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

Tor Browser Bundle 7.0.7 - Anonymize Web...
The Tor Browser Bundle is an easy-to-use portable package of Tor, Vidalia, Torbutton, and a Firefox fork preconfigured to work together out of the box. It contains a modified copy of Firefox that... Read more
Data Rescue 5.0.1 - Powerful hard drive...
Data Rescue’s new and improved features let you scan, search, and recover your files faster than ever before. We have modernized the file-preview capabilities, added new files types to the recovery... Read more
Alfred 3.5.1 - Quick launcher for apps a...
Alfred is an award-winning productivity application for OS X. Alfred saves you time when you search for files online or on your Mac. Be more productive with hotkeys, keywords, and file actions at... Read more
Tunnelblick 3.7.3 - GUI for OpenVPN.
Tunnelblick is a free, open source graphic user interface for OpenVPN on OS X. It provides easy control of OpenVPN client and/or server connections. It comes as a ready-to-use application with all... Read more
DEVONthink Pro 2.9.16 - Knowledge base,...
Save 10% with our exclusive coupon code: MACUPDATE10 DEVONthink Pro is your essential assistant for today's world, where almost everything is digital. From shopping receipts to important research... Read more
AirRadar 4.0 - $9.95
With AirRadar, scanning for wireless networks is now easier and more personalized! It allows you to scan for open networks and tag them as favourites or filter them out. View detailed network... Read more
ForkLift 3.0.8 Beta - Powerful file mana...
ForkLift is a powerful file manager and ferociously fast FTP client clothed in a clean and versatile UI that offers the combination of absolute simplicity and raw power expected from a well-executed... Read more
Opera 48.0.2685.50 - High-performance We...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more
FotoMagico 5.5 - Powerful slideshow crea...
FotoMagico lets you create professional slideshows from your photos and music with just a few, simple mouse clicks. It sports a very clean and intuitive yet powerful user interface. High image... Read more
Adobe Audition CC 2018 11.0.0 - Professi...
Audition CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Audition customer). Adobe Audition CC 2018 empowers you to create and... Read more

Wheels of Aurelia (Games)
Wheels of Aurelia 1.0.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0.1 (iTunes) Description: | Read more »
Halcyon 6: Starbase Commander guide - ti...
Halcyon 6 is a well-loved indie RPG with stellar tactical combat and some pretty good writing, too. It's now landed on the App Store, so mobile fans, if you're itching for a good intergalactic adventure, here's your game. Being a strategy RPG, the... | Read more »
Game of Thrones: Conquest guide - how to...
Fans of base building games might be excited to know that yet another entry in the genre has materialized - Game of Thrones: Conquest. Yes, you can now join the many kingdoms of the famed book series, or create your own, as you try to conquer... | Read more »
Halcyon 6: Starbase Commander (Games)
Halcyon 6: Starbase Commander 1.4.2.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.4.2.0 (iTunes) Description: An epic space strategy RPG with base building, deep tactical combat, crew management, alien diplomacy,... | Read more »
Legacy of Discord celebrates its 1 year...
It’s been a thrilling first year for fans of Legacy of Discord, the stunning PvP dungeon-crawling ARPG from YOOZOO Games, and now it’s time to celebrate the game’s first anniversary. The developers are amping up the festivities with some exciting... | Read more »
3 reasons to play Thunder Armada - the n...
The bygone days of the Battleship board game might have past, but naval combat simulators still find an audience on mobile. Thunder Armada is Chinese developer Chyogames latest entry into the genre, drawing inspiration from the explosive exchanges... | Read more »
Experience a full 3D fantasy MMORPG, as...
Those hoping to sink their teeth into a meaty hack and slash RPG that encourages you to fight with others might want to check out EZFun’s new Eternity Guardians. Available to download for iOS and Android, Eternity Guardians is an MMORPG that lets... | Read more »
Warhammer Quest 2 (Games)
Warhammer Quest 2 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Dungeon adventures in the Warhammer World are back! | Read more »
4 of the best Halloween updates for mobi...
Halloween is certainly one of our favorite times for mobile game updates. Many popular titles celebrate this spooky season with fun festivities that can stretch from one week to even the whole month. As we draw closer and closer to Halloween, we'... | Read more »
Fire Rides guide - how to swing to succe...
It's another day, which means another Voodoo game has come to glue our hands to our mobile phones. Yes, it's been an especially prolific month for this particular mobile publisher, but we're certainly not complaining. Fire Rides is yet another... | Read more »

