creating dynamical output file names

I'm trying to write to output files that have dynamically created names. I can do this (I think) by using an ostringstream variable, but the file variable expects a pointer to a constant char. How do I convert this ostringstream variable (called 'result' here) to a pointer to a constant char? 'r' is an integer here. I tried converting the ostringstream variable to a string variable, but the ofstream variable won't accept that either. This is the few lines of code that are important:

Code:

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result << "testfiles_" << r;
std::string bufoutput_s = result.str();
ofstream outputfile (bufoutput_s);

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ostringstream can be converted to a string by mean of str() , and a string can be converted to a c style string by c_str()

Code:

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result << "testfiles_" << r;
ofstream outputfile (result.str().c_str());

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awesome, that works. I didn't know it was possible to use a member function of a member function. Thanks.

It's not a member function of a member function. The str() member function return's a std::string object in this case a temporary string object that then has it's c_str() member called. It just happens to all be on one line and looks like the chaining concept seen so often in the use of the stream insertion/extraction operators (<</>>).