Mail::Box::File(3pm)

📦
version 4.02 · 9 versions
, in ubuntu stonking

💖 NAME 💖

Mail::Box::File(3pm) — from the User Contributed Perl Documentation — handles file-based folders. Bestie, this is the manpage for it, and it's iconic. 🎀

🌈 INHERITANCE 🌈

Like, the family tree goes:

  • Mail::Box::File
    • is a Mail::Box
    • is a Mail::Reporter
  • Mail::Box::File is extended by
    • Mail::Box::Mbox

✨ SYNOPSIS ✨

(Yeah bestie, this one's empty. Nothing to see here, moving on. 💅)

🦋 DESCRIPTION 🦋

So Mail::Box::File is the base-class for all file-based folders — meaning folders that bundle multiple messages into one single file. 🫶 Usually those messages get separated by a special line that says "hey, the next one starts here."

Extends "DESCRIPTION" in Mail::Box.

💜 OVERLOADED 💜

Extends "OVERLOADED" in Mail::Box.

  • overload: '""' stringification — inherited, see "OVERLOADED" in Mail::Box
  • overload: '@{}' use as ARRAY — inherited, see "OVERLOADED" in Mail::Box
  • overload: cmp string comparison — inherited, see "OVERLOADED" in Mail::Box

👑 METHODS 👑

Extends "METHODS" in Mail::Box.

🧚 Constructors

Extends "Constructors" in Mail::Box.

  • $class->new(%options) — inherited, see "Constructors" in Mail::Box

Okay so here's the whole options lineup, with where each one comes from and what it defaults to:

  • access — from Mail::Box, default 'r'
  • body_delayed_type — from Mail::Box, default Mail::Message::Body::Delayed
  • body_type — default <see description>
  • coerce_options — from Mail::Box, default +[]
  • create — from Mail::Box, default false
  • extract — from Mail::Box, default 10240
  • field_type — from Mail::Box, default undef
  • fix_headers — from Mail::Box, default false
  • folder — from Mail::Box, default $ENV{MAIL}
  • folderdir — from Mail::Box, default $ENV{HOME}.'/Mail'
  • head_delayed_type — from Mail::Box, default Mail::Message::Head::Delayed
  • head_type — from Mail::Box, default Mail::Message::Head::Complete
  • keep_dups — from Mail::Box, default false
  • lock_extension — default '.lock'
  • lock_file — from Mail::Box, default <foldername><lock-extension>
  • lock_timeout — from Mail::Box, default 1 hour
  • lock_type — from Mail::Box, default Mail::Box::Locker::DotLock
  • lock_wait — from Mail::Box, default 10 seconds
  • locker — from Mail::Box, default undef
  • manager — from Mail::Box, default undef
  • message_type — from Mail::Box, default Mail::Box::File::Message
  • multipart_type — from Mail::Box, default Mail::Message::Body::Multipart
  • remove_when_empty — from Mail::Box, default true
  • save_on_exit — from Mail::Box, default true
  • trusted — from Mail::Box, default <depends on folder location>
  • write_policy — default undef

And now the deets on each one, in order:

  • access => $mode
  • body_delayed_type => CLASS
  • body_type => CLASS|CODE — so the default body_type option for File folders is what makes messages bigger than 10kB get stored in files, and smaller ones stay in memory. It's implemented like this:
sub determine_body_type($$)
{   my $head = shift;
    my $size = shift || 0;
    'Mail::Message::Body::' . ($size > 10000 ? 'File' : 'Lines');
}
  • coerce_options => ARRAY
  • create => BOOLEAN
  • extract => INTEGER|CODE|METHOD|'LAZY'|'ALWAYS'
  • field_type => $class
  • fix_headers => BOOLEAN
  • folder => $name
  • folderdir => $directory
  • head_delayed_type => $class
  • head_type => $class
  • keep_dups => BOOLEAN
  • lock_extension => $file|STRING — when the dotlock locking mechanism is in play, the lock gets created with a hardlink to the folder file. For Mail::Box::File type folders, this filename is by default the folder-file itself, followed by .lock. Example bestie: the Mail/inbox folder file will have a hardlink made as Mail/inbox.lock.

