diff --git a/cpp/cmake.txt b/cpp/cmake.txt
index bce9840..19b6740 100644
--- a/cpp/cmake.txt
+++ b/cpp/cmake.txt
@@ -310,3 +310,11 @@ target_link_libraries(useopencv4 PRIVATE
 其中可以使用find_library
 find_library(SDL2MAIN SDL2main ${SDL2_DIR}/lib)
 不过貌似只能单个找寻。
+
+:: build pre or after to do
+get_target_property(LIB_TYPE xxx TYPE)
+add_custom_command(TARGET xxx POST_BUILD/PRE_BUILD
+    COMMAND ${CMAKE_COMMAND} -E copy
+            ${LIBRARY_OUTPUT_PATH}/libxxx.a
+            /home/typ/3rd/)
+