bionic (5) groff_out.5.gz

Provided by: groff_1.22.3-10_amd64 bug

NAME

       groff_out - groff intermediate output format

DESCRIPTION

       This  manual  page  describes  the  intermediate  output format of the GNU roff(7) text processing system
       groff(1).  This output is produced by a run of the GNU troff(1) program.  It contains already all device-
       specific information, but it is not yet fed into a device postprocessor program.

       As  the  GNU  roff  processor  groff(1)  is  a  wrapper  program  around troff that automatically calls a
       postprocessor, this output does not show up normally.  This is why it is called intermediate  within  the
       groff system.  The groff program provides the option -Z to inhibit postprocessing, such that the produced
       intermediate output is sent to standard output just like calling troff manually.

       In this document, the term troff output describes  what  is  output  by  the  GNU  troff  program,  while
       intermediate  output  refers to the language that is accepted by the parser that prepares this output for
       the postprocessors.   This  parser  is  smarter  on  whitespace  and  implements  obsolete  elements  for
       compatibility,  otherwise  both  formats  are  the  same.   Both  formats  can  be  viewed  directly with
       gxditview(1).

       The main purpose of the intermediate output concept is to facilitate the development of postprocessors by
       providing  a  common  programming  interface  for  all  devices.   It  has  a language of its own that is
       completely different from the groff(7) language.  While the groff language is  a  high-level  programming
       language  for text processing, the intermediate output language is a kind of low-level assembler language
       by specifying all positions on the page for writing and drawing.

       The pre-groff roff versions are denoted as classical troff.  The intermediate output produced by groff is
       fairly  readable,  while classical troff output was hard to understand because of strange habits that are
       still supported, but not used any longer by GNU troff.

LANGUAGE CONCEPTS

       During the run of troff, the roff input is cracked down to the information on what has to be  printed  at
       what  position  on  the  intended device.  So the language of the intermediate output format can be quite
       small.  Its only elements are commands with or without arguments.  In this document, the  term  “command”
       always  refers  to  the  intermediate  output  language,  never  to  the  roff language used for document
       formatting.  There  are  commands  for  positioning  and  text  writing,  for  drawing,  and  for  device
       controlling.

   Separation
       Classical  troff  output  had  strange  requirements on whitespace.  The groff output parser, however, is
       smart about whitespace by making it maximally optional.  The whitespace characters, i.e., the tab, space,
       and  newline  characters,  always  have  a syntactical meaning.  They are never printable because spacing
       within the output is always done by positioning commands.

       Any sequence of space or tab characters is treated as a single syntactical space.  It separates  commands
       and  arguments,  but  is only required when there would occur a clashing between the command code and the
       arguments without the space.  Most often, this happens when variable  length  command  names,  arguments,
       argument  lists, or command clusters meet.  Commands and arguments with a known, fixed length need not be
       separated by syntactical space.

       A line break is a syntactical element, too.  Every command argument can  be  followed  by  whitespace,  a
       comment,  or  a  newline  character.   Thus  a  syntactical  line break is defined to consist of optional
       syntactical space that is optionally followed by a comment, and a newline character.

       The normal commands, those for positioning and text, consist of a single letter taking a fixed number  of
       arguments.   For  historical  reasons,  the  parser  allows  to stack such commands on the same line, but
       fortunately, in groff intermediate output, every command with at least one argument is followed by a line
       break, thus providing excellent readability.

       The  other  commands — those for drawing and device controlling — have a more complicated structure; some
       recognize long command names, and some take a variable number of arguments.  So all D and x commands were
       designed  to  request a syntactical line break after their last argument.  Only one command, ‘x X’ has an
       argument that can stretch over several lines, all other commands must have all of their arguments on  the
       same line as the command, i.e., the arguments may not be split by a line break.

       Empty  lines,  i.e.,  lines  containing only space and/or a comment, can occur everywhere.  They are just
       ignored.

