+.TH MHSHOW %manext1% "March 24, 2016" "%nmhversion%"
.\"
.\" %nmhwarning%
-.\" $Id$
.\"
-.TH MHSHOW %manext1% "%nmhdate%" MH.6.8 [%nmhversion%]
.SH NAME
mhshow \- display MIME messages
.SH SYNOPSIS
.HP 5
.na
.B mhshow
+.RB [ \-help ]
+.RB [ \-version ]
.RI [ +folder ]
.RI [ msgs ]
.RB [ \-file
.RB [ \-type
.IR content ]
\&...
-.RB [ \-serialonly " | " \-noserialonly ]
-.RB [ \-pause " | " \-nopause ]
+.RB [ \-prefer
+.IR content ]
+\&...
+.RB [ \-concat " | " \-noconcat ]
+.RB [ \-textonly " | " \-notextonly ]
+.RB [ \-inlineonly " | " \-noinlineonly ]
+.RB [ \-header " | " \-noheader ]
.RB [ \-form
.IR formfile ]
+.RB [ \-markform
+.IR formfile ]
.RB [ \-rcache
.IR policy ]
.RB [ \-wcache
.IR policy ]
.RB [ \-check " | " \-nocheck ]
-.RB [ \-version ]
-.RB [ \-help ]
.ad
.SH DESCRIPTION
The
.PP
.B mhshow
manipulates multi-media messages as specified in
-RFC\-2045 thru RFC\-2049. Currently
+RFC 2045 to RFC 2049. Currently
.B mhshow
only supports
encodings in message bodies, and does not support the encoding of
-message headers as specified in RFC\-2047.
+message headers as specified in RFC 2047.
.PP
By default
.B mhshow
-will display all parts of a multipart
-message. By using the
-.B \-part
+will display only text parts of a message that are not marked as attachments.
+This behavior can be changed by the
+.B \-notextonly
+and
+.B \-noinlineonly
+switches.
+In addition, by using the
+.BR \-part ,
+.BR \-type ,
and
+.B \-prefer
+switches, you may limit and reorder the set of parts to be displayed,
+based on part number and/or content type.
+The inclusion of any
+.B \-part
+or
.B \-type
-switches, you may
-limit the scope of
+switches will override the default settings of
+.B \-textonly
+and
+.BR \-inlineonly.
+.PP
+The
+.B \-header
+switch control whether
+.B mhshow
+will print a message separator header before each message that it
+displays. The header format can be controlled using
+.B \-headerform
+to specify a file containing
+.IR mh\-format (5)
+instructions. A copy of the built-in default
+headerform can be found in %nmhetcdir%/mhshow.header, for reference.
+In addition to the normal set of
+.IR mh\-format (5)
+instructions, a "%{folder}" escape provides a
+string representing the current folder.
+.PP
+By default
.B mhshow
-to particular subparts (of a
-multipart content) and/or particular content types.
+will concatenate all content under one pager. If you want each part to
+displayed separately, you can override the default behavior with
+.B \-noconcat.
.PP
The option
.B \-file
mail drop format to a folder of
.B nmh
messages, see
-.BR inc (1)).
+.IR inc (1)).
+.PP
+The
+.B \-part
+switch can be used (one or more times) to restrict the
+set of subparts that will be displayed. (Obviously with no
+.B \-part
+switches, all parts will be considered.) If a
+.B \-part
+switch specifies a specific subpart (i.e., a "leaf" in the tree of
+MIME parts), then that part will always be displayed. If a
+.B \-part
+switch references a multipart/alternative part, then (in
+the absence of a
+.B \-type
+switch) only the default subpart of that multipart will be displayed.
.PP
A part specification consists of a series of numbers separated by dots.
For example, in a multipart content containing three parts, these
multipart content containing two parts, these would be named as 2.1 and
2.2, respectively. Note that the
.B \-part
-switch is effective for only
+switch is effective only for
messages containing a multipart content. If a message has some other
kind of content, or if the part is itself another multipart content, the
.B \-part
switch will not prevent the content from being acted upon.
.PP
+The
+.B \-type
+switch can also be used to restrict (or, when used in conjunction with
+.BR \-part ,
+to further restrict) the display of parts according to content type.
+One or more
+.B \-type
+switches part will only select the first match
+from a multipart/alternative, even if there is more than one
+subpart that matches (one of) the given content type(s).
