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  • What would happen if a same file being read and appended at the same time(python programming)?

    - by Shane
    I'm writing a script using two separate thread one doing file reading operation and the other doing appending, both threads run fairly frequently. My question is, if one thread happens to read the file while the other is just in the middle of appending strings such as "This is a test" into this file, what would happen? I know if you are appending a smaller-than-buffer string, no matter how frequently you read the file in other threads, there would never be incomplete line such as "This i" appearing in your read file, I mean the os would either do: append "This is a test" - read info from the file; or: read info from the file - append "This is a test" to the file; and such would never happen: append "This i" - read info from the file - append "s a test". But if "This is a test" is big enough(assuming it's a bigger-than-buffer string), the os can't do appending job in one operation, so the appending job would be divided into two: first append "This i" to the file, then append "s a test", so in this kind of situation if I happen to read the file in the middle of the whole appending operation, would I get such result: append "This i" - read info from the file - append "s a test", which means I might read a file that includes an incomplete string?

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  • What is the fastest way to write hundreds of files to disk using C#?

    - by Ehsan
    My program should write hundreds of files to disk, received by external resources (network) each file is a simple document that I'm currently store it with the name of GUID in a specific folder but creating hundred files, writing, closing is a lengthy process. Is there any better way to store these amount of files to disk? I've come to a solution, but I don't know if it is the best. First, I create 2 files, one of them is like allocation table and the second one is a huge file storing all the content of my documents. But reading from this file would be a nightmare; maybe a memory-mapped file technique could help. Could working with 30GB or more create a problem?

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  • Write to the second line of a PHP file

    - by Woz
    I have a php file that I want to add an include path to on the second line. I need to open the file and inset a line of code on line 2. I have tried a few techniques none of which are working but I think it has something to do with the text I am trying to write and possibly not escaping character correctly as I am not too familiar with file writing. So here is the file I want to write to: $file = $_SERVER['DOCUMENT_ROOT'].'/'.$domaindir.'/test.php'; Here is the piece of text I want to insert into the file: $dbfile = "include('".$_SERVER['DOCUMENT_ROOT']."/".$domaindir."/web_".$dbname.".inc.php');"; Then what I was doing was a string replace but all it did was bump the "session_start();" bit to a newline! Can anyone point me in the direction of a tutorial that might tell me how to insert this into the second line of my php file or indeed if anyone has any ideas? I can say for sure that the path to the PHP file is fully tested so i know its not that the file is not being open or written to. Any ideas would be much appreciated. Thanks in advance.

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  • Fastest Way To Format a Plain Text Using Javascript

    - by Nathan Campos
    I have a huge plain text document, about 700kb which is very big for plain texts and I need to format it on cloud converting it to HTML, but the only things that I need to replace, format to HTML so it can be displayed by the browser, are bold and italic. For bold at the plain text they are like this: Not on bold... **bold text here** not bold here And italic like this: Not italic... *italic text* no italic Just like StackOverflow does for their formatting, but the problem is that I need to make it a lot faster, since the text is so big... One of my ideas was to add a page slide, so I the script just need to format some part of the text, not it all, then after the user changes the page the script would be called again, but the problem is how I can make the code for this all?

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  • Calling class in Java after editing file used in as source for table

