Ubuntu Manpage: groff - a short reference for the GNU roff language

NAME

       groff - a short reference for the GNU roff language

DESCRIPTION

The name groff stands for GNU roff and is the free implementation of the roff type-setting
system. See roff(7) for a survey and the background of the groff system.

This document provides only short descriptions of roff language elements. Groff: The GNU
Implementation of troff, by Trent A. Fisher and Werner Lemberg, is the primary groff
manual, and is written in Texinfo. You can browse it interactively with “info groff”.

Historically, the roff language was called troff. groff is compatible with the classical
system and provides proper extensions. So in GNU, the terms roff, troff, and groff
language could be used as synonyms. However troff slightly tends to refer more to the
classical aspects, whereas groff emphasizes the GNU extensions, and roff is the general
term for the language.

The general syntax for writing groff documents is relatively easy, but writing extensions
to the roff language can be a bit harder.

The roff language is line-oriented. There are only two kinds of lines, control lines and
text lines. The control lines start with a control character, by default a period “.” or
a single quote “'”; all other lines are text lines.

Control lines represent commands, optionally with arguments. They have the following
syntax. The leading control character can be followed by a command name; arguments, if
any, are separated by spaces (but not tab characters) from the command name and among
themselves, for example,

.command_name arg1 arg2

For indentation, any number of space or tab characters can be inserted between the leading
control character and the command name, but the control character must be on the first
position of the line.

Text lines represent the parts that is printed. They can be modified by escape sequences,
which are recognized by a leading backslash ‘\’. These are in-line or even in-word
formatting elements or functions. Some of these take arguments separated by single quotes
“'”, others are regulated by a length encoding introduced by an open parenthesis ‘(’ or
enclosed in brackets ‘[’ and ‘]’.

The roff language provides flexible instruments for writing language extension, such as
macros. When interpreting macro definitions, the roff system enters a special operating
mode, called the copy mode.

The copy mode behaviour can be quite tricky, but there are some rules that ensure a safe
usage.

1. Printable backslashes must be denoted as \e. To be more precise, \e represents the
current escape character. To get a backslash glyph, use \(rs or \[rs].

2. Double all backslashes.

3. Begin all text lines with the special non-spacing character \&.

This does not produce the most efficient code, but it should work as a first measure. For
better strategies, see the groff Texinfo manual and groff_tmac(5).

Reading roff source files is easier, just reduce all double backslashes to a single one in
all macro definitions.

GROFF ELEMENTS

The roff language elements add formatting information to a text file. The fundamental
elements are predefined commands and variables that make roff a full-blown programming
language.

There are two kinds of roff commands, possibly with arguments. Requests are written on a
line of their own starting with a dot ‘.’ or a “'”, whereas Escape sequences are in-line
functions and in-word formatting elements starting with a backslash ‘\’.

The user can define her own formatting commands using the de request. These commands are
called macros, but they are used exactly like requests. Macro packages are pre-defined
sets of macros written in the groff language. A user's possibilities to create escape
sequences herself is very limited, only special characters can be mapped.

The groff language provides several kinds of variables with different interfaces. There
are pre-defined variables, but the user can define her own variables as well.

String variables store character sequences. They are set with the ds request and
retrieved by the \* escape sequences. Strings can have variables.

Register variables can store numerical values, numbers with a scale unit, and occasionally
string-like objects. They are set with the nr request and retrieved by the \n escape
sequences.

Environments allow the user to temporarily store global formatting parameters like line
length, font size, etc. for later reuse. This is done by the ev request.

Fonts are identified either by a name or by an internal number. The current font is
chosen by the ft request or by the \f escape sequences. Each device has special fonts,
but the following fonts are available for all devices. R is the standard font Roman. B
is its bold counterpart. The italic font is called I and is available everywhere, but on
text devices it is displayed as an underlined Roman font. For the graphical output
devices, there exist constant-width pendants of these fonts, CR, CI, and CB. On text
devices, all glyphs have a constant width anyway.

Glyphs are visual representation forms of characters. In groff, the distinction between
those two elements is not always obvious (and a full discussion is beyond the scope of
this man page). A first approximation is that glyphs have a specific size and colour and
are taken from a specific font; they can't be modified any more – characters are the
input, and glyphs are the output. As soon as an output line has been generated, it no
longer contains characters but glyphs. In this man page, we use either ‘glyph’ or
‘character’, whatever is more appropriate.

Moreover, there are some advanced roff elements. A diversion stores (formatted)
information into a macro for later usage. See groff_tmac(5) for more details. A trap is
a positional condition like a certain number of lines from page top or in a diversion or
in the input. Some action can be prescribed to be run automatically when the condition is
met.

More detailed information and examples can be found in the groff Texinfo manual.

CONTROL CHARACTERS

There is a small set of characters that have a special controlling task in certain
conditions.

. A dot is only special at the beginning of a line or after the condition in the
requests if, ie, el, and while. There it is the control character that introduces
a request (or macro). By using the cc request, the control character can be set to
a different character, making the dot ‘.’ a non-special character.

In all other positions, it just means a dot character. In text paragraphs, it is
advantageous to start each sentence at a line of its own.

' The single quote has two controlling tasks. At the beginning of a line and in the
conditional requests it is the non-breaking control character. That means that it
introduces a request like the dot, but with the additional property that this
request doesn't cause a linebreak. By using the c2 request, the non-break control
character can be set to a different character.

As a second task, it is the most commonly used argument separator in some
functional escape sequences (but any pair of characters not part of the argument do
work). In all other positions, it denotes the single quote or apostrophe
character. Groff provides a printable representation with the \(cq escape
sequence.

" The double quote is used to enclose arguments in macros (but not in requests and
strings). In the ds and as requests, a leading double quote in the argument is
stripped off, making everything else afterwards the string to be defined (enabling
leading whitespace). The escaped double quote \" introduces a comment. Otherwise,
it is not special. Groff provides a printable representation with the \(dq escape
sequence.

\ The backslash usually introduces an escape sequence (this can be changed with the
ec request). A printed version of the escape character is the \e escape; a
backslash glyph can be obtained by \(rs.

( The open parenthesis is only special in escape sequences when introducing an escape
name or argument consisting of exactly two characters. In groff, this behaviour
can be replaced by the [] construct.

