Programming :: Python: Simple Message Queues / IPC?
Mar 10, 2010
I have this daemon I'm writing in Python, but I still a Python n00b. I've coded the part of the daemon that does the work, but not the part that receives messages. I need a simple system so that other processes on the same (Linux) computer can occasionally send text-string messages to the daemon (without needing to stay running all the time themselves). Once in the past we did something similar by (mis)using pyliblo to listen for OSC messages coming in on a certain port. That option isn't as workable here because the pyliblo interface (as near as I can tell) requires you to know in advance specifically what messages you are expecting, and forward them to specified functions, rather than just allowing you to generically process incoming messages as you see fit.
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Jan 26, 2011
I am implementing an IPC mechanism using message queues (Sys V).I can receive the messages using msgrcv() function. I am wondering how can I listen on the new messages. I would like to implement a mechanism that would notify me when there is a new message in the queue for me and I will call the msgrcv() function to retrieve the message.
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Mar 1, 2011
recently I had been to interview where I had a question to be answered, that what are advantages and disadvantages when desiging an application in linux.
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Apr 15, 2011
I have a pthread waiting forever on a POSIX message queue and then call mq_close and mq_unlink on the POSIX message queue. I've found that the pthread never wakes up from it's call to mq_receive and remains blocked indefinitely. Is there a way to wakeup all pthreads blocked on a POSIX message queue after calling mq_close/mq_unlink? The goal is to include error handling during message queue deletion to avoid leaving any pthreads blocked forever.
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Jan 3, 2011
I want to communicate between two threads, each belonging to a different process. Iam using message queues for this. I use mq_open()call. I created the queues with the same queue name starting with a '/'. But when I open the queue, the queue ID is different in both the process. What should I do so that both the process have the same queue ID?
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Jun 24, 2010
I have a render script that uses several Blender 3D instances on several machines to co-render one still image. The image is split into squares of 64 x 64 pixels. In the end, I have like 200 image files, each one with a puzzle piece of the whole.
Now I would like to assembe these pieces into whole with PIL and Python, but so far cannot figure out how. I am new to PIL, but in imagemagick, a convert image1.png image2.png image3.png +append finalimage.png works a charme. But convert chokes on so many image files, so I need something automatic and scalable. I think that pictures are RGBA, so black should be the alpha channel and transparent.
I think I have to mention that the pieces are in the right position and that every piece has the original dimensions of the full picture, so it is not a problem figuring out where each piece should be. Just putting all the pictures on top of eachother and ignoring anything that is black would do the trick nicely.
How can I reach this with PIL? Which functions do I need for that? PIL does a lot of stuff, so finding my simple function is daunting.
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Apr 16, 2010
I was trying to use Message Queues for sending message from aninserted kernel module to user space. The function sys_msgsnd failedgiving the obvious error -EFAULT.However, I was able to send the message from kernel to user space when I had made the same driver part of kernel (and not inserting it).How is that possible?I am using linux.2.6.19.x (arch=ppc)I now use Netlink socket to communicate from kernel to user, but the aboveproblem seemed strange to me.
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Mar 17, 2010
I just wrote a simple perl script to compare the following two files
[Code]...
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Jan 17, 2011
i am working on a project that uses message queues. i am able to successfully create them and they are working fine. now the problem is to close/remove message queues without software or mq_close / mq_unlink command. earlier when i worked on rh9, there is ipcs utility. we use ipcs to see all the existing message queues and ipcrm to remove them. however ipcs is not working for message queues in RHEL 5.3. Neither ipcs shows the exisiting message queues and neither we are able to use ipcrm. Plz guide to close/remove the queues with ipcs or any other command/utility from shell itself.
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Oct 7, 2010
i'm a college student studying pc programing, and i was given today a special work and i have to program using miranda... which i've never used it >.< can anyone give me a hand to where to download, how to compile, and a simple tutorial for making a simple program or something?
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Apr 27, 2010
Trying to learn python. Going well, but I have run into a minor speed bump. I wrote a simple program to see if Python was set up correctly. Wouldn't you know it, the thing pops open and then closes again. I put raw input fields there to stop the program, but they didn't work. The program is:
Code:
x = raw_input("Please input your name: ")
print "Hello " + x + ". Good to meet you."
raw_input("Press Enter to exit")
And as for python, I have installed the following packages. The program was made in IDLE using Python2.6 I just started learning python a few days ago, so this may be a really small mistake.
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Mar 22, 2009
I want to be able to do
sudo ./program.py
instead of always having to do
sudo python program.py
What do I need to change?
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Nov 30, 2009
I've already used line split stuff to transform my data into something like this in a text file:
Code:
['1', '1', '3', '20.7505207']
['2', '1', '3', '23.0488319']
['3', '1', '3', '-1.5768747']
['4', '1', '3', '-26.4772491']
[code]....
How can I get this on a python program so I can manipulate it as an array?
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Dec 22, 2010
I'm using the Posix's mutexes in a project. I have 3 threads and 3 queues. The problem is: I used the mutexes to "protect" the access to the queues. But the first started thread monopolizes the use of the queues. See a example code:
[Code].....
