1ROFF(7) Miscellaneous Information Manual ROFF(7)
2
6 roff - concepts and history of roff typesetting
7
9 roff is the general name for a set of type-setting programs, known
10 under names like troff, nroff, ditroff, groff, etc. A roff type-set‐
11 ting system consists of an extensible text formatting language and a
12 set of programs for printing and converting to other text formats.
13 Traditionally, it is the main text processing system of Unix; every
14 Unix-like operating system still distributes a roff system as a core
15 package.
16 The most common roff system today is the free software implementation
18 GNU roff, groff(1). The pre-groff implementations are referred to as
19 classical (dating back as long as 1973). groff implements the look-
20 and-feel and functionality of its classical ancestors, but has many
21 extensions. As groff is the only roff system that is available for
22 every (or almost every) computer system it is the de-facto roff stan‐
23 dard today.
24 In some ancient Unix systems, there was a binary called roff that
26 implemented the even more ancient runoff of the Multics operating sys‐
27 tem, cf. section HISTORY. The functionality of this program was very
28 restricted even in comparison to ancient troff; it is not supported any
29 longer. Consequently, in this document, the term roff always refers to
30 the general meaning of roff system, not to the ancient roff binary.
31 In spite of its age, roff is in wide use today, for example, the manual
33 pages on UNIX systems (man pages), many software books, system documen‐
34 tation, standards, and corporate documents are written in roff. The
35 roff output for text devices is still unmatched, and its graphical out‐
36 put has the same quality as other free type-setting programs and is
37 better than some of the commercial systems.
38 The most popular application of roff is the concept of manual pages or
40 shortly man pages; this is the standard documentation system on many
41 operating systems.
42 This document describes the historical facts around the development of
44 the roff system; some usage aspects common to all roff versions,
45 details on the roff pipeline, which is usually hidden behind front-ends
46 like groff(1); an general overview of the formatting language; some
47 tips for editing roff files; and many pointers to further readings.
48
50 The roff text processing system has a very long history, dating back to
51 the 1960s. The roff system itself is intimately connected to the Unix
52 operating system, but its roots go back to the earlier operating sys‐
53 tems CTSS and Multics.
54 The Predecessor runoff
56 The evolution of roff is intimately related to the history of the oper‐
57 ating systems. Its predecessor runoff was written by Jerry Saltzer on
58 the CTSS operating system (Compatible Time Sharing System) as early as
59 1961. When CTTS was further developed into the operating system Mul‐
60 tics ⟨http://www.multicians.org⟩, the famous predecessor of Unix from
61 1963, runoff became the main format for documentation and text process‐
62 ing. Both operating systems could only be run on very expensive com‐
63 puters at that time, so they were mostly used in research and for offi‐
64 cial and military tasks.
65 The possibilities of the runoff language were quite limited as compared
67 to modern roff. Only text output was possible in the 1960s. This
68 could be implemented by a set of requests of length 2, many of which
69 are still identically used in roff. The language was modelled accord‐
70 ing to the habits of typesetting in the pre-computer age, where lines
71 starting with a dot were used in manuscripts to denote formatting
72 requests to the person who would perform the typesetting manually later
73 on.
74 The runoff program was written in the PL/1 language first, later on in
76 BCPL, the grandmother of the C programming language. In the Multics
77 operating system, the help system was handled by runoff, similar to
78 roff's task to manage the Unix manual pages. There are still documents
79 written in the runoff language; for examples see Saltzer's home page,
80 cf. section SEE ALSO.
81 The Classical nroff/troff System
83 In the 1970s, the Multics off-spring Unix became more and more popular
84 because it could be run on affordable machines and was easily available
85 for universities at that time. At MIT (the Massachusetts Institute of
86 Technology), there was a need to drive the Wang Graphic Systems CAT
87 typesetter, a graphical output device from a PDP-11 computer running
88 Unix. As runoff was too limited for this task it was further developed
89 into a more powerful text formatting system by Josef F. Osanna, a main
90 developer of the Multics operating system and programmer of several
91 runoff ports.
92 The name runoff was shortened to roff. The greatly enlarged language
94 of Osanna's concept included already all elements of a full roff sys‐
95 tem. All modern roff systems try to implement compatibility to this
96 system. So Joe Osanna can be called the father of all roff systems.
97 This first roff system had three formatter programs.
99 troff (typesetter roff) generated a graphical output for the CAT type‐
101 setter as its only device.
102 nroff produced text output suitable for terminals and line printers.
104 roff was the reimplementation of the former runoff program with its
106 limited features; this program was abandoned in later versions.
