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  • What are the differences between Special Edition and the Third Edition of Stroustrup's The C++ Programming Language?

    - by TheBlueCat
    I'm buying a few C++ books after moving from Java. I obviously want to read the reference manual from the man himself, though I cannot tell the difference between these two editions. The special edition is ten pages shorter than the third edition. However, the special edition is recommended over the third edition and it seems this version covers the ASCII standard when the other edition does not. Can anyone shed a bit of light on this?

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  • Is programming or computer science in general, all about algorithms?

    - by wakandan
    As a grad student, I find it more and more common for prestigious companies (like Google, Facebook, Microsoft,...) to put algorithm questions in their test and interviews. A few startups I applied to also asked about algorithms. I wonder if algorithms fluency is the most important thing for software developer in those companies? If the answer being yes, what are the best method or resources for one to learn & practice about algorithms effectively? I can't seem to get interested in solving seemingly too complicated problems found in most textbook or websites. Though easily understand basic algorithms (like quicksort, bubblesort,...), I find it immensely difficult to remember and reuse them later. Thanks. P/S: If you ask me what I like, it's building good softwares to solve users' problems innovatively. I suppose that does not necessarily mean the software has to be very complicated.

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  • Programming ... where to start?

    - by agnesb
    For the last 4 months, I've working tirelessly on a project with my partner, who is a super programmer. He did 100% of the whole mechanism that makes our site work. My job is to take care of the cosmetic aspects of the site ... thus I should say I am good enough at CSS and html. However, since we are using Drupal to build our site, from time to time, I need his help in order to figure out how to do the customization. Sometimes, I got frustrated. I know that as a partner, I should know a little bit on how to program. However, during the crunch time when you have to deliver lightning fast (we have our site built from scratch to finish in 4 weeks ... and you are all welcome to come join the fun! It's a site for programmers!) there is no time to learn from the basics. All I can do is to pick up whatever I need at the moment. Now the site is launched, I am thinking it should be time to do some learning. So, where should I start? My partner always said I need to start with Python. What's your take on this? Thanks.

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  • Schliemann's method of programming language learning

    - by DVK
    Background: 19th-century German archeologist Heinrich Schliemann was of course famous for his successful quest to find and excavate the city of Troy (an actual archeological site for the Troy of Homer's Iliad). However, he is just as famous for being an astonishing learner of languages - within the space of two years, he taught himself fluent Dutch, English, French, Spanish, Italian and Portuguese, and later went on to learn seven more, including both modern and ancient Greek. One of the methods he famously used was comparison of a known text, e.g. take a book in a language one is fluent in, take a good translation of a book in a language you wish to learn, and go over them in parallel. (various sources cited the book used by Schliemann to be the Bible, or, as the link above states, a novel). Now, for the actual question. Has anyone used (or heard of) an equivalent of Schliemann's method for learning a new programming language? E.g. instead of basing the leaning on references and tutorials, take a somewhat comprehensive set of programs known to have high-quality code in both languages implementing similar/identical algorithms and learn by comparing them? I'm curious about either personal experiences of applying such an approach, or references to something published, or existance of codebases which could be used for such an approach? What got me thinking about the idea was Project Euler and some code snippets I saw on SO, in C++, Perl and Lisp.

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  • Compile time Meta-programming, with string literals.

    - by Hassan Syed
    I'm writing some code which could really do with some simple compile time metaprogramming. It is common practise to use empty-struct tags as compile time symbols. I need to decorate the tags with some run-time config elements. static variables seem the only way to go (to enable meta-programming), however static variables require global declarations. to side step this Scott Myers suggestion (from the third edition of Effective C++), about sequencing the initialization of static variables by declaring them inside a function instead of as class variables, came to mind. So I came up with the following code, my hypothesis is that it will let me have a compile-time symbols with string literals use-able at runtime. I'm not missing anything I hope. template<class Instance> class TheBestThing { public: void set_name(const char * name_in) { get_name() = std::string(name_in); } void set_fs_location(const char * fs_location_in) { get_fs_location() = std::string(fs_location_in); } std::string & get_fs_location() { static std::string fs_location; return fs_location; } std::string & get_name() { static std::string name; return name; } }; struct tag {}; int main() { TheBestThing<tag> x; x.set_name("xyz"); x.set_fs_location("/etc/lala"); ImportantObject<x> SinceSlicedBread; }

