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Mail::Message::Field(3User Contributed Perl DocumentaMail::Message::Field(3pm)

       Mail::Message::Field - one line of a message header

          is a Mail::Reporter

        Mail::Message::Field is extended by

        my $field = Mail::Message::Field->new(From => 'fishATtux.aq');
        print $field->name;
        print $field->body;
        print $field->comment;
        print $field->content;  # body & comment
        print $field->string;
        print "$field\n";
        print $field->attribute('charset') || 'us-ascii';

       This implementation follows the guidelines of rfc2822 as close as
       possible, and may there produce a different output than implementations
       based on the obsolete rfc822.  However, the old output will still be

       These objects each store one header line, and facilitates access
       routines to the information hidden in it.  Also, you may want to have a
       look at the added methods of a message:

        my @from    = $message->from;
        my $sender  = $message->sender;
        my $subject = $message->subject;
        my $msgid   = $message->messageId;

        my @to      = $message->to;
        my @cc      = $message->cc;
        my @bcc     = $message->bcc;
        my @dest    = $message->destinations;

        my $other   = $message->get('Reply-To');

       overload: ""

           (stringification) produces the unfolded body of the field, which
           may be what you expect.  This is what makes what the field object
           seems to be a simple string. The string is produced by


            print $msg->get('subject');  # via overloading
            print $msg->get('subject')->unfoldedBody; # same

            my $subject = $msg->get('subject') || 'your mail';
            print "Re: $subject\n";

       overload: +0

           (numification) When the field is numeric, the value will be
           returned.  The result is produced by toInt().  If the value is not
           correct, a 0 is produced, to simplify calculations.

       overload: <&lt;=>

           (numeric comparison) Compare the integer field contents with
           something else.


            if($msg->get('Content-Length') > 10000) ...
            if($msg->size > 10000) ... ; # same, but better

       overload: bool

           Always true, to make it possible to say "if($field)".

       overload: cmp

           (string comparison) Compare the unfolded body of a field with an
           other field or a string, using the buildin "cmp".



           Create a copy of this field object.


           See Mail::Message::Field::Fast::new(),
           Mail::Message::Field::Flex::new(), and
           Mail::Message::Field::Full::new().  By default, a "Fast" field is

            Option--Defined in     --Default
            log     Mail::Reporter   'WARNINGS'
            trace   Mail::Reporter   'WARNINGS'

           . log => LEVEL

           . trace => LEVEL

       The field



           Some fields are described in the RFCs as being structured: having a
           well described syntax.  These fields have common ideas about
           comments and the like, what they do not share with unstructured
           fields, like the "Subject" field.


            my $field = Mail::Message::Field->new(From => 'me');



           Returns the total length of the field in characters, which includes
           the field's name, body and folding characters.


           Returns the number of lines needed to display this header-line.


           Print the whole header-line to the specified file-handle. One line
           may result in more than one printed line, because of the folding of
           long lines.  The FILEHANDLE defaults to the selected handle.


           Returns the number of bytes needed to display this header-line,
           Same as length().


           Returns the field as string.  By default, this returns the same as
           folded(). However, the optional WRAP will cause to re-fold to take
           place (without changing the folding stored inside the field).


           Returns whether this field can be disclosed to other people, for
           instance when sending the message to an other party.  Returns a
           "true" or "false" condition.  See also

       Access to the name


           Returns the name of this field in original casing.  See name() as


           Returns the name of this field, with all characters lower-cased for
           ease of comparison.  See Name() as well.


           (Instance method class method) As instance method, the current
           field's name is correctly formatted and returned.  When a STRING is
           used, that one is formatted.


            print Mail::Message::Field->Name('content-type')
              # -->  Content-Type

            my $field = $head->get('date');
            print $field->Name;
              # -->  Date

       Access to the body


           This method may be what you want, but usually, the foldedBody() and
           unfoldedBody() are what you are looking for.  This method is
           cultural heritage, and should be avoided.

           Returns the body of the field.  When this field is structured, it
           will be stripped from everything what is behind the first semi-
           color (";").  In any case, the string is unfolded.  Whether the
           field is structured is defined by isStructured().


           Returns the folded version of the whole header.  When the header is
           shorter than the wrap length, a list of one line is returned.
           Otherwise more lines will be returned, all but the first starting
           with at least one blank.  See also foldedBody() to get the same
           information without the field's name.

