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  • aio_read from file error on OS X

    - by Pyetras
    The following code: #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <aio.h> #include <errno.h> int main (int argc, char const *argv[]) { char name[] = "abc"; int fdes; if ((fdes = open(name, O_RDWR | O_CREAT, 0600 )) < 0) printf("%d, create file", errno); int buffer[] = {0, 1, 2, 3, 4, 5}; if (write(fdes, &buffer, sizeof(buffer)) == 0){ printf("writerr\n"); } struct aiocb aio; int n = 2; while (n--){ aio.aio_reqprio = 0; aio.aio_fildes = fdes; aio.aio_offset = sizeof(int); aio.aio_sigevent.sigev_notify = SIGEV_NONE; int buffer2; aio.aio_buf = &buffer2; aio.aio_nbytes = sizeof(buffer2); if (aio_read(&aio) != 0){ printf("%d, readerr\n", errno); }else{ const struct aiocb *aio_l[] = {&aio}; if (aio_suspend(aio_l, 1, 0) != 0){ printf("%d, suspenderr\n", errno); }else{ printf("%d\n", *(int *)aio.aio_buf); } } } return 0; } Works fine on Linux (Ubuntu 9.10, compiled with -lrt), printing 1 1 But fails on OS X (10.6.6 and 10.6.5, I've tested it on two machines): 1 35, readerr Is this possible that this is due to some library error on OS X, or am I doing something wrong?

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  • Problem with reading file line-by-line

    - by Maulrus
    I'm trying to complete an exercise to write a program that takes the following command line arguments: an input file, an output file, and an unspecified number of words. The program is to read the contents of the input file line by line, find for each word given which lines contain the word, and print the lines with their line number to the output file. Here's my code: #include <iostream> #include <fstream> #include <string> #include <sstream> using namespace std; int main(int argc, char* argv[]) { if (argc < 4) { cerr << "Error #1: not enough arguments provided\n"; return 1; } ifstream in(argv[1]); if (!in.is_open()) { cerr << "Error #2: input file could not be opened\n"; return 2; } ofstream out(argv[2]); if (!out.is_open()) { cerr << "Error #3: output file could not be opened\n"; return 3; } ostringstream oss; for (int i = 3; i < argc; ++i) { int k = 0; string temp; oss << argv[i] << ":\n\n"; while (getline(in, temp)) { ++k; unsigned x = temp.find(argv[i]); if (x != string::npos) oss << "Line #" << k << ": " << temp << endl; } } string copy = oss.str(); out << copy; in.close(); out.close(); return 0; } If I try to run that, I get the predicted output for the first word given, but any words following it aren't found. For example, for the source code above will give the following output: in: Line #1: #include <iostream> Line #2: #include <fstream> Line #3: #include <string> Line #4: #include <sstream> Line #5: using namespace std; Line #7: int main(int argc, char* argv[]) { Line #12: ifstream in(argv[1]); Line #13: if (!in.is_open()) { Line #14: cerr << "Error #2: input file could not be opened\n"; Line #22: ostringstream oss; Line #23: string temp; Line #24: for (int i = 3; i < argc; ++i) { Line #26: int k = 0; Line #28: while (getline(in, temp)) { Line #30: unsigned x = temp.find(argv[i]); Line #31: if (x != string::npos) Line #32: oss << "Line #" << k << ": " << temp << endl; Line #35: string copy = oss.str(); Line #37: in.close(); out: That is, it'll find all the instances of the first word given but not any following. What am I doing wrong here?