107 Today, the name roff is used to refer to a troff/nroff sytem as
108 a whole.
109 Osanna first version was written in the PDP-11 assembly language and
111 released in 1973. Brian Kernighan joined the roff development by
112 rewriting it in the C programming language. The C version was released
113 in 1975.
114 The syntax of the formatting language of the nroff/troff programs was
116 documented in the famous Troff User's Manual [CSTR #54], first pub‐
117 lished in 1976, with further revisions up to 1992 by Brian Kernighan.
118 This document is the specification of the classical troff. All later
119 roff systems tried to establish compatibility with this specification.
120 After Osanna had died in 1977 by a heart-attack at the age of about 50,
122 Kernighan went on with developing troff. The next milestone was to
123 equip troff with a general interface to support more devices, the
124 intermediate output format and the postprocessor system. This com‐
125 pleted the structure of a roff system as it is still in use today; see
126 section USING ROFF. In 1979, these novelties were described in the
127 paper [CSTR #97]. This new troff version is the basis for all existing
128 newer troff systems, including groff. On some systems, this device
129 independent troff got a binary of its own, called ditroff(7). All mod‐
130 ern troff programs already provide the full ditroff capabilities auto‐
131 matically.
132 Commercialization
134 A major degradation occurred when the easily available Unix 7 operating
135 system was commercialized. A whole bunch of divergent operating sys‐
136 tems emerged, fighting each other with incompatibilities in their
137 extensions. Luckily, the incompatibilities did not fight the original
138 troff. All of the different commercial roff systems made heavy use of
139 Osanna/Kernighan's open source code and documentation, but sold them as
140 “their” system — with only minor additions.
141 The source code of both the ancient Unix and classical troff weren't
143 available for two decades. Fortunately, Caldera bought SCO UNIX in
144 2001. In the following, Caldera made the ancient source code accessi‐
145 ble on-line for non-commercial use, cf. section SEE ALSO.
146 Free roff
148 None of the commercial roff systems could attain the status of a suc‐
149 cessor for the general roff development. Everyone was only interested
150 in their own stuff. This led to a steep downfall of the once excellent
151 Unix operating system during the 1980s.
152 As a counter-measure to the galopping commercialization, AT&T Bell Labs
154 tried to launch a rescue project with their Plan 9 operating system.
155 It is freely available for non-commercial use, even the source code,
156 but has a proprietary license that empedes the free development. This
157 concept is outdated, so Plan 9 was not accepted as a platform to bundle
158 the main-stream development.
159 The only remedy came from the emerging free operatings systems (386BSD,
161 GNU/Linux, etc.) and software projects during the 1980s and 1990s.
162 These implemented the ancient Unix features and many extensions, such
163 that the old experience is not lost. In the 21st century, Unix-like
164 systems are again a major factor in computer industry — thanks to free
165 software.
166 The most important free roff project was the GNU port of troff, created
168 by James Clark and put under the GNU Public License ⟨http://
169 www.gnu.org/copyleft⟩. It was called groff (GNU roff). See groff(1)
170 for an overview.
171 The groff system is still actively developed. It is compatible to the
173 classical troff, but many extensions were added. It is the first roff
174 system that is available on almost all operating systems — and it is
175 free. This makes groff the de-facto roff standard today.
176
178 Most people won't even notice that they are actually using roff. When
179 you read a system manual page (man page) roff is working in the back‐
180 ground. Roff documents can be viewed with a native viewer called
181 xditview(1x), a standard program of the X window distribution, see
182 X(7x). But using roff explicitly isn't difficult either.
183 Some roff implementations provide wrapper programs that make it easy to
185 use the roff system on the shell command line. For example, the GNU
186 roff implementation groff(1) provides command line options to avoid the
187 long command pipes of classical troff; a program grog(1) tries to guess
188 from the document which arguments should be used for a run of groff;
189 people who do not like specifying command line options should try the
190 groffer(1) program for graphically displaying groff files and man
191 pages.
192 The roff Pipe
194 Each roff system consists of preprocessors, roff formatter programs,
195 and a set of device postprocessors. This concept makes heavy use of
196 the piping mechanism, that is, a series of programs is called one after
197 the other, where the output of each program in the queue is taken as
198 the input for the next program.
199 sh# cat file | ... | preproc | ... | troff options | postproc
201 The preprocessors generate roff code that is fed into a roff formatter
203 (e.g. troff), which in turn generates intermediate output that is fed
204 into a device postprocessor program for printing or final output.
