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  • Double paging definition

    - by Albinoswordfish
    This is not a programming question but more of an operating system question Right now I'm trying to learn what exactly Double paging means. I see two different terms, double paging on disk and double paging in memory. Apparently this problem arises when we introduce a buffer cache to store disk blocks when doing File I/O But I'm not really sure what exactly this term means. If anybody could specify it would be very helpful.

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  • undo continually vi

    - by wowrt
    Hi, I am using vi(not Vim) and I would like to continually undo the changes made. u works for a single command undo and Ufor a single line undo. But Is there a way to undo continuously like vim(I recall a command in vim can even undo changes by time!) in vi? Thanks in Advance.

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  • Condition Variable in Shared Memory - is this code POSIX-conformant?

    - by GrahamS
    We've been trying to use a mutex and condition variable to synchronise access to named shared memory on a LynuxWorks LynxOS-SE system (POSIX-conformant). One shared memory block is called "/sync" and contains the mutex and condition variable, the other is "/data" and contains the actual data we are syncing access to. We're seeing failures from pthread_cond_signal() if both processes don't perform the mmap() calls in exactly the same order, or if one process mmaps in some other piece of shared memory before it mmaps the sync memory. This example code is about as short as I can make it: #include <sys/types.h> #include <sys/stat.h> #include <sys/mman.h> #include <sys/file.h> #include <stdlib.h> #include <pthread.h> #include <errno.h> #include <iostream> #include <string> using namespace std; static const string shm_name_sync("/sync"); static const string shm_name_data("/data"); struct shared_memory_sync { pthread_mutex_t mutex; pthread_cond_t condition; }; struct shared_memory_data { int a; int b; }; //Create 2 shared memory objects // - sync contains 2 shared synchronisation objects (mutex and condition) // - data not important void create() { // Create and map 'sync' shared memory int fd_sync = shm_open(shm_name_sync.c_str(), O_CREAT|O_RDWR, S_IRUSR|S_IWUSR); ftruncate(fd_sync, sizeof(shared_memory_sync)); void* addr_sync = mmap(0, sizeof(shared_memory_sync), PROT_READ|PROT_WRITE, MAP_SHARED, fd_sync, 0); shared_memory_sync* p_sync = static_cast<shared_memory_sync*> (addr_sync); // init the cond and mutex pthread_condattr_t cond_attr; pthread_condattr_init(&cond_attr); pthread_condattr_setpshared(&cond_attr, PTHREAD_PROCESS_SHARED); pthread_cond_init(&(p_sync->condition), &cond_attr); pthread_condattr_destroy(&cond_attr); pthread_mutexattr_t m_attr; pthread_mutexattr_init(&m_attr); pthread_mutexattr_setpshared(&m_attr, PTHREAD_PROCESS_SHARED); pthread_mutex_init(&(p_sync->mutex), &m_attr); pthread_mutexattr_destroy(&m_attr); // Create the 'data' shared memory int fd_data = shm_open(shm_name_data.c_str(), O_CREAT|O_RDWR, S_IRUSR|S_IWUSR); ftruncate(fd_data, sizeof(shared_memory_data)); void* addr_data = mmap(0, sizeof(shared_memory_data), PROT_READ|PROT_WRITE, MAP_SHARED, fd_data, 0); shared_memory_data* p_data = static_cast<shared_memory_data*> (addr_data); // Run the second process while it sleeps here. sleep(10); int res = pthread_cond_signal(&(p_sync->condition)); assert(res==0); // <--- !!!THIS ASSERT WILL FAIL ON LYNXOS!!! munmap(addr_sync, sizeof(shared_memory_sync)); shm_unlink(shm_name_sync.c_str()); munmap(addr_data, sizeof(shared_memory_data)); shm_unlink(shm_name_data.c_str()); } //Open the same 2 shared memory objects but in reverse order // - data // - sync void open() { sleep(2); int fd_data = shm_open(shm_name_data.c_str(), O_RDWR, S_IRUSR|S_IWUSR); void* addr_data = mmap(0, sizeof(shared_memory_data), PROT_READ|PROT_WRITE, MAP_SHARED, fd_data, 0); shared_memory_data* p_data = static_cast<shared_memory_data*> (addr_data); int fd_sync = shm_open(shm_name_sync.c_str(), O_RDWR, S_IRUSR|S_IWUSR); void* addr_sync = mmap(0, sizeof(shared_memory_sync), PROT_READ|PROT_WRITE, MAP_SHARED, fd_sync, 0); shared_memory_sync* p_sync = static_cast<shared_memory_sync*> (addr_sync); // Wait on the condvar pthread_mutex_lock(&(p_sync->mutex)); pthread_cond_wait(&(p_sync->condition), &(p_sync->mutex)); pthread_mutex_unlock(&(p_sync->mutex)); munmap(addr_sync, sizeof(shared_memory_sync)); munmap(addr_data, sizeof(shared_memory_data)); } int main(int argc, char** argv) { if(argc>1) { open(); } else { create(); } return (0); } Run this program with no args, then another copy with args, and the first one will fail at the assert checking the pthread_cond_signal(). But change the open() function to mmap() the "/sync" memory first and it will all work fine. This seems like a major bug in LynxOS but LynuxWorks claim that using mutex and condition variable in this way is not covered by the POSIX standard, so they are not interested. Can anyone determine if this code does violate POSIX? Or does anyone have any convincing documentation that it is POSIX compliant?

