MH-FORMAT(5)

NAME
mh-format - format file for MH message system

SYNOPSIS
some MH commands

DESCRIPTION
Several MH commands utilize either a format string or a format file during their execution. For example, scan (1) uses a format string which directs it how to generate the scan listing for each message; repl (1) uses a format file which directs it how to generate the reply to a message, and so on. Format strings are designed to be efficiently parsed by MH which means they are not necessarily simple to write and understand. This means that novice, casual, or even advanced users of MH should not have to deal with them. Some canned scan listing formats are in /usr/local/lib/mh/scan.time, /usr/local/lib/mh/scan.size, and /usr/local/lib/mh/scan.timely. Look in /usr/local/lib/mh for other scan and repl format files which may have been written at your site. It suffices to have your local MH expert actually write new format commands or modify existing ones. This manual section explains how to do that. Note: familiarity with the C printf routine is assumed. A format string consists of ordinary text, and special multi-character escape sequences which begin with `%'. When specifying a format string, the usual C backslash characters are honored: `\b', `\f', `\n', `\r', and `\t'. Continuation lines in format files end with `\' followed by the newline character. To put a literal `%' or `\' in a format string, use two of them: `%%' and `\\'. There are three types of escape sequences: header components, built-in functions, and flow control. A component escape is specified as `%{component}', and exists for each header found in the message being processed. For example `%{date}' refers to the “Date:” field of the appropriate message. All component escapes have a string value. Normally, component values are compressed by converting any control characters (tab and newline included) to spaces, then eliding any leading or multiple spaces. However, commands may give different interpretations to some component escapes; be sure to refer to each command's manual entry for complete details. A function escape is specified as `%(function)'. All functions are built-in, and most have a string or numeric value. A control escape is one of: `%<', `%?', `%|', or `%>'. These are combined into the conditional execution construct:

	%<condition
		format text 1
	%?condition2
		format text 2
	%?condition3
		format text 3
	...
	%|
		format text N
	%>

Extra white space is shown here only for clarity. These constructs may be nested without ambiguity. They form a general if-elseif-else-endif block where only one of the format text segments is interpreted. The `%<' and `%?' control escapes causes a condition to be evaluated. This condition may be either a component or a function. The four constructs have the following syntax:

	%<{component}
	%<(function)
	%?{component}
	%?(function)

These control escapes test whether the function or component value is non-zero (for integer-valued escapes), or non-empty (for string-valued escapes). If this test evaulates true, then the format text up to the next corresponding control escape (one of `%|', `%?', or `%>') is interpreted normally. Next, all format text (if any) up to the corresponding `%>' control escape is skipped. The `%>' control escape is not interpreted; normal interpretation resumes after the `%>' escape. If the test evaluates false, however, then the format text up to the next corresponding control escape (again, one of `%|', `%?', or `%>') is skipped, instead of being interpreted. If the control escape encountered was `%?', then the condition associated with that control escape is evaluated, and interpretation proceeds after that test as described in the previous paragraph. If the control escape encountered was `%|', then the format text up to the corresponding `%>' escape is interpreted normally. As above, the `%>' escape is not interpreted and normal interpretation resumes after the `%>' escape. The `%?' control escape and its following format text is optional, and may be included zero or more times. The `%|' control escape and its following format text is also optional, and may be included zero or one times. Most functions expect an argument of a particular type:

