[TriLUG] a C question (overkill)

[P. L. Charles Fischer]

Here is the overkill version of your program.  It checks for buffer overflow
and shows two way to get the text into the program.

#include <stdio.h>				/* needed for file input and output			*/
#include <stdlib.h>				/* needed for malloc and free if you use them		*/

#define STR_LENGTH	256			/* define the maximum string input length		*/

#define ALLOC_MEM	1			/* comment this line out if you want to avoid malloc	*/

int main(int argc, char *argv[])		/* do not worry about argc and argv at
this time	*/
{
#ifdef ALLOC_MEM					/* only one text variable will be used		*/
	char			*text;			/* Folks will argue which way is better		*/
							/* this way leaves the stack small, which is	*/
							/* good for debuging.  Stack overflows can be	*/
							/* hard to find.				*/
#else
	char			text[STR_LENGTH];	/* in this small of a progam it does not matter	*/
							/* if you use the stack, but you may get into	*/
							/* bad habits.					*/
#endif

	int			fav_num;		/* integer variable for your input integer	*/
	char			*ret_str;		/* string returned from fgets function		*/
	int			ret_int;		/* number of fields converted from sscanf	*/

#ifdef ALLOC_MEM
	text = malloc(STR_LENGTH);		/* get the memory for the text input variable	*/
	if (text == NULL)			/* check to make sure you got your memory	*/
	{
		fprintf(stderr, "Could not get the memory for some odd reason.\n");
		exit(-1);
	}
#endif

	printf("What is your favorite number?\n");	/* prompt the user to enter a
number	*/
	ret_str = fgets(text, STR_LENGTH, stdin);	/* get the input string, limit
the input to STR_LENGTH	*/
							/* characters this will solve buffer overflow problems	*/
	if (ret_str == NULL)				/* check for nothing entered		*/
	{
		fprintf(stderr, "Could not read input string for some odd reason\n");
		exit(-2);
	}

	ret_int = sscanf(text, "%d", &fav_num);		/* take the input string and read
the first field as an integer	*/
	if (ret_int != 1)
	{
		fprintf(stderr, "You did not input a integer as the first part of the
input string.\n");
		exit(-3);
	}

	printf("\n\nYour favorite number is %d\n\n", fav_num);

#ifdef ALLOC_MEM					/* free memory from text input for other use	*/
	free(text);					/* some say you should do this, but when the 	*/
							/* program ends the OS will do it for you	*/
#endif

	return(0);
}
____________________________________________________________________________
P. L. Charles Fischer                                      fischer at zedec.com
					VOX: 919.465.2306	800.894.0058
ZEDEC Technologies                                         FAX: 919.465.2309
____________________________________________________________________________