lseek - not working

avatarClient.c

@@ -48,6 +48,7 @@ int main(int argc, char const *argv[])
         {
             int av_open = open("package.jpg", O_CREAT | O_RDWR);
             int av_write = write(av_open, buffer, sizeof(buffer));
+            lseek(av_open, sizeof(buffer), 0);
             int av_close = close(av_open);
         }
         printf("%s", "Received");