04-07-2003
try this:
man -k semaphore
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
hi, is there any command where we can monitor semaphores? (1 Reply)
Discussion started by: yls177
1 Replies
2. Programming
I'm running one multithreaded application, in that one of my thread
is waiting infinitely in a semphore. Is there a way to determine, in
which semaphore the particular thread is waiting and which thread(s)
is holding the semaphore. (5 Replies)
Discussion started by: ptprabu
5 Replies
3. UNIX for Advanced & Expert Users
Hi All,
I am going through the semaphore concept and have a doubt regarding the same and hope to get a resolution here.
I have a file which has a number of records.
I want to write an application (in C) which will be able to do concurrent read/write on these records.
Of what I have... (8 Replies)
Discussion started by: maverix
8 Replies
4. Shell Programming and Scripting
Hi,
I am looking to use a semaphore for the first time in one of my scripts. I am just wondering if there are any simple examples or tutorials around?
I am a beginner so the simpler the better :)
Thanks
-Jaken (2 Replies)
Discussion started by: Jaken
2 Replies
5. UNIX for Dummies Questions & Answers
what is semaphore? can any body explain it in a more simple way than the manual ??
replies appreciated
Regards
raguram R (7 Replies)
Discussion started by: raguramtgr
7 Replies
6. Programming
In my server code there is a thread per client...
The server call accept() and after that start the thread.
So there is a thread for client that save in RAM the client's message, that will be send to other clients.
Now in RAM I have created a shared memory in which thread read and write(save)... (2 Replies)
Discussion started by: italian_boy
2 Replies
7. Shell Programming and Scripting
Control two exclusively shared resources(semaphore). The two resources are two files. The producer will write even numbers to one file, and odd numbers to another one. The consumer respectively reads from each file until it gets 5 even numbers and 5 odd numbers.
Can any one help me with the... (0 Replies)
Discussion started by: gokult
0 Replies
8. Programming
If I create a semaphore and then I fork a number of child processes then all the child process use that same semaphore.
Since the process address spaces are different rfom each other then how all the child process are able to access the same semaphore?
I understand that semaphore/mutex is at os... (0 Replies)
Discussion started by: rupeshkp728
0 Replies
9. Solaris
Can anyone tell me abt the Semaphore concept and what is semaphore???
is semaphore id is associated in terms as in resources like semaphore id 1 indicates cpu share unit is given and semaphore id 2 will indicate abt the memore or semaphore id 3 will tell us the i/o components (1 Reply)
Discussion started by: aarjun07
1 Replies
10. UNIX for Beginners Questions & Answers
I was asked to add this piece of code to a c program which I will execute through the shell:
for(long i = 0; i < NITER; i++)
{ sem_wait( &sema);
count++;
sem_post( &sema); }
I didn't get it, which is the critical section ? if it's "count++" how would a thread wake up in order to enter it... (1 Reply)
Discussion started by: uniran
1 Replies
LEARN ABOUT REDHAT
ipc::semaphore
IPC::Semaphore(3pm) Perl Programmers Reference Guide IPC::Semaphore(3pm)
NAME
IPC::Semaphore - SysV Semaphore IPC object class
SYNOPSIS
use IPC::SysV qw(IPC_PRIVATE S_IRWXU IPC_CREAT);
use IPC::Semaphore;
$sem = new IPC::Semaphore(IPC_PRIVATE, 10, S_IRWXU | IPC_CREAT);
$sem->setall( (0) x 10);
@sem = $sem->getall;
$ncnt = $sem->getncnt;
$zcnt = $sem->getzcnt;
$ds = $sem->stat;
$sem->remove;
DESCRIPTION
A class providing an object based interface to SysV IPC semaphores.
METHODS
new ( KEY , NSEMS , FLAGS )
Create a new semaphore set associated with "KEY". "NSEMS" is the number of semaphores in the set. A new set is created if
o "KEY" is equal to "IPC_PRIVATE"
o "KEY" does not already have a semaphore identifier associated with it, and "FLAGS & IPC_CREAT" is true.
On creation of a new semaphore set "FLAGS" is used to set the permissions.
getall
Returns the values of the semaphore set as an array.
getncnt ( SEM )
Returns the number of processes waiting for the semaphore "SEM" to become greater than its current value
getpid ( SEM )
Returns the process id of the last process that performed an operation on the semaphore "SEM".
getval ( SEM )
Returns the current value of the semaphore "SEM".
getzcnt ( SEM )
Returns the number of processes waiting for the semaphore "SEM" to become zero.
id Returns the system identifier for the semaphore set.
op ( OPLIST )
"OPLIST" is a list of operations to pass to "semop". "OPLIST" is a concatenation of smaller lists, each which has three values. The
first is the semaphore number, the second is the operation and the last is a flags value. See semop for more details. For example
$sem->op(
0, -1, IPC_NOWAIT,
1, 1, IPC_NOWAIT
);
remove
Remove and destroy the semaphore set from the system.
set ( STAT )
set ( NAME => VALUE [, NAME => VALUE ...] )
"set" will set the following values of the "stat" structure associated with the semaphore set.
uid
gid
mode (only the permission bits)
"set" accepts either a stat object, as returned by the "stat" method, or a list of name-value pairs.
setall ( VALUES )
Sets all values in the semaphore set to those given on the "VALUES" list. "VALUES" must contain the correct number of values.
setval ( N , VALUE )
Set the "N"th value in the semaphore set to "VALUE"
stat
Returns an object of type "IPC::Semaphore::stat" which is a sub-class of "Class::Struct". It provides the following fields. For a
description of these fields see your system documentation.
uid
gid
cuid
cgid
mode
ctime
otime
nsems
SEE ALSO
IPC::SysV Class::Struct semget semctl semop
AUTHOR
Graham Barr <gbarr@pobox.com>
COPYRIGHT
Copyright (c) 1997 Graham Barr. All rights reserved. This program is free software; you can redistribute it and/or modify it under the
same terms as Perl itself.
perl v5.8.0 2002-06-01 IPC::Semaphore(3pm)