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  • Dynamic Programming Recursion and a sprinkle of Memoization

    - by Auburnate
    I have this massive array of ints from 0-4 in this triangle. I am trying to learn dynamic programming with Ruby and would like some assistance in calculating the number of paths in the triangle that meet three criterion: You must start at one of the zero points in the row with 70 elements. Your path can be directly above you one row (if there is a number directly above) or one row up heading diagonal to the left. One of these options is always available The sum of the path you take to get to the zero on the first row must add up to 140. Example, start at the second zero in the bottom row. You can move directly up to the one or diagonal left to the 4. In either case, the number you arrive at must be added to the running count of all the numbers you have visited. From the 1 you can travel to a 2 (running sum = 3) directly above or to the 0 (running sum = 1) diagonal to the left. 0 41 302 2413 13024 024130 4130241 30241302 241302413 1302413024 02413024130 413024130241 3024130241302 24130241302413 130241302413024 0241302413024130 41302413024130241 302413024130241302 2413024130241302413 13024130241302413024 024130241302413024130 4130241302413024130241 30241302413024130241302 241302413024130241302413 1302413024130241302413024 02413024130241302413024130 413024130241302413024130241 3024130241302413024130241302 24130241302413024130241302413 130241302413024130241302413024 0241302413024130241302413024130 41302413024130241302413024130241 302413024130241302413024130241302 2413024130241302413024130241302413 13024130241302413024130241302413024 024130241302413024130241302413024130 4130241302413024130241302413024130241 30241302413024130241302413024130241302 241302413024130241302413024130241302413 1302413024130241302413024130241302413024 02413024130241302413024130241302413024130 413024130241302413024130241302413024130241 3024130241302413024130241302413024130241302 24130241302413024130241302413024130241302413 130241302413024130241302413024130241302413024 0241302413024130241302413024130241302413024130 41302413024130241302413024130241302413024130241 302413024130241302413024130241302413024130241302 2413024130241302413024130241302413024130241302413 13024130241302413024130241302413024130241302413024 024130241302413024130241302413024130241302413024130 4130241302413024130241302413024130241302413024130241 30241302413024130241302413024130241302413024130241302 241302413024130241302413024130241302413024130241302413 1302413024130241302413024130241302413024130241302413024 02413024130241302413024130241302413024130241302413024130 413024130241302413024130241302413024130241302413024130241 3024130241302413024130241302413024130241302413024130241302 24130241302413024130241302413024130241302413024130241302413 130241302413024130241302413024130241302413024130241302413024 0241302413024130241302413024130241302413024130241302413024130 41302413024130241302413024130241302413024130241302413024130241 302413024130241302413024130241302413024130241302413024130241302 2413024130241302413024130241302413024130241302413024130241302413 13024130241302413024130241302413024130241302413024130241302413024 024130241302413024130241302413024130241302413024130241302413024130 4130241302413024130241302413024130241302413024130241302413024130241 30241302413024130241302413024130241302413024130241302413024130241302 241302413024130241302413024130241302413024130241302413024130241302413 1302413024130241302413024130241302413024130241302413024130241302413024 02413024130241302413024130241302413024130241302413024130241302413024130

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  • How to create reactive tasks for programming competitions?

