1GROFF(7)               Miscellaneous Information Manual               GROFF(7)
2
3
4

NAME

6       groff - a short reference for the GNU roff language
7

DESCRIPTION

9       The  name  groff  stands for GNU roff and is the free implementation of
10       the roff type-setting system.  See roff(7) for a survey and  the  back‐
11       ground of the groff system.
12
13       This document gives only short descriptions of the predefined roff lan‐
14       guage elements as used in groff.  Both the classical features  and  the
15       groff extensions are provided.
16
17       Historically,  the roff language was called troff.  groff is compatible
18       with the classical system and provides proper extensions.  So  in  GNU,
19       the  terms  roff,  troff, and groff language could be used as synonyms.
20       However troff slightly tends to refer more to  the  classical  aspects,
21       whereas  groff  emphasizes  the GNU extensions, and roff is the general
22       term for the language.
23
24       This file is only a short version of the complete documentation that is
25       found  in the groff info(1) file, which contains more detailed, actual,
26       and concise information.
27
28       The general syntax for writing groff documents is relatively easy,  but
29       writing extensions to the roff language can be a bit harder.
30
31       The roff language is line-oriented.  There are only two kinds of lines,
32       control lines and text lines.  The control lines start with  a  control
33       character,  by  default  a period “.”  or a single quote “'”; all other
34       lines are text lines.
35
36       Control lines represent commands, optionally with arguments.  They have
37       the following syntax.  The leading control character can be followed by
38       a command name; arguments, if any, are separated by spaces (but not tab
39       characters) from the command name and among themselves, for example,
40
41              .command_name arg1 arg2
42
43       For  indentation, any number of space or tab characters can be inserted
44       between the leading control character and the  command  name,  but  the
45       control character must be on the first position of the line.
46
47       Text  lines  represent the parts that is printed.  They can be modified
48       by escape sequences, which are recognized by a leading  backslash  ‘\’.
49       These  are  in-line  or  even in-word formatting elements or functions.
50       Some of these take arguments separated by single quotes “'”, others are
51       regulated by a length encoding introduced by an open parenthesis ‘(’ or
52       enclosed in brackets ‘[’ and ‘]’.
53
54       The roff language provides flexible instruments  for  writing  language
55       extension,  such  as  macros.  When interpreting macro definitions, the
56       roff system enters a special operating mode, called the copy mode.
57
58       The copy mode behaviour can be quite tricky, but there are  some  rules
59       that ensure a safe usage.
60
61       1.     Printable  backslashes  must  be denoted as \e.  To be more pre‐
62              cise, \e represents the current  escape  character.   To  get  a
63              backslash glyph, use \(rs or \[rs].
64
65       2.     Double all backslashes.
66
67       3.     Begin all text lines with the special non-spacing character \&.
68
69       This  does not produce the most efficient code, but it should work as a
70       first measure.  For better strategies, see  the  groff  info  file  and
71       groff_tmac(5).
72
73       Reading roff source files is easier, just reduce all double backslashes
74       to a single one in all macro definitions.
75

GROFF ELEMENTS

77       The roff language elements add formatting information to a  text  file.
78       The  fundamental  elements  are  predefined commands and variables that
79       make roff a full-blown programming language.
80
81       There  are  two  kinds  of  roff  commands,  possibly  with  arguments.
82       Requests  are written on a line of their own starting with a dot ‘.’ or
83       a “'”, whereas Escape sequences are in-line functions and in-word  for‐
84       matting elements starting with a backslash ‘\’.
85
86       The  user  can define her own formatting commands using the de request.
87       These commands are called  macros,  but  they  are  used  exactly  like
88       requests.  Macro packages are pre-defined sets of macros written in the
89       groff language.  A user's possibilities to create escape sequences her‐
90       self is very limited, only special characters can be mapped.
91
92       The  groff  language provides several kinds of variables with different
93       interfaces.  There are pre-defined variables, but the user  can  define
94       her own variables as well.
95
96       String  variables  store character sequences.  They are set with the ds
97       request and retrieved by the \* escape  sequences.   Strings  can  have
98       variables.
99
100       Register  variables  can  store  numerical values, numbers with a scale
101       unit, and occasionally string-like objects.  They are set with  the  nr
102       request and retrieved by the \n escape sequences.
103
104       Environments  allow  the  user  to  temporarily store global formatting
105       parameters like line length, font size, etc. for later reuse.  This  is
106       done by the ev request.
107
108       Fonts  are  identified  either by a name or by an internal number.  The
109       current font is chosen by the ft request or by the \f escape sequences.
110       Each  device  has  special fonts, but the following fonts are available
111       for all devices.  R is the standard font Roman.  B is its bold counter‐
112       part.   The italic font is called I and is available everywhere, but on
113       text devices it is displayed as an  underlined  Roman  font.   For  the
114       graphical  output devices, there exist constant-width pendants of these
115       fonts, CR, CI, and CB.  On text devices, all  glyphs  have  a  constant
116       width anyway.
117
118       Glyphs  are  visual  representation forms of characters.  In groff, the
119       distinction between those two elements is not  always  obvious  (and  a
120       full discussion is beyond the scope of this man page).  A first approx‐
121       imation is that glyphs have a specific size and colour  and  are  taken
122       from  a specific font; they can't be modified any more – characters are
123       the input, and glyphs are the output.  As soon as an  output  line  has
124       been  generated,  it no longer contains characters but glyphs.  In this
125       man page, we use either `glyph' or `character', whatever is more appro‐
126       priate.
127
128       Moreover,  there  are  some advanced roff elements.  A diversion stores
129       (formatted) information into a macro for later  usage.   A  trap  is  a
130       positional condition like a certain number of lines from page top or in
131       a diversion or in the input.  Some action can be prescribed to  be  run
132       automatically when the condition is met.
133
134       More  detailed  information and examples can be found in the groff info
135       file.
136

