TweetFollow Us on Twitter

December 96 - KON & BAL'S PUZZLE PAGE: Folder Fun

KON & BAL'S PUZZLE PAGE: Folder Fun

Konstantin Othmer and Bruce Leak

See if you can solve this programming puzzle, presented in the form of a dialog between Konstantin Othmer (KON) and Bruce Leak (BAL). The dialog gives clues to help you. Keep guessing until you're done; your score is the number to the left of the clue that gave you the correct answer. Even if you never run into the particular problems being solved here, you'll learn some valuable debugging techniques that will help you solve your own programming conundrums. And you'll also learn interesting Macintosh trivia.

>
KON It's you again.
BAL It seems our bid for drumming up Puzzle Page authors hasn't gone well.
KON I guess everyone's waiting for the Mac OS 8 release. From what I hear, they'll be waiting quite a while.
BAL I've got a lot of work to do. Can we get on with this?
KON OK. Have you ever heard of Retrospect Remote?
BAL Yeah, we run it. It's that backup program. It slows your machine to a crawl when it's doing its thing, but we've never had a problem with it. Our engineers don't allow it on their machines, though.
KON Apparently someone went around one morning and installed it while we were all sleeping. It's been running great for the last year, but suddenly one of the machines started showing an execution error.
BAL Easy enough. Go check out the logs and see what it's complaining about.