Argument	Description	Example Syntax
literal	A literal number,	%(func 1234)
	or string	%(func text string)
comp	Any header component	%(func{in-reply-to})
date	A date component	%(func{date})
addr	An address component	%(func{from})
expr	An optional component,	%(func(func2))
	function or control,	%(func %<{reply-to}%|%{from}%>)
	perhaps nested	%(func(func2{comp}))
The types date and addr have the same syntax as comp, but require that the header component be a date string, or address string, respectively. All arguments except those of type expr are required. For the expr argument type, the leading `%' must be omitted for component and function escape arguments, and must be present (with a leading space) for control escape arguments. The evaluation of format strings is based on a simple machine with an integer register num, and a text string register str. When a function escape is processed, if it accepts an optional expr argument which is not present, it reads the current value of either num or str as appropriate. Component escapes write the value of their message header in str. Function escapes write their return value in num for functions returning integer or boolean values, and in str for functions returning string values. (The boolean type is a subset of integers with usual values 0=false and 1=true.) Control escapes return a boolean value, and set num. All component escapes, and those function escapes which return an integer or string value, pass this value back to their caller in addition to setting str or num. These escapes will print out this value unless called as part of an argument to another escape sequence. Escapes which return a boolean value do pass this value back to their caller in num, but will never print out the value.
Function	Argument	Return	Description
msg		integer	message number
cur		integer	message is current
size		integer	size of message
strlen		integer	length of str
width		integer	output buffer size in bytes
charleft		integer	bytes left in output buffer
timenow		integer	seconds since the UNIX epoch
me		string	the user's mailbox
eq	literal	boolean	num == arg
ne	literal	boolean	num != arg
gt	literal	boolean	num > arg
match	literal	boolean	str contains arg
amatch	literal	boolean	str starts with arg
plus	literal	integer	arg plus num
minus	literal	integer	arg minus num
divide	literal	integer	num divided by arg
modulo	literal	integer	num modulo arg
num	literal	integer	Set num to arg
lit 	literal	string	Set str to arg
getenv 	literal	string	Set str to environment value of arg
profile	literal	string	Set str to profile component arg value
nonzero	expr	boolean	num is non-zero
zero	expr	boolean	num is zero
null	expr	boolean	str is empty
nonnull	expr	boolean	str is non-empty
void	expr		Set str or num
comp	comp	string	Set str to component text
compval	comp	integer	num set to “atoi(comp)”
trim	expr		trim trailing white-space from str
putstr	expr		print str
putstrf	expr		print str in a fixed width
putnum	expr		print num
putnumf	expr		print num in a fixed width
These functions require a date component as an argument:

Function	Argument	Return	Description
sec	date	integer	seconds of the minute
min	date	integer	minutes of the hour
hour	date	integer	hours of the day (0-23)
wday	date	integer	day of the week (Sun=0)
day	date	string	day of the week (abbrev.)
weekday	date	string	day of the week
sday	date	integer	day of the week known?
			(0=implicit,-1=unknown)
mday	date	integer	day of the month
yday	date	integer	day of the year
mon	date	integer	month of the year
month	date	string	month of the year (abbrev.)
lmonth	date	string	month of the year
year	date	integer	year (may be > 100)
zone	date	integer	timezone in hours
tzone	date	string	timezone string
szone	date	integer	timezone explicit?
			(0=implicit,-1=unknown)
date2local	date		coerce date to local timezone
date2gmt	date		coerce date to GMT
dst	date	integer	daylight savings in effect?
clock	date	integer	seconds since the UNIX epoch
rclock	date	integer	seconds prior to current time
tws	date	string	official 822 rendering
pretty	date	string	user-friendly rendering
nodate	date	integer	str not a date string
These functions require an address component as an argument. The return value of functions noted with `*' pertain only to the first address present in the header component.

