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Wrong/ inconsistent responses from diff


(Very sorry if this arrives twice: one sent 3H ago seems not to have made it and I think maybe a AV induced signature was the cause: not provided with this despatch.)

Ouch, this is weird and inexplicable.

Somehow diff identifies differences in two identical binary files. In the following example two duplicate files are located (i) in my home directory (/m/home/user) and (ii) at the root of a different drive (D:).

But this is just an example. The spurious differences are identified for all binary files. (As I found when comparing two identical trees, containing many binaries, using diff -rqs.)

First, confirm they are identical. Notice the 5 different ways I may use to identify the file in my home directory. Using md5sum confirms they are identical (so does cmp -bl, say).

~> md5sum INTERVAL.pdf /d/INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf *INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf */d/INTERVAL.pdf
~> md5sum ./INTERVAL.pdf /d/INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf *./INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf */d/INTERVAL.pdf
~> md5sum ~/INTERVAL.pdf /d/INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf */home/user/INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf */d/INTERVAL.pdf
~> md5sum /home/user/INTERVAL.pdf /d/INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf */home/user/INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf */d/INTERVAL.pdf
~> md5sum /m/home/user/INTERVAL.pdf /d/INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf */m/home/user/INTERVAL.pdf
5f6ac8c4882f4804805ff41291a665bf */d/INTERVAL.pdf

Now test for differences in the files (there are none, of course). Only the 5th of the 5 different ways by which I may identify the file in my home directory demonstrates that the two files are the same. Otherwise they are reported as being different.

~> diff -s INTERVAL.pdf /d/INTERVAL.pdf
Files INTERVAL.pdf and /d/INTERVAL.pdf differ
~> diff -s ./INTERVAL.pdf /d/INTERVAL.pdf
Files ./INTERVAL.pdf and /d/INTERVAL.pdf differ
~> diff -s ~/INTERVAL.pdf /d/INTERVAL.pdf
Files /home/user/INTERVAL.pdf and /d/INTERVAL.pdf differ
~> diff -s /home/user/INTERVAL.pdf /d/INTERVAL.pdf
Files /home/user/INTERVAL.pdf and /d/INTERVAL.pdf differ
~> diff -s /m/home/user/INTERVAL.pdf /d/INTERVAL.pdf
Files /m/home/user/INTERVAL.pdf and /d/INTERVAL.pdf are identical

Using XP Pro SP3. This happens with the current cygwin1.dll and the snapshot dated 20100822.

Attached, cygcheck.out.

Fergus

Attachment: cygcheck.out.bz2
Description: Binary data

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