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 text formatting programs, known
10 under names like troff, nroff, ditroff, groff, etc. A roff system con‐
11 sists of an extensible text formatting language and a set of programs
12 for printing and converting to other text formats. Unix-like operating
13 systems distribute a roff system as a core package.
14 The most common roff system today is the free software implementation
16 GNU roff, groff(1). groff implements the look-and-feel and functional‐
17 ity of its ancestors, with many extensions.
18 The ancestry of roff is described in section HISTORY. In this docu‐
20 ment, the term roff always refers to the general class of roff pro‐
21 grams, not to the roff command provided in early UNIX systems.
22 In spite of its age, roff is in wide use today, for example, the manual
24 pages on UNIX systems (man pages), many software books, system documen‐
25 tation, standards, and corporate documents are written in roff. The
26 roff output for text devices is still unmatched, and its graphical out‐
27 put has the same quality as other free type-setting programs and is
28 better than some of the commercial systems.
29 roff is used to format UNIX manual pages, (or man pages), the standard
31 documentation system on many UNIX-derived operating systems.
32 This document describes the history of the development of the roff sys‐
34 tem; some usage aspects common to all roff versions, details on the
35 roff pipeline, which is usually hidden behind front-ends like groff(1);
36 a general overview of the formatting language; some tips for editing
37 roff files; and many pointers to further readings.
38
40 Document formatting by computer dates back to the 1960s. The roff sys‐
41 tem itself is intimately connected to the Unix operating system, but
42 its roots go back to the earlier operating systems CTSS and Multics.
43 The Predecessor RUNOFF
45 roff's ancestor RUNOFF was written in the MAD language by Jerry Saltzer
46 for the Compatible Time Sharing System (CTSS), a project of the Massa‐
47 chusetts Institute of Technology (MIT), in 1963 and 1964 – note that
48 CTSS commands were all uppercase.
49 In 1965, MIT's Project MAC teamed with Bell Telephone Laboratories
51 (BTL) and General Electric to begin the Multics system ⟨http://
52 www.multicians.org⟩. A command called runoff was written for Multics
53 in the late 60s in the BCPL language, by Bob Morris, Doug McIlroy, and
54 other members of the Multics team.
55 Like its CTSS ancestor, Multics runoff formatted an input file consist‐
57 ing of text and command lines; commands began with a period and were
58 two letters. Output from these commands was to terminal devices such
59 as IBM Selectric terminals. Multics runoff had additional features
60 added, such as the ability to do two-pass formatting; it became the
61 main format for Multics documentation and text processing.
62 BCPL and runoff were ported to the GCOS system at Bell Labs when BTL
64 left the development of Multics.
65 The Classical nroff/troff System
67 At BTL, there was a need to drive the Graphic Systems CAT typesetter, a
68 graphical output device from a PDP-11 computer running Unix. As runoff
69 was too limited for this task it was further developed into a more pow‐
70 erful text formatting system by Joseph F. Ossanna, who already pro‐
71 grammed several runoff ports.
72 The name runoff was shortened to roff. The greatly enlarged language
74 of Ossanna's version already included all elements of a full roff sys‐
75 tem. All modern roff systems try to implement compatibility to this
76 system. So Joe Ossanna can be called the father of all roff systems.
77 This first roff system had three formatter programs.
79 troff (typesetter roff) generated a graphical output for the CAT type‐
81 setter as its only device.
82 nroff produced text output suitable for terminals and line printers.
84 roff was the reimplementation of the former runoff program with its
86 limited features; this program was abandoned in later versions.
87 Today, the name roff is used to refer to a troff/nroff system as
88 a whole.
89 Ossanna's first version was written in the PDP-11 assembly language and
91 released in 1973. Brian Kernighan joined the roff development by
92 rewriting it in the C programming language. The C version was released
93 in 1975.
94 The syntax of the formatting language of the nroff/troff programs was
96 documented in the famous Troff User's Manual [CSTR #54], first pub‐
97 lished in 1976, with further revisions up to 1992 by Brian Kernighan.
98 This document is the specification of the classical troff. All later
99 roff systems tried to establish compatibility with this specification.
100 After Ossanna's death in 1977, Kernighan went on with developing troff.
102 In the late 1970s, Kernighan equipped troff with a general interface to
103 support more devices, the intermediate output format, and the postpro‐
104 cessor system. This completed the structure of a roff system as it is
105 still in use today; see section USING ROFF. In 1979, these novelties
106 were described in the paper [CSTR #97]. This new troff version is the
107 basis for all existing newer troff systems, including groff. On some
108 systems, this device independent troff got a binary of its own, called
109 ditroff(7). All modern troff programs already provide the full ditroff
110 capabilities automatically.
111 Availability
113 The source code of both the ancient Unix and classical troff weren't
114 available for two decades. Meanwhile, it is accessible again (on-line)
115 for non-commercial use, cf. section SEE ALSO.
116 Free roff
118 The most important free roff project was the GNU implementation of
119 troff, written from scratch by James Clark and put under the GNU Public
120 License ⟨http://www.gnu.org/copyleft⟩. It was called groff (GNU roff).
121 See groff(1) for an overview.
122 The groff system is still actively developed. It is compatible to the
124 classical troff, but many extensions were added. It is the first roff
125 system that is available on almost all operating systems – and it is
126 free. This makes groff the de-facto roff standard today.
127 An alternative is Gunnar Ritter's Heirloom Documentation Tools ⟨http://
129 heirloom.sf.net⟩ project, started in 2005, which provides enhanced ver‐
130 sions of the various roff tools found in the OpenSolaris and Plan 9
131 operating systems, now available under free licenses.
132
134 Most people won't even notice that they are actually using roff. When
135 you read a system manual page (man page) roff is working in the back‐
136 ground. roff documents can be viewed with a native viewer called
137 xditview(1x), a standard program of the X window distribution, see
138 X(7x). But using roff explicitly isn't difficult either.
139 Some roff implementations provide wrapper programs that make it easy to
141 use the roff system on the shell command line. For example, the GNU
142 roff implementation groff(1) provides command line options to avoid the
143 long command pipes of classical troff; a program grog(1) tries to guess
144 from the document which arguments should be used for a run of groff;
145 people who do not like specifying command line options should try the
146 groffer(1) program for graphically displaying groff files and man
147 pages.
148 The roff Pipe
150 Each roff system consists of preprocessors, roff formatter programs,
151 and a set of device postprocessors. This concept makes heavy use of
152 the piping mechanism, that is, a series of programs is called one after
153 the other, where the output of each program in the queue is taken as
154 the input for the next program.
155 cat file | ... | preproc | ... | troff options | postproc
157 The preprocessors generate roff code that is fed into a roff formatter
159 (e.g. troff), which in turn generates intermediate output that is fed
160 into a device postprocessor program for printing or final output.
161 All of these parts use programming languages of their own; each lan‐
163 guage is totally unrelated to the other parts. Moreover, roff macro
164 packages that were tailored for special purposes can be included.
165 Most roff documents use the macros of some package, intermixed with
167 code for one or more preprocessors, spiced with some elements from the
168 plain roff language. The full power of the roff formatting language is
169 seldom needed by users; only programmers of macro packages need to know
170 about the gory details.
171 Preprocessors
173 A roff preprocessor is any program that generates output that syntacti‐
174 cally obeys the rules of the roff formatting language. Each preproces‐
175 sor defines a language of its own that is translated into roff code
176 when run through the preprocessor program. Parts written in these lan‐
177 guages may be included within a roff document; they are identified by
178 special roff requests or macros. Each document that is enhanced by
179 preprocessor code must be run through all corresponding preprocessors
180 before it is fed into the actual roff formatter program, for the for‐
181 matter just ignores all alien code. The preprocessor programs extract
182 and transform only the document parts that are determined for them.
183 There are a lot of free and commercial roff preprocessors. Some of
185 them aren't available on each system, but there is a small set of pre‐
186 processors that are considered as an integral part of each roff system.
187 The classical preprocessors are
188 tbl for tables.
190 eqn for mathematical formulæ.
191 pic for drawing diagrams.
