NSIS 检测文件存在

!define MUI_PAGE_CUSTOMFUNCTION_LEAVE DirectoryLeave

!insertmacro MUI_PAGE_DIRECTORY

Function DirectoryLeave

IfFileExists "$INSTDIR\*.*" 0 +3

 MessageBox MB_OKCANCEL|MB_ICONEXCLAMATION \

 "The destination folder already exists. $\r$\n \

Would you like to use it anyway?" MB_OK +2

 Abort

FunctionEnd