if [ -n "$BASH_VERSION" -o -n "$KSH_VERSION" -o -n "$ZSH_VERSION" ]; then
  [ -x /bin/id ] || return
  [ `/bin/id -u` -le 100 ] && return
  # for bash and zsh, only if no alias is already set
  alias vi >/dev/null 2>&1 || alias vi=vim
fi