GNU bug report logs - #72850
Can't match ] in [ ] regexp bug?

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Khoa Ton <khoa <at> puresynergy.com>
To: bug-grep <at> gnu.org
Subject: Can't match ] in [ ] regexp bug?
Date: Tue, 27 Aug 2024 23:02:04 -0700

I'm on Ubuntu:

$ uname -a
Linux nile 5.15.0-118-generic #128-Ubuntu SMP Fri Jul 5 09:28:59 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

I can't seem to get grep to match lines with ] in them when using [ ] expression.
grep only matches two characters string "\]" instead:

$ echo ']' | grep -E "[\]]" # supposed to return ] but doesn't
$ echo '\]' | grep -E "[\]]" # incorrectly matches '\]' but not ']'
\]

Possible grep bug:
grep doesn't seem to correctly handle escaped "\]" inside [ ] expressions.

Thank you,
Khoa

Message #8 received at 72850 <at> debbugs.gnu.org (full text, mbox):

From: arnold <at> skeeve.com
To: khoa <at> puresynergy.com, 72850 <at> debbugs.gnu.org
Subject: Re: bug#72850: Can't match ] in [ ] regexp bug?
Date: Wed, 28 Aug 2024 02:32:12 -0600

Khoa Ton <khoa <at> puresynergy.com> wrote:

> I'm on Ubuntu:
>
> $ uname -a
> Linux nile 5.15.0-118-generic #128-Ubuntu SMP Fri Jul 5 09:28:59 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
>
> I can't seem to get grep to match lines with ] in them when using [ ] expression.
> grep only matches two characters string "\]" instead:
>
> $ echo ']' | grep -E "[\]]" # supposed to return ] but doesn't
> $ echo '\]' | grep -E "[\]]" # incorrectly matches '\]' but not ']'
> \]
>
> Possible grep bug:
> grep doesn't seem to correctly handle escaped "\]" inside [ ] expressions.
>
> Thank you,
> Khoa

Grep doesn't support backslash escapes inside [...] (although awk does).

The correct way to do this is to place the ] as the first character
inside the [...], like so:

$ echo ] | grep -E '[]]'
]

HTH,

Arnold

Message #11 received at 72850 <at> debbugs.gnu.org (full text, mbox):

From: Khoa Ton <khoa <at> puresynergy.com>
To: arnold <at> skeeve.com, 72850 <at> debbugs.gnu.org
Subject: Re: bug#72850: Can't match ] in [ ] regexp bug?
Date: Thu, 29 Aug 2024 00:53:10 -0700

On 8/28/2024 1:32 AM, arnold <at> skeeve.com wrote:
> Khoa Ton <khoa <at> puresynergy.com> wrote:
> 
>> I'm on Ubuntu:
>>
>> $ uname -a
>> Linux nile 5.15.0-118-generic #128-Ubuntu SMP Fri Jul 5 09:28:59 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
>>
>> I can't seem to get grep to match lines with ] in them when using [ ] expression.
>> grep only matches two characters string "\]" instead:
>>
>> $ echo ']' | grep -E "[\]]" # supposed to return ] but doesn't
>> $ echo '\]' | grep -E "[\]]" # incorrectly matches '\]' but not ']'
>> \]
>>
>> Possible grep bug:
>> grep doesn't seem to correctly handle escaped "\]" inside [ ] expressions.
>>
>> Thank you,
>> Khoa
> 
> Grep doesn't support backslash escapes inside [...] (although awk does).
> 
> The correct way to do this is to place the ] as the first character
> inside the [...], like so:
> 
> $ echo ] | grep -E '[]]'
> ]
> 
> HTH,
> 
> Arnold
>

Thank you.

Khoa

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