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TROFF(1)							      TROFF(1)

NAME
       troff - format documents

SYNOPSIS
       troff [ -abivzCERU ] [ -wname ] [ -Wname	] [ -dcs ] [ -ffam ]
	     [ -mname ]	[ -nnum	] [ -olist ] [ -rcn ] [	-Tname ] [ -Fdir ]
	     [ -Mdir ] [ files... ]

DESCRIPTION
       This  manual  page describes the	GNU version of troff, which is part of
       the groff document formatting system.  It  is  highly  compatible  with
       Unix  troff.   Usually  it  should  be invoked using the	groff command,
       which will also run preprocessors and postprocessors in the appropriate
       order and with the appropriate options.

OPTIONS
       -a	 Generate an ASCII approximation of the	typeset	output.

       -b	 Print	a  backtrace with each warning or error	message.  This
		 backtrace should help track down the cause of the error.  The
		 line  numbers	given  in the backtrace	may not	always be cor-
		 rect: troff 's	idea of	line numbers gets confused by as or am
		 requests.

       -i	 Read  the standard input after	all the	named input files have
		 been processed.

       -v	 Print the version number.

       -wname	 Enable	warning	name.  Available warnings are described	in the
		 Warnings  subsection below.  Multiple -w options are allowed.

       -Wname	 Inhibit warning name.	Multiple -W options are	allowed.

       -E	 Inhibit all error messages.

       -z	 Suppress formatted output.

       -C	 Enable	compatibility mode.

       -dcs
       -dname=s	 Define	c or name to be	a string s; c must  be	a  one	letter
		 name.

       -ffam	 Use fam as the	default	font family.

       -mname	 Read  in  the file tmac.name.	Normally this will be searched
		 for in	/usr/share/tmac.  By default is	used the  safer	 macro
		 (reverted using -U ).

       -U	 Unsafe	option,	avoids default use of safer macro.

       -R	 Don't load troffrc.

       -nnum	 Number	the first page num.

       -olist	 Output	only pages in list, which is a comma-separated list of
		 page ranges; n	means print page n, m-n	means print every page
		 between  m and	n, -n means print every	page up	to n, n- means
		 print every page from n.  Troff will exit after printing  the
		 last page in the list.

       -rcn
       -rname=n	 Set number register c or name to n; c must be a one character
		 name; n can be	any troff numeric expression.

       -Tname	 Prepare output	for device name, rather	than the default ps.

       -Fdir	 Search	dir for	subdirectories devname (name is	 the  name  of
		 the  device) for the DESC file	and font files before the nor-
		 mal /usr/share/groff_font.

       -Mdir	 Search	directory  dir	for  macro  files  before  the	normal
		 /usr/share/tmac.

USAGE
       Only the	features not in	Unix troff are described here.

   Long	names
       The  names  of number registers,	fonts, strings/macros/diversions, spe-
       cial characters can be of any length. In	escape	sequences,  where  you
       can  use	 (xx for a two character name, you can use [xxx] for a name of
       arbitrary length:

       \[xxx] Print the	special	character called xxx.

       \f[xxx]
	      Set font xxx.

       \*[xxx]
	      Interpolate string xxx.

       \n[xxx]
	      Interpolate number register xxx.

   Fractional pointsizes
       A scaled	point is equal to 1/sizescale points, where sizescale is spec-
       ified  in the DESC file (1 by default.)	There is a new scale indicator
       z which has the effect  of  multiplying	by  sizescale.	 Requests  and
       escape  sequences  in troff interpret arguments that represent a	point-
       size as being in	units of scaled	points,	but they  evaluate  each  such
       argument	 using	a  default scale indicator of z.  Arguments treated in
       this way	are the	argument to the	ps request, the	third argument to  the
       cs  request,  the  second  and fourth arguments to the tkf request, the
       argument	to the \H escape sequence, and those variants of the \s	escape
       sequence	that take a numeric expression as their	argument.

       For  example,  suppose  sizescale  is 1000; then	a scaled point will be
       equivalent to a millipoint; the request .ps 10.25 is equivalent to  .ps
       10.25z and so sets the pointsize	to 10250 scaled	points,	which is equal
       to 10.25	points.

       The number register \n(.s returns the pointsize in  points  as  decimal
       fraction.  There	is also	a new number register \n[.ps] that returns the
       pointsize in scaled points.

       It would	make no	sense to use  the  z  scale  indicator	in  a  numeric
       expression  whose  default  scale indicator was neither u nor z,	and so
       troff disallows this.  Similarly	it would make no sense to use a	 scal-
       ing  indicator  other than z or u in a numeric expression whose default
       scale indicator was z, and so troff disallows this as well.

       There is	also new scale indicator s which multiplies by the  number  of
       units in	a scaled point.	 So, for example, \n[.ps]s is equal to 1m.  Be
       sure not	to confuse the s and z scale indicators.

   Numeric expressions
       Spaces are permitted in a number	expression within parentheses.