+.PP
+Using either
+.B \-part
+or
+.B -type
+switches alone will cause either to select
+the part(s) they match. Using them together will select only
+the part(s) matched by both (sets of) switches. In other
+words, the result is the intersection, and not the union, of their
+separate match results.
+.PP
A content specification consists of a content type and a subtype.
The initial list of \*(lqstandard\*(rq content types and subtypes can
-be found in RFC\-2046.
+be found in RFC 2046.
.PP
A list of commonly used contents is briefly reproduced here:
.PP
To specify a content, regardless of its subtype, just use the
name of the content, e.g., \*(lqaudio\*(rq. To specify a specific
subtype, separate the two with a slash, e.g., \*(lqaudio/basic\*(rq.
-Note that regardless of the values given to the `\-type' switch, a
+Note that regardless of the values given to the
+.B \-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
+Further note that if the
+.B \-type
+switch is used, and it is desirable to
+act on a message/external-body content, then the
+.B \-type
+switch must
be used twice: once for message/external-body and once for the content
externally referenced.
+.PP
+In the absence of
+.BR \-prefer ,
+.B mhshow
+will select the "best" displayable subpart from
+multipart/alternative content. The
+.B \-prefer
+switch can be used (one or more times, in order of descending
+preference) to let MH know which content types from a
+multipart/alternative MIME part are preferred by the user, in order to
+override the default selection for display. For example, mail is
+often sent containing both plaintext and HTML-formatted versions of
+the same content, and the HTML version is usually indicated to be the
+"best" format for viewing. Using \*(lq-prefer text/plain\*(rq will
+cause the plaintext version to be displayed if possible, but still
+allow display of the HTML part if there is no plaintext subpart
+available. Using \*(lq-prefer text/plain -prefer image/png\*(rq
+would add a preference for PNG images, which might or might not
+ever appear in the same multipart/alternative section with text/plain.
+Implementation note: RFC 2046 requires that the subparts
+of a multipart/alternative be ordered according to "faithfulness to
+the original content", and MH by default selects the subpart ranked
+most "faithful" by that ordering. The
+.B \-prefer
+switch reorders the alternative parts (only internally, never changing
+the message file) to move the user's preferred part(s) to the "most
+faithful" position. Thus, when viewed by
+.BR mhlist ,
+the ordering of multipart/alternative parts will appear to change when
+invoked with or without various
+.B \-prefer
+switches.
.SS "Unseen Sequence"
If the profile entry \*(lqUnseen\-Sequence\*(rq is present and
non\-empty, then
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
+Similarly, older versions of the
.B gs
command append a \*(lq.ps\*(rq suffix to
the filename if one was missing. As a result, these cannot be used to read
.PP
.RS 5
.nf
-.ta \w'%F 'u
-%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 %
+.ta \w'%F 'u
+%a Insert parameters from Content-Type field
+%{parameter} Insert the parameter value from the Content-Type field
+%f Insert filename containing content
+%F %f, and stdin is terminal not content
+%l display listing prior to displaying content
+%s Insert content subtype
+%d Insert content description
+%% Insert the character %
.fi
.RE
.PP
-For those display strings containing the e- or F-escape,
-.B mhshow
+.B 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.
+execute at most one display string at any given time, and wait for the
+current display string to finish execution before executing the next
+display string.
.PP
-When the p-escape prompts for confirmation, typing INTR (usually
-control-C) will tell
-.B mhshow
-not to display that content.
-The p-escape can be disabled by specifying the switch
-.BR \-nopause .
-Further, when
-.B mhshow
-is display a content, typing QUIT (usually
-control-\\) will tell
-.B mhshow
-to wrap things up immediately.
+The {parameter} escape is typically used in a command line argument
+that should only be present if it has a non-null value. Its value
+will be wrapped with single quotes if the escape is not so wrapped.
+Shell parameter expansion can construct the argument only when it is
+non-null, e.g.,
+.PP
+.RS 5
+.nf
+mhshow-show-text/html: charset=%{charset};
+ w3m ${charset:+-I $charset} -T text/html %F
+.fi
+.RE
+.PP
+That example also shows the use of indentation to signify continuation:
+the two text lines combine to form a single entry. Note that when
+dealing with text that has been converted internally by
+.IR iconv (3),
+the \*(lqcharset\*(rq parameter will reflect the target character set
+of the text, rather than the original character set in the message.
