GROFF(7)                                                              GROFF(7)



NAME
       groff - a short reference for the GNU roff language

DESCRIPTION
       The  name  groff  stands for GNU roff and is the free implementation of
       the roff type-setting system.  See roff(7) for a survey and  the  back-
       ground of the groff system.

       This document gives only short descriptions of the predefined roff lan-
       guage elements as used in groff.  Both the classical features  and  the
       groff extensions are provided.

       Historically,  the roff language was called troff.  groff is compatible
       with the classical system and provides proper extensions.  So  in  GNU,
       the  terms  roff,  troff, and groff language could be used as synonyms.
       However troff slightly tends to refer more to  the  classical  aspects,
       whereas  groff  emphasizes  the GNU extensions, and roff is the general
       term for the language.

       This file is only a short version of the complete documentation that is
       found  in the groff info(1) file, which contains more detailed, actual,
       and concise information.

       The general syntax for writing groff documents is relatively easy,  but
       writing extensions to the roff language can be a bit harder.

       The roff language is line-oriented.  There are only two kinds of lines,
       control lines and text lines.  The control lines start with  a  control
       character,  by  default  a period "."  or a single quote "'"; all other
       lines are text lines.

       Control lines represent commands, optionally with arguments.  They have
       the following syntax.  The leading control character can be followed by
       a command name; arguments, if any, are separated  by  blanks  from  the
       command name and among themselves, for example,

              .command_name arg1 arg2

       For  indentation, any number of space or tab characters can be inserted
       between the leading control character and the  command  name,  but  the
       control character must be on the first position of the line.

       Text lines represent the parts that will be printed.  They can be modi-
       fied by escape sequences, which are recognized by a  leading  backslash
       `\'.   These  are  in-line or even in-word formatting elements or func-
       tions.  Some of these take arguments separated by  single  quotes  "'",
       others  are regulated by a length encoding introduced by an open paren-
       thesis `(' or enclosed in brackets `[' and `]'.

       The roff language provides flexible instruments  for  writing  language
       extension,  such  as  macros.  When interpreting macro definitions, the
       roff system enters a special operating mode, called the copy mode.

       The copy mode behavior can be quite tricky, but there  are  some  rules
       that ensure a safe usage.

       1.     Printable  backslashes  must  be denoted as \e.  To be more pre-
              cise, \e represents the current  escape  character.   To  get  a
              backslash glyph, use \(rs or \[rs].

       2.     Double all backslashes.

       3.     Begin  all text lines with the special non-spacing character \&.

       This does not produce the most efficient code, but it should work as  a
       first  measure.   For  better  strategies,  see the groff info file and
       groff_tmac(5).

       Reading roff source files is easier, just reduce all double backslashes
       to a single one in all macro definitions.

GROFF ELEMENTS
       The  roff  language elements add formatting information to a text file.
       The fundamental elements are predefined  commands  and  variables  that
       make roff a full-blown programming language.

       There  are  two  kinds  of  roff  commands,  possibly  with  arguments.
       Requests are written on a line of their own starting with a dot `.'  or
       a  "'", whereas Escape sequences are in-line functions and in-word for-
       matting elements starting with a backslash `\'.

       The user can define her own formatting commands using the  de  request.
       These  commands  are  called  macros,  but  they  are used exactly like
       requests.  Macro packages are pre-defined sets of macros written in the
       groff language.  A user's possibilities to create escape sequences her-
       self is very limited, only special characters can be mapped.

       The groff language provides several kinds of variables  with  different
       interfaces.   There  are pre-defined variables, but the user can define
       her own variables as well.

       String variables store character sequences.  They are set with  the  ds
       request  and  retrieved  by  the \* escape sequences.  Strings can have
       variables.

       Register variables can store numerical values,  numbers  with  a  scale
       unit,  and  occasionally string-like objects.  They are set with the nr
       request and retrieved by the \n escape sequences.

       Environments allow the user  to  temporarily  store  global  formatting
       parameters  like line length, font size, etc. for later reuse.  This is
       done by the ev request.

       Fonts are identified either by a name or by an  internal  number.   The
       current font is chosen by the ft request or by the \f escape sequences.
       Each device has special fonts, but the following  fonts  are  available
       for all devices.  R is the standard font Roman.  B is its bold counter-
       part.  The italic font is called I and is available everywhere, but  on
       text  devices  it  is  displayed  as an underlined Roman font.  For the
       graphical output devices, there exist constant-width pendants of  these
       fonts, CR, CI, and CB.  On text devices, all characters have a constant
       width anyway.

       Moreover, there are some advanced roff elements.   A  diversion  stores
       information  into a macro for later usage.  A trap is a positional con-
       dition like a certain number of lines from page top or in  a  diversion
       or in the input.  Some action can be prescribed to be run automatically
       when the condition is met.

       More detailed information and examples can be found in the  groff  info
       file.

CONTROL CHARACTERS
       There is a small set of characters that have a special controlling task
       in certain conditions.

       .      A dot is only special at the beginning of a line  or  after  the
              condition  in  the  requests if, ie, el, and while.  There it is
              the control character that introduces a request (or macro).  The
              special  behavior  can  be  delayed by using the \.  escape.  By
              using the cc request, the control character can be set to a dif-
              ferent character, making the dot `.' a non-special character.

              In  all other positions, it just means a dot character.  In text
              paragraphs, it is advantageous to start each sentence at a  line
              of its own.

       '      The single quote has two controlling tasks.  At the beginning of
              a line and in the conditional requests it  is  the  non-breaking
              control character.  That means that it introduces a request like
              the dot, but with the  additional  property  that  this  request
              doesn't  cause  a  linebreak.  By using the c2 request, the non-
              break control character can be set to a different character.

              As a second task, it is the most commonly used argument  separa-
              tor in some functional escape sequences (but any pair of charac-
              ters not part of the argument will work).  In  all  other  posi-
              tions,  it  denotes  the  single  quote or apostrophe character.
              Groff provides a printable representation with the  \(cq  escape
              sequence.

