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• cloning a kvm guest os to a vmdk file

  - by Bond

  I have a production environment where I am having 4 Guest OS running on a Ubuntu server which uses kvm. These OS are in an LVM based setup.I want these Virtual Machines to be in a vmdk format also.Where people would do experiments with these Virtual Machines so this in a vmware environment (or it can be Xen too) would be different from the kvm server.I would not have any control on that other environment so I want to give people vmdk images of these virtual machines. The production Virtual Machines will still keep running on kvm server but the VMs on which experiments would be done would be of type vmdk.(vmdk is a constraint) Here is output of lvscan ACTIVE '/dev/abcd/lvm1' [100.00 GiB] inherit ACTIVE '/dev/abcd/lvm2' [150.00 GiB] inherit ACTIVE '/dev/abcd/lvm3' [50.00 GiB] inherit ACTIVE '/dev/abcd/lvm4' [100.00 GiB] inherit I was reading man page of qemu-img and what I understand is I need to first create a qcow image file which I need to populate and then convert that to a vmdk file. Is that understanding correct? Now suppose /dev/abcd/lvm4 is the virtual machine with which I am going to start this experiment.I can shutdown the production VMs for some time to do this. So is the following way correct to go on server 1 (where kvm is running) qemu-img convert -c -f raw -O vmdk /dev/abcd/lvm4 /backup/lvm4.img or it will affect the lvm4 on kvm server 1. I do not want the VM running on original server to at all loose its any of the content but also have a vmdk file for each of the Guest OS on kvm. Before I proceed with any of the above things on the production machine I just want to make sure that I am doing the correct thing so I asking here.

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• How do I increase the buffer size for domain sockets in OS X 10.6

  - by Chas. Owens

  In Linux I have no problem dumping tons of data into a domain socket, but the same code on OS X 10.6.2 blows up after about 65 records. The socket reader code looks like #!/usr/bin/perl use strict; use warnings; use IO::Socket; unlink "foo"; my $sock = IO::Socket::UNIX->new ( Local => 'foo', Type => SOCK_DGRAM, Timeout => 600, ) or die "Could not create socket: $!\n"; while (<$sock>) { chomp; print "[$_]\n"; } And the client code looks like #!/usr/bin/perl use strict; use warnings; use IO::Socket; my $sock = IO::Socket::UNIX->new ( Peer => 'foo', Type => SOCK_DGRAM, Timeout => 600, ) or die "Could not create socket: $!\n"; for my $i (1 .. 1_000_000) { print $sock "$i\n" or die $!; } close $sock; The error message I get is No buffer space available at write.pl line 15.. It seems fairly obvious that there is a difference in the buffer size between Linux and OS X, but I don't know how to set it OS X (or what the possible negative side effects might be).

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• Mac OS X Lion (10.7) Drive Encryption

  - by Skoota

  My iMac has two drives (a 256 GB solid-state drive, and regular 2 TB hard drive). The Mac OS X Lion system is installed on the solid-state drive and, like many other users, I have moved my user profile folder onto the secondary 2 TB drive. However, as you may be aware, FileVault 2 on Mac OS X Lion (10.7) only encrypts the system drive. This leaves my data drive (containing my user profile folder, with all of my data) unencrypted. I am aware that work arounds for this issue exist (such as https://github.com/jridgewell/Unlock) but I am not happy with the results since they involve decrypting the data drive on startup using a LaunchDaemon (before any users have logged into the computer) essentially meaning that any user who logs onto the computer will see the unencrypted drive. I would like a method which will only unencrypted the data when an authorised user logs into the computer. As such, is there a way to do one of the following? Encrypt the entire data drive and only decrypt the drive when an authorised user logs into the computer. This would be equivalent behaviour to the Lion FileVault 2 feature, but on a secondary drive rather than the system drive. Encrypt only the user profile folder on the data drive, and only decrypt the folder when the user logs into the computer. This would be equivalent to the behaviour of FileVault 1 on previous versions of Mac OS X? I am happy to pay for a commercial third-party product that provides the required feature(s), but I have not yet been able to find one. Thanks in advance for any assistance.

