1groff_out(5) File Formats Manual groff_out(5)
2
6 groff_out - GNU roff intermediate output format
7
9 The fundamental operation of the troff(1) formatter is the translation
10 of the groff(7) input language into a series of instructions concerned
11 primarily with placing glyphs or geometric objects at specific posi‐
12 tions on a rectangular page. In the following discussion, the term
13 command refers to this intermediate output language, never to the
14 groff(7) language intended for use by document authors. Intermediate
15 output commands comprise several categories: glyph output; font, color,
16 and text size selection; motion of the printing position; page advance‐
17 ment; drawing of geometric primitives; and device control commands, a
18 catch-all for other operations. The last includes directives to start
19 and stop output, identify the intended output device, and embed URL hy‐
20 perlinks in supported output formats.
21 Because the front-end command groff(1) is a wrapper that normally runs
23 the troff formatter to generate intermediate output and an output
24 driver (“postprocessor”) to consume it, users normally do not encounter
25 this language. The groff program's -Z option inhibits postprocessing
26 such that this intermediate output is sent to the standard output
27 stream as when troff is run manually.
28 groff's intermediate output facilitates the development of output driv‐
30 ers and other postprocessors by offering a common programming inter‐
31 face. It is an extension of the page description language developed by
32 Brian Kernighan for AT&T device-independent troff circa 1980. Where a
33 distinction is necessary, we will say “troff output” to describe the
34 output of GNU troff, and “intermediate output” to denote the language
35 accepted by the parser implemented in groff's internal C++ library used
36 by most of its output drivers.
37
39 During the run of troff, the roff input is cracked down to the informa‐
40 tion on what has to be printed at what position on the intended device.
41 So the language of the intermediate output format can be quite small.
42 Its only elements are commands with or without arguments. In this doc‐
43 ument, the term “command” always refers to the intermediate output lan‐
44 guage, never to the roff language used for document formatting. There
45 are commands for positioning and text writing, for drawing, and for de‐
46 vice controlling.
47 Separation
49 Classical troff output had strange requirements on whitespace. The
50 groff output parser, however, is smart about whitespace by making it
51 maximally optional. The whitespace characters, i.e., the tab, space,
52 and newline characters, always have a syntactical meaning. They are
53 never printable because spacing within the output is always done by po‐
54 sitioning commands.
55 Any sequence of space or tab characters is treated as a single syntac‐
57 tical space. It separates commands and arguments, but is only required
58 when there would occur a clashing between the command code and the ar‐
59 guments without the space. Most often, this happens when variable
60 length command names, arguments, argument lists, or command clusters
61 meet. Commands and arguments with a known, fixed length need not be
62 separated by syntactical space.
63 A line break is a syntactical element, too. Every command argument can
65 be followed by whitespace, a comment, or a newline character. Thus a
66 syntactical line break is defined to consist of optional syntactical
67 space that is optionally followed by a comment, and a newline charac‐
68 ter.
69 The normal commands, those for positioning and text, consist of a sin‐
71 gle letter taking a fixed number of arguments. For historical reasons,
72 the parser allows stacking of such commands on the same line, but for‐
73 tunately, in groff intermediate output, every command with at least one
74 argument is followed by a line break, thus providing excellent read‐
75 ability.
76 The other commands — those for drawing and device controlling — have a
78 more complicated structure; some recognize long command names, and some
79 take a variable number of arguments. So all D and x commands were de‐
80 signed to request a syntactical line break after their last argument.
81 Only one command, ‘x X’ has an argument that can stretch over several
82 lines, all other commands must have all of their arguments on the same
83 line as the command, i.e., the arguments may not be split by a line
84 break.
85 Lines containing only spaces and/or a comment are treated as empty and
87 ignored.
88 Argument units
90 Some commands accept integer arguments that represent measurements, but
91 the scaling units of the formatter's language are never used. Most
92 commands assume a scaling unit of “u” (basic units), and others use “z”
93 (scaled points); These are defined by the parameters specified in the
94 device's DESC file; see groff_font(5) and, for more on scaling units,
95 groff(7) and Groff: The GNU Implementation of troff, the groff Texinfo
96 manual. Color-related commands use dimensionless integers.
97 Note that single characters can have the eighth bit set, as can the
99 names of fonts and special characters (this is, glyphs). The names of
100 glyphs and fonts can be of arbitrary length. A glyph that is to be
101 printed will always be in the current font.
102 A string argument is always terminated by the next whitespace character
104 (space, tab, or newline); an embedded # character is regarded as part
105 of the argument, not as the beginning of a comment command. An integer
106 argument is already terminated by the next non-digit character, which
107 then is regarded as the first character of the next argument or com‐
108 mand.
109 Document parts
111 A correct intermediate output document consists of two parts, the pro‐
112 logue and the body.
113 The task of the prologue is to set the general device parameters using
115 three exactly specified commands. The groff prologue is guaranteed to
116 consist of the following three lines (in that order):
117 x T device
119 x res n h v
120 x init
121 with the arguments set as outlined in subsection “Device Control Com‐
123 mands” below. However, the parser for the intermediate output format
124 is able to swallow additional whitespace and comments as well.
125 The body is the main section for processing the document data. Syntac‐
127 tically, it is a sequence of any commands different from the ones used
128 in the prologue. Processing is terminated as soon as the first x stop
129 command is encountered; the last line of any groff intermediate output
130 always contains such a command.
131 Semantically, the body is page oriented. A new page is started by a
133 p command. Positioning, writing, and drawing commands are always done
134 within the current page, so they cannot occur before the first p com‐
135 mand. Absolute positioning (by the H and V commands) is done relative
136 to the current page, all other positioning is done relative to the cur‐
137 rent location within this page.
138
140 This section describes all intermediate output commands, the classical
141 commands as well as the groff extensions.
142 Comment command
144 #anything⟨line-break⟩
145 A comment. Ignore any characters from the # character up to the
146 next newline. Each comment can be preceded by arbitrary syntac‐
147 tical space; every command can be terminated by a comment.
148 Simple commands
150 The commands in this subsection have a command code consisting of a
151 single character, taking a fixed number of arguments. Most of them are
152 commands for positioning and text writing. These commands are smart
153 about whitespace. Optionally, syntactical space can be inserted be‐
154 fore, after, and between the command letter and its arguments. All of
155 these commands are stackable, i.e., they can be preceded by other sim‐
156 ple commands or followed by arbitrary other commands on the same line.
157 A separating syntactical space is necessary only when two integer argu‐
158 ments would clash or if the preceding argument ends with a string argu‐
159 ment.
160 C id⟨white-space⟩
162 Typeset the glyph of the special character id. Trailing syntac‐
163 tical space is necessary to allow special character names of ar‐
164 bitrary length. The drawing position is not advanced.
165 c c Typeset the glyph of the ordinary character character c. The
167 drawing position is not advanced.
168 f n Select the font mounted at position n. n cannot be negative.
170 H n Horizontally move the drawing position to n basic units from the
172 left edge of the page. n cannot be negative.
173 h n Move the drawing position right n basic units. AT&T troff al‐
175 lowed negative n; GNU troff does not produce such values, but
176 groff's output driver library handles them.
177 m scheme [component ...]
179 Select the stroke color using the components in the color space
180 scheme. Each component is an integer between 0 and 65536. The
181 quantity of components and their meanings vary with each scheme.
182 This command is a groff extension.
183 mc cyan magenta yellow
185 Use the CMY color scheme with components cyan, magenta,
186 and yellow.
187 md Use the default color (no components; black in most
189 cases).
190 mg gray
192 Use a grayscale color scheme with a component ranging be‐
193 tween 0 (black) and 65536 (white).
194 mk cyan magenta yellow black
196 Use the CMYK color scheme with components cyan, magenta,
197 yellow, and black.
198 mr red green blue
200 Use the RGB color scheme with components red, green, and
201 blue.
202 N n Typeset the glyph with index n in the current font. n is nor‐
204 mally a non-negative integer. The drawing position is not ad‐
205 vanced. The html and xhtml devices use this command with nega‐
206 tive n to produce unbreakable space; the absolute value of n is
207 taken and interpreted in basic units.
208 n b a Indicate a break. No action is performed; the command is
210 present to make the output more easily parsed. The integers b
211 and a describe the vertical space amounts before and after the
212 break, respectively. GNU troff issues this command but groff's
213 output driver library ignores it. See v and V.
214 p n Begin a new page, setting its number to n. Each page is inde‐
216 pendent, even from those using the same number. The vertical
217 drawing position is set to 0. All positioning, writing, and
218 drawing commands are interpreted in the context of a page, so a
219 p command must precede them.
220 s n Set type size to n scaled points (unit z in GNU troff). AT&T
222 troff used unscaled points (p) instead; see section “Compatibil‐
223 ity” below.
224 t xyz...⟨white-space⟩
226 t xyz... dummy-arg⟨white-space⟩
227 Typeset word xyz; that is, set a sequence of ordinary glyphs
228 named x, y, z, ..., terminated by a space or newline; an op‐
229 tional second integer argument is ignored (this allows the for‐
230 matter to generate an even number of arguments). Each glyph is
231 set at the current drawing position, and the position is then
232 advanced horizontally by the glyph's width. A glyph's width is
233 read from its metrics in the font description file, scaled to
234 the current type size, and rounded to a multiple of the horizon‐
235 tal motion quantum. Use the C command to emplace glyphs of spe‐
236 cial characters. The t command is a groff extension and is out‐
237 put only for devices whose DESC file contains the tcommand di‐
238 rective; see groff_font(5).
239 u n xyz...
241 u xyz... dummy-arg⟨white-space⟩
242 Typeset word xyz with track kerning. As t, but after placing
243 each glyph, the drawing position is further advanced horizon‐
244 tally by n basic units. The u command is a groff extension and
245 is output only for devices whose DESC file contains the tcommand
246 directive; see groff_font(5).
247 V n Vertically move the drawing position to n basic units from the
249 top edge of the page. n cannot be negative.
250 v n Move the drawing position down n basic units. AT&T troff al‐
252 lowed negative n; GNU troff does not produce such values, but
253 groff's output driver library handles them.
254 w Indicate an inter-word space. No action is performed; the com‐
256 mand is present to make the output more easily parsed. Only ad‐
257 justable, breakable inter-word spaces are thus described; those
258 resulting from \~ or horizontal motion escape sequences are not.
259 GNU troff issues this command but groff's output driver library
260 ignores it. See h and H.
261 Graphics commands
263 Each graphics or drawing command in the intermediate output starts with
264 the letter D followed by one or two characters that specify a subcom‐
265 mand; this is followed by a fixed or variable number of integer argu‐
266 ments that are separated by a single space character. A D command may
267 not be followed by another command on the same line (apart from a com‐
268 ment), so each D command is terminated by a syntactical line break.
269 troff output follows the classical spacing rules (no space between com‐
271 mand and subcommand, all arguments are preceded by a single space char‐
272 acter), but the parser allows optional space between the command let‐
273 ters and makes the space before the first argument optional. As usual,
274 each space can be any sequence of tab and space characters.
275 Some graphics commands can take a variable number of arguments. In
277 this case, they are integers representing a size measured in basic
278 units u. The h arguments stand for horizontal distances where positive
279 means right, negative left. The v arguments stand for vertical dis‐
280 tances where positive means down, negative up. All these distances are
281 offsets relative to the current location.
282 Unless indicated otherwise, each graphics command directly corresponds
284 to a similar groff \D escape sequence; see groff(7).
285 Unknown D commands are assumed to be device-specific. Its arguments
287 are parsed as strings; the whole information is then sent to the post‐
288 processor.
289 In the following command reference, the syntax element ⟨line-break⟩
291 means a syntactical line break as defined in subsection “Separation”
292 above.
293 D~ h1 v1 h2 v2 ... hn vn⟨line-break⟩
295 Draw B-spline from current position to offset (h1, v1), then to
296 offset (h2, v2) if given, etc., up to (hn, vn). This command
297 takes a variable number of argument pairs; the current position
298 is moved to the terminal point of the drawn curve.
299 Da h1 v1 h2 v2⟨line-break⟩
301 Draw arc from current position to (h1, v1)+(h2, v2) with center
302 at (h1, v1); then move the current position to the final point
303 of the arc.
304 DC d⟨line-break⟩
306 DC d dummy-arg⟨line-break⟩
307 Draw a solid circle using the current fill color with diameter d
308 (integer in basic units u) with leftmost point at the current
309 position; then move the current position to the rightmost point
310 of the circle. An optional second integer argument is ignored
311 (this allows the formatter to generate an even number of argu‐
312 ments). This command is a groff extension.
313 Dc d⟨line-break⟩
315 Draw circle line with diameter d (integer in basic units u) with
316 leftmost point at the current position; then move the current
317 position to the rightmost point of the circle.
318 DE h v⟨line-break⟩
320 Draw a solid ellipse in the current fill color with a horizontal
321 diameter of h and a vertical diameter of v (both integers in ba‐
322 sic units u) with the leftmost point at the current position;
323 then move to the rightmost point of the ellipse. This command
324 is a groff extension.
325 De h v⟨line-break⟩
327 Draw an outlined ellipse with a horizontal diameter of h and a
328 vertical diameter of v (both integers in basic units u) with the
329 leftmost point at current position; then move to the rightmost
330 point of the ellipse.
331 DF color-scheme [component ...]⟨line-break⟩
333 Set fill color for solid drawing objects using different color
334 schemes; the analogous command for setting the color of text,
335 line graphics, and the outline of graphic objects is m. The
336 color components are specified as integer arguments between 0
337 and 65536. The number of color components and their meaning
338 vary for the different color schemes. These commands are gener‐
339 ated by the groff escape sequences \D'F ...' and \M (with no
340 other corresponding graphics commands). This command is a groff
341 extension.
342 DFc cyan magenta yellow⟨line-break⟩
344 Set fill color for solid drawing objects using the CMY
345 color scheme, having the 3 color components cyan, ma‐
346 genta, and yellow.
347 DFd ⟨line-break⟩
349 Set fill color for solid drawing objects to the default
350 fill color value (black in most cases). No component ar‐
351 guments.
352 DFg gray⟨line-break⟩
354 Set fill color for solid drawing objects to the shade of
355 gray given by the argument, an integer between 0 (black)
356 and 65536 (white).
357 DFk cyan magenta yellow black⟨line-break⟩
359 Set fill color for solid drawing objects using the CMYK
360 color scheme, having the 4 color components cyan, ma‐
361 genta, yellow, and black.
362 DFr red green blue⟨line-break⟩
364 Set fill color for solid drawing objects using the RGB
365 color scheme, having the 3 color components red, green,
366 and blue.
367 Df n⟨line-break⟩
369 The argument n must be an integer in the range -32767 to 32767.
370 0≤n≤1000
372 Set the color for filling solid drawing objects to a
373 shade of gray, where 0 corresponds to solid white, 1000
374 (the default) to solid black, and values in between to
375 intermediate shades of gray; this is obsoleted by command
376 DFg.
377 n<0 or n>1000
379 Set the filling color to the color that is currently be‐
380 ing used for the text and the outline, see command m.
381 For example, the command sequence
382 mg 0 0 65536
384 Df -1
385 sets all colors to blue.
387 This command is a groff extension.
389 Dl h v⟨line-break⟩
391 Draw line from current position to offset (h, v) (integers in
392 basic units u); then set current position to the end of the
393 drawn line.
394 Dp h1 v1 h2 v2 ... hn vn⟨line-break⟩
396 Draw a polygon line from current position to offset (h1, v1),
397 from there to offset (h2, v2), etc., up to offset (hn, vn), and
398 from there back to the starting position. For historical rea‐
399 sons, the position is changed by adding the sum of all arguments
400 with odd index to the current horizontal position and the even
401 ones to the vertical position. Although this doesn't make sense
402 it is kept for compatibility. This command is a groff exten‐
403 sion.
404 DP h1 v1 h2 v2 ... hn vn⟨line-break⟩
406 The same macro as the corresponding Dp command with the same ar‐
407 guments, but draws a solid polygon in the current fill color
408 rather than an outlined polygon. The position is changed in the
409 same way as with Dp. This command is a groff extension.
410 Dt n⟨line-break⟩
412 Set the current line thickness to n (an integer in basic
413 units u) if n>0; if n=0 select the smallest available line
414 thickness; otherwise, the line thickness is made proportional to
415 the type size, which is the default. For historical reasons,
416 the horizontal position is changed by adding the argument to the
417 current horizontal position, while the vertical position is not
418 changed. Although this doesn't make sense, it is kept for com‐
419 patibility. This command is a groff extension.
420 Device control commands
422 Each device control command starts with the letter x followed by a
423 space character (optional or arbitrary space/tab in groff) and a sub‐
424 command letter or word; each argument (if any) must be preceded by a
425 syntactical space. All x commands are terminated by a syntactical line
426 break; no device control command can be followed by another command on
427 the same line (except a comment).
428 The subcommand is basically a single letter, but to increase readabil‐
430 ity, it can be written as a word, i.e., an arbitrary sequence of char‐
431 acters terminated by the next tab, space, or newline character. All
432 characters of the subcommand word but the first are simply ignored.
433 For example, troff outputs the initialization command x i as x init and
434 the resolution command x r as x res. But writings like x i_like_groff
435 and x roff_is_groff are accepted as well to mean the same commands.
436 In the following, the syntax element ⟨line-break⟩ means a syntactical
438 line break as defined in subsection “Separation” above.
439 xF name⟨line-break⟩
441 (Filename control command)
442 Use name as the intended name for the current file in error re‐
443 ports. This is useful for remembering the original file name
444 when groff uses an internal piping mechanism. The input file is
445 not changed by this command. This command is a groff extension.
446 xf n s⟨line-break⟩
448 (font control command)
449 Mount font position n (a non-negative integer) with font named s
450 (a text word); see groff_font(5).
451 xH n⟨line-break⟩
453 (Height control command)
454 Set character height to n (a positive integer in scaled
455 points z). Classical troff used the unit points (p) instead;
456 see section “Compatibility” below.
457 xi ⟨line-break⟩
459 (init control command)
460 Initialize device. This is the third command of the prologue.
461 xp ⟨line-break⟩
463 (pause control command)
464 Parsed but ignored. The classical documentation reads pause de‐
465 vice, can be restarted.
466 xr n h v⟨line-break⟩
468 (resolution control command)
469 Resolution is n, while h is the minimal horizontal motion, and v
470 the minimal vertical motion possible with this device; all argu‐
471 ments are positive integers in basic units u per inch. This is
472 the second command of the prologue.
473 xS n⟨line-break⟩
475 (Slant control command)
476 Set slant to n degrees (an integer in basic units u).
477 xs ⟨line-break⟩
479 (stop control command)
480 Terminates the processing of the current file; issued as the
481 last command of any intermediate troff output.
482 xt ⟨line-break⟩
484 (trailer control command)
485 Generate trailer information, if any. In groff, this is cur‐
486 rently ignored.
487 xT xxx⟨line-break⟩
489 (Typesetter control command)
490 Set the name of the output driver to xxx, a sequence of non-
491 whitespace characters terminated by whitespace. The possible
492 names correspond to those of groff's -T option. This is the
493 first command of the prologue.
494 xu n⟨line-break⟩
496 (underline control command)
497 Configure underlining of spaces. If n is 1, start underlining
498 of spaces; if n is 0, stop underlining of spaces. This is
499 needed for the cu request in nroff mode and is ignored other‐
500 wise. This command is a groff extension.
