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groff(7) Miscellaneous Information Manual groff(7)
groff - GNU roff language reference
groff is short for GNU roff, a free reimplementation of the AT&T
device-independent troff typesetting system. See roff(7) for a
survey of and background on roff systems.
This document is intended as a reference. The primary groff
manual, Groff: The GNU Implementation of troff, by Trent A. Fisher
and Werner Lemberg, is a better resource for learners, containing
many examples and much discussion. It is written in Texinfo; you
can browse it interactively with “info groff”. Additional
formats, including plain text, HTML, DVI, and PDF, may be
available in /usr/local/share/doc/groff-1.23.0.
groff is also a name for an extended dialect of the roff language.
We use “roff” to denote features that are universal, or nearly so,
among implementations of this family. We apply the term “groff”
to the language documented here, the GNU implementation of the
overall system, the project that develops that system, and the
command of that name.
GNU troff, installed on this system as troff(1), is the formatter:
a program that reads device and font descriptions (groff_font(5)),
interprets the groff language expressed in text input files, and
translates that input into a device-independent output format
(groff_out(5)) that is usually then post-processed by an output
driver to produce PostScript, PDF, HTML, DVI, or terminal output.
Input to GNU troff is organized into lines separated by the Unix
newline character (U+000A), and must be in one of two character
encodings it can recognize: IBM code page 1047 on EBCDIC systems,
and ISO Latin-1 (8859-1) otherwise. Use of ISO 646-1991:IRV (“US-
ASCII”) or (equivalently) the “Basic Latin” subset of ISO 10646
(“Unicode”) is recommended; see groff_char(7). The preconv(1)
preprocessor transforms other encodings, including UTF-8, to
satisfy troff's requirements.
Several input characters are syntactically significant to groff.
. A dot at the beginning of an input line marks it as a control
line. It can also follow the .el and .nop requests, and the
condition in .if, .ie, and .while requests. The control
character invokes requests and calls macros by the name that
follows it. The .cc request can change the control character.
' The neutral apostrophe is the no-break control character,
recognized where the control character is. It suppresses the
(first) break implied by the .bp, .cf, .fi, .fl, .in, .nf,
.rj, .sp, .ti, and .trf requests. The requested operation
takes effect at the next break. It makes .br nilpotent. The
no-break control character can be changed with the .c2
request. When formatted, “'” may be typeset as a
typographical quotation mark; use the \[aq] special character
escape sequence to format a neutral apostrophe glyph.
" The neutral double quote can be used to enclose arguments to
macros and strings, and is required if those arguments contain
space or tab characters. In the .ds, .ds1, .as, and .as1
requests, an initial neutral double quote in the second
argument is stripped off to allow embedding of leading spaces.
To include a double quote inside a quoted argument, use the
\[dq] special character escape sequence (which also serves to
typeset the glyph in text).
\ A backslash introduces an escape sequence. The escape
character can be changed with the .ec request; .eo disables
escape sequence recognition. Use the \[rs] special character
escape sequence to format a backslash glyph, and \e to typeset
the glyph of the current escape character.
( An opening parenthesis is special only in certain escape
sequences; when recognized, it introduces an argument of
exactly two characters. groff offers the more flexible square
bracket syntax.
[ An opening bracket is special only in certain escape
sequences; when recognized, it introduces an argument (list)
of any length, not including a closing bracket.
] A closing bracket is special only when an escape sequence
using an opening bracket as an argument delimiter is being
interpreted. It ends the argument (list).
Additionally, the Control+A character (U+0001) in text is
interpreted as a leader (see below).
Horizontal white space characters are significant to groff, but
trailing spaces on text lines are ignored.
space Space characters separate arguments in request
invocations, macro calls, and string interpolations. In
text, they separate words. Multiple adjacent space
characters in text cause groff to attempt end-of-sentence
detection on the preceding word (and trailing
punctuation). The amount of space between words and
sentences is controlled by the .ss request. When filling
is enabled (the default), a line may be broken at a space.
When adjustment is enabled (the default), inter-word
spaces are expanded until the output line reaches the
configured length. An adjustable but non-breaking space
is available with \~. To get a space of fixed width, use
one of the escape sequences ‘\ ’ (the escape character
followed by a space), \0, \|, \^, or \h; see section
“Escape sequences” below.
newline In text, a newline puts an inter-word space onto the
output and, if filling is enabled, triggers end-of-
sentence recognition on the preceding text. See section
“Line continuation” below.
tab A tab character in text causes the drawing position to
advance to the next defined tab stop.
The formatter interprets input horizontal tab characters (“tabs”)
and Control+A characters (“leaders”) into movements to the next
tab stop. Tabs simply move to the next tab stop; leaders place
enough periods to fill the space. Tab stops are by default
located every half inch measured from the drawing position
corresponding to the beginning of the input line; see section
“Page geometry” of roff(7). Tabs and leaders do not cause breaks
and therefore do not interrupt filling. Tab stops can be
configured with the ta request, and tab and leader glyphs with the
tc and lc requests, respectively.
When filling is enabled, input and output line breaks generally do
not correspond. The roff language therefore distinguishes input
and output line continuation.
A backslash \ immediately followed by a newline, sometimes
discussed as \newline, suppresses the effects of that newline on
the input. The next input line thus retains the classification of
its predecessor as a control or text line. \newline is useful for
managing line lengths in the input during document maintenance;
you can break an input line in the middle of a request invocation,
macro call, or escape sequence. Input line continuation is
invisible to the formatter, with two exceptions: the | operator
recognizes the new input line, and the input line counter register
.c is incremented.
The \c escape sequence continues an output line. Nothing on the
input line after it is formatted. In contrast to \newline, a line
after \c is treated as a new input line, so a control character is
recognized at its beginning. The visual results depend on whether
filling is enabled. An intervening control line that causes a
break overrides \c, flushing out the pending output line in the
usual way. The register .int contains a positive value if the
last output line was continued with \c; this datum is associated
with the environment.
groff supports color output with a variety of color spaces and up
to 16 bits per channel. Some devices, particularly terminals, may
be more limited. When color support is enabled, two colors are
current at any given time: the stroke color, with which glyphs,
rules (lines), and geometric objects like circles and polygons are
drawn, and the fill color, which can be used to paint the interior
of a closed geometric figure. The color, defcolor, gcolor, and
fcolor requests; \m and \M escape sequences; and .color, .m, and
.M registers exercise color support.
Each output device has a color named “default”, which cannot be
redefined. A device's default stroke and fill colors are not
necessarily the same. For the dvi, html, pdf, ps, and xhtml
output devices, troff automatically loads a macro file defining
many color names at startup. By the same mechanism, the devices
supported by grotty(1) recognize the eight standard
ISO 6429/ECMA-48 color names (also known vulgarly as “ANSI
colors”).
Numeric parameters that specify measurements are expressed as
integers or decimal fractions with an optional scaling unit
suffixed. A scaling unit is a letter that immediately follows the
last digit of a number. Digits after the decimal point are
optional.
Measurements are scaled by the scaling unit and stored internally
(with any fractional part discarded) in basic units. The device
resolution can therefore be obtained by storing a value of “1i” to
a register. The only constraint on the basic unit is that it is
at least as small as any other unit.
u Basic unit.
i Inch; defined as 2.54 centimeters.
c Centimeter.
p Point; a typesetter's unit used for measuring type size.
There are 72 points to an inch.
P Pica; another typesetter's unit. There are 6 picas to an
inch and 12 points to a pica.
s, z Scaled points and multiplication by the output device's
sizescale parameter, respectively.
f Multiplication by 65,536; scales decimal fractions in the
interval [0, 1] to 16-bit unsigned integers.
The magnitudes of other scaling units depend on the text
formatting parameters in effect.
m Em; an em is equal to the current type size in points.
n En; an en is one-half em.
v Vee; distance between text baselines.
M Hundredth of an em.
Motion quanta
An output device's basic unit u is not necessarily its smallest
addressable length; u can be smaller to avoid problems with
integer roundoff. The minimum distances that a device can work
with in the horizontal and vertical directions are termed its
motion quanta, stored in the .H and .V registers, respectively.
Measurements are rounded to applicable motion quanta. Half-
quantum fractions round toward zero.
Default units
A general-purpose register (one created or updated with the nr
request; see section “Registers” below) is implicitly
dimensionless, or reckoned in basic units if interpreted in a
measurement context. But it is convenient for many requests and
escape sequences to infer a scaling unit for an argument if none
is specified. An explicit scaling unit (not after a closing
parenthesis) can override an undesirable default. Effectively,
the default unit is suffixed to the expression if a scaling unit
is not already present. GNU troff's use of integer arithmetic
should also be kept in mind; see below.
A numeric expression evaluates to an integer. The following
operators are recognized.
+ addition
- subtraction
* multiplication
/ truncating division
% modulus
────────────────────────────────────────────
unary + assertion, motion, incrementation
unary - negation, motion, decrementation
────────────────────────────────────────────
; scaling
>? maximum
<? minimum
────────────────────────────────────────────
< less than
> greater than
<= less than or equal
>= greater than or equal
= equal
== equal
────────────────────────────────────────────
& logical conjunction (“and”)
: logical disjunction (“or”)
! logical complementation (“not”)
────────────────────────────────────────────
( ) precedence
────────────────────────────────────────────
| boundary-relative motion
troff provides a set of mathematical and logical operators
familiar to programmers—as well as some unusual ones—but supports
only integer arithmetic. (Provision is made for interpreting and
reporting decimal fractions in certain cases.) The internal data
type used for computing results is usually a 32-bit signed
integer, which suffices to represent magnitudes within a range of
±2 billion. (If that's not enough, see groff_tmac(5) for the
62bit.tmac macro package.)
Arithmetic infix operators perform a function on the numeric
expressions to their left and right; they are + (addition), -
(subtraction), * (multiplication), / (truncating division), and %
(modulus). Truncating division rounds to the integer nearer to
zero, no matter how large the fractional portion. Overflow and
division (or modulus) by zero are errors and abort evaluation of a
numeric expression.
Arithmetic unary operators operate on the numeric expression to
their right; they are - (negation) and + (assertion—for
completeness; it does nothing). The unary minus must often be
used with parentheses to avoid confusion with the decrementation
operator, discussed below.
The sign of the modulus of operands of mixed signs is determined
by the sign of the first. Division and modulus operators satisfy
the following property: given a dividend a and a divisor b, a
quotient q formed by “(a / b)” and a remainder r by “(a % b)”,
then qb + r = a.
GNU troff's scaling operator, used with parentheses as (c;e),
evaluates a numeric expression e using c as the default scaling
unit. If c is omitted, scaling units are ignored in the
evaluation of e. GNU troff also provides a pair of operators to
compute the extrema of two operands: >? (maximum) and <?
