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From S Abirami <s.abir...@ericsson.com.INVALID>
Subject RE: PaxHeaders folder is missing upgrade from 1.8.2 to 1.10.9
Date Fri, 29 Jan 2021 08:51:54 GMT
Hi Stefan,

Our untar task will just untar *.so file and  *.dll file inside gzip and tar.gz.
We didn't store anything inside a PaxHeader folder.

I aware the usage of PaxHeader to determine the higher size of file names available in tar.
In our application, we don't have big file name which has more than 100 characters.
Just to confirm the PaxHeader missing is expected in Ant build of 1.10.9 version or we are
missing anything.

Regards,
Abirami.S
-----Original Message-----
From: Stefan Bodewig <bodewig@apache.org> 
Sent: Friday, January 29, 2021 1:40 PM
To: dev@ant.apache.org
Subject: Re: PaxHeaders folder is missing upgrade from 1.8.2 to 1.10.9

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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