IPC::Semaphore::Set
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'.
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
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.
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.
Attempts to get a lock on the resource and returns boolean.
Waits until a lock becomes available on the resource then returns 1.
Attempts to get a lock on the resource and dies if it can not. Returns 1 otherwise.
Adds a single point of value to the resource
Returns the number 'value' of the resource, indicating it's current availability.
Returns the number of the resource in its semaphore set
Returns the IPC::Semaphore::Set the resource is a part of.
Same as available, just more traditional language.
Returns a list or arrayref of all the IPC::Semaphore::Set::Resource objects available for this semaphore set.
Returns the numeric system ID of the semaphore set.
Returns the numeric key if available.
Returns the 'word' key if used.
Remove the semaphore set entirely from the system.
Returns the internal 'IPC::Semaphore' object.
To install IPC::Semaphore::Set, copy and paste the appropriate command in to your terminal.
cpanm
cpanm IPC::Semaphore::Set
CPAN shell
perl -MCPAN -e shell install IPC::Semaphore::Set
For more information on module installation, please visit the detailed CPAN module installation guide.