Provided by: nmh_1.3-1build1_i386 bug


       mhshow - display MIME messages


       mhshow [+folder] [msgs] [-file file] [-part number] ...  [-type
            content] ...  [-serialonly | -noserialonly] [-pause | -nopause]
            [-form formfile] [-rcache policy] [-wcache policy] [-check |
            -nocheck] [-version] [-help]


       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

       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

       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

       A legal MIME message must contain a subtype specification.

       To specify a content, regardless of its subtype, just use the  name  of
       the  content,  e.g.,  “audio”.  To specify a specific subtype, separate
       the two with a slash, e.g., “audio/basic”.  Note that regardless of the
       values given to the `-type' switch, a multipart content (of any subtype
       listed above) is always acted upon.  Further note that if  the  `-type'
       switch  is  used, and it is desirable to act on a message/external-body
       content,  then  the  `-type'  switch  must  be  used  twice:  once  for
       message/external-body and once for the content externally referenced.

   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

   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

       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>


            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

       to automatically append a suffix to the temporary files.

       The method used to display  the  different  contents  in  the  messages
       bodies  will  be determined by a “display string”.  To find the display
       string, mhshow will first search your profile for an entry of the form:


       to determine the display string.  If  this  isn't  found,  mhshow  will
       search for an entry of the form:


       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 %

       For  those  display  strings containing the e- or F-escape, mhshow will
       execute at most one of these at any given time.  Although the  F-escape
       expands  to be the filename containing the content, the e-escape has no
       expansion as far as the shell is concerned.

       When the  p-escape  prompts  for  confirmation,  typing  INTR  (usually
       control-C)  will tell mhshow not to display that content.  The p-escape
       can be disabled by  specifying  the  switch  -nopause.   Further,  when
       mhshow  is display a content, typing QUIT (usually control-\) will tell
       mhshow to wrap things up immediately.

       Note that if the content being displayed is multipart, but not  one  of
       the subtypes listed above, then the f- and F-escapes expand to multiple
       filenames, one for each subordinate content.   Further,  stdin  is  not
       redirected from the terminal to the content.

       If a display string is not found, mhshow has several default values:

            mhshow-show-text/plain: %pmoreproc '%F'
            mhshow-show-message/rfc822: %pshow -file '%F'

       If  a  subtype  of  type  text doesn't have a profile entry, it will be
       treated as text/plain.

       mhshow has default methods for handling multipart messages  of  subtype
       mixed,  alternative, parallel, and digest.  Any unknown subtype of type
       multipart   (without   a   profile   entry),   will   be   treated   as

       If  none  of  these apply, then mhshow will check to see if the message
       has an application/octet-stream content with parameter “type=tar”.   If
       so,  mhshow  will  use  an  appropriate  command.   If not, mhshow will

       Example entries might be:

            mhshow-show-audio/basic: raw2audio 2>/dev/null | play
            mhshow-show-image: xv '%f'
            mhshow-show-application/PostScript: lpr -Pps

       Note that when using the f- or  F-escape,  it's  a  good  idea  to  use
       single-quotes  around  the  escape.  This prevents misinterpretation by
       the shell of  any  funny  characters  that  might  be  present  in  the

       Finally,  mhshow  will  process each message serially -- it won't start
       showing the next message until all the commands executed to display the
       current  message  have  terminated.  In the case of a multipart content
       (of any subtype listed above), the content contains  advice  indicating
       if the parts should be displayed serially or in parallel.  Because this
       may  cause  confusion,  particularly  on   uni-window   displays,   the
       -serialonly  switch  can be given to tell mhshow to never display parts
       in parallel.

   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:


       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


            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

       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"

       The  first  line  tells  less  to  use  the  ISO-8859-1  definition for
       determining whether a character is “normal”,  “control“,  or  “binary”.
       The second line tells less not to warn you if it encounters a file that
       has non-ASCII characters.  Then, simply set the moreproc profile  entry
       to  less,  and  it  will  get  called  automatically.  (To handle other
       single-octet character sets, look  at  the  less(1)  manual  entry  for
       information about the $LESSCHARDEF environment variable.)

   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

       ·   afs

       ·   anon-ftp

       ·   ftp

       ·   local-file

       ·   mail-server

       For the “anon-ftp” and “ftp” access types, mhshow  will  look  for  the
       “nmh-access-ftp” profile entry, e.g.,


       to determine the pathname of a program to perform the FTP retrieval.

       This program is invoked with these arguments:

            domain name of FTP-site
            remote directory
            remote filename
            local filename
            “ascii” or “binary”

       The  program  should  terminate  with  an  exit  status  of zero if the
       retrieval is successful, and a non-zero exit status otherwise.

       If this entry is not provided, then mhshow will use a  simple  built-in
       FTP client to perform the retrieval.

   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

       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

       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  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 subtypes


       need be present  in  this  additional  profile.  Finally,  mhshow  will
       attempt to consult one other additional user profile, e.g.,


       which is created automatically during nmh installation.


       $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


       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-<charsTe>mplate for environment to render character sets
       mhshow-show-<type>*  Template for displaying contents
       moreproc:            Default program to display text/plain content


       mhbuild(1), mhl(1), mhlist(1), mhstore(1), sendfiles(1)


       `+folder' defaults to the current folder
       `msgs' defaults to cur


       If  a  folder  is  given,  it will become the current folder.  The last
       message selected will become the current message.