    - by directx
    A reactive task is sometimes seen in the IOI programming competition. Unlike batch tasks, reactive solutions take input from another program as well as outputting it. The program typically 'query' the judge program a certain number of times, then output a final answer. An example The client program accepts lines one by one, and simply echoes it back. When it encountered a line with "done", it exists immediately. The client program in Java looks like this: import java.util.*; class Main{ public static void main (String[] args){ Scanner in = new Scanner(System.in); String s; while (!(s=in.nextLine()).equals("done")) System.out.println(s); } } The judge program gives the input and processes output from the client program. In this example, it feeds it a predefined input and checks if the client program has echoed it back correctly. A session might go like this: Judge Client ------------------ Hello Hello World World done I'm having trouble writing the judge program and having it judge the client program. I'd appreciate if someone could write a judge program for my example.

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  • Advice on improving programming skills, learning capabilities?

    - by anonymous-coward1234
    Hi all, After 2,5 years of professional Java programing, I still have problems that make my job difficult and, more importantly - more times that I would like to admit - not enjoyable. I would like to ask for advice by more experienced people on ways that would help me overcome them. These are the problems I have: I do not absorb new knowledge easily. Even when I understand something, after a couple of days I easily forget even basic stuff. Other co-workers, even with the same working experience, when reading new technologies put things easily into "context", and are able to compare in "real time| similar technologies they already have used. I always try to address all the issues to whatever I am doing at one go, which results in me trying to resolve too many problems at the same time, losing completely control. I find it difficult to make my mind on a single problem that I should address first, and even when I do, and find myself throwing away code that I wrote because I started addressing the wrong issue first. As far as architecture and data modeling is concerned, I have difficulty making decisions on what objects must be created, with what hierarchy, interfaces, abstraction etc. I imagine that - to a certain degree - these things come with experience. But after 2,5 years of Java programming, I would expect myself to have come much farther that I have come, both in terms of absorption and experience. Is there a way to improve my learning speed? Any books, methods, advice is welcome.

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  • Handling incremental Data Modeling Changes in Functional Programming

    - by Adam Gent
    Most of the problems I have to solve in my job as a developer have to do with data modeling. For example in a OOP Web Application world I often have to change the data properties that are in a object to meet new requirements. If I'm lucky I don't even need to programmatically add new "behavior" code (functions,methods). Instead I can declarative add validation and even UI options by annotating the property (Java). In Functional Programming it seems that adding new data properties requires lots of code changes because of pattern matching and data constructors (Haskell, ML). How do I minimize this problem? This seems to be a recognized problem as Xavier Leroy states nicely on page 24 of "Objects and Classes vs. Modules" - To summarize for those that don't have a PostScript viewer it basically says FP languages are better than OOP languages for adding new behavior over data objects but OOP languages are better for adding new data objects/properties. Are there any design pattern used in FP languages to help mitigate this problem? I have read Phillip Wadler's recommendation of using Monads to help this modularity problem but I'm not sure I understand how?

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  • Which linear programming package should I use for high numbers of constraints and "warm starts"

    - by davidsd
    I have a "continuous" linear programming problem that involves maximizing a linear function over a curved convex space. In typical LP problems, the convex space is a polytope, but in this case the convex space is piecewise curved -- that is, it has faces, edges, and vertices, but the edges aren't straight and the faces aren't flat. Instead of being specified by a finite number of linear inequalities, I have a continuously infinite number. I'm currently dealing with this by approximating the surface by a polytope, which means discretizing the continuously infinite constraints into a very large finite number of constraints. I'm also in the situation where I'd like to know how the answer changes under small perturbations to the underlying problem. Thus, I'd like to be able to supply an initial condition to the solver based on a nearby solution. I believe this capability is called a "warm start." Can someone help me distinguish between the various LP packages out there? I'm not so concerned with user-friendliness as speed (for large numbers of constraints), high-precision arithmetic, and warm starts. Thanks!

