How to use session-closed hook

[RobertWadeSteele]

I'm running tmux 3.5a. I had an idea for a popup script that can start sessions linked to the current session in a popup and then attach and detach when the hotkey is pressed repeatedly.

Everything works great except that I want to clean up the popup sessions when the "parent" session is closed. I assumed hooks would be the obvious solution. When the popup session is created I set a hook on the "parent" session as follows.

tmux set-hook -t ${parent_session_name} session-closed "kill-session -t ${popup_session_name}"

When I enter tmux show-hooks -t ${parent_session_name} I can see that there is what looks like a hook entry that looks like the following.

session-closed[0] kill-session -t dotfiles__popup__scratch

This hook entry is not on any other session so it seems I am correctly targeting the "parent" session. No matter how I close the parent session however the script never seems to run. I tried logging to a file and nothing was logged. Is this hook just not running for some reason? What am I doing wrong? The session-closed[0] portion makes me question if this hook is somehow targeting a session that doesn't exist despite passing a valid target session and only seeing the hook show up on said target session.

The script is below. This is pretty much the first script I've written in bash, period, let alone for tmux so I assume I'm just missing something but the man page doesn't seem to show anything beyond what I've already tried.

#!/usr/bin/env bash
# https://blog.meain.io/2020/tmux-flating-scratch-terminal/
# https://github.com/tmux/tmux/wiki/Formats

command=${1}
[ -z "$command" ] && command="scratch"
session_path=$(tmux display-message -p -F "#{session_path}")
session_path=$(basename "$session_path" | tr . _)

popup_session_name="${session_path}__popup__"${command}""
current_session_name="$(tmux display-message -p -F "#{session_name}")"

if [[ "${current_session_name}" =~ .*__popup__.* ]]; then
    tmux detach-client
fi

if [ "${current_session_name}" != "${popup_session_name}" ]; then
    tmux has-session -t ${popup_session_name} 2> /dev/null || \
        tmux new -d -s ${popup_session_name} ${@:1} && \
        tmux set-hook -t ${current_session_name} session-closed "kill-session -t ${popup_session_name}"
    tmux popup -w "90%" -h "90%" -E "tmux attach -t ${popup_session_name}"
fi

This discussion looks like it could be related but it's from so long ago that I can't imagine this is still the same issue. #1245 If this is the same issue then is there a reason this wasn't fixed back in 2018? Seems like this is a pretty useful hook which should work for targeted sessions.

[nicm]

Don't think per-session session-closed works, try making it a global hook and checking hook_session_name or hook_session.

[RobertWadeSteele]

Ok thanks I'll try that. Any particular reason per session session-closed doesn't work? I guess the issue I linked from 2018 is still relevant.

Would you accept a PR addressing this? At the very least I could make a PR mentioning this limitation for the man pages. Could save someone else an hour in the future.

[nicm]

I don't know if it doesn't work or why someone would need to investigate. There is also #4267.

[nicm]

Actually I already looked at in that issue and there is a fix there, but it makes tmux crash on exit so it is not quite right.