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   5 .TH MH-FORMAT %manext5% "%nmhdate%" MH.6.8 [%nmhversion%]
   6 .SH NAME
   7 mh-format \- format file for nmh message system
   8 .SH DESCRIPTION
   9 Several
  10 .B nmh
  11 commands utilize either a
  12 .I format
  13 string or a
  14 .I format
  15 file during their execution.  For example,
  16 .B scan
  17 uses a format string which directs it how to generate the scan listing
  18 for each message;
  19 .B repl
  20 uses a format file which directs it
  21 how to generate the reply to a message, and so on.
  22 .PP
  23 There are a few alternate scan listing formats available
  24 in
  25 .IR nmh/etc/scan.time ,
  26 .IR nmh/etc/scan.size ,
  27 and
  28 .IR nmh/etc/scan.timely .
  29 Look in
  30 .I nmh/etc
  31 for other
  32 .B scan
  33 and
  34 .B repl
  35 format files which may have been written at your site.
  36 .PP
  37 It suffices to have your local
  38 .B nmh
  39 expert actually write new format
  40 commands or modify existing ones.  This manual section explains how to
  41 do that.  Note: familiarity with the C
  42 .B printf
  43 routine is assumed.
  44 .PP
  45 A format string consists of ordinary text, and special multi-character
  46 escape sequences which begin with `%'.  When specifying a format
  47 string, the usual C backslash characters are honored: `\\b', `\\f',
  48 `\\n', `\\r', and `\\t'.  Continuation lines in format files end with
  49 `\\' followed by the newline character.
  50
  51 .\" TALK ABOUT SYNTAX FIRST, THEN SEMANTICS
  52 .SS SYNTAX
  53 Format strings are built around
  54 .IR "escape sequences" .
  55 There are three types of escape sequences: header
  56 .IR components ,
  57 built-in
  58 .IR functions ,
  59 and flow
  60 .IR control .
  61 Comments may be inserted in most places where a function argument is
  62 not expected.  A comment begins with `%;' and ends with a (non-escaped)
  63 newline.
  64 .PP
  65 A
  66 .I component
  67 escape is specified as
  68 .RI `%{ component }',
  69 and
  70 exists for each header found in the message being processed.  For example
  71 .RI `%{ date }'
  72 refers to the \*(lqDate:\*(rq field of the appropriate message.
  73 All component escapes have a string value.  Normally, component values are
  74 compressed by converting any control characters (tab and newline included)
  75 to spaces, then eliding any leading or multiple spaces.  However, commands
  76 may give different interpretations to some component escapes; be sure
  77 to refer to each command's manual entry for complete details.
  78 .PP
  79 A
  80 .I function
  81 escape is specified as
  82 .RI `%( function )'.
  83 All functions are built-in, and most have a string or numeric value.
  84 A function escape may have an
  85 .IR argument .
  86 The argument follows the function escape: separating
  87 whitespace is discarded:
  88 .RI `%( function " " argument )'.
  89 .PP
  90 In addition to literal numbers or strings,
  91 the argument to a function escape can be another function, a component,
  92 or a control escape.  When the argument is a function or a
  93 component, they are listed without a leading `%'.  When control escapes
  94 are used as function arguments, they written as normally, with
  95 a leading `%';
  96
  97 .SS "Control escapes"
  98 .PP
  99 A
 100 .I control
 101 escape is one of: `%<', `%?', `%|', or `%>'.
 102 These are combined into the conditional execution construct:
 103 .PP
 104 .RS 5
 105 .nf
 106 .RI "%< " condition " " "format-text"
 107 .RI "%? " condition " " "format-text"
 108     \&...
 109 .RI "%| " "format-text"
 110 %>
 111 .fi
 112 .RE
 113 .PP
 114 Extra white space is shown here only for clarity.  These
 115 constructs may be nested without ambiguity.  They form a general
 116 .B if\-elseif\-else\-endif
 117 block where only one of the
 118 format-texts
 119 is interpreted.  In other
 120 words, `%<' is like the "if", `%?' is like the "elseif", `%|' is like
 121 "else", and `%>' is like "endif".
