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I have written this code
The call to CreateSharedMem creates and returns the id of shared memory segment but when i call GetSharedMem it returns 0?
Any idea what i am doing wrong ?
Thank You
int CreateSharedMem(char* key_file, char id, int seg_size)
{
int shm_id;
key_t keyval;
if ((keyval = ftok(key_file,id))==-1)
{
perror("ftok");
return -1;
}
// Can use IPC_EXCL which will fail and returns -1 if a segment with the same key exists
if((shm_id = shmget( keyval, seg_size, IPC_CREAT | 0666 | IPC_EXCL )) == -1)
{
perror("shmget");
return(-1);
}
return(shm_id);
}
int GetSharedMem(char* key_file,char id, int seg_size)
{
int shm_id;
key_t key_val;
if ((key_val = ftok(key_file,id))==-1)
{
perror("ftok");
return -1;
}
printf("Key is %d",key_val);
// Can use IPC_EXCL which will fail and returns -1 if a segment with the same key exists
if((shm_id = shmget( key_val , seg_size, IPC_CREAT | 0666 ) == -1))
{
perror("shmget");
return(-1);
}
return(shm_id);
}
main()
{
.
.
/* Create a shared memory */
int my_shm_id = CreateSharedMem("MySharedMem.c",'A',1000);
printf("%d : Shared mem is created\n",my_shm_id);
/* Get the same shared memory */
int my_shm_id = GetSharedMem("MySharedMem.c",'A',1000);
printf("%d is Shared mem that is created\n",my_shm_id);
.
.
}
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Why are you using IPC_CREAT again in GetSharedMem function when you are only trying to get a shared memory?
shouldn't it be something like....
<br />
if((shm_id = shmget( key_val , seg_size, 0666 ) == -1))<br />
-------------------------------------------
It's code that drives you - Shyam
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Let me ask you a straight question to all the Linux.com users. Is linux good enuff?
First i hear that it is free software. We kno that enything free sucks. My office has free coffee which sucks. So Linux does suck. The software / installation / maintainance all sucks.
But windows xp / vista is very stable and secure. They have frequent releases of service packs and vital security updates. All because u pay for it. So i advice all Linux users to stop believing in free and buy Windows / MAC OS X. Let me know ur views on it
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I think it's not about free or not ,it's about the open source ,a open soft spirit!
however , it does depend on your own choice .no one can deny your choice except yourself... 
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I've taken a course in the past that covered unix/linux and I have one coming up my final semester. The course I took covered the command line using mainly the bash shell and a few programs like vim and emacs. Anyways I wanted to practice a little at home since alot of programming jobs want unix or linux experience.
I was wondering what is the unix/linux defacto programming environment or do people actually use vim and emacs for that? Also do people still use the command line alot and if so why? I really don't see the advantage of using the command line as compared to using a GUI. Also what distro would you recommend I try?
thanks for you help.
Mike
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Mike command line and GUI are two different worlds. Most jobs that require UNIX / LINUX experience involve you writing shell scripts, scripts that automate processes etc. They don't really require you to develop a GUI.
The defacto programming enviornment for GUI based apps differ because of variety of choices Linux offers  . KDevelop, Eclipse, Glade Designer, MonoDevelop are some of the great GUI development tools available. Some distributions have this in-built into them.
MikeMarq wrote: Also what distro would you recommend I try?
Each distro has its own plus and minus. However OpenSUSE 11 was my fav because i came inbuilt with so many dev tools that i rarely needed to connect to internet to download them.
I found the articles written by pseudonym67 at codeproject are a great place to start if you are looking for learning gui development in Linux, though i never spent time in reading them  . Hope I do that this diwali.
http://lamp.codeproject.com/script/Articles/MemberArticles.aspx?amid=441940[^]
I have written a simple article on MonoDevelop to consume web services.
http://lamp.codeproject.com/KB/webservices/MonoStockInformation.aspx[^]
As you can see, development in Linux seriously lacked proper articles and was the birth-right of a few people. I personally remember during my college days browsing through page 10 of google search results to learn APIs in Linux. But I feel with the LAMP section of CodeProject this would change and there would be wonderful articles that can teach development in Linux
-------------------------------------------
It's code that drives you - Shyam
modified on Monday, October 27, 2008 2:35 AM
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Thank you for your excellent reply.
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Hi All,
I m fighting against a problem that drove me crazy for long hours, I wanna create a simple prog like Client/Server under linux using C code. I wrote a Server.c and Client.c Files but when i type
$gcc -c Server.c Client.c
$gcc -o Blood *.o
it told me that there is a double declarion of the function main
So could some one tell me how could i test my prog on the same mchine ??? (local) Thank you !!!!
i Need Help so plz !!!
"The Ultimate Limit Is Only Your Imagination."
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Blood_HaZaRd wrote: $gcc -c Server.c Client.c
$gcc -o Blood *.o
it told me that there is a double declarion of the function main
Did you try this?
