Using the grap Command (with examples)

In this article, we will explore different use cases of the grap command, a charting preprocessor for the GNU Troff document formatting system. We will illustrate how to process grap files and save the resulting output for future processing with pic and groff. Additionally, we will show how to typeset a grap file to PDF using the pic and groff commands.

Use Case 1: Processing a grap file for future processing

Code:

grap path/to/input.grap > path/to/output.pic

Motivation:

When working with complex charts and graphs, it is often beneficial to process the grap file separately from the final output generation. By redirecting the output to a .pic file, we can store the intermediate representation and use it for further modifications or outputs in the future.

Explanation:

• grap: The grap command is used to preprocess the input.grap file, which contains the graph definitions.
• path/to/input.grap: This is the path to the input grap file that we want to process.
• >: The output redirection operator, which redirects the output of the grap command to the specified file.
• path/to/output.pic: This is the path where the processed output will be saved as a .pic file, ready for future processing.

Example Output:

After executing the code above, the processed output will be saved as output.pic in the specified directory. This file can then be used later in other commands or modifications.

Use Case 2: Typesetting a grap file to PDF

Code:

grap path/to/input.grap | pic -T pdf | groff -me -T pdf > path/to/output.pdf

Motivation:

In many cases, we need to generate high-quality PDF output from grap files containing charts or graphs. By combining the grap, pic, and groff commands, we can typeset the grap file to PDF using the [me] macro package.

Explanation:

• grap: The grap command preprocesses the input.grap file.
• path/to/input.grap: This is the path to the input grap file that we want to typeset.
• |: The pipe operator, used to pass the output of one command as input to the next command.
• pic -T pdf: The pic command is used to format the processed grap output, and with the -T pdf argument, we specify the output format as PDF.
• groff -me -T pdf: The groff command then processes the output of pic using the [me] macro package and sets the output format as PDF.
• >: The output redirection operator, which redirects the final PDF output to the specified file.
• path/to/output.pdf: This is the path where the resulting PDF will be saved.

Example Output:

Upon executing the code above, the command will process the input.grap file and generate a PDF file named output.pdf in the specified directory. The PDF will contain the typeset version of the graph or chart defined in the grap file.

In this article, we have explored different use cases of the grap command. We have learned how to process grap files for future processing with pic and groff, as well as how to typeset grap files to PDF using the pic and groff commands. These examples demonstrate the versatility of grap and its integration with other tools to produce high-quality charts and graphs for various purposes.