Minecraft chat logger

Hi /prog/,

I have a problem with a Bash script.
I tried to write a little script to create a chat only log for minecraft.
The script is here:
http://pastebin.com/6TVkgvsc

However, when I test it, this is written to chat.log:

21:02:17 <tim> blah
21:03:49 <tim> hi
21:06:13 <tim> test
21:06:13 <tim> test
<tim> test
<tim> dayum
21:07:52 <tim> dayum
21:07:52 <tim> dayum
21:10:08 <tim> talk
21:10:08 <tim> talk
21:10:08 <tim> talk
<tim> talk

I said all those things only once.

I have no fucking idea why this happens.
For each message, the output of the script is just once "not the same; updating", it's not like Minecraft was just nog finished with logging.

Could someone help me out here?

>>3
the problem is that it is printing the same thing too many times, just make it stop doing that by checking if it is already written