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  • Using many mutex locks

    - by hanno
    I have a large tree structure on which several threads are working at the same time. Ideally, I would like to have an individual mutex lock for each cell. I looked at the definition of pthread_mutex_t in bits/pthreadtypes.h and it is fairly short, so the memory usage should not be an issue in my case. However, is there any performance penalty when using many (let's say a few thousand) different pthread_mutex_ts for only 8 threads?

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  • Why does my Perl TCP server script hang with many TCP connections?

    - by viraptor
    I've got a strange issue with a server accepting TCP connections. Even though there are normally some processes waiting, at some volume of connections it hangs. Long version: The server is written in Perl and binds a $srv socket with the reuse flag and listen == 5. Afterwards, it forks into 10 processes with a loop of $clt=$srv->accept(); do_processing($clt); $clt->shutdown(2); The client written in C is also very simple - it sends some lines, then receives all lines available and does a shutdown(sockfd, 2); There's nothing async going on and at the end both send and receive queues are empty (as reported by netstat). Connections last only ~20ms. All clients behave the same way, are the same implementation, etc. Now let's say I'm accepting X connections from client 1 and another X from client 2. Processes still report that they're idle all the time. If I add another X connections from client 3, suddenly the server processes start hanging just after accepting. The first blocking thing they do after accept(); is while (<$clt>) ... - but they don't get any data (on the first try already). Suddenly all 10 processes are in this state and do not stop waiting. On strace, the server processes seem to hang on read(), which makes sense. There are loads of connections in TIME_WAIT state belonging to that server (~100 when the problem starts to manifest), but this might be a red herring. What could be happening here?

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  • Interacts with dialog/whiptail on early boot rcX.d stage?

    - by nm
    Hi buddies, I'm developing on Ubuntu based, actually I got one script in-charged on GUI(console) setup. It runs before another scripts (rcX.d) start. Currently, I installed this script on rc2.d and start earlier than other ones. But when run on real machine, I can't input any keystroke on "dialog --inputbox" or whiptail through shell script. Additionally, It runs well on my Virtual Machine (Virtual Box and Vmware), that's so strange! So, does anybody give some help or point me any clues for overcome this ? Thanks

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  • Need a very simple bash-based webserver for logging XML in HTTP POST

    - by Syffys
    As in title, it's for testing purpose and I need it to be extremely light (1 line to 1 single light file). Here is a XML query sample: XML_QUERY=$(cat <<EOF <?xml version='1.0' encoding='UTF-8'?> <Test></Test> EOF ) curl -H "Content-type: text/xml; charset=utf-8" -H "Soapaction: \"\"" -k -d "${XML_QUERY}" http://localhost:8088 Here are some of the tracks I have found so far even if I wasnt able to adapt them to work as I expect: Netcat minimal webserver: Problem is that my nc does not have the -q option, so the connection is closing before delivering the XML content Netcat Only webserver: Same as above Python based: But does not handle POST Thanks in advance!

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  • What to do if exec() fails?

    - by Grigory
    Let's suppose we have a code doing something like this: int pipes[2]; pipe(pipes); pid_t p = fork(); if(0 == p) { dup2(pipes[1], STDOUT_FILENO); execv("/path/to/my/program", NULL); ... } else { //... parent process stuff } As you can see, it's creating a pipe, forking and using the pipe to read the child's output (I can't use popen here, because I also need the PID of the child process for other purposes). Question is, what should happen if in the above code, execv fails? Should I call exit() or abort()? As far as I know, those functions close the open file descriptors. Since fork-ed process inherits the parent's file descriptors, does it mean that the file descriptors used by the parent process will become unusable?

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  • fopen() fails to open stream: permission denied, yet permissions should be valid

    - by about blank
    So, I have this error: Warning: fopen(/path/to/test-in.txt) [function.fopen]: failed to open stream: Permission denied Performing ls -l in the directory where test-in.txt is produces the following output: -rw-r--r-- 1 $USER $USER 1921 Sep 6 20:09 test-in.txt -rw-r--r-- 1 $USER $USER 0 Sep 6 20:08 test-out.txt In order to get past this, I decided to perform the following: chgrp -R www-data /path/to/php/webroot And then did: chmod g+rw /path/to/php/webroot Yet, I still get this error when I run my php5 script to open the file. Why is this happening? I've tried this using LAMP as well as cherokee through CGI, so it can't be this. Is there a solution of some sort? Edit I'll also add that I'm just developing via localhost right now. Update - PHP fopen() line $fullpath = $this->fileRoot . $this->fileInData['fileName']; $file_ptr = fopen( $fullpath, 'r+' ); I should also mention I'd like to stick with Cherokee if possible. What's this deal about setting file permissions for Apache/Cherokee?

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  • Memory Management with returning char* function

    - by RageD
    Hello all, Today, without much thought, I wrote a simple function return to a char* based on a switch statement of given enum values. This, however, made me wonder how I could release that memory. What I did was something like this: char* func() { char* retval = new char; // Switch blah blah - will always return some value other than NULL since default: return retval; } I apologize if this is a naive question, but what is the best way to release the memory seeing as I cannot delete the memory after the return and, obviously, if I delete it before, I won't have a returned value. What I was thinking as a viable solution was something like this void func(char*& in) { // blah blah switch make it do something } int main() { char* val = new char; func(val); // Do whatever with func (normally func within a data structure with specific enum set so could run multiple times to change output) val = NULL; delete val; val = NULL; return 0; } Would anyone have anymore insight on this and/or explanation on which to use? Regards, Dennis M.

