Path: utzoo!attcan!uunet!midway!linac!uwm.edu!cs.utexas.edu!rutgers!mephisto!mcnc!uvaarpa!mmdf
From: telxon!ping!gorpong@uunet.uu.net
Newsgroups: comp.lang.perl
Subject: PERL PL28 and reading raw devices (problem)
Message-ID: <1990Sep26.122859.18935@uvaarpa.Virginia.EDU>
Date: 26 Sep 90 12:28:59 GMT
Sender: mmdf@uvaarpa.Virginia.EDU (Uvaarpa Mail System)
Reply-To: telxon!ping!gorpong@uunet.uu.net
Organization: The Internet
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I am writing a perl program which will handle tape copying from remote or
local devices.  The scheme I use for a local source device is to open up
the device via:
	open(SRC_TAPE, "< $SRC_TAPE");
I then open up a pipe to write the remote tape (or pipe to read the remote).
When going remote for the device, I use the 'dd' command to do the reading
and/or writing.  Enough background, now to the question.

When copying a tape which is in boot format, the program tells me that it
has read and written the exact same number of bytes.  When attempting to
boot this tape, it fails every time, on every tape drive.  When forcing
the program to use 'dd' to read the tape and write the tape, it also tells
me that the correct number of bytes have been written.  However, the
copy made with 'dd' on both ends boots correctly.

I am reading the tape with the perl read(SRC_TAPE, $_, $blksize); and
SRC_TAPE is opened either "< device" or "dd if=device |"
The exact same code works when the open is opening up a 'dd' command to
read the device.  Is there something which perl is doing to the bytes
read in from the raw device which it does not do when reading from a pipe?

I should note that when copying things like 'tar' format tapes, it is still
in tar format, and it unarchives correctly.  It really screws up boot 
format tapes.  My question is, why?  It is perl patchlevel 28 on a Sun 3/50
or 3/anything (or 4/anything) running SunOS 4.1.  Any help you may be able
to give me would be greatly appreciated.

		-- Gordon.

-- 
Gordon C. Galligher	9127 Potter Rd. #2E	Des. Plaines, Ill.    60016-4881
     telxon!ping%gorpong@uunet.uu.net (not tested)  (Is this even legal??)
     ...!uunet!telxon!ping!gorpong      (tested)    (And it works!)
"It seems to me, Golan, that the advance of civilization is nothing but an
 exercise in the limiting of privacy." - Janov Pelorat -- _Foundation's Edge_