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MIME::Tools(3) User Contributed Perl Documentation MIME::Tools(3)
NAME
MIME-tools - modules for parsing (and creating!) MIME entities
SYNOPSIS
Here's some pretty basic code for parsing a MIME message, and outputting its decoded components to a
given directory:
use MIME::Parser;
### Create parser, and set some parsing options:
my $parser = new MIME::Parser;
$parser->output_under("$ENV{HOME}/mimemail");
### Parse input:
$entity = $parser->parse(\*STDIN) or die "parse failed\n";
### Take a look at the top-level entity (and any parts it has):
$entity->dump_skeleton;
Here's some code which composes and sends a MIME message containing three parts: a text file, an
attached GIF, and some more text:
use MIME::Entity;
### Create the top-level, and set up the mail headers:
$top = MIME::Entity->build(Type =>"multipart/mixed",
From => "me\@myhost.com",
To => "you\@yourhost.com",
Subject => "Hello, nurse!");
### Part #1: a simple text document:
$top->attach(Path=>"./testin/short.txt");
### Part #2: a GIF file:
$top->attach(Path => "./docs/mime-sm.gif",
Type => "image/gif",
Encoding => "base64");
### Part #3: some literal text:
$top->attach(Data=>$message);
### Send it:
open MAIL, "| /usr/lib/sendmail -t -oi -oem" or die "open: $!";
$top->print(\*MAIL);
close MAIL;
For more examples, look at the scripts in the examples directory of the MIME-tools distribution.
DESCRIPTION
MIME-tools is a collection of Perl5 MIME:: modules for parsing, decoding, and generating single- or
multipart (even nested multipart) MIME messages. (Yes, kids, that means you can send messages with
attached GIF files).
REQUIREMENTS
You will need the following installed on your system:
File::Path
File::Spec
IPC::Open2 (optional)
MIME::Base64
MIME::QuotedPrint
Net::SMTP
Mail::Internet, ... from the MailTools distribution.
See the Makefile.PL in your distribution for the most-comprehensive list of prerequisite modules and
their version numbers.
A QUICK TOUR
Overview of the classes
Here are the classes you'll generally be dealing with directly:
(START HERE) results() .-----------------.
\ .-------->| MIME:: |
.-----------. / | Parser::Results |
| MIME:: |--' `-----------------'
| Parser |--. .-----------------.
`-----------' \ filer() | MIME:: |
| parse() `-------->| Parser::Filer |
| gives you `-----------------'
| a... | output_path()
| | determines
| | path() of...
| head() .--------. |
| returns... | MIME:: | get() |
V .-------->| Head | etc... |
.--------./ `--------' |
.---> | MIME:: | |
`-----| Entity | .--------. |
parts() `--------'\ | MIME:: | /
returns `-------->| Body |<---------'
sub-entities bodyhandle() `--------'
(if any) returns... | open()
| returns...
|
V
.--------. read()
| IO:: | getline()
| Handle | print()
`--------' etc...
To illustrate, parsing works this way:
• The "parser" parses the MIME stream. A parser is an instance of "MIME::Parser". You hand it an
input stream (like a filehandle) to parse a message from: if the parse is successful, the result
is an "entity".
• A parsed message is represented by an "entity". An entity is an instance of "MIME::Entity" (a
subclass of "Mail::Internet"). If the message had "parts" (e.g., attachments), then those parts
are "entities" as well, contained inside the top-level entity. Each entity has a "head" and a
"body".
• The entity's "head" contains information about the message. A "head" is an instance of
"MIME::Head" (a subclass of "Mail::Header"). It contains information from the message header:
content type, sender, subject line, etc.
• The entity's "body" knows where the message data is. You can ask to "open" this data source for
reading or writing, and you will get back an "I/O handle".
• You can open() a "body" and get an "I/O handle" to read/write message data. This handle is an
object that is basically like an IO::Handle... it can be any class, so long as it supports a
small, standard set of methods for reading from or writing to the underlying data source.
A typical multipart message containing two parts -- a textual greeting and an "attached" GIF file --
would be a tree of MIME::Entity objects, each of which would have its own MIME::Head. Like this:
.--------.
| MIME:: | Content-type: multipart/mixed
| Entity | Subject: Happy Samhaine!
`--------'
|
`----.
parts |
| .--------.
|---| MIME:: | Content-type: text/plain; charset=us-ascii
| | Entity | Content-transfer-encoding: 7bit
| `--------'
| .--------.
|---| MIME:: | Content-type: image/gif
| Entity | Content-transfer-encoding: base64
`--------' Content-disposition: inline;
filename="hs.gif"
Parsing messages
You usually start by creating an instance of MIME::Parser and setting up certain parsing parameters:
what directory to save extracted files to, how to name the files, etc.
