I used global-set-key for a test and now I overwrote an important
emacs keybinding...
reddit / emacs

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Dumb-Ptr · 2022-01-24 17:04

In particular, I overwrote C-h, not essential but I want it back to be
the help command...

I used (global-set-key (kbd "C-h") 'evil-window-left) in my init.el
file, how do I undo this?

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mina86ng · 2022-01-24 17:15

Remove the line from `init.el` and restart Emacs.

By the way, everyone knows that proper binding for `C-h` is `(global-
set-key "\C-h" [(backspace)])`.

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Dumb-Ptr · 2022-01-24 17:54

ah sorry, dumb question. I just re-evaluated the init.el file instead
of restarting emacs...

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BettaGeorge · 2022-01-24 18:06

Out of curiosity, why should it be backspace? Some kind of emacs meme
I've been missing out on?

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oantolin · 2022-01-24 18:54

Backspace and `C-h` are the same character in a sense, some terminals
don't distinguish them, for example. You can read about it [in the man
ual](https://www.gnu.org/software/emacs/manual/html_node/efaq/Backspac
e-invokes-help.html).

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7890yuiop · 2022-01-24 20:04

Run a separate new instance:

* `emacs -Q`
* `C-h k C-h`

Back in the 'broken' instance:

* `M-: (global-set-key (kbd "C-h") #'THING)` where THING is what you
learned from the other instance.

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BettaGeorge · 2022-01-24 20:07

Thanks!

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kiki_lamb · 2022-01-24 20:42

> By the way, everyone knows that proper binding for C-h is (global-
set-key "\C-h" [(backspace)]).

Yes.

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kagevf · 2022-01-25 03:32

This was the answer I was looking for, but when I tried it emacs waits
for the "next part" of the command, I guess since C-h is a "prefix"
(not sure of the correct terminology).

I tried C-h RET but that's it's own command combo.

Any other ideas similar to your original suggestion?

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7890yuiop · 2022-01-25 06:42

Sorry -- that was dumb of me.  For a prefix binding I think the
easiest thing would be `C-h b` to list all bindings for the current
buffer, and then isearch in that for `C-h`.  That gives us:

    Global Bindings:
    key             binding
    ---             -------
    C-h             help-command

Which tells us the command, and that it's in the global keymap, so we
can then do this:

    (global-set-key (kbd "C-h") 'help-command)

or if it wasn't the global keymap, we'd use:

    (define-key KEYMAP (kbd "C-h") 'help-command)

---

If it's useful to know, `help-command` is a so-called "prefix command"
which means that the symbol's *function* slot contains a keymap.  You
can see that with `(symbol-function 'help-command)`

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kagevf · 2022-01-25 08:09

Wow, thank you ... very useful information!

Thanks to lossage, I see that C-h b is " C-h b \[describe-bindings\]"
which apropos describes as "Display a buffer showing a list of all
defined keys, and their definitions."

I'll need to learn more about what keymap is and how it works ... I'll
go through [http://www.gnu.org/software/emacs/manual/html\_node/elisp/
Keymaps.html](http://www.gnu.org/software/emacs/manual/html_node/elisp
/Keymaps.html) maybe tomorrow ...

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7890yuiop · 2022-01-25 11:09

https://www.masteringemacs.org/article/mastering-key-bindings-emacs is
a really good overview.  I recommend reading that to begin with.

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kagevf · 2022-01-25 15:16

That was a great read! Still going through the comments which have
useful bits of info as well ... thank you! :)

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_pkal · 2022-01-25 16:44

It was the [traditional binding](https://web.archive.org/web/201107230
33542/http://www.burlingtontelecom.net/~ashawley/gnu/emacs/doc/emacs-
1978.html#Preface) for backspace, and allegedly [goes
back](https://unix-kb.cat-v.org/) to
[TOPS-20](https://en.wikipedia.org/wiki/TOPS-20), as the ASCII code
for backspace is the same as `^H` (if you open the
[ascii(7)](https://man7.org/linux/man-pages/man7/ascii.7.html) man
page, you will see that H (0x48) and BS (0x08) are shifted by 64. This
explains some other bindings other bindings `^M` -> return and `^I` ->
tab, `^J` -> newline, `^[` -> escape, but might also be the reason for
things like `^G` -> bell).