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  • writing to an ioport resulting in segfaults...

    - by Sniperchild
    I'm writing for an atmel at91sam9260 arm 9 cored single board computer [glomation gesbc9260] Using request_mem_region(0xFFFFFC00,0x100,"name"); //port range runs from fc00 to fcff that works fine and shows up in /proc/iomem then i try to write to the last bit of the port at fc20 with writel(0x1, 0xFFFFFC20); and i segfault...specifically "unable to handle kernel paging request at virtual address fffffc20. I'm of the mind that i'm not allocating the right memory space... any helpful insight would be great...

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  • How can I do block-oriented disk I/O with Java? Or similar for a B+ tree

    - by Sanoj
    I would like to implement an B+ tree in Java and try to optimize it for disk based I/O. Is there an API for accessing individual disk blocks from Java? or is there an API that can do similar block-oriented access that fits my purpose? I would like to create something like Tokyo Cabinet in 100% Java. Is there anyone that knows what Java only databases like JavaDB is using in the back-end for this? I know that there are probably other languages than Java that can do this better, but I do this in a learning purpose only.

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  • How to grab the lines AFTER a matched line in python

    - by toofly
    Hi All, I am an amateur using Python on and off for some time now. Sorry if this is a silly question, but I was wondering if anyone knew an easy way to grab a bunch of lines if the format in the input file is like this: " Heading 1 Line 1 Line 2 Line 3 Heading 2 Line 1 Line 2 Line 3 " I won't know how many lines are after each heading, but I want to grab them all. All I know is the name, or a regular expression pattern for the heading. The only way I know to read a file is the "for line in file:" way, but I don't know how to grab the lines AFTER the line I'm currently on. Hope this makes sense, and thanks for the help!

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  • Simple binary File I/O problem with cstdio(c++)

    - by Atilla Filiz
    The c++ program below fails to read the file. I know using cstdio is not good practice but that what I am used to and it should work anyway. $ ls -l l.uyvy -rw-r--r-- 1 atilla atilla 614400 2010-04-24 18:11 l.uyvy $ ./a.out l.uyvy Read 0 bytes out of 614400, possibly wrong file code: #include<cstdio> int main(int argc, char* argv[]) { FILE *fp; if(argc<2) { printf("usage: %s <input>\n",argv[0]); return 1; } fp=fopen(argv[1],"rb"); if(!fp) { printf("erör, cannot open %s for reading\n",argv[1]); return -1; } int bytes_read=fread(imgdata,1,2*IMAGE_SIZE,fp); //2bytes per pixel fclose(fp); if(bytes_read < 2*IMAGE_SIZE) { printf("Read %d bytes out of %d, possibly wrong file\n", bytes_read, 2*IMAGE_SIZE); return -1; } return 0; }

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  • How to get proper alignment when printing to file

    - by user1067334
    I have this Structure the elements of which that I need to write in a text file struct Stage3ADisplay { int nSlot; char *Item; char *Type; int nIndex; unsigned char attributesMD[17]; //the last character is \0 unsigned char contentsMD[17]; //only for regular files - //the last character is \0 }; buffer = malloc(sizeof(Stage3ADisplayVar[nIterator]->nSlot) + sizeof(Stage3ADisplayVar[nIterator]->Item) + sizeof(Stage3ADisplayVar[nIterator]->Type) + sizeof(Stage3ADisplayVar[nIterator]->nIndex) + sizeof(Stage3ADisplayVar[nIterator]->attributesMD) + sizeof(Stage3ADisplayVar[nIterator]->contentsMD) + 1); sprintf (buffer,"%d %s %s %d %x %x",Stage3ADisplayVar[nIterator]->nSlot, Stage3ADisplayVar[nIterator]->Item,Stage3ADisplayVar[nIterator]->Type,Stage3ADisplayVar[nIterator]->nIndex,Stage3ADisplayVar[nIterator]->attributesMD,Stage3ADisplayVar[nIterator]->contentsMD); How do I make sure the rows in the file are properly aligned. Thank you.

