source: trunk/third/nmh/man/mh-format.man @ 12455

.\"
.\" %nmhwarning%
.\" $Id: mh-format.man,v 1.1.1.1 1999-02-07 18:14:20 danw Exp $
.\"
.\" include the -mh macro file
.so %etcdir%/tmac.h
.\"
.TH MH-FORMAT %manext5% MH.6.8 [%nmhversion%]
.SH NAME
mh-format \- format file for nmh message system
.SH SYNOPSIS
.in +.5i
.ti -.5i
some \fInmh\fR commands
.in -.5i
.SH DESCRIPTION
Several \fInmh\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 \fInmh\fR
which means they are not necessarily simple to write and understand.
This means that novice, casual, or even advanced users of \fInmh\fR
should not have to deal with them.

There are a few alternate scan listing formats available
in %etcdir%/scan.time, %etcdir%/scan.size, and %etcdir%/scan.timely.
Look in %etcdir% for other \fIscan\fR and \fIrepl\fR format files which
may have been written at your site.

It suffices to have your local \fInmh\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 virtual 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.

.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 Set \fInum\fR to \*(lq\fBatoi\fR(\fIcomp\fR\^)\*(rq
.\" compflag    comp    integer Set \fInum\fR to component flags bits (internal)
.\" decodecomp  comp    string  Set \fIstr\fR to RFC-2047 decoded component text
decode  expr    string  decode \fIstr\fR as RFC-2047 component
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

.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
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 \fIarg\fR to \fIstr\fR as a
                        (comma separated) address list
putaddr literal         print \fIstr\fR address list with
                        \fIarg\fR as optional label;
                        get line width from \fInum\fR
.re     
.fi

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,

.ti +.5i
%<(mymbox{from}) To: %{to}%>

writes the value of the header component \*(lqFrom:\*(rq to \fIstr\fR\^;
then (\fImymbox\fR\^) reads \fIstr\fR and writes its result to \fInum\fR;
then the control escape evaluates \fInum\fR.  If \fInum\fR is non-zero,
the string \*(lqTo: \*(rq is printed followed by the value of the header
component \*(lqTo:\*(rq.

A minor explanation of (\fImymbox\fR\^{\fIcomp\fR\^}) is in order.
In general, it checks each of the addresses in the header component
\*(lq\fIcomp\fR\*(rq against the user's mailbox name and any
\fIAlternate-Mailboxes\fR.  It returns true if any address matches,
however, it also returns true if the \*(lq\fIcomp\fR\*(rq header is not
present in the message.  If needed, the (\fInull\fR\^) 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(\fIsize\fR\^) 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(\fIme\fR\^) 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 (\fIputnumf\fR\^) and (\fIputstrf\fR\^)
print their result in exactly the number of characters
specified by their leading field width argument.  For example,
%06(\fIputnumf\fR\^(\fIsize\fR\^)) will print the message
size in a field six characters wide filled with leading zeros;
%14(\fIputstrf\^\fR{\fIfrom\^\fR}) will print the \*(lqFrom:\*(rq header
component in fourteen characters with trailing spaces added as needed.
For \fIputstrf\fR, 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 (\fIputnum\fR\^) and
(\fIputstr\fR\^) 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 \fIscan\fR.
It's been divided into several pieces for readability.
The first part is:

.ti +.5i
%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 \*(lqReplied:\*(rq field is present then a `\-'
else if an \*(lqEncrypted:\*(rq field is present then an `E' otherwise
a space should be printed.  Next:

.ti +.5i
%02(mon{date})/%02(mday{date})

the month and date are printed in two digits (zero filled) separated by
a slash.
Next,

.ti +.5i
%<{date} %|*>

If a \*(lqDate:\*(rq field was present,
then a space is printed, otherwise a `*'.
Next,

.ti +.5i
%<(mymbox{from})%<{to}To:%14(friendly{to})%>%>

if the message is from me,
and there is a \*(lqTo:\*(rq header,
print `To:' followed by a \*(lquser-friendly\*(rq rendering of the 
first address in the \*(lqTo:\*(rq field.
Continuing,

.ti +.5i
%<(zero)%17(friendly{from})%>

if either of the above two tests failed,
then the \*(lqFrom:\*(rq address is printed
in a \*(lquser-friendly\*(rq format.
And finally,

.ti +.5i
%{subject}%<{body}<<%{body}%>

the subject and initial body (if any) are printed.

For a more complicated example, next consider
the default \fIreplcomps\fR format file.

.ti +.5i
%(lit)%(formataddr %<{reply-to}

This clears \fIstr\fR and formats the \*(lqReply-To:\*(rq header 
if present.  If not present, the else-if clause is executed.

.ti +.5i
%?{from}%?{sender}%?{return-path}%>)\\

This formats the 
\*(lqFrom:\*(rq, \*(lqSender:\*(rq and \*(lqReturn-Path:\*(rq
headers, stopping as soon as one of them is present.  Next:

.ti +.5i
%<(nonnull)%(void(width))%(putaddr To: )\\n%>\\

If the \fIformataddr\fR result is non-null, it is printed as
an address (with line folding if needed) in a field \fIwidth\fR
wide with a leading label of \*(lqTo: \*(rq.

.ti +.5i
%(lit)%(formataddr{to})%(formataddr{cc})%(formataddr(me))\\

\fIstr\fR is cleared, and the 
\*(lqTo:\*(rq and \*(lqCc:\*(rq headers, along with the user's
address 
(depending on what was specified with
the \*(lq\-cc\*(rq switch to \fIrepl\fR\^) are formatted.

.ti +.5i
%<(nonnull)%(void(width))%(putaddr cc: )\\n%>\\

If the result is non-null, it is printed as above with a
leading label of \*(lqcc: \*(rq.

.ti +.5i
%<{fcc}Fcc: %{fcc}\\n%>\\

If a \*(lq\-fcc\ folder\*(rq switch was given to \fIrepl\fR
(see \fIrepl\fR\0(1) for more details about %{\fIfcc\fR\^}),
an \*(lqFcc:\*(rq header is output.

.ti +.5i
%<{subject}Subject: Re: %{subject}\\n%>\\

If a subject component was present,
a suitable reply subject is output.

.nf
.ti +.5i
%<{date}In-reply-to: Your message of "\\
.ti +.5i
%<(nodate{date})%{date}%|%(pretty{date})%>."%<{message-id}
.ti +.5i
             %{message-id}%>\\n%>\\
.ti +.5i
\-\-\-\-\-\-\-\-
.fi

If a date component was present, an \*(lqIn-Reply-To:\*(rq header is
output with the preface \*(lqYour message of \*(rq.  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:
.sp 1
.nf
.in +.5i
.ta .5i 1i 1.5i 2i
if (comp_exists(date))  then
        print (\*(lqIn-reply-to: Your message of \\\*(lq\*(rq)
        if (not_date_string(date.value) then
                print (date.value)
        else
                print (pretty(date.value))
        endif
        print (\*(lq\\\*(rq\*(rq)
        if (comp_exists(message-id)) then
                print (\*(lq\\n\\t\*(rq)
                print (message-id.value)
        endif
        print (\*(lq\\n\*(rq)
endif
.re
.in -.5i
.fi
.sp 1
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.
.Fi
None
.Pr
None
.Sa
scan(1), repl(1), ap(8), dp(8)
.De
None
.Co
None
.En