Manual Pages for UNIX Darwin command on man groff

Manual Pages for UNIX Darwin command on man groff_diff

GROFFDIFF(7) GROFFDIFF(7)

NAME

groffdiff - differences between GNU troff and classical troff

DESCRIPTION

This manual page describes the language differences between groff, the GNU roff text processing system and the classical roff formatter of the freely available Unix 7 of the 1970s, documented in the Troff User's Manual by Osanna and Kernighan. This inludes the roff language as well as the intermediate output format (troff output).

The section SEE ALSO gives pointers to both the classical roff and the

modern groff documentation. GGRROOFFFF LLAANNGGUUAAGGEE

In this section, all additional features of groff compared to the clas-

sical Unix 7 troff are described in detail. LLoonngg nnaammeess

The names of number registers, fonts, strings/macros/diversions, spe-

cial characters (glyphs), and colors can be of any length. In escape

sequences, additionally to the classical ((xx construction for a two-

character name, you can use [[xxx]] for a name of arbitrary length. \\[[xxx]] Print the special character (glyph) called xxx. \\[[comp1 comp2 ...]]

Print composite glyph consisting of multiple components. Exam-

ple: `\[A ho]' is capital letter A with ogonek which finally maps to glyph name `u00410328'. See the groff info file for details how a glyph name for a composite glyph is constructed,

and ggrrooffffcchhaarr(7) for list of glyph name components used compos-

ite glyph names. \\ff[[xxx]] Set font xxx. Additionally, \\ff[[]] is a new syntax equal to \\ffPP, i.e., to return to the previous font. \\**[[xxx arg1 arg2 ...]] Interpolate string xxx, taking arg1, arg2, ... as arguments. \\nn[[xxx]] Interpolate number register xxx. FFrraaccttiioonnaall ppooiinnttssiizzeess

A scaled point is equal to 11//ssiizzeessccaallee points, where ssiizzeessccaallee is spec-

ified in the DDEESSCC file (1 by default). There is a new scale indicator zz that has the effect of multiplying by sizescale. Requests and escape sequences in troff interpret arguments that represent a pointsize as being in units of scaled points, but they evaluate each such argument using a default scale indicator of zz. Arguments treated in this way are the argument to the ppss request, the third argument to the ccss

request, the second and fourth arguments to the ttkkff request, the argu-

ment to the \\HH escape sequence, and those variants of the \\ss escape sequence that take a numeric expression as their argument. For example, suppose sizescale is 1000; then a scaled point will be equivalent to a millipoint; the call ..ppss 1100..2255 is equivalent to ..ppss 1100..2255zz and so sets the pointsize to 10250 scaled points, which is equal to 10.25 points. The number register \\nn[[..ss]] returns the pointsize in points as decimal fraction. There is also a new number register \\nn[[..ppss]] that returns the pointsize in scaled points. It would make no sense to use the zz scale indicator in a numeric expression whose default scale indicator was neither uu nor zz, and so

ttrrooffff disallows this. Similarly it would make no sense to use a scal-

ing indicator other than zz or uu in a numeric expression whose default scale indicator was zz, and so ttrrooffff disallows this as well. There is also new scale indicator ss which multiplies by the number of units in a scaled point. So, for example, \\nn[[..ppss]]ss is equal to 11mm. Be sure not to confuse the ss and zz scale indicators. NNuummeerriicc eexxpprreessssiioonnss Spaces are permitted in a number expression within parentheses. MM indicates a scale of 100ths of an em. ff indicates a scale of 65536 units, providing fractions for color definitions with the ddeeffccoolloorr request. For example, 0.5f = 32768u. e1>>??e2 The maximum of e1 and e2. e1< or is not a valid numeric expression. It will return 00 if any-

thing is empty. \\CC''xxx'' Typeset glyph named xxx. Normally it is more convenient to use \\[[xxx]]. But \\CC has the advantage that it is compatible with recent versions of UNIX and is available in compatibility mode.

\\EE This is equivalent to an escape character, but it is not inter-

preted in copy-mode. For example, strings to start and end

superscripting could be defined like this

.ds { \v'-.3m'\s'\En[.s]*6u/10u'

.ds } \s0\v'.3m' The use of \\EE ensures that these definitions will work even if

\\**{{ gets interpreted in copy-mode (for example, by being used in

a macro argument). \\FFf \\FF((fm \\FF[[fam]] Change font family. This is the same as the ffaamm request. \\FF[[]] switches back to the previous color (note that \\FFPP won't work; it selects font family `P' instead). \\mmx \\mm((xx \\mm[[xxx]] Set drawing color. \\mm[[]] switches back to the previous color. \\MMx \\MM((xx \\MM[[xxx]] Set background color for filled objects drawn with the \\DD''...'' commands. \\MM[[]] switches back to the previous color. \\NN''n'' Typeset the glyph with index n in the current font. n can be any integer. Most devices only have glyphs with indices between 0 and 255. If the current font does not contain a glyph with that code, special fonts will not be searched. The \\NN escape sequence can be conveniently used in conjunction with the cchhaarr request, for example .char \[phone] \f(ZD\N'37' The index of each glyph is given in the fourth column in the font description file after the cchhaarrsseett command. It is possible to include unnamed glyphs in the font description file by using

a name of ---; the \\NN escape sequence is the only way to use

these. \\OOn \\OO[[n]] Suppressing troff output. The escapes \\0022, \\OO33, \\OO44, and \\OO55 are intended for internal use by ggrroohhttmmll. \\OO00 Disable any ditroff glyphs from being emitted to the device driver, provided that the escape occurs at the outer level (see \\OO33 and \\OO44). \\OO11 Enable output of glyphs, provided that the escape occurs at the outer level. \\OO00 and \\OO11 also reset the registers \\nn[[ooppmmiinnxx]],

\\nn[[ooppmmiinnyy]], \\nn[[ooppmmaaxxxx]], and \\nn[[ooppmmaaxxyy]] to -1. These four

registers mark the top left and bottom right hand corners of a box which encompasses all written glyphs. \\OO22 Provided that the escape occurs at the outer level, enable output of glyphs and also write out to stderr the page number and four registers encompassing the glyphs previously written since the last call to \\OO.