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Mar 4, 2010
I have a function definition in a Python 2.x script which take a tuple as one of its arguments, but 2to3 has no answers nor any of my searching on how to represent the same in Python 3.x
Code:
def blah(self, (string1, string2))
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Aug 18, 2009
i wanted to install screenlets under fedora 11 but python wont let me, is there a way to do it i keep getting the Python(abi) dependency missing message I've tryed both 32 and the 64 bits version, even the noarch i found here with no results at all
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Mar 25, 2011
I was doing a update via Synaptic Package Manager, after it is nearly finished i get that message: Processing triggers for python-central ... Nothing happend so i ctrl-c it and the packet manger shows me no other errors or something else, even all the packages who was marked for upgrade are now upgraded but what about that python message? Do i have to do some check ? or maybe even a repair or even worse re install the OS?
[Code]...
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Apr 11, 2011
I need help as I am not proficient with Linux C++ Programming. There are two parts which I need to do in the coding provided below.
1. Produce the program so it can output the word "Hey there!" and wait two minute and print the word "See you later!".
2. Produce the program that will output the text "Cool" every 20 seconds by setting a periodic task.
Quote:
#include <linux/kernel.h>
#include <linux/module.h>
MODULE_LICENSE("GPL");
int init_module(void)
{
printk("Hey there!
[Code]...
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Feb 12, 2011
im trying to build a simple program for my C programming class, this is the source code
#include <stdio.h>
int main()
{
int length, width, length, height, area, perimeter;
perimeter = width + length + height;
area = width * length + heigth;
[Code]...
i dont see any error (you might)but every time i run it it runs but after it asks me to input for the width i do it but it doesn't take me to the length, it just stays blank until i input another value in the same place for the width, it asks me for 4 inputs in total i don;t know why, and after i run it different times it gives me different values for the perimeter and are. how can I fix this?
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Feb 9, 2011
I want that I click with the mouse on the video, it paused.I notice that there is "BaconVideoWidget" which I guess is the video rendering widget but it don't have signal named "clicked":
Code:
vd = totem_object.get_video_widget()
vd.connect("clicked", vd.hide)
[code]....
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Sep 6, 2010
We are trying to create a message forwarder program that receive a message on Port A and pass it on t Port B. Also receive a message from Port C and Pass it on to Port D as follows.
[Code]...
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Mar 26, 2011
How to create a simple Makefile using C....
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Feb 16, 2011
This is my sub;
Code:
sub projName
{
print "Enter project name: " ;
$PROJ = <STDIN>;
print "";
[code]....
I can call this routine and it works fine when I enter a valid name for $PROJ. If I enter an invalid name it goes to the else block and prints the statement. However, it does not call itself. Instead the script just exits.I've googled 'perl recursive subroutines' and the example don't appear to be doing anything different.
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Nov 7, 2010
I have been looking at: ut a lot of it is to do with files and numerical comparisonswhat would be the bash equivalent of:if (http isin $2) { do something }
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Nov 4, 2009
I am trying to create a function that takes a pair of a high and a low limit, and returns an arbitrary number between them. Below is my attempt to create a function that accomplishes this by checking to see if they are equal, and if not, subtracts a very small number from the high limit and returns the result.
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Mar 22, 2011
This is probably hopelessly ambitious as I'm not a C or C++ programmer (I normally like to stick to scripting languages like BASH or Perl). Basically I'm looking on good advice to get me started with writing a Application Dock with the functionality of the OSX dock but without the overly flamboyant graphics that have characterised the Linux versions.At the moment the closest I've found to what I would like is bbdock. However it falls well short of the functionality of what I would like.
What bbdock does is read a file to create an icon for the openbox dock/fluxbox slit/wmaker whatever that launches an application when first clicked, shows an little arrow when the application is running, and brings the application to the fore when clicked once running.Here's a screenshot of it doing just that.The drawback to bbdock is that it doesn't really look for running applications, only those launched from bbdock. So for example it wont notice if I've launched an instance of pcmanfm from the openbox menu. And therefore it obviously also doesn't add icons for other applications that are running.
What I would like to be able to do is detect new running applications and add a bbdock icon for them. Also to detect if an application already with a shortcut has been run and update it's status to show it's open. Probably have an up and down arrow to move the icons up and down when there are too many to fit on the screen. None of the above needs fancy animation. The fade to gray effect used by bbdock is quite nice and could probably be augmented with a fade in and out to grey to represent another action, say fading to grey and back when launching and greyed when iconified.So, my question is what do I need to get started doing this? Am I best using the pretty outdated bbdock wmaker dockapp style? What functions and libraries am I likely to need to achieve the effects I want? Are there any examples of how to monitor running applications (well windows and figure out what constitutes a new application) that I could look at for inspiration. Is there anyone who's into C++ for linux who would be interested in helping me out to get this small project working?
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Apr 1, 2011
have a simple script for comparing two directories. I want to list all differences between this directories.
here is my function for compare:
function comp
{
for i in $1/*; do
if [ ! -e "$2/${i##*/}" ]; then
echo $i
[Code]....
in my script these two files are equal(my script ignored last time modified)
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Apr 13, 2010
I want to create simple webcam effects filters. I am only interested in doing relatively simple image processing like blurring or averaging the color. I would like to create the filters in either C or Python.
So before I dive into using Gstreamer or V4L I wanted to ask the forum if they have had any experience with webcam development?
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Dec 16, 2010
I made a string key-value mapping struct in C, and functions to add and remove entries. I would also like to write a function to read in this file format:
Code:
key: value
another: another value
[code]...
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May 13, 2010
I am creating a simple program using C# to print the contents of the todo.txt file once it has run. Problem is when I run the program, I get this warning.
PHP Code:
[code]....
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