LISP to compare two list and export a txt file

[Irishpotato]

I am trying to subtract a pre determined layer list from my current drawing layers and have the results export to a txt file. 

I was able to write part of the lisp myself and I found a lisp online for writing to a text file however I think that is my issue. 

Below is what i have so far. Thank you in advance for your help.

 

(DEFUN C:testing ()
(setvar "cmdecho" 1)
(vl-load-com)
(vlax-for lyr (vla-get-layers (vla-get-activedocument (vlax-get-acad-object)))(setq then (cons (vla-get-name lyr) table))) ;retrieve layers in current file

(setq now '(BERM BORDER CABLE LINE)) ;preassigned layers to look for

(defun ListsDifference ( now then )(if l1(if (vl-some '(lambda ( l ) (member (car now) l)) then)(ListsDifference (cdr now) ls)(cons (car l1) (ListsDifference (cdr now) then))))) ;subtract layers in active file from preassigned list

   (setq ;attempting to create txt file from of the list differences 
         lyrent   (tblnext LListDifference t)
         dprefx   (getvar "dwgprefix")
         dname1   (getvar "dwgname")
         dname2   (substr dname1 1 (- (strlen dname1) 4))        ;remove old extension
         filename (strcat dname2 ".txt")                ;add new extension
         padding  "                                        "
         header1   (substr (strcat "LAYER"        padding) 1 30)
         header    (strcat header1)
         prmpt (strcat dprefx filename)
         file     (open prmpt "a")
   )
     (write-line filename file)
     (write-line "" file)
     (write-line header file)
     (write-line "" file)

   (while lyrent
     (setq
           lyrname   (substr (strcat (strcase (cdr (assoc 2 lyrent))) padding)   1 30)
           lyrdata   (strcat lyrname)
     )
     (write-line lyrdata file)
     (setq lyrent (tblnext LListDifference))
   )
   (close file)
(prompt (strcat "\nCreated " prmpt))
(princ)
)

[Emmanuel Delay]

Can you repeat what end result you want?

 

You want the current layer list; except skip the layers "BERM",  "BORDER",  "CABLE", "LINE"

Then export that list, right?

So just the layer names?