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• How to protect/monitor your site from crawling by malicious user

  - by deathy

  Situation: Site with content protected by username/password (not all controlled since they can be trial/test users) a normal search engine can't get at it because of username/password restrictions a malicious user can still login and pass the session cookie to a "wget -r" or something else. The question would be what is the best solution to monitor such activity and respond to it (considering the site policy is no-crawling/scraping allowed) I can think of some options: Set up some traffic monitoring solution to limit the number of requests for a given user/IP. Related to the first point: Automatically block some user-agents (Evil :)) Set up a hidden link that when accessed logs out the user and disables his account. (Presumably this would not be accessed by a normal user since he wouldn't see it to click it, but a bot will crawl all links.) For point 1. do you know of a good already-implemented solution? Any experiences with it? One problem would be that some false positives might show up for very active but human users. For point 3: do you think this is really evil? Or do you see any possible problems with it? Also accepting other suggestions.

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• Why use SQL database?

  - by martinthenext

  I'm not quite sure stackoverflow is a place for such a general question, but let's give it a try. Being exposed to the need of storing application data somewhere, I've always used MySQL or sqlite, just because it's always done like that. As it seems like the whole world is using these databases, most of all software products, frameworks, etc. It is rather hard for a beginning developer like me to ask a question - why? Ok, say we have some object-oriented logic in our application, and objects are related to each other somehow. We need to map this logic to the storage logic, so we need relations between database objects too. This leads us to using relational database and I'm ok with that - to put it simple, our database rows sometimes will need to have references to other tables' rows. But why do use SQL language for interaction with such a database? SQL query is a text message. I can understand this is cool for actually understanding what it does, but isn't it silly to use text table and column names for a part of application that no one ever seen after deploynment? If you had to write a data storage from scratch, you would have never used this kind of solution. Personally, I would have used some 'compiled db query' bytecode, that would be assembled once inside a client application and passed to the database. And it surely would name tables and colons by id numbers, not ascii-strings. In the case of changes in table structure those byte queries could be recompiled according to new db schema, stored in XML or something like that. What are the problems of my idea? Is there any reason for me not to write it myself and to use SQL database instead?

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• "Public" nested classes or not

  - by Frederick

  Suppose I have a class 'Application'. In order to be initialised it takes certain settings in the constructor. Let's also assume that the number of settings is so many that it's compelling to place them in a class of their own. Compare the following two implementations of this scenario. Implementation 1: class Application { Application(ApplicationSettings settings) { //Do initialisation here } } class ApplicationSettings { //Settings related methods and properties here } Implementation 2: class Application { Application(Application.Settings settings) { //Do initialisation here } class Settings { //Settings related methods and properties here } } To me, the second approach is very much preferable. It is more readable because it strongly emphasises the relation between the two classes. When I write code to instantiate Application class anywhere, the second approach is going to look prettier. Now just imagine the Settings class itself in turn had some similarly "related" class and that class in turn did so too. Go only three such levels and the class naming gets out out of hand in the 'non-nested' case. If you nest, however, things still stay elegant. Despite the above, I've read people saying on StackOverflow that nested classes are justified only if they're not visible to the outside world; that is if they are used only for the internal implementation of the containing class. The commonly cited objection is bloating the size of containing class's source file, but partial classes is the perfect solution for that problem. My question is, why are we wary of the "publicly exposed" use of nested classes? Are there any other arguments against such use?