You then give that instance a readable filehandle on which waits a MIME message. If all goes well,
you will get back a MIME::Entity object (a subclass of Mail::Internet), which consists of...
• A MIME::Head (a subclass of Mail::Header) which holds the MIME header data.
• A MIME::Body, which is a object that knows where the body data is. You ask this object to "open"
itself for reading, and it will hand you back an "I/O handle" for reading the data: this could be
of any class, so long as it conforms to a subset of the IO::Handle interface.
If the original message was a multipart document, the MIME::Entity object will have a non-empty list
of "parts", each of which is in turn a MIME::Entity (which might also be a multipart entity, etc,
etc...).
Internally, the parser (in MIME::Parser) asks for instances of MIME::Decoder whenever it needs to
decode an encoded file. MIME::Decoder has a mapping from supported encodings (e.g., 'base64') to
classes whose instances can decode them. You can add to this mapping to try out new/experiment
encodings. You can also use MIME::Decoder by itself.
Composing messages
All message composition is done via the MIME::Entity class. For single-part messages, you can use
the MIME::Entity/build constructor to create MIME entities very easily.
For multipart messages, you can start by creating a top-level "multipart" entity with
MIME::Entity::build(), and then use the similar MIME::Entity::attach() method to attach parts to that
message. Please note: what most people think of as "a text message with an attached GIF file" is
really a multipart message with 2 parts: the first being the text message, and the second being the
GIF file.
When building MIME a entity, you'll have to provide two very important pieces of information: the
content type and the content transfer encoding. The type is usually easy, as it is directly
determined by the file format; e.g., an HTML file is "text/html". The encoding, however, is
trickier... for example, some HTML files are "7bit"-compliant, but others might have very long lines
and would need to be sent "quoted-printable" for reliability.
See the section on encoding/decoding for more details, as well as "A MIME PRIMER".
Sending email
Since MIME::Entity inherits directly from Mail::Internet, you can use the normal Mail::Internet
mechanisms to send email. For example,
$entity->smtpsend;
Encoding/decoding support
The MIME::Decoder class can be used to encode as well; this is done when printing MIME entities. All
the standard encodings are supported (see "A MIME PRIMER" for details):
Encoding: | Normally used when message contents are:
-------------------------------------------------------------------7bit ------------------------------------------------------------------7bit
7bit | 7-bit data with under 1000 chars/line, or multipart.
8bit | 8-bit data with under 1000 chars/line.
binary | 8-bit data with some long lines (or no line breaks).
quoted-printable | Text files with some 8-bit chars (e.g., Latin-1 text).
base64 | Binary files.
Which encoding you choose for a given document depends largely on (1) what you know about the
document's contents (text vs binary), and (2) whether you need the resulting message to have a
reliable encoding for 7-bit Internet email transport.
In general, only "quoted-printable" and "base64" guarantee reliable transport of all data; the other
three "no-encoding" encodings simply pass the data through, and are only reliable if that data is
7bit ASCII with under 1000 characters per line, and has no conflicts with the multipart boundaries.
I've considered making it so that the content-type and encoding can be automatically inferred from
the file's path, but that seems to be asking for trouble... or at least, for Mail::Cap...
Message-logging
MIME-tools is a large and complex toolkit which tries to deal with a wide variety of external input.
It's sometimes helpful to see what's really going on behind the scenes. There are several kinds of
messages logged by the toolkit itself:
Debug messages
These are printed directly to the STDERR, with a prefix of "MIME-tools: debug".
Debug message are only logged if you have turned "debugging" on in the MIME::Tools configuration.
Warning messages
These are logged by the standard Perl warn() mechanism to indicate an unusual situation. They
all have a prefix of "MIME-tools: warning".
Warning messages are only logged if $^W is set true and MIME::Tools is not configured to be
"quiet".
Error messages
These are logged by the standard Perl warn() mechanism to indicate that something actually
failed. They all have a prefix of "MIME-tools: error".
Error messages are only logged if $^W is set true and MIME::Tools is not configured to be
"quiet".
Usage messages
Unlike "typical" warnings above, which warn about problems processing data, usage-warnings are
for alerting developers of deprecated methods and suspicious invocations.
Usage messages are currently only logged if $^W is set true and MIME::Tools is not configured to
be "quiet".
