Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
GROFF_DIFF(7)							 GROFF_DIFF(7)

NAME
       groff_diff - differences	between	GNU troff and classical	troff

DESCRIPTION
       This  manual page describes the language	differences between groff, the
       GNU roff	text processing	system and the classical roff formatter	of the
       freely  available  Unix	7 of the 1970s,	documented in the Troff	User's
       Manual by Osanna	and Kernighan.	This inludes the roff language as well
       as the intermediate output format (troff	output).

       The  section SEE	ALSO gives pointers to both the	classical roff and the
       modern groff documentation.

GROFF LANGUAGE
       In this section,	all additional features	of groff compared to the clas-
       sical Unix 7 troff are described	in detail.

   Long	names
       The  names  of number registers,	fonts, strings/macros/diversions, spe-
       cial characters (glyphs), and colors can	be of any length.   In	escape
       sequences,  additionally	 to  the classical (xx construction for	a two-
       character name, you can use [xxx] for a name of arbitrary length.

       \[xxx] Print the	special	character (glyph) called xxx.

       \[comp1 comp2 ...]
	      Print composite glyph consisting of multiple components.	 Exam-
	      ple:  `\[A  ho]'	is  capital letter A with ogonek which finally
	      maps to glyph name `u0041_0328'.	See the	groff  info  file  for
	      details  how  a glyph name for a composite glyph is constructed,
	      and groff_char(7)	for list of glyph name components used compos-
	      ite glyph	names.

       \f[xxx]
	      Set  font	xxx.  Additionally, \f[] is a new syntax equal to \fP,
	      i.e., to return to the previous font.

       \*[xxx arg1 arg2	...]
	      Interpolate string xxx, taking arg1, arg2, ... as	arguments.

       \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 that has the effect of	multiplying by sizescale.  Requests and	escape
       sequences  in  troff  interpret arguments that represent	a pointsize 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 argu-
       ment 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  call	 .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.	f indicates a scale  of	 65536
       units,  providing  fractions  for  color	 definitions with the defcolor
       request.	 For example, 0.5f = 32768u.

       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 resp., depending	on whether anything is
	      or is not	acceptable as the name of a string, macro,  diversion,
	      number  register,	environment, font, or color.  It will return 0
	      if anything is empty.  This is useful if you want	to lookup user
	      input in some sort of associative	table.

       \B'anything'
	      This  expands  to	1 or 0 resp., depending	on whether anything is
	      or is not	a valid	numeric	expression.  It	will return 0 if  any-
	      thing is empty.

       \C'xxx'
	      Typeset  glyph 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	is 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).

       \Ff
       \F(fm
       \F[fam]
	      Change font family.  This	is the same as the fam request.	  \F[]
	      switches	back  to the previous color (note that \FP won't work;
	      it selects font family `P' instead).

       \mx
       \m(xx
       \m[xxx]
	      Set drawing color.  \m[] switches	back to	the previous color.

       \Mx
       \M(xx
       \M[xxx]
	      Set background color for filled objects drawn with  the  \D'...'
	      commands.	 \M[] switches back to the previous color.

       \N'n'  Typeset  the  glyph  with	index n	in the current font.  n	can be
	      any integer.  Most devices only have glyphs with indices between
	      0	 and  255.   If	the current font does not contain a glyph with
	      that code, special fonts will not	be searched.   The  \N	escape
	      sequence	can  be	conveniently used in conjunction with the char
	      request, for example

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

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

       \On
       \O[n]  Suppressing troff	output.	 The escapes \02, \O3,	\O4,  and  \O5
	      are intended for internal	use by grohtml.

	      \O0    Disable  any  ditroff  glyphs  from  being	emitted	to the
		     device driver, provided that the  escape  occurs  at  the
		     outer level (see \O3 and \O4).

	      \O1    Enable  output of glyphs, provided	that the escape	occurs
		     at	the outer level.

		     \O0  and  \O1  also  reset	 the   registers   \n[opminx],
		     \n[opminy], \n[opmaxx], and \n[opmaxy] to -1.  These four
		     registers mark the	top left and bottom right hand corners
		     of	a box which encompasses	all written glyphs.

	      \O2    Provided  that  the  escape  occurs  at  the outer	level,
		     enable output of glyphs and also write out	to stderr  the
		     page  number  and	four registers encompassing the	glyphs
		     previously	written	since the last call to \O.

	      \O3    Begin a nesting level.  At	start-up, troff	 is  at	 outer
		     level.   This is really an	internal mechanism for grohtml
		     while producing images.  They are	generated  by  running
		     the  troff	 source	through	troff to the postscript	device
		     and ghostscript to	produce	images in PNG format.  The \O3
		     escape  will  start  a new	page if	the device is not html
		     (to reduce	the possibility	 of  images  crossing  a  page
		     boundary).

	      \O4    End a nesting level.

	      \O5[Pfilename]
		     This  escape  is  grohtml	specific.   Provided that this
		     escape occurs at the outer	nesting	level, write  filename
		     to	 stderr.  The position of the image, P,	must be	speci-
		     fied and must be one of l,	r, c, or i (left, right,  cen-
		     tered,  inline).	filename  will	be associated with the
		     production	of the next inline image.

