I am doing prior art searching. I want to to know whether I need to search for patents which are not yet published. If so, how do I do this?
A related question is: Can I search all patents which are filed today (or less than 18 months ago)?
Patents that aren't yet published aren't searchable unless you're a patent examiner. As an outside searcher, you're limited to issued patents and published applications (in addition to non-patent literature, e.g., everything on the internet).
No, you can't search all patents that were filed today. You have to wait until they are published.