3 @setfilename emacs-mime
4 @settitle Emacs MIME Manual
10 * Emacs MIME: (emacs-mime). The MIME de/composition library.
14 @documentencoding ISO-8859-1
18 @setchapternewpage odd
22 This file documents the Emacs MIME interface functionality.
24 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004
25 Free Software Foundation, Inc.
27 Permission is granted to copy, distribute and/or modify this document
28 under the terms of the GNU Free Documentation License, Version 1.1 or
29 any later version published by the Free Software Foundation; with no
30 Invariant Sections, with the Front-Cover texts being ``A GNU
31 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
32 license is included in the section entitled ``GNU Free Documentation
33 License'' in the Emacs manual.
35 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
36 this GNU Manual, like GNU software. Copies published by the Free
37 Software Foundation raise funds for GNU development.''
39 This document is part of a collection distributed under the GNU Free
40 Documentation License. If you want to distribute this document
41 separately from the collection, you can do so by adding a copy of the
42 license to the document, as described in section 6 of the license.
48 @title Emacs MIME Manual
50 @author by Lars Magne Ingebrigtsen
53 @vskip 0pt plus 1filll
54 Copyright @copyright{} 1998, 1999, 2000, 2001, 2002, 2003 Free Software
57 Permission is granted to copy, distribute and/or modify this document
58 under the terms of the GNU Free Documentation License, Version 1.1 or
59 any later version published by the Free Software Foundation; with the
60 Invariant Sections being none, with the Front-Cover texts being ``A GNU
61 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
62 license is included in the section entitled ``GNU Free Documentation
63 License'' in the Emacs manual.
65 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
66 this GNU Manual, like GNU software. Copies published by the Free
67 Software Foundation raise funds for GNU development.''
69 This document is part of a collection distributed under the GNU Free
70 Documentation License. If you want to distribute this document
71 separately from the collection, you can do so by adding a copy of the
72 license to the document, as described in section 6 of the license.
81 This manual documents the libraries used to compose and display
82 @acronym{MIME} messages.
84 This manual is directed at users who want to modify the behaviour of
85 the @acronym{MIME} encoding/decoding process or want a more detailed
86 picture of how the Emacs @acronym{MIME} library works, and people who want
87 to write functions and commands that manipulate @acronym{MIME} elements.
89 @acronym{MIME} is short for @dfn{Multipurpose Internet Mail Extensions}.
90 This standard is documented in a number of RFCs; mainly RFC2045 (Format
91 of Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
92 Header Extensions for Non-@acronym{ASCII} Text), RFC2048 (Registration
93 Procedures), RFC2049 (Conformance Criteria and Examples). It is highly
94 recommended that anyone who intends writing @acronym{MIME}-compliant software
95 read at least RFC2045 and RFC2047.
98 * Decoding and Viewing:: A framework for decoding and viewing.
99 * Composing:: @acronym{MML}; a language for describing @acronym{MIME} parts.
100 * Interface Functions:: An abstraction over the basic functions.
101 * Basic Functions:: Utility and basic parsing functions.
102 * Standards:: A summary of RFCs and working documents used.
103 * Index:: Function and variable index.
107 @node Decoding and Viewing
108 @chapter Decoding and Viewing
110 This chapter deals with decoding and viewing @acronym{MIME} messages on a
113 The main idea is to first analyze a @acronym{MIME} article, and then allow
114 other programs to do things based on the list of @dfn{handles} that are
115 returned as a result of this analysis.
118 * Dissection:: Analyzing a @acronym{MIME} message.
119 * Non-MIME:: Analyzing a non-@acronym{MIME} message.
120 * Handles:: Handle manipulations.
121 * Display:: Displaying handles.
122 * Display Customization:: Variables that affect display.
123 * Files and Directories:: Saving and naming attachments.
124 * New Viewers:: How to write your own viewers.
131 The @code{mm-dissect-buffer} is the function responsible for dissecting
132 a @acronym{MIME} article. If given a multipart message, it will recursively
133 descend the message, following the structure, and return a tree of
134 @acronym{MIME} handles that describes the structure of the message.
138 @vindex mm-uu-configure-list
140 Gnus also understands some non-@acronym{MIME} attachments, such as
141 postscript, uuencode, binhex, yenc, shar, forward, gnatsweb, pgp,
142 diff. Each of these features can be disabled by add an item into
143 @code{mm-uu-configure-list}. For example,
147 (add-to-list 'mm-uu-configure-list '(pgp-signed . disabled))
173 Non-@acronym{MIME} forwarded message.
181 @acronym{PGP} signed clear text.
184 @findex pgp-encrypted
185 @acronym{PGP} encrypted clear text.
189 @acronym{PGP} public keys.
192 @findex emacs-sources
193 @vindex mm-uu-emacs-sources-regexp
194 Emacs source code. This item works only in the groups matching
195 @code{mm-uu-emacs-sources-regexp}.
199 @vindex mm-uu-diff-groups-regexp
200 Patches. This is intended for groups where diffs of committed files
201 are automatically sent to. It only works in groups matching
202 @code{mm-uu-diff-groups-regexp}.