       "      The  double  quote  is  used  to  enclose arguments in requests,
              macros, and strings.  In the ds and as requests, a leading  dou-
              ble  quote  in  the argument will be stripped off, making every-
              thing else afterwards the string to be defined (enabling leading
              whitespace).   The escaped double quote \" introduces a comment.
              Otherwise, it is not special.  Groff provides a printable repre-
              sentation with the \(dq escape sequence.

       \      The backslash usually introduces an escape sequence (this can be
              changed with the ec request).  A printed version of  the  escape
              character is the \e escape; a backslash glyph can be obtained by
              \(rs.

       (      The open parenthesis is only special in  escape  sequences  when
              introducing an escape name or argument consisting of exactly two
              characters.  In groff, this behavior can be replaced by  the  []
              construct.

       [      The  opening  bracket is only special in groff escape sequences;
              there it is used to introduce a long escape name or long  escape
              argument.  Otherwise, it is non-special, e.g. in macro calls.

       ]      The  closing  bracket is only special in groff escape sequences;
              there it terminates a long escape name or long escape  argument.
              Otherwise, it is non-special.

       space  Space  characters are only functional characters.  They separate
              the arguments in requests, macros, and strings, and the words in
              text lines.  They are subject to groff's horizontal spacing cal-
              culations.  To get a defined space width, escape sequences  like
              `\ ' (this is the escape character followed by a space), \|, \^,
              or \h should be used.

       newline
              In text paragraphs, newlines mostly behave  like  space  charac-
              ters.   Continuation  lines  can be specified by an escaped new-
              line, i.e., by specifying a backslash `\' as the last  character
              of a line.

       tab    If  a  tab  character occurs during text the interpreter makes a
              horizontal jump to the next pre-defined tab position.  There  is
              a sophisticated interface for handling tab positions.

NUMERICAL EXPRESSIONS
       A  numerical  value  is  a  signed or unsigned integer or float with or
       without an appended scaling indicator.  A scaling indicator is  a  one-
       character abbreviation for a unit of measurement.  A number followed by
       a scaling indicator signifies a size value.  By default, numerical val-
       ues do not have a scaling indicator, i.e., they are normal numbers.

       The roff language defines the following scaling indicators.

              c         Centimeter
              i         Inch
              P         Pica = 1/6 inch
              p         Point = 1/72 inch
              m         Em = the font size in points (width of letter `m')
              M         100th of an Em
              n         En = Em/2
              u         Basic unit for actual output device
              v         Vertical    line   space   in   basic   units   scaled
                        point = 1/sizescale of a point (defined in  font  DESC
                        file)
              f         Scale by 65536.

       Numerical  expressions are combinations of the numerical values defined
       above with the following  arithmetical  operators  already  defined  in
       classical troff.

              +         Addition
              -         Subtraction
              *         Multiplication
              /         Division
              %         Modulo
              =         Equals
              ==        Equals
              <         Less than
              >         Greater than
              <=        Less or equal
              >=        Greater or equal
              &         Logical and
              :         Logical or
              !         Logical not
              (         Grouping of expressions
              )         Close current grouping

       Moreover,  groff  added  the  following operators for numerical expres-
       sions:

              e1>?e2    The maximum of e1 and e2.
              e1<?e2    The minimum of e1 and e2.
              (c;e)     Evaluate e using c as the default scaling indicator.

       For details see the groff info file.

CONDITIONS
       Conditions occur in tests raised by the if, ie, and the while requests.
       The following table characterizes the different types of conditions.

              N         A  numerical  expression N yields true if its value is
                        greater than 0.
              !N        True if the value of I is 0.
              's1's2'   True if string s1 is identical to string s2.
              !'s1's2'  True if string s1 is not identical to string s2.
              cch       True if there is a character ch available.
              dname     True if  there  is  a  string,  macro,  diversion,  or
                        request called name.
              e         Current page number is even.
              o         Current page number is odd.
              mname     True if there is a color called name.
              n         Formatter is nroff.
              rreg      True if there is a register named reg.
              t         Formatter is troff.
              Ffont     True if there exists a font named font.
              Sstyle    True if a style named style has been registered.

REQUESTS
       This  section  provides  a short reference for the predefined requests.
       In groff, request and macro names can be arbitrarily long.  No bracket-
       ing or marking of long names is needed.

       Most  requests take one or more arguments.  The arguments are separated
       by space characters (no tabs!); there is no inherent  limit  for  their
       length  or  number.   An  argument  can be enclosed by a pair of double
       quotes.  This is very handy if an argument contains  space  characters,
       e.g., "arg with space" denotes a single argument.

       Some  requests have optional arguments with a different behaviour.  Not
       all of these details are outlined here.  Refer to the groff  info  file
       and groff_diff(7) for all details.

       In  the following request specifications, most argument names were cho-
       sen to be descriptive.  Only the following denotations need  clarifica-
       tion.

              c         denotes a single character.
              font      a  font either specified as a font name or a font num-
                        ber.
              anything  all characters up to the end of the line or within  \{
                        and \}.
              n         is a numerical expression that evaluates to an integer
                        value.
              N         is  an  arbitrary  numerical  expression,  signed   or
                        unsigned.
              +-N       has  three  meanings  depending on its sign, described
                        below.

       If an expression defined as +-N starts with a `+'  sign  the  resulting
       value  of  the  expression  will  be added to an already existing value
       inherent to the related request, e.g. adding to a number register.   If
       the  expression  starts  with a `-' the value of the expression will be
       subtracted from the request value.

       Without a sign, N replaces the existing value directly.   To  assign  a
       negative  number  either  prepend  0  or enclose the negative number in
       parentheses.

