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Original Question:

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Hi Sun-Managers,

tcopy /dev/rstx

gives the following output :

file 1: records 1 to 279729: size 10240

file 1: eof after 279729 records: -1430542336 bytes

eot

total length: -1430542336 bytes

How should I interpret the "total length" - as 1.4GB

or as an erroneous output?

Regards,

Pravin

prchavan@pcsbom.patni.com

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Thanks to:

---------

keener@upenn5.hep.upenn.edu (Paul T. Keener)

Derek Terveer <derek.terveer@ci.saint-paul.mn.us>

Igor Schein <igor@txc.com>

"K.Ravi" <RAVKRISH.IN.ORACLE.COM.ofcmail@in.oracle.com>

Jochen Bern <bern@penthesilea.uni-trier.de>

"Carsten B. Knudsen" <cbk@terma.dk>

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The answer:

I would like to quote Jochen Bern's reply which was

more detailed:

1. As an Overflow. Your tcopy uses some Kind of Variable Type internally

which

-- should better be some Kind of Integer Number, rather than a Real ;-)

-- uses one Bit as a Sign (rather than using unsigned Integers)

Conclusion: It consists of n Bits (n a Multiple of 8) and, thus, can

represent positive Numbers from 1 (Bits 0...01) through

(2^(n-1))-1 (Bits 01...1) and negative Numbers from -1 (Bits 1...1)

through -(2^(n-1)) (Bits 10...0). (The Sign Bit is always the left-

most one.) As you see, when the Bits go from 01...1 to 10...0 (the

"Increase by 1" that actually does the Overflow), the Number

represented changes from (2^(n-1))-1 (MAX-1) to -(2^(n-1))

(-MAX), i.e., by (- 2 MAX + 1) instead of +1. Thus, every Over-

flow needs to be corrected by adding 2 MAX.

Assuming that you had only ONE Overflow, your tcopy likely uses

n = 4*8 = 32 (normal int/long on sun4 Architectures), hence

MAX = 2147483648 (2 Gig) and corrected Value approximately

- 1.4 GB + 2*2 GB = 2.6 GB.

2. As a Hint that you need a better tcopy. ;-) Isn't there a GNU Version?

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