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" below.
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" below for details):
Encoding: | Normally used when message contents are:
-------------------------------------------------------------------
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.
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¶
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.
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", 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.
LICENSE¶
This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
See the COPYING file for more details.