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TROFF(1)		    General Commands Manual		      TROFF(1)

NAME
       troff - format documents

SYNOPSIS
       troff [ -abivzCER ] [ -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 correct:
		 troff's idea of line numbers gets confused by as  or  am  re-
		 quests.

       -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.

       -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  es-
       cape  sequences in troff	interpret arguments that represent a pointsize
       as being	in units of scaled points, but they evaluate each  such	 argu-
       ment  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 argu-
       ment to the \H escape sequence, and those variants of the \s escape se-
       quence 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  ex-
       pression	 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 ac-
	      ceptable as the name of a	string,	macro, diversion, number  reg-
	      ister,  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  su-
	      perscripting 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  be-
	      tween 0 and 255.	If the current font does not contain a charac-
	      ter 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  po-
	      sition; anything may not contain tabs or leaders.

       \$0    The  name	 by  which the current macro was invoked.  The als re-
	      quest 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  di-
	      version  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  un-
	      defined,	a  warning  of type reg	will be	generated, and the re-
	      quest will be ignored.

       .als xx yy
	      Create an	alias xx for request, string, macro, or	diversion  ob-
	      ject  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 re-
	      quests only create a new object if the name of the macro,	diver-
	      sion or string diversion is currently undefined or if it is  de-
	      fined  to	be a request; normally they modify the value of	an ex-
	      isting 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 di-
	      version xx in such a way that ASCII characters that were format-
	      ted  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  re-
	      quests.  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 hy-
	      phenation	 code.	There is a special anti-recursion feature: use
	      of character within the character's definition will  be  handled
	      like normal characters not defined with char.  A character defi-
	      nition 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  ac-
	      ceptable 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  ex-
	      ceptions	specified with the hw request and hyphenation patterns
	      specified	with the hpf request are both associated with the cur-
	      rent  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 ar-
	      gument to	the \patterns primitive	in TeX;	the letters  appearing
	      in  this file are	interpreted as hyphenation codes.  A % charac-
	      ter in the patterns file introduces a comment that continues  to
	      the end of the line.  The	set of hyphenation patterns is associ-
	      ated 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  hyphena-
	      tion  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 de-
	      fault 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 op-
	      tion 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 hy-
	      phen 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 re-
	      quest) nor translations (specified with the tr request) are con-
	      sidered when finding the soft hyphen character.

       .shift n
	      In a macro, shift	the arguments by n positions: argument	i  be-
	      comes  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 di-
	      version 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 re-
	      quest, 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  re-
	      quest.

       \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 en-
	      abled  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  ap-
       pear  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  in-
       put-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 de-
			  fault.

       number	      2	  Invalid numeric expressions.	This is	enabled	by de-
			  fault.

       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 au-
			  tomatically defined to have a	value of 0.  a defini-
			  tion	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 ar-
			  gument.  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 in-
       terpret	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  se-
       quences 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, in-
       put characters, and formatted, output characters.  Everything that  af-
       fects how an output character will be output is stored with the charac-
       ter; 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 character does not
       behave like an input character for the purposes of macro	processing; it
       does not	inherit	any of the special properties that the input character
       from which it was constructed might have	had.  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 se-
       quence: this will always	print a	single instance	of the current	escape
       character,  regardless  of whether or not it is used in a diversion; it
       will also work in both GNU troff	and Unix troff.	 If you	wish for  some
       reason  to  store in a diversion	an escape sequence that	will be	inter-
       preted when the diversion is reread, you	can either use the traditional
       \!   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),
       groff_font(5), groff_out(5), groff_char(7)

Groff Version 1.11	       8 September 1996			      TROFF(1)

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

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