You can pass an absolute $file, a relative (to the folder's directory) filename, or an extension (preceded by a dot). So valid examples are:

.lock                  # appended to the folder's filename
my_own_lockfile.test   # full filename, same dir
/etc/passwd            # somewhere else

When the program runs with less privileges (as a normal user), often the default inbox folder can not be locked with the lockfile name that gets produced by default. 😭

  • lock_file => $file
  • lock_timeout => $seconds
  • lock_type => $class|$name|\@names
  • lock_wait => $seconds
  • locker => $locker
  • manager => $manager
  • message_type => $class
  • multipart_type => CLASS
  • remove_when_empty => BOOLEAN
  • save_on_exit => BOOLEAN
  • trusted => BOOLEAN
  • write_policy => 'REPLACE'|'INPLACE'|undef — sets the default write policy, which acts as the default for a later call to write(policy). With undef, the best policy gets autodetected. ✨

🌸 Attributes

Extends "Attributes" in Mail::Box.

  • $obj->filename() — returns the filename for this folder, which may be an absolute or relative path to the file. » example:
print $folder->filename;
  • $obj->fixHeaders() — inherited, see "Attributes" in Mail::Box
  • $obj->folderdir( [$directory] ) — inherited, see "Attributes" in Mail::Box
  • $obj->isTrusted() — inherited, see "Attributes" in Mail::Box
  • $obj->name() — inherited, see "Attributes" in Mail::Box
  • $obj->removeEmpty() — inherited, see "Attributes" in Mail::Box
  • $obj->type() — inherited, see "Attributes" in Mail::Box

🎀 The folder

Extends "The folder" in Mail::Box.

  • $obj->addMessage($message, %options) — inherited, see "The folder" in Mail::Box
  • $obj->addMessages(@messages) — inherited, see "The folder" in Mail::Box
  • $class->appendMessages(%options) — appending messages to a file based folder that is not opened is a little risky, ngl. In practice this often gets done without locking the folder, so another application may write to the folder at the same time... 😭 Hopefully everything goes fast enough that the chance on collision stays small.

All %options of Mail::Box::Mbox::new() can be supplied. Improves base, see "The folder" in Mail::Box.

Here's the option rundown:

  • folder — from Mail::Box, default <required>
  • lock_type — default NONE
  • message — from Mail::Box, default undef
  • messages — from Mail::Box, default undef
  • share — from Mail::Box, default false

And now the details:

  • folder => $name
  • lock_type => ... — see Mail::Box::new(lock_type) for the possible values.
  • message => $message
  • messages => $message|\@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->organization() — inherited, see "The folder" in Mail::Box
  • $obj->size() — 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.

  • $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.

  • $obj->current( [$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.

  • $any->listSubFolders(%options) — inherited, see "Sub-folders" in Mail::Box
  • $any->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
  • $any->topFolderWithMessages() — inherited, see "Sub-folders" in Mail::Box

⭐ Internals

Extends "Internals" in Mail::Box.

  • $obj->coerce($message, %options) — inherited, see "Internals" in Mail::Box
  • $any->create($foldername, %options) — inherited, see "Internals" in Mail::Box

The one option here:

  • folderdir — from Mail::Box, default undef

And in detail:

  • folderdir => $directory
  • $obj->determineBodyType($message, $head) — inherited, see "Internals" in Mail::Box
  • $any->folderToFilename( $foldername, $folderdir, [$subext] ) — translates a $foldername into a filename, using the $folderdir value to replace a leading <=. The optional $subext is only used for MBOX folders.
  • $class->foundIn( [$foldername], %options ) — inherited, see "Internals" in Mail::Box
  • $obj->lineSeparator( [<STRING|'CR'|'LF'|'CRLF'>] ) — inherited, see "Internals" in Mail::Box
  • $obj->locker() — inherited, see "Internals" in Mail::Box
  • $obj->messageCreateOptions( [$type, $config] ) — returns a key-value list of options to be used each time a new message is read from a file. The list is preceded by the $type of message which has to be created.