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• Replacing all disks in a non-OS RAID 5 volume

  - by molecule

  Hi all, We currently have a server with 8 x HDD slots. It is a HP DL380G5 with a P400 controller. 2 x HDD are in a RAID 1+0 config and this hosts the OS. 6 x HDD are in a RAID 5 config and holds an Oracle DB. Basically the RAID 5 volume is running out of space and we would like to swap all 6 with higher capacity disks. Excuse my ignorance as I am pretty new to this... I believe we will need to backup the data, delete the RAID volume, insert the new disks, recreate the volume, and restore the data. 2 questions: Do we need to worry about the OS partition or is it completely independent so we can simply take out the 6 and insert 6 new disks and get the controller to recognize the 6 new disks and form a new RAID 5 volume? We should not need to reinstall OS or Oracle correct? Since we are going to restore the data on the volume from another source (our vendor will take care of this) but we would like to keep the existing data on the 6 disks just in case we run into issues and want to fall back, is this possible? Thanks in advance.

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• VPN Setup: Mac OS X and SonicWall

  - by noloader

  I'm trying to get VPN access up and running. The company has a SonicWall firewall/concentrator and I'm working on a Mac. I'm not sure of the SonicWall's hardware or software level. My MacBook Pro is OS X 10.8, x64, fully patched. The Mac Networking applet claims the remote server is not responding. The connection attempt subsequently fails: This is utter bullshit, as a Wireshark trace shows the Protected Mode negotiation, and then the fallback to Quick Mode: I have two questions (1) does Mac OS X VPN work in real life? (2) Are there any trustworthy (non-Apple) tools to test and diagnose the connection problem (Wireshark is a cannon and I have to interpret the results)? And a third question (off topic): what is broken in Cupertino such that so much broken software gets past their QA department? EDIT (12/14/2012): The network guy sent me "VPN Configuration Guide" (Equinox document SonicOS_Standard-6-EN). It seems an IPSec VPN now requires a Firewall Unique Identifier. Just to be sure, I revisited RFC 2409, where Main Mode, Aggressive Mode, and Quick Mode are discussed. I cannot find a reference to Firewall Unique Identifier. I think I am screwed here: I am trying to connect to a broken (non-standard) firewall, with a broken Mac OS X client. Fortunately, I can purchase VPN Tracker Personal (a {SonicWall|Equinox}-authored client) for $129US from Equinox. So much for standards....

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• How do I increase the buffer size for domain sockets in OS X 10.6

  - by Chas. Owens

  In Linux I have no problem dumping tons of data into a domain socket, but the same code on OS X 10.6.2 blows up after about 65 records. The socket reader code looks like #!/usr/bin/perl use strict; use warnings; use IO::Socket; unlink "foo"; my $sock = IO::Socket::UNIX->new ( Local => 'foo', Type => SOCK_DGRAM, Timeout => 600, ) or die "Could not create socket: $!\n"; while (<$sock>) { chomp; print "[$_]\n"; } And the client code looks like #!/usr/bin/perl use strict; use warnings; use IO::Socket; my $sock = IO::Socket::UNIX->new ( Peer => 'foo', Type => SOCK_DGRAM, Timeout => 600, ) or die "Could not create socket: $!\n"; for my $i (1 .. 1_000_000) { print $sock "$i\n" or die $!; } close $sock; The error message I get is No buffer space available at write.pl line 15.. It seems fairly obvious that there is a difference in the buffer size between Linux and OS X, but I don't know how to set it OS X (or what the possible negative side effects might be).

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• Logitech Performance MX Mouse Jumps on OS X Lion (10.7.4)

  - by Adam Thompson

  I have a Logitech MX Revolution wireless mouse that I am trying to use with OS X Lion. Everything is working except for one problem... there is a small, but quite noticeable, jump when the mouse cursor is moved. The problem is mostly prevalent when dragging and dropping files or trying to highlight items. It makes performing any task with the mouse accurately next to impossible. I did quite a bit of looking and found that all kinds of people have had mouse issues with OS X. I've tried all of the following with absolutely no success: Using the official drivers from Logitech (these performed worse than the default mouse drivers in OS X) Using SteerMouse as a third party mouse driver. This worked ever so slightly better than the default driver, but still suffered quite frequently from the skipping problem Cleaning the sensor on the mouse and ensuring it's not the result of the surface that it's being used on. Tested the mouse on a Windows machine. The mouse worked absolutely flawlessly on the other machine. Changed the channel that my wireless router operates on by the off chance my problems were the result of interference. This also had no effect. I can't think of anything else that could possibly interfere with the mouse. I'm am out of ideas on what to try, so I would really appreciate if anyone has any suggestions. I should also mention that an old wired mouse I had laying around worked just fine when I plugged it in. This really isn't the best solution, however, as I really prefer the MX Revolution.

