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IPC::Semaphore - SysV Semaphore IPC object class


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 Nth 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

the IPC::SysV manpage, the Class::Struct manpage, 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.