Function	Argument	Return	Description
proper	addr	string	official 822 rendering
friendly	addr	string	user-friendly rendering
addr	addr	string	mbox@host or host!mbox rendering*
pers	addr	string	the personal name*
note	addr	string	commentary text*
mbox	addr	string	the local mailbox*
mymbox	addr	integer	the user's addresses? (0=no,1=yes)
host	addr	string	the host domain*
nohost	addr	integer	no host was present*
type	addr	integer	host type* (0=local,1=network,
			-1=uucp,2=unknown)
path	addr	string	any leading host route*
ingrp	addr	integer	address was inside a group*
gname	addr	string	name of group*
formataddr	expr		append arg to str as a
			(comma separated) address list
putaddr	literal		print str address list with
			arg as optional label;
			get line width from num
When escapes are nested, evaluation is done from inner-most to outer-most. The outer-most escape must begin with `%'; the inner escapes must not. For example,
%<(mymbox{from}) To: %{to}%> writes the value of the header component “From:” to str; then (mymbox) reads str and writes its result to num; then the control escape evaluates num. If num is non-zero, the string “To: ” is printed followed by the value of the header component “To:”. A minor explanation of (mymbox{comp}) is in order. In general, it checks each of the addresses in the header component “comp” against the user's mailbox name and any Alternate-Mailboxes. It returns true if any address matches, however, it also returns true if the “comp” header is not present in the message. If needed, the (null) function can be used to explicitly test for this condition. When a function or component escape is interpreted and the result will be immediately printed, an optional field width can be specified to print the field in exactly a given number of characters. For example, a numeric escape like %4(size) will print at most 4 digits of the message size; overflow will be indicated by a `?' in the first position (like `?234'). A string escape like %4(me) will print the first 4 characters and truncate at the end. Short fields are padded at the right with the fill character (normally, a blank). If the field width argument begins with a leading zero, then the fill character is set to a zero. As above, the functions (putnumf) and (putstrf) print their result in exactly the number of characters specified by their leading field width argument. For example, %06(putnumf(size)) will print the message size in a field six characters wide filled with leading zeros; %14(putstrf{from}) will print the “From:” header component in fourteen characters with trailing spaces added as needed. For putstrf, using a negative value for the field width causes right-justification of the string within the field, with padding on the left up to the field width. The functions (putnum) and (putstr) print their result in the minimum number of characters required, and ignore any leading field width argument. The available output width is kept in an internal register; any output past this width will be truncated. Comments may be inserted in most places where a function argument is not expected. A comment begins with `%;' and ends with a (non-escaped) newline. With all this in mind, here's the default format string for scan. It's been divided into several pieces for readability. The first part is:
%4(msg)%<(cur)+%| %>%<{replied}-%?{encrypted}E%| %> which says that the message number should be printed in four digits, if the message is the current message then a `+' else a space should be printed, and if a “Replied:” field is present then a `-' else if an “Encrypted:” field is present then an `E' otherwise a space should be printed. Next:
%02(mon{date})/%02(mday{date}) the month and date are printed in two digits (zero filled) separated by a slash. Next,
%<{date} %|*> If a “Date:” field was present, then a space is printed, otherwise a `*'. Next,
%<(mymbox{from})%<{to}To:%14(friendly{to})%>%> if the message is from me, and there is a “To:” header, print `To:' followed by a “user-friendly” rendering of the first address in the “To:” field. Continuing,
%<(zero)%17(friendly{from})%> if either of the above two tests failed, then the “From:” address is printed in a “user-friendly” format. And finally,
%{subject}%<{body}<<%{body}%> the subject and initial body (if any) are printed. For a more complicated example, next consider the default replcomps format file.
%(lit)%(formataddr %<{reply-to} This clears str and formats the “Reply-To:” header if present. If not present, the else-if clause is executed.
%?{from}%?{sender}%?{return-path}%>)\ This formats the “From:”, “Sender:” and “Return-Path:” headers, stopping as soon as one of them is present. Next:
%<(nonnull)%(void(width))%(putaddr To: )\n%>\ If the formataddr result is non-null, it is printed as an address (with line folding if needed) in a field width wide with a leading label of “To: ”.
%(lit)%(formataddr{to})%(formataddr{cc})%(formataddr(me))\ str is cleared, and the “To:” and “Cc:” headers, along with the user's address (depending on what was specified with the “-cc” switch to repl) are formatted.
%<(nonnull)%(void(width))%(putaddr cc: )\n%>\ If the result is non-null, it is printed as above with a leading label of “cc: ”.
%<{fcc}Fcc: %{fcc}\n%>\ If a “-fcc folder” switch was given to repl (see repl (1) for more details about %{fcc}), an “Fcc:” header is output.
%<{subject}Subject: Re: %{subject}\n%>\ If a subject component was present, a suitable reply subject is output.
%<{date}In-reply-to: Your message of "\
%<(nodate{date})%{date}%|%(pretty{date})%>."%<{message-id}
             %{message-id}%>\n%>\
--------
If a date component was present, an “In-Reply-To:” header is output with the preface “Your message of ”. If the date was parseable, it is output in a user-friendly format, otherwise it is output as-is. The message-id is included if present. As with all plain-text, the row of dashes are output as-is. This last part is a good example for a little more elaboration. Here's that part again in pseudo-code:

if (comp_exists(date))  then
	print (“In-reply-to: Your message of \“”)
	if (not_date_string(date.value) then
		print (date.value)
	else
		print (pretty(date.value))
	endif
	print (“\””)
	if (comp_exists(message-id)) then
		print (“\n\t”)
		print (message-id.value)
	endif
	print (“\n”)
endif

Although this seems complicated, in point of fact, this method is flexible enough to extract individual fields and print them in any format the user desires. None None scan(1), repl(1), ap(8), dp(8) None None This software was contributed for MH 6.3. Prior to this, output format specifications were much easier to write, but considerably less flexible. On hosts where MH was configured with the BERK option, address parsing is not enabled.