TweetFollow Us on Twitter

Puzzle 1: Send it by RegEx

Volume Number: 19 (2003)
Issue Number: 6
Column Tag: John and Pals' Puzzle Page

Puzzle 1: Send it by RegEx

by John A. Vink

Try to solve this programming puzzle before the score drops to zero. The puzzle is presented as a discussion among engineers in a chat room. As the engineers gather information and make suggestions, see if you can find the solution. If you solve the problem before you get to the end of the puzzle, you get the score in the left hand column.

We start off our initial monthly puzzle with something simple.

ChrisE: OK, serious question.

100 ChrisE: find . -regex ".*/Versions/[ABCDEFG]/[^/]*" finds me all the dylibs in /System/Library/Frameworks

ChrisE: But it also finds the _debug and _profile versions. What do I do to the regex to exclude files that have a _ in them?

95 JAV: Is a pipe to grep -v out of the question?

ChrisE: Yes 'cuz it's the -regex arg to find and I want to do a -exec.

90 Pie R. Square: You want [^_] in there somewhere.

ChrisE: tried [^_]*

85 BMA: Pie, the problem is that regular expression matches any substring of the path.

BMA: ChrisE, I believe you want -prune.

80 Pie R. Square: Does this give you want you want: find . -regex ".*/Versions/[ABCDEFG]/[^/_]*"

ChrisE: Yes, it does. Thx.

75 BMA: No, Pie, because [^/_]* matches the empty string.

Keith: Wouldn't you want [^_]+, since you always want at least 1 character in the filename?

70 ChrisE: Luckily I'm not passing it any empty strings.

BMA: I believe you need to put the regular expression between ^ and $ in addition.

65 BMA: Ah, i see, -regex in find is implicitly ^$.

BMA: No, Pie, consider this:

60 BMA: "foo_bar"

BMA: matches "foo[^_]*"

BMA: because there is nothing saying "match the entire string".

55 BMA: OK, then what Pie said will work, ChrisE. But in general, you can't assume that.

ChrisE: Well, the problem is to find all dylibs in /System/Library/Frameworks and exclude _debug and _profile libs, and it works for this one case, so I'm there.

ChrisE: This is just adhocery, not production.

Pie R. Square: How could it not be?

50 BMA: Pie, regular expression "a" is matched by string "bab".

BMA: Likewise regular expression "a*" is matched by string "bcb".

Pie R. Square: I just meant, I wouldn't expect find to work that way.

45 BMA: It is the only tool that i have ever seen that takes a regexp and implicitly puts it inside ^$

40 Keith: Can you pass two -regex arguments to find, and have the second one be [^(_debug)|(_profile)]. I can't tell from the manpage whether that would work or not.

35 Pie R. Square: It didn't produce any output.

30 BMA: ^ doesn't work that way, Keith.

ChrisE: It worked. Give it up. I've done what I need to do and have moved on.

Pie R. Square: ChrisE, you don't know us very well, do you?

25 BMA: Also, I do want to consider the more general problem.

BMA: It turns out that you could match your exact set with a regular expression in this case.

BMA: But what if the include and exclude sets need a regular expression?

20 BMA: Looks like find -regex RE1 -and \! -regex RE2 works.

15 Keith: Try adding a \! -name '"*_debug"' \! -name '"*_profile"' to the find, ChrisE.

ChrisE: No. It worked. I'm done. You try it.

Keith: I did. It seemed to work for me.

ChrisE: Lucky you.

10 JAV: Remember Kon & Bal's Puzzle Page? Lots of conversations here sound like that.

BMA: I looooooooooooooove Kon and Bal!

5 BMA: I am so sad there is nothing like that now.

JAV: Well, we can extract the chats from here and make one.

Pie R. Square: How about this chat?

Bubba: You should play poker with Kon.

Bubba: Hey, we could get a column in that programmers magazine!

JAV: MacTech?

ChrisE: Gotta go, see y'all later. Thanks!

Score:

85-100 Can I borrow your regular expressions handbook?

65-80 Don't go away, maybe you can help me with this

other problem...

45-60 Yeah, I remember using Unix in college too.

25-40 If you can't find it, the Terminal application is in

/Applications/Utilities

Still using Mac OS 9? Time to upgrade to that new OS.


John A. Vink (aka "JAV") is a software engineer for Apple Computer, Inc. He takes a break in the summer to follow INXS on tour. His pals are a bunch of smart friends scattered throughout the Mac programming landscape. You can contact him at vink@apple.com. (The pals reference makes sense with the "John And Pals' Puzzle Page" title)

