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

GROFF ELEMENTS

74       The  roff  language elements add formatting information to a text file.
75       The fundamental elements are predefined  commands  and  variables  that
76       make roff a full-blown programming language.
77
78       There  are  two  kinds  of roff commands, possibly with arguments.  Re‐
79       quests are written on a line of their own starting with a dot ‘.’  or a
80'”, whereas Escape sequences are in-line functions and in-word format‐
81       ting elements starting with a backslash ‘\’.
82
83       The user can define her own formatting commands using the  de  request.
84       These  commands  are  called macros, but they are used exactly like re‐
85       quests.  Macro packages are pre-defined sets of macros written  in  the
86       groff language.  A user's possibilities to create escape sequences her‐
87       self is very limited, only special characters can be mapped.
88
89       The groff language provides several kinds of variables  with  different
90       interfaces.   There  are pre-defined variables, but the user can define
91       her own variables as well.
92
93       String variables store character sequences.  They are set with  the  ds
94       request  and  retrieved  by  the \* escape sequences.  Strings can have
95       variables.
96
97       Register variables can store numerical values,  numbers  with  a  scale
98       unit,  and  occasionally string-like objects.  They are set with the nr
99       request and retrieved by the \n escape sequences.
100
101       Environments allow the user to temporarily store global formatting  pa‐
102       rameters  like  line  length, font size, etc. for later reuse.  This is
103       done by the ev request.
104
105       Fonts are identified either by a name or by an  internal  number.   The
106       current font is chosen by the ft request or by the \f escape sequences.
107       Each device has special fonts, but the following  fonts  are  available
108       for all devices.  R is the standard font Roman.  B is its bold counter‐
109       part.  The italic font is called I and is available everywhere, but  on
110       text  devices  it  is  displayed  as an underlined Roman font.  For the
111       graphical output devices, there exist constant-width pendants of  these
112       fonts,  CR,  CI,  and  CB.  On text devices, all glyphs have a constant
113       width anyway.
114
115       Glyphs are visual representation forms of characters.   In  groff,  the
116       distinction  between  those  two  elements is not always obvious (and a
117       full discussion is beyond the scope of this man page).  A first approx‐
118       imation  is  that  glyphs have a specific size and colour and are taken
119       from a specific font; they can't be modified any more – characters  are
120       the  input,  and  glyphs are the output.  As soon as an output line has
121       been generated, it no longer contains characters but glyphs.   In  this
122       man page, we use either ‘glyph’ or ‘character’, whatever is more appro‐
123       priate.
124
125       Moreover, there are some advanced roff elements.   A  diversion  stores
126       (formatted)   information   into   a   macro   for  later  usage.   See
127       groff_tmac(5) for more details.  A trap is a positional condition  like
128       a certain number of lines from page top or in a diversion or in the in‐
129       put.  Some action can be prescribed to be run  automatically  when  the
130       condition is met.
131
132       More  detailed  information and examples can be found in the groff Tex‐
133       info manual.
134

