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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(2) 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(2), semctl(2), semop(2)

AUTHORS

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

COPYRIGHT

       Version 2.x, Copyright (C) 2007-2013, 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.