4 .TH MH-FORMAT %manext5% "%nmhdate%" MH.6.8 [%nmhversion%]
6 mh-format \- format file for mh 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, e.g.
35 This manual section explains how to write and modify format commands.
36 Note: familiarity with the C
40 A format string consists of ordinary text, and special multi-character
41 escape sequences which begin with `%'. When specifying a format
42 string, the usual C backslash characters are honored: `\\b', `\\f',
43 `\\n', `\\r', and `\\t'. Continuation lines in format files end with
44 `\\' followed by the newline character.
46 .\" TALK ABOUT SYNTAX FIRST, THEN SEMANTICS
48 Format strings are built around
49 .IR "escape sequences" .
50 There are four types of escape sequences:
54 .ta +\w'name of escape class xxxxxxx'u
55 .RI "1) header components %{" component }
56 .RI "2) built-in functions %(" "function arg" )
57 .RI "3) flow control %< ... %? ... %| ... %>
58 .RI "4) comments %; ...
62 Comments may be inserted in most places where no function argument is
63 expected. A comment begins with `%;' and ends with a (non-escaped)
68 escape is specified as
71 exists for each header found in the message being processed. For example
73 refers to the `Date:' field of the appropriate message.
74 All component escapes have a string value. Normally, component values are
75 compressed by converting any control characters (tab and newline included)
76 to spaces, then eliding any leading or multiple spaces. However, commands
77 may give different interpretations to some component escapes; be sure
78 to refer to each command's manual entry for complete details.
82 escape is specified as
84 All functions are built-in, and most have a string or numeric value.
85 A function escape may have an
87 The argument follows the function escape: separating
88 whitespace is discarded:
89 .RI `%( function " " argument )'.
91 In addition to literal numbers or strings,
92 the argument to a function escape can be another function, a component,
93 or a control escape. When the argument is a function or a
94 component, they are listed without a leading `%'. When control escapes
95 are used as function arguments, they written as normally, with
102 escape is one of: `%<', `%?', `%|', or `%>'.
103 These are combined into the conditional execution construct:
107 .RI "%< " condition " " "format-text"
108 .RI "%? " condition " " "format-text"
110 .RI "%| " "format-text"
115 (Extra white space is shown here only for clarity.) These
116 constructs may be nested without ambiguity. They form a general
117 .B if\-elseif\-else\-endif
118 block where only one of the
120 is interpreted. In other
121 words, `%<' is like the "if", `%?' is like the "elseif", `%|' is like
122 "else", and `%>' is like "endif".
124 A `%<' or `%?' control escape causes its condition to be evaluated.
129 For integer valued functions or components, the condition is true
130 if the function return or component value is non-zero, and false if zero.
131 For string valued functions or components, the condition is true
132 if the function return or component value is
133 a non-empty string, and false for an empty string.
136 The `%?' control escape is optional, and there may be more
137 than one `%?' control escape in a conditional block.
138 The `%|' control escape
139 is also optional, but may be included at most once.
141 .SS "Function escapes"
142 Functions expecting an argument generally
143 require an argument of a particular type.
144 In addition to the number and string types,
149 .ta +\w'Argument 'u +\w'An optional component, 'u
150 .I "Argument Description Example Syntax
151 literal A literal number %(\fIfunc\fR 1234)
152 or string %(\fIfunc\fR text string)
153 comp Any component %(\fIfunc\fR\^{\fIin-reply-to\fR\^})
154 date A date component %(\fIfunc\fR\^{\fIdate\fR\^})
155 addr An address component %(\fIfunc\fR\^{\fIfrom\fR\^})
156 expr Nothing %(\fIfunc\fR)
157 or a subexpression %(\fIfunc\fR\^(\fIfunc2\fR\^))
158 or control escape %(\fIfunc\fR %<{\fIreply-to\fR\^}%|%{\fIfrom\fR\^}%>)
166 have the same syntax as
168 but require that the header component be a date string, or address
169 string, respectively.
