@G@TROFF(1) @G@TROFF(1)NAME
@g@troff - format documents
SYNOPSIS
@g@troff [ -abivzCER ] [ -wname ] [ -Wname ] [ -dcs ] [ -ffam ]
[ -mname ] [ -nnum ] [ -olist ] [ -rcn ] [ -Tname ] [ -Fdir ]
[ -Mdir ] [ files... ]
DESCRIPTION
This manual page describes the GNU version of troff, which is part of
the groff document formatting system. It is highly compatible with
Unix 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 be cor‐
rect: troff'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@.
-R Don't load troffrc.
-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 means 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 troff 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 nor‐
mal @FONTDIR@.
-Mdir Search directory dir for macro files before the normal
@MACRODIR@.
USAGE
Only the features not in Unix troff are described here.
Long names
The names of number registers, fonts, strings/macros/diversions, spe‐
cial 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 spec‐
ified 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 troff interpret arguments that represent a point‐
size 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 a 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. Similarily it would make no sense to use a scal‐
ing indicator other than z or u in a numeric expression whose default
scale indicator was z, and so troff disallows this as well.
There is also a 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
\A'anything'
This expands to 1 or 0 according as anything is or is not
acceptable as the name of a string, macro, diversion, number
register, environment or font. It will return 0 if anything is
empty. This is useful if you want to lookup user input in some
sort of associative table.
\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 inter‐
preted in copy-mode. For example, strings to start and end
superscripting could be defined like this:
.ds { \v'-.3m'\s'\En[.s]*6u/10u'
.ds } \s0\v'.3m'
The use of \E ensures that these definitions will work even if
\*{ gets interpreted in copy-mode (for example, by being used in
a macro argument.)
\N'n' Typeset the character with code n in the current font. n can be
any integer. Most devices only have characters with codes
between 0 and 255. If the current font does not contain a char‐
acter with that code, 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.
\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 exten‐
sion to the Unix troff output format, and will confuse drivers
that do not know about this extension.
\Z'anything'
Print anything and then restore the horizontal and vertical
position; anything may not contain tabs or leaders.
\$0 The name by which the current macro was invoked. The als
request can make a macro have more than one name.
\$* In a macro, 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 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 prob‐
lem. 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 when‐
ever 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.
\~ This produces an unbreakable space that stretches like a normal
inter-word space when a line is adjusted.
\# Everything up to and including the next newline is ignored.
This is interpreted in copy mode. This 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.
.asciify xx
This request only exists in order to make it possible to make
certain gross hacks work with GNU troff. It `unformats' the
diversion xx in such a way that ASCII characters that were for‐
matted and diverted into xx will be treated like ordinary input
characters when xx is reread. For example, this
.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 char‐
acters -\(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 hav‐
ing a zero space factor in TeX (initially characters
"')]*\(dg\(rq 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 environ‐
ment 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 embolden‐
ing, constant spacing or track kerning will be applied to this
object rather than to individual characters in string. A char‐
acter 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 pat‐
terns can be drawn with the character using the \l and \L escape
sequences; words containing the character can be hyphenated cor‐
rectly, if the hcode request is used to give the character a
hyphenation code. There is a special anti-recursion feature:
use of character within the character's definition will be han‐
dled like normal characters not defined with char. A character
definition can be removed with the rchar request.
.chop xx
Chop the last character off macro, string, or diversion xx.
This is useful for removing the newline from the end of diver‐
sions 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, other‐
wise disable it. In compatibility mode, long names are not
recognised, and the incompatibilities caused by long names do
not arise.
.do xxx
Interpret .xxx with compatibility mode disabled. For example,
.do fam T
would have the same effect as
.fam T
except that it would work even if compatibility mode had been
enabled. Note that the previous compatibility mode is restored
before any files sourced by xxx are interpreted.
.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 equal to f then font f will not be translated.
.hcode c1 code1 c2 code2...
Set the hyphenation code of character c1 to code1 and that of c2
to code2. A hyphenation code must be a single input character
(not a special character) other than a digit or a space. Ini‐
tially each lower-case letter has a hyphenation code, which is
itself, and each upper-case letter has a hyphenation code which
is the lower case version of itself. See also the hpf request.
.hla lang
Set the current hyphenation language to lang. Hyphenation
exceptions specified with the hw request and hyphenation pat‐
terns specified with the hpf request are both associated with
the current hyphenation language. The hla request is usually
invoked by the troffrc file.
