Provided by: libmail-box-perl_3.009-1_all 
NAME
Mail::Box::MH - handle MH folders
INHERITANCE
Mail::Box::MH
is a Mail::Box::Dir
is a Mail::Box
is a Mail::Reporter
SYNOPSIS
use Mail::Box::MH;
my $folder = new Mail::Box::MH folder => $ENV{MAIL}, ...;
DESCRIPTION
This documentation describes how MH mailboxes work, and what you can do with the MH folder
object "Mail::Box::MH".
Extends "DESCRIPTION" in Mail::Box::Dir.
OVERLOADED
Extends "OVERLOADED" in Mail::Box::Dir.
overload: ""
Inherited, see "OVERLOADED" in Mail::Box
overload: @{}
Inherited, see "OVERLOADED" in Mail::Box
overload: cmp
Inherited, see "OVERLOADED" in Mail::Box
METHODS
Extends "METHODS" in Mail::Box::Dir.
Constructors
Extends "Constructors" in Mail::Box::Dir.
Mail::Box::MH->new(%options)
-Option --Defined in --Default
access Mail::Box 'r'
body_delayed_type Mail::Box Mail::Message::Body::Delayed
body_type Mail::Box Mail::Message::Body::Lines
coerce_options Mail::Box []
create Mail::Box <false>
directory Mail::Box::Dir <derived from folder name>
extract Mail::Box 10240
field_type Mail::Box undef
fix_headers Mail::Box <false>
folder Mail::Box $ENV{MAIL}
folderdir Mail::Box $ENV{HOME}/.mh
head_delayed_type Mail::Box Mail::Message::Head::Delayed
head_type Mail::Box Mail::Message::Head::Complete
index undef
index_filename <foldername>/.index
index_type Mail::Box::MH::Index
keep_dups Mail::Box <false>
keep_index 0
labels undef
labels_filename <foldername>/.mh_sequence
labels_type Mail::Box::MH::Labels
lock_file Mail::Box <index_file>
lock_timeout Mail::Box 1 hour
lock_type Mail::Box Mail::Box::Locker::DotLock
lock_wait Mail::Box 10 seconds
locker Mail::Box undef
log Mail::Reporter 'WARNINGS'
manager Mail::Box undef
message_type Mail::Box <folder-class>::Message
multipart_type Mail::Box Mail::Message::Body::Multipart
remove_when_empty Mail::Box <true>
save_on_exit Mail::Box <true>
trace Mail::Reporter 'WARNINGS'
trusted Mail::Box <depends on folder location>
access => MODE
body_delayed_type => CLASS
body_type => CLASS|CODE
coerce_options => ARRAY
create => BOOLEAN
directory => DIRECTORY
extract => INTEGER | CODE | METHOD | 'LAZY'|'ALWAYS'
field_type => CLASS
fix_headers => BOOLEAN
folder => FOLDERNAME
folderdir => DIRECTORY
head_delayed_type => CLASS
head_type => CLASS
index => OBJECT
You may specify an OBJECT of a type which extends Mail::Box::MH::Index (at least
implements a "get()" method), as alternative for an index file reader as created by
"Mail::Box::MH".
index_filename => FILENAME
The FILENAME which is used in each directory to store the headers of all mails. The
filename shall not contain a directory path. (e.g. Do not use
"/usr/people/jan/.index", nor "subdir/.index", but say ".index".)
index_type => CLASS
keep_dups => BOOLEAN
keep_index => BOOLEAN
Keep an index file of the specified mailbox, one file per directory. Using an index
file will speed up things considerably, because it avoids reading all the message
files the moment that you open the folder. When you open a folder, you can use the
index file to retrieve information such as the subject of each message, instead of
having to read possibly thousands of messages.
labels => OBJECT
You may specify an OBJECT of a type which extends Mail::Box::MH::Labels (at least
implements the "get()" method), as alternative for labels file reader as created by
"Mail::Box::MH".