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• Mac OS X will only upload zero-byte files through FTP

  - by tabacitu

  I'm using Mac OS X Lion and i've been having this problem with FTP (any FTP client, mind you. I tried Transmit, FileZilla, Cyberduck and the Terminal, all with the same result) I can browse files in my FTP Client, but when I upload files, the client hangs for a few seconds, then thinks it uploaded the files successfully, but it only creates a new file with one blank line in it. Sometimes, it manages to upload 4-5 lines. It then returns: 226 - Error during read from data connection 226 Transfer aborted But 2xx is a success message. It is not a server issue, since any Windows machine will upload just fine using the same network. Can anybody figure out what the problem is? It renders my mac useless for web development. The problem persists with SFTP and FTP with SSL/TLS. Later edit: Solved! Ok, turns out the problem goes away when I take out my router and connect directly through PPPoE. So the problem is with the router, I thought. But no, the problem is with the mac that connects through a router that connects through a PPPoE and tries to upload using FTP. Pretty specific, I know. The problem is with the MTU (maximum transmission unit). Apparently, mac os x breaks the file into chunks that are too large for the router to send, because the router's MTU was set lower than Mac OS X's. My router's was 1492, which is ok, but my Mac's MTU was 1500, which is unacceptable. I don't even understand why it works directly with PPPoE. Anyway, if you encounter the same problem, this is how you diagnose and fix it: In terminal, run: ifconfig | grep mtu to see what the MTU is for en0 (or en1, mine was en0) If it's 1500, run sudo ifconfig en0 mtu 1300 This should solve it. If so, it may only be until the next restart. You can also change the MTU in System Preferences \ Network \ Ethernet - Advanced \ Hardware

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• UIDs for service users in Mac OS X

  - by LaC

  Some third-party servers should be run under a special user for security reasons (eg, PostgreSQL is typically run by "postgres"). Of course, these service users should not show up in the Mac OS X login windows. I know how to create hidden users using dscl or dsimport, but I'm wondering what the best policy is for assigning UIDs (and matching GIDs). Apple's documentation states that UIDs from 0 to 100 are reserved (pg. 69), but OS X comes with several special users and groups outside that range. I used to use ids from 401 onwards for services, but I noticed that OS X 10.6 has started using that range for groups created by the Sharing pane in System Preferences. What is the recommended ID range to use for third-party services, then? Perhaps I should just use IDs in the 500 range, since all that is needed to hide a user in Snow Leopard is setting his password to "*"? Also, most of Apple's services have names starting with an underscore, with an alias sans underscore; eg, _sandbox and sandbox. Is there any special significance to this? Should I do the same for my services?

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• Cloning a git repository from a machine running OS X

  - by Mike

  Hi folks, I'm trying to host a git repository from my home OS X machine, and I'm stuck on the last step of cloning the repository from a remote system. Here's what I've done so far: On the OS X (10.6.6) machine (heretofore dubbed the "server") I created a new admin user Logged into the new user's account Installed git Created an empty git repository via "git init" Turned on remote login Set port mapping on my router (airport extreme) to send ssh traffic to the server Added a ".ssh" directory to the user's home directory From the remote machine (also an OS X 10.6.6 machine), I sent that machine's public key to the server using scp and the login credentials of the user created in step 1 To test that the server would use the remote machine's public key, I ssh'd to the server using the username of the user created in step 1 and indeed was able to connect successfully without being asked for a password I installed git on the remote machine From the remote machine I attempted to "git clone ssh://[email protected]:myrepo" (where "user", "my.server.address", and "myrepo" are all replaced by the actual username, server address and repo folder name, respectively) However, every time I try the command in step 11, I get asked to confirm the server's RSA fingerprint, then I'm asked for a password, but the password for the user I set up for that machine never works. Any advice on how to make this work would be greatly appreciated!

