Thread: Still Practicing, Too Much To Learn

Did a tutorial on arrays and pointers today and wrote this little program.

#

Code:

include <stdio.h> 

int main()
{
	int position;
	int length;
	char arr [5];	
	char *cptr;
	cptr = arr;
	printf ("Please enter a character array: ");
	scanf ("%s", &arr);
	length = strlen(arr);
		while (length > 5)
		{
			printf ("Too big, please try again: ");
			scanf ("%s", &arr);
			length = strlen(arr);
		}
	printf ("Which letter would you like to point to? ");
	scanf ("%d", &position);
	position = position - 1;
	printf("%c\n", arr[position]);
	return 0;
}

It sort of works! If I enter a string of 5 characters I get the correct answer but get a run time error as well stating the stack around arr is corrupt. If i enter a string larger than 5 characters i go into the loop as expected but if I then enter a string of less than 5 characters, again i get the right answer and the same run time erros. Any suggestions?

I hope you know that you can only enter 5 - 1 (for the terminating NUL character) = 4 characters into your keyboard without giving your program a reason to fail.

Maybe I'm miss interpreting you but i don't beleive that is the case. I am testing the length of the string, I've run the program with letters and it works, just bombs out at the end for the message I posted above.

Is there a way to specify how much room scanf can use?

%4s would mean "read up to 4 characters". If you want to know how scanf works, you should type "man scanf" at your terminal or at google (once you stop playing pacman).

On the other hand, the "f" in scanf stands for "formatted", and unless you are only planning to use this code on redirected files as input, you shouldn't use scanf for monkey-at-the-keyboard input. Look at fgets.

Originally Posted by tabstop

%4s would mean "read up to 4 characters". If you want to know how scanf works, you should type "man scanf" at your terminal or at google (once you stop playing pacman).

On the other hand, the "f" in scanf stands for "formatted", and unless you are only planning to use this code on redirected files as input, you shouldn't use scanf for monkey-at-the-keyboard input. Look at fgets.

Thanks!