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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 background of the groff system.

       This document gives only short descriptions of the predefined  roff  language  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 empha-sizes emphasizes
       sizes 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 modified by escape sequences, which
       are  recognized by a leading backslash `\'.  These are in-line or even in-word formatting elements or
       functions.  Some of these take arguments separated by single quotes "'", others are  regulated  by  a
       length encoding introduced by an open parenthesis `(' 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 precise, \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 inword
       word formatting 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 writ-ten written
       ten  in  the  groff language.  A user's possibilities to create escape sequences herself is very lim-ited, limited,
       ited, only special characters can be mapped.

       The groff language provides several kinds of variables with different  interfaces.   There  are  pre-defined predefined
       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 stringlike
       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  counterpart.   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 condition 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 different character, making the dot `.' a non-special char-acter. character.
              acter.

              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 separator in some functional escape
              sequences (but any pair of characters not part of the argument will work).  In all other posi-tions, positions,
              tions, it denotes the single quote or apostrophe character.  Groff provides a printable repre-sentation representation
              sentation 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 double quote in the argument will be stripped off, making everything
              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 rep-resentation representation
              resentation 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  calculations.   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 characters.  Continuation lines  can  be
              specified  by an escaped newline, 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 predefined
              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 indi-cator. indicator.
       cator.  A scaling indicator is a one-character abbreviation for a unit of measurement.  A number fol-lowed followed
       lowed  by  a  scaling  indicator  signifies a size value.  By default, numerical values 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 expressions:

              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  charac-
       terizes 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 bracketing 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 out-lined outlined
       lined here.  Refer to the groff info file and groff_diff(7) for all details.

       In the following request specifications, most argument names were chosen to be descriptive.  Only the
       following denotations need clarification.

              c         denotes a single character.
              font      a font either specified as a font name or a font number.
              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 register macro until .. is encoun-tered. encountered.
                 tered.
       .ami macro end
                 Append to a macro indirectly.  macro and end are string registers whose contents are inter-polated interpolated
                 polated 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 components 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 indicator 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 environment.  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 indicator 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  indica-tor indicator
                 tor 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 com-mand. command.
                 mand.
       .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 scaling 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 characters 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 character translation.
       .trnt abcd...
                 This  is  the same as the tr request except that the translations do not apply to text that
                 is transparently throughput into a diversion with \!.
       .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 information 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 separation 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 functions and system related tasks,
       the 2-letter names following the \( construct are used for special characters predefined by the  roff
       system.   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 interpretation as escape character in copy
              mode.  For a printable backslash, 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 \(ga.  Unescaped: left quote, backquote (ASCII 0x60).
       \-     The - sign in the current font.
       \.     An uninterpreted dot (period), even at start of line.
       \%     Default optional hyphenation character.
       \!     Transparent line indicator.
       \?anything?
              In a diversion, this will transparently embed anything in the diversion.  anything is read  in
              copy mode.  See also the escape sequences \!  and \?.
       \space Unpaddable space-size space character (no line break).
       \0     Digit width.
       \|     1/6 em narrow space character; zero width in nroff.
       \^     1/12 em half-narrow space character; zero width in nroff.
       \&     Non-printable, zero width character.
       \)     Like  \& except that it behaves like a character declared with the cflags request to be trans-parent transparent
              parent for the purposes of end of sentence recognition.
       \/     Increases the width of the preceding character so that the spacing between that character  and
              the following character will be correct if the following character is a roman character.
       \,     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 Special 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, diversion,  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 arbitrary length name reg.
       \N'n'  Typeset the character with code n in the current font, no special fonts are searched.   Useful
              for adding characters to a font using the char request.
       \o'abc...'
              Overstrike characters a, b, c, etc.
       \O_    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  character  escape  sequences,  but
       introduce escape names with two or more characters.

       If  a  backslash  is  followed  by a character that does not constitute a defined escape sequence the
       backslash is silently ignored and the character 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
       unpredictable 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 regis-
       ter.

       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 reg-ister register
       ister called register name to make clear that we speak about registers.  Please keep in mind that the
       \n[] decoration is not part of the register name.

   Read-only Registers
       The following registers have predefined values that should not be modified by the user (usually, reg-isters registers
       isters 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 environment.  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 environment.  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 environment.  The skew of a character
                 is how far to the right of the center of a character the center  of  an  accent  over  that
                 character should be placed.
       \n[.d]    Current vertical place in current diversion; equal to register nl.
       \n[.ev]   The name or number of the current environment (string-valued).
       \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 running 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 represents the difference  of  what
                 the  vertical  position  would  have  been but for the trap, and what the vertical position
                 actually is.  Useful in conjunction with the 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 warnings.
       \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 continue until virtual memory is exhausted.
       \n[ssc]   The amount of horizontal space (possibly negative) that should be added to the last charac-
                 ter 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 reproduced, and say which version of groff you are using.

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

       This  document is distributed under the terms of the FDL (GNU Free Documentation 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 authorita-tive authoritative
              tive 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 systems, and pointers to further doc-umentation. documentation.
              umentation.

       [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                          16 February 2005                                      GROFF(7)

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