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Name | Description | groff Elements | Control Characters | Numerical Expressions | Conditions | Requests | Escape Sequences | Registers | Hyphenation | Traps | Underlining | Compatibility | Debugging | Authors | See also | COLOPHON |
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groff(7) Miscellaneous Information Manual groff(7)
groff - GNU roff language reference
The name groff stands for GNU roff and is the free implementation
of the roff type-setting system. See roff(7) for a survey and
the background of the groff system.
This document provides only short descriptions of roff language
elements. Groff: The GNU Implementation of troff, by Trent A.
Fisher and Werner Lemberg, is the primary groff manual, and is
written in Texinfo. You can browse it interactively with “info
groff”.
Historically, the roff language was called troff. groff is
compatible with the classical system and provides proper
extensions. So in GNU, the terms roff, troff, and groff language
could be used as synonyms. However troff slightly tends to refer
more to the classical aspects, whereas groff emphasizes the GNU
extensions, and roff is the general term for the language.
The general syntax for writing groff documents is relatively
easy, but writing extensions to the roff language can be a bit
harder.
The roff language is line-oriented. There are only two kinds of
lines, control lines and text lines. The control lines start
with a control character, by default a period “.” or a single
quote “'”; all other lines are text lines.
Control lines represent commands, optionally with arguments.
They have the following syntax. The leading control character
can be followed by a command name; arguments, if any, are
separated by spaces (but not tab characters) from the command
name and among themselves, for example,
.command_name arg1 arg2
For indentation, any number of space or tab characters can be
inserted between the leading control character and the command
name, but the control character must be on the first position of
the line.
Text lines represent the parts that is printed. They can be
modified by escape sequences, which are recognized by a leading
backslash ‘\’. These are in-line or even in-word formatting
elements or functions. Some of these take arguments separated by
single quotes “'”, others are regulated by a length encoding
introduced by an open parenthesis ‘(’ or enclosed in brackets ‘[’
and ‘]’.
The roff language provides flexible instruments for writing
language extension, such as macros. When interpreting macro
definitions, the roff system enters a special operating mode,
called the copy mode.
The copy mode behaviour can be quite tricky, but there are some
rules that ensure a safe usage.
1. Printable backslashes must be denoted as \e. To be more
precise, \e represents the current escape character. To
get a backslash glyph, use \(rs or \[rs].
2. Double all backslashes.
3. Begin all text lines with the non-printing input break \&.
This does not produce the most efficient code, but it should work
as a first measure. For better strategies, see the groff Texinfo
manual and groff_tmac(5).
Reading roff source files is easier, just reduce all double
backslashes to a single one in all macro definitions.
The roff language elements add formatting information to a text
file. The fundamental elements are predefined commands and
variables that make roff a full-blown programming language.
There are two kinds of roff commands, possibly with arguments.
Requests are written on a line of their own starting with a dot
‘.’ or a “'”, whereas Escape sequences are in-line functions and
in-word formatting elements starting with a backslash ‘\’.
The user can define her own formatting commands using the .de
request. These commands are called macros, but they are used
exactly like requests. Macro packages are pre-defined sets of
macros written in the groff language. A user's possibilities to
create escape sequences herself is very limited, only special
characters can be mapped.
The groff language provides several kinds of variables with
different interfaces. There are pre-defined variables, but the
user can define her own variables as well.
String variables store character sequences. They are set with
the .ds request and retrieved by the \* escape sequences.
Strings can have variables.
Register variables can store numerical values, numbers with a
scale unit, and occasionally string-like objects. They are set
with the .nr request and retrieved by the \n escape sequences.
Environments allow the user to temporarily store global
formatting parameters like line length, font size, etc. for later
reuse. This is done by the .ev request.
Fonts are identified either by a name or by an internal number.
The current font is chosen by the .ft request or by the \f escape
sequences. Each device has special fonts, but the following
fonts are available for all devices. R is the standard font
Roman. B is its bold counterpart. The italic font is called I
and is available everywhere, but on text devices it is displayed
as an underlined Roman font. For the graphical output devices,
there exist constant-width pendants of these fonts, CR, CI, and
CB. On text devices, all glyphs have a constant width anyway.
Glyphs are visual representation forms of characters. In groff,
the distinction between those two elements is not always obvious
(and a full discussion is beyond the scope of this man page). A
first approximation is that glyphs have a specific size and
colour and are taken from a specific font; they can't be modified
any more – characters are the input, and glyphs are the output.
As soon as an output line has been generated, it no longer
contains characters but glyphs. In this man page, we use either
‘glyph’ or ‘character’, whatever is more appropriate. A few
characters commonly seen on keyboards are treated specially by
roff languages and may not look correct in output; they are the
(double) quotation mark ("), the apostrophe ('), the hyphen-minus
(-), the backslash (\), the caret or circumflex accent (^), the
grave accent (`), and the tilde (~). All are available if
required; see groff_char(7).
Moreover, there are some advanced roff elements. A diversion
stores (formatted) information into a macro for later usage. See
groff_tmac(5) for more details. A trap is a positional condition
like a certain number of lines from page top or in a diversion or
in the input. Some action can be prescribed to be run
automatically when the condition is met.
More detailed information and examples can be found in the groff
Texinfo manual.
There is a small set of characters that have a special
controlling task in certain conditions.
. A dot is only special at the beginning of a line or after
the condition in the requests .if, .ie, .el, and .while.
There it is the control character that introduces a
request (or macro). By using the .cc request, the control
character can be set to a different character, making the
dot ‘.’ a non-special character.
In all other positions, it just means a dot character. In
text paragraphs, it is advantageous to start each sentence
at a line of its own.
' The apostrophe has two controlling tasks. At the
beginning of a line and in the conditional requests it is
the non-breaking control character. That means that it
introduces a request like the dot, but with the additional
property that this request doesn't cause a linebreak. By
using the .c2 request, the non-break control character can
be set to a different character.
As a second task, it is the most commonly used argument
separator in some functional escape sequences (but any
pair of characters not part of the argument do work). In
all other positions, it denotes a single quote or
apostrophe character, depending on the output device's
glyph repertoire. groff provides a printable
representation with the \(aq escape sequence.
" The double quote can be used to enclose arguments to
macros and strings, but not requests. In the .ds, .ds1,
.as, and .as1 requests, a leading double quote in the
second argument is stripped off, enabling the inclusion of
leading space characters in the string definition or
appendment. The escaped double quote \" introduces a
comment. Otherwise, it is not special. groff provides a
printable representation with the \[dq] escape sequence.
\ The backslash usually introduces an escape sequence (this
can be changed with the .ec request). A printed version
of the escape character is the \e escape; a backslash
glyph can be obtained by \(rs.
