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1. Solaris
Hi,
Can somebody please explain me what semaphores are? there purpose? and there effects?
Thanks in advance:) (0 Replies)
Discussion started by: Laxxi
0 Replies
2. Solaris
Hi, I've used the following way to set ssh public key authentication and it is working fine on Solaris 10, RedHat Linux and SuSE Linux servers without any problem. But I got error 'Server refused our key' on Solaris 8 system. Solaris 8 uses SSH2 too. Why? Please help. Thanks.
... (1 Reply)
Discussion started by: aixlover
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3. UNIX for Dummies Questions & Answers
I am having problem with semaphores. I am trying to protect line where process prints so that every process with print in proper order.This is the code..
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/types.h>
union... (3 Replies)
Discussion started by: joker40
3 Replies
4. UNIX for Advanced & Expert Users
Hello, first of all I apologize if this thread is not in the correct section of this forum, but this one just seemed the most appropriate.
The question I have does not concern Unix specifically, it applies to virtually any OS, however it is in Unix where I learned about this problem.
So, the... (8 Replies)
Discussion started by: Watto86
8 Replies
5. Programming
been searching around on how to use an up and down function with semaphores but i can't find an example. i looked into using: "semop" but i have no idea how to use it. I have been able to declared the semaphores using semget and initializing them using semctl. (7 Replies)
Discussion started by: ddx08
7 Replies
6. Shell Programming and Scripting
Hi Friends,
If i execute this command it comes back with 300 lines:
ipcs|grep cerebrus >>> i would like to clear the semaphores but ipcrm can remove one id at a time. is there a quicker way of removing semaphores maybe using awk?
Regards, (1 Reply)
Discussion started by: kekanap
1 Replies
7. Programming
Hi there,
Could someone please confirm which POSIX semaphore routines should be used for a multiprocess (and not multithreaded) environment?
sys/sem.h definitely works. but the routines, semget, semctl, semop are pretty unwieldy. So, I am looking for an easier way out.
From the man pages... (2 Replies)
Discussion started by: qntmteleporter
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8. UNIX for Dummies Questions & Answers
Hi all,
I am using HP 10.20 on A 9000/785. My question is:
If I am the only person logged in as root at the moment, how many "semaphore proccesses" should I have?? Is it only one, or it is relevant to other system proccesses?
Here is what I get listing the current semaphores
# ipcs -sp... (1 Reply)
Discussion started by: guest100
1 Replies
9. Programming
Dear Reader,
I'm in a multiprocess environment working with shared mem and semaphores as mutex.. The problem is -- If one of the process hooked up with the semaphore and accessing the shared mem, terminates abruptly ( or got killed ), other process which are in want of the semaphore are... (1 Reply)
Discussion started by: joseph_shibu
1 Replies
SEMGET(2) BSD System Calls Manual SEMGET(2)
NAME
semget -- obtain a semaphore id
SYNOPSIS
#include <sys/sem.h>
int
semget(key_t key, int nsems, int semflg);
DESCRIPTION
Based on the values of key and semflg, semget() returns the identifier of a newly created or previously existing set of semaphores. The key
is analogous to a filename: it provides a handle that names an IPC object. There are three ways to specify a key:
o IPC_PRIVATE may be specified, in which case a new IPC object will be created.
o An integer constant may be specified. If no IPC object corresponding to key is specified and the IPC_CREAT bit is set in semflg, a new
one will be created.
o The ftok(3) function may be used to generate a key from a pathname.
The mode of a newly created IPC object is determined by OR'ing the following constants into the semflg argument:
SEM_R Read access for user.
SEM_A Alter access for user.
(SEM_R>>3) Read access for group.
(SEM_A>>3) Alter access for group.
(SEM_R>>6) Read access for other.
(SEM_A>>6) Alter access for other.
If a new set of semaphores is being created, nsems is used to indicate the number of semaphores the set should contain. Otherwise, nsems may
be specified as 0.
RETURN VALUES
The semget() system call returns the id of a semaphore set if successful; otherwise, -1 is returned and errno is set to indicate the error.
ERRORS
The semget() system call will fail if:
[EACCES] Access permission failure.
[EEXIST] IPC_CREAT and IPC_EXCL were specified, and a semaphore set corresponding to key already exists.
[EINVAL] The number of semaphores requested is either less than 1 or greater than the system imposed maximum per set.
[EINVAL] A semaphore identifier exists for the argument key, but the number of semaphores in the set associated with it is less
than nsems, and nsems is non-zero.
[ENOENT] No semaphore set was found corresponding to key, and IPC_CREAT was not specified.
[ENOSPC] Insufficiently many semaphores are available.
[ENOSPC] The kernel could not allocate a struct semid_ds.
LEGACY SYNOPSIS
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
The include files <sys/types.h> and <sys/ipc.h> are necessary.
SEE ALSO
semctl(2), semop(2), ftok(3), compat(5)
BSD
September 12, 1995 BSD