Provided by: libmail-message-perl_3.015-1_all 
NAME
Mail::Message::Field - one line of a message header
INHERITANCE
Mail::Message::Field
is a Mail::Reporter
Mail::Message::Field is extended by
Mail::Message::Field::Fast
Mail::Message::Field::Flex
Mail::Message::Field::Full
SYNOPSIS
my $field = Mail::Message::Field->new(From => 'fish@tux.aq');
print $field->name;
print $field->body;
print $field->comment;
print $field->content; # body & comment
$field->print(\*OUT);
print $field->string;
print "$field\n";
print $field->attribute('charset') || 'us-ascii';
DESCRIPTION
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 accepted.
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');
Extends "DESCRIPTION" in Mail::Reporter.
OVERLOADED
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 unfoldedBody().
example:
print $msg->get('subject'); # via overloading
print $msg->get('subject')->unfoldedBody; # same
my $subject = $msg->get('subject') || 'your mail';
print "Re: $subject\n";
overload: 0+
(numification) When the field is numeric, the value will be returned. The result is
produced by toInt(). If the value is not correct, a 0 is produced, to simplify
calculations.
overload: <=>
(numeric comparison) Compare the integer field contents with something else.
example:
if($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 another field or a
string, using the buildin "cmp".
METHODS
Extends "METHODS" in Mail::Reporter.
Constructors
Extends "Constructors" in Mail::Reporter.
$obj->clone()
Create a copy of this field object.
Mail::Message::Field->new($data)
See Mail::Message::Field::Fast::new(), Mail::Message::Field::Flex::new(), and
Mail::Message::Field::Full::new(). By default, a "Fast" field is produced.
-Option--Defined in --Default
log Mail::Reporter 'WARNINGS'
trace Mail::Reporter 'WARNINGS'
log => LEVEL
trace => LEVEL
The field
$obj->isStructured()
Mail::Message::Field->isStructured()
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.
example:
my $field = Mail::Message::Field->new(From => 'me');
if($field->isStructured)
Mail::Message::Field->isStructured('From');
$obj->length()
Returns the total length of the field in characters, which includes the field's name,
body and folding characters.
$obj->nrLines()
Returns the number of lines needed to display this header-line.
$obj->print( [$fh] )
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 $fh defaults to the
selected handle.
$obj->size()
Returns the number of bytes needed to display this header-line, Same as length().
$obj->string( [$wrap] )
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).
$obj->toDisclose()
Returns whether this field can be disclosed to other people, for instance when sending
the message to another party. Returns a "true" or "false" condition. See also
Mail::Message::Head::Complete::printUndisclosed().
Access to the name
$obj->Name()
Returns the name of this field in original casing. See name() as well.
$obj->name()
Returns the name of this field, with all characters lower-cased for ease of
comparison. See Name() as well.
$obj->wellformedName( [STRING] )
(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.
example:
print Mail::Message::Field->Name('content-type')
# --> Content-Type
my $field = $head->get('date');
print $field->Name;
# --> Date
Access to the body
$obj->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().
$obj->folded()
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 internally...
example:
my @lines = $field->folded;
print $field->folded;
print scalar $field->folded; # faster
$obj->foldedBody( [$body] )
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 this method.
The optional $body argument changes the field's body. The folding of the argument
must be correct.
$obj->stripCFWS( [STRING] )
Mail::Message::Field->stripCFWS( [STRING] )
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-line.
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.
example:
my $body = $field->unfoldedBody;
print "$field"; # via overloading
Access to the content
$obj->addresses()
Returns a list of Mail::Address objects, which represent the e-mail addresses found in
this header line.
example:
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.
example:
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');
$field->print;
# --> Content-Type: text/plain; charset="us-ascii";
# filename="/tmp/xyz"
# Automatically folded, and no doubles created.
$obj->attributes()
Returns a list of key-value pairs, where the values are not yet decoded. Keys may
appear more than once.
example:
my @pairs = $head->get('Content-Disposition')->attributes;
$obj->comment( [STRING] )
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
isStructured().
