Provided by: groff_1.22.4-3_amd64 bug

NAME

       roff - concepts and history of roff typesetting

DESCRIPTION

       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” below.  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.

HISTORY

       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 ⟨http://www.multicians.org⟩.  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.

       There is a free archive about historical RUNOFF documents.  You can get it anonymously  by
       the shell command
              $git clone https://github.com/bwarken/RUNOFF_historical.git

       As  well, there is a new project for writing a program that can read RUNOFF files , but it
       does not yet work so far.  You can get an early version anonymously by the shell command
              $git clone https://github.com/bwarken/runoff.git

   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 system 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 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 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” below.  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.

   Availability
       The  source  code  of  both the ancient Unix and classical troff weren't available for two
       decades.  Nowadays, it is accessible again (on-line) for non-commercial use; see SEE ALSO,
       below.

   groff  free GNU 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 ⟨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
       today.

   Free Heirloom roff
       An alternative is Gunnar  Ritter's  Heirloom  roff  project  ⟨https://github.com/n-t-roff/
       heirloom-doctools⟩  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.  You can get this package with the shell command:
              $ git clone https://github.com/n-t-roff/heirloom-doctools

       Moreover,  one  finds  there  the  Original  Documenter's  Workbench Release 3.3 ⟨https://
       github.com/n-t-roff/DWB3.3⟩.

USING ROFF

       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.  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 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.

              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.

   Preprocessors
       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 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
       integral 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.
              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 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
       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.

ROFF PROGRAMMING

       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 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
       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  User's  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 features.

       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.

FILE NAME EXTENSIONS

       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. 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:

              LESSOPEN='|lesspipe %s'

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

       More details for file name extensions can be found at groff_filenames(5).

EDITING ROFF

       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 judicious line breaking in a roff input file.

              This is an example of a
              .I roff
              document that you can type into your text editor.
              .
              This is the next sentence in the same paragraph.
              .
              This is a longer sentence stretching over several input lines;
              abbreviations like cf. are easily identified because the dot is
              not followed by a line break.
              .
              In the output, this sentence continues the same paragraph.

   Editing with Emacs
       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 press 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.

   Editing with Vim
       Besides Emacs, some other editors provide nroff style files too, e.g. vim(1), an extension
       of  the  vi(1) program.  Vim's highlighting can be made to recognize roff files by setting
       the filetype option in a Vim modeline.  For this feature to work, your copy of vim must be
       built  with  support for, and configured to enable, several features; consult the editor's
       online help topics “auto-setting”, “filetype”, and “syntax”.  Then put  the  following  at
       the end of your roff files, after any Emacs configuration:

                     .\" vim: set filetype=groff:

       Replace  “groff” in the above with “nroff” if you want highlighing that does not recognize
       many of the GNU extensions to roff, such as request, register,  and  string  names  longer
       than two characters.

AUTHORS

       This document was written by Bernd Warken ⟨groff-bernd.warken-72@web.de⟩.

SEE ALSO

       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
       History of Unix Manpages
              The  history  page  ⟨http://manpages.bsd.lv/history.html⟩  of  the  mdocml  project
              provides  an  overview  of  roff  development  up  to  date, with links to original
              documentation and comments of the original authors.

       troff.org
              The historical troff site ⟨http://www.troff.org⟩ provides an overview and  pointers
              to the historical aspects of roff.

       Multics
              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/
              V7⟩.

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

       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   (now   Alcatel)   CSTR   site  ⟨https://www.alcatel-lucent.com/
              bell-labs-journals⟩ stores the original 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
              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 User's Manualhttp://www.troff.org/54.pdf⟩; Bell Labs,
              1976; revised by Brian Kernighan, 1992.

       [CSTR #97]
              Brian Kernighan,  A  Typesetter-independent  TROFFhttp://cm.bell-labs.com/cm/cs/
              cstr/97.ps.gz⟩, 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 Graphshttp://cm.bell-labs.com/cm/cs/cstr/114.ps.gz⟩; Bell Labs, August 1984.

       [CSTR #116]
              Brian  W.  Kernighan,  PIC    A  Graphics  Language   for   Typesetting   ⟨http://
              cm.bell-labs.com/cm/cs/cstr/116.ps.gz⟩; 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   ⟨http://
              cm.bell-labs.com/cm/cs/cstr/122.ps.gz⟩; Bell Labs, April 1986.

       You  can  get an archive with most classical roff documentation as reasonable PDF files at
       github using the shell command
              $ git clone https://github.com/bwarken/roff_classical.git

   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 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.