.hlm n Set the maximum number of consecutive hyphenated lines to n. If
n is negative, there is no maximum. The default value is -1.
This value is associated with the current environment. Only
lines output from an environment count towards the maximum asso‐
ciated with that environment. Hyphens resulting from \% are
counted; explicit hyphens are not.
.hpf file
Read hyphenation patterns from file; this will be searched for
in the same way that tmac.name is searched for when the -mname
option is specified. It should have the same format as the
argument to the \patterns primitive in TeX; the letters appear‐
ing in this file are interpreted as hyphenation codes. A %
character in the patterns file introduces a comment that contin‐
ues to the end of the line. 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.
.hym n Set the hyphenation margin to n: when the current adjustment
mode is not b, the line will not be hyphenated if the line is no
more than n short. The default hyphenation margin is 0. The
default scaling indicator for this request is m. The hyphen‐
ation margin is associated with the current environment. The
current hyphenation margin is available in the \n[.hym] regis‐
ter.
.hys n Set the hyphenation space to n: when the current adjustment mode
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.
.mso file
The same as the so request except that file is searched for in
the same way that tmac.name is searched for when the -mname
option is specified.
.nroff Make the n built-in condition true and the t built-in condition
false. This can be reversed using the troff request.
.open stream filename
Open filename for writing and associate the stream named stream
with it. See also the close and write requests.
.opena stream filename
Like open, but if filename exists, append to it instead of trun‐
cating it.
.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.
.rchar c1 c2...
Remove the definitions of characters c1, c2,... This undoes the
effect of a char 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
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.
.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 character which will be inserted when a
word is hyphenated at a line break. If the soft hyphen charac‐
ter does not exist in the font of the character immediately pre‐
ceding 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 avail‐
able. If n is missing, arguments will be shifted by 1. Shift‐
ing 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 exam‐
ple, if the current font is 1 and font position 1 is associated
with style R and the current font family is T, then font TR will
be used. If the current font is not a style, then the current
family is ignored. When the requests cs, bd, tkf, uf, or fspe‐
cial are applied to a style, then they will instead be applied
to the member of the current family corresponding to that style.
The default family can be set with the -f option. The styles
command in the DESC file controls which font positions (if any)
are initially associated with styles rather than fonts.
.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 troff input characters.
.trnt abcd
This is the same as the tr request except that the translations
do not apply to text that is transparently throughput into a
diversion with \!. For example,
.tr ab
.di x
\!.tm a
.di
.x
will print b; if trnt is used instead of tr it will print a.
.troff Make the n built-in condition false, and the t built-in condi‐
tion true. This undoes the effect of the nroff request.
.vpt n Enable vertical position traps if n is non-zero, disable them
otherwise. Vertical position traps are traps set by the wh or
dt requests. Traps set by the it request are not vertical posi‐
tion traps. The parameter that controls whether vertical posi‐
tion traps are enabled is global. Initially vertical position
traps are enabled.
.warn n
Control warnings. n is the sum of the numbers associated with
each warning that is to be enabled; all other warnings will be
disabled. The number associated with each warning is listed in
the `Warnings' section. For example, .warn 0 will disable all
warnings, and .warn 1 will disable all 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 previ‐
ously 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 Unix
troff, the contents of filename is immediately copied through to
the output regardless of whether there is a current diversion;
this behavior is so anomalous that it must be considered a bug.
.ev xx If xx is not a number, this will switch to a named environment
called xx. The environment should be popped with a matching ev
request without any arguments, just as for numbered environ‐
ments. 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 inter‐
nal name of the font which is used to refer to the font in troff
after it has been mounted. If there is no third argument then
the internal name will be used as the external name. This fea‐
ture 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 argu‐
ment 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. The sentence space size is used in two circum‐
stances: if the end of a sentence occurs at the end of a line in
fill mode, then both an inter-word space and a sentence space
will be added; if two spaces follow the end of a sentence in the
middle of a line, then the second space will be a sentence
space. Note that the behaviour of Unix troff will be exactly
that exhibited by GNU troff if a second argument is never given
to the ss request. In GNU troff, as in Unix troff, you should
always follow a sentence with either a newline or two spaces.