       M indicates a scale of 100ths of	an em.

       e1>?e2 The maximum of e1	and e2.

       e1<?e2 The minimum of e1	and e2.

       (c;e)  Evaluate e using c as the	default	scaling	indicator.   If	 c  is
	      missing, ignore scaling indicators in the	evaluation of e.

   New escape sequences
       \A'anything'
	      This  expands  to	 1  or	0  according  as anything is or	is not
	      acceptable as the	name of	a  string,  macro,  diversion,	number
	      register,	 environment or	font.  It will return 0	if anything is
	      empty.  This is useful if	you want to lookup user	input in  some
	      sort of associative table.

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

       \E     This is equivalent to an escape character, but it's  not	inter-
	      preted  in  copy-mode.   For  example,  strings to start and end
	      superscripting could be defined like this:

		     .ds { \v'-.3m'\s'\En[.s]*6u/10u'
		     .ds } \s0\v'.3m'

	      The use of \E ensures that these definitions will	work  even  if
	      \*{ gets interpreted in copy-mode	(for example, by being used in
	      a	macro argument.)

       \N'n'  Typeset the character with code n	in the current font.  n	can be
	      any  integer.   Most  devices  only  have	 characters with codes
	      between 0	and 255.  If the current font does not contain a char-
	      acter  with  that	code, special fonts will not be	searched.  The
	      \N escape	sequence can be	conveniently used on conjunction  with
	      the char request:

		     .char \[phone] \f(ZD\N'37'

	      The  code	of each	character is given in the fourth column	in the
	      font description file after the charset command.	It is possible
	      to  include  unnamed  characters in the font description file by
	      using a name of ---; the \N escape sequence is the only  way  to
	      use these.

       \R'name +-n'
	      This has the same	effect as

		     .nr name +-n

       \s(nn
       \s+-(nn
	      Set  the point size to nn	points;	nn must	be exactly two digits.

       \s[+-n]
       \s+-[n]
       \s'+-n'
       \s+-'n'
	      Set the point size to n scaled points; n is a numeric expression
	      with a default scale indicator of	z.

       \Vx
       \V(xx
       \V[xxx]
	      Interpolate  the	contents  of the environment variable xxx , as
	      returned by getenv(3).  \V is interpreted	in copy-mode.

       \Yx
       \Y(xx
       \Y[xxx]
	      This is approximately equivalent to  \X'\*[xxx]'.	  However  the
	      contents of the string or	macro xxx are not interpreted; also it
	      is permitted for xxx to have been	defined	as a  macro  and  thus
	      contain  newlines	(it is not permitted for the argument to \X to
	      contain newlines).  The inclusion	of newlines requires an	exten-
	      sion  to	the Unix troff output format, and will confuse drivers
	      that do not know about this extension.

       \Z'anything'
	      Print anything and then  restore	the  horizontal	 and  vertical
	      position;	anything may not contain tabs or leaders.

       \$0    The  name	 by  which  the	 current  macro	 was invoked.  The als
	      request can make a macro have more than one name.

       \$*    In a macro, the concatenation of all the arguments separated  by
	      spaces.

       \$@    In  a  macro,  the  concatenation	of all the arguments with each
	      surrounded by double quotes, and separated by spaces.

       \$(nn
       \$[nnn]
	      In a macro, this gives the nn-th or nnn-th argument.  Macros can
	      have a unlimited number of arguments.

       \?anything\?
	      When used	in a diversion,	this will transparently	embed anything
	      in the diversion.	 anything is read  in  copy  mode.   When  the
	      diversion	is reread, anything will be interpreted.  anything may
	      not contain newlines; use	\!  if you want	to embed newlines in a
	      diversion.   The	escape sequence	\?  is also recognised in copy
	      mode and turned into a single internal code;  it	is  this  code
	      that terminates anything.	 Thus
		     .nr x 1
		     .nf
		     .di d
		     \?\\?\\\\?\\\\\\\\nx\\\\?\\?\?
		     .di
		     .nr x 2
		     .di e
		     .d
		     .di
		     .nr x 3
		     .di f
		     .e
		     .di
		     .nr x 4
		     .f

	      will print 4.

       \/     This  increases the width	of the preceding character so that the
	      spacing between that character and the following character  will
	      be correct if the	following character is a roman character.  For
	      example, if an italic f is immediately followed by a roman right
	      parenthesis,  then  in many fonts	the top	right portion of the f
	      will overlap the top left	of the right parenthesis producing f),
	      which  is	 ugly.	Inserting \/ produces f) and avoids this prob-
	      lem.  It is a good idea to use this escape sequence whenever  an
	      italic  character	 is  immediately followed by a roman character
	      without any intervening space.

       \,     This modifies the	spacing	of the following character so that the
	      spacing  between that character and the preceding	character will
	      correct if the preceding character is a  roman  character.   For
	      example,	inserting \, between the parenthesis and the f changes
	      (f to (f.	 It is a good idea to use this escape  sequence	 when-
	      ever  a  roman  character	 is  immediately followed by an	italic
	      character	without	any intervening	space.

