I use tmux on most boxes, but not all.
I have the following line in my .bashrc file:
[ -z "$TMUX" ] && export TERM=xterm-256color && exec tmux
which invoke tmux if it exists.
I thought the
[ -z $TMUX ] meant that it would only be used if tmux exists.
However on another system, without tmux, I get
-bash: exec: tmux: not found
and the login attempt fails
On my main system I see
$ echo $TMUX /private/var/folders/ks/266xy5lj7x35gfj4csc66444b48rvq/T/tmux-373580663/default,55084,4
I also tried just
[ $TMUX ] (i.e. no
-z) but that didn't help
I'm also looking for a robust solution that works in Ubuntu as well as OSX