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  • Unable to access Java-created file -- sometimes

    - by BlairHippo
    In Java, I'm working with code running under WinXP that creates a file like this: public synchronized void store(Properties props, byte[] data) { try { File file = filenameBasedOnProperties(props); if ( file.exists() ) { return; } File temp = File.createTempFile("tempfile", null); FileOutputStream out = new FileOutputStream(temp); out.write(data); out.flush(); out.close(); file.getParentFile().mkdirs(); temp.renameTo(file); } catch (IOException ex) { // Complain and whine and stuff } } Sometimes, when a file is created this way, it's just about totally inaccessible from outside the code (though the code responsible for opening and reading the file has no problem), even when the application isn't running. When accessed via Windows Explorer, I can't move, rename, delete, or even open the file. Under Cygwin, I get the following when I ls -l the directory: ls: cannot access [big-honkin-filename] total 0 ?????????? ? ? ? ? ? [big-honkin-filename] As implied, the filenames are big, but under the 260-character max for XP (though they are slightly over 200 characters). To further add to the sense the my computer just wants me to feel stupid, sometimes the files created by this code are perfectly normal. The only pattern I've spotted is that once one file in the directory "locks", the rest are screwed. Anybody ever run into something like this before, or have any insights into what's going on here?

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  • Abort a slow flush to disk after write?

    - by Therealstubot
    Is there a way to abort a python write operation in such a way that the OS doesn't feel it's necessary to flush the unwritten data to the disc? I'm writing data to a USB device, typically many megabytes. I'm using 4096 bytes as my block size on the write, but it appears that Linux caches up a bunch of data early on, and write it out to the USB device slowly. If at some point during the write, my user decides to cancel, I want the app to just stop writing immediately. I can see that there's a delay between when the data stops flowing from the application, and the USB activity light stops blinking. Several seconds, up to about 10 seconds typically. I find that the app is holding in the close() method, I'm assuming, waiting for the OS to finish writing the buffered data. I call flush() after every write, but that doesn't appear to have any impact on the delay. I've scoured the python docs for an answer but have found nothing.

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  • C++: Is there any good way to read/write without specifically stating character type in function nam

    - by Mark L.
    I'm having a problem getting a program to read from a file based on a template, for example: bool parse(basic_ifstream<T> &file) { T ch; locale loc = file.getloc(); basic_string<T> buf; file.unsetf(ios_base::skipws); if (file.is_open()) { while (file >> ch) { if(isalnum(ch, loc)) { buf += ch; } else if(!buf.empty()) { addWord(buf); buf.clear(); } } if(!buf.empty()) { addWord(buf); } return true; } return false; } This will work when I instantiate this class with <char>, but has problems when I use <wchar_t> (clearly). Outside of the class, I'm using: for (iter = mp.begin(); iter != mp.end(); ++iter ) { cout << iter->first << setw(textwidth - iter->first.length() + 1); cout << " " << iter->second << endl; } To write all of the information from this data struct (it's a map<basic_string<T>, int>), and as predicted, cout explodes if iter->first isn't a char array. I've looked online and the consensus is to use wcout, but unfortunately, since this program requires that the template can be changed at compile time (<char> - <wchar_t>) I'm not sure how I could get away with simply choosing cout or wcout. That is, unless there way a way to read/write wide characters without changing lots of code. If this explanation sounds awkwardly complicated, let me know and I'll address it as best I can.

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  • Java Scanner won't follow file

    - by Steve Renyolds
    Trying to tail / parse some log files. Entries start with a date then can span many lines. This works, but does not ever see new entries to file. File inputFile = new File("C:/test.txt"); InputStream is = new FileInputStream(inputFile); InputStream bis = new BufferedInputStream(is); //bis.skip(inputFile.length()); Scanner src = new Scanner(bis); src.useDelimiter("\n2010-05-01 "); while (true) { while(src.hasNext()){ System.out.println("[ " + src.next() + " ]"); } } Doesn't seem like Scanner's next() or hasNext() detects new entries to file. Any idea how else I can implement, basically, a tail -f with custom delimiter. ok - using Kelly's advise i'm checking & refreshing the scanner, this works. Thank you !! if anyone has improvement suggestions plz do! File inputFile = new File("C:/test.txt"); InputStream is = new FileInputStream(inputFile); InputStream bis = new BufferedInputStream(is); //bis.skip(inputFile.length()); Scanner src = new Scanner(bis); src.useDelimiter("\n2010-05-01 "); while (true) { while(src.hasNext()){ System.out.println("[ " + src.next() + " ]"); } Thread.sleep(50); if(bis.available() > 0){ src = new Scanner(bis); src.useDelimiter("\n2010-05-01 "); } }

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  • Ten latest files on disk

    - by Artic
    I need effective algorithm to keep only ten latest files on disk in particular folder to support some kind of publishing process. Only 10 files should present in this folder at any point of time. Please, give your advises what should be used here.