   Argument Units
       Some commands take integer arguments that are assumed to represent values in a measurement unit, but  the
       letter  for  the  corresponding  scale  indicator  is  not written with the output command arguments; see
       groff(7) and the groff info file for more on this topic.  Most commands assume the scale indicator u, the
       basic  unit  of  the  device,  some use z, the scaled point unit of the device, while others, such as the
       color commands expect plain integers.  Note that these  scale  indicators  are  relative  to  the  chosen
       device.  They are defined by the parameters specified in the device's DESC file; see groff_font(5).

       Note that single characters can have the eighth bit set, as can the names of fonts and special characters
       (this is, glyphs).  The names of glyphs and fonts can be of arbitrary length.  A  glyph  that  is  to  be
       printed will always be in the current font.

       A  string  argument  is  always  terminated by the next whitespace character (space, tab, or newline); an
       embedded # character is regarded as part of the argument, not as the beginning of a comment command.   An
       integer  argument  is  already  terminated by the next non-digit character, which then is regarded as the
       first character of the next argument or command.

   Document Parts
       A correct intermediate output document consists of two parts, the prologue and the body.

       The task of the prologue is to set the general device parameters using three exactly specified  commands.
       The groff prologue is guaranteed to consist of the following three lines (in that order):

              x T device
              x res n h v
              x init

       with  the  arguments set as outlined in the section Device Control Commands.  However, the parser for the
       intermediate output format is able to swallow additional whitespace and comments as well.

       The body is the main section for processing the document data.  Syntactically, it is a  sequence  of  any
       commands  different  from  the  ones used in the prologue.  Processing is terminated as soon as the first
       x stop command is encountered; the last line of any groff intermediate  output  always  contains  such  a
       command.

       Semantically,  the  body  is page oriented.  A new page is started by a p command.  Positioning, writing,
       and drawing commands are always done within the current page, so  they  cannot  occur  before  the  first
       p  command.   Absolute  positioning  (by  the H and V commands) is done relative to the current page, all
       other positioning is done relative to the current location within this page.

COMMAND REFERENCE

       This section describes all intermediate output commands, the classical commands  as  well  as  the  groff
       extensions.

   Comment Command
       #anything⟨end-of-line⟩
              A comment.  Ignore any characters from the # character up to the next newline character.

       This  command  is  the  only  possibility for commenting in the intermediate output.  Each comment can be
       preceded by arbitrary syntactical space; every command can be terminated by a comment.

   Simple Commands
       The commands in this subsection have a command code consisting of a  single  character,  taking  a  fixed
       number  of  arguments.   Most  of them are commands for positioning and text writing.  These commands are
       smart about whitespace.  Optionally, syntactical space can be inserted before,  after,  and  between  the
       command  letter  and  its  arguments.  All of these commands are stackable, i.e., they can be preceded by
       other simple commands or followed by arbitrary other commands on the same line.  A separating syntactical
       space  is  only necessary when two integer arguments would clash or if the preceding argument ends with a
       string argument.

       C xxx⟨white-space⟩
              Print a glyph (special character) named xxx.  The trailing syntactical  space  or  line  break  is
              necessary  to  allow  glyph  names of arbitrary length.  The glyph is printed at the current print
              position; the glyph's size is read from the font file.  The print position is not changed.

       c c    Print glyph with single-letter name c at the current print position; the glyph's size is read from
              the font file.  The print position is not changed.

       f n    Set font to font number n (a non-negative integer).

       H n    Move  right to the absolute vertical position n (a non-negative integer in basic units u) relative
              to left edge of current page.

       h n    Move n (a non-negative integer) basic units u  horizontally  to  the  right.   [CSTR  #54]  allows
              negative values for n also, but groff doesn't use this.

       m color-scheme [component ...]
              Set  the color for text (glyphs), line drawing, and the outline of graphic objects using different
              color schemes; the analogous command for the filling color of graphic objects is  DF.   The  color
              components are specified as integer arguments between 0 and 65536.  The number of color components
              and their meaning vary for the different color schemes.  These commands are generated by the groff
              escape sequence \m.  No position changing.  These commands are a groff extension.

              mc cyan magenta yellow
                     Set  color  using  the  CMY  color scheme, having the 3 color components cyan, magenta, and
                     yellow.

              md     Set color to the default color value (black in most cases).  No component arguments.

              mg gray
                     Set color to the shade of gray given by the argument, an  integer  between  0  (black)  and
                     65536 (white).

              mk cyan magenta yellow black
                     Set color using the CMYK color scheme, having the 4 color components cyan, magenta, yellow,
                     and black.

              mr red green blue
                     Set color using the RGB color scheme, having the 3 color components red, green, and blue.

