Tmux refresh display after terminal width change

Launching anything from .zshenv is definitely the wrong approach. This file is executed by every instance of zsh, even when running a script. Use .zshrc for things that should be done in interactive shells, and .profile (or .zprofile, if you've set zsh as your login shell) for things that should be done when you log in.

If you want tmux in every terminal, start tmux directly under the terminal, e.g., gnome-terminal -e tmux (change your GUI launcher to pass these arguments). You can pass arguments even with -e (though be careful with quoting), e.g. gnome-termminal -e 'tmux -s ~/.alternate.tmux.conf'.

If you also want to start tmux when you log in over ssh, you'll have to launch it from your ~/.profile. Do this only if the parent process of the login shell is sshd:

parent_process_name=$(ps -o comm= -p $PPID`)
case ${parent_process_name##*/} in
  sshd) type tmux >/dev/null 2>/dev/null && exec tmux;;
esac

Another approach to starting tmux over ssh would be to obtain a session name from the environment. That way you could attach to an existing session. The easiest way is to write a small script on the server side, e.g. ~/bin/tmux-login-session:

#!/bin/sh
if tmux has-session -t "$1"; then
  exec tmux attach-session -t "$1"
else
  . ~/.profile
  exec tmux new-session -s "$1"
fi

Then use an ssh command like the following:

ssh -t hostname.example.com bin/tmux-login-session SESSION_NAME

This is possible in both GNU screen and in tmux and the workaround is similar: to fool the multiplexers into thinking that the terminal has no "alternate screen" mode (such as that used by pico, mutt, etc). This is accomplished by setting termcap commands for the session.

For GNU screen, put this in your .screenrc:

termcapinfo xterm*|xs|rxvt|terminal ti@:te@

and for tmux, add this to your .tmux.conf:

set -ga terminal-overrides ',xterm*:smcup@:rmcup@'

The 'xterm*' part of the command should be set to whatever your terminal-emulator is declared as. Some form of xterm is a good guess, but you can check yours on most sane *nix systems with:

echo $TERM

and this can usually be set in the preferences of your terminal program (ie: For Apple's Terminal.app, it's in Settings->Profile->Advanced (or Settings->Advanced->Emulation pre-yosemite) "Declare terminal as".

The end result is that the overflow ends up in the terminal's scrollback buffer instead of disappearing. Of course, since this is one static buffer, things will get messy as you switch between screen or tmux windows, but this is handy for quickly flicking up to see the output of an ls command or the such.