[ The opening bracket is only special in groff escape sequences; there it is used to
introduce a long escape name or long escape argument. Otherwise, it is non-
special, e.g. in macro calls.

] The closing bracket is only special in groff escape sequences; there it terminates
a long escape name or long escape argument. Otherwise, it is non-special.

space Space characters are only functional characters. They separate the arguments in
requests, macros, and strings, and the words in text lines. They are subject to
groff's horizontal spacing calculations. To get a defined space width, escape
sequences like ‘\ ’ (this is the escape character followed by a space), \|, \^, or
\h should be used.

newline
In text paragraphs, newlines mostly behave like space characters. Continuation
lines can be specified by an escaped newline, i.e., by specifying a backslash ‘\’
as the last character of a line.

tab If a tab character occurs during text the interpreter makes a horizontal jump to
the next pre-defined tab position. There is a sophisticated interface for handling
tab positions.

NUMERICAL EXPRESSIONS

A numerical value is a signed or unsigned integer or float with or without an appended
scaling indicator. A scaling indicator is a one-character abbreviation for a unit of
measurement. A number followed by a scaling indicator signifies a size value. By
default, numerical values do not have a scaling indicator, i.e., they are normal numbers.

The roff language defines the following scaling indicators.

c centimeter
i inch
P pica = 1/6 inch
p point = 1/72 inch
m em = the font size in points (approx. width of letter ‘m’)
M 100th of an em
n en = em/2
u Basic unit for actual output device
v Vertical line space in basic units
s scaled point = 1/sizescale of a point (defined in font DESC file)
f Scale by 65536.

Numerical expressions are combinations of the numerical values defined above with the
following arithmetical operators already defined in classical troff.

+ Addition
- Subtraction
* Multiplication
/ Division
% Modulo
= Equals
== Equals
< Less than
> Greater than
<= Less or equal
>= Greater or equal
& Logical and
: Logical or
! Logical not
( Grouping of expressions
) Close current grouping

Moreover, groff added the following operators for numerical expressions:

e1>?e2 The maximum of e1 and e2.
e1<?e2 The minimum of e1 and e2.
(c;e) Evaluate e using c as the default scaling indicator.

For details see the groff Texinfo manual.

CONDITIONS

       Conditions  occur  in  tests  raised by the if, ie, and the while requests.  The following
       table characterizes the different types of conditions.

              N         A numerical expression N yields true if its value is greater than 0.
              !N        True if the value of N is 0 (see below).
              's1's2'   True if string s1 is identical to string s2.
              !'s1's2'  True if string s1 is not identical to string s2 (see below).
              cch       True if there is a glyph ch available.
              dname     True if there is a string, macro, diversion, or request called name.
              e         Current page number is even.
              o         Current page number is odd.
              mname     True if there is a color called name.
              n         Formatter is nroff.
              rreg      True if there is a register named reg.
              t         Formatter is troff.
              Ffont     True if there exists a font named font.
              Sstyle    True if a style named style has been registered.

       Note that the !  operator may only appear at the beginning of an expression,  and  negates
       the entire expression.  This maintains bug-compatibility with AT&T troff.

REQUESTS

This section provides a short reference for the predefined requests. In groff, request,
macro, and string names can be arbitrarily long. No bracketing or marking of long names
is needed.

Most requests take one or more arguments. The arguments are separated by space characters
(no tabs!); there is no inherent limit for their length or number.

Some requests have optional arguments with a different behaviour. Not all of these
details are outlined here. Refer to the groff Texinfo manual and groff_diff(7) for all
details.

In the following request specifications, most argument names were chosen to be
descriptive. Only the following denotations need clarification.

c denotes a single character.
font a font either specified as a font name or a font number.
anything all characters up to the end of the line or within \{ and \}.
n is a numerical expression that evaluates to an integer value.
N is an arbitrary numerical expression, signed or unsigned.
±N has three meanings depending on its sign, described below.

If an expression defined as ±N starts with a ‘+’ sign the resulting value of the
expression is added to an already existing value inherent to the related request, e.g.
adding to a number register. If the expression starts with a ‘-’ the value of the
expression is subtracted from the request value.

Without a sign, N replaces the existing value directly. To assign a negative number
either prepend 0 or enclose the negative number in parentheses.

