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 _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 )

  • 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 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@pobox.com, Marcus Holland-Moritz mhx@cpan.org