CODEWITHSUNDEEP
emacsfile-permissionssudo
Chris Conway
Chris Conway

Reputation: 55979

Open a file with su/sudo inside Emacs

Suppose I want to open a file in an existing Emacs session using su or sudo, without dropping down to a shell and doing sudoedit or sudo emacs. One way to do this is

C-x C-f /sudo::/path/to/file

but this requires an expensive round-trip through SSH. Is there a more direct way?

[EDIT] @JBB is right. I want to be able to invoke su/sudo to save as well as open. It would be OK (but not ideal) to re-authorize when saving. What I'm looking for is variations of find-file and save-buffer that can be "piped" through su/sudo.

Upvotes: 192

Views: 70943

Answers (11)

Burton Samograd
Burton Samograd

Reputation: 3638

Not really an answer to the original question, but here's a helper function to make doing the tramp/sudo route a bit easier:

(defun sudo-find-file (file-name)
  "Like find file, but opens the file as root."
  (interactive "FSudo Find File: ")
  (let ((tramp-file-name (concat "/sudo::" (expand-file-name file-name))))
    (find-file tramp-file-name)))

Upvotes: 18

Mehrad
Mehrad

Reputation: 3829

In this blog post Bozhidar Batsov explains three easy methods for opening files with escalated permissions. I think the most elegant one is the following. I just did a minor modification to make it more compatible with Emacs default ecosystem so that it can automatically Vertico and other completion platforms:

(defun er-sudo-edit (&optional arg)
  "Edit currently visited file as root.

With a prefix ARG prompt for a file to visit.
Will also prompt for a file to visit if current
buffer is not visiting a file."
  (interactive "P")
  (if (or arg (not buffer-file-name))
      (find-file (concat "/sudo:root@localhost:"
                         (read-file-name "Find file(as root): ")))
    (find-alternate-file (concat "/sudo:root@localhost:" buffer-file-name))))

Upvotes: 0

Daoist Paul
Daoist Paul

Reputation: 161

I find sudo edit function very useful for that. After opening a file, press s-e to have sudo access to edit/save the file.

Upvotes: 0

alex_1948511
alex_1948511

Reputation: 7299

(works only locally. Need to be updated to work correctly via tramp)

A little bit extended Burton's answer:

(defun sudo-find-file (file-name)
"Like find file, but opens the file as root."
(interactive "FSudo Find File: ")
(let ((tramp-file-name (concat "/sudo::" (expand-file-name file-name))))
(find-file tramp-file-name)))


(add-hook 'dired-mode-hook
    (lambda ()
      ;; open current file as sudo 
      (local-set-key (kbd "C-x <M-S-return>") (lambda()
        (interactive)
        (message "!!! SUDO opening %s" (dired-file-name-at-point))
        (sudo-find-file (dired-file-name-at-point))
      ))
    )
)

Upvotes: 1

Qudit
Qudit

Reputation: 467

If you use helm, helm-find-files supports opening a file as root with C-c r.

Upvotes: 19

anquegi
anquegi

Reputation: 11522

I recommend you to use advising commands. Put this function in your ~/.emacs

(defadvice ido-find-file (after find-file-sudo activate)
  "Find file as root if necessary."
  (unless (and buffer-file-name
               (file-writable-p buffer-file-name))
    (find-alternate-file (concat "/sudo:root@localhost:" buffer-file-name))))

Upvotes: 3

Teddy
Teddy

Reputation: 6163

Tramp does not round-trip sudo via SSH, it uses a subshell. See the manual: https://www.gnu.org/software/tramp/#Inline-methods

Therefore, I recommend that you stick with TRAMP.

Upvotes: 71

EfForEffort
EfForEffort

Reputation: 55858

The nice thing about Tramp is that you only pay for that round-trip to SSH when you open the first file. Sudo then caches your credentials, and Emacs saves a handle, so that subsequent sudo-opened files take much less time.

I haven't found the extra time it takes to save burdening, either. It's fast enough, IMO.

Upvotes: 70

Francois G
Francois G

Reputation: 11985

At least for saving, a sudo-save package was written exactly for that kind of problem.

Upvotes: 5

jfm3
jfm3

Reputation: 37774

Your example doesn't start ssh at all, at least not with my version of TRAMP ("2.1.13-pre"). Both find-file and save-buffer work great.

Upvotes: 5

JBB
JBB

Reputation: 4841

Ugh. Perhaps you could open a shell in Emacs and exec sudo emacs.

The problem is that you presumably don't just want to open the file. You want to be able to save it later. Thus you need your root privs to persist, not just exist for opening the file.

Sounds like you want Emacs to become your window manager. It's bloated enough without that. :)

Upvotes: 0

Related Questions