3 @setfilename ../info/emacs-mime
4 @settitle Emacs MIME Manual
10 This file documents the Emacs MIME interface functionality.
12 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
13 Free Software Foundation, Inc.
16 Permission is granted to copy, distribute and/or modify this document
17 under the terms of the GNU Free Documentation License, Version 1.2 or
18 any later version published by the Free Software Foundation; with no
19 Invariant Sections, with the Front-Cover texts being ``A GNU
20 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
21 license is included in the section entitled ``GNU Free Documentation
22 License'' in the Emacs manual.
24 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
25 this GNU Manual, like GNU software. Copies published by the Free
26 Software Foundation raise funds for GNU development.''
28 This document is part of a collection distributed under the GNU Free
29 Documentation License. If you want to distribute this document
30 separately from the collection, you can do so by adding a copy of the
31 license to the document, as described in section 6 of the license.
37 * Emacs MIME: (emacs-mime). Emacs MIME de/composition library.
42 @setchapternewpage odd
45 @title Emacs MIME Manual
47 @author by Lars Magne Ingebrigtsen
49 @vskip 0pt plus 1filll
56 This manual documents the libraries used to compose and display
57 @acronym{MIME} messages.
59 This manual is directed at users who want to modify the behavior of
60 the @acronym{MIME} encoding/decoding process or want a more detailed
61 picture of how the Emacs @acronym{MIME} library works, and people who want
62 to write functions and commands that manipulate @acronym{MIME} elements.
64 @acronym{MIME} is short for @dfn{Multipurpose Internet Mail Extensions}.
65 This standard is documented in a number of RFCs; mainly RFC2045 (Format
66 of Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
67 Header Extensions for Non-@acronym{ASCII} Text), RFC2048 (Registration
68 Procedures), RFC2049 (Conformance Criteria and Examples). It is highly
69 recommended that anyone who intends writing @acronym{MIME}-compliant software
70 read at least RFC2045 and RFC2047.
73 * Decoding and Viewing:: A framework for decoding and viewing.
74 * Composing:: @acronym{MML}; a language for describing @acronym{MIME} parts.
75 * Interface Functions:: An abstraction over the basic functions.
76 * Basic Functions:: Utility and basic parsing functions.
77 * Standards:: A summary of RFCs and working documents used.
78 * Index:: Function and variable index.
82 @node Decoding and Viewing
83 @chapter Decoding and Viewing
85 This chapter deals with decoding and viewing @acronym{MIME} messages on a
88 The main idea is to first analyze a @acronym{MIME} article, and then allow
89 other programs to do things based on the list of @dfn{handles} that are
90 returned as a result of this analysis.
93 * Dissection:: Analyzing a @acronym{MIME} message.
94 * Non-MIME:: Analyzing a non-@acronym{MIME} message.
95 * Handles:: Handle manipulations.
96 * Display:: Displaying handles.
97 * Display Customization:: Variables that affect display.
98 * Files and Directories:: Saving and naming attachments.
99 * New Viewers:: How to write your own viewers.
106 The @code{mm-dissect-buffer} is the function responsible for dissecting
107 a @acronym{MIME} article. If given a multipart message, it will recursively
108 descend the message, following the structure, and return a tree of
109 @acronym{MIME} handles that describes the structure of the message.
113 @vindex mm-uu-configure-list
115 Gnus also understands some non-@acronym{MIME} attachments, such as
116 postscript, uuencode, binhex, yenc, shar, forward, gnatsweb, pgp,
117 diff. Each of these features can be disabled by add an item into
118 @code{mm-uu-configure-list}. For example,
122 (add-to-list 'mm-uu-configure-list '(pgp-signed . disabled))
148 Non-@acronym{MIME} forwarded message.
156 @acronym{PGP} signed clear text.
159 @findex pgp-encrypted
160 @acronym{PGP} encrypted clear text.
164 @acronym{PGP} public keys.
167 @findex emacs-sources
168 @vindex mm-uu-emacs-sources-regexp
169 Emacs source code. This item works only in the groups matching
170 @code{mm-uu-emacs-sources-regexp}.
174 @vindex mm-uu-diff-groups-regexp
175 Patches. This is intended for groups where diffs of committed files
176 are automatically sent to. It only works in groups matching
177 @code{mm-uu-diff-groups-regexp}.
184 A @acronym{MIME} handle is a list that fully describes a @acronym{MIME}
187 The following macros can be used to access elements in a handle:
190 @item mm-handle-buffer
191 @findex mm-handle-buffer
192 Return the buffer that holds the contents of the undecoded @acronym{MIME}
196 @findex mm-handle-type
197 Return the parsed @code{Content-Type} of the part.
199 @item mm-handle-encoding
200 @findex mm-handle-encoding
201 Return the @code{Content-Transfer-Encoding} of the part.
203 @item mm-handle-undisplayer
204 @findex mm-handle-undisplayer
205 Return the object that can be used to remove the displayed part (if it
208 @item mm-handle-set-undisplayer
209 @findex mm-handle-set-undisplayer
210 Set the undisplayer object.
212 @item mm-handle-disposition
213 @findex mm-handle-disposition
214 Return the parsed @code{Content-Disposition} of the part.
216 @item mm-get-content-id
217 Returns the handle(s) referred to by @code{Content-ID}.
225 Functions for displaying, removing and saving.
228 @item mm-display-part
229 @findex mm-display-part
233 @findex mm-remove-part
234 Remove the part (if it has been displayed).
237 @findex mm-inlinable-p
238 Say whether a @acronym{MIME} type can be displayed inline.
240 @item mm-automatic-display-p
241 @findex mm-automatic-display-p
242 Say whether a @acronym{MIME} type should be displayed automatically.
244 @item mm-destroy-part
245 @findex mm-destroy-part
246 Free all resources occupied by a part.
250 Offer to save the part in a file.
254 Offer to pipe the part to some process.
256 @item mm-interactively-view-part
257 @findex mm-interactively-view-part
258 Prompt for a mailcap method to use to view the part.
263 @node Display Customization
264 @section Display Customization
268 @item mm-inline-media-tests
269 @vindex mm-inline-media-tests
270 This is an alist where the key is a @acronym{MIME} type, the second element
271 is a function to display the part @dfn{inline} (i.e., inside Emacs), and
272 the third element is a form to be @code{eval}ed to say whether the part
273 can be displayed inline.
