mjhjmtu

It seems like a simple enough procedure that I'm trying to accomplish, yet I've searched to no avail. I would like to create a key binding which does a split-window and then send-keys to the newly-created pane; however I need the pane id to use with the send-keys command. The catch is that I WILL NOT know how many panes are currently open in the window; thus I know of no way for the code running in the original pane to deduce what the new pane index will be. Is there any way to find out this new index or id (either one can be used as a target)?

Thanks.

You are over-thinking your problem. When you do split-window the new pane becomes the current target for send-keys. You should not be calling tmux in the binding as you are already in tmux. Try

bind-key s split-window ; send-keys "pwd" Enter

Well, I'd still prefer to find a direct way to get at the new pane ID, but I was at least able to accomplish my goal by calling a shell script instead of trying to do it all in the tmux.conf. Seems kludgy to me, but it works. tmux.conf:

bind s run-shell "~/bin/tmux_split_pane.sh '#window_id' '#pane_id'"

and the script:

#!/bin/sh

current_window_id=$1
current_pane_id=$2

tmux split-window -t $current_pane_id
new_pane_id=$(tmux list-panes -F '#pane_id' -t "$current_window_id" | sort -n --key=1.2 | tail -1)
tmux send-keys -t $new_pane_id -l "update_env" ; send-keys -t $new_pane_id Enter

In tmux, each new pane gets an unique value, which you can access using environment variable TMUX_PANE.
tmux display -pt "$TMUX_PANE:?" '#pane_index'
this will show pane number.

I did it by sending the new pane's id back through a named pipe.

mkfifo pane_id
tmux split-window -h ; send-keys 'echo $TMUX_PANE > pane_id' Enter ; select-pane -t "$TMUX_PANE"
cat pane_id