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  • python gio waiting for async operations to be done

    - by pygabriel
    I have to mount a WebDav location and wait for the operation to be finished before to proceed (it's a script). So I'm using the library in this way: location = gio.File("dav://server.bb") location.mount_enclosing_volume(*args,**kw) # The setup is not much relevant location.get_path() # Returns None because it's not yet mounted since the call is async How to wait until the device is mounted?

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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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  • Reading a file N lines at a time in ruby

    - by Sam
    I have a large file (hundreds of megs) that consists of filenames, one per line. I need to loop through the list of filenames, and fork off a process for each filename. I want a maximum of 8 forked processes at a time and I don't want to read the whole filename list into RAM at once. I'm not even sure where to begin, can anyone help me out?

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  • "Unable to open file", when the program tries to open file in /proc

    - by tristartom
    Hi, I try to read file /proc/'pid'/status, using c program. The code is as follows, and even I use sudo to run it, the prompt still keeps throwing "Unable to open file". Please let me know if you have any ideas on how to fix this. thanks Richard ... int main (int argc, char* argv[]) { string line; char* fileLoc; if(argc != 2) { cout << "a.out file_path" << endl; fileLoc = "/proc/net/dev"; } else { sprintf(fileLoc, "/proc/%d/status", atoi(argv[1])); } cout<< fileLoc << endl; ifstream myfile (fileLoc); if (myfile.is_open()) { while (! myfile.eof() ) { getline (myfile,line); cout << line << endl; } myfile.close(); } else cout << "Unable to open file"; return 0; }

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  • C# DriveInfo FileInfo

    - by maxfridbe
    This may seem like a stupid question, so here goes: Other than parsing the string of FileInfo.FullPath for the drive letter to then use DriveInfo("c") etc to see if there is enough space to write this file. Is there a way to get the drive letter from FileInfo?

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  • C++: ifstream::getline problem

    - by Jay
    I am reading a file like this: char string[256]; std::ifstream file( "file.txt" ); // open the level file. if ( ! file ) // check if the file loaded fine. { // error } while ( file.getline( string, 256, ' ' ) ) { // handle input } Just for testing purposes, my file is just one line, with a space at the end: 12345 My code first reads the 12345 successfully. But then instead of the loop ending, it reads another string, which seems to be a return/newline. I have saved my file both in gedit and in nano. And I have also outputted it with the Linux cat command, and there is no return on the end. So the file should be fine. Why is my code reading a return/newline? Thanks.

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  • serving files using django - is this a security vulnerability

    - by Tom Tom
    I'm using the following code to serve uploaded files from a login secured view in a django app. Do you think that there is a security vulnerability in this code? I'm a bit concerned about that the user could place arbitrary strings in the url after the upload/ and this is directly mapped to the local filesystem. Actually I don't think that it is a vulnerability issue, since the access to the filesystem is restricted to the files in the folder defined with the UPLOAD_LOCATION setting. UPLOAD_LOCATION = is set to a not publicly available folder on the webserver url(r'^upload/(?P<file_url>[/,.,\s,_,\-,\w]+)', 'aeon_infrastructure.views.serve_upload_files', name='project_detail'), @login_required def serve_upload_files(request, file_url): import os.path import mimetypes mimetypes.init() try: file_path = settings.UPLOAD_LOCATION + '/' + file_url fsock = open(file_path,"r") file_name = os.path.basename(file_path) file_size = os.path.getsize(file_path) print "file size is: " + str(file_size) mime_type_guess = mimetypes.guess_type(file_name) if mime_type_guess is not None: response = HttpResponse(fsock, mimetype=mime_type_guess[0]) response['Content-Disposition'] = 'attachment; filename=' + file_name #response.write(file) except IOError: response = HttpResponseNotFound() return response

