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 classical Unix 7
troff
are described in detail.
Long names
The names of number registers, fonts, strings/macros/diversions,
special 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.
Example: `\[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 composite 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 specified 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 argument to the
\H
escape sequence, and those variants of the
\s
escape sequence that take a numeric expression as their argument.
For example, suppose sizescale is 1000; then a scaled point will be
equivalent to a millipoint; the call
.ps 10.25
is equivalent to
.ps 10.25z
and so sets the pointsize to 10250 scaled points, which is equal to
10.25 points.
The number register
\n[.s]
returns the pointsize in points as decimal fraction.
There is also a new number register
\n[.ps]
that returns the pointsize in scaled points.
It would make no sense to use the
z
scale indicator in a numeric expression whose default scale indicator
was neither
u
nor
z,
and so
troff
disallows this.
Similarly it would make no sense to use a scaling indicator other than
z
or
u
in a numeric expression whose default scale indicator was
z,
and so
troff
disallows this as well.
There is also new scale indicator s
which multiplies by the number of units in a scaled point.
So, for example,
\n[.ps]s
is equal to
1m.
Be sure not to confuse the
s
and
z
scale indicators.
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.
-
e1e2
-
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
anything
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 interpreted in
copy-mode.
For example, strings to start and end superscripting could be defined
like this
-
<>
<>
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[]
switches back to the previous color (note that
\FP
won't work; it selects font family `P' instead).
-
\mx
-
-
\m(xx
-
-
\m[xxx]
-
Set drawing color.
\m[]
switches back to the previous color.
-
\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
<>
<></bb>>
-
-
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 specified and must be one of l, r, c, or i (left, right,
centered, inline).
filename
will be associated with the production of the next inline image.
-
\R'name ±n'
-
This has the same effect as
-
.nr name ±n
-
-
\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 extension 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
-
<>
<>
<
>
</pprree>>
-
will print
-
4.
-
\/
-
This increases the width of the preceding glyph so that the
spacing between that glyph and the following glyph will be
correct if the following glyph is a roman glyph.
It is a good idea to use this escape sequence whenever an italic
glyph is immediately 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.
-
.am1 xx yy
-
Similar to
.am,
but compatibility mode is switched off during execution.
To be more precise, a `compatibility save' token is inserted at the
beginning of the macro addition, and a `compatibility restore' token at
the end.
As a consequence, the requests
am,
am1,
de,
and
de1
can be intermixed freely since the compatibility save/restore tokens
only affect the macro parts defined by
.am1
and
.ds1.
-
.ami xx yy
-
Append to macro indirectly.
See the
dei
request below for more information.
-
.ami1 xx yy
-
Same as the
ami
request but compatibility mode is switched off during execution.
-
.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 compatibility save/restore tokens
only affect the (sub)strings defined by
as1
and
ds1.
-
.asciify xx
-
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
-
<>
<>
<
>
</pprree>>
-
will set register
-
n
to 1.
Note that glyph information (font, font size, etc.) is not preserved;
use
.unformat
instead.
-
.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 at a character with this
property unless the characters on each side both have non-zero
hyphenation codes.
-
4
Lines can be broken after the character (initially characters
-
-\[hy]\[em]
have this property); a line will not be broken at a character with
this property unless the characters on each side both have non-zero
hyphenation codes.
-
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
having 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.
Compatibility mode will be turned off and the escape character will be
set to
\
while
string
is being processed.
Any emboldening, constant spacing or track kerning will be applied to
this object rather than to individual 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 characters can be translated to it with the
tr
request; it can be made the leader character by the
lc
request; repeated patterns can be drawn with the character using the
\l
and
\L
escape sequences; words containing the character can be hyphenated
correctly, if the
hcode
request is used to give the character a hyphenation code.
-
There is a special anti-recursion feature: Use of 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 default), otherwise
disable them.
-
.cp n
-
If
n
is non-zero or missing, enable compatibility mode, otherwise disable
it.
In compatibility mode, long names are not recognised, and the
incompatibilities caused by long names do not arise.
-
.defcolor xxx scheme color_components
-
Define color.
scheme
can be one of the following values:
rgb
(three components),
cym
(three components),
cmyk
(four components), 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 specify color components as fractions in the range 0
to 1.
