NAME
mhshow - display MIME messagesSYNOPSIS
mhshow
[+folder] [msgs] [-file file] [-part
number] ... [-type content] ... [-serialonly |
-noserialonly] [-pause | -nopause] [-form
formfile] [-rcache policy] [-wcache policy]
[-check | -nocheck] [-version] [-help]
DESCRIPTION
The mhshow command display contents of a MIME (multi-media) message or collection of messages. mhshow manipulates multi-media messages as specified in RFC-2045 thru RFC-2049. Currently mhshow only supports encodings in message bodies, and does not support the encoding of message headers as specified in RFC-2047. By default mhshow will display all parts of a multipart message. By using the -part and -type switches, you may limit the scope of mhshow to particular subparts (of a multipart content) and/or particular content types. The option -file file directs mhshow to use the specified file as the source message, rather than a message from a folder. If you specify this file as “-”, then mhshow will accept the source message on the standard input. Note that the file, or input from standard input should be a validly formatted message, just like any other nmh message. It should NOT be in mail drop format (to convert a file in mail drop format to a folder of nmh messages, see inc(1)). A part specification consists of a series of numbers separated by dots. For example, in a multipart content containing three parts, these would be named as 1, 2, and 3, respectively. If part 2 was also a multipart content containing two parts, these would be named as 2.1 and 2.2, respectively. Note that the -part switch is effective for only messages containing a multipart content. If a message has some other kind of content, or if the part is itself another multipart content, the -part switch will not prevent the content from being acted upon. A content specification consists of a content type and a subtype. The initial list of “standard” content types and subtypes can be found in RFC-2046. A list of commonly used contents is briefly reproduced here:Type Subtypes ---- -------- text plain, enriched multipart mixed, alternative, digest, parallel message rfc822, partial, external-body application octet-stream, postscript image jpeg, gif, png audio basic video mpeg
Unseen Sequence
If the profile entry “Unseen-Sequence” is present and non-empty, then mhshow will remove each of the messages shown from each sequence named by the profile entry.Checking the Contents
The -check switch tells mhshow to check each content for an integrity checksum. If a content has such a checksum (specified as a Content-MD5 header field), then mhshow will attempt to verify the integrity of the content.Showing the Contents
The headers of each message are displayed with the mhlproc (usually mhl), using the standard format file mhl.headers. You may specify an alternate format file with the -form formfile switch. If the format file mhl.null is specified, then the display of the message headers is suppressed. Next, the contents are extracted from the message and are stored in a temporary file. Usually, the name of the temporary file is the word “mhshow” followed by a string of characters. Occasionally, the method used to display a content (described next), requires that the file end in a specific suffix. For example, the soffice command (part of the StarOffice package) can be used to display Microsoft Word content, but it uses the suffix to determine how to display the file. If no suffix is present, the file is not correctly loaded. Similarily, older versions of the gs command append a “.ps” suffix to the filename if one was missing. As a result, these cannot be used to read the default temporary file. To get around this, your profile can contain lines of the form:mhshow-suffix-<type>/<subtype>:
<suffix>
or
mhshow-suffix-<type>:
<suffix>
to specify a suffix which can be automatically added to the temporary file
created for a specific content type. For example, the following lines might
appear in your profile:
mhshow-suffix-text: .txt mhshow-suffix-application/msword: .doc mhshow-suffix-application/PostScript: .ps
mhshow-show-<type>/<subtype>
to determine the display string. If this isn't found, mhshow will search
for an entry of the form:
mhshow-show-<type>
to determine the display string.
If a display string is found, any escapes (given below) will be expanded. The
result will be executed under “/bin/sh”, with the standard input
set to the content.
The display string may contain the following escapes:
%a Insert parameters from Content-Type field %e exclusive execution %f Insert filename containing content %F %e, %f, and stdin is terminal not content %l display listing prior to displaying content %p %l, and ask for confirmation %s Insert content subtype %d Insert content description %% Insert the character %
mhshow-show-text/plain: %pmoreproc '%F' mhshow-show-message/rfc822: %pshow -file '%F'
mhshow-show-audio/basic: raw2audio 2>/dev/null | play mhshow-show-image: xv '%f' mhshow-show-application/PostScript: lpr -Pps
Showing Alternate Character Sets
Because a content of type text might be in a non-ASCII character set, when mhshow encounters a “charset” parameter for this content, it checks if your terminal can display this character set natively. mhn checks this by examining the the environment variable $MM_CHARSET. If the value of this environment variable is equal to the value of the charset parameter, then mhshow assumes it can display this content without any additional setup. If this environment variable is not set, mhshow will assume a value of “US-ASCII”. If the character set cannot be displayed natively, then mhshow will look for an entry of the form:mhshow-charset-<charset>
which should contain a command creating an environment to render the character
set. This command string should containing a single “%s”, which
will be filled-in with the command to display the content.
