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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	 back‐
       ground of the groff system.

       This document gives only short descriptions of the predefined roff lan‐
       guage 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 language could be used as synonyms.
       However troff slightly tends to refer more to  the  classical  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 syntax.  The leading control character can be followed by
       a command name; arguments, if any, are separated by spaces (but not tab
       characters) 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 is 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 behaviour 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 pre‐
	      cise, \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  for‐
       matting 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 her‐
       self 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 chosen 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 counter‐
       part.   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  glyphs  have  a  constant
       width anyway.

       Glyphs  are  visual  representation forms of characters.	 In groff, the
       distinction between those two elements is not  always  obvious  (and  a
       full discussion is beyond the scope of this man page).  A first approx‐
       imation is that glyphs have a specific size and colour  and  are	 taken
       from  a specific font; they can't be modified any more – characters are
       the input, and glyphs are the output.  As soon as an  output  line  has
       been  generated,	 it no longer contains characters but glyphs.  In this
       man page, we use either `glyph' or `character', whatever is more appro‐
       priate.

       Moreover,  there	 are  some advanced roff elements.  A diversion stores
       (formatted) 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 conditions.

       .      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).  By
	      using the cc request, the control character can be set to a dif‐
	      ferent 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  separa‐
	      tor in some functional escape sequences (but any pair of charac‐
	      ters not part of the argument do work).  In all other positions,
	      it denotes the single quote or apostrophe character.  Groff pro‐
	      vides a printable representation with the \(cq escape sequence.

       "      The double quote is used to enclose arguments in macros (but not
	      in  requests and strings).  In the ds and as requests, a leading
	      double quote in the argument is 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 repre‐
	      sentation 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 backslash 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 behaviour 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-special, 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 cal‐
	      culations.   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 charac‐
	      ters.  Continuation lines can be specified by  an	 escaped  new‐
	      line,  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 measurement.  A number followed by
       a scaling indicator signifies a size value.  By default, numerical val‐
       ues 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 (approx. 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 following	 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 expres‐
       sions:

	      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 table 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 N is 0 (see below).
	      's1's2'	True if string s1 is identical to string s2.
	      !'s1's2'	True if string s1 is not identical to string  s2  (see
			below).
	      cch	True if there is a glyph 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.

       Note that the !	operator may  only  appear  at	the  beginning	of  an
       expression, and negates the entire expression.  This maintains bug-com‐
       patibility with AT&T troff.

REQUESTS
       This section provides a short reference for  the	 predefined  requests.
       In groff, request, macro, and string 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.

       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  cho‐
       sen  to be descriptive.	Only the following denotations need clarifica‐
       tion.