\\OO33 Begin a nesting level. At start-up, ttrrooffff is at outer

level. This is really an internal mechanism for ggrroohhttmmll while producing images. They are generated by running the troff source through ttrrooffff to the postscript device and gghhoossttssccrriipptt to produce images in PNG format. The \\OO33 escape will start a new page if the device is not html (to reduce the possibility of images crossing a page boundary). \\OO44 End a nesting level. \\OO55[[Pfilename]] This escape is ggrroohhttmmll specific. Provided that this escape occurs at the outer nesting level, write filename

to stderr. The position of the image, P, must be speci-

fied and must be one of l, r, c, or i (left, right, cen-

tered, inline). filename will be associated with the production of the next inline image.

\\RR''name +-n''

This has the same effect as

..nnrr name +-n

\\ss((nn

\\ss++-((nn

Set the point size to nn points; nn must be exactly two digits.

\\ss[[++-n]]

\\ss++-[[n]]

\\ss''++-n''

\\ss++-''n''

Set the point size to n scaled points; n is a numeric expression with a default scale indicator of zz. \\VVx \\VV((xx \\VV[[xxx]] Interpolate the contents of the environment variable xxx, as

returned by ggeetteennvv(3). \\VV is interpreted in copy-mode.

\\YYx \\YY((xx \\YY[[xxx]] This is approximately equivalent to \\XX''\\**[[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 \\XX 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. \\ZZ''anything'' Print anything and then restore the horizontal and vertical position; anything may not contain tabs or leaders.

\\$$00 The name by which the current macro was invoked. The aallss

request can make a macro have more than one name.

\\$$** In a macro or string, the concatenation of all the arguments

separated by spaces.

\\$$@@ In a macro or string, the concatenation of all the arguments

with each surrounded by double quotes, and separated by spaces.

\\$$((nn

\\$$[[nnn]]

In a macro or string, this gives the nn-th or nnn-th argument.

Macros and strings can have an unlimited number of arguments. \\??anything\\?? When used in a diversion, this will transparently embed anything in the diversion. anything is read in copy mode. When the diversion is reread, anything will be interpreted. anything may not contain newlines; use \\!! if you want to embed newlines in a diversion. The escape sequence \\?? is also recognised in copy mode and turned into a single internal code; it is this code that terminates anything. Thus .nr x 1 .nf .di d \?\\?\\\\?\\\\\\\\nx\\\\?\\?\? .di .nr x 2 .di e .d .di .nr x 3 .di f .e .di .nr x 4 .f will print 44. \\// This increases the width of the preceding glyph so that the

spacing between that glyph and the following glyph will be cor-

rect if the following glyph is a roman glyph. It is a good idea

to use this escape sequence whenever an italic glyph is immedi-

ately followed by a roman glyph without any intervening space. \\,, This modifies the spacing of the following glyph so that the spacing between that glyph and the preceding glyph will correct if the preceding glyph is a roman glyph. It is a good idea to use this escape sequence whenever a roman glyph is immediately followed by an italic glyph without any intervening space. \\)) Like \\&& except that it behaves like a character declared with

the ccffllaaggss request to be transparent for the purposes of end-of-

sentence recognition. \\~~ This produces an unbreakable space that stretches like a normal

inter-word space when a line is adjusted.

\\:: This causes the insertion of a zero-width break point. It is

equal to \\%% within a word but without insertion of a soft hyphen

character.

\\## Everything up to and including the next newline is ignored.

This is interpreted in copy mode. It is like \\"" except that \\"" does not ignore the terminating newline. NNeeww rreeqquueessttss ..aallnn 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 rreegg will be generated, and the request will be ignored. ..aallss 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 mmaacc will be generated, and the request will be ignored. The ddee, aamm, ddii, ddaa, ddss, and aass 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. ..aamm11 xx yy Similar to ..aamm, but compatibility mode is switched off during execution. To be more precise, a `compatibility save' token is

inserted at the beginning of the macro addition, and a `compati-

bility restore' token at the end. As a consequence, the requests aamm, aamm11, ddee, and ddee11 can be intermixed freely since the compatibility save/restore tokens only affect the macro parts defined by ..aamm11 and ..ddss11. ..aammii xx yy Append to macro indirectly. See the ddeeii request below for more information. ..aammii11 xx yy Same as the aammii request but compatibility mode is switched off during execution. ..aass11 xx yy Similar to ..aass, but compatibility mode is switched off during expansion. To be more precise, a `compatibility save' token is inserted at the beginning of the string, and a `compatibility restore' token at the end. As a consequence, the requests aass,

aass11, ddss, and ddss11 can be intermixed freely since the compatibil-

ity save/restore tokens only affect the (sub)strings defined by aass11 and ddss11. ..aasscciiiiffyy xx This request `unformats' the diversion xx in such a way that ASCII and space characters (and some escape sequences) that were formatted and diverted into xx will be treated like ordinary input characters when xx is reread. Useful for diversions in conjunction with the ..wwrriitteemm request. It can be also used for gross hacks; for example, this .tr @. .di x @nr n 1 .br .di .tr @@ .asciify x .x will set register nn to 1. Note that glyph information (font, font size, etc.) is not preserved; use ..uunnffoorrmmaatt instead. ..bbaacckkttrraaccee Print a backtrace of the input stack on stderr. ..bbllmm xx Set the blank line macro to xx. If there is a blank line macro, it will be invoked when a blank line is encountered instead of the usual troff behaviour. ..bbooxx xx ..bbooxxaa xx These requests are similar to the ddii and ddaa requests with the exception that a partially filled line will not become part of the diversion (i.e., the diversion always starts with a new line) but restored after ending the diversion, discarding the partially filled line which possibly comes from the diversion. ..bbrreeaakk Break out of a while loop. See also the wwhhiillee and ccoonnttiinnuuee requests. Be sure not to confuse this with the bbrr request. ..bbrrpp This is the same as \\pp. ..ccffllaaggss 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 char-

acters -\\[[hhyy]]\\[[eemm]] 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 \\[[uull]]\\[[rrnn]]\\[[rruu]]\\[[rraaddiiccaalleexx]]\\[[ssqqrrtteexx]] have this property). 16 The character overlaps vertically (initially character \\[[bbrr]] 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 ""''))]]**\\((ddgg\\((rrqq have this property). ..cchhaarr c string Define glyph c to be string. Every time glyph c needs to be printed, string will be processed in a temporary environment and

the result will be wrapped up into a single object. Compatibil-

ity mode will be turned off and the escape character will be set to \\ while string is being processed. Any emboldening, constant spacing or track kerning will be applied to this object rather than to individual glyphs in string. A glyph defined by this request can be used just like a normal

glyph provided by the output device. In particular other char-

acters can be translated to it with the ttrr request; it can be made the leader character by the llcc request; repeated patterns can be drawn with the character using the \\ll and \\LL escape

sequences; words containing the character can be hyphenated cor-

rectly, if the hhccooddee request is used to give the character a hyphenation code.

