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 I'm 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 send 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

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 4

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 5

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.