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From: rjchen@phoenix.Princeton.EDU (Raymond Juimong Chen)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Oooh Yeccheo. How Does This One Really Work?!?
Message-ID: <1269@phoenix.Princeton.EDU>
Date: Mon, 7-Dec-87 14:41:23 EST
Article-I.D.: phoenix.1269
Posted: Mon Dec  7 14:41:23 1987
Date-Received: Sat, 12-Dec-87 14:54:30 EST
References: <164300022@uiucdcsb> <412@wa3wbu.UUCP> <13091@beta.UUCP>
Reply-To: rjchen@phoenix.Princeton.EDU (Raymond Juimong Chen)
Organization: Princeton University, NJ
Lines: 71
Summary: Thou shalt not overwrite files behind DOS's back, at least not without good reason.

Apologies to the net, but my mail bounced.

In article <13091@beta.UUCP> it was written:
>I want to have a file called C:\AUTOEXEC.DDD that looks like this:
>
>prompt $p$g
>path c:\bin;c:\bat;c:\fluff;c:\dandruf;c:\batch;c:\dos;c:\freen;c:\gunk
>echo this is only a test and if you buy it you are a potato head
>echo if you realy think you are cool than you will jot down the date
>echo and time now.
>date
>time
>
>Now, I have this other file C:\AUTOEXEC.BAT that looks like this...
>
>echo Eat this one foo bar!
>copy c:\autoexec.ddd c:\autoexec.bat
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  This is bad.
>del c:\autoexec.ddd
>echo You can do it too!
>rem Now I want the machine to do a Ctrl/Alt/Del Warmboot at this point
>reboot
when you copy the autoexec.ddd to autoexec.bat, autoexec.bat gets overwritten,
and you have essentially erased the program you are trying to execute!
This is the reason for the strange events which follow:

><<CLEAR SCREEN>> <<HELLO COUNT RAM>> <<NOW HANG ON WHILE I BOOT TO DOS>>
>;c:\dos;c:\freen;c:\gunk
^^^^^^^^^^^^^^^^^^^^^^^^^^^
The batch file got as far as "copy \autoexec.ddd \autoexec.bat".
When DOS looked for the next command in the file, it found somebody
else inside the autoexec.bat file.  Being stupid, DOS assumed that nothing
happened at all and proceeds to continue execution from where it thinks
it left off.  Thus, you get a partial command and all the rest of the
nonsense.  (If you're really into that sort of thing, you could verify
that the garbage command ";c:\dos;..." actually appears in the file
autoexec.ddd exactly where the "del c:\autoexec.ddd" appears in the file
autoexec.bat.)

What you'd probably want is something like

AUTOEXEC.BAT:
  doit

DOIT.BAT:
  copy \autoexec.ddd \autoexec.bat
  del \autoexec.ddd
  do other stuff
  reboot.

AUTOEXEC.DDD:
  same as before

This time, when DOS copies autoexec.dd to autoexec.bat, nobody cares,
since the current batch file is DOIT.BAT.

It seems to me you're trying to pull a fast one on the normal person who
boots up the computer.  I shall not pass moral judgement.

-- 
Raymond Chen	UUCP: ...allegra!princeton!{pucc|phoenix}!rjchen
		BITNET: 6101695@pucc, rjchen@pucc
		ARPA: rjchen@pucc.PRINCETON.EDU
"Say something, please!  ('Yes' would be best.)" - The Doctor


-- 
Raymond Chen	UUCP: ...allegra!princeton!{pucc|phoenix}!rjchen
		BITNET: 6101695@pucc, rjchen@pucc
		ARPA: rjchen@pucc.PRINCETON.EDU
"Say something, please!  ('Yes' would be best.)" - The Doctor