209 A @acronym{MIME} handle is a list that fully describes a @acronym{MIME}
212 The following macros can be used to access elements in a handle:
215 @item mm-handle-buffer
216 @findex mm-handle-buffer
217 Return the buffer that holds the contents of the undecoded @acronym{MIME}
221 @findex mm-handle-type
222 Return the parsed @code{Content-Type} of the part.
224 @item mm-handle-encoding
225 @findex mm-handle-encoding
226 Return the @code{Content-Transfer-Encoding} of the part.
228 @item mm-handle-undisplayer
229 @findex mm-handle-undisplayer
230 Return the object that can be used to remove the displayed part (if it
233 @item mm-handle-set-undisplayer
234 @findex mm-handle-set-undisplayer
235 Set the undisplayer object.
237 @item mm-handle-disposition
238 @findex mm-handle-disposition
239 Return the parsed @code{Content-Disposition} of the part.
241 @item mm-handle-disposition
242 @findex mm-handle-disposition
243 Return the description of the part.
245 @item mm-get-content-id
246 Returns the handle(s) referred to by @code{Content-ID}.
254 Functions for displaying, removing and saving.
257 @item mm-display-part
258 @findex mm-display-part
262 @findex mm-remove-part
263 Remove the part (if it has been displayed).
266 @findex mm-inlinable-p
267 Say whether a @acronym{MIME} type can be displayed inline.
269 @item mm-automatic-display-p
270 @findex mm-automatic-display-p
271 Say whether a @acronym{MIME} type should be displayed automatically.
273 @item mm-destroy-part
274 @findex mm-destroy-part
275 Free all resources occupied by a part.
279 Offer to save the part in a file.
283 Offer to pipe the part to some process.
285 @item mm-interactively-view-part
286 @findex mm-interactively-view-part
287 Prompt for a mailcap method to use to view the part.
292 @node Display Customization
293 @section Display Customization
297 @item mm-inline-media-tests
298 @vindex mm-inline-media-tests
299 This is an alist where the key is a @acronym{MIME} type, the second element
300 is a function to display the part @dfn{inline} (i.e., inside Emacs), and
301 the third element is a form to be @code{eval}ed to say whether the part
302 can be displayed inline.
304 This variable specifies whether a part @emph{can} be displayed inline,
305 and, if so, how to do it. It does not say whether parts are
306 @emph{actually} displayed inline.
308 @item mm-inlined-types
309 @vindex mm-inlined-types
310 This, on the other hand, says what types are to be displayed inline, if
311 they satisfy the conditions set by the variable above. It's a list of
312 @acronym{MIME} media types.
314 @item mm-automatic-display
315 @vindex mm-automatic-display
316 This is a list of types that are to be displayed ``automatically'', but
317 only if the above variable allows it. That is, only inlinable parts can
318 be displayed automatically.
320 @item mm-automatic-external-display
321 @vindex mm-automatic-external-display
322 This is a list of types that will be displayed automatically in an
325 @item mm-keep-viewer-alive-types
326 @vindex mm-keep-viewer-alive-types
327 This is a list of media types for which the external viewer will not
328 be killed when selecting a different article.
330 @item mm-attachment-override-types
331 @vindex mm-attachment-override-types
332 Some @acronym{MIME} agents create parts that have a content-disposition of
333 @samp{attachment}. This variable allows overriding that disposition and
334 displaying the part inline. (Note that the disposition is only
335 overridden if we are able to, and want to, display the part inline.)
337 @item mm-discouraged-alternatives
338 @vindex mm-discouraged-alternatives
339 List of @acronym{MIME} types that are discouraged when viewing
340 @samp{multipart/alternative}. Viewing agents are supposed to view the
341 last possible part of a message, as that is supposed to be the richest.
342 However, users may prefer other types instead, and this list says what
343 types are most unwanted. If, for instance, @samp{text/html} parts are
344 very unwanted, and @samp{text/richtext} parts are somewhat unwanted,
345 you could say something like:
348 (setq mm-discouraged-alternatives
349 '("text/html" "text/richtext")
351 (remove "text/html" mm-automatic-display))
354 @item mm-inline-large-images
355 @vindex mm-inline-large-images
356 When displaying inline images that are larger than the window, XEmacs
357 does not enable scrolling, which means that you cannot see the whole
358 image. To prevent this, the library tries to determine the image size
359 before displaying it inline, and if it doesn't fit the window, the
360 library will display it externally (e.g. with @samp{ImageMagick} or
361 @samp{xv}). Setting this variable to @code{t} disables this check and
362 makes the library display all inline images as inline, regardless of
365 @item mm-inline-override-types
366 @vindex mm-inline-override-types
367 @code{mm-inlined-types} may include regular expressions, for example to
368 specify that all @samp{text/.*} parts be displayed inline. If a user
369 prefers to have a type that matches such a regular expression be treated
370 as an attachment, that can be accomplished by setting this variable to a
371 list containing that type. For example assuming @code{mm-inlined-types}
372 includes @samp{text/.*}, then including @samp{text/html} in this
373 variable will cause @samp{text/html} parts to be treated as attachments.
375 @item mm-text-html-renderer
376 @vindex mm-text-html-renderer
377 This selects the function used to render @acronym{HTML}. The predefined
378 renderers are selected by the symbols @code{w3},
379 @code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
380 information about emacs-w3m}, @code{links}, @code{lynx},
381 @code{w3m-standalone} or @code{html2text}. If @code{nil} use an
382 external viewer. You can also specify a function, which will be
383 called with a @acronym{MIME} handle as the argument.
385 @item mm-inline-text-html-with-images
386 @vindex mm-inline-text-html-with-images
387 Some @acronym{HTML} mails might have the trick of spammers using
388 @samp{<img>} tags. It is likely to be intended to verify whether you
389 have read the mail. You can prevent your personal informations from
390 leaking by setting this option to @code{nil} (which is the default).
391 It is currently ignored by Emacs/w3. For emacs-w3m, you may use the
392 command @kbd{t} on the image anchor to show an image even if it is
393 @code{nil}.@footnote{The command @kbd{T} will load all images. If you
394 have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
397 @item mm-w3m-safe-url-regexp
398 @vindex mm-w3m-safe-url-regexp
399 A regular expression that matches safe URL names, i.e. URLs that are
400 unlikely to leak personal information when rendering @acronym{HTML}
401 email (the default value is @samp{\\`cid:}). If @code{nil} consider
404 @item mm-inline-text-html-with-w3m-keymap
405 @vindex mm-inline-text-html-with-w3m-keymap
406 You can use emacs-w3m command keys in the inlined text/html part by
407 setting this option to non-@code{nil}. The default value is @code{t}.
409 @item mm-external-terminal-program
410 @vindex mm-external-terminal-program
411 The program used to start an external terminal.
413 @item mm-enable-external
414 @vindex mm-enable-external
415 Indicate whether external MIME handlers should be used.
417 If @code{t}, all defined external MIME handlers are used. If
418 @code{nil}, files are saved to disk (@code{mailcap-save-binary-file}).
