IPC::Semaphore

NAME
SYNOPSIS
DESCRIPTION
METHODS
SEE ALSO
AUTHORS
COPYRIGHT

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 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
```

AUTHORS

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

COPYRIGHT

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

NAME
SYNOPSIS
DESCRIPTION
METHODS
SEE ALSO
AUTHORS
COPYRIGHT