IPC::Semaphore

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

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 namevalue 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"

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>

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.