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  • How to R/W hard disk when CPU is in Protect Mode?

    - by smwikipedia
    I am doing some OS experiment. Until now, all my code utilized the real mode BIOS interrupt to manipulate hard disk and floppy. But once my code enabled the Protect Mode of the CPU, all the real mode BIOS interrupt service routine won't be available. How could I R/W the hard disk and floppy? I have a feeling that I need to do some hardware drivers now. Am I right? Is this why an OS is so difficult to develop? I know that hardwares are all controlled by reading from and writing to certain control or data registers. For example, I know that the Command Block Registers of hard disk range from 0x1F0 to 0x1F7. But I am wondering whether the register addresses of so many different hardwares are the same on the PC platform? Or do I have to detect that before using them? How to detect them?? For any responses I present my deep appreciation.

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  • BASH: Checking for environment variables

    - by Hamza
    Hi folks, I am trying to check the value of an environment variable and depending on the value do certain things and it works fine as long as the variable is set. When it isn't though I get a whole bunch of errors (as BASH is trying to compare the string I specify with an undefined variable, I guess) I tried implementing an extra check to prevent it happening but no luck. The block of code I am using is: #!/bin/bash if [ -n $TESTVAR ] then if [ $TESTVAR == "x" ] then echo "foo" exit elif [ $TESTVAR == "y" ] then echo "bar" exit else echo "baz" exit fi else echo -e "TESTVAR not set\n" fi And this the output: $ export TESTVAR=x $ ./testenv.sh foo $ export TESTVAR=y $ ./testenv.sh bar $ export TESTVAR=q $ ./testenv.sh baz $ unset TESTVAR $ ./testenv.sh ./testenv.sh: line 5: [: ==: unary operator expected ./testenv.sh: line 9: [: ==: unary operator expected baz My question is, shouldn't 'unset TESTVAR' nullify it? It doesn't seem to be the case... Thanks.

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  • How do I find the current virtual terminal

    - by camh
    I am working around a problem in Ubuntu 10.04 where after resume, the mouse cursor disappears. This can be "fixed" by running chvt 1; chvt 7 in a script in /etc/pm/sleep.d, such that those commands run on thaw and resume. However, the X console is not always vt #7, so chvt 7 is wrong in those cases. What I would like to do is find out the current vt in the fix-up script and make sure I change back to that vt. How can I find the current vt? (tty(1) just reports "not a tty")

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  • problem in reading output of dd command using pipe

    - by Ummar
    I am developing an application, in which I want to redirect the output (progress information) of dd command to my C++ program, but it is not actually getting the output, here is the code FILE * progressInfo = popen("gzip -dc backup/backup.img.gz | pv -ptrbe -i 2 -s 2339876653 | dd of=/dev/sdb","r"); if(!progressInfo) { return -1; } char buf[1024]; while(fgets(buff, sizeof(buff),progressInfo)!=NULL) { std::cout << buff << endl; } but the problem is the progress information is not received in buff, and the output is continuously printed on terminal, and above program halts on while(fgets(buff, sizeof(buff),progressInfo)!=NULL), and as soon as the dd operation is completed, the very next line to loop block is executed. if anyone has any idea why the output is not returned to buff, and its continuously retuned on terminal?

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  • How to implement/debug a sensor driver in ANDROID

    - by CVS-2600Hertz-wordpress-com
    Does anyone know of a walk-through or any examples of any code to setup sensors in android. I have the drivers available to me. Also i have implemented the sensors library as instructed in the Android-Reference along the sensors.h template. I am still unable to get any response at the apps level. How do i trace this issue? what might be the problem? Thanks in advance UPDATE: Jorgesys's link below points to a great APP to test if the sensor drivers are functioning properly or not. Not that i know they are not functioning, Any ideas of on where to dig??...

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  • Why I'm not getting "Multiple definition" error from the g++?