CONTROL CHARACTERS

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

NUMERICAL EXPRESSIONS

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

CONDITIONS

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

REQUESTS

285       This  section  provides  a short reference for the predefined requests.
286       In groff, request, macro, and string names can be arbitrarily long.  No
287       bracketing or marking of long names is needed.
288
289       Most  requests take one or more arguments.  The arguments are separated
290       by space characters (no tabs!); there is no inherent  limit  for  their
291       length or number.
292
293       Some  requests have optional arguments with a different behaviour.  Not
294       all of these details are outlined here.  Refer  to  the  groff  Texinfo
295       manual and groff_diff(7) for all details.
296
297       In  the following request specifications, most argument names were cho‐
298       sen to be descriptive.  Only the following denotations need  clarifica‐
299       tion.
300
301              c         denotes a single character.
302              font      a  font either specified as a font name or a font num‐
303                        ber.
304              anything  all characters up to the end of the line or within  \{
305                        and \}.
306              n         is a numerical expression that evaluates to an integer
307                        value.
308              N         is an arbitrary numerical expression,  signed  or  un‐
309                        signed.
310              ±N        has  three  meanings  depending on its sign, described
311                        below.
312
313       If an expression defined as ±N starts with a  ‘+’  sign  the  resulting
314       value  of the expression is added to an already existing value inherent
315       to the related request, e.g. adding to a number register.  If  the  ex‐
316       pression  starts  with  a ‘-’ the value of the expression is subtracted
317       from the request value.
318
319       Without a sign, N replaces the existing value directly.   To  assign  a
320       negative  number  either  prepend  0  or enclose the negative number in
321       parentheses.
322
323   Request Short Reference
324       .         Empty line, ignored.  Useful for structuring documents.
325       .\" anything
326                 Complete line is a comment.
327       .ab string
328                 Print string on standard error, exit program.
329       .ad       Begin line adjustment for  output  lines  in  current  adjust
330                 mode.
331       .ad c     Start line adjustment in mode c (c=l,r,c,b,n).
332       .af register c
333                 Assign format c to register (c=l,i,I,a,A).
334       .aln alias register
335                 Create alias name for register.
336       .als alias object
337                 Create  alias  name  for request, string, macro, or diversion
338                 object.
339       .am macro Append to macro until .. is encountered.
340       .am macro end
341                 Append to macro until .end is called.
342       .am1 macro
343                 Same as .am but with compatibility mode switched  off  during
344                 macro expansion.
345       .am1 macro end
346                 Same  as  .am but with compatibility mode switched off during
347                 macro expansion.
348       .ami macro
349                 Append to a macro whose name is contained in the string  reg‐
350                 ister macro until .. is encountered.
351       .ami macro end
352                 Append  to a macro indirectly.  macro and end are string reg‐
353                 isters whose contents are interpolated for the macro name and
354                 the end macro, respectively.
355       .ami1 macro
356                 Same  as .ami but with compatibility mode switched off during
357                 macro expansion.
358       .ami1 macro end
359                 Same as .ami but with compatibility mode switched off  during
360                 macro expansion.
361       .as stringvar anything
362                 Append anything to stringvar.
363       .as1 stringvar anything
364                 Same  as  .as but with compatibility mode switched off during
365                 string expansion.
366       .asciify diversion
367                 Unformat ASCII characters, spaces, and some escape  sequences
368                 in diversion.
369       .backtrace
370                 Print a backtrace of the input on stderr.
371       .bd font N
372                 Embolden font by N-1 units.
373       .bd S font N
374                 Embolden Special Font S when current font is font.
375       .blm      Unset the blank line macro.
376       .blm macro
377                 Set the blank line macro to macro.
378       .box      End current diversion.
379       .box macro
380                 Divert to macro, omitting a partially filled line.
381       .boxa     End current diversion.
382       .boxa macro
383                 Divert and append to macro, omitting a partially filled line.
384       .bp       Eject current page and begin new page.
385       .bp ±N    Eject current page; next page number ±N.
386       .br       Line break.
387       .brp      Break output line; adjust if applicable.
388       .break    Break out of a while loop.
389       .c2       Reset no-break control character to “'”.
390       .c2 c     Set no-break control character to c.
391       .cc       Reset control character to ‘.’.
392       .cc c     Set control character to c.
393       .ce       Center the next input line.
394       .ce N     Center following N input lines.
395       .cf filename
396                 Copy  contents  of  file filename unprocessed to stdout or to
397                 the diversion.
398       .cflags mode c1 c2 ...
399                 Treat characters c1, c2, ... according to mode number.
400       .ch trap N
401                 Change trap location to N.
402       .char c anything
403                 Define entity c as string anything.
404       .chop object
405                 Chop the last character off macro, string, or  diversion  ob‐
406                 ject.
407       .class name c1 c2 ...
408                 Assign  a set of characters, character ranges, or classes c1,
409                 c2, ... to name.
410       .close stream
411                 Close the stream.
412       .color    Enable colors.
413       .color N  If N is zero disable colors, otherwise enable them.
414       .composite from to
415                 Map glyph name from to glyph name  to  while  constructing  a
416                 composite glyph name.
417       .continue Finish the current iteration of a while loop.
418       .cp       Enable compatibility mode.
419       .cp N     If N is zero disable compatibility mode, otherwise enable it.
420       .cs font N M
421                 Set  constant  character width mode for font to N/36 ems with
422                 em M.
423       .cu N     Continuous underline in nroff, like .ul in troff.
424       .da       End current diversion.
425       .da macro Divert and append to macro.
426       .de macro Define or redefine macro until .. is encountered.
427       .de macro end
428                 Define or redefine macro until .end is called.
429       .de1 macro
430                 Same as .de but with compatibility mode switched  off  during
431                 macro expansion.
432       .de1 macro end
433                 Same  as  .de but with compatibility mode switched off during
434                 macro expansion.
435       .defcolor color scheme component
436                 Define or redefine a color with name color.   scheme  can  be
437                 rgb,  cym, cymk, gray, or grey.  component can be single com‐
438                 ponents specified as fractions in the range 0 to  1  (default
439                 scaling  indicator  f),  as a string of two-digit hexadecimal
440                 color components with a leading #, or as a  string  of  four-
441                 digit  hexadecimal  components with two leading #.  The color
442                 default can't be redefined.
443       .dei macro
444                 Define or redefine a macro whose name  is  contained  in  the
445                 string register macro until .. is encountered.
446       .dei macro end
447                 Define  or  redefine  a  macro indirectly.  macro and end are
448                 string registers whose  contents  are  interpolated  for  the
449                 macro name and the end macro, respectively.
450       .dei1 macro
451                 Same  as .dei but with compatibility mode switched off during
452                 macro expansion.
