ComputerCraft Tutorial: radio_ctrl(turtle)0_2

-- ############################################
-- radio_ctrl  (turtle side)
-- version 0.2
-- http://hevohevo.hatenablog.com/
--   1. Refer to controller side program (http://pastebin.com/h93ywUvS).
--   2. Input to the following and reboot TurtleOS
--     > pastebin get z6QVrviC startup

-- ################## config ##################
ModemSide = "right"
Logfile = "Logfile"
ControllerID = nil -- set ID, if you need to restrict controller ID.

-- ################## functions ###############

function writeLogfile(filename, str, err)
  local fh = fs.open(filename,"a")
  if not err then
    fh.writeLine(str)
  else
    fh.writeLine("--[[ "..err)
    fh.writeLine(str)
    fh.writeLine("--]]")
  end
  fh.close()
end

function eval(str)
  local status, err = pcall(loadstring(str))
  if status then  -- success
    if string.find(str, "os.run") then
      writeLogfile(Logfile, str, "os.run: Logfile")
    elseif string.find(str, "clearLogfile") then
      -- do nothing
    else
      writeLogfile(Logfile, str)
    end
  else  -- error
    writeLogfile(Logfile, str, err)
    print('Error: ',err)
  end
end

function clearLogfile()
  if fs.exists(Logfile) then fs.delete(Logfile) end
  local fh = fs.open(Logfile,"w")
  fh.writeLine("-- received messages log")
  fh.close()
end

-- ###############################
-- Define usable functions in received messages
_G["clearLogfile"]  = clearLogfile


-- ###############################
-- Main
rednet.open(ModemSide)
clearLogfile()

repeat
  local sender_id, message, distance = rednet.receive()
  print(message)
  if not ControllerID or (sender_id == ControllerID) then eval(message) end
until message == "exit()"