   Request Short Reference
       .         Empty line, ignored.  Useful for structuring documents.
       .\" anything
                 Complete line is a comment.
       .ab string
                 Print string on standard error, exit program.
       .ad       Begin line adjustment for  output  lines  in  current  adjust
                 mode.
       .ad c     Start line adjustment in mode c (c=l,r,b,n).
       .af register c
                 Assign format c to register (c=l,i,I,a,A).
       .aln alias register
                 Create alias name for register.
       .als alias object
                 Create  alias  name  for request, string, macro, or diversion
                 object.
       .am macro Append to macro until .. is encountered.
       .am macro end
                 Append to macro until .end is called.
       .am1 macro
                 Same as .am but with compatibility mode switched  off  during
                 macro expansion.
       .am1 macro end
                 Same  as  .am but with compatibility mode switched off during
                 macro expansion.
       .ami macro
                 Append to a macro whose name is contained in the string  reg-
                 ister macro until .. is encountered.
       .ami macro end
                 Append  to a macro indirectly.  macro and end are string reg-
                 isters whose contents are interpolated for the macro name and
                 the end macro, respectively.
       .ami1 macro
                 Same  as .ami but with compatibility mode switched off during
                 macro expansion.
       .ami1 macro end
                 Same as .ami but with compatibility mode switched off  during
                 macro expansion.
       .as stringvar anything
                 Append anything to stringvar.
       .as1 stringvar anything
                 Same  as  .as but with compatibility mode switched off during
                 string expansion.
       .asciify diversion
                 Unformat ASCII characters, spaces, and some escape  sequences
                 in diversion.
       .backtrace
                 Print a backtrace of the input on stderr.
       .bd font N
                 Embolden font by N-1 units.
       .bd S font N
                 Embolden Special Font S when current font is font.
       .blm      Unset the blank line macro.
       .blm macro
                 Set the blank line macro to macro.
       .box      End current diversion.
       .box macro
                 Divert to macro, omitting a partially filled line.
       .boxa     End current diversion.
       .boxa macro
                 Divert and append to macro, omitting a partially filled line.
       .bp       Eject current page and begin new page.
       .bp +-N   Eject current page; next page number +-N.
       .br       Line break.
       .brp      Break and spread output line.  Same as \p.
       .break    Break out of a while loop.
       .c2       Reset no-break control character to "'".
       .c2 c     Set no-break control character to c.
       .cc       Reset control character to `.'.
       .cc c     Set control character to c.
       .ce       Center the next input line.
       .ce N     Center following N input lines.
       .cf filename
                 Copy contents of file filename unprocessed to  stdout  or  to
                 the diversion.
       .cflags mode c1 c2 ...
                 Treat characters c1, c2, ... according to mode number.
       .ch trap N
                 Change trap location to N .
       .char c anything
                 Define character c as string anything.
       .chop object
                 Chop  the  last  character  off  macro,  string, or diversion
                 object.
       .close stream
                 Close the stream.
       .color    Enable colors.
       .color N  If N is zero disable colors, otherwise enable them.
       .composite from to
                 Map glyph name from to glyph name  to  while  constructing  a
                 composite glyph name.
       .continue Finish the current iteration of a while loop.
       .cp       Enable compatibility mode.
       .cp N     If N is zero disable compatibility mode, otherwise enable it.
       .cs font N M
                 Set constant character width mode for font to N/36  ems  with
                 em M.
       .cu N     Continuous underline in nroff, like .ul in troff.
       .da       End current diversion.
       .da macro Divert and append to macro.
       .de macro Define or redefine macro until .. is encountered.
       .de macro end
                 Define or redefine macro until .end is called.
       .de1 macro
                 Same  as  .de but with compatibility mode switched off during
                 macro expansion.
       .de1 macro end
                 Same as .de but with compatibility mode switched  off  during
                 macro expansion.
       .defcolor color scheme component
                 Define  or  redefine  a color with name color.  scheme can be
                 rgb, cym, cymk, gray, or grey.  component can be single  com-
                 ponents  specified  as fractions in the range 0 to 1 (default
                 scaling indicator f), as a string  of  two-digit  hexadecimal
                 color  components  with  a leading #, or as a string of four-
                 digit hexadecimal components with two leading #.   The  color
                 default can't be redefined.
       .dei macro
                 Define  or  redefine  a  macro whose name is contained in the
                 string register macro until .. is encountered.
       .dei macro end
                 Define or redefine a macro indirectly.   macro  and  end  are
                 string  registers  whose  contents  are  interpolated for the
                 macro name and the end macro, respectively.
       .dei1 macro
                 Same as .dei but with compatibility mode switched off  during
                 macro expansion.
       .dei1 macro end
                 Same  as .dei but with compatibility mode switched off during
                 macro expansion.
       .di       End current diversion.
       .di macro Divert to macro .
       .do name  Interpret .name with compatibility mode disabled.
       .ds stringvar anything
                 Set stringvar to anything.
       .ds1 stringvar anything
                 Same as .ds but with compatibility mode switched  off  during
                 string expansion.
       .dt N trap
                 Set  diversion  trap  to  position N (default scaling indica-
                 tor v).
       .ec       Reset escape character to `\'.
       .ec c     Set escape character to c.
       .ecr      Restore escape character saved with .ecs.
       .ecs      Save current escape character.
       .el anything
                 Else part for if-else (ie) request.
       .em macro The macro will be run after the end of input.
       .eo       Turn off escape character mechanism.
       .ev       Switch to previous environment.
       .ev env   Push down environment number or name env and switch to it.
       .evc env  Copy the contents of environment env to the current  environ-
                 ment.  No pushing or popping.
       .ex       Exit from roff processing.
       .fam      Return to previous font family.
       .fam name Set the current font family to name.
       .fc       Disable field mechanism.
       .fc a     Set field delimiter to a and pad character to space.
       .fc a b   Set field delimiter to a and pad character to b.
       .fchar c anything
                 Define fallback character c as string anything.
       .fcolor   Set fill color to previous fill color.
       .fcolor c Set fill color to c.
       .fi       Fill output lines.
       .fl       Flush output buffer.
       .fp n font
                 Mount font on position n.
       .fp n internal external
                 Mount  font with long external name to short internal name on
                 position n.
       .fschar f c anything
                 Define fallback character c for font f as string anything.
       .fspecial font
                 Reset list of special fonts for font to be empty.
       .fspecial font s1 s2 ...
                 When the current font is font, then the  fonts  s1,  s2,  ...
                 will be special.
       .ft       Return to previous font.  Same as \f[] or \fP.
       .ft font  Change  to  font name or number font; same as \f[font] escape
                 sequence.
       .ftr font1 font2
                 Translate font1 to font2.
       .gcolor   Set glyph color to previous glyph color.
       .gcolor c Set glyph color to c.
       .hc       Remove additional hyphenation indicator character.
       .hc c     Set up additional hyphenation indicator character c.
       .hcode c1 code1 c2 code2 ...
                 Set the hyphenation code of character c1 to code1, that of c2
                 to code2, etc.
       .hla lang Set the current hyphenation language to lang.
       .hlm n    Set  the maximum number of consecutive hyphenated lines to n.
       .hpf file Read hyphenation patterns from file.
       .hpfa file
                 Append hyphenation patterns from file.
       .hpfcode file
                 Set input mapping for .hpf.
       .hw words List of words with exceptional hyphenation.
       .hy N     Switch to hyphenation mode N.
       .hym n    Set the hyphenation margin  to  n  (default  scaling  indica-
                 tor m).
       .hys n    Set the hyphenation space to n.
       .ie cond anything
                 If cond then anything else goto .el.
       .if cond anything
                 If cond then anything; otherwise do nothing.
       .ig       Ignore text until .. is encountered.
       .ig end   Ignore text until .end.
       .in       Change to previous indent value.
       .in +-N   Change indent according to +-N (default scaling indicator m).
       .it N trap
                 Set an input-line count trap for the next N lines.
       .itc N trap
                 Same as .it but count lines interrupted with \c as one  line.
       .kern     Enable pairwise kerning.