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• OS X Application icons missing after filesystem tampering

  - by dylan

  A while back I installed some Google software, I forget what it was, but it was something that attached itself to Google Chrome and was un-uninstallable short of uninstalling all of Chrome. It was a total pain in the a$$. Anyways, I was trying to put up a fight before going nuclear and just wiping Chrome, and during that fight, something went wrong (i.e., I didn't know what I was doing). I remember messing around with the Applications folder somehow. I don't remember what exactly I did, but it perhaps involved some interchanging between the /Applications and /User/Username/Applications folders? Definitely some tampering in those areas, I'm sure at least about that. Anyways, I've since updated and restarted my computer. Now, while all my apps work fine, many of them have blank icons - not on the Dock, those icons are fine, but in Spotlight search results, etc. Currently, my /Applications folder contains only OS X-cooked-in applications. My ~/Applications folder contains cooked in apps AND post-OS/third-party apps. There hasn't been any functionality deficit so far, but I don't like working on a machine where something isn't how it should be. I know my information was vague, but does anyone know what went wrong / how to fix it? OS X Mavericks 10.9.3

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• Simulating aspects of static-typing in a duck-typed language

  - by Mike

  In my current job I'm building a suite of Perl scripts that depend heavily on objects. (using Perl's bless() on a Hash to get as close to OO as possible) Now, for lack of a better way of putting this, most programmers at my company aren't very smart. Worse, they don't like reading documentation and seem to have a problem understanding other people's code. Cowboy coding is the game here. Whenever they encounter a problem and try to fix it, they come up with a horrendous solution that actually solves nothing and usually makes it worse. This results in me, frankly, not trusting them with code written in duck typed language. As an example, I see too many problems with them not getting an explicit error for misusing objects. For instance, if type A has member foo, and they do something like, instance->goo, they aren't going to see the problem immediately. It will return a null/undefined value, and they will probably waste an hour finding the cause. Then end up changing something else because they didn't properly identify the original problem. So I'm brainstorming for a way to keep my scripting language (its rapid development is an advantage) but give an explicit error message when an an object isn't used properly. I realize that since there isn't a compile stage or static typing, the error will have to be at run time. I'm fine with this, so long as the user gets a very explicit notice saying "this object doesn't have X" As part of my solution, I don't want it to be required that they check if a method/variable exists before trying to use it. Even though my work is in Perl, I think this can be language agnostic.

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• Program Structure Design Tools? (Top Down Design)

  - by Lee Olayvar

  I have been looking to expand my methodologies to better involve Unit testing, and i stumbled upon Behavioral Driven Design (Namely Cucumber, and a few others). I am quite intrigued by the concept as i have never been able to properly design top down, only because keeping track of the design gets lost without a decent way to record it. So on that note, in a mostly language agnostic way, are there any useful tools out there i am (probably) unaware of? Eg, i have often been tempted to try building flow charts for my programs, but i am not sure how much that will help, and it seems a bit confusing to me how i could make a complex enough flow chart to handle the logic of a full program, and all its features.. ie, it just seems like flow charts would be limiting in the design scheme.. or possibly grow to an unmaintainable scale. BDD methods are nice, but with a system that is so tied to structure, tying into the language and unit testing seems like a must (for it to be worth it) and it seems to be hard to find something to work well with both Python and Java (my two main languages). So anyway.. on that note, any comments are much appreciated. I have searched around on here and it seems like top down design is a well discussed topic, but i haven't seen too much reference to tools themselves, eg, flow chart programs, etc. I am on Linux, if it matters (in the case of programs).

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• What Language Feature Can You Just Not Live Without?

  - by akdom

  I always miss python's built-in doc strings when working in other languages. I know this may seem odd, but it allows me to cut down significantly on excess comments while still providing a clean description of my code and any interfaces therein. What Language Feature Can You Just Not Live Without? If someone were building a new language and they asked you what one feature they absolutely must include, what would it be? This is getting kind of long, so I figured I'd do my best to summarize: Paraphrased to be language agnostic. If you know of a language which uses something mentioned, please at it in the parenthesis to the right of the feature. And if you have a better format for this list, by all means try it out (if it doesn't seem to work, I'll just roll back). Regular Expressions ~ torial (Perl) Garbage Collection ~ SaaS Developer (Python, Perl, Ruby, Java, .NET) Anonymous Functions ~ Vinko Vrsalovic (Lisp, Python) Arithmetic Operators ~ Jeremy Ross (Python, Perl, Ruby, Java, C#, Visual Basic, C, C++, Pascal, Smalltalk, etc.) Exception Handling ~ torial (Python, Java, .NET) Pass By Reference ~ Chris (Python) Unified String Format WalloWizard (C#) Generics ~ torial (Python, Java, C#) Integrated Query Equivalent to LINQ ~ Vyrotek (C#) Namespacing ~ Garry Shutler () Short Circuit Logic ~ Adam Bellaire ()

