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OpenDarwin 7.2.1 - man page for roff (opendarwin section 7)

ROFF(7) 			 Miscellaneous Information Manual			  ROFF(7)

       roff - concepts and history of roff typesetting

       roff is the general name for a set of type-setting programs, known under names like troff,
       nroff, ditroff, groff, etc.  A roff type-setting system consists  of  an  extensible  text
       formatting  language  and a set of programs for printing and converting to other text for-
       mats.  Traditionally, it is the main text processing system of Unix; every Unix-like oper-
       ating system still distributes a roff system as a core package.

       The  most common roff system today is the free software implementation GNU roff, groff(1).
       The pre-groff implementations are referred to as classical (dating back as long as  1973).
       groff  implements  the look-and-feel and functionality of its classical ancestors, but has
       many extensions.  As groff is the only roff system that is available for every (or  almost
       every) computer system it is the de-facto roff standard today.

       In  some  ancient  Unix	systems, there was a binary called roff that implemented the even
       more ancient runoff of the Multics operating system, cf. section HISTORY.  The functional-
       ity  of	this  program  was very restricted even in comparison to ancient troff; it is not
       supported any longer.  Consequently, in this document, the term roff always refers to  the
       general meaning of roff system, not to the ancient roff binary.

       In spite of its age, roff is in wide use today, for example, the manual pages on UNIX sys-
       tems (man pages), many software books, system documentation, standards, and corporate doc-
       uments  are written in roff.  The roff output for text devices is still unmatched, and its
       graphical output has the same quality as other free type-setting programs  and  is  better
       than some of the commercial systems.

       The  most popular application of roff is the concept of manual pages or shortly man pages;
       this is the standard documentation system on many operating systems.

       This document describes the historical facts around the development of  the  roff  system;
       some  usage  aspects  common  to all roff versions, details on the roff pipeline, which is
       usually hidden behind front-ends like groff(1); an general overview of the formatting lan-
       guage; some tips for editing roff files; and many pointers to further readings.

       The  roff  text	processing system has a very long history, dating back to the 1960s.  The
       roff system itself is intimately connected to the Unix operating system, but its roots  go
       back to the earlier operating systems CTSS and Multics.

   The Predecessor runoff
       The  evolution of roff is intimately related to the history of the operating systems.  Its
       predecessor runoff was written by Jerry Saltzer on the CTSS operating  system  (Compatible
       Time Sharing System) as early as 1961.  When CTTS was further developed into the operating
       system Multics <http://www.multicians.org>, the famous  predecessor  of	Unix  from  1963,
       runoff  became the main format for documentation and text processing.  Both operating sys-
       tems could only be run on very expensive computers at that time, so they were mostly  used
       in research and for official and military tasks.

       The  possibilities  of  the runoff language were quite limited as compared to modern roff.
       Only text output was possible in the 1960s.   This  could  be  implemented  by  a  set  of
       requests  of length 2, many of which are still identically used in roff.  The language was
       modelled according to the habits of typesetting	in  the  pre-computer  age,  where  lines
       starting  with  a dot were used in manuscripts to denote formatting requests to the person
       who would perform the typesetting manually later on.

       The runoff program was written in the PL/1 language first, later on in  BCPL,  the  grand-
       mother  of  the	C programming language.  In the Multics operating system, the help system
       was handled by runoff, similar to roff's task to manage the Unix manual pages.  There  are
       still  documents written in the runoff language; for examples see Saltzer's home page, cf.
       section SEE ALSO.

   The Classical nroff/troff System
       In the 1970s, the Multics off-spring Unix became more and more popular because it could be
       run on affordable machines and was easily available for universities at that time.  At MIT
       (the Massachusetts Institute of Technology), there was a need to drive  the  Wang  Graphic
       Systems CAT typesetter, a graphical output device from a PDP-11 computer running Unix.  As
       runoff was too limited for this task it was further developed into a  more  powerful  text
       formatting system by Josef F. Osanna, a main developer of the Multics operating system and
       programmer of several runoff ports.

       The name runoff was shortened to roff.  The greatly enlarged language of Osanna's  concept
       included  already  all  elements  of  a	full roff system.  All modern roff systems try to
       implement compatibility to this system.	So Joe Osanna can be called  the  father  of  all
       roff systems.

