CODEWITHSUNDEEP
c++
liaquore
liaquore

Reputation: 397

C++ - cin spams terminal

I'm trying to get input for an integer in C++ through cin and when I try this:

int port = 0;

do
{
  std::cout << "Enter port for server: ";
  std::cin >> port;
} while (port <= 0);

It spams my terminal with "Enter port for server: " if I don't enter a valid integer. How do I handle this situation and why does this spam my terminal?

Upvotes: 0

Views: 3057

Answers (2)

Xchg0x5f375d
Xchg0x5f375d

Reputation: 427

if (std::cin.fail())
{
    std::cout << "Enter valid port, please. " << std::endl;
}

while (std::cin.fail())
{
    std::cin.clear();
    std::cin.ignore(numeric_limits<streamsize>::max(), '\n');
    std::cin >> port;
}

After std::cin fails, you need to clear error flag. You don't even have to use fail function:

while (!(std::cin >> port)) { std::cin.clear(); std::cin.ignore(); }

Upvotes: 1

Tofu
Tofu

Reputation: 3613

You're not validating input. Ideally what you should do is take input as strings then perform the conversion to the type you want after. If you do want to take them as integers, You can check the value of cin after the user enters input. If input is invalid, the failbit in cin is set.

int main(){
    int port = 0;

    do
    {
        std::cout << "Enter port for server: ";
        if(!(cin >> port)){//error occurred
            std::cout << "invalid input" << std::endl;
            cin.clear();//Clear the error
            break;
        }
    } while (port <= 0);

}

Upvotes: 2

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