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  • How can I get read-ahead bytes?

    - by Bruno Martinez
    Operating systems read from disk more than what a program actually requests, because a program is likely to need nearby information in the future. In my application, when I fetch an item from disk, I would like to show an interval of information around the element. There's a trade off between how much information I request and show, and speed. However, since the OS already reads more than what I requested, accessing these bytes already in memory is free. What API can I use to find out what's in the OS caches? Alternatively, I could use memory mapped files. In that case, the problem reduces to finding out whether a page is swapped to disk or not. Can this be done in any common OS?

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  • Can someone explain me this code ?

    - by VaioIsBorn
    #include <stdio.h> #include <unistd.h> #include <string.h> int good(int addr) { printf("Address of hmm: %p\n", addr); } int hmm() { printf("Win.\n"); execl("/bin/sh", "sh", NULL); } extern char **environ; int main(int argc, char **argv) { int i, limit; for(i = 0; environ[i] != NULL; i++) memset(environ[i], 0x00, strlen(environ[i])); int (*fptr)(int) = good; char buf[32]; if(strlen(argv[1]) <= 40) limit = strlen(argv[1]); for(i = 0; i <= limit; i++) { buf[i] = argv[1][i]; if(i < 36) buf[i] = 0x41; } int (*hmmptr)(int) = hmm; (*fptr)((int)hmmptr); return 0; } I don't really understand the code above, i have it from an online game - i should supply something in the arguments so it would give me shell, but i don't get it how it works so i don't know what to do. So i need someone that would explain it what it does, how it's working and the stuff. Thanks.

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  • Extracting numeric value from output of a uder defined aggregate in netezza using bash script

    - by Ankit
    I am executing a shell script to execute my user defined aggregate which is taking inputs yavg=nzsql -c 'select avg(x) from Input1' which is giving output like this AVG ---------- 2.000000 (1 row) I want to pass only the numeric(double) value which is 2.0000(where xavg is expected) from this to S4(x,y,$xavg,$yavg) where x and y are the whole column from table Input1, xavg=nzsql -c 'select avg(y) from Input1' Below is my InputTable.txt which is a text file from which I am popluating my "Input1" table in the shell script. 1 2 3 2 1 2 3 2 1 nzsql -c 'create table Input1(x integer, y integer, v integer)' nzload -t Input1 -df InputTable.txt nzsql -c 'select * from Input1 yavg=`nzsql -c 'select avg(x) from Input1'` xavg=`nzsql -c 'select avg(y) from Input1' nzsql -c 'select S4(x,y,$xavg,$yavg) from test' Below is the output : xavg := AVG ---------- 2.000000 (1 row) yavg := AVG ---------- 1.666667 (1 row) and i am passing this value to S4(x,y,$xavg,$yavg) which is a User defined aggregate

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  • Copying sectors?

    - by baltusaj
    Is there a script i can use to copy some particular sectors of my Harddisk? I actually have two partitions say A and B, on my Harddisk. Both are of same sizes. What i want is to run a program which starts copying data from the starting sector of A to the starting sector of B until the end sector of A is copied to the end sector of B. Looking for possible solutions... Thanks a lot

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  • Help with Perl Regex Recursive Replace One Liner? Replace MySQL comments '--' with '#'

    - by NJTechie
    I have various SQL files with '--' comments and we migrated to the latest version of MySQL and it hates these comments. I want to replace -- with #. I am looking for a recursive, inplace replace one-liner. This is what I have : perl -p -i -e 's/--/# /g' `fgrep -- -- * ` A sample .sql file : use myDB; --did you get an error I get the following error : Unrecognized switch: --did (-h will show valid options). p.s : fgrep skipping 2 dashes was just discussed here if you are interested. Any help is appreciated.

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  • tcpdf - HTML table showing up way too small

    - by LinuxGnut
    Hi folks. I'm using tcpdf (http://www.tcpdf.org/) to generate PDFs of some tables and images. The images are loaded without an issue, but I'm having issues with the writeHTML() function. I can't seem to control the font sizes or table width/height through the HTML, so I end up with a tiny, tiny, tiny table that you have to print of and squint at to even attempt reading. I've tried editing the table itself, CSS, even putting the table itself inside an h1, but nothing is changing the font size. I have the font size in tcpdf set to 16, but this also has no affect. Has anyone else run into this issue?