When a MIME::Parser (or one of its internal helper classes) wants to report a message, it generally
does so by recording the message to the MIME::Parser::Results object immediately before invoking the
appropriate function above. That means each parsing run has its own trace-log which can be examined
for problems.
Configuring the toolkit
If you want to tweak the way this toolkit works (for example, to turn on debugging), use the routines
in the MIME::Tools module.
debugging
Turn debugging on or off. Default is false (off).
MIME::Tools->debugging(1);
quiet
Turn the reporting of warning/error messages on or off. Default is true, meaning that these
message are silenced.
MIME::Tools->quiet(1);
version
Return the toolkit version.
print MIME::Tools->version, "\n";
THINGS YOU SHOULD DO
Take a look at the examples
The MIME-Tools distribution comes with an "examples" directory. The scripts in there are basically
just tossed-together, but they'll give you some ideas of how to use the parser.
Run with warnings enabled
Always run your Perl script with "-w". If you see a warning about a deprecated method, change your
code ASAP. This will ease upgrades tremendously.
Avoid non-standard encodings
Don't try to MIME-encode using the non-standard MIME encodings. It's just not a good practice if you
want people to be able to read your messages.
Plan for thrown exceptions
For example, if your mail-handling code absolutely must not die, then perform mail parsing like this:
$entity = eval { $parser->parse(\*INPUT) };
Parsing is a complex process, and some components may throw exceptions if seriously-bad things
happen. Since "seriously-bad" is in the eye of the beholder, you're better off catching possible
exceptions instead of asking me to propagate "undef" up the stack. Use of exceptions in reusable
modules is one of those religious issues we're never all going to agree upon; thankfully, that's what
"eval{}" is good for.
Check the parser results for warnings/errors
As of 5.3xx, the parser tries extremely hard to give you a MIME::Entity. If there were any problems,
it logs warnings/errors to the underlying "results" object (see MIME::Parser::Results). Look at that
object after each parse. Print out the warnings and errors, especially if messages don't parse the
way you thought they would.
Don't plan on printing exactly what you parsed!
Parsing is a (slightly) lossy operation. Because of things like ambiguities in base64-encoding, the
following is not going to spit out its input unchanged in all cases:
$entity = $parser->parse(\*STDIN);
$entity->print(\*STDOUT);
If you're using MIME::Tools to process email, remember to save the data you parse if you want to send
it on unchanged. This is vital for things like PGP-signed email.
Understand how international characters are represented
The MIME standard allows for text strings in headers to contain characters from any character set, by
using special sequences which look like this:
=?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?=
To be consistent with the existing Mail::Field classes, MIME::Tools does not automatically unencode
these strings, since doing so would lose the character-set information and interfere with the parsing
of fields (see "decode_headers" in MIME::Parser for a full explanation). That means you should be
prepared to deal with these encoded strings.
The most common question then is, how do I decode these encoded strings? The answer depends on what
you want to decode them to: ASCII, Latin1, UTF-8, etc. Be aware that your "target" representation
may not support all possible character sets you might encounter; for example, Latin1 (ISO-8859-1) has
no way of representing Big5 (Chinese) characters. A common practice is to represent
"untranslateable" characters as "?"s, or to ignore them completely.
To unencode the strings into some of the more-popular Western byte representations (e.g., Latin1,
Latin2, etc.), you can use the decoders in MIME::WordDecoder (see MIME::WordDecoder). The simplest
way is by using "unmime()", a function wrapped around your "default" decoder, as follows:
use MIME::WordDecoder;
...
$subject = unmime $entity->head->get('subject');
One place this is done automatically is in extracting the recommended filename for a part while
parsing. That's why you should start by setting up the best "default" decoder if the default target
of Latin1 isn't to your liking.
THINGS I DO THAT YOU SHOULD KNOW ABOUT
Fuzzing of CRLF and newline on input
RFC 2045 dictates that MIME streams have lines terminated by CRLF ("\r\n"). However, it is extremely
likely that folks will want to parse MIME streams where each line ends in the local newline character
"\n" instead.
An attempt has been made to allow the parser to handle both CRLF and newline-terminated input.
Fuzzing of CRLF and newline when decoding
The "7bit" and "8bit" decoders will decode both a "\n" and a "\r\n" end-of-line sequence into a "\n".
The "binary" decoder (default if no encoding specified) still outputs stuff verbatim... so a MIME
message with CRLFs and no explicit encoding will be output as a text file that, on many systems, will
have an annoying ^M at the end of each line... but this is as it should be.
Fuzzing of CRLF and newline when encoding/composing
TODO FIXME All encoders currently output the end-of-line sequence as a "\n", with the assumption that
the local mail agent will perform the conversion from newline to CRLF when sending the mail.
