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  • file_operations Question, how do i know if a process that opened a file for writing has decided to c

    - by djTeller
    Hi Kernel Gurus, I'm currently writing a simple "multicaster" module. Only one process can open a proc filesystem file for writing, and the rest can open it for reading. To do so i use the inode_operation .permission callback, I check the operation and when i detect someone open a file for writing I set a flag ON. i need a way to detect if a process that opened a file for writing has decided to close the file so i can set the flag OFF, so someone else can open for writing. Currently in case someone is open for writing i save the current-pid of that process and when the .close callback is called I check if that process is the one I saved earlier. Is there a better way to do that? Without saving the pid, perhaps checking the files that the current process has opened and it's permission... Thanks!

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  • Convert HTML to RTF (HTML2RTF converter)

    - by Luca Matteis
    I'm looking for a simple HTML2RTF converter that I can use on my website which is using a *nix like Operating System. I haven't found anything on the internet, and was hoping the SO community would help me. PS: I don't want to implement this from scratch, and it doesn't really matter what language it's in, as long as I can run it on a *nix like system. If you guys have already some personalized implementation, the language preferred would be PHP.

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  • ZeroMQ REQ/REP on ipc:// and concurrency

    - by Metiu
    I implemented a JSON-RPC server using a REQ/REP 0MQ ipc:// socket and I'm experiencing strange behavior which I suspect is due to the fact that the ipc:// underlying unix socket is not a real socket, but rather a single pipe. From the documentation, one has to enforce strict zmq_send()/zmq_recv() alternation, otherwise the out-of-order zmq_send() will return an error. However, I expected the enforcement to be per-client, not per-socket. Of course with a Unix socket there is just one pipeline from multiple clients to the server, so the server won't know who it is talking with. Two clients could zmq_send() simultaneously and the server would see this as an alternation violation. The sequence could be: ClientA: zmq_send() ClientB: zmq_send() : will it block until the other send/receive completes? will it return -1? (I suspect it will with ipc:// due to inherent low-level problems, but with TCP it could distinguish the two clients) ClientA: zmq_recv() ClientB: zmq_recv() so what about tcp:// sockets? Will it work concurrently? Should I use some other locking mechanism to work around this?

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  • overview/history of resident memory usage

    - by kapet
    I have a fairly complicated program (Python with SWIG'ed C++ code, long running server) that shows a constantly growing resident memory usage. I've been digging with the usual tools for the leak (valgrind, Pythons gc module, etc.) but to no avail so far. I'm a bit afraid that the actual problem is memory fragmentation within Python and/or libc managed memory. Anyway, my question is more specific right now: Is there a tool to visualize resident memory usage and ideally show how it develops over time? I think the raw data is in /proc/$PID/smaps but I was hoping there's some tool that shows me a nice graph of the amounts used by mmap'ed files vs. anonymous mmap'ed memory vs. heap over time so that it's easier to see (literally) what's changing. I couldn't find anything though. Does anybody know of a ready to use tool that graphs memory usage over space and time in an intuitive way?

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  • Howto Plot "Reverse" Cumulative Frequency Graph With ECDF

    - by neversaint
    I have no problem plotting the following cumulative frequency graph plot like this. library(Hmisc) pre.test <- rnorm(100,50,10) post.test <- rnorm(100,55,10) x <- c(pre.test, post.test) g <- c(rep('Pre',length(pre.test)),rep('Post',length(post.test))) Ecdf(x, group=g, what="f", xlab='Test Results', label.curves=list(keys=1:2)) But I want to show the graph in forms of the "reverse" cumulative frequency of values x ? (i.e. something equivalent to what="1-f"). Is there a way to do it? Other suggestions in R other than using Hmisc are also very much welcomed.

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  • waiting for 2 different events in a single thread

    - by João Portela
    component A (in C++) - is blocked waiting for alarm signals (not relevant) and IO signals (1 udp socket). has one handler for each of these. component B (java) - has to receive the same information the component A udp socket receives. periodicaly gives instructions that should be sent through component A udp socket. How to join both components? it is strongly desirable that: the changes to attach component B to component A are minimal (its not my code and it is not very pleasent to mess with). the time taken by the new operations (usually communicating with component B) interfere very little with the usual processing time of component A - this means that if the operations are going to take a "some" time I would rather use a thread or something to do them. note: since component A receives udp packets more frequently that it has component B instructions to forward, if necessary, it can only forward the instructions (when available) from the IO handler. my initial ideia was to develop a component C (in C++) that would sit inside the component A code (is this called an adapter?) that when instanciated starts the java process and makes the necessary connections (that not so little overhead in the initialization is not a problem). It would have 2 stacks, one for the data to give component B (lets call it Bstack) and for the data to give component A (lets call it Astack). It would sit on its thread (lets call it new-thread) waiting for data to be available in Bstack to send it over udp, and listen on the udp socket to put data on the Astack. This means that the changes to component A are only: when it receives a new UDP packet put it on the Bstack, and if there is something on the Astack sent it over its UDP socket (I decided for this because this socket would only be used in the main thread). One of the problems is that I don't know how to wait for both of these events at the same time using only one thread. so my questions are: Do I really need to use the main thread to send the data over component A socket or can I do it from the new-thread? (I think the answer is no, but I'm not sure about race conditions on sockets) how to I wait for both events? boost::condition_variable or something similar seems the solution in the case of the stack and boost::asio::io_service io_service.run() seems like the thing to use for the socket. Is there any other alternative solution for this problem that I'm not aware of? Thanks for reading this long text but I really wanted you to understand the problem.