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• Design pattern to use instead of multiple inheritance

  - by mizipzor

  Coming from a C++ background, Im used to multiple inheritance. I like the feeling of a shotgun squarely aimed at my foot. Nowadays, I work more in C# and Java, where you can only inherit one baseclass but implement any number of interfaces (did I get the terminology right?). For example, lets consider two classes that implement a common interface but different (yet required) baseclasses: public class TypeA : CustomButtonUserControl, IMagician { public void DoMagic() { // ... } } public class TypeB : CustomTextUserControl, IMagician { public void DoMagic() { // ... } } Both classes are UserControls so I cant substitute the base class. Both needs to implement the DoMagic function. My problem now is that both implementations of the function are identical. And I hate copy-and-paste code. The (possible) solutions: I naturally want TypeA and TypeB to share a common baseclass, where I can write that identical function definition just once. However, due to having the limit of just one baseclass, I cant find a place along the hierarchy where it fits. One could also try to implement a sort of composite pattern. Putting the DoMagic function in a separate helper class, but the function here needs (and modifies) quite a lot of internal variables/fields. Sending them all as (reference) parameters would just look bad. My gut tells me that the adapter pattern could have a place here, some class to convert between the two when necessery. But it also feels hacky. I tagged this with language-agnostic since it applies to all languages that use this one-baseclass-many-interfaces approach. Also, please point out if I seem to have misunderstood any of the patterns I named. In C++ I would just make a class with the private fields, that function implementation and put it in the inheritance list. Whats the proper approach in C#/Java and the like?

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• is there a Universal Model for languages?

  - by Smandoli

  Many programming languages share generic and even fairly universal features. For example, if you compared Java, VB6, .NET, PHP, Python, then you would find common functions such as control structures, numeric and string manipulation, etc. What has been done to define these features at a meta-language (or language-agnostic) level? UML offers a descriptive reference of software in every aspect, but the real-world focus seems to be data processes. Is UML relevant? I'm not asking "Why we don't have a single language that replaces the current plethora." We need many different tools (at least in this eon). I'm not asking that all languages fit a template -- assembly vs. compiled languages are different enough to make that unfeasible (and some folks call HTML a language, though I wouldn't). Any attempt would start with a properly narrow scope. In line with this, I wouldn't expect the model to cover even a small selection with full validity. I would expect however that such a model could be used to transpose from one language to another (with limited goals -- think jist translation).

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• Is this a variation of the traveling salesman problem?

  - by Ville Koskinen

  I'm interested in a function of two word lists, which would return an order agnostic edit distance between them. That is, the arguments would be two lists of (let's say space delimited) words and return value would be the minimum sum of the edit (or Levenshtein) distances of the words in the lists. Distance between "cat rat bat" and "rat bat cat" would be 0. Distance between "cat rat bat" and "fat had bad" would be the same as distance between "rat bat cat" and "had fat bad", 4. In the case the number of words in the lists are not the same, the shorter list would be padded with 0-length words. My intuition (which hasn't been nurtured with computer science classes) does not find any other solution than to use brute force: |had|fat|bad| a solution ---+---+---+---+ +---+---+---+ cat| 2 | 1 | 2 | | | 1 | | ---+---+---+---+ +---+---+---+ rat| 2 | 1 | 2 | | 3 | | | ---+---+---+---+ +---+---+---+ bat| 2 | 1 | 1 | | | | 4 | ---+---+---+---+ +---+---+---+ Starting from the first row, pick a column and go to the next rows without ever revisiting a column you have already visited. Do this over and over again until you've tried all combinations. To me this sounds a bit like the traveling salesman problem. Is it, and how would you solve my particular problem?