       This first roff system had three formatter programs.

       troff  (typesetter  roff)  generated a graphical output for the CAT typesetter as its only

       nroff  produced text output suitable for terminals and line printers.

       roff   was the reimplementation of the former runoff program with  its  limited	features;
	      this  program  was  abandoned  in  later versions.  Today, the name roff is used to
	      refer to a troff/nroff sytem as a whole.

       Osanna first version was written in the PDP-11 assembly language  and  released	in  1973.
       Brian Kernighan joined the roff development by rewriting it in the C programming language.
       The C version was released in 1975.

       The syntax of the formatting language of the nroff/troff programs was  documented  in  the
       famous  Troff User's Manual [CSTR #54], first published in 1976, with further revisions up
       to 1992 by Brian Kernighan.  This document is the specification of  the	classical  troff.
       All later roff systems tried to establish compatibility with this specification.

       After  Osanna had died in 1977 by a heart-attack at the age of about 50, Kernighan went on
       with developing troff.  The next milestone was to equip troff with a general interface  to
       support	more  devices, the intermediate output format and the postprocessor system.  This
       completed the structure of a roff system as it is still in use today;  see  section  USING
       ROFF.   In  1979,  these novelties were described in the paper [CSTR #97].  This new troff
       version is the basis for all existing newer troff systems, including groff.  On some  sys-
       tems,  this device independent troff got a binary of its own, called ditroff(7).  All mod-
       ern troff programs already provide the full ditroff capabilities automatically.

       A major degradation occurred when the easily available Unix 7 operating system was commer-
       cialized.   A whole bunch of divergent operating systems emerged, fighting each other with
       incompatibilities in their extensions.  Luckily, the incompatibilities did not  fight  the
       original  troff.   All  of the different commercial roff systems made heavy use of Osanna/
       Kernighan's open source code and documentation, but sold them as "their"  system  --  with
       only minor additions.

       The  source  code  of  both the ancient Unix and classical troff weren't available for two
       decades.  Fortunately, Caldera bought SCO UNIX in 2001.	In the	following,  Caldera  made
       the ancient source code accessible on-line for non-commercial use, cf. section SEE ALSO.

   Free roff
       None of the commercial roff systems could attain the status of a successor for the general
       roff development.  Everyone was only interested in their own stuff.  This led to  a  steep
       downfall of the once excellent Unix operating system during the 1980s.

       As  a counter-measure to the galopping commercialization, AT&T Bell Labs tried to launch a
       rescue project with their Plan 9 operating system.  It is freely available for non-commer-
       cial use, even the source code, but has a proprietary license that empedes the free devel-
       opment.	This concept is outdated, so Plan 9 was not accepted as a platform to bundle  the
       main-stream development.

       The  only  remedy came from the emerging free operatings systems (386BSD, GNU/Linux, etc.)
       and software projects during the 1980s and 1990s.  These implemented the ancient Unix fea-
       tures and many extensions, such that the old experience is not lost.  In the 21st century,
       Unix-like systems are again a major factor in computer industry -- thanks  to  free  soft-

       The most important free roff project was the GNU port of troff, created by James Clark and
       put under the GNU Public License <http://www.gnu.org/copyleft>.	It was called groff  (GNU
       roff).  See groff(1) for an overview.

       The  groff  system  is still actively developed.  It is compatible to the classical troff,
       but many extensions were added.	It is the first roff system that is available  on  almost
       all  operating  systems	--  and  it is free.  This makes groff the de-facto roff standard

       Most people won't even notice that they are actually using roff.  When you read	a  system
       manual  page  (man  page) roff is working in the background.  Roff documents can be viewed
       with a native viewer called xditview(1x), a standard program of the X window distribution,
       see X(7x).  But using roff explicitly isn't difficult either.

       Some  roff implementations provide wrapper programs that make it easy to use the roff sys-
       tem on the shell command line.  For example, the GNU roff implementation groff(1) provides
       command line options to avoid the long command pipes of classical troff; a program grog(1)
       tries to guess from the document which arguments should be used for a run of groff; people
       who  do	not  like  specifying  command line options should try the groffer(1) program for
       graphically displaying groff files and man pages.

   The roff Pipe
       Each roff system consists of preprocessors, roff formatter programs, and a set  of  device
       postprocessors.	 This  concept makes heavy use of the piping mechanism, that is, a series
       of programs is called one after the other, where the output of each program in  the  queue
       is taken as the input for the next program.

       sh# cat file | ... | preproc | ... | troff options | postproc

       The preprocessors generate roff code that is fed into a roff formatter (e.g. troff), which
       in turn generates intermediate output that is fed into a device postprocessor program  for
       printing or final output.