    - by ban
    I tried to link my executable program with 2 static libraries using g++. The 2 static libraries have the same function name. I'm expecting a "multiple definition" linking error from the linker, but I did not received. Can anyone help to explain why is this so? staticLibA.h #ifndef _STATIC_LIBA_HEADER #define _STATIC_LIBA_HEADER int hello(void); #endif staticLibA.cpp #include "staticLibA.h" int hello(void) { printf("\nI'm in staticLibA\n"); return 0; } output: g++ -c -Wall -fPIC -m32 -o staticLibA.o staticLibA.cpp ar -cvq ../libstaticLibA.a staticLibA.o a - staticLibA.o staticLibB.h #ifndef _STATIC_LIBB_HEADER #define _STATIC_LIBB_HEADER int hello(void); #endif staticLibB.cpp #include "staticLibB.h" int hello(void) { printf("\nI'm in staticLibB\n"); return 0; } output: g++ -c -Wall -fPIC -m32 -o staticLibB.o staticLibB.cpp ar -cvq ../libstaticLibB.a staticLibB.o a - staticLibB.o main.cpp extern int hello(void); int main(void) { hello(); return 0; } output: g++ -c -o main.o main.cpp g++ -o multipleLibsTest main.o -L. -lstaticLibA -lstaticLibB -lstaticLibC -ldl -lpthread -lrt

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  • Tee a Pipe Asynchronously

    - by User1
    I would like to write the same information to two pipes, but I don't want to wait for the first pipe to read. Here's an example mkfifo one mkfifo two echo hi | tee one two & cat one & cat two & cat one does not start reading until cat two is run. Is there a way to make cat one run without waiting?

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  • gem install giving error that I can't change permissions.. chown and chmod not working

    - by user2321289
    so I am trying to install hmac gem install ruby-hmac -v 0.4.0 I am getting the following error message: You don't have write permissions into the /opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1 directory So the output from ls -l is as such: ubuntu@ip-10-38-121-211:~/workspace/cf-release$ sudo ls -l /opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/ I perform a chown on this directory: sudo chown -R ubuntu:ubuntu /opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/ Try to install the gem: ubuntu@ip-10-38-121-211:~/workspace/cf-release$ sudo chown -v ubuntu:ubuntu /opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/ ownership of `/opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/' retained as ubuntu:ubuntu I do another ls -l on the directory: ubuntu@ip-10-38-121-211:~/workspace/cf-release$ ls -l /opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/ total 4 d--------- 8 ubuntu ubuntu 4096 Nov 1 20:43 1.9.1 Doing a chmod 777 to make the directory writeable: ubuntu@ip-10-38-121-211:~/workspace/cf-release$ sudo chmod -v 777 /opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/ mode of `/opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/' retained as 0777 (rwxrwxrwx) ubuntu@ip-10-38-121-211:~/workspace/cf-release$ ls -l /opt/rbenv/versions/1.9.3-p448/lib/ruby/gems/ total 4 d--------- 8 ubuntu ubuntu 4096 Nov 1 20:43 1.9.1 Any idea as to why this would be acting up like this? I am at a loss here.. any help appreciated

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  • inode_operations , warning: initialization from incompatible pointer type

    - by djTeller
    Hi everyone, I'm trying to compile a simple Kernel program that read and write from a proc file. I'm trying to set permission to that file by overriding the permission fp in inode_operations struct (.permission) static int module_permission(struct inode *inode, int op, struct nameidata *foo) { . . . } static struct inode_operations Inode_Ops_4_Our_Proc_File = { .permission = module_permission, /* check for permissions */ }; Our_Proc_File->proc_iops = &Inode_Ops_4_Our_Proc_File; For some reason, when I compile this i get - warning: initialization from incompatible pointer type on the following line: .permission = module_permission, /* check for permissions */ Any idea how to solve this? Thanks!

