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GROFF(7)										 GROFF(7)

NAME
       groff - a short reference for the GNU roff language

DESCRIPTION
       The name groff stands for GNU roff and is the free implementation of the roff type-setting
       system.	See roff(7) for a survey and the background of the groff system.

       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.

       Historically,  the roff language was called troff.  groff is compatible with the classical
       system and provides proper extensions.  So in GNU, the terms roff, troff, and  groff  lan-
       guage  could be used as synonyms.  However troff slightly tends to refer more to the clas-
       sical aspects, whereas groff emphasizes the GNU extensions, and roff is the  general  term
       for the language.

       This file is only a short version of the complete documentation that is found in the groff
       info(1) file, which contains more detailed, actual, and concise information.

       The general syntax for writing groff documents is relatively easy, but writing  extensions
       to the roff language can be a bit harder.

       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 "."  or
       a single quote "'"; all other lines are text lines.

       Control lines represent commands, optionally with arguments.  They have the following syn-
       tax.  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,

	      .command_name arg1 arg2

       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.

       Text  lines  represent  the  parts  that  will be printed.  They can be modified by escape
       sequences, which are recognized by a leading backslash '\'.  These are in-line or even in-
       word  formatting  elements or functions.  Some of these take arguments separated by single
       quotes "'", others are regulated by a length encoding introduced by  an	open  parenthesis
       '(' or enclosed in brackets '[' and ']'.

       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 copy mode.

       The  copy  mode	behavior can be quite tricky, but there are some rules that ensure a safe
       usage.

       1.     Printable backslashes must be denoted as \e.  To be more precise, \e represents the
	      current escape character.  To get a backslash glyph, use \(rs or \[rs].

       2.     Double all backslashes.

       3.     Begin all text lines with the special non-spacing character \&.

       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 groff_tmac(5).

       Reading roff source files is easier, just reduce all double backslashes to a single one in
       all macro definitions.

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.

       There  are two kinds of roff commands, possibly with arguments.	Requests are written on a
       line of their own starting with a dot '.' or a "'", whereas Escape sequences  are  in-line
       functions and in-word formatting elements starting with a backslash '\'.

       The  user can define her own formatting commands using the de request.  These commands are
       called 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.

       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.

       String  variables  store  character  sequences.	 They  are  set  with  the ds request and
       retrieved by the \* escape sequences.  Strings can have variables.

       Register variables can store numerical values, numbers with a scale unit, and occasionally
       string-like  objects.   They  are  set  with the nr request and retrieved by the \n escape
       sequences.

       Environments allow the user to temporarily store global formatting  parameters  like  line
       length, font size, etc. for later reuse.  This is done by the ev request.

       Fonts  are identified either by a name or by an internal number.  The current font is cho-
       sen by the ft request or by the \f escape sequences.  Each device has special  fonts,  but
       the  following  fonts  are available for all devices.  R is the standard font Roman.  B is
       its bold counterpart.  The italic font is called I and is  available  everywhere,  but  on
       text  devices  it  is  displayed  as  an  underlined Roman font.  For the graphical output
       devices, there exist constant-width pendants of these fonts, CR,  CI,  and  CB.	 On  text
       devices, all characters have a constant width anyway.

       Moreover,  there  are  some advanced roff elements.  A diversion stores information into a
       macro for later usage.  A 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.

       More detailed information and examples can be found in the groff info file.

CONTROL CHARACTERS
       There is a small set of characters that have a special controlling task in certain  condi-
       tions.

       .      A  dot  is  only	special  at the beginning of a line or after the condition in the
	      requests if, ie, el, and while.  There it is the control character that  introduces
	      a request (or macro).  The special behavior can be delayed by using the \.  escape.
	      By using the cc request, the control character can be set to a different character,
	      making the dot '.' a non-special character.

	      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.

       '      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 c2 request, the non-break control
	      character can be set to a different character.

	      As a second task, it is the most commonly used argument  separator  in  some  func-
	      tional  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  charac-
	      ter.  Groff provides a printable representation with the \(cq escape sequence.

       "      The double quote is used to enclose arguments in requests, macros, and strings.  In
	      the ds and as requests, a leading double quote in the  argument  will  be  stripped
	      off,  making  everything else afterwards the string to be defined (enabling leading
	      whitespace).  The escaped double quote \" introduces a comment.  Otherwise,  it  is
	      not  special.   Groff  provides  a  printable  representation  with the \(dq escape
	      sequence.

       \      The backslash usually introduces an escape sequence (this can be changed	with  the
	      ec  request).   A printed version of the escape character is the \e escape; a back-
	      slash glyph can be obtained by \(rs.

       (      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 [] construct.

       [      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-spe-
	      cial, e.g. in macro calls.

       ]      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.

       space  Space  characters  are  only functional characters.  They separate the arguments in
	      requests, macros, and strings, and the words in text lines.  They  are  subject  to
	      groff's  horizontal  spacing  calculations.   To	get a defined space width, escape
	      sequences like '\ ' (this is the escape character followed by a space), \|, \^,  or
	      \h should be used.

       newline
	      In  text	paragraphs,  newlines  mostly behave like space characters.  Continuation
	      lines can be specified by an escaped newline, i.e., by specifying a  backslash  '\'
	      as the last character of a line.

       tab    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.

