Ideas for error checking from command line

**matsp** · 01-15-2009

Originally Posted by NuNn

Thank you that helped for the infinite loop issue, is there a way to make scanf() stop waiting if not enough inputs were entered and if there are too many inputs scanf() just ignore's the extras correct?

My code works also to clean out extraneous "valid" input. It does not solve the problem of only one or two inputs when you expect 3. To solve that, you will need to read a string (for example fgets()) and then use sscanf() to read from the string - that ALSO solves the problem of dealing with "bad" input nicely, so you don't actually need any loops or such).

--
Mats

**NuNn** · 01-15-2009

I have updated my file and it seemed to be working fine, however there is a minor glitch:

Code:

int main() {
	double a, b, c, x1, x2;
	int qret, count;
	char line[30];

	while(1) {
		count=0;
		printf("Enter variables for quadratic equation (Enter 'q' or 'quit' to exit):  ");
		fgets(line, 30, stdin);
	
		if((strncmp(line, "quit", 4) > 0) || (strncmp(line, "q", 4) > 0))
			return 0;
		else
			count = sscanf(line, "%lf %lf %lf", &a, &b, &c);

		if(count != 3) 
			printf("Invalid Input: Format Is <double> <double> <double>\n\n");		
					

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

for some reason the count returned by sscanf is 30 some of the time and im unsure as to why this is. I see that my array size is 30, but shouldn't sscanf() return the number of correctly read items?

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