CounterFile(3) User Contributed Perl Documentation CounterFile(3)NAMEFile::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 simulta‐
neously 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 if no environment variable is defined. You may
want to assign a different value to this variable before creating coun‐
ters.
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::Counter‐
File object. This means that you can use the "++" operator for incre‐
menting 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>
perl v5.8.8 2004-01-23 CounterFile(3)
