What is the difference between istreambuf_iterator and istream_iterator?
And in general what is the difference between streams and streambufs?
I really can't find any clear explanation for this so decided to ask here.
IOstreams use streambufs to as their source / target of input / output. Effectively, the streambuf-family does all the work regarding IO and the IOstream-family is only used for formatting and to-string / from-string transformation.
Now, istream_iterator takes a template argument that says what the unformatted string-sequence from the streambuf should be formatted as, like istream_iterator<int> will interpret (whitespace-delimited) all incoming text as ints.
On the other hand, istreambuf_iterator only cares about the raw characters and iterates directly over the associated streambuf of the istream that it gets passed.
Generally, if you're only interested in the raw characters, use an istreambuf_iterator. If you're interested in the formatted input, use an istream_iterator.
All of what I said also applies to ostream_iterator and ostreambuf_iterator.