man 3 printf
...... One can also specify explicitly which argument is taken, at each place where an argument  is  required,  by  writing
       "%m$"  instead  of  '%'  and "*m$" instead of '*', where the decimal integer m denotes the position in the argument list of the desired
       argument, indexed starting from 1.  Thus,
           printf("%*d", width, num);
       and
           printf("%2$*1$d", width, num);
       are equivalent.  The second style allows repeated references to the same argument.

#include <stdio.h>

int main()
{
    int i;
    char c;
    char string[15];
    printf("Please input a line:\n"); 
    
   scanf("%d , %*s %% %c %5s %s", &i, &c, string, &string[5]);
    //input: 45 , ignore_this, % C read_in_this**
    
    printf("%d , %*s %% %c %5s %c", &i, &c, string, &string[5]);
    return 0;
}

pg503.c: In function ‘main’:
pg503.c:13:2: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘int *’ [-Wformat]
pg503.c:13:2: warning: field width specifier ‘*’ expects argument of type ‘int’, but argument 3 has type ‘char *’ [-Wformat]
pg503.c:13:2: warning: format ‘%c’ expects argument of type ‘int’, but argument 5 has type ‘char *’ [-Wformat]
pg503.c:13:2: warning: format ‘%s’ expects a matching ‘char *’ argument [-Wformat]
pg503.c:13:2: warning: format ‘%c’ expects a matching ‘int’ argument [-Wformat]

./a.out 
Please input a line:
45 , ignore_this, % C read_in_this**

45
, 
read_
in_this**