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  • Database Functional Programming in Clojure

    - by Ralph
    "It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail." - Abraham Maslow I need to write a tool to dump a large hierarchical (SQL) database to XML. The hierarchy consists of a Person table with subsidiary Address, Phone, etc. tables. I have to dump thousands of rows, so I would like to do so incrementally and not keep the whole XML file in memory. I would like to isolate non-pure function code to a small portion of the application. I am thinking that this might be a good opportunity to explore FP and concurrency in Clojure. I can also show the benefits of immutable data and multi-core utilization to my skeptical co-workers. I'm not sure how the overall architecture of the application should be. I am thinking that I can use an impure function to retrieve the database rows and return a lazy sequence that can then be processed by a pure function that returns an XML fragment. For each Person row, I can create a Future and have several processed in parallel (the output order does not matter). As each Person is processed, the task will retrieve the appropriate rows from the Address, Phone, etc. tables and generate the nested XML. I can use a a generic function to process most of the tables, relying on database meta-data to get the column information, with special functions for the few tables that need custom processing. These functions could be listed in a map(table name -> function). Am I going about this in the right way? I can easily fall back to doing it in OO using Java, but that would be no fun. BTW, are there any good books on FP patterns or architecture? I have several good books on Clojure, Scala, and F#, but although each covers the language well, none look at the "big picture" of function programming design.

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  • Are functional programming languages good for practical tasks?

    - by Clueless
    It seems to me from my experimenting with Haskell, Erlang and Scheme that functional programming languages are a fantastic way to answer scientific questions. For example, taking a small set of data and performing some extensive analysis on it to return a significant answer. It's great for working through some tough Project Euler questions or trying out the Google Code Jam in an original way. At the same time it seems that by their very nature, they are more suited to finding analytical solutions than actually performing practical tasks. I noticed this most strongly in Haskell, where everything is evaluated lazily and your whole program boils down to one giant analytical solution for some given data that you either hard-code into the program or tack on messily through Haskell's limited IO capabilities. Basically, the tasks I would call 'practical' such as Aceept a request, find and process requested data, and return it formatted as needed seem to translate much more directly into procedural languages. The most luck I have had finding a functional language that works like this is Factor, which I would liken to a reverse-polish-notation version of Python. So I am just curious whether I have missed something in these languages or I am just way off the ball in how I ask this question. Does anyone have examples of functional languages that are great at performing practical tasks or practical tasks that are best performed by functional languages?

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  • Programming style question on how to code functions

    - by shawnjan
    Hey all! So, I was just coding a bit today, and I realized that I don't have much consistency when it comes to a coding style when programming functions. One of my main concerns is whether or not its proper to code it so that you check that the input of the user is valid OUTSIDE of the function, or just throw the values passed by the user into the function and check if the values are valid in there. Let me sketch an example: I have a function that lists hosts based on an environment, and I want to be able to split the environment into chunks of hosts. So an example of the usage is this: listhosts -e testenv -s 2 1 This will get all the hosts from the "testenv", split it up into two parts, and it is displaying part one. In my code, I have a function that you pass it in a list, and it returns a list of lists based on you parameters for splitting. BUT, before I pass it a list, I first verify the parameters in my MAIN during the getops process, so in the main I check to make sure there are no negatives passed by the user, I make sure the user didnt request to split into say, 4 parts, but asking to display part 5 (which would not be valid), etc. tl;dr: Would you check the validity of a users input the flow of you're MAIN class, or would you do a check in your function itself, and either return a valid response in the case of valid input, or return NULL in the case of invalid input? Obviously both methods work, I'm just interested to hear from experts as to which approach is better :) Thanks for any comments and suggestions you guys have!