 122 .PP
 123 A `%<' or `%?' control escape causes its condition to be evaluated.
 124 This condition is a
 125 .I component
 126 or
 127 .IR function .
 128 For integer valued functions or components, the condition is true
 129 if the function return or component value is non-zero, and false if zero.
 130 For string valued functions or components, the condition is true
 131 if the function return or component value is
 132 a non-empty string, and false for an empty string.
 133
 134 .PP
 135 The `%?' control escape is optional, and may there may be more
 136 than one `%?' control escape in a conditional block.
 137 The `%|' control escape
 138 is also optional, but may be included at most once.
 139
 140 .SS "Function escapes"
 141 Functions expecting an argument generally
 142 require an argument of a particular type.
 143 In addition to the number and string types,
 144 these include:
 145 .PP
 146 .RS 5
 147 .nf
 148 .ta +\w'Argument 'u +\w'An optional component, 'u
 149 .I Argument     Description     Example Syntax
 150 literal A literal number        %(\fIfunc\fR 1234)
 151         or string               %(\fIfunc\fR text string)
 152 comp    Any component           %(\fIfunc\fR\^{\fIin-reply-to\fR\^})
 153 date    A date component        %(\fIfunc\fR\^{\fIdate\fR\^})
 154 addr    An address component    %(\fIfunc\fR\^{\fIfrom\fR\^})
 155 expr    Nothing %(\fIfunc\fR)
 156         or a subexpression      %(\fIfunc\fR\^(\fIfunc2\fR\^))
 157         or control escape       %(\fIfunc\fR %<{\fIreply-to\fR\^}%|%{\fIfrom\fR\^}%>)
 158 .fi
 159 .RE
 160 .PP
 161 The types
 162 .I date
 163 and
 164 .I addr
 165 have the same syntax as
 166 .IR comp ,
 167 but require that the header component be a date string, or address
 168 string, respectively.
 169 .PP
 170 Most arguments not of type
 171 .IR expr
 172 are required.
 173 When escapes are nested (via expr arguments), evaluation is done from inner-most to outer-most.
 174 As noted above, for the
 175 expr
 176 argument type,
 177 functions and components are written without a
 178 leading `%'.
 179 Control escape arguments must use a leading `%', preceded by a space.
 180 .PP
 181 For example,
 182 .PP
 183 .RS 5
 184 .nf
 185 %<(mymbox{from}) To: %{to}%>
 186 .fi
 187 .RE
 188 .PP
 189 writes  the  value of the header component \*(lqFrom:\*(rq to the
 190 internal register named str; then (\fImymbox\fR\^) reads str and
 191 writes its result to the internal register named
 192 .IR num ;
 193 then the control escape evaluates
 194 .IR num .
 195 If
 196 .IR num
 197 is non-zero, the
 198 string \*(lqTo:\*(rq is printed  followed  by  the  value  of  the
 199 header component \*(lqTo:\*(rq.
 200 .SS Evaluation
 201 The evaluation of format strings is performed
 202 by a small virtual machine.
 203 The machine is capable of evaluating nested expressions
 204 as described above, and in addition
 205 has an integer register
 206 .IR num ,
 207 and a text string register
 208 .IR str .
 209 When a function escape that
 210 accepts an optional argument is processed,
 211 and the argument is not present, the current value of either
 212 .I num
 213 or
 214 .I str
 215 is used as the argument: which register is
 216 used depends on the function, as listed below.
 217 .PP
 218 Component escapes write the value of their message header in
 219 .IR str .
 220 Function escapes write their return value in
 221 .I num
 222 for functions returning integer or boolean values, and in
 223 .I str
 224 for functions returning string values.  (The boolean type is a subset
 225 of integers with usual values 0=false and 1=true.)  Control escapes
 226 return a boolean value, setting
 227 .I num
 228 to 1 if the last explicit condition
 229 evaluated by a `%<' or `%?' control
 230 succeeded, and 0 otherwise.
 231 .PP
 232 All component escapes, and those function escapes which return an
 233 integer or string value, evaluate to their value as well as setting
 234 .I str
 235 or
 236 .IR num .