       \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  or	string,	the concatenation of all the arguments
	      separated	by spaces.

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

       \$(nn
       \$[nnn]
	      In a macro or string, this gives the nn-th or  nnn-th  argument.
	      Macros and strings can have an 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 glyph so that the
	      spacing between that glyph and the following glyph will be  cor-
	      rect if the following glyph is a roman glyph.  It	is a good idea
	      to use this escape sequence whenever an italic glyph is  immedi-
	      ately followed by	a roman	glyph without any intervening space.

       \,     This  modifies  the  spacing  of the following glyph so that the
	      spacing between that glyph and the preceding glyph will  correct
	      if  the  preceding glyph is a roman glyph.  It is	a good idea to
	      use this escape sequence whenever	a roman	glyph  is  immediately
	      followed by an italic glyph 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.

       \:     This causes the insertion	of a zero-width	break  point.	It  is
	      equal to \% within a word	but without insertion of a soft	hyphen
	      character.

       \#     Everything up to and including  the  next	 newline  is  ignored.
	      This  is interpreted in copy mode.  It 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.

       .am1 xx yy
	      Similar  to  .am,	 but compatibility mode	is switched off	during
	      execution.  To be	more precise, a	`compatibility save' token  is
	      inserted at the beginning	of the macro addition, and a `compati-
	      bility restore'  token  at  the  end.   As  a  consequence,  the
	      requests am, am1,	de, and	de1 can	be intermixed freely since the
	      compatibility save/restore tokens	only affect  the  macro	 parts
	      defined by .am1 and .ds1.

       .ami xx yy
	      Append  to macro indirectly.  See	the dei	request	below for more
	      information.

       .ami1 xx	yy
	      Same as the ami request but compatibility	mode is	 switched  off
	      during execution.

       .as1 xx yy
	      Similar  to  .as,	 but compatibility mode	is switched off	during
	      expansion.  To be	more precise, a	`compatibility save' token  is
	      inserted	at  the	 beginning of the string, and a	`compatibility
	      restore' token at	the end.  As a consequence, the	 requests  as,
	      as1,  ds,	and ds1	can be intermixed freely since the compatibil-
	      ity save/restore tokens only affect the (sub)strings defined  by
	      as1 and ds1.

       .asciify	xx
	      This  request  `unformats'  the  diversion xx in such a way that
	      ASCII and	space characters (and some escape sequences) that were
	      formatted	 and  diverted	into  xx will be treated like ordinary
	      input characters when xx is reread.  Useful  for	diversions  in
	      conjunction  with	 the .writem request.  It can be also used for
	      gross hacks; for example,	this

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

	      will set register	n to 1.	 Note that  glyph  information	(font,
	      font size, etc.) is not preserved; use .unformat instead.

       .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.

       .box xx
       .boxa xx
	      These  requests  are  similar to the di and da requests with the
	      exception	that a partially filled	line will not become  part  of
	      the  diversion  (i.e.,  the  diversion  always starts with a new
	      line) but	restored after ending the  diversion,  discarding  the
	      partially	filled line which possibly comes from the diversion.

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

       .brp   This is the same as \p.

       .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
		     characters	on each	side both  have	 non-zero  hyphenation
		     codes.

	      8	     The character overlaps horizontally (initially characters
		     \[ul]\[rn]\[ru]\[radicalex]\[sqrtex] 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 glyph c to	be string.  Every time glyph  c	 needs	to  be
	      printed, string will be processed	in a temporary environment and
	      the result will be wrapped up into a single object.  Compatibil-
	      ity mode will be turned off and the escape character will	be set
	      to \ while string	is being processed.  Any emboldening, constant
	      spacing  or  track kerning will be applied to this object	rather
	      than to individual glyphs	in string.

	      A	glyph defined by this request can be used just like  a	normal
	      glyph  provided by the output device.  In	particular other char-
	      acters can be translated to it with the tr request;  it  can  be
	      made  the	 leader	character by the lc request; repeated patterns
	      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 glyph	within
	      the glyph's definition will be handled like  normal  glyphs  not
	      defined with char.

	      A	glyph definition can be	removed	with the rchar request.

       .chop xx
	      Chop  the	last element off macro,	string,	or diversion xx.  This
	      is useful	for removing the newline from the  end	of  diversions
	      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.

       .composite glyph1 glyph2
	      Map  glyph  name	glyph1	to  glyph name glyph2 if it is used in
	      \[...]  with more	than one component.

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

       .color n
	      If  n  is	 non-zero  or  missing,	 enable	 colors	 (this	is the
	      default),	otherwise disable them.

       .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.

