The first constructor initializes the base class by calling basic_ostream(sb), where sb is the stored object of class basic_filebuf<Elem, Tr>. It also initializes sb by calling basic_filebuf<Elem, Tr>.

The second and third constructors initializes the base class by calling basic_ostream(sb). It also initializes sb by calling basic_filebuf<Elem, Tr> and then sb.open(_Filename, _Mode | ios_base::out). If the latter function returns a null pointer, the constructor calls setstate(failbit).

The following example shows how to create a basic_ofstream object and write text to it.

// basic_ofstream_ctor.cpp
// compile with: /EHsc
#include <fstream>

using namespace std;

int main(int argc, char **argv)
{
    ofstream ofs("C:\\ofstream.txt");
    if (!ofs.bad())
    {
        ofs << "Writing to a basic_ofstream object..." << endl;
        ofs.close();
    }
}

Header: <fstream>

Reference

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