       \)     Like \& except that it behaves like a  character	declared  with
	      the  cflags request to be	transparent for	the purposes of	end of
	      sentence recognition.

       \~     This produces an unbreakable space that stretches	like a	normal
	      inter-word space when a line is adjusted.

       \#     Everything  up  to  and  including  the next newline is ignored.
	      This is interpreted in copy mode.	 This is like \"  except  that
	      \" does not ignore the terminating newline.

   New requests
       .aln xx yy
	      Create an	alias xx for number register object named yy.  The new
	      name and the old name will be  exactly  equivalent.   If	yy  is
	      undefined,  a  warning  of  type	reg will be generated, and the
	      request will be ignored.

       .als xx yy
	      Create an	alias xx for  request,	string,	 macro,	 or  diversion
	      object  named yy.	 The new name and the old name will be exactly
	      equivalent (it is	similar	to a hard rather than  a  soft	link).
	      If yy is undefined, a warning of type mac	will be	generated, and
	      the request will be ignored.  The	de, am,	di,  da,  ds,  and  as
	      requests	only  create  a	 new  object if	the name of the	macro,
	      diversion	or string diversion is currently undefined or if it is
	      defined  to  be  a request; normally they	modify the value of an
	      existing object.

       .asciify	xx
	      This request only	exists in order	to make	it  possible  to  make
	      certain  gross  hacks  work  with	GNU troff.  It `unformats' the
	      diversion	xx in such a way that ASCII characters that were  for-
	      matted  and diverted into	xx will	be treated like	ordinary input
	      characters when xx is reread.  For example, this

		     .tr  @.
		     .di  x
		     @nr\  n\  1
		     .br
		     .di
		     .tr  @@
		     .asciify  x
		     .x

	      will set register	n to 1.

       .backtrace
	      Print a backtrace	of the input stack on stderr.

       .blm xx
	      Set the blank line macro to xx.  If there	is a blank line	macro,
	      it  will	be invoked when	a blank	line is	encountered instead of
	      the usual	troff behaviour.

       .break Break out	of a while loop.  See  also  the  while	 and  continue
	      requests.	 Be sure not to	confuse	this with the br request.

       .cflags n c1 c2...
	      Characters c1, c2,...  have properties determined	by n, which is
	      ORed from	the following:

	      1	     the character ends	sentences  (initially  characters  .?!
		     have this property);

	      2	     lines  can	 be  broken before the character (initially no
		     characters	have this property); a line will not be	broken
		     at	 a  character with this	property unless	the characters
		     on	each side both have non-zero hyphenation codes.

	      4	     lines can be broken after the character (initially	 char-
		     acters  -\(hy\(em have this property); a line will	not be
		     broken at a character with	this property unless the char-
		     acters on each side both have non-zero hyphenation	codes.

	      8	     the character overlaps horizontally (initially characters
		     \(ul\(rn\(ru have this property);

	      16     the  character  overlaps  vertically (initially character
		     \(br has this property);

	      32     an	end of sentence	character followed by  any  number  of
		     characters	 with this property will be treated as the end
		     of	a sentence if followed by a newline or two spaces;  in
		     other words the character is transparent for the purposes
		     of	end of sentence	recognition; this is the same as  hav-
		     ing  a  zero  space  factor  in TeX (initially characters
		     "')]*\(dg\(rq have	this property).

       .char c string
	      Define character c to be string.	Every time character  c	 needs
	      to  be printed, string will be processed in a temporary environ-
	      ment and the result will be wrapped up  into  a  single  object.
	      Compatibility  mode  will	be turned off and the escape character
	      will be set to \ while string is being processed.	 Any embolden-
	      ing,  constant  spacing or track kerning will be applied to this
	      object rather than to individual characters in string.  A	 char-
	      acter  defined  by  this	request	can be used just like a	normal
	      character	provided by the	output device.	 In  particular	 other
	      characters  can  be translated to	it with	the tr request;	it can
	      be made the leader character by the lc  request;	repeated  pat-
	      terns can	be drawn with the character using the \l and \L	escape
	      sequences; words containing the character	can be hyphenated cor-
	      rectly,  if  the	hcode  request is used to give the character a
	      hyphenation code.	 There is a  special  anti-recursion  feature:
	      use  of character	within the character's definition will be han-
	      dled like	normal characters not defined with char.  A  character
	      definition can be	removed	with the rchar request.

       .chop xx
	      Chop  the	 last  character  off  macro, string, or diversion xx.
	      This is useful for removing the newline from the end  of	diver-
	      sions that are to	be interpolated	as strings.

       .close stream
	      Close  the  stream  named	 stream;  stream  will no longer be an
	      acceptable argument to the write request.	 See the open request.

       .continue
	      Finish  the  current  iteration  of  a while loop.  See also the
	      while and	break requests.

       .cp n  If n is non-zero or missing, enable compatibility	 mode,	other-
	      wise  disable  it.   In  compatibility  mode, long names are not
	      recognised, and the incompatibilities caused by  long  names  do
	      not arise.

