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Mail::Box::Locker(3pm) User Contributed Perl Documentation Mail::Box::Locker(3pm)
NAME
Mail::Box::Locker - manage the locking of mail folders
INHERITANCE
Mail::Box::Locker
is a Mail::Reporter
Mail::Box::Locker is extended by
Mail::Box::Locker::DotLock
Mail::Box::Locker::Flock
Mail::Box::Locker::Multi
Mail::Box::Locker::Mutt
Mail::Box::Locker::NFS
Mail::Box::Locker::POSIX
SYNOPSIS
use Mail::Box::Locker;
my $locker = new Mail::Box::Locker(folder => $folder);
$locker->lock;
$locker->isLocked;
$locker->hasLock;
$locker->unlock;
use Mail::Box;
my $folder = Mail::Box->new(lock_method => 'DOTLOCK');
print $folder->locker->type;
DESCRIPTION
Each Mail::Box will create its own "Mail::Box::Locker" object which will handle the
locking for it. You can access of the object directly from the folder, as shown in the
examples below.
METHODS
Constructors
Mail::Box::Locker->new(OPTIONS)
Create a new lock. You may do this directly. However, in most cases the lock will not
be separately instantiated but will be the second class in a multiple inheritance
construction with a Mail::Box.
Generally the client program specifies the locking behavior through options given to
the folder class.
Option --Defined in --Default
expires 1 hour
file undef
folder <required>
log Mail::Reporter 'WARNINGS'
method 'DOTLOCK'
timeout 10 seconds
trace Mail::Reporter 'WARNINGS'
. expires => SECONDS
How long can a lock exist? If a different e-mail program leaves a stale lock,
then this lock will be removed automatically after the specified number of
seconds.
. file => FILENAME
Name of the file to lock. By default, the name of the folder is taken.
. folder => FOLDER
Which FOLDER is to be locked, a Mail::Box object.
. log => LEVEL
. method => STRING|CLASS|ARRAY
Which kind of locking, specified as one of the following names as STRING. You may
also specify a CLASS name, or an ARRAY of names. In case of an ARRAY, a 'multi'
locker is started with all thee full CLASS name.
Supported locking names are
'DOTLOCK' | 'dotlock'
The folder handler creates a file which signals that it is in use. This is a
bit problematic, because not all mail-handling software agree on the name of
the file to be created.
On various folder types, the lockfile differs. See the documentation for each
folder, which describes the locking strategy as well as special options to
change the default behavior.
'FLOCK' | 'flock'
For some folder handlers, locking is based on a file locking mechanism
provided by the operating system. However, this does not work on all systems,
such as network filesystems, and such. This also doesn't work on folders based
on directories (Mail::Box::Dir and derived).
'POSIX' | 'posix'
Use the POSIX standard fcntl locking.
'MULTI' | 'multi'
Use ALL available locking methods at the same time, to have a bigger chance
that the folder will not be modified by some other application which uses an
unspecified locking method. When one of the locking methods disallows access,
the locking fails.
'MUTT'| 'mutt'
Use the external program 'mutt_dotlock' to lock and unlock.
'NFS' | 'nfs'
A kind of "dotlock" file-locking mechanism, but adapted to work over NFS.
Extra precaution is needed because an "open O_EXCL" on NFS is not an atomic
action.
'NONE' | 'none'
Do not use locking.
The other option is to produce your own "Mail::Box::Locker" derived class, which
implements the desired locking method. (Please consider offering it for inclusion
in the public Mail::Box module!) Create an instance of that class with this
parameter:
my $locker = Mail::Box::Locker::MyOwn->new;
$folder->open(locker => $locker);
. timeout => SECONDS|'NOTIMEOUT'
How long to wait while trying to acquire the lock. The lock request will fail when
the specified number of seconds is reached. If 'NOTIMEOUT' is specified, the
module will wait until the lock can be taken.
Whether it is possible to limit the wait time is platform- and locking-method-
specific. For instance, the `dotlock' method on Windows will always wait until
the lock has been received.
. trace => LEVEL
The Locker
$obj->filename([FILENAME])
Returns the filename which is used to lock the folder, optionally after setting it to
the specified FILENAME.
example:
print $locker->filename;
$obj->folder
Returns the folder object which is locker.
$obj->name
Returns the method used to lock the folder. See the new(method) for details on how to
specify the lock method. The name of the method is returned in upper-case.
example:
if($locker->name eq 'FLOCK') ...
Locking
$obj->hasLock
Check whether the folder has the lock.
example:
if($locker->hasLock) {...}
if($folder->locker->hasLock) {...}
$obj->isLocked
Test if the folder is locked by this or a different application.
example:
if($locker->isLocked) {...}
if($folder->locker->isLocked) {...}
$obj->lock(FOLDER)
Get a lock on a folder. This will return false if the lock fails.
example:
die unless $locker->lock;
if($folder->locker->lock) {...}
$obj->unlock
Undo the lock on a folder.
example:
$locker->unlock;
$folder->locker->unlock;
Error handling
$obj->AUTOLOAD
See "Error handling" in Mail::Reporter
$obj->addReport(OBJECT)
See "Error handling" in Mail::Reporter
$obj->defaultTrace([LEVEL]|[LOGLEVEL, TRACELEVEL]|[LEVEL, CALLBACK])
Mail::Box::Locker->defaultTrace([LEVEL]|[LOGLEVEL, TRACELEVEL]|[LEVEL, CALLBACK])
See "Error handling" in Mail::Reporter
$obj->errors
See "Error handling" in Mail::Reporter
$obj->log([LEVEL [,STRINGS]])
Mail::Box::Locker->log([LEVEL [,STRINGS]])
See "Error handling" in Mail::Reporter
$obj->logPriority(LEVEL)
Mail::Box::Locker->logPriority(LEVEL)
See "Error handling" in Mail::Reporter
$obj->logSettings
See "Error handling" in Mail::Reporter
$obj->notImplemented
See "Error handling" in Mail::Reporter
$obj->report([LEVEL])
See "Error handling" in Mail::Reporter
$obj->reportAll([LEVEL])
See "Error handling" in Mail::Reporter
$obj->trace([LEVEL])
See "Error handling" in Mail::Reporter
$obj->warnings
See "Error handling" in Mail::Reporter
Cleanup
$obj->DESTROY
When the locker is destroyed, for instance when the folder is closed or the program
ends, the lock will be automatically removed.
$obj->inGlobalDestruction
See "Cleanup" in Mail::Reporter
DIAGNOSTICS
Error: Package $package does not implement $method.
Fatal error: the specific package (or one of its superclasses) does not implement this
method where it should. This message means that some other related classes do
implement this method however the class at hand does not. Probably you should
investigate this and probably inform the author of the package.
SEE ALSO
This module is part of Mail-Box distribution version 2.082, built on April 28, 2008.
Website: http://perl.overmeer.net/mailbox/
LICENSE
Copyrights 2001-2008 by Mark Overmeer. For other contributors see ChangeLog.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself. See http://www.perl.com/perl/misc/Artistic.html
perl v5.10.0 2008-04-28 Mail::Box::Locker(3pm)
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