( The open parenthesis is only special in escape sequences
when introducing an escape name or argument consisting of
exactly two characters. In groff, this behaviour can be
replaced by the [] construct.
[ The opening bracket is only special in groff escape
sequences; there it is used to introduce a long escape
name or long escape argument. Otherwise, it is non-
special, e.g., in macro calls.
] The closing bracket is only special in groff escape
sequences; there it terminates a long escape name or long
escape argument. Otherwise, it is non-special.
space Space characters separate arguments in requests, macros,
and strings. In text, they separate words. When filling
is enabled (the default), a line may be broken at a space.
Further, in fill mode, multiple adjacent space characters
cause groff to attempt end-of-sentence detection on the
preceding word (and trailing punctuation). The amount of
space between sentences in fill mode is controlled by the
.ss request. When adjustment is enabled, a space's width
may be expanded to justify the line. To get a space of
definite width, use the escape sequences ‘\ ’ (this is the
escape character followed by a space), \0, \|, \^, or \h;
see section “Escape Sequences” below. An adjustable but
non-breaking space is available with \~.
newline
In text, newlines behave like space characters and trigger
end-of-sentence recognition on the preceding text.
Continuation lines can be specified by an escaped newline,
i.e., by specifying a backslash ‘\’ as the last character
of a line.
tab If a tab character occurs during text the interpreter
makes a horizontal jump to the next pre-defined tab
position. There is a sophisticated interface for handling
tab positions.
A numerical value is a signed or unsigned integer or float with
or without an appended scaling indicator. A scaling indicator is
a one-character abbreviation for a unit of measurement. A number
followed by a scaling indicator signifies a size value. By
default, numerical values do not have a scaling indicator, i.e.,
they are normal numbers.
The roff language defines the following scaling indicators.
c centimeter
i inch
P pica = 1/6 inch
p point = 1/72 inch
m em = the font size in points (approx. width of
letter ‘m’)
M 100th of an em
n en = em/2
u Basic unit for actual output device
v Vertical line space in basic units
s scaled point = 1/sizescale of a point (defined
in font DESC file)
f Scale by 65536.
Numerical expressions are combinations of the numerical values
defined above with the following arithmetical operators already
defined in classical troff.
+ Addition
- Subtraction
* Multiplication
/ Division
% Modulo
= Equals
== Equals
< Less than
> Greater than
<= Less or equal
>= Greater or equal
& Logical and
: Logical or
! Logical not
( Grouping of expressions
) Close current grouping
Moreover, groff added the following operators for numerical
expressions:
e1>?e2 The maximum of e1 and e2.
e1<?e2 The minimum of e1 and e2.
(c;e) Evaluate e using c as the default scaling
indicator.
For details see the groff Texinfo manual.
Conditions are expressions tested by the .if, .ie, and the .while
requests. The following table characterizes the different types
of conditions.
N A numerical expression N yields true if its
value is greater than 0.
!N True if the value of N is ≤ 0 (see below).
's1's2' True if string s1 is identical to string s2.
!'s1's2' True if string s1 is not identical to string s2
(see below).
c g True if a glyph g is available.
d name True if there is a string, macro, diversion, or
request called name.
e Current page number is even.
F font True if a font called font exists.
m color True if there is a color called color.
n Formatter is nroff.
o Current page number is odd.
r reg True if there is a number register called reg.
S style True if a style called style has been
registered.
t Formatter is troff.
v Always false (for compatibilty with other troff
implementations).
Note that the ! operator may only appear at the beginning of an
expression, and negates the entire expression. This maintains
bug-compatibility with AT&T troff.
This section provides a short reference for the predefined
requests. In groff, request, macro, and string names can be
arbitrarily long. No bracketing or marking of long names is
needed.
Most requests take one or more arguments. The arguments are
separated by space characters (no tabs!); there is no inherent
limit for their length or number.
Some requests have optional arguments with a different behaviour.
Not all of these details are outlined here. Refer to the groff
Texinfo manual and groff_diff(7) for all details.
In the following request specifications, most argument names were
chosen to be descriptive. Only the following denotations need
clarification.
c denotes a single character.
font a font either specified as a font name or a font
number.
anything all characters up to the end of the line or
within \{ and \}.
n is a numerical expression that evaluates to an
integer value.
N is an arbitrary numerical expression, signed or
unsigned.
±N has three meanings depending on its sign,
described below.
If an expression defined as ±N starts with a ‘+’ sign the
resulting value of the expression is added to an already existing
value inherent to the related request, e.g., adding to a number
register. If the expression starts with a ‘-’ the value of the
expression is subtracted from the request value.
Without a sign, N replaces the existing value directly. To
assign a negative number either prepend 0 or enclose the negative
number in parentheses.
Request short reference
. Empty line, ignored. Useful for structuring documents.
.\" anything
Complete line is a comment.
.ab string
Print string on standard error, exit program.
.ad Begin line adjustment for output lines in current
adjust mode.
.ad c Start line adjustment in mode c (c=l,r,c,b,n).
.af register c
Assign format c to register, 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 base-26 Latin alphabetics, respectively,
in the lettercase specified. The default is “0”.
.aln new old
Create alias (additional name) new for existing number
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
register macro until .. is encountered.
.ami macro end
Append to a macro indirectly. macro and end are string
registers whose contents are interpolated for the macro
name and the end macro, respectively.
.ami1 macro
Same as .ami but with compatibility mode switched off
during macro expansion.
.ami1 macro end
Same as .ami but with compatibility mode switched off
during macro expansion.
.as name [string]
Append string to the string name; no operation if
string is omitted.
.as1 name [string]
Same as .as but with compatibility mode switched off
during string expansion.
.asciify diversion
Unformat ASCII characters, spaces, and some escape
sequences in diversion.
.backtrace
Write a backtrace of the input stack to the standard
error stream. Also see the -b option of groff(1).
.bd font N
Embolden font by N-1 units.
.bd S font N
Embolden Special Font S when current font is font.
.blm Unset blank line macro (trap). Restore default
handling of blank lines.
.blm name Set blank line macro (trap) to name.
.box End current diversion.
.box macro
Divert to macro, omitting a partially filled line.
.boxa End current diversion.
.boxa macro
Divert and append to macro, omitting a partially filled
line.
.bp Eject current page and begin new page.
.bp ±N Eject current page; next page number ±N.
.br Line break.
.brp Break output line; adjust if applicable.
.break Break out of a while loop.
.c2 Reset no-break control character to “'”.
.c2 c Set no-break control character to c.
.cc Reset control character to ‘.’.
.cc c Set control character to c.
