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NAME
groff_diff - differences between GNU troff and classical troff
DESCRIPTION
This manual page describes the language differences between groff, the
GNU roff text processing system and the classical roff formatter of the
freely available Unix 7 of the 1970s, documented in the Troff User's
Manual by Osanna and Kernighan. This inludes the roff language as well
as the intermediate output format (troff output).
The section SEE ALSO gives pointers to both the classical roff and the
modern groff documentation.
GROFF LANGUAGE
In this section, all additional features of groff compared to the clas-
sical Unix 7 troff are described in detail.
Long names
The names of number registers, fonts, strings/macros/diversions, spe-
cial characters (glyphs), and colors can be of any length. In escape
sequences, additionally to the classical (xx construction for a two-
character name, you can use [xxx] for a name of arbitrary length.
\[xxx] Print the special character (glyph) called xxx.
\[comp1 comp2 ...]
Print composite glyph consisting of multiple components. Exam-
ple: `\[A ho]' is capital letter A with ogonek which finally
maps to glyph name `u0041_0328'. See the groff info file for
details how a glyph name for a composite glyph is constructed,
and groff_char(7) for list of glyph name components used compos-
ite glyph names.
\f[xxx]
Set font xxx. Additionally, \f[] is a new syntax equal to \fP,
i.e., to return to the previous font.
\*[xxx arg1 arg2 ...]
Interpolate string xxx, taking arg1, arg2, ... as arguments.
\n[xxx]
Interpolate number register xxx.
Fractional pointsizes
A scaled point is equal to 1/sizescale points, where sizescale is spec-
ified in the DESC file (1 by default). There is a new scale indicator
z that has the effect of multiplying by sizescale. Requests and escape
sequences in troff interpret arguments that represent a pointsize as
being in units of scaled points, but they evaluate each such argument
using a default scale indicator of z. Arguments treated in this way
are the argument to the ps request, the third argument to the cs
request, the second and fourth arguments to the tkf request, the argu-
ment to the \H escape sequence, and those variants of the \s escape
sequence that take a numeric expression as their argument.
It would make no sense to use the z scale indicator in a numeric
expression whose default scale indicator was neither u nor z, and so
troff disallows this. Similarly it would make no sense to use a scal-
ing indicator other than z or u in a numeric expression whose default
scale indicator was z, and so troff disallows this as well.
There is also new scale indicator s which multiplies by the number of
units in a scaled point. So, for example, \n[.ps]s is equal to 1m. Be
sure not to confuse the s and z scale indicators.
Numeric expressions
Spaces are permitted in a number expression within parentheses.
M indicates a scale of 100ths of an em. f indicates a scale of 65536
units, providing fractions for color definitions with the defcolor
request. For example, 0.5f = 32768u.
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. If c is
missing, ignore scaling indicators in the evaluation of e.
New escape sequences
\A'anything'
This expands to 1 or 0 resp., depending on whether anything is
or is not acceptable as the name of a string, macro, diversion,
number register, environment, font, or color. It will return 0
if anything is empty. This is useful if you want to lookup user
input in some sort of associative table.
\B'anything'
This expands to 1 or 0 resp., depending on whether anything is
or is not a valid numeric expression. It will return 0 if any-
thing is empty.
\C'xxx'
Typeset glyph named xxx. Normally it is more convenient to use
\[xxx]. But \C has the advantage that it is compatible with
recent versions of UNIX and is available in compatibility mode.
\E This is equivalent to an escape character, but it is not inter-
preted in copy-mode. For example, strings to start and end
superscripting could be defined like this
.ds { \v'-.3m'\s'\En[.s]*6u/10u'
.ds } \s0\v'.3m'
The use of \E ensures that these definitions will work even if
\*{ gets interpreted in copy-mode (for example, by being used in
a macro argument).
\Ff
\F(fm
\F[fam]
Change font family. This is the same as the fam request. \F[]
\Mx
\M(xx
\M[xxx]
Set background color for filled objects drawn with the \D'...'
commands. \M[] switches back to the previous color.
\N'n' Typeset the glyph with index n in the current font. n can be
any integer. Most devices only have glyphs with indices between
0 and 255. If the current font does not contain a glyph with
that code, special fonts will not be searched. The \N escape
sequence can be conveniently used in conjunction with the char
request, for example
.char \[phone] \f(ZD\N'37'
The index of each glyph is given in the fourth column in the
font description file after the charset command. It is possible
to include unnamed glyphs in the font description file by using
a name of ---; the \N escape sequence is the only way to use
these.
\On
\O[n] Suppressing troff output. The escapes \02, \O3, \O4, and \O5
are intended for internal use by grohtml.
\O0 Disable any ditroff glyphs from being emitted to the
device driver, provided that the escape occurs at the
outer level (see \O3 and \O4).
\O1 Enable output of glyphs, provided that the escape occurs
at the outer level.
\O0 and \O1 also reset the registers \n[opminx],
\n[opminy], \n[opmaxx], and \n[opmaxy] to -1. These four
registers mark the top left and bottom right hand corners
of a box which encompasses all written glyphs.
\O2 Provided that the escape occurs at the outer level,
enable output of glyphs and also write out to stderr the
page number and four registers encompassing the glyphs
previously written since the last call to \O.
\O3 Begin a nesting level. At start-up, troff is at outer
level. This is really an internal mechanism for grohtml
while producing images. They are generated by running
the troff source through troff to the postscript device
and ghostscript to produce images in PNG format. The \O3
escape will start a new page if the device is not html
(to reduce the possibility of images crossing a page
boundary).