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  • How to use C to write to flash drive bootsector despite error 'Failed to open file to write.:Permiss

    - by updateraj
    My goal is to manipulate the boot-sector in my flashdrive (volume E:) I am using XP. I am able to read the boot-sector FILE *fp_read = fopen("\\\\.\\E:", "rb"); /* Able to proceed to read boot sector */ however i am not able to open the file to write using fopen in 'wb' mode. FILE *fp_read = fopen("\\\\.\\E:", "wb"); /* Unable to proceed due to Failed to open file to write.:Permission Denied */ The flash-drive is not in use at the moment of execution. Hex-editors are able to manipulated boot sector etc, i believe it possible to do so in c. Any suggestion or insight to overcome the access problem so as to be able to write?

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  • How can I check the version of an assembly then delete the assembly?

    - by Nescio
    I am using the FileVersionInfo to retrieve the version of a .Net assembly. Then, I want to immediately delete the file. Unfortunately after I call GetVersionInfo, any attempt to delete the file results in an error “…in use by another process…” Is there another technique to determine the version that does not lock the file? Or, is it possible to ensure the lock is released after calling GetVersionInfo? The below example is heavily simplified, but scope matches my real code. void Main() { var fvi = GetVersion("myPath"); if (fvi.ToString() == "2.0.0.7") DeleteFile("myPath"); } FileVersionInfo GetVersion(string path) { return FileVersionInfo.GetVersionInfo(path); } void DeleteFile(string path) { File.Delete(path); }

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  • mmap() for large file I/O?

    - by Boatzart
    I'm creating a utility in C++ to be run on Linux which can convert videos to a proprietary format. The video frames are very large (up to 16 megapixels), and we need to be able to seek directly to exact frame numbers, so our file format uses libz to compress each frame individually, and append the compressed data onto a file. Once all frames are finished being written, a journal which includes meta data for each frame (including their file offsets and sizes) is written to the end of the file. I'm currently using ifstream and ofstream to do the file i/o, but I am looking to optimize as much as possible. I've heard that mmap() can increase performance in a lot of cases, and I'm wondering if mine is one of them. Our files will be in the tens to hundreds of gigabytes, and although writing will always be done sequentially, random access reads should be done in constant time. Any thoughts as to whether I should investigate this further, and if so does anyone have any tips for things to look out for? Thanks!

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  • Performance of fopen vs stat

    - by Alex Marshall
    Hello, I'm writing several C programs for an embedded system where every bit of performance we can squeeze out will matter. Part of that is accessing log files. When determining if a file exists, is there any performance difference between using open / fopen, and stat ? I've been using stat on the assumption that it only has to do a quick check against the file system, whereas fopen would have to actually gain access to a file and manipulate internal data structures before returning. Is there any merit to this ?

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  • Interface for reading variable length files with header and footer.

    - by John S
    I could use some hints or tips for a decent interface for reading file of special characteristics. The files in question has a header (~120 bytes), a body (1 byte - 3gb) and a footer (4 bytes). The header contains information about the body and the footer is only a simple CRC32-value of the body. I use Java so my idea was to extend the "InputStream" class and add a constructor such as "public MyInStream( InputStream in)" where I immediately read the header and the direct the overridden read()'s the body. Problem is, I can't give the user of the class the CRC32-value until the whole body has been read. Because the file can be 3gb large, putting it all in memory is a be an idea. Reading it all in to a temporary file is going to be a performance hit if there are many small files. I don't know how large the file is because the InputStream doesn't have to be a file, it could be a socket. Looking at it again, maybe extending InputStream is a bad idea. Thank you for reading the confused thoughts of a tired programmer. :)

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