       N n    Print glyph with index n (an integer, normally non-negative)  of  the  current  font.   The  print
              position  is  not  changed.   If  -T html or -T xhtml is used, negative values are emitted also to
              indicate an unbreakable space with given width.  For example, N  -193  represents  an  unbreakable
              space which has a width of 193u.  This command is a groff extension.

       n b a  Inform  the  device  about a line break, but no positioning is done by this command.  In classical
              troff, the integer arguments b and a informed about the space before and after the current line to
              make  the  intermediate  output more human readable without performing any action.  In groff, they
              are just ignored, but they must be provided for compatibility reasons.

       p n    Begin a new page in the outprint.  The  page  number  is  set  to  n.   This  page  is  completely
              independent  of  pages  formerly  processed even if those have the same page number.  The vertical
              position on the outprint is automatically set to 0.  All  positioning,  writing,  and  drawing  is
              always done relative to a page, so a p command must be issued before any of these commands.

       s n    Set  point  size  to n scaled points (this is unit z in GNU troff).  Classical troff used the unit
              points (p) instead; see section COMPATIBILITY.

       t xyz...⟨white-space⟩
       t xyz... dummy-arg⟨white-space⟩
              Print a word, i.e., a sequence of glyphs with single-letter names x, y, z, etc., terminated  by  a
              space  character  or a line break; an optional second integer argument is ignored (this allows the
              formatter to generate an even number of arguments).  The first glyph  should  be  printed  at  the
              current  position,  the  current  horizontal position should then be increased by the width of the
              first glyph, and so on for each glyph.  The widths of the glyph  are  read  from  the  font  file,
              scaled  for  the  current  point  size,  and  rounded  to a multiple of the horizontal resolution.
              Special characters (glyphs with names longer than a single letter) cannot be  printed  using  this
              command;  use  the C command for those glyphs.  This command is a groff extension; it is only used
              for devices whose DESC file contains the tcommand keyword; see groff_font(5).

       u n xyz...⟨white-space⟩
              Print word with track kerning.  This is the same as the t command except that after printing  each
              glyph,  the  current  horizontal position is increased by the sum of the width of that glyph and n
              (an integer in basic units u).  This command is a groff extension; it is  only  used  for  devices
              whose DESC file contains the tcommand keyword; see groff_font(5).

       V n    Move  down  to the absolute vertical position n (a non-negative integer in basic units u) relative
              to upper edge of current page.

       v n    Move n basic units u down (n is a non-negative integer).  [CSTR #54] allows negative values for  n
              also, but groff doesn't use this.

       w      Informs about a paddable whitespace to increase readability.  The spacing itself must be performed
              explicitly by a move command.

   Graphics Commands
       Each graphics or drawing command in the intermediate output starts with the letter D followed by  one  or
       two  characters  that  specify  a  subcommand;  this is followed by a fixed or variable number of integer
       arguments that are separated by a single space character.  A D command may not  be  followed  by  another
       command  on  the  same line (apart from a comment), so each D command is terminated by a syntactical line
       break.

       troff output follows the classical spacing rules (no space between command and subcommand, all  arguments
       are  preceded  by  a  single  space  character), but the parser allows optional space between the command
       letters and makes the space before the first argument optional.  As usual, each space can be any sequence
       of tab and space characters.

       Some  graphics  commands  can  take  a  variable  number  of  arguments.  In this case, they are integers
       representing a size measured in basic units u.  The h arguments  stand  for  horizontal  distances  where
       positive  means  right, negative left.  The v arguments stand for vertical distances where positive means
       down, negative up.  All these distances are offsets relative to the current location.

       Unless indicated otherwise, each graphics command directly corresponds  to  a  similar  groff  \D  escape
       sequence; see groff(7).