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• Logging exceptions during bean injection

  - by Marc W

  I think this is a pretty basic question, but after Googling around I can't seem to find the answer. What I need is a way to log some custom output with log4j during Spring bean construction. I have a factory class called ResponderFactory (being used as an instance factory in Spring) with a factory method that can throw 2 different types of exception. public CollectorResponder collectorResponder(String inputQueueName) throws ConfigurationException, BrokerConnectionException {} Now, normally I could wrap a call to this method in a try-catch block with 2 catch clauses to handle the logging situations for each of the exceptions. However, if I'm using Spring to inject this CollectorResponder, created with the factory, into another class I don't see how this is possible. <bean id="responderFactory" class="com.package.ResponderFactory"> <constructor-arg index="0" ref="basicDispatcher" /> <constructor-arg index="1" value="http://localhost:9000" /> </bean> <bean id="collectorResponder" class="com.package.CollectorResponder" factory-bean="responderFactory" factory-method="collectorResponder"> <constructor-arg value="collector.in" /> </bean> <bean id="collectorConsumer" class="com.package.CollectorConsumer"> <constructor-arg ref="collectorResponder" /> </bean> Again, I want to catch these exceptions when the collectorResponder bean is instantiated. Right now I'm dealing with this is CollectorConsumer when I instantiate using new CollectorResponder(...). Is there any way I can do this?

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• Can't get SFTP to work in PHP

  - by Chris Kloberdanz

  I am writing a simple SFTP client in PHP because we have the need to programatically retrieve files via n remote servers. I am using the PECL SSH2 extension. I have run up against a road block, though. The documentation on php.net suggests that you can do this: $stream = fopen("ssh2.sftp://$sftp/path/to/file", 'r'); However, I have an ls method that attempts to something similar public function ls($dir) { $rd = "ssh2.sftp://{$this->sftp}/$dir"; $handle = opendir($rd); if (!is_resource($handle)) { throw new SFTPException("Could not open directory."); } while (false !== ($file = readdir($handle))) { if (substr($file, 0, 1) != '.'){ print $file . "\n"; } } closedir($handle); } I get the following error: PHP Warning: opendir(): Unable to open ssh2.sftp://Resource id #5/outgoing on remote host This makes perfect sense because that's what happens when you cast a resource to string. Is the documentation wrong? I tried replacing the resource with host, username, and host and that didn't work either. I know the path is correct because I can run SFTP from the command line and it works fine. Has anyone else tried to use the SSH2 extenstion with SFTP? Am I missing something obvious here? UPDATE: I setup sftp on another machine in-house and it works just fine. So, there must be something about the server I am trying to connect to that isn't working.

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• iphone: problem playing youtube mp4's over 3g network

  - by Alex1987

  Hi guys I'm am developing an app that enables the user to stream youtube mp4 videos on the iphone. What I did was very simple - I just took a url of the form http://youtube.com/get_video?*&fmt=18 (for example http://youtube.com/get_video?video_id=KUXGVfmrEN4&&t=vjVQa1PpcFNrxzfbeI6WrJfK6s0BdQ9ypMgV_6yqwjo=&fmt=18) and used mpmovieplayercontroller or UIWebView to stream the video. It works great over WIFI but doesn't work at all on 3g network . On 3g I get a blank page in the UIWebView or file format not supported on mpmovieplayercontroller. Does youtube block access from 3g networks to its mp4 videos? How to bypass this? You can check this easily yourself on your own iphone by preforming the following steps: 1. Obtain the download link. You can do this easily by downloading the following plugin for firefox: https://addons.mozilla.org/en-US/firefox/addon/13990. 2. Email the link to your email. 3. Open your mail on the iphone and click on the link. Try this on WIFI and 3g.

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• Does anyone know how to detect whether a Windows Service is running through Java

