manipulate

            char* ex_ptr= strchr(a_p,'.') + 1;
            char* end_ex = strrchr(a_p,' ') - 1;
            char extension[end_ex - ex_ptr + 1];
            strncpy(extension,ex_ptr,end_ex - ex_ptr);
            extension[end_ex - ex_ptr + 1] = '\0';