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Neil Bothwick <neil@××××××××××.uk> wrote: |
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> On Wed, 26 Sep 2007 10:14:58 +0200, Alexander Skwar wrote: |
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> |
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>> Back to tar: Why use "tar -j" in scripts, when "bzip2 | tar" |
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>> does the same thing? I very much disagree that "tar -j" is |
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>> the "better" option here; |
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> |
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> Either way requires that you first determine the type of compression used |
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> before you can decide where to pipe tar's output, if at all. Whereas |
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> something like "tar xf somefile" avoids the need to do" file somefile" |
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> and parse the output first. |
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Pardon? "tar xf somefile" doesn't do any compression at all. |
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I don't get what you mean. |
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>> in fact, I'd say that "bzip2 | tar" |
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>> is the better option, as it works on a lot more systems than |
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>> "tar -j" does. Heck, "tar -j" even does not work on all GNU |
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>> tar implementations, as very old GNU tars don't have bzip2 |
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>> support at all and -j wasn't always used for bzip2. |
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> |
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> If you don't know the details of the platform running your script, you |
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> should of course stick to POSIX, which tar can do fine. |
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No, GNU tar is not completely POSIX compliant. The files it creates |
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don't completely comply to the standard. But that's another story. |
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> But if your |
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> script in running in an environment you control, why not make use of more |
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> efficient methods? |
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If there are more efficient methods: Maybe. But if the non standard |
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options aren't more efficient, why use them at all? "tar -j" is a |
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good example here: Internally, tar invokes the external "bzip2" |
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command. So with "tar | bzip2" vs. "tar -j", both are equally |
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efficient. |
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Alexander Skwar |
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-- |
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