(minimum).
Comparison operators comprise < (less than), > (greater than), <=
(less than or equal), >= (greater than or equal), and = (equal).
== is a synonym for =. When evaluated, a comparison is replaced
with “0” if it is false and “1” if true. In the roff language,
positive values are true, others false.
We can operate on truth values with the logical operators &
(logical conjunction or “and”) and : (logical disjunction or
“or”). They evaluate as comparison operators do. A logical
complementation (“not”) operator, !, works only within “if”, “ie”,
and “while” requests. Furthermore, ! is recognized only at the
beginning of a numeric expression not contained by another numeric
expression. In other words, it must be the “outermost” operator.
Including it elsewhere in the expression produces a warning in the
“number” category (see troff(1)), and its expression evaluates
false. This unfortunate limitation maintains compatibility with
AT&T troff. Test a numeric expression for falsity by comparing it
to a false value.
The roff language has no operator precedence: expressions are
evaluated strictly from left to right, in contrast to schoolhouse
arithmetic. Use parentheses ( ) to impose a desired precedence
upon subexpressions.
For many requests and escape sequences that cause motion on the
page, the unary operators + and - work differently when leading a
numeric expression. They then indicate a motion relative to the
drawing position: positive is down in vertical contexts, right in
horizontal ones.
+ and - are also treated differently by the following requests and
escape sequences: bp, in, ll, pl, pn, po, ps, pvs, rt, ti, \H, \R,
and \s. Here, leading plus and minus signs serve as
incrementation and decrementation operators, respectively. To
negate an expression, subtract it from zero or include the unary
minus in parentheses with its argument.
A leading | operator indicates a motion relative not to the
drawing position but to a boundary. For horizontal motions, the
measurement specifies a distance relative to a drawing position
corresponding to the beginning of the input line. By default, tab
stops reckon movements in this way. Most escape sequences do not;
| tells them to do so. For vertical motions, the | operator
specifies a distance from the first text baseline on the page or
in the current diversion, using the current vertical spacing.
The \B escape sequence tests its argument for validity as a
numeric expression.
A register interpolated as an operand in a numeric expression must
have an Arabic format; luckily, this is the default.
Due to the way arguments are parsed, spaces are not allowed in
numeric expressions unless the (sub)expression containing them is
surrounded by parentheses.
An identifier labels a GNU troff datum such as a register, name
(macro, string, or diversion), typeface, color, special character,
character class, environment, or stream. Valid identifiers
consist of one or more ordinary characters. An ordinary character
is an input character that is not the escape character, a leader,
tab, newline, or invalid as GNU troff input.
Invalid input characters are subset of control characters (from
the sets “C0 Controls” and “C1 Controls” as Unicode describes
them). When troff encounters one in an identifier, it produces a
warning in category “input” (see section “Warnings” in troff(1)).
They are removed during interpretation: an identifier “foo”,
followed by an invalid character and then “bar”, is processed as
“foobar”.
On a machine using the ISO 646, 8859, or 10646 character
encodings, invalid input characters are 0x00, 0x08, 0x0B,
0x0D–0x1F, and 0x80–0x9F. On an EBCDIC host, they are 0x00–0x01,
0x08, 0x09, 0x0B, 0x0D–0x14, 0x17–0x1F, and 0x30–0x3F. Some of
these code points are used by troff internally, making it non-
trivial to extend the program to accept UTF-8 or other encodings
that use characters from these ranges.
An identifier with a closing bracket (“]”) in its name can't be
accessed with bracket-form escape sequences that expect an
identifier as a parameter. Similarly, the identifier “(” can't be
interpolated except with bracket forms.
If you begin a macro, string, or diversion name with either of the
characters “[” or “]”, you foreclose use of the refer(1)
preprocessor, which recognizes “.[” and “.]” as bibliographic
reference delimiters.
The escape sequence \A tests its argument for validity as an
identifier.
How GNU troff handles the interpretation of an undefined
identifier depends on the context. There is no way to invoke an
undefined request; such syntax is interpreted as a macro call
instead. If the identifier is interpreted as a string, macro, or
diversion, troff emits a warning in category “mac”, defines it as
empty, and interpolates nothing. If the identifier is interpreted
as a register, troff emits a warning in category “reg”,
initializes it to zero, and interpolates that value. See section
“Warnings” in troff(1), and subsection “Interpolating registers”
and section “Strings” below. Attempting to use an undefined
typeface, style, special character, color, character class,
environment, or stream generally provokes an error diagnostic.
Identifiers for requests, macros, strings, and diversions share
one name space; special characters and character classes another.
No other object types do.
Control characters are recognized only at the beginning of an
input line, or at the beginning of the branch of a control
structure request; see section “Control structures” below.
A few requests cause a break implicitly; use the no-break control
character to prevent the break. Break suppression is its sole
behavioral distinction. Employing the no-break control character
to invoke requests that don't cause breaks is harmless but poor
style.
The control character “.” and the no-break control character “'”
can be changed with the cc and c2 requests, respectively. Within
a macro definition, register .br indicates the control character
used to call it.
A control character is optionally followed by tabs and/or spaces
and then an identifier naming a request or macro. The invocation
of an unrecognized request is interpreted as a macro call.
Defining a macro with the same name as a request replaces the
request. Deleting a request name with the rm request makes it
unavailable. The als request can alias requests, permitting them
to be wrapped or non-destructively replaced. See section
“Strings” below.
There is no inherent limit on argument length or quantity. Most
requests take one or more arguments, and ignore any they do not
expect. A request may be separated from its arguments by tabs or
spaces, but only spaces can separate an argument from its
successor. Only one between arguments is necessary; any excess is
ignored. GNU troff does not allow tabs for argument separation.
Generally, a space within a request argument is not relevant, not
meaningful, or is supported by bespoke provisions, as with the tl
request's delimiters. Some requests, like ds, interpret the
remainder of the control line as a single argument. See section
“Strings” below.
Spaces and tabs immediately after a control character are ignored.
Commonly, authors structure the source of documents or macro files
with them.
If a macro of the desired name does not exist when called, it is
created, assigned an empty definition, and a warning in category
“mac” is emitted. Calling an undefined macro does end a macro
definition naming it as its end macro (see section “Writing
macros” below).
To embed spaces within a macro argument, enclose the argument in
neutral double quotes ‘"’. Horizontal motion escape sequences are
sometimes a better choice for arguments to be formatted as text.
The foregoing raises the question of how to embed neutral double
quotes or backslashes in macro arguments when those characters are
desired as literals. In GNU troff, the special character escape
sequence \[rs] produces a backslash and \[dq] a neutral double
quote.
In GNU troff's AT&T compatibility mode, these characters remain
available as \(rs and \(dq, respectively. AT&T troff did not
consistently define these special characters, but its descendants
can be made to support them. See groff_font(5). If even that is
not feasible, see the “Calling Macros” section of the groff
Texinfo manual for the complex macro argument quoting rules of
AT&T troff.
Whereas requests must occur on control lines, escape sequences can
occur intermixed with text and may appear in arguments to
requests, macros, and other escape sequences. An escape sequence
is introduced by the escape character, a backslash \. The next
character selects the escape's function.
Escape sequences vary in length. Some take an argument, and of
those, some have different syntactical forms for a one-character,
two-character, or arbitrary-length argument. Others accept only
an arbitrary-length argument. In the former scheme, a one-
character argument follows the function character immediately, an
opening parenthesis “(” introduces a two-character argument (no
closing parenthesis is used), and an argument of arbitrary length
is enclosed in brackets “[]”. In the latter scheme, the user
selects a delimiter character. A few escape sequences are
idiosyncratic, and support both of the foregoing conventions (\s),
designate their own termination sequence (\?), consume input until
the next newline (\!, \", \#), or support an additional modifier
character (\s again, and \n).
If an escape character is followed by a character that does not
identify a defined operation, the escape character is ignored
(producing a diagnostic of the “escape” warning category, which is
not enabled by default) and the following character is processed
normally.
Escape sequence interpolation is of higher precedence than escape
sequence argument interpretation. This rule affords flexibility
in using escape sequences to construct parameters to other escape
sequences.
The escape character can be interpolated (\e). Requests permit
the escape mechanism to be deactivated (eo) and restored, or the
escape character changed (ec), and to save and restore it (ecs and
ecr).
Some escape sequences that require parameters use delimiters. The
neutral apostrophe ' is a popular choice and shown in this
document. The neutral double quote " is also commonly seen.
Letters, numerals, and leaders can be used. Punctuation
characters are likely better choices, except for those defined as
infix operators in numeric expressions; see below.
The following escape sequences don't take arguments and thus are
allowed as delimiters: \space, \%, \|, \^, \{, \}, \', \`, \-, \_,
\!, \?, \), \/, \,, \&, \:, \~, \0, \a, \c, \d, \e, \E, \p, \r,
\t, and \u. However, using them this way is discouraged; they can
make the input confusing to read.
A few escape sequences, \A, \b, \o, \w, \X, and \Z, accept a
newline as a delimiter. Newlines that serve as delimiters
continue to be recognized as input line terminators. Use of
newlines as delimiters in escape sequences is also discouraged.
Finally, the escape sequences \D, \h, \H, \l, \L, \N, \R, \s, \S,
\v, and \x prohibit many delimiters.
• the numerals 0–9 and the decimal point “.”
• the (single-character) operators +-/*%<>=&:()
• any escape sequences other than \%, \:, \{, \}, \', \`,
\-, \_, \!, \/, \c, \e, and \p
Delimiter syntax is complex and flexible primarily for historical
reasons; the foregoing restrictions need be kept in mind mainly
when using groff in AT&T compatibility mode. GNU troff keeps
track of the nesting depth of escape sequence interpolations, so
the only characters you need to avoid using as delimiters are
those that appear in the arguments you input, not any that result
from interpolation. Typically, ' works fine. See section
“Implementation differences” in groff_diff(7).
As discussed in roff(7), the first character on an input line is
treated specially. Further, formatting a glyph has many
consequences on formatter state (see section “Environments”
below). Occasionally, we want to escape this context or embrace
some of those consequences without actually rendering a glyph to
the output. \& interpolates a dummy character, which is
constitutive of output but invisible. Its presence alters the
interpretation context of a subsequent input character, and enjoys
several applications: preventing the insertion of extra space
after an end-of-sentence character, preventing interpretation of a
control character at the beginning of an input line, preventing
kerning between two glyphs, and permitting the tr request to remap
a character to “nothing”. \) works as \& does, except that it
does not cancel a pending end-of-sentence state.
groff has “if” and “while” control structures like other
languages. However, the syntax for grouping multiple input lines
in the branches or bodies of these structures is unusual.
