I use: Emacs 26.1 on Windows 10 with tramp with plink/pscp to edit perl scripts on a remote Linux server
The scripts are executable (permissions 755).
When I load and then save them, if short time has passed, the permissions are preserved. However, when I don't save the buffer for somewhat longer time, it corrupts remote file permissions and set them to 666.
Even after switching off the saving of backups problem persists.
How do I fix that? Are there workarounds?
So I got fed up and made this workaround. It just checks the file name of file that has been saved and set permissions based on path.
;;
;; workaround for TRAMP always corrupting file permissions
(defcustom file-mode-alist nil
"Automatically set file permissions based on filename.
Each element has the form (REGEXP . MODE)
where REGEXP is a regexp to match against your file name and
MODE - (integer) file mode (permissions) to set.
Pairs are checked in order of appearance, first one to match is used.
"
:type '(alist :key-type regexp :value-type integer)
:group 'personal)
(setq file-mode-alist '(( "^/pscp:host:.+/lib/.*\\.pm$" . #o644)
( "^/pscp:host:.+/web/.*\\.pl$" . #o755)))
(defun run-regexps (alist str)
"Iterate over association list alist and try to match regexps with string str"
(if (null alist) nil
(let ((a (car alist)))
(if (string-match (car a) str)
(cdr a)
(run-regexps (cdr alist) str)))))
(defun set-remote-permissions ()
"Set permissions of remote file if filename matched against file-mode-alist"
(let* ((fn (buffer-file-name (current-buffer)))
(mode (run-regexps file-mode-alist fn)))
(when mode (chmod fn mode))))
(add-hook 'after-save-hook 'set-remote-permissions)
C-h v make-backup-files. If the backups are made by renaming, then there's a greater chance of the new file not acquiring the same attributes as the original file, so you might find thatbackup-by-copyingis your answer. – phils Jan 16 '19 at 23:33