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  • RAKE won'tt create xml file

    - by user296507
    hi, i'm a bit lost here as to why my RAKE task will not create the desired XML file, however it works fine when i have the method 'build_xml' in the .RB file. require 'rubygems' require 'nokogiri' require 'open-uri' namespace :xml do desc "xml build test" task :xml_build => :environment do build_xml end end def build_xml #build xml docoument builder = Nokogiri::XML::Builder.new do |xml| xml.root { xml.location { xml.value "test" } } end File.open("test.xml", 'w') {|f| f.write(builder.to_xml) } end

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  • Execute a Application On The Server Using PHP(With safe_mode enabled)

    - by Nathan Campos
    I have an application on my server that is called leaf.exe, that haves two arguments needed to run, they are: inputfile and outputfile, that will be like this example: pnote.exe input.pnt output.txt The executable is at exec/, inputfile is at upload/ and outputfile is on compiled/. But I need that a PHP could run the application like that, then I want to know: How could I do this on a server that have exec() disabled and I can't turn it on, because I don't have privileges to do it? How could I echo the output of the program?

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  • Out-of-memory algorithms for addressing large arrays

    - by reve_etrange
    I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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  • close file with fclose() but file still in use

    - by Marco
    Hi all, I've got a problem with deleting/overwriting a file using my program which is also being used(read) by my program. The problem seems to be that because of the fact my program is reading data from the file (output.txt) it puts the file in a 'in use' state which makes it impossible to delete or overwrite the file. I don't understand why the file stays 'in use' because I close the file after use with fclose(); this is my code: bool bBool = true while(bBool){ //Run myprogram.exe tot generate (a new) output.txt //Create file pointer and open file FILE* pInputFile = NULL; pInputFile = fopen("output.txt", "r"); // //then I do some reading using fscanf() // //And when I'm done reading I close the file using fclose() fclose(pInputFile); //The next step is deleting the output.txt if( remove( "output.txt" ) == -1 ){ //ERROR }else{ //Succesfull } } I use fclose() to close the file but the file remains in use by my program until my program is totally shut down. What is the solution to free the file so it can be deleted/overwrited? In reality my code isn't a loop without an end ; ) Thanks in advance! Marco Update Like ask a part of my code which also generates the file 'in use'. This is not a loop and this function is being called from the main(); Here is a piece of code: int iShapeNr = 0; void firstRun() { //Run program that generates output.txt runProgram(); //Open Shape data file FILE* pInputFile = NULL; int iNumber = 0; pInputFile = fopen("output.txt", "r"); //Put all orientations of al detected shapes in an array int iShapeNr = 0; int iRotationBuffer[1024];//1024 is maximum detectable shapes, can be changed in RoboRealm int iXMinBuffer[1024]; int iXMaxBuffer[1024]; int iYMinBuffer[1024]; int iYMaxBuffer[1024]; while(feof(pInputFile) == 0){ for(int i=0;i<9;i++){ fscanf(pInputFile, "%d", &iNumber); fscanf(pInputFile, ","); if(i == 1) { iRotationBuffer[iShapeNr] = iNumber; } if(i == 3){//xmin iXMinBuffer[iShapeNr] = iNumber; } if(i == 4){//xmax iXMaxBuffer[iShapeNr] = iNumber; } if(i == 5){//ymin iYMinBuffer[iShapeNr] = iNumber; } if(i == 6){//ymax iYMaxBuffer[iShapeNr] = iNumber; } } iShapeNr++; } fflush(pInputFile); fclose(pInputFile); } The while loop parses the file. The output.txt contains sets of 9 variables, the number of sets is unknown but always in sets of 9. output.txt could contain for example: 0,1,2,3,4,5,6,7,8,8,7,6,5,4,1,2,3,0

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  • Java file searching problem

    - by Infinity
    Hello guys! I need to search a file for a word and return the whole line and the line number with this word, then edit the line and write back to the file. Maybe the line number isn't necesary to edit a line in a file. I `was reading after seraching with regexp and opening the filechannel of the file, but I can't get the line number. Maybe there are other better ways to do this. Can you help me how to start this?

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  • how to write floating value accurately to a bin file.

    - by user319873
    Hi I am trying to dump the floating point values from my program to a bin file. Since I can't use any stdlib function, I am thinking of writting it char by char to a big char array which I am dumping in my test application to a file. It's like float a=3132.000001; I will be dumping this to a char array in 4 bytes. Code example would be:- if((a < 1.0) && (a > 1.0) || (a > -1.0 && a < 0.0)) a = a*1000000 // 6 bit fraction part. Can you please help me writting this in a better way.

