Let's say that you exported all articles in a myexport folder and that the Article class contains an ezimage datatype.
Now you want to import all those articles thanks to this command line :
php bin/php/ezcsvimport.php --class=article --creator=14 --storage-dir=myexport/images 2 myexport/article.csv
If an article contains an image, there is no problem, the attribute will get, for instance, the file myexport/images/my-flowers.jpg. But if an article does not contain any image, it will set the attribute with myexport/images instead of nothing.