Request Short Reference
. Empty line, ignored. Useful for structuring documents.
.\" anything
Complete line is a comment.
.ab string
Print string on standard error, exit program.
.ad Begin line adjustment for output lines in current adjust mode.
.ad c Start line adjustment in mode c (c=l,r,c,b,n).
.af register c
Assign format c to register (c=l,i,I,a,A).
.aln alias register
Create alias name for register.
.als alias object
Create alias name for request, string, macro, or diversion object.
.am macro Append to macro until .. is encountered.
.am macro end
Append to macro until .end is called.
.am1 macro
Same as .am but with compatibility mode switched off during macro expansion.
.am1 macro end
Same as .am but with compatibility mode switched off during macro expansion.
.ami macro
Append to a macro whose name is contained in the string register macro until ..
is encountered.
.ami macro end
Append to a macro indirectly. macro and end are string registers whose contents
are interpolated for the macro name and the end macro, respectively.
.ami1 macro
Same as .ami but with compatibility mode switched off during macro expansion.
.ami1 macro end
Same as .ami but with compatibility mode switched off during macro expansion.
.as stringvar anything
Append anything to stringvar.
.as1 stringvar anything
Same as .as but with compatibility mode switched off during string expansion.
.asciify diversion
Unformat ASCII characters, spaces, and some escape sequences in diversion.
.backtrace
Print a backtrace of the input on stderr.
.bd font N
Embolden font by N-1 units.
.bd S font N
Embolden Special Font S when current font is font.
.blm Unset the blank line macro.
.blm macro
Set the blank line macro to macro.
.box End current diversion.
.box macro
Divert to macro, omitting a partially filled line.
.boxa End current diversion.
.boxa macro
Divert and append to macro, omitting a partially filled line.
.bp Eject current page and begin new page.
.bp ±N Eject current page; next page number ±N.
.br Line break.
.brp Break output line; adjust if applicable.
.break Break out of a while loop.
.c2 Reset no-break control character to “'”.
.c2 c Set no-break control character to c.
.cc Reset control character to ‘.’.
.cc c Set control character to c.
.ce Center the next input line.
.ce N Center following N input lines.
.cf filename
Copy contents of file filename unprocessed to stdout or to the diversion.
.cflags mode c1 c2 ...
Treat characters c1, c2, ... according to mode number.
.ch trap N
Change trap location to N.
.char c anything
Define entity c as string anything.
.chop object
Chop the last character off macro, string, or diversion object.
.class name c1 c2 ...
Assign a set of characters, character ranges, or classes c1, c2, ... to name.
.close stream
Close the stream.
.color Enable colors.
.color N If N is zero disable colors, otherwise enable them.
.composite from to
Map glyph name from to glyph name to while constructing a composite glyph name.
.continue Finish the current iteration of a while loop.
.cp Enable compatibility mode.
.cp N If N is zero disable compatibility mode, otherwise enable it.
.cs font N M
Set constant character width mode for font to N/36 ems with em M.
.cu N Continuous underline in nroff, like .ul in troff.
.da End current diversion.
.da macro Divert and append to macro.
.de macro Define or redefine macro until .. is encountered.
.de macro end
Define or redefine macro until .end is called.
.de1 macro
Same as .de but with compatibility mode switched off during macro expansion.
.de1 macro end
Same as .de but with compatibility mode switched off during macro expansion.
.defcolor color scheme component
Define or redefine a color with name color. scheme can be rgb, cym, cymk, gray,
or grey. component can be single components specified as fractions in the range
0 to 1 (default scaling indicator f), as a string of two-digit hexadecimal color
components with a leading #, or as a string of four-digit hexadecimal components
with two leading #. The color default can't be redefined.
.dei macro
Define or redefine a macro whose name is contained in the string register macro
until .. is encountered.
.dei macro end
Define or redefine a macro indirectly. macro and end are string registers whose
contents are interpolated for the macro name and the end macro, respectively.
.dei1 macro
Same as .dei but with compatibility mode switched off during macro expansion.
.dei1 macro end
Same as .dei but with compatibility mode switched off during macro expansion.
.device anything
Write anything to the intermediate output as a device control function.
.devicem name
Write contents of macro or string name uninterpreted to the intermediate output
as a device control function.
.di End current diversion.
.di macro Divert to macro. See groff_tmac(5) for more details.
.do name Interpret .name with compatibility mode disabled.
.ds stringvar anything
Set stringvar to anything.
.ds1 stringvar anything
Same as .ds but with compatibility mode switched off during string expansion.
.dt N trap
Set diversion trap to position N (default scaling indicator v).
.ec Reset escape character to ‘\’.
.ec c Set escape character to c.
.ecr Restore escape character saved with .ecs.
.ecs Save current escape character.
.el anything
Else part for if-else (.ie) request.
.em macro The macro is run after the end of input.
.eo Turn off escape character mechanism.
.ev Switch to previous environment and pop it off the stack.
.ev env Push down environment number or name env to the stack and switch to it.
.evc env Copy the contents of environment env to the current environment. No pushing or
popping.
.ex Exit from roff processing.
.fam Return to previous font family.
.fam name Set the current font family to name.
.fc Disable field mechanism.
.fc a Set field delimiter to a and pad glyph to space.
.fc a b Set field delimiter to a and pad glyph to b.
.fchar c anything
Define fallback character (or glyph) c as string anything.
.fcolor Set fill color to previous fill color.
.fcolor c Set fill color to c.
.fi Fill output lines.
.fl Flush output buffer.
.fp n font
Mount font on position n.
.fp n internal external
Mount font with long external name to short internal name on position n.
.fschar f c anything
Define fallback character (or glyph) c for font f as string anything.
.fspecial font
Reset list of special fonts for font to be empty.
.fspecial font s1 s2 ...
When the current font is font, then the fonts s1, s2, ... are special.
.ft Return to previous font. Same as \ or \.
.ft font Change to font name or number font; same as \f[font] escape sequence.
.ftr font1 font2
Translate font1 to font2.
.fzoom font
Don't magnify font.
.fzoom font zoom
Set zoom factor for font (in multiples of 1/1000th).
.gcolor Set glyph color to previous glyph color.
.gcolor c Set glyph color to c.
.hc Remove additional hyphenation indicator character.
.hc c Set up additional hyphenation indicator character c.
.hcode c1 code1 [c2 code2] ...
Set the hyphenation code of character c1 to code1, that of c2 to code2, etc.
.hla lang Set the current hyphenation language to lang.
.hlm n Set the maximum number of consecutive hyphenated lines to n.
.hpf file Read hyphenation patterns from file.
.hpfa file
Append hyphenation patterns from file.
.hpfcode a b c d ...
Set input mapping for .hpf.
.hw words List of words with exceptional hyphenation.
.hy N Switch to hyphenation mode N.
.hym n Set the hyphenation margin to n (default scaling indicator m).
.hys n Set the hyphenation space to n.
.ie cond anything
If cond then anything else goto .el.
.if cond anything
If cond then anything; otherwise do nothing.
.ig Ignore text until .. is encountered.
.ig end Ignore text until .end is called.
.in Change to previous indentation value.
.in ±N Change indentation according to ±N (default scaling indicator m).
.it N trap