       .kern n   If  n is zero, disable pairwise kerning, otherwise enable it.
       .lc       Remove leader repetition character.
       .lc c     Set leader repetition character to c.
       .length register anything
                 Write the length of the string anything in register.
       .linetabs Enable line-tabs mode (i.e., calculate tab positions relative
                 to output line).
       .linetabs n
                 If n is zero, disable line-tabs mode, otherwise enable it.
       .lf N     Set input line number to N.
       .lf N file
                 Set input line number to N and filename to file.
       .lg N     Ligature mode on if N>0.
       .ll       Change to previous line length.
       .ll +-N   Set  line length according to +-N (default size 6.5i, default
                 scaling indicator m).
       .ls       Change to the previous value of additional intra-line skip.
       .ls N     Set additional intra-line skip value to N,  i.e.,  N-1  blank
                 lines are inserted after each text output line.
       .lt +-N   Length of title (default scaling indicator m).
       .mc       Margin character off.
       .mc c     Print  character  c  after  each text line at actual distance
                 from right margin.
       .mc c N   Set margin character to c and distance to N from right margin
                 (default scaling indicator m).
       .mk register
                 Mark current vertical position in register.
       .mso file The  same  as the .so request except that file is searched in
                 the tmac directories.
       .na       No output-line adjusting.
       .ne       Need a one-line vertical space.
       .ne N     Need N vertical space (default scaling indicator v).
       .nf       No filling or adjusting of output-lines.
       .nh       No hyphenation.
       .nm       Number mode off.
       .nm +-N [M [S [I]]]
                 In line number  mode,  set  number,  multiple,  spacing,  and
                 indent.
       .nn       Do not number next line.
       .nn N     Do not number next N lines.
       .nop anything
                 Always execute anything.
       .nr register +-N M
                 Define or modify register using +-N with auto-increment M.
       .nroff    Make the built-in condition n true and t false.
       .ns       Turn no-space mode on.
       .nx       Immediately jump to end of current file.
       .nx filename
                 Next file.
       .open stream filename
                 Open  register  filename for writing and associate the stream
                 named register stream with it.
       .opena stream filename
                 Like .open but append to it.
       .os       Output vertical distance that was saved by the sv request.
       .output string
                 Emit string directly to intermediate output, allowing leading
                 whitespace  if  string  starts with " (which will be stripped
                 off).
       .pc       Reset page number character to `%'.
       .pc c     Page number character.
       .pi program
                 Pipe output to program (nroff only).
       .pl       Set page length to default 11i.  The current page  length  is
                 stored in register .p.
       .pl +-N   Change page length to +-N (default scaling indicator v).
       .pm       Print  macro names and sizes (number of blocks of 128 bytes).
       .pm t     Print only total of sizes of  macros  (number  of  128  bytes
                 blocks).
       .pn +-N   Next page number N.
       .pnr      Print  the names and contents of all currently defined number
                 registers on stderr.
       .po       Change to previous page offset.  The current page  offset  is
                 available in register .o.
       .po +-N   Page offset N.
       .ps       Return to previous point-size.
       .ps +-N   Point size; same as \s[+-N].
       .psbb filename
                 Get the bounding box of a PostScript image filename.
       .pso command
                 This behaves like the so request except that input comes from
                 the standard output of command.
       .ptr      Print the names and positions of  all  traps  (not  including
                 input line traps and diversion traps) on stderr.
       .pvs      Change to previous post-vertical line spacing.
       .pvs +-N  Change  post-vertical  line spacing according to +-N (default
                 scaling indicator p).
       .rchar c1 c2 ...
                 Remove the definitions of characters c1, c2, ...
       .rd prompt
                 Read insertion.
       .return   Return from a macro.
       .return anything
                 Return twice, namely from the macro at the current level  and
                 from the macro one level higher.
       .rfschar f c1 c2 ...
                 Remove  the definitions of characters c1, c2, ... for font f.
       .rj n     Right justify the next n input lines.
       .rm name  Remove request, macro, or string name.
       .rn old new
                 Rename request, macro, or string old to new.
       .rnn reg1 reg2
                 Rename register reg1 to reg2.
       .rr register
                 Remove register.
       .rs       Restore spacing; turn no-space mode off.
       .rt +-N   Return (upward only) to marked vertical place (default  scal-
                 ing indicator v).
       .schar c anything
                 Define global fallback character c as string anything.
       .shc      Reset soft hyphen character to \(hy.
       .shc c    Set the soft hyphen character to c.
       .shift n  In a macro, shift the arguments by n positions.
       .sizes s1 s2 ... sn [0]
                 Set  available  font  sizes similar to the sizes command in a
                 DESC file.
       .so filename
                 Include source file.
       .sp       Skip one line vertically.
       .sp N     Space vertical distance N up or down according to sign  of  N
                 (default scaling indicator v).
       .special  Reset global list of special fonts to be empty.
       .special s1 s2 ...
                 Fonts s1, s2, etc. are special and will be searched for char-
                 acters not in the current font.
       .spreadwarn
                 Toggle the spread warning on and  off  without  changing  its
                 value.
       .spreadwarn limit
                 Emit  a warning if each space in an output line is widened by
                 limit or more (default scaling indicator m).
       .ss N     Space-character size set to N/12 of  the  spacewidth  in  the
                 current font.
       .ss N M   Space-character  size set to N/12 and sentence space size set
                 to M/12 of the spacewidth in the current font (=1/3 em).
       .sty n style
                 Associate style with font position n.
       .substring xx n1 n2
                 Replace the string named xx with the substring defined by the
                 indices n1 and n2.
       .sv       Save 1v of vertical space.
       .sv N     Save  the  vertical  distance  N  for  later  output  with os
                 request.
       .sy command-line
                 Execute program command-line.
       .ta T N   Set tabs after  every  position  that  is  a  multiple  of  N
                 (default scaling indicator m).
       .ta n1 n2 ... nn T r1 r2 ... rn
                 Set  tabs  at  positions  n1,  n2,  ..., nn, then set tabs at
                 nn+r1, nn+r2, ..., nn+rn, then at  nn+rn+r1,  nn+rn+r2,  ...,
                 nn+rn+rn, and so on.
       .tc       Remove tab repition character.
       .tc c     Set tab repetition character to c.
       .ti +-N   Temporary indent next line (default scaling indicator m).
       .tkf font s1 n1 s2 n2
                 Enable track kerning for font.
       .tl 'left'center'right'
                 Three-part title.
       .tm anything
                 Print anything on terminal (UNIX standard message output).
       .tm1 anything
                 Print  anything  on  terminal (UNIX standard message output),
                 allowing leading whitespace if anything starts with "  (which
                 will be stripped off).
       .tmc anything
                 Similar to .tm1 without emitting a final newline.
       .tr abcd...
                 Translate a to b, c to d, etc. on output.
       .trf filename
                 Transparently output the contents of file filename.
       .trin abcd...
                 This  is  the  same as the tr request except that the asciify
                 request will use the character code (if any) before the char-
                 acter translation.
       .trnt abcd...
                 This  is  the same as the tr request except that the transla-
                 tions do not apply to text that is  transparently  throughput
                 into a diversion with \!.
       .troff    Make the built-in condition t true and n false.
       .uf font  Underline font set to font (to be switched to by .ul).
       .ul N     Underline (italicize in troff) N input lines.
       .unformat diversion
                 Unformat  space characters and tabs, preserving font informa-
                 tion in diversion.
       .vpt n    Enable vertical position traps if n is non-zero, disable them
                 otherwise.
       .vs       Change to previous vertical base line spacing.
       .vs +-N   Set  vertical  base  line  spacing  according to +-N (default
                 scaling indicator p).  Default value is 12p.
       .warn n   Set warnings code to n.
       .warnscale si
                 Set scaling indicator used in warnings to si.
       .wh N     Remove (first) trap at position N.
       .wh N trap
                 Set location trap; negative means from page bottom.
       .while cond anything
                 While condition cond is true, accept anything as input.
       .write stream anything
                 Write anything to the stream named stream.
       .writec stream anything
                 Similar to .write without emitting a final newline.
       .writem stream xx
                 Write contents of macro or string  xx  to  the  stream  named
                 stream.

