I've got auto-complete package working for functions for *.R files, but now I'm struggling with auto-complete for file paths.

I've bound the "TAB" key to:

(global-set-key (kbd "TAB") 'ac-complete-filename)

And it does work after "/" symbol as suggested here. However it works only on new line. As in:


And it does not work from within a function such as:


Placing pointer after "/" when anything precedes it does not do anything. Any suggestions?


Changing binding to ess-mode instead of global fixed it. Why? No idea...

(define-key ess-mode-map (kbd "TAB") 'ac-complete-filename)
  • Could there have been a pre-existing key-binding for tab in ess-mode? That would have overridden the global key-binding.
    – InHarmsWay
    Commented Aug 16, 2015 at 13:35
  • ac-complete-filename is sort of conditional keybind, that works only after "/" symbol. I wonder how it interferes with other bindings? And after some more struggle with setting up auto-complete, I'm still far off my initial goal. Trying to mimic auto-complete feature as in RStudio. Otherwise switching to emacs will not make any sense.
    – statespace
    Commented Aug 16, 2015 at 15:31
  • Thanks. This solution also worked for me. Now, after typing the "/" symbol, auto complete brings up the file directories. Interestingly, when I'm in the R session within emacs, e.g. iESS [R], file completion works using the standard emacs file completion, but auto-complete also works for functions (this works with or without (define-key ess-mode-map (kbd "TAB") 'ac-complete-filename). This seems to be the best of both worlds. It would be great if someone with a deeper knowledge of ESS could shed some light on how to get this formulation to work for *.R files as well.
    – chandler
    Commented Dec 14, 2016 at 9:37
  • ESS r-mode comes with file-name completion built-in. You shouldn't have to bind ac-complete-filename to anything, as by default ess modifies completion-at-point-functions to work as you want without further configuration. That is, tab completes R objects in code, and completes filenames inside strings, which is what you'd normally want.
    – Tyler
    Commented Jan 13, 2017 at 15:11

1 Answer 1


Just in case someone comes across this question; I was able to do this by essentially turning on tab completion from R as follows:

(require 'auto-complete-config)
(define-key ac-completing-map (kbd "M-h") 'ac-quick-help)
;; Get tab completion in R script files
;; See this page here
;; https://stat.ethz.ch/pipermail/ess-help/2013-March/008719.html
;; Make sure that this is after the auto-complete package initialization
(setq  ess-tab-complete-in-script t)

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