| Mail::Message::Field(3pm) | User Contributed Perl Documentation | Mail::Message::Field(3pm) |
Mail::Message::Field - one line of a message header
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
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';
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.
example:
print $msg->get('subject'); # via overloading
print $msg->get('subject')->unfoldedBody; # same
my $subject = $msg->get('subject') || 'your mail';
print "Re: $subject\n";
example:
if($msg->get('Content-Length') > 10000) ...
if($msg->size > 10000) ... ; # same, but better
Extends "METHODS" in Mail::Reporter.
Extends "Constructors" in Mail::Reporter.
-Option--Defined in --Default
log Mail::Reporter 'WARNINGS'
trace Mail::Reporter 'WARNINGS'
example:
my $field = Mail::Message::Field->new(From => 'me');
if($field->isStructured)
Mail::Message::Field->isStructured('From');
example:
print Mail::Message::Field->Name('content-type')
# --> Content-Type
my $field = $head->get('date');
print $field->Name;
# --> Date
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().
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
The optional $body argument changes the field's body. The folding of the argument must be correct.
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.
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
example:
my @addr = $message->head->get('to')->addresses;
my @addr = $message->to;
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.
example:
my @pairs = $head->get('Content-Disposition')->attributes;
The comment part of a header field often contains "attributes". Often it is preferred to use attribute() on them.
example:
my $subject = $msg->head->get('subject')->study;
my $subject = $msg->head->study('subject'); # same
my $subject = $msg->study('subject'); # same
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
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".
The RFC requests for folding on nice spots, but this request is mainly ignored because it would make folding too slow.
example: refolding the field
$field->setWrapLength(99);
Extends "Error handling" in Mail::Reporter.
Extends "Cleanup" in Mail::Reporter.
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.
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;
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
Returns the text of the body exactly as will be printed to file when print() is called, so name, main body, and attributes.
Returns the text of the body, like string(), but without the name of the field.
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.
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.
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 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:
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.
The most used Perl object to parse and produce address lines. This object does not understand character set encodings in phrases.
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 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.
All Mail::Identity objects in the collection will be included in the field as a group carying the name of the collection.
For all other objects, the stringification overload is used to produce the field content.
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>
For performance reasons only, there are three types of fields: the fast, the flexible, and the full understander:
"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.
The flexible implementation uses a hash to store the data. The new() and "init" methods are split, so this object is extensible.
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.
This module is part of Mail-Message distribution version 3.012, built on February 11, 2022. Website: http://perl.overmeer.net/CPAN/
Copyrights 2001-2022 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/
| 2022-02-14 | perl v5.34.0 |