NUMERICAL EXPRESSIONS
       A  numerical  value  is	a signed or unsigned integer or float with or without an appended
       scaling indicator.  A scaling indicator is a one-character abbreviation for a unit of mea-
       surement.   A  number followed by a scaling indicator signifies a size value.  By default,
       numerical values do not have a scaling indicator, i.e., they are normal numbers.

       The roff language defines the following scaling indicators.

	      c 	Centimeter
	      i 	Inch
	      P 	Pica = 1/6 inch
	      p 	Point = 1/72 inch
	      m 	Em = the font size in points (width of letter `m')
	      M 	100th of an Em
	      n 	En = Em/2
	      u 	Basic unit for actual output device
	      v 	Vertical line space in basic units scaled point = 1/sizescale of a  point
			(defined in font DESC file)
	      f 	Scale by 65536.

       Numerical expressions are combinations of the numerical values defined above with the fol-
       lowing arithmetical operators already defined in classical troff.

	      + 	Addition
	      - 	Subtraction
	      * 	Multiplication
	      / 	Division
	      % 	Modulo
	      = 	Equals
	      ==	Equals
	      < 	Less than
	      > 	Greater than
	      <=	Less or equal
	      >=	Greater or equal
	      & 	Logical and
	      : 	Logical or
	      ! 	Logical not
	      ( 	Grouping of expressions
	      ) 	Close current grouping

       Moreover, groff added the following operators for numerical expressions:

	      e1>?e2	The maximum of e1 and e2.
	      e1<?e2	The minimum of e1 and e2.
	      (c;e)	Evaluate e using c as the default scaling indicator.

       For details see the groff info file.

CONDITIONS
       Conditions occur in tests raised by the if, ie, and the while requests.	The following ta-
       ble characterizes the different types of conditions.

	      N 	A numerical expression N yields true if its value is greater than 0.
	      !N	True if the value of I is 0.
	      's1's2'	True if string s1 is identical to string s2.
	      !'s1's2'	True if string s1 is not identical to string s2.
	      cch	True if there is a character ch available.
	      dname	True if there is a string, macro, diversion, or request called name.
	      e 	Current page number is even.
	      o 	Current page number is odd.
	      mname	True if there is a color called name.
	      n 	Formatter is nroff.
	      rreg	True if there is a register named reg.
	      t 	Formatter is troff.
	      Ffont	True if there exists a font named font.
	      Sstyle	True if a style named style has been registered.

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.

       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., "arg with space" denotes a single argument.

       Some requests have optional arguments with  a  different  behaviour.   Not  all	of  these
       details	are  outlined  here.   Refer  to  the  groff  info file and groff_diff(7) for all
       details.

       In the following request specifications, most argument names were chosen  to  be  descrip-
       tive.  Only the following denotations need clarification.

	      c 	denotes a single character.
	      font	a font either specified as a font name or a font number.
	      anything	all characters up to the end of the line or within \{ and \}.
	      n 	is a numerical expression that evaluates to an integer value.
	      N 	is an arbitrary numerical expression, signed or unsigned.
	      +-N	has three meanings depending on its sign, described below.

       If  an expression defined as +-N starts with a '+' sign the resulting value of the expres-
       sion 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 '-' the value of the expres-
       sion will be subtracted from the request value.

       Without a sign, N replaces the existing value  directly.   To  assign  a  negative  number
       either prepend 0 or enclose the negative number in parentheses.

