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  • Débuter avec Node.js partie 2 : Cloud9, un IDE pour le développement JavaScript et Node.js, par Romain Maton

    Suite à son premier article, Romain Maton, de Web Tambouille continue sa série d'introduction à Node.js en vous présentant un IDE particulièrement adapté au développement JavaScript : Cloud9 : IDE pour le développement JavaScript et Node.js. Note : cet article a été publié en février 2011. Entre-temps, Cloud9 a significativement évolué (ainsi que les versions de Node) et certaines informations...

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  • Maîtriser les flux de données sous Node : partie 2, article de Roly Fentanes traduit par vermine

    Je vous propose une traduction de l'article Mastering Node Streams: Part 2 de Roly Fentanes publié sur DailyJS. Roly Fentanes est un développeur de logiciels qui apprécie travailler avec le JavaScript et particulièrement avec Node.js. Il a d'ailleurs créé plusieurs plugins. Aujourd'hui il désire nous apprendre à maîtriser efficacement les flux de données avec Node car il estime que leur potentiel est trop souvent mis de côté.

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  • Maîtriser les flux de données sous Node : partie 1, article de Roly Fentanes traduit par vermine

    Je vous propose une traduction de l'article Mastering Node Streams: Part 1 de Roly Fentanes publié sur DailyJS. Roly Fentanes est un développeur de logiciels qui apprécie travailler avec le JavaScript et particulièrement avec Node.js. Il a d'ailleurs créé plusieurs plugins. Aujourd'hui il désire nous apprendre à maîtriser efficacement les flux de données avec Node car il estime que leur potentiel est trop souvent mis de côté.

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  • Scaling a node.js application, nginx as a base server, but varnish or redis for caching?

    - by AntelopeSalad
    I'm not close to being well versed in using nginx or varnish but this is my setup at the moment. I have a node.js server running which is serving either json, html templates, or socket.io events. Then I have nginx running in front of node which is serving all static content (css, js, etc.). At this point I would like to cache both static content and dynamic content to memory. It's to my understanding that varnish can cache static content quite well and it wouldn't require touching my application code. I also think it's capable of caching dynamic content too but there cannot be any cookie headers? I do use redis at the moment for holding session data and planned to use it for other things in the future like keeping track of non-crucial but fun stats. I just have no idea how I should handle caching everything on the site. I think it comes down to these options but there might be more: Throw varnish in front of nginx and let varnish cache static pages, no app code changes. Redis would cache dynamic db calls which would require modifying my app code. Ignore using varnish completely and let redis handle caching everything, then use one of the nginx-redis modules. I'm not sure if this would require a lot of app code changes (for the static files). I'm not having any luck finding benchmarks that compare nginx+varnish vs nginx+redis and I'm too inexperienced to bench it myself (high chances of my configs being awful). I'm basically looking for the solution that would be the most efficient in terms of req/sec and scalable in the future (throw new hardware at the problem + maybe adjust some values in a config = new servers up and running semi-painlessly).

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  • aufs user permissions

    - by user56395
    Anyone know why this doesn't work? Is this user error, AUFS feature or bug maybe: rac@tecraS1:~/tmp$ mkdir orig tmp au rac@tecraS1:~/tmp$ sudo mount -t tmpfs none tmp rac@tecraS1:~/tmp$ sudo chown -R rac tmp rac@tecraS1:~/tmp$ echo hello > orig/hello rac@tecraS1:~/tmp$ sudo mount -t aufs -o br=tmp:orig none au rac@tecraS1:~/tmp$ ls -al au total 8 drwxrwxrwt 4 rac root 100 2011-01-06 13:53 . drwxr-xr-x 5 rac rac 4096 2011-01-06 13:52 .. -rw-r--r-- 1 rac rac 6 2011-01-06 13:53 hello rac@tecraS1:~/tmp$ rm au/hello rm: cannot remove `au/hello': Operation not permitted rac@tecraS1:~/tmp$ Seems the aufs files were created as root and user has no access to them: rac@tecraS1:~/tmp$ sudo rm au/hello rac@tecraS1:~/tmp$ ls -al tmp total 4 drwxrwxrwt 4 rac root 120 2011-01-06 13:53 . drwxr-xr-x 5 rac rac 4096 2011-01-06 13:52 .. -r--r--r-- 2 root root 0 2011-01-06 13:53 .wh.hello -r--r--r-- 2 root root 0 2011-01-06 13:53 .wh..wh.aufs drwx------ 2 root root 40 2011-01-06 13:53 .wh..wh.orph drwx------ 2 root root 40 2011-01-06 13:53 .wh..wh.plnk rac@tecraS1:~/tmp$ OS is the latest Lucid with 2.6.35-23 stock kernel. No idea about aufs version. Using sudo chown -R rac tmp/.wh* fixes the problem. Thanks for looking.