           In scalar context, the lines are delived into one string, which is
           a little faster because that's the way they are stored


            my @lines = $field->folded;
            print $field->folded;
            print scalar $field->folded; # faster


           Returns the body as a set of lines. In scalar context, this will be
           one line containing newlines.  Be warned about the newlines when
           you do pattern-matching on the result of thie method.

           The optional BODY argument changes the field's body.  The folding
           of the argument must be correct.



           Remove the comments and folding white spaces from the STRING.
           Without string and only as instance method, the unfoldedBody() is
           being stripped and returned.

           WARNING: This operation is only allowed for structured header
           fields (which are defined by the various RFCs as being so.  You
           don't want parts within braces which are in the Subject header line
           to be removed, to give an example.

       $obj->unfoldedBody([BODY, [WRAP]])

           Returns the body as one single line, where all folding information
           (if available) is removed.  This line will also NOT end on a new-

           The optional BODY argument changes the field's body.  The right
           folding is performed before assignment.  The WRAP may be specified
           to enforce a folding size.


            my $body = $field->unfoldedBody;
            print "$field";   # via overloading

       Access to the content


           Returns a list of Mail::Address objects, which represent the e-mail
           addresses found in this header line.


            my @addr = $message->head->get('to')->addresses;
            my @addr = $message->to;

       $obj->attribute(NAME [, VALUE])

           Get the value of an attribute, optionally after setting it to a new
           value.  Attributes are part of some header lines, and hide
           themselves in the comment field.  If the attribute does not exist,
           then "undef" is returned.  The attribute is still encoded.


            my $field = Mail::Message::Field->new(
             'Content-Type: text/plain; charset="us-ascii"');

            print $field->attribute('charset');
              # --> us-ascii

            print $field->attribute('bitmap') || 'no'
              # --> no

            $field->atrribute(filename => '/tmp/xyz');
              # --> Content-Type: text/plain; charset="us-ascii";
              #       filename="/tmp/xyz"
              # Automatically folded, and no doubles created.


           Returns a list of key-value pairs, where the values are not yet


            my %attributes = $head->get('Content-Disposition')->attributes;


           Returns the unfolded comment (part after a semi-colon) in a
           structureed header-line. optionally after setting it to a new
           STRING first.  When "undef" is specified as STRING, the comment is
           removed.  Whether the field is structured is defined by

           The comment part of a header field often contains "attributes".
           Often it is preferred to use attribute() on them.


           Study the header field in detail: turn on the full parsing and
           detailed understanding of the content of the fields.
           Mail::Message::Field::Fast and Mail::Message::Field::Fast objects
           will be transformed into any Mail::Message::Field::Full object.


            my $subject = $msg->head->get('subject')->study;
            my $subject = $msg->head->study('subject');  # same
            my $subject = $msg->study('subject');        # same



           Convert a timestamp into an rfc2822 compliant date format.  This
           differs from the default output of "localtime" in scalar context.
           Without argument, the "localtime" is used to get the current time.
           TIME can be specified as one numeric (like the result of "time()")
           and as list (like produced by c<localtime()> in list context).

           Be sure to have your timezone set right, especially when this
           script runs automatically.


            my $now = time;

            Mail::Message::Field->toDate;      # same
            # returns someting like:
            #     Wed, 28 Aug 2002 10:40:25 +0200


           Returns the value which is related to this field as integer.  A
           check is performed whether this is right.

       Other methods



           Convert a STRING which represents and RFC compliant time string
           into a timestamp like is produced by the "time" function.


       $obj->consume(LINE | (NAME,BODY|OBJECTS))

           Accepts a whole field LINE, or a pair with the field's NAME and
           BODY. In the latter case, the BODY data may be specified as array
           of OBJECTS which are stringified.  Returned is a nicely formatted
           pair of two strings: the field's name and a folded body.

           This method is called by new(), and usually not by an application
           program. The details about converting the OBJECTS to a field
           content are explained in "Specifying field data".


           Any field from any header for any message will have this default
           wrapping.  This is maintained in one global variable.  Without a
           specified LENGTH, the current value is returned.  The default is

       $obj->fold(NAME, BODY, [MAXCHARS])

       Mail::Message::Field->fold(NAME, BODY, [MAXCHARS])

           Make the header field with NAME fold into multiple lines.  Wrapping
           is performed by inserting newlines before a blanks in the BODY,
           such that no line exceeds the MAXCHARS and each line is as long as

           The RFC requests for folding on nice spots, but this request is
           mainly ignored because it would make folding too slow.


