# tmux 1.8 added -b flag to run-shell. Prior to 1.8 we must detach.
tmux_version=$($tmux -V)
tmux_version=${tmux_version#tmux }
+ tmux_version=${tmux_version//[^0-9]/}
tmux_major=${tmux_version%%.*}
tmux_minor=${tmux_version#*.}
tmux_minor=${tmux_minor%%.*}