start_tmux() {
  __TMUX_BIN__=`which tmux`
  [ ! -x ${__TMUX_BIN__:-""} ] && echo "RET" && unset __TMUX_BIN__ && return
  __TMUX_SESS__=`hostname`
  __TMUX_SESS__="${__TMUX_SESS__%%.*}"
  [ ! -z ${__TMUX_SESS__:-""} ] && __TMUX_SESS__="${__TMUX_SESS__}"

  if [ -z ${TMUX:-""} -a -z ${STY:-""} ]; then
    __TMUX_OPTION__=""
    if ${__TMUX_BIN__} has-session -t ${__TMUX_SESS__} > /dev/null 2>&1 ; then
      __TMUX_OPTION__="attach -t ${__TMUX_SESS__}"
    else
      __TMUX_OPTION__="new-session -s ${__TMUX_SESS__} ; split-window -h"
    fi
    ${__TMUX_BIN__} ${__TMUX_OPTION__}
  fi
  unset __TMUX_BIN__ __TMUX_SESS__ __TMUX_OPTION__
}