fmt (Unix)

The fmt utility on Unix-like operating systems is a simple text formatter. Its primary purpose is to take input text and reformat it to fit within a specified line width, wrapping lines as necessary. It is designed to improve the readability of text, especially when dealing with long lines that exceed terminal or document boundaries.

fmt typically reads text from standard input, or from files specified as arguments. It then breaks the input into paragraphs, using blank lines as paragraph delimiters. Within each paragraph, fmt joins short lines together and splits long lines, ensuring that the resulting lines are no longer than the defined width. By default, fmt attempts to fill lines as full as possible, creating a more visually appealing block of text.

The utility is often used in scripting and command-line workflows to automatically format text, such as email messages, documentation, or configuration files. fmt focuses primarily on reformatting paragraphs and does not offer advanced text processing features like hyphenation or justification found in more sophisticated text editors or word processors.

Options commonly available in implementations of fmt allow users to specify the desired line width, control the handling of indentation, and modify other aspects of the formatting process. The utility is a standard part of many Unix-like distributions and is often a useful tool for quickly improving the readability of text-based files.