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Articles indexed Monday April 26 2010

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  • On Ubuntu, how to design a monitor to run a process when a file is written to a directory?

    - by J G
    I want to run a process when a file is written to a directory on Ubuntu. I understand I can write a monitor to do this. (ie not an event based trigger but a 'monitor'). To implement this - other than writing a for loop of infinite duration in C that polls the directory - what steps would you take to implement this? What steps would you take to implement a monitor on Ubuntu that runs a process (another application) when a file is written to a directory? (The reason that you'd do this is the that process writing the file is under a limited set of permissions (eg tomcat6) but the executed process (an existing software package) needs root (ie to run a process in a chroot jail))

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  • How to actually use Swing Application Framework?

    - by Joonas Pulakka
    Hello, I'd like to learn how to effectively use Swing Application Framework. Most of the the examples I've found are blog entries that just explain how to great it is to extend SingleFrameApplication and override its startup method, but that's about it. Sun's article is almost two years old, as is the project's own introduction, and there has apparently been some evolution since then. Are there any recent and thorough tutorials/HOWTOs available anywhere? There is JavaDoc of course, but it's hard to get the big picture from there. Any pointers are appreciated. Update: I realized that there's a mailing list archive at the project's site. While somewhat clumsy (compared to StackOverflow ;) it seems to be quite active. Still it's a pity that there are no real tutorials anywhere. The information is scattered here and there. Update 2: Let me clarify - I'm not having trouble using Swing (the widget toolkit) itself, I'm talking about its Application Framework, which is supposed to ease things like application lifecycle (startup, exit and whatever happens between them), action management etc. - that is, things that most Swing applications will need. It's cool to get such framework to be standard part of Java. The only problem is to learn how it's intended to be used. Update 3: For the interested, there was just some discussion at the project's forum regarding the current state and future of JSR 296. Shortly: the current version 1.03 is considered to be quite usable, but the API is not stable and it will change to the final version in Java 7. The package name will also change so Java 7 will not break current applications made on SAF. Update 4: Karsten Lentzsch stated at the above mentioned forum: "I doubt that it can be included in Java 7; and I'll vote against it.". I would rather not question the sincerity of this great guru, and it's certainly wise not to let anything flawed to slip into the core JDK, but frankly it's a strange situation - he is the author of JGoodies Swing Suite which is partly a commercial competitor of JSR 296, and he is sitting in the committee that will decide whether this JSR will be included to standard Java. It was the same thing with JSR 295 Beans Binding which I wrote about earlier. Given the current state of SAF, I think the best solution is to wrap the current implementation into a "homebrew" framework, which can then accommodate possible changes to the existing API.

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  • An old flaw in X Window System. How does it work?

    - by Legend
    I was going through an article today when it mentioned the following: "We've found many errors over the years. One of the absolute best was the following in the X Window System: if(getuid() != 0 && geteuid == 0) { ErrorF("Only root"); exit(1); } It allowed any local user to get root access. (The tautological check geteuid == 0 was intended to be geteuid() == 0. In its current form, it compress the address of geteuid to 0; given that the function exists, its address is never 0)." The article explained what was wrong with the code but I would like to know what it means to say that "It allowed any local user to get root access". I am not an expert in C but can someone give me an exact context in which this exploit would work? Specifically, what I mean is, lets say I am the local user, how would I get root access if we assume this code to be present somewhere?

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  • Multiple WCF Services implementing same Service Contract interface

    - by andrewczwu
    Is it possible for multiple wcf services to implement the same service contract interface? What I want to do is allow for a test service to be interchangeable for the real service, and to specify which service to be used in the configuration file. For example: [ServiceContract] public interface IUselessService { [OperationContract] string GetData(int value); } Test implementation public class TestService : IUselessService { public string GetData(int value) { return "This is a test"; } } Real class public class RealService : IUselessService { public string GetData(int value) { return string.Format("You entered: {0}", value); } }

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  • static arrays defined with unspecified size, empty brackets?

    - by ahmadabdolkader
    For the C++ code fragment below: class Foo { int a[]; // no error }; int a[]; // error: storage size of 'a' isn't known void bar() { int a[]; // error: storage size of 'a' isn't known } why isn't the member variable causing an error too? and what is the meaning of this member variable? I'm using gcc version 3.4.5 (mingw-vista special) through CodeBlocks 8.02. On Visual Studio Express 2008 - Microsoft(R) C/C++ Optimizing Compiler 15.00.30729.01 for 80x86, I got the following messages: class Foo { int a[]; // warning C4200: nonstandard extension used : zero-sized array in struct/union - Cannot generate copy-ctor or copy-assignment operator when UDT contains a zero-sized array }; int a[]; void bar() { int a[]; // error C2133: 'a' : unknown size } Now, this needs some explaination too.