       Unknown  D  commands  are  assumed to be device-specific.  Its arguments are parsed as strings; the whole
       information is then sent to the postprocessor.

       In the following command reference, the syntax element ⟨line-break⟩ means a  syntactical  line  break  as
       defined in section Separation.

       D~ h1 v1 h2 v2 ... hn vn⟨line-break⟩
              Draw B-spline from current position to offset (h1, v1), then to offset (h2, v2) if given, etc., up
              to (hn, vn). This command takes a variable number of argument pairs; the current position is moved
              to the terminal point of the drawn curve.

       Da h1 v1 h2 v2⟨line-break⟩
              Draw arc from current position to (h1, v1)+(h2, v2) with center at (h1, v1); then move the current
              position to the final point of the arc.

       DC d⟨line-break⟩
       DC d dummy-arg⟨line-break⟩
              Draw a solid circle using the current fill color with diameter d (integer in basic units  u)  with
              leftmost  point  at the current position; then move the current position to the rightmost point of
              the circle.  An optional second integer argument is ignored  (this  allows  to  the  formatter  to
              generate an even number of arguments).  This command is a groff extension.

       Dc d⟨line-break⟩
              Draw  circle  line  with  diameter d (integer in basic units u) with leftmost point at the current
              position; then move the current position to the rightmost point of the circle.

       DE h v⟨line-break⟩
              Draw a solid ellipse in the current fill color with a horizontal diameter  of  h  and  a  vertical
              diameter  of  v  (both integers in basic units u) with the leftmost point at the current position;
              then move to the rightmost point of the ellipse.  This command is a groff extension.

       De h v⟨line-break⟩
              Draw an outlined ellipse with a horizontal diameter of h  and  a  vertical  diameter  of  v  (both
              integers in basic units u) with the leftmost point at current position; then move to the rightmost
              point of the ellipse.

       DF color-scheme [component ...]⟨line-break⟩
              Set fill color for solid drawing objects using different color schemes; the analogous command  for
              setting  the  color  of  text,  line graphics, and the outline of graphic objects is m.  The color
              components are specified as integer arguments between 0 and 65536.  The number of color components
              and their meaning vary for the different color schemes.  These commands are generated by the groff
              escape sequences \D'F ...'  and \M (with no other corresponding graphics commands).   No  position
              changing.  This command is a groff extension.

              DFc cyan magenta yellow⟨line-break⟩
                     Set  fill  color  for  solid drawing objects using the CMY color scheme, having the 3 color
                     components cyan, magenta, and yellow.

              DFd ⟨line-break⟩
                     Set fill color for solid drawing objects to the default fill color  value  (black  in  most
                     cases).  No component arguments.

              DFg gray⟨line-break⟩
                     Set  fill  color  for  solid drawing objects to the shade of gray given by the argument, an
                     integer between 0 (black) and 65536 (white).

              DFk cyan magenta yellow black⟨line-break⟩
                     Set fill color for solid drawing objects using the CMYK color scheme, having  the  4  color
                     components cyan, magenta, yellow, and black.

              DFr red green blue⟨line-break⟩
                     Set  fill  color  for  solid drawing objects using the RGB color scheme, having the 3 color
                     components red, green, and blue.

       Df n⟨line-break⟩
              The argument n must be an integer in the range -32767 to 32767.

              0≤n≤1000
                     Set the color for filling solid drawing objects to a shade of gray, where 0 corresponds  to
                     solid  white,  1000  (the  default)  to  solid black, and values in between to intermediate
                     shades of gray; this is obsoleted by command DFg.

              n<0 or n>1000
                     Set the filling color to the color that is currently  being  used  for  the  text  and  the
                     outline, see command m.  For example, the command sequence

                            mg 0 0 65536
                            Df -1

                     sets all colors to blue.

              No position changing.  This command is a groff extension.

       Dl h v⟨line-break⟩
              Draw  line  from  current  position to offset (h, v) (integers in basic units u); then set current
              position to the end of the drawn line.

