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  • How to store and echo multiple lines elegantly in bash?

    - by EmpireJones
    I'm trying to capture a block of text into a variable, with newlines maintained, then echo it. However, the newlines don't seemed to be maintained when I am either capturing the text or displaying it. Any ideas regarding how I can accomplish this? Example: #!/bin/bash read -d '' my_var <<"BLOCK" this is a test BLOCK echo $my_var Output: this is a test Desired output: this is a test

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  • writing to an ioport resulting in segfaults...

    - by Sniperchild
    I'm writing for an atmel at91sam9260 arm 9 cored single board computer [glomation gesbc9260] Using request_mem_region(0xFFFFFC00,0x100,"name"); //port range runs from fc00 to fcff that works fine and shows up in /proc/iomem then i try to write to the last bit of the port at fc20 with writel(0x1, 0xFFFFFC20); and i segfault...specifically "unable to handle kernel paging request at virtual address fffffc20. I'm of the mind that i'm not allocating the right memory space... any helpful insight would be great...

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  • debugfs_create_file doesn't create file

    - by bala1486
    Hello, I am trying to create a debugfs file using the debugfs_create_file(...). I have written a sample code for this. static int __init mmapexample_module_init(void) { file1 = debugfs_create_file("mmap_example", 0644, NULL, NULL, &my_fops)\ ; printk(KERN_ALERT "Hello, World\n"); if(file1==NULL) { printk(KERN_ALERT "Error occured\n"); } if(file1==-ENODEV) { printk(KERN_ALERT "ENODEV occured\n"); } return 0; } When i ran insmod i could get the Hello, World message but no the error message. So i think the debugfs_create_file worked fine. However i couldn't find any file in /sys/kernel/debug. The folder is there but it is empty. Can anyone help me with this? Thank you... Thanks, Bala

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  • How do you return stolen packets back to Netfilter

    - by meg18019
    Let's say I have intercepted a packet from Netfilter and subsequently returned NF_STOLEN. At some point I want to re-inject that packet back to, in this case, the TCP stream it came from. I want to do this from Kernel space. So far I have been unable to find a way to do this. Thanks for the help.

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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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  • 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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  • 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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  • SOLVED - UBIFS partition mounting at startup [closed]

    - by Bartlomiej Grzeskowiak
    [SOLVED] - add ubi.mtd=volume_name to bootargs in uboot I want to mount UBIFS partition via /etc/fstab at startup. I created UBIFS and Volume: # ubiformat /dev/mtdX # ubiattach -p /dev/mtdX # ubimkvol /dev/ubi0 -N volume_name -s 64MiB # ubiupdatevol /dev/ubi0_0 /path/to/ubifs.img # mount -t ubifs ubi0:volume_name /mount/point but after reboot this line in etc/fstab doesn't work: ubi0:volume_name /mnt/user ubifs defaults 0 0 There is no fs mounted in /mnt/user. Also when I try to call mount -a: mount: mounting ubi0:volume_name on /mnt/user failed: No such device There are no ubi0,ubi0_0 in /dev. I also don't see any UBI calls in dmesg like here: UBIFS boot error

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  • ios::nocreate error while compiling a C++ code

    - by Mohit Nanda
    While, compiling a package, written in C++ on RHEL 5.0. I am getting the following error. error: nocreate is not a member of std::ios The source-code corresponds to: ifstream tempStr(argv[4],ios::in|ios::nocreate); I have tried #g++ -O -Wno-deprecated <file.cpp> -o <file> as well as: #g++ -O -o <file> Please suggest a solution.