Example:
-
<>
<>
-
Note that
-
f
is the default scaling indicator for the
defcolor
request, thus the above statement is equivalent to
-
<>
<>
-
The color named
-
default
(which is device-specific) can't be redefined.
It is possible that the default color for
and
is not the same.
-
.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.
-
.dei xx yy
-
Define macro indirectly.
The following example
-
<>
<>
<
>
</pprree>>
-
is equivalent to
-
-
<>
<>
-
.dei1 xx yy
-
Similar to the
dei
request but compatibility mode is switched off during execution.
-
.do xxx
-
Interpret
.xxx
with compatibility mode disabled.
For example,
-
<>
<>
would have the same effect as
-
<>
<>
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.
-
.ecs
-
Save current escape character.
-
.ecr
-
Restore escape character saved with
ecs.
Without a previous call to
ecs,
will be the new escape character.
-
.evc xx
-
Copy the contents of environment
xx
to the current environment.
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 families.
-
.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.
-
.fcolor c
-
Set the fill color to
c.
If
c
is missing,
switch to the previous fill color.
-
.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 argument, 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, in the
F
and
S
conditional operators, or in the
ft,
ul,
bd,
cs,
tkf,
special,
fspecial,
fp,
or
sty
requests, font
g
will be used.
If
g
is missing, or equal to
f
then font
f
will not be translated.
-
.gcolor c
-
Set the glyph color to
c.
If
c
is missing,
switch to the previous glyph color.
-
.hcode c1 code1 c2 code2...
-
Set the hyphenation code of character
c1
to
code1
and that of
c2
to
code2.
A hyphenation code must be a single input character (not a special
character) other than a digit or a space.
Initially each lower-case letter 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 patterns 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
associated with that environment.
Hyphens resulting from
\%
are counted; explicit hyphens are not.
-
.hpf file
-
Read hyphenation patterns from
file;
this will be searched for in the same way that
name.tmac
is searched for when the
-mname
option is specified.
It should have the same format as (simple) TeX patterns files.
More specifically, the following scanning rules are implemented.
-
·
A percent sign starts a comment (up to the end of the line) even if
-
preceded by a backslash.
-
·
No support for `digraphs' like
-
\$.
-
·
^^xx
-
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.
-
·
No macro expansion.
-
-
·
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.
-
·
Similarly,
-
\hyphenation{...}
gives a list of hyphenation exceptions.
-
·
\endinput
-
is recognized also.
-
·
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 comment).
-
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 patterns 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 language.
-
.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 hyphenation margin is associated with the current environment.
The current hyphenation margin is available in the
\n[.hym]
register.
-
.hys n
-
Set the
hyphenation space
to n:
when the current adjustment mode is b
don't hyphenate the line if the line can be justified by adding no
more than
n
extra space to each word space.
The default hyphenation space is 0.
The default scaling indicator for this request is m.
The hyphenation space is associated with the current environment.
The current hyphenation space is available in the
\n[.hys]
register.
-
.itc n macro
-
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 register
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 distances are computed relative to the
(current) output line.
Otherwise they are taken relative to the input line.
For example, the following
-
<>
<>
<
>
</pprree>>
-
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 truncating it.
-
.output string
-
Emit
string
directly to the intermediate output (subject to copy-mode interpretation);
this is similar to
\!
used at the top level.
An initial double quote in
string
is stripped off to allow initial blanks.
-
.pnr
-
Print the names and contents of all currently defined number 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 bounding 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.
If called with an argument, return twice, namely from the current macro and
from the macro one level higher.
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
special
request but before the mounted special fonts.
-
.shc c
-
Set the soft hyphen character to
c.
If
c
is omitted, the soft hyphen character will be set to the default
\(hy.
The soft hyphen character is the glyph which will be inserted when
a word is hyphenated at a line break.
If the soft hyphen character does not exist in the font of the
glyph immediately preceding a potential break point, then the line
will not be broken at that point.
Neither definitions (specified with the
char
request) nor translations (specified with the
tr
request) are considered when finding the soft hyphen character.
-
.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 available.
If
n
is missing, arguments will be shifted by 1.
Shifting 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 interword 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 example, 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
fspecial
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
character has index -2, etc.
-
.tkf f s1 n1 s2 n2
-
Enable track kerning for font
f.
When the current font is
f
the width of every glyph will be increased by an amount between
n1
and
n2;
when the current point size is less than or equal to
s1
the width will be increased by
n1;
when it is greater than or equal to
s2
the width will be increased by
n2;
when the point size is greater than or equal to
s1
and less than or equal to
s2
the increase in width is a linear function of the point size.
-
.tm1 string
-
Similar to the
tm
request,
string
is read in copy mode and written 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 subject to copy-mode interpretation.
If the file does not end with a newline, then a newline will be added.
For example, you can define a macro x
containing the contents of file f,
using
-
<>
<>
<
>
</pprree>>
-
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 character
translation.
Example:
-
-
</pprree>>
-
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,
-
-
</pprree>>
-
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 condition true.
This undoes the effect of the
nroff
request.
-
.unformat xx
-
This request `unformats' the diversion
xx.
Contrary to the
.asciify
request, which tries to convert formatted elements of the diversion
back to input tokens as much as possible,
.unformat
will only handle tabs and spaces between words (usually caused by
spaces or newlines in the input) specially.
The former are treated as if they were input tokens, and the latter
are stretchable again.
Note that the vertical size of lines is not preserved.
Glyph information (font, font size, space width, etc.) is retained.
Useful in conjunction with the
.box
and
.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 position traps.
The parameter that controls whether vertical position 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 previously 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 information.
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.
-
.de xx yy
-
-
.am xx yy
-
-
.ds xx yy
-
-
.as xx yy
-
In compatibility mode, these requests behaves similar to
.de1,
.am1,
.ds1,
and
.as1,
respectively: A `compatibility save' token is inserted at the
beginning, and a `compatibility restore' token at the end, with
compatibility mode switched on during execution.
-
.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 environments.
There is no limit on the number of named environments; they will be
created the first time that they are referenced.
-
.ss m n
-
When two arguments are given to the
ss
request, the second argument gives the
sentence space size.
If the second argument is not given, the sentence space size
will be the same as the word space size.
Like the word space size, the sentence space is in 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,
-
<>
<>
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 register.
If the current font is a style, the value of
\n[.fn]
is the proper concatenation of family and style name.
-
\n[.fp]
-
The number of the next free font position.
-
\n[.g]
-
Always 1.
Macros should use this to determine whether they are running under GNU
troff.
-
\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[.m]
-
The name of the current drawing color.
This is a string-valued register.
-
\n[.M]
-
The name of the current background color.
This is a string-valued register.
-
\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]
-
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 pointsize in scaled points.
-
\n[.psr]
-
The last-requested pointsize in scaled points.
-
\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[.sty]
-
The current font style.
This is a string-valued register.
-
\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[.U]
-
Set to 1 if in safer mode and to 0 if in unsafe mode (as given with the
-U
command line option).
-
\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 PostScript image.
The following read/write registers are set by the
\w
escape sequence:
-
\n[rst]
-
-
\n[rsb]
-
Like the
st
and
sb
registers, but take account of the heights and depths of glyphs.
-
\n[ssc]
-
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
argument, 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 register
\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
-
.xx \\$@
-
is
-
\\*[xx]\\
-
If the font description file contains pairwise kerning information,
glyphs from that font will be kerned.
Kerning between two glyphs can be inhibited by placing a
\&
between them.
In a string comparison in a condition, characters that appear at
different input levels to the first delimiter character will not be
recognised as the second or third delimiters.
This applies also to the
tl
request.
In a
\w
escape sequence, a character that appears at a different 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 implementation 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 recognized 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.
-
.if Ff
-
True if font
f
exists.
f
is handled as if it was opened with the
ft
request (this is, font translation and styles are applied), without
actually mounting it.
-
.if Ss
-
True if style
s
has been registered.
Font translation is applied.
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:
-
<>
<>
<
>
</pprree>>
</ddll>>
<> IINNTTEERRMMEEDDIIAATTEE OOUUTTPPUUTT FFOORRMMAATT </hh33>>
TThhiiss sseeccttiioonn ddeessccrriibbeess tthhee ffoorrmmaatt oouuttppuutt bbyy GGNNUU ttrrooffff..
TThhee oouuttppuutt ffoorrmmaatt uusseedd bbyy GGNNUU ttrrooffff iiss vveerryy ssiimmiillaarr ttoo tthhaatt uusseedd
bbyy UUnniixx ddeevviiccee--iinnddeeppeennddeenntt ttrrooffff..