There is a special anti-recursion feature: Use of glyph within

the glyph's definition will be handled like normal glyphs not defined with cchhaarr. A glyph definition can be removed with the rrcchhaarr request. ..cchhoopp xx Chop the last element off macro, string, or diversion xx. This is useful for removing the newline from the end of diversions that are to be interpolated as strings. ..cclloossee stream Close the stream named stream; stream will no longer be an acceptable argument to the wwrriittee request. See the ooppeenn request. ..ccoommppoossiittee glyph1 glyph2 Map glyph name glyph1 to glyph name glyph2 if it is used in \\[[...]] with more than one component. ..ccoonnttiinnuuee Finish the current iteration of a while loop. See also the wwhhiillee and bbrreeaakk requests. ..ccoolloorr n

If n is non-zero or missing, enable colors (this is the

default), otherwise disable them.

..ccpp 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. ..ddeeffccoolloorr xxx scheme colorcomponents Define color. scheme can be one of the following values: rrggbb

(three components), ccyymm (three components), ccmmyykk (four compo-

nents), and ggrraayy or ggrreeyy (one component). Color components can be given either as a hexadecimal string or as positive decimal

integers in the range 0-65535. A hexadecimal string contains

all color components concatenated; it must start with either ##

or ####. The former specifies hex values in the range 0-255

(which are internally multiplied by 257), the latter in the

range 0-65535. Examples: #FFC0CB (pink), ##ffff0000ffff

(magenta). A new scaling indicator ff has been introduced which

multiplies its value by 65536; this makes it convenient to spec-

ify color components as fractions in the range 0 to 1. Example: .defcolor darkgreen rgb 0.1f 0.5f 0.2f Note that ff is the default scaling indicator for the ddeeffccoolloorr request, thus the above statement is equivalent to .defcolor darkgreen rgb 0.1 0.5 0.2

The color named ddeeffaauulltt (which is device-specific) can't be

redefined. It is possible that the default color for \\MM and \\mm is not the same. ..ddee11 xx yy Similar to ..ddee, but compatibility mode is switched off during execution. On entry, the current compatibility mode is saved and restored at exit. ..ddeeii xx yy Define macro indirectly. The following example .ds xx aa .ds yy bb .dei xx yy is equivalent to .de aa bb ..ddeeii11 xx yy Similar to the ddeeii request but compatibility mode is switched off during execution. ..ddoo 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. ..ddss11 xx yy Similar to ..ddss, but compatibility mode is switched off during expansion. To be more precise, a `compatibility save' token is inserted at the beginning of the string, and a `compatibility restore' token at the end. ..eeccss Save current escape character. ..eeccrr Restore escape character saved with eeccss. Without a previous call to eeccss, `\\' will be the new escape character. ..eevvcc xx Copy the contents of environment xx to the current environment. No pushing or popping of environments will be done. ..ffaamm xx Set the current font family to xx. The current font family is part of the current environment. If xx is missing, switch back

to previous font family. The value at start-up is `T'. See the

description of the ssttyy request for more information on font fam-

ilies. ..ffcchhaarr c string Define fallback glyph c to be string. The syntax of this request is the same as the cchhaarr request; the only difference is that a glyph defined with cchhaarr hides the glyph with the same name in the current font, whereas a glyph defined with ffcchhaarr is checked only if the particular glyph isn't found in the current font. This test happens before checking special fonts. ..ffsscchhaarr f c string Define fallback glyph c for font f to be string. The syntax of this request is the same as the cchhaarr request (with an additional argument to specify the font); a glyph defined with ffsscchhaarr is searched after the list of fonts declared with the ffssppeecciiaall request but before the list of fonts declared with ssppeecciiaall. ..ffssppeecciiaall f s1 s2... When the current font is f, fonts s1, s2,... will be special, that is, they will searched for glyphs not in the current font. Any fonts specified in the ssppeecciiaall request will be searched

after fonts specified in the ffssppeecciiaall request. Without argu-

ment, reset the list of global special fonts to be empty. ..ffttrr f g Translate font f to g. Whenever a font named f is referred to

in an \\ff escape sequence, or in the fftt, uull, bbdd, ccss, ttkkff, ssppee-

cciiaall, ffssppeecciiaall, ffpp, or ssttyy requests, font g will be used. If g is missing, or equal to f then font f will not be translated. ..hhccooddee c1 code1 c2 code2... Set the hyphenation code of character c1 to code1 and that of c2 to code2. A hyphenation code must be a single input character

(not a special character) other than a digit or a space. Ini-

tially each lower-case letter a-z has a hyphenation code, which

is itself, and each upper-case letter A-Z has a hyphenation code

which is the lower-case version of itself. See also the hhppff

request. ..hhllaa lang Set the current hyphenation language to lang. Hyphenation

exceptions specified with the hhww request and hyphenation pat-

terns specified with the hhppff request are both associated with the current hyphenation language. The hhllaa request is usually invoked by the ttrrooffffrrcc file. ..hhllmm 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. ..hhppff file Read hyphenation patterns from file; this will be searched for

in the same way that name..ttmmaacc is searched for when the -mmname

option is specified. It should have the same format as (simple) TeX patterns files. More specifically, the following scanning rules are implemented. +o A percent sign starts a comment (up to the end of the line) even if preceded by a backslash.