.ce Center the next input line.
.ce N Center following N input lines.
.cf filename
Copy contents of file filename unprocessed to stdout or
to the diversion.
.cflags n c1 c2 ...
Assign properties encoded by the number n to characters
c1, c2, and so on.
.ch name N
Change location of page location trap by moving macro
name to new location N, or by unplanting it altogether
if N absent.
.char c anything
Define entity c as string anything.
.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 colors.
.color N If N is zero disable colors, otherwise enable them.
.composite from to
Map glyph name from to glyph name to while constructing
a composite glyph name.
.continue Finish the current iteration of a while loop.
.cp Enable compatibility mode.
.cp N If N is zero disable compatibility mode, otherwise
enable it.
.cs font N M
Set constant character width mode for font to N/36 ems
with em M.
.cu N Continuous underline in nroff, like .ul in troff.
.da End current diversion.
.da macro Divert and append to macro.
.de macro Define or redefine macro until .. is encountered.
.de macro end
Define or redefine macro until .end is called.
.de1 macro
Same as .de but with compatibility mode switched off
during macro expansion.
.de1 macro end
Same as .de but with compatibility mode switched off
during macro expansion.
.defcolor color scheme component
Define or redefine a color with name color. scheme can
be rgb, cym, cymk, gray, or grey. component can be
single components specified as fractions in the range 0
to 1 (default scaling indicator f), as a string of two-
digit hexadecimal color components with a leading #, or
as a string of four-digit hexadecimal components with
two leading #. The color default can't be redefined.
.dei macro
Define or redefine a macro whose name is contained in
the string register macro until .. is encountered.
.dei macro end
Define or redefine a macro indirectly. macro and end
are string registers whose contents are interpolated
for the macro name and the end macro, respectively.
.dei1 macro
Same as .dei but with compatibility mode switched off
during macro expansion.
.dei1 macro end
Same as .dei but with compatibility mode switched off
during macro expansion.
.device anything
Write anything to the intermediate output as a device
control function.
.devicem name
Write contents of macro or string name uninterpreted to
the intermediate output as a device control function.
.di End current diversion.
.di macro Divert to macro. See groff_tmac(5) for more details.
.do name ...
Interpret the string, request, diversion, or macro name
(along with any arguments) with compatibility mode
disabled. Note that compatibility mode is restored (if
and only if it was active) when the expansion of name
is interpreted.
.ds name [string]
Define a string variable name with contents string, or
as empty if string is omitted.
.ds1 name [string]
Same as .ds but with compatibility mode switched off
during string expansion.
.dt Clear diversion trap.
.dt N name
Set diversion trap to macro name at position N (default
scaling indicator v).
.ec Reset escape character to ‘\’.
.ec c Set escape character to c.
.ecr Restore escape character saved with .ecs.
.ecs Save current escape character.
.el anything
Else part for if-else (.ie) request.
.em name Invoke macro name after the end of input.
.eo Turn off escape character mechanism.
.ev Switch to previous environment and pop it off the
stack.
.ev env Push down environment number or name env to the stack
and switch to it.
.evc env Copy the contents of environment env to the current
environment. No pushing or popping.
.ex Exit from roff processing.
.fam Return to previous font family.
.fam name Set the current font family to name.
.fc Disable field mechanism.
.fc a Set field delimiter to a and pad glyph to space.
.fc a b Set field delimiter to a and pad glyph to b.
.fchar c anything
Define fallback character (or glyph) c as string
anything.
.fcolor Set fill color to previous fill color.
.fcolor c Set fill color to c.
.fi Fill output lines.
.fl Flush output buffer.
.fp n font
Mount font on position n.
.fp n internal external
Mount font with long external name to short internal
name on position n.
.fschar f c anything
Define fallback character (or glyph) c for font f as
string anything.
.fspecial font
Reset list of special fonts for font to be empty.
.fspecial font s1 s2 ...
When the current font is font, then the fonts s1, s2,
... are special.
.ft Return to previous font. Same as \f[] or \fP.
.ft font Change to font name or number font; same as \f[font]
escape sequence.
.ftr font1 font2
Translate font1 to font2.
.fzoom font
Don't magnify font.
.fzoom font zoom
Set zoom factor for font (in multiples of 1/1000th).
.gcolor Set glyph color to previous glyph color.
.gcolor c Set glyph color to c.
.hc 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 number 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 mapping values for character codes in pattern
files read with the .hpf and .hpfa requests.
.hw word ...
Define how each word is to be hyphenated, with each
hyphen “-” indicating a hyphenation point.
.hy Set hyphenation mode to 1 (the default).
.hy 0 Disable hyphenation; same as .nh.
.hy mode Set 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 indicator m).
.hys Set the hyphenation space to 0 (the default).
.hys hyphenation-space
Suppress hyphenation of the line in adjustment modes
“b” or “n” if it can be justified by adding no more
than hyphenation-space extra space to each inter-word
space (default scaling indicator m).
.ie cond anything
If cond then anything, otherwise skip to .el.
.if cond anything
If cond then anything; otherwise do nothing.
.ig Ignore text until .. is encountered.
.ig end Ignore text until .end is called.
.in Change to previous indentation value.
.in ±N Change indentation according to ±N (default scaling
indicator m).
.it n name
Set an input line trap, calling macro name, after the
next n lines lines of text input have been read.
.itc n name
As .it, but don't count lines interrupted with \c.
.kern Enable pairwise kerning.
.kern n If n is zero, disable pairwise kerning, otherwise
enable it.
.lc Remove leader repetition glyph.
.lc c Set leader repetition glyph to c (default: “.”).
.length reg anything
Compute the number of characters of anything and store
the count in the number register reg.
.linetabs Enable line-tabs mode (i.e., calculate tab positions
relative to output line).
.linetabs n
If n is zero, disable line-tabs mode, otherwise enable
it.
.lf N Set input line number to N.
.lf N file
Set input line number to N and filename to file.
.lg N Ligature mode on if N>0.
.ll Change to previous line length.
.ll ±N Set line length according to ±N (default length 6.5i,
default scaling indicator m).
.lsm Unset the leading 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 ±N Length of title (default scaling indicator m).
.mc Margin glyph off.
.mc c Print glyph c after each text line at actual distance
from right margin.
.mc c N Set margin glyph to c and distance to N from right
margin (default scaling indicator m).
.mk [register]
Mark current vertical position in register, or in an
internal register used by .rt if no argument.
.mso file The same as .so except that file is searched in the
tmac directories.
.na No output-line adjusting.
.ne Need a one-line vertical space.
.ne N Need N vertical space (default scaling indicator v).
