Use write-region in read-only buffer

Question

I am writing a custom function which is supposed to write selected text to some arbitrary file on the system. It does something like

(defun write-region-to-file (&optional arg)
  (interactive "*p")
  (write-region (point) (mark-marker) "/path/to/file/other/then/visited"))

If I then run it in a read-only buffer I get

command-execute: Buffer is read-only: #<buffer ...>

Why is this happening? I don't do any modification to the visited one, I am writing to a completely different file.

Any ideas?

Answer 1

The interactive code * is used to: "Signal an error if the current buffer is read-only. Special."

https://www.gnu.org/software/emacs/manual/html_node/elisp/Interactive-Codes.html

Thus, the line that reads (interactive "*p") can be changed to eliminate the asterisk.

NOTE: In the example, the optional argument ARG is not used. Thus, consider changing (&optional arg) to just (); and, consider changing the interactive statement to just (interactive).