   Request Short Reference
       .	 Empty line, ignored.  Useful for structuring documents.
       .\" anything
		 Complete line is a comment.
       .ab string
		 Print string on standard error, exit program.
       .ad	 Begin line adjustment for output lines in current adjust mode.
       .ad c	 Start line adjustment in mode c (c=l,r,b,n).
       .af register c
		 Assign format c to register (c=l,i,I,a,A).
       .aln alias register
		 Create alias name for register.
       .als alias object
		 Create alias name for request, string, macro, or diversion object.
       .am macro Append to macro until .. is encountered.
       .am macro end
		 Append to macro until .end is called.
       .am1 macro
		 Same as .am but with compatibility mode switched off during macro expansion.
       .am1 macro end
		 Same as .am but with compatibility mode switched off during macro expansion.
       .ami macro
		 Append  to a macro whose name is contained in the string register macro until ..
		 is encountered.
       .ami macro end
		 Append to a macro indirectly.	macro and end are string registers whose contents
		 are interpolated for the macro name and the end macro, respectively.
       .ami1 macro
		 Same as .ami but with compatibility mode switched off during macro expansion.
       .ami1 macro end
		 Same as .ami but with compatibility mode switched off during macro expansion.
       .as stringvar anything
		 Append anything to stringvar.
       .as1 stringvar anything
		 Same as .as but with compatibility mode switched off during string expansion.
       .asciify diversion
		 Unformat ASCII characters, spaces, and some escape sequences in diversion.
       .backtrace
		 Print a backtrace of the input on stderr.
       .bd font N
		 Embolden font by N-1 units.
       .bd S font N
		 Embolden Special Font S when current font is font.
       .blm	 Unset the blank line macro.
       .blm macro
		 Set the blank line macro to macro.
       .box	 End current diversion.
       .box macro
		 Divert to macro, omitting a partially filled line.
       .boxa	 End current diversion.
       .boxa macro
		 Divert and append to macro, omitting a partially filled line.
       .bp	 Eject current page and begin new page.
       .bp +-N	 Eject current page; next page number +-N.
       .br	 Line break.
       .brp	 Break and spread output line.	Same as \p.
       .break	 Break out of a while loop.
       .c2	 Reset no-break control character to "'".
       .c2 c	 Set no-break control character to c.
       .cc	 Reset control character to '.'.
       .cc c	 Set control character to c.
       .ce	 Center the next input line.
       .ce N	 Center following N input lines.
       .cf filename
		 Copy contents of file filename unprocessed to stdout or to the diversion.
       .cflags mode c1 c2 ...
		 Treat characters c1, c2, ... according to mode number.
       .ch trap N
		 Change trap location to N .
       .char c anything
		 Define character c as string anything.
       .chop object
		 Chop the last character off macro, string, or diversion object.
       .close stream
		 Close the stream.
       .color	 Enable colors.
       .color N  If N is zero disable colors, otherwise enable them.
       .composite from to
		 Map glyph name from to glyph name to while constructing a composite glyph name.
       .continue Finish the current iteration of a while loop.
       .cp	 Enable compatibility mode.
       .cp N	 If N is zero disable compatibility mode, otherwise enable it.
       .cs font N M
		 Set constant character width mode for font to N/36 ems with em M.
       .cu N	 Continuous underline in nroff, like .ul in troff.
       .da	 End current diversion.
       .da macro Divert and append to macro.
       .de macro Define or redefine macro until .. is encountered.
       .de macro end
		 Define or redefine macro until .end is called.
       .de1 macro
		 Same as .de but with compatibility mode switched off during macro expansion.
       .de1 macro end
		 Same as .de but with compatibility mode switched off during macro expansion.
       .defcolor color scheme component
		 Define or redefine a color with name color.  scheme can be rgb, cym, cymk, gray,
		 or grey.  component can be single components specified as fractions in the range
		 0 to 1 (default scaling indicator f), as a string of two-digit hexadecimal color
		 components with a leading #, or as a string of four-digit hexadecimal components
		 with two leading #.  The color default can't be redefined.
       .dei macro
		 Define  or redefine a macro whose name is contained in the string register macro
		 until .. is encountered.
       .dei macro end
		 Define or redefine a macro indirectly.  macro and end are string registers whose
		 contents are interpolated for the macro name and the end macro, respectively.
       .dei1 macro
		 Same as .dei but with compatibility mode switched off during macro expansion.
       .dei1 macro end
		 Same as .dei but with compatibility mode switched off during macro expansion.
       .di	 End current diversion.
       .di macro Divert to macro .
       .do name  Interpret .name with compatibility mode disabled.
       .ds stringvar anything
		 Set stringvar to anything.
       .ds1 stringvar anything
		 Same as .ds but with compatibility mode switched off during string expansion.
       .dt N trap
		 Set diversion trap to position N (default scaling indicator v).
       .ec	 Reset escape character to '\'.
       .ec c	 Set escape character to c.
       .ecr	 Restore escape character saved with .ecs.
       .ecs	 Save current escape character.
       .el anything
		 Else part for if-else (ie) request.
       .em macro The macro will be run after the end of input.
       .eo	 Turn off escape character mechanism.
       .ev	 Switch to previous environment.
       .ev env	 Push down environment number or name env and switch to it.
       .evc env  Copy  the contents of environment env to the current environment.  No pushing or
		 popping.
       .ex	 Exit from roff processing.
       .fam	 Return to previous font family.
       .fam name Set the current font family to name.
       .fc	 Disable field mechanism.
       .fc a	 Set field delimiter to a and pad character to space.
       .fc a b	 Set field delimiter to a and pad character to b.
       .fchar c anything
		 Define fallback character c as string anything.
       .fcolor	 Set fill color to previous fill color.
       .fcolor c Set fill color to c.
       .fi	 Fill output lines.
       .fl	 Flush output buffer.
       .fp n font
		 Mount font on position n.
       .fp n internal external
		 Mount font with long external name to short internal name on position n.
       .fschar f c anything
		 Define fallback character c for font f as string anything.
       .fspecial font
		 Reset list of special fonts for font to be empty.
       .fspecial font s1 s2 ...
		 When the current font is font, then the fonts s1, s2, ... will be special.
       .ft	 Return to previous font.  Same as \f[] or \fP.
       .ft font  Change to font name or number font; same as \f[font] escape sequence.
       .ftr font1 font2
		 Translate font1 to font2.
       .gcolor	 Set glyph color to previous glyph color.
       .gcolor c Set glyph color to c.
       .hc	 Remove additional hyphenation indicator character.
       .hc c	 Set up additional hyphenation indicator character c.
       .hcode c1 code1 c2 code2 ...
		 Set the hyphenation code of character c1 to code1, that of c2 to code2, etc.
       .hla lang Set the current hyphenation language to lang.
       .hlm n	 Set the maximum number of consecutive hyphenated lines to n.
       .hpf file Read hyphenation patterns from file.
       .hpfa file
		 Append hyphenation patterns from file.
       .hpfcode file
		 Set input mapping for .hpf.
       .hw words List of words with exceptional hyphenation.
       .hy N	 Switch to hyphenation mode N.
       .hym n	 Set the hyphenation margin to n (default scaling indicator m).
       .hys n	 Set the hyphenation space to n.
       .ie cond anything
		 If cond then anything else goto .el.
       .if cond anything
		 If cond then anything; otherwise do nothing.
       .ig	 Ignore text until .. is encountered.
       .ig end	 Ignore text until .end.
       .in	 Change to previous indent value.
       .in +-N	 Change indent according to +-N (default scaling indicator m).
       .it N trap
		 Set an input-line count trap for the next N lines.
       .itc N trap
		 Same as .it but count lines interrupted with \c as one line.
       .kern	 Enable pairwise kerning.
       .kern n	 If n is zero, disable pairwise kerning, otherwise enable it.