100KON It says folders are nested too deep on that machine. Sure enough, the machine has a folder called "<unknown name>," and inside that folder is another called "<unknown name>," and so on. It was mixed in with our project files.
BAL What system are you running?
KON A Power Mac 7100/66 with 32 MB of RAM and an 800 MB hard disk, running system version 7.1.2 -- the "last trusted system," according to Chris Derossi.
BAL What happens when you use the Finder to get info on the folder?
90 KON It says there are 99 items inside this one for zero K of disk space.
BAL Go in a level and try the same thing. Still 99 items?
KON Yep.
BAL Go in a few more levels and rename one of the folders. Come back out and go back in. Anything unusual?
KON Nope. The renamed folder kept its new name. The Finder tells you there are 99 items inside it.
BAL Just keep opening folders. How deep does it go?
80 KON After opening folders for a few minutes, you get too bored to continue.
BAL Rename every tenth folder or so, to create some landmarks. Dig down doing this. Can you Command-click on the window title and see the whole hierarchy?
KON Yes. You're doing one heck of a test on the pop-up menu manager.
BAL So, what happens?
70 KON After you do this about 150 times, the Finder displays the familiar "out of memory" message. It says you might try closing some windows to make more memory available. I have the feeling this might be one case where that advice actually works!
BAL Do a Get Info on the hard drive. How many items does it have?
KON 16,774 items on disk.
BAL Somehow I was expecting a larger number! Try copying the folder.
KON We crash.
BAL Where? Any clues?
KON In CopyDoubler.
BAL That sounds like a subject for another column. Hold down the Control key when copying the folder to tell CopyDoubler to stay out of it.
60 KON The Finder puts up the copy dialog, waits about two minutes, advances the thermometer the entire way in about three seconds, and then waits another two minutes before finishing. The copy dialog says there are 100 items to be copied. You now have two folder hierarchies.
BAL That's interesting. I've seen the Finder copy way more than 100 items at one time, but somehow its knowledge of folder nesting is limited to 99 or 100. Do a Get Info on the drive again and see how many new items were created.
KON Now there are 18,679 items on disk -- 1,905 new ones.
BAL Copy it to a file server.
55 KON OK. Now the Finder does the copy the same as before, except after the thermometer is finished, the dialog stays up, waiting for a long time.
BAL How long?
KON Suppose we go to a long dinner at the Peppermill Lounge. When we come back it still won't be done.
BAL Look at the folder hierarchy on the network from another Mac.
KON While it's still copying?
BAL Sure.
50 KON You see a bunch of folders, as you'd expect, except the network is really slow. Apparently the Finder is generating a lot of network traffic trying to create all those directories.
BAL Stop that file copy.
45 KON The Stop button in the copy dialog is highlighted (indicating that you pressed it), and the network is back to normal, but the copy dialog doesn't go away.
BAL Reboot and look at the folders in Standard File.
KON No new clues. How deep do you want do go?
BAL Hmm. Try running Norton Utilities on the disk.
KON There were a few bundle bits that are wrong. But once those are fixed, Norton says the disk is fine.
BAL Try DropStuffing the folder.
KON DropStuff crashes.
BAL Try Disk First Aid.
40 KON It tells you that the folder nesting exceeds the Finder-recommended nesting of 100. But other than that, it says the disk is fine.
BAL I guess those folders are really there. The system is running into a bunch of boundary conditions trying to deal with them. The question is how they got there, and I'm not sure how we figure that out given that all we have is a smoking gun.
KON Wait a second...the column isn't supposed to end this way!
BAL OK. I've got an idea. I'll try looking at these folders from MPW with a files -r -c command.
35 KON MPW prints out a bunch of folders and then crashes. The interesting thing is that it crashed right after printing out the 100th level down, which we know from the "rename every tenth folder" exercise we did earlier.
BAL Well, there are some mysteries that we should be able to solve. Clearly, some software on this machine created the folder called "<unknown name>," probably when a directory with a null name or some other exception condition was encountered.
KON OK.
BAL It's probably the Finder, the File Manager, or one of the applications that's commonly used on the machine. Let's ask Paul Mercer if he knows anything about it.
30 Paul First of all, the Finder isn't going to rename a folder on you. And second, even if it did, no one on the Finder team would give the folder a name that contains an angle bracket -- that's just too unpleasant aesthetically. Maybe the File Manager would do such a thing, though.
KON We could try Dave Feldman. I'm not sure he'd have the same issues with angle brackets that Paul has.
25 Dave No issue with angle brackets here! But the File Manager doesn't ever attempt to detect or fix damaged catalog info. It will rebuild the volume bitmap (that long pause when remounting a disk after a system crash), but it leaves everything else alone. No matter how much it's abused by the Finder, the File Manager will never surreptitiously set a folder to "<unknown name>." Tell Paul I said what does he know, he's been gone from Apple long enough to have forgotten what little he once knew about the File Manager. Furthermore, the File Manager doesn't care how deep you nest folders; that's a Finder problem.
BAL Well, the system hasn't changed much since either of those guys left Apple, so it's probably something else. Maybe you can get someone at Apple to search all the system sources and see if they can come up with a hit on "unknown name."
20 KON I talked to Jim Luther about it and he said it shows up in only one place -- the Alias Manager. Apparently the Alias Manager will store the name of the user who created the alias as part of the alias record. If a user who logs on as a guest creates an alias, the name of the alias creator is set to "unknown name," but there are no angle brackets.
BAL Let's grep the hard disk and see if we can find any hits on "<unknown name>."
KON How do you propose we do that?
BAL Have you seen AltaVista?
KON You mean the search engine on the Internet? Totally awesome. When you do a query they can instantly give you a list of the top hits from any Web site. But what does that have to do with this puzzle?
BAL Well, I figure they can search huge amounts of data way faster than we could ever do it on our local machine. So we dump the entire contents of the hard disk to a Web page, register it with AltaVista, and perform the search.
KON A little unrealistic, but not a bad idea.
BAL Ron Avitzur thought it up.
KON For those keeping score, you're approaching 15.
BAL OK, OK. I'll use Norton Disk Editor and search the whole volume for the string "<unknown name>."
15 KON The first hit is in the catalog. I get the feeling you're going to find at least 1905 of these on this disk, probably more since you duplicated the folders so many times.
BAL OK. Try it on one of your other development machines.
10 KON The string is found in a bunch of places but the sectors aren't owned by a file. But then the needle in the haystack pokes your probing finger -- you find the string in the MPW Shell application.
BAL Open up MPW Shell with ResEdit and find out which resource it's in.
KON Duh! Wrong tool for the job! ResEdit can't search the entire resource fork.
BAL OK. Use Resorcerer.
KON You find the string in CODE resource 27, called %A5Init.
BAL So, it sounds like we should contact someone in MPW land and see if they know what's going on. Here's Alex McKale; maybe he can help us.
5 Alex Sure enough, Projector will create folders with the name "<unknown name>." CheckOutDir creates a folder hierarchy that matches the project hierarchy.
BAL The project hierarchy on this machine is only three or four levels deep, not 1905! Any explanation for that?
Alex Did the machine ever crash while checking out? Maybe some script got in an infinite loop, and you hit the reset button or crashed after some time. This would mean the depth of the hierarchy is based on how long the machine was running in the loop, rather than on some magic number, such as everyone's favorite year plus 1.
KON It happened on Richard's machine. He says his Mac crashes all the time, and he'd be hard pressed to tell you what it was doing during any particular crash.
BAL Hmm. I guess we just need a plausible explanation. Any ideas, Alex?
Alex Your guess is as good as mine. CheckOutDir does very little error checking, so if the project tree got munged -- for example, if there was no terminator in the project folder hierarchy -- it would keep creating folders called "<unknown name>" until it hit a terminator. Give me a reproducible case, and this thing is dead meat.
KON No can do. I guess the exact cause will remain a mystery, along with the true nature of consciousness, the details of Jimmy Hoffa's demise, and the location of my other red sock. Well, at least we managed to narrow it down to Projector, so we can point both our accusatory fingers in the same direction. If nothing else, maybe this will get the Projector folks to add a little more error checking to CheckOutDir.
BAL Nasty.
KON Yeah.

