NAME
gtroff - format documents
SYNOPSIS
gtroff [ -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 correct: 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
/usr/products/src2/gcc/AIX.d/lib/groff/tmac.
-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. Troff will exit after printing
the last page in the list.
-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 ps.
-Fdir Search dir for subdirectories devname (name is the
name of the device) for the DESC file and font
files before the normal
/usr/products/src2/gcc/AIX.d/lib/groff/font.
-Mdir Search directory dir for macro files before the
normal
/usr/products/src2/gcc/AIX.d/lib/groff/tmac.
USAGE
Only the features not in Unix 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
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 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 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.
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
interpreted 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 character 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 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, 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 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.
\~ 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 formatted 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); 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 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 character c to be string. Every time character
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 characters in
string. 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. 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 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.
.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 after 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. 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. 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 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 appearing in this file
are interpreted as hyphenation codes. A % character in
the patterns file introduces a comment that continues
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 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.
.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 truncating it.
.pnr Print the names and contents of all currently defined
number registers on stderr.
.pso command
This is 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.
.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 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.
.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 character does not exist in
the font of the character 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.
.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 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
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 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 Unix troff, the contents of filename
is immediately copied through to the output regardless
of whether there is a current diversion; this behaviour
is so anomalous that it must be considered a bug.
.ev xx
If xx is not a number, this will switch to a named
environment called xx. The environment should be
popped with a matching ev request without any
arguments, just as for numbered 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 troff 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 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 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
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.
\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
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.
\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 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
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 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 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 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 Inappropriate use of a tab character.
Either use of a tab character where a
number was expected, or use of tab
character in an unquoted macro argument.
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. This warning
will never occur in compatibility mode.
font 131072 Non-existent fonts. This is enabled by
default.
ig 262144 Illegal escapes in text ignored with the
ig request. These are conditions that
are errors when they do not occur in
ignored text.
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 packages.
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 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.
GNU troff does not allow the use of the escape sequences
\\|\^\&\}\{\(space)\'\`\-\_\!\%\c in names of strings,
macros, diversions, 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 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
.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 diversion; 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 traditional
\! 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
(.:/usr/products/src2/gcc/AIX.d/lib/groff/font:/usr/products/src2/gcc/AIX.d/lib/font:/usr/lib/font)
after these.
FILES
/usr/products/src2/gcc/AIX.d/lib/groff/tmac/troffrc
Initialization file
/usr/products/src2/gcc/AIX.d/lib/groff/tmac/tmac.name
Macro files
/usr/products/src2/gcc/AIX.d/lib/groff/font/devname/DESC
Device description file for device name.
/usr/products/src2/gcc/AIX.d/lib/groff/font/devname/F
Font file for font F of device name.
SEE ALSO
groff(1) gtbl(1), gpic(1), geqn(1), grops(1), grodvi(1),
grotty(1), groff_font(5), groff_out(5), groff_char(7)