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  • Class hierarchy problem (with generic's variance!)

    - by devoured elysium
    The problem: class StatesChain : IState, IHasStateList { private TasksChain tasks = new TasksChain(); ... public IList<IState> States { get { return _taskChain.Tasks; } } IList<ITask> IHasTasksCollection.Tasks { get { return _taskChain.Tasks; } <-- ERROR! You can't do this in C#! I want to return an IList<ITask> from an IList<IStates>. } } Assuming the IList returned will be read-only, I know that what I'm trying to achieve is safe (or is it not?). Is there any way I can accomplish what I'm trying? I wouldn't want to try to implement myself the TasksChain algorithm (again!), as it would be error prone and would lead to code duplication. Maybe I could just define an abstract Chain and then implement both TasksChain and StatesChain from there? Or maybe implementing a Chain<T> class? How would you approach this situation? The Details: I have defined an ITask interface: public interface ITask { bool Run(); ITask FailureTask { get; } } and a IState interface that inherits from ITask: public interface IState : ITask { IState FailureState { get; } } I have also defined an IHasTasksList interface: interface IHasTasksList { List<Tasks> Tasks { get; } } and an IHasStatesList: interface IHasTasksList { List<Tasks> States { get; } } Now, I have defined a TasksChain, that is a class that has some code logic that will manipulate a chain of tasks (beware that TasksChain is itself a kind of ITask!): class TasksChain : ITask, IHasTasksList { IList<ITask> tasks = new List<ITask>(); ... public List<ITask> Tasks { get { return _tasks; } } ... } I am implementing a State the following way: public class State : IState { private readonly TaskChain _taskChain = new TaskChain(); public State(Precondition precondition, Execution execution) { _taskChain.Tasks.Add(precondition); _taskChain.Tasks.Add(execution); } public bool Run() { return _taskChain.Run(); } public IState FailureState { get { return (IState)_taskChain.Tasks[0].FailureTask; } } ITask ITask.FailureTask { get { return FailureState; } } } which, as you can see, makes use of explicit interface implementations to "hide" FailureTask and instead show FailureState property. The problem comes from the fact that I also want to define a StatesChain, that inherits both from IState and IHasStateList (and that also imples ITask and IHasTaskList, implemented as explicit interfaces) and I want it to also hide IHasTaskList's Tasks and only show IHasStateList's States. (What is contained in "The problem" section should really be after this, but I thought puting it first would be way more reader friendly). (pff..long text) Thanks!

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  • SQL Server: preventing dirty reads in a stored procedure

    - by pcampbell
    Consider a SQL Server database and its two stored procs: *1. A proc that performs 3 important things in a transaction: Create a customer, call a sproc to perform another insert, and conditionally insert a third record with the new identity. BEGIN TRAN INSERT INTO Customer(CustName) (@CustomerName) SELECT @NewID = SCOPE_IDENTITY() EXEC CreateNewCustomerAccount @NewID, @CustomerPhoneNumber IF @InvoiceTotal > 100000 INSERT INTO PreferredCust(InvoiceTotal, CustID) VALUES (@InvoiceTotal, @NewID) COMMIT TRAN *2. A stored proc which polls the Customer table for new entries that don't have a related PreferredCust entry. The client app performs the polling by calling this stored proc every 500ms. A problem has arisen where the polling stored procedure has found an entry in the Customer table, and returned it as part of its results. The problem was that it has picked up that record, I am assuming, as part of a dirty read. The record ended up having an entry in PreferredCust later, and ended up creating a problem downstream. Question How can you explicitly prevent dirty reads by that second stored proc? The environment is SQL Server 2005 with the default configuration out of the box. No other locking hits are given in either of these stored procedures.

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  • SQL Design: representing a default value with overrides?

