Updated: 2021/Apr/14


GROFF(7)               Miscellaneous Information Manual               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 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,

              \)\$*

       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 \[rs]\$1\$2 To be more
              precise, \[rs]\$1\$2 represents the current escape character.
              To get a backslash glyph, use \[rs]\$1\$2 or \[rs]\$1\$2

       2.     Double all backslashes.

       3.     Begin all text lines with the special non-spacing character
              \[rs]\$1\$2

       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 formatting
       elements starting with a backslash

       The user can define her own formatting commands using the \$* 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
       herself 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 \$*
       request and retrieved by the \[rs]\$1\$2 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 \$*
       request and retrieved by the \[rs]\$1\$2 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 \$* request.

       Fonts are identified either by a name or by an internal number.  The
       current font is chosen by the \$* request or by the \[rs]\$1\$2 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 \$* \$* \$* and \$* There it is the
              control character that introduces a request (or macro).  The
              special behavior can be delayed by using the \[rs]\$1\$2 escape.
              By using the \$* request, the control character can be set to a
              different 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 \$* 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
              positions, it denotes the single quote or apostrophe character.
              Groff provides a printable representation with the \[rs]\$1\$2
              escape sequence.

       The double quote is used to enclose arguments in requests, macros, and
              strings.  In the \$* and \$* 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 \[rs]\$1\$2 introduces a
              comment.  Otherwise, it is not special.  Groff provides a
              printable representation with the \[rs]\$1\$2 escape sequence.

       The backslash usually introduces an escape sequence (this can be
              changed with the \$* request).  A printed version of the escape
              character is the \[rs]\$1\$2 escape; a backslash glyph can be
              obtained by \[rs]\$1\$2

       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),
              \[rs]\$1\$2 \[rs]\$1\$2 or \[rs]\$1\$2 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 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
       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:

              The maximum of
                        e1 and e2.
              The minimum of
                        e1 and e2.
              Evaluate  e using c as the default scaling indicator.

       For details see the groff info file.