171 Most arguments not of type
174 When escapes are nested (via expr arguments), evaluation is done from inner-most to outer-most.
175 As noted above, for the
178 functions and components are written without a
180 Control escape arguments must use a leading `%', preceded by a space.
186 %<(mymbox{from}) To: %{to}%>
190 writes the value of the header component `From:' to the
191 internal register named str; then (\fImymbox\fR\^) reads str and
192 writes its result to the internal register named
194 then the control escape evaluates
199 string `To:' is printed followed by the value of the
200 header component `To:'.
202 The evaluation of format strings is performed
203 by a small virtual machine.
204 The machine is capable of evaluating nested expressions
205 as described above, and in addition
206 has an integer register
208 and a text string register
210 When a function escape that
211 accepts an optional argument is processed,
212 and the argument is not present, the current value of either
216 is used as the argument: which register is
217 used depends on the function, as listed below.
218 .\" What is the difference between these two lines:
219 .\" %(void{comp})%(trim)%(putstr)
220 .\" %(putstr(trim{comp}))
221 .\" The latter can be used as a single expression for %<.
222 .\" It does make a difference for (decode) because in the former
223 .\" way, wrapping (decode) with (void) can be necessary.
224 .\" What is the preferred way?
226 Component escapes write the value of their message header in
228 Function escapes write their return value in
230 for functions returning integer or boolean values, and in
232 for functions returning string values. (The boolean type is a subset
233 of integers with usual values 0=false and 1=true.) Control escapes
234 return a boolean value, setting
236 to 1 if the last explicit condition
237 evaluated by a `%<' or `%?' control
238 succeeded, and 0 otherwise.
240 All component escapes, and those function escapes which return an
241 integer or string value, evaluate to their value as well as setting
245 Outermost escape expressions in
246 these forms will print
247 their value, but outermost escapes which return a boolean value
248 do not result in printed output.
250 The function escapes may be roughly grouped into a few categories.
254 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
255 .I "Function Argument Result Description
256 msg integer message number
257 cur integer message is current (0 or 1)
258 unseen integer message is unseen (0 or 1)
259 size integer size of message
260 strlen integer length of \fIstr\fR
261 width integer output buffer size in bytes
262 charleft integer bytes left in output buffer
263 timenow integer seconds since the UNIX epoch
264 me string the user's mailbox
265 eq literal boolean \fInum\fR == \fIarg\fR
266 ne literal boolean \fInum\fR != \fIarg\fR
267 gt literal boolean \fInum\fR > \fIarg\fR
268 match literal boolean \fIstr\fR contains \fIarg\fR
269 amatch literal boolean \fIstr\fR starts with \fIarg\fR
270 plus literal integer \fIarg\fR plus \fInum\fR
271 minus literal integer \fIarg\fR minus \fInum\fR
272 divide literal integer \fInum\fR divided by \fIarg\fR
273 modulo literal integer \fInum\fR modulo \fIarg\fR
274 num literal integer Set \fInum\fR to \fIarg\fR.
275 num integer Set \fInum\fR to zero.
276 lit literal string Set \fIstr\fR to \fIarg\fR.
277 lit string Clear \fIstr\fR.
278 getenv literal string Set \fIstr\fR to environment value of \fIarg\fR
279 profile literal string Set \fIstr\fR to profile component \fIarg\fR
281 .\" dat literal int return value of dat[arg]
282 nonzero expr boolean \fInum\fR is non-zero
283 zero expr boolean \fInum\fR is zero
284 null expr boolean \fIstr\fR is empty
285 nonnull expr boolean \fIstr\fR is non-empty
286 void expr Set \fIstr\fR or \fInum\fR
287 comp comp string Set \fIstr\fR to component text
288 compval comp integer Set \fInum\fR to `\fBatoi\fR(\fIcomp\fR\^)'
289 .\" compflag comp integer Set \fInum\fR to component flags bits (internal)
290 .\" decodecomp comp string Set \fIstr\fR to RFC-2047 decoded component text
291 decode expr string decode \fIstr\fR as RFC-2047 (MIME-encoded)
292 component and print it
293 unquote expr string remove RFC-2822 quotes from \fIstr\fR
294 unmailto expr string remove `mailto:' and < > from \fIstr\fR
295 trim expr trim white-space from \fIstr\fR
296 putstr expr print \fIstr\fR
297 putstrf expr print \fIstr\fR in a fixed width
298 putnum expr print \fInum\fR
299 putnumf expr print \fInum\fR in a fixed width
300 nodate string integer Argument not a date string (0 or 1)
301 formataddr expr append \fIarg\fR to \fIstr\fR as a
302 (comma separated) address list
303 putaddr literal print \fIstr\fR address list with
304 \fIarg\fR as optional label;
305 get line width from \fInum\fR
309 The following functions require a date component as an argument:
313 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
314 .I "Function Argument Return Description
315 sec date integer seconds of the minute
316 min date integer minutes of the hour
317 hour date integer hours of the day (0-23)
318 wday date integer day of the week (Sun=0)
319 day date string day of the week (abbrev.)
