C assignment

gistfile1.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main () {
   char filename[50];

   printf("Please enter a filename : ");
   gets(filename);

   int ext_size = 3;
   char *extension;
   extension = malloc(ext_size);
   char* ptr = strrchr(filename, '.');
   strncpy(extension, ptr, ext_size);
   
   printf("The file extension is: %s", extension);
}