Thread: isdigit woes

Im trying to use isdigit to invoke an error if a string has anything other than a digit in it and having no luck. My old code line will kick out something that starts with a non integer value, ex. e356, it will error but not error out with 3e56. I tried to utilize isdigit in place but I cant seem to get the syntax right. Am I even barking up the right tree trying to invoke isdigit for this kind of task?

Code:

#include <stdio.h>
#include <ctype.h>
// THIS IS BROKEN!!!!
#define MAXLINE 40

int main(void)
{
int error, n ;
char line[MAXLINE];
do {
	printf("Input a positive integer:  ");
	fgets(line, MAXLINE, stdin);
	//error = sscanf(line, "%d", &n) !=1 || n <= 0;// Old code
	error = sscanf(line, "%d", &n) !=isdigit(n); //DOES NOT WORK
	if(error)
	printf("\nERROR: Do it again.\n");
	}while(error);	
	
printf("your line was:  %s",line);

return 0;
}