192 refer for bibliographic references.
193 soelim for including macro files from standard locations.
194 chem for drawing chemical formulæ.
195 Other known preprocessors that are not available on all systems include
197 grap for constructing graphical elements.
199 grn for including gremlin(1) pictures.
200 Formatter Programs
202 A roff formatter is a program that parses documents written in the roff
203 formatting language or uses some of the roff macro packages. It gener‐
204 ates intermediate output, which is intended to be fed into a single
205 device postprocessor that must be specified by a command-line option to
206 the formatter program. The documents must have been run through all
207 necessary preprocessors before.
208 The output produced by a roff formatter is represented in yet another
210 language, the intermediate output format or troff output. This lan‐
211 guage was first specified in [CSTR #97]; its GNU extension is docu‐
212 mented in groff_out(5). The intermediate output language is a kind of
213 assembly language compared to the high-level roff language. The gener‐
214 ated intermediate output is optimized for a special device, but the
215 language is the same for every device.
216 The roff formatter is the heart of the roff system. The traditional
218 roff had two formatters, nroff for text devices and troff for graphical
219 devices.
220 Often, the name troff is used as a general term to refer to both for‐
222 matters.
223 Devices and Postprocessors
225 Devices are hardware interfaces like printers, text or graphical termi‐
226 nals, etc., or software interfaces such as a conversion into a differ‐
227 ent text or graphical format.
228 A roff postprocessor is a program that transforms troff output into a
230 form suitable for a special device. The roff postprocessors are like
231 device drivers for the output target.
232 For each device there is a postprocessor program that fits the device
234 optimally. The postprocessor parses the generated intermediate output
235 and generates device-specific code that is sent directly to the device.
236 The names of the devices and the postprocessor programs are not fixed
238 because they greatly depend on the software and hardware abilities of
239 the actual computer. For example, the classical devices mentioned in
240 [CSTR #54] have greatly changed since the classical times. The old
241 hardware doesn't exist any longer and the old graphical conversions
242 were quite imprecise when compared to their modern counterparts.
243 For example, the Postscript device post in classical troff had a reso‐
245 lution of 720 units per inch, while groff's ps device has 72000, a
246 refinement of factor 100.
247 Today the operating systems provide device drivers for most printer-
249 like hardware, so it isn't necessary to write a special hardware post‐
250 processor for each printer.
251
253 Documents using roff are normal text files decorated by roff formatting
254 elements. The roff formatting language is quite powerful; it is almost
255 a full programming language and provides elements to enlarge the lan‐
256 guage. With these, it became possible to develop macro packages that
257 are tailored for special applications. Such macro packages are much
258 handier than plain roff. So most people will choose a macro package
259 without worrying about the internals of the roff language.
260 Macro Packages
262 Macro packages are collections of macros that are suitable to format a
263 special kind of documents in a convenient way. This greatly eases the
264 usage of roff. The macro definitions of a package are kept in a file
265 called name.tmac (classically tmac.name). All tmac files are stored in
266 one or more directories at standardized positions. Details on the nam‐
267 ing of macro packages and their placement is found in groff_tmac(5).
268 A macro package that is to be used in a document can be announced to
270 the formatter by the command line option -m, see troff(1), or it can be
271 specified within a document using the file inclusion requests of the
272 roff language, see groff(7).
273 Famous classical macro packages are man for traditional man pages, mdoc
275 for BSD-style manual pages; the macro sets for books, articles, and
276 letters are me (probably from the first name of its creator Eric All‐
277 man), ms (from Manuscript Macros), and mm (from Memorandum Macros).
278 The roff Formatting Language
280 The classical roff formatting language is documented in the Troff
281 User's Manual [CSTR #54]. The roff language is a full programming lan‐
282 guage providing requests, definition of macros, escape sequences,
283 string variables, number or size registers, and flow controls.
284 Requests are the predefined basic formatting commands similar to the
286 commands at the shell prompt. The user can define request-like ele‐
287 ments using predefined roff elements. These are then called macros. A
288 document writer will not note any difference in usage for requests or
289 macros; both are written on a line on their own starting with a dot.
