1MHSHOW(1) [nmh-1.3] MHSHOW(1)
2
6 mhshow - display MIME messages
7
9 mhshow [+folder] [msgs] [-file file] [-part number] ... [-type con‐
10 tent] ... [-serialonly | -noserialonly] [-pause | -nopause]
11 [-form formfile] [-rcache policy] [-wcache policy] [-check |
12 -nocheck] [-version] [-help]
13
15 The mhshow command display contents of a MIME (multi-media) message or
16 collection of messages.
17 mhshow manipulates multi-media messages as specified in RFC-2045 thru
19 RFC-2049. Currently mhshow only supports encodings in message bodies,
20 and does not support the encoding of message headers as specified in
21 RFC-2047.
22 By default mhshow will display all parts of a multipart message. By
24 using the -part and -type switches, you may limit the scope of mhshow
25 to particular subparts (of a multipart content) and/or particular con‐
26 tent types.
27 The option -file file directs mhshow to use the specified file as the
29 source message, rather than a message from a folder. If you specify
30 this file as “-”, then mhshow will accept the source message on the
31 standard input. Note that the file, or input from standard input
32 should be a validly formatted message, just like any other nmh message.
33 It should NOT be in mail drop format (to convert a file in mail drop
34 format to a folder of nmh messages, see inc(1)).
35 A part specification consists of a series of numbers separated by dots.
37 For example, in a multipart content containing three parts, these would
38 be named as 1, 2, and 3, respectively. If part 2 was also a multipart
39 content containing two parts, these would be named as 2.1 and 2.2,
40 respectively. Note that the -part switch is effective for only mes‐
41 sages containing a multipart content. If a message has some other kind
42 of content, or if the part is itself another multipart content, the
43 -part switch will not prevent the content from being acted upon.
44 A content specification consists of a content type and a subtype. The
46 initial list of “standard” content types and subtypes can be found in
47 RFC-2046.
48 A list of commonly used contents is briefly reproduced here:
50 Type Subtypes
52 ---- --------
53 text plain, enriched
54 multipart mixed, alternative, digest, parallel
55 message rfc822, partial, external-body
56 application octet-stream, postscript
57 image jpeg, gif, png
58 audio basic
59 video mpeg
60 A legal MIME message must contain a subtype specification.
62 To specify a content, regardless of its subtype, just use the name of
64 the content, e.g., “audio”. To specify a specific subtype, separate
65 the two with a slash, e.g., “audio/basic”. Note that regardless of the
66 values given to the `-type' switch, a multipart content (of any subtype
67 listed above) is always acted upon. Further note that if the `-type'
68 switch is used, and it is desirable to act on a message/external-body
69 content, then the `-type' switch must be used twice: once for mes‐
70 sage/external-body and once for the content externally referenced.
71 Unseen Sequence
73 If the profile entry “Unseen-Sequence” is present and non-empty, then
74 mhshow will remove each of the messages shown from each sequence named
75 by the profile entry.
76 Checking the Contents
78 The -check switch tells mhshow to check each content for an integrity
79 checksum. If a content has such a checksum (specified as a Content-MD5
80 header field), then mhshow will attempt to verify the integrity of the
81 content.
82 Showing the Contents
84 The headers of each message are displayed with the mhlproc (usually
85 mhl), using the standard format file mhl.headers. You may specify an
86 alternate format file with the -form formfile switch. If the format
87 file mhl.null is specified, then the display of the message headers is
88 suppressed.
89 Next, the contents are extracted from the message and are stored in a
91 temporary file. Usually, the name of the temporary file is the word
92 “mhshow” followed by a string of characters. Occasionally, the method
93 used to display a content (described next), requires that the file end
94 in a specific suffix. For example, the soffice command (part of the
95 StarOffice package) can be used to display Microsoft Word content, but
96 it uses the suffix to determine how to display the file. If no suffix
97 is present, the file is not correctly loaded. Similarily, older ver‐
98 sions of the gs command append a “.ps” suffix to the filename if one
99 was missing. As a result, these cannot be used to read the default
100 temporary file.
101 To get around this, your profile can contain lines of the form:
103 mhshow-suffix-<type>/<subtype>: <suffix>
105 or
107 mhshow-suffix-<type>: <suffix>
109 to specify a suffix which can be automatically added to the temporary
111 file created for a specific content type. For example, the following
112 lines might appear in your profile:
113 mhshow-suffix-text: .txt
115 mhshow-suffix-application/msword: .doc
116 mhshow-suffix-application/PostScript: .ps
117 to automatically append a suffix to the temporary files.
