tmux used in ubuntu code example

Example 1: install tmux ubuntu

sudo apt-get update
sudo apt-get install tmux

Example 2: ubuntu default tmux shell

if command -v tmux &> /dev/null && [ -n "$PS1" ] && [[ ! "$TERM" =~ screen ]] && [[ ! "$TERM" =~ tmux ]] && [ -z "$TMUX" ]; then
  exec tmux
fi