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Re: Is tar -cjf deterministic?
- From: ericblake at comcast dot net (Eric Blake)
- To: antiskid56-cygwin at yahoo dot com, cygwin at cygwin dot com
- Cc: "James R. Phillips" <antiskid56-cygwin at yahoo dot com>
- Date: Mon, 12 Sep 2005 19:27:22 +0000
- Subject: Re: Is tar -cjf deterministic?
> I've noticed more than once that when I recreate a bzip2'ed tar archive on
> cygwin, the file length is slightly different. Yet it expands into the same
> directory tree (as determined by recursive diff).
>
> Is there something nondeterministic about tar and bzip2 on cygwin? If so, is
> it unique to cygwin?
Not unique to cygwin - file timestamps are preserved in tar, and
when the timestamps change, the compression dictionary changes,
hence leading to different compression ratios.
--
Eric Blake
volunteer cygwin tar maintainer
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