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• should the builder reset its build environment after delivering the product

  - by Sudhi

  I am implementing a builder where in the deliverable is retrieved by calling Builder::getProduct() . The director asks various parts to build Builder::buildPartA() , Builder::buildPartB() etc. in order to completely build the product. My question is, once the product is delivered by the Builder by calling Builder::getProduct(), should it reset its environment (Builder::partA = NULL;, Builder::partB = NULL;) so that it is ready to build another product? (with same or different configuration?) I ask this as I am using PHP wherein the objects are by default passed by reference (nope, I don't want to clone them, as one of their field is a Resource) . However, even if you think from a language agnostic point of view, should the Builder reset its build environment ? If your answer is 'it depends on the case' what use cases would justify reseting the environment (and other way round) ? For the sake of providing code sample here's my Builder::gerProcessor() which shows what I mean by reseting the environment /** * @see IBuilder::getProessor() */ public function getProcessor() { if($this->_processor == NULL) { throw new LogicException('Processor not yet built!'); } else { $retval = $this->_processor; $this->_product = NULL, $this->_processor = NULL; } return $retval; }

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• Should client-server code be written in one "project" or two?

  - by Ricket

  I've been beginning a client-server application. At first I naturally created two projects in Eclipse, two source control repositories, etc. But I'm quickly seeing that there is a bit of shared code between the two that would probably benefit to sharing instead of copying. In addition, I've been learning and trying test-driven development, and it seems to me that it would be easier to test based on real client components rather than having to set up a huge amount of code just to mock something, when the code is probably mostly in the client. My biggest concern in merging the client and server is of security; how do I ensure that the server pieces of the code do not reach an user's computer? So especially if you are writing client-server applications yourself (and especially in Java, though this can turn into a language-agnostic question if you'd like to share your experience with this in other languages), what sort of separation do you keep between your client and server code? Are they just in different packages/namespaces or completely different binaries using shared libraries, or something else entirely? How do you test the code together and yet ship separately?

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• How to keep confirmation messages after POST while doing a post-submit redirect?

  - by MicE

  Hello, I'm looking for advise on how to share certain bits of data (i.e. post-submit confirmation messages) between individual requests in a web application. Let me explain: Current approach: user submits an add/edit form for a resource if there were no errors, user is shown a confirmation with links to: submit a new resource (for "add" form) view the submitted/edited resource view all resources (one step above in hierarchy) user then has to click on one of the three links to proceed (i.e. to the page "above") Progmatically, the form and its confirmation page are one set of classes. The page above that is another. They can technically share code, but at the moment they are both independent during processing of individual requests. We would like to amend the above as follows: user submits an add/edit form for a resource if there were no errors, the user is redirected to the page with all resources (one step above in hierarchy) with one or more confirmation messages displayed at the top of the page (i.e. success message, to whom was the request assigned, etc) This will: save users one click (they have to go through a lot of these add/edit forms) the post-submit redirect will address common problems with browser refresh / back-buttons What approach would you recommend for sharing data needed for the confirmation messages between the two requests, please? I'm not sure if it helps, it's a PHP application backed by a RESTful API, but I think that this is a language-agnostic question. A few simple solutions that come to mind are to share the data via cookies or in the session, this however breaks statelessness and would pose a significant problem for users who work in several tabs (the data could clash together). Passing the data as GET parameters is not suitable as we are talking about several messages which are dynamic (e.g. changing actors, dates). Thanks, M.

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• How would I code a complex formula parser manually?

  - by StormianRootSolver

  Hm, this is language - agnostic, I would prefer doing it in C# or F#, but I'm more interested this time in the question "how would that work anyway". What I want to accomplish ist: a) I want to LEARN it - it's about my ego this time, it's for a fun project where I want to show myself that I'm a really good at this stuff b) I know a tiny little bit about EBNF (although I don't know yet, how operator precedence works in EBNF - Irony.NET does it right, I checked the examples, but this is a bit ominous to me) c) My parser should be able to take this: 5 * (3 + (2 - 9 * (5 / 7)) + 9) for example and give me the right results d) To be quite frankly, this seems to be the biggest problem in writing a compiler or even an interpreter for me. I would have no problem generating even 64 bit assembler code (I CAN write assembler manually), but the formula parser... e) Another thought: even simple computers (like my old Sharp 1246S with only about 2kB of RAM) can do that... it can't be THAT hard, right? And even very, very old programming languages have formula evaluation... BASIC is from 1964 and they already could calculate the kind of formula I presented as an example f) A few ideas, a few inspirations would be really enough - I just have no clue how to do operator precedence and the parentheses - I DO, however, know that it involves an AST and that many people use a stack So, what do you think?

