1GROFF_OUT(5) File Formats Manual GROFF_OUT(5)
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6 groff_out - groff intermediate output format
7
9 This manual page describes the intermediate output format of the GNU
10 roff(7) text processing system groff(1). This output is produced by a
11 run of the GNU troff(1) program. It contains already all device-spe‐
12 cific information, but it is not yet fed into a device postprocessor
13 program.
14 As the GNU roff processor groff(1) is a wrapper program around troff
16 that automatically calls a postprocessor, this output does not show up
17 normally. This is why it is called intermediate within the groff sys‐
18 tem. The groff program provides the option -Z to inhibit postprocess‐
19 ing, such that the produced intermediate output is sent to standard
20 output just like calling troff manually.
21 In this document, the term troff output describes what is output by the
23 GNU troff program, while intermediate output refers to the language
24 that is accepted by the parser that prepares this output for the post‐
25 processors. This parser is smarter on whitespace and implements obso‐
26 lete elements for compatibility, otherwise both formats are the same.
27 Both formats can be viewed directly with gxditview(1).
28 The main purpose of the intermediate output concept is to facilitate
30 the development of postprocessors by providing a common programming
31 interface for all devices. It has a language of its own that is com‐
32 pletely different from the groff(7) language. While the groff language
33 is a high-level programming language for text processing, the interme‐
34 diate output language is a kind of low-level assembler language by
35 specifying all positions on the page for writing and drawing.
36 The pre-groff roff versions are denoted as classical troff. The inter‐
38 mediate output produced by groff is fairly readable, while classical
39 troff output was hard to understand because of strange habits that are
40 still supported, but not used any longer by GNU troff.
41
43 During the run of troff, the roff input is cracked down to the informa‐
44 tion on what has to be printed at what position on the intended device.
45 So the language of the intermediate output format can be quite small.
46 Its only elements are commands with or without arguments. In this doc‐
47 ument, the term “command” always refers to the intermediate output lan‐
48 guage, never to the roff language used for document formatting. There
49 are commands for positioning and text writing, for drawing, and for
50 device controlling.
51 Separation
53 Classical troff output had strange requirements on whitespace. The
54 groff output parser, however, is smart about whitespace by making it
55 maximally optional. The whitespace characters, i.e., the tab, space,
56 and newline characters, always have a syntactical meaning. They are
57 never printable because spacing within the output is always done by
58 positioning commands.
59 Any sequence of space or tab characters is treated as a single syntac‐
61 tical space. It separates commands and arguments, but is only required
62 when there would occur a clashing between the command code and the
63 arguments without the space. Most often, this happens when variable
64 length command names, arguments, argument lists, or command clusters
65 meet. Commands and arguments with a known, fixed length need not be
66 separated by syntactical space.
67 A line break is a syntactical element, too. Every command argument can
69 be followed by whitespace, a comment, or a newline character. Thus a
70 syntactical line break is defined to consist of optional syntactical
71 space that is optionally followed by a comment, and a newline charac‐
72 ter.
73 The normal commands, those for positioning and text, consist of a sin‐
75 gle letter taking a fixed number of arguments. For historical reasons,
76 the parser allows to stack such commands on the same line, but fortu‐
77 nately, in groff intermediate output, every command with at least one
78 argument is followed by a line break, thus providing excellent read‐
79 ability.
80 The other commands — those for drawing and device controlling — have a
82 more complicated structure; some recognize long command names, and some
83 take a variable number of arguments. So all D and x commands were
84 designed to request a syntactical line break after their last argument.
85 Only one command, `x X' has an argument that can stretch over several
86 lines, all other commands must have all of their arguments on the same
87 line as the command, i.e., the arguments may not be split by a line
88 break.
89 Empty lines, i.e., lines containing only space and/or a comment, can
91 occur everywhere. They are just ignored.
92 Argument Units
94 Some commands take integer arguments that are assumed to represent val‐
95 ues in a measurement unit, but the letter for the corresponding scale
96 indicator is not written with the output command arguments; see
97 groff(7) and the groff info file for more on this topic. Most commands
98 assume the scale indicator u, the basic unit of the device, some use z,
99 the scaled point unit of the device, while others, such as the color
100 commands expect plain integers. Note that these scale indicators are
101 relative to the chosen device. They are defined by the parameters
102 specified in the device's DESC file; see groff_font(5).