275 This variable specifies whether a part @emph{can} be displayed inline,
276 and, if so, how to do it. It does not say whether parts are
277 @emph{actually} displayed inline.
279 @item mm-inlined-types
280 @vindex mm-inlined-types
281 This, on the other hand, says what types are to be displayed inline, if
282 they satisfy the conditions set by the variable above. It's a list of
283 @acronym{MIME} media types.
285 @item mm-automatic-display
286 @vindex mm-automatic-display
287 This is a list of types that are to be displayed ``automatically'', but
288 only if the above variable allows it. That is, only inlinable parts can
289 be displayed automatically.
291 @item mm-automatic-external-display
292 @vindex mm-automatic-external-display
293 This is a list of types that will be displayed automatically in an
296 @item mm-keep-viewer-alive-types
297 @vindex mm-keep-viewer-alive-types
298 This is a list of media types for which the external viewer will not
299 be killed when selecting a different article.
301 @item mm-attachment-override-types
302 @vindex mm-attachment-override-types
303 Some @acronym{MIME} agents create parts that have a content-disposition of
304 @samp{attachment}. This variable allows overriding that disposition and
305 displaying the part inline. (Note that the disposition is only
306 overridden if we are able to, and want to, display the part inline.)
308 @item mm-discouraged-alternatives
309 @vindex mm-discouraged-alternatives
310 List of @acronym{MIME} types that are discouraged when viewing
311 @samp{multipart/alternative}. Viewing agents are supposed to view the
312 last possible part of a message, as that is supposed to be the richest.
313 However, users may prefer other types instead, and this list says what
314 types are most unwanted. If, for instance, @samp{text/html} parts are
315 very unwanted, and @samp{text/richtext} parts are somewhat unwanted,
316 you could say something like:
319 (setq mm-discouraged-alternatives
320 '("text/html" "text/richtext")
322 (remove "text/html" mm-automatic-display))
325 Adding @code{"image/.*"} might also be useful. Spammers use it as the
326 prefered part of @samp{multipart/alternative} messages. See also
327 @code{gnus-buttonized-mime-types} (@pxref{MIME Commands, ,MIME Commands,
328 gnus, Gnus Manual}), to which adding @code{"multipart/alternative"}
329 enables you to choose manually one of two types those mails include.
331 @item mm-inline-large-images
332 @vindex mm-inline-large-images
333 When displaying inline images that are larger than the window, Emacs
334 does not enable scrolling, which means that you cannot see the whole
335 image. To prevent this, the library tries to determine the image size
336 before displaying it inline, and if it doesn't fit the window, the
337 library will display it externally (e.g. with @samp{ImageMagick} or
338 @samp{xv}). Setting this variable to @code{t} disables this check and
339 makes the library display all inline images as inline, regardless of
342 @item mm-inline-override-types
343 @vindex mm-inline-override-types
344 @code{mm-inlined-types} may include regular expressions, for example to
345 specify that all @samp{text/.*} parts be displayed inline. If a user
346 prefers to have a type that matches such a regular expression be treated
347 as an attachment, that can be accomplished by setting this variable to a
348 list containing that type. For example assuming @code{mm-inlined-types}
349 includes @samp{text/.*}, then including @samp{text/html} in this
350 variable will cause @samp{text/html} parts to be treated as attachments.
352 @item mm-text-html-renderer
353 @vindex mm-text-html-renderer
354 This selects the function used to render @acronym{HTML}. The predefined
355 renderers are selected by the symbols @code{w3},
356 @code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
357 information about emacs-w3m}, @code{links}, @code{lynx},
358 @code{w3m-standalone} or @code{html2text}. If @code{nil} use an
359 external viewer. You can also specify a function, which will be
360 called with a @acronym{MIME} handle as the argument.
362 @item mm-inline-text-html-with-images
363 @vindex mm-inline-text-html-with-images
364 Some @acronym{HTML} mails might have the trick of spammers using
365 @samp{<img>} tags. It is likely to be intended to verify whether you
366 have read the mail. You can prevent your personal informations from
367 leaking by setting this option to @code{nil} (which is the default).
368 It is currently ignored by Emacs/w3. For emacs-w3m, you may use the
369 command @kbd{t} on the image anchor to show an image even if it is
370 @code{nil}.@footnote{The command @kbd{T} will load all images. If you
371 have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
374 @item mm-w3m-safe-url-regexp
375 @vindex mm-w3m-safe-url-regexp
376 A regular expression that matches safe URL names, i.e. URLs that are
377 unlikely to leak personal information when rendering @acronym{HTML}
378 email (the default value is @samp{\\`cid:}). If @code{nil} consider
381 @item mm-inline-text-html-with-w3m-keymap
382 @vindex mm-inline-text-html-with-w3m-keymap
383 You can use emacs-w3m command keys in the inlined text/html part by
384 setting this option to non-@code{nil}. The default value is @code{t}.
386 @item mm-external-terminal-program
387 @vindex mm-external-terminal-program
388 The program used to start an external terminal.
390 @item mm-enable-external
391 @vindex mm-enable-external
392 Indicate whether external @acronym{MIME} handlers should be used.
394 If @code{t}, all defined external @acronym{MIME} handlers are used. If
395 @code{nil}, files are saved to disk (@code{mailcap-save-binary-file}).
396 If it is the symbol @code{ask}, you are prompted before the external
397 @acronym{MIME} handler is invoked.
399 When you launch an attachment through mailcap (@pxref{mailcap}) an
400 attempt is made to use a safe viewer with the safest options---this isn't
401 the case if you save it to disk and launch it in a different way
402 (command line or double-clicking). Anyhow, if you want to be sure not
403 to launch any external programs, set this variable to @code{nil} or
408 @node Files and Directories
409 @section Files and Directories
413 @item mm-default-directory
414 @vindex mm-default-directory
415 The default directory for saving attachments. If @code{nil} use
416 @code{default-directory}.
