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     grap - Kernighan and Bentley’s language for typesetting graphs


     grap [-d defines_file] [-D] [-l] [-M include path] [-R] [-r] [-v] [-u]
          [-C] [-c] [-h] [filename ...]


     grap is an implementation of Kernighan and Bentley’s language for
     typesetting graphs, as described in ‘‘Grap-A Language for Typesetting
     Graphs, Tutorial and User Manual,’’ by Jon L. Bentley and Brian W.
     Kernighan, revised May 1991, which is the primary source for information
     on how to use grap.  As of this writing, it is available electronically
     at  Additional
     documentation and examples, packaged with grap, may have been installed
     locally as well.  If available, paths to them can be displayed using grap
     -h or grap -v (or grap --help / grap --version)

     This version is a black box implementation of grap, and some
     inconsistencies are to be expected.  The remainder of this manual page
     will briefly outline the grap language as implemented here.

     grap is a pic(1) pre-processor.  It takes commands embedded in a troff(1)
     source file which are surrounded by .G1 and .G2 macros, and rewrites them
     into pic commands to display the graph.  Other lines are copied.  Output
     is always to the standard output, which is usually redirected.  Input is
     from the given filenames, which are read in order.  A filename of - is
     the standard input.  If no filenames are given, input is read from the
     standard input.

     Because grap is a pic preprocessor, and GNU pic will output TeX, it is
     possible to use grap with TeX.

     The -d option specifies a file of macro definitions to be read at
     startup, and defaults to /usr/share/grap/grap.defines .  The -D option
     inhibits the reading of any initial macros file (the -l flag is a synonym
     for -D, though I do not remember why).  The defines file can also be
     given using the GRAP_DEFINES environment variable. (See below).

     -v prints the version information on the standard output and exits.
     --version is a synonym for -v.

     -u makes labels unaligned by default.  This version of grap uses new
     features of GNU pic to align the left and right labels with the axes,
     that is that the left and right labels run at right angles to the text of
     the paper.  This may be useful in porting old grap programs.  -c makes
     plot strings unclipped by default.  Some versions of grap allow users to
     place a string anywhere in the coordinate space, rather than only in the
     frame.  By default this version of grap does not plot any string centered
     outside the frame.  -c allows strings to be placed anywhere.  See also
     the clipped and unclipped string modifiers described in the plot

     -M is followed by a colon-separated list of directories used to search
     for relative pathnames included via copy.  The path is also used to
     locate the defines file, so if the -d changes the defines file name to a
     relative name, it will be searched for in the path given by -M.  The
     search path always includes the current directory, and by default that
     directory is searched last.

     All numbers used internally by grap are double precision floating point
     values.  Sometimes using floating point numbers has unintended
     consequences.  To help avoid these problems, grap can use two thresholds
     for comparison of floating point numbers, set by -R or -r.  The -R flag
     sets coarse comparison mode, which is suitable for most applications.  If
     you are plotting small values – less than 1e-6 or so – consider using -r
     which uses very fine comparisons between numbers.  You may also want to
     rescale your plotted values to be larger in magnitude. The coarse
     comarisons are used by default.

     To be precise, the value by which two numbers must differ for grap to
     consider them not equal is called the comparison limit and the smallest
     non-zero number is called the minimum value.  The values a given version
     of grap uses for these are included in the output of -v or -h.

     All grap commands are included between .G1 and .G2 macros, which are
     consumed by grap.  The output contains pic between .PS and .PE macros.
     Any arguments to the .G1 macro in the input are arguments to the .PS
     macro in the output, so graphs can be scaled just like pic diagrams.  If
     -C is given, any macro beginning with .G1 or .G2 is treated as a .G1 or
     .G2 macro, for compatibility with old versions of troff.  Using -C also
     forces pure troff syntax on embedded font change commands when strings
     have the size attribute, and all strings to be unclipped.

