phpMan > perldoc > Mail::Message::Head

NAME
    Mail::Message::Head - the header of one message

INHERITANCE
     Mail::Message::Head
       is a Mail::Reporter

     Mail::Message::Head is extended by
       Mail::Message::Head::Complete
       Mail::Message::Head::Delayed
       Mail::Message::Head::Subset

SYNOPSIS
     my $head = Mail::Message::Head->new;
     $head->add('From: me@localhost');
     $head->add(From => 'me@localhost');
     $head->add(Mail::Message::Field->new(From => 'me'));
     my $subject = $head->get('subject');
     my @rec = $head->get('received');
     $head->delete('From');

DESCRIPTION
    "Mail::Message::Head" MIME headers are part of Mail::Message messages, which are grouped in
    Mail::Box folders.

    ATTENTION!!! most functionality about e-mail headers is described in
    Mail::Message::Head::Complete, which is a matured header object. Other kinds of headers will be
    translated to that type when time comes.

    On this page, the general methods which are available on any header are described. Read about
    differences in the sub-class specific pages.

    Extends "DESCRIPTION" in Mail::Reporter.

OVERLOADED
    overload: ""
        (stringifaction) The header, when used as string, will format as if
        Mail::Message::Head::Complete::string() was called, so return a nicely folder full header.
        An exception is made for Carp, which will get a simplified string to avoid unreadible
        messages from "croak" and "confess".

        example: using a header object as string

         print $head;     # implicit stringification by print
         $head->print;    # the same

         print "$head";   # explicit stringication

    overload: bool
        When the header does not contain any lines (which is illegal, according to the RFCs), false
        is returned. In all other cases, a true value is produced.

METHODS
    Extends "METHODS" in Mail::Reporter.

  Constructors
    Extends "Constructors" in Mail::Reporter.

    Mail::Message::Head->build( [PAIR|$field]-LIST )
        A fast way to construct a header with many lines. The PAIRs are "(name, content)" pairs of
        the header, but it is also possible to pass Mail::Message::Field objects. A
        Mail::Message::Head::Complete header is created by simply calling
        Mail::Message::Head::Complete::build(), and then each field is added. Double field names are
        permitted.

        example:

         my $subject = Mail::Message::Field->new(Subject => 'xyz');

         my $head = Mail::Message::Head->build
          ( From     => 'me AT example.com'
          , To       => 'you AT anywhere.aq'
          , $subject
          , Received => 'one'
          , Received => 'two'
          );

         print ref $head;
          # -->  Mail::Message::Head::Complete

    Mail::Message::Head->new(%options)
        Create a new message header object. The object will store all the fields of a header. When
        you get information from the header, it will be returned to you as Mail::Message::Field
        objects, although the fields may be stored differently internally.

        If you try to instantiate a Mail::Message::Head, you will automatically be upgraded to a
        Mail::Message::Head::Complete --a full head.

         -Option    --Defined in     --Default
          field_type                   Mail::Message::Field::Fast
          log         Mail::Reporter   'WARNINGS'
          message                      undef
          modified                     <false>
          trace       Mail::Reporter   'WARNINGS'

        field_type => CLASS
          The type of objects that all the fields will have. This must be an extension of
          Mail::Message::Field.

        log => LEVEL
        message => MESSAGE
          The MESSAGE where this header belongs to. Usually, this is not known at creation of the
          header, but sometimes it is. If not, call the message() method later to set it.

        modified => BOOLEAN
        trace => LEVEL

  The header
    $obj->isDelayed()
        Headers may only be partially read, in which case they are called delayed. This method
        returns true if some header information still needs to be read. Returns false if all header
        data has been read. Will never trigger completion.

    $obj->isEmpty()
        Are there any fields defined in the current header? Be warned that the header will not be
        loaded for this: delayed headers will return true in any case.

    $obj->isModified()
        Returns whether the header has been modified after being read.

        example:

         if($head->isModified) { ... }

    $obj->knownNames()
        Like Mail::Message::Head::Complete::names(), but only returns the known header fields, which
        may be less than "names" for header types which are partial. "names()" will trigger
        completion, where "knownNames()" does not.

    $obj->message( [$message] )
        Get (after setting) the message where this header belongs to. This does not trigger
        completion.

    $obj->modified( [BOOLEAN] )
        Sets the modified flag to BOOLEAN. Without value, the current setting is returned, but in
        that case you can better use isModified(). Changing this flag will not trigger header
        completion.

        example:

         $head->modified(1);
         if($head->modified) { ... }
         if($head->isModified) { ... }

    $obj->orderedFields()
        Returns the fields ordered the way they were read or added.

  Access to the header
    $obj->get( $name, [$index] )
        Get the data which is related to the field with the $name. The case of the characters in
        $name does not matter.

