.\" $NetBSD: groff.7,v 1.3 2003/01/03 12:11:49 wiz Exp $ .\" .\" st -*- nroff -*- .ig groff.7 This file is part of groff, the GNU roff type-setting system. Copyright (C) 2000 Free Software Foundation, Inc. written by Bernd Warken Last update: 17 May 2000 Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being this .ig-section and AUTHOR, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the Free Documentation License is included as a file called FDL in the main directory of the groff source package. .. . .\" -------------------------------------------------------------------- .\" Setup .\" -------------------------------------------------------------------- . .if n \{\ . mso tmac.tty-char . ftr CR R . ftr CI I . ftr CB B .\} . .if '\*[.T]'dvi' \{\ . ftr CB CW .\} . .\" a comment macro which does nothing .de c .. . .\" a tab string .ds t "\t . .eo . .c text lines in macro definitions or bracketed sections \{...\} .de text . if 1 \&\$*\& .. . .de option . ds @tmp@ \f(CB\$1\fP . shift 1 . text \*[@tmp@]\$* . rm @tmp@ .. . .als shellcommand option . .c --------- characters --------- . .de character . ds @tmp@ \f(CB\$1\fP . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .de 'char . ds @tmp@ \(oq\f(CB\$1\fP\(cq . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .de ''char . ds @tmp@ \(lq\f(CB\$1\fP\(rq . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .c --------- requests --------- . .c request synopsis .de REQ . ds @tmp@ \&\$1 . shift 1 . IP "\f(CB\&\*[@tmp@] \fP\f(CI\&\$*\fP" 10n . rm @tmp@ .. . .de request . ds @tmp@ \f(CB\$1\fP . shift 1 . text \*[@tmp@]\$* . rm @tmp@ .. . .c --------- macro or function arguments --------- . .de argument . ds @tmp@ \f(CI\$1\fP . shift 1 . while (\n[.$] >= 2) \{\ . as @tmp@ \/\f(CR\$1\fP\f(CI\,\$2\fP . shift 2 . \} . if \n[.$] .as @tmp@ \/\f(CR\$1\fP . text \*[@tmp@] . rm @tmp@ .. . .c argument followed by a numerical expression .de argterm . ds @tmp@ \f(CI\$1\fP\|\f(CR\$2\fP . shift 2 . text \*[@tmp@]\$* . rm @tmp@ .. . .c --------- numerical elements --------- . .de number . ds @tmp@ \f(CR\$1\fP . shift 1 . text \*[@tmp@]\$* . rm @tmp@ .. . .de prefixednumber . ds @tmp@ \&\$1\ \f(CR\$2\fP . shift 2 . text \*[@tmp@]\$* . rm @tmp@ .. . .als scaleindicator request . .de scalednumber . ds @tmp@ \f(CR\$1\fP\f(CB\$2\fP . shift 2 . text \*[@tmp@]\$* . rm @tmp@ .. . .de operator . ds @tmp@ \(oq\f(CB\$1\fP\(cq . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .c --------- escape sequences --------- . .de esc[arg] . ds @tmp@ \f(CB\(rs\$1[\fP\f(CI\$2\fP\f(CB]\fP . shift 2 . text \*[@tmp@]\$* . rm @tmp@ .. . .de esc(arg . ds @tmp@ \f(CB\(rs\$1(\fP\f(CI\$2\fP . shift 2 . text \*[@tmp@]\$* . rm @tmp@ .. . .de escarg . ds @tmp@ \f(CB\(rs\$1\fP\f(CI\$2\fP . shift 2 . text \*[@tmp@]\$* . rm @tmp@ .. . .de esc[] . ds @tmp@ \f(CB\(rs[\fP\f(CI\$1\fP\f(CB]\fP . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .de esc( . ds @tmp@ \f(CB\(rs(\fP\f(CI\$1\fP . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .de esc . ds @tmp@ \f(CB\(rs\$1\fP . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .de (esc . ds @tmp@ \f(CB\(rs(\$1\fP . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .de [esc] . ds @tmp@ \f(CB\(rs[\$1]\fP . shift . text \*[@tmp@]\$* . rm @tmp@ .. . .c escape sequence synopsis .de ESC . ds @tmp@ \&\$1 . shift 1 . IP "\f(CB\(rs\&\*[@tmp@]\fP\f(CI\&\$*\fP" . rm @tmp@ .. . .c synopsis for escape sequences with a long name .de ESC[] . ds @arg1@ \&\$1 . ds @arg2@ \&\$2 . shift 2 . IP "\f(CB\(rs\&\*[@arg1@][\fP\f(CI\&\*[@arg2@]\fP\f(CB]\&\$*\fP" . rm @arg1@ . rm @arg2@ .. . .c synopsis escape sequence with quoted argument . de ESCq . ds @tmp@ \&\$1 . shift 1 . IP "\f(CB\(rs\&\*[@tmp@]\(cq\fP\f(CI\h'-0.2m'\$*\/\fP\f(CB\(cq\fP" . rm @tmp@ .. . .c synopsis for 2-escapes (special characters) .de ESc . ds @tmp@ \$1 . TP 14n . text \f(CB\(rs(\&\*[@tmp@]\ \ \ \fP\fR\(\*[@tmp@]\fP . shift 1 . text \$*. . rm @tmp@ .. . .c --------- registers --------- . .c synopsis for registers .de REG . TP 10n . text \&\f(CR\(rsn[\fP\f(CB\$1\fP\f(CR]\fP . shift 1 .if \n[.$] \&\$* .. . .als register request . .c --------- warnings --------- . .als warning request . .c description of warnings .de Warning . ne (2v + 1) . TP 12n . text \f(CB\$1\fP . text \f(CI\$2\fP . br .. . .ec . .\" -------------------------------------------------------------------- .\" Title .\" -------------------------------------------------------------------- . .TH GROFF 7 "April 8, 2001" "Groff Version 1.16.1" .SH NAME groff \- a short reference for the GNU roff language . .\" -------------------------------------------------------------------- .SH DESCRIPTION .\" -------------------------------------------------------------------- .I groff stands for .I GNU roff and is the free implementation of the roff type-setting system. See .BR roff (7) for a survey and the background of the groff system. .LP This document gives only short descriptions of the predefined roff language elements as used in groff. Both the classical features and the groff extensions are provided. .LP Historically, the .I roff language was called .IR troff . .I groff is compatible with the classical system and provides proper extensions. So in GNU, the terms .IR roff , .IR troff , and .I groff language could be used as synonyms. However .I troff slightly tends to refer more to the classical aspects, whereas .I groff emphasizes the GNU extensions, and .I roff is the general term for the language. .LP This file is only a short version of the complete documentation that is found in the .I groff .BR info (1) file, which contains more detailed, actual, and concise information. .LP The general syntax for writing groff documents is relatively easy, but writing extensions to the roff language can be a bit harder. .LP The roff language is line-oriented. There are only two kinds of lines, control lines and text lines. The control lines start with a control character, by default a period .''char . or a single quote .''char ' ; all other lines are text lines. .LP .B Control lines represent commands, optionally with arguments. They have the following syntax. The leading control character can be followed by a command name; arguments, if any, are separated by blanks from the command name and among themselves, for example, .RS .LP \&\.command_name arg1 arg2 .RE .LP For indentation, any number of space or tab characters can be inserted between the leading control character and the command name, but the control character must be on the first position of the line. .LP .B Text lines represent the parts that will be printed. They can be modified by escape sequences, which are recognized by a leading backslash .'char \(rs . These are in-line or even in-word formatting elements or functions. Some of these take arguments separated by single quotes .''char ' , others are regulated by a length encoding introduced by an open parenthesis .'char ( or enclosed in brackets .'char [ and .'char ] . .LP The roff language provides flexible instruments for writing language extension, such as macros. When interpreting macro definitions, the roff system enters a special operating mode, called the .BR "copy mode" . .LP The copy mode behavior can be quite tricky, but there are some rules that ensure a safe usage. .IP 1. Printable backslashes must be denoted as .esc e . To be more precise, .esc e represents the current escape character. To get a backslash glyph, use .esc (rs . .IP 2. Double all backslashes. .IP 3. Begin all text lines with the special non-spacing character .esc & . .LP This does not produce the most efficient code, but it should work as a first measure. For better strategies, see the groff info file and .BR groff_tmac (5). .LP Reading roff source files is easier, just reduce all double backslashes to a single one in all macro definitions. . .