       .lc	 Remove leader repetition character.
       .lc c	 Set leader repetition character to c.
       .length register anything
		 Write the length of the string anything in register.
       .linetabs Enable line-tabs mode (i.e., calculate tab positions relative to output line).
       .linetabs n
		 If n is zero, disable line-tabs mode, otherwise enable it.
       .lf N	 Set input line number to N.
       .lf N file
		 Set input line number to N and filename to file.
       .lg N	 Ligature mode on if N>0.
       .ll	 Change to previous line length.
       .ll +-N	 Set line length according to +-N (default size  6.5i,	default  scaling  indica-
		 tor m).
       .ls	 Change to the previous value of additional intra-line skip.
       .ls N	 Set  additional  intra-line  skip value to N, i.e., N-1 blank lines are inserted
		 after each text output line.
       .lt +-N	 Length of title (default scaling indicator m).
       .mc	 Margin character off.
       .mc c	 Print character c after each text line at actual distance from right margin.
       .mc c N	 Set margin character to c and distance to N from right margin	(default  scaling
		 indicator m).
       .mk register
		 Mark current vertical position in register.
       .mso file The  same  as	the .so request except that file is searched in the tmac directo-
		 ries.
       .na	 No output-line adjusting.
       .ne	 Need a one-line vertical space.
       .ne N	 Need N vertical space (default scaling indicator v).
       .nf	 No filling or adjusting of output-lines.
       .nh	 No hyphenation.
       .nm	 Number mode off.
       .nm +-N [M [S [I]]]
		 In line number mode, set number, multiple, spacing, and indent.
       .nn	 Do not number next line.
       .nn N	 Do not number next N lines.
       .nop anything
		 Always execute anything.
       .nr register +-N M
		 Define or modify register using +-N with auto-increment M.
       .nroff	 Make the built-in condition n true and t false.
       .ns	 Turn no-space mode on.
       .nx	 Immediately jump to end of current file.
       .nx filename
		 Next file.
       .open stream filename
		 Open register filename for writing  and  associate  the  stream  named  register
		 stream with it.
       .opena stream filename
		 Like .open but append to it.
       .os	 Output vertical distance that was saved by the sv request.
       .output string
		 Emit  string  directly  to  intermediate  output, allowing leading whitespace if
		 string starts with " (which will be stripped off).
       .pc	 Reset page number character to '%'.
       .pc c	 Page number character.
       .pi program
		 Pipe output to program (nroff only).
       .pl	 Set page length to default 11i.  The current page length is stored  in  register
		 .p.
       .pl +-N	 Change page length to +-N (default scaling indicator v).
       .pm	 Print macro names and sizes (number of blocks of 128 bytes).
       .pm t	 Print only total of sizes of macros (number of 128 bytes blocks).
       .pn +-N	 Next page number N.
       .pnr	 Print	the  names  and  contents  of  all  currently defined number registers on
		 stderr.
       .po	 Change to previous page offset.  The current page offset is available in  regis-
		 ter .o.
       .po +-N	 Page offset N.
       .ps	 Return to previous point-size.
       .ps +-N	 Point size; same as \s[+-N].
       .psbb filename
		 Get the bounding box of a PostScript image filename.
       .pso command
		 This  behaves like the so request except that input comes from the standard out-
		 put of command.
       .ptr	 Print the names and positions of all traps (not including input line  traps  and
		 diversion traps) on stderr.
       .pvs	 Change to previous post-vertical line spacing.
       .pvs +-N  Change  post-vertical	line  spacing  according  to +-N (default scaling indica-
		 tor p).
       .rchar c1 c2 ...
		 Remove the definitions of characters c1, c2, ...
       .rd prompt
		 Read insertion.
       .return	 Return from a macro.
       .return anything
		 Return twice, namely from the macro at the current level and from the macro  one
		 level higher.
       .rfschar f c1 c2 ...
		 Remove the definitions of characters c1, c2, ... for font f.
       .rj n	 Right justify the next n input lines.
       .rm name  Remove request, macro, or string name.
       .rn old new
		 Rename request, macro, or string old to new.
       .rnn reg1 reg2
		 Rename register reg1 to reg2.
       .rr register
		 Remove register.
       .rs	 Restore spacing; turn no-space mode off.
       .rt +-N	 Return (upward only) to marked vertical place (default scaling indicator v).
       .schar c anything
		 Define global fallback character c as string anything.
       .shc	 Reset soft hyphen character to \(hy.
       .shc c	 Set the soft hyphen character to c.
       .shift n  In a macro, shift the arguments by n positions.
       .sizes s1 s2 ... sn [0]
		 Set available font sizes similar to the sizes command in a DESC file.
       .so filename
		 Include source file.
       .sp	 Skip one line vertically.
       .sp N	 Space	vertical  distance  N  up or down according to sign of N (default scaling
		 indicator v).
       .special  Reset global list of special fonts to be empty.
       .special s1 s2 ...
		 Fonts s1, s2, etc. are special and will be searched for characters  not  in  the
		 current font.
       .spreadwarn
		 Toggle the spread warning on and off without changing its value.
       .spreadwarn limit
		 Emit  a  warning  if  each  space  in an output line is widened by limit or more
		 (default scaling indicator m).
       .ss N	 Space-character size set to N/12 of the spacewidth in the current font.
       .ss N M	 Space-character size set to N/12 and sentence space size  set	to  M/12  of  the
		 spacewidth in the current font (=1/3 em).
       .sty n style
		 Associate style with font position n.
       .substring xx n1 n2
		 Replace the string named xx with the substring defined by the indices n1 and n2.
       .sv	 Save 1v of vertical space.
       .sv N	 Save the vertical distance N for later output with os request.
       .sy command-line
		 Execute program command-line.
       .ta T N	 Set  tabs  after every position that is a multiple of N (default scaling indica-
		 tor m).
       .ta n1 n2 ... nn T r1 r2 ... rn
		 Set tabs at positions n1, n2, ..., nn, then  set  tabs  at  nn+r1,  nn+r2,  ...,
		 nn+rn, then at nn+rn+r1, nn+rn+r2, ..., nn+rn+rn, and so on.
       .tc	 Remove tab repition character.
       .tc c	 Set tab repetition character to c.
       .ti +-N	 Temporary indent next line (default scaling indicator m).
       .tkf font s1 n1 s2 n2
		 Enable track kerning for font.
       .tl 'left'center'right'
		 Three-part title.
       .tm anything
		 Print anything on terminal (UNIX standard message output).
       .tm1 anything
		 Print	anything  on  terminal	(UNIX  standard message output), allowing leading
		 whitespace if anything starts with " (which will be stripped off).
       .tmc anything
		 Similar to .tm1 without emitting a final newline.
       .tr abcd...
		 Translate a to b, c to d, etc. on output.
       .trf filename
		 Transparently output the contents of file filename.
       .trin abcd...
		 This is the same as the tr request except that the asciify request will use  the
		 character code (if any) before the character translation.
       .trnt abcd...
		 This  is the same as the tr request except that the translations do not apply to
		 text that is transparently throughput into a diversion with \!.
       .troff	 Make the built-in condition t true and n false.
       .uf font  Underline font set to font (to be switched to by .ul).
       .ul N	 Underline (italicize in troff) N input lines.
       .unformat diversion
		 Unformat space characters and tabs, preserving font information in diversion.
       .vpt n	 Enable vertical position traps if n is non-zero, disable them otherwise.
       .vs	 Change to previous vertical base line spacing.
       .vs +-N	 Set vertical base line spacing according to +-N (default scaling  indicator  p).
		 Default value is 12p.
       .warn n	 Set warnings code to n.
       .warnscale si
		 Set scaling indicator used in warnings to si.
       .wh N	 Remove (first) trap at position N.
       .wh N trap
		 Set location trap; negative means from page bottom.
       .while cond anything
		 While condition cond is true, accept anything as input.
       .write stream anything
		 Write anything to the stream named stream.
       .writec stream anything
		 Similar to .write without emitting a final newline.
       .writem stream xx
		 Write contents of macro or string xx to the stream named stream.