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  • Flowcharting functional programming languages

    - by Sadface
    Flowcharting. This ancient old practice that's been in use for over 1000 years now, being forced upon us poor students, without any usefulness (or so do I think). It might work well with imperative, sequentially running languages, but what about my beloved functional programming? Sadly, I'm forced to create a flow chart for my programm (that is written in Haskell). I imagine it being easy for something like this: main :: IO () main = do someInput <- getLine let upped = map toUpper someInput putStrLn upped Which is just 3 sequenced steps, fetching data, uppercasing it, outputting it. Things look worse this time: main :: IO () main = do someInput <- fmap toUpper getLine putStrLn someInput Or like this: main :: IO () main = interact (map toUpper) Okay, that was IO, you can handle that like an imperative language. What about pure functions? An actual example: onlyMatching :: String -> [FilePath] -> [FilePath] onlyMatching ext = filter f where f name = lower ('.' : ext) == (lower . takeExtension $ name) lower = map toLower How would you flowchart that last one?

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  • Dynamic programming Approach- Knapsack Puzzle

    - by idalsin
    I'm trying to solve the Knapsack problem with the dynamical programming(DP) approach, with Python 3.x. My TA pointed us towards this code for a head start. I've tried to implement it, as below: def take_input(infile): f_open = open(infile, 'r') lines = [] for line in f_open: lines.append(line.strip()) f_open.close() return lines def create_list(jewel_lines): #turns the jewels into a list of lists jewels_list = [] for x in jewel_lines: weight = x.split()[0] value = x.split()[1] jewels_list.append((int(value), int(weight))) jewels_list = sorted(jewels_list, key = lambda x : (-x[0], x[1])) return jewels_list def dynamic_grab(items, max_weight): table = [[0 for weight in range(max_weight+1)] for j in range(len(items)+1)] for j in range(1,len(items)+1): val= items[j-1][0] wt= items[j-1][1] for weight in range(1, max_weight+1): if wt > weight: table[j][weight] = table[j-1][weight] else: table[j][weight] = max(table[j-1][weight],table[j-1][weight-wt] + val) result = [] weight = max_weight for j in range(len(items),0,-1): was_added = table[j][weight] != table[j-1][weight] if was_added: val = items[j-1][0] wt = items[j-1][1] result.append(items[j-1]) weight -= wt return result def totalvalue(comb): #total of a combo of items totwt = totval = 0 for val, wt in comb: totwt += wt totval += val return (totval, -totwt) if totwt <= max_weight else (0,0) #required setup of variables infile = "JT_test1.txt" given_input = take_input(infile) max_weight = int(given_input[0]) given_input.pop(0) jewels_list = create_list(given_input) #test lines print(jewels_list) print(greedy_grab(jewels_list, max_weight)) bagged = dynamic_grab(jewels_list, max_weight) print(totalvalue(bagged)) The sample case is below. It is in the format line[0] = bag_max, line[1:] is in form(weight, value): 575 125 3000 50 100 500 6000 25 30 I'm confused as to the logic of this code in that it returns me a tuple and I'm not sure what the output tuple represents. I've been looking at this for a while and just don't understand what the code is pointing me at. Any help would be appreciated.

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  • Why can't we have a single programming Language ? [closed]

    - by Kiran
    I am no expert in Programming Languages. But whenever I change the project, I am faced with Herculean challenge of learning the new programming language which takes weeks to master if not months.. With the previous experience of programming in different languages, I believe it takes few months of continuous programming to understand the amazing features the prog.language has to offer and to exploit. It makes me wonder, why cannot we have a single programming language which boasts all the amazing features from the existing programming language and make it mandatory for all the programmers to learn it.

