Provided by: libmail-box-perl_3.009-1_all bug

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/