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• [java] Efficiency of while(true) ServerSocket Listen

  - by Submerged

  I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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• External log4j.xml file

  - by javamonkey79

  I am trying to run a jar with the log4j.xml file on the file system outside the jar like so: java -jar MyJarName.jar -cp=/opt/companyName/pathToJar/ log4j.configuration=log4j.xml argToJar1 argToJar2 I have also tried: java -jar MyJarName.jar -cp=/opt/companyName/pathToJar/ log4j.configuration=/opt/companyName/pathToJar/log4j.xml argToJar1 argToJar2 The log4j.xml is file is in the same directory as the jar (/opt/companyName/pathToJar/), yet I still get the standard warning message: log4j:WARN No appenders could be found for logger (org.apache.axis.i18n.ProjectResourceBundle). log4j:WARN Please initialize the log4j system properly. Is it possible to have the config file outside the jar, or do I have to package it with the jar? TIA

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• extract digg data by digg api

  - by vamsivanka

  I am trying to extract digg data for a user using this url "http://services.digg.com/user/vamsivanka/diggs?count=25&appkey=34asd56asdf789as87df65s4fas6" and the web response is throwing an error "The remote server returned an error: (403) Forbidden." Please let me know. public static XmlTextReader CreateWebRequest(string url) { HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url); webRequest.UserAgent = ".NET Framework digg Test Client"; webRequest.Credentials = System.Net.CredentialCache.DefaultCredentials; webRequest.Accept = "text/xml"; HttpWebResponse webResponse = (HttpWebResponse)webRequest.GetResponse(); System.IO.Stream responseStream = webResponse.GetResponseStream(); XmlTextReader reader = new XmlTextReader(responseStream); return reader; }

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• How is ImmutableObjectAttribute used?

  - by Thomas Levesque

  I was looking for a built-in attribute to specify that a type is immutable, and I found only System.ComponentModel.ImmutableObjectAttribute. Using Reflector, I checked where it was used, and it seems that the only public class that uses it is System.Drawing.Image... WTF? It could have been used on string, int or any of the primitive types, but Image is definitely not immutable, there are plenty of ways to alter its internal state (using a Graphics or the Bitmap.SetPixel method for instance). So the only class in the BCL that is explicitly declared as immutable, is mutable! Or am I missing something?

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• NFS Server in Java

  - by dmeister

  I search an implementation of a network (or distributed) file system like NFS in Java. The goal is to extend it and do some research stuff with it. On the web I found some implementation e.g. DJ NFS, but the open question is how mature and fast they are. Can anyone purpose a good starting point, has anyone experience with such things? P.S. I know Hadoop DFS and I used it for some projects, but Hadoop is not a good fit for the things I want to do here. --EDIT-- Hadoop is really focused on highly scalable, high throughput computing without the possibilities to overwrite parts of a file and so an. The goal is you could use the filesystem e.g. for user home directories. --EDIT-- More Details: The idea is to modify such a implementation so that the files are not stored directly on a local filesystem, but to apply data de-duplication.

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• Accents in file name using Java on Solaris

  - by Stef

  I have a problem where I can't write files with accents in the file name on Solaris. Given following code public static void main(String[] args) { System.out.println("Charset = "+ Charset.defaultCharset().toString()); System.out.println("testéörtkuoë"); FileWriter fw = null; try { fw = new FileWriter("testéörtkuoë"); fw.write("testéörtkuoëéörtkuoë"); fw.close(); I get following output Charset = ISO-8859-1 test??rtkuo? and I get a file called "test??rtkuo?" Based on info I found on StackOverflow, I tried to call the Java app by adding "-Dfile.encoding=UTF-8" at startup. This returns following output Charset = UTF-8 testéörtkuoë But the filename is still "test??rtkuo?" Any help is much appreciated. Stef

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• I've got my 2D/3D conversion working perfectly, how to do perspective