       .do xxx
	      Interpret	.xxx with compatibility	mode disabled.	For example,

		     .do fam T

	      would have the same effect as

		     .fam T

	      except  that  it	would work even	if compatibility mode had been
	      enabled.	Note that the previous compatibility mode is  restored
	      before any files sourced by xxx are interpreted.

       .fam xx
	      Set  the	current	font family to xx.  The	current	font family is
	      part of the current environment.	See the	description of the sty
	      request for more information on font families.

       .fspecial f s1 s2...
	      When  the	 current font is f, fonts s1, s2,...  will be special,
	      that is, they will searched for characters not  in  the  current
	      font.   Any  fonts  specified  in	 the  special  request will be
	      searched after fonts specified in	the fspecial request.

       .ftr f g
	      Translate	font f to g.  Whenever a font named f is  referred  to
	      in  \f  escape sequence, or in the ft, ul, bd, cs, tkf, special,
	      fspecial,	fp, or sty requests, font g will be  used.   If	 g  is
	      missing, or equal	to f then font f will not be translated.

       .hcode c1 code1 c2 code2...
	      Set the hyphenation code of character c1 to code1	and that of c2
	      to code2.	 A hyphenation code must be a single  input  character
	      (not  a  special character) other	than a digit or	a space.  Ini-
	      tially each lower-case letter has	a hyphenation code,  which  is
	      itself,  and each	upper-case letter has a	hyphenation code which
	      is the lower case	version	of itself.  See	also the hpf  request.

       .hla lang
	      Set  the	current	 hyphenation  language	to  lang.  Hyphenation
	      exceptions specified with	the hw request	and  hyphenation  pat-
	      terns  specified	with  the hpf request are both associated with
	      the current hyphenation language.	 The hla  request  is  usually
	      invoked by the troffrc file.

       .hlm n Set the maximum number of	consecutive hyphenated lines to	n.  If
	      n	is negative, there is no maximum.  The default	value  is  -1.
	      This  value  is  associated  with	the current environment.  Only
	      lines output from	an environment count towards the maximum asso-
	      ciated  with  that  environment.	 Hyphens resulting from	\% are
	      counted; explicit	hyphens	are not.

       .hpf file
	      Read hyphenation patterns	from file; this	will be	 searched  for
	      in  the  same way	that tmac.name is searched for when the	-mname
	      option is	specified.  It should have  the	 same  format  as  the
	      argument	to the \patterns primitive in TeX; the letters appear-
	      ing in this file are interpreted	as  hyphenation	 codes.	  A  %
	      character	in the patterns	file introduces	a comment that contin-
	      ues to the end of	the line.  The set of hyphenation patterns  is
	      associated  with	the  current  language set by the hla request.
	      The hpf request is usually invoked by the	troffrc	file.

       .hym n Set the hyphenation margin to n:	when  the  current  adjustment
	      mode is not b, the line will not be hyphenated if	the line is no
	      more than	n short.  The default hyphenation margin  is  0.   The
	      default  scaling	indicator  for this request is m.  The hyphen-
	      ation margin is associated with the  current  environment.   The
	      current  hyphenation  margin is available	in the \n[.hym]	regis-
	      ter.

       .hys n Set the hyphenation space	to n: when the current adjustment mode
	      is  b  don't  hyphenate the line if the line can be justified by
	      adding no	more than n extra  space  to  each  word  space.   The
	      default  hyphenation  space is 0.	 The default scaling indicator
	      for this request is m.  The hyphenation space is associated with
	      the  current  environment.   The	current	 hyphenation  space is
	      available	in the \n[.hys]	register.

       .kern n
	      If n is non-zero or missing, enable pairwise kerning,  otherwise
	      disable it.

       .mso file
	      The  same	 as the	so request except that file is searched	for in
	      the same way that	tmac.name is  searched	for  when  the	-mname
	      option is	specified.

       .nroff Make  the	n built-in condition true and the t built-in condition
	      false.  This can be reversed using the troff request.

       .open stream filename
	      Open filename for	writing	and associate the stream named	stream
	      with it.	See also the close and write requests.

       .opena stream filename
	      Like open, but if	filename exists, append	to it instead of trun-
	      cating it.

       .pnr   Print the	names and contents of  all  currently  defined	number
	      registers	on stderr.

       .pso command
	      This is behaves like the so request except that input comes from
	      the standard output of command.

       .ptr   Print the	names and positions of all traps (not including	 input
	      line  traps  and diversion traps)	on stderr.  Empty slots	in the
	      page trap	list are printed as well, because they can affect  the
	      priority of subsequently planted traps.

       .rchar c1 c2...
	      Remove the definitions of	characters c1, c2,...  This undoes the
	      effect of	a char request.

       .rj
       .rj n  Right justify the	next n input lines.  Without an	argument right
	      justify  the  next  input	line.  The number of lines to be right
	      justified	is available in	the \n[.rj] register.  This implicitly
	      does .ce 0.  The ce request implicitly does .rj 0.