\" -------------------------------------------------------------------- .SH "GROFF ELEMENTS" .\" -------------------------------------------------------------------- The roff language elements add formatting information to a text file. The fundamental elements are predefined commands and variables that make roff a full-blown programming language. .LP There are two kinds of roff commands, possibly with arguments. .B Requests are written on a line of their own starting with a dot .'char . or a .''char ' , whereas .B Escape sequences are in-line functions and in-word formatting elements starting with a backslash .'char \(rs . .LP The user can define her own formatting commands using the .request .de request. These commands are called .BR macros , but they are used exactly like requests. Macro packages are pre-defined sets of macros written in the groff language. A user's possibilities to create escape sequences herself is very limited, only special characters can be mapped. .LP The groff language provides several kinds of variables with different interfaces. There are pre-defined variables, but the user can define her own variables as well. .LP .B String variables store character sequences. They are set with the .request .ds request and retrieved by the .esc * escape sequences. .LP .B Register variables can store numerical values, numbers with a scale unit, and occasionally string-like objects. They are set with the .request .nr request and retrieved by the .esc n escape sequences. .LP .B Environments allow the user to temporarily store global formatting parameters like line length, font size, etc. for later reuse. This is done by the .request .ev request. .LP .B Fonts are identified either by a name or by an internal number. The current font is chosen by the .request .ft request or by the .esc f escape sequences. Each device has special fonts, but the following fonts are available for all devices. .B R is the standard font Roman. .B B is its .B bold counterpart. The .I italic font is called .B I is everywhere available, but on text devices, it is displayed as an underlined Roman font. For the graphical output devices, there exist constant-width pendants of these font, .BR CR , .BR CI , and .BR CB . On text devices, all characters have a constant width anyway. .LP Moreover, there are some advanced roff elements. A .B diversion stores information into a macro for later usage. A .B trap is a positional condition like a certain number of lines from page top or in a diversion or in the input. Some action can be prescribed to be run automatically when the condition is met. .LP More detailed information can be found in the groff info file. . .\" -------------------------------------------------------------------- .SH "CONTROL CHARACTERS" .\" -------------------------------------------------------------------- There is a small set of characters that have a special controlling task in certain conditions. .TP .character . A dot is only special at the beginning of a line or after the condition in the requests .request .if , .request .ie , .request .el , and .request .while . There it is the control character that introduces a request (or macro). The special behavior can be delayed by using the .esc . escape. By using the .request .cc request, the control character can be set to a different character, making the dot .'char . a non-special character. .IP "" In all other positions, it just means a dot character. In text paragraphs, it is advantageous to start each sentence at a line of its own. .TP .character ' The single quote has two controlling tasks. At the beginning of a line and in the conditional requests it is the non-breaking control character. That means that it introduces a request like the dot, but with the additional property that this request doesn't cause a linebreak. By using the .request .c2 request, the non-break control character can be set to a different character. .IP "" As a second task, it is the most commonly used argument separator in some functional escape sequences (but any pair of characters not part of the argument will work). In all other positions, it denotes the single quote or apostrophe character. Groff provides a printable representation with the .esc (cq escape sequence. .TP .character \(dq The double quote is used to enclose arguments in requests and macros. The escaped double quote .esc \(dq introduces a comment. Otherwise, it is not special. Groff provides a printable representation with the .esc (dq escape sequence. .TP .character \(rs The backslash usually introduces an escape sequence (this can be changed with the .request ec request). A printed version of the escape character is the .esc e escape; a backslash glyph can be obtained by .esc (rs . .TP .character ( The open parenthesis is only special in escape sequences when introducing an escape name or argument consisting of exactly two characters. In groff, this behavior can be replaced by the \f(CB[]\fP construct. .TP .character [ The opening bracket is only special in groff escape sequences; there it is used to introduce a long escape name or long escape argument. Otherwise, it is non-special, e.g. in macro calls. .TP .character ] The closing bracket is only special in groff escape sequences; there it terminates a long escape name or long escape argument. Otherwise, it is non-special. .TP \f(CIspace\fP Space characters are only functional characters. They separate the arguments in requests or macros, and the words in text lines. They are subject to groff's horizontal spacing calculations. To get a defined space width, escape sequences like .'char "\(rs\ " (this is the escape character followed by a space), .esc | , .esc ^ , or .esc h should be used. .IP \f(CInewline\fP In text paragraphs, newlines mostly behave like space characters. Continuation lines can be specified by an escaped newline, i.e., by specifying a backslash .'char \(rs as the last character of a line. .IP \f(CItab\fP If a tab character occurs during text the interpreter makes a horizontal jump to the next pre-defined tab position. There is a sophisticated interface for handling tab positions. . .\" -------------------------------------------------------------------- .SH "NUMERICAL EXPRESSIONS" .