std::strstream::str (3) - Linux Manuals

std::strstream::str: std::strstream::str


std::strstream::str - std::strstream::str


char* str();

Returns the pointer to the beginning of the buffer, after freezing it. Effectively calls rdbuf()->str()


Before a call to str() that uses the result as a C string, the stream buffer must be null-terminated. Regular output such as with stream << 1.2 does not store a null terminator, it must be appended explicitly, typically with the manipulator std::ends.
After a call to str(), dynamic streams become frozen. A call to freeze(false) is required before exiting the scope in which this strstream object was created. otherwise the destructor will leak memory. Also, additional output to a frozen stream may be truncated once it reaches the end of the allocated buffer, which may leave the buffer not null-terminated.



Return value

Pointer to the beginning of the buffer in the associated std::strsteambuf or NULL if no buffer is available.


// Run this code

  #include <strstream>
  #include <iostream>

  int main()
      std::strstream dyn; // dynamically-allocated output buffer
      dyn << "Test: " << 1.23; // not adding std::ends to demonstrate append behavior
      std::cout << "The output stream holds \"";
      std::cout.write(dyn.str(), dyn.pcount()) << "\"\n";
      // the stream is now frozen due to str()
      dyn << " More text" << std::ends;
      std::cout << "The output stream holds \"";
      std::cout.write(dyn.str(), dyn.pcount()) << "\"\n";

Possible output:

  The stream holds "Test: 1.23"
  The stream holds "Test: 1.23 More "

See also

    marks the buffer frozen and returns the beginning pointer of the input sequence
str (public member function of std::strstreambuf)