Using the Command 'eqn' for Document Formatting (with examples)

The eqn command is a powerful tool used for processing equations within the GNU Troff (groff) document formatting system. It is particularly useful for typesetting documents that include mathematical notation and complex equations, ensuring that they are correctly formatted for various output formats such as PostScript and PDF. eqn works by interpreting and formatting equations from the input file and arranging them properly for subsequent typesetting through groff.

Use Case 1: Process Input with Equations, Saving the Output for Future Typesetting with Groff to PostScript

Code:

eqn path/to/input.eqn > path/to/output.roff

Motivation:

This use case is pivotal for users who wish to prepare their mathematical typesetting documents for future formatting with groff. By processing the input file with eqn and saving the output as a .roff file, users have a processed file that is ready for rendering into a PostScript document at any later time. This step is essential for maintaining a workflow that allows for meticulous editing and review of document equations before final typesetting.

Explanation of Arguments:

• eqn: This is the command that processes the equations within the specified input file.
• path/to/input.eqn: This argument specifies the path to the input file that contains equations to be processed. The file format .eqn implies it contains the necessary mathematical notation that eqn will interpret.
• >: This is a redirection operator in Unix-like systems that directs the processed output to a specified file.
• path/to/output.roff: This argument specifies the output path where the processed content will be saved as a .roff file, which can later be typeset with groff.

Example Output:

The output would be a .roff file, which when inspected, will contain troff-compatible equations ready for conversion to a PostScript document. While the .roff file itself is not typically human-readable, its proper rendering is crucial for subsequent document typesetting steps.

Use Case 2: Typeset an Input File with Equations to PDF Using the [me] Macro Package

Code:

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

Motivation:

This use case is invaluable for users wanting to produce a final, polished document in PDF format directly from a file containing written equations. By utilizing the [me] macro package in tandem with eqn and groff, users can ensure their documents adhere to specific macro-styling conventions, guaranteeing a uniformly professional appearance suitable for publishing or presentation.

Explanation of Arguments:

• eqn: Again, this is the command responsible for processing the equations.
• -T pdf: This option specifies the output type expected, which in this case is PDF. It is crucial for ensuring the correct formatting process is initiated from the start.
• path/to/input.eqn: This argument provides the location of the file containing equations.
• |: A pipe operator utilized to direct the output from eqn into the second command (groff -me -T pdf) seamlessly.
• groff: The troff processing command that takes the input (processed by eqn) and formats it according to specified styles and output types.
• -me: This option invokes the [me] macro package within groff. This package is well-regarded for its formatting capabilities, especially in document typesetting that requires structured styles like academic papers or technical reports.
• >
• path/to/output.pdf: The final argument designates the file name and path for the output PDF, which will include all the correctly formatted text and equations from the original input.

Example Output:

The outcome is a PDF file featuring well-typeset text and equations, formatted according to the [me] macro specifications. This file is ready for any purpose requiring professional documentation of mathematical content, such as academic submissions or internal company reports.

Conclusion:

The eqn command presents invaluable functionalities for processing and typesetting documents containing mathematical equations. Whether preparing a .roff file for later conversion to PostScript or creating a PDF with ready-to-use formatted equations, eqn, in conjunction with groff and specific macro packages, offers robust, reliable options for maintaining quality in document presentation. These use cases illustrate eqn’s versatility in managing and rendering complex mathematical content across different output formats.