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ROFF(7)								       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-set‐
       ting  system  consists  of an extensible text formatting language and a
       set of programs for printing and	 converting  to	 other	text  formats.
       Traditionally,  it  is  the  main text processing system of Unix; every
       Unix-like operating system still distributes a roff system  as  a  core

       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	 stan‐
       dard today.

       In  some	 ancient  Unix	systems,  there	 was a binary called roff that
       implemented the even more ancient runoff of the Multics operating  sys‐
       tem,  cf.  section HISTORY.  The functionality 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 systems (man pages), many software books, system documen‐
       tation, standards, and corporate documents are written  in  roff.   The
       roff output for text devices is still unmatched, and its graphical out‐
       put 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  language;  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 sys‐
       tems CTSS and Multics.

   The Predecessor runoff
       The evolution of roff is intimately related to the history of the oper‐
       ating  systems.	Its predecessor runoff was written by Jerry Saltzer on
       the CTSS operating system (Compatible Time Sharing System) as early  as
       1961.  When CTSS was further developed into the operating system Mul‐
       tics ⟨⟩, the famous predecessor of  Unix  from
       1963, runoff became the main format for documentation and text process‐
       ing.  Both operating systems could only be run on very  expensive  com‐
       puters at that time, so they were mostly used in research and for offi‐
       cial 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 accord‐
       ing 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

       The  runoff program was written in the PL/1 language first, later on in
       BCPL, the grandmother 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 sys‐
       tem.  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 type‐
	      setter as its only device.

       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 pub‐
       lished 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 com‐
       pleted 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 systems, this device
       independent troff got a binary of its own, called ditroff(7).  All mod‐
       ern  troff programs already provide the full ditroff capabilities auto‐

       A major degradation occurred when the easily available Unix 7 operating
       system  was  commercialized.  A whole bunch of divergent operating sys‐
       tems 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  accessi‐
       ble on-line for non-commercial use, cf. section SEE ALSO.

   Free roff
       None  of	 the commercial roff systems could attain the status of a suc‐
       cessor 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-commercial use, even  the	 source	 code,
       but  has a proprietary license that impedes the free development.  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 features 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

       The most important free roff project was the GNU port of troff, created
       by James Clark and put under the GNU Public License ⟨http://⟩.  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 today.

       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 back‐
       ground.	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  system 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

   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 lan‐
       guage is totally unrelated 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 syntacti‐
       cally obeys the rules of the roff formatting language.  Each preproces‐
       sor  defines  a	language  of its own that is translated into roff code
       when run through the preprocessor program.  Parts written in these lan‐
       guages  may  be included within a roff document; they are identified by
       special 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 formatter program, for  the  for‐
       matter  just ignores all alien code.  The preprocessor programs extract
       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 pre‐
       processors that are considered as an integral part of each roff system.
       The classical preprocessors are

	      tbl     for tables
	      eqn     for mathematical formulæ
	      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 formulæ.
	      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 language or uses some of the roff macro packages.  It gener‐
       ates intermediate output, which is intended to be fed into a single de‐
       vice postprocessor that must be specified by a command-line  option  to
       the  formatter  program.	  The documents must have been run through all
       necessary preprocessors before.

       The output produced by a roff formatter is represented in  yet  another
       language,  the  intermediate  output format or troff output.  This lan‐
       guage was first specified in [CSTR #97]; its GNU extension is document‐
       ed  in groff_out(5).  The intermediate output language is a kind of as‐
       sembly language compared to the high-level roff language.  The generat‐
       ed  intermediate output is optimized for a special device, but the lan‐
       guage is the same for every device.

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

       Often, the name troff is used as a general term to refer to  both  for‐

   Devices and Postprocessors
       Devices are hardware interfaces like printers, text or graphical termi‐
       nals, etc., or software interfaces such as a conversion into a  differ‐
       ent 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 imprecise when compared to their modern counterparts.

       For example, the Postscript device post in classical troff had a	 reso‐
       lution  of 720, while groff's ps device has 72000, a refinement of fac‐
       tor 100.

       Today the operating systems provide device drivers  for	most  printer-
       like  hardware, so it isn't necessary to write a special hardware post‐
       processor 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  lan‐
       guage.	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 definitions of a package are kept in  a  file
       called name.tmac (classically  All tmac files are stored in
       one or more directories at standardized positions.  Details on the nam‐
       ing 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  manual  pages;  the macro sets for books, articles, and
       letters are me (probably from the first name of its creator  Eric  All‐
       man), ms (from Manuscript Macros), and mm (from Memorandum Macros).