They have a common form: the request name is (except for .el
“else”) followed by a conditional expression cond-expr; the
remainder of the line, anything, is interpreted as if it were an
input line. Any quantity of spaces between arguments to requests
serves only to separate them; leading spaces in anything are
therefore not seen. anything effectively cannot be omitted; if
cond-expr is true and anything is empty, the newline at the end of
the control line is interpreted as a blank line (and therefore a
blank text line).
It is frequently desirable for a control structure to govern more
than one request, macro call, or text line, or a combination of
the foregoing. The opening and closing brace escape sequences \{
and \} perform such grouping. Brace escape sequences outside of
control structures have no meaning and produce no output.
\{ should appear (after optional spaces and tabs) immediately
subsequent to the request's conditional expression. \} should
appear on a line with other occurrences of itself as necessary to
match \{ sequences. It can be preceded by a control character,
spaces, and tabs. Input after any quantity of \} sequences on the
same line is processed only if all the preceding conditions to
which they correspond are true. Furthermore, a \} closing the
body of a .while request must be the last such escape sequence on
an input line.
Conditional expressions
The .if, .ie, and .while requests test the truth values of numeric
expressions. They also support several additional Boolean
operators; the members of this expanded class are termed
conditional expressions; their truth values are as shown below.
cond-expr... ...is true if...
───────────────────────────────────────────────────────────────────
's1's2' s1 produces the same formatted output as s2.
c g a glyph g is available.
d m a string, macro, diversion, or request m is
defined.
e the current page number is even.
F f a font named f is available.
m c a color named c is defined.
n the formatter is in nroff mode.
o the current page number is odd.
r n a register named n is defined.
S s a font style named s is available.
t the formatter is in troff mode.
v n/a (historical artifact; always false).
If the first argument to an .if, .ie, or .while request begins
with a non-alphanumeric character apart from ! (see below); it
performs an output comparison test. Shown first in the table
above, the output comparison operator interpolates a true value if
formatting its comparands s1 and s2 produces the same output
commands. Other delimiters can be used in place of the neutral
apostrophes. troff formats s1 and s2 in separate environments;
after the comparison, the resulting data are discarded. The
resulting glyph properties, including font family, style, size,
and slant, must match, but not necessarily the requests and/or
escape sequences used to obtain them. Motions must match in
orientation and magnitude to within the applicable horizontal or
vertical motion quantum of the device, after rounding.
Surround the comparands with \? to avoid formatting them; this
causes them to be compared character by character, as with string
comparisons in other programming languages. Since comparands
protected with \? are read in copy mode, they need not even be
valid groff syntax. The escape character is still lexically
recognized, however, and consumes the next character.
The above operators can't be combined with most others, but a
leading “!”, not followed immediately by spaces or tabs,
complements an expression. Spaces and tabs are optional
immediately after the “c”, “d”, “F”, “m”, “r”, and “S” operators,
but right after “!”, they end the predicate and the conditional
evaluates true. (This bizarre behavior maintains compatibility
with AT&T troff.)
In the following request and escape sequence specifications, most
argument names were chosen to be descriptive. A few denotations
may require introduction.
c denotes a single input character.
font a font either specified as a font name or a
numeric mounting position.
anything all characters up to the end of the line, to the
ending delimiter for the escape sequence, or
within \{ and \}. Escape sequences may generally
be used freely in anything, except when it is
read in copy mode.
message is a character sequence to be emitted on the
standard error stream. Special character escape
sequences are not interpreted.
n is a numeric expression that evaluates to a non-
negative integer.
npl is a numeric expression constituting a count of
subsequent productive input lines; that is, those
that directly produce formatted output. Text
lines produce output, as do control lines
containing requests like .tl or escape sequences
like \D. Macro calls are not themselves
productive, but their interpolated contents can
be.
±N is a numeric expression with a meaning dependent
on its sign.
If a numeric expression presented as ±N starts with a ‘+’ sign, an
increment in the amount of of N is applied to the value applicable
to the request or escape sequence. If it starts with a ‘-’ sign,
a decrement of magnitude N is applied instead. Without a sign, N
replaces any existing value. A leading minus sign in N is always
interpreted as a decrementation operator, not an algebraic sign.
To assign a register a negative value or the negated value of
another register, enclose it with its operand in parentheses or
subtract it from zero. If a prior value does not exist (the
register was undefined), an increment or decrement is applied as
if to 0.
Not all details of request behavior are outlined here. See the
groff Texinfo manual or, for features new to GNU troff,
groff_diff(7).
.ab Abort processing; exit with failure status.
.ab message
Abort processing; write message to the standard error
stream and exit with failure status.
.ad Enable output line alignment and adjustment using the
mode stored in \n[.j].
.ad c Enable output line alignment and adjustment in mode c
(c=b,c,l,n,r). Sets \n[.j].
.af register c
Assign format c to register, where c is “i”, “I”, “a”,
“A”, or a sequence of decimal digits whose quantity
denotes the minimum width in digits to be used when the
register is interpolated. “i” and “a” indicate Roman
numerals and basic Latin alphabetics, respectively, in
the lettercase specified. The default is 0.
.aln new old
Create alias (additional name) new for existing register
named old.
.als new old
Create alias (additional name) new for existing request,
string, macro, or diversion old.
.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
macro until .. is encountered.
.ami macro end
Append to a macro indirectly. macro and end are strings
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 name Create string name with empty contents; no operation if
name already exists.
.as name contents
Append contents to string name.
.as1 string
.as1 string contents
As .as, but with compatibility mode disabled when
contents interpolated.
.asciify diversion
Unformat ASCII characters, spaces, and some escape
sequences in diversion.
.backtrace
Write the state of the input stack to the standard error
stream. See the -b option of groff(1).
.bd font Stop emboldening font font.
.bd font n
Embolden font by overstriking its glyphs offset by n-1
units. See register .b.
.bd special-font font
Stop emboldening special-font when font is selected.
.bd special-font font n
Embolden special-font, overstriking its glyphs offset by
n-1 units when font is selected. See register .b.
.blm Unset blank line macro (trap). Restore default handling
of blank lines.
.blm name Set blank line macro (trap) to name.
.box Stop directing output to current diversion; any pending
output line is discarded.
.box name Direct output to diversion name, omitting a partially
collected line.
.boxa Stop appending output to current diversion; any pending
output line is discarded.
.boxa name
Append output to diversion name, omitting a partially
collected line.
.bp Break page and start a new one.
.bp ±N Break page, starting a new one numbered ±N.
.br Break output line.
.brp Break output line; adjust if applicable.
.break Break out of a while loop.
.c2 Reset no-break control character to “'”.
.c2 o Recognize ordinary character o as no-break control
character.
.cc Reset control character to ‘.’.
.cc o Recognize ordinary character o as the control character.
.ce Break, center the output of the next productive input
line without filling, and break again.
.ce npl Break, center the output of the next npl productive
input lines without filling, then break again. If npl ≤
0, stop centering.
.cf file Copy contents of file without formatting to the (top-
level) diversion.
.cflags n c1 c2 ...
Assign properties encoded by n to characters c1, c2, and
so on.
.ch name Unplant page location trap name.
.ch name vpos
Change page location trap name planted by .wh by moving
its location to vpos (default scaling unit v).
.char c contents
Define ordinary or special character c as contents.
.chop object
Remove the last character from the macro, string, or
diversion named object.
.class name c1 c2 ...
Define a (character) class name comprising the
characters or range expressions c1, c2, and so on.
.close stream
Close the stream.
.color Enable output of color-related device-independent output
commands.
.color n If n is zero, disable output of color-related device-
independent output commands; 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 Continuously underline the output of the next productive
input line.
.cu npl Continuously underline the output of the next npl
productive input lines. If npl=0, stop continuously
underlining.
.da Stop appending output to current diversion.
.da name Append output to diversion name.
.de macro Define or redefine macro until “..” occurs at the start
of a control line in the current conditional block.
.de macro end
Define or redefine macro until end is invoked or called
at the start of a control line in the current
conditional block.
.de1 macro
As .de, but disable compatibility mode during macro
expansion.
.de1 macro end
As “.de macro end”, but disable compatibility mode
during macro expansion.
.defcolor ident scheme color-component ...
Define a color named ident. scheme identifies a color
space and determines the number of required color-
components; it must be one of “rgb” (three components),
“cmy” (three), “cmyk” (four), or “gray” (one). “grey”
is accepted as a synonym of “gray”. The color
components can be encoded as a single hexadecimal value
starting with # or ##. The former indicates that each
component is in the range 0–255 (0–FF), the latter the
range 0–65,535 (0–FFFF). Alternatively, each color
component can be specified as a decimal fraction in the
range 0–1, interpreted using a default scaling unit
of “f”, which multiplies its value by 65,536 (but clamps
it at 65,535). Each output device has a color named
“default”, which cannot be redefined. A device's
default stroke and fill colors are not necessarily the
same.
.dei macro
Define macro indirectly. As .de, but use interpolation
of string macro as the name of the defined macro.
.dei macro end
Define macro indirectly. As .de, but use interpolations
of strings macro and end as the names of the defined and
end macros.
.dei1 macro
As .dei, but disable compatibility mode during macro
expansion.
.dei1 macro end
As .dei macro end, but disable compatibility mode during
macro expansion.
.device anything
Write anything, read in copy mode, to troff output as a
device control command. An initial neutral double quote
is stripped to allow embedding of leading spaces.
.devicem name
Write contents of macro or string name to troff output
as a device control command.
.di Stop directing output to current diversion.
.di name Direct output to diversion name.
.do name ...
Interpret the string, request, diversion, or macro name
(along with any arguments) with compatibility mode
disabled. Compatibility mode is restored (only if it
was active) when the expansion of name is interpreted.
.ds name Create empty string name.
.ds name contents
Create a string name containing contents.
.ds1 name
.ds1 name contents
As .ds, but with compatibility mode disabled when
contents interpolated.
.dt Clear diversion trap.
.dt vertical-position name
Set the diversion trap to macro name at vertical-
position (default scaling unit v).
.ec Recognize \ as the escape character.
.ec o Recognize ordinary character o as the escape character.
.ecr Restore escape character saved with .ecs.
.ecs Save the escape character.
.el anything
Interpret anything as if it were an input line if the
conditional expression of the corresponding .ie request
was false.
.em name Call macro name after the end of input.
.eo Disable the escape mechanism in interpretation mode.
.ev Pop environment stack, returning to previous one.
.ev env Push current environment onto stack and switch to env.
.evc env Copy environment env to the current one.
.ex Exit with successful status.
.fam Set default font family to previous value.
.fam name Set default 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 contents
Define fallback character (or glyph) c as contents.
.fcolor Restore previous fill color.
.fcolor c Set fill color to c.
.fi Enable filling of output lines; a pending output line is
broken. Sets \n[.u].
.fl Flush output buffer.
.fp pos id
Mount font with font description file name id at non-
negative position n.
.fp pos id font-description-file-name
Mount font with font-description-file-name as name id at
non-negative 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
.ft P Select previous font mounting position (abstract style
or font); same as \f[] or \fP.
.ft font Select typeface font, which can be a mounting position,
abstract style, or font name; same as \f[font] escape
sequence. font cannot be P.
.ftr font1 font2
Translate font1 to font2.
.fzoom font
.fzoom font 0
Stop magnifying font.
.fzoom font z
Set zoom factor for font to z (in thousandths; default:
1000).
.gcolor Restore previous stroke color.
.gcolor c Set stroke color to c.
.hc Reset the hyphenation character to \% (the default).
.hc char Change the hyphenation character to char.
.hcode c1 code1 [c2 code2] ...
Set the hyphenation code of character c1 to code1, that
of c2 to code2, and so on.
.hla lang Set the hyphenation language to lang.
.hlm n Set the maximum quantity of consecutive hyphenated lines
to n.
.hpf pattern-file
Read hyphenation patterns from pattern-file.
.hpfa pattern-file
Append hyphenation patterns from pattern-file.
.hpfcode a b [c d] ...
Define mappings for character codes in hyphenation
pattern files read with .hpf and .hpfa.
.hw word ...
Define hyphenation overrides for each word; a hyphen “-”
indicates a hyphenation point.
.hy Set automatic hyphenation mode to 1.
.hy 0 Disable automatic hyphenation; same as .nh.
.hy mode Set automatic hyphenation mode to mode; see section
“Hyphenation” below.
.hym Set the (right) hyphenation margin to 0 (the default).
.hym length
Set the (right) hyphenation margin to length (default
scaling unit m).
.hys Set the hyphenation space to 0 (the default).
.hys hyphenation-space
Suppress automatic hyphenation in adjustment modes “b”
or “n” if the line can be justified with the addition of
up to hyphenation-space to each inter-word space
(default scaling unit m).
.ie cond-expr anything
If cond-expr is true, interpret anything as if it were
an input line, otherwise skip to a corresponding .el
request.
.if cond-expr anything
If cond-expr is true, then interpret anything as if it
were an input line.
.ig Ignore input (except for side effects of \R on auto-
incrementing registers) until “..” occurs at the start
of a control line in the current conditional block.
.ig end Ignore input (except for side effects of \R on auto-
incrementing registers) until .end is called at the
start of a control line in the current conditional
block.
.in Set indentation amount to previous value.
.in ±N Set indentation to ±N (default scaling unit m).
.it Cancel any pending input line trap.
.it npl name
Set (or replace) an input line trap in the environment,
calling macro name, after the next npl productive input
lines have been read. Lines interrupted with the \c
escape sequence are counted separately.
.itc Cancel any pending input line trap.
.itc npl name
As .it, except that input lines interrupted with the \c
escape sequence are not counted.
.kern Enable pairwise kerning.
.kern n If n is zero, disable pairwise kerning, otherwise enable
it.
.lc Unset leader repetition character.
.lc c Set leader repetition character to c (default: “.”).
.length reg anything
Compute the number of characters of anything and store
the count in the register reg.
.linetabs Enable line-tabs mode (calculate tab positions relative
to beginning of output line).
.linetabs 0
Disable line-tabs mode.
.lf n Set number of next input line to n.
.lf n file
Set number of next input line to n and input file name
to file.
.lg m Set ligature mode to m (0 = disable, 1 = enable, 2 =
enable for two-letter ligatures only).
.ll Set line length to previous value. Does not affect a
pending output line.
.ll ±N Set line length to ±N (default length 6.5i, default
scaling unit m). Does not affect a pending output line.
.lsm Unset the leading space macro (trap). Restore default
handling of lines with leading spaces.
.lsm name Set the leading space macro (trap) to name.
.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 Set length of title lines to previous value.
.lt ±N Set length of title lines (default length 6.5i, default
scaling unit m).
.mc Cease writing margin character.
.mc c Begin writing margin character c to the right of each
output line.
.mc c d Begin writing margin character c on each output line at
distance d to the right of the right margin (default
distance 10p, default scaling unit m).
.mk Mark vertical drawing position in an internal register;
see .rt.
.mk register
Mark vertical drawing position in register.
.mso file As .so, except that file is sought in the tmac
directories.
.msoquiet file
As .mso, but no warning is emitted if file does not
exist.
.na Disable output line adjustment.
.ne Break page if distance to next page location trap is
less than one vee.
.ne d Break page if distance to next page location trap is
less than distance d (default scaling unit v).
.nf Disable filling of output lines; a pending output line
is broken. Clears \n[.u].
.nh Disable automatic hyphenation; same as “.hy 0”.
.nm Deactivate output line numbering.
.nm ±N
.nm ±N m
.nm ±N m s
.nm ±N m s i
Activate output line numbering: number the next output
line ±N, writing numbers every m lines, with s numeral
widths (\0) between the line number and the output
(default 1), and indenting the line number by i numeral
widths (default 0).
.nn Suppress numbering of the next output line to be
numbered with nm.
.nn n Suppress numbering of the next n output lines to be
numbered with nm. If n=0, cancel suppression.
.nop anything
Interpret anything as if it were an input line.
.nr reg ±N
Define or update register reg with value N.
.nr reg ±N I
Define or update register reg with value N and auto-
increment I.
.nroff Make the conditional expressions n true and t false.
.ns Enable no-space mode, ignoring .sp requests until a
glyph or \D primitive is output. See .rs.
.nx Immediately jump to end of current file.
.nx file Stop formatting current file and begin reading file.
.open stream file
Open file for writing and associate the stream named
stream with it. Unsafe request; disabled by default.
.opena stream file
As .open, but append to file. Unsafe request; disabled
by default.
.os Output vertical distance that was saved by the .sv
request.
.output contents
Emit contents 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 Report the state of the current environment followed by
that of all other environments to the standard error
stream.
.pi program
Pipe output to program (nroff only). Unsafe request;
disabled by default.
.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 unit v).
.pm Report, to the standard error stream, the names and
sizes in bytes of defined macros, strings, and
diversions.
.pn ±N Next page number N.
.pnr Write the names and contents of all defined registers to
the standard error stream.
.po Change to previous page offset. The current page offset
is available in register .o.
.po ±N Page offset N.
.ps Return to previous type size.
.ps ±N Set/increase/decrease the type size to/by N scaled
points (a non-positive resulting type size is set to
1 u); also see \s[±N].
.psbb file
Retrieve the bounding box of the PostScript image found
in file, which must conform to Adobe's Document
Structuring Conventions (DSC). See registers llx, lly,
urx, ury.
.pso command-line
Execute command-line with popen(3) and interpolate its
output. Unsafe request; disabled by default.
.ptr Report names and positions of all page location traps to
the standard error stream.
.pvs Change to previous post-vertical line spacing.
.pvs ±N Change post-vertical line spacing according to ±N
(default scaling unit p).
.rchar c1 c2 ...
Remove definition of each ordinary or special character
c1, c2, ... defined by a .char, .fchar, or .schar
request.
.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 font-specific definitions of glyphs c1, c2,
... for font f.
.rj npl Break, right-align the output of the next productive
input line without filling, then break again.
.rj npl Break, right-align the output of the next npl productive
input lines without filling, then break again. If npl ≤
0, stop right-aligning.
.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 ident Remove register ident.
.rs Restore spacing; disable no-space mode. See .ns.
.rt Return (upward only) to vertical position marked by .mk
on the current page.
.rt N Return (upward only) to vertical position N (default
scaling unit v).
.schar c contents
Define global fallback character (or glyph) c as
contents.
.shc Reset the soft hyphen character to \[hy].
.shc c Set the soft hyphen character to c.
.shift n In a macro definition, left-shift arguments by
n positions.
.sizes s1 s2 ... sn [0]
Set available type sizes similarly to the sizes
directive in a DESC file. Each si is interpreted in
units of scaled points (z).
.so file Replace the request's control line with the contents of
file, “sourcing” it.
.soquiet file
As .so, but no warning is emitted if file does not
exist.
.sp Break and move the next text baseline down by one vee,
or until springing a page location trap.
.sp dist Break and move the next text baseline down by dist, or
until springing a page location trap (default scaling
unit v). A negative dist will not reduce the position
of the text baseline below zero. Prefixing dist with
the | operator moves to a position relative to the page
top for positive N, and the bottom if N is negative; in
all cases, one line height (vee) is added to dist. dist
is ignored inside a diversion.
.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 (the default)
without changing its value.
.spreadwarn N
Emit a break warning if the additional space inserted
for each space between words in an adjusted output line
is greater than or equal to N. A negative N is treated
as 0. The default scaling unit is m. At startup,
.spreadwarn is inactive and N is 3 m.
.ss n Set minimal inter-word spacing to n 12ths of current
font's space width.
.ss n m As “.ss n”, and set additional inter-sentence space to
m 12ths of current font's space width.
.stringdown stringvar
Replace each byte in the string named stringvar with its
lowercase version.
.stringup stringvar
Replace each byte in the string named stringvar with its
uppercase version.
.sty n style
Associate abstract style with font position n.
.substring str start [end]
Replace the string named str with its substring bounded
by the indices start and end, inclusive. Negative
indices count backwards from the end of the string.
.sv As .ne, but save 1 v for output with .os request.
.sv d As .ne, but save distance d for later output with .os
request (default scaling unit v).
.sy command-line
Execute command-line with system(3). Unsafe request;
disabled by default.
.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 the output line length. Each n argument
can be prefixed with a “+” to place the tab stop ni at a
distance relative to the previous, n(i-1). Each
argument ni or ri can be suffixed with a letter to align
text within the tab column bounded by tab stops
i and i+1; “L” for left-aligned (the default), “C” for
centered, and “R” for right-aligned.
.tag
.taga Reserved for internal use.
.tc Unset tab repetition character.
.tc c Set tab repetition character to c (default: none).
.ti ±N Temporarily indent next output line (default scaling
unit m).
.tkf font s1 n1 s2 n2
Enable track kerning for font.
.tl 'left'center'right'
Format three-part title.
.tm message
Write message, followed by a newline, to the standard
error stream.
.tm1 message
As .tm, but an initial neutral double quote in message
is removed, allowing it to contain leading spaces.
.tmc message
As .tm1, without emitting a newline.
.tr abcd...
Translate ordinary or special characters a to b, c to d,
and so on prior to output.
.trf file Transparently output the contents of file. Unlike .cf,
invalid input characters in file are rejected.
.trin abcd...
As .tr, except that .asciify ignores the translation
when a diversion is interpolated.
.trnt abcd...
As .tr, except that translations are suppressed in the
argument to \!.
.troff Make the conditional expressions t true and n false.
.uf font Set underline font used by .ul to font.