418 @item mm-tmp-directory
419 @vindex mm-tmp-directory
420 Directory for storing temporary files.
422 @item mm-file-name-rewrite-functions
423 @vindex mm-file-name-rewrite-functions
424 A list of functions used for rewriting file names of @acronym{MIME}
425 parts. Each function is applied successively to the file name.
426 Ready-made functions include
429 @item mm-file-name-delete-control
430 @findex mm-file-name-delete-control
431 Delete all control characters.
433 @item mm-file-name-delete-gotchas
434 @findex mm-file-name-delete-gotchas
435 Delete characters that could have unintended consequences when used
436 with flawed shell scripts, i.e. @samp{|}, @samp{>} and @samp{<}; and
437 @samp{-}, @samp{.} as the first character.
439 @item mm-file-name-delete-whitespace
440 @findex mm-file-name-delete-whitespace
441 Remove all whitespace.
443 @item mm-file-name-trim-whitespace
444 @findex mm-file-name-trim-whitespace
445 Remove leading and trailing whitespace.
447 @item mm-file-name-collapse-whitespace
448 @findex mm-file-name-collapse-whitespace
449 Collapse multiple whitespace characters.
451 @item mm-file-name-replace-whitespace
452 @findex mm-file-name-replace-whitespace
453 @vindex mm-file-name-replace-whitespace
454 Replace whitespace with underscores. Set the variable
455 @code{mm-file-name-replace-whitespace} to any other string if you do
456 not like underscores.
459 The standard Emacs functions @code{capitalize}, @code{downcase},
460 @code{upcase} and @code{upcase-initials} might also prove useful.
462 @item mm-path-name-rewrite-functions
463 @vindex mm-path-name-rewrite-functions
464 List of functions used for rewriting the full file names of @acronym{MIME}
465 parts. This is used when viewing parts externally, and is meant for
466 transforming the absolute name so that non-compliant programs can find
467 the file where it's saved.
474 Here's an example viewer for displaying @code{text/enriched} inline:
477 (defun mm-display-enriched-inline (handle)
480 (mm-insert-part handle)
481 (save-window-excursion
482 (enriched-decode (point-min) (point-max))
483 (setq text (buffer-string))))
484 (mm-insert-inline handle text)))
487 We see that the function takes a @acronym{MIME} handle as its parameter. It
488 then goes to a temporary buffer, inserts the text of the part, does some
489 work on the text, stores the result, goes back to the buffer it was
490 called from and inserts the result.
492 The two important helper functions here are @code{mm-insert-part} and
493 @code{mm-insert-inline}. The first function inserts the text of the
494 handle in the current buffer. It handles charset and/or content
495 transfer decoding. The second function just inserts whatever text you
496 tell it to insert, but it also sets things up so that the text can be
497 ``undisplayed'' in a convenient manner.
503 @cindex MIME Composing
505 @cindex MIME Meta Language
507 Creating a @acronym{MIME} message is boring and non-trivial. Therefore,
508 a library called @code{mml} has been defined that parses a language
509 called @acronym{MML} (@acronym{MIME} Meta Language) and generates
510 @acronym{MIME} messages.
512 @findex mml-generate-mime
513 The main interface function is @code{mml-generate-mime}. It will
514 examine the contents of the current (narrowed-to) buffer and return a
515 string containing the @acronym{MIME} message.
518 * Simple MML Example:: An example @acronym{MML} document.
519 * MML Definition:: All valid @acronym{MML} elements.
520 * Advanced MML Example:: Another example @acronym{MML} document.
521 * Encoding Customization:: Variables that affect encoding.
522 * Charset Translation:: How charsets are mapped from @sc{mule} to @acronym{MIME}.
523 * Conversion:: Going from @acronym{MIME} to @acronym{MML} and vice versa.
524 * Flowed text:: Soft and hard newlines.
528 @node Simple MML Example
529 @section Simple MML Example
531 Here's a simple @samp{multipart/alternative}:
534 <#multipart type=alternative>
535 This is a plain text part.
536 <#part type=text/enriched>
537 <center>This is a centered enriched part</center>
541 After running this through @code{mml-generate-mime}, we get this:
544 Content-Type: multipart/alternative; boundary="=-=-="
550 This is a plain text part.
553 Content-Type: text/enriched
556 <center>This is a centered enriched part</center>
563 @section MML Definition
565 The @acronym{MML} language is very simple. It looks a bit like an SGML
566 application, but it's not.
568 The main concept of @acronym{MML} is the @dfn{part}. Each part can be of a
569 different type or use a different charset. The way to delineate a part
570 is with a @samp{<#part ...>} tag. Multipart parts can be introduced
571 with the @samp{<#multipart ...>} tag. Parts are ended by the
572 @samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
573 @samp{<#part ...>} tags are also closed by the next open tag.
575 There's also the @samp{<#external ...>} tag. These introduce
576 @samp{external/message-body} parts.
578 Each tag can contain zero or more parameters on the form
579 @samp{parameter=value}. The values may be enclosed in quotation marks,
580 but that's not necessary unless the value contains white space. So
581 @samp{filename=/home/user/#hello$^yes} is perfectly valid.
583 The following parameters have meaning in @acronym{MML}; parameters that have no
584 meaning are ignored. The @acronym{MML} parameter names are the same as the
585 @acronym{MIME} parameter names; the things in the parentheses say which
586 header it will be used in.
590 The @acronym{MIME} type of the part (@code{Content-Type}).
593 Use the contents of the file in the body of the part
594 (@code{Content-Disposition}).
597 The contents of the body of the part are to be encoded in the character
598 set specified (@code{Content-Type}). @xref{Charset Translation}.
601 Might be used to suggest a file name if the part is to be saved
602 to a file (@code{Content-Type}).
605 Valid values are @samp{inline} and @samp{attachment}
606 (@code{Content-Disposition}).
609 Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
610 @samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset
614 A description of the part (@code{Content-Description}).
617 RFC822 date when the part was created (@code{Content-Disposition}).
619 @item modification-date
620 RFC822 date when the part was modified (@code{Content-Disposition}).
623 RFC822 date when the part was read (@code{Content-Disposition}).
626 Who to encrypt/sign the part to. This field is used to override any
627 auto-detection based on the To/CC headers.
