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1 .TH MH-FORMAT %manext5% "November 4, 2012" "%nmhversion%"
2 .\"
3 .\" %nmhwarning%
4 .\"
5 .SH NAME
6 mh-format \- format file for nmh message system
7 .SH DESCRIPTION
8 Several
9 .B nmh
10 commands utilize either a
11 .I format
12 string or a
13 .I format
14 file during their execution. For example,
15 .B scan
16 uses a format string which directs it how to generate the scan listing
17 for each message;
18 .B repl
19 uses a format file which directs it
20 how to generate the reply to a message, and so on.
21 .PP
22 There are a few alternate scan listing formats available
23 in
24 .IR nmh/etc/scan.time ,
25 .IR nmh/etc/scan.size ,
26 and
27 .IR nmh/etc/scan.timely .
28 Look in
29 .I nmh/etc
30 for other
31 .B scan
32 and
33 .B repl
34 format files which may have been written at your site.
35 .PP
36 It suffices to have your local
37 .B nmh
38 expert actually write new format
39 commands or modify existing ones. This manual section explains how to
40 do that. Note: familiarity with the C
41 .B printf
42 routine is assumed.
43 .PP
44 A format string consists of ordinary text, and special multi-character
45 escape sequences which begin with `%'. When specifying a format
46 string, the usual C backslash characters are honored: `\\b', `\\f',
47 `\\n', `\\r', and `\\t'. Continuation lines in format files end with
48 `\\' followed by the newline character.
49 .\" TALK ABOUT SYNTAX FIRST, THEN SEMANTICS
50 .SS SYNTAX
51 Format strings are built around
52 .IR "escape sequences" .
53 There are three types of escape sequences: header
54 .IR components ,
55 built-in
56 .IR functions ,
57 and flow
58 .IR control .
59 Comments may be inserted in most places where a function argument is
60 not expected. A comment begins with `%;' and ends with a (non-escaped)
61 newline.
62 .PP
63 A
64 .I component
65 escape is specified as
66 .RI `%{ component }',
67 and
68 exists for each header found in the message being processed. For example
69 .RI `%{ date }'
70 refers to the \*(lqDate:\*(rq field of the appropriate message.
71 All component escapes have a string value. Normally, component values are
72 compressed by converting any control characters (tab and newline included)
73 to spaces, then eliding any leading or multiple spaces. However, commands
74 may give different interpretations to some component escapes; be sure
75 to refer to each command's manual entry for complete details. Some commands
76 (such as
77 .B ap
78 and
79 .BR mhl )
80 use a special component
81 .RI `%{ text }'
82 to refer to the text being processed; see their respective man pages for
83 details and examples.
84 .PP
85 A
86 .I function
87 escape is specified as
88 .RI `%( function )'.
89 All functions are built-in, and most have a string or numeric value.
90 A function escape may have an
91 .IR argument .
92 The argument follows the function escape: separating
93 whitespace is discarded:
94 .RI `%( function " " argument )'.
95 .PP
96 In addition to literal numbers or strings,
97 the argument to a function escape can be another function, a component,
98 or a control escape. When the argument is a function or a
99 component, they are listed without a leading `%'. When control escapes
100 are used as function arguments, they written as normally, with
101 a leading `%';
102 .SS "Control escapes"
103 .PP
104 A
105 .I control
106 escape is one of: `%<', `%?', `%|', or `%>'.
107 These are combined into the conditional execution construct:
108 .PP
109 .RS 5
110 .nf
111 .RI "%< " condition " " "format-text"
112 .RI "%? " condition " " "format-text"
113 \&...
114 .RI "%| " "format-text"
115 %>
116 .fi
117 .RE
118 .PP
119 Extra white space is shown here only for clarity. These
120 constructs may be nested without ambiguity. They form a general
121 .B if\-elseif\-else\-endif
122 block where only one of the
123 format-texts
124 is interpreted. In other
125 words, `%<' is like the "if", `%?' is like the "elseif", `%|' is like
126 "else", and `%>' is like "endif".
127 .PP
128 A `%<' or `%?' control escape causes its condition to be evaluated.
129 This condition is a
130 .I component
131 or
132 .IR function .