419 If it is the symbol @code{ask}, you are prompted before the external
420 @acronym{MIME} handler is invoked.
422 When you launch an attachment through mailcap (@pxref{mailcap}) an
423 attempt is made to use a safe viewer with the safest options--this isn't
424 the case if you save it to disk and launch it in a different way
425 (command line or double-clicking). Anyhow, if you want to be sure not
426 to launch any external programs, set this variable to @code{nil} or
431 @node Files and Directories
432 @section Files and Directories
436 @item mm-default-directory
437 @vindex mm-default-directory
438 The default directory for saving attachments. If @code{nil} use
439 @code{default-directory}.
441 @item mm-tmp-directory
442 @vindex mm-tmp-directory
443 Directory for storing temporary files.
445 @item mm-file-name-rewrite-functions
446 @vindex mm-file-name-rewrite-functions
447 A list of functions used for rewriting file names of @acronym{MIME}
448 parts. Each function is applied successively to the file name.
449 Ready-made functions include
452 @item mm-file-name-delete-control
453 @findex mm-file-name-delete-control
454 Delete all control characters.
456 @item mm-file-name-delete-gotchas
457 @findex mm-file-name-delete-gotchas
458 Delete characters that could have unintended consequences when used
459 with flawed shell scripts, i.e. @samp{|}, @samp{>} and @samp{<}; and
460 @samp{-}, @samp{.} as the first character.
462 @item mm-file-name-delete-whitespace
463 @findex mm-file-name-delete-whitespace
464 Remove all whitespace.
466 @item mm-file-name-trim-whitespace
467 @findex mm-file-name-trim-whitespace
468 Remove leading and trailing whitespace.
470 @item mm-file-name-collapse-whitespace
471 @findex mm-file-name-collapse-whitespace
472 Collapse multiple whitespace characters.
474 @item mm-file-name-replace-whitespace
475 @findex mm-file-name-replace-whitespace
476 @vindex mm-file-name-replace-whitespace
477 Replace whitespace with underscores. Set the variable
478 @code{mm-file-name-replace-whitespace} to any other string if you do
479 not like underscores.
482 The standard Emacs functions @code{capitalize}, @code{downcase},
483 @code{upcase} and @code{upcase-initials} might also prove useful.
485 @item mm-path-name-rewrite-functions
486 @vindex mm-path-name-rewrite-functions
487 List of functions used for rewriting the full file names of @acronym{MIME}
488 parts. This is used when viewing parts externally, and is meant for
489 transforming the absolute name so that non-compliant programs can find
490 the file where it's saved.
497 Here's an example viewer for displaying @code{text/enriched} inline:
500 (defun mm-display-enriched-inline (handle)
503 (mm-insert-part handle)
504 (save-window-excursion
505 (enriched-decode (point-min) (point-max))
506 (setq text (buffer-string))))
507 (mm-insert-inline handle text)))
510 We see that the function takes a @acronym{MIME} handle as its parameter. It
511 then goes to a temporary buffer, inserts the text of the part, does some
512 work on the text, stores the result, goes back to the buffer it was
513 called from and inserts the result.
515 The two important helper functions here are @code{mm-insert-part} and
516 @code{mm-insert-inline}. The first function inserts the text of the
517 handle in the current buffer. It handles charset and/or content
518 transfer decoding. The second function just inserts whatever text you
519 tell it to insert, but it also sets things up so that the text can be
520 ``undisplayed'' in a convenient manner.
526 @cindex MIME Composing
528 @cindex MIME Meta Language
530 Creating a @acronym{MIME} message is boring and non-trivial. Therefore,
531 a library called @code{mml} has been defined that parses a language
532 called @acronym{MML} (@acronym{MIME} Meta Language) and generates
533 @acronym{MIME} messages.
535 @findex mml-generate-mime
536 The main interface function is @code{mml-generate-mime}. It will
537 examine the contents of the current (narrowed-to) buffer and return a
538 string containing the @acronym{MIME} message.
541 * Simple MML Example:: An example @acronym{MML} document.
542 * MML Definition:: All valid @acronym{MML} elements.
543 * Advanced MML Example:: Another example @acronym{MML} document.
544 * Encoding Customization:: Variables that affect encoding.
545 * Charset Translation:: How charsets are mapped from @sc{mule} to @acronym{MIME}.
546 * Conversion:: Going from @acronym{MIME} to @acronym{MML} and vice versa.
547 * Flowed text:: Soft and hard newlines.
551 @node Simple MML Example
552 @section Simple MML Example
554 Here's a simple @samp{multipart/alternative}:
557 <#multipart type=alternative>
558 This is a plain text part.
559 <#part type=text/enriched>
560 <center>This is a centered enriched part</center>
564 After running this through @code{mml-generate-mime}, we get this:
567 Content-Type: multipart/alternative; boundary="=-=-="
573 This is a plain text part.
576 Content-Type: text/enriched
579 <center>This is a centered enriched part</center>
586 @section MML Definition
588 The @acronym{MML} language is very simple. It looks a bit like an SGML
589 application, but it's not.
591 The main concept of @acronym{MML} is the @dfn{part}. Each part can be of a
592 different type or use a different charset. The way to delineate a part
593 is with a @samp{<#part ...>} tag. Multipart parts can be introduced
594 with the @samp{<#multipart ...>} tag. Parts are ended by the
595 @samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
596 @samp{<#part ...>} tags are also closed by the next open tag.
598 There's also the @samp{<#external ...>} tag. These introduce
599 @samp{external/message-body} parts.
601 Each tag can contain zero or more parameters on the form
602 @samp{parameter=value}. The values may be enclosed in quotation marks,
603 but that's not necessary unless the value contains white space. So
604 @samp{filename=/home/user/#hello$^yes} is perfectly valid.
606 The following parameters have meaning in @acronym{MML}; parameters that have no
607 meaning are ignored. The @acronym{MML} parameter names are the same as the
608 @acronym{MIME} parameter names; the things in the parentheses say which
609 header it will be used in.
