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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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  • Question with "extern" in C

    - by why
    When programming, I would like to split one large file(which contains main function) to many small files, so there is one common case: functions in small files can modify the var from main file, so i think extern is very useful! for instance: in main.c extern int i = 100; in small.c extern int i; fprintf(stdout, "var from main file: %d\n", i); I just want to know is my understanding right?

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  • Getting n-th line of text output

    - by syker
    I have a script that generates two lines as output each time. I'm really just interested in the second line. Moreover I'm only interested in the text that appears between a pair of #'s on the second line. Additionally, between the hashes, another delimiter is used: ^A. It would be great if I can also break apart each part of text that is ^A-delimited (Note that ^A is SOH special character and can be typed by using Ctrl-A)

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  • Solr; What does this mean?

    - by Camran
    At the end of the README.txt file which is located in the example directory under solr, I find this line: NOTE: This Solr example server references SolrCell jars outside of the server directory with statements in the solrconfig.xml. If you make a copy of this example server and wish to use the ExtractingRequestHandler (SolrCell), you will need to copy the required jars into solr/lib or update the paths to the jars in your solrconfig.xml What does this mean? Do I have to make some adjustment before uploading solr to my server? Also, if you know, what is Solr-nightly:s difference to regular solr? The tutorial states "solr-nightly.zip" but on their download section I cant find it.

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  • Bash PWD Shortening

    - by dlibby00
    I'm looking for a bash function that will shorten long path names to keep my PS1 variable from getting excessively long. Something along the lines of: /this/is/the/path/to/a/really/long/directory/i/would/like/shortened might end up as: /t../i../t../p../to/a/r../l../d../i/w../like/shortened something that the took the path and a maximum acceptable number of characters to shorten to would be perfect for my .bashrc file.

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  • Regarding PID Shell Script

    - by arav
    I am calling another shell script testarg.sh within my main script. the logfiles of testarg.sh are stored in $CUSTLOGS in the below format testarg.DDMONYY.PID.log example: testarg.09Jun10.21165.log In the main script after the testarg process gets completed i need to grep the log file for the text "ERROR" and "COMPLETED SUCCESSFULLY". How do i get the PID of the process and combine with DDMONYY for grepping. Also i need to check whether file exists before grepping $CUSTBIN/testarg.sh $CUSTBIN/testarg.sh rc=$? if [ $rc -ne 0 ]; then return $CODE_WARN fi

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  • spin_lock_irqsave vs spin_lock_irq

    - by cojocar
    On a SMP machine we must use spin_lock_irqsave and not spin_lock_irq from interrupt context. Why would we want to save the flags (which contains the IF)? Is there another interrupt routine that could interrupt us? The flags are per CPU?

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  • Bash script to (more or less) reliably check if the internet is up

    - by João Portela
    I need a bash script to put in a cron job that every minute checks if the internet is up. This is how I did it: #! /bin/sh host1=google.com host2=wikipedia.org curr_date=`date +"%Y%m%d%H%M"` echo -n "${curr_date};" ((ping -w5 -c3 $host1 || ping -w5 -c3 $host2) > /dev/null 2>&1) && echo "up" || (echo "down" && exit 1) How would you do it? Which hosts would you ping? Thanks in advance.

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  • sigprocmask not working

    - by EpsilonVector
    I'm using sigprocmask as follows: void mask(){ sigset_t new_set,old_set; sigemptyset(&new_set); sigaddset(&new_set,SIGALRM); sigprocmask(SIG_BLOCK, &new_set, &old_set); } and to my surprise a function which prints a big list somehow gets interrupted by the signal, even though I invoke mask() at its beginning. It looks as if mask fails, since my function doesn't invoke any other functions and therefore nowhere in its run should an unmask() happen. What can cause sigprocmask to fail?

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  • grep a rar in cygwin

    - by Tomer
    Hi, I want to do grep texts files inside a rar without extracting the rar file to disk, I tried a couple of combinations with pipes however it didnt work i tried for example unrar e myrar.rar | grep mysearchedline however it actually opened it to disk, I don't want to open it to disk, I don't have enough space for it to be opened (its real big with real big logs). Thanks.

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  • gcc compilations (sometimes) result in cpu underload

    - by confusedCoder
    I have a larger C++ program which starts out by reading thousands of small text files into memory and storing data in stl containers. This takes about a minute. Periodically, a compilation will exhibit behavior where that initial part of the program will run at about 22-23% CPU load. Once that step is over, it goes back to ~100% CPU. It is more likely to happen with O2 flag turned on but not consistently. It happens even less often with the -p flag which makes it almost impossible to profile. I did capture it once but the gprof output wasn't helpful - everything runs with the same relative speed just at low cpu usage. I am quite certain that this has nothing to do with multiple cores. I do have a quad-core cpu, and most of the code is multi-threaded, but I tested this issue running a single thread. Also, when I run the problematic step in multiple threads, each thread only runs at ~20% CPU. I apologize ahead of time for the vagueness of the question but I have run out of ideas as to how to troubleshoot it further, so any hints might be helpful. UPDATE: Just to make sure it's clear, the problematic part of the code does sometimes (~30-40% of the compilations) run at 100% CPU, so it's hard to buy the (otherwise reasonable) argument that I/O is the bottleneck

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  • stream output of a command continuously run in php

    - by chandan kharbanda
    i am running this simple command { ./a.out < in; } & output.txt using exec and i want to output what's coming in output.txt through ajax request continuously. Also i want a way to turn off my output buffering.I tried flush() and ob functions but didn't succedded.In my /etc/php5/apache2/php.ini php.ini value of output_buffering = 4096.When I change it to Off and restart my apache2 server it fails to restart.P.S. I am using lamp server.