\O4 End a nesting level.
\O5[Pfilename]
This escape is grohtml specific. Provided that this
escape occurs at the outer nesting level, write filename
to stderr. The position of the image, P, must be speci-
fied and must be one of l, r, c, or i (left, right, cen-
\s(nn
\s+-(nn
Set the point size to nn points; nn must be exactly two digits.
\s[+-n]
\s+-[n]
\s'+-n'
\s+-'n'
Set the point size to n scaled points; n is a numeric expression
with a default scale indicator of z.
\Vx
\V(xx
\V[xxx]
Interpolate the contents of the environment variable xxx, as
returned by getenv(3). \V is interpreted in copy-mode.
\Yx
\Y(xx
\Y[xxx]
This is approximately equivalent to \X'\*[xxx]'. However the
contents of the string or macro xxx are not interpreted; also it
is permitted for xxx to have been defined as a macro and thus
contain newlines (it is not permitted for the argument to \X to
contain newlines). The inclusion of newlines requires an exten-
sion to the UNIX troff output format, and will confuse drivers
that do not know about this extension.
\Z'anything'
Print anything and then restore the horizontal and vertical
position; anything may not contain tabs or leaders.
\$0 The name by which the current macro was invoked. The als
request can make a macro have more than one name.
\$* 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.
\$(nn
\$[nnn]
In a macro or string, this gives the nn-th or nnn-th argument.
Macros and strings can have an unlimited number of arguments.
\?anything\?
When used in a diversion, this will transparently embed anything
in the diversion. anything is read in copy mode. When the
diversion is reread, anything will be interpreted. anything may
not contain newlines; use \! if you want to embed newlines in a
diversion. The escape sequence \? is also recognised in copy
mode and turned into a single internal code; it is this code
that terminates anything. Thus
.nr x 1
.nf
.di d
.e
.di
.nr x 4
.f
will print 4.
\/ This increases the width of the preceding glyph so that the
spacing between that glyph and the following glyph will be cor-
rect if the following glyph is a roman glyph. It is a good idea
to use this escape sequence whenever an italic glyph is immedi-
ately followed by a roman glyph without any intervening space.
\, This modifies the spacing of the following glyph so that the
spacing between that glyph and the preceding glyph will correct
if the preceding glyph is a roman glyph. It is a good idea to
use this escape sequence whenever a roman glyph is immediately
followed by an italic glyph without any intervening space.
\) Like \& except that it behaves like a character declared with
the cflags request to be transparent for the purposes of end-of-
sentence recognition.
\~ This produces an unbreakable space that stretches like a normal
inter-word space when a line is adjusted.
\: This causes the insertion of a zero-width break point. It is
equal to \% within a word but without insertion of a soft hyphen
character.
\# Everything up to and including the next newline is ignored.
This is interpreted in copy mode. It is like \" except that \"
does not ignore the terminating newline.
New requests
.aln xx yy
Create an alias xx for number register object named yy. The new
name and the old name will be exactly equivalent. If yy is
undefined, a warning of type reg will be generated, and the
request will be ignored.
.als xx yy
Create an alias xx for request, string, macro, or diversion
object named yy. The new name and the old name will be exactly
equivalent (it is similar to a hard rather than a soft link).
If yy is undefined, a warning of type mac will be generated, and
the request will be ignored. The de, am, di, da, ds, and as
requests only create a new object if the name of the macro,
diversion or string diversion is currently undefined or if it is
defined to be a request; normally they modify the value of an
existing object.
.ami xx yy
Append to macro indirectly. See the dei request below for more
information.
.am1 xx yy
Similar to .am, but compatibility mode is switched off during
This request `unformats' the diversion xx in such a way that
ASCII and space characters (and some escape sequences) that were
formatted and diverted into xx will be treated like ordinary
input characters when xx is reread. Useful for diversions in
conjunction with the .writem request. It can be also used for
gross hacks; for example, this
.tr @.
.di x
@nr n 1
.br
.di
.tr @@
.asciify x
.x
will set register n to 1. Note that glyph information (font,
font size, etc.) is not preserved; use .unformat instead.
.as1 xx yy
Similar to .as, but compatibility mode is switched off during
expansion. To be more precise, a `compatibility save' token is
inserted at the beginning of the string, and a `compatibility
restore' token at the end. As a consequence, the requests as,
as1, ds, and ds1 can be intermixed freely since the compatibil-
ity save/restore tokens only affect the (sub)strings defined by
as1 and ds1.
.backtrace
Print a backtrace of the input stack on stderr.
.blm xx
Set the blank line macro to xx. If there is a blank line macro,
it will be invoked when a blank line is encountered instead of
the usual troff behaviour.
.box xx
.boxa xx
These requests are similar to the di and da requests with the
exception that a partially filled line will not become part of
the diversion (i.e., the diversion always starts with a new
line) but restored after ending the diversion, discarding the
partially filled line which possibly comes from the diversion.
.break Break out of a while loop. See also the while and continue
requests. Be sure not to confuse this with the br request.
.brp This is the same as \p.
.cflags n c1 c2...
Characters c1, c2,... have properties determined by n, which is
ORed from the following:
1 The character ends sentences (initially characters .?!
have this property).
2 Lines can be broken before the character (initially no
characters have this property); a line will not be broken
8 The character overlaps horizontally (initially characters
\[ul]\[rn]\[ru]\[radicalex]\[sqrtex] have this property).
