Copyright (C) 1994 Free Software Foundation, Inc.
This is Edition XX of Groff,
for the XX version of the GNU implementation
of Groff
Published by the Free Software Foundation
675 Massachusetts Avenue,
Cambridge, MA 02139 USA
Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation.
GNU Troff (or Groff) is a system for typesetting documents. Troff is very flexible and has been in existence (and use) for about 2 decades. It is quite widespread and firmly entrenched in the UNIX community.
Groff is of an older generation of document preparation systems, which operate more like compilers than the more recent interactive WYSIWYG (1) systems. Groff and it's contemporary counterpart, TeX, both work using a batch paradigm: the input (or source) files are normal text files with the text and embedded formatting commands. These files can then be processed by Groff to produce a typeset document on a variety of devices.
Likewise, groff should not be confused with a word processor, since that term connotes an integrated system which includes an editor and a text formatter. Also, many word processors follow the WYSIWYG paradigm which was discussed earlier.
Although WYSIWYG systems may be easier to use, they have a number of disadvantages compared to Troff:
"GUIs normally make it simple to accomplish simple actions and impossible to accomplish complex actions." --Doug Gwyn (22/Jun/91 in comp.unix.wizards)
Troff can trace it's origins back to a formatting program called
runoff which ran on MIT's CTSS system. This name came from the
common phrase of the time "I'll run off a document."
The first version of UNIX was developed on a PDP7 which was sitting
around Bell Labs. In 1971 the developers wanted to get a PDP11 for
further work on the operating system. In order to justify the cost
for this system, they proposed that they would implement a document
formatting system for the AT&T patents division.
This first formatting program was a reimplementation of runoff.
In accordance with UNIX's penchant for abreviations, it was named
roff (an abreviation of runoff).
When they needed a more flexible language, a new version of
roff called nroff (Newer roff) was written. It
had a much more complicated syntax, but provided the basis for all
future versions. When they got a Graphic Systems CAT Phototypesetter,
J. F. Ossanna wrote a version of nroff which would drive it.
It was dubbed troff for typesetter roff, although many
people have speculated that it actually means Times roff because of
troff's use of the Times font family by default. As such, the name
troff is pronounced t-roff rather an trough.
With troff came nroff (they were actually the same program except for some `#ifdefs'), which was for producing output for line printers and ascii terminals. It understood everything troff did, and ignored the commands which were not aplicable (i.e. font changes).
Since there are several things which cannot be done easily in troff, work on several pre-processors began. These programs would transform certain parts of a document into troff, which made a very natural use of pipes in UNIX.
The eqn preprocessor allowed mathematical formulas to be specified in a much simpler and more intuitive manner. Tbl is a preprocessor for formatting tables. The refer pre-processor (and the similar program, bib) processing citations in a document according to a bibliographic database.
Unfortunately, Ossanna's troff was written in PDP-11 assembly language and produced output specifically for the CAT phototypesetter. He rewrote it in C, although it was now 7000 lines of uncommented code and still dependent on the CAT. As the CAT became less commom, and was no longer supported by the manufacurer, the need to make it support other devides became a priority. However, before this could be done, he was killed in an auto accident.
So, Brian Kernighan took on the task of rewriting troff. The newly rewritten version produced a device independent code which was very easy for post-processors to read and translate to the appropriate printer codes. Also, this new version of troff (called ditroff) had several extentions, which included drawing functions.
Due to the additional abilities of the new version of troff, several new preprocessors appeared. The pic preprocessor provides a wide range of drawing functions. Likewise the ideal preprocessor did the same, although via a much different paradigm. The grap preprocessor took specifications for graphs, but, unlike other preprocessors, produced pic code.
James Clark began work on a GNU implementation of ditroff in Early 1989. The first version, Groff 0.3.1, was released June 1990. Groff included
Also, a front-end was included which could construct the, sometimes painfully long, pipelines required for all the post- and pre-processors.
Development of GNU Troff progressed rapidly, and saw the additions of a replacement for refer an implemtation of the -ms and -mm macros and a program to deduce how to format a document (grog)
It was declared a stable (i.e. non beta) package with the release of version 1.04 around Nov 1991.
So what, exactly is groff capable of doing? Groff provides a wide range of low-level text formatting operations. Using these, you can perform a wide range of formatting tasks, such as, footnotes, table of contents, multiple columns, etc.
Since groff provides such low level facilities, it can be quite
difficult to use by itself. However, groff provides a macro
facility which allows you to specify how certain routine operations
(e.g. starting paragraphs, printing headers and footers, &c.) should
be done. These macros can be collected together into a macro
package. There are a number of macro packages available, the most
common (and the ones described in this manual) are -man
-me, -ms and -mm.
Although Groff provides most functions needed to format a document, some operations would be unwieldy (i.e. drawing pictures). Therefore, programs called pre-processors were written which understand their own language and produce the necessary groff operations. These pre-processors are able to differentiate their own input from the rest of the document via markers.
To use a pre-processor, UNIX pipes are used to feed the output from the pre-processor into Groff. Any number of pre-processors may be used on a given document, in this case, the pre-processors are linked together into one pipeline. However, in Groff, the user does not need to construct the pipe, but only tell groff what pre-processors to use.
Groff currently has pre-processors for producing tables (tbl), typesetting equations (eqn), drawing pictures (pic), and for processing bibliographies (refer). An associated program which is useful when dealing with preprocessors is soelim.
There are other pre-processors in existence, but there are, unfortunately, no free implementations available. They are for drawing pictures (ideal and gremlin), for drawing graphs (grap), chemical structures (chem).
Groff actually produces device independent code which may be fed into a post-processor which will produce output for a particular device. Currently, Groff has post-processors for Postscript, ASCII terminals, X windows (for previewing) and TeX DVI format.
Large portions of this manual were taken from existing documents, most notably, the manual pages for the groff package by James Clark, and Eric Allman's papers on the -me macro package.
This section focuses on how to invoke the groff front end.
This front end takes care of the details of constructing the pipeline
among the pre-processors, gtroff and the post-processor.
groff is a front-end to the groff document formatting system.
Normally it runs the gtroff program and a postprocessor
appropriate for the selected device. The default device is `ps'.
It can optionally preprocess with any of gpic, geqn,
gtbl, grefer, or gsoelim.
This section only documents options to the groff front end.
Many of the arguments to groff are passed on to gtroff,
therefore those are also included.
Arguments to pre- or post-processors are can be found in
@xref{Invoking gpic}, @xref{Invoking geqn}, @xref{Invoking gtbl},
@xref{Invoking grefer}, @xref{Invoking gsoelim},
section Invoking grotty, section Invoking grops, section Invoking grodvi
and section Invoking gxditview
The command line format for groff is:
groff [ -tpeszaivhblCENRVXZ ] [ -wname ] [ -Wname ]
[ -mname ] [ -Fdir ] [ -Tdev ] [ -ffam ]
[ -Mdir ] [ -dcs ] [ -rcn ] [ -nnum ]
[ -olist ] [ -Parg ] [ files... ]
The command line format for gtroff is as follows.
As you can see many of the options to groff are actually
passed on to gtroff.
gtroff [ -abivzCER ] [ -wname ] [ -Wname ] [ -dcs ]
[ -ffam ] [ -mname ] [ -nnum ]
[ -olist ] [ -rcn ] [ -Tdev ]
[ -Fdir ] [ -Mdir ] [ files... ]
Options without an argument can be grouped behind a single `-'. A filename of `-' denotes the standard input.
The grog command can be used to guess the correct groff
command to use to format a file.
geqn.
gtbl.
gpic.
gsoelim.
grefer.
No mechanism is provided for passing arguments
to grefer because most grefer options have equivalent
commands which can be included in the file.
@xref{Grefer}, for more details.
Note that gtroff also accepts a `-R' option, which is not
accessible via groff. This option prevents the loading of the
`troffrc' file.
groff print out their version number.
gtroff. Only error messages will be printed.
gtroff. Normally groff will
automatically run the appropriate postprocessor.
The postprocessor to be used for a device is specified by the postpro
command in the device description file. (See section Font files, for more info.)
This can be overridden with the
`-X' option.
gxditview instead of using the usual postprocessor.
This is unlikely to produce good results except with `-Tps'.
as or am
requests.
There are also several environment variables which can modify groff's behavior.
GROFF_COMMAND_PREFIX
GROFF_TMAC_PATH
GROFF_TYPESETTER
GROFF_FONT_PATH
PATH
GROFF_TMPDIR
TMPDIR is set, temporary files will be created in that
directory. Otherwise temporary files will be created in /tmp. The
grops and grefer commands can create temporary files.
This section will list several common uses of groff and the command line which will accomplish it.
groff file groff -X -me file groff -mm -rD1 -z file groff -tps -me file | lpr -Plw2 ... any more?? ...
grog reads files and guesses which of the groff preprocessors
and/or macro packages are are required for formatting them, and prints
the groff command including those options on the standard output.
The options generated are one of `-e', `-man', `-me',
`-mm', `-ms', `-p', `-s', and `-t'.
A filename of `-' is taken to refer to the standard input. If no files are specified the standard input will be read. Any specified options will be included in the printed command. No space is allowed between options and their arguments. For example,
`grog -Tdvi paper.ms`
will guess the approriate command to print `paper.ms' and then run it after adding the `-Tdvi' option.
Most users tend to use a macro package to format their papers. This means that the whole breadth of groff is not neccessary for most people. This chapter covers the material needed to efficiently use a macro package.
This section covers some of the basic concepts you will need to understand to use a macro package.(2) References are made throughout to more detailed information, if desired.
Groff reads an input file prepared by the user and outputs a formatted paper suitable for publication or framing. The input consists of text, or words to be printed, and embedded commands (requests and escapes), which tell groff how to format the printed copy. For more detail on this @xref{Embedded Commands}.
The word argument is used in this manual to mean a word or number which appears on the same line as a request which modifies the meaning of that request. For example, the request
.sp
spaces one line, but
.sp 4
spaces four lines. The number 4 is an argument to the sp
request which says to space four lines instead of one. Arguments
are separated from the request and from each other by spaces.
More details on this can be found in section Request Arguments.
