grn

grn [ -G ] [ -v ] [ file ... ]

-G
    Enable groff extensions; use extended graph format from gpic(1)

-v
    Print version number and exit

The grn command is a filter in the groff suite that converts ASCII graph files, typically produced by the graph(1) utility, into input suitable for the pic(1) macro package. This enables the inclusion of diagrams and graphs in troff or groff documents.

Graph files describe nodes, edges, labels, and attributes in a simple textual format. grn translates these into pic primitives such as boxes for nodes, lines or arrows for edges, and text for labels, preserving layout, colors, and styles where supported.

Common workflow: generate graph data with graph, pipe to grn for pic conversion, then process with pic, troff, or groff for output to PostScript, PDF, or other formats.

It supports basic graph features like directed/undirected edges, node shapes, and positioning. For modern use, pair with gpic (groff's pic) for enhanced compatibility.

Processes only graph(1) output; limited support for complex attributes or large graphs; stdin used if no files specified.

graph data | grn | pic | groff -Tps > output.ps
Example: grn graphfile.pic | gpic | groff -Tpdf -ms > doc.pdf

Developed at AT&T Bell Labs as part of the graph/pic/troff ecosystem in the 1970s-1980s; ported and maintained in GNU groff since 1990s for Unix-like systems.

graph(1), pic(1), gpic(1), groff(1), troff(1)