613 The @acronym{MIME} type of the part (@code{Content-Type}).
616 Use the contents of the file in the body of the part
617 (@code{Content-Disposition}).
620 The contents of the body of the part are to be encoded in the character
621 set specified (@code{Content-Type}). @xref{Charset Translation}.
624 Might be used to suggest a file name if the part is to be saved
625 to a file (@code{Content-Type}).
628 Valid values are @samp{inline} and @samp{attachment}
629 (@code{Content-Disposition}).
632 Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
633 @samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset
637 A description of the part (@code{Content-Description}).
640 RFC822 date when the part was created (@code{Content-Disposition}).
642 @item modification-date
643 RFC822 date when the part was modified (@code{Content-Disposition}).
646 RFC822 date when the part was read (@code{Content-Disposition}).
649 Who to encrypt/sign the part to. This field is used to override any
650 auto-detection based on the To/CC headers.
653 Identity used to sign the part. This field is used to override the
657 The size (in octets) of the part (@code{Content-Disposition}).
660 What technology to sign this @acronym{MML} part with (@code{smime}, @code{pgp}
664 What technology to encrypt this @acronym{MML} part with (@code{smime},
665 @code{pgp} or @code{pgpmime})
669 Parameters for @samp{text/plain}:
673 Formatting parameter for the text, valid values include @samp{fixed}
674 (the default) and @samp{flowed}. Normally you do not specify this
675 manually, since it requires the textual body to be formatted in a
676 special way described in RFC 2646. @xref{Flowed text}.
679 Parameters for @samp{application/octet-stream}:
683 Type of the part; informal---meant for human readers
684 (@code{Content-Type}).
687 Parameters for @samp{message/external-body}:
691 A word indicating the supported access mechanism by which the file may
692 be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
693 @samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
696 The RFC822 date after which the file may no longer be fetched.
697 (@code{Content-Type}.)
700 The size (in octets) of the file. (@code{Content-Type}.)
703 Valid values are @samp{read} and @samp{read-write}
704 (@code{Content-Type}).
708 Parameters for @samp{sign=smime}:
713 File containing key and certificate for signer.
717 Parameters for @samp{encrypt=smime}:
722 File containing certificate for recipient.
727 @node Advanced MML Example
728 @section Advanced MML Example
730 Here's a complex multipart message. It's a @samp{multipart/mixed} that
731 contains many parts, one of which is a @samp{multipart/alternative}.
734 <#multipart type=mixed>
735 <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
736 <#multipart type=alternative>
737 This is a plain text part.
738 <#part type=text/enriched name=enriched.txt>
739 <center>This is a centered enriched part</center>
741 This is a new plain text part.
742 <#part disposition=attachment>
743 This plain text part is an attachment.
747 And this is the resulting @acronym{MIME} message:
750 Content-Type: multipart/mixed; boundary="=-=-="
758 Content-Type: image/jpeg;
760 Content-Disposition: inline;
762 Content-Transfer-Encoding: base64
764 /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
765 Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
766 AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
767 BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
768 RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
769 qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
770 AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
771 AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
772 sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
773 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
774 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
775 L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
776 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
777 tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
778 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
779 pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
780 jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
783 Content-Type: multipart/alternative; boundary="==-=-="
789 This is a plain text part.
792 Content-Type: text/enriched;
796 <center>This is a centered enriched part</center>
802 This is a new plain text part.
805 Content-Disposition: attachment
808 This plain text part is an attachment.
813 @node Encoding Customization
814 @section Encoding Customization
818 @item mm-body-charset-encoding-alist
819 @vindex mm-body-charset-encoding-alist
820 Mapping from @acronym{MIME} charset to encoding to use. This variable is
821 usually used except, e.g., when other requirements force a specific
822 encoding (digitally signed messages require 7bit encodings). The
826 ((iso-2022-jp . 7bit)
827 (iso-2022-jp-2 . 7bit)
833 As an example, if you do not want to have ISO-8859-1 characters
834 quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
835 this variable. You can override this setting on a per-message basis
836 by using the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
838 @item mm-coding-system-priorities
839 @vindex mm-coding-system-priorities
840 Prioritize coding systems to use for outgoing messages. The default
841 is @code{nil}, which means to use the defaults in Emacs. It is a list of
842 coding system symbols (aliases of coding systems does not work, use
843 @kbd{M-x describe-coding-system} to make sure you are not specifying
844 an alias in this variable). For example, if you have configured Emacs
845 to prefer UTF-8, but wish that outgoing messages should be sent in
846 ISO-8859-1 if possible, you can set this variable to
847 @code{(iso-latin-1)}. You can override this setting on a per-message
848 basis by using the @code{charset} @acronym{MML} tag (@pxref{MML Definition}).
850 @item mm-content-transfer-encoding-defaults
851 @vindex mm-content-transfer-encoding-defaults
852 Mapping from @acronym{MIME} types to encoding to use. This variable is usually
853 used except, e.g., when other requirements force a safer encoding
854 (digitally signed messages require 7bit encoding). Besides the normal
855 @acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
856 each case the most efficient of quoted-printable and base64 should be
857 used. You can override this setting on a per-message basis by using
858 the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
860 @item mm-use-ultra-safe-encoding
861 @vindex mm-use-ultra-safe-encoding
862 When this is non-@code{nil}, it means that textual parts are encoded as
863 quoted-printable if they contain lines longer than 76 characters or
864 starting with "From " in the body. Non-7bit encodings (8bit, binary)
865 are generally disallowed. This reduce the probability that a non-8bit
866 clean MTA or MDA changes the message. This should never be set
867 directly, but bound by other functions when necessary (e.g., when
868 encoding messages that are to be digitally signed).
872 @node Charset Translation
873 @section Charset Translation
876 During translation from @acronym{MML} to @acronym{MIME}, for each
877 @acronym{MIME} part which has been composed inside Emacs, an appropriate
878 charset has to be chosen.
