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TROFF(1)		    General Commands Manual		      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 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), 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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