  - by user346992

  Although the context of this question is about making a 2d/3d game, the problem i have boils down to some math. Although its a 2.5D world, lets pretend its just 2d for this question. // xa: x-accent, the x coordinate of the projection // mapP: a coordinate on a map which need to be projected // _Dist_ values are constants for the projection, choosing them correctly will result in i.e. an isometric projection xa = mapP.x * xDistX + mapP.y * xDistY; ya = mapP.x * yDistX + mapP.y * yDistY; xDistX and yDistX determine the angle of the x-axis, and xDistY and yDistY determine the angle of the y-axis on the projection (and also the size of the grid, but lets assume this is 1-pixel for simplicity). x-axis-angle = atan(yDistX/xDistX) y-axis-angle = atan(yDistY/yDistY) a "normal" coordinate system like this --------------- x | | | | | y has values like this: xDistX = 1; yDistX = 0; xDistY = 0; YDistY = 1; So every step in x direction will result on the projection to 1 pixel to the right end 0 pixels down. Every step in the y direction of the projection will result in 0 steps to the right and 1 pixel down. When choosing the correct xDistX, yDistX, xDistY, yDistY, you can project any trimetric or dimetric system (which is why i chose this). So far so good, when this is drawn everything turns out okay. If "my system" and mindset are clear, lets move on to perspective. I wanted to add some perspective to this grid so i added some extra's like this: camera = new MapPoint(60, 60); dx = mapP.x - camera.x; // delta x dy = mapP.y - camera.y; // delta y dist = Math.sqrt(dx * dx + dy * dy); // dist is the distance to the camera, Pythagoras etc.. all objects must be in front of the camera fac = 1 - dist / 100; // this formula determines the amount of perspective xa = fac * (mapP.x * xDistX + mapP.y * xDistY) ; ya = fac * (mapP.x * yDistX + mapP.y * yDistY ); Now the real hard part... what if you got a (xa,ya) point on the projection and want to calculate the original point (x,y). For the first case (without perspective) i did find the inverse function, but how can this be done for the formula with the perspective. May math skills are not quite up to the challenge to solve this. ( I vaguely remember from a long time ago mathematica could create inverse function for some special cases... could it solve this problem? Could someone maybe try?)

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• how to convert datetime to string in linqtosql?

  - by kwon

  I am using linqtosql and inside of linq query, I tried to convert datetime type column to string like 'dd-MM-yy'. However, I got error as following : NotSupportedException: Method 'System.String ToString(System.String)' has no supported translation to SQL. following is my linq query : from ffv in Flo_flowsheet_values where ffv.Flowsheet_key == 2489 && ffv.Variable_key == 70010558 && ffv.Status == 'A' && ffv.Column_time >= DateTime.ParseExact("2010-06-13 00:00", "yyyy-MM-dd HH:mm", null) && ffv.Column_time <= DateTime.ParseExact("2010-06-13 22:59", "yyyy-MM-dd HH:mm", null) select new { ColumnTime = ffv.Column_time ,ColumnTimeForXCategory = ffv.Column_time.Value.ToString("dd-MM-yy") ***====> this statement invoke error*** ,BTValue = Convert.ToDouble( ffv.Value) } what is problem? Thanks in advance

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• Impersonation in asp.net, confused about implmentation when used with Active Directory & Sql Server

  - by AWC

  I have an internal website that is using integrated windows authentication and this website uses sql server & active directory queries via the System.Directory.Services namespace. To use the System.Directory.Services namespace in ASP.NET I have to run IIS under an account that has the correct privileges and importantly have impersonation set to true in the web config. If this is done then when I make a query against AD then the credentials of the wroker process (IIS) are used instead of the ASPNET account and therefore the queries will now succeed. Now if I am also using Sql Server with a connection string configured for integrated security ('Integrated Security=SSPI') then this interprets the ASP.NET impersonation to mean that I want to access the database as the windows credentials of the request no the worker process. I hope I'm wrong and that I've got the config wrong, but I don't think I have and this seems not to be inconsistent? It should be noted I'm using IIS 5.1 for development and obivously this doesn't have the concept of app-pools which I believe would resolve the problem.

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• Java assert nasty side-effect - compiler bug?

  - by Alex

  This public class test { public static void main(String[] args) { Object o = null; assert o != null; if(o != null) System.out.println("o != null"); } } prints out "o != null"; both 1.5_22 and 1.6_18. Compiler bug? Commenting out the assert fixes it. The byte code appears to jump directly to the print statement when assertions are disabled: public static main(String[]) : void L0 LINENUMBER 5 L0 ACONST_NULL ASTORE 1 L1 LINENUMBER 6 L1 GETSTATIC test.$assertionsDisabled : boolean IFNE L2 ALOAD 1: o IFNONNULL L2 NEW AssertionError DUP INVOKESPECIAL AssertionError.<init>() : void ATHROW L2 LINENUMBER 8 L2 GETSTATIC System.out : PrintStream LDC "o != null" INVOKEVIRTUAL PrintStream.println(String) : void L3 LINENUMBER 9 L3 RETURN L4

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• Webservice won't accept JSON requests