16 The character overlaps vertically (initially character
\[br] has this property).
32 An end-of-sentence character followed by any number of
characters with this property will be treated as the end
of a sentence if followed by a newline or two spaces; in
other words the character is transparent for the purposes
of end-of-sentence recognition; this is the same as hav-
ing a zero space factor in TeX (initially characters
"')]*\(dg\(rq have this property).
.char c string
Define glyph c to be string. Every time glyph c needs to be
printed, string will be processed in a temporary environment and
the result will be wrapped up into a single object. Compatibil-
ity mode will be turned off and the escape character will be set
to \ while string is being processed. Any emboldening, constant
spacing or track kerning will be applied to this object rather
than to individual glyphs in string.
A glyph defined by this request can be used just like a normal
glyph provided by the output device. In particular other char-
acters can be translated to it with the tr request; it can be
made the leader character by the lc request; repeated patterns
can be drawn with the character using the \l and \L escape
sequences; words containing the character can be hyphenated cor-
rectly, if the hcode request is used to give the character a
hyphenation code.
There is a special anti-recursion feature: Use of glyph within
the glyph's definition will be handled like normal glyphs not
defined with char.
A glyph definition can be removed with the rchar request.
.chop xx
Chop the last element off macro, string, or diversion xx. This
is useful for removing the newline from the end of diversions
that are to be interpolated as strings.
.close stream
Close the stream named stream; stream will no longer be an
acceptable argument to the write request. See the open request.
.composite glyph1 glyph2
Map glyph name glyph1 to glyph name glyph2 if it is used in
\[...] with more than one component.
.continue
Finish the current iteration of a while loop. See also the
while and break requests.
.color n
If n is non-zero or missing, enable colors (this is the
Define color. scheme can be one of the following values: rgb
(three components), cym (three components), cmyk (four compo-
nents), and gray or grey (one component). Color components can
be given either as a hexadecimal string or as positive decimal
integers in the range 0-65535. A hexadecimal string contains
all color components concatenated; it must start with either #
or ##. The former specifies hex values in the range 0-255
(which are internally multiplied by 257), the latter in the
range 0-65535. Examples: #FFC0CB (pink), ##ffff0000ffff
(magenta). A new scaling indicator f has been introduced which
multiplies its value by 65536; this makes it convenient to spec-
ify color components as fractions in the range 0 to 1. Example:
.defcolor darkgreen rgb 0.1f 0.5f 0.2f
Note that f is the default scaling indicator for the defcolor
request, thus the above statement is equivalent to
.defcolor darkgreen rgb 0.1 0.5 0.2
The color named default (which is device-specific) can't be
redefined. It is possible that the default color for \M and \m
is not the same.
.dei xx yy
Define macro indirectly. The following example
.ds xx aa
.ds yy bb
.dei xx yy
is equivalent to
.de aa bb
.de1 xx yy
Similar to .de, but compatibility mode is switched off during
execution. On entry, the current compatibility mode is saved
and restored at exit.
.do xxx
Interpret .xxx with compatibility mode disabled. For example,
.do fam T
would have the same effect as
.fam T
except that it would work even if compatibility mode had been
enabled. Note that the previous compatibility mode is restored
before any files sourced by xxx are interpreted.
.ds1 xx yy
Similar to .ds, but compatibility mode is switched off during
expansion. To be more precise, a `compatibility save' token is
inserted at the beginning of the string, and a `compatibility
restore' token at the end.
No pushing or popping of environments will be done.
.fam xx
Set the current font family to xx. The current font family is
part of the current environment. If xx is missing, switch back
to previous font family. The value at start-up is `T'. See the
description of the sty request for more information on font fam-
ilies.
.fchar c string
Define fallback glyph c to be string. The syntax of this
request is the same as the char request; the only difference is
that a glyph defined with char hides the glyph with the same
name in the current font, whereas a glyph defined with fchar is
checked only if the particular glyph isn't found in the current
font. This test happens before checking special fonts.
.fschar f c string
Define fallback glyph c for font f to be string. The syntax of
this request is the same as the char request (with an additional
argument to specify the font); a glyph defined with fschar is
searched after the list of fonts declared with the fspecial
request but before the list of fonts declared with special.
.fspecial f s1 s2...
When the current font is f, fonts s1, s2,... will be special,
that is, they will searched for glyphs not in the current font.
Any fonts specified in the special request will be searched
after fonts specified in the fspecial request. Without argu-
ment, reset the list of global special fonts to be empty.
.ftr f g
Translate font f to g. Whenever a font named f is referred to
in an \f escape sequence, or in the ft, ul, bd, cs, tkf, spe-
cial, fspecial, fp, or sty requests, font g will be used. If g
is missing, or equal to f then font f will not be translated.
.hcode c1 code1 c2 code2...
Set the hyphenation code of character c1 to code1 and that of c2
to code2. A hyphenation code must be a single input character
(not a special character) other than a digit or a space. Ini-
tially each lower-case letter a-z has a hyphenation code, which
is itself, and each upper-case letter A-Z has a hyphenation code
which is the lower-case version of itself. See also the hpf
request.
.hla lang
Set the current hyphenation language to lang. Hyphenation
exceptions specified with the hw request and hyphenation pat-
terns specified with the hpf request are both associated with
the current hyphenation language. The hla request is usually
invoked by the troffrc file.