       All  of these parts use programming languages of their own; each language is totally unre-
       lated to the other parts.  Moreover, roff macro packages that were  tailored  for  special
       purposes can be included.

       Most  roff  documents use the macros of some package, intermixed with code for one or more
       preprocessors, spiced with some elements from the plain roff language.  The full power  of
       the roff formatting language is seldom needed by users; only programmers of macro packages
       need to know about the gory details.

       A roff preprocessor is any program that generates  output  that	syntactically  obeys  the
       rules  of  the  roff formatting language.  Each preprocessor defines a language of its own
       that is translated into roff code when run through the preprocessor program.  Parts  writ-
       ten in these languages may be included within a roff document; they are identified by spe-
       cial roff requests or macros.  Each document that is enhanced by preprocessor code must be
       run  through all corresponding preprocessors before it is fed into the actual roff format-
       ter program, for the formatter just ignores all alien code.  The preprocessor programs ex-
       tract and transform only the document parts that are determined for them.

       There  are a lot of free and commercial roff preprocessors.  Some of them aren't available
       on each system, but there is a small set of preprocessors that are considered as an  inte-
       gral part of each roff system.  The classical preprocessors are

	      tbl     for tables
	      eqn     for mathematical formulae
	      pic     for drawing diagrams
	      refer   for bibliographic references
	      soelim  for including macro files from standard locations

       Other known preprocessors that are not available on all systems include

	      chem    for drawing chemical formulae.
	      grap    for constructing graphical elements.
	      grn     for including gremlin(1) pictures.

   Formatter Programs
       A  roff	formatter  is a program that parses documents written in the roff formatting lan-
       guage or uses some of the roff macro packages.  It generates intermediate output, which is
       intended to be fed into a single device postprocessor that must be specified by a command-
       line option to the formatter program.  The documents must have been run through all neces-
       sary preprocessors before.

       The output produced by a roff formatter is represented in yet another language, the inter-
       mediate output format or troff output.  This language was first specified in  [CSTR  #97];
       its  GNU  extension  is documented in groff_out(5).  The intermediate output language is a
       kind of assembly language compared to the high-level roff language.  The generated  inter-
       mediate	output	is optimized for a special device, but the language is the same for every

       The roff formatter is the heart of the roff system.  The traditional roff had two  format-
       ters, nroff for text devices and troff for graphical devices.

       Often, the name troff is used as a general term to refer to both formatters.

   Devices and Postprocessors
       Devices are hardware interfaces like printers, text or graphical terminals, etc., or soft-
       ware interfaces such as a conversion into a different text or graphical format.

       A roff postprocessor is a program that transforms troff output into a form suitable for	a
       special device.	The roff postprocessors are like device drivers for the output target.

       For  each  device  there  is  a postprocessor program that fits the device optimally.  The
       postprocessor parses the generated intermediate output and generates device-specific  code
       that is sent directly to the device.

       The names of the devices and the postprocessor programs are not fixed because they greatly
       depend on the software and hardware abilities of the actual computer.   For  example,  the
       classical  devices mentioned in [CSTR #54] have greatly changed since the classical times.
       The old hardware doesn't exist any longer and the old graphical conversions were quite im-
       precise when compared to their modern counterparts.

       For  example, the Postscript device post in classical troff had a resolution of 720, while
       groff's ps device has 72000, a refinement of factor 100.

       Today the operating systems provide device drivers for most printer-like hardware,  so  it
       isn't necessary to write a special hardware postprocessor for each printer.

       Documents  using  roff  are  normal text files decorated by roff formatting elements.  The
       roff formatting language is quite powerful; it is almost a full programming  language  and
       provides  elements  to  enlarge	the  language.	With these, it became possible to develop
       macro packages that are tailored for special applications.  Such macro packages	are  much
       handier	than  plain  roff.   So  most people will choose a macro package without worrying
       about the internals of the roff language.

   Macro Packages
       Macro packages are collections of macros that are suitable to format  a	special  kind  of
       documents  in  a convenient way.  This greatly eases the usage of roff.	The macro defini-
       tions of a package are kept in a file called name.tmac (classically tmac.name).	All  tmac
       files  are  stored  in  one or more directories at standardized positions.  Details on the
       naming of macro packages and their placement is found in groff_tmac(5).