.nf No filling or adjusting of output lines.
.nh Disable hyphenation; same as “.hy 0”.
.nm Number mode off.
.nm ±N [M [S [I]]]
In line number mode, set number, multiple, spacing, and
indentation.
.nn Do not number next line.
.nn N Do not number next N lines.
.nop anything
Always process anything.
.nr register ±N [M]
Define or modify register using ±N with auto-increment
M.
.nroff Make the built-in conditions n true and t false.
.ns Turn on no-space mode.
.nx Immediately jump to end of current file.
.nx filename
Immediately continue processing with file file.
.open stream filename
Open filename for writing and associate the stream
named stream with it.
.opena stream filename
Like .open but append to it.
.os Output vertical distance that was saved by the .sv
request.
.output string
Emit string directly to intermediate output, allowing
leading whitespace if string starts with " (which is
stripped off).
.pc Reset page number character to ‘%’.
.pc c Page number character.
.pev Print the current environment and each defined
environment state to stderr.
.pi program
Pipe output to program (nroff only).
.pl Set page length to default 11i. The current page
length is stored in register .p.
.pl ±N Change page length to ±N (default scaling indicator v).
.pm 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 Print the names and contents of all currently defined
number registers on stderr.
.po Change to previous page offset. The current page
offset is available in register .o.
.po ±N Page offset N.
.ps Return to previous point size.
.ps ±N Set/increase/decrease the point size to/by N scaled
points (a non-positive resulting point size is set to
1 u); also see \s[±N].
.psbb filename
Get the bounding box of a PostScript image filename.
.pso command
This behaves like the .so request except that input
comes from the standard output of command.
.ptr 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 indicator p).
.rchar c1 c2 ...
Remove the definitions of entities c1, c2, ...
.rd prompt
Read insertion.
.return Return from a macro.
.return anything
Return twice, namely from the macro at the current
level and from the macro one level higher.
.rfschar f c1 c2 ...
Remove the font-specific definitions of glyphs c1, c2,
... for font f.
.rj n Right justify the next n input lines.
.rm name Remove request, macro, diversion, or string name.
.rn old new
Rename request, macro, diversion, or string old to new.
.rnn reg1 reg2
Rename register reg1 to reg2.
.rr ident Remove name of number register ident.
.rs Restore spacing; turn no-space mode off.
.rt Return (upward only) to vertical position marked by .mk
on the current page.
.rt ±N Return (upward only) to specified distance from the top
of the page (default scaling indicator v).
.schar c anything
Define global fallback character (or glyph) c as string
anything.
.shc Reset soft hyphen glyph to \(hy.
.shc c Set the soft hyphen glyph to c.
.shift n In a macro, shift the arguments by n positions.
.sizes s1 s2 ... sn [0]
Set available font sizes similar to the sizes command
in a DESC file.
.so filename
Include source file.
.sp Skip one line vertically.
.sp N Space vertical distance N up or down according to sign
of N (default scaling indicator v).
.special Reset global list of special fonts to be empty.
.special s1 s2 ...
Fonts s1, s2, etc. are special and are searched for
glyphs not in the current font.
.spreadwarn
Toggle the spread warning on and off (the default)
without changing its value.
.spreadwarn N
Emit a break warning if the additional space inserted
for each space between words in an output line adjusted
to both margins is larger than or equal to N. A
negative N is treated as 0. The default scaling
indicator is m. At startup, .spreadwarn is inactive
and N is 3 m.
.ss N Set minimal inter-word spacing to N 12ths of the space
width of the current font.
.ss N M As .ss N, and set additional inter-sentence spacing to
M 12ths of the space width of the current font.
.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 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 Save 1 v of vertical space.
.sv N Save the vertical distance N for later output with .os
request (default scaling indicator v).
.sy command-line
Execute program command-line.
.ta T N Set tabs after every position that is a multiple of N
(default scaling indicator m).
.ta n1 n2 ... nn T r1 r2 ... rn
Set tabs at positions n1, n2, ..., nn, then set tabs at
nn+m×rn+r1 through nn+m×rn+rn, where m increments from
0, 1, 2, ... to infinity.
.tc Remove tab repetition glyph.
.tc c Set tab repetition glyph to c (default: none).
.ti ±N Temporary indent next line (default scaling
indicator m).
.tkf font s1 n1 s2 n2
Enable track kerning for font.
.tl 'left'center'right'
Three-part title.
.tm anything
Print anything on stderr.
.tm1 anything
Print anything on stderr, allowing leading whitespace
if anything starts with " (which is stripped off).
.tmc anything
Similar to .tm1 without emitting a final newline.
.tr abcd...
Translate a to b, c to d, etc. on output.
.trf filename
Transparently output the contents of file filename.
.trin abcd...
This is the same as the .tr request except that the
asciify request uses the character code (if any) before
the character translation.
.trnt abcd...
This is the same as the .tr request except that the
translations do not apply to text that is transparently
throughput into a diversion with \!.
.troff Make the built-in conditions t true and n false.
.uf font Set underline font to font (to be switched to by .ul).
.ul N Underline (italicize in troff) N input lines.
.unformat diversion
Unformat space characters and tabs in diversion,
preserving font information.
.vpt Enable vertical position traps.
.vpt 0 Disable vertical position traps.
.vs Change to previous vertical base line spacing.
.vs ±N Set vertical base line spacing to ±N (default scaling
indicator p).
.warn Enable all warnings.
.warn n Set warnings code to n.
.warnscale si
Set scaling indicator used in warnings to si.
.wh N Remove active trap at vertical position N; a negative
value is measured upward from page bottom.
.wh N name
Plant trap, calling macro name when page location N is
reached or passed; a negative value is measured upward
from page bottom. Any active trap already present at N
is replaced.
.while cond anything
While condition cond is true, accept anything as input.
.write stream anything
Write anything to the stream named stream.
.writec stream anything
Similar to .write without emitting a final newline.
.writem stream xx
Write contents of macro or string xx to the stream
named stream.
Besides these standard groff requests, there might be further
macro calls. They can originate from a macro package (see
roff(7) for an overview) or from a preprocessor.
Preprocessor macros are easy to recognize. They enclose their
code between a pair of characteristic macros.
┌─────────────┬─────────────────┬────────────────┐
│preprocessor │ start macro │ end macro │
├─────────────┼─────────────────┼────────────────┤
│ chem │ .cstart │ .cend │
│ eqn │ .EQ │ .EN │
│ grap │ .G1 │ .G2 │
│ grn │ .GS │ .GE │
│ ideal │ .IS │ .IE │
│ │ │ .IF │
│ pic │ .PS │ .PE │
│ refer │ .R1 │ .R2 │
│ soelim │ none │ none │
│ tbl │ .TS │ .TE │
├─────────────┼─────────────────┼────────────────┤
│ glilypond │ .lilypond start │ .lilypond stop │
│ gperl │ .Perl start │ .Perl stop │
│ gpinyin │ .pinyin start │ .pinyin stop │
└─────────────┴─────────────────┴────────────────┘
The ‘ideal’ preprocessor is not available in groff yet.
