vim ~/.tmux.conf
# split pane (tmux 1.9+)
bind-key \ split-window -h -c "#{pane_current_path}" # vertical split (default prefix-%)
bind-key - split-window -v -c "#{pane_current_path}" # horizontal split (default prefix-")
# split full window (tmux 2.3+)
bind-key | split-window -fh -c "#{pane_current_path}" # vertical split
bind-key _ split-window -fv -c "#{pane_current_path}" # horizontal split
_ _ _ _
__ _ ___ | |_| |__ | | ___| |_ _ _
/ _` |/ _ \| __| '_ \| |/ _ \ __| | | |
| (_| | (_) | |_| |_) | | __/ |_| |_| |
\__, |\___/ \__|_.__/|_|\___|\__|\__,_|
|___/