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  • selecting ppp of multiple interfaces

    - by Neeraj
    Hi everyone, I am currently having a hard time on getting the mobile broadband connection running on ubuntu 10.04(lucid lynx). I am using a USB modem and used wvdial to connect to the web It went like: Sending ATZ ... OK sending some more flags OK modem initialized connecting Local IP x.x.x.x Remote IP y.y.y.y Primary DNS z.z.z.z Secondary DNS a.a.a.a (Some more output) I tested this with invalid username to make sure it is really connected and i think it was connected as connection failed with invalid usernames. Now when I do a remote ping say 8.8.8.8 (Google DNS servers), the ping says unreachable I think this might be because the system may be using the ethernet to send packets which was indeed disconnected. So can anyone help me out with this. How can I select ppp as the interface to send packets or is there some other problem. A command line solution will be appreciated as my network manager applet doesnt works correctly. Any help is much much appreciated. -- thx

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  • Parsing line with delimiter in Python

    - by neversaint
    I have lines of data which I want to parse. The data looks like this: a score=216 expect=1.05e-06 a score=180 expect=0.0394 What I want to do is to have a subroutine that parse them and return 2 values (score and expect) for each line. However this function of mine doesn't seem to work: def scoreEvalFromMaf(mafLines): for word in mafLines[0]: if word.startswith("score="): theScore = word.split('=')[1] theEval = word.split('=')[2] return [theScore, theEval] raise Exception("encountered an alignment without a score") Please advice what's the right way to do it?

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  • How can I quickly sum all numbers in a file?

    - by Mark Roberts
    I have a file which contains several thousand numbers, each on it's own line: 34 42 11 6 2 99 ... I'm looking to write a script which will print the sum of all numbers in the file. I've got a solution, but it's not very efficient. (It takes several minutes to run.) I'm looking for a more efficient solution. Any suggestions?

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  • filter log file by defining regexes

    - by fmpdmb
    I have some HUGE log files (50Mb; ~500K lines) I need to start filtering some of the crap out of. The log files are being produced using log4j and have the basic pattern of: [log-level] date-time class etc, etc log-message I'm looking for a way that I can identify a regex start and regex end (or something similar) that will filter out the matching entries from the file so I can more easily wade through these massive files. I'm sure I could write a java program to accomplish this task, but I thought I'd ask the community before going down that path. Thanks in advance.

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  • How to Implement Web Based Find File Database Via Text Search

    - by neversaint
    I have series of files like this: foo1.txt.gz foo2.txt.gz bar1.txt.gz ..etc.. and a tabular format file that describe those files: foo1 - Explain foo1 foo2 - Explain foo2 bar1 - Explain bar1 ..etc.. What I want to do is to have a website with a simple search bar and allow people to type foo1 or just foo and finally return the gzipped file(s) and the related explanation of the file(s). What's the best way to implement this and what kind of tools should I use. Sorry I am totally new in this area.

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  • How to maipulate the shell output in php

    - by Mirage
    I am trying to write php script which does some shell functions like reporting. So i am starting with diskusage report I want in following format drive path ------------total-size --------free-space Nothing else My script is $output = shell_exec('df -h -T'); echo "<pre>$output</pre>"; and its ouput is like below Filesystem Type Size Used Avail Use% Mounted on /dev/sda6 ext3 92G 6.6G 81G 8% / none devtmpfs 3.9G 216K 3.9G 1% /dev none tmpfs 4.0G 176K 4.0G 1% /dev/shm none tmpfs 4.0G 1.1M 4.0G 1% /var/run none tmpfs 4.0G 0 4.0G 0% /var/lock none tmpfs 4.0G 0 4.0G 0% /lib/init/rw /dev/sdb1 ext3 459G 232G 204G 54% /media/Server /dev/sdb2 fuseblk 466G 254G 212G 55% /media/BACKUPS /dev/sda5 fuseblk 738G 243G 495G 33% /media/virtual_machines How can i convert that ouput into my forn\matted output

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  • Getting error that the database is locked when refreshing the page

    - by acidzombie24
    The title is a joke. However it is serious as far as my app is concerned. I am running apache with mod mono and my asp.net app is using mono sqlite as its db. When i refresh the page twice i get the DB is locked error. The folder it is in is chmod 777. The webapp is creating sqlite.db and sqlite.db-journal but it doesnt seem to be able to delete the journal. i'm confused. What permissions do i need to set these? i tried precreating the files using 777 and had no luck.