    - by user2892290
    I'm currently working on a project, I'll try to subrscibe first. I save data into text file, that I use as a source for browser of that data. The browser is based on table that contains the data. I have to rewrite the source file everytime I delete or edit data. That's where the problem comes in. After deleting or editing data I call a method to create the table again, but the table never creates. Is it possibly made by editing the file and calling the method right after that? If I restart my app the table is successfully created with right data. Take in note that I don't get any error message. This is the method I use for loading data from source file: try (BufferedReader input1 = new BufferedReader(new FileReader("./src/data.src"))) { int lines = 0; while (input1.read() != -1) { if (!(input1.readLine()).equals("")) { lines++; } } input1.close(); if (lines == 0) { JOptionPane.showMessageDialog(null, "No data to load, create a note first!"); new Writer().build(frame); } else { try (BufferedReader input = new BufferedReader(new FileReader("./src/data.src"))) { Game[] g = new Game[lines]; String currentLine; String[] help; int counter = 0; while (lines > 0) { currentLine = input.readLine(); help = currentLine.split("#"); g[counter] = new Game(help[0],help[1], help[2], help[3], help[4], help[5], help[6], help[7], help[8], help[9]); counter++; lines--; } input.close(); final JButton bButton = new backButton().create(frame, mPanel); build(g, frame, bButton); mPanel.add(panel); mPanel.add(panel2); mPanel.add(searchPanel); mPanel.add(bButton); bButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { frame.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR)); panel.removeAll(); frame.setCursor(Cursor.getDefaultCursor()); } }); mPanel.setPreferredSize(new Dimension(1000, 750)); panel.setBorder(new EmptyBorder(10, 10, 10, 10)); frame.setLayout(new FlowLayout()); frame.add(mPanel); frame.pack(); JMenuBar menuBar = new Menu().create(frame, mPanel); frame.setJMenuBar(menuBar); frame.setVisible(true); Rectangle rec = GraphicsEnvironment.getLocalGraphicsEnvironment().getMaximumWindowBounds(); int width = (int) rec.getWidth(); int height = (int) rec.getHeight(); frame.setBounds(1, 3, width, height); frame.addComponentListener(new ComponentAdapter() { @Override public void componentMoved(ComponentEvent e) { frame.setLocation(1, 3); } }); And this is the method I use for creating the table: String[][] tableData = new String[g.length][9]; for (int i = 0; i < tableData.length; i++) { tableData[i][0] = g[i].getChampion(); tableData[i][1] = g[i].getRole(); tableData[i][2] = g[i].getEnemy(); tableData[i][3] = g[i].getDifficulty(); tableData[i][4] = g[i].getResult(); tableData[i][5] = g[i].getScore(); tableData[i][6] = g[i].getGameType(); tableData[i][7] = g[i].getPoints(); tableData[i][8] = g[i].getLeague(); } final JLabel searchLabel = new JLabel("Search for champion played."); final JButton searchButton = new JButton("Search"); final JTextField searchText = new JTextField(20); frame.setTitle("LoL Notepad - reading your notes"); JTable table = new JTable(tableData, columnNames); final JScrollPane scrollPane = new JScrollPane(table); scrollPane.setPreferredSize(new Dimension(980, 500)); panel2.setPreferredSize(new Dimension(1000, 550)); panel2.setVisible(false); panel2.setBorder(new EmptyBorder(10, 10, 10, 10)); panel3.setVisible(false); panel.setLayout(new FlowLayout()); panel.add(scrollPane); searchPanel.add(searchLabel); searchPanel.add(searchText); searchPanel.add(searchButton); searchButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { try { frame.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR)); search(g, searchText.getText(), frame, bButton); frame.setCursor(Cursor.getDefaultCursor()); } catch (IOException ex) { Logger.getLogger(Reader.class.getName()).log(Level.SEVERE, null, ex); } } }); table.addMouseListener(new MouseAdapter() { @Override public void mousePressed(MouseEvent e) { if (e.getClickCount() == 1) { JTable target = (JTable) e.getSource(); panel.setVisible(false); searchPanel.setVisible(false); bButton.setVisible(false); int row = target.getSelectedRow(); specific(row, g, frame, bButton); } } });

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  • How to create custom filenames in C?

    - by eSKay
    Please see this piece of code: #include<stdio.h> #include<string.h> #include<stdlib.h> int main() { int i = 0; FILE *fp; for(i = 0; i < 100; i++) { fp = fopen("/*what should go here??*/","w"); //I need to create files with names: file0.txt, file1.txt, file2.txt etc //i.e. file{i}.txt } }

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  • Could I return a FileStream as a generic interface to a file?

