Vend::CounterFile(3pm)					User Contributed Perl Documentation				    Vend::CounterFile(3pm)

NAME

       Vend::CounterFile - Persistent counter class

SYNOPSIS

	use Vend::CounterFile;
	$c = new Vend::CounterFile "COUNTER", "aa00";

	$id = $c->inc;
	open(F, ">F$id");

DESCRIPTION

       (This module is modified from Gisle Aas File::CounterFile to use
	Interchange's locking protocols -- lack of fcntl locking was causing
	counter problems.)

       This module implements a persistent counter class.  Each counter is represented by a separate file in the file system.  File locking is
       applied, so multiple processes might try to access the same counters at the same time without risk of counter destruction.

       You give the file name as the first parameter to the object constructor ("new").  The file is created if it does not exist.

       If the file name does not start with "/" or ".", then it is interpreted as a file relative to $Vend::CounterFile::DEFAULT_DIR.  The default
       value for this variable is initialized from the environment variable "TMPDIR", or /usr/tmp is no environment variable is defined.  You may
       want to assign a different value to this variable before creating counters.

       If you pass a second parameter to the constructor, that sets the initial value for a new counter.  This parameter only takes effect when
       the file is created (i.e. it does not exist before the call).

       When you call the "inc()" method, you increment the counter value by one. When you call "dec()" the counter value is decrementd.  In both
       cases the new value is returned.  The "dec()" method only works for numerical counters (digits only).

       You can peek at the value of the counter (without incrementing it) by using the "value()" method.

       The counter can be locked and unlocked with the "lock()" and "unlock()" methods.  Incrementing and value retrieval is faster when the
       counter is locked, because we do not have to update the counter file all the time.  You can query whether the counter is locked with the
       "locked()" method.

       There is also an operator overloading interface to the Vend::CounterFile object.  This means that you might use the "++" operator for
       incrementing the counter, "--" operator for decrementing and you can interpolate counters diretly into strings.

BUGS

       (This problem alleviated by this modified module)

       It uses flock(2) to lock the counter file.  This does not work on all systems.  Perhaps we should use the File::Lock module?

COPYRIGHT

       Copyright (c) 1995-1998 Gisle Aas. All rights reserved.	Modifications made by and copyright (C) 2002 Red Hat, Inc.  and (c) 2002-2007
       Interchange Development Group

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

AUTHOR

       Gisle Aas <aas@sn.no>

perl v5.14.2							    2010-03-25						    Vend::CounterFile(3pm)