501 xX anything⟨line-break⟩
503 (X-escape control command)
504 Send string anything uninterpreted to the device. If the line
505 following this command starts with a + character this line is
506 interpreted as a continuation line in the following sense. The
507 + is ignored, but a newline character is sent instead to the de‐
508 vice, the rest of the line is sent uninterpreted. The same ap‐
509 plies to all following lines until the first character of a line
510 is not a + character. This command is generated by the groff
511 escape sequence \X. The line-continuing feature is a groff ex‐
512 tension.
513 Obsolete command
515 In classical troff output, emitting a single glyph was mostly done by a
516 very strange command that combined a horizontal move and the printing
517 of a glyph. It didn't have a command code, but is represented by a
518 3-character argument consisting of exactly 2 digits and a character.
519 ddc Move right dd (exactly two decimal digits) basic units u, then
521 print glyph with single-letter name c.
522 In groff, arbitrary syntactical space around and within this
524 command is allowed to be added. Only when a preceding command
525 on the same line ends with an argument of variable length a sep‐
526 arating space is obligatory. In classical troff, large clusters
527 of these and other commands were used, mostly without spaces;
528 this made such output almost unreadable.
529 For modern high-resolution devices, this command does not make sense
531 because the width of the glyphs can become much larger than two decimal
532 digits. In groff, it is used only for output to the X75, X75-12, X100,
533 and X100-12 devices. For others, the commands t and u provide greater
534 functionality and superior troubleshooting capacity.
535
537 The roff postprocessors are programs that have the task to translate
538 the intermediate output into actions that are sent to a device. A de‐
539 vice can be some piece of hardware such as a printer, or a software
540 file format suitable for graphical or text processing. The groff sys‐
541 tem provides powerful means that make the programming of such postpro‐
542 cessors an easy task.
543 There is a library function that parses the intermediate output and
545 sends the information obtained to the device via methods of a class
546 with a common interface for each device. So a groff postprocessor must
547 only redefine the methods of this class. For details, see the refer‐
548 ence in section “Files” below.
549
551 This section presents the intermediate output generated from the same
552 input for three different devices. The input is the sentence hell
553 world fed into groff on the command line.
554 • High-resolution device ps
556 shell> echo "hell world" | groff -Z -T ps
558 x T ps
560 x res 72000 1 1
561 x init
562 p1
563 x font 5 TR
564 f5
565 s10000
566 V12000
567 H72000
568 thell
569 wh2500
570 tw
571 H96620
572 torld
573 n12000 0
574 x trailer
575 V792000
576 x stop
577 This output can be fed into the postprocessor grops(1) to get its rep‐
579 resentation as a PostScript file, or gropdf(1) to output directly to
580 PDF.
581 • Low-resolution device latin1
583 This is similar to the high-resolution device except that the posi‐
585 tioning is done at a minor scale. Some comments (lines starting with
586 #) were added for clarification; they were not generated by the for‐
587 matter.
588 shell> "hell world" | groff -Z -T latin1
590 # prologue
592 x T latin1
593 x res 240 24 40
594 x init
595 # begin a new page
596 p1
597 # font setup
598 x font 1 R
599 f1
600 s10
601 # initial positioning on the page
602 V40
603 H0
604 # write text 'hell'
605 thell
606 # inform about a space, and do it by a horizontal jump
607 wh24
608 # write text 'world'
609 tworld
610 # announce line break, but do nothing because ...
611 n40 0
612 # ... the end of the document has been reached
613 x trailer
614 V2640
615 x stop
616 This output can be fed into the postprocessor grotty(1) to get a for‐
618 matted text document.
619 • Classical style output
621 As a computer monitor has a very low resolution compared to modern
623 printers the intermediate output for the X devices can use the jump-
624 and-write command with its 2-digit displacements.
