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
2 Replies
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
msgget(2) System Calls Manual msgget(2)
Name
msgget - get message queue
Syntax
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
int msgget (key, msgflg)
key_t key;
int msgflg;
Description
The system call returns the message queue identifier associated with key.
A message queue identifier and associated message queue and data structure are created for key if one of the following is true:
o The key is equal to IPC_PRIVATE
o The key does not already have a message queue identifier associated with it, and (msgflg & IPC_CREAT) is true. For further informa-
tion, see
Upon creation, the data structure associated with the new message queue identifier is initialized as follows:
o The msg_perm.cuid, msg_perm.uid, msg_perm.cgid and msg_perm.gid members are set equal to the effective user ID and effective group ID,
respectively, of the calling process.
o The low-order nine bits of msg_perm.mode are set equal to the low-order nine bits of msgflg.
o The msg_qnum, msg_lspid, msg_lrpid, msg_stime, and mgs_rtime members are set equal to 0.
o The msg_ctime is set equal to the current time.
o The msg_qbytes is set equal to the system limit.
Return Values
Upon successful completion, a non-negative integer, which is a message queue identifier, is returned. Otherwise, a value of -1 is
returned, and errno is set to indicate the error.
Diagnostics
The system call fails under the following conditions:
[EACCES] A message queue identifier exists for key but operations permission, as specified by the low-order nine bits of msgflg,
would not be granted. For further information, see
[ENOENT] A message queue identifier does not exist for key and the logical operation (msgflg & IPC_CREAT) is false.
[ENOSPC] A message queue identifier is to be created, but the system-imposed limit on the maximum number of allowed message queue
identifiers system wide would be exceeded.
[EEXIST] A message queue identifier exists for key but the logical operation ((msgflg & IPC_CREAT ) & (msgflg & IPC_EXCL )) is true.
See Also
msgctl(2), msgop(2), ftok(3)
msgget(2)
How to limit max no of message in a posix message queue