[COFF] Requesting thoughts on extended regular expressions in grep.

[Clem Cole]

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 at 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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