GNU bug report logs - #41262
Weird behavior with grep regex

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Message #13 received at 41262 <at> debbugs.gnu.org (full text, mbox):

From: Shlomi Fish <shlomif <at> shlomifish.org>
To: <loic.tregouet <at> orange.com>
Cc: 41262 <at> debbugs.gnu.org
Subject: Re: bug#41262: Weird behavior with grep regex
Date: Thu, 14 May 2020 21:52:11 +0300

Hi Loic!

On Thu, 14 May 2020 13:57:48 +0000
<loic.tregouet <at> orange.com> wrote:

> Hi,
> 
> I've reproduced a strange behaviour of grep command when a file name of a
> single letter is present in current directory .
> 
> $ echo a | grep [a-z]
> a
> $ touch t
> $ echo a | grep [a-z]
> $ rm t
> $ echo a | grep [a-z]
> a
> $
> 

This is standard Unix shell ( sh / ksh / bash ) globbing behaviour:

https://en.wikipedia.org/wiki/Glob_%28programming%29

Quoting works:

```
[shlomif <at> localhost ~]$ cd tmp
[shlomif <at> localhost tmp]$ touch t
[shlomif <at> localhost tmp]$ echo a | grep [a-z]
[shlomif <at> localhost tmp]$ echo a | grep '[a-z]'
a
[shlomif <at> localhost tmp]$ echo a | grep "[a-z]"
a
[shlomif <at> localhost tmp]$ 
```

Also see https://perl-begin.org/topics/security/code-markup-injection/ .

> 
> Any idea ?
> 
> Regards
> 
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Ahem :(

-- 

Shlomi Fish       https://www.shlomifish.org/
https://www.shlomifish.org/humour/Summerschool-at-the-NSA/

Knuth is not God! Typing “God” into Google and pressing “I’m Feeling Lucky”
will not lead you to his homepage.
    — https://www.shlomifish.org/humour/bits/facts/Knuth/

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