 237 Outermost escape expressions in
 238 these forms will print
 239 their value, but outermost escapes which return a boolean value
 240 do not result in printed output.
 241 .SS Functions
 242 The function escapes may be roughly grouped into a few categories.
 243 .PP
 244 .RS 5
 245 .nf
 246 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
 247 .I Function     Argument   Result       Description
 248 msg             integer message number
 249 cur             integer message is current (0 or 1)
 250 unseen          integer message is unseen (0 or 1)
 251 size            integer size of message
 252 strlen          integer length of \fIstr\fR
 253 width           integer output buffer size in bytes
 254 charleft                integer bytes left in output buffer
 255 timenow         integer seconds since the UNIX epoch
 256 me              string  the user's mailbox
 257 eq      literal boolean \fInum\fR == \fIarg\fR
 258 ne      literal boolean \fInum\fR != \fIarg\fR
 259 gt      literal boolean \fInum\fR > \fIarg\fR
 260 match   literal boolean \fIstr\fR contains \fIarg\fR
 261 amatch  literal boolean \fIstr\fR starts with \fIarg\fR
 262 plus    literal integer \fIarg\fR plus \fInum\fR
 263 minus   literal integer \fIarg\fR minus \fInum\fR
 264 divide  literal integer \fInum\fR divided by \fIarg\fR
 265 modulo  literal integer \fInum\fR modulo \fIarg\fR
 266 num     literal integer Set \fInum\fR to \fIarg\fR.
 267 num             integer Set \fInum\fR to zero.
 268 lit     literal string  Set \fIstr\fR to \fIarg\fR.
 269 lit             string  Clear \fIstr\fR.
 270 getenv  literal string  Set \fIstr\fR to environment value of \fIarg\fR
 271 profile literal string  Set \fIstr\fR to profile component \fIarg\fR
 272                         value
 273 .\" dat literal int     return value of dat[arg]
 274 nonzero expr    boolean \fInum\fR is non-zero
 275 zero    expr    boolean \fInum\fR is zero
 276 null    expr    boolean \fIstr\fR is empty
 277 nonnull expr    boolean \fIstr\fR is non-empty
 278 void    expr            Set \fIstr\fR or \fInum\fR
 279 comp    comp    string  Set \fIstr\fR to component text
 280 compval comp    integer Set \fInum\fR to \*(lq\fBatoi\fR(\fIcomp\fR\^)\*(rq
 281 .\" compflag    comp    integer Set \fInum\fR to component flags bits (internal)
 282 .\" decodecomp  comp    string  Set \fIstr\fR to RFC-2047 decoded component text
 283 decode  expr    string  decode \fIstr\fR as RFC-2047 (MIME-encoded)
 284                         component
 285 unquote expr    string  remove RFC-2822 quotes from \fIstr\fR
 286 trim    expr            trim trailing white-space from \fIstr\fR
 287 putstr  expr            print \fIstr\fR
 288 putstrf expr            print \fIstr\fR in a fixed width
 289 putnum  expr            print \fInum\fR
 290 putnumf expr            print \fInum\fR in a fixed width
 291 .\" addtoseq literal    add msg to sequence (LBL option)
 292 nodate  string  integer Argument not a date string (0 or 1)
 293 formataddr      expr            append \fIarg\fR to \fIstr\fR as a
 294                         (comma separated) address list
 295 putaddr literal         print \fIstr\fR address list with
 296                         \fIarg\fR as optional label;
 297                         get line width from \fInum\fR
 298 .fi
 299 .RE
 300 .PP
 301 The following functions require a date component as an argument:
 302 .PP
 303 .RS 5
 304 .nf
 305 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
 306 .I Function     Argument        Return  Description
 307 sec     date    integer seconds of the minute
 308 min     date    integer minutes of the hour
 309 hour    date    integer hours of the day (0-23)
 310 wday    date    integer day of the week (Sun=0)
 311 day     date    string  day of the week (abbrev.)
 312 weekday date    string  day of the week
 313 sday    date    integer day of the week known?