103 Note that single characters can have the eighth bit set, as can the
105 names of fonts and special characters (this is, glyphs). The names of
106 glyphs and fonts can be of arbitrary length. A glyph that is to be
107 printed will always be in the current font.
108 A string argument is always terminated by the next whitespace character
110 (space, tab, or newline); an embedded # character is regarded as part
111 of the argument, not as the beginning of a comment command. An integer
112 argument is already terminated by the next non-digit character, which
113 then is regarded as the first character of the next argument or com‐
114 mand.
115 Document Parts
117 A correct intermediate output document consists of two parts, the pro‐
118 logue and the body.
119 The task of the prologue is to set the general device parameters using
121 three exactly specified commands. The groff prologue is guaranteed to
122 consist of the following three lines (in that order):
123 x T device
125 x res n h v
126 x init
127 with the arguments set as outlined in the section Device Control Com‐
129 mands. However, the parser for the intermediate output format is able
130 to swallow additional whitespace and comments as well.
131 The body is the main section for processing the document data. Syntac‐
133 tically, it is a sequence of any commands different from the ones used
134 in the prologue. Processing is terminated as soon as the first x stop
135 command is encountered; the last line of any groff intermediate output
136 always contains such a command.
137 Semantically, the body is page oriented. A new page is started by a
139 p command. Positioning, writing, and drawing commands are always done
140 within the current page, so they cannot occur before the first p com‐
141 mand. Absolute positioning (by the H and V commands) is done relative
142 to the current page, all other positioning is done relative to the cur‐
143 rent location within this page.
144
146 This section describes all intermediate output commands, the classical
147 commands as well as the groff extensions.
148 Comment Command
150 #anything⟨end-of-line⟩
151 A comment. Ignore any characters from the # character up to the
152 next newline character.
153 This command is the only possibility for commenting in the intermediate
155 output. Each comment can be preceded by arbitrary syntactical space;
156 every command can be terminated by a comment.
157 Simple Commands
159 The commands in this subsection have a command code consisting of a
160 single character, taking a fixed number of arguments. Most of them are
161 commands for positioning and text writing. These commands are smart
162 about whitespace. Optionally, syntactical space can be inserted
163 before, after, and between the command letter and its arguments. All
164 of these commands are stackable, i.e., they can be preceded by other
165 simple commands or followed by arbitrary other commands on the same
166 line. A separating syntactical space is only necessary when two inte‐
167 ger arguments would clash or if the preceding argument ends with a
168 string argument.
169 C xxx⟨white-space⟩
171 Print a glyph (special character) named xxx. The trailing syn‐
172 tactical space or line break is necessary to allow glyph names
173 of arbitrary length. The glyph is printed at the current print
174 position; the glyph's size is read from the font file. The
175 print position is not changed.
176 c c Print glyph with single-letter name c at the current print posi‐
178 tion; the glyph's size is read from the font file. The print
179 position is not changed.
180 f n Set font to font number n (a non-negative integer).
182 H n Move right to the absolute vertical position n (a non-negative
184 integer in basic units u) relative to left edge of current page.
185 h n Move n (a non-negative integer) basic units u horizontally to
187 the right. [CSTR #54] allows negative values for n also, but
188 groff doesn't use this.
189 m color-scheme [component ...]
191 Set the color for text (glyphs), line drawing, and the outline
192 of graphic objects using different color schemes; the analoguous
193 command for the filling color of graphic objects is DF. The
194 color components are specified as integer arguments between 0
195 and 65536. The number of color components and their meaning
196 vary for the different color schemes. These commands are gener‐
197 ated by the groff escape sequence \m. No position changing.
198 These commands are a groff extension.
199 mc cyan magenta yellow
201 Set color using the CMY color scheme, having the 3 color
202 components cyan, magenta, and yellow.
203 md Set color to the default color value (black in most
205 cases). No component arguments.
206 mg gray
208 Set color to the shade of gray given by the argument, an
209 integer between 0 (black) and 65536 (white).
210 mk cyan magenta yellow black
212 Set color using the CMYK color scheme, having the 4 color
213 components cyan, magenta, yellow, and black.