Whereas requests must occur on control lines, escape sequences
can occur intermixed with text and appear in arguments to
requests and macros (and sometimes other escape sequences). An
escape sequence (or simply “escape”) is introduced by the escape
character, a backslash “\” (but see the .ec request). The next
character identifies the escape's function. Escapes 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 convention, 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 convention, the user
selects a delimiter character; the neutral apostrophe “'” is a
popular choice and shown in this document. Some characters
cannot be used as delimiters; see section “Escapes” in the groff
Texinfo manual for details. A few escapes are idiosyncratic, and
support both of the foregoing conventions (“\s”), designate their
own terminating character (“\?”), consume input until the next
newline (“\!”, “\"”, “\#”), or support an additional modifier
character (“\s” again).
Escape sequences serve a variety of purposes. Widespread uses
include commenting the source document; changing the font style;
setting the point size; interpolating special characters, number
registers, and strings into the text; and placing or suppressing
break and hyphenation points. As with requests, use of escapes
in source documents may interact poorly with a macro package you
use; consult its documentation to learn of “safe” escapes or
alternative facilities it provides to achieve the desired result.
Escape short reference
\" Start of a comment. Everything up to the end of the line
is ignored.
\# Everything up to and including the next newline is
ignored. This is interpreted in copy mode. This is like
\" except that the terminating newline is ignored as well.
\*s The string stored in the string variable with one-
character name s.
\*(st The string stored in the string variable with two-
character name st.
\*[string]
The string stored in the string variable with name string
(with arbitrary length).
\*[stringvar arg1 arg2 ...]
The string stored in the string variable with arbitrarily
long name stringvar, taking arg1, arg2, ... as arguments.
\$0 The name by which the current macro was invoked. The .als
request can make a macro have more than one name.
\$x Macro or string argument with one-digit number x in the
range 1 to 9.
\$(xy Macro or string argument with two-digit number xy (larger
than zero).
\$[nexp]
Macro or string argument with number nexp, where nexp is a
numerical expression evaluating to an integer ≥1.
\$* In a macro or string, the concatenation of all the
arguments separated by spaces.
\$@ In a macro or string, the concatenation of all the
arguments with each surrounded by double quotes, and
separated by spaces.
\$^ In a macro, the representation of all parameters as if
they were an argument to the .ds request.
\\ reduces to a single backslash; useful to delay its
interpretation as escape character in copy mode. For a
printable backslash, use \e, or even better \[rs], to be
independent from the current escape character.
\' The acute accent ´; same as \(aa.
\` The grave accent `; same as \(ga.
\- The - (minus) sign in the current font.
\_ The same as \(ul, the underline character.
\. The same as a dot (‘.’). Necessary in nested macro
definitions so that ‘\\..’ expands to ‘..’.
\% Default hyphenation character.
\! Transparent line indicator.
\?anything?
In a diversion, this transparently embeds anything in the
diversion. anything is read in copy mode. See also the
escape sequences \! and \?.
\space Unpaddable space size space glyph (no line break).
\0 Digit-width unbreakable space.
\| 1/6 em narrow unbreakable space glyph; zero-width in
nroff.
\^ 1/12 em half-narrow unbreakable space glyph; zero-width in
nroff.
\& Non-printing input break.
\) Like \& except that it behaves like a glyph declared with
the .cflags request to be transparent for the purposes of
end-of-sentence recognition.
\/ Increases the width of the preceding glyph so that the
spacing between that glyph and the following glyph is
correct if the following glyph is a roman glyph.
\, Modifies the spacing of the following glyph so that the
spacing between that glyph and the preceding glyph is
correct if the preceding glyph is a roman glyph.
\~ Unbreakable space that stretches like a normal inter-word
space when a line is adjusted.
\: Insert a non-printing break point (similar to \% but
without a soft hyphen character).
\newline
Ignored newline, for continuation lines.
\{ Begin conditional input.
\} End conditional input.
\(sc A glyph with two-character name sc; see section “Special
Characters” below.
\[name]
A glyph with name name (of arbitrary length).
\[comp1 comp2 ...]
A composite glyph with components comp1, comp2, ...
\a Non-interpreted leader character.
\A'anything'
If anything is acceptable as a name of a string, macro,
diversion, register, environment or font it expands to 1,
and to 0 otherwise.
\b'abc...'
Bracket building function.
\B'anything'
If anything is acceptable as a valid numeric expression it
expands to 1, and to 0 otherwise.
\c Continue output line at next input line. Anything after
this escape on the same line is ignored except \R (which
works as usual). Anything before \c on the same line is
appended to the current partial output line. The next
non-command line after a line interrupted with \c counts
as a new input line.
\C'glyph'
The glyph called glyph; same as \[glyph], but compatible
to other roff versions.
\d Forward (down) 1/2 em (1/2 line in nroff).
\D'charseq'
Draw a graphical element defined by the characters in
charseq; see the groff Texinfo manual for details.
\e Printable version of the current escape character.
\E Equivalent to an escape character, but is not interpreted
in copy mode.
\fF Change to font with one-character name or one-digit
number F.
\fP Switch back to previous font.
\f(fo Change to font with two-character name or two-digit number
fo.
\f[font]
Change to font with arbitrarily long name or number
expression font.
\f[] Switch back to previous font.
\Ff Change to font family with one-character name f.
\F(fm Change to font family with two-character name fm.
\F[fam]
Change to font family with arbitrarily long name fam.
\F[] Switch back to previous font family.
\gr Return format of register with one-character name r
suitable for .af request.
\g(rg Return format of register with two-character name rg
suitable for .af request.
\g[reg]
Return format of register with arbitrarily long name reg
suitable for .af request.
\h'N' Local horizontal motion; move right N (left if negative).
\H'N' Set height of current font to N.
\kr Mark horizontal position in one-character register r.
\k(rg Mark horizontal position in two-character register rg.
\k[reg]
Mark horizontal position in register with arbitrarily long
name reg.
\l'Nc' Horizontal line drawing function (optionally using
character c).
\L'Nc' Vertical line drawing function (optionally using character
c).
\mc Change to color with one-character name c.
\m(cl Change to color with two-character name cl.
\m[color]
Change to color with arbitrarily long name color.