OOnnllyy tthhee ddiiffffeerreenncceess aarree ddooccuummeenntteedd hheerree..
<> UUnniittss </hh44>>
TThhee aarrgguummeenntt ttoo tthhee
<>ss</bb>>
ccoommmmaanndd iiss iinn ssccaalleedd ppooiinnttss ((uunniittss ooff
wwhheerree
<>nn</ii>>
iiss tthhee aarrgguummeenntt ttoo tthhee
<>ssiizzeessccaallee</bb>>
ccoommmmaanndd iinn tthhee DDEESSCC ffiillee))..
TThhee aarrgguummeenntt ttoo tthhee
<>xx HHeeiigghhtt</bb>>
ccoommmmaanndd iiss aallssoo iinn ssccaalleedd ppooiinnttss..
<> TTeexxtt CCoommmmaannddss </hh44>>
<>
<>
<>NN</bb>><>nn</ii>>
<>
PPrriinntt ggllyypphh wwiitthh iinnddeexx <>nn</ii>>
((aa nnoonn--nneeggaattiivvee iinntteeggeerr)) ooff tthhee ccuurrrreenntt ffoonntt..
</ddll>>
<>
IIff tthhee
<>ttccoommmmaanndd</bb>>
lliinnee iiss pprreesseenntt iinn tthhee DDEESSCC ffiillee,, ttrrooffff wwiillll uussee tthhee ffoolllloowwiinngg ttwwoo
ccoommmmaannddss..
<>
<>
<>tt</bb>><>xxxxxx</ii>>
<>
<>xxxxxx</ii>>
iiss aannyy sseeqquueennccee ooff cchhaarraacctteerrss tteerrmmiinnaatteedd bbyy aa ssppaaccee oorr aa nneewwlliinnee ((ttoo
bbee mmoorree pprreecciissee,, iitt iiss aa sseeqquueennccee ooff ggllyypphhss wwhhiicchh aarree aacccceesssseedd wwiitthh
tthhee ccoorrrreessppoonnddiinngg cchhaarraacctteerrss));; tthhee ffiirrsstt cchhaarraacctteerr sshhoouulldd bbee pprriinntteedd aatt
tthhee ccuurrrreenntt ppoossiittiioonn,, tthhee ccuurrrreenntt hhoorriizzoonnttaall ppoossiittiioonn sshhoouulldd bbee iinnccrreeaasseedd
bbyy tthhee wwiiddtthh ooff tthhee ffiirrsstt cchhaarraacctteerr,, aanndd ssoo oonn ffoorr eeaacchh cchhaarraacctteerr..
TThhee wwiiddtthh ooff tthhee ggllyypphh iiss tthhaatt ggiivveenn iinn tthhee ffoonntt ffiillee,,
aapppprroopprriiaatteellyy ssccaalleedd ffoorr tthhee ccuurrrreenntt ppooiinntt ssiizzee,, aanndd rroouunnddeedd ssoo tthhaatt
iitt iiss aa mmuullttiippllee ooff tthhee hhoorriizzoonnttaall rreessoolluuttiioonn..
SSppeecciiaall cchhaarraacctteerrss ccaannnnoott bbee pprriinntteedd uussiinngg tthhiiss ccoommmmaanndd..
<>
<>uu</bb>><>nn xxxxxx</ii>>
<>
TThhiiss iiss ssaammee aass tthhee
<>tt</bb>>
ccoommmmaanndd eexxcceepptt tthhaatt aafftteerr pprriinnttiinngg eeaacchh cchhaarraacctteerr,, tthhee ccuurrrreenntt
hhoorriizzoonnttaall ppoossiittiioonn iiss iinnccrreeaasseedd bbyy tthhee ssuumm ooff tthhee wwiiddtthh ooff tthhaatt
cchhaarraacctteerr aanndd
<>nn</ii>>..
</ddll>>
<>
NNoottee tthhaatt ssiinnggllee cchhaarraacctteerrss ccaann hhaavvee tthhee eeiigghhtthh bbiitt sseett,, aass ccaann tthhee
nnaammeess ooff ffoonnttss aanndd ssppeecciiaall cchhaarraacctteerrss..