           Force the wrapping of this field to the specified LENGTH
           characters. The wrapping is performed with fold() and the results
           stored within the field object.

           example: refolding the field



           This method implements the translation of user supplied objects
           into ascii fields.  The process is explained in "Specifying field


           The reverse action of fold(): all lines which form the body of a
           field are joined into one by removing all line terminators (even
           the last).  Possible leading blanks on the first line are removed
           as well.

       Error handling


           See "Error handling" in Mail::Reporter


           See "Error handling" in Mail::Reporter

       $obj->defaultTrace([LEVEL]|[LOGLEVEL, TRACELEVEL]|[LEVEL, CALLBACK])


           See "Error handling" in Mail::Reporter


           See "Error handling" in Mail::Reporter

       $obj->log([LEVEL [,STRINGS]])

       Mail::Message::Field->log([LEVEL [,STRINGS]])

           See "Error handling" in Mail::Reporter



           See "Error handling" in Mail::Reporter


           See "Error handling" in Mail::Reporter


           See "Error handling" in Mail::Reporter


           See "Error handling" in Mail::Reporter


           See "Error handling" in Mail::Reporter


           See "Error handling" in Mail::Reporter


           See "Error handling" in Mail::Reporter



           See "Cleanup" in Mail::Reporter


           See "Cleanup" in Mail::Reporter

       Field syntax

       Fields are stored in the header of a message, which are represented by
       Mail::Message::Head objects. A field is a combination of a name, body,
       and attributes.  Especially the term "body" is cause for confusion:
       sometimes the attributes are considered to be part of the body.

       The name of the field is followed by a colon ("":"", not preceeded by
       blanks, but followed by one blank).  Each attribute is preceeded by a
       separate semi-colon ("";"").  Names of fields are case-insensitive and
       cannot contain blanks.

       example: of fields

       Correct fields:

        Field: hi!
        Content-Type: text/html; charset=latin1

       Incorrect fields, but accepted:

        Field : wrong, blank before colon
        Field:                 # wrong, empty
        Field:not nice, blank preferred after colon
        One Two: wrong, blank in name

       Folding fields

       Fields which are long can be folded to span more than one line.  The
       real limit for lines in messages is only at 998 characters, however
       such long lines are not easy to read without support of an application.
       Therefore rfc2822 (which defines the message syntax) specifies
       explicitly that field lines can be re-formatted into multiple sorter
       lines without change of meaning, by adding new-line characters to any
       field before any blank or tab.

       Usually, the lines are reformatted to create lines which are 78
       characters maximum. Some applications try harder to fold on nice spots,
       like before attributes.  Especially the "Received" field is often
       manually folded into some nice layout.  In most cases however, it is
       preferred to produce lines which are as long as possible but max 78.

       BE WARNED that all fields can be subjected to folding, and that you
       usually want the unfolded value.

       example: of field folding

        Subject: this is a short line, and not folded

        Subject: this subject field is much longer, and therefore
         folded into multiple
         lines, although one more than needed.

       Structured fields

       The rfc2822 describes a large number of header fields explicitly.
       These fields have a defined meaning.  For some of the fields, like the
       "Subject" field, the meaning is straight forward the contents itself.
       These fields are the Unstructured Fields.

       Other fields have a well defined internal syntax because their content
       is needed by e-mail applications. For instance, the "To" field contains
       addresses which must be understood by all applications in the same way.
       These are the Structured Fields, see isStructured().

       Comments in fields

       Stuctured fields can contain comments, which are pieces of text
       enclosed in parenthesis.  These comments can be placed close to
       anywhere in the line and must be ignored be the application.  Not all
       applications are capable of handling comments correctly in all

       example: of field comments

        To: mailbox (Mail::Box mailinglist) <mailboxATovermeer.net>
        Date: Thu, 13 Sep 2001 09:40:48 +0200 (CEST)
        Subject: goodbye (was: hi!)

       On the first line, the text "Mail::Box mailinglist" is used as comment.
       Be warned that rfc2822 explicitly states that comments in e-mail
       address specifications should not be considered to contain any usable

       On the second line, the timezone is specified as comment. The "Date"
       field format has no way to indicate the timezone of the sender, but
       only contains the timezone difference to UTC, however one could decide
       to add this as comment.  Application must ignore this data because the
       "Date" field is structured.

