1NAME 2 File::CounterFile - Persistent counter class 3 4SYNOPSIS 5 use File::CounterFile; 6 $c = File::CounterFile->new("COUNTER", "aa00"); 7 8 $id = $c->inc; 9 open(F, ">F$id"); 10 11DESCRIPTION 12 This module implements a persistent counter class. Each counter is 13 represented by a separate file in the file system. File locking is 14 applied, so multiple processes might try to access the same counters at 15 the same time without risk of counter destruction. 16 17 You give the file name as the first parameter to the object constructor 18 ("new"). The file is created if it does not exist. 19 20 If the file name does not start with "/" or ".", then it is interpreted 21 as a file relative to $File::CounterFile::DEFAULT_DIR. The default value 22 for this variable is initialized from the environment variable "TMPDIR", 23 or /usr/tmp is no environment variable is defined. You may want to 24 assign a different value to this variable before creating counters. 25 26 If you pass a second parameter to the constructor, that sets the initial 27 value for a new counter. This parameter only takes effect when the file 28 is created (i.e. it does not exist before the call). 29 30 When you call the "inc()" method, you increment the counter value by 31 one. When you call "dec()" the counter value is decrementd. In both 32 cases the new value is returned. The "dec()" method only works for 33 numerical counters (digits only). 34 35 You can peek at the value of the counter (without incrementing it) by 36 using the "value()" method. 37 38 The counter can be locked and unlocked with the "lock()" and "unlock()" 39 methods. Incrementing and value retrieval is faster when the counter is 40 locked, because we do not have to update the counter file all the time. 41 You can query whether the counter is locked with the "locked()" method. 42 43 There is also an operator overloading interface to the File::CounterFile 44 object. This means that you might use the "++" operator for incrementing 45 the counter, "--" operator for decrementing and you can interpolate 46 counters diretly into strings. 47 48COPYRIGHT 49 Copyright (c) 1995-1998,2002,2003 Gisle Aas. All rights reserved. 50 51 This library is free software; you can redistribute it and/or modify it 52 under the same terms as Perl itself. 53 54AUTHOR 55 Gisle Aas <gisle@aas.no> 56 57