I am doing prior art searching. Now I want to to know do 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.