labels_filename => FILENAME
In MH-folders, messages can be labeled, for instance based on the sender or whether
it is read or not. This status is kept in a file which is usually called
".mh_sequences", but that name can be overruled with this flag.
labels_type => CLASS
lock_file => FILENAME
lock_timeout => SECONDS
lock_type => CLASS|STRING|ARRAY
lock_wait => SECONDS
locker => OBJECT
log => LEVEL
manager => MANAGER
message_type => CLASS
multipart_type => CLASS
remove_when_empty => BOOLEAN
save_on_exit => BOOLEAN
trace => LEVEL
trusted => BOOLEAN
The folder
Extends "The folder" in Mail::Box::Dir.
$obj->addMessage($message, %options)
Inherited, see "The folder" in Mail::Box
$obj->addMessages(@messages)
Inherited, see "The folder" in Mail::Box
Mail::Box::MH->appendMessages(%options)
Append a message to a folder which is not open.
-Option --Defined in --Default
folder Mail::Box <required>
message Mail::Box undef
messages Mail::Box undef
share Mail::Box <false>
folder => FOLDERNAME
message => MESSAGE
messages => ARRAY-OF-MESSAGES
share => BOOLEAN
$obj->close(%options)
Inherited, see "The folder" in Mail::Box
$obj->copyTo($folder, %options)
Inherited, see "The folder" in Mail::Box
$obj->delete(%options)
Inherited, see "The folder" in Mail::Box
$obj->directory()
Inherited, see "The folder" in Mail::Box::Dir
$obj->folderdir( [$directory] )
Inherited, see "The folder" in Mail::Box
$obj->name()
Inherited, see "The folder" in Mail::Box
$obj->organization()
Inherited, see "The folder" in Mail::Box
$obj->size()
Inherited, see "The folder" in Mail::Box
$obj->type()
Inherited, see "The folder" in Mail::Box
$obj->update(%options)
Inherited, see "The folder" in Mail::Box
$obj->url()
Inherited, see "The folder" in Mail::Box
Folder flags
Extends "Folder flags" in Mail::Box::Dir.
$obj->access()
Inherited, see "Folder flags" in Mail::Box
$obj->isModified()
Inherited, see "Folder flags" in Mail::Box
$obj->modified( [BOOLEAN] )
Inherited, see "Folder flags" in Mail::Box
$obj->writable()
Inherited, see "Folder flags" in Mail::Box
The messages
Extends "The messages" in Mail::Box::Dir.
$obj->current( [$number|$message|$message_id] )
Inherited, see "The messages" in Mail::Box
$obj->find($message_id)
Inherited, see "The messages" in Mail::Box
$obj->findFirstLabeled( $label, [BOOLEAN, [$msgs]] )
Inherited, see "The messages" in Mail::Box
$obj->message( $index, [$message] )
Inherited, see "The messages" in Mail::Box
$obj->messageId( $message_id, [$message] )
Inherited, see "The messages" in Mail::Box
$obj->messageIds()
Inherited, see "The messages" in Mail::Box
$obj->messages( <'ALL'|$range|'ACTIVE'|'DELETED'|$label| !$label|$filter> )
Inherited, see "The messages" in Mail::Box
$obj->nrMessages(%options)
Inherited, see "The messages" in Mail::Box
$obj->scanForMessages($message, $message_ids, $timespan, $window)
Inherited, see "The messages" in Mail::Box
Sub-folders
Extends "Sub-folders" in Mail::Box::Dir.
$obj->listSubFolders(%options)
Mail::Box::MH->listSubFolders(%options)
Inherited, see "Sub-folders" in Mail::Box
$obj->nameOfSubFolder( $subname, [$parentname] )
Mail::Box::MH->nameOfSubFolder( $subname, [$parentname] )
Inherited, see "Sub-folders" in Mail::Box
$obj->openRelatedFolder(%options)
Inherited, see "Sub-folders" in Mail::Box
$obj->openSubFolder($subname, %options)
Inherited, see "Sub-folders" in Mail::Box
$obj->topFolderWithMessages()
Mail::Box::MH->topFolderWithMessages()
Inherited, see "Sub-folders" in Mail::Box
Internals
Extends "Internals" in Mail::Box::Dir.
