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I have two files, one I produced with zip 2.3.1 and the other I produced with zip 3.0. Both are a zip of the same directory. Here are the two files and their sizes:

1.7G from-2.3.1.zip  
1.7G from-3.0.zip

My plan is to transition my system to the new zip, so that I can potentially created larger zip files, like up to 3 gb or so.

However, my concern is that when I unzip these files, with a slightly older version of unzip, I get errors when I try to unzip the zip created with zip 3.0.

$ unzip -t from-2.3.1.zip > /dev/null  # NO Errors
$ unzip -t from-3.0.zip > /dev/null
warning [from-3.0.zip]:  76 extra bytes at beginning or within zipfile
  (attempting to process anyway)
error [from-3.0.zip]:  reported length of central directory is
  -76 bytes too long (Atari STZip zipfile?  J.H.Holm ZIPSPLIT 1.1
  zipfile?).  Compensating...
error:  expected central file header signature not found (file #67358).
  (please check that you have transferred or created the zipfile in the
  appropriate BINARY mode and that you have compiled UnZip properly)
$

The reason I am concerned, is that it seems like if I move to zip 3.0, I will be forcing my downstream users to all upgrade to a newer version of unzip, since unzip 6.0, for example, unzips both these files without error.

This anomaly doesn't occur in all cases, so I am unsure of it's full extent.

Any suggestions? Did I somehow incorrectly build zip 3.0?

Thanks.

Ted Gilchrist
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  • This is really a question for the vendor of your `zip` software. If they've broken backward compatibility they're the ones who can tell you what steps (if any) can be taken to restore it... – voretaq7 Dec 04 '12 at 17:37

1 Answers1

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The difference is the Zip64 file format, which was introduced in order to be able to compress larger files. Older utilities (such as Windows XP's File Explorer) don't understand it.

As far as Linux goes, Debian Stable included unzip 6.0 since at least its 2011 release (the changelog says zip 3.0a was released in 2004 and unzip 6.00 was released in 2009) so my personal opinion is that if you're "forcing" your users to upgrade, you're doing them a favor.

DerfK
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  • Thanks. I notice that my Mac Air, acquired within the past couple of months, has unzip 5.5.2 on it, so I would guess that this earlier version of unzip is still somewhat common. But I appreciate your response. – Ted Gilchrist Dec 04 '12 at 16:25