  - by GKelly

  There's plenty of information on running Java apps as services, but I need to know how to detect whether a windows service is running or not. Does anyone know how??? At the DOS prompt, I can run: tasklist /svc|findstr "NonRunningService" echo Return code for N onRunningService is %ERRORLEVEL% tasklist /svc|findstr "RunningService" echo Return code for RunningService is %ERRORLEVEL% I get the following: Return code for NonRunningService is 1 Return code for RunningService is 0 In code, I have: int retCode = Runtime.getRuntime.exec("tasklist /svc|findstr \"NonRunningService\"").waitFor(); System.out.println("Return code for NonRunningService is " + retCode); retCode = Runtime.getRuntime.exec("tasklist /svc|findstr \"RunningService\"").waitFor(); System.out.println("Return code for RunningService is " + retCode); I get the following output Return code for NonRunningService is 1 Return code for RunningService is 1 According to the JavaDocs, the waitFor() should block until the process finishes, and give me the exit value of the process. I've also tried using the Process/ProcessBuilder command line calls: //'tasklist /nh /fi "SERVICES eq RunningService"' will return a line for // each running service of the requested type. Process p1 = new ProcessBuilder("tasklist", "/nh", "/fi" "SERVICES eq RunningService").start(); p1.waitFor(); BufferedReader is = new BufferedReader(new InputStreamReader(p1.getInputStream())); String line = is.readLine(); System.out.println("Service - " + line); System.out.println("Running? ", (line==null?"No":"Yes"); gives: Service - Running? No even when I get lines in the output at the command line!

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• HTML button to NOT submit form

  - by arik-so

  Hello, I have a form. Outside that form, I have a button. A simple button, like this: <button>My Button</button> Nevertheless, when I click it, it submits the form. Here's the code: <form id="myform"> <input /> </form> <button>My Button</button> All this button should do is some JavaScript. But even when it looks just like in the code above, it submits the form. When I change the tag button to span, it works perfectly. But unfortunately, it needs to be a button. Is there any way to block that button from submitting the form? Like e. g. <button onclick="document.getElementById('myform').doNotSubmit();">My Button</button> Thanks in advance!

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• "Decompile" Javascript function? *ADVANCED*

  - by caesar2k

  [1] Ok, I don't even know how to call this, to be honest. So let me get some semi-pseudo code, to show what I'm trying to do. I'm using jquery to get an already existing script declared inside the page, inside a createDocument() element, from an AJAX call. GM_xmlhttprequest({ ... load:function(r){ var doc = document_from_string(r.responseText); script_content = $('body script:regex(html, local_xw_sig)', doc).html(); var scriptEl = document.createElement('script'); scriptEl.type = 'text/javascript'; scriptEl.innerHTML = script_content; // good till here (function(sc){ eval(sc.innerHTML); // not exactly like this, but you get the idea, errors alert('wont get here ' + local_xw_sig); // local_xw_sig is a global "var" inside the source })(scriptEl); } }); so far so good, the script indeed contains the source from the entire script block. Now, inside this "script_content", there are auto executing functions, like $(document).ready(function(){...}) that, everything I "eval" the innerHTML, it executes this code, halting my encapsulated script. like variables that doesn't exist, etc removing certain parts of the script using regex isn't really an option... what I really wanted is to "walk" inside the function. like do a (completely fictional): script = eval("function(){" + script_content + "};"); alert(script['local_xw_sig']); // a03ucc34095cw3495 is there any way to 'disassemble' the function, and be able to reach the "var"s inside of it? like this function: function hello(){ var message = "hello"; } alert(hello.message); // message = var inside the function is it possible at all? or I will have to hack my way using regex? ;P [2] also, is there any way I can access javascript inside a document created with "createDocument"?

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• How to not pass around the container when using IoC in Winforms

  - by L2Type

  I'm new to the world of IoC and having a problem with implementing it in a Winforms application. I have an extremely basic application Winform application that uses MVC, it is one controller that does all the work and a working dialog (obviously with a controller). So I load all my classes in to my IoC container in program.cs and create the main form controller using the container. But this is where I am having problems, I only want to create the working dialog controller when it's used and inside a using statement. At first I passed in the container but I've read this is bad practice and more over the container is a static and I want to unit test this class. So how do you create classes in a unit test friendly way without passing in the container, I was considering the abstract factory pattern but that alone would solve my problem without using the IoC. I'm not using any famous framework, I borrowed a basic one from this blog post http://www.kenegozi.com/Blog/2008/01/17/its-my-turn-to-build-an-ioc-container-in-15-minutes-and-33-lines.aspx How do I do this with IoC? Is this the wrong use for IoC?