The primary function of groff is to collect words from input lines, fill output lines with those words, justify the right hand margin by inserting extra spaces in the line, and output the result. For example, the input:
Now is the time for all good men to come to the aid of their party. Four score and seven years ago,...
will be read, packed onto output lines, and justified to produce:
Now is the time for all good men to come to the aid of their party. Four score and seven years ago,...
Sometimes you may want to start a new output line even though the line you are on is not yet full; for example, at the end of a paragraph. To do this you can cause a break, which starts a new output line. Some requests cause a break automatically, as do blank input lines and input lines beginning with a space.
Not all input lines are text to be formatted. Some of the input lines are requests which describe how to format the text. Requests always have a period or an apostrophe (`'') as the first character of the input line.
The text formatter also does more complex things, such as automatically numbering pages, skipping over page boundaries putting footnotes in the correct place, and so forth.
I can offer you a few hints for preparing text for input to groff. First, keep the input lines short. Short input lines are easier to edit, and groff will pack words onto longer lines for you anyhow. In keeping with this, it is helpful to begin a new line after every period, comma, or phrase, since common corrections are to add or delete sentences or phrases. Secondly, do not hyphenate words at the end of lines groff is smart enough to hyphenate words for you as needed, but is not smart enough to take hyphens out and join a word back together. Also, words such as "mother-in-law" should not be broken over a line, since then you will get a space where not wanted, such as "mother- in-law".
Groff will double space output text automatically if you use the request `.ls 2', as is done in this section. You can revert to single spaced mode by typing `.ls 1'.
A number of requests allow you to change the way the printed copy looks, sometimes called the layout of the output page. Most of these requests adjust the placing of "white space" (blank lines or spaces). In these explanations, characters in italics should be replaced with values you wish to use; bold characters represent characters which should actually be typed.
The `.bp' request starts a new page.
The request `.sp N' leaves N lines of blank space. N can be omitted (meaning skip a single line) or can be of the form Ni (for N inches) or Nc (for N centimeters). For example, the input:
.sp 1.5i My thoughts on the subject .sp
leaves one and a half inches of space, followed by the line "My thoughts on the subject", followed by a single blank line.
Text lines can be centered by using the `.ce' request. The line after the `.ce' is centered (horizontally) on the page. To center more than one line, use `.ce N' (where N is the number of lines to center), followed by the N lines. If you want to center many lines but don't want to count them, type:
.ce 1000 lines to center .ce 0
The `.ce 0' request tells groff to center zero more lines, in other words, stop centering.
All of these requests cause a break; that is, they always start a new line. If you want to start a new line without performing any other action, use `.br'.
Groff provides very low level operations for formatting a document. There are many common routine operations which are done in all documents. These common operations are written into macros and collected into a macro package.
All macro packages provide certain common capabilities which fall into the following categories.
One of the most common and most used capability is starting a paragraph. There are a number of different types of paragraphs, any of which can be initiated with macros supplied by the macro package. Normally paragraphs start with a blank line and the first line indented, like the text in this manual. There are also block style paragraphs, which omit the indentation:
Some men look at constitutions with sanctimonious reverence, and deem them like the ark of the covenant, too sacred to be touched.
And there are also indented paragraphs which begin with a tag or label at the margin and the remaining text indented.
one This is the first paragraph. Notice how the first
line of the resulting paragraph lines up with the
other lines in the paragraph.
longlabel
This paragraph had a long label. The first character
of text on the first line will not line up with the
text on second and subsequent lines, although they
will line up with each other.
A variation of this is a bulleted list....
Most macro packages supply some form of section headers. The simplest kind is simply the heading on a line by itself in bold type. Others supply automatically numbered section heading or different heading styles at different levels. Some, more sophisticated, macro packages supply macros for starting chapters and appendicies.
Every macro packages gives you some way to manipulate the headers and footers (or titles on each page. Some packages will allow you to have different ones on the even and odd pages (for material printed in a book form). The titles are called three-part titles, that is, there is a left-justified part, a centered part, and a right-justified part. An automatically generated page number may be put in any of these fields with the `%' character.
Most macro packages let you specify top and bottom margins and other details about the appearance of the printed pages.
Displays are sections of text to be set off from the body of the paper. Major quotes, tables, and figures are types of displays, as are all the examples used in this document.
Major quotes are quotes which are several lines long, and hence are set in from the rest of the text without quote marks around them.
A list is an indented, single spaced, unfilled display. Lists should be used when the material to be printed should not be filled and justified like normal text, such as columns of figures or the examples used in this paper.
A keep is a display of lines which are kept on a single page if possible. An example of where you would use a keep might be a diagram. Keeps differ from lists in that lists may be broken over a page boundary whereas keeps will not.
Floating keeps move relative to the text. Hence, they are good for things which will be referred to by name, such as "See figure 3". A floating keep will appear at the bottom of the current page if it will fit; otherwise, it will appear at the top of the next page. Meanwhile, the surrounding text will `flow' around the keep, thus leaving now blank areas.
There are a number of requests to save text for later printing. Footnotes are printed at the bottom of the current page. Delayed text is intended to be a variant form of foot- note; the text is printed only when explicitly called for, such as at the end of each chapter.
Delayed text is very similar to a footnote except that it is printed when called for explicitly. This allows a list of references to appear (for example) at the end of each chapter, as is the convention in some disciplines.
Most macro packages which supply this functionality also supply a means of automatically numbering either type of annotation.
Tables of contents are a type of delayed text having a tag (usually the page number) attached to each entry after a row of dots. The table accumulates throughought the paper until printed, usually after the paper has ended. Many macro packages will provide the abilitly to have several tables of contents (i.e. one standard one, one for tables, &c.)
While some macro packages will use the term index, none actually provide that functionality. The facilities they call indexes are actually more appropriate for tables of contents.
Some macro packages provide stock formats for various kinds of documents. Many of them provide a common format for the title and opening pages of a technical paper. The -mm macros in particular provide formats for letters and memorandums.
Some macro packages (except -man) provide the ability to have two or more columns on a page.
The builtin font and size functions are not always intuitive, so all macro packages provide macros to make these operations simpler.
Most macro packages provide various predefined strings for a variety of uses, examples are sub- and super-scripts, printable dates, quotes and various special characters.
All macro packages provide support for the various preprocessors.
Some macro packages provide means of customizing many of details of how the package behaves. This ranges from setting the default type size to changing the appearance of section headers.
This chapter covers all of the facilities of groff. If you are intending to use a macro package, you probably do not want to read this chapter.
groff input files contain text with control commands
interspersed throughout. But, even without control codes,
groff will still do several things with your text:
filling and adjusting,
adding additional space after sentences,
hyphenating
and
inserting implicit line breaks.
When troff reads in text it collects words from input and fits as many of them together on one output line as it can. This is known as filling.
Once troff has a filled line it will try to adjust it. which means it will widen the spacing between words until the text reaches the right margin (in the default adjustment mode). Extra spaces between words are preserved, but spaces at the end of lines are ignored. Spaces at the front of a line will cause a break (breaks will be explained in section Implicit Line Breaks)
See section Manipulating filling and adjusting
Since the odds of finding a set of words, for every output line, which will fit nicely on a line without inserting excessive amounts of space between words is not great, troff will hyphenate words so that lines can be justified without there being too much space between words. It uses an internal hyphenation algorithm, to indicate which words can be hyphenated and how to do so. When a word is hyphenated the first part of the word will be added to the current filled line being output (with an attached hyphen), and the other portion will be added to the next line to be filled.
See section Manipulating hyphenation
Although it is often debated, some typesetting rules say there should be different amounts of space after various puctuation marks. For example, a period at the end of a sentence should have twice as much space following it as would a comma or a period as part of an abbreviation.
Troff does this by flagging certain characters (normally `!', `?' and `.') as end of sentence characters. When troff encounters one of these characters at the end of a line it will append two sentence spaces in the formatted output. (thus, one of the conventions mentioned in section Input Conventions).
Groff translates tabs in the input into movements to the next tab stop. These tab stops are initially located every half inch across the page. Using this you can make simple tables. However, this can often be deceptive as the appearance (and width) of your text on a terminal and the results from groff can vary greatly.
Also, a possible sticking point is that lines beginning with tab characters will still be filled, again producing unexpected results. For example, the following input
1 2 3 4 5
will produce
1 2 3 4 5
See section Tabs and Fields
An important concept in troff is the break. When a break occurs, troff will output the partially filled line (unadjusted), and resume collecting and filling text on the next output line.
There are several ways to cause a break in troff. A blank line will not only cause a break, but it will also cause a one line vertical space (effectively a blank line) to be output.
A line which begins with a space will cause a break and the space will be output at the beginning of the next line. Note that this space isn't adjusted, even in fill mode.
The end of file will also cause a break (otherwise the last line of your document may vanish!)
Certain requests also cause breaks, implicitly or explicity. This will be discussed later.
See section Manipulating filling and adjusting
Since groff does filling automatically, it is traditional in groff not to try and type things in as nicely formatted paragraphs. These are some conventions commonly used when typing groff text:
Troff (like any other programs) requires numeric parameters to specify various measurements. Most numeric parameters (3) may have a measurement unit attached. These units are specified as a single character which immediately follows the number or expression. Each of these units are understood, by troff, to be a multiple of its basic unit. So, whenever a different measurement unit is specified troff converts this into its basic units. This basic unit, represented by a `u' is a device dependent measurement which is quite small, ranging from 1/75th to 1/72000th of an inch.
Some of the measurement units are compleatly independent of any of the current settings (e.g. type size) of groff.
The other measurements understood by troff are dependent on settings currently in effect in troff. These are very useful for specifying measurements which should look proper with any size of text.
See section Fractional Type Sizes
Many requests take a default unit. While this can be helpful at times, it can cause strange errors in some expressions. For example, the line length request expects em's. Here are several attempts to get 3.5 inches and the results:
3.5i => 3.5i 7/2 => 0i 7/2i => 0i 7i/2 => .1i 7i/2u => 3.5i
As you can see, the safest way to specify measurements is to always attach a scaling indicator.
Troff has most of operators common to other languages:
Parenthesis may be used as in any other language. However, in groff they are necessary to ensure order of evaluation. Groff has no operator precedence, expressions are evaluated left to right. This means that `3+5*4' is evaluated as if it were parenthesized like `(3+5)*4', not as `3+(5*4)', like you may expect.