453       .dei1 macro end
454                 Same as .dei but with compatibility mode switched off  during
455                 macro expansion.
456       .device anything
457                 Write anything to the intermediate output as a device control
458                 function.
459       .devicem name
460                 Write contents of macro or string name uninterpreted  to  the
461                 intermediate output as a device control function.
462       .di       End current diversion.
463       .di macro Divert to macro.  See groff_tmac(5) for more details.
464       .do name  Interpret .name with compatibility mode disabled.
465       .ds stringvar anything
466                 Set stringvar to anything.
467       .ds1 stringvar anything
468                 Same  as  .ds but with compatibility mode switched off during
469                 string expansion.
470       .dt N trap
471                 Set diversion trap to position  N  (default  scaling  indica‐
472                 tor v).
473       .ec       Reset escape character to ‘\’.
474       .ec c     Set escape character to c.
475       .ecr      Restore escape character saved with .ecs.
476       .ecs      Save current escape character.
477       .el anything
478                 Else part for if-else (.ie) request.
479       .em macro The macro is run after the end of input.
480       .eo       Turn off escape character mechanism.
481       .ev       Switch to previous environment and pop it off the stack.
482       .ev env   Push  down  environment  number  or name env to the stack and
483                 switch to it.
484       .evc env  Copy the contents of environment env to the current  environ‐
485                 ment.  No pushing or popping.
486       .ex       Exit from roff processing.
487       .fam      Return to previous font family.
488       .fam name Set the current font family to name.
489       .fc       Disable field mechanism.
490       .fc a     Set field delimiter to a and pad glyph to space.
491       .fc a b   Set field delimiter to a and pad glyph to b.
492       .fchar c anything
493                 Define fallback character (or glyph) c as string anything.
494       .fcolor   Set fill color to previous fill color.
495       .fcolor c Set fill color to c.
496       .fi       Fill output lines.
497       .fl       Flush output buffer.
498       .fp n font
499                 Mount font on position n.
500       .fp n internal external
501                 Mount  font with long external name to short internal name on
502                 position n.
503       .fschar f c anything
504                 Define fallback character (or glyph) c for font f  as  string
505                 anything.
506       .fspecial font
507                 Reset list of special fonts for font to be empty.
508       .fspecial font s1 s2 ...
509                 When the current font is font, then the fonts s1, s2, ... are
510                 special.
511       .ft       Return to previous font.  Same as \ or \.
512       .ft font  Change to font name or number font; same as  \f[font]  escape
513                 sequence.
514       .ftr font1 font2
515                 Translate font1 to font2.
516       .fzoom font
517                 Don't magnify font.
518       .fzoom font zoom
519                 Set zoom factor for font (in multiples of 1/1000th).
520       .gcolor   Set glyph color to previous glyph color.
521       .gcolor c Set glyph color to c.
522       .hc       Remove additional hyphenation indicator character.
523       .hc c     Set up additional hyphenation indicator character c.
524       .hcode c1 code1 [c2 code2] ...
525                 Set the hyphenation code of character c1 to code1, that of c2
526                 to code2, etc.
527       .hla lang Set the current hyphenation language to lang.
528       .hlm n    Set the maximum number of consecutive hyphenated lines to n.
529       .hpf file Read hyphenation patterns from file.
530       .hpfa file
531                 Append hyphenation patterns from file.
532       .hpfcode a b c d ...
533                 Set input mapping for .hpf.
534       .hw words List of words with exceptional hyphenation.
535       .hy N     Switch to hyphenation mode N.
536       .hym n    Set the hyphenation margin  to  n  (default  scaling  indica‐
537                 tor m).
538       .hys n    Set the hyphenation space to n.
539       .ie cond anything
540                 If cond then anything else goto .el.
541       .if cond anything
542                 If cond then anything; otherwise do nothing.
543       .ig       Ignore text until .. is encountered.
544       .ig end   Ignore text until .end is called.
545       .in       Change to previous indentation value.
546       .in ±N    Change  indentation  according to ±N (default scaling indica‐
547                 tor m).
548       .it N trap
549                 Set an input-line count trap for the next N lines.
550       .itc N trap
551                 Same as .it but don't count lines interrupted with \c.
552       .kern     Enable pairwise kerning.
553       .kern n   If n is zero, disable pairwise kerning, otherwise enable it.
554       .lc       Remove leader repetition glyph.
555       .lc c     Set leader repetition glyph to c.
556       .length register anything
557                 Write the length of the string anything to register.
558       .linetabs Enable line-tabs mode (i.e., calculate tab positions relative
559                 to output line).
560       .linetabs n
561                 If n is zero, disable line-tabs mode, otherwise enable it.
562       .lf N     Set input line number to N.
563       .lf N file
564                 Set input line number to N and filename to file.
565       .lg N     Ligature mode on if N>0.
566       .ll       Change to previous line length.
567       .ll ±N    Set line length according to ±N (default length 6.5i, default
568                 scaling indicator m).
569       .lsm      Unset the leading spaces macro.
570       .lsm macro
571                 Set the leading spaces macro to macro.
572       .ls       Change to the previous value of additional intra-line skip.
573       .ls N     Set additional intra-line skip value to N,  i.e.,  N-1  blank
574                 lines are inserted after each text output line.
575       .lt ±N    Length of title (default scaling indicator m).
576       .mc       Margin glyph off.
577       .mc c     Print  glyph  c  after each text line at actual distance from
578                 right margin.
579       .mc c N   Set margin glyph to c and distance to  N  from  right  margin
580                 (default scaling indicator m).
581       .mk [register]
582                 Mark current vertical position in register, or in an internal
583                 register used by .rt if no argument.
584       .mso file The same as .so except that file is searched in the tmac  di‐
585                 rectories.
586       .na       No output-line adjusting.
587       .ne       Need a one-line vertical space.
588       .ne N     Need N vertical space (default scaling indicator v).
589       .nf       No filling or adjusting of output lines.
590       .nh       No hyphenation.
591       .nm       Number mode off.
592       .nm ±N [M [S [I]]]
593                 In  line  number mode, set number, multiple, spacing, and in‐
594                 dentation.
595       .nn       Do not number next line.
596       .nn N     Do not number next N lines.
597       .nop anything
598                 Always process anything.
599       .nr register ±N [M]
600                 Define or modify register using ±N with auto-increment M.
601       .nroff    Make the built-in conditions n true and t false.
602       .ns       Turn on no-space mode.
603       .nx       Immediately jump to end of current file.
604       .nx filename
605                 Immediately continue processing with file file.
606       .open stream filename
607                 Open filename for writing  and  associate  the  stream  named
608                 stream with it.
609       .opena stream filename
610                 Like .open but append to it.
611       .os       Output vertical distance that was saved by the sv request.
612       .output string
613                 Emit string directly to intermediate output, allowing leading
614                 whitespace if string starts with " (which is stripped off).
615       .pc       Reset page number character to ‘%’.
616       .pc c     Page number character.
617       .pev      Print the current environment and  each  defined  environment
618                 state to stderr.
619       .pi program
620                 Pipe output to program (nroff only).
621       .pl       Set  page  length to default 11i.  The current page length is