<
>
TThhee nnaammeess ooff ggllyypphhss aanndd ffoonnttss ccaann bbee ooff aarrbbiittrraarryy lleennggtthh;; ddrriivveerrss
sshhoouulldd nnoott aassssuummee tthhaatt tthheeyy wwiillll bbee oonnllyy ttwwoo cchhaarraacctteerrss lloonngg..
<
>
WWhheenn aa ggllyypphh iiss ttoo bbee pprriinntteedd,, tthhaatt ggllyypphh wwiillll aallwwaayyss bbee
iinn tthhee ccuurrrreenntt ffoonntt..
UUnnlliikkee ddeevviiccee--iinnddeeppeennddeenntt ttrrooffff,, iitt iiss nnoott nneecceessssaarryy ffoorr ddrriivveerrss ttoo
sseeaarrcchh ssppeecciiaall ffoonnttss ttoo ffiinndd aa ggllyypphh..
<
>
FFoorr ccoolloorr ssuuppppoorrtt,, ssoommee nneeww ccoommmmaannddss hhaavvee bbeeeenn aaddddeedd::
<>
<>
<>
<>
<>
<>
<>
<>
<>
<>
<>
<>
<>
<>
SSeett tthhee ccoolloorr ccoommppoonneennttss ooff tthhee ccuurrrreenntt ddrraawwiinngg ccoolloorr,, uussiinngg vvaarriioouuss
<>
ccoolloorr sscchheemmeess..
<>mmdd</bb>>
rreesseettss tthhee ddrraawwiinngg ccoolloorr ttoo tthhee ddeeffaauulltt vvaalluuee..
TThhee aarrgguummeennttss aarree iinntteeggeerrss iinn tthhee rraannggee 00 ttoo 6655553366..
</ddll>>
<>
TThhee
<>xx</bb>>
ddeevviiccee ccoonnttrrooll ccoommmmaanndd hhaass bbeeeenn eexxtteennddeedd..
<>
<>
IIff
<>
<>nn</ii>>
iiss 11,, ssttaarrtt uunnddeerrlliinniinngg ooff ssppaacceess..
IIff
<>nn</ii>>
iiss 00,, ssttoopp uunnddeerrlliinniinngg ooff ssppaacceess..
TThhiiss iiss nneeeeddeedd ffoorr tthhee
<>ccuu</bb>>
rreeqquueesstt iinn nnrrooffff mmooddee aanndd iiss iiggnnoorreedd ootthheerrwwiissee..
</ddll>>
<> DDrraawwiinngg CCoommmmaannddss </hh44>>
TThhee
<>DD</bb>>
ddrraawwiinngg ccoommmmaanndd hhaass bbeeeenn eexxtteennddeedd..
TThheessee eexxtteennssiioonnss wwiillll nnoott bbee uusseedd bbyy GGNNUU ppiicc iiff tthhee
<>--nn</bb>>
ooppttiioonn iiss ggiivveenn..
<>
<>
SSeett tthhee sshhaaddee ooff ggrraayy ttoo bbee uusseedd ffoorr ffiilllliinngg ssoolliidd oobbjjeeccttss ttoo
<>
<>nn</ii>>;;
<>nn</ii>>
mmuusstt bbee aann iinntteeggeerr bbeettwweeeenn 00 aanndd 11000000,, wwhheerree 00 ccoorrrreessppoonnddss ssoolliidd wwhhiittee
aanndd 11000000 ttoo ssoolliidd bbllaacckk,, aanndd vvaalluueess iinn bbeettwweeeenn ccoorrrreessppoonndd ttoo
iinntteerrmmeeddiiaattee sshhaaddeess ooff ggrraayy..
TThhiiss aapppplliieess oonnllyy ttoo ssoolliidd cciirrcclleess,, ssoolliidd eelllliippsseess aanndd ssoolliidd
ppoollyyggoonnss..
BByy ddeeffaauulltt,, aa lleevveell ooff 11000000 wwiillll bbee uusseedd..
WWhhaatteevveerr ccoolloorr aa ssoolliidd oobbjjeecctt hhaass,, iitt sshhoouulldd ccoommpplleetteellyy oobbssccuurree
eevveerryytthhiinngg bbeenneeaatthh iitt..
