Using << operator to write to both a file and cout

Question

I\'d like to overload << operator to write the value it takes to a file and cout. I have tried to do it with following code, but couldn\'t succeed it. It just writes t

Answer 1

Create a helper class and overload operators that takes care of streaming to two streams. Use the helper class instead of trying to override the standard library implementations of the overloaded operator<< functions.

This should work:

#include 
#include 

struct MyStreamingHelper
{
    MyStreamingHelper(std::ostream& out1,
                      std::ostream& out2) : out1_(out1), out2_(out2) {}
    std::ostream& out1_;
    std::ostream& out2_;
};

template 
MyStreamingHelper& operator<<(MyStreamingHelper& h, T const& t)
{
   h.out1_ << t;
   h.out2_ << t;
   return h;
}

MyStreamingHelper& operator<<(MyStreamingHelper& h, std::ostream&(*f)(std::ostream&))
{
   h.out1_ << f;
   h.out2_ << f;
   return h;
}

int main()
{
   std::ofstream fl;
   fl.open("test.txt");
   MyStreamingHelper h(fl, std::cout);
   h << "!!!Hello World!!!" << std::endl;
   return 0;
}