630 Identity used to sign the part. This field is used to override the
634 The size (in octets) of the part (@code{Content-Disposition}).
637 What technology to sign this @acronym{MML} part with (@code{smime}, @code{pgp}
641 What technology to encrypt this @acronym{MML} part with (@code{smime},
642 @code{pgp} or @code{pgpmime})
646 Parameters for @samp{text/plain}:
650 Formatting parameter for the text, valid values include @samp{fixed}
651 (the default) and @samp{flowed}. Normally you do not specify this
652 manually, since it requires the textual body to be formatted in a
653 special way described in RFC 2646. @xref{Flowed text}.
656 Parameters for @samp{application/octet-stream}:
660 Type of the part; informal---meant for human readers
661 (@code{Content-Type}).
664 Parameters for @samp{message/external-body}:
668 A word indicating the supported access mechanism by which the file may
669 be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
670 @samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
673 The RFC822 date after which the file may no longer be fetched.
674 (@code{Content-Type}.)
677 The size (in octets) of the file. (@code{Content-Type}.)
680 Valid values are @samp{read} and @samp{read-write}
681 (@code{Content-Type}).
685 Parameters for @samp{sign=smime}:
690 File containing key and certificate for signer.
694 Parameters for @samp{encrypt=smime}:
699 File containing certificate for recipient.
704 @node Advanced MML Example
705 @section Advanced MML Example
707 Here's a complex multipart message. It's a @samp{multipart/mixed} that
708 contains many parts, one of which is a @samp{multipart/alternative}.
711 <#multipart type=mixed>
712 <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
713 <#multipart type=alternative>
714 This is a plain text part.
715 <#part type=text/enriched name=enriched.txt>
716 <center>This is a centered enriched part</center>
718 This is a new plain text part.
719 <#part disposition=attachment>
720 This plain text part is an attachment.
724 And this is the resulting @acronym{MIME} message:
727 Content-Type: multipart/mixed; boundary="=-=-="
735 Content-Type: image/jpeg;
737 Content-Disposition: inline;
739 Content-Transfer-Encoding: base64
741 /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
742 Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
743 AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
744 BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
745 RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
746 qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
747 AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
748 AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
749 sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
750 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
751 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
752 L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
753 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
754 tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
755 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
756 pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
757 jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
760 Content-Type: multipart/alternative; boundary="==-=-="
766 This is a plain text part.
769 Content-Type: text/enriched;
773 <center>This is a centered enriched part</center>
779 This is a new plain text part.
782 Content-Disposition: attachment
785 This plain text part is an attachment.
790 @node Encoding Customization
791 @section Encoding Customization
795 @item mm-body-charset-encoding-alist
796 @vindex mm-body-charset-encoding-alist
797 Mapping from @acronym{MIME} charset to encoding to use. This variable is
798 usually used except, e.g., when other requirements force a specific
799 encoding (digitally signed messages require 7bit encodings). The
803 ((iso-2022-jp . 7bit)
804 (iso-2022-jp-2 . 7bit)
810 As an example, if you do not want to have ISO-8859-1 characters
811 quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
812 this variable. You can override this setting on a per-message basis
813 by using the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
815 @item mm-coding-system-priorities
816 @vindex mm-coding-system-priorities
817 Prioritize coding systems to use for outgoing messages. The default
818 is @code{nil}, which means to use the defaults in Emacs, but is
819 @code{(iso-8859-1 iso-2022-jp iso-2022-jp-2 shift_jis utf-8)} when
820 running Emacs in the Japanese language environment. It is a list of
821 coding system symbols (aliases of coding systems are also allowed, use
822 @kbd{M-x describe-coding-system} to make sure you are specifying correct
823 coding system names). For example, if you have configured Emacs
824 to prefer UTF-8, but wish that outgoing messages should be sent in
825 ISO-8859-1 if possible, you can set this variable to
826 @code{(iso-8859-1)}. You can override this setting on a per-message
827 basis by using the @code{charset} @acronym{MML} tag (@pxref{MML Definition}).
829 @item mm-content-transfer-encoding-defaults
830 @vindex mm-content-transfer-encoding-defaults
831 Mapping from @acronym{MIME} types to encoding to use. This variable is usually
832 used except, e.g., when other requirements force a safer encoding
833 (digitally signed messages require 7bit encoding). Besides the normal
834 @acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
835 each case the most efficient of quoted-printable and base64 should be
838 @code{qp-or-base64} has another effect. It will fold long lines so that
839 MIME parts may not be broken by MTA. So do @code{quoted-printable} and
842 Note that it affects body encoding only when a part is a raw forwarded
843 message (which will be made by @code{gnus-summary-mail-forward} with the
844 arg 2 for example) or is neither the @samp{text/*} type nor the
845 @samp{message/*} type. Even though in those cases, you can override
846 this setting on a per-message basis by using the @code{encoding}
847 @acronym{MML} tag (@pxref{MML Definition}).
849 @item mm-use-ultra-safe-encoding
850 @vindex mm-use-ultra-safe-encoding
851 When this is non-@code{nil}, it means that textual parts are encoded as
852 quoted-printable if they contain lines longer than 76 characters or
853 starting with "From " in the body. Non-7bit encodings (8bit, binary)
854 are generally disallowed. This reduce the probability that a non-8bit
855 clean MTA or MDA changes the message. This should never be set
856 directly, but bound by other functions when necessary (e.g., when
857 encoding messages that are to be digitally signed).
861 @node Charset Translation
862 @section Charset Translation
865 During translation from @acronym{MML} to @acronym{MIME}, for each
866 @acronym{MIME} part which has been composed inside Emacs, an appropriate
867 charset has to be chosen.
869 @vindex mail-parse-charset
870 If you are running a non-@sc{mule} Emacs, this process is simple: If the
871 part contains any non-@acronym{ASCII} (8-bit) characters, the @acronym{MIME} charset
872 given by @code{mail-parse-charset} (a symbol) is used. (Never set this
873 variable directly, though. If you want to change the default charset,
874 please consult the documentation of the package which you use to process
875 @acronym{MIME} messages.
876 @xref{Various Message Variables, , Various Message Variables, message,
877 Message Manual}, for example.)
878 If there are only @acronym{ASCII} characters, the @acronym{MIME} charset US-ASCII is
884 @vindex mm-mime-mule-charset-alist
885 Things are slightly more complicated when running Emacs with @sc{mule}
886 support. In this case, a list of the @sc{mule} charsets used in the
887 part is obtained, and the @sc{mule} charsets are translated to
888 @acronym{MIME} charsets by consulting the table provided by Emacs itself
889 or the variable @code{mm-mime-mule-charset-alist} for XEmacs.
890 If this results in a single @acronym{MIME} charset, this is used to encode
891 the part. But if the resulting list of @acronym{MIME} charsets contains more
892 than one element, two things can happen: If it is possible to encode the
893 part via UTF-8, this charset is used. (For this, Emacs must support
894 the @code{utf-8} coding system, and the part must consist entirely of
895 characters which have Unicode counterparts.) If UTF-8 is not available
896 for some reason, the part is split into several ones, so that each one
897 can be encoded with a single @acronym{MIME} charset. The part can only be
898 split at line boundaries, though---if more than one @acronym{MIME} charset is
899 required to encode a single line, it is not possible to encode the part.
901 When running Emacs with @sc{mule} support, the preferences for which
902 coding system to use is inherited from Emacs itself. This means that
903 if Emacs is set up to prefer UTF-8, it will be used when encoding
904 messages. You can modify this by altering the
905 @code{mm-coding-system-priorities} variable though (@pxref{Encoding
908 The charset to be used can be overridden by setting the @code{charset}
909 @acronym{MML} tag (@pxref{MML Definition}) when composing the message.
911 The encoding of characters (quoted-printable, 8bit etc) is orthogonal
912 to the discussion here, and is controlled by the variables
913 @code{mm-body-charset-encoding-alist} and
914 @code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
921 A (multipart) @acronym{MIME} message can be converted to @acronym{MML}
922 with the @code{mime-to-mml} function. It works on the message in the
923 current buffer, and substitutes @acronym{MML} markup for @acronym{MIME}
924 boundaries. Non-textual parts do not have their contents in the buffer,
925 but instead have the contents in separate buffers that are referred to
926 from the @acronym{MML} tags.
929 An @acronym{MML} message can be converted back to @acronym{MIME} by the
930 @code{mml-to-mime} function.
932 These functions are in certain senses ``lossy''---you will not get back
933 an identical message if you run @code{mime-to-mml} and then
934 @code{mml-to-mime}. Not only will trivial things like the order of the
935 headers differ, but the contents of the headers may also be different.
936 For instance, the original message may use base64 encoding on text,
937 while @code{mml-to-mime} may decide to use quoted-printable encoding, and
940 In essence, however, these two functions should be the inverse of each
941 other. The resulting contents of the message should remain equivalent,
947 @cindex format=flowed
949 The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
950 variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
951 emacs, Emacs Manual}) when encoding a message, and the
952 ``format=flowed'' Content-Type parameter when decoding a message.
954 On encoding text, regardless of @code{use-hard-newlines}, lines
955 terminated by soft newline characters are filled together and wrapped
956 after the column decided by @code{fill-flowed-encode-column}.
957 Quotation marks (matching @samp{^>* ?}) are respected. The variable
958 controls how the text will look in a client that does not support
959 flowed text, the default is to wrap after 66 characters. If hard
960 newline characters are not present in the buffer, no flow encoding
963 On decoding flowed text, lines with soft newline characters are filled
964 together and wrapped after the column decided by
965 @code{fill-flowed-display-column}. The default is to wrap after
971 @node Interface Functions
972 @chapter Interface Functions
973 @cindex interface functions
976 The @code{mail-parse} library is an abstraction over the actual
977 low-level libraries that are described in the next chapter.
979 Standards change, and so programs have to change to fit in the new
980 mold. For instance, RFC2045 describes a syntax for the
981 @code{Content-Type} header that only allows @acronym{ASCII} characters in the
982 parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
983 for continuation headers and non-@acronym{ASCII} characters.
985 The traditional way to deal with this is just to update the library
986 functions to parse the new syntax. However, this is sometimes the wrong
987 thing to do. In some instances it may be vital to be able to understand
988 both the old syntax as well as the new syntax, and if there is only one
989 library, one must choose between the old version of the library and the
990 new version of the library.
992 The Emacs @acronym{MIME} library takes a different tack. It defines a
993 series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
994 and so on) that parses strictly according to the corresponding
995 standard. However, normal programs would not use the functions
996 provided by these libraries directly, but instead use the functions
997 provided by the @code{mail-parse} library. The functions in this
998 library are just aliases to the corresponding functions in the latest
999 low-level libraries. Using this scheme, programs get a consistent
1000 interface they can use, and library developers are free to create
1001 write code that handles new standards.
1003 The following functions are defined by this library:
1006 @item mail-header-parse-content-type
1007 @findex mail-header-parse-content-type
1008 Parse a @code{Content-Type} header and return a list on the following
1013 (attribute1 . value1)
1014 (attribute2 . value2)
1021 (mail-header-parse-content-type
1022 "image/gif; name=\"b980912.gif\"")
1023 @result{} ("image/gif" (name . "b980912.gif"))
1026 @item mail-header-parse-content-disposition
1027 @findex mail-header-parse-content-disposition
1028 Parse a @code{Content-Disposition} header and return a list on the same
1029 format as the function above.
1031 @item mail-content-type-get
1032 @findex mail-content-type-get
1033 Takes two parameters---a list on the format above, and an attribute.
1034 Returns the value of the attribute.
1037 (mail-content-type-get
1038 '("image/gif" (name . "b980912.gif")) 'name)
1039 @result{} "b980912.gif"
1042 @item mail-header-encode-parameter
1043 @findex mail-header-encode-parameter
1044 Takes a parameter string and returns an encoded version of the string.
1045 This is used for parameters in headers like @code{Content-Type} and
1046 @code{Content-Disposition}.