  - by V-Man

  Hi, The main issue is that I cannot run a webservice that accepts requests in JSON format. I keep getting a 500 Server error stating that the "request format is invalid." My ASP.NET AJAX extensions are installed. My server is running Plesk Control Panel 8.6 which is undoubtedly causing these problems. The default handler for this specified extension is shown in the web.config like so: For my applications webservice to handle JSON it needs to have this reference: <add name="ScriptHandlerFactory" verb="*" path="*.asmx" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> Plesk is not allowing the request to be handled properly. I need to know the correct http directive(s) to put into the web.config to properly handle JSON webservices. I tried posting to the Plesk forum two days ago but no response yet. Any insight would be great =)

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• Unable to connect to a local MYSQL server on wireles LAN.

  - by Arnab

  Ok, Here is the technical description. My laptop's config: Ip Adress:192.168.2.5 Mysqlserver 5.0 on port : 3306 Operating system: Ubuntu jaunty (9.04) 3306 is open for both incoming and outgoing. My friend's laptop config: Ip Adress:192.168.2.4 Mysqlserver 5.0 on port : 3306 Operating system: Windows XP pro 3306 is open for both incoming and outgoing. Both are on a wireless LAN connected through a belkin router (192.168.2.1) Both the MYSQL servers have been given the sufficient GRANT privileges. I am also able to connect from 192.168.2.4 to 192.168.2.5's MYSQL instance but the vice versa is not happening. I am getting an (100061) error. Tried Telnetting on 3306; again happening from 192.168.2.4 to 192.168.2.5 but not the vice versa. Am I doing something wrong? Kindly suggest.

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• Linq SqlMethods.Like fails

  - by Russell Steen

  I'm following the tips here, trying to leverage the statement that the sql doesn't get created until the enumerator is tripped. However I get the following error on the code below. I'm using Linq2Entities, not linq2sql. Is there a way to do this in Linq2entities? Method 'Boolean Like(System.String, System.String)' cannot be used on the client; it is only for translation to SQL. query = db.MyTables.Where(x => astringvar.Contains(x.Field1)); if (!String.IsNullOrEmpty(typeFilter)) { if (typeFilter.Contains('*')) { typeFilter = typeFilter.Replace('*', '%'); query = query.Where(x=> SqlMethods.Like(x.Type, typeFilter)); } else { query = query.Where(x => x.Type == typeFilter); } }

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• Possible Encoding Issue Reading HTM File using .Net Streamreader

  - by Brian Boatright

  I have an HTML file with a ® (copyright) and ™ (trademark) symbol in the text. These are just two among many other symbols. When I read the html file into a literal control it converts the symbols to something else. The copyright symbol converts to ? (open box in ff) The trademark symbol converts to ™ (as expected) If (System.IO.File.Exists(FullName)) Then Dim StreamReader1 As New System.IO.StreamReader(FullName) Contents.Text = StreamReader1.ReadToEnd() StreamReader1.Close() End If Contents is a <asp:Literal runat="server" ID="Contents"></asp:Literal> and it's the only control in the aspx page. From some research I think this is related to the encoding but I don't know why it would change how to fix it. The html file does not contain any Content-Type settings in the head section.

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• What are the causes and solutions of exception code c0000005 in mscorwks.dll?

  - by Erick

  The exception code c0000005 is thrown from mscorwks.dll when the application is run on Windows Server 2008 R2. Other platforms (WinXP, Server 2003 R2, Windows 7 32-bit and 64-bit) do not present this exception. The event log from a single execution has many of the following event with event ID 1023 raised by the .NET Runtime: .NET Runtime version 2.0.50727.4952 - Fatal Execution Engine Error (7383851A) (80131506) The application itself makes use of a SOAP interface generated by visual studio from a wsdl, a COM object with an embedded interop, and is targeting .Net 4. sfc /scannow was run and found no problems with system files on the affected system. What trouble shooting can be done to identify a solution?

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• Programmatic resource monitoring per process in Linux

  - by tuxx

  Hi, I want to know if there is an efficient solution to monitor a process resource consumption (cpu, memory, network bandwidth) in Linux. I want to write a daemon in C++ that does this monitoring for some given PIDs. From what I know, the classic solution is to periodically read the information from /proc, but this doesn't seem the most efficient way (it involves many system calls). For example to monitor the memory usage every second for 50 processes, I have to open, read and close 50 files (that means 150 system calls) every second from /proc. Not to mention the parsing involved when reading these files. Another problem is the network bandwidth consumption: this cannot be easily computed for each process I want to monitor. The solution adopted by NetHogs involves a pretty high overhead in my opinion: it captures and analyzes every packet using libpcap, then for each packet the local port is determined and searched in /proc to find the corresponding process. Do you know if there are more efficient alternatives to these methods presented or any libraries that deal with this problems?