       .rnn xx yy
	      Rename number register xx	to yy.

       .shc c Set  the	soft hyphen character to c.  If	c is omitted, the soft
	      hyphen character will be set to  the  default  \(hy.   The  soft
	      hyphen  character	is the character which will be inserted	when a
	      word is hyphenated at a line break.  If the soft hyphen  charac-
	      ter does not exist in the	font of	the character immediately pre-
	      ceding a potential break point, then the line will not be	broken
	      at  that	point.	 Neither  definitions (specified with the char
	      request) nor translations	(specified with	the  tr	 request)  are
	      considered when finding the soft hyphen character.

       .shift n
	      In  a  macro,  shift  the	 arguments  by n positions: argument i
	      becomes argument i-n; arguments 1	to n will no longer be	avail-
	      able.   If n is missing, arguments will be shifted by 1.	Shift-
	      ing by negative amounts is currently undefined.

       .special	s1 s2...
	      Fonts s1,	s2, are	special	and will be  searched  for  characters
	      not in the current font.

       .sty n f
	      Associate	 style f with font position n.	A font position	can be
	      associated either	with a font or with a style.  The current font
	      is  the index of a font position and so is also either a font or
	      a	style.	When it	is a style, the	font that is actually used  is
	      the  font	 the name of which is the concatenation	of the name of
	      the current family and the name of the current style.  For exam-
	      ple,  if the current font	is 1 and font position 1 is associated
	      with style R and the current font	family is T, then font TR will
	      be  used.	  If the current font is not a style, then the current
	      family is	ignored.  When the requests cs,	bd, tkf, uf, or	 fspe-
	      cial  are	 applied to a style, then they will instead be applied
	      to the member of the current family corresponding	to that	style.
	      The  default  family  can	be set with the	-f option.  The	styles
	      command in the DESC file controls	which font positions (if  any)
	      are initially associated with styles rather than fonts.

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

       .trf filename
	      Transparently  output  the contents of file filename.  Each line
	      is output	as it would be were it preceded	by  \!;	 however,  the
	      lines  are not subject to	copy-mode interpretation.  If the file
	      does not end with	a newline, then	a newline will be added.   For
	      example,	you  can  define  a macro x containing the contents of
	      file f, using

		     .di x
		     .trf f
		     .di

	      Unlike with the cf request, the file cannot  contain  characters
	      such as NUL that are not legal troff input characters.

       .trnt abcd
	      This  is the same	as the tr request except that the translations
	      do not apply to text that	is  transparently  throughput  into  a
	      diversion	with \!.  For example,

	      .tr ab
	      .di x
	      \!.tm a
	      .di
	      .x

	      will print b; if trnt is used instead of tr it will print	a.

       .troff Make  the	 n built-in condition false, and the t built-in	condi-
	      tion true.  This undoes the effect of the	nroff request.

       .vpt n Enable vertical position traps if	n is  non-zero,	 disable  them
	      otherwise.   Vertical  position traps are	traps set by the wh or
	      dt requests.  Traps set by the it	request	are not	vertical posi-
	      tion  traps.  The	parameter that controls	whether	vertical posi-
	      tion traps are enabled is	global.	 Initially  vertical  position
	      traps are	enabled.

       .warn n
	      Control  warnings.   n is	the sum	of the numbers associated with
	      each warning that	is to be enabled; all other warnings  will  be
	      disabled.	  The number associated	with each warning is listed in
	      the `Warnings' section.  For example, .warn 0 will  disable  all
	      warnings,	 and  .warn  1	will  disable all warnings except that
	      about missing characters.	 If n is not given, all	warnings  will
	      be enabled.

       .while c	anything
	      While  condition	c  is true, accept anything as input; c	can be
	      any condition acceptable to an if	request; anything can comprise
	      multiple	lines  if  the	first line starts with \{ and the last
	      line ends	with \}.  See also the break and continue requests.

       .write stream anything
	      Write anything to	the stream named stream.  stream  must	previ-
	      ously  have  been	 the  subject of an open request.  anything is
	      read in copy mode; a leading " will be stripped.

   Extended requests
       .cf filename
	      When used	in a diversion,	this will embed	in  the	 diversion  an
	      object  which,  when reread, will	cause the contents of filename
	      to be transparently copied  through  to  the  output.   In  Unix
	      troff, the contents of filename is immediately copied through to
	      the output regardless of whether there is	a  current  diversion;
	      this  behavior is	so anomalous that it must be considered	a bug.

       .ev xx If xx is not a number, this will switch to a  named  environment
	      called  xx.  The environment should be popped with a matching ev
	      request without any arguments, just  as  for  numbered  environ-
	      ments.   There  is no limit on the number	of named environments;
	      they will	be created the first time that they are	referenced.