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  • Get active window title in X

    - by dutt
    I'm trying to get the title of the active window. The application is a background task so if the user has Eclipse open the function returns "Eclipse - blabla", so it's not getting the window title of my own window. I'm developing this in Python 2.6 using PyQt4. My current solution, borrowed and slightly modified from an old answer here at SO, looks like this: def get_active_window_title(): title = '' root_check = '' root = Popen(['xprop', '-root'], stdout=PIPE) if root.stdout != root_check: root_check = root.stdout for i in root.stdout: if '_NET_ACTIVE_WINDOW(WINDOW):' in i: id_ = i.split()[4] id_w = Popen(['xprop', '-id', id_], stdout=PIPE) for j in id_w.stdout: if 'WM_ICON_NAME(STRING)' in j: if title != j.split()[2]: return j.split("= ")[1].strip(' \n\"') It works for most windows, but not all. For example it can't find my kopete chat windows, or the name of the application i'm currently developing. My next try looks like this: def get_active_window_title(self): screen = wnck.screen_get_default() if screen == None: return "Could not get screen" window = screen.get_active_window() if window == None: return "Could not get window" title = window.get_name() return title; But for some reason window is always None. Does somebody have a better way of getting the current window title, or how to modify one of my ways, that works for all windows? Edit: In case anybody is wondering this is the way I found that seems to work for all windows. def get_active_window_title(self): root_check = '' root = Popen(['xprop', '-root'], stdout=PIPE) if root.stdout != root_check: root_check = root.stdout for i in root.stdout: if '_NET_ACTIVE_WINDOW(WINDOW):' in i: id_ = i.split()[4] id_w = Popen(['xprop', '-id', id_], stdout=PIPE) id_w.wait() buff = [] for j in id_w.stdout: buff.append(j) for line in buff: match = re.match("WM_NAME\((?P<type>.+)\) = (?P<name>.+)", line) if match != None: type = match.group("type") if type == "STRING" or type == "COMPOUND_TEXT": return match.group("name") return "Active window not found"

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  • objdump -S - source code listing

    - by anon
    How does objdump manage to display source code? Is there a reference to the source file in the binary? I tried running strings on the binary and couldn't find any reference to the source file listed... Thanks.

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  • Microbenchmark showing process-switching faster than thread-switching; what's wrong?

