Controlling Vim from outside

Question

Is there a way to control the opened instance of Vim from outside?

Let me clarify, I saw many posts about controlling an external program from Vim by simply executing commands on special key strokes occasions. But what I need is the complete opposite, sending instructions to modify how things look in the currently opened instance.

Here's what I want to accomplish: I am trying to make a webapp WYSIWYG, what you write in the textarea is processed and rendered in a box, that requires a lot of typing and modification like writing a program, but the original textarea has not a lot under the hood.

That's why I want to use Vim, and not only should I be able to use Vim to send information to the browser (which is possible I already know) I should also be able to send some messages to Vim from the browser because the box is also editable and modifies the textarea.

What would be the easiest way to accomplish that? As a start I want to know if changing the caret position (line) from an external signal is doable.

Answer 1

For Vim you can use the --remote-send flag. It takes as an argument the Vim command that you would like to be executed.

For example:

vim --remote-send ":echo 'hello'<CR>"

Will echo hello into your running Vim.

You can execute any command you would like instead of :echo this way.

You can use --servername to specify the remote instance of Vim which should receive the command.

Remark: you need Vim to be compiled with the +clientserver option. More information with: :help clientserver

Answer 2

You can also use a JSON channel to send commands to Vim. For more information about this refer to https://vimhelp.org/channel.txt.html#channel-commands. Note that Vim can only be a client and not a server. So the Vim instance needs to open a channel in JSON mode to the external server.