 314                         (1=explicit,0=implicit,\-1=unknown)
 315 mday    date    integer day of the month
 316 yday    date    integer day of the year
 317 mon     date    integer month of the year
 318 month   date    string  month of the year (abbrev.)
 319 lmonth  date    string  month of the year
 320 year    date    integer year (may be > 100)
 321 zone    date    integer timezone in hours
 322 tzone   date    string  timezone string
 323 szone   date    integer timezone explicit?
 324                         (1=explicit,0=implicit,\-1=unknown)
 325 date2local      date            coerce date to local timezone
 326 date2gmt        date            coerce date to GMT
 327 dst     date    integer daylight savings in effect? (0 or 1)
 328 clock   date    integer seconds since the UNIX epoch
 329 rclock  date    integer seconds prior to current time
 330 tws     date    string  official 822 rendering
 331 pretty  date    string  user-friendly rendering
 332 .fi
 333 .RE
 334 .PP
 335 These functions require an address component as an argument.
 336 The return value of functions noted with `*' is computed from
 337 the first address present in the header component.
 338 .PP
 339 .RS 5
 340 .nf
 341 .ta \w'Fformataddr 'u +\w'Aboolean 'u +\w'Rboolean 'u
 342 .I Function     Argument        Return  Description
 343 proper  addr    string  official 822 rendering
 344 friendly        addr    string  user-friendly rendering
 345 addr    addr    string  mbox@host or host!mbox rendering*
 346 pers    addr    string  the personal name*
 347 note    addr    string  commentary text*
 348 mbox    addr    string  the local mailbox*
 349 mymbox  addr    integer List has the user's address? (0 or 1)
 350 host    addr    string  the host domain*
 351 nohost  addr    integer no host was present (0 or 1)*
 352 type    addr    integer host type* (0=local,1=network,
 353                         \-1=uucp,2=unknown)
 354 path    addr    string  any leading host route*
 355 ingrp   addr    integer address was inside a group (0 or 1)*
 356 gname   addr    string  name of group*
 357 .fi
 358 .RE
 359 .PP
 360 (A clarification on (\fImymbox\fR\^{\fIcomp\fR\^}) is in order.
 361 This function checks each of the addresses in the header component
 362 \*(lq\fIcomp\fR\*(rq against the user's mailbox name and any
 363 .RI \*(lq Alternate-Mailboxes \*(rq.
 364 It returns true if any address matches,
 365 however, it also returns true if the \*(lq\fIcomp\fR\*(rq header is not
 366 present in the message.  If needed, the (\fInull\fR\^) function can be
 367 used to explicitly test for this case.)
 368 .SS Formatting
 369 When a function or component escape is interpreted and the result will
 370 be immediately printed, an optional field width can be specified to
 371 print the field in exactly a given number of characters.  For example, a
 372 numeric escape like %4(\fIsize\fR\^) will print at most 4 digits of the
 373 message size; overflow will be indicated by a `?' in the first position
 374 (like `?234').  A string escape like %4(\fIme\fR\^) will print the first 4
 375 characters and truncate at the end.  Short fields are padded at the right
 376 with the fill character (normally, a blank).  If the field width argument
 377 begins with a leading zero, then the fill character is set to a zero.
 378 .PP
 379 The functions (\fIputnumf\fR\^) and (\fIputstrf\fR\^)
 380 print their result in exactly the number of characters
 381 specified by their leading field width argument.  For example,
 382 %06(\fIputnumf\fR\^(\fIsize\fR\^)) will print the message
 383 size in a field six characters wide filled with leading zeros;
 384 %14(\fIputstrf\^\fR{\fIfrom\^\fR}) will print the \*(lqFrom:\*(rq header
 385 component in fourteen characters with trailing spaces added as needed.
 386 For \fIputstrf\fR, using a negative value for the field width causes
 387 right-justification of the string within the field, with padding on
 388 the left up to the field width.
 389 The functions (\fIputnum\fR\^) and
 390 (\fIputstr\fR\^) are somewhat special: they print their result in the minimum number of characters
 391 required, and ignore any leading field width argument.