+o No support for `digraphs' like \\$$.

+o ^^^^xx (x is 0-9 or a-f) and ^^^^x (character code of x in

the range 0-127) are recognized; other use of ^^ causes an

error. +o No macro expansion. +o hhppff checks for the expression \\ppaatttteerrnnss{{......}} (possibly with whitespace before and after the braces). Everything between the braces is taken as hyphenation patterns. Consequently, {{ and }} are not allowed in patterns. +o Similarly, \\hhyypphheennaattiioonn{{......}} gives a list of hyphenation exceptions. +o \\eennddiinnppuutt is recognized also. +o For backwards compatibility, if \\ppaatttteerrnnss is missing, the whole file is treated as a list of hyphenation patterns

(only recognizing the %% character as the start of a com-

ment). Use the hhppffccooddee request to map the encoding used in hyphenation patterns files to ggrrooffff's input encoding. The set of hyphenation patterns is associated with the current language set by the hhllaa request. The hhppff request is usually

invoked by the ttrrooffffrrcc file; a second call replaces the old pat-

terns with the new ones. ..hhppffaa file The same as hhppff except that the hyphenation patterns from file

are appended to the patterns already loaded in the current lan-

guage. ..hhppffccooddee a b c d ... After reading a hyphenation patterns file with the hhppff or hhppffaa request, convert all characters with character code a in the recently read patterns to character code b, character code c to d, etc. Initially, all character codes map to themselves. The arguments of hhppffccooddee must be integers in the range 0 to 255. Note that it is even possible to use character codes which are invalid in ggrrooffff otherwise. ..hhyymm n Set the hyphenation margin to n: when the current adjustment mode is not bb, 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 \\nn[[..hhyymm]] regis-

ter. ..hhyyss n Set the hyphenation space to n: when the current adjustment mode is bb 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 mm. The hyphenation space is associated with the current environment. The current hyphenation space is available in the \\nn[[..hhyyss]] register. ..iittcc n macro Variant of ..iitt for which a line interrupted with \\cc counts as one input line. ..kkeerrnn n

If n is non-zero or missing, enable pairwise kerning, otherwise

disable it. ..lleennggtthh xx string

Compute the length of string and return it in the number regis-

ter xx (which is not necessarily defined before). ..lliinneettaabbss n

If n is non-zero or missing, enable line-tabs mode, otherwise

disable it (which is the default). In line-tabs mode, tab dis-

tances are computed relative to the (current) output line. Oth-

erwise they are taken relative to the input line. For example, the following .ds x a\t\c .ds y b\t\c .ds z c .ta 1i 3i \*x \*y \*z yields a b c

In line-tabs mode, the same code gives

a b c

Line-tabs mode is associated with the current environment; the

read-only number register \\nn[[..lliinneettaabbss]] is set to 1 if in line-

tabs mode, and 0 otherwise. ..mmssoo file The same as the ssoo request except that file is searched for in

the same directories as macro files for the the -mm command line

option. If the file name to be included has the form name..ttmmaacc and it isn't found, mmssoo tries to include ttmmaacc..name instead and vice versa. ..nnoopp anything Execute anything. This is similar to `.if 1'.

..nnrrooffff Make the nn built-in condition true and the tt built-in condition

false. This can be reversed using the ttrrooffff request. ..ooppeenn stream filename Open filename for writing and associate the stream named stream with it. See also the cclloossee and wwrriittee requests. ..ooppeennaa stream filename

Like ooppeenn, but if filename exists, append to it instead of trun-

cating it. ..oouuttppuutt string Emit string directly to the intermediate output (subject to

copy-mode interpretation); this is similar to \\!! used at the

top level. An initial double quote in string is stripped off to allow initial blanks. ..ppnnrr Print the names and contents of all currently defined number registers on stderr. ..ppssbbbb filename Get the bounding box of a PostScript image filename. This file must conform to Adobe's Document Structuring Conventions; the

command looks for a %%%%BBoouunnddiinnggBBooxx comment to extract the bound-

ing box values. After a successful call, the coordinates (in PostScript units) of the lower left and upper right corner can be found in the registers \\nn[[llllxx]], \\nn[[llllyy]], \\nn[[uurrxx]], and \\nn[[uurryy]], respectively. If some error has occurred, the four registers are set to zero. ..ppssoo command This behaves like the ssoo request except that input comes from the standard output of command. ..ppttrr 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.

..ppvvss +-n

Set the post-vertical line space to n; default scale indicator

is pp. This value will be added to each line after it has been

output. With no argument, the post-vertical line space is set

to its previous value. The total vertical line spacing consists of four components: ..vvss and \\xx with a negative value which are applied before the line is output, and ..ppvvss and \\xx with a positive value which are applied after the line is output. ..rrcchhaarr c1 c2... Remove the definitions of glyphs c1, c2,... This undoes the effect of a cchhaarr request. ..rreettuurrnn Within a macro, return immediately. If called with an argument, return twice, namely from the current macro and from the macro one level higher. No effect otherwise. ..rrffsscchhaarr c1 c2...

Remove the font-specific definitions of glyphs c1, c2,... This

undoes the effect of a ffsscchhaarr request. ..rrjj ..rrjj 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 \\nn[[..rrjj]] register. This implicitly does ..ccee 0.. The ccee request implicitly does ..rrjj 0.. ..rrnnnn xx yy Rename number register xx to yy. ..sscchhaarr c string Define global fallback glyph c to be string. The syntax of this request is the same as the cchhaarr request; a glyph defined with

sscchhaarr is searched after the list of fonts declared with the ssppee-

cciiaall request but before the mounted special fonts. ..sshhcc c Set the soft hyphen character to c. If c is omitted, the soft hyphen character will be set to the default \\((hhyy. The soft hyphen character is the glyph which will be inserted when a word is hyphenated at a line break. If the soft hyphen character does not exist in the font of the glyph immediately preceding a potential break point, then the line will not be broken at that point. Neither definitions (specified with the cchhaarr request) nor translations (specified with the ttrr request) are considered when finding the soft hyphen character. ..sshhiifftt 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. ..ssiizzeess s1 s2...sn [[00]] This command is similar to the ssiizzeess command of a DDEESSCC file. It sets the available font sizes for the current font to s1, s2,..., sn scaled points. The list of sizes can be terminated

by an optional 00. Each si can also be a range of sizes m-n.

