Ubuntu Manpage: IPC::Semaphore - SysV Semaphore IPC object class

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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
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>

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