c++ std::cout unespected output

Question

Hi I'm writing some debug output with std::cout with this code:

EDIT: as suggested I added a std::flush on each cout and an std::endl on each iteration

int
    index = 0,
    size = vector.size();
for (iterate trough a vector)
{
    std::cout << "Actual element: " << index+1 << "/" << size << std::flush;
    ...
    if (bad element)
    {
        std::cout << " -> Bad Element" << std::flush;
    }
    std::cout << std::endl;
}

The bad element string appear only after the successive element, why? What am I missing?

Thanks a lot!

Yes, it actually print the bad element string. I wrote it in pseudo code because the condition and the iteration weren't the problem — Michele mpp Marostica, Sep 07 '13 at 09:15
Please show us the real code as the problem is most likely there. — Daniel Frey, Sep 07 '13 at 09:45

score 1 · Answer 1 · answered Sep 07 '13 at 08:25

1

You should have a std::cout << std::flush (or std::cout << std::endl) in your for loop which is always done (even without bad elements), or at least after your for loop....

answered Sep 07 '13 at 08:25

Basile Starynkevitch

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+1 Or just use `std::cerr`, especially nice if stdout is redirected and you still want a console-debug log. – WhozCraig Sep 07 '13 at 08:57
Or even `std::clog` maybe? – Basile Starynkevitch Sep 07 '13 at 08:58
But if I use the flush it doesn't print anything on output until it reach an endl, why? – Michele mpp Marostica Sep 07 '13 at 09:18
1

@BasileStarynkevitch Both write to stderr, but `cerr` is unbuffered (so each output to it is visible immediately), whereas `clog` is buffered (so you would still need to flush) – gx_ Sep 07 '13 at 10:34

c++ std::cout unespected output

1 Answers1