205 All of these parts use programming languages of their own; each lan‐
207 guage is totally unrelated to the other parts. Moreover, roff macro
208 packages that were tailored for special purposes can be included.
209 Most roff documents use the macros of some package, intermixed with
211 code for one or more preprocessors, spiced with some elements from the
212 plain roff language. The full power of the roff formatting language is
213 seldom needed by users; only programmers of macro packages need to know
214 about the gory details.
215 Preprocessors
217 A roff preprocessor is any program that generates output that syntacti‐
218 cally obeys the rules of the roff formatting language. Each preproces‐
219 sor defines a language of its own that is translated into roff code
220 when run through the preprocessor program. Parts written in these lan‐
221 guages may be included within a roff document; they are identified by
222 special roff requests or macros. Each document that is enhanced by
223 preprocessor code must be run through all corresponding preprocessors
224 before it is fed into the actual roff formatter program, for the for‐
225 matter just ignores all alien code. The preprocessor programs extract
226 and transform only the document parts that are determined for them.
227 There are a lot of free and commercial roff preprocessors. Some of
229 them aren't available on each system, but there is a small set of pre‐
230 processors that are considered as an integral part of each roff system.
231 The classical preprocessors are
232 tbl for tables
235 eqn for mathematical formulæ
236 pic for drawing diagrams
237 refer for bibliographic references
238 soelim for including macro files from standard locations
239 Other known preprocessors that are not available on all systems include
241 chem for drawing chemical formulæ.
243 grap for constructing graphical elements.
244 grn for including gremlin(1) pictures.
245 Formatter Programs
247 A roff formatter is a program that parses documents written in the roff
248 formatting language or uses some of the roff macro packages. It gener‐
249 ates intermediate output, which is intended to be fed into a single de‐
250 vice postprocessor that must be specified by a command-line option to
251 the formatter program. The documents must have been run through all
252 necessary preprocessors before.
253 The output produced by a roff formatter is represented in yet another
255 language, the intermediate output format or troff output. This lan‐
256 guage was first specified in [CSTR #97]; its GNU extension is document‐
257 ed in groff_out(5). The intermediate output language is a kind of as‐
258 sembly language compared to the high-level roff language. The generat‐
259 ed intermediate output is optimized for a special device, but the lan‐
260 guage is the same for every device.
261 The roff formatter is the heart of the roff system. The traditional
263 roff had two formatters, nroff for text devices and troff for graphical
264 devices.
265 Often, the name troff is used as a general term to refer to both for‐
267 matters.
268 Devices and Postprocessors
270 Devices are hardware interfaces like printers, text or graphical termi‐
271 nals, etc., or software interfaces such as a conversion into a differ‐
272 ent text or graphical format.
273 A roff postprocessor is a program that transforms troff output into a
275 form suitable for a special device. The roff postprocessors are like
276 device drivers for the output target.
277 For each device there is a postprocessor program that fits the device
279 optimally. The postprocessor parses the generated intermediate output
280 and generates device-specific code that is sent directly to the device.
281 The names of the devices and the postprocessor programs are not fixed
283 because they greatly depend on the software and hardware abilities of
284 the actual computer. For example, the classical devices mentioned in
285 [CSTR #54] have greatly changed since the classical times. The old
286 hardware doesn't exist any longer and the old graphical conversions
287 were quite imprecise when compared to their modern counterparts.
288 For example, the Postscript device post in classical troff had a reso‐
290 lution of 720, while groff's ps device has 72000, a refinement of fac‐
291 tor 100.
292 Today the operating systems provide device drivers for most printer-
294 like hardware, so it isn't necessary to write a special hardware post‐
295 processor for each printer.
296
298 Documents using roff are normal text files decorated by roff formatting
299 elements. The roff formatting language is quite powerful; it is almost
300 a full programming language and provides elements to enlarge the lan‐
301 guage. With these, it became possible to develop macro packages that
302 are tailored for special applications. Such macro packages are much
303 handier than plain roff. So most people will choose a macro package
304 without worrying about the internals of the roff language.
305 Macro Packages
307 Macro packages are collections of macros that are suitable to format a
308 special kind of documents in a convenient way. This greatly eases the
309 usage of roff. The macro definitions of a package are kept in a file
310 called name.tmac (classically tmac.name). All tmac files are stored in
311 one or more directories at standardized positions. Details on the nam‐
312 ing of macro packages and their placement is found in groff_tmac(5).
313 A macro package that is to be used in a document can be announced to
315 the formatter by the command line option -m, see troff(1), or it can be
316 specified within a document using the file inclusion requests of the
317 roff language, see groff(7).