133 For integer valued functions or components, the condition is true
134 if the function return or component value is non-zero, and false if zero.
135 For string valued functions or components, the condition is true
136 if the function return or component value is
137 a non-empty string, and false for an empty string.
138 .PP
139 The `%?' control escape is optional, and may there may be more
140 than one `%?' control escape in a conditional block.
141 The `%|' control escape
142 is also optional, but may be included at most once.
143 .SS "Function escapes"
144 Functions expecting an argument generally
145 require an argument of a particular type.
146 In addition to the number and string types,
147 these include:
148 .PP
149 .RS 5
150 .nf
151 .ta +\w'Argument 'u +\w'An optional component, 'u
152 .I "Argument Description Example Syntax"
153 literal A literal number %(\fIfunc\fR 1234)
154 or string %(\fIfunc\fR text string)
155 comp Any component %(\fIfunc\fR\^{\fIin-reply-to\fR\^})
156 date A date component %(\fIfunc\fR\^{\fIdate\fR\^})
157 addr An address component %(\fIfunc\fR\^{\fIfrom\fR\^})
158 expr Nothing %(\fIfunc\fR)
159 or a subexpression %(\fIfunc\fR\^(\fIfunc2\fR\^))
160 or control escape %(\fIfunc\fR %<{\fIreply-to\fR\^}%|%{\fIfrom\fR\^}%>)
161 .fi
162 .RE
163 .PP
164 The types
165 .I date
166 and
167 .I addr
168 have the same syntax as
169 .IR comp ,
170 but require that the header component be a date string, or address
171 string, respectively.
172 .PP
173 Most arguments not of type
174 .IR expr
175 are required.
176 When escapes are nested (via expr arguments), evaluation is done from inner-most to outer-most.
177 As noted above, for the
178 expr
179 argument type,
180 functions and components are written without a
181 leading `%'.
182 Control escape arguments must use a leading `%', preceded by a space.
183 .PP
184 For example,
185 .PP
186 .RS 5
187 .nf
188 %<(mymbox{from}) To: %{to}%>
189 .fi
190 .RE
191 .PP
192 writes the value of the header component \*(lqFrom:\*(rq to the
193 internal register named str; then (\fImymbox\fR\^) reads str and
194 writes its result to the internal register named
195 .IR num ;
196 then the control escape evaluates
197 .IR num .
198 If
199 .IR num
200 is non-zero, the
201 string \*(lqTo:\*(rq is printed followed by the value of the
202 header component \*(lqTo:\*(rq.
203 .SS Evaluation
204 The evaluation of format strings is performed
205 by a small virtual machine.
206 The machine is capable of evaluating nested expressions
207 as described above, and in addition
208 has an integer register
209 .IR num ,
210 and a text string register
211 .IR str .
212 When a function escape that
213 accepts an optional argument is processed,
214 and the argument is not present, the current value of either
215 .I num
216 or
217 .I str
218 is used as the argument: which register is
219 used depends on the function, as listed below.
220 .PP
221 Component escapes write the value of their message header in
222 .IR str .
223 Function escapes write their return value in
224 .I num
225 for functions returning integer or boolean values, and in
226 .I str
227 for functions returning string values. (The boolean type is a subset
228 of integers with usual values 0=false and 1=true.) Control escapes
229 return a boolean value, setting
230 .I num
231 to 1 if the last explicit condition
232 evaluated by a `%<' or `%?' control
233 succeeded, and 0 otherwise.
234 .PP
235 All component escapes, and those function escapes which return an
236 integer or string value, evaluate to their value as well as setting
237 .I str
238 or
239 .IR num .
240 Outermost escape expressions in
241 these forms will print
242 their value, but outermost escapes which return a boolean value
243 do not result in printed output.