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  • How can I get `find` to ignore .svn directories?

    - by John Kugelman
    I often use the find command to search through source code, delete files, whatever. Annoyingly, because Subversion stores duplicates of each file in its .svn/text-base/ directories my simple searches end up getting lots of duplicate results. For example, I want to recursively search for uint in multiple messages.h and messages.cpp files: # find -name 'messages.*' -exec grep -Iw uint {} + ./messages.cpp: Log::verbose << "Discarding out of date message: id " << uint(olderMessage.id) ./messages.cpp: Log::verbose << "Added to send queue: " << *message << ": id " << uint(preparedMessage->id) ./messages.cpp: Log::error << "Received message with invalid SHA-1 hash: id " << uint(incomingMessage.id) ./messages.cpp: Log::verbose << "Received " << *message << ": id " << uint(incomingMessage.id) ./messages.cpp: Log::verbose << "Sent message: id " << uint(preparedMessage->id) ./messages.cpp: Log::verbose << "Discarding unsent message: id " << uint(preparedMessage->id) ./messages.cpp: for (uint i = 0; i < 10 && !_stopThreads; ++i) { ./.svn/text-base/messages.cpp.svn-base: Log::verbose << "Discarding out of date message: id " << uint(olderMessage.id) ./.svn/text-base/messages.cpp.svn-base: Log::verbose << "Added to send queue: " << *message << ": id " << uint(preparedMessage->id) ./.svn/text-base/messages.cpp.svn-base: Log::error << "Received message with invalid SHA-1 hash: id " << uint(incomingMessage.id) ./.svn/text-base/messages.cpp.svn-base: Log::verbose << "Received " << *message << ": id " << uint(incomingMessage.id) ./.svn/text-base/messages.cpp.svn-base: Log::verbose << "Sent message: id " << uint(preparedMessage->id) ./.svn/text-base/messages.cpp.svn-base: Log::verbose << "Discarding unsent message: id " << uint(preparedMessage->id) ./.svn/text-base/messages.cpp.svn-base: for (uint i = 0; i < 10 && !_stopThreads; ++i) { ./virus/messages.cpp:void VsMessageProcessor::_progress(const string &fileName, uint scanCount) ./virus/messages.cpp:ProgressMessage::ProgressMessage(const string &fileName, uint scanCount) ./virus/messages.h: void _progress(const std::string &fileName, uint scanCount); ./virus/messages.h: ProgressMessage(const std::string &fileName, uint scanCount); ./virus/messages.h: uint _scanCount; ./virus/.svn/text-base/messages.cpp.svn-base:void VsMessageProcessor::_progress(const string &fileName, uint scanCount) ./virus/.svn/text-base/messages.cpp.svn-base:ProgressMessage::ProgressMessage(const string &fileName, uint scanCount) ./virus/.svn/text-base/messages.h.svn-base: void _progress(const std::string &fileName, uint scanCount); ./virus/.svn/text-base/messages.h.svn-base: ProgressMessage(const std::string &fileName, uint scanCount); ./virus/.svn/text-base/messages.h.svn-base: uint _scanCount; How can I tell find to ignore the .svn directories?

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  • compare time using date command

    - by Andrei
    Say I want a certain block of bash script execute only if it is between 8 am (8:00) and 5 pm (17:00), and do nothing otherwise. The script is running continuously So far I am using date command. How to use it compare it current time within the range? Thanks

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  • Use the output of a command as input of the next command

    - by r2b2
    so i call this php script from the command line : /usr/bin/php /var/www/bims/index.php "projects/output" and it's output is : file1 file2 file3 What I would like to do is get this output and feed to the "rm" command but i think im not doing it right : /usr/bin/php /var/www/bims/index.php "projects/output" | rm My goal is to delete whatever file names the php script outputs. What should be the proper way to do this? Thanks!

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  • Replacing a website on a Tomcat Server with a static HTML website

    - by Ashin Mandal
    I made a small static website for my client and now they want me to replace their present dynamic website with the static one. They have Ubuntu with SSH installed on the remote location. Their existing website is running on a Tomcat6 server and the site root is in "/var/lib/tomcat6/webapps/ROOT/". My website consists of just static HTML pages. How can I reconfigure/ replace the present website with the one I made? Should I just stop the server and replace the files in the site root with my files?

