Am 10.10.2014 um 20:48 schrieb David Aguilar:
> On Fri, Oct 10, 2014 at 01:19:40PM +0200, Jakub Narębski wrote:
>> David Aguilar wrote:
>>> Avoid filenames with multiple dots so that overly-picky tools do
>>> not misinterpret their extension.
>>>
>>> Previously, foo/bar.ext in the worktree would result in e.g.
>>>
>>> ./foo/bar.ext.BASE.1234.ext
>>>
>>> This can be improved by having only a single .ext and using
>>> underscore instead of dot so that the extension cannot be
>>> misinterpreted. The resulting path becomes:
>>>
>>> ./foo/bar_BASE_1234.ext
>>>
>>> Suggested-by: Sergio Ferrero <[email protected]>
>>> Helped-by: Junio C Hamano <[email protected]>
>>> Signed-off-by: David Aguilar <[email protected]>
>>> ---
>>
>>> + if BASE=$(expr "$MERGED" : '\(.*\)\.[^/]*$')
>>> + then
>>> + ext=$(expr "$MERGED" : '.*\(\.[^/]*\)$')
>>> + else
>>> + BASE=$MERGED
>>> + ext=
>>> + fi
>>
>> Why use expr and not POSIX shell parameter substitution?
>>
>> BASE=${MERGED%.*}
>> ext=.${MERGED##*.}
>>
>> Or something like that...
>
> Thanks for the sug.
>
> My POSIX shell parameter expansion-fu is not super advanced, but
> if you can help me rework it I'd be happy to reroll.
>
> It does seem simple and robust with expr, though. Extending the
> parameter expansion approach to work in all cases may end up
> with more complexity than with the expr method, it seems.
>
> Here are the use cases:
>
> $ MERGED=foo.bar.baz && echo ${MERGED%.*} ${MERGED##*.}
> foo.bar baz
>
> Good.
>
> $ MERGED=foo && echo ${MERGED%.*} ${MERGED##*.}
> foo foo
>
> Bad.
> There's no extension and the substitution doesn't handle it.
>
> $ MERGED=foo.bar/baz && echo ${MERGED%.*} ${MERGED##*.}
> foo bar/baz
>
> Bad.
> There's no extension but the substitution thinks the parent directory's
> extension-less name is the basename, and thinks that bar/baz is the extension.
>
> I am curious to know whether there's a nice and elegant way to do it
> with shell expansions. Let me know what you think.
It's not exactly elegant to do it:
First, you extract the last path part:
file=${MERGED##*/}
Then the directory including the trailing slash:
dir=${MERGED%"$file"}
Then the basename without an extension:
base=${file%.*}
Finally the extension including the dot:
ext=${file#"$base"}
Beware of empty $base and $dir (e.g., for files named .gitignore or so)
-- Hannes
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