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ROFF(7)                Miscellaneous Information Manual                ROFF(7)

       roff - concepts and history of roff typesetting

       roff is the general name for a set of type-setting programs, known
       under names like troff, nroff, ditroff, groff, etc.  A roff type-
       setting system consists of an extensible text formatting language and a
       set of programs for printing and converting to other text 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
       standard today.

       In some ancient Unix systems, there was a binary called roff that
       implemented the even more ancient runoff of the Multics operating
       system, cf. section HISTORY.  The 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
       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.

       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
       systems CTSS and Multics.

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

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

       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
       system.  All modern roff systems try to implement compatibility to this
       system.  So Joe Osanna can be called the father of all roff systems.

       This first roff system had three formatter programs.

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

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

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

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

       As a counter-measure to the galopping commercialization, AT&T Bell Labs
       tried to launch a rescue project with their Plan 9 operating system.
       It is freely available for non-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 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
       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.


       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 formulae
              pic   for drawing diagrams
              refer for bibliographic references
                    for including macro files from standard locations

       Other known preprocessors that are not available on all systems include

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

   Formatter Programs
       A roff formatter is a program that parses documents written in the roff
       formatting 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, 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 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 \)\$* 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
       `\f[B]\*[@1]\f[]'\$* 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 \)\$* 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.

       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:


       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

       The following example shows how optimal roff editing could look.

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

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

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

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

   Internet sites
              provides an overview and pointers to all historical aspects of

              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
              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

       Developers at AT&T Bell Labs
              provides a search facility for tracking information on the early

       Plan 9 by AT&T Bell Labs.

       runoff stores some documents using the ancient runoff formatting

       CSTR Papers
              stores the original troff manuals (CSTR #54, #97, #114, #116,
              #122) and famous historical documents on programming.

       GNU roff
              provides the free roff implementation groff, the actual standard

   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, Bell Labs, 1976; revised by Brian Kernighan, 1992.

       [CSTR #97]
              Brian Kernighan, Bell Labs, 1981, revised March 1982.

       The "little language" roff papers are

       [CSTR #114]
              Jon L. Bentley and Brian W. Kernighan, Bell Labs, August 1984.

       [CSTR #116]
              Brian W. Kernighan, Bell Labs, December 1984.

       [CSTR #122]
              J. L. Bentley, L. W. Jelinski, and B. W. Kernighan, 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
       Documentation License) version 1.1 or later.  You should have received
       a copy of the FDL on your system, it is also available on-line at the

       This document is part of groff, the GNU roff distribution.  It was
       written by it is maintained by

Groff Version 1.19.2           September 4, 2005                       ROFF(7)