     The -h flag prints a brief help message and exits.  --help is a synonym
     for -h.

     It is possible for someone to cause grap to fail by passing a bad format
     string and data to the sprintf command.  If grap is integrated as part of
     the printing system, this could conceivably provided a path to breaching
     security on the machine.  If you choose to use grap as part of a printing
     system run by the super-user, you should disable sprintf commands.  This
     can be done by calling grap with the -S flag, setting the GRAP_SAFER
     environment variable, or compiling with the GRAP_SAFER preprocessor
     symbol defined.  (The GNU configure script included with grap will define
     that preprocessor symbol if the --with-grap-safe option is given.)

     The grap commands are sketched below.  Refer to Kernighan and Bentley’s
     paper for the details.

     New versions of groff(1) will invoke grap if -G is given.

     Commands are separated from one another by newlines or semicolons (;).

     frame [line_description] [ht height | wid width] [[(top|bottom|left|
     right) line_description] ...]

     frame [ht height | wid width] [line_description] [[(top|bottom|left|
     right) line_description] ...]

           This  describes  how  the  axes  for  the  graph   are   drawn.   A
           line_description  is  a  pic line description, e.g., dashed 0.5, or
           the literal solid.  It may also include a color keyword followed by
           the  color  to  draw  the  string  in  double  quotes.   Any  color
           understood by the underlying groff system can be used.   Color  can
           only  be  used under GNU pic, and is not available in compatibility
           mode.   Similarly,  for   pic   implementations   that   understand
           thickness, that attribute may be used with a real valued parameter.
           Thickness is not available in compatibility mode.

           If the first line_description is given, the  frame  is  drawn  with
           that  style.   The  default  is solid.  The height and width of the
           frame can also be specified in inches.  The default line style  can
           be  over-ridden  for  sides  of  the frame by specifying additional
           parameters to frame.

           If no plotting commands have been given before the frame command is
           issued,  the  frame  will  be  output at that point in the plotting
           stream relative to embedded troff or pic commands.   Otherwise  the
           frame  is  output  before  the first plotted object (even invisible

           ht and wid are in inches by default, but can be any groff unit.  If
           omitted, the dimensions are 2 inches high by 3 inches wide.

     coord [name] [x expr, expr] [y expr, expr] [log x | log y | log log]

           The  coord command specifies a new coordinate system or sets limits
           on the default system.  It defines the largest and smallest  values
           that  can  be  plotted,  and therefore the scale of the data in the
           frame.  The limits for the x and y coordinate systems can be  given
           separately.  If a name is given, that coordinate system is defined,
           if not the default system is modified.

           A coordinate system created by one coord command may be modified by
           subsequent coord commands.  A grap program may declare a coordinate
           space using coord, copy a file of data through a macro  that  plots
           the  data and finds its maxima and minima, and then define the size
           of the coordinate system with a second coord statement.

           This command also determines if a scale is plotted logarithmically.
           log log means the same thing as log x log y.

     draw [line_name] [line_description] [plot_string]

           The  draw command defines the style with which a given line will be
           plotted.  If line_name is given, the style is associated with  that
           name,  otherwise  the  default style is set.  line_description is a
           pic line description, and the optional plot_string is a  string  to
           be  centered at each point.  The default line description is invis,
           and the default plotting string is a centered bullet, so by default
           each point is a filled circle, and they are unconnected.  If points
           are being connected, each draw command ends any  current  line  and
           begins a new one.

           When  defining  a  line style, that is the first draw command for a
           given line name, specifying no plot string means that there are  to
           be  no  plot  strings.  Omitting the plot string on subsequent draw
           commands addressing the same named line means  not  to  change  the
           plot  string.   If  a line has been defined with a plot string, and
           the format is changed by a  subsequent  draw  statement,  the  plot
           string can be removed by specifying "" in the draw statement.

           The  plot  string  can  have  its  format  changed  through several
           string_modifiers.    String_modifiers   are   described   in    the
           description of the plot command.