214 mr red green blue
216 Set color using the RGB color scheme, having the 3 color
217 components red, green, and blue.
218 N n Print glyph with index n (an integer, normally non-negative) of
220 the current font. The print position is not changed. If
221 -T html or -T xhtml is used, negative values are emitted also to
222 indicate an unbreakable space with given width. For example,
223 N -193 represents an unbreakable space which has a width of
224 193u. This command is a groff extension.
225 n b a Inform the device about a line break, but no positioning is done
227 by this command. In classical troff, the integer arguments b
228 and a informed about the space before and after the current line
229 to make the intermediate output more human readable without per‐
230 forming any action. In groff, they are just ignored, but they
231 must be provided for compatibility reasons.
232 p n Begin a new page in the outprint. The page number is set to n.
234 This page is completely independent of pages formerly processed
235 even if those have the same page number. The vertical position
236 on the outprint is automatically set to 0. All positioning,
237 writing, and drawing is always done relative to a page, so a
238 p command must be issued before any of these commands.
239 s n Set point size to n scaled points (this is unit z in GNU troff).
241 Classical troff used the unit points (p) instead; see section
242 COMPATIBILITY.
243 t xyz...⟨white-space⟩
245 t xyz... dummy-arg⟨white-space⟩
246 Print a word, i.e., a sequence of glyphs with single-letter
247 names x, y, z, etc., terminated by a space character or a line
248 break; an optional second integer argument is ignored (this
249 allows the formatter to generate an even number of arguments).
250 The first glyph should be printed at the current position, the
251 current horizontal position should then be increased by the
252 width of the first glyph, and so on for each glyph. The widths
253 of the glyph are read from the font file, scaled for the current
254 point size, and rounded to a multiple of the horizontal resolu‐
255 tion. Special characters (glyphs with names longer than a sin‐
256 gle letter) cannot be printed using this command; use the C com‐
257 mand for those glyphs. This command is a groff extension; it is
258 only used for devices whose DESC file contains the tcommand key‐
259 word; see groff_font(5).
260 u n xyz...⟨white-space⟩
262 Print word with track kerning. This is the same as the t com‐
263 mand except that after printing each glyph, the current horizon‐
264 tal position is increased by the sum of the width of that glyph
265 and n (an integer in basic units u). This command is a groff
266 extension; it is only used for devices whose DESC file contains
267 the tcommand keyword; see groff_font(5).
268 V n Move down to the absolute vertical position n (a non-negative
270 integer in basic units u) relative to upper edge of current
271 page.
272 v n Move n basic units u down (n is a non-negative integer).
274 [CSTR #54] allows negative values for n also, but groff doesn't
275 use this.
276 w Informs about a paddable whitespace to increase readability.
278 The spacing itself must be performed explicitly by a move com‐
279 mand.
280 Graphics Commands
282 Each graphics or drawing command in the intermediate output starts with
283 the letter D followed by one or two characters that specify a subcom‐
284 mand; this is followed by a fixed or variable number of integer argu‐
285 ments that are separated by a single space character. A D command may
286 not be followed by another command on the same line (apart from a com‐
287 ment), so each D command is terminated by a syntactical line break.
288 troff output follows the classical spacing rules (no space between com‐
290 mand and subcommand, all arguments are preceded by a single space char‐
291 acter), but the parser allows optional space between the command let‐
292 ters and makes the space before the first argument optional. As usual,
293 each space can be any sequence of tab and space characters.
294 Some graphics commands can take a variable number of arguments. In
296 this case, they are integers representing a size measured in basic
297 units u. The h arguments stand for horizontal distances where positive
298 means right, negative left. The v arguments stand for vertical dis‐
299 tances where positive means down, negative up. All these distances are
300 offsets relative to the current location.
301 Unless indicated otherwise, each graphics command directly corresponds
303 to a similar groff \D escape sequence; see groff(7).
304 Unknown D commands are assumed to be device-specific. Its arguments
306 are parsed as strings; the whole information is then sent to the post‐
307 processor.
308 In the following command reference, the syntax element ⟨line-break⟩
310 means a syntactical line break as defined in section Separation.
