NAME

       File::CounterFile - Persistent counter class

SYNOPSIS

        use File::CounterFile;
        $c = File::CounterFile->new("COUNTER", "aa00");

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

DESCRIPTION

       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 can attempt to access a counter
       simultaneously 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
       $File::CounterFile::DEFAULT_DIR.  The default value for this variable is initialized from the environment
       variable "TMPDIR", or /var/tmp if 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, it 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 decremented.  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 are 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 File::CounterFile object.  This means that you can
       use the "++" operator for incrementing and the "--" operator for decrementing the counter, and you can
       interpolate counters directly into strings.

COPYRIGHT

       Copyright (c) 1995-1998,2002,2003 Gisle Aas. All rights reserved.

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

AUTHOR

       Gisle Aas <gisle@aas.no>