CONTROL CHARACTERS

138       There is a small set of characters that have a special controlling task
139       in certain conditions.
140
141       .      A  dot  is  only special at the beginning of a line or after the
142              condition in the requests if, ie, el, and while.   There  it  is
143              the  control character that introduces a request (or macro).  By
144              using the cc request, the control character can be set to a dif‐
145              ferent character, making the dot ‘.’ a non-special character.
146
147              In  all other positions, it just means a dot character.  In text
148              paragraphs, it is advantageous to start each sentence at a  line
149              of its own.
150
151       '      The single quote has two controlling tasks.  At the beginning of
152              a line and in the conditional requests it  is  the  non-breaking
153              control character.  That means that it introduces a request like
154              the dot, but with the  additional  property  that  this  request
155              doesn't  cause  a  linebreak.  By using the c2 request, the non-
156              break control character can be set to a different character.
157
158              As a second task, it is the most commonly used argument  separa‐
159              tor in some functional escape sequences (but any pair of charac‐
160              ters not part of the argument do work).  In all other positions,
161              it denotes the single quote or apostrophe character.  Groff pro‐
162              vides a printable representation with the \(cq escape sequence.
163
164       "      The double quote is used to enclose arguments in macros (but not
165              in  requests and strings).  In the ds and as requests, a leading
166              double quote in the argument is stripped off, making  everything
167              else  afterwards  the  string  to  be  defined (enabling leading
168              whitespace).  The escaped double quote \" introduces a  comment.
169              Otherwise, it is not special.  Groff provides a printable repre‐
170              sentation with the \(dq escape sequence.
171
172       \      The backslash usually introduces an escape sequence (this can be
173              changed  with  the ec request).  A printed version of the escape
174              character is the \e escape; a backslash glyph can be obtained by
175              \(rs.
176
177       (      The  open  parenthesis  is only special in escape sequences when
178              introducing an escape name or argument consisting of exactly two
179              characters.   In groff, this behaviour can be replaced by the []
180              construct.
181
182       [      The opening bracket is only special in groff  escape  sequences;
183              there  it is used to introduce a long escape name or long escape
184              argument.  Otherwise, it is non-special, e.g. in macro calls.
185
186       ]      The closing bracket is only special in groff  escape  sequences;
187              there  it terminates a long escape name or long escape argument.
188              Otherwise, it is non-special.
189
190       space  Space characters are only functional characters.  They  separate
191              the arguments in requests, macros, and strings, and the words in
192              text lines.  They are subject to groff's horizontal spacing cal‐
193              culations.   To get a defined space width, escape sequences like
194\ ’ (this is the escape character followed by a space), \|, \^,
195              or \h should be used.
196
197       newline
198              In  text  paragraphs,  newlines mostly behave like space charac‐
199              ters.  Continuation lines can be specified by  an  escaped  new‐
200              line,  i.e., by specifying a backslash ‘\’ as the last character
201              of a line.
202
203       tab    If a tab character occurs during text the  interpreter  makes  a
204              horizontal  jump to the next pre-defined tab position.  There is
205              a sophisticated interface for handling tab positions.
206

NUMERICAL EXPRESSIONS

208       A numerical value is a signed or unsigned  integer  or  float  with  or
209       without  an  appended scaling indicator.  A scaling indicator is a one-
210       character abbreviation for a unit of measurement.  A number followed by
211       a scaling indicator signifies a size value.  By default, numerical val‐
212       ues do not have a scaling indicator, i.e., they are normal numbers.
213
214       The roff language defines the following scaling indicators.
215
216              c         Centimeter
217              i         Inch
218              P         Pica = 1/6 inch
219              p         Point = 1/72 inch
220              m         Em = the font size in points (approx. width of  letter
221                        `m')
222              M         100th of an Em
223              n         En = Em/2
224              u         Basic unit for actual output device
225              v         Vertical    line   space   in   basic   units   scaled
226                        point = 1/sizescale of a point (defined in  font  DESC
227                        file)
228              f         Scale by 65536.
229
230       Numerical  expressions are combinations of the numerical values defined
231       above with the following  arithmetical  operators  already  defined  in
232       classical troff.
233
234              +         Addition
235              -         Subtraction
236              *         Multiplication
237              /         Division
238              %         Modulo
239              =         Equals
240              ==        Equals
241              <         Less than
242              >         Greater than
243              <=        Less or equal
244              >=        Greater or equal
245              &         Logical and
246              :         Logical or
247              !         Logical not
248              (         Grouping of expressions
249              )         Close current grouping
250
251       Moreover,  groff  added  the  following operators for numerical expres‐
252       sions:
253
254              e1>?e2    The maximum of e1 and e2.
255              e1<?e2    The minimum of e1 and e2.
256              (c;e)     Evaluate e using c as the default scaling indicator.
257
258       For details see the groff info file.
259

CONDITIONS

261       Conditions occur in tests raised by the if, ie, and the while requests.
262       The following table characterizes the different types of conditions.
263
264              N         A  numerical  expression N yields true if its value is
265                        greater than 0.
266              !N        True if the value of N is 0 (see below).
267              's1's2'   True if string s1 is identical to string s2.
268              !'s1's2'  True if string s1 is not identical to string  s2  (see
269                        below).
270              cch       True if there is a glyph ch available.
271              dname     True  if  there  is  a  string,  macro,  diversion, or
272                        request called name.
273              e         Current page number is even.
274              o         Current page number is odd.
275              mname     True if there is a color called name.
276              n         Formatter is nroff.
277              rreg      True if there is a register named reg.
278              t         Formatter is troff.
279              Ffont     True if there exists a font named font.
280              Sstyle    True if a style named style has been registered.
281
282       Note that the !  operator may  only  appear  at  the  beginning  of  an
283       expression, and negates the entire expression.  This maintains bug-com‐
284       patibility with AT&T troff.
285

