Question

int main(void) {     char tmp, arr[100];     int i, k;      printf('Enter a string: ');     scanf_s('%s', arr);      for ( k = 0, i = (strlen(arr) - 1); k < (int) (strlen(arr) / 2); --i, ++k) {             tmp = arr[k];             arr[k] = arr[i];             arr[i] = tmp;     }      puts(arr);      return 0; } 

I know that there is something weird about scanf_s() but I could NOT resolve the issue. My code works well by using scanf() but this does NOT reverse the elements of the array 🙁 Any help will be strongly appreciated. Thanks.

Answer 1

scanf_s requires the buffer size in chars to be passed as the second parameter.

int iNumFilled1 = scanf_s('%s', arr); int iNumFilled2 = scanf_s('%s', arr, _countof(arr)); assert(iNumFilled1 == 0); assert(iNumFilled2 == 1); 

You can also pass a width specifier. If passed and it does not fit into the buffer you will have only the first ‘width specified’ chars.

//Input a string longer than 99 chars int iNumFilled3 = _tscanf_s(_T('%99s'), arr, _countof(arr)); assert(iNumFilled3 == 1);  //Again insert a string longer than 99 chars, but with no width specifier int iNumFilled4 = _tscanf_s(_T('%s'), arr, _countof(arr)); assert(iNumFilled4 == 0);