\" -------------------------------------------------------------------- A .B numerical value is a signed or unsigned integer or float with or without an appended scale indicator. A .B scale indicator is a one-character abbreviation for a unit of measurement. A number followed by a scale indicator signifies a size value. By default, numerical values do not have a scale indicator, i.e., they are normal numbers. .LP The roff language defines the following scale indicators. .LP .na .nh .TS center, tab(@); LfCB Lw(4i). c@Centimeter i@Inch P@Pica\ \(eq\ 1/6\ inch p@Point\ \(eq\ 1/72\ inch m@T{ Em\ \(eq\ \fRthe font size in points (width of letter `\f(CRm\fR') T} M@100th \fRof an \f(CREm n@En\ \(eq\ Em/2 u@\fRBasic unit for actual output device v@\fRVertical line space in basic units z@T{ scaled point\ \(eq\ 1/\f(CIsizescale\fR of a point (defined in font \fIDESC\fP file) T} .TE .LP .ad .hy .B Numerical expressions are combinations of the numerical values defined above with the arithmetical operators .operator + , .operator \- , .operator * , .operator / , .operator % .RI ( modulo ), the comparative operators .operator == (this is the same as .operator = ), .operator <= , .operator >= , .operator < , .operator > , the logical operators .operator & .RI ( and ), .operator : .RI ( or ), .operator ! .RI ( not ), and the parentheses .operator ( and .operator ) . .LP Moreover, .I groff added the following operators for numerical expressions: .LP .na .nh .TS center, tab(@); LfCB Lw(4i). e1\f(CB>?\fPe2@The maximum of \f(CIe1\fP and \f(CIe2\fP. e1\f(CB0\fP. T} !\f(CIN\fP@T{ True if the value of \f(CIN\fP is\ \f(CR\(<=0\fP. T} \&'\f(CIs1\fP'\f(CIs2\fP'@T{ True if string\ \f(CIs1\fP is identical to string\ \f(CIs2\fP. T} !'\f(CIs1\fP'\f(CIs2\fP'@T{ True if string\ \f(CIs1\fP is not identical to string\ \f(CIs2\fP. T} c\f(CIch@T{ True if there is a character\ \f(CIch\fP available. T} d\f(CIname@T{ True if there is a string, macro, diversion, or request called \f(CIname\fP. T} e@Current page number is even. o@Current page number is odd. n@Formatter is \fBnroff\fP. r\f(CIreg@T{ True if there is a register named \f(CIreg\fP. T} t@Formatter is \fBtroff\fR. .TE .LP .ad .hy . .\" -------------------------------------------------------------------- .SH REQUESTS .\" -------------------------------------------------------------------- This section provides a short reference for the predefined requests. In groff, request and macro names can be arbitrarily long. No bracketing or marking of long names is needed. .LP Most requests take one or more arguments. The arguments are separated by space characters (no tabs!); there is no inherent limit for their length or number. An argument can be enclosed by a pair of double quotes: This is very handy if an argument contains space characters, e.g., .argument "\(dqarg\ with\ space\(dq" denotes a single argument. .LP Some requests have optional arguments with a different behaviour. Not all of these details are outlined here. Refer to the groff info file for all details. .LP In the following request specifications, most argument names were chosen to be descriptive. Only the following denotations need clarification. .LP .na .nh .TS center, tab(@); LfCI Lw(4i). c@denotes a single character. font@T{ a font either specified as a font name or a font number. T} anything@T{ all characters up to the end of the line or within \f(CB\(rs{\fP and \f(CB\(rs}\fP. T} n@T{ is a numerical expression that evaluates to an integer value. T} N@T{ is an arbitrary numerical expression, signed or unsigned. T} \(+-N@T{ has three meanings depending on its sign, described below. T} .TE .LP .ad .hy If an expression defined as .argument \(+-N starts with a .operator + sign the resulting value of the expression will be added to an already existing value inherent to the related request, e.g. adding to a number register. If the expression starts with a .operator - the value of the expression will be subtracted from the request value. .LP Without a sign, .argument N replaces the existing value directly. To assign a negative number either prepend\ \c .number 0 or enclose the negative number in parentheses. . .\" -------------------------------------------------------------------- .SS "REQUEST SHORT REFERENCE" .\" -------------------------------------------------------------------- .PD 0 . .REQ . Empty line, ignored. Useful for structuring documents. . .REQ .\(rs\(dq anything Complete line is a comment. . .REQ .ab string Print .argument string on standard error, exit program. . .REQ .ad Begin line adjustment for output lines in current adjust mode. . .REQ .ad c Start line adjustment in mode .argument c (\f(CIc\fP\f(CR\|\^\(eq\|l,r,b,n\fP). . .REQ .af register c Assign format .argument c to .argument register (\f(CIc\fP\f(CR\|\^\(eq\|l,i,I,a,A\fP). . .REQ .aln alias register Create alias name for .argument register . . .REQ .als alias object Create alias name for request, string, macro, or diversion .argument object . . .REQ .am macro Append to .argument macro until .request .. is called. . .REQ .am macro end Append to .argument macro until .request .end is called. . .REQ .as stringvar anything Append .argument anything to .argument stringvar . . .REQ .asciify diversion Unformat special ASCII characters in .argument diversion . . .REQ .backtrace Print a backtrace of the input on stderr. . .REQ .bd font N Embolden .argument font by .argterm N -1 units. . .REQ .bd S font N Embolden Special Font .argument S when current font is .argument font . . .REQ .bp Eject current page and begin new page. . .REQ .bp \(+-N Eject current page; next page number .argument \(+-N . . .REQ .blm macro Set the blank line macro to .argument macro . . .REQ .br Line break. . .REQ .break Break out of a while loop. . .REQ .c2 Reset no-break control character to .''char ' . . .REQ .c2 c Set no-break control character to .argument c . . .REQ .cc Reset control character to .'char . . . .REQ .cc c Set control character to .argument c . . .REQ .ce Center the next input line. . .REQ .ce N Center following .argument N input lines. . .REQ .cf filename Copy contents of file .argument filename unprocessed to stdout or to the diversion. . .REQ .cflags mode c1 c2 ... Treat characters .argument c1 , .argument c2 , .argument ... according to .argument mode number. . .REQ .ch trap N Change .argument trap location to .argument N . . .REQ .char c anything Define character .argument c to string .argument anything . . .REQ .chop object Chop the last character off macro, string, or diversion .argument object . . .REQ .close stream Close the .argument stream . . .REQ .continue Finish the current iteration of a while loop. . .REQ .cp Enable compatibility mode. . .REQ .cp N If .I N is zero disable compatibility mode, otherwise enable it. . .REQ .cs font N M Set constant character width mode for .argument font to .argterm N /36 ems with em .argument M . . .REQ .cu N Continuous underline in nroff, like .request .ul in troff. . .REQ .da macro Divert and append to .argument macro . . .REQ .de macro Define or redefine .argument macro until .request .. is called. . .REQ .de macro end Define or redefine .argument macro until .request .end is called. . .REQ .di End current diversion. . .REQ .di macro Divert to .argument macro . . .REQ .do name Interpret .request .name with compatibility mode enabled. . .REQ .ds stringvar anything Set .argument stringvar to .argument anything . . .REQ .dt N trap Set diversion trap to position .argument N (default scale indicator\ \c .scaleindicator v ). . .REQ .ec Reset escape character to .'char \(rs . . .REQ .ec c Set escape character to .argument c . . .REQ .el anything Else part for if-else (\c .argument .ie ) request. . .REQ .em macro The .argument macro will be run after the end of input. . .REQ .eo Turn off escape character mechanism. . .REQ .ev Switch to previous environment. . .REQ .ev env Push down environment number or name .argument env and switch to it. . .REQ .evc env Copy the contents of environment .argument env to the current environment. No pushing or popping. . .REQ .ex Exit from roff processing. . .REQ .fam name Set the current font family to .argument name . . .REQ .fc Disable field mechanism. . .REQ .fc a Set field delimiter to .argument a and pad character to space. .REQ .fc a b Set field delimiter to .argument a and pad character to .argument b . . .REQ .fi Fill output lines. . .REQ .fl Flush output buffer. . .REQ .fp n font Mount .argument font on position .argument n . . .REQ .fp n internal external Mount font with long .argument external name to short .argument internal name on position .argument n . . .REQ .fspecial font s1 s2... When the current font is .argument font , then the fonts .argument s1 , .argument s2 , .argument ... will be special. . .REQ .ft Return to previous font. Same as .request \(rsfP . .REQ .ft font Change to font name or number .argument font ; same as .esc[arg] f font escape sequence. . .REQ .ftr font1 font2 Translate .argument font1 to .argument font2 . . .REQ .hc Remove additional hyphenation indicator character. . .REQ .hc c Set up additional hyphenation indicator character\ \c .argument c . . .REQ .hcode c1 code1 c2 code2 ... Set the hyphenation code of character .argument c1 to .argument code1 , that of .argument c2 to .argument code2 , etc. . .REQ .hla lang Set the current hyphenation language to .argument lang . . .REQ .hlm n Set the maximum number of consecutive hyphenated lines to .argument n . . .REQ .hpf file Read hyphenation patterns from .argument file . . .REQ .hw words List of .argument words with exceptional hyphenation. . .REQ .hy N Switch to hyphenation mode .argument N . . .REQ .hym n Set the hyphenation margin to .argument n (default scale indicator\ \c .scaleindicator m ). . .REQ .hys n Set the hyphenation space to .argument n . . .REQ .ie cond anything If .argument cond then .argument anything else goto .request .el . . .REQ .if cond anything If .argument cond then .argument anything ; otherwise do nothing. . .REQ .ig Ignore text until .request .. is called. . .REQ .ig end Ignore text until .request .end . . .REQ .in Change to previous indent value. . .REQ .in \(+-N Change indent according to .argument \(+-N (default scale indicator\ \c .scaleindicator m ). . .REQ .it N trap Set an input-line count trap at position .argument N . . .REQ .kern Enable pairwise kerning. . .REQ .kern n If .argument n is zero, disable pairwise kerning, otherwise enable it. . .REQ .lc Remove leader repetition character. . .REQ .lc c Set leader repetition character to\ \c .argument c . . .REQ .length register anything Write the length of the string .argument anything in .argument register . . .REQ .lf N file Set input line number to .argument N and filename to .argument file . . .REQ .lg N Ligature mode on if .argterm N >0 . . .REQ .ll Change to previous line length. . .REQ .ll \(+-N Set line length according to .argument \(+-N (default size .scalednumber 6.5 i , default scale indicator\ \c .scaleindicator m ). . .REQ .ls Change to the previous value of additional intra-line skip. . .REQ .ls N Set additional intra-line skip value to .argument N , i.e., .argterm N -1 blank lines are inserted after each text output line. . .REQ .lt \(+-N Length of title (default scale indicator\ \c .scaleindicator m ). . .REQ .mc Margin character off. . .REQ .mc c Print character .argument c after each text line at actual distance from right margin. . .REQ .mc c N Set margin character to .argument c and distance to .argument N from right margin (default scale indicator\ \c .scaleindicator m ). . .REQ .mk register Mark current vertical position in .argument register . . .REQ .mso file The same as the .so request except that .I file is also searched in the tmac directories. . .REQ .na No output-line adjusting. . .REQ .ne Need a one-line vertical space. . .REQ .ne N Need .argument N vertical space (default scale indicator\ \c .scaleindicator v ). . .REQ .nf No filling or adjusting of output-lines. . .REQ .nh No hyphenation. . .REQ .nm Number mode off. . .REQ .nm \(+-N M S I In line number mode, set number, multiple, spacing, and indent. . .REQ .nn Do not number next line. . .REQ .nn N Do not number next .argument N lines. . .REQ .nr register \(+-N M Define or modify .argument register using .argument \(+-N with auto-increment .argument M . . .REQ .nroff Make the built-in condition .B n true and .B t false. . .REQ .ns Turn no-space mode on. . .REQ .nx filename Next file. . .REQ .open stream filename Open .register filename for writing and associate the stream named .register stream with it. . .REQ .opena stream filename Like .request .open but append to it. . .REQ .os Output vertical distance that was saved by the .request .sv request. . .REQ .pc Reset page number character to\ \c .'char % . . .REQ .pc c Page number character. . .REQ .pi program Pipe output to .argument program (nroff only). . .REQ .pl Set page length to default .scalednumber 11 i . The current page length is stored in .register .p . . .REQ .pl \(+-N Change page length to .argument \(+-N (default scale indicator\ \c .scaleindicator v ). . .REQ .pm Print macro names and sizes (number of blocks of 128 bytes). . .REQ ".pm t" Print only total of sizes of macros (number of 128 bytes blocks). . .REQ .pn \(+-N Next page number .argument N . . .REQ .pnr Print the names and contents of all currently defined number registers on stderr. . .REQ .po Change to previous page offset. The current page offset is available in .register .o . . .REQ .po \(+-N Page offset .argument N . . .REQ .ps Return to previous point-size. .REQ .ps \(+-N Point size; same as .esc[arg] s \(+-N . . .REQ .psbb filename Get the bounding box of a PostScript image .argument filename . . .REQ .pso command This behaves like the .request .so request except that input comes from the standard output of .argument command . . .REQ .ptr Print the names and positions of all traps (not including input line traps and diversion traps) on stderr. . .REQ .rchar c1 c2... Remove the definitions of characters .argument c1 , .argument c2 , .argument ... . .REQ .rd prompt Read insertion. . .REQ .rj n Right justify the next .argument n input lines. . .REQ .rm name Remove request, macro, or string .argument name . . .REQ .rn old new Rename request, macro, or string .argument old to .argument new . . .REQ .rnn reg1 reg2 Rename register .argument reg1 to .argument reg2 . . .REQ .rr register Remove .argument register . . .REQ .rs Restore spacing; turn no-space mode off. . .REQ .rt \(+-N Return .I (upward only) to marked vertical place (default scale indicator\ \c .scaleindicator v ). . .REQ .shc Reset soft hyphen character to .esc (hy . . .REQ .shc c Set the soft hyphen character to .argument c . . .REQ .shift n In a macro, shift the arguments by .argument n \ \c positions. . .REQ .so filename Include source file. . .REQ .sp Skip one line vertically. . .REQ .sp N Space vertical distance .argument N up or down according to sign of .argument N (default scaling indicator\ \c .scaleindicator v ). . .REQ .special s1 s2 ... Fonts .argument s1 , .argument s2 , etc. are special and will be searched for characters not in the current font. . .REQ .ss N Space-character size set to .argument N /12 of the spacewidth in the current font. . .REQ .ss N M Space-character size set to .argterm N /12 and sentence space size set to .argterm M /12 of the spacewidth in the current font (\f(CR\(eq1/3 em\fP). . .REQ .sty n style Associate .argument style with font position .argument n . . .REQ .substring register n1 n2 Replace the string in .argument register with the substring defined by the indices .argument n1 and .argument n2 . . .REQ .sv Save .scalednumber 1 v of vertical space. . .REQ .sv N Save the vertical distance .argument N for later output with .request .os request. . .REQ .sy command-line Execute program .argument command-line . . .REQ ".ta T" N Set tabs after every position that is a multiple of .argument N (default scaling indicator\ \c .scaleindicator m ). .REQ .ta n1 n2 ... nn \f(CBT\fP r1 r2 ... rn Set tabs at positions .argument n1 , .argument n2 , \&..., .argument nn , then set tabs at .argument nn + r1 , .argument nn + r2 , \&..., .argument nn + rn , then at .argument nn + rn + r1 , .argument nn + rn + r2 , \&..., .argument nn + rn + rn , and so on. . .\".REQ .tar .\"Restore internally saved tab positions. .\". .\".REQ .tas .\"Save tab positions internally. . .REQ .tc Remove tab repetition character. .REQ .tc c Set tab repetition character to\ \c .argument c . . .REQ .ti \(+-N Temporary indent next line (default scaling indicator\ \c .scaleindicator m ). . .REQ .tkf font s1 n1 s2 n2 Enable track kerning for .argument font . . .REQ .tl \f(CB\(cq\fPleft\f(CB\(cq\fPcenter\f(CB\(cq\fPright\f(CB\(cq\fP Three-part title. . .REQ .trf filename Transparently output the contents of file .argument filename . . .REQ .tm anything Print .argument anything on terminal (UNIX standard message output). . .REQ .tr abcd.... Translate .argument a to .argument b , .argument c to .argument d , etc. on output. . .REQ .trnt abcd.... This is the same as the .request .tr request except that the translations do not apply to text that is transparently throughput into a diversion with .esc ! . . .REQ .troff Make the built-in condition .B t true and .B n false. . .REQ .uf font Underline font set to .argument font (to be switched to by .request .ul ). . .REQ .ul N Underline (italicize in troff) .argument N input lines. . .REQ .vpt n Enable vertical position traps if .argument n is non-zero, disable them otherwise. . .REQ .vs Change to previous vertical base line spacing. . .REQ .vs N Set vertical base line spacing to .argument N . Default value is .scalednumber 12 p . . .REQ .warn n Set warnings code to .argument n . . .REQ .wh N trap Set location trap; negative means from page bottom. . .REQ .while cond anything While condition .argument cond is true, accept .argument anything as input. . .REQ .write stream anything Write .argument anything to the stream named .argument stream . . .PD .LP Besides these standard groff requests, there might be further macro calls. They can originate from a macro package (see .BR roff (7) for an overview) or from a preprocessor. .LP Preprocessor macros are easy to be recognized. They enclose their code into a pair of characteristic macros. .LP .TS box, center, tab (@); c | c | c CfCB | CfCB | CfCB. preprocessor@start macro@ end macro = eqn@.PS@.PE grap@.G1@.G2 grn@.GS@.GE pic@.PS@.PE refer@.R1@.R2 soelim@\fInone@\fInone tbl@.TS@.TE .TE .LP . .\" -------------------------------------------------------------------- .SH "ESCAPE SEQUENCES" .\" -------------------------------------------------------------------- . Escape sequences are in-line language elements usually introduced by a backslash .'char \(rs and followed by an escape name and sometimes by a required argument. Input processing is continued directly after the escaped character or the argument resp. without an intervening separation character. So there must be a way to determine the end of the escape name and the end of the argument. .LP This is done by enclosing names (escape name and arguments consisting of a variable name) by a pair of brackets .esc[] name and constant arguments (number expressions and characters) by apostrophes (ASCII 0x27) like .IR \(cqconstant\(cq . .LP There are abbreviations for short names. Two character escape names can be specified by an opening parenthesis like .esc( xy without a closing counterpart. And all one-character names different from the special characters .'char [ and .'char ( can even be specified without a marker in the form .esc \fP\f(CIc . .LP Constant arguments of length .number 1 can omit the marker apostrophes, too, but there is no two-character analogue. .LP While 1-character escape sequences are mainly used for in-line functions and system related tasks, the 2-letter names following the .esc( "" construct are used for special characters predefined by the roff system. Names with more than two characters .esc[] name mostly denote user defined named characters (see the .request .char request). . .\" -------------------------------------------------------------------- .SS "SINGLE CHARACTER ESCAPES" .\" -------------------------------------------------------------------- . .PD 0 . .\" --------- comments --------- . .ESC \(dq Beginning of a comment. Everything up to the end of the line is ignored. . .ESC # Everything up to and including the next newline is ignored. This is interpreted in copy mode. This is like .esc \(dq except the ignoring of the terminating newline. . .\" --------- strings --------- . .ESC * s The string stored in the string variable with 1-character name .argument s . . .ESC *( st The string stored in the string variable with 2-character name .argument st . . .ESC[] * stringvar The string stored in the string variable with arbitrary length name .argument stringvar . . .\" --------- macro arguments --------- . .ESC $0 The name by which the current macro was invoked. The .request .als request can make a macro have more than one name. . .ESC $ x Macro argument with 1-place number .argument x , where .argument x is a digit between 1 and 9. . .ESC $( xy Macro argument with 2-digit number .argument xy . . .ESC[] $ nexp Macro argument with number .argument nexp , where .argument nexp is a numerical expression evaluating to an integer \(>=1. . .ESC $* In a macro, the concatenation of all the arguments separated by spaces. . .ESC $@ In a macro, the concatenation of all the arguments with each surrounded by double quotes, and separated by spaces. . .\" --------- escaped characters --------- . .ESC \(rs reduces to a single backslash; useful to delay its interpretation as escape character in copy mode. For a printable backslash, use .esc e . . .ESC \(cq The acute accent \(aa; same as .esc( aa . Unescaped: apostrophe, right quotation mark, single quote (ASCII 0x27). . .ESC ` The grave accent \(ga; same as .esc( ga . Unescaped: left quote, backquote (ASCII 0x60). . .ESC \- The \- sign in the current font. . .ESC . An uninterpreted dot (period), even at start of line. . .ESC % Default optional hyphenation character. . .ESC ! Transparent line indicator. . .ESC ? anything\fB?