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From: Clem Cole <clemc@ccc.com>
To: Grant Taylor <gtaylor@tnetconsulting.net>
Cc: COFF <coff@tuhs.org>
Subject: [COFF] Re: Requesting thoughts on extended regular expressions in grep.
Date: Thu, 2 Mar 2023 14:23:25 -0500	[thread overview]
Message-ID: <CAC20D2MS5Pp7tJ7Q10cUn-nBhNEzbaZ8_Hn-5J0wAfzd3s3M9A@mail.gmail.com> (raw)
In-Reply-To: <8d1de5c8-1f34-3d37-395d-0f1da7b062ec@spamtrap.tnetconsulting.net>

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Grant - check out Russ Cox's web page on this very subject: Implementing
Regular Expressions
<https://streaklinks.com/BaglRcA5OeZepwiX_AELMUI5/https%3A%2F%2Fswtch.com%2F%7Ersc%2Fregexp%2F>
ᐧ

On Thu, Mar 2, 2023 at 1:55 PM Grant Taylor via COFF <coff@tuhs.org> wrote:

> Hi,
>
> I'd like some thoughts ~> input on extended regular expressions used
> with grep, specifically GNU grep -e / egrep.
>
> What are the pros / cons to creating extended regular expressions like
> the following:
>
>     ^\w{3}
>
> vs:
>
>     ^(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)
>
> Or:
>
>     [ :[:digit:]]{11}
>
> vs:
>
>     ( 1| 2| 3| 4| 5| 6| 7| 8|
> 9|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31)
> (0|1|2)[[:digit:]]:(0|1|2|3|4|5)[[:digit:]]:(0|1|2|3|4|5)[[:digit:]]
>
> I'm currently eliding the 61st (60) second, the 32nd day, and dealing
> with February having fewer days for simplicity.
>
> For matching patterns like the following in log files?
>
>     Mar  2 03:23:38
>
> I'm working on organically training logcheck to match known good log
> entries.  So I'm *DEEP* in the bowels of extended regular expressions
> (GNU egrep) that runs over all logs hourly.  As such, I'm interested in
> making sure that my REs are both efficient and accurate or at least not
> WILDLY badly structured.  The pedantic part of me wants to avoid
> wildcard type matches (\w), even if they are bounded (\w{3}), unless it
> truly is for unpredictable text.
>
> I'd appreciate any feedback and recommendations from people who have
> been using and / or optimizing (extended) regular expressions for longer
> than I have been using them.
>
> Thank you for your time and input.
>
>
>
> --
> Grant. . . .
> unix || die
>
>

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  reply	other threads:[~2023-03-02 19:24 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-02 18:54 [COFF] " Grant Taylor via COFF
2023-03-02 19:23 ` Clem Cole [this message]
2023-03-02 19:38   ` [COFF] " Grant Taylor via COFF
2023-03-02 23:01   ` Stuff Received
2023-03-02 23:46     ` Steffen Nurpmeso
2023-03-03  1:08     ` Grant Taylor via COFF
2023-03-03  2:10       ` Dave Horsfall
2023-03-03  3:34         ` Grant Taylor via COFF
2023-03-02 21:53 ` Dan Cross
2023-03-03  1:05   ` Grant Taylor via COFF
2023-03-03  3:04     ` Dan Cross
2023-03-03  3:53       ` Grant Taylor via COFF
2023-03-03 13:47         ` Dan Cross
2023-03-03 19:26           ` Grant Taylor via COFF
2023-03-03 10:59 ` Ralph Corderoy
2023-03-03 13:11   ` Dan Cross
2023-03-03 13:42     ` Ralph Corderoy
2023-03-03 19:19       ` Grant Taylor via COFF
2023-03-04 10:15         ` [COFF] Reading PDFs on a mobile. (Was: Requesting thoughts on extended regular expressions in grep.) Ralph Corderoy
2023-03-07 21:49           ` [COFF] " Tomasz Rola
2023-03-07 22:46             ` Tomasz Rola
2023-06-20 16:02           ` Michael Parson
2023-06-20 21:26             ` Tomasz Rola
2023-06-22 15:45               ` Michael Parson
2023-07-10  9:08                 ` [COFF] Re: Reader, paper, tablet, phone (was: Re: Reading PDFs on a mobile. (Was: Requesting thoughts on extended regular expressions in grep.)) Tomasz Rola
2023-03-03 16:12   ` [COFF] Re: Requesting thoughts on extended regular expressions in grep Dave Horsfall
2023-03-03 17:13     ` Dan Cross
2023-03-03 17:38       ` Ralph Corderoy
2023-03-03 19:09         ` Dan Cross
2023-03-03 19:36     ` Grant Taylor via COFF
2023-03-04 10:26       ` Ralph Corderoy
2023-03-03 19:06 ` Grant Taylor via COFF
2023-03-03 19:31   ` Dan Cross
2023-03-04 10:07   ` Ralph Corderoy
2023-03-06 10:01 ` Ed Bradford
2023-03-06 21:01   ` Dan Cross
2023-03-06 21:49     ` Steffen Nurpmeso
2023-03-07  1:43     ` Larry McVoy
2023-03-07  4:01       ` Ed Bradford
2023-03-07 11:39         ` [COFF] " Ralph Corderoy
2023-03-07 18:31           ` [COFF] " Grant Taylor via COFF
2023-03-08 11:22           ` Ed Bradford
2023-03-07 16:14         ` Dan Cross
2023-03-07 17:34           ` [COFF] " Ralph Corderoy
2023-03-07 18:33             ` [COFF] " Dan Cross
2023-03-07  4:19     ` Ed Bradford

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