       Dp h1 v1 h2 v2 ... hn vn⟨line-break⟩
              Draw a polygon line from current position to offset (h1, v1), from there to offset (h2, v2), etc.,
              up  to offset (hn, vn), and from there back to the starting position.  For historical reasons, the
              position is changed by adding the sum of all arguments with odd index  to  the  actual  horizontal
              position  and the even ones to the vertical position.  Although this doesn't make sense it is kept
              for compatibility.  This command is a groff extension.

       DP h1 v1 h2 v2 ... hn vn⟨line-break⟩
              The same macro as the corresponding Dp command with the same arguments, but draws a solid  polygon
              in  the  current  fill color rather than an outlined polygon.  The position is changed in the same
              way as with Dp.  This command is a groff extension.

       Dt n⟨line-break⟩
              Set the current line thickness to n (an integer in basic units  u)  if  n>0;  if  n=0  select  the
              smallest  available  line  thickness; if n<0 set the line thickness proportional to the point size
              (this is the default before the first Dt command was  specified).   For  historical  reasons,  the
              horizontal position is changed by adding the argument to the actual horizontal position, while the
              vertical position is not changed.  Although this doesn't make sense it is kept for  compatibility.
              This command is a groff extension.

   Device Control Commands
       Each device control command starts with the letter x followed by a space character (optional or arbitrary
       space/tab in groff) and a subcommand letter or word; each  argument  (if  any)  must  be  preceded  by  a
       syntactical  space.  All x commands are terminated by a syntactical line break; no device control command
       can be followed by another command on the same line (except a comment).

       The subcommand is basically a single letter, but to increase readability, it can be written  as  a  word,
       i.e.,  an  arbitrary sequence of characters terminated by the next tab, space, or newline character.  All
       characters of the subcommand word but the first are simply  ignored.   For  example,  troff  outputs  the
       initialization  command  x i  as  x init  and  the  resolution  command  x r as x res.  But writings like
       x i_like_groff and x roff_is_groff are accepted as well to mean the same commands.

       In the following, the syntax element ⟨line-break⟩ means a syntactical line break as  defined  in  section
       Separation.

       xF name⟨line-break⟩
              (Filename control command)
              Use  name  as  the  intended  name  for  the  current  file  in error reports.  This is useful for
              remembering the original file name when groff uses an internal piping mechanism.  The  input  file
              is not changed by this command.  This command is a groff extension.

       xf n s⟨line-break⟩
              (font control command)
              Mount   font  position  n  (a  non-negative  integer)  with  font  named  s  (a  text  word),  cf.
              groff_font(5).

       xH n⟨line-break⟩
              (Height control command)
              Set character height to n (a positive integer in scaled points z).  Classical troff used the  unit
              points (p) instead; see section COMPATIBILITY.

       xi ⟨line-break⟩
              (init control command)
              Initialize device.  This is the third command of the prologue.

       xp ⟨line-break⟩
              (pause control command)
              Parsed but ignored.  The classical documentation reads pause device, can be restarted.

       xr n h v⟨line-break⟩
              (resolution control command)
              Resolution  is  n,  while  h  is  the minimal horizontal motion, and v the minimal vertical motion
              possible with this device; all arguments are positive integers in basic units u per inch.  This is
              the second command of the prologue.

       xS n⟨line-break⟩
              (Slant control command)
              Set slant to n degrees (an integer in basic units u).

       xs ⟨line-break⟩
              (stop control command)
              Terminates  the  processing  of  the  current file; issued as the last command of any intermediate
              troff output.

       xt ⟨line-break⟩
              (trailer control command)
              Generate trailer information, if any.  In groff, this is actually just ignored.

       xT xxx⟨line-break⟩
              (Typesetter control command)
              Set name of device to word xxx, a sequence of characters ended by the next  whitespace  character.
              The possible device names coincide with those from the groff -T option.  This is the first command
              of the prologue.

       xu n⟨line-break⟩
              (underline control command)
              Configure underlining of spaces.  If n is 1,  start  underlining  of  spaces;  if  n  is  0,  stop
              underlining  of spaces.  This is needed for the cu request in nroff mode and is ignored otherwise.
              This command is a groff extension.

       xX anything⟨line-break⟩
              (X-escape control command)
              Send string anything uninterpreted to the device.  If the line following this command starts  with
              a  +  character  this line is interpreted as a continuation line in the following sense.  The + is
              ignored, but a newline character is sent instead to the device, the  rest  of  the  line  is  sent
              uninterpreted.  The same applies to all following lines until the first character of a line is not
              a + character.  This command is generated by the groff escape sequence  \X.   The  line-continuing
              feature is a groff extension.

