1 .TH MHSHOW %manext1% "May 4, 2013" "%nmhversion%"
6 mhshow \- display MIME messages
21 .RB [ \-serialonly " | " \-noserialonly ]
22 .RB [ \-pause " | " \-nopause ]
29 .RB [ \-check " | " \-nocheck ]
36 command display contents of a MIME (multi-media)
37 message or collection of messages.
40 manipulates multi-media messages as specified in
41 RFC 2045 to RFC 2049. Currently
44 encodings in message bodies, and does not support the encoding of
45 message headers as specified in RFC 2047.
49 will display all parts of a multipart
57 to particular subparts (of a
58 multipart content) and/or particular content types.
65 to use the specified file as
66 the source message, rather than a message from a folder. If you specify
67 this file as \*(lq-\*(rq, then
69 will accept the source message
70 on the standard input. Note that the file, or input from standard input
71 should be a validly formatted message, just like any other
75 be in mail drop format (to convert a file in
76 mail drop format to a folder of
81 A part specification consists of a series of numbers separated by dots.
82 For example, in a multipart content containing three parts, these
83 would be named as 1, 2, and 3, respectively. If part 2 was also a
84 multipart content containing two parts, these would be named as 2.1 and
85 2.2, respectively. Note that the
87 switch is effective for only
88 messages containing a multipart content. If a message has some other
89 kind of content, or if the part is itself another multipart content, the
91 switch will not prevent the content from being acted upon.
93 A content specification consists of a content type and a subtype.
94 The initial list of \*(lqstandard\*(rq content types and subtypes can
97 A list of commonly used contents is briefly reproduced here:
101 .ta \w'application 'u
105 multipart mixed, alternative, digest, parallel
106 message rfc822, partial, external-body
107 application octet-stream, postscript
114 A legal MIME message must contain a subtype specification.
116 To specify a content, regardless of its subtype, just use the
117 name of the content, e.g., \*(lqaudio\*(rq. To specify a specific
118 subtype, separate the two with a slash, e.g., \*(lqaudio/basic\*(rq.
119 Note that regardless of the values given to the `\-type' switch, a
120 multipart content (of any subtype listed above) is always acted upon.
121 Further note that if the `\-type' switch is used, and it is desirable to
122 act on a message/external-body content, then the `\-type' switch must
123 be used twice: once for message/external-body and once for the content
124 externally referenced.
125 .SS "Unseen Sequence"
126 If the profile entry \*(lqUnseen\-Sequence\*(rq is present and
129 will remove each of the messages shown
130 from each sequence named by the profile entry.
131 .SS "Checking the Contents"
136 to check each content for an
137 integrity checksum. If a content has such a checksum (specified as a
138 Content-MD5 header field), then
140 will attempt to verify the
141 integrity of the content.
142 .SS "Showing the Contents"
143 The headers of each message are displayed with the
147 using the standard format file
149 You may specify an alternate format file with the
152 switch. If the format file
154 is specified, then the display
155 of the message headers is suppressed.
157 Next, the contents are extracted from the message and are stored in
158 a temporary file. Usually, the name of the temporary file is the
159 word \*(lqmhshow\*(rq followed by a string of characters. Occasionally,
160 the method used to display a content (described next), requires that
161 the file end in a specific suffix. For example, the
163 command (part of the StarOffice package) can be used to display
164 Microsoft Word content, but it uses the suffix to determine how to display
165 the file. If no suffix is present, the file is not correctly loaded.
166 Similarily, older versions of the
168 command append a \*(lq.ps\*(rq suffix to
169 the filename if one was missing. As a result, these cannot be used to read
170 the default temporary file.
172 To get around this, your profile can contain lines of the form:
175 mhshow-suffix-<type>/<subtype>: <suffix>
181 mhshow-suffix-<type>: <suffix>
184 to specify a suffix which can be automatically added to the temporary
185 file created for a specific content type. For example, the following
186 lines might appear in your profile:
190 mhshow-suffix-text: .txt
191 mhshow-suffix-application/msword: .doc
192 mhshow-suffix-application/PostScript: .ps
196 to automatically append a suffix to the temporary files.
198 The method used to display the different contents in the messages bodies
199 will be determined by a \*(lqdisplay string\*(rq. To find the display
202 will first search your profile for an entry of the form:
205 mhshow-show-<type>/<subtype>
208 to determine the display string. If this isn't found,
210 will search for an entry of the form:
216 to determine the display string.
218 If a display string is found, any escapes (given below) will be expanded.
219 The result will be executed under
220 \*(lq/bin/sh\*(rq, with the standard input
223 The display string may contain the following escapes:
228 %a Insert parameters from Content-Type field
229 %e exclusive execution
230 %f Insert filename containing content
231 %F %e, %f, and stdin is terminal not content
232 %l display listing prior to displaying content
233 %p %l, and ask for confirmation
234 %s Insert content subtype
235 %d Insert content description
236 %% Insert the character %
240 For those display strings containing the e- or F-escape,
243 execute at most one of these at any given time. Although the F-escape
244 expands to be the filename containing the content, the e-escape has no
245 expansion as far as the shell is concerned.
247 When the p-escape prompts for confirmation, typing INTR (usually
250 not to display that content.
251 The p-escape can be disabled by specifying the switch
255 is display a content, typing QUIT (usually
256 control-\\) will tell
258 to wrap things up immediately.
260 Note that if the content being displayed is multipart, but not one of
261 the subtypes listed above, then the f- and F-escapes expand to multiple
262 filenames, one for each subordinate content. Further, stdin is not
263 redirected from the terminal to the content.
265 If a display string is not found,
267 behaves as if these profile entries were supplied and supported:
271 mhshow-show-text/plain: %pmoreproc '%F'
272 mhshow-show-message/rfc822: %pshow -file '%F'
276 Note that \*(lqmoreproc\*(rq is not supported in user profile display
279 If a subtype of type text doesn't have a profile entry, it will be
280 treated as text/plain.
283 has default methods for handling multipart messages of subtype
284 mixed, alternative, parallel, and digest. Any unknown subtype of type
285 multipart (without a profile entry), will be treated as multipart/mixed.
287 If none of these apply, then
289 will check to see if the message
290 has an application/octet-stream content with parameter \*(lqtype=tar\*(rq.
293 will use an appropriate command. If not,
297 Example entries might be:
301 mhshow-show-audio/basic: raw2audio 2>/dev/null | play
302 mhshow-show-image: xv '%f'
303 mhshow-show-application/PostScript: lpr -Pps
307 Note that when using the f- or F-escape, it's a good idea to use
308 single-quotes around the escape. This prevents misinterpretation by
309 the shell of any funny characters that might be present in the filename.
313 will process each message serially\0--\0it won't start
314 showing the next message until all the commands executed to display the
315 current message have terminated. In the case of a multipart content
316 (of any subtype listed above), the content contains advice indicating if
317 the parts should be displayed serially or in parallel. Because this may
318 cause confusion, particularly on uni-window displays, the
320 switch can be given to tell
322 to never display parts in parallel.
323 .SS "Showing Alternate Character Sets"
324 Because a content of type text might be in a non-ASCII character
327 encounters a \*(lqcharset\*(rq parameter for
328 this content, it checks if your terminal can display this character
331 checks this by examining the current character set defined by the
333 environment variables.
334 If the value of the locale character set is equal
335 to the value of the charset parameter, then
338 display this content without any additional setup. If the locale is not
341 will assume a value of \*(lqUS-ASCII\*(rq.
342 If the character set cannot be displayed natively, then
344 will look for an entry of the form:
347 mhshow-charset-<charset>
350 which should contain a command creating an environment to render
351 the character set. This command string should containing a single
352 \*(lq%s\*(rq, which will be filled-in with the command to display the
355 Example entries might be:
358 mhshow-charset-iso-8859-1: xterm -fn '-*-*-medium-r-normal-*-*-120-*-*-c-*-iso8859-*' -e %s
364 mhshow-charset-iso-8859-1: '%s'
367 The first example tells
372 appropriate character set for that message content. The second example
375 that your pager (or other program handling that content
376 type) can handle that character set, and that no special processing is
379 Note that many pagers strip off the high-order bit or have problems
380 displaying text with the high-order bit set. However, the pager
382 has support for single-octet character sets. The source
385 is available on many ftp sites carrying free software.
386 In order to view messages sent in the ISO-8859-1 character set using
389 put these lines in your
395 setenv LESSCHARSET latin1
402 to use the ISO-8859-1 definition for
403 determining whether a character is \*(lqnormal\*(rq, \*(lqcontrol\*(lq,
404 or \*(lqbinary\*(rq. The second line tells
407 if it encounters a file that has non-ASCII characters. Then, simply
413 called automatically. (To handle other single-octet character sets,
416 manual entry for information about the
418 environment variable.)
