Lua console coded in Lua.

console.lua

-- Print a prompt an read an input line
local function getline(line)

  if line ~= "" then
    io.write(">> ")
    return line .. "\n" .. io.read()
  end

  io.write("> ")
  return io.read()
end

-- Print an error message
local function printerr(error_msg)

  error_msg = error_msg:gsub("%[.*%]:", "")
  print(error_msg)
end

-- Load code from string
local function getcode(line)

  local code, error_msg = loadstring(line)              -- try to load the code

  if code == nil then                                   -- if syntax error
    code = loadstring("print(" .. line .. ")")            -- try auto print
  else                                                  -- else
    local retcode, err = loadstring("return " .. line)    -- try auto return
    if not err then
      code = retcode
    end
  end

  return code, error_msg
end

-- main

print(_VERSION)
local line = getline("")

while line ~= nil do

  local code, error_msg = getcode(line)         -- load code from line

  if code ~= nil then                           -- if code is valid

    local results = table.pack(pcall(code))       -- execute the code
    local success = table.remove(results, 1)
    line = ""                                     -- clear the line

    if not success then                           -- if failure
      printerr(results[1])                          -- print error
    elseif #results > 0 then                      -- else if has results
      print(table.unpack(results))                  -- print results
    end

  elseif error_msg:sub(-5) ~= "<eof>" then      -- else if not incomplete
    line = ""                                     -- clear the line
    printerr(error_msg)                           -- print error
  end

  line = getline(line)                          -- read next line
end

print()