880 @vindex mail-parse-charset
881 If you are running a non-@sc{mule} Emacs, this process is simple: If the
882 part contains any non-@acronym{ASCII} (8-bit) characters, the @acronym{MIME} charset
883 given by @code{mail-parse-charset} (a symbol) is used. (Never set this
884 variable directly, though. If you want to change the default charset,
885 please consult the documentation of the package which you use to process
886 @acronym{MIME} messages.
887 @xref{Various Message Variables, , Various Message Variables, message,
888 Message Manual}, for example.)
889 If there are only @acronym{ASCII} characters, the @acronym{MIME} charset US-ASCII is
895 @vindex mm-mime-mule-charset-alist
896 Things are slightly more complicated when running Emacs with @sc{mule}
897 support. In this case, a list of the @sc{mule} charsets used in the
898 part is obtained, and the @sc{mule} charsets are translated to @acronym{MIME}
899 charsets by consulting the variable @code{mm-mime-mule-charset-alist}.
900 If this results in a single @acronym{MIME} charset, this is used to encode
901 the part. But if the resulting list of @acronym{MIME} charsets contains more
902 than one element, two things can happen: If it is possible to encode the
903 part via UTF-8, this charset is used. (For this, Emacs must support
904 the @code{utf-8} coding system, and the part must consist entirely of
905 characters which have Unicode counterparts.) If UTF-8 is not available
906 for some reason, the part is split into several ones, so that each one
907 can be encoded with a single @acronym{MIME} charset. The part can only be
908 split at line boundaries, though---if more than one @acronym{MIME} charset is
909 required to encode a single line, it is not possible to encode the part.
911 When running Emacs with @sc{mule} support, the preferences for which
912 coding system to use is inherited from Emacs itself. This means that
913 if Emacs is set up to prefer UTF-8, it will be used when encoding
914 messages. You can modify this by altering the
915 @code{mm-coding-system-priorities} variable though (@pxref{Encoding
918 The charset to be used can be overridden by setting the @code{charset}
919 @acronym{MML} tag (@pxref{MML Definition}) when composing the message.
921 The encoding of characters (quoted-printable, 8bit etc) is orthogonal
922 to the discussion here, and is controlled by the variables
923 @code{mm-body-charset-encoding-alist} and
924 @code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
931 A (multipart) @acronym{MIME} message can be converted to @acronym{MML}
932 with the @code{mime-to-mml} function. It works on the message in the
933 current buffer, and substitutes @acronym{MML} markup for @acronym{MIME}
934 boundaries. Non-textual parts do not have their contents in the buffer,
935 but instead have the contents in separate buffers that are referred to
936 from the @acronym{MML} tags.
939 An @acronym{MML} message can be converted back to @acronym{MIME} by the
940 @code{mml-to-mime} function.
942 These functions are in certain senses ``lossy''---you will not get back
943 an identical message if you run @code{mime-to-mml} and then
944 @code{mml-to-mime}. Not only will trivial things like the order of the
945 headers differ, but the contents of the headers may also be different.
946 For instance, the original message may use base64 encoding on text,
947 while @code{mml-to-mime} may decide to use quoted-printable encoding, and
950 In essence, however, these two functions should be the inverse of each
951 other. The resulting contents of the message should remain equivalent,
957 @cindex format=flowed
959 The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
960 variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
961 emacs, Emacs Manual}) when encoding a message, and the
962 ``format=flowed'' Content-Type parameter when decoding a message.
964 On encoding text, regardless of @code{use-hard-newlines}, lines
965 terminated by soft newline characters are filled together and wrapped
966 after the column decided by @code{fill-flowed-encode-column}.
967 Quotation marks (matching @samp{^>* ?}) are respected. The variable
968 controls how the text will look in a client that does not support
969 flowed text, the default is to wrap after 66 characters. If hard
970 newline characters are not present in the buffer, no flow encoding
973 On decoding flowed text, lines with soft newline characters are filled
974 together and wrapped after the column decided by
975 @code{fill-flowed-display-column}. The default is to wrap after
980 @findex mm-fill-flowed
981 If non-nil a format=flowed article will be displayed flowed.
985 @node Interface Functions
986 @chapter Interface Functions
987 @cindex interface functions
990 The @code{mail-parse} library is an abstraction over the actual
991 low-level libraries that are described in the next chapter.
993 Standards change, and so programs have to change to fit in the new
994 mold. For instance, RFC2045 describes a syntax for the
995 @code{Content-Type} header that only allows @acronym{ASCII} characters in the
996 parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
997 for continuation headers and non-@acronym{ASCII} characters.
999 The traditional way to deal with this is just to update the library
1000 functions to parse the new syntax. However, this is sometimes the wrong
1001 thing to do. In some instances it may be vital to be able to understand
1002 both the old syntax as well as the new syntax, and if there is only one
1003 library, one must choose between the old version of the library and the
1004 new version of the library.
1006 The Emacs @acronym{MIME} library takes a different tack. It defines a
1007 series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
1008 and so on) that parses strictly according to the corresponding
1009 standard. However, normal programs would not use the functions
1010 provided by these libraries directly, but instead use the functions
1011 provided by the @code{mail-parse} library. The functions in this
1012 library are just aliases to the corresponding functions in the latest
1013 low-level libraries. Using this scheme, programs get a consistent
1014 interface they can use, and library developers are free to create
1015 write code that handles new standards.
1017 The following functions are defined by this library:
1020 @item mail-header-parse-content-type
1021 @findex mail-header-parse-content-type
1022 Parse a @code{Content-Type} header and return a list on the following
1027 (attribute1 . value1)
1028 (attribute2 . value2)
1035 (mail-header-parse-content-type
1036 "image/gif; name=\"b980912.gif\"")
1037 @result{} ("image/gif" (name . "b980912.gif"))
1040 @item mail-header-parse-content-disposition
1041 @findex mail-header-parse-content-disposition
1042 Parse a @code{Content-Disposition} header and return a list on the same
1043 format as the function above.
