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There are several formats of tar archives, ustar, gnu, etc. Is there some tool that can show which format a given archive is in? (Haven't found it in manpage of bsdtar nor in info pages of GNU tar).

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Are you sure these actually produce different formats? implies that tar files follow POSIX IEEE P1003.1 – ChrisInEdmonton May 26 '14 at 17:43
I normally just use : file <filename.tar> . I get (for example) : ./dojo-release-1.5.0.tar: POSIX tar archive (GNU) – FreudianSlip May 26 '14 at 22:13
Running tar --help I find out that it defaults to "--format=gnu". The generated file is not accepted on with the message that it isn't in ustar format. – Magnus May 27 '14 at 18:07

Use 7Zip to open it then click Info button.
It will show information about compression methods and so on.
Click on Info button
By far 7Zip isn't the only program which can do it (it's my choice because it's open source and free), a lot of archivers can do the same.

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That's good to know, but for home I'd really like a way that doesn't require me to first go out buying a license for an OS I don't particularly like :) – Magnus May 27 '14 at 18:15
@Magnus Which OS do you use? As I know there are a lot of versions for various systems (look here), but I'm not sure if they have UI. – Jet May 28 '14 at 8:55
I'm on Linux and I have the CLI version of 7z installed, but it offers no way to extract that information AFAICS. – Magnus May 30 '14 at 19:44

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