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• compact Number formatting behavior in Java (automatically switch between decimal and scientific notation)

  - by kostmo

  I am looking for a way to format a floating point number dynamically in either standard decimal format or scientific notation, depending on the value of the number. For moderate magnitudes, the number should be formatted as a decimal with trailing zeros suppressed. If the floating point number is equal to an integral value, the decimal point should also be suppressed. For extreme magnitudes (very small or very large), the number should be expressed in scientific notation. Alternately stated, if the number of characters in the expression as standard decimal notation exceeds a certain threshold, switch to scientific notation. I should have control over the maximum number of digits of precision, but I don't want trailing zeros appended to express the minimum precision; all trailing zeros should be suppressed. Basically, it should optimize for compactness and readability. 2.80000 - 2.8 765.000000 - 765 0.0073943162953 - 0.00739432 (limit digits of precision—to 6 in this case) 0.0000073943162953 - 7.39432E-6 (switch to scientific notation if the magnitude is small enough—less than 1E-5 in this case) 7394316295300000 - 7.39432E+6 (switch to scientific notation if the magnitude is large enough—for example, when greater than 1E+10) 0.0000073900000000 - 7.39E-6 (strip trailing zeros from significand in scientific notation) 0.000007299998344 - 7.3E-6 (rounding from the 6-digit precision limit causes this number to have trailing zeros which are stripped) Here's what I've found so far: The .toString() method of the Number class does most of what I want, except it doesn't upconvert to integer representation when possible, and it will not express large integral magnitudes in scientific notation. Also, I'm not sure how to adjust the precision. The "%G" format string to the String.format(...) function allows me to express numbers in scientific notation with adjustable precision, but does not strip trailing zeros. I'm wondering if there's already some library function out there that meets these criteria. I guess the only stumbling block for writing this myself is having to strip the trailing zeros from the significand in scientific notation produced by %G.

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• Custom Modal Window in WPF?

  - by Dan Bryant

  I have a WPF application where I'd like to create a custom pop-up that has modal behavior. I've been able to hack up a solution using an equivalent to 'DoEvents', but is there a better way to do this? Here is what I have currently: private void ShowModalHost(FrameworkElement element) { //Create new modal host var host = new ModalHost(element); //Lock out UI with blur WindowSurface.Effect = new BlurEffect(); ModalSurface.IsHitTestVisible = true; //Display control in modal surface ModalSurface.Children.Add(host); //Block until ModalHost is done while (ModalSurface.IsHitTestVisible) { DoEvents(); } } private void DoEvents() { var frame = new DispatcherFrame(); Dispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(ExitFrame), frame); Dispatcher.PushFrame(frame); } private object ExitFrame(object f) { ((DispatcherFrame)f).Continue = false; return null; } public void CloseModal() { //Remove any controls from the modal surface and make UI available again ModalSurface.Children.Clear(); ModalSurface.IsHitTestVisible = false; WindowSurface.Effect = null; } Where my ModalHost is a user control designed to host another element with animation and other support.

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• Switching from Java to .NET from a career change point of view

  - by Joe

  Could anyone share with me their experience with switching from Java to .NET from a career point of view? I've been a Java developer for 12 years and am just getting tired of how fragmented the Java world has become. For my liking, there's just too many frameworks, tools, application servers, etc.. And it seems each new tool just adds complexity and time to even the simplest of projects. I'm not trying to start any wars - I'm just giving you the reason I ask the main question. I've read a few books on .NET and have done one WebForms job. I love the integrated environment and would like to hear how others transitioned from Java to .NET. What I mean by that is did you do it somehow as a contractor or did you join a company as a beginner .NET developer with much Java experience? Personally, I'm ready to take the leap if I can figure out how to not lose too much income in the process (Senior Java developer to beginner .NET developer). I would really appreciate hearing your stories.

