GTROFF(1) 386BSD Reference Manual GTROFF(1)
NAME
gtroff - format documents
SYNOPIS
gtroff [ -abivzCE ] [ -wname ] [ -Wname ] [ -dcs ]
[ -ffam ] [ -mname ] [ -nnum ] [ -olist ] [ -rcn ]
[ -Tname ] [ -Fdir ] [ -Mdir ] [ -Hfile ]
[ files... ]
DESCRIPTION
gtroff is the central part of the groff document
formatting system. It is highly compatible with device-
independent troff. Usually it should be invoked using the
groff command, which will also run preprocessors and
postprocessors in the appropriate order and with the
appropriate options.
OPTIONS
-a Generate an ASCII approximation of the typeset
output.
-b Print a backtrace with each warning or error
message. This backtrace should help track down
the cause of the error. The line numbers given
in the backtrace may not always correct:
gtroff's idea of line numbers gets confused by
as or am requests.
-i Read the standard input after all the named
input files have been processed.
-v Print the version number.
-wname Enable warning name. Available warnings are
described in the Warnings subsection below.
Multiple -w options are allowed.
-Wname Inhibit warning name. Multiple -W options are
allowed.
-E Inhibit all error messages.
-z Suppress formatted output.
-C Enable compatibility mode.
-dcs
-dname=s Define c or name to be a string s; c must be a
one letter name.
-ffam Use fam as the default font family.
-mname Read in the file tmac.name. Normally this will
be searched for in @MACRODIR@.
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-nnum Number the first page num.
-olist Output only pages in list, which is a comma-
separated list of page ranges; n means print
page n, m-n means print every page between m and
n, -n mans print every page up to n, n- means
print every page from n.
-rcn
-rname=n Set number register c or name to n; c must be a
one character name; n can be any gtroff numeric
expression.
-Tname Prepare output for device name, rather than the
default @DEVICE@.
-Fdir Search dir for subdirectories devname (name is
the name of the device) for the DESC file and
font files before the normal @FONTDIR@.
-Hfile Read hyphenation patterns from file, rather than
the default @HYPHENFILE@.
-Mdir Search directory dir for macro files before the
normal @MACRODIR@.
USAGE
Only the features not in device-independent troff are
described here.
Long names
The names of number registers, fonts,
strings/macros/diversions, special characters can be of
any length. In escape sequences, where you can use (xx for
a two character name, you can use [xxx] for a name of
arbitrary length:
\[xxx] Print the special character called xxx.
\f[xxx]
Set font xxx.
\*[xxx]
Interpolate string xxx.
\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 which has the effect of
multiplying by sizescale. Requests and escape sequences
in gtroff interpret arguments that represent a pointsize
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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 request .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 gtroff disallows this. Similarily
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 gtroff 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.
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
\C'xxx'
Typeset character 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's
not interpreted in copy-mode. For example, strings
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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.)
\N'n' Typeset the character with code n in the current
font. n must be a decimal integer between 0 and
255. If the current font does not contain the
character, special fonts will not be searched. The
\N escape sequence can be conveniently used on
conjunction with the char request:
.char \[phone] \f(ZD\N'37'
The code of each character is given in the fourth
column in the font description file after the
charset command. It is possible to include unnamed
characters in the font description file by using a
name of ---; the \N escape sequence is the only way
to use these.
\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.
\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 troff output format,
and will confuse drivers that do not know about
this extension.
\Z'anything'
Print anything and then restore the horizontal and
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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 can have more than
one name.
\$* In a macro, the concatenation of all the arguments
separated by spaces.
\$@ In a macro, the concatenation of all the arguments
with each surrounded by double quotes, and
separated by spaces.
\$(nn
\$[nnn]
In a macro, this gives the nn-th or nnn-th
argument. Macros can have a 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
\?\\?\\\\?\\\\\\\\nx\\\\?\\?\?
.di
.nr x 2
.di e
.d
.di
.nr x 3
.di f
.e
.di
.nr x 4
.f
will print 4.
\/ This increases the width of the preceding character
so that the spacing between that character and the
following character will be correct if the
following character is a roman character. For
example, if an italic f is immediately followed by
a roman right parenthesis, then in many fonts the
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top right portion of the f will overlap the top
left of the right parenthesis producing f), which
is ugly. Inserting \/ produces f) and avoids this
problem. It is a good idea to use this escape
sequence whenever an italic character is
immediately followed by a roman character without
any intervening space.
\, This modifies the spacing of the following
character so that the spacing between that
character and the preceding character will correct
if the preceding character is a roman character.
For example, inserting \, between the parenthesis
and the f changes (f to (f. It is a good idea to
use this escape sequence whenever a roman character
is immediately followed by an italic character
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.
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.
.asciify xx
This request only exists in order to make it
possible to make certain gross troff hacks work
with gtroff. It `unformats' the diversion xx in
such a way that ASCII characters that were
formatted and diverted into xx will be treated like
ordinary input characters when xx is reread. For
example, this
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.tr @.
