Introduction to the Linux Command Line

Linux uses plain text as the foundation for data representation, logging, configuration, and documentation. To create well-structured output—whether for printing, scripting, or reports—users can rely on formatting utilities designed to control line numbering, wrapping, spacing, and even typesetting.

nl – Number Lines

nl adds line numbers with control over logical page sections and custom numbering formats.

• Basic usage:
  

  nl distros.txt

• Custom numbering:
  

  nl -n rz -w 3 -s ' '

• Logical page markup: \\:\\:\\: (header), \\:\\: (body), \\: (footer)

fold – Wrap Lines

fold wraps long lines to a fixed width, useful for display limitations.

echo "Sample sentence here." | fold -w 12 -s

fmt – Format Text Paragraphs

fmt reformats paragraph-style input to a consistent width and spacing, ideal for comments and structured notes.

fmt -w 50 file.txt

fmt -p '# ' file.txt

pr – Prepare for Printing

pr paginates content with headers, page breaks, and margins.

pr -l 15 -w 65 distros.txt

printf – Structured Output

printf formats values using placeholders and field controls, ideal for scripts and reports.

printf "Line: %05d\t%.2f\t%s\n" 7 3.14 "Done"

Specifier	Usage
%d	Decimal integer
%f	Floating-point
%s	String
%x / %X	Hexadecimal
%%	Literal percent sign

groff – Advanced Document Formatting

groff formats documents with macros, supporting output for screen or print (PostScript, PDF).

• Preview ASCII man page:
  

  zcat man.1.gz | groff -mandoc -T ascii

• Generate PDF:
  

  groff -mandoc man.1 > page.ps
  ps2pdf page.ps page.pdf

• Create styled tables with tbl:
  

  groff -t -T ascii formatted-table.txt

Conclusion

Linux formatting tools like nl, fold, fmt, pr, printf, and groff help users present structured output professionally. Whether preparing printed documents, structured terminal data, or formatted scripts, these utilities are indispensable for clear communication in the Unix world.