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• Is it possible to disable user sessions for guest in Joomla 1.5

  - by WebolizeR

  Hi; Is it possible to disable session handling in Joomla 1.5 for guests. I donot use user system in the frontend, i assumed that it's not needed to run queries like below: Site will use APC or Memcache as caching system under heavy load, so it's important for me tHanks for your comments # DELETE FROM jos_session WHERE ( time < '1274709357' ) # SELECT * FROM jos_session WHERE session_id = '70c247cde8dcc4dad1ce111991772475' # UPDATE jos_session SET time='1274710257',userid='0',usertype='',username='',gid='0',guest='1',client_id='0',data='__default|a:8:{s:15:\"session.counter\";i:5;s:19:\"session.timer.start\";i:1274709740;s:18:\"session.timer.last\";i:1274709749;s:17:\"session.timer.now\";i:1274709754;s:22:\"session.client.browser\";s:88:\"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3\";s:8:\"registry\";O:9:\"JRegistry\":3:{s:17:\"_defaultNameSpace\";s:7:\"session\";s:9:\"_registry\";a:1:{s:7:\"session\";a:1:{s:4:\"data\";O:8:\"stdClass\":0:{}}}s:7:\"_errors\";a:0:{}}s:4:\"user\";O:5:\"JUser\":19:{s:2:\"id\";i:0;s:4:\"name\";N;s:8:\"username\";N;s:5:\"email\";N;s:8:\"password\";N;s:14:\"password_clear\";s:0:\"\";s:8:\"usertype\";N;s:5:\"block\";N;s:9:\"sendEmail\";i:0;s:3:\"gid\";i:0;s:12:\"registerDate\";N;s:13:\"lastvisitDate\";N;s:10:\"activation\";N;s:6:\"params\";N;s:3:\"aid\";i:0;s:5:\"guest\";i:1;s:7:\"_params\";O:10:\"JParameter\":7:{s:4:\"_raw\";s:0:\"\";s:4:\"_xml\";N;s:9:\"_elements\";a:0:{}s:12:\"_elementPath\";a:1:{i:0;s:74:\"C:\xampp\htdocs\sites\iv.mynet.com\libraries\joomla\html\parameter\element\";}s:17:\"_defaultNameSpace\";s:8:\"_default\";s:9:\"_registry\";a:1:{s:8:\"_default\";a:1:{s:4:\"data\";O:8:\"stdClass\":0:{}}}s:7:\"_errors\";a:0:{}}s:9:\"_errorMsg\";N;s:7:\"_errors\";a:0:{}}s:13:\"session.token\";s:32:\"a2b19c7baf223ad5fd2d5503e18ed323\";}' WHERE session_id='70c247cde8dcc4dad1ce111991772475'

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• How to write C++ audio processing applications?

  - by cesko82

  Hi everyone, I'm an Electronics and Telecommunications student, next to my graduation. I'm gonna work on a project that involves my knowledge about DSP, music and audio in general. I allready know all the basic mathematic instruments and all the stuff I need to manage it, such as FFT, circular convolution ecc ecc. I want to learn C++ programming basically for one reason: it's very important in the professional world!!! And I think it's one of the most used to write applications working with audio, especially when it's about real time processing. Ok, after this small introduction I would like to know first, which are the most used libraries to work with audio processing in c++?? I was longer looking on the web but i couldn't find a lo of working stuff. (I work under linux with eclipse CDT enviroment). Then I would like to know if there are good sources to learn how to write some working code, such as for example how to write a simple low pass filter. Basically now i will not write real time applications, I would like to start from the processing of a WAV file, or even better an MP3 file, so basically on vectors of samples. Let's say that basically for now I would like to extract the waveform from an audio file, and save it to a thumbnail or to a PNG image. Ok, for now I think it's all I would need. Any ideas, advices, libraries, books, interesting sources about that? Thanks a lot in advance for any kind of answer. Giovanni.