.ul Underline (italicize in troff mode) the output of the
next productive input line.
.ul npl Underline (italicize in troff mode) the output of the
next npl productive input line. If npl=0, stop
underlining.
.unformat diversion
Unformat space characters and tabs in diversion,
preserving font information.
.vpt Enable vertical position traps.
.vpt 0 Disable vertical position traps.
.vs Change to previous vertical spacing.
.vs ±N Set vertical spacing to ±N (default scaling unit p).
.warn Enable all warning categories.
.warn 0 Disable all warning categories.
.warn n Enable warnings in categories whose codes sum to n; see
troff(1).
.warnscale su
Set scaling unit used in certain warnings to su (one of
u, i, c, p, or P; default: i).
.wh vpos Remove visible page location trap at vpos (default
scaling unit v).
.wh vpos name
Plant macro name as page location trap at vpos (default
scaling unit v), removing any visible trap already
there.
.while cond-expr anything
Repeatedly execute anything unless and until cond-expr
evaluates false.
.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.
The escape sequences \", \#, \$, \*, \?, \a, \e, \n, \t, \g, \V,
and \newline are interpreted even in copy mode.
\" Comment. Everything up to the end of the line is ignored.
\# Comment. Everything up to and including the next newline
is ignored.
\*s Interpolate string with one-character name s.
\*(st Interpolate string with two-character name st.
\*[string]
Interpolate string with name string (of arbitrary length).
\*[string arg ...]
Interpolate string with name string (of arbitrary length),
taking arg ... as arguments.
\$0 Interpolate name by which currently executing macro was
invoked.
\$n Interpolate macro or string parameter numbered n (1≤n≤9).
\$(nn Interpolate macro or string parameter numbered nn
(01≤nn≤99).
\$[nnn]
Interpolate macro or string parameter numbered nnn (nnn≥1).
\$* Interpolate concatenation of all macro or string
parameters, separated by spaces.
\$@ Interpolate concatenation of all macro or string
parameters, with each surrounded by double quotes and
separated by spaces.
\$^ Interpolate concatenation of all macro or string parameters
as if they were arguments to the .ds request.
\' is a synonym for \[aa], the acute accent special character.
\` is a synonym for \[ga], the grave accent special character.
\- is a synonym for \[-], the minus sign special character.
\_ is a synonym for \[ul], the underrule special character.
\% Control hyphenation.
\! Transparent line. The remainder of the input line is
interpreted (1) when the current diversion is read; or (2)
if in the top-level diversion, by the postprocessor (if
any).
\?anything\?
Transparently embed anything, read in copy mode, in a
diversion, or unformatted as an output comparand in a
conditional expression.
\space Move right one word space.
\~ Insert an unbreakable, adjustable space.
\0 Move right by the width of a numeral in the current font.
\| Move one-sixth em to the right on typesetters.
\^ Move one-twelfth em to the right on typesetters.
\& Interpolate a dummy character.
\) Interpolate a dummy character that is transparent to end-
of-sentence recognition.
\/ Apply italic correction. Use between an immediately
adjacent oblique glyph on the left and an upright glyph on
the right.
\, Apply left italic correction. Use between an immediately
adjacent upright glyph on the left and an oblique glyph on
the right.
\: Non-printing break point (similar to \%, but never produces
a hyphen glyph).
\newline
Continue current input line on the next.
\{ Begin conditional input.
\} End conditional input.
\(gl Interpolate glyph with two-character name gl.
\[glyph]
Interpolate glyph with name glyph (of arbitrary length).
\[base-char comp ...]
Interpolate composite glyph constructed from base-char and
each component comp.
\[charnnn]
Interpolate glyph of eight-bit encoded character nnn, where
0≤nnn≤255.
\[unnnn[n[n]]]
Interpolate glyph of Unicode character with code point
nnnn[n[n]] in uppercase hexadecimal.
\[ubase-char[_combining-component]...]
Interpolate composite glyph from Unicode character base-
char and combining-components.
\a Interpolate a leader in copy mode.
\A'anything'
Interpolate 1 if anything is a valid identifier, and 0
otherwise.
\b'string'
Build bracket: pile a sequence of glyphs corresponding to
each character in string vertically, and center it
vertically on the output line.
\B'anything'
Interpolate 1 if anything is a valid numeric expression,
and 0 otherwise.
\c Continue output line at next input line.
\C'glyph'
As \[glyph], but compatible with other troff
implementations.
\d Move downward ½ em on typesetters.
\D'drawing-command'
See subsection “Drawing commands” below.
\e Interpolate the escape character.
\E As \e, but not interpreted in copy mode.
\fP Select previous font mounting position (abstract style or
font); same as “.ft” or “.ft P”.
\fF Select font mounting position, abstract style, or font with
one-character name or one-digit position F. F cannot be P.
\f(ft Select font mounting position, abstract style, or font with
two-character name or two-digit position ft.
\f[font]
Select font mounting position, abstract style, or font with
arbitrarily long name or position font. font cannot be P.
\f[] Select previous font mounting position (abstract style or
font).
\Ff Set default font family to that with one-character name f.
\F(fm Set default font family to that with two-character name fm.
\F[fam]
Set default font family to that with arbitrarily long name
fam.
\F[] Set default font family to previous value.
\gr Interpolate format of register with one-character name r.
\g(rg Interpolate format of register with two-character name rg.
\g[reg]
Interpolate format of register with arbitrarily long name
reg.
\h'N' Horizontally move the drawing position by N ems (or
specified units); | may be used. Positive motion is
rightward.
\H'N' Set height of current font to N scaled points (or specified
units).
\kr Mark horizontal position in one-character register name r.
\k(rg Mark horizontal position in two-character register name rg.
\k[reg]
Mark horizontal position in register with arbitrarily long
name reg.
\l'N[c]'
Draw horizontal line of length N with character c (default:
\[ru]; default scaling unit m).
\L'N[c]'
Draw vertical line of length N with character c (default:
\[br]; default scaling unit v).
\mc Set stroke color to that with one-character name c.
\m(cl Set stroke color to that with two-character name cl.
\m[color]
Set stroke color to that with arbitrarily long name color.
\m[] Restore previous stroke color.
\Mc Set fill color to that with one-character name c.
\M(cl Set fill color to that with two-character name cl.
\M[color]
Set fill color to that with arbitrarily long name color.
\M[] Restore previous fill color.
\nr Interpolate contents of register with one-character name r.
\n(rg Interpolate contents of register with two-character
name rg.
\n[reg]
Interpolate contents of register with arbitrarily long
name reg.
\N'n' Interpolate glyph with index n in the current font.
\o'abc...'
Overstrike centered glyphs of characters a, b, c, and so
on.
\O0 At the outermost suppression level, disable emission of
glyphs and geometric objects to the output driver.
\O1 At the outermost suppression level, enable emission of
glyphs and geometric objects to the output driver.
\O2 At the outermost suppression level, enable glyph and
geometric primitive emission to the output driver and write
to the standard error stream the page number, four bounding
box registers enclosing glyphs written since the previous
\O escape sequence, the page offset, line length, image
file name (if any), horizontal and vertical device motion
quanta, and input file name.
\O3 Begin a nested suppression level.
\O4 End a nested suppression level.
\O[5Pfile]
At the outermost suppression level, write the name file to
the standard error stream at position P, which must be one
of l, r, c, or i.
\p Break output line at next word boundary; adjust if
applicable.
\r Move “in reverse” (upward) 1 em.
\R'name ±N'
Set, increment, or decrement register name by N.
\s±N Set/increase/decrease the type size to/by N scaled points.
N must be a single digit; 0 restores the previous type
size. (In compatibility mode only, a non-zero N must be in
the range 4–39.) Otherwise, as .ps request.
\s(±N
\s±(N Set/increase/decrease the type size to/by N scaled points;
N is a two-digit number ≥1. As .ps request.
\s[±N]
\s±[N]
\s'±N'
\s±'N' Set/increase/decrease the type size to/by N scaled points.
As .ps request.
\S'N' Slant output glyphs by N degrees; the direction of text
flow is positive.
\t Interpolate a tab in copy mode.
\u Move upward ½ em on typesetters.
\v'N' Vertically move the drawing position by N vees (or
specified units); | may be used. Positive motion is
downward.
\Ve Interpolate contents of environment variable with one-
character name e.
\V(ev Interpolate contents of environment variable with two-
character name ev.
\V[env]
Interpolate contents of environment variable with
arbitrarily long name env.
\w'anything'
Interpolate width of anything, formatted in a dummy
environment.
\x'N' Increase vertical spacing of pending output line by N vees
(or specified units; negative before, positive after).
\X'anything'
Write anything to troff output as a device control command.
Within anything, the escape sequences \&, \), \%, and \:
are ignored; \space and \~ are converted to single space
characters; and \\ has its escape character stripped. So
that the basic Latin subset of the Unicode character set
can be reliably encoded in anything, the special character
escape sequences \-, \[aq], \[dq], \[ga], \[ha], \[rs], and
\[ti] are mapped to basic Latin characters; see
groff_char(7). For this transformation, character
translations and special character definitions are ignored.
\Yn Write contents of macro or string n to troff output as a
device control command.
\Y(nm Write contents of macro or string nm to troff output as a
device control command.
\Y[name]
Write contents of macro or string name to troff output as a
device control command.
\zc Format character c with zero width—without advancing the
drawing position.
\Z'anything'
Save the drawing position, format anything, then restore
it.
Drawing commands
Drawing commands direct the output device to render geometrical
objects rather than glyphs. Specific devices may support only a
subset, or may feature additional ones; consult the man page for
the output driver in use. Terminal devices in particular
implement almost none.
Rendering starts at the drawing position; when finished, the
drawing position is left at the rightmost point of the object,
even for closed figures, except where noted. GNU troff draws
stroked (outlined) objects with the stroke color, and shades
filled ones with the fill color. See section “Colors” above.
Coordinates h and v are horizontal and vertical motions relative
to the drawing position or previous point in the command. The
default scaling unit for horizontal measurements (and diameters of
circles) is m; for vertical ones, v.
Circles, ellipses, and polygons can be drawn stroked or filled.
These are independent properties; if you want a filled, stroked
figure, you must draw the same figure twice using each drawing
command. A filled figure is always smaller than an outlined one
because the former is drawn only within its defined area, whereas
strokes have a line thickness (set with \D't').
\D'~ h1 v1 ... hn vn'
Draw B-spline to each point in sequence, leaving drawing
position at (hn, vn).
\D'a hc vc h v'
Draw circular arc centered at (hc, vc) counterclockwise
from the drawing position to a point (h, v) relative to the
center. (hc, vc) is adjusted to the point nearest the
perpendicular bisector of the arc's chord.
\D'c d'
Draw circle of diameter d with its leftmost point at the
drawing position.
