How it’s done

Continue to use cout<< in your code

in an online environment, we globally modify the behavior of the cout object to achieve the desired functionality

cout (and in general, all objects of type "ostream") are only the formatting engine. They enlist the services of another object (of type "streambuf") to handle their formatted output.

We can provide a new "streambuf" object to be used by cout which has the functionality which we want. This is a standard procedure in C++, not some "dirty trick".

cout

streambuf

{

if ( file_is_open) return -1;

sprintf( ctrlbuf->current_filename, ctrlbuf->filerule, run_number);

if ( (the_file = fopen(ctrlbuf->current_filename, "w") )==NULL )

{

cerr << "file not opened " << strerror(errno) << endl;

*fp = 0;

return -1;

}

*fp = the_file;

file_is_open = 1;

// cout << "opened file " << ctrlbuf->current_filename << endl;

return 0;

}

int ndd_control::close_file()

{

if ( !file_is_open) return -1;

fclose(the_file);

{