       .defcolor xxx scheme color_components
	      Define  color.   scheme  can be one of the following values: rgb
	      (three components), cym (three components),  cmyk	 (four	compo-
	      nents),  and gray	or grey	(one component).  Color	components can
	      be given either as a hexadecimal string or as  positive  decimal
	      integers	in  the	 range 0-65535.	 A hexadecimal string contains
	      all color	components concatenated; it must start with  either  #
	      or  ##.	The  former  specifies	hex  values in the range 0-255
	      (which are internally multiplied by  257),  the  latter  in  the
	      range   0-65535.	  Examples:   #FFC0CB  (pink),	##ffff0000ffff
	      (magenta).  A new	scaling	indicator f has	been introduced	 which
	      multiplies its value by 65536; this makes	it convenient to spec-
	      ify color	components as fractions	in the range 0 to 1.  Example:

		     .defcolor darkgreen rgb 0.1f 0.5f 0.2f

	      Note  that  f  is	the default scaling indicator for the defcolor
	      request, thus the	above statement	is equivalent to

		     .defcolor darkgreen rgb 0.1 0.5 0.2

	      The color	named default  (which  is  device-specific)  can't  be
	      redefined.   It is possible that the default color for \M	and \m
	      is not the same.

       .de1 xx yy
	      Similar to .de, but compatibility	mode is	 switched  off	during
	      execution.   On  entry,  the current compatibility mode is saved
	      and restored at exit.

       .dei xx yy
	      Define macro indirectly.	The following example

		     .ds xx aa
		     .ds yy bb
		     .dei xx yy

	      is equivalent to

		     .de aa bb

       .dei1 xx	yy
	      Similar to the dei request but compatibility  mode  is  switched
	      off during execution.

       .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.

       .ds1 xx yy
	      Similar  to  .ds,	 but compatibility mode	is switched off	during
	      expansion.  To be	more precise, a	`compatibility save' token  is
	      inserted	at  the	 beginning of the string, and a	`compatibility
	      restore' token at	the end.

       .ecs   Save current escape character.

       .ecr   Restore escape character saved with  ecs.	  Without  a  previous
	      call to ecs, `\' will be the new escape character.

       .evc xx
	      Copy  the	contents of environment	xx to the current environment.
	      No pushing or popping of environments will be done.

       .fam xx
	      Set the current font family to xx.  The current font  family  is
	      part  of the current environment.	 If xx is missing, switch back
	      to previous font family.	The value at start-up is `T'.  See the
	      description of the sty request for more information on font fam-
	      ilies.

       .fchar c	string
	      Define fallback glyph c  to  be  string.	 The  syntax  of  this
	      request  is the same as the char request;	the only difference is
	      that a glyph defined with	char hides the	glyph  with  the  same
	      name  in the current font, whereas a glyph defined with fchar is
	      checked only if the particular glyph isn't found in the  current
	      font.  This test happens before checking special fonts.

       .fcolor c
	      Set  the fill color to c.	 If c is missing, switch to the	previ-
	      ous fill color.

       .fschar f c string
	      Define fallback glyph c for font f to be string.	The syntax  of
	      this request is the same as the char request (with an additional
	      argument to specify the font); a glyph defined  with  fschar  is
	      searched	after  the  list  of  fonts declared with the fspecial
	      request but before the list of fonts declared with special.

       .fspecial f s1 s2...
	      When the current font is f, fonts	s1, s2,...  will  be  special,
	      that  is,	they will searched for glyphs not in the current font.
	      Any fonts	specified in the  special  request  will  be  searched
	      after  fonts  specified  in the fspecial request.	 Without argu-
	      ment, reset the list of global special fonts to be empty.

       .ftr f g
	      Translate	font f to g.  Whenever a font named f is  referred  to
	      in  an \f	escape sequence, in the	F and S	conditional operators,
	      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.

       .gcolor c
	      Set the glyph color to c.	 If c is missing, switch to the	previ-
	      ous glyph	color.

       .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 a-z	has a hyphenation code,	 which
	      is itself, and each upper-case letter A-Z	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 name.tmac is searched for when the	-mname
	      option is	specified.  It should have the same format as (simple)
	      TeX  patterns  files.  More specifically,	the following scanning
	      rules are	implemented.

	      o	     A percent sign starts a comment (up to  the  end  of  the
		     line) even	if preceded by a backslash.

	      o	     No	support	for `digraphs' like \$.

	      o	     ^^xx  (x  is  0-9 or a-f) and ^^x (character code of x in
		     the range 0-127) are recognized; other use	of ^ causes an
		     error.

	      o	     No	macro expansion.

	      o	     hpf  checks  for  the expression \patterns{...} (possibly
		     with whitespace before and	after the braces).  Everything
		     between  the  braces  is  taken  as hyphenation patterns.
		     Consequently, { and } are not allowed in patterns.

	      o	     Similarly,	\hyphenation{...} gives	a list of  hyphenation
		     exceptions.

	      o	     \endinput is recognized also.

	      o	     For backwards compatibility, if \patterns is missing, the
		     whole file	is treated as a	list of	 hyphenation  patterns
		     (only  recognizing	the % character	as the start of	a com-
		     ment).

	      Use the hpfcode request to map the encoding used in  hyphenation
	      patterns files to	groff's	input encoding.

	      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; a second call replaces the old pat-
	      terns with the new ones.

       .hpfa file
	      The same as hpf except that the hyphenation patterns  from  file
	      are  appended to the patterns already loaded in the current lan-
	      guage.

