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• Wastage of resources in Virtualization

  - by Sabeen Malik

  I am not sure if this is the write place to ask the question. However i hope it is. When looking for a VPS earlier today, I was trying to understand how each container would work in the background. Keeping in mind the fact that the operating system uses most of the power and power on a system, wouldn't having multiple operating systems in the same machine mean more wastage of resources. For instance if i was running centOS on a dedicated box and it was running lets say 20 background OS level processes. Then i go and install a virtualization platform and install 5 more centOS virtual machines in the same system which are exactly the same as the host operating system. Doesn't this mean duplication of those 20 processes 6 times? So internally the context switching is happening between 120 processes instead of 20?

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• Best directory to store application data with read\write rights for all users?

  - by Wodzu

  Hi guys. Until Windows Vista I was saving my application data into the directory where the program was located. The most common place was "C:\Program Files\MyApplication". As we know, under Vista and later the common user does't have rights to write under "Program Files" folder. So my first idea was to save the application data under "All Useres\Application Data" folder. But it seams that this folder has writing restrictions too! So to sum up, my requirements are: Folder should exist under Windows XP and above Microsoft's systems. All useres of the system should read\write\creation rights to this folder and it subfolders and files. I want to have only one copy of file\files for all useres. Thanks for your time.

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• Looking for ideas on automatically arranging a set of objects (furniture) in a virtual room in AS3

  - by raf

  First of all, I don't want to visually arrange 3D models dragging them with the mouse, all I want is: Given a room of certain dimensions (L,W,H) and given a set of elements like beds, chairs, etc (with L,W,H dimensions, of course) I want to automatically arrange those elements to take advantage of the space as much as I can. So I want to be able to put as much furniture as I can in a given room. At the end I need to represent the arranged items visually, inside the room. My first thought was to use an array of items and sorting it with array.sortOn(["l","w","h"] Array.NUMERIC) and then define a gap between the objects and make the maths to put the objects one next to another, etc. but that isn't a good approach because some items may be placed on top of another ones (boxes of the same size, boxes on top of tables, etc). I really don't have experience on 3D programming, that's why I'm asking for help. Thanks in advance.

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• Database system that is not relational.

  - by paan

  What are the other types of database systems out there. I've recently came across couchDB that handles data in a non relational way. It got me thinking about what other models are other people is using. So, I want to know what other types of data model is out there. (I'm not looking for any specifics, just want to look at how other people are handling data storage, my interest are purely academic) The ones I already know are: RDBMS (mysql,postgres etc..) Document based approach (couchDB, lotus notes) Key/value pair (BerkeleyDB)

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• Django: Data corrupted after loading? (possible programmer error)

  - by Rosarch

  I may be loading data the wrong way. excerpt of data.json: { "pk": "1", "model": "myapp.Course", "fields": { "name": "Introduction to Web Design", "requiredFor": [9], "offeringSchool": 1, "pre_reqs": [], "offeredIn": [1, 5, 9] } }, I run python manage.py loaddata -v2 data: Installed 36 object(s) from 1 fixture(s) Then, I go to check the above object using the Django shell: >>> info = Course.objects.filter(id=1) >>> info.get().pre_reqs.all() [<Course: Intermediate Web Programming>] # WRONG! There should be no pre-reqs >>> from django.core import serializers >>> serializers.serialize("json", info) '[{"pk": 1, "model": "Apollo.course", "fields": {"pre_reqs": [11], "offeredIn": [1, 5, 9], "offeringSchool": 1, "name": "Introduction to Web Design", "requiredFor": [9]}}]' The serialized output of the model is not the same as the input that was given to loaddata. The output has a non-empty pre_req list, whereas the input's pre_reqs field is empty. What am I doing wrong?

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• Questions about "casting operation" in OOP

  - by rhapsodyn

  When programming, we usually use some type-casting operations. When the casting happens on the objects "on the same level", it feels ok. But when it happens on the ojects "on the different levels"(mainly between father and son), it feels weird. Considering this: Class Son extends Father WhenSon s = (Son)father;, it's absolutely unreasonable. Because a "Son" is not a "Father" anymore, "Son" may grow up with some new properties "Father" doesn't have, the casting operation makes these properties unknown. On the other hand, Father f = (Father)son seems reasonable, but according to LSP "An instance of a derived should be able to replace any instance of its superclass" A "Son" can do anything his "Father" can, so the casting operation seems useless. So can i say that these casting operations are agaisnt OO design principle but necessary?