622                 stored in register .p.
623       .pl ±N    Change page length to ±N (default scaling indicator v).
624       .pm       Print macro names and sizes (number of blocks of 128 bytes).
625       .pm t     Print only total of sizes of  macros  (number  of  128  bytes
626                 blocks).
627       .pn ±N    Next page number N.
628       .pnr      Print  the names and contents of all currently defined number
629                 registers on stderr.
630       .po       Change to previous page offset.  The current page  offset  is
631                 available in register .o.
632       .po ±N    Page offset N.
633       .ps       Return to previous point size.
634       .ps ±N    Point size; same as \s[±N].
635       .psbb filename
636                 Get the bounding box of a PostScript image filename.
637       .pso command
638                 This behaves like the so request except that input comes from
639                 the standard output of command.
640       .ptr      Print the names and positions of all traps (not including in‐
641                 put line traps and diversion traps) on stderr.
642       .pvs      Change to previous post-vertical line spacing.
643       .pvs ±N   Change  post-vertical  line  spacing according to ±N (default
644                 scaling indicator p).
645       .rchar c1 c2 ...
646                 Remove the definitions of entities c1, c2, ...
647       .rd prompt
648                 Read insertion.
649       .return   Return from a macro.
650       .return anything
651                 Return twice, namely from the macro at the current level  and
652                 from the macro one level higher.
653       .rfschar f c1 c2 ...
654                 Remove the definitions of entities c1, c2, ... for font f.
655       .rj n     Right justify the next n input lines.
656       .rm name  Remove request, macro, diversion, or string name.
657       .rn old new
658                 Rename request, macro, diversion, or string old to new.
659       .rnn reg1 reg2
660                 Rename register reg1 to reg2.
661       .rr register
662                 Remove register.
663       .rs       Restore spacing; turn no-space mode off.
664       .rt       Return  (upward  only)  to vertical position marked by .mk on
665                 the current page.
666       .rt ±N    Return (upward only) to specified distance from  the  top  of
667                 the page (default scaling indicator v).
668       .schar c anything
669                 Define  global fallback character (or glyph) c as string any‐
670                 thing.
671       .shc      Reset soft hyphen glyph to \(hy.
672       .shc c    Set the soft hyphen glyph to c.
673       .shift n  In a macro, shift the arguments by n positions.
674       .sizes s1 s2 ... sn [0]
675                 Set available font sizes similar to the sizes  command  in  a
676                 DESC file.
677       .so filename
678                 Include source file.
679       .sp       Skip one line vertically.
680       .sp N     Space  vertical  distance N up or down according to sign of N
681                 (default scaling indicator v).
682       .special  Reset global list of special fonts to be empty.
683       .special s1 s2 ...
684                 Fonts s1, s2, etc. are special and are  searched  for  glyphs
685                 not in the current font.
686       .spreadwarn
687                 Toggle  the  spread  warning  on and off without changing its
688                 value.
689       .spreadwarn limit
690                 Emit a warning if each space in an output line is widened  by
691                 limit or more (default scaling indicator m).
692       .ss N     Set  space  glyph size to N/12 of the space width in the cur‐
693                 rent font.
694       .ss N M   Set space glyph size to N/12 and sentence space size  set  to
695                 M/12 of the space width in the current font.
696       .sty n style
697                 Associate style with font position n.
698       .substring xx n1 n2
699                 Replace the string named xx with the substring defined by the
700                 indices n1 and n2.
701       .sv       Save 1 v of vertical space.
702       .sv N     Save the vertical distance N for later output with os request
703                 (default scaling indicator v).
704       .sy command-line
705                 Execute program command-line.
706       .ta T N   Set  tabs  after  every position that is a multiple of N (de‐
707                 fault scaling indicator m).
708       .ta n1 n2 ... nn T r1 r2 ... rn
709                 Set tabs at positions n1, n2,  ...,  nn,  then  set  tabs  at
710                 nn+m×rn+r1  through nn+m×rn+rn, where m increments from 0, 1,
711                 2, ... to infinity.
712       .tc       Remove tab repetition glyph.
713       .tc c     Set tab repetition glyph to c.
714       .ti ±N    Temporary indent next line (default scaling indicator m).
715       .tkf font s1 n1 s2 n2
716                 Enable track kerning for font.
717       .tl ’leftcenterright
718                 Three-part title.
719       .tm anything
720                 Print anything on stderr.
721       .tm1 anything
722                 Print anything on stderr, allowing leading whitespace if any‐
723                 thing starts with " (which is stripped off).
724       .tmc anything
725                 Similar to .tm1 without emitting a final newline.
726       .tr abcd...
727                 Translate a to b, c to d, etc. on output.
728       .trf filename
729                 Transparently output the contents of file filename.
730       .trin abcd...
731                 This  is  the  same as the tr request except that the asciify
732                 request uses the character code (if any) before the character
733                 translation.
734       .trnt abcd...
735                 This  is  the same as the tr request except that the transla‐
736                 tions do not apply to text that is  transparently  throughput
737                 into a diversion with \!.
738       .troff    Make the built-in conditions t true and n false.
739       .uf font  Set underline font to font (to be switched to by .ul).
740       .ul N     Underline (italicize in troff) N input lines.
741       .unformat diversion
742                 Unformat  space  characters and tabs in diversion, preserving
743                 font information.
744       .vpt n    Enable vertical position traps if n is non-zero, disable them
745                 otherwise.
746       .vs       Change to previous vertical base line spacing.
747       .vs ±N    Set vertical base line spacing to ±N (default scaling indica‐
748                 tor p).
749       .warn n   Set warnings code to n.
750       .warnscale si
751                 Set scaling indicator used in warnings to si.
752       .wh N     Remove (first) trap at position N.
753       .wh N trap
754                 Set location trap; negative means from page bottom.
755       .while cond anything
756                 While condition cond is true, accept anything as input.
757       .write stream anything
758                 Write anything to the stream named stream.
759       .writec stream anything
760                 Similar to .write without emitting a final newline.
761       .writem stream xx
762                 Write contents of macro or string  xx  to  the  stream  named
763                 stream.
764
765       Besides  these  standard  groff  requests, there might be further macro
766       calls.  They can originate from a macro package  (see  roff(7)  for  an
767       overview) or from a preprocessor.
768
769       Preprocessor macros are easy to recognize.  They enclose their code be‐
770       tween a pair of characteristic macros.
771
772                  ┌─────────────┬─────────────────┬────────────────┐
773                  │preprocessor │   start macro   │    end macro   │
774                  ├─────────────┼─────────────────┼────────────────┤
775chem     .cstart     .cend      
776eqn      .EQ       .EN       
777grap     .G1       .G2       
778grn      .GS       .GE       
779ideal     .IS       .IE       
780                  │             │                 │      .IF       
781pic      .PS       .PE       
782refer     .R1       .R2       
783soelim    nonenone
784tbl      .TS       .TE       
785                  ├─────────────┼─────────────────┼────────────────┤
786glilypond   .lilypond start .lilypond stop 
787gperl     .Perl start   .Perl stop   
788gpinyin    .pinyin start  .pinyin stop  
789                  └─────────────┴─────────────────┴────────────────┘
790       Note that the ‘ideal’ preprocessor is not available in groff yet.
791

