IPC::Semaphore(3perl) Perl Programmers Reference Guide IPC::Semaphore(3perl)

IPC::Semaphore - SysV Semaphore IPC object class

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;


A class providing an object based interface to SysV IPC semaphores.

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.

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.
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) for more details. For example

    0, -1, IPC_NOWAIT,
    1,  1, IPC_NOWAIT
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.

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"
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.


IPC::SysV, Class::Struct, semget(2), semctl(2), semop(2)

Graham Barr <gbarr@pobox.com>, Marcus Holland-Moritz <mhx@cpan.org>

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.

2021-05-23 perl v5.34.0