   Obsolete Command
       In  classical  troff  output,  emitting  a  single  glyph  was mostly done by a very strange command that
       combined a horizontal move and the printing  of  a  glyph.   It  didn't  have  a  command  code,  but  is
       represented by a 3-character argument consisting of exactly 2 digits and a character.

       ddc    Move  right  dd  (exactly  two  decimal digits) basic units u, then print glyph with single-letter
              name c.

              In groff, arbitrary syntactical space around and within this command is allowed to be added.  Only
              when  a  preceding  command on the same line ends with an argument of variable length a separating
              space is obligatory.  In classical troff, large clusters of these and other  commands  were  used,
              mostly without spaces; this made such output almost unreadable.

       For  modern high-resolution devices, this command does not make sense because the width of the glyphs can
       become much larger than two decimal digits.  In groff, this is only used for  the  devices  X75,  X75-12,
       X100, and X100-12.  For other devices, the commands t and u provide a better functionality.

POSTPROCESSING

       The roff postprocessors are programs that have the task to translate the intermediate output into actions
       that are sent to a device.  A device can be some piece of hardware such as a printer, or a software  file
       format suitable for graphical or text processing.  The groff system provides powerful means that make the
       programming of such postprocessors an easy task.

       There is a library function that parses the intermediate output and sends the information obtained to the
       device  via  methods  of  a class with a common interface for each device.  So a groff postprocessor must
       only redefine the methods of this class.  For details, see the reference in section FILES.

EXAMPLES

       This section presents the intermediate output generated from the same input for three different  devices.
       The input is the sentence hell world fed into groff on the command line.

       • High-resolution device ps

         shell> echo "hell world" | groff -Z -T ps

         x T ps
         x res 72000 1 1
         x init
         p1
         x font 5 TR
         f5
         s10000
         V12000
         H72000
         thell
         wh2500
         tw
         H96620
         torld
         n12000 0
         x trailer
         V792000
         x stop

       This output can be fed into the postprocessor grops(1) to get its representation as a PostScript file, or
       gropdf(1) to output directly to PDF.

       • Low-resolution device latin1

         This is similar to the high-resolution device except that the positioning is done  at  a  minor  scale.
         Some  comments  (lines  starting  with  #) were added for clarification; they were not generated by the
         formatter.

         shell> "hell world" | groff -Z -T latin1

         # prologue
         x T latin1
         x res 240 24 40
         x init
         # begin a new page
         p1
         # font setup
         x font 1 R
         f1
         s10
         # initial positioning on the page
         V40
         H0
         # write text ‘hell’
         thell
         # inform about a space, and do it by a horizontal jump
         wh24
         # write text ‘world’
         tworld
         # announce line break, but do nothing because ...
         n40 0
         # ... the end of the document has been reached
         x trailer
         V2640
         x stop

       This output can be fed into the postprocessor grotty(1) to get a formatted text document.

       • Classical style output

         As a computer monitor has a very low resolution compared to modern printers the intermediate output for
         the X devices can use the jump-and-write command with its 2-digit displacements.

         shell> "hell world" | groff -Z -T X100

         x T X100
         x res 100 1 1
         x init
         p1
         x font 5 TR
         f5
         s10
         V16
         H100
         # write text with old-style jump-and-write command
         ch07e07l03lw06w11o07r05l03dh7
         n16 0
         x trailer
         V1100
         x stop

       This output can be fed into the postprocessor xditview(1x) or gxditview(1) for displaying in X.

       Due  to  the  obsolete  jump-and-write  command,  the  text  clusters  in the classical output are almost
       unreadable.

COMPATIBILITY

       The intermediate output language of the classical troff was first documented in [CSTR  #97].   The  groff
       intermediate output format is compatible with this specification except for the following features.