1045 @item mail-content-type-get
1046 @findex mail-content-type-get
1047 Takes two parameters---a list on the format above, and an attribute.
1048 Returns the value of the attribute.
1051 (mail-content-type-get
1052 '("image/gif" (name . "b980912.gif")) 'name)
1053 @result{} "b980912.gif"
1056 @item mail-header-encode-parameter
1057 @findex mail-header-encode-parameter
1058 Takes a parameter string and returns an encoded version of the string.
1059 This is used for parameters in headers like @code{Content-Type} and
1060 @code{Content-Disposition}.
1062 @item mail-header-remove-comments
1063 @findex mail-header-remove-comments
1064 Return a comment-free version of a header.
1067 (mail-header-remove-comments
1068 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1069 @result{} "Gnus/5.070027 "
1072 @item mail-header-remove-whitespace
1073 @findex mail-header-remove-whitespace
1074 Remove linear white space from a header. Space inside quoted strings
1075 and comments is preserved.
1078 (mail-header-remove-whitespace
1079 "image/gif; name=\"Name with spaces\"")
1080 @result{} "image/gif;name=\"Name with spaces\""
1083 @item mail-header-get-comment
1084 @findex mail-header-get-comment
1085 Return the last comment in a header.
1088 (mail-header-get-comment
1089 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1090 @result{} "Finnish Landrace"
1093 @item mail-header-parse-address
1094 @findex mail-header-parse-address
1095 Parse an address and return a list containing the mailbox and the
1099 (mail-header-parse-address
1100 "Hrvoje Niksic <hniksic@@srce.hr>")
1101 @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
1104 @item mail-header-parse-addresses
1105 @findex mail-header-parse-addresses
1106 Parse a string with list of addresses and return a list of elements like
1107 the one described above.
1110 (mail-header-parse-addresses
1111 "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
1112 @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
1113 ("sb@@metis.no" . "Steinar Bang"))
1116 @item mail-header-parse-date
1117 @findex mail-header-parse-date
1118 Parse a date string and return an Emacs time structure.
1120 @item mail-narrow-to-head
1121 @findex mail-narrow-to-head
1122 Narrow the buffer to the header section of the buffer. Point is placed
1123 at the beginning of the narrowed buffer.
1125 @item mail-header-narrow-to-field
1126 @findex mail-header-narrow-to-field
1127 Narrow the buffer to the header under point. Understands continuation
1130 @item mail-header-fold-field
1131 @findex mail-header-fold-field
1132 Fold the header under point.
1134 @item mail-header-unfold-field
1135 @findex mail-header-unfold-field
1136 Unfold the header under point.
1138 @item mail-header-field-value
1139 @findex mail-header-field-value
1140 Return the value of the field under point.
1142 @item mail-encode-encoded-word-region
1143 @findex mail-encode-encoded-word-region
1144 Encode the non-@acronym{ASCII} words in the region. For instance,
1145 @samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
1147 @item mail-encode-encoded-word-buffer
1148 @findex mail-encode-encoded-word-buffer
1149 Encode the non-@acronym{ASCII} words in the current buffer. This function is
1150 meant to be called narrowed to the headers of a message.
1152 @item mail-encode-encoded-word-string
1153 @findex mail-encode-encoded-word-string
1154 Encode the words that need encoding in a string, and return the result.
1157 (mail-encode-encoded-word-string
1158 "This is naïve, baby")
1159 @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
1162 @item mail-decode-encoded-word-region
1163 @findex mail-decode-encoded-word-region
1164 Decode the encoded words in the region.
1166 @item mail-decode-encoded-word-string
1167 @findex mail-decode-encoded-word-string
1168 Decode the encoded words in the string and return the result.
1171 (mail-decode-encoded-word-string
1172 "This is =?iso-8859-1?q?na=EFve,?= baby")
1173 @result{} "This is naïve, baby"
1178 Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
1179 @code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
1180 in the subsequent sections.
1184 @node Basic Functions
1185 @chapter Basic Functions
1187 This chapter describes the basic, ground-level functions for parsing and
1188 handling. Covered here is parsing @code{From} lines, removing comments
1189 from header lines, decoding encoded words, parsing date headers and so
1190 on. High-level functionality is dealt with in the next chapter
1191 (@pxref{Decoding and Viewing}).
1194 * rfc2045:: Encoding @code{Content-Type} headers.
1195 * rfc2231:: Parsing @code{Content-Type} headers.
1196 * ietf-drums:: Handling mail headers defined by RFC822bis.
1197 * rfc2047:: En/decoding encoded words in headers.
1198 * time-date:: Functions for parsing dates and manipulating time.
1199 * qp:: Quoted-Printable en/decoding.
1200 * base64:: Base64 en/decoding.
1201 * binhex:: Binhex decoding.
1202 * uudecode:: Uuencode decoding.
1203 * yenc:: Yenc decoding.
1204 * rfc1843:: Decoding HZ-encoded text.
1205 * mailcap:: How parts are displayed is specified by the @file{.mailcap} file
1212 RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
1213 imagine that there would be a lot to implement. But there isn't, since
1214 most of the implementation details are delegated to the subsequent
1217 So @file{rfc2045.el} has only a single function:
1220 @item rfc2045-encode-string
1221 @findex rfc2045-encode-string
1222 Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
1223 @var{value} will be quoted if there are non-safe characters in it.
1230 RFC2231 defines a syntax for the @code{Content-Type} and
1231 @code{Content-Disposition} headers. Its snappy name is @dfn{MIME
1232 Parameter Value and Encoded Word Extensions: Character Sets, Languages,
1235 In short, these headers look something like this:
1238 Content-Type: application/x-stuff;
1239 title*0*=us-ascii'en'This%20is%20even%20more%20;
1240 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1244 They usually aren't this bad, though.
1246 The following functions are defined by this library:
1249 @item rfc2231-parse-string
1250 @findex rfc2231-parse-string
1251 Parse a @code{Content-Type} header and return a list describing its
1255 (rfc2231-parse-string
1256 "application/x-stuff;
1257 title*0*=us-ascii'en'This%20is%20even%20more%20;
1258 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1259 title*2=\"isn't it!\"")
1260 @result{} ("application/x-stuff"
1261 (title . "This is even more ***fun*** isn't it!"))