119 The method used to display the different contents in the messages bod‐
121 ies will be determined by a “display string”. To find the display
122 string, mhshow will first search your profile for an entry of the form:
123 mhshow-show-<type>/<subtype>
125 to determine the display string. If this isn't found, mhshow will
127 search for an entry of the form:
128 mhshow-show-<type>
130 to determine the display string.
132 If a display string is found, any escapes (given below) will be
134 expanded. The result will be executed under “/bin/sh”, with the stan‐
135 dard input set to the content.
136 The display string may contain the following escapes:
138 %a Insert parameters from Content-Type field
140 %e exclusive execution
141 %f Insert filename containing content
142 %F %e, %f, and stdin is terminal not content
143 %l display listing prior to displaying content
144 %p %l, and ask for confirmation
145 %s Insert content subtype
146 %d Insert content description
147 %% Insert the character %
148 For those display strings containing the e- or F-escape, mhshow will
150 execute at most one of these at any given time. Although the F-escape
151 expands to be the filename containing the content, the e-escape has no
152 expansion as far as the shell is concerned.
153 When the p-escape prompts for confirmation, typing INTR (usually con‐
155 trol-C) will tell mhshow not to display that content. The p-escape can
156 be disabled by specifying the switch -nopause. Further, when mhshow is
157 display a content, typing QUIT (usually control-\) will tell mhshow to
158 wrap things up immediately.
159 Note that if the content being displayed is multipart, but not one of
161 the subtypes listed above, then the f- and F-escapes expand to multiple
162 filenames, one for each subordinate content. Further, stdin is not
163 redirected from the terminal to the content.
164 If a display string is not found, mhshow has several default values:
166 mhshow-show-text/plain: %pmoreproc '%F'
168 mhshow-show-message/rfc822: %pshow -file '%F'
169 If a subtype of type text doesn't have a profile entry, it will be
171 treated as text/plain.
172 mhshow has default methods for handling multipart messages of subtype
174 mixed, alternative, parallel, and digest. Any unknown subtype of type
175 multipart (without a profile entry), will be treated as multi‐
176 part/mixed.
177 If none of these apply, then mhshow will check to see if the message
179 has an application/octet-stream content with parameter “type=tar”. If
180 so, mhshow will use an appropriate command. If not, mhshow will com‐
181 plain.
182 Example entries might be:
184 mhshow-show-audio/basic: raw2audio 2>/dev/null | play
186 mhshow-show-image: xv '%f'
187 mhshow-show-application/PostScript: lpr -Pps
188 Note that when using the f- or F-escape, it's a good idea to use sin‐
190 gle-quotes around the escape. This prevents misinterpretation by the
191 shell of any funny characters that might be present in the filename.
192 Finally, mhshow will process each message serially -- it won't start
194 showing the next message until all the commands executed to display the
195 current message have terminated. In the case of a multipart content
196 (of any subtype listed above), the content contains advice indicating
197 if the parts should be displayed serially or in parallel. Because this
198 may cause confusion, particularly on uni-window displays, the -seri‐
199 alonly switch can be given to tell mhshow to never display parts in
200 parallel.
201 Showing Alternate Character Sets
203 Because a content of type text might be in a non-ASCII character set,
204 when mhshow encounters a “charset” parameter for this content, it
205 checks if your terminal can display this character set natively. mhn
206 checks this by examining the the environment variable $MM_CHARSET. If
207 the value of this environment variable is equal to the value of the
208 charset parameter, then mhshow assumes it can display this content
209 without any additional setup. If this environment variable is not set,
210 mhshow will assume a value of “US-ASCII”. If the character set cannot
211 be displayed natively, then mhshow will look for an entry of the form:
212 mhshow-charset-<charset>
214 which should contain a command creating an environment to render the
216 character set. This command string should containing a single “%s”,
217 which will be filled-in with the command to display the content.
218 Example entries might be:
220 mhshow-charset-iso-8859-1: xterm -fn '-*-*-medium-r-nor‐
222 mal-*-*-120-*-*-c-*-iso8859-*' -e %s
223 or
225 mhshow-charset-iso-8859-1: '%s'
227 The first example tells mhshow to start xterm and load the appropriate
229 character set for that message content. The second example tells
230 mhshow that your pager (or other program handling that content type)
231 can handle that character set, and that no special processing is needed
232 beforehand.
