local chat = peripheral.wrap("left")
local online = rs.getInput("back")

while true do
  if online == true then
    local event, user, message = os.pullEvent("chat")
    local h = fs.open("chat.log", "a")
    h.writeLine(user..": "..message)
    h.close()
    sleep(0)
  end

  online = rs.getInput("back")
end