419 .SS "Messages of Type message/partial"
421 cannot directly display messages of type partial.
422 You must reassemble them first into a normal message using
424 Check the man page for
427 .SS "External Access"
428 For contents of type message/external-body,
430 supports these access-types:
445 For the \*(lqanon-ftp\*(rq and \*(lqftp\*(rq access types,
447 will look for the \*(lqnmh-access-ftp\*(rq
451 nmh-access-ftp: myftp.sh
454 to determine the pathname of a program to perform the FTP retrieval.
456 This program is invoked with these arguments:
460 domain name of FTP-site
466 \*(lqascii\*(rq or \*(lqbinary\*(rq
470 The program should terminate with an exit status of zero if the
471 retrieval is successful, and a non-zero exit status otherwise.
473 For the \*(lqurl\*(rq access\-type,
475 will look for the \*(lqnmh-access-url\*(rq
480 .SS "The Content Cache"
483 encounters an external content containing a
484 \*(lqContent-ID:\*(rq field, and if the content allows caching, then
485 depending on the caching behavior of
487 the content might be read from or written to a cache.
489 The caching behavior of
491 is controlled with the
495 switches, which define the policy for reading from,
496 and writing to, the cache, respectively. One of four policies may be
497 specified: \*(lqpublic\*(rq, indicating that
500 of a publically-accessible content cache; \*(lqprivate\*(rq, indicating
503 should make use of the user's private content cache;
504 \*(lqnever\*(rq, indicating that
506 should never make use of
507 caching; and, \*(lqask\*(rq, indicating that
511 There are two directories where contents may be cached: the profile entry
512 \*(lqnmh-cache\*(rq names a directory containing world-readable contents, and,
513 the profile entry \*(lqnmh-private-cache\*(rq names a directory containing
514 private contents. The former should be an absolute (rooted) directory
523 might be used if you didn't care that the cache got wiped after each
524 reboot of the system. The latter is interpreted relative to the user's
525 nmh directory, if not rooted, e.g.,
528 nmh-private-cache: .cache
531 (which is the default value).
532 .SS "User Environment"
533 Because the display environment in which
535 operates may vary for
538 will look for the environment variable
540 If present, this specifies the name of an additional
541 user profile which should be read. Hence, when a user logs in on a
542 particular display device, this environment variable should be set to
543 refer to a file containing definitions useful for the given display device.
544 Normally, only entries that deal with the methods to display different
545 content type and subtypes
549 mhshow-show-<type>/<subtype>
554 need be present in this additional profile. Finally,
556 will attempt to consult one other additional user profile,
560 %etcdir%/mhn.defaults
563 which is created automatically during
568 looks for all format files and mhn.defaults in multiple locations:
569 absolute pathnames are accessed directly, tilde expansion is done on
570 usernames, and files are searched for in the user's
572 directory as specified in their profile. If not found there, the directory
573 .RI \*(lq %etcdir% \*(rq
578 .ta \w'%etcdir%/ExtraBigFileName 'u
579 ^$HOME/\&.mh\(ruprofile~^The user profile
580 ^$MHSHOW~^Additional profile entries
581 ^%etcdir%/mhn.defaults~^System default MIME profile entries
582 ^%etcdir%/mhl.headers~^The headers template
584 .SH "PROFILE COMPONENTS"
588 .ta \w'ExtraBigProfileName 'u
589 ^Path:~^To determine the user's nmh directory
590 ^Current\-Folder:~^To find the default current folder
591 ^Unseen\-Sequence:~^To name sequences denoting unseen messages
592 ^mhlproc:~^Default program to display message headers
593 ^nmh-access-ftp:~^Program to retrieve contents via FTP
594 ^nmh-access-url:~^Program to retrieve contents via HTTP
595 ^nmh-cache~^Public directory to store cached external contents
596 ^nmh-private-cache~^Personal directory to store cached external contents
597 ^mhshow-charset-<charset>~^Template for environment to render character sets
598 ^mhshow-show-<type>*~^Template for displaying contents
599 ^moreproc:~^Default program to display text/plain content
609 .RB ` +folder "' defaults to the current folder"
610 .RB ` msgs "' defaults to cur"
612 .RB ` \-form\ mhl.headers '
614 .RB ` \-rcache\ ask '
615 .RB ` \-noserialonly '
616 .RB ` \-wcache\ ask '
619 If a folder is given, it will become the current folder. The last
620 message selected will become the current message.
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