c++ - Printing out a stringstream using str() and rdbuf() -

c++ - Printing out a stringstream using str() and rdbuf() -

when have:

std::ostringstream oss("hello");

why work:

std::cout << oss.str();

but doesn't print anything:

std::cout << oss.rdbuf();

reading definition of operator<<(std::ostream&, std::streambuf*) print characters buffer. oss.rdbuf() not contain anything?

this issue related fact here, oss ostringstream object (ostringstream output stream destination write it , not read it) , fact how streams manage internal buffer.

you can alter

std::ostringstream oss("hello");

to

std::istringstream oss("hello"); // or std::stringstream oss("hello");

and work expected. alternatively use

std::cout << oss.rdbuf()->str(); // print re-create of buffer content

example:

#include <iostream> #include <sstream> int main() { std::ostringstream oss("hello"); std::istringstream oss2("hello"); cout << oss.rdbuf()->str() << endl; // prints "hello" cout << oss2.rdbuf(); // prints "hello" homecoming 0; }

c++