the best u()

# in ~/.zshrc

alias uu='u 2'
alias uuu='u 3'

# u
# u CMD [ARG...]
# u INTEGER
# u INTEGER CMD [ARG...]
# u DOTS                 e.g. `u ....` goes up four directories
# u DOTS CMD [ARG...]
function u {
  local count where
  if [[ $# = 0 ]]; then
    # `u`
    cd ..; return 0
  fi
  if [[ $1 =~ /^[1-9][0-9]*$/ ]]; then
    # `u INTEGER [CMD [ARG...]]`
    where=$(_u_cds $1); shift 1
  else if [[ $1 =~ /^\.+$/ ]]; then
    # `u DOTS [CMD [ARG...]]`
    where=$(_u_cds ${#1}; shift 1
  else
    # `u CMD [ARG...]`
    where=.
  fi
  if [[ $# = 0 ]]; then
    # `u [INTEGER | DOTS]`
    # change cwd and return
    cd $where; return $?
  fi
  # `u [INTEGER | DOTS] CMD [ARG...]
  # run $@ from the directory; don't change our cwd
  (cd $where && $@); return $?
}

function _u_cds {
  local count=$1 where=.
  for ((i = 0; i < $count; i++)); do where=$where/..; done
  # strip leading ./
  [[ $where != . ]] && where=${where:2}
  echo $where
}