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  • Show last command with up arrow on a linux c shell

    - by nunos
    I have implemented a simple linux shell in c. Now, I am adding some features and one I immediately thought about was to be able to show the last commands with the up arrow. Question 1: However, I have no idea how to accomplish this. Do you? Question 2: Any comment on how to store the "history" commands are also appreciated. I suppose something like a queue which allows access to all elements would be a good idea. Am I wrong? Do I have to implement it or is there already some good implementation out there I should know about? Thanks.

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  • How to tell binary from text files in linux

    - by gabor
    The linux file command does a very good job in recognising file types and gives very fine-grained results. The diff tool is able to tell binary files from text files, producing a different output. Is there a way to tell binary files form text files? All I want is a yes/no answer whether a given file is binary. Because it's difficult to define binary, let's say I want to know if diff will attempt a text-based comparison. To clarify the question: I do not care if it's ASCII text or XML as long as it's text. Also, I do not want to differentiate between MP3 and JPEG files, as they're all binary.

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  • Questions about linux root file system.

    - by smwikipedia
    I read the manual page of the "mount" command, at it reads as below: All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the file system found on some device to the big file tree. My questions are: Where is this "big tree" located? Suppose I have 2 disks, if I mount them onto some point in the "big tree", does linux place some "special marks" in the mount point to indicate that these 2 "mount directories" are indeed seperate disks?

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  • Execute a PyQt app from an acpi event in linux

    - by alfredozn
    Hi, I want to use a PyQt application to display an image when some acpi event is triggered under linux. I already setting up the configuration for the event and the python scrip is executed when the event is triggered, but when program reach the creation of the QApplication app = QApplication(sys.argv) it stops without error. I tried setting up the same DISPLAY and PATH environment variables as my current user but it doesn't work. This is my event file: event=sony/hotkey SNC 00000001 00000011 action=/etc/acpi/vaio-tools/brightness/sonybright.sh up 2>&1>/tmp/vaio-tools_brightness.log I tried to find some error in the /tmp/vaio-tools_brightness.log but it doesn't log anything after it reach the QApp creation in code. any hints??

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  • Problems compiling an external library on linux...

    - by Kris
    So I am trying to compile the libssh2 library on linux, but when I try to compile the example it comes up with a lot of errors, and even though I include the headerfile it asks for, it still asks for it. Here are the error messages and the resulting messages: ~/ gcc -include /home/Roosevelt/libssh2-1.2.5/src/libssh2_config.h -o lolbaise /home/Roosevelt/libssh2-1.2.5/example/scp.c /home/Roosevelt/libssh2-1.2.5/example/scp.c:7:28: error: libssh2_config.h: No such file or directory /home/Roosevelt/libssh2-1.2.5/example/scp.c: In function 'main': /home/Roosevelt/libssh2-1.2.5/example/scp.c:39: error: storage size of 'sin' isn't known /home/Roosevelt/libssh2-1.2.5/example/scp.c:81: error: 'AF_INET' undeclared (first use in this function) /home/Roosevelt/libssh2-1.2.5/example/scp.c:81: error: (Each undeclared identifier is reported only once /home/Roosevelt/libssh2-1.2.5/example/scp.c:81: error: for each function it appears in.) /home/Roosevelt/libssh2-1.2.5/example/scp.c:81: error: 'SOCK_STREAM' undeclared (first use in this function) /home/Roosevelt/libssh2-1.2.5/example/scp.c:87: error: invalid application of 'sizeof' to incomplete type 'struct sockaddr_in'

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  • Embedded Linux: Memory Fragmentation

    - by waffleman
    In many embedded systems, memory fragmentation is a concern. Particularly, for software that runs for long periods of time (months, years, etc...). For many projects, the solution is to simply not use dynamic memory allocation such as malloc/free and new/delete. Global memory is used whenever possible and memory pools for types that are frequently allocated and deallocated are good strategies to avoid dynamic memory management use. In Embedded Linux how is this addressed? I see many libraries use dynamic memory. Is there mechanism that the OS uses to prevent memory fragmentation? Does it clean up the heap periodically? Or should one avoid using these libraries in an embedded environment?