Set an input-line count trap for the next N lines.
.itc N trap
Same as .it but don't count lines interrupted with \c.
.kern Enable pairwise kerning.
.kern n If n is zero, disable pairwise kerning, otherwise enable it.
.lc Remove leader repetition glyph.
.lc c Set leader repetition glyph to c.
.length register anything
Write the length of the string anything to register.
.linetabs Enable line-tabs mode (i.e., calculate tab positions relative to output line).
.linetabs n
If n is zero, disable line-tabs mode, otherwise enable it.
.lf N Set input line number to N.
.lf N file
Set input line number to N and filename to file.
.lg N Ligature mode on if N>0.
.ll Change to previous line length.
.ll ±N Set line length according to ±N (default length 6.5i, default scaling
indicator m).
.lsm Unset the leading spaces macro.
.lsm macro
Set the leading spaces macro to macro.
.ls Change to the previous value of additional intra-line skip.
.ls N Set additional intra-line skip value to N, i.e., N-1 blank lines are inserted
after each text output line.
.lt ±N Length of title (default scaling indicator m).
.mc Margin glyph off.
.mc c Print glyph c after each text line at actual distance from right margin.
.mc c N Set margin glyph to c and distance to N from right margin (default scaling
indicator m).
.mk [register]
Mark current vertical position in register, or in an internal register used by
.rt if no argument.
.mso file The same as .so except that file is searched in the tmac directories.
.na No output-line adjusting.
.ne Need a one-line vertical space.
.ne N Need N vertical space (default scaling indicator v).
.nf No filling or adjusting of output lines.
.nh No hyphenation.
.nm Number mode off.
.nm ±N [M [S [I]]]
In line number mode, set number, multiple, spacing, and indentation.
.nn Do not number next line.
.nn N Do not number next N lines.
.nop anything
Always process anything.
.nr register ±N [M]
Define or modify register using ±N with auto-increment M.
.nroff Make the built-in conditions n true and t false.
.ns Turn on no-space mode.
.nx Immediately jump to end of current file.
.nx filename
Immediately continue processing with file file.
.open stream filename
Open filename for writing and associate the stream named stream with it.
.opena stream filename
Like .open but append to it.
.os Output vertical distance that was saved by the sv request.
.output string
Emit string directly to intermediate output, allowing leading whitespace if
string starts with " (which is stripped off).
.pc Reset page number character to ‘%’.
.pc c Page number character.
.pev Print the current environment and each defined environment state to stderr.
.pi program
Pipe output to program (nroff only).
.pl Set page length to default 11i. The current page length is stored in register
.p.
.pl ±N Change page length to ±N (default scaling indicator v).
.pm Print macro names and sizes (number of blocks of 128 bytes).
.pm t Print only total of sizes of macros (number of 128 bytes blocks).
.pn ±N Next page number N.
.pnr Print the names and contents of all currently defined number registers on
stderr.
.po Change to previous page offset. The current page offset is available in
register .o.
.po ±N Page offset N.
.ps Return to previous point size.
.ps ±N Point size; same as \s[±N].
.psbb filename
Get the bounding box of a PostScript image filename.
.pso command
This behaves like the so request except that input comes from the standard
output of command.
.ptr Print the names and positions of all traps (not including input line traps and
diversion traps) on stderr.
.pvs Change to previous post-vertical line spacing.
.pvs ±N Change post-vertical line spacing according to ±N (default scaling indicator p).
.rchar c1 c2 ...
Remove the definitions of entities c1, c2, ...
.rd prompt
Read insertion.
.return Return from a macro.
.return anything
Return twice, namely from the macro at the current level and from the macro one
level higher.
.rfschar f c1 c2 ...
Remove the definitions of entities c1, c2, ... for font f.
.rj n Right justify the next n input lines.
.rm name Remove request, macro, diversion, or string name.
.rn old new
Rename request, macro, diversion, or string old to new.
.rnn reg1 reg2
Rename register reg1 to reg2.
.rr register
Remove register.
.rs Restore spacing; turn no-space mode off.
.rt Return (upward only) to vertical position marked by .mk on the current page.
.rt ±N Return (upward only) to specified distance from the top of the page (default
scaling indicator v).
.schar c anything
Define global fallback character (or glyph) c as string anything.
.shc Reset soft hyphen glyph to \(hy.
.shc c Set the soft hyphen glyph to c.
.shift n In a macro, shift the arguments by n positions.
.sizes s1 s2 ... sn [0]
Set available font sizes similar to the sizes command in a DESC file.
.so filename
Include source file.
.sp Skip one line vertically.
.sp N Space vertical distance N up or down according to sign of N (default scaling
indicator v).
.special Reset global list of special fonts to be empty.
.special s1 s2 ...
Fonts s1, s2, etc. are special and are searched for glyphs not in the current
font.
.spreadwarn
Toggle the spread warning on and off without changing its value.
.spreadwarn limit
Emit a warning if each space in an output line is widened by limit or more
(default scaling indicator m).
.ss N Set space glyph size to N/12 of the space width in the current font.
.ss N M Set space glyph size to N/12 and sentence space size set to M/12 of the space
width in the current font.
.sty n style
Associate style with font position n.
.substring xx n1 n2
Replace the string named xx with the substring defined by the indices n1 and n2.
.sv Save 1 v of vertical space.
.sv N Save the vertical distance N for later output with os request (default scaling
indicator v).
.sy command-line
Execute program command-line.
.ta T N Set tabs after every position that is a multiple of N (default scaling
indicator m).
.ta n1 n2 ... nn T r1 r2 ... rn
Set tabs at positions n1, n2, ..., nn, then set tabs at nn+m×rn+r1 through
nn+m×rn+rn, where m increments from 0, 1, 2, ... to infinity.
.tc Remove tab repetition glyph.
.tc c Set tab repetition glyph to c.
.ti ±N Temporary indent next line (default scaling indicator m).
.tkf font s1 n1 s2 n2
Enable track kerning for font.
.tl ’left’center’right’
Three-part title.
.tm anything
Print anything on stderr.
.tm1 anything
Print anything on stderr, allowing leading whitespace if anything starts with "
(which is stripped off).
.tmc anything
Similar to .tm1 without emitting a final newline.
.tr abcd...
Translate a to b, c to d, etc. on output.
.trf filename
Transparently output the contents of file filename.
.trin abcd...
This is the same as the tr request except that the asciify request uses the
character code (if any) before the character translation.
.trnt abcd...
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 \!.
.troff Make the built-in conditions t true and n false.
.uf font Set underline font to font (to be switched to by .ul).
.ul N Underline (italicize in troff) N input lines.
.unformat diversion
Unformat space characters and tabs in diversion, preserving font information.
.vpt n Enable vertical position traps if n is non-zero, disable them otherwise.
.vs Change to previous vertical base line spacing.
.vs ±N Set vertical base line spacing to ±N (default scaling indicator p).
.warn n Set warnings code to n.
.warnscale si
Set scaling indicator used in warnings to si.
.wh N Remove (first) trap at position N.
.wh N trap
Set location trap; negative means from page bottom.
.while cond anything
While condition cond is true, accept anything as input.
.write stream anything
Write anything to the stream named stream.
.writec stream anything
Similar to .write without emitting a final newline.
.writem stream xx
Write contents of macro or string xx to the stream named stream.