.ta n1 n2...nn T r1 r2...rn
Set tabs at positions n1, n2,..., nn and then set tabs at nn+r1,
nn+r2,...., nn+rn and then at nn+rn+r1, nn+rn+r2,..., nn+rn+rn,
and so on. For example,
.ta T .5i
will set tabs every half an inch.
New number registers
The following read-only registers are available:
\n[.C] 1 if compatibility mode is in effect, 0 otherwise.
\n[.cdp]
The depth of the last character added to the current environ‐
ment. It is positive if the character extends below the base‐
line.
\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 environ‐
ment. It is positive if the character extends above the base‐
line.
\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.
\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 GNU troff.
\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[.kern]
1 if pairwise kerning is enabled, 0 otherwise.
\n[.lg]
The current ligature mode (as set by the lg request.)
\n[.ll]
The line length that applies to the current output line.
\n[.lt]
The title length as set by the lt request.
\n[.ne]
The amount of space that was needed in the last ne request that
caused a trap to be sprung. Useful in conjunction with the
\n[.trunc] register.
\n[.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[.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 actu‐
ally 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.
\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 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,
characters from that font will be kerned. Kerning between two charac‐
ters can be inhibited by placing a \& between them.
In a string comparison in a condition, characters that appear at dif‐
ferent input levels to the first delimiter character will not be recog‐
nized as the second or third delimiters. This applies also to the tl
request. In a \w escape sequence, a character that appears at a dif‐
ferent input level to the starting delimiter character will not be
recognised as the closing delimiter character. 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 at the same input level, which will be different to the input
level of the argument itself. In a long escape name ] will not be rec‐
ognized as a closing delimiter except when it occurs at the same input
level as the opening ]. In compatibility mode, no attention is paid to
the input-level.
There are some new types of condition:
.if rxxx
True if there is a number register named xxx.
.if dxxx
True if there is a string, macro, diversion, or request named
xxx.
.if 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 troff 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.
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 unde‐
fined number register is used, that register is
automatically defined to have a value of 0. a defi‐
nition 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 unde‐
fined name longer than two characters is encoun‐
tered, 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.
This warning will never occur in compatibility mode.
font 131072 Non-existent fonts. This is enabled by default.
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 useful with traditional macro pack‐
ages.
w All warnings.
Incompatibilities
Long names cause some incompatibilities. Unix troff will interpret
.dsabcd
as defining a string ab with contents cd. Normally, GNU troff will
interpret this as a call of a macro named dsabcd. Also Unix troff will
interpret \*[ or \n[ as references to a string or number register
called [. In GNU troff, however, this will normally be interpreted as
the start of a long name. In compatibility mode GNU troff will inter‐
pret these things in the traditional way. In compatibility mode, how‐
ever, 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.
GNU troff does not allow the use of the escape sequences
\\|\^\&\}\{\(space)\'\`\-\_\!\%\c in names of strings, macros, diver‐
sions, number registers, fonts or environments; Unix troff does. The
\A escape sequence may be helpful in avoiding use of these escape
sequences in names.
Fractional pointsizes cause one noteworthy incompatibility. In Unix
troff the ps request ignores scale indicators and so
.ps 10u
will set the pointsize to 10 points, whereas in GNU troff it will set
the pointsize to 10 scaled points.
In GNU troff 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 char‐
acter; 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 charac‐
ter 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
.x
will print \\ in GNU troff; 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. Unix 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 diver‐
sion; it will also work in both GNU troff and Unix 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 tradi‐
tional \! transparent output facility, or, if this is unsuitable, the
new \? escape sequence.
ENVIRONMENT
GROFF_TMAC_PATH
A colon separated list of directories in which to search for
macro files.
GROFF_TYPESETTER
Default device.
GROFF_FONT_PATH
A colon separated list of directories in which to search for the
devname directory. troff will search in directories given in
the -F option before these, and in standard directories (@FONT‐
PATH@) after these.
FILES
@MACRODIR@/troffrc Initialization file
@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@) @g@tbl(@MAN1EXT@), @g@pic(@MAN1EXT@),
@g@eqn(@MAN1EXT@), grops(@MAN1EXT@), grodvi(@MAN1EXT@),
grotty(@MAN1EXT@), groff_font(@MAN5EXT@), groff_out(@MAN5EXT@),
groff_char(@MAN7EXT@)
Groff Version @VERSION@ @MDATE@ @G@TROFF(1)