           The  standard  defines  file includes several macros useful as plot
           strings, including bullet, square, and delta.

           new is a synonym for draw.

     next [line_name] at [coordinates_name] expr, expr [line_description]

           The next command plots the given point using the line  style  given
           by  line_name,  or  the  default if none is given.  If line_name is
           given, it should have been defined by an earlier draw  command,  if
           not  a  new  line  style with that name is created, initialized the
           same way as the  default  style.   The  two  expressions  give  the
           point’s x and y values, relative to the optional coordinate system.
           That system should have been defined by an earlier  coord  command,
           if not, grap will exit.  If the optional line_description is given,
           it overrides the style’s  default  line  description.   You  cannot
           over-ride  the plotting string.  To use a different plotting string
           use the plot command.

           The coordinates may optionally be enclosed in  parentheses:  (expr,

     quoted_string [string_modifiers] [, quoted_string [string_modifiers]] ...
     at [coordinates_name] expr, expr

     plot expr [format_string] at [coordinates_name] expr, expr

           These commands both plot a string at the given point.  In the first
           case  the  literal  strings  are  stacked  above  each  other.  The
           string_modifiers include the pic  justification  modifiers  (ljust,
           rjust, above, and below), and absolute and relative size modifiers.
           See the pic documentation for the description of the  justification
           modifiers.   grap also supports the aligned and unaligned modifiers
           which are briefly noted in the description of the label command.

           The standard defines file includes several macros  useful  as  plot
           strings, including bullet, square, and delta.

           Strings  placed by either format of the plot command are restricted
           to being within the frame.  This can  be  overriden  by  using  the
           unclipped  attribute, which allows a string to be plotted in or out
           of the frame.  The -c and -C flags set unclipped  on  all  strings,
           and  to  prevent a string from being plotted outside the frame when
           those flags are active, the clipped attribute can be used to retore
           clipping  behavior.   Though clipped or unclipped can be applied to
           any string, it only has meaning for plot statements.

           size expr sets the string size to expr points.  If expr is preceded
           by  a  +  or  -,  the  size  is increased or decreased by that many

           If color and a color name in double quotes appears, the string will
           be  rendered  in  that  color  under  a  version  of GNU troff that
           supports color.  Color is not available in compatibility mode.

           In the second version, the expr is converted to a string and placed
           on  the  graph.   format_string is a printf(3) format string.  Only
           formatting escapes for printing floating point numbers make  sense.
           The  format string is only respected if the sprintf command is also
           active.  See the description of sprintf for  the  various  ways  to
           disable  it.   Plot  and  sprintf  respond differently when grap is
           running safely.  Sprintf ignores any arguments, passing the  format
           string  through  without  substitution.   plot  ignores  the format
           string completely, plotting expr using the "%g" format.

           Points are specified the same way as for next  commands,  with  the
           same consequences for undefined coordinate systems.

           The  second  form  of this command is because the first form can be
           used with a grap sprintf expression (See Expressions).

     ticks (left|right|top|bottom)[ (in|out) [expr]] [on|auto coord_name]

     ticks (left|right|top|bottom) (in|out) [expr] [up expr | down expr | left
     expr | right expr] at [coord_name] expr [format_string] [[, expr
     [format_string]] ...]

     ticks (left|right|top|bottom) (in|out) [expr] [up expr | down expr | left
     expr | right expr] from [coord_name] start_expr to end_expr [by [+|-|*|/]
     by_expr] [format_string]

     ticks [left|right|top|bottom] off

           This command controls the placement of  ticks  on  the  frame.   By
           default,  ticks  are automatically generated on the left and bottom
           sides of the frame.