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  • optimal folder structure for storing 100k files on a USB drive

    - by cherouvim
    I need to store 100k files (around 40GB) in a USB drive. Each file has a unique int id (e.g 45000). Option one is to put all files in a single folder: root/ root/1.pdf root/2.pdf root/3.pdf ... root/567.pdf root/568.pdf root/569.pdf ... root/10001.pdf root/10002.pdf root/10003.pdf ... root/99998.pdf root/99999.pdf root/100000.pdf Option two is to create a [1-9][0-9]* folder hierarchy based on that id: root/ root/1/file.pdf root/2/file.pdf root/3/file.pdf ... root/5/6/7/file.pdf root/5/6/8/file.pdf root/5/6/9/file.pdf ... root/1/0/0/0/1/file.pdf root/1/0/0/0/2/file.pdf root/1/0/0/0/3/file.pdf ... root/9/9/9/9/8/file.pdf root/9/9/9/9/9/file.pdf root/1/0/0/0/0/0/file.pdf Which option will scale better? I can understand that the second option will require tons of folders but each folder will at most contain 10 folders and 1 file. Maintenance will not be an issue since everything will be controlled by an application. Note that this is a USB drive on linux and based on the above I'd also like to know whether I should go with FAT32 or NTFS.

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  • Learning AngularJS by Example – The Customer Manager Application

    - by dwahlin
    I’m always tinkering around with different ideas and toward the beginning of 2013 decided to build a sample application using AngularJS that I call Customer Manager. It’s not exactly the most creative name or concept, but I wanted to build something that highlighted a lot of the different features offered by AngularJS and how they could be used together to build a full-featured app. One of the goals of the application was to ensure that it was approachable by people new to Angular since I’ve never found overly complex applications great for learning new concepts. The application initially started out small and was used in my AngularJS in 60-ish Minutes video on YouTube but has gradually had more and more features added to it and will continue to be enhanced over time. It’ll be used in a new “end-to-end” training course my company is working on for AngularjS as well as in some video courses that will be coming out. Here’s a quick look at what the application home page looks like: In this post I’m going to provide an overview about how the application is organized, back-end options that are available, and some of the features it demonstrates. I’ve already written about some of the features so if you’re interested check out the following posts: Building an AngularJS Modal Service Building a Custom AngularJS Unique Value Directive Using an AngularJS Factory to Interact with a RESTful Service Application Structure The structure of the application is shown to the right. The  homepage is index.html and is located at the root of the application folder. It defines where application views will be loaded using the ng-view directive and includes script references to AngularJS, AngularJS routing and animation scripts, plus a few others located in the Scripts folder and to custom application scripts located in the app folder. The app folder contains all of the key scripts used in the application. There are several techniques that can be used for organizing script files but after experimenting with several of them I decided that I prefer things in folders such as controllers, views, services, etc. Doing that helps me find things a lot faster and allows me to categorize files (such as controllers) by functionality. My recommendation is to go with whatever works best for you. Anyone who says, “You’re doing it wrong!” should be ignored. Contrary to what some people think, there is no “one right way” to organize scripts and other files. As long as the scripts make it down to the client properly (you’ll likely minify and concatenate them anyway to reduce bandwidth and minimize HTTP calls), the way you organize them is completely up to you. Here’s what I ended up doing for this application: Animation code for some custom animations is located in the animations folder. In addition to AngularJS animations (which are defined using CSS in Content/animations.css), it also animates the initial customer data load using a 3rd party script called GreenSock. Controllers are located in the controllers folder. Some of the controllers are placed in subfolders based upon the their functionality while others are placed at the root of the controllers folder since they’re more generic:   The directives folder contains the custom directives created for the application. The filters folder contains the custom filters created for the application that filter city/state and product information. The partials folder contains partial views. This includes things like modal dialogs used in the application. The services folder contains AngularJS factories and services used for various purposes in the application. Most of the scripts in this folder provide data functionality. The views folder contains the different views used in the application. Like the controllers folder, the views are organized into subfolders based on their functionality:   Back-End Services The Customer Manager application (grab it from Github) provides two different options on the back-end including ASP.NET Web API and Node.js. The ASP.NET Web API back-end uses Entity Framework for data access and stores data in SQL Server (LocalDb). The other option on the back-end is Node.js, Express, and MongoDB.   Using the ASP.NET Web API Back-End To run the application using ASP.NET Web API/SQL Server back-end open the .sln file at the root of the project in Visual Studio 2012 or higher (the free Express 2013 for Web version is fine). Press F5 and a browser will automatically launch and display the application. Using the Node.js Back-End To run the application using the Node.js/MongoDB back-end follow these steps: In the CustomerManager directory execute 'npm install' to install Express, MongoDB and Mongoose (package.json). Load sample data into MongoDB by performing the following steps: Execute 'mongod' to start the MongoDB daemon Navigate to the CustomerManager directory (the one that has initMongoCustData.js in it) then execute 'mongo' to start the MongoDB shell Enter the following in the mongo shell to load the seed files that handle seeding the database with initial data: use custmgr load("initMongoCustData.js") load("initMongoSettingsData.js") load("initMongoStateData.js") Start the Node/Express server by navigating to the CustomerManager/server directory and executing 'node app.js' View the application at http://localhost:3000 in your browser. Key Features The Customer Manager application certainly doesn’t cover every feature provided by AngularJS (as mentioned the intent was to keep it as simple as possible) but does provide insight into several key areas: Using factories and services as re-useable data services (see the app/services folder) Creating custom directives (see the app/directives folder) Custom paging (see app/views/customers/customers.html and app/controllers/customers/customersController.js) Custom filters (see app/filters) Showing custom modal dialogs with a re-useable service (see app/services/modalService.js) Making Ajax calls using a factory (see app/services/customersService.js) Using Breeze to retrieve and work with data (see app/services/customersBreezeService.js). Switch the application to use the Breeze factory by opening app/services.config.js and changing the useBreeze property to true. Intercepting HTTP requests to display a custom overlay during Ajax calls (see app/directives/wcOverlay.js) Custom animations using the GreenSock library (see app/animations/listAnimations.js) Creating custom AngularJS animations using CSS (see Content/animations.css) JavaScript patterns for defining controllers, services/factories, directives, filters, and more (see any JavaScript file in the app folder) Card View and List View display of data (see app/views/customers/customers.html and app/controllers/customers/customersController.js) Using AngularJS validation functionality (see app/views/customerEdit.html, app/controllers/customerEditController.js, and app/directives/wcUnique.js) More… Conclusion I’ll be enhancing the application even more over time and welcome contributions as well. Tony Quinn contributed the initial Node.js/MongoDB code which is very cool to have as a back-end option. Access the standard application here and a version that has custom routing in it here. Additional information about the custom routing can be found in this post.