311 D~ h1 v1 h2 v2 ... hn vn⟨line-break⟩
313 Draw B-spline from current position to offset (h1, v1), then to
314 offset (h2, v2) if given, etc., up to (hn, vn). This command
315 takes a variable number of argument pairs; the current position
316 is moved to the terminal point of the drawn curve.
317 Da h1 v1 h2 v2⟨line-break⟩
319 Draw arc from current position to (h1, v1)+(h2, v2) with center
320 at (h1, v1); then move the current position to the final point
321 of the arc.
322 DC d⟨line-break⟩
324 DC d dummy-arg⟨line-break⟩
325 Draw a solid circle using the current fill color with diameter d
326 (integer in basic units u) with leftmost point at the current
327 position; then move the current position to the rightmost point
328 of the circle. An optional second integer argument is ignored
329 (this allows to the formatter to generate an even number of
330 arguments). This command is a groff extension.
331 Dc d⟨line-break⟩
333 Draw circle line with diameter d (integer in basic units u) with
334 leftmost point at the current position; then move the current
335 position to the rightmost point of the circle.
336 DE h v⟨line-break⟩
338 Draw a solid ellipse in the current fill color with a horizontal
339 diameter of h and a vertical diameter of v (both integers in
340 basic units u) with the leftmost point at the current position;
341 then move to the rightmost point of the ellipse. This command
342 is a groff extension.
343 De h v⟨line-break⟩
345 Draw an outlined ellipse with a horizontal diameter of h and a
346 vertical diameter of v (both integers in basic units u) with the
347 leftmost point at current position; then move to the rightmost
348 point of the ellipse.
349 DF color-scheme [component ...]⟨line-break⟩
351 Set fill color for solid drawing objects using different color
352 schemes; the analoguous command for setting the color of text,
353 line graphics, and the outline of graphic objects is m. The
354 color components are specified as integer arguments between 0
355 and 65536. The number of color components and their meaning
356 vary for the different color schemes. These commands are gener‐
357 ated by the groff escape sequences \D'F ...' and \M (with no
358 other corresponding graphics commands). No position changing.
359 This command is a groff extension.
360 DFc cyan magenta yellow⟨line-break⟩
362 Set fill color for solid drawing objects using the CMY
363 color scheme, having the 3 color components cyan,
364 magenta, and yellow.
365 DFd ⟨line-break⟩
367 Set fill color for solid drawing objects to the default
368 fill color value (black in most cases). No component
369 arguments.
370 DFg gray⟨line-break⟩
372 Set fill color for solid drawing objects to the shade of
373 gray given by the argument, an integer between 0 (black)
374 and 65536 (white).
375 DFk cyan magenta yellow black⟨line-break⟩
377 Set fill color for solid drawing objects using the CMYK
378 color scheme, having the 4 color components cyan,
379 magenta, yellow, and black.
380 DFr red green blue⟨line-break⟩
382 Set fill color for solid drawing objects using the RGB
383 color scheme, having the 3 color components red, green,
384 and blue.
385 Df n⟨line-break⟩
387 The argument n must be an integer in the range -32767 to 32767.
388 0≤n≤1000
390 Set the color for filling solid drawing objects to a
391 shade of gray, where 0 corresponds to solid white, 1000
392 (the default) to solid black, and values in between to
393 intermediate shades of gray; this is obsoleted by command
394 DFg.
395 n<0 or n>1000
397 Set the filling color to the color that is currently
398 being used for the text and the outline, see command m.
399 For example, the command sequence
400 mg 0 0 65536
402 Df -1
403 sets all colors to blue.
405 No position changing. This command is a groff extension.
407 Dl h v⟨line-break⟩
409 Draw line from current position to offset (h, v) (integers in
410 basic units u); then set current position to the end of the
411 drawn line.
412 Dp h1 v1 h2 v2 ... hn vn⟨line-break⟩
414 Draw a polygon line from current position to offset (h1, v1),
415 from there to offset (h2, v2), etc., up to offset (hn, vn), and
416 from there back to the starting position. For historical rea‐
417 sons, the position is changed by adding the sum of all arguments
418 with odd index to the actual horizontal position and the even
419 ones to the vertical position. Although this doesn't make sense
420 it is kept for compatibility. This command is a groff exten‐
421 sion.
