How to use the command twopi (with examples)

The twopi command is a part of graphviz, a popular graph visualization software. twopi is used to render a radial network graph from a Graphviz file. It supports various layouts such as dot, neato, twopi, circo, fdp, sfdp, osage, and patchwork.

Use case 1: Render a png image with a filename based on the input filename and output format

Code:

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

Motivation: This example shows how to generate a png image of a radial network graph using the twopi layout algorithm. The output file is automatically named based on the input file name with the appropriate file extension (input.png).

Explanation:

• -T png: Specifies the output format as png.
• -O path/to/input.gv: Specifies the input Graphviz file.

Example output: The input.png file will be generated in the specified directory.

Use case 2: Render a svg image with the specified output filename

Code:

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

Motivation: In this example, we render a radial network graph as an svg image and specify the output filename (image.svg). This allows us to easily customize the output file name.

Explanation:

• -T svg: Specifies the output format as svg.
• -o path/to/image.svg: Specifies the output filename as image.svg.
• path/to/input.gv: Specifies the input Graphviz file.

Example output: The image.svg file will be generated in the specified directory.

Use case 3: Render the output in various formats

Code:

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

Motivation: This example demonstrates how twopi can render the output in various formats (ps, pdf, svg, fig, png, gif, jpg, json, or dot). By specifying the desired format, we can generate the graph visualization in the preferred output format.

Explanation:

• -T format: Specifies the desired output format.
• -O path/to/input.gv: Specifies the input Graphviz file.

Example output: The graph visualization will be generated in the specified format (ps, pdf, svg, fig, png, gif, jpg, json, or dot).

Use case 4: Render a gif image using stdin and stdout

Code:

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

Motivation: This example shows how to generate a gif image of a radial network graph using stdin and stdout. It is useful when we want to generate visualizations programmatically or as part of a script.

Explanation:

• echo "digraph {this -> that} ": Generates the input Graphviz file using echo command.
• |: Redirects the output of the previous command as the input of the next command.
• twopi -T gif: Specifies the output format as gif.
• > path/to/image.gif: Redirects the output to the specified file (image.gif).

Example output: The image.gif file will be generated in the specified directory.

Use case 5: Display help

Code:

twopi -?

Motivation: This example illustrates how to display the help information for the twopi command. It provides details about the different command-line options and their usage.

Explanation:

• -?: Displays the help information.

Example output: The help information for the twopi command will be displayed, providing details about the options and usage.

Conclusion:

The twopi command is a versatile tool for rendering radial network graphs from Graphviz files. It offers various output formats and layout algorithms, allowing for flexible and customizable visualizations. Whether you need to generate images or interact with the command programmatically, twopi provides a powerful solution for graph visualization tasks.