625 shell> "hell world" | groff -Z -T X100
627 x T X100
629 x res 100 1 1
630 x init
631 p1
632 x font 5 TR
633 f5
634 s10
635 V16
636 H100
637 # write text with old-style jump-and-write command
638 ch07e07l03lw06w11o07r05l03dh7
639 n16 0
640 x trailer
641 V1100
642 x stop
643 This output can be fed into the postprocessor xditview(1x) or
645 gxditview(1) for displaying in X.
646 Due to the obsolete jump-and-write command, the text clusters in the
648 classical output are almost unreadable.
649
651 The intermediate output language of the classical troff was first docu‐
652 mented in [CSTR #97]. The groff intermediate output format is compati‐
653 ble with this specification except for the following features.
654 • The classical quasi device independence is not yet implemented.
656 • The old hardware was very different from what we use today. So the
658 groff devices are also fundamentally different from the ones in clas‐
659 sical troff. For example, the classical PostScript device was called
660 post and had a resolution of 720 units per inch, while groff's ps de‐
661 vice has a resolution of 72000 units per inch. Maybe, by implement‐
662 ing some rescaling mechanism similar to the classical quasi device
663 independence, these could be integrated into modern groff.
664 • The B-spline command D~ is correctly handled by the intermediate out‐
666 put parser, but the drawing routines aren't implemented in some of
667 the postprocessor programs.
668 • The argument of the commands s and x H has the implicit unit scaled
670 point z in groff, while classical troff had point (p). This isn't an
671 incompatibility, but a compatible extension, for both units coincide
672 for all devices without a sizescale parameter, including all classi‐
673 cal and the groff text devices. The few groff devices with a
674 sizescale parameter either did not exist, had a different name, or
675 seem to have had a different resolution. So conflicts with classical
676 devices are very unlikely.
677 • The position changing after the commands Dp, DP, and Dt is illogical,
679 but as old versions of groff used this feature it is kept for compat‐
680 ibility reasons.
681 The differences between groff and classical troff are documented in
683 groff_diff(7).
684
686 /usr/share/groff/1.23.0/font/devname/DESC
687 describes the output device name.
688
690 James Clark wrote an early version of this document, which described
691 only the differences between AT&T device-independent troff's output
692 format and that of GNU roff. The present version was completely
693 rewritten in 2001 by Bernd Warken ⟨groff-bernd.warken-72@web.de⟩.
694
696 Groff: The GNU Implementation of troff, by Trent A. Fisher and Werner
697 Lemberg, is the primary groff manual. You can browse it interactively
698 with “info groff”.
699 “Troff User's Manual” by Joseph F. Ossanna, 1976 (revised by Brian W.
701 Kernighan, 1992), AT&T Bell Laboratories Computing Science Technical
702 Report No. 54, widely called simply “CSTR #54”, documents the language,
703 device and font description file formats, and device-independent output
704 format referred to collectively in groff documentation as “AT&T troff”.
705 “A Typesetter-independent TROFF” by Brian W. Kernighan, 1982, AT&T Bell
707 Laboratories Computing Science Technical Report No. 97, provides addi‐
708 tional insights into the device and font description file formats and
709 device-independent output format.
710 groff(1)
712 documents the -Z option and contains pointers to further groff
713 documentation.
714 groff(7)
716 describes the groff language, including its escape sequences and
717 system of units.
718 groff_font(5)
720 details the device scaling parameters of device DESC files.
721 troff(1)
723 generates the device-independent intermediate output documented
724 here.
725 roff(7)
727 presents historical aspects and the general structure of roff
728 systems.
729 groff_diff(7)
731 enumerates differences between the intermediate output produced
732 by AT&T troff and that of groff.
733 gxditview(1)
735 is a viewer for intermediate output.
736 Roff.js
738 ⟨https://github.com/Alhadis/Roff.js/⟩ is a viewer for intermedi‐
739 ate output written in JavaScript.
740 grodvi(1), grohtml(1), grolbp(1), grolj4(1), gropdf(1), grops(1), and
742 grotty(1) are groff postprocessors.
743groff 1.23.0 2 November 2023 groff_out(5)