422 DP h1 v1 h2 v2 ... hn vn⟨line-break⟩
424 The same macro as the corresponding Dp command with the same
425 arguments, but draws a solid polygon in the current fill color
426 rather than an outlined polygon. The position is changed in the
427 same way as with Dp. This command is a groff extension.
428 Dt n⟨line-break⟩
430 Set the current line thickness to n (an integer in basic
431 units u) if n>0; if n=0 select the smallest available line
432 thickness; if n<0 set the line thickness proportional to the
433 point size (this is the default before the first Dt command was
434 specified). For historical reasons, the horizontal position is
435 changed by adding the argument to the actual horizontal posi‐
436 tion, while the vertical position is not changed. Although this
437 doesn't make sense it is kept for compatibility. This command
438 is a groff extension.
439 Device Control Commands
441 Each device control command starts with the letter x followed by a
442 space character (optional or arbitrary space/tab in groff) and a sub‐
443 command letter or word; each argument (if any) must be preceded by a
444 syntactical space. All x commands are terminated by a syntactical line
445 break; no device control command can be followed by another command on
446 the same line (except a comment).
447 The subcommand is basically a single letter, but to increase readabil‐
449 ity, it can be written as a word, i.e., an arbitrary sequence of char‐
450 acters terminated by the next tab, space, or newline character. All
451 characters of the subcommand word but the first are simply ignored.
452 For example, troff outputs the initialization command x i as x init and
453 the resolution command x r as x res. But writings like x i_like_groff
454 and x roff_is_groff are accepted as well to mean the same commands.
455 In the following, the syntax element ⟨line-break⟩ means a syntactical
457 line break as defined in section Separation.
458 xF name⟨line-break⟩
460 (Filename control command)
461 Use name as the intended name for the current file in error
462 reports. This is useful for remembering the original file name
463 when groff uses an internal piping mechanism. The input file is
464 not changed by this command. This command is a groff extension.
465 xf n s⟨line-break⟩
467 (font control command)
468 Mount font position n (a non-negative integer) with font named s
469 (a text word), cf. groff_font(5).
470 xH n⟨line-break⟩
472 (Height control command)
473 Set character height to n (a positive integer in scaled
474 points z). Classical troff used the unit points (p) instead;
475 see section COMPATIBILITY.
476 xi ⟨line-break⟩
478 (init control command)
479 Initialize device. This is the third command of the prologue.
480 xp ⟨line-break⟩
482 (pause control command)
483 Parsed but ignored. The classical documentation reads pause
484 device, can be restarted.
485 xr n h v⟨line-break⟩
487 (resolution control command)
488 Resolution is n, while h is the minimal horizontal motion, and v
489 the minimal vertical motion possible with this device; all argu‐
490 ments are positive integers in basic units u per inch. This is
491 the second command of the prologue.
492 xS n⟨line-break⟩
494 (Slant control command)
495 Set slant to n degrees (an integer in basic units u).
496 xs ⟨line-break⟩
498 (stop control command)
499 Terminates the processing of the current file; issued as the
500 last command of any intermediate troff output.
501 xt ⟨line-break⟩
503 (trailer control command)
504 Generate trailer information, if any. In groff, this is actu‐
505 ally just ignored.
506 xT xxx⟨line-break⟩
508 (Typesetter control command)
509 Set name of device to word xxx, a sequence of characters ended
510 by the next whitespace character. The possible device names
511 coincide with those from the groff -T option. This is the first
512 command of the prologue.
513 xu n⟨line-break⟩
515 (underline control command)
516 Configure underlining of spaces. If n is 1, start underlining
517 of spaces; if n is 0, stop underlining of spaces. This is
518 needed for the cu request in nroff mode and is ignored other‐
519 wise. This command is a groff extension.
520 xX anything⟨line-break⟩
522 (X-escape control command)
523 Send string anything uninterpreted to the device. If the line
524 following this command starts with a + character this line is
525 interpreted as a continuation line in the following sense. The
526 + is ignored, but a newline character is sent instead to the
527 device, the rest of the line is sent uninterpreted. The same
528 applies to all following lines until the first character of a
529 line is not a + character. This command is generated by the
530 groff escape sequence \X. The line-continuing feature is a
531 groff extension.
