Sponsored Content
Top Forums Programming Message Queue Problem Again.. Post 77175 by mbb on Tuesday 5th of July 2005 10:52:08 AM
Old 07-05-2005
Just to elaborate on Blow Torch's answer. The message queues are internal kernel structures and cannot be viewed or changed directly by your process.

On some implementations you can get the memory address of the first and last message in a queue, but because this is outside your programs alloted memory area, the OS will never let you access the address directly with a pointer.

The only way your process can get at the contents on the message queue is to use the defined interface - msgrecv().
 

10 More Discussions You Might Find Interesting

1. UNIX for Advanced & Expert Users

Unix message Queue

Hi, I am working closly with unix message queues i have encountered the following - after creating the Q and start working with it (pushing & pulling) i receive the following stange parameters on the q's - STIME=no_entry Qnum=0 CBYTES=4140 when this happens, the Q is disabled (meaning i... (3 Replies)
Discussion started by: kel
3 Replies

2. UNIX for Dummies Questions & Answers

Cron message queue problem

I have a problem with running jobs out of cron on Solaris 8. Initially when one of the users on the box (other than root) attempted to save the crontab after modification by using "crontab -e", the message "Crontab: cannot open the crontab file in the crontab directory" was given. I then... (7 Replies)
Discussion started by: mattd
7 Replies

3. Programming

a message queue question..

Hi there: Thanks first. When I use a message queue amony severl processes, will I have to synchronize the queue? I don't think I would have to because a message queue is implemented in a link listed. Correct me If I am wrong... (0 Replies)
Discussion started by: yanhu
0 Replies

4. IP Networking

message queue problem

I am sending and retriving the message to the queue the problem is after retrieving the message can i see what is there in my message queue. (actually in my application i am encountring some garbage value) so i want to retieve this garbage value and also want to know its size how... (0 Replies)
Discussion started by: ramneek
0 Replies

5. Programming

Message Queue with fork() help

hi all... ive been trying this program where i spawn 4 threads... and i am trying to use message queue to send msgs from 3 of the threads to the parent thread... but it doent seem to be working... ive almost pulled out my hair tryin to fix the prob :confused: another wierd thing... (1 Reply)
Discussion started by: strider
1 Replies

6. Programming

message queue

Hello, i need to write a message queue "chat server", that should work only localy. Can anyone please help me with some ideas and peshaps code. I'm studying the UNIX IPC mechanisms right now. So far, i understand how it works but i still cannot get an idea how to write a chat programm... ... (2 Replies)
Discussion started by: etenv
2 Replies

7. Programming

[C]Problem removing a message queue

Hi!! This code works if I don't remove the message queue. In A.c I create 3 processes that send a message in a message queue. in B.c other 3 processes receive 1 message for each (the messages sent from A), change the value of "dato" and put again the message in the queue. The processes in A.c... (0 Replies)
Discussion started by: Sentinella
0 Replies

8. Programming

How to limit max no of message in a posix message queue

Hii can anyone pls tell how to limit the max no of message in a posix message queue. I have made changes in proc/sys/fs/mqueue/msg_max But still whenever i try to read the value of max. message in the queue using attr.mq_curmsgs (where struct mq_attr attr) its giving the default value as 10.... (0 Replies)
Discussion started by: mohit3884
0 Replies

9. Programming

Message Queue Problem

Hi all, I need help about message queues, i have a server-client program that communicates each other via msg queue, firstly server opens its msg queue and waits for msg then client opens server msg queue and its own msg queue(for receiving msg from server,clients sends msg to server msg... (7 Replies)
Discussion started by: SaTYR
7 Replies

10. Programming

UNIX Message Queue

Hello !!!!! I have a simple question but i can't find the answer anywhere hope to meet it here. Why it is a bad idea to pass pointers through message queues ? Most structs i see all of their char types are arrays... Is it becase having pointers means we could possibily send wrong bytes ? For... (2 Replies)
Discussion started by: qlyine
2 Replies
mq_close(2)							System Calls Manual						       mq_close(2)

NAME
mq_close - close a message queue descriptor SYNOPSIS
DESCRIPTION
The system call removes the association between the message queue descriptor, mqdes, and a message queue. Use of this message queue descriptor by the process, after a successful return from this and until this descriptor is returned by a subsequent will result in the failure of message queue system calls, with set to If the process has a registered notification request with the message queue associated with this mqdes, the registration is canceled and the queue becomes available for another process to register a notification request. If the message queue has been unlinked and mqdes is the only existing open descriptor for the queue, the queue is destroyed. To use this function, link in the realtime library by specifying on the compiler or linker command line. RETURN VALUE
returns the following values: Successful completion. Failure. is set to indicate the error. ERRORS
If fails, is set to one of the following values: mqdes is not a valid message queue descriptor. is not supported by the implementation. SEE ALSO
mq_open(2), mq_unlink(2), mq_notify(2). STANDARDS CONFORMANCE
mq_close(2)
All times are GMT -4. The time now is 10:53 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy