Mastering Graphviz: Quick Guide to Creating Diagrams with the dot Command

Installation

sudo apt install graphviz

Installs the dot executable.

Hello World Example

Create test.dot: graph g { "Hello" -- "world" } Render PNG:

dot -Tpng -o test.png test.dot

DOT Language Basics

Use graph for undirected graphs and digraph for directed graphs. Graph description is enclosed in { }. Comments: // single‑line, /* … */ block.

Node Attributes

Nodes can be defined implicitly; attributes are set in square brackets after the node name or via a default node block.

shape – geometric shape (e.g., box, ellipse, circle)

label – text displayed inside the node

style – filled or solid color – outline color

fillcolor – interior color

Example:

node [shape="box", style="filled", color="red", fillcolor="green"];

Edge Attributes

Edges connect nodes; direction is determined by the graph type.

style – solid or dotted color – line color

label – text label on the edge

labelfontcolor – label font color

headlabel / taillabel – labels at the arrow head or tail

decorate – draw a decorative line for the label

For directed edges you can specify attachment points using compass points e, s, w, n.

Graph Attributes and Subgraphs

Graph‑level attributes affect layout and appearance:

size – canvas size

label – title

labelloc – position of the title ( t top, b bottom)

labeljust – alignment of the title

bgcolor – background color

rankdir – layout direction ( LR, TB, etc.)

Subgraphs (clusters) group nodes and can have their own attributes. Prefix the subgraph name with cluster to obtain a boxed grouping.

digraph graph_settings {
    start [shape="Mdiamond"];
    end   [shape="Msquare"];

    subgraph cluster_sub1 {
        label="process #1";
        labelloc="t";
        bgcolor="gray55";
        node [style="filled", color="white"];
        a0 -> a1 -> a2 -> a3 -> a0;
    }

    subgraph cluster_sub2 {
        label="process #2";
        labelloc="t";
        color="blue";
        node [style="filled", color="black", fillcolor="gray55"];
        b0 -> b1 -> b2 -> b3;
    }

    start -> {a0,b0};
    a1 -> b3;
    b2 -> a3;
    {a3,b3} -> end;
}

Complete Example with Node and Edge Defaults

digraph edge_settings {
    edge [color="green", decorate=false];   // default edge attributes
    node [shape="polygon", sides=4, color="blue"]; // default node attributes

    a -> b [style="dotted", color="red", label="a to b"];
    b:se -> c:w [headlabel="end", taillabel="start"]; // compass points
    {c, f} -> {d, e} [label="multi-lines", decorate=true];
}

Summary

The dot command provides a scriptable way to generate high‑quality diagrams. Mastering node, edge, and graph attributes covers the majority of everyday use cases; the official Graphviz documentation offers additional advanced features.