However, there probably should be an option to output CRLF as per RFC 2045
Inability to handle multipart boundaries with embedded newlines
Let's get something straight: this is an evil, EVIL practice. If your mailer creates multipart
boundary strings that contain newlines, give it two weeks notice and find another one. If your mail
robot receives MIME mail like this, regard it as syntactically incorrect, which it is.
Ignoring non-header headers
People like to hand the parser raw messages straight from POP3 or from a mailbox. There is often
predictable non-header information in front of the real headers; e.g., the initial "From" line in the
following message:
From - Wed Mar 22 02:13:18 2000
Return-Path: <eryq@zeegee.com>
Subject: Hello
The parser simply ignores such stuff quietly. Perhaps it shouldn't, but most people seem to want
that behavior.
Fuzzing of empty multipart preambles
Please note that there is currently an ambiguity in the way preambles are parsed in. The following
message fragments both are regarded as having an empty preamble (where "\n" indicates a newline
character):
Content-type: multipart/mixed; boundary="xyz"\n
Subject: This message (#1) has an empty preamble\n
\n
--xyz\n
...
Content-type: multipart/mixed; boundary="xyz"\n
Subject: This message (#2) also has an empty preamble\n
\n
\n
--xyz\n
...
In both cases, the first completely-empty line (after the "Subject") marks the end of the header.
But we should clearly ignore the second empty line in message #2, since it fills the role of "the
newline which is only there to make sure that the boundary is at the beginning of a line". Such
newlines are never part of the content preceding the boundary; thus, there is no preamble "content"
in message #2.
However, it seems clear that message #1 also has no preamble "content", and is in fact merely a
compact representation of an empty preamble.
Use of a temp file during parsing
Why not do everything in core? Although the amount of core available on even a modest home system
continues to grow, the size of attachments continues to grow with it. I wanted to make sure that
even users with small systems could deal with decoding multi-megabyte sounds and movie files. That
means not being core-bound.
As of the released 5.3xx, MIME::Parser gets by with only one temp file open per parser. This temp
file provides a sort of infinite scratch space for dealing with the current message part. It's fast
and lightweight, but you should know about it anyway.
Why do I assume that MIME objects are email objects?
Achim Bohnet once pointed out that MIME headers do nothing more than store a collection of
attributes, and thus could be represented as objects which don't inherit from Mail::Header.
I agree in principle, but RFC 2045 says otherwise. RFC 2045 [MIME] headers are a syntactic subset of
RFC-822 [email] headers. Perhaps a better name for these modules would have been RFC1521:: instead
of MIME::, but we're a little beyond that stage now.
When I originally wrote these modules for the CPAN, I agonized for a long time about whether or not
they really should subclass from Mail::Internet (then at version 1.17). Thanks to Graham Barr, who
graciously evolved MailTools 1.06 to be more MIME-friendly, unification was achieved at MIME-tools
release 2.0. The benefits in reuse alone have been substantial.
A MIME PRIMER
So you need to parse (or create) MIME, but you're not quite up on the specifics? No problem...
Glossary
Here are some definitions adapted from RFC 1521 (predecessor of the current RFC 204[56789] defining
MIME) explaining the terminology we use; each is accompanied by the equivalent in MIME:: module
terms...
attachment
An "attachment" is common slang for any part of a multipart message -- except, perhaps, for the
first part, which normally carries a user message describing the attachments that follow (e.g.:
"Hey dude, here's that GIF file I promised you.").
In our system, an attachment is just a MIME::Entity under the top-level entity, probably one of
its parts.
body
The "body" of an entity is that portion of the entity which follows the header and which contains
the real message content. For example, if your MIME message has a GIF file attachment, then the
body of that attachment is the base64-encoded GIF file itself.
A body is represented by an instance of MIME::Body. You get the body of an entity by sending it
a bodyhandle() message.
body part
One of the parts of the body of a multipart /entity. A body part has a /header and a /body, so
it makes sense to speak about the body of a body part.
Since a body part is just a kind of entity, it's represented by an instance of MIME::Entity.
entity
An "entity" means either a /message or a /body part. All entities have a /header and a /body.
An entity is represented by an instance of MIME::Entity. There are instance methods for
recovering the header (a MIME::Head) and the body (a MIME::Body).
header
This is the top portion of the MIME message, which contains the "Content-type", "Content-transfer-encoding", "Contenttransfer-encoding",
transfer-encoding", etc. Every MIME entity has a header, represented by an instance of
MIME::Head. You get the header of an entity by sending it a head() message.
message
A "message" generally means the complete (or "top-level") message being transferred on a network.