For many requests which cause a motion on the page, the unary
operators work differently.
The `+' and `-' operators indicate a motion relative to the
current position (down or up, respectively). The `|' operator
indicates an absolute position on the page or input line. (????)
+ and - are also treated differently by nr (?)
Due to the way arguments are parsed, spaces are not allowed in expressions, unless the entire expression is surrounded by parenthesis.
See section Request Arguments See section Conditionals and Loops
Like any other language troff, has rules for properly formed identifiers. In troff an identifier can be made up of most any printable character. The only exception is characters which are interpreted by troff (backslash, square bracket and ?). So, for example, any of the following are valid.
br PP (l end-list @_
You can test whether an identifier is valid in groff with the
\A escape. It expands to 1 or 0 according whether its argument
(given in quotes) is or is not acceptable as the name of a string,
macro, diversion, number register, environment or font. It will return
0 if no argument is given. This is useful if you want to lookup user
input in some sort of associative table.
Identifiers in groff can be any length, but, in some contexts, groff needs to told where identifiers end and text begins (and in different ways depending on their length)
Unlike many other programming languages, undefined identifiers are silently ignored or expanded to nothing.
See section Interpolating Registers See section Strings
With most documents you need more funtionality beyond filling, adjusting and implicit line breaking. In order to gain further functionality, groff allows commands to be embeded into your text, in two ways.
The first is a request which takes up an entire line, and does some large scale operation (e.g. break lines, start new pages).
The other is an escape which can be embeded anywhere in your text, or even as an argument to a request. (Not always?) Escapes generally do more minor operations like sub- and super- scripts, print a symbol, &c.
A request line begins with a control character, which is either a single quote (`'') or a period (`.'). These can be changed see section Character Translations, for details. After this there may be optional tabs or spaces followed by an identifier which is the name of the request. This may be followed by any number of space separated arguments.
If you want to begin a line with a control character without it being
interpreted, precede it with a \&. This represents a zero
width space, which means it will not affect you output.
In most cases you will use the period as a control character. Several requests will cause a break, using the single quote control character will prevent this.
Argument to requests (and macros) are processed much like the shell: The line is split into arguments according to spaces. An argument which is intended to contain spaces can either be enclosed in quotes (single or double), or have the spaces escaped with backslashes.
So, for example:
.uh The Mouse Problem .uh "The Mouse Problem" .uh The\ Mouse\ Problem
The first line is the .uh macro being called with 3 arguments,
`The', `Mouse', and `Problem'.
The latter two have the same effect or calling the .uh macro
with one argument `The Mouse Problem'.
Note, however, that the .ds request works differently.
See section Strings
Troff has a macro facility for defining a series of lines which can be invoked by name. They are called in the same manner as requests and arguments may be passed in the same manner.
See section Writing Macros See section Request Arguments
Escapes may occur anywhere in the input to groff.
They begin with a backslash and are followed by a single character
which indicates the function to be performed.
If you want to have a backslash appear in your document, you should
use the escape sequence \e. Merely escaping the backslash
with another backslash will work in some curcumstances.
Many escapes have no parameters, those that do, do so in one of two ways. For escapes which require an identifier there must be a way for groff to tell where the identifier ends and the text begins. It assumes that the next single character is the identifier, but if that character is an open parenthesis, it takes the next two characters as the identifier; and if the next character is an open bracket, all characters until a close bracket are taken as the identifier. Note that in the second case there is no closing parenthesis. For example:
\fB \n(XX \*[TeX]
Other escapes may require several arguments and/or some special format. In these cases the argument is enclosed in single quotes (not required??) and the enclosing text is decoded according to what that escape expects.
\l'1.5i\(bu'
If you want to have a backslash appear in your output, you can use several
escapes: \\, \e or \E.
These are very similar, and only differ with respect to being used in
macros or diversions (See section Copy-in Mode, and section Diversions, for
more information)
See section Identifiers
Probably one of the most(4)
common forms of escapes is the comment.
They begin with the \" escape and end at the end of the input
line.
This may sound simple, but it can be tricky to keep the comments from interfering with the apperarance of your final outupt.
If the escape is to the right of some text or a request, that portion
of the line will be ignored, but the space leading up to it will be
noticed by groff. This only affects the .ds request (any
others?).
One possibly irritating idiosyncracy is that you mustn't use tabs to line up your comments. Tabs are not treated as white space between request and macro arguments.
If you have a comment on a line by itself, it will be treated as a
blank line, because after eliminating the comment, that is all that
remains. So, it is common to start the line with .\" which
will cause the line to be treated as an undefined request.
Another commenting scheme seen sometimes is three consecutive single
quotes ("') at the begining of a line. This works, but groff
will give a warning about an undefined macro, which is harmless, but
irritating.
Now to avoid all this groff has a new comment mechanism using the
\# escape. This escape works the same as \" except
that the newline is also ignored.
For large blocks of text, the ig request may be useful.
See section Strings
Registers are groff's numeric variables. groff has a number of builtin registers, supplying anything from the date to details of formatting parameters.
See section Identifiers
Registers are defined/set via the nr
request or the \R escape, for example, the following two lines
are equivalent:
.nr a 1 \R'a 1'
The rr request will
remove the register specified by the argument.
The rnn request will rename a number register.
The format is `.rnn x y', which will
rename number register x to y.
Aliases can be created for a number register. The format is `.aln xx yy', which will create an alias xx for number register object named yy. The new name and the old name will be exactly equivalent. If yy is undefined, a warning of type `reg' will be generated, and the request will be ignored. See section Debugging, for information about warnings.
Numeric registers are interpolated via the \n escape.
.nr as \na+\na \n(as
Number registers can also be auto incremented/decremented. You can
specify the increment/decrement factor with third argument to the
nr request. The default value is 0. For example:
.nr a 0 1 .nr xx 0 5 \n+a, \n+a, \n+a, \n+a, \n+a .br \n+(xx, \n+(xx, \n+(xx, \n+(xx, \n+(xx
Produces:
1, 2, 3, 4, 5 5, 10, 15, 20, 25
If you want to change the increment factor without changing the value of a register, the following can be used.
.nr a \na 10
When a register is used in the text of an input file
(as opposed to part of an expression)
it is textually replaced (or interpolated) with a representation of
that number.
This output format can be changed to a variety of formats
(numbers, roman numerals, etc)
This is done using the af request.
The first argument to af is the name of the number register to
be changed,
and the second argument is the output format.
The following output formats are available:
The following example will produce `10, X, j, 010'.
.nr a 10 .af a 1 \" the default format \na, .af a I \na, .af a a \na, .af a 001 \na
The \g escape returns the current format of the specified
register. For example, `\ga' after the following example would
produce `001'.
The following are some builtin registers, which are not listed elsewhere in this manual. Any registers which begin with a `.' are read-only. A compleat listing of all builtin registers can be found in section Register Index.
.H
.V
dw
dy
mo
yr
.c
c.
ln
.x
.x will contain 1.
.y
.y will contain 03.
.g
.A
.P
Several ways of causing breaks were given in
section Implicit Line Breaks.
The br request will likewise cause a break.
Several other requests will also cause breaks, implicitly.
They are
bp,
ce,
fi,
fl,
in,
nf,
sp and
ti.
Initially, groff will fill and ajust text to both margins.
Filling can be disabled via the nf request
and re-enabled with the fi request.
These implicitly disable and re-enable adjusting.
Both of these will cause break in text currently being filled.
The number register .u is equal to 1 in fill mode and 0 in
no-fill mode.
Adjusting can be disabled with the ad request and re-enabled
with the na request.
The ad request takes a single argument to indicate how to
adjust text.
The current adjustment mode is available in the number register
.j.
With no argument to ad, troff will adjust lines the same way
it was the last time it was filling. For example:
text .ad r text .ad c text .na text .ad \" back to centering text
The escape \p will cause a break and cause the remaining text
to be adjusted.
The ss request allows you to change the minimum size of a
space between filled words.
This request takes it's units as one twelfth of the
spacewidth parameter for the current font. Initially both the word
space size and the sentence space size are 12.
When two arguments are given to the ss request, the second argument
gives the sentence space size. If the second argument is not given, the
sentence space size will be the same as the word space size.
The sentence space size
is used in two circumstances: if the end of a sentence occurs at the end
of a line in fill mode, then both an inter-word space and a sentence
space will be added; if two spaces follow the end of a sentence in the
middle of a line, then the second space will be a sentence space. Note
that the behaviour of Unix troff will be exactly that exhibited by GNU
troff if a second argument is never given to the ss request. In GNU
troff, as in Unix troff, you should always follow a sentence with either
a newline or two spaces.
The number registers .ss and .sss are
the values of the parameters set by the first and second
arguments of the ss request.
The ce request will center text.
While the `ad c' request will also center text, it has the side
effect of filling the text. The .ce request will not fill the
text it affects.
This request causes a break.
With no arguments, ce will fill the next line of text.
The single argument ce takes is a number indicating the
number of lines to be centered. With no argument centering is
disabled.
A common idiom is to turn on centering for a large number of lines, and then turn off centering when you are done with the centered text. This is useful for any request which takes a number of lines as an argument.
.ce 1000 replace this with something more interesting ... .ce 0
The .ce number register contains the number of lines remaining
to be centered, as set by the ce request.
A similar request is rj request which will justify unfilled
text to the right margin. Its arguments are identical to the
ce request.
The .rj number register is
the number of lines to be right-justified as set by the rj
request.
As discussed in section Hyphenation, groff will hyphenate words. There are a number of ways to modify the how hyphenation is done.
This hyphenation can be turned off with the nh request, and
turned back on with the hy request. However, troff's
hyphenation facilities are far more flexible than this. The hy
request can be used to tell troff to restrict hypenation to certain
cases. The request takes a single numeric argument.
The current hyphenation restrictions can be found in the number
register .hy
The hlm request will
set the maximum number of consecutive hyphenated lines to the value
given as the first argument.
If this number is
negative, there is no maximum. The default value is -1.
This value is
associated with the current environment. Only lines output from an
environment count towards the maximum associated with that environment.
Hyphens resulting from \% are counted; explicit hyphens are not.
The current setting of this is available in the .hlm request.
Also the number of immediately preceding consecutive hyphenated lines
are available in the number register .hlc.
