IPC::Semaphore(3perl)					 Perl Programmers Reference Guide				     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

	   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.  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) 2007-2010, 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.

perl v5.14.2							    2011-09-19						     IPC::Semaphore(3perl)