Bash: tmux or screen

# Tmux or screen
export TMUX_BIN=$(type -P tmux)
TMUX_DIR=${HOME}/tmux
TMUX_FILE=$TMUX_DIR/shared.${HOSTNAME}
if [ -x $TMUX_BIN ] ; then
  [[ !(-d $TMUX_DIR) ]] && mkdir -p $TMUX_DIR
  alias scr="$TMUX_BIN -l"
  function shscr {
    if [ -f $TMUX_FILE ] ; then
      $TMUX_BIN -l
    else
      $TMUX_BIN -l -S $TMUX_FILE
      chgrp wheel $TMUX_FILE
    fi
  }
  alias shsrd="$TMUX_BIN -S $TMUX_FILE attach"
  alias srd="$TMUX_BIN attach"
  alias srt="$TMUX_BIN attach -t"
  alias sls="$TMUX_BIN ls"
  alias slsc="$TMUX_BIN lsc"
elif [ -x /usr/bin/screen ] ; then
  alias scr="screen -l -h 50000"
  alias sls="screen -ls"
  alias srd="screen -rd"
fi