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  • Possible to use a .dll on Linux

    - by random_hero
    Question: Is it possible to compile a program on linux using a .dll file? Where this is going: This .dll will be used to write a php extension to some proprietary software from a third party. Background and Research: I have been given a library called proprietary.lib. I was curious, as I have never seen the .lib extension before, so I typed: file proprietary.lib The output was: proprietary.lib: current ar archive I did some research and found that ar is more-or-less tar (and in fact, I guess tar has since replaced ar in most *nix environments). Upon inspecting the ar manpage, I saw the t option, which displays a table listing of the contents of that archive. Cool. So I type: ar t proprietary.lib And get: proprietary.dll proprietary.dll ... (snip X lines) ...

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  • Linux program in FreeBSD

    - by Alex Farber
    Trying to run my program in FreeBSD OS, I have the following results: $ ./myprogram ELF binary type "0" not known ./myprogram: 1: Syntax error: "&" unexpected (expecting ")") $ file myprogram myprogram: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, not stripped The program is built In GCC on Ubuntu computer. What can I do? Can I build the program for FreeBSD on my Ubuntu computer by changing some build options, or I need to build it in FreeBSD OS? Maybe there is some way to convert executable to format recognized by FreeBSD?

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  • ASCII in Windows XP and Ubuntu Linux

    - by Mikey D
    I've made a program in MVSC++ which outputs memory contents (in ASCII). The ASCII I see in windows console seem to match what I see in various ASCII tables (smiley, diamond, club, right arrow etc). This program needs to compile under Linux (which is does), but the ASCII output looks completely different. A few symbols are the same but the rest are so different. Is there any way to change how terminal displays ASCII code? EDIT: The program executes correctly, it's just the ASCII that is being displayed differently.

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  • C++ Linux getpeername IP family

    - by gln
    hi In my Linux C++ application I'm using getpeername in order to get the peer IP. my problem is: when I enable the IPv6 on my machine the IP I got from the peer is with family IF_INET6 although it is IPv4. code: int GetSockPeerIP( int sock) { struct sockaddr_storage ss; struct socklen_t salen = sizeof(ss); struct sockaddr *sa; memset(&ss,0,salen); sa = (sockaddr *)&ss; if(getpeername(sock,sa,&salen) != 0) { return -1; } char * ip=NULL: if(sa->sa_family == AF_INET) { ip = inet_ntoa((struct sockaddr_in *)sa)->sin_addr); } else { //ip = how to convert IPv6 to char IP? } return 0; } how can I fix it? thanks1

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  • tracing a linux kernel, function-by function (biggest only) with us timer

    - by osgx
    Hello I want to know, how does the linux kernel do some stuff (receiving a tcp packet). In what order main tcp functions are called. I want to see both interrupt handler (top half), bottom half and even work done by kernel after user calls "read()". How can I get a function trace from kernel with some linear time scale? I want to get a trace from single packet, not the profile of kernel when receiving 1000th of packets. Kernel is 2.6.18 or 2.6.23 (supported in my debian). I can add some patches to it.

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  • Linux standard input issue

    - by George2
    Hello everyone, I am new to Linux. And I am using Red Hat Enterprise Version 5. There is a ruby program which use standard input as its input (e.g. the Ruby program process input from standard input). I think standard input should be keyboard, correct? So, I think other kinds of input (non-standard input) should not work (i.e. the ruby program should not be able to read input from such non-standard input), but actually I have tried using pipe works, I am so confused because I think pipe should be some other kinds of input -- other than standard input, why it could work? i.e. put text "123" in abc.txt with pipe, could achieve the same result as using keyboard as input to type "123" for the ruby program. Here is the sample which works and makes me confused, cat abc.txt | ~/test/rubysrc/foo.rb thanks in advance, George

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  • Deferring signal handling in Linux

    - by EpsilonVector
    I'm trying to figure out how to block a signal in Linux kernel 2.4 (user space) from invoking its handler, but keep it available to be handled later, preferably as soon as I re activate the handling of said signal. The function sigprocmask seem to come up in all my search results, but I can't find a good, clear description that explains whether the blocked signal gets "saved" to be handled later, and if so where and how do I handle it when I'm ready for it. Can someone please clarify what's going on, preferably with a code example? Thanks in advance.