There currently is no explicit package for "messages"; under MIME::, messages are streams of data
which may be read in from files or filehandles. You can think of the MIME::Entity returned by
the MIME::Parser as representing the full message.
Content types
This indicates what kind of data is in the MIME message, usually as majortype/minortype. The
standard major types are shown below. A more-comprehensive listing may be found in RFC-2046.
application
Data which does not fit in any of the other categories, particularly data to be processed by some
type of application program. "application/octet-stream", "application/gzip",
"application/postscript"...
audio
Audio data. "audio/basic"...
image
Graphics data. "image/gif", "image/jpeg"...
message
A message, usually another mail or MIME message. "message/rfc822"...
multipart
A message containing other messages. "multipart/mixed", "multipart/alternative"...
text
Textual data, meant for humans to read. "text/plain", "text/html"...
video
Video or video+audio data. "video/mpeg"...
Content transfer encodings
This is how the message body is packaged up for safe transit. There are the 5 major MIME encodings.
A more-comprehensive listing may be found in RFC-2045.
7bit
No encoding is done at all. This label simply asserts that no 8-bit characters are present, and
that lines do not exceed 1000 characters in length (including the CRLF).
8bit
No encoding is done at all. This label simply asserts that the message might contain 8-bit
characters, and that lines do not exceed 1000 characters in length (including the CRLF).
binary
No encoding is done at all. This label simply asserts that the message might contain 8-bit
characters, and that lines may exceed 1000 characters in length. Such messages are the least
likely to get through mail gateways.
base64
A standard encoding, which maps arbitrary binary data to the 7bit domain. Like "uuencode", but
very well-defined. This is how you should send essentially binary information (tar files, GIFs,
JPEGs, etc.).
quoted-printable
A standard encoding, which maps arbitrary line-oriented data to the 7bit domain. Useful for
encoding messages which are textual in nature, yet which contain non-ASCII characters (e.g.,
Latin-1, Latin-2, or any other 8-bit alphabet).
SEE ALSO
MIME::Parser, MIME::Head, MIME::Body, MIME::Entity, MIME::Decoder, Mail::Header, Mail::Internet
At the time of this writing, the MIME-tools homepage was
http://www.mimedefang.org/static/mime-tools.php. Check there for updates and support.
The MIME format is documented in RFCs 1521-1522, and more recently in RFCs 2045-2049.
The MIME header format is an outgrowth of the mail header format documented in RFC 822.
SUPPORT
Please file support requests via rt.cpan.org.
CHANGE LOG
Released as MIME-parser (1.0): 28 April 1996. Released as MIME-tools (2.0): Halloween 1996.
Released as MIME-tools (4.0): Christmas 1997. Released as MIME-tools (5.0): Mother's Day 2000.
See ChangeLog file for full details.
AUTHOR
Eryq (eryq@zeegee.com), ZeeGee Software Inc (http://www.zeegee.com). David F. Skoll
(dfs@roaringpenguin.com) http://www.roaringpenguin.com.
Copyright (c) 1998, 1999 by ZeeGee Software Inc (www.zeegee.com). Copyright (c) 2004 by Roaring
Penguin Software Inc (www.roaringpenguin.com)
This program is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.
See the COPYING file in the distribution for details.
ACKNOWLEDGMENTS
This kit would not have been possible but for the direct contributions of the following:
Gisle Aas The MIME encoding/decoding modules.
Laurent Amon Bug reports and suggestions.
Graham Barr The new MailTools.
Achim Bohnet Numerous good suggestions, including the I/O model.
Kent Boortz Initial code for RFC-1522-decoding of MIME headers.
Andreas Koenig Numerous good ideas, tons of beta testing,
and help with CPAN-friendly packaging.
Igor Starovoitov Bug reports and suggestions.
Jason L Tibbitts III Bug reports, suggestions, patches.
Not to mention the Accidental Beta Test Team, whose bug reports (and comments) have been invaluable
in improving the whole:
Phil Abercrombie
Mike Blazer
Brandon Browning
Kurt Freytag
Steve Kilbane
Jake Morrison
Rolf Nelson
Joel Noble
Michael W. Normandin
Tim Pierce
Andrew Pimlott
Dragomir R. Radev
Nickolay Saukh
Russell Sutherland
Larry Virden
Zyx
Please forgive me if I've accidentally left you out. Better yet, email me, and I'll put you in.
perl v5.16.2 2012-06-08 MIME::Tools(3)
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