1048 @item mail-header-remove-comments
1049 @findex mail-header-remove-comments
1050 Return a comment-free version of a header.
1053 (mail-header-remove-comments
1054 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1055 @result{} "Gnus/5.070027 "
1058 @item mail-header-remove-whitespace
1059 @findex mail-header-remove-whitespace
1060 Remove linear white space from a header. Space inside quoted strings
1061 and comments is preserved.
1064 (mail-header-remove-whitespace
1065 "image/gif; name=\"Name with spaces\"")
1066 @result{} "image/gif;name=\"Name with spaces\""
1069 @item mail-header-get-comment
1070 @findex mail-header-get-comment
1071 Return the last comment in a header.
1074 (mail-header-get-comment
1075 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1076 @result{} "Finnish Landrace"
1079 @item mail-header-parse-address
1080 @findex mail-header-parse-address
1081 Parse an address and return a list containing the mailbox and the
1085 (mail-header-parse-address
1086 "Hrvoje Niksic <hniksic@@srce.hr>")
1087 @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
1090 @item mail-header-parse-addresses
1091 @findex mail-header-parse-addresses
1092 Parse a string with list of addresses and return a list of elements like
1093 the one described above.
1096 (mail-header-parse-addresses
1097 "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
1098 @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
1099 ("sb@@metis.no" . "Steinar Bang"))
1102 @item mail-header-parse-date
1103 @findex mail-header-parse-date
1104 Parse a date string and return an Emacs time structure.
1106 @item mail-narrow-to-head
1107 @findex mail-narrow-to-head
1108 Narrow the buffer to the header section of the buffer. Point is placed
1109 at the beginning of the narrowed buffer.
1111 @item mail-header-narrow-to-field
1112 @findex mail-header-narrow-to-field
1113 Narrow the buffer to the header under point. Understands continuation
1116 @item mail-header-fold-field
1117 @findex mail-header-fold-field
1118 Fold the header under point.
1120 @item mail-header-unfold-field
1121 @findex mail-header-unfold-field
1122 Unfold the header under point.
1124 @item mail-header-field-value
1125 @findex mail-header-field-value
1126 Return the value of the field under point.
1128 @item mail-encode-encoded-word-region
1129 @findex mail-encode-encoded-word-region
1130 Encode the non-@acronym{ASCII} words in the region. For instance,
1131 @samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
1133 @item mail-encode-encoded-word-buffer
1134 @findex mail-encode-encoded-word-buffer
1135 Encode the non-@acronym{ASCII} words in the current buffer. This function is
1136 meant to be called narrowed to the headers of a message.
1138 @item mail-encode-encoded-word-string
1139 @findex mail-encode-encoded-word-string
1140 Encode the words that need encoding in a string, and return the result.
1143 (mail-encode-encoded-word-string
1144 "This is naïve, baby")
1145 @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
1148 @item mail-decode-encoded-word-region
1149 @findex mail-decode-encoded-word-region
1150 Decode the encoded words in the region.
1152 @item mail-decode-encoded-word-string
1153 @findex mail-decode-encoded-word-string
1154 Decode the encoded words in the string and return the result.
1157 (mail-decode-encoded-word-string
1158 "This is =?iso-8859-1?q?na=EFve,?= baby")
1159 @result{} "This is naïve, baby"
1164 Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
1165 @code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
1166 in the subsequent sections.
1170 @node Basic Functions
1171 @chapter Basic Functions
1173 This chapter describes the basic, ground-level functions for parsing and
1174 handling. Covered here is parsing @code{From} lines, removing comments
1175 from header lines, decoding encoded words, parsing date headers and so
1176 on. High-level functionality is dealt with in the first chapter
1177 (@pxref{Decoding and Viewing}).
1180 * rfc2045:: Encoding @code{Content-Type} headers.
1181 * rfc2231:: Parsing @code{Content-Type} headers.
1182 * ietf-drums:: Handling mail headers defined by RFC822bis.
1183 * rfc2047:: En/decoding encoded words in headers.
1184 * time-date:: Functions for parsing dates and manipulating time.
1185 * qp:: Quoted-Printable en/decoding.
1186 * base64:: Base64 en/decoding.
1187 * binhex:: Binhex decoding.
1188 * uudecode:: Uuencode decoding.
1189 * yenc:: Yenc decoding.
1190 * rfc1843:: Decoding HZ-encoded text.
1191 * mailcap:: How parts are displayed is specified by the @file{.mailcap} file
1198 RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
1199 imagine that there would be a lot to implement. But there isn't, since
1200 most of the implementation details are delegated to the subsequent
1203 So @file{rfc2045.el} has only a single function:
1206 @item rfc2045-encode-string
1207 @findex rfc2045-encode-string
1208 Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
1209 @var{value} will be quoted if there are non-safe characters in it.
1216 RFC2231 defines a syntax for the @code{Content-Type} and
1217 @code{Content-Disposition} headers. Its snappy name is @dfn{MIME
1218 Parameter Value and Encoded Word Extensions: Character Sets, Languages,
1221 In short, these headers look something like this:
1224 Content-Type: application/x-stuff;
1225 title*0*=us-ascii'en'This%20is%20even%20more%20;
1226 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1230 They usually aren't this bad, though.
1232 The following functions are defined by this library:
1235 @item rfc2231-parse-string
1236 @findex rfc2231-parse-string
1237 Parse a @code{Content-Type} header and return a list describing its
1241 (rfc2231-parse-string
1242 "application/x-stuff;
1243 title*0*=us-ascii'en'This%20is%20even%20more%20;
1244 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1245 title*2=\"isn't it!\"")
1246 @result{} ("application/x-stuff"
1247 (title . "This is even more ***fun*** isn't it!"))
1250 @item rfc2231-get-value
1251 @findex rfc2231-get-value
1252 Takes one of the lists on the format above and returns
1253 the value of the specified attribute.
1255 @item rfc2231-encode-string
1256 @findex rfc2231-encode-string
1257 Encode a parameter in headers likes @code{Content-Type} and
1258 @code{Content-Disposition}.
