if i use
it doesn't work, it gives segmentation fault and also if i use ftok function...
maybe i'm wrong to use ftok(), which type of file i use in path argument?
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)
what i want to do is have an int that can been written into by 2 processes but my code doesn't seem to work.
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include<stdio.h>
#define KEY1 (1492)
int main()
{
int shmid;
volatile int * addr;... (6 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)
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 FREEBSD
ftok
FTOK(3) BSD Library Functions Manual FTOK(3)NAME
ftok -- create IPC identifier from path name
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <sys/ipc.h>
key_t
ftok(const char *path, int id);
DESCRIPTION
The ftok() function attempts to create a unique key suitable for use with the msgget(2), semget(2) and shmget(2) functions given the path of
an existing file and a user-selectable id.
The specified path must specify an existing file that is accessible to the calling process or the call will fail. Also, note that links to
files will return the same key, given the same id.
RETURN VALUES
The ftok() function will return -1 if path does not exist or if it cannot be accessed by the calling process.
SEE ALSO msgget(2), semget(2), shmget(2)HISTORY
The ftok() function originates with System V and is typically used by programs that use the System V IPC routines.
AUTHORS
Thorsten Lockert <tholo@sigmasoft.com>
BUGS
The returned key is computed based on the device minor number and inode of the specified path in combination with the lower 8 bits of the
given id. Thus it is quite possible for the routine to return duplicate keys.
BSD July 9, 2009 BSD