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GRN(1) General Commands Manual GRN(1)

NAME
grn - groff preprocessor for gremlin files

SYNOPSIS
grn [-Cv] [-T dev] [-M dir] [-F dir] [file ...]

DESCRIPTION
grn is a preprocessor for including gremlin pictures in groff input. grn writes to standard
output, processing only input lines between two that start with .GS and .GE. Those lines
must contain grn commands (see below). These commands request a gremlin file, and the pic‐
ture in that file is converted and placed in the troff input stream. The .GS request may be
followed by a C, L, or R to center, left, or right justify the whole gremlin picture (default
justification is center). If no file is mentioned, the standard input is read. At the end
of the picture, the position on the page is the bottom of the gremlin picture. If the grn
entry is ended with .GF instead of .GE, the position is left at the top of the picture.

Please note that currently only the -me macro package has support for .GS, .GE, and .GF.

OPTIONS
Whitespace is permitted between a command-line option and its argument.

-Tdev Prepare output for printer dev. The default device is ps. See groff(1) for accept‐
able devices.

-Mdir Prepend dir to the default search path for gremlin files. The default path is (in
that order) the current directory, the home directory, /usr/lib/groff/site-tmac, /usr/
share/groff/site-tmac, and /usr/share/groff/1.22.4/tmac.

-Fdir Search dir for subdirectories devname (name is the name of the device) for the DESC
file before the default font directories /usr/share/groff/site-font, /usr/share/groff/
1.22.4/font, and /usr/lib/font.

-C Recognize .GS and .GE (and .GF) even when followed by a character other than space or
newline.

-v Print the version number.

GRN COMMANDS
Each input line between .GS and .GE may have one grn command. Commands consist of one or two
strings separated by white space, the first string being the command and the second its oper‐
and. Commands may be upper or lower case and abbreviated down to one character.

Commands that affect a picture's environment (those listed before default, see below) are
only in effect for the current picture: The environment is reinitialized to the defaults at
the start of the next picture. The commands are as follows:

1 N
2 N
3 N
4 N Set gremlin's text size number 1 (2, 3, or 4) to N points. The default is 12 (16, 24,
and 36, respectively).

roman f
italics f
bold f
special f
Set the roman (italics, bold, or special) font to troff's font f (either a name or
number). The default is R (I, B, and S, respectively).

l f
stipple f
Set the stipple font to troff's stipple font f (name or number). The command stipple
may be abbreviated down as far as ‘st’ (to avoid confusion with special). There is no
default for stipples (unless one is set by the default command), and it is invalid to
include a gremlin picture with polygons without specifying a stipple font.

x N
scale N
Magnify the picture (in addition to any default magnification) by N, a floating point
number larger than zero. The command scale may be abbreviated down to ‘sc’.

narrow N
medium N
thick N
Set the thickness of gremlin's narrow (medium and thick, respectively) lines to N
times 0.15pt (this value can be changed at compile time). The default is 1.0 (3.0 and
5.0, respectively), which corresponds to 0.15pt (0.45pt and 0.75pt, respectively). A
thickness value of zero selects the smallest available line thickness. Negative val‐
ues cause the line thickness to be proportional to the current point size.

pointscale <off/on>
Scale text to match the picture. Gremlin text is usually printed in the point size
specified with the commands 1, 2, 3, or 4, regardless of any scaling factors in the
picture. Setting pointscale will cause the point sizes to scale with the picture
(within troff's limitations, of course). An operand of anything but off will turn
text scaling on.

default
Reset the picture environment defaults to the settings in the current picture. This
is meant to be used as a global parameter setting mechanism at the beginning of the
troff input file, but can be used at any time to reset the default settings.

width N
Forces the picture to be N inches wide. This overrides any scaling factors present in
the same picture. ‘width 0’ is ignored.

height N
Forces picture to be N inches high, overriding other scaling factors. If both ‘width’
and ‘height’ are specified the tighter constraint will determine the scale of the pic‐
ture. Height and width commands are not saved with a default command. They will,
however, affect point size scaling if that option is set.

file name
Get picture from gremlin file name located the current directory (or in the library
directory; see the -M option above). If two file commands are given, the second one
overrides the first. If name doesn't exist, an error message is reported and process‐
ing continues from the .GE line.

NOTES ABOUT GROFF
Since grn is a preprocessor, it doesn't know about current indents, point sizes, margins,
number registers, etc. Consequently, no troff input can be placed between the .GS and .GE
requests. However, gremlin text is now processed by troff, so anything valid in a single
line of troff input is valid in a line of gremlin text (barring ‘.’ directives at the begin‐
ning of a line). Thus, it is possible to have equations within a gremlin figure by including
in the gremlin file eqn expressions enclosed by previously defined delimiters (e.g. $$).

When using grn along with other preprocessors, it is best to run tbl before grn, pic, and/or
ideal to avoid overworking tbl. Eqn should always be run last.

A picture is considered an entity, but that doesn't stop troff from trying to break it up if
it falls off the end of a page. Placing the picture between ‘keeps’ in -me macros will en‐
sure proper placement.

grn uses troff's number registers g1 through g9 and sets registers g1 and g2 to the width and
height of the gremlin figure (in device units) before entering the .GS request (this is for
those who want to rewrite these macros).