318 Famous classical macro packages are man for traditional man pages, mdoc
320 for BSD-style manual pages; the macro sets for books, articles, and
321 letters are me (probably from the first name of its creator Eric All‐
322 man), ms (from Manuscript Macros), and mm (from Memorandum Macros).
323 The roff Formatting Language
325 The classical roff formatting language is documented in the Troff Us‐
326 er's Manual [CSTR #54]. The roff language is a full programming lan‐
327 guage providing requests, definition of macros, escape sequences,
328 string variables, number or size registers, and flow controls.
329 Requests are the predefined basic formatting commands similar to the
331 commands at the shell prompt. The user can define request-like ele‐
332 ments using predefined roff elements. These are then called macros. A
333 document writer will not note any difference in usage for requests or
334 macros; both are written on a line on their own starting with a dot.
335 Escape sequences are roff elements starting with a backslash `\'. They
337 can be inserted anywhere, also in the midst of text in a line. They
338 are used to implement various features, including the insertion of non-
339 ASCII characters with \(, font changes with \f, in-line comments with
340 \", the escaping of special control characters like \\, and many other
341 features.
342 Strings are variables that can store a string. A string is stored by
344 the .ds request. The stored string can be retrieved later by the \*
345 escape sequence.
346 Registers store numbers and sizes. A register can be set with the re‐
348 quest .nr and its value can be retrieved by the escape sequence \n.
349
351 Manual pages (man pages) take the section number as a file name exten‐
352 sion, e.g., the filename for this document is roff.7, i.e., it is kept
353 in section 7 of the man pages.
354 The classical macro packages take the package name as an extension,
356 e.g. file.me for a document using the me macro package, file.mm for
357 mm, file.ms for ms, file.pic for pic files, etc.
358 But there is no general naming scheme for roff documents, though
360 file.tr for troff file is seen now and then. Maybe there should be a
361 standardization for the filename extensions of roff files.
362 File name extensions can be very handy in conjunction with the less(1)
364 pager. It provides the possibility to feed all input into a command-
365 line pipe that is specified in the shell environment variable LESSOPEN.
366 This process is not well documented, so here an example:
367 sh# LESSOPEN='|lesspipe %s'
369 where lesspipe is either a system supplied command or a shell script of
371 your own.
372
374 The best program for editing a roff document is Emacs (or Xemacs), see
375 emacs(1). It provides an nroff mode that is suitable for all kinds of
376 roff dialects. This mode can be activated by the following methods.
377 When editing a file within Emacs the mode can be changed by typing `M-x
379 nroff-mode', where M-x means to hold down the Meta key (or Alt) and
380 hitting the x key at the same time.
381 But it is also possible to have the mode automatically selected when
383 the file is loaded into the editor.
384 · The most general method is to include the following 3 comment lines
386 at the end of the file.
387 .\" Local Variables:
389 .\" mode: nroff
390 .\" End:
391 · There is a set of file name extensions, e.g. the man pages that trig‐
393 ger the automatic activation of the nroff mode.
394 · Theoretically, it is possible to write the sequence
396 .\" -*- nroff -*-
398 as the first line of a file to have it started in nroff mode when
400 loaded. Unfortunately, some applications such as the man program are
401 confused by this; so this is deprecated.
402 All roff formatters provide automated line breaks and horizontal and
404 vertical spacing. In order to not disturb this, the following tips can
405 be helpful.
406 · Never include empty or blank lines in a roff document. Instead, use
408 the empty request (a line consisting of a dot only) or a line comment
409 .\" if a structuring element is needed.
410 · Never start a line with whitespace because this can lead to unexpect‐
412 ed behavior. Indented paragraphs can be constructed in a controlled
413 way by roff requests.
414 · Start each sentence on a line of its own, for the spacing after a dot
416 is handled differently depending on whether it terminates an abbrevi‐
417 ation or a sentence. To distinguish both cases, do a line break af‐
418 ter each sentence.
419 · To additionally use the auto-fill mode in Emacs, it is best to insert
421 an empty roff request (a line consisting of a dot only) after each
422 sentence.
423 The following example shows how optimal roff editing could look.
425 This is an example for a roff document.
427 .
428 This is the next sentence in the same paragraph.
429 .
430 This is a longer sentence stretching over several
431 lines; abbreviations like `cf.' are easily
432 identified because the dot is not followed by a
433 line break.
434 .
435 In the output, this will still go to the same
436 paragraph.
437 Besides Emacs, some other editors provide nroff style files too, e.g.
439 vim(1), an extension of the vi(1) program.
