I am using ido-mode to select files from Emacs. This works well for most cases, but for some cases I would like to modify the files that are shown in the completion buffer with ido-find-file.

In some folders I have a lot of *.bak files, and I would like to have the possiblity to remove them from the completion buffer by pressing the F1 key, for example. This is how far I got on this task:

(add-hook 'ido-minibuffer-setup-hook 'ido-my-keys)

(defun ido-my-keys ()
  (define-key ido-file-completion-map (kbd "<f1>") 'my-modify-files))

(defun my-modify-files ()
  (message-box "Here I would like to delete the .bak files from the minibuffer"))

2 Answers 2


ido-mode has built-in support for hiding files matching specific regexps. All you need to do is add \.bak to ido-ignore-files:

(add-to-list 'ido-ignore-files "\.bak")

After invoking ido-find-file, you can then hit C-a (ido-toggle-ignore) to toggle hiding of .bak files.

  • Perfect! It works like a charm :) Nov 13, 2014 at 10:05
  • 1
    @HåkonHægland Great! :) If you're interested, have a look at the documentation of ido-find-file (C-h f ido-find-file RET) for a full list of commands and options you can toggle while the Ido prompt is active.
    – itsjeyd
    Nov 13, 2014 at 10:12

The correct way to ignore files by extension for file name completion purposes is using the variable completion-ignored-extensions. The variable holds a list of strict suffix strings that are ignored for:

  • directory completion, if the list element ends in a /, or
  • file completion otherwise.

The ido-ignore-files variable, on the other hand, is a list of regular expressions, and matches anywhere in the file name, unless the regex is anchored. In particular, the recommendation in another answer,

(add-to-list 'ido-ignore-files "\.bak")

tells Ido to match the substring .bak anywhere in file name, which may or may not be what you really want. On the other hand,

(add-to-list 'completion-ignored-extensions ".bak")

makes all Emacs completion machinery, not only Ido, but also out-of-the-box file completion and Dired, and likely other places, ignore files ending in .bak (including full name match). Note that this variable is not a list of regexes, but rather a list of literal suffixes; the dot should not be \-escaped.

The default completion-ignored-extensions list contains commonly ignored suffixes such as .elc, .o, .a, .so, ~, .git/, and many more. This is why the default ido-ignore-files list is suspiciously short.

The completion behavior is actually more complex than just always ignoring the files; see the docstring of the variable. One important point is that if all completions are to be ignored according to completion-ignored-extensions, then none are. This allows, for example, descending into the .git/ subdirectory: as soon as it becomes the only completion (after typing .g/, if no other directories matching .g*/ exist), it is shown by Ido as a possible completion. Similarly, in the original question case, typing .bak makes Emacs "un-ignore" and immediately show files ending in .bak, unless other non-ignored files match by Ido rules, so that the C-a is not always necessary to find an ignored file.

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