	      c		denotes a single character.
	      font	a font either specified as a font name or a font  num‐
			ber.
	      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 expression is 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 expression is  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,c,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 reg‐
		 ister macro until .. is encountered.
       .ami macro end
		 Append to a macro indirectly.	macro and end are string  reg‐
		 isters 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 entity c as string anything.
       .chop object
		 Chop  the  last  character  off  macro,  string, or diversion
		 object.
       .class name c1 c2 ...
		 Assign a set of characters, character ranges, or classes  c1,
		 c2, ... to name.
       .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  com‐
		 ponents  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.
       .device anything
		 Write anything to the intermediate output as a device control
		 function.
       .devicem name
		 Write	contents  of macro or string name uninterpreted to the
		 intermediate output as a device control function.
       .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 indica‐
		 tor 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 is run after the end of input.
       .eo	 Turn off escape character mechanism.
       .ev	 Switch to previous environment and pop it off the stack.
       .ev env	 Push down environment number or name env  to  the  stack  and
		 switch to it.
       .evc env	 Copy  the contents of environment env to the current environ‐
		 ment.	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 glyph to space.
       .fc a b	 Set field delimiter to a and pad glyph to b.
       .fchar c anything
		 Define fallback character (or glyph) 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 (or glyph) 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, ... are
		 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.
       .fzoom font
		 Don't magnify font.
       .fzoom font zoom
		 Set zoom factor for font (in multiples of 1/1000th).
       .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 a b c d ...
		 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 indica‐
		 tor 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 is called.
       .in	 Change to previous indentation value.
       .in ±N	 Change indentation according to ±N (default  scaling  indica‐
		 tor 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 glyph.
       .lc c	 Set leader repetition glyph to c.
       .length register anything
		 Write the length of the string anything to 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 length 6.5i, default
		 scaling indicator m).
       .lsm	 Unset the leading spaces macro.
       .lsm macro
		 Set the leading spaces macro to macro.
       .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 glyph off.
       .mc c	 Print glyph c after each text line at	actual	distance  from
		 right margin.
       .mc c N	 Set  margin  glyph  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 .so except that file  is  searched	 in  the  tmac
		 directories.
       .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
		 indentation.
       .nn	 Do not number next line.
       .nn N	 Do not number next N lines.
       .nop anything
		 Always process anything.
       .nr register ±N [M]
		 Define or modify register using ±N with auto-increment M.
       .nroff	 Make the built-in conditions n true and t false.
       .ns	 Turn on no-space mode.
       .nx	 Immediately jump to end of current file.
       .nx filename
		 Immediately continue processing with file file.
       .open stream filename
		 Open filename for writing  and	 associate  the	 stream	 named
		 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 is stripped off).
       .pc	 Reset page number character to ‘%’.
       .pc c	 Page number character.
       .pev	 Print the current environment and  each  defined  environment
		 state to stderr.
       .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 register .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 output 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 indicator p).
       .rchar c1 c2 ...
		 Remove the definitions of entities 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 entities 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 scal‐
		 ing indicator v).
       .schar c anything
		 Define global fallback character (or glyph) c as string  any‐
		 thing.
       .shc	 Reset soft hyphen glyph to \(hy.
       .shc c	 Set the soft hyphen glyph 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 are searched for glyphs
		 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	 Set space glyph size to N/12 of the space width in  the  cur‐
		 rent font.
       .ss N M	 Set  space  glyph size to N/12 and sentence space size set to
		 M/12 of the space width in the current font.
       .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 1 v of vertical space.
       .sv N	 Save the vertical distance N for later output with os request
		 (default scaling indicator v).
       .sy command-line
		 Execute program command-line.
       .ta T N	 Set tabs after	 every	position  that	is  a  multiple	 of  N
		 (default scaling indicator 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 repetition glyph.
       .tc c	 Set tab repetition glyph 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 stdout.
       .tm1 anything
		 Print anything on stdout, allowing leading whitespace if any‐
		 thing starts with " (which is 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 uses the character code (if any) before the character
		 translation.
       .trnt abcd...
		 This is the same as the tr request except that	 the  transla‐
		 tions	do  not apply to text that is transparently throughput
		 into a diversion with \!.
       .troff	 Make the built-in conditions t true and n false.
       .uf font	 Set underline font to font (to be switched to by .ul).
       .ul N	 Underline (italicize in troff) N input lines.
       .unformat diversion
		 Unformat space characters and tabs in	diversion,  preserving
		 font information.
       .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 to ±N (default scaling indica‐
		 tor p).
       .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  originate  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	    │	  .EQ	  │    .EN     │
		      │	   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 continued directly after the
       escaped character or the argument (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 or \*(xy without a
       closing	counterpart.   And  all one-character names different from the
       special characters ‘[’ and ‘(’ can even be specified without a  marker,
       for example \nc or \$c.

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

       While one-character escape sequences are mainly used for in-line	 func‐
       tions  and  system related tasks, the two-letter names following the \(
       construct are glyphs predefined by the roff system;  these  are	called
       `Special Characters' in the classical documentation.  Escapes sequences
       of the form \[name] denote glyphs too.