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• Is there a c++ library that provides functionality to execute an external program and read its outpu

  - by BD at Rivenhill

  Basically, I'm looking for something that will allow me to replicate the following Perl code: my $fh = new FileHandle; $fh->open("foo |"); while (<$fh>) { # Do something with this line of data. } This is in the context of Linux, so a library that is specific to Windows will not help. I know how to write a program that does fork/exec/dup2 and all that basic shell-type jazz, but there are some fiddly details involving terminals that I don't feel like messing around with (and I don't have a copy of "Advanced Programming in the UNIX Environment" or a similar reference handy), so I'm hoping that someone has already solved this problem.

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• Open two new tabs using Javascript

  - by Permana

  I have this situation: There are a login page with a login form (form action is $_SERVER['PHP_SELF']). When user login, it will check what application the user can access and open all the application that available for that user in new tab. If user can access application (for example) 'Docs' and 'Sites', it will open 2 tabs. I Open new tab using window.open('app1.html','_newhtml');, some people say that it only works in Firefox. It's OK, no big deal for me. The problem is, It only open 1 tab, although I write it 2 times window.open('app1.html','_newhtml'); window.open('app2.html','_newhtml'); How can I open 2 tabs? are there any hacks from server side or client side programming?

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• How do I protect python code?

  - by Jordfräs

  I am developing a piece of software in python that will be distributed to my employer's customers. My employer wants to limit the usage of the software with a time restricted license file. If we distribute the .py files or even .pyc files it will be easy to (decompile), and remove the code that checks the license file. Another aspect is that my employer do not want the code to be read by our customers, fearing that the code may be stolen or at least the "novel ideas". Is there a good way to handle this problem? Preferably with an off-the-shelf solution. The software will run on Linux systems (so I don't think py2exe will do the trick)

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• What are the things Java got right?

  - by hamletdarcy

  What are the things that Java (the language and platform) got categorically right? In other words, what things are more recent programming languages preserving and carrying forward? Some easy answer are: garbage collection, a VM, lack of pointers, classloaders, reflection(?) What about language based answers? Please don't list the things Java did wrong, just right. (note by Mark Harrison) This is an interesting and useful question, especially for those of us who don't use java regularly. I'm voting for reopening. Please don't close as argumentative, as it doesn't seem to be causing any arguments.

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• How does exactly Qt works?

  - by Somebody still uses you MS-DOS

  I have seen that you can write your application in Qt, and it can be run in different operating systems. And - correct me if I'm wrong - you don't need to have Qt already installed in all of these platforms. How exactly this approach works? Does Qt compiles to the desired platform, does it bundle some "dlls" (libs), how does it do it? Is different from programming a Java application for the sake of cross-platform? If you use Python to write a Qt application with Python bindings, does the final user needs to have Python installed?

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• How can a language be interpreted by itself (like Rubinius)?

  - by japancheese

  I've been programming in Ruby for a while now with just the standard MRI implementation of Ruby, but I've always been curious about the other implementations I hear so much about. I was reading about Rubinius the other day, a Ruby interpreter written in Ruby. I tried looking it up in various places, but I was having a hard time figuring out exactly how something like this works. I've never had much experience in compilers or language writing but I'm really interested to figure it out. How exactly can a language be interpreted by itself? Is there a basic step in compiling that I don't understand where this makes sense? Can someone explain this to me like I'm an idiot (because that wouldn't be too far off base anyways)

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• Accessing a webpage in C++

  - by wyatt

  Is there a good, simple library which allows C++ to load a webpage? I just want to grab the source as text. I'm not using any IDE or significant library, just straight command line. Tangentially, is there something fundamental I'm missing about programming in C++? I would think any language in common use today would have droves of web-based functionality, being so central to computer usage, but I can find next to no discussion on how to accomplish it. I realise C++ significantly predates the modern internet, so it lacking any core ability in the regard is reasonable, but the fact that relevant libraries seem so sparse is baffling. Thanks for your help.