This data is used by readMessages() and updateMessages(). With $type and $config, a new configuration is set.

  • $obj->moveAwaySubFolder($directory, $extension) — the $directory gets renamed by appending the $extension, which defaults to ".d", to make place for a folder file on that specific location. false is returned if this failed.
  • $obj->parser() — creates a parser for this mailbox. The parser stays alive as long as the folder is open. 🫶
  • $obj->read(%options) — inherited, see "Internals" in Mail::Box
  • $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, so go read "Internals" in Mail::Box, bestie ✨
  • $obj->updateMessages(%options) — for file-based folders, the file handle stays open until the folder is closed. Update is therefore rather simple: move to the end of the last known message, and keep reading... improves base, see "Internals" in Mail::Box 💅
  • $obj->write(%options) — inherited, see "Internals" in Mail::Box. The options hit different though, so look:
 -Option      --Defined in     --Default
  force         Mail::Box        false
  policy                         undef
  save_deleted  Mail::Box        false
  • force => BOOLEAN — inherited from Mail::Box, default false. It's giving "do it anyway" energy.
  • policy => 'REPLACE'|'INPLACE'|undef — in what way will the mail folder be updated? If you don't specify it during the write, the value of new(write_policy) from folder creation gets taken. Valid values are:
    • "REPLACE" — first a new folder is written in the same directory as the folder that has to be updated, and then a call to move will throw away the old one, immediately replacing it by the new. Writing in REPLACE mode is slightly optimized: messages that aren't modified are copied from file to file, byte by byte. That's much faster than printing the data, which is what happens for modified messages. Slay.
    • "INPLACE" — the original folder file will be opened read/write. All messages that weren't changed are left untouched, until the first deleted or modified message is detected. All further messages are printed again.
    • "undef" — as default, or when undef is explicitly specified, first REPLACE mode is tried. Only when that fails, an INPLACE update is performed.

INPLACE will be much faster than REPLACE when applied on large folders, however it requires the truncate function to be implemented on your operating system (at least available for recent versions of Linux, Solaris, Tru64, HPUX). It's also dangerous: when the program is interrupted during the update process, the folder is corrupted. Data may be lost. 😭

However, in some cases it's not possible to write the folder with REPLACE. For instance, the usual incoming mail folder on UNIX is stored in a directory where a user cannot write. Of course, the root and mail users can, but if you want to use this Perl module with permission of a normal user, you can only get it to work in INPLACE mode. Be warned that in this case folder locking via a lockfile is not possible as well.

  • save_deleted => BOOLEAN — inherited from Mail::Box, default false. Just a boolean, bestie.
  • $obj->writeMessages(%options) — inherited, see "Internals" in Mail::Box.

✨ Other methods ✨

Extends "Other methods" in Mail::Box.

  • $any->timespan2seconds($time) — inherited, see "Other methods" in Mail::Box.

💅 Error handling 💅

Extends "Error handling" in Mail::Box.

  • $obj->AUTOLOAD() — inherited, see "Error handling" in Mail::Reporter.
  • $obj->notImplemented() — inherited, see "Error handling" in Mail::Reporter.

🧹 Cleanup 🧹

Extends "Cleanup" in Mail::Box.

  • $obj->DESTROY() — inherited, see "Cleanup" in Mail::Box.

👑 DETAILS 👑

Extends "DETAILS" in Mail::Box.

🌸 Different kinds of folders 🌸

Extends "Different kinds of folders" in Mail::Box.

🦋 Available folder types 🦋

Extends "Available folder types" in Mail::Box.

🎀 Folder class implementation 🎀

Extends "Folder class implementation" in Mail::Box.

