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📛 NAME

IPC::Semaphore - SysV Semaphore IPC object class

🚀 Quick Reference

Use Case	Command	Description
Create semaphore set	$sem = IPC::Semaphore->new($key, $nsems, $flags)	Create a set with a key, number of semaphores, and access flags
Get all values	@values = $sem->getall	Return all semaphore values as an array
Get wait count (increase)	$ncnt = $sem->getncnt($sem_num)	Number of processes waiting for semaphore to become greater
Get PID of last operation	$pid = $sem->getpid($sem_num)	PID of last process that performed an operation on the semaphore
Get current value	$val = $sem->getval($sem_num)	Current value of a specific semaphore
Get wait count (zero)	$zcnt = $sem->getzcnt($sem_num)	Number of processes waiting for semaphore to become zero
Perform operations	$sem->op(@oplist)	Pass a list of semaphore operations (number, operation, flags)
Set all values	$sem->setall(@values)	Set every semaphore in the set at once
Set a single value	$sem->setval($n, $value)	Set the value of semaphore N
Get stat object	$ds = $sem->stat	Return an object with uid, gid, mode, etc.
Remove semaphore set	$sem->remove	Destroy and remove the semaphore set from the system

🔖 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(2) 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) or set(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

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

✍️ AUTHORS

Graham Barr <gbarr AT pobox.com>, Marcus Holland-Moritz <mhx AT 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.

📛 NAME 🚀 Quick Reference 🔖 SYNOPSIS 📖 DESCRIPTION 🛠️ METHODS 🔗 SEE ALSO ✍️ AUTHORS © COPYRIGHT