$obj->coerce($message, %options)
Inherited, see "Internals" in Mail::Box
$obj->create($foldername, %options)
Mail::Box::MH->create($foldername, %options)
-Option --Defined in--Default
folderdir Mail::Box undef
folderdir => DIRECTORY
$obj->determineBodyType($message, $head)
Inherited, see "Internals" in Mail::Box
$obj->folderToDirectory($foldername, $folderdir)
Inherited, see "Internals" in Mail::Box::Dir
Mail::Box::MH->foundIn( [$foldername], %options )
Inherited, see "Internals" in Mail::Box
$obj->highestMessageNumber()
Returns the highest number which is used in the folder to store a file. This method
may be called when the folder is read (then this number can be derived without file-
system access), but also when the folder is not read (yet).
$obj->index()
Create a index reader/writer object.
$obj->labels()
Create a label reader/writer object.
$obj->lineSeparator( [<STRING|'CR'|'LF'|'CRLF'>] )
Inherited, see "Internals" in Mail::Box
$obj->locker()
Inherited, see "Internals" in Mail::Box
$obj->messageInFile($filename)
Inherited, see "Internals" in Mail::Box::Dir
$obj->read(%options)
Inherited, see "Internals" in Mail::Box
$obj->readMessageFilenames($directory)
Inherited, see "Internals" in Mail::Box::Dir
$obj->readMessages(%options)
Inherited, see "Internals" in Mail::Box
$obj->storeMessage($message)
Inherited, see "Internals" in Mail::Box
$obj->toBeThreaded($messages)
Inherited, see "Internals" in Mail::Box
$obj->toBeUnthreaded($messages)
Inherited, see "Internals" in Mail::Box
$obj->updateMessages(%options)
Inherited, see "Internals" in Mail::Box
$obj->write(%options)
Inherited, see "Internals" in Mail::Box
$obj->writeMessages(%options)
-Option --Defined in --Default
messages Mail::Box <required>
renumber <true>
messages => ARRAY
renumber => BOOLEAN
Permit renumbering of message. By default this is true, but for some unknown
reason, you may be thinking that messages should not be renumbered.
Other methods
Extends "Other methods" in Mail::Box::Dir.
$obj->timespan2seconds($time)
Mail::Box::MH->timespan2seconds($time)
Inherited, see "Other methods" in Mail::Box
Error handling
Extends "Error handling" in Mail::Box::Dir.
$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, $callback] )
Mail::Box::MH->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
Inherited, see "Error handling" in Mail::Reporter
$obj->errors()
Inherited, see "Error handling" in Mail::Reporter
$obj->log( [$level, [$strings]] )
Mail::Box::MH->log( [$level, [$strings]] )
Inherited, see "Error handling" in Mail::Reporter
$obj->logPriority($level)
Mail::Box::MH->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::Box::Dir.
$obj->DESTROY()
Inherited, see "Cleanup" in Mail::Box
DETAILS
Extends "DETAILS" in Mail::Box::Dir.
Different kinds of folders
Extends "Different kinds of folders" in Mail::Box::Dir.
Available folder types
Extends "Available folder types" in Mail::Box::Dir.
Folder class implementation
Extends "Folder class implementation" in Mail::Box::Dir.
How MH folders work
MH-type folders use a directory to store the messages of one folder. Each message is
stored in a separate file. This seems useful, because changes in a folder change only a
few of these small files, in contrast with file-based folders where changes in a folder
cause rewrites of huge folder files.
However, MH-based folders perform very bad if you need header information of all messages.
For instance, if you want to have full knowledge about all message-threads (see
Mail::Box::Thread::Manager) in the folder, it requires to read all header lines in all
message files. And usually, reading your messages in threads is desired.
