10 More Discussions You Might Find Interesting
1. Programming
hello, I try to test the POSIX mq_open function on book unp like below:
#include "unpipc.h"
# include <mqueue.h>
int main(int argc, char **argv)
{
int c, flags;
mqd_t mqd;
flags = O_RDWR | O_CREAT;
while ((c = getopt(argc, argv, "e")) != -1) {
... (3 Replies)
Discussion started by: anpufeng
3 Replies
2. Programming
Hi,
I wanted to know whether the POSIX message queues are statically allocated memory by the kernel based on the parameters specified in the open or as and when we send messages, memory are allocated?
Does the kernel reserve the specified memory for the message queue irrespective of whether... (1 Reply)
Discussion started by: sumtata
1 Replies
3. Programming
in a single main() function,so need signal handling. Use Posix Message Queue IPC mechanism , can ignore the priority and other linked list message,to implement the scenario:
client:Knock Knock
server:who's there
client: Eric
Server:Eric,Welcome.
client:exit
all process terminated
... (1 Reply)
Discussion started by: ouou
1 Replies
4. Programming
Hello,
I am trying to implement posix message queue application. I am faced with an error on the mq_receive section. It says "Message too long". I've tried couple of small tweeks, but to no result. Please do suggest any rectificaitons.
mq_send section-works successfully
#include... (2 Replies)
Discussion started by: katwalatapan
2 Replies
5. Linux
Hi all,
Please tell me how to change POSIX message queue maximum size? "ulimit" is not a solution because it controls shell resources. But i need to control queue size before login in and starting the shell. It is needed to limit queue size for applications started before login in.
Sorry for my... (7 Replies)
Discussion started by: Vourhey
7 Replies
6. Programming
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
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7. HP-UX
Hello,
My question is related to "pipcs -qa" command under HP-UX 11i PA-RISC 64 bits.
We have a little C program that creates posix ipc message queues using the mq_open() system function.
The program fail with 'No space left on device' error when we create big queues. What is the system... (6 Replies)
Discussion started by: cadanir
6 Replies
8. Programming
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
9. UNIX for Advanced & Expert Users
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
10. Programming
How can I increase the POSIX Msg Q parameter SC_MQ_PRIO_MAX? The maximum is defined as 32. Can I increase the number? If so, how?
Deepa (0 Replies)
Discussion started by: Deepa
0 Replies
mq_notify(3C) Standard C Library Functions mq_notify(3C)
NAME
mq_notify - notify process (or thread) that a message is available on a queue
SYNOPSIS
#include <mqueue.h>
int mq_notify(mqd_t mqdes, const struct sigevent *notification);
DESCRIPTION
The mq_notify() function provides an asynchronous mechanism for processes to receive notice that messages are available in a message queue,
rather than synchronously blocking (waiting) in mq_receive(3C).
If notification is not NULL, this function registers the calling process to be notified of message arrival at an empty message queue asso-
ciated with the message queue descriptor, mqdes. The notification specified by notification will be sent to the process when the message
queue transitions from empty to non-empty. See signal.h(3HEAD). At any time, only one process may be registered for notification by a spe-
cific message queue. If the calling process or any other process has already registered for notification of message arrival at the speci-
fied message queue, subsequent attempts to register for that message queue will fail.
If notification is NULL and the process is currently registered for notification by the specified message queue, the existing registration
is removed. The message queue is then available for future registration.
When the notification is sent to the registered process, its registration is removed. The message queue is then available for registration.
If a process has registered for notification of message arrival at a message queue and some processes is blocked in mq_receive(3C) waiting
to receive a message when a message arrives at the queue, the arriving message will be received by the appropriate mq_receive(3C), and no
notification will be sent to the registered process. The resulting behavior is as if the message queue remains empty, and this notification
will not be sent until the next arrival of a message at this queue.
Any notification registration is removed if the calling process either closes the message queue or exits.
RETURN VALUES
Upon successful completion, mq_notify() returns 0; otherwise, it returns -1 and sets errno to indicate the error.
ERRORS
The mq_notify() function will fail if:
EBADF The mqdes argument is not a valid message queue descriptor.
EBUSY A process is already registered for notification by the message queue.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Committed |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
|Standard |See standards(5). |
+-----------------------------+-----------------------------+
SEE ALSO
mq_close(3C), mq_open(3C), mq_receive(3C), mq_send(3C), mqueue.h(3HEAD), siginfo.h(3HEAD), signal.h(3HEAD), attributes(5), standards(5)
SunOS 5.11 5 Feb 2008 mq_notify(3C)