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  • Is there a solution that lets Node.js act as an HTTP reverse proxy?

    - by Igor Zinov'yev
    Our company has a project that right now uses nginx as a reverse proxy for serving static content and supporting comet connections. We use long polling connections to get rid of constant refresh requests and let users get updates immediately. Now, I know there is a lot of code already written for Node.js, but is there a solution that lets Node.js act as a reverse proxy for serving static content as nginx does? Or maybe there is a framework that allows to quickly develop such a layer using Node.js?

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  • Drupal 6: getting particular fields from Node Reference types...

    - by artmania
    Hi friends, I'm a drupal newbie... <?php print $node->field_date[0]['view']; ?> I can get the custom created CCK fields' value and display in tpl.php files as above... that's fine. my question is how can I get the Node reference fields' in-fields? for example, I have an event content type, and I have defined Node Reference for Location (title, address, img, etc.). When I write the code below, it displays all location content; <?php print $node->field_location[0]['view']; ?> but I need to get only address field from this location content type. sth like below would be great :D but not working; <?php print $node->field_location[0]['field_address']['view']; ?> so how can get that? appreciate helps so much! thanks a lot!

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  • Is it possible to run node script from a web page as differnt user?

    - by Blame
    I'am searching for days now but could not get an answer. I would like to do the following: User connects to editor.html (Apache2 with basic http auth) User want to open a file on the server with his user/pass (same as in passwd) Node.js Script gets startet with user rights from above and user can edit file The Node Script will handly the connection via websockets and read/writes files. I think the biggest problem is that its not possible to run a node script on the server from a web page... and I don´t want to involve any php/cgi scripts... only Apache and Node.js / JS. Please also comment or answer if you know that it is really not possible... Thanks! Kodak

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  • How to set up Node server for production on own machine?

    - by Matt Hintzke
    This must be a pretty basic thing to do, but I cannot find any good guide on how to do it on the internet. I only find how to set up a development environment for Node. I want to be able to forward my R-Pi's port 80 to my Node server, which I want to obviously listen on port 80. How can I close the native port 80 so that I can let me Node server listen on that port. Ultimately, I want to be able to access my pi from any remote location. I know how to set up a static IP and forward the port on my router, but now how do I allow Node into port 80?

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  • When parsing XML with jquery, how can we pass the current node from within each() to another functio

    - by Johusa
    Say we have an XML document with many book nodes... When parsing XML with jquery, how can i pass the current node from each() iteration to another function that will do some stuff until something is reached and then go back to the previous function (passing along the current node from this function back to the first function)? Here something more descriptive (this is just an example out of my head, not accurate): function MyParser(x1,x2,dom) { // if i am called by anotherFunction(thisNode) proceed from the passed node dom.find('book').each(function() { var Letter = thisNode.find(author).charAt(0); if(x1 == Letter) { // print everything till the next letter (x2) anotherFunction(thisNode) } } } function anotherFunction(x2,thisNode) { //continue parsing here until you reached x2 //when x2 is reached, return to previous function passing again the current node }

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  • How to represent a tree structure in NoSQL

    - by Vlad Nicula
    I'm new to NoSQL and have been playing around with a personal project on the MEAN stack (Mongo ExpressJs AngularJs NodeJs). I'm building a document editor of sorts that manages nodes of data. Each document is actually a tree. I have a CRUD api for documents, to create new trees and a CRUD api for nodes in a given document. Right now the documents are represented as a collection that holds everything, including nodes. The children parent relationship is done by ids. So the nodes are an map by id, and each node has references to what nodes are their children. I chose this "flat" approach because it is easier to get a node by id from a document. Being used to having a relation table between nodes and documents, a relation table between nodes and children nodes I find it a bit weird that I have to save the entire "nodes" map each time I update a node. Is there a better way to represent such a data type in NoSQL?

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  • For nodejs what are best design practices for native modules which share dependencies?

    - by Mark Essel
    Hypothetical situation, I have 3 node modules all native, A, B, and C.  A is a utilities module which exposes several functions to javascript through the node interface, in addition it declares/defines a rich set of native structures and functions B is a module which is dependent on data structures and source in A, it exposes some functions to javascript, in addition it declares/defines native structures and functions C is a module which is dependent on data structures and source in A & B, it exploses some functions to javascript, in addition it declares/defines native structures and functions So far when setting up these modules I have a preinstall script to install other dependent includes, but in order to access all of another modules source what is the best way to link to it's share library object (*.node) ? Is there an alternative best practice for native modules (such as installing all source from other modules before building that single module)? Reply

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  • my webserver with 16GB ram shows all RAM as used, but is it really, see the 'top'

    - by Alex
    I have some questions about my web server. Its a LAMP web server running centos 5.5 and php5, mysql5. The server gets hundreds (maybe thousand) of concurrent users during peak hours. I'm trying to optimize a little and understand "top". From what I can see: all 16GB of my ram have been used up? does that mean that my server needs more memory? My swap is only 2GB, should it be increased? usually during peak hours my server load average first number is about 2.5-3. What could I do to optimize the server so that the load average even during peak doesn't go above 1? In the past I was told a good working server should stay under 1 load, is this still true? Although even during load of 2.5-3, server pages and applications seem to load with pretty good speed. what should the memory size in php.ini be set to? top - 14:30:18 up 2 days, 12:41, 5 users, load average: 1.25, 1.74, 2.92 Tasks: 305 total, 2 running, 302 sleeping, 0 stopped, 1 zombie Cpu(s): 6.3%us, 0.9%sy, 0.0%ni, 92.5%id, 0.2%wa, 0.0%hi, 0.1%si, 0.0%st Mem: 16427200k total, 16111472k used, 315728k free, 3120316k buffers Swap: 2104496k total, 268k used, 2104228k free, 6216756k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 29080 apache 15 0 358m 36m 5192 S 20.2 0.2 2:08.40 httpd 29093 apache 18 0 357m 36m 5192 S 18.2 0.2 2:02.52 httpd 29079 apache 15 0 370m 49m 5832 S 10.0 0.3 2:32.14 httpd 1812 apache 15 0 370m 49m 5196 S 7.3 0.3 2:25.30 httpd 5204 apache 15 0 358m 36m 5168 S 5.3 0.2 0:59.28 httpd 29075 apache 15 0 370m 48m 5184 S 3.3 0.3 2:15.93 httpd 9712 apache 15 0 360m 38m 5180 S 3.0 0.2 0:54.81 httpd 29072 apache 16 0 358m 36m 5192 S 2.7 0.2 2:24.43 httpd 6310 apache 17 0 388m 67m 5180 S 2.3 0.4 0:58.85 httpd 8674 apache 15 0 343m 21m 4980 S 2.0 0.1 0:07.91 httpd 29085 apache 15 0 371m 49m 5224 S 2.0 0.3 2:16.86 httpd 29083 apache 15 0 370m 48m 5196 S 1.7 0.3 2:10.64 httpd 5575 apache 15 0 357m 36m 5228 S 1.3 0.2 0:53.78 httpd 29066 apache 15 0 379m 59m 5860 R 1.3 0.4 2:11.93 httpd 29078 apache 15 0 370m 48m 5188 S 1.3 0.3 2:14.52 httpd 29084 apache 15 0 370m 48m 5208 S 1.0 0.3 2:02.49 httpd 29089 apache 15 0 370m 48m 5188 S 1.0 0.3 2:27.61 httpd 29082 apache 15 0 390m 68m 5188 S 0.7 0.4 2:32.48 httpd 29984 apache 15 0 358m 36m 5228 S 0.7 0.2 2:08.32 httpd 3571 root 16 0 13400 1792 848 S 0.3 0.0 2:37.89 top 4419 mysql 15 0 668m 175m 7204 S 0.3 1.1 3:32.25 mysqld 28181 root 15 0 90460 3624 2680 S 0.3 0.0 0:17.60 sshd 29091 apache 15 0 390m 69m 5196 S 0.3 0.4 2:29.99 httpd 32476 root 15 0 12900 1320 848 R 0.3 0.0 0:06.46 top 1 root 15 0 10372 680 572 S 0.0 0.0 0:02.01 init 2 root RT -5 0 0 0 S 0.0 0.0 0:00.51 migration/0 3 root 34 19 0 0 0 S 0.0 0.0 0:00.07 ksoftirqd/0 4 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/0 5 root RT -5 0 0 0 S 0.0 0.0 0:00.12 migration/1 6 root 34 19 0 0 0 S 0.0 0.0 0:00.03 ksoftirqd/1 7 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/1 8 root RT -5 0 0 0 S 0.0 0.0 0:00.06 migration/2 9 root 34 19 0 0 0 S 0.0 0.0 0:00.03 ksoftirqd/2 10 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/2 11 root RT -5 0 0 0 S 0.0 0.0 0:00.06 migration/3 12 root 34 19 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/3 13 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/3 14 root RT -5 0 0 0 S 0.0 0.0 0:01.45 migration/4 15 root 34 19 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/4 16 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/4 17 root RT -5 0 0 0 S 0.0 0.0 0:00.22 migration/5 18 root 34 19 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/5 19 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/5 20 root RT -5 0 0 0 S 0.0 0.0 0:00.15 migration/6 21 root 34 19 0 0 0 S 0.0 0.0 0:00.02 ksoftirqd/6 22 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/6 23 root RT -5 0 0 0 S 0.0 0.0 0:00.15 migration/7 24 root 34 19 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/7 25 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/7 26 root RT -5 0 0 0 S 0.0 0.0 0:00.19 migration/8 27 root 34 19 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/8 28 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/8 29 root RT -5 0 0 0 S 0.0 0.0 0:00.34 migration/9 30 root 34 19 0 0 0 S 0.0 0.0 0:00.03 ksoftirqd/9 31 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/9 32 root RT -5 0 0 0 S 0.0 0.0 0:00.16 migration/10 33 root 34 19 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/10 34 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/10 35 root RT -5 0 0 0 S 0.0 0.0 0:00.12 migration/11 36 root 34 19 0 0 0 S 0.0 0.0 0:00.05 ksoftirqd/11 37 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/11 38 root RT -5 0 0 0 S 0.0 0.0 0:00.35 migration/12