GREMLIN FILE FORMAT
There exist two distinct gremlin file formats, the original format from the AED graphic ter‐
minal version, and the SUN or X11 version. An extension to the SUN/X11 version allowing ref‐
erence points with negative coordinates is not compatible with the AED version. As long as a
gremlin file does not contain negative coordinates, either format will be read correctly by
either version of gremlin or grn. The other difference from SUN/X11 format is the use of
names for picture objects (e.g., POLYGON, CURVE) instead of numbers. Files representing the
same picture are shown in Table 1 in each format.

sungremlinfile gremlinfile
0 240.00 128.00 0 240.00 128.00
CENTCENT 2
240.00 128.00 240.00 128.00
185.00 120.00 185.00 120.00
240.00 120.00 240.00 120.00
296.00 120.00 296.00 120.00
* -1.00 -1.00
2 3 2 3
10 A Triangle 10 A Triangle
POLYGON 6
224.00 416.00 224.00 416.00
96.00 160.00 96.00 160.00
384.00 160.00 384.00 160.00
* -1.00 -1.00
5 1 5 1
0 0
-1 -1

Table 1. File examples

• The first line of each gremlin file contains either the string gremlinfile (AED ver‐
sion) or sungremlinfile (SUN/X11)

• The second line of the file contains an orientation, and x and y values for a posi‐
tioning point, separated by spaces. The orientation, either 0 or 1, is ignored by the
SUN/X11 version. 0 means that gremlin will display things in horizontal format (draw‐
ing area wider than it is tall, with menu across top). 1 means that gremlin will dis‐
play things in vertical format (drawing area taller than it is wide, with menu on left
side). x and y are floating point values giving a positioning point to be used when
this file is read into another file. The stuff on this line really isn't all that im‐
portant; a value of “1 0.00 0.00” is suggested.

• The rest of the file consists of zero or more element specifications. After the last
element specification is a line containing the string “-1”.

• Lines longer than 127 characters are chopped to this limit.

ELEMENT SPECIFICATIONS
• The first line of each element contains a single decimal number giving the type of the
element (AED version) or its ASCII name (SUN/X11 version). See Table 2.

gremlin File Format − Object Type Specification

AED Number SUN/X11 Name Description
0 BOTLEFT bottom-left-justified text
1 BOTRIGHT bottom-right-justified text
2 CENTCENT center-justified text
3 VECTOR vector
4 ARC arc
5 CURVE curve
6 POLYGON polygon
7 BSPLINE b-spline
8 BEZIER Bézier
10 TOPLEFT top-left-justified text
11 TOPCENT top-center-justified text
12 TOPRIGHT top-right-justified text

13 CENTLEFT left-center-justified text
14 CENTRIGHT right-center-justified text
15 BOTCENT bottom-center-justified text

Table 2.
Type Specifications in gremlin Files

• After the object type comes a variable number of lines, each specifying a point used
to display the element. Each line contains an x-coordinate and a y-coordinate in
floating point format, separated by spaces. The list of points is terminated by a
line containing the string “-1.0 -1.0” (AED version) or a single asterisk, “*”
(SUN/X11 version).

• After the points comes a line containing two decimal values, giving the brush and size
for the element. The brush determines the style in which things are drawn. For vec‐
tors, arcs, and curves there are six valid brush values:

1 − thin dotted lines
2 − thin dot-dashed lines
3 − thick solid lines
4 − thin dashed lines
5 − thin solid lines
6 − medium solid lines

For polygons, one more value, 0, is valid. It specifies a polygon with an invisible
border. For text, the brush selects a font as follows:

1 − roman (R font in groff)
2 − italics (I font in groff)
3 − bold (B font in groff)
4 − special (S font in groff)

If you're using grn to run your pictures through groff, the font is really just a
starting font: The text string can contain formatting sequences like “\fI” or “\d”
which may change the font (as well as do many other things). For text, the size field
is a decimal value between 1 and 4. It selects the size of the font in which the text
will be drawn. For polygons, this size field is interpreted as a stipple number to
fill the polygon with. The number is used to index into a stipple font at print time.

• The last line of each element contains a decimal number and a string of characters,
separated by a single space. The number is a count of the number of characters in the
string. This information is only used for text elements, and contains the text
string. There can be spaces inside the text. For arcs, curves, and vectors, this
line of the element contains the string “0”.

NOTES ON COORDINATES
gremlin was designed for AEDs, and its coordinates reflect the AED coordinate space. For
vertical pictures, x-values range 116 to 511, and y-values from 0 to 483. For horizontal
pictures, x-values range from 0 to 511 and y-values range from 0 to 367. Although you
needn't absolutely stick to this range, you'll get best results if you at least stay in this
vicinity. Also, point lists are terminated by a point of (-1, -1), so you shouldn't ever use
negative coordinates. gremlin writes out coordinates using format “%f1.2”; it's probably a
good idea to use the same format if you want to modify the grn code.

NOTES ON SUN/X11 COORDINATES
There is no longer a restriction on the range of coordinates used to create objects in the
SUN/X11 version of gremlin. However, files with negative coordinates will cause problems if
displayed on the AED.

FILES
/usr/share/groff/1.22.4/font/devname/DESC
Device description file for device name.

AUTHORS
David Slattengren and Barry Roitblat wrote the original Berkeley grn. Daniel Senderowicz and
Werner Lemberg modified it for groff.

SEE ALSO
gremlin(1), groff(1), pic(1), ideal(1)

groff 1.22.4 23 March 2022 GRN(1)