Can I use a non-modifier key as a modifier key in Emacs?

I am experimenting with Emacs and trying to make some weird key-bindings just as a playful activity. I know that something simple like this works fine: (global-unset-key (kbd "/")) (global-set-key (kbd "/ s") 'save-buffer) Now I can type `/s` to save the current buffer and I can type `C-q /` when I need to insert a literal `/`. But can I now make a key binding where `/` is a modifier key? For example, can I somehow get this to work? (global-unset-key (kbd "/")) (global-set-key (kbd "/-s") 'save-buffer) This does not work for me of course. When I type `/-s` (press and hold `/`, press `s`, release `/`) I get this error, / s is undefined I see why this error happens. But is there anyway to make this work and treat `/` as a modifier key?

Yes, it is possible. Look at [`define-prefix-command`](https://www.gnu.org/software/emacs/manual/html_node/elisp/Prefix-Keys.html#index-define_002dprefix_002dcommand). Edit: Wait, no. This would just define `/` as a prefix to further commands, so exactly the same as you’ve done. I don’t think it’s possible to define new modifiers, [according to this page](https://www.gnu.org/software/emacs/manual/html_node/emacs/Modifier-Keys.html).

Yes. See event-apply-alt-modifier and friends but it will behave more like modifiers with sticky keys turned on.

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Is it going to offer something that is different from my first example? In my first code example, `/ s` already feels like sticky keys where I need to first type `/` and then type `s` to save a file. Is there a minimal example I can use to get started with `event-apply-control-modifier`? I tried this: (global-unset-key (kbd "a")) (global-set-key (kbd "a") (lambda () (interactive) (event-apply-control-modifier t))) Now I type `a s` but it does nothing. How could I fix this example so that `a s` invokes `save-buffer`?

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It is not hard to do M-? event-apply-control-modifier RET and read the results. If you do, you will see that the standard bindings for these are defined in the function-key-map keymap.

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I setup my app key to be hyper mod using xmodmap. Are you trying to gain a mod key? I’ve added hyper and super which is great

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Sorry but I don't see how this is helping. I did this, (global-unset-key (kbd "/")) (define-key function-key-map (kbd "/") 'event-apply-control-modifier) But how does this help? Now `/ s` just translates to `C-s` which invokes `isearch-forward`. So to work around this I add this, (global-set-key (kbd "/-s") 'save-buffer) But this behaves like my first example. I now need to type `/ s` to invoke `save-buffer` which my first example in the post already does. That brings back to my previous question. > _viz_: Yes. See event-apply-alt-modifier and friends but it will behave more like modifiers with sticky keys turned on. >> biggrben: Is it going to offer something that is different from my first example? In my first code example, `/ s` already feels like sticky keys where I need to first type `/` and then type `s` to save a file.

Not really possible within Emacs. But there are several tools for doing it outside of Emacs. However, the [key-chord](https://github.com/emacsorphanage/key-chord) package comes sort of close. It lets you bind a command to 2 keys that you press at the same time.

Unbind C-z its a dumb bind anyway, then make a new map for C-z and dump your bits and bobs there. You could have C-z \\ do save. Or just use builtin CUA mode. I think that makes C-s C-f function as File Save and File Open. [CUA-mode](https://www.gnu.org/software/emacs/manual/html_node/emacs/CUA-Bindings.html) Or use evil-mode and make / a leader key

Not sure I understand. `C-z \` does not help with turning `/` into a modifier key where pressing `/-s` together can run `save-buffer`. Likewise for `C-s C-f`. And evil-mode with `/` leader key requires typing `ESC / s` for saving, not `/ s`, due to its modal nature. Again it does not make `/` a modifier key. I think at this point it is safe to say now that it is impossible to turn a non-modifier key into a modifier key within Emacs. The most one can do is use `/ s` (both keys pressed separately) to run `save-buffer`. I think that's a good conclusion of all the discussion in this post.

Sorry, I got confused by the title. Your title says "modifier" but what you're after is emulating the partial keysequence "C-x C-" am I right? It is not immediately obvious what you need from the body text since no one stops anyone from binding <Some-modifier>-s to save-buffer. Anyway, I think you can do this by looking up the relevant binding but I'm not sure how exactly.

Yes, emulating the partial keysequence `C-x C-` would indeed be a way to do it. Thanks for the idea. That thought did not even occur to me. It's a clever thought. Thanks! So far I was trying to figure out if there is a way in Emacs to make a keybinding for `/`+`s` where Emacs can recognize that I am pressing `/` and `s` together (holding `/` and pressing `s`). From the discussion so far, it looks like this is not possible. But maybe your idea of emulating `C-x C-` to produce the same desired effect may be possible!

I think you are pissin up a rope. Basically what you are trying to do is not gonna happen (I could be wrong, but you'd need a detailed understanding of emacs and emacs lisp) but what I was offering were a couple of alternatives. I think maybe you are trying to save a few key strokes and that is why I suggested CUA mode. CUA mode gives you key bindings similar to windows gui apps, but if I remember right it costs you emacs motion keys (again, could be wrong) I think there is a god-mode that is some weird hybrid of the two. But, why not give good old vanilla emacs keybindings a shot? Especially if you are new to emacs. Mostly (except for C-z) they are well thought out and in not too terribly difficult to learn.

You are right that I am doing something pointless for fun and I stated as much in my post. I am not trying to save key strokes. I use good old vanilla emacs key bindings myself. As stated in my post, I am experimenting with Emacs and trying to see what is possible and what isn't by making weird key-bindings as a playful activity.

So sorry for the misunderstanding. I understand now.