mh-format.rf

早期freebsd实现

.\"	@(MHWARNING)
.\" @(#)$Id: mh-format.rf,v 1.45 1993/08/19 20:26:17 jromine Exp $
.SC MH-FORMAT 5
.NA
mh-format \- format file for MH message system
.SY
some \fIMH\fR commands
.DE
Several \fIMH\fR commands utilize either a \fIformat\fR string or a
\fIformat\fR file during their execution.
For example,
\fIscan\fR\0(1) uses a format string which directs it how to generate the
scan listing for each message;
\fIrepl\fR\0(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 \fIMH\fR which
means they are not necessarily simple to write and understand.
This means that novice, casual, or even advanced users of \fIMH\fR should
not have to deal with them.
Some canned scan listing formats are in
@(MHETCPATH)/scan.time, @(MHETCPATH)/scan.size, and @(MHETCPATH)/scan.timely.
Look in @(MHETCPATH) for other \fIscan\fR and \fIrepl\fR format files
which may have been written at your site.

It suffices to have your local \fIMH\fR expert actually write new format
commands or modify existing ones.
This manual section explains how to do that.
Note: familiarity with the C \fIprintf\fR routine is assumed.

A format string consists of ordinary text, and special
multi-character \fIescape\fR 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.
.\" talk about syntax first, then semantics
There are three types of \fIescape\fR sequences:
header \fIcomponents\fR, built-in \fIfunctions\fR, and flow \fIcontrol\fR.

A \fIcomponent\fR escape is specified as `%{\fIcomponent\fR\^}',
and exists for each header found in the message being processed.
For example `%{date}' refers to the \*(lqDate:\*(rq 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 \fIfunction\fR escape is specified as `%(\fIfunction\fR\^)'.
All functions are built-in, and most have a string or numeric value.

.ne 12
.Uh "Control-flow escapes"
A \fIcontrol\fR escape is one of: `%<', `%?', `%|', or `%>'. 
These are combined into the conditional execution construct:
.sp
.nf
	%<condition
		\fIformat text 1\fP
	%?condition2
		\fIformat text 2\fP
	%?condition3
		\fIformat text 3\fP
	\.\.\.
	%|
		\fIformat text N\fP
	%>
.fi
.sp
Extra white space is shown here only for clarity.
These constructs may be nested without ambiguity.
They form a general \fBif\-elseif\-else\-endif\fP block where
only one of the \fIformat text\fP segments is interpreted.

The `%<' and `%?' control escapes causes a condition to be evaluated.  
This condition
may be either a \fIcomponent\fP or a \fIfunction\fP.
The four constructs have the following syntax:
.sp 1
.nf
	%<{component}
	%<(function)
	%?{component}
	%?(function)
.fi
.sp
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.

.Uh "Function escapes"
.ne 10
Most functions expect an argument of a particular type:
.sp 1
.nf
.ta +\w'Argument 'u +\w'An optional component, 'u
\fIArgument\fR	\fIDescription\fR	\fIExample Syntax\fR
literal	A literal number,	%(\fIfunc\fR 1234)
	or string	%(\fIfunc\fR text string)
comp	Any header component	%(\fIfunc\fR\^{\fIin-reply-to\fR\^})
date	A date component	%(\fIfunc\fR\^{\fIdate\fR\^})
addr	An address component	%(\fIfunc\fR\^{\fIfrom\fR\^})
expr	An optional component,	%(\fIfunc\fR\^(\fIfunc2\fR\^))
	function or control,	%(\fIfunc\fR %<{\fIreply-to\fR\^}%|%{\fIfrom\fR\^}%>)
	perhaps nested	%(\fIfunc\fR\^(\fIfunc2\fR\^{\fIcomp\fR\^}))
.re
.fi

The types \fIdate\fR and \fIaddr\fR have the same syntax
as \fIcomp\fR, but require that the header 
component be a date string, or address string, respectively.

All arguments except those of type \fIexpr\fR are required.
For the \fIexpr\fR 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 \fInum\fR, and a text string register \fIstr\fR.
When a function escape is processed,
if it accepts an optional \fIexpr\fR argument which is not present, 
it reads the current value of either \fInum\fR or \fIstr\fR as appropriate.

.\" return values
.Uh "Return values"
Component escapes write the value of their message header in \fIstr\fR.
Function escapes write their return value in
\fInum\fR for functions returning \fIinteger\fR or \fIboolean\fR values,
and in \fIstr\fR for functions returning string values.
(The \fIboolean\fR type is a subset of integers with usual
values 0=false and 1=true.)
Control escapes return a \fIboolean\fP value, and set \fInum\fP.

All component escapes, and those
function escapes which return an \fIinteger\fR or \fIstring\fR value,
pass this value back to their caller
in addition to setting \fIstr\fR or \fInum\fR.
These escapes will print out this value
unless called as part of an argument to another escape sequence.
Escapes which return a \fIboolean\fR value do pass this value
back to their caller in \fInum\fP, but will never print out the value.

.nf
.ta \w'Formataddr 'u +\w'Argument 'u +\w'Rboolean 'u
\fIFunction\fR	\fIArgument\fR	\fIReturn\fR	\fIDescription\fR
msg		integer	message number
cur		integer	message is current
.\" unseen		integer	message is unseen
size		integer	size of message
strlen		integer	length of \fIstr\fR
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	\fInum\fR == \fIarg\fR
ne	literal	boolean	\fInum\fR != \fIarg\fR
gt	literal	boolean	\fInum\fR > \fIarg\fR
match	literal	boolean	\fIstr\fR contains \fIarg\fR
amatch	literal	boolean	\fIstr\fR starts with \fIarg\fR
plus	literal	integer	\fIarg\fR plus \fInum\fR
minus	literal	integer	\fIarg\fR minus \fInum\fR
divide	literal	integer	\fInum\fR divided by \fIarg\fR
modulo	literal	integer	\fInum\fR modulo \fIarg\fR
num	literal	integer	Set \fInum\fR to \fIarg\fR
lit 	literal	string	Set \fIstr\fR to \fIarg\fR
getenv 	literal	string	Set \fIstr\fR to environment value of \fIarg\fR
profile	literal	string	Set \fIstr\fR to profile component \fIarg\fR value
.\" dat	literal	int	return value of dat[arg]
nonzero	expr	boolean	\fInum\fR is non-zero
zero	expr	boolean	\fInum\fR is zero
null	expr	boolean	\fIstr\fR is empty
nonnull	expr	boolean	\fIstr\fR is non-empty
void	expr		Set \fIstr\fR or \fInum\fR
comp	comp	string	Set \fIstr\fR to component text
compval	comp	integer	\fInum\fR set to \*(lq\fBatoi\fR(\fIcomp\fR\^)\*(rq
.\" compflag	comp	integer	Set \fInum\fR to component flags bits
trim	expr		trim trailing white-space from \fIstr\fR
putstr	expr		print \fIstr\fR
putstrf	expr		print \fIstr\fR in a fixed width
putnum	expr		print \fInum\fR
putnumf	expr		print \fInum\fR in a fixed width
.\" addtoseq literal    add msg to sequence (LBL option)
.re	
.fi

These functions require a date component as an argument:
.sp 1
.nf
.ta \w'Formataddr 'u +\w'Argument 'u +\w'Rboolean 'u
\fIFunction\fR	\fIArgument\fR	\fIReturn\fR	\fIDescription\fR
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	\fIstr\fR not a date string
.re	
.fi