       The last field is unstructured.  The text between parantheses is an
       integral part of the subject line.

       Getting a field

       As many programs as there are handling e-mail, as many variations on
       accessing the header information are requested.  Be careful which way
       you access the data: read the variations described here and decide
       which solution suites your needs best.

       Using get() field

       The "get()" interface is copied from other Perl modules which can
       handle e-mail messages.  Many applications which simply replace
       Mail::Internet objects by Mail::Message objects will work without

       There is more than one get method.  The exact results depend on which
       get you use.  When Mail::Message::get() is called, you will get the
       unfolded, stripped from comments, stripped from attributes contents of
       the field as string.  Character-set encodings will still be in the
       string.  If the same fieldname appears more than once in the header,
       only the last value is returned.

       When Mail::Message::Head::get() is called in scalar context, the last
       field with the specified name is returned as field object.  This object
       strinigfies into the unfolded contents of the field, including
       attributes and comments.  In list context, all appearances of the field
       in the header are returned as objects.

       BE WARNED that some lines seem unique, but are not according to the
       official rfc.  For instance, "To" fields can appear more than once.  If
       your program calls "get('to')" in scalar context, some information is

       example: of using get()

        print $msg->get('subject') || 'no subject';
        print $msg->head->get('subject') || 'no subject';

        my @to = $msg->head->get('to');

       Using study() field

       As the name "study" already implies, this way of accessing the fields
       is much more thorough but also slower.  The "study" of a field is like
       a "get", but provides easy access to the content of the field and
       handles character-set decoding correctly.

       The Mail::Message::study() method will only return the last field with
       that name as object.  Mail::Message::Head::study() and
       Mail::Message::Field::study() return all fields when used in list

       example: of using study()

        print $msg->study('subject') || 'no subject';
        my @rec  = $msg->head->study('Received');

        my $from = $msg->head->get('From')->study;
        my $from = $msg->head->study('From');  # same
        my @addr = $from->addresses;

       Using resent groups

       Some fields belong together in a group of fields.  For instance, a set
       of lines is used to define one step in the mail transport process.
       Each step adds a "Received" line, and optionally some "Resent-*" lines
       and "Return-Path".  These groups of lines shall stay together and in
       order when the message header is processed.

       The "Mail::Message::Head::ResentGroup" object simplifies the access to
       these related fields.  These resent groups can be deleted as a whole,
       or correctly constructed.

       example: of using resent groups

        my $rgs = $msg->head->resentGroups;
        $rgs[0]->delete if @rgs;


       The field's data

       There are many ways to get the fields info as object, and there are
       also many ways to process this data within the field.

       Access to the field

       o   string()

           Returns the text of the body exactly as will be printed to file
           when print() is called, so name, main body, and attributes.

       o   foldedBody()

           Returns the text of the body, like string(), but without the name
           of the field.

       o   unfoldedBody()

           Returns the text of the body, like foldedBody(), but then with all
           new-lines removed.  This is the normal way to get the content of
           unstructured fields.  Character-set encodings will still be in
           place.  Fields are stringified into their unfolded representation.

       o   stripCFWS()

           Returns the text of structured fields, where new-lines and comments
           are removed from the string.  This is a good start for parsing the
           field, for instance to find e-mail addresses in them.

       o   Mail::Message::Field::Full::decodedBody()

           Studied fields can produce the unfolded text decoded into utf8
           strings.  This is an expensive process, but the only correct way to
           get the field's data.  More useful for people who are not living in
           ASCII space.

       o   Studied fields

           Studied fields have powerful methods to provide ways to access and
           produce the contents of (structured) fields exactly as the involved
           rfcs prescribe.

       Using simplified field access

       Some fields are accessed that often that there are support methods to
       provide simplified access.  All these methods are called upon a message

       example: of simplified field access

        print $message->subject;
        print $message->get('subject') || '';  # same

        my @from = $message->from; # returns addresses
        $message->reply->send if $message->sender;

       The "sender" method will return the address specified in the "Sender"
       field, or the first named in the "From" field.  It will return "undef"
       in case no address is known.

       Specifying field data

       Field data can be anything, strongly dependent on the type of field at
       hand. If you decide to contruct the fields very carefully via some
       Mail::Message::Field::Full extension (like via
       Mail::Message::Field::Addresses objects), then you will have protection
       build-in.  However, you can bluntly create any Mail::Message::Field
       object based on some data.

