quotation marks surrounding string during writing to file with FileStorage in Qt

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Hi Everybody My problem are quotation marks during writing to file. The code is

cv::FileStorage fs(outputname.toStdString(), cv::FileStorage::WRITE); … std::string str=“test”; fs << str.c_str(); …

In file I got “test”, but what I want is just test without quotations marks. Can anybody give me a hand?

best regards