244 .SS Functions
245 The function escapes may be roughly grouped into a few categories.
246 .PP
247 .RS 5
248 .nf
249 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
250 .I "Function Argument Result Description"
251 msg integer message number
252 cur integer message is current (0 or 1)
253 unseen integer message is unseen (0 or 1)
254 size integer size of message
255 strlen integer length of \fIstr\fR
256 width integer column width of terminal
257 charleft integer bytes left in output buffer
258 timenow integer seconds since the UNIX epoch
259 me string the user's mailbox (username)
260 myhost string the user's local hostname
261 myname string the user's name
262 localmbox string the complete local mailbox
263 eq literal boolean \fInum\fR == \fIarg\fR
264 ne literal boolean \fInum\fR != \fIarg\fR
265 gt literal boolean \fInum\fR > \fIarg\fR
266 match literal boolean \fIstr\fR contains \fIarg\fR
267 amatch literal boolean \fIstr\fR starts with \fIarg\fR
268 plus literal integer \fIarg\fR plus \fInum\fR
269 minus literal integer \fIarg\fR minus \fInum\fR
270 divide literal integer \fInum\fR divided by \fIarg\fR
271 modulo literal integer \fInum\fR modulo \fIarg\fR
272 num literal integer Set \fInum\fR to \fIarg\fR.
273 num integer Set \fInum\fR to zero.
274 lit literal string Set \fIstr\fR to \fIarg\fR.
275 lit string Clear \fIstr\fR.
276 getenv literal string Set \fIstr\fR to environment value of \fIarg\fR
277 profile literal string Set \fIstr\fR to profile component \fIarg\fR
278 value
279 .\" dat literal int return value of dat[arg]
280 nonzero expr boolean \fInum\fR is non-zero
281 zero expr boolean \fInum\fR is zero
282 null expr boolean \fIstr\fR is empty
283 nonnull expr boolean \fIstr\fR is non-empty
284 void expr Set \fIstr\fR or \fInum\fR
285 comp comp string Set \fIstr\fR to component text
286 compval comp integer Set \fInum\fR to \*(lq\fBatoi\fR(\fIcomp\fR\^)\*(rq
287 .\" compflag comp integer Set \fInum\fR to component flags bits (internal)
288 .\" decodecomp comp string Set \fIstr\fR to RFC 2047 decoded component text
289 decode expr string decode \fIstr\fR as RFC 2047 (MIME-encoded)
290 component
291 unquote expr string remove RFC 2822 quotes from \fIstr\fR
292 trim expr trim trailing whitespace from \fIstr\fR
293 putstr expr print \fIstr\fR
294 putstrf expr print \fIstr\fR in a fixed width
295 putnum expr print \fInum\fR
296 putnumf expr print \fInum\fR in a fixed width
297 .\" addtoseq literal add msg to sequence (LBL option)
298 putlit expr print \fIstr\fR without space compression
299 zputlit expr print \fIstr\fR without space compression;
300 \fIstr\fR must occupy no width on display
301 bold string set terminal bold mode
302 underline string set terminal underlined mode
303 standout string set terminal standout mode
304 resetterm string reset all terminal attributes
305 hascolor boolean terminal supports color
306 fgcolor literal string set terminal foreground color
307 bgcolor literal string set terminal background color
308 formataddr expr append \fIarg\fR to \fIstr\fR as a
309 (comma separated) address list
310 concataddr expr append \fIarg\fR to \fIstr\fR as a
311 (comma separated) address list,
312 including duplicates,
313 see Special Handling
314 putaddr literal print \fIstr\fR address list with
315 \fIarg\fR as optional label;
316 get line width from \fInum\fR
317 .fi
318 .RE
319 .PP
320 The (\fIme\fR\^) function returns the username of the current user. The
321 (\fImyhost\fR\^) function returns the
322 .B localname
323 entry in
324 .IR mts.conf ,
325 or the local hostname if
326 .B localname
327 is not configured. The (\fImyname\fR\^) function will return the value of
328 the
329 .B SIGNATURE
330 environment variable if set, otherwise will return the passwd GECOS field
331 (truncated at the first comma if it contains one) for
332 the current user. The (\fIlocalmbox\fR\^) function will return the complete
333 form of the local mailbox, suitable for use in a \*(lqFrom\*(rq header.