\fP In a diversion, this will transparently embed .argument anything in the diversion. .argument anything is read in copy mode. See also the escape sequences .esc ! and .esc ? . . . .\" --------- spacing --------- . .ESC \& space Unpaddable space-size space character (no line break). . .ESC 0 Digit width. . .ESC | 1/6\ em narrow space character; zero width in nroff. . .ESC ^ 1/12\ em half-narrow space character; zero width in nroff. . .ESC & Non-printable, zero width character. . .ESC ) Like .esc & except that it behaves like a character declared with the cflags request to be transparent for the purposes of end of sentence recognition. . .ESC / 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. . .ESC , 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. . .ESC ~ Unbreakable space that stretches like a normal inter-word space when a line is adjusted. . .ESC \& newline Ignored newline, for continuation lines. . .\" --------- structuring --------- . .ESC { Begin conditional input. . .ESC } End conditional input. . .\" --------- longer escape names --------- . .ESC ( st The special character with 2-character name .argument st , see section .BR "SPECIAL CHARACTERS" . . .ESC[] \& name The named character with arbitrary length name .argument name . . .\" --------- alphabetical escapes --------- . .ESC a Non-interpreted leader character. . .ESCq A anything If .argument anything acceptable as name of a string, macro, diversion, register, environment or font it is .number 1 otherwise .number 0 . . .ESCq b abc... Bracket building function. . .ESC c Interrupt text processing. . .ESCq C char The character called .argument char ; same as .esc[] char , but compatible to other roff versions. . .ESC d Forward (down) 1/2 em vertical unit (1/2 line in nroff). . .ESCq D charseq Draw a graphical element defined by the characters in .argument charseq ; see groff info file for details. . .ESC e Printable version of the current escape character. . .ESC E Equivalent to an escape character, but is not interpreted in copy-mode. . .ESC f F Change to font with 1-character name or 1-digit number .argument F . . .ESC f( fo Change to font with 2-character name or 2-digit number .argument fo . . .ESC[] f font Change to font with arbitrary length name or number expression .argument font . . .ESC[] g reg Return format of register with name .argument reg suitable for .request .af . Alternative forms .esc(arg g xy and .escarg g x . . .ESCq h N Local horizontal motion; move right .argument N (left if negative). . .ESCq H N Set height of current font to .argument N . . .ESC[] k reg Mark horizontal input place in register with arbitrary length name .argument reg . Alternative forms .esc(arg k xy and .escarg k x . . .ESCq l Nc Horizontal line drawing function (optionally using character .argument c ). . .ESCq L Nc Vertical line drawing function (optionally using character .argument c ). . .ESC n r The numerical value stored in the register variable with the 1-character name .argument r . . .ESC n( re The numerical value stored in the register variable with the 2-character name .argument re . . .ESC[] n reg The numerical value stored in the register variable with arbitrary length name .argument reg . . .ESCq N n Typeset the character with code .argument n in the current font, no special fonts are searched. Useful for adding characters to a font using the .request .char request. . .ESCq o abc... Overstrike characters .argument a , .argument b , .argument c , etc. . .ESC p Break and spread output line. . .ESC r Reverse 1\ em vertical motion (reverse line in nroff). . .ESCq R name \(+-n The same as .request .nr .argument name .argument \(+-n . . .ESC[] s \(+-N Set the point size to .I N scaled points. Note the alternative forms .BI \(rss \(+- [ N ]\c , .BI \(rss' \(+-N '\c , .BI \(rss \(+- ' N '\c , .esc(arg s \(+-xy , .BI \(rss \(+- ( xy\c , .escarg s \(+-x . Same as .request .ps request. . .ESCq S N Slant output .argument N degrees. . .ESC t Non-interpreted horizontal tab. . .ESC u Reverse (up) 1/2 em vertical motion (1/2 line in nroff). . .ESCq v N Local vertical motion; move down .argument N (up if negative). . .ESC[] V env The contents of the environment variable .argument env . Alternative forms .esc(arg V xy and .escarg V x . . .ESCq w string The width of the character sequence .argument string . . .ESCq x N Extra line-space function (negative before, positive after). . .ESCq X string Output .argument string as device control function. . .ESC[] Y name Output string variable or macro .argument name uninterpreted as device control function. Alternative forms .esc(arg Y xy and .escarg Y x . . .ESC z c Print .argument c with zero width (without spacing). . .ESCq Z anything Print .argument anything and then restore the horizontal and vertical position; .argument anything may not contain tabs or leaders. .PD .LP The escape sequences .esc e , .esc . , .esc \(dq , .esc $ , .esc * , .esc a , .esc n , .esc t , .esc g , and .escarg \& newline are interpreted in copy mode. .LP Escape sequences starting with .esc ( or .esc [ do not represent single character escape sequences, but introduce escape names with two or more characters. .LP If a backslash is followed by a character that does not constitute a defined escape sequence the backslash is silently ignored and the character maps to itself. . .\" -------------------------------------------------------------------- .SS "SPECIAL CHARACTERS" .\" -------------------------------------------------------------------- Common special characters are predefined by escape sequences of the form .(esc \fP\f(CIxy with characters .argument x and .argument y . Some of these exist in the usual font while most of them are only available in the special font. Below you'll find a selection of the most important glyphs; a complete list can be found in .BR groff_char (7). .RS .LP .PD 0 . .ESc bu Bullet sign .ESc co Copyright .ESc ct Cent .ESc dd Double dagger .ESc de Degree .ESc dg Dagger .ESc em Em-dash .ESc hy Hyphen .ESc rg Registered sign .ESc sc Section sign .ESc ul Underline character .ESc == Identical .ESc >= Larger or equal .ESc <= Less or equal .ESc != Not equal .ESc -> Right arrow .ESc <- Left arrow .ESc +- Plus-minus sign .PD .RE . .\" -------------------------------------------------------------------- .SH REGISTERS .\" -------------------------------------------------------------------- Registers are variables that store a value. In groff, most registers store numerical values (see section .B NUMERICAL EXPRESSIONS above), but some can also hold a string value. .LP Each register is given a name. Arbitrary registers can be defined and set with the request .request .nr .argument register . .LP The value stored in a register can be retrieved by the escape sequences introduced by .esc n . .LP Most useful are predefined registers. In the following the notation .argument name is used to refer to a register called .register name to make clear that we speak about registers. Please keep in mind that the .esc en[] decoration is not part of the register name. . .