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• C# WinForms. Multiple Forms in separate threads

  - by Calum Murray

  I'm trying to run an ATM Simulation in C# with Windows Forms that can have more than one instance of an ATM machine transacting with a bank account simultaneously. The idea is to use semaphores/locking to block critical code that may lead to race conditions. My question is this: How can I run two Forms simultaneously on separate threads? In particular, how does all of this fit in with the Application.Run() that's already there? Here's my main class: public class Bank { private Account[] ac = new Account[3]; private ATM atm; public Bank() { ac[0] = new Account(300, 1111, 111111); ac[1] = new Account(750, 2222, 222222); ac[2] = new Account(3000, 3333, 333333); Application.Run(new ATM(ac)); } static void Main(string[] args) { new Bank(); } } ...that I want to run two of these forms on separate threads... public partial class ATM : Form { //local reference to the array of accounts private Account[] ac; //this is a reference to the account that is being used private Account activeAccount = null; private static int stepCount = 0; private string buffer = ""; // the ATM constructor takes an array of account objects as a reference public ATM(Account[] ac) { InitializeComponent(); //Sets up Form ATM GUI in ATM.Designer.cs this.ac = ac; } ... I've tried using Thread ATM2 = new Thread(new ThreadStart(/*What goes in here?*/)); But what method do I put in the ThreadStart constructor, since the ATM form is event-driven and there's no one method controlling it? Thanks, Calum

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• mysql: Average over multiple columns in one row, ignoring nulls

  - by Sai Emrys

  I have a large table (of sites) with several numeric columns - say a through f. (These are site rankings from different organizations, like alexa, google, quantcast, etc. Each has a different range and format; they're straight dumps from the outside DBs.) For many of the records, one or more of these columns is null, because the outside DB doesn't have data for it. They all cover different subsets of my DB. I want column t to be their weighted average (each of a..f have static weights which I assign), ignoring null values (which can occur in any of them), except being null if they're all null. I would prefer to do this with a simple SQL calculation, rather than doing it in app code or using some huge ugly nested if block to handle every permutation of nulls. (Given that I have an increasing number of columns to average over as I add in more outside DB sources, this would be exponentially more ugly and bug-prone.) I'd use AVG but that's only for group by, and this is w/in one record. The data is semantically nullable, and I don't want to average in some "average" value in place of the nulls; I want to only be counting the columns for which data is there. Is there a good way to do this? Ideally, what I want is something like UPDATE sites SET t = AVG(a*a_weight,b*b_weight,...) where any null values are just ignored and no grouping is happening.

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• x86_64 printf segfault after brk call

  - by gmb11

  While i was trying do use brk (int 0x80 with 45 in %rax) to implement a simple memory manager program in assembly and print the blocks in order, i kept getting segfault. After a while i could only reproduce the error, but have no idea why is this happening: .section .data helloworld: .ascii "hello world" .section .text .globl _start _start: push %rbp mov %rsp, %rbp movq $45, %rax movq $0, %rbx #brk(0) should just return the current break of the programm int $0x80 #incq %rax #segfault #addq $1, %rax #segfault movq $0, %rax #works fine? #addq $1, %rax #segfault again? movq $helloworld, %rdi call printf movq $1, %rax #exit int $0x80 In the example here, if the commented lines are uncommented, i have a segfault, but some commands (like de movq $0, %rax) work just fine. In my other program, the first couple printf work, but the third crashes... Looking for other questions, i heard that printf sometimes allocates some memory, and that the brk shouldn't be used, because in this case it corrupts the heap or something... I'm very confused, does anyone know something about that? EDIT: I've just found out that for printf to work you need %rax=0.