           The first version of this  command  turns  on  the  automatic  tick
           generation  for a given side.  The in or out parameter controls the
           direction and length of the ticks.  If a coord_name  is  specified,
           the ticks are automatically generated using that coordinate system.
           If no system is specified, the default coordinate system  is  used.
           As  with  next  and  plot,  the  coordinate system must be declared
           before the ticks statement that references  it.   This  syntax  for
           requesting  automatically generated ticks is an extension, and will
           not port to older grap implementations.

           The second version of the ticks  command  overrides  the  automatic
           placement of the ticks by specifying a list of coordinates at which
           to place the ticks.  If the ticks are not defined with  respect  to
           the  default  coordinate  system,  the coord_name parameter must be
           given.  For each tick a printf(3) style format string can be given.
           The  format_string  defaults  to  "%g".  The format string can also
           take string modifiers as described in the plot command.   To  place
           ticks with no labels, specify format_string as "".

           If  sprintf  is disabled, ticks behaves as plot with respect to the
           format string.

           The labels on the ticks may be shifted by  specifying  a  direction
           and  the  distance  in  inches  to  offset  the label.  That is the
           optional direction and expression immediately preceding the at.

           The third format of the ticks command over-rides the  default  tick
           generation with a set of ticks ar regular intervals.  The syntax is
           reminiscent of programming language for loops.   Ticks  are  placed
           starting  at  start_expr ending at end_expr one unit apart.  If the
           by clause is specified, ticks  are  by_expr  units  apart.   If  an
           operator  appears  before  by_expr each tick is operated on by that
           operator instead of +.  For example

                       ticks left out from 2 to 32 by *2

           will put ticks at 2,  4,  8,  16,  and  32.   If  format_string  is
           specified, all ticks are formatted using it.

           The parameters preceding the from act as described above.

           The at and for forms of tick command may both be issued on the same
           side of a frame.  For example:

                       ticks left out from 2 to 32 by *2
                       ticks left in 3, 5, 7

           will put ticks on the left side of the frame pointing out at 2,  4,
           8, 16, and 32 and in at 3, 5, and 7.

           The  final  form  of  ticks turns off ticks on a given side.  If no
           side is given the ticks for all sides are cancelled.

           tick is a synonym for ticks.

     grid (left|right|top|bottom) [ticks off] [line_description] [up expr |
     down expr | left expr | right expr] [on|auto [coord_name]]

     grid (left|right|top|bottom) [ticks off] [line_description] [up expr |
     down expr | left expr | right expr] at [coord_name] expr [format_string]
     [[, expr [format_string]] ...]

     grid (left|right|top|bottom) [ticks off] [line_description] [up expr |
     down expr | left expr | right expr] from [coord_name] start_expr to
     end_expr [by [+|-|*|/] by_expr] [format_string]

           The  grid  command is similar to the ticks command except that grid
           specifies the placement of lines  in  the  frame.   The  syntax  is
           similar to ticks as well.

           By  specifying ticks off in the command, no ticks are drawn on that
           side of the frame.  If ticks appear on a side by default,  or  have
           been  declared  by  an  earlier ticks command, grid does not cancel
           them unless ticks off is specified.

           Instead of a direction for ticks, grid allows the user  to  pick  a
           line   description   for  the  grid  lines.   The  usual  pic  line
           descriptions are allowed.

           Grids are labelled by default.  To omit labels, specify the  format
           string as "".

           If  sprintf  is  disabled, grid behaves as plot with respect to the
           format string.

     label (left|right|top|bottom) quoted_string [string_modifiers] [,
     quoted_string [string_modifiers]] ...  [up expr | down expr | left expr |
     right expr]

           The label command places a label on the given axis.  It is possible
           to specify several labels, which will be stacked over each other as
           in pic.  The final argument, if present, specifies how many  inches
           the label is shifted from the axis.

