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cmplus - When you say "save the books in csv format [files]" do you mean "add csv format [files] to the library"?
If so, then you should read the following:
Want to change folder structure or file names in the Calibre library? make sure you read the hidden text by click the
Show button.
Why doesn’t calibre let me store books in my own directory structure? from the Frequently Asked Questions section of the Calibre User manual.
BR