Error when reading user input and storing into array

Question

I have encounter an error when running this code. There will be a "program stop working" windows once it reaches the loop to scan for user input for the names ("scanf_s(%s", &nameptr[i]); ). Any help or advice will be greatly appreciated!

#include <stdio.h>
#include <string.h>
#define SIZE 10
int findTarget(char *target, char nameptr[SIZE][80], int size);

int main()
    {
    char nameptr[SIZE][80];
    char t[40];
    int i, result, size;
    printf("Enter no. of names: ");
    scanf_s("%d", &size);
    printf("Enter %d names: ", size);


    for (i = 0; i < size; i++) 
            scanf_s("%s", &nameptr[i]); 

    printf("Enter target name: ");
    scanf_s("\n");
    gets(t);
    result = findTarget(t, nameptr, size);
    printf("findTarget(): %d\n", result);

    return 0;

    }

    int findTarget(char *target, char nameptr[SIZE][80], int size)
      {
      int i;
      for (i = 0; i<size; i++) {
      if (strcmp(nameptr[i], target) == 0)
        return i;
        }
    return -1;
      }

Avoid gets as it does not provide any protection against buffer overflows. Use fgets instead: fgets(t, sizeof(t), stdin); — Spikatrix
– Spikatrix, Commented Sep 19, 2015 at 11:12

Spikatrix · Accepted Answer · 2015-09-19 11:04:12Z

1

This:

scanf_s("%s", &nameptr[i]);

should be

scanf_s("%s", nameptr[i], sizeof(nameptr[i])); 
/* Or better */
scanf_s("%79s", nameptr[i], sizeof(nameptr[i]));

or

scanf_s("%s", nameptr[i], _countof(nameptr[i])); 
/* Or better */
scanf_s("%79s", nameptr[i], _countof(nameptr[i]));

because the %s in scanf_s expects a third argument denoting the maximum size of the string argument used. More information on this can be found at the msdn documentation of scanf_s

answered Sep 19, 2015 at 11:04

Spikatrix

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2 Comments

JWH_ Over a year ago

Thanks! Its working now! May I know what is the use of the 3rd parameter for scanf_s and when does one need to use it?

Spikatrix Over a year ago

@Jackelll The third parameter is to prevent buffer overflows. It is needed when using %s, %c and %[. Otherwise, it is not required.

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