           By  default the labels on the left and right labels run parallel to
           the frame.  You can  cancel  this  by  specifying  unaligned  as  a

     circle at [coordinate_name] expr, expr [radius expr] [linedesc]

           This  draws  an  circle  at  the  point indicated.  By default, the
           circle  is  small,  0.025  inches.   This  can  be  over-ridden  by
           specifying  a radius.  The coordinates of the point are relative to
           the named coordinate system, or  the  default  system  if  none  is

           This  command  has  been extended to take a line description, e.g.,
           dotted.  It also accepts the filling extensions described below  in
           the  bar  command.   It will also accept a color keyword that gives
           the color of the outline of the  circle  in  double  quotes  and  a
           fillcolor  command  that  sets  the  color  to fill the circle with
           similarly.  Colors are only available when  compatibility  mode  is
           off, and using a version of GNU pic that supports color.

     line [line_description] from [coordinate_name] expr, expr to
     [coordinate_name] expr, expr [line_description]

     arrow [line_description] from [coordinate_name] expr, expr to
     [coordinate_name] expr, expr [line_description]

           This draws a line or arrow from the first point to the second using
           the  given  style.   The  default  line  style   is   solid.    The
           line_description  can  be given either before the from or after the
           to clause.  If both are given the second is used.  It  is  possible
           to  specify  one point in one coordinate system and one in another,
           note that if both points are in a named coordinate system (even  if
           they  are  in  the  same named coordinate system), both points must
           have coordinate_name given.

     copy ["filename"] [until "string"] [thru macro]

           The copy command imports data from another file  into  the  current
           graph.   The  form  with  only  a  filename  given is a simple file
           inclusion; the included file is simply read into the  input  stream
           and  can  contain arbitrary grap commands.  The more common case is
           that it is a number list; see Number Lists below.

           The second form takes lines from the file, splits them  into  words
           delimited  by  one  or  more spaces, and calls the given macro with
           those words as parameters.  The macro may either be  defined  here,
           or  be a macro defined earlier.  See Macros for more information on

           The filename may be omitted if the until clause is present.  If  so
           the  current  file  is  treated  as  the input file until string is
           encountered at the beginning of the line.

           copy is one of the workhorses of grap.  Check  out  the  paper  and
           /usr/share/doc/grap/examples   for   more   details.   Confirm  the
           location of the examples directory using the -v flag.
     print (expr|string)

           Prints its argument to the standard error.

     sh block

           This passes block to sh(1).  Unlike K&B grap no macro  or  variable
           expansion  is  done.   I believe that this is also true for GNU pic
           version 1.10.  See the Macros section for information  on  defining

     pic pic_statement

           This  issues the given pic statements  in the enclosing .PS and .PE
           at the point where the command is issued.

           Statements  that  begin  with  a  period  are  considered   to   be
           troff(statements)  and  are  output in the enclosing .PS and .PE at
           the point where the command appears.

           For the purposes of relative placement of pic  or  troff  commands,
           the frame is output immediately before the first plotted object, or
           the frame statement, if any.  If the user specifies  pic  or  troff
           commands  and  neither any plotable object nor a frame command, the
           commands will not be output.

     graph Name pic_commands

           This command is used to position graphs with respect to each other.
           The  current  graph  is  given the pic name Name (names used by pic
           begin with capital letters).  Any pic commands following the  graph
           are  used  to  position  the next graph.  The frame of the graph is
           available for use with pic  name  Frame.  The  following  places  a
           second graph below the first:

                       graph Linear
                       [ graph description ]
                       graph Exponential with .Frame.n at \
                               Linear.Frame.s - (0, .05)
                       [ graph description ]

     name = expr

           This  assigns  expr  to  the  variable name.  grap has only numeric
           (double) variables.