\" -------------------------------------------------------------------- .SS "READ-ONLY REGISTERS" .\" -------------------------------------------------------------------- The following registers have predefined values that should not be modified by the user (usually, registers starting with a dot a read-only). Mostly, they provide information on the current settings or store results from request calls. .LP .PD 0 .REG .$ Number of arguments in the current macro. .REG .A Set to .number 1 in .B troff if option .B \-A is used; always .number 1 in .BR nroff . .REG .H Available horizontal resolution in basic units. .REG .T Set to .number 1 if option .B \-T is used. .REG .V Available vertical resolution in basic units. .REG .a Post-line extra line-space most recently utilized using .escarg x 'N' . .REG .C 1 if compatibility mode is in effect, 0 otherwise. .REG .c Current input line number. .REG .cdp The depth of the last character added to the current environment. It is positive if the character extends below the baseline. .REG .ce The number of lines remaining to be centered, as set by the .request .ce request. .REG .cht The height of the last character added to the current environment. It is positive if the character extends above the baseline. .REG .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. .REG .d Current vertical place in current diversion; equal to register .register nl . .REG .ev The name or number of the current environment (string-valued). .REG .f Current font number. .REG .fam The current font family (string-valued). .REG .fp The number of the next free font position. .REG .g Always 1 in GNU troff. Macros should use it to test if running under groff. .REG .h Text base-line high-water mark on current page or diversion. .REG .hla The current hyphenation language as set by the .B .hla request. .REG .hlc The number of immediately preceding consecutive hyphenated lines. .REG .hlm The maximum allowed number of consecutive hyphenated lines, as set by the .request .hlm request. .REG .hy The current hyphenation flags (as set by the .request .hy request). .REG .hym The current hyphenation margin (as set by the .request .hym request). .REG .hys The current hyphenation space (as set by the .request .hys request). .REG .i Current indent. .REG .in The indent that applies to the current output line. .REG .kern .number 1 if pairwise kerning is enabled, .number 0 otherwise. .REG .l Current line length. .REG .lg The current ligature mode (as set by the .request .lg request). .REG .ll The line length that applies to the current output line. .REG .lt The title length (as set by the .request .lt request). .REG .n Length of text portion on previous output line. .REG .ne The amount of space that was needed in the last .request .ne request that caused a trap to be sprung. Useful in conjunction with .register .trunc . .REG .o Current page offset. .REG .p Current page length. .REG .pn The number of the next page: either the value set by a .request .pn request, or the number of the current page plus\ 1. .REG .ps The current pointsize in scaled points. .REG .psr The last-requested pointsize in scaled points. .REG .rj The number of lines to be right-justified as set by the rj request. .REG .s Current point size as a decimal fraction. .REG .sr The last requested pointsize in points as a decimal fraction (string-valued). .REG .t Distance to the next trap. .REG .tabs A string representation of the current tab settings suitable for use as an argument to the .request .ta request. .REG .trunc The amount of vertical space truncated by the most recently sprung vertical position trap, or, if the trap was sprung by a .request .ne request, minus the amount of vertical motion produced by .request .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 .register .ne register. .REG .ss The value of the parameters set by the first argument of the .request .ss request. .REG .sss The value of the parameters set by the second argument of the .request .ss request. .REG .u Equal to 1 bin fill mode and 0 in nofill mode. .REG .v Current vertical line spacing. .REG .vpt .number 1 if vertical position traps are enabled, .number 0 otherwise. .REG .w Width of previous character. .REG .warn The sum of the number codes of the currently enabled warnings. .REG .x The major version number. .REG .y The minor version number. .REG .Y The revision number of groff. .REG .z Name of current diversion. .REG llx Lower left x-coordinate (in PostScript units) of a given PostScript image (set by .request .psbb ). .REG lly Lower left y-coordinate (in PostScript units) of a given PostScript image (set by .request .psbb ). .REG rsb Like .register sb , but takes account of the heights and depths of characters. .REG rst Like .register st , but takes account of the heights and depths of characters. .REG sb Depth of string below base line (generated by width function .esc w ). .REG skw Right skip width from the center of the last character in the .esc w argument. .REG ssc The amount of horizontal space (possibly negative) that should be added to the last character before a subscript (generated by width function .esc w ). .REG st Height of string above base line (generated by width function .esc w ). .REG urx Upper right x-coordinate (in PostScript units) of a given PostScript image (set by .request .psbb ). .REG ury Upper right y-coordinate (in PostScript units) of a given PostScript image (set by .request .psbb ). .PD . .\" -------------------------------------------------------------------- .SS "WRITABLE REGISTERS" .\" -------------------------------------------------------------------- The following registers can be read and written by the user. They have predefined default values, but these can be modified for customizing a document. .LP .PD 0 .REG % Current page number. .REG c. Current input line number. .REG ct Character type (set by width function .esc w ). .REG dl Maximal width of last completed diversion. .REG dw Current day of week (1-7). .REG dy Current day of month (1-31). .REG hp Current horizontal position at input line. .REG ln Output line number. .REG mo Current month (1-12). .REG nl Vertical position of last printed text base-line. .REG slimit If greater than 0, the maximum number of objects on the input stack. If \(<=0 there is no limit, i.e., recursion can continue until virtual memory is exhausted. .REG systat The return value of the .I system() function executed by the last .request .sy request. .REG year The current year (year 2000 compliant). .REG yr Current year minus 1900. For Y2K compliance use register .register year instead. .PD . .\" -------------------------------------------------------------------- .SH WARNINGS .