mhl - produce formatted listings of nmh messages
/usr/lib/mh/mhl [-bell | -nobell] [-clear | -noclear] [-folder +folder]
[-form formfile] [-length lines] [-width columns] [-moreproc
program] [-nomoreproc] [files ...] [-version] [-help]
Mhl is an nmh command for filtering and/or displaying text messages.
It is the default method of displaying text messages for nmh (it is the
As with 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).
The -bell option tells mhl to ring the terminal’s bell at the end of
each page, while the -clear option tells 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 moreproc is defined but empty, and mhl is outputting to a
terminal. If the moreproc entry is defined and non-empty, and mhl is
outputting to a terminal, then mhl will cause the moreproc to be placed
between the terminal and mhl and the switches are ignored.
Furthermore, if the -clear switch is used and mhls output is directed
to a terminal, then mhl will consult the $TERM and $TERMCAP environment
variables to determine the user’s terminal type in order to find out
how to clear the screen. If the -clear switch is used and mhl’s output
is not directed to a terminal (e.g., a pipe or a file), then mhl will
send a formfeed after each message.
To override the default moreproc and the profile entry, use the
-moreproc program switch. Note that mhl will never start a moreproc if
invoked on a hardcopy terminal.
The -length length and -width width switches set the screen length and
width, respectively. These default to the values indicated by
$TERMCAP, if appropriate, otherwise they default to 40 and 80,
The default format file used by mhl is called “mhl.format”. mhl will
first search for this file in the user’s nmh directory, and will then
search in the directory /etc/nmh. This default can be changed by using
the -form formatfile switch.
Finally, the -folder +folder switch sets the nmh folder name, which is
used for the “messagename:” field described below. The environment
variable $mhfolder is consulted for the default value, which show,
next, and prev initialize appropriately.
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 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 “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:
· A line beginning with a ‘;’ is a comment, and is ignored.
· A line beginning with a ‘:’ is clear text, and is output exactly as
· A line containing only a ‘:’ produces a blank line in the output.
· A line beginning with “component:” defines the format for the
· Remaining lines define the global environment.
For example, the line:
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 “***”.
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).
variable type semantics
width integer screen width or component width
length integer screen length or component length
offset integer positions to indent “component: ”
overflowtext string text to use at the beginning of an
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
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 “component” for
nocomponent flag don’t output “component: ” for this
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
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
decode flag decode text as RFC-2047 encoded
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:
specifies a list of components which are never output.
The component “MessageName” (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 -header option to show.
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:
; default message filter for ‘show’
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.
/etc/nmh/mhl.format The message template
or <mh-dir>/mhl.format Rather than the standard template
$HOME/.mh_profile The user profile
moreproc: Program to use as interactive front-end
show(1), ap(8), dp(8)
There should be some way to pass ‘bell’ and ‘clear’ information to the
The “nonewline” option interacts badly with “compress” and “split”.