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  • C# System.Xml.Serialization Self-nested elements

    - by Jake
    Hi, I am trying to deserialize <graph> <node> <node> <node></node> </node> </node> <node> <node> <node></node> </node> </node> </graph> with [XmlRoot("graph")] class graph { List<node> _children = new List<node>(); [XmlElement("node")] public Node[] node { get { return _children.ToArray(); } set { foreach(node n in value) children.add(n) } }; } class node { List<node> _children = new List<node>(); [XmlElement("node")] public Node[] node { get { return _children.ToArray(); } set { foreach(node n in value) children.add(n) } }; } but it keeps saying object not created, null reference encountered when trying to set children nodes. What is wrong above? Thanks in advance~

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  • how to debug application as root in eclipse in Ubuntu?

    - by futang
    I'm programming application using libpcap. when I debug the application in normal mode, pcap cannot get the network device. it seems that I have to debug the application in root. How can I debug the application in root? I have the root password. I think eclipse has such an option that can add root for the debugging application,but I don't know how to do it. please help.

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  • C++ linked list based tree structure. Sanely copy nodes between lists.

    - by krunk
    edit Clafification: The intention is not to remove the node from the original list. But to create an identical node (data and children wise) to the original and insert that into the new list. In other words, a "move" does not imply a "remove" from the original. endedit The requirements: Each Node in the list must contain a reference to its previous sibling Each Node in the list must contain a reference to its next sibling Each Node may have a list of child nodes Each child Node must have a reference to its parent node Basically what we have is a tree structure of arbitrary depth and length. Something like: -root(NULL) --Node1 ----ChildNode1 ------ChildOfChild --------AnotherChild ----ChildNode2 --Node2 ----ChildNode1 ------ChildOfChild ----ChildNode2 ------ChildOfChild --Node3 ----ChildNode1 ----ChildNode2 Given any individual node, you need to be able to either traverse its siblings. the children, or up the tree to the root node. A Node ends up looking something like this: class Node { Node* previoius; Node* next; Node* child; Node* parent; } I have a container class that stores these and provides STL iterators. It performs your typical linked list accessors. So insertAfter looks like: void insertAfter(Node* after, Node* newNode) { Node* next = after->next; after->next = newNode; newNode->previous = after; next->previous = newNode; newNode->next = next; newNode->parent = after->parent; } That's the setup, now for the question. How would one move a node (and its children etc) to another list without leaving the previous list dangling? For example, if Node* myNode exists in ListOne and I want to append it to listTwo. Using pointers, listOne is left with a hole in its list since the next and previous pointers are changed. One solution is pass by value of the appended Node. So our insertAfter method would become: void insertAfter(Node* after, Node newNode); This seems like an awkward syntax. Another option is doing the copying internally, so you'd have: void insertAfter(Node* after, const Node* newNode) { Node *new_node = new Node(*newNode); Node* next = after->next; after->next = new_node; new_node->previous = after; next->previous = new_node; new_node->next = next; new_node->parent = after->parent; } Finally, you might create a moveNode method for moving and prevent raw insertion or appending of a node that already has been assigned siblings and parents. // default pointer value is 0 in constructor and a operator bool(..) // is defined for the Node bool isInList(const Node* node) const { return (node->previous || node->next || node->parent); } // then in insertAfter and friends if(isInList(newNode) // throw some error and bail I thought I'd toss this out there and see what folks came up with.

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  • Command does not execute in crontab while command itself works just fine