       .fp n f1	f2
	      The fp request has an optional third  argument.	This  argument
	      gives  the  external name	of the font, which is used for finding
	      the font description file.  The second argument gives the	inter-
	      nal name of the font which is used to refer to the font in troff
	      after it has been	mounted.  If there is no third	argument  then
	      the  internal name will be used as the external name.  This fea-
	      ture allows you to use fonts with	long  names  in	 compatibility
	      mode.

       .ss m n
	      When two arguments are given to the ss request, the second argu-
	      ment gives the sentence space size.  If the second  argument  is
	      not  given, the sentence space size will be the same as the word
	      space size.  Like	the word space size, the sentence space	is  in
	      units of one twelfth of the spacewidth parameter for the current
	      font.  Initially both the	word space size	and the	sentence space
	      size  are	 12.   The  sentence space size	is used	in two circum-
	      stances: if the end of a sentence	occurs at the end of a line in
	      fill  mode,  then	 both an inter-word space and a	sentence space
	      will be added; if	two spaces follow the end of a sentence	in the
	      middle  of  a  line,  then  the  second space will be a sentence
	      space.  Note that	the behavior of	Unix  troff  will  be  exactly
	      that  exhibited by GNU troff if a	second argument	is never given
	      to the ss	request.  In GNU troff,	as in Unix troff,  you	should
	      always follow a sentence with either a newline or	two spaces.

       .ta n1 n2...nn T	r1 r2...rn
	      Set tabs at positions n1,	n2,...,	nn and then set	tabs at	nn+r1,
	      nn+r2,...., nn+rn	and then at nn+rn+r1, nn+rn+r2,...,  nn+rn+rn,
	      and so on.  For example,

		     .ta T .5i

	      will set tabs every half an inch.

   New number registers
       The following read-only registers are available:

       \n[.C] 1	if compatibility mode is in effect, 0 otherwise.

       \n[.cdp]
	      The  depth  of  the last character added to the current environ-
	      ment.  It	is positive if the character extends below  the	 base-
	      line.

       \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  environ-
	      ment.   It  is positive if the character extends above the base-
	      line.

       \n[.csk]
	      The skew of the last character added to the current environment.
	      The skew of a character is how far to the	right of the center of
	      a	character the center of	an accent over that  character	should
	      be placed.

       \n[.ev]
	      The  name	 or  number  of	 the  current  environment.  This is a
	      string-valued register.

       \n[.fam]
	      The current font family.	This is	a string-valued	register.

       \n[.fp]
	      The number of the	next free font position.

       \n[.g] Always 1.	 Macros	should use this	to determine whether they  are
	      running under GNU	troff.

       \n[.hla]
	      The current hyphenation language as set by the hla request.

       \n[.hlc]
	      The  number  of  immediately  preceding  consecutive  hyphenated
	      lines.

       \n[.hlm]
	      The maximum allowed number of consecutive	hyphenated  lines,  as
	      set by the hlm request.

       \n[.hy]
	      The current hyphenation flags (as	set by the hy request.)

       \n[.hym]
	      The current hyphenation margin (as set by	the hym	request.)

       \n[.hys]
	      The current hyphenation space (as	set by the hys request.)

       \n[.in]
	      The indent that applies to the current output line.

       \n[.kern]
	      1	if pairwise kerning is enabled,	0 otherwise.

       \n[.lg]
	      The current ligature mode	(as set	by the lg request.)

       \n[.ll]
	      The line length that applies to the current output line.

       \n[.lt]
	      The title	length as set by the lt	request.

       \n[.ne]
	      The  amount of space that	was needed in the last ne request that
	      caused a trap to be sprung.   Useful  in	conjunction  with  the
	      \n[.trunc] register.

       \n[.pn]
	      The  number  of  the  next  page:	 either	 the value set by a pn
	      request, or the number of	the current page plus 1.

       \n[.ps]
	      The current pointsize in scaled points.

       \n[.psr]
	      The last-requested pointsize in scaled points.

       \n[.rj]
	      The number of lines to be	 right-justified  as  set  by  the  rj
	      request.

       \n[.sr]
	      The  last	 requested  pointsize in points	as a decimal fraction.
	      This is a	string-valued register.

       \n[.tabs]
	      A	string representation of the current tab settings suitable for
	      use as an	argument to the	ta request.

       \n[.trunc]
	      The  amount  of  vertical	 space	truncated by the most recently
	      sprung vertical position trap, or, if the	trap was sprung	 by  a
	      ne  request, minus the amount of vertical	motion produced	by the
	      ne request.  In other words, at the point	a trap is  sprung,  it
	      represents  the  difference  of what the vertical	position would
	      have been	but for	the trap, and what the vertical	position actu-
	      ally is.	Useful in conjunction with the \n[.ne] register.

       \n[.ss]
       \n[.sss]
	      These  give  the	values	of the parameters set by the first and
	      second arguments of the ss request.

       \n[.vpt]
	      1	if vertical position traps are enabled,	0 otherwise.

       \n[.warn]
	      The sum of the numbers associated	with  each  of	the  currently
	      enabled  warnings.   The	number associated with each warning is
	      listed in	the `Warnings' subsection.

