Send keys to a terminal buffer

Question

I want to map a keyboard shortcut to execute the last command in a terminal buffer that I have open.

I've made some progress: I am storing the buffer's channel id correctly but when I try to send keys to the terminal (up arrow and enter) they always appear as literal characters in the terminal rather than actually going to the previous command and executing it.

" remember the chan id (buffer id) of the last terminal buffer
augroup Terminal
  au!
  au TermOpen * let g:last_terminal_chan_id = b:terminal_job_id
augroup END


" WIP: doesn't work yet
function! REPLSend()
    " the following commented out lines were taken from another plugin that sends keys to a terminal - it doesn't seem to work
    " let isnormal = mode() ==# 'n'
    " let curwin = winnr()
    " exe "sb " . g:last_terminal_chan_id
    " call cursor('$', 1)
    " exe curwin . 'wincmd w'
    " if isnormal
    "     stopinsert
    " endif
    " call chansend(g:last_terminal_chan_id, '<Up>' . '\n')
    call term_sendkeys(g:last_terminal_chan_id, "i\<Up>\<cr>")
endfunction

command! REPLSendLine call REPLSend()

nnoremap <silent> <f5> :REPLSendLine<cr>

Answer 1

I don't have term_sendkeys() in my neovim instance, so I'll use chandsend() in my example. Also, the i is unnecessary, since this function can't put you into insert mode.

Now, regarding your problem. "\<Up>" does indeed have some unexpected behavior inside double quotes. But, I managed to work around it like this:

1. Open vim preemptively to not get error on load.
2. While in terminal, start by writing echo -n '' >> ~/.vimrc, then put cursor between quotes and press control-v followed by Up, then enter to execute your command.
3. Reload .vimrc with :e!, delete the last line with literal Up sequence, and p it wherever you want (in this case, into chansend function).

Upd: Another way: enter keys by hex code directly in vim:

1. Find out your Up key byte sequence in terminal by piping it to hexdump -C (same method with echo as described above). This is important, because Up key may produce different sequences based on your $TERM value, shell, and system-global key remappings. Here's what mine looks like:

    echo -n '^[OA' | hexdump -C
    6 00000000  1b 4f 41                                          |.OA|
    5 00000003

2. Enter every byte in vim by pressing C-v, followed by x, and then hex code. E.g. C-v x 1 b for first byte, and so on...

This seem to work correctly:

call chansend(b:terminal_job_id, '^[OA' . "\<cr>")

Do not try to copy code from here, though. You need to get actual literal Up sequence from your shell.

Upd.2: Actually, scratch almost all of above, and just specify bytes as hex sequences, like this:

call chansend(b:terminal_job_id, "\x1b\x4f\x41\<cr>")

Answer 2

the neovim-lua 0.5 + fish shell + kitty terminal solution for this is

vim.cmd("call chansend(" .. job_id .. ', "\x1b\x5b\x41\\<cr>")')

its a different hex code, ^[[A for the mentioned combination. Took me a while to figure out, so I figured this is the best place to mention it.

Answer 3

I couldn't get the up arrow key working, it seems tricky and I don't think it's the best way. But thanks to @thunderbeef's answer I got the enter key working, and a solution I'm happy with:

    call chansend(g:last_terminal_chan_id, "!!\<cr>")

Answer 4

I had been wanting to do the same thing. Your question helped so much! I wrote a super small plugin that does just this: https://gist.github.com/cowlicks/5d70685346bf341a71f26e564b795a76