334 It will return the
335 .RI \*(lq Local-Mailbox \*(rq
336 profile entry if it is set; if it is not, it will be equivalent to:
337 .PP
338 .RS 5
339 .nf
340 %(myname) <%(me)@%(myhost)>
341 .fi
342 .RE
343 .PP
344 The following functions require a date component as an argument:
345 .PP
346 .RS 5
347 .nf
348 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
349 .I "Function Argument Return Description"
350 sec date integer seconds of the minute
351 min date integer minutes of the hour
352 hour date integer hours of the day (0-23)
353 wday date integer day of the week (Sun=0)
354 day date string day of the week (abbrev.)
355 weekday date string day of the week
356 sday date integer day of the week known?
357 (1=explicit,0=implicit,\-1=unknown)
358 mday date integer day of the month
359 yday date integer day of the year
360 mon date integer month of the year
361 month date string month of the year (abbrev.)
362 lmonth date string month of the year
363 year date integer year (may be > 100)
364 zone date integer timezone in hours
365 tzone date string timezone string
366 szone date integer timezone explicit?
367 (1=explicit,0=implicit,\-1=unknown)
368 date2local date coerce date to local timezone
369 date2gmt date coerce date to GMT
370 dst date integer daylight savings in effect? (0 or 1)
371 clock date integer seconds since the UNIX epoch
372 rclock date integer seconds prior to current time
373 tws date string official RFC 822 rendering
374 pretty date string user-friendly rendering
375 nodate date integer returns 1 if date is invalid
376 .fi
377 .RE
378 .PP
379 These functions require an address component as an argument.
380 The return value of functions noted with `*' is computed from
381 the first address present in the header component.
382 .PP
383 .RS 5
384 .nf
385 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
386 .I "Function Argument Return Description"
387 proper addr string official RFC 822 rendering
388 friendly addr string user-friendly rendering
389 addr addr string mbox@host or host!mbox rendering*
390 pers addr string the personal name*
391 note addr string commentary text*
392 mbox addr string the local mailbox*
393 mymbox addr integer List has the user's address? (0 or 1)
394 host addr string the host domain*
395 nohost addr integer no host was present (0 or 1)*
396 type addr integer host type* (0=local,1=network,
397 \-1=uucp,2=unknown)
398 path addr string any leading host route*
399 ingrp addr integer address was inside a group (0 or 1)*
400 gname addr string name of group*
401 .fi
402 .RE
403 .PP
404 (A clarification on (\fImymbox\fR\^{\fIcomp\fR\^}) is in order.
405 This function checks each of the addresses in the header component
406 \*(lq\fIcomp\fR\*(rq against the user's mailbox name and any
407 .RI \*(lq Alternate-Mailboxes \*(rq.
408 It returns true if any address matches,
409 however, it also returns true if the \*(lq\fIcomp\fR\*(rq header is not
410 present in the message. If needed, the (\fInull\fR\^) function can be
411 used to explicitly test for this case.)
412 .SS Formatting
413 When a function or component escape is interpreted and the result will
414 be immediately printed, an optional field width can be specified to
415 print the field in exactly a given number of characters. For example, a
416 numeric escape like %4(\fIsize\fR\^) will print at most 4 digits of the
417 message size; overflow will be indicated by a `?' in the first position
418 (like `?234'). A string escape like %4(\fIme\fR\^) will print the first 4
419 characters and truncate at the end. Short fields are padded at the right
420 with the fill character (normally, a blank). If the field width argument
421 begins with a leading zero, then the fill character is set to a zero.
422 .PP
423 The functions (\fIputnumf\fR\^) and (\fIputstrf\fR\^)
424 print their result in exactly the number of characters
425 specified by their leading field width argument. For example,
426 %06(\fIputnumf\fR\^(\fIsize\fR\^)) will print the message
427 size in a field six characters wide filled with leading zeros;
428 %14(\fIputstrf\^\fR{\fIfrom\^\fR}) will print the \*(lqFrom:\*(rq header
429 component in fourteen characters with trailing spaces added as needed.
430 For \fIputstrf\fR, using a negative value for the field width causes
431 right-justification of the string within the field, with padding on
432 the left up to the field width.
