Graphviz `nop` Command Examples (with examples)

Pretty-printing graphs in canonical format

The nop command in Graphviz can be used to pretty-print one or more graphs in the canonical format. The canonical format represents a graph in a structured and standardized way, making it easier to read and understand.

To pretty-print one or more graphs, you can use the following command:

nop path/to/input1.gv path/to/input2.gv ... > path/to/output.gv

In this command:

• path/to/input1.gv, path/to/input2.gv, etc. are the paths to the input graph files that you want to pretty-print.
• path/to/output.gv is the path to the output file where the pretty-printed graph will be saved.

Motivation: The motivation behind pretty-printing a graph in the canonical format is to improve its readability and maintainability. Having a well-formatted graph can make it easier for developers and designers to understand its structure and relationships.

Example: Let’s say we have an input graph file named input.gv with the following content:

digraph {
    A -> B
    B -> C
    C -> D
}

By running the nop command:

nop input.gv > output.gv

The content of the output.gv file will be beautifully formatted as:

digraph {
    A -> B;
    B -> C;
    C -> D;
}

Check validity of graphs without producing an output graph

Additionally, the nop command can be used to check the validity of one or more graphs without producing an output graph. This can be useful to identify any potential issues or errors in the graph files.

To check the validity of one or more graphs, you can use the following command:

nop -p path/to/input1.gv path/to/input2.gv ...

In this command:

• path/to/input1.gv, path/to/input2.gv, etc. are the paths to the input graph files that you want to check for validity.

Motivation: Checking the validity of graphs is crucial to ensure that they adhere to the syntax and rules defined in the Graphviz specification. Identifying any errors or issues early on can help prevent unexpected behavior or incorrect visualizations.

Example: Let’s assume we have an input graph file named invalid.gv with the following content, which contains a syntax error (missing semicolon):

digraph {
    A -> B
    B -> C
    C -> D
}

By running the nop command:

nop -p invalid.gv

The command will not produce any output, indicating that the graph file is valid.

Displaying help for nop

To get help and learn more about the usage and options of the nop command, you can use the following command:

nop -?

Motivation: Displaying help for the nop command can be helpful for users who are new to Graphviz or need a quick reference on various available options.

Example: Running the nop command with the -? option will display the help message with detailed information about the command and its options. The output will include a usage section, description, and a list of available filters and their purposes.

Overall, the nop command in Graphviz provides useful functionalities for prettifying and validating graphs. By understanding its different use cases, you can effectively utilize it in your graph visualization workflows.