CONDITIONS
       Conditions occur in tests raised by the \$* \$* and the \$* 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
       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 outlined 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
                        \[rs]\$1\$2 and \[rs]\$1\$2
              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.  Complete line
       is a comment.  Print string on standard error, exit program.  Begin
       line adjustment for output lines in current adjust mode.  Start line
       adjustment in mode c (c=l,r,b,n).  Assign format c to register
       (c=l,i,I,a,A).  Create alias name for register.  Create alias name for
       request, string, macro, or diversion object.  Append to macro until ..
       is encountered.  Append to macro until \$* is called.  Same as \$* but
       with compatibility mode switched off during macro expansion.  Same as
       \$* but with compatibility mode switched off during macro expansion.
       Append to a macro whose name is contained in the string register macro
       until .. is encountered.  Append to a macro indirectly.  macro and end
       are string registers whose contents are interpolated for the macro name
       and the end macro, respectively.  Same as \$* but with compatibility
       mode switched off during macro expansion.  Same as \$* but with
       compatibility mode switched off during macro expansion.  Append
       anything to stringvar.  Same as \$* but with compatibility mode
       switched off during string expansion.  Unformat ASCII characters,
       spaces, and some escape sequences in diversion.  Print a backtrace of
       the input on stderr.  Embolden font by N-1 units.  Embolden Special
       Font S when current font is font.  Unset the blank line macro.  Set the
       blank line macro to macro.  End current diversion.  Divert to macro,
       omitting a partially filled line.  End current diversion.  Divert and
       append to macro, omitting a partially filled line.  Eject current page
       and begin new page.  Eject current page; next page number +-N.  Line
       break.  Break and spread output line.  Same as \[rs]\$1\$2 Break out of
       a while loop.  Reset no-break control character to Set no-break control
       character to c.  Reset control character to Set control character to c.
       Center the next input line.  Center following N input lines.  Copy
       contents of file filename unprocessed to stdout or to the diversion.
       Treat characters c1, c2, ... according to mode number.  Change trap
       location to N .  Define character c as string anything.  Chop the last
       character off macro, string, or diversion object.  Close the stream.
       Enable colors.  If N is zero disable colors, otherwise enable them.
       Map glyph name from to glyph name to while constructing a composite
       glyph name.  Finish the current iteration of a while loop.  Enable
       compatibility mode.  If N is zero disable compatibility mode, otherwise
       enable it.  Set constant character width mode for font to N/36 ems with
       em M.  Continuous underline in nroff, like \$* in troff.  End current
       diversion.  Divert and append to macro.  Define or redefine macro until
       .. is encountered.  Define or redefine macro until \$* is called.  Same
       as \$* but with compatibility mode switched off during macro expansion.
       Same as \$* but with compatibility mode switched off during macro
       expansion.  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 \)\$* 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.  Define or
       redefine a macro whose name is contained in the string register macro
       until .. is encountered.  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.  Same as \$* but with
       compatibility mode switched off during macro expansion.  Same as \$*
       but with compatibility mode switched off during macro expansion.  End
       current diversion.  Divert to macro .  Interpret \$* with compatibility
       mode disabled.  Set stringvar to anything.  Same as \$* but with
       compatibility mode switched off during string expansion.  Set diversion
       trap to position N (default scaling indicator \)\$* Reset escape
       character to Set escape character to c.  Restore escape character saved
       with \$* Save current escape character.  Else part for if-else (\$*
       request.  The macro will be run after the end of input.  Turn off
       escape character mechanism.  Switch to previous environment.  Push down
