String input using C scanf_s

Question

I've been trying to look for answer myself, but I can't find one. I want to insert a part of the programming that reads in a string like "Hello" and stores and can display it when I want, so that printf("%s", blah); produces Hello.

Here's the code part that's giving me trouble

char name[64];
scanf_s("%s", name);
printf("Your name is %s", name);

I know that printf isn't the problem; the program crashes after something is input after a prompt. Please help?

Answer 1

From the specification of fscanf_s() in Annex K.3.5.3.2 of the ISO/IEC 9899:2011 standard:

The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion specifiers apply to a pair of arguments (unless assignment suppression is indicated by a *). The first of these arguments is the same as for fscanf. That argument is immediately followed in the argument list by the second argument, which has type rsize_t and gives the number of elements in the array pointed to by the first argument of the pair. If the first argument points to a scalar object, it is considered to be an array of one element.

and:

The scanf_s function is equivalent to fscanf_s with the argument stdin interposed before the arguments to scanf_s.

MSDN says similar things (scanf_s() and fscanf_s()).

Your code doesn't provide the length argument, so some other number is used. It isn't determinate what value it finds, so you get eccentric behaviour from the code. You need something more like this, where the newline helps ensure that the output is actually seen.

char name[64];
if (scanf_s("%s", name, sizeof(name)) == 1)
    printf("Your name is %s\n", name);