ostringstream

Ostringstream is an output stream class in the C++ standard library that writes formatted data into a string buffer. It is defined in the header <sstream> and resides in the std namespace. std::ostringstream is a typedef of std::basic_ostringstream<char>, used when data should be assembled into a string rather than written to an external device.

The class uses an internal string buffer to accumulate characters. Data inserted by operator<< is stored in a std::string and can be retrieved with str(), which returns the current contents. str(const std::string&) replaces the current contents. The underlying buffer can be accessed via rdbuf(). The object supports the usual stream manipulators and type insertion rules of iostreams.

Usage typically involves creating an ostringstream, streaming values into it, and then extracting the resulting string with str(). Example: std::ostringstream oss; oss << "Value: " << 42; std::string s = oss.str();

Compared with direct formatting, ostringstream offers type safety and integrates with locale and iomanip facilities provided by the iostreams library. It is one of a family of string-based streams that also includes std::istringstream for input and std::stringstream for combined input and output. Overall, ostringstream is a convenient tool for composing strings from multiple values without manual formatting or temporary buffers.