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  • Simple POSIX threads question

    - by Andy
    Hi, I have this POSIX thread: void subthread(void) { while(!quit_thread) { // do something ... // don't waste cpu cycles if(!quit_thread) usleep(500); } // free resources ... // tell main thread we're done quit_thread = FALSE; } Now I want to terminate subthread() from my main thread. I've tried the following: quit_thread = TRUE; // wait until subthread() has cleaned its resources while(quit_thread); But it does not work! The while() clause does never exit although my subthread clearly sets quit_thread to FALSE after having freed its resources! If I modify my shutdown code like this: quit_thread = TRUE; // wait until subthread() has cleaned its resources while(quit_thread) usleep(10); Then everything is working fine! Could someone explain to me why the first solution does not work and why the version with usleep(10) suddenly works? I know that this is not a pretty solution. I could use semaphores/signals for this but I'd like to learn something about multithreading, so I'd like to know why my first solution doesn't work. Thanks!

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  • Kernel error causing cpu to go into shutdown state

    - by EpsilonVector
    What kind of Kernel error can cause the cpu to go into a shut down state? I'm doing a homework assignment in OS, and we did changes in sched.c (adding a new scheduling policy, which involved ading another prio_array to the queue and switching between them when needed). Processes using this policy cause the cpu to enter a shut down state when they finish. Any suggestions where to look?

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  • sudo changes PATH - why?

    - by Michiel de Mare
    This is the PATH variable without sudo: $ echo 'echo $PATH' | sh /opt/local/ruby/bin:/usr/bin:/bin This is the PATH variable with sudo: $echo 'echo $PATH' | sudo sh /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/X11R6/bin As far as I can tell, sudo is supposed to leave PATH untouched. What's going on? How do I change this? (This is on Ubuntu 8.04). UPDATE: as far as I can see, none of the scripts started as root change PATH in any way. From man sudo: To prevent command spoofing, sudo checks ``.'' and ``'' (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Note, however, that the actual PATH environment variable is not modified and is passed unchanged to the program that sudo executes.

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  • Bash scripting - Iterating through "variable" variable names for a list of associative arrays

    - by user1550254
    I've got a variable list of associative arrays that I want to iterate through and retrieve their key/value pairs. I iterate through a single associative array by listing all its keys and getting the values, ie. for key in "${!queue1[@]}" do echo "key : $key" echo "value : ${queue1[$key]}" done The tricky part is that the names of the associative arrays are variable variables, e.g. given count = 5, the associative arrays would be named queue1, queue2, queue3, queue4, queue5. I'm trying to replace the sequence above based on a count, but so far every combination of parentheses and eval has not yielded much more then bad substitution errors. e.g below: for count in {1,2,3,4,5} do for key in "${!queue${count}[@]}" do echo "key : $key" echo "value : ${queue${count}[$key]}" done done Help would be very much appreciated!

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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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  • Easily measure elapsed time

    - by hap497
    I am trying to use time() to measure various points of my program. What I don't understand is why the values in the before and after are the same? I understand this is not the best way to profile my program, I just want to see how long something take. printf("**MyProgram::before time= %ld\n", time(NULL)); doSomthing(); doSomthingLong(); printf("**MyProgram::after time= %ld\n", time(NULL)); I have tried: struct timeval diff, startTV, endTV; gettimeofday(&startTV, NULL); doSomething(); doSomethingLong(); gettimeofday(&endTV, NULL); timersub(&endTV, &startTV, &diff); printf("**time taken = %ld %ld\n", diff.tv_sec, diff.tv_usec); How do I read a result of **time taken = 0 26339? Does that mean 26,339 nanoseconds = 26.3 msec? What about **time taken = 4 45025, does that mean 4 seconds and 25 msec?

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  • rsyncing - ignoring checksums

    - by paulj3000
    Trying to copy a bunch of data over and time, unfortunately, is of the essence. I'd like to do an rsync of all the data in one direction, pretty much rsync just clobbers what's over on the destination server. Is there a way to do an rsync and just say, "overwrite all files" Is there a better way of doing this? We're talking 500GB of data that only has to go in one direction.

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  • Bash PATH: How long is too long?

    - by ajwood
    Hi, I'm currently designing a software quarantine pattern to use on Ubuntu. I'm not sure how standard "quarantine" is in this context, so here is what I hope to accomplish... Inside a particular quarantine is all of the stuff one needs to run an application (bin, share, lib, etc.). Ideally, the quarantine has no leaks, which means it's not relying on any code outside of itself on the system. A quarantine can be defined as a set of executables (and some environment settings needed to make them run). I think it will be beneficial to separate the built packages enough such that upgrading to a newer version of the quarantine won't require rebuilding the whole thing. I'll be able to update just a few packages, and then the new quarantine can use some of old parts and some of the new parts. One issue I'm wondering about is the environment variables I'll be setting up to use a particular quarantines. Is there a hard limit on how big PATH can be? (either in number of characters, or in the number of directories it contains) Might a path be so long that it affects performance? Thanks very much, Andrew p.s. Any other wisdom that might help my design would be greatly appreciated :)

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  • Question about using awk to print all columns great then nth

    - by Andy
    right now I have this line, and it worked until I had whitespace in the second field. svn status | grep '\!' | gawk '{print $2;}' > removedProjs is there a way to have awk print everything in $2 or greater? ($3, $4.. until we don't have anymore columns?) I suppose I should add that I'm doing this in a windows environment with cygwin.

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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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