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  • flex open source sdk compile error of samples on linux

    - by Oki
    I downloaded lastest version of flex open source sdk. I wanted to compile some samples specifically explorer example. At first build.sh gave me weird error and with little search I nailed it by converting all bash files and mxml files with dos2unix. It is file type error. However now I get this error ./build.sh Error: Could not resolve <mx:Script> to a component implementation. <mx:Script> When I execute build.sh, some of the samples give this weird error. I searched this error on the net, their solution is to add -Duser.language=en -Duser.region=US as jre parameters. However, this solution is for Turkish Windows XP. My system is Pardus, yet another linux distribution.

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  • C functions invoked as threads - Linux userland program

    - by Einar
    I'm writing a linux daemon in C which gets values from an ADC by SPI interface (ioctl). The SPI (spidev - userland) seems to be a bit unstable and freezes the daemon at random times. I need to have some better control of the calls to the functions getting the values, and I was thinking of making it as a thread which I could wait for to finish and get the return value and if it times out assume that it froze and kill it without this new thread taking down the daemon itself. Also I could do other things like resetting the ADC before restarting. Is this possible? Pseudo example of what I want to achieve: (function int get_adc_value(int adc_channel, float *value) ) pid = thread( get_adc_value(1,&value); //makes thread wait_until_finish(pid, timeout); //waits until function finishes/timesout if(timeout) kill pid, start over //if thread do not return in given time, kill it (it is frozen) else if return value sane, continue //if successful, handle return variable value and continue Thanks for any input on the matter, examples highly appreciated!

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  • Linux and I/O completion ports?

    - by someguy
    Using winsock, you can configure sockets or seperate I/O operations to "overlap". This means that calls to perform I/O are returned immediately, while the actual operations are completed asynchronously by separate worker threads. Winsock also provides "completion ports". From what I understand, a completion port acts as a multiplexer of handles (sockets). A handle can be demultiplexed if it isn't in the middle of an I/O operation, i.e. if all its I/O operations are completed. So, on to my question... does linux support completion ports or even asynchronous I/O for sockets?

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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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  • C / JSON Library in popular Linux distros?

    - by Tim Post
    I have a program written in C that has to input and output JSON over a local domain socket. I've found several C / JSON libraries that 'almost work' through searches. Prior to taking one of the libraries that I found .. I want to be sure that I'm not over-looking a library that is commonly found on modern Linux distros. I'd also really appreciate links to libraries that you use. Most likely, I'll just drop it in tree, unless I realize that I've over looked something widely distributed. I am tagging this as subjective because the answer that I select is the one linking to a library that works for me, that does not mean its the 'best' library. I want to take an existing array and easily convert it to a buffer that can be sent, or take a buffer and easily convert it into an allocated array. Thanks in advance!

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  • Test for external undefined references in Linux

    - by Charles
    Is there a built in linux utility that I can use to test a newly compiled shared library for external undefined references? Gcc seems to be intelligent enough to check for undefined symbols in my own binary, but if the symbol is a reference to another library gcc does not check at link time. Instead I only get the message when I try to link to my new library from another program. It seems a little silly to get undefined reference messages in a library when I am compiling a different project so I want to know if I can do a check on all references internal and external when I build the library not when I link to it. Example error: make -C UnitTests debug make[1]: Entering directory `~/projects/Foo/UnitTests` g++ [ tons of objects ] -L../libbar/bin -lbar -o UnitTests libbar.so: undefined reference to `DoSomethingFromAnotherLibrary` collect2: ld returned 1 exit status make[1]: *** [~/projects/Foo/UnitTests] Error 1