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Whitethorn Games combines two completely...
If you have ever gone fishing then you know that it is a lesson in patience, sitting around waiting for a bite that may never come. Well, that's because you have been doing it wrong, since as Whitehorn Games now demonstrates in new release Skate... | Read more »
Call of Duty Warzone is a Waiting Simula...
It's always fun when a splashy multiplayer game comes to mobile because they are few and far between, so I was excited to see the notification about Call of Duty: Warzone Mobile (finally) launching last week and wanted to try it out. As someone who... | Read more »
Albion Online introduces some massive ne...
Sandbox Interactive has announced an upcoming update to its flagship MMORPG Albion Online, containing massive updates to its existing guild Vs guild systems. Someone clearly rewatched the Helms Deep battle in Lord of the Rings and spent the next... | Read more »
Chucklefish announces launch date of the...
Chucklefish, the indie London-based team we probably all know from developing Terraria or their stint publishing Stardew Valley, has revealed the mobile release date for roguelike deck-builder Wildfrost. Developed by Gaziter and Deadpan Games, the... | Read more »
Netmarble opens pre-registration for act...
It has been close to three years since Netmarble announced they would be adapting the smash series Solo Leveling into a video game, and at last, they have announced the opening of pre-orders for Solo Leveling: Arise. [Read more] | Read more »
PUBG Mobile celebrates sixth anniversary...
For the past six years, PUBG Mobile has been one of the most popular shooters you can play in the palm of your hand, and Krafton is celebrating this milestone and many years of ups by teaming up with hit music man JVKE to create a special song for... | Read more »
ASTRA: Knights of Veda refuse to pump th...
In perhaps the most recent example of being incredibly eager, ASTRA: Knights of Veda has dropped its second collaboration with South Korean boyband Seventeen, named so as it consists of exactly thirteen members and a video collaboration with Lee... | Read more »
Collect all your cats and caterpillars a...
If you are growing tired of trying to build a town with your phone by using it as a tiny, ineffectual shover then fear no longer, as Independent Arts Software has announced the upcoming release of Construction Simulator 4, from the critically... | Read more »
Backbone complete its lineup of 2nd Gene...
With all the ports of big AAA games that have been coming to mobile, it is becoming more convenient than ever to own a good controller, and to help with this Backbone has announced the completion of their 2nd generation product lineup with their... | Read more »
Zenless Zone Zero opens entries for its...
miHoYo, aka HoYoverse, has become such a big name in mobile gaming that it's hard to believe that arguably their flagship title, Genshin Impact, is only three and a half years old. Now, they continue the road to the next title in their world, with... | Read more »

Price Scanner via MacPrices.net

B&H has Apple’s 13-inch M2 MacBook Airs o...
B&H Photo has 13″ MacBook Airs with M2 CPUs and 256GB of storage in stock and on sale for up to $150 off Apple’s new MSRP, starting at only $849. Free 1-2 day delivery is available to most US... Read more
M2 Mac minis on sale for $100-$200 off MSRP,...
B&H Photo has Apple’s M2-powered Mac minis back in stock and on sale today for $100-$200 off MSRP. Free 1-2 day shipping is available for most US addresses: – Mac mini M2/256GB SSD: $499, save $... Read more
Mac Studios with M2 Max and M2 Ultra CPUs on...
B&H Photo has standard-configuration Mac Studios with Apple’s M2 Max & Ultra CPUs in stock today and on Easter sale for $200 off MSRP. Their prices are the lowest available for these models... Read more
Deal Alert! B&H Photo has Apple’s 14-inch...
B&H Photo has new Gray and Black 14″ M3, M3 Pro, and M3 Max MacBook Pros on sale for $200-$300 off MSRP, starting at only $1399. B&H offers free 1-2 day delivery to most US addresses: – 14″ 8... Read more
Department Of Justice Sets Sights On Apple In...
NEWS – The ball has finally dropped on the big Apple. The ball (metaphorically speaking) — an antitrust lawsuit filed in the U.S. on March 21 by the Department of Justice (DOJ) — came down following... Read more
New 13-inch M3 MacBook Air on sale for $999,...
Amazon has Apple’s new 13″ M3 MacBook Air on sale for $100 off MSRP for the first time, now just $999 shipped. Shipping is free: – 13″ MacBook Air (8GB RAM/256GB SSD/Space Gray): $999 $100 off MSRP... Read more
Amazon has Apple’s 9th-generation WiFi iPads...
Amazon has Apple’s 9th generation 10.2″ WiFi iPads on sale for $80-$100 off MSRP, starting only $249. Their prices are the lowest available for new iPads anywhere: – 10″ 64GB WiFi iPad (Space Gray or... Read more
Discounted 14-inch M3 MacBook Pros with 16GB...
Apple retailer Expercom has 14″ MacBook Pros with M3 CPUs and 16GB of standard memory discounted by up to $120 off Apple’s MSRP: – 14″ M3 MacBook Pro (16GB RAM/256GB SSD): $1691.06 $108 off MSRP – 14... Read more
Clearance 15-inch M2 MacBook Airs on sale for...
B&H Photo has Apple’s 15″ MacBook Airs with M2 CPUs (8GB RAM/256GB SSD) in stock today and on clearance sale for $999 in all four colors. Free 1-2 delivery is available to most US addresses.... Read more
Clearance 13-inch M1 MacBook Airs drop to onl...
B&H has Apple’s base 13″ M1 MacBook Air (Space Gray, Silver, & Gold) in stock and on clearance sale today for $300 off MSRP, only $699. Free 1-2 day shipping is available to most addresses in... Read more

Jobs Board

Medical Assistant - Surgical Oncology- *Apple...
Medical Assistant - Surgical Oncology- Apple Hill Location: WellSpan Medical Group, York, PA Schedule: Full Time Sign-On Bonus Eligible Remote/Hybrid Regular Apply Read more
Omnichannel Associate - *Apple* Blossom Mal...
Omnichannel Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Cashier - *Apple* Blossom Mall - JCPenney (...
Cashier - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Blossom Mall Read more
Operations Associate - *Apple* Blossom Mall...
Operations Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Business Analyst | *Apple* Pay - Banco Popu...
Business Analyst | Apple PayApply now " Apply now + Apply Now + Start applying with LinkedIn Start + Please wait Date:Mar 19, 2024 Location: San Juan-Cupey, PR Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.