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  • Is there a way to efficiently yield every file in a directory containing millions of files?

    - by Josh Smeaton
    I'm aware of os.listdir, but as far as I can gather, that gets all the filenames in a directory into memory, and then returns the list. What I want, is a way to yield a filename, work on it, and then yield the next one, without reading them all into memory. Is there any way to do this? I worry about the case where filenames change, new files are added, and files are deleted using such a method. Some iterators prevent you from modifying the collection during iteration, essentially by taking a snapshot of the state of the collection at the beginning, and comparing that state on each move operation. If there is an iterator capable of yielding filenames from a path, does it raise an error if there are filesystem changes (add, remove, rename files within the iterated directory) which modify the collection? There could potentially be a few cases that could cause the iterator to fail, and it all depends on how the iterator maintains state. Using S.Lotts example: filea.txt fileb.txt filec.txt Iterator yields filea.txt. During processing, filea.txt is renamed to filey.txt and fileb.txt is renamed to filez.txt. When the iterator attempts to get the next file, if it were to use the filename filea.txt to find it's current position in order to find the next file and filea.txt is not there, what would happen? It may not be able to recover it's position in the collection. Similarly, if the iterator were to fetch fileb.txt when yielding filea.txt, it could look up the position of fileb.txt, fail, and produce an error. If the iterator instead was able to somehow maintain an index dir.get_file(0), then maintaining positional state would not be affected, but some files could be missed, as their indexes could be moved to an index 'behind' the iterator. This is all theoretical of course, since there appears to be no built-in (python) way of iterating over the files in a directory. There are some great answers below, however, that solve the problem by using queues and notifications. Edit: The OS of concern is Redhat. My use case is this: Process A is continuously writing files to a storage location. Process B (the one I'm writing), will be iterating over these files, doing some processing based on the filename, and moving the files to another location. Edit: Definition of valid: Adjective 1. Well grounded or justifiable, pertinent. (Sorry S.Lott, I couldn't resist). I've edited the paragraph in question above.

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  • Best way to initialise / clear a string variable cocoa

    - by Spider-Paddy
    I have a routine that parses text via a loop. At the end of each record I need to clear my string variables but I read that someString = @"" actually just points to a new string & causes a memory leak. What is the best way to handle this? Should I rather use mutable string vars and use setString:@"" between iterations?

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  • Does anyone know of a good guide to configure GC in Java?

    - by evilpenguin
    I'm having trouble with a JVM running an app, whose heap memory looks like a comb. It's constantly jumping from 1.5 GB to 3 GB and slowly deteriorating to higher values. I'm using G1 GC algorithm, but have no idea how to configure it. I do not have access to the code of the app I'm running and, needless to say, it's a rather large app. So, bottom line, does anyone know of a good guide to configure GC in Java?

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  • load balance timeout SQL connection string

    - by george9170
    It seems that if there is a sql memory leak somewhere and you dont have time to find it you can use the load balance timeout option in a sql connection string to destory the connection after x seconds. Am i right in assuming I can set the load balance time out to 30-40 seconds and then hunt for the leak latter, while in the mean time the leak will not affect my application too much.

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  • Hardest concept to grasp as a beginner

    - by noizetoys
    When you were starting to program, what was the hardest concept for you to grasp? Was it recursion, pointers, linked lists, assignments, memory management? I was wondering what gave you headaches and how you overcame this issue and learned to love the bomb, I mean understand it. EDIT: As a followup, what helped you grok your hard-to-grasp concept?

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  • How can I use one stream and save result to many places?

    - by plasticrabbit
    I using servlet and Apache ServletFileUpload that provides stream to uploaded image. All I want to do is to store that image to db and also store resized (I using JAI) version to db. How can I achieve this without saving image to drive. As I understand stream can be read only once. So I need to store whole image in memory? Is it expensive for performance? Or there are another way?

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  • Backup software for Ubuntu - which one?

    - by Industrial
    Hi everybody, I have spent some time testing out different backup solutions for my small home office during the last weeks, but still haven't found anything that have been working out too well yet. We can definitely work with a non-GUI script if that's what it takes, if only the requirements are fulfilled: Upload to Amazon S3 Europe. We get unbelievable slow uploading speed to US, so uploading 400+ GB of data will not be happening anytime this year... Incremental backups - only changed files shall be uploaded or we will have a big bill from Amazon in the end of each month.. Files should not be uploaded in one big per-folder archive. This is not efficient at all, since if we change one file in a subfolder, a huge two-digit GB sized file would have to be uploaded during next backup. Not good for economy again, or traffic overhead on our internet connection. What options are available to us? Thanks!