💖 File based folders 💖

File based folders maintain a folder (a set of messages) in one single file. The advantage is that your folder has only one single name, which speeds up access to all messages at once.

The disadvantage over directory based folders (see Mail::Box::Dir) is that you have to construct some means to keep all messages apart, for instance by adding a message separator, and this will cause problems. Where access to all messages at once is faster in file based folders, access to a single message is (much) slower, because the whole folder must be read. 💀

🚨 DIAGNOSTICS 🚨

  • Error: cannot append messages to folder file $file: $! — Appending messages to a not-opened file-organized folder may fail when the operating system does not allow write access to the file at hand. Cast by appendMessages().
  • Fault: cannot create directory $dir for folder $name: $! — While creating a file-organized folder, at most one level of directories is created above it. Apparently, more levels of directories are needed, or the operating system does not allow you to create the directory. Cast by create().
  • Fault: cannot create folder file $file: $! — The file-organized folder file cannot be created for the indicated reason. In common cases, the operating system does not grant you write access to the directory where the folder file should be stored. Cast by create().
  • Error: cannot get a lock on $type folder $name. — Cast by new().
  • Fault: cannot move away sub-folder $dir: $! — Cast by moveAwaySubFolder().
  • Warning: cannot remove folder $name file $filename: $! — Writing an empty folder will usually cause that folder to be removed, which fails for the indicated reason. new(remove_when_empty) controls whether the empty folder will be removed; setting it to "false" (0) may be needed to avoid this message. Cast by write().
  • Fault: cannot replace $to by $from to update folder $name: $! — The replace policy wrote a new folder file to update the existing one, but was unable to give the final touch: replacing the old version of the folder file for the indicated reason. Cast by write().
  • Warning: changes not written to read-only folder $name. — 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". Cast by close().
  • Error: class $package does not implement method $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. Cast by notImplemented().
  • Error: copying failed for one message. — For some reason, for instance disk full, removed by external process, or read-protection, it is impossible to copy one of the messages. Copying will proceed for the other messages. Cast by copyTo().
  • 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. Cast by copyTo().
  • 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. Cast by messageId().
  • Error: file $name too short to get write message $msgnr ($size < $expect) — Mail::Box is lazy: it tries to leave messages in the folders until they are used, which saves time and memory usage. When this message appears, something is terribly wrong: some lazy messages are needed for updating the folder, but they cannot be retrieved from the original file anymore. In this case, messages can be lost.

This message does appear regularly on Windows systems when using the 'replace' write policy. Please help to find the cause, probably something to do with Windows incorrectly handling multiple filehandles open in the same file. Cast by write().

  • Warning: folder $name file $file is write-protected. — The folder is opened writable or for appending via new(access), but the operating system does not permit writing to the $file. The folder will be opened read-only. Cast by new().
  • Warning: 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. Cast by delete().
  • Error: folder file $name does not exist. — Cast by new().
  • Error: invalid timespan '$span'. — The string does not follow the strict rules of the time span syntax which is permitted as parameter. Cast by timespan2seconds().
  • 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. Cast by messageId().
  • Error: unable to update folder $name. — When a folder is to be written, both replace and inplace write policies are tried. If both fail, the whole update fails. You may see other, related, error messages to indicate the real problem. Cast by write().
  • Error: unknown value to folder->close(write => $when). — Cast by close().
  • Error: you cannot add a message which is already part of a folder to a new one. Please use moveTo or copyTo. — Cast by addMessage().

🌈 SEE ALSO 🌈

This module is part of Mail-Box version 4.02, built on April 10, 2026. Website: http://perl.overmeer.net/CPAN/

📜 LICENSE 📜

For contributors see file ChangeLog.

This software is copyright (c) 2001-2026 by Mark Overmeer.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

okurrr that's literally the whole page bestie 🫶 this was Mail::Box::File(3pm) from perl v5.40.1, dated 2026-05-09 — go lock your folders, drink some water, and stay iconic 👑💖 mwah

📦 where this page comes from