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  • Dynamic loaded libraries and shared global symbols

    - by phlipsy
    Since I observed some strange behavior of global variables in my dynamically loaded libraries, I wrote the following test. At first we need a statically linked library: The header test.hpp #ifndef __BASE_HPP #define __BASE_HPP #include <iostream> class test { private: int value; public: test(int value) : value(value) { std::cout << "test::test(int) : value = " << value << std::endl; } ~test() { std::cout << "test::~test() : value = " << value << std::endl; } int get_value() const { return value; } void set_value(int new_value) { value = new_value; } }; extern test global_test; #endif // __BASE_HPP and the source test.cpp #include "base.hpp" test global_test = test(1); Then I wrote a dynamically loaded library: library.cpp #include "base.hpp" extern "C" { test* get_global_test() { return &global_test; } } and a client program loading this library: client.cpp #include <iostream> #include <dlfcn.h> #include "base.hpp" typedef test* get_global_test_t(); int main() { global_test.set_value(2); // global_test from libbase.a std::cout << "client: " << global_test.get_value() << std::endl; void* handle = dlopen("./liblibrary.so", RTLD_LAZY); if (handle == NULL) { std::cout << dlerror() << std::endl; return 1; } get_global_test_t* get_global_test = NULL; void* func = dlsym(handle, "get_global_test"); if (func == NULL) { std::cout << dlerror() << std::endl; return 1; } else get_global_test = reinterpret_cast<get_global_test_t*>(func); test* t = get_global_test(); // global_test from liblibrary.so std::cout << "liblibrary.so: " << t->get_value() << std::endl; std::cout << "client: " << global_test.get_value() << std::endl; dlclose(handle); return 0; } Now I compile the statically loaded library with g++ -Wall -g -c base.cpp ar rcs libbase.a base.o the dynamically loaded library g++ -Wall -g -fPIC -shared library.cpp libbase.a -o liblibrary.so and the client g++ -Wall -g -ldl client.cpp libbase.a -o client Now I observe: The client and the dynamically loaded library possess a different version of the variable global_test. But in my project I'm using cmake. The build script looks like this: CMAKE_MINIMUM_REQUIRED(VERSION 2.6) PROJECT(globaltest) ADD_LIBRARY(base STATIC base.cpp) ADD_LIBRARY(library MODULE library.cpp) TARGET_LINK_LIBRARIES(library base) ADD_EXECUTABLE(client client.cpp) TARGET_LINK_LIBRARIES(client base dl) analyzing the created makefiles I found that cmake builds the client with g++ -Wall -g -ldl -rdynamic client.cpp libbase.a -o client This ends up in a slightly different but fatal behavior: The global_test of the client and the dynamically loaded library are the same but will be destroyed two times at the end of the program. Am I using cmake in a wrong way? Is it possible that the client and the dynamically loaded library use the same global_test but without this double destruction problem?

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  • Grep in XML file

    - by nishant
    I have to find some patters from a XML file, but i am unable to do it. <field> <uniqueid>account </uniqueod> <tableid>afs</tableid> </field> <field> <uniqueid>address</uniqueod> <tableid>afs</tableid> </field> what i have to do is to search the entries between these two fields and redirect them to a file.txt.and output should be such that uniqueid tableid uniqueid tableid i.e. for each uniqueid tableid should be printed along with it. The entries can be different or same. Guys help me out...

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  • Is there a way to find a specific file and then change into the directory containing it in one go?

    - by bergyman
    I'm looking for a way to find what I know will be a unique file, and then change into the directory containing that file. Something along the lines of: find . -name 'Subscription.java' | xargs cd Or: find . -name 'Subscription.java' -exec cd {} \; I know this won't work because it's both trying to cd supplying the entire absolute path, which contains the file, and also because xargs can't do any built in shell commands...but you get the point of what I want to accomplish.

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  • are runtime linking library globals shared among plugins loaded with dlopen?

    - by conejoroy
    I've a C++ program that links at runtime with, lets say, mylib.so. then, the same program uses dlopen()/dlsym() to load a function from myplugin.so, dynamic library that in turn has dependencies to mylib.so. My question is: will the program AND the function in the plugin access the same globals defined in mydlib.so in the same memory area reserved for the program, or each will be assigned different, unrelated copies in its own memory space? if the latter is the default behaviour, is it possible to change that? Thanks in advance =)!

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