Re: inheriting from ostream to customize standard output

James Kanze <>
Sun, 3 Apr 2011 05:39:39 -0700 (PDT)
On Mar 29, 11:48 am, aaragon <> wrote:

I was wondering if there is an easy way that one could create
a custom class that inherits from std::ostream to override the
functionality of operator<<.

No, thank goodness. The behavior of the operator<< is part of
the contract of ostream, and too much other code counts on it.
What you can do is define your own streaming class; when
appropriate, it could delegate to an ostream.

Since I work with several processes, I want to avoid some of them to
print information to standard output (or enable that to print
information concurrently).

I tried the following but it didn't work:

        class Output_strem : public std::ostream {

            typedef std::ostream base_type;
            Output_strem() : base_type() {}

            template <typename T>
            std::ostream& operator<<(T t) {

#ifdef MPI
                std::ostream& os = *this;
                os<<"["<<Parallel_base::rank_<<"] ";
                return *this;

Can someone point me in the right direction?

Use delegation instead of inheritance.

James Kanze

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