The hw request allows you to specify how a specific word is
to be hyphenated. It takes only one argument which is the word with
hyphens at the hyphenation points. For example:
`.hw in-sa-lub-rious'.
You can also tell troff how to hyphenate words on the fly with the
use of the \% escape, also known as the hyphenation
character. Preceding a word with this character will prevent it
from being hyphenated, putting it in a word will indicate to troff
that the word may be hyphenated at that point. Note that this
mechanism will only affect one word, if you want to change the
hyphenation of a word for the entire document, use the hw
request.
The hc request allows you to change the hyphenation character.
The character specified as an argument will then work the same as the
\% escape, and, thus, no longer appear in the output. Without
an argument it will return the hyphenation character to \%.
To further customize hyphenation the hpf request will read in
a file of hyphenation patterns.
This file will be searched for in the
same way that `tmac.name' is searched for when the
`-mname' option is specified.
It should have the same format as the argument to the \patterns primitive in TeX; the letters appearing in this file are interpreted as hyphenation codes. A `%' character in the patterns file introduces a comment that continues to the end of the line.
The set of
hyphenation patterns is associated with the current language set by the
hla request. The hpf request is usually invoked by the
`troffrc' file.
.hcode c1 code1 c2 code2...
Set the hyphenation code of character c1 to code1 and that of
c2 to code2.
A hyphenation code must be a single input character (not a
special character) other than a digit or a space. Initially each
lower-case letter has a hyphenation code, which is itself, and each
upper-case letter has a hyphenation code which is the lower case
version of itself.
The hym request will set the hyphenation margin to the value
given as the first argument: when the current adjustment mode is not
`b', the line will not be hyphenated if the line is no more than
that amount short.
The default hyphenation margin is 0. The default scaling
indicator for this request is m. The hyphenation margin is associated
with the current environment. The current hyphenation margin is
available in the .hym register.
The hys request set the hyphenation space to the value given as
the first argument: when the current adjustment mode is b, don't
hyphenate the line if the line can be justified by adding no more than
that amount of extra space to each word space. The default
hyphenation space is 0. The default scaling indicator for this
request is m. The hyphenation space is associated with the current
environment. The current hyphenation space is available in the
.hys register.
The shc request will set the soft hyphen character to the
argument given as an argument. If the argument is omitted, the soft
hyphen character will be set to the default \(hy. The soft
hyphen character is the character which will be inserted when a word
is hyphenated at a line break. If the soft hyphen character does not
exist in the font of the character immediately preceding a potential
break point, then the line will not be broken at that point. Neither
definitions (specified with the char request) nor translations
(specified with the tr request) are considered when finding the soft
hyphen character.
The hla request will set the current hyphenation language to
that given by the first argument. Hyphenation exceptions specified
with the hw request and hyphenation patterns specified with the
hpf request are both associated with the current hyphenation
language. The hla request is usually invoked by the
`troffrc' file. The current hyphenation language is available
in the number register .hla.
The sp request will cause troff to space downwards the
distance specified as the first argument. With no argument it will
advance 1 line.
A negative argument will cause troff to move up the page the
specified distance.
If the argument is preceded by a `|' troff will move that
distance from the top of the page.
Often you may want your output to be double or triple spaced.
The ls request will cause troff to output n-1 blank
lines after each line of text, where n is the argument given to
the ls request. With no argument troff will go back to single
spacing. The number register .L contains the current line
spacing setting.
Sometimes, extra vertical spacing is only needed occasionaly,
i.e. to allow space for a tall construct (like an equation).
The \x escape will do this.
The escape is given a numerical argument (like `\x'3p'').
If this number is positive extra vertical space will be inserted
below the current line. A negative number will add space above.
If this escape is used multiple times on the same line, the maximum
values are used.
The .a number register contains the most recent
extra vertical emph line space.
... example of inline equation ...
Spacing (via either sp or via blank lines) can be disabled
with the ns request. This will enable no-space mode.
This mode will end when actual text is output or the rs
request is encountered. No-space mode will also prevent requests to
advance to the next page unless they are accompanied by a page number
(see section Page Control, for more information.)
Tab stops are much like those on a typewriter: a tab character (or the
\t escape) on input will cause horizontal motion to the next
tab stop.
Tab stops can be changed with the ta request.
This request takes a series of numbers as arguments which indicate
where each tab stop is to be (overriding any previous settings).
These can be specified absolutely,
i.e. as the distance from the left margin.
For example, the following wil set tab stops every one inch.
.ta 1i 2i 3i 4i 5i 6i
Tab stops can also be specified relatively (using a leading `+') which means that the specified tab stop will be set that distance from the previous tab stop. For example the following is equivalent to the previous example.
.ta 1i +1i +1i +1i +1i +1i
After the specified tab stops repeat values may be set for tabs beyond
the last one specified. This is most commonly used to specify tabs
set at equal intervals. The compleat syntax for setting tabs is
ta n1 n2 ... nn T r1 r2
... rn This will set tabs at positions n1, n2,
..., nn and then set tabs at nn+r1,
nn+r2, ..., nn+rn and then at
nn+rn+r1, nn+rn+r2, ...,
nn+rn+rn, and so on. For example the following is,
yet again, the same as the previous examples.
.ta T 1i
The material in each tab column may be justified to the right or left or centered in the column. This is specified by appending an `R', `L' or `C' to the number specifying that tab stop. The default justification is `L'.
.ta 1i 2iC 2iR
The number register .tabs contains
a string representation of the current tab settings suitable for use as
an argument to the ta request.
Normally troff will fill the space to the next tab stop with spaces.
In some cases you may wish to change this. The tc request
will do this. With no argument troff will revert to using spaces.
Sometimes you may wish to use the tc request to fill a tab
stop with a given character, but also, you want to use normal tab
stops on the rest of the line. For this groff provides an alternate
tab mechanism, called leaders which will do just that.
They are used exclusively to produce a repeated run of characters to
the next tab stop.
You can declare what character will be repeated with the lc
request. If you do not give it an argument, the leaders will act the
same as tabs.
The difference is that a leader is invoked by using the \a
escape.
So for a table of contents you may want to have tab stops defined so that the section number is one tab stop, the title is the second with the remaining space being filled with a line of dots and then the page number slightly separated from the dots.
.lc . .ta .5iR 5i +.25i 1.1\tFoo\a\t12
Fields are a more general way of laying out tabular data.
fc
The control character (`.') and the no-break control character
(`'') can be changed with the cc and c2 requests,
respectively.
The single argument is the new character to be used, with no argument
the normal control character is restored.
The eo request will compleatly disable the escape mechanism.
The ec request can be used to change the escape character from
the default `\' to what is specified as an argument.
The tr request will translate characters.
trnt
This is the same as the tr request except that the
translations do not
apply to text that is transparently throughput into a diversion with
\!. See section Diversions, for more information.
For example,
.tr ab .di x \!.tm a .di .x
will print `b'; if trnt is used instead of tr it
will print `a'.
The following drawing shows the dimensions which troff uses for placing a line of output onto the page. They are labeled with the request which manipulates that dimension.
| -->| in |<-- |
-->| po |<-----------ll------------>|
+----+----+----------------------+----+
| : : : |
+----+----+----------------------+----+
These dimensions are:
po
po request, and the
current setting can be found in the builtin number register .o
Note, that this request does not cause a break, so changing the page
offset in the middle of text being filled may not do what you expect.
in
in request, and
the current setting can be found in the builtin number register.
.i
This request causes a break.
There is also the request ti which will cause one output line
to be indented, after which the indentation returns to 0.
This request causes a break.
The number register .in is the indent that applies to the
current output line.
ll
.ll request, and the
current setting can be found in the builtin number register .l
Note, as the figure implies, line length is not affected by the current
indentation.
The number register .ll is
the line length that applies to the current output line.
.in +.5i .ll -.5i A bunch of really boring text which should be indented from both margins. replace me with a better (and more) example! .in -.5i .ll +.5i
Troff provides some very primitive operations for controlling page layout.
Troff lets you specify the page length via the pl request.
This is the length of the physical output page.
The current setting can
be found in the builtin number register .p. Note that this only
specifies the size of the page, not the not the top and bottom margins.
Those are not done by groff directly, See section Traps, for further
information on how to do this.
Troff provides several operations which help in setting up top and bottom titles (or headers and footers)
The tl request will print a title line, which consists
of three parts: a left justified portion, a centered portion and a
right justified portion. The argument to tl is specified as
'left'center'right'
The `%' character is replaced with the current page number.
The title line is printed using its own line length, which is
specified with the lt request. The current setting of this is
available in the .lt number register.
The pn request will change the page number of the next
page. The only argument is the page number.
The current page number is stored in the number register %.
The number register .pn contains the
number of the next page:
either the value set by a pn request, or
the number of the current page plus 1.
The pc request will change the page number character (used by
the tl request) to a different character. With no argument,
this mechanism is disabled.
See section Traps
To stop processing the current page, and move to the next page, you
can invoke the bp request. This request will also cause a
break. This request can also take an argument of what the next page
should be numbered.
The only difference
between bp and pn is that pn does not cause a
break or actually eject a page.
.de newpage 'bp 'sp .5i .tl 'left top'center top'right top' 'sp .3i ..
Often you may want to make sure that you have a certain amount of
space before a new page occurs. This is most useful to make sure
that there is not a single orphan line left at the bottom of a
page. The ne request will ensure that there is a certain
distance, specified by the first argument, before the next page is
triggered (see section Traps, for further information).
The default unit for ne is v's and the default argument
is 1v.
For example, to make sure that no fewer than 2 lines get orphaned, you can do the following before each paragraph.
.ne 2 .ti +5n text
The sv is similar to the ne request, it reserves the
specified amount of vertical space. If the desired amount of space
exists before the next trap (bottom page boundary), the space will be
output immediately. If there is not enough space, it is stored for
later output via the os request.
The default argument is 1v and the default units are v's.
Groff gives you the ability to switch fonts at any point in your
text. There are two ways to do this, via the ft request and
the \f escape.
Fonts are generaly specified as uppercase strings, which are usually 1 to 4 characters representing an abreviation of acronym of the font name.
The basic set of fonts are R, I, B, and BI. These are Times Roman, Italic, Bold, and Bold Italic. There is also at least one symbol font which contains various special symbols (greek, mathematics). These latter fonts cannot be used directly, but should be used via an escape.
