How to determine if the cin is keyboard or from file

Question

I have an input function I'm writing:

void input(istream& ins)

As well as output function:

void output(ostream& outs)

My question is inside of these two functions, I want an if statement that determines if I'm writing from file or writing from keyboard. This is because inside of my input I am using the input to also cout statements if the data is not coming from a file.

I want my output file to determine if its writing to file, or its writing to the screen. Basically, I just want to know how to check for writing from/to file if I want to pass the streams into the functions.

Answer 1

You can do a simple address compare:

if(&ins == &cin){
//then you using cin, since there is only one cin object
}else{
//other istream
}

same for cout...

if(&outs == &cout || &outs == &cerr){
//then you using standard outputs: cout or cerr
}else{
//other ostream
}