Find the length of the string using printf library function

Given a string, find the length of the string using printf() library function

#include <stdio.h>
int main(void) {
   char *s;
   int size;
   s=(char*)malloc(sizeof(char));
   scanf("%s",s);
   printf("length of ");
   size=printf("%s",s);
   printf(" is %d",size);
   return 0;
}