How to check if input is numeric in C++ -

i want create program takes in integer input user , terminates when user doesn't enter @ (ie, presses enter). however, i'm having trouble validating input (making sure user inputting integers, not strings. atoi() won't work, since integer inputs can more 1 digit.

what best way of validating input? tried following, i'm not sure how complete it:

char input  while( cin>>input != '\n') {      //some way check if input valid number      while(!inputisnumeric)      {          cin>>input;      } } 

when cin gets input can't use, sets failbit:

int n; cin >> n; if(!cin) // or if(cin.fail()) {     // user didn't input number     cin.clear(); // reset failbit     cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); //skip bad input     // next, request user reinput } 

when cin's failbit set, use cin.clear() reset state of stream, cin.ignore() expunge remaining input, , request user re-input. stream misbehave long failure state set , stream contains bad input.