Switch -U - update files
Can be used when creating or extracting an archive. Command string "a -u" is the equivalent of command u. Switch -u can also be used with command m.
If switch -u is used with commands x or e, then old files are replaced only if newer versions extracted from the archive are more recent, but unlike -f if an archived file has no matching unpacked file, it is still extracted.
Shell mode equivalent of this switch is "Add and update files" option in Archive name and parameters dialog and "Extract and update files" option in Extraction path and options dialog.
Supported only for RAR and ZIP formats.