REQUESTS

287       This section provides a short reference for  the  predefined  requests.
288       In groff, request, macro, and string names can be arbitrarily long.  No
289       bracketing or marking of long names is needed.
290
291       Most requests take one or more arguments.  The arguments are  separated
292       by  space  characters  (no tabs!); there is no inherent limit for their
293       length or number.
294
295       Some requests have optional arguments with a different behaviour.   Not
296       all  of  these details are outlined here.  Refer to the groff info file
297       and groff_diff(7) for all details.
298
299       In the following request specifications, most argument names were  cho‐
300       sen  to be descriptive.  Only the following denotations need clarifica‐
301       tion.
302
303              c         denotes a single character.
304              font      a font either specified as a font name or a font  num‐
305                        ber.
306              anything  all  characters up to the end of the line or within \{
307                        and \}.
308              n         is a numerical expression that evaluates to an integer
309                        value.
310              N         is   an  arbitrary  numerical  expression,  signed  or
311                        unsigned.
312              ±N        has three meanings depending on  its  sign,  described
313                        below.
314
315       If  an  expression  defined  as ±N starts with a ‘+’ sign the resulting
316       value of the expression is added to an already existing value  inherent
317       to  the  related  request,  e.g.  adding  to a number register.  If the
318       expression starts with a ‘-’ the value of the expression is  subtracted
319       from the request value.
320
321       Without  a  sign,  N replaces the existing value directly.  To assign a
322       negative number either prepend 0 or  enclose  the  negative  number  in
323       parentheses.
324
325   Request Short Reference
326       .         Empty line, ignored.  Useful for structuring documents.
327       .\" anything
328                 Complete line is a comment.
329       .ab string
330                 Print string on standard error, exit program.
331       .ad       Begin  line  adjustment  for  output  lines in current adjust
332                 mode.
333       .ad c     Start line adjustment in mode c (c=l,r,c,b,n).
334       .af register c
335                 Assign format c to register (c=l,i,I,a,A).
336       .aln alias register
337                 Create alias name for register.
338       .als alias object
339                 Create alias name for request, string,  macro,  or  diversion
340                 object.
341       .am macro Append to macro until .. is encountered.
342       .am macro end
343                 Append to macro until .end is called.
344       .am1 macro
345                 Same  as  .am but with compatibility mode switched off during
346                 macro expansion.
347       .am1 macro end
348                 Same as .am but with compatibility mode switched  off  during
349                 macro expansion.
350       .ami macro
351                 Append  to a macro whose name is contained in the string reg‐
352                 ister macro until .. is encountered.
353       .ami macro end
354                 Append to a macro indirectly.  macro and end are string  reg‐
355                 isters whose contents are interpolated for the macro name and
356                 the end macro, respectively.
357       .ami1 macro
358                 Same as .ami but with compatibility mode switched off  during
359                 macro expansion.
360       .ami1 macro end
361                 Same  as .ami but with compatibility mode switched off during
362                 macro expansion.
363       .as stringvar anything
364                 Append anything to stringvar.
365       .as1 stringvar anything
366                 Same as .as but with compatibility mode switched  off  during
367                 string expansion.
368       .asciify diversion
369                 Unformat  ASCII characters, spaces, and some escape sequences
370                 in diversion.
371       .backtrace
372                 Print a backtrace of the input on stderr.
373       .bd font N
374                 Embolden font by N-1 units.
375       .bd S font N
376                 Embolden Special Font S when current font is font.
377       .blm      Unset the blank line macro.
378       .blm macro
379                 Set the blank line macro to macro.
380       .box      End current diversion.
381       .box macro
382                 Divert to macro, omitting a partially filled line.
383       .boxa     End current diversion.
384       .boxa macro
385                 Divert and append to macro, omitting a partially filled line.
386       .bp       Eject current page and begin new page.
387       .bp ±N    Eject current page; next page number ±N.
388       .br       Line break.
389       .brp      Break and spread output line.  Same as \p.
390       .break    Break out of a while loop.
391       .c2       Reset no-break control character to “'”.
392       .c2 c     Set no-break control character to c.
393       .cc       Reset control character to ‘.’.
394       .cc c     Set control character to c.
395       .ce       Center the next input line.
396       .ce N     Center following N input lines.
397       .cf filename
398                 Copy contents of file filename unprocessed to  stdout  or  to
399                 the diversion.
400       .cflags mode c1 c2 ...
401                 Treat characters c1, c2, ... according to mode number.
402       .ch trap N
403                 Change trap location to N.
404       .char c anything
405                 Define entity c as string anything.
406       .chop object
407                 Chop  the  last  character  off  macro,  string, or diversion
408                 object.
409       .class name c1 c2 ...
410                 Assign a set of characters, character ranges, or classes  c1,
411                 c2, ... to name.
412       .close stream
413                 Close the stream.
414       .color    Enable colors.
415       .color N  If N is zero disable colors, otherwise enable them.
416       .composite from to
417                 Map  glyph  name  from  to glyph name to while constructing a
418                 composite glyph name.
419       .continue Finish the current iteration of a while loop.
420       .cp       Enable compatibility mode.
421       .cp N     If N is zero disable compatibility mode, otherwise enable it.
422       .cs font N M
423                 Set constant character width mode for font to N/36  ems  with
424                 em M.
425       .cu N     Continuous underline in nroff, like .ul in troff.
426       .da       End current diversion.
427       .da macro Divert and append to macro.
428       .de macro Define or redefine macro until .. is encountered.
429       .de macro end
430                 Define or redefine macro until .end is called.
431       .de1 macro
432                 Same  as  .de but with compatibility mode switched off during
433                 macro expansion.
434       .de1 macro end
435                 Same as .de but with compatibility mode switched  off  during
436                 macro expansion.
437       .defcolor color scheme component
438                 Define  or  redefine  a color with name color.  scheme can be
439                 rgb, cym, cymk, gray, or grey.  component can be single  com‐
440                 ponents  specified  as fractions in the range 0 to 1 (default
441                 scaling indicator f), as a string  of  two-digit  hexadecimal
442                 color  components  with  a leading #, or as a string of four-
443                 digit hexadecimal components with two leading #.   The  color
444                 default can't be redefined.
445       .dei macro
446                 Define  or  redefine  a  macro whose name is contained in the
447                 string register macro until .. is encountered.
448       .dei macro end
449                 Define or redefine a macro indirectly.   macro  and  end  are
450                 string  registers  whose  contents  are  interpolated for the
451                 macro name and the end macro, respectively.
452       .dei1 macro