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  • How to get data from a incoming email and then copy data to some directory

    - by Zegnhabi
    First of all, I have some time reading this page and I find very interesting, the content also has many questions and are very entertaining. My question is about handling my incoming mail server, no matter if you use PHP, Perl, or Python. I do not care, what if I want is the result which should be as close to: I send an email to [email protected], this post will add a case such as photos, then when the mail reaches the server, the server takes to process mail and copy the attached files, in this case the photos to a folder / home / public_html / photos and then, if possible notify you if it was successful or not. In advance thank you very much. And I hope and can be done. ñ_ñ

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  • Using vim, how do you quickly refresh a web page you're working on?

    - by aLostMonkey
    I've been using VIM for a few weeks now while messing with various web languages and I'm really enjoying it. I find it cumbersome having to tab or click into my browser and refresh the page to see the effect of a code change. It's even more annoying as I'm using Virtual Box and I tend to be working from PDF files on the host system so I have limited window space. Do you gurus have any fancy ways of doing this? I was wondering if it's possible to split the VIM workspace and have links/lynx in a window of its own or something to that effect?

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  • Kernel dealing with the section headers in an ELF

    - by uki
    I recently read that the kernel and the dynamic loader mostly deal with the program header tables in an ELF file and that assemblers, compilers and linkers deal with the section header tables. The number of program header tables and section header tables are mentioned in the ELF header in fields named e_phnum and e_shnum respectively. e_phnum is two bytes in size, so if the number of program headers is 65535, we use a scheme known as extended numbering where, e_phnum is set to 0xffff and sh_link field of the zeroth section header table holds the actual count. My doubt is : If the count of program headers exceeds 65535, does that mean the kernel and/or the dynamic loader end up having to read the section table?

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  • What is the Effect of Declaring 'extern "C"' in the Header to a C++ Shared Library?

    - by Adam
    Based on this question I understand the purpose of the construct in linking C libraries with C++ code. Now suppose the following: I have a '.so' shared library compiled with a C++ compiler. The header has a 'typedef stuct' and a number of function declarations. If the header includes the extern "C" declaration... #ifdef __cplusplus extern "C" { #endif // typedef struct ...; // function decls #ifdef __cplusplus } #endif ... what is the effect? Specifically I'm wondering if there are any detrimental side effects of that declaration since the shared library is compiled as C++, not C. Is there any reason to have the extern "C" declaration in this case?

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  • how to make this "action-packed, random data" being echoed in a terminal?

    - by RiMMER
    OK, this isn't really a question to achieve anything practical, but still it is a serious question and I hope it will be taken seriously and mods won't punish me for this :) I'm sure majority of you have seen some good action movie, where CIA or FBI or hackers or any other "pc nerds" are "retrieving some information" and when they actually show their screens/monitors/desktops, there is a lot of random data being displayed and it's just so thrilling :D So, we're shooting a movie and I need to reconstruct such a scene. My OS is ubuntu 10.10. I think i've read somewhere on the internet once that shell can actually be recorded and then played back, but I'm not sure how it worked. If there's anyone who could come up with a solution, it would be so cool! Let's make this fun, shall we?

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  • Create Directory, 'cd' to it and download a file pipeline in Perl

    - by neversaint
    I have a file that looks like this: ftp://url1/files1.tar.gz dir1 ftp://url2/files2.txt dir2 .... many more... What I want to do are these steps: Create directory based on column 2 Unix 'cd' to that directory Download file with 'wget' based on column1 But how come this approach of mine doesn't work while(<>) { chomp; my ($url,$dir) = split(/\t/,$_); system("mkdir $dir"); system("cd $dir"); # Fail here system("wget $url"); # here too } What's the right way to do it?

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  • How can I determine if a file is read-only for my process on *nix?

    - by user109078
    Using the stat function, I can get the read/write permissions for: owner user other ...but this isn't what I want. I want to know the read/write permissions of a file for my process (i.e. the application I'm writing). The owner/user/other is only helpful if I know if my process is running as the owner/user/other of the file...so maybe that's the solution but I'm not sure of the steps to get there.

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  • Possible to view PHP code of a website?

    - by Camran
    Is it possible to somehow view another websites php files/codes? Or to rephrase the question, Can my php codes be viewed by anybody except for those who have access to the file? If so, how cant I best prevent this? Thanks Ps: Server OS is Ubuntu 9.10 and PHP version is 5+ (Apache2)

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  • boost::this_thread::disable_interruption usage confusion

    - by Evgenii
    boost/thread/pthread/shared_mutex.hpp contains this code: ... #include <boost/thread/detail/thread_interruption.hpp> ... class shared_mutex { ... void lock_shared() { boost::this_thread::disable_interruption do_not_disturb; boost::mutex::scoped_lock lk(state_change); while(state.exclusive || state.exclusive_waiting_blocked) { shared_cond.wait(lk); } ++state.shared_count; } ... }; but boost/thread/detail/thread_interruption.hpp does not contain implementation of disable_interruption, only the prototype. in boost_1_42_0/libs/thread/src/pthread we don't have the implementation too how does it work!???

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