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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_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.



perl v5.12.5                                     2012-11-03                              IPC::Semaphore(3pm)