You can change fonts with both the ft request.
With no arguments it
will switch to the previous font (also known as P).
eggs, bacon, .ft B spam .ft and sausage.
The \f escape is useful for changing fonts in the middle of words
eggs, bacon, \fBspam\fP and sausage.
Both of the above examples will produce the same output.
Sometimes when putting letters of different fonts, you need more or less space at such boundaries. There are two escapes to help with this.
The \/ escape
increases the width of the preceding character so that the spacing
between that character and the following character will be correct if
the following character is a roman character. For example, if an italic
f is immediately followed by a roman right parenthesis, then in many
fonts the top right portion of the f will overlap the top left of the
right parenthesis.
It is a good idea to use this escape sequence
whenever an italic character is immediately followed by a roman
character without any intervening space.
The \, escape
modifies the spacing of the following character so that the spacing
between that character and the preceding character will correct if the
preceding character is a roman character.
It is a good idea
to use this escape sequence whenever a roman character is immediately
followed by an italic character without any intervening space.
The ftr request will translate fonts, it is called as
`.ftr F G', which
Translate font F to G.
Whenever a font named F is referred to in \f
escape sequence,
or in the ft, ul, bd, cs, tkf,
special, fspecial, fp,
or sty requests, font G will be used. If G is
missing, or equal to F then font F will not be translated.
Due to the variety of fonts available, groff has added the concept of font families. Each of these families has four styles (R, I, B and BI),
The fonts are specified as the concatenation of the font family and style. Specifying a font without the family part will cause groff to use that style of the current family. By default, groff uses the Times family.
This way, you can just use the basic four fonts and select a different font family on the command line.
You can also switch font families with the fam request
The current font family is available in the number register
.fam.
This is a string-valued register.
spam, .fam H spam, .ft B spam, .fam T spam, .ft AR baked beans, .ft R and spam.
For the sake of old phototypesetters and compatability with old versions of troff, groff has the concept of font positions, on which various fonts are mounted. The last one or two are reserved for the symbol font(s).
New fonts can be mounted with the fp request.
These numeric positions can then be refered to with font changing commands.
When groff starts it is using font number one.
.fp 1 H .fp 2 HI .fp 3 HB wink, wink, .ft 2 nudge, nudge, .ft .ft 3 say no more! .ft
(note that after these font changes have taken place the original font is restored.)
The current font in use, as a font position. This can be useful to remember the current font, for later recall.
.nr save-font \n(.f ... lots 'o text ... .ft \n[save-font]
The number of the next free font position is available in the number
register .fp. This is useful when mounting a new font, like so:
.fp \n[.fp] NEATOFONT
Fonts not listed in the `DESC' file are automatically mounted on
the next available font position when they are referenced.
If a font is to be
mountfed explicitly with the fp request on an unused font position, it
should be mounted on the first unused font position, which can be found
in the .fp register; although troff does not enforce this strictly,
it will not allow a font to be mounted at a position whose number is
much greater than that of any currently used position.
The fp request has an optional third argument.
This argument gives the
external name of the font, which is used for finding the font
description file. The second argument gives the internal name of the
font which is used to refer to the font in troff after it has been
mounted. If there is no third argument then the internal name will be
used as the external name. This feature allows you to use fonts with
long names in compatibility mode.
Symbols can be inserted by using a special escape sequence.
This escape is simply the escape character (a backslash) followed by
an identifier. The symbol identifiers have to be two or more
characters, since single characters conflict with all the other
escapes. The identifier can be either preceded by a parenthesis if
it is two character, or surrounded by square brackets.
So, the symbol for pi can be produced either by \(*p or
\[*p].
area = \(*p\fIr\fP\u2\d
The escape \C'xxx' will typeset character named
xxx. Normally it is more convenient to use \[xxx].
But \C has the advantage that it is compatible with recent
versions of ditroff and is available in compatibility mode.
The escape \N'n' will typeset the character with code
n in the current font. n can be any integer. Most devices only
have characters with codes between 0 and 255. If the current font
does not contain a character with that code, special fonts will not be
searched. The \N escape sequence can be conveniently used on
conjunction with the char request:
.char \[phone] \f(ZD\N'37'
The code of each character is given in the fourth column in the font
description file after the charset command. It is possible to include
unnamed characters in the font description file by using a name of
`---'; the \N escape sequence is the only way to use these.
Each character has certain properties associated with it.
These properties can be modified with the cflags request.
The first argument is the the sum of the desired flags and the
remaining arguments are the characters to have those properties.
1
2
4
8
16
32
You can create new characters with the char request. It is
called as `.char c string' Define character c
to be string. Every time character c needs to be printed,
string will be processed in a temporary environment and the
result will be wrapped up into a single object. Compatibility mode
will be turned off and the escape character will be set to \ while
string is being processed. Any emboldening, constant spacing or
track kerning will be applied to this object rather than to individual
characters in string. A character defined by this request can
be used just like a normal character provided by the output device.
In particular other characters can be translated to it with the
tr request; it can be made the leader character by the
lc request; repeated patterns can be drawn with the character
using the \l and \L escape sequences; words containing
the character can be hyphenated correctly, if the hcode request
is used to give the character a hyphenation code. There is a special
anti-recursion feature: use of character within the character's
definition will be handled like normal characters not defined with
char.
A character definition can be removed with the rchar request. Its
arguments are the characters to be removed. This undoes the effect of
a char request.
See section Special characters
There are a number of requests for artificially creating fonts. These are largely vestigal remains from the days when output devices did not have a wide variety of fonts, and when nroff and troff were separate programs. These are no longer necessary in GNU Troff.
The ul request will print subsequent lines in italics on a
device capable of it, or underline the text on an ascii output device.
The single argument is the number of lines to be "underlined,"
with no argument, the next line will be underlined.
The cu request is similar to ul ...
The uf request will set the underline font used by ul
and cu.
The bd request artificially creates a bold font by printing
each character twice, slightly offset.
The first argument specifies the font to embolden, and the second is
the number of basic units, minus one, by which the two characters
will be offset. If the second argument is missing, emboldening will
be turned off.
lg
.lg
The current ligature mode.
What is kerning??
If the font description file contains pairwise kerning information,
characters from that font will be kerned. Kerning between two
characters can be inhibited by placing a \& between them.
kern
If n is non-zero or missing, enable pairwise kerning, otherwise disable
it.
.kern
1 if pairwise kerning is enabled, 0 otherwise.
.tkf f s1 n1 s2 n2 Enable track kerning for font f. When the current font is f the width of every character will be increased by an amount between n1 and n2; when the current point size is less than or equal to s1 the width will be increased by n1; when it is greater than or equal to s2 the width will be increased by n2; when the point size is greater than or equal to s1 and less than or equal to s2 the increase in width is a linear function of the point size.
Groff uses two dimensions with each line of text, type size and vertical spacing. The type size is the height from the text baseline to the top of the tallest character (decenders may drop below this baseline). Vertical spacing is the amount of space groff allows for a line of text, normally, this is about 20% larger than the current type size. Ratios smaller than this can result in hard-to-read text, larger that this, it will spread your text out more vertically (useful for term papers). By default, troff uses 10 point type on 12 point spacing.
The difference between type size and vertical spacing is known, by typesetters, as leading.
Using the ps request and the \s escape you can change
the type size. The vs request will change the vertical
spacing. The default unit for the ps and vs requests are
points.
The number registers .s and .v contain the current
type size and vertical spacing.
These requests take parameters in units of points. You can specify sizes as an absolute size, or as a relative change from the current size. The size 0 means go back to the previous size. With no argument it will revert to the previous size.
snap, snap, .ps +2 grin, grin, .ps +2 wink, wink, \s+2nudge, nudge,\s+8 say no more! .ps 10
The \s escape may be called in a variety of ways.
Much like other escapes there must be a way to determine where the
argument ends and the text begins.
Any of the following forms are valid:
\sn,
\s+n,
\s-n,
\s(nn,
\s+(nn,
\s-(nn,
\s[+nnn],
\s[-nnn],
\s+[nnn],
\s-[nnn].
Some devices may only have certain permissible sizes, in which case groff will round to the nearest permissible size.
... .sz macro example?? ...
A scaled point is equal to 1/sizescale points, where
sizescale is specified in the `DESC' file (1 by default.)
There is a new scale indicator `z' which has the effect of
multiplying by sizescale. Requests and escape sequences in
troff interpret arguments that represent a pointsize as being in units
of scaled points, but they evaluate each such argument using a default
scale indicator of `z'. Arguments treated in this way are the
argument to the ps request, the third argument to the cs
request, the second and fourth arguments to the tkf request,
the argument to the \H escape sequence, and those variants of
the \s escape sequence that take a numeric expression as their
argument.
For example, suppose sizescale is 1000; then a scaled point will be equivalent to a millipoint; the request `.ps 10.25' is equivalent to `.ps 10.25z' and so sets the pointsize to 10250 scaled points, which is equal to 10.25 points.
The number register \n(.s returns the pointsize in points as
decimal fraction. There is also a new number register \n[.ps]
that returns the pointsize in scaled points.
It would make no sense to use the `z' scale indicator in a numeric expression whose default scale indicator was neither `u' nor `z', and so troff disallows this. Similarily it would make no sense to use a scaling indicator other than `z' or `u' in a numeric expression whose default scale indicator was `z', and so troff disallows this as well.
There is also new scale indicator `s' which multiplies by the number of units in a scaled point. So, for example, `\n[.ps]s' is equal to 1m. Be sure not to confuse the `s' and `z' scale indicators.
\s'+n'
\s'-n'
\s+'n'
\s-'n'
Set the point size to n scaled points; n is a numeric
expression with a default scale indicator of `z'.
\n[.ps]
The current pointsize in scaled points.
\n[.psr]
The last-requested pointsize in scaled points.
\n[.sr]
The last requested pointsize in points as a decimal fraction. This is a
string-valued register.
See section Font files
Groff has string variables, which are entirely for user convenience
(i.e. there are no builtin strings) They are defined via the
ds request.
.ds UX \s-1UNIX\s0\u\s-3tm\s0\d
The are interpolated, or expanded in-place, via the \* escape:
The \*(UX Operating System
Will produce:
The UNIXtm Operating System
If the string named by the \* does not exist, the escape will
be replaced by nothing.