.hlm n Set the maximum number of consecutive hyphenated lines to n. If
n is negative, there is no maximum. The default value is -1.
This value is associated with the current environment. Only
lines output from an environment count towards the maximum asso-
ciated with that environment. Hyphens resulting from \% are
o A percent sign starts a comment (up to the end of the
line) even if preceded by a backslash.
o No support for `digraphs' like \$.
o ^^xx (x is 0-9 or a-f) and ^^x (character code of x in
the range 0-127) are recognized; other use of ^ causes an
error.
o No macro expansion.
o hpf checks for the expression \patterns{...} (possibly
with whitespace before and after the braces). Everything
between the braces is taken as hyphenation patterns.
Consequently, { and } are not allowed in patterns.
o Similarly, \hyphenation{...} gives a list of hyphenation
exceptions.
o \endinput is recognized also.
o For backwards compatibility, if \patterns is missing, the
whole file is treated as a list of hyphenation patterns
(only recognizing the % character as the start of a com-
ment).
Use the hpfcode request to map the encoding used in hyphenation
patterns files to groff's input encoding.
The set of hyphenation patterns is associated with the current
language set by the hla request. The hpf request is usually
invoked by the troffrc file; a second call replaces the old pat-
terns with the new ones.
.hpfa file
The same as hpf except that the hyphenation patterns from file
are appended to the patterns already loaded in the current lan-
guage.
.hpfcode a b c d ...
After reading a hyphenation patterns file with the hpf or hpfa
request, convert all characters with character code a in the
recently read patterns to character code b, character code c
to d, etc. Initially, all character codes map to themselves.
The arguments of hpfcode must be integers in the range 0 to 255.
Note that it is even possible to use character codes which are
invalid in groff otherwise.
.hym n Set the hyphenation margin to n: when the current adjustment
mode is not b, the line will not be hyphenated if the line is no
more than n short. The default hyphenation margin is 0. The
default scaling indicator for this request is m. The hyphen-
ation margin is associated with the current environment. The
current hyphenation margin is available in the \n[.hym] regis-
ter.
.hys n Set the hyphenation space to n: when the current adjustment mode
Variant of .it for which a line interrupted with \c counts as
one input line.
.kern n
If n is non-zero or missing, enable pairwise kerning, otherwise
disable it.
.length xx string
Compute the length of string and return it in the number regis-
ter xx (which is not necessarily defined before).
.linetabs n
If n is non-zero or missing, enable line-tabs mode, otherwise
disable it (which is the default). In line-tabs mode, tab dis-
tances are computed relative to the (current) output line. Oth-
erwise they are taken relative to the input line. For example,
the following
.ds x a\t\c
.ds y b\t\c
.ds z c
.ta 1i 3i
\*x
\*y
\*z
yields
a b c
In line-tabs mode, the same code gives
a b c
Line-tabs mode is associated with the current environment; the
read-only number register \n[.linetabs] is set to 1 if in line-
tabs mode, and 0 otherwise.
.mso file
The same as the so request except that file is searched for in
the same directories as macro files for the the -m command line
option. If the file name to be included has the form name.tmac
and it isn't found, mso tries to include tmac.name instead and
vice versa.
.nop anything
Execute anything. This is similar to `.if 1'.
.nroff Make the n built-in condition true and the t built-in condition
false. This can be reversed using the troff request.
.open stream filename
Open filename for writing and associate the stream named stream
with it. See also the close and write requests.
.opena stream filename
Like open, but if filename exists, append to it instead of trun-
cating it.
registers on stderr.
.psbb filename
Get the bounding box of a PostScript image filename. This file
must conform to Adobe's Document Structuring Conventions; the
command looks for a %%BoundingBox comment to extract the bound-
ing box values. After a successful call, the coordinates (in
PostScript units) of the lower left and upper right corner can
be found in the registers \n[llx], \n[lly], \n[urx], and
\n[ury], respectively. If some error has occurred, the four
registers are set to zero.
.pso command
This behaves like the so request except that input comes from
the standard output of command.
.ptr Print the names and positions of all traps (not including input
line traps and diversion traps) on stderr. Empty slots in the
page trap list are printed as well, because they can affect the
priority of subsequently planted traps.
.pvs +-n
Set the post-vertical line space to n; default scale indicator
is p. This value will be added to each line after it has been
output. With no argument, the post-vertical line space is set
to its previous value.
The total vertical line spacing consists of four components: .vs
and \x with a negative value which are applied before the line
is output, and .pvs and \x with a positive value which are
applied after the line is output.
.rchar c1 c2...
Remove the definitions of glyphs c1, c2,... This undoes the
effect of a char request.
.return
Within a macro, return immediately. No effect otherwise.
.rfschar c1 c2...
Remove the font-specific definitions of glyphs c1, c2,... This
undoes the effect of a fschar request.
.rj
.rj n Right justify the next n input lines. Without an argument right
justify the next input line. The number of lines to be right
justified is available in the \n[.rj] register. This implicitly
does .ce 0. The ce request implicitly does .rj 0.
.rnn xx yy
Rename number register xx to yy.
.schar c string
Define global fallback glyph c to be string. The syntax of this
request is the same as the char request; a glyph defined with
schar is searched after the list of fonts declared with the spe-
cial request but before the mounted special fonts.
when finding the soft hyphen character.
.shift n
In a macro, shift the arguments by n positions: argument i
becomes argument i-n; arguments 1 to n will no longer be avail-
able. If n is missing, arguments will be shifted by 1. Shift-
ing by negative amounts is currently undefined.