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  • Cross platform /dev/null in Python

    - by Tristan
    I'm using the following code to hide stderr on Linux/OSX for a Python library I do not control that writes to stderr by default: f = open("/dev/null","w") zookeeper.set_log_stream(f) Is there an easy cross platform alternative to /dev/null? Ideally it would not consume memory since this is a long running process.

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  • How to find crc32 of big files ?

    - by Arsheep
    The PHP's crc32 support string as input.And For a file , below code will work OFC. crc32(file_get_contents("myfile.CSV")); But if file goes huge (2 GB) it might raise out of memory Fatal error. So any way around to find checksum of huge files ?

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  • Folder sync application which can sync over Internet (the other machine specified by an IP)?

    - by Adal
    I need to sync some folders between two Win 7 machines. While they are connected to the same LAN, they can't see each-other over Windows Networking since sharing is disabled on both of them (security reasons). Do you know any sync app which can work over IP? The folder I need to sync has 500,000 files in it (80 GB in total), so the sync app should be pretty efficient. At the moment I copy the files from one machine to the other over FTP, but it takes forever, since a separate connection is opened for each file. Or maybe you know some app which can efficiently transfer a large number of files between two machines on the Internet?

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  • iPhone Application failing to come back from sigkill

    - by overscore
    I have no idea if this is intended behaviour, but whenever the application exits (say, the user is double-clicking the home button and pressing on the red dash on the icon) I get the dreaded SIGKILL. Now, when I try to launch the app again all I get is the old screen state and a frozen (I presume ?) program. It could be because of clunky memory management, but NSZombieEnabled doesn't seem to agree. Any thoughts ?

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  • Viewing large XML files in eclipse?

    - by Paul Wicks
    I'm working on a project involving some large XML files (from 50MB to over 1GB) and it would be nice if I could view them in eclipse (simple text view is fine) without Java running out of heap space. I've tried tweaking the amount of memory available to the jvm in eclipse.ini but haven't had much success. Any ideas?

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  • Alias for a C++ template?

    - by porgarmingduod
    typedef boost::interprocess::managed_shared_memory::segment_manager segment_manager_t; // Works fine, segment_manager is a class typedef boost::interprocess::adaptive_pool allocator_t; // Can't do this, adaptive_pool is a template The idea is that if I want to switch between boost interprocess' several different options for shared memory and allocators, I just modify the typedefs. Unfortunately the allocators are templates, so I can't typedef the allocator I want to use. Is there a way to achieve an alias to a template in C++? (Except for the obvious #define ALLOCATOR_T boost::interprocess::adaptive_pool)

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  • Problem intialising 2D array

    - by TeeJay
    Ok, so I have a 2D Array that is initialised with values from a file (format: x y z). My file reads in the values correctly but when adding the z value to the matrix/2DArray, I run into a segfault and I have no idea why. It is possibly incorrect use of pointers? I still don't quite have the hang of them yet. This is my intialiser, works fine, even intialises all "z" values to 0. int** make2DArray(int rows, int columns) { int** newArray; newArray = (int**)malloc(rows*sizeof(int*)); if (newArray == NULL) { printf("out of memory for newArray.\n"); } for (int i = 0; i < rows; i++) { newArray[i] = (int*)malloc(columns*sizeof(int)); if (newArray[i] == NULL) { printf("out of memory for newArray[%d].\n", i); } } //intialise all values to 0 for (int i = 0; i < rows; i++) { for (int j = 0; j < columns; j++) { newArray[i][j] = 0; } } return newArray; } This is how I call the initialiser (and problem function). int** map = make2DArray(rows, columns); fillMatrix(&map, mapFile); And this is the problem code. void fillMatrix(int*** inMatrix, FILE* inFile) { int x, y, z; char line[100]; while(fgets(line, sizeof(line), inFile) != NULL) { sscanf(line, "%d %d %d", &x, &y, &z); *inMatrix[x][y] = z; } } From what I can gather through the use of ddd, the problem comes when y gets to 47. The map file has a max "x" value of 47 and a max "y" value of 63, I'm pretty sure I haven't got the order mixed up, so I don't know why the program is segfault-ing? I'm sure it's some newbie mistake...

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  • Is it a good practice to always use smart pointers ?

    - by Dony Borris
    Hi, I find smart pointers to be a lot more comfortable than raw pointers. So is it a good idea to always use smart pointers? ( Please note that I am from Java background and hence don't much like the idea of explicit memory management. So unless there are some serious performance issues with smart pointers, I'd like to stick with them. ) Any advice would be greatly appreciated. Thanks.

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