    - by Mark Harrison
    I need a sparse table which contains a set of "override" values for another table. I also need to specify the default value for the items overridden. For example, if the default value is 17, then foo,bar,baz will have the values 17,21,17: table "things" table "xvalue" name stuff name xval ---- ----- ---- ---- foo ... bar 21 bar ... baz ... If I don't care about a FK from xvalue.name - things.name, I could simply put a "DEFAULT" name: table "xvalue" name xval ---- ---- DEFAULT 17 bar 21 But I like having a FK. I could have a separate default table, but it seems odd to have 2x the number of tables. table "xvalue_default" xval ---- 17 table "xvalue" name xval ---- ---- bar 21 I could have a "defaults table" tablename attributename defaultvalue xvalue xval 17 but then I run into type issues on defaultvalue. My operations guys prefer as compact a representation as possible, so they can most easily see the "diff" or deviations from the default. What's the best way to represent this, including the default value? This will be for Oracle 10.2 if that makes a difference.

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  • suggestions for declarative GUI programming in Java

    - by Jason S
    I wonder if there are any suggestions for declarative GUI programming in Java. (I abhor visual-based GUI creator/editor software, but am getting a little tired of manually instantiating JPanels and Boxes and JLabels and JLists etc.) That's my overall question, but I have two specific questions for approaches I'm thinking of taking: JavaFX: is there an example somewhere of a realistic GUI display (e.g. not circles and rectangles, but listboxes and buttons and labels and the like) in JavaFX, which can interface with a Java sourcefile that accesses and updates various elements? Plain Old Swing with something to parse XUL-ish XML: has anyone invented a declarative syntax (like XUL) for XML for use with Java Swing? I suppose it wouldn't be hard to do, to create some code based on STaX which reads an XML file, instantiates a hierarchy of Swing elements, and makes the hierarchy accessible through some kind of object model. But I'd rather use something that's well-known and documented and tested than to try to invent such a thing myself. JGoodies Forms -- not exactly declarative, but kinda close & I've had good luck with JGoodies Binding. But their syntax for Form Layout seems kinda cryptic. edit: lots of great answers here! (& I added #3 above) I'd be especially grateful for hearing any experiences any of you have had with using one of these frameworks for real-world applications. p.s. I did try a few google searches ("java gui declarative"), just didn't quite know what to look for.

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  • Show random string.

    - by zaid
    i am trying to display a random string each time a button is pressed from a set of strings defined in strings.xml . this is an example of the strings ID's <string name="q0"> <string name="q1"> <string name="q2"> <string name="q3"> <string name="q4"> java code for getting a random string. private static final Random rgenerator = null; int RandomQ = R.string.q0 (rgenerator.nextInt(5) + 1); String q = getString(RandomQ); if i try to use this java code i get an error at "q0" in R.string.q0 which is The method q0(int) is undefined for the type R.string if i try to use the quick fix and create a method, it works. but it wont let me save or run the app because it replaces my create method and shows this message R.java was modified manually! Reverting to generated version! thanks for reading.

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  • The Perfect Desktop - PCLinuxOS 2010 (KDE)

    <b>Howtoforge:</b> "This tutorial shows how you can set up a PCLinuxOS 2010 desktop (with KDE) that is a full-fledged replacement for a Windows desktop, i.e. that has all the software that people need to do the things they do on their Windows desktops."

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  • Should '#include' and 'using' statements be repeated in both header and implementation files (C++)?

    - by Dr. Monkey
    I'm fairly new to C++, but my understanding is that a #include statement will essentially just dump the contents of the #included file into the location of that statement. This means that if I have a number of '#include' and 'using' statements in my header file, my implementation file can just #include the header file, and the compiler won't mind if I don't repeat the other statements. What about people though? My main concern is that if I don't repeat the '#include', 'using', and also 'typedef' (now that I think of it) statements, it takes that information away from the file in which it's used, which could lead to confusion. I am just working on small projects at the moment where it won't really cause any issues, but I can imagine that in larger projects with more people working on them it could become a significant issue. An example follows: //Unit.h #include <string> #include <ostream> #include "StringSet.h" using std::string; using std::ostream; class Unit { public: //public members private: //private members //unrelated side-question: should private members //even be included in the header file? } ; //Unit.cpp #include "Unit.h" //The following are all redundant from a compiler perspective: #include <string> #include <ostream> #include "StringSet.h" using std::string; using std::ostream; //implementation goes here

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  • Will VS2010 work with VSS2005?

    - by DanH
    Until I can convince others to convert over to Team Foundation Server 2010 (TFS2010), I'm still going to use Visual Source Safe 2005 (VSS2005). I will be upgrade to Visual Studio 2010 (VS2010) soon. What do I need to get VS2010 to work with VSS2005? I understand there is a patch for VSS.