453                 Same as .dei but with compatibility mode switched off  during
454                 macro expansion.
455       .dei1 macro end
456                 Same  as .dei but with compatibility mode switched off during
457                 macro expansion.
458       .device anything
459                 Write anything to the intermediate output as a device control
460                 function.
461       .devicem name
462                 Write  contents  of macro or string name uninterpreted to the
463                 intermediate output as a device control function.
464       .di       End current diversion.
465       .di macro Divert to macro.
466       .do name  Interpret .name with compatibility mode disabled.
467       .ds stringvar anything
468                 Set stringvar to anything.
469       .ds1 stringvar anything
470                 Same as .ds but with compatibility mode switched  off  during
471                 string expansion.
472       .dt N trap
473                 Set  diversion  trap  to  position N (default scaling indica‐
474                 tor v).
475       .ec       Reset escape character to ‘\’.
476       .ec c     Set escape character to c.
477       .ecr      Restore escape character saved with .ecs.
478       .ecs      Save current escape character.
479       .el anything
480                 Else part for if-else (ie) request.
481       .em macro The macro is run after the end of input.
482       .eo       Turn off escape character mechanism.
483       .ev       Switch to previous environment and pop it off the stack.
484       .ev env   Push down environment number or name env  to  the  stack  and
485                 switch to it.
486       .evc env  Copy  the contents of environment env to the current environ‐
487                 ment.  No pushing or popping.
488       .ex       Exit from roff processing.
489       .fam      Return to previous font family.
490       .fam name Set the current font family to name.
491       .fc       Disable field mechanism.
492       .fc a     Set field delimiter to a and pad glyph to space.
493       .fc a b   Set field delimiter to a and pad glyph to b.
494       .fchar c anything
495                 Define fallback character (or glyph) c as string anything.
496       .fcolor   Set fill color to previous fill color.
497       .fcolor c Set fill color to c.
498       .fi       Fill output lines.
499       .fl       Flush output buffer.
500       .fp n font
501                 Mount font on position n.
502       .fp n internal external
503                 Mount font with long external name to short internal name  on
504                 position n.
505       .fschar f c anything
506                 Define  fallback  character (or glyph) c for font f as string
507                 anything.
508       .fspecial font
509                 Reset list of special fonts for font to be empty.
510       .fspecial font s1 s2 ...
511                 When the current font is font, then the fonts s1, s2, ... are
512                 special.
513       .ft       Return to previous font.  Same as \f[] or \fP.
514       .ft font  Change  to  font name or number font; same as \f[font] escape
515                 sequence.
516       .ftr font1 font2
517                 Translate font1 to font2.
518       .fzoom font
519                 Don't magnify font.
520       .fzoom font zoom
521                 Set zoom factor for font (in multiples of 1/1000th).
522       .gcolor   Set glyph color to previous glyph color.
523       .gcolor c Set glyph color to c.
524       .hc       Remove additional hyphenation indicator character.
525       .hc c     Set up additional hyphenation indicator character c.
526       .hcode c1 code1 c2 code2 ...
527                 Set the hyphenation code of character c1 to code1, that of c2
528                 to code2, etc.
529       .hla lang Set the current hyphenation language to lang.
530       .hlm n    Set the maximum number of consecutive hyphenated lines to n.
531       .hpf file Read hyphenation patterns from file.
532       .hpfa file
533                 Append hyphenation patterns from file.
534       .hpfcode a b c d ...
535                 Set input mapping for .hpf.
536       .hw words List of words with exceptional hyphenation.
537       .hy N     Switch to hyphenation mode N.
538       .hym n    Set  the  hyphenation  margin  to  n (default scaling indica‐
539                 tor m).
540       .hys n    Set the hyphenation space to n.
541       .ie cond anything
542                 If cond then anything else goto .el.
543       .if cond anything
544                 If cond then anything; otherwise do nothing.
545       .ig       Ignore text until .. is encountered.
546       .ig end   Ignore text until .end is called.
547       .in       Change to previous indentation value.
548       .in ±N    Change indentation according to ±N (default  scaling  indica‐
549                 tor m).
550       .it N trap
551                 Set an input-line count trap for the next N lines.
552       .itc N trap
553                 Same as .it but count lines interrupted with \c as one line.
554       .kern     Enable pairwise kerning.
555       .kern n   If n is zero, disable pairwise kerning, otherwise enable it.
556       .lc       Remove leader repetition glyph.
557       .lc c     Set leader repetition glyph to c.
558       .length register anything
559                 Write the length of the string anything to register.
560       .linetabs Enable line-tabs mode (i.e., calculate tab positions relative
561                 to output line).
562       .linetabs n
563                 If n is zero, disable line-tabs mode, otherwise enable it.
564       .lf N     Set input line number to N.
565       .lf N file
566                 Set input line number to N and filename to file.
567       .lg N     Ligature mode on if N>0.
568       .ll       Change to previous line length.
569       .ll ±N    Set line length according to ±N (default length 6.5i, default
570                 scaling indicator m).
571       .lsm      Unset the leading spaces macro.
572       .lsm macro
573                 Set the leading spaces macro to macro.
574       .ls       Change to the previous value of additional intra-line skip.
575       .ls N     Set  additional  intra-line  skip value to N, i.e., N-1 blank
576                 lines are inserted after each text output line.
577       .lt ±N    Length of title (default scaling indicator m).
578       .mc       Margin glyph off.
579       .mc c     Print glyph c after each text line at  actual  distance  from
580                 right margin.
581       .mc c N   Set  margin  glyph  to  c and distance to N from right margin
582                 (default scaling indicator m).
583       .mk register
584                 Mark current vertical position in register.
585       .mso file The same as .so except that file  is  searched  in  the  tmac
586                 directories.
587       .na       No output-line adjusting.
588       .ne       Need a one-line vertical space.
589       .ne N     Need N vertical space (default scaling indicator v).
590       .nf       No filling or adjusting of output-lines.
591       .nh       No hyphenation.
592       .nm       Number mode off.
593       .nm ±N [M [S [I]]]
594                 In  line  number  mode,  set  number,  multiple, spacing, and
595                 indentation.
596       .nn       Do not number next line.
597       .nn N     Do not number next N lines.
598       .nop anything
599                 Always process anything.
600       .nr register ±N [M]
601                 Define or modify register using ±N with auto-increment M.
602       .nroff    Make the built-in conditions n true and t false.
603       .ns       Turn on no-space mode.
604       .nx       Immediately jump to end of current file.
605       .nx filename
606                 Immediately continue processing with file file.
607       .open stream filename
608                 Open filename for writing  and  associate  the  stream  named
609                 stream with it.
610       .opena stream filename
611                 Like .open but append to it.
612       .os       Output vertical distance that was saved by the sv request.
613       .output string
614                 Emit string directly to intermediate output, allowing leading
615                 whitespace if string starts with " (which is stripped off).
616       .pc       Reset page number character to ‘%’.
