Thread: scanf problem

peace upon you all every one :

I’m having a little problem with the scanf() function

the following code asks three users about their age using
scanf("%i",&user_age)

and then it matches if user_age >= 18 and user_age <= 100 and scanf() returned something except zero.

if the user entered a character or any except integer scanf() fails and return zero then the code loop back and try to reread the user age .

the problem is that scanf() won’t re prompt the user to enter any thing !!

but just keep returning 0 and the program keep trying to reread the age

here is the code :

Code:

#include <stdio.h>

int main()
{
	int i = 0;
	int user_age = 0;
	int scanf_result = 0;

	for (i=1 ; i<=5 ; i++)
	{
		printf("user number %i Enter your Age : ",i);
		scanf_result = scanf("%i",&user_age);

		if (user_age >= 18 && user_age <= 100 && scanf_result > 0)
		{
			//if the user input is >= 18 and <= 100 and scanf() returned non zero (succeeded) then
			//do some work with the user input
		}
		else
		{
			printf("your age should be an integer from 18 to 100 try again\n");
			i = i -1;
		}
	}

	printf ("\n");
	return 0;
}

scanf does not remove invalid input. That's your responsibility. Check the FAQ.

Test the return value from scanf() ... if you're looking for one variable, anything but a 1 returned is an error... scanf("%d",&x) will return 0 if the user types in a letter instead of a number.

Functions have return values for a reason.