    - by fuzzybee
    I have this script from Colin Johnson on Github - https://github.com/colinbjohnson/aws-missing-tools/tree/master/ec2-automate-backup It seems great. I have modified it to send email to myself every time an EBS snapshot is created or deleted. The following works like a charm ec2-automate-backup.sh -v "vol-myvolumeid" -k 3 However, it does not execute at all as part of my crontab (I didn't receive any emails) #some command that got commented out */5 * * * * ec2-automate-backup.sh -v "vol-fb2fbcdf" -k 3; * * * * * date /root/logs/crontab.log; */5 * * * * date /root/logs/crontab2.log Please note that the 2nd and 3rd execute just fines as I can see the date and time in log files. What could I have missed here? The full ec2-automate-backup.sh is as follows: #!/bin/bash - # Author: Colin Johnson / [email protected] # Date: 2012-09-24 # Version 0.1 # License Type: GNU GENERAL PUBLIC LICENSE, Version 3 # #confirms that executables required for succesful script execution are available prerequisite_check() { for prerequisite in basename ec2-create-snapshot ec2-create-tags ec2-describe-snapshots ec2-delete-snapshot date do #use of "hash" chosen as it is a shell builtin and will add programs to hash table, possibly speeding execution. Use of type also considered - open to suggestions. hash $prerequisite &> /dev/null if [[ $? == 1 ]] #has exits with exit status of 70, executable was not found then echo "In order to use `basename $0`, the executable \"$prerequisite\" must be installed." 1>&2 | mailx -s "Error happened 0" [email protected] ; exit 70 fi done } #get_EBS_List gets a list of available EBS instances depending upon the selection_method of EBS selection that is provided by user input get_EBS_List() { case $selection_method in volumeid) if [[ -z $volumeid ]] then echo "The selection method \"volumeid\" (which is $app_name's default selection_method of operation or requested by using the -s volumeid parameter) requires a volumeid (-v volumeid) for operation. Correct usage is as follows: \"-v vol-6d6a0527\",\"-s volumeid -v vol-6d6a0527\" or \"-v \"vol-6d6a0527 vol-636a0112\"\" if multiple volumes are to be selected." 1>&2 | mailx -s "Error happened 1" [email protected] ; exit 64 fi ebs_selection_string="$volumeid" ;; tag) if [[ -z $tag ]] then echo "The selected selection_method \"tag\" (-s tag) requires a valid tag (-t key=value) for operation. Correct usage is as follows: \"-s tag -t backup=true\" or \"-s tag -t Name=my_tag.\"" 1>&2 | mailx -s "Error happened 2" [email protected] ; exit 64 fi ebs_selection_string="--filter tag:$tag" ;; *) echo "If you specify a selection_method (-s selection_method) for selecting EBS volumes you must select either \"volumeid\" (-s volumeid) or \"tag\" (-s tag)." 1>&2 | mailx -s "Error happened 3" [email protected] ; exit 64 ;; esac #creates a list of all ebs volumes that match the selection string from above ebs_backup_list_complete=`ec2-describe-volumes --show-empty-fields --region $region $ebs_selection_string 2>&1` #takes the output of the previous command ebs_backup_list_result=`echo $?` if [[ $ebs_backup_list_result -gt 0 ]] then echo -e "An error occured when running ec2-describe-volumes. The error returned is below:\n$ebs_backup_list_complete" 1>&2 | mailx -s "Error happened 4" [email protected] ; exit 70 fi ebs_backup_list=`echo "$ebs_backup_list_complete" | grep ^VOLUME | cut -f 2` #code to right will output list of EBS volumes to be backed up: echo -e "Now outputting ebs_backup_list:\n$ebs_backup_list" } create_EBS_Snapshot_Tags() { #snapshot tags holds all tags that need to be applied to a given snapshot - by aggregating tags we ensure that ec2-create-tags is called only onece snapshot_tags="" #if $name_tag_create is true then append ec2ab_${ebs_selected}_$date_current to the variable $snapshot_tags if $name_tag_create then ec2_snapshot_resource_id=`echo "$ec2_create_snapshot_result" | cut -f 2` snapshot_tags="$snapshot_tags --tag Name=ec2ab_${ebs_selected}_$date_current" fi #if $purge_after_days is true, then append $purge_after_date to the variable $snapshot_tags if [[ -n $purge_after_days ]] then snapshot_tags="$snapshot_tags --tag PurgeAfter=$purge_after_date --tag PurgeAllow=true" fi #if $snapshot_tags is not zero length then set the tag on the snapshot using ec2-create-tags if [[ -n $snapshot_tags ]] then echo "Tagging Snapshot $ec2_snapshot_resource_id with the following Tags:" ec2-create-tags $ec2_snapshot_resource_id --region $region $snapshot_tags #echo "Snapshot tags successfully created" | mailx -s "Snapshot tags successfully created" [email protected] fi } date_command_get() { #finds full path to date binary date_binary_full_path=`which date` #command below is used to determine if date binary is gnu, macosx or other date_binary_file_result=`file -b $date_binary_full_path` case $date_binary_file_result in "Mach-O 64-bit executable x86_64") date_binary="macosx" ;; "ELF 64-bit LSB executable, x86-64, version 1 (SYSV)"*) date_binary="gnu" ;; *) date_binary="unknown" ;; esac #based on the installed date binary the case statement below will determine the method to use to determine "purge_after_days" in the future case $date_binary in gnu) date_command="date -d +${purge_after_days}days -u +%Y-%m-%d" ;; macosx) date_command="date -v+${purge_after_days}d -u +%Y-%m-%d" ;; unknown) date_command="date -d +${purge_after_days}days -u +%Y-%m-%d" ;; *) date_command="date -d +${purge_after_days}days -u +%Y-%m-%d" ;; esac } purge_EBS_Snapshots() { #snapshot_tag_list is a string that contains all snapshots with either the key PurgeAllow or PurgeAfter set snapshot_tag_list=`ec2-describe-tags --show-empty-fields --region $region --filter resource-type=snapshot --filter key=PurgeAllow,PurgeAfter` #snapshot_purge_allowed is a list of all snapshot_ids with PurgeAllow=true snapshot_purge_allowed=`echo "$snapshot_tag_list" | grep .*PurgeAllow'\t'true | cut -f 3` for snapshot_id_evaluated in $snapshot_purge_allowed do #gets the "PurgeAfter" date which is in UTC with YYYY-MM-DD format (or %Y-%m-%d) purge_after_date=`echo "$snapshot_tag_list" | grep .*$snapshot_id_evaluated'\t'PurgeAfter.