9 More Discussions You Might Find Interesting
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
1 Replies
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
2 Replies
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) System Calls Manual semget(2)
Name
semget - get set of semaphores
Syntax
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
int semget (key, nsems, semflg)
key_t key;
int nsems, semflg;
Description
The system call returns the semaphore identifier associated with key. A semaphore identifier and associated data structure and set con-
taining nsems semaphores 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 semaphore identifier associated with it, and (semflg & IPC_CREAT ) is true.
For further information, see
Upon creation, the data structure associated with the new semaphore identifier is initialized as follows:
o The sem_perm.cuid, sem_perm.uid, sem_perm.cgid and sem_perm.gid are set equal to the effective user ID and effective group ID, respec-
tively, of the calling process.
o The low-order nine bits of sem_perm.mode are set equal to the low-order nine bits of semflg.
o The sem_nsems is set equal to the value of nsems.
o The sem_otime is set equal to zero (0) and sem_ctime is set equal to the current time.
Return Values
Upon successful completion, a nonnegative integer, namely a semaphore identifier, is returned. Otherwise, a value of -1 is returned and
errno is set to indicate the error.
Diagnostics
The semget system call fails if any of the following is true:
[EINVAL] The nsems is either less than or equal to zero or greater than the system-imposed limit
[EACCES] A semaphore identifier exists for key, but operation permission, as specified by the low-order nine bits of semflg would not
be granted. For further information, see
[EINVAL] A semaphore identifier exists for key, but the number of semaphores in the set associated with it is less than nsems and
nsems is not equal to zero.
[ENOENT] A semaphore identifier does not exist for key and (semflg & IPC_CREAT ) is false.
[ENOSPC] A semaphore identifier is to be created but the system-imposed limit on the maximum number of allowed semaphore identifiers
in the system would be exceeded.
[EEXIST] A semaphore identifier exists for key but ((semflg & IPC_CREAT ) & (semflg & IPC_EXCL )) is true.
See Also
semctl(2), semop(2), ftok(3)
semget(2)