           Assignment creates a variable if  it  does  not  exist.   Variables
           persist across graphs.  Assignments can cascade; a = b = 35 assigns
           35 to a and b.

     bar (up|right) [coordinates_name] offset ht height [wid width] [base
     base_offset] [line_description]

     bar [coordinates_name] expr, expr, [coordinates_name] expr, expr,

           The bar command facilitates drawing bar graphs.  The first form  of
           the command describes the bar somewhat generally and has grap place
           it.  The bar may extend up or to the right, is centered  on  offset
           and  extends  up  or  right  height  units (in the given coordinate
           system).  For example

                       bar up 3 ht 2

           draws a 2 unit high bar sitting on the x axis, centered on x=3.  By
           default  bars are 1 unit wide, but this can be changed with the wid
           keyword.  By default bars sit on the base axis, i.e., bars directed
           up  will  extend  from  y=0.   That  may  be overridden by the base
           keyword.  (The bar described above has corners (2.5, 0)  and  (3.5,

           The  line  description  has  been  extended  to include a fill expr
           keyword that specifies the shading inside the  bar.   Bars  may  be
           drawn  in  any  line  style.   They support the color and fillcolor
           keywords described under circle.

           The second form of the command draws a box with the two  points  as
           corners.   This can be used to draw boxes highlighting certain data
           as well as bar graphs.  Note that filled bars will cover data drawn
           under them.

   Control Flow
     if expr then block [else block]

           The if statement provides simple conditional execution.  If expr is
           non-zero, the block after the then statement is executed.   If  not
           the  block  after the else is executed, if present.  See Macros for
           the definition of blocks.  Early versions of this implementation of
           grap treated the blocks as macros that were defined and expanded in
           place.   This  led  to  unnecessary  confusion   because   explicit
           separators   were  sometimes  called  for.   Now,  grap  inserts  a
           separator (;) after the last character in block, so constructs like

           if (x == 3) { y = y + 1 }
           x = x + 1

           behave  as  expected.  A separator is also appended to the end of a
           for block.

     for name from from_expr to to_expr [by [+|-|*|/] by_expr] do block

           This command executes block iteratively.  The variable name is  set
           to  from_expr  and incremented by by_expr until it exceeds to_expr.
           The iteration has the semantics defined in the ticks command.   The
           definition  of  block  is  discussed  in Marcos.  See also the note
           about implicit separators in the description of the if command.

           An = can be used in place of from.

     grap supports most standard arithmetic operators: + - / * ^.  The carat
     (^) is exponentiation.  In an if statement grap also supports the C
     logical operators ==, !=, &&, || and unary !.  Also in an if, == and !=
     are overloaded for the comparison of quoted strings.  Parentheses are
     used for grouping.

     Assignment is not allowed in an expression in any context, except for
     simple cascading of assignments.  a = b = 35 works as expected; a = 3.5 *
     (b = 10) does not execute.

     grap supports the following functions that take one argument: log, exp,
     int, sin, cos, sqrt, rand.  The logarithms are base 10 and the
     trigonometric functions are in radians.  eexp returns Euler’s number to
     the given power and ln returns the natural logarithm.  The natural log
     and exponentiation functions are extensions and are probably not
     available in other grap implementations.

     rand returns a random number uniformly distributed on [0,1).  The
     following two-argument functions are supported: atan2, min, max.  atan2
     works just like atan2(3).  The random number generator can be seeded by
     calling srand with a single parameter (converted internally to an
     integer).  Because its return value is of no use, you must use srand as a
     separate statement, it is not part of a valid expression.  srand is not

     The getpid function takes no arguments and returns the process id.  This
     may be used to seed the random number generator, but do not expect
     cryptographically random values to result.

     Other than string comparison, no expressions can use strings.  One string
     valued function exists: sprintf (format, [expr [, expr]] ).  It operates
     like sprintf(3), except returning the value.  It can be used anywhere a
     quoted string is used.  If grap is run with -S, the environment variable
     GRAP_SAFER is defined, or grap has been compiled for safer operation, the
     sprintf command will return the format string.  This mode of operation is
     only intended to be used only if grap is being used as part of a super-
     user enabled print system.

     grap has a simple but powerful macro facility.  Macros are defined using
     the define command :

     define name block
     undefine name

           Every  occurrence  of  name  in the program text is replaced by the
           contents of block.  block is defined by a series of  statements  in
           nested  {  }’s,  or  a  series of statements surrounded by the same
           letter.  An example of the latter is

                       define foo  X coord x 1,3 X
           Each time foo appears in the text, it will be replaced by  coord  x
           1,3.   Macros  are  literal,  and can contain newlines.  If a macro
           does not span multiple lines, it should end in a semicolon to avoid
           parsing errors.

