How to map Alt key?

Question

I'm trying to map Alt key in the following way:

:map <A-j> j
:map <A-k> k

but it doesn't work (bell is rang on Alt + j/Alt + k).

What am I missing?

I'm using Terminal on OSX, the same happens on remote Linux.

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On Ctrl + v, Alt + j, I've got: ?~H~F (∆ when encoding=utf-8).

On Ctrl + v, Alt + k, I've got: ?~Z (˚ when encoding=utf-8).

Running vim without plugins (-u NONE) doesn't make any difference.

Answer 1

That's how I do it on Linux or Cygwin:

First check what chars are sent by your terminal when you press ALT+J:

In order to do this I go to console and run sed -n l (you can also use cat for it). Then I press ALT+J and see that the chars on the screen are ^[j .

I replace ^[ with \e (because that's what is sent by my terminal when I press esc) and the final string for me is \ej.

Then I write it to my .vimrc:

execute "set <M-j>=\ej"
nnoremap <M-j> j

And the mapping works.

Answer 2

With help of Carpetsmoker, it seems that Terminal wasn't configured to 'Use Alt/option as meta key' (this is especially common for GUI Terminals).

For Terminal on OSX, it's in Preferences -> Settings -> Keyboard tab -> 'Use option as meta key'. Check: How can I change Terminal to use option as meta key? (Mavericks).

For XTerm, check: Configuring XTerm to Default to Meta Sends Escape which says:

Add this line anywhere in your personal .Xdefaults file (~/.Xdefaults):

xterm*metaSendsEscape: true

Then reload the config with xrdb. Without this step the changes in .Xdefaults won't take effect until the next X restart:

xrdb -l ~/.Xdefaults

Then standard mappings with Alt key like:

:map <A-j> j
:map <A-k> k

works fine.

For help, see: :h :map-alt-keys.

Answer 3

Similar to Kossak's answer but a bit simpler, by mapping literal key presses.

Either in normal mode after pressing :, or inserted into your .vimrc, map the input directly by starting the mapping:

nnoremap 

then hitting Ctrl + V then the keystroke to record, e.g. Alt + ←. This will show as something like this:

nnoremap ^[[1;3D

but each ^[ is a single, literal escape character and syntax highlighting should show this. Replace the literal escape(s) with the text <Esc>, and append the command you wish to use:

nnoremap <Esc>[1;3D <C-w>h

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I know OP was mapping Alt + letters, but I used arrows to show how do it for something that may not be mapped by default.

Answer 4

If Control+V followed by ALT-x shows ^[x (type in terminal) you can fix it with this small script from vim.wikia.com:

for i in range(97,122)
  let c = nr2char(i)
  exec "map \e".c." <M-".c.">"
  exec "map! \e".c." <M-".c.">"
endfor

Add to .vimrc for all alt key mappings.

Answer 5

This works for me on Ubuntu 16.04 xfce terminal (and alacritty rust terminal)

Set ultisnip snippet trigger to Meta-/ (just like emacs snippet)

let g:UltiSnipsExpandTrigger="^[/"

Here's now I type ^[/ in vim

In insert mode Ctrl-V Alt-/

(Meta is the Alt key on my PC keyboard)

Answer 6

I'm using Terminal on OSX, the same happens on remote Linux.

I don't know about Terminal, but if you are on OSX, your mappings should work out of the box, provided that you use a recent Vim version, and a recent iTerm2 terminal.

You need at least the Vim patch 8.1.2134. Having the patch 8.1.2194 also helps, because it automatically enables the modifyOtherKeys feature on which Vim relies to let the user map various chords.

For iterm2, I think you need at least the version 3.4.0. From the changelog:

• Modifier keys in vim should work better now. CSI u mode is no longer enabled by a control sequence. Instead, a "modifyOtherKeys" mode has been added which is compatible with xterm.

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On Linux, xterm also supports the modifyOtherKeys feature.

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You are not limited to meta chords. You can map many other chords, like <C-;> for example:

vim -Nu NONE +'nno <c-;> :echo "c-; was hit"<cr>'

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For more info, see :h modifyOtherKeys.

Answer 7

You have another option. NeoVim works with M-x out of the box when you have terminal sending ESC + sequence, which mostly every terminal could.

As a summary for other answers, I think your two options are

1. Turning using "opt as meta" off, using the actual sent code in mapping
2. Turning using "opt as meta" on, using <esc>x type of sequence for mapping.

There are some answers stating that just turning on opt as meta would make <A-x>/<M-x> work. That is not true. At least, it will not work on macOS.