How do I delete everything on a layer and purge it in AutoCAD?

What cadssistant does

1. Selects everything on TEMP with (ssget "_X" '((8 . "TEMP"))) and notes how many that is.
2. Runs ERASE on that selection in one command, then -PURGE with the Layers option naming TEMP, no confirmation prompt.
3. Replies with the count and the purge result. If TEMP is the current layer PURGE refuses; it switches to layer 0 first and says so.

The same task in AutoLISP

(progn
  (setq ss (ssget "_X" '((8 . "TEMP"))))
  (if ss (command "_.ERASE" ss ""))
  (if (= (getvar "CLAYER") "TEMP") (setvar "CLAYER" "0"))
  (command "_.-PURGE" "_LA" "TEMP" "_N")
  (if ss (sslength ss) 0))

Erases, makes sure TEMP isn't current, purges it. The layer only goes when nothing references it, block definitions and xrefs included.

Good to know

• "Delete the layer" alone would leave its objects. LAYDEL does both in one step but also deletes the objects inside block definitions, which this doesn't; say "LAYDEL" if that's what you want.
• ERASE skips objects on a locked layer silently. Say "unlock it first" and it does.

More in edit in bulk

• How do I move all objects of one type to another layer in AutoCAD?
• How do I change the height of all text in an AutoCAD drawing at once?
• How do I replace one block with another throughout an AutoCAD drawing?
• How do I rename many layers at once in AutoCAD?