       Besides  these  standard  groff  requests, there might be further macro
       calls.  They can originate from a macro package  (see  roff(7)  for  an
       overview) or from a preprocessor.

       Preprocessor macros are easy to be recognized.  They enclose their code
       into a pair of characteristic macros.


                      +-------------+-------------+------------+
                      |preprocessor | start macro |  end macro |
                      +-------------+-------------+------------+
                      |    eqn      |     .PS     |    .PE     |
                      |    grap     |     .G1     |    .G2     |
                      |    grn      |     .GS     |    .GE     |
                      |    pic      |     .PS     |    .PE     |
                      |   refer     |     .R1     |    .R2     |
                      |   soelim    |    none     |    none    |
                      |    tbl      |     .TS     |    .TE     |
                      +-------------+-------------+------------+

ESCAPE SEQUENCES
       Escape sequences are in-line language elements usually introduced by  a
       backslash  `\'  and  followed  by  an  escape  name  and sometimes by a
       required argument.  Input processing is continued  directly  after  the
       escaped  character or the argument resp. without an intervening separa-
       tion character.  So there must be a way to determine  the  end  of  the
       escape name and the end of the argument.

       This  is  done by enclosing names (escape name and arguments consisting
       of a variable name) by a pair of brackets [name] and constant arguments
       (number  expressions  and  characters) by apostrophes (ASCII 0x27) like
       'constant'.

       There are abbreviations for short names.  Two  character  escape  names
       can  be specified by an opening parenthesis like \(xy without a closing
       counterpart.  And all one-character names different  from  the  special
       characters  `['  and  `(' can even be specified without a marker in the
       form \c.

       Constant arguments of length 1 can omit the  marker  apostrophes,  too,
       but there is no two-character analogue.

       While  1-character  escape  sequences are mainly used for in-line func-
       tions and system related tasks, the 2-letter  names  following  the  \(
       construct  are  used for special characters predefined by the roff sys-
       tem.  Escapes sequences with names of more than two characters  \[name]
       denote user defined named characters (see the char request).