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  • Linux - File was deleted and then reappeared when folder was zipped

    - by davee9
    Hello, I am using Backtrack 4 Final, which is a Linux distro that is Ubuntu based. I had a directory that contained around 5 files. I deleted one of the files, which sent it to the trash. I then zipped the directory up (now containing 4 files), using this command: zip -r directory.zip directory/ When I then unzipped directory.zip, the file I deleted was in there again. I couldn't believe this, so I zipped up the directory again, and the file reappeared again but this time could not be opened because the operating system said it didn't exist or something. I don't remember the exact error, and I cannot make this happen again. Would anyone happen to know why a file that was deleted from a directory would reappear in that directory after it was zipped up? Thank you.

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  • trivial linux sound playback

    - by anon
    The classical C program is something like: int main() { fprintf(stderr, "hello world\n"); } a classical OpenGL program is: open up a window setup ortho view draw a colored triangle Now, I want to do the most basic thing for sound in Linux. I want to: 1) open up speakers 2) send a bunch of data, meant to be interpreted at 40Khz, 3) have pseakers play said data no midi, no instruments, ... just playing back raw data What is the easiest way to do this in a C program? [and what libraries; what's the equiv to OpenGL for sound?] Thanks!

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  • Performance Overhead of Perf Event Subsystem in Linux Kernel

    - by Bo Xiao
    Performance counters for Linux are a new kernel-based subsystem that provide a framework for all things performance analysis. It covers hardware level (CPU/PMU, Performance Monitoring Unit) features and software features (software counters, tracepoints) as well. Since 2.6.33, the kernel provide 'perf_event_create_kernel_counter' kernel api for developers to create kernel counter to collect system runtime information. What I concern most is the performance impact on overall system when tracepoint/ftrace is enabled. There are no docs I can find about them. I was once told that ftrace was implemented by dynamically patching code, will it slow the system dramatically?

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  • Understanding top output in Linux

    - by Rayne
    Hi, I'm trying to determine the CPU usage of a program by looking at the output from Top in Linux. I understand that %us means userspace and %sy means system/kernel etc. But say I see 100%us. Does this mean that the CPU is really only doing useful work? What if a CPU is tied up waiting for resources that are not avaliable, or cache misses, would it also show up in the %us column, or any other column? Thank you.

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  • Debug Linux kernel pre-decompression stage

    - by Shawn J. Goff
    I am trying to use GDB to debug a Linux kernel zImage before it is decompressed. The kernel is running on an ARM target and I have a JTAG debugger connected to it with a GDB server stub. The target has to load a boot loader. The boot loader reads the kernel image from flash and puts it in RAM at 0x20008000, then branches to that location. I have started GDB and connected to the remote target, then I use GDB's add-symbol-file command like so: add-symbol-file arch/arm/boot/compressed/vmlinux 0x20008000 -readnow When I set a breakpoint for that address, it does trap at the correct place - right when it branches to the kernel. However, GDB shows the wrong line from the source of arch/arm/boot/compressed/head.S. It's 4 lines behind. How can I fix this? I also have tried adding the -s section addr option to add-symbol-file with -s .start 0x20008000; this results in exactly the same problem.

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  • audio stream sampling rate in linux

    - by farhan
    Im trying read and store samples from an audio microphone in linux using C/C++. Using PCM ioctls i setup the device to have a certain sampling rate say 10Khz using the SOUND_PCM_WRITE_RATE ioctl etc. The device gets setup correctly and im able to read back from the device after setup using the "read". int got = read(itsFd, b.getDataPtr(), b.sizeBytes()); The problem i have is that after setting the appropriate sampling rate i have a thread that continuously reads from /dev/dsp1 and stores these samples, but the number of samples that i get for 1 second of recording are way off the sampling rate and always orders of magnitude more than the set sampling rate. Any ideas where to begin on figuring out what might be the problem?

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