Besides these standard groff requests, there might be further macro calls. They can
originate from a macro package (see roff(7) for an overview) or from a preprocessor.

Preprocessor macros are easy to recognize. They enclose their code between a pair of
characteristic macros.

┌─────────────┬─────────────────┬────────────────┐
│preprocessor │ start macro │ end macro │
├─────────────┼─────────────────┼────────────────┤
│ chem │ .cstart │ .cend │
│ eqn │ .EQ │ .EN │
│ grap │ .G1 │ .G2 │
│ grn │ .GS │ .GE │
│ ideal │ .IS │ .IE │
│ │ │ .IF │
│ pic │ .PS │ .PE │
│ refer │ .R1 │ .R2 │
│ soelim │ none │ none │
│ tbl │ .TS │ .TE │
├─────────────┼─────────────────┼────────────────┤
│ glilypond │ .lilypond start │ .lilypond stop │
│ gperl │ .Perl start │ .Perl stop │
│ gpinyin │ .pinyin start │ .pinyin stop │
└─────────────┴─────────────────┴────────────────┘
Note that the ‘ideal’ preprocessor is not available in groff yet.

ESCAPE SEQUENCES

Escape sequences are in-line language elements usually introduced by a backslash ‘\’ and
followed by an escape name and sometimes by a required argument. Input processing is
continued directly after the escaped character or the argument (without an intervening
separation character). So there must be a way to determine the end of the escape name and
the end of the argument.

This is done by enclosing names (escape name and arguments consisting of a variable name)
by a pair of brackets [name] and constant arguments (number expressions and characters) by
apostrophes (ASCII 0x27) like ’constant’.

There are abbreviations for short names. Two-character escape names can be specified by
an opening parenthesis like \(xy or \*(xy without a closing counterpart. And all one-
character names different from the special characters ‘[’ and ‘(’ can even be specified
without a marker, for example \nc or \$c.

Constant arguments of length 1 can omit the marker apostrophes, too, but there is no two-
character analogue.

While one-character escape sequences are mainly used for in-line functions and system-
related tasks, the two-letter names following the \( construct are glyphs predefined by
the roff system; these are called ‘Special Characters’ in the classical documentation.
Escapes sequences of the form \[name] denote glyphs too.

Single-Character Escapes
\" Start of a comment. Everything up to the end of the line is ignored.
\# Everything up to and including the next newline is ignored. This is interpreted in
copy mode. This is like \" except that the terminating newline is ignored as well.
\*s The string stored in the string variable with one-character name s.
\*(st The string stored in the string variable with two-character name st.
\*[string]
The string stored in the string variable with name string (with arbitrary length).
\*[stringvar arg1 arg2 ...]
The string stored in the string variable with arbitrarily long name stringvar,
taking arg1, arg2, ... as arguments.
\$0 The name by which the current macro was invoked. The als request can make a macro
have more than one name.
\$x Macro or string argument with one-digit number x in the range 1 to 9.
\$(xy Macro or string argument with two-digit number xy (larger than zero).
\$[nexp]
Macro or string argument with number nexp, where nexp is a numerical expression
evaluating to an integer ≥1.
\$* In a macro or string, the concatenation of all the arguments separated by spaces.
\$@ In a macro or string, the concatenation of all the arguments with each surrounded
by double quotes, and separated by spaces.
\$^ In a macro, the representation of all parameters as if they were an argument to the
ds request.
\\ reduces to a single backslash; useful to delay its interpretation as escape
character in copy mode. For a printable backslash, use \e, or even better \[rs],
to be independent from the current escape character.
\´ The acute accent ´; same as $aa. Unescaped: apostrophe, right quotation mark,
single quote (ASCII 0x27).
\` The grave accent `; same as \(ga. Unescaped: left quote, backquote (ASCII 0x60).
\- The - (minus) sign in the current font.
\_ The same as \(ul, the underline character.
\. The same as a dot (‘.’). Necessary in nested macro definitions so that ‘\\..’
expands to ‘..’.
\% Default optional hyphenation character.
\! Transparent line indicator.
\?anything?
In a diversion, this transparently embeds anything in the diversion. anything is
read in copy mode. See also the escape sequences \! and \?.
\space Unpaddable space size space glyph (no line break).
\0 Digit-width space.
\| 1/6 em narrow space glyph; zero width in nroff.
\^ 1/12 em half-narrow space glyph; zero width in nroff.
\& Non-printable, zero-width glyph.
$ Like \& except that it behaves like a glyph declared with the cflags request to be
transparent for the purposes of end-of-sentence recognition.
\/ Increases the width of the preceding glyph so that the spacing between that glyph
and the following glyph is correct if the following glyph is a roman glyph.
\, Modifies the spacing of the following glyph so that the spacing between that glyph
and the preceding glyph is correct if the preceding glyph is a roman glyph.
\~ Unbreakable space that stretches like a normal inter-word space when a line is
adjusted.
\: Inserts a zero-width break point (similar to \% but without a soft hyphen
character).
\newline
Ignored newline, for continuation lines.
\{ Begin conditional input.
\} End conditional input.
\(sc A glyph with two-character name sc; see section “Special Characters” below.
\[name]
A glyph with name name (of arbitrary length).
\[comp1 comp2 ...]
A composite glyph with components comp1, comp2, ...
\a Non-interpreted leader character.
\A’anything’
If anything is acceptable as a name of a string, macro, diversion, register,
environment or font it expands to 1, and to 0 otherwise.
\b’abc...’
Bracket building function.
\B’anything’
If anything is acceptable as a valid numeric expression it expands to 1, and to 0
otherwise.
\c Continue output line at next input line. Anything after this escape on the same
line is ignored except \R (which works as usual). Anything before \c on the same
line is appended to the current partial output line. The next non-command line
after a line interrupted with \c counts as a new input line.
\C’glyph’
The glyph called glyph; same as \[glyph], but compatible to other roff versions.
\d Forward (down) 1/2 em (1/2 line in nroff).
\D’charseq’
Draw a graphical element defined by the characters in charseq; see the groff
Texinfo manual for details.
\e Printable version of the current escape character.
\E Equivalent to an escape character, but is not interpreted in copy mode.
\fF Change to font with one-character name or one-digit number F.
\fP Switch back to previous font.
\f(fo Change to font with two-character name or two-digit number fo.
\f[font]
Change to font with arbitrarily long name or number expression font.
\f[] Switch back to previous font.
\Ff Change to font family with one-character name f.
\F(fm Change to font family with two-character name fm.
\F[fam]
Change to font family with arbitrarily long name fam.
\F[] Switch back to previous font family.
\gr Return format of register with one-character name r suitable for af request.
\g(rg Return format of register with two-character name rg suitable for af request.
\g[reg]
Return format of register with arbitrarily long name reg suitable for af request.
\h’N’ Local horizontal motion; move right N (left if negative).
\H’N’ Set height of current font to N.
\kr Mark horizontal input place in one-character register r.
\k(rg Mark horizontal input place in two-character register rg.
\k[reg]
Mark horizontal input place in register with arbitrarily long name reg.
\l’Nc’ Horizontal line drawing function (optionally using character c).
\L’Nc’ Vertical line drawing function (optionally using character c).
\mc Change to color with one-character name c.
\m(cl Change to color with two-character name cl.
\m[color]
Change to color with arbitrarily long name color.
\m[] Switch back to previous color.
\Mc Change filling color for closed drawn objects to color with one-character name c.
\M(cl Change filling color for closed drawn objects to color with two-character name cl.
\M[color]
Change filling color for closed drawn objects to color with arbitrarily long name
color.
\M[] Switch to previous fill color.
\nr The numerical value stored in the register variable with the one-character name r.
\n(re The numerical value stored in the register variable with the two-character name re.
\n[reg]
The numerical value stored in the register variable with arbitrarily long name reg.
\N’n’ Typeset the glyph with index n in the current font. No special fonts are searched.
Useful for adding (named) entities to a document using the char request and
friends.
\o’abc...’
Overstrike glyphs a, b, c, etc.
\O0 Disable glyph output. Mainly for internal use.
\O1 Enable glyph output. Mainly for internal use.
\p Break output line at next word boundary; adjust if applicable.
\r Reverse 1 em vertical motion (reverse line in nroff).
\R’name ±n’
The same as .nr name ±n.
\s±N Set/increase/decrease the point size to/by N scaled points; N is a one-digit number
in the range 1 to 9. Same as ps request.
\s(±N
\s±(N Set/increase/decrease the point size to/by N scaled points; N is a two-digit number
≥1. Same as ps request.
\s[±N]
\s±[N]
\s’±N’
\s±’N’ Set/increase/decrease the point size to/by N scaled points. Same as ps request.
\S’N’ Slant output by N degrees.
\t Non-interpreted horizontal tab.
\u Reverse (up) 1/2 em vertical motion (1/2 line in nroff).
\v’N’ Local vertical motion; move down N (up if negative).
\Ve The contents of the environment variable with one-character name e.
\V(ev The contents of the environment variable with two-character name ev.
\V[env]
The contents of the environment variable with arbitrarily long name env.
\w’string’
The width of the glyph sequence string.
\x’N’ Extra line-space function (negative before, positive after).
\X’string’
Output string as device control function.
\Yn Output string variable or macro with one-character name n uninterpreted as device
control function.
\Y(nm Output string variable or macro with two-character name nm uninterpreted as device
control function.
\Y[name]
Output string variable or macro with arbitrarily long name name uninterpreted as
device control function.
\zc Print c with zero width (without spacing).
\Z’anything’
Print anything and then restore the horizontal and vertical position; anything may
not contain tabs or leaders.