Contrary to the font file command, the list can't extend over more than a single line. ..ssppeecciiaall s1 s2... Fonts s1, s2, are special and will be searched for glyphs not in the current font. Without arguments, reset the list of special fonts to be empty. ..sspprreeaaddwwaarrnn limit Make ttrrooffff emit a warning if the additional space inserted for each space between words in an output line is larger or equal to limit. A negative value is changed to zero; no argument toggles the warning on and off without changing limit. The default scaling indicator is mm. At startup, sspprreeaaddwwaarrnn is deactivated, and limit is set to 3m. For example, ..sspprreeaaddwwaarrnn 00..22mm will

cause a warning if ttrrooffff must add 0.2m or more for each inter-

word space in a line. This request is active only if text is justified to both margins (using ..aadd bb). ..ssttyy 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 RR and the current font family is TT, then font TTRR will be used. If the current font is not a style, then the current

family is ignored. When the requests ccss, bbdd, ttkkff, uuff, or ffssppee-

cciiaall 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 -ff option. The ssttyylleess

command in the DESC file controls which font positions (if any) are initially associated with styles rather than fonts. ..ssuubbssttrriinngg xx n1 [[n2]] Replace the string named xx with the substring defined by the indices n1 and n2. The first character in the string has index 0. If n2 is omitted, it is taken to be equal to the string's length. If the index value n1 or n2 is negative, it will be counted from the end of the string, going backwards: The

last character has index -1, the character before the last char-

acter has index -2, etc.

..ttkkff f s1 n1 s2 n2 Enable track kerning for font f. When the current font is f the width of every glyph will be increased by an amount between n1 and n2; when the current point size is less than or equal to s1 the width will be increased by n1; when it is greater than or equal to s2 the width will be increased by n2; when the point size is greater than or equal to s1 and less than or equal to s2 the increase in width is a linear function of the point size. ..ttmm11 string

Similar to the ttmm request, string is read in copy mode and writ-

ten on the standard error, but an initial double quote in string is stripped off to allow initial blanks. ..ttmmcc string Similar to ttmm11 but without writing a final newline. ..ttrrff filename Transparently output the contents of file filename. Each line

is output as if preceded by \\!!; however, the lines are not sub-

ject to copy-mode interpretation. If the file does not end with

a newline, then a newline will be added. For example, you can define a macro x containing the contents of file f, using .di x .trf f .di Unlike with the ccff request, the file cannot contain characters such as NUL that are not legal troff input characters. ..ttrriinn abcd This is the same as the ttrr request except that the aasscciiiiffyy

request will use the character code (if any) before the charac-

ter translation. Example: .trin ax .di xxx a .br .di .xxx .trin aa .asciify xxx .xxx The result is xx aa. Using ttrr, the result would be xx xx. ..ttrrnntt abcd This is the same as the ttrr 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 bb; if ttrrnntt is used instead of ttrr it will print aa.

..ttrrooffff Make the nn built-in condition false, and the tt built-in condi-

tion true. This undoes the effect of the nnrrooffff request. ..uunnffoorrmmaatt xx This request `unformats' the diversion xx. Contrary to the ..aasscciiiiffyy request, which tries to convert formatted elements of

the diversion back to input tokens as much as possible, ..uunnffoorr-

mmaatt will only handle tabs and spaces between words (usually

caused by spaces or newlines in the input) specially. The for-

mer are treated as if they were input tokens, and the latter are stretchable again. Note that the vertical size of lines is not preserved. Glyph information (font, font size, space width, etc.) is retained. Useful in conjunction with the ..bbooxx and ..bbooxxaa requests.

..vvpptt n Enable vertical position traps if n is non-zero, disable them

otherwise. Vertical position traps are traps set by the wwhh or

ddtt requests. Traps set by the iitt 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. ..wwaarrnn 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 ttrrooffff(1). For example, ..wwaarrnn 00 will disable all warnings, and ..wwaarrnn 11 will disable all warnings except that about missing glyphs. If n is not given, all warnings will be enabled. ..wwaarrnnssccaallee si Set the scaling indicator used in warnings to si. Valid values for si are uu, ii, cc, pp, and PP. At startup, it is set to ii. ..wwhhiillee c anything While condition c is true, accept anything as input; c can be any condition acceptable to an iiff request; anything can comprise multiple lines if the first line starts with \\{{ and the last line ends with \\}}. See also the bbrreeaakk and ccoonnttiinnuuee requests. ..wwrriittee stream anything

Write anything to the stream named stream. stream must previ-

ously have been the subject of an ooppeenn request. anything is read in copy mode; a leading "" will be stripped. ..wwrriitteecc stream anything Similar to wwrriittee but without writing a final newline. ..wwrriitteemm stream xx Write the contents of the macro or string xx to the stream named stream. stream must previously have been the subject of an ooppeenn request. xx is read in copy mode. EExxtteennddeedd eessccaappee sseeqquueenncceess \\DD''...'' All drawing commands of groff's intermediate output are

accepted. See subsection DDrraawwiinngg CCoommmmaannddss below for more infor-

mation. EExxtteennddeedd rreeqquueessttss ..ccff 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. ..eevv xx If xx is not a number, this will switch to a named environment called xx. The environment should be popped with a matching eevv

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. ..ssss m n

When two arguments are given to the ssss 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. Contrary to UNIX troff, GNU troff handles this request in nroff mode also; a given value is then rounded down to the nearest multiple of 12. The sentence space size is used in two circumstances. If the end of a sentence occurs at the

end of a line in fill mode, then both an inter-word space and a

sentence space will be added; if two spaces follow the end of a sentence in the middle of a line, then the second space will be a sentence space. Note that the behaviour of UNIX troff will be exactly that exhibited by GNU troff if a second argument is never given to the ssss request. In GNU troff, as in UNIX troff, you should always follow a sentence with either a newline or two spaces. ..ttaa n1 n2...nn TT 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. NNeeww nnuummbbeerr rreeggiisstteerrss

The following read-only registers are available:

\\nn[[..CC]] 1 if compatibility mode is in effect, 0 otherwise. \\nn[[..ccddpp]] The depth of the last glyph added to the current environment. It is positive if the glyph extends below the baseline. \\nn[[..ccee]] The number of lines remaining to be centered, as set by the ccee request. \\nn[[..cchhtt]] The height of the last glyph added to the current environment. It is positive if the glyph extends above the baseline. \\nn[[..ccoolloorr]] 1 if colors are enabled, 0 otherwise. \\nn[[..ccsskk]] The skew of the last glyph added to the current environment. The skew of a glyph is how far to the right of the center of a glyph the center of an accent over that glyph should be placed. \\nn[[..eevv]] The name or number of the current environment. This is a

string-valued register.