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• POCO inherited type could not pass addObject method

  - by bryanevil

  Hi all I am using a POCO class name "Company" generate from the T4 POCO code generator to create a derived class - name "CompanyBO" by "public class CompanyBO:Company", but when i call addObject method: public void Delete(T entity) { CustomerWebPortalEntities entities = new CustomerWebPortalEntities(); entities.AddObject(entity.GetType().BaseType.Name, entity); entities.DeleteObject(entity); SaveChanges(); } it compliant this: The EntitySet name 'CustomerWebPortalEntities.Company' could not be found. System.Data.Objects.ObjectContext.GetEntitySet(String entitySetName, String entityContainerName) at System.Data.Objects.ObjectContext.GetEntitySetFromName(String entitySetName) Could you please tell me whats going wrong here? How do I resolve this problem? Best Regards Bryan

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• Why looping in Delphi faster than C#?

  - by isa

  Delphi: procedure TForm1.Button1Click(Sender: TObject); var I,Tick:Integer; begin Tick := GetTickCount(); for I := 0 to 1000000000 do begin end; Button1.Caption := IntToStr(GetTickCount()-Tick)+' ms'; end; C#: private void button1_Click(object sender, EventArgs e) { int tick = System.Environment.TickCount; for (int i = 0; i < 1000000000; ++i) { } tick = System.Environment.TickCount - tick; button1.Text = tick.ToString()+" ms"; } Delphi gives around 515 ms C# gives around 3775 ms

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• Internet Explorer visual element stacking issue

  - by Michael

  Gday All, I know this issue is well known, however I have searched high and low for a solution to no avail. I have created a menu system using nested ordered lists where the menu functionality is controlled by CSS and Jquery. The menu works perfectly in FF, Chrome, Opera and Epiphany. However in IE 6/7/8 my popup menu is being displayed underneath a table. See the image below. The very top box is a div element containing my menu system. I am working with legacy code that uses tables for display so the next box and the "ts found. Try a different subcate" text is in a "td" element of a table. I have tried to force the table to have a lower z-index but this does not work. Any insights into why this is only present in IE would be appreciated. Cheers, Michael

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• how random is Math.random() in java across different jvms or different machines

  - by user881480

  I have a large distributed program across many different physical servers, each program spawns many threads, each thread use Math.random() in its operations to draw a piece from many common resource pools. The goal is to utilize the pools evenly across all operations. Sometimes, it doesn't appear so random by looking at a snapshot on a resource pool to see which pieces it's getting at that instant (it might actually be, but it's hard to measure and find out for sure). Is there something that's better than Math.random() and performs just as good (not much worse at least)?

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• Parallelism in Python

  - by fmark

  What are the options for achieving parallelism in Python? I want to perform a bunch of CPU bound calculations over some very large rasters, and would like to parallelise them. Coming from a C background, I am familiar with three approaches to parallelism: Message passing processes, possibly distributed across a cluster, e.g. MPI. Explicit shared memory parallelism, either using pthreads or fork(), pipe(), et. al Implicit shared memory parallelism, using OpenMP. Deciding on an approach to use is an exercise in trade-offs. In Python, what approaches are available and what are their characteristics? Is there a clusterable MPI clone? What are the preferred ways of achieving shared memory parallelism? I have heard reference to problems with the GIL, as well as references to tasklets. In short, what do I need to know about the different parallelization strategies in Python before choosing between them?

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• Ignore errors when scanning for files in C:\

  - by Shane

  I am trying to search the C:\ drive for all files with a certain extension. I am using the following code which is working fine, however when it encounters an error the whole process stops rather than continuing with the scan. (running in backgroundworker, hence the invoke) Private Sub ScanFiles(ByVal rootFolder As String, ByVal fileExtension As String) 'Determine if the current folder contains any sub folders Dim subFolders() As String = System.IO.Directory.GetDirectories(rootFolder) For Each subFolder As String In subFolders ScanFiles(subFolder, fileExtension) Next For Each file As String In System.IO.Directory.GetFiles(rootFolder, fileExtension) lb.BeginInvoke(New AddValue(AddressOf AddItems), file) Next End Sub How can I make this code continue once an error is encountered? Thanks for your help.