       A macro package that is to be used in a document can be announced to the formatter by  the
       command	line  option -m, see troff(1), or it can be specified within a document using the
       file inclusion requests of the roff language, see groff(7).

       Famous classical macro packages are man for traditional man pages, mdoc for BSD-style man-
       ual pages; the macro sets for books, articles, and letters are me (probably from the first
       name of its creator Eric Allman), ms (from Manuscript Macros),  and  mm	(from  Memorandum

   The roff Formatting Language
       The  classical  roff  formatting  language  is  documented  in  the  Troff  User's  Manual
       [CSTR #54].  The roff language is a full programming language providing requests,  defini-
       tion  of  macros,  escape  sequences, string variables, number or size registers, and flow

       Requests are the predefined basic formatting commands similar to the commands at the shell
       prompt.	 The user can define request-like elements using predefined roff elements.  These
       are then called macros.	A document writer will not note any difference in usage  for  re-
       quests or macros; both are written on a line on their own starting with a dot.

       Escape  sequences  are  roff elements starting with a backslash `\'.  They can be inserted
       anywhere, also in the midst of text in a line.  They are used to  implement  various  fea-
       tures,  including the insertion of non-ASCII characters with \(, font changes with \f, in-
       line comments with \", the escaping of special control characters like \\, and many  other

       Strings	are  variables	that  can store a string.  A string is stored by the .ds request.
       The stored string can be retrieved later by the \* escape sequence.

       Registers store numbers and sizes.  A register can be set with the  request  .nr  and  its
       value can be retrieved by the escape sequence \n.

       Manual pages (man pages) take the section number as a file name extension, e.g., the file-
       name for this document is roff.7, i.e., it is kept in section 7 of the man pages.

       The classical macro packages take the package name as an extension, e.g.   file.me  for	a
       document  using	the  me  macro	package, file.mm for mm, file.ms for ms, file.pic for pic
       files, etc.

       But there is no general naming scheme for roff documents, though file.tr for troff file is
       seen now and then.  Maybe there should be a standardization for the filename extensions of
       roff files.

       File name extensions can be very handy in conjunction with the less(1) pager.  It provides
       the  possibility to feed all input into a command-line pipe that is specified in the shell
       environment variable LESSOPEN.  This process is not well documented, so here an example:

       sh# LESSOPEN='|lesspipe %s'

       where lesspipe is either a system supplied command or a shell script of your own.

       The best program for editing a roff document is Emacs (or Xemacs), see emacs(1).  It  pro-
       vides an nroff mode that is suitable for all kinds of roff dialects.  This mode can be ac-
       tivated by the following methods.

       When editing a file within Emacs the mode can be changed by typing `M-x nroff-mode', where
       M-x means to hold down the Meta key (or Alt) and hitting the x key at the same time.

       But  it	is  also possible to have the mode automatically selected when the file is loaded
       into the editor.

       o The most general method is to include the following 3 comment lines at the  end  of  the

	 .\" Local Variables:
	 .\" mode: nroff
	 .\" End:

       o There	is  a  set of file name extensions, e.g. the man pages that trigger the automatic
	 activation of the nroff mode.

       o Theoretically, it is possible to write the sequence

	 .\" -*- nroff -*-

	 as the first line of a file to have it started in nroff mode when loaded.   Unfortunate-
	 ly, some applications such as the man program are confused by this; so this is deprecat-

       All roff formatters provide automated line breaks and horizontal and vertical spacing.  In
       order to not disturb this, the following tips can be helpful.

       o Never	include  empty or blank lines in a roff document.  Instead, use the empty request
	 (a line consisting of a dot only) or a line comment .\"  if  a  structuring  element  is

       o Never	start  a  line with whitespace because this can lead to unexpected behavior.  In-
	 dented paragraphs can be constructed in a controlled way by roff requests.

       o Start each sentence on a line of its own, for the spacing after a dot is handled differ-
	 ently	depending on whether it terminates an abbreviation or a sentence.  To distinguish
	 both cases, do a line break after each sentence.

       o To additionally use the auto-fill mode in Emacs, it is best to insert an empty roff  re-
	 quest (a line consisting of a dot only) after each sentence.

       The following example shows how optimal roff editing could look.