\\nn[[..ffaamm]]

The current font family. This is a string-valued register.

\\nn[[..ffnn]]

The current (internal) real font name. This is a string-valued

register. If the current font is a style, the value of \\nn[[..ffnn]] is the proper concatenation of family and style name. \\nn[[..ffpp]] The number of the next free font position. \\nn[[..gg]] Always 1. Macros should use this to determine whether they are running under GNU troff. \\nn[[..hheeiigghhtt]] The current height of the font as set with \\HH. \\nn[[..hhllaa]] The current hyphenation language as set by the hhllaa request. \\nn[[..hhllcc]] The number of immediately preceding consecutive hyphenated lines. \\nn[[..hhllmm]] The maximum allowed number of consecutive hyphenated lines, as set by the hhllmm request. \\nn[[..hhyy]] The current hyphenation flags (as set by the hhyy request). \\nn[[..hhyymm]] The current hyphenation margin (as set by the hhyymm request). \\nn[[..hhyyss]] The current hyphenation space (as set by the hhyyss request). \\nn[[..iinn]] The indent that applies to the current output line. \\nn[[..iinntt]] Set to a positive value if last output line is interrupted (i.e., if it contains \c). \\nn[[..kkeerrnn]] 1 if pairwise kerning is enabled, 0 otherwise. \\nn[[..llgg]] The current ligature mode (as set by the llgg request). \\nn[[..lliinneettaabbss]]

The current line-tabs mode (as set by the lliinneettaabbss request).

\\nn[[..llll]] The line length that applies to the current output line. \\nn[[..lltt]] The title length as set by the lltt request.

\\nn[[..mm]] The name of the current drawing color. This is a string-valued

\\nn[[..MM]] The name of the current background color. This is a string-val-

ued register. \\nn[[..nnee]] The amount of space that was needed in the last nnee request that caused a trap to be sprung. Useful in conjunction with the \\nn[[..ttrruunncc]] register. \\nn[[..nnss]]

1 if no-space mode is active, 0 otherwise.

\\nn[[..ppee]] 1 during a page ejection caused by the bbpp request, 0 otherwise. \\nn[[..ppnn]] The number of the next page, either the value set by a ppnn request, or the number of the current page plus 1. \\nn[[..ppss]] The current pointsize in scaled points. \\nn[[..ppssrr]]

The last-requested pointsize in scaled points.

\\nn[[..ppvvss]]

The current post-vertical line space as set with the ppvvss

request. \\nn[[..rrjj]]

The number of lines to be right-justified as set by the rrjj

request. \\nn[[..ssllaanntt]] The slant of the current font as set with \\SS. \\nn[[..ssrr]] The last requested pointsize in points as a decimal fraction.

This is a string-valued register.

\\nn[[..ssss]] \\nn[[..ssssss]] These give the values of the parameters set by the first and second arguments of the ssss request. \\nn[[..ttaabbss]] A string representation of the current tab settings suitable for use as an argument to the ttaa request. \\nn[[..ttrruunncc]] The amount of vertical space truncated by the most recently sprung vertical position trap, or, if the trap was sprung by a nnee request, minus the amount of vertical motion produced by the nnee 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 \\nn[[..nnee]] register. \\nn[[..UU]] Set to 1 if in safer mode and to 0 if in unsafe mode (as given

with the -UU command line option).

\\nn[[..vvpptt]] 1 if vertical position traps are enabled, 0 otherwise. \\nn[[..wwaarrnn]] The sum of the numbers associated with each of the currently enabled warnings. The number associated with each warning is listed in ttrrooffff(1). \\nn[[..xx]] The major version number. For example, if the version number is 1.03, then \\nn[[..xx]] will contain 1. \\nn[[..yy]] The minor version number. For example, if the version number is 1.03, then \\nn[[..yy]] will contain 03. \\nn[[..YY]] The revision number of groff. \\nn[[llllxx]] \\nn[[llllyy]] \\nn[[uurrxx]] \\nn[[uurryy]] These four registers are set by the ..ppssbbbb request and contain

the bounding box values (in PostScript units) of a given Post-

Script image. The following read/write registers are set by the \\ww escape sequence: \\nn[[rrsstt]] \\nn[[rrssbb]] Like the sstt and ssbb registers, but take account of the heights and depths of glyphs. \\nn[[sssscc]] The amount of horizontal space (possibly negative) that should be added to the last glyph before a subscript. \\nn[[sskkww]]

How far to right of the center of the last glyph in the \\ww argu-

ment, the center of an accent from a roman font should be placed over that glyph. Other available read/write number registers are:

\\nn[[cc..]] The current input line number. \\nn[[..cc]] is a read-only alias to

this register. \\nn[[hhoouurrss]]

The number of hours past midnight. Initialized at start-up.

\\nn[[hhpp]] The current horizontal position at input line. \\nn[[mmiinnuutteess]]

The number of minutes after the hour. Initialized at start-up.

