1 .TH MH-FORMAT %manext5% "November 4, 2012" "%nmhversion%"
6 mh-format \- format file for nmh message system
10 commands utilize either a
14 file during their execution. For example,
16 uses a format string which directs it how to generate the scan listing
19 uses a format file which directs it
20 how to generate the reply to a message, and so on.
22 There are a few alternate scan listing formats available
24 .IR nmh/etc/scan.time ,
25 .IR nmh/etc/scan.size ,
27 .IR nmh/etc/scan.timely .
34 format files which may have been written at your site.
36 It suffices to have your local
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
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
51 Format strings are built around
52 .IR "escape sequences" .
53 There are three types of escape sequences: header
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)
65 escape is specified as
68 exists for each header found in the message being processed. For example
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
80 use a special component
82 to refer to the text being processed; see their respective man pages for
87 escape is specified as
89 All functions are built-in, and most have a string or numeric value.
90 A function escape may have an
92 The argument follows the function escape: separating
93 whitespace is discarded:
94 .RI `%( function " " argument )'.
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
102 .SS "Control escapes"
106 escape is one of: `%<', `%?', `%|', or `%>'.
107 These are combined into the conditional execution construct:
111 .RI "%< " condition " " "format-text"
112 .RI "%? " condition " " "format-text"
114 .RI "%| " "format-text"
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
124 is interpreted. In other
125 words, `%<' is like the "if", `%?' is like the "elseif", `%|' is like
126 "else", and `%>' is like "endif".
128 A `%<' or `%?' control escape causes its condition to be evaluated.
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.
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,
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\^}%>)
168 have the same syntax as
170 but require that the header component be a date string, or address
171 string, respectively.
173 Most arguments not of type
176 When escapes are nested (via expr arguments), evaluation is done from inner-most to outer-most.
177 As noted above, for the
180 functions and components are written without a
182 Control escape arguments must use a leading `%', preceded by a space.
188 %<(mymbox{from}) To: %{to}%>
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
196 then the control escape evaluates
201 string \*(lqTo:\*(rq is printed followed by the value of the
202 header component \*(lqTo:\*(rq.
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
210 and a text string register
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
218 is used as the argument: which register is
219 used depends on the function, as listed below.
221 Component escapes write the value of their message header in
223 Function escapes write their return value in
225 for functions returning integer or boolean values, and in
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
231 to 1 if the last explicit condition
232 evaluated by a `%<' or `%?' control
233 succeeded, and 0 otherwise.
235 All component escapes, and those function escapes which return an
236 integer or string value, evaluate to their value as well as setting
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.
245 The function escapes may be roughly grouped into a few categories.
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 output buffer size in bytes
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
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)
291 unquote expr string remove RFC-2822 quotes from \fIstr\fR
292 trim expr trim trailing white-space 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 formataddr expr append \fIarg\fR to \fIstr\fR as a
302 (comma separated) address list
303 concataddr expr append \fIarg\fR to \fIstr\fR as a
304 (comma separated) address list,
305 including duplicates,
307 putaddr literal print \fIstr\fR address list with
308 \fIarg\fR as optional label;
309 get line width from \fInum\fR
313 The (\fIme\fR\^) function returns the username of the current user. The
314 (\fImyhost\fR\^) function returns the
318 or the local hostname if
320 is not configured. The (\fImyname\fR\^) function will return the value of
323 environment variable if set, otherwise will return the passwd GECOS field
324 (truncated at the first comma if it contains one) for
325 the current user. The (\fIlocalmbox\fR\^) function will return the complete
326 form of the local mailbox, suitable for use in a \*(lqFrom\*(rq header.
328 .RI \*(lq Local-Mailbox \*(rq
329 profile entry if it is set; if it is not, it will be equivalent to:
333 %(myname) <%(me)@%(myhost)>
337 The following functions require a date component as an argument:
341 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
342 .I "Function Argument Return Description"
343 sec date integer seconds of the minute
344 min date integer minutes of the hour
345 hour date integer hours of the day (0-23)
346 wday date integer day of the week (Sun=0)
347 day date string day of the week (abbrev.)
348 weekday date string day of the week
349 sday date integer day of the week known?
350 (1=explicit,0=implicit,\-1=unknown)
351 mday date integer day of the month
352 yday date integer day of the year
353 mon date integer month of the year
354 month date string month of the year (abbrev.)
355 lmonth date string month of the year
356 year date integer year (may be > 100)
357 zone date integer timezone in hours
358 tzone date string timezone string
359 szone date integer timezone explicit?
360 (1=explicit,0=implicit,\-1=unknown)
361 date2local date coerce date to local timezone
362 date2gmt date coerce date to GMT
363 dst date integer daylight savings in effect? (0 or 1)
364 clock date integer seconds since the UNIX epoch
365 rclock date integer seconds prior to current time
366 tws date string official 822 rendering
367 pretty date string user-friendly rendering
371 These functions require an address component as an argument.
372 The return value of functions noted with `*' is computed from
373 the first address present in the header component.