       .hpfcode	a b c d	...
	      After reading a hyphenation patterns file	with the hpf  or  hpfa
	      request,	convert	 all  characters  with character code a	in the
	      recently read patterns to	character code	b,  character  code  c
	      to  d,  etc.   Initially,	all character codes map	to themselves.
	      The arguments of hpfcode must be integers	in the range 0 to 255.
	      Note  that  it is	even possible to use character codes which are
	      invalid in groff otherwise.

       .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.

       .itc n macro
	      Variant of .it for which a line interrupted with	\c  counts  as
	      one input	line.

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

       .length xx string
	      Compute the length of string and return it in the	number	regis-
	      ter xx (which is not necessarily defined before).

       .linetabs n
	      If  n  is	 non-zero or missing, enable line-tabs mode, otherwise
	      disable it (which	is the default).  In line-tabs mode, tab  dis-
	      tances are computed relative to the (current) output line.  Oth-
	      erwise they are taken relative to	the input line.	 For  example,
	      the following

		     .ds x a\t\c
		     .ds y b\t\c
		     .ds z c
		     .ta 1i 3i
		     \*x
		     \*y
		     \*z

	      yields

		     a	       b	 c

	      In line-tabs mode, the same code gives

		     a	       b		   c

	      Line-tabs	 mode  is associated with the current environment; the
	      read-only	number register	\n[.linetabs] is set to	1 if in	 line-
	      tabs mode, and 0 otherwise.

       .mso file
	      The  same	 as the	so request except that file is searched	for in
	      the same directories as macro files for the the -m command  line
	      option.	If the file name to be included	has the	form name.tmac
	      and it isn't found, mso tries to include tmac.name  instead  and
	      vice versa.

       .nop anything
	      Execute anything.	 This is similar to `.if 1'.

       .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.

       .output string
	      Emit string directly to  the  intermediate  output  (subject  to
	      copy-mode	 interpretation);  this	 is similar to \!  used	at the
	      top level.  An initial double quote in string is stripped	off to
	      allow initial blanks.

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

       .psbb filename
	      Get the bounding box of a	PostScript image filename.  This  file
	      must  conform  to	 Adobe's Document Structuring Conventions; the
	      command looks for	a %%BoundingBox	comment	to extract the	bound-
	      ing  box	values.	  After	a successful call, the coordinates (in
	      PostScript units)	of the lower left and upper right  corner  can
	      be  found	 in  the  registers  \n[llx],  \n[lly],	 \n[urx],  and
	      \n[ury], respectively.  If some error  has  occurred,  the  four
	      registers	are set	to zero.

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

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

       .pvs +-n
	      Set  the	post-vertical line space to n; default scale indicator
	      is p.  This value	will be	added to each line after it  has  been
	      output.	With  no argument, the post-vertical line space	is set
	      to its previous value.

	      The total	vertical line spacing consists of four components: .vs
	      and  \x  with a negative value which are applied before the line
	      is output, and .pvs and \x  with	a  positive  value  which  are
	      applied after the	line is	output.

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

       .return
	      Within a macro, return immediately.  If called with an argument,
	      return  twice,  namely from the current macro and	from the macro
	      one level	higher.	 No effect otherwise.

       .rfschar	c1 c2...
	      Remove the font-specific definitions of glyphs c1, c2,...	  This
	      undoes the effect	of a fschar 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.

       .schar c	string
	      Define global fallback glyph c to	be string.  The	syntax of this
	      request  is  the	same as	the char request; a glyph defined with
	      schar is searched	after the list of fonts	declared with the spe-
	      cial request but before the mounted special fonts.

       .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 glyph which will be inserted when	a word
	      is hyphenated at a line break.  If  the  soft  hyphen  character
	      does  not	exist in the font of the glyph immediately preceding 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.

       .sizes s1 s2...sn [0]
	      This command is similar to the sizes command of a	DESC file.  It
	      sets  the	 available  font  sizes	 for  the  current font	to s1,
	      s2,..., sn scaled	points.	 The list of sizes can	be  terminated
	      by  an  optional	0.   Each si can also be a range of sizes m-n.
	      Contrary to the font file	command, the list  can't  extend  over
	      more than	a single line.

       .special	s1 s2...
	      Fonts s1,	s2, are	special	and will be searched for glyphs	not in
	      the current font.	 Without arguments, reset the list of  special
	      fonts to be empty.

       .spreadwarn limit
	      Make  troff  emit	a warning if the additional space inserted for
	      each space between words in an output line is larger or equal to
	      limit.  A	negative value is changed to zero; no argument toggles
	      the warning on and off  without  changing	 limit.	  The  default
	      scaling  indicator is m.	At startup, spreadwarn is deactivated,
	      and limit	is set to  3m.	 For  example,	.spreadwarn 0.2m  will
	      cause  a	warning	if troff must add 0.2m or more for each	inter-
	      word space in a line.  This request is active only  if  text  is
	      justified	to both	margins	(using .ad b).

       .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.