Example entries might be:
mhshow-charset-iso-8859-1: xterm -fn
'-*-*-medium-r-normal-*-*-120-*-*-c-*-iso8859-*' -e %s
or
mhshow-charset-iso-8859-1: '%s'
The first example tells mhshow to start xterm and load the
appropriate character set for that message content. The second example tells
mhshow that your pager (or other program handling that content type)
can handle that character set, and that no special processing is needed
beforehand.
Note that many pagers strip off the high-order bit or have problems displaying
text with the high-order bit set. However, the pager less has support
for single-octet character sets. The source to less is available on
many ftp sites carrying free software. In order to view messages sent in the
ISO-8859-1 character set using less,
put these lines in your .login file:
setenv LESSCHARSET latin1 setenv LESS "-f"
Messages of Type message/partial
mhshow cannot directly display messages of type partial. You must reassemble them first into a normal message using mhstore. Check the man page for mhstore(1) for details.External Access
For contents of type message/external-body, mhshow supports these access-types:- •
- afs
- •
- anon-ftp
- •
- ftp
- •
- local-file
- •
- mail-server
nmh-access-ftp: myftp.sh
to determine the pathname of a program to perform the FTP retrieval.
This program is invoked with these arguments:
domain name of FTP-site username password remote directory remote filename local filename “ascii” or “binary”
The Content Cache
When mhshow encounters an external content containing a “Content-ID:” field, and if the content allows caching, then depending on the caching behavior of mhshow, the content might be read from or written to a cache. The caching behavior of mhshow is controlled with the -rcache and -wcache switches, which define the policy for reading from, and writing to, the cache, respectively. One of four policies may be specified: “public”, indicating that mhshow should make use of a publically-accessible content cache; “private”, indicating that mhshow should make use of the user's private content cache; “never”, indicating that mhshow should never make use of caching; and, “ask”, indicating that mhshow should ask the user. There are two directories where contents may be cached: the profile entry “nmh-cache” names a directory containing world-readable contents, and, the profile entry “nmh-private-cache” names a directory containing private contents. The former should be an absolute (rooted) directory name. For example,nmh-cache: /tmp
might be used if you didn't care that the cache got wiped after each reboot of
the system. The latter is interpreted relative to the user's nmh directory, if
not rooted, e.g.,
nmh-private-cache: .cache
(which is the default value).
User Environment
Because the display environment in which mhshow operates may vary for different machines, mhshow will look for the environment variable $MHSHOW. If present, this specifies the name of an additional user profile which should be read. Hence, when a user logs in on a particular display device, this environment variable should be set to refer to a file containing definitions useful for the given display device. Normally, only entries that deal with the methods to display different content type and subtypesmhshow-show-<type>/<subtype> mhshow-show-<type>
/etc/nmh/mhn.defaults
which is created automatically during nmh installation.
FILES
^$HOME/.mh_profile~^The user profile ^$MHSHOW~^Additional profile entries ^/etc/nmh/mhn.defaults~^System default MIME profile entries ^/etc/nmh/mhl.headers~^The headers template
PROFILE COMPONENTS
^Path:~^To determine the user's nmh directory ^Current-Folder:~^To find the default current folder ^Unseen-Sequence:~^To name sequences denoting unseen messages ^mhlproc:~^Default program to display message headers ^nmh-access-ftp:~^Program to retrieve contents via FTP ^nmh-cache~^Public directory to store cached external contents ^nmh-private-cache~^Personal directory to store cached external contents ^mhshow-charset-<charset>~^Template for environment to render character sets ^mhshow-show-<type>*~^Template for displaying contents ^moreproc:~^Default program to display text/plain content
SEE ALSO
mhbuild(1), mhl(1), mhlist(1), mhstore(1), sendfiles(1)DEFAULTS
`+folder' defaults to the current folder `msgs' defaults to cur `-nocheck' `-form mhl.headers' `-pause' `-rcache ask' `-noserialonly' `-wcache ask'
CONTEXT
If a folder is given, it will become the current folder. The last message selected will become the current message.11 June 2012 | MH.6.8 |