Thread: Ideas for error checking from command line

I am trying to read three doubles from a user's input on the command line. However, my error checking is something to be desired. If I don't enter the correct number of doubles or don't enter a double the program goes into an infinite loop. Here is the main which is handling the I/O:

Code:

int main() {
	double a, b, c, x1, x2;
	int qret, count;

	while(1) {
		printf("Enter variables for quadratic equation:  ");
		
		if( (count = scanf("%lf %lf %lf", &a, &b, &c)) != 3) {
			printf("Invalid Input: Format Is <double> <double> <double>\n");
			printf("%d \n", count);			
		}			

		else if((qret = qsolver(a, b, c, &x1, &x2)) == 3) {
			printf("Error Value:  %d\n", qret);		
			printf("X1 = %lf   X2 = %lf\n\n", x1, x2);
		}
	}
	return 0;
}