* | cut -f 5` #if purge_after_date is not set then we have a problem. Need to alter user. if [[ -z $purge_after_date ]] #Alerts user to the fact that a Snapshot was found with PurgeAllow=true but with no PurgeAfter date. then echo "A Snapshot with the Snapshot ID $snapshot_id_evaluated has the tag \"PurgeAllow=true\" but does not have a \"PurgeAfter=YYYY-MM-DD\" date. $app_name is unable to determine if $snapshot_id_evaluated should be purged." 1>&2 | mailx -s "Error happened 5" [email protected] else #convert both the date_current and purge_after_date into epoch time to allow for comparison date_current_epoch=`date -j -f "%Y-%m-%d" "$date_current" "+%s"` purge_after_date_epoch=`date -j -f "%Y-%m-%d" "$purge_after_date" "+%s"` #perform compparison - if $purge_after_date_epoch is a lower number than $date_current_epoch than the PurgeAfter date is earlier than the current date - and the snapshot can be safely removed if [[ $purge_after_date_epoch < $date_current_epoch ]] then echo "The snapshot \"$snapshot_id_evaluated\" with the Purge After date of $purge_after_date will be deleted." ec2-delete-snapshot --region $region $snapshot_id_evaluated echo "Old snapshots successfully deleted for $volumeid" | mailx -s "Old snapshots successfully deleted for $volumeid" [email protected] fi fi done } #calls prerequisitecheck function to ensure that all executables required for script execution are available prerequisite_check app_name=`basename $0` #sets defaults selection_method="volumeid" region="ap-southeast-1" #date_binary allows a user to set the "date" binary that is installed on their system and, therefore, the options that will be given to the date binary to perform date calculations date_binary="" #sets the "Name" tag set for a snapshot to false - using "Name" requires that ec2-create-tags be called in addition to ec2-create-snapshot name_tag_create=false #sets the Purge Snapshot feature to false - this feature will eventually allow the removal of snapshots that have a "PurgeAfter" tag that is earlier than current date purge_snapshots=false #handles options processing while getopts :s:r:v:t:k:pn opt do case $opt in s) selection_method="$OPTARG";; r) region="$OPTARG";; v) volumeid="$OPTARG";; t) tag="$OPTARG";; k) purge_after_days="$OPTARG";; n) name_tag_create=true;; p) purge_snapshots=true;; *) echo "Error with Options Input. Cause of failure is most likely that an unsupported parameter was passed or a parameter was passed without a corresponding option." 1>&2 ; exit 64;; esac done #sets date variable date_current=`date -u +%Y-%m-%d` #sets the PurgeAfter tag to the number of days that a snapshot should be retained if [[ -n $purge_after_days ]] then #if the date_binary is not set, call the date_command_get function if [[ -z $date_binary ]] then date_command_get fi purge_after_date=`$date_command` echo "Snapshots taken by $app_name will be eligible for purging after the following date: $purge_after_date." fi #get_EBS_List gets a list of EBS instances for which a snapshot is desired. The list of EBS instances depends upon the selection_method that is provided by user input get_EBS_List #the loop below is called once for each volume in $ebs_backup_list - the currently selected EBS volume is passed in as "ebs_selected" for ebs_selected in $ebs_backup_list do ec2_snapshot_description="ec2ab_${ebs_selected}_$date_current" ec2_create_snapshot_result=`ec2-create-snapshot --region $region -d $ec2_snapshot_description $ebs_selected 2>&1` if [[ $? != 0 ]] then echo -e "An error occured when running ec2-create-snapshot. The error returned is below:\n$ec2_create_snapshot_result" 1>&2 ; exit 70 else ec2_snapshot_resource_id=`echo "$ec2_create_snapshot_result" | cut -f 2` echo "Snapshots successfully created for volume $volumeid" | mailx -s "Snapshots successfully created for $volumeid" [email protected] fi create_EBS_Snapshot_Tags done #if purge_snapshots is true, then run purge_EBS_Snapshots function if $purge_snapshots then echo "Snapshot Purging is Starting Now." purge_EBS_Snapshots fi cron log Oct 23 10:24:01 ip-10-130-153-227 CROND[28214]: (root) CMD (root (ec2-automate-backup.sh -v "vol-fb2fbcdf" -k 3;)) Oct 23 10:24:01 ip-10-130-153-227 CROND[28215]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:25:01 ip-10-130-153-227 CROND[28228]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:25:01 ip-10-130-153-227 CROND[28229]: (root) CMD (date >> /root/logs/crontab2.log) Oct 23 10:26:01 ip-10-130-153-227 CROND[28239]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:27:01 ip-10-130-153-227 CROND[28247]: (root) CMD (root (ec2-automate-backup.sh -v "vol-fb2fbcdf" -k 3;)) Oct 23 10:27:01 ip-10-130-153-227 CROND[28248]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:28:01 ip-10-130-153-227 CROND[28263]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:29:01 ip-10-130-153-227 CROND[28275]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:30:01 ip-10-130-153-227 CROND[28292]: (root) CMD (root (ec2-automate-backup.sh -v "vol-fb2fbcdf" -k 3;)) Oct 23 10:30:01 ip-10-130-153-227 CROND[28293]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:30:01 ip-10-130-153-227 CROND[28294]: (root) CMD (date >> /root/logs/crontab2.log) Oct 23 10:31:01 ip-10-130-153-227 CROND[28312]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:32:01 ip-10-130-153-227 CROND[28319]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:33:01 ip-10-130-153-227 CROND[28325]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:33:01 ip-10-130-153-227 CROND[28324]: (root) CMD (root (ec2-automate-backup.sh -v "vol-fb2fbcdf" -k 3;)) Oct 23 10:34:01 ip-10-130-153-227 CROND[28345]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:35:01 ip-10-130-153-227 CROND[28362]: (root) CMD (date >> /root/logs/crontab.log;) Oct 23 10:35:01 ip-10-130-153-227 CROND[28363]: (root) CMD (date >> /root/logs/crontab2.log) Mails to root From [email protected] Tue Oct 23 06:00:01 2012 Return-Path: <[email protected]> Date: Tue, 23 Oct 2012 06:00:01 GMT From: [email protected] (Cron Daemon) To: [email protected] Subject: Cron <root@ip-10-130-153-227> root ec2-automate-backup.sh -v "vol-fb2fbcdf" -k 3 Content-Type: text/plain; charset=UTF-8 Auto-Submitted: auto-generated X-Cron-Env: <SHELL=/bin/sh> X-Cron-Env: <HOME=/root> X-Cron-Env: <PATH=/usr/bin:/bin> X-Cron-Env: <LOGNAME=root> X-Cron-Env: <USER=root> Status: R /bin/sh: root: command not found