617       .pc c     Page number character.
618       .pev      Print the current environment and  each  defined  environment
619                 state to stderr.
620       .pi program
621                 Pipe output to program (nroff only).
622       .pl       Set  page  length to default 11i.  The current page length is
623                 stored in register .p.
624       .pl ±N    Change page length to ±N (default scaling indicator v).
625       .pm       Print macro names and sizes (number of blocks of 128 bytes).
626       .pm t     Print only total of sizes of  macros  (number  of  128  bytes
627                 blocks).
628       .pn ±N    Next page number N.
629       .pnr      Print  the names and contents of all currently defined number
630                 registers on stderr.
631       .po       Change to previous page offset.  The current page  offset  is
632                 available in register .o.
633       .po ±N    Page offset N.
634       .ps       Return to previous point size.
635       .ps ±N    Point size; same as \s[±N].
636       .psbb filename
637                 Get the bounding box of a PostScript image filename.
638       .pso command
639                 This behaves like the so request except that input comes from
640                 the standard output of command.
641       .ptr      Print the names and positions of  all  traps  (not  including
642                 input line traps and diversion traps) on stderr.
643       .pvs      Change to previous post-vertical line spacing.
644       .pvs ±N   Change  post-vertical  line  spacing according to ±N (default
645                 scaling indicator p).
646       .rchar c1 c2 ...
647                 Remove the definitions of entities c1, c2, ...
648       .rd prompt
649                 Read insertion.
650       .return   Return from a macro.
651       .return anything
652                 Return twice, namely from the macro at the current level  and
653                 from the macro one level higher.
654       .rfschar f c1 c2 ...
655                 Remove the definitions of entities c1, c2, ... for font f.
656       .rj n     Right justify the next n input lines.
657       .rm name  Remove request, macro, or string name.
658       .rn old new
659                 Rename request, macro, or string old to new.
660       .rnn reg1 reg2
661                 Rename register reg1 to reg2.
662       .rr register
663                 Remove register.
664       .rs       Restore spacing; turn no-space mode off.
665       .rt ±N    Return  (upward only) to marked vertical place (default scal‐
666                 ing indicator v).
667       .schar c anything
668                 Define global fallback character (or glyph) c as string  any‐
669                 thing.
670       .shc      Reset soft hyphen glyph to \(hy.
671       .shc c    Set the soft hyphen glyph to c.
672       .shift n  In a macro, shift the arguments by n positions.
673       .sizes s1 s2 ... sn [0]
674                 Set  available  font  sizes similar to the sizes command in a
675                 DESC file.
676       .so filename
677                 Include source file.
678       .sp       Skip one line vertically.
679       .sp N     Space vertical distance N up or down according to sign  of  N
680                 (default scaling indicator v).
681       .special  Reset global list of special fonts to be empty.
682       .special s1 s2 ...
683                 Fonts  s1,  s2,  etc. are special and are searched for glyphs
684                 not in the current font.
685       .spreadwarn
686                 Toggle the spread warning on and  off  without  changing  its
687                 value.
688       .spreadwarn limit
689                 Emit  a warning if each space in an output line is widened by
690                 limit or more (default scaling indicator m).
691       .ss N     Set space glyph size to N/12 of the space width in  the  cur‐
692                 rent font.
693       .ss N M   Set  space  glyph size to N/12 and sentence space size set to
694                 M/12 of the space width in the current font.
695       .sty n style
696                 Associate style with font position n.
697       .substring xx n1 n2
698                 Replace the string named xx with the substring defined by the
699                 indices n1 and n2.
700       .sv       Save 1 v of vertical space.
701       .sv N     Save the vertical distance N for later output with os request
702                 (default scaling indicator v).
703       .sy command-line
704                 Execute program command-line.
705       .ta T N   Set tabs after  every  position  that  is  a  multiple  of  N
706                 (default scaling indicator m).
707       .ta n1 n2 ... nn T r1 r2 ... rn
708                 Set  tabs  at  positions  n1,  n2,  ..., nn, then set tabs at
709                 nn+r1, nn+r2, ..., nn+rn, then at  nn+rn+r1,  nn+rn+r2,  ...,
710                 nn+rn+rn, and so on.
711       .tc       Remove tab repetition glyph.
712       .tc c     Set tab repetition glyph to c.
713       .ti ±N    Temporary indent next line (default scaling indicator m).
714       .tkf font s1 n1 s2 n2
715                 Enable track kerning for font.
716       .tl ’leftcenterright
717                 Three-part title.
718       .tm anything
719                 Print anything on stdout.
720       .tm1 anything
721                 Print anything on stdout, allowing leading whitespace if any‐
722                 thing starts with " (which is stripped off).
723       .tmc anything
724                 Similar to .tm1 without emitting a final newline.
725       .tr abcd...
726                 Translate a to b, c to d, etc. on output.
727       .trf filename
728                 Transparently output the contents of file filename.
729       .trin abcd...
730                 This is the same as the tr request except  that  the  asciify
731                 request uses the character code (if any) before the character
732                 translation.
733       .trnt abcd...
734                 This is the same as the tr request except that  the  transla‐
735                 tions  do  not apply to text that is transparently throughput
736                 into a diversion with \!.
737       .troff    Make the built-in conditions t true and n false.
738       .uf font  Set underline font to font (to be switched to by .ul).
739       .ul N     Underline (italicize in troff) N input lines.
740       .unformat diversion
741                 Unformat space characters and tabs in  diversion,  preserving
742                 font information.
743       .vpt n    Enable vertical position traps if n is non-zero, disable them
744                 otherwise.
745       .vs       Change to previous vertical base line spacing.
746       .vs ±N    Set vertical base line spacing to ±N (default scaling indica‐
747                 tor p).
748       .warn n   Set warnings code to n.
749       .warnscale si
750                 Set scaling indicator used in warnings to si.
751       .wh N     Remove (first) trap at position N.
752       .wh N trap
753                 Set location trap; negative means from page bottom.
754       .while cond anything
755                 While condition cond is true, accept anything as input.
756       .write stream anything
757                 Write anything to the stream named stream.
758       .writec stream anything
759                 Similar to .write without emitting a final newline.
760       .writem stream xx
761                 Write  contents  of  macro  or  string xx to the stream named
762                 stream.
763
764       Besides these standard groff requests, there  might  be  further  macro
765       calls.   They  can  originate  from a macro package (see roff(7) for an
766       overview) or from a preprocessor.
767
768       Preprocessor macros are easy to be recognized.  They enclose their code
769       into a pair of characteristic macros.
770
771                      ┌─────────────┬─────────────┬────────────┐
772                      │preprocessor │ start macro │  end macro │
773                      ├─────────────┼─────────────┼────────────┤
774eqn      .EQ     .EN     
775grap     .G1     .G2     
776grn      .GS     .GE     
777pic      .PS     .PE     
778refer     .R1     .R2     
779soelim    nonenone
780tbl      .TS     .TE     
781                      └─────────────┴─────────────┴────────────┘

