Help with a function!

[phufool]

how do you make it so that if the user inputs anything but integers the program will give an error and prompt the user to enter again?
ex. 123456## or ?? should give an error and prompt the user to enter again
help?

[Dino]

You use an input function to get the data, then you parse the data yourself, or use built-in functions to parse the data, and check their output, and you put all of that in a loop.

[MK27]

One way would be to take your input as a char string and check each character against it's ascii value:

#include <string.h>
#include <stdio.h>


int main() {
	int i;
	char input[1024];
	scanf("%s",input);
	for (i=0;i<strlen(input);i++) {
		if (input[i]<48 || input[i]>57) {
			puts("Not a number!");
			return -1;
		}
	}
	printf("Number was %d\n",atoi(input));
	return 0;
}

This doesn't accept decimals or + or - in "the number" but you should be able to modify it to do so.

Also you could look at the documentation for atoi and strtol for another strategy.

[phufool]

i appreciate the replies!
is there anyway i can use it with an int instead of a char?
the digit has to be a 6 digit number, so this is what i have so far

while(int < 100000 || int > 999999) {
			printf("Invalid! Enter again: ");
			scanf("&#37;d", &int);
		}

Of course, this is so only integers that are 6 digits are allowed.. but im having trouble with anything besides integers. How would I implement what you have above into this? O.O

[matsp]

		if (input[i]<'0' || input[i]>'9')

Why not use the character constants, instead of numeric values. Not only does it make it easier to read, but also allows for the code to compile on platforms that have other character sets than ASCII.

--
Mats

[matsp]

i appreciate the replies!
is there anyway i can use it with an int instead of a char?
the digit has to be a 6 digit number, so this is what i have so far

while(int < 100000 || int > 999999) {
			printf("Invalid! Enter again: ");
			scanf("%d", &int);
		}

Of course, this is so only integers that are 6 digits are allowed.. but im having trouble with anything besides integers. How would I implement what you have above into this? O.O

If you are using scanf, then you need to check the return value of scanf to see if the number of items accepted is 1. If not, you should empty the input buffer - see the FAQ entry on that subject.

--
Mats