320 weekday date string day of the week
321 sday date integer day of the week known?
322 (1=explicit,0=implicit,\-1=unknown)
323 mday date integer day of the month
324 yday date integer day of the year
325 mon date integer month of the year
326 month date string month of the year (abbrev.)
327 lmonth date string month of the year
328 year date integer year (may be > 100)
329 zone date integer timezone in hours
330 tzone date string timezone string
331 szone date integer timezone explicit?
332 (1=explicit,0=implicit,\-1=unknown)
333 date2local date coerce date to local timezone
334 date2gmt date coerce date to GMT
335 dst date integer daylight savings in effect? (0 or 1)
336 clock date integer seconds since the UNIX epoch
337 rclock date integer seconds prior to current time
338 tws date string official RFC-822 rendering
339 pretty date string user-friendly rendering
343 These functions require an address component as an argument.
344 The return value of functions noted with `*' is computed from
345 the first address present in the header component.
349 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
350 .I "Function Argument Return Description
351 proper addr string official RFC-822 rendering
352 friendly addr string user-friendly rendering
353 addr addr string mbox@host or host!mbox rendering*
354 pers addr string the personal name*
355 note addr string commentary text*
356 mbox addr string the local mailbox*
357 mymbox addr integer List has the user's address? (0 or 1)
358 host addr string the host domain*
359 nohost addr integer no host was present (0 or 1)*
360 type addr integer host type* (0=local,1=network,
362 path addr string any leading host route*
363 ingrp addr integer address was inside a group (0 or 1)*
364 gname addr string name of group*
368 (A clarification on (\fImymbox\fR\^{\fIcomp\fR\^}) is in order.
369 This function checks each of the addresses in the header component
370 `\fIcomp\fR' against the user's mailbox name and any
371 .RI ` Alternate-Mailboxes '.
372 It returns true if any address matches,
373 however, it also returns true if the `\fIcomp\fR' header is not
374 present in the message. If needed, the (\fInull\fR\^) function can be
375 used to explicitly test for this case.)
377 When a function or component escape is interpreted and the result will
378 be immediately printed, an optional field width can be specified to
379 print the field in exactly a given number of characters. For example, a
380 numeric escape like %4(\fIsize\fR\^) will print at most 4 digits of the
381 message size; overflow will be indicated by a `?' in the first position
382 (like `?234'). A string escape like %4(\fIme\fR\^) will print the first 4
383 characters and truncate at the end. Short fields are padded at the right
384 with the fill character (normally, a blank). If the field width argument
385 begins with a leading zero, then the fill character is set to a zero.
387 The functions (\fIputnumf\fR\^) and (\fIputstrf\fR\^)
388 print their result in exactly the number of characters
389 specified by their leading field width argument. For example,
390 %06(\fIputnumf\fR\^(\fIsize\fR\^)) will print the message
391 size in a field six characters wide filled with leading zeros;
392 %14(\fIputstrf\^\fR{\fIfrom\^\fR}) will print the `From:' header
393 component in fourteen characters with trailing spaces added as needed.
394 For \fIputstrf\fR, using a negative value for the field width causes
395 right-justification of the string within the field, with padding on
396 the left up to the field width. The functions (\fIputnum\fR\^) and
397 (\fIputstr\fR\^) are somewhat special: they print their result in
398 the minimum number of characters required, and ignore any leading
399 field width argument.