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  • CUDA SDK compilation error

    - by ZeroDivide
    I am in the process of setting up a CUDA workstation. Platform specs: Intel Core 2 Duo Nvidia GTX 280 Fedora 10 GCC version 4.3.2 I have installed the developer driver, toolkit, and the SDK. When I try to compile the SDK example code I get the following errors: make[1]: * [obj/i386/release/cutil.cpp.o] Error 1 make: * [lib/libcutil.so] Error 2 I think this means that I am missing a library file but I'm not sure.

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  • killing all instances of chrome on the command line?

    - by Fedor
    In some cases killing a single tab/process doesn't do it and I need to close Chrome entirely. Since Chrome has multiple processes, how can I close all of them at once? I know that... pgrep chrome returns all the pids, can someone tell me a trick that would allow me to close all of them by feeding them to another command or merging them to a csv or something?

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  • Calling SDL/OpenGL from Assembly code on Linux

    - by Lie Ryan
    I'm write a simple graphic-based program in Assembly for learning purpose; for this, I intended to use either OpenGL or SDL. I'm trying to call OpenGL/SDL's function from assembly. The problem is, unlike many assembly and OpenGL/SDL tutorials I found in the internet, the OpenGL/SDL in my machine apparently doesn't use C calling convention. I wrote a simple program in C, compile it to assembly (using -S switch), and apparently the assembly code that is generated by GCC calls the OpenGL/SDL functions by passing parameters in the registers instead of being pushed to the stack. Now, the question is, how do I determine how to pass arguments to these OpenGL/SDL functions? That is, how do I figure out which argument corresponds to which registers? Obviously since GCC can compile C code to call OpenGL/SDL, so therefore there must be a way to figure out the correspondence between function arguments and registers. In C calling conventions, the rule is easy, push parameters backwards and return value in eax/rax, I can simply read their C documentation and I can easily figure out how to pass the parameters. But how about these? Is there a way to call OpenGL/SDL using C calling convention? btw, I'm using yasm, with gcc/ld as the linker on Gentoo Linux amd64.

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  • Headless HTML rendering to image on CentOS 5.4

    - by Jim Tough
    Hello, I have a project requirement to render HTML and capture the rendered image as a file on a headless CentOS 5.4 server. My specific requirements are: 1) Input will be a URL to the page to render, output will be an image file containing the rendered image of the page 2) CSS must be supported by the renderer up to CSS level-1 3) Static images in the page must be displayed properly in the rendered image, including any transparent color in .GIF files 4) Must be able to run on a headless CentOS 5.4 server. 5) Solution must not depend on any product or component that is not free for commercial use I do not need to do anything with the page other than get the screen capture and save it to an image. The hard part seems to be doing this in a headless environment. Some of the solutions that I've seen discussed need a display in order to work. Any suggestions? Thanks in advance, Jim

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  • Using bash to copy file to spec folders

    - by Franko
    I have a folder with a fair amount of subfolders. In some of the subfolders do I have a folder.jpg picture. What I try to do find that folder(s) and copy it to all other subfolders that got the same artist and album information then continue on to the next album etc. The structure of all the folders are "artist - year - album - [encoding information]". I have made a really simple one liner that find the folders that got the file but there am I stuck. ls -F | grep / | while read folders;do find "$folders" -name folder.jpg; done Anyone have any good tip or ideas how to solve this or pointers how to proceed? Edit: First of all, i´m real new to this (like you cant tell) so please have patience. Ok, let me break it down even more. I have a folder structure that looks like this: artist1 - year - album - [flac] artist1 - year - album - [mp3] artist1 - year - album - [AAC] artist2 - year - album - [flac] etc I like to loop over the set of folders that have the same artist and album information and look for a folder.jpg file. When I find that file do I like to copy it to all of the other folders in the same set. Ex if I find one folder.jpg in artist1 - year - album - [flac] folder do I like to have that folder.jpg copied to artist1 - year - album - [mp3] & artist1 - year - album - [AAC] but not to artist2 - year - album - [flac]. The continue the loop until all the sets been processed. I really hope that makes it a bit more easy to understand what I try to do :)

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  • Using find and tar with files with special characters in the name

    - by Costi
    I want to archive all .ctl files in a folder, recursively. tar -cf ctlfiles.tar `find /home/db -name "*.ctl" -print` The error message : tar: Removing leading `/' from member names tar: /home/db/dunn/j: Cannot stat: No such file or directory tar: 74.ctl: Cannot stat: No such file or directory I have these files: /home/db/dunn/j 74.ctl and j 75. Notice the extra space. What if the files have other special characters? How do I archive these files recursively?