.sizes s1 s2...sn [0]
This command is similar to the sizes command of a DESC file. It
sets the available font sizes for the current font to s1,
s2,..., sn scaled points. The list of sizes can be terminated
by an optional 0. Each si can also be a range of sizes m-n.
Contrary to the font file command, the list can't extend over
more than a single line.
.special s1 s2...
Fonts s1, s2, are special and will be searched for glyphs not in
the current font. Without arguments, reset the list of special
fonts to be empty.
.spreadwarn limit
Make troff emit a warning if the additional space inserted for
each space between words in an output line is larger or equal to
limit. A negative value is changed to zero; no argument toggles
the warning on and off without changing limit. The default
scaling indicator is m. At startup, spreadwarn is deactivated,
and limit is set to 3m. For example, .spreadwarn 0.2m will
cause a warning if troff must add 0.2m or more for each inter-
word space in a line. This request is active only if text is
justified to both margins (using .ad b).
.sty n f
Associate style f with font position n. A font position can be
associated either with a font or with a style. The current font
is the index of a font position and so is also either a font or
a style. When it is a style, the font that is actually used is
the font the name of which is the concatenation of the name of
the current family and the name of the current style. For exam-
ple, if the current font is 1 and font position 1 is associated
with style R and the current font family is T, then font TR will
be used. If the current font is not a style, then the current
family is ignored. When the requests cs, bd, tkf, uf, or fspe-
cial are applied to a style, then they will instead be applied
to the member of the current family corresponding to that style.
The default family can be set with the -f option. The styles
command in the DESC file controls which font positions (if any)
are initially associated with styles rather than fonts.
.substring xx n1 [n2]
Replace the string named xx with the substring defined by the
indices n1 and n2. The first character in the string has
index 0. If n2 is omitted, it is taken to be equal to the
string's length. If the index value n1 or n2 is negative, it
will be counted from the end of the string, going backwards: The
last character has index -1, the character before the last char-
acter has index -2, etc.
.tm1 string
Similar to the tm request, string is read in copy mode and writ-
ten on the standard error, but an initial double quote in string
is stripped off to allow initial blanks.
.tmc string
Similar to tm1 but without writing a final newline.
.trf filename
Transparently output the contents of file filename. Each line
is output as if preceded by \!; however, the lines are not sub-
ject to copy-mode interpretation. If the file does not end with
a newline, then a newline will be added. For example, you can
define a macro x containing the contents of file f, using
.di x
.trf f
.di
Unlike with the cf request, the file cannot contain characters
such as NUL that are not legal troff input characters.
.trin abcd
This is the same as the tr request except that the asciify
request will use the character code (if any) before the charac-
ter translation. Example:
.trin ax
.di xxx
a
.br
.di
.xxx
.trin aa
.asciify xxx
.xxx
The result is x a. Using tr, the result would be x x.
.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 \!. For example,
.tr ab
.di x
\!.tm a
.di
.x
will print b; if trnt is used instead of tr it will print a.
.troff Make the n built-in condition false, and the t built-in condi-
tion true. This undoes the effect of the nroff request.
.unformat xx
This request `unformats' the diversion xx. Contrary to the
.boxa requests.
.vpt n Enable vertical position traps if n is non-zero, disable them
otherwise. Vertical position traps are traps set by the wh or
dt requests. Traps set by the it request are not vertical posi-
tion traps. The parameter that controls whether vertical posi-
tion traps are enabled is global. Initially vertical position
traps are enabled.
.warn n
Control warnings. n is the sum of the numbers associated with
each warning that is to be enabled; all other warnings will be
disabled. The number associated with each warning is listed in
troff(1). For example, .warn 0 will disable all warnings, and
.warn 1 will disable all warnings except that about missing
glyphs. If n is not given, all warnings will be enabled.
.warnscale si
Set the scaling indicator used in warnings to si. Valid values
for si are u, i, c, p, and P. At startup, it is set to i.
.while c anything
While condition c is true, accept anything as input; c can be
any condition acceptable to an if request; anything can comprise
multiple lines if the first line starts with \{ and the last
line ends with \}. See also the break and continue requests.
.write stream anything
Write anything to the stream named stream. stream must previ-
ously have been the subject of an open request. anything is
read in copy mode; a leading " will be stripped.
.writec stream anything
Similar to write but without writing a final newline.
.writem stream xx
Write the contents of the macro or string xx to the stream named
stream. stream must previously have been the subject of an open
request. xx is read in copy mode.
Extended escape sequences
\D'...'
All drawing commands of groff's intermediate output are
accepted. See subsection Drawing Commands below for more infor-
mation.
Extended requests
.cf filename
When used in a diversion, this will embed in the diversion an
object which, when reread, will cause the contents of filename
to be transparently copied through to the output. In UNIX
troff, the contents of filename is immediately copied through to
the output regardless of whether there is a current diversion;
this behaviour is so anomalous that it must be considered a bug.
.ev xx If xx is not a number, this will switch to a named environment
called xx. The environment should be popped with a matching ev
request without any arguments, just as for numbered environ-
units of one twelfth of the spacewidth parameter for the current
font. Initially both the word space size and the sentence space
size are 12. Contrary to UNIX troff, GNU troff handles this
request in nroff mode also; a given value is then rounded down
to the nearest multiple of 12. The sentence space size is used
in two circumstances. If the end of a sentence occurs at the
end of a line in fill mode, then both an inter-word space and a
sentence space will be added; if two spaces follow the end of a
sentence in the middle of a line, then the second space will be
a sentence space. Note that the behaviour of UNIX troff will be
exactly that exhibited by GNU troff if a second argument is
never given to the ss request. In GNU troff, as in UNIX troff,
you should always follow a sentence with either a newline or two
spaces.