 392 .PP
 393 The available output width is kept in an internal register; any output
 394 past this width will be truncated.
 395 .SS Examples
 396 With all this in mind,
 397 here's the default format string for
 398 .BR scan .
 399 It's been divided into several pieces for readability.
 400 The first part is:
 401 .PP
 402 .RS
 403 .nf
 404 %4(msg)%<(cur)+%| %>%<{replied}\-%?{encrypted}E%| %>
 405 .fi
 406 .RE
 407 .PP
 408 which says that the message number should be printed in four digits.
 409 If the message is the current message then a `+' else a space should
 410 be printed; if a \*(lqReplied:\*(rq field is present then a `\-'
 411 else if an \*(lqEncrypted:\*(rq field is present then an `E' otherwise
 412 a space should be printed.  Next:
 413 .PP
 414 .RS
 415 .nf
 416 %02(mon{date})/%02(mday{date})
 417 .fi
 418 .RE
 419 .PP
 420 the month and date are printed in two digits (zero filled) separated by
 421 a slash. Next,
 422 .PP
 423 .RS 5
 424 .nf
 425 %<{date} %|*%>
 426 .fi
 427 .RE
 428 .PP
 429 If a \*(lqDate:\*(rq field was present,
 430 then a space is printed, otherwise a `*'.
 431 Next,
 432 .PP
 433 .RS 5
 434 .nf
 435 %<(mymbox{from})%<{to}To:%14(decode(friendly{to}))%>%>
 436 .fi
 437 .RE
 438 .PP
 439 if the message is from me, and there is a \*(lqTo:\*(rq header,
 440 print \*(lqTo:\*(rq followed by a \*(lquser-friendly\*(rq rendering of the
 441 first address in the \*(lqTo:\*(rq field; any MIME-encoded
 442 characters are decoded into the actual characters.
 443 Continuing,
 444 .PP
 445 .RS 5
 446 .nf
 447 %<(zero)%17(decode(friendly{from}))%>
 448 .fi
 449 .RE
 450 .PP
 451 if either of the above two tests failed,
 452 then the \*(lqFrom:\*(rq address is printed
 453 in a mime-decoded, \*(lquser-friendly\*(rq format.
 454 And finally,
 455 .PP
 456 .RS 5
 457 .nf
 458 %(decode{subject})%<{body}<<%{body}>>%>
 459 .fi
 460 .RE
 461 .PP
 462 the mime-decoded subject and initial body (if any) are printed.
 463 .PP
 464 For a more complicated example, next consider
 465 a possible
 466 .I replcomps
 467 format file.
 468 .PP
 469 .RS 5
 470 .nf
 471 %(lit)%(formataddr %<{reply-to}
 472 .fi
 473 .RE
 474 .PP
 475 This clears
 476 .I str
 477 and formats the \*(lqReply-To:\*(rq header
 478 if present.  If not present, the else-if clause is executed.
 479 .PP
 480 .RS 5
 481 .nf
 482 %?{from}%?{sender}%?{return-path}%>)\\
 483 .fi
 484 .RE
 485 .PP
 486 This formats the
 487 \*(lqFrom:\*(rq, \*(lqSender:\*(rq and \*(lqReturn-Path:\*(rq
 488 headers, stopping as soon as one of them is present.  Next:
 489 .PP
 490 .RS 5
 491 .nf
 492 %<(nonnull)%(void(width))%(putaddr To: )\\n%>\\
 493 .fi
 494 .RE
 495 .PP
 496 If the \fIformataddr\fR result is non-null, it is printed as
 497 an address (with line folding if needed) in a field \fIwidth\fR
 498 wide with a leading label of \*(lqTo:\*(rq.
 499 .PP
 500 .RS 5
 501 .nf
 502 %(lit)%(formataddr{to})%(formataddr{cc})%(formataddr(me))\\
 503 .fi
 504 .RE
 505 .PP
 506 .I str
 507 is cleared, and the \*(lqTo:\*(rq and \*(lqCc:\*(rq headers, along with the user's
 508 address (depending on what was specified with
 509 the \*(lq\-cc\*(rq switch to \fIrepl\fR\^) are formatted.
