grn man page

grn — groff preprocessor for gremlin files


grn [ -Cv ] [ -Tdev ] [ -Mdir ] [ -Fdir ] [ file... ]


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 picture 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.

The following command-line options are understood:


Prepare output for printer dev. The default device is ps. See groff(1) for acceptable devices.


Prepend dir to the default search path for gremlin files. The default path is (in that order) the current directory, the home directory, /etc/groff/site-tmac, /etc/groff/site-tmac, and /usr/share/groff/1.22.3/tmac.


Search dir for subdirectories devname (name is the name of the device) for the DESC file before the default font directories /etc/groff/site-font, /usr/share/groff/1.22.3/font, and /usr/lib/font.


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


Print the version number.

It is possible to have whitespace between a command line option and its parameter.

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 operand. 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 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.


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 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 two file commands are given, the second one overrides the first. If name doesn't exist, an error message is reported and processing 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 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, 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 ensure 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 terminal version, and the SUN or X11 version. An extension to 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 to the 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
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
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

Element Specifications

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.



Device description file for device name.

See Also

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


Copyright © 2000-2014 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be included in translations approved by the Free Software Foundation instead of in the original English.


David Slattengren and Barry Roitblat wrote the original Berkeley grn.

Daniel Senderowicz and Werner Lemberg modified it for groff.

Referenced By

groff(1), groff_filenames(7), grog(1).

4 November 2014 Groff Version 1.22.3