433 The functions (\fIputnum\fR\^) and
434 (\fIputstr\fR\^) are somewhat special: they print their result in the minimum number of characters
435 required, and ignore any leading field width argument. The (\fIputlit\fR\^)
436 function outputs the exact contents of the str register without any changes
437 such as duplicate space removal or control character conversion.
438 The (\fIzputlit\fR\^) function similarly outputs the exact contents of
439 the str register, but requires that those contents not occupy any
440 output width. It can therefore be used for outputting terminal escape
441 sequences.
442 .PP
443 There are a limited number of function escapes to output terminal escape
444 sequences. These sequences are retrieved from the
445 .IR terminfo (5)
446 database according to the current terminal setting. The (\fIbold\fR\^),
447 (\fIunderline\fR\^), and (\fIstandout\fR\^) escapes set bold mode,
448 underline mode, and standout mode respectively.
449 .PP
450 (\fIhascolor\fR\^)
451 can be used to determine if the current terminal supports color.
452 (\fIfgcolor\fR\^) and (\fIbgcolor\fR\^) set the foreground and
453 background colors respectively. Both of these escapes take one literal
454 argument, the color name, which can be one of: black, red, green, yellow,
455 blue, magenta, cyan, white. (\fIresetterm\fR\^) resets all terminal
456 attributes back to their default setting.
457 .PP
458 All of these terminal escape should be used in conjunction with
459 (\fIzputlit\fR\^) (preferred) or (\fIputlit\fR\^), as the normal
460 (\fputstr\fR\^) function will strip out control characters.
461 .PP
462 The available output width is kept in an internal register; any output
463 past this width will be truncated. The one exception to this is
464 (\fIzputlit\fR\^) functions will still be executed in case a terminal reset
465 code is being placed at the end of the line.
466 .SS Special Handling
467 A few functions have different behavior depending on what command they are
468 being invoked from.
469 .PP
470 In
471 .BR repl
472 the (\fIformataddr\fR\^) function stores all email addresses encountered into
473 an internal cache and will use this cache to suppress duplicate addresses.
474 If you need to create an address list that includes previously-seen
475 addresses you may use the (\fIconcataddr\fR\^) function, which is identical
476 to (\fIformataddr\fR\^) in all other respects. Note that (\fIconcataddr\fR\^)
477 will NOT add addresses to the duplicate-suppression cache.
478 .SS Other Hints and Tips
479 Sometimes to format function writers it is confusing as to why output is
480 duplicated. The general rule to remember is simple: If a function or
481 component escape is used where it starts with a %, then it will generate
482 text in the output file. Otherwise, it will not.
483 .PP
484 A good example is a simple attempt to generate a To: header based on
485 the From: and Reply-To: headers:
486 .PP
487 .RS 5
488 .nf
489 %(formataddr %<{reply-to}%|%{from})%(putaddr To: )
490 .fi
491 .RE
492 .PP
493 Unfortuantely if the Reply-to: header is NOT present, the output line that is
494 generated will be something like:
495 .PP
496 .RS 5
497 .nf
498 My From User <from@example.com>To: My From User <from@example.com>
499 .fi
500 .RE
501 .PP
502 What went wrong? When performing the test for the
503 .B if
504 clause (%<), the component is not output because it is considered an
505 argument to the
506 .B if
507 statement (hence the rule about the lack of % applies). But the component
508 escape in our
509 .B else
510 statement (everything after the `%|') is NOT an argument to anything; the
511 syntax is that it is written with a %, and thus the value of that component
512 is output. This also has the side effect of setting the
513 .I str
514 register, which is later picked up by the (\fIformataddr\fR\^) function
515 and then output by (\fIputaddr\fR\^). This format string has another bug
516 as well; there should always be a valid width value in the
517 .I num
518 register when (\fIputaddr\fR\^) is called, otherwise bad formatting can take
519 place.