       Besides these standard groff requests, there might be further macro calls.  They can orig-
       inate from a macro package (see roff(7) for an overview) or from a preprocessor.

       Preprocessor macros are easy to be recognized.  They enclose their code	into  a  pair  of
       characteristic macros.

			       +-------------+-------------+------------+
			       |preprocessor | start macro |  end macro |
			       +-------------+-------------+------------+
			       |    eqn      |	   .PS	   |	.PE	|
			       |    grap     |	   .G1	   |	.G2	|
			       |    grn      |	   .GS	   |	.GE	|
			       |    pic      |	   .PS	   |	.PE	|
			       |   refer     |	   .R1	   |	.R2	|
			       |   soelim    |	  none	   |	none	|
			       |    tbl      |	   .TS	   |	.TE	|
			       +-------------+-------------+------------+
ESCAPE SEQUENCES
       Escape  sequences  are in-line language elements usually introduced by a backslash '\' and
       followed by an escape name and sometimes by a required argument.  Input processing is con-
       tinued  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.

       This  is done by enclosing names (escape name and arguments consisting of a variable name)
       by a pair of brackets [name] and constant arguments (number expressions and characters) by
       apostrophes (ASCII 0x27) like 'constant'.

       There  are  abbreviations for short names.  Two character escape names can be specified by
       an opening parenthesis like \(xy without a closing  counterpart.   And  all  one-character
       names  different  from  the special characters '[' and '(' can even be specified without a
       marker in the form \c.

       Constant arguments of length 1 can omit the marker apostrophes, too, but there is no  two-
       character analogue.

       While  1-character  escape  sequences  are  mainly  used  for in-line functions and system
       related tasks, the 2-letter names following the \( construct are used for special  charac-
       ters predefined by the roff system.  Escapes sequences with names of more than two charac-
       ters \[name] denote user defined named characters (see the char request).

   Single Character Escapes
       \"     Beginning of a comment.  Everything up to the end of the line is ignored.
       \#     Everything up to and including the next newline is ignored.  This is interpreted in
	      copy mode.  This is like \" except that the terminating newline is ignored as well.
       \*s    The string stored in the string variable with 1-character name s.
       \*(st  The string stored in the string variable with 2-character name st.
       \*[stringvar arg1 arg2 ...]
	      The string stored in the string variable with arbitrary length name stringvar, tak-
	      ing arg1, arg2, ... as arguments.
       \$0    The name by which the current macro was invoked.	The als request can make a  macro
	      have more than one name.
       \$x    Macro or string argument with 1-place number x, where x is a digit between 1 and 9.
       \$(xy  Macro or string argument with 2-digit number xy.
       \$[nexp]
	      Macro  or  string  argument  with number nexp, where nexp is a numerical expression
	      evaluating to an integer >=1.
       \$*    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.
       \\     reduces to a single backslash; useful to delay its interpretation as escape charac-
	      ter in copy mode.  For a printable backslash, use \e, or even better \[rs],  to  be
	      independent from the current escape character.
       \'     The  acute  accent  ';  same as \(aa.  Unescaped: apostrophe, right quotation mark,
	      single quote (ASCII 0x27).
       \`     The grave accent `; same as \(ga.  Unescaped: left quote, backquote (ASCII 0x60).
       \-     The - sign in the current font.
       \.     An uninterpreted dot (period), even at start of line.
       \%     Default optional hyphenation character.
       \!     Transparent line indicator.
       \?anything?
	      In a diversion, this will transparently embed anything in the diversion.	 anything
	      is read in copy mode.  See also the escape sequences \!  and \?.
       \space Unpaddable space-size space character (no line break).
       \0     Digit width.
       \|     1/6 em narrow space character; zero width in nroff.
       \^     1/12 em half-narrow space character; zero width in nroff.
       \&     Non-printable, zero width character.
       \)     Like \& except that it behaves like a character declared with the cflags request to
	      be transparent for the purposes of end of sentence recognition.
       \/     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.
       \,     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.
       \~     Unbreakable space that stretches like a normal inter-word  space	when  a  line  is
	      adjusted.
       \:     Inserts  a  zero-width break point (similar to \% but without a soft hyphen charac-
	      ter).
       \newline
	      Ignored newline, for continuation lines.
       \{     Begin conditional input.
       \}     End conditional input.
       \(sc   The special character with 2-character name sc, see section Special Characters.
       \[name]
	      The named character (or rather glyph) with arbitrary length name name.
       \[comp1 comp2 ...]
	      A composite glyph with components comp1, comp2, ...
       \a     Non-interpreted leader character.
       \A'anything'
	      If anything is acceptable as a name of a string, macro, diversion, register,  envi-
	      ronment or font it expands to 1, and to 0 otherwise.
       \b'abc...'
	      Bracket building function.
       \B'anything'
	      If  anything  is acceptable as a valid numeric expression it expands to 1, and to 0
	      otherwise.
       \c     Interrupt text processing.
       \C'char'
	      The character called char; same as \[char], but compatible to other roff versions.
       \d     Forward (down) 1/2 em vertical unit (1/2 line in nroff).
       \D'charseq'
	      Draw a graphical element defined by the characters in charseq; see groff info  file
	      for details.
       \e     Printable version of the current escape character.
       \E     Equivalent to an escape character, but is not interpreted in copy-mode.
       \fF    Change to font with 1-character name or 1-digit number F.
       \fP    Switch back to previous font.
       \f(fo  Change to font with 2-character name or 2-digit number fo.
       \f[font]
	      Change to font with arbitrary length name or number expression font.
       \f[]   Switch back to previous font.
       \Ff    Change to font family with 1-character name f.
       \F(fm  Change to font family with 2-character name fm.
       \F[fam]
	      Change to font family with arbitrary length name fam.
       \F[]   Switch back to previous font family.
       \g[reg]
	      Return  format of register with name reg suitable for .af.  Alternative forms \g(xy
	      and \gx.
       \h'N'  Local horizontal motion; move right N (left if negative).
       \H'N'  Set height of current font to N.
       \k[reg]
	      Mark horizontal input place in register with arbitrary length name  reg.	 Alterna-
	      tive forms \k(xy and \kx.
       \l'Nc' Horizontal line drawing function (optionally using character c).
       \L'Nc' Vertical line drawing function (optionally using character c).
       \m[color]
	      Change to color color.  Alternative forms \m(co and \mc.
       \m[]   Switch back to previous color.
       \M[color]
	      Change  filling  color  for closed drawn objects to color color.	Alternative forms
	      \M(co and \Mc.
       \M[]   Switch to previous fill color.
       \nr    The numerical value stored in the register variable with the 1-character name r.
       \n(re  The numerical value stored in the register variable with the 2-character name re.
       \n[reg]
	      The numerical value stored in the register variable with arbitrary length name reg.
       \N'n'  Typeset the character with code n  in  the  current  font,  no  special  fonts  are
	      searched.  Useful for adding characters to a font using the char request.
       \o'abc...'
	      Overstrike characters a, b, c, etc.
       \O0    Disable glyph output.  Mainly for internal use.
       \O1    Enable glyph output.  Mainly for internal use.
       \p     Break and spread output line.
       \r     Reverse 1 em vertical motion (reverse line in nroff).
       \R'name +-n'
	      The same as .nr name +-n.
       \s[+-N]
	      Set  the	point  size  to  N  scaled  points.   Note the alternative forms \s+-[N],
	      \s'+-N', \s+-'N', \s(+-xy, \s+-(xy, \s+-x.  Same as ps request.
       \S'N'  Slant output N degrees.
       \t     Non-interpreted horizontal tab.
       \u     Reverse (up) 1/2 em vertical motion (1/2 line in nroff).
       \v'N'  Local vertical motion; move down N (up if negative).
       \V[env]
	      The contents of the environment variable env.  Alternative forms \V(xy and \Vx.
       \w'string'
	      The width of the character sequence string.
       \x'N'  Extra line-space function (negative before, positive after).
       \X'string'
	      Output string as device control function.
       \Y[name]
	      Output string variable or macro name  uninterpreted  as  device  control	function.
	      Alternative forms \Y(xy and \Yx.
       \zc    Print c with zero width (without spacing).
       \Z'anything'
	      Print  anything and then restore the horizontal and vertical position; anything may
	      not contain tabs or leaders.