ESCAPE SEQUENCES

793       Escape sequences are in-line language elements usually introduced by  a
794       backslash  ‘\’  and  followed  by an escape name and sometimes by a re‐
795       quired argument.  Input processing is continued directly after the  es‐
796       caped  character  or  the  argument  (without an intervening separation
797       character).  So there must be a way to determine the end of the  escape
798       name and the end of the argument.
799
800       This  is  done by enclosing names (escape name and arguments consisting
801       of a variable name) by a pair of brackets [name] and constant arguments
802       (number  expressions  and  characters) by apostrophes (ASCII 0x27) like
803       constant.
804
805       There are abbreviations for short names.   Two-character  escape  names
806       can be specified by an opening parenthesis like \(xy or \*(xy without a
807       closing counterpart.  And all one-character names  different  from  the
808       special  characters ‘[’ and ‘(’ can even be specified without a marker,
809       for example \nc or \$c.
810
811       Constant arguments of length 1 can omit the  marker  apostrophes,  too,
812       but there is no two-character analogue.
813
814       While  one-character escape sequences are mainly used for in-line func‐
815       tions and system-related tasks, the two-letter names following  the  \(
816       construct  are  glyphs  predefined by the roff system; these are called
817       ‘Special Characters’ in the classical documentation.  Escapes sequences
818       of the form \[name] denote glyphs too.
819
820   Single-Character Escapes
821       \"     Start of a comment.  Everything up to the end of the line is ig‐
822              nored.
823       \#     Everything up to and including  the  next  newline  is  ignored.
824              This  is  interpreted in copy mode.  This is like \" except that
825              the terminating newline is ignored as well.
826       \*s    The string stored in  the  string  variable  with  one-character
827              name s.
828       \*(st  The string stored in the string variable with two-character name
829              st.
830       \*[string]
831              The string stored in the string variable with name string  (with
832              arbitrary length).
833       \*[stringvar arg1 arg2 ...]
834              The  string  stored in the string variable with arbitrarily long
835              name stringvar, taking arg1, arg2, ... as arguments.
836       \$0    The name by which the current macro was invoked.   The  als  re‐
837              quest can make a macro have more than one name.
838       \$x    Macro  or string argument with one-digit number x in the range 1
839              to 9.
840       \$(xy  Macro or string argument with two-digit number xy  (larger  than
841              zero).
842       \$[nexp]
843              Macro  or  string argument with number nexp, where nexp is a nu‐
844              merical expression evaluating to an integer ≥1.
845       \$*    In a macro or string, the concatenation  of  all  the  arguments
846              separated by spaces.
847       \$@    In  a  macro  or  string, the concatenation of all the arguments
848              with each surrounded by double quotes, and separated by spaces.
849       \$^    In a macro, the representation of all parameters as if they were
850              an argument to the ds request.
851       \\     reduces  to  a single backslash; useful to delay its interpreta‐
852              tion as escape character in copy mode.  For  a  printable  back‐
853              slash,  use \e, or even better \[rs], to be independent from the
854              current escape character.
855       The acute accent ´; same as \(aa.  Unescaped: apostrophe,  right
856              quotation mark, single quote (ASCII 0x27).
857       \`     The  grave accent `; same as \(ga.  Unescaped: left quote, back‐
858              quote (ASCII 0x60).
859       \-     The - (minus) sign in the current font.
860       \_     The same as \(ul, the underline character.
861       \.     The same as a dot (‘.’).  Necessary in nested macro  definitions
862              so that ‘\\..’ expands to ‘..’.
863       \%     Default optional hyphenation character.
864       \!     Transparent line indicator.
865       \?anything?
866              In a diversion, this transparently embeds anything in the diver‐
867              sion.  anything is read in copy mode.  See also the  escape  se‐
868              quences \!  and \?.
869       \space Unpaddable space size space glyph (no line break).
870       \0     Digit-width space.
871       \|     1/6 em narrow space glyph; zero width in nroff.
872       \^     1/12 em half-narrow space glyph; zero width in nroff.
873       \&     Non-printable, zero-width glyph.
874       \)     Like  \&  except  that it behaves like a glyph declared with the
875              cflags request to be transparent for the purposes of end-of-sen‐
876              tence recognition.
877       \/     Increases  the  width of the preceding glyph so that the spacing
878              between that glyph and the following glyph  is  correct  if  the
879              following glyph is a roman glyph.
880       \,     Modifies  the spacing of the following glyph so that the spacing
881              between that glyph and the preceding glyph  is  correct  if  the
882              preceding glyph is a roman glyph.
883       \~     Unbreakable  space that stretches like a normal inter-word space
884              when a line is adjusted.
885       \:     Inserts a zero-width break point (similar to \%  but  without  a
886              soft hyphen character).
887       \newline
888              Ignored newline, for continuation lines.
889       \{     Begin conditional input.
890       \}     End conditional input.
891       \(sc   A glyph with two-character name sc; see section “Special Charac‐
892              ters” below.
893       \[name]
894              A glyph with name name (of arbitrary length).
895       \[comp1 comp2 ...]
896              A composite glyph with components comp1, comp2, ...
897       \a     Non-interpreted leader character.
898       \A’anything
899              If anything is acceptable as a name of a string,  macro,  diver‐
900              sion,  register,  environment  or font it expands to 1, and to 0
901              otherwise.
902       \b’abc...
903              Bracket building function.
904       \B’anything
905              If anything is acceptable as a valid numeric expression  it  ex‐
906              pands to 1, and to 0 otherwise.
907       \c     Continue  output  line  at next input line.  Anything after this
908              escape on the same line is ignored except  \R  (which  works  as
909              usual).   Anything before \c on the same line is appended to the
910              current partial output line.  The next non-command line after  a
911              line interrupted with \c counts as a new input line.
912       \C’glyph
913              The  glyph  called  glyph;  same  as \[glyph], but compatible to
914              other roff versions.
915       \d     Forward (down) 1/2 em (1/2 line in nroff).
916       \D’charseq
917              Draw a graphical element defined by the characters  in  charseq;
918              see the groff Texinfo manual for details.
919       \e     Printable version of the current escape character.
920       \E     Equivalent  to  an  escape  character, but is not interpreted in
921              copy mode.
922       \fF    Change to font with one-character name or one-digit number F.
923       \fP    Switch back to previous font.
924       \f(fo  Change to font with two-character name or two-digit number fo.
925       \f[font]
926              Change to font with arbitrarily long name or  number  expression
927              font.
928       \f[]   Switch back to previous font.
929       \Ff    Change to font family with one-character name f.
930       \F(fm  Change to font family with two-character name fm.
931       \F[fam]
932              Change to font family with arbitrarily long name fam.
933       \F[]   Switch back to previous font family.
934       \gr    Return format of register with one-character name r suitable for
935              af request.
936       \g(rg  Return format of register with two-character  name  rg  suitable
937              for af request.
938       \g[reg]
939              Return  format  of register with arbitrarily long name reg suit‐
940              able for af request.
