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Section: Environments, Tables, and Troff Macros (7)
Updated: 23 April 2002
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roff - concepts and history of roff typesetting
is the general name for a set of type-setting programs, known under
A roff type-setting system consists of an extensible text formatting
language and a set of programs for printing and converting to other
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
The pre-groff implementations are referred to as
(dating back as long as 1973).
implements the look-and-feel and functionality of its classical
ancestors, but has many extensions.
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
that implemented the even more ancient
operating system, cf. section
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
always refers to the general meaning of
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
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
this is the standard documentation system on many operating systems.
This document describes the historical facts around the development
some usage aspects common to all roff versions, details on the roff
pipeline, which is usually hidden behind front-ends like
an general overview of the formatting language; some tips for editing
roff files; and many pointers to further readings.
text processing system has a very long history, dating back to the
The roff system itself is intimately connected to the Unix operating
system, but its roots go back to the earlier operating systems CTSS
The Predecessor runoff
The evolution of
is intimately related to the history of the operating systems.
was written by
(Compatible Time Sharing System)
as early as 1961.
When CTTS was further developed into the operating system
the famous predecessor of Unix from 1963,
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
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 on.
The runoff program was written in the
language first, later on in
the grandmother of the
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
The Classical nroff/troff System
In the 1970s, the Multics off-spring
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
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.
was shortened to
The greatly enlarged language of Osanna's concept included already all
elements of a full
All modern roff systems try to implement compatibility to this system.
So Joe Osanna can be called the father of all roff systems.
had three formatter programs.
generated a graphical output for the
typesetter as its only device.
produced text output suitable for terminals and line printers.
was the reimplementation of the former runoff program with its limited
features; this program was abandoned in later versions.
Today, the name
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.
development by rewriting it in the C~programming language.
The C~version was released in 1975.
The syntax of the formatting language of the
programs was documented in the famous
Troff User's Manual [CSTR~#54],
first published in 1976, with further revisions up to 1992 by Brian
This document is the specification of the
systems tried to establish compatibility with this specification.
After Osanna had died in 1977 by a heart-attack at the age of about~50,
Kernighan went on with developing troff.
The next milestone was to equip troff with a general interface to
support more devices, the intermediate output format and the
This completed the structure of a
as it is still in use today; see section
In 1979, these novelties were described in the paper
This new troff version is the basis for all existing newer troff
On some systems, this
device independent troff
got a binary of its own, called
programs already provide the full ditroff capabilities automatically.
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 [lq]their[rq] system [em] 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
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
It is freely available for non-commercial use, even the source code,
but has a proprietary license that empedes 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
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 [em] thanks to free software.
The most important free roff project was the GNU port of troff,
created by James Clark and put under the
It was called
for an overview.
The groff system is still actively developed.
It is compatible to the classical troff, but many extensions were
It is the first roff system that is available on almost all operating
systems [em] 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
Roff documents can be viewed with a native viewer called
a standard program of the X window distribution, see
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
provides command line options to avoid the long command pipes of
classical troff; a program
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
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
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.
ellCommand @1] @2] @3]
The preprocessors generate roff code that is fed into a roff formatter
(e.g. troff), which in turn generates
that is fed into a device postprocessor program for printing or final
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
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
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
The classical preprocessors are
Other known preprocessors that are not available on all systems
- for tables
- for mathematical formul[ae]
- for drawing diagrams
- for bibliographic references
- for including macro files from standard locations
- for drawing chemical formul[ae].
- for constructing graphical elements.
- for including
is a program that parses documents written in the roff formatting
language or uses some of the roff macro packages.
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
The output produced by a roff formatter is represented in yet another
intermediate output format
This language was first specified in
its GNU extension is documented in
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,
for text devices and
for graphical devices.
Often, the name
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
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
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
For example, the Postscript device
in classical troff had a resolution
of 720, while groff's
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
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 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
All tmac files are stored in one or more directories at standardized
Details on the naming of macro packages and their placement is found
A macro package that is to be used in a document can be announced to
the formatter by the command line option
or it can be specified within a document using the file inclusion
requests of the roff language, see
Famous classical macro packages are
for traditional man pages,
for BSD-style manual pages;
the macro sets for books, articles, and letters are
(probably from the first name of its creator
The roff Formatting Language
The classical roff formatting language is documented in the
Troff User's Manual
The roff language is a full programming language providing requests,
definition of macros, escape sequences, string variables, number or
size registers, and flow controls.
are the predefined basic formatting commands similar to the commands
at the shell prompt.
The user can define request-like elements using predefined roff
These are then called
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.
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
in-line comments with
the escaping of special control characters like
and many other features.
are variables that can store a string.
A string is stored by the
The stored string can be retrieved later by the
store numbers and sizes.
A register can be set with the request
and its value can be retrieved by the escape sequence
FILE NAME EXTENSIONS
Manual pages (man pages) take the section number as a file name
extension, e.g., the filename for this document is
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
But there is no general naming scheme for roff documents, though
is seen now and then.
Maybe there should be a standardization for the filename extensions of
File name extensions can be very handy in conjunction with the
It provides the possibility to feed all input into a command-line pipe
that is specified in the shell environment variable
This process is not well documented, so here an example:
ellCommand LESSOPEN='|lesspipe %s'
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
It provides an
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
means to hold down the
and hitting the
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.
Comment] Local Variables:
Comment] mode: nroff
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
Comment] -*- nroff -*-
as the first line of a file to have it started in nroff mode when
Unfortunately, some applications such as the
program are confused by this; so this is deprecated.
All roff formatters provide automated line breaks and horizontal and
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
if a structuring element is needed.
Never start a line with whitespace because this can lead to
Indented paragraphs can be constructed in a controlled way by roff
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
In the output, this will still go to the same
Besides Emacs, some other editors provide nroff style files too, e.g.
an extension of the
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.
provides an overview and pointers to all historical aspects of roff.
This web site is under construction; once, it will be the major source
for roff history.
contains a lot of information on the MIT projects, CTSS, Multics,
early Unix, including
especially useful are a glossary and the many links to ancient
- 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.
stores some documents using the ancient runoff formatting language.
- 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 roff.
Historical roff Documentation
documents are still available on-line.
The two main manuals of the troff language are
J. F. Osanna,
Bell Labs, 1976; revised by Brian Kernighan, 1992.
Bell Labs, 1981, revised March 1982.
The "little language" roff papers are
Jon L. Bentley and Brian W. Kernighan,
Bell Labs, August 1984.
Brian W. Kernighan,
Bell Labs, December 1984.
J. L. Bentley, L. W. Jelinski, and B. W. Kernighan,
Bell Labs, April 1986.
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.
the man page
contains a survey of all documentation available in groff.
On other systems, you are on your own, but
might be a good starting point.
Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.
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
the GNU roff distribution.
It was written by
it is maintained by
- The Predecessor runoff
- The Classical nroff/troff System
- Free roff
- USING ROFF
- The roff Pipe
- ellCommand @1] @2] @3]
- Formatter Programs
- Devices and Postprocessors
- ROFF PROGRAMMING
- Macro Packages
- ortOpt m ,
- The roff Formatting Language
- FILE NAME EXTENSIONS
- ellCommand LESSOPEN='|lesspipe (null)'
- EDITING ROFF
- SEE ALSO
- Internet sites
- Historical roff Documentation
- Manual Pages
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