\m[] Switch back to previous color.
\Mc Change filling color for closed drawn objects to color
with one-character name c.
\M(cl Change filling color for closed drawn objects to color
with two-character name cl.
\M[color]
Change filling color for closed drawn objects to color
with arbitrarily long name color.
\M[] Switch to previous fill color.
\nr The numerical value stored in the register variable with
the one-character name r.
\n(re The numerical value stored in the register variable with
the two-character name re.
\n[reg]
The numerical value stored in the register variable with
arbitrarily long name reg.
\N'n' Typeset the glyph with index n in the current font. No
special fonts are searched. Useful for adding (named)
entities to a document using the .char request and
friends.
\o'abc...'
Overstrike glyphs a, b, c, etc.
\O0 Disable glyph output. Mainly for internal use.
\O1 Enable glyph output. Mainly for internal use.
\p Break output line at next word boundary; adjust if
applicable.
\r Reverse 1 em vertical motion (reverse line in nroff).
\R'name ±n'
The same as .nr name ±n.
\s±N Set/increase/decrease the point size to/by N scaled
points. N must be a single digit; 0 restores the previous
point size. (In compatibility mode only, a non-zero N
must be in the range 4–39.) Otherwise, same as .ps
request.
\s(±N
\s±(N Set/increase/decrease the point size to/by N scaled
points; N is a two-digit number ≥1. Same as .ps request.
\s[±N]
\s±[N]
\s'±N'
\s±'N' Set/increase/decrease the point size to/by N scaled
points. Same as .ps request.
\S'N' Slant output by N degrees.
\t Non-interpreted horizontal tab.
\u Reverse (up) 1/2 em vertical motion (1/2 line in nroff).
\v'N' Local vertical motion; move down N (up if negative).
\Ve The contents of the environment variable with one-
character name e.
\V(ev The contents of the environment variable with two-
character name ev.
\V[env]
The contents of the environment variable with arbitrarily
long name env.
\w'string'
The width of the glyph sequence string.
\x'N' Extra line-space function (negative before, positive
after).
\X'string'
Output string as device control function.
\Yn Output string variable or macro with one-character name n
uninterpreted as device control function.
\Y(nm Output string variable or macro with two-character name nm
uninterpreted as device control function.
\Y[name]
Output string variable or macro with arbitrarily long name
name uninterpreted as device control function.
\zc Print c with zero width (without spacing).
\Z'anything'
Print anything and then restore the horizontal and
vertical position; anything may not contain tabs or
leaders.
The escape sequences \e, \., \", \$, \*, \a, \n, \t, \g, and
\newline are interpreted in copy mode.
Escape sequences starting with \( or \[ do not represent single
character escape sequences, but introduce escape names with two
or more characters.
If a backslash is followed by a character that does not
constitute a defined escape sequence, the backslash is silently
ignored and the character maps to itself.
Identifiers
An identifier is a label for an object of syntactical importance
like a register, a name (macro, string, diversion, or box), an
environment, a font, a style, or a glyph, comprising a sequence
of one or more characters with the following exceptions.
• Spaces, tabs, or newlines.
• Invalid input characters; these are certain 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 diagnostic of type
“input” (see section “Warnings” in troff(1)).
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 cover
Unicode or other character encodings that use characters
from these ranges. (Consider what happens when a C1
control 0x80–0x9F is necessary as a continuation byte in a
UTF-8 sequence.}
Invalid characters are removed during parsing; an
identifier “foo”, followed by an invalid character,
followed by “bar” is treated as “foobar”.
Special characters
[Note: ‘Special Characters’ is a misnomer; those entities are
(output) glyphs, not (input) characters.]
Common special characters are predefined by escape sequences of
the form \(xy with characters x and y. In groff, it is also
possible to use the form \[xy].
Some of these special characters exist in the usual font while
most of them are only available in the special font. Below you
can see a small selection of the most important glyphs; a
complete list can be found in groff_char(7).
\(Do Dollar $
\(Eu Euro €
\(Po British pound sterling £
\(aq Apostrophe quote '
\(bu Bullet sign •
\(co Copyright ©
\(cq Single closing quote (right) ’
\(ct Cent ¢
\(dd Double dagger ‡
\(de Degree sign °
\(dg Dagger †
\(dq Double quote "
\(em Em-dash —
\(en En-dash –
\(ha Caret/spacing circumflex accent (“hat”) ^
\(hy Hyphen ‐
\(lq Double quote left “
\(oq Single opening quote (left) ‘
\(rg Registered sign ®
\(rq Double quote right ”
\(rs Reverse solidus/backslash \
\(sc Section sign §
\(ti Tilde (spacing) ~
\(tm Trademark symbol ™
\(ul Underline character _
\(== Identical ≡
\(>= Larger or equal ≥
\(<= Less or equal ≤
\(!= Not equal ≠
\(-> Right arrow →
\(<- Left arrow ←
\(+- Plus-minus sign ±
Unicode characters
The extended escape u allows the inclusion of all available
Unicode characters into a roff file.
\[uxxxx]
u is the escape name. xxxx is a hexadecimal number of
four hex digits, such as 0041 for the letter A, thus
\[u0041].
\[uyyyyy]
u is the escape name. yyyyy is a hexadecimal number of
five hex digits, such as 2FA1A for a Chinese-looking
character from the Unicode block CJK Compatibility
Ideographs Supplement, thus \[u2FA1A].
The hexadecimal value indicates the corresponding Unicode code
point for a character.
\[uhex1_hex2]
\[uhex1_hex2_hex3]
hex1, hex2, and hex3 are all Unicode hexadecimal codes (4
or 5 hex digits) that are used for overstriking, e.g.,
\[u0041_0301] is A acute, which can also be specified as
Á; see groff_char(7).
The availability of the Unicode characters depends on the font
used. For text mode, the device -Tutf8 is quite complete; for
troff modes it might happen that some or many characters will not
be displayed. Please check your fonts.
Strings
groff has string variables primarily for user convenience. Only
one string is predefined by the language.
\*[.T] Contains the name of the output driver (for example,
“utf8” or “pdf”).
The .ds request creates a string with a specified name and
contents and the \* escape dereferences its name, retrieving the
contents. Dereferencing an undefined string name defines it as
empty.
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 it).
The .ds1 request defines a string such that compatibility mode is
off when the string is later interpolated. To be more precise, a
compatibility save input token is inserted at the beginning of
the string, and a compatibility restore input token at the end.
Likewise, the .as1 request is similar to .as, but compatibility
mode is switched off 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. It is good style to end string definitions (and
appendments) with a comment, even an empty one, to prevent
unwanted space from creeping into them during source document
maintenance.