       The escape sequences \e, \., \", \$, \*, \a, \n, \t, \g, and \newline are  interpreted  in
       copy mode.

       Escape  sequences  starting  with  \(  or  \[  do  not  represent  single character escape
       sequences, but introduce escape names with two or more characters.

       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.

   Special Characters
       Common special characters are predefined by escape sequences of the form \(xy with charac-
       ters x and 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 com-
       plete list can be found in groff_char(7).

	      \(bu   Bullet sign
	      \(co   Copyright
	      \(ct   Cent
	      \(dd   Double dagger
	      \(de   Degree
	      \(dg   Dagger
	      \(rs   Printable double quote
	      \(em   Em-dash
	      \(hy   Hyphen
	      \(rg   Registered sign
	      \(rs   Printable backslash character
	      \(sc   Section sign
	      \(ul   Underline character
	      \(==   Identical
	      \(>=   Larger or equal
	      \(<=   Less or equal
	      \(!=   Not equal
	      \(->   Right arrow
	      \(<-   Left arrow
	      \(+-   Plus-minus sign

   Strings
       Strings are defined by the ds request and can be retrieved by the \* escape sequence.

       Strings share their name space with macros.  So strings and macros without  arguments  are
       roughly	equivalent; it is possible to call a string like a macro and vice-versa, but this
       often leads to unpredictable results.  The following strings are predefined in groff.

       \*[.T]	 The name of the current output device	as  specified  by  the	-T  command  line
		 option.

REGISTERS
       Registers are variables that store a value.  In groff, most registers store numerical val-
       ues (see section NUMERICAL EXPRESSIONS above), but some can also hold a string value.

       Each register is given a name.  Arbitrary registers  can  be  defined  and  set	with  the
       request nr register.

       The value stored in a register can be retrieved by the escape sequences introduced by \n.

       Most useful are predefined registers.  In the following the notation 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 \n[] decoration is not part of the register name.

   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.

       \n[.$]	 Number of arguments in the current macro or string.
       \n[.a]	 Post-line extra line-space most recently utilized using \x'N'.
       \n[.A]	 Set to 1 in troff if option -A is used; always 1 in nroff.
       \n[.c]	 Current input line number.
       \n[.C]	 1 if compatibility mode is in effect, 0 otherwise.
       \n[.cdp]  The  depth  of the last character added to the current environment.  It is posi-
		 tive if the character extends below the baseline.
       \n[.ce]	 The number of lines remaining to be centered, as set by the ce request.
       \n[.cht]  The height of the last character added to the current environment.  It is  posi-
		 tive if the character extends above the baseline.
       \n[.color]
		 1 if colors are enabled, 0 otherwise.
       \n[.csk]  The  skew of the last character added to the current environment.  The skew of a
		 character is how far to the right of the center of a character the center of  an
		 accent over that character should be placed.
       \n[.d]	 Current vertical place in current diversion; equal to register nl.
       \n[.ev]	 The name or number of the current environment (string-valued).
       \n[.f]	 Current font number.
       \n[.fam]  The current font family (string-valued).
       \n[.fn]	 The current (internal) real font name (string-valued).
       \n[.fp]	 The number of the next free font position.
       \n[.g]	 Always 1 in GNU troff.  Macros should use it to test if running under groff.
       \n[.h]	 Text base-line high-water mark on current page or diversion.
       \n[.H]	 Available horizontal resolution in basic units.
       \n[.height]
		 The current font height as set with \H.
       \n[.hla]  The current hyphenation language as set by the .hla request.
       \n[.hlc]  The number of immediately preceding consecutive hyphenated lines.
       \n[.hlm]  The  maximum  allowed	number of consecutive hyphenated lines, as set by the hlm
		 request.
       \n[.hy]	 The current hyphenation flags (as set by the hy request).
       \n[.hym]  The current hyphenation margin (as set by the hym request).
       \n[.hys]  The current hyphenation space (as set by the hys request).
       \n[.i]	 Current ident.
       \n[.in]	 The indent that applies to the current output line.
       \n[.int]  Positive if last output line contains \c.
       \n[.kern] 1 if pairwise kerning is enabled, 0 otherwise.
       \n[.l]	 Current line length.
       \n[.lg]	 The current ligature mode (as set by the lg request).
       \n[.linetabs]
		 The current line-tabs mode (as set by the linetabs request).
       \n[.ll]	 The line length that applies to the current output line.
       \n[.lt]	 The title length (as set by the lt request).
       \n[.m]	 The current drawing color (string-valued).
       \n[.M]	 The current background color (string-valued).
       \n[.n]	 Length of text portion on previous output line.
       \n[.ne]	 The amount of space that was needed in the last ne request that caused a trap to
		 be sprung.  Useful in conjunction with register .trunc.
       \n[.ns]	 1 if in no-space mode, 0 otherwise.
       \n[.o]	 Current page offset.
       \n[.p]	 Current page length.
       \n[.pe]	 1 during page ejection, 0 otherwise.
       \n[.pn]	 The number of the next page: either the value set by a pn request, or the number
		 of the current page plus 1.
       \n[.ps]	 The current pointsize in scaled points.
       \n[.psr]  The last-requested pointsize in scaled points.
       \n[.pvs]  The current post-vertical line spacing.
       \n[.rj]	 The number of lines to be right-justified as set by the rj request.
       \n[.s]	 Current point size as a decimal fraction.
       \n[.slant]
		 The slant of the current font as set with \S.
       \n[.sr]	 The last requested pointsize in points as a decimal fraction (string-valued).
       \n[.ss]	 The value of the parameters set by the first argument of the ss request.
       \n[.sss]  The value of the parameters set by the second argument of the ss request.
       \n[.sty]  The current font style (string-valued).
       \n[.t]	 Distance to the next trap.
       \n[.T]	 Set to 1 if option -T is used.
       \n[.tabs] A string representation of the current tab settings suitable for use as an argu-
		 ment to the ta request.
       \n[.trunc]
		 The  amount  of  vertical  space  truncated by the most recently sprung vertical
		 position trap, or, if the trap was sprung by a ne request, minus the  amount  of
		 vertical motion produced by .ne.  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.
       \n[.u]	 Equal to 1 in fill mode and 0 in nofill mode.
       \n[.U]	 Equal to 1 in safer mode and 0 in unsafe mode.
       \n[.v]	 Current vertical line spacing.
       \n[.V]	 Available vertical resolution in basic units.
       \n[.vpt]  1  if vertical position traps are enabled, 0 otherwise.
       \n[.w]	 Width of previous character.
       \n[.warn] The sum of the number codes of the currently enabled warnings.
       \n[.x]	 The major version number.
       \n[.y]	 The minor version number.
       \n[.Y]	 The revision number of groff.
       \n[.z]	 Name of current diversion.