.PP
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
.PP
If a display string is not found,
.B mhshow
-has several default values:
+behaves as if these profile entries were supplied and supported:
.PP
.RS 5
.nf
-mhshow-show-text/plain: %pmoreproc '%F'
-mhshow-show-message/rfc822: %pshow -file '%F'
+mhshow-show-text/plain: %lmoreproc %F
+mhshow-show-message/rfc822: %lshow -file %F
.fi
.RE
.PP
+Note that \*(lqmoreproc\*(rq is not supported in user profile display
+strings.
+.PP
If a subtype of type text doesn't have a profile entry, it will be
treated as text/plain.
.PP
.RS 5
.nf
mhshow-show-audio/basic: raw2audio 2>/dev/null | play
-mhshow-show-image: xv '%f'
+mhshow-show-image: xv %f
mhshow-show-application/PostScript: lpr -Pps
.fi
.RE
.PP
-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 filename.
+If an f- or F-escape is not quoted with single quotes, its expansion
+will be wrapped with single quotes.
.PP
Finally,
.B mhshow
will process each message serially\0--\0it 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
-.B \-serialonly
-switch can be given to tell
-.B mhshow
-to never display parts in parallel.
+current message have terminated.
.SS "Showing Alternate Character Sets"
+If
+.B mhshow
+was built with
+.IR iconv (3),
+then all text/plain parts of the message(s) will be displayed using
+the character set of the current locale. See the
+.IR mhparam (1)
+man page for how determine whether your
+.B nmh
+installation includes
+.IR iconv (3)
+support. To convert text parts other
+than text/plain, or if
+.B mhshow
+was not built with
+.IR iconv ,
+an external program can be used, as described next.
+.PP
Because a content of type text might be in a non-ASCII character
set, when
.B mhshow
encounters a \*(lqcharset\*(rq parameter for
this content, it checks if your terminal can display this character
set natively.
-.B mhn
-checks this by examining the the environment
-variable
-.BR $MM_CHARSET .
-If the value of this environment variable is equal
+.B mhshow
+checks this by examining the current character set defined by the
+.IR locale (1)
+environment variables.
+If the value of the locale character set is equal
to the value of the charset parameter, then
.B mhshow
assumes it can
-display this content without any additional setup. If this environment
-variable is not set,
+display this content without any additional setup. If the locale is not
+set properly,
.B mhshow
will assume a value of \*(lqUS-ASCII\*(rq.
If the character set cannot be displayed natively, then
Note that many pagers strip off the high-order bit or have problems
displaying text with the high-order bit set. However, the pager
.B less
-has support for single-octet character sets. The source
-to
-.B less
-is available on many ftp sites carrying free software.
-In order to view messages sent in the ISO-8859-1 character set using
+has support for single-octet character sets. For example, messages
+encoded in the ISO-8859-1 character set can be view using
.BR less ,
-.PP
-put these lines in your
-.I \&.login
-file:
+with these environment variable settings:
.PP
.RS 5
.nf
-setenv LESSCHARSET latin1
-setenv LESS "-f"
+.ta \w'%F 'u
+LESSCHARSET latin1
+LESS -f
.fi
.RE
.PP
-The first line tells
+The first setting tells
.B less
to use the ISO-8859-1 definition for
determining whether a character is \*(lqnormal\*(rq, \*(lqcontrol\*(lq,
-or \*(lqbinary\*(rq. The second line tells
+or \*(lqbinary\*(rq. The second setting tells
.B less
not to warn you
if it encounters a file that has non-ASCII characters. Then, simply
and it will get
called automatically. (To handle other single-octet character sets,
look at the
-.BR less (1)
+.IR less (1)
manual entry for information about the
.B $LESSCHARDEF
environment variable.)
You must reassemble them first into a normal message using
.BR mhstore .
Check the man page for
-.BR mhstore (1)
+.IR mhstore (1)
for details.
.SS "External Access"
For contents of type message/external-body,
local-file
.IP \(bu 4
mail-server
+.IP \(bu 4
+url
.PP
For the \*(lqanon-ftp\*(rq and \*(lqftp\*(rq access types,
.B mhshow
The program should terminate with an exit status of zero if the
retrieval is successful, and a non-zero exit status otherwise.
.PP
-If this entry is not provided, then
+For the \*(lqurl\*(rq access\-type,
.B mhshow
-will use a simple
-built-in FTP client to perform the retrieval.
+will look for the \*(lqnmh-access-url\*(rq
+profile entry. See
+.IR mhstore (1)
+for more details.
