Is tar -cjf deterministic?

[Eric Blake]

> 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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