#include <stdio.h>
main(){
             printf("%*d\n", 5, 10); 
             printf("%.*d\n", 3, 10); 
             printf("%.*s\n", 3, "akshay");
      }

$ ./a.out 
   10
010
aks

#include <stdio.h>
main(){
           // Equal
           printf("%.*s\n", 3, "akshay");
           printf("%.3s\n", "akshay" );
      }

$ ./a.out 
aks
aks

#include <stdio.h>
main(){
          int count = 3;
          char fmt[10];
          char src[6] = "akshay";
          char dst[6];

          // Don's approach : following statements creates format that is
          // fmt will be "%.3s"
          sprintf(fmt, "%%.%ds", count);

          printf("Format is : %s\n", fmt);

          // following statement is equal to sprintf(dst,"%.3s",src)
          sprintf(dst, fmt, src);
          printf("output is : %s\n", dst);
      }

$ ./a.out 
Format is : %.3s
output is : aks