1266 @dfn{drums} is an IETF working group that is working on the replacement
1269 The functions provided by this library include:
1272 @item ietf-drums-remove-comments
1273 @findex ietf-drums-remove-comments
1274 Remove the comments from the argument and return the results.
1276 @item ietf-drums-remove-whitespace
1277 @findex ietf-drums-remove-whitespace
1278 Remove linear white space from the string and return the results.
1279 Spaces inside quoted strings and comments are left untouched.
1281 @item ietf-drums-get-comment
1282 @findex ietf-drums-get-comment
1283 Return the last most comment from the string.
1285 @item ietf-drums-parse-address
1286 @findex ietf-drums-parse-address
1287 Parse an address string and return a list that contains the mailbox and
1288 the plain text name.
1290 @item ietf-drums-parse-addresses
1291 @findex ietf-drums-parse-addresses
1292 Parse a string that contains any number of comma-separated addresses and
1293 return a list that contains mailbox/plain text pairs.
1295 @item ietf-drums-parse-date
1296 @findex ietf-drums-parse-date
1297 Parse a date string and return an Emacs time structure.
1299 @item ietf-drums-narrow-to-header
1300 @findex ietf-drums-narrow-to-header
1301 Narrow the buffer to the header section of the current buffer.
1309 RFC2047 (Message Header Extensions for Non-@acronym{ASCII} Text) specifies how
1310 non-@acronym{ASCII} text in headers are to be encoded. This is actually rather
1311 complicated, so a number of variables are necessary to tweak what this
1314 The following variables are tweakable:
1317 @item rfc2047-header-encoding-alist
1318 @vindex rfc2047-header-encoding-alist
1319 This is an alist of header / encoding-type pairs. Its main purpose is
1320 to prevent encoding of certain headers.
1322 The keys can either be header regexps, or @code{t}.
1324 The values can be @code{nil}, in which case the header(s) in question
1325 won't be encoded, @code{mime}, which means that they will be encoded, or
1326 @code{address-mime}, which means the header(s) will be encoded carefully
1327 assuming they contain addresses.
1329 @item rfc2047-charset-encoding-alist
1330 @vindex rfc2047-charset-encoding-alist
1331 RFC2047 specifies two forms of encoding---@code{Q} (a
1332 Quoted-Printable-like encoding) and @code{B} (base64). This alist
1333 specifies which charset should use which encoding.
1335 @item rfc2047-encode-function-alist
1336 @vindex rfc2047-encode-function-alist
1337 This is an alist of encoding / function pairs. The encodings are
1338 @code{Q}, @code{B} and @code{nil}.
1340 @item rfc2047-encoded-word-regexp
1341 @vindex rfc2047-encoded-word-regexp
1342 When decoding words, this library looks for matches to this regexp.
1344 @item rfc2047-encode-encoded-words
1345 @vindex rfc2047-encode-encoded-words
1346 The boolean variable specifies whether encoded words
1347 (e.g. @samp{=?hello?=}) should be encoded again.
1351 Those were the variables, and these are this functions:
1354 @item rfc2047-narrow-to-field
1355 @findex rfc2047-narrow-to-field
1356 Narrow the buffer to the header on the current line.
1358 @item rfc2047-encode-message-header
1359 @findex rfc2047-encode-message-header
1360 Should be called narrowed to the header of a message. Encodes according
1361 to @code{rfc2047-header-encoding-alist}.
1363 @item rfc2047-encode-region
1364 @findex rfc2047-encode-region
1365 Encodes all encodable words in the region specified.
1367 @item rfc2047-encode-string
1368 @findex rfc2047-encode-string
1369 Encode a string and return the results.
1371 @item rfc2047-decode-region
1372 @findex rfc2047-decode-region
1373 Decode the encoded words in the region.
1375 @item rfc2047-decode-string
1376 @findex rfc2047-decode-string
1377 Decode a string and return the results.
1379 @item rfc2047-encode-parameter
1380 @findex rfc2047-encode-parameter
1381 Encode a parameter in the RFC2047-like style. This is a replacement for
1382 the @code{rfc2231-encode-string} function. @xref{rfc2231}.
1384 When attaching files as @acronym{MIME} parts, we should use the RFC2231
1385 encoding to specify the file names containing non-@acronym{ASCII}
1386 characters. However, many mail softwares don't support it in practice
1387 and recipients won't be able to extract files with correct names.
1388 Instead, the RFC2047-like encoding is acceptable generally. This
1389 function provides the very RFC2047-like encoding, resigning to such a
1390 regrettable trend. To use it, put the following line in your
1391 @file{~/.gnus.el} file:
1394 (defalias 'mail-header-encode-parameter 'rfc2047-encode-parameter)
1403 While not really a part of the @acronym{MIME} library, it is convenient to
1404 document this library here. It deals with parsing @code{Date} headers
1405 and manipulating time. (Not by using tesseracts, though, I'm sorry to
1408 These functions convert between five formats: A date string, an Emacs
1409 time structure, a decoded time list, a second number, and a day number.
1411 Here's a bunch of time/date/second/day examples:
1414 (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
1415 @result{} (54 21 12 12 9 1998 6 nil 7200)
1417 (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
1418 @result{} (13818 19266)
1420 (time-to-seconds '(13818 19266))
1421 @result{} 905595714.0
1423 (seconds-to-time 905595714.0)
1424 @result{} (13818 19266 0)
1426 (time-to-days '(13818 19266))
1429 (days-to-time 729644)
1430 @result{} (961933 65536)
1432 (time-since '(13818 19266))
1435 (time-less-p '(13818 19266) '(13818 19145))
1438 (subtract-time '(13818 19266) '(13818 19145))
1441 (days-between "Sat Sep 12 12:21:54 1998 +0200"
1442 "Sat Sep 07 12:21:54 1998 +0200")
1445 (date-leap-year-p 2000)
1448 (time-to-day-in-year '(13818 19266))
1451 (time-to-number-of-days
1453 (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
1454 @result{} 4.146122685185185
1457 And finally, we have @code{safe-date-to-time}, which does the same as
1458 @code{date-to-time}, but returns a zero time if the date is
1459 syntactically malformed.
1461 The five data representations used are the following:
1465 An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
1466 12:21:54 1998 +0200"}.
1469 An internal Emacs time. For instance: @code{(13818 26466)}.
1472 A floating point representation of the internal Emacs time. For
1473 instance: @code{905595714.0}.