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• InetAddress.getLocalHost() throws UnknownHostException

  - by jhwist

  Hi, I am testing our server-application (written Java) on different operating systems and thought that OpenSolaris (2008.11) would be the least troublesome due to the nice Java integration. Turns out I was wrong, as I end up with a UnknownHostException try { computerName = InetAddress.getLocalHost().getHostName(); if (computerName.indexOf(".") > -1) computerName = computerName.substring(0, computerName.indexOf(".")).toUpperCase(); } catch (UnknownHostException e) { e.printStackTrace(); } The output is: java.net.UnknownHostException: desvearth01: desvearth01 at java.net.InetAddress.getLocalHost(InetAddress.java:1353) However, nslookup desvearth01 returns the correct IP address, and nslookup localhost returns 127.0.0.1 as expected. Also, the same code works perfectly on FreeBSD. Is there anything special to OpenSolaris that I am not aware of? Any hints appreciated, thanks.

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• Shortest command to calculate the sum of a column of output on Unix?

  - by Andrew

  I'm sure there is a quick and easy way to calculate the sum of a column of values on Unix systems (using something like awk or xargs perhaps), but writing a shell script to parse the rows line by line is the only thing that comes to mind at the moment. For example, what's the simplest way to modify the command below to compute and display the total for the SEGSZ column (70300)? ipcs -mb | head -6 IPC status from /dev/kmem as of Mon Nov 17 08:58:17 2008 T ID KEY MODE OWNER GROUP SEGSZ Shared Memory: m 0 0x411c322e --rw-rw-rw- root root 348 m 1 0x4e0c0002 --rw-rw-rw- root root 61760 m 2 0x412013f5 --rw-rw-rw- root root 8192

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• gdb + nasm debug info not being created

  - by cpowel2

  I am relatively new to assembly language programming and am trying to debug a small .asm file that I wrote in Ubuntu. I am however running into an issue where my symbol table is not being loaded and was looking for some help. I am compiling my program as follows. nasm -f elf -g -F dwarf bs.asm gcc -m32 -g bs.o -o bs which produces the executable bs when I run gdb bs I get a message that says no debugging symbols and when I try to set a break point by b main it says function not defined even though its in the file and I can run it using ./bs I read a couple posts that suggested adding the -F dwarf when assembling but that didn't help if anyone has any insight I would greatly appreciated your input. Thanks in advance

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• I need to pad IP addresses with Zeroes for each octet

  - by Felipe Alvarez

  Starting with a string of an unspecified length, I need to make it exactly 43 characters long (front-padded with zeroes). It is going to contain IP addresses and port numbers. Something like: ### BEFORE # Unfortunately includes ':' colon 66.35.205.123.80-137.30.123.78.52172: ### AFTER # Colon removed. # Digits padded to three (3) and five (5) # characters (for IP address and port numbers, respectively) 066.035.05.123.00080-137.030.123.078.52172 This is similar to the output produced by tcpflow. Programming in Bash. I can provide copy of script if required. If it's at all possible, it would be nice to use a bash built-in, for speed. Is printf suitable for this type of thing?

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• How is fseek() implemented in the filesystem?

  - by pajton

  This is not a pure programming question, however it impacts the performance of programs using fseek(), hence it is important to know how it works. A little disclaimer so that it doesn't get closed. I am wondering how efficient it is to insert data in the middle of the file. Supposing I have a file with 1MB data and then I insert something at the 512KB offset. How efficient would that be compared to appending my data at the end of the file? Just to make the example complete lets say I want to insert 16KB of data. I understand the answer varies depending on the filesystem, however I assume that the techniques used in common filesystems are quite similar and I just want to get the right notion of it.

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• How Proxy server works with tcp/http connections?