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  • Bridged network between Ubuntu Desktop 10.10 host and Ubuntu Server 10.10 Guest

    - by Jon Cram
    I run Ubuntu 10.10 Desktop on my machine and have installed Ubuntu Server 10.10 in a Virtualbox VM. I'm running Virtualbox 4.0.2. It is not virtualbox-ose. I'd like the guest OS to have an IP address on my local network so that I can run server software and access this from the host OS. My intention is to run a Hudson CI server in the guest OS. I understand I need to set up a network bridge for this to work, however I don't understand what I need to do for this to happen. I have tried following the instructions at https://help.ubuntu.com/community/VirtualBox/Networking, however I run into two issues towards the end: "To take the modifications into account, restart the VirtualBox host networking script". I don't have Virtualbox-ose installed and guide suggests sudo /etc/init.d/vboxnet restart, however /etc/init.d/vboxnet does not exist for me. The end of the guide refers to the vboxusers group. I don't have such a group and am not sure why I need this or how it should be created. I'm simply looking to allow the guest OS to have an IP on my local network so that I can access servers on the guest OS from the host OS. What changes do I need to make to both the host and guest OSs for this to work?

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  • Static IP configuration causing apt-get errors

    - by JPbuntu
    I am getting errors when running apt-get update or when installing new packages. Although this only happens when the server configured for a static IP address. Changing the configuration back to DHCP and restarting networking fixes the problem, although I want a static IP. Once it is working I can change back to my static IP address and restart networking. Although this only works until I restart the server (restarting the router is ok), and then I start getting the same errors and have to switch back to DHCP. Any ideas on what could be causing this or tips on troubleshooting it? Thanks in advance. here is my static IP configuration: auto eth0 iface eth0 inet static address 192.168.2.2 netmask 255.255.255.0 gateway 192.168.2.1 The apt-get update errors go something like this: A few of these Ign http://us.archive.ubuntu.com precise-backports InRelease then a lot of these Err http://security.ubuntu.com precise-security Release.gpg Something wicked happened resolving 'security.ubuntu.com:http' (-5 - No address associated with hostname) and a lot of these W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise-backports/universe/i18n/Translation-en Something wicked happened resolving 'us.archive.ubuntu.com:http' (-5 - No address associated with hostname)

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  • 12.04 wired network doesn't work RTL8111/8168B

    - by laket
    its a fresh 12.04 install 64bits. wifi works fine, wired stays off with cable connected and network-manager shows as if cable is disconnected. Turning off networking lights up my network-cards leds, turning networking on shuts off the leds and no communication is possible. I already tried, turning off the network-manager (sudo service network-manager stop) and setting up my eth0 manually, as soon as I switch off the network-manager my leds light up, but after setting up manually eth0 (sudo ifconfig eth0 10.2.10.114 netmask 255.255.0.0 up) the leds turn off again. I am still dual booting with 10.04 where I have no issues at all, leaving the cable connected all time to my notebook and a switch. Here is some hardware info: lshw: *-network description: Ethernet interface product: RTL8111/8168B PCI Express Gigabit Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:03:00.0 logical name: eth0 version: 03 serial: c8:0a:a9:d7:05:97 size: 10Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix vpd bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half firmware=rtl_nic/rtl8168d-2.fw latency=0 link=no multicast=yes port=MII speed=10Mbit/s resources: irq:42 ioport:2000(size=256) memory:f0004000-f0004fff memory:f0000000-f0003fff memory:f0010000-f001ffff lspci: 02:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express) (rev 01) 03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03) ifconfig eth0: eth0 Link encap:Ethernet HWaddr c8:0a:a9:d7:05:97 inet addr:10.2.10.114 Bcast:10.2.255.255 Mask:255.255.0.0 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:42 Base address:0xc000 cat /etc/network/interfaces: (already tried here with and w/o eth0) auto lo eth0 iface lo inet loopback cat /etc/NetworkManager/NetworkManager.conf [main] plugins=ifupdown,keyfile dns=dnsmasq [ifupdown] managed=false Any help is welcome ;) Laket

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  • Cat 6 Only 100mbit speed