\D'C d'
As \D'C', but the circle is filled.
\D'e h v'
Draw ellipse of width h and height v with its leftmost
point at the drawing position.
\D'E h v'
As \D'e', but the ellipse is filled.
\D'l h v'
Draw line from the drawing position to (h, v).
\D'p h1 v1 ... hn vn'
Draw polygon with vertices at drawing position and each
point in sequence. GNU troff closes the polygon by drawing
a line from (hn, vn) back to the initial drawing position.
Afterward, the drawing position is left at (hn, vn).
\D'P h1 v1 ... hn vn'
As \D'p', but the polygon is filled.
\D't n'
Set stroke thickness of geometric objects to to n basic
units. A zero n selects the minimal supported thickness.
A negative n selects a thickness proportional to the type
size; this is the default.
Device control commands
The .device and .devicem requests, and \X and \Y escape sequences,
enable documents to pass information directly to a postprocessor.
These are useful for exercising device-specific capabilities that
the groff language does not abstract or generalize; such functions
include the embedding of hyperlinks and image files. Device-
specific functions are documented in each output driver's man
page.
groff supports strings primarily for user convenience.
Conventionally, if one would define a macro only to interpolate a
small amount of text, without invoking requests or calling any
other macros, one defines a string instead. Only one string is
predefined by the language.
\*[.T] Contains the name of the output device (for example,
“utf8” or “pdf”).
The .ds request creates a string with a specified name and
contents. If the identifier named by .ds already exists as an
alias, the target of the alias is redefined. If .ds is called
with only one argument, the named string becomes empty.
Otherwise, troff stores the remainder of the control line in copy
mode; see subsection “Copy mode” below.
The \* escape sequence dereferences a string's name, interpolating
its contents. If the name does not exist, it is defined as empty,
nothing is interpolated, and a warning in category “mac” is
emitted. See section “Warnings” in troff(1). The bracketed
interpolation form accepts arguments that are handled as macro
arguments are; see section “Calling macros” above. In contrast to
macro calls, however, if a closing bracket ] occurs in a string
argument, that argument must be enclosed in double quotes. \* is
interpreted even in copy mode. When defining strings, argument
interpolations must be escaped if they are to reference parameters
from the calling context; see section “Parameters” below.
An initial neutral double quote " in the string contents is
stripped to allow embedding of leading spaces. Any other " is
interpreted literally, but it is wise to use the special character
escape sequence \[dq] instead if the string might be interpolated
as part of a macro argument; see section “Calling macros” above.
Strings are not limited to a single input line of text. \newline
works just as it does elsewhere. The resulting string is stored
without the newlines. Care is therefore required when
interpolating strings while filling is disabled. It is not
possible to embed a newline in a string that will be interpreted
as such when the string is interpolated. To achieve that effect,
use \* to interpolate a macro instead.
The .as request is similar to .ds but appends to a string instead
of redefining it. If .as is called with only one argument, no
operation is performed (beyond dereferencing the string).
Because strings are similar to macros, they too can be defined to
suppress AT&T troff compatibility mode enablement when
interpolated; see section “Compatibility mode” below. The .ds1
request defines a string that suspends compatibility mode when the
string is later interpolated. .as1 is likewise similar to .as,
with compatibility mode suspended when the appended portion of the
string is later interpolated.
Caution: Unlike other requests, the second argument to these
requests consumes the remainder of the input line, including
trailing spaces. Ending string definitions (and appendments) with
a comment, even an empty one, prevents unwanted space from
creeping into them during source document maintenance.
Several requests exist to perform rudimentary string operations.
Strings can be queried (.length) and modified (.chop, .substring,
.stringup, .stringdown), and their names can be manipulated
through renaming, removal, and aliasing (.rn, .rm, .als).
When a request, macro, string, or diversion is aliased,
redefinitions and appendments “write through” alias names. To
replace an alias with a separately defined object, you must use
the rm request on its name first.
In the roff language, numbers can be stored in registers. Many
built-in registers exist, supplying anything from the date to
details of formatting parameters. You can also define your own.
See section “Identifiers” above for information on constructing a
valid name for a register.
Define registers and update their values with the nr request or
the \R escape sequence.
Registers can also be incremented or decremented by a configured
amount at the time they are interpolated. The value of the
increment is specified with a third argument to the .nr request,
and a special interpolation syntax, \n± is used to alter and then
retrieve the register's value. Together, these features are
called auto-increment. (A negative auto-increment can be
considered an “auto-decrement”.)
Many predefined registers are available. In the following
presentation, the register interpolation syntax \n[name] is used
to refer to a register name to clearly distinguish it from a
string or request name. The register name space is separate from
that used for requests, macros, strings, and diversions. Bear in
mind that the symbols \n[] are not part of the register name.
Read-only registers
Predefined registers whose identifiers start with a dot are read-
only. Many are Boolean-valued. Some are string-valued, meaning
that they interpolate text. A register name (without the dot) is
often associated with a request of the same name; exceptions are
noted.
\n[.$] Count of arguments passed to currently interpolated macro
or string.
\n[.a] Amount of extra post-vertical line space; see \x.
\n[.A] Approximate output is being formatted (Boolean-valued); see
troff -a option.
\n[.b] Font emboldening offset; see .bd.
\n[.br]
The normal control character was used to call the currently
interpolated macro (Boolean-valued).
\n[.c] Input line number; see .lf and register “c.”.
\n[.C] Compatibility mode is enabled (Boolean-valued); see .cp.
Always false when processing .do; see register .cp.
\n[.cdp]
Depth of last glyph formatted in the environment; positive
if glyph extends below the baseline.
\n[.ce]
Count of output lines remaining to be centered.
\n[.cht]
Height of last glyph formatted in the environment; positive
if glyph extends above the baseline.
\n[.color]
Color output is enabled (Boolean-valued).
\n[.cp]
Within .do, the saved value of compatibility mode; see
register .C.
\n[.csk]
Skew of the last glyph formatted in the environment; skew
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] Vertical drawing position in diversion.
\n[.ev]
Name of environment (string-valued).
\n[.f] Mounting position of selected font; see .ft and \f.
\n[.F] Name of input file (string-valued); see .lf.
\n[.fam]
Name of default font family (string-valued).
\n[.fn]
Resolved name of selected font (string-valued); see .ft and
\f.
\n[.fp]
Next non-zero free font mounting position index.
\n[.g] Always true in GNU troff (Boolean-valued).
\n[.h] Text baseline high-water mark on page or in diversion.
\n[.H] Horizontal motion quantum of output device in basic units.
\n[.height]
Font height; see \H.
\n[.hla]
Hyphenation language in environment (string-valued).
\n[.hlc]
Count of immediately preceding consecutive hyphenated lines
in environment.
\n[.hlm]
Maximum quantity of consecutive hyphenated lines allowed in
environment.
\n[.hy]
Automatic hyphenation mode in environment.
\n[.hym]
Hyphenation margin in environment.
\n[.hys]
Hyphenation space adjustment threshold in environment.
\n[.i] Indentation amount; see .in.
\n[.in]
Indentation amount applicable to the pending output line;
see .ti.
\n[.int]
Previous output line was “interrupted” or continued with \c
(Boolean-valued).
\n[.j] Adjustment mode encoded as an integer; see .ad and .na. Do
not interpret or perform arithmetic on its value.
\n[.k] Horizontal drawing position relative to indentation.
\n[.kern]
Pairwise kerning is enabled (Boolean-valued).
\n[.l] Line length; see .ll.
\n[.L] Line spacing; see .ls.
\n[.lg]
Ligature mode.
\n[.linetabs]
Line-tabs mode is enabled (Boolean-valued).
\n[.ll]
Line length applicable to the pending output line.
\n[.lt]
Title length.
\n[.m] Stroke color (string-valued); see .gcolor and \m. Empty if
the stroke color is the default.
\n[.M] Fill color (string-valued); see .fcolor and \M. Empty if
the fill color is the default.
\n[.n] Length of formatted output on previous output line.
\n[.ne]
Amount of vertical space required by last .ne that caused a
trap to be sprung; also see register .trunc.
\n[.nm]
Output line numbering is enabled (Boolean-valued).
\n[.nn]
Count of output lines remaining to have numbering
suppressed.
\n[.ns]
No-space mode is enabled (Boolean-valued).
\n[.o] Page offset; see .po.
\n[.O] Output suppression nesting level; see \O.
\n[.p] Page length; see .pl.
\n[.P] The page is selected for output (Boolean-valued); see troff
-o option.
\n[.pe]
Page ejection is in progress (Boolean-valued).
\n[.pn]
Number of the next page.
\n[.ps]
Type size in scaled points.
\n[.psr]
Most recently requested type size in scaled points; see .ps
and \s.
\n[.pvs]
Post-vertical line spacing.
\n[.R] Count of available unused registers; always 10,000 in GNU
troff.
\n[.rj]
Count of lines remaining to be right-aligned.
\n[.s] Type size in points as a decimal fraction (string-valued);
see .ps and \s.
\n[.slant]
Slant of font in degrees; see \S.
\n[.sr]
Most recently requested type size in points as a decimal
fraction (string-valued); see .ps and \s.
\n[.ss]
Size of minimal inter-word space in twelfths of the space
width of the selected font.
\n[.sss]
Size of additional inter-sentence space in twelfths of the
space width of the selected font.
\n[.sty]
Selected abstract style (string-valued); see .ft and \f.
\n[.t] Distance to next vertical position trap; see .wh and .ch.
\n[.T] An output device was explicitly selected (Boolean-valued);
see troff -T option.
\n[.tabs]
Representation of tab settings suitable for use as argument
to .ta (string-valued).
\n[.trunc]
Amount of vertical space truncated by the most recently
sprung vertical position trap, or, if the trap was sprung
by an .ne, minus the amount of vertical motion produced by
.ne; also see register .ne.
\n[.u] Filling is enabled (Boolean-valued); see .fi and .nf.
\n[.U] Unsafe mode is enabled (Boolean-valued); see troff -U
option.
\n[.v] Vertical line spacing; see .vs.
\n[.V] Vertical motion quantum of the output device in basic
units.
\n[.vpt]
Vertical position traps are enabled (Boolean-valued).
\n[.w] Width of previous glyph formatted in the environment.
\n[.warn]
Sum of the numeric codes of enabled warning categories.
\n[.x] Major version number of the running troff formatter.
\n[.y] Minor version number of the running troff formatter.
\n[.Y] Revision number of the running troff formatter.
\n[.z] Name of diversion (string-valued). Empty if output is
directed to the top-level diversion.
\n[.zoom]
Zoom multiplier of current font (in thousandths; zero if no
magnification); see .fzoom.