290 Escape sequences are roff elements starting with a backslash `\'. They
292 can be inserted anywhere, also in the midst of text in a line. They
293 are used to implement various features, including the insertion of non-
294 ASCII characters with \(, font changes with \f, in-line comments with
295 \", the escaping of special control characters like \\, and many other
296 features.
297 Strings are variables that can store a string. A string is stored by
299 the .ds request. The stored string can be retrieved later by the \*
300 escape sequence.
301 Registers store numbers and sizes. A register can be set with the
303 request .nr and its value can be retrieved by the escape sequence \n.
304
306 Manual pages (man pages) take the section number as a file name exten‐
307 sion, e.g., the filename for this document is roff.7, i.e., it is kept
308 in section 7 of the man pages.
309 The classical macro packages take the package name as an extension,
311 e.g. file.me for a document using the me macro package, file.mm for mm,
312 file.ms for ms, file.pic for pic files, etc.
313 But there is no general naming scheme for roff documents, though
315 file.tr for troff file is seen now and then. Maybe there should be a
316 standardization for the filename extensions of roff files.
317 File name extensions can be very handy in conjunction with the less(1)
319 pager. It provides the possibility to feed all input into a command-
320 line pipe that is specified in the shell environment variable LESSOPEN.
321 This process is not well documented, so here an example:
322 LESSOPEN='|lesspipe %s'
324 where lesspipe is either a system supplied command or a shell script of
326 your own.
327
329 The best program for editing a roff document is Emacs (or Xemacs), see
330 emacs(1). It provides an nroff mode that is suitable for all kinds of
331 roff dialects. This mode can be activated by the following methods.
332 When editing a file within Emacs the mode can be changed by typing `M-x
334 nroff-mode', where M-x means to hold down the Meta key (or Alt) and
335 hitting the x key at the same time.
336 But it is also possible to have the mode automatically selected when
338 the file is loaded into the editor.
339 · The most general method is to include the following 3 comment
341 lines at the end of the file.
342 .\" Local Variables:
344 .\" mode: nroff
345 .\" End:
346 · There is a set of file name extensions, e.g. the man pages that
348 trigger the automatic activation of the nroff mode.
349 · Theoretically, it is possible to write the sequence
351 .\" -*- nroff -*-
353 as the first line of a file to have it started in nroff mode
355 when loaded. Unfortunately, some applications such as the man
356 program are confused by this; so this is deprecated.
357 All roff formatters provide automated line breaks and horizontal and
359 vertical spacing. In order to not disturb this, the following tips can
360 be helpful.
361 · Never include empty or blank lines in a roff document. Instead,
363 use the empty request (a line consisting of a dot only) or a
364 line comment .\" if a structuring element is needed.
365 · Never start a line with whitespace because this can lead to
367 unexpected behavior. Indented paragraphs can be constructed in
368 a controlled way by roff requests.
369 · Start each sentence on a line of its own, for the spacing after
371 a dot is handled differently depending on whether it terminates
372 an abbreviation or a sentence. To distinguish both cases, do a
373 line break after each sentence.
374 · To additionally use the auto-fill mode in Emacs, it is best to
376 insert an empty roff request (a line consisting of a dot only)
377 after each sentence.
378 The following example shows how optimal roff editing could look.
380 This is an example for a
382 .I roff
383 document.
384 .
385 This is the next sentence in the same paragraph.
386 .
387 This is a longer sentence stretching over several
388 lines; abbreviations like `cf.' are easily
389 identified because the dot is not followed by a
390 line break.
391 .
392 In the output, this will still go to the same
393 paragraph.
394 Besides Emacs, some other editors provide nroff style files too, e.g.
396 vim(1), an extension of the vi(1) program.
397
399 There is a lot of documentation on roff. The original papers on clas‐
400 sical troff are still available, and all aspects of groff are docu‐
401 mented in great detail.
402 Internet sites
404 troff.org
405 The historical troff site ⟨http://www.troff.org⟩ provides an
406 overview and pointers to all historical aspects of roff.