       \n(.x  The major	version	number.	 For example, if the version number is
	      1.03 then	\n(.x will contain 1.

       \n(.y  The minor	version	number.	 For example, if the version number is
	      1.03 then	\n(.y will contain 03.

       The following registers are set by the \w escape	sequence:

       \n[rst]
       \n[rsb]
	      Like the st and sb registers, but	takes account of  the  heights
	      and depths of characters.

       \n[ssc]
	      The  amount  of horizontal space (possibly negative) that	should
	      be added to the last character before a subscript.

       \n[skw]
	      How far to right of the center of	the last character in  the  \w
	      argument,	 the  center  of an accent from	a roman	font should be
	      placed over that character.

       The following read/write	number registers are available:

       \n[systat]
	      The return value of the system() function	executed by  the  last
	      sy request.

       \n[slimit]
	      If  greater  than	 0, the	maximum	number of objects on the input
	      stack.  If less than or equal to 0, there	is  no	limit  on  the
	      number  of objects on the	input stack.  With no limit, recursion
	      can continue until virtual memory	is exhausted.

   Miscellaneous
       Fonts not listed	in the DESC file are automatically mounted on the next
       available  font	position when they are referenced.  If a font is to be
       mounted explicitly with the fp request on an unused font	 position,  it
       should be mounted on the	first unused font position, which can be found
       in the \n[.fp] register;	although troff does not	enforce	this strictly,
       it  will	 not  allow a font to be mounted at a position whose number is
       much greater than that of any currently used position.

       Interpolating a string does not hide existing macro arguments.  Thus in
       a macro,	a more efficient way of	doing

	      .xx \\$@

       is

	      \\*[xx]\\

       If  the	font  description  file	contains pairwise kerning information,
       characters from that font will be kerned.  Kerning between two  charac-
       ters can	be inhibited by	placing	a \& between them.

       In  a  string comparison	in a condition,	characters that	appear at dif-
       ferent input levels to the first	delimiter character will not be	recog-
       nised  as  the second or	third delimiters.  This	applies	also to	the tl
       request.	 In a \w escape	sequence, a character that appears at  a  dif-
       ferent  input  level  to	 the  starting delimiter character will	not be
       recognised as the closing delimiter character.  When decoding  a	 macro
       argument	 that  is delimited by double quotes, a	character that appears
       at a different input level to the starting delimiter character will not
       be  recognised  as the closing delimiter	character.  The	implementation
       of \$@ ensures that the double  quotes  surrounding  an	argument  will
       appear the same input level, which will be different to the input level
       of the argument itself.	In a long escape name ]	will not be recognized
       as a closing delimiter except when it occurs at the same	input level as
       the opening ].  In compatibility	mode, no  attention  is	 paid  to  the
       input-level.

       There are some new types	of condition:

       .if rxxx
	      True if there is a number	register named xxx.

       .if dxxx
	      True  if	there  is a string, macro, diversion, or request named
	      xxx.

       .if cch
	      True if there is a character ch available; ch is either an ASCII
	      character	 or  a special character \(xx or \[xxx]; the condition
	      will also	be true	if ch has been defined by the char request.

   Warnings
       The warnings that can be	given by troff are divided into	the  following
       categories.   The  name	associated with	each warning is	used by	the -w
       and -W options; the number is used by the  warn	request,  and  by  the
       .warn register.

       char	      1	  Non-existent	 characters.	This   is  enabled  by
			  default.

       number	      2	  Invalid numeric expressions.	 This  is  enabled  by
			  default.

       break	      4	  In  fill  mode,  lines  which	could not be broken so
			  that their length was	less  than  the	 line  length.
			  This is enabled by default.

       delim	      8	  Missing or mismatched	closing	delimiters.

       el	     16	  Use of the el	request	with no	matching ie request.

       scale	     32	  Meaningless scaling indicators.

       range	     64	  Out of range arguments.

       syntax	    128	  Dubious syntax in numeric expressions.

       di	    256	  Use of di or da without an argument when there is no
			  current diversion.

       mac	    512	  Use of undefined  strings,  macros  and  diversions.
			  When	an  undefined  string,	macro  or diversion is
			  used,	that string is automatically defined as	empty.
			  So, in most cases, at	most one warning will be given
			  for each name.

       reg	   1024	  Use of undefined number registers.   When  an	 unde-
			  fined	 number	 register  is  used,  that register is
			  automatically	defined	to have	a value	of 0.  a defi-
			  nition is automatically made with a value of 0.  So,
			  in most cases, at most one warning will be given for
			  use of a particular name.

       tab	   2048	  Inappropriate	use of a tab character.	 Either	use of
			  a tab	character where	a number was expected, or  use
			  of tab character in an unquoted macro	argument.

       right-brace 4096	  Use of \} where a number was expected.

       missing	   8192	  Requests that	are missing non-optional arguments.

       input	  16384	  Illegal input	characters.

       escape	  32768	  Unrecognized escape sequences.  When an unrecognized
			  escape sequence is encountered, the escape character
			  is ignored.

       space	  65536	  Missing  space  between  a  request or macro and its
			  argument.  This warning will be given	when an	 unde-
			  fined	 name  longer  than  two characters is encoun-
			  tered, and the first two characters of the name make
			  a  defined  name.   The request or macro will	not be
			  invoked.  When this warning is given,	 no  macro  is
			  automatically	 defined.  This	is enabled by default.
			  This warning will never occur	in compatibility mode.

       font	 131072	  Non-existent fonts.  This is enabled by default.

       ig	 262144	  Illegal escapes in text ignored with the ig request.
			  These	are conditions that are	errors	when  they  do
			  not occur in ignored text.