        If there is only one data element defined for the $name, or if there is an $index specified
        as the second argument, only the specified element will be returned. If the field $name
        matches more than one header the return value depends on the context. In LIST context, all
        values will be returned in the order they are read. In SCALAR context, only the last value
        will be returned.

        example:

         my $head = Mail::Message::Head->new;
         $head->add('Received: abc');
         $head->add('Received: xyz');
         $head->add('Subject: greetings');

         my @rec_list   = $head->get('Received');
         my $rec_scalar = $head->get('Received');
         print ",@rec_list,$rec_scalar,"     # ,abc xyz, xyz,
         print $head->get('Received', 0);    # abc
         my @sub_list   = $head->get('Subject');
         my $sub_scalar = $head->get('Subject');
         print ",@sub_list,$sub_scalar,"     # ,greetings, greetings,

    $obj->study( $name, [$index] )
        Like get(), but puts more effort in understanding the contents of the field.
        Mail::Message::Field::study() will be called for the field with the specified FIELDNAME,
        which returns Mail::Message::Field::Full objects. In scalar context only the last field with
        that name is returned. When an $index is specified, that element is returned.

  About the body
    $obj->guessBodySize()
        Try to estimate the size of the body of this message, but without parsing the header or
        body. The result might be "undef" or a few percent of the real size. It may even be very far
        of the real value, that's why this is a guess.

    $obj->isMultipart()
        Returns whether the body of the related message is a multipart body. May trigger completion,
        when the "Content-Type" field is not defined.

  Internals
    $obj->addNoRealize($field)
        Add a field, like Mail::Message::Head::Complete::add() does, but avoid the loading of a
        possibly partial header. This method does not test the validity of the argument, nor flag
        the header as changed. This does not trigger completion.

    $obj->addOrderedFields($fields)
    $obj->fileLocation()
        Returns the location of the header in the file, as a pair begin and end. The begin is the
        first byte of the header. The end is the first byte after the header.

    $obj->load()
        Be sure that the header is loaded. This returns the loaded header object.

    $obj->moveLocation($distance)
        Move the registration of the header in the file.

    $obj->read($parser)
        Read the header information of one message into this header structure. This method is called
        by the folder object (some Mail::Box sub-class), which passes the $parser as an argument.

    $obj->setNoRealize($field)
        Set a field, but avoid the loading of a possibly partial header as set() does. This method
        does not test the validity of the argument, nor flag the header as changed. This does not
        trigger completion.

  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, $callback] )
    Mail::Message::Head->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
        Inherited, see "Error handling" in Mail::Reporter

    $obj->errors()
        Inherited, see "Error handling" in Mail::Reporter

    $obj->log( [$level, [$strings]] )
    Mail::Message::Head->log( [$level, [$strings]] )
        Inherited, see "Error handling" in Mail::Reporter

    $obj->logPriority($level)
    Mail::Message::Head->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()
        Inherited, see "Cleanup" in Mail::Reporter

DETAILS
  Ordered header fields
    Many Perl implementations make a big mistake by disturbing the order of header fields. For some
    fields (especially the *resent groups*, see Mail::Message::Head::ResentGroup) the order shall be
    maintained.

    MailBox will keep the order of the fields as they were found in the source. When your add a new
    field, it will be added at the end. If your replace a field with a new value, it will stay in
    the original order.

  Head class implementation
    The header of a MIME message object contains a set of lines, which are called *fields* (by
    default represented by Mail::Message::Field objects). Dependent on the situation, the knowledge
    about the fields can be in one of three situations, each represented by a sub-class of this
    module:

    *   Mail::Message::Head::Complete

        In this case, it is sure that all knowledge about the header is available. When you get()
        information from the header and it is not there, it will never be there.

    *   Mail::Message::Head::Subset

        There is no certainty whether all header lines are known (probably not). This may be caused
        as result of reading a fast index file, as described in Mail::Box::MH::Index. The object is
        automatically transformed into a Mail::Message::Head::Complete when all header lines must be
        known.

    *   Mail::Message::Head::Partial

        A partial header is like a subset header: probably the header is incomplete. The means that
        you are not sure whether a get() for a field fails because the field is not a part of the
        message or that it fails because it is not yet known to the program. Where the subset header
        knows where to get the other fields, the partial header does not know it. It cannot hide its
        imperfection.

    *   Mail::Message::Head::Delayed

        In this case, there is no single field known. Access to this header will always trigger the
        loading of the full header.

  Subsets of header fields
    Message headers can be quite large, and therefore MailBox provides simplified access to some
    subsets of information. You can grab these sets of fields together, create and delete them as
    group.

    On the moment, the following sets are defined:

    *   Mail::Message::Head::ResentGroup

        A *resent group* is a set of fields which is used to log one step in the transmission of the
        message from the original sender to the destination.

        Each step adds a set of headers to indicate when the message was received and how it was
        forwarded (without modification). These fields are best created using
        Mail::Message::bounce().

    *   Mail::Message::Head::ListGroup

        Fields which are used to administer and log mailing list activity. Mailing list software has
        to play trics with the original message to be able to get the reply on that message back to
        the mailing list. Usually a large number of lines are added.

    *   Mail::Message::Head::SpamGroup

        A set of fields which contains header fields which are produced by spam detection software.
        You may want to remove these fields when you store a message for a longer period of time.

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-Message distribution version 3.012, built on February 11, 2022.
    Website: http://perl.overmeer.net/CPAN/

LICENSE
    Copyrights 2001-2022 by [Mark Overmeer <markov AT cpan.org>]. 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/