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mhl(1mh)

MH.6.8
2019-01-06

nmh

A capable MIME-email-handling system with a command-line interface

mmh

set of electronic mail handling programs

NAME

mhl - produce formatted listings of mh messages

SYNOPSIS

mhl [-form formfile] [-width columns] [files ...] [-Version] [-help]

DESCRIPTION

Mhl is an mmh command for filtering and/or displaying text messages. It is the default method of displaying text messages for mmh (it is the default showproc).
The -width width switch sets the screen width. This defaults to the value indicated by $TERMCAP, if appropriate, otherwise it defaults to 80.
The default format file used by mhl is called ‘mhl.format’. mhl will first search for this file in the user’s mmh directory, and will then search in the directory /etc/mmh. This default can be changed by using the -form formatfile switch. Note: In contrast to any other mmh tool, the -form switch does only take file names, but no format strings with a prepended equal sign ‘=’.
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.
The format file can contain information controlling 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 ‘special’ components are defined to provide added functionality. Message output will be in the order specified by the order in the format file.
Each line of a format file has one of the following forms:
;comment
:cleartext
variable[,variable...]
component:[variable,...]
o A line beginning with a ‘;’ is a comment, and is ignored.
o A line beginning with a ‘:’ is clear text, and is output exactly as is.
o A line containing only a ‘:’ produces a blank line in the output.
o A line beginning with ‘component:’ defines the format for the specified component,
o Remaining lines define the global environment.
For example, the line:
width=80,overflowtext="***",overflowoffset=5
defines the screen size to be 80 columns by 40 rows, specifies that the overflow indentation is 5, and that overflow text should be flagged with ‘***’.
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., width).
variable type semantics
width         integer   screen width or component width
length        integer   component length
offset        integer   positions to indent ‘component: ’
overflowtext  string    text to use at the beginning of an
                        overflow line
overflowoffset          integerpositions 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
component     string/L  name to use instead of ‘component’ for
                        this component
nocomponent   flag      don’t output ‘component: ’ 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
rtrim         flag      trim whitespace at end of text lines
nortrim       flag      retain whitespace at end of text lines (default)
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
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 ‘/G’ or ‘/L’, then its value is useful in a global-only or local-only context (respectively).
A line of the form:
ignores=component,...
specifies a list of components which are never output. This option supports some simple globbing, so a ’*’ at the end of a component will match for all components which start which the string. When you want to match a component which ends with a ’*’, you can escape the ’*’ with a ’#146;.
The component ‘MessageName’ (case-insensitive) will output the message file name as a one-line header, similar to show. E.g. ‘‘(Message 42)’’
The component ‘Extras’ 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.
If ‘nocomponent’ is NOT specified, then the component name will be output as it appears in the format file.
The default format file is:

; mhl.format ; ; default message filter for ‘show’ ; : overflowtext="***",overflowoffset=5 leftadjust,compwidth=9 ignores=msgid,message-id,received,content-type,content-transfer-encoding,content-id Date:formatfield="%<(nodate{text})%{text}%|%(pretty{text})%>" From:decode To:decode Cc:decode Subject:decode : extras:nocomponent : body:nocomponent,overflowtext=,overflowoffset=0,noleftadjust
The variable ‘formatfield’ specifies a format string (see mh-format(5)). The flag variables ‘addrfield’ and ‘datefield’ (which are mutually exclusive), tell mhl to interpret the escapes in the format string as either addresses or dates, respectively.
By default, mhl does not apply any formatting string to fields containing address or dates (see mh-mail(5) for a list of these fields). Note that this results in faster operation since mhl must parse both addresses and dates in order to apply a format string to them. If desired, 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.

FILES

^/etc/mmh/mhl.format~^The message template
^or $HOME/.mmh/mhl.format~^Rather than the standard template
^$HOME/.mmh/profile~^The user profile

PROFILE COMPONENTS

none

SEE ALSO

DEFAULTS

-width 80’

CONTEXT

None

BUGS

In contrast to any other mmh tool, the -form switch does only take file names, but no format strings with a prepended equal sign ‘=’.
The ‘nonewline’ option interacts badly with ‘compress’ and ‘split’.
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