Your receive is not likely to work. You're not putting the message into a buffer that "char *msg" points to, your putting it into the bytes (probably 4) that make up the "char *msg" variable itself along with randomly overwriting your stack, because sizeof( msg ) is probably 4, but you're telling the mq_receive() call that the address you're passing points to 16 bytes.
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)
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)
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)
Hi
I have a log file which contain XML message. I want to extract the value between the tag : <businessEventId>13201330</businessEventId> i.e., 13201330.
I tried the following commands but as the message is very long, unable to do it. Attached is the log file. Please provide inputs.
--... (3 Replies)
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)
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)
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)
I have a ksh script (script1) that calls another ksh script (script2). If script2.ksh hangs or takes too long to execute I want script1.ksh to kill the call to script2.ksh and instead just display "Script2 can't run right now". Could someone help me with coding this? (1 Reply)
Discussion started by: mrskittles99
1 Replies
LEARN ABOUT OSF1
mq_receive
mq_receive(3) Library Functions Manual mq_receive(3)NAME
mq_receive - Receives the oldest, highest-priority message from the message queue (P1003.1b)
LIBRARY
Realtime Library (librt.so, librt.a)
SYNOPSIS
#include <mqueue.h>
ssize_t mq_receive (
mqd_t mqdes,
char *msg_ptr,
size_t msg_len,
unsigned int *msg_prio);
PARAMETERS
mqdes Specifies a message queue by descriptor.
*msg_ptr Specifies a pointer to a buffer to receive the message.
msg_len Specifies the size of the receive buffer identified by the msg_ptr argument.
*msg_prio Specifies a pointer to a location to receive the message priority.
DESCRIPTION
The mq_receive function receives the oldest, highest-priority message from the message queue. The message is removed from the queue and
transferred to the buffer pointed to by the msg_ptr argument.
If the specified message queue is empty and the O_NONBLOCK flag is not set with the mqdes argument, the mq_receive function blocks until a
message is put on the queue or until the mq_receive function is interrupted by a signal. If more than one process is waiting to receive a
message when a message arrives at an empty queue, the highest-priority process that has been waiting the longest is selected to receive the
message. If the message queue is empty and the O_NONBLOCK flag is set, no message is removed from the queue, and an error is returned.
RETURN VALUES
On successful completion, the function returns the length of the selected message.
Otherwise, the function returns the value -1 and sets errno to indicate the error. No message is removed from the queue.
ERRORS
The mq_receive function fails under the following conditions:
[EAGAIN] O_NONBLOCK was set in the message description associated with mqdes, and the specified message queue is empty.
[EBADF] The mqdes argument is not a valid message queue descriptor open for reading.
[EBADMSG] The implementation has detected a data corruption problem with the message.
[EFAULT] An internal virtual memory error occurred.
[EINTR] The mq_receive function was interrupted by a signal.
[EMSGSIZE] The specified message buffer size, msg_len, is less than the message size attribute of the message queue.
RELATED INFORMATION
Functions: mq_send(3)
Guide to Realtime Programming delim off
mq_receive(3)