    - by Stu2000
    I tried two different cat6 cables directly connected between my two ubuntu machines. This one I ordered online: http://www.amazon.co.uk/gp/product/B002SQPDXS/ref=wms_ohs_product only achieves 100mbit speeds, but does appear to be supporting cross-talk (direct pc to pc), the other cat 6 cable, worked perfectly and gets the full 1gigabit speed. Both tests were performed using ftp and checking the network monitor with direct pc to pc connection. Did the product from amazon lie to me or do I need to manually set a setting somewhere in ubuntu for some cables? I had thought 10 quid for 20m of gigabit ethernet cable was a bit cheap, you get what you pay for... Regards, Stu Update: It seems that after rebooting, the device is set to 1000mbit sec when looking it up with sudo ethtool eth0 However after a while, this will drop down to just 100, after which to reset it to 1000 again, I have to reboot, and simply unpugging and re-plugging in the cable doesn't do it. I tried setting this in networking config file as suggested here: auto eth0 iface eth0 inet static pre-up /usr/sbin/ethtool -s eth0 speed 1000 duplex full but that resulted in my networking failing to start. Is there a problem with my 'auto-negotiation' or something? Can I manually override a setting to 1000mbit?

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  • IPv6 tunnels - any easy way to turn them on and off?

    - by Rob Hoare
    I've set up a tunnelbroker.net (Hurricane Electric) IPv6 tunnel from my laptop running 12.04. Works fine, and allows me to test the dual-stack configuration on my remote webservers etc. until native IPv6 is available on my ISP. However, there are times when I don't want the tunnel. For example if I'm accessing something that requires an IPv4 address in my own country rather than the Tunnelbroker tunnel endpoint, or if I'm away from the local IPv4 tunnel endpoint, or if I simply want to test without IPv6. Is there a simple way to disable and then re-enable the IPv6 tunnel, without rebooting? For context, here's what's in my /etc/network/interfaces (NNN replaces numbers): auto he-ipv6 iface he-ipv6 inet6 v4tunnel endpoint 216.218.NNN.NNN address 2001:470:NNN:NNN::2 netmask 64 up ip -6 route add default dev he-ipv6 down ip -6 route del default dev he-ipv6 Is there a network manager application (gui or command line) to selectively enable/disable parts of /etc/network/interfaces, or IPv6 in general? I found even by commenting out that out (and reloading networking) it's tough to get the IPv6 to go away. A "tunnel on/off" button in networking would be great, like using a VPN.

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  • Network: Incoming connections work, outgoing fails

    - by anirvan
    i recently set up my own server at home to run Ubuntu 12.04 server ed. on booting up, i noticed that a message related to networking comes up, and the booting process pauses. the message read something like - waiting for network configuration and after a while - waiting another 60 seconds... on booting up, I realised that any command which requires a network connection was not working - ping, apt-get install, etc. on firing the ifup eth0 command, I get the error RTNETLINK answers: File exists. Failed to bring up eth0. I also realised, while searching the web for this problem, that this is probably one of the most common networking related issues - however, most of the questions are around setting up multiple IPs for the same machine. ifdown eth0 also fails, stating that eth0 is not configured. my /etc/network/interfaces file has a simple configuration for a static IP: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address xx.xx.xx.xx netmask xx.xx.xx.xx broadcast xx.xx.xx.xx gateway xx.xx.xx.xx dns-nameservers xx.xx.xx.xx The strangest part of this problem is that, while I can't connect to anything outside, I can ping to this particular server using the static IP configured in the interface file, and, i can even SSH into it! I'm really at ends here with this problem, and any guidance is much appreciated. Thanks!

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  • What are all things that do/can happen when a user enters in a web page's URL?

    - by Job
    Sorry if this is a naive title. I am trying to break into web development, which is so far a foreign world to me. I have taken a basic intro to OS, intro to Networking as part of my bachelors degree several years ago. I cannot say that we went into things deeply, beyond academic assignments. I would like to understand things much better regarding to this specific task (e.g what goes on in at the OS level, at networking level, what are other computers involved, where do proxy servers and hackers come in). Again, at the very basic level this has been covered, but I would like to review this specific thing better. Are there chapter(s) os a specific book, or specific SHORT reading that you recommend? I have nothing against your list of 20 favorite books, but I want to understand this one thing better in 2-3 weeks of reading after work / on the weekends (realistically 5-10 hrs per week, so I am looking for about 15-20 hrs of reading material, NO MORE). I am not a fast reader :) Thanks.