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• Program structure in long running data processing python script

  - by fmark

  For my current job I am writing some long-running (think hours to days) scripts that do CPU intensive data-processing. The program flow is very simple - it proceeds into the main loop, completes the main loop, saves output and terminates: The basic structure of my programs tends to be like so: <import statements> <constant declarations> <misc function declarations> def main(): for blah in blahs(): <lots of local variables> <lots of tightly coupled computation> for something in somethings(): <lots more local variables> <lots more computation> <etc., etc.> <save results> if __name__ == "__main__": main() This gets unmanageable quickly, so I want to refactor it into something more manageable. I want to make this more maintainable, without sacrificing execution speed. Each chuck of code relies on a large number of variables however, so refactoring parts of the computation out to functions would make parameters list grow out of hand very quickly. Should I put this sort of code into a python class, and change the local variables into class variables? It doesn't make a great deal of sense tp me conceptually to turn the program into a class, as the class would never be reused, and only one instance would ever be created per instance. What is the best practice structure for this kind of program? I am using python but the question is relatively language-agnostic, assuming a modern object-oriented language features.

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• Download the ‘Getting Started with Ubuntu 12.04' Manual for Free

  - by Asian Angel

  If you or someone you know is new to Ubuntu, then the release of this free 143 page manual for the latest LTS edition of Ubuntu is the perfect download. The manual will take you from installing Ubuntu 12.04 all the way through to trouble-shooting the system if you run into problems. On the downloads page you can select a preferred language version, the specific version of Ubuntu you would like a manual for (10.04, 10.10, 11.10, and 12.04), and whether you prefer a ‘print or screen‘ version. Multiple Options Download Page for the Ubuntu Manual (Free Electronic Version) Note: Manual is in PDF format. Here is the link for those of you who prefer to use a regular print paperback copy of the manual. Purchase the ‘Getting Started with Ubuntu 12.04′ Manual Download the Official How-To Geek Trivia App for Windows 8 How to Banish Duplicate Photos with VisiPic How to Make Your Laptop Choose a Wired Connection Instead of Wireless

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• Why do programmers use or recommend Mac OS X?

  - by codingbear

  I've worked on both Mac and Windows for awhile. However, I'm still having a hard time understanding why programmers enthusiastically choose Mac OS X over Windows and Linux? I know that there are programmers who prefer Windows and Linux, but I'm asking the programmers who would just use Mac OS X and nothing else, because they think Mac OS X is the greatest fit for programmers. Some might argue that Mac OS X got the beautiful UI and is nix based, but Linux can do that. Although Windows is not nix based, you can pretty much develop on any platform or language, except Cocoa/Objective-C. Is it the softwares that offer only on Mac OS X? Does that really worth using Mac? Is it to develop iPhone apps? Is it because you need to buy new Windows every 2 years (less backwards compatible)? I understand why people, who are working in multimedia/entertainment industry, would use Mac OS X; however, I don't have strong merits of Mac OS X over Windows. If you develop daily on Mac and prefer Mac over anything else, can you give me a merit that Mac has over Windows/Linux? Maybe something you can do on Mac that cannot be done in Windows/Linux with the same level of ease? I'm not trying to do another Mac vs. Windows here. I tried to find things that I do on Mac that cannot be done on Windows with the same level of ease, but I couldn't. So, I'm asking for some help.

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• Download the ‘Getting Started with Ubuntu 12.10' Manual for Free

  - by Asian Angel

  Today is the official release date for Ubuntu’s latest version, so why not download the manual to go with it? This free manual is available to view online or download as a 145 page PDF file to best suits your needs. The home page for the manual will display a large Download Button, but the best option is to click on the Alternative Download Options link. Clicking on the Alternative Download Options link will let you select the language version you want, choose a system version, and let you download the manual directly or view it online. What To Do If You Get a Virus on Your Computer Why Enabling “Do Not Track” Doesn’t Stop You From Being Tracked HTG Explains: What is the Windows Page File and Should You Disable It?

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