Question

I have written code for performing calculations. There is a loop in the code. Each loop corresponds to a different time.

For each loop, I want to write a string to an external file. The string should contain “filename_” and the number of the loop–for example:

‘fileName_4’

The problem is that it is appearing as (with the closing ‘ on the line below):

‘fileName_4
‘

If anyone could help, I would be very grateful. Here is what I have tried:

std::string       convertedToString;
std::stringstream numberConverted; 

storeNumberForConversion << time << endl;   // time is a number, like the 4 in the example above
convertedToString = numberConverted.str() += "'";


fileNameHighestTimeStream.open ("fileName.txt", ios::out | ios::app );
fileNameHighestTimeStream << "'fileName_" << convertedToString << endl; 
fileNameHighestTimeStream.close();

I have also tried:

storeNumberForConversion << time << endl;   // time is a number, like the 4 in the example above
convertedToString = numberConverted.str();


fileNameHighestTimeStream.open ("fileName.txt", ios::out | ios::app );
fileNameHighestTimeStream << "'fileName_" << convertedToString << "'" << endl; 
fileNameHighestTimeStream.close();

Answer 1

std::string       convertedToString;
std::stringstream numberConverted; 

storeNumberForConversion << time << endl;   // time is a number, like the 4 in the example above
convertedToString = numberConverted.str() += "'";

Presumably this is a typo, and you have:

std::string       convertedToString;
std::stringstream numberConverted; 

numberConverted << time << endl;   // time is a number, like the 4 in the example above
convertedToString = numberConverted.str() += "'";

You streamed endl to numberConverted, so it contains a newline. Simple!

From your comment elsewhere:

I thought the endl would flush the stream? If I DON’T include the endl, should I worry about flushing the stream? If so, how would I do it without endl?

<< endl is the same as << '\n' << flush. So you can still do the flushing yourself with << flush, but actually usually you should just leave this up to the stream object to handle in its own time.

Also the use of += is suspect (though it happens to yield the correct result in this case).

Fixed:

std::stringstream numberConverted;
numberConverted << time;

std::string       convertedToString;
convertedToString = numberConverted.str() + "'";