   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.

       \n[%]	 Current page number.
       \n[c.]	 Current input line number.
       \n[ct]	 Character type (set by width function \w).
       \n[dl]	 Maximal width of last completed diversion.
       \n[dn]	 Height of last completed diversion.
       \n[dw]	 Current day of week (1-7).
       \n[dy]	 Current day of month (1-31).
       \n[hours] The number of hours past midnight.  Initialized at start-up.
       \n[hp]	 Current horizontal position at input line.
       \n[llx]	 Lower	left  x-coordinate (in PostScript units) of a given PostScript image (set
		 by .psbb).
       \n[lly]	 Lower left y-coordinate (in PostScript units) of a given PostScript  image  (set
		 by .psbb).
       \n[ln]	 Output line number.
       \n[minutes]
		 The number of minutes after the hour.	Initialized at start-up.
       \n[mo]	 Current month (1-12).
       \n[nl]	 Vertical position of last printed text base-line.
       \n[rsb]	 Like register sb, but takes account of the heights and depths of characters.
       \n[rst]	 Like register st, but takes account of the heights and depths of characters.
       \n[sb]	 Depth of string below base line (generated by width function \w).
       \n[seconds]
		 The number of seconds after the minute.  Initialized at start-up.
       \n[skw]	 Right skip width from the center of the last character in the \w argument.
       \n[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.
       \n[ssc]	 The  amount  of horizontal space (possibly negative) that should be added to the
		 last character before a subscript (generated by width function \w).
       \n[st]	 Height of string above base line (generated by width function \w).
       \n[systat]
		 The return value of the system() function executed by the last sy request.
       \n[urx]	 Upper right x-coordinate (in PostScript units) of a given PostScript image  (set
		 by .psbb).
       \n[ury]	 Upper	right y-coordinate (in PostScript units) of a given PostScript image (set
		 by .psbb).
       \n[year]  The current year (year 2000 compliant).
       \n[yr]	 Current year minus 1900.  For Y2K compliance use register year instead.

COMPATIBILITY
       The differences of the groff language in comparison  to	classical  troff  as  defined  by
       [CSTR #54] are documented in groff_diff(7).

       The groff system provides a compatibility mode, see groff(1) on how to invoke this.

BUGS
       Report  bugs to the groff bug mailing list <bug-groff@gnu.org>.	Include a complete, self-
       contained example that will allow the bug to be reproduced, and say which version of groff
       you are using.

AUTHORS
       Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.

       This  document  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 at the GNU copyleft site <http://www.gnu.org/copyleft/fdl.html>.

       This document is part of groff, the GNU roff distribution.  It was written by Bernd Warken
       <bwarken@mayn.de>; it is maintained by Werner Lemberg <wl@gnu.org>.

SEE ALSO
       The main source of information for the groff language is the groff info(1) file.   Besides
       the gory details, it contains many examples.

       groff(1)
	      the  usage  of the groff program and pointers to the documentation and availability
	      of the groff system.

       groff_diff(7)
	      the differences of the groff language as compared to classical roff.  This  is  the
	      authoritative  document  for  the predefined language elements that are specific to
	      groff.

       groff_char(7)
	      the predefined groff characters (glyphs).

       groff_font(5)
	      the specification of fonts and the DESC file.

       roff(7)
	      the history of roff, the common parts shared by all roff systems, and  pointers  to
	      further documentation.

       [CSTR #54]
	      Nroff/Troff User's Manual by Osanna & Kernighan <http://cm.bell-labs.com/cm/cs/
	      54.ps> -- the bible for classical troff.

Groff Version 1.19.2			 February 6, 2006				 GROFF(7)
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