NAME
    File::CounterFile - Persistent counter class

SYNOPSIS
     use File::CounterFile;
     $c = new File::CounterFile "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 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
    `$File::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
    File::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
    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.

    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>