941       \h’NLocal horizontal motion; move right N (left if negative).
942       \H’NSet height of current font to N.
943       \kr    Mark horizontal input place in one-character register r.
944       \k(rg  Mark horizontal input place in two-character register rg.
945       \k[reg]
946              Mark horizontal input place in register  with  arbitrarily  long
947              name reg.
948       \l’NcHorizontal line drawing function (optionally using character c).
949       \L’NcVertical line drawing function (optionally using character c).
950       \mc    Change to color with one-character name c.
951       \m(cl  Change to color with two-character name cl.
952       \m[color]
953              Change to color with arbitrarily long name color.
954       \m[]   Switch back to previous color.
955       \Mc    Change filling color for closed drawn objects to color with one-
956              character name c.
957       \M(cl  Change filling color for closed drawn objects to color with two-
958              character name cl.
959       \M[color]
960              Change  filling color for closed drawn objects to color with ar‐
961              bitrarily long name color.
962       \M[]   Switch to previous fill color.
963       \nr    The numerical value stored in the  register  variable  with  the
964              one-character name r.
965       \n(re  The  numerical  value  stored  in the register variable with the
966              two-character name re.
967       \n[reg]
968              The numerical value stored in the register variable  with  arbi‐
969              trarily long name reg.
970       \N’nTypeset  the glyph with index n in the current font.  No special
971              fonts are searched.  Useful for adding  (named)  entities  to  a
972              document using the char request and friends.
973       \o’abc...
974              Overstrike glyphs a, b, c, etc.
975       \O0    Disable glyph output.  Mainly for internal use.
976       \O1    Enable glyph output.  Mainly for internal use.
977       \p     Break output line at next word boundary; adjust if applicable.
978       \r     Reverse 1 em vertical motion (reverse line in nroff).
979       \R’name ±n
980              The same as .nr name ±n.
981       \s±N   Set/increase/decrease the point size to/by N scaled points; N is
982              a one-digit number in the range 1 to 9.  Same as ps request.
983       \s(±N
984       \s±(N  Set/increase/decrease the point size to/by N scaled points; N is
985              a two-digit number ≥1.  Same as ps request.
986       \s[±N]
987       \s±[N]
988       \s’±N
989       \s±’NSet/increase/decrease  the  point  size  to/by  N scaled points.
990              Same as ps request.
991       \S’NSlant output by N degrees.
992       \t     Non-interpreted horizontal tab.
993       \u     Reverse (up) 1/2 em vertical motion (1/2 line in nroff).
994       \v’NLocal vertical motion; move down N (up if negative).
995       \Ve    The contents of  the  environment  variable  with  one-character
996              name e.
997       \V(ev  The contents of the environment variable with two-character name
998              ev.
999       \V[env]
1000              The contents of the environment variable with  arbitrarily  long
1001              name env.
1002       \w’string
1003              The width of the glyph sequence string.
1004       \x’NExtra line-space function (negative before, positive after).
1005       \X’string
1006              Output string as device control function.
1007       \Yn    Output  string variable or macro with one-character name n unin‐
1008              terpreted as device control function.
1009       \Y(nm  Output string variable or macro with two-character name nm unin‐
1010              terpreted as device control function.
1011       \Y[name]
1012              Output  string variable or macro with arbitrarily long name name
1013              uninterpreted as device control function.
1014       \zc    Print c with zero width (without spacing).
1015       \Z’anything
1016              Print anything and then restore the horizontal and vertical  po‐
1017              sition; anything may not contain tabs or leaders.
1018
1019       The  escape  sequences \e, \., \", \$, \*, \a, \n, \t, \g, and \newline
1020       are interpreted in copy mode.
1021
1022       Escape sequences starting with \( or \[ do not represent single charac‐
1023       ter escape sequences, but introduce escape names with two or more char‐
1024       acters.
1025
1026       If a backslash is followed by a character that does  not  constitute  a
1027       defined  escape  sequence,  the  backslash  is silently ignored and the
1028       character maps to itself.
1029
1030   Special Characters
1031       [Note: ‘Special Characters’ is a misnomer; those entities are  (output)
1032       glyphs, not (input) characters.]
1033
1034       Common  special  characters  are  predefined by escape sequences of the
1035       form \(xy with characters x and y.  In groff, it is  also  possible  to
1036       use the writing \[xy] as well.
1037
1038       Some  of these special characters exist in the usual font while most of
1039       them are only available in the special font.  Below you can see a small
1040       selection of the most important glyphs; a complete list can be found in
1041       groff_char(7).
1042
1043              \(Do   Dollar $
1044              \(Eu   Euro 
1045              \(Po   British pound sterling £
1046              \(aq   Apostrophe quote '
1047              \(bu   Bullet sign 
1048              \(co   Copyright ©
1049              \(cq   Single closing quote (right) 
1050              \(ct   Cent ¢
1051              \(dd   Double dagger 
1052              \(de   Degree °
1053              \(dg   Dagger 
1054              \(dq   Double quote (ASCII 34) "
1055              \(em   Em-dash 
1056              \(en   En-dash 
1057              \(hy   Hyphen 
1058              \(lq   Double quote left 
1059              \(oq   Single opening quote (left) 
1060              \(rg   Registered sign ®
1061              \(rq   Double quote right 
1062              \(rs   Printable backslash character \
1063              \(sc   Section sign §
1064              \(tm   Trademark symbol 
1065              \(ul   Underline character _
1066              \(==   Identical 
1067              \(>=   Larger or equal 
1068              \(<=   Less or equal 
1069              \(!=   Not equal 
1070              \(->   Right arrow 
1071              \(<-   Left arrow 
1072              \(+-   Plus-minus sign ±
1073
1074   Unicode Characters
1075       The extended escape u allows the inclusion  of  all  available  Unicode
1076       characters into a roff file.
1077
1078       \[uxxxx]
1079              u  is the escape name.  xxxx is a hexadecimal number of four hex
1080              digits, such as 0041 for the letter A, thus \[u0041].
1081
1082       \[uyyyyy]
1083              u is the escape name.  yyyyy is a hexadecimal number of five hex
1084              digits,  such  as 2FA1A for a Chinese-looking character from the
1085              Unicode block  CJK  Compatibility  Ideographs  Supplement,  thus
1086              \[u2FA1A].
1087
1088       The  hexadecimal  value  indicates the corresponding Unicode code point
1089       for a character.
1090
1091       \[uhex1_hex2]
1092       \[uhex1_hex2_hex3]
1093              hex1, hex2, and hex3 are all Unicode hexadecimal codes (4  or  5
1094              hex  digits)  that are used for overstriking, e.g. \[u0041_0301]
1095              is A acute, which can also be specified as Á; see groff_char(7).
1096
1097       The availability of the Unicode characters depends on  the  font  used.
1098       For  text mode, the device -Tutf8 is quite complete; for troff modes it
1099       might happen that some  or  many  characters  will  not  be  displayed.
1100       Please check your fonts.
1101
1102   Strings
1103       Strings  are  defined  by the ds request and can be retrieved by the \*
1104       escape sequence.
1105
1106       Strings share their name space with  macros.   So  strings  and  macros
1107       without  arguments  are  roughly  equivalent;  it is possible to call a
1108       string like a macro and vice versa, but  this  often  leads  to  unpre‐
1109       dictable  results.   The following string is the only one predefined in
1110       groff.
1111
1112       \*[.T]    The name of the current output device as specified by the  -T
1113                 command-line option.
1114