       • The classical quasi device independence is not yet implemented.

       • The  old  hardware  was  very  different  from  what  we  use  today.   So  the  groff devices are also
         fundamentally different from the ones in classical troff.  For example, the classical PostScript device
         was called post and had a resolution of 720 units per inch, while groff's ps device has a resolution of
         72000 units per inch.  Maybe, by implementing some rescaling mechanism similar to the  classical  quasi
         device independence, these could be integrated into modern groff.

       • The  B-spline  command  D~  is  correctly  handled  by  the intermediate output parser, but the drawing
         routines aren't implemented in some of the postprocessor programs.

       • The argument of the commands s and x H has the implicit unit scaled point z in groff,  while  classical
         troff  had  point  (p).   This  isn't  an  incompatibility,  but a compatible extension, for both units
         coincide for all devices without a sizescale parameter, including all  classical  and  the  groff  text
         devices.   The few groff devices with a sizescale parameter either did not exist, had a different name,
         or seem to have had a different resolution.  So conflicts with classical devices are very unlikely.

       • The position changing after the commands Dp, DP, and Dt is illogical, but as old versions of groff used
         this feature it is kept for compatibility reasons.

       The differences between groff and classical troff are documented in groff_diff(7).

FILES

       /usr/share/groff/1.22.3/font/devname/DESC
              Device description file for device name.

       ⟨groff-source-dir⟩/src/libs/libdriver/input.cpp
              Defines  the  parser and postprocessor for the intermediate output.  It is located relative to the
              top directory of the groff source tree.  This parser is the definitive specification of the  groff
              intermediate output format.

SEE ALSO

       A  reference like groff(7) refers to a manual page; here groff in section 7 of the man-page documentation
       system.  To read the example, look up section 7 in your desktop help system or call from the shell prompt

              shell> man 7 groff

       For more details, see man(1).

       groff(1)
              option -Z and further readings on groff.

       groff(7)
              for details of the groff language such as numerical units and escape sequences.

       groff_font(5)
              for details on the device scaling parameters of the DESC file.

       troff(1)
              generates the device-independent intermediate output.

       roff(7)
              for historical aspects and the general structure of roff systems.

       groff_diff(7)
              The differences between the intermediate output in groff and classical troff.

       gxditview(1)
              Viewer for the intermediate output.

       grodvi(1), grohtml(1), grolbp(1), grolj4(1), grops(1), grotty(1)
              the groff postprocessor programs.

       For a treatment of all aspects of the groff system within a single document, see the groff info file.  It
       can be read within the integrated help systems, within emacs(1) or from the shell prompt by
              shell> info groff

       The  classical  troff output language is described in two AT&T Bell Labs CSTR documents available on-line
       at Bell Labs CSTR site ⟨http://cm.bell-labs.com/cm/cs/cstr.html⟩.

       [CSTR #97]
              A Typesetter-independent  TROFF  by  Brian  Kernighan  is  the  original  and  most  comprehensive
              documentation on the output language; see CSTR #97 ⟨http://cm.bell-labs.com/cm/cs/cstr/97.ps.gz⟩.

       [CSTR #54]
              The  1992  revision of the Nroff/Troff User's Manual by J. F. Ossanna and Brian Kernighan isn't as
              comprehensive as [CSTR #97] regarding the output language; see CSTR #54  ⟨http://cm.bell-labs.com/
              cm/cs/cstr/54.ps.gz⟩.

COPYING

       Copyright © 1989-2014 Free Software Foundation, Inc.

       This file is part of groff, the GNU roff type-setting system, which is a free software project.

       Permission  is  granted  to  copy, distribute and/or modify this document under the terms of the GNU Free
       Documentation License, Version 1.3 or any later version published by the Free Software  Foundation;  with
       no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.

       A  copy  of  the Free Documentation License is included as a file called FDL in the main directory of the
       groff source package, it is also available in  the  internet  at  GNU  FDL  license  ⟨http://www.gnu.org/
       copyleft/fdl.html⟩.

AUTHORS

       In 2001, this document was rewritten from scrach by Bernd Warken ⟨groff-bernd.warken-72@web.de⟩.