1#include <stdio.h>
2#include <stdlib.h>
3
4int
5main(int argc, char *argv[])
6{
7 int a, b;
8
9 a = b = -1;
10 sscanf ("12ab", "%dab%n", &a, &b);
11 printf (format: "%d, %d\n", a, b);
12 if (a != 12 || b != 4)
13 abort ();
14
15 a = b = -1;
16 sscanf ("12ab100", "%dab%n100", &a, &b);
17 printf (format: "%d, %d\n", a, b);
18 if (a != 12 || b != 4)
19 abort ();
20 return 0;
21}
22

source code of glibc/stdio-common/scanf5.c