       .substring xx n1	[n2]
	      Replace  the  string  named xx with the substring	defined	by the
	      indices n1 and n2.   The	first  character  in  the  string  has
	      index  0.	  If  n2  is  omitted,	it is taken to be equal	to the
	      string's length.	If the index value n1 or n2  is	 negative,  it
	      will be counted from the end of the string, going	backwards: The
	      last character has index -1, the character before	the last char-
	      acter has	index -2, etc.

       .tkf f s1 n1 s2 n2
	      Enable track kerning for font f.	When the current font is f the
	      width of every glyph 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.

       .tm1 string
	      Similar to the tm	request, string	is read	in copy	mode and writ-
	      ten on the standard error, but an	initial	double quote in	string
	      is stripped off to allow initial blanks.

       .tmc string
	      Similar to tm1 but without writing a final newline.

       .trf filename
	      Transparently  output  the contents of file filename.  Each line
	      is output	as if preceded by \!; however, the lines are not  sub-
	      ject 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.

       .trin abcd
	      This is the same as the  tr  request  except  that  the  asciify
	      request  will use	the character code (if any) before the charac-
	      ter translation.	Example:

		     .trin ax
		     .di xxx
		     a
		     .br
		     .di
		     .xxx
		     .trin aa
		     .asciify xxx
		     .xxx

	      The result is x a.  Using	tr, the	result would be	x x.

       .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.

       .unformat xx
	      This  request  `unformats'  the  diversion  xx.  Contrary	to the
	      .asciify request,	which tries to convert formatted  elements  of
	      the  diversion back to input tokens as much as possible, .unfor-
	      mat will only handle tabs	 and  spaces  between  words  (usually
	      caused  by spaces	or newlines in the input) specially.  The for-
	      mer are treated as if they were input tokens, and	the latter are
	      stretchable  again.  Note	that the vertical size of lines	is not
	      preserved.  Glyph	information (font,  font  size,	 space	width,
	      etc.)  is	 retained.   Useful  in	 conjunction with the .box and
	      .boxa requests.

       .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
	      troff(1).	 For example, .warn 0 will disable all	warnings,  and
	      .warn  1	will  disable  all  warnings except that about missing
	      glyphs.  If n is not given, all warnings will be enabled.

       .warnscale si
	      Set the scaling indicator	used in	warnings to si.	 Valid	values
	      for si are u, i, c, p, and P.  At	startup, it is set to i.

       .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.

       .writec stream anything
	      Similar to write but without writing a final newline.

       .writem stream xx
	      Write the	contents of the	macro or string	xx to the stream named
	      stream.  stream must previously have been	the subject of an open
	      request.	xx is read in copy mode.

   Extended escape sequences
       \D'...'
	      All  drawing  commands  of  groff's  intermediate	  output   are
	      accepted.	 See subsection	Drawing	Commands below for more	infor-
	      mation.

   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 behaviour is	so anomalous that it must be considered	a bug.

       .de xx yy
       .am xx yy
       .ds xx yy
       .as xx yy
	      In compatibility mode, these requests behaves similar  to	 .de1,
	      .am1, .ds1, and .as1, respectively: A `compatibility save' token
	      is inserted at the  beginning,  and  a  `compatibility  restore'
	      token  at	 the  end,  with compatibility mode switched on	during
	      execution.

       .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.

       .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.  Contrary to	UNIX troff,  GNU  troff	 handles  this
	      request  in  nroff mode also; a given value is then rounded down
	      to the nearest multiple of 12.  The sentence space size is  used
	      in  two  circumstances.	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 behaviour 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 glyph added to the current environment.
	      It is positive if	the glyph extends below	the baseline.

       \n[.ce]
	      The number of lines remaining to be centered, as set by  the  ce
	      request.

       \n[.cht]
	      The  height  of the last glyph added to the current environment.
	      It is positive if	the glyph extends above	the baseline.

       \n[.color]
	      1	if colors are enabled, 0 otherwise.

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

       \n[.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[.fn]
	      The current (internal) real font name.  This is a	 string-valued
	      register.	  If the current font is a style, the value of \n[.fn]
	      is the proper concatenation of family and	style name.

       \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[.height]
	      The current height of the	font as	set with \H.

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

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

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

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

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

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

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

       \n[.int]
	      Set  to  a  positive  value  if  last output line	is interrupted
	      (i.e., if	it contains \c).

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

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

       \n[.linetabs]
	      The current line-tabs mode (as set by the	linetabs request).

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

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

       \n[.m] The name of the current drawing color.  This is a	 string-valued
	      register.

       \n[.M] The name of the current background color.	 This is a string-val-
	      ued register.

       \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[.ns]
	      1	if no-space mode is active, 0 otherwise.

       \n[.pe]
	      1	during a page ejection caused by the bp	request, 0  otherwise.

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

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

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

       \n[.pvs]
	      The current  post-vertical  line	space  as  set	with  the  pvs
	      request.

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

       \n[.slant]
	      The slant	of the current font as set with	\S.

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

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

       \n[.sty]
	      The current font style.  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
	      actually is.  Useful in conjunction with the \n[.ne] register.

       \n[.U] Set  to  1 if in safer mode and to 0 if in unsafe	mode (as given
	      with the -U command line option).

