input only integer

[Superman99]

Please someone help me out with this question.
I want to input only integer number, except character and even <whitespace>
if I enter character or Whitespace >> then output " Please enter an integer:"
(I want to use the form as below by using While loop)
thank u

cout << "How many student would you like to add: ";
	
	while (!(cin >> istudent)) 
	{
		cout << "Please enter an integer:\n";
		cin.clear();
		cin.ignore(256, '\n');
	}

[SakurasouBusters]

cout << "How many student would you like to add: ";
	
	while (true) 
	{
		cout << "Please enter an integer : "; cin >> numStudents;
                if(!cin)
                {
   		    cin.clear();
		    cin.ignore(numeric_limits<streamsize>::max(), '\n');
                    cout << "Invalid integer!!! Please try again\n\n";
                    continue;
               }
               else break;
	}

[Handy Andy]

Hello Superman99,

Your while is a good start, but I have seen it this way:

cin >> istudent

while (!cin)
{
    cout << "Invalid integer!!! Please try again\n\n"
    cin.ignore(numeric_limits<streamsize>::max(), '\n');
    cout << "Invalid integer!!! Please try again\n\n";
    cin >> istudent
}

this way if you enter something that is not an integer it will say in the while loop until you do. SakurasouBusters's code will work also.

Hope that helps,

Andy

[Superman99]

Thank you Handy Andy and SakurasouBusters. But I could not run your code perfectly, I did not know why bros. could you guys check for me once again please. Thank you

And we need user can input: <whitespace> enter
then run the output after that . that's is something that i could not fix it. thank u 2 you.

[SakurasouBusters]

For example :

How many student would you like to add : 411 663 772 455

Is that the case you want to handle?

[Duthomhas]

Get input as a std::string.

Check your string to verify it only contains digits. (#include <cctype> and use std::isdigit().)
(If you wish to act on user just pressing Enter or anything else, now is the time to do it.)

Convert to int using one of the functions in <string>.

[Superman99]

SakurasouBusters, my case is

How many student would you like to add : @$%^$% < enter >
---> output : please enter an integer number : hdnfvjfn < enter >
---> output : please enter an integer number : <whitespace> <enter>
---> output : please enter an integer number:
that is what I want to do, especially WHITESPACE is which I could not make it

when i type an space and then enter, the output is :
_
_
_
_

so it mean the computer can not read the whitespace. hopefully you understand my case , ~.~ thank you so much for helping me SakurasouBusters.

[keskiverto]

It can read whitespace, but the formatted input does skip whitespace by default.
Therefore, when you have typed <whitespace> <enter>, which are both white, it is still reading input until you give non-white.
E.g. ---> output : please enter an integer number : <whitespace> <enter>7<whitespace>
will read the 7.

There is http://www.cplusplus.com/reference/ios/noskipws/


What about the case:
---> output : please enter an integer number : <whitespace>42<enter>

[Duthomhas]

If you do as I said, you can catch whitespace as an error.

[Superman99]

Thank u for all that you guys help me, i did find the way to do it :)

i used : cin >> noskipws >> istudent;

that is how i can catch the space .