+.PP
.SS "The Content Cache"
When
.B mhshow
different machines,
.B mhshow
will look for the environment variable
-.BE $MHSHOW .
+.BR $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
.fi
.RE
.PP
-need be present in this additional profile. Finally,
+need be present in this additional profile. Finally,
.B mhshow
-will attempt to consult one other additional user profile,
-e.g.,
+will attempt to consult
.PP
.RS 5
-%etcdir%/mhn.defaults
+%nmhetcdir%/mhn.defaults
.RE
.PP
which is created automatically during
.B nmh
installation.
-
+.PP
+See "Profile Lookup" in
+.IR mh-profile (5)
+for the profile search order, and for how duplicate entries are treated.
+.SS Content\-Type Marker
+.B mhshow
+will display a marker containing information about the part being displayed
+next. The default marker can be changed using the
+.B \-markform
+switch to specify a file containing
+.IR mh\-format (5)
+instructions to use when displaying the content marker. A copy of the
+default markform can be found in %nmhetcdir%/mhshow.marker, for
+reference. In addition to the normal set of
+.IR mh\-format (5)
+instructions, the following
+.I component
+escapes are supported:
+.PP
+.RS 5
+.nf
+.ta \w'cdispo-<PARAM> 'u +\w'Returns 'u
+.I "Escape Returns Description"
+part string MIME part number
+content\-type string MIME Content\-Type of part
+description string Content\-Description header
+disposition string Content disposition (attachment or inline)
+ctype-<PARAM> string Value of <PARAM> from Content\-Type header
+cdispo-<PARAM> string Value of <PARAM> from
+ Content\-Disposition header
+%(size) integer The size of the decoded part, in bytes
+%(unseen) boolean Returns true for suppressed parts
+.fi
+In this context, the %(unseen) function indicates whether
+.B mhshow
+has decided to not display a particular part due to the
+.B \-textonly
+or
+.B \-inlineonly
+switches.
+.RE
+All MIME parameters and the \*(lqContent-Description\*(rq header will have
+RFC 2231 decoding applied and be converted
+to the local character set.
+.PP
.SH FILES
+.B mhshow
+looks for all format files and mhn.defaults in multiple locations:
+absolute pathnames are accessed directly, tilde expansion is done on
+usernames, and files are searched for in the user's
+.I Mail
+directory as specified in their profile. If not found there, the directory
+.RI \*(lq %nmhetcdir% \*(rq
+is checked.
+.PP
.fc ^ ~
.nf
-.ta \w'%etcdir%/ExtraBigFileName 'u
+.ta \w'%nmhetcdir%/ExtraBigFileName 'u
^$HOME/\&.mh\(ruprofile~^The user profile
^$MHSHOW~^Additional profile entries
-^%etcdir%/mhn.defaults~^System default MIME profile entries
-^%etcdir%/mhl.headers~^The headers template
+^%nmhetcdir%/mhn.defaults~^System default MIME profile entries
+^%nmhetcdir%/mhl.headers~^The headers template
+^%nmhetcdir%/mhshow.marker~^Example content marker
+^%nmhetcdir%/mhshow.header~^Example message separator header
.fi
-
.SH "PROFILE COMPONENTS"
.fc ^ ~
.nf
^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-access-url:~^Program to retrieve contents via HTTP
^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
.fi
-
.SH "SEE ALSO"
-mhbuild(1), mhl(1), mhlist(1), mhstore(1), sendfiles(1)
-
+.IR iconv (3),
+.IR mhbuild (1),
+.IR mhl (1),
+.IR mhlist (1),
+.IR mhparam (1),
+.IR mhstore (1),
+.IR sendfiles (1)
.SH DEFAULTS
.nf
.RB ` +folder "' defaults to the current folder"
.RB ` msgs "' defaults to cur"
.RB ` \-nocheck '
-.RB ` \-form mhl.headers '
-.RB ` \-pause '
-.RB ` \-rcache ask '
-.RB ` \-realsize '
-.RB ` \-noserialonly '
-.RB ` \-noverbose '
-.RB ` \-wcache ask '
+.RB ` \-concat '
+.RB ` \-textonly '
+.RB ` \-inlineonly '
+.RB ` \-form\ mhl.headers '
+.RB ` \-rcache\ ask '
+.RB ` \-wcache\ ask '
.fi
-
.SH CONTEXT
If a folder is given, it will become the current folder. The last
message selected will become the current message.
projects / nmh / blobdiff