Talking to vim from outside

Question

Can I change a variable in an instance of vim from another shell (without sending keys through tmux)?

I ask because I would like to use latexmk's compiling_cmd, success_cmd, and failure_cmd options to show compilation status on the statusline.

Perhaps I could have vim look for the existence or non-existence of certain files (using files as boolean variables)? But this seems a bit dirty; hopefully there is a better way.

Answer 1

If you launch your first Vim session with the argument --servername VIM:

$ vim --servername VIM

then you can send any command from any other shell with the argument --remote-send.

For example, if you use your statusline to display the value of some variable g:myvar, and you have the following lines in your vimrc:

let g:myvar = "foo"
set stl+=%{g:myvar}

Then you can change its value (:let g:myvar = "bar") from another shell:

$ vim --remote-send ':let g:myvar = "bar"<cr>'

The statusline should reflect the change of the value.

---

As your last comment says it, if your Vim instance is not in normal mode, the previous command will not work as expected. There may be simpler, but here are 2 possible solutions:

1) add the key <esc> to be in normal mode
2) use the argument --remote-expr instead of --remote-send to evaluate an expression and write a small helper function whose code will assign the new value to your variable

First solution:

$ vim --remote-send '<esc>:let g:myvar = "bar"<cr>'

Second solution:

Define the following function in your vimrc:

function! Myfunc(value)
    let g:myvar = a:value
endfunction

Then, in your shell:

$ vim --remote-expr 'Myfunc("bar")'