pager (less) -- get current scroll position?

Question

I am scripting the display of the output of a script (well, it is just the program git diff) with tmux: Once a filesystem change is detected the shell script executes tmux send-keys q enter C-l "git diff" enter which has it effectively refresh the git diff view.

You might consider this similar to functionality provided by iTerm's coprocesses.

Problem is, I want it on refresh to scroll back to the same position that it was in.

One of the reasons for using tmux is that the window is actually a totally normal and interactive terminal session that can be interacted with as normal to scroll around to look at the full output.

But I want to obtain the scroll position somehow.

Suppose I want to actually do computation on the text content of the terminal window itself, exactly like iTerm2's coprocess does, but so that I can use it on Linux (over ssh). Does tmux provide this ability?

Answer 1

I'm unsure about capturing this with a script, but less -N will show line numbers. And -jn or --jump-target=n can jump to a location.

Answer 2

About iTerm's coprocesses,

tmux has a command pipe-pane that can be used to pipe the input and output of a shell command to the output and input of a target pane specified by -t.

So if I have a shell program, ~/script.sh for example:

#!/usr/bin/env bash
while read line; do
    if [[ "$line" = "are you there?"* ]]; then
        echo "echo yes"
    fi
done

Note that read line will read every line printed to the pane, i.e. the prompt as well.

I can connect its stdin and stdout to pane 0 in my-session:my-window like so:

tmux pipe-pane -IO -t my-session:my-window.0 "~/script.sh"

and then at the prompt, type echo are you there?, and it responds:

$ echo are you there?
are you there?
$ echo yes
yes

Be careful using -IO together as it can easily cause a feedback loop (I had to kill the tmux server a few times while experimenting with this feature, lol).