520 .PP
521 The solution is to use the (\fIvoid\fR\^) function; this will prevent the
522 function or component from outputting any text. With this in place (and
523 using (\fIwidth\fR\^) to set the
524 .I num
525 register for the width, a better implementation would look like:
526 .PP
527 .RS 3
528 .nf
529 %(formataddr %<{reply-to}%|%(void{from})%(void(width))%(putaddr To: )
530 .fi
531 .RE
532 .PP
533 It should be noted here that the side-effects of functions and component
534 escapes still are in force: as a result each component
535 test in the
536 .B if\-elseif\-else\-endif
537 clause sets the
538 .I str
539 register.
540 .PP
541 As an additional note, the (\fIformataddr\fR\^) and (\fIconcataddr\fR\^)
542 functions have special behavior when it comes to the
543 .I str
544 register. The starting point of the register is saved and is used to
545 build up entries in the address list.
546 .PP
547 You will find the
548 .B fmttest
549 utility invaluable when debugging problems with format strings.
550 .SS Examples
551 With all this in mind,
552 here's the default format string for
553 .BR scan .
554 It's been divided into several pieces for readability.
555 The first part is:
556 .PP
557 .RS
558 .nf
559 %4(msg)%<(cur)+%| %>%<{replied}\-%?{encrypted}E%| %>
560 .fi
561 .RE
562 .PP
563 which says that the message number should be printed in four digits.
564 If the message is the current message then a `+' else a space should
565 be printed; if a \*(lqReplied:\*(rq field is present then a `\-'
566 else if an \*(lqEncrypted:\*(rq field is present then an `E' otherwise
567 a space should be printed. Next:
568 .PP
569 .RS
570 .nf
571 %02(mon{date})/%02(mday{date})
572 .fi
573 .RE
574 .PP
575 the month and date are printed in two digits (zero filled) separated by
576 a slash. Next,
577 .PP
578 .RS 5
579 .nf
580 %<{date} %|*%>
581 .fi
582 .RE
583 .PP
584 If a \*(lqDate:\*(rq field was present,
585 then a space is printed, otherwise a `*'.
586 Next,
587 .PP
588 .RS 5
589 .nf
590 %<(mymbox{from})%<{to}To:%14(decode(friendly{to}))%>%>
591 .fi
592 .RE
593 .PP
594 if the message is from me, and there is a \*(lqTo:\*(rq header,
595 print \*(lqTo:\*(rq followed by a \*(lquser-friendly\*(rq rendering of the
596 first address in the \*(lqTo:\*(rq field; any MIME-encoded
597 characters are decoded into the actual characters.
598 Continuing,
599 .PP
600 .RS 5
601 .nf
602 %<(zero)%17(decode(friendly{from}))%>
603 .fi
604 .RE
605 .PP
606 if either of the above two tests failed,
607 then the \*(lqFrom:\*(rq address is printed
608 in a mime-decoded, \*(lquser-friendly\*(rq format.
609 And finally,
610 .PP
611 .RS 5
612 .nf
613 %(decode{subject})%<{body}<<%{body}>>%>
614 .fi
615 .RE
616 .PP
617 the mime-decoded subject and initial body (if any) are printed.
618 .PP
619 For a more complicated example, next consider
620 a possible
621 .I replcomps
622 format file.
623 .PP
624 .RS 5
625 .nf
626 %(lit)%(formataddr %<{reply-to}
627 .fi
628 .RE
629 .PP
630 This clears
631 .I str
632 and formats the \*(lqReply-To:\*(rq header
633 if present. If not present, the else-if clause is executed.
634 .PP
635 .RS 5
636 .nf
637 %?{from}%?{sender}%?{return-path}%>)\\
638 .fi
639 .RE
640 .PP
641 This formats the
642 \*(lqFrom:\*(rq, \*(lqSender:\*(rq and \*(lqReturn-Path:\*(rq
643 headers, stopping as soon as one of them is present. Next:
644 .PP
645 .RS 5
646 .nf
647 %<(nonnull)%(void(width))%(putaddr To: )\\n%>\\
648 .fi
649 .RE
650 .PP
651 If the \fIformataddr\fR result is non-null, it is printed as
652 an address (with line folding if needed) in a field \fIwidth\fR
653 wide with a leading label of \*(lqTo:\*(rq.