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  • Which topics do I need to research to enable me to complete my self-assigned "Learning Project"?

    - by Anonymous -
    I want to continue learning C#. I've read parts of a few books recommended on here and the language is feeling more familiar by the day. I'd like to tackle a mid-sized personal project to take my expertise to the next level. What I'd like to do, is create an application that 'manages expenses', that runs on multiple machines on a LAN. So for example, say we have person1 and person2 on seperate machines running the application, when person1 enters an expense, it will appear on person2's (pretty UI) view of the expenses database and vice versa. What topics do I need to research to make this possible for me? I plan on learning WPF for the UI (though the steep learning curve (or so I'm told) has me a little anxious about that at this stage. With regards to the database, which database would you recommend I use? I don't want a 'server' for the database to run on, so do I need to use an embedded database that each client machine runs a copy of that updates to each other (upon startup/entering of expense on any machine etc)? What topics under networking should I be looking at? I haven't studied networking before in any language, so do I need to learn about sockets or?

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  • Book Review: Programming Windows Identity Foundation

    - by DigiMortal
    Programming Windows Identity Foundation by Vittorio Bertocci is right now the only serious book about Windows Identity Foundation available. I started using Windows Identity Foundation when I made my first experiments on Windows Azure AppFabric Access Control Service. I wanted to generalize the way how people authenticate theirselves to my systems and AppFabric ACS seemed to me like good point where to start. My first steps trying to get things work opened the door to whole new authentication world for me. As I went through different blog postings and articles to get more information I discovered that the thing I am trying to use is the one I am looking for. As best security API for .NET was found I wanted to know more about it and this is how I found Programming Windows Identity Foundation. What’s inside? Programming WIF focuses on architecture, design and implementation of WIF. I think Vittorio is very good at teaching people because you find no too complex topics from the book. You learn more and more as you read and as a good thing you will find that you can also try out your new knowledge on WIF immediately. After giving good overview about WIF author moves on and introduces how to use WIF in ASP.NET applications. You will get complete picture how WIF integrates to ASP.NET request processing pipeline and how you can control the process by yourself. There are two chapters about ASP.NET. First one is more like introduction and the second one goes deeper and deeper until you have very good idea about how to use ASP.NET and WIF together, what issues you may face and how you can configure and extend WIF. Other two chapters cover using WIF with Windows Communication Foundation (WCF) band   Windows Azure. WCF chapter expects that you know WCF very well. This is not introductory chapter for beginners, this is heavy reading if you are not familiar with WCF. The chapter about Windows Azure describes how to use WIF in cloud applications. Last chapter talks about some future developments of WIF and describer some problems and their solutions. Most interesting part of this chapter is section about Silverlight. Who should read this book? Programming WIF is targeted to developers. It does not matter if you are beginner or old bullet-proof professional – every developer should be able to be read this book with no difficulties. I don’t recommend this book to administrators and project managers because they find almost nothing that is related to their work. I strongly recommend this book to all developers who are interested in modern authentication methods on Microsoft platform. The book is written so well that I almost forgot all things around me when I was reading the book. All additional tools you need are free. There is also Azure AppFabric ACS test version available and you can try it out for free. Table of contents Foreword Acknowledgments Introduction Part I Windows Identity Foundation for Everybody 1 Claims-Based Identity 2 Core ASP.NET Programming Part II Windows Identity Foundation for Identity Developers 3 WIF Processing Pipeline in ASP.NET 4 Advanced ASP.NET Programming 5 WIF and WCF 6 WIF and Windows Azure 7 The Road Ahead Index

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