    - by Eric
    I'm writing a class interface that needs to return references to binary files. Typically I would provide a reference to a file as a file path. However, I'm considering storing some of the files (such as a small thumbnail) in a database directly rather then on a file system. In this case I don't want to add the extra step of reading the thumbnail out of the database onto the disc and then returning a path to the file for my program to read. I'd want to stream the image directly out of the database into my program and avoid writing anything to the disc unless the user explicit wants to save something. Would having my interface return a FileStreamor even a Imagemake sense? Then it would be up to the implementing class to determine if the source of the FileStream or Image is a file on a disc or binary data in a database. public interface MyInterface { string Thumbnail {get;} string Attachment {get;} } vs public interface MyInterface { Image Thumbnail {get;} FileStream Attachment {get;} }

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  • Java: Inputting text from a file using split

    - by 00PS
    I am inputting an adjacency list for a graph. There are three columns of data (vertex, destination, edge) separated by a single space. Here is my implementation so far: FileStream in = new FileStream("input1.txt"); Scanner s = new Scanner(in); String buffer; String [] line = null; while (s.hasNext()) { buffer = s.nextLine(); line = buffer.split("\\s+"); g.add(line[0]); System.out.println("Added vertex " + line[0] + "."); g.addEdge(line[0], line[1], Integer.parseInt(line[2])); System.out.println("Added edge from " + line[0] + " to " + line[1] + " with a weight of " + Integer.parseInt(line[2]) + "."); } System.out.println("Size of graph = " + g.size()); Here is the output: Added vertex a. Added edge from a to b with a weight of 9. Exception in thread "main" java.lang.NullPointerException at structure5.GraphListDirected.addEdge(GraphListDirected.java:93) at Driver.main(Driver.java:28) I was under the impression that line = buffer.split("\\s+"); would return a 2 dimensional array of Strings to the variable line. It seemed to work the first time but not the second. Any thoughts? I would also like some feedback on my implementation of this problem. Is there a better way? Anything to help out a novice! :)

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  • How can chunks be allocated in a node.js stream in object mode all at once?

    - by Quentin Engles
    I can see how buffers, and strings can be sent as chunks, but I'm having a problem thinking about how streams can be dealt when working in object mode. Say I have a byte stream from an http request message. I want to take that message, parse, and then transform it into one big object. I already know how to parse the message. What I'm wondering is if the message is big so it has many chunks, but I want to make one object for the output how can I make sure the data event waits for the whole thing? Is this just a matter of not using the push method until the chunked data has finished being sent? That would then restrict the stream data output to a smaller object which I think I'm fine with for now. As an added condition the larger data will be reduced in size after the the transform.

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  • How can I determine if a file is read-only for my process on *nix?

    - by user109078
    Using the stat function, I can get the read/write permissions for: owner user other ...but this isn't what I want. I want to know the read/write permissions of a file for my process (i.e. the application I'm writing). The owner/user/other is only helpful if I know if my process is running as the owner/user/other of the file...so maybe that's the solution but I'm not sure of the steps to get there.

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  • File mode for creating+reading+appending+binary

    - by MihaiD
    I need to open a file for reading and writing. If the file is not found, it should be created. It should also be treated as a binary for Windows. Can you tell me the file mode sequence I need to use for this? I tried 'r+ab' but that doesn't create the files if they are not found. Thanks

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  • threading in Python taking up too much CPU

    - by KevinShaffer
    I wrote a chat program and have a GUI running using Tkinter, and to go and check when new messages have arrived, I create a new thread so Tkinter keeps doing its thing without locking up while the new thread goes and grabs what I need and updates the Tkinter window. This however becomes a huge CPU hog, and my guess is that it has to do somehow with the fact that the Thread is started and never really released when the function is done. Here's the relevant code (it's ugly and not optimized at the moment, but it gets the job done, and itself does not use too much processing power, as when I run it not threaded, it doesn't take up much CPU but it locks up Tkinter) Note: This is inside of a class, hence the extra tab. def interim(self): threading.Thread(target=self.readLog).start() self.after(5000,self.interim) def readLog(self): print 'reading' try: length = len(str(self.readNumber)) f = open('chatlog'+str(myport),'r') temp = f.readline().replace('\n','') while (temp[:length] != str(self.readNumber)) or temp[0] == '<': temp = f.readline().replace('\n','') while temp: if temp[0] != '<': self.updateChat(temp[length:]) self.readNumber +=1 else: self.updateChat(temp) temp = f.readline().replace('\n','') f.close() Is there a way to better manage the threading so I don't consume 100% of the CPU very quickly?