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  • Does it matter the direction of a Huffman's tree child node?

    - by Omega
    So, I'm on my quest about creating a Java implementation of Huffman's algorithm for compressing/decompressing files (as you might know, ever since Why create a Huffman tree per character instead of a Node?) for a school assignment. I now have a better understanding of how is this thing supposed to work. Wikipedia has a great-looking algorithm here that seemed to make my life way easier. Taken from http://en.wikipedia.org/wiki/Huffman_coding: Create a leaf node for each symbol and add it to the priority queue. While there is more than one node in the queue: Remove the two nodes of highest priority (lowest probability) from the queue Create a new internal node with these two nodes as children and with probability equal to the sum of the two nodes' probabilities. Add the new node to the queue. The remaining node is the root node and the tree is complete. It looks simple and great. However, it left me wondering: when I "merge" two nodes (make them children of a new internal node), does it even matter what direction (left or right) will each node be afterwards? I still don't fully understand Huffman coding, and I'm not very sure if there is a criteria used to tell whether a node should go to the right or to the left. I assumed that, perhaps the highest-frequency node would go to the right, but I've seen some Huffman trees in the web that don't seem to follow such criteria. For instance, Wikipedia's example image http://upload.wikimedia.org/wikipedia/commons/thumb/8/82/Huffman_tree_2.svg/625px-Huffman_tree_2.svg.png seems to put the highest ones to the right. But other images like this one http://thalia.spec.gmu.edu/~pparis/classes/notes_101/img25.gif has them all to the left. However, they're never mixed up in the same image (some to the right and others to the left). So, does it matter? Why?

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  • BST insert operation. don't insert a node if a duplicate exists already

    - by jeev
    the following code reads an input array, and constructs a BST from it. if the current arr[i] is a duplicate, of a node in the tree, then arr[i] is discarded. count in the struct node refers to the number of times a number appears in the array. fi refers to the first index of the element found in the array. after the insertion, i am doing a post-order traversal of the tree and printing the data, count and index (in this order). the output i am getting when i run this code is: 0 0 7 0 0 6 thank you for your help. Jeev struct node{ int data; struct node *left; struct node *right; int fi; int count; }; struct node* binSearchTree(int arr[], int size); int setdata(struct node**node, int data, int index); void insert(int data, struct node **root, int index); void sortOnCount(struct node* root); void main(){ int arr[] = {2,5,2,8,5,6,8,8}; int size = sizeof(arr)/sizeof(arr[0]); struct node* temp = binSearchTree(arr, size); sortOnCount(temp); } struct node* binSearchTree(int arr[], int size){ struct node* root = (struct node*)malloc(sizeof(struct node)); if(!setdata(&root, arr[0], 0)) fprintf(stderr, "root couldn't be initialized"); int i = 1; for(;i<size;i++){ insert(arr[i], &root, i); } return root; } int setdata(struct node** nod, int data, int index){ if(*nod!=NULL){ (*nod)->fi = index; (*nod)->left = NULL; (*nod)->right = NULL; return 1; } return 0; } void insert(int data, struct node **root, int index){ struct node* new = (struct node*)malloc(sizeof(struct node)); setdata(&new, data, index); struct node** temp = root; while(1){ if(data<=(*temp)->data){ if((*temp)->left!=NULL) *temp=(*temp)->left; else{ (*temp)->left = new; break; } } else if(data>(*temp)->data){ if((*temp)->right!=NULL) *temp=(*temp)->right; else{ (*temp)->right = new; break; } } else{ (*temp)->count++; free(new); break; } } } void sortOnCount(struct node* root){ if(root!=NULL){ sortOnCount(root->left); sortOnCount(root->right); printf("%d %d %d\n", (root)->data, (root)->count, (root)->fi); } }

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