C++, regarding fprintf and ofstream

问题:

I've been using fprintf for a while now and I'd like to ask a question. What is the equivalent of this fprintf line:

fprintf(OutputFile, "%s", "SomeStringValue");

using ofstream ?

How to use the "%s" in ofstream is what I'd really like to know. How to take the next argument and print it as a string?

回答1:

You don't use it.

The equivalent is essentially:

std::ofstream x("your_file");
x << "SomeStringValue";
x.close();

Go read about it on any of several reference pages. Such as http://www.cplusplus.com/reference/ostream/ostream/operator%3C%3C/

回答2:

You can't. You just write the string to the stream.

If you mean you want to provide some additional formatting to the string (like right justified with space padding), then you can use the I/O manipulators setfill(' ') (set the fill character to be the space character) and setw(length) (setting the width of the output). If you want something that mimics the syntax of the C style format strings, you can use Boost.format.

std::cout << boost::format("%s") % "SomeStringValue";