How can I kill buffers based on mode?

Question

I know about kill-matching-buffers but that searches buffer names, I want instead to search buffer modes. For example, I might want to kill all buffers that have "notmuch-" or "[Notmuch]" as substrings in the mode column in the *Buffer List*.

Answer 1

You can use M-x ibuffer which I recommend binding to C-xC-b to replace the default (or whatever binding you prefer).

Use %m to mark buffers by matching a regexp against the displayed mode-name (e.g. Emacs-Lisp). Then use D to kill the marked buffers.

"notmuch-" or "[Notmuch]"

Note that, as we're dealing with regexps, you would need to enter \[Notmuch\] for the latter.

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You could alternatively use *M to match a specific mode symbol (e.g. emacs-lisp-mode). You get completion for the possible values with this approach.

ibuffer is very powerful; be sure to use C-hm to learn about its grouping and filtering abilities, amongst other features.

Answer 2

You can do this with Helm by entering a partial major-mode name prefixed with *. For example: *lisp, *sh etc. You can also use negation, e.g. !*org to narrow down all non-Org mode buffers, or specify multiple major modes, e.g. *!lisp,!sh,!fun etc.

Then press M-a to mark those buffers and M-D to kill them. For example, to kill all dired buffers:

1. M-x helm-buffer-list
2. *dired
3. M-a
4. M-D

Answer 3

If you use Icicles then, with any command that completes against buffer names, you can filter (include or exclude) the candidates by mode (either exact mode match or derived-mode-p).

And with Icicles you can act on all matching candidates at once, with C-!.

If you use a plain prefix arg (C-u) with a command with buffer candidates then the candidates are only buffers with the same mode (or a mode derived from the same mode) as the current buffer.

So for example, if you use C-u C-x k then the only candidates for completion are buffers in the same mode as the buffer you're currently in. You can then use C-! to kill them all.

Or you can use C-x k (no prefix arg), and then hit a key to remove some candidates, then use C-! to kill all the remaining candidate buffers.

To remove buffer candidates that have a given mode, you can use C-x C-m -. You're prompted for the mode. Or to remove all candidates except those with a given mode (i.e., keep only buffers with that mode), use C-x C-m +. Again, once you've filtered out candidates, you can kill all remaining candidate buffers using C-!.

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More generally, when you use any Icicles command that completes against buffer names, you can filter the candidates (by mode, as indicated above, or in other ways) and then use C-u S-delete to kill all remaining candidates. So you need not use C-x k - you can kill buffers even when you use C-x b or whatever. Obviously, since this is not the main purpose of a command such as C-x b, if you use S-delete you're asked to confirm killing.