377 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
378 .I "Function Argument Return Description"
379 proper addr string official 822 rendering
380 friendly addr string user-friendly rendering
381 addr addr string mbox@host or host!mbox rendering*
382 pers addr string the personal name*
383 note addr string commentary text*
384 mbox addr string the local mailbox*
385 mymbox addr integer List has the user's address? (0 or 1)
386 host addr string the host domain*
387 nohost addr integer no host was present (0 or 1)*
388 type addr integer host type* (0=local,1=network,
390 path addr string any leading host route*
391 ingrp addr integer address was inside a group (0 or 1)*
392 gname addr string name of group*
396 (A clarification on (\fImymbox\fR\^{\fIcomp\fR\^}) is in order.
397 This function checks each of the addresses in the header component
398 \*(lq\fIcomp\fR\*(rq against the user's mailbox name and any
399 .RI \*(lq Alternate-Mailboxes \*(rq.
400 It returns true if any address matches,
401 however, it also returns true if the \*(lq\fIcomp\fR\*(rq header is not
402 present in the message. If needed, the (\fInull\fR\^) function can be
403 used to explicitly test for this case.)
405 When a function or component escape is interpreted and the result will
406 be immediately printed, an optional field width can be specified to
407 print the field in exactly a given number of characters. For example, a
408 numeric escape like %4(\fIsize\fR\^) will print at most 4 digits of the
409 message size; overflow will be indicated by a `?' in the first position
410 (like `?234'). A string escape like %4(\fIme\fR\^) will print the first 4
411 characters and truncate at the end. Short fields are padded at the right
412 with the fill character (normally, a blank). If the field width argument
413 begins with a leading zero, then the fill character is set to a zero.
415 The functions (\fIputnumf\fR\^) and (\fIputstrf\fR\^)
416 print their result in exactly the number of characters
417 specified by their leading field width argument. For example,
418 %06(\fIputnumf\fR\^(\fIsize\fR\^)) will print the message
419 size in a field six characters wide filled with leading zeros;
420 %14(\fIputstrf\^\fR{\fIfrom\^\fR}) will print the \*(lqFrom:\*(rq header
421 component in fourteen characters with trailing spaces added as needed.
422 For \fIputstrf\fR, using a negative value for the field width causes
423 right-justification of the string within the field, with padding on
424 the left up to the field width.
425 The functions (\fIputnum\fR\^) and
426 (\fIputstr\fR\^) are somewhat special: they print their result in the minimum number of characters
427 required, and ignore any leading field width argument. The (\fIputlit\fR\^)
428 function outputs the exact contents of the str register without any changes
429 such as duplicate space removal or control character conversion.
430 The (\fIzputlit\fR\^) function similarly outputs the exact contents of
431 the str register, but requires that those contents not occupy any
432 output width. It can therefore be used for outputting terminal escape
435 The available output width is kept in an internal register; any output
436 past this width will be truncated.
438 A few functions have different behavior depending on what command they are
443 the (\fIformataddr\fR\^) function stores all email addresses encountered into
444 an internal cache and will use this cache to suppress duplicate addresses.
445 If you need to create an address list that includes previously-seen
446 addresses you may use the (\fIconcataddr\fR\^) function, which is identical
447 to (\fIformataddr\fR\^) in all other respects. Note that (\fIconcataddr\fR\^)
448 will NOT add addresses to the duplicate-suppression cache.
449 .SS Other Hints and Tips
450 Sometimes to format function writers it is confusing as to why output is
451 duplicated. The general rule to remember is simple: If a function or
452 component escape is used where it starts with a %, then it will generate
453 text in the output file. Otherwise, it will not.
455 A good example is a simple attempt to generate a To: header based on
456 the From: and Reply-To: headers:
460 %(formataddr %<{reply-to}%|%{from})%(putaddr To: )
464 Unfortuantely if the Reply-to: header is NOT present, the output line that is
465 generated will be something like:
469 My From User <from@example.com>To: My From User <from@example.com>
473 What went wrong? When performing the test for the
475 clause (%<), the component is not output because it is considered an
478 statement (hence the rule about the lack of % applies). But the component
481 statement (everything after the `%|') is NOT an argument to anything; the
482 syntax is that it is written with a %, and thus the value of that component
483 is output. This also has the side effect of setting the
485 register, which is later picked up by the (\fIformataddr\fR\^) function
486 and then output by (\fIputaddr\fR\^). This format string has another bug
487 as well; there should always be a valid width value in the
489 register when (\fIputaddr\fR\^) is called, otherwise bad formatting can take
492 The solution is to use the (\fIvoid\fR\^) function; this will prevent the
493 function or component from outputting any text. With this in place (and
494 using (\fIwidth\fR\^) to set the
496 register for the width, a better implementation would look like:
500 %(formataddr %<{reply-to}%|%(void{from})%(void(width))%(putaddr To: )
504 It should be noted here that the side-effects of functions and component
505 escapes still are in force: as a result each component
507 .B if\-elseif\-else\-endif
512 As an additional note, the (\fIformataddr\fR\^) and (\fIconcataddr\fR\^)
513 functions have some behavior when it comes to the
515 register. The starting point of the register is saved and is used to
516 build up entries in the address list.