       environment number or name env and switch to it.  Copy the contents of
       environment env to the current environment.  No pushing or popping.
       Exit from roff processing.  Return to previous font family.  Set the
       current font family to name.  Disable field mechanism.  Set field
       delimiter to a and pad character to space.  Set field delimiter to a
       and pad character to b.  Define fallback character c as string
       anything.  Set fill color to previous fill color.  Set fill color to c.
       Fill output lines.  Flush output buffer.  Mount font on position n.
       Mount font with long external name to short internal name on position
       n.  Define fallback character c for font f as string anything.  Reset
       list of special fonts for font to be empty.  When the current font is
       font, then the fonts s1, s2, ... will be special.  Return to previous
       font.  Same as \$* or \$* Change to font name or number font; same as
       \)\$* escape sequence.  Translate font1 to font2.  Set glyph color to
       previous glyph color.  Set glyph color to c.  Remove additional
       hyphenation indicator character.  Set up additional hyphenation
       indicator character c.  Set the hyphenation code of character c1 to
       code1, that of c2 to code2, etc.  Set the current hyphenation language
       to lang.  Set the maximum number of consecutive hyphenated lines to n.
       Read hyphenation patterns from file.  Append hyphenation patterns from
       file.  Set input mapping for \$* List of words with exceptional
       hyphenation.  Switch to hyphenation mode N.  Set the hyphenation margin
       to n (default scaling indicator \)\$* Set the hyphenation space to n.
       If cond then anything else goto \$* If cond then anything; otherwise do
       nothing.  Ignore text until .. is encountered.  Ignore text until \$*
       Change to previous indent value.  Change indent according to +-N
       (default scaling indicator \)\$* Set an input-line count trap for the
       next N lines.  Same as \$* but count lines interrupted with \[rs]\$1\$2
       as one line.  Enable pairwise kerning.  If n is zero, disable pairwise
       kerning, otherwise enable it.  Remove leader repetition character.  Set
       leader repetition character to c.  Write the length of the string
       anything in register.  Enable line-tabs mode (i.e., calculate tab
       positions relative to output line).  If n is zero, disable line-tabs
       mode, otherwise enable it.  Set input line number to N.  Set input line
       number to N and filename to file.  Ligature mode on if N>0.  Change to
       previous line length.  Set line length according to +-N (default size
       \)\$* default scaling indicator \)\$* Change to the previous value of
       additional intra-line skip.  Set additional intra-line skip value to N,
       i.e., N-1 blank lines are inserted after each text output line.  Length
       of title (default scaling indicator \)\$* Margin character off.  Print
       character c after each text line at actual distance from right margin.
       Set margin character to c and distance to N from right margin (default
       scaling indicator \)\$* Mark current vertical position in register.
       The same as the .so request except that file is searched in the tmac
       directories.  No output-line adjusting.  Need a one-line vertical
       space.  Need N vertical space (default scaling indicator \)\$* No
       filling or adjusting of output-lines.  No hyphenation.  Number mode
       off.  In line number mode, set number, multiple, spacing, and indent.
       Do not number next line.  Do not number next N lines.  Always execute
       anything.  Define or modify register using +-N with auto-increment M.
       Make the built-in condition n true and t false.  Turn no-space mode on.
       Immediately jump to end of current file.  Next file.  Open \)\$* \$*
       for writing and associate the stream named \)\$* \$* with it.  Like \$*
       but append to it.  Output vertical distance that was saved by the \$*
       request.  Emit string directly to intermediate output, allowing leading
       whitespace if string starts with (which will be stripped off).  Reset
       page number character to Page number character.  Pipe output to program
       (nroff only).  Set page length to default \)\$* The current page length
       is stored in \)\$* \$* Change page length to +-N (default scaling
       indicator \)\$* Print macro names and sizes (number of blocks of 128