  - by Vivek

  Since I am a beginner in the world of internet/networking, I always mess up with these kinds of doubts in my head while programming ;) .. My doubts are, While working behind a proxy, how my requests and responses work? Means my request headers and data will first reach to Proxy server- then proxy server sends it(same headers and data) to corresponding server. And server responses to it with a response header and body to the proxy server-then proxy server sends it to my computer. Wright? While using websockets we are upgrading our http connection to tcp. At this time what is happening @ Proxy server? Does the proxyserver also upgrades its connection to plain TCP? After opening such TCP connections, does the proxy server able to track/log those socket messsages? And most importantly, Is the proxy server transparent or acting like an original server infront of a client? Thanks for any answers or helpful links in advance.

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• Are frameworks really necessary for beginners/intermediates? (PHP)

  - by ggfan

  I have been programming for around 6months and currently learning PHP/Mysql. I can create basic functionally sites starting from a plain sheet of paper. Is it necessary I use frameworks to create sites? Currently, everything I do is from scratch. I'll borrow codes from old codes, ask people for help, etc. Are frameworks going to help me much more? Is it alright if I put a site public without using a framework? (I have not looked a lot into frameworks, so my knowledge is limited, but I'm just curious)

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• Save user names on .txt file witch username is listed in /etc/passwd file. Bash

  - by user1448637

  well my goal is to make bash script to check if the username exist in /etc/passwd, if true i want to add it to the users.txt file. i am not really good at UNIX programming so i hope somebody help me. while(get to the end of /etc/passwd){ name=$(cat /etc/passwd | cut -d: -f1); num1=$(cat /etc/passwd | cut -d: -f3); num2=$(cat /etc/passwd | cut -d: -f4); if(num1==num2) /*i compare argv[0] with $name */ /* if true i=1 */ } if(i==1) save folowing string "argv[0]=agrv[1]" else "error message"

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• How do you compare music data

  - by Chris

  i want to write an app to rename sort and organize my music library (mp3's, wav's, flac's). I wanted to take a portion of the song, say the first minutes, and compare that to a database and then retrieve the song name and tag information. I have heard that you can do this with last.fm but a look through their api info didn't help. My question is, what is this called so i can google it better? nothing i am trying is helping much. This would be similar to the shazam android app. My prefered language would be java, so i can run it on a few operating systems easier, but that might be subject to change depending on how i can do it. Thanks

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• Java: How can I create good looking class docs with Javadoc?

  - by Cheeso

  I'd like to create HTNML documentation for a Java class library that includes programming guide information - beyond just a class reference code examples in the reference doc collapsible regions I want it to look well-styled. Something like this: I think that Javadoc exposes a doclet API that allows other parties to provide doc generation integrated in Javadoc. Is there a doclet option that I can use (for free) that does something a little nicer than the standard javadoc output? I tried googling for this but no luck. Suggestions?

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• databind a DropDownList control with a list of all sub directories that exist in a particular direct

  - by sushant

  I am wanting to databind a DropDownList control with a list of all sub directories that exist in a particular directory on the server. The directory I want to search is in the root of the application. I am fairly new to programming and I'm not sure where to even start. I found this code on a website: Dim root As String = "C;\" Dim folders() As String = Directory.GetDirectories(root) Dim sb As New StringBuilder(2048) Dim f As String For Each f In folders Dim foldername As String = Path.GetFileName(f) sb.Append("<option>") sb.Append(foldername) sb.Append("</option>") Next Label3.Text = "<select runat=""sever"" id=""folderlist""" & sb.ToString() & "</select>" I guess this is vb. but my tool is in asp, so is their something similar in vbscript so that I can use it.

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• Is It Worth Using Bitwise Operators In Methods?

  - by user1626141

  I am very new to Java (and programming in general, my previous experience is with ActionScript 2.0 and some simple JavaScript), and I am working my way slowly and methodically through Java: A Beginner's Guide by Herbert Schildt. It is an incredible book. For one thing, I finally understand more-or-less what bitwise operators (which I first encountered in ActionScript 2.0) do, and that they are more efficient than other methods for certain sums. My question is, is it more efficient to use a method that uses, say, a shift right, to perform all your divisions/2 (or divisions/even) for you in a large program with many calculations (in this case, a sprawling RPG), or is it more efficient to simply use standard mathematical operations because the compiler will optimise it all for you? Or, am I asking the wrong question entirely?

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