522 utilities invaluable in debugging problems with format strings.
524 With all this in mind,
525 here's the default format string for
527 It's been divided into several pieces for readability.
532 %4(msg)%<(cur)+%| %>%<{replied}\-%?{encrypted}E%| %>
536 which says that the message number should be printed in four digits.
537 If the message is the current message then a `+' else a space should
538 be printed; if a \*(lqReplied:\*(rq field is present then a `\-'
539 else if an \*(lqEncrypted:\*(rq field is present then an `E' otherwise
540 a space should be printed. Next:
544 %02(mon{date})/%02(mday{date})
548 the month and date are printed in two digits (zero filled) separated by
557 If a \*(lqDate:\*(rq field was present,
558 then a space is printed, otherwise a `*'.
563 %<(mymbox{from})%<{to}To:%14(decode(friendly{to}))%>%>
567 if the message is from me, and there is a \*(lqTo:\*(rq header,
568 print \*(lqTo:\*(rq followed by a \*(lquser-friendly\*(rq rendering of the
569 first address in the \*(lqTo:\*(rq field; any MIME-encoded
570 characters are decoded into the actual characters.
575 %<(zero)%17(decode(friendly{from}))%>
579 if either of the above two tests failed,
580 then the \*(lqFrom:\*(rq address is printed
581 in a mime-decoded, \*(lquser-friendly\*(rq format.
586 %(decode{subject})%<{body}<<%{body}>>%>
590 the mime-decoded subject and initial body (if any) are printed.
592 For a more complicated example, next consider
599 %(lit)%(formataddr %<{reply-to}
605 and formats the \*(lqReply-To:\*(rq header
606 if present. If not present, the else-if clause is executed.
610 %?{from}%?{sender}%?{return-path}%>)\\
615 \*(lqFrom:\*(rq, \*(lqSender:\*(rq and \*(lqReturn-Path:\*(rq
616 headers, stopping as soon as one of them is present. Next:
620 %<(nonnull)%(void(width))%(putaddr To: )\\n%>\\
624 If the \fIformataddr\fR result is non-null, it is printed as
625 an address (with line folding if needed) in a field \fIwidth\fR
626 wide with a leading label of \*(lqTo:\*(rq.
630 %(lit)%(formataddr{to})%(formataddr{cc})%(formataddr(me))\\
635 is cleared, and the \*(lqTo:\*(rq and \*(lqCc:\*(rq headers, along with the user's
636 address (depending on what was specified with
637 the \*(lq\-cc\*(rq switch to \fIrepl\fR\^) are formatted.
641 %<(nonnull)%(void(width))%(putaddr cc: )\\n%>\\
645 If the result is non-null, it is printed as above with a
646 leading label of \*(lqcc:\*(rq.
650 %<{fcc}Fcc: %{fcc}\\n%>\\
661 for more details about %{\fIfcc\fR\^}),
662 an \*(lqFcc:\*(rq header is output.
666 %<{subject}Subject: Re: %{subject}\\n%>\\
670 If a subject component was present,
671 a suitable reply subject is output.
675 %<{message-id}In-Reply-To: %{message-id}\\n%>\\
676 %<{message-id}References: %<{references} %{references}%>\\
682 If a message-id component was present, an \*(lqIn-Reply-To:\*(rq header is
683 output including the message-id, followed by a \*(lqReferences:\*(rq
684 header with references, if present, and the message-id.
686 plain-text, the row of dashes are output as-is.
688 This last part is a good example for a little more elaboration.
689 Here's that part again in pseudo-code:
694 if (comp_exists(message-id)) then
695 print (\*(lqIn-reply-to: \*(rq)
696 print (message-id.value)
697 print (\*(lq\\n\*(rq)
699 if (comp_exists(message-id)) then
700 print (\*(lqReferences: \*(rq)
701 if (comp_exists(references)) then
702 print(references.value);
704 print (message-id.value)
705 print (\*(lq\\n\*(rq)
710 .\" (Note that this pseudocode begs the question ``why not just
711 .\" support this syntax?'' MH has been hacked on for a long time...)
713 One more example: Currently,
716 large message numbers, and it is not uncommon for a folder
717 to have far more than 10000 messages.
718 .\" (Indeed, the original MH
719 .\" tutorial document by Rose and Romine is entitled "How to
720 .\" process 200 messages a day and still get some real work
721 .\" done." The authors apparently only planned to get
722 .\" real work done for about 50 days per folder.)
723 Nontheless (as noted above)
724 the various scan format strings are inherited
725 from older MH versions, and are generally hard-coded to 4
726 digits of message number before formatting problems
728 The nmh format strings can be modified to behave more sensibly with larger
733 %(void(msg))%<(gt 9999)%(msg)%|%4(msg)%>
737 The current message number is placed in \fInum\fP.
740 is an int function, not a component.)
744 is used to test whether the message number
747 If so, it is printed at full width, otherwise