ESCAPE SEQUENCES

783       Escape  sequences are in-line language elements usually introduced by a
784       backslash ‘\’ and followed  by  an  escape  name  and  sometimes  by  a
785       required  argument.   Input  processing is continued directly after the
786       escaped character or the argument (without  an  intervening  separation
787       character).   So there must be a way to determine the end of the escape
788       name and the end of the argument.
789
790       This is done by enclosing names (escape name and  arguments  consisting
791       of a variable name) by a pair of brackets [name] and constant arguments
792       (number expressions and characters) by apostrophes  (ASCII  0x27)  like
793       constant.
794
795       There  are  abbreviations  for short names.  Two-character escape names
796       can be specified by an opening parenthesis like \(xy or \*(xy without a
797       closing  counterpart.   And  all one-character names different from the
798       special characters ‘[’ and ‘(’ can even be specified without a  marker,
799       for example \nc or \$c.
800
801       Constant  arguments  of  length 1 can omit the marker apostrophes, too,
802       but there is no two-character analogue.
803
804       While one-character escape sequences are mainly used for in-line  func‐
805       tions  and  system related tasks, the two-letter names following the \(
806       construct are glyphs predefined by the roff system;  these  are  called
807       `Special Characters' in the classical documentation.  Escapes sequences
808       of the form \[name] denote glyphs too.
809
810   Single-Character Escapes
811       \"     Start of a comment.  Everything up to the end  of  the  line  is
812              ignored.
813       \#     Everything  up  to  and  including  the next newline is ignored.
814              This is interpreted in copy mode.  This is like \"  except  that
815              the terminating newline is ignored as well.
816       \*s    The  string  stored  in  the  string variable with one-character
817              name s.
818       \*(st  The string stored in the string variable with two-character name
819              st.
820       \*[string]
821              The  string stored in the string variable with name string (with
822              arbitrary length).
823       \*[stringvar arg1 arg2 ...]
824              The string stored in the string variable with  arbitrarily  long
825              name stringvar, taking arg1, arg2, ... as arguments.
826       \$0    The  name  by  which  the  current  macro  was invoked.  The als
827              request can make a macro have more than one name.
828       \$x    Macro or string argument with one-digit number x in the range  1
829              to 9.
830       \$(xy  Macro  or  string argument with two-digit number xy (larger than
831              zero).
832       \$[nexp]
833              Macro or string argument with  number  nexp,  where  nexp  is  a
834              numerical expression evaluating to an integer ≥1.
835       \$*    In  a  macro  or  string, the concatenation of all the arguments
836              separated by spaces.
837       \$@    In a macro or string, the concatenation  of  all  the  arguments
838              with each surrounded by double quotes, and separated by spaces.
839       \$^    In a macro, the representation of all parameters as if they were
840              an argument to the ds request.
841       \\     reduces to a single backslash; useful to delay  its  interpreta‐
842              tion  as  escape  character in copy mode.  For a printable back‐
843              slash, use \e, or even better \[rs], to be independent from  the
844              current escape character.
845       \’     The  acute accent ´; same as \(aa.  Unescaped: apostrophe, right
846              quotation mark, single quote (ASCII 0x27).
847       \`     The grave accent `; same as \(ga.  Unescaped: left quote,  back‐
848              quote (ASCII 0x60).
849       \-     The - (minus) sign in the current font.
850       \_     The same as \(ul, the underline character.
851       \.     The  same as a dot (`.').  Necessary in nested macro definitions
852              so that `\\..' expands to `..'.
853       \%     Default optional hyphenation character.
854       \!     Transparent line indicator.
855       \?anything?
856              In a diversion, this transparently embeds anything in the diver‐
857              sion.   anything  is  read  in  copy  mode.  See also the escape
858              sequences \!  and \?.
859       \space Unpaddable space size space glyph (no line break).
860       \0     Digit-width space.
861       \|     1/6 em narrow space glyph; zero width in nroff.
862       \^     1/12 em half-narrow space glyph; zero width in nroff.
863       \&     Non-printable, zero-width glyph.
864       \)     Like \& except that it behaves like a glyph  declared  with  the
865              cflags request to be transparent for the purposes of end-of-sen‐
866              tence recognition.
867       \/     Increases the width of the preceding glyph so that  the  spacing
868              between  that  glyph  and  the following glyph is correct if the
869              following glyph is a roman glyph.
870       \,     Modifies the spacing of the following glyph so that the  spacing
871              between  that  glyph  and  the preceding glyph is correct if the
872              preceding glyph is a roman glyph.
873       \~     Unbreakable space that stretches like a normal inter-word  space
874              when a line is adjusted.
875       \:     Inserts  a  zero-width  break point (similar to \% but without a
876              soft hyphen character).
877       \newline
878              Ignored newline, for continuation lines.
879       \{     Begin conditional input.
880       \}     End conditional input.
881       \(sc   A glyph with two-character name sc; see section Special  Charac‐
882              ters.
883       \[name]
884              A glyph with name name (of arbitrary length).
885       \[comp1 comp2 ...]
886              A composite glyph with components comp1, comp2, ...
887       \a     Non-interpreted leader character.
888       \A’anything
889              If  anything  is acceptable as a name of a string, macro, diver‐
890              sion, register, environment or font it expands to 1,  and  to  0
891              otherwise.
892       \b’abc...
893              Bracket building function.
894       \B’anything
895              If  anything  is  acceptable  as  a  valid numeric expression it
896              expands to 1, and to 0 otherwise.
897       \c     Interrupt text processing.
898       \C’glyph
899              The glyph called glyph; same  as  \[glyph],  but  compatible  to
900              other roff versions.
901       \d     Forward (down) 1/2 em (1/2 line in nroff).
902       \D’charseq
903              Draw  a  graphical element defined by the characters in charseq;
904              see the groff info file for details.
905       \e     Printable version of the current escape character.
906       \E     Equivalent to an escape character, but  is  not  interpreted  in
907              copy mode.
908       \fF    Change to font with one-character name or one-digit number F.
909       \fP    Switch back to previous font.
910       \f(fo  Change to font with two-character name or two-digit number fo.
911       \f[font]
912              Change  to  font with arbitrarily long name or number expression
913              font.
914       \f[]   Switch back to previous font.
915       \Ff    Change to font family with one-character name f.
916       \F(fm  Change to font family with two-character name fm.
917       \F[fam]
918              Change to font family with arbitrarily long name fam.
919       \F[]   Switch back to previous font family.
920       \gr    Return format of register with one-character name r suitable for
921              af request.
922       \g(rg  Return  format  of  register with two-character name rg suitable
923              for af request.
924       \g[reg]
925              Return format of register with arbitrarily long name  reg  suit‐
926              able for af request.
927       \h’NLocal horizontal motion; move right N (left if negative).
928       \H’NSet height of current font to N.
929       \kr    Mark horizontal input place in one-character register r.
930       \k(rg  Mark horizontal input place in two-character register rg.
931       \k[reg]
932              Mark  horizontal  input  place in register with arbitrarily long
933              name reg.
934       \l’NcHorizontal line drawing function (optionally using character c).
935       \L’NcVertical line drawing function (optionally using character c).
936       \mc    Change to color with one-character name c.
937       \m(cl  Change to color with two-character name cl.
938       \m[color]
939              Change to color with arbitrarily long name color.
940       \m[]   Switch back to previous color.
941       \Mc    Change filling color for closed drawn objects to color with one-
942              character name c.
943       \M(cl  Change filling color for closed drawn objects to color with two-
944              character name cl.
945       \M[color]
946              Change filling color for closed  drawn  objects  to  color  with
947              arbitrarily long name color.
948       \M[]   Switch to previous fill color.
949       \nr    The  numerical  value  stored  in the register variable with the
950              one-character name r.
951       \n(re  The numerical value stored in the  register  variable  with  the
952              two-character name re.
953       \n[reg]
954              The  numerical  value stored in the register variable with arbi‐
955              trarily long name reg.
956       \N’nTypeset the glyph with index n in the current font.  No  special
957              fonts  are  searched.   Useful  for adding (named) entities to a
958              document using the char request and friends.
959       \o’abc...
960              Overstrike glyphs a, b, c, etc.
961       \O0    Disable glyph output.  Mainly for internal use.
962       \O1    Enable glyph output.  Mainly for internal use.
963       \p     Break and spread output line.
964       \r     Reverse 1 em vertical motion (reverse line in nroff).
965       \R’name ±n
966              The same as .nr name ±n.
967       \s±N   Set/increase/decrease the point size to/by N scaled points; N is
968              a one-digit number in the range 1 to 9.  Same as ps request.
969       \s(±N
970       \s±(N  Set/increase/decrease the point size to/by N scaled points; N is
971              a two-digit number ≥1.  Same as ps request.
972       \s[±N]
973       \s±[N]
974       \s’±N
975       \s±’NSet/increase/decrease the point  size  to/by  N  scaled  points.
976              Same as ps request.
977       \S’NSlant output by N degrees.
978       \t     Non-interpreted horizontal tab.
979       \u     Reverse (up) 1/2 em vertical motion (1/2 line in nroff).
980       \v’NLocal vertical motion; move down N (up if negative).
981       \Ve    The  contents  of  the  environment  variable with one-character
982              name e.
983       \V(ev  The contents of the environment variable with two-character name
984              ev.
985       \V[env]
986              The  contents  of the environment variable with arbitrarily long
987              name env.
988       \w’string
989              The width of the glyph sequence string.
990       \x’NExtra line-space function (negative before, positive after).
991       \X’string
992              Output string as device control function.
993       \Yn    Output string variable or macro with one-character name n  unin‐
994              terpreted as device control function.
995       \Y(nm  Output string variable or macro with two-character name nm unin‐
996              terpreted as device control function.
997       \Y[name]
998              Output string variable or macro with arbitrarily long name  name
999              uninterpreted as device control function.
1000       \zc    Print c with zero width (without spacing).
1001       \Z’anything
1002              Print  anything  and  then  restore  the horizontal and vertical
1003              position; anything may not contain tabs or leaders.
1004
1005       The escape sequences \e, \., \", \$, \*, \a, \n, \t, \g,  and  \newline
1006       are interpreted in copy mode.
1007
1008       Escape sequences starting with \( or \[ do not represent single charac‐
1009       ter escape sequences, but introduce escape names with two or more char‐
1010       acters.
1011
1012       If  a  backslash  is followed by a character that does not constitute a
1013       defined escape sequence, the backslash  is  silently  ignored  and  the
1014       character maps to itself.
1015
1016   Special Characters
1017       [Note:  `Special Characters' is a misnomer; those entities are (output)
1018       glyphs, not (input) characters.]
1019
1020       Common special characters are predefined by  escape  sequences  of  the
1021       form  \(xy  with  characters x and y.  Some of these exist in the usual
1022       font while most of them are only available in the special font.   Below
1023       you  can find a selection of the most important glyphs; a complete list
1024       can be found in groff_char(7).
1025
1026              \(bu   Bullet sign
1027              \(co   Copyright
1028              \(ct   Cent
1029              \(dd   Double dagger
1030              \(de   Degree
1031              \(dg   Dagger
1032              \(rq   Printable double quote
1033              \(em   Em-dash
1034              \(hy   Hyphen
1035              \(rg   Registered sign
1036              \(rs   Printable backslash character
1037              \(sc   Section sign
1038              \(ul   Underline character
1039              \(==   Identical
1040              \(>=   Larger or equal
1041              \(<=   Less or equal
1042              \(!=   Not equal
1043              \(->   Right arrow
1044              \(<-   Left arrow
1045              \(+-   Plus-minus sign
1046
1047   Strings
1048       Strings are defined by the ds request and can be retrieved  by  the  \*
1049       escape sequence.
1050
1051       Strings  share  their  name  space  with macros.  So strings and macros
1052       without arguments are roughly equivalent; it  is  possible  to  call  a
1053       string  like  a  macro  and  vice-versa, but this often leads to unpre‐
1054       dictable results.  The following string is the only one  predefined  in
1055       groff.
1056
1057       \*[.T]    The  name of the current output device as specified by the -T
1058                 command line option.
1059