1476 An integer number representing the number of days since 00000101. For
1477 instance: @code{729644}.
1480 A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
1484 All the examples above represent the same moment.
1486 These are the functions available:
1490 Take a date and return a time.
1492 @item time-to-seconds
1493 Take a time and return seconds.
1495 @item seconds-to-time
1496 Take seconds and return a time.
1499 Take a time and return days.
1502 Take days and return a time.
1505 Take a date and return days.
1507 @item time-to-number-of-days
1508 Take a time and return the number of days that represents.
1510 @item safe-date-to-time
1511 Take a date and return a time. If the date is not syntactically valid,
1512 return a ``zero'' time.
1515 Take two times and say whether the first time is less (i. e., earlier)
1516 than the second time.
1519 Take a time and return a time saying how long it was since that time.
1522 Take two times and subtract the second from the first. I. e., return
1523 the time between the two times.
1526 Take two days and return the number of days between those two days.
1528 @item date-leap-year-p
1529 Take a year number and say whether it's a leap year.
1531 @item time-to-day-in-year
1532 Take a time and return the day number within the year that the time is
1541 This library deals with decoding and encoding Quoted-Printable text.
1543 Very briefly explained, qp encoding means translating all 8-bit
1544 characters (and lots of control characters) into things that look like
1545 @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
1548 The following functions are defined by the library:
1551 @item quoted-printable-decode-region
1552 @findex quoted-printable-decode-region
1553 QP-decode all the encoded text in the specified region.
1555 @item quoted-printable-decode-string
1556 @findex quoted-printable-decode-string
1557 Decode the QP-encoded text in a string and return the results.
1559 @item quoted-printable-encode-region
1560 @findex quoted-printable-encode-region
1561 QP-encode all the encodable characters in the specified region. The third
1562 optional parameter @var{fold} specifies whether to fold long lines.
1563 (Long here means 72.)
1565 @item quoted-printable-encode-string
1566 @findex quoted-printable-encode-string
1567 QP-encode all the encodable characters in a string and return the
1577 Base64 is an encoding that encodes three bytes into four characters,
1578 thereby increasing the size by about 33%. The alphabet used for
1579 encoding is very resistant to mangling during transit.
1581 The following functions are defined by this library:
1584 @item base64-encode-region
1585 @findex base64-encode-region
1586 base64 encode the selected region. Return the length of the encoded
1587 text. Optional third argument @var{no-line-break} means do not break
1588 long lines into shorter lines.
1590 @item base64-encode-string
1591 @findex base64-encode-string
1592 base64 encode a string and return the result.
1594 @item base64-decode-region
1595 @findex base64-decode-region
1596 base64 decode the selected region. Return the length of the decoded
1597 text. If the region can't be decoded, return @code{nil} and don't
1600 @item base64-decode-string
1601 @findex base64-decode-string
1602 base64 decode a string and return the result. If the string can't be
1603 decoded, @code{nil} is returned.
1614 @code{binhex} is an encoding that originated in Macintosh environments.
1615 The following function is supplied to deal with these:
1618 @item binhex-decode-region
1619 @findex binhex-decode-region
1620 Decode the encoded text in the region. If given a third parameter, only
1621 decode the @code{binhex} header and return the filename.
1630 @code{uuencode} is probably still the most popular encoding of binaries
1631 used on Usenet, although @code{base64} rules the mail world.
1633 The following function is supplied by this package:
1636 @item uudecode-decode-region
1637 @findex uudecode-decode-region
1638 Decode the text in the region.
1646 @code{yenc} is used for encoding binaries on Usenet. The following
1647 function is supplied by this package:
1650 @item yenc-decode-region
1651 @findex yenc-decode-region
1652 Decode the encoded text in the region.
1663 RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. In
1664 essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
1667 This sentence is in @acronym{ASCII}.
1668 The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
1671 Simple enough, and widely used in China.
1673 The following functions are available to handle this encoding:
1676 @item rfc1843-decode-region
1677 Decode HZ-encoded text in the region.
1679 @item rfc1843-decode-string
1680 Decode a HZ-encoded string and return the result.
1688 The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
1689 handlers and describes how elements are supposed to be displayed.
1690 Here's an example file:
1694 audio/wav; wavplayer %s
1695 application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
1698 This says that all image files should be displayed with @code{gimp},
1699 that WAVE audio files should be played by @code{wavplayer}, and that
1700 MS-WORD files should be inlined by @code{catdoc}.
1702 The @code{mailcap} library parses this file, and provides functions for
1706 @item mailcap-mime-data
1707 @vindex mailcap-mime-data
1708 This variable is an alist of alists containing backup viewing rules.
1712 Interface functions:
1715 @item mailcap-parse-mailcaps
1716 @findex mailcap-parse-mailcaps
1717 Parse the @file{~/.mailcap} file.
1719 @item mailcap-mime-info
1720 Takes a @acronym{MIME} type as its argument and returns the matching viewer.
1730 The Emacs @acronym{MIME} library implements handling of various elements
1731 according to a (somewhat) large number of RFCs, drafts and standards
1732 documents. This chapter lists the relevant ones. They can all be
1733 fetched from @uref{http://quimby.gnus.org/notes/}.
1738 Standard for the Format of ARPA Internet Text Messages.
1741 Standard for Interchange of USENET Messages
1744 Format of Internet Message Bodies
1750 Message Header Extensions for Non-@acronym{ASCII} Text
1753 Registration Procedures
1756 Conformance Criteria and Examples
1759 @acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
1760 Languages, and Continuations
1763 HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
1764 @acronym{ASCII} characters
1766 @item draft-ietf-drums-msg-fmt-05.txt
1767 Draft for the successor of RFC822
1770 The @acronym{MIME} Multipart/Related Content-type
1773 The Multipart/Report Content Type for the Reporting of Mail System
1774 Administrative Messages
1777 Communicating Presentation Information in Internet Messages: The
1778 Content-Disposition Header Field
1781 Documentation of the text/plain format parameter for flowed text.
1797 @c coding: iso-8859-1
1801 arch-tag: c7ef2fd0-a91c-4e10-aa52-c1a2b11b1a8d