Question

In ANSI C++, how can I assign the cout stream to a variable name? What I want to do is, if the user has specified an output file name, I send output there, otherwise, send it to the screen. So something like:

ofstream outFile; if (outFileRequested)      outFile.open('foo.txt', ios::out); else     outFile = cout;  // Will not compile because outFile does not have an                       // assignment operator  outFile << 'whatever' << endl; 

I tried doing this as a Macro function as well:

#define OUTPUT outFileRequested?outFile:cout  OUTPUT << 'whatever' << endl; 

But that gave me a compiler error as well.

I supposed I could either use an IF-THEN block for every output, but I’d like to avoid that if I could. Any ideas?

Answer 1

Use a reference. Note that the reference must be of type std::ostream, not std::ofstream, since std::cout is an std::ostream, so you must use the least common denominator.

std::ofstream realOutFile;  if(outFileRequested)     realOutFile.open('foo.txt', std::ios::out);  std::ostream & outFile = (outFileRequested ? realOutFile : std::cout);