[mmh] / mhl.man

.\"
.\" %nmhwarning%
.\"
.TH MHL %manext1% "%nmhdate%" MH.6.8 [%nmhversion%]
.SH NAME
mhl \- produce formatted listings of nmh messages
.SH SYNOPSIS
.HP 5
.na
.B %libdir%/mhl
.RB [ \-bell " | " \-nobell ]
.RB [ \-clear " | " \-noclear ]
.RB [ \-folder
.IR +folder ]
.RB [ \-form
.IR formfile ]
.RB [ \-length
.IR lines ]
.RB [ \-width
.IR columns ]
.RB [ \-moreproc
.IR program ]
.RB [ \-nomoreproc ]
.RI [ files
.IR \&... ]
.RB [ \-version ]
.RB [ \-help ]
.ad
.SH DESCRIPTION
.B Mhl
is an
.B nmh
command for filtering and/or displaying text
messages.  It is the default method of displaying text messages for
.B nmh
(it is the default
.IR showproc ).
.PP
As with
.BR more ,
each of the messages specified as arguments (or
the standard input) will be output.  If more than one message file is
specified, the user will be prompted prior to each one, and a <RETURN>
or <EOT> will begin the output, with <RETURN> clearing the screen (if
appropriate), and <EOT> (usually CTRL\-D) suppressing the screen clear.
An <INTERRUPT> (usually CTRL\-C) will abort the current message output,
prompting for the next message (if there is one), and a <QUIT> (usually
CTRL-\\) will terminate the program (without core dump).
.PP
The
.B \-bell
option tells
.B mhl
to ring the terminal's bell at the
end of each page, while the
.B \-clear
option tells
.B mhl
to clear the
screen at the end of each page (or output a formfeed after each message).
Both of these switches (and their inverse counterparts) take effect only
if the profile entry
.I moreproc
is defined but empty, and
.B mhl
is outputting to a terminal.  If the
.I moreproc
entry is defined and
non-empty, and
.B mhl
is outputting to a terminal, then
.B mhl
will
cause the
.I moreproc
to be placed between the terminal and
.B mhl
and the switches are ignored.  Furthermore, if the
.B \-clear
switch is
used and \fImhl's\fR output is directed to a terminal, then
.B mhl
will consult the
.B $TERM
and
.B $TERMCAP
environment variables
to determine the user's terminal type in order to find out how to clear
the screen.  If the
.B \-clear
switch is used and
.BR mhl 's
output is
not directed to a terminal (e.g., a pipe or a file), then
.B mhl
will
send a formfeed after each message.
.PP
To override the default
.I moreproc
and the profile entry, use the
.B \-moreproc
.I program
switch.  Note that
.B mhl
will never start a
.I moreproc
if invoked on a hardcopy terminal.
.PP
The
.B \-length
.I length
and
.B \-width
.I width
switches set the screen
length and width, respectively.  These default to the values indicated by
.BR $TERMCAP ,
if appropriate, otherwise they default to 40 and 80, respectively.
.PP
The default format file used by
.B mhl
is called
.RI \*(lq mhl.format \*(rq.
.B mhl
will first search for this file in the user's
.B nmh
directory, and will then search in the directory
.IR %etcdir% .
This default
can be changed by using the
.B \-form
.I formatfile
switch.
.PP
Finally, the
.B \-folder
.I +folder
switch sets the
.B nmh
folder name,
which is used for the \*(lqmessagename:\*(rq field described below.  The
environment variable
.B $mhfolder
is consulted for the default value,
which
.BR show ,
.BR next ,
and
.B prev
initialize appropriately.
.PP
.B Mhl
operates in two phases: 1) read and parse the format file, and
2) process each message (file).  During phase 1, an internal description
of the format is produced as a structured list.  In phase 2, this list
is walked for each message, outputting message information under the
format constraints from the format file.
.PP
The format file can contain information controlling screen clearing,
screen size, wrap\-around control, transparent text, component ordering,
and component formatting.  Also, a list of components to ignore may be
specified, and a couple of \*(lqspecial\*(rq components are defined
to provide added functionality.  Message output will be in the order
specified by the order in the format file.
.PP
Each line of a format file has one of the following forms:
.PP
.RS 5
.nf
;comment
:cleartext
variable[,variable...]
component:[variable,...]
.fi
.RE
.PP
.IP \(bu 4
A line beginning with a `;' is a comment, and is ignored.
.IP \(bu 4
A line beginning with a `:' is clear text, and is output exactly as is.
.IP \(bu 4
A line containing only a `:' produces a blank line in the output.
.IP \(bu 4
A line beginning with \*(lqcomponent:\*(rq defines the format for the specified
component,
.IP \(bu 4
Remaining lines define the global environment.
.PP
For example, the line:
.PP
.RS 5
width=80,length=40,clearscreen,overflowtext="***",overflowoffset=5
.RE
.PP
defines the screen size to be 80 columns by 40 rows, specifies that the
screen should be cleared prior to each page, that the overflow indentation
is 5, and that overflow text should be flagged with \*(lq***\*(rq.
.PP
Following are all of the current variables and their arguments.  If they
follow a component, they apply only to that component, otherwise, their
affect is global.  Since the whole format is parsed before any output
processing, the last global switch setting for a variable applies to
the whole message if that variable is used in a global context (i.e.,
bell, clearscreen, width, length).
.PP
.RS 5
.nf
.ta \w'noclearscreen  'u +\w'integer/G  'u
.I "variable    type    semantics"
width   integer screen width or component width
length  integer screen length or component length
offset  integer positions to indent \*(lqcomponent: \*(rq