.di x
@nr\ n\ 1
.br
.di
.tr @@
.asciify x
.x
will set register n to 1.
.backtrace
Print a backtrace of the input stack on stderr.
.break Break out of a while loop. See also the while and
continue requests. Be sure not to confuse this
with the br request.
.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);
4 lines can be broken after the character
(initially characters -\(hy\(em have this
property);
8 the character overlaps horizontally
(initially characters \(ul\(rn\(ru 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 have this property).
.char c string
Define character c to be string. Every time
character c needs to be printed, string will be
processed in a temporary environment and the result
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will be wrapped up into a single object. A
character defined by this request can be used just
like a normal character 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 character within the
character's definition will be handled like normal
characters not defined with char.
.chop xx
Chop the last character 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.
.continue
Finish the current iteration of a while loop. See
also the while and break requests.
.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.
.fam xx
Set the current font family to xx. The current
font family is part of the current environment.
See the description of the sty request for more
information on font families.
.fspecial f s1 s2...
When the current font is f, fonts s1, s2,... will
be special, that is, they will searched for
characters not in the current font. Any fonts
specified in the special request will be searched
before fonts specified in the fspecial request.
.ftr f g
Translate font f to g. Whenever a font named f is
referred to in \f escape sequence, or in the ft,
ul, bd, cs, tkf, special, fspecial, fp, or sty
requests, font g will be used. If g is missing, or
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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.
Initially each lower-case letter has a hyphenation
code, which is itself, and each upper-case letter
has a hyphenation code which is the lower case
version of itself. Hyphenation is controlled by a
file of hyphenation patterns (normally
@HYPHENFILE@); this file should have the same
format as the argument to the \patterns primitive
in TeX; the letters appearing in this file are
interpreted as hyphenation codes.
.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.
.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.
.kern n
If n is non-zero or missing, enable pairwise
kerning, otherwise disable it.
.nroff Make the n built-in condition true and the t built-
in condition false. This can be reversed using the
troff request.
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.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.
.pnr Print the names and contents of all currently
defined number registers on stderr.
.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.
.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 justifed 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.
.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.
.special s1 s2...
Fonts s1, s2, are special and will be searched for
characters not in the current font.
.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
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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.
.tkf f s1 n1 s2 n2
Enable track kerning for font f. When the current
font is f the width of every character 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.
.trf filename
Transparently output the contents of file filename.
Each line is output as it would be were it 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
.di x
.trf f
.di
Unlike with the cf request, the file cannot contain
characters such as NUL that are not legal gtroff
input characters.
.troff Make the n built-in condition false, and the t
built-in condition true. This undoes the effect of
the nroff request.
.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 the
`Warnings' section. For example, .warn 0 will
disable all warnings, and .warn 1 will disable all
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warnings except that about missing characters. If
n is not given, all warnings will be enabled.
.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.
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 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 environments.
There is no limit on the number of named
environments; they will be created the first time
that they are referenced.
.fp n f1 f2
The fp request has an optional third argument.
This argument gives the external name of the font,
which is used for finding the font description
file. The second argument gives the internal name
of the font which is used to refer to the font in
gtroff after it has been mounted. If there is no
third argument then the internal name will be used
as the external name. This feature allows you to
use fonts with long names in compatibility mode.
.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
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for the current font. Initially both the word
space size and the sentence space size are 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 troff will be
exactly that exhibited by gtroff if a second
argument is never given to the ss request. In
gtroff, as in 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 character added to the
current environment. It is positive if the
character 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 character added to the
current environment. It is positive if the
character extends above the baseline.
\n[.csk]
The skew of the last character added to the current
environment. The skew of a character is how far to
the right of the center of a character the center
of an accent over that character should be placed.
\n[.ev]
The name or number of the current environment.
This is a string-valued register.
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\n[.fam]
The current font family. This is a string-valued
register.
\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 gtroff.
\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[.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[.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.
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\n[.psr]
The last-requested pointsize in scaled points.
\n[.rj]
The number of lines to be right-justified as set by
the rj request.
\n[.sr]
The last requested pointsize in points as a decimal
fraction. 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[.ss]
\n[.sss]
These give the values of the parameters set by the
first and second arguments of the ss request.
\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 the `Warnings'
subsection.
\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.
The following registers are set by the \w escape sequence:
\n[rst]
\n[rsb]
Like the st and sb registers, but takes account of
the heights and depths of characters.
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\n[ssc]
The amount of horizontal space (possibly negative)
that should be added to the last character before a
subscript.
\n[skw]
How far to right of the center of the last
character in the \w argument, the center of an
accent from a roman font should be placed over that
character.
The following read/write number registers are available:
\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.
Miscellaneous
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 gtroff 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, characters from that font will be kerned.