REGISTERS

1061       Registers are variables that store a value.  In groff,  most  registers
1062       store  numerical  values (see section NUMERICAL EXPRESSIONS above), but
1063       some can also hold a string value.
1064
1065       Each register is given a name.  Arbitrary registers can be defined  and
1066       set with the nr request.
1067
1068       The value stored in a register can be retrieved by the escape sequences
1069       introduced by \n.
1070
1071       Most useful are predefined registers.  In the  following  the  notation
1072       name  is  used  to  refer  to register name to make clear that we speak
1073       about registers.  Please keep in mind that the \n[] decoration  is  not
1074       part of the register name.
1075
1076   Read-only Registers
1077       The following registers have predefined values that should not be modi‐
1078       fied by the user (usually, registers starting  with  a  dot  are  read-
1079       only).   Mostly,  they  provide  information on the current settings or
1080       store results from request calls.
1081
1082       \n[$$]    The process ID of troff.
1083       \n[.$]    Number of arguments in the current macro or string.
1084       \n[.a]    Post-line extra line-space most recently utilized using \x.
1085       \n[.A]    Set to 1 in troff if option -A is used; always 1 in nroff.
1086       \n[.b]    The emboldening offset while .bd is active.
1087       \n[.br]   Within a macro, set to 1 if macro called  with  the  `normal'
1088                 control character, and to 0 otherwise.
1089       \n[.c]    Current input line number.
1090       \n[.C]    1 if compatibility mode is in effect, 0 otherwise.
1091       \n[.cdp]  The depth of the last glyph added to the current environment.
1092                 It is positive if the glyph extends below the baseline.
1093       \n[.ce]   The number of lines remaining to be centered, as set  by  the
1094                 ce request.
1095       \n[.cht]  The  height  of  the last glyph added to the current environ‐
1096                 ment.  It is positive if the glyph extends  above  the  base‐
1097                 line.
1098       \n[.color]
1099                 1 if colors are enabled, 0 otherwise.
1100       \n[.csk]  The  skew of the last glyph added to the current environment.
1101                 The skew of a glyph is how far to the right of the center  of
1102                 a  glyph  the  center  of an accent over that glyph should be
1103                 placed.
1104       \n[.d]    Current vertical place in current diversion; equal to  regis‐
1105                 ter nl.
1106       \n[.ev]   The  name  or  number of the current environment (string-val‐
1107                 ued).
1108       \n[.f]    Current font number.
1109       \n[.F]    The name of the current input file (string-valued).
1110       \n[.fam]  The current font family (string-valued).
1111       \n[.fn]   The current (internal) real font name (string-valued).
1112       \n[.fp]   The number of the next free font position.
1113       \n[.g]    Always 1 in GNU troff.  Macros should use it to test if  run‐
1114                 ning under groff.
1115       \n[.h]    Text base-line high-water mark on current page or diversion.
1116       \n[.H]    Available horizontal resolution in basic units.
1117       \n[.height]
1118                 The current font height as set with \H.
1119       \n[.hla]  The current hyphenation language as set by the hla request.
1120       \n[.hlc]  The  number  of  immediately preceding consecutive hyphenated
1121                 lines.
1122       \n[.hlm]  The maximum allowed number of consecutive  hyphenated  lines,
1123                 as set by the hlm request.
1124       \n[.hy]   The current hyphenation flags (as set by the hy request).
1125       \n[.hym]  The current hyphenation margin (as set by the hym request).
1126       \n[.hys]  The current hyphenation space (as set by the hys request).
1127       \n[.i]    Current indentation.
1128       \n[.in]   The indentation that applies to the current output line.
1129       \n[.int]  Positive if last output line contains \c.
1130       \n[.j]    The  current  adjustment  mode.  It can be stored and used to
1131                 set adjustment.  (n = 1, b = 1, l = 0, r = 5, c = 3).
1132       \n[.k]    The current horizontal output position (relative to the  cur‐
1133                 rent indentation).
1134       \n[.kern] 1 if pairwise kerning is enabled, 0 otherwise.
1135       \n[.l]    Current line length.
1136       \n[.L]    The current line spacing setting as set by .ls.
1137       \n[.lg]   The current ligature mode (as set by the lg request).
1138       \n[.linetabs]
1139                 The current line-tabs mode (as set by the linetabs request).
1140       \n[.ll]   The line length that applies to the current output line.
1141       \n[.lt]   The title length (as set by the lt request).
1142       \n[.m]    The current drawing color (string-valued).
1143       \n[.M]    The current background color (string-valued).
1144       \n[.n]    Length of text portion on previous output line.
1145       \n[.ne]   The  amount  of  space that was needed in the last ne request
1146                 that caused a trap to be sprung.  Useful in conjunction  with
1147                 register .trunc.
1148       \n[.ns]   1 if in no-space mode, 0 otherwise.
1149       \n[.o]    Current page offset.
1150       \n[.O]    The suppression nesting level (see \O).
1151       \n[.p]    Current page length.
1152       \n[.P]    1  if  the  current  page  is  being printed, 0 otherwise (as
1153                 determined by the -o command line option).
1154       \n[.pe]   1 during page ejection, 0 otherwise.
1155       \n[.pn]   The number of the next page: either the value  set  by  a  pn
1156                 request, or the number of the current page plus 1.
1157       \n[.ps]   The current point size in scaled points.
1158       \n[.psr]  The last-requested point size in scaled points.
1159       \n[.pvs]  The current post-vertical line spacing.
1160       \n[.R]    The  number  of unused number registers.  Always 10000 in GNU
1161                 troff.
1162       \n[.rj]   The number of lines to be right-justified as set  by  the  rj
1163                 request.
1164       \n[.s]    Current point size as a decimal fraction.
1165       \n[.slant]
1166                 The slant of the current font as set with \S.
1167       \n[.sr]   The last requested point size in points as a decimal fraction
1168                 (string-valued).
1169       \n[.ss]   The value of the parameters set by the first argument of  the
1170                 ss request.
1171       \n[.sss]  The value of the parameters set by the second argument of the
1172                 ss request.
1173       \n[.sty]  The current font style (string-valued).
1174       \n[.t]    Vertical distance to the next trap.
1175       \n[.T]    Set to 1 if option -T is used.
1176       \n[.tabs] A string representation of the current tab settings  suitable
1177                 for use as an argument to the ta request.
1178       \n[.trunc]
1179                 The  amount  of vertical space truncated by the most recently
1180                 sprung vertical position trap, or, if the trap was sprung  by
1181                 a ne request, minus the amount of vertical motion produced by
1182                 .ne.  Useful in conjunction with the register .ne.
1183       \n[.u]    Equal to 1 in fill mode and 0 in no-fill mode.
1184       \n[.U]    Equal to 1 in safer mode and 0 in unsafe mode.
1185       \n[.v]    Current vertical line spacing.
1186       \n[.V]    Available vertical resolution in basic units.
1187       \n[.vpt]  1 if vertical position traps are enabled, 0 otherwise.
1188       \n[.w]    Width of previous glyph.
1189       \n[.warn] The sum of the number codes of the  currently  enabled  warn‐
1190                 ings.
1191       \n[.x]    The major version number.
1192       \n[.y]    The minor version number.
1193       \n[.Y]    The revision number of groff.
1194       \n[.z]    Name of current diversion.
1195       \n[.zoom] Zoom  factor for current font (in multiples of 1/1000th; zero
1196                 if no magnification).
1197
1198   Writable Registers
1199       The following registers can be read and written by the user.  They have
1200       predefined  default values, but these can be modified for customizing a
1201       document.
1202
1203       \n[%]     Current page number.
1204       \n[c.]    Current input line number.
1205       \n[ct]    Character type (set by width function \w).
1206       \n[dl]    Maximal width of last completed diversion.
1207       \n[dn]    Height of last completed diversion.
1208       \n[dw]    Current day of week (1–7).
1209       \n[dy]    Current day of month (1–31).
1210       \n[hours] The number of hours past midnight.  Initialized at start-up.
1211       \n[hp]    Current horizontal position at input line.
1212       \n[llx]   Lower left x-coordinate (in  PostScript  units)  of  a  given
1213                 PostScript image (set by .psbb).
1214       \n[lly]   Lower  left  y-coordinate  (in  PostScript  units) of a given
1215                 PostScript image (set by .psbb).
1216       \n[ln]    Output line number.
1217       \n[lsn]   The number of leading spaces of an input line.
1218       \n[lss]   The horizontal space corresponding to the leading  spaces  of
1219                 an input line.
1220       \n[minutes]
1221                 The  number of minutes after the hour.  Initialized at start-
1222                 up.
1223       \n[mo]    Current month (1–12).
1224       \n[nl]    Vertical position of last printed text base-line.
1225       \n[opmaxx]
1226       \n[opmaxy]
1227       \n[opminx]
1228       \n[opminy]
1229                 These four registers mark the top left and bottom right  hand
1230                 corners  of a box which encompasses all written glyphs.  They
1231                 are reset to -1 by \O0 or \O1.
1232       \n[rsb]   Like register sb, but takes account of the heights and depths
1233                 of glyphs.
1234       \n[rst]   Like register st, but takes account of the heights and depths
1235                 of glyphs.
1236       \n[sb]    Depth of string below base line (generated by width  function
1237                 \w).
1238       \n[seconds]
1239                 The  number  of  seconds  after  the  minute.  Initialized at
1240                 start-up.
1241       \n[skw]   Right skip width from the center of the last glyph in the  \w
1242                 argument.
1243       \n[slimit]
1244                 If greater than 0, the maximum number of objects on the input
1245                 stack.  If ≤0 there is no limit, i.e., recursion can continue
1246                 until virtual memory is exhausted.
1247       \n[ssc]   The  amount  of  horizontal  space  (possibly  negative) that
1248                 should be added to the last glyph before a subscript  (gener‐
1249                 ated by width function \w).
1250       \n[st]    Height of string above base line (generated by width function
1251                 \w).
1252       \n[systat]
1253                 The return value of the system()  function  executed  by  the
1254                 last sy request.
1255       \n[urx]   Upper  right  x-coordinate  (in  PostScript units) of a given
1256                 PostScript image (set by .psbb).
1257       \n[ury]   Upper right y-coordinate (in PostScript  units)  of  a  given
1258                 PostScript image (set by .psbb).
1259       \n[year]  The current year (year 2000 compliant).
1260       \n[yr]    Current  year  minus  1900.   For Y2K compliance use register
1261                 year instead.
1262

