I was recently struck by a curious idea to take input from /dev/urandom, convert relevant characters to random integers, and use those integers as the rgb/x-y values for pixels to paint onto the screen. I’ve done some research (here on StackOverflow and elsewhere) and many suggest that you can simply wr…
Sharing memory between processes through the use of mmap()
I’m in Linux 2.6. I have an environment where 2 processes simulate (using shared memory) the exchange of data through a simple implementation of the message passing mode. I have a client process (forked from the parent, which is the server) which writes a struct(message) to a memory mapped region create…
What are the GCC default include directories?
When I compile a very simple source file with gcc I don’t have to specify the path to standard include files such as stdio or stdlib. How does GCC know how to find these files? Does it have the /usr/include path hardwired inside, or it will get the paths from other OS components? Answer In order to figu…
JAR Dependency Resolution from Within /usr/share/java
Can someone please explain how JAR files and the Java class loader make use of /usr/share/java? Is this a special directory that the JVM will perform automatic JAR loading and class lookups in, but no other? For example, if I have x.jar that depends on y.jar. If both jars are in/usr/share/java the dependency,…
using C code to get same info as ifconfig
Is there a way in Linux, using C code, to get the same information that “ifconfig eth0” would return? I’m interested in things like IP address, link status, and MAC address. Here’s sample output from ifconfig: Answer Yes, ifconfig itself is written in C. 🙂 See: http://cvsweb.netbsd.org…
Why are designated initializers not implemented in g++
Is there any specific reason why has support for designated initializers not been added to g++? Is the reason that C99 standards came late and g++ was developed earlier and later people didn’t care about this issue, or there is some inherent difficulty in implementing designated initializers in the gram…
How do I get out of ‘screen’ without typing ‘exit’?
I screen -r’d into a Django server that’s running and I can’t simply Ctrl + C and exit out of it. Are there any alternative ways to get out of screen? Currently, I manually close the tab on my local PC and ssh back in, but that’s becoming tiresome. Answer Ctrl-a d or Ctrl-a Ctrl-d. See…
scraping website for info when the URL has product id’s instead of true values
Im guessing its php cURL, but Whats the best way to make a loop to scrape the DOM for info from a webpage that uses id’s in the URL Query like (?ProductId=103) There is about 1200 pages. I need to find the innerHTML of the 9th span on each page. This info will just get stored in a mySQL table
Bash script to delete all but N files when sorted alphabetically
It’s hard to explain in the title. I have a bash script that runs daily to backup one folder into a zip file. The zip files are named worldYYYYMMDD.zip with YYYYMMDD being the date of backup. What I want to do is delete all but the 5 most recent backups. Sorting the files alphabetically will list the ol…
What is the difference between “source script.sh” and “./script.sh”?
What is the difference between source <script> and ./<script>? Answer source script.sh runs the script within the current process, thus all variable assignments are preserved as variables even after the script finishes (and don’t have to be explicitly export’d). ./script.sh just runs t…