   The roff Formatting Language
       The  classical  roff formatting language is documented in the Troff Us‐
       er's Manual [CSTR #54].	The roff language is a full  programming  lan‐
       guage  providing	 requests,  definition	of  macros,  escape sequences,
       string variables, number or size registers, and flow controls.

       Requests are the predefined basic formatting commands  similar  to  the
       commands	 at  the  shell prompt.	 The user can define request-like ele‐
       ments using predefined roff elements.  These are then called macros.  A
       document	 writer	 will not note any difference in usage for requests 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 features, 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 re‐
       quest .nr and its value can be retrieved by the escape sequence \n.

       Manual pages (man pages) take the section number as a file name	exten‐
       sion,  e.g., the filename 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.  for  a document using the me macro package, for
       mm, for ms, file.pic for pic files, etc.

       But there is no	general	 naming	 scheme	 for  roff  documents,	though	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 provides an nroff mode that is suitable for all kinds of
       roff dialects.  This mode can be activated 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.

       · The  most  general method is to include the following 3 comment lines
	 at the end of the file.

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

       · There is a set of file name extensions, e.g. the man pages that trig‐
	 ger the automatic activation of the nroff mode.

       · 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.  Unfortunately, some applications such as the man program are
	 confused by this; so this is deprecated.

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

       · 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 needed.

       · Never start a line with whitespace because this can lead to unexpect‐
	 ed behavior.  Indented paragraphs can be constructed in a  controlled
	 way by roff requests.

       · Start each sentence on a line of its own, for the spacing after a dot
	 is handled differently depending on whether it terminates an abbrevi‐
	 ation	or a sentence.	To distinguish both cases, do a line break af‐
	 ter each sentence.

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

       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® is a registered trademark of the Open Group.  But things have im‐
       proved considerably after Caldera had bought SCO UNIX in 2001.

       There is a lot of documentation on roff.	 The original papers on	 clas‐
       sical troff are still available, and all aspects of groff are document‐
       ed in great detail.

   Internet sites
	      The historical troff  site  ⟨⟩  provides  an
	      overview and pointers to all historical aspects of roff.

	      The  Multics  site ⟨⟩ contains a lot of
	      information on the MIT projects, CTSS, Multics, early Unix,  in‐
	      cluding  runoff;	especially  useful are a glossary and the many
	      links to ancient documents.

       Unix Archive
	      The Ancient Unixes Archive  ⟨⟩  pro‐
	      vides  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 ⟨

       Developers at AT&T Bell Labs
	      Bell Labs Computing and Mathematical Sciences Research ⟨http://⟩ provides a search	 facility  for
	      tracking information on the early developers.

       Plan 9 The Plan 9 operating system ⟨⟩ by AT&T
	      Bell Labs.

       runoff Jerry Saltzer's home page ⟨
	      publications/pubs.html⟩  stores some documents using the ancient
	      runoff formatting language.

       CSTR Papers
	      The Bell Labs CSTR site ⟨
	      cstr.html⟩  stores  the  original	 troff manuals (CSTR #54, #97,
	      #114, #116, #122) and famous historical  documents  on  program‐

       GNU roff
	      The  groff web site ⟨⟩ provides
	      the free roff implementation groff, the actual standard roff.

   Historical roff Documentation
       Many classical troff 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://⟩; Bell Labs, 1976; revised by Brian
	      Kernighan, 1992.

       [CSTR #97]
	      Brian Kernighan, A Typesetter-independent TROFF ⟨http://⟩, Bell Labs,	 1981,	revised	 March

       The "little language" roff papers are

       [CSTR #114]
	      Jon L. Bentley and Brian W. Kernighan, GRAP — A Language for
	      Typesetting Graphs ⟨⟩;  Bell
	      Labs, August 1984.

       [CSTR #116]
	      Brian W. Kernighan, PIC -- A Graphics Language for Typesetting
	      ⟨⟩;  Bell   Labs,   December

       [CSTR #122]
	      J. L. Bentley, L. W. Jelinski, and B. W. Kernighan, CHEM — A
	      Program for Typesetting Chemical Structure Diagrams, Computers
	      and Chemistry ⟨⟩; 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 documentation among  the  different  roff

       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, 2003, 2004 Free Software Foundation,

       This document is distributed under the terms of the FDL (GNU Free Docu‐
       mentation  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 ⟨⟩.

       This  document  is  part	 of  groff, the GNU roff distribution.	It was
       written by Bernd Warken ⟨⟩; it is maintained  by	Werner
       Lemberg ⟨⟩.

Groff Version 1.19.2		20 October 2005			       ROFF(7)

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