The escape sequences \e, \., \", \$, \*, \a, \n, \t, \g, and \newline are interpreted in
copy mode.

Escape sequences starting with \( or \[ do not represent single character escape
sequences, but introduce escape names with two or more characters.

If a backslash is followed by a character that does not constitute a defined escape
sequence, the backslash is silently ignored and the character maps to itself.

Special Characters
[Note: ‘Special Characters’ is a misnomer; those entities are (output) glyphs, not (input)
characters.]

Common special characters are predefined by escape sequences of the form \(xy with
characters x and y. In groff, it is also possible to use the writing \[xy] as well.

Some of these special characters exist in the usual font while most of them are only
available in the special font. Below you can see a small selection of the most important
glyphs; a complete list can be found in groff_char(7).

\(Do Dollar $
\(Eu Euro €
\(Po British pound sterling £
\(aq Apostrophe quote '
\(bu Bullet sign •
\(co Copyright ©
\(cq Single closing quote (right) ’
\(ct Cent ¢
\(dd Double dagger ‡
\(de Degree °
\(dg Dagger †
\(dq Double quote (ASCII 34) "
\(em Em-dash —
\(en En-dash –
\(hy Hyphen ‐
\(lq Double quote left “
\(oq Single opening quote (left) ‘
\(rg Registered sign ®
\(rq Double quote right ”
\(rs Printable backslash character \
\(sc Section sign §
\(tm Trademark symbol ™
\(ul Underline character _
\(== Identical ≡
\(>= Larger or equal ≥
\(<= Less or equal ≤
\(!= Not equal ≠
\(-> Right arrow →
\(<- Left arrow ←
\(+- Plus-minus sign ±

Unicode Characters
The extended escape u allows the inclusion of all available Unicode characters into a roff
file.

\[uxxxx]
u is the escape name. xxxx is a hexadecimal number of four hex digits, such as
0041 for the letter A, thus \[u0041].

\[uyyyyy]
u is the escape name. yyyyy is a hexadecimal number of five hex digits, such as
2FA1A for a Chinese-looking character from the Unicode block CJK Compatibility
Ideographs Supplement, thus \[u2FA1A].

The hexadecimal value indicates the corresponding Unicode code point for a character.

\[uhex1_hex2]
\[uhex1_hex2_hex3]
hex1, hex2, and hex3 are all Unicode hexadecimal codes (4 or 5 hex digits) that are
used for overstriking, e.g. \[u0041_0301] is A acute, which can also be specified
as Á; see groff_char(7).

The availability of the Unicode characters depends on the font used. For text mode, the
device -Tutf8 is quite complete; for troff modes it might happen that some or many
characters will not be displayed. Please check your fonts.

Strings
Strings are defined by the ds request and can be retrieved by the \* escape sequence.

Strings share their name space with macros. So strings and macros without arguments are
roughly equivalent; it is possible to call a string like a macro and vice versa, but this
often leads to unpredictable results. The following string is the only one predefined in
groff.

\*[.T] The name of the current output device as specified by the -T command-line
option.

REGISTERS

       Registers are variables that store a value.  In  groff,  most  registers  store  numerical
       values (see section “Numerical Expressions” above), but some can also hold a string value.