654 .PP
655 .RS 5
656 .nf
657 %(lit)%(formataddr{to})%(formataddr{cc})%(formataddr(me))\\
658 .fi
659 .RE
660 .PP
661 .I str
662 is cleared, and the \*(lqTo:\*(rq and \*(lqCc:\*(rq headers, along with the user's
663 address (depending on what was specified with
664 the \*(lq\-cc\*(rq switch to \fIrepl\fR\^) are formatted.
665 .PP
666 .RS 5
667 .nf
668 %<(nonnull)%(void(width))%(putaddr cc: )\\n%>\\
669 .fi
670 .RE
671 .PP
672 If the result is non-null, it is printed as above with a
673 leading label of \*(lqcc:\*(rq.
674 .PP
675 .RS 5
676 .nf
677 %<{fcc}Fcc: %{fcc}\\n%>\\
678 .fi
679 .RE
680 .PP
681 If a
682 .B \-fcc
683 .I folder
684 switch was given to
685 .B repl
686 (see
687 .IR repl (1)
688 for more details about %{\fIfcc\fR\^}),
689 an \*(lqFcc:\*(rq header is output.
690 .PP
691 .RS 5
692 .nf
693 %<{subject}Subject: Re: %{subject}\\n%>\\
694 .fi
695 .RE
696 .PP
697 If a subject component was present,
698 a suitable reply subject is output.
699 .PP
700 .RS 5
701 .nf
702 %<{message-id}In-Reply-To: %{message-id}\\n%>\\
703 %<{message-id}References: %<{references} %{references}%>\\
704 %{message-id}\\n%>
705 \-\-\-\-\-\-\-\-
706 .fi
707 .RE
708 .PP
709 If a message-id component was present, an \*(lqIn-Reply-To:\*(rq header is
710 output including the message-id, followed by a \*(lqReferences:\*(rq
711 header with references, if present, and the message-id.
712 As with all
713 plain-text, the row of dashes are output as-is.
714 .PP
715 This last part is a good example for a little more elaboration.
716 Here's that part again in pseudo-code:
717 .PP
718 .RS 5
719 .nf
720 .ta .5i 1i 1.5i 2i
721 if (comp_exists(message-id)) then
722 print (\*(lqIn-reply-to: \*(rq)
723 print (message-id.value)
724 print (\*(lq\\n\*(rq)
725 endif
726 if (comp_exists(message-id)) then
727 print (\*(lqReferences: \*(rq)
728 if (comp_exists(references)) then
729 print(references.value);
730 endif
731 print (message-id.value)
732 print (\*(lq\\n\*(rq)
733 endif
734 .fi
735 .RE
736 .PP
737 .\" (Note that this pseudocode begs the question ``why not just
738 .\" support this syntax?'' MH has been hacked on for a long time...)
739 .\".PP
740 One more example: Currently,
741 .B nmh
742 supports very
743 large message numbers, and it is not uncommon for a folder
744 to have far more than 10000 messages.
745 .\" (Indeed, the original MH
746 .\" tutorial document by Rose and Romine is entitled "How to
747 .\" process 200 messages a day and still get some real work
748 .\" done." The authors apparently only planned to get
749 .\" real work done for about 50 days per folder.)
750 Nontheless (as noted above)
751 the various scan format strings are inherited
752 from older MH versions, and are generally hard-coded to 4
753 digits of message number before formatting problems
754 start to occur.
755 The nmh format strings can be modified to behave more sensibly with larger
756 message numbers:
757 .PP
758 .RS
759 .nf
760 %(void(msg))%<(gt 9999)%(msg)%|%4(msg)%>
761 .fi
762 .RE
763 .PP
764 The current message number is placed in \fInum\fP.
765 (Note that
766 .RI ( msg )
767 is an int function, not a component.)
768 The
769 .RI ( gt )
770 conditional
771 is used to test whether the message number
772 has 5
773 or more digits.
774 If so, it is printed at full width, otherwise
775 at 4 digits.
776 .SH "SEE ALSO"
777 .IR scan (1),
778 .IR repl (1),
779 .IR fmttest (1),
780 .SH CONTEXT
781 None