diff --git a/CMakeLists.txt b/CMakeLists.txt
index c1c5a35..892d420 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,15 +52,13 @@ target_link_libraries(${APP_NAME}
     ${CMAKE_SOURCE_DIR}/third_party/lib/libpaho-mqtt3c.a
 )
 
-# 拷贝配置文件
+# 拷贝配置文件（仅在不存在时）
 add_custom_command(TARGET ${APP_NAME} POST_BUILD
     COMMAND sh -c
-    "if [ ! -f \"$<TARGET_FILE_DIR:${APP_NAME}>/${CONFIG_FILE}\" ]; then \
-        mkdir -p \"$<TARGET_FILE_DIR:${APP_NAME}>\" && \
-        cp \"${CMAKE_SOURCE_DIR}/${CONFIG_EXAMPLE_FILE}\" \
-           \"$<TARGET_FILE_DIR:${APP_NAME}>/${CONFIG_FILE}\" && \
-        echo \"config.json created from example\"; \
-     else \
-        echo \"config.json exists, keep it\"; \
-     fi"
+    "test -f \"$<TARGET_FILE_DIR:${APP_NAME}>/${CONFIG_FILE}\" || \
+     (mkdir -p \"$<TARGET_FILE_DIR:${APP_NAME}>\" && \
+      cp \"${CMAKE_SOURCE_DIR}/${CONFIG_EXAMPLE_FILE}\" \
+         \"$<TARGET_FILE_DIR:${APP_NAME}>/${CONFIG_FILE}\" && \
+      echo \"config.json created from example\")"
 )
+