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  • How to repair Java in Ubuntu after trying to switch to Java 6 using update-java-alternatives

    - by Kau-Boy
    I tried to switch from Java 5 to Java 6 using the "update-java-alternatives" command like explained on this page: https://help.ubuntu.com/community/Java But afterwards I get the following error when I tried to execute java: root@webserver:~# java Error occurred during initialization of VM Could not reserve enough space for object heap Could not create the Java virtual machine. I also tried to reinstall the java binaries using "apt-get" but I didn't succeed reinstalling it. I would like to post the "apt-get" errors, but unfortunately I don't know how to print out the error messages in English and not in German. My system is a Ubuntu 8.04 ROOT server. Here is the (Google translated) english text tring to install Java 6 again: root@server:~# apt-get install sun-java6-jdk Reading package lists ... Ready Dependency tree Reading state information ... Ready sun-java6-jdk is already the newest version. sun-java6-jdk set to manually installed. 0 upgraded, 0 newly installed, 0 to remove and 86 not upgraded. 1 not fully installed or removed. After this operation, 0B of additional disk space will be used. Set up a sun-java6-bin (6-03-0ubuntu2) ... Could not create the Java virtual machine. dpkg: error processing sun-java6-bin (- configure): Subprocess post-installation script returned error exit status 1 Errors were encountered while processing: sun-java6-bin E: Sub-process / usr / bin / dpkg returned an error code (1) I hope that this might help you helping me.

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  • ImageMagick bash script issue

    - by gAMBOOKa
    // This works convert ${path}${dst} -crop ${crop} ${path}${dst} // but when changed to this, it fails convert ${path}${src} -trim ${path}${dst} convert ${path}${dst} -crop ${crop} ${path}"pdf_"${dst} What am I doing wrong?

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  • change shell directory from a script?

    - by ajsie
    i want to make a script (to) that makes it easier for me to enter folders. so eg. if i type "to apache" i want it to change the current directory to /etc/apache2. however, when i use the "cd" command inside the script, it seems like it changes the path WITHIN the script, so the path in the shell has not changed. how could i make this work?

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  • Notify via email if something wrong got happened in the shell script

    - by Nevzz03
    fileexist=0 for i in $( ls /data/read-only/clv/daily/Finished-HADOOP_EXPORT_&processDate#.done); do mv /data/read-only/clv/daily/Finished-HADOOP_EXPORT_&processDate#.done /data/read-only/clv/daily/archieve-wip/ fileexist=1 done --some other script below Above is the shell script I have in which in the for loop, I am moving some files. I want to notify myself via email if something wrong got happened in the moving process, as I am running this script on the Hadoop Cluster, so it might be possible that cluster went down while this was running etc etc. So how can I have better error handling mechanism in this shell script? Any thoughts?

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  • The conventional location for storing my Java libraries and applications in UNIX based systems

    - by Bytecode Ninja
    I usually store the Java applications and JAR files that I download from the Web in the ~/Java folder on my computer (an OS X machine). I have been doing this since the days when I was a Windows user. However I think in UNIX based systems user local apps are conventionally stored in another directory. I have a feeling that this directory should either be /usr/local/, /usr/local/USERNAME, /opt/local, or /opt/local/USERNAME but I am not sure. Any ideas which directory can I use for this purpose? Please note that, I am talking about archive files that I download from the Web, unpack and use locally and not programs that have installation scripts or MacPorts, etc.

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  • How to enable 'wget' to download the whole content of HTML with Javascript

    - by neversaint
    I have a site which I want to download using Unix wget. If you look at the source code and content of the file it contain section called SUMMARY. However after issuing a wget command like this: wget -O downdloadedtext.txt http://www.ncbi.nlm.nih.gov/IEB/Research/Acembly/av.cgi?db=mouse&c=gene&a=fiche&l=2610008E11Rik The content of the downdloadedtext.txt is incomplete and different with the source code of that site. For example it doesn't contain SUMMARY section. Is there a correct way to obtain the full content correctly? The reason I ask this because I want to automate the download from different values in that HTML.

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  • Simulation tree command in C

    - by Ecle
    I have to create the simulation of tree command in C, this is my current code: #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <dirent.h> #include <string.h> main(int argc, char *argv[]){ int i; if(argc < 2){ printf("\nError. Use: %s directory\n", argv[0]); system("exit"); } for(i=1;i<argc;i++) //if(argv[i][0] != '-') tree(argv[i]); } tree(char *ruta){ DIR *dirp; struct dirent *dp; static nivel = 0; struct stat buf; char fichero[256]; int i; if((dirp = opendir(path)) == NULL){ perror(path); return; } while((dp = readdir(dirp)) != NULL){ printf(fichero, "%s/%s", path, dp->d_name); if((buf.st_mode & S_IFMT) == S_IFDIR){ for(i=0;i<nivel;i++) printf("\t"); printf("%s\n", dp->d_name); ++nivel; tree(fichero); --nivel; } } } Apparently, it works! (due to it compiles correctly) But I don't why. I can't pass the correct arguments to execute this. Thank you so much, people.

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  • Application Distribution

    - by FrozenWasteland
    I have a SDL app that compiles fine, and the images show up, but only if they are in the correct folder with the binary next to them, if the images are moved they wont show up next time the application is run. How can I make a complete binary that will allow me to compile the images as well as the code, so that I can distribute one single binary, and not a zip file with all of my assets. I have looked into writing a .deb file which is what I think I need, but the process looked complicated. I am running Ubuntu 10.10 I only need to distribute to Ubuntu

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  • [sed] Multiline trimming

    - by wwrob
    I have a html file that I want to trim. I want to remove a section from the beginning all the way to a given string, and from another string to the end. How do I do that, preferably using sed?

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