NOTE: Unlike other requests the third argument takes up the entire line including trailing spaces. This means that comments on a line with such a request can introduce unwanted space into a string.
.ds UX \s-1UNIX\s0\u\s-3tm\s0\d \" trademark of you-know-who
Instead you should either put the comment on another line or have the comment escape adjacent with the end of the string.
.ds UX \s-1UNIX\s0\u\s-3tm\s0\d\" trademark of you-know-who
If you need leading space you can start the string with a double quote. No trailing quote is needed, in fact any trailing quote is included in your string.
.ds sign " Yours in a white wine sauce,
You can also append onto a string with the as request.
It works the same as the ds request except that it appends the
second argument onto the string named by the first argument.
.as sign " with shallots, onions and garlic,
Strings are not limited to a sigle line of text. A string can span several lines by escaping the newlines with a backslash. The resulting string will be stored without the newlines.
.ds foo lots and lots \ of text are on these \ next several lines
chop
See section Identifiers See section Comments
In if and while requests, there are several more operators
available:
e
o
n
t
'xxx'yyy'
rxxx
dxxx
cch
\(ch or
\[ch]; the condition will also be true if ch has been
defined by the char request.
Troff has if-then-else constructs like other languages, although the formatting can be painful.
The if request is troff's if statement, it is called as
`.if expr anything', where expr is the
expression to be evaluated,
and anything (the remainder of the line)
which will be executed if
the expr evaluates to non-zero (true).
anything will be interpreted as though it was on a line by
itself.
See section Expressions, for more info.
Here are some examples:
.if t .ls 2 \" double spacing in troff .if 0 .ab how'd this happen??
An if-then-else is written using two requests ie and el
the first request is the if part and the latter is the else part.
.ie .el
In many cases you will want more than one request to be executed as a result of any of these requests, this can be done using the \{ and \} escapes. The following example shows the possible ways to use these escapes.
.ie t \{\
. ds lq "
. ds rq "
.\}
.el \
.\{\
. ds lq "
. ds rq "\}
.ds qq "
See section Expressions
Groff provides a looping construct using the while request,
which is used much like the if (and related) requests.
The first argument is an expression which will be evaluated.
The while request will interpret the remainder of the line
until the expression evaluates to 0 or false.
.nr a 0 1 .while (\na<9) \&\n+a, \&\n+a
The preceding example produces:
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
The break request will
break out of a while loop.
Be sure not to confuse this with the .br request.
The continue request will
finish the current iteration of a while loop.
See section Expressions
A macro is a collection of text and embeded commands which can be
invoked multiple times. Macros are used for defining common operations.
Macros are defined using the de request. This request takes
a name for the macro as the first argument. Subsequent lines are
copied into an internal buffer until the line .. is
encountered. The optional second argument to de can change
this ending token.
For example, suppose at the beginning of each paragraph, you want cause a break, move down a partial line and indent the first line. Such a macro could be defined as follows:
.de P .br .sp .8v ..
The am request works similarily to de except it appends
onto the macro named by the first argument. So, if we decide we want
our previously P macro to actually do indented instead of
block paragraphs we can add the necessary code to our existing macro.
.am P .ti +5n ..
Macros can be aliased with the als request.
chop
When troff reads in the test for a macro or diversion it copies the
text (including request lines) into an internal buffer, except for
escapes. Escapes will be converted into an internal form, except for
\n, \$, \*, \\ and \RET which
are evaluated and inserted into the text where the escape was located.
This is known as copy-in mode.
What this means is that you can specify when these escapes are to be evaluated (copy-in time or time of use) by insulating the escapes with an extra backslash.
For example, the following will result in the numbers 20 and 10 being printed.
.nr x 20 .de y .nr x 10 \&\nx \&\\nx .. .y
The arguments to a macro can be examined using a variety of escapes.
The number of arguments is available in the .$ number register.
Any individual argument can be retrieved with one of the following
escapes:
The escapes \$n, \$(nn
and \$[nnn]
will result in the nth, nnth or nnnth
argument. Macros can have a unlimited number of arguments.
Note that due to copy-in mode, you will want to have two backslashes
on these in actual use, since you do not want them interpolated until
the macro is actually invoked.
The request shift will shift the arguments 1 position, or as
many positions as specified by the first argument.
After executing this request, argument
i will become argument i-n; arguments 1 to n
will no longer be available.
Shifting by negative amounts is currently undefined.
In some cases you will want to just use all of the arguments at once.
For example if you pass the arguments along to another macro.
The \$* escape is
the concatenation of all the arguments separated by spaces.
A similar escape is \$@,
which is
the concatenation of all the arguments with each surrounded
by double quotes, and separated by spaces.
The \$0 escape is
the name by which the current macro was invoked. The als
request can make a macro have more than one name.
.de vl .ie \\n(.$=1 .ds Vl Pre-Release Version .el .ds Vl Version \\$3, \\$4. ..
This would be called as
.vl $Id: tprog.mo,v 1.2 93/01/22 13:29:46 trent Exp $
See section Request Arguments
Motions up and down the page can be done with the sp request.
However, this causes a break so that the actual effect is to move to
the left margin and then to the specified location.
The request mk can be used to mark a location on a page, for
movement to later. This request takes a register name as an
argument in which to store the current page location, with no
argument it will store the location in an internal register.
The results of this can be used later by the rt or the
sp request. The rt request will return
upwards to the location given in the register name given as
an argument, with no argument it will return to the location marked
with the mk request
... dual column example ...
There are escapes which will give you much finer control of movements about the page.
The \v'e' will let you do arbitrary vertical motion from
the current location on the page. The argument e specifies the
distance to move, positive is downwards and negative upwards. The
default unit for this escape is vertical spaces, v's. Beware,
however, that troff will leave text processing to continue wherever
the motion ends, so if you don't want to interfere with text
processing, make sure your motions are balanced.
There are some special case escapes for vertical motion.
\r
\u
\d
Horizontal motions can be done via the \h'e' escape.
The expression e indicates how far to move: positive is
rightwards and negative leftwards.
There are a number of special case escapes for horizontal motion:
\SP
\~
\|
\^
\0
\&
\)
\& except that it behaves like a character declared with
the cflags request to be transparent for the purposes of end
of sentence recognition.
... tex logo example ...
Often you will want to do horizontal movement based on the width of
some arbitrary text (e.g. given as an argument to a macro).
For that, there is the escape \w'text' which will
interpolate to the width of the given text in basic units.
... strlen example ...
Font changes may occur in text and not affect current settings.
Also after use, \w sets several registers:
st
sb
rst
rsb
st and sb registers, but takes account of the
heights and depths of characters.
ct
\w
argument, the center of an accent from a roman font should be
placed over that character.
\k
.k
Groff provides a number of ways to draw lines, and other figures on the page. Used in combination with the page motion commands (see section Page Motions, for more info) you can draw a wide variety of figures. However, for complex drawings these operations can be quite cumbersome, and it may be wise to use the pic preprocessor. @xref{pic}, for more information.
All drawing is done via escapes.
The \l will draw a line rightwards from the current location.
The full syntax for this escape is `\l'lc'', where
l is the length of the line to be drawn, starting at the
current location, positive numbers will draw to the right, and
negative will draw towards the left. This can also be specified
absolutely (i.e. with a leading |) which will draw back to the
begining of the line.
The optional second parameter c is a character to draw the line with. If this second argument is not specified, troff will use the underscore character.
If you need to separate the two arguments (to prevent troff from
interpreting a drawing character as a scaling indicator), you can
separate them with \&.
And now, for a useful example:
.de box \(br\\$*\(br\l'|0\(rn'\l'|0\(ul' ..
Note that this works by outputing a box rule (a vertical line), then the text given as an argument and then another box rule. Then the line drawing escapes both draw from the current location to the beginning of the input line.
Vertical lines are drawn using the \L escape. It's parameters
are specified the same as the \l escape. If the length is
positive, the movement will be downwards, and upwards for negative.
The default character is the box rule character.
As with the vertical motion escapes, text processing will blindly
continue where the line ends.
...box macro...
More flexible drawing functions are available via the \D
escape. While the previous escapes will work on an ascii device,
these escapes will not.
\D'l x y'
...revised box macro...
\D'c d'
\D'C d'
\D'e dx dy'
\D'E dx dy'
\D'a dx1 dy1 dx2 dy2'
\D'~ dx1 dy1 dx2 dy2 ...'
\D'f n'
\D'p dx1 dy1 dx2 dy2 ...'
... box example (yes, again)...
\D'P dx1 dy1 dx2 dy2 ...'
... shaded box example ...
\D't n'
The \b escape will pile a sequence of characters
vertically, and center it vertically on the current line.
This can be used to build large brackets and braces.
\b'\(lt\(bv\(lk\(bv\(lb'
Traps are locations, which, when reached, will call a specified macro. These traps can occur at a given location on the page, at a given location in the current diversion, after a certain number of input lines or at the end of input.
Any of these traps can be changed after they have been set with the
ch request. The first arguemnt is the name of the trap or
macro, and the second is the new value for that trap.
Page location traps are frequently used for page headers and footers. The following is a simple example of this.
.de hd \" Page header 'sp .5i .tl 'Title"date' 'sp .3i .. .de fo \" Page footer 'sp 1v .tl "%" 'bp .. .wh 0 hd \" top of the page .wh -1i fo \" one inch from bottom
The number register .t is the distance to the next trap.
The location of a trap can be changed later on with the ch
request.
The first argument is the name of the macro to be invoked at the trap
and the second argument is the new location for the trap.
This is useful when you are building up footnotes in a diversion, and
you need to allow more space at the bottom of the page for them.
... (simplified) footnote example ...
The vpt request will enable vertical position traps if the argment is
non-zero, disable them otherwise. Vertical position traps are traps
set by the wh or dt requests. Traps set by the
it request are not vertical position traps. The parameter that
controls whether vertical position traps are enabled is global.
Initially vertical position traps are enabled. The current setting of
this is available in the number register .vpt.
The number register .trunc contains
the amount of vertical space truncated by the most recently
sprung vertical position trap, or, if the trap was sprung by a
ne request, minus the amount of vertical motion produced by
the ne request. In other words, at the point a trap is
sprung, it represents the difference of what the vertical position
would have been but for the trap, and what the vertical position
actually is.