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  • basic file input using C

    - by user1781966
    So im working on learning how to do file I/O, but the book I'm using is terrible at teaching how to receive input from a file. Below is is their example of how to receive input from a file, but it doesn't work. I have copied it word for word, and it should loop through a list of names until it reaches the end of the file( or so they say in the book), but it doesn't. In fact if I leave the while loop in there, it doesn't print anything. #include <stdio.h> #include <conio.h> int main() { char name[10]; FILE*pRead; pRead=fopen("test.txt", "r"); if (pRead==NULL) { printf("file cannot be opened"); }else printf("contents of test.txt"); fscanf(pRead,"%s",name); while(!feof(pRead)) { printf("%s\n",name); fscanf(pRead, "%s", name); } getch(); } Even online, every beginners tutorial I see does some variation of this, but I can't seem to get it to work even a little bit.

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  • Reading a simple Avro file from HDFS

    - by John Galt... who
    I am trying to do a simple read of an Avro file stored in HDFS. I found out how to read it when it is on the local file system.... FileReader reader = DataFileReader.openReader(new File(filename), new GenericDatumReader()); for (GenericRecord datum : fileReader) { String value = datum.get(1).toString(); System.out.println("value = " value); } reader.close(); My file is in HDFS, however. I cannot give the openReader a Path or an FSDataInputStream. How can I simply read an Avro file in HDFS? EDIT: I got this to work by creating a custom class (SeekableHadoopInput) that implements SeekableInput. I "stole" this from "Ganglion" on github. Still, seems like there would be a Hadoop/Avro integration path for this. Thanks

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  • How to get size of file in visual c++?

    - by karikari
    Below is my code. My problem is, my destination file always has a lot more strings than the originating file. Then, inside the for loop, instead of using i < sizeof more, I realized that I should use i < sizeof file2 . Now my problem is, how to get the size of file2? int i = 0; FILE *file2 = fopen(LOG_FILE_NAME,"r"); wfstream file3 (myfile, ios_base::out); // char more[1024]; char more[SIZE-OF-file2]; for(i = 0; i < SIZE-OF-file2 ; i++) { fgets(more, SIZE-OF-file2, file2); file3 << more; } fclose(file2); file3.close();

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  • Reading and writing in parallel

    - by Malfist
    I want to be able to read and write a large file in parallel, or if not in parallel, at least in blocks so that I don't use up so much memory. This is my current code: // Define memory stream which will be used to hold encrypted data. MemoryStream memoryStream = new MemoryStream(); // Define cryptographic stream (always use Write mode for encryption). CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write); //start encrypting using (BinaryReader reader = new BinaryReader(File.Open(fileIn, FileMode.Open))) { byte[] buffer = new byte[1024 * 1024]; int read = 0; do { read = reader.Read(buffer, 0, buffer.Length); cryptoStream.Write(buffer, 0, read); } while (read == buffer.Length); } // Finish encrypting. cryptoStream.FlushFinalBlock(); // Convert our encrypted data from a memory stream into a byte array. //byte[] cipherTextBytes = memoryStream.ToArray(); //write our memory stream to a file memoryStream.Position = 0; using (BinaryWriter writer = new BinaryWriter(File.Open(fileOut, FileMode.Create))) { byte[] buffer = new byte[1024 * 1024]; int read = 0; do { read = memoryStream.Read(buffer, 0, buffer.Length); writer.Write(buffer, 0, read); } while (read == buffer.Length); } // Close both streams. memoryStream.Close(); cryptoStream.Close(); As you can see, it reads the entire file into memory, encrypts it, then writes it out. If I happen to be encrypting files that are very large (2GB+) it tends not to work, or at the very least, consumes ~97% of my memory. How could I do it in a more effective manner?