   Single Character Escapes
       \"     Beginning of a comment.  Everything up to the end of the line is
              ignored.
       \#     Everything up to and including  the  next  newline  is  ignored.
              This  is  interpreted in copy mode.  This is like \" except that
              the terminating newline is ignored as well.
       \*s    The string stored in the string variable with  1-character  name
              s.
       \*(st  The  string  stored in the string variable with 2-character name
              st.
       \*[stringvar arg1 arg2 ...]
              The string stored in the string variable with  arbitrary  length
              name stringvar, taking arg1, arg2, ... as arguments.
       \$0    The  name  by  which  the  current  macro  was invoked.  The als
              request can make a macro have more than one name.
       \$x    Macro or string argument with 1-place number x,  where  x  is  a
              digit between 1 and 9.
       \$(xy  Macro or string argument with 2-digit number xy.
       \$[nexp]
              Macro  or  string  argument  with  number  nexp, where nexp is a
              numerical expression evaluating to an integer >=1.
       \$*    In a macro or string, the concatenation  of  all  the  arguments
              separated by spaces.
       \$@    In  a  macro  or  string, the concatenation of all the arguments
              with each surrounded by double quotes, and separated by  spaces.
       \\     reduces  to  a single backslash; useful to delay its interpreta-
              tion as escape character in copy mode.  For  a  printable  back-
              slash,  use \e, or even better \[rs], to be independent from the
              current escape character.
       \'     The acute accent '; same as \(aa.  Unescaped: apostrophe,  right
              quotation mark, single quote (ASCII 0x27).
       \`     The  grave accent `; same as \(ga.  Unescaped: left quote, back-
              quote (ASCII 0x60).
       \-     The - sign in the current font.
       \.     An uninterpreted dot (period), even at start of line.
       \%     Default optional hyphenation character.
       \!     Transparent line indicator.
       \?anything?
              In a diversion, this will transparently embed  anything  in  the
              diversion.   anything is read in copy mode.  See also the escape
              sequences \!  and \?.
       \space Unpaddable space-size space character (no line break).
       \0     Digit width.
       \|     1/6 em narrow space character; zero width in nroff.
       \^     1/12 em half-narrow space character; zero width in nroff.
       \&     Non-printable, zero width character.
       \)     Like \& except that it behaves like a  character  declared  with
              the  cflags request to be transparent for the purposes of end of
              sentence recognition.
       \/     Increases the width of the preceding character so that the spac-
              ing  between  that character and the following character will be
              correct if the following character is a roman character.
       \,     Modifies the spacing of the  following  character  so  that  the
              spacing  between that character and the preceding character will
              correct if the preceding character is a roman character.
       \~     Unbreakable space that stretches like a normal inter-word  space
              when a line is adjusted.
       \:     Inserts  a  zero-width  break point (similar to \% but without a
              soft hyphen character).
       \newline
              Ignored newline, for continuation lines.
       \{     Begin conditional input.
       \}     End conditional input.
       \(sc   The special character with 2-character name sc, see section Spe-
              cial Characters.
       \[name]
              The named character (or rather glyph) with arbitrary length name
              name.
       \[comp1 comp2 ...]
              A composite glyph with components comp1, comp2, ...
       \a     Non-interpreted leader character.
       \A'anything'
              If anything is acceptable as a name of a string,  macro,  diver-
              sion,  register,  environment  or font it expands to 1, and to 0
              otherwise.
       \b'abc...'
              Bracket building function.
       \B'anything'
              If anything is acceptable  as  a  valid  numeric  expression  it
              expands to 1, and to 0 otherwise.
       \c     Interrupt text processing.
       \C'char'
              The  character  called  char; same as \[char], but compatible to
              other roff versions.
       \d     Forward (down) 1/2 em vertical unit (1/2 line in nroff).
       \D'charseq'
              Draw a graphical element defined by the characters  in  charseq;
              see groff info file for details.
       \e     Printable version of the current escape character.
       \E     Equivalent  to  an  escape  character, but is not interpreted in
              copy-mode.
       \fF    Change to font with 1-character name or 1-digit number F.
       \fP    Switch back to previous font.
       \f(fo  Change to font with 2-character name or 2-digit number fo.
       \f[font]
              Change to font with arbitrary length name or  number  expression
              font.
       \f[]   Switch back to previous font.
       \Ff    Change to font family with 1-character name f.
       \F(fm  Change to font family with 2-character name fm.
       \F[fam]
              Change to font family with arbitrary length name fam.
       \F[]   Switch back to previous font family.
       \g[reg]
              Return  format  of  register  with  name  reg  suitable for .af.
              Alternative forms \g(xy and \gx.
       \h'N'  Local horizontal motion; move right N (left if negative).
       \H'N'  Set height of current font to N.
       \k[reg]
              Mark horizontal input place in register  with  arbitrary  length
              name reg.  Alternative forms \k(xy and \kx.
       \l'Nc' Horizontal line drawing function (optionally using character c).
       \L'Nc' Vertical line drawing function (optionally using character c).
       \m[color]
              Change to color color.  Alternative forms \m(co and \mc.
       \m[]   Switch back to previous color.
       \M[color]
              Change filling color for closed drawn objects  to  color  color.
              Alternative forms \M(co and \Mc.
       \M[]   Switch to previous fill color.
       \nr    The  numerical  value  stored  in the register variable with the
              1-character name r.
       \n(re  The numerical value stored in the  register  variable  with  the
              2-character name re.
       \n[reg]
              The  numerical  value stored in the register variable with arbi-
              trary length name reg.
       \N'n'  Typeset the character with code n in the current font,  no  spe-
              cial fonts are searched.  Useful for adding characters to a font
              using the char request.
       \o'abc...'
              Overstrike characters a, b, c, etc.
       \O0    Disable glyph output.  Mainly for internal use.
       \O1    Enable glyph output.  Mainly for internal use.
       \p     Break and spread output line.
       \r     Reverse 1 em vertical motion (reverse line in nroff).
       \R'name +-n'
              The same as .nr name +-n.
       \s[+-N]
              Set the point size to N scaled  points.   Note  the  alternative
              forms  \s+-[N], \s'+-N', \s+-'N', \s(+-xy, \s+-(xy, \s+-x.  Same
              as ps request.
       \S'N'  Slant output N degrees.
       \t     Non-interpreted horizontal tab.
       \u     Reverse (up) 1/2 em vertical motion (1/2 line in nroff).
       \v'N'  Local vertical motion; move down N (up if negative).
       \V[env]
              The contents of the environment variable env.  Alternative forms
              \V(xy and \Vx.
       \w'string'
              The width of the character sequence string.
       \x'N'  Extra line-space function (negative before, positive after).
       \X'string'
              Output string as device control function.
       \Y[name]
              Output  string  variable  or  macro name uninterpreted as device
              control function.  Alternative forms \Y(xy and \Yx.
       \zc    Print c with zero width (without spacing).
       \Z'anything'
              Print anything and then  restore  the  horizontal  and  vertical
              position; anything may not contain tabs or leaders.