The number register .ne contains
the amount of space that was needed in the last ne request that caused
a trap to be sprung. Useful in conjunction with the .trunc
register. See section Page Control, for more information.
Traps can also be set within a diversion using the dt
request. Like wh the first argument is the location of the
trap and the second argument is the name of the macro to be invoked.
The number register .t will still work within diversions.
See section Diversions, for more information.
The it request will set an input line trap. The format for
calling this is `.it n name', where n is the
number of lines of input which may be read before springing the
trap, name is the macro to be invoked. Request lines are not
counted as input lines.
For example, one possible use is to have a macro which will print the next n lines in a bold font.
.de B .it B-end \\$1 .ft B .. .de B-end .ft R ..
The em request will set a trap at the end of input.
The macro specified as an arguement will be executed after the last
line of the input file has been processed.
For example, if your document had to have a section at the bottom of
the last page for someone to approve you document, you could set it
up with em.
.de approval .ne 5v .sp |(\\n(.t-6v) .in +4i .lc _ .br Approved:\t\a .sp Date:\t\t\a .. .em approval
In Troff you can divert text into a named storage area, due to the similarity to defining macros it is sometimes said to be stored in a macro. This is used for saving text for output at a later time, which is useful for keeping blocks of text on the same page, footnotes, tables of contents and indexes.
Diversion is initiated by the di request, like the de
request it takes an argument of a macro name to divert subsequent
text to into. The da macro will append to an existing diversion.
... end-note example ...
Diversions may be nested.
The number register .z contains the name of the current diversion.
The number register .d contains the current vertical place in
the diversion. If not in a diversion it is the same as the register
nl.
.h
After compleating a diversion, the builtin number registers dn
and dl contain the vertical and horizontal size of the diversion.
.\" Center text both horizontally & vertically .de (c .br .nf .di @c .. .de )c .br .di .nr @s (((\\n(.tu-\\n(dnu)/2u)-1v) .sp \\n(@su .ce 1000 .nf .@c .br .ce 0 .sp \\n(@su .br .fi .rr @s ..
Requests, macros and escapes are interpreted when read into a
diversion.
There are two ways to prevent this, either way will take the given
text and transparently embed it into the diversion.
The first method is to prefix the line with \!. This will
cause the entire line to be transparently inserted into the diversion.
This is useful for macros you do not want invoked until the diverted
text is actually output.
The other way is to surround the text by the \? escape, i.e.
`\?anything\?'.
anything may not contain
newlines; use \! if you want to embed newlines in a diversion. The
escape sequence \? is also recognised in copy mode and turned into a
single internal code; it is this code that terminates anything. Thus
the followin example will print 4.
.nr x 1 .nf .di d \?\\?\\\\?\\\\\\\\nx\\\\?\\?\? .di .nr x 2 .di e .d .di .nr x 3 .di f .e .di .nr x 4 .f
asciify
This request only exists in order to make it possible to make certain
gross hacks work with GNU troff. It unformats the diversion
specified as an argument in
such a way that ASCII characters that were formatted and diverted
will be treated like ordinary input characters when the diversion is
reread. For example, the following will set register n to 1.
.tr @. .di x @nr\ n\ 1 .br .di .tr @@ .asciify x .x
See section Copy-in Mode
Often you will need to print some text in a certain format regardless of what may be in effect at the time, for example, in a trap invoked macro to print headers and footers. To solve this groff has environments in which text is processed. An environment contains most of the parameters that control text processing. You can switch amongst these environments, by default groff processes text in environment 0. The following is the information kept in an environment.
These environments may be given arbitrary names (see section Identifiers, for more info.) Old versions of troff only had environments named 0, 1 and 2.
The ev request will switch among these environments.
The single argument is the name of the environment to switch to, with
no argument groff will switch back to the previous enviroment.
There is no limit on the number of named environments;
they will be created the first time that they are referenced.
The .ev number register contains
the name or number of the current environment. This is a string-valued
register.
... page break macro, revised ...
.ev footnote-env .fam N .ps 6 .vs 8 .ll -.5i .ev ... .ev footnote-env \(dg Note the large, friendly letters. .ev
The so request will read in the file given as an argument and
include it in place of the so request. This is quite useful
for large documents, i.e. keeping each chapter in a separate file.
@xref{soelim}, and @xref{Invocation}, for more information.
The mso request is
the same as the so request except that file is searched for in
the same way that `tmac.name' is searched for when the
`-mname' option is specified. @xref{Invocation}, for more
information.
The cf and trf requests are to include a file.
It will transparently output the contents of file filename. Each
line is output
as it would be were it preceded by \!; however, the lines are not
subject to copy-mode interpretation. If the file does not end with a
newline, then a newline will be added. For example, you can define a
macro x containing the contents of file `f', using
.di x .trf f .di
.cf filename When used in a diversion, this will embed in the diversion an object which, when reread, will cause the contents of filename to be transparently copied through to the output. In Unix troff, the contents of filename is immediately copied through to the output regardless of whether there is a current diversion; this behaviour is so anomalous that it must be considered a bug.
With trf, unlike cf, the file cannot contain characters
such as NUL that are not legal troff input characters.
The nx request will force groff to continue processing of the
file specified as an argument.
The rd request will read from standard input, and include what
is read as though it were part of the input file. Text is read until
a blank line is encountered.
Using these two requests you can set up form letters. The form letter template is constructed like this:
.ce \*(td .sp 2 .nf .rd .sp .rd .fi Body of letter. .bp .nx repeat.let
When this is run, the following file should be redirected in.
Note that requests included in this file are executed as though they
were part of the form letter. The last block of input is the
ex requests which tells groff to stop processing. If this was
not there, groff would not know when to stop.
Trent A. Fisher 708 NW 19th Av., #202 Portland, OR 97209 Dear Trent, Len Adollar 4315 Sierra Vista San Diego, CA 92103 Dear Mr. Adollar, .ex
The sy request will allow arbitrary system commands to be
executed from within a groff document. The output is not saved
anyplace, so it is up to you to do so.
For example, the following example will introduce the current time into your document:
.sy perl -e 'printf ".nr H %d\\n.nr M %d\\n.nr S %d\\n",\ (localtime(time))[2,1,0]' > /tmp/x\n[$$] .so /tmp/x\n[$$] .sy rm /tmp/x\n[$$] \nH:\nM:\nS
Note that this works by having the perl script (run by sy)
print out the nr requests which will set the number registers
`H', `M' and `S', and then reads those commands in
with the so request.
The systat number register contains
The return value of the system() function executed by the last
sy request.
The open request will open
a file (specified as the second argument) for writing and associate
the stream (specified as the first argument) with it.
The opena is
like open, but if filename exists, append to it instead of truncating
it.
The write request will write to the file associated with the
stream specified by the first argument. The stream must previously
have been the subject of an open request. The remainder of the line
in interpreted as the ds request reads its second argument: a
leading " will be stripped, and it will be read in copy-in mode.
The close request will
close the stream specified by the first argument; stream will no
longer be an acceptable argument to the write request.
... example of open write &c...
The \V escape will
interpolate the contents of the specified environment variable, as returned
by getenv(3).
The argument to \V is specified as an identifier, i.e.
`\Vx', `\V(xx' or `\V[xxx]'.
\V is interpreted in copy-in mode.
There are two escapes which will allow you to give information directly to the post-processor. This is particularly useful for embeding postscript into your final document.
The \X escape will embed its argument into the gtroff output
preceded with `x X'.
The \Y escape is called with an identifier (i.e.
\Yx,
\Y(xx or
\Y[xxx]).
This is approximately equivalent to `\X'\*[xxx]''.
However the contents
of the string or macro xxx are not interpreted; also it is
permitted for
xxx to have been defined as a macro and thus contain newlines
(it is not permitted for the argument to \X to contain newlines).
The inclusion of
newlines requires an extetension to the Unix troff output format, and will
confuse drivers that do not know about this extension.
See section Devices
This section contains parts of troff which cannot (yet) be categorized elsewhere in this manual.
Line numbers can be printed in the left margin
using the nm request.
The first argument is the line number of the next output line,
this defaults to 1.
The second argument indicates on which lines numbers will be printed,
i.e. 5 means put line numbers on every 5 lines, this defaults to 1.
The third argument is the space to be left between the number and
your text, this defaults to 1.
The fourth argument is the indentation of the line numbers.
Without arguments, line numbers are turned off.
The nn request will temporarily turn off line numbering.
The first argument is the number of lines not to be numbered,
this defaults to 1. (does this disable incrementing or display?)
... line numbering example ...
margin characters can be automatically printed to the right of your
text with the mc request.
The first argument is the character to be printed and the second
argument is the distance away from your text.
With no arguments the margin characters are turned off.
If this occurs before a break, no margin character will be printed.
This is quite useful for indicating text that has changed, and, in
fact, there are programs available for doing this (they are called
nrchbar and changebar and can be found in any
`comp.sources.unix' archive.
... margin char example ...
The lf primary reason for existence is to make debugging
documents which are split into many files, which are then put
together with soelim and other pre-processors.
The first argument is the name of the file and the second argument is
the input line number in that file.
This way troff can produce error messages which are intelligible to
the user.
... example of soelim'ed doc ...
Troff is not easy to debug, but there are some useful features and strategies for debugging.
tm request will send output to stderr, this is very useful for
printing debugging output.
.if \n(DB .tm debugging output
Then you can activate these statements with:
groff -rDB=1 file
ab request is similar to the tm request,
except that it will cause groff to stop processing.
With no argument it will print `User Abort'.
ex request will also cause groff to stop processing.
pm request will dump out the entire symbol table.
pnr request will print the names and contents of all
currently defined number registers on stderr.
ptr request will
print the names and positions of all traps (not including input line
traps and diversion traps) on stderr. Empty slots in the page trap list
are printed as well, because they can affect the priority of
subsequently planted traps.
fl request instructs groff to flush its output immediately.
The intention is that this be used when using troff interactively.
There is little other use for it.
backtrace request will
print a backtrace of the input stack on stderr.
warn request controls the level of warnings checked for.
