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Name | Synopsis | Description | Options | Exit status | Files | Authors | See also | COLOPHON |
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grn(1) General Commands Manual grn(1)
grn - embed Gremlin images in groff documents
grn [-C] [-T dev] [-M dir] [-F dir] [file ...]
grn -?
grn --help
grn -v
grn --version
grn is a preprocessor for including gremlin pictures in troff(1)
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 macros request a gremlin file;
the picture in that file is converted and placed in the troff
input stream. .GS may be called with a C, L, or R argument to
center, left-, or right-align the whole gremlin picture (the
default is to 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.
Currently only the me macro package has support for .GS, .GE, and
.GF.
grn produces drawing escape sequences that use groff's color
scheme extension (\D'F ...'), and thus may not work with other
troffs.
[1mgrn[24m commands
Each input line between .GS and .GE may have one grn command.
Commands consist of one or two strings separated by whitespace,
the first string being the command and the second its operand.
Commands may be upper- or lowercase 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 values
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, but can be used at any time to reset the default
settings.
width N
Force the picture to be N inches wide. This overrides any
scaling factors present in the same picture. “width 0” is
ignored.
height N
Force the 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
picture. 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 multiple file commands are given, the last one
controls. If name doesn't exist, an error message is
reported and processing continues from the .GE line.
[1mUsage with groff
Since grn is a preprocessor, it has no access to elements of
formatter state, such as indentation, line length, type size, or
register values. Consequently, no troff input can be placed
between the .GS and .GE macros. However, gremlin text elements
are subsequently processed by troff, so anything valid in a single
line of troff input is valid in a line of gremlin text (barring
the dot control character “.” at the beginning 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, run tbl(1) before
grn, pic(1), and/or ideal. If eqn(1) is needed, run it as the
last preprocessor. groff(1) automatically runs preprocessors in
the correct order.
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 the me macros will ensure
proper placement.
grn uses troff's 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 macro (this is for those who want to
rewrite these macros).
Gremlin file format
There exist two distinct gremlin file formats: the original format
for AED graphic terminals, and the Sun or X11 version. An
extension used by the Sun/X11 version allowing reference 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 in 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 below.
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
• The first line of each gremlin file contains either the string
“gremlinfile” (AED) or “sungremlinfile” (Sun/X11).
• The second line of the file contains an orientation and x and y
values for a positioning 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
(a drawing area wider than it is tall, with a menu across the
top). 1 means that gremlin will display things in vertical
format (a drawing area taller than it is wide, with a menu on
the 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
important; 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 truncated to that length.
Element specifications
• The first line of each element contains a single decimal number
giving the type of the element (AED) or its name (Sun/X11).
gremlin File Format: Object Type Specification
──────────────────────────────────────────────────────────
AED Number Sun/X11 Name Description
0 BOTLEFT text aligned to bottom left
1 BOTRIGHT text aligned to bottom right
2 CENTCENT center object
3 VECTOR vector
4 ARC arc
5 CURVE curve
6 POLYGON polygon
7 BSPLINE b-spline
8 BEZIER Bézier
10 TOPLEFT text aligned to top left
11 TOPCENT text aligned to top center
12 TOPRIGHT text aligned to top right
13 CENTLEFT text aligned to center left
14 CENTRIGHT text aligned to center right
15 BOTCENT text aligned to bottom center
• Each line after the object type specifies a point used to
display the element. It contains an x 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)
or a single asterisk, “*” (Sun/X11).
• 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 vectors,
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, 0 is also valid: it specifies an invisible
border. For text, the brush selects a font as follows.
1 roman (R font in troff)
2 italics (I font in troff)
3 bold (B font in troff)
4 special (S font in troff)
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 used only for text elements, and contains the
text string. There can be spaces inside the text. For arcs,
curves, and vectors, the character count is zero (0), followed
by exactly one space before the newline.
Coordinates
gremlin was designed for AED terminals, 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 from 0 to
367. Although you needn't absolutely stick to this range, you'll
get better 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 the printf(3) format “%f1.2”; it's probably a
good idea to use the same format if you want to modify the grn
code.
Sun/X11 coordinates
There is no 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.
-? and --help display a usage message, while -v and --version show
version information; all exit afterward.
-C Recognize .GS and .GE (and .GF) even when followed by a
character other than space or newline.
-F dir Search dir for subdirectories devname (name is the name of
the output driver) for the DESC file before the default
font directories /usr/local/share/groff/site-font, /usr/
local/share/groff/1.23.0/font, and /usr/lib/font.
-M dir Prepend dir to the search path for gremlin files. The
default search path is the current directory, the home
directory, /usr/local/share/groff/site-tmac, and /usr/
local/share/groff/1.23.0/tmac, in that order.
-T dev Prepare device output using output driver dev. The default
is ps. See groff(1) for a list of valid devices.
grn exits with status 0 on successful operation, status 2 if the
program cannot interpret its command-line arguments, and status 1
if it encounters an error during operation.
/usr/local/share/groff/1.23.0/font/devname/DESC
describes the output device name.
David Slattengren and Barry Roitblat wrote the original Berkeley
grn. Daniel Senderowicz and Werner Lemberg ⟨wl@gnu.org⟩ modified
it for groff.
gremlin(1), groff(1), pic(1), ideal(1)
This page is part of the groff (GNU troff) project. Information
about the project can be found at
⟨http://www.gnu.org/software/groff/⟩. If you have a bug report for
this manual page, see ⟨http://www.gnu.org/software/groff/⟩. This
page was obtained from the project's upstream Git repository
⟨https://git.savannah.gnu.org/git/groff.git⟩ on 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2025-08-09.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
groff 1.23.0.2722-658f-dirty 2025-01-02 grn(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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