Tips for using Emacs Ibuffer

I’ve found that one of the most useful features of Emacs is also one of the most sparsely documented: Ibuffer. It provides a way of filtering and then grouping the list of buffers that you currently have open, and greatly improves Emacs’ usability.

Using Ibuffer

First of all, rebind the standard buffer list key binding C-x C-b to use Ibuffer:

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(global-set-key (kbd "C-x C-b") 'ibuffer) ;; Use Ibuffer for Buffer List

Once you’ve used Ibuffer you won’t be going back so you should put this in your .emacs.

Defining your filter groups

You can define your filters and groups in the buffer list itself, but I find that it is easier to specify them in my .emacs:

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(setq ibuffer-saved-filter-groups
      '(("home"
	 ("emacs-config" (or (filename . ".emacs.d")
			     (filename . "emacs-config")))
         ("martinowen.net" (filename . "martinowen.net"))
	 ("Org" (or (mode . org-mode)
		    (filename . "OrgMode")))
         ("code" (filename . "code"))
	 ("Web Dev" (or (mode . html-mode)
			(mode . css-mode)))
	 ("Subversion" (name . "\*svn"))
	 ("Magit" (name . "\*magit"))
	 ("ERC" (mode . erc-mode))
	 ("Help" (or (name . "\*Help\*")
		     (name . "\*Apropos\*")
		     (name . "\*info\*"))))))

I then load the saved filter group by name in the ibuffer-mode-hook so that a particular filter is always loaded automatically:

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(add-hook 'ibuffer-mode-hook
	  '(lambda ()
	     (ibuffer-switch-to-saved-filter-groups "home")))

I actually have different filter groups for work and home, and load them according to a global location variable.

Other useful options

There are a few other useful options that I didn’t find out about until I looked through the source:

ibuffer-expert

Unless you turn this variable on you will be prompted every time you want to delete a buffer, even unmodified ones, which is way too cautious for most people. You’ll still be prompted for confirmation when deleting modified buffers after the option has been turned off.

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(setq ibuffer-expert t)

ibuffer-show-empty-filter-groups

Turning off ibuffer-show-empty-filter-groups is particularly useful, because the empty filter groups can really clutter things up.

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(setq ibuffer-show-empty-filter-groups nil)

ibuffer-auto-mode

ibuffer-auto-mode is a minor mode that automatically keeps the buffer list up to date. I turn it on in my ibuffer-mode-hook:

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(add-hook 'ibuffer-mode-hook
	  '(lambda ()
	     (ibuffer-auto-mode 1)
	     (ibuffer-switch-to-saved-filter-groups "home")))

Filtering Dired buffers by filename

This is something I had a problem with when I upgraded to Emacs 23.1. The latest version of Ibuffer doesn’t filter Dired buffers by the filename of the directory. This isn’t what I want – if I specify I filename filter I want any buffer with that filename to appear.

Rather than doing diffs against the 22.3 versions of the Ibuffer files to determine the changes (and possibly undo them) I’ve just copied the old versions from the ‘lisp’ directory of Emacs 22.3 To a ‘vendor’ directory in my .emacs.d and loaded that.

If I find a better way to solve this problem I’ll post an update.