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  • Difficulty to start up with basic unit test (Sample from my book -- SportsStore)

    - by Richard77
    Hello, I'm really new in TDD and, actually, I'm trying to follow the sample from my book (SportsStore -- Pro ASP.NET MVC Framework/Steve Sanderson/APRESS). I'm on pages 103-105. Although there are more on this, as new to all of this, I'm concerned with the following statements. ProductsController controller = new ProductsController(repository); var result = controller.List(2); //... regarding the above statements, when I write this (as in the book), var products = result.ViewData.Model as IList<Product>; I get a compiler error "System.Web.MVC.ActionResult" does not contain a definition for ViewData ..." But, when I remove the List() from the statement, then the compiler error disapear. var result = controller.List(2);//Doesn't work var result = controller;//It works Is something wrong there? I checked Apress website for that book, but there is nothing listed as Errata or issue. So I'm really lost. Thanks for helping

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  • Why is this basic equality test failing?

    - by Goose Bumper
    I have a pointer m to an object, and calling m->det() returns 14 (the return type is a double). Why would the following statement evaluate to false? cout << (m->det()==14) << endl; I just don't understand how this could be failing. Using cout << m->det() << endl; cout << (m->det()==14) << endl; gives me: 14 0

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  • Pattern Matching in Columns

    - by Chronicles
    File 1 A11;F1;BMW A23;F2;BMW B12;F3;BMW H11;F4;JBW File 2 P01;A1;0;0--00 ;123;456;150 P01;A11;0;0--00 ;123;444;208 P01;B12;0;0--00 ;123;111;36 P01;V11;0;0--00 ;123;787;33.9 Output -;-;-;P01;A1;0;0--00 ;123;456;150 A11;F1;BMW;P01;A11;0;0--00 ;123;444;208 B12;F3;BMW;P01;B12;0;0--00 ;123;111;36 -;-;-;P01;V11;0;0--00 ;123;787;33.9 I TRIED awk 'FNR==NR {a[$2] = $0; next }{ if($1 in a) {p=$1;$1="";print a[p],$0}}' File1 File2 But didnt work. Basically I want to get the details from FILE 1 and compare with FILE2 (master list) . Example : A1 in FILE2 was not available in FILE1 , so in output file we have “-“ for 1st three fields and rest from FILE2 . Now, we have A11 and we got the detail in FILE1. So we write details of A11 from both File 1 & 2

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  • basic unique ModelForm field for Google App Engine

    - by Alexander Vasiljev
    I do not care about concurrency issues. It is relatively easy to build unique form field: from django import forms class UniqueUserEmailField(forms.CharField): def clean(self, value): self.check_uniqueness(super(UniqueUserEmailField, self).clean(value)) def check_uniqueness(self, value): same_user = users.User.all().filter('email', value).get() if same_user: raise forms.ValidationError('%s already_registered' % value) so one could add users on-the-fly. Editing existing user is tricky. This field would not allow to save user having other user email. At the same time it would not allow to save a user with the same email. What code do you use to put a field with uniqueness check into ModelForm?