To store leading space in a string, start it with a double quote.
A double quote is special only in that position; double quotes in
any other location are included in the string (the effects of
escape sequences notwithstanding).
Strings, macros, and diversions (and boxes) share the same name
space. Internally, the same mechanism is used to store them.
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).
Registers are variables that store a value. In groff, most
registers store numerical values (see section “Numerical
Expressions” above), but some can also hold a string value.
Each register is given a name. Arbitrary registers can be
defined and set with the .nr request.
The value stored in a register can be retrieved by the escape
sequences introduced by \n.
Most useful are predefined registers. In the following the
notation name is used to refer to register name to make clear
that we speak about registers. Please keep in mind that the \n[]
decoration is not part of the register name.
Read-only registers
The following registers have predefined values that should not be
modified by the user (usually, registers starting with a dot are
read-only). Mostly, they provide information on the current
settings or store results from request calls.
\n[$$] The process ID of troff.
\n[.$] Number of arguments in the current macro or string.
\n[.a] Post-line extra line-space most recently utilized using
\x.
\n[.A] Set to 1 in troff if option -A is used; always 1 in
nroff.
\n[.b] The emboldening offset while .bd is active.
\n[.br] Within a macro, set to 1 if macro called with the
‘normal’ control character, and to 0 otherwise.
\n[.c] Current input line number.
\n[.C] 1 if compatibility mode is in effect, 0 otherwise.
Always 0 in a .do request; see register .cp below.
\n[.cdp] The depth of the last glyph added to the current
environment. It is positive if the glyph extends below
the baseline.
\n[.ce] The number of lines remaining to be centered, as set by
the .ce request.
\n[.cht] The height of the last glyph added to the current
environment. It is positive if the glyph extends above
the baseline.
\n[.color]
1 if colors are enabled, 0 otherwise.
\n[.cp] Within a .do request, the saved value of compatibility
mode (see register .C above).
\n[.csk] The skew of the last glyph added to the current
environment. The skew of a glyph is how far to the
right of the center of a glyph the center of an accent
over that glyph should be placed.
\n[.d] Current vertical place in current diversion; equal to
register nl.
\n[.ev] The name or number of the current environment (string-
valued).
\n[.f] Current font number.
\n[.F] The name of the current input file (string-valued).
\n[.fam] The current font family (string-valued).
\n[.fn] The current (internal) real font name (string-valued).
\n[.fp] The number of the next free font position.
\n[.g] Always 1 in GNU troff. Macros should use it to test if
running under groff.
\n[.h] Text base-line high-water mark on current page or
diversion.
\n[.H] Number of basic units per horizontal unit of output
device resolution.
\n[.height]
The current font height as set with \H.
\n[.hla] The hyphenation language in the current environment.
\n[.hlc] The count of immediately preceding consecutive
hyphenated lines in the current environment.
\n[.hlm] The maximum number of consecutive hyphenated lines
allowed in the current environment.
\n[.hy] The hyphenation mode in the current environment.
\n[.hym] The hyphenation margin in the current environment.
\n[.hys] The hyphenation space adjustment threshold in the
current environment.
\n[.i] Current indentation.
\n[.in] The indentation that applies to the current output
line.
\n[.int] Positive if last output line contains \c.
\n[.j] The current adjustment mode. It can be stored and used
to set adjustment. (n = 1, b = 1, l = 0, r = 5,
c = 3).
\n[.k] The current horizontal output position (relative to the
current indentation).
\n[.kern] 1 if pairwise kerning is enabled, 0 otherwise.
\n[.l] Current line length.
\n[.L] The current line spacing setting as set by .ls.
\n[.lg] The current ligature mode (as set by the .lg request).
\n[.linetabs]
The current line-tabs mode (as set by the .linetabs
request).
\n[.ll] The line length that applies to the current output
line.
\n[.lt] The title length (as set by the .lt request).
\n[.m] The current drawing color (string-valued).
\n[.M] The current background color (string-valued).
\n[.n] Length of text portion on previous output line.
\n[.ne] The amount of space that was needed in the last .ne
request that caused a trap to be sprung. Useful in
conjunction with register .trunc.
\n[.ns] 1 if in no-space mode, 0 otherwise.
\n[.o] Current page offset.
\n[.O] The suppression nesting level (see \O).
\n[.p] Current page length.
\n[.P] 1 if the current page is being printed, 0 otherwise (as
determined by the -o command-line option).
\n[.pe] 1 during page ejection, 0 otherwise.
\n[.pn] The number of the next page: either the value set by a
.pn request, or the number of the current page plus 1.
\n[.ps] The current point size in scaled points.
\n[.psr] The last-requested point size in scaled points.
\n[.pvs] The current post-vertical line spacing.
\n[.R] The number of unused number registers. Always 10000 in
GNU troff.
\n[.rj] The number of lines to be right-justified as set by the
.rj request.
\n[.s] Current point size as a decimal fraction.
\n[.slant]
The slant of the current font as set with \S.
\n[.sr] The last requested point size in points as a decimal
fraction (string-valued).
\n[.ss] Size of minimal inter-word spacing in twelfths of the
space width of the current font.
\n[.sss] Size of additional inter-sentence spacing in twelfths
of the space width of the current font.
\n[.sty] The current font style (string-valued).
\n[.t] Distance to the next vertical position trap.
\n[.T] Set to 1 if option -T is used.
\n[.tabs] A string representation of the current tab settings
suitable for use as an argument to the .ta request.
\n[.trunc]
The amount of vertical space truncated by the most
recently sprung vertical position trap, or, if the trap
was sprung by an .ne request, minus the amount of
vertical motion produced by .ne. Useful in conjunction
with the register .ne.
\n[.u] Equal to 1 in fill mode and 0 in no-fill mode.
\n[.U] Equal to 1 in safer mode and 0 in unsafe mode.
\n[.v] Current vertical line spacing.
\n[.V] Number of basic units per vertical unit of output
device resolution.
\n[.vpt] 1 if vertical position traps are enabled, 0 otherwise.
\n[.w] Width of previous glyph.
\n[.warn] The sum of the number codes of the currently enabled
warnings.
\n[.x] The major version number.
\n[.y] The minor version number.
\n[.Y] The revision number of groff.
\n[.z] Name of current diversion.
\n[.zoom] Zoom factor for current font (in multiples of 1/1000th;
zero if no magnification).
Writable registers
The following registers can be read and written by the user.
They have predefined default values, but these can be modified
for customizing a document.
\n[%] Current page number.
\n[c.] Current input line number.
\n[ct] Character type (set by width function \w).
\n[dl] Maximal width of last completed diversion.