SCORING

70-100Congratulations! You win free lifetime upgrades to MPW.
45-60You win a free copy of Mac OS 8.
25-40You win a lifetime subscription to eWorld.
5-20You win a dinner with Paul and Dave.


KONSTANTIN OTHMER AND BRUCE LEAK are cashing in on the enormous popularity of the Puzzle Page by starting their own online magazine. After rejecting titles like MacsBug Life and Dead Mackerel, they've settled on Mired as the name for their daily diary of debugging. The first issue will include hard-hitting articles like "MacsBug: The Best Command-Line Interface for the Mac?" and "Celebrity dcmds." Watch for it soon in your local cybernews shop!*

Thanks to Chris Derossi, Dave Feldman, Jim Luther, Alex McKale, and Paul Mercer for reviewing this column.*

 
AAPL
$100.96
Apple Inc.
-0.83
MSFT
$47.52
Microsoft Corpora
+0.84
GOOG
$596.08
Google Inc.
+6.81

MacTech Search:
Community Search:

Software Updates via MacUpdate

WhatRoute 1.13.0 - Geographically trace...
WhatRoute is designed to find the names of all the routers an IP packet passes through on its way from your Mac to a destination host. It also measures the round-trip time from your Mac to the... Read more
Chromium 37.0.2062.122 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. FreeSMUG-Free OpenSource Mac User Group build is... Read more
Attachment Tamer 3.1.14b9 - Take control...
Attachment Tamer gives you control over attachment handling in Apple Mail. It fixes the most annoying Apple Mail flaws, ensures compatibility with other email software, and allows you to set up how... Read more
Duplicate Annihilator 5.0 - Find and del...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator detects... Read more
jAlbum Pro 12.2 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code!... Read more
jAlbum 12.2 - Create custom photo galler...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results Simply drag and drop photos into groups, choose a design... Read more
Quicken 2015 2.0.4 - Complete personal f...
Quicken 2015 helps you manage all your personal finances in one place, so you can see where you're spending and where you can save. Quicken automatically categorizes your financial transactions,... Read more
iMazing 1.0 - Complete iOS device manage...
iMazing (formerly DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and... Read more
Xcode 6.0.1 - Integrated development env...
Apple Xcode is Apple Computer's integrated development environment (IDE) for OS X. The full Xcode package is free to ADC members and includes all the tools you need to create, debug, and optimize... Read more
Apple Safari 7.1 - Apple's Web brow...
Apple Safari in OS X Mavericks brings you all-new ways to find and enjoy the best of the web. It works with iCloud to give you a seamless browsing experience across all your devices. It looks out for... Read more

