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From: Chet Ramey <chet.ramey@case.edu>
Newsgroups: gnu.bash.bug
Subject: Re: Backslash missing in brace expansion
Date: Fri, 6 Dec 2019 14:14:00 -0800
Organization: ITS, Case Western Reserve University
Lines: 31
Approved: bug-bash@gnu.org
Message-ID: <mailman.438.1575670451.1979.bug-bash@gnu.org>
References: <20191205201157.cd481936f76d95bbdfabc73c@schrader-schulte.de> <662e2328-f331-c554-afcf-fd3819f6beab@case.edu> <20191206055304.076d6115afa3a4f2a6a21c34@schrader-schulte.de> <5b5064a8-7175-42e7-1eb5-6374dee6c11e@redhat.com> <21761e28-c496-ff67-d7b7-628c9325085f@iki.fi> <9dd3a388-39b1-c059-de99-813f1e411764@case.edu>
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To: Ilkka Virta <itvirta@iki.fi>, Eric Blake <eblake@redhat.com>, Martin Schulte <gnu@schrader-schulte.de>, bug-bash@gnu.org
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Xref: csiph.com gnu.bash.bug:15705

On 12/6/19 12:29 PM, Ilkka Virta wrote:

>>> Yes - sure. But then I'm wondering why the unquoted backtick doesn't
>>> start command substitution:
>>
>> It may be version dependent:
>>
>> $ echo ${BASH_VERSINFO[@]}
>> 5 0 7 1 release x86_64-redhat-linux-gnu
>>
>> $ echo b{Z..a}d
>> bash: bad substitution: no closing "`" in `d
> 
> I get that with 4.4 and 'echo b{Z..a}d' too, the trailing letter seems to
> trigger it.

That's an implementation decision bash makes. What you get from the above
brace expansion is the list

bZa, b[a, b\a, b]a, b^a, b_a, b`a, baa

As I said in the previous message, the expansion code leaves a single "`"
unchanged (it always has), but throws an error when it's an unterminated
command substitution that's more than a bare backquote.


-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
		 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/