       The  escape  sequences \e, \., \", \$, \*, \a, \n, \t, \g, and \newline
       are interpreted in copy mode.

       Escape sequences starting with \( or \[ do not represent single charac-
       ter escape sequences, but introduce escape names with two or more char-
       acters.

       If a backslash is followed by a character that does  not  constitute  a
       defined escape sequence the backslash is silently ignored and the char-
       acter maps to itself.

   Special Characters
       Common special characters are predefined by  escape  sequences  of  the
       form  \(xy  with  characters x and y.  Some of these exist in the usual
       font while most of them are only available in the special font.   Below
       you'll  find  a selection of the most important glyphs; a complete list
       can be found in groff_char(7).

              \(bu   Bullet sign
              \(co   Copyright
              \(ct   Cent
              \(dd   Double dagger
              \(de   Degree
              \(dg   Dagger
              \(rs   Printable double quote
              \(em   Em-dash
              \(hy   Hyphen
              \(rg   Registered sign
              \(rs   Printable backslash character
              \(sc   Section sign
              \(ul   Underline character
              \(==   Identical
              \(>=   Larger or equal
              \(<=   Less or equal
              \(!=   Not equal
              \(->   Right arrow
              \(<-   Left arrow
              \(+-   Plus-minus sign

   Strings
       Strings are defined by the ds request and can be retrieved  by  the  \*
       escape sequence.

       Strings  share  their  name  space  with macros.  So strings and macros
       without arguments are roughly equivalent; it  is  possible  to  call  a
       string  like  a  macro  and  vice-versa, but this often leads to unpre-
       dictable results.  The following strings are predefined in groff.

       \*[.T]    The name of the current output device as specified by the  -T
                 command line option.

REGISTERS
       Registers  are  variables that store a value.  In groff, most registers
       store numerical values (see section NUMERICAL EXPRESSIONS  above),  but
       some can also hold a string value.

       Each  register is given a name.  Arbitrary registers can be defined and
       set with the request nr register.

       The value stored in a register can be retrieved by the escape sequences
       introduced by \n.

       Most  useful  are  predefined registers.  In the following the notation
       name is used to refer to a register called register name to make  clear
       that we speak about registers.  Please keep in mind that the \n[] deco-
       ration is not part of the register name.

   Read-only Registers
       The following registers have predefined values that should not be modi-
       fied  by the user (usually, registers starting with a dot a read-only).
       Mostly, they provide information  on  the  current  settings  or  store
       results from request calls.

       \n[.$]    Number of arguments in the current macro or string.
       \n[.a]    Post-line  extra  line-space  most  recently  utilized  using
                 \x'N'.
       \n[.A]    Set to 1 in troff if option -A is used; always 1 in nroff.
       \n[.c]    Current input line number.
       \n[.C]    1 if compatibility mode is in effect, 0 otherwise.
       \n[.cdp]  The depth of the last character added to the current environ-
                 ment.   It  is  positive  if  the character extends below the
                 baseline.
       \n[.ce]   The number of lines remaining to be centered, as set  by  the
                 ce request.
       \n[.cht]  The  height  of the last character added to the current envi-
                 ronment.  It is positive if the character extends  above  the
                 baseline.
       \n[.color]
                 1 if colors are enabled, 0 otherwise.
       \n[.csk]  The  skew of the last character added to the current environ-
                 ment.  The skew of a character is how far to the right of the
                 center of a character the center of an accent over that char-
                 acter should be placed.
       \n[.d]    Current vertical place in current diversion; equal to  regis-
                 ter nl.
       \n[.ev]   The  name  or  number of the current environment (string-val-
                 ued).
       \n[.f]    Current font number.
       \n[.fam]  The current font family (string-valued).
       \n[.fn]   The current (internal) real font name (string-valued).
       \n[.fp]   The number of the next free font position.
       \n[.g]    Always 1 in GNU troff.  Macros should use it to test if  run-
                 ning under groff.
       \n[.h]    Text  base-line high-water mark on current page or diversion.
       \n[.H]    Available horizontal resolution in basic units.
       \n[.height]
                 The current font height as set with \H.
       \n[.hla]  The current hyphenation language as set by the .hla  request.
       \n[.hlc]  The  number  of  immediately preceding consecutive hyphenated
                 lines.
       \n[.hlm]  The maximum allowed number of consecutive  hyphenated  lines,
                 as set by the hlm request.
       \n[.hy]   The current hyphenation flags (as set by the hy request).
       \n[.hym]  The current hyphenation margin (as set by the hym request).
       \n[.hys]  The current hyphenation space (as set by the hys request).
       \n[.i]    Current ident.
       \n[.in]   The indent that applies to the current output line.
       \n[.int]  Positive if last output line contains \c.
       \n[.kern] 1 if pairwise kerning is enabled, 0 otherwise.
       \n[.l]    Current line length.
       \n[.lg]   The current ligature mode (as set by the lg request).
       \n[.linetabs]
                 The  current line-tabs mode (as set by the linetabs request).
       \n[.ll]   The line length that applies to the current output line.
       \n[.lt]   The title length (as set by the lt request).
       \n[.m]    The current drawing color (string-valued).
       \n[.M]    The current background color (string-valued).
       \n[.n]    Length of text portion on previous output line.
       \n[.ne]   The amount of space that was needed in the  last  ne  request
                 that  caused a trap to be sprung.  Useful in conjunction with
                 register .trunc.
       \n[.ns]   1 if in no-space mode, 0 otherwise.
       \n[.o]    Current page offset.
       \n[.p]    Current page length.
       \n[.pe]   1 during page ejection, 0 otherwise.
       \n[.pn]   The number of the next page: either the value  set  by  a  pn
                 request, or the number of the current page plus 1.
       \n[.ps]   The current pointsize in scaled points.
       \n[.psr]  The last-requested pointsize in scaled points.
       \n[.pvs]  The current post-vertical line spacing.
       \n[.rj]   The  number  of  lines to be right-justified as set by the rj
                 request.
       \n[.s]    Current point size as a decimal fraction.
       \n[.slant]
                 The slant of the current font as set with \S.
       \n[.sr]   The last requested pointsize in points as a decimal  fraction
                 (string-valued).
       \n[.ss]   The  value of the parameters set by the first argument of the
                 ss request.
       \n[.sss]  The value of the parameters set by the second argument of the
                 ss request.
       \n[.sty]  The current font style (string-valued).
       \n[.t]    Distance to the next trap.
       \n[.T]    Set to 1 if option -T is used.
       \n[.tabs] A  string representation of the current tab settings suitable
                 for use as an argument to the ta request.
       \n[.trunc]
                 The amount of vertical space truncated by the  most  recently
                 sprung  vertical position trap, or, if the trap was sprung by
                 a ne request, minus the amount of vertical motion produced by
                 .ne.   In other words, at the point a trap is sprung, it rep-
                 resents the difference of what the  vertical  position  would
                 have  been  but  for the trap, and what the vertical position
                 actually is.  Useful in conjunction with the register .ne.
       \n[.u]    Equal to 1 in fill mode and 0 in nofill mode.
       \n[.U]    Equal to 1 in safer mode and 0 in unsafe mode.
       \n[.v]    Current vertical line spacing.
       \n[.V]    Available vertical resolution in basic units.
       \n[.vpt]  1  if vertical position traps are enabled, 0 otherwise.
       \n[.w]    Width of previous character.
       \n[.warn] The sum of the number codes of the  currently  enabled  warn-
                 ings.
       \n[.x]    The major version number.
       \n[.y]    The minor version number.
       \n[.Y]    The revision number of groff.
       \n[.z]    Name of current diversion.

