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# IPC::Semaphore

Perl 5 version 10.1 documentation
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# IPC::Semaphore

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

# 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 `<i>FLAGS</i> & 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.

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- NAME
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- SEE ALSO
- AUTHORS
- COPYRIGHT

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