233 Note that many pagers strip off the high-order bit or have problems
235 displaying text with the high-order bit set. However, the pager less
236 has support for single-octet character sets. The source to less is
237 available on many ftp sites carrying free software. In order to view
238 messages sent in the ISO-8859-1 character set using less,
239 put these lines in your .login file:
241 setenv LESSCHARSET latin1
243 setenv LESS "-f"
244 The first line tells less to use the ISO-8859-1 definition for deter‐
246 mining whether a character is “normal”, “control“, or “binary”. The
247 second line tells less not to warn you if it encounters a file that has
248 non-ASCII characters. Then, simply set the moreproc profile entry to
249 less, and it will get called automatically. (To handle other single-
250 octet character sets, look at the less(1) manual entry for information
251 about the $LESSCHARDEF environment variable.)
252 Messages of Type message/partial
254 mhshow cannot directly display messages of type partial. You must
255 reassemble them first into a normal message using mhstore. Check the
256 man page for mhstore(1) for details.
257 External Access
259 For contents of type message/external-body, mhshow supports these
260 access-types:
261 · afs
263 · anon-ftp
265 · ftp
267 · local-file
269 · mail-server
271 For the “anon-ftp” and “ftp” access types, mhshow will look for the
273 “nmh-access-ftp” profile entry, e.g.,
274 nmh-access-ftp: myftp.sh
276 to determine the pathname of a program to perform the FTP retrieval.
278 This program is invoked with these arguments:
280 domain name of FTP-site
282 username
283 password
284 remote directory
285 remote filename
286 local filename
287 “ascii” or “binary”
288 The program should terminate with an exit status of zero if the
290 retrieval is successful, and a non-zero exit status otherwise.
291 If this entry is not provided, then mhshow will use a simple built-in
293 FTP client to perform the retrieval.
294 The Content Cache
296 When mhshow encounters an external content containing a “Content-ID:”
297 field, and if the content allows caching, then depending on the caching
298 behavior of mhshow, the content might be read from or written to a
299 cache.
300 The caching behavior of mhshow is controlled with the -rcache and
302 -wcache switches, which define the policy for reading from, and writing
303 to, the cache, respectively. One of four policies may be specified:
304 “public”, indicating that mhshow should make use of a publically-acces‐
305 sible content cache; “private”, indicating that mhshow should make use
306 of the user's private content cache; “never”, indicating that mhshow
307 should never make use of caching; and, “ask”, indicating that mhshow
308 should ask the user.
309 There are two directories where contents may be cached: the profile
311 entry “nmh-cache” names a directory containing world-readable contents,
312 and, the profile entry “nmh-private-cache” names a directory containing
313 private contents. The former should be an absolute (rooted) directory
314 name.
315 For example,
317 nmh-cache: /tmp
319 might be used if you didn't care that the cache got wiped after each
321 reboot of the system. The latter is interpreted relative to the user's
322 nmh directory, if not rooted, e.g.,
323 nmh-private-cache: .cache
325 (which is the default value).
327 User Environment
329 Because the display environment in which mhshow operates may vary for
330 different machines, mhshow will look for the environment variable If
331 present, this specifies the name of an additional user profile which
332 should be read. Hence, when a user logs in on a particular display
333 device, this environment variable should be set to refer to a file con‐
334 taining definitions useful for the given display device. Normally,
335 only entries that deal with the methods to display different content
336 type and subtypes
337 mhshow-show-<type>/<subtype>
339 mhshow-show-<type>
340 need be present in this additional profile. Finally, mhshow will
342 attempt to consult one other additional user profile, e.g.,
343 /etc/nmh/mhn.defaults
345 which is created automatically during nmh installation.
347
350 $HOME/.mh_profile The user profile
351 $MHSHOW Additional profile entries
352 /etc/nmh/mhn.defaults System default MIME profile entries
353 /etc/nmh/mhl.headers The headers template
354
357 Path: To determine the user's nmh directory
358 Current-Folder: To find the default current folder
359 Unseen-Sequence: To name sequences denoting unseen messages
360 mhlproc: Default program to display message headers
361 nmh-access-ftp: Program to retrieve contents via FTP
362 nmh-cache Public directory to store cached external contents
363 nmh-private-cache Personal directory to store cached external contents
364 mhshow-charset-<charseTte>mplate for environment to render character sets
365 mhshow-show-<type>* Template for displaying contents
366 moreproc: Default program to display text/plain content
367
370 mhbuild(1), mhl(1), mhlist(1), mhstore(1), sendfiles(1)
371
374 `+folder' defaults to the current folder
375 `msgs' defaults to cur
376 `-nocheck'
377 `-formmhl.headers'
378 `-pause'
379 `-rcacheask'
380 `-realsize'
381 `-noserialonly'
382 `-noverbose'
383 `-wcacheask'
384
387 If a folder is given, it will become the current folder. The last mes‐
388 sage selected will become the current message.
389MH.6.8 1 June 2008 MHSHOW(1)