Writable predefined registers
Several registers are predefined but also modifiable; some are
updated upon interpretation of certain requests or escape
sequences. Date- and time-related registers are set to the local
time as determined by localtime(3) when the formatter launches.
This initialization can be overridden by SOURCE_DATE_EPOCH and TZ;
see section “Environment” of groff(1).
\n[$$] Process ID of troff.
\n[%] Page number.
\n[c.] Input line number.
\n[ct] Union of character types of each glyph rendered into dummy
environment by \w.
\n[dl] Width of last closed diversion.
\n[dn] Height of last closed diversion.
\n[dw] Day of the week (1–7; 1 is Sunday).
\n[dy] Day of the month (1–31).
\n[hours]
Count of hours elapsed since midnight (0–23).
\n[hp] Horizontal drawing position relative to start of input
line.
\n[llx]
Lower-left x coordinate (in PostScript units) of PostScript
image; see .psbb.
\n[lly]
Lower-left y coordinate (in PostScript units) of PostScript
image; see .psbb.
\n[ln] Output line number; see .nm.
\n[lsn]
Count of leading spaces on input line.
\n[lss]
Amount of horizontal space corresponding to leading spaces
on input line.
\n[minutes]
Count of minutes elapsed in the hour (0–59).
\n[mo] Month of the year (1–12).
\n[nl] Vertical drawing position.
\n[opmaxx]
\n[opmaxy]
\n[opminx]
\n[opminy]
These four registers mark the top left- and bottom right-
hand corners of a rectangle encompassing all formatted
output on the page. They are reset to -1 by \O0 or \O1.
\n[rsb]
As register sb, adding maximum glyph height to measurement.
\n[rst]
As register st, adding maximum glyph depth to measurement.
\n[sb] Maximum displacement of text baseline below its original
position after rendering into dummy environment by \w.
\n[seconds]
Count of seconds elapsed in the minute (0–60).
\n[skw]
Skew of last glyph rendered into dummy environment by \w.
\n[slimit]
The maximum depth of troff's internal input stack. If ≤0,
there is no limit: recursion can continue until available
memory is exhausted. The default is 1,000.
\n[ssc]
Subscript correction of last glyph rendered into dummy
environment by \w.
\n[st] Maximum displacement of text baseline above its original
position after rendering into dummy environment by \w.
\n[systat]
Return value of system() function; see .sy.
\n[urx]
Upper-right x coordinate (in PostScript units) of
PostScript image; see .psbb.
\n[ury]
Upper-right y coordinate (in PostScript units) of
PostScript image; see .psbb.
\n[year]
Gregorian year.
\n[yr] Gregorian year minus 1900.
In digital typography, a font is a collection of characters in a
specific typeface that a device can render as glyphs at a desired
size. (Terminals and some output devices have fonts that render
at only one or two sizes. As examples of the latter, take the
groff lj4 device's Lineprinter, and lbp's Courier and Elite
faces.) A roff formatter can change typefaces at any point in the
text. The basic faces are a set of styles combining upright and
slanted shapes with normal and heavy stroke weights: “R”, “I”,
“B”, and “BI”—these stand for roman, bold, italic, and bold-
italic. For linguistic text, GNU troff groups typefaces into
families containing each of these styles. (Font designers prepare
families such that the styles share esthetic properties.) A text
font is thus often a family combined with a style, but it need not
be: consider the ps and pdf devices' ZCMI (Zapf Chancery Medium
italic)—often, no other style of Zapf Chancery Medium is provided.
On typesetting devices, at least one special font is available,
comprising unstyled glyphs for mathematical operators and other
purposes.
Like AT&T troff, GNU troff does not itself load or manipulate a
digital font file; instead it works with a font description file
that characterizes it, including its glyph repertoire and the
metrics (dimensions) of each glyph. This information permits the
formatter to accurately place glyphs with respect to each other.
Before using a font description, the formatter associates it with
a mounting position, a place in an ordered list of available
typefaces. So that a document need not be strongly coupled to a
specific font family, in GNU troff an output device can associate
a style in the abstract sense with a mounting position. Thus the
default family can be combined with a style dynamically, producing
a resolved font name.
Fonts often have trademarked names, and even Free Software fonts
can require renaming upon modification. groff maintains a
convention that a device's serif font family is given the name T
(“Times”), its sans-serif family H (“Helvetica”), and its
monospaced family C (“Courier”). Historical inertia has driven
groff's font identifiers to short uppercase abbreviations of font
names, as with TR, TB, TI, TBI, and a special font S.
The default family used with abstract styles can be changed at any
time; initially, it is T. Typically, abstract styles are arranged
in the first four mounting positions in the order shown above.
The default mounting position, and therefore style, is always 1
(R). By issuing appropriate formatter instructions, you can
override these defaults before your document writes its first
glyph.
Terminal output devices cannot change font families and lack
special fonts. They support style changes by overstriking, or by
altering ISO 6429/ECMA-48 graphic renditions (character cell
attributes).
When filling, groff hyphenates words as needed at user-specified
and automatically determined hyphenation points. Explicitly
hyphenated words such as “mother-in-law” are always eligible for
breaking after each of their hyphens. The hyphenation
character \% and non-printing break point \: escape sequences may
be used to control the hyphenation and breaking of individual
words. The .hw request sets user-defined hyphenation points for
specified words at any subsequent occurrence. Otherwise, groff
determines hyphenation points automatically by default.
Several requests influence automatic hyphenation. Because
conventions vary, a variety of hyphenation modes is available to
the .hy request; these determine whether hyphenation will apply to
a word prior to breaking a line at the end of a page (more or
less; see below for details), and at which positions within that
word automatically determined hyphenation points are permissible.
The default is “1” for historical reasons, but this is not an
appropriate value for the English hyphenation patterns used by
groff; localization macro files loaded by troffrc and macro
packages often override it.
0 disables hyphenation.
1 enables hyphenation except after the first and before the
last character of a word.
The remaining values “imply” 1; that is, they enable hyphenation
under the same conditions as “.hy 1”, and then apply or lift
restrictions relative to that basis.
2 disables hyphenation of the last word on a page.
(Hyphenation is prevented if the next page location trap is
closer to the vertical drawing position than the next text
baseline would be. See section “Traps” below.)
4 disables hyphenation before the last two characters of a
word.
8 disables hyphenation 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.
Apart from value 2, restrictions imposed by the hyphenation mode
are not respected for words whose hyphenations have been specified
with the hyphenation character (“\%” by default) or the .hw
request.
Nonzero values are additive. For example, mode 12 causes groff to
hyphenate neither the last two nor the first two characters of a
word. Some values cannot be used together because they
contradict; for instance, values 4 and 16, and values 8 and 32.
As noted, it is superfluous to add 1 to any non-zero even mode.
The places within a word that are eligible for hyphenation are
determined by language-specific data (.hla, .hpf, and .hpfa) and
lettercase relationships (.hcode and .hpfcode). Furthermore,
hyphenation of a word might be suppressed due to a limit on
consecutive hyphenated lines (.hlm), a minimum line length
threshold (.hym), or because the line can instead be adjusted with
additional inter-word space (.hys).
The set of hyphenation patterns is associated with the hyphenation
language set by the .hla request. The .hpf request is usually
invoked by a localization file loaded by the troffrc file. groff
provides localization files for several languages; see
groff_tmac(5).
The .de request defines a macro named for its argument. If that
name already exists as an alias, the target of the alias is
redefined; see section “Strings” above. troff enters “copy mode”
(see below), storing subsequent input lines as the definition. If
the optional second argument is not specified, the definition ends
with the control line “..” (two dots). Alternatively, a second
argument names a macro whose call syntax ends the definition; this
“end macro” is then called normally. Spaces or tabs are permitted
after the first control character in the line containing this
ending token, but a tab immediately after the token prevents its
recognition as the end of a macro definition. Macro definitions
can be nested if they use distinct end macros or if their ending
tokens are sufficiently escaped. An end macro need not be defined
until it is called. This fact enables a nested macro definition
to begin inside one macro and end inside another.
Variants of .de disable compatibility mode and/or indirect the
names of the macros specified for definition or termination: these
are .de1, .dei, and .dei1. Append to macro definitions with .am,
.am1, .ami, and .ami1. The .als, .rm, and .rn requests create an
alias of, remove, and rename a macro, respectively. .return stops
the execution of a macro immediately, returning to the enclosing
context.
Parameters
Macro call and string interpolation parameters can be accessed
using escape sequences starting with “\$”. The \n[.$] read-only
register stores the count of parameters available to a macro or
string; its value can be changed by the .shift request, which
dequeues parameters from the current list. The \$0 escape
sequence interpolates the name by which a macro was called.
Applying string interpolation to a macro does not change this
name.
Copy mode
When troff processes certain requests, most importantly those
which define or append to a macro or string, it does so in copy
mode: it copies the characters of the definition into a dedicated
storage region, interpolating the escape sequences \n, \g, \$, \*,
\V, and \? normally; interpreting \newline immediately; discarding
comments \" and \#; interpolating the current leader, escape, or
tab character with \a, \e, and \t, respectively; and storing all
other escape sequences in an encoded form. The complement of copy
mode—a roff formatter's behavior when not defining or appending to
a macro, string, or diversion—where all macros are interpolated,
requests invoked, and valid escape sequences processed immediately
upon recognition, can be termed interpretation mode.
The escape character, \ by default, can escape itself. This
enables you to control whether a given \n, \g, \$, \*, \V, or \?
escape sequence is interpreted at the time the macro containing it
is defined, or later when the macro is called.
You can think of \\ as a “delayed” backslash; it is the escape
character followed by a backslash from which the escape character
has removed its special meaning. Consequently, \\ is not an
escape sequence in the usual sense. In any escape sequence \X
that troff does not recognize, the escape character is ignored and
X is output. An unrecognized escape sequence causes a warning in
category “escape”, with two exceptions, \\ being one. The other
is \., which escapes the control character. It is used to permit
nested macro definitions to end without a named macro call to
conclude them. Without a syntax for escaping the control
character, this would not be possible. roff documents should not
use the \\ or \. character sequences outside of copy mode; they
serve only to obfuscate the input. Use \e to represent the escape
character, \[rs] to obtain a backslash glyph, and \& before . and
' where troff expects them as control characters if you mean to
use them literally.
Macro definitions can be nested to arbitrary depth. In “\\”, each
escape character is interpreted twice—once in copy mode, when the
macro is defined, and once in interpretation mode, when the macro
is called. This fact leads to exponential growth in the quantity
of escape characters required to delay interpolation of \n, \g,
\$, \*, \V, and \? at each nesting level. An alternative is to
use \E, which represents an escape character that is not
interpreted in copy mode. Because \. is not a true escape
sequence, we can't use \E to keep “..” from ending a macro
definition prematurely. If the multiplicity of backslashes
complicates maintenance, use end macros.