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  • [FIXED] Scan file contents into an array of a structure.

    - by ZaZu
    Hello, I have a structure in my program that contains a particular array. I want to scan a random file with numbers and put the contents into that array. This is my code : ( NOTE : This is a sample from a bigger program, so I need the structure and arrays as declared ) The contents of the file are basically : 5 4 3 2 5 3 4 2 #include<stdio.h> #define first 500 #define sec 500 struct trial{ int f; int r; float what[first][sec]; }; int trialtest(trial *test); main(){ trial test; trialtest(&test); } int trialtest(trial *test){ int z,x,i; FILE *fin; fin=fopen("randomfile.txt","r"); for(i=0;i<5;i++){ fscanf(fin,"%5.2f\t",(*test).what[z][x]); } fclose(fin); return 0; } But the problem is, whenever this I run this code, I get this error : (25) : warning 508 - Data of type 'double' supplied where a pointer is required I tried adding do{ for(i=0;i<5;i++){ q=fscanf(fin,"%5.2f\t",(*test).what[z][x]); } }while(q!=EOF); But that didnt work either, it gives the same error. Does anyone have a solution to this problem ?

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  • How can I speed up line by line reading of an ASCII file? (C++)

    - by Jon
    Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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  • R problem with apply + rbind

    - by Carl
    I cannot seem to get the following to work directory <- "./" files.15x16 <- c("15x16-70d.out", "15x16-71d.out") data.15x16<-rbind( lapply( as.array(paste(directory, files.15x16, sep="")), FUN=read.csv, sep=" ", header=F) ) What it should be doing is pretty straightforward - I have a directory name, some file names, and actual files of data. I paste the directory and file names together, read the data from the files in, and then rbind them all together into a single chunk of data. Except the result of the lapply has the data in [[]] - i.e., accessing it occurs via a[[1]], a[[2]], etc which rbind doesn't seem to accept. Suggestions?

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  • Using scanf() in C++ programs is faster than using cin ?

    - by zeroDivisible
    Hello, I don't know if this is true, but when I was reading FAQ on one of the problem providing sites, I found something, that poke my attention: Check your input/output methods. In C++, using cin and cout is too slow. Use these, and you will guarantee not being able to solve any problem with a decent amount of input or output. Use printf and scanf instead. Can someone please clarify this? Is really using scanf() in C++ programs faster than using cin something ? If yes, that is it a good practice to use it in C++ programs? I thought that it was C specific, though I am just learning C++...

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  • Write file need to optimised for heavy traffic part 2

    - by Clayton Leung
    For anyone interest to see where I come from you can refer to part 1, but it is not necessary. write file need to optimised for heavy traffic Below is a snippet of code I have written to capture some financial tick data from the broker API. The code will run without error. I need to optimize the code, because in peak hours the zf_TickEvent method will be call more than 10000 times a second. I use a memorystream to hold the data until it reaches a certain size, then I output it into a text file. The broker API is only single threaded. void zf_TickEvent(object sender, ZenFire.TickEventArgs e) { outputString = string.Format("{0},{1},{2},{3},{4}\r\n", e.TimeStamp.ToString(timeFmt), e.Product.ToString(), Enum.GetName(typeof(ZenFire.TickType), e.Type), e.Price, e.Volume); fillBuffer(outputString); } public class memoryStreamClass { public static MemoryStream ms = new MemoryStream(); } void fillBuffer(string outputString) { byte[] outputByte = Encoding.ASCII.GetBytes(outputString); memoryStreamClass.ms.Write(outputByte, 0, outputByte.Length); if (memoryStreamClass.ms.Length > 8192) { emptyBuffer(memoryStreamClass.ms); memoryStreamClass.ms.SetLength(0); memoryStreamClass.ms.Position = 0; } } void emptyBuffer(MemoryStream ms) { FileStream outStream = new FileStream("c:\\test.txt", FileMode.Append); ms.WriteTo(outStream); outStream.Flush(); outStream.Close(); } Question: Any suggestion to make this even faster? I will try to vary the buffer length but in terms of code structure, is this (almost) the fastest? When memorystream is filled up and I am emptying it to the file, what would happen to the new data coming in? Do I need to implement a second buffer to hold that data while I am emptying my first buffer? Or is c# smart enough to figure it out? Thanks for any advice

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