AA vvaalluuee ggrreeaatteerr tthhaann 11000000 oorr lleessss tthhaann 00 ccaann aallssoo bbee uusseedd:: tthhiiss mmeeaannss
ffiillll wwiitthh tthhee sshhaaddee ooff ggrraayy tthhaatt iiss ccuurrrreennttllyy bbeeiinngg uusseedd ffoorr lliinneess aanndd
tteexxtt..
NNoorrmmaallllyy tthhiiss wwiillll bbee bbllaacckk,, bbuutt ssoommee ddrriivveerrss mmaayy pprroovviiddee aa wwaayy ooff
cchhaannggiinngg tthhiiss..
<>
<></bb>>
TThhee ccoorrrreessppoonnddiinngg
<>
<>\\DD''ff</bb>><>......</ii>>''
ccoommmmaanndd sshhoouullddnn''tt bbee uusseedd ssiinnccee iittss aarrgguummeenntt iiss aallwwaayyss rroouunnddeedd ttoo aann
iinntteeggeerr mmuullttiippllee ooff tthhee hhoorriizzoonnttaall rreessoolluuttiioonn wwhhiicchh ccaann lleeaadd ttoo
ssuurrpprriissiinngg rreessuullttss..
<>
DDrraaww aa ssoolliidd cciirrccllee wwiitthh aa ddiiaammeetteerr ooff
<>
<>dd</ii>>
wwiitthh tthhee lleeffttmmoosstt ppooiinntt aatt tthhee ccuurrrreenntt ppoossiittiioonn..
<>
DDrraaww aa ssoolliidd eelllliippssee wwiitthh aa hhoorriizzoonnttaall ddiiaammeetteerr ooff
<>
<>ddxx</ii>>
aanndd aa vveerrttiiccaall ddiiaammeetteerr ooff
<>ddyy</ii>>
wwiitthh tthhee lleeffttmmoosstt ppooiinntt aatt tthhee ccuurrrreenntt ppoossiittiioonn..
HHTTMMLL--IIMMAAGGEEddeelliimm $$$$
HHTTMMLL--IIMMAAGGEE--EENNDD..
<>
DDrraaww aa ppoollyyggoonn wwiitthh,, ffoorr $$ii == 11 ,,......,, nn++11$$,, tthhee
<>
<>ii</ii>>--tthh
vveerrtteexx aatt tthhee ccuurrrreenntt ppoossiittiioonn
$$++ ssuumm ffrroomm jj==11 ttoo ii--11 (( ddxx ssuubb jj ,, ddyy ssuubb jj ))$$..
AAtt tthhee mmoommeenntt,, GGNNUU ppiicc oonnllyy uusseess tthhiiss ccoommmmaanndd ttoo ggeenneerraattee ttrriiaanngglleess
aanndd rreeccttaanngglleess..
<>
LLiikkee
<>
<>DDpp</bb>>
bbuutt ddrraaww aa ssoolliidd rraatthheerr tthhaann oouuttlliinneedd ppoollyyggoonn..
<>
SSeett tthhee ccuurrrreenntt lliinnee tthhiicckknneessss ttoo
<>
<>nn</ii>>
mmaacchhiinnee uunniittss..
TTrraaddiittiioonnaallllyy UUnniixx ttrrooffff ddrriivveerrss uussee aa lliinnee tthhiicckknneessss pprrooppoorrttiioonnaall ttoo
tthhee ccuurrrreenntt ppooiinntt ssiizzee;; ddrriivveerrss sshhoouulldd ccoonnttiinnuuee ttoo ddoo tthhiiss iiff nnoo
<>DDtt</bb>>
ccoommmmaanndd hhaass bbeeeenn ggiivveenn,, oorr iiff aa
<>DDtt</bb>>
ccoommmmaanndd hhaass bbeeeenn ggiivveenn wwiitthh aa nneeggaattiivvee vvaalluuee ooff
<>nn</ii>>..
AA zzeerroo vvaalluuee ooff
<>nn</ii>>
sseelleeccttss tthhee ssmmaalllleesstt aavvaaiillaabbllee lliinnee tthhiicckknneessss..
</ddll>>
<>
AA ddiiffffiiccuullttyy aarriisseess iinn hhooww tthhee ccuurrrreenntt ppoossiittiioonn sshhoouulldd bbee cchhaannggeedd aafftteerr
tthhee eexxeeccuuttiioonn ooff tthheessee ccoommmmaannddss..