       bytes).  Print only total of sizes of macros (number of 128 bytes
       blocks).  Next page number N.  Print the names and contents of all
       currently defined number registers on stderr.  Change to previous page
       offset.  The current page offset is available in \)\$* \$* Page offset
       N.  Return to previous point-size.  Point size; same as \)\$* Get the
       bounding box of a PostScript image filename.  This behaves like the \$*
       request except that input comes from the standard output of command.
       Print the names and positions of all traps (not including input line
       traps and diversion traps) on stderr.  Change to previous post-vertical
       line spacing.  Change post-vertical line spacing according to +-N
       (default scaling indicator \)\$* Remove the definitions of characters
       c1, c2, ... Read insertion.  Return from a macro.  Return twice, namely
       from the macro at the current level and from the macro one level
       higher.  Remove the definitions of characters c1, c2, ... for font f.
       Right justify the next n input lines.  Remove request, macro, or string
       name.  Rename request, macro, or string old to new.  Rename register
       reg1 to reg2.  Remove register.  Restore spacing; turn no-space mode
       off.  Return (upward only) to marked vertical place (default scaling
       indicator \)\$* Define global fallback character c as string anything.
       Reset soft hyphen character to \[rs]\$1\$2 Set the soft hyphen
       character to c.  In a macro, shift the arguments by n positions.  Set
       available font sizes similar to the sizes command in a DESC file.
       Include source file.  Skip one line vertically.  Space vertical
       distance N up or down according to sign of N (default scaling
       indicator \)\$* Reset global list of special fonts to be empty.  Fonts
       s1, s2, etc. are special and will be searched for characters not in the
       current font.  Toggle the spread warning on and off without changing
       its value.  Emit a warning if each space in an output line is widened
       by limit or more (default scaling indicator \)\$* Space-character size
       set to N/12 of the spacewidth in the current font.  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).  Associate style with font position n.
       Replace the string named xx with the substring defined by the indices
       n1 and n2.  Save \)\$* of vertical space.  Save the vertical distance N
       for later output with \$* request.  Execute program command-line.  Set
       tabs after every position that is a multiple of N (default scaling
       indicator \)\$* 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.  Remove tab repition character.  Set tab
       repetition character to c.  Temporary indent next line (default scaling
       indicator \)\$* Enable track kerning for font.  Three-part title.
       Print anything on terminal (UNIX standard message output).  Print
       anything on terminal (UNIX standard message output), allowing leading
       whitespace if anything starts with (which will be stripped off).
       Similar to \$* without emitting a final newline.  Translate a to b, c
       to d, etc. on output.  Transparently output the contents of file
       filename.  This is the same as the \$* request except that the asciify
       request will use the character code (if any) before the character
       translation.  This is the same as the \$* request except that the
       translations do not apply to text that is transparently throughput into
       a diversion with \[rs]\$1\$2 Make the built-in condition t true and n
       false.  Underline font set to font (to be switched to by \$* Underline
       (italicize in troff) N input lines.  Unformat space characters and
       tabs, preserving font information in diversion.  Enable vertical
       position traps if n is non-zero, disable them otherwise.  Change to
       previous vertical base line spacing.  Set vertical base line spacing
       according to +-N (default scaling indicator \)\$* Default value is
       \)\$* Set warnings code to n.  Set scaling indicator used in warnings
       to si.  Remove (first) trap at position N.  Set location trap; negative
       means from page bottom.  While condition cond is true, accept anything
       as input.  Write anything to the stream named stream.  Similar to \$*
       without emitting a final newline.  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 \[rs]\$1\$2 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 \[rs]\$1\$2