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  • How to close reconnect SocketIOClient on android?

    - by erginduran
    My problem is reconnect.I connect SocketIOClient.connect(..) in background service.I close service when internet connection is off.and I re-start service again connection on. How to close this reconnection?I don't want to reconnect SocketIOClient. Its my code: ConnectCallback mConnectCallback = new ConnectCallback() { @Override public void onConnectCompleted(Exception ex, SocketIOClient client) { if (ex != null) { ex.printStackTrace(); return; } client.setReconnectCallback(new ReconnectCallback() { @Override public void onReconnect() { // TODO Auto-generated method stub } }); client.setDisconnectCallback(new DisconnectCallback() { @Override public void onDisconnect(Exception arg0) { // TODO Auto-generated method stub } }); client.setErrorCallback(new ErrorCallback() { @Override public void onError(String arg0) { // TODO Auto-generated method stub } }); client.on("event", new EventCallback() { @Override public void onEvent(JSONArray jsonArray, Acknowledge acknowledge) { ///bla bla } }); ScreenChat.mClient = client; } };

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  • File.Exists() returns false, but not in debug

    - by Tor Haugen
    I'm being completely confused here folks, My code throws an exception because File.Exists() returns false public override sealed TCargo ReadFile(string fileName) { if (!File.Exists(fileName)) { throw new ArgumentException("Provided file name does not exist", "fileName"); } Visual studio breaks at the throw statement, and I immediately check the value of File.Exists(fileName) in the immediate window. It returns true. When I drag the breakpoint back up to the if statement and execute it again, it throws again. fileName is an absolute path to a file. I'm not creating the file, nor writing to it (it's there all along). If I paste the path into the open dialog in Notepad, it reads the file without problems. The code is executing in a background worker. It's the only complicating factor I can think of. I am positive the file has not been opened already, either in the worker thread or elsewhere. What's going on here?

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  • python open does not create file if it doesnt exist

    - by Toddeman
    I am using Python. What is the best way to open a file in rw if it exists, or if it does not, then create it and open it in rw? From what i read, file = open('myfile.dat', 'rw') should do this, no? it is not working for me (python 2.6.2) and im wondering if it is a version problem, or not supposed to work like that or what. The bottom line is, i just need a solution for the problem. I am curious about the other stuff, but all i need is a nice way to do the opening part. thanks in advance

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  • Optimizing memory usage and changing file contents with PHP

    - by errata
    In a function like this function download($file_source, $file_target) { $rh = fopen($file_source, 'rb'); $wh = fopen($file_target, 'wb'); if (!$rh || !$wh) { return false; } while (!feof($rh)) { if (fwrite($wh, fread($rh, 1024)) === FALSE) { return false; } } fclose($rh); fclose($wh); return true; } what is the best way to rewrite last few bytes of a file with my custom string? Thanks!

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  • fopen() fails to open stream: permission denied, yet permissions should be valid

    - by about blank
    So, I have this error: Warning: fopen(/path/to/test-in.txt) [function.fopen]: failed to open stream: Permission denied Performing ls -l in the directory where test-in.txt is produces the following output: -rw-r--r-- 1 $USER $USER 1921 Sep 6 20:09 test-in.txt -rw-r--r-- 1 $USER $USER 0 Sep 6 20:08 test-out.txt In order to get past this, I decided to perform the following: chgrp -R www-data /path/to/php/webroot And then did: chmod g+rw /path/to/php/webroot Yet, I still get this error when I run my php5 script to open the file. Why is this happening? I've tried this using LAMP as well as cherokee through CGI, so it can't be this. Is there a solution of some sort? Edit I'll also add that I'm just developing via localhost right now. Update - PHP fopen() line $fullpath = $this->fileRoot . $this->fileInData['fileName']; $file_ptr = fopen( $fullpath, 'r+' ); I should also mention I'd like to stick with Cherokee if possible. What's this deal about setting file permissions for Apache/Cherokee?

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