Grant - check out Russ Cox's web page on this very subject: Implementing Regular Expressions ᐧ On Thu, Mar 2, 2023 at 1:55 PM Grant Taylor via COFF 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 > >