REGISTERS

1116       Registers  are  variables that store a value.  In groff, most registers
1117       store numerical values (see section “Numerical Expressions” above), but
1118       some can also hold a string value.
1119
1120       Each  register is given a name.  Arbitrary registers can be defined and
1121       set with the nr request.
1122
1123       The value stored in a register can be retrieved by the escape sequences
1124       introduced by \n.
1125
1126       Most  useful  are  predefined registers.  In the following the notation
1127       name is used to refer to register name to  make  clear  that  we  speak
1128       about  registers.   Please keep in mind that the \n[] decoration is not
1129       part of the register name.
1130
1131   Read-only Registers
1132       The following registers have predefined values that should not be modi‐
1133       fied  by  the  user  (usually,  registers starting with a dot are read-
1134       only).  Mostly, they provide information on  the  current  settings  or
1135       store results from request calls.
1136
1137       \n[$$]    The process ID of troff.
1138       \n[.$]    Number of arguments in the current macro or string.
1139       \n[.a]    Post-line extra line-space most recently utilized using \x.
1140       \n[.A]    Set to 1 in troff if option -A is used; always 1 in nroff.
1141       \n[.b]    The emboldening offset while .bd is active.
1142       \n[.br]   Within  a  macro,  set to 1 if macro called with the ‘normal’
1143                 control character, and to 0 otherwise.
1144       \n[.c]    Current input line number.
1145       \n[.C]    1 if compatibility mode is in effect, 0 otherwise.
1146       \n[.cdp]  The depth of the last glyph added to the current environment.
1147                 It is positive if the glyph extends below the baseline.
1148       \n[.ce]   The  number  of lines remaining to be centered, as set by the
1149                 ce request.
1150       \n[.cht]  The height of the last glyph added to  the  current  environ‐
1151                 ment.   It  is  positive if the glyph extends above the base‐
1152                 line.
1153       \n[.color]
1154                 1 if colors are enabled, 0 otherwise.
1155       \n[.csk]  The skew of the last glyph added to the current  environment.
1156                 The  skew of a glyph is how far to the right of the center of
1157                 a glyph the center of an accent over  that  glyph  should  be
1158                 placed.
1159       \n[.d]    Current  vertical place in current diversion; equal to regis‐
1160                 ter nl.
1161       \n[.ev]   The name or number of the  current  environment  (string-val‐
1162                 ued).
1163       \n[.f]    Current font number.
1164       \n[.F]    The name of the current input file (string-valued).
1165       \n[.fam]  The current font family (string-valued).
1166       \n[.fn]   The current (internal) real font name (string-valued).
1167       \n[.fp]   The number of the next free font position.
1168       \n[.g]    Always  1 in GNU troff.  Macros should use it to test if run‐
1169                 ning under groff.
1170       \n[.h]    Text base-line high-water mark on current page or diversion.
1171       \n[.H]    Number of basic units per horizontal unit  of  output  device
1172                 resolution.
1173       \n[.height]
1174                 The current font height as set with \H.
1175       \n[.hla]  The current hyphenation language as set by the hla request.
1176       \n[.hlc]  The  number  of  immediately preceding consecutive hyphenated
1177                 lines.
1178       \n[.hlm]  The maximum allowed number of consecutive  hyphenated  lines,
1179                 as set by the hlm request.
1180       \n[.hy]   The current hyphenation flags (as set by the hy request).
1181       \n[.hym]  The current hyphenation margin (as set by the hym request).
1182       \n[.hys]  The current hyphenation space (as set by the hys request).
1183       \n[.i]    Current indentation.
1184       \n[.in]   The indentation that applies to the current output line.
1185       \n[.int]  Positive if last output line contains \c.
1186       \n[.j]    The  current  adjustment  mode.  It can be stored and used to
1187                 set adjustment.  (n = 1, b = 1, l = 0, r = 5, c = 3).
1188       \n[.k]    The current horizontal output position (relative to the  cur‐
1189                 rent indentation).
1190       \n[.kern] 1 if pairwise kerning is enabled, 0 otherwise.
1191       \n[.l]    Current line length.
1192       \n[.L]    The current line spacing setting as set by .ls.
1193       \n[.lg]   The current ligature mode (as set by the lg request).
1194       \n[.linetabs]
1195                 The current line-tabs mode (as set by the linetabs request).
1196       \n[.ll]   The line length that applies to the current output line.
1197       \n[.lt]   The title length (as set by the lt request).
1198       \n[.m]    The current drawing color (string-valued).
1199       \n[.M]    The current background color (string-valued).
1200       \n[.n]    Length of text portion on previous output line.
1201       \n[.ne]   The  amount  of  space that was needed in the last ne request
1202                 that caused a trap to be sprung.  Useful in conjunction  with
1203                 register .trunc.
1204       \n[.ns]   1 if in no-space mode, 0 otherwise.
1205       \n[.o]    Current page offset.
1206       \n[.O]    The suppression nesting level (see \O).
1207       \n[.p]    Current page length.
1208       \n[.P]    1  if  the current page is being printed, 0 otherwise (as de‐
1209                 termined by the -o command-line option).
1210       \n[.pe]   1 during page ejection, 0 otherwise.
1211       \n[.pn]   The number of the next page: either the value set by a pn re‐
1212                 quest, or the number of the current page plus 1.
1213       \n[.ps]   The current point size in scaled points.
1214       \n[.psr]  The last-requested point size in scaled points.
1215       \n[.pvs]  The current post-vertical line spacing.
1216       \n[.R]    The  number  of unused number registers.  Always 10000 in GNU
1217                 troff.
1218       \n[.rj]   The number of lines to be right-justified as set  by  the  rj
1219                 request.
1220       \n[.s]    Current point size as a decimal fraction.
1221       \n[.slant]
1222                 The slant of the current font as set with \S.
1223       \n[.sr]   The last requested point size in points as a decimal fraction
1224                 (string-valued).
1225       \n[.ss]   The value of the parameters set by the first argument of  the
1226                 ss request.
1227       \n[.sss]  The value of the parameters set by the second argument of the
1228                 ss request.
1229       \n[.sty]  The current font style (string-valued).
1230       \n[.t]    Vertical distance to the next trap.
1231       \n[.T]    Set to 1 if option -T is used.
1232       \n[.tabs] A string representation of the current tab settings  suitable
1233                 for use as an argument to the ta request.
1234       \n[.trunc]
1235                 The  amount  of vertical space truncated by the most recently
1236                 sprung vertical position trap, or, if the trap was sprung  by
1237                 an  ne  request, minus the amount of vertical motion produced
1238                 by .ne.  Useful in conjunction with the register .ne.
1239       \n[.u]    Equal to 1 in fill mode and 0 in no-fill mode.
1240       \n[.U]    Equal to 1 in safer mode and 0 in unsafe mode.
1241       \n[.v]    Current vertical line spacing.
1242       \n[.V]    Number of basic units per vertical unit of output device res‐
1243                 olution.
1244       \n[.vpt]  1 if vertical position traps are enabled, 0 otherwise.
1245       \n[.w]    Width of previous glyph.
1246       \n[.warn] The  sum  of  the number codes of the currently enabled warn‐
1247                 ings.
1248       \n[.x]    The major version number.
1249       \n[.y]    The minor version number.
1250       \n[.Y]    The revision number of groff.
1251       \n[.z]    Name of current diversion.
1252       \n[.zoom] Zoom factor for current font (in multiples of 1/1000th;  zero
1253                 if no magnification).
1254
1255   Writable Registers
1256       The following registers can be read and written by the user.  They have
1257       predefined default values, but these can be modified for customizing  a
1258       document.
1259
1260       \n[%]     Current page number.
1261       \n[c.]    Current input line number.
1262       \n[ct]    Character type (set by width function \w).
1263       \n[dl]    Maximal width of last completed diversion.
1264       \n[dn]    Height of last completed diversion.
1265       \n[dw]    Current day of week (1–7).
1266       \n[dy]    Current day of month (1–31).
1267       \n[hours] The number of hours past midnight.  Initialized at start-up.
1268       \n[hp]    Current horizontal position at input line.
1269       \n[llx]   Lower  left  x-coordinate  (in  PostScript  units) of a given
1270                 PostScript image (set by .psbb).
1271       \n[lly]   Lower left y-coordinate (in  PostScript  units)  of  a  given
1272                 PostScript image (set by .psbb).
1273       \n[ln]    Output line number.
1274       \n[lsn]   The number of leading spaces of an input line.
1275       \n[lss]   The  horizontal  space corresponding to the leading spaces of
1276                 an input line.
1277       \n[minutes]
1278                 The number of minutes after the hour.  Initialized at  start-
1279                 up.
1280       \n[mo]    Current month (1–12).
1281       \n[nl]    Vertical position of last printed text base-line.
1282       \n[opmaxx]
1283       \n[opmaxy]
1284       \n[opminx]
1285       \n[opminy]
1286                 These  four registers mark the top left and bottom right hand
1287                 corners of a box which encompasses all written glyphs.   They
1288                 are reset to -1 by \O0 or \O1.
1289       \n[rsb]   Like register sb, but takes account of the heights and depths
1290                 of glyphs.
1291       \n[rst]   Like register st, but takes account of the heights and depths
1292                 of glyphs.
1293       \n[sb]    Depth  of string below base line (generated by width function
1294                 \w).
1295       \n[seconds]
1296                 The number of  seconds  after  the  minute.   Initialized  at
1297                 start-up.
1298       \n[skw]   Right  skip width from the center of the last glyph in the \w
1299                 argument.
1300       \n[slimit]
1301                 If greater than 0, the maximum number of objects on the input
1302                 stack.  If ≤0 there is no limit, i.e., recursion can continue
1303                 until virtual memory is exhausted.
1304       \n[ssc]   The amount  of  horizontal  space  (possibly  negative)  that
1305                 should  be added to the last glyph before a subscript (gener‐
1306                 ated by width function \w).
1307       \n[st]    Height of string above base line (generated by width function
1308                 \w).
1309       \n[systat]
1310                 The  return  value  of  the system() function executed by the
1311                 last sy request.
1312       \n[urx]   Upper right x-coordinate (in PostScript  units)  of  a  given
1313                 PostScript image (set by .psbb).
1314       \n[ury]   Upper  right  y-coordinate  (in  PostScript units) of a given
1315                 PostScript image (set by .psbb).
1316       \n[year]  The current year (year 2000 compliant).
1317       \n[yr]    Current year minus 1900.  For  Y2K  compliance  use  register
1318                 year instead.
1319

