gv(3guile)

💖 NAME 💖

gv_guile — graph manipulation in guile. (Yeah bestie, this is the gv(3guile) page from the guile manual, section 3, and we're about to have a whole moment together.) 🦋

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✨ SYNOPSIS ✨

(load-extension "/usr/lib/graphviz/guile/libgv.so" "SWIG_init")

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🌸 USAGE 🌸

🌈 INTRODUCTION 🌈

gv_guile is a dynamically loaded extension for guile that hands you the keys to the graph facilities of graphviz. That's the whole vibe. Load it, and suddenly you're building graphs in scheme like it's nothing. 💅

🎀 COMMANDS 🎀

🫶 New graphs

New empty graph

graph_handle gv.graph (name);
graph_handle gv.digraph (name);
graph_handle gv.strictgraph (name);
graph_handle gv.strictdigraph (name);

New graph from a dot-syntax string or file

graph_handle gv.readstring (string);
graph_handle gv.read (string filename);
graph_handle gv.read (channel);

Add new subgraph to existing graph

graph_handle gv.graph (graph_handle, name);

🧚 New nodes

Add new node to existing graph

node_handle gv.node (graph_handle, name);

💜 New edges

Add new edge between existing nodes

edge_handle gv.edge (tail_node_handle, head_node_handle);

Add a new edge between an existing tail node, and a named head node which will be induced in the graph if it doesn't already exist

edge_handle gv.edge (tail_node_handle, head_name);

Add a new edge between an existing head node, and a named tail node which will be induced in the graph if it doesn't already exist

edge_handle gv.edge (tail_name, head_node_handle);

Add a new edge between named tail and head nodes which will be induced in the graph if they don't already exist

edge_handle gv.edge (graph_handle, tail_name, head_name);

🍓 Setting attribute values

Set value of named attribute of graph/node/edge — creating attribute if necessary

string gv.setv (graph_handle, attr_name, attr_value);
string gv.setv (node_handle, attr_name, attr_value);
string gv.setv (edge_handle, attr_name, attr_value);

Set value of existing attribute of graph/node/edge (using attribute handle)

string gv.setv (graph_handle, attr_handle, attr_value);
string gv.setv (node_handle, attr_handle, attr_value);
string gv.setv (edge_handle, attr_handle, attr_value);

🌟 Getting attribute values

Get value of named attribute of graph/node/edge

string gv.getv (graph_handle, attr_name);
string gv.getv (node_handle, attr_name);
string gv.getv (edge_handle, attr_name);

Get value of attribute of graph/node/edge (using attribute handle)

string gv.getv (graph_handle, attr_handle);
string gv.getv (node_handle, attr_handle);
string gv.getv (edge_handle, attr_handle);

🌈 Obtain names from handles

string gv.nameof (graph_handle);
string gv.nameof (node_handle);
string gv.nameof (attr_handle);

🔥 Find handles from names

graph_handle gv.findsubg (graph_handle, name);
node_handle gv.findnode (graph_handle, name);
edge_handle gv.findedge (tail_node_handle, head_node_handle);
attribute_handle gv.findattr (graph_handle, name);
attribute_handle gv.findattr (node_handle, name);
attribute_handle gv.findattr (edge_handle, name);

💫 Misc graph navigators returning handles

node_handle gv.headof (edge_handle);
node_handle gv.tailof (edge_handle);
graph_handle gv.graphof (graph_handle);
graph_handle gv.graphof (edge_handle);
graph_handle gv.graphof (node_handle);
graph_handle gv.rootof (graph_handle);

👑 Obtain handles of proto node/edge for setting default attribute values

node_handle gv.protonode (graph_handle);
edge_handle gv.protoedge (graph_handle);

🦋 Iterators

Iteration termination tests

bool gv.ok (graph_handle);
bool gv.ok (node_handle);
bool gv.ok (edge_handle);
bool gv.ok (attr_handle);

