delete-file

(delete-file pathname)

Deletes the named file and returns t. Anything that leaves the file in place is an error -- including "it was not there to begin with", which Common Lisp also makes a file-error. Probe first with probe-file when a missing file should be tolerated, or wrap the call in ignore-errors.

Both WASM backends signal at call time. No WASI unlink call is imported there, and unlike file-write-date this operation has no "cannot be determined" answer in its contract: either the file is gone afterwards or it is not, so answering anything but an error would be a lie. This is the same deal ensure-directories-exist makes, for the same reason -- a program merely CONTAINING the call still compiles there; only executing it signals.

(with-open-file (out "notes.txt" :direction :output)
  (write-line "draft" out))
(delete-file "notes.txt")   ; => T
(probe-file "notes.txt")    ; => NIL
(delete-file "notes.txt")   ; signals: DELETE-FILE: cannot delete notes.txt