File.cp-exclamation-mark

You're seeing just the function cp-exclamation-mark, go back to File module for more information.

cp!(source_file, destination_file, callback \\ fn _, _ -> true end)

cp!(Path.t(), Path.t(), (Path.t(), Path.t() -> boolean())) :: :ok

The same as cp/3, but raises a File.CopyError exception if it fails. Returns :ok otherwise.