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IPC::Semaphore

Section: Perl Programmers Reference Guide (3)
Updated: 2001-09-21
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NAME

IPC::Semaphore - SysV Semaphore IPC object class  

SYNOPSIS

    use IPC::SysV qw(IPC_PRIVATE S_IRWXU IPC_CREAT);
    use IPC::Semaphore;

    $sem = new IPC::Semaphore(IPC_PRIVATE, 10, S_IRWXU | 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.

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 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 "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 semctl semop  

AUTHOR

Graham Barr <gbarr@pobox.com>  

COPYRIGHT

Copyright (c) 1997 Graham Barr. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


 

Index

NAME
SYNOPSIS
DESCRIPTION
METHODS
SEE ALSO
AUTHOR
COPYRIGHT




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