1264 @item rfc2231-get-value
1265 @findex rfc2231-get-value
1266 Takes one of the lists on the format above and returns
1267 the value of the specified attribute.
1269 @item rfc2231-encode-string
1270 @findex rfc2231-encode-string
1271 Encode a parameter in headers likes @code{Content-Type} and
1272 @code{Content-Disposition}.
1280 @dfn{drums} is an IETF working group that is working on the replacement
1283 The functions provided by this library include:
1286 @item ietf-drums-remove-comments
1287 @findex ietf-drums-remove-comments
1288 Remove the comments from the argument and return the results.
1290 @item ietf-drums-remove-whitespace
1291 @findex ietf-drums-remove-whitespace
1292 Remove linear white space from the string and return the results.
1293 Spaces inside quoted strings and comments are left untouched.
1295 @item ietf-drums-get-comment
1296 @findex ietf-drums-get-comment
1297 Return the last most comment from the string.
1299 @item ietf-drums-parse-address
1300 @findex ietf-drums-parse-address
1301 Parse an address string and return a list that contains the mailbox and
1302 the plain text name.
1304 @item ietf-drums-parse-addresses
1305 @findex ietf-drums-parse-addresses
1306 Parse a string that contains any number of comma-separated addresses and
1307 return a list that contains mailbox/plain text pairs.
1309 @item ietf-drums-parse-date
1310 @findex ietf-drums-parse-date
1311 Parse a date string and return an Emacs time structure.
1313 @item ietf-drums-narrow-to-header
1314 @findex ietf-drums-narrow-to-header
1315 Narrow the buffer to the header section of the current buffer.
1323 RFC2047 (Message Header Extensions for Non-@acronym{ASCII} Text) specifies how
1324 non-@acronym{ASCII} text in headers are to be encoded. This is actually rather
1325 complicated, so a number of variables are necessary to tweak what this
1328 The following variables are tweakable:
1331 @item rfc2047-default-charset
1332 @vindex rfc2047-default-charset
1333 Characters in this charset should not be decoded by this library.
1334 This defaults to @code{iso-8859-1}.
1336 @item rfc2047-header-encoding-alist
1337 @vindex rfc2047-header-encoding-alist
1338 This is an alist of header / encoding-type pairs. Its main purpose is
1339 to prevent encoding of certain headers.
1341 The keys can either be header regexps, or @code{t}.
1343 The values can be either @code{nil}, in which case the header(s) in
1344 question won't be encoded, or @code{mime}, which means that they will be
1347 @item rfc2047-charset-encoding-alist
1348 @vindex rfc2047-charset-encoding-alist
1349 RFC2047 specifies two forms of encoding---@code{Q} (a
1350 Quoted-Printable-like encoding) and @code{B} (base64). This alist
1351 specifies which charset should use which encoding.
1353 @item rfc2047-encoding-function-alist
1354 @vindex rfc2047-encoding-function-alist
1355 This is an alist of encoding / function pairs. The encodings are
1356 @code{Q}, @code{B} and @code{nil}.
1358 @item rfc2047-q-encoding-alist
1359 @vindex rfc2047-q-encoding-alist
1360 The @code{Q} encoding isn't quite the same for all headers. Some
1361 headers allow a narrower range of characters, and that is what this
1362 variable is for. It's an alist of header regexps / allowable character
1365 @item rfc2047-encoded-word-regexp
1366 @vindex rfc2047-encoded-word-regexp
1367 When decoding words, this library looks for matches to this regexp.
1371 Those were the variables, and these are this functions:
1374 @item rfc2047-narrow-to-field
1375 @findex rfc2047-narrow-to-field
1376 Narrow the buffer to the header on the current line.
1378 @item rfc2047-encode-message-header
1379 @findex rfc2047-encode-message-header
1380 Should be called narrowed to the header of a message. Encodes according
1381 to @code{rfc2047-header-encoding-alist}.
1383 @item rfc2047-encode-region
1384 @findex rfc2047-encode-region
1385 Encodes all encodable words in the region specified.
1387 @item rfc2047-encode-string
1388 @findex rfc2047-encode-string
1389 Encode a string and return the results.
1391 @item rfc2047-decode-region
1392 @findex rfc2047-decode-region
1393 Decode the encoded words in the region.
1395 @item rfc2047-decode-string
1396 @findex rfc2047-decode-string
1397 Decode a string and return the results.
1405 While not really a part of the @acronym{MIME} library, it is convenient to
1406 document this library here. It deals with parsing @code{Date} headers
1407 and manipulating time. (Not by using tesseracts, though, I'm sorry to
1410 These functions convert between five formats: A date string, an Emacs
1411 time structure, a decoded time list, a second number, and a day number.
1413 Here's a bunch of time/date/second/day examples:
1416 (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
1417 @result{} (54 21 12 12 9 1998 6 nil 7200)
1419 (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
1420 @result{} (13818 19266)
1422 (time-to-seconds '(13818 19266))
1423 @result{} 905595714.0
1425 (seconds-to-time 905595714.0)
1426 @result{} (13818 19266 0)
1428 (time-to-days '(13818 19266))
1431 (days-to-time 729644)
1432 @result{} (961933 65536)
1434 (time-since '(13818 19266))
1437 (time-less-p '(13818 19266) '(13818 19145))
1440 (subtract-time '(13818 19266) '(13818 19145))
1443 (days-between "Sat Sep 12 12:21:54 1998 +0200"
1444 "Sat Sep 07 12:21:54 1998 +0200")
1447 (date-leap-year-p 2000)
1450 (time-to-day-in-year '(13818 19266))
1453 (time-to-number-of-days
1455 (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
1456 @result{} 4.146122685185185
1459 And finally, we have @code{safe-date-to-time}, which does the same as
1460 @code{date-to-time}, but returns a zero time if the date is
1461 syntactically malformed.
1463 The five data representations used are the following:
1467 An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
1468 12:21:54 1998 +0200"}.
1471 An internal Emacs time. For instance: @code{(13818 26466)}.
1474 A floating point representation of the internal Emacs time. For
1475 instance: @code{905595714.0}.
