How can I fix tmux not showing messages at startup?

Question

I have a command in my .tmux.conf file which checks to see if a directory exists, then displays a message if it doesn't; and another command which tries to run a shell script.

file: ~/.tmux.conf

# do a check and display message if non-zero exit
if-shell "! [-d $HOME/.tmux]" 'display-message "tmux plugins are not installed"'

# try run a shell script
run-shell ~/.tmux/plugins/tmux-resurrect/resurrect.tmux

The problem is that tmux won't display any messages that are generated during startup - which is the time I would expect diagnostic errors and warnings to be generated.

What I start tmux, I get an error message in tmux's pager

(null):0: no current session 

where it's clearly not liking being sent messages.

If I run the same commands by using source-file ~/.tmux-conf in the middle of a tmux session, all messages are reported successfully. How can I get tmux to report messages during startup?

Answer 1

I know this is old, but I was also interested in displaying some sort of startup message and came across this question. After searching around I eventually found out about tmux hooks (introduced internally in tmux 2.2) which can be configured to display a one time startup message (read more here).

You can use the session-created hook to run tmux commands on a new session. display-message -p "message" outputs a message straight to the newly created window. So you can display a message like so:

MESSAGE='display-message -p "tmux plugins are not installed" ; \
         display-message -p "please press Leader + I to install" ; \
         set-hook -gu session-created ;'
if-shell "[ ! -d $HOME/.tmux ]" 'set-hook -g session-created ${MESSAGE}'

the set-hook -gu session-created unregisters this hook, so that this message is shown only on the first session created, and not all subsequent ones.

Answer 2

It works for me from the command-line as follows:

tmux new-session \; if-shell "! [-d $HOME/.tmux]" 'display-message "tmux plugins are not installed"'