- NAME
- SYNOPSIS
- DESCRIPTION
- METHODS
- SEE ALSO
- AUTHOR
- COPYRIGHT

# 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 `<EM>FLAGS</EM> & 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 `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 you system documentation.

          uid
          gid
          cuid
          cgid
          mode
          ctime
          otime
          nsems

# SEE ALSO

SysV 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.