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IPC::Semaphore.3perl

NAME

IPC::Semaphore - SysV Semaphore IPC object class

SYNOPSIS

     use IPC::SysV qw(IPC_PRIVATE S_IRUSR S_IWUSR IPC_CREAT);
     use IPC::Semaphore;
 
     $sem = IPC::Semaphore->new(IPC_PRIVATE, 10, S_IRUSR | S_IWUSR | 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

•

"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. Be careful not to set any flags that the Sys V IPC implementation does not allow: in some systems setting execute bits makes the operations fail.

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

AUTHORS

Graham Barr <gbarr@pobox.com>, Marcus Holland-Moritz <mhx@cpan.org>

COPYRIGHT

Version 2.x, Copyright (C) 2007, Marcus Holland-Moritz.

Version 1.x, Copyright (c) 1997, Graham Barr.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.