NAME
    IPC::Semaphore::Set

DESCRIPTION
    An abstract interface to semaphore sets and their resources.

    A semaphore is an abstract data type that is provided by the system to
    give access control to common resources by multiple processes in
    parallel programming or in a multi-user environment.

    A semaphore 'set' is the set of resources the system provides by an
    identification number, and the values (availability) of those resources.

    You could, for instance, use a semaphore to lock on a single file
    between multiple processes by saying that the set has one resource (one
    file) and that the resource has one availability (one process can use it
    at one time). You could also represent a series of network printers.
    Perhaps you have five printers that all have the ability to do ten jobs.
    You could create the semaphore set with five resources, each resource
    with ten availability.

    This module tries to "Do The Right Thing". It assumes a lot about what
    you're looking for when you call '->new', and basically will set you up
    with a semaphore set that has at least one resource with at least one
    availability. If this assumption is wrong for your purposes, pay close
    attention to the options for '->new'.

SYNOPSIS
    Get/Create a semaphore set:

            my $semset = IPC::Semaphore::Set->new(
                    key_name     => 'my_lock',
                    resources    => 2,
                    availability => 3,
            );

    The above semaphore set has two resource, each of those resources has an
    availability of three.

    Now you can get the first resource (resource 0):

            my $resource = $semset->resource;

    Or you can select the resource explicitly:

            my $resource = $semset->resource(1);

    But note that with two resources total, one is our last resource because
    we start at "0".

    You can make conditionals checking whether or not a lock is available on
    the resource:

            if ($semset->resource->lock) {
                    # ... can use resource!
            } else {
                    # ... can't use resource!
            }

    You can simply wait for resource availability:

            $semset->resource->lockWait;
            # ... resource is now available

    You can die if the resource isn't currently available:

            $semset->resource->lockOrDie;
            # ... if we're here we have a lock

METHODS
    new Get a new IPC::Semaphore::Set object. If 'key' is provided, get or
        create a semaphore with that key. if 'key_name' is provided,
        generate a key based off of the ascii character codes of that name.
        If neither is provided, a new 'private' semaphore set will be
        created (note that 'private' is how SysV refers to it, but this is
        something of a misnomer).

        New uses the following flags by default:

                S_IRUSR | S_IWUSR | IPC_CREAT | SEM_UNDO

        Which means it creates it if it doesn't exist, keeps track of
        ownership, and will clean up it's changes after exit.

    resource
        Returns a IPC::Semaphore::Set::Resource object given the resource
        number, or the last Resource accessed by number.

        If a number isn't passed to it, and it hasn't yet encountered a
        resource, it assumes resource 0 (the first resource in the set) is
        what you wanted and tries to get that.

        RESOURCE METHODS

            lock
                Attempts to get a lock on the resource and returns boolean.

            lockWait
                Waits until a lock becomes available on the resource then
                returns 1.

            lockOrDie
                Attempts to get a lock on the resource and dies if it can
                not. Returns 1 otherwise.

            unlock
                Unlocks on the resource manually (this will also happen when
                the program exits).

            available
                Returns the number 'value' of the resource, indicating it's
                current availability.

            number
                Returns the number of the resource in its semaphore set

            set Returns the IPC::Semaphore::Set the resource is a part of.

            value
                Same as available, just more traditional language.

    resources
        Returns a list or arrayref of all the IPC::Semaphore::Set::Resource
        objects available for this semaphore set.

    id  Returns the numeric system ID of the semaphore set.

    key Returns the numeric key if available.

    keyName
        Returns the 'word' key if used.

    remove
        Remove the semaphore set entirely from the system.

    sem Returns the internal 'IPC::Semaphore' object.