--- name: "grn" section: "1" platform: "linux" package: "groff" version: "1.24.2-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/grn" --- # grn(1) embed Gremlin images in groff documents ## Name grn - embed Gremlin images in *groff* documents ## Synopsis **grn** \[**-C**\] \[**-T** *dev*\] \[**-M** *dir*\] \[**-F** *dir*\] \[*file* ...\] **grn** **-?** **grn** **--help** **grn** **-v** **grn** **--version** ## Description *grn* is a preprocessor for including *gremlin* pictures in [*troff*(1)](/troff/1.md) 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 *troff*s. ### *grn* 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. ### Usage 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)](/tbl/1.md) before *grn*, [*pic*(1)](/pic/1.md), and/or *ideal*. If [*eqn*(1)](/eqn/1.md) is needed, run it as the last preprocessor. [*groff*(1)](/groff/1.md) 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)](/printf/3.md) 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. ## Options **-?** 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 *dev*name (*name* is the name of the output driver) for the *DESC* file before the default font directories */usr/share/groff/site-font*, */usr/share/groff/1.24.2/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/share/groff/site-tmac*, and */usr/share/groff/1.24.2/tmac*, in that order. - **-T** *dev* Prepare device output using output driver *dev*. The default is **ps**. See [*groff*(1)](/groff/1.md) for a list of valid devices. ## Exit status *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. ## Files - */usr/share/groff/1.24.2/font/dev*name*/DESC* describes the output device *name*. ## Authors David Slattengren and Barry Roitblat wrote the original Berkeley *grn*. Daniel Senderowicz and Werner Lemberg ⟨wl@\\:gnu\\:.org⟩ modified it for *groff*. ## See also *gremlin*(1), [*groff*(1)](/groff/1.md), [*pic*(1)](/pic/1.md), *ideal*(1)