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CONTENTS

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

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

  • KEY is equal to IPC_PRIVATE

  • 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 processed waiting for the semaphore SEM to become greater than it's 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 processed 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 (oly 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 Nth 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 you 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.