    - by Yang
    I have two simple microbenchmarks trying to measure thread- and process-switching overheads, but the process-switching overhead. The code is living here, and r1667 is pasted below: https://assorted.svn.sourceforge.net/svnroot/assorted/sandbox/trunk/src/c/process_switch_bench.c // on zs, ~2.1-2.4us/switch #include <stdlib.h> #include <fcntl.h> #include <stdint.h> #include <stdio.h> #include <semaphore.h> #include <unistd.h> #include <sys/wait.h> #include <sys/types.h> #include <sys/time.h> #include <pthread.h> uint32_t COUNTER; pthread_mutex_t LOCK; pthread_mutex_t START; sem_t *s0, *s1, *s2; void * threads ( void * unused ) { // Wait till we may fire away sem_wait(s2); for (;;) { pthread_mutex_lock(&LOCK); pthread_mutex_unlock(&LOCK); COUNTER++; sem_post(s0); sem_wait(s1); } return 0; } int64_t timeInMS () { struct timeval t; gettimeofday(&t, NULL); return ( (int64_t)t.tv_sec * 1000 + (int64_t)t.tv_usec / 1000 ); } int main ( int argc, char ** argv ) { int64_t start; pthread_t t1; pthread_mutex_init(&LOCK, NULL); COUNTER = 0; s0 = sem_open("/s0", O_CREAT, 0022, 0); if (s0 == 0) { perror("sem_open"); exit(1); } s1 = sem_open("/s1", O_CREAT, 0022, 0); if (s1 == 0) { perror("sem_open"); exit(1); } s2 = sem_open("/s2", O_CREAT, 0022, 0); if (s2 == 0) { perror("sem_open"); exit(1); } int x, y, z; sem_getvalue(s0, &x); sem_getvalue(s1, &y); sem_getvalue(s2, &z); printf("%d %d %d\n", x, y, z); pid_t pid = fork(); if (pid) { pthread_create(&t1, NULL, threads, NULL); pthread_detach(t1); // Get start time and fire away start = timeInMS(); sem_post(s2); sem_post(s2); // Wait for about a second sleep(1); // Stop thread pthread_mutex_lock(&LOCK); // Find out how much time has really passed. sleep won't guarantee me that // I sleep exactly one second, I might sleep longer since even after being // woken up, it can take some time before I gain back CPU time. Further // some more time might have passed before I obtained the lock! int64_t time = timeInMS() - start; // Correct the number of thread switches accordingly COUNTER = (uint32_t)(((uint64_t)COUNTER * 2 * 1000) / time); printf("Number of process switches in about one second was %u\n", COUNTER); printf("roughly %f microseconds per switch\n", 1000000.0 / COUNTER); // clean up kill(pid, 9); wait(0); sem_close(s0); sem_close(s1); sem_unlink("/s0"); sem_unlink("/s1"); sem_unlink("/s2"); } else { if (1) { sem_t *t = s0; s0 = s1; s1 = t; } threads(0); // never return } return 0; } https://assorted.svn.sourceforge.net/svnroot/assorted/sandbox/trunk/src/c/thread_switch_bench.c // From <http://stackoverflow.com/questions/304752/how-to-estimate-the-thread-context-switching-overhead> // on zs, ~4-5us/switch; tried making COUNTER updated only by one thread, but no difference #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <pthread.h> #include <unistd.h> #include <sys/time.h> uint32_t COUNTER; pthread_mutex_t LOCK; pthread_mutex_t START; pthread_cond_t CONDITION; void * threads ( void * unused ) { // Wait till we may fire away pthread_mutex_lock(&START); pthread_mutex_unlock(&START); int first=1; pthread_mutex_lock(&LOCK); // If I'm not the first thread, the other thread is already waiting on // the condition, thus Ihave to wake it up first, otherwise we'll deadlock if (COUNTER > 0) { pthread_cond_signal(&CONDITION); first=0; } for (;;) { if (first) COUNTER++; pthread_cond_wait(&CONDITION, &LOCK); // Always wake up the other thread before processing. The other // thread will not be able to do anything as long as I don't go // back to sleep first. pthread_cond_signal(&CONDITION); } pthread_mutex_unlock(&LOCK); return 0; } int64_t timeInMS () { struct timeval t; gettimeofday(&t, NULL); return ( (int64_t)t.tv_sec * 1000 + (int64_t)t.tv_usec / 1000 ); } int main ( int argc, char ** argv ) { int64_t start; pthread_t t1; pthread_t t2; pthread_mutex_init(&LOCK, NULL); pthread_mutex_init(&START, NULL); pthread_cond_init(&CONDITION, NULL); pthread_mutex_lock(&START); COUNTER = 0; pthread_create(&t1, NULL, threads, NULL); pthread_create(&t2, NULL, threads, NULL); pthread_detach(t1); pthread_detach(t2); // Get start time and fire away start = timeInMS(); pthread_mutex_unlock(&START); // Wait for about a second sleep(1); // Stop both threads pthread_mutex_lock(&LOCK); // Find out how much time has really passed. sleep won't guarantee me that // I sleep exactly one second, I might sleep longer since even after being // woken up, it can take some time before I gain back CPU time. Further // some more time might have passed before I obtained the lock! int64_t time = timeInMS() - start; // Correct the number of thread switches accordingly COUNTER = (uint32_t)(((uint64_t)COUNTER * 2 * 1000) / time); printf("Number of thread switches in about one second was %u\n", COUNTER); printf("roughly %f microseconds per switch\n", 1000000.0 / COUNTER); return 0; }

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  • How to create a bash function with variable parameters/arguments to grep several keywords/tags

    - by CornSmith
    I'm using the :!grep "tag1" filename | grep "tag2" filename | grep -n "tag3 or more" filename command in vim to search for my code snippets based on their tags (a simple comment at the top of a snippet) in one big file. I use snippets to remember tricky things. This is painful to write out each time. I'd like to make an alias, or function to do something like this: :!greptag tag1 tag2 ... tag39 And it should search the current doc and return the lines with all the tags on them. Vim is set to interactive shell mode so that it can parse my bashrc for aliases/functions. set shellcmdflag=-ic How can I construct a function that allows for variable arguments like this in bash?