           Macros  can take parameters, too.  If a macro call is followed by a
           parenthesized, comma-separated list the  values  starting  with  $1
           will  be  replaced in the macro with the elements of the list.  A $
           not followed by a digit is left unchanged.  This  parsing  is  very
           rudimentary;  no  nesting  or  parentheses or escaping of commas is
           allowed.  Also, there is no way to say argument  1  followed  by  a
           digit (${1}0 in sh(1)).

           The following will draw a line with slope 1.

                       define foo { next at $1, $2 }
                       for i from 1 to 5 { foo(i,i) }
           Macros       persist       across       graphs.       The      file
           /usr/share/grap/grap.defines contains simple  macros  for  plotting
           common characters.  The undefine command deletes a macro.

           See the directory /usr/share/doc/grap/examples for more examples of
           macros.  Confirm the location of the examples directory  using  the
           -v flag.

   Number Lists
     A whitespace-separated list of numbers is treated specially.  The list is
     taken to be points to be plotted using the default line style on the
     default coordinate system.  If more than two numbers are given, the extra
     numbers are taken to be additional y values to plot at the first x value.
     Number lists in DWB grap can be comma-separated, and this grap supports
     that as well.  More precisely, numbers in number lists can be separated
     by either whitespace, commas, or both.

           1 2 3
           4 5 6

     Will plot points using the default line style at (1,2), (1,3),(4,5) and
     (4,6).  A simple way to plot a set of numbers in a file named ./data is:

           copy "./data"

   Pic Macros
     grap defines pic macros that can be used in embedded pic code to place
     elements in the graph.  The macros are x_gg, y_gg, and xy_gg.  These
     macros define pic distances that correspond to the given argument.  They
     can be used to size boxes or to plot pic constructs on the graph.  To
     place a given construct on the graph, you should add Frame.Origin to it.
     Other coordinate spaces can be used by replacing gg with the name of the
     coordinate space.  A coordinate space named gg cannot be reliably
     accessed by these macros.

     The macros are emitted immediately before the frame is drawn.

     DWB grap may use these as part of its implementation.  This grap provides
     them only for compatibility.  Note that these are very simple macros, and
     may not do what you expect under complex conditions.


     If the environment variable GRAP_DEFINES is defined, grap will look for
     its defines file there.  If that value is a relative path name the path
     specified in the -M option will be searched for it.  GRAP_DEFINES
     overrides the compiled in location of the defines file, but may be
     overridden by the -d or -D flags.

     If GRAP_SAFER is set, sprintf is disabled to prevent forcing grap to core
     dump or smash the stack.




     atan2(3), groff(1), pic(1), printf(3), sh(1), sprintf(3), troff(1)

     If documentation and examples have been installed, grap --version or grap
     --help will display the locations.


     There are several small incompatibilities with K&R grap.  They include
     the sh command not expanding variables and macros, and a more strict
     adherence to parameter order in the internal commands.

     Although much improved, the error reporting code can still be confused.
     Notably, an error in a macro is not detected until the macro is used, and
     it produces unusual output in the error message.

     Iterating many times over a macro with no newlines can run grap out of


     This implementation was done by Ted Faber 〈〉.  Bruce
     Lilly 〈〉 contributed many bug fixes, including a
     considerable revamp of the error reporting code.  If you can actually
     find an error in your grap code, you can probably thank him.  grap was
     designed and specified by Brian Kernighan and Jon Bentley.