$gcc -c Server.c Client.c
$gcc -o blood_server Server.o
$gcc -o blood_client Client.o
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Ok i asked my professor and here what he told me to do:
after compiling the 2 files:
$gcc - client client.c
$gcc - server server.c
i ha to add a & when calling ther server:
$./server &
then i run the clien
$./client
that's all. i didn't try it yet but i hope that it'll works.
Thank you All for your Help. I appreciate it Well.
![Rose | [Rose]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/rose.gif)
"The Ultimate Limit Is Only Your Imagination."
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you will need to compile each file separately. each file creates a different exe, one will create a client exe and the other a server exe.
each file has a main method, when you compile files together it to create a single exe, so what you are doing is incorrect. in short you can't have multiple definitions of a function, in your case that would be 'main'
try:
gcc -o server server.c
gcc -o client client.c
hope this helps
---
Yours Truly, The One and Only!
web: devmentor.org
Design, Code, Test, Deploy
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Dear friends,
I'll appreciate if anyone could help me this problem.
I'm now trying to program with multi-core. For instant, with C/C++, how can I assign a task for the first core and another task for the second core? Is there any instructions support this? Or could you show me where can I find any documents relate to this field.
Thank you very much.
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I think pthreads handle this automatically, but I don't know how much manual control you can get. Maybe this Linux magazine article (google cache) helps.
/M
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Thanks. I'm checking.
Can otherone help me this? I'd like to receive more information.
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You can use the sched_setaffinity() system call to lock a thread to a specific set of CPUs/cores. In most cases doing that is a bad idea and it will only slow down your system.
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Thank you very much. This instruction was created so it must have some useful functions beside causing system slow down. But first of all, I need to try it. Once again, thanks.
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hi i would like to know how to sort my dynamic generated table in php when i click on any header row on first click sort acending and on another click sort on decending order.
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If you wanna sort Mysql Data, you should use two difference Mysql Query.
For example :
SELECT * FROM table1 ORDER BY filed ASC
SELECT * FROM table1 ORDER BY filed DESC
Else if you wanna sort a table in client you should use JavaScript.
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ya i know these are two commands to show asc and desc but i would like to know that i have a grid table in php and on every field i want to do this and show a image full process to do this this grid is filled by while loop as used in php all dataare there but i want to show sorting on header of the fields click.
thanks for reply
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I think you want to load a table and then be able to sort the data by a column after the data is loaded by clicking on the col header, correct? Uh oh, i think i may like jQuery too much as i just posted a different response pointing the user to the jQuery library.
Take a look at ajaxrain.com for table plugins to jQuery. I know there's a couple of them out there, if this is what you're looking for
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There would be 3 components to this process-
1. User-facing page with <div id=data></div>
2. AJAX Javascript
3. Dynamic PHP page
The user-facing page will contain an empty div marked by an ID. The AJAX script will be something like-
http://whatsaranjit.com/includes/grabData.js[^]
Lastly, the PHP page will contain a script like-
$sql = "SELECT * FROM table";
if (isset($_GET['q'])) {
$q = $_GET['q'];
$sql .= " ORDER BY $q ASC";
}
On your user-facing page, you can make your table header a hyperlink-
<a href='javascript: grabData('headerName', 'data', page.php)'>Sort</a>
When you click the link, it will refresh the SQL query data into the div named 'data' appending the SQL query to order by whatever variable you pass to the AJAX script. You can expand on this to to get it to ascend/descend. Good luck!
Ranjit Viswakumar
Professional Services Specialist
rviswakumar@hostmysite.com
http://hostmysite.com/?utm_source=bb[^]
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Need Linux library to get the pixel information from any image.
Example: By providing location(widht, height) x, y values, we should get the information of the pixel which is located at x and y position.
If any one knows about this, please help me.
Thanks in Advance
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Have you tried following function?
unsigned long XGetPixel(XImage *ximage, int x, int y);
For more information you can see man XGetPixel.
regards,
Divyang Mithaiwala
Software Engineer
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hi i have a problem with my sql i have a field date and its not mandatory field show user can leave this field blank but when i store this i found and error not data in correct format and if i use 0000-00-00 then its store value 1/1/1970. while i want not use this date.
thanks in advance.
I will do my best?
Integrated Solutions, Bikaner (Raj.), India
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You could always make this field a VARCHAR (10) instead, which means that the field can take a null value; then, just insert any actual dates in the format YYYY-MM-DD, leaving fields blank where you want to, and then when you read the data from the database again, check if it's not null and if so parse it using a function like date_parse().
Regards,
--Perspx
"I've got my kids brainwashed: You don't use Google, and you don't use an iPod." - Steve Ballmer
"Some people have told me they don't think a fat penguin really embodies the grace of Linux, which just tells me they have never seen an angry penguin charging at them in excess of 100mph." - Linus Torvalds
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