return function(con)

local sh = {
  prompt = function() return '>' end,
  runs = true,
  env = {
    code = 0,
    path = 'sysapps:apps',
  }
}

function sh:which(cmd)
  local file = cmd or ''
  if file:sub(-4) ~= '.lua'
  then file = file.. '.lua'
  end
  if fsHas(file)
  then return '', file end
  for path in self.env.path:gmatch '[^:]+' do
    if fsHas(path..'/'..file)
    then return path, '/'..file
    end
  end
end

function sh:parseArgs(ln)
  local iq, buf, args = false, '', {}
  local qt, esc = nil, false

  ln = ln:gsub('%$(%S+)%s*=%s*(.*)$', function(k, v)
    env[k] = self:parseArgs(v)[1]
    return ''
  end)

  -- helper function
  local function psh()
    if buf:sub(1,1) == '$'
    then buf = tostring(self.env[buf:sub(2)] or '') end
    if #buf > 0 then table.insert(args, buf) end
    buf, qt = '', nil
  end

  for i = 1, #ln + 1 do
    local v = ln:sub(i, i)
    if ((v == ' ' or v == '\n' or v == '\t') and not iq)
    or v == ''
    then psh()

    elseif esc then esc, buf = false, buf.. v
    elseif v == '\\' then esc = true

    elseif (not qt or qt == v)
    and (v == '"' or v == "'")
    then psh()
      qt, iq = v, not iq

    else buf = buf.. v
    end
  end

  return args
end

function sh:run()
  return 'TODO'
end

function sh:loop()
  await(function()
    con.print(self:prompt())
    local ln = con.getln()
    con.down()

    local res = self:run(ln)
    if res then con.println(res) end

    return not self.runs
  end)
end

return sh

end