# phpman > perldoc > IPC::Semaphore

## NAME
    [IPC::Semaphore](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASemaphore/markdown) - SysV Semaphore IPC object class

## SYNOPSIS
        use [IPC::SysV](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASysV/markdown) qw(IPC_PRIVATE S_IRUSR S_IWUSR IPC_CREAT);
        use [IPC::Semaphore](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASemaphore/markdown);

        $sem = [IPC::Semaphore](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASemaphore/markdown)->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)](https://www.chedong.com/phpMan.php/man/semop/2/markdown) 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](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASemaphore%3A%3Astat/markdown)" which is a sub-class of "[Class::Struct](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3AStruct/markdown)". 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](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASysV/markdown), [Class::Struct](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3AStruct/markdown), [semget(2)](https://www.chedong.com/phpMan.php/man/semget/2/markdown), [semctl(2)](https://www.chedong.com/phpMan.php/man/semctl/2/markdown), [semop(2)](https://www.chedong.com/phpMan.php/man/semop/2/markdown)

## 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.