 510 .PP
 511 .RS 5
 512 .nf
 513 %<(nonnull)%(void(width))%(putaddr cc: )\\n%>\\
 514 .fi
 515 .RE
 516 .PP
 517 If the result is non-null, it is printed as above with a
 518 leading label of \*(lqcc:\*(rq.
 519 .PP
 520 .RS 5
 521 .nf
 522 %<{fcc}Fcc: %{fcc}\\n%>\\
 523 .fi
 524 .RE
 525 .PP
 526 If a
 527 .B \-fcc
 528 .I folder
 529 switch was given to
 530 .B repl
 531 (see
 532 .BR repl (1)
 533 for more details about %{\fIfcc\fR\^}),
 534 an \*(lqFcc:\*(rq header is output.
 535 .PP
 536 .RS 5
 537 .nf
 538 %<{subject}Subject: Re: %{subject}\\n%>\\
 539 .fi
 540 .RE
 541 .PP
 542 If a subject component was present,
 543 a suitable reply subject is output.
 544 .PP
 545 .RS 5
 546 .nf
 547 %<{message-id}In-Reply-To: %{message-id}\\n%>\\
 548 %<{message-id}References: %<{references} %{references}%>\\
 549 %{message-id}\\n%>
 550 \-\-\-\-\-\-\-\-
 551 .fi
 552 .RE
 553 .PP
 554 If a message-id component was present, an \*(lqIn-Reply-To:\*(rq header is
 555 output including the message-id, followed by a \*(lqReferences:\*(rq
 556 header with references, if present, and the message-id.
 557 As with all
 558 plain-text, the row of dashes are output as-is.
 559 .PP
 560 This last part is a good example for a little more elaboration.
 561 Here's that part again in pseudo-code:
 562 .PP
 563 .RS 5
 564 .nf
 565 .ta .5i 1i 1.5i 2i
 566 if (comp_exists(message-id))  then
 567         print (\*(lqIn-reply-to: \*(rq)
 568         print (message-id.value)
 569         print (\*(lq\\n\*(rq)
 570 endif
 571 if (comp_exists(message-id)) then
 572         print (\*(lqReferences: \*(rq)
 573         if (comp_exists(references)) then
 574               print(references.value);
 575         endif
 576         print (message-id.value)
 577         print (\*(lq\\n\*(rq)
 578 endif
 579 .fi
 580 .RE
 581 .PP
 582 .\" (Note that this pseudocode begs the question ``why not just
 583 .\" support this syntax?''  MH has been hacked on for a long time...)
 584 .\".PP
 585 One more example: Currently,
 586 .B nmh
 587 supports very
 588 large message numbers, and it is not uncommon for a folder
 589 to have far more than 10000 messages.
 590 .\" (Indeed, the original MH
 591 .\" tutorial document by Rose and Romine is entitled "How to
 592 .\" process 200 messages a day and still get some real work
 593 .\" done."  The authors apparently only planned to get
 594 .\" real work done for about 50 days per folder.)
 595 Nontheless (as noted above)
 596 the various scan format strings are inherited
 597 from older MH versions, and are generally hard-coded to 4
 598 digits of message number before formatting problems
 599 start to occur.
 600 The nmh format strings can be modified to behave more sensibly with larger
 601 message numbers:
 602 .PP
 603 .RS
 604 .nf
 605 %(void(msg))%<(gt 9999)%(msg)%|%4(msg)%>
 606 .fi
 607 .RE
 608 .PP
 609 The current message number is placed in \fInum\fP.
 610 (Note that
 611 .RI ( msg )
 612 is an int function, not a component.)
 613 The
 614 .RI ( gt )
 615 conditional
 616 is used to test whether the message number
 617 has 5
 618 or more digits.
 619 If so, it is printed at full width: otherwise
 620 at 4 digits.
 621 .SH "SEE ALSO"
 622 scan(1), repl(1), ap(8), dp(8)
 623
 624 .SH CONTEXT
 625 None