The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#include <streambuf>
#include <locale>
#include <cstdio>
class outbuf : public std::streambuf
{
protected:
// central output function
// - print characters in uppercase mode
virtual int_type overflow (int_type c) {
if (c != EOF) {
// convert lowercase to uppercase
c = std::toupper(c,getloc());
// and write the character to the standard output
if (std::putchar(c) == EOF) {
return EOF;
}
}
return c;
}
};