440
442 UNIX® is a registered trademark of the Open Group. But things have im‐
443 proved considerably after Caldera had bought SCO UNIX in 2001.
444
446 There is a lot of documentation on roff. The original papers on clas‐
447 sical troff are still available, and all aspects of groff are document‐
448 ed in great detail.
449 Internet sites
451 troff.org
452 The historical troff site ⟨http://www.troff.org⟩ provides an
453 overview and pointers to all historical aspects of roff. This
454 web site is under construction; once, it will be the major
455 source for roff history.
456 Multics
458 The Multics site ⟨http://www.multicians.org⟩ contains a lot of
459 information on the MIT projects, CTSS, Multics, early Unix, in‐
460 cluding runoff; especially useful are a glossary and the many
461 links to ancient documents.
462 Unix Archive
464 The Ancient Unixes Archive ⟨http://www.tuhs.org/Archive/⟩ pro‐
465 vides the source code and some binaries of the ancient Unixes
466 (including the source code of troff and its documentation) that
467 were made public by Caldera since 2001, e.g. of the famous Unix
468 version 7 for PDP-11 at the Unix V7 site ⟨http://www.tuhs.org/
469 Archive/PDP-11/Trees/V7⟩.
470 Developers at AT&T Bell Labs
472 Bell Labs Computing and Mathematical Sciences Research ⟨http://
473 cm.bell-labs.com/cm/index.html⟩ provides a search facility for
474 tracking information on the early developers.
475 Plan 9 The Plan 9 operating system ⟨http://plan9.bell-labs.com⟩ by AT&T
477 Bell Labs.
478 runoff Jerry Saltzer's home page ⟨http://web.mit.edu/Saltzer/www/
480 publications/pubs.html⟩ stores some documents using the ancient
481 runoff formatting language.
482 CSTR Papers
484 The Bell Labs CSTR site ⟨http://cm.bell-labs.com/cm/cs/
485 cstr.html⟩ stores the original troff manuals (CSTR #54, #97,
486 #114, #116, #122) and famous historical documents on program‐
487 ming.
488 GNU roff
490 The groff web site ⟨http://www.gnu.org/software/groff⟩ provides
491 the free roff implementation groff, the actual standard roff.
492 Historical roff Documentation
494 Many classical documents are still available on-line. The two main
495 manuals of the troff language are
496 [CSTR #54]
498 J. F. Osanna, Nroff/Troff User's Manual ⟨http://
499 cm.bell-labs.com/cm/cs/54.ps⟩; Bell Labs, 1976; revised by Brian
500 Kernighan, 1992.
501 [CSTR #97]
504 Brian Kernighan, A Typesetter-independent TROFF ⟨http://
505 cm.bell-labs.com/cm/cs/97.ps⟩, Bell Labs, 1981, revised March
506 1982.
507 The "little language" roff papers are
509 [CSTR #114]
511 Jon L. Bentley and Brian W. Kernighan, GRAP — A Language for
512 Typesetting Graphs ⟨http://cm.bell-labs.com/cm/cs/114.ps⟩; Bell
513 Labs, August 1984.
514 [CSTR #116]
516 Brian W. Kernighan, PIC -- A Graphics Language for Typesetting
517 ⟨http://cm.bell-labs.com/cm/cs/116.ps⟩; Bell Labs, December
518 1984.
519 [CSTR #122]
521 J. L. Bentley, L. W. Jelinski, and B. W. Kernighan, CHEM — A
522 Program for Typesetting Chemical Structure Diagrams, Computers
523 and Chemistry ⟨http://cm.bell-labs.com/cm/cs/122.ps⟩; Bell Labs,
524 April 1986.
525 Manual Pages
527 Due to its complex structure, a full roff system has many man pages,
528 each describing a single aspect of roff. Unfortunately, there is no
529 general naming scheme for the documentation among the different roff
530 implementations.
531 In groff, the man page groff(1) contains a survey of all documentation
533 available in groff.
534 On other systems, you are on your own, but troff(1) might be a good
536 starting point.
537
539 Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.
540 This document is distributed under the terms of the FDL (GNU Free Docu‐
542 mentation License) version 1.1 or later. You should have received a
543 copy of the FDL on your system, it is also available on-line at the GNU
544 copyleft site ⟨http://www.gnu.org/copyleft/fdl.html⟩.
545 This document is part of groff, the GNU roff distribution. It was
547 written by Bernd Warken ⟨bwarken@mayn.de⟩; it is maintained by Werner
548 Lemberg ⟨wl@gnu.org⟩.
549Groff Version 1.18.1.4 23 April 2002 ROFF(7)