CXLAYRENLayersVersion 1.0.0Tested in AutoCAD

Rename layers by find and replace

Renames many layers at once by replacing part of their names, for example OLD- with NEW-, and tells you what was changed.

Download cxlayren.lsp LISP terms

How to use it

Type CXLAYREN.
Enter the text to find in layer names.
Enter the replacement (- for nothing).

Good to know

Layer 0, Defpoints and names that would clash with an existing layer are left alone.

Load it in AutoCAD

Save the file anywhere you like.
Type APPLOAD, pick the file and choose Load.
Type the command name: CXLAYREN.

To have it at every start, add it to the Startup Suite in the same dialog, or load a whole folder at once with the optional loader. About the optional loader

Tested in AutoCAD (full version). Other programs that run AutoLISP may work, but they are not tested.

The code

Plain text, nothing hidden. Copy it into a file named cxlayren.lsp, or download it.

;;; ============================================================================
;;; CXLAYREN - Rename layers by find and replace
;;; Version 1.0.0
;;; CADXChange LISP tools - https://cadxchange.net/resources/lisp/cxlayren
;;; Tested in: AutoCAD (full version). Other programs that run AutoLISP may work but are not tested.
;;; Copyright (c) CADXChange. Free for personal and commercial use; do not resell or
;;; republish it as a collection. Terms: https://cadxchange.net/legal/lisp-terms
;;; ============================================================================

;; Rename layers by replacing the text FIND with REPL in every layer name (case ignored). Layer 0, Defpoints and
;; names that would clash with an existing layer are left alone.
;; Returns the changes as ((old . new) ...).
(defun cx:layren-run (find repl / out new)
  (if (> (strlen find) 0)
    (foreach name (cx:layers)
      (setq new (cx:replace-ci name find repl))
      (if (and (/= new name)
               (/= name "0")
               (/= (strcase name) "DEFPOINTS")
               (> (strlen new) 0)
               (not (cx:bad-name new))
               (not (tblsearch "LAYER" new)))
        (if (cx:lay-rename name new)
          (setq out (cons (cons name new) out))))))
  (reverse out))

(defun c:CXLAYREN ( / *error* cx:sv find repl r)
  (setq *error* cx:err)
  (setq find (cx:ask-str "Text to find in layer names" ""))
  (if (= find "")
    (princ "\nNothing to find.")
    (progn
      (setq repl (cx:ask-str "Replace it with (- for nothing)" ""))
      (cx:start '(("CMDECHO" . 0)))
      (setq r (cx:layren-run find repl))
      (foreach p r (princ (strcat "\n" (car p) "  ->  " (cdr p))))
      (princ (strcat "\n" (itoa (length r)) " layer(s) renamed."))
      (cx:end)))
  (princ))


;;; ---- Shared helpers (used by the command above; identical in every CADXChange tool) ----

(defun cx:dxf (code ed)
  (cdr (assoc code ed)))

;; Names of all layers.
(defun cx:layers (/ r out)
  (setq r (tblnext "LAYER" T))
  (while r
    (setq out (cons (cx:dxf 2 r) out) r (tblnext "LAYER")))
  (reverse out))

;; Replace every OLD in STR by NEW, ignoring case.
(defun cx:replace-ci (str old new / n out pos up uo)
  (setq n (strlen old) out "" pos 1 up (strcase str) uo (strcase old))
  (if (= n 0)
    str
    (progn
      (while (<= pos (1+ (- (strlen str) n)))
        (if (= (substr up pos n) uo)
          (setq out (strcat out new) pos (+ pos n))
          (setq out (strcat out (substr str pos 1)) pos (1+ pos))))
      (strcat out (substr str pos)))))

;; 1-based position of SUB in STR at or after START, or nil.
(defun cx:find (str sub start / n i r)
  (setq n (strlen sub) i start r nil)
  (if (> n 0)
    (while (and (not r) (<= i (1+ (- (strlen str) n))))
      (if (= (substr str i n) sub) (setq r i))
      (setq i (1+ i))))
  r)

;; True when STR holds a character that is not allowed in a layer, block or style name.
(defun cx:bad-name (str / bad)
  (foreach ch '("<" ">" "/" "\\" "\"" ":" ";" "?" "*" "|" "=" "`" ",")
    (if (cx:find str ch 1) (setq bad T)))
  bad)

;;; List helpers. See helpers.lsp for the format.

;; Rename layer OLD to NEW; returns T when it worked.
(defun cx:lay-rename (old new)
  (command "_.RENAME" "_LA" old new)
  (if (and (tblsearch "LAYER" new) (not (tblsearch "LAYER" old))) T))

;; Close the undo step and put the system variables back.
(defun cx:end ()
  (foreach v cx:sv (setvar (car v) (cdr v)))
  (command "_.UNDO" "_End")
  (setq cx:sv nil)
  (princ))

;; Error handler: restores everything, stays quiet on Esc.
(defun cx:err (msg)
  (if (> (getvar "CMDACTIVE") 0) (command))
  (cx:end)
  (if (and msg (not (wcmatch (strcase msg) "*BREAK*,*CANCEL*,*EXIT*")))
    (princ (strcat "\nError: " msg)))
  (princ))

;; Ask for a string (spaces allowed) with a default; "-" means an empty string.
(defun cx:ask-str (msg def / v)
  (setq v (getstring T (strcat "\n" msg " <" def ">: ")))
  (cond ((= v "") def) ((= v "-") "") (T v)))

;; Save the system variables in VARS ((name . value) ...), set them, and open one undo step.
;; The caller declares cx:sv as a local so the saved values live exactly as long as the command.
(defun cx:start (vars)
  (setq cx:sv (mapcar (function (lambda (v) (cons (car v) (getvar (car v))))) vars))
  (command "_.UNDO" "_Begin")
  (foreach v vars (setvar (car v) (cdr v)))
  (princ))

(princ "\nCXLAYREN loaded. Type CXLAYREN to start.")
(princ)

Version history

Version 1.0.0 · October 27, 2026

First release.

Need this across many drawings?

LayerSync does this kind of job on a whole folder of drawings in one run.

LayerSync