.ta n1 n2...nn T r1 r2...rn
Set tabs at positions n1, n2,..., nn and then set tabs at nn+r1,
nn+r2,..., nn+rn and then at nn+rn+r1, nn+rn+r2,..., nn+rn+rn,
and so on. For example,
.ta T .5i
will set tabs every half an inch.
New number registers
The following read-only registers are available:
\n[.C] 1 if compatibility mode is in effect, 0 otherwise.
\n[.cdp]
The depth of the last glyph added to the current environment.
It is positive if the glyph extends below the baseline.
\n[.ce]
The number of lines remaining to be centered, as set by the ce
request.
\n[.cht]
The height of the last glyph added to the current environment.
It is positive if the glyph extends above the baseline.
\n[.color]
1 if colors are enabled, 0 otherwise.
\n[.csk]
The skew of the last glyph added to the current environment.
The skew of a glyph is how far to the right of the center of a
glyph the center of an accent over that glyph should be placed.
\n[.ev]
The name or number of the current environment. This is a
string-valued register.
\n[.fam]
The current font family. This is a string-valued register.
\n[.fn]
The current (internal) real font name. This is a string-valued
\n[.height]
The current height of the font as set with \H.
\n[.hla]
The current hyphenation language as set by the hla request.
\n[.hlc]
The number of immediately preceding consecutive hyphenated
lines.
\n[.hlm]
The maximum allowed number of consecutive hyphenated lines, as
set by the hlm request.
\n[.hy]
The current hyphenation flags (as set by the hy request).
\n[.hym]
The current hyphenation margin (as set by the hym request).
\n[.hys]
The current hyphenation space (as set by the hys request).
\n[.in]
The indent that applies to the current output line.
\n[.int]
Set to a positive value if last output line is interrupted
(i.e., if it contains \c).
\n[.kern]
1 if pairwise kerning is enabled, 0 otherwise.
\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[.ne]
The amount of space that was needed in the last ne request that
caused a trap to be sprung. Useful in conjunction with the
\n[.trunc] register.
\n[.ns]
1 if no-space mode is active, 0 otherwise.
\n[.pe]
1 during a page ejection caused by the bp request, 0 otherwise.
\n[.pn]
\n[.pvs]
The current post-vertical line space as set with the pvs
request.
\n[.rj]
The number of lines to be right-justified as set by the rj
request.
\n[.slant]
The slant of the current font as set with \S.
\n[.sr]
The last requested pointsize in points as a decimal fraction.
This is a string-valued register.
\n[.ss]
\n[.sss]
These give the values of the parameters set by the first and
second arguments of the ss request.
\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 a
ne request, minus the amount of vertical motion produced by the
ne request. In other words, at the point a trap is sprung,
it represents the difference of what the vertical position
would have been but for the trap, and what the vertical position
actually is. Useful in conjunction with the \n[.ne] register.
\n[.vpt]
1 if vertical position traps are enabled, 0 otherwise.
\n[.warn]
The sum of the numbers associated with each of the currently
enabled warnings. The number associated with each warning is
listed in troff(1).
\n[.x] The major version number. For example, if the version number is
1.03, then \n[.x] will contain 1.
\n[.y] The minor version number. For example, if the version number is
1.03, then \n[.y] will contain 03.
\n[.Y] The revision number of groff.
\n[llx]
\n[lly]
\n[urx]
\n[ury]
These four registers are set by the .psbb request and contain
the bounding box values (in PostScript units) of a given Post-
Script image.
The amount of horizontal space (possibly negative) that should
be added to the last glyph before a subscript.
\n[skw]
How far to right of the center of the last glyph in the \w argu-
ment, the center of an accent from a roman font should be placed
over that glyph.
Other available read/write number registers are:
\n[c.] The current input line number. \n[.c] is a read-only alias to
this register.
\n[hours]
The number of hours past midnight. Initialized at start-up.
\n[hp] The current horizontal position at input line.
\n[minutes]
The number of minutes after the hour. Initialized at start-up.
\n[seconds]
The number of seconds after the minute. Initialized at start-
up.
\n[systat]
The return value of the system() function executed by the last
sy request.
\n[slimit]
If greater than 0, the maximum number of objects on the input
stack. If less than or equal to 0, there is no limit on the
number of objects on the input stack. With no limit, recursion
can continue until virtual memory is exhausted.
\n[year]
The current year. Note that the traditional troff number regis-
ter \n[yr] is the current year minus 1900.
Miscellaneous
troff predefines a single (read/write) string-based register, \*(.T,
which contains the argument given to the -T command line option, namely
the current output device (for example, latin1 or ascii). Note that
this is not the same as the (read-only) number register \n[.T] which is
defined to be 1 if troff is called with the -T command line option, and
zero otherwise. This behaviour is different to UNIX troff.
Fonts not listed in the DESC file are automatically mounted on the next
available font position when they are referenced. If a font is to be
mounted explicitly with the fp request on an unused font position, it
should be mounted on the first unused font position, which can be found
in the \n[.fp] register; although troff does not enforce this strictly,
it will not allow a font to be mounted at a position whose number is
much greater than that of any currently used position.