COMPATIBILITY

1264       The differences of the groff language in comparison to classical  troff
1265       as defined by [CSTR #54] are documented in groff_diff(7).
1266
1267       The  groff system provides a compatibility mode, see groff(1) on how to
1268       invoke this.
1269

BUGS

1271       Report bugs to the groff bug mailing list ⟨bug-groff@gnu.org⟩.  Include
1272       a complete, self-contained example that will allow the bug to be repro‐
1273       duced, and say which version of groff you are using.
1274

AUTHORS

1276       Copyright (C) 2000–2010, 2012 Free Software Foundation, Inc.
1277
1278       This document is distributed under the terms of the FDL (GNU Free Docu‐
1279       mentation  License)  version  1.3 or later.  You should have received a
1280       copy of the FDL on your system, it is also available on-line at the GNU
1281       copyleft site ⟨http://www.gnu.org/copyleft/fdl.html⟩.
1282
1283       This  document  is  part  of  groff, the GNU roff distribution.  It was
1284       written by Bernd Warken  ⟨groff-bernd.warken-72@web.de⟩;  it  is  main‐
1285       tained by Werner Lemberg ⟨wl@gnu.org⟩.
1286

SEE ALSO

1288       The  main  source  of  information  for the groff language is the groff
1289       info(1) file.  Besides the gory details, it contains many examples.
1290
1291       groff(1)
1292              the usage of the groff program and pointers to the documentation
1293              and availability of the groff system.
1294
1295       groff_diff(7)
1296              the  differences  of the groff language as compared to classical
1297              roff.  This is the authoritative  document  for  the  predefined
1298              language elements that are specific to groff.
1299
1300       groff_char(7)
1301              the predefined groff special characters (glyphs).
1302
1303       groff_font(5)
1304              the specification of fonts and the DESC file.
1305
1306       roff(7)
1307              the  history  of  roff, the common parts shared by all roff sys‐
1308              tems, and pointers to further documentation.
1309
1310       [CSTR #54]
1311              Nroff/Troff  User's  Manual  by  Ossanna  &  Kernighan  ⟨http://
1312              cm.bell-labs.com/cm/cs/cstr/54.ps.gz⟩  — the bible for classical
1313              troff.
1314
1315
1316
1317Groff Version 1.22.2            7 February 2013                       GROFF(7)
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