The comment part of a header field often contains "attributes". Often it is preferred
to use attribute() on them.
$obj->study()
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.
example:
my $subject = $msg->head->get('subject')->study;
my $subject = $msg->head->study('subject'); # same
my $subject = $msg->study('subject'); # same
$obj->toDate( [$time] )
Mail::Message::Field->toDate( [$time] )
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.
example:
my $now = time;
Mail::Message::Field->toDate($now);
Mail::Message::Field->toDate(time);
Mail::Message::Field->toDate(localtime);
Mail::Message::Field->toDate; # same
# returns something like:
# Wed, 28 Aug 2002 10:40:25 +0200
$obj->toInt()
Returns the value which is related to this field as integer. A check is performed
whether this is right.
Other methods
$obj->dateToTimestamp(STRING)
Mail::Message::Field->dateToTimestamp(STRING)
Convert a STRING which represents and RFC compliant time string into a timestamp like
is produced by the "time" function.
Internals
$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".
$obj->defaultWrapLength( [$length] )
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 78.
$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 possible.
The RFC requests for folding on nice spots, but this request is mainly ignored because
it would make folding too slow.
$obj->setWrapLength( [$length] )
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
$field->setWrapLength(99);
$obj->stringifyData(STRING|ARRAY|$objects)
This method implements the translation of user supplied objects into ascii fields.
The process is explained in "Specifying field data".
$obj->unfold(STRING)
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
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, $callback] )
Mail::Message::Field->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback]
)
Inherited, see "Error handling" in Mail::Reporter
$obj->errors()
Inherited, see "Error handling" in Mail::Reporter
$obj->log( [$level, [$strings]] )
Mail::Message::Field->log( [$level, [$strings]] )
Inherited, see "Error handling" in Mail::Reporter
$obj->logPriority($level)
Mail::Message::Field->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
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 preceded by blanks, but followed
by one blank). Each attribute is preceded 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
circumstances.
. Example: of field comments
To: mailbox (Mail::Box mailinglist) <mailbox@overmeer.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 information.
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 parentheses 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 modification.
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 lost.
. 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 context.
. 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;
$msg->head->removeResentGroups;
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
• string()
Returns the text of the body exactly as will be printed to file when print() is
called, so name, main body, and attributes.
• foldedBody()
Returns the text of the body, like string(), but without the name of the field.
• 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.
• 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.
• 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.
• 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 directly.
. 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 construct 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 own.
The following rules (implemented in stringifyData()) are obeyed given the argument is:
• 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.
• 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.
• 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.
• 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.
• 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.
• any other object
For all other objects, the stringification overload is used to produce the field
content.
• 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 yourself.
. 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', 'fish@tux.aq');
print $fish->format; # ==> Mail::Box <fish@tux.aq>
my $exa = Mail::Address->new(undef, 'me@example.com');
print $exa->format; # ==> me@example.com
my $b = $msg->build(To => "you@example.com");
my $b = $msg->build(To => $fish);
my $b = $msg->build(To => [ $fish, $exa ]);
my @all = ($fish, "you@example.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 Fältström" # from rfc
, charset => "ISO-8859-1"
);
$patrik->add
( email => "him@home.net"
);
my $b = $msg->build(To => $patrik);
$b->get('To')->print;
# ==> =?ISO-8859-1?Q?Patrik_F=E4ltstr=F6m?=
# <him@home.net>
Field class implementation
For performance reasons only, there are three types of fields: the fast, the flexible, and
the full understander:
• 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 method.
• 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.
• 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.
DIAGNOSTICS
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.
Error: Field name too long (max $length), in '$name'
It is not specified in the RFCs how long a field name can be, but at least it should
be a few characters shorter than the line wrap.
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.
SEE ALSO
This module is part of Mail-Message distribution version 3.015, built on December 11,
2023. Website: http://perl.overmeer.net/CPAN/
LICENSE
Copyrights 2001-2023 by [Mark Overmeer <markov@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/