	      This is an example for a roff document.
	      This is the next sentence in the same paragraph.
	      This is a longer sentence stretching over several
	      lines; abbreviations like `cf.' are easily
	      identified because the dot is not followed by a
	      line break.
	      In the output, this will still go to the same

       Besides Emacs, some other editors provide nroff style files too, e.g. vim(1), an extension
       of the vi(1) program.

       UNIX(R) is a registered trademark of the Open Group.  But things have  improved	consider-
       ably after Caldera had bought SCO UNIX in 2001.

       There is a lot of documentation on roff.  The original papers on classical troff are still
       available, and all aspects of groff are documented in great detail.

   Internet sites
	      The historical troff site <http://www.troff.org> provides an overview and  pointers
	      to  all  historical aspects of roff.  This web site is under construction; once, it
	      will be the major source for roff history.

	      The Multics site <http://www.multicians.org> contains a lot of information  on  the
	      MIT  projects, CTSS, Multics, early Unix, including runoff; especially useful are a
	      glossary and the many links to ancient documents.

       Unix Archive
	      The Ancient Unixes Archive <http://www.tuhs.org/Archive/> provides the source  code
	      and some binaries of the ancient Unixes (including the source code of troff and its
	      documentation) that were made public by Caldera since 2001, e.g. of the famous Unix
	      version 7 for PDP-11 at the Unix V7 site <http://www.tuhs.org/Archive/PDP-11/Trees/

       Developers at AT&T Bell Labs
	      Bell Labs Computing and Mathematical Sciences Research <http://cm.bell-labs.com/cm/
	      index.html> provides a search facility for tracking information on the early devel-

       Plan 9 The Plan 9 operating system <http://plan9.bell-labs.com> by AT&T Bell Labs.

       runoff Jerry Saltzer's home  page  <http://web.mit.edu/Saltzer/www/publications/pubs.html>
	      stores some documents using the ancient runoff formatting language.

       CSTR Papers
	      The Bell Labs CSTR site <http://cm.bell-labs.com/cm/cs/cstr.html> stores the origi-
	      nal troff manuals (CSTR #54, #97, #114, #116, #122) and famous historical documents
	      on programming.

       GNU roff
	      The  groff  web site <http://www.gnu.org/software/groff> provides the free roff im-
	      plementation groff, the actual standard roff.

   Historical roff Documentation
       Many classical documents are still available on-line.  The two main manuals of  the  troff
       language are

       [CSTR #54]
	      J. F. Osanna, Nroff/Troff User's Manual <http://cm.bell-labs.com/cm/cs/54.ps>; Bell
	      Labs, 1976; revised by Brian Kernighan, 1992.

       [CSTR #97]
	      Brian Kernighan, A Typesetter-independent TROFF <http://cm.bell-labs.com/cm/cs/
	      97.ps>, Bell Labs, 1981, revised March 1982.

       The "little language" roff papers are

       [CSTR #114]
	      Jon L. Bentley and Brian W. Kernighan, GRAP -- A Language for Typesetting Graphs
	      <http://cm.bell-labs.com/cm/cs/114.ps>; Bell Labs, August 1984.

       [CSTR #116]
	      Brian W. Kernighan, PIC -- A Graphics Language for Typesetting <http://
	      cm.bell-labs.com/cm/cs/116.ps>; Bell Labs, December 1984.

       [CSTR #122]
	      J. L. Bentley, L. W. Jelinski, and B. W. Kernighan, CHEM -- A Program for Typeset-
	      ting Chemical Structure Diagrams, Computers and Chemistry <http://cm.bell-labs.com/
	      cm/cs/122.ps>; Bell Labs, April 1986.

   Manual Pages
       Due  to	its  complex  structure, a full roff system has many man pages, each describing a
       single aspect of roff.  Unfortunately, there is no general naming scheme for the  documen-
       tation among the different roff implementations.

       In groff, the man page groff(1) contains a survey of all documentation available in groff.

       On other systems, you are on your own, but troff(1) might be a good starting point.

       Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.

       This  document  is distributed under the terms of the FDL (GNU Free Documentation License)
       version 1.1 or later.  You should have received a copy of the FDL on your  system,  it  is
       also available on-line at the GNU copyleft site <http://www.gnu.org/copyleft/fdl.html>.

       This document is part of groff, the GNU roff distribution.  It was written by Bernd Warken
       <bwarken@mayn.de>; it is maintained by Werner Lemberg <wl@gnu.org>.

Groff Version 1.18.1			    Nov  2003					  ROFF(7)

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