532 Obsolete Command
534 In classical troff output, emitting a single glyph was mostly done by a
535 very strange command that combined a horizontal move and the printing
536 of a glyph. It didn't have a command code, but is represented by a
537 3-character argument consisting of exactly 2 digits and a character.
538 ddc Move right dd (exactly two decimal digits) basic units u, then
540 print glyph with single-letter name c.
541 In groff, arbitrary syntactical space around and within this
543 command is allowed to be added. Only when a preceding command
544 on the same line ends with an argument of variable length a sep‐
545 arating space is obligatory. In classical troff, large clusters
546 of these and other commands were used, mostly without spaces;
547 this made such output almost unreadable.
548 For modern high-resolution devices, this command does not make sense
550 because the width of the glyphs can become much larger than two decimal
551 digits. In groff, this is only used for the devices X75, X75-12, X100,
552 and X100-12. For other devices, the commands t and u provide a better
553 functionality.
554
556 The roff postprocessors are programs that have the task to translate
557 the intermediate output into actions that are sent to a device. A
558 device can be some piece of hardware such as a printer, or a software
559 file format suitable for graphical or text processing. The groff sys‐
560 tem provides powerful means that make the programming of such postpro‐
561 cessors an easy task.
562 There is a library function that parses the intermediate output and
564 sends the information obtained to the device via methods of a class
565 with a common interface for each device. So a groff postprocessor must
566 only redefine the methods of this class. For details, see the refer‐
567 ence in section FILES.
568
570 This section presents the intermediate output generated from the same
571 input for three different devices. The input is the sentence hell
572 world fed into groff on the command line.
573 · High-resolution device ps
575 shell> echo "hell world" | groff -Z -T ps
577 x T ps
579 x res 72000 1 1
580 x init
581 p1
582 x font 5 TR
583 f5
584 s10000
585 V12000
586 H72000
587 thell
588 wh2500
589 tw
590 H96620
591 torld
592 n12000 0
593 x trailer
594 V792000
595 x stop
596 This output can be fed into the postprocessor grops(1) to get its rep‐
598 resentation as a PostScript file, or gropdf(1) to output directly to
599 PDF.
600 · Low-resolution device latin1
602 This is similar to the high-resolution device except that the posi‐
604 tioning is done at a minor scale. Some comments (lines starting with
605 #) were added for clarification; they were not generated by the for‐
606 matter.
607 shell> "hell world" | groff -Z -T latin1
609 # prologue
611 x T latin1
612 x res 240 24 40
613 x init
614 # begin a new page
615 p1
616 # font setup
617 x font 1 R
618 f1
619 s10
620 # initial positioning on the page
621 V40
622 H0
623 # write text `hell'
624 thell
625 # inform about a space, and do it by a horizontal jump
626 wh24
627 # write text `world'
628 tworld
629 # announce line break, but do nothing because ...
630 n40 0
631 # ... the end of the document has been reached
632 x trailer
633 V2640
634 x stop
635 This output can be fed into the postprocessor grotty(1) to get a for‐
637 matted text document.
638 · Classical style output
640 As a computer monitor has a very low resolution compared to modern
642 printers the intermediate output for the X devices can use the jump-
643 and-write command with its 2-digit displacements.
644 shell> "hell world" | groff -Z -T X100
646 x T X100
648 x res 100 1 1
649 x init
650 p1
651 x font 5 TR
652 f5
653 s10
654 V16
655 H100
656 # write text with old-style jump-and-write command
657 ch07e07l03lw06w11o07r05l03dh7
658 n16 0
659 x trailer
660 V1100
661 x stop
662 This output can be fed into the postprocessor xditview(1x) or
664 gxditview(1) for displaying in X.
665 Due to the obsolete jump-and-write command, the text clusters in the
667 classical output are almost unreadable.
668
670 The intermediate output language of the classical troff was first docu‐
671 mented in [CSTR #97]. The groff intermediate output format is compati‐
672 ble with this specification except for the following features.
673 · The classical quasi device independence is not yet implemented.