       \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	troff(1).

       \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.

       \n[.Y] The revision number of groff.

       \n[llx]
       \n[lly]
       \n[urx]
       \n[ury]
	      These four registers are set by the .psbb	 request  and  contain
	      the  bounding  box values	(in PostScript units) of a given Post-
	      Script image.

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

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

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

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

       Other available read/write number registers are:

       \n[c.] The current input	line number.  \n[.c] is	a read-only  alias  to
	      this register.

       \n[hours]
	      The number of hours past midnight.  Initialized at start-up.

       \n[hp] The current horizontal position at input line.

       \n[minutes]
	      The  number of minutes after the hour.  Initialized at start-up.

       \n[seconds]
	      The number of seconds after the minute.  Initialized  at	start-
	      up.

       \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.

       \n[year]
	      The current year.	 Note that the traditional troff number	regis-
	      ter \n[yr] is the	current	year minus 1900.

   Miscellaneous
       troff predefines	a single (read/write)  string-based  register,	\*(.T,
       which contains the argument given to the	-T command line	option,	namely
       the current output device (for example, latin1 or  ascii).   Note  that
       this is not the same as the (read-only) number register \n[.T] which is
       defined to be 1 if troff	is called with the -T command line option, and
       zero otherwise.	This behaviour is different to UNIX troff.

       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,
       glyphs  from  that font will be kerned.	Kerning	between	two glyphs 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.  The same is true for
       \A, \b, \B, \C, \l, \L, \o, \X, and  \Z.	  When	decoding  a  macro  or
       string  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	imple-
       mentation 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 rec-
       ognized	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 mxxx
	      True if there is a color named xxx.

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

       .if Ff True  if	font  f	exists.	 f is handled as if it was opened with
	      the ft  request  (this  is,  font	 translation  and  styles  are
	      applied),	without	actually mounting it.

       .if Ss True  if	style  s  has  been  registered.   Font	translation is
	      applied.

       The tr request can now map characters onto \~.

       It is now possible to have whitespace between the first and second  dot
       (or the name of the ending macro) to end	a macro	definition.  Example:

	      .if t \{\
	      .	de bar
	      .	nop Hello, I'm `bar'.
	      .	.
	      .\}

INTERMEDIATE OUTPUT FORMAT
       This section describes the format output	by GNU troff.  The output for-
       mat used	by GNU troff is	very similar to	that used by Unix device-inde-
       pendent troff.  Only the	differences are	documented here.

   Units
       The  argument  to the s command is in scaled points (units of points/n,
       where n is the argument to the sizescale	command	 in  the  DESC	file).
       The argument to the x Height command is also in scaled points.

   Text	Commands
       Nn     Print glyph with index n (a non-negative integer)	of the current
	      font.

       If the tcommand line is present in the DESC file, troff	will  use  the
       following two commands.

       txxx   xxx  is  any  sequence  of characters terminated by a space or a
	      newline (to be more precise, it is a sequence  of	 glyphs	 which
	      are accessed with	the corresponding characters); the first char-
	      acter should be printed at the  current  position,  the  current
	      horizontal  position  should  be	increased  by the width	of the
	      first character, and so on for each character.  The width	of the
	      glyph  is	 that given in the font	file, appropriately scaled for
	      the current point	size, and rounded so that it is	a multiple  of
	      the horizontal resolution.  Special characters cannot be printed
	      using this command.

       un xxx This is same as the t command except that	 after	printing  each
	      character,  the  current horizontal position is increased	by the
	      sum of the width of that character and n.

       Note that single	characters can have the	eighth bit  set,  as  can  the
       names of	fonts and special characters.

       The  names  of  glyphs  and  fonts  can be of arbitrary length; drivers
       should not assume that they will	be only	two characters long.

       When a glyph is to be printed, that glyph will always be	in the current
       font.  Unlike device-independent	troff, it is not necessary for drivers
       to search special fonts to find a glyph.

       For color support, some new commands have been added:

       mc cyan magenta yellow
       md
       mg gray
       mk cyan magenta yellow black
       mr red green blue
	      Set the color components of the  current	drawing	 color,	 using
	      various  color  schemes.	 md  resets  the  drawing color	to the
	      default value.  The arguments are	integers in  the  range	 0  to
	      65536.

       The x device control command has	been extended.

       x u n  If  n is 1, start	underlining of spaces.	If n is	0, stop	under-
	      lining of	spaces.	 This is needed	for the	cu  request  in	 nroff
	      mode and is ignored otherwise.

   Drawing Commands
       The  D drawing command has been extended.  These	extensions will	not be
       used by GNU pic if the -n option	is given.

       Df n\n Set the shade of gray to be used for filling solid objects to n;
	      n	 must  be  an  integer between 0 and 1000, where 0 corresponds
	      solid white and 1000 to solid black, and values in between  cor-
	      respond  to  intermediate	 shades	of gray.  This applies only to
	      solid circles, solid ellipses and	solid polygons.	 By default, a
	      level  of	1000 will be used.  Whatever color a solid object has,
	      it should	completely obscure everything  beneath	it.   A	 value
	      greater  than  1000  or less than	0 can also be used: this means
	      fill with	the shade of gray that is  currently  being  used  for
	      lines  and  text.	 Normally this will be black, but some drivers
	      may provide a way	of changing this.