       Each  register  is  given  a name.  Arbitrary registers can be defined and set with the nr
       request.

       The value stored in a register can be retrieved by the escape sequences introduced by \n.

       Most useful are predefined registers.  In the following the notation name is used to refer
       to  register  name  to make clear that we speak about registers.  Please keep in mind that
       the \n[] decoration is not part of the register name.

   Read-only Registers
       The following registers have predefined values that should not be  modified  by  the  user
       (usually,  registers starting with a dot are read-only).  Mostly, they provide information
       on the current settings or store results from request calls.

       \n[$$]    The process ID of troff.
       \n[.$]    Number of arguments in the current macro or string.
       \n[.a]    Post-line extra line-space most recently utilized using \x.
       \n[.A]    Set to 1 in troff if option -A is used; always 1 in nroff.
       \n[.b]    The emboldening offset while .bd is active.
       \n[.br]   Within a macro, set to 1 if macro called with the  ‘normal’  control  character,
                 and to 0 otherwise.
       \n[.c]    Current input line number.
       \n[.C]    1 if compatibility mode is in effect, 0 otherwise.
       \n[.cdp]  The depth of the last glyph added to the current environment.  It is positive if
                 the glyph extends below the baseline.
       \n[.ce]   The number of lines remaining to be centered, as set by the ce request.
       \n[.cht]  The height of the last glyph added to the current environment.  It  is  positive
                 if the glyph extends above the baseline.
       \n[.color]
                 1 if colors are enabled, 0 otherwise.
       \n[.csk]  The  skew  of  the  last  glyph added to the current environment.  The skew of a
                 glyph is how far to the right of the center of a glyph the center of  an  accent
                 over that glyph should be placed.
       \n[.d]    Current vertical place in current diversion; equal to register nl.
       \n[.ev]   The name or number of the current environment (string-valued).
       \n[.f]    Current font number.
       \n[.F]    The name of the current input file (string-valued).
       \n[.fam]  The current font family (string-valued).
       \n[.fn]   The current (internal) real font name (string-valued).
       \n[.fp]   The number of the next free font position.
       \n[.g]    Always 1 in GNU troff.  Macros should use it to test if running under groff.
       \n[.h]    Text base-line high-water mark on current page or diversion.
       \n[.H]    Number of basic units per horizontal unit of output device resolution.
       \n[.height]
                 The current font height as set with \H.
       \n[.hla]  The current hyphenation language as set by the hla request.
       \n[.hlc]  The number of immediately preceding consecutive hyphenated lines.
       \n[.hlm]  The  maximum  allowed  number of consecutive hyphenated lines, as set by the hlm
                 request.
       \n[.hy]   The current hyphenation flags (as set by the hy request).
       \n[.hym]  The current hyphenation margin (as set by the hym request).
       \n[.hys]  The current hyphenation space (as set by the hys request).
       \n[.i]    Current indentation.
       \n[.in]   The indentation that applies to the current output line.
       \n[.int]  Positive if last output line contains \c.
       \n[.j]    The current adjustment mode.  It can be  stored  and  used  to  set  adjustment.
                 (n = 1, b = 1, l = 0, r = 5, c = 3).
       \n[.k]    The current horizontal output position (relative to the current indentation).
       \n[.kern] 1 if pairwise kerning is enabled, 0 otherwise.
       \n[.l]    Current line length.
       \n[.L]    The current line spacing setting as set by .ls.
       \n[.lg]   The current ligature mode (as set by the lg request).
       \n[.linetabs]
                 The current line-tabs mode (as set by the linetabs request).
       \n[.ll]   The line length that applies to the current output line.
       \n[.lt]   The title length (as set by the lt request).
       \n[.m]    The current drawing color (string-valued).
       \n[.M]    The current background color (string-valued).
       \n[.n]    Length of text portion on previous output line.
       \n[.ne]   The amount of space that was needed in the last ne request that caused a trap to
                 be sprung.  Useful in conjunction with register .trunc.
       \n[.ns]   1 if in no-space mode, 0 otherwise.
       \n[.o]    Current page offset.
       \n[.O]    The suppression nesting level (see \O).
       \n[.p]    Current page length.
       \n[.P]    1 if the current page is being printed, 0 otherwise (as  determined  by  the  -o
                 command-line option).
       \n[.pe]   1 during page ejection, 0 otherwise.
       \n[.pn]   The number of the next page: either the value set by a pn request, or the number
                 of the current page plus 1.
       \n[.ps]   The current point size in scaled points.
       \n[.psr]  The last-requested point size in scaled points.
       \n[.pvs]  The current post-vertical line spacing.
       \n[.R]    The number of unused number registers.  Always 10000 in GNU troff.
       \n[.rj]   The number of lines to be right-justified as set by the rj request.
       \n[.s]    Current point size as a decimal fraction.
       \n[.slant]
                 The slant of the current font as set with \S.
       \n[.sr]   The last requested point size in points as a decimal fraction (string-valued).
       \n[.ss]   The value of the parameters set by the first argument of the ss request.
       \n[.sss]  The value of the parameters set by the second argument of the ss request.
       \n[.sty]  The current font style (string-valued).
       \n[.t]    Vertical distance to the next trap.
       \n[.T]    Set to 1 if option -T is used.
       \n[.tabs] A string representation of the current tab  settings  suitable  for  use  as  an
                 argument to the ta request.
       \n[.trunc]
                 The  amount  of  vertical  space  truncated by the most recently sprung vertical
                 position trap, or, if the trap was sprung by an ne request, minus the amount  of
                 vertical motion produced by .ne.  Useful in conjunction with the register .ne.
       \n[.u]    Equal to 1 in fill mode and 0 in no-fill mode.
       \n[.U]    Equal to 1 in safer mode and 0 in unsafe mode.
       \n[.v]    Current vertical line spacing.
       \n[.V]    Number of basic units per vertical unit of output device resolution.
       \n[.vpt]  1 if vertical position traps are enabled, 0 otherwise.
       \n[.w]    Width of previous glyph.
       \n[.warn] The sum of the number codes of the currently enabled warnings.
       \n[.x]    The major version number.
       \n[.y]    The minor version number.
       \n[.Y]    The revision number of groff.
       \n[.z]    Name of current diversion.
       \n[.zoom] Zoom   factor   for   current  font  (in  multiples  of  1/1000th;  zero  if  no
                 magnification).

