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 scree 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 mhl's 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, respectively.
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 is. A line containing only a `:' produces a blank line in the output. A line beginning with ``component:'' defines the format for the specified component, and finally, 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 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 ``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 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:
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:
man2html: unable to open or read file /etc/nmh/mhl.format
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) `-bell' `-noclear' `-length 40' `-width 80' None There should be some way to pass `bell' and `clear' information to the front-end.
The ``nonewline'' option interacts badly with ``compress'' and ``split''.