407 Multics
409 The Multics site ⟨http://www.multicians.org⟩ contains a lot of
410 information on the MIT projects, CTSS, Multics, early Unix,
411 including runoff; especially useful are a glossary and the many
412 links to ancient documents.
413 Unix Archive
415 The Ancient Unixes Archive ⟨http://www.tuhs.org/Archive/⟩ pro‐
416 vides the source code and some binaries of the ancient Unixes
417 (including the source code of troff and its documentation) that
418 were made public by Caldera since 2001, e.g. of the famous Unix
419 version 7 for PDP-11 at the Unix V7 site ⟨http://www.tuhs.org/
420 Archive/PDP-11/Trees/V7⟩.
421 Developers at AT&T Bell Labs
423 Bell Labs Computing and Mathematical Sciences Research ⟨http://
424 www.bell-labs.com/⟩ provides a search facility for tracking
425 information on the early developers.
426 Plan 9 The Plan 9 operating system ⟨http://plan9.bell-labs.com⟩ by AT&T
428 Bell Labs.
429 runoff Jerry Saltzer's home page ⟨http://web.mit.edu/Saltzer/www/
431 publications/pubs.html⟩ stores some documents using the ancient
432 RUNOFF formatting language.
433 CSTR Papers
435 The Bell Labs CSTR site ⟨http://cm.bell-labs.com/cm/cs/
436 cstr.html⟩ stores the original troff manuals (CSTR #54, #97,
437 #114, #116, #122) and famous historical documents on program‐
438 ming.
439 GNU roff
441 The groff web site ⟨http://www.gnu.org/software/groff⟩ provides
442 the free roff implementation groff, the actual standard roff.
443 Historical roff Documentation
445 Many classical troff documents are still available on-line. The two
446 main manuals of the troff language are
447 [CSTR #54]
449 J. F. Ossanna, Nroff/Troff User's Manual ⟨http://cm.bell-
450 labs.com/cm/cs/cstr/54.ps.gz⟩; Bell Labs, 1976; revised by Brian
451 Kernighan, 1992.
452 [CSTR #97]
454 Brian Kernighan, A Typesetter-independent TROFF ⟨http://cm.bell-
455 labs.com/cm/cs/cstr/97.ps.gz⟩, Bell Labs, 1981, revised March
456 1982.
457 The “little language” roff papers are
459 [CSTR #114]
461 Jon L. Bentley and Brian W. Kernighan, GRAP – A Language for
462 Typesetting Graphs ⟨http://cm.bell-labs.com/cm/cs/cstr/
463 114.ps.gz⟩; Bell Labs, August 1984.
464 [CSTR #116]
466 Brian W. Kernighan, PIC – A Graphics Language for Typesetting
467 ⟨http://cm.bell-labs.com/cm/cs/cstr/116.ps.gz⟩; Bell Labs,
468 December 1984.
469 [CSTR #122]
471 J. L. Bentley, L. W. Jelinski, and B. W. Kernighan, CHEM – A
472 Program for Typesetting Chemical Structure Diagrams, Computers
473 and Chemistry ⟨http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz⟩;
474 Bell Labs, April 1986.
475 Manual Pages
477 Due to its complex structure, a full roff system has many man pages,
478 each describing a single aspect of roff. Unfortunately, there is no
479 general naming scheme for the documentation among the different roff
480 implementations.
481 In groff, the man page groff(1) contains a survey of all documentation
483 available in groff.
484 On other systems, you are on your own, but troff(1) might be a good
486 starting point.
487
489 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009 Free
490 Software Foundation, Inc.
491 This document is distributed under the terms of the FDL (GNU Free Docu‐
493 mentation License) version 1.3 or later. You should have received a
494 copy of the FDL on your system, it is also available on-line at the GNU
495 copyleft site ⟨http://www.gnu.org/copyleft/fdl.html⟩.
496 This document is part of groff, the GNU roff distribution. It was
498 written by Bernd Warken ⟨bwarken@mayn.de⟩; it is maintained by Werner
499 Lemberg ⟨wl@gnu.org⟩.
500Groff Version 1.20.1 21 January 2011 ROFF(7)