   Single-Character Escapes
       \"     Start 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 one-character
	      name s.
       \*(st  The string stored in the string variable with two-character name
	      st.
       \*[string]
	      The  string stored in the string variable with name string (with
	      arbitrary length).
       \*[stringvar arg1 arg2 ...]
	      The string stored in the string variable with  arbitrarily  long
	      name stringvar, taking 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 one-digit number x in the range  1
	      to 9.
       \$(xy  Macro  or	 string argument with two-digit number xy (larger than
	      zero).
       \$[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.
       \$^    In a macro, the representation of all parameters as if they were
	      an argument to the ds request.
       \\     reduces to a single backslash; useful to delay  its  interpreta‐
	      tion  as	escape	character in copy mode.	 For a printable back‐
	      slash, 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,	 back‐
	      quote (ASCII 0x60).
       \-     The - (minus) sign in the current font.
       \_     The same as \(ul, the underline character.
       \.     The  same as a dot (`.').	 Necessary in nested macro definitions
	      so that `\\..' expands to `..'.
       \%     Default optional hyphenation character.
       \!     Transparent line indicator.
       \?anything?
	      In a diversion, this transparently embeds anything in the diver‐
	      sion.   anything	is  read  in  copy  mode.  See also the escape
	      sequences \!  and \?.
       \space Unpaddable space size space glyph (no line break).
       \0     Digit-width space.
       \|     1/6 em narrow space glyph; zero width in nroff.
       \^     1/12 em half-narrow space glyph; zero width in nroff.
       \&     Non-printable, zero-width glyph.
       \)     Like \& except that it behaves like a glyph  declared  with  the
	      cflags request to be transparent for the purposes of end-of-sen‐
	      tence recognition.
       \/     Increases the width of the preceding glyph so that  the  spacing
	      between  that  glyph  and	 the following glyph is correct if the
	      following glyph is a roman glyph.
       \,     Modifies the spacing of the following glyph so that the  spacing
	      between  that  glyph  and	 the preceding glyph is correct if the
	      preceding glyph is a roman glyph.
       \~     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 character).
       \newline
	      Ignored newline, for continuation lines.
       \{     Begin conditional input.
       \}     End conditional input.
       \(sc   A glyph with two-character name sc; see section Special  Charac‐
	      ters.
       \[name]
	      A glyph with name name (of arbitrary length).
       \[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, diver‐
	      sion, register, environment 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’glyph’
	      The glyph called glyph; same  as	\[glyph],  but	compatible  to
	      other roff versions.
       \d     Forward (down) 1/2 em (1/2 line in nroff).
       \D’charseq’
	      Draw  a  graphical element defined by the characters in charseq;
	      see the 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 one-character name or one-digit number F.
       \fP    Switch back to previous font.
       \f(fo  Change to font with two-character name or two-digit number fo.
       \f[font]
	      Change  to  font with arbitrarily long name or number expression
	      font.
       \f[]   Switch back to previous font.
       \Ff    Change to font family with one-character name f.
       \F(fm  Change to font family with two-character name fm.
       \F[fam]
	      Change to font family with arbitrarily long name fam.
       \F[]   Switch back to previous font family.
       \gr    Return format of register with one-character name r suitable for
	      af request.
       \g(rg  Return  format  of  register with two-character name rg suitable
	      for af request.
       \g[reg]
	      Return format of register with arbitrarily long name  reg	 suit‐
	      able for af request.
       \h’N’  Local horizontal motion; move right N (left if negative).
       \H’N’  Set height of current font to N.
       \kr    Mark horizontal input place in one-character register r.
       \k(rg  Mark horizontal input place in two-character register rg.
       \k[reg]
	      Mark  horizontal	input  place in register with arbitrarily long
	      name reg.
       \l’Nc’ Horizontal line drawing function (optionally using character c).
       \L’Nc’ Vertical line drawing function (optionally using character c).
       \mc    Change to color with one-character name c.
       \m(cl  Change to color with two-character name cl.
       \m[color]
	      Change to color with arbitrarily long name color.
       \m[]   Switch back to previous color.
       \Mc    Change filling color for closed drawn objects to color with one-
	      character name c.
       \M(cl  Change filling color for closed drawn objects to color with two-
	      character name cl.
       \M[color]
	      Change filling color for closed  drawn  objects  to  color  with
	      arbitrarily long name color.
       \M[]   Switch to previous fill color.
       \nr    The  numerical  value  stored  in the register variable with the
	      one-character name r.
       \n(re  The numerical value stored in the	 register  variable  with  the
	      two-character name re.
       \n[reg]
	      The  numerical  value stored in the register variable with arbi‐
	      trarily long name reg.
       \N’n’  Typeset the glyph with index n in the current font.  No  special
	      fonts  are  searched.   Useful  for adding (named) entities to a
	      document using the char request and friends.
       \o’abc...’
	      Overstrike glyphs 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/increase/decrease the point size to/by N scaled points; N is
	      a one-digit number in the range 1 to 9.  Same as ps request.
       \s(±N
       \s±(N  Set/increase/decrease the point size to/by N scaled points; N is
	      a two-digit number ≥1.  Same as ps request.
       \s[±N]
       \s±[N]
       \s’±N’
       \s±’N’ Set/increase/decrease the point  size  to/by  N  scaled  points.
	      Same as ps request.
       \S’N’  Slant output by 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).
       \Ve    The  contents  of	 the  environment  variable with one-character
	      name e.
       \V(ev  The contents of the environment variable with two-character name
	      ev.
       \V[env]
	      The  contents  of the environment variable with arbitrarily long
	      name env.
       \w’string’
	      The width of the glyph sequence string.
       \x’N’  Extra line-space function (negative before, positive after).
       \X’string’
	      Output string as device control function.
       \Yn    Output string variable or macro with one-character name n	 unin‐
	      terpreted as device control function.
       \Y(nm  Output string variable or macro with two-character name nm unin‐
	      terpreted as device control function.
       \Y[name]
	      Output string variable or macro with arbitrarily long name  name
	      uninterpreted as device control function.
       \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 charac‐
       ter escape sequences, but introduce escape names with two or more char‐
       acters.

       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
       [Note:  `Special Characters' is a misnomer; those entities are (output)
       glyphs, not (input) characters.]

       Common special characters are predefined by  escape  sequences  of  the
       form  \(xy  with	 characters x and y.  Some of these exist in the usual
       font while most of them are only available in the special font.	 Below
       you  can find a selection of the most important glyphs; a complete list
       can be found in groff_char(7).

