}