The one argument is the sum of the numbers associated with each
warning that is to be enabled; all other warnings will be disabled.
The number associated with each warning is listed below.
For example, .warn 0 will disable all warnings, and
.warn 1 will disable
all warnings except that about missing characters. If an argument
is not given, all warnings will be enabled.
The number register .warn contains the current warning level.
The warnings that can be given by troff are divided into the
following categories. The name associated with each warning is used
by the `-w' and `-W' options; the number is used by the
warn request, and by the .warn register.
el request with no matching ie request.
See section if-else, for more information.
di or da without an argument when there is no
current diversion.
\} where a number was expected.
GNU troff has a number of features which cause incompatibilites with documents written with old versions of troff.
Long names cause some incompatibilities. Unix troff will interpret
.dsabcd
as defining a string `ab' with contents `cd'.
Normally, GNU troff will interpret this as a call of a macro named
dsabcd. Also Unix troff will interpret \*[ or
\n[ as references to a string or number register called
`['. In GNU troff, however, this will normally be interpreted as the
start of a long name. In compatibility mode GNU troff will interpret
these things in the traditional way. In compatibility mode, however,
long names are not recognised. Compatibility mode can be turned on with
the `-C' command line option, and turned on or off with the
cp request.
The number register .C is 1 if compatibility mode is on, 0 otherwise.
GNU troff does not allow the use of the escape sequences
`\| \^ \& \} \{ \SP \' \` \- \_ \! \% \c' in names of
strings, macros,
diversions, number registers, fonts or environments; Unix troff does.
The \A escape sequence may be helpful in avoiding use of these escape
sequences in names.
Fractional pointsizes cause one noteworthy incompatibility. In Unix
troff the ps request ignores scale indicators and so
.ps 10u
will set the pointsize to 10 points, whereas in GNU troff it will set the pointsize to 10 scaled points. See section Fractional Type Sizes, for more information.
In GNU troff there is a fundamental difference between unformatted,
input characters, and formatted, output characters. Everything that
affects how an output character will be output is stored with the
character; once an output character has been constructed it is
unaffected by any subsequent requests that are executed, including
bd, cs, tkf, tr, or fp
requests. Normally output characters are constructed
from input characters at the moment immediately before the character is
added to the current output line. Macros, diversions and strings are
all, in fact, the same type of object; they contain lists of input
characters and output characters in any combination. An output
character does not behave like an input character for the purposes of
macro processing; it does not inherit any of the special properties that
the input character from which it was constructed might have had. For
example,
.di x \\\\ .br .di .x
will print `\\' in GNU troff; each pair of input backslashes is
turned into one
output backslash and the resulting output backslashes are not
interpreted as escape
characters when they are reread. Unix troff would interpret them as
escape characters when they were reread and would end up printing one
`\'.
The correct way to obtain a printable backslash is to use the
\e escape
sequence: this will always print a single instance of the current escape
character, regardless of whether or not it is used in a diversion; it
will also work in both GNU troff and Unix troff. If you wish for some
reason to store in a diversion an escape sequence that will be
interpreted when the diversion is reread, you can either use the
traditional \! transparent output facility, or, if this is unsuitable,
the new \? escape sequence. See section Diversions, for more information.
See section Font files
This section describes the format output by GNU troff. The output format used by GNU troff is very similar to that used by Unix device-independent troff.
The output format is ascii based, as opposed to a binary format (like TeX dvi). The output format is 8 bit clean, thus single characters can have the eighth bit set, as can the names of fonts and special characters.
The output format consists of single command characters with attached parameters which are separated from subsequent text by whitespace, or a newline.
The names of characters and fonts an be of arbitrary length; drivers should not assume that they will be only two characters long (as device-independent troff did).
When a character is to be printed, that character will always be in the current font. Unlike device-independent troff, it is not necessary for drivers to search special fonts to find a character.
Hn
Vn
hn
vn
cn
Cn
nnc
txxx
This command is only allowed if the `tcommand' line is present in the `DESC' file.
un xxx
t command except that after printing each
character, the current horizontal position is increased by the sum of
the width of that character and n.
This command is only allowed if the `tcommand' line is present in the `DESC' file.
nab
pn
sn
fn
x ... \n
Dc x...\n
The x command is normally followed by a letter or word
indicating the function to perform, followed by white space separated
arguments.
The first argument can be abreviated to the first letter.
x init
x T
x res n h v
x H
The first three output commands are guaranteed to be:
x T device x res n h v x init
For example, the input `crunchy \fH\s+2frog\s0\fP!?' will produce:
... sample output here ...
The D drawing command has been extended. These extensions will only be used by GNU pic if the -x option is given.
Df n\n
DC d\n
DE dx dy\n
Dp $dx sub 1$ $dy sub 1$ $dx sub 2$ $dy sub 2$ $...$ $dx sub n$ $dy sub
DP $dx sub 1$ $dy sub 1$ $dx sub 2$ $dy sub 2$ $...$ $dx sub n$ $dy sub
Dt n\n
A difficulty arises in how the current position should be changed after the execution of these commands. This is not of great importance since the code generated by GNU pic does not depend on this. Given a drawing command of the form
\D'c $x sub 1$ $y sub 1$ $x sub 2$ $y sub 2$ $...$ $x sub n$ $y sub n$'
where c is not one of c, e, l, a or ~, Unix troff will treat each of the $x sub i$ as a horizontal quantity, and each of the $y sub i$ as a vertical quantity and will assume that the width of the drawn object is $sum from i=1 to n x sub i$, and that the height is $sum from i=1 to n y sub i$. (The assumption about the height can be seen by examining the st and sb registers after using such a D command in a \w escape sequence.) This rule also holds for all the original drawing commands with the exception of De. For the sake of compatibility GNU troff also follows this rule, even though it produces an ugly result in the case of the Df, Dt, and, to a lesser extent, DE commands. Thus after executing a D command of the form
Dc $x sub 1$ $y sub 1$ $x sub 2$ $y sub 2$ $...$ $x sub n$ $y sub n$\n
the current position should be increased by $( sum from i=1 to n x sub i , sum from i=1 to n y sub i )$.
There is a continuation convention which permits the argument to the x X command to contain newlines: when outputting the argument to the x X command, GNU troff will follow each newline in the argument with a + character (as usual, it will terminate the entire argument with a newline); thus if the line after the line containing the x X command starts with +, then the newline ending the line containing the x X command should be treated as part of the argument to the x X command, the + should be ignored, and the part of the line following the + should be treated like the part of the line following the x X command.
The groff font format is roughly a superset of the ditroff font format. Unlike the ditroff font format, there is no associated binary format. The font files for device name are stored in a directory `devname'. There are two types of file: a device description file called `DESC' and for each font `F' a font file called `F'. These are text files; there is no associated binary format.
The `DESC' file can contain the following types of line:
res n
hor n
vert n
sizescale n
unitwidth and sizes commands are given in scaled points.
See section Fractional Type Sizes, for more information.
unitwidth n
tcommand
t and
u output commands.
sizes s1 s2...sn 0
styles S1 S2...Sm
fonts n F1 F2 F3...Fn
family fam
charset
The res, unitwidth, fonts and sizes lines
are compulsory. Other commands are ignored by troff but may be used
by postprocessors to store arbitrary information about the device in
the `DESC' file.
A font file has two sections. The first section is a sequence of lines each containing a sequence of blank delimited words; the first word in the line is a key, and subsequent words give a value for that key.
name F
spacewidth n
slant n
ligatures lig1 lig2...lign [0]
special
Other commands are ignored by troff but may be used by postprocessors to store arbitrary information about the font in the font file.
The first section can contain comments which start with the # character and extend to the end of a line.
The second section contains one or two subsections. It must contain a
charset subsection and it may also contain a kernpairs
subsection. These subsections can appear in any order. Each
subsection starts with a word on a line by itself.
The word charset starts the charset subsection. The
charset line is followed by a sequence of lines. Each line
gives information for one character. A line comprises a number of
fields separated by blanks or tabs. The format is
name metrics type code comment
name identifies the character: if name is a single
character c then it corresponds to the groff input character
c; if it is of the form `\c' where c is a
single character, then it corresponds to the groff input character
`\c'; otherwise it corresponds to the groff input character
`\[name]' (if it is exactly two characters xx it can
be entered as `\(xx'.) Groff supports eight bit characters;
however some utilities has difficulties with eight bit characters.
For this reason, there is a convention that the name
`charn' is equivalent to the single character whose code is
n. For example, `char163' would be equivalent to the
character with code 163 which is the pounds sterling sign in ISO
Latin-1 character set. The name `---' is special and indicates
that the character is unnamed; such characters can only be used by
means of the \N escape sequence in troff.
The type field gives the character type:
1
2
3
The code field gives the code which the postprocessor uses to print the
character. The character can also be input to groff using this code by
means of the \N escape sequence. The code can be any integer. If it
starts with a 0 it will be interpreted as octal; if it starts with 0x or
0X it will be intepreted as hexdecimal.
Anything on the line after the code field will be ignored.
The metrics field has the form:
width[,height[,depth[,italic_correction[,left_italic_correction[,subscript_correction]]]]]
There must not be any spaces between these subfields. Missing subfields are assumed to be 0. The subfields are all decimal integers. Since there is no associated binary format, these values are not required to fit into a variable of type `char' as they are in ditroff. The width subfields gives the width of the character. The height subfield gives the height of the character (upwards is positive); if a character does not extend above the baseline, it should be given a zero height, rather than a negative height. The depth subfield gives the depth of the character, that is, the distance below the lowest point below the baseline to which the character extends (downwards is positive); if a character does not extend below above the baseline, it should be given a zero depth, rather than a negative depth. The italic_correction subfield gives the amount of space that should be added after the character when it is immediately to be followed by a character from a roman font. The left_italic_correction subfield gives the amount of space that should be added before the character when it is immediately to be preceded by a character from a roman font. The subscript_correction gives the amount of space that should be added after a character before adding a subscript. This should be less than the italic correction.
A line in the charset section can also have the format
name "
This indicates that name is just another name for the character mentioned in the preceding line.
The word kernpairs starts the kernpairs section. This contains a
sequence of lines of the form:
c1 c2 n
This means that when character c1 appears next to character c2 the space between them should be increased by n. Most entries in kernpairs section will have a negative value for n.
ds