\" -------------------------------------------------------------------- Each warning generated by groff is identified by a name and a code number. The codes are powers of 2 to allow bit-encoding with a single integer. There are also names that can be used to refer to groups of warnings. .LP The name associated with a warning is used by the .option \-w and .option \-W options; the number code is used by the .request .warn request and by the .esc[arg] n warn register. .LP .PD 0 .Warning all group All warnings except .warning di , .warning mac and .warning reg . Intended to cover all warnings with traditional macro packages. .Warning 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. .Warning char 1 Non-existent characters. This is enabled by default. .Warning delim 8 Missing or mismatched closing delimiters. .Warning di 256 Use of .request .di or .request .da without an argument when there is no current diversion. .Warning el 16 Use of the .request .el request with no matching .request .ie request. .Warning escape 32768 Unrecognized escape sequence. Then the escape character is ignored. .Warning font 131072 Non-existent fonts. This is enabled by default. .Warning ig 262144 Illegal escapes in text ignored with the .request \.ig request. These are conditions that are errors when they occur outside of ignored text. .Warning mac 512 Use of undefined strings, macros, and diversions. Automatically handled as empty. Usually, only one warning per name. .Warning missing 8192 Request that is missing non-optional arguments. .Warning input 16384 Illegal input character. .Warning number 2 Invalid numeric expressions. This is enabled by default. .Warning range 64 Out of range arguments. .Warning reg 1024 Use of undefined number register. Automatically defined as having value 0. Usually, only one warning per name. .Warning right-brace 4096 Use of .esc } where a number was expected. .Warning scale 32 Meaningless scaling indicators. .Warning space 65536 Missing space between a request or macro and its argument. Then no macro is automatically defined. This is enabled by default. This warning will never occur in compatibility mode. .Warning syntax 128 Dubious syntax in numeric expressions. .Warning tab 2048 Inappropriate use of a tab character (either in an unquoted macro argument or where a number was expected). .Warning w group All warnings. .PD .LP .TS tab(@), box, expand; c c c | c c c | c c c R RI CB | R RI CB | R RI CB. Bit@Code@Warning@Bit@Code@Warning@Bit@Code@Warning _ 0@1@char@8@256@di@16@65536@space 1@2@number@9@512@mac@17@131072@font 2@4@break@10@1024@reg@18@262144@ig 3@8@delim@11@2048@tab 4@16@el@12@4096@right-brace 5@32@scale@13@8192@missing 6@64@range@14@16384@input 7@128@syntax@15@32768@escape .TE .LP . .\" -------------------------------------------------------------------- .SH COMPATIBILITY .\" -------------------------------------------------------------------- .I groff provides a .B compatibility mode that allows to process roff code written for classical .troff or for other implementations of roff in a consistent way. .LP Compatibility mode can be turned on with the .option \-C command line option, and turned on or off with the .request .cp request. The number register .esc(arg n .C is .number 1 if compatibility mode is on, .number 0 otherwise. .LP This became necessary because the GNU concept for long names causes some incompatibilities. .I Classical troff will interpret .IP .B \&.dsabcd .LP as defining a string .B ab with contents .BR cd . Normally, .I groff will interpret this as a call of a macro named .request dsabcd . .LP Also .I classical troff will interpret .esc *[ or .esc n[ as references to a string or number register called .register [ . In .I GNU native .IR mode , however, this will normally be interpreted as the start of a long name. .LP In .I compatibility .IR mode , groff will interpret these things in the traditional way, but long names are not recognized. .LP On the other hand, groff in .I GNU native mode does not allow to use the escape sequences .esc e , .esc | , .esc ^ , .esc & , .esc } , .esc { , .esc "\ " (space), .esc ' , .esc ` , .esc - , .esc _ , .esc ! , .esc % , and .esc c in names of strings, macros, diversions, number registers, fonts or environments, whereas .I classical troff does. The .esc A escape sequence can be helpful in avoiding these escape sequences in names. .LP Fractional pointsizes cause one noteworthy incompatibility. In .I classical .IR troff , the .request .ps request ignores scale indicators and so .RS .LP .B .ps\ 10u .RE .LP will set the pointsize to 10 points, whereas in groff native mode the pointsize will be set to 10 scaled points. .LP In .I groff mode, 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 the .request .bd , .request .cs , .request .tkf , .request .tr , or .request .fp requests. .LP 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. .LP 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. The following example will make things clearer. .LP .RS .nf .ft B \&.di x \(rs\(rs\(rs\(rs \&.br \&.di \&.x .ft .fi .RE .LP In .I GNU mode this will be printed as .esc \(rs . So each pair of input backslashes .'char \(rs\(rs is turned into a single output backslash .'char \(rs and the resulting output backslashes are not interpreted as escape characters when they are reread. .LP .I Classical troff would interpret them as escape characters when they were reread and would end up printing a single backslash .'char \(rs . .LP The correct way to get a printable .'char \(rs is to use the .esc 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 mode and compatibility mode. .LP To store an escape sequence in a diversion that will be interpreted when the diversion is reread, either the traditional .esc ! transparent output facility or the new .esc ? escape sequence can be used. . .\" -------------------------------------------------------------------- .SH BUGS .\" -------------------------------------------------------------------- At the moment, the documentation of the groff system is in a state of change and evolution. It is possible that there are small inconsistencies between different documents temporarily. .LP The .B WARNINGS section belongs to .BR troff (1). . .\" -------------------------------------------------------------------- .SH AUTHOR .\" -------------------------------------------------------------------- This document is part of groff, the GNU roff distribution. It was written by Bernd Warken . .LP It is distributed under the terms of the FDL (GNU Free Documentation License) version 1.1 or later. You should have received a copy of the FDL on your system, it is also available on-line under .RS .LP .IR http://www.gnu.org/copyleft/fdl.html . .RE .LP Formerly, the extensions of the groff language were kept in the manual page .BR troff (1). This document contains the essential parts of that documentation, but the gory details are found in the groff info file. . .\" -------------------------------------------------------------------- .SH "SEE ALSO" .\" -------------------------------------------------------------------- The main source of information for the groff language is the .B groff .BR info (1) file. .LP For a survey of roff and the groff system and further documentation pointers see .BR roff (7). .LP The formatter programs are described in .BR groff (1) and .BR troff (1); a complete of all predefined glyph names can be found in .BR groff_char (7). .LP The classical .I troff documentation is available on-line at .RS .LP .I http://cm.bell-labs.com/cm/cs/cstr.html .RE and .RS .IR http://www.kohala.com/start/troff/ .