Price Scanner via MacPrices.net

Apple restocks full line of refurbished 13″ M...
Apple has restocked a full line of Apple Certified Refurbished 2017 13″ MacBook Pros for $200-$300 off MSRP. A standard Apple one-year warranty is included with each MacBook, and shipping is free.... Read more
13″ 3.1GHz/256GB MacBook Pro on sale for $167...
Amazon has the 2017 13″ 3.1GHz/256GB Space Gray MacBook Pro on sale today for $121 off MSRP including free shipping: – 13″ 3.1GHz/256GB Space Gray MacBook Pro (MPXV2LL/A): $1678 $121 off MSRP Keep an... Read more
13″ MacBook Pros on sale for up to $120 off M...
B&H Photo has 2017 13″ MacBook Pros in stock today and on sale for up to $120 off MSRP, each including free shipping plus NY & NJ sales tax only: – 13-inch 2.3GHz/128GB Space Gray MacBook... Read more
15″ MacBook Pros on sale for up to $200 off M...
B&H Photo has 15″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 15″ 2.8GHz MacBook Pro Space Gray (MPTR2LL/A): $2249, $150... Read more
Roundup of Apple Certified Refurbished iMacs,...
Apple has a full line of Certified Refurbished 2017 21″ and 27″ iMacs available starting at $1019 and ranging up to $350 off original MSRP. Apple’s one-year warranty is standard, and shipping is free... Read more
Sale! 27″ 3.8GHz 5K iMac for $2098, save $201...
Amazon has the 27″ 3.8GHz 5K iMac (MNED2LL/A) on sale today for $2098 including free shipping. Their price is $201 off MSRP, and it’s the lowest price available for this model (Apple’s $1949... Read more
Sale! 10″ Apple WiFi iPad Pros for up to $100...
B&H Photo has 10.5″ WiFi iPad Pros in stock today and on sale for $50-$100 off MSRP. Each iPad includes free shipping, and B&H charges sales tax in NY & NJ only: – 10.5″ 64GB iPad Pro: $... Read more
Apple iMacs on sale for up to $130 off MSRP w...
B&H Photo has 21-inch and 27-inch iMacs in stock and on sale for up to $130 off MSRP including free shipping. B&H charges sales tax in NY & NJ only: – 27″ 3.8GHz iMac (MNED2LL/A): $2179 $... Read more
2017 3.5GHz 6-Core Mac Pro on sale for $2799,...
B&H Photo has the 2017 3.5GHz 6-Core Mac Pro (MD878LL/A) on sale today for $2799 including free shipping plus NY & NJ sales tax only . Their price is $200 off MSRP. Read more
12″ 1.2GHz Space Gray MacBook on sale for $11...
Amazon has the 2017 12″ 1.2GHz Space Gray Retina MacBook on sale for $100 off MSRP. Shipping is free: 12″ 1.2GHz Space Gray MacBook: $1199.99 $100 off MSRP Read more

Jobs Board

Product Manager - *Apple* Pay on the *Appl...
Job Summary Apple is looking for a talented product manager to drive the expansion of Apple Pay on the Apple Online Store. This position includes a unique Read more
*Apple* Retail - Multiple Positions - Farmin...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Frameworks Engineer, *Apple* Watch - Apple...
Job Summary Join the team that is shaping the future of software development for Apple Watch! As a software engineer on the Apple Watch Frameworks team you will Read more
*Apple* News Product Marketing Mgr., Publish...
Job Summary The Apple News Product Marketing Manager will work closely with a cross-functional group to assist in defining and marketing new features and services. Read more
Fraud Analyst, *Apple* Advertising Platform...
Job Summary Apple Ad Platforms has an opportunity to redefine advertising on mobile devices. Apple reaches hundreds of millions of iPhone, iPod touch, and iPad Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.