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  • Read the audio input level peak in Cocoa

    - by Kenneth Ballenegger
    I'm trying to make an audio-sensitive animation, and for that purpose, I'm looking for a way to look up the current audio level. I'm looking for the peak within a set amount of time. (Think the red bar that stays on for a second or so, on an audio meter.) I've searched around for for something like this, and the only thing I could find was how to read a movie's audio levels, and how Quartz Compositions have access to this thru their iTunes Visualizer protocol. I'm looking for a way to read this from the microphone, although I'm also interested if you know how to read this from an audio file. Thanks!

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  • Eclipse And Linux: Keyboard unusable after gnome-screen-saver

    - by Martijn Courteaux
    Hi, I know this is not programming related. But I can't find any topics on Google or UbuntuForums. So the problem is: When gnome-screensaver starts on the moment Eclipse has the focus and I wake up again my laptop, Eclipse doesn't listen to keyboard-events. To solve this I have to change the focus to another program and then back to Eclipse. Than it works again. This isn't a real problem, but it would be nice if someone can solve it. Thanks

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  • Grid related UI design question

    - by younevertell
    Grid related UI design question I want some 16-grid (4 rows and 4 columns) user interface, and fill the grid with some round shapes. I also want to use the MouseOver, mouse left button down, and Mouse Left Button Up events to set the state of grids as selected or not selected. My questions: 1. How fill the grid with some round shapes? by SetColumn and SetRow? 2. How to make the grids respond to the mouse please? Thanks <Grid.ColumnDefinitions> <ColumnDefinition /> <ColumnDefinition /> <ColumnDefinition /> <ColumnDefinition /> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions>

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  • Anyone saw a worst written function than this? [closed]

    - by fvoncina
    string sUrl = "http://www.ipinfodb.com/ip_query.php?ip=" + ip + "&output=xml"; StringBuilder oBuilder = new StringBuilder(); StringWriter oStringWriter = new StringWriter(oBuilder); XmlTextReader oXmlReader = new XmlTextReader(sUrl); XmlTextWriter oXmlWriter = new XmlTextWriter(oStringWriter); while (oXmlReader.Read()) { oXmlWriter.WriteNode(oXmlReader, true); } oXmlReader.Close(); oXmlWriter.Close(); // richTextBox1.Text = oBuilder.ToString(); XmlDocument doc = new XmlDocument(); doc.LoadXml(oBuilder.ToString()); doc.Save(System.Web.HttpContext.Current.Server.MapPath(".") + "data.xml"); DataSet ds = new DataSet(); ds.ReadXml(System.Web.HttpContext.Current.Server.MapPath(".") + "data.xml"); string strcountry = "India"; if (ds.Tables[0].Rows.Count > 0) { strcountry = ds.Tables[0].Rows[0]["CountryName"].ToString(); }

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  • LinqtoSql Pre-compile Query problem with Count() on a group by

    - by Joe Pitz
    Have a LinqtoSql query that I now want to precompile. var unorderedc = from insp in sq.Inspections where insp.TestTimeStamp > dStartTime && insp.TestTimeStamp < dEndTime && insp.Model == "EP" && insp.TestResults != "P" group insp by new { insp.TestResults, insp.FailStep } into grp select new { FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0), CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0), grp.Key.TestResults, grp.Key.FailStep, PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100) }; I have created this delegate: public static readonly Funct<SQLDataDataContext, int, string, string, DateTime, DateTime, IQueryable<CalcFailedTestResult>> GetInspData = CompiledQuery.Compile((SQLDataDataContext sq, int tcount, string strModel, string strTest, DateTime dStartTime, DateTime dEndTime, IQueryable<CalcFailedTestResult> CalcFailed) => from insp in sq.Inspections where insp.TestTimeStamp > dStartTime && insp.TestTimeStamp < dEndTime && insp.Model == strModel && insp.TestResults != strTest group insp by new { insp.TestResults, insp.FailStep } into grp select new { FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0), CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0), grp.Key.TestResults, grp.Key.FailStep, PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100) }); The syntax error is on the CompileQuery.Compile() statement It appears to be related to the use of the select new {} syntax. In other pre-compiled queries I have written I have had to just use the select projection by it self. In this case I need to perform the grp.count() and the immediate if logic. I have searched SO and other references but cannot find the answer.

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