According to the document, it seems that no formal parameters seem to be required for the question discussed here:

NotebookFileName[]
gives the file name of the current evaluation notebook. 

NotebookFileName[nb]
gives the file name for the notebook specified by nb. 

Dear Rohit Namjoshi,

Thank you for your in depth, systematic, detailed and insightful analysis and interpretation. But I still have some additional confusion as described below:

[{path}, fileName, __]

I tried the following methods, and they all gave the same results:

_[{path__}, fileName_, _]
_[{path__}, fileName_, __]
_[{path__}, fileName_, ___]

One thing to be aware of is that path is a Sequence not a List so there is no need to Append fileName to it before passing to FileNameJoin.

1. What's the difference between a Sequence and a List?
2. In my humble opinion, Wolfram language in nature is a type (dialect) of lisp, as described here. If so, all things in Wolfram language should be List. Is there anything wrong with my understanding?

3. As per you said above, how can I check the data type of specific object? For example, in this case, if I don't run the following command, how can I know the Sequence data type of the result?

   "FileName" /. NotebookInformation[] /. _[{path__}, fileName_, __] :> path
   

Hi Hongyi

Take a look at

NotebookInformation[] // InputForm

it is a List of Rule. We are interested in the "FileName" Rule so extract it (similar to how one would extract a solution from Solve)

"FileName" /. NotebookInformation[]
(* FrontEnd`FileName[{$RootDirectory, "Users", "rohit", "Documents", 
  "Mathematica"}, "test.nb", CharacterEncoding -> "UTF-8"] *)

We are interested in the first argument, the List passed to FrontEnd`FileName which are components of the path, and the second argument which is the file name. We can extract them using the pattern

_[{path__}, fileName_, __]

The first _ matches any head, in this case FrontEnd`FileName. The {path__} matches the first argument as a list of something and binds it to path. The fileName_ matches the second argument and binds it to fileName, the __ matches the rest of the arguments which we don't care about so it is not bound to anything. We now have the pieces we need

"FileName" /. NotebookInformation[] /. _[{path__}, fileName_, __] :> {path, fileName}
(* {"/", "Users", "rohit", "Documents", "Mathematica", "test.nb"} *)

So we pass it to FileNameJoin to add the right directory delimiters for the OS

"FileName" /. NotebookInformation[] /. _[{path__}, fileName_, __] :> FileNameJoin@{path, fileName}
(* "/Users/rohit/Documents/Mathematica/test.nb" *)

One thing to be aware of is that path is a Sequence not a List so there is no need to Append fileName to it before passing to FileNameJoin.

"FileName" /. NotebookInformation[] /. _[{path__}, fileName_, __] :> path
(* Sequence["/", "Users", "rohit", "Documents", "Mathematica"] *)

Hope you enjoy your Wolfram Language journey. 千里之行，始于足下

Hongyi,

Easier to do it using Pattern and ReplaceAll, rather than Part.

"FileName" /. NotebookInformation[] /. _[{path__}, fileName_, __] :> FileNameJoin@{path, fileName}

Thank you for your tip. It does the trick. BTW, I also tried the following, but still can't tweak out the result I want:

In[38]:= StringRiffle[{NotebookInformation[][[1]][[2]][[1]], 
      NotebookInformation[][[1]][[2]][[2]] }, "/"]
Out[38]= "{/, home, werner}/Untitled-1.nb"

NotebookDirectory[] can only give the result as follows:

/home/werner/git-mathematica

But I want to generate the full path name including the notebook's name without inputting it manually.