overflowtext    string  text to use at the beginning of an
                overflow line
overflowoffset  integer positions to indent overflow lines
compwidth       integer positions to indent component text
                after the first line is output
uppercase       flag    output text of this component in all
                upper case
nouppercase     flag    don't uppercase
clearscreen     flag/G  clear the screen prior to each page
noclearscreen   flag/G  don't clearscreen
bell    flag/G  ring the bell at the end of each page
nobell  flag/G  don't bell
component       string/L        name to use instead of \*(lqcomponent\*(rq for
                this component
nocomponent     flag    don't output \*(lqcomponent: \*(rq for this
                component
center  flag    center component on line (works for
                one\-line components only)
nocenter        flag    don't center
leftadjust      flag    strip off leading whitespace on each
                line of text
noleftadjust    flag    don't leftadjust
compress        flag    change newlines in text to spaces
nocompress      flag    don't compress
wrap    flag    Wrap lines that exceed width (default)
nowrap  flag    Do not perform line wrapping
split   flag    don't combine multiple fields into
                a single field
nosplit flag    combine multiple fields into
                a single field
newline flag    print newline at end of components
                (this is the default)
nonewline       flag    don't print newline at end of components
formatfield     string  format string for this component
                (see below)
decode  flag    decode text as RFC-2047 encoded
                header field
addrfield       flag    field contains addresses
datefield       flag    field contains dates
format  flag    Run component through formatproc filter
                (body only)
noformat        flag    Do not run component through
                formatproc filter (default)
.fi
.RE
.PP
To specify the value of integer\-valued and string\-valued variables,
follow their name with an equals\-sign and the value.  Integer\-valued
variables are given decimal values, while string\-valued variables
are given arbitrary text bracketed by double\-quotes.  If a value is
suffixed by \*(lq/G\*(rq or \*(lq/L\*(rq, then its value is useful in
a global\-only or local\-only context (respectively).
.PP
A line of the form:
.PP
.RS 5
ignores=component,...
.RE
.PP
specifies a list of components which are never output.
.PP
The component \*(lqMessageName\*(rq (case\-insensitive) will output the
actual message name (file name) preceded by the folder name if one is
specified or found in the environment.  The format is identical to that
produced by the
.B \-header
option to
.BR show .
.PP
The component \*(lqExtras\*(rq will output all of the components of the
message which were not matched by explicit components, or included in
the ignore list.  If this component is not specified, an ignore list is
not needed since all non\-specified components will be ignored.
.PP
If \*(lqnocomponent\*(rq is NOT specified, then the component name will
be output as it appears in the format file.
.PP
The default format file is:
.PP
.RS 5
.nf
%mhl_format%
.fi
.RE
.PP
The variable \*(lqformatfield\*(rq specifies a format string (see
.BR mh\-format (5)).
The flag variables \*(lqaddrfield\*(rq and
\*(lqdatefield\*(rq (which are mutually exclusive), tell
.B mhl
to interpret the escapes in the format string as either addresses or
dates, respectively.
.PP
By default,
.B mhl
does not apply any formatting string to fields
containing address or dates (see
.BR mh\-mail (5)
for a list of these
fields).  Note that this results in faster operation since
.B mhl
must parse both addresses and dates in order to apply a format string
to them.  If desired,
.B mhl
can be given a default format string for
either address or date fields (but not both).  To do this, on a global
line specify: either the flag addrfield or datefield, along with the
appropriate formatfield variable string.
.PP
The \*(lqformat\*(rq flag specifies that this component will be run through
the filter program specified by the 
.IR formatproc
profile entry.  This filter program is expected to read data on standard
input and output data on standard output.  Currently the \*(lqformat\*(rq
flag is only supported for the \(*lqbody\*(rq component.  The component
name will be prefixed to the output
.IR after
the filter has been run.  The expected use of this is to filter a message
body to create more pleasing text to use in a reply message.
A suggested filter to use for
.BR repl(1)
is as follows:
.PP
.RS 5
body:component=">",overflowtext=">",overflowoffset=0,format,nowrap
.RE
.SH FILES
.fc ^ ~
.nf
.ta \w'%etcdir%/ExtraBigFileName  'u
^%etcdir%/mhl.format~^The message template
^or <mh\-dir>/mhl.format~^Rather than the standard template
^$HOME/\&.mh\(ruprofile~^The user profile
.fi

.SH "PROFILE COMPONENTS"
.fc ^ ~
.nf
.ta 2.4i
.ta \w'ExtraBigProfileName  'u
^moreproc:~^Program to use as interactive front\-end
^formatproc:~^Program to use as a filter for components that
^^have the \*(lqformat\*(rq flag set.
.fi

.SH "SEE ALSO"
show(1), ap(8), dp(8)

.SH DEFAULTS
.nf
.RB ` \-bell '
.RB ` \-noclear '
.RB ` \-length\ 40 '
.RB ` \-width\ 80 '
.fi

.SH CONTEXT
None

.SH BUGS
There should be some way to pass `bell' and `clear' information to the 
front\-end.
.PP
The \*(lqnonewline\*(rq option interacts badly with \*(lqcompress\*(rq
and \*(lqsplit\*(rq.