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thanks, very helpful. |
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On Thu, Sep 17, 2009 at 10:26 AM, Frank Peters <frank.peters@×××××××.net> wrote: |
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> On Thu, 17 Sep 2009 09:04:22 +0800 |
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> Xi Shen <davidshen84@××××××××××.com> wrote: |
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> |
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>> i searched for a while, but cannot find the reference of that syntax. |
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>> thanks a lot. |
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>> |
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> |
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> The ordinary syntax is ${string:position:length}, but in the ordinary case |
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> the position is referenced from the LEFT end of the string. To reference |
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> from the RIGHT end of the string, as in the Gentoo script, a negative value |
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> must be specified, but the negative value has to the result of an EXPRESSION, |
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> hence the apparently unusual syntax. |
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> |
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> Why? See question E12 at this link: |
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> http://www.faqs.org/faqs/unix-faq/shell/bash/ |
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> |
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> Just try it out. Copy the following two lines to a file, give the file |
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> executable permission, and create different symbolic links to it. |
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> Then invoke the file using any of the symlinks. |
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> |
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> #! /bin/bash |
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> echo ${0:$[-2]} |
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> |
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> |
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> Frank Peters |
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> |
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> |
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> |
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-- |
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Best Regards, |
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David Shen |
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|
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http://twitter.com/davidshen84/ |
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http://meme.yahoo.com/davidshen84/ |
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