Kerning between two characters 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
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input level to the starting delimiter character will not
be recognised as the closing delimiter character. When
decoding a macro 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 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 cch
True if there is a character ch available; ch is
either an ASCII character or a special character
\(xx or \[xxx]; the condition will also be true if
ch has been defined by the char request.
Warnings
The warnings that can be given by gtroff are divided into
the following categories. The name associated with each
warning is used by the -w and -W options; the number is
used by the warn request, and by the .warn register.
char 1 Non-existent characters. This is
enabled by default.
number 2 Invalid numeric expressions. This is
enabled by default.
break 4 In fill mode, lines which could not be
broken so that their length was less
than the line length. This is enabled
by default.
delim 8 Missing or mismatched closing
delimiters.
el 16 Use of the el request with no matching
ie request.
scale 32 Meaningless scaling indicators.
range 64 Out of range arguments.
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syntax 128 Dubious syntax in numeric expressions.
di 256 Use of di or da without an argument
when there is no current diversion.
mac 512 Use of undefined strings, macros and
diversions. When an undefined string,
macro or diversion is used, that string
is automatically defined as empty. So,
in most cases, at most one warning will
be given for each name.
reg 1024 Use of undefined number registers.
When an undefined number register is
used, that register is automatically
defined to have a value of 0. a
definition is automatically made with a
value of 0. So, in most cases, at most
one warning will be given for use of a
particular name.
tab 2048 Use of a tab character where a number
was expected.
right-brace 4096 Use of \} where a number was expected.
missing 8192 Requests that are missing non-optional
arguments.
input 16384 Illegal input characters.
escape 32768 Unrecognized escape sequences. When an
unrecognized escape sequence is
encountered, the escape character is
ignored.
space 65536 Missing space between a request or
macro and its argument. This warning
will be given when an undefined name
longer than two characters is
encountered, and the first two
characters of the name make a defined
name. The request or macro will not be
invoked. When this warning is given,
no macro is automatically defined.
This is enabled by default. mac is
given. This warning will never occur
in compatibility mode.
There are also names that can be used to refer to groups
of warnings:
all All warnings except di, mac and reg. It is
intended that this covers all warnings that are
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useful with traditional macro packages.
w All warnings.
Incompatibilities
Long names cause some incompatibilities. Troff will
interpret
.dsabcd
as defining a string ab with contents cd. Normally,
gtroff will interpret this as a call of a macro named
dsabcd. Also troff will interpret \*[ or \n[ as
references to a string or number register called [. In
gtroff, however, this will normally be interpreted as the
start of a long name. In compatibility mode gtroff will
interpret these things in the traditional way. In
compatibility mode, however, long names are not
recognised. 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.
Fractional pointsizes cause one noteworthy
incompatibility. In troff the ps request ignores scale
indicators and so
.ps 10u
will set the pointsize to 10 points, whereas in gtroff it
will set the pointsize to 10 scaled points.
In gtroff there is a fundamental difference between
unformatted, input characters, and formatted, output
characters. Everything that affects how an output
character will be output is stored with the character;
once an output character has been constructed it is
unaffected by any subsequent requests that are executed,
including bd, cs, tkf, tr, or fp requests. Normally
output characters are constructed from input characters at
the moment immediately before the character 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 output characters in any
combination. An output character 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. For example,
.di x
\\\\
.br
.di
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.x
will print \\ in gtroff; each pair of input \s is turned
into one output \ and the resulting output \s are not
interpreted as escape characters when they are reread.
Troff would interpret them as escape characters when they
were reread and would end up printing one \. The correct
way to obtain a printable \ is to use the \e escape
sequence: this will always print a single instance of the
current escape character, regardless of whether or not it
is used in a diversion; it will also work in both gtroff
and troff. If you wish for some reason to store in a
diversion an escape sequence that will be interpreted when
the diversion is reread, you can either use the
traditional \! transparent output facility, or, if this
is unsuitable, the new \? escape sequence.
ENVIRONMENT
GROFFTMACPATH
A colon separated list of directories in which to
search for macro files.
GROFFTYPESETTER
Default device.
GROFFFONTPATH
A colon separated list of directories in which to
search for the devname directory. Gtroff will
search in directories given in the -F option before
these, and in standard directories (@FONTPATH@)
after these.
GROFFHYPHEN
File containing hyphenation patterns.
FILES
@HYPHENFILE@ Hyphenation patterns
@MACRODIR@/tmac.name Macro files
@FONTDIR@/devname/DESC Device description file for
device name.
@FONTDIR@/devname/F Font file for font F of device
name.
SEE ALSO
groff(@MAN1EXT@) gtbl(@MAN1EXT@), gpic(@MAN1EXT@),
geqn(@MAN1EXT@), grops(@MAN1EXT@), grodvi(@MAN1EXT@),
grotty(@MAN1EXT@), grofffont(@MAN5EXT@),
groffout(@MAN5EXT@)
Groff Character Names
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