       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
       \[rs]\$1\$2 construct are used for special characters predefined by the
       roff system.  Escapes sequences with names of more than two characters
       \)\$* denote user defined named characters (see the \$* 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 \[rs]\$1\$2 except that
       the terminating newline is ignored as well.  The string stored in the
       string variable with 1-character name s.  The string stored in the
       string variable with 2-character name st.  The string stored in the
       string variable with arbitrary length name stringvar, taking arg1,
       arg2, ... as arguments.  The name by which the current macro was
       invoked.  The \$* request can make a macro have more than one name.
       Macro or string argument with 1-place number x, where x is a digit
       between 1 and 9.  Macro or string argument with 2-digit number xy.
       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 \[rs]\$1\$2 or even better \[rs]\$1\$2
       to be independent from the current escape character.  The acute accent
       '; same as \[rs]\$1\$2 Unescaped: apostrophe, right quotation mark,
       single quote (ASCII 0x27).  The grave accent `; same as \[rs]\$1\$2
       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.
       In a diversion, this will transparently embed anything in the
       diversion.  anything is read in copy mode.  See also the escape
       sequences \[rs]\$1\$2 and \[rs]\$1\$2 Unpaddable space-size space
       character (no line break).  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
       \[rs]\$1\$2 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 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 \[rs]\$1\$2 but without a soft hyphen
       character).  Ignored newline, for continuation lines.  Begin
       conditional input.  End conditional input.  The special character with
       2-character name sc, see section Special Characters.  The named
       character (or rather glyph) with arbitrary length name name.  A
       composite glyph with components comp1, comp2, ...  Non-interpreted
       leader character.  If anything is acceptable as a name of a string,
       macro, diversion, register, environment or font it expands to 1, and
       to 0 otherwise.  Bracket building function.  If anything is acceptable
       as a valid numeric expression it expands to 1, and to 0 otherwise.
       Interrupt text processing.  The character called char; same as \)\$*
       but compatible to other roff versions.  Forward (down) 1/2 em vertical
       unit (1/2 line in nroff).  Draw a graphical element defined by the
       characters in charseq; see groff info file for details.  Printable
       version of the current escape character.  Equivalent to an escape
       character, but is not interpreted in copy-mode.  Change to font with
       1-character name or 1-digit number F.  Switch back to previous font.
       Change to font with 2-character name or 2-digit number fo.  Change to
       font with arbitrary length name or number expression font.  Switch back
       to previous font.  Change to font family with 1-character name f.
       Change to font family with 2-character name fm.  Change to font family
       with arbitrary length name fam.  Switch back to previous font family.
       Return format of register with name reg suitable for \$* Alternative
       forms \)\$* and \)\$* Local horizontal motion; move right N (left if
       negative).  Set height of current font to N.  Mark horizontal input
       place in register with arbitrary length name reg.  Alternative forms
       \)\$* and \)\$* Horizontal line drawing function (optionally using
       character c).  Vertical line drawing function (optionally using
       character c).  Change to color color.  Alternative forms \)\$* and
       \)\$* Switch back to previous color.  Change filling color for closed
       drawn objects to color color.  Alternative forms \)\$* and \)\$* Switch
       to previous fill color.  The numerical value stored in the register
       variable with the 1-character name r.  The numerical value stored in
       the register variable with the 2-character name re.  The numerical
       value stored in the register variable with arbitrary length name reg.
       Typeset the character with code n in the current font, no special fonts
       are searched.  Useful for adding characters to a font using the \$*
       request.  Overstrike characters a, b, c, etc.  Disable glyph output.
       Mainly for internal use.  Enable glyph output.  Mainly for internal
       use.  Break and spread output line.  Reverse 1 em vertical motion
       (reverse line in nroff).  The same as \$* name +-n.  Set the point size
       to N scaled points.  Note the alternative forms \s+-[N], \s'+-N'\)\$*
       \s+-'N'\)\$* \)\$* \)\$* \s+-(xy\)\$* \)\$* Same as \$* request.  Slant
       output N degrees.  Non-interpreted horizontal tab.  Reverse (up) 1/2 em
       vertical motion (1/2 line in nroff).  Local vertical motion; move down
       N (up if negative).  The contents of the environment variable env.
       Alternative forms \)\$* and \)\$* The width of the character sequence
       string.  Extra line-space function (negative before, positive after).
       Output string as device control function.  Output string variable or
       macro name uninterpreted as device control function.  Alternative forms
       \)\$* and \)\$* Print c with zero width (without spacing).  Print
       anything and then restore the horizontal and vertical position;
       anything may not contain tabs or leaders.

