mh-format.rf

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\"	@(MHWARNING)
.\" @(#)$Id: mh-format.rf,v 1.1 90/07/20 09:41:11 sharpe Exp Locker: sharpe $
.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 7
A \fIcontrol\fR escape is one of: `%<', `%|', or `%>'.
These form one of four conditional execution constructs with the
following syntax:
.sp 1
.nf
	%<(\fIfunction\fR\^)Command-String%>
	%<{\fIcomponent\fR\^}Command-String%>
	%<(\fIfunction\fR\^)Then-Command-String%|Else-Command-String%>
	%<{\fIcomponent\fR\^}Then-Command-String%|Else-Command-String%>
.fi
.sp
These constructs may be nested without ambiguity.

In the first two forms of the construct,
if the function or component value is non\-zero (for integer\-valued escapes),
or non\-empty (for string\-valued escapes),
then everything up to the corresponding `%>'
is interpreted, otherwise, skip to the corresponding '%>' and
start interpreting again.

In the second two forms of the construct, 
the first command string is interpreted
if the function or component value is non\-zero or non\-null,
and the second command string is interpreted otherwise.  Only one
of the command strings will be interpreted.
Interpreting the '%|' control escape causes 
a skip to the corresponding '%>'.  

.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
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.)

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.
Function escapes which return a \fIboolean\fR value do pass this value
back to their caller, 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
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
num	literal	integer	Set \fInum\fR to \fIarg\fR
lit 	literal	string	Set \fIstr\fR to \fIarg\fR
.\" dat	literal	int	?
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(\fIstr\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
.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 of the century
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

.ne 12
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.
.sp 1
.nf
.ta \w'Formataddr 'u +\w'Argument 'u +\w'Rboolean 'u
\fIFunction\fR	\fIArgument\fR	\fIReturn\fR	\fIDescription\fR
proper	addr	string	official 822 rendering
friendly	addr	string	user\-friendly 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 \fIarg\fR to \fIstr\fR as a
			(comma separated) address list