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• Data in linux FIFO seems lost

  - by Utoah

  Hi, I have a bash script which wants to do some work in parallel, I did this by putting each job in an subshell which is run in the background. While the number of job running simultaneously should under some limit, I achieve this by first put some lines in a FIFO, then just before forking the subshell, the parent script is required to read a line from this FIFO. Only after it gets a line can it fork the subshell. Up to now, everything works fine. But when I tried to read a line from the FIFO in the subshell, it seems that only one subshell can get a line, even if there are apparently more lines in the FIFO. So I wonder why cannot other subshell(s) read a line even when there are more lines in the FIFO. My testing code looks something like this: #!/bin/sh fifo_path="/tmp/fy_u_test2.fifo" mkfifo $fifo_path #open fifo for r/w at fd 6 exec 6 $fifo_path process_num=5 #put $process_num lines in the FIFO for ((i=0; i<${process_num}; i++)); do echo "$i" done &6 delay_some(){ local index="$1" echo "This is what u can see. $index \n" sleep 20; } #In each iteration, try to read 2 lines from FIFO, one from this shell, #the other from the subshell for i in 1 2 do date /tmp/fy_date #If a line can be read from FIFO, run a subshell in bk, otherwise, block. read -u6 echo " $$ Read --- $REPLY --- from 6 \n" /tmp/fy_date { delay_some $i #Try to read a line from FIFO read -u6 echo " $$ This is in child # $i, read --- $REPLY --- from 6 \n" /tmp/fy_date } & done And the output file /tmp/fy_date has content of: Mon Apr 26 16:02:18 CST 2010 32561 Read --- 0 --- from 6 \n Mon Apr 26 16:02:18 CST 2010 32561 Read --- 1 --- from 6 \n 32561 This is in child # 1, read --- 2 --- from 6 \n

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• #indent "off" in F#

  - by anta40

  I just started learning F#, and tried a code from the wiki: I prefer tabs to spaces, so I change the code a bit into this: #indent "off" open System open System.Windows.Forms let form = new Form(Visible=true, TopMost=true, Text="Welcome to F#") let label = let temp = new Label() let x = 3 + (4 * 5) temp.Text <- sprintf "x = %d" x temp form.Controls.Add(label) [<STAThread>] Application.Run(form) The output is: Microsoft (R) F# 2.0 Compiler build 4.0.30319.1 Copyright (c) Microsoft Corporation. All Rights Reserved. fstest2.fs(1,1): warning FS0062: This construct is for ML compatibility. Conside r using a file with extension '.ml' or '.mli' instead. You can disable this warn ing by using '--mlcompatibility' or '--nowarn:62'. fstest2.fs(9,2): error FS0010: Unexpected keyword 'let' or 'use' in expression. Expected 'in' or other token. fstest2.fs(13,1): error FS0597: Successive arguments should be separated by spac es or tupled, and arguments involving function or method applications should be parenthesized fstest2.fs(9,14): error FS0374: Invalid expression on left of assignment fstest2.fs(16,1): error FS0010: Unexpected identifier in definition Guess the error is somewhere in the let label block, but couldn't figure it out.

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• What is happening in this T-SQL code?

  - by Ben McCormack

  I'm just starting to learn T-SQL and could use some help in understanding what's going on in a particular block of code. I modified some code in an answer I received in a previous question, and here is the code in question: DECLARE @column_list AS varchar(max) SELECT @column_list = COALESCE(@column_list, ',') + 'SUM(Case When Sku2=' + CONVERT(varchar, Sku2) + ' Then Quantity Else 0 End) As [' + CONVERT(varchar, Sku2) + ' - ' + Convert(varchar,Description) +'],' FROM OrderDetailDeliveryReview Inner Join InvMast on SKU2 = SKU and LocationTypeID=4 GROUP BY Sku2 , Description ORDER BY Sku2 Set @column_list = Left(@column_list,Len(@column_list)-1) Select @column_list ---------------------------------------- 1 row is returned: ,SUM(Case When Sku2=157 Then Quantity Else 0 End) As [157 -..., SUM(Case ... The T-SQL code does exactly what I want, which is to make a single result based on the results of a query, which will then be used in another query. However, I can't figure out how the SELECT @column_list =... statement is putting multiple values into a single string of characters by being inside a SELECT statement. Without the assignment to @column_list, the SELECT statement would simply return multiple rows. How is it that by having the variable within the SELECT statement that the results get "flattened" down into one value? How should I read this T-SQL to properly understand what's going on?

