C++ Prepend DateTime to console output - c++

Question

Searched around and couldn't find any info on this besides redirecting to files so hopefully someone can help me out.
I have a console application that launches and hooks another process, by default the new process output displays in the first console application.
What I would like to do is prepend a datetime value to all the output, the problem is that I don't control the output from the child process (3rd party app) so the easy solution of adding a datetime to all printed values is unavailable. Is it possible to prepend a string to all stdout?

Answer 1

Since you confirmed C++ (which implies a solution for
std::cout is what is needed, and not for stdout): the
obvious solution is a filtering streambuf:
class TimeStampStreambuf : public std::streambuf
{
std::streambuf* myDest;
std::ostream* myOwner;
bool myIsAtStartOfLine;
protected:
int overflow( int ch )
{
// To allow truly empty lines, otherwise drop the
// first condition...
if ( ch != '\n' && myIsAtStartOfLine ) {
std::string tmp = now();
// function now() should return the timestamp as a string
myDest->sputn( tmp.data(), tmp.size() );
}
myIsAtStartOfLine = ch == '\n';
ch = myDest->sputc( ch );
return ch;
}
public:
TimeStampStreambuf( std::streambuf* dest )
: myDest( dest )
, myOwner( nullptr )
, myIsAtStartOfLine( false )
{
}
TimeStampStreambuf( std::ostream& owner )
: myDest( dest.rdbuf() )
, myOwner( &owner )
, myIsAtStartOfLine( false )
{
myOwner->rdbuf( this );
}
~TimeStampStreambuf()
{
if ( myOwner != nullptr ) {
myOwner->rdbuf( myDest );
}
}
};
And to install it:
// scoped:
TimeStampStreambuf anyName( std::cout );
// Time stamping will be turned off when variable goes out
// of scope.
// unscoped:
std::streambuf* savedStreambuf = std::cout.rdbuf();
TimeStampStreambuf name( savedStreambuf );
// In this case, you have to restore the original streambuf
// yourself before calling exit.
As far as I know, the articles explaining this (from C++
Reports, Sept. 1998) are not on line.
EDIT:
I've actually found them:
http://gabisoft.free.fr/articles-en.html. I can't believe that
the link still works; it's been years since I had an account
with Free.