HYPHENATION

1321       The  .hy  request, given an integer argument, controls when hyphenation
1322       applies.  The default value is 1, which enables hyphenation almost  ev‐
1323       erywhere (see below).  Macro packages often override this default.
1324
1325       1      disables  hyphenation  only  after the first and before the last
1326              character of a word.
1327
1328       2      disables hyphenation only of the last word on a page or column.
1329
1330       4      disables hyphenation only before the last two  characters  of  a
1331              word.
1332
1333       8      disables  hyphenation  only  after the first two characters of a
1334              word.
1335
1336       16     enables hyphenation before the last character of a word.
1337
1338       32     enables hyphenation after the first character of a word.
1339
1340       The values are additive.  Some values cannot be used  together  because
1341       they contradict; for instance, 4 and 16; 8 and 32.
1342

UNDERLINING

1344       In  the  RUNOFF  language, the underlining was quite easy.  But in roff
1345       this is much more difficult.
1346
1347   Underlining with .ul
1348       There exists a groff request .ul (see above)  that  can  underline  the
1349       next  or further source lines in nroff, but in troff it produces only a
1350       font change into italic.  So this request is not really useful.
1351
1352   Underlining with .UL from ms
1353       In the ‘ms’ macro package in  tmac/s.tmac  groff_ms(7),  there  is  the
1354       macro .UL.  But this works only in troff, not in nroff.
1355
1356   Underlining macro definitions
1357       So  one can use the italic nroff idea from .ul and the troff definition
1358       in ms for writing a useful new macro, something like
1359              .de UNDERLINE
1360              . ie n \\$1\f[I]\\$2\f[P]\\$3
1361              . el \\$1\Z'\\$2'\v'.25m'\D'l \w'\\$2'u 0'\v'-.25m'\\$3
1362              ..
1363       If doclifter(1) makes trouble, change the  macro  name  UNDERLINE  into
1364       some  2-letter  word,  like  Ul.  Moreover change the font writing from
1365       \f[P] to \fP.
1366
1367   Underlining without macro definitions
1368       If one does not want to use macro  definitions,  e.g.,  when  doclifter
1369       gets lost, use the following:
1370              .ds u1 before
1371              .ds u2 in
1372              .ds u3 after
1373              .ie n \*[u1]\f[I]\*[u2]\f[P]\*[u3]
1374              .el \*[u1]\Z'\*[u2]'\v'.25m'\D'l \w'\*[u2]'u 0'\v'-.25m'\*[u3]
1375       Due  to doclifter, it might be necessary to change the variable writing
1376       \[xy] and \*[xy] into the strange ancient writing \*(xy and  \(xy,  and
1377       so on.
1378
1379       Then these lines could look like
1380              .ds u1 before
1381              .ds u2 in
1382              .ds u3 after
1383              .ie n \*[u1]\fI\*(u2\fP\*(u3
1384              .el \*(u1\Z'\*(u2'\v'.25m'\D'l \w'\*(u2'u 0'\v'-.25m'\*(u3
1385
1386       The result looks like
1387              before _i_n after
1388
1389   Underlining with Overstriking \z and \(ul
1390       There is another possibility for underlining by using overstriking with
1391       \zc (print c with zero width without spacing) and \(ul (underline char‐
1392       acter).   This  produces  the underlining of 1 character, both in nroff
1393       and in troff.
1394
1395       For example the underlining of a character say t looks like \z\[ul]t or
1396       \z\(ult
1397
1398       Longer  words  look  then  a bit strange, but a useful mode is to write
1399       each character into a whole own line.  To underlines  the  3  character
1400       part "tar" of the word "start":
1401              before s\
1402              \z\[ul]t\
1403              \z\[ul]a\
1404              \z\[ul]r\
1405              t after
1406       or
1407              before s\
1408              \z\(ult\
1409              \z\(ula\
1410              \z\(ulr\
1411              t after
1412
1413       The result looks like
1414              before s_t_a_rt after
1415

COMPATIBILITY

1417       The  differences  between the groff language and classical troff as de‐
1418       fined by [CSTR #54] are documented in groff_diff(7).
1419
1420       The groff system provides a compatibility mode, see groff(1) on how  to
1421       invoke this.
1422

AUTHORS

1424       This  document  was  written  by  Bernd  Warken ⟨groff-bernd.warken-72@
1425       web.de⟩.
1426

SEE ALSO

1428       Groff: The GNU Implementation of troff, by Trent A. Fisher  and  Werner
1429       Lemberg,  is the primary groff manual.  You can browse it interactively
1430       with “info groff”.  Besides the gory details, it  contains  many  exam‐
1431       ples.
1432
1433       groff(1)
1434              the usage of the groff program and pointers to the documentation
1435              and availability of the groff system.
1436
1437       groff_diff(7)
1438              describes the differences between the groff language and classi‐
1439              cal troff.
1440
1441              This  is  the authoritative document for the predefined language
1442              elements that are specific to groff.
1443
1444       groff_char(7)
1445              the predefined groff special characters (glyphs).
1446
1447       groff_font(5)
1448              the specification of fonts and the DESC file.
1449
1450       groff_tmac(5)
1451              contains an overview of available groff macro packages, instruc‐
1452              tions  on  how  to  interface  them with a document, guidance on
1453              writing macro packages and using diversions, and historical  in‐
1454              formation on macro package naming conventions.
1455
1456       roff(7)
1457              the  history  of  roff, the common parts shared by all roff sys‐
1458              tems, and pointers to further documentation.
1459
1460       [CSTR #54]
1461              Nroff/Troff  User's  Manual  by  Ossanna  &  Kernighan  ⟨http://
1462              cm.bell-labs.com/cm/cs/cstr/54.ps.gz⟩  — the bible for classical
1463              troff.
1464
1465       Wikipedia
1466              article     about     groffhttps://en.wikipedia.org/wiki/
1467              Groff_%28software%29⟩.
1468
1469       Tutorial about groff
1470              Manas  Laha  -  An Introduction to the GNU Groff Text Processing
1471              System ⟨dl.dropbox.com/u/4299293/grofftut.pdf⟩
1472
1473       troff.org
1474              This is a collection of internet sites with classical roff docu‐
1475              mentations and other information.
1476
1477
1478
1479groff 1.22.4                     21 July 2022                         GROFF(7)
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