-none rule is very useful in the case where a file that should not be seen within a view and the other methods of hiding the file are not a viable choice.
In a dynamic view:
=> Generates a File not found or No such file or directory error when an operating system program references the element by name.
=> No error occurs when an operating system command or utility program lists the element's containing directory, though the element is not included in such a listing. This also applies to situations such as expansion of wildcard characters and file name completion.
=> The cleartool ls command always lists the element, annotating it with no version selected.
=> In ClearCase and ClearCase LT commands, the element's standard path name refers to the element itself. (–none suppresses the transparency mechanism—translation of an element's standard path name into a reference to a particular version.)
In a snapshot or Web view:
=> For elements that are not loaded into the view, generates an error and does not load the element.
=> For elements that are loaded into the view, generates an error during update but does not unload the element.
element * CHECKEDOUT
element file.txt -none
element * /main/LATEST