How to use the command `dot` (with examples)

The dot command is part of Graphviz, a suite of tools developed to visualize graphs as diagrams. It processes descriptions of graphs in a simple text language and renders them into visual formats such as PNG, SVG, PDF, and more. Using different layout engines, dot provides versatile options to represent relational data in clearer and more understandable visuals.

Render a PNG image with a filename based on the input filename and output format

Code:

dot -T png -O path/to/input.gv

Motivation:

This use case is pivotal when you want to quickly generate a visual representation of a graph and maintain a clear connection to the original source file. By automatically deriving the output filename from the input, it reduces the risk of human error and keeps the organization of files seamless, especially in batch processing or when frequently updating graphs.

Explanation:

• dot: This initiates the Graphviz tool to process the input data.
• -T png: Specifies the desired output format, which in this instance is PNG. PNG is a popular image format due to its lossless compression and wide compatibility.
• -O: This option directs dot to generate an output filename based on the input filename and append the output format extension to it. This saves time and ensures consistency in file naming.
• path/to/input.gv: This is the path to the Graphviz file that contains the graph description you wish to visualize.

Example Output:

If your input file is named network.gv, after running this command, you’ll get an output file named network.gv.png in the same directory, depicting your graph in a PNG format.

Render an SVG image with the specified output filename

Code:

dot -T svg -o path/to/image.svg path/to/input.gv

Motivation:

Defining explicit output filenames is crucial when filenames need to follow a particular naming convention, or when you want to save the output to a different directory. SVG is particularly useful for web applications because it’s scalable and can be manipulated via CSS.

Explanation:

• dot: Invokes the Graphviz processing command.
• -T svg: Sets the output format to SVG, which is ideal for scalable graphics suitable for web display.
• -o path/to/image.svg: The -o option allows you to specify the exact output filename, giving you control over where and how the file is saved.
• path/to/input.gv: Indicates the source file containing the graph description.

Example Output:

You will obtain a file named image.svg at the specified path, which showcases the graph described in input.gv.

Render the output in various formats (PS, PDF, SVG, Fig, PNG, GIF, JPEG, JSON, or DOT format)

Code:

dot -T format -O path/to/input.gv

Motivation:

This example demonstrates the flexibility and range of formats that Graphviz can render. By converting graphs into different formats, you have the ability to use these visuals across various platforms and media, catering to both print and digital needs alike.

Explanation:

• dot: Starts the graph rendering process.
• -T format: This placeholder specifies any one of the available output formats like PS, PDF, PNG, etc. The actual format needs to be indicated in place of ‘format’.
• -O: As before, this flag ensures the output filename is based on the input filename with the added format extension.
• path/to/input.gv: This denotes the input file with graph data ready for rendering.

Example Output:

Executing this command with -T pdf will yield a input.gv.pdf file, offering a high-quality printable document of your graph.

Render a GIF image using stdin and stdout

Code:

echo "digraph {this -> that}" | dot -T gif > path/to/image.gif

Motivation:

This use case is incredibly efficient when dealing with dynamic inputs or scripts that generate graphs. By using stdin and stdout, it eliminates the need for temporary files and streamlines the process of generating images from command-line input, all within a single step.

Explanation:

• echo "digraph {this -> that}": This sends a simple graph description directly to the shell, which represents a directed edge from “this” to “that”.
• |: The pipe symbol directs the output of the echo command to be used as input for the next command.
• dot -T gif: Processes the input as a graph and instructs dot to output it in the GIF format, a widely supported format for simple animations or images.
• > path/to/image.gif: Redirects the resulting GIF output from stdout to be saved in a file at the specified path.

Example Output:

After running the command, you will find an image file named image.gif at the specified path, showing the graph structure from “this” to “that”.

Display help

Code:

dot -?

Motivation:

Accessing help documentation is fundamental for both novice users who are learning the tool or experienced users who wish to refresh their memory on specific commands and options. It quickly provides a comprehensive overview of all capabilities, enhancing user efficiency and command mastery.

Explanation:

• dot: This begins the use of the Graphviz command.
• -?: This argument requests the help information, which includes descriptions of all available command-line options for dot.

Example Output:

The command provides a detailed list of options, usages, and functionality descriptions for utilizing dot, assisting users in effectively employing the tool for their specific use cases.

Conclusion

The dot command offers a robust set of options for visualizing complex data structures as easily comprehensible graphics. By understanding and utilizing its various functionalities, you can produce high-quality graph visuals tailored to any format requirement or workflow necessity. Whether dealing with static files or dynamic stream inputs, dot provides a reliable and adaptable toolset for graph visualization needs.