       There are also names that can be	used to	refer to groups	of warnings:

       all    All  warnings  except di,	mac and	reg.  It is intended that this
	      covers all warnings that are useful with traditional macro pack-
	      ages.

       w      All warnings.

   Incompatibilities
       Long names cause	some incompatibilities.	 Unix troff will interpret

	      .dsabcd

       as  defining  a	string	ab with	contents cd.  Normally,	GNU troff will
       interpret this as a call	of a macro named dsabcd.  Also Unix troff will
       interpret  \*[  or  \n[	as  references	to a string or number register
       called [.  In GNU troff,	however, this will normally be interpreted  as
       the  start of a long name.  In compatibility mode GNU troff will	inter-
       pret these things in the	traditional way.  In compatibility mode,  how-
       ever,  long names are not recognised.  Compatibility mode can be	turned
       on with the -C command line option, and turned on or off	 with  the  cp
       request.	 The number register \n(.C is 1	if compatibility mode is on, 0
       otherwise.

       GNU  troff  does	 not  allow  the   use	 of   the   escape   sequences
       \\|\^\&\}\{\(space)\'\`\-\_\!\%\c  in  names of strings,	macros,	diver-
       sions, number registers,	fonts or environments; Unix troff  does.   The
       \A  escape  sequence  may  be  helpful  in avoiding use of these	escape
       sequences in names.

       Fractional pointsizes cause one noteworthy  incompatibility.   In  Unix
       troff the ps request ignores scale indicators and so

	      .ps 10u

       will  set  the pointsize	to 10 points, whereas in GNU troff it will set
       the pointsize to	10 scaled points.

       In GNU troff there is a	fundamental  difference	 between  unformatted,
       input  characters,  and	formatted, output characters.  Everything that
       affects how an output character will be output is stored	with the char-
       acter;  once  an	output character has been constructed it is unaffected
       by any subsequent requests that are executed, including	bd,  cs,  tkf,
       tr,  or	fp  requests.  Normally	output characters are constructed from
       input characters	at the moment  immediately  before  the	 character  is
       added  to  the current output line.  Macros, diversions and strings are
       all, in fact, the same type of object;  they  contain  lists  of	 input
       characters and output characters	in any combination.  An	output charac-
       ter does	not behave like	an input character for the purposes  of	 macro
       processing;  it does not	inherit	any of the special properties that the
       input character from which it was  constructed  might  have  had.   For
       example,

	      .di x
	      \\\\
	      .br
	      .di
	      .x

       will  print  \\	in GNU troff; each pair	of input \s is turned into one
       output \	and the	resulting output \s  are  not  interpreted  as	escape
       characters  when	 they  are reread.  Unix troff would interpret them as
       escape characters when they were	reread and would end up	 printing  one
       \.   The	 correct  way  to obtain a printable \ is to use the \e	escape
       sequence: this will always print	 a  single  instance  of  the  current
       escape  character,  regardless of whether or not	it is used in a	diver-
       sion; it	will also work in both GNU troff and Unix troff.  If you  wish
       for some	reason to store	in a diversion an escape sequence that will be
       interpreted when	the diversion is reread, you can either	use the	tradi-
       tional  \!  transparent output facility,	or, if this is unsuitable, the
       new \?  escape sequence.

ENVIRONMENT
       GROFF_TMAC_PATH
	      A	colon separated	list of	directories in	which  to  search  for
	      macro files.

       GROFF_TYPESETTER
	      Default device.

       GROFF_FONT_PATH
	      A	colon separated	list of	directories in which to	search for the
	      devname directory.  troff	will search in	directories  given  in
	      the   -F	option	before	these,	and  in	 standard  directories
	      (/usr/share/groff_font) after these.

FILES
       /usr/share/tmac/troffrc
	      Initialization file

       /usr/share/tmac/tmac.name
	      Macro files

       /usr/share/groff_font/devname/DESC
	      Device description file for device name.

       /usr/share/groff_font/devname/F
	      Font file	for font F of device name.

SEE ALSO
       groff(1)	tbl(1),	pic(1),	eqn(1),	grops(1), grodvi(1),  grotty(1),  gro-
       html(1),	groff_font(5), groff_out(5), groff_char(7)

Groff Version 1.15		12 January 2000			      TROFF(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | USAGE | ENVIRONMENT | FILES | SEE ALSO

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