\\nn[[sseeccoonnddss]]

The number of seconds after the minute. Initialized at start-

up. \\nn[[ssyyssttaatt]] The return value of the system() function executed by the last ssyy request. \\nn[[sslliimmiitt]] 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. \\nn[[yyeeaarr]]

The current year. Note that the traditional ttrrooffff number regis-

ter \\nn[[yyrr]] is the current year minus 1900. MMiisscceellllaanneeoouuss

ttrrooffff predefines a single (read/write) string-based register, \\**((..TT,

which contains the argument given to the -TT command line option, namely

the current output device (for example, latin1 or ascii). Note that

this is not the same as the (read-only) number register \\nn[[..TT]] which is

defined to be 1 if ttrrooffff is called with the -TT command line option, and

zero otherwise. This behaviour is different to UNIX troff. Fonts not listed in the DESC file are automatically mounted on the next available font position when they are referenced. If a font is to be mounted explicitly with the ffpp request on an unused font position, it should be mounted on the first unused font position, which can be found in the \\nn[[..ffpp]] register; although ttrrooffff does not enforce this strictly, it will not allow a font to be mounted at a position whose number is much greater than that of any currently used position. Interpolating a string does not hide existing macro arguments. Thus in a macro, a more efficient way of doing

..xx \\\\$$@@

is \\\\**[[xx]]\\\\ If the font description file contains pairwise kerning information, glyphs from that font will be kerned. Kerning between two glyphs can be inhibited by placing a \\&& between them.

In a string comparison in a condition, characters that appear at dif-

ferent input levels to the first delimiter character will not be recog-

nised as the second or third delimiters. This applies also to the ttll

request. In a \\ww escape sequence, a character that appears at a dif-

ferent input level to the starting delimiter character will not be recognised as the closing delimiter character. The same is true for \\AA, \\bb, \\BB, \\CC, \\ll, \\LL, \\oo, \\XX, and \\ZZ. When decoding a macro or string argument that is delimited by double quotes, a character that appears at a different input level to the starting delimiter character

will not be recognised as the closing delimiter character. The imple-

mentation of \\$$@@ ensures that the double quotes surrounding an argument

will appear the same input level, which will be different to the input

level of the argument itself. In a long escape name ]] will not be rec-

ognized as a closing delimiter except when it occurs at the same input level as the opening ]]. In compatibility mode, no attention is paid to

the input-level.

There are some new types of condition: ..iiff rrxxx True if there is a number register named xxx. ..iiff ddxxx True if there is a string, macro, diversion, or request named xxx. ..iiff mmxxx True if there is a color named xxx. ..iiff ccch True if there is a glyph ch available; ch is either an ASCII character or a glyph (special character) \\((xx or \\[[xxx]]; the condition will also be true if ch has been defined by the cchhaarr request. The ttrr request can now map characters onto \\~~. It is now possible to have whitespace between the first and second dot (or the name of the ending macro) to end a macro definition. Example: .de foo . nop Hello, I'm `foo'. . nop I will now define `bar'. . de bar . nop Hello, I'm `bar'. . . . nop Done. .. .foo .bar IINNTTEERRMMEEDDIIAATTEE OOUUTTPPUUTT FFOORRMMAATT

This section describes the format output by GNU troff. The output for-

mat used by GNU troff is very similar to that used by Unix device-inde-

pendent troff. Only the differences are documented here. UUnniittss The argument to the ss command is in scaled points (units of points/n, where n is the argument to the ssiizzeessccaallee command in the DESC file). The argument to the xx HHeeiigghhtt command is also in scaled points. TTeexxtt CCoommmmaannddss

NNn Print glyph with index n (a non-negative integer) of the current

font. If the ttccoommmmaanndd line is present in the DESC file, troff will use the following two commands. ttxxx xxx is any sequence of characters terminated by a space or a newline (to be more precise, it is a sequence of glyphs which

are accessed with the corresponding characters); the first char-

acter should be printed at the current position, the current horizontal position should be increased by the width of the first character, and so on for each character. The width of the glyph is that given in the font file, appropriately scaled for the current point size, and rounded so that it is a multiple of the horizontal resolution. Special characters cannot be printed using this command. uun xxx This is same as the tt command except that after printing each character, the current horizontal position is increased by the sum of the width of that character and n. Note that single characters can have the eighth bit set, as can the names of fonts and special characters. The names of glyphs and fonts can be of arbitrary length; drivers should not assume that they will be only two characters long. When a glyph is to be printed, that glyph will always be in the current

font. Unlike device-independent troff, it is not necessary for drivers

to search special fonts to find a glyph. For color support, some new commands have been added: mmcc cyan magenta yellow mmdd mmgg gray mmkk cyan magenta yellow black mmrr red green blue Set the color components of the current drawing color, using various color schemes. mmdd resets the drawing color to the default value. The arguments are integers in the range 0 to 65536. The xx device control command has been extended.

xx uu n If n is 1, start underlining of spaces. If n is 0, stop under-

lining of spaces. This is needed for the ccuu request in nroff mode and is ignored otherwise. DDrraawwiinngg CCoommmmaannddss The DD drawing command has been extended. These extensions will not be

used by GNU pic if the -nn option is given.

DDff n\n Set the shade of gray to be used for filling solid objects to n; n must be an integer between 0 and 1000, where 0 corresponds

solid white and 1000 to solid black, and values in between cor-

respond to intermediate shades of gray. This applies only to solid circles, solid ellipses and solid polygons. By default, a level of 1000 will be used. Whatever color a solid object has, it should completely obscure everything beneath it. A value greater than 1000 or less than 0 can also be used: this means fill with the shade of gray that is currently being used for lines and text. Normally this will be black, but some drivers may provide a way of changing this. The corresponding \\DD''ff...'' command shouldn't be used since its

argument is always rounded to an integer multiple of the hori-

zontal resolution which can lead to surprising results. DDCC d\n Draw a solid circle with a diameter of d with the leftmost point at the current position. DDEE dx dy\n

Draw a solid ellipse with a horizontal diameter of dx and a ver-

tical diameter of dy with the leftmost point at the current position.

DDpp \n Draw a polygon with, for , the i-th vertex at the current posi-

tion At the moment, GNU pic only uses this command to generate triangles and rectangles. DDPP \n Like DDpp but draw a solid rather than outlined polygon.

