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Re: yes I'm root but want 444 files found readonly

From: Jeff Sheinberg
Subject: Re: yes I'm root but want 444 files found readonly
Date: 01 Jul 2002 21:31:51 -0400
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

address@hidden (Dan Jacobson) writes:
 > and the files are found without the "%%" readonly in the mode line.
 > OK, I'm root with the royal blood.  But that doesn't mean I don't want
 > to enjoy the same protection against altering my files all over the
 > place just like the other guy.  Sure wish there was an option in emacs
 > that would respect the hints from the file modes even if I'm root.  Or
 > what, do you expect me to do C-x C-q on each file?  Unfair.
 > Yes, for my mode 0 file the option could have a third etc. choice, not
 > only find-readonly, but also ask the user if he really wants to see it
 > etc.

Greetings Zen Master "jidanni",

See below for a sample implementation that finds such files in
read-only mode.  IMO, there is no need for prompting, since %%
shows in the mode line, and C-x C-q will easily toggle read-only
off when and if desired.

 > Also there's the case of 444 but not owned by root.  Here also I would
 > find-readonly. 

My version of Emacs (GNU Emacs 21.2.1) already finds files with
mode 444 read-only, just like versions 18, 19, and 20 did.

;; Put buffer in read-only mode if there are no write bits set in the
;; file's mode.  This can occur when uid=0 edits a non-writable file.

(defun my-set-read-only-if-no-writeable-mode-bits ()
  "This function is used to warn the super-user that the current buffer
has been set read-only because none of the file's write mode bits
are set."
  (let* ((file (buffer-file-name))
         (mode (file-modes file)))
    (if mode
          (if (and (not buffer-read-only)
                   (file-writable-p file)
                   (= (logand mode 146) 0)) ; 146 decimal is 222 octal.
                (setq buffer-read-only t)
                (message "File's mode is %o, buffer set read-only, use 
`toggle-read-only' wisely!" mode)))))))

(add-hook 'find-file-hooks 'my-set-read-only-if-no-writeable-mode-bits)

;; Put all buffers in `/usr/share/*' hierarchy in read-only mode.
(defun my-set-read-only-usr-share-files ()
  "This function is used to warn the user that the current buffer has
been set read-only because the file being visited is in the
`/usr/share/*' hierarchy."
  (let* ((dir "/usr/share/")
         (len (- (length dir) 1)))
    (if (and (not buffer-read-only)
             (stringp buffer-file-truename)
             (file-writable-p buffer-file-truename)
             (fboundp 'compare-strings) ; keep emacs-19 happy
             (eq t
              (compare-strings dir 0 len buffer-file-truename 0 len)))
          (setq buffer-read-only t)
          (message "Buffer %s set read-only, use `toggle-read-only' wisely!" 

(add-hook 'find-file-hooks 'my-set-read-only-usr-share-files)

Jeff Sheinberg  <address@hidden>

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