   Writable Registers
       The following registers can be read and written by the user.  They have predefined default
       values, but these can be modified for customizing a document.

       \n[%]     Current page number.
       \n[c.]    Current input line number.
       \n[ct]    Character type (set by width function \w).
       \n[dl]    Maximal width of last completed diversion.
       \n[dn]    Height of last completed diversion.
       \n[dw]    Current day of week (1–7).
       \n[dy]    Current day of month (1–31).
       \n[hours] The number of hours past midnight.  Initialized at start-up.
       \n[hp]    Current horizontal position at input line.
       \n[llx]   Lower  left  x-coordinate (in PostScript units) of a given PostScript image (set
                 by .psbb).
       \n[lly]   Lower left y-coordinate (in PostScript units) of a given PostScript  image  (set
                 by .psbb).
       \n[ln]    Output line number.
       \n[lsn]   The number of leading spaces of an input line.
       \n[lss]   The horizontal space corresponding to the leading spaces of an input line.
       \n[minutes]
                 The number of minutes after the hour.  Initialized at start-up.
       \n[mo]    Current month (1–12).
       \n[nl]    Vertical position of last printed text base-line.
       \n[opmaxx]
       \n[opmaxy]
       \n[opminx]
       \n[opminy]
                 These  four  registers  mark the top left and bottom right hand corners of a box
                 which encompasses all written glyphs.  They are reset to -1 by \O0 or \O1.
       \n[rsb]   Like register sb, but takes account of the heights and depths of glyphs.
       \n[rst]   Like register st, but takes account of the heights and depths of glyphs.
       \n[sb]    Depth of string below base line (generated by width function \w).
       \n[seconds]
                 The number of seconds after the minute.  Initialized at start-up.
       \n[skw]   Right skip width from the center of the last glyph in the \w argument.
       \n[slimit]
                 If greater than 0, the maximum number of objects on  the  input  stack.   If  ≤0
                 there  is  no  limit,  i.e.,  recursion  can  continue  until  virtual memory is
                 exhausted.
       \n[ssc]   The amount of horizontal space (possibly negative) that should be added  to  the
                 last glyph before a subscript (generated by width function \w).
       \n[st]    Height of string above base line (generated by width function \w).
       \n[systat]
                 The return value of the system() function executed by the last sy request.
       \n[urx]   Upper  right x-coordinate (in PostScript units) of a given PostScript image (set
                 by .psbb).
       \n[ury]   Upper right y-coordinate (in PostScript units) of a given PostScript image  (set
                 by .psbb).
       \n[year]  The current year (year 2000 compliant).
       \n[yr]    Current year minus 1900.  For Y2K compliance use register year instead.

HYPHENATION

       The  .hy  request,  given  an  integer  argument,  controls when hyphenation applies.  The
       default value is 1, which  enables  hyphenation  almost  everywhere  (see  below).   Macro
       packages often override this default.

       1      disables hyphenation only after the first and before the last character of a word.

       2      disables hyphenation only of the last word on a page or column.

       4      disables hyphenation only before the last two characters of a word.

       8      disables hyphenation only after the first two characters of a word.

       16     enables hyphenation before the last character of a word.

       32     enables hyphenation after the first character of a word.

       The values are additive.  Some values cannot be used together because they contradict; for
       instance, 4 and 16; 8 and 32.

UNDERLINING

       In the RUNOFF language, the underlining was quite easy.  But in roff  this  is  much  more
       difficult.

   Underlining with .ul
       There exists a groff request .ul (see above) that can underline the next or further source
       lines in nroff, but in troff it produces only a font change into italic.  So this  request
       is not really useful.

   Underlining with .UL from ms
       In  the  ‘ms’  macro package in tmac/s.tmac groff_ms(7), there is the macro .UL.  But this
       works only in troff, not in nroff.

   Underlining macro definitions
       So one can use the italic nroff idea from .ul and the troff definition in ms for writing a
       useful new macro, something like
              .de UNDERLINE
              . ie n \\$1\f[I]\\$2\f[P]\\$3
              . el \\$1\Z'\\$2'\v'.25m'\D'l \w'\\$2'u 0'\v'-.25m'\\$3
              ..
       If  doclifter(1)  makes  trouble, change the macro name UNDERLINE into some 2-letter word,
       like Ul.  Moreover change the font writing from \f[P] to \fP.

   Underlining without macro definitions
       If one does not want to use macro definitions, e.g., when doclifter  gets  lost,  use  the
       following:
              .ds u1 before
              .ds u2 in
              .ds u3 after
              .ie n \*[u1]\f[I]\*[u2]\f[P]\*[u3]
              .el \*[u1]\Z'\*[u2]'\v'.25m'\D'l \w'\*[u2]'u 0'\v'-.25m'\*[u3]
       Due  to  doclifter,  it might be necessary to change the variable writing \[xy] and \*[xy]
       into the strange ancient writing \*(xy and \(xy, and so on.

       Then these lines could look like
              .ds u1 before
              .ds u2 in
              .ds u3 after
              .ie n \*[u1]\fI\*(u2\fP\*(u3
              .el \*(u1\Z'\*(u2'\v'.25m'\D'l \w'\*(u2'u 0'\v'-.25m'\*(u3

       The result looks like
              before in after

   Underlining with Overstriking \z and \(ul
       There is another possibility for underlining by using overstriking with \zc (print c  with
       zero width without spacing) and \(ul (underline character).  This produces the underlining
       of 1 character, both in nroff and in troff.

       For example the underlining of a character say t looks like \z\[ul]t or \z\(ult

       Longer words look then a bit strange, but a useful mode is to write each character into  a
       whole own line.  To underlines the 3 character part "tar" of the word "start":
              before s\
              \z\[ul]t\
              \z\[ul]a\
              \z\[ul]r\
              t after
       or
              before s\
              \z\(ult\
              \z\(ula\
              \z\(ulr\
              t after

       The result looks like
              before start after

COMPATIBILITY

       The  differences  between  the groff language and classical troff as defined by [CSTR #54]
       are documented in groff_diff(7).

       The groff system provides a compatibility mode, see groff(1) on how to invoke this.

AUTHORS

       This document was written by Bernd Warken ⟨groff-bernd.warken-72@web.de⟩.