1478 An integer number representing the number of days since 00000101. For
1479 instance: @code{729644}.
1482 A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
1486 All the examples above represent the same moment.
1488 These are the functions available:
1492 Take a date and return a time.
1494 @item time-to-seconds
1495 Take a time and return seconds.
1497 @item seconds-to-time
1498 Take seconds and return a time.
1501 Take a time and return days.
1504 Take days and return a time.
1507 Take a date and return days.
1509 @item time-to-number-of-days
1510 Take a time and return the number of days that represents.
1512 @item safe-date-to-time
1513 Take a date and return a time. If the date is not syntactically valid,
1514 return a ``zero'' date.
1517 Take two times and say whether the first time is less (i. e., earlier)
1518 than the second time.
1521 Take a time and return a time saying how long it was since that time.
1524 Take two times and subtract the second from the first. I. e., return
1525 the time between the two times.
1528 Take two days and return the number of days between those two days.
1530 @item date-leap-year-p
1531 Take a year number and say whether it's a leap year.
1533 @item time-to-day-in-year
1534 Take a time and return the day number within the year that the time is
1543 This library deals with decoding and encoding Quoted-Printable text.
1545 Very briefly explained, qp encoding means translating all 8-bit
1546 characters (and lots of control characters) into things that look like
1547 @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
1550 The following functions are defined by the library:
1553 @item quoted-printable-decode-region
1554 @findex quoted-printable-decode-region
1555 QP-decode all the encoded text in the specified region.
1557 @item quoted-printable-decode-string
1558 @findex quoted-printable-decode-string
1559 Decode the QP-encoded text in a string and return the results.
1561 @item quoted-printable-encode-region
1562 @findex quoted-printable-encode-region
1563 QP-encode all the encodable characters in the specified region. The third
1564 optional parameter @var{fold} specifies whether to fold long lines.
1565 (Long here means 72.)
1567 @item quoted-printable-encode-string
1568 @findex quoted-printable-encode-string
1569 QP-encode all the encodable characters in a string and return the
1579 Base64 is an encoding that encodes three bytes into four characters,
1580 thereby increasing the size by about 33%. The alphabet used for
1581 encoding is very resistant to mangling during transit.
1583 The following functions are defined by this library:
1586 @item base64-encode-region
1587 @findex base64-encode-region
1588 base64 encode the selected region. Return the length of the encoded
1589 text. Optional third argument @var{no-line-break} means do not break
1590 long lines into shorter lines.
1592 @item base64-encode-string
1593 @findex base64-encode-string
1594 base64 encode a string and return the result.
1596 @item base64-decode-region
1597 @findex base64-decode-region
1598 base64 decode the selected region. Return the length of the decoded
1599 text. If the region can't be decoded, return @code{nil} and don't
1602 @item base64-decode-string
1603 @findex base64-decode-string
1604 base64 decode a string and return the result. If the string can't be
1605 decoded, @code{nil} is returned.
1616 @code{binhex} is an encoding that originated in Macintosh environments.
1617 The following function is supplied to deal with these:
1620 @item binhex-decode-region
1621 @findex binhex-decode-region
1622 Decode the encoded text in the region. If given a third parameter, only
1623 decode the @code{binhex} header and return the filename.
1632 @code{uuencode} is probably still the most popular encoding of binaries
1633 used on Usenet, although @code{base64} rules the mail world.
1635 The following function is supplied by this package:
1638 @item uudecode-decode-region
1639 @findex uudecode-decode-region
1640 Decode the text in the region.
1648 @code{yenc} is used for encoding binaries on Usenet. The following
1649 function is supplied by this package:
1652 @item yenc-decode-region
1653 @findex yenc-decode-region
1654 Decode the encoded text in the region.
1665 RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. In
1666 essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
1669 This sentence is in @acronym{ASCII}.
1670 The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
1673 Simple enough, and widely used in China.
1675 The following functions are available to handle this encoding:
1678 @item rfc1843-decode-region
1679 Decode HZ-encoded text in the region.
1681 @item rfc1843-decode-string
1682 Decode a HZ-encoded string and return the result.
1690 The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
1691 handlers and describes how elements are supposed to be displayed.
1692 Here's an example file:
1696 audio/wav; wavplayer %s
1697 application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
1700 This says that all image files should be displayed with @code{gimp},
1701 that WAVE audio files should be played by @code{wavplayer}, and that
1702 MS-WORD files should be inlined by @code{catdoc}.
1704 The @code{mailcap} library parses this file, and provides functions for
1708 @item mailcap-mime-data
1709 @vindex mailcap-mime-data
1710 This variable is an alist of alists containing backup viewing rules.
1714 Interface functions:
1717 @item mailcap-parse-mailcaps
1718 @findex mailcap-parse-mailcaps
1719 Parse the @file{~/.mailcap} file.
1721 @item mailcap-mime-info
1722 Takes a @acronym{MIME} type as its argument and returns the matching viewer.
1732 The Emacs @acronym{MIME} library implements handling of various elements
1733 according to a (somewhat) large number of RFCs, drafts and standards
1734 documents. This chapter lists the relevant ones. They can all be
1735 fetched from @uref{http://quimby.gnus.org/notes/}.
1740 Standard for the Format of ARPA Internet Text Messages.
1743 Standard for Interchange of USENET Messages
1746 Format of Internet Message Bodies
1752 Message Header Extensions for Non-@acronym{ASCII} Text
1755 Registration Procedures
1758 Conformance Criteria and Examples
1761 @acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
1762 Languages, and Continuations
1765 HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
1766 @acronym{ASCII} characters
1768 @item draft-ietf-drums-msg-fmt-05.txt
1769 Draft for the successor of RFC822
1772 The @acronym{MIME} Multipart/Related Content-type
1775 The Multipart/Report Content Type for the Reporting of Mail System
1776 Administrative Messages
1779 Communicating Presentation Information in Internet Messages: The
1780 Content-Disposition Header Field
1783 Documentation of the text/plain format parameter for flowed text.
1799 @c coding: iso-8859-1