You can check like this:
int x; cin >> x; if (cin.fail()) { //Not an int. }
Furthermore, you can continue to get input until you get an int via:
#include <iostream> int main() { int x; std::cin >> x; while(std::cin.fail()) { std::cout << "Error" << std::endl; std::cin.clear(); std::cin.ignore(256,'\n'); std::cin >> x; } std::cout << x << std::endl; return 0; }
EDIT: To address the comment below regarding input like 10abc, one could modify the loop to accept a string as an input. Then check the string for any character not a number and handle that situation accordingly. One needs not clear/ignore the input stream in that situation. Verifying the string is just numbers, convert the string back to an integer. I mean, this was just off the cuff. There might be a better way. This won’t work if you’re accepting floats/doubles (would have to add ‘.’ in the search string).
#include <iostream> #include <string> int main() { std::string theInput; int inputAsInt; std::getline(std::cin, theInput); while(std::cin.fail() || std::cin.eof() || theInput.find_first_not_of("0123456789") != std::string::npos) { std::cout << "Error" << std::endl; if( theInput.find_first_not_of("0123456789") == std::string::npos) { std::cin.clear(); std::cin.ignore(256,'\n'); } std::getline(std::cin, theInput); } std::string::size_type st; inputAsInt = std::stoi(theInput,&st); std::cout << inputAsInt << std::endl; return 0; }