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

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

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.
Returns the number of processes waiting for the semaphore "SEM" to become greater than its current value
Returns the process id of the last process that performed an operation on the semaphore "SEM".
Returns the current value of the semaphore "SEM".
Returns the number of processes waiting for the semaphore "SEM" to become zero.
Returns the system identifier for the semaphore set.
"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 and destroy the semaphore set from the system.
"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.

Sets all values in the semaphore set to those given on the "VALUES" list. "VALUES" must contain the correct number of values.
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. 

    uid
    gid
    cuid
    cgid
    mode
    ctime
    otime
    nsems

SEE ALSO

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

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.

2025-07-11 perl v5.42.0