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  • ldd output showing shared object file whose function is not called

    - by iamrohitbanga
    I ran ldd command on an executable created by Open MPI. It shows a reference to libpthread.so Using LD_PRELOAD variable I created my own implementation of pthread_create, but from the it output it seems that MPI implementation is not calling pthread_create as I had expected. Why does ldd show pthread so file in output if it is not being used? does Open MPI not use a separate MPI thread for every node to implement the functionality?

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  • How to install the program depending on libstdc++ library

    - by Alex Farber
    My program is written in C++, using GCC on Ubuntu 9.10 64 bit. If depends on /usr/lib64/libstdc++.so.6 which actually points to /usr/lib64/libstdc++.so.6.0.13. Now I copy this program to virgin Ubuntu 7.04 system and try to run it. It doesn't run, as expected. Then I add to the program directory the following files: libstdc++.so.6.0.13 libstdc++.so.6 (links to libstdc++.so.6.0.13) and execute command: LD_LIBRARY_PATH=. ./myprogram Now everything is OK. The question: how can I write installation script for such program? myprogram file itself should be placed to /usr/local/bin. What can I do with dependencies? For example, on destination computer, /usr/lib64/libstdc++.so.6 link points to /usr/lib64/libstdc++.so.6.0.8. What can I do with this? Note: the program is closed-source, I cannot provide source code and makefile.

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  • pthreads recursively calling system command and segfault appears

    - by jess
    I have a code base where i am creating 8 threads and each thread just calls system command to display date in a continuous cycle, as shown below: void * system_thread(void *arg) { int cpu = (int)arg; printf("thread : start %d\n", cpu); for (;;) { // date ã³ãã³ãã®å®è¡ if (mode == 0) { system("date"); } else { f_hfp_nlc_Fsystem("date"); } } sleep(timerval); return NULL; } This application segfaults after running for 2-3 seconds, due to following 2 reasons: 1. read access, where the address is out of VM area 2. write acces, where it does not of write permission and its trying to modify some structure.

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  • what is the relation between SIGTSTP and SIGCHLD

    - by Rawhi
    I have tow handlers for each one of them (SIGTSTP, SIGCHLD), the thing is that when I pause a process using SIGTSTP the handler function of SIGCHLD run too. what should I do to prevent this . void ExeExternal(char *args[MAX_ARG], char* cmdString, LIST_ELEMENT** pList, int *Susp_Bg_Pid, int *susp) { int pID, status, w; switch (pID = fork()) { case -1: perror("smash error: >"); break; case 0: // Child Process setpgrp(); execv(args[0], args); execvp(args[0], args); perror("error"); exit(EXIT_FAILURE); break; default: if (cmdString[strlen(cmdString) - 1] != '&') { *Susp_Bg_Pid = pID; *susp = 1; while(*susp); } else { InsertElem(pList, args[0], getpid(), pID, 0); } break; } } signal handlers : void signalHandler(int signal) { int pid, cstatus; if (signal == SIGCHLD) { susp = 0; pid = waitpid(-1, &cstatus, WNOHANG); printf("[[child %d terminated]]\n", pid); DelPID(&JobsList, pid); } } void ctrlZsignal(int signal){ kill(Susp_Bg_Pid, SIGTSTP); susp = 0; printf("\nchild %d suspended\n", Susp_Bg_Pid); } Susp_Bg_Pid used to save the paused process id. susp indicates the state of the "smash" the parent process if it is suspended or not .

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  • Fade unfocused GNU Emacs frame (X window)

    - by Mischa Arefiev
    Is it possible to make GNU Emacs 24 dim unfocused windows a bit? For example, I can set my rxvt-unicode clients to become darker when their windows don't have focus with this string in ~/.Xdefaults: URxvt*fading: 50 It greatly reduces discomfort when you have a lot of terminal windows on 2+ monitors. I would like a similar feature in Emacs, but couldn't google up anything. Here is how it looks like with urxvt (png, 1.43 MB)

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