Provided by: libmail-box-perl_3.010-2_all 
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::FcntlLock
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.
Extends "DESCRIPTION" in Mail::Reporter.
METHODS
Extends "METHODS" in Mail::Reporter.
Constructors
Extends "Constructors" in Mail::Reporter.
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 <undef>
log Mail::Reporter 'WARNINGS'
method 'DOTLOCK'
timeout 10
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).
'FCNTLLOCK' | 'fcntllock'
POSIX locking via File::FcntlLock, which works on more platforms. However, that module
requires a C compiler to install.
'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
Attributes
$obj->expires( [SECONDS] )
Get/Set the expiration time. Not available for all lockers.
$obj->timeout( [SECONDS] )
Get/Set the timeout. Not available for all lockers.
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;
$obj->folder( [$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
Extends "Error handling" in Mail::Reporter.
$obj->AUTOLOAD()
Inherited, see "Error handling" in Mail::Reporter
$obj->addReport($object)
Inherited, see "Error handling" in Mail::Reporter
$obj->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
Mail::Box::Locker->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
Inherited, see "Error handling" in Mail::Reporter
$obj->errors()
Inherited, see "Error handling" in Mail::Reporter
$obj->log( [$level, [$strings]] )
Mail::Box::Locker->log( [$level, [$strings]] )
Inherited, see "Error handling" in Mail::Reporter
$obj->logPriority($level)
Mail::Box::Locker->logPriority($level)
Inherited, see "Error handling" in Mail::Reporter
$obj->logSettings()
Inherited, see "Error handling" in Mail::Reporter
$obj->notImplemented()
Inherited, see "Error handling" in Mail::Reporter
$obj->report( [$level] )
Inherited, see "Error handling" in Mail::Reporter
$obj->reportAll( [$level] )
Inherited, see "Error handling" in Mail::Reporter
$obj->trace( [$level] )
Inherited, see "Error handling" in Mail::Reporter
$obj->warnings()
Inherited, see "Error handling" in Mail::Reporter
Cleanup
Extends "Cleanup" in Mail::Reporter.
$obj->DESTROY()
When the locker is destroyed, for instance when the folder is closed or the program ends, the lock
will be automatically removed.
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 3.010, built on July 18, 2023. Website:
http://perl.overmeer.net/CPAN/
LICENSE
Copyrights 2001-2023 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://dev.perl.org/licenses/
perl v5.36.0 2023-12-11 Mail::Box::Locker(3pm)