So, each message is written in a separate file. The filenames are numbers, which count
from 1. Next to these message files, a directory may contain a file named
".mh_sequences", storing labels which relate to the messages. Furthermore, a folder-
directory may contain sub-directories, which are seen as sub-folders.
This implementation
This implementation supports the ".mh-sequences" file and sub-folders. Next to this,
considerable effort it made to avoid reading each message-file. This should boost
performance of the MailBox distribution over other Perl-modules which are able to read
folders.
Folder types which store their messages each in one file, together in one directory, are
bad for performance. Consider that you want to know the subjects of all messages, while
browser through a folder with your mail-reading client. This would cause all message-
files to be read.
Mail::Box::MH has two ways to try improve performance. You can use an index-file, and use
on delay-loading. The combination performs even better. Both are explained in the next
sections.
An index-file
If you specify new(keep_index), then all header-lines of all messages from the folder
which have been read once, will also be written into one dedicated index-file (one file
per folder). The default filename is ".index"
However, index-files are not supported by any other reader which supports MH (as far as I
know). If you read the folders with such I client, it will not cause unrecoverable
conflicts with this index-file, but at most be bad for performance.
If you do not (want to) use an index-file, then delay-loading may save your day.
DIAGNOSTICS
Error: Cannot append message without lock on $folder.
It is impossible to append one or more messages to the folder which is not opened,
because locking it fails. The folder may be in use by an other application, or you
may need to specify some lock related options (see new()).
Error: Cannot create MH folder $name: $!
For some reason, it is impossible to create the folder. Check the permissions and the
name of the folder. Does the path to the directory to be created exist?
Error: Cannot write folder $name without lock.
It is impossible to get a lock on the folder, which means that the changes can not be
made. You may need to tune the lock related options which are available at folder
creation.
Warning: Changes not written to read-only folder $self.
You have opened the folder read-only --which is the default set by new(access)--, made
modifications, and now want to close it. Set close(force) if you want to overrule the
access mode, or close the folder with close(write) set to "NEVER".
Error: Copying failed for one message.
For some reason, for instance disc full, removed by external process, or read-
protection, it is impossible to copy one of the messages. Copying will proceed for
the other messages.
Error: Destination folder $name is not writable.
The folder where the messages are copied to is not opened with write access (see
new(access)). This has no relation with write permission to the folder which is
controlled by your operating system.
Warning: Different messages with id $msgid
The message id is discovered more than once within the same folder, but the content of
the message seems to be different. This should not be possible: each message must be
unique.
Error: Folder $name is opened read-only
You can not write to this folder unless you have opened the folder to write or append
with new(access), or the "force" option is set true.
Error: Folder $name not deleted: not writable.
The folder must be opened with write access via new(access), otherwise removing it
will be refused. So, you may have write-access according to the operating system, but
that will not automatically mean that this "delete" method permits you to. The
reverse remark is valid as well.
Error: Invalid timespan '$timespan' specified.
The string does not follow the strict rules of the time span syntax which is permitted
as parameter.
Warning: Message-id '$msgid' does not contain a domain.
According to the RFCs, message-ids need to contain a unique random part, then an "@",
and then a domain name. This is made to avoid the creation of two messages with the
same id. The warning emerges when the "@" is missing from the string.
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.
Error: Unable to create subfolder $name of $folder.
The copy includes the subfolders, but for some reason it was not possible to copy one
of these. Copying will proceed for all other sub-folders.
Error: Unable to write message for $folder to $filename: $!
The new message could not be written to its new file, for the specific reason.
Error: Writing folder $name failed
For some reason (you probably got more error messages about this problem) it is
impossible to write the folder, although you should because there were changes made.
SEE ALSO
This module is part of Mail-Box distribution version 3.009, built on August 18, 2020.
Website: http://perl.overmeer.net/CPAN/
LICENSE
Copyrights 2001-2020 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/