In above program i m able to assign name ins szName and able view it in child, but when i change szName in child it doesn't reflected in parent.
One thing might be because it is (szName) given space using new in parent process in shared memory that's why child process is not able to change value at that location. but still child is able to view that value then why can't it change the value at that location.
Last edited by vino; 03-19-2010 at 03:31 AM..
Reason: added code tags
Dear Reader,
Is is necessary to attach / dettach the shared memory segments for write operations , if more than one program is accessing same shared memory segments..
I have used semaphore mutex and still I'm getting segmentation fault when I write to the segment when other program is already... (1 Reply)
I am running HP-UX B.11.11.
I'm increasing a parameter for a database engine so that it uses more memory to buffer the disk drive (to speed up performance). I have over 5GB of memory not being used.
But when I try to start the DB with the increased buffer parameter I get told.
"Not... (1 Reply)
Hi all :confused: ,
I am new to unix.I have been asked to implement shared memory in user's mode.What does this mean?What is the difference it makes in kernel mode and in users mode?What are the advantages of this impemenation(user's mode)?
And also i would like to know why exactly shared... (0 Replies)
hi,
this is the problem: i want to swap a linked list between 4 processes (unrelated), is there any way i can do that just by sending a pointer to a structure?
//example
typedef struct node
{
int x;
char c;
struct node *next;
} node;
or i should send the items ( x,c ) by... (9 Replies)
I need to create a shared library to access an in memory DB. The DB is not huge, but big enough to make it cumbersome to carry around in every single process using the shared library. Luckily, it is pretty static information, so I don't need to worry much about synchronizing the data between... (12 Replies)
I am writing a shared library in Linux (but compatible with other UNIXes) and I want to allow multiple instances to share a piece of memory -- 1 byte is enough. What's the "best" way to do this? I want to optimize for speed and portability.
Obviously, I'll have to worry about mutual exclusion. (0 Replies)
Basically I'm trying to avoid writing paragraphs to do it. It is possible I could convert over to a vector<int>'s if that may help. Does anyone know how to do this without really turning it into a huge brainbuster? I have considered using a for() loop but I wasn't able to put anything into practice... (1 Reply)
Hello.
I am new to this forum and I would like to ask for advice about low level POSIX programming.
I have to implement a POSIX compliant C shared library.
A file will have some variables and the shared library will have some functions which need those variables.
There is one special... (5 Replies)
Discussion started by: iamjag
5 Replies
LEARN ABOUT NETBSD
ipcrm
IPCRM(1) BSD General Commands Manual IPCRM(1)NAME
ipcrm -- remove the specified message queues, semaphore sets, and shared memory segments
SYNOPSIS
ipcrm [-M shmkey] [-m shmid] [-Q msgkey] [-q msqid] [-S semkey] [-s semid] ...
DESCRIPTION
ipcrm removes the specified message queues, semaphores, and shared memory segments. These System V IPC objects can be specified by their
creation ID or any associated key.
The following options are used to specify which IPC objects will be removed. Any number and combination of these options can be used:
-M shmkey
Mark the shared memory segment associated with key shmkey for removal. This marked segment will be destroyed after the last detach.
-m shmid
Mark the shared memory segment associated with ID shmid for removal. This marked segment will be destroyed after the last detach.
-Q msgkey
Remove the message queue associated with key msgkey from the system.
-q msqid
Remove the message queue associated with the ID msqid from the system.
-S semkey
Remove the semaphore set associated with key semkey from the system.
-s semid
Removes the semaphore set associated with ID semid from the system.
If the id or key argument is ``all'' then all entries of the appropriate type are removed.
The identifiers and keys associated with these System V IPC objects can be determined by using ipcs(1).
SEE ALSO ipcs(1), shmat(2), shmctl(2), shmdt(2), shmget(2)BSD May 31, 2008 BSD