roff

ROFF(7)                Miscellaneous Information Manual                ROFF(7)



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 Manual http://www.troff.org/
              54.pdf⟩; Bell Labs, 1976; revised by Brian Kernighan, 1992.

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

       [CSTR #116]
              Brian W. Kernighan, PIC – A Graphics Language for Typesettinghttp://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.



groff 1.22.4                   23 December 2019                        ROFF(7)