   Writable Registers
       The following registers can be read and written by the user.  They have
       predefined default values, but these can be modified for customizing  a
       document.

       \n[%]     Current page number.
       \n[c.]    Current input line number.
       \n[ct]    Character type (set by width function \w).
       \n[dl]    Maximal width of last completed diversion.
       \n[dn]    Height of last completed diversion.
       \n[dw]    Current day of week (1-7).
       \n[dy]    Current day of month (1-31).
       \n[hours] The  number of hours past midnight.  Initialized at start-up.
       \n[hp]    Current horizontal position at input line.
       \n[llx]   Lower left x-coordinate (in  PostScript  units)  of  a  given
                 PostScript image (set by .psbb).
       \n[lly]   Lower  left  y-coordinate  (in  PostScript  units) of a given
                 PostScript image (set by .psbb).
       \n[ln]    Output line number.
       \n[minutes]
                 The number of minutes after the hour.  Initialized at  start-
                 up.
       \n[mo]    Current month (1-12).
       \n[nl]    Vertical position of last printed text base-line.
       \n[rsb]   Like register sb, but takes account of the heights and depths
                 of characters.
       \n[rst]   Like register st, but takes account of the heights and depths
                 of characters.
       \n[sb]    Depth  of string below base line (generated by width function
                 \w).
       \n[seconds]
                 The number of  seconds  after  the  minute.   Initialized  at
                 start-up.
       \n[skw]   Right skip width from the center of the last character in the
                 \w argument.
       \n[slimit]
                 If greater than 0, the maximum number of objects on the input
                 stack.   If  <=0  there is no limit, i.e., recursion can con-
                 tinue until virtual memory is exhausted.
       \n[ssc]   The amount  of  horizontal  space  (possibly  negative)  that
                 should  be  added  to  the  last character before a subscript
                 (generated by width function \w).
       \n[st]    Height of string above base line (generated by width function
                 \w).
       \n[systat]
                 The  return  value  of  the system() function executed by the
                 last sy request.
       \n[urx]   Upper right x-coordinate (in PostScript  units)  of  a  given
                 PostScript image (set by .psbb).
       \n[ury]   Upper  right  y-coordinate  (in  PostScript units) of a given
                 PostScript image (set by .psbb).
       \n[year]  The current year (year 2000 compliant).
       \n[yr]    Current year minus 1900.  For  Y2K  compliance  use  register
                 year instead.

COMPATIBILITY
       The  differences of the groff language in comparison to classical troff
       as defined by [CSTR #54] are documented in groff_diff(7).

       The groff system provides a compatibility mode, see groff(1) on how  to
       invoke this.

BUGS
       Report bugs to the groff bug mailing list <bug-groff@gnu.org>.  Include
       a complete, self-contained example that will allow the bug to be repro-
       duced, and say which version of groff you are using.

AUTHORS
       Copyright  (C) 2000, 2001, 2002, 2003, 2004, 2005 Free Software Founda-
       tion, Inc.

       This document is distributed under the terms of the FDL (GNU Free Docu-
       mentation  License)  version  1.1 or later.  You should have received a
       copy of the FDL on your system, it is also available on-line at the GNU
       copyleft site <http://www.gnu.org/copyleft/fdl.html>.

       This  document  is  part  of  groff, the GNU roff distribution.  It was
       written by Bernd Warken <bwarken@mayn.de>; it is maintained  by  Werner
       Lemberg <wl@gnu.org>.

SEE ALSO
       The  main  source  of  information  for the groff language is the groff
       info(1) file.  Besides the gory details, it contains many examples.

       groff(1)
              the usage of the groff program and pointers to the documentation
              and availability of the groff system.

       groff_diff(7)
              the  differences  of the groff language as compared to classical
              roff.  This is the authoritative  document  for  the  predefined
              language elements that are specific to groff.

       groff_char(7)
              the predefined groff characters (glyphs).

       groff_font(5)
              the specification of fonts and the DESC file.

       roff(7)
              the  history  of  roff, the common parts shared by all roff sys-
              tems, and pointers to further documentation.

       [CSTR #54]
              Nroff/Troff User's Manual by Osanna & Kernighan <http://
              cm.bell-labs.com/cm/cs/54.ps>  -- the bible for classical troff.



Groff Version 1.19.2            6 February 2006                       GROFF(7)
