Question

For example, I want to write std::string my_str( "foobar\n" ); literally into std::ostream& with the backslash-n intact (no formatting).

Perhaps I need to convert my_str with a formatting function that converts backslash to double-backslash first? Is there a standard library function for that?

Or maybe there is a directive I can pass to std::ostream&?

Answer 1

The easiest way to do this for larger strings is with raw string literals:

std::string my_str(R"(foobar\n)");

If you want parentheses in it, use a delimiter:

R"delim(foobar\n)delim"

I don’t know of anything that will let you keep the escape codes etc. in the string, but output it without, but std::transform with an std::ostream_iterator<std::string> destination and a function that handles the cases you want should do it, as it does in this example:

std::string filter(char c) {
   if (c == '\n') return "\\n";
   if (c == '\t') return "\\t";
   //etc
   return {1, c};
}

int main() {
   std::string str{"abc\nr\tt"};
   std::cout << "Without transform: " << str << '\n';

   std::cout << "With transform: ";
   std::transform(std::begin(str), std::end(str), std::ostream_iterator<std::string>(std::cout), filter);
}