tmux_pane_wait.sh

#!/bin/bash
#
# tmux_pane_wait.sh: Launch an interactive process in a second tmux pane and
# wait for it to complete before continuing the script in the first pane.
#
# Ben Cohen, February 2022.
#
set -x
set -e
if [ -z "$TMUX" ]
then
    # If we aren't already in tmux, start this script again in tmux.
    tmux new-session -- "$0" "$@"
    exit $?
fi

# Do something here before launching the other pane.
echo Initial stuff.

# Start some command in another pane and get its id.
# Signal on the channel "pane_$TMUX_PANE" when finished.
other_pane_id=$(tmux split-window -P -F "#{pane_id}" 'echo "This is tmux pane $TMUX_PANE." ; echo "You can type stuff in here." ; echo ; bash ; tmux wait -S "pane_$TMUX_PANE"')

# Do some more stuff here after launching the other pane.
echo More stuff.

# Maybe this pane will simply block until the other pane is finished...
sleep 1

# ... or perhaps we want it to wait for the signal from the other pane.
tmux wait pane_$other_pane_id

# Do stuff after the other pane has closed.
echo Done.