401 The available output width is kept in an internal register; any output
402 past this width will be truncated.
404 With all this in mind, here's a format string for
406 It's been divided into several pieces for readability.
411 %4(msg)%<(cur)+%| %>%<{replied}\-%| %>
415 which says that the message number should be printed in four digits.
416 If the message is the current message then a `+' else a space should
417 be printed; if a `Replied:' field is present then a `\-'
418 else a space should be printed. Next:
422 %02(mon{date})/%02(mday{date})
426 the month and date are printed in two digits (zero filled) separated by
435 If a `Date:' field was present,
436 then a space is printed, otherwise a `*'.
441 %<(mymbox{from})%<{to}To:%14(decode(friendly{to}))%>%>
445 if the message is from me, and there is a `To:' header,
446 print `To:' followed by a `user-friendly' rendering of the
447 first address in the `To:' field; any MIME-encoded
448 characters are decoded into the actual characters.
453 %<(zero)%17(decode(friendly{from}))%>
457 if either of the above two tests failed,
458 then the `From:' address is printed
459 in a mime-decoded, `user-friendly' format.
468 the mime-decoded subject is printed.
470 For a more complicated example, next consider
477 %(lit)%(formataddr %<{reply-to}
483 and formats the `Reply-To:' header
484 if present. If not present, the else-if clause is executed.
488 %?{from}%?{sender}%?{return-path}%>)\\
493 `From:', `Sender:' or `Return-Path:'
494 headers, stopping as soon as one of them is present. Next:
498 %<(nonnull)%(void(width))%(putaddr To: )\\n%>\\
502 If the \fIformataddr\fR result is non-null, it is printed as
503 an address (with line folding if needed) in a field \fIwidth\fR
504 wide with a leading label of `To:'.
508 %(lit)%(formataddr{to})%(formataddr{cc})%(formataddr(me))\\
513 is cleared, and the `To:' and `Cc:' headers, along with the user's
514 address (depending on what was specified with
515 the `\-cc' switch to \fIrepl\fR\^) are formatted.
519 %<(nonnull)%(void(width))%(putaddr cc: )\\n%>\\
523 If the result is non-null, it is printed as above with a
524 leading label of `Cc:'.
528 %<{subject}Subject: Re: %(decode{subject})\\n%>\\
532 If a subject component was present,
533 a suitable reply subject is output.
537 %<{message-id}In-Reply-To: %{message-id}\\n%>\\
538 %<{message-id}References: %<{references} %{references}%>\\
544 If a message-id component was present, an `In-Reply-To:' header is
545 output including the message-id, followed by a `References:'
546 header with references, if present, and the message-id.
548 plain-text, the row of dashes are output as-is.
550 This last part is a good example for a little more elaboration.
551 Here's that part again in pseudo-code:
556 if (comp_exists(message-id)) then
557 print("In-reply-to: ")
558 print(message-id.value)
561 if (comp_exists(message-id)) then
562 print("References: ")
563 if (comp_exists(references)) then
564 print(references.value);
566 print(message-id.value)
572 .\" (Note that this pseudocode begs the question ``why not just
573 .\" support this syntax?'' MH has been hacked on for a long time...)
578 large message numbers, and it is not uncommon for a folder
579 to have far more than 10000 messages.
580 .\" (Indeed, the original MH
581 .\" tutorial document by Rose and Romine is entitled "How to
582 .\" process 200 messages a day and still get some real work
583 .\" done." The authors apparently only planned to get
584 .\" real work done for about 50 days per folder.)
585 Nonetheless several scan format strings are inherited
586 from older MH versions, and are generally hard-coded to 4
587 digits of message number before formatting problems
589 The mh format strings can be modified to behave more sensibly with larger
594 %(void(msg))%<(gt 9999)%(msg)%|%4(msg)%>
598 The current message number is placed in \fInum\fP.
601 is an int function, not a component.)
605 is used to test whether the message number
608 If so, it is printed at full width: otherwise
611 scan(1), repl(1), ap(8), dp(8)
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