Man Linux: Main Page and Category List


       roff - concepts and history of roff typesetting


       roff  is  the general name for a set of text formatting programs, known
       under names like troff, nroff, ditroff,  groff,  etc.   A  roff  system
       consists  of  an  extensible  text  formatting  language  and  a set of
       programs for printing and converting to other text formats.   Unix-like
       operating systems distribute a roff system as a core package.

       The  most  common roff system today is the free software implementation
       GNU  roff,  groff(1).    groff   implements   the   look-and-feel   and
       functionality of its ancestors, with many extensions.

       The  ancestry  of  roff  is  described  in  section  HISTORY.   In this
       document, the term roff always refers to  the  general  class  of  roff
       programs, not to the roff command provided in early UNIX systems.

       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
       documentation,  standards, and corporate documents 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.

       roff is used to format UNIX manual pages, (or man pages), the  standard
       documentation system on many UNIX-derived operating systems.

       This  document  describes  the  history  of 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);
       a general overview of the formatting language; some  tips  for  editing
       roff files; and many pointers to further readings.


       Document  formatting  by  computer  dates  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
       roff’s ancestor RUNOFF was written in the MAD language by Jerry Saltzer
       for the Compatible  Time  Sharing  System  (CTSS),  a  project  of  the
       Massachusetts  Institute  of  Technology (MIT), in 1963 and 1964 – note
       that CTSS commands were all uppercase.

       In 1965, MIT’s Project MAC  teamed  with  Bell  Telephone  Laboratories
       (BTL) and General Electric to begin the Multics system A command called
       runoff was written for Multics in the late 60s in the BCPL language, by
       Bob Morris, Doug McIlroy, and other members of the Multics team.

       Like  its  CTSS  ancestor,  Multics  runoff  formatted  an  input  file
       consisting of text and command lines; commands began with a period  and
       were  two  letters.  Output from these commands was to terminal devices
       such  as  IBM  Selectric  terminals.   Multics  runoff  had  additional
       features  added,  such  as  the  ability  to do two-pass formatting; it
       became the main format for Multics documentation and text processing.

       BCPL and runoff were ported to the GCOS system at Bell  Labs  when  BTL
       left the development of Multics.

   The Classical nroff/troff System
       At BTL, there was a need to drive the 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  Joseph  F.  Ossanna,  who  already
       programmed several runoff ports.

       The  name  runoff was shortened to roff.  The greatly enlarged language
       of Ossanna’s version already included  all  elements  of  a  full  roff
       system.  All modern roff systems try to implement compatibility to this
       system.  So Joe Ossanna 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 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.

       Ossanna’s 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  Users  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

       After Ossanna’s death in 1977, Kernighan went on with developing troff.
       In the late 1970s, Kernighan equipped 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 systems, this device independent troff got a binary of
       its own, called ditroff(7).  All modern troff programs already  provide
       the full ditroff capabilities automatically.

       The  source  code  of both the ancient Unix and classical troff weren’t
       available for two decades.  Meanwhile, it is accessible again (on-line)
       for non-commercial use, cf. section SEE ALSO.

   Free roff
       The  most  important  free  roff  project was the GNU implementation of
       troff, written from scratch by James Clark and put under the GNU Public
       License  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.

       An alternative is Gunnar Ritter’s Heirloom Documentation Tools project,
       started in 2005, which provides enhanced versions of the  various  roff
       tools  found  in  the  OpenSolaris  and  Plan  9 operating systems, now
       available under free licenses.


       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  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.

              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 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
       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 written in these
       languages  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
       formatter  just  ignores  all  alien  code.   The preprocessor programs
       extract and transform only the document parts that are  determined  for

       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 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.
              chem     for drawing chemical formulæ.

       Other known preprocessors that are not available on all systems include

              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
       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 necessary preprocessors before.

       The output produced by a roff formatter is represented in  yet  another
       language,  the  intermediate  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  intermediate  output  is optimized for a special device, but
       the language 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

   Devices and Postprocessors
       Devices  are  hardware  interfaces  like  printers,  text  or graphical
       terminals, etc., or software 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 imprecise when compared to their modern counterparts.

       For  example,  the  Postscript  device  post  in  classical troff had a
       resolution of 720 units per inch, 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 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
       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  manual  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 Macros).

   The roff Formatting Language
       The classical roff formatting  language  is  documented  in  the  Troff
       Users  Manual  [CSTR  #54].   The  roff language is a full programming
       language 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
       elements 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
       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 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:

              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
              trigger 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
              unexpected  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 abbreviation or a sentence.  To distinguish both cases, do  a
              line break after 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 sentence.

       The following example shows how optimal roff editing could look.

              This  is an example for a .I 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.


       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 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,  including  runoff;
              especially useful are a glossary and the many links  to  ancient

       Unix Archive
              The  Ancient  Unixes  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

       Developers at AT&T Bell Labs
              Bell  Labs Computing and Mathematical Sciences Research provides
              a  search  facility  for  tracking  information  on  the   early

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

       runoff Jerry  Saltzer’s  home  page  stores  some  documents  using the
              ancient RUNOFF formatting language.

       CSTR Papers
              The Bell Labs CSTR site stores the original troff manuals  (CSTR
              #54,  #97,  #114, #116, #122) and famous historical documents on

       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.  Ossanna,  Nroff/Troff  Users  Manual  Bell  Labs,  1976;
              revised by Brian Kernighan, 1992.

       [CSTR #97]
              Brian Kernighan, A Typesetter-independent TROFF 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 Bell Labs, August 1984.

       [CSTR #116]
              Brian  W.  Kernighan,  PIC  A Graphics Language for Typesetting
              Bell Labs, December 1984.

       [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, 2006, 2007, 2008, 2009 Free
       Software Foundation, Inc.

       This document is distributed under the  terms  of  the  FDL  (GNU  Free
       Documentation  License) version 1.3 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