675 · The old hardware was very different from what we use today. So the
677 groff devices are also fundamentally different from the ones in clas‐
678 sical troff. For example, the classical PostScript device was called
679 post and had a resolution of 720 units per inch, while groff's ps
680 device has a resolution of 72000 units per inch. Maybe, by imple‐
681 menting some rescaling mechanism similar to the classical quasi
682 device independence, these could be integrated into modern groff.
683 · The B-spline command D~ is correctly handled by the intermediate out‐
685 put parser, but the drawing routines aren't implemented in some of
686 the postprocessor programs.
687 · The argument of the commands s and x H has the implicit unit scaled
689 point z in groff, while classical troff had point (p). This isn't an
690 incompatibility, but a compatible extension, for both units coincide
691 for all devices without a sizescale parameter, including all classi‐
692 cal and the groff text devices. The few groff devices with a
693 sizescale parameter either did not exist, had a different name, or
694 seem to have had a different resolution. So conflicts with classical
695 devices are very unlikely.
696 · The position changing after the commands Dp, DP, and Dt is illogical,
698 but as old versions of groff used this feature it is kept for compat‐
699 ibility reasons.
700 The differences between groff and classical troff are documented in
702 groff_diff(7).
703
705 /usr/share/groff/1.22.2/font/devname/DESC
706 Device description file for device name.
707 ⟨groff-source-dir⟩/src/libs/libdriver/input.cpp
709 Defines the parser and postprocessor for the intermediate out‐
710 put. It is located relative to the top directory of the groff
711 source tree. This parser is the definitive specification of the
712 groff intermediate output format.
713
715 A reference like groff(7) refers to a manual page; here groff in sec‐
716 tion 7 of the man-page documentation system. To read the example, look
717 up section 7 in your desktop help system or call from the shell prompt
718 shell> man 7 groff
720 For more details, see man(1).
722 groff(1)
724 option -Z and further readings on groff.
725 groff(7)
727 for details of the groff language such as numerical units and
728 escape sequences.
729 groff_font(5)
731 for details on the device scaling parameters of the DESC file.
732 troff(1)
734 generates the device-independent intermediate output.
735 roff(7)
737 for historical aspects and the general structure of roff sys‐
738 tems.
739 groff_diff(7)
741 The differences between the intermediate output in groff and
742 classical troff.
743 gxditview(1)
745 Viewer for the intermediate output.
746 grodvi(1), grohtml(1), grolbp(1), grolj4(1), grops(1), grotty(1)
748 the groff postprocessor programs.
749 For a treatment of all aspects of the groff system within a single doc‐
751 ument, see the groff info file. It can be read within the integrated
752 help systems, within emacs(1) or from the shell prompt by
753 shell> info groff
754 The classical troff output language is described in two AT&T Bell Labs
756 CSTR documents available on-line at Bell Labs CSTR site ⟨http://
757 cm.bell-labs.com/cm/cs/cstr.html⟩.
758 [CSTR #97]
760 A Typesetter-independent TROFF by Brian Kernighan is the origi‐
761 nal and most comprehensive documentation on the output language;
762 see CSTR #97 ⟨http://cm.bell-labs.com/cm/cs/cstr/97.ps.gz⟩.
763 [CSTR #54]
765 The 1992 revision of the Nroff/Troff User's Manual by J. F.
766 Ossanna and Brian Kernighan isn't as comprehensive as [CSTR #97]
767 regarding the output language; see CSTR #54 ⟨http://cm.bell-
768 labs.com/cm/cs/cstr/54.ps.gz⟩.
769
771 Copyright (C) 1989, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
772 2009 Free Software Foundation, Inc.
773 This document is distributed under the terms of the FDL (GNU Free Docu‐
775 mentation License) version 1.3 or later. You should have received a
776 copy of the FDL with this package; it is also available on-line at the
777 GNU copyleft site ⟨http://www.gnu.org/copyleft/fdl.html⟩.
778 This document is part of groff, the GNU roff distribution. It is based
780 on a former version - published under the GPL - that described only
781 parts of the groff extensions of the output language. It was rewritten
782 in 2002 by Bernd Warken and is maintained by Werner Lemberg
783 ⟨wl@gnu.org⟩.
784Groff Version 1.22.2 7 February 2013 GROFF_OUT(5)