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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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  • Basic Scolling Question

    - by localgamer
    Hey guys, im pretty new to android platform and have a really simple question. Im putting buttons as layouts with text boxes, but im running out of room. How would i make it possible for the user to scroll down to view more buttons and stuff. For example, if i have 6 buttons, and 3 are in the field of view, i wanna be able to scroll with my finger and be able to see those buttons as I scroll. Thanks for the help guys -Localgamer

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  • How to deal with 'bad' decision forced on you regarding basic software for your product

    - by raticulin
    Here is my situation, our product used to support several of the major databases. Now management has decided to move all products to MaxDB (aka SapDB previously), and even if we keep supporting some of the previous dbs, all new installations are on MaxDB. I am sure MaxDB is a great db and can support huge SAP installations. But from the point of view of a software developper, its a nightmare. Every time you need to do something not trivial (write an stored procedure, some fancy trigger...) and you google for some info, you get like 0.1% of the hits you would with things like MySql, PostgreSql or MSSql. Mailing lists are nearly non existant. SAP does support it commercially but it is not clear wether we'll buy support. And the decision cannot be rolled back. The product works with MaxDB, but with lots of inefficiency on development and a lot of frustration, is there something one could do?

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  • generate sha256 with openssl and C++

    - by Stanislav Palatnik
    Hello, I'm looking to create a hash with sha256 using openssl and C++. I know there's a similar post about this here: http://stackoverflow.com/questions/918676/generate-sha-hash-in-openssl, but I'm looking to specifically create sha256. UPDATE: Seems to be a problem witht he include paths. It can't find any openssl functions even though I included #include "openssl/sha.h" and I included the paths in my build -I/opt/ssl/include/ -L/opt/ssl/lib/ -lcrypto

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  • Parsing Chunk of Data into Hash of Array With Perl

    - by neversaint
    I have data that looks like this: #info #info2 1:SRX004541 Submitter: UT-MGS, UT-MGS Study: Glossina morsitans transcript sequencing project(SRP000741) Sample: Glossina morsitans(SRS002835) Instrument: Illumina Genome Analyzer Total: 1 run, 8.3M spots, 299.9M bases Run #1: SRR016086, 8330172 spots, 299886192 bases 2:SRX004540 Submitter: UT-MGS Study: Anopheles stephensi transcript sequencing project(SRP000747) Sample: Anopheles stephensi(SRS002864) Instrument: Solexa 1G Genome Analyzer Total: 1 run, 8.4M spots, 401M bases Run #1: SRR017875, 8354743 spots, 401027664 bases 3:SRX002521 Submitter: UT-MGS Study: Massive transcriptional start site mapping of human cells under hypoxic conditions.(SRP000403) Sample: Human DLD-1 tissue culture cell line(SRS001843) Instrument: Solexa 1G Genome Analyzer Total: 6 runs, 27.1M spots, 977M bases Run #1: SRR013356, 4801519 spots, 172854684 bases Run #2: SRR013357, 3603355 spots, 129720780 bases Run #3: SRR013358, 3459692 spots, 124548912 bases Run #4: SRR013360, 5219342 spots, 187896312 bases Run #5: SRR013361, 5140152 spots, 185045472 bases Run #6: SRR013370, 4916054 spots, 176977944 bases What I want to do is to create a hash of array with first line of each chunk as keys and SR## part of lines with "^Run" as its array member: $VAR = { 'SRX004541' => ['SRR016086'], # etc } But why my construct doesn't work. And it must be a better way to do it. use Data::Dumper; my %bighash; my $head = ""; my @temp = (); while ( <> ) { chomp; next if (/^\#/); if ( /^\d{1,2}:(\w+)/ ) { print "$1\n"; $head = $1; } elsif (/^Run \#\d+: (\w+),.*/){ print "\t$1\n"; push @temp, $1; } elsif (/^$/) { push @{$bighash{$head}}, [@temp]; @temp =(); } } print Dumper \%bighash ;

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  • basic question with a dtd

    - by voodoomsr
    i need an element with the characteristics <!ELEMENT section ((comment*)|definition|(comment*))> but that is ambiguous, i get the next message in visual studio Multiple definition of element 'comment' causes the content model to become ambiguous. A content model must be formed such that during validation of an element information item sequence, the particle contained directly, indirectly or implicitly therein with which to attempt to validate each item in the sequence in turn can be uniquely determined without examining the content or attributes of that item, and without any information about the items in the remainder of the sequence. So how can i write correctly that? the correct structure is one definition surrounded by possibles comments elements.