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• Disabling Task manager using c# in OS Hardened machine

  - by srk

  I am using the below code to disable the task manager for a kiosk application which works perfectly public void DisableTaskManager() { RegistryKey regkey; string keyValueInt = "1"; string subKey = "Software\\Microsoft\\Windows\\CurrentVersion\\Policies\\System"; try { regkey = Registry.CurrentUser.CreateSubKey(subKey); regkey.SetValue("DisableTaskMgr", keyValueInt); regkey.Close(); } catch (Exception ex) { MessageBox.Show("DisableTaskManager" + ex.ToString()); } } But when i run this in OS hardened machine i get the following error, DisableTaskManagerSystem.UnauthorizedAccessException: Access to the registry key 'HKey_Current_User\Software\Mictrosoft\Windows\CurrentVersion\Policies\System' is denied. at Microsoft.win32.RegistryKey.win32Error(int32 errorcode, String str) How can i overcome this ? I need to do this for a Kiosk application.

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• Can .NET load and parse a properties file equivalent to Java Properties class?

  - by Tai Squared

  Is there an easy way in C# to read a properties file that has each property on a separate line followed by an equals sign and the value, such as the following: ServerName=prod-srv1 Port=8888 CustomProperty=Any value In Java, the Properties class handles this parsing easily: Properties myProperties=new Properties(); FileInputStream fis = new FileInputStream (new File("CustomProps.properties")); myProperties.load(fis); System.out.println(myProperties.getProperty("ServerName")); System.out.println(myProperties.getProperty("CustomProperty")); I can easily load the file in C# and parse each line, but is there a built in way to easily get a property without having to parse out the key name and equals sign myself? The C# information I have found seems to always favor XML, but this is an existing file that I don't control and I would prefer to keep it in the existing format as it will require more time to get another team to change it to XML than parsing the existing file.

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• Adobe Reader process fails when starting second instance

  - by Reddog

  In our C# WinForms application, we generate PDF files and launch Adobe Reader (or whatever the default system .pdf handler is) via the Process class. Since our PDF files can be large (approx 200K), we handle the Exited event to then clean up the temp file afterwards. The system works as required when a file is opened and then closed again. However, when a second file is opened (before closing Adobe Reader) the second process immediately exits (since Reader is now using it's MDI powers) and in our Exited handler our File.Delete call should fail because it's locked by the now joined Adobe process. However, in Reader we instead get: There was an error opening this document. This file cannot be found. The unusual thing is that if I put a debugger breakpoint before the file deletion and allow it to attempt (and fail) the deletion, then the system behaves as expected! I'm positive that the file exists and fairly positive that all handles/file streams to the file are closed before starting the process. We are launching with the following code: // Open the file for viewing/printing (if the default program supports it) var pdfProcess = new Process(); pdfProcess.StartInfo.FileName = tempFileName; if (pdfProcess.StartInfo.Verbs.Contains("open", StringComparer.InvariantCultureIgnoreCase)) { var verb = pdfProcess.StartInfo.Verbs.First(v => v.Equals("open", StringComparison.InvariantCultureIgnoreCase)); pdfProcess.StartInfo.Verb = verb; } pdfProcess.StartInfo.Arguments = "/N"; // Specifies a new window will be used! (But not definitely...) pdfProcess.SynchronizingObject = this; pdfProcess.EnableRaisingEvents = true; pdfProcess.Exited += new EventHandler(pdfProcess_Exited); _pdfProcessDictionary.Add(pdfProcess, tempFileName); pdfProcess.Start(); Note: We are using the _pdfProcessDictionary to store references to the Process objects so that they stay in scope so that Exited event can successfully be raised. Our cleanup/exited event is: void pdfProcess_Exited(object sender, EventArgs e) { Debug.Assert(!InvokeRequired); var p = sender as Process; try { if (_pdfProcessDictionary.ContainsKey(p)) { var tempFileName = _pdfProcessDictionary[p]; if (File.Exists(tempFileName)) // How else can I check if I can delete it!!?? { // NOTE: Will fail if the Adobe Reader application instance has been re-used! File.Delete(tempFileName); _pdfProcessDictionary.Remove(p); } CleanOtherFiles(); // This function will clean up files for any other previously exited processes in our dictionary } } catch (IOException ex) { // Just swallow it up, we will deal with trying to delete it at another point } } Possible solutions: Detect that the file is still open in another process Detect that the second process hasn't really been fully exited and that the file is opened in the first process instead

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