       The escape sequences \[rs]\$1\$2 \[rs]\$1\$2 \[rs]\$1\$2 \[rs]\$1\$2
       \[rs]\$1\$2 \[rs]\$1\$2 \[rs]\$1\$2 \[rs]\$1\$2 \[rs]\$1\$2 and \)\$*
       are interpreted in copy mode.

       Escape sequences starting with \[rs]\$1\$2 or \[rs]\$1\$2 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).

              Bullet sign Copyright Cent Double dagger Degree Dagger Printable
              double quote Em-dash Hyphen Registered sign Printable backslash
              character Section sign Underline character Identical Larger or
              equal Less or equal Not equal Right arrow Left arrow Plus-minus
              sign

   Strings
       Strings are defined by the \$* request and can be retrieved by the
       \[rs]\$1\$2 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.

       The name of the current output device as specified by the
                 \)\$* 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 \$* register.

       The value stored in a register can be retrieved by the escape sequences
       introduced by \[rs]\$1\$2

       Most useful are predefined registers.  In the following the notation
       name is used to refer to a register called \)\$* \$* to make clear that
       we speak about registers.  Please keep in mind that the \)\$*
       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, registers starting with a dot a read-
       only).  Mostly, they provide information on the current settings or
       store results from request calls.

       Number of arguments in the current macro or string.
       Post-line extra line-space most recently utilized using
                 \)\$*
       Set to 1 in
                 troff if option -A is used; always 1 in nroff.
       Current input line number.
       1 if compatibility mode is in effect, 0 otherwise.
       The depth of the last character added to the current environment.
                 It is positive if the character extends below the baseline.
       The number of lines remaining to be centered, as set by the
                 \$* request.
       The height of the last character added to the current environment.
                 It is positive if the character extends above the baseline.
       1 if colors are enabled, 0 otherwise.
       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.
       Current vertical place in current diversion; equal to
                 \)\$* \$*
       The name or number of the current environment (string-valued).
       Current font number.
       The current font family (string-valued).
       The current (internal) real font name (string-valued).
       The number of the next free font position.
       Always 1 in GNU troff.
                 Macros should use it to test if running under groff.
       Text base-line high-water mark on current page or diversion.
       Available horizontal resolution in basic units.
       The current font height as set with
                 \$*
       The current hyphenation language as set by the
                 .hla request.
       The number of immediately preceding consecutive hyphenated lines.
       The maximum allowed number of consecutive hyphenated lines, as set by
                 the \$* request.
       The current hyphenation flags (as set by the
                 \$* request).
       The current hyphenation margin (as set by the
                 \$* request).
       The current hyphenation space (as set by the
                 \$* request).
       Current ident.
       The indent that applies to the current output line.
       Positive if last output line contains
                 \[rs]\$1\$2
       1 if pairwise kerning is enabled, 0 otherwise.
       Current line length.
       The current ligature mode (as set by the
                 \$* request).
       The current line-tabs mode (as set by the
                 \$* request).
       The line length that applies to the current output line.
       The title length (as set by the
                 \$* request).
       The current drawing color (string-valued).
       The current background color (string-valued).
       Length of text portion on previous output line.
       The amount of space that was needed in the last
                 \$* request that caused a trap to be sprung.  Useful in
                 conjunction with \)\$* \$*
       1 if in no-space mode, 0 otherwise.
       Current page offset.
       Current page length.
       1 during page ejection, 0 otherwise.
       The number of the next page: either the value set by a
                 \$* request, or the number of the current page plus 1.
       The current pointsize in scaled points.
       The last-requested pointsize in scaled points.
       The current post-vertical line spacing.
       The number of lines to be right-justified as set by the rj request.
       Current point size as a decimal fraction.
       The slant of the current font as set with
                 \$*
       The last requested pointsize in points as a decimal fraction
                 (string-valued).
       The value of the parameters set by the first argument of the
                 \$* request.
       The value of the parameters set by the second argument of the
                 \$* request.
       The current font style (string-valued).
       Distance to the next trap.
       Set to 1  if option -T is used.
       A string representation of the current tab settings suitable for use
                 as an argument to the \$* request.
       The amount of vertical space truncated by the most recently sprung
                 vertical position trap, or, if the trap was sprung by a \$*
                 request, minus the amount of vertical motion produced by \$*
                 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 \)\$* \$*
       Equal to 1 in fill mode and 0 in nofill mode.
       Equal to 1 in safer mode and 0 in unsafe mode.
       Current vertical line spacing.
       Available vertical resolution in basic units.
       1  if vertical position traps are enabled, 0 otherwise.
       Width of previous character.
       The sum of the number codes of the currently enabled warnings.
       The major version number.
       The minor version number.
       The revision number of groff.
       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.

       Current page number.
       Current input line number.
       Character type (set by width function
                 \[rs]\$1\$2
       Maximal width of last completed diversion.
       Height of last completed diversion.
       Current day of week (1-7).
       Current day of month (1-31).
       The number of hours past midnight.
                 Initialized at start-up.
       Current horizontal position at input line.
       Lower left x-coordinate (in PostScript units) of a given PostScript
                 image (set by \$*
       Lower left y-coordinate (in PostScript units) of a given PostScript
                 image (set by \$*
       Output line number.
       The number of minutes after the hour.
                 Initialized at start-up.
       Current month (1-12).
       Vertical position of last printed text base-line.
       Like      \)\$* \$* but takes account of the heights and depths of
                 characters.
       Like      \)\$* \$* but takes account of the heights and depths of
                 characters.
       Depth of string below base line (generated by width function
                 \[rs]\$1\$2
       The number of seconds after the minute.
                 Initialized at start-up.
       Right skip width from the center of the last character in the
                 \[rs]\$1\$2 argument.
       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.
       The amount of horizontal space (possibly negative) that should be
                 added to the last character before a subscript (generated by
                 width function \[rs]\$1\$2
       Height of string above base line (generated by width function
                 \[rs]\$1\$2
       The return value of the
                 system() function executed by the last \$* request.
       Upper right x-coordinate (in PostScript units) of a given PostScript
                 image (set by \$*
       Upper right y-coordinate (in PostScript units) of a given PostScript
                 image (set by \$*
       The current year (year 2000 compliant).
       Current year minus 1900.
                 For Y2K compliance use \)\$* \$* 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 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

       This document is part of groff, the GNU roff distribution.  It was
       written by it is maintained by

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
              systems, and pointers to further documentation.

       [CSTR #54]
              -- the bible for classical troff.



Groff Version 1.19.2           September 4, 2005                      GROFF(7)