Interpolating a string does not hide existing macro arguments. Thus in
a macro, a more efficient way of doing
be inhibited by placing a \& between them.
In a string comparison in a condition, characters that appear at dif-
ferent input levels to the first delimiter character will not be recog-
nised as the second or third delimiters. This applies also to the tl
request. In a \w escape sequence, a character that appears at a dif-
ferent input level to the starting delimiter character will not be
recognised as the closing delimiter character. The same is true for
\A, \b, \B, \C, \l, \L, \o, \X, and \Z. When decoding a macro or
string argument that is delimited by double quotes, a character that
appears at a different input level to the starting delimiter character
will not be recognised as the closing delimiter character. The imple-
mentation of \$@ ensures that the double quotes surrounding an argument
will appear the same input level, which will be different to the input
level of the argument itself. In a long escape name ] will not be rec-
ognized as a closing delimiter except when it occurs at the same input
level as the opening ]. In compatibility mode, no attention is paid to
the input-level.
There are some new types of condition:
.if rxxx
True if there is a number register named xxx.
.if dxxx
True if there is a string, macro, diversion, or request named
xxx.
.if mxxx
True if there is a color named xxx.
.if cch
True if there is a glyph ch available; ch is either an ASCII
character or a glyph (special character) \(xx or \[xxx]; the
condition will also be true if ch has been defined by the char
request.
The tr request can now map characters onto \~.
It is now possible to have whitespace between the first and second dot
(or the name of the ending macro) to end a macro definition. Example:
.de foo
. nop Hello, I'm `foo'.
. nop I will now define `bar'.
. de bar
. nop Hello, I'm `bar'.
. .
. nop Done.
..
.foo
.bar
INTERMEDIATE OUTPUT FORMAT
This section describes the format output by GNU troff. The output for-
mat used by GNU troff is very similar to that used by Unix device-inde-
pendent troff. Only the differences are documented here.
If the tcommand line is present in the DESC file, troff will use the
following two commands.
txxx xxx is any sequence of characters terminated by a space or a
newline (to be more precise, it is a sequence of glyphs which
are accessed with the corresponding characters); the first char-
acter should be printed at the current position, the current
horizontal position should be increased by the width of the
first character, and so on for each character. The width of the
glyph is that given in the font file, appropriately scaled for
the current point size, and rounded so that it is a multiple of
the horizontal resolution. Special characters cannot be printed
using this command.
un xxx This is same as the t command except that after printing each
character, the current horizontal position is increased by the
sum of the width of that character and n.
Note that single characters can have the eighth bit set, as can the
names of fonts and special characters.
The names of glyphs and fonts can be of arbitrary length; drivers
should not assume that they will be only two characters long.
When a glyph is to be printed, that glyph will always be in the current
font. Unlike device-independent troff, it is not necessary for drivers
to search special fonts to find a glyph.
For color support, some new commands have been added:
mc cyan magenta yellow
md
mg gray
mk cyan magenta yellow black
mr red green blue
Set the color components of the current drawing color, using
various color schemes. md resets the drawing color to the
default value. The arguments are integers in the range 0 to
65536.
The x device control command has been extended.
x u n If n is 1, start underlining of spaces. If n is 0, stop under-
lining of spaces. This is needed for the cu request in nroff
mode and is ignored otherwise.
Drawing Commands
The D drawing command has been extended. These extensions will not be
used by GNU pic if the -n option is given.
Df n\n Set the shade of gray to be used for filling solid objects to n;
n must be an integer between 0 and 1000, where 0 corresponds
solid white and 1000 to solid black, and values in between cor-
respond to intermediate shades of gray. This applies only to
solid circles, solid ellipses and solid polygons. By default, a
level of 1000 will be used. Whatever color a solid object has,
it should completely obscure everything beneath it. A value
DC d\n Draw a solid circle with a diameter of d with the leftmost point
at the current position.
DE dx dy\n
Draw a solid ellipse with a horizontal diameter of dx and a ver-
tical diameter of dy with the leftmost point at the current
position.
Dp dx1 dy1 dx2 dy2 ... dxn dyn\n
Draw a polygon with,i_1r i=1,...,n+1, the i-th vertex at the
current position + > (dxj,dyj). At the moment, GNU pic only
j=1
uses this command to generate triangles and rectangles.
DP dx1 dy1 dx2 dy2 ... dxn dyn\n
Like Dp but draw a solid rather than outlined polygon.
Dt n\n Set the current line thickness to n machine units. Tradition-
ally Unix troff drivers use a line thickness proportional to the
current point size; drivers should continue to do this if no Dt
command has been given, or if a Dt command has been given with a
negative value of n. A zero value of n selects the smallest
available line thickness.
