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NAME | DESCRIPTION | HISTORY | USING ROFF | ROFF PROGRAMMING | FILE NAME EXTENSIONS | EDITING ROFF | AUTHORS | SEE ALSO | COLOPHON |
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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 text formatting programs, known
under names like troff, nroff, ditroff, groff, etc. A roff system
consists of an extensible text formatting language and a set of
programs for printing and converting to other text formats. Unix-
like operating systems distribute a roff system as a core package.
The most common roff system today is the free software implementation
GNU roff, groff(1). groff implements the look-and-feel and
functionality of its ancestors, with many extensions.
The ancestry of roff is described in section HISTORY. In this
document, the term roff always refers to the general class of roff
programs, not to the roff command provided in early UNIX systems.
In spite of its age, roff is in wide use today, for example, the
manual pages on UNIX systems (man pages), many software books, system
documentation, standards, and corporate documents are written in
roff. The roff output for text devices is still unmatched, and its
graphical output has the same quality as other free type-setting
programs and is better than some of the commercial systems.
roff is used to format UNIX manual pages, (or man pages), the
standard documentation system on many UNIX-derived operating systems.
This document describes the history of the development of the roff
system; some usage aspects common to all roff versions, details on
the roff pipeline, which is usually hidden behind front-ends like
groff(1); a general overview of the formatting language; some tips
for editing roff files; and many pointers to further readings.
Document formatting by computer dates back to the 1960s. The roff
system itself is intimately connected to the Unix operating system,
but its roots go back to the earlier operating systems CTSS and
Multics.
The Predecessor RUNOFF
roff's ancestor RUNOFF was written in the MAD language by Jerry
Saltzer for the Compatible Time Sharing System (CTSS), a project of
the Massachusetts Institute of Technology (MIT), in 1963 and
1964—note that CTSS commands were all uppercase.
In 1965, MIT's Project MAC teamed with Bell Telephone Laboratories
(BTL) and General Electric to begin the Multics system
⟨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 con‐
sisting 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 fea‐
tures 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 ver‐
sions. 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 pub‐
lished 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 specifica‐
tion.
After Ossanna's death in 1977, Kernighan went on with developing
troff. In the late 1970s, Kernighan equipped troff with a general
interface to support more devices, the intermediate output format,
and the postprocessor system. This completed the structure of a roff
system as it is still in use today; see section USING ROFF. In 1979,
these novelties were described in the paper [CSTR #97]. This new
troff version is the basis for all existing newer troff systems,
including groff. On some systems, this device independent troff got
a binary of its own, called ditroff(7). All modern troff programs
already provide the full ditroff capabilities automatically.
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 com‐
mand:
$ 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⟩.
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.
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.
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(7).
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 “syn‐
tax”. 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.
This document was written by Bernd Warken ⟨groff-bernd.warken-72@
web.de⟩.
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/⟩ pro‐
vides 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⟩ pro‐
vides 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 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 rea‐
sonable 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 documenta‐
tion available in groff.
On other systems, you are on your own, but troff(1) might be a good
starting point.
This page is part of the groff (GNU troff) project. Information
about the project can be found at
⟨http://www.gnu.org/software/groff/⟩. If you have a bug report for
this manual page, see ⟨http://www.gnu.org/software/groff/⟩. This
page was obtained from the project's upstream Git repository
⟨https://git.savannah.gnu.org/git/groff.git⟩ on 2018-02-02. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2018-02-02.) If you discover any rendering problems in
this HTML version of the page, or you believe there is a better or
more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not part
of the original manual page), send a mail to man-pages@man7.org
Groff Version 1.22.3 24 November 2017 ROFF(7)
Pages that refer to this page: groff(1), groffer(1), troff(1), groff_filenames(5), groff_out(5), groff_tmac(5), ditroff(7), groff(7), groff_diff(7)
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