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

# [NAME](#NAME)

IPC::Semaphore - SysV Semaphore IPC object class

# [SYNOPSIS](#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](#DESCRIPTION)

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

# [METHODS](#METHODS)

[new ( KEY , NSEMS , FLAGS )](#new)

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](#getall)

Returns the values of the semaphore set as an array.

[getncnt ( SEM )](#getncnt)

Returns the number of processes waiting for the semaphore "SEM" to become greater than its current value

[getpid ( SEM )](#getpid)

Returns the process id of the last process that performed an operation on the semaphore "SEM".

[getval ( SEM )](#getval)

Returns the current value of the semaphore "SEM".

[getzcnt ( SEM )](#getzcnt)

Returns the number of processes waiting for the semaphore "SEM" to become zero.

[id](#id)

Returns the system identifier for the semaphore set.

[op ( OPLIST )](#op)

"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)](/man/os/perl/semop.2) for more details. For example

```
    $sem->op(
        0, -1, IPC_NOWAIT,
        1,  1, IPC_NOWAIT
    );
    
```

[remove](#remove)

Remove and destroy the semaphore set from the system.

[set ( STAT )](#set)

[set ( NAME => VALUE \[, NAME => VALUE ...\] )](#set~2)

"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 )](#setall)

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 )](#setval)

Set the "N"th value in the semaphore set to "VALUE"

[stat](#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](#SEE_ALSO)

IPC::SysV, Class::Struct, [**semget**(2)](/man/os/perl/semget.2), [**semctl**(2)](/man/os/perl/semctl.2), [**semop**(2)](/man/os/perl/semop.2)

# [AUTHORS](#AUTHORS)

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

# [COPYRIGHT](#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.

2026-10-26 perl v5.44.0

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Document: IPC::Semaphore(3pm) from perl 5.44.0-r3 (Chainguard OS)
Source: https://github.com/Perl/perl5.git