DDtt n\n Set the current line thickness to n machine units. Tradition-

ally Unix troff drivers use a line thickness proportional to the current point size; drivers should continue to do this if no DDtt command has been given, or if a DDtt command has been given with a negative value of n. A zero value of n selects the smallest available line thickness. A difficulty arises in how the current position should be changed after the execution of these commands. This is not of great importance since the code generated by GNU pic does not depend on this. Given a drawing command of the form \\DD''c ' where c is not one of cc, ee, ll, aa, or ~~, Unix troff will treat each of the as a horizontal quantity, and each of the as a vertical quantity and will assume that the width of the drawn object is , and that the height is . (The assumption about the height can be seen by examining the sstt and ssbb registers after using such a DD command in a \w escape sequence). This rule also holds for all the original drawing commands with the exception of DDee. For the sake of compatibility GNU troff also follows this rule, even though it produces an ugly result in the case of the DDtt and DDff, and, to a lesser extent, DDEE commands. Thus after executing a DD command of the form DDc \n the current position should be increased by Another set of extensions is DDFFcc cyan magenta yellow\n DDFFdd\n DDFFgg gray\n DDFFkk cyan magenta yellow black\n DDFFrr red green blue\n Set the color components of the filling color similar to the mm commands above. The current position isn't changed by those colour commands (contrary to DDff). DDeevviiccee CCoonnttrrooll CCoommmmaannddss There is a continuation convention which permits the argument to the xx XX command to contain newlines: when outputting the argument to the xx XX command, GNU troff will follow each newline in the argument with a ++ character (as usual, it will terminate the entire argument with a newline); thus if the line after the line containing the xx XX command

starts with ++, then the newline ending the line containing the xx XX com-

mand should be treated as part of the argument to the xx XX command, the ++ should be ignored, and the part of the line following the ++ should be treated like the part of the line following the xx XX command. The first three output commands are guaranteed to be: xx TT device xx rreess n h v xx iinniitt IINNCCOOMMPPAATTIIBBIILLIITTIIEESS In spite of the many extensions, groff has retained compatibility to classical troff to a large degree. For the cases where the extensions lead to collisions, a special compatibility mode with the restricted, old functionality was created for groff. GGrrooffff LLaanngguuaaggee groff provides a ccoommppaattiibbiilliittyy mmooddee that allows to process roff code

written for classical or for other implementations of roff in a consis-

tent way.

Compatibility mode can be turned on with the -CC command line option,

and turned on or off with the ..ccpp request. The number register \\nn((..CC is 1 if compatibility mode is on, 0 otherwise. This became necessary because the GNU concept for long names causes some incompatibilities. Classical troff interprets ..ddssaabbccdd as defining a string aabb with contents ccdd. In groff mode, this will be considered as a call of a macro named ddssaabbccdd. Also classical troff interprets \\**[[ or \\nn[[ as references to a string or number register called [[ while groff takes this as the start of a long name. In compatibility mode, groff interprets these things in the traditional way; so long names are not recognized. On the other hand, groff in GNU native mode does not allow to use the

single-character escapes \\\\ (backslash), \\|| (vertical bar), \\^^ (caret),

\\&& (ampersand), \\{{ (opening brace), \\}} (closing brace), `\\ ' (space),

\\'' (single quote), \\`` (backquote), \\- (minus), \\ (underline), \\!!

(bang), \\%% (percent), and \\cc (character c) in names of strings, macros,

diversions, number registers, fonts or environments, whereas classical troff does. The \\AA escape sequence can be helpful in avoiding these escape sequences in names.

Fractional pointsizes cause one noteworthy incompatibility. In classi-

cal troff, the ppss request ignores scale indicators and so ..ppss 1100uu will set the pointsize to 10 points, whereas in groff native mode the pointsize will be set to 10 scaled points. In groff, there is a fundamental difference between unformatted input characters, and formatted output characters (glyphs). Everything that affects how a glyph will be output is stored with the glyph; once a glyph has been constructed it is unaffected by any subsequent requests that are executed, including the bbdd, ccss, ttkkff, ttrr, or ffpp requests. Normally glyphs are constructed from input characters at the moment immediately before the glyph is added to the current output line. Macros, diversions and strings are all, in fact, the same type of

object; they contain lists of input characters and glyphs in any combi-

nation. Special characters can be both; before being added to the output, they act as input entities, afterwards they denote glyphs. A glyph does not behave like an input character for the purposes of macro processing; it does not inherit any of the special properties that the input character from which it was constructed might have had. The following example will make things clearer. .di x \\\\ .br .di .x

With GNU troff this will be printed as \\\\. So each pair of input back-

slashes `\\\\' is turned into a single output backslash glyph `\\' and the resulting output backslashes are not interpreted as escape characters when they are reread. Classical troff would interpret them as escape characters when they were reread and would end up printing a single backslash `\\'. In GNU, the correct way to get a printable version of the backslash character `\\' is the \\((rrss escape sequence, but classical troff does not

provide a clean feature for getting a non-syntactical backslash. A

close method is the printable version of the current escape character

using the \\ee escape sequence; this works if the current escape charac-

ter is not redefined. It works in both GNU mode and compatibility

mode, while dirty tricks like specifying a sequence of multiple back-

slashes do not work reliably; for the different handling in diversions, macro definitions, or text mode quickly leads to a confusion about the necessary number of backslashes. To store an escape sequence in a diversion that will be interpreted when the diversion is reread, either the traditional \\!! transparent output facility or the new \\?? escape sequence can be used. IInntteerrmmeeddiiaattee OOuuttppuutt The groff intermediate output format is in a state of evolution. So far it has some incompatibilities, but it is intended to establish a full compatibility to the classical troff output format. Actually the following incompatibilities exist: +o The positioning after the drawing of the polygons conflicts with the classical definition.

+o The intermediate output cannot be rescaled to other devices as clas-

sical "device-independent" troff did.

This document is distributed under the terms of the FDL (GNU Free Docu-

mentation License) version 1.1 or later. You should have received a

copy of the FDL on your system, it is also available on-line at the GGNNUU

ccooppyylleefftt ssiittee . This document was written by James Clark, with modifications by WWeerrnneerr LLeemmbbeerrgg and BBeerrnndd WWaarrkkeenn . This document is part of groff, the GNU roff distribution. Formerly, the contents of this document was kept in the manual page ttrrooffff(1). Only the parts dealing with the language aspects of the different roff systems were carried over into this document. The troff command line options and warnings are still documented in ttrrooffff(1).