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  • How do I route watir through a proxy pragmatically?

    - by feydr
    I'm trying to route watir through a proxy pragmatically -- this means within the script I'd like to change my proxy dynamically before launching the browser. Here's what I've tried so far (and so far am failing): I'm running chrome and lucid lynx ubuntu. I chose TREX cause I thought watir might be making use of PROXY or something. I rewrote /usr/bin/google-chrome as: #!/bin/bash /opt/google/chrome/chrome --proxy-server="$TREX" $@ The reason I'm passing in the environment variable to proxy-server rather than http_proxy is because I never could get http_proxy to work as is anyways then I did a simple: require 'rubygems' require 'watir-webdriver' ENV['TREX'] = "XX.XX.XX.XX:YY" browser = Watir::Browser.new(:chrome) browser.goto("http://mysite.com") Anyways, what is happening here is that it is forwarding me to the login page of the proxy rather than just forwarding the request. What am I missing here? I feel like I'm pretty close.

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  • Using static mutex in a class

    - by Dmitry Yudakov
    I have a class that I can have many instances of. Inside it creates and initializes some members from a 3rd party library (that use some global variables) and is not thread-safe. I thought about using static boost::mutex, that would be locked in my class constructor and destructor. Thus creating and destroying instances among my threads would be safe for the 3rd party members. class MyClass { static boost::mutex mx; // 3rd party library members public: MyClass(); ~MyClass(); }; MyClass::MyClass() { boost::mutex::scoped_lock scoped_lock(mx); // create and init 3rd party library stuff } MyClass::~MyClass() { boost::mutex::scoped_lock scoped_lock(mx); // destroy 3rd party library stuff } I cannot link because I receive error: undefined reference to `MyClass::mx` Do I need some special initialization of such static member? Is the whole conception of static mutex wrong?

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  • unix message queue

    - by Betamoo
    Is there an ipc option to get the last message in message queue but not removing it? I want this to allow many clients reading same messages from the same server.. Thanks

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  • Sum in shell script

    - by Dinis Monteiro
    Why can't I create a sum of total words in this script? I get the result something like: 120+130 but it isn't 250 (as I expected)! Is there any reason? #!/bin/bash while [ -z "$count" ] ; do echo -e "request :: please enter file name " echo -e "\n\tfile one : \c" read count itself=counter.sh countWords=`wc -w $count |cut -d ' ' -f 1` countLines=`wc -l $count |cut -d ' ' -f 1` countWords_=`wc -w $itself |cut -d ' ' -f 1` echo "Number of lines: " $countLines echo "Number of words: " $countWords echo "Number of words -script: " $countWords_ echo "Number of words -total " $countWords+$countWords_ done if [ ! -e $count ] ; then echo -e "error :: file one $count doesn't exist. can't proceed." read empty exit 1 fi

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  • getnameinfo specifies socklen_t

    - by bobby
    The 2nd arg for the getnameinfo prototype asks for a socklen_t type but sizeof uses size_t. So how can I get socklen_t ? Prototype: int getnameinfo(const struct sockaddr *restrict sa, socklen_t salen, char *restrict node, socklen_t nodelen, char *restrict service, socklen_t servicelen, int flags); Example: struct sockaddr_in SIN; memset(&SIN, 0, sizeof(SIN)); // This should also be socklen_t ? SIN.sin_family = AF_INET; SIN.sin_addr.s_addr = inet_addr(IP); SIN.sin_port = 0; getnameinfo((struct sockaddr *)&SIN, sizeof(SIN) /* socklen_t */, BUFFER, NI_MAXHOST, NULL, 0, 0);

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  • I am currently serving my static files in Django. How do I use Apache2 to do this?

    - by alex
    (r'^media/(?P<path>.*)$', 'django.views.static.serve',{'document_root': settings.MEDIA_ROOT}), As you can see, I have a directory called "media" under my Django project. I would like to delete this line in my urls.py and instead us Apache to serve my static files. What do I do to my Apache configs (which files do I change) in order to do this? By the way, I installed Apache2 like normal: sudo aptitude install apache2

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  • Navigating multiples files vi editor

    - by learner135
    According to http://www.lagmonster.org/docs/vi2.html the command :p would make vi go to the previous file. Unfortunately, this isn't working for me. However :n works and goes to the next page. What should I use to go to the previous file? For :p I get the message, Hit Return to continue and it stays in the same page. Thanks. Edit: I am sshing to an AIX box and using the vi in Ksh if that helps.

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