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  • Checking status after wait()

    - by Helper Method
    After creating a child process and exiting it immediately (_exit()), I want to perform a wait and check the status. Now I wonder if in the 'else' branch of the if/else construct I also need to check for WIFSIGNALED. As far as I understand, if I perform a wait, a) an error could have occured (-1), the child could have terminated normally by an (exit() or _exit()), or it could have been terminated by a signal, so the check could be omitted, right? //remainder omitted int status; pid_t t_pid = wait(&status); if (t_pid == -1) { perror("wait"); exit(EXIT_FAILURE); } if (WIFEXITED(status)) { printf("child terminated normally, status = %d\n", WEXITSTATUS(status) ); } else { // <-- do it have to check for WIFSIGNALED() here? printf("child was terminated by a signal, signum = %d\n", WTERMSIG(status) ); }

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  • how to grep for the whole word

    - by josh
    I am using the following command to grep stuff in subdirs find . | xargs grep -s 's:text' However, this also finds stuff like <s:textfield name="sdfsf"...../> What can I do to avoid that so it just finds stuff like <s:text name="sdfsdf"/> OR for that matter....also finds <s:text somethingElse="lkjkj" name="lkkj" basically s:text and name should be on same line....

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  • Fixing permissions after FTPing ASP.NET code to a Linux system

    - by dnord
    First off, I'm running Mono to run ASP.NET on Linux, but that's not the question. It appears that, every time I clear out my application directory and upload, I have to go back in and fix the permissions. What I'm doing is chmod -R -c 755 /var/www/* ...and there are two questions. What's the deal with having to do this every time I FTP? Feels flaky. Is there a better permissions set than 755? Do I want different permissions for the /bin directory? Or can I fix this all with one fell swoop of chown?

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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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  • Stopping httpd causes a process started from perl CGI script to receive SIGTERM

    - by Pranav Pal
    I am running a shell script from a perl CGI script: #!/usr/bin/perl my $command = "./script.sh &"; my $pid = fork(); if (defined($pid) && $pid==0) { # background process system( $command ); } The shell script looks like this: #!/bin/sh trap 'echo trapped' 15 tail -f test.log When I run the CGI script from browser, and then stop httpd using /etc/init.d/httpd stop, the script receives a SIGTERM signal. I was expecting the script to run as a separate process and not be tied in anyway to httpd. Though I can trap the SIGTERM, I would like to understand why the script is receiving SIGTERM at all. What wrong am I doing here? I am running RHEL 5.8 and Apache HTTP server 2.4. Thanks, Pranav

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  • Unescpaing huge single-line string on Linux

    - by Lajos Nagy
    I ended up with a huge, single line string literal (don't ask me how) where everything is escaped (mostly), including new lines and double quotes. Problem is, I want the original string. The string is huge so I'm not even sure how to begin. Here's what I have: "This\n is \"nice\",\nain\'t it?" This is what I want: This is "nice", ain't it? Again, the problem is that other shell sensitive stuff is not escaped (like $, or !), and that the string is couple of megabytes.

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  • How to use FTP's APPEND command in a script?

    - by btelles
    Hi there, For some reason when I try to use "append" while inside an FTP script, the ftp client appears to hang. I've tried all sorts of different variations (for example, including the destination filee and not, using quotes and not), and all I ever get is a "No such file or directory" error (and I KNOW it's there) or it hangs on an 200 Request OK and never does anything. ftp> open ibm.some_server Connected to ibm.some_server 230 USER1 is logged on. Working directory is "USER1.". Remote system type is MVS. ftp> cd 'Z.TABS.' 250 "Z.TABS." is the working directory name prefix. ftp> append 'SAMASCPY' 'SAMASCPY': No such file or directory ftp> append SAMASCPY 200 Port request OK. Anyone know what could be going on?

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  • How to run a shell command and selectively ignore the status?

    - by Walter Nissen
    I've got a shell script that I would like to stop with an error on nonzero status most of the time, but in some cases I want to ignore it. For example: #!/bin/tcsh -vxef cp file/that/might/not/exist . #Want to ignore this status cp file/that/might/not/exist . ; echo "this doesn't work" cp file/that/must/exist . #Want to stop if this status is nonzero

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