\n[dn] Height of last completed diversion.
\n[dw] Current day of week (1–7).
\n[dy] Current day of month (1–31).
\n[hours] The number of hours past midnight. Initialized at
start-up.
\n[hp] Current horizontal position at input line.
\n[llx] Lower left x-coordinate (in PostScript units) of a
given PostScript image (set by .psbb).
\n[lly] Lower left y-coordinate (in PostScript units) of a
given PostScript image (set by .psbb).
\n[ln] Output line number.
\n[lsn] The count of leading spaces on an input line.
\n[lss] The amount of horizontal space corresponding to the
leading spaces on an input line.
\n[minutes]
The number of minutes after the hour. Initialized at
start-up.
\n[mo] Current month (1–12).
\n[nl] Vertical position of last printed text base-line.
\n[opmaxx]
\n[opmaxy]
\n[opminx]
\n[opminy]
These four registers mark the top left and bottom right
hand corners of a box which encompasses all written
glyphs. They are reset to -1 by \O0 or \O1.
\n[rsb] Like register sb, but takes account of the heights and
depths of glyphs.
\n[rst] Like register st, but takes account of the heights and
depths of glyphs.
\n[sb] Depth of string below base line (generated by width
function \w).
\n[seconds]
The number of seconds after the minute. Initialized at
start-up.
\n[skw] Right skip width from the center of the last glyph in
the \w argument.
\n[slimit]
If greater than 0, the maximum number of objects on the
input stack. If ≤0 there is no limit, i.e., recursion
can continue until virtual memory is exhausted.
\n[ssc] The amount of horizontal space (possibly negative) that
should be added to the last glyph before a subscript
(generated by width function \w).
\n[st] Height of string above base line (generated by width
function \w).
\n[systat]
The return value of the system() function executed by
the last .sy request.
\n[urx] Upper right x-coordinate (in PostScript units) of a
given PostScript image (set by .psbb).
\n[ury] Upper right y-coordinate (in PostScript units) of a
given PostScript image (set by .psbb).
\n[year] The current year (year 2000 compliant).
\n[yr] Current year minus 1900. For Y2K compliance use
register year instead.
Several requests influence hyphenation. Because conventions
vary, a variety of hyphenation modes are available to the .hy
request; these determine whether automatic 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 hyphenation is permissible. The default is “1” for
historical reasons, but this is not an appropriate value for the
U.S. English hyphenation patterns used by groff, 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.
(Technically, this value prevents hyphenation if the next
page position trap is closer than the next line of text
would be. groff automatically inserts an implicit page
position trap at the end of each page to cause a page
transition. This value can be used in traps planted by
users or macro packages to prevent hyphenation of the last
word in a column in multi-column page layouts or before
floating figures or tables.)
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.
Note that any restrictions imposed by the hyphenation mode are
not respected for words whose hyphenations have been explicitly
specified with the hyphenation character (“\%” by default) or the
.hw request.
The nonzero values above are additive. For example, value 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
nonzero 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 because too many
previous lines have been hyphenated (.hlm), the line has not
reached a certain minimum length (.hym), or the line can instead
be adjusted with up to a certain amount of additional inter-word
space (.hys). See groff_diff(7) or the groff Texinfo manual for
further details.
Traps are locations in the output, or conditions on the input
that, when reached or fulfilled, cause a specified macro to be
called. 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); at a blank line (.blm); at
a line with leading space characters (.lsm); after a certain
number of input lines (.it, .itc); or at the end of input (.em).
Macros invoked by traps have no arguments. Setting a trap is
also called planting. It is also said that a trap is sprung if
the associated macro is executed.
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]).
In the RUNOFF language, the underlining was quite easy. But in
roff this is much more difficult.
Underlining with .ul
There exists a groff request .ul (see above) that can underline
the next or further source lines in nroff, but in troff it
produces only a font change into italic. So this request is not
really useful.
Underlining with .UL from ms
In the ‘ms’ macro package in tmac/s.tmac groff_ms(7), there is
the macro .UL. But this works only in troff, not in nroff.
Underlining macro definitions
So one can use the italic nroff idea from .ul and the troff
definition in ms for writing a useful new macro, something like
.de UNDERLINE
. ie n \\$1\f[I]\\$2\f[P]\\$3
. el \\$1\Z'\\$2'\v'.25m'\D'l \w'\\$2'u 0'\v'-.25m'\\$3
..
If doclifter(1) makes trouble, change the macro name UNDERLINE
into some 2-letter word, like Ul. Moreover, change the form of
the font escape 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 with overstriking \z and \(ul
There is another possibility for underlining by using
overstriking with \zc (print c with zero width without spacing)
and \(ul (underline character). This produces the underlining of
1 character, both in nroff and in troff.
For example the underlining of a character say t looks like
\z\[ul]t or \z\(ult
Longer words look then a bit strange, but a useful mode is to
write each character into a whole own line. To underlines the 3
character part "tar" of the word "start":
before s\
\z\[ul]t\
\z\[ul]a\
\z\[ul]r\
t after
or
before s\
\z\(ult\
\z\(ula\
\z\(ulr\
t after
The result looks like
before s_t_a_rt after
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; see groff(1).
groff is not the easiest language to debug, in part thanks to its
design features of recursive interpolation and multi-stage
pipeline processing. Nevertheless there exist several features
useful for troubleshooting.
Preprocessors use the .lf request to preserve the identity of the
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)). Backtraces can be
automatically produced when errors or warnings occur (the -b
option of troff(1)) or generated on demand (.backtrace). .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. The state of the formatter can be examined with
requests that write lists of defined macros, strings, diversions,
and boxes (.pm); environments (.pev), registers (.pnr), and page
location traps (.ptr) to the standard error stream.
This document was 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 Techical 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 Techical 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
all of 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 escapes.
groff_diff(7)
covers the differences between the GNU troff formatter,
its device and font description file format, and its
device-independent output format, and those of AT&T troff,
whose design it re-implements.
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 project's upstream Git repository
⟨https://git.savannah.gnu.org/git/groff.git⟩ on 2020-12-18. (At
that time, the date of the most recent commit that was found in
the repository was 2020-12-09.) 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.rc1.56-5346-dirty3 December 2020 groff(7)
Pages that refer to this page: eqn(1), glilypond(1), gperl(1), gpinyin(1), groff(1), groffer(1), man(1), pdfroff(1), refer(1), troff(1), groff_filenames(5), groff_out(5), groff_tmac(5), groff_char(7), groff_diff(7), groff_hdtbl(7), groff_man(7), groff_man_style(7), groff_mm(7), groff_trace(7), man-pages(7), roff(7)
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