A difficulty arises in how the current position should be changed after
the execution of these commands. This is not of great importance since
the code generated by GNU pic does not depend on this. Given a drawing
command of the form
\D'c x1 y1 x2 y2 ... xn yn'
where c is not one of c, e, l, a, or ~, Unix troff will treat each of
the xi as a horizontal quantity, and each of the yi as a vert<I>n_cal quan-
tity and will assume that the width of the drawn object is > xi, and
n_ i=1
that the height is > yi. (The assumption about the height can be seen
i=1
by examining the st and sb registers after using such a D command in a
\w escape sequence). This rule also holds for all the original drawing
commands with the exception of De. For the sake of compatibility GNU
troff also follows this rule, even though it produces an ugly result in
the case of the Dt and Df, and, to a lesser extent, DE commands. Thus
after executing a D command of the form
Dc x1 y1 x2 y2 ... xn yn\n
n_ n_
the current position should be increased by ( > xi, > yi).
i=1 i=1
Another set of extensions is
DFc cyan magenta yellow\n
DFd\n
DFg gray\n
DFk cyan magenta yellow black\n
DFr red green blue\n
Set the color components of the filling color similar to the m
x X command, GNU troff will follow each newline in the argument with a
+ character (as usual, it will terminate the entire argument with a
newline); thus if the line after the line containing the x X command
starts with +, then the newline ending the line containing the x X com-
mand should be treated as part of the argument to the x X command, the
+ should be ignored, and the part of the line following the + should be
treated like the part of the line following the x X command.
The first three output commands are guaranteed to be:
x T device
x res n h v
x init
INCOMPATIBILITIES
In spite of the many extensions, groff has retained compatibility to
classical troff to a large degree. For the cases where the extensions
lead to collisions, a special compatibility mode with the restricted,
old functionality was created for groff.
Groff Language
groff provides a compatibility mode that allows to process roff code
written for classical or for other implementations of roff in a consis-
tent way.
Compatibility mode can be turned on with the -C command line option,
and turned on or off with the .cp request. The number register \n(.C
is 1 if compatibility mode is on, 0 otherwise.
This became necessary because the GNU concept for long names causes
some incompatibilities. Classical troff interprets
.dsabcd
as defining a string ab with contents cd. In groff mode, this will be
considered as a call of a macro named dsabcd.
Also classical troff interprets \*[ or \n[ as references to a string or
number register called [ while groff takes this as the start of a long
name.
In compatibility mode, groff interprets these things in the traditional
way; so long names are not recognized.
On the other hand, groff in GNU native mode does not allow to use the
single-character escapes \\ (backslash), \| (vertical bar), \^ (caret),
\& (ampersand), \{ (opening brace), \} (closing brace), `\ ' (space),
\' (single quote), \` (backquote), \- (minus), \_ (underline), \!
(bang), \% (percent), and \c (character c) in names of strings, macros,
diversions, number registers, fonts or environments, whereas classical
troff does.
The \A escape sequence can be helpful in avoiding these escape
sequences in names.
Fractional pointsizes cause one noteworthy incompatibility. In classi-
cal troff, the ps request ignores scale indicators and so
a glyph has been constructed it is unaffected by any subsequent
requests that are executed, including the bd, cs, tkf, tr, or fp
requests.
Normally glyphs are constructed from input characters at the moment
immediately before the glyph is added to the current output line.
Macros, diversions and strings are all, in fact, the same type of
object; they contain lists of input characters and glyphs in any combi-
nation.
Special characters can be both; before being added to the output, they
act as input entities, afterwards they denote glyphs.
A glyph does not behave like an input character for the purposes of
macro processing; it does not inherit any of the special properties
that the input character from which it was constructed might have had.
The following example will make things clearer.
.di x
\\\\
.br
.di
.x
In GNU mode this will be printed as \\. So each pair of input back-
slashes `\\' is turned into a single output backslash glyph `\' and the
resulting output backslashes are not interpreted as escape characters
when they are reread.
Classical troff would interpret them as escape characters when they
were reread and would end up printing a single backslash `\'.
In GNU, the correct way to get a printable version of the backslash
character `\' is the \(rs escape sequence, but classical troff does not
provide a clean feature for getting a non-syntactical backslash. A
close method is the printable version of the current escape character
using the \e escape sequence; this works if the current escape charac-
ter is not redefined. It works in both GNU mode and compatibility
mode, while dirty tricks like specifying a sequence of multiple back-
slashes do not work reliably; for the different handling in diversions,
macro definitions, or text mode quickly leads to a confusion about the
necessary number of backslashes.
To store an escape sequence in a diversion that will be interpreted
when the diversion is reread, either the traditional \! transparent
output facility or the new \? escape sequence can be used.
Intermediate Output
The groff intermediate output format is in a state of evolution. So
far it has some incompatibilities, but it is intended to establish a
full compatibility to the classical troff output format. Actually the
following incompatibilities exist:
o The positioning after the drawing of the polygons conflicts with the
classical definition.
o The intermediate output cannot be rescaled to other devices as clas-
sical "device-independent" troff did.
was written by James Clark, with modifications by Werner Lemberg
<wl@gnu.org> and Bernd Warken <bwarken@mayn.de>.
This document is part of groff, the GNU roff distribution. Formerly,
the contents of this document was kept in the manual page troff(1).
Only the parts dealing with the language aspects of the different roff
systems were carried over into this document. The troff command line
options and warnings are still documented in troff(1).
SEE ALSO
The groff info file, cf. info(1) presents all groff documentation
within a single document.
groff(1)
A list of all documentation around groff.
groff(7)
A description of the groff language, including a short, but com-
plete reference of all predefined requests, registers, and
escapes of plain groff. From the command line, this is called
using
shell# man 7 groff
roff(7)
A survey of roff systems, including pointers to further histori-
cal documentation.
[CSTR #54]
The Nroff/Troff User's Manual by J. F. Osanna of 1976 in the
revision of Brian Kernighan of 1992, being the classical troff
documentation <http://cm.bell-labs.com/cm/cs/cstr/54.ps.gz>.
Groff Version 1.19 1 May 2003 GROFF_DIFF(7)
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