	      The corresponding	\D'f...'  command shouldn't be used since  its
	      argument	is  always rounded to an integer multiple of the hori-
	      zontal resolution	which can lead to surprising results.

       DC d\n Draw a solid circle with a diameter of d with the	leftmost point
	      at the current position.

       DE dx dy\n
	      Draw a solid ellipse with	a horizontal diameter of dx and	a ver-
	      tical diameter of	dy with	the  leftmost  point  at  the  current
	      position.	 delim $$

       Dp $dx sub 1$ $dy sub 1$	$dx sub	2$ $dy sub 2$ $...$ $dx	sub n$ $dy sub
       n$\n
	      Draw  a  polygon with, for $i = 1	,..., n+1$, the	i-th vertex at
	      the current position $+ sum from j=1 to i-1 ( dx sub j , dy  sub
	      j	)$.  At	the moment, GNU	pic only uses this command to generate
	      triangles	and rectangles.

       DP $dx sub 1$ $dy sub 1$	$dx sub	2$ $dy sub 2$ $...$ $dx	sub n$ $dy sub
       n$\n
	      Like Dp but draw a solid rather than outlined polygon.

       Dt n\n Set the current line thickness to	n machine  units.   Tradition-
	      ally Unix	troff drivers use a line thickness proportional	to the
	      current point size; drivers should continue to do	this if	no  Dt
	      command has been given, or if a Dt command has been given	with a
	      negative value of	n.  A zero value of  n	selects	 the  smallest
	      available	line thickness.

       A difficulty arises in how the current position should be changed after
       the execution of	these commands.	 This is not of	great importance since
       the code	generated by GNU pic does not depend on	this.  Given a drawing
       command of the form

	      \D'c $x sub 1$ $y	sub 1$ $x sub 2$ $y sub	2$ $...$ $x sub	n$  $y
	      sub n$'

       where  c	 is not	one of c, e, l,	a, or ~, Unix troff will treat each of
       the $x sub i$ as	a horizontal quantity, and each	of the $y sub i$ as  a
       vertical	quantity and will assume that the width	of the drawn object is
       $sum from i=1 to	n x sub	i$, and	that the height	is $sum	from i=1 to  n
       y  sub  i$.   (The assumption about the height can be seen by examining
       the st and sb registers after using such	a D command  in	 a  \w	escape
       sequence).   This rule also holds for all the original drawing commands
       with the	exception of De.  For the sake of compatibility	GNU troff also
       follows	this  rule, even though	it produces an ugly result in the case
       of the Dt and Df, and, to a lesser extent,  DE  commands.   Thus	 after
       executing a D command of	the form

	      Dc  $x  sub  1$ $y sub 1$	$x sub 2$ $y sub 2$ $...$ $x sub n$ $y
	      sub n$\n

       the current position should be increased	by $( sum from i=1 to n	x  sub
       i , sum from i=1	to n y sub i )$.

       Another set of extensions is

       DFc cyan	magenta	yellow\n
       DFd\n
       DFg gray\n
       DFk cyan	magenta	yellow black\n
       DFr red green blue\n
	      Set  the	color components of the	filling	color similar to the m
	      commands above.

       The current position isn't changed by those colour  commands  (contrary
       to Df).

   Device Control Commands
       There  is  a  continuation convention which permits the argument	to the
       x X command to contain newlines:	when outputting	the  argument  to  the
       x X  command, GNU troff will follow each	newline	in the argument	with a
       + character (as usual, it will terminate	the  entire  argument  with  a
       newline);  thus	if  the	line after the line containing the x X command
       starts with +, then the newline ending the line containing the x	X com-
       mand  should be treated as part of the argument to the x	X command, the
       + should	be ignored, and	the part of the	line following the + should be
       treated like the	part of	the line following the x X command.

       The first three output commands are guaranteed to be:

	      x	T device
	      x	res n h	v
	      x	init

INCOMPATIBILITIES
       In  spite  of  the many extensions, groff has retained compatibility to
       classical troff to a large degree.  For the cases where the  extensions
       lead  to	 collisions, a special compatibility mode with the restricted,
       old functionality was created for groff.

   Groff Language
       groff provides a	compatibility mode that	allows to  process  roff  code
       written	for  classical troff or	for other implementations of roff in a
       consistent way.

       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.

       This became necessary because the GNU concept  for  long	 names	causes
       some incompatibilities.	Classical troff	interprets

	      .dsabcd

       as  defining a string ab	with contents cd.  In groff mode, this will be
       considered as a call of a macro named dsabcd.

       Also classical troff interprets \*[ or \n[ as references	to a string or
       number  register	called [ while groff takes this	as the start of	a long
       name.

       In compatibility	mode, groff interprets these things in the traditional
       way; so long names are not recognized.

