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From Stefan Bodewig <bode...@apache.org>
Subject Re: PaxHeaders folder is missing upgrade from 1.8.2 to 1.10.9
Date Fri, 29 Jan 2021 08:10:02 GMT
On 2021-01-28, S Abirami wrote:

> In our build.xml, we are using the untar task to untar gzip and tar.gz file.
> When we tar, always we saw a PaxHeaders.* folder in the untar location.
> After upgrading from 1.8.2 to 1.10.9 version of Ant build.

> We are not seeing this folder. We want to know whether missing of that
> folder will have any impact on the untar files.

1.8.2 is a looong time ago and a lot has changed. :-)

When tar became a POSIX standard a few ways to break out of the limits
of the original format have been been invented. One of them was the
introduction of an additional type of entry - a so called PAX header -
that could contain (meta-)data not compatible with the original
format. A common example would be non-ASCII filenames or paths longer
than 250 characters.

A tar implementation that doesn't understand these extensions will see
them as files inside a directory called PaXHeaders - an tar
implementation that does understand them will parse them and not treat
the headers as actual files at all.

The Java classes implementing tar initially didn't understand the POSIX
extensions and have ben gradually improved. Looking through Ant's
changelogs I believe with 1.9.0 they started to understand PAX headers.

So what your untar task does now is actually applying the data contained
inside the PAX headers where possible instead of ignoring them.

Stefan

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