	      \(bu   Bullet sign
	      \(co   Copyright
	      \(ct   Cent
	      \(dd   Double dagger
	      \(de   Degree
	      \(dg   Dagger
	      \(rq   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 unpre‐
       dictable results.  The following string is the only one	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	 values (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 nr request.

       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 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 modi‐
       fied by the user (usually, registers starting  with  a  dot  are	 read-
       only).	Mostly,	 they  provide	information on the current settings or
       store results from request calls.

       \n[$$]	 The process ID of troff.
       \n[.$]	 Number of arguments in the current macro or string.
       \n[.a]	 Post-line extra line-space most recently utilized using \x.
       \n[.A]	 Set to 1 in troff if option -A is used; always 1 in nroff.
       \n[.b]	 The emboldening offset while .bd is active.
       \n[.br]	 Within a macro, set to 1 if macro called  with	 the  `normal'
		 control character, and to 0 otherwise.
       \n[.c]	 Current input line number.
       \n[.C]	 1 if compatibility mode is in effect, 0 otherwise.
       \n[.cdp]	 The depth of the last glyph added to the current environment.
		 It is positive if the glyph 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 glyph added to the current environ‐
		 ment.	It is positive if the glyph extends  above  the	 base‐
		 line.
       \n[.color]
		 1 if colors are enabled, 0 otherwise.
       \n[.csk]	 The  skew of the last glyph added to the current environment.
		 The skew of a glyph is how far to the right of the center  of
		 a  glyph  the	center	of an accent over that glyph should be
		 placed.
       \n[.d]	 Current vertical place in current diversion; equal to	regis‐
		 ter nl.
       \n[.ev]	 The  name  or	number of the current environment (string-val‐
		 ued).
       \n[.f]	 Current font number.
       \n[.F]	 The name of the current input file (string-valued).
       \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  run‐
		 ning 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 indentation.
       \n[.in]	 The indentation that applies to the current output line.
       \n[.int]	 Positive if last output line contains \c.
       \n[.j]	 The  current  adjustment  mode.  It can be stored and used to
		 set adjustment.  (n = 1, b = 1, l = 0, r = 5, c = 3).
       \n[.k]	 The current horizontal output position (relative to the  cur‐
		 rent indentation).
       \n[.kern] 1 if pairwise kerning is enabled, 0 otherwise.
       \n[.l]	 Current line length.
       \n[.L]	 The current line spacing setting as set by .ls.
       \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[.O]	 The suppression nesting level (see \O).
       \n[.p]	 Current page length.
       \n[.P]	 1  if	the  current  page  is	being printed, 0 otherwise (as
		 determined by the -o command line option).
       \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 point size in scaled points.
       \n[.psr]	 The last-requested point size in scaled points.
       \n[.pvs]	 The current post-vertical line spacing.
       \n[.R]	 The  number  of unused number registers.  Always 10000 in GNU
		 troff.
       \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 point size 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]	 Vertical 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 argument to the ta request.
       \n[.trunc]
		 The  amount  of vertical space truncated by the most recently
		 sprung vertical position trap, or, if the trap was sprung  by
		 a ne request, minus the amount of vertical motion produced by
		 .ne.  Useful in conjunction with the register .ne.
       \n[.u]	 Equal to 1 in fill mode and 0 in no-fill 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 glyph.
       \n[.warn] The sum of the number codes of the  currently	enabled	 warn‐
		 ings.
       \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.
       \n[.zoom] Zoom  factor for current font (in multiples of 1/1000th; zero
		 if no magnification).

   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[lsn]	 The number of leading spaces of an input line.
       \n[lss]	 The horizontal space corresponding to the leading  spaces  of
		 an input line.
       \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[opmaxx]
       \n[opmaxy]
       \n[opminx]
       \n[opminy]
		 These four registers mark the top left and bottom right  hand
		 corners  of a box which encompasses all written glyphs.  They
		 are reset to -1 by \O0 or \O1.
       \n[rsb]	 Like register sb, but takes account of the heights and depths
		 of glyphs.
       \n[rst]	 Like register st, but takes account of the heights and depths
		 of glyphs.
       \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 glyph 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 glyph before a subscript  (gener‐
		 ated 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 repro‐
       duced, and say which version of groff you are using.

AUTHORS
       Copyright (C) 2000–2010, 2012 Free Software Foundation, Inc.

       This document is distributed under the terms of the FDL (GNU Free Docu‐
       mentation  License)  version  1.3 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	⟨groff-bernd.warken-72@web.de⟩;	 it  is	 main‐
       tained 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 special 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 sys‐
	      tems, and pointers to further documentation.

       [CSTR #54]
	      Nroff/Troff  User's  Manual  by  Ossanna	&  Kernighan  ⟨http://
	      cm.bell-labs.com/cm/cs/cstr/54.ps.gz⟩  — the bible for classical
	      troff.

Groff Version 1.22.2		7 February 2013			      GROFF(7)
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