       When you create a field, you may specify a string, object, or an array
       of strings and objects.  On the moment, objects are only used to help
       the construction on e-mail addresses, however you may add some of your

       The following rules (implemented in stringifyData()) are obeyed given
       the argument is:

       o   a string

           The string must be following the (complicated) rules of the
           rfc2822, and is made field content as specified.  When the string
           is not terminated by a new-line ("\n") it will be folded according
           to the standard rules.

       o   a Mail::Address object

           The most used Perl object to parse and produce address lines.  This
           object does not understand character set encodings in phrases.

       o   a Mail::Identity object

           As part of the User::Identity distribution, this object has full
           understanding of the meaning of one e-mail address, related to a
           person.  All features defined by rfc2822 are implemented.

       o   a User::Identity object

           A person is specified, which may have more than one
           Mail::Identity's defined.  Some methods, like
           Mail::Message::reply() and Mail::Message::forward() try to select
           the right e-mail address smart (see their method descriptions), but
           in other cases the first e-mail address found is used.

       o   a User::Identity::Collection::Emails object

           All Mail::Identity objects in the collection will be included in
           the field as a group carying the name of the collection.

       o   any other object

           For all other objects, the stringification overload is used to
           produce the field content.

       o   an ARRAY

           You may also specify an array with a mixture of any of the above.
           The elements will be joined as comma-separated list.  If you do not
           want comma's inbetween, you will have to process the array

       example: specifying simple field data

        my $f = Mail::Message::Field->new(Subject => 'hi!');
        my $b = Mail::Message->build(Subject => 'monkey');

       example: s specifying e-mail addresses for a field

        use Mail::Address;
        my $fish = Mail::Address->new('Mail::Box', 'fishATtux.aq');
        print $fish->format;   # ==> Mail::Box <fishATtux.aq>
        my $exa  = Mail::Address->new(undef, 'meATexample.com');
        print $exa->format;    # ==> meATexample.com

        my $b = $msg->build(To => "youATexample.com");
        my $b = $msg->build(To => $fish);
        my $b = $msg->build(To => [ $fish, $exa ]);

        my @all = ($fish, "youATexample.com", $exa);
        my $b = $msg->build(To => \@all);
        my $b = $msg->build(To => [ "xyz", @all ]);

       example: specifying identities for a field

        use User::Identity;
        my $patrik = User::Identity->new
         ( name      => 'patrik'
         , full_name => "Patrik Faeltstroem"  # from rfc
         , charset   => "ISO-8859-1"
         ( email    => "himAThome.net"

        my $b = $msg->build(To => $patrik);

          # ==> =?ISO-8859-1?Q?Patrik_F=E4ltstr=F6m?=
          #     <himAThome.net>

       Field class implementation

       For performance reasons only, there are three types of fields: the
       fast, the flexible, and the full understander:

       o   Mail::Message::Field::Fast

           "Fast" objects are not derived from a "Mail::Reporter".  The
           consideration is that fields are so often created, and such a small
           objects at the same time, that setting-up a logging for each of the
           objects is relatively expensive and not really useful.  The fast
           field implementation uses an array to store the data: that will be
           faster than using a hash.  Fast fields are not easily inheritable,
           because the object creation and initiation is merged into one

       o   Mail::Message::Field::Flex

           The flexible implementation uses a hash to store the data.  The
           new() and "init" methods are split, so this object is extensible.

       o   Mail::Message::Field::Full

           With a full implementation of all applicable RFCs (about 5), the
           best understanding of the fields is reached.  However, this comes
           with a serious memory and performance penalty.  These objects are
           created from fast or flex header fields when study() is called.

       Warning: Field content is not numerical: $content

           The numeric value of a field is requested (for instance the "Lines"
           or "Content-Length" fields should be numerical), however the data
           contains weird characters.

       Warning: Illegal character in field name $name

           A new field is being created which does contain characters not
           permitted by the RFCs.  Using this field in messages may break
           other e-mail clients or transfer agents, and therefore mutulate or
           extinguish your message.

       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.

       This module is part of Mail-Box distribution version 2.082, built on
       April 28, 2008. Website: http://perl.overmeer.net/mailbox/

       Copyrights 2001-2008 by Mark Overmeer. For other contributors see

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.  See

perl v5.10.0                      2008-04-28         Mail::Message::Field(3pm)