Traps are locations in the output, or conditions on the input
that, when reached or fulfilled, call a specified macro. A
vertical position trap calls a macro when the formatter's vertical
drawing position reaches or passes, in the downward direction, a
certain location on the output page or in a diversion. Its
applications include setting page headers and footers, body text
in multiple columns, and footnotes. These traps can occur at a
given location on the page (.wh, .ch); at a given location in the
current diversion (.dt)—together, these are known as vertical
position traps, which can be disabled and re-enabled (.vpt).
A diversion is not formatted in the context of a page, so it lacks
page location traps; instead it can have a diversion trap. There
can exist at most one such vertical position trap per diversion.
Other kinds of trap can be planted at a blank line (.blm); at a
line with leading space characters (.lsm); after a certain number
of productive input lines (.it, .itc); or at the end of input
(.em). Macros called by traps are passed no arguments. Setting a
trap is also called planting one. It is said that a trap is
sprung if its condition is fulfilled.
Registers associated with trap management include vertical
position trap enablement status (\n[.vpt]), distance to the next
trap (\n[.t]), amount of needed (.ne-requested) space that caused
the most recent vertical position trap to be sprung (\n[.ne]),
amount of needed space truncated from the amount requested
(\n[.trunc]), page ejection status (\n[.pe]), and leading space
count (\n[.lsn]) with its corresponding amount of motion
(\n[.lss]).
Page location traps
A page location trap is a vertical position trap that applies to
the page; that is, to undiverted output. Many can be present;
manage them with the wh and ch requests. Non-negative page
locations given to these requests set the trap relative to the top
of the page; negative values set the trap relative to the bottom
of the page. It is not possible to plant a trap less than one
basic unit from the page bottom: a location of “-0” is interpreted
as “0”, the top of the page. An existing visible trap (see below)
at the same location is removed; this is .wh's sole function if
its second argument is missing.
A trap is sprung only if it is visible, meaning that its location
is reachable on the page and it is not hidden by another trap at
the same location already planted there. (A trap planted at “20i”
or “-30i” will not be sprung on a page of length “11i”.)
A trap above the top or at or below the bottom of the page can be
made visible by either moving it into the page area or increasing
the page length so that the trap is on the page. Negative trap
values always use the current page length; they are not converted
to an absolute vertical position. Use .ptr to dump page location
traps to the standard error stream; their positions are reported
in basic units.
The implicit page trap
An implicit page trap always exists in the top-level diversion; it
works like a trap in some ways but not others. Its purpose is to
eject the current page and start the next one. It has no name, so
it cannot be moved or deleted with wh or ch requests. You cannot
hide it by placing another trap at its location, and can move it
only by redefining the page length with .pl. Its operation is
suppressed when vertical page traps are disabled with the vpt
request.
In roff systems it is possible to format text as if for output,
but instead of writing it immediately, one can divert the
formatted text into a named storage area. It is retrieved later
by specifying its name after a control character. The same name
space is used for such diversions as for strings and macros; see
section “Identifiers” above. Such text is sometimes said to be
“stored in a macro”, but this coinage obscures the important
distinction between macros and strings on one hand and diversions
on the other; the former store unformatted input text, and the
latter capture formatted output. Diversions also do not interpret
arguments. Applications of diversions include “keeps” (preventing
a page break from occurring at an inconvenient place by forcing a
set of output lines to be set as a group), footnotes, tables of
contents, and indices. For orthogonality it is said that GNU
troff is in the top-level diversion if no diversion is active
(that is, formatted output is being “diverted” immediately to the
output device.
Dereferencing an undefined diversion will create an empty one of
that name and cause a warning in category mac to be emitted. (see
section “Warnings” in troff(1)). A diversion does not exist for
the purpose of testing with the d conditional operator until its
initial definition ends (see subsection “Conditional expressions”
above).
The di request creates a diversion, including any partially
collected line. da appends to a diversion, creating one if it
does not already exist. If the diversion's name already exists as
an alias, the target of the alias is replaced or appended to; see
section “Strings” above. box and boxa works similarly, but ignore
partially collected lines. Call any of these macros again without
an argument to end the diversion.
Diversions can be nested. The registers .d, .z, dn, and dl report
information about the current (or last closed) diversion. .h is
meaningful in diversions, including the top level.
The \! and \? escape sequences and output request escape from a
diversion, the first two to the enclosing level and the last to
the top level. This facility is termed transparent embedding.
The asciify and unformat requests reprocess diversions.
Macros, strings, and diversions share a name space; see section
“Identifiers” above. Internally, the same mechanism is used to
store them. You can thus call a macro with string interpolation
syntax and vice versa. Interpolating a string does not hide
existing macro arguments. The sequence \\ can be placed at the
end of a line in a macro definition or, within a macro definition,
immediately after the interpolation of a macro as a string to
suppress the effect of a newline.
Environments store most of the parameters that control text
processing. A default environment named “0” exists when troff
starts up; it is modified by formatting-related requests and
escape sequences.
You can create new environments and switch among them. Only one
is current at any given time. Active environments are managed
using a stack, a data structure supporting “push” and “pop”
operations. The current environment is at the top of the stack.
The same environment name can be pushed onto the stack multiple
times, possibly interleaved with others. Popping the environment
stack does not destroy the current environment; it remains
accessible by name and can be made current again by pushing it at
any time. Environments cannot be renamed or deleted, and can only
be modified when current. To inspect the environment stack, use
the pev request; see section “Debugging” below.
Environments store the following information.
• a partially collected line, if any
• data about the most recently output glyph and line (registers
.cdp, .cht, .csk, .n, .w)
• typeface parameters (size, family, style, height and slant,
inter-word and inter-sentence space sizes)
• page parameters (line length, title length, vertical spacing,
line spacing, indentation, line numbering, centering, right-
alignment, underlining, hyphenation parameters)
• filling enablement; adjustment enablement and mode
• tab stops; tab, leader, escape, control, no-break control,
hyphenation, and margin characters
• input line traps
• stroke and fill colors
The ev request pushes to and pops from the environment stack,
while evc copies a named environment's contents to the current
one.
In RUNOFF (see roff(7)), underlining, even of lengthy passages,
was straightforward because only fixed-pitch printing devices were
targeted. Typesetter output posed a greater challenge. There
exists a groff request .ul (see above) that underlines subsequent
source lines on terminal devices, but on typesetters, it selects
an italic font style instead. The ms macro package (see
groff_ms(7)) offers a macro .UL, but it too produces the desired
effect only on typesetters, and has other limitations.
One could adapt ms's approach to the construction of a macro as
follows.
.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 form of
the font selection escape sequence 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]
When using doclifter, it might be necessary to change syntax forms
such as \[xy] and \*[xy] to those supported by AT&T troff: \*(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 _i_n after
Underlining by overstriking with \(ul
The \z escape sequence writes a glyph without advancing the
drawing position, enabling overstriking. Thus, \zc\(ul formats c
with an underrule glyph on top of it. Video terminals implement
the underrule by setting a character cell's underline attribute,
so this technique works in both nroff and troff modes.
Long words may then look intimidating in the input; a clarifying
approach might be to use the input line continuation escape
sequence \newline to place each underlined character on its own
input line. Thus,
.nf
\&\fB: ${\fIvar\fR\c
\zo\(ul\
\zp\(ul\c
\&\fIvalue\fB}
.fi
produces
: ${varo_p_value}
as output.
The differences between the roff language recognized by GNU troff
and that of AT&T troff, as well as the device, font, and device-
independent intermediate output formats described by CSTR #54 are
documented in groff_diff(7). groff provides an AT&T compatibility
mode. The .cp request and registers .C and .cp set and test the
enablement of this mode.
Preprocessors use the .lf request to preserve the identities of
line numbers and names of input files. groff emits a variety of
error diagnostics and supports several categories of warning; the
output of these can be selectively suppressed with .warn (and see
the -E, -w, and -W options of troff(1)). A trace of the
formatter's input processing stack can be emitted when errors or
warnings occur by means of troff(1)'s -b option, or produced on
demand with the .backtrace request. .tm, .tmc, and .tm1 can be
used to emit customized diagnostic messages or for instrumentation
while troubleshooting. .ex and .ab cause early termination with
successful and error exit codes respectively, to halt further
processing when continuing would be fruitless. Examine the state
of the formatter with requests that write lists of defined names—
macros, strings, and diversions—(.pm); environments (.pev),
registers (.pnr), and page location traps (.ptr) to the standard
error stream.
This document was written by by Trent A. Fisher, Werner Lemberg,
and G. Branden Robinson ⟨g.branden.robinson@gmail.com⟩. Section
“Underlining” was primarily written by Bernd Warken ⟨groff-bernd
.warken-72@web.de⟩.
Groff: The GNU Implementation of troff, by Trent A. Fisher and
Werner Lemberg, is the primary groff manual. You can browse it
interactively with “info groff”.
“Troff User's Manual” by Joseph F. Ossanna, 1976 (revised by Brian
W. Kernighan, 1992), AT&T Bell Laboratories Computing Science
Technical Report No. 54, widely called simply “CSTR #54”,
documents the language, device and font description file formats,
and device-independent output format referred to collectively in
groff documentation as “AT&T troff”.
“A Typesetter-independent TROFF” by Brian W. Kernighan, 1982, AT&T
Bell Laboratories Computing Science Technical Report No. 97
(CSTR #97), provides additional insights into the device and font
description file formats and device-independent output format.
groff(1)
is the preferred interface to the groff system; it manages
the pipeline that carries a source document through
preprocessors, the troff formatter, and an output driver to
viewable or printable form. It also exhaustively lists the
man pages provided with the GNU roff system.
groff_char(7)
discusses character encoding issues, escape sequences that
produce glyphs, and enumerates groff's predefined special
character escape sequences.
groff_diff(7)
covers differences between the GNU troff formatter, its
device and font description file formats, its device-
independent output format, and those of AT&T troff, whose
design it reimplements.
groff_font(5)
describes the formats of the files that describe devices
(DESC) and fonts.
groff_tmac(5)
surveys macro packages provided with groff, describes how
documents can take advantage of them, offers guidance on
writing macro packages and using diversions, and includes
historical information on macro package naming conventions.
roff(7)
presents a detailed history of roff systems and summarizes
concepts common to them.
This page is part of the groff (GNU troff) project. Information
about the project can be found at
⟨http://www.gnu.org/software/groff/⟩. If you have a bug report for
this manual page, see ⟨http://www.gnu.org/software/groff/⟩. This
page was obtained from the tarball groff-1.23.0.tar.gz fetched
from ⟨https://ftp.gnu.org/gnu/groff/⟩ on 2026-01-16. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
groff 1.23.0 2 July 2023 groff(7)
Pages that refer to this page: man(1), man-pages(7)
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