Latest Forum Discussions

See All

View Source – HTML, JavaScript and CSS...
View Source – HTML, JavaScript and CSS 1.0 Device: iOS Universal Category: Utilities Price: $.99, Version: 1.0 (iTunes) Description: View Source is an app plus an iOS 8 Safari extension that makes it easy to do one key web developer... | Read more »
Avenged Sevenfold’s Hail To The King: De...
Avenged Sevenfold’s Hail To The King: Deathbat is Coming to iOS on October 16th Posted by Jessica Fisher on September 19th, 2014 [ permalink ] Just in time for Halloween, on October 16 Avenged Sevenfold will be launching | Read more »
Talisman Has Gone Universal – Can Now be...
Talisman Has Gone Universal – Can Now be Played on the iPhone Posted by Jessica Fisher on September 19th, 2014 [ permalink ] | Read more »
Tap Army Review
Tap Army Review By Jennifer Allen on September 19th, 2014 Our Rating: :: SHOOT EM ALLUniversal App - Designed for iPhone and iPad Mindless but fun, Tap Army is a lane-based shooter that should help you relieve some stress.   | Read more »
Monsters! Volcanoes! Loot! Epic Island f...
Monsters! Volcanoes! Loot! | Read more »
Plunder Pirates: Tips, Tricks, Strategie...
Ahoy There, Seadogs: Interested in knowing our thoughts on all this plundering and pirating? Check out our Plunder Pirates Review! Have you just downloaded the rather enjoyable pirate-em-up Plunder Pirates and are in need of some assistance? Never... | Read more »
Goat Simulator Review
Goat Simulator Review By Lee Hamlet on September 19th, 2014 Our Rating: :: THE GRUFFEST OF BILLY GOATSUniversal App - Designed for iPhone and iPad Unleash chaos as a grumpy goat in this humorous but short-lived casual game.   | Read more »
A New and Improved Wunderlist is Here fo...
A New and Improved Wunderlist is Here for iOS 8 Posted by Jessica Fisher on September 19th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Evernote Update for iOS 8 Adds Web Clipp...
Evernote Update for iOS 8 Adds Web Clipping, Quick Notes, and More Posted by Ellis Spice on September 19th, 2014 [ permalink ] | Read more »
Apple Names Ultimate Productivity Bundl...
Apple Names Ultimate Productivity Bundle by Readdle as the Essential Bundle on the App Store Posted by Jessica Fisher on September 19th, 2014 [ permalink | Read more »

Price Scanner via MacPrices.net

Mac Pros available for up to $260 off MSRP
Adorama has Mac Pros on sale for up to $260 off MSRP. Shipping is free, and Adorama charges sales tax in NY & NJ only: - 4-core Mac Pro: $2839.99, $160 off MSRP - 6-core Mac Pro: $3739.99, $260... Read more
13-inch 2.6GHz/256GB Retina MacBook Pros avai...
B&H Photo has the 13″ 2.6GHz/256GB Retina MacBook Pro on sale for $1379 including free shipping plus NY sales tax only. Their price is $120 off MSRP. Read more
Previous-generation 15-inch 2.0GHz Retina Mac...
B&H Photo has leftover previous-generation 15″ 2.0GHz Retina MacBook Pros now available for $1599 including free shipping plus NY sales tax only. Their price is $400 off original MSRP. B&H... Read more
21″ 2.7GHz iMac available for $1179, save $12...
Adorama has 21″ 2.7GHz Hawell iMacs on sale for $1179.99 including free shipping. Their price is $120 off MSRP. NY and NJ sales tax only. Read more
iOS 8 Adoption Rate Slower than iOS 7, 6, Hit...
Apple began pushing out iOS 8 updates to eligible devices around 1pm ET on September 17, 2014. However, unlike with iOS 7, which boasted a wide variety of differences from its predecessor iOS 6, in... Read more
LIkely Final Definitive OS X 10.9.5 Mavericks...
Apple has released what will almost certainly be the last incremental version number update of OS X 10.9 Mavericks (save for futire security updates) before OS X 10.10 Yosemite is released next month... Read more
Fingerprints, Apple Pay and Identity Theft Wa...
On Sep 9th, CEO Tim Cook unveiled Apple Pay, along with the new iPhone 6 and iWatch. Apple Pay is a newly developed technology that utilizes a near field communication (NFC) to enable customer... Read more
Amazon Introduces Two All-New Kindles
Amazon on Thursday introduced the 7th generation of its Kindle dedicated e-reader device: Kindle Voyage, its top-of-the-line e-reader, and the new $79 Kindle, with a 20% faster processor, twice the... Read more
Save up to $300 on the price of a new Mac wit...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
13-inch 2.8GHz Retina MacBook Pro available f...
B&H Photo has the new 2014 13″ 2.8GHz Retina MacBook Pro on sale for $1699.99 including free shipping plus NY sales tax only. They’ll also include free copies of Parallels Desktop and LoJack for... Read more

Jobs Board

Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
*Apple* Retail - Multiple Positions (US) - A...
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
*Apple* Retail - Multiple Positions (US) - A...
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
*Apple* Retail - Multiple Positions (US) - A...
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
*Apple* Retail - Multiple Positions (US) - A...
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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.