       On  the	other hand, groff in GNU native	mode does not allow to use the
       single-character	escapes	\\ (backslash),	\| (vertical bar), \^ (caret),
       \&  (ampersand),	 \{ (opening brace), \}	(closing brace), `\ ' (space),
       \' (single quote), \`  (backquote),  \-	(minus),  \_  (underline),  \!
       (bang), \% (percent), and \c (character c) in names of strings, macros,
       diversions, number registers, fonts or environments, whereas  classical
       troff does.

       The  \A	escape	sequence  can  be  helpful  in	avoiding  these	escape
       sequences in names.

       Fractional pointsizes cause one noteworthy incompatibility.  In classi-
       cal troff, the ps request ignores scale indicators and so

	      .ps 10u

       will  set  the pointsize	to 10 points, whereas in groff native mode the
       pointsize will be set to	10 scaled points.

       In groff, there is a fundamental	difference between  unformatted	 input
       characters,  and	formatted output characters (glyphs).  Everything that
       affects how a glyph will	be output is stored with  the  glyph;  once  a
       glyph  has been constructed it is unaffected by any subsequent requests
       that are	executed, including the	bd, cs,	tkf, tr, or fp requests.

       Normally	glyphs are constructed from input  characters  at  the	moment
       immediately  before  the	 glyph	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 glyphs in any	combi-
       nation.

       Special characters can be both; before being added to the output,  they
       act as input entities, afterwards they denote glyphs.

       A  glyph	 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.
       The following example will make things clearer.

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

       With GNU	troff this will	be printed as \\.  So each pair	of input back-
       slashes `\\' is turned into a single output backslash glyph `\' and the
       resulting output	backslashes are	not interpreted	as  escape  characters
       when they are reread.

       Classical  troff	 would	interpret  them	as escape characters when they
       were reread and would end up printing a single backslash	`\'.

       In GNU, the correct way to get a	printable  version  of	the  backslash
       character `\' is	the \(rs escape	sequence, but classical	troff does not
       provide a clean feature for getting  a  non-syntactical	backslash.   A
       close  method  is the printable version of the current escape character
       using the \e escape sequence; this works	if the current escape  charac-
       ter  is	not  redefined.	  It  works in both GNU	mode and compatibility
       mode, while dirty tricks	like specifying	a sequence of  multiple	 back-
       slashes do not work reliably; for the different handling	in diversions,
       macro definitions, or text mode quickly leads to	a confusion about  the
       necessary number	of backslashes.

       To  store  an  escape  sequence in a diversion that will	be interpreted
       when the	diversion is reread, either  the  traditional  \!  transparent
       output facility or the new \? escape sequence can be used.

   Intermediate	Output
       The  groff  intermediate	 output	format is in a state of	evolution.  So
       far it has some incompatibilities, but it is intended  to  establish  a
       full  compatibility to the classical troff output format.  Actually the
       following incompatibilities exist:

       o The positioning after the drawing of the polygons conflicts with  the
	 classical definition.

       o The  intermediate output cannot be rescaled to	other devices as clas-
	 sical "device-independent" troff did.

AUTHORS
       Copyright (C) 1989, 2001, 2002, 2003, 2004  Free	 Software  Foundation,
       Inc.

       This document is	distributed under the terms of the FDL (GNU Free Docu-
       mentation License) version 1.1 or later.	 You should  have  received  a
       copy of the FDL on your system, it is also available on-line at the GNU
       copyleft	site  <http://www.gnu.org/copyleft/fdl.html>.	This  document
       was  written  by	 James	Clark,	with  modifications  by	Werner Lemberg
       <wl@gnu.org> and	Bernd Warken <bwarken@mayn.de>.

       This document is	part of	groff, the GNU roff  distribution.   Formerly,
       the  contents  of  this	document was kept in the manual	page troff(1).
       Only the	parts dealing with the language	aspects	of the different  roff
       systems	were  carried over into	this document.	The troff command line
       options and warnings are	still documented in troff(1).

SEE ALSO
       The groff info file,  cf.  info(1)  presents  all  groff	 documentation
       within a	single document.

       groff(1)
	      A	list of	all documentation around groff.

       groff(7)
	      A	description of the groff language, including a short, but com-
	      plete reference  of  all	predefined  requests,  registers,  and
	      escapes  of  plain groff.	 From the command line,	this is	called
	      using

	      shell# man 7 groff

       roff(7)
	      A	survey of roff systems,	including pointers to further histori-
	      cal documentation.

       [CSTR #54]
	      The  Nroff/Troff	User's	Manual	by J. F. Osanna	of 1976	in the
	      revision of Brian	Kernighan of 1992, being the classical troff
	      documentation <http://cm.bell-labs.com/cm/cs/cstr/54.ps.gz>.

Groff Version 1.19.2	       27 September 2013		 GROFF_DIFF(7)

NAME | DESCRIPTION | GROFF LANGUAGE | INTERMEDIATE OUTPUT FORMAT | INCOMPATIBILITIES | AUTHORS | SEE ALSO

Want to link to this manual page? Use this URL:
<http://www.freebsd.org/cgi/man.cgi?query=groff_diff&sektion=7&manpath=FreeBSD+9.2-RELEASE>

home | help