TThhiiss iiss nnoott ooff ggrreeaatt iimmppoorrttaannccee ssiinnccee tthhee ccooddee ggeenneerraatteedd bbyy GGNNUU ppiicc
ddooeess nnoott ddeeppeenndd oonn tthhiiss..
GGiivveenn aa ddrraawwiinngg ccoommmmaanndd ooff tthhee ffoorrmm
<>
<>
<></bb>>
\\DD''_c $x sub 1$ $y sub 1$ $x sub 2$ $y sub 2$ $...$ $x sub n$ $y sub n$'
-
where
c
is not one of
c,
e,
l,
a,
or
~,
Unix troff will treat each of the $x sub i$ as a horizontal quantity,
and each of the $y sub i$ as a vertical quantity and will assume that
the width of the drawn object is $sum from i=1 to n x sub i$,
and that the height is $sum from i=1 to n y sub i$.
(The assumption about the height can be seen by examining the
st
and
sb
registers after using such a
D
command in a \w escape sequence).
This rule also holds for all the original drawing commands with the
exception of
De.
For the sake of compatibility GNU troff also follows this rule, even
though it produces an ugly result in the case of the
Dt
and
Df,
and, to a lesser extent,
DE
commands.
Thus after executing a
D
command of the form
-
DD_c $x sub 1$ $y sub 1$ $x sub 2$ $y sub 2$ $...$
-
$x sub n$ $y sub n$\n
the current position should be increased by
$( sum from i=1 to n x sub i , sum from i=1 to n y sub i )$.
Another set of extensions is
-
-
-
-
-
-
-
-
-
Set the color components of the filling color similar to the
-
m
commands above.
The current position isn't changed by those colour commands (contrary to
Df).
Device Control Commands
There is a continuation convention which permits the argument to the
x X
command to contain newlines: when outputting the argument to the
x X
command, GNU troff will follow each newline in the argument with a
+
character (as usual, it will terminate the entire argument with a
newline); thus if the line after the line containing the
x X
command starts with
+,
then the newline ending the line containing the
x X
command should be treated as part of the argument to the
x X
command, the
+
should be ignored, and the part of the line following the
+
should be treated like the part of the line following the
x X
command.
The 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
troff
or for other implementations of roff in a consistent way.
Compatibility mode can be turned on with the
command line option, and turned on or off with the
request.
The number register
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
-
as defining a string
ab
with contents
cd.
In
groff
mode, this will be considered as a call of a macro named
Also
classical troff
interprets
or
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
(character c) in names of strings, macros, diversions, number
registers, fonts or environments, whereas
classical troff
does.
The
escape sequence can be helpful in avoiding these escape sequences in
names.
Fractional pointsizes cause one noteworthy incompatibility.
In
classical
troff,
the
request ignores scale indicators and so
.ps 10u
will set the pointsize to 10 points, whereas in groff native mode the
pointsize will be set to 10 scaled points.
In
groff,
there is a fundamental difference between unformatted input
characters, and formatted output characters (glyphs).
Everything that affects how a glyph will be output is
stored with the glyph; once a glyph has been
constructed it is unaffected by any subsequent requests that are
executed, including the
or
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 combination.
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.
With
GNU troff
this will be printed as
So each pair of input backslashes
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
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
escape sequence; this works if the current escape character is not
redefined.
It works in both GNU mode and compatibility mode, while dirty tricks
like specifying a sequence of multiple backslashes 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.
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:
-
The positioning after the drawing of the polygons conflicts with the
-
classical definition.
-
The intermediate output cannot be rescaled to other devices as
-
classical "device-independent" troff did.
AUTHORS
Copyright (C) 1989, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
This document is distributed under the terms of the FDL (GNU Free
Documentation License) version 1.1 or later.
You should have received a copy of the FDL on your system, it is also
available on-line at the
GNU copyleft site .
This document was written by James Clark, with modifications by
Werner Lemberg
and
Bernd Warken .
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 complete reference of all predefined
requests, registers, and escapes of plain
groff.
From the command line, this is called using
-
-
shell# mmaann 77 ggrrooffff
-
roff(7)
-
A survey of
roff
systems, including pointers to further historical documentation.
-
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 .