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• Hide list on blur

  - by bah

  Hi, I have a list showing up when i click on button, the problem is that i want to hide the list whenever it loses focus i.e. user clicks anywhere on a page, but not on that list. How can i do this? Also, you can see how it should look at last.fm, where's list of profile settings (li.profileItem). (ul.del li ul by default is display:none) Basic list structure: <ul class='del'> <li> <button class='deletePage'></button> <ul> <li></li> <li></li> </ul> </li> </ul> My function for displaying this list: $(".deletePage").click(function(){ if( $(this).siblings(0).css("display") == "block" ){ $(this).siblings(0).hide(); } else { $(this).siblings(0).show(); } });

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• WPF ComboBox binding

  - by Budda

  Here is peace of the XAML code from my page: <ComboBox Grid.Row="2" Grid.Column="1" Name="Player2" MinWidth="50" ItemsSource="{Binding PlayersTest}" DisplayMemberPath="ShortName"> custom object is binded to the page data context: page.DataContext = new SquadViewModel(); Here is part the source code of 'SquadViewModel' class: public class SquadViewModel { public SquadViewModel() { PlayersTest = new ObservableCollection<SostavPlayerData>(); PlayersTest.Add(new SostavPlayerData { ShortName = "A. Sereda", }); PlayersTest.Add(new SostavPlayerData { ShortName = "D. Sereda", }); } public readonly ObservableCollection<SostavPlayerData> PlayersTest; public string TestText { get { return "Binding works perfectly!"; } } } As a result ComboBox should display a list of objects, but it is empty. Do you know why and how to get this list? Thank you. P.S. I've tried another XAML markup <ComboBox Grid.Row="1" Grid.Column="1" Name="Player1" MinWidth="50" ItemsSource="{Binding PlayersTest}"> <ComboBox.ItemTemplate> <DataTemplate> <TextBlock Text="{Binding ShortName}"/> </DataTemplate> </ComboBox.ItemTemplate> </ComboBox> It doesn't work also, but binding to simple text block: <TextBlock Grid.Row="2" Grid.Column="1" Text="{Binding TestText}"/> Works perfectly.

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• Why when I render a scene with a revolving camera objects that you'd expect to appear behind others

  - by seaworthy

  Hello, I am rendering a scene in which I have two spheres. I am revolving a camera around one of them. What happens is counter-intuitive. When the camera goes around the sphere the other gets in front of it when you'd expect it to be behind. So it appears as though the spheres aren't revolving around each other and the one the should go around is always upfront. Please help. Here is the code that renders the scene: glLoadIdentity(); [self positionCamera]; glutSolidSphere(2, 12,12); glPushMatrix(); glTranslatef(5, 0, 0); glutSolidSphere(0.5, 12,12); glPopMatrix(); glFlush(); This block is part of a class that gets called on using. [NSTimer scheduledTimerWithTimeInterval:DEFAULT_ANIMATION_INTERVAL target:self selector:@selector(drawRect) userInfo:nil repeats:YES]; And -(void)positionCamera{} Contains math do camera revolution and gluLookAt()

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• Semaphore race condition?

  - by poindexter12

  I have created a "Manager" class that contains a limited set of resources. The resources are stored in the "Manager" as a Queue. I initialize the Queue and a Semaphore to the same size, using the semaphore to block a thread if there are no resources available. I have multiple threads calling into this class to request a resource. Here is the psuedo code: public IResource RequestResource() { IResource resource = null; _semaphore.WaitOne(); lock (_syncLock) { resource = _resources.Dequeue(); } return resource; } public void ReleaseResource(IResource resource) { lock (_syncLock) { _resources.Enqueue(resource); } _semaphore.Release(); } While running this application, it seems to run fine for a while. Then, it seems like my Queue is giving out the same object. Does this seem like its possible? I'm pulling my hair out over here, and any help would be greatly appreciated. Feel free to ask for more information if you need it. Thanks!

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