Iterate over subgraphs of a graph

graph_handle gv.firstsubg (graph_handle);
graph_handle gv.nextsubg (graph_handle, subgraph_handle);

Iterate over supergraphs of a graph (obscure and rarely useful)

graph_handle gv.firstsupg (graph_handle);
graph_handle gv.nextsupg (graph_handle, subgraph_handle);

Iterate over edges of a graph

edge_handle gv.firstedge (graph_handle);
edge_handle gv.nextedge (graph_handle, edge_handle);

Iterate over outedges of a graph

edge_handle gv.firstout (graph_handle);
edge_handle gv.nextout (graph_handle, edge_handle);

Iterate over edges of a node

edge_handle gv.firstedge (node_handle);
edge_handle gv.nextedge (node_handle, edge_handle);

Iterate over out-edges of a node

edge_handle gv.firstout (node_handle);
edge_handle gv.nextout (node_handle, edge_handle);

Iterate over head nodes reachable from out-edges of a node

node_handle gv.firsthead (node_handle);
node_handle gv.nexthead (node_handle, head_node_handle);

Iterate over in-edges of a graph

edge_handle gv.firstin (graph_handle);
edge_handle gv.nextin (node_handle, edge_handle);

Iterate over in-edges of a node

edge_handle gv.firstin (node_handle);
edge_handle gv.nextin (graph_handle, edge_handle);

ok bestie yes, those last two literally swap graph_handle and node_handle between firstin and nextin. That is exactly what the page says, so we're typing it exactly, no notes. 😭

Iterate over tail nodes reachable from in-edges of a node

node_handle gv.firsttail (node_handle);
node_handle gv.nexttail (node_handle, tail_node_handle);

Iterate over nodes of a graph

node_handle gv.firstnode (graph_handle);
node_handle gv.nextnode (graph_handle, node_handle);

Iterate over nodes of an edge

node_handle gv.firstnode (edge_handle);
node_handle gv.nextnode (edge_handle, node_handle);

Iterate over attributes of a graph

attribute_handle gv.firstattr (graph_handle);
attribute_handle gv.nextattr (graph_handle, attr_handle);

Iterate over attributes of an edge

attribute_handle gv.firstattr (edge_handle);
attribute_handle gv.nextattr (edge_handle, attr_handle);

Iterate over attributes of a node

attribute_handle gv.firstattr (node_handle);
attribute_handle gv.nextattr (node_handle, attr_handle);

💀 Remove graph objects

bool gv.rm (graph_handle);
bool gv.rm (node_handle);
bool gv.rm (edge_handle);

🌸 Layout

Annotate a graph with layout attributes and values using a specific layout engine

bool gv.layout (graph_handle, string engine);

⭐ Render

Render a layout into attributes of the graph

bool gv.render (graph_handle);

Render a layout to stdout

bool gv.render (graph_handle, string format);

Render to an open file

bool gv.render (graph_handle, string format, channel fout);

Render a layout to an unopened file by name

bool gv.render (graph_handle, string format, string filename);

Render to a string result

string gv.renderresult (graph_handle ing, string format);
gv.renderresult (graph_handle, string format, string outdata);

Render to an open channel

bool gv.renderchannel (graph_handle, string format, string
channelname);

Render a layout to a malloc'ed string, to be free'd by the caller

⚠️ (deprecated - too easy to leak memory)

(still needed for "eval [gv::renderdata $G tk]" )

string gv.renderdata (graph_handle, string format);

Writing graph back to file

bool gv.write (graph_handle, string filename);
bool gv.write (graph_